GRANITE FIORDS WILDERNESS STUDY AREA, ALASKA.

USGS Publications Warehouse

Berg, Henry C.; Pittman, Tom L.

1984-01-01

Mineral surveys of the Granite Fiords Wilderness study area revealed areas with probable and substantiated mineral-resource potential. In the northeastern sector, areas of probable and substantiated resource potential for gold, sivler, and base metals in small, locally high grade vein and disseminated deposits occur in recrystallized Mesozoic volcanic, sedimentary, and intrusive rocks. In the central part, areas of probable resource potential for gold, silver, copper, and zinc in disseminated and locally massive sulfide deposits occur in undated pelitic paragneiss roof pendants. A molybdenite-bearing quartz vein has been prospected in western Granite Fiords, and molybdenum also occurs along with other metals in veins in the northeastern sector and in geochemical samples collected from areas where there is probable resource potential for low-grade porphyry molybdenum deposits in several Cenozoic plutons. No energy resource potential was identified in the course of this study.

Magmatism in the Shapinggou district of the Dabie orogen, China: Implications for the formation of porphyry Mo deposits in a collisional orogenic belt

NASA Astrophysics Data System (ADS)

Ren, Zhi; Zhou, Taofa; Hollings, Pete; White, Noel C.

2018-05-01

The Shapinggou molybdenum deposit is located in the Qinling-Dabie Orogen, which hosts the world's largest molybdenum belt. The igneous rocks at Shapinggou can be divided into two stages (136-127 Ma and 118-114 Ma), the early suite of felsic (136-127 Ma, SiO2 = 58.0 to 72.9 wt%) and mafic rocks (133-128 Ma, SiO2 = 45.2 to 57.0 wt%), and a later suite comprising syenite (117 Ma, SiO2 = 64.2 to 65.0 wt%), quartz syenite porphyry (116 Ma, 62.5 to 70.0 wt%), granite porphyry (112 Ma, SiO2 = 75.5 to 77.6 wt%) and diorite porphyry (111 Ma, SiO2 = 56.6 to 59.7 wt%). The early-stage felsic rocks display high SiO2, Al2O3, Na2O, K2O, Sr, LREE contents, and Sr/Y, (La/Yb)N ratios, initial Sr isotope ratios of 0.7076 to 0.7089, but low MgO, FeOT, Y, Yb contents and negative εNd(t) values, consistent with partial melting of the lower continental crust. The early-stage mafic rocks exhibit low SiO2, high MgO, Ni and Cr contents, consistent with an upper mantle source, but trace element and isotope data suggest a role for crustal contamination. The late-stage syenite and quartz syenite porphyry show high abundances of Na2O, K2O, Al2O3, HFSEs (e.g., Th, U, Zr, Hf) and significant negative Eu anomalies. The late-stage granite porphyry displays high SiO2 contents, and depletions in Ba, Sr, Eu and Ti. The geochemical features of the late-stage intrusions are similar to A-type granites. Crystal fractionation of plagioclase, K-feldspar, biotite/ muscovite, amphibole/ garnet and Fe-Ti oxides controlled the evolution of the magma. The geochemical and isotopic data suggest that the rocks at Shapinggou were likely derived from a mixed source of lithospheric mantle, subducted continental crust of the Yangtze Block (Kongling Group) and partial melts of the Dabie Complex. Early stage rocks represent melts of the source with a lower proportion of Dabie Complex materials, whereas late stage rocks were derived from a source with a higher proportion Dabie Complex component. The geochemical and

Ore genesis and geodynamic setting of the Lianhuashan porphyry tungsten deposit, eastern Guangdong Province, SE China: constraints from muscovite 40Ar-39Ar and zircon U-Pb dating and Hf isotopes

NASA Astrophysics Data System (ADS)

Liu, Peng; Mao, Jingwen; Pirajno, Franco; Jia, Lihui; Zhang, Feng; Li, Yang

2017-12-01

The Lianhuashan deposit has long been regarded as a typical tungsten porphyry deposit, located in the eastern Guangdong Province, in the Southeastern Coastal Metallogenic Belt (SCMB). LA-MC-ICP-MS zircon U-Pb dating of the quartz porphyry yielded a weighted mean 206Pb/238U age of 137.3 ± 2.0 Ma, which is interpreted as the emplacement age of the quartz porphyry. Hydrothermal muscovite yielded a plateau 40Ar/39Ar age of 133.2 ± 0.9 Ma, which is consistent with the zircon U-Pb age, suggesting that the tungsten mineralization is genetically related to the quartz porphyry. Combined with previous studies, we suggest that there is a 145-135 Ma episode linking the granitic magmas with W-Sn ore systems in the SCMB. Zircon ɛHf (t) values of the quartz porphyry are in range of - 3.8 to 0.9, and the two-stage Hf model ages (TDM2) are 1.1-1.4 Ga, which is younger than the basement rocks in the Cathaysia Block (1.8-2.2 Ga), signifying that the quartz porphyry was predominantly derived from melting of Mesoproterozoic crust containing variable amounts of mantle components. In combination with the newly recognized coeval alkaline/bimodal magmatism and A-type granites in eastern Guangdong, we suggest that the 145-135 Ma W-Sn metallogenic event of the SCMB is related to a geodynamic setting of large-scale lithospheric extension and thinning, which can be ascribed to melting of the crust caused by mantle upwelling, triggered by the oblique subduction of the Izanagi plate.

Petrogenesis of the Baishan granite stock, Eastern Tianshan, NW China: Geodynamic setting and implications for potential mineralization

NASA Astrophysics Data System (ADS)

Cao, MingJian; Qin, KeZhang; Li, GuangMing; Evans, Noreen J.; McInnes, Brent I. A.; Lu, WeiWei; Deng, Gang

2017-11-01

Located in a region rich in Cu-Ni and Mo mineralization, the Baishan granitic stock is barren for reasons that remain enigmatic. Whole rock elemental and Sr-Nd isotope analysis, major element analysis of a number of minerals, and zircon trace element, U-Pb and Hf isotope analysis were undertaken in order to reveal the petrogenesis of the granites. All granites show typical I-type characteristics including metaluminous to slightly peraluminous, calc-alkaline signatures with a strong depletion of Nb, Ta, Ti and P, enrichment of light rare earth elements and large ion lithophile elements (e.g., Cs, Rb, Th, U, K). In addition, a strong depletion in Ti and P, highly fractionated light rare earth element patterns and less fractionated heavy rare earth element patterns, and negative correlations between SiO2 and TiO2, Al2O3, MgO, FeOT, P2O5, Zr and Hf suggest significant fractional crystallization of amphibole, apatite, zircon and Ti-bearing minerals. Whole rock Sr-Nd and zircon Hf isotopic compositions show wide variations with (87Sr/86Sr)i values of 0.70358 to 0.70505, εNd (t) of 3.8 to 7.2, and εHf (t) of 2.4 to 12.2 indicating derivation from partial melting of juvenile lower crust with obvious addition of ancient crust. Zircon U-Pb ages indicate a formation age of 292 Ma, significantly older than the ore-forming granite porphyry and slightly older than the regional mafic-ultramafic, A-type and diabase magmatism of Eastern Tianshan. The granite stocks were likely derived during heating of ascending asthenospheric mantle above a mantle plume in the Early Permian. Mineral chemistry, saturation thermometry, mineral species and whole rock Fe2O3/FeO ratios indicate a crystallization temperature of > 980 to 665 °C, pressure of 1.6 kbar and oxygen fugacity of ≤ NNO for the granite stock. Comparing the geochemistry, magma source and crystallization environment for the Early Permian barren granite and Late Triassic ore-related granite porphyry, the low ratios of Sr/Y and

Geochronology and geochemistry of the granites from the Zhuxi W-Cu ore deposit in South China: Implication for petrogenesis, geodynamical setting and mineralization

NASA Astrophysics Data System (ADS)

Pan, Xiaofei; Hou, Zengqian; Zhao, Miao; Chen, Guohua; Rao, Jianfeng; Li, Yan; Wei, Jin; Ouyang, Yongpeng

2018-04-01

The giant Zhuxi tungsten deposit is located in the Taqian-Fuchun Ore Belt in northeastern Jiangxi province, and genetically associated with the Zhuxi granitic stocks and dykes. Three mineralization-related granites including granite porphyry dykes (GP), biotite granitic stocks (BG), and white granitic dykes (WG), were identified in the Zhuxi deposit. SHRIMP zircon U-Pb analysis for the three granitic rocks present ages ranging from 153.5 ± 1.0 Ma to 150.4 ± 1.0 Ma. The BG mainly contains quartz, microcline, albite, biotite and muscovite with minor accessory minerals including zircon, apatite, monazite, Ti/Fe oxides, and dolerite. However, the WG is mainly composed of quartz, microcline and albite with minor muscovite and accessory minerals. The GP is a medium-grained porphyritic granite and its phenocrysts include quartz, alkali feldspar, muscovite and plagioclase. All the Zhuxi granites have high SiO2 content (71.97 wt%-81.19 wt%) and total alkali (3.25 wt%-9.42 wt%), and their valid aluminum saturation index (ASI) values show a wide range of 1.03 to 2.49. High Rb/Sr ratios, low Sr content (<50 ppm) and markedly negative Eu anomalies of GP, WG and BG demonstrated that the Zhuxi granites are highly fractioned and intensive crystal differentiated. Because they display the features of both I- and S-types granites, they were confirmed to be I-S transform-type granites. Whole rock εNd(t) and zircon εHf(t) values fall into the ranges of -6.98 to -11.97, and -3.1 to -11.5, and the Nd (TDM2) and Hf two-stage model ages (TDMc) are 1.51-1.92 Ga and 1.42-2.01 Ga, respectively. Geochemical and isotopic data suggest that these highly fractionated I-S transform-type granites were originated from magmas which showed affinity with the Proterozoic continent and the Shuangqiaoshan Group and little mantle contribution was involved during the generation of Zhuxi granitic rocks. Extreme fractional crystallization resulted in further enrichment of tungsten in the evolved granitic

Porphyry copper deposit density

USGS Publications Warehouse

Singer, Donald A.; Berger, Vladimir; Menzie, W. David; Berger, Byron R.

2005-01-01

Estimating numbers of undiscovered mineral deposits has been a source of unease among economic geologists yet is a fundamental task in considering future supplies of resources. Estimates can be based on frequencies of deposits per unit of permissive area in control areas around the world in the same way that grade and tonnage frequencies are models of sizes and qualities of undiscovered deposits. To prevent biased estimates it is critical that, for a particular deposit type, these deposit density models be internally consistent with descriptive and grade and tonnage models of the same type. In this analysis only deposits and prospects that are likely to be included in future grade and tonnage models are employed, and deposits that have mineralization or alteration separated by less than an arbitrary but consistent distance—2 km for porphyry copper deposits—are combined into one deposit. Only 286 deposits and prospects that have more than half of the deposit not covered by postmineral rocks, sediments, or ice were counted.Nineteen control areas were selected and outlined along borders of hosting magmatic arc terranes based on three main features: (1) extensive exploration for porphyry copper deposits, (2) definable geologic settings of the porphyry copper deposits in island and continental volcanic-arc subduction-boundary zones, and (3) diversity of epochs of porphyry copper deposit formation.Porphyry copper deposit densities vary from 2 to 128 deposits per 100,000 km2 of exposed permissive rock, and the density histogram is skewed to high values. Ninety percent of the control areas have densities of four or more deposits, 50 percent have densities of 15 or more deposits, and 10 percent have densities of 35 or more deposits per 100,000 km2. Deposit density is not related to age or depth of emplacement. Porphyry copper deposit density is inversely related to the exposed area of permissive rock. The linear regression line and confidence limits constructed with

Mining Operations.

DTIC Science & Technology

1984-09-12

hardness; (15) very hard granite rocks. Quartz- porphyry , very hard granite, flinty slate, and quartzite that are less hard than the above. Hardest...7) quartzites in general; (8) basalts in general;(9) Volyn basalt; (10) porphuries in general; (11) Gohland porphyry ; (12) very hard granite; (13...57) Tethmayer; (58) new edition; (59) Gus’kov; (60) old edition; (61) hard quartzite; (62) hard basalt; (63) very hard porphyry ; (64) porphyry in

Late Cretaceous porphyry copper mineralization in Sonora, Mexico: Implications for the evolution of the Southwest North America porphyry copper province

NASA Astrophysics Data System (ADS)

Barra, Fernando; Valencia, Victor A.

2014-10-01

Two porphyry Cu-Mo prospects in northern Sonora, Mexico (Fortuna del Cobre and Los Humos) located within the southwestern North American porphyry province have been dated in order to constrain the timing of crystallization and mineralization of these ore deposits. In Fortuna del Cobre, the pre-mineralization granodiorite porphyry yielded an U-Pb zircon age of 76.5 ± 2.3 Ma, whereas two samples from the ore-bearing quartz feldespathic porphyry were dated at 74.6 ± 1.3 and 75.0 ± 1.4 Ma. Four molybdenite samples from Los Humos porphyry Cu prospect yielded a weighted average Re-Os age of 73.5 ± 0.2 Ma, whereas two samples from the ore-bearing quartz monzonite porphyry gave U-Pb zircon ages of 74.4 ± 1.1 and 74.5 ± 1.3 Ma, showing a Late Cretaceous age for the emplacement of this ore deposit. The results indicate that Laramide porphyry Cu mineralization of Late Cretaceous age is not restricted to northern Arizona as previously thought and provide evidence for the definition of NS trending metallogenic belts that are parallel to the paleo-trench. Porphyry copper mineralization follows the inland migration trend of the magmatic arc as a result of the Farallon slab flattening during the Laramide orogeny.

Petrology, zircon U-Pb ages, geochemistry and Sr-Nd-Hf isotopes of the Late Paleozoic gold-bearing magmatic rocks (porphyry intrusions) in Jiamante area, Northwest Tianshan: Implications for petrogenesis and mineralization

NASA Astrophysics Data System (ADS)

Zhang, Tongliang; Cai, Keda; Wang, Xiangsong

2017-04-01

A series of Cu-Au-Mo deposits distributed from east to west in the Northwestern Tianshan Orogenic Belt (NTOB), which is located in the northwestern China. The tectonic settings and associated geodynamic processes of these deposits have been disputed. This paper presents whole-rock geochemical data, in-situ U-Th-Pb ages and Sr-Nd-Hf isotopic composition for granite porphyry and quartz porphyry in the Jiamante gold deposit from the Yelimodun Basin, in the NTOB. These two type representative high potassium granitic intrusions have the LA-ICP-MS zircon U-Pb ages of 350.8±4 Ma, 351.7±3 Ma and 350.4±5 Ma, 353.9±2.5 Ma, interpreted as the crystallization ages. High contents of SiO2 ( 71.1-75.2wt.%), K2O (4.96-6.33 wt.%), Al2O3 (12.45-14.35 wt.%) and low contents of Fe2O3T (1.47-3.25 wt.%), MgO (0.3-0.5 wt.% ), and CaO (0.49-1.29wt.%), High ASI (Alumina Saturation Index, Al2O3/(CaO+Na2O+K2O)=1.37-1.80 molecular ratios) can be found in these rocks. These porphyries are enriched in both large ion lithophile and light rare earth elements, but deplet in high field strength elements and are characterized by moderately negative Eu anomalies (Eu/Eu*=0.27-0.66) and strong depletion in Ba, Nb,Ti and Sr elements. These two porphyries have negative and positive zircon ɛHf(t) (-11.6 to +6.7) values, low Mg# ratios (21.85-35.51wt%), and low Cr (3.24ppm -11.35ppm) and Ni (1.88ppm-13.41ppm) contents. The regional geological and geochemical characteristics of the Early Carboniferous rocks in the Northwestern Tianshan show that peraluminous granitoids, with hybrid Sr-Nd-Hf isotopic signatures, suggesting that their parental magmas could be derived from the subduction of Paleo-Junggar Ocean beneath the Yili Block and the sediments from the Yili Block. In combination with the compositions of the volcanic rocks and basic lavas in the region in the Early Carboniferous, we suggest that the Jiamante peraluminous granitic porphyries and quartz porphyries were generated by the interaction

Post-collisional magmatism and ore-forming systems in the Menderes massif: new constraints from the Miocene porphyry Mo-Cu Pınarbaşı system, Gediz-Kütahya, western Turkey

NASA Astrophysics Data System (ADS)

Delibaş, Okan; Moritz, Robert; Chiaradia, Massimo; Selby, David; Ulianov, Alexey; Revan, Mustafa Kemal

2017-12-01

The Pınarbaşı Mo-Cu prospect is hosted within the Pınarbaşı intrusion, which is exposed together with the NW-SE-trending Koyunoba, Eğrigöz, and Baklan plutons along the northeastern border of the Menderes massif. The Pınarbaşı intrusion predominantly comprises monzonite, porphyritic granite, and monzodiorite. All units of the Pınarbaşı intrusion have sharp intrusive contacts with each other. The principal mineralization style at the Pınarbaşı prospect is a porphyry-type Mo-Cu mineralization hosted predominantly by monzonite and porphyritic granite. The porphyry type Mo-Cu mineralization consists mostly of stockwork and NE- and EW-striking sub-vertical quartz veins. Stockwork-type quartz veins hosted by the upper parts of the porphyritic granite within the monzonite, are typically enriched in chalcopyrite, molybdenite, pyrite, and limonite. The late NE- and EW-striking normal faults cut the stockwork vein system and control the quartz-molybdenite-chalcopyrite-sphalerite-fahlore-galena veins, as well as molybdenite-hematite-bearing silicified zones. Lithogeochemical and whole-rock radiogenic isotope data (Sr, Nd and Pb) of the host rocks, together with Re-Os molybdenite ages (18.3 ± 0.1 Ma - 18.2 ± 0.1 Ma) reveal that the monzonitic and granitic rocks of the Pınarbaşı intrusion were derived from an enriched lithospheric mantle-lower crust during Oligo-Miocene post-collisional magmatism. The lithospheric mantle was metasomatised by fluids and subducted sediments, and the mantle-derived melts interacted with lower crust at 35-40 km depth. This mechanism explains the Mo and Cu enrichments of the Pınarbaşı intrusion during back-arc magmatism. We conclude that the melt of the Pınarbaşı intrusion could have rapidly ascended to mid-crustal levels, with only limited crustal assimilation along major trans-lithospheric faults as a result of thinning of the middle to upper crust during regional extension, and resulted in the development of porphyry

Porphyry copper enrichment linked to excess aluminium in plagioclase

NASA Astrophysics Data System (ADS)

Williamson, B. J.; Herrington, R. J.; Morris, A.

2016-03-01

Porphyry copper deposits provide around 75%, 50% and 20% of world copper, molybdenum and gold, respectively. The deposits are mainly centred on calc-alkaline porphyry magmatic systems in subduction zone settings. Although calc-alkaline magmas are relatively common, large porphyry copper deposits are extremely rare and increasingly difficult to discover. Here, we compile existing geochemical data for magmatic plagioclase, a dominant mineral in calc-alkaline rocks, from fertile (porphyry-associated) and barren magmatic systems worldwide, barren examples having no associated porphyry deposit. We show that plagioclase from fertile systems is distinct in containing `excess’ aluminium. This signature is clearly demonstrated in a case study carried out on plagioclase from the fertile La Paloma and Los Sulfatos copper porphyry systems in Chile. Further, the presence of concentric zones of high excess aluminium suggests its incorporation as a result of magmatic processes. As excess aluminium has been linked to high melt water contents, the concentric zones may record injections of hydrous fluid or fluid-rich melts into the sub-porphyry magma chamber. We propose that excess aluminium may exclude copper from plagioclase, so enriching the remaining melts. Furthermore, this chemical signature can be used as an exploration indicator for copper porphyry deposits.

Fluid inclusion studies in quartz veinlets in the porphyry copper deposit at Sungun, East-Azarbaidjan, Iran

NASA Astrophysics Data System (ADS)

Calagari, Ali Asghar

2004-05-01

The porphyry copper deposit (PCD) at Sungun is located in East Azarbaidjan, in the NW of Iran.The Sungun porphyries occur as stocks and dikes ranging in composition from quartz monzodiorite through quartz monzonite and granodiorite to granite. The stocks are divided into two groups (1) Porphyry Stocks I and (2) Porphyry Stock II. Porphyry Stock II, hosting the copper ore, experienced intense hydro-fracturing leading to the formation of stockwork-type and anastomozing veinlets and micro-veinlets of quartz, sulfides, carbonates, and sulfates. Three distinct types of hydrothermal alteration and sulfide mineralization are recognized at Sungun (1) hypogene, (2) contact metasomatic (skarn), and (3) supergene. Four types of hypogene alteration are developed at Sungun, potassic, propylitic, potassic-phyllic, and phyllic. Four types of inclusion are common at Sungun based upon their phase content (1) mono-phase vapor, (2) vapor-rich 2-phase, (3) liquid-rich 2-phase, and (4) multi-phase solid. Halite is the principal solid phase. The distribution pattern, shape, and phase contents of fluid inclusions in quartz veinlets at Sungun are analogous to those from Bingham and Globe-Miami in western USA. The fluid inclusion data at Sungun showed that the liquid-vapor homogenization temperature [ TH(L-V)] values for liquid-rich 2-phase, vapor-rich 2-phase, and halite-bearing inclusions vary from 160 to 580 °C, from 200 to 600 °C, and from 160 to 580 °C, respectively. The ascending unboiled fluid at the onset of the phyllic alteration episode had temperatures ˜580 °C and was moderately saline (˜15 wt%). With the gradual decrease in temperature, the salinity of this fluid gradually decreased, so that its salinity at temperatures of ˜370 and <270 °C were ˜7 and <2 wt%, respectively. Multiple boiling events occurred in Porphyry Stock II during phyllic alteration. With each boiling event the salinity of the residual fluid increased substantially. The first boiling event occurred

Geochronology and geochemistry constraints of the Early Cretaceous Taibudai porphyry Cu deposit, northeast China, and its tectonic significance

NASA Astrophysics Data System (ADS)

Zhou, Zhen-Hua; Mao, Jing-Wen; Wu, Xin-Li; Ouyang, Hen-Gen

2015-05-01

The southern Great Xing'an Range (SGXR), located in the southeastern part of Inner Mongolia, China, shows intense Mesozoic tectono-magmatic activity and hosts economically important polymetallic (Cu-Pb-Zn-Sn-Fe-Ag-Au-Mo) mineralization. Here, we present new zircon U-Pb ages, whole-rock geochemical data, Nd-Sr-Hf isotopic data and Re-Os ages for the Taibudai deposit in the SGXR. The Taibudai granitoids show high SiO2 (70.62-72.13 wt.%) and alkali (Na2O + K2O = 7.04-8.60 wt.%) concentrations, low MgO (0.89-1.37 wt.%) and Al2O3 (∼14 wt.%), ASI ratios <1.1 (0.94-0.97), LILEs (e.g., Rb) enriched, HFSEs (e.g., Nb, Ta, Ti, and P) depleted, and have low Sr and Yb concentrations, classifying these rocks as fractionated I-type granites. The Taibudai granitoids have negative εNd (t) values ranging from -2.2 to -1.6 and relatively low initial 87Sr/86Sr ratios from 0.70536 to 0.70581. In situ Hf isotopic analyses on zircons using LA-MC-ICP-MS show variable positive εHf (t) values ranging from +0.80 to +13.55, corresponding to relatively young two-stage Hf model ages from 801 to 942 Ma (excluding one spot). These mineralogical, geochemical, and isotopic features strongly suggest that the primary magmas of the Taibudai granitoids were derived mainly from the partial remelting of Neoproterozoic juvenile crustal material, with no remarkable modification through incorporation of continental or subduction-related material. Re-Os isotope analyses of molybdenite from the deposit yield an ore-forming age of 137.1 ± 1.4 Ma. Re contents range from 4.37 to 41.77 ppm, implying ore material components have a mixed crust-mantle origin. SHRIMP analysis of zircons show that the monzogranitic porphyry and biotite granite in the Taibudai deposit were formed at 137.0 ± 0.9 Ma and 138.3 ± 0.9 Ma, respectively, indicating a temporal link between granitic magmatism and Cu mineralization. This result, combined with the regional geology, tectonic evolution, and age data from the literature

Molybdenite Re/Os dating, zircon U-Pb age and geochemistry of granitoids in the Yangchuling porphyry W-Mo deposit (Jiangnan tungsten ore belt), China: Implications for petrogenesis, mineralization and geodynamic setting

NASA Astrophysics Data System (ADS)

Mao, Jingwen; Xiong, Bikang; Liu, Jun; Pirajno, Franco; Cheng, Yanbo; Ye, Huishou; Song, Shiwei; Dai, Pan

2017-08-01

The Yangchuling W-Mo deposit, located in the Jiangnan porphyry-skarn (JNB) tungsten ore belt, is the first recognized typical porphyry W-Mo deposit in China in the 1980's. Stockworks and disseminated W-Mo mineralization occur in the roof pendant of a 0.3 km2 monzogranitic porphyry stock that intruded into a granodiorite stock, hosted by Neoproterozoic phyllite and slate. LA-ICPMS zircon U-Pb analyses suggest that of the monzogranitic porphyry and granodiorite were formed at 143.8 ± 0.5 Ma and 149.8 ± 0.6 Ma, respectively. Six molybdenite samples yielded a Re-Os weighted mean age of 146.4 ± 1.0 Ma. Geochemical data show that both granodiorite and monzogranitic porphyry are characterized by enrichment of large ion lithophile elements (LILE) relative to high field strength elements (HFSE), indicating a peraluminous nature (A/CNK = 1.01-1.08). Two granitoids are characterized by a negative slope with significant light REE/heavy REE fractionation [(La/Yb)N = 8.38-23.20] and negative Eu anomalies (Eu/Eu* = 0.69-0.76). The P2O5 contents of the Yangchuling granitoids range from 0.12% to 0.17% and exhibit a negative correlation with SiO2, reflecting that they are highly fractionated I-type. They have high initial 87Sr/86Sr ratios (0.7104-0.7116), low negative εNd(t) (- 5.05 to - 5.67), and homogeneous εHf(t) between - 1.39 and - 2.17, indicating similar sources. Additionally, two-stage Nd model ages (TDM2) of 1.3-1.4 Ga and two-stage Hf model ages (TDM2) of 1.2-1.3 Ga are consistent, indicating that Neoproterozoic crustal rocks of the Shuangqiaoshan Group could have contributed to form the Yangchuling magmas. Considering the two groups of parallel Late Mesozoic ore belts, namely the Jiangnan porphyry-skarn tungsten belt (JNB) in the south and the Middle-Lower Yangtze River porphyry-skarn Cu-Au-Mo-Fe ore belt (YRB) in the north, the Nanling granite-related W-Sn ore belt (NLB) in the south, the neighboring Qin-Hang porphyry-skarn Cu-Mo-hydrothermal Pb-Zn-Ag ore belt (QHB

Sorption--desorption studies on granite. I. Initial studies of strontium, technetium, cesium, barium, cerium, europium, uranium, plutonium, and americium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erdal, B.R.; Aguilar, R.D.; Bayhurst, B.P.

Distribution ratios were determined for sorption--desorption of radioactive tracers between the Climax Stock granite (quartz monzonite porphyry) obtained at Nevada Test Site and a water prepared to be resonably representative of the natural composition of water in equilibrium with the Climax Stock granite. The measurements were performed at 22 and 70{sup 0}C under atmospheric oxygen conditions. Elements given in order of increasing distribution coefficient at ambient temperature are: U(VI), Sr, Tc(VII), Ba, Ce(III), Cs, Eu(III), Pu, and Am. At 70{sup 0}C the order is: Tc(VII), Sr, Ce(III), Eu(III), Ba, Cs, Pu, and Am. The effects of surface area and mineralogymore » on sorption were also investigated.« less

Geology and ore fluid geochemistry of the Jinduicheng porphyry molybdenum deposit, East Qinling, China

NASA Astrophysics Data System (ADS)

Li, Hongying; Ye, Huishou; Wang, Xiaoxia; Yang, Lei; Wang, Xiuyuan

2014-01-01

Jinduicheng deposit is a giant Mesozoic porphyry Mo system deposit in the East Qinling molybdenum belt, Shaanxi Province, China. The mineralization is associated with the I-type Jinduicheng granite porphyry. Both the porphyry stock and country rocks underwent intense hydrothermal alteration. The alteration, with increasing distance from the parent intrusion, changes from silicification, through potassic and phyllic assemblages, carbonation, to propylitic assemblages. Molybdenite, the dominant ore mineral, occurs in veinlets, most of which are hosted by the altered country rocks, with less than 25% of the ore in the porphyry body. The hydrothermal system comprises four stages, including pre-ore quartz and K-feldspar; two ore stages of quartz, K-feldspar, molybdenite, and Pb- And Zn-bearing sulfides; and post-ore quartz and carbonate. Six main types of primary fluid inclusions are present in hydrothermal quartz, including two-phase aqueous, one-phase aqueous, three-phase CO2-bearing, CO2-dominated fluid inclusions, gas inclusions, and melt inclusions. The homogenization temperatures of fluid inclusions range from 210 to 290 °C in the pre-ore stage, 150-310 °C in ore stage I, 150-360 °C in the ore stage II, and 195-325 °C in the post-ore stage quartz. Estimated salinities of the ore-forming fluids range from 6.9 to 13.5, 4.3 to 12.3, 6.2 to 12.4, and 3.4 to 9.9 wt.% NaCl equiv. in stages 1-4, respectively. The δ34S values of pyrite in the two ore stages range from 2.8‰ to 4.3‰, whereas the δ34S values of molybdenite range from 2.9‰ to 6.2‰. The data suggest both magmatic and crustal sources of sulfur. The δD and δ18O values for the hydrothermal fluids are -57.2‰ to -84.4‰ and 8.0‰ to -3.2‰, respectively. The fluid inclusion and stable data indicate that the pre-ore hydrothermal fluids were mostly of magmatic origin, but the fluids responsible for ore deposition were mixed magmatic and meteoric, and eventually meteoric water dominated the system

Porphyry of Russian Empires in Paris

NASA Astrophysics Data System (ADS)

Bulakh, Andrey

2014-05-01

Porphyry of Russian Empires in Paris A. G. Bulakh (St Petersburg State University, Russia) So called "Schokhan porphyry" from Lake Onega, Russia, belongs surely to stones of World cultural heritage. One can see this "porphyry" at facades of a lovely palace of Pavel I and in pedestal of the monument after Nicolas I in St Petersburg. There are many other cases of using this stone in Russia. In Paris, sarcophagus of Napoleon I Bonaparte is constructed of blocks of this stone. Really, it is Proterozoic quartzite. Geology situation, petrography and mineralogical characteristic will be reported too. Comparison with antique porphyre from the Egyptian Province of the Roma Empire is given. References: 1) A.G.Bulakh, N.B.Abakumova, J.V.Romanovsky. St Petersburg: a History in Stone. 2010. Print House of St Petersburg State University. 173 p.

Chronology, geochemistry and Sr-Nd isotope studies of Jurassic intrusions in the Diyanqinamu porphyry Mo mine, central Inner Mongolia, China

NASA Astrophysics Data System (ADS)

Sun, Hairui; Huang, Zhilong; Li, Wenbo; Leng, Chengbiao; Ma, Deyun; Zhang, Xingchun

2014-07-01

Available cores of porphyritic granite and aplitic granite from the Diyanqinamu porphyry Mo deposit in the north central Great Xing’an Range presented an opportunity to examine and analyze Mesozoic igneous rocks far from the Paleo-Pacific subduction zone. The Diyanqinamu granites are highly fractionated I-type, distinguished from the M-, A- or S-type granite by: high SiO2, and Rb; low Zr, Nb, Y, and Ce; low Fe2O3total/MgO and (K2O + Na2O)/CaO ratios; low alumina saturation index (<1.1); low initial ISr ratios (0.70137-0.70451); positive εNd(t) values (2.37-3.77); and negative correlation between P2O5 and SiO2. The aplitic granites were generated by fractional crystallization of the porphyritic granite, as evidenced by: spatial proximity; consistent zircon U-Pb ages (156 Ma) within error; correlations between other oxides and SiO2 in Haker diagrams; low Ba, Sr, Nb, P, Ti, Eu; linear relationship in both (La/Yb)N vs. La and Sr vs. Ba diagrams; and, decreasing LREE and ∑REE with increasing SiO2. The Diyanqinamu granites have young depleted-mantle two-stage model ages (avg. TDM2 = 660 Ma) similar to those of most Mesozoic voluminous felsic magmas in northeastern China, and were likely sourced from pre-existent crustal components both “old” and juvenile that had been juxtaposed during the tectonic evolution of the Paleo-Asian Ocean. These granites project in the transitional field from syn-collision to post-collision tectonic settings on tectonic discrimination diagrams, implying emplacement in an extensional environment. Extensional volcanism and basin formation in the Great Xing’an Range region in Late Jurassic is coeval with the Diyanqinamu granites, demonstrating that post-orogenic lithospheric extension related to the closure of the Mongol-Okhotsk Ocean was the main driving force for Late Jurassic magmatism in this region.

Geochemical characteristics and origin of the Lebowa Granite Suite, Bushveld Complex

USGS Publications Warehouse

Hill, M.; Barker, F.; Hunter, D.; Knight, R.

1996-01-01

The ??? 2052-Ma Lebowa Granite Suite (LGS) represents the culminating phase of an Early Proterozoic magmatic cycle in the Central Transvaal area of the Kaapvaal Province. Following extrusion of at least 200,000 km3 of intermediate to acid volcanics (Rooiberg Felsite), mafic and ultramafic magmas intruded at 2065 Ma to form the Rustenburg Layered Suite (RLS). The LGS includes the Nebo, Makhutso, Bobbejaankop, Lease, and Klipkloof granites. The Nebo Granite intruded the Rooiberg Felsite as sheets up to 4 km thick above the RLS. Smaller stocks of the other granites crosscut the Nebo. We determined major- and trace-element compositions and oxygen, Rb-Sr, and Sm-Nd isotope ratios for samples of: Nebo Granite; Rooiberg Felsite; granophyre and granophyric granite; Makhutso, Bobbejaankop, and Lease granites; and feldspar porphyry from areas throughout the exposed area of the LGS (Dennilton, Verena Balmoral, Enkeldoorn, Sekhukhune Plateau, Zaaiplaats-Potgeitersrus, and Western Transvaal). Coherent floor-to-roof geochemical trends exist in some areas, although it is not possible to model them convincingly. Regional variations in geochemistry exist and likely are related to source variations in the estimated 200,000 km3 of the Nebo Granite sheets. ??18O for the LGS range from +5.9??? to +9.5???; if these are approximate primary magmatic values, pelitic sediments cannot have been an important source for the LGS. The Rb-Sr isotope system has been altered, a finding consistent with previous studies. A mineral isochron for Nebo Granite near Dennilton yields a York regression age of 1995 ?? 99 Ma, with initial 143Nd/144Nd = 0.50978??8 and ???CHUR=-5.12. Samples from the Sekhukhune Plateau have higher 143Nd/144Nd ratios than do Dennilton-area samples, suggesting that the former originated from older or less LREE-enriched sources. We suggest that intrusion of mafic to ultramafic magmas at depth in the continental crust triggered melting of Archean quartzofeldspathic crystalline

Preliminary Model of Porphyry Copper Deposits

USGS Publications Warehouse

Berger, Byron R.; Ayuso, Robert A.; Wynn, Jeffrey C.; Seal, Robert R.

2008-01-01

The U.S. Geological Survey (USGS) Mineral Resources Program develops mineral-deposit models for application in USGS mineral-resource assessments and other mineral resource-related activities within the USGS as well as for nongovernmental applications. Periodic updates of models are published in order to incorporate new concepts and findings on the occurrence, nature, and origin of specific mineral deposit types. This update is a preliminary model of porphyry copper deposits that begins an update process of porphyry copper models published in USGS Bulletin 1693 in 1986. This update includes a greater variety of deposit attributes than were included in the 1986 model as well as more information about each attribute. It also includes an expanded discussion of geophysical and remote sensing attributes and tools useful in resource evaluations, a summary of current theoretical concepts of porphyry copper deposit genesis, and a summary of the environmental attributes of unmined and mined deposits.

Reduced granitic magmas in an arc setting: The Catface porphyry Cu-Mo deposit of the Paleogene Cascade Arc

NASA Astrophysics Data System (ADS)

Smith, C. M.; Canil, D.; Rowins, S. M.; Friedman, R.

2012-12-01

The Catface porphyry Cu (Mo-Au) deposit, Vancouver Island, British Columbia was studied to characterize the age, geometry and geochemical affinity of its different intrusive phases, and their tectonic setting. Four different intrusive phases of quartz diorite are broadly calc-alkaline, moderately metaluminous, and have typical arc geochemical affinity. U-Pb age dating of zircons showing two intrusive phases was emplaced at 41.26 ± 0.11 and 41.15 ± 0.10 Ma, and a second two 40.93 ± 0.11 and 40.88 ± 0.10 (95% confidence). The latter ages are identical to the Re-Os age of molybdenite mineralization of 40.9 ± 0.2 Ma. The depth of emplacement is less than 4 km, as determined by amphibole-plagioclase thermobarometry (630-815 °C and 50-300 MPa). A reduced magmatic-hydrothermal system is evidenced by: (1) presence of pyrrhotite and absence of anhydrite and hematite, (2) low SO3 (< 450 ppm) in apatite, and (3) oxygen fugacities (fO2) of 0.5-3.0 log units below the quartz-fayalite-magnetite (QFM) buffer recorded by the assemblage K-feldspar-biotite-ilmenite-quartz. Reduced porphyry-related magmas on Vancouver Island of similar age to those at North Fork, Washington (37 Ma) suggests consanguinity of reduced arc magmatism and related ore deposits within the Paleogene Cascade arc of the Pacific Northwest. Reduced evolved magmas at Catface are atypical in an arc setting, but can be attributed to thorough degassing of S from the magmas as evidenced by low S in apatite.

Petrogenesis of Cretaceous volcanic-intrusive complex from the giant Yanbei tin deposit, South China: Implication for multiple magma sources, tin mineralization, and geodynamic setting

NASA Astrophysics Data System (ADS)

Li, Qian; Zhao, Kui-Dong; Lai, Pan-Chen; Jiang, Shao-Yong; Chen, Wei

2018-01-01

The giant Yanbei tin ore deposit is the largest porphyry-type tin deposit in South China. The orebodies are hosted by the granite porphyry in the central part of the Yanbei volcanic basin in southern Jiangxi Province. The Yanbei volcanic-intrusive complex mainly consists of dacitic-rhyolitic volcanic rocks, granite, granite porphyry and diabase dikes. In previous papers, the granite porphyry was considered as subvolcanic rocks, which came from the same single magma chamber with the volcanic rocks. In this study, zircon U-Pb ages and Hf isotope data, as well as whole-rock geochemical and Sr-Nd isotopic compositions of different magmatic units in the Yanbei complex are reported. Geochronologic results show that various magmatic units have different formation ages. The dacite yielded a zircon U-Pb age of 143 ± 1 Ma, and the granite porphyry has the emplacement age of 138 ± 1 Ma. Diabase dikes which represented the final stage of magmatism, yielded a zircon U-Pb age of 128 ± 1 Ma. Distinctive whole rock Sr-Nd and zircon Hf isotopic compositions suggest that these magmatic units were derived from different magma sources. The volcanic rocks were mainly derived from the partial melting of Paleoproterozoic metasedimentary rocks without additions of mantle-derived magma. The granite porphyry has an A-type geochemical affinity, and was derived from remelting of Paleo-Mesoproterozoic crustal source with involvement of a subordinate mantle-derived magma. The granite porphyry is also a typical stanniferous granite with high F (4070-6090 ppm) and Sn (7-39 ppm) contents. It underwent strongly crystal fractionation of plagioclase, K-feldspar, and accessory minerals (like apatite, Fe-Ti oxides), which may contribute to the tin mineralization. The diabase was derived by partial melting of enriched lithospheric mantle which had been metasomatised by slab-derived fluids. The change of magmatic sources reflected an increasing extensional tectonic environment, perhaps induced by slab

Porphyry Cu indicator minerals in till as an exploration tool: Example from the giant pebble porphyry Cu-Au-Mo deposit, Alaska, USA

USGS Publications Warehouse

Kelley, Karen D.; Eppinger, Robert G.; Lang, J.; Smith, Steven M.; Fey, David L.

2011-01-01

Porphyry Cu indicator minerals are mineral species in clastic sediments that indicate the presence of mineralization and hydrothermal alteration associated with porphyry Cu and associated skarn deposits. Porphyry Cu indicator minerals recovered from shallow till samples near the giant Pebble Cu-Au-Mo porphyry deposit in SW Alaska, USA, include apatite, andradite garnet, Mn-epidote, visible gold, jarosite, pyrite, and cinnabar. Sulphide minerals other than pyrite are absent from till, most likely due to the oxidation of the till. The distribution of till samples with abundant apatite and cinnabar suggest sources other than the Pebble deposit. With three exceptions, all till samples up-ice of the Pebble deposit contain 40grains/10kg) are in close proximity to smaller porphyry and skarn occurrences in the region. The distribution of Mn-epidote closely mimics the distribution of garnet in the till samples and further supports the interpretation that these minerals most likely reflect skarns associated with the porphyry deposits. All but two till samples, including those up-ice from the deposit, contain some gold grains. However, tills immediately west and down-ice of Pebble contain more abundant gold grains, and the overall number of grains decreases in the down-ice direction. Furthermore, all samples in the immediate vicinity of Pebble contain more than 65% pristine and modified grains compared to mostly re-shaped grains in distal samples. The pristine gold in till reflects short transport distances and/or liberation of gold during in-situ weathering of transported chalcopyrite grains. Jarosite is also abundant (1-2 500 grains/10kg) in samples adjacent to and up to 7 km down-ice from the deposit. Most jarosite grains are rounded and preliminary Ar/Ar dates suggest the jarosite formed prior to glaciation and it implies that a supergene cap existed over Pebble West. Assuming this interpretation is accurate, it suggests a shallow level of erosion of the Pebble deposit by

The Root of the Butte Porphyry Cu Deposit: A Zone of Fluid Accumulation, Discharge and Collapse

NASA Astrophysics Data System (ADS)

Acosta, M. D.; Reed, M. H.; Watkins, J. M.

2017-12-01

The deep zones of porphyry Cu deposits are the focus of the hydrothermal-magmatic transition, where hydrothermal fluid emerges from crystallizing magma. In the Butte, MT porphyry Cu deposit at a paleodepth of 8 km, we observe a zone of intense silicification and brecciation. This deep in the system, where the distinction between hydrothermal and magmatic processes is ambiguous, we obtain a rare look into how a magma and its coeval fluid phase feed into porphyry Cu deposits. We characterize this zone through a suite of analyses. We used rock pulps from 15m lengths of drill core to estimate the volume percentage of quartz veins. Estimates based upon Si, Ti, and Zr are 2-12%, 14-41%, and 15-48%, respectively. In thin section, three texturally distinct populations of quartz are present: quartz that permeates altered granite such that the sample consists of 40-50% quartz of variable grain size, quartz in veins with diffuse and non-planar boundaries, and quartz in quartz-pyrite veins with sharp walls that merge with quartz-pyrite veins with irregular and diffuse boundaries. The concentrations of Ti in of each of the quartz populations do not exceed 50 ppm, and the lowest is below the detection limit of 4 ppm. Temperature estimates based on the TitaniQ thermobarometer for 50 ppm Ti range from 583 °C at hydrostatic pressure (0.7 kb), to 665 °C at lithostatic pressure (2.5 kb). Cathodoluminescence (CL) images of each population are also remarkably similar, being almost entirely homogeneous/mottled cut by CL-dark later quartz veinlets. Only the quartz-pyrite veinlet with planar walls contained euhedral CL oscillations. The large abundance of quartz in these deep samples, combined with the lack of sharp, planar boundaries, and the temperature estimates suggest that the rock was at least locally ductile as the quartz veins formed, and afterwards. The large quartz abundance further indicates that the base of the porphyry Cu deposit underwent intermittent fluid accumulation

Coarse muscovite veins and alteration deep in the Yerington batholith, Nevada: insights into fluid exsolution in the roots of porphyry copper systems

NASA Astrophysics Data System (ADS)

Runyon, Simone E.; Steele-MacInnis, Matthew; Seedorff, Eric; Lecumberri-Sanchez, Pilar; Mazdab, Frank K.

2017-04-01

Veins and pervasive wall-rock alteration composed of coarse muscovite±quartz±pyrite are documented for the first time in a porphyritic granite at Luhr Hill in the Yerington District, Nevada. Coarse muscovite at Luhr Hill occurs at paleodepths of 6-7 km in the roots of a porphyry copper system and crops out on the scale of tens to hundreds of meters, surrounded by rock that is unaltered or variably altered to sodic-calcic assemblages. Coarse muscovite veins exhibit a consistent orientation, subvertical and N-S striking, which structurally restores to subhorizontal at the time of formation. Along strike, coarse muscovite veins swell from distal, millimeter-thick muscovite-only veinlets to proximal, centimeter-thick quartz-sulfide-bearing muscovite veins. Crosscutting relationships between coarse muscovite veins, pegmatite dikes, and sodic-calcic veins indicate that muscovite veins are late-stage magmatic-hydrothermal features predating final solidification of the Luhr Hill porphyritic granite. Fluid inclusions in the muscovite-quartz veins are high-density aqueous inclusions of 3-9 wt% NaCl eq. and <1 mol% CO2 that homogenize between 150 and 200 °C, similar to fluid inclusions from greisen veins in Sn-W-Mo vein systems. Our results indicate that muscovite-forming fluids at Luhr Hill were mildly acidic, of low to moderate salinity and sulfur content and low CO2 content, and that muscovite in deep veins and alteration differs in texture, composition, and process of formation from sericite at shallower levels of the hydrothermal system. Although the definition of greisen is controversial, we suggest that coarse muscovite alteration is more similar to alteration in greisen-type Sn-W-Mo districts worldwide than to sericitic alteration at higher levels of porphyry copper systems. The fluids that form coarse muscovite veins and alteration in the roots of porphyry copper systems are distinct from fluids that formed copper ore or widespread, shallower, acidic alteration

El Salvador, Chile porphyry copper deposit revisited: Geologic and geochronologic framework

USGS Publications Warehouse

Cornejo, P.; Tosdal, R.M.; Mpodozis, C.; Tomlinson, A.J.; Rivera, O.; Fanning, C.M.

1997-01-01

The Eocene (42 to 41 Ma) El Salvador porphyry copper deposit in the Indio Muerto district, northern Chile (26?? 15??? S Lat.), formerly thought to have formed at the culmination of a 9-m.y. period of episodic magmatism, is shown by new mapping, U-Pb and K-Ar geochronology, and petrologic data to have formed during the younger of two distinct but superposed magmatic events - a Paleocene (???63 to 58 Ma) and an Eocene (44 to 41 Ma) event. In the district, high-K Paleocene volcano-plutonic activity was characterized by a variety of eruptive styles and magmatic compositions, including a collapse caldera associated with explosive rhyolitic magmatism (El Salvador trap-door caldera), a post-collapse rhyolite dome field (Cerro Indio Muerto), and andesitic-trachyandesitic stratovolcanos (Kilo??metro Catorce-Los Amarillos sequence). Precaldera basement faults were reactivated during Paleocene volcanism as part of the collapse margin of the caldera. Beneath Cerro Indio Muerto, where the porphyry Cu deposit subsequently formed, the intersection of two major basement faults and the NNE-striking rotational axis of tilted ignimbrites of the Paleocene El Salvador caldera localized emplacement of post-collapse rhyolite domes and peripheral dikes and sills. Subsequent Eocene rhyolitic and granodioritic-dacitic porphyries intruded ???14 m.y. after cessation of Paleocene magmatism along the same NNE-striking structural belt through Cerro Indio Muerto as did the post-collapse Paleocene rhyolite domes. Eocene plutonism over a 3-m.y. period was contemporaneous with NW-SE-directed shortening associated with regional sinistral transpression along the Sierra Castillo fault, lying ???10 km to the east. Older Eocene rhyolitic porphyries in the Indio Muerto district were emplaced between 44 and 43 Ma, and have a small uneconomic Cu center associated with a porphyry at Old Camp. The oldest granodioritic-dacitic porphyries also were emplaced at ???44 to 43 Ma, but their petrogenetic relation to

Geology and ore deposits of the Chicago Creek area, Clear Creek County, Colorado

USGS Publications Warehouse

Harrison, J.E.; Wells, J.D.

1956-01-01

The Chicago Creek area, Clear Creek County, Colo., forms part of the Front Range mineral belt, which is a northeast-trending belt of coextensive porphyry intrusive rocks and hydrothermal veins of Tertiary age. More than $4.5 million worth of gold, silver, copper, lead, zinc, and uranium was produced from the mines in the area between 1859 and 1954. This investigation was made by the Geological survey on behalf of the Division of Raw Materials of the U.S. Atomic Energy Commission. The bedrock in the area is Precambrian and consists of igneous rocks, some of which have been metamorphosed , and metasedimentary rocks. The metasedimentary rocks include biotite-quartz-plagioclase gneiss that is locally garnetiferous, sillimanitic biotite-quartz gneiss, amphibolite, and lime-silicate gneiss. Rocks that may be metasedimentary or meta-igneous are quartz monzonite gneiss and granite gneiss and pegmatite. The granite gneiss and pegmatite locally form a migmatite with the biotitic metasedimentary rocks. These older rocks have been intruded by granodiorite, quartz, and granite pegmatite. During Tertiary time the Precambrian rocks were invaded by dikes and plugs of quartz monzonite porphyry, alaskite porphyry, granite porphyry, monzonite porphyry, bostonite and garnetiferous bostonite porphyry, quartz bostonite porphyry, trachytic granite porphyry, and biotite-quartz latite-porphyry. Solifluction debris of Wisconsin age forms sheets filling some of the high basins, covering some of the steep slopes, and filling parts of some of the valleys; talus and talus slides of Wisconsin age rest of or are mixed with solifluction debris in some of the high basins. Recent and/or Pleistocene alluvium is present along valley flats of the larger streams and gulches. Two periods of Precambrian folding can be recognized in the area. The older folding crumpled the metasedimentary rocks into a series of upright and overturned north-northeast plunging anticlines and synclines. Quartz monzonite

Age, tectonic setting, and metallogenic implication of Phanerozoic granitic magmatism at the eastern margin of the Xing'an-Mongolian Orogenic Belt, NE China

NASA Astrophysics Data System (ADS)

Chen, Cong; Ren, Yunsheng; Zhao, Hualei; Yang, Qun; Shang, Qingqing

2017-08-01

The eastern margin of the Xing'an-Mongolian Orogenic Belt is characterised by widespread Phanerozoic granitic magmatism, some of which is closely related to significant ore mineralisation. This paper presents new geochronological, petrogenetic, and tectonic data for selected intrusions. Zircon U-Pb geochronology for five granitoid plutons indicates they were emplaced during the middle-late Permian (264-255 Ma) and Cretaceous (106-94 Ma), and thus granitic magmatism occurred throughout the Phanerozoic, Permian (268-252 Ma), Early-Middle Triassic (248-240 Ma), Early Jurassic (183 Ma), and Cretaceous (112-94 Ma). The Permian granitoids consist of monzogranite, granodiorite, tonalite, and quartz diorite, characterised by enrichment in Na2O (3.60-4.72 wt.%), depletion in K2O (0.97-2.66 wt.%), and a negative correlation between P2O5 and SiO2. Together with the presence of hornblende, these geochemical features are indicative of an I-type affinity. The Permian granitic magmatism is associated with quartz-vein-type tungsten deposits (252 Ma; unpublished Sm-Nd isochron age), which formed in an active continental margin setting related to subduction of the Palaeo-Asian Ocean. The Cretaceous quartz diorites have an adakitic affinity, having relatively high Sr (374-502 ppm), low Yb (0.51-0.67 ppm) and Y (8.7-10.7 ppm), and high Sr/Y (39.4-46.8) and (La/Yb)N values (16.2-34.7), suggesting that they were related to the partial melting of subducted oceanic crust. In addition, they are associated with porphyry Au-Cu deposits. We conclude that the Cretaceous granitic rocks and associated porphyry Au-Cu mineralisation occurred in an extensional tectonic setting related to the subduction of the Palaeo-Pacific Plate beneath the Eurasian Plate. In addition, the large-scale Early-Middle Triassic syn-collisional granite belt at the eastern margin of the Xing'an-Mongolian Orogenic Belt extends from the middle of Jilin Province to the Wangqing-Hunchun region, constraining the timing of the

Summary of Methods for Measuring Electrical Properties of Geological Strata to Estimate Electromagnetic Shielding Effectiveness

DTIC Science & Technology

1988-04-01

commercially for conventional surface resistivity measure- ments. Lead or copper wire wrapped around an insulating cable is used for the downhole...3 x 106 -- Igneous rocks, basic Augite porphyry Kola Peninsula 9.5-12.6 105-107 Dry Basalt Berestovetskoe 15.6 5 x 10 5 Dry Basalt Kutai 10.3 5 x...acidic Granite Azerbaidjan 3.0 x 107 -- Granite Ubinskoe 0.36 x 109 3.2 x 1018 Granite Kola Peninsula 0.16 x 105 0.3 x 1016 Granite porphyry 4.5 x 10 5

Petrogenesis of low-δ18O quartz porphyry dykes, Koegel Fontein complex, South Africa

NASA Astrophysics Data System (ADS)

Harris, Chris; Mulder, Kwenidyn; Sarkar, Saheli; Whitehead, Benjamin; Roopnarain, Sherissa

2018-04-01

This paper investigates the origin of low-δ18O quartz porphyry dykes associated with the 144-133 Ma Koegel Fontein Igneous Complex, which was intruded during the initial phase of breakup of Africa and South America. The 25-km diameter Rietpoort Granite is the largest and youngest phase of activity, and is roofed by a 10-km diameter pendant of gneiss. Quartz porphyry (QP) dykes, up to 15 m in width, strike NW-SE across the complex. The QP dykes that intruded outside the granite have similar quartz phenocryst δ18O values (average 8.0‰, ± 0.7, n = 33) to the granite (average 8.3 ± 1.0, n = 7). The QP dykes that intruded the roof pendant have quartz phenocrysts with more variable δ18O values (average 1.6‰, ± 2.1, n = 55). In some cases quartz phenocrysts have δ18O values as low as - 2.5‰. The variation in δ18O value within the quartz crystal population of individual dykes is small relative to the overall range, and core and rim material from individual quartz phenocrysts in three samples are identical within error. There is no evidence that quartz phenocryst δ18O values have been affected by fluid-rock interaction. Based on a Δquartz-magma value of 0.6‰, magma δ18O values must have been as low as - 3.1‰. Samples collected along the length of the two main QP dykes that traverse the roof pendant have quartz phenocryst δ18O values that range from + 1.1 to + 4.6‰, and - 2.3 to + 5.6‰, respectively. These δ18O values correlate negatively ( r = - 0.96) with initial 87Sr/86Sr, which can be explained by the event that lowered δ18O values of the source being older than the dykes. We suggest that the QP dykes were fed by magma produced by partial melting of gneiss, which had been variably altered at high temperature by 18O-depleted meteoric water during global glaciation at 550 Ma. The early melts had variable δ18O value but as melt pockets interconnected during melting, the δ18O values approached that of average gneiss. Variable quartz phenocryst �

Tempo of magma degassing and the genesis of porphyry copper deposits.

PubMed

Chelle-Michou, Cyril; Rottier, Bertrand; Caricchi, Luca; Simpson, Guy

2017-01-12

Porphyry deposits are copper-rich orebodies formed by precipitation of metal sulphides from hydrothermal fluids released from magmatic intrusions that cooled at depth within the Earth's crust. Finding new porphyry deposits is essential because they are our largest source of copper and they also contain other strategic metals including gold and molybdenum. However, the discovery of giant porphyry deposits is hindered by a lack of understanding of the factors governing their size. Here, we use thermal modelling and statistical simulations to quantify the tempo and the chemistry of fluids released from cooling magmatic systems. We confirm that typical arc magmas produce fluids similar in composition to those that form porphyry deposits and conclude that the volume and duration of magmatic activity exert a first order control on the endowment (total mass of deposited copper) of economic porphyry copper deposits. Therefore, initial magma enrichment in copper and sulphur, although adding to the metallogenic potential, is not necessary to form a giant deposit. Our results link the respective durations of magmatic and hydrothermal activity from well-known large to supergiant deposits to their metal endowment. This novel approach can readily be implemented as an additional exploration tool that can help assess the economic potential of magmatic-hydrothermal systems.

Tempo of magma degassing and the genesis of porphyry copper deposits

PubMed Central

Chelle-Michou, Cyril; Rottier, Bertrand; Caricchi, Luca; Simpson, Guy

2017-01-01

Porphyry deposits are copper-rich orebodies formed by precipitation of metal sulphides from hydrothermal fluids released from magmatic intrusions that cooled at depth within the Earth’s crust. Finding new porphyry deposits is essential because they are our largest source of copper and they also contain other strategic metals including gold and molybdenum. However, the discovery of giant porphyry deposits is hindered by a lack of understanding of the factors governing their size. Here, we use thermal modelling and statistical simulations to quantify the tempo and the chemistry of fluids released from cooling magmatic systems. We confirm that typical arc magmas produce fluids similar in composition to those that form porphyry deposits and conclude that the volume and duration of magmatic activity exert a first order control on the endowment (total mass of deposited copper) of economic porphyry copper deposits. Therefore, initial magma enrichment in copper and sulphur, although adding to the metallogenic potential, is not necessary to form a giant deposit. Our results link the respective durations of magmatic and hydrothermal activity from well-known large to supergiant deposits to their metal endowment. This novel approach can readily be implemented as an additional exploration tool that can help assess the economic potential of magmatic-hydrothermal systems. PMID:28079160

The Myszkow porphyry copper-molybdenum deposit, Poland

USGS Publications Warehouse

Chaffee, M.A.; Eppinger, R.G.; Lason, K.; Slosarz, J.; Podemski, M.

1994-01-01

The porphyry copper-molybdenum deposit at Myszkow, south-central Poland, lies in the Cracow-Silesian orogenic belt, in the vicinity of a Paleozoic boundary between two tectonic plates. The deposit is hosted in a complex that includes early Paleozoic metasedimentary rocks intruded in the late Paleozoic by a predominantly granodioritic pluton. This deposit exhibits many features that are typical of porphyry copper deposits associated with calc-alkaline intrusive rocks, including ore- and alteration-mineral suites, zoning of ore and alteration minerals, fluid-inclusion chemistry, tectonic setting, and structural style of veining. Unusual features of the Myszkow deposit include high concentrations of tungsten and the late Paleozoic (Variscan) age. -Authors

Geologic and geochemical insights into the formation of the Taiyangshan porphyry copper–molybdenum deposit, Western Qinling Orogenic Belt, China

USGS Publications Warehouse

Kun-Feng Qiu,; Taylor, Ryan D.; Yao-Hui Song,; Hao-Cheng Yu,; Kai-Rui Song,; Nan Li,

2016-01-01

Taiyangshan is a poorly studied copper–molybdenum deposit located in the Triassic Western Qinling collisional belt of northwest China. The intrusions exposed in the vicinity of the Taiyangshan deposit record episodic magmatism over 20–30 million years. Pre-mineralization quartz diorite porphyries, which host some of the deposit, were emplaced at 226.6 ± 6.2 Ma. Syn-collisional monzonite and quartz monzonite porphyries, which also host mineralization, were emplaced at 218.0 ± 6.1 Ma and 215.0 ± 5.8 Ma, respectively. Mineralization occurred during the transition from a syn-collisional to a post-collisional setting at ca. 208 Ma. A barren post-mineralization granite porphyry marked the end of post-collisional magmatism at 200.7 ± 5.1 Ma. The ore-bearing monzonite and quartz monzonite porphyries have a εHf(t) range from − 2.0 to + 12.5, which is much more variable than that of the slightly older quartz diorite porphyries, with TDM2 of 1.15–1.23 Ga corresponding to the positive εHf(t) values and TDM1 of 0.62–0.90 Ga corresponding to the negative εHf(t) values. Molybdenite in the Taiyangshan deposit with 27.70 to 38.43 ppm Re suggests metal sourced from a mantle–crust mixture or from mafic and ultramafic rocks in the lower crust. The δ34S values obtained for pyrite, chalcopyrite, and molybdenite from the deposit range from + 1.3‰ to + 4.0‰, + 0.2‰ to + 1.1‰, and + 5.3‰ to + 5.9‰, respectively, suggesting a magmatic source for the sulfur. Calculated δ18Ofluid values for magmatic K-feldspar from porphyries (+ 13.3‰), hydrothermal K-feldspar from stockwork veins related to potassic alteration (+ 11.6‰), and hydrothermal sericite from quartz–pyrite veins (+ 8.6 to + 10.6‰) indicate the Taiyangshan deposit formed dominantly from magmatic water. Hydrogen isotope values for hydrothermal sericite ranging from − 85 to − 50‰ may indicate that magma degassing progressively depleted residual liquid in

Time scales of porphyry Cu deposit formation: insights from titanium diffusion in quartz

USGS Publications Warehouse

Mercer, Celestine N.; Reed, Mark H.; Mercer, Cameron M.

2015-01-01

Porphyry dikes and hydrothermal veins from the porphyry Cu-Mo deposit at Butte, Montana, contain multiple generations of quartz that are distinct in scanning electron microscope-cathodoluminescence (SEM-CL) images and in Ti concentrations. A comparison of microprobe trace element profiles and maps to SEM-CL images shows that the concentration of Ti in quartz correlates positively with CL brightness but Al, K, and Fe do not. After calibrating CL brightness in relation to Ti concentration, we use the brightness gradient between different quartz generations as a proxy for Ti gradients that we model to determine time scales of quartz formation and cooling. Model results indicate that time scales of porphyry magma residence are ~1,000s of years and time scales from porphyry quartz phenocryst rim formation to porphyry dike injection and cooling are ~10s of years. Time scales for the formation and cooling of various generations of hydrothermal vein quartz range from 10s to 10,000s of years. These time scales are considerably shorter than the ~0.6 m.y. overall time frame for each porphyry-style mineralization pulse determined from isotopic studies at Butte, Montana. Simple heat conduction models provide a temporal reference point to compare chemical diffusion time scales, and we find that they support short dike and vein formation time scales. We interpret these relatively short time scales to indicate that the Butte porphyry deposit formed by short-lived episodes of hydrofracturing, dike injection, and vein formation, each with discrete thermal pulses, which repeated over the ~3 m.y. generation of the deposit.

Magma emplacement mechanisms and syn-magmatic deformation - a new approach to the Knaben area in Vest Agder, Norway

NASA Astrophysics Data System (ADS)

Stormoen, Martin Austin; Slagstad, Trond; Henderson, Iain

2014-05-01

The Knaben area, known for its molybdenite mining, defines a N-S striking (~30 degrees dip towards the east) belt, consisting of porphyry granite with a varying density of amphibolite and varieties of deformed granite, lying within the Sirdal Magmatic Belt, is important for understanding the emplacement- and deformation mechanisms of the batholith. Detailed geological mapping combined with geochronology, geochemistry, and structural geology will be the focus areas. Last autumn's fieldwork indicated that several of the formerly mapped enclaves of amphibolite and deformed granite are more coherent then previously indicated, and some have been followed for a few kilometres. Several varieties of granite make up the area, mainly a dominating red porphyry granite, and a grey molybdenite-bearing finer grained granite. Structural investigations revealed consistent "top to the west" compressional kinematics on mappable shear zone networks often displaying west-directed duplex geometries. The Knaben area could possibly comprise a boundary between two individual plutons in the Sirdal Magmatic Belt, or a zone with remaining host rock. Geochronology of the eastern and western plutons will be done. Currently, largely different paleomagnetic vectors of the eastern and western porphyry granites indicate that they are separate plutons. Exploring how the emplacement- and deformation mechanisms have acted and are related, will be one of the main objectives. If the deformed granite is host rock, or syn- to post-magmatic deformed porphyry granite has been one of the major questions. A better understanding of the formation of the Knaben area, also regarding the emplacement of molybdenite, will prove useful for understanding the regional batholith, and possibly the possibility for molybdenite to occur elsewhere. The Sirdal Magmatic Belt, and also Knaben, seem to be of great value for studying magmatic processes.

Permian magmatic sequences of the Bilihe gold deposit in central Inner Mongolia, China: Petrogenesis and tectonic significance

NASA Astrophysics Data System (ADS)

Liu, Chunhua; Nie, Fengjun

2015-08-01

The Bilihe gold deposit is located in the eastern section of the Ondor Sum-Yanji Suture at the southern margin of the Xing'an-Mongolian Orogenic Belt (XMOB) and the northern margin of the North China Craton (NCC), central Inner Mongolia. The magmatic rocks in the ore district are generally high-K calc-alkaline, enriched in LREE, Zr, and Hf, and depleted in HREE, Nb, Ta, and P. The magmatic evolution sequences are norite gabbro → granodiorite porphyry → granite or norite gabbro → andesite → dacite porphyry → granodiorite, which show a trend of decreasing TiO2, FeO, MgO, CaO, and P2O5 with increasing SiO2. In the Bilihe ore district, hydrothermal processes were coeval with granitic magmatism for a period of ~ 17 Myr (272-255 Ma). The ages of the granite, granodiorite porphyry, granodiorite, and dacite porphyry are 271.5-264.1 Ma, 269.8-255.8 Ma, 268.3 Ma, and 268.6-259.4 Ma, respectively. The magmatic rocks contain magmatic, hydrothermal, and magmatic-hydrothermal zircons. The magmatic zircons have δCe > 4, La < 3 ppm, and SmN/LaN > 2.5; the hydrothermal zircons have δCe < 4, La > 3 ppm, and SmN/LaN < 2.5. The Nb/Ta and Zr/Hf ratios of granodiorite are 12.7-14.99 and 40.2-46.56, respectively. The Zr/Hf ratios successively increase in the sequence of granite (27.4-29.02) → granodiorite porphyry (29.19-32.18) → dacite porphyry (33.54-38.5) → norite gabbro (36.75-38.37), and their Nb/Ta ratios are 9.09-12.38. Zircons in granodiorite yield ε Hf (t) values of - 0.29 to - 56 (n = 13) and 2.07-7.62 (n = 5), and they give a Hf two-stage model age (tDM2) of 807-4765 Ma. The ε Hf (t) values of the zircons in granite, granodiorite porphyry, and dacite porphyry are - 0.46 to 8.03, 3.17 to 10.32, and - 0.78 to 6.58, respectively, and their Hf tDM2 ages are 787-1324 Ma, 638-1091 Ma, and 868-1343 Ma, respectively. Dehydration partial melting of subducted oceanic crust resulted in the formation of dacite porphyry; partial melting of depleted mantle resulted in

Rapakivi texture from the O'Leary Porphyry, Arizona (U.S.A.)

NASA Astrophysics Data System (ADS)

Bladh, K. Laing

1980-03-01

The rhyodactic O’Leary Porphyry which forms the Pleistocene (0.233±0.37 m.y.) volcanic domes of O’Leary Peak and Darton Dome in the San Francisco Volcanic Field (northern Arizona, U.S.A.) contains sanidine phenocrysts with oligoclase mantles (rapakivi texture). Rapakivi texture occurs worldwide in silicic rocks of many ages and has been attributed to various igneous and metamorphic processes. The O’Leary Porphyry contains both mantled and unmantled sanidine (both are Or63-69 Ab30-36An1), oligoclase and quartz phenocrysts, labradorite (An53Ab45Or2) and kaersutite xenocrysts and andesite xenoliths. The compositional range of oligoclase is the same (An11-26Ab70-80Orr-10) for the rapakivi mantles, the oligoclase phenocrysts, and the oligoclase crystals poikilitic within sanidines. Most mantles are discontinuous. The sanidine appears to have been resorbed prior to mantling. Experimental melting studies on the O’Leary Prophyry show that, for a 15 wgt.% water system, plagioclase crystallized prior to sanidine and quartz crystallized last. The O’Leary Porphyry, although inhomogeneous, plots on a Q-Or-Ab-An diagram well within the plagioclase stability field. Poikilitic plagioclases within sanidines further support crystallization of plagioclase prior to sanidine in the O’Leary Porphyry. Exsolution of a ternary feldspar to form a plagioclase mantle is the most commonly accepted igneous theory of rapakivi texture formation but has been eliminated as the origin of the O’Leary Porphyry rapakivi. Petrologic models by Tuttle and Bowen and by Stewart are rejected for the O’Leary rapakivi because of inconsistencies with the O’Leary occurrences. Two theories are viable for the O’Leary rapakivi texture. First, is a decrease in water vapor pressure which would enlarge the plagioclase stability field possibility causing mantling of metastable sanidines. The second and preferred theory is that of an addition of sodium and calcium by basification (chemical

The genesis of the Hashitu porphyry molybdenum deposit, Inner Mongolia, NE China: constraints from mineralogical, fluid inclusion, and multiple isotope (H, O, S, Mo, Pb) studies

NASA Astrophysics Data System (ADS)

Zhai, Degao; Liu, Jiajun; Tombros, Stylianos; Williams-Jones, Anthony E.

2018-03-01

The Hashitu porphyry molybdenum deposit is located in the Great Hinggan Range Cu-Mo-Pb-Zn-Ag polymetallic metallogenic province of NE China, in which the Mo-bearing quartz veins are hosted in approximately coeval granites and porphyries. The deposit contains more than 100 Mt of ore with an average grade of 0.13 wt.% Mo. This well-preserved magmatic-hydrothermal system provides an excellent opportunity to determine the source of the molybdenum, the evolution of the hydrothermal fluids and the controls on molybdenite precipitation in a potentially important but poorly understood metallogenic province. Studies of fluid inclusions hosted in quartz veins demonstrate that the Hashitu hydrothermal system evolved to progressively lower pressure and temperature. Mineralogical and fluid inclusion analyses and physicochemical calculations suggest that molybdenite deposition occurred at a temperature of 285 to 325 °C, a pressure from 80 to 230 bars, a pH from 3.5 to 5.6, and a Δlog fO2 (HM) of -3.0, respectively. Results of multiple isotope (O, H, S, Mo, and Pb) analyses are consistent in indicating a genetic relationship between the ore-forming fluids, metals, and the Mesozoic granitic magmatism (i.e., δ 18OH2O from +1.9 to +9.7‰, δDH2O from -106 to -87‰, δ 34SH2S from +0.3 to +3.9‰, δ 98/95Mo from 0 to +0.37‰, 206Pb/204Pb from 18.2579 to 18.8958, 207Pb/204Pb from 15.5384 to 15.5783, and 208Pb/204Pb from 38.0984 to 42.9744). Molybdenite deposition is interpreted to have occurred from a low-density magmatic-hydrothermal fluid in response to decreases in temperature, pressure, and fO2.

Undiscovered porphyry copper resources in the Urals—A probabilistic mineral resource assessment

USGS Publications Warehouse

Hammarstrom, Jane M.; Mihalasky, Mark J.; Ludington, Stephen; Phillips, Jeffrey; Berger, Byron R.; Denning, Paul; Dicken, Connie; Mars, John; Zientek, Michael L.; Herrington, Richard J.; Seltmann, Reimar

2017-01-01

A probabilistic mineral resource assessment of metal resources in undiscovered porphyry copper deposits of the Ural Mountains in Russia and Kazakhstan was done using a quantitative form of mineral resource assessment. Permissive tracts were delineated on the basis of mapped and inferred subsurface distributions of igneous rocks assigned to tectonic zones that include magmatic arcs where the occurrence of porphyry copper deposits within 1 km of the Earth's surface are possible. These permissive tracts outline four north-south trending volcano-plutonic belts in major structural zones of the Urals. From west to east, these include permissive lithologies for porphyry copper deposits associated with Paleozoic subduction-related island-arc complexes preserved in the Tagil and Magnitogorsk arcs, Paleozoic island-arc fragments and associated tonalite-granodiorite intrusions in the East Uralian zone, and Carboniferous continental-margin arcs developed on the Kazakh craton in the Transuralian zone. The tracts range from about 50,000 to 130,000 km2 in area. The Urals host 8 known porphyry copper deposits with total identified resources of about 6.4 million metric tons of copper, at least 20 additional porphyry copper prospect areas, and numerous copper-bearing skarns and copper occurrences.Probabilistic estimates predict a mean of 22 undiscovered porphyry copper deposits within the four permissive tracts delineated in the Urals. Combining estimates with established grade and tonnage models predicts a mean of 82 million metric tons of undiscovered copper. Application of an economic filter suggests that about half of that amount could be economically recoverable based on assumed depth distributions, availability of infrastructure, recovery rates, current metals prices, and investment environment.

A climate signal in exhumation patterns revealed by porphyry copper deposits

NASA Astrophysics Data System (ADS)

Yanites, Brian J.; Kesler, Stephen E.

2015-06-01

The processes that build and shape mountain landscapes expose important mineral resources. Mountain landscapes are widely thought to result from the interaction between tectonic uplift and exhumation by erosion. Both climate and tectonics affect rates of exhumation, but estimates of their relative importance vary. Porphyry copper deposits are emplaced at a depth of about 2 km in convergent tectonic settings; their exposure at the surface therefore can be used to track landscape exhumation. Here we analyse the distribution, ages and spatial density of exposed Cenozoic porphyry copper deposits using a global data set to quantify exhumation. We find that the deposits exhibit young ages and are sparsely distributed--both consistent with rapid exhumation--in regions with high precipitation, and deposits are older and more abundant in dry regions. This suggests that climate is driving erosion and mineral exposure in deposit-bearing mountain landscapes. Our findings show that the emplacement ages of porphyry copper deposits provide a means to estimate long-term exhumation rates in active orogens, and we conclude that climate-driven exhumation influences the age and abundance of exposed porphyry copper deposits around the world.

Paleozoic tectonic evolution of the Dananhu-Tousuquan island arc belt, Eastern Tianshan: Constraints from the magmatism of the Yuhai porphyry Cu deposit, Xinjiang, NW China

NASA Astrophysics Data System (ADS)

Wang, Yunfeng; Chen, Huayong; Han, Jinsheng; Chen, Shoubo; Huang, Baoqiang; Li, Chen; Tian, Qinglei; Wang, Chao; Wu, Jianxin; Chen, Mingxia

2018-03-01

The Yuhai intrusions (quartz diorite, granite and pyroxene diorite) are located in the eastern part of the Dananhu-Tousuquan island arc belt of the Eastern Tianshan, and associated with the early Paleozoic porphyry Cu mineralization. LA-ICP-MS zircon U-Pb dating yielded emplacement ages of 443.5 ± 4.1 Ma for the quartz diorite, 325.4 ± 2.5 Ma for the granite, and 291 ± 3.0 Ma for the pyroxene diorite. These rocks are tholeiitic to calc-alkaline and metaluminous, with A/CNK values ranging from 0.66 to 1.10. The Silurian ore-bearing Yuhai quartz diorite is rich in LREEs and LILEs (e.g., K, Ba, Pb and Sr), and depleted in HREEs and HFSEs (e.g., Nb, Ta and Ti). These rocks are MgO-rich (1.90-3.80 wt.%; Mg# = 37-72), with high Sr/Y, La/Yb and Ba/Th ratios, positive εNd(t) (6.31-6.84) and εHf(t) (13.26-16.40), low (87Sr/86Sr)i (0.7037-0.7039), and low Nb/U and Ta/U ratios. The data suggest that the quartz diorite was generated by the partial melting of subducted juvenile oceanic slab. The oxygen fugacity (ƒO2) of the quartz diorite, calculated by zircon Ce4+/Ce3+ ratios, is higher than that of the granite and pyroxene diorite, implying that the quartz diorite was more favorable to porphyry Cu mineralization. The Carboniferous Yuhai granite reveals similar geochemical features with the quartz diorite, except for the lower Mg# (27-33), and the more elevated Th/U and Th/La ratios. Furthermore, these rocks also show high εNd(t) (5.2-5.8) and εHf(t) (11.03-14.85) values, and low (87Sr/86Sr)i (0.7036-0.7037). These features indicate that the parental magma of the granite was probably derived from a juvenile lower crust with no significant mantle component involvement. Different from the Yuhai quartz diorite and granite, the early Permian Yuhai pyroxene diorite contains low SiO2 (50.76-55.74 wt.%) and high MgO (3.96-4.33 wt.%; Mg# = 40-44). The εNd(t), εHf(t) and (87Sr/86Sr)i values of the pyroxene diorite are 5.77-6.42, 7.99-12.10 and 0.7035-0.7040, respectively. The

Porphyry Cu-Au and associated polymetallic Fe-Cu-Au deposits in the Beiya Area, western Yunnan Province, south China

USGS Publications Warehouse

Xu, X.-W.; Cai, X.-P.; Xiao, Q.-B.; Peters, S.G.

2007-01-01

The Alkaline porphyries in the Beiya area are located east of the Jinshajiang suture, as part of a Cenozoic alkali-rich porphyry belt in western Yunnan. The main rock types include quartz-albite porphyry, quartz-K-feldspar porphyry and biotite-K-feldspar porphyry. These porphyries are characterised by high alkalinity [(K2O + Na2O)% > 10%], high silica (SiO2% > 65%), high Sr (> 400??ppm) and 87Sr/86Sr (> 0.706)] ratio and were intruded at 65.5??Ma, between 25.5 to 32.5??Ma, and about 3.8??Ma, respectively. There are five main types of mineral deposits in the Beiya area: (1) porphyry Cu-Au deposits, (2) magmatic Fe-Au deposits, (3) sedimentary polymetallic deposits, (4) polymetallic skarn deposits, and (5) palaeoplacers associated with karsts. The porphyry Cu-Au and polymetallic skarn deposits are associated with quartz-albite porphyry bodies. The Fe-Au and polymetallic sedimentary deposits are part of an ore-forming system that produced considerable Au in the Beiya area, and are characterised by low concentrations of La, Ti, and Co, and high concentrations of Y, Yb, and Sc. The Cenozoic porphyries in western Yunnan display increased alkalinity away from the Triassic Jinshajiang suture. Distribution of both the porphyries and sedimentary deposits in the Beiya area are interpreted to be related to partial melting in a disjointed region between upper mantle lithosphere of the Yangtze Plate and Gondwana continent, and lie within a shear zone between buried Palaeo-Tethyan oceanic lithosphere and upper mantle lithosphere, caused by the subduction and collision of India and Asia. ?? 2006 Elsevier B.V. All rights reserved.

Why large porphyry Cu deposits like high Sr/Y magmas?

PubMed Central

Chiaradia, Massimo; Ulianov, Alexey; Kouzmanov, Kalin; Beate, Bernardo

2012-01-01

Porphyry systems supply most copper and significant gold to our economy. Recent studies indicate that they are frequently associated with high Sr/Y magmatic rocks, but the meaning of this association remains elusive. Understanding the association between high Sr/Y magmatic rocks and porphyry-type deposits is essential to develop genetic models that can be used for exploration purposes. Here we present results on a Pleistocene volcano of Ecuador that highlight the behaviour of copper in magmas with variable (but generally high) Sr/Y values. We provide indirect evidence for Cu partitioning into a fluid phase exsolved at depths of ~15 km from high Sr/Y (>70) andesitic magmas before sulphide saturation. This lends support to the hypothesis that large amounts of Cu- and S-bearing fluids can be accumulated into and released from a long-lived high Sr/Y deep andesitic reservoir to a shallower magmatic-hydrothermal system with the potential of generating large porphyry-type deposits. PMID:23008750

Why large porphyry Cu deposits like high Sr/Y magmas?

PubMed

Chiaradia, Massimo; Ulianov, Alexey; Kouzmanov, Kalin; Beate, Bernardo

2012-01-01

Porphyry systems supply most copper and significant gold to our economy. Recent studies indicate that they are frequently associated with high Sr/Y magmatic rocks, but the meaning of this association remains elusive. Understanding the association between high Sr/Y magmatic rocks and porphyry-type deposits is essential to develop genetic models that can be used for exploration purposes. Here we present results on a Pleistocene volcano of Ecuador that highlight the behaviour of copper in magmas with variable (but generally high) Sr/Y values. We provide indirect evidence for Cu partitioning into a fluid phase exsolved at depths of ~15 km from high Sr/Y (>70) andesitic magmas before sulphide saturation. This lends support to the hypothesis that large amounts of Cu- and S-bearing fluids can be accumulated into and released from a long-lived high Sr/Y deep andesitic reservoir to a shallower magmatic-hydrothermal system with the potential of generating large porphyry-type deposits.

Empirical and Theoretical Seismic Energy Partitioning from Explosions Under Different Confinement and Media Conditions

DTIC Science & Technology

2008-09-01

Mesa, AZ or in a faster- velocity granite porphyry at a copper mine near Morenci, AZ. The results from prior research conducted by the SPE consortium...08NA286551,2; DE-FC52-06NA273243; and DE-AC52-06NA253964 Proposal No. BAA08-97 ABSTRACT Some of the data-analysis results from the 2003 Arizona ...conditions, while explosions in higher-velocity granite porphyry are marked by interesting source anisotropy. Even though the emplacement media were

Stochastic modelling of deep magmatic controls on porphyry copper deposit endowment.

PubMed

Chiaradia, Massimo; Caricchi, Luca

2017-03-15

Porphyry deposits, our main source of copper and of significant amounts of Mo, Re and Au, form at convergent margins in association with intermediate-felsic magmas. Although it is accepted that copper is transported and precipitated by fluids released by these magmas, the magmatic processes leading to the formation of economic deposits remain elusive. Here we perform Monte Carlo petrological and geochemical modelling to quantitatively link crustal magmatic processes and the geochemical signatures of magmas (i.e., Sr/Y) to the formation of porphyry Cu deposits of different sizes. Our analysis shows that economic deposits (particularly the largest ones) may only form in association with magma accumulated in the lower-middle crust (P > ~0.5 GPa) during ≥2-3 Ma, and subsequently transferred to and degassed in the upper crust over periods of up to ~2.0 Ma. Magma accumulation and evolution at shallower depths (<~0.4 GPa) dramatically reduces the potential of magmatic systems to produce economic deposits. Our modelling also predicts the association of the largest porphyry deposits with a specific Sr/Y interval (~100 ± 50) of the associated magmatic rocks, which is virtually identical to the range measured in giant porphyry copper deposits.

Stochastic modelling of deep magmatic controls on porphyry copper deposit endowment

PubMed Central

Chiaradia, Massimo; Caricchi, Luca

2017-01-01

Porphyry deposits, our main source of copper and of significant amounts of Mo, Re and Au, form at convergent margins in association with intermediate-felsic magmas. Although it is accepted that copper is transported and precipitated by fluids released by these magmas, the magmatic processes leading to the formation of economic deposits remain elusive. Here we perform Monte Carlo petrological and geochemical modelling to quantitatively link crustal magmatic processes and the geochemical signatures of magmas (i.e., Sr/Y) to the formation of porphyry Cu deposits of different sizes. Our analysis shows that economic deposits (particularly the largest ones) may only form in association with magma accumulated in the lower-middle crust (P > ~0.5 GPa) during ≥2–3 Ma, and subsequently transferred to and degassed in the upper crust over periods of up to ~2.0 Ma. Magma accumulation and evolution at shallower depths (<~0.4 GPa) dramatically reduces the potential of magmatic systems to produce economic deposits. Our modelling also predicts the association of the largest porphyry deposits with a specific Sr/Y interval (~100 ± 50) of the associated magmatic rocks, which is virtually identical to the range measured in giant porphyry copper deposits. PMID:28295045

The physical hydrology of magmatic-hydrothermal systems: High-resolution 18O records of magmatic-meteoric water interaction from the Yankee Lode tin deposit (Mole Granite, Australia)

NASA Astrophysics Data System (ADS)

Fekete, Szandra; Weis, Philipp; Driesner, Thomas; Heinrich, Christoph A.; Baumgartner, Lukas; Bouvier, Anne-Sophie

2016-04-01

apparent discrepancy can be explained by the presence of a fluid of meteoric origin that was isotopically equilibrated with a hot, but already solidified and fractured granitic intrusion under rock-dominated conditions prior their transfer to the cold ore deposition site (Heinrich, 1990). Conversely, in porphyry copper systems meteoric fluid incursion has been assumed to participate in formation of peripheral or post-mineralization processes (Bowman et al., 1987; Sillitoe, 2010; Williams-Jones and Migdisov, 2014). However, recent numerical simulations of porphyry copper systems identify a significant role of meteoric fluids for the enrichment process, providing a cooling mechanism for metal-rich fluids expelled from an upper crustal magma chamber (Weis et al. 2012, Weis 2015). Furthermore, new petrographic and fluid inclusion work of ore-mineralized quartz veins (Landtwing et al., 2010; Stefanova et al., 2014) indicates lower (˜ 450r{ }C) than magmatic fluid temperatures for copper precipitation. Given that the Yankee Lode study validated the capability of high resolution, in situ δ 18O analysis to trace meteoric water incursion, we will apply this method to hydrothermal quartz samples from two significant porphyry copper deposits (Bingham Canyon, USA and Elatsite, Bulgaria). By this we intend to better constrain a potential role of meteoric water incursion in porphyry copper ore precipitation. REFERENCES Audétat, A., Günther, D., Heinrich, C. A. 1998: Formation of a Magmatic-Hydrothermal Ore Deposit: Insights with LA-ICP-MS Analysis of Fluid Inclusions: Science, 279, 2091-2094. Audétat, A. 1999: The magmatic-hydrothermal evolution of the Sn/W-mineralized Mole Granite (Eastern Australia): PhD Thesis, 211. Bowman, J. R., Parry, W. T., Kropp, W. P., and Kruer, S. A., 1987: Chemical and isotopic evolution of hydrothermal solutions at Bingham, Utah: Economic Geology, 82, 395-428. Heinrich, C.A. 1990: The Chemistry of Hydrothermal Tin(-Tungsten) Ore Deposition: Economic

Rapid thermal rejuvenation of high-crystallinity magma linked to porphyry copper deposit formation; evidence from the Koloula Porphyry Prospect, Solomon Islands

NASA Astrophysics Data System (ADS)

Tapster, S.; Condon, D. J.; Naden, J.; Noble, S. R.; Petterson, M. G.; Roberts, N. M. W.; Saunders, A. D.; Smith, D. J.

2016-05-01

Magmas containing the components needed to form porphyry copper deposits are relatively common within arcs, yet mineralising events are uncommon within the long-lived magmatic systems that host them. Understanding what causes the transition from barren to productive intrusions is critical to the development of conceptual deposit models. We have constrained the tempo of pre- and syn-mineralisation magmatic events in relationship to the thermal evolution of the plutonic body that underlies one of the world's youngest exposed plutonic-porphyry systems, the Inamumu Zoned Pluton, Koloula Porphyry Prospect, Solomon Islands. High precision ID-TIMS U-Pb dates of texturally and chemically characterised zircons indicate pluton emplacement over <150 kyr was superseded after ca. 50 kyr by two discrete episodes of mineralising porphyritic melt emplacement. Their associated hydrothermal systems initiated within ca. 30 kyrs of each other. Zircon populations within evolved intrusions contain resorbed cores that were recycled from the deeper magmatic system, yet their youngest dates are statistically indistinguishable from those yielded by crystals lacking resorption. Comparisons of Ti-in-zircon proxy temperatures, modelled zircon saturation temperatures and temperature-crystallinity relationships suggest that prior to being heated and emplaced within the shallow level pluton, magmas were stored at depth in a high-crystallinity (>50% crystals) state, past the point of rheological lock-up. We estimate that thermal rejuvenation of the deeper high-crystallinity magma and generation of a mobile melt fraction may have occurred ≤10 kyr before its transport and emplacement within the porphyry environment. The underlying pluton likely cooled and returned to high-crystallinity states prior to subsequent remobilisation-emplacement events. Titanium-in-zircon geothermometry and whole-rock geochemistry suggest pre-mineralisation intrusions were remobilised by mixing of a silicic magma with a

Re-Os dating of mineralization in Siah Kamar porphyry Mo deposit (NW Iran) and investigating on its temporal relationship with porphyry Cu-Mo deposits in the southern Lesser Caucasus, NW and central Iran

NASA Astrophysics Data System (ADS)

Simmonds, Vartan; Moazzen, Mohssen; Selby, David

2017-04-01

The Neo-Tethyan basin closure in Iran is characterized by the Urumieh-Dokhtar magmatic arc (UDMA), formed by north-eastward subduction of the Neo-Tethyan oceanic crust during the Alpine orogeny. This belt also coincides with the porphyry copper metallogenic belt of Iran, which hosts many porphyry Cu-Mo deposits (PCDs) and prospects, such as Sungun (NW Iran) and Sarcheshmeh (central Iran). The Siah Kamar porphyry Mo deposit (PMD) is the first discovered porphyry molybdenum deposit on this belt, which is located 10 km west of Mianeh (NW Iran), with 39.2 Mt proved reserves @ 539 ppm Mo and 66.4 Mt probable reserves @ 266 ppm Mo. The host porphyry stock has quartz-monzonitic composition, which intruded the volcanic and pyroclastic rocks of Eocene age. Re content of molybdenites is about 10.44-41.05 ppm which, considering the several tens of ppm concentration, is comparable with porphyry Mo deposits (e.g., Climax in USA), being clearly distinguished from porphyry Cu-Mo deposits. Re-Os dating of molybdenites from this PMD has given model ages between 28.1±0.15 to 29.06±0.2 Ma, and isochron age of 28.0±2.1 Ma, corresponding to the middle Oligocene (upper part of Rupelian). Comparing the ages determined for Siah Kamar PMD with porphyry Cu-Mo mineralizations in the Lesser Caucasus indicates that it is younger than most of the dated PCDs and prospects there, especially those of upper Eocene, while it is a little older than Paragachay and first-stage Kadjaran PCDs [1]. In a regional scale of NW Iran, it shows a narrow overlap with vein-type Cu-Mo-Au mineralizations in Qarachilar (Qaradagh batholith) and is nearly coeval with Haftcheshmeh PCD, indicating that mineralization in the Siah Kamar PMD corresponds to the second porphyry mineralization epoch in NW Iran, proposed by [2]. Meanwhile, mineralization in Siah Kamar is older than all the porphyry Cu-Mo mineralizations along the central and SE parts of the UDMA, except the Bondar Hanza PCD in Kerman zone, which nearly

Generation of Late Mesozoic Qianlishan A2-type granite in Nanling Range, South China: Implications for Shizhuyuan W-Sn mineralization and tectonic evolution

NASA Astrophysics Data System (ADS)

Chen, Yuxiao; Li, He; Sun, Weidong; Ireland, Trevor; Tian, Xufeng; Hu, Yongbin; Yang, Wubin; Chen, Chen; Xu, Deru

2016-12-01

The Late Mesozoic Qianlishan granitic complex in the western Nanling Range, South China is associated with the Shizhuyuan giant W-Sn-Mo-Bi polymetallic deposit. It mainly consists of three phases of intrusions, P-1 porphyritic biotite granite, P-2 equigranular biotite granite and P-3 granite porphyry. All three phases of granite contain quartz, plagioclase, K-feldspar and Fe-rich biotite. They have geochemical affinities of A-type granites, e.g., high FeOT/(FeOT + MgO) ratios (0.84-0.99), total alkali (Na2O + K2O, 7.50-9.04 wt.%), high Ga/Al ratios (10,000*Ga/Al > 2.6) and high Zr + Nb + Y + Ce concentrations (> 350 ppm). High Y/Nb ratios (> 1.2) suggest that the Qianlishan complex belongs to A2-type granite. Zircon U-Pb ages indicate a short age interval decreasing from 158-157 Ma, to 158-155 Ma and to 154 Ma for the P-1, P-2 and P-3 granites, respectively. These ages are similar to the mineralization age of the Shizhuyuan tungsten polymetallic deposit, within error. The Qianlishan granites were generated at low oxygen fugacity conditions based on the low values of zircon Ce4 +/Ce3 + ratios (1.53-198) and significantly negative Eu anomalies (EuN/EuN*, 0.03-0.13) in apatite. New zircon εHf(t) values for the P-3 granite range from - 13.0 to - 4.4, similar to those previously obtained for the P-1 and P-2 granites. Both the granite and apatite grains therein are characterized by high F but low Cl concentrations, suggesting the influx of a high F/Cl component. The P-2 granites especially contain higher F contents (1840-8690 ppm) and W (7-158 ppm) and Sn (6-51 ppm) concentrations and with stronger evolution features. Positive trends between F and W and Sn of Qianlishan complex indicate that high F source is crucial for mineralization of W and Sn. We consider that the lithospheric mantle source may have been metasomatized by subduction fluids in the far end of subduction zones to produce the A2 feature of the Qianlishan granite and the fluorine was introduced through

The Stypsi-Megala Therma porphyry-epithermal mineralization, Lesvos Island, Greece: new mineralogical and geochemical data

NASA Astrophysics Data System (ADS)

Periferakis, Argyrios; Voudouris, Panagiotis; Melfos, Vasilios; Mavrogonatos, Constantinos; Alfieris, Dimitrios

2017-04-01

Lesvos Island is located at the NE part of the Aegean Sea and mostly comprises post-collisional Miocene volcanic rocks of shoshonitic to calc-alkaline geochemical affinities. In the northern part of the Island, the Stypsi Cu-Mo±Au porphyry prospect, part of the Stypsi caldera, is hosted within hydrothermally altered intrusives and volcanics [1]. Porphyry-style mineralization is developed in a microgranite porphyry that has intruded basaltic trachyandesitic lavas. Propylitic alteration occurs distal to the mineralization, whereas sodic-calcic alteration related to quartz-actinolite veinlets, and a phyllic overprint associated with a dense stockwork of banded black quartz±carbonate veinlets, characterizes the core of the system. Alunite-kaolinite advanced argillic alteration occurs at higher topographic levels and represents a barren lithocap to the porphyry mineralization. Intermediate-sulfidation (IS) milky quartz-carbonate veins overprint the porphyry mineralization along a NNE-trending fault that extends further northwards to Megala Therma, where it hosts IS base metal-rich Ag-Au mineralization [2]. New mineralogical data from the Megala Therma deposit suggest Ag-famatinite, Te-polybasite and Ag-tetrahedrite as the main carriers of Ag in the mineralization. Porphyry-style ores at Stypsi consist of magnetite postdated by pyrite and then by chalcopyrite, molybdenite, sphalerite, galena and bismuthinite within the black quartz stockworks or disseminated in the wallrock [1]. The dark coloration of quartz in the veinlets is due to abundant vapor-rich fluid inclusions. Quartz is granular and fine-grained and locally elongated perpendicular to the vein walls. Botryoidal textures are continuous through quartz grains, suggesting quartz recrystallization from a silica gel, a feature already described by [3] from banded quartz veinlets in porphyry Au deposits at Maricunga, Chile. Bulk ore analyses from porphyry-style mineralization at Stypsi displayed similar geochemical

Tests of Rock Cores Scott Study Area, Missouri

DTIC Science & Technology

1970-05-01

porphyry with some granodiorite and small amounts of dolomite, acid metavolcanics, and dark gray volcanic breccia. Specific gravity, * Schmidt...petrographically identified as predominantly rhyolite and dacite porphyry with some granodiorite and small amounts of dolomite, acid metavolcanics, and dark...exhibit- ing little, if any, hysteresis. 9. Direct and indirect tensile strengths exhibited by tne rhyro- lite and dacite porphyry and granite are very high

A new look on Imperial Porphyry: a famous ancient dimension stone from the Eastern Desert of Egypt—petrogenesis and cultural relevance

NASA Astrophysics Data System (ADS)

Abu El-Enen, Mahrous M.; Lorenz, Joachim; Ali, Kamal A.; von Seckendorff, Volker; Okrusch, Martin; Schüssler, Ulrich; Brätz, Helene; Schmitt, Ralf-Thomas

2018-03-01

Imperial Porphyry, a famous dimension stone of spectacular purple color, was quarried in the Mons Porphyrites area north of Jabal Dokhan in the Eastern Desert of Egypt, from the beginning of the first until the middle of the fifth century AD. During this period, the valuable material was processed as decorative stone and was used for objects of art, reserved exclusively for the Imperial court of the Roman Empire. Later on, only antique spoils of smaller or bigger size have been re-used for these purposes. The Imperial Porphyry is a porphyritic rock of trachyandesitic to dacitic composition that occurs in the uppermost levels of shallow subvolcanic sill-like intrusions, forming a member of the Dokhan Volcanic Suite. Its purple color is mainly due to dispersed flakes of hematite, resulting from hydrothermal alteration of a dark green Common Porphyry of similar composition, underlying the Imperial Porphyry. Both, the Common Porphyry and the purple Imperial Porphyry', are extensively exposed in the Roman quarries. Contacts between Common and Imperial Porphyry are irregular and gradational. In both rock types, intrusive breccias are frequent, indicating a complex intrusion history. U-Th-Pb zircon geochronology on two samples of Imperial Porphyry and one sample of the Common Porphyry yielded an age range of 609-600 Ma, thus confirming earlier results of radiometric dating. Geochemical evidence indicates that both the Imperial and the Common Porphyry are of medium- to high-K calc-alkaline affinity. The magmas have formed by partial melting of a subduction-modified upper mantle. The subsequent intrusion took place within a highly extended terrane (HET).

Porphyry copper deposit tract definition - A global analysis comparing geologic map scales

USGS Publications Warehouse

Raines, G.L.; Connors, K.A.; Chorlton, L.B.

2007-01-01

Geologic maps are a fundamental data source used to define mineral-resource potential tracts for the first step of a mineral resource assessment. Further, it is generally believed that the scale of the geologic map is a critical consideration. Previously published research has demonstrated that the U.S. Geological Survey porphyry tracts identified for the United States, which are based on 1:500,000-scale geology and larger scale data and published at 1:1,000,000 scale, can be approximated using a more generalized 1:2,500,000-scale geologic map. Comparison of the USGS porphyry tracts for the United States with weights-of-evidence models made using a 1:10,000,000-scale geologic map, which was made for petroleum applications, and a 1:35,000,000-scale geologic map, which was created as context for the distribution of porphyry deposits, demonstrates that, again, the USGS US porphyry tracts identified are similar to tracts defined on features from these small scale maps. In fact, the results using the 1:35,000,000-scale map show a slightly higher correlation with the USGS US tract definition, probably because the conceptual context for this small-scale map is more appropriate for porphyry tract definition than either of the other maps. This finding demonstrates that geologic maps are conceptual maps. The map information shown in each map is selected and generalized for the map to display the concepts deemed important for the map maker's purpose. Some geologic maps of small scale prove to be useful for regional mineral-resource tract definition, despite the decrease in spatial accuracy with decreasing scale. The utility of a particular geologic map for a particular application is critically dependent on the alignment of the intention of the map maker with the application. ?? International Association for Mathematical Geology 2007.

Geology and porphyry copper-type alteration-mineralization of igneous rocks at the Christmas Mine, Gila County, Arizona

USGS Publications Warehouse

Koski, Randolph A.

1979-01-01

The Christmas copper deposit, located in southern Gila County, Arizona, is part of the major porphyry copper province of southwestern North America. Although Christmas is known for skarn deposits in Paleozoic carbonate rocks, ore-grade porphyry-type copper mineralization also occurs in a composite granodioritic intrusive complex and adjacent mafic volcanic country rocks. This study considers the nature, distribution, and genesis of alteration-mineralization in the igneous rock environment at Christmas. At the southeast end of the Dripping Spring Mountains, the Pennsylvanian Naco Limestone is unconformably overlain by the Cretaceous Williamson Canyon Volcanics, a westward-thinning sequence of basaltic volcanic breccia and lava flows, and subordinate clastic sedimentary rocks. Paleozoic and Mesozoic strata are intruded by Laramide-age dikes, sills, and small stocks of hornblende andesite porphyry and hornblende rhyodacite porphyry, and the mineralized Christmas intrusive complex. Rocks of the elongate Christmas stock, intruded along an east-northeast-trending fracture zone, are grouped into early, veined quartz diorite (Dark Phase), biotite granodiorite porphyry (Light Phase), and granodiorite; and late, unveined dacite porphyry and granodiorite porphyry. Biotite rhyodacite porphyry dikes extending east and west from the vicinity of the stock are probably coeval with biotite granodiorite porphyry. Accumulated normal displacement of approximately 1 km along the northwest-trending Christmas-Joker fault system has juxtaposed contrasting levels (lower, intrusive-carbonate rock environment and upper, intrusive-volcanic rock environment) within the porphyry copper system. K-Ar age determinations and whole-rock chemical analyses of the major intrusive rock types indicate that Laramide calc-alkaline magmatism and ore deposition at Christmas evolved over an extended period from within the Late Cretaceous (~75-80 m.y. ago) to early Paleocene (~63-61 m.y. ago). The sequence of

Identification of hydrothermal alteration minerals for exploring of porphyry copper deposit using ASTER data, SE Iran

NASA Astrophysics Data System (ADS)

Pour, Amin Beiranvnd; Hashim, Mazlan

2011-11-01

The NW-SE trending Central Iranian Volcanic Belt hosts many well-known porphyry copper deposits in Iran. It becomes an interesting area for remote sensing investigations to explore the new prospects of porphyry copper and vein type epithermal gold mineralization. Two copper mining districts in southeastern segment of the volcanic belt, including Meiduk and Sarcheshmeh have been selected in the present study. The performance of Principal Component Analysis, band ratio and Minimum Noise Fraction transformation has been evaluated for the visible and near infrared (VNIR) and, shortwave infrared (SWIR) subsystems of ASTER data. The image processing techniques indicated the distribution of iron oxides and vegetation in the VNIR subsystem. Hydrothermal alteration mineral zones associated with porphyry copper mineralization identified and discriminated based on distinctive shortwave infrared (SWIR) properties of the ASTER data in a regional scale. These techniques identified new prospects of porphyry copper mineralization in the study areas. The spatial distribution of hydrothermal alteration zones has been verified by in situ inspection, X-ray diffraction (XRD) analysis, and spectral reflectance measurements. Results indicated that the integration of the image processing techniques has a great ability to obtain significant and comprehensive information for the reconnaissance stages of porphyry copper exploration in a regional scale. The results of this research can assist exploration geologists to find new prospects of porphyry copper and gold deposits in the other virgin regions before costly detailed ground investigations. Consequently, the introduced image processing techniques can create an optimum idea about possible location of the new prospects.

Geochronology and geochemistry of the Badaguan porphyry Cu-Mo deposit in Derbugan metallogenic belt of the NE China, and their geological significances

NASA Astrophysics Data System (ADS)

Gao, Bingyu; Zhang, Lianchang; Jin, Xindi; Li, Wenjun; Chen, Zhiguang; Zhu, Mingtian

2016-03-01

The Badaguan porphyry Cu-Mo deposit belongs to the Derbugan metallogenic belt, which is located in the Ergun block, NE China. In the mining area, the Cu-Mo mineralization mainly occurs in quartz diorite porphyry and is hosted within silicified-sericitized and sericite alteration zone. Geochemical results of the host porphyry is characterized by high SiO2, high Al2O3, low MgO, weak positive Eu anomalies and clearly HREE depletion, high Sr, low Y and low Yb, similar to those of adakite. The Sr-Nd isotopic composition of the host porphyry displays an initial (87Sr/86Sr)i ratio of 0.7036-0.7055 and positive Nd( t) values of +0.1 to +0.6, which are similar to the OIB, reflecting the source of the host porphyry may derive from subducted ocean slab, and the new lower crust also had some contribution to the magma sources. The SIMS zircon U-Pb age from the host porphyry is 229 ± 2 Ma. The Re-Os isochron age for the molybdenite in the deposit is 225 ± 2 Ma closed to zircon U-Pb age of the host porphyry, indicating that Cu-Mo mineralization event occurred in Triassic. Combining the geology-geochemistry of the host porphyry and the regional tectonic evolution, we infer that the subduction processes of Mongol-Okhotsk oceanic slab under the Ergun block led to the formation of the Badaguan porphyry Cu-Mo deposit during the Triassic.

Porphyry copper deposits of the world: database, map, and grade and tonnage models

USGS Publications Warehouse

Singer, Donald A.; Berger, Vladimir Iosifovich; Moring, Barry C.

2005-01-01

Mineral deposit models are important in exploration planning and quantitative resource assessments for two reasons: (1) grades and tonnages among deposit types are significantly different, and (2) many types occur in different geologic settings that can be identified from geologic maps. Mineral deposit models are the keystone in combining the diverse geoscience information on geology, mineral occurrences, geophysics, and geochemistry used in resource assessments and mineral exploration. Too few thoroughly explored mineral deposits are available in most local areas for reliable identification of the important geoscience variables or for robust estimation of undiscovered deposits-thus we need mineral-deposit models. Globally based deposit models allow recognition of important features because the global models demonstrate how common different features are. Well-designed and -constructed deposit models allow geologists to know from observed geologic environments the possible mineral deposit types that might exist, and allow economists to determine the possible economic viability of these resources in the region. Thus, mineral deposit models play the central role in transforming geoscience information to a form useful to policy makers. The foundation of mineral deposit models is information about known deposits-the purpose of this publication is to make this kind of information available in digital form for porphyry copper deposits. This report is an update of an earlier publication about porphyry copper deposits. In this report we have added 84 new porphyry copper deposits and removed 12 deposits. In addition, some errors have been corrected and a number of deposits have had some information, such as grades, tonnages, locations, or ages revised. This publication contains a computer file of information on porphyry copper deposits from around the world. It also presents new grade and tonnage models for porphyry copper deposits and for three subtypes of porphyry copper

Geochemistry of magnetite from porphyry Cu and skarn deposits in the southwestern United States

USGS Publications Warehouse

Nadoll, Patrick; Mauk, Jeffrey L.; LeVeille, Richard A.; Koenig, Alan E.

2015-01-01

A combination of petrographic observations, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and statistical data exploration was used in this study to determine compositional variations in hydrothermal and igneous magnetite from five porphyry Cu–Mo and skarn deposits in the southwestern United States, and igneous magnetite from the unmineralized, granodioritic Inner Zone Batholith, Japan. The most important overall discriminators for the minor and trace element chemistry of magnetite from the investigated porphyry and skarn deposits are Mg, Al, Ti, V, Mn, Co, Zn, and Ga—of these the elements with the highest variance for (I) igneous magnetite are Mg, Al, Ti, V, Mn, Zn, for (II) hydrothermal porphyry magnetite are Mg, Ti, V, Mn, Co, Zn, and for (III) hydrothermal skarn magnetite are Mg, Ti, Mn, Zn, and Ga. Nickel could only be detected at levels above the limit of reporting (LOR) in two igneous magnetites. Equally, Cr could only be detected in one igneous occurrence. Copper, As, Mo, Ag, Au, and Pb have been reported in magnetite by other authors but could not be detected at levels greater than their respective LORs in our samples. Comparison with the chemical signature of igneous magnetite from the barren Inner Zone Batholith, Japan, suggests that V, Mn, Co, and Ga concentrations are relatively depleted in magnetite from the porphyry and skarn deposits. Higher formation conditions in combination with distinct differences between melt and hydrothermal fluid compositions are reflected in Al, Ti, V, and Ga concentrations that are, on average, higher in igneous magnetite than in hydrothermal magnetite (including porphyry and skarn magnetite). Low Ti and V concentrations in combination with high Mn concentrations are characteristic features of magnetite from skarn deposits. High Mg concentrations (<1,000 ppm) are characteristic for magnetite from magnesian skarn and likely reflect extensive fluid/rock interaction. In porphyry deposits

Porphyry Cu-Au mineralization in the Mirkuh Ali Mirza magmatic complex, NW Iran

NASA Astrophysics Data System (ADS)

Maghsoudi, A.; Yazdi, M.; Mehrpartou, M.; Vosoughi, M.; Younesi, S.

2014-01-01

The Mirkuh Ali Mirza Cu-Au porphyry system in East Azerbaijan Province is located on the western part of the Cenozoic Alborz-Azerbaijan volcanic belt. The belt is also an important Cu-Mo-Au metallogenic province in northwestern Iran. The exposed rocks in the study area consist of a volcaniclastic sequence, subvolcanic rocks and intermediate to mafic lava flows of Neogene age. The volcanic rocks show a typical subduction-related magmatic arc geological and geochemical signature, with low concentration of Nb, Ta, and Ti. Mineralization is hosted by Neogene dacitic tuff and porphyritic dacite situated at the intersections of northeast and northwest faults. Field observations, alteration zonation, geochemical haloes and isotopic data of the Mirkuh Ali Mirza magmatic complex show similarities with typical convergent margin Cu-Au porphyry type deposits. The following features confirm the classic model for Cu-Au porphyry systems: (a) close spatial association with high-K calcalkaline to shoshonitic rock related to post-collision extensional setting (b) low grade Cu (0.57%) (c) stockworks as well as disseminated sulfides (c) zonality of the alteration patterns from intense phyllic at the center to outward weak-phyllic, argillic, and propylitic (d) the presence of a pyritic halo (e) accompanied by sheeted veins and low-sulfidation epithermal gold (f) mineralization spatially associated with intersection of structures, (g) genetically related to diorite porphyry stocks at depth (h) geochemical zonation of (Cu ± Au ± Ag ± Bi) → (Cu + Mo ± Bi ± Au ± Pb ± Zn ± As) → (Au + Mo ± Pb ± Zn) → (As + Ag + Sb + Mn + Ba + Pb + Zn + Hg) → Hg from center to outwards (i) The range of sulfur isotopic values is approximately zero (interpreted to have magmatic source) and similar to other subduction-related porphyry Cu deposits.

Age of Supergene oxidation and enrichment in the chilean porphyry copper province

USGS Publications Warehouse

Sillitoe, R.H.; McKee, E.H.

1996-01-01

Twenty-five samples of supergene alunite collected from deeply developed supergene profiles in porphyry copper deposits and prospects between latitudes 20?? and 27?? S in northern Chile yield K/Ar ages ranging from about 34 to 14 Ma. Therefore supergene oxidation and enrichment processes were active from the early Oligocene to the middle Miocene, a minimum of 20 m.y. Supergene activity at individual deposits lasted for at least 0.4 to 6.2 m.y. The early Oligocene supergene activity affected deposits in the Paleocene porphyry copper belt, whereas early and middle Miocene supergene processes are documented in the Early Cretaceous, Paleocene, and late Eocene to early Oligocene porphyry copper belts. Middle Miocene oxidation also affected the oldest epithermal gold-silver deposits in the Maricunga belt farther east. Supergene activity commenced no less than 11 m.y. after generation of each porphyry copper deposit because of the time required to unroof the copper-bearing parts of the system. Supergene activity throughout northern Chile ceased at -14 Ma. The geologic features of deposits and prospects and their morphotectonic positions, present latitudes, and present elevations display no obvious correlations with the supergene chronology. Exploration for major cumulative enrichment blankets should not be carried out either beneath thick sequences of piedmont gravels (?? ignimbrites) of Oligocene through middle Miocene age unless their accumulation is demonstrably late in the documented history of supergene activity, or in porphyry copper provinces, such as those of central Chile and northwestern Argentina, which formed after ??? 14 Ma. The uplift responsible for efficient cumulative copper enrichment is difficult to correlate convincingly with the brief pulses of compressive tectonism postulated for northern Chile and contiguous areas unless their effects were much more prolonged. Intensifying aridity is confirmed as the likely reason for the cessation of supergene

Igneous phenocrystic origin of K-feldspar megacrysts in granitic rocks from the Sierra Nevada batholith

USGS Publications Warehouse

Moore, J.G.; Sisson, T.W.

2008-01-01

Study of four K-feldspar megacrystic granitic plutons and related dikes in the Sierra Nevada composite batholith indicates that the megacrysts are phenocrysts that grew in contact with granitic melt. Growth to megacrystic sizes was due to repeated replenishment of the magma bodies by fresh granitic melt that maintained temperatures above the solidus for extended time periods and that provided components necessary for K-feldspar growth. These intrusions cooled 89-83 Ma, are the youngest in the range, and represent the culminating magmatic phase of the Sierra Nevada batholith. They are the granodiorite of Topaz Lake, the Cathedral Peak Granodiorite, the Mono Creek Granite, the Whitney Granodiorite, the Johnson Granite Porphyry, and the Golden Bear Dike. Megacrysts in these igneous bodies attain 4-10 cm in length. All have sawtooth oscillatory zoning marked by varying concentration of BaO ranging generally from 3.5 to 0.5 wt%. Some of the more pronounced zones begin with resorption and channeling of the underlying zone. Layers of mineral inclusions, principally plagioclase, but also biotite, quartz, hornblende, titanite, and accessory minerals, are parallel to the BaO-delineated zones, are sorted by size along the boundaries, and have their long axes preferentially aligned parallel to the boundaries. These features indicate that the K-feldspar megacrysts grew while surrounded by melt, allowing the inclusion minerals to periodically attach themselves to the faces of the growing crystals. The temperature of growth of titanite included within the K-feldspar megacrysts is estimated by use of a Zr-in-titanite geothermometer. Megacryst-hosted titanite grains all yield temperatures typical of felsic magmas, mainly 735-760 ??C. Titanite grains in the granodiorite hosts marginal to the megacrysts range to lower growth temperatures, in some instances into the subsolidus. The limited range and igneous values of growth temperatures for megacryst-hosted titanite grains support the

Retention of Anionic Species on Granite: Influence of Granite Composition - 12129

DOE Office of Scientific and Technical Information (OSTI.GOV)

Videnska, Katerina; Havlova, Vaclava

Technetium (Tc-99, T{sub 1/2} = 2.1.10{sup 5} yrs) and selenium (Se-79, T{sub 1/2} = 6.5.10{sup 4} yrs) belong among fission products, being produced by fission of nuclear fuel. Both elements can significantly contribute to risk due to their complicated chemistry, long life times, high mobility and prevailing anionic character. Therefore, knowledge of migration behaviour under different conditions can significantly improve input into performance and safety assessment models. Granite is considered as a potential host rock for deep geological disposal of radioactive waste in many countries. Granitic rocks consist usually of quartz, feldspar, plagioclase (main components), mica, chlorite, kaolinite (minor components).more » The main feature of the rock is advection governed transport in fractures, complemented with diffusion process from fracture towards undisturbed rock matrix. The presented work is focused on interaction of anionic species (TcO{sub 4}{sup -}, SeO{sub 4}{sup 2-}, SeO{sub 3}{sup 2-}) with granitic rock. Furthermore, the importance of mineral composition on sorption of anionic species was also studied. The batch sorption experiments were conducted on the crushed granite from Bohemian Massive. Five fractions with defined grain size were used for static batch method. Mineral composition of each granitic fraction was evaluated using X-ray diffraction. The results showed differences in composition of granitic fractions, even though originating from one homogenized material. Sorption experiments showed influence of granite composition on adsorption of both TcO4{sup -} and SeO3{sup 2-} on granitic rock. Generally, Se(IV) showed higher retention than Tc(VII). Se(VI) was not almost sorbed at all. Fe containing minerals are pronounced as a selective Se and Tc sorbent, being reduced on their surface. As micas in granite are usually enriched in Fe, increased sorption of anionic species onto mica enriched fractions can be explained by this reason. On the other

Mine drainage water from the Sar Cheshmeh porphyry copper mine, Kerman, IR Iran.

PubMed

Shahabpour, J; Doorandish, M

2008-06-01

This paper presents the results of a study on stream and mine waters in the area of one of the world largest porphyry copper deposit located in the southeastern Iran, the Sar Cheshmeh porphyry copper mine. Trace metals are present as adsorption on Fe and Mn oxide and hydroxide particles, as sulfate, simple metal ions, and scarcely as adsorption on clay particles and hydrous aluminium oxides. Mean pH decreases and the mean concentration of trace elements, EC and SO4(2-) increases from the maximum discharge period (MXDP) during snow melt run off (May), through the moderate discharge period (MDDP; March and July) to the minimum discharge period (MNDP; September). Water samples have sulfatic character essentially, however, from the MNDP through the MDDP towards the MXDP they show a bicarbonate tendency. This study indicates that the surface waters draining the Sar Cheshmeh open pit have a higher pH and lower concentration of trace metals compared with some other porphyry copper deposits.

Spatial coincidence and similar geochemistry of Late Triassic and Eocene-Oligocene magmatism in the Andes of northern Chile: evidence from the MMH porphyry type Cu-Mo deposit, Chuquicamata District

NASA Astrophysics Data System (ADS)

Zentilli, Marcos; Maksaev, Victor; Boric, Ricardo; Wilson, Jessica

2018-04-01

The MMH porphyry type copper-molybdenum deposit in northern Chile is the newest mine in the Chuquicamata District, one of largest copper concentrations on Earth. Mineralized Eocene-Oligocene porphyry intrusions are hosted by essentially barren Triassic granodiorites. Despite a century of exploitation, geologists still have problems in the mine distinguishing the Triassic granodiorite from the most important ore-carrying Eocene porphyries in the district. To resolve the problem, internally consistent high-quality geochemical analyses of the Triassic and Tertiary intrusives were carried out: explaining the confusion, they show that the rock units in question are nearly identical in composition and thus respond equally to hydrothermal alteration. In detail, the only difference in terms of chemical composition is that the main Eocene-Oligocene porphyries carry relatively less Fe and Ni. Unexpectedly, the mineralized Eocene-Oligocene porphyries have consistently less U and Th than other Tertiary intrusions in the district, a characteristic that may be valuable in exploration. The supergiant copper-molybdenum deposits in the Central Andes were formed within a narrow interval between 45 and 31 Ma, close to 7% of the 200 My duration of "Andean" magmatism, which resulted from subduction of oceanic lithosphere under South America since the Jurassic. Although recent work has shown that subduction was active on the margin since Paleozoic times, pre-Andean (pre-Jurassic) "Gondwanan" magmatism is often described as being very different, having involved crustal melting and the generation of massive peraluminous rhyolites and granites. This study shows that the indistinguishable Late Triassic and Eocene-Oligocene intrusions occupy the same narrow NS geographic belt in northern Chile. If it is accepted that magma character may determine the potential to generate economic Cu-Mo deposits, then Late Triassic volcano-plutonic centres in the same location in the South American margin

Late Carboniferous porphyry copper mineralization at La Voluntad, Neuquén, Argentina: Constraints from Re-Os molybdenite dating

NASA Astrophysics Data System (ADS)

Garrido, Mirta; Barra, Fernando; Domínguez, Eduardo; Ruiz, Joaquin; Valencia, Victor A.

2008-07-01

The La Voluntad porphyry Cu-Mo deposit in Neuquén, Argentina, is one of several poorly known porphyry-type deposits of Paleozoic to Early Jurassic age in the central and southern Andes. Mineralization at La Voluntad is related to a tonalite porphyry from the Chachil Plutonic Complex that intruded metasedimentary units of the Piedra Santa Complex. Five new Re-Os molybdenite ages from four samples representing three different vein types (i.e., quartz-molybdenite, quartz-sericite-molybdenite and quartz-sericite-molybdenite ± chalcopyrite-pyrite) are identical within error and were formed between ~312 to ~316 Ma. Rhenium and Os concentrations range between 34 to 183 ppm and 112 to 599 ppb, respectively. The new Re-Os ages indicate that the main mineralization event at La Voluntad, associated to sericitic alteration, was emplaced during a time span of 1.7 ± 3.2 Ma and that the deposit is Carboniferous in age, not Permian as previously thought. La Voluntad is the oldest porphyry copper deposit so far recognized in the Andes and indicates the presence of an active magmatic arc, with associated porphyry style mineralization, at the proto-Pacific margin of Gondwana during the Early Pennsylvanian.

The origin of Cu/Au ratios in porphyry-type ore deposits.

PubMed

Halter, Werner E; Pettke, Thomas; Heinrich, Christoph A

2002-06-07

Microanalysis of major and trace elements in sulfide and silicate melt inclusions by laser-ablation inductively coupled plasma mass spectrometry indicates a direct link between a magmatic sulfide liquid and the composition of porphyry-type ore deposits. Copper (Cu), gold (Au), and iron (Fe) are first concentrated in a sulfide melt during magmatic evolution and then released to an ore-forming hydrothermal fluid exsolved late in the history of a magma chamber. The composition of sulfide liquids depends on the initial composition and source of the magma, but it also changes during the evolution of the magma in the crust. Magmatic sulfide melts may exert the dominant direct control on the economic metal ratios of porphyry-type ore deposits.

The plutonic-volcanic connection in porphyry copper deposits: Evidence from zircon geochemistry and high-precision CA-ID-TIMS geochronology

NASA Astrophysics Data System (ADS)

Buret, Y.; Von Quadt, A.; Wotzlaw, J. F.; Heinrich, C. A.

2016-12-01

Porphyry Cu deposits represent the interface between plutonic and volcanic domains of upper crustal magmatic systems. These deposits are typically composed of multiple porphyritic intrusions which constrain the duration of ore formation to a maximum of several 104 years [1] and are commonly intruded into the base of volcanoes. The relationship between volcanic activity and porphyry stocks is often difficult to establish, as they are rarely exposed together unless later faulting and/or tilting occurred [2]. In order to investigate the relationships between extrusive magmatism and porphyry Cu formation we compare zircon petrochronology from late stage volcanic units with the nearby world class Bajo de la Alumbrera porphyry Cu deposit, from the Late Miocene Farallón Negro Volcanic Complex (FNVC) in Northwest Argentina. In this study we texturally characterise zircon crystals by CL-imaging prior to obtaining in-situ geochemical and geochronological information by LA-ICP-MS. Analysed zircon grains were then extracted and analysed by high precision CA-ID-TIMS. This approach has the two-fold benefit of screening for inherited cores, and obtaining texturally defined geochemical information, prior to dissolution of the zircon crystal for CA-ID-TIMS analysis. We use this information to establish temporal and geochemical links between studied volcanic and porphyry units in the FNVC. The results of this study suggest a close temporal and genetic link between the Bajo de la Alumbrera porphyry Cu deposit and the late stage volcanism at the FNVC. Voluminous explosive volcanism immediately following porphyry formation has important implications for the thermal and rheological state of the magma that is parental to the porphyries and fed the eruption. Further work investigating the geochemistry of other accessory and major minerals could shed further light on the evolution of the magmatic body prior to eruption/ emplacement. References: [1] Buret et al. (2016) EPSL 450:120-131; [2

Hydrothermal alteration mapping using ASTER data in Baogutu porphyry deposit, China

NASA Astrophysics Data System (ADS)

Li, Q.; Zhang, B.; Lu, L.; Lin, Q.

2014-03-01

Remote sensing plays an important role in mineral exploration. One of its proven applications is extracting host-rock lithology and alteration zones that are related to porphyry copper deposits. An Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) was used to map the Baogutu porphyry deposit alteration area. A circular alteration mineral zoning pattern was clearly observed in the classification result of potassic, phyllic, argillic, propylitic zones. The potassic is characterized by biotite and anhydrite with an absorption feature centered at 1.94 and 2.1um. The phyllic zone is characterized by illite and sericite that indicates an intense Al-OH absorption feature centered at 2.20um. The narrower argillic zone including kaolinite and alunite displays a secondary Al-OH absorption feature at 2.17 um. The mineral assemblages of the outer propylitic zone are epidote, chlorite and calcite that exhibit absorption features at 2.335um.The performance of Principal Component Analysis(PCA), Minimum Noise Fraction (MNF), band ratio(BR) and Constrained Energy Minimization(CEM) has been evaluated. These techniques identified new prospects of porphyry copper mineralization in the study areas. These results indicate that ASTER is a powerful tool in the initial steps of mineral exploration.

Magma Fertility is the First-Order Factor for the Formation of Porphyry Cu±Au Deposits

NASA Astrophysics Data System (ADS)

Park, J. W.; Campbell, I. H.; Malaviarachchi, S. P. K.; Cocker, H.; Nakamura, E.; Kay, S. M.

2017-12-01

Magma fertility, the metal abundance in magma, has been considered to be one of the key factors for the formation of porphyry Cu±Au deposits. In this study we provide clear evidence to support the hypothesis that the platinum group element (PGE) can be used to distinguish barren from ore-bearing Cu±Au felsic suites. We determined the PGE contents of three barren volcanic and subvolcanic suites from Argentina and Japan, and compare the results with two porphyry Cu-bearing subvolcanic suites from Chile and two porphyry Cu-Au-bearing suites from Australia. The barren suites are significantly depleted in PGE abundances by the time of fluid exsolution, which is attributed to early sulfide saturation at mid to lower crust depths or assimilation of chalcophile element-poor crustal materials. Barren magma, produced by melting continental crust, may have been initially deficient in chalcophile elements. In contrast, the Cu±Au ore-bearing suites contain at least an order of magnitude higher PGE contents than those of the barren suites by the time of fluid saturation. They are characterized by late sulfide saturation in a shallow magma chamber, which allows the chalcophile elements to concentrate in the fractionating magma from which they are sequestered by ore-forming fluids. We suggest the Pd/MgO and Pd/Pt ratios of igneous rocks can be used as magma fertility indicators, and to distinguish between barren, porphyry Cu and porphyry Cu-Au magmatic systems.

Highly differentiated magmas linked with polymetallic mineralization: A case study from the Cuihongshan granitic intrusions, Lesser Xing'an Range, NE China

NASA Astrophysics Data System (ADS)

Fei, Xianghui; Zhang, Zhaochong; Cheng, Zhiguo; Santosh, M.; Jin, Ziliang; Wen, Bingbing; Li, Zixi; Xu, Lijuan

2018-03-01

The genetic link between granitoids and polymetallic skarn mineralization has remained equivocal. The Cuihongshan skarn-porphyry W-Mo-Pb-Zn-(Fe-Cu) deposit in the eastern part of the Central Asian Orogenic Belt provides a unique example to address this issue. The major rock types in the mine area are Early Paleozoic intrusions composed of biotite syenogranite and biotite porphyritic granite and Early Mesozoic intrusions represented by porphyritic quartz monzonite, biotite monzogranite, and porphyritic granite. The diagnostic mineralogical and geochemical features indicate that the rocks belong to A2-type granites. The Early Paleozoic suite shows zircon U-Pb ages of 501 Ma, and εHf(t) values of - 4.4 to + 2.7 and + 2.4 to + 7.6, respectively. In combination with their coherent geochemical trends, these rocks are inferred to be products of in-situ differentiation. Although the Mesozoic suite shows crystallization ages of 194-196 Ma, εHf(t) values are in the range of - 2.5 to + 7.5 for the porphyritic quartz monzonite, the - 1.8 to + 4.5 values for the monzogranite and the + 2.3 to + 8.0 range for the porphyritic granite. The porphyritic quartz monzonite displays distinct mineral assemblage and shows significant compositional gap with the other two lithofacies. In contrast, the monzogranite and porphyritic granite have similar geochemical features, and are thus inferred to be co-magmatic. Considering the high SiO2 contents, variable εHf(t) (- 4.4 to + 8.0) and εNd(t) values (- 8.4 to + 0.28) for the two suites, we infer that both episodes of granitoid magmatism resulted from partial melting of crustal materials with a mixed source containing varying proportions of juvenile and Precambrian crustal components. The Early Mesozoic porphyritic granite shows a highly evolved F-rich geochemical affinity, and experienced magma-fluid interaction. Cassiterite from the calcic skarn and the magnesian skarn that coexists with magnetite orebodies shows a mean U-Pb age of 195

Recognition of the geologic framework of porphyry deposits on ERTS-1 imagery

NASA Technical Reports Server (NTRS)

Wilson, J. C. (Principal Investigator)

1973-01-01

The author has identified the following significant results. Photointerpretation methods have been most successfully applied in the less vegetated test sites where several previously unknown geologic features have been recognized and known ones extended. Northwest mid-Tertiary faults in the ELY, Nevada area are observed to offset north-trending ranges and abruptly terminate older Mesozoic structures. In the Ray, Arizona area the observed patterns of fault and fracture systems appear to be related to the locations of known porphyry copper deposits. In the Tanacross, Alaska area a number of regional circular features observed may represent near surface intrusions and, therefore, permissive environments for copper porphyries.

Recognition of the geologic framework of porphyry deposits on ERTS-1 imagery. [copper/molybdenum porphyrys

NASA Technical Reports Server (NTRS)

Wilson, J. C. (Principal Investigator)

1974-01-01

The author has identified the following significant results. Three major tectonic provinces have been mapped by geologic photointerpretation of ERTS-1 imagery over the Ok Tedi test site. These areas can be characterized as follows: (1) A broad area of low relief and mature topography suggesting a history of relative tectonic stability. (2) A narrow belt of moderate to high relief, broad open folds and prominent linear features. The Mount Fubilan-type porphyry copper deposits and recent volcanic effusive centers occur in this province. (3) A heterogeneous zone of high relief and high drainage density suggestive of relative structural complexity.

Model of the porphyry copper and polymetallic vein family of deposits - Applications in Slovakia, Hungary, and Romania

USGS Publications Warehouse

Drew, L.J.

2003-01-01

A tectonic model useful in estimating the occurrence of undiscovered porphyry copper and polymetallic vein systems has been developed. This model is based on the manner in which magmatic and hydrothermal fluids flow and are trapped in fault systems as far-field stress is released in tectonic strain features above subducting plates (e.g. strike-slip fault systems). The structural traps include preferred locations for stock emplacement and tensional-shear fault meshes within the step-overs that localize porphyry- and vein-style deposits. The application of the model is illustrated for the porphyry copper and polymetallic vein deposits in the Central Slovakian Volcanic Field, Slovakia; the Ma??tra Mountains, Hungary; and the Apuseni Mountains, Romania.

Petrogenesis of the Pulang porphyry complex, southwestern China: Implications for porphyry copper metallogenesis and subduction of the Paleo-Tethys Oceanic lithosphere

NASA Astrophysics Data System (ADS)

Wang, Peng; Dong, Guo-Chen; Zhao, Guo-Chun; Han, Yi-Gui; Li, Yong-Ping

2018-04-01

The Pulang complex is located in the southern segment of the Yidun Arc in the Sanjiang Tethys belt, southwestern China. It is composed of quartz diorite, quartz monzonite and granodiorite porphyries, and hosts the super-large Pulang deposit. This study presents new U-Pb geochronological, major-trace elemental and Sr-Nd-Hf isotopic data to constrain the petrogenesis of the Pulang complex and to evaluate its significances for porphyric mineralization and tectonic evolution of the Paleo-Tethys Ocean. The zircon U-Pb dating yields ages ranging from 208 Ma to 214 Ma. Geochemically, the Pulang complex has high Sr and MgO contents, and high Sr/Y and La/Yb ratios, but low Yb and Y contents, displaying adakitic affinities. However, it has moderate Sr/Y and La/Yb ratios, and high Rb contents (32 to 202 ppm). The Pulang samples plot into the transitional field between adakites and normal arc rocks, differing from typical adakites. It is attributed to the assimilation of 10-15% crustal components. The zircon εHf(t) (-4.6 to -2.5), whole-rock (87Sr/86Sr)i (0.7052 to 0.7102), εNd(t) (-0.62 to 2.12) values and adakitic affinities suggest that the Pulang complex was derived from a basaltic slab-melt source and reacted with peridotite during ascending through an enriched asthenospheric mantle wedge. The basaltic slab-melts likely resulted from the westward subduction of the Ganzi-Litang oceanic plate (a branch of the Paleo-Tethys). As far as the metallogenesis concerned, three factors in mineralization are proposed in this paper. The country rock, quartz diorite porphyry, has higher Cu contents than the mantle (average 30 ppm), suggesting that ore-forming magma was derived from a Cu-enriched source, which is a crucial contribution to the late mineralization to form the super-large Pulang deposit. In addition, the barren quartz diorite, granodiorite, and ore-bearing quartz monzonite porphyries are all characterized by high oxygen fugacity, which is another important factor for the

Concealed basalt-matrix diatremes with Cu-Au-Ag-(Mo)-mineralized xenoliths, Santa Cruz Porphyry Cu-(Mo) System, Pinal County, Arizona

USGS Publications Warehouse

Vikre, Peter; Graybeal, Frederick T.; Koutz, Fleetwood R.

2014-01-01

The Santa Cruz porphyry Cu-(Mo) system near Casa Grande, Arizona, includes the Sacaton mine deposits and at least five other concealed, mineralized fault blocks with an estimated minimum resource of 1.5 Gt @ 0.6% Cu. The Late Cretaceous-Paleocene system has been dismembered and rotated by Tertiary extension, partially eroded, and covered by Tertiary-Quaternary basin-fill deposits. The mine and mineralized fault blocks, which form an 11 km (~7 miles) by 1.6 km (~1 mile) NE-SW–trending alignment, represent either pieces of one large deposit, several deposits, or pieces of several deposits. The southwestern part of the known system is penetrated by three or more diatremes that consist of heterolithic breccia pipes with basalt and clastic matrices, and subannular tuff ring and maar-fill sedimentary deposits associated with vents. The tephra and maar-fill deposits, which are covered by ~485 to 910 m (~1,600–3,000 ft) of basin fill, lie on a mid-Tertiary erosion surface of Middle Proterozoic granite and Late Cretaceous porphyry, which compose most xenoliths in pipes and are the host rocks of the system. Some igneous xenoliths in the pipes contain bornite-chalcopyrite-covellite assemblages with hypogene grades >1 wt % Cu, 0.01 ounces per ton (oz/t) Au, 0.5 oz/t Ag, and small amounts of Mo (<0.01 wt %). These xenoliths were derived from mineralized rocks that have not been encountered in drill holes, and attest to additional, possibly higher-grade deposits within or subjacent to the known system.The geometry, stratigraphy, and temporal relationships of pipes and tephras, interpreted from drill hole spacing and intercepts, multigenerational breccias and matrices, reequilibrated and partially decomposed sulfide-oxide mineral assemblages, melted xenoliths, and breccia matrix compositions show that the diatremes formed in repeated stages. Initial pulses of basalt magma fractured granite, porphyry, and other crustal rocks during intrusion, transported multi-sized fragments

A tectonic model for the spatial occurrence of porphyry copper and polymetallic vein deposits - applications to Central Europe

USGS Publications Warehouse

Drew, Lawrence J.

2006-01-01

A structural-tectonic model, which was developed to assess the occurrence of undiscovered porphyry copper deposits and associated polymetallic vein systems for the Matra Mountains, Hungary, has been expanded here and applied to other parts of central Europe. The model explains how granitoid stocks are emplaced and hydrothermal fluids flow within local strain features (duplexes) within strike-slip fault systems that develop in continental crust above subducting plates. Areas of extension that lack shear at the corners and along the edges of the fault duplexes are structural traps for the granitoid stocks associated with porphyry copper deposits. By contrast, polymetallic vein deposits are emplaced where shear and extension are prevalent in the interior of the duplexes. This model was applied to the Late Cretaceous-age porphyry copper and polymetallic vein deposits in the Banat-Timok-Srednogorie region of Romania-Serbia-Bulgaria and the middle Miocene-age deposits in Romania and Slovakia. In the first area, porphyry copper deposits are most commonly located at the corners, and occasionally along the edges, of strike-slip fault duplexes, and the few polymetallic vein deposits identified are located at interior sites of the duplexes. In the second area, the model accounts for the preferred sites of porphyry copper and polymetallic vein deposits in the Apuseni Mountains (Romania) and central Slovakian volcanic field (Slovakia).

Magnetotelluric survey to characterize the Sunnyside porphyry copper system in the Patagonia Mountains, Arizona

USGS Publications Warehouse

Rodriguez, Brian D.; Sampson, Jay A.

2010-01-01

The Sunnyside porphyry copper system is part of the concealed San Rafael Valley porphyry system located in the Patagonia Mountains of Arizona. The U.S. Geological Survey is conducting a series of multidisciplinary studies as part of the Assessment Techniques for Concealed Mineral Resources project. To help characterize the size and resistivity of the mineralized area beneath overburden, a regional east-west magnetotelluric sounding profile was acquired. This is a data release report of the magnetotelluric sounding data collected along the east-west profile; no interpretation of the data is included.

Geological Model of Supercritical Geothermal Reservoir on the Top of the Magma Chamber

NASA Astrophysics Data System (ADS)

Tsuchiya, N.

2017-12-01

We are conducting supercritical geothermal project, and deep drilling project named as "JBBP: Japan Beyond Brittle Project" The temperatures of geothermal fields operating in Japan range from 200 to 300 °C (average 250 °C), and the depths range from 1000 to 2000 m (average 1500 m). In conventional geothermal reservoirs, the mechanical behavior of the rocks is presumed to be brittle, and convection of the hydrothermal fluid through existing network is the main method of circulation in the reservoir. In order to minimize induced seismicity, a rock mass that is "beyond brittle" is one possible candidate, because the rock mechanics of "beyond brittle" material is one of plastic deformation rather than brittle failure. To understand the geological model of a supercritical geothermal reservoir, granite-porphyry system, which had been formed in subduction zone, was investigated as a natural analog of the supercritical geothermal energy system. Quartz veins, hydrothermal breccia veins, and glassy veins are observed in a granitic body. The glassy veins formed at 500-550 °C under lithostatic pressures, and then pressures dropped drastically. The solubility of silica also dropped, resulting in formation of quartz veins under a hydrostatic pressure regime. Connections between the lithostatic and hydrostatic pressure regimes were key to the formation of the hydrothermal breccia veins, and the granite-porphyry system provides useful information for creation of fracture clouds in supercritical geothermal reservoirs. A granite-porphyry system, associated with hydrothermal activity and mineralization, provides a suitable natural analog for studying a deep-seated geothermal reservoir where stockwork fracture systems are created in the presence of supercritical geothermal fluids. I describe fracture networks and their formation mechanisms using petrology and fluid inclusion studies in order to understand this "beyond brittle" supercritical geothermal reservoir, and a geological

Petrography, geochemistry and geochronology of the host porphyries and associated alteration at the Tuwu Cu deposit, NW China: a case for increased depositional efficiency by reaction with mafic hostrock?

NASA Astrophysics Data System (ADS)

Shen, Ping; Pan, Hongdi; Zhou, Taofa; Wang, Jingbin

2014-08-01

Tuwu is the largest porphyry copper deposit discovered in the Eastern Tianshan Mountains, Xinjiang, China. A newly recognized volcanic complex in the Early Carboniferous Qi'eshan Group at Tuwu consists of basalt, andesite, and diorite porphyry. The plagiogranite porphyry was emplaced into this complex at 332.8±2.5 Ma (U-Pb zircon SIMS determination). Whole-rock element geochemistry shows that the volcanic complex and plagiogranite porphyry formed in the same island arc, although the complex was derived by partial melting of the mantle wedge and the plagiogranite porphyry by partial melting of a subducting slab. The diorite and the plagiogranite porphyries have both been subjected to intense hydrothermal alteration and associated mineralization, but the productive porphyry is the plagiogranite porphyry. Three alteration and mineralization stages, including pre-, syn- and post-ore stages, have been recognized. The pre-ore stage formed a barren propylitic alteration which is widespread in the volcanic complex. The syn-ore stage is divided into three sub-stages: Stage 1 is characterized by potassic alteration with chalcopyrite + bornite + chalcocite; Stage 2 is marked by chlorite-sericite-albite alteration with chalcopyrite ± pyrite ± bornite; Stage 3 is represented by phyllic alteration with chalcopyrite + pyrite ± molybdenite. The post-ore stage produced a barren argillic alteration limited to the diorite porphyry. A specific feature of the Tuwu deposit is that the productive porphyry was emplaced into a very mafic package, and reaction of the resulting fluids with the ferrous iron-rich hostrocks was a likely reason that Tuwu is the largest porphyry in the district.

Magma mixing in granite petrogenesis: Insights from biotite inclusions in quartz and feldspar of Mesozoic granites from South China

NASA Astrophysics Data System (ADS)

Gao, Peng; Zhao, Zi-Fu; Zheng, Yong-Fei

2016-06-01

Magma mixing is a common process in granite petrogenesis. The major element composition of biotites in granites is primarily controlled by the composition of magmas from which they crystallized. Biotite grains enclosed in quartz and feldspars of granites are naturally protected by their host minerals, so that their compositions are likely original and can potentially be used to track the magma mixing. This is illustrated by a combined study of matrix and inclusion biotites from Mesozoic granites in the Nanling Range, South China. Three granite samples have been used in this study: one two-mica granite and two biotite granites. The biotites of different occurrences in the two-mica granite have no compositional distinctions. Biotites in the two-mica granite have higher Al2O3 and lower MgO than those in the biotite granites. The former is consistent with biotites from typical S-type granites of metasedimentary origin. In contrast, biotites from the biotite granites can be categorized into different groups based on their paragenetic minerals and geochemical compositions. They have relatively low aluminous saturation indices but higher Mg numbers, falling in the transitional field between typical S- and I-type granites. In addition, there are two contrasting zircon populations with nearly identical U-Pb ages in the biotite granites. One shows clearly oscillatory zonings in CL images, whereas the other is totally dark and often overgrew on the former one. The zircons with oscillatory zonings have higher δ18O values than the dark ones, indicating their growth from two compositionally different magmas, respectively, with different sources. An integrated interpretation of all these data indicates that mixing of two different magmas was responsible for the petrogenesis of biotite granites. Therefore, the study of biotite inclusions provides insights into the magma mixing in granite petrogenesis.

Relationship between porphyry copper occurrences, crustal preservation levels, and amount of exploration in magmatic belts of the Central Tethys region

USGS Publications Warehouse

Zürcher, Lukas; Bookstrom, Arthur A.; Hammarstrom, Jane M.; Mars, John; Ludington, Stephen; Zientek, Michael L.; Dunlap, Pamela; Wallis, John C.

2014-01-01

A probabilistic assessment of undiscovered resources in porphyry copper deposits in the Central Tethys region of Turkey, the Caucasus, Iran, western Pakistan, and southern Afghanistan was conducted as part of a U.S.G.S. global mineral resource assessment. The purpose was to delineate areas as permissive tracts for the occurrence of porphyry Cu-Mo and Cu-Au deposits, and to provide estimates of amounts of Cu, Mo, and Au likely to be contained in undiscovered porphyry deposits (Zürcher et al., 2013; Zürcher et al., in review). Tectonic, geologic, geochemical, geochronologic, and ore deposits data compiled and analyzed for this assessment show that magmatism in the region can be rationalized in terms of fundamental plate tectonic principles, including mantle-involved post-subduction processes. However, uplift, erosion, subsidence, and burial of porphyry copper deposits also played an important role in shaping the observed metallogenic patterns.

Porphyry copper assessment of British Columbia and Yukon Territory, Canada: Chapter C in Global mineral resource assessment

USGS Publications Warehouse

Mihalasky, Mark J.; Bookstrom, Arthur A.; Frost, Thomas P.; Ludington, Steve

2011-01-01

Western Canada has been thoroughly explored for porphyry copper deposits. The total estimated copper contained in known deposits is about 66.8 Mt (based on 2010 data), as compared to a 49 Mt mean of estimated copper in undiscovered deposits and a 34 Mt median of estimated copper in undiscovered deposits. The copper contained in known porphyry copper deposits represents about 58 percent of the total of known and undiscovered porphyry copper deposits (based on mean values). About 86 percent of the increase in estimated copper resources between 1993 and 2009 resulted from the discovery of extensions to known deposits. Nevertheless, exploration for undiscovered deposits continues, especially in and around significant prospects and in parts of permissive tracts that are mostly hidden beneath younger volcanic, sedimentary, or vegetated surficial cover.

Multivariate analyses of Erzgebirge granite and rhyolite composition: Implications for classification of granites and their genetic relations

USGS Publications Warehouse

Forster, H.-J.; Davis, J.C.; Tischendorf, G.; Seltmann, R.

1999-01-01

High-precision major, minor and trace element analyses for 44 elements have been made of 329 Late Variscan granitic and rhyolitic rocks from the Erzgebirge metallogenic province of Germany. The intrusive histories of some of these granites are not completely understood and exposures of rock are not adequate to resolve relationships between what apparently are different plutons. Therefore, it is necessary to turn to chemical analyses to decipher the evolution of the plutons and their relationships. A new classification of Erzgebirge plutons into five major groups of granites, based on petrologic interpretations of geochemical and mineralogical relationships (low-F biotite granites; low-F two-mica granites; high-F, high-P2O5 Li-mica granites; high-F, low-P2O5 Li-mica granites; high-F, low-P2O5 biotite granites) was tested by multivariate techniques. Canonical analyses of major elements, minor elements, trace elements and ratio variables all distinguish the groups with differing amounts of success. Univariate ANOVA's, in combination with forward-stepwise and backward-elimination canonical analyses, were used to select ten variables which were most effective in distinguishing groups. In a biplot, groups form distinct clusters roughly arranged along a quadratic path. Within groups, individual plutons tend to be arranged in patterns possibly reflecting granitic evolution. Canonical functions were used to classify samples of rhyolites of unknown association into the five groups. Another canonical analysis was based on ten elements traditionally used in petrology and which were important in the new classification of granites. Their biplot pattern is similar to that from statistically chosen variables but less effective at distinguishing the five groups of granites. This study shows that multivariate statistical techniques can provide significant insight into problems of granitic petrogenesis and may be superior to conventional procedures for petrological interpretation.

Emanation of radon from household granite.

PubMed

Kitto, Michael E; Haines, Douglas K; Arauzo, Hernando Diaz

2009-04-01

Emanation of radon (222Rn) from granite used for countertops and mantels was measured with continuous and integrating radon monitors. Each of the 24 granite samples emitted a measurable amount of radon. Of the two analytical methods that utilized electret-based detectors, one measured the flux of radon from the granite surfaces, and the other one measured radon levels in a glass jar containing granite cores. Additional methods that were applied utilized alpha-scintillation cells and a continuous radon monitor. Measured radon flux from the granites ranged from 2 to 310 mBq m-2 s-1, with most granites emitting <20 mBq m-2 s-1. Emanation of radon from granites encapsulated in airtight containers produced equilibrium concentrations ranging from <0.01 to 11 Bq kg-1 when alpha-scintillation cells were used, and from <0.01 to 4.0 Bq kg-1 when the continuous radon monitor was used.

Geochronology and geochemistry of the granitoids and ore - forming age in the Xiaoyao tungsten polymetallic skarn deposit in the Jiangnan Massif tungsten belt, China: Implications for their petrogenesis, geodynamic setting, and mineralization

NASA Astrophysics Data System (ADS)

Su, Qiangwei; Mao, Jingwen; Wu, Shenghua; Zhang, Zhaochong; Xu, Shengfa

2018-01-01

The Xiaoyao tungsten polymetallic skarn deposit in the eastern Jiangnan Massif of Yangtze Block is located at the contact between a granodiorite pluton and Sinian-Cambrian limestone. The intrusions in the tungsten-rich district comprise the Xiaoyao and other granodiorite plutons and granite porphyry dikes. The age determinations by LA-ICP-MS U-Pb dating of zircons indicate that the granodiorite formed at 149.4 ± 1.1 Ma, whereas the granite porphyry was emplaced at 133.2 ± 0.7 Ma. Re-Os dating of molybdenite from the skarn orebodies yielded a weighted average age of 148.7 ± 2.3 Ma (n = 5). These ages indicate that the tungsten mineralization is temporally related to the granodiorite. The granodiorites are metaluminous (A/CNK = 0.86-0.98) and in the high-K calc-alkaline series. They contain hornblende and have a negative correlation between P2O5 and SiO2, indicating that they are typical I-type intrusions. The granite porphyries exhibit high alkali contents (Na2O + K2O = 7.97-9.53%), elevated FeOT/(FeOT + MgO) ratios (0.83-0.94), high concentrations of Zr, Nb, Ce, and Y, and high Zr saturation temperatures (average of 812 °C); thus, they are geochemically similar to A-type intrusions. The initial 87Sr/86Sr and εNd(t) values range respectively from 0.7074 to 0.7083 and from - 7.9 to - 1.3 for the granodiorite, and from 0.7008 to 0.7083 and from - 6.3 to - 4.7 for the granite porphyry. In addition, two-stage Nd model ages (T2DM) of 1.0-1.6 Ga for the granodiorite and 1.3-1.4 Ga for the granite porphyry indicate that the Proterozoic crustal rocks of the Shangxi Group could have contributed to the Xiaoyao magmas. The rhenium contents of the molybdenite grains vary from 32 to 136 ppm, suggesting that the molybdenum was derived mainly from a mixture of mantle and crustal sources. Based on the new geochemical data and regional geological investigations, we propose that the Late Jurassic mineralization-related I-type granodiorite was derived from the Neoproterozoic

Gold paragenesis and chemistry at Batu Hijau, Indoneisa: implications for gold-rich porphyry copper deposits

NASA Astrophysics Data System (ADS)

Arif, J.; Baker, T.

2004-10-01

Gold is an important by-product in many porphyry-type deposits but the distribution and chemistry of gold in such systems remains poorly understood. Here we report the results of petrographic, electron microprobe, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and flotation test studies of gold and associated copper sulfides within a paragenetic framework from the world-class Batu Hijau (914 mt @ 0.53% Cu, 0.40 g/t Au) porphyry copper gold deposit, Indonesia. Unlike many other porphyry copper gold deposits, early copper minerals (bornite digenite chalcocite) are well preserved at Batu Hijau and the chalcopyrite pyrite overprint is less developed. Hence, it provides an excellent opportunity to study the entire gold paragenesis of the porphyry system. In 105 polished thin sections, 699 native gold grains were identified. Almost all of the native gold grains occurred either within quartz veins, attached to sulfide, or as free gold along quartz or silicate grain boundaries. The native gold grains are dominantly round in shape and mostly 1 12 μm in size. The majority of gold was deposited during the formation of early ‘A’ veins and is dominantly associated with bornite rather than chalcopyrite. The petrographic and LA-ICP-MS study results indicate that in bornite-rich ores gold mostly occurs within copper sulfide grains as invisible gold (i.e., within the sulfide structure) or as native gold grains. In chalcopyrite-rich ores gold mostly occurs as native gold grains with lesser invisible gold. Petrographic observations also indicate a higher proportion of free gold (native gold not attached to any sulfide) in chalcopyrite-rich ores compared to bornite rich ores. The pattern of free gold distribution appears to correlate with the flotation test data, where the average gold recovery value from chalcopyrite-rich ores is consistently lower than bornite-rich ores. Our data suggest that porphyry copper-gold deposits with chalcopyrite-rich ores

Porphyry copper assessment of northeast Asia: Far East Russia and northeasternmost China: Chapter W in Global mineral resource assessment

USGS Publications Warehouse

Mihalasky, Mark J.; Ludington, Stephen; Alexeiev, Dmitriy V.; Frost, Thomas P.; Light, Thomas D.; Briggs, Deborah A.; Hammarstrom, Jane M.; Wallis, John C.; Bookstrom, Arthur A.; Panteleyev, Andre

2015-01-01

The database of known deposits, significant prospects, and prospects includes an inventory of mineral resources in two known porphyry copper deposits, as well as key characteristics derived from available exploration reports for 70 significant porphyry copper prospects and 86 other prospects. Resource and exploration and development activity are updated with information current through February 2013.

The El Teniente porphyry Cu-Mo deposit from a hydrothermal rutile perspective

NASA Astrophysics Data System (ADS)

Rabbia, Osvaldo M.; Hernández, Laura B.; French, David H.; King, Robert W.; Ayers, John C.

2009-11-01

Mineralogical, textural, and chemical analyses (EPMA and PIXE) of hydrothermal rutile in the El Teniente porphyry Cu-Mo deposit help to better constrain ore formation processes. Rutile formed from igneous Ti-rich phases (sphene, biotite, Ti-magnetite, and ilmenite) by re-equilibration and/or breakdown under hydrothermal conditions at temperatures ranging between 400°C and 700°C. Most rutile nucleate and grow at the original textural position of its Ti-rich igneous parent mineral phase. The distribution of Mo content in rutile indicates that low-temperature (˜400-550°C), Mo-poor rutile (5.4 ± 1.1 ppm) is dominantly in the Mo-rich mafic wallrocks (high-grade ore), while high-temperature (˜550-700°C), Mo-rich rutile (186 ± 20 ppm) is found in the Mo-poor felsic porphyries (low-grade ore). Rutile from late dacite ring dikes is a notable exception to this distribution pattern. The Sb content in rutile from the high-temperature potassic core of the deposit to its low-temperature propylitic fringe remains relatively constant (35 ± 3 ppm). Temperature and Mo content of the hydrothermal fluids in addition to Mo/Ti ratio, modal abundance and stability of Ti-rich parental phases are key factors constraining Mo content and provenance in high-temperature (≥550°C) rutile. The initial Mo content of parent mineral phases is controlled by melt composition and oxygen fugacity as well as timing and efficiency of fluid-melt separation. Enhanced reduction of SO2-rich fluids and sulfide deposition in the Fe-rich mafic wallrocks influences the low-temperature (≤550°C) rutile chemistry. The data are consistent with a model of fluid circulation of hot (>550°C), oxidized (ƒO2 ≥ NNO + 1.3), SO2-rich and Mo-bearing fluids, likely exsolved from deeper crystallizing parts of the porphyry system and fluxed through the upper dacite porphyries and related structures, with metal deposition dominantly in the Fe-rich mafic wallrocks.

Porphyry copper deposits of the world: database, maps, and preliminary analysis

USGS Publications Warehouse

Singer, Donald A.; Berger, Vladimir I.; Moring, Barry C.

2002-01-01

Mineral deposit models are important in exploration planning and quantitative resource assessments for two reasons: (1) grades and tonnages among deposit types are significantly different, and (2) many types occur in different geologic settings that can be identified from geologic maps. Mineral deposit models are the keystone in combining the diverse geoscience information on geology, mineral occurrences, geophysics, and geochemistry used in resource assessments and mineral exploration. Far too few thoroughly explored mineral deposits are available in most local areas for reliable identification of the important geoscience variables or for robust estimation of undiscovered deposits—thus we need mineral-deposit models. Globally based deposit models, such as those presented here, allow recognition of important features because the global models demonstrate how common different features are. Well-designed and -constructed deposit models allow geologists to know from observed geologic environments the possible mineral deposit types that might exist, and allow economists to determine the possible economic viability of these resources in the region. Thus, mineral deposit models play the central role in transforming geoscience information to a form useful to policy makers. The foundation of mineral deposit models is information about known deposits—the purpose of this publication is to make this kind of information available in digital form for a group of porphyry copper deposits. This publication contains a computer file of information on porphyry copper deposits around the world. It also presents new grade and tonnage models for three subtypes of porphyry copper deposits, maps showing locations and general ages of these deposits, and a preliminary analysis with a number of figures summarizing many of the properties of these porphyry-style deposits. These summaries can be considered a new, quantified, form of most parts of descriptive models such as those in Cox and

Table Mountain Shoshonite Porphyry Lava Flows and Their Vents, Golden, Colorado

USGS Publications Warehouse

Drewes, Harald

2008-01-01

During early Paleocene time shoshonite porphyry lava was extruded from several plugs about 5 km north of Golden, Colo., to form lava flows intercalated in the upper part of the Denver Formation. These flows now form the caps of North and South Table Mountains. Detailed field and petrographic studies provide insights into magma development, linkage between vents and flows, and the history of the lava flows. The magma was derived from a deep (mantle) source, was somewhat turbulent on its way up, paused on its way up in a shallow granite-hosted chamber, and near the surface followed the steep Golden fault and the thick, weak, steeply dipping Upper Cretaceous Pierre Shale. At the surface the lava flowed out of several plug and dike vents in a nonexplosive manner, four times during a span of about 1 m.y. Potassium-rich material acquired in the shallow chamber produced distinctive textures and mineral associations in the igneous rocks. Lava flows 1 (the lowest) and 2 are channel deposits derived from the southeastern group of intrusions, and flow 1 (a composite, multiple-tongued flow) lies about 50 m below the capping flows. Provisionally, the unit termed flow 1 is considered to include older, felty-textured flows that are distinguished from a blocky-textured unit, flow 1a. Flow 2, newly recognized in this study, lies immediately beneath the capping flows. Lava flows 3 and 4, more voluminous than the earlier ones, were derived from a plug vent 1?2 km farther north-northwest and flowed south-southeast across a broad alluvial plain. This plug is a composite body; the rim phase fed flow 3, and the core phase was the source of flow 4. During the time between the effusion of the four flows, the composition of the shoshonite porphyry magma changed subtly; the later flows contain more alkali, as shown by higher proportions of sanidine. On North Table Mountain, lava flows 3 and 4 form an elongate tumulus above a stream channel that carried water at the time of their eruption. On

AMS studies in Portuguese variscan granites

NASA Astrophysics Data System (ADS)

Sant'Ovaia, Helena; Martins, Helena; Noronha, Fernando

2014-05-01

A large volume of Variscan granitic rocks outcrop in Central Iberian Zone which are well documented concerning geological mapping, petrography and geochemistry but whose magnetic characteristics and fabric remain unknown. In this study we summarize the available AMS data from approximately 644 sampling stations (5152 samples) on different massifs of Variscan Portuguese granites. Despite their different geological, petrographic and geochemical characteristics, magnetic susceptibility (K) values obtained for the majority of the studied granites range from 15 to 300 × 10-6 SI. The dominant paramagnetic behaviour of the granite bodies reflects the presence of ilmenite as the main iron oxide. This feature indicates the reduced conditions involved in the granite melt formation during the Variscan orogeny. The two-mica granites show K values ranging between 15 to 70 × 10-6 SI which are lower than values displayed by the biotite-rich facies scattered within the interval of 70 and 300 × 10-6 SI. The magnetite-bearing granites are scarce but represented in Lavadores, Gerês and Manteigas. Even so, only the Lavadores body could be considered as a true magnetite-type granite (K >3.0 × 10-3 SI) in face of its K, comprised between 1550 and 19303 × 10-6 SI. Magnetic anisotropy can be used as a "marker" for the deformation experienced by granite mushes during their crustal emplacement and further cooling. Magnetic anisotropy can thus be correlated with the finite deformation of a rock, as record by mineral fabrics. Post-tectonic granites, such as those from Vila Pouca de Aguiar, Pedras Salgadas, Caria, Vila da Ponte, Chaves and Lamas de Olo, have a magnetic anisotropy <2.5% which corresponds to a deformation hardly visible to the naked eye. Nevertheless, at microscopic scale, these granites display almost ubiquitous magmatic to submagmatic microstructures (rare wavy extinction in quartz, erratic subgrain boundaries in quartz and, eventually, folded or kinked biotites). For

Reconnaissance geology of the Precambrian rocks in the Ayn Qunay quadrangle, Kingdom of Saudi Arabia

USGS Publications Warehouse

Overstreet, William C.; Whitlow, Jesse William; Ankary, Abdullah O.

1972-01-01

The Aya Qunay quadrangle covers an area of 2833 sq km in central Saudi Arabia, Only the western edge of the quadrangle is underlain by Precambrian rocks, which were the subject of this investigation. Toward the east the Precambrian rocks are unconformably overlain by Permian and younger sedimentary rocks. The Permian rocks at the west edge of the Ayn Qunay quadrangle consist mainly of a granitic intrusive complex of batholithic dimensions. Parts of the eastern edge of the granitic complex are exposed just west of the overlying Khuff Formation of Permian age, where biotite-hornblende granite of the complex intrudes chlorite-sericite schist of the Precambrian Bi'r Khountina Group. The biotite-hornblende granite of the complex also intrudes plutons of diorite, gabbro, and pyroxenite and is itself intruded by granite porphyry, thereby indicating some difference in age between the granitic rocks in the complex. A sequence of metamorphosed volcanic rocks composed mainly of andesite, rhyolite, and kindred rocks, and called the Halaban Group, is older than the Bi'r Khountina Group. Relations between the Halaban and a gray hornblende-biotite granite gneiss are uncertain, but the gneiss may be older than the Halaban. The few observed contacts disclosed parallel foliation in the two units, but the foliation may have been imposed after the Halaban was deposited on the granite gneiss. Two major left-lateral faults extend west-northwest across the Precambrian rocks but are not in the Permian rocks. These faults parallel to the Najd fault zone found farther south. Seemingly they correlate in time with early movements on the Najd fault zone, but not with the latest. Saprolitic material-of variable thickness is present on the upper surface of the Precambrian rocks beneath the Khuff Formation at many places. Where the Khuff Formation has been removed by erosion, the saprolite is also stripped away. The weathering probably took place in pre-Khuff time. No ancient mines or prospects

Tectonic environments of South American porphyry copper magmatism through time revealed by spatiotemporal data mining

NASA Astrophysics Data System (ADS)

Butterworth, N.; Steinberg, D.; Müller, R. D.; Williams, S.; Merdith, A. S.; Hardy, S.

2016-12-01

Porphyry ore deposits are known to be associated with arc magmatism on the overriding plate at subduction zones. While general mechanisms for driving magmatism are well established, specific subduction-related parameters linking episodes of ore deposit formation to specific tectonic environments have only been qualitatively inferred and have not been formally tested. We develop a four-dimensional approach to reconstruct age-dated ore deposits, with the aim of isolating the tectonomagmatic parameters leading to the formation of copper deposits during subduction. We use a plate tectonic model with continuously closing plate boundaries, combined with reconstructions of the spatiotemporal distribution of the ocean floor, including subducted portions of the Nazca/Farallon plates. The models compute convergence rates and directions, as well as the age of the downgoing plate through time. To identify and quantify tectonic parameters that are robust predictors of Andean porphyry copper magmatism and ore deposit formation, we test two alternative supervised machine learning methods; the "random forest" (RF) ensemble and "support vector machines" (SVM). We find that a combination of rapid convergence rates ( 100 km/Myr), subduction obliquity of 15°, a subducting plate age between 25-70 Myr old, and a location far from the subducting trench boundary (>2000 km) represents favorable conditions for porphyry magmatism and related ore deposits to occur. These parameters are linked to the availability of oceanic sediments, the changing small-scale convection around the subduction zone, and the availability of the partial melt in the mantle wedge. When coupled, these parameters could influence the genesis and exhumation of porphyry copper deposits.

From a long-lived upper-crustal magma chamber to rapid porphyry copper emplacement: Reading the geochemistry of zircon crystals at Bajo de la Alumbrera (NW Argentina)

NASA Astrophysics Data System (ADS)

Buret, Yannick; von Quadt, Albrecht; Heinrich, Christoph; Selby, David; Wälle, Markus; Peytcheva, Irena

2016-09-01

The formation of world class porphyry copper deposits reflect magmatic processes that take place in a deeper and much larger underlying magmatic system, which provides the source of porphyry magmas, as well as metal and sulphur-charged mineralising fluids. Reading the geochemical record of this large magmatic source region, as well as constraining the time-scales for creating a much smaller porphyry copper deposit, are critical in order to fully understand and quantify the processes that lead to metal concentration within these valuable mineral deposits. This study focuses on the Bajo de la Alumbrera porphyry copper deposit in Northwest Argentina. The deposit is centred on a dacitic porphyry intrusive stock that was mineralised by several pulses of porphyry magma emplacement and hydrothermal fluid injections. To constrain the duration of ore formation, we dated zircons from four porphyry intrusions, including pre-, syn- and post-mineralisation porphyries based on intersection relations between successive intrusion and vein generations, using high precision CA-ID-TIMS. Based on the youngest assemblages of zircon grains, which overlap within analytical error, all four intrusions were emplaced within 29 ka, which places an upper limit on the total duration of hydrothermal mineralisation. Re/Os dating of hydrothermal molybdenite fully overlaps with this high-precision age bracket. However, all four porphyries contain zircon antecrysts which record protracted zircon crystallisation during the ∼200 ka preceding the emplacement of the porphyries. Zircon trace element variations, Ti-in-zircon temperatures, and Hf isotopic compositions indicate that the four porphyry magmas record a common geochemical and thermal history, and that the four intrusions were derived from the same upper-crustal magma chamber. Trace element zoning within single zircon crystals confirms a fractional crystallisation trend dominated by titanite and apatite crystallisation. However, zircon

Audio-magnetotelluric survey to characterize the Sunnyside porphyry copper system in the Patagonia Mountains, Arizona

USGS Publications Warehouse

Sampson, Jay A.; Rodriguez, Brian D.

2010-01-01

The Sunnyside porphyry copper system is part of the concealed San Rafael Valley porphyry system located in the Patagonia Mountains of Arizona. The U.S. Geological Survey is conducting a series of multidisciplinary studies as part of the Assessment Techniques for Concealed Mineral Resources project. To help characterize the size, resistivity, and skin depth of the polarizable mineral deposit concealed beneath thick overburden, a regional east-west audio-magnetotelluric sounding profile was acquired. The purpose of this report is to release the audio-magnetotelluric sounding data collected along that east-west profile. No interpretation of the data is included.

Melt recharge, f O2-T conditions, and metal fertility of felsic magmas: zircon trace element chemistry of Cu-Au porphyries in the Sanjiang orogenic belt, southwest China

NASA Astrophysics Data System (ADS)

Meng, Xuyang; Mao, Jingwen; Zhang, Changqing; Zhang, Dongyang; Liu, Huan

2018-06-01

The magmatic hydrothermal Pulang Cu deposit (Triassic) and the Beiya Au-Cu deposits (Eocene) are located in the Sanjiang copper porphyry belt, southwest China. Zircon chemistry was used to constrain the magmatic evolution and oxidation state of the porphyries. The results show that porphyries of the Beiya district formed from an early oxidized melt and a later relatively reduced and more evolved magma, whereas Pulang experienced a normal Cu porphyry evolutionary trend. The Pulang porphyries crystallized from more oxidized magma (ΔFMQ + 2.9-4.6, average = 4.0 ± 1.0, n = 3) with an average temperature of 709 ± 6 °C compared to the Beiya porphyries (ΔFMQ + 0.6-3.5, average = 1.9 ± 1.3, n = 5) with a mean magmatic temperature of 780 ± 22 °C. These data, combined with data from other Cu- and Au-rich porphyries in the Sanjiang belt (i.e., Machangjing Cu, Yao'an Au), are consistent with previous experimental work showing that elevated Cu and Au solubilities in magma require oxidizing conditions. A compilation of existing geochemical data for magmatic zircons from fertile and barren porphyry systems worldwide establishes an optimal diagnostic interval on CeIV/CeIII-TTi-in-zircon and (Eu/Eu*)N plots for generating magmatic hydrothermal Cu-Au deposits.

A geochemical study of the Sweet Home Mine, Colorado Mineral Belt, USA: hydrothermal fluid evolution above a hypothesized granite cupola

NASA Astrophysics Data System (ADS)

Lüders, Volker; Romer, Rolf L.; Gilg, H. Albert; Bodnar, Robert J.; Pettke, Thomas; Misantoni, Dean

2009-05-01

Deposition of quartz-molybdenite-pyrite-topaz-muscovite-fluorite and subsequent hübnerite and sulfide-fluorite-rhodochrosite mineralization at the Sweet Home Mine occurred coeval with the final stage of magmatic activity and ore formation at the nearby world-class Climax molybdenum deposit about 26 to 25 m.y. ago. The mineralization occurred at depths of about 3,000 m and is related to at least two major fluid systems: (1) one dominated by magmatic fluids, and (2) another dominated by meteoric water. The sulfur isotopic composition of pyrite, strontium isotopes and REY distribution in fluorite suggest that the early-stage quartz-molybdenite-pyrite-topaz-muscovite-fluorite mineral assemblage was deposited from magmatic fluids under a fluctuating pressure regime at temperatures of about 400°C as indicated by CO2-bearing, moderately saline (7.5-12.5 wt.% NaCl equiv.) fluid inclusions. LA-ICPMS analyses of fluid inclusions in quartz demonstrate that fluids from the Sweet Home Mine are enriched in incompatible elements but have considerably lower metal contents than those reported from porphyry-Cu-Au-Mo or Climax-type deposits. The ore-forming fluid exsolved from a highly differentiated magma possibly related to the deep-seated Alma Batholith or distal porphyry stock(s). Sulfide mineralization, marking the periphery of Climax-type porphyry systems, with fluorite and rhodochrosite as gangue minerals was deposited under a hydrostatic pressure regime from low-salinity ± CO2-bearing fluids with low metal content at temperatures below 400°C. The sulfide mineralization is characterized by mostly negative δ34S values for sphalerite, galena, chalcopyrite, and tetrahedrite, highly variable δ18O values for rhodochrosite, and low REE contents in fluorite. The Pb isotopic composition of galena as well as the highly variable 87Sr/86Sr ratios of fluorite, rhodochrosite, and apatite indicates that at least part of the Pb and Sr originated from a much more radiogenic source than

HUNTER-FRYINGPAN WILDERNESS AND PORPHYRY MOUNTAIN WILDERNESS STUDY AREA, COLORADO.

USGS Publications Warehouse

Ludington, Steve; Ellis, Clarence E.

1984-01-01

A mineral survey of the Hunter-Fryingpan Wilderness and the Porphyry Mountain Wilderness study area, Colorado was conducted. Substantiated gold and silver resource potential was identified in one area and a surrounding area is judged to have probable mineral-resource potential for gold and silver. No other mineral or energy resources were identified in the study.

Variscan potassic dyke magmatism of durbachitic affinity at the southern end of the Bohemian Massif (Lower Austria)

NASA Astrophysics Data System (ADS)

Zeitlhofer, Helga; Grasemann, Bernhard; Petrakakis, Konstantin

2016-06-01

Dykes in the Strudengau area (SW Moldanubian Zone, Austria) can be mineralogically divided into lamprophyres (spessartites and kersantites) and felsic dykes (granite porphyries, granitic dykes and pegmatoid dykes). Geochemical analyses of 11 lamprophyres and 7 felsic dykes show evidence of fractional crystallization. The lamprophyres are characterized by metaluminous compositions, intermediate SiO2 contents and high amounts of MgO and K2O; these rocks have high Ba (800-3000 ppm) and Sr (250-1000 ppm) contents as well as an enrichment of large-ion lithophile elements over high field strength elements, typical for enriched mantle sources with variable modifications due to fractionation and crustal contamination. This geochemical signature has been reported from durbachites (biotite- and K feldspar-rich mela-syenites particularly characteristic of the Variscan orogen in Central Europe). For most major elements, calculated fractionation trends from crystallization experiments of durbachites give an excellent match with the data from the Strudengau dykes. This suggests that the lamprophyres and felsic dykes were both products of fractional crystallization and subsequent magma mixing of durbachitic and leucogranitic melts. Rb-Sr geochronological data on biotite from five undeformed kersantites and a locally deformed granite porphyry gave cooling ages of c. 334-318 Ma, indicating synchronous intrusion of the dykes with the nearby outcropping Weinsberger granite (part of the South Bohemian Batholith, c. 330-310 Ma). Oriented matrix biotite separated from the locally deformed granite porphyry gave an Rb-Sr age of c. 318 Ma, interpreted as a deformation age during extensional tectonics. We propose a large-scale extensional regime at c. 320 Ma in the Strudengau area, accompanied by plutonism of fractionated magmas of syncollisional mantle-derived sources, mixed with crustal components. This geodynamic setting is comparable to other areas in the Variscan belt documenting an

Two-mica granites of northeastern Nevada.

USGS Publications Warehouse

Lee, D.E.; Kistler, R.W.; Friedman, I.; Van Loenen, R. E.

1981-01-01

The field settings are described and analytical data are presented for six two-mica granites from NE Nevada. High delta 18O and 87Sr/86Sr values indicate that all are S-type granite, derived from continental crust. The major element chemistry and accessory mineral contents of these rocks also are characteristic of S-type granites. Chemical, X ray, and other data are presented for the micas recovered from these granites. The muscovites are notably high in Fe2O3, FeO, and MgO. Except for one hydrobiotite, each of the biotites has an MgO content near 6.0 wt%. Two different types of two-mica granites are recognized in the area of this study. One type is distinguished by the presence of many biotite euhedra within muscovite phenocrysts and by an unusual suite of accessory minerals completely devoid of opaque oxides. This type probably resulted from anatexis of late Precambrian argillites under conditions of relatively low oxygen fugacity, along a line that roughly coincides with the westward disappearance of continental basement. In the other textural type of two-mica granite the micas are equigranular and there is a greater variety of accessory minerals. The magmatic evolution of this type also appears to reflect the influence of late Precambrian argillites; there may be age differences between the two types of two-mica granites.-Author

Late Triassic granites from Bangka, Indonesia: A continuation of the Main Range granite province of the South-East Asian Tin Belt

NASA Astrophysics Data System (ADS)

Ng, Samuel Wai-Pan; Whitehouse, Martin J.; Roselee, Muhammad H.; Teschner, Claudia; Murtadha, Sayed; Oliver, Grahame J. H.; Ghani, Azman A.; Chang, Su-Chin

2017-05-01

The South-East Asian Tin Belt is one of the most tin-productive regions in the world. It comprises three north-south oriented granite provinces, of which the arc-related Eastern granite province and the collision-related Main Range granite province run across Thailand, Singapore, and Indonesia. These tin-producing granite provinces with different mineral assemblages are separated by Paleo-Tethyan sutures exposed in Thailand and Malaysia. The Eastern Province is usually characterised by granites with biotite ± hornblende. Main Range granites are sometimes characterised by the presence of biotite ± muscovite. However, the physical boundary between the two types of granite is not well-defined on the Indonesian Tin Islands, because the Paleo-Tethyan suture is not exposed on land there. Both hornblende-bearing (previously interpreted as I-type) and hornblende-barren (previously interpreted as S-type) granites are apparently randomly distributed on the Indonesian Tin Islands. Granites exposed on Bangka, the largest and southernmost Tin Island, no matter whether they are hornblende-bearing or hornblende-barren, are geochemically similar to Malaysian Main Range granites. The average ɛNd(t) value obtained from the granites from Bangka (average ɛNd(t) = -8.2) falls within the range of the Main Range Province (-9.6 to -5.4). These granites have SIMS zircon U-Pb ages of ca. 225 Ma and ca. 220 Ma, respectively that are both within the period of Main Range magmatism (∼226-201 Ma) in the Peninsular Malaysia. We suggest that the granites exposed on Bangka represent the continuation of the Main Range Province, and that the Paleo-Tethyan suture lies to the east of the island.

The architecture of the porphyry-metal system as a prospecting stratagem in the Southern Rocky Mountains

USGS Publications Warehouse

Neuerburg, George J.

1978-01-01

A model of the porphyry-metal system characteristic of the consanguineous Cretaceous and Tertiary igneous rocks and associated ores of the southern Rocky Mountains is constructed from the bits and pieces exposed in the Colorado mineral belt and the San Juan volcanic field. Hydrothermally altered rocks in a part of the areas of mineralized rock associated with the Platoro caldera are matched against the model, to locate and to characterize latent mineral deposits for optimal prospecting and exploration. The latent deposits are two stockwork molybdenite deposits (porphyry-molybdenum) and one or two copper-gold-silver chimney deposits.

Variation of molybdenum isotopes in molybdenite from porphyry and vein Mo deposits in the Gangdese metallogenic belt, Tibetan plateau and its implications

NASA Astrophysics Data System (ADS)

Wang, Yong; Zhou, Lian; Gao, Shan; Li, Jian-Wei; Hu, Zhi-Fang; Yang, Lu; Hu, Zhao-Chu

2016-02-01

We present Mo isotopic ratios of molybdenite from five porphyry molybdenum deposits (Chagele, Sharang, Jiru, Qulong, and Zhuonuo) and one quartz-molybdenite vein-type deposit (Jigongcun) along the Gangdese metallogenic belt in the Tibetan Plateau. These deposits represent a sequence of consecutive events of the India-Asia collision at different periods. Additional molybdenite samples from the Henderson Mo deposit (USA), the oceanic subduction-related El Teniente (Chile), and Bingham (USA) porphyry Cu-(Mo) deposits were analyzed for better understanding the controls on the Mo isotope systematics of molybdenite. The results show that molybdenite from Sharang, Jiru, Qulong, and Zhuonuo deposits have similar δ97Mo (˜0 ‰), in agreement with the values of the Henderson Mo deposit (-0.10 ‰). In contrast, samples from the Changle and Jigongcun deposit have δ97Mo of 0.85 ‰ to 0.88 ‰ and -0.48 %, respectively. Molybdenite from the El Teniente and Bingham deposits yields intermediate δ97Mo of 0.27 and 0.46 ‰, respectively. The Mo isotopes, combined with Nd isotope data of the ore-bearing porphyries, indicate that source of the ore-related magmas has fundamental effects on the Mo isotopic compositions of molybdenite. Our study indicates that molybdenite related to crustal-, and mantle-derived magmas has positive or negative δ97Mo values, respectively, whereas molybdenite from porphyries formed by crust-mantle mixing has δ97Mo close to 0 ‰. It is concluded that the Mo isotope composition in the porphyry system is a huge source signature, without relation to the tectonic setting under which the porphyry deposits formed.

Amphibole and apatite insights into the evolution and mass balance of Cl and S in magmas associated with porphyry copper deposits

NASA Astrophysics Data System (ADS)

Chelle-Michou, Cyril; Chiaradia, Massimo

2017-12-01

Chlorine and sulfur are of paramount importance for supporting the transport and deposition of ore metals at magmatic-hydrothermal systems such as the Coroccohuayco Fe-Cu-Au porphyry-skarn deposit, Peru. Here, we used recent partitioning models to determine the Cl and S concentration of the melts from the Coroccohuayco magmatic suite using apatite and amphibole chemical analyses. The pre-mineralization gabbrodiorite complex hosts S-poor apatite, while the syn- and post-ore dacitic porphyries host S-rich apatite. Our apatite data on the Coroccohuayco magmatic suite are consistent with an increasing oxygen fugacity (from the gabbrodiorite complex to the porphyries) causing the dominant sulfur species to shift from S2- to S6+ at upper crustal pressure where the magmas were emplaced. We suggest that this change in sulfur speciation could have favored S degassing, rather than its sequestration in magmatic sulfides. Using available partitioning models for apatite from the porphyries, pre-degassing S melt concentration was 20-200 ppm. Estimates of absolute magmatic Cl concentrations using amphibole and apatite gave highly contrasting results. Cl melt concentrations obtained from apatite (0.60 wt% for the gabbrodiorite complex; 0.2-0.3 wt% for the porphyries) seems much more reasonable than those obtained from amphibole which are very low (0.37 wt% for the gabbrodiorite complex; 0.10 wt% for the porphyries). In turn, relative variations of the Cl melt concentrations obtained from amphibole during magma cooling are compatible with previous petrological constraints on the Coroccohuayco magmatic suite. This confirms that the gabbrodioritic magma was initially fluid undersaturated upon emplacement, and that magmatic fluid exsolution of the gabbrodiorite and the pluton rooting the porphyry stocks and dikes were emplaced and degassed at 100-200 MPa. Finally, mass balance constraints on S, Cu and Cl were used to estimate the minimum volume of magma required to form the

Temporal Evolution of Volcanic and Plutonic Magmas Related to Porphyry Copper Ores Based on Zircon Geochemistry

NASA Astrophysics Data System (ADS)

Dilles, J. H.; Lee, R. G.; Wooden, J. L.; Koleszar, A. M.

2015-12-01

Porphyry Cu (Mo-Au) and epithermal Au-Ag ores are globally associated with shallow hydrous, strongly oxidized, and sulfur-rich arc intrusions. In many localities, long-lived magmatism includes evolution from early andesitic volcanic (v) and plutonic (p) rocks to later dacitic or rhyolitic compositions dominated by plutons. We compare zircon compositions from three igneous suites with different time spans: Yerington, USA (1 m.y., p>v), El Salvador, Chile (4 m.y., p>v), and Yanacocha, Peru (6 m.y., v>p). At Yerington granite dikes and ores formed in one event, at ES in 2 to 3 events spanning 3 m.y., and at Yanacocha in 6 events spanning 5 m.y. At both ES and Yanacocha, high-Al amphiboles likely crystallized at high temperature in the mid-crust and attest to deep magmas that periodically recharged the shallow chambers. At Yanacocha, these amphiboles contain anhydrite inclusions that require magmas were sulfur-rich and strongly oxidized (~NNO+2). The Ti-in-zircon geothermometer provides estimates of 920º to 620º C for zircon crystallization, and records both core to rim cooling and locally high temperature rim overgrowths. Ore-related silicic porphyries yield near-solidus crystallization temperatures of 750-650°C consistent with low zircon saturation temperatures. The latter zircons have large positive Ce/Ce* and small negative Eu/Eu*≥0.4 anomalies attesting to strongly oxidized conditions (Ballard et al., 2001), which we propose result from crystallization and SO2 loss to the magmatic-hydrothermal ore fluid (Dilles et al., 2015). The Hf, REE, Y, U, and Th contents of zircons are diverse in the magma suites, and Th/U vs Yb/Gd plots suggest a dominant role of crystal fractionation with lesser roles for both crustal contamination and mixing with high temperature deep-sourced mafic magma. Ce/Sm vs Yb/Gd plots suggest that magma REE contents at <900°C are dominated by early crystallization of hornblende and apatite, and late crystallization (~<780°C) of titanite

U-Pb zircon, geochemical and Sr-Nd-Hf-O isotopic constraints on age and origin of the ore-bearing intrusions from the Nurkazgan porphyry Cu-Au deposit in Kazakhstan

NASA Astrophysics Data System (ADS)

Shen, Ping; Pan, Hongdi; Seitmuratova, Eleonora; Jakupova, Sholpan

2016-02-01

Nurkazgan, located in northeastern Kazakhstan, is a super-large porphyry Cu-Au deposit with 3.9 Mt metal copper and 229 tonnage gold. We report in situ zircon U-Pb age and Hf-O isotope data, whole rock geochemical and Sr-Nd isotopic data for the ore-bearing intrusions from the Nurkazgan deposit. The ore-bearing intrusions include the granodiorite porphyry, quartz diorite porphyry, quartz diorite, and diorite. Secondary ion mass spectrometry (SIMS) zircon U-Pb dating indicates that the granodiorite porphyry and quartz diorite porphyry emplaced at 440 ± 3 Ma and 437 ± 3 Ma, respectively. All host rocks have low initial 87Sr/86Sr ratios (0.70338-0.70439), high whole-rock εNd(t) values (+5.9 to +6.3) and very high zircon εHf(t) values (+13.4 to +16.5), young whole-rock Nd and zircon Hf model ages, and consistent and slightly high zircon O values (+5.7 to +6.7), indicating that the ore-bearing magmas derived from the mantle without old continental crust involvement and without marked sediment contamination during magma emplacement. The granodiorite porphyry and quartz diorite porphyry are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE) and depleted in high-field strength elements (HFSE), Eu, Ba, Nb, Sr, P and Ti. The diorite and quartz diorite have also LILE and LREE enrichment and HFSE, Nb and Ti depletion, but have not negative Eu, Ba, Sr, and P anomalies. These features suggest that the parental magma of the granodiorite porphyry and quartz diorite porphyry originated from melting of a lithospheric mantle and experienced fractional crystallization, whereas the diorite and quartz diorite has a relatively deeper lithospheric mantle source region and has not experienced strong fractional crystallization. Based on these, together with the coeval ophiolites in the area, we propose that a subduction of the Balkhash-Junggar oceanic plate took place during the Early Silurian and the ore-bearing intrusions and associated Nurkazgan

Preface to special issue: Granite magmatism in Brazil

NASA Astrophysics Data System (ADS)

Janasi, Valdecir de Assis; de Pinho Guimarães, Ignez; Nardi, Lauro Valentim Stoll

2016-07-01

Granites are important both to the geologic evolution and to the economy of Brazil. Deposits of precious and rare metals, such as Au, Sn and many others, are directly or indirectly associated with granites, especially in the geologically under-explored Amazon region. On the opposite eastern side of the country, expanding exploitation of natural granite as dimension stone makes Brazil currently the world's second largest exporter of granite blocks. Granites are a major constituent of the Brazilian Archean-Proterozoic cratonic domains (the Amazon and São Francisco cratons) and their surrounding Neoproterozoic fold belts. The granites are thus fundamental markers of the major events of crustal generation and recycling that shaped the South American Platform. As a result, Brazilian granites have received great attention from the national and international community, and a number of influential meetings focused on the study of granites were held in the country in the last three decades. These meetings include the two International Symposia on Granites and Associated Mineralization (Salvador, January 21-31, 1987, and August 24-29, 1997), the Symposium on Rapakivi Granites and Related Rocks (Belém, August 2-5, 1995) and the Symposium on Magmatism, Crustal Evolution, and Metallogenesis of the Amazonian Craton (Belém, August 2006). Special issues dedicated to contributions presented at these meetings in the Journal of South American Earth Sciences (Sial et al., 1998), Lithos (Stephens et al., 1999), Canadian Mineralogist (Dall'Agnol and Ramo, 2006), Precambrian Research (Ramo et al., 2002) and Anais da Academia Brasileira de Ciências (Dall'Agnol and Bettencourt, 1997; Sial et al., 1999a) are still important references on the knowledge of Brazilian granites and granite petrology in general.

Petrogenesis of Late Jurassic granodiorites from Gutian, Fujian Province, South China: Implications for multiple magma sources and origin of porphyry Cu-Mo mineralization

NASA Astrophysics Data System (ADS)

Li, Bin; Jiang, Shao-Yong; Lu, An-Huai; Lai, Jian-Qing; Zhao, Kui-Dong; Yang, Tao

2016-11-01

The Gutian porphyry Cu-Mo deposit is a newly proved porphyry copper deposit in the coastal South China associated with granodioritic porphyries. In this study, zircon U-Pb ages and Hf isotope data, as well as geochemical and Sr-Nd-Pb-Re-Os isotopic compositions, are reported for these intrusions and minerals. Both zircon U-Pb and molybdenite Re-Os dating suggest that the Gutian granodiorite porphyries and related mineralization formed at 160 Ma. The Gutian granodiorites show a low-Mg adakitic geochemical affinity, with relatively high K2O but low Cr and Ni contents. These rocks have initial (87Sr/86Sr)i ratios of 0.7085 to 0.7097, negative εNd(t) values (- 12.5 to - 7.8), (206Pb/204Pb)t ratios of 18.048 to 18.241, (207Pb/204Pb)t ratios of 15.609 to 15.628, and (208Pb/204Pb)t ratios of 38.494 to 38.667. Zircons from the granodiorites have negative εHf(t) values of - 15.7 to - 8.5, which are close to those of Cathaysia crust-derived melts. Geochemical and Sr-Nd-Pb-Hf isotopic compositions suggest that they may be derived from Late Jurassic thickened juvenile lower crust. These lower crustal magma sources may not only contain pre-Proterozoic basement rocks, but also involve Triassic and Middle-Late Jurassic arc magmas within the lower crust, which were likely derived from an enriched mantle source associated with paleo-Pacific Plate subduction from the Middle to Late Jurassic. The Gutian ore-related granodiorites represent a new example for significant contributions of ancient subduction melts and enriched mantle-derived sources for porphyry-type magmatism and Cu-Mo mineralization, which occurred in response to an arc regime during the Middle to Late Jurassic in South China. Supplemental Table S2. Hf isotopic compositions of zircons from the studied rocks from the Gutian porphyry deposit in South China. Supplemental Table S3. Statistics for zircon U-Pb ages and Hf isotope compositions from Gutian granodiorites in South China Supplemental Table S4. Major element (wt

Mo isotope fractionation during hydrothermal evolution of porphyry Cu systems

NASA Astrophysics Data System (ADS)

Shafiei, Behnam; Shamanian, GholamHossein; Mathur, Ryan; Mirnejad, Hassan

2015-03-01

We present Mo isotope compositions of molybdenite types from three successive stages of ore deposition in several porphyry copper deposits of the Kerman region, Iran. The data provide new insights into controlling processes on Mo isotope fractionation during the hydrothermal evolution of porphyry systems. The Mo isotope compositions of 27 molybdenite samples show wide variations in δ97Mo ranging from -0.37 to +0.92 ‰. The data reveal that molybdenites in the early and transitional stages of mineralization (preferentially 2H polytypes; δ97Mo mean = 0.35 ‰) have higher δ97Mo values than late stage (mainly 3R polytypes; δ97Mo mean = 0.02 ‰) molybdenites. This trend suggests that fractionation of Mo isotopes occurred in high-temperature stages of mineralization and that hydrothermal systems generally evolve towards precipitation of molybdenite with lower δ97Mo values. Taking into account the genetic models proposed for porphyry Cu deposits along with the temperature-dependent fractionation of Mo isotope ratios, it is proposed that large variations of Mo isotopes in the early and the transitional stages of ore deposition could be controlled by the separation of the immiscible ore-forming fluid phases with different density, pH, and ƒO2 properties (i.e., brine and vapor). The fractionation of Mo isotopes during fluid boiling and Rayleigh distillation processes likely dominates the Mo isotope budget of the remaining ore-forming fluids for the late stage of mineralization. The lower δ97Mo values in the late stage of mineralization can be explained by depletion of the late ore-forming hydrothermal solutions in 97Mo, as these fluids have moved to considerable distance from the source. Finally, the relationship observed between MoS2 polytypes (2H and 3R) and their Mo isotopic compositions can be explained by the molecular vibration theory, in which heavier isotopes are preferentially partitioned into denser primary 2H MoS2 crystals.

Geology of Nicholson's point granite, Natal Metamorphic Province, South Africa: the chemistry of charnockitic alteration and origin of the granite

NASA Astrophysics Data System (ADS)

Grantham, G. H.; Allen, A. R.; Cornell, D. H.; Harris, C.

1996-10-01

In the Port Edward area of southern Kwa-Zulu Natal, South Africa, charnockitic aureoles up to ˜4 m in width are developed adjacent to contacts with Port Edward enderbite and pegmatites intruded into the normally garnetiferous Nicholson's Point granite. Other mineralogical differences between the aureoles and the granite include increased myrmekite and significantly less biotite in the former and the replacement of pyrite by pyrrhotite in the charnockitic rocks. No significant differences in major element chemistry between the garnet-biotite Nicholson's Point granite and charnockitic Nicholson's Point granite are seen, except possibly for higher CaO and TiO 2 in the charnockite. Higher Rb, Th, Nb and Y contents in the garnet-biotite granite suggest that these elements have been locally depleted from garnet-biotite granite during char nockitisation. This depletion is considered to be related to the reduction in biotite. Strontium and Ba contents are significantly higher in the charnockite. Generally higher S contents in the charnockite suggest S metasomatism, with S possibly being added from the enderbite. No differences in δ18O isotope data are seen between the garnetiferous and hypersthene bearing granite. In the charnockite the LREEs are weakly depleted whereas the HREEs show greater depletion compared to the garnetiferous granite. The depletions in REEs are thought to be related to the breakdown of garnet. Europium is marginally enriched or unchanged in the charnockite relative to the garnetiferous granite. Two-pyroxene thermometry on the Port Edward enderbite suggests that it was intruded at temperatures of ˜1000-1100°C. The replacement of pyrite by pyrrhotite is also consistent with a thermal auroele. Consequently the charnockitic zones developed around the intrusions of Port Edward enderbite may result from the thermally driven dehydration of biotite. The aureoles developed adjacent to pegmatites are not considered to have resulted from heat but probably

The research frontier and beyond: granitic terrains

NASA Astrophysics Data System (ADS)

Twidale, C. R.

1993-07-01

Investigations of granite forms and landscapes over the past two centuries suggest that many features, major and minor, are shaped by fracture-controlled subsurface weathering, and particularly moisture-driven alteration: in other words etch forms are especially well represented in granitic terrains. Commonly referred to as two stage forms, many are in reality multistage in origin, for the structural contrasts exploited by weathering and erosion that are essential to the mechanism originated as magmatic, thermal or tectonic events in the distant geological past. Fracture patterns are critical to landform and landscape development in granitic terrains, but other structural factors also come into play. Location with respect to water table and moisture contact are also important. Once exposed and comparatively dry, granite forms tend to stability; they are developed and diversified, and many are gradually destroyed as new, epigene, forms evolve, but many granite forms persist over long ages. Reinforcement effects frequently play a part in landform development. Several granite forms are convergent, i.e. features of similar morphology evolve under the influence of different processes, frequently in contrasted environments. On the other hand many landforms considered to be typical of granitic terrains are also developed in bedrock that is petrologically different but physically similar to granite; and in particular is subdivided by fractures of similar pattern and density. To date, most of the general statements concerning the evolution of granitic terrains have been based in work in the tropics but other climatic settings, and notably those of cold land, are now yielding significant results. Future research will extend and develop these avenues, but biotic factors, and particularly the role of bacteria, in such areas as weathering, will take on a new importance. Structural variations inherited from the magnetic, thermal and tectonic events to which granite bodies have

Identification of granite varieties from colour spectrum data.

PubMed

Araújo, María; Martínez, Javier; Ordóñez, Celestino; Vilán, José Antonio

2010-01-01

The granite processing sector of the northwest of Spain handles many varieties of granite with specific technical and aesthetic properties that command different prices in the natural stone market. Hence, correct granite identification and classification from the outset of processing to the end-product stage optimizes the management and control of stocks of granite slabs and tiles and facilitates the operation of traceability systems. We describe a methodology for automatically identifying granite varieties by processing spectral information captured by a spectrophotometer at various stages of processing using functional machine learning techniques.

Identification of Granite Varieties from Colour Spectrum Data

PubMed Central

Araújo, María; Martínez, Javier; Ordóñez, Celestino; Vilán, José Antonio

2010-01-01

The granite processing sector of the northwest of Spain handles many varieties of granite with specific technical and aesthetic properties that command different prices in the natural stone market. Hence, correct granite identification and classification from the outset of processing to the end-product stage optimizes the management and control of stocks of granite slabs and tiles and facilitates the operation of traceability systems. We describe a methodology for automatically identifying granite varieties by processing spectral information captured by a spectrophotometer at various stages of processing using functional machine learning techniques. PMID:22163673

Neponset River Basin Massachusetts, Flood Plain Management Study.

DTIC Science & Technology

1982-03-01

extensive water power. There are in the southern village, two rolling mills, for the manufacture of copper bolts and sheathing, on a large scale; two...furnaces for refining copper , and casting bells and brass cannon (operated by Paul Revere): forges and furnaces for the manufacture of iron wheels and...Dedha Granodiorite, Westwood Granite, Sharon Syenite, and Blue Rills Granite Porphyry . Crushed Stone. The Mattapan Volcanic Complex and Westwood

Radiological implications of granite of northern Pakistan.

PubMed

Asghar, M; Tufail, M; Sabiha-Javied; Abid, A; Waqas, M

2008-09-01

Granite is an igneous rock that contains natural radioactivity of primordial radionuclides. In Pakistan, granite is distributed in a vast area called the Ambela Granitic Complex (AGC) in North West Frontier Province (NWFP). Granite is a hard rock that exists in different colours and is used to decorate floors, kitchen counter tops, etc. The use of granite in a building as a decor material is a potential source of radiation dose; therefore, natural radioactivity has been measured in 20 granite samples of the AGC with an HPGe (high purity germanium) based gamma ray spectrometer. The average specific activities and their range (given in parentheses) for primordial radionuclides (40)K, (226)Ra and (232)Th were 1218 (899-1927), 659 (46-6120) and 598 (92-3214) Bq kg(-1), respectively. The measured activity concentrations were used for the assessment of hazard indices and radiation dose which were evaluated based on the permissible limits defined for these parameters. The measured specific activities and the derived quantities, hazard indices and radiation dose, have been compared with those given in the literature for these parameters.

The transition from granite to banded aplite-pegmatite sheet complexes: An example from Megiliggar Rocks, Tregonning topaz granite, Cornwall

NASA Astrophysics Data System (ADS)

Breiter, K.; Ďurišová, J.; Hrstka, T.; Korbelová, Z.; Vašinová Galiová, M.; Müller, A.; Simons, B.; Shail, R. K.; Williamson, B. J.; Davies, J. A.

2018-03-01

The genetic relationship between a granite pluton and adjacent complex of rare-metal pegmatite-aplite-banded sheets (Megiliggar Sheet Complex - MSC) has been studied at the border of the Tregonning topaz granite at Megiliggar Rocks, Cornwall, SW England. Similarities in whole-rock chemical and mineralogical compositions, together with a gradual change in textures away from the granite margin, provide strong evidence for a genetic link between the Tregonning Granite and MSC. The sheets are likely to represent apophyses of residual melt which escaped from the largely crystallized roof of the granite pluton. The escaping melt was peraluminous, had a composition near the F, B, Li slightly enriched granite minimum, and, in comparison with other Cornish granites, was enriched in F, Li, Rb, Cs, Sn, W, Nb, Ta, and U, and depleted in Fe, Mg, Ca, Sr, Th, Zr, and REE. With increasing distance from the Tregonning Granite, the silicate melt crystallized as homogeneous leucogranite sheets and banded complex sheets (i.e. combinations of bands with granitic, aplitic and pegmatitic textures), then layered aplite-pegmatites; this sequence becoming progressively more depleted in the fluxing and volatile elements F, Li, Rb, and Cs, but showing no change in Zr/Hf ratios. The fixed Zr/Hf ratio is interpreted as indicating a direct genetic link (parental melt) between all rock types, however the melt progressively lost fluxing and volatile elements with distance from the granite pluton, probably due to wall-rock reaction or fluid exsolution and migration via fractures. Differentiation of the primary melt into Na-Li-F-rich and separate K-B-rich domains was the dominant chemical process responsible for the textural and mineral diversity of the MSC. On a large (cliff-section) scale, the proximal Na-Li-F-rich leucogranite passes through complex sheets into K-B-rich aplite-pegmatites, whilst at a smaller (<1 m) scale, the K-B-rich bands are interspersed (largely overlain) by Na

Timing of porphyry (Cu-Mo) and base metal (Zn-Pb-Ag-Cu) mineralisation in a magmatic-hydrothermal system—Morococha district, Peru

NASA Astrophysics Data System (ADS)

Catchpole, Honza; Kouzmanov, Kalin; Bendezú, Aldo; Ovtcharova, Maria; Spikings, Richard; Stein, Holly; Fontboté, Lluís

2015-12-01

The Morococha district in central Peru is characterised by economically important Cordilleran polymetallic (Zn-Pb-Ag-Cu) vein and replacement bodies and the large Toromocho porphyry Cu-Mo deposit in its centre. U-Pb, Re-Os, and 40Ar/39Ar geochronology data for various porphyry-related hydrothermal mineralisation styles record a 3.5-Ma multi-stage history of magmatic-hydrothermal activity in the district. In the late Miocene, three individual magmatic-hydrothermal centres were active: the Codiciada, Toromocho, and Ticlio centres, each separated in time and space. The Codiciada centre is the oldest magmatic-hydrothermal system in the district and consists of a composite porphyry stock associated with anhydrous skarn and quartz-molybdenite veins. The hydrothermal events are recorded by a titanite U-Pb age at 9.3 ± 0.2 Ma and a molybdenite Re-Os age at 9.26 ± 0.03 Ma. These ages are indistinguishable from zircon U-Pb ages for porphyry intrusions of the composite stock and indicate a time span of 0.2 Ma for magmatic-hydrothermal activity. The small Ticlio magmatic-hydrothermal centre in the west of the district has a maximum duration of 0.3 Ma, ranging from porphyry emplacement to porphyry mineralisation at 8.04 ± 0.14 Ma (40Ar/39Ar muscovite cooling age). The Toromocho magmatic-hydrothermal centre has a minimum of five recorded porphyry intrusions that span a total of 1.3 Ma and is responsible for the formation of the giant Toromocho Cu-Mo deposit. At least two hydrothermal pulses are identified. Post-dating a first pulse of molybdenite mineralisation, wide-spread hydrous skarn covers an area of over 6 km2 and is recorded by five 40Ar/39Ar cooling ages at 7.2-6.8 Ma. These ages mark the end of the slowly cooling and long-lived Toromocho magmatic-hydrothermal centre soon after last magmatic activity at 7.26 ± 0.02 Ma. District-wide (50 km2) Cordilleran base metal vein and replacement bodies post-date the youngest recorded porphyry mineralisation event at Toromocho

Origin of dioritic magma and its contribution to porphyry Cu-Au mineralization at Pulang in the Yidun arc, eastern Tibet

NASA Astrophysics Data System (ADS)

Cao, Kang; Yang, Zhi-Ming; Xu, Ji-Feng; Fu, Bin; Li, Wei-Kai; Sun, Mao-Yu

2018-04-01

The giant Pulang porphyry Cu-Au deposit in the Yidun arc, eastern Tibet, formed due to westward subduction of the Garze-Litang oceanic plate in the Late Triassic. The deposit is hosted in an intrusive complex comprising primarily coarse-grained quartz diorite and cored quartz monzonite. Here, we investigate a suite of simultaneous (216.6 ± 1.9 Ma) diorite porphyries within the complex. The diorite porphyries are geochemically similar to mafic magmatic enclaves (MME) hosted in coarse-grained quartz diorite, and both are characterized by low SiO2 (59.4-63.0 wt%) and high total alkali (Na2O + K2O = 7.0-9.2 wt%), K2O (3.5-6.4 wt%), MgO (3.2-5.5 wt%), and compatible trace element (e.g., Cr = 72-149 ppm) concentrations. They are enriched in large-ion lithophile and light rare earth elements (LILE and LREE, respectively), but depleted in high field-strength and heavy rare earth elements (HFSE and HREE, respectively), and yield variably high (La/Yb)N ratios (17-126, average 65) with weak to negligible Eu anomalies. Furthermore, they yield low (87Sr/86Sr)i ratios (0.7054-0.7067), weakly negative εNd(t) (-2.8 to -0.8) values, and variable zircon εHf(t) (-5.4 to +0.8) and δ18O (6.0‰-6.7‰) values. These geochemical features indicate that the diorite porphyry and MME formed through crustal assimilation of a magma produced during low-degree partial melting of metasomatized phlogopite-rich subcontinental lithospheric mantle. In contrast, the coarse-grained quartz diorite and quartz monzonite have relatively high concentrations of SiO2 (61.1-65.3 wt%), K2O (4.1-5.4 wt%), and total alkali (Na2O + K2O = 7.1-8.1 wt%), and low concentrations of MgO (generally <3.0 wt%) and compatible trace elements (e.g., Cr = 38-61 ppm). They yield high Sr/Y ratios (50-63) that indicate an adakitic affinity, and are enriched in LILE, depleted in HFSE, and yield lower (La/Yb)N values (13-20, average 17) than the diorite porphyry and MME. They yield low (87Sr/86Sr)i ratios (0

Geochronology and trace element geochemistry of titanite in the Machangqing Cu-Mo-dominated polymetallic deposit, Yunnan Province, southwest China

NASA Astrophysics Data System (ADS)

Fu, Yu; Sun, Xiaoming; Hollings, Pete; Li, Dengfeng; Yang, Tianjian

2018-06-01

The Machangqing Cu-Mo-dominated polymetallic deposit is a porphyry-skarn-epithermal Cu-Mo (-Au) metallogenic system located in the middle part of the Jinshajiang-Ailaoshan alkaline porphyry metallogenic belt. The skarn mineralization of the Machangqing deposit mainly occurs along the contacts between the alkalic porphyry intrusions and the surrounding Lower Ordovician Xiangyang Formation rocks. We present LA-ICP-MS U-Pb ages and trace element data for titanite from the Machangqing deposit in order to investigate the origin of this deposit. Based on mineral textures and assemblages, two types of titanite are recognized in Machangqing: magmatic titanite (Type I) from the granite porphyry and hydrothermal titanite from the mineralized skarn. The coarse-grained magmatic titanite is euhedral and occurs as discrete grains in the interstices of feldspar, quartz and biotite, whereas fine- to medium-grained hydrothermal titanite crystals (Type II) are euhedral to subhedral and occur in association with skarn minerals such as garnet, pyroxene and magnetite. Magmatic titanite has lower FeO, Al2O3, F and Nb/Ta but higher TiO2, Th/U, HFSEs and Lu/Hf than hydrothermal titanite. The magmatic titanite has higher LREE/HREE ratios and total REE contents with stronger negative Eu anomalies than its mineralized skarn counterpart. Trace elemental characteristics of hydrothermal titanite in Machangqing are consistent with relatively low F contents and oxygen fugacities when compared to the neighboring Beiya gold-dominated polymetallic deposit in the same metallogenic belt. The weighted average 206Pb/238U age of 34.3 ± 1.2 Ma of hydrothermal titanite is within error but slightly younger than the age of magmatic titanite (37.5 ± 4.1 Ma), indicating that the skarn mineralization followed the emplacement of the granite porphyry and was broadly coeval with the porphyry mineralization. The porphyry and skarn types of mineralization at Machangqing were formed from the same metallogenic

Copper isotopic zonation in the Northparkes porphyry Cu-Au deposit, SE Australia

NASA Astrophysics Data System (ADS)

Li, Weiqiang; Jackson, Simon E.; Pearson, Norman J.; Graham, Stuart

2010-07-01

Significant, systematic Cu isotopic variations have been found in the Northparkes porphyry Cu-Au deposit, NSW, Australia, which is an orthomagmatic porphyry Cu deposit. Copper isotope ratios have been measured in sulfide minerals (chalcopyrite and bornite) by both solution and laser ablation multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). The results from both methods show a variation in δ 65Cu of hypogene sulfide minerals of greater than 1‰ (relative to NIST976). Significantly, the results from four drill holes through two separate ore bodies show strikingly similar patterns of Cu isotope variation. The patterns are characterized by a sharp down-hole decrease from up to 0.8‰ (0.29 ± 0.56‰, 1 σ, n = 20) in the low-grade peripheral alteration zones (phyllic-propylitic alteration zone) to a low of ˜-0.4‰ (-0.25 ± 0.36‰, 1 σ, n = 30) at the margins of the most mineralized zones (Cu grade >1 wt%). In the high-grade cores of the systems, the compositions are more consistent at around 0.2‰ (0.19 ± 0.14‰, 1 σ, n = 40). The Cu isotopic zonation may be explained by isotope fractionation of Cu between vapor, solution and sulfides at high temperature, during boiling and sulfide precipitation processes. Sulfur isotopes also show an isotopically light shell at the margins of the high-grade ore zones, but these are displaced from the low δ 65Cu shells, such that there is no correlation between the Cu and S isotope signatures. Fe isotope data do not show any discernable variation along the drill core. This work demonstrates that Cu isotopes show a large response to high-temperature porphyry mineralizing processes, and that they may act as a vector to buried mineralization.

Modeling the formation of porphyry-copper ores

USGS Publications Warehouse

Ingebritsen, Steven E.

2012-01-01

Porphyry-copper ore systems, the source of much of the world's copper and molybdenum, form when metal-bearing fluids are expelled from shallow, degassing magmas. On page 1613 of this issue, Weis et al. (1) demonstrate that self-organizing processes focus metal deposition. Specifically, their simulation studies indicate that ores develop as consequences of dynamic variations in rock permeability driven by injection of volatile species from rising magmas. Scenarios with a static permeability structure could not reproduce key field observations, whereas dynamic permeability responses to magmatic-fluid injection localized a metal-precipitation front where enrichment by a factor of 103 could be achieved [for an overview of their numerical-simulation model CSMP++, see (2)].

Zircon petrochronology reveals the temporal link between porphyry systems and the magmatic evolution of their hidden plutonic roots (the Eocene Coroccohuayco deposit, Peru)

NASA Astrophysics Data System (ADS)

Chelle-Michou, Cyril; Chiaradia, Massimo; Ovtcharova, Maria; Ulianov, Alexey; Wotzlaw, Jörn-Frederik

2014-06-01

We present zircon geochronologic (LA-ICPMS and ID-TIMS), trace element and Hf isotopic evidence for a complex evolution of the plutonic roots of the Eocene Coroccohuayco porphyry system, southern Peru. LA-ICPMS U-Pb dating has initially been carried out to optimize grain selection for subsequent high-precision ID-TIMS dating and to characterize crustal assimilation (xenocrystic cores). This combined in-situ and whole-grain U-Pb dating of the same grains has been further exploited to derive a robust temporal interpretation of the complex magmatic system associated with the Coroccohuayco porphyry-skarn deposit. Our data reveal that a heterogeneous gabbrodioritic complex was emplaced at ca. 40.4 Ma and was followed by a nearly 5 Ma-long magmatic lull until the emplacement of dacitic porphyry stocks and dykes associated with the mineralizing event at ca. 35.6 Ma. However, at the sample scale, zircons from the porphyries provide insight into a 2 Ma-long lived “hidden” magmatism (probably at 4-9 km paleodepth) prior to porphyry intrusion and mineralization for which no other evidence can be found on the surface today. These dates together with zircon trace element analysis and Hf isotopes argue for the development of a long-lived magmatic system dominated by amphibole fractionation with an increasing amount of crustal assimilation and the development of a large and sustained thermal anomaly. The system was probably rejuvenated at an increasing rate from 37.5 to 35.6 Ma with injection of fresh and oxidized magma from the lower crust, which caused cannibalism and remelting of proto-plutons. The porphyry intrusions at Coroccohuayco were emplaced at the peak thermal conditions of this upper crustal magma chamber, which subsequently cooled and expelled ore fluids. Zircon xenocrysts and Hf isotopes in the porphyritic rocks suggest that this large upper crustal system evolved at stratigraphic levels corresponding to Triassic sediments similar to the Mitu group that may be

IRETHERM: The geothermal energy potential of Irish radiothermal granites

NASA Astrophysics Data System (ADS)

Farrell, Thomas; Jones, Alan; Muller, Mark; Feely, Martin; Brock, Andrew; Long, Mike; Waters, Tim

2014-05-01

The IRETHERM project is developing a strategic understanding of Ireland's deep geothermal energy potential through integrated modelling of new and existing geophysical and geological data. One aspect of IRETHERM's research focuses on Ireland's radiothermal granites, where increased concentrations of radioelements provide elevated heat-production (HP), surface heat-flow (SHF) and subsurface temperatures. An understanding of the contribution of granites to the thermal field of Ireland is important to assessing the geothermal energy potential of this low-enthalpy setting. This study focuses on the Galway granite in western Ireland, and the Leinster and the buried Kentstown granites in eastern Ireland. Shallow (<250 m) boreholes were drilled into the exposed Caledonian Leinster and Galway granites as part of a 1980's geothermal project. These studies yielded HP = 2-3 μWm-3 and HF = 80 mWm-2 at the Sally Gap borehole in the Northern Units of the Leinster granite, to the SW of Dublin. In the Galway granite batholith, on the west coast of Ireland, the Costelloe-Murvey granite returned HP = 7 μWm-3 and HF = 77 mWm-2, measured at the Rossaveal borehole. The buried Kentstown granite, 35 km NW of Dublin, has an associated negative Bouguer anomaly and was intersected by two mineral exploration boreholes at depths of 660 m and 490 m. Heat production is measured at 2.4 μWm-3 in core samples taken from the weathered top 30 m of the granite. The core of this study consists of a program of magnetotelluric (MT) and audio-magnetotelluric (AMT) data acquisition across the three granite bodies, over three fieldwork seasons. MT and AMT data were collected at 59 locations along two profiles over the Leinster granite. Preliminary results show that the northern units of the Leinster granite (40 km SW of Dublin) extend to depths of 2-5 km. Preliminary results from the southern profile suggest a greater thickness of granite to a depth of 6-9 km beneath the Tullow pluton, 75 km SW of

Alteration Mineralogy and Geochemical Characteristics of Porphyry Cu-Mo Mineralization in Domaniç (Kütahya) Area

NASA Astrophysics Data System (ADS)

Sariiz, K.; Sendir, H.

2012-04-01

The study area is located at 30 km northwest of Domaniç (Kütahya) and covers on approximately 250 square kilometers. The Devonian (Paleozoic) schists which are composed of gneiss, mica schist and chlorite schist is the oldest unit of the study area. This units are overlain unconformably by the Permian Allıkaya Marbles. Eocene granodioritic intrusives cut other rock series and located as a batholite. Magmatic units present porphyric and holocrystalline textures. Granodioritic intrusions are represented by tonalite, tonalite porphyr, granodiorite, granodiorite porphyr, granite, diorite, diorite porphyries. Potassic, phyllitic and prophyllitic hydrothermal alteration zones are determined in host rocks and wallrocks. Mineralizations are observed as disseminated, and stockwork types within the granodioritic rocks. Ore minerals are pyrotine, pyrite, chalcopyrite, molybdenite, rutile, bornite, sphalerite, marcasite and limonite. Geochemically, it is of sub-alkaline affinity, belongs to the high-K, calc-alkaline series and displays features of typical I-type affinity. They show enrichment in large-ion lithophile elements (LIL) and depletion Nb and Ti indicating a subduction zone related magmatic signature for their origin. δ18O (quartz) values range from 8,8 to 12,1 ‰. δ18O (biotite) and δD (biotite) values range from 2,6 to 6,1 ‰ and -87 - -125 (SMOW). These values indicate that mixture magmatic-meteoric of hydrothermal solutions origin which are potassic to propylitic zones. δ13C (calcite) values range from 1,9 to 3,3 ‰ (PDB). Calcite values within the marine carbonates in the study area.

Petrogenesis of the Late Jurassic peraluminous biotite granites and muscovite-bearing granites in SE China: geochronological, elemental and Sr-Nd-O-Hf isotopic constraints

NASA Astrophysics Data System (ADS)

Jiang, Yao-Hui; Zhu, Shu-Qi

2017-12-01

Biotite granites and muscovite-bearing granites are dominant rock types of the widespread granites in SE China. However, their petrogenesis has been enigmatic. A combined study of zircon U-Pb dating and Lu-Hf isotopes, whole-rock element geochemistry and Sr-Nd-O isotopes was performed for three late Mesozoic granitic plutons (Xinfengjie, Jiangbei and Dabu) in central Jiangxi province, SE China. All the plutons are composed of biotite granites and muscovite-bearing granites that have been poorly investigated previously. The new data not only allow us to assess their sources and magma evolution processes, but also helps us to better understand the genetic link to the large-scale polymetallic mineralization in SE China. LA-ICP-MS zircon U-Pb dating shows that three plutons were emplaced in the Late Jurassic (159-148 Ma) and that the muscovite-bearing granites are almost contemporaneous with the biotite granites. The biotite granites have SiO2 contents of 70.3-74.4 wt% and are weakly to strongly peraluminous with ASI from 1.00 to 1.26, and show a general decrease in ASI with increasing SiO2. They have relatively high zircon saturation temperatures ( T Zr = 707-817 °C, most > 745 °C) and show a general decrease in T Zr with increasing SiO2. They have high initial 87Sr/86Sr ratios (0.7136 to 0.7166) and high δ18O values (9.1-12.8‰, most > 9.5‰) and clearly negative ɛ Nd (T) (- 9.5 to - 11.8) and ɛ Hf (T) (in situ zircon) (- 13.1 to - 13.5). The muscovite-bearing granites have high SiO2 contents (74.7-78.2 wt%). They are also weakly to strongly peraluminous with ASI of 1.04-1.18 but show a general increase in ASI with increasing SiO2. They have relatively low T Zr (671-764 °C, most < 745 °C) and also show a general decrease in T Zr with increasing SiO2. The muscovite-bearing granites have high Rb (up to 810 ppm) and high (K2O + Na2O)/CaO (up to 270), Rb/Sr (up to 42) and Rb/Ba (up to 30) as well as low K/Rb (< 150, down to 50), Zr/Hf (< 24, down to 11) and Nb

Frictional slip of granite at hydrothermal conditions

USGS Publications Warehouse

Blanpied, M.L.; Lockner, D.A.; Byerlee, J.D.

1995-01-01

To measure the strength, sliding behavior, and friction constitutive properties of faults at hydrothermal conditions, laboratory granite faults containing a layer of granite powder (simulated gouge) were slid. The mechanical results define two regimes. The first regime includes dry granite up to at least 845?? and wet granite below 250??C. In this regime the coefficient of friction is high (?? = 0.7 to 0.8) and depends only modestly on temperature, slip rate, and PH2O. The second regime includes wet granite above ~350??C. In this regime friction decreases considerably with increasing temperature (temperature weakening) and with decreasing slip rate (velocity strengthening). These regimes correspond well to those identified in sliding tests on ultrafine quartz. The results highlight the importance of fluid-assisted deformation processes active in faults at depth and the need for laboratory studies on the roles of additional factors such as fluid chemistry, large displacements, higher concentrations of phyllosilicates, and time-dependent fault healing. -from Authors

Thermometers and thermobarometers in granitic systems

USGS Publications Warehouse

Anderson, J.L.; Barth, A.P.; Wooden, J.L.; Mazdab, F.; ,

2008-01-01

The ability to determine the thermal and barometric history during crystallization and emplacement of granitic plutons has been enhanced by several new calibrations applicable to granitic mineral assemblages. Other existing calibrations for granitic plutons have continued to be popular and fairly robust. Recent advances include the trace element thermometers Ti-in-quartz, Ti-in-zircon, and Zr-in-sphene (titanite), which need to be further evaluated on the roles of reduced activities due to lack of a saturating phase, the effect of pressure dependence (particularly for the Ti-in-zircon thermometer), and how resistive these thermometers are to subsolidus reequilibration. As zircon and sphene are also hosts to radiogenic isotopes, these minerals potentially also provide new insights into the temperature - time history of magmas. When used in conjunction with pressure-sensitive mineral equilibria in the same rocks, a complete assessment of the P-T-t (pressure-temperature-time) path is possible given that the mineralogy of plutons can reflect crystallization over a range of pressure and temperature during ascent and emplacement and that many intrusions are now seen as forming over several millions of years during the protracted history of batholith construction. Accessory mineral saturation thermometers, such as those for zircon, apatite, and allanite, provide a different and powerful perspective, specifically that of the temperature of the onset of crystallization of these minerals, which can allow an estimate of the range of temperature between the liquidus and solidus of a given pluton. In assessment of the depth of crystallization and emplacement of granitic plutons, the Al-in-hornblende remains popular for metaluminous granites when appropriately corrected for temperature. For peraluminous granites, potential new calibrations exist for the assemblages bearing garnet, biotite, plagioclase, muscovite, and quartz. Other thermometers, based on oxygen abundance, and

Radionuclide Transport in Fracture-Granite Interface Zones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Q; Mori, A

In situ radionuclide migration experiments, followed by excavation and sample characterization, were conducted in a water-conducting shear zone at the Grimsel Test Site (GTS) in Switzerland to study diffusion paths of radionuclides in fractured granite. In this work, we employed a micro-scale mapping technique that interfaces laser ablation sampling with inductively coupled plasma-mass spectrometry (LA/ICP-MS) to measure the fine-scale (micron-range) distribution of actinides ({sup 234}U, {sup 235}U, and {sup 237}Np) in the fracture-granite interface zones. Long-lived {sup 234}U, {sup 235}U, and {sup 237}Np were detected in flow channels, as well as in the adjacent rock matrix, using the sensitive, feature-basedmore » mapping of the LA/ICP-MS technique. The injected sorbing actinides are mainly located within the advective flowing fractures and the immediately adjacent regions. The water-conducting fracture studied in this work is bounded on one side by mylonite and the other by granitic matrix regions. These actinides did not penetrate into the mylonite side as much as the relatively higher-porosity granite matrix, most likely due to the low porosity, hydraulic conductivity, and diffusivity of the fracture wall (a thickness of about 0.4 mm separates the mylonite region from the fracture) and the mylonite region itself. Overall, the maximum penetration depth detected with this technique for the more diffusive {sup 237}Np over the field experimental time scale of about 60 days was about 10 mm in the granitic matrix, illustrating the importance of matrix diffusion in retarding radionuclide transport from the advective fractures. Laboratory tests and numerical modeling of radionuclide diffusion into granitic matrix was conducted to complement and help interpret the field results. Measured apparent diffusivity of multiple tracers in granite provided consistent predictions for radionuclide transport in the fractured granitic rock.« less

"Normal" to adakite-like arc magmatism associated with the El Abra porphyry copper deposit, Central Andes, Northern Chile

NASA Astrophysics Data System (ADS)

Rabbia, Osvaldo M.; Correa, Karen J.; Hernández, Laura B.; Ulrich, Thomas

2017-03-01

The El Abra porphyry copper deposit belongs to the Late Eocene—Early Oligocene metallogenic belt of northern Chile, which host several world-class porphyry copper deposits. Our previous geochronological work done on this deposit provides the temporal framework for petrological data interpretation. The magmatic history of the El Abra deposit lasts for 8.6 Ma and can be divided into two stages. An early period, from about 45 to 38.7 Ma, dominated by diorites and quartz monzodiorites with "normal" (non-adakite) arc geochemistry and a late period, with rocks younger than 38.7 Ma that developed adakite-like geochemistry, where equigranular granodiorites are the volumetrically dominant rock type (e.g., Clara granodiorite 38 Ma). These granodiorites are then intruded by leucocratic porphyry dikes and aplites. Most copper mineralization is associated with multiple intrusions of these younger porphyritic rocks, described as the El Abra porphyry unit, and emplaced over a 1.4 Ma period, from 37.5 to 36.1 Ma. The adakite-like geochemistry of the younger rock units (<38.7 Ma) is attested by a significant depletion in REE contents, particularly MREE and HREE (concave MREE distribution patterns), high La/Yb and Sr/Y ratios, and Na2O and Al2O3 contents, along with the absence of the Eu anomaly in normalized REE distribution patterns. The evolution of this large, long-lived magmatic system from "normal" to adakite-like arc magmatism is discussed in a tectonic context of crust overthickening due to a major orogenic episode (Incaic compressive phase). This tectonic setting may have promoted higher pressure conditions at the lower crust "hot zone" and increased the crustal residence time of derivative melts favoring extensive differentiation leading to water-rich (and oxidized?) felsic melts, where amphibole fractionation played an important role. Strontium, Nd, and Pb isotope data suggest a common mantle source for both the non-adakite and adakite-like rocks. This implies that

The Jebel Ohier deposit—a newly discovered porphyry copper-gold system in the Neoproterozoic Arabian-Nubian Shield, Red Sea Hills, NE Sudan

NASA Astrophysics Data System (ADS)

Bierlein, F. P.; McKeag, S.; Reynolds, N.; Bargmann, C. J.; Bullen, W.; Murphy, F. C.; Al-Athbah, H.; Brauhart, C.; Potma, W.; Meffre, S.; McKnight, S.

2016-08-01

Ongoing exploration in the Red Sea Hills of NE Sudan has led to the identification of a large alteration-mineralization system within a relatively undeformed Neoproterozoic intrusive-extrusive succession centered on Jebel Ohier. The style of mineralization, presence of an extensive stockwork vein network within a zoned potassic-propylitic-argillic-advanced argillic-altered system, a mineralization assemblage comprising magnetite-pyrite-chalcopyrite-bornite (±gold, silver and tellurides), and the recurrence of fertile mafic to intermediate magmatism in a developing convergent plate setting all point to a porphyry copper-gold association, analogous to major porphyry Cu-Au-Mo deposits in Phanerozoic supra-subduction settings such as the SW Pacific. Preliminary U-Pb age dating yielded a maximum constraint of c. 730 Ma for the emplacement of the stockwork system into a significantly older ( c. 800 Ma) volcanic edifice. The mineralization formed prior to regional deformation and accretion of the host terrane to a stable continental margin at by c. 700 Ma, thus ensuring preservation of the deposit. The Jebel Ohier deposit is interpreted as a relatively well-preserved, rare example of a Neoproterozoic porphyry Cu-Au system and the first porphyry Cu-Au deposit to be identified in the Arabian-Nubian Shield.

Metal endowment reflected in chemical composition of silicates and sulfides of mineralized porphyry copper systems, Urumieh-Dokhtar magmatic arc, Iran

NASA Astrophysics Data System (ADS)

Zarasvandi, Alireza; Rezaei, Mohsen; Raith, Johann G.; Pourkaseb, Houshang; Asadi, Sina; Saed, Madineh; Lentz, David R.

2018-02-01

The present work attempts to discriminate between the geochemical features of magmatic-hydrothermal systems involved in the early stages of mineralization in high grade versus low grade porphyry copper systems, using chemical compositions of silicate and sulfide minerals (i.e., plagioclase, biotite, pyrite and chalcopyrite). The data indicate that magmatic plagioclase in all of the porphyry copper systems studied here has high An% and Al content with a significant trend of evolution toward AlAl3SiO8 and □Si4O8 endmembers, providing insight into the high melt water contents of the parental magmas. Comparably, excess Al and An% in the high grade deposits appears to be higher than that of selected low grade deposits, representing a direct link between the amounts of exsolving hydrothermal fluids and the potential of metal endowment in porphyry copper deposits (PCDs). Also, higher Al contents accompanied by elevated An% are linked to the increasing intensity of disruptive alteration (phyllic) in feldspars from the high grade deposits. As calculated from biotite compositions, chloride contents are higher in the exsolving hydrothermal fluids that contributed to the early mineralization stages of highly mineralized porphyry systems. However, as evidenced by scattered and elevated log (fH2O)/(fHF) and log (fH2O)/(fHCl) values, chloride contents recorded in biotite could be influenced by post potassic fluids. Geothermometry of biotite associated with the onset of sulfide mineralization indicates that there is a trend of increasing temperature from high grade to low grade porphyry systems. Significantly, this is coupled with a sharp change in copper content of pyrite assemblages precipitated at the early stages of mineralization such that Cu decreased with increasing temperature. Based on EMPA and detailed WDS elemental mapping, trace elements do not exhibit complex compositional zoning or solid solution in the sulfide structure. Nevertheless, significant amounts of Cu and

A combined geochronological approach to investigating long lived granite magmatism, the Shap granite, UK

NASA Astrophysics Data System (ADS)

Miles, A. J.; Woodcock, N. H.

2018-04-01

With the advent of more precise dating methods, it has become apparent that zircon dates from granite plutons frequently indicate older emplacement ages than other dating methods. Here we attempt to reconcile a number of dating methods from the c. 5 km2 Caledonian Shap granite, Northern England. The results reveal a more complex and protracted evolution than indicated by application of any single dating method. Zircon U-Pb dates give a weighted mean age of 415.6 ± 1.4 (2σ) Ma. A mafic enclave, dated at 412 ± 2 (2σ) Ma (revised Rb-Sr feldspar age from Davidson et al., 2005), contains resorbed K-feldspar and zircon crystals scavenged from the host crystal mush. These ages are at odds with field relations in the thermal aureole that suggest final emplacement at approximately 404 Ma or later during Acadian deformation. Previously reported Re-Os ages on molybdenites associated with magmatic fluids, have given ages of 405.2 ± 1.8 (2σ) Ma (Selby et al., 2008) and confirm the overlap of at least some magmatic activity with Acadian deformation. A similar emplacement age is supported by Rb-Sr whole-rock-mineral and biotite K-Ar dates when adjusted for revised decay constants (402 ± 3 Ma and 401 ± 7 Ma, respectively, Wadge et al., 1978). The lower closure temperatures of these systems relative to the U-Pb system in zircon means that they are more likely to record the timing of final granite emplacement. These data suggest that most zircons grew before final granite emplacement, by about 10 Ma on average. We suggest that the majority of zircon crystals record pre-emplacement magmatic activity within a deeper part of the system. Mafic enclaves and their scavenged cargo of crystals record the assembly of a mid-crustal batholith where crystals remained at least locally mobile at 412 Ma. Gravity data support the existence of an extensive, 1500 km2 intrusive body, originally at about 15 km depth beneath Shap. This batholith is likely to have remained below the granite

Effect of Anisotropy on the Long-Term Strength of Granite

NASA Astrophysics Data System (ADS)

Nara, Yoshitaka

2015-05-01

Granite rock mass is used for various rock engineering purposes. To ensure long-term stability, information about the subcritical crack growth (SCG) and an estimate of the long-term strength (LTS) of the rock are necessary. The influence of the anisotropy of granite on its LTS has not yet been clarified. In this study, the anisotropy of the long-term rock strength was investigated for two types of granite rocks, Oshima granite and Inada granite. Specifically, the effect of the anisotropy in crack propagation on the LTS was examined. The results showed that the LTS of granite is anisotropic, as are the fracture toughness and Brazilian tensile strength measured in this study. The LTS was lowest when crack propagation occurred parallel to the rift plane, where most of the microcracks occur. For Inada granite, which has an anisotropic SCG index, the degree of anisotropy of the LTS increased as the time-to-failure increased. This suggests that the LTS of granite is anisotropic.

Zircon U-Pb and molybdenite Re-Os geochronology and Sr-Nd-Pb-Hf isotopic constraints on the genesis of the Xuejiping porphyry copper deposit in Zhongdian, Northwest Yunnan, China

NASA Astrophysics Data System (ADS)

Leng, Cheng-Biao; Zhang, Xing-Chun; Hu, Rui-Zhong; Wang, Shou-Xu; Zhong, Hong; Wang, Wai-Quan; Bi, Xian-Wu

2012-10-01

The Xuejiping porphyry copper deposit is located in northwestern Yunnan Province, China. Tectonically, it lies in the southern part of the Triassic Yidun island arc. The copper mineralization is mainly hosted in quartz-dioritic and quartz-monzonitic porphyries which intruded into clastic-volcanic rocks of the Late Triassic Tumugou Formation. There are several alteration zones including potassic, strong silicific and phyllic, argillic, and propylitic alteration zones from inner to outer of the mineralized porphyry bodies. The ages of ore-bearing quartz-monzonitic porphyry and its host andesite are obtained by using the zircon SIMS U-Pb dating method, with results of 218.3 ± 1.6 Ma (MSWD = 0.31, N = 15) and 218.5 ± 1.6 Ma (MSWD = 0.91, N = 16), respectively. Meanwhile, the molybdenite Re-Os dating yields a Re-Os isochronal age of 221.4 ± 2.3 Ma (MSWD = 0.54, N = 5) and a weighted mean age of 219.9 ± 0.7 Ma (MSWD = 0.88). They are quite in accordance with the zircon U-Pb ages within errors. Furthermore, all of them are contemporary with the timing of the Garzê-Litang oceanic crust subduction in the Yidun arc. Therefore, the Xuejiping deposit could be formed in a continental margin setting. There are negative ɛNd(t) values ranging from -3.8 to -2.1 and relatively high initial 87Sr/86Sr ratios from 0.7051 to 0.7059 for the Xuejiping porphyries and host andesites. The (206Pb/204Pb)t, (207Pb/204Pb)t and (208Pb/204Pb)t values of the Xuejiping porphyries and host andesites vary from 17.899 to 18.654, from 15.529 to 15.626, and from 37.864 to 38.52, respectively, indicative of high radiogenic Pb isotopic features. In situ Hf isotopic analyses on zircons by using LA-MC-ICP-MS exhibit that there are quite uniform and slightly positive ɛHf(t) values ranging from -0.2 to +3.2 (mostly between 0 and +2), corresponding to relatively young single-stage Hf model ages from 735 Ma to 871 Ma. These isotopic features suggest that the primary magmas of the Xuejiping porphyries and

Digital data base application to porphyry copper mineralization in Alaska; case study summary

USGS Publications Warehouse

Trautwein, Charles M.; Greenlee, David D.; Orr, Donald G.

1982-01-01

The purpose of this report is to summarize the progress in use of digital image analysis techniques in developing a conceptual model for assessing porphyry copper mineral potential. The study area consists of approximately the southern one-half of the 1? by 3? Nabesna quadrangle in east-central Alaska. The digital geologic data base consists of data compiled under the Alaskan Mineral Resource Assessment Program (AMRAP) as well as digital elevation data and Landsat spectral reflectance data from the Multispectral Scanner System. The digital data base used to develop and implement a conceptual model for porphyry-type copper mineralization consisted of 16 original data types and 18 derived data sets formatted in a grid-cell (raster) structure and registered to a map base in the Universal Transverse Mercator (UTM) projection. Minimum curvature and inverse distance squared interpolation techniques were used to generate continuous surfaces from sets of irregularly spaced data points. Processing requirements included: (1) merging or overlaying of data sets, (2) display and color coding of maps and images, (3) univariate and multivariate statistical analyses, and (4) compound overlaying operations. Data sets were merged and processed to create stereoscopic displays of continuous surfaces. The ratio of several data sets were calculated to evaluate relative variations and to enhance the display of surface alteration (gossans). Factor analysis and principal components analysis techniques were used to determine complex relationships and correlations between data sets. The resultant model consists of 10 parameters that identify three areas most likely to contain porphyry copper mineralization; two of these areas are known occurrences of mineralization and the third is not well known. Field studies confirmed that the three areas identified by the model have significant copper potential.

The Taitao Granites: I-type granites formed by subduction of the Chile Ridge and its implication in growth of continental crusts

NASA Astrophysics Data System (ADS)

Anma, Ryo

2016-04-01

Late Miocene to Early Pliocene granite plutons are exposed at the tip of the Taitao peninsula, the westernmost promontory of the Chilean coast, together with a contemporaneous ophiolite with a Penrose-type stratigraphy. Namely, the Taitao granites and the Taitao ohiolite, respectively, are located at ~30 km southeast of the Chile triple junction, where a spreading center of the Chile ridge system is subducting underneath the South America plate. This unique tectonic setting provides an excellent opportunity to study the generation processes of granitic magmas at a ridge subduction environment, and the complex magmatic interactions between the subducting ridge, overlying crust and sediments, and mantle. This paper reviews previous studies on the Taitao ophiolite/granite complex and use geochemical data and U-Pb age distributions of zircons separated from igneous and sedimentary rocks from the area to discuss the mechanism that formed juvenile magma of calc-alkaline I-type granites during ridge subduction. Our model implies that the magmas of the Taitao granites formed mainly due to partial melting of hot oceanic crust adjacent to the subducting mid-oceanic ridge that has been under influence of deep crustal contamination and/or metasomatized sub-arc mantle through slab window. The partial melting took place under garnet-free-amphibolite conditions. The juvenile magmas then incorporated a different amount of subducted sediments to form the I-type granites with various compositions. The Taitao granites provide an ideal case study field that shows the processes to develop continental crusts out of oceanic crusts through ridge subduction.

Quantitative Mineral Resource Assessment of Copper, Molybdenum, Gold, and Silver in Undiscovered Porphyry Copper Deposits in the Andes Mountains of South America

USGS Publications Warehouse

Cunningham, Charles G.; Zappettini, Eduardo O.; Vivallo S., Waldo; Celada, Carlos Mario; Quispe, Jorge; Singer, Donald A.; Briskey, Joseph A.; Sutphin, David M.; Gajardo M., Mariano; Diaz, Alejandro; Portigliati, Carlos; Berger, Vladimir I.; Carrasco, Rodrigo; Schulz, Klaus J.

2008-01-01

Quantitative information on the general locations and amounts of undiscovered porphyry copper resources of the world is important to exploration managers, land-use and environmental planners, economists, and policy makers. This publication contains the results of probabilistic estimates of the amounts of copper (Cu), molybdenum (Mo), gold (Au), and silver (Ag) in undiscovered porphyry copper deposits in the Andes Mountains of South America. The methodology used to make these estimates is called the 'Three-Part Form'. It was developed to explicitly express estimates of undiscovered resources and associated uncertainty in a form that allows economic analysis and is useful to decisionmakers. The three-part form of assessment includes: (1) delineation of tracts of land where the geology is permissive for porphyry copper deposits to form; (2) selection of grade and tonnage models appropriate for estimating grades and tonnages of the undiscovered porphyry copper deposits in each tract; and (3) estimation of the number of undiscovered porphyry copper deposits in each tract consistent with the grade and tonnage model. A Monte Carlo simulation computer program (EMINERS) was used to combine the probability distributions of the estimated number of undiscovered deposits, the grades, and the tonnages of the selected model to obtain the probability distributions for undiscovered metals in each tract. These distributions of grades and tonnages then can be used to conduct economic evaluations of undiscovered resources in a format usable by decisionmakers. Economic evaluations are not part of this report. The results of this assessment are presented in two principal parts. The first part identifies 26 regional tracts of land where the geology is permissive for the occurrence of undiscovered porphyry copper deposits of Phanerozoic age to a depth of 1 km below the Earth's surface. These tracts are believed to contain most of South America's undiscovered resources of copper. The

Investigation on the age of mineralization in the Sungun porphyry Cu-Mo deposit, NW Iran with a regional metallogenic perspective

NASA Astrophysics Data System (ADS)

Simmonds, Vartan; Moazzen, Mohssen; Mathur, Ryan

2016-04-01

The Sungun porphyry copper deposit (PCD) is located in NW Iran, neighbouring several other PCDs and prospects in the region and the Lesser Caucasus (south Armenia). It lies on the Urumieh-Dokhtar magmatic arc (UDMA), which formed through the northeast-ward subduction of the Neo-Tethyan oceanic crust beneath the Central Iranian plate during late-Mesozoic and early-Cenozoic [1], and hosts the porphyry copper metallogenic belt of Iran. The Sungun PCD is the second largest deposit in Iran with ore reserves of about 850 Mt at 0.62 wt% Cu and 0.01 wt% Mo and probable reserves over 1Gt. The monzonitic to quartz monzonitic porphyry stock intruded the upper Cretaceous carbonates and Eocene volcano-sedimentary rocks. It produced a skarn-type mineralization at its contact zone with the carbonate rocks, as well as vast hydrothermal alteration zones and porphyry-type Cu and Mo mineralization. The zircon U-Pb age of the host porphyry stock is about 22.5±0.4 to 20.1±0.4 Ma [2]. Re-Os dating of four molybdenite separates from this PCD shows ages ranging between 22.9±0.2 to 21.7±0.2 Ma, with an average of 22.57±0.2 Ma, corresponding to the early Miocene (Aquitanian). These ages indicate that both the porphyry stock and the Cu-Mo mineralization are post-collisional events, similar to many other deposits and prospects in NW and central Iran and south Armenia, and the mineralization occurred shortly after the emplacement of the host stock, corresponding better to the ages obtained from the marginal parts of the stock. Magmatism and mineralization in Sungun coincides with the third metallogenic epoch in the Lesser Caucasus (Eocene to Miocene; [3]), though it is considerably younger than all of the dated PCDs and prospects in the south Armenia. It also postdates Cu-Mo mineralizations in the Saheb Divan (35 Ma), Qaradagh batholith (31.22±0.28 to 25.19±0.19 Ma), as well as Haft Cheshmeh PCD (28.18±0.42 to 27.05±0.37 Ma) in NW Iran, while it seems to be coeval with the Kighal

Geological analysis of aeromagnetic data from southwestern Alaska: implications for exploration in the area of the Pebble porphyry Cu-Au-Mo deposit

USGS Publications Warehouse

Anderson, Eric D.; Hitzman, Murray W.; Monecke, Thomas; Bedrosian, Paul A.; Shah, Anjana K.; Kelley, Karen D.

2013-01-01

Aeromagnetic data are used to better understand the geology and mineral resources near the Late Cretaceous Pebble porphyry Cu-Au-Mo deposit in southwestern Alaska. The reduced-to-pole (RTP) transformation of regional-scale aeromagnetic data shows that the Pebble deposit is within a cluster of magnetic anomaly highs. Similar to Pebble, the Iliamna, Kijik, and Neacola porphyry copper occurrences are in magnetic highs that trend northeast along the crustal-scale Lake Clark fault. A high-amplitude, short- to moderate-wavelength anomaly is centered over the Kemuk occurrence, an Alaska-type ultramafic complex. Similar anomalies are found west and north of Kemuk. A moderate-amplitude, moderate-wavelength magnetic low surrounded by a moderate-amplitude, short-wavelength magnetic high is associated with the gold-bearing Shotgun intrusive complex. The RTP transformation of the district-scale aeromagnetic data acquired over Pebble permits differentiation of a variety of Jurassic to Tertiary magmatic rock suites. Jurassic-Cretaceous basalt and gabbro units and Late Cretaceous biotite pyroxenite and granodiorite rocks produce magnetic highs. Tertiary basalt units also produce magnetic highs, but appear to be volumetrically minor. Eocene monzonite units have associated magnetic lows. The RTP data do not suggest a magnetite-rich hydrothermal system at the Pebble deposit. The 10-km upward continuation transformation of the regional-scale data shows a linear northeast trend of magnetic anomaly highs. These anomalies are spatially correlated with Late Cretaceous igneous rocks and in the Pebble district are centered over the granodiorite rocks genetically related to porphyry copper systems. The spacing of these anomalies is similar to patterns shown by the numerous porphyry copper deposits in northern Chile. These anomalies are interpreted to reflect a Late Cretaceous magmatic arc that is favorable for additional discoveries of Late Cretaceous porphyry copper systems in southwestern

Porphyry copper assessment of Central America and the Caribbean Basin: Chapter I in Global mineral resource assessment

USGS Publications Warehouse

Gray, Floyd; Hammarstrom, Jane M.; Ludington, Stephen; Zürcher, Lukas; Nelson, Carl E.; Robinson, Gilpin R.; Miller, Robert J.; Moring, Barry C.

2014-01-01

This assessment estimated a total mean of 37 undiscovered porphyry copper deposits within the assessed permissive tracts in Central America and the Caribbean Basin. This represents more than five times the seven known deposits. Predicted mean (arithmetic) resources that could be associated with these undiscovered deposits are about 130 million metric tons of copper and about 5,200 metric tons of gold, as well as byproduct molybdenum and silver. The reported identified resources for the seven known deposits total about 39 million metric tons of copper and about 930 metric tons of gold. The assessment area is estimated to contain nearly four times as much copper and six times as much gold in undiscovered porphyry copper deposits as has been identified to date.

Mineralized breccia clasts: a window into hidden porphyry-type mineralization underlying the epithermal polymetallic deposit of Cerro de Pasco (Peru)

NASA Astrophysics Data System (ADS)

Rottier, Bertrand; Kouzmanov, Kalin; Casanova, Vincent; Bouvier, Anne-Sophie; Baumgartner, Lukas P.; Wälle, Markus; Fontboté, Lluís

2018-01-01

Cerro de Pasco (Peru) is known for its large epithermal polymetallic (Zn-Pb-Ag-Cu-Bi) mineralization emplaced at shallow level, a few hundred meters below the paleo-surface, at the border of a large diatreme-dome complex. Porphyry-style veins crosscutting hornfels and magmatic rock clasts are found in the diatreme breccia and in quartz-monzonite porphyry dikes. Such mineralized veins in clasts allow investigation of high-temperature porphyry-style mineralization developed in the deep portions of magmatic-hydrothermal systems. Quartz in porphyry-style veins contains silicate melt inclusions as well as fluid and solid mineral inclusions. Two types of high-temperature (> 600 °C) quartz-molybdenite-(chalcopyrite)-(pyrite) veins are found in the clasts. Early, thin (1-2 mm), and sinuous HT1 veins are crosscut by slightly thicker (up to 2 cm) and more regular HT2 veins. The HT1 vein quartz hosts CO2- and sulfur-rich high-density vapor inclusions. Two subtypes of the HT1 veins have been defined, based on the nature of mineral inclusions hosted in quartz: (i) HT1bt veins with inclusions of K-feldspar, biotite, rutile, and minor titanite and (ii) HT1px veins with inclusions of actinolite, augite, titanite, apatite, and minor rutile. Using an emplacement depth of the veins of between 2 and 3 km (500 to 800 bar), derived from the diatreme breccia architecture and the supposed erosion preceding the diatreme formation, multiple mineral thermobarometers are applied. The data indicate that HT1 veins were formed at temperatures > 700 °C. HT2 veins host assemblages of polyphase brine inclusions, generally coexisting with low-density vapor-rich inclusions, trapped at temperatures around 600 °C. Rhyolitic silicate melt inclusions found in both HT1 and HT2 veins represent melt droplets transported by the ascending hydrothermal fluids. LA-ICP-MS analyses reveal a chemical evolution coherent with the crystallization of an evolved rhyolitic melt. Quartz from both HT1 and HT2 veins

Geological and geochemical studies of the Shujiadian porphyry Cu deposit, Anhui Province, Eastern China: Implications for ore genesis

NASA Astrophysics Data System (ADS)

Wang, Shiwei; Zhou, Taofa; Yuan, Feng; Fan, Yu; White, Noel C.; Lin, Fengjie

2015-05-01

Most porphyry deposits in the world occur in magmatic arc settings and are related to subduction of oceanic plates. A small proportion of porphyry deposits occur in intracontinental settings, however they are still poorly understood. Shujiadian, a newly-discovered porphyry Cu deposit, is located in the Middle-Lower Yangtze River Valley metallogenic belt and belongs to the intracontinental class. The deposit has classic alteration zones defined by a core of potassic alteration and local Ca-silicate alteration, which is overprinted by a feldspar-destructive alteration zone and cut by veins containing epidote and chlorite. Wallrocks of the deposit are unreactive quartz-rich sedimentary rocks. Three main paragenetic stages have been recognized based on petrographic observations; silicate stage, quartz-sulfide stage, and sulfide-carbonate stage. Quartz + pyrite + chalcopyrite ± molybdenite veins, and quartz + chalcopyrite + pyrite veins of the quartz-sulfide stage contribute most of the copper, and chalcopyrite + chlorite ± pyrite ± pyrrhotite ± quartz ± illite veins of the sulfide-carbonate stage also contribute part of the copper; all the mineralized veins are associated with feldspar-destructive alteration. Investigations on the fluid inclusions in Shujiadian indicate that the ore-forming fluids had four evolutionary episodes: immiscibility and overpressure in the silicate stage, boiling in the quartz-sulfide stage and mixing with meteoric water in the sulfide-carbonate stage. Sulfur and strontium isotope studies suggest that ore metals were mainly derived from magmatic-hydrothermal fluids, and combined with our study of fluid inclusions, we infer that decompression, changes in oxygen fugacity and sulfur content were the main factors that caused Cu precipitation. Compared with porphyry deposits in magmatic arc settings, there are some differences in the ore-bearing rock, alteration, and the composition of ore-forming fluids.

Effect of Bacillus subtilis on Granite Weathering: A Laboratory Experiment

NASA Astrophysics Data System (ADS)

Song, W.; Ogawa, N.; Oguchi, C. T.; Hatta, T.; Matsukura, Y.

2006-12-01

We performed a comparative experiment to investigate how the ubiquitous soil bacterium Bacillus subtilis weathers granite and which granite-forming minerals weather more rapidly via biological processes. Batch type experiments (granite specimen in a 500 ml solution including NaCl, glucose, yeast extract and bacteria Bacillus subtilis at 27°E C) were carried out for 30 days. Granite surfaces were observed by SEM before and after the experiment. Bacillus subtilis had a strong influence on granite weathering by forming pits. There were 2.4 times as many pits and micropores were 2.3 times wider in granite exposed to Bacillus subtilis when compared with bacteria-free samples. Bacillus subtilis appear to preferentially select an optimum place to adhere to the mineral and dissolve essential elements from the mineral to live. Plagioclase was more vulnerable to bacterial weathering than biotite among the granite composing minerals.

Porphyry copper assessment of western Central Asia: Chapter N in Global mineral resource assessment

USGS Publications Warehouse

Berger, Byron R.; Mars, John L.; Denning, Paul; Phillips, Jeffrey D.; Hammarstrom, Jane M.; Zientek, Michael L.; Dicken, Connie L.; Drew, Lawrence J.; with contributions from Alexeiev, Dmitriy; Seltmann, Reimar; Herrington, Richard J.

2014-01-01

Detailed descriptions of each permissive tract, including the rationales for delineation and assessment, are given in appendixes, along with a geographic information system (GIS) that includes permissive tract boundaries, point locations of known porphyry copper deposits and significant occurrences, and hydrothermal alteration data based on analysis of remote sensing data.

Depositional features and stratigraphic sections in granitic plutons: implications for the emplacement and crystallization of granitic magma

NASA Astrophysics Data System (ADS)

Wiebe, R. A.; Collins, W. J.

1998-09-01

Many granitic plutons contain sheet-like masses of dioritic to gabbroic rocks or swarms of mafic to intermediate enclaves which represent the input of higher temperature, more mafic magma during crystallization of the granitic plutons. Small-scale structures associated with these bodies (e.g. load-cast and compaction features, silicic pipes extending from granitic layers into adjacent gabbroic sheets) indicate that the sheets and enclave swarms were deposited on a floor of the magma chamber (on granitic crystal mush and beneath crystal-poor magma) while the mafic magma was incompletely crystallized. These structures indicate 'way up', typically toward the interior of the intrusions, and appear to indicate that packages of mafic sheets and enclave concentrations in these plutons are a record of sequential deposition. Hence, these plutons preserve a stratigraphic history of events involved in the construction (filling, replenishment) and crystallization of the magma chamber. The distinctive features of these depositional portions of plutons allow them to be distinguished from sheeted intrusions, which usually preserve mutual intrusive contacts and 'dike-sill' relations of different magma types. The considerable thickness of material that can be interpreted as depositional, and the evidence for replenishment, suggest that magma chamber volumes at any one time were probably much less than the final size of the pluton. Thus, magma chambers may be constructed much more slowly than presently envisaged. The present steep attitudes of these structures in many plutons may have developed gradually as the floor of the chamber (along with the underlying solidified granite and country rock) sank during continuing episodes of magma chamber replenishment. These internal magmatic structures support recent suggestions that the room problem for granites could be largely accommodated by downward movement of country rock beneath the magma chamber.

Geochemistry, zircon U-Pb dating and Hf isotopies composition of Paleozoic granitoids in Jinchuan, NW China: Constraints on their petrogenesis, source characteristics and tectonic implication

NASA Astrophysics Data System (ADS)

Zeng, Renyu; Lai, Jianqing; Mao, Xiancheng; Li, Bin; Ju, Peijiao; Tao, Shilong

2016-05-01

Granitoids are widely distributed in Jinchuan at the southwestern margin of the North China plate, which is also an important area of mineral deposits. The research subject of this article are two Paleozoic granitoids, a cataclastic syenogranite and a granodiorite porphyry. This study presents whole rock geochemistry and zircon U-Pb-Hf isotope data for the two granitoids to determine their petrogenesis, source characteristics and tectonic significance. The cataclastic syenogranite is characterized by metaluminous composition with high potassium, and LaN/YbN from 39 to 48. The composition with strong negative Eu anomalies and Zircon saturation temperatures (TZr) from 947 to 1072 °C classify this intrusion as an A-type granite. The granodiorite porphyry is metaluminous with high sodium, sub-alkaline, LaN/YbN ratios from 27 to 32. These I-type intrusions have no Eu anomalies and TZr ranges from 818 to 845 °C. Both the cataclastic syenogranite and granodiorite porphyry show enrichment of LREE and LILE and depletion of HREE and HFSE, except Hf and Zr. Using single zircon LA-ICP-MS U-Pb dating, the emplacement age of the cataclastic syenogranite and granodiorite porphyry are determined at 433.4 ± 3.7 Ma and 361.7 ± 4.6 Ma, respectively. Zircons from the cataclastic syenogranits have uniform negative εHf(t) values (-11 ± 0.5 to -9 ± 0.5), implying the involvement of an old Palaeoproterozoic crustal source in magma genesis. The zircons from the granodiorite porphyry have εHf(t) values that range from -8 ± 1.0 to +10 ± 0.6, suggesting heterogeneous source materials involving both juvenile and ancient crust reworked crustal components. Based on the geological significance of granites at the southwestern margin of the North China plate, the closure of the North Qilian Ocean occurred at ∼444 Ma. Geochemical features suggest that the cataclastic syenogranite and granodiorite porphyry formed in an intraplate extensional and compressional setting, respectively. Hence

Granite-related Yangjiashan tungsten deposit, southern China

NASA Astrophysics Data System (ADS)

Xie, Guiqing; Mao, Jingwen; Li, Wei; Fu, Bin; Zhang, Zhiyuan

2018-04-01

The Yangjiashan scheelite-bearing deposit (38,663 metric tons of WO3 with an average ore grade of 0.70% WO3) is hosted in quartz veins in a biotite monzogranite intrusion and surrounding slate in the Xiangzhong Metallogenic Province of southern China. The monzogranite has a zircon SHRIMP U-Pb age of 406.6 ± 2.8 Ma (2σ, n = 20, MSWD = 1.4). Cassiterite coexisting with scheelite yields a weighted mean 206Pb/238U age of 409.8 ± 5.9 Ma (2σ, n = 30, MSWD = 0.20), and molybdenite intergrown with scheelite yields a weighted mean Re-Os age of 404.2 ± 3.2 Ma (2σ, n = 3, MSWD = 0.10). These results suggest that the Yangjiashan tungsten deposit is temporally related to the Devonian intrusion. The δD and calculated δ18OH2O values of quartz intergrown with scheelite range from - 87 to - 68‰, and - 1.2 to 3.4‰, respectively. Sulfides have a narrow range of δ34S values of - 2.9 to - 0.7‰ with an average value of - 1.6‰ (n = 16). The integration of geological, stable isotope, and geochronological data, combined with the quartz-muscovite greisen style of ore, supports a magmatic-hydrothermal origin for the tungsten mineralization. Compared to the more common tungsten skarn, quartz-wolframite vein, and porphyry tungsten deposits, as well as orogenic gold deposits worldwide, the Yangjiashan tungsten deposit is an unusual example of a granite-related, gold-poor, scheelite-bearing quartz vein type of deposit. The calcium needed for the formation of scheelite is derived from the sericitization of calcic plagioclase in the monzogranite and Ca-bearing psammitic country rocks, and the relatively high pH, reduced and Ca-rich mineralizing fluid may be the main reasons for the formation of scheelite rather than wolframite at Yangjiashan.

Geochemistry and petrogenesis of the Mesoarchean granites from the Canaã dos Carajás area, Carajás Province, Brazil: Implications for the origin of Archean granites

NASA Astrophysics Data System (ADS)

Feio, G. R. L.; Dall'Agnol, R.

2012-12-01

Four Mesoarchean (2.93 to 2.83 Ga) granite units, which encompass the Canaã dos Carajás, Bom Jesus, Cruzadão and Serra Dourada granites, were recognized in the Canaã dos Carajás area of the Archean Carajás Province. The Mesoarchean units are composed dominantly of biotite leucomonzogranites. They are compared with the Neoarchean Planalto suite (2.73 Ga) which encompasses biotite-hornblende monzogranites to syenogranites. The Canaã dos Carajás, Bom Jesus and the variety of the Cruzadão granite with higher (La/Yb)N are geochemically more akin to the calc-alkaline granites, whereas the other varieties of the Cruzadão granite are transitional between calc-alkaline and alkaline granites. The Serra Dourada granite has an ambiguous geochemical character with some features similar to those of calc-alkaline granites and other peraluminous granites. The Planalto granites have ferroan character, are similar geochemically to reduced A-type granites and show a strong geochemical contrast with the Mesoarchean studied granites. The Mesoarchean granites described in the Canaã dos Carajás area are geochemically distinct to those of the Rio Maria domain of the Carajás Province. The Canaã dos Carajás and Bom Jesus granites are similar to the high-Ca granites, whereas the Cruzadão and Serra Dourada are more akin to the low-CaO granites of the Yilgarn craton. The geochemical characteristics of the Mesoarchean studied granites approach those of the biotite granite group of Dharwar but the latter are enriched in HFSE and HREE compared to the Canaã dos Carajás granites. The Neoarchean Planalto suite granite has no counterpart in the Mesoarchean Rio Maria domain of the Carajás Province, neither in the Yilgarn and Dharwar cratons. Geochemical modeling suggests that partial melting of a source similar in composition to an Archean basaltic andesite of the Carajás Province could give origin to the Bom Jesus and Cruzadão granites. In the case of the Bom Jesus granite the

Tectonic setting of the pebble and other copper-gold-molybdenum porphyry deposits within the evolving middle cretaceous continental margin of Northwestern North America

USGS Publications Warehouse

Goldfarb, Richard J.; Anderson, Eric; Hart, Craig J.R.

2013-01-01

The Pebble Cu-Au-Mo deposit in southwestern Alaska, containing the largest gold resource of any known porphyry in the world, developed in a tectonic setting significantly different from that of the present-day. It is one of a series of metalliferous middle Cretaceous porphyritic granodiorite, quartz monzonite, and diorite bodies, evolved from lower crust and metasomatized lithospheric mantle melts, which formed along much of the length of the North American craton suture with the Peninsular-Alexander-Wrangellia arc. The porphyry deposits were emplaced within the northernmost two of a series of ca. 130 to 80 Ma flysch basins that define the suture, as well as into arc rocks immediately seaward of the two basins. Deposits include the ca. 100 to 90 Ma Pebble, Neacola, and other porphyry prospects along the Kahiltna basin-Peninsula terrane boundary, and the ca. 115 to 105 Ma Baultoff, Carl Creek, Horsfeld, Orange Hill, Bond Creek, and Chisna porphyries along the Nutzotin basin-Wrangellia terrane boundary.The porphyry deposits probably formed along the craton margin more than 1,000 km to the south of their present latitude. Palinspastic reconstructions of plate kinematics from this period are particularly difficult because magmatism overlaps the 119 to 83 Ma Cretaceous Normal Superchron, a period when sea-floor magnetic data are lacking. Our favored scenario is that ore formation broadly overlaps the cessation of sedimentation and contraction and the transition to a transpressional continental margin regime, such that the remnant ocean basins were converted to strike-slip basins. The basins and outboard Peninsular-Alexander-Wrangellia composite superterrane, which are all located seaward of the deep crustal Denali-Farewell fault system, were subjected to northerly dextral transpression for as long as perhaps 50 m.y., beginning at ca. 95 ± 10 Ma. The onset of this transpression was marked by development of the mineralized bodies along fault segments on the seaward side

Constraints on the origin of adakites and porphyry Cu-Mo mineralization in Chongjiang, Southern Gangdese, the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Hu, Yong-bin; Liu, Ji-qiang; Ling, Ming-xing; Liu, Yan; Ding, Xing; Liu, Dun-yi; Sun, Wei-dong

2017-11-01

Chongjiang is a low-grade porphyry Cu deposit, located in the Gangdese belt, south Tibet. The petrogenesis and geodynamic settings of the Miocene intrusions associated with the deposit remain controversial. This study presents new results on in situ zircon Hf-O isotopic compositions and U-Pb ages, whole rock major and trace elements, and Sr-Nd isotopes for the adakitic intrusions from Chongjiang deposit. The ore-bearing biotite monzogranite porphyry has adakitic characteristics, with enriched large-ion-lithophile elements (LILE) and light rare earth elements (LREE), and depleted in high-field-strength elements (HFSE), P and Ti. LA-ICP-MS zircon U-Pb dating indicates that the ore-bearing and barren adakites were emplaced at 14.9 ± 0.3 Ma and 12.9 ± 0.3 Ma, respectively. The porphyry is characterized by relatively high initial 87Sr/86Sr ratios (0.7059 to 0.7066), and negative whole-rock εNd(t) values (- 3.8 to - 2.6). Zircon δ18O is slightly higher than mantle values (5.0 to 7.2‰), with varied εHf(t) (- 1.0 to 7.6). Most of the in situ zircon Hf-O isotopic data plot in a binary mixing trend between MORB and lower continental crust-derived melts. These results indicate contributions from mixing of a mantle-like source (e.g., slab melts) with continental crust. Interestingly, most of the samples plot in the field defined by Dabie adakites (representing partial melting of the lower continental crust), with several samples near/in the circum-Pacific adakite field (representing partial melting of subducted oceanic slabs), which seemingly indicates that Chongjiang adakites mostly formed through partial melting of lower continental crust, with a small amount derived from oceanic slab melts. These may be plausibly explained by plagioclase retention in the thickened Tibetan continental crust, which lowers Sr contents in the magmas during crustal assimilation. Such a model is supported by other adakite discrimination diagrams, which all point towards slab melting

Magmatic Enclaves in Granitic Rocks: Paragons or Parasites?

NASA Astrophysics Data System (ADS)

Clemens, John; Stevens, Gary; Elburg, Marlina

2017-04-01

Granitic rocks form the fundamental building blocks of Earth's continents and provide us with a wide range of resources, so their formation is worth trying to understand. Fine-grained, igneous-textured microgranular enclaves of tonalitic to monzogranitic composition (ME) are common in granitic rocks and their origins have been hotly debated, with some workers suggesting that ME are not igneous. These ME have been studied intensively enough that we are now certain that they are of igneous origin - globules of mingled and quenched magma. Although a mantle connection is evident in many cases, their ultimate origin (including where in the lithosphere they originate) is still debated. This contribution explores the systematics of chemical variation in ME and their host granites, with the aim of uncovering any systematics in their behaviour and modelling the processes that have led to the variations that we measure, comparing host-rock series to their respective ME series. As always, the hope is that the study of ME may lead to improved understanding and modelling of the processes that are responsible for the formation of the host granitic magmas. Using variations between the molecular quantities Ti and M (Fe+Mn+Mg), we demonstrate that the petrogenetic processes that operated within a diverse group of S- and I-type granitic host magmas and their ME suites are dissimilar. Variations within the granitic series result from a variety of what might be called 'orderly' processes, resulting in linear or curvilinear trends in chemical variation diagrams. In contrast, processes that affected the ME series commonly resulted in scattered, chaotic variations. Even in cases in which an ME series displays more orderly variation, it can be shown that the hypothesis of simple mixing between a parent enclave magma and its host granitic magma, to produce the overall variations, cannot be supported. ME magmas had vastly smaller volumes compared with their host granitic magmas. Thus, they

Geophysical Studies of Irish Granites Using Magnetotelluric and Gravity Data

NASA Astrophysics Data System (ADS)

Farrell, T. F.; Muller, M. R.; Rath, V.; Feely, M.; Hogg, C.

2014-12-01

We present results of on-going geophysical studies of Caledonian radiothermal granite bodies in Ireland, which are being undertaken to investigate the volumetric depth extent and structural features of these granites. During three field seasons, magnetotelluric (MT) and audio-magnetotelluric (AMT) data were acquired at 156 sites targeting three separate granite bodies. These studies will contribute to a crustal-scale investigation of the geothermal energy potential of the granites and their contribution to the thermal field of the Irish crust. Across the calc-alkaline Galway granite, located on the Irish west coast, MT and AMT data were acquired at 75 sites distributed in a grid. Preliminary 3D inversion reveals the presence of a resistor, thickest beneath the central block of the granite where it extends to depths of 11 - 12 km. The greater depth of the resistor beneath the central block is in contrast to previous thinking that proposed the central block granites to have shallower depth extent than those of the western block, based on Bouguer anomaly maps of the area in which the western block exhibited a more pronounced negative Bouguer anomaly than the central block. At the S-type Leinster granite, in eastern Ireland and to the south of Dublin, MT and AMT data were acquired along two profiles (LGN - 27 sites and LGS - 32 sites). Preliminary 1D inversions of AMT data along profile LGN show the Northern Units of the Leinster granite to extend to a depth of 4.5 km and the Lugnaquilla pluton extending to 2.5 km depth. MT and AMT data were acquired at 22 sites along a profile across the buried Kentstown granite, 35 km to the NW of Dublin. The Kentstown granite was intersected by two mineral exploration boreholes at depths of 492 m and 663 m. Preliminary 2D inversions do not yet satisfactorily resolve the top of the buried granite. Inversion of MT and AMT data is continuing, with the electrical conductivity structures revealed by these inversions being used to

Porphyry copper assessment of the Tibetan Plateau, China: Chapter F in Global mineral resource assessment

USGS Publications Warehouse

Ludington, Steve; Hammarstrom, Jane M.; Robinson, Gilpin R.; Mars, John L.; Miller, Robert J.

2012-01-01

Assessment results, presented in tables and graphs, show mean expected amounts of metal and rock in undiscovered deposits at different quantile levels, as well as the arithmetic mean for each tract. This assessment estimated a mean of 39 undiscovered porphyry copper deposits within the assessed permissive tracts on the Tibetan Plateau. This represents nearly four times the number of known deposits (11) already discovered. Predicted mean (arithmetic) resources that could be associated with the undiscovered deposits are about 145,000,000 t of copper and about 4,900 t of gold, as well as byproduct molybdenum and silver. Reliable reports of the identified resources in the 11 known deposits total about 27,000,000 t of copper and about 800 t of gold. Therefore, based on the assessments of undiscovered Tibetan Plateau resources in this report, about six times as much copper may occur in undiscovered porphyry copper deposits as has been identified to date.

6. Photocopied August 1971 from Photo 13731, Granite Folder #1, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. Photocopied August 1971 from Photo 13731, Granite Folder #1, Engineering Department, Utah Power and Light Co., Salt Lake City, Utah. GRANITE STATION, MAY 24, 1915. - Utah Power Company, Granite Hydroelectric Plant, Holladay, Salt Lake County, UT

Zircon U-Pb and molybdenite Re-Os geochronology and geological significance of the Baoshan porphyry Cu polymetallic deposit in Jiangxi province

NASA Astrophysics Data System (ADS)

Jia, Liqiong; Wang, Liang

2017-10-01

Baoshan porphyry Cu polymetallic deposit belongs to Jiujiang-Ruichang Cu-Au ore field, which is a component part of the Middle-Lower Yangtze River Cu-Au metallogenic belt. The U-Pb LA-MC-TCP MS dating of the zircons from Baoshan granodiorite porphyry yields an age of 147.81±0.48Ma (MSWD=1.07). Six molybdenite samples separated from Baoshan deposit are used for Re-Os dating and obtained the weighted average age of 147.42±0.84Ma and an isochron age of 147.7±1.2Ma. These ages suggest that the mineralization in the Baoshan deposit is genetically associated to the granodiorite porphyry, and the process of rock-and ore-forming is continuous. These data indicate that ages of intrusion and ore-body from Baoshan deposit are almost identical to other typical magmatic intrusion and deposits in Jiujiang-Ruichang metallogenic district. Tt is inferred that the Baoshan deposit was formed in the transition from EW-striking Tndosinian tectonic domain to NE-striking Paleo-Pacific tectonic domain.

Porphyry copper deposits distribution along the western Tethyan and Andean subductions: insights from a paleogeographic approach

NASA Astrophysics Data System (ADS)

Bertrand, G.

2012-12-01

The genesis of many types of mineral deposits is closely linked to tectonic and petrographic conditions resulting from specific geodynamic contexts. Porphyry deposits, for instance, are associated to calc-alkaline magmatism of subduction zones. In order to better understand the relationships between ore deposit distribution and their tectonic context, and help identifying geodynamic-related criteria of favorability that would, in turn, help mineral exploration, we propose a paleogeographic approach. Paleogeographic reconstructions, based on global or regional plate tectonic models, are crucial tools to assess tectonic and kinematic contexts of the past. We use this approach to study the distribution of porphyry copper deposits along the western Tethyan and Andean subductions since Lower Cretaceous and Paleocene, respectively. For both convergent contexts, databases of porphyry copper deposits, including, among other data, their age and location, were compiled. Spatial and temporal distribution of the deposits is not random and show that they were emplaced in distinct clusters. Five clusters are identified along the western Tethyan suture, from Lower Cretaceous to Pleistocene, and at least three along the Andes, from Paleocene to Miocene. Two clusters in the Aegean-Balkan-Carpathian area, that were emplaced in Upper Cretaceous and Oligo-Miocene, and two others in the Andes, that were emplaced in late Eocene and Miocene, are studied in details and correlated with the past kinematics of the Africa-Eurasia and Nazca-South America plate convergences, respectively. All these clusters are associated with a similar polyphased kinematic context that is closely related to the dynamics of the subductions. This context is characterized by 1) a relatively fast convergence rate, shortly followed by 2) a drastic decrease of this rate. To explain these results, we propose a polyphased genetic model for porphyry copper deposits with 1) a first stage of rapid subduction rate

Crystalline rocks of the Strawberry Lake area, Front Range, Colorado

USGS Publications Warehouse

Young, Edward J.

1991-01-01

This report is a petrographic and geochemical study of the bedrock and a petrologic discussion based on felsic-mafic and silica-saturation ratios of the Strawberry Lake area. This volume is published as chapters A and B. These chapters are not available separatelyThe Strawberry lake area lies between the Continental Divide and Granby, Colorado, just north of Tabernash. It is underlain by Proterozoic rocks composed of biotite gneiss and two plutons-Boulder Creek Granodiorite of the Routt Plutonic Suite and Silver Plume Granite of the Berthoud Plutonic Suite. Relict enclaves of biotite gneiss are not uncommon in the Boulder Creek Granodiorite, in the Silver Plume Granite, and in the granitic enclaves in the biotite gneiss. Granitic and mafic enclaves in the Boulder Creek Granodiorite, granitic enclaves in the Silver Plume Granite and in the biotite gneiss, and a Tertiary andesite porphyry dike complete the rock types.

Lead isotope compositions of Late Cretaceous and early Tertiary igneous rocks and sulfide minerals in Arizona: Implications for the sources of plutons and metals in porphyry copper deposits

USGS Publications Warehouse

Bouse, R.M.; Ruiz, J.; Titley, S.R.; Tosdal, R.M.; Wooden, J.L.

1999-01-01

Porphyry copper deposits in Arizona are genetically associated with Late Cretaceous and early Tertiary igneous complexes that consist of older intermediate volcanic rocks and younger intermediate to felsic intrusions. The igneous complexes and their associated porphyry copper deposits were emplaced into an Early Proterozoic basement characterized by different rocks, geologic histories, and isotopic compositions. Lead isotope compositions of the Proterozoic basement rocks define, from northwest to southeast, the Mojave, central Arizona, and southeastern Arizona provinces. Porphyry copper deposits are present in each Pb isotope province. Lead isotope compositions of Late Cretaceous and early Tertiary plutons, together with those of sulfide minerals in porphyry copper deposits and of Proterozoic country rocks, place important constraints on genesis of the magmatic suites and the porphyry copper deposits themselves. The range of age-corrected Pb isotope compositions of plutons in 12 Late Cretaceous and early Tertiary igneous complexes is 206Pb/204Pb = 17.34 to 22.66, 207Pb/204Pb = 15.43 to 15.96, and 208Pb/204Pb = 37.19 to 40.33. These Pb isotope compositions and calculated model Th/U are similar to those of the Proterozoic rocks in which the plutons were emplaced, thereby indicating that Pb in the younger rocks and ore deposits was inherited from the basement rocks and their sources. No Pb isotope differences distinguish Late Cretaceous and early Tertiary igneous complexes that contain large economic porphyry copper deposits from less rich or smaller deposits that have not been considered economic for mining. Lead isotope compositions of Late Cretaceous and early Tertiary plutons and sulfide minerals from 30 metallic mineral districts, furthermore, require that the southeastern Arizona Pb province be divided into two subprovinces. The northern subprovince has generally lower 206Pb/204Pb and higher model Th/U, and the southern subprovince has higher 206Pb/204Pb and

Geologic map of the Ahankashan-Rakhna basin, Badghis, Ghor, and Herat Provinces, Afghanistan, modified from the 1974 original map compilation of Y.I. Shcherbina and others

USGS Publications Warehouse

Tucker, Robert D.; Stettner, Will R.; Masonic, Linda M.; Bogdanow, Anya K.

2014-01-01

The Ahankashan and Rakhna prospect area is one of several gold and copper deposits within west-central Afghanistan. Here, various felsic to intermediate igneous porphyries intrude Lower Triassic to lower Paleogene sedimentary rocks, producing mineral and ore-bearing zones related to hydrothermal alteration, skarns, silicification, and crushing (brecciation). Mineralized skarns contain assemblages such as magnetite, magnetite-hematite, epidote-hematite, and epidote-garnet, as well as disseminations of chalcopyrite, covellite, chalcocite, cuprite, malachite, and azurite. Gold mineralization is mainly associated with zones of crushing along faults, and with small silicified igneous veins within granite and quartz porphyry.

Hydrothermal Evolution of the Giant Cenozoic Kadjaran porphyry Cu-Mo deposit, Tethyan metallogenic belt, Armenia, Lesser Caucasus: mineral paragenetic, cathodoluminescence and fluid inclusion constraints

NASA Astrophysics Data System (ADS)

Hovakimyan, Samvel; Moritz, Robert; Tayan, Rodrik; Rezeau, Hervé

2016-04-01

The Lesser Caucasus belongs to the Central segment of the Tethyan metallogenic belt and it is a key area to understand the metallogenic evolution between the Western & Central parts of the Tethyan belt and its extension into Iran. Zangezur is the most important mineral district in the southernmost Lesser Caucasus. It is a component of the South Armenian block, and it was generated during the convergence and collision of the southern margin of the Eurasian plate and the northern margin of the Arabian plate, and terranes of Gondwana origin (Moritz et al., in press). The Zangezur ore district consists of the Tertiary Meghri-Ordubad composite pluton, which is characterized by a long-lasting Eocene to Pliocene magmatic, tectonic and metallogenic evolution. It hosts major porphyries Cu-Mo and epithermal Au - polymetallic deposits and occurrences, including the giant world class Kadjaran porphyry Cu-Mo deposit (2244 Mt reserves, 0.3% Cu, 0.05% Mo and 0.02 g/t Au). The Kadjaran deposit is hosted by a monzonite intrusion (31.83±0.02Ma; Moritz et al., in press). Detailed field studies of the porphyry stockwork and veins of the different mineralization stages, their crosscutting and displacement relationships and the age relationship between different paragenetic mineral associations were the criteria for distinction of the main stages of porphyry mineralization at the Kadjaran deposit. The economic stages being: quartz- molybdenite, quartz-molybdenite-chalcopyrite, and quartz-chalcopyrite. The main paragenetic association of the Kadjaran porphyry deposit includes pyrite, molybdenite, chalcopyrite, bornite, chalcocite, pyrrhotite, covellite, sphalerite, and galena. Recent field observations in the Kadjaran open pit revealed the presence of epithermal veins with late vuggy silica and advanced argillic alteration in the north-eastern and eastern parts of the deposit. They are distributed as separate veins and have also been recognized in re-opened porphyry veins and in

Emplacement and magnetic fabrics of rapakivi granite intrusions within Wiborg and Åland rapakivi granite batholiths in Finland

NASA Astrophysics Data System (ADS)

Karell, Fredrik; Ehlers, Carl; Airo, Meri-Liisa

2014-02-01

Anisotropy of magnetic susceptibility (AMS) studies were carried out in two areas in Finland: the Ruotsinpyhtää intrusion within the Wiborg rapakivi granite batholith and the Saltvik intrusions within the Åland rapakivi granite batholith. The main aim of this study was to understand the emplacement history of these mid-Proterozoic rapakivi granites. Aeromagnetic images reveal structures of ca. 5-10 km intrusions that build up the large rapakivi granite batholiths of Åland and Wiborg. Magnetic susceptibility data from the database of the Geological Survey of Finland, including more than 1700 samples from the Wiborg rapakivi batholith and almost 900 samples from the Åland rapakivi batholith, were compared with measurements from the present study. The mean susceptibility is ca. 1500 μSI for the Wiborg batholith and ca. 10,000 μSI for the Åland batholith. Samples taken for this study demonstrate that the mean value for the Ruotsinpyhtää intrusion is ca. 1200 μSI and for the Saltvik intrusions ca. 24,000 μSI. Thermomagnetic measurements reveal that the magnetic susceptibility is mainly derived either from paramagnetic minerals or from magnetite. The absence of solid-state deformation features such as breccia or contact deformation indicates a cauldron-type subsidence emplacement. The AMS measurements from Ruotsinpyhtää confirm these proposals, with concentric gently dipping magnetic foliations that support a ring complex structure above a piston-type subsidence system. The Saltvik area consists of a number of smaller elliptical intrusions of different rapakivi granites forming a multiple intrusive complex. The magnetic fabric shows a general westward dipping of the pyterlite and eastward dipping of the contiguous even-grained rapakivi granite, which indicates a central inflow of magma batches towards the east and west resulting from a laccolitic emplacement of magma batches, while the main mechanism for space creation was derived from subsidence.

Zircon U-Pb and Hf-O isotopes trace the architecture of polymetallic deposits: A case study of the Jurassic ore-forming porphyries in the Qin-Hang metallogenic belt, China

NASA Astrophysics Data System (ADS)

Zhao, Panlao; Yuan, Shunda; Mao, Jingwen; Santosh, M.; Zhang, Dongliang

2017-11-01

The Qin-Hang intra-continental porphyry-skarn Cu polymetallic belt (QHMB) is among the economically important metallogenic belts in South China. The significant differences in the size and metal assemblage of the Jurassic magmatic-hydrothermal ore deposits in this belt remain as an enigma. Here we employ zircon U-Pb and Hf-O isotopes of the Tongshanling and Baoshan Cu-Pb-Zn deposits in the central part of the QHMB to investigate the contrasting metallogenic architecture. Our SIMS zircon U-Pb data indicate that the Tongshanling and Baoshan granodiorite formed at 160 Ma. These rocks show high Mg# values, and negative zircon εHf(t) and high δ18O values suggesting that the magmas of the granodiorite porphyries were mainly generated through the anatexis of older crustal components triggered by the input of mantle-derived magma. The minor content of amphibole phenocrysts, low Sr/Y ratios, negative Eu anomaly, and low zircon Ce4 +/Ce3 + ratios indicate that the porphyries are relatively less oxidized with less water content compared with the ore-bearing porphyries in the Dexing and Yuanzhuding porphyry Cu deposits in the northern and southern part of the QHMB, suggesting that high magmatic water content and oxidation state are important prerequisites for the formation of large size porphyry-skarn copper deposits in the QHMB. The positive correlation between zircon εHf(t) values with the Cu reserves, as well as zircon δ18O values with the Cu/(Cu + Pb + Zn) ratios of the deposits indicate that the magmatic sources exerted a first-order control on the volume and metal assemblage of deposits in the QHMB. The Hf and Nd isotope contour maps indicate that the central part of the QHMB has high potential for Pb-Zn-dominated magmatic-hydrothermal deposits, whereas the northern and southern part of the QHMB are prospective for large Cu deposits. Our results have important implications in formulating regional exploration strategies for Jurassic porphyry-skarn Cu-Pb-Zn deposits in

Petrogenetic modeling of a potential uranium source rock, Granite Mountains, Wyoming

USGS Publications Warehouse

Stuckless, J.S.; Miesch, A.T.

1981-01-01

Previous studies of the granite of Lankin Dome have led to the conclusion that this granite was a source for the sandstone-type uranium deposits in the basins that surround the Granite Mountains, Wyo. Q-mode factor analysis of 29 samples of this granite shows that five bulk compositions are required to explain the observed variances of 33 constituents in these samples. Models presented in this paper show that the origin of the granite can be accounted for by the mixing of a starting liquid with two ranges of solid compositions such that all five compositions are granitic. There are several features of the granite of Lankin Dome that suggest derivation by partial melting and, because the proposed source region was inhomogeneous, that more than one of the five end members may have been a liquid. Data for the granite are compatible with derivation from rocks similar to those of the metamorphic complex that the granite intrudes. Evidence for crustal derivation by partial melting includes a strongly peraluminous nature, extremely high differentiation indices, high contents of incompatible elements, generally large negative Eu anomalies, and high initial lead and strontium isotopic ratios. If the granite of Lankin Dome originated by partial melting of a heterogeneous metamorphic complex, the initial magma could reasonably have been composed of a range of granitic liquids. Five variables were not well accounted for by a five-end-member model. Water, CO 2 , and U0 2 contents and the oxidation state of iron are all subject to variations caused by near-surface processes. The Q-mode factor analysis suggests that these four variables have a distribution determined by postmagmatic processes. The reason for failure of Cs0 2 to vary systematically with the other 33 variables is not known. Other granites that have lost large amounts of uranium possibly can be identified by Q-mode factor analysis.

S-type granitic magmas—petrogenetic issues, models and evidence

NASA Astrophysics Data System (ADS)

Clemens, J. D.

2003-04-01

Despite a perception that it represents a perverse divergence, it is perfectly possible to believe in the existence of S- and I-type granites (and the implications for the nature of their protoliths), and to disbelieve in the applicability of the restite-unmixing model for chemical variation in granitic magmas. White and Chappell erected the S-I classification with impeccable validity. The isotopic evidence demands contrasting source reservoirs for S- and I-type granitic magmas. However, the major advance was not the classification, but the recognition that highly contrasting parental materials must be involved in the genesis of granitic magmas. The restite-unmixing model is commonly seen as a companion to the S-I classification, but it is really a separate issue. This model implies that the compositions of granites 'image' those of their source rocks in a simple way. However, there are other equally valid models that can explain the data, and none of them represents a unique solution. The most cogent explanation for the high-grade metasedimentary enclaves in most S-type granites is that they represent mid-crustal xenoliths; restitic enclaves are either rare or absent. Inherited zircons in S-type rocks are certainly restitic. However, the occurrence of a substantial restitic zircon population does not imply an equally substantial restitic component in the rest of the rock. Zircon and zirconium behaviours are controlled by disequilibrium and kinetics, and Zr contents of granitic rocks can rarely be used to infer magma temperatures. Since the dominant ages among inherited zircons in Lachlan Fold Belt (LFB) S-type granites are Ordovician and Proterozoic, it seems likely that crust of this age, but geochemically different from the exposed rocks, not only underlies much of the LFB but also forms a component in the granite magma sources. The evidence is overwhelming that the dark, microgranular enclaves that occur in both S- and I-type granites are igneous in origin

7. Photocopied August 1971 from Photo 13729, Granite Station Special ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

7. Photocopied August 1971 from Photo 13729, Granite Station Special Folder, Engineering Department, Utah Power and Light Co., Salt Lake City, Utah. GRANITE HYDRO-ELECTRIC PLANT (1500KW) STATION. PENSTOCK AND SPILWAY, NOVEMBER 1914. - Utah Power Company, Granite Hydroelectric Plant, Holladay, Salt Lake County, UT

8. Photocopied August 1971 from Photo 11479, Granite Station Special ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

8. Photocopied August 1971 from Photo 11479, Granite Station Special Folder, Engineering Department, Utah Power and Light Co., Salt Lake City, Utah. GRANITE HYDRO-ELECTRIC PLANT (1500 KW) STATION. PENSTOCK AND SPILWAY, NOVEMBER 1914. - Utah Power Company, Granite Hydroelectric Plant, Holladay, Salt Lake County, UT

Effectiveness of granite cleaning procedures in cultural heritage: A review.

PubMed

Pozo-Antonio, J S; Rivas, T; López, A J; Fiorucci, M P; Ramil, A

2016-11-15

Most of the Cultural Heritage built in NW Iberian Peninsula is made of granite which exposition to the environment leads to the formation of deposits and coatings, mainly two types: biological colonization and sulphated black crusts. Nowadays, another form of alteration derives from graffiti paints when these are applied as an act of vandalism. A deep revision needs to be addressed considering the severity of these deterioration forms on granite and the different cleaning effectiveness achieved by cleaning procedures used to remove them. The scientific literature about these topics on granite is scarcer than on sedimentary carbonate stones and marbles, but the importance of the granite in NW Iberian Peninsula Cultural Heritage claims this review centred on biological colonization, sulphated black crusts and graffiti on granite and their effectiveness of the common cleaning procedures. Furthermore, this paper carried out a review of the knowledge about those three alteration forms on granite, as well as bringing together all the major studies in the field of the granite cleaning with traditional procedures (chemical and mechanical) and with the recent developed technique based on the laser ablation. Findings concerning the effectiveness evaluation of these cleaning procedures, considering the coating extraction ability and the damage induced on the granite surface, are described. Finally, some futures research lines are pointed out. Copyright © 2016 Elsevier B.V. All rights reserved.

Origin of peralkaline granites of Saudi Arabia

NASA Astrophysics Data System (ADS)

Radain, A. A. M.; Fyfe, W. S.; Kerrich, R.

1982-01-01

Small volumes of peralkaline granites were generated as the final phase of a Pan African calc-alkaline igneous event which built the Arabian Peninsula. The peralkaline granites are closely associated with trends or sutures related to ophiolites. Peralkaline rocks are chemically heterogeneous, with anomalous abundances of Zr (average 2,150 ppm±2,600 1σ), Y (200±190), and Nb (105±100), representing up to ten-fold enrichments of these elements relative to abundances in calc alkaline granite counterparts. Large enrichments of some rare earth elements and fluorine are also present. The peralkaline granites have scattered whole rock 18O values, averaging 8.7±0.6% in the Hadb Aldyaheen Complex and 10.7±1% in the Jabal Sayid Complex. Quartz-albite fractionations of 0.5 to 1.5% signify that the heavier whole rock δ-values probably represent the oxygen isotope composition of the peralkaline magma. Small variable enrichments of 18O, in conjunction with slightly elevated 87Sr/86Sr initial ratios relative to broadly contemporaneous calc alkaline granites, are both suggestive of a small degree of involvement of crustal, or crustal derived material in the peralkaline magmas. It is proposed that the peculiar magma genesis is associated with a relaxation event which followed continental collision and underthrusting of salt rich sediments.

Formation of a paleothermal anomaly and disseminated gold deposits associated with the Bingham Canyon porphyry Cu-Au-Mo system, Utah

USGS Publications Warehouse

Cunningham, C.G.; Austin, G.W.; Naeser, C.W.; Rye, R.O.; Ballantyne, G.H.; Stamm, R.G.; Barker, C.E.

2004-01-01

The thermal history of the Oquirrh Mountains, Utah, indicates that hydrothermal fluids associated with emplacement of the 37 Ma Bingham Canyon porphyry Cu-Au-Mo deposit extended at least 10 km north of the Bingham pit. An associated paleothermal anomaly enclosed the Barneys Canyon and Melco disseminated gold deposits and several smaller gold deposits between them. Previous studies have shown the Barneys Canyon deposit is near the outer limit of an irregular distal Au-As geochemical halo, about 3 km beyond an intermediate Pb-Zn halo, and 7 km beyond a proximal pyrite halo centered on the Bingham porphyry copper deposit. The Melco deposit also lies near the outer limit of the Au-As halo. Analysis of several geothermometers from samples collected tip to 22 km north of the Bingham Canyon porphyry Cu-Au-Mo deposit indicate that most sedimentary rocks of the Oquirrh Mountains, including those at the gold deposits, have not been regionally heated beyond the "oil window" (less than about 150??C). For geologically reasonable heating durations, the maximum sustained temperature at Melco, 6 km north of the Bingham pit, and at Barneys Canyon, 7.5 km north of the pit, was between 100??C and 140??C, as indicated by combinations of conodont color alteration indices of 1.5 to 2, mean random solid bitumen reflectance of about 1.0 percent, lack of annealing of zircon fission tracks, and partial to complete annealing of apatite fission tracks. The pattern of reset apatite fission-track ages indicates that the gold deposits are located approximately on the 120??C isotherm of the 37 Ma paleothermal anomaly assuming a heating duration of about 106 years. The conodont data further constrain the duration of heating to between 5 ?? 104 and 106 years at approximately 120??C. The ??18O of quartzite host rocks generally increases from about 12.6 per mil at the porphyry to about 15.8 per mil approximately 11 km from the Bingham deposit. This change reflects interaction of interstitial clays in

Two-types of Early Cretaceous adakitic porphyries from the Luxi terrane, eastern North China Block: Melting of subducted Paleo-Pacific slab and delaminated newly underplated lower crust

NASA Astrophysics Data System (ADS)

Wang, Hao; Xu, Zhaowen; Lu, Xiancai; Fu, Bin; Lu, Jianjun; Yang, Xiaonan; Zhao, Zengxia

2016-01-01

The origin and tectonic setting of Early Cretaceous adakitic rocks from the Luxi terrane in the eastern North China Block (NCB) remain debated. To resolve this issue, we determined whole-rock geochemistry, zircon U-Pb ages, and in situ Hf-O isotopes of the Mengyin and Liujing adakitic porphyries from the Luxi terrane. Zircon U-Pb dating results reveal that both the Mengyin and Liujing plutons were emplaced during the Early Cretaceous, with weighted mean 206Pb/238U ages of 130 ± 1 Ma (2σ) and 131 ± 2 Ma (2σ), respectively. In addition, abundant Neoarchean-Paleoproterozoic inherited zircon cores are identified in the Mengyin adakitic porphyry with 207Pb/206Pb ages ranging from 2.53 to 2.42 Ga. Rocks of both plutons are silicic (SiO2 = 65.4-70.2 wt.%), metaluminous, and alkaline in composition, comprising mainly quartz syenite porphyries. Samples from both plutons are enriched in large ion lithophile elements (LILEs) (e.g., Rb, Sr, and Ba), and light rare earth elements (LREEs), depleted in high field strength elements (HFSEs) (e.g., Nb, Ta, and Ti), and heavy rare earth elements (HREEs), and have either positive or no Eu anomalies. In addition, both adakitic porphyries have high Mg# values (51-64), high Sr and La contents, low Y and Yb contents, and high Sr/Y (Mengyin = 149-264; Liujing = 58-110) and (La/Yb)N (Mengyin = 32.4-45.3; Liujing = 43.8-53.1) ratios, similar to adakitic rocks worldwide. The Mengyin adakitic porphyry has higher whole-rock εNd(t) values (-5.8 to - 4.1), more radiogenic Pb [(206Pb/204Pb)i = 18.35-18.39, (207Pb/204Pb)i = 15.55-15.56, (208Pb/204Pb)i = 38.20-38.23], higher zircon rim εHf(t) values (+ 3.3 to + 8.8) and δ18O values (+ 6.5‰ to + 7.9‰), and lower (87Sr/86Sr)i ratios (0.7049-0.7050) than the Liujing adakitic porphyry [εNd(t) = - 12.4 to - 12.2, (206Pb/204Pb)i = 17.63-17.72, (207Pb/204Pb)i = 15.56-15.58, (208Pb/204Pb)i = 37.76-37.94, εHf(t) = - 14.8 to - 11.2, δ18O = + 5.9‰ to + 7.1‰, (87Sr/86Sr)i = 0.7090-0.7091]. The

Skarn-mineralized porphyry adakites in the Harlik arc at Kalatage, E. Tianshan (NW China): Slab melting in the Devonian-early Carboniferous in the southern Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Mao, Qigui; Yu, Mingjie; Xiao, Wenjiao; Windley, Brian F.; Li, Yuechen; Wei, Xiaofeng; Zhu, Jiangjian; Lü, Xiaoqiang

2018-03-01

The geodynamic control of mineralization in the accretionary evolution of the Central Asian Orogenic Belt (CAOB) has long been controversial. Here we report new field, geochemical and geochronological data on recently defined porphyry and skarn-type ore deposits (Devonian-Early Carboniferous) in the Kalatage area in the middle of the Harlik-Dananhu arc, Eastern Tianshan, NW China in the southern CAOB, with the aim of better understanding the accretionary tectonics and genesis of porphyry and skarn-type mineralization. The Yudai porphyry Cu-(Au) deposits and the Xierqu skarn Cu-Fe-(Au) deposits are closely associated with Middle Devonian adakitic diorite porphyries (382-390 Ma), which are calc-alkaline and characterized by high Na2O/K2O ratios and Sr contents (310-1020 ppm), strong depletion of HREE (e.g., Yb = 0.80-1.44 ppm) and Y (7.68-14.50 ppm), and all enriched in Rb, Sr, Ba, K and depleted in Nb and Ti. They are characterized by distinctive Eu positive anomalies, high Na2O contents and MORB-like Sr and Nd isotope signatures (high εNd(t) = +6.1 to +7.0 and low (87Sr/86Sr)i = 0.70412-0.70462). These adakites most likely formed by melting of a young/hot subducted oceanic slab, and adakites in general are important carriers of porphyry Cu ± (Au) deposits. Early Carboniferous adakites in the Tuwu area south of Kalatage are known to have similar features. Therefore, skarn-mineralized porphyry adakites get younger from north to south, suggesting southward migration of the Harlik-Dananhu arc from 390 Ma to 322 Ma. These data indicate that partial melting of hot (and/or young) oceanic crustal slabs were an important mechanism of accretionary crustal growth and mineralization in the southern CAOB.

U-Pb (zircon) and geochemical constraints on the age, origin, and evolution of Paleozoic arc magmas in the Oyu Tolgoi porphyry Cu-Au district, southern Mongolia

USGS Publications Warehouse

Wainwright, A.J.; Tosdal, R.M.; Wooden, J.L.; Mazdab, F.K.; Friedman, R.M.

2011-01-01

Uranium-Pb (zircon) ages are linked with geochemical data for porphyry intrusions associated with giant porphyry Cu-Au systems at Oyu Tolgoi to place those rocks within the petrochemical framework of Devonian and Carboniferous rocks of southern Mongolia. In this part of the Gurvansayhan terrane within the Central Asian Orogenic Belt, the transition from Devonian tholeiitic marine rocks to unconformably overlying Carboniferous calc-alkaline subaerial to shallow marine volcanic rocks reflects volcanic arc thickening and maturation. Radiogenic Nd and Pb isotopic compositions (??Nd(t) range from +3.1 to +7.5 and 206Pb/204Pb values for feldspars range from 17.97 to 18.72), as well as low high-field strength element (HFSE) contents of most rocks (mafic rocks typically have <1.5% TiO2) are consistent with magma derivation from depleted mantle in an intra-oceanic volcanic arc. The Late Devonian and Carboniferous felsic rocks are dominantly medium- to high-K calc-alkaline and characterized by a decrease in Sr/Y ratios through time, with the Carboniferous rocks being more felsic than those of Devonian age. Porphyry Cu-Au related intrusions were emplaced in the Late Devonian during the transition from tholeiitic to calc-alkaline arc magmatism. Uranium-Pb (zircon) geochronology indicates that the Late Devonian pre- to syn-mineral quartz monzodiorite intrusions associated with the porphyry Cu-Au deposits are ~372Ma, whereas granodiorite intrusions that post-date major shortening and are associated with less well-developed porphyry Cu-Au mineralization are ~366Ma. Trace element geochemistry of zircons in the Late Devonian intrusions associated with the porphyry Cu-Au systems contain distinct Th/U and Yb/Gd ratios, as well as Hf and Y concentrations that reflect mixing of magma of distinct compositions. These characteristics are missing in the unmineralized Carboniferous intrusions. High Sr/Y and evidence for magma mixing in syn- to late-mineral intrusions distinguish the Late

9. Photocopied August 1971 from Photo 13730, Granite Folder #1, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

9. Photocopied August 1971 from Photo 13730, Granite Folder #1, Engineering Department, Utah Power and Light Co., Salt Lake City, Utah. GRANITE STATION: WESTINGHOUSE 750 K.V.A., 2- PHASE GENERATORS AND SWITCHBOARD, MAY 24, 1915. - Utah Power Company, Granite Hydroelectric Plant, Holladay, Salt Lake County, UT

Melt inclusions in veins: linking magmas and porphyry Cu deposits.

PubMed

Harris, Anthony C; Kamenetsky, Vadim S; White, Noel C; van Achterbergh, Esmé; Ryan, Chris G

2003-12-19

At a porphyry copper-gold deposit in Bajo de la Alumbrera, Argentina, silicate-melt inclusions coexist with hypersaline liquid- and vapor-rich inclusions in the earliest magmatic-hydrothermal quartz veins. Copper concentrations of the hypersaline liquid and vapor inclusions reached maxima of 10.0 weight % (wt %) and 4.5 wt %, respectively. These unusually copper-rich inclusions are considered to be the most primitive ore fluid found thus far. Their preservation with coexisting melt allows for the direct quantification of important oreforming processes, including determination of bulk partition coefficients of metals from magma into ore-forming magmatic volatile phases.

A 3D Magnetotelluric Perspective on the Galway Granite, Western Ireland

NASA Astrophysics Data System (ADS)

Farrell, Thomas; Muller, Mark; Vozar, Jan; Feely, Martin; Hogg, Colin

2017-04-01

Magnetotelluric (MT) and audi-magnetotelluric (AMT) data were acquired at 75 locations across the exposed calc-alkaline Caledonian Galway granite batholith and surrounding country rocks into which the granite intruded. The Galway granite is located in western Ireland on the north shore of Galway bay, and has an ESE-WNW long axis. The granite is cut by trans-batholith faults, the Shannawona Fault Zone (SFZ) in the western part of the batholith, which has a NE-SW trend, and the Bearna Fault Zone (BFZ) in the eastern sector that has a NW-SE trend. Geobarometry data indicate that the central granite block between these fault zones has been uplifted, with the interpretation being that the granite in this central block is thinned. To the west of the SFZ, much of the Galway granite is below sea level, with the majority of the southern granite contact also beneath the sea in Galway bay. To the east of the batholith, the Carboniferous successions, consisting of mainly limestone with shale, overlie the basement rocks. The country rock to the north includes the metagabbro-gneiss suite, which itself intruded the deformed Dalradian successions that were deposited on the Laurentian margin of the Iapetus Ocean. The deformation of the Dalradian rocks, the intrusion of the metagabbro-gneiss suite and the intrusion of the Galway granite were major events in the protracted closure of the Iapetus Ocean. It is clear from geological mapping, from geobarometry and from the present submergence by the sea of a large part of the Galway granite, that inversion of MT data in this structurally complex geology is likely to require a 3D approach. We present a summary of 3D inversion of the Galway MT and AMT data. The study shows that the structure of the Galway granite is quite different from the pre-existing perspective. The central block, thought by its uplifting to be thinned, is shown to be the thickest part of the batholith. A geological model of granite intrusion is offered to explain this

Miocene rapakivi granites in the southern Death Valley region, California, USA

USGS Publications Warehouse

Calzia, J.P.; Ramo, O.T.

2005-01-01

Rapakivi granites in the southern Death Valley region, California, include the 12.4-Ma granite of Kingston Peak, the ca. 10.6-Ma Little Chief stock, and the 9.8-Ma Shoshone pluton. All of these granitic rocks are texturally zoned from a porphyritic rim facies, characterized by rapakivi textures and miarolitic cavities, to an equigranular aplite core. These granites crystallized from anhydrous and peraluminous to metaluminous magmas that were more oxidized and less alkalic than type rapakivi granites from southern Finland. Chemical and isotope (Nd-Sr-Pb) data suggest that rapakivi granites of the southern Death Valley region were derived by partial melting of lower crustal rocks (possibly including Mesozoic plutonic component) with some mantle input as well; they were emplaced at shallow crustal levels (4 km) in an actively extending orogen.

Miocene rapakivi granites in the southern Death Valley region, California, USA

USGS Publications Warehouse

Calzia, James P.; Ramo, O.T.

2005-01-01

Rapakivi granites in the southern Death Valley region, California, include the 12.4-Ma granite of Kingston Peak, the ca. 10.6-Ma Little Chief stock, and the 9.8-Ma Shoshone pluton. All of these granitic rocks are texturally zoned from a porphyritic rim facies, characterized by rapakivi textures and miarolitic cavities, to an equigranular aplite core. These granites crystallized from anhydrous and peraluminous to metaluminous magmas that were more oxidized and less alkalic than type rapakivi granites from southern Finland. Chemical and isotope (Nd–Sr–Pb) data suggest that rapakivi granites of the southern Death Valley region were derived by partial melting of lower crustal rocks (possibly including Mesozoic plutonic component) with some mantle input as well; they were emplaced at shallow crustal levels (4 km) in an actively extending orogen.

Porphyry copper assessment of the Tethys region of western and southern Asia: Chapter V in Global mineral resource assessment

USGS Publications Warehouse

Zürcher, Lukas; Bookstrom, Arthur A.; Hammarstrom, Jane M.; Mars, John C.; Ludington, Stephen; Zientek, Michael L.; Dunlap, Pamela; Wallis, John C.; Drew, Lawrence J.; Sutphin, David M.; Berger, Byron R.; Herrington, Richard J.; Billa, Mario; Kuşcu, Ilkay; Moon, Charles J.; Richards, Jeremy P.; Zientek, Michael L.; Hammarstrom, Jane M.; Johnson, Kathleen M.

2015-11-18

The assessment estimates that the Tethys region contains 47 undiscovered deposits within 1 kilometer of the surface. Probabilistic estimates of numbers of undiscovered deposits were combined with grade and tonnage models in a Monte Carlo simulation to estimate probable amounts of contained metal. The 47 undiscovered deposits are estimated to contain a mean of 180 million metric tons (Mt) of copper distributed among the 18 tracts for which probabilistic estimates were made, in addition to the 62 Mt of copper already identified in the 42 known porphyry deposits in the study area. Results of Monte Carlo simulations show that 80 percent of the estimated undiscovered porphyry copper resources in the Tethys region are located in four tracts or sub-tracts.

Geology of the Andover Granite and surrounding rocks, Massachusetts

USGS Publications Warehouse

Castle, Robert O.

1964-01-01

Field and petrographic studies of the Andover Granite and surrounding rocks have afforded an opportunity for an explanation of its emplacement and crystallization. The investigation has contributed secondarily to an understanding of the geologic history of southeastern New England, particularly as it is revealed in the Lawrence, Wilmington, South Groveland, and Reading quadrangles of Massachusetts. The Andover Granite and Sharpners Pond Tonalite together comprise up to 90 percent of the Acadian(?) subalkaline intrusive series cropping out within the area of study. The subalkaline series locally invades a sequence of early to middle Paleozoic and possibly Precambrian metasedimentary and metavolcanic rocks. Much of the subalkaline series and most of the Andover Granite is confined between two prominent east-northeast trending faults or fault systems. The northern fault separates the mildly metamorphosed Middle Silurian(?) Merrimack Group on the north from a highly metamorphosed and thoroughly intruded Ordovician(?) sequence on the south. The southern 'boundary '' fault is a major structural discontinuity characterized by penetrative, diffuse shearing over a zone one-half mile or more in width. The magmatic nature of the Andover Granite is demonstrated by: (1) sharply crosscutting relationships with surrounding rocks; (2) the occurrence of tabular-shaped xenoliths whose long directions parallel the foliation within the granite and whose internal foliation trends at a high angle to that of the granite; (3) continuity with the clearly intrusive Sharpners Pond Tonalite; (4) the compositional uniformity of the granite as contrasted with the compositional diversity of the rocks it invades; (5) its modal and normative correspondence with (a) calculated norms of salic extrusives and (b) that of the ternary (granite) minimum for the system NaAlSi3O8-KAlSi3O8-SiO2. Orogenic granites, as represented by the Andover, contrast with post-orogenic granites, represented locally by

Brother is high Sr/Y two-mica granite and sister is leucogranite: twin granites in the Northern Himalayan Gneiss Domes, southern Tibet

NASA Astrophysics Data System (ADS)

Zeng, L.; Gao, L.; Xie, K.

2011-12-01

Leucogranites in the Himalayan orogen is widely considered as the type example of crustal melts, which provides a probe to investigate the interplay among high-grade metamorphism, crustal anatexis, and tectonic transition in large-scale collisional belts. Whether the leucogranite was a daughter product from a more primitive granitic melt is an interesting question that deserves careful examination to address the above issue. We report a new suite of two-mica granite (TMG) and leucogranite (LG) in the Yardoi gneiss dome (YGD) in the easternmost of the Northern Himalayan Gneiss Domes (NHGD), south of the Yarlung-Tsangpo suture. SHRIMP and LA-ICP-MS zircon U/Pb dating show that TMG and LG formed at ~17.7 Ma to ~20.0 Ma and at ~17.1 Ma, respectively. Both suites of granite have high Na/K (>1.30) ratios. The TMGs are characterized by (1) high Sr (>450 ppm), low Rb (<95 ppm) and Y (<6 ppm), and high Sr/Y (>86) ratios; (2) no Eu anomalies; and (3) low initial 87Sr/86Sr ratios (<0.7098) and higher ɛNd (>-8.5) values. In contrast, the LGs have (1) lower Sr (<130 ppm) and higher Rb (92-130 ppm); (2) pronounced negative Eu anomalies with Eu/Eu*<0.55; and (3) relatively higher Sr (87Sr/86Sr(t) =0.7136-0.7148) and unradiogenic Nd (ɛNd(t)=-7.7~-11.1). These data demonstrate that these Mid-Miocene granites have major and trace element and radiogenic isotope compositions similar to those of >35 Ma granites, but significantly different from those granites of similar ages in the High Himalaya as well as in the NHGD. High Sr/Y and relatively unradiogenic Sr isotope compositions in the TMGs could be derived from partial melting of mafic materials formed during previous compressional thickening event which was triggered by the input of juvenile heat and material associated with the Miocene E-W extension. An AFC process (plagioclase fractional crystallization and contamination by crustal materials) could be a primary factor leading to the formation of these LGs. Concurrence of high Sr

Experimental methods of determining thermal properties of granite

USDA-ARS?s Scientific Manuscript database

Determination of thermal properties of granite using the block method is discussed and compared with other methods. Problems that limit the accuracy of contact method in determining thermal properties of porous media are evaluated. Thermal properties of granite is determined in the laboratory with a...

Fluid inclusion characteristics and molybdenite Re-Os geochronology of the Qulong porphyry copper-molybdenum deposit, Tibet

NASA Astrophysics Data System (ADS)

Li, Yang; Selby, David; Feely, Martin; Costanzo, Alessandra; Li, Xian-Hua

2017-02-01

The Qulong porphyry copper and molybdenum deposit is located at the southwest margin of the Lhasa Terrane and in the eastern region of the Gangdese magmatic belt. It represents China's largest porphyry copper system, with ˜2200 million tonnes of ore comprising 0.5 % Cu and 0.03 % Mo. The mineralization is associated with Miocene granodiorite, monzogranite and quartz-diorite units, which intruded into Jurassic volcanic units in a post-collisional (Indian-Asian) tectonic setting. Field observations and core logging demonstrate the alteration and mineralization at Qulong are akin to typical porphyry copper systems in subduction settings, which comprise similar magmatic-hydrothermal, potassic, propylitic and phyllic alteration assemblages. Molybdenite Re-Os geochronology confirms the relative timeframe defined by field observations and core logging and indicates that the bulk copper and molybdenum at Qulong were deposited within 350,000 years: between 16.10 ± 0.06 [0.08] (without and with decay constant uncertainty) and 15.88 ± 0.06 [0.08] Ma. This duration for mineralization is in direct contrast to a long-lived intrusive episode associated with mineralization based on previous zircon U-Pb data. Our fluid inclusion study indicates that the ore-forming fluid was oxidized and contained Na, K, Ca, Fe, Cu, Mo, Cl and S. The magmatic-hydrothermal transition occurred at ˜425 °C under lithostatic pressure, while potassic, propylitic and phyllic alteration occurred at hydrostatic pressure with temperature progressively decreasing from 425 to 280 °C. The fluid inclusion data presented here suggests that there has been ˜2.3 km of erosion at Qulong after its formation, and this erosion may be related to regional uplift of the Lhasa Terrane.

Noble Gas Isotope Evidence for Mantle Volatiles in the Cu-Mo Porphyry and Main Stage Polymetallic Veins at Butte, Montana

NASA Astrophysics Data System (ADS)

Hofstra, A. H.; Rusk, B. G.; Manning, A. H.; Hunt, A. G.; Landis, G. P.

2017-12-01

Recent studies suggest that volatiles released from mafic intrusions may be important sources of heat, sulfur, and metals in porphyry Cu-Mo-Au and epithermal Au-Ag deposits associated with intermediate to silicic stocks. The huge Cu-Mo porphyry and Main Stage polymetallic vein deposits at Butte are well suited to test this hypothesis because there is no geologic or isotopic evidence of basaltic intrusions in the mine or drill holes. The Butte porphyry-vein system is associated with quartz monzonite stocks and dikes within the southwest part of the Late Cretaceous Boulder batholith. The Boulder batholith was emplaced into Mesoproterozoic to Mesozoic sedimentary rocks and Late Cretaceous volcanic rocks. The Boulder batholith and Butte intrusions have Sri and eNd values indicative of crustal contamination. Eu and Ce anomalies in zircon from Butte intrusions provide evidence of oxidation due to magma degassing. To ascertain the source of volatiles in this system, 11 samples from the Cu-Mo porphyry and 16 from Main Stage veins were selected. The isotopic composition of Ar, Ne, and He extracted from fluid inclusions in quartz, magnetite, pyrite, chalcopyrite, sphalerite, galena, enargite, and covellite were determined. Helium isotopes exceed blank levels in all samples and Ne and Ar in some samples. On a 38Ar/36Ar vs. 40Ar/36Ar diagram, data plot near air. On a 20Ne/22Ne vs. 21Ne/22Ne diagram, data extend from air along the trajectories of OIB and MORB. On a 36Ar/4He vs. 3He/4He RA diagram, data extend from crust toward the air-mantle mixing line. The maximum 3He/4He RA values in the Cu-Mo porphyry (2.86) and Main Stage veins (3.46) are from pyrite and these values correspond to 36 and 43 % mantle helium. The Ne and He results show that fluid inclusions contain volatiles discharged from mantle magmas and that these volatiles were diluted by groundwater containing He derived from country rocks. Despite the lack of mafic intrusions in the Butte magmatic center, noble gas

IRETHERM: Magnetotelluric studies of Irish radiothermal granites and their geothermal energy potential

NASA Astrophysics Data System (ADS)

Farrell, T. F.; Jones, A. G.; Muller, M. R.; Feely, M.

2013-12-01

The IRETHERM project seeks to develop a strategic understanding of Ireland's deep geothermal energy potential through integrated modeling of new and existing geophysical and geological data. One aspect of IRETHERM's research focuses on Ireland's radiothermal granites, where increased concentrations of radioelements provide elevated heat-production (HP), heat-flow (HF) and subsurface temperatures. An understanding of the contribution of granites to the thermal field of Ireland is of key importance in assessing the geothermal energy potential of this low-enthalpy setting. This study focuses on the Leinster granite, the Galway granite and the buried Kentstown granite. Shallow (<250 m) boreholes were drilled into the exposed Caledonian Leinster and Galway granites as part of an early 1980's EU-funded geothermal project. These studies yielded HP = 2-3 μWm-3 and HF = 80 mWm-2 at the Sally Gap borehole in the Northern Units of the Leinster granite. In the Galway granite batholith, the Costelloe-Murvey granite returned HP = 7 μWm-3 and HF = 77 mWm-2, measured at the Ros a Mhil borehole. The lower heat-flow encountered at the Ros a Mhil borehole suggests that the associated high heat production does not extend to great depth. The buried Kentstown granite has associated with it a significant negative Bouguer anomaly and was intersected by two mineral exploration boreholes at depths of 660 m and 485 m. Heat production has been measured at 2.4 μWm-3 in core samples taken from the weathered top 30m of the granite. The core of this study consists of an ambitious program of magnetotelluric (MT) and audio-magnetotelluric (AMT) data acquisition across the three granite bodies, extending over three fieldwork seasons. MT and AMT data were collected at 59 locations along two profiles over the Leinster granite. Preliminary results show that the northern units of the Leinster granite extend to depths of 2-5 km. Over the Galway granite, MT and AMT data have been collected at a total

Contrasting hydrological processes of meteoric water incursion during magmatic-hydrothermal ore deposition: An oxygen isotope study by ion microprobe

NASA Astrophysics Data System (ADS)

Fekete, Szandra; Weis, Philipp; Driesner, Thomas; Bouvier, Anne-Sophie; Baumgartner, Lukas; Heinrich, Christoph A.

2016-10-01

Meteoric water convection has long been recognized as an efficient means to cool magmatic intrusions in the Earth's upper crust. This interplay between magmatic and hydrothermal activity thus exerts a primary control on the structure and evolution of volcanic, geothermal and ore-forming systems. Incursion of meteoric water into magmatic-hydrothermal systems has been linked to tin ore deposition in granitic plutons. In contrast, evidence from porphyry copper ore deposits suggests that crystallizing subvolcanic magma bodies are only affected by meteoric water incursion in peripheral zones and during late post-ore stages. We apply high-resolution secondary ion mass spectrometry (SIMS) to analyze oxygen isotope ratios of individual growth zones in vein quartz crystals, imaged by cathodo-luminescence microscopy (SEM-CL). Existing microthermometric information from fluid inclusions enables calculation of the oxygen isotope composition of the fluid from which the quartz precipitated, constraining the relative timing of meteoric water input into these two different settings. Our results confirm that incursion of meteoric water directly contributes to cooling of shallow granitic plutons and plays a key role in concurrent tin mineralization. By contrast, data from two porphyry copper deposits suggest that downward circulating meteoric water is counteracted by up-flowing hot magmatic fluids. Our data show that porphyry copper ore deposition occurs close to a magmatic-meteoric water interface, rather than in a purely magmatic fluid plume, confirming recent hydrological modeling. On a larger scale, the expulsion of magmatic fluids against the meteoric water interface can shield plutons from rapid convective cooling, which may aid the build-up of large magma chambers required for porphyry copper ore formation.

The zonal distribution of selected elements above the Kalamazoo porphyry copper deposit, San Manuel district, Pinal County, Arizona

USGS Publications Warehouse

Chaffee, M.A.

1976-01-01

There may be many as-yet-undiscovered porphyry copper deposits that exist as blind deposits deep within exposed rock bodies. The Kalamazoo porphyry copper-molybdenum deposit is a blind deposit present at depths up to at least 1,000 m (about 3,200 ft) that contains zoning features common to many of the known porphyry copper deposits found in western North and South America. As the preliminary phase in a geochemical study of the Kalamazoo deposit, whole-rock samples of core and cuttings from two drill holes have been analyzed for 60 different elements. Each hole represents a different major rock unit and each has penetrated completely through all the existing alteration zones and the ore zone. Plots of concentration vs. depth for 17 selected elements show distinct high- or low-concentration zones that are spatially related to the ore zone. For most of the ore-related elements no significant correlation with the two lithologies is apparent. The spatial distribution and abundance of elements such as Co, Cu, S, Se, Mn, Tl, Rb, Zn, B, and Li may be useful in determining the direction for exploration to proceed to locate a blind deposit. Trace element studies should be valuable in evaluating areas containing extensive outcrops of rocks with disseminated pyrite. Elemental zoning should be at least as useful as alteration-mineralization zoning for evaluating rock bodies thought to contain blind deposits similar to the Kalamazoo deposit. ?? 1976.

The global age distribution of granitic pegmatites

USGS Publications Warehouse

McCauley, Andrew; Bradley, Dwight C.

2014-01-01

An updated global compilation of 377 new and previously published ages indicates that granitic pegmatites range in age from Mesoarchean to Neogene and have a semi-periodic age distribution. Undivided granitic pegmatites show twelve age maxima: 2913, 2687, 2501, 1853, 1379, 1174, 988, 525, 483, 391, 319, and 72 Ma. These peaks correspond broadly with various proxy records of supercontinent assembly, including the age distributions of granites, detrital zircon grains, and passive margins. Lithium-cesium-tantalum (LCT) pegmatites have a similar age distribution to the undivided granitic pegmatites, with maxima at 2638, 1800, 962, 529, 485, 371, 309, and 274 Ma. Lithium and Ta resources in LCT pegmatites are concentrated in the Archean and Phanerozoic. While there are some Li resources from the Proterozoic, the dominantly bimodal distribution of resources is particularly evident for Ta. This distribution is similar to that of orogenic gold deposits, and has been interpreted to reflect the preservation potential of the orogenic belts where these deposits are formed. Niobium-yttrium-fluorine (NYF) pegmatites show similar age distributions to LCT pegmatites, but with a strong maximum at ca. 1000 Ma.

Geochemical element mobility during the hydrothermal alteration in the Tepeoba porphyry Cu-Mo-Au deposits at Balikesir, NW Turkey

NASA Astrophysics Data System (ADS)

Abdelnasser, Amr; Kiran Yildirim, Demet; Doner, Zeynep; Kumral, Mustafa

2016-04-01

The Tepeoba porphyry Cu-Mo-Au deposit represents one of the important copper source and mineral deposits in the Anatolian tectonic belt at Balikesir province, NW Turkey. It considered as a vein-type deposit locally associated with intense hydrothermal alteration within the brecciation, quartz stockwork veining, and brittle fracture zones in the main host rock that represented by hornfels, as well as generally related to the shallow intermediate to silicic intrusive Eybek pluton. Based on the field and geologic relationships and types of ore mineral assemblages and the accompanied alteration types, there are two mineralization zones; hypogene (primary) and oxidation/supergene zones are observed associated with three alteration zones; potassic, phyllic, and propylitic zones related to this porphyry deposit. The phyllic and propylitic alterations locally surrounded the potassic alteration. The ore minerals related to the hypogene zone represented by mostly chalcopyrite, Molybdenite, and pyrite with subordinate amount of marcasite, enargite, and gold. On the other hand they include mainly cuprite with chalcopyrite, pyrite and gold as well as hematite and goethite at the oxidation/supergene zone. This study deals with the quantitative calculations of the mass/volume changes (gains and losses) of the major and trace elements during the different episodes of alteration in this porphyry deposit. These mass balance data reveal that the potassic alteration zone that the main Cu- and Mo-enriched zone, has enrichment of K, Si, Fe, and Mg, and depletion of Na referring to replacement of plagioclase and amphibole by K-feldspar, sericite and biotite. While the propylitic alteration that is the main Mo- and Au-enriched zone is accompanied with K and Na depletion with enrichment of Si, Fe, Mg, and Ca forming chlorite, epidote, carbonate and pyrite. On the other hand the phyllic alteration that occurred in the outer part around the potassic alteration, characterized by less amount

Permian ultrafelsic A-type granite from Besar Islands group, Johor, peninsular Malaysia

NASA Astrophysics Data System (ADS)

Ghani, Azman A.; Hazad, Fatin Izzani; Jamil, Azmiah; Xiang, Quek Long; Atiqah Wan Ismail, Wan Nur; Chung, Sun-Lin; Lai, Yu-Ming; Roselee, Muhammad Hatta; Islami, Nur; Nyein, Kyaw Kyaw; Amir Hassan, Meor Hakif; Abu Bakar, Mohd Farid; Umor, Mohd Rozi

2014-12-01

The granitic rocks of the peninsula have traditionally been divided into two provinces, i.e., Western and Eastern provinces, corresponding to S- and I-type granite respectively. The Western Province granite is characterised by megacrystic and coarse-grained biotite, tin-mineralised, continental collision granite, whereas, the Eastern Province granite is bimodal I-type dominated by granodiorite and associated gabbroic of arc type granite. This paper reports the occurrence of an A-type granite from peninsular Malaysia. The rocks occur in the Besar, Tengah, and Hujung islands located in the southeastern part of the peninsula. The granite is highly felsic with SiO2 ranging from 75.70% to 77.90% (differentiation index = 94.2-97.04). It is weakly peraluminous (average ACNK =1.02), has normative hypersthene (0.09-2.19%) and high alkali content (8.32-8.60%). The granites have many A-type characteristics, among them are shallow level of emplacement, high Ga, FeT/MgO and low P, Sr, Ti, CaO and Nb. Calculated zircon saturation temperatures for the Besar magma ranging from 793 ∘ to 806 ∘C is consistent with high temperature partial melting of a felsic infracrustal source which is taken as one of the mechanisms to produce A-type magma. The occurrence of the A-type granite can be related to the extensional back arc basin in the Indo-China terrane during the earliest Permian.

Spatial and mineralogic variation of Na-Ca alteration in Laramide porphyry systems of Arizona

NASA Astrophysics Data System (ADS)

Runyon, S.; Seedorff, E.; Barton, M. D.; Mazdab, F. K.; Lecumberri-Sanchez, P.; Steele-MacInnis, M.

2017-12-01

Na-Ca alteration is characterized by the metasomatic addition of Ca ± Na and the loss of K. Minor volumes of Na-Ca alteration in Laramide porphyry systems develops from 3 to 8 km paleodepth. Mineral assemblages, mineral compositions, hydrogen isotopes, whole-rock analyses, and reconnaissance fluid inclusion characteristics have been documented for Na-Ca alteration in Laramide porphyry systems such as Tea Cup and Sierrita. Volumetrically minor Na-Ca alteration in Laramide porphyry systems documented in this study commonly takes the form of one of three mineral assemblages: albite-epidote-chlorite, Na-plagioclase-actinolite ± epidote, and garnet- or diopside-stable Na-plagioclase-actinolite ± epidote. These different Na-Ca mineral assemblages have broad spatial relationships, from shallow albite-chlorite-epidote to deeper Na-plagioclase-actinolite within a given district. Hydrogen isotope data on Na-Ca alteration minerals shows consistently distinct δD compositions of Na-Ca alteration minerals compared to igneous minerals in a given district. Further, calculated hydrogen isotope composition of fluids in equilibrium with Na-Ca alteration minerals are consistently enriched in δD compared to magmatic-hydrothermal fluids. Whole-rock analyses show consistent losses of K and variable addition of Na and Ca across different Na-Ca alteration assemblages. Na-Ca alteration has been well documented associated with the Jurassic arc. Previous studies demonstrated through mass balance, timing and spatial relationships, isotopic, and fluid inclusion studies that Na-Ca alteration associated with the Jurassic arc likely formed from the circulation of external, highly saline, non-magmatic fluids (e.g., Battles and Barton, 1995; Dilles et al., 1995). Na-Ca alteration documented in Laramide systems is generally similar to Na-Ca alteration documented along the Jurassic arc in mineral assemblages, compositions, and timing, but the volume of Na-Ca alteration in the Laramide systems is

Assessing exposure to granite countertops--Part 1: Radiation.

PubMed

Myatt, Theodore A; Allen, Joseph G; Minegishi, Taeko; McCarthy, William B; Stewart, James H; Macintosh, David L; McCarthy, John F

2010-05-01

Humans are continuously exposed to low levels of ionizing radiation. Known sources include radon, soil, cosmic rays, medical treatment, food, and building products such as gypsum board and concrete. Little information exists about radiation emissions and associated doses from natural stone finish materials such as granite countertops in homes. To address this knowledge gap, gross radioactivity, gamma ray activity, and dose rate were determined for slabs of granite marketed for use as countertops. Annual effective radiation doses were estimated from measured dose rates and human activity patterns while accounting for the geometry of granite countertops in a model kitchen. Gross radioactivity, gamma activity, and dose rate varied significantly among and within slabs of granite with ranges for median levels at the slab surface of ND to 3000 cpm, ND to 98,000 cpm, and ND to 1.5E-4 mSv/h, respectively. The maximum activity concentrations of the (40)K, (232)Th, and (226)Ra series were 2715, 231, and 450 Bq/kg, respectively. The estimated annual radiation dose from spending 4 h/day in a hypothetical kitchen ranged from 0.005 to 0.18 mSv/a depending on the type of granite. In summary, our results show that the types of granite characterized in this study contain varying levels of radioactive isotopes and that their observed emissions are consistent with those reported in the scientific literature. We also conclude from our analyses that these emissions are likely to be a minor source of external radiation dose when used as countertop material within the home and present a negligible risk to human health.

Magmatic and hydrothermal R.E.E. fractionation in the Xihuashan granites (SE China)

NASA Astrophysics Data System (ADS)

Maruéjol, Patricia; Cuney, Michel; Turpin, Laurent

1990-11-01

The Xihuashan stock (South Jiangxi, China) is composed of cogenetic granitic units (granites Xe, γa, γc, γd and γb) and emplaced during the Yanshanian orogeny (153±0.2 Ma). They are two feldspars, Fe-rich biotite±garnet and slightly peraluminous granites. Primary accessory minerals are apatite 1, monazite, zircon, uranothorite±xenotime in granites Xe and γa, zircon, uranothorite, uraninite, betafite, xenotime 1; hydrothermal minerals are monazite altered into parisite and apatite 2, Y-rich parisite, yttroparisite, Y-rich fluorite and xenotime 2 in granites γc and γb. Petrographic observations, major element, REE, Y and Rb-Sr isotropic data point to a magmatic suite (granites Xe and γa → granites γc and γd → granite γb) distinct from hydrothermal Na-or K-alteration of γb. From granite Xe to granite γb, LREE, Eu, Th and Zr content are strongly depleted, while HREE, Y and U content increase. During K-alteration of γb, these variations are of minor importance. Major and accessory mineral evidences, geochemical and fluid inclusion results indicate two successive alteration fluids interacting with γb, (1) a late-magmatic F- and CO2-rich fluid and (2) a post-magmatic, aqueous and slightly saline fluid. The depletion of LREE and Th content and the increase in HREE, Y and U content correspond, in the magmatic suite to the early fractionation of monazite in the granites where there is no hydrothermal alteration (granites Xe and γe) and to the hydrothermal alteration of monazite into parisite and secondary apatite, intense new formation of yttroparisite, Y enrichment and U loss in the uranothorite and late crystallization of uraninite in the granites γc and γb. Moreover, simulated crystallization of monazite and temperature of monazite saturation show early fractionation of monazite from the magma in the less evolved granites (Xe and γe) and prevailing hydrothermal leaching of monazite in the most evolved granites (γc-γd and γb) related to a late

Contribution of Portuguese two-mica granites to stone built heritage

NASA Astrophysics Data System (ADS)

Almeida, Angela; Begonha, Arlindo

2013-04-01

The present study deals with the importance of the application of natural stone in monuments in urban setting, both as the main building material during the historical evolution of a city and as a means to increase the public awareness of the social role of geological resources of a specific region. The City of Oporto, World Heritage of the Humanity , has been selected to illustrate the use of the local granite since ancient times to the present day, a two-mica peraluminous granite ,classified as syn-tectonic relatively to the third tectonic deformation phase of the Hercynian orogeny, included in an expressive group that occurs extensively in northern Portugal . The Oporto granite has been the object of several geochemical, structural and geotechnical approaches. Despite the urban development, outcrops of this granite can be observed in different areas of the city, side by side with the urban constructions, and particularly in the imposing and intensely fractured escarpments carved by the river Douro. Oporto monumental heritage goes back to Roman occupation and the profile has been developed by the construction of granite buildings, following history and the social evolution, of an impressive grey architecture according to different styles of granite work that characterize the city in all its aspects, namely the old city wall, the medieval and baroque churches, the neoclassic houses but also the small humble habitations. The Oporto granite is always affected by weathering processes and the buildings exhibit various aspects of stone decay such as granular desintegration, plates, flakes, black crusts, thin black layers, efflorescences and biological colonization. The description of selected sites within the historical centre , where it is possible to recognize the importance of the granite in the character of the city, aims to call the attention to the inextricable role of geology in built heritage and in the culture, as well as to diagnose the deterioration

Porphyry Copper Deposits of the World: Database and Grade and Tonnage Models, 2008

USGS Publications Warehouse

Singer, Donald A.; Berger, Vladimir I.; Moring, Barry C.

2008-01-01

This report is an update of earlier publications about porphyry copper deposits (Singer, Berger, and Moring, 2002; Singer, D.A., Berger, V.I., and Moring, B.C., 2005). The update was necessary because of new information about substantial increases in resources in some deposits and because we revised locations of some deposits so that they are consistent with images in GoogleEarth. In this report we have added new porphyry copper deposits and removed a few incorrectly classed deposits. In addition, some errors have been corrected and a number of deposits have had some information, such as grades, tonnages, locations, or ages revised. Colleagues have helped identify places where improvements were needed. Mineral deposit models are important in exploration planning and quantitative resource assessments for a number of reasons including: (1) grades and tonnages among deposit types are significantly different, and (2) many types occur in different geologic settings that can be identified from geologic maps. Mineral deposit models are the keystone in combining the diverse geoscience information on geology, mineral occurrences, geophysics, and geochemistry used in resource assessments and mineral exploration. Too few thoroughly explored mineral deposits are available in most local areas for reliable identification of the important geoscience variables or for robust estimation of undiscovered deposits?thus we need mineral-deposit models. Globally based deposit models allow recognition of important features because the global models demonstrate how common different features are. Well-designed and -constructed deposit models allow geologists to know from observed geologic environments the possible mineral deposit types that might exist, and allow economists to determine the possible economic viability of these resources in the region. Thus, mineral deposit models play the central role in transforming geoscience information to a form useful to policy makers. The foundation of

Granite Exfoliation, Cosumnes River Watershed, Somerset, California

NASA Astrophysics Data System (ADS)

Crockett, I. Q.; Neiss-Cortez, M.

2015-12-01

In the Sierra Nevada foothills of California there are many exposed granite plutons within the greater Sierra Nevada batholith. As with most exposed parts of the batholith, these granite slabs exfoliate. It is important to understand exfoliation for issues of public safety as it can cause rock slides near homes, roads, and recreation areas. Through observation, measuring, and mapping we characterize exfoliation in our Cosumnes River watershed community.

First find of platinum group metals in the ore of Kirganik copper-porphyry deposit (Kamchatka)

NASA Astrophysics Data System (ADS)

Sidorov, E. G.; Ignatyev, E. K.; Chubarov, V. M.

2017-08-01

The Kirganik copper-porphyry deposit is situated in the central part of the Sredinnyi Mountain Range of Kamchatka and is confined to fields of development of potassic orthoclase metasomatite and hypabyssal intrusions of shonkinite. Platinum group metals (PGMs), such as merenskyite, kotulskite, keithconnite, and temagamite, were discovered in the chalcopyrite-bornite and chalcopyrite-bornite-chalcosine ore of the deposit for the first time.

Granite disposal of U.S. high-level radioactive waste.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freeze, Geoffrey A.; Mariner, Paul E.; Lee, Joon H.

This report evaluates the feasibility of disposing U.S. high-level radioactive waste in granite several hundred meters below the surface of the earth. The U.S. has many granite formations with positive attributes for permanent disposal. Similar crystalline formations have been extensively studied by international programs, two of which, in Sweden and Finland, are the host rocks of submitted or imminent repository license applications. This report is enabled by the advanced work of the international community to establish functional and operational requirements for disposal of a range of waste forms in granite media. In this report we develop scoping performance analyses, basedmore » on the applicable features, events, and processes (FEPs) identified by international investigators, to support generic conclusions regarding post-closure safety. Unlike the safety analyses for disposal in salt, shale/clay, or deep boreholes, the safety analysis for a mined granite repository depends largely on waste package preservation. In crystalline rock, waste packages are preserved by the high mechanical stability of the excavations, the diffusive barrier of the buffer, and favorable chemical conditions. The buffer is preserved by low groundwater fluxes, favorable chemical conditions, backfill, and the rigid confines of the host rock. An added advantage of a mined granite repository is that waste packages would be fairly easy to retrieve, should retrievability be an important objective. The results of the safety analyses performed in this study are consistent with the results of comprehensive safety assessments performed for sites in Sweden, Finland, and Canada. They indicate that a granite repository would satisfy established safety criteria and suggest that a small number of FEPs would largely control the release and transport of radionuclides. In the event the U.S. decides to pursue a potential repository in granite, a detailed evaluation of these FEPs would be needed to

Geochemical and textural characterization of phosphate accessory phases in the vein assemblage and metasomatically altered Llallagua tin porphyry

NASA Astrophysics Data System (ADS)

Betkowski, Wladyslaw B.; Rakovan, John; Harlov, Daniel E.

2017-09-01

Petrographic and geochemical characterization of phosphate accessory minerals represents a powerful tool in understanding the mineralization and metasomatic history of one of the world's biggest tin deposits, the Siglo XX mine, Salvadora stock, Llallagua, Bolivia. The Llallagua tin deposit lies in a hydrothermally altered porphyry stock that is part of the subduction-related Bolivian tin belt. Despite numerous studies, there is still a debate over the timing and characteristics of mineralization history of the deposit. Primary igneous fluorapatite and monazite (for the first time) were recognized in the altered porphyry. The igneous monazite is enriched in Th, unlike the hydrothermal monazite that is recognized for its low Th concentration. Fluorapatite, monazite, and xenotime also coexist with cassiterite within the hydrothermal vein assemblage. Fluorapatite and xenotime are essentially pristine. Monazite, however, shows various degrees of alteration in the form of regenerative mineral replacement (RMR). This exemplifies differential reactivity and selective mineral replacement/alteration of three accessory phosphate minerals, that are all important geochemical tracers of magmatic and hydrothermal processes, and which can all be used as geochronometers. Mineral textures and composition in the altered porphyry and vein assemblages have been evaluated. Monazite-xenotime geothermometry indicates monazite crystallization beginning around 550 °C. Monazite continues to grow as temperatures gradually decrease to about 300 °C, when most of cassiterite precipitation occurred in the samples studied. The primary mechanism of phosphate alteration has been identified as a coupled dissolution-reprecipitation process, which led to REE exchange in the igneous fluorapatite and hydrothermal monazite. In Type I local alteration, La and Pr-Nd show continuity across the pre- and post- alteration concentric zones indicating that they were not affected by alteration. This is an

Porphyry copper assessment of Europe, exclusive of the Fennoscandian Shield: Chapter K in Global mineral resource assessment

USGS Publications Warehouse

Sutphin, David M.; Hammarstrom, Jane M.; Drew, Lawrence J.; Large, Duncan E.; Berger, Byron R.; Dicken, Connie L.; DeMarr, Michael W.; with contributions from Billa, Mario; Briskey, Joseph A.; Cassard, Daniel; Lips, Andor; Pertold, Zdeněk; Roşu, Emilian

2013-01-01

The assessment includes an overview with summary tables. Detailed descriptions of each tract, including the rationales for delineation and assessment, are given in appendixes A–G. Appendix H describes a geographic information system (GIS) that includes tract boundaries and point locations of known porphyry copper deposits and significant prospects.

[Analysis of X-ray fluorescence spectroscopy and plasma mass spectrometry of the Guidong granite body and its implications to granite evolution].

PubMed

Li, Hong-Wei; Chen, Guo-Neng; Peng, Zhuo-Lun

2013-07-01

The Guidong composite granite body (CGB) located in the north Guangdong Province consists of numerous rock bodies formed respectively in the early and late Jurassic and early Cretaceous. Analysis of the granites of different period with X-ray fluorescence spectroscopy and plasma mass spectrometry indicates: (1) From the top of a granite body downwards, the felsic components of rock decrease, while the mafic and sigmaREE, LREE/HREE, (La/Yb)N, as well as delta Eu value increase, suggesting the material differentiation in the in-situ melting of crustal rocks and crystallisation of magma; (2) From old to young of the different period granite-massifs in the Guidong CGB, the felsic compositions totally decrease, and the mafic components, sigmaEE, LREE/HREE, (La/Yb)N, and delta Eu value increase as well, implying multiple crustal melting (remelting) events in the Mesozoic in this area; and (3) Primitive mantle-normalized spider diagram for trace elements of Guidong CGB suggests high maturity of the crust involved in the in-situ melting.

Geochemistry of biotite granites from the Lamas de Olo Pluton, northern Portugal

NASA Astrophysics Data System (ADS)

Fernandes, Susana; Gomes, Maria; Teixeira, Rui; Corfu, Fernando

2013-04-01

In the Central Iberian Zone (CIZ) extensive crustal recycling occurred during the post-thickening extension stage of the Variscan orogeny (~330-290 Ma). After the ductile deformation phase D3 (~320-300 Ma), characterized by the intrusion of large volumes of highly peraluminous granitic magmas, rapid and drastic tectonic changes at about 300 Ma gave rise to the brittle phase of deformation D4 that controlled the emplacement of Fe-K subalkaline granites (296-290 Ma; Dias et al. 1998). The Lamas de Olo Pluton (LOP) is controlled by NE-SW and NW-SE fracture systems, probably related to the Régua-Verin fault zone (Pereira, 1989). The LOP is a medium to coarse-grained, porphyritic biotite granite, accompanied by medium- to fine grained, porphyritic biotite granite (Alto dos Cabeços- AC) and a more leucocratic, fine-grained, slightly porphyritic biotite-muscovite granite (Barragens- BA). The contacts between LO and AC are generally diffuse, whereas those to BA are sharp. In fact, the BA granite can occur in dykes and sills cutting LO and AC. Microgranular enclaves and xenoliths are very rare. The LOP intrudes the Douro Group, presumably of Precambrian to Cambrian age, and two-mica granites from the Vila Real composite massif. The LOP granites consist of quartz, microcline, plagioclase, biotite, zircon, titanite, tourmaline apatite, fluorite, ilmenite, magnetite, and rutile, with muscovite in BA granite and rare allanite in the LO and AC granites. The plagioclase composition is of oligoclase (An12) - andesine (An35) for LO granite, albite (An9) - andesine (An30) for CA granite and albite (An5) - oligoclase (An20) for BA granite. There are decreases in: a) anorthite content from phenocryst to matrix plagioclase; b) Ba content from phenocryst to matrix microcline in all granites. The Fe2+ biotite has a composition similar to that of biotite from calc-alkaline to sub-alkaline rock series. The LO and AC granites are meta- to peraluminous with ASI variable between 1.05 and 1

The effect of titanite crystallisation on Eu and Ce anomalies in zircon and its implications for the assessment of porphyry Cu deposit fertility

NASA Astrophysics Data System (ADS)

Loader, Matthew A.; Wilkinson, Jamie J.; Armstrong, Robin N.

2017-08-01

The redox sensitivity of Ce and Eu anomalies in zircon has been clearly demonstrated by experimental studies, and these may represent an important tool in the exploration for porphyry Cu deposits which are thought to be derived from oxidised magmas. These deposits are significant because they are the source of much of the world's copper and almost all of the molybdenum and rhenium, key elements in many modern technologies. However, Ce and Eu anomalies in zircon are also affected by the co-crystallisation of REE bearing phases, such as titanite. Here, we report the trace element chemistry of zircons from titanite-bearing intrusions associated with mineralisation at the world class Oyu Tolgoi porphyry Cu-Au deposit (Mongolia). Based on these data, we suggest that neither zircon Eu/Eu*, nor Ce4+/Ce3+ are robust proxies for melt redox conditions, because they are both too strongly dependent on melt REE concentrations, which are usually poorly constrained and controlled by the crystallisation of titanite and other REE-bearing phases. In spite of this, Eu/Eu* can broadly distinguish between fertile and barren systems, so may still be an indicator of porphyry magma fertility, and a useful tool for exploration.

Heat production in granitic rocks: Global analysis based on a new data compilation

NASA Astrophysics Data System (ADS)

Artemieva, I. M.; Thybo, H.; Jakobsen, K.; Sørensen, N. K.; Nielsen, L. S. K.

2017-12-01

Granitic rocks play special role in the evolution of the Earth and its thermal regime. Their compositional variability provides constraints on global differentiation processes and large scale planetary evolution, while heat production by radioactive decay is among the main heat sources in the Earth. We analyze a new global database GRANITE2017 on the abundances of Th, U, K and heat production in granitic rocks based on all available published data. Statistical analysis of the data shows a huge scatter in all parameters, but the following conclusions can be made. (i) Bulk heat production in granitic rocks of all ages is ca. 2.0 microW/m3 . It is very low in Archean-Early Proterozoic granitic rocks and there is a remarkable peak in Middle Proterozoic granites followed by a gradual decrease towards Cenozoic granites. (ii) There is no systematic correlation between the tectonically controlled granite-type and bulk heat production, although A-type (anorogenic) granites are the most radioactive, and many of them were emplaced in Middle Proterozoic. (iii) There is no systematic correlation between heat flow and concentrations of radiogenic elements. (iv) The present-day global average Th/U value is 4.75 with a maximum in Archean-Early Proterozoic granites (5.75) and a minimum in Middle-Late Proterozoic granites (3.78). The Th/U ratio at the time of granite emplacement has a minimum in Archean (2.78). (v) The present-day K/U ratio is close to a global estimate for the continental crust only for the entire dataset (1460), but differs from the global ratio for each geological time. (vi) We recognize a sharp change in radiogenic concentrations and ratios from the Early Proterozoic to Middle Proterozoic granites. The Proterozoic anomaly may be caused by major plate reorganizations possibly related to the supercontinent cycle when changes in the granite forming processes may be expected, or it may even indicate a change in global thermal regime, mantle dynamics and plate

Mobility of heavy metals through granitic soils using mini column infiltration test

NASA Astrophysics Data System (ADS)

Zarime, Nur'Aishah; Yaacob, W. Z. W.

2014-09-01

This study is about the mobility of cadmium through compacted granitic soils. Two granitic soils namely the Broga (BGR) and Kajang (KGR) granitic soils were collected in Selangor, Malaysia. Physical and chemical tests were applied for both granitic soils to determine the physical and chemical properties of soil materials. Physical test results shows granitic soils (BGR and KGR) have high percentage of sand ranging between 54%-63% and 46%-54% respectively, an intermediate and intermediate to high plasticity index as well as high specific gravity ie; 2.50-2.59 and 2.45-2.66 respectively. For chemical test, granitic soils shows acidic pH values ranged from 5.35-5.85 for BGR and pH 5.32-5.54 for KGR. For organic matter, SSA and CEC test, it shows low values ranged from 0.22%-0.34% and 0.39%- 0.50% respectively for organic matter test, 17.96 m2/g-21.93 m2/g and 25.76 m2/g-26.83 m2/g respectively for SSA test and 0.79 meq/100g-1.35 meq/100g and 1.31 meq/100g-1.35 meq/100g respectively for CEC test. Mini column infiltration test was conducted to determine the retention of cadmium while flowing through granite soils. This test conducted based on the falling head permeability concepts. Different G-force ranging from 231G to 1442G was used in this test. The breakthrough curves show the concentration of Cd becomes higher with the increasing of G-force for both granitic samples (BGR and KGR). The selectivity sorption for both granites ranked in the following decreasing order of; 231G>519G>923G>1442G. Results demonstrated that granitic soils also have low buffering capacity due to low resist of pH changes.

2.8-Ma ash-flow caldera at Chegem River in the northern Caucasus Mountains (Russia), contemporaneous granites, and associated ore deposits

USGS Publications Warehouse

Lipman, P.W.; Bogatikov, O.A.; Tsvetkov, A.A.; Gazis, C.; Gurbanov, A.G.; Hon, K.; Koronovsky, N.V.; Kovalenko, V.I.; Marchev, P.

1993-01-01

, and associated aplitic phases have textural features of Climax-type molybdenite porphyries in the western USA. Similar 40Ar/39Ar ages, mineral chemistry, and bulk-rock compositions indicate that the Chegem Tuff, intracaldera intrusion, and Eldjurta Granite are all parts of a large magmatic system that broadly resembles the middle Tertiary Questa caldera system and associated Mo deposits in northern New Mexico, USA. Because of their young age and superb three-dimensional exposures, rocks of the Chegem-Tirniauz region offer exceptional opportunities for detailed study of caldera structures, compositional gradients in volcanic rocks relative to cogenetic granites, and the thermal and fluid-flow history of a large young upper-crustal magmatic system. ?? 1993.

Assessment of occupational exposure in a granite quarry and processing factory.

PubMed

Tejado, J J; Guillén, J; Baeza, A

2016-09-01

Workers in the granite industry face an occupational hazard: silicosis due to the crystalline silica present in inhalable dust. As granite can also present a variable, and occasionally significant, content of naturally occurring radionuclides, they may also face a radiological hazard. In order to assess the risk, a granite industry with a quarry and processing factory was selected to assess the occupational exposure. Three main potential pathways were observed: external irradiation, inhalation of granite dust, and radon exposure. The external dose rate was similar to that in a nearby farming area. A slight increment (0.016-0.076 mSv yr -1 ) was observed in the quarry and stockpile, due to quarry faces and granite blocks. The effective dose due to granite dust inhalation was 0.182  ±  0.009 mSv yr -1 in the worst case scenario (3 mg m -3 dust load in air and no use of filter masks). Thus, the mean value of the effective dose from these two pathways was 0.26 mSv yr -1 , lower than the reference level of 1 mSv yr -1 for the general population. The annual mean value of radon concentration in the indoor air was 33 Bq m -3 . However, during granite processing works the radon concentration can increase up to 216 Bq m -3 , due to mechanical operations (sawing, polishing, sanding, etc). This radon concentration was below the 600 Bq m -3 reference level for action in working places. Therefore, workers in this granite factory face no significant additional radiological exposure, and no-one needs to be designated as occupationally exposed and subject to individual dosimetry.

Perogenesis of granites, Sharm El-Sheikh area, South Sinai, Egypt: petrological constrains and tectonic evolution

NASA Astrophysics Data System (ADS)

Sherif, Mahmoud I.; Ghoneim, Mohamed F.; Heikal, Mohamed Th. S.; El Dosuky, Bothina T.

2013-10-01

Precambrian granites of the Sharm El-Sheikh area in south Sinai, Egypt belong to collisional and post-collisional Magmatism (610-580 Ma). The granites are widely distributed in the northern part of the Neoproterozoic Arabian-Nubian Shield. South Sinai includes important components of successive multiple stages of upper crust granitic rocks. The earliest stages include monzogranite and syenogranites while the later stages produced alkali feldspar granites and riebeckite-bearing granites. Numerous felsic, mafic dikes and quartz veins traverse the study granites. Petrographically, the granitic rocks consist mainly of perthite, plagioclase, quartz, biotite and riebeckite. Analysis results portray monzogranites displaying calc-alkaline characteristics and emplaced in island-arc tectonic settings, whereas the syenogranites, alkali-feldspar granites and the riebeckite bearing-granites exhibit an alkaline nature and are enriched in HFSEs similar to granites within an extensional regime. Multi-element variation diagrams and geochemical characteristics reinforce a post-collision tectonic setting. REEs geochemical modeling reveals that the rocks were generated as a result of partial melting and fractionation of lower crust basaltic magma giving rise to A1 and A2 subtype granites. They were subsequently emplaced within an intraplate environment at the end of the Pan-African Orogeny.

Petrogenesis and magmatic evolution of ∼130 Ma A-type granites in Southeast China

NASA Astrophysics Data System (ADS)

Sun, Fajun; Xu, Xisheng; Zou, Haibo; Xia, Yan

2015-02-01

A number of Late Mesozoic (∼130 Ma) A-type granitic plutons have been identified in Southeast China. Here we investigate the petrogenesis of one of these granitic plutons in Southeast China, the Sanqingshan-Damaoshan (SD) granites in northeastern Jiangxi Province, using zircon U-Pb geochronology, Hf isotopic analyses, and major and trace element analyses. The SD granites are metaluminous to weakly peraluminous and show typical A-type affinity, which is characterized by high SiO2, Na2O + K2O, rare earth element (REE), high field strength element (HFSE) contents, Ga/Al and Fe# [FeOt/(FeOt + MgO)] values. Zircon grains from the SD granites and some other ∼130 Ma A-type granites commonly contain oscillatory zoning ;cores; surrounded by unzoned to weakly zoned ;rims;. Detailed studies of zircons from the SD granites show that ;rims; are enriched in LREE, Th and U compared with ;cores;. Chondrite-normalized REE patterns of the ;cores; increase steeply from La to Lu and show pronounced Ce and Eu anomalies, while REE patterns of the ;rims; display higher REE abundances with flatter LREE patterns and moderate Ce anomalies. Nevertheless, Lu-Hf isotopic analyses and Ti-in zircon thermometer show similar characteristics between ;rims; and ;cores;, indicating that the ;rims; may crystallize under the effect of internal magmatic hydrothermal fluids. U-rich ;rims; are more susceptible to Pb loss caused by self-irradiation, which may lead to significant younger U-Pb ages. As a result, U-Pb ages of zircon ;cores; (∼130 Ma) represent crystallization ages of the SD granites. εHf(t) values of zircon grains from the SD granites are between -6.4 and -0.4 with Mesoproterozoic model ages (T2DM) ranging from 1.22 to 1.59 Ga, suggesting that the granites may be formed by partial melting of Proterozoic basement. Compared with other adjacent ∼130 Ma A-type granitic plutons in SE China, the SD granites have similar geochemical characteristics and Hf isotopic compositions to those of

Genesis of a zoned granite stock, Seward Peninsula, Alaska

USGS Publications Warehouse

Hudson, Travis

1977-01-01

A composite epizonal stock of biotite granite has intruded a diverse assemblage of metamorphic rocks in the Serpentine Hot Springs area of north-central Seward Peninsula, Alaska. The metamorphic rocks include amphibolite-facies orthogneiss and paragneiss, greenschist-facies fine-grained siliceous and graphitic metasediments, and a variety of carbonate rocks. Lithologic units within the metamorphic terrane trend generally north-northeast and dip moderately toward the southeast. Thrust faults locally juxtapose lithologic units in the metamorphic assemblage, and normal faults displace both the metamorphic rocks and some parts of the granite stock. The gneisses and graphitic metasediments are believed to be late Precambrian in age, but the carbonate rocks are in part Paleozoic. Dating by the potassium-argon method indicates that the granite stock is Late Cretaceous. The stock has sharp discordant contacts, beyond which is a well-developed thermal aureole with rocks of hornblende hornfels facies. The average mode of the granite is 29 percent plagioclase, 31 percent quartz, 36 percent K-feldspar, and 4 percent biotite. Accessory minerals include apatite, magnetite, sphene, allanite, and zircon. Late-stage or deuteric minerals include muscovite, fluorite, tourmaline, quartz, and albite. The stock is a zoned complex containing rocks with several textural facies that are present in four partly concentric zones. Zone 1 is a discontinuous border unit, containing fine- to coarse-grained biotite granite, that grades inward into zone 2. Zone 2 consists of porphyritic biotite granite with oriented phenocrysts of pinkish-gray microcline in a coarse-grained equigranular groundmass of plagioclase, quartz, and biotite. It is in sharp, concordant to discordant contact with rocks of zone 3. Zone 3 consists of seriate-textured biotite granite that has been intruded by bodies of porphyritic biotite granite containing phenocrysts of plagioclase, K-feldspar, quartz, and biotite in an

A-type granite and the Red Sea opening

USGS Publications Warehouse

Coleman, R.G.; DeBari, S.; Peterman, Z.

1992-01-01

Miocene-Oligocene A-type granite intrudes the eastern side of the Red Sea margin within the zone of extension from Jiddah, Saudi Arabia south to Yemen. The intrusions developed in the early stages of continental extension as Arabia began to move slowly away from Africa (around 30-20 Ma). Within the narrow zone of extension silicic magmas formed dikes, sills, small plutons and extrusive equivalents. In the Jabal Tirf area of Saudi Arabia these rocks occur in an elongate zone consisting of late Precambrian basement to the east, which is gradually invaded by mafic dikes. The number of dikes increases westward until an igneous complex is produced parallel to the present Red Sea axis. The Jabal Tirf igneous complex consists of diabase and rhyolite-granophyre sills (20-24 Ma). Although these are intrusine intrusive rocks their textures indicate shallow depths of intrusion (< 1 km). To the south, in the Yemen, contemporaneous with alkali basaltic eruptions (26-30 Ma) and later silicic eruptions, small plutons, dikes, and stocks of alkali granite invaded thick (1500 m) volcanic series, at various levels and times. Erosion within the uplifted margin of Yemen suggests that the maximum depth of intrusion was less than 1-2 km. Granophyric intrusions (20-30 Ma) within mafic dike swarms similar to the Jabal Tirf complex are present along the western edge of the Yemen volcanic plateau, marking a north-south zone of continental extension. The alkali granites of Yemen consist primarily of perthitic feldspar and quartz with some minor alkali amphiboles and acmite. These granites represent water-poor, hypersolvus magmas generated from parent alkali basalt magmas. The granophyric, two-feldspar granites associated with the mafic dike swarms and layered gabbros formed by fractional crystallization from tholeiitic basalt parent developed in the early stages of extension. Initial 87Sr/86Sr ratios of these rocks and their bulk chemistry indicate that production of peralkaline and

[Study on the fine structure of K-feldspar of Qichun granite].

PubMed

Du, Deng-Wen; Hong, Han-Lie; Fan, Kan; Wang, Chao-Wen; Yin, Ke

2013-03-01

Fine structure of K-feldspar from the Qichun granite was investigated using X-ray diffraction (XRD), Fourier infrared absorption spectroscopy (FTIR), and inductively coupled plasma mass spectrometry methods to understand the evolution of the granitic magmatism and its correlation to molybdenite mineralization. The XRD results showed that K-feldspar of the potassic alteration veins has higher ordering index and triclinicity and is namely microcline with triclinic symmetry. K-feldspar of the early cretaceous granite has relatively lower ordering index and has widening [131] peak and is locally triclinic ordering. K-feldspar of the late cretaceous granite has lowest ordering index and sharp [131] peak and is honiogeneously monoclinic. The FTIR results showed that the IR spectra of the Qichun K-feldspar are similar to that of orthoclase reported by Farmer (1974). The 640 cm-1 absorption band increases while the 540 cm-' absorption band decreases with increase in K-feldspar ordering index, also, the 1,010 cm-1 absorption band separates into 1,010 and 1,046 cm-1 absorption bands, with a change in the band shape from widening to sharp outline. The ICP-MS results suggested that K-feldspar of the early cretaceous granite has relatively higher metal elements and rare earth elements, and the granite exhibits better mineralization background, K-feldspar of the potassic alteration veins has markedly lower Sr and Ba, indicating that the alteration fluid originated from the granitic magmatism, and hence, potassic alteration is a good indicator for molybdenite exploration.

OVERALL VIEW OF QUARRY, FACING NORTH, WITH UNQUARRIED GRANITE OUTCROP ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

OVERALL VIEW OF QUARRY, FACING NORTH, WITH UN-QUARRIED GRANITE OUTCROP IN BACKGROUND - Granite Hill Plantation, Quarry No. 3, South side of State Route 16, 1.3 miles northeast east of Sparta, Sparta, Hancock County, GA

Age and tectonomagmatic setting of the Eocene Çöpler-Kabataş magmatic complex and porphyry-epithermal Au deposit, East Central Anatolia, Turkey

NASA Astrophysics Data System (ADS)

İmer, Ali; Richards, Jeremy P.; Creaser, Robert A.

2013-06-01

The Çöpler epithermal Au deposit and related subeconomic porphyry Cu-Au deposit is hosted by the middle Eocene Çöpler-Kabataş magmatic complex in central eastern Anatolia. The intrusive rocks of the complex were emplaced into Late Paleozoic-Mesozoic metamorphosed sedimentary basement rocks near the northeastern margin of the Tauride-Anatolide Block. Igneous biotite from two samples of the magmatic complex yielded 40Ar/39Ar plateau ages of 43.75 ± 0.26 Ma and 44.19 ± 0.23, whereas igneous hornblende from a third sample yielded a plateau age of 44.13 ± 0.38. These ages closely overlap with 40Ar/39Ar ages of hydrothermal sericite (44.44 ± 0.28 Ma) and biotite (43.84 ± 0.26 Ma), and Re-Os ages from two molybdenite samples (44.6 ± 0.2 and 43.9 ± 0.2 Ma) suggesting a short-lived (<1 my) magmatic and hydrothermal history at Çöpler. No suitable minerals were found that could be used to date the epithermal system, but it is inferred to be close in age to the precursor porphyry system. The Çöpler-Kabataş intrusive rocks show I-type calc-alkaline affinities. Their normalized trace element patterns show enrichments in large ion lithophile and light rare earth elements and relative depletions in middle and heavy rare earth elements, resembling magmas generated in convergent margins. However, given its distance from the coeval Eocene Maden-Helete volcanic arc, the complex is interpreted to be formed in a back-arc setting, in response to Paleocene slab roll-back and upper-plate extension. The tectonomagmatic environment of porphyry-epithermal mineralization at Çöpler is comparable to some other isolated back-arc porphyry systems such as Bajo de la Alumbrera (Argentina) or Bingham Canyon (USA).

A weathering-related origin of widespread monazite in S-type granites

NASA Astrophysics Data System (ADS)

Sawka, Wayne N.; Banfield, Jillian F.; Chappell, Bruch W.

1986-01-01

The S-type granite suites comprising more than a quarter of the extensively developed granites in the Lachlan Fold Belt, Australia, contain monazite which may be related to the chemical weathering of the sedimentary source rocks. We report a process whereby chemical weathering fixes mobile rare-earth elements (REE) in hydrous phosphate phases such as florencite and rhabdophane. This material contains up to 50 wt% LREE and occurs as very small particles (~3μm). Dehydration of these hydrous REE phases during anatexis directly yields monazite. The low solubility of phosphorus in S-type granite melts inhibits dissolution of both monazite and apatite. Refractory monazite may be thus entrained and transported in S-type granites in a manner similar to processes resulting in inherited zircon. Since both Th and the light REE are major components in monazite, materials containing this minute phase may be of widespread geochemical significance in both granites and metamorphic rocks.

Mobility of heavy metals through granitic soils using mini column infiltration test

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zarime, Nur 'Aishah; Yaacob, W. Z.W.

This study is about the mobility of cadmium through compacted granitic soils. Two granitic soils namely the Broga (BGR) and Kajang (KGR) granitic soils were collected in Selangor, Malaysia. Physical and chemical tests were applied for both granitic soils to determine the physical and chemical properties of soil materials. Physical test results shows granitic soils (BGR and KGR) have high percentage of sand ranging between 54%–63% and 46%–54% respectively, an intermediate and intermediate to high plasticity index as well as high specific gravity ie; 2.50–2.59 and 2.45–2.66 respectively. For chemical test, granitic soils shows acidic pH values ranged from 5.35–5.85more » for BGR and pH 5.32–5.54 for KGR. For organic matter, SSA and CEC test, it shows low values ranged from 0.22%–0.34% and 0.39%– 0.50% respectively for organic matter test, 17.96 m{sup 2}/g–21.93 m{sup 2}/g and 25.76 m{sup 2}/g–26.83 m{sup 2}/g respectively for SSA test and 0.79 meq/100g–1.35 meq/100g and 1.31 meq/100g–1.35 meq/100g respectively for CEC test. Mini column infiltration test was conducted to determine the retention of cadmium while flowing through granite soils. This test conducted based on the falling head permeability concepts. Different G-force ranging from 231G to 1442G was used in this test. The breakthrough curves show the concentration of Cd becomes higher with the increasing of G-force for both granitic samples (BGR and KGR). The selectivity sorption for both granites ranked in the following decreasing order of; 231G>519G>923G>1442G. Results demonstrated that granitic soils also have low buffering capacity due to low resist of pH changes.« less

The metal content of molybdenum-mineralizing fluids

NASA Astrophysics Data System (ADS)

Lerchbaumer, L.; Audétat, A.

2012-04-01

Molybdenum can be found in porphyry-type systems as well as in hydrothermal veins and breccias associated with granite systems. Up to now our knowledge on the metal content of fluids forming molybdenum ore deposits has been very limited. The only data available so far are from the porphyry Mo deposit at Questa, New Mexico, and from the Cave Peak porphyry Mo-Nb deposit in Texas. We have studied early, intermediate-density fluid inclusions in quartz crystals from miarolitic cavities in the Drammen and Glitrevann granites (Norway) and the Treasure Mountain Dome (Colorado/USA) to obtain more information about the bulk composition of magmatic-hydrothermal fluids exsolved from these plutons. The Treasure Mountain Dome contains weak Mo mineralization and is an apophysis of the Alma Batholith that produced also the famous Climax and Henderson porphyry Mo deposits; the Glitrevann granite hosts a sub-economic Mo stockwork, and the Drammen Granite contains numerous vein-type Mo mineralizations. As a preliminary result, based on analyses of fluid inclusions using optical microscopy, microthermometry, Raman spectroscopy, and LA-ICP-MS we conclude that the primordial fluid of the Drammen granite was of high acidity and carried certain amounts of metals at conditions of 650°C and 1.3-1.5 kbar. The total elemental budget is: 3 wt% Na, 1.8 wt% K, 0.5 wt% S, 0.4 wt% Fe, 0.3 wt% Cu, 0.2 wt% Mn, 40 ppm Mo, 800 ppm Zn, 600 ppm Rb, 300 ppm Cs, 180 ppm Pb, 150 ppm As, 40 ppm W, 15 ppm Bi, and minor amounts of Ag, Sn, and Ce. Striking is the fact, that all the metal concentrations show little variability except the one of Cu. In view of recent studies (Lerchbaumer & Audétat, 2011) showing that the Cu-values in quartz-hosted fluid inclusions are not always representative of the primary fluid and in fact can be too high, we want to check if this could be the case for the Cu-values measured in the samples from Norway and Colorado. The alteration of the original Cu-concentrations stems from

ASTEROIDAL GRANITE-LIKE MAGMATISM 4.53 GYR AGO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terada, Kentaro; Bischoff, Addi

Constraining the timescales for the evolution of planetary bodies in our solar system is essential for a complete understanding of planet-forming processes. However, frequent collisions between planetesimals in the early solar system obscured and destroyed much of the primitive features of the old, first-generation planetary bodies. The presence of differentiated, achondritic clasts in brecciated chondrites and of chondritic fragments in achondritic breccias clearly witness multiple processes such as metamorphism, magmatism, fragmentation, mixing, and reaccretion. Here, we report the results of ion microprobe Pb-Pb dating of a granite-like fragment found in a meteorite, the LL3-6 ordinary chondrite regolith breccia Adzhi-Bogdo. Eightmore » spot analyses of two phosphate grains and other co-genetic phases of the granitoid give a Pb-Pb isochron age of 4.48 {+-} 0.12 billion years (95% confidence) and a model age of 4.53 {+-} 0.03 billion years (1{sigma}), respectively. These ages represent the crystallization age of a parental granite-like magma that is significantly older than those of terrestrial (4.00-4.40 Gyr) and lunar granites (3.88-4.32 Gyr) indicating that the clast in Adzhi-Bogdo is the oldest known granitoid in the solar system. This is the first evidence that granite-like formation is not only a common process on Earth, but also occurred on primitive asteroids in the early solar system 4.53 Gyr ago. Thus, the discovery of granite magmatism recorded in a brecciated meteorite provides an innovative idea within the framework of scenarios for the formation and evolution of planetary bodies and possibly exoplanetary bodies.« less

Monte Carlo simulations for generic granite repository studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, Shaoping; Lee, Joon H; Wang, Yifeng

In a collaborative study between Los Alamos National Laboratory (LANL) and Sandia National Laboratories (SNL) for the DOE-NE Office of Fuel Cycle Technologies Used Fuel Disposition (UFD) Campaign project, we have conducted preliminary system-level analyses to support the development of a long-term strategy for geologic disposal of high-level radioactive waste. A general modeling framework consisting of a near- and a far-field submodel for a granite GDSE was developed. A representative far-field transport model for a generic granite repository was merged with an integrated systems (GoldSim) near-field model. Integrated Monte Carlo model runs with the combined near- and farfield transport modelsmore » were performed, and the parameter sensitivities were evaluated for the combined system. In addition, a sub-set of radionuclides that are potentially important to repository performance were identified and evaluated for a series of model runs. The analyses were conducted with different waste inventory scenarios. Analyses were also conducted for different repository radionuelide release scenarios. While the results to date are for a generic granite repository, the work establishes the method to be used in the future to provide guidance on the development of strategy for long-term disposal of high-level radioactive waste in a granite repository.« less

Porphyry copper assessment of eastern Australia: Chapter L in Global mineral resource assessment

USGS Publications Warehouse

Bookstrom, Arthur A.; Len, Richard A.; Hammarstrom, Jane M.; Robinson, Gilpin R.; Zientek, Michael L.; Drenth, Benjamin J.; Jaireth, Subhash; Cossette, Pamela M.; Wallis, John C.

2014-01-01

This assessment estimates that 15 undiscovered deposits contain an arithmetic mean of ~21 million metric tons or more of copper in four tracts, in addition to the 24 known porphyry copper deposits that contain identified resources of ~16 million metric tons of copper. In addition to copper, the mean expected amount of undiscovered byproduct gold predicted by the simulation is ~1,500 metric tons. The probability associated with these arithmetic means is on the order of 30 percent. Median expected amounts of metals predicted by the simulations may be ~50 percent lower than mean estimates.

26. Detail of south granite pier revealing riveted truss ends ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

26. Detail of south granite pier revealing riveted truss ends and iron footing plates on top of granite cap stones. View north - New York, New Haven & Hartford Railroad, Fort Point Channel Rolling Lift Bridge, Spanning Fort Point Channel, Boston, Suffolk County, MA

Determination of geochemical affinities of granitic rocks from the Aue-Schwarzenberg zone (Erzgebirge, Germany) by multivariate statistics

USGS Publications Warehouse

Forster, H.-J.; Davis, J.C.

2000-01-01

Variscan granites of the Erzgebirge region can be effectively classified into five genetically distinct major groups by canonical analysis of geochemical variables. The same classification procedure, when applied to small plutons in the Aue-Schwarzenberg granite zone (ASGZ), shows that all ASGZ granites have compositional affinities to low-F biotite or low-F two-mica granite groups. This suggests that the ASGZ granites were emplaced during the first, late-collisional stage of silicic magmatism in the region, which occurred between about 325 and 318 Ma. The numerous biotite granite bodies in the zone are geochemically distinct from both the neighboring Kirchberg granite pluton and the spatially displaced Niederbobritzsch biotite granite massif. Instead, these bodies seem to constitute a third sub-group within the low-F biotite granite class. The ASGZ biotite granites represent three or more genetically distinct bodies, thus highlighting the enormous compositional variability within this group of granites. Least evolved samples of two-mica granites from the ASGZ apparently reflect the assimilation of low-grade metamorphic country rocks during emplacement, altering the original composition of the melts by enhancing primary Al content. The same genesis is implied for the rare "cordierite granite" facies of the Bergen massif, the type pluton for the low-F two-mica granite group in the Erzgebirge.

Porphyry copper assessment of Southeast Asia and Melanesia: Chapter D in Global mineral resource assessment

USGS Publications Warehouse

Hammarstrom, Jane M.; Bookstrom, Arthur A.; Dicken, Connie L.; Drenth, Benjamin J.; Ludington, Steve; Robinson, Gilpin R.; Setiabudi, Bambang Tjahjono; Sukserm, Wudhikarn; Sunuhadi, Dwi Nugroho; Wah, Alexander Yan Sze; Zientek, Michael L.

2013-01-01

This assessment includes an overview of the assessment results with summary tables. Detailed descriptions of each tract are included in appendixes, with estimates of numbers of undiscovered deposits, and probabilistic estimates of amounts of copper, molybdenum, gold, and silver that could be contained in undiscovered deposits for each permissive tract. A geographic information system (GIS) that accompanies the report includes tract boundaries and a database of known porphyry copper deposits and significant prospects.

Lead isotopic evidence for mixed sources of Proterozoic granites and pegmatites, Black Hills, South Dakota, USA

NASA Astrophysics Data System (ADS)

Krogstad, Eirik J.; Walker, Richard J.; Nabelek, Peter I.; Russ-Nabelek, Carol

1993-10-01

The lead isotopic compositions of K-feldspars separated from the ca. 1700 Ma Harney Peak Granite complex and spatially associated granitic pegmatites indicate that these rocks were derived from at least two sources. It has been reported previously that the core of the Harney Peak Granite complex is dominated by relatively lower/ gd18O (avg. 11.5 %.) granites, whereas higher / gd18O (avg. 13.2%.) granites occur around the periphery of the complex. The higher δ 18O granites and one simple pegmatite have low values of 207Pb /204Pb for their 206Pb /204Pb Thus, they likely were derived from a source with a short crustal residence time. This source may have been the pelitic schists into which the Harney Peak Granite complex and pegmatites were intruded. Feldspars from granites with lower / gd18O values have significantly higher 207Pb /204Pb for their 206Pb /204Pb . The data define a linear array with a slope equivalent to an age of ca. 2.6 Ga with t 2 defined to be 1.7 Ga. Such a slope could represent a mixing array or a secondary isochron for the source. These low δ18O granites could have been derived from a source with a high U/ Pb and with a crustal residence beginning before the Proterozoic. The source (s) of these granites may have been a sediment derived from late Archean continental crust. The highly evolved Tin Mountain pegmatite has lead isotopic systematics intermediate between those of the two granite groups, suggesting either a mixed source or contamination. Two late Archean granites, the Little Elk Granite and the Bear Mountain Granite, had precursors with high U/Pb and low Th/U histories. The Th/U history of the Bear Mountain Granite is too low for this rock to have been an important component of the source of the Proterozoic granites. However, crustal rocks with lead isotopic compositions similar to those of the Little Elk Granite were an important source of lead for some of the Proterozoic granitic rocks.

Application of support vector machine for the separation of mineralised zones in the Takht-e-Gonbad porphyry deposit, SE Iran

NASA Astrophysics Data System (ADS)

Mahvash Mohammadi, Neda; Hezarkhani, Ardeshir

2018-07-01

Classification of mineralised zones is an important factor for the analysis of economic deposits. In this paper, the support vector machine (SVM), a supervised learning algorithm, based on subsurface data is proposed for classification of mineralised zones in the Takht-e-Gonbad porphyry Cu-deposit (SE Iran). The effects of the input features are evaluated via calculating the accuracy rates on the SVM performance. Ultimately, the SVM model, is developed based on input features namely lithology, alteration, mineralisation, the level and, radial basis function (RBF) as a kernel function. Moreover, the optimal amount of parameters λ and C, using n-fold cross-validation method, are calculated at level 0.001 and 0.01 respectively. The accuracy of this model is 0.931 for classification of mineralised zones in the Takht-e-Gonbad porphyry deposit. The results of the study confirm the efficiency of SVM method for classification the mineralised zones.

A new indicator mineral methodology based on a generic Bi-Pb-Te-S mineral inclusion signature in detrital gold from porphyry and low/intermediate sulfidation epithermal environments in Yukon Territory, Canada

NASA Astrophysics Data System (ADS)

Chapman, R. J.; Allan, M. M.; Mortensen, J. K.; Wrighton, T. M.; Grimshaw, M. R.

2017-12-01

Porphyry-epithermal and orogenic gold are two of the most important styles of gold-bearing mineralization within orogenic belts. Populations of detrital gold resulting from bulk erosion of such regions may exhibit a compositional continuum wherein Ag, Cu, and Hg in the gold alloy may vary across the full range exhibited by natural gold. This paper describes a new methodology whereby orogenic and porphyry-epithermal gold may be distinguished according to the mineralogy of microscopic inclusions observed within detrital gold particles. A total of 1459 gold grains from hypogene, eluvial, and placer environments around calc-alkaline porphyry deposits in Yukon (Nucleus-Revenue, Casino, Sonora Gulch, and Cyprus-Klaza) have been characterized in terms of their alloy compositions (Au, Ag, Cu, and Hg) and their inclusion mineralogy. Despite differences in the evolution of the different magmatic hydrothermal systems, the gold exhibits a clear Bi-Pb-Te-S mineralogy in the inclusion suite, a signature which is either extremely weak or (most commonly) absent in both Yukon orogenic gold and gold from orogenic settings worldwide. Generic systematic compositional changes in ore mineralogy previously identified across the porphyry-epithermal transition have been identified in the corresponding inclusion suites observed in samples from Yukon. However, the Bi-Te association repeatedly observed in gold from the porphyry mineralization persists into the epithermal environment. Ranges of P-T-X conditions are replicated in the geological environments which define generic styles of mineralization. These parameters influence both gold alloy composition and ore mineralogy, of which inclusion suites are a manifestation. Consequently, we propose that this methodology approach can underpin a widely applicable indicator methodology based on detrital gold.

Preliminary mineralogical data on epithermal ore veins associated with Rosia Poieni porphyry copper deposit, Apuseni Mountains, Romania

NASA Astrophysics Data System (ADS)

Iatan, E. L.; Popescu, Gh. C.

2012-04-01

Rosia Poieni is the largest porphyry copper (±Au±Mo) deposits associated with Neogene magmatic rocks from the South Apuseni Mountains, being located approximately 8 km northeast of the town of Abrud. During a recent examination of some epithermal mineralized veins, crosscutting the porphyry mineralization from the Roşia Poieni deposit, two species of tellurides and one tellurosulfide minerals were identified. The studied samples were collected from the + 1045 m level, SW side of the open pit and are represented by epithermal veins, crosscutting the porphyry copper mineralized body. The thickness of the veins is almost 4 cm. Following reflected-polarized light microscopy to identify the ore-mineral assemblages, the polished sections were studied with a Scanning Electron Microscope (SEM) equipped with a back-scattered electron (BSE) detector to study fine-sized minerals. Quantitative compositional data were determined using a Cameca SX 50 electron microprobe (EMP). Based on optical microscopy, SEM and EMPA three mineral associations have been separated inside the epithermal vein, from the margins to the centre: 1. quartz+tennantite-tetrahedrite+goldfieldite+pyrite+sphalerite; 2. quartz+pyrite+tellurobismutite; 3. chalcopyrite+hessite+vivianite. Goldfieldite occurs in anhedral grains and it is associated with tennantite-tetrahedrite and quartz. The electron microprobe analysis gave a variable content in Te between 13.28-13.39 wt.%, 43.34 wt.% Cu, 0.1 wt. % Fe, 0.2 wt.% Zn, 14.68 wt.% As, 4.35 wt.% Sb and 24.84 wt.% S. The calculated formula for the goldfieldite is Cu11.8Te1.8(Sb,As)4S13.4. The EPM analyses on tetrahedrite-tennantite revealed a low content in Te (0.02-0.03 wt.%) and 42.23 wt.% Cu, 2.67 wt.% Fe, 7.34 wt.% Zn, 0.04 wt.% Sb, 19.28 wt.% As and 28.4 wt.% S. The calculated formula is Cu9.8(Fe,Zn)2.4(Sb,As,Te)3.8S13. The variable ratio of the Te content may reflect a variable content of Te in the hydrothermal fluids from which the tellurian tetrahedrite

Geochemistry, geochronology and Nd isotopes of the Gogó da Onça Granite: A new Paleoproterozoic A-type granite of Carajás Province, Brazil

NASA Astrophysics Data System (ADS)

Teixeira, Mayara Fraeda Barbosa; Dall'Agnol, Roberto; Santos, João Orestes Schneider; de Sousa, Luan Alexandre Martins; Lafon, Jean-Michel

2017-12-01

The Gogó da Onça Granite (GOG) comprise a stock located in the Carajás Province in the southeastern part of Amazonian Craton near its border with the Araguaia Belt. Three facies were identified in the pluton: biotite-amphibole granodiorite, biotite-amphibole monzogranite and amphibole-biotite syenogranite. The GGO crosscut discordantly the Archean country rocks and are not foliated. All Gogó da Onça Granite varieties are metaluminous, ferroan A2-subtype granites with reduced character. The major and trace element behavior suggests that its different facies are related by fractional crystallization. Zircon and titanite U-Pb SHRIMP ages show that the pluton crystallized at ∼1880-1870 Ma and is related to the remarkable Paleoproterozoic magmatic event identified in the Carajás Province. Whole-rock Nd isotope data (TDM ages 2.78 to 2.81, εNd values of -9.07 to -9.48) indicate that the GOG magmas derived from an Archaean source compatible with that of some other Paleoproterozoic suites from Carajás Province. The GOG show significant contrasts with the Jamon and Velho Guilherme Paleoproterozoic suites from Carajás Province and the inclusion of the Gogó da Onça granite in any of these suites is not justified. The GOG is more akin to the Serra dos Carajás Suite and to the Seringa and São João granites of Carajás and to the Mesoproterozoic Sherman granite of USA and the Paleoproterozoic Suomenniemi Batholith of Finland. This study puts in evidence the relevance of precise geochronological data and estimation of magma oxidation state in the characterization and correlation of A-type granites.

Composition, Age, and Origin of Cretaceous Granitic Magmatism on the Eastern Chukchi Peninsula

NASA Astrophysics Data System (ADS)

Luchitskaya, M. V.; Sokolov, S. D.; Pease, V.; Miller, E.; Belyatsky, B. V.

2018-05-01

New geochronological and isotopic geochemical data are given, which make it possible to recognize two types of granitic rocks on the eastern Chukchi Peninsula. Early Cretaceous Tkachen and Dolina granitic plutons with zircon ages (U-Pb SIMS) of 119-122 and 131-136 Ma are related to the first type. They cut through Devonian-Lower Carboniferous basement rocks and are overlain by the Aptian-Albian Etelkuyum Formation. Basal units of the latter contain fragments of granitic rocks. Late Cretaceous Provideniya and Rumilet granitic plutons, which contain zircons with ages of 94 and 85 Ma (U-Pb SIMS), respectively, belong to the second type. They cut through volcanic-sedimentary rocks of the Etelkuyum and Leurvaam formations pertaining to the Okhotsk-Chukotka Volcanic Belt. In petrographic and geochemical features, the Early Cretaceous granitic rocks of the Tkachen Pluton are commensurable with I-type granites, while Late Cretaceous granite of the Rumilet Pluton is comparable to A2-type granite. The Sr-Nd isotopic data provide evidence that from the Early Cretaceous Tkachen and Dolina plutons to the Late Cretaceous Provideniya and Rumilet plutons, the degree of crustal assimilation of suprasubduction mantle-derived melts increases up to partial melting of heterogeneous continental crust enriched in rubidium. An unconformity and various degrees of secondary alteration of volcanic-sedimentary rocks have been established in the Okhotsk-Chukotka Volcanic Belt, and this was apparently caused by transition of the tectonic setting from suprasubduction to a transform margin with local extension.

Mineralogical, stable isotope, and fluid inclusion studies of spatially related porphyry Cu and epithermal Au-Te mineralization, Fakos Peninsula, Limnos Island, Greece

NASA Astrophysics Data System (ADS)

Fornadel, Andrew P.; Voudouris, Panagiotis Ch.; Spry, Paul G.; Melfos, Vasilios

2012-05-01

The Fakos porphyry Cu and epithermal Au-Te deposit, Limnos Island, Greece, is hosted in a ~20 Ma quartz monzonite and shoshonitic subvolcanic rocks that intruded middle Eocene to lower Miocene sedimentary basement rocks. Metallic mineralization formed in three stages in quartz and quartz-calcite veins. Early porphyry-style (Stage 1) metallic minerals consist of pyrite, chalcopyrite, galena, bornite, sphalerite, molybdenite, and iron oxides, which are surrounded by halos of potassic and propylitic alteration. Stage 2 mineralization is composed mostly of quartz-tourmaline veins associated with sericitic alteration and disseminated pyrite and molybdenite, whereas Stage 3, epithermal-style mineralization is characterized by polymetallic veins containing pyrite, chalcopyrite, sphalerite, galena, enargite, bournonite, tetrahedrite-tennantite, hessite, petzite, altaite, an unknown cervelleite-like Ag-telluride, native Au, and Au-Ag alloy. Stage 3 veins are spatially associated with sericitic and argillic alteration. Fluid inclusions in quartz from Stage 1 (porphyry-style) mineralization contain five types of inclusions. Type I, liquid-vapor inclusions, which homogenize at temperatures ranging from 189.5°C to 403.3°C have salinities of 14.8 to 19.9 wt. % NaCl equiv. Type II, liquid-vapor-NaCl, Type III liquid-vapor-NaCl-XCl2 (where XCl is an unknown chloride phase, likely CaCl2), and Type IV, liquid-vapor-hematite ± NaCl homogenize to the liquid phase by liquid-vapor homogenization or by daughter crystal dissolution at temperatures of 209.3 to 740.5 °C, 267.6 to 780.8 °C, and 357.9 to 684.2 °C, respectively, and, Type V, vapor-rich inclusions. Stage 2 veins are devoid of interpretable fluid inclusions. Quartz from Stage 3 (epithermal-style) veins contains two types of fluid inclusions, Type I, liquid-vapor inclusions that homogenize to the liquid phase (191.6 to 310.0 °C) with salinities of 1.40 to 9.73 wt. % NaCl equiv., and Type II, vapor-rich inclusions. Mixing

Chemical composition and origin of black patinas on granite.

PubMed

Silva, Benita; Aira, Noelia; Martínez-Cortizas, Antonio; Prieto, Beatriz

2009-12-15

Black patinas from the surfaces of granite outcrops (including some with engravings) and granite buildings were analysed. Rock samples were also taken from areas of the same surfaces where there were no black patinas. The constituent elements of the granite rocks, elements of essentially biological origin (C, N, H) and other minor elements, including some typical from pollution, were all determined. The ratios between the concentrations of each element in the patinas and in the corresponding rock samples without patina were calculated in order to determine which elements form the patinas. The data were then examined by hierarchical cluster analysis and principal components analysis to establish the factors that determine the differences between samples. It was found that the elements that differentiate the patinas from the samples of rock without patina are those unrelated to granite, which indicates that, at least from a geochemical point of view, the rocky substrate does not affect patina formation. In all patinas analysed, the concentrations of carbon were higher than in the corresponding samples without patina; there were also relatively higher concentrations of sulphur, phosphorus, chlorine, calcium, etc. in some patinas, depending on the situation of the outcrop or monument.

Mineral exploration potential of ERTS-1 data. [porphyry copper deposits in Arizona

NASA Technical Reports Server (NTRS)

Brewer, W. A. (Principal Investigator); Erskine, M. C., Jr.; Prindle, R. O.; Haenggi, W. T.

1974-01-01

The author has identified the following significant results. ERTS-1 imagery of an area approximately 15,000 square miles in Arizona was interpreted for regional structure and tectonic units. Eight fault systems were identified by trend, of which two, northeast and northwest, are considered to be related to porphyry copper mineralization. Nine tectonic units can be identified on the imagery as distinct geological identities. The boundaries between these units can be correlated with theoretical shear directions related to the San Andreas stress system. Fourier analysis of the N 50 W fault trend indicates a fundamental spacing between Fourier energy maxima that can be related to distances between copper deposits.

SHRIMP U-Pb and 40Ar/39Ar age constraints for relating plutonism and mineralization in the Boulder batholith region, Montana

USGS Publications Warehouse

Lund, K.; Aleinikoff, J.N.; Kunk, Michael J.; Unruh, D.M.; Zeihen, G.D.; Hodges, W.C.; du Bray, E.A.; O'Neill, J. M.

2002-01-01

The composite Boulder batholith, Montana, hosts a variety of mineral deposit types, including important silver-rich polymetallic quartz vein districts in the northern part of the batholith and the giant Butte porphyry copper-molybdenum pre-Main Stage system and crosscutting copper-rich Main Stage vein system in the southern part of the batholith. Previous dating studies have identified ambiguous relationships among igneous and mineralizing events. Mineralizing hydrothermal fluids for these types of deposits and magma for quartz porphyry dikes at Butte have all been considered to be late-stage differentiates of the Boulder batholith. However, previous dating studies indicated that the Boulder batholith plutons cooled from about 78 to 72 Ma, whereas copper-rich Main Stage veins at Butte were dated at about 61 Ma. Recent efforts to date the porphyry copper-molybdenum pre-Main Stage deposits at Butte resulted in conflicting estimates of both 64 and 76 Ma for the mineralizing events. Silver-rich polymetallic quartz vein deposits elsewhere in the batholith have not been dated previously. To resolve this controversy, we used the U.S. Geological Survey, Stanford, SHRIMP RG ion mic??roprobe to date single-age domains within zircons from plutonic rock samples and 40Ar/39Ar geochronology to date white mica, biotite, and K-feldspar from mineral deposits. U-Pb zircon ages are Rader Creek Granodiorite, 80.4 ?? 1.2 Ma; Unionville Granodiorite, 78.2 ?? 0.8 Ma; Pulpit Rock granite, 76.5 ?? 0.8 Ma; Butte Granite, 74.5 ?? 0.9 Ma; altered Steward-type quartz porphyry dike (I-15 roadcut), 66.5 ?? 1.0 Ma; altered Steward-type quartz porphyry dike (Continental pit), 65.7 ?? 0.9 Ma; and quartz monzodiorite of Boulder Baldy (Big Belt Mountains), 66.2 ?? 0.9 Ma. Zircons from Rader Creek Granodiorite and quartz porphyry dike samples contain Archean inheritance. The 40Ar/39Ar ages are muscovite, silver-rich polymetallic quartz vein (Basin district), 74.4 ?? 0.3 Ma; muscovite, silver

Geochemistry and petrogenesis of a peralkaline granite complex from the Midian Mountains, Saudi Arabia

NASA Astrophysics Data System (ADS)

Harris, N. B. W.; Marriner, G. F.

1980-10-01

A zoned intrusion with a biotite granodiorite core and arfvedsonite granite rim represents the source magma for an albitised granite plug near its eastern margin and radioactive siliceous veins along its western margin. A study of selected REE and trace elements of samples from this complex reveals that the albitised granite plug has at least a tenfold enrichment in Zr, Hf, Nb, Ta, Y, Th, U and Sr, and a greatly enhanced heavy/light REE ratio compared with the peralkaline granite. The siliceous veins have even stronger enrichment of these trace elements, but a heavy/light REE ratio and negative eu anomaly similar to the peralkaline granite. It is suggested that the veins were formed from acidic volatile activity and the plug from a combination of highly fractionated magma and co-existing alkaline volatile phase. The granodiorite core intrudes the peralkaline granite and has similar trace element geochemistry. The peralkaline granite is probably derived from the partial melting of the lower crust in the presence of halide-rich volatiles, and the granodiorite from further partial melting under volatile-free conditions.

The Swedish Bohus granite - a stone with a fascinating history

NASA Astrophysics Data System (ADS)

Schouenborg, Björn; Eliasson, Thomas

2015-04-01

One of the most well-known and well spread Swedish stone types used as building stones is the Bonus granite. It outcrops in an area north of Gothenburgh (SW Sweden), along the coastline, approximately 35 km wide and 85 km long. The granite continues into Norway as the Iddefjord granite. The Bohus granite is one of Sweden's youngest granites. Isotopic dating shows that the magma cooled at about 920 M years ago and thus marking the end of the Sveconorwegian orogoney. It is a composite granite massif area with several granitic intrusions but with rather homogeneous mineralogy. However, colour and texture varies quite a lot and the colour ranges from red to reddish grey although some pure grey varieties occur sparsely. The grain size ranges from medium grained to coarse grained and even with some porphyric parts. Quarrying in an industrial scale started 1842. The merchant A C Kullgren opened the first quarry and produced stones for the construction of the 86 km long Trollhättan channel connecting lake Vänern and the Atlantic ocean in the SW Sweden The stone was used for constructing harbors and wharves along the channel. Several quarries opened in the late 1800 around 1870 - 1890 and the export increased steadily with deliveries to Germany, Denmark, Holland, England and even to South America. The stone industries in Bohuslän (Bohus county), at its peak in 1929, engaged around 7 000 employees. During the depression in 1930 almost all of them became unemployed. However, as a curiosity, production and export continued to Germany for construction of Germania, the future World capital city ("Welthauptstadt Germania"), planned by Adolf Hitler and Albert Speer. About 500 stone workers were kept employed for this project during the late thirties. Today several varieties are still produced: Evja/Ävja, Tossene, Brastad, Näsinge, Broberg, Nolby, Allemarken and Skarstad. However, the number of stone workers is far from that of the early 1900. The Swedish production is mainly

Magmatic anhydrite and calcite in the ore-forming quartz-monzodiorite magma at Santa Rita, New Mexico (USA): genetic constraints on porphyry-Cu mineralization

NASA Astrophysics Data System (ADS)

Audétat, A.; Pettke, T.; Dolejš, D.

2004-02-01

A quartz-monzodioritic dike associated with the porphyry-Cu mineralized stock at Santa Rita, NM, has been studied to constrain physico-chemical factors ( P, T, fO 2, and volatile content) responsible for mineralization. The dike contains a low-variance mineral assemblage of amphibole, plagioclase (An 30-50), quartz, biotite, sphene, magnetite, and apatite, plus anhydrite and calcite preserved as primary inclusions within the major phenocryst phases. Petrographic relationships demonstrate that anhydrite originally was abundant in the form of phenocrysts (1-2 vol.%), but later was replaced by either quartz or calcite. Hornblende-plagioclase thermobarometry suggests that several magmas were involved in the formation of the quartz-monzodiorite, with one magma having ascended directly from ≥14 km depth. Rapid magma ascent is supported by the presence of intact calcite inclusions within quartz phenocrysts. The assemblage quartz+sphene+magnetite+Mg-rich amphibole in the quartz-monzodiorite constrains magmatic oxygen fugacity at log fO 2>NNO+1, in agreement with the presence of magmatic anhydrite and a lack of magmatic sulfides. The same reasoning generally applies for rocks hosting porphyry-Cu deposits, seemingly speaking against a major role of magmatic sulfides in the formation of such mineralizations. There is increasing evidence, however, that magmatic sulfides play an important role in earlier stages of porphyry-Cu evolution, the record of which is often obliterated by later processes.

Prevalence of dry methods in granite countertop fabrication in Oklahoma.

PubMed

Phillips, Margaret L; Johnson, Andrew C

2012-01-01

Granite countertop fabricators are at risk of exposure to respirable crystalline silica, which may cause silicosis and other lung conditions. The purpose of this study was to estimate the prevalence of exposure control methods, especially wet methods, in granite countertop fabrication in Oklahoma to assess how many workers might be at risk of overexposure to crystalline silica in this industry. Granite fabrication shops in the three largest metropolitan areas in Oklahoma were enumerated, and 47 of the 52 shops participated in a survey on fabrication methods. Countertop shops were small businesses with average work forces of fewer than 10 employees. Ten shops (21%) reported using exclusively wet methods during all fabrication steps. Thirty-five shops (74%) employing a total of about 200 workers reported using dry methods all or most of the time in at least one fabrication step. The tasks most often performed dry were edge profiling (17% of shops), cutting of grooves for reinforcing rods (62% of shops), and cutting of sink openings (45% of shops). All shops reported providing either half-face or full-face respirators for use during fabrication, but none reported doing respirator fit testing. Few shops reported using any kind of dust collection system. These findings suggest that current consumer demand for granite countertops is giving rise to a new wave of workers at risk of silicosis due to potential overexposure to granite dust.

The Luanchuan Mo-W-Pb-Zn-Ag magmatic-hydrothermal system in the East Qinling metallogenic belt, China: Constrains on metallogenesis from C-H-O-S-Pb isotope compositions and Rb-Sr isochron ages

NASA Astrophysics Data System (ADS)

Cao, Hua-Wen; Zhang, Shou-Ting; Santosh, M.; Zheng, Luo; Tang, Li; Li, Dong; Zhang, Xu-Huang; Zhang, Yun-Hui

2015-11-01

The Luanchuan Mo-W-Pb-Zn-Ag polymetallic ore district is located in the East Qinling metallogenic belt on the southern margin of the North China Craton. Two ore fields (Nannihu and Yuku) are recognized in the district, and three types of deposits are identified from the two ore fields as follows: (1) the 6 proximal porphyry-skarn type Mo-W deposits occurring at the inner contact zone of the granite porphyries, (2) the 3 middle skarn-hydrothermal type Zn deposits, and (3) the 8 distal hydrothermal type Pb-Zn-Ag deposits at the periphery of the porphyry. We present C-H-O isotope compositions of hydrothermal quartz and calcite, S-Pb isotope compositions of sulfide minerals, and sphalerite Rb-Sr isochron ages from the 17 deposits. The geochemical and geochronological data from the two ore fields all show systematic temporal and spatial variation, and primarily lead to the following inferences. (1) The temperatures and salinities of the ore-forming fluids decreased during mineralization. The ore-forming fluids gradually evolved from magmatic water to mixed magmatic-meteoric water. (2) The metallogenic components were primarily derived from igneous rocks, with increasing proportions of the materials from the ore-bearing rocks. (3) The mineralization ages of these deposits are close (147-136 Ma), which correspond to the emplacement of the granite intrusions. (4) The three types of deposits and the ore-related late Mesozoic intrusives constitute a unified magmatic-hydrothermal-mineralization system. Finally, we also suggest exploration strategies for the Luanchuan ore district.

Reconnaissance geology and geochronology of the Precambrian of the Granite Mountains, Wyoming

USGS Publications Warehouse

Peterman, Zell E.; Hildreth, Robert A.

1978-01-01

The Precambrian of the western part of the Granite Mountains, Wyoming, contains a metamorphic complex of gneisses, schists, and amphibolites that were derived through amphibolite-grade metamorphism from a sedimentary-volcanic sequence perhaps similar to that exposed in the southeastern Wind River Mountains. Whole-rock Rb-Sr dating places the time of metamorphism at 2,860?80 million years. A high initial 87Sr/ 86 S r ratio of 0.7048 suggests that either the protoliths or the source terrane of the sedimentary component is several hundred million years older than the time of metamorphism. Following an interval of 300:t100 million years for which the geologic record is lacking or still undeciphered, the metamorphic complex was intruded by a batholith and satellite bodies of medium- to coarse-grained, generally massive biotite granite and related pegmatite and aplite. The main body of granite is dated at 2,550?60 million years by the Rb-Sr method. Limited data suggest that diabase dikes were emplaced and nephrite veins were formed only shortly after intrusion of the granite. Emplacement of the granite at about 2,550 million years ago appears to be related to a major period of regional granitic plutonism in the Precambrian of southern and western Wyoming. Granites, in the strict sense, that are dated between 2,450 and 2,600 million years occur in the Teton Range, the Sierra Madre, the Medicine Bow Mountains and the Laramie Range. This episode of granitic plutonism occured some 50 to 100 million years later than the major tonalitic to granitic plutonism in the Superior province of northern Minnesota and adjacent Ontario-the nearest exposed Precambrian W terrane that is analogous to the Wyoming province. Initial 87Sr / 86Sr ratios of some of the Wyoming granites are higher than expected if the rocks had been derived from juvenile magmas and it is likely that older crustal rocks were involved to some degree in the generation of these granites. Slightly to highly disturbed

Voluminous low-T granite: fluid present partial melting of the crust?

NASA Astrophysics Data System (ADS)

Hand, Martin; Barovich, Karin; Morrissey, Laura; Bockmann, Kiara; Kelsey, David; Williams, Megan

2017-04-01

Voluminous low-T granite: fluid present partial melting of the crust? Martin Hand(1), Karin Barovich(1), Laura Morrissey(1), Vicki Lau(1), Kiara Bockmann(1), David Kelsey(1), Megan Williams(1) (1) Department of Earth Sciences, University of Adelaide, Adelaide, Australia Two general schools of thought exist for the formation of granites from predominantly crustal sources. One is that large-scale anatexis occurs via fluid-absent partial melting. This essentially thermal argument is based on the reasonable premise that the lower crust is typically fluid depleted, and experimental evidence which indicates that fluid-absent partial melting can produce significant volumes of melt, creating compositionally depleted residua that many believe are recorded by granulite facies terranes. The other school of thought is that large-scale anatexis can occur via fluid-fluxed melting. This essentially compositional-based contention is also supported by experimental evidence which shows that fluid-fluxed melting is efficient, including at temperatures not much above the solidus. However, generating significant volumes of melt at low temperatures requires a large reservoir of fluid. If fluid-fluxed melting is a realistic model, the resultant granites should be comparatively low temperature compared to those derived from predominantly fluid-absent partial melting. Using a voluminous suite of aluminous granites in the Aileron Province in the North Australian Craton together with metasedimentary granulites as models for source behaviour, we evaluate fluid-absent verse fluid-present regimes for generating large volumes of crustally-derived melt. The central Aileron Province granites occupy 32,500km2, and in places are in excess of 8 km thick. They are characterised by abundant zircon inheritance that can be matched with metasedimentary successions in the region, suggesting they were derived in large part from melting of crust similar to that presently exposed. A notable feature of many of

The newly-discovered Late Cretaceous igneous rocks in the Nuocang district: Products of ancient crust melting trigged by Neo-Tethyan slab rollback in the western Gangdese

NASA Astrophysics Data System (ADS)

Jiang, Jun-Sheng; Zheng, You-Ye; Gao, Shun-Bao; Zhang, Yong-Chao; Huang, Jian; Liu, Jun; Wu, Song; Xu, Jing; Huang, Liang-Liang

2018-05-01

The newly discovered polymetallic Nuocang Pb-Zn skarn deposit is located in the southern Lhasa subterrane, western Gangdese, Tibet. The orebodies occur primarily at the contact zone between the Angjie Formation and the Linzizong volcanic rocks of Dianzhong Formation (LDF) that are dominated by basaltic andesitic tuff and rhyolite. Zircon U-Pb dating for two granite porphyries yield ages of 72.4 ± 0.2 Ma and 73.4 ± 0.9 Ma, which are different from the ages ( 69-60 Ma) of the LDF in the eastern Gangdese. The basaltic andesite tuff at Nuocang exhibits enrichment of MgO, TiO2, LILE, and LREE, with a relative depletion of SiO2, K2O, HFSE, and HREE, low Sr/Y ratios (32.9-38.0), and weak negative Eu anomalies (mean 0.86). They have 87Sr/86Sr(i) from 0.70695 to 0.70807 and εNd(t) values between -4.3 and -5.9. These features are similar to the Linzizong volcanic rocks of Dianzhong Formation in the Linzhou basin, indicating that they were associated with partial melting of mantle wedge mixing with 25-35% ancient Lhasa terrane basement. The rhyolite and granite porphyry show high SiO2 and K2O, and low Sr/Y ratio (1.2-9.9), enrichment of LILE and LREE and strong depletion of the HFSEs. They have pronounced negative Eu anomalies (mean 0.46), and εHf (t) values of the granite porphyry zircons range from -22.0 to -6.0. All these features suggest that they are the product of anatexis of ancient crustal materials heated by mantle-derived magma, the latter derived from Neo-Tethyan slab dehydration mechanisms. Combined with the previous geochronological and geochemical data, we proposed that the Nuocang district of western Gangdese in the southern Lhasa subterrane contains an ancient block, and the igneous rocks here were triggered by the Neo-Tethyan slab rollback starting at 82 Ma. The western Gangdese contains more ancient continental crustal materials and Late Cretaceous-Eocene Linzizong volcanic rocks and coeval intrusions than in the eastern Gangdese. Thus the western

Th-REE- and Nb-Ta-accessory minerals in post-collisional Ediacaran felsic rocks from the Katerina Ring Complex (S. Sinai, Egypt): An assessment for the fractionation of Y/Nb, Th/Nb, La/Nb and Ce/Pb in highly evolved A-type granites

NASA Astrophysics Data System (ADS)

Moreno, J. A.; Molina, J. F.; Bea, F.; Abu Anbar, M.; Montero, P.

2016-08-01

The relationships of Y/Nb, Th/Nb, La/Nb and Ce/Pb ratios in A-type felsic rocks from the Ediacaran Katerina Ring Complex, northernmost Arabian-Nubian Shield (ANS; S. Sinai, Egypt), are investigated in this work to understand their behavior during generation of highly evolved granitic magmas and to explore the nature of magma sources. Textural and compositional relationships of cognate Th-REE- and Nb-Ta-accessory minerals in Katerina felsic rocks show that chevkinite-group minerals (CGM), monazite, thorite, allanite and xenotime formed from residual liquids in quartz syenite porphyries, quartz monzonites and peralkaline granites, whereas in aluminous granites, allanite and monazite crystallized early, and thorite and columbite formed from residual liquids. Relationships of Y/Nb, Th/Nb, La/Nb and Ce/Pb ratios with Zr/Hf ratios in the aluminous granites and with Be abundances in the peralkaline granites suggest a decrease in La/Nb and Ce/Pb ratios in the former, and in Y/Nb and La/Nb ratios in the latter with crystallization progress. This contrasts with absence of systematic variations of Th/Nb and Ce/Pb ratios in the peralkaline compositions and of Y/Nb ratio in the aluminous ones. In this latter, Th/Nb ratio can present a significant decrease only in highly evolved compositions. An analysis of Y/Nb, Th/Nb, La/Nb and Ce/Pb relationships in worldwide OIB and subduction-related magmatic suites reveals that A-type felsic rocks with (Th/Nb)N < 1.3, (La/Nb)N < 1.3, and (Ce/Pb)N > 1 may have A1-type affinity, and those with (Th/Nb)N > 2, (La/Nb)N > 2, and (Ce/Pb)N < 1 tend to present A2-type affinity. The crystal fractionation of Th-LREE- and Nb-Ta-accessory minerals and mixing of components derived from the two granite groups may cause deviations from these compositional limits that can be evaluated using constraints imposed by Th/Nb-La/Nb, Ce/Pb-Th/Nb and Ce/Pb-La/Nb relationships in OIB and subduction-related magmatic suites. Three mantle sources might have been

Generation of post-collisional normal calc-alkaline and adakitic granites in the Tongbai orogen, central China

NASA Astrophysics Data System (ADS)

Zhang, Wen-Xiang; Zhu, Liu-Qin; Wang, Hao; Wu, Yuan-Bao

2018-01-01

Post-collisional granites are generally generated by partial melting of continental crust during orogenic extension. The occurrence of normal calc-alkaline granites following adakitic granites in a collisional orogen is frequently supposed as a sign of tectonic regime transition from compression to extension, which has been debated yet. In this paper, we present a comprehensive study of zircon U-Pb ages, Hf-O isotopes, as well as whole-rock major and trace elements and Sr-Nd isotopes, for Tongbai and Jigongshan post-collisional granitic plutons in the Tongbai orogen. Zircon U-Pb dating yields intrusion ages of ca. 140 and 135 Ma for the Tongbai and Jigongshan plutons, respectively, suggesting they are post-collisional granites. These granites are high-K calc-alkaline series, metaluminous to weakly peraluminous with A/CNK ratios of 0.85-1.08. The Tongbai gneissic granites are normal calc-alkaline granite, having variable SiO2 (61.93-76.74 wt%) and Sr/Y (2.9-38.9) and (La/Yb)N (1.7-30.1) ratios with variably negative Eu anomalies (0.41-0.92). They have relatively high initial Sr isotope ratios of 0.707571 to 0.710317, and low εNd(t) (- 15.74 to - 11.09) and εHf(t) (- 17.6 to - 16.9) values. Their Nd and Hf model ages range from 2.2 to 1.8 Ga and 2.3 to 2.2 Ga. On the contrary, the Jigongshan granites show higher SiO2 (66.56-72.11 wt%) and Sr/Y (30.1-182.0) and (La/Yb)N (27.4-91.4) ratios with insignificant Eu anomalies (0.73-1.00), belonging to adakitic granite. They have Isr = 0.707843-0.708366, εNd(t) = - 19.83 to - 17.59, and εHf(t) = - 26.0 to - 23.5. Their Nd and Hf model ages vary from ca. 2.5 to 2.4 Ga and ca. 2.8 to 2.6 Ga. The Tongbai and Jigongshan granites are characterized by mantle-like zircon δ18O values (5.17-5.46‰). These geochemical features suggest that the Tongbai and Jigongshan granites were derived from partial melting of Paleoproterozoic and Archean continental crust, respectively. Fractional crystallization affected the geochemical

Electrical properties of granite with implications for the lower crust.

USGS Publications Warehouse

Olhoeft, G.R.

1981-01-01

The electrical properties of granite appear to be dominantly controlled by the amount of free water in the granite and by temperature. Minor contributions to the electrical properties are provided by hydrostatic and lithostatic pressure, structurally bound water, oxygen fugacity, and other parameters. The effect of sulphur fugacity may be important but is experimentally unconfirmed. In addition to changing the magnitude of electrical properties, the amount and chemistry of water in granite significantly changes the temperature dependence of the electrical properties. With increasing temperature, changes in water content retain large, but lessened, effects on electrical properties. Near room temperature, a monolayer of water will decrease the electrical resistivity by an order of magnitude. Several weight-percent water may decrease the electrical resistivity by as much as nine orders of magnitude and decrease the thermal activation energy by a factor of five. At elevated temperatures just below granitic melting, a few weight-percent water may still decrease the resistivity by as much as 3 orders of magnitude and the activation energy by a factor of two.-Author

Age and geochemistry of host rocks of the Cobre Panama porphyry Cu-Au deposit, central Panama: Implications for the Paleogene evolution of the Panamanian magmatic arc

NASA Astrophysics Data System (ADS)

Baker, Michael J.; Hollings, Peter; Thompson, Jennifer A.; Thompson, Jay M.; Burge, Colin

2016-04-01

The Cobre Panama porphyry Cu-Au deposit, located in the Petaquilla district of central Panama, is hosted by a sequence of medium- to high-K calc-alkaline volcanic and sub-volcanic rocks. New crystallisation ages obtained from a granodiorite Petaquilla batholith and associated mineralised diorite to granodiorite porphyry stocks and dikes at Cobre Panama indicate that the batholith was emplaced as a multi-phase intrusion, over a period of 4 million years from 32.20 ± 0.76 Ma to 28.26 ± 0.61 Ma, while the porphyritic rocks were emplaced over a 2 million year period from 28.96 ± 0.62 Ma to 27.48 ± 0.68 Ma. Both the volcanic to sub-volcanic host rocks and intrusive rocks of the Cobre Panama deposit evolved via fractional crystallisation processes, as demonstrated by the major elements (e.g. Al2O3, Fe2O3, TiO2 and MgO) displaying negative trends with increasing SiO2. The Petaquilla intrusive rocks, including the diorite-granodiorite porphyries and granodiorite batholith, are geochemically evolved and appear to have formed from more hydrous magmas than the preceding host volcanic rocks, as evidenced by the presence of hornblende phenocrysts, higher degrees of large-ion lithophile element (LILE) and light rare earth element (LREE) enrichment and heavy rare earth element (HREE) depletion, and higher Sr/Y and La/Yb values. However, the degree of LREE enrichment, HREE depletion and La/Yb values are insufficient for the intrusive rocks to be considered as adakites. Collectively, the volcanic and intrusive rocks have LILE, REE and mobile trace element concentrations similar to enriched Miocene-age Cordilleran arc magmatism found throughout central and western Panama. Both the Petaquilla and Cordilleran arc magmatic suites are geochemically more evolved than the late Cretaceous to Eocene Chagres-Bayano arc magmas from northeastern Panama, as they display higher degrees of LILE and LREE enrichment. The geochemical similarities between the Petaquilla and Cordilleran arc magmas

Ponderosa pine progenies: differential response to ultramafic and granitic soils

Treesearch

James L. Jenkinson

1974-01-01

Progenies of nine ponderosa pines native to one granitic and several ultramafic soils in the northern Sierra Nevada were grown on both soil types in a greenhouse. The progenies differed markedly in first-year growth on infertile ultramafic soils, but not on a fertile granitic soil. Growth differences between progenies were primarily related to differences in calcium...

Gravity and magnetic modeling of granitic bodies in Central Portugal

NASA Astrophysics Data System (ADS)

Machadinho, Ana; Figueiredo, Fernando; Pereira, Alcides

2015-04-01

A better understanding of the subsurface geometry of the granitic bodies in Central Portugal is the main goal of this work. The results are also relevant for the assessment of the geothermal potential of the same region. The study area is located in the Central Iberian Zone where the Beiras granite batholith outcrops. These variscan granitoids were emplaced into the "Complexo Xisto-Grauváquico" (CXG), a thick and monotonous megasequences of metapelites and metagreywackes. This metasedimentary sequence is affected by the Variscan deformation phases and a late Proterozoic to Cambrian age has been generally assumed for this rocks. The granitoids in the region are attributed to the magmatic activity associated to the post-collisional stages of the Variscan orogeny during the D3 stage. The granitic bodies in the study area are considered syn-D3 and late to post-D3. To achieve the goal of the research, magnetic and gravimetric surveys where performed in order to obtain the Bouguer and magnetic anomalies. All the standard corrections were applied to the gravimetric and magnetic data. Considering and integrating all the available geological data and physical proprieties (density and magnetic susceptibility) the mentioned potential fields were simultaneously modeled. In this way it was possible to characterize the subsurface geometry of the granitic bodies in the studied region. The modeling results show that the regional tectonic setting controls the geometry of the granitic bodies as well as the structure of the host CXG metasedimentary sequence. Through the modeling of the potential field the overall geometry, average and maximum depths of the granitic bodies in the study area was obtained. Some late to post-D3 plutons outcrop in spatial continuity and as they have similar ages, a common feeding zone is assumed as the most likely scenario. The sin-D3 pluton is more abrupt and vertical, suggesting the presence of a fault contact with the late-D3 pluton. According to the

Mineralogy of metasomatic rocks and geochronology of the Olhovka porphyry-copper deposit, Chukotka, Russia

NASA Astrophysics Data System (ADS)

Rogacheva, Lyuba; Baksheev, Ivan

2010-05-01

The Olkhovka porphyry-copper deposit located on the border of foreland of the Okhotsk-Chukotka volcanic belt (OCVB) and a ledge composed of the Late Jurassic-Early Cretaceous Uda-Murgal arc (J3-K1) rocks is hosted by monzonite stock attributed to the Upper Cretaceous Kavralyan complex - K2) We estimated age of the Olkhovka monzonite by Rb-Sr and U-Pb methods. Rb-Sr age was determine om the basis of isotopic analysis of 8 monomineralic samples (potassium feldspar, plagioclase, amphibole, and dark mica). Isochron constructed on the basis of Rb-Sr data corresponds to the age of 78 + 2.6 Ma (MSWD=0.23). The Rb-Sr age is supported by U-Pb data derived from zircon of the same rock. One hundred and three single crystals of zircon were analyzed. Uranium content ranges from 52.66 ppm to 579.64 ppm; U/Th isotopic ratio varies from 0.567 to 1.746; age is 78.02+0.65 Ma (MSWD = 2.8). Monzonite is propylitized in variable degree. Propylite is composed of actinolite, chlorite, albite, quartz, and calcite. Propylite are cut by quartz-tourmaline veins. In addition, quartz-tourmaline metasomatic rock was identified in rhyolite ignimbrite out of the stock. Microscopically, tourmaline crystals of both types are oscilatory zoned that is caused by variable Fe content. Tourmalines of both assemblages can be classified as intermediate member of the schorl ("oxy-schorl")-dravite ("oxy-dravite") series. The Fetot/ (Fetot+Mg) varies from 0.31 to 0.95 in propylitic tourmaline and from 0.11 to 0.49, in quartz-tourmaline altered rocks from ignimbrite. Despite similar composition of both tourmalines, the major isomorphic substitutions in them are different. In propylite tourmaline, it is Fe → Al, whereas in the second case, it is Fe → Mg with certain effect of the Fe → Al type. Fe → Al isomorphic substitution is typical of porphyry style deposits (Baksheev et al., 2009 [1]). Therefore, we can conclude that quartz-tourmaline alteration in ignimbrite does not related to the formation of

Figure-Ground Processing: A Reassessment of Gelb and Granit.

PubMed

Nelson, Rolf; Hebda, Nicholas

2018-03-01

In 1923, Adhemar Gelb and Ragnar Granit, two prominent researchers in early Gestalt perceptual theory, reported a lower threshold for detection of a target (a small colored dot) on the ground region of an image than on an adjacent figural region. Although their results had a wide influence on the understanding of figure-ground perception, they are at odds with more recent investigations in which figural regions appear to have a processing advantage over ground regions. The two present studies replicated Gelb and Granit's experiment using a similar figure-ground stimulus albeit with a two-alternative forced choice procedure rather than their original method of adjustment. Experiment 1 found that, contrary to Gelb and Granit's findings, a detection advantage was found for the figural over the ground region. Experiment 2 indicated that explicit contours might have played a role in detection.

Element migration of pyrites during ductile deformation of the Yuleken porphyry Cu deposit (NW-China)

USGS Publications Warehouse

Hong, Tao; Xu, Xing-Wang; Gao, Jun; Peters, Stephen; Li, Jilei; Cao, Mingjian; Xiang, Peng; Wu, Chu; You, Jun

2017-01-01

The strongly deformed Yuleken porphyry Cu deposit (YPCD) occurs in the Kalaxiangar porphyry Cu belt (KPCB), which occupies the central area of the Central Asian Orogenic Belt (CAOB) between the Sawu’er island arc and the Altay Terrane in northern Xinjiang. The YPCD is one of several typical subduction-related deposits in the KPCB, which has undergone syn-collisional and post-collisional metallogenic overprinting. The YPCD is characterized by three pyrite-forming stages, namely a hydrothermal stage A (Py I), a syn-ductile deformation stage B (Py II) characterized by Cu-Au enrichment, and a fracture-filling stage C (Py III). In this study, we conducted systematic petrographic and geochemical studies of pyrites and coexist biotite, which formed during different stages, in order to constrain the physicochemical conditions of the ore formation. Euhedral, fragmented Py I has low Pb and high Te and Se concentration and Ni contents are low with Co/Ni ratios mostly between 1 and 10 (average 9.00). Py I is further characterized by enrichments of Bi, As, Ni, Cu, Te and Se in the core relative to the rim domains. Anhedral round Py II has moderate Co and Ni contents with high Co/Ni ratios >10 (average 95.2), and average contents of 46.5 ppm Pb and 5.80 ppm Te. Py II is further characterized by decreasing Bi, Cu, Pb, Zn, Ag, Te, Mo, Sb and Au contents from the rim to the core domains. Annealed Py III has the lowest Co content of all pyrite types with Co/Ni ratios mostly <0.1 (average 1.33). Furthermore, Py III has average contents of 3.31 ppm Pb, 1.33 ppm Te and 94.6 ppm Se. In addition, Fe does not correlate with Cu and S in the Py I and Py III, while Py II displays a negative correlation between Fe and Cu as well as a positive correlation between Fe and S. Therefore, pyrites which formed during different tectonic regimes also have different chemical compositions. Biotite geothermometer and oxygen fugacity estimates display increasing temperatures and oxygen

Link between the granitic and volcanic rocks of the Bushveld Complex, South Africa

NASA Astrophysics Data System (ADS)

Schweitzer, J. K.; Hatton, C. J.; De Waal, S. A.

1997-02-01

Until recently, it was proposed that the Bushveld Complex, consisting of the extrusive Rooiberg Group and the intrusive Rashoop Granophyre, Rustenburg Layered and Lebowa Granite Suites, evolved over a long period of time, possibly exceeding 100 Ma. Most workers therefore considered that the various intrusive and extrusive episodes were unrelated. Recent findings suggest that the intrusive, mafic Rustenburg Layered Suite, siliceous Rashoop Granophyre Suite and the volcanic Rooiberg Group were synchronous, implying that the Bushveld igneous event was short-lived. Accepting the short-lived nature of the complex, the hypothesis that the granites are genetically unrelated to the other events of the Bushveld Complex can be reconsidered. Re-examination of the potential Rooiberg Group/Lebowa Granite Suite relationship suggests that the granites form part of the Bushveld event. Rhyolite lava, granite and granophyre melts originated from a source similar in composition to upper crustal rocks. This source is interpreted to have been melted by a thermal input associated with a mantle plume. Granite intruded after extrusion of the last Rooiberg rhyolite, or possibly overlapped in time with the formation of the youngest volcanic flows.

Magnetic susceptibility and AMS of the Bushveld alkaline granites, South Africa

NASA Astrophysics Data System (ADS)

Ferré, Eric C.; Wilson, Jeff; Gleizes, Gérard

1999-06-01

The Bushveld Complex in South Africa includes one of the world's largest anorogenic alkaline granite intrusions (66,000 km 2). The granite forms a composite laccolith, of 350 × 250 km in area and about 2 km in thickness, which was emplaced at about 5 km depth into sediments overlying the Kaapvaal craton, at 2054 Ma. The Bushveld granite and its roof-rocks have long been mined for Sn, W and F. The Bushveld granites have high magnetic susceptibilities ( Km from 1000 to 4000 μSI), and a quantitative model is presented, suggesting that susceptibility fabrics are primarily carried by ferromagnetic minerals. The measured AMS foliations coincide with observed subhorizontal mineral lineations and compositional layering. Magnetic lineation trends vary considerably within the horizontal plane. The existence of a weak planar fabric and, an almost absent linear component may reflect (a) laccolithic emplacement by roof uplift, causing flattening magmatic fabrics, or (b) emplacement of largely crystal-free magma crystallizing in-situ and developing horizontal compositional layering from thermal chemical diffusion fronts and gravity-driven mechanisms. Weak magnétic fabrics, like those identified in the Bushveld granites require specific sampling schemes and procedures, in addition to rigorous constraint of magnetic mineralogy and crystallization sequence.

Hydrogen analysis for granite using proton-proton elastic recoil coincidence spectrometry.

PubMed

Komatsubara, T; Sasa, K; Ohshima, H; Kimura, H; Tajima, Y; Takahashi, T; Ishii, S; Yamato, Y; Kurosawa, M

2008-07-01

In an effort to develop DS02, a new radiation dosimetry system for the atomic bomb survivors of Hiroshima and Nagasaki, measurements of neutron-induced activities have provided valuable information to reconstruct the radiation situation at the time of the bombings. In Hiroshima, the depth profile of (152)Eu activity measured in a granite pillar of the Motoyasu Bridge (128 m from the hypocenter) was compared with that calculated using the DS02 methodology. For calculation of the (152)Eu production due to the thermal-neutron activation reaction, (151)Eu(n,gamma)(152)Eu, information on the hydrogen content in granite is important because the transport and slowing-down process of neutrons penetrating into the pillar is strongly affected by collisions with the protons of hydrogen. In this study, proton-proton elastic recoil coincidence spectrometry has been used to deduce the proton density in the Motoyasu pillar granite. Slices of granite samples were irradiated by a 20 MeV proton beam, and the energies of scattered and recoil protons were measured with a coincidence method. The water concentration in the pillar granite was evaluated to be 0.30 +/- 0.07%wt. This result is consistent with earlier data on adsorptive water (II) and bound water obtained by the Karl Fisher method.

Petrogenesis of Mesozoic granites in the Xitian, South China: Evidence from whole-rock geochemistry and zircon isotopes

NASA Astrophysics Data System (ADS)

Liu, Q.; Sun, J.; He, M.; Hou, Q.; Niu, R.

2017-12-01

Mesozoic granitoids are widespread in southeastern China, which accompanied with lots of world-famous polymetallic deposits. The mineralization is believed to be related to the Mesozoic granitic magmatism. However, the petrogenesis of these granites and their relation to the mineralization are still debated. As a typical granitic pluton, Xitian granites from the eastern Hunan Province are formed during this period and associated with tungsten-tin deposit. Whole-rock geochemical, SIMS zircon geochronology and oxygen isotopes, as well as LA-ICPMS zircon Lu-Hf isotopic analyses, were carried out on a suite of rocks from Xitian granitic pluton to constrain their magmatic sources and petrogenesis. Xitian granitic pluton is mainly composed of biotite adamellite, biotite granite, fine-grained granite. SIMS and LA-ICPMS U-Pb dating of zircons indicate that there are two episodes of these rocks, i.e., Late Triassic granites (227-233Ma) and Late Jurassic granites (150-154Ma). The Xitian granites are silica-rich, potassic and weakly peraluminous. Petrographic and geochemical features show that they are highly fractionated I-type granites. The combined elemental and isotopic results indicated that the Late Triassic granite in Xitian area experienced a process of crystal fractionation of crustal-derived magmas coupled with strong assimilation of the surrounding rocks. The occurrence of Jurassic granitoids in Xitian area is attributed to ascending of mantle-derived magmas, which provide heat for partial melting of crustal materials. The Late Jurassic granite may be derived from juvenile crust or partial melting of ancient crustal rocks, whereas high degrees of crystal fractionation further enriched tungsten-tin in the evolved granitic rocks. This work was financially supported by the Research Cooperation between Institute and University of Chinese Academy of Sciences grant (Y552012Y00), Public Welfare Project of the Ministry of land and Resources of China (201211024

Structural changes in a heterogeneous solid (granite) under shock wave action

NASA Astrophysics Data System (ADS)

Vettegren, V. I.; Shcherbakov, I. P.; Mamalimov, R. I.; Kulik, V. B.

2016-04-01

The structure of two granite types (plagiogranite and alaskite) before and after shock wave action has been studied by infrared, Raman, and photoluminescence spectroscopy methods. It has been found that the shock wave caused transformation of quartz and feldspar crystals composing these granites into diaplectic glasses.

Effects of Mineral Compositions on Matrix Diffusion and Sorption of 75Se(IV) in Granite.

PubMed

Yang, Xiaoyu; Ge, Xiangkun; He, Jiangang; Wang, Chunli; Qi, Liye; Wang, Xiangyun; Liu, Chunli

2018-02-06

Exploring the migration behaviors of selenium in granite is critical for the safe disposal of radioactive waste. The matrix diffusion and sorption of 75 Se(IV) (analogue for 79 Se) in granite were systematically studied to set reliable parameters in this work. Through-diffusion and batch sorption experiments were conduct with four types of Beishan granite. The magnitudes of the obtained apparent diffusion coefficient (D a ) values are of the following order: monzogranite > granodiorite-2 > granodiorite-1, which is opposite to the sequence of the K d values obtained from both the diffusion model and batch sorption experiments. The EPMA results of the granitic flakes showed that there was no obvious enrichment of Se(IV) on quartz, microcline and albite. Only biotite showed a weak affinity for Se(IV). Macroscopic sorption behaviors of Se(IV) on the four types of granite were identical with the sequence of the granitic biotite contents. Quantitative fitting results were also provided. XPS and XANES spectroscopy data revealed that bidentate inner-sphere complexes were formed between Se(IV) and Fe(III). Our results indicate that biotite can be representative of the Se(IV) sorption in complex mineral assemblages such as granite, and the biotite contents are critically important to evaluate Se(IV) transport in granite.

Analysis of Shield Construction in Spherical Weathered Granite Development Area

NASA Astrophysics Data System (ADS)

Cao, Quan; Li, Peigang; Gong, Shuhua

2018-01-01

The distribution of spherical weathered bodies (commonly known as "boulder") in the granite development area directly affects the shield construction of urban rail transit engineering. This paper is based on the case of shield construction of granite globular development area in Southern China area, the parameter control in shield machine selection and shield advancing during the shield tunneling in this special geological environment is analyzed. And it is suggested that shield machine should be selected for shield construction of granite spherical weathered zone. Driving speed, cutter torque, shield machine thrust, the amount of penetration and the speed of the cutter head of shield machine should be controlled when driving the boulder formation, in order to achieve smooth excavation and reduce the disturbance to the formation.

Geologic and environmental characteristics of porphyry copper deposits with emphasis on potential future development in the Bristol Bay Watershed, Alaska (Appendix H)

USGS Publications Warehouse

Seal, Robert R.

2012-01-01

Pebble; Big Chunk is approximately 30 miles (48 km) north-northwest of Pebble; and Shotgun is approximately 110 miles (177 km) northwest of Pebble. The H and D Block prospects, west of Pebble, represent additional porphyry copper exploration targets in the watershed.

Silicosis in West Country Granite Workers

PubMed Central

Hale, L. W.; Sheers, G.

1963-01-01

The granite industry in Cornwall and Devon is briefly described, especially the production of dust in dressing the stone. In 1951, 210 granite masons were examined (about 84% of the total at that time) and 37 (17·6%) showed silicosis. These men were followed up for 10 years. No silicosis was seen in men with less than 15 years' exposure, but after this time the risk increased to 11 out of 14 in those with over 35 years' exposure. Nine deaths occurred, two of which were due to silicosis. Radiological progression was observed in 13 of the 28 survivors. It was not necessarily associated with additional exposure but was related to age. More young men progressed. In 1961, 132 of the granite masons (about 93% of the total at that time) were re-examined and nine new cases of silicosis were found to have developed during the 10-year interval. The exposure in the 1961 cases was comparable with that of similar cases in 1951. Thus the risk has not been much reduced over this period. Pulmonary tuberculosis occurred in eight of the 37 cases of silicosis in 1951, and between 1951 and 1961 a further five cases were diagnosed, four being from one locality. This was by far the most frequent and disabling complication. Only one case of progressive massive fibrosis was seen. More extensive use of protective antituberculous chemotherapy is advocated, and also better dust control. Images PMID:14046159

76 FR 60493 - Settlement Agreements for Recovery of Past Response Costs; Granite Timber Post and Pole Site...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-29

... Costs; Granite Timber Post and Pole Site, Philipsburg, Granite County, MT AGENCY: Environmental... Agency (EPA) and Margery Metesh (Settling Party) and Mark Metesh (Settling Party), regarding the Granite... Granite County, Montana. The Settlement Agreements propose to compromise a claim the United States has at...

Geochronology and thermobarometry of the granitoid rocks within the Vaasa granite-migmatite complex, western Finland

NASA Astrophysics Data System (ADS)

Kurhila, Matti; Kotilainen, Anna; Tiljander, Mia; Hölttä, Pentti; Korja, Annakaisa

2015-04-01

The Vaasa granite-migmatite dome in west-central Finland has been formed in the Svecofennian orogeny, after the main collisional stage at ~1.9 Ga. The structure consists of a granite-migmatite core surrounded by metasedimentary rocks with outward decreasing metamorphic grade. The core comprises anatectic garnet-bearing granites, diatexites, pyroxene granites, and minor intrusive granodiorites. Geochemically, all of the rocks are peraluminous and magnesian. The Vaasa granites have close to average upper crustal compositions, and they show signs of titanite and plagioclase fractionation. The heavy REEs vary strongly according to garnet retention. Zircon U-Pb ages for these rock types indicate crystallization at 1875 Ma for the diatexites and garnet-bearing granites and at 1870 Ma for the pyroxene granites. Melt-forming temperatures are estimated by zircon and monazite saturation temperatures, and by Al/Ti ratios. No clear difference in the melting temperatures of the various rock types could be detected. However, while the monazite and zircon saturation temperatures point to temperatures around 800 ° C, the Al-Ti thermometer gives consistently about 100 ° C degrees higher results. Given the anatectic and felsic nature of the rocks, the lower temperature estimates seem more probable. Crystallization temperatures and pressures were calculated with the help of mineral chemical analyses. Garnet-biotite-plagioclase-quartz thermobarometry, and Al-in-hornblende barometry indicate pressures of 5.5-6 kbars for the diatexites, the pyroxene granites and an intrusive granodiorite. Significantly lower pressures of 2-4 kbars are recorded for the garnet-bearing granites. The garnet-biotite thermometer implies crystallization temperatures between 650 - 700 ° C for the pyroxene granites and the diatexites, and upto 600 ° C for the garnet-bearing granites. These results are markedly lower than those indicated by the whole-rock saturation temperatures of the same rocks. This may

Diffusion-driven magnesium and iron isotope fractionation at a gabbro-granite boundary

NASA Astrophysics Data System (ADS)

Wu, Hongjie; He, Yongsheng; Teng, Fang-Zhen; Ke, Shan; Hou, Zhenhui; Li, Shuguang

2018-02-01

Significant magnesium and iron isotope fractionations were observed in an adjacent gabbro and granite profile from the Dabie Orogen, China. Chilled margin and granitic veins at the gabbro side and gabbro xenoliths in the granite indicate the two intrusions were emplaced simultaneously. The δ26Mg decreases from -0.28 ± 0.04‰ to -0.63 ± 0.08‰ and δ56Fe increases from -0.07 ± 0.03‰ to +0.25 ± 0.03‰ along a ∼16 cm traverse from the contact to the granite. Concentrations of major elements such as Al, Na, Ti and most trace elements also systematically change with distance to the contact. All the observations suggest that weathering, magma mixing, fluid exsolution, fractional crystallization and thermal diffusion are not the major processes responsible for the observed elemental and isotopic variations. Rather, the negatively correlated Mg and Fe isotopic compositions as well as co-variations of Mg and Fe isotopes with Mg# reflect Mg-Fe inter-diffusion driven isotope fractionation, with Mg diffusing from the chilled gabbro into the granitic melt and Fe oppositely. The diffusion modeling yields a characteristic diffusive transport distance of ∼6 cm. Consequently, the diffusion duration, during which the granite may have maintained a molten state, can be constrained to ∼2 My. The cooling rate of the granite is calculated to be 52-107 °C/My. Our study suggests diffusion profiles can be a powerful geospeedometry. The observed isotope fractionations also indicate that Mg-Fe inter-diffusion can produce large stable isotope fractionations at least on a decimeter scale, with implications for Mg and Fe isotope study of mantle xenoliths, mafic dikes, and inter-bedded lavas.

Petrogenesis of selected A-type granitic intrusions from Central Eastern Desert of Egypt

NASA Astrophysics Data System (ADS)

Hassan, Tharwat; Asran, Asran; Amron, Taha; Hauzenberger, Christoph

2014-05-01

The Pan-African orogeny in the Arabian-Nubian Shield was terminated by intrusion of A-type granites (~ 595 Ma; Greenberg, 1981) and its volcanic equivalents. Subsequent to the intrusions of these granitic bodies the shield was exhumed. Eroded A-type granite pebbles were found in the molasse sediments that were deposited in intermountain basins. Therefore the A-type granites provide information about the last stage of the Pan-African geochemical system. Preliminary whole-rock geochemical data of three granitic intrusions (Kadabora, Um Naggat and El shiekh Salem) from the Central Eastern Desert of Egypt; indicate that all of them are peraluminous and with A-type characteristics. These intrusions show low CaO content (average 0.43 %wt), high FeOT/MgO ratio (10.46-121.88), high Na2O+K2O (average 8.04 %wt), marked enrichment of high field strength elements (Y, Nb and Ga except Zr), depletion in MgO (0.01-0.11 %wt) and with low concentration of Sr and Ba. The studied granitoids were emplaced in within plate tectonic regime. References: Greenberg, J.K. (1981): Characteristic and origin of Egyptian younger granites. Bull. Geol. Soc. Am. Part 1, v.92: 224-232.

Hydrothermally-induced changes in mineralogy and magnetic properties of oxidized A-type granites

NASA Astrophysics Data System (ADS)

Nédélec, Anne; Trindade, Ricardo; Peschler, Anne; Archanjo, Carlos; Macouin, Mélina; Poitrasson, Franck; Bouchez, Jean-Luc

2015-01-01

The changes in magnetic mineralogy due to the hydrothermal alteration of A-type granitic rocks have been thoroughly investigated in samples from the granite of Tana (Corsica, France), and compared with other A-type granites: Meruoca (NE Brazil), Bushveld (South Africa), Mount Scott (Wichita Mountains, Oklahoma, USA) and the stratoid hypersolvus granites of Madagascar. The altered red-colored samples and their non-altered equivalents were magnetically characterized by means of magnetic susceptibility measurements, hysteresis loops, remanent coercivity spectra, and Lowrie test. It is shown that hydrothermalization in magnetite-bearing granites is related to the formation of fine-grained magnetite and hematite, and to coeval depletion in the content of primary low-coercive coarse-grained magnetite. These mineralogical changes give typical rock magnetic signatures, namely lower susceptibility magnitudes and anisotropy degrees, prolate AMS (anisotropy of magnetic susceptibility) fabrics and increased coercivities. Optical microscopy and SEM (scanning electronic microscopy) images suggest that the orientation of the secondary magnetic minerals is related to fluid-pathways and micro-fractures formed during the hydrothermal event and therefore may be unrelated to magma emplacement and crystallization fabrics. Changes in magnetic mineralogy and grain-size distribution have also to be considered for any paleomagnetic and iron isotope studies in granites.

The emplacement, geochemistry and petrogenesis of two central Morocco Hercynian granites. Geotectonic implications

NASA Astrophysics Data System (ADS)

Giuliani, G.; Cheilletz, A.; Zimmermann, J. L.

New field, petrographic and geochemical data including REE, Rb-Sr, and K-Ar, are presented concerning the emplacement and petrogenesis of two calc-alkaline Moroccan Hercynian granites: the Zaër pluton and the Djebel Aouam stocks. Zonation in the Zaër pluton does not appear to result from simple fractional crystallization nor from hydrothermal alteration but is rather the diapiric intrusion of two interlocked bodies. REE geochemistry supports the interpretation that the biotite-granodiorite magma (301 ± 8.2 M.a.) and the Djebel Aouam stocks appear to have been derived by fusion of crustal materials with possible mantle contamination ( Initial87Sr/ 86Srratio = 0.70514 ). The second two-mica granitic magma (283.4 ± 6.2 M.a.) corresponds to a peraluminous granite (1.22 < A/ CNK < 1.33) generated by fusion of continental crust including mature sedimentarr materials (Initial 87Sr/ 86Sr ratio = 0.70836). These granites are compared to the Acadian granites of north Appalachian and classified in the «post-collision, uplift environmentå type. An illustrative four step model presenting the generation and emplacement of these two granites together with the associated W-Sn-Pb-Zn-Ag mineralizations is proposed: (1) first magma generation, (2) first melt emplacement, (3) second melt emplacement, (4) late convective flow.

Permeability of Granite Including Macro-Fracture Naturally Filled with Fine-Grained Minerals

NASA Astrophysics Data System (ADS)

Nara, Yoshitaka; Kato, Masaji; Niri, Ryuhei; Kohno, Masanori; Sato, Toshinori; Fukuda, Daisuke; Sato, Tsutomu; Takahashi, Manabu

2018-03-01

Information on the permeability of rock is essential for various geoengineering projects, such as geological disposal of radioactive wastes, hydrocarbon extraction, and natural hazard risk mitigation. It is especially important to investigate how fractures and pores influence the physical and transport properties of rock. Infiltration of groundwater through the damage zone fills fractures in granite with fine-grained minerals. However, the permeability of rock possessing a fracture naturally filled with fine-grained mineral grains has yet to be investigated. In this study, the permeabilities of granite samples, including a macro-fracture filled with clay and a mineral vein, are investigated. The permeability of granite with a fine-grained mineral vein agrees well with that of the intact sample, whereas the permeability of granite possessing a macro-fracture filled with clay is lower than that of the macro-fractured sample. The decrease in the permeability is due to the filling of fine-grained minerals and clay in the macro-fracture. It is concluded that the permeability of granite increases due to the existence of the fractures, but decreases upon filling them with fine-grained minerals.

Major magmatic events in Mt Meredith, Prince Charles Mountains: First evidence for early Palaeozoic syntectonic granites

USGS Publications Warehouse

Gongurov, N.A.; Laiba, A.A.; Beliatsky, B.V.

2007-01-01

Precambrian rocks at Mt Meredith underwent granulite-facies metamorphism M1. Zircon isotope dating for two orthogneisses revealed the following age signatures: 1294±3 and 957±4Ma; 1105±5 and 887±2Ma. The oldest ages could reflect the time of orthogneiss protolith crystallization and the latest age determinations date Grenvillian metamorphism. The metamorphic rocks were intruded by two-mica and garnet-biotite granites. The granites and host rocks underwent amphibolite-facies metamorphism M2. Zircon isotope analysis of the two-mica granites showed age estimation within 550-510Ma and zircon dating of the garnet-biotite granites revealed the ages of 1107±5, 953±8, and 551±4Ma. As Pan-African age signatures were obtained from only the granite samples, it is possible to suggest that the granites were formed at the time of 510-550Ma and the zircons with greater age values were captured by granites from the host rocks.

Petrogenesis of Mesoproterozoic granitic plutons, eastern Llano Uplift, central Texas, USA

NASA Astrophysics Data System (ADS)

Smith, R. K.; Gray, Walt; Gibbs, Tyson; Gallegos, M. A.

2010-08-01

The Llano Uplift of central Texas is a gentle structural dome exposing ˜ 1370 to 1230 Ma metaigneous and metasedimentary rocks of Grenville affinity along the southern margin of Laurentia. The metamorphic rocks were subsequently intruded by ˜ 1119 to 1070 Ma late syn- to post-tectonic granites collectively known as the Town Mountain Granite (TMG). The eastern most of the TMG, the Marble Falls (MF), Kingsland (KL), and Lone Grove (LG) plutons, are metaluminous to marginally peraluminous, high-K, calc-alkaline, ferroan, biotite-calcic amphibole granites [Fe/(Fe + Mg) = 0.71-0.92 and 0.78-0.91 for biotite and calcic amphibole, respectively] displaying distinct variation trends with increasing silica content. They are chemically and texturally zoned and have mineralogical and chemical characteristics similar to A-type granites; i.e., 1) Fe-rich biotites, calcic amphiboles, accessory fluorite, and sporadic rapakivi texture, 2) high K 2O (> 4 wt.%), 3) low Al 2O 3 (< 16 wt.%) and CaO (< 3 wt.%), 4) high Fe/(Fe + Mg), 5) enrichments in Zr, Nb, REE, Ga/Al, and 6) depleted Eu. However, in contrast to typical A-type granites (having low Sr and Ba) the MF, KL,and LG plutons are enriched in Sr and Ba; i.e., up to 229 ppm and 1090 ppm, respectively. On granite discrimination diagrams [(K 2O + Na 2O)/CaO vs. Zr + Nb + Ce + Y (ppm) and Zr (ppm) vs. Ga/Al*10,000] the KL and MF plutons plot within the A-type field, whereas the LG pluton compositions are divided between A-type and fractionated granite fields (I-, S- and M-types). On tectonic discrimination diagrams (Y vs. Nb ) the MF and KL granites plot in the "within-plate" granite field, but the LG pluton plots across several fields including "within-plate" and "volcanic arc plus syn-collisional" fields. Consequently the tectonic classification on a geochemical basis for the LG pluton is unclear. Based on thermal metamorphic mineral assemblages, normative Q-Ab-Or plots, and Q-Ab-Or-H 2O experimental data (Johannes and Holtz

Magmatic and Crustal Differentiation History of Granitic Rocks from Hf-O Isotopes in Zircon

NASA Astrophysics Data System (ADS)

Kemp, , A. I. S.; Hawkesworth, , C. J.; Foster, , G. L.; Paterson, , B. A.; Woodhead, , J. D.; Hergt, , J. M.; Gray, , C. M.; Whitehouse, M. J.

2007-02-01

Granitic plutonism is the principal agent of crustal differentiation, but linking granite emplacement to crust formation requires knowledge of the magmatic evolution, which is notoriously difficult to reconstruct from bulk rock compositions. We unlocked the plutonic archive through hafnium (Hf) and oxygen (O) isotope analysis of zoned zircon crystals from the classic hornblende-bearing (I-type) granites of eastern Australia. This granite type forms by the reworking of sedimentary materials by mantle-like magmas instead of by remelting ancient metamorphosed igneous rocks as widely believed. I-type magmatism thus drives the coupled growth and differentiation of continental crust.

Time-Dependent Behaviors of Granite: Loading-Rate Dependence, Creep, and Relaxation

NASA Astrophysics Data System (ADS)

Hashiba, K.; Fukui, K.

2016-07-01

To assess the long-term stability of underground structures, it is important to understand the time-dependent behaviors of rocks, such as their loading-rate dependence, creep, and relaxation. However, there have been fewer studies on crystalline rocks than on tuff, mudstone, and rock salt, because the high strength of crystalline rocks makes the detection of their time-dependent behaviors much more difficult. Moreover, studies on the relaxation, temporal change of stress and strain (TCSS) conditions, and relations between various time-dependent behaviors are scarce for not only granites, but also other rocks. In this study, previous reports on the time-dependent behaviors of granites were reviewed and various laboratory tests were conducted using Toki granite. These tests included an alternating-loading-rate test, creep test, relaxation test, and TCSS test. The results showed that the degree of time dependence of Toki granite is similar to other granites, and that the TCSS resembles the stress-relaxation curve and creep-strain curve. A viscoelastic constitutive model, proposed in a previous study, was modified to investigate the relations between the time-dependent behaviors in the pre- and post-peak regions. The modified model reproduced the stress-strain curve, creep, relaxation, and the results of the TCSS test. Based on a comparison of the results of the laboratory tests and numerical simulations, close relations between the time-dependent behaviors were revealed quantitatively.

Regional mapping of hydrothermally altered igneous rocks along the Urumieh-Dokhtar, Chagai, and Alborz Belts of western Asia using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and Interactive Data Language (IDL) logical operators: a tool for porphyry copper exploration and assessment: Chapter O in Global mineral resource assessment

USGS Publications Warehouse

Mars, John L.; Zientek, M.L.; Hammarstrom, J.M.; Johnson, K.M.; Pierce, F.W.

2014-01-01

The ASTER alteration map and corresponding geologic maps were used to select circular to elliptical patterns of argillic- and phyllic-altered volcanic and intrusive rocks as potential porphyry copper sites. One hundred and seventy eight potential porphyry copper sites were mapped along the UDVB, and 23 sites were mapped along the CVB. The potential sites were selected to assist in further exploration and assessments of undiscovered porphyry copper deposits.

Oxygen isotope studies of early Precambrian granitic rocks from the Giants Range batholith, northeastern Minnesota, U.S.A.

USGS Publications Warehouse

Viswanathan, S.

1974-01-01

Oxygen isotope studies of granitic rocks from the 2.7 b.y.-old composite Giants Range batholith show that: (1) ??(O18)quartz values of 9 to 10 permil characterize relatively uncontaminated Lower Precambrian, magmatic granodiorites and granites; (2) granitic rocks thought to have formed by static granitization have ??(O18)quartz values that are 1 to 2 permil higher than magmatic granitic rocks; (3) satellite leucogranite bodies have values nearly identical to those of the main intrusive phases even where they transect O18-rich metasedimentary wall rocks; (4) oxygen isotopic interaction between the granitic melts and their O18-rich wall rocks was minimal; and (5) O18/O18 ratios of quartz grains in a metasomatic granite are largely inherited from the precursor rock, but during the progression - sedimentary parent ??? partially granitized parent ??? metasomatic granite ??? there is gradual decrease in ??(O18)quartz by 1 to 2 permil. ?? 1974.

Zarzalejo granite (Spain). A nomination for 'Global Heritage Stone Resource'

NASA Astrophysics Data System (ADS)

Freire Lista, David Martin; Fort, Rafael; José Varas-Muriel, María

2015-04-01

Zarzalejo granite is quarried in the Sierra de Guadarrama (Spanish Central System) foothills, in and around Zarzalejo village, in the province of Madrid, Spain. It is an inequigranular monzogranite medium-to-coarse grained, with a slight porphyritic texture (feldspar phenocrysts) and mafic micro-grained enclaves. In this abstract the candidacy of Zarzalejo granite as a "Global Heritage Resource Stone" (GHSR) is presented. This stone ideally fits the newly proposed designation as it has been used in many heritage buildings and its good petrophysical properties and durability have allowed well preserved constructions such as a Roman road, San Pedro Church in Zarzalejo (1492), Descalzas Reales Monastery in Madrid (1559-1564) and the San Lorenzo del Escorial Royal Monastery (1563-1584), to be declared a World Heritage Site by UNESCO. This level of construction has been a landmark in the extraction and proliferation of historic quarries created due to the high demand that such colossal monuments and buildings with granite, have required for their construction. In the mid-20th century, More, Zarzalejo granite has also been used in restoration works including the Royal Palace and the Reina Sofía Museum (2001-2005), both buildings in Madrid, Spain. Extraction of granite ashlars from tors has been a very frequent activity in the Zarzalejo neighbourhood until mid-twentieth century. So there is also a need to preserve these historic quarries. This type of stone has created a landscape that has been preserved as an open-air museum today where you can see the marks left in the granite due to historic quarry operations. The granite industry has been one of the main pillars of the Zarzalejo regional economy. For centuries, the local community have been engaged in quarrying and have created a cultural landscape based on its building stone. A quarryman monument has been erected in Zarzalejo in honor of this traditional craft as well as an architecture museum at San Lorenzo del

Emplacement and deformation of the A-type Madeira granite (Amazonian Craton, Brazil)

NASA Astrophysics Data System (ADS)

Siachoque, Astrid; Salazar, Carlos Alejandro; Trindade, Ricardo

2017-04-01

The Madeira granite is one of the Paleoproterozoic (1.82 Ga) A-type granite intrusions in the Amazonian Craton. It is elongated in the NE-SW direction and is composed of four facies. Classical structural techniques and the anisotropy of magnetic susceptibility (AMS) method were applied to the study of its internal fabric. Magnetic susceptibility measurements, thermomagnetic curves, remanent coercivity spectra, optical microscopy and SEM (scanning electron microscopy) analyses were carried out on the earlier and later facies of the Madeira granite: the rapakivi granite (RG) and the albite granite (AG) respectively. The last one is subdivided into the border albite granite (BAG) and the core albite granite (CAG) subfacies. AMS fabric pattern is controlled by pure magnetite in all facies, despite significant amounts of hematite in the BAG subfacies. Microstructural observations show that in almost all sites, magnetic fabric correlates to magmatic state fabrics that are defined by a weak NE-SW orientation of mafic and felsic silicates. However, strain mechanisms in both subfacies of AG also exhibit evidence for solid-state deformation at high to moderate temperatures. Pegmatite dyke, strike slip fault (SFA-B-C), hydrothermal vein, normal fault (F1-2) and joint (J) structures were observed and their orientation and kinematics is consistent with the magmatic and solid-state structures. Dykes, SFA-C and F1, are usually orientated along the N70°E/40°N plane, which is nearly parallel to the strike of AMS and magmatic foliations. In contrast, veins, SFB, F2 and some J are oriented perpendicular to the N70°E trend. Kinematic analysis in these structures shows evidence for a dextral sense of movement in the system in the brittle regime. The coherent structural pattern for the three facies of Madeira granite suggests that the different facies form a nested pluton. The coherence in orientation and kinematics from magmatic to high-temperature solid-state, and into the brittle

Lithium and boron in late-orogenic granites - Isotopic fingerprints for the source of crustal melts?

NASA Astrophysics Data System (ADS)

Romer, Rolf L.; Meixner, Anette; Förster, Hans-Jürgen

2014-04-01

Geochemically diverse late- and post-Variscan granites of the Erzgebirge-Vogtland, the Saxon Granulite Massif, and Thuringia (Germany) formed by anatectic melting of Palaeozoic sedimentary successions and associated mafic to felsic volcanic rocks. The compositional diversity of the least evolved of these granites is largely inherited from the protoliths. We present Li and B-isotopic data of these granites and compare them with the isotopic composition of their protoliths, to investigate whether (i) there exist systematic differences in the Li and B-isotopic composition among different granite types and (ii) Li and B-isotopic compositions provide information on the granite sources complementary to information from the isotopic composition of Sr, Nd, and Pb and the trace-element signatures. Low-F biotite and two-mica granite types have flat upper continental crust (UCC)-normalized trace-element pattern with variable enrichments in Li, Rb, Cs, Sn, and W and depletions in Sr, Ba, and Eu. These signatures are least pronounced for the Niederbobritzsch biotite granite, which has the largest contribution of mafic material, and most pronounced for the two-mica granites. The granites show a relatively narrow range of δ7Li values (-3.0 to -0.5) and a broad range of δ11B values (-13.4 to +20.1). The δ11B values are lower in rocks with distinctly higher contents of Li, Rb, Cs, and Sn. The high δ11B of the Niederbobritzsch granite may be explained by the melting of former altered oceanic crust in its source. Relative to UCC, intermediate-F to high-F low-P granites show strong depletions in Sr, Ba, Eu as well as Zr and Hf, strong enrichments in Li, Rb, and Cs as well as Nb, Sn, Ta, and W, and REE pattern with stronger enrichments for HREE than for LREE. These granites show narrow ranges of δ7Li (-2.0 to +1.6) and δ11B values (-14.7 to -9.1), reflecting the smaller variability of the Li and B-isotopic composition in their source lithologies. The anomalously high δ7Li value

"Gris Quintana": a Spanish granite from the Past into the Future.

NASA Astrophysics Data System (ADS)

José Tejado, Juan; Mota, M. Isabel; Pereira, Dolores

2014-05-01

"Gris Quintana" is a medium-grained, biotite and amphibole granodiorite extracted in the Pluton of Quintana de la Serena (Extremadura, Spain). It is a constant light grey granite from the Hercynian geologic with excellent physicomechanical and physicochemical properties. The granodiorite is composed of plagioclase, biotite, quartz and alkali feldspar, with accessory allanite, titanite, apatite, zircon and ilmenite, mostly as inclusions within the biotite crystals. This commercial variety is extracted from many quarries in the late Hercynian plutons located in the Iberian Massif in Spain period (transition between Central Iberian and Ossa-Moren Zones), having large reserves of granite. Many of the quarries have their own transformation factory (high production zone), with which the sector is offered an endless variety of finishes and constructive rock typologies. A wide range of solutions to architects and designers are offered. Gris Quintana granite is one of the materials with highest technological benefits that are used in arquitecture. "Gris Quintana" granite has been used since ancient times, not only at a regional, but also at national and international level: paving, building (structural, exterior façadas, interior uses), urban decoration and funeral art. It can be found in monuments and more recently, in buildings of different styles and uses, that stand out in beauty and splendor, lasting in time. Some singular works in "Gris Quintana" granite all over the world: extension to the "Congreso de Diputados" (Parliament) in Madrid, "Puerta de San Vicente" in Madrid, Andalucia Parliament columns in Sevilla, New Senate Buiding in Madird, "Gran Vía" pavement in Madrid, "Teatro Real façade" in Madrid… "Gris Quintana" granite accomplishes all the requirements for its nomination as Global Heritage Stone Resource, for both its use in construction and for artistic purposes.

Importance of lunar granite and KREEP in very high potassium (VHK) basalt petrogenesis

NASA Technical Reports Server (NTRS)

Neal, Clive R.; Taylor, Lawrence A.; Lindstrom, Marilyn M.

1988-01-01

Analysis of five very high potassium (VHK) basalts from Apollo 14 breccia 14303 shows the presence of a KREEP component. An assimilation and fractional crystallization model is presented to describe the basalt evolution. The influence of granite assimilation on the basalt evolution is discussed. The presence of VHK basalts containing only a granite signature and those with both granite and KREEP signatures suggests that there are at least two different VHK basalt flows at the Apollo 14 site.

76 FR 62758 - Wallowa-Whitman and Umatilla National Forests, Oregon Granite Creek Watershed Mining Plans

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-11

... Granite Creek Watershed Mining Plans AGENCY: Forest Service, USDA. ACTION: Notice of intent to prepare an... to authorize the approval of mining Plans of Operation in the Granite Creek Watershed Mining Plans... environmental analyses for proposed mining Plans in the portions of the Granite Creek Watershed under their...

Comparison of hydrothermal alteration patterns associated with porphyry Cu deposits hosted by granitoids and intermediate-mafic volcanic rocks, Kerman Magmatic Arc, Iran: Application of geological, mineralogical and remote sensing data

NASA Astrophysics Data System (ADS)

Yousefi, Seyyed Jabber; Ranjbar, Hojjatollah; Alirezaei, Saeed; Dargahi, Sara; Lentz, David R.

2018-06-01

The southern section of the Cenozoic Urumieh-Dokhtar Magmatic Arc (UDMA) of Iran, known as Kerman Magmatic Arc (KMA) or Kerman copper belt, is a major host to porphyry Cu ± Mo ± Au deposits, collectively known as PCDs. In this study, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and spectral angle mapper (SAM) method, combined with field data, mineralogical studies, and spectral analysis are used to determine hydrothermal alteration patterns related to PCDs in the KMA. Gossans developed over some of these porphyry type deposits were mapped using Landsat 8 data. In the NKMA gossans are more developed than in the SKMA due to comparatively lower rate of erosion. The hydrothermal alteration pattern mapped by ASTER data were evaluated using mineralogical and spectral data. ASTER data proved to be useful for mapping the hydrothermal alteration in this semi-arid type of climate. Also Landsat 8 was useful for mapping the iron oxide minerals in the gossans that are associated with the porphyry copper deposits. Our multidisciplinary approach indicates that unlike the PCDs in the northern KMA that are associated with distinct and widespread propylitic alteration, those in the granitoid country rocks lack propylitic alteration or the alteration is only weakly and irregularly developed. The porphyry systems in southern KMA are further distinguished by development of quartz-rich phyllic alteration zones in the outer parts of the PCDs that could be mapped using remote sensing data. Consideration of variations in alteration patterns and specific alteration assemblages are critical in regional exploration for PCDs.

Origin of the subduction-related Carboniferous intrusions associated with the Yandong porphyry Cu deposit in eastern Tianshan, NW China: constraints from geology, geochronology, geochemistry, and Sr-Nd-Pb-Hf-O isotopes

NASA Astrophysics Data System (ADS)

Wang, Yin-Hong; Xue, Chun-Ji; Liu, Jia-Jun; Zhang, Fang-Fang

2017-10-01

The Yandong porphyry Cu deposit is located at the south margin of the Dananhu-Tousuquan arc belt in eastern Tianshan, northwest China. The Cu ores comprise mainly disseminations and vein zones in the potassic and phyllic alteration zones, and are predominantly hosted in diorite porphyry, tonalite, and quartz porphyry, which intruded into Carboniferous Qi'eshan Group volcanic rocks. The U-Pb ages indicate that four intrusions were emplaced between 338.6 ± 2.9 and 326.1 ± 2.6 Ma. Five molybdenite samples yield Re-Os model ages of 333.8-329.5 Ma with a weighted average age of 331.8 ± 2.1 Ma. Fourteen pyrite samples have 206Pb/204Pb of 17.776-18.959, 207Pb/204Pb of 15.410-15.534, and 208Pb/204Pb of 37.323-38.127, similar to the age-corrected data of the Yandong tonalite. The tonalite shows adakite-like characteristics (e.g., high Sr/Y ratios and low Y contents), and has positive ɛNd(t) and ɛHf(t) values, and low zircon O isotopes (3.7-4.6 ‰), suggesting that the melt was derived from partial melting of a subducted oceanic slab followed by mantle peridotite interaction. The diorite porphyry exhibits high Mg# and low Sr/Y values, slightly negative Eu anomalies, and positive ɛHf(t) values, indicating a lithospheric mantle source. The quartz porphyry, with stronger negative Eu anomalies, less evolved ɛHf(t) values, and low δ18O values (4.7-5.5 ‰), was probably derived from mantle melts that experienced mixing with lower crustal materials (melts or assimilation). The new data suggest that the Yandong intrusions formed in an arc setting. As the tonalite is genetically linked to the Cu mineralization, subduction-related slab melts must have played a key role in the formation of the Yandong deposit.

Origin of the subduction-related Carboniferous intrusions associated with the Yandong porphyry Cu deposit in eastern Tianshan, NW China: constraints from geology, geochronology, geochemistry, and Sr-Nd-Pb-Hf-O isotopes

NASA Astrophysics Data System (ADS)

Wang, Yin-Hong; Xue, Chun-Ji; Liu, Jia-Jun; Zhang, Fang-Fang

2018-06-01

The Yandong porphyry Cu deposit is located at the south margin of the Dananhu-Tousuquan arc belt in eastern Tianshan, northwest China. The Cu ores comprise mainly disseminations and vein zones in the potassic and phyllic alteration zones, and are predominantly hosted in diorite porphyry, tonalite, and quartz porphyry, which intruded into Carboniferous Qi'eshan Group volcanic rocks. The U-Pb ages indicate that four intrusions were emplaced between 338.6 ± 2.9 and 326.1 ± 2.6 Ma. Five molybdenite samples yield Re-Os model ages of 333.8-329.5 Ma with a weighted average age of 331.8 ± 2.1 Ma. Fourteen pyrite samples have 206Pb/204Pb of 17.776-18.959, 207Pb/204Pb of 15.410-15.534, and 208Pb/204Pb of 37.323-38.127, similar to the age-corrected data of the Yandong tonalite. The tonalite shows adakite-like characteristics (e.g., high Sr/Y ratios and low Y contents), and has positive ɛNd(t) and ɛHf(t) values, and low zircon O isotopes (3.7-4.6 ‰), suggesting that the melt was derived from partial melting of a subducted oceanic slab followed by mantle peridotite interaction. The diorite porphyry exhibits high Mg# and low Sr/Y values, slightly negative Eu anomalies, and positive ɛHf(t) values, indicating a lithospheric mantle source. The quartz porphyry, with stronger negative Eu anomalies, less evolved ɛHf(t) values, and low δ18O values (4.7-5.5 ‰), was probably derived from mantle melts that experienced mixing with lower crustal materials (melts or assimilation). The new data suggest that the Yandong intrusions formed in an arc setting. As the tonalite is genetically linked to the Cu mineralization, subduction-related slab melts must have played a key role in the formation of the Yandong deposit.

Activity concentrations and dose rates from decorative granite countertops.

PubMed

Llope, W J

2011-06-01

The gamma radiation emitted from a variety of commercial decorative granites available for use in U.S. homes has been measured with portable survey meters as well as an NaI(Th) gamma spectrometer. The (40)K, U-nat, and (232)Th activity concentrations were determined using a full-spectrum analysis. The dose rates that would result from two different arrangements of decorative granite slabs as countertops were explored in simulations involving an adult anthropomorphic phantom. Copyright © 2011 Elsevier Ltd. All rights reserved.

Microcracking and healing in granites: new evidence from cathodoluminescence.

PubMed

Sprunt, E S; Nur, A

1979-08-03

Quartz grains in granitic rocks usually have blue cathodoluminescence (CL). Within the blue-luminescing grains, there are often red-luminescing domains which are frequently impossible to detect without CL contrast. This finding suggests that the red-luminescing quartz is sealing preexisting mnicrocracks. The presence of these now-healed microcracks has important implications with respect to the role of pore fluid pressure and fluid transfer in metamorphism, the origih of granites, longperiod crustal deformation, earthquake mechanics, physical properties of rocks, and deep-seated geothermal energy.

Subsurface profiling of granite pluton using microtremor method: southern Aravalli, Gujarat, India

NASA Astrophysics Data System (ADS)

Joshi, Aditya U.; Sant, Dhananjay A.; Parvez, Imtiyaz A.; Rangarajan, Govindan; Limaye, Manoj A.; Mukherjee, Soumyajit; Charola, Mitesh J.; Bhatt, Meghnath N.; Mistry, Sagar P.

2018-01-01

We report, using the microtremor method, a subsurface granitic pluton underneath the Narukot Dome and in its western extension along a WNW profile, in proximity of eastern fringe of Cambay Rift, India. The dome and its extension is a part of the Champaner Group of rocks belonging to the Mesoproterozoic Aravalli Supergroup. The present finding elucidates development of an asymmetric double plunge along Narukot Dome. Microtremor measurements at 32 sites were carried out along the axial trace (N95°) of the dome. Fourier amplitude spectral studies were applied to obtain the ratio between the horizontal and vertical components of persisting Rayleigh waves as local ambient noise. Fundamental resonant frequencies with amplitude ≥1-sigma for each site are considered to distinguish rheological boundary. Two distinct rheological boundaries are identified based on frequency ranges determined in the terrain: (1) 0.2219-10.364 Hz recorded at 31 stations identified as the Champaner metasediment and granite boundary, and (2) 10.902-27.1119 Hz recorded at 22 stations identified as the phyllite and quartzite boundary. The proposed equation describing frequency-depth relationship between granite and overlaying regolith matches with those already published in the literature. The morphology of granite pluton highlights the rootless character of Champaner Group showing sharp discordance with granitic pluton. The findings of manifestation of pluton at a shallower depth imply a steep easterly plunge within the Champaner metasediments, whereas signature of pluton at a deeper level implies a gentle westerly plunge. The present method enables to assess how granite emplacement influences the surface structure.

Reconstructing Magmatic-Hydrothermal Systems via Geologic Mapping of the Tilted, Cross-sectional Exposures of the Yerington District, Nevada

NASA Astrophysics Data System (ADS)

Dilles, J. H.; Proffett, J. M.

2011-12-01

The Jurassic Yerington batholith was cut by Miocene to recent normal faults and tilted ~90° west (Proffett, 1977). Exposures range from the volcanic environment to ~6 km depth in the batholith. Magmatic-hydrothermal fluids derived from the Luhr Hill granite and associated porphyry dikes produced characteristic porphyry copper mineralization and rock alteration (K-silicate, sericitic, and advanced argillic) in near-vertical columnar zones above cupolas on the deep granite. In addition, saline brines derived from the early Mesozoic volcanic and sedimentary section intruded by the batholith were heated and circulated through the batholith producing voluminous sodic-calcic and propylitic alteration. The magnetite-copper ore body at Pumpkin Hollow is hosted in early Mesozoic sedimentary rocks in the contact aureole of the batholith, and appears to be an IOCG type deposit produced where the sedimentary brines exited the batholith. Although many advances in understanding of Yerington have been made by lab-based geochronology and geochemistry studies, the first order igneous and hydrothermal features were recognized first in the 1960s and 1970s and are best documented by geological mapping at a variety of scales ranging from 1:500 to 1:24,000. The Anaconda technique of mapping mine benches, trenches, and drill cores was perfected here (Einaudi, 1997), and other techniques were used for surface exposures. The geologic and hydrothermal alteration maps establish that hydrothermal alteration accompanied each of several porphyry dike intrusions, and affected more than 100 km3 of rock. Both zonation in alteration mineralogy and vein orientations allow reconstruction of source areas and >5 km-long flow-paths of hydrothermal fluids through the batholith and contact aureole.

Geothermal potential of Caledonian granites underlying Upper Palaeozoic sedimentary basins astride the Iapetus Suture Zone in Ireland

NASA Astrophysics Data System (ADS)

Fritschle, Tobias; Daly, J. Stephen; Whitehouse, Martin J.; McConnell, Brian; Buhre, Stephan

2014-05-01

Upper Palaeozoic sedimentary basins in Ireland overlie crystalline rocks within the Caledonian Iapetus Suture Zone. Beneath these basins, Lower Palaeozoic rocks, formed and deformed during the Caledonian orogenic cycle, were intruded by c. 420-390 Ma late-tectonic granites at various tectonic levels. These include the subsurface Kentstown and Glenamaddy granites discovered by mineral exploration drilling. While these granites comprise actual targets for Enhanced Geothermal System (EGS) exploration, several others likely exist based on geophysical considerations. In order to test the regional geothermal potential, the buried granites as well as analogue exposed rocks are being investigated geochemically. The geothermal potential of the intrusives depends on their heat production rate (HPR), which is calculated using rock density and concentrations of the heat producing elements (HPE) uranium, thorium and potassium. In spite of their close spacing and similar ages, the whole-rock geochemistry of the granites varies significantly, but with no obvious geographical control (Fritschle et al., 2013; 2014). The granite HPR values range from 1.4 μW/m3 for the Dhoon Granite (Isle of Man) to 4.9 μW/m3 for the Drogheda Granite (Ireland). This compares with the average HPR for a 'typical' granite of 2.7 μW/m3 (Goldstein et al., 2009). It is demonstrated that an elevated HPR of a granite can be related to enrichment in one of the HPE alone (e.g., uranium-enrichment in the Foxdale Granite (Isle of Man), or thorium-enrichment in the Drogheda Granite). Enrichment in HPE in a granite may occur due to different reasons including hydrothermal (re-) distribution of uranium, or the assimilation of thorium-rich wall-rocks. Hence, the distribution of the HPE in particular minerals, veins and source lithologies, along with the petrophysical characteristics of the sedimentary basins and the granites' petrogenesis, are currently being investigated as possible mechanisms controlling their

Adsorption of Se species on crushed granite: a direct linkage with its internal iron-related minerals.

PubMed

Jan, Yi-Lin; Wang, Tsing-Hai; Li, Ming-Hsu; Tsai, Shih-Chin; Wei, Yuan-Yaw; Teng, Shi-Ping

2008-01-01

The adsorption of selenium species on crushed granite is investigated directly linking to its internal iron-related minerals. Experimental results demonstrated that granite has higher affinity toward Se(IV) adsorption than Se(VI) adsorption. Se(IV) adsorption on granite is insensitive to background electrolytes while the effect of ionic strength on Se(VI) adsorption is not observed, which is attributed to the overloading of Se(VI) ions. Results of chemical sequential extraction showed that the removal of crystalline iron oxides dramatically reduces Se(IV) adsorption, which corresponds to the disappearance of goethite signal within XRD pattern. Based on our results, it is proposed that goethite within granite dominates Se adsorption in crushed granite. Although these goethites probably stem from some sample preparation processes including drilling in situ, crushing, washing and drying granite samples in laboratory, the formation of goethite enhances the granite affinity toward Se species adsorption. Images of SEM/EDS furthermore revealed that goethite is embedded within the fractures. In addition, quantification by standard addition method by spiking goethite suspension indicates that only around 20% of goethite minerals are available during Se(IV) adsorption.

Radiation dose to workers due to the inhalation of dust during granite fabrication.

PubMed

Zwack, L M; McCarthy, W B; Stewart, J H; McCarthy, J F; Allen, J G

2014-03-01

There has been very little research conducted to determine internal radiation doses resulting from worker exposure to ionising radiation in granite fabrication shops. To address this issue, we estimated the effective radiation dose of granite workers in US fabrication shops who were exposed to the maximum respirable dust and silica concentrations allowed under current US regulations, and also to concentrations reported in the literature. Radiation doses were calculated using standard methods developed by the International Commission on Radiological Protection. The calculated internal doses were very low, and below both US occupational standards (50 mSv yr(-1)) and limits applicable to the general public (1 mSv yr(-1)). Workers exposed to respirable granite dust concentrations at the US Occupational Safety and Health Administration (OSHA) respirable dust permissible exposure limit (PEL) of 5 mg m(-3) over a full year had an estimated radiation dose of 0.062 mSv yr(-1). Workers exposed to respirable granite dust concentrations at the OSHA silica PEL and at the American Conference of Governmental Industrial Hygienists Threshold Limit Value for a full year had expected radiation doses of 0.007 mSv yr(-1) and 0.002 mSv yr(-1), respectively. Using data from studies of respirable granite dust and silica concentrations measured in granite fabrication shops, we calculated median expected radiation doses that ranged from <0.001 to 0.101 mSv yr(-1).

The Ajo Mining District, Pima County, Arizona--Evidence for Middle Cenozoic Detachment Faulting, Plutonism, Volcanism, and Hydrothermal Alteration

USGS Publications Warehouse

Cox, Dennis P.; Force, Eric R.; Wilkinson, William H.; More, Syver W.; Rivera, John S.; Wooden, Joseph L.

2006-01-01

Introduction: The Ajo porphyry copper deposit and surrounding Upper Cretaceous rocks have been separated from their plutonic source and rotated by detachment faulting. Overlying middle Cenozoic sedimentary and volcanic rocks have been tilted and show evidence for two periods of rotation. Following these rotations, a granitic stock (23.7?0.2 Ma) intruded basement rocks west of the Ajo deposit. This stock was uplifted 2.5 km to expose deep-seated Na-Ca alteration.

Geochemical, microtextural and petrological studies of the Samba prospect in the Zambian Copperbelt basement: a metamorphosed Palaeoproterozoic porphyry Cu deposit.

NASA Astrophysics Data System (ADS)

Master, Sharad; Mirrander Ndhlovu, N.

2015-04-01

Ever since Wakefield (1978, IMM Trans., B87, 43-52) described a porphyry-type meta-morphosed Cu prospect, the ca 50 Mt, 0.5% Cu Samba deposit (12.717°S, 27.833°E), hosted by porphyry-associated quartz-sericite-biotite schists in northern Zambia, there has been controversy about its origin and significance. This is because it is situated in the basement to the world's largest stratabound sediment-hosted copper province, the Central African Copperbelt, which is hosted by rocks of the Neoproterozoic Katanga Supergroup. Mineralization in the pre-Katangan basement has long played a prominent role in ore genetic models, with some authors suggesting that basement Cu mineralization may have been recycled into the Katangan basin through erosion and redeposition, while others have suggested that the circulation of fluids through Cu-rich basement may have leached out the metals which are found concentrated in the Katangan orebodies. On the basis of ca 490-460 Ma Ar-Ar ages, Hitzman et al. (2012, Sillitoe Vol., SEG Spec. Publ., 16, 487-514) suggested that Samba represents late-stage impregnation of copper mineralization into the basement, and that it was one of the youngest copper deposits known in the Central African Copperbelt. If the Samba deposit really is that young, then it would have post-dated regional deformation and metamorphism (560-510 Ma), and it ought to be undeformed and unmetamorphosed. The Samba mineralization consists of chalcopyrite and bornite, occurring as disseminations, stringers and veinlets, found in a zone >1 km along strike, in steeply-dipping lenses up to 10m thick and >150m deep. Our new major and trace element XRF geochemical data (14 samples) show that the host rocks are mainly calc-alkaline metadacites. Cu is correlated with Ag (Cu/Ag ~10,000:1) with no Au or Mo. Our study focused on the microtextures and petrology of the Samba ores. We confirm that there is alteration of similar style to that accompanying classical porphyry Cu mineralization

Fracture controls on valley persistence: the Cairngorm Granite pluton, Scotland

NASA Astrophysics Data System (ADS)

Hall, A. M.; Gillespie, M. R.

2017-09-01

Valleys are remarkably persistent features in many different tectonic settings, but the reasons for this persistence are rarely explored. Here, we examine the structural controls on valleys in the Cairngorms Mountains, Scotland, part of the passive margin of the eastern North Atlantic. We consider valleys at three scales: straths, glens and headwater valleys. The structural controls on valleys in and around the Cairngorm Granite pluton were examined on satellite and aerial photographs and by field survey. Topographic lineaments, including valleys, show no consistent orientation with joint sets or with sheets of microgranite and pegmatitic granite. In this granite landscape, jointing is not a first-order control on valley development. Instead, glens and headwater valleys align closely to quartz veins and linear alteration zones (LAZs). LAZs are zones of weakness in the granite pluton in which late-stage hydrothermal alteration and hydro-fracturing have greatly reduced rock mass strength and increased permeability. LAZs, which can be kilometres long and >700 m deep, are the dominant controls on the orientation of valleys in the Cairngorms. LAZs formed in the roof zone of the granite intrusion. Although the Cairngorm pluton was unroofed soon after emplacement, the presence of Old Red Sandstone (ORS) outliers in the terrain to the north and east indicates that the lower relief of the sub-ORS basement surface has been lowered by <500 m. Hence, the valley patterns in and around the Cairngorms have persisted through >1 km of vertical erosion and for 400 Myr. This valley persistence is a combined product of regionally low rates of basement exhumation and of the existence of LAZs in the Cairngorm pluton and sub-parallel Caledonide fractures in the surrounding terrain with depths that exceed 1 km.

Getting granite dikes out of the source region

NASA Technical Reports Server (NTRS)

Rubin, Allan M.

1995-01-01

Whether a dike can propagate far from a magma reservoir depends upon the competition between the rate at which propagation widens the dike and the rate at which freezing constricts the aperture available for magma flow. Various formulations are developed for a viscous fluid at temperature T(sub m) intruding a growing crack in an elastic solid. The initial solid temperature equals T(sub m) at the source and decreases linearly with distance from the source. If T(sub m) is the unique freezing temperature of the fluid, dike growth is initially self-similar and an essentially exact solution is obtained; if T(sub m) is above the solidus temperature, the solution is approximate but is designed to overestimate the distance the dike may propagate. The ability of a dike to survive thermally depends primarily upon a single parameter that is a measure of the ratio of the dike frozen margin thickness to elastic thickness. Perhaps more intuitively, one may define a minimum distance from the essentially solid reservoir wall to the point at which the host rock temperature drops below the solidus, necessary for dikes to propagate far into subsolidus rock. It is concluded that for reasonable material properties and source conditions, most basalt dikes will have little difficulty leaving the source region, but most rhyolite dikes will be halted by freezing soon after the magma encounters rock at temperatures below the magma solidus. While these results can explain why granitic dikes are common near granitic plutons but rare elsewhere, the potentially large variation in magmatic systems makes it premature to rule out the possibility that most granites are transported through the crust in dikes. Nonetheless, these results highlight difficulties with such proposals and suggest that it may also be premature to rule out the possibility that most granite plutons ascend as more equidimensional bodies.

Subsurface drainage erodes forested granitic terrane

Treesearch

Philip Durgin

1984-01-01

Abstract - Solution and landsliding, the dominant erosion processes in undisturbed forested mountainous watersheds, are both influenced by subsurface drainage. Biological processes that generate organic acids accelerate loss of dissolved solids by promoting the dissolution of primary minerals in granitic rock. These organic acids can also disperse the secondary...

Formation of the Vysoká-Zlatno Cu-Au skarn-porphyry deposit, Slovakia

NASA Astrophysics Data System (ADS)

Koděra, Peter; Lexa, Jaroslav; Fallick, Anthony E.

2010-12-01

The central zone of the Miocene Štiavnica stratovolcano hosts several occurrences of Cu-Au skarn-porphyry mineralisation, related to granodiorite/quartz-diorite porphyry dyke clusters and stocks. Vysoká-Zlatno is the largest deposit (13.4 Mt at 0.52% Cu), with mineralised Mg-Ca exo- and endoskarns, developed at the prevolcanic basement level. The alteration pattern includes an internal K- and Na-Ca silicate zone, surrounded by phyllic and argillic zones, laterally grading into a propylitic zone. Fluid inclusions in quartz veinlets in the internal zone contain mostly saline brines with 31-70 wt.% NaCl eq. and temperatures of liquid-vapour homogenization (Th) of 186-575°C, indicating fluid heterogenisation. Garnet contains inclusions of variable salinity with 1-31 wt.% NaCl eq. and Th of 320-360°C. Quartz-chalcopyrite veinlets host mostly low-salinity fluid inclusions with 0-3 wt.% NaCl eq. and Th of 323-364°C. Data from sphalerite from the margin of the system indicate mixing with dilute and cooler fluids. The isotopic composition of fluids in equilibrium with K-alteration and most skarn minerals (both prograde and retrograde) indicates predominantly a magmatic origin (δ18Ofluid 2.5-12.3‰) with a minor meteoric component. Corresponding low δDfluid values are probably related to isotopic fractionation during exsolution of the fluid from crystallising magma in an open system. The data suggest the general pattern of a distant source of magmatic fluids that ascended above a zone of hydraulic fracturing below the temperature of ductile-brittle transition. The magma chamber at ˜5-6 km depth exsolved single-phase fluids, whose properties were controlled by changing PT conditions along their fluid paths. During early stages, ascending fluids display liquid-vapour immiscibility, followed by physical separation of both phases. Low-salinity liquid associated with ore veinlets probably represents a single-phase magmatic fluid/magmatic vapour which contracted into

Smolt Monitoring at the Head of Lower Granite Reservoir and Lower Granite Dam, 2005 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buettner, Edwin W.; Putnam, Scott A.

This project monitored the daily passage of Chinook salmon Oncorhynchus tshawytscha, steelhead trout O. mykiss, and sockeye salmon O. nerka smolts during the 2005 spring out-migration at migrant traps on the Snake River and Salmon River. In 2005 fish management agencies released significant numbers of hatchery Chinook salmon and steelhead trout above Lower Granite Dam that were not marked with a fin clip or coded-wire tag. Generally, the age-1 and older fish were distinguishable from wild fish by the occurrence of fin erosion. Age-0 Chinook salmon are more difficult to distinguish between wild and non-adclipped hatchery fish and therefore classifiedmore » as unknown rearing. The total annual hatchery spring/summer Chinook salmon catch at the Snake River trap was 0.34 times greater in 2005 than in 2004. The wild spring/summer Chinook catch was 0.34 times less than the previous year. Hatchery steelhead trout catch was 0.67 times less than in 2004. Wild steelhead trout catch was 0.72 times less than the previous year. The Snake River trap collected 1,152 age-0 Chinook salmon of unknown rearing. During 2005, the Snake River trap captured 219 hatchery and 44 wild/natural sockeye salmon and 110 coho salmon O. kisutch of unknown rearing. Differences in trap catch between years are due to fluctuations not only in smolt production, but also differences in trap efficiency and duration of trap operation associated with flow. Trap operations began on March 6 and were terminated on June 3. The trap was out of operation for a total of one day due to heavy debris. FPC requested that the trap be restarted on June 15 through June 22 to collect and PIT tag age-0 Chinook salmon. Hatchery Chinook salmon catch at the Salmon River trap was 1.06 times greater and wild Chinook salmon catch was 1.26 times greater than in 2004. The hatchery steelhead trout collection in 2005 was 1.41 times greater and wild steelhead trout collection was 1.27 times greater than the previous year. Trap

Smolt Monitoring at the Head of Lower Granite Reservoir and Lower Granite Dam, 2004 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buettner, Edwin W.; Putnam, Scott A.

This project monitored the daily passage of Chinook salmon Oncorhynchus tshawytscha, steelhead trout O. mykiss, and sockeye salmon O. nerka smolts during the 2004 spring out-migration at migrant traps on the Snake River and Salmon River. In 2004 fish management agencies released significant numbers of hatchery Chinook salmon and steelhead trout above Lower Granite Dam that were not marked with a fin clip or coded-wire tag. Generally, these fish were distinguishable from wild fish by the occurrence of fin erosion. Total annual hatchery Chinook salmon catch at the Snake River trap was 1.1 times greater in 2004 than in 2003.more » The wild Chinook catch was 1.1 times greater than the previous year. Hatchery steelhead trout catch was 1.2 times greater than in 2003. Wild steelhead trout catch was 1.6 times greater than the previous year. The Snake River trap collected 978 age-0 Chinook salmon of unknown rearing. During 2004, the Snake River trap captured 23 hatchery and 18 wild/natural sockeye salmon and 60 coho salmon O. kisutch of unknown rearing. Differences in trap catch between years are due to fluctuations not only in smolt production, but also differences in trap efficiency and duration of trap operation associated with flow. Trap operations began on March 7 and were terminated on June 4. The trap was out of operation for a total of zero days due to mechanical failure or debris. Hatchery Chinook salmon catch at the Salmon River trap was 10.8% less and wild Chinook salmon catch was 19.0% less than in 2003. The hatchery steelhead trout collection in 2004 was 20.0% less and wild steelhead trout collection was 22.3% less than the previous year. Trap operations began on March 7 and were terminated on May 28 due to high flows. There were two days when the trap was taken out of service because wild Chinook catch was very low, hatchery Chinook catch was very high, and the weekly quota of PIT tagged hatchery Chinook had been met. Travel time (d) and migration rate (km

Extra-terrestrial igneous granites and related rocks: A review of their occurrence and petrogenesis

NASA Astrophysics Data System (ADS)

Bonin, Bernard

2012-11-01

The telluric planets and the asteroid belt display the same internal structure with a metallic inner core and a silicate outer shell. Experimental data and petrological evidence in silicate systems show that granite can be produced by extreme igneous differentiation through various types of igneous processes. On Moon, 4.4-3.9 Ga granite clasts display dry mineral assemblages. They correspond to at least 8 discrete intrusive events. Large K/Ca enrichment and low REE abundances in granite relative to KREEP are consistent with silicate liquid immiscibility, a process observed in melt inclusions within olivine of lunar basalts and in lunar meteorites. Steep-sided domes identified by remote sensing can represent intrusive or extrusive felsic formations. On Mars, black-and-white rhythmic layers observed on the Tharsis rise along the flanks of the peripheral scarps of the Tharsis Montes giant volcanoes suggest the possible eruption of felsic pyroclastites. Though no true granites were found so far in the Martian SNC meteorites, felsic glasses and mesostases were identified and a component close to terrestrial continental (granitic) crust is inferred from trace element and isotope systematics. Venus has suffered extensive volcanic resurfacing, whereas folded and faulted areas resemble terrestrial continents. Near large shield volcanoes, with dominant basaltic compositions, steep-sided domes have been interpreted as non-degassed silicic extrusions. The hypothesis of a granitic component is "tantalising". Extra-terrestrial granite is frequently found as clasts and mesostases in asteroidal meteorites. Porphyritic textures, with alkali feldspar crystals up to several centimetres in size, were observed in silicate enclaves within iron meteorites. In the chondrite clan, polymict breccias can contain granitic clasts, whose provenance is debated. One clast from the Adzhi-Bogdo meteorite yields a 4.53 ± 0.03 Ga Pb-Pb age, making it the oldest known granite in the solar system. The

Formation of A-type granites in the Lower Yangtze River Belt: A perspective from apatite geochemistry

NASA Astrophysics Data System (ADS)

Jiang, Xiao-Yan; Li, He; Ding, Xing; Wu, Kai; Guo, Jia; Liu, Ji-Qiang; Sun, Wei-Dong

2018-04-01

Apatite is ubiquitous in A-type granites, and can be used to elucidate the volatile contents of the silicate melt, which reflect its source characteristics. A-type granites have been recognized as a distinct group of granites. A1- and A2-type subgroups are produced under different extensional settings. However, the details of the mechanisms behind the distinctive geochemical characteristics of A1- and A2-type granites remain obscure. Belts of Cretaceous A1- and A2-type granites occur along the Lower Yangtze River Belt in eastern China. Here we investigated the major and trace element compositions of apatites from contemporary A1- and A2-type granites at different localities along the Lower Yangtze River Belt, in order to decipher their discrepant source processes. Apatites from A1- and A2-type granites show similar major and trace elements, but differ in their F and Cl concentrations. Apatites from A1-type granites in the eastern part of the Lower Yangtze River Belt have much lower F and higher Cl concentrations compared to A2-type granites in the western part. Moreover, from the east to the west, the F concentrations of apatites from A1-type granites increase, while the Cl concentrations decline. In a subducted plate, F is retained by amphibole, chlorite, serpentine and mica minerals through the amphibolite stage, and finally by phengite and lawsonite during the eclogite stage, whereas, Cl is controlled by amphibole, chlorite and serpentine. The high and varied Cl concentrations in A1 subgroup apatites, therefore, may be attributed to the breakdown of amphibole, chlorite and/or serpentine decomposition during partial melting of subducted oceanic crust releasing a large amount of Cl at shallower depth. In contrast, F is transported to deeper depths in the subducted oceanic crust, and released through breakdown of phengite and lawsonite, making an important contribution to the formation of A2-type granites. Apatites from A1- and A2-type granite samples show regular

Global mineral resource assessment: porphyry copper assessment of Mexico: Chapter A in Global mineral resource assessment

USGS Publications Warehouse

Hammarstrom, Jane M.; Robinson, Gilpin R.; Ludington, Steve; Gray, Floyd; Drenth, Benjamin J.; Cendejas-Cruz, Francisco; Espinosa, Enrique; Pérez-Segura, Efrén; Valencia-Moreno, Martín; Rodríguez-Castañeda, José Luis; Vásquez-Mendoza, Rigobert; Zürcher, Lukas

2010-01-01

This report includes a brief overview of porphyry copper deposits in Mexico, a description of the assessment process used, a summary of results, and appendixes. Appendixes A through K contain summary information for each tract, as follows: location, the geologic feature assessed, the rationale for tract delineation, tables and descriptions of known deposits and significant prospects, exploration history, model selection, rationale for the estimates, assessment results, and references. The accompanying digital map files (shapefiles) provide permissive tract outlines, assessment results, and data for deposits and prospects in a GIS format (appendix L).

Igneous petrogenesis and tectonic setting of granitic rocks from the eastern Blue Ridge, Alabama Appalachians

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drummond, M.S.; Allison, D.T.; Tull, J.F.

1994-03-01

A span of 150 my of orogenic activity is recorded within the granitic rocks of the eastern Blue Ridge of Alabama (EBR). Four discrete episodes of plutonism can be differentiated, each event exhibiting distinct field relations and geochemical signatures. (1) Penobscotian stage: this initial stage of plutonic activity is represented by the Elkahatchee Quartz Diorite (EQD), a premetamorphic (495 Ma) batholith and the largest intrusive complex (880 km[sup 2]) exposed in the Blue Ridge. Calc-alkaline I-type tonalite-granodiorite are the principal lithologies, with subordinate cumulate hbl-bt diorite, metadacite, granite and trondhjemite. The parental tonalitic magmas are interpreted to have been derivedmore » from a subducted MORB source under eclogite to get amphibolite conditions. (2) Taconic stage: the Kowaliga augen gneiss (KAG) and the Zana granite gneiss (ZG) are 460 Ma granitic bodies that reside in the SE extremity and structurally highest portion of the EBR. Both of these bodies are pre-metamorphic with strongly elongate sill- and pod-like shapes concordant with S[sub 1] foliation. Granite and granodiorite comprise the bulk of the KAG. (3) Acadian stage: Rockford Granite (RG), Bluff springs Granite (BSG, 366 Ma), and Almond Trondhjemite represent a suite of pre- to syn-metamorphic granitic intrusions. (4) late-Acadian stage: The Blakes Ferry pluton (BFP) is a post-kinematic pluton displaying spectacular by schlieren igneous flow structures, but no metamorphic fabric. The pluton's age can be bracketed between a 366 Ma age on the BSG and a 324 Ma K-Ar muscovite age on the BFP. BFP's petrogenesis has involved partial melting a MORB source followed by assimilation of metasedimentary host rock.« less

Adsorption, desorption and fractionation of As(V) on untreated and mussel shell-treated granitic material

NASA Astrophysics Data System (ADS)

Seco-Reigosa, N.; Cutillas-Barreiro, L.; Nóvoa-Muñoz, J. C.; Arias-Estévez, M.; Álvarez-Rodríguez, E.; Fernández-Sanjurjo, M. J.; Núñez-Delgado, A.

2014-12-01

As(V) adsorption and desorption were studied on granitic material, coarse and fine mussel shell, and granitic material amended with 12 and 24 t ha-1 fine shell, investigating the effect of different As(V) concentrations and different pH, as well as the fractions where the adsorbed As(V) was retained. As(V) adsorption was higher on fine than on coarse shell. Mussel shell amendment increased As(V) adsorption on granitic material. Adsorption data corresponding to the un-amended and shell-amended granitic material were satisfactory fitted to the Langmuir and Freundlich models. Desorption was always < 19% when the highest As(V) concentration (100 mg L-1) was added. Regarding the effect of pH, the granitic material showed its highest adsorption (66%) at pH < 6, and it was lower as pH increased. Fine shell presented notable adsorption in the whole pH range between 6 and 12, with a maximum of 83%. The shell-amended granitic material showed high As(V) adsorption, with a maximum (99%) at pH near 8, but decreasing as pH increased. Desorption varying pH was always < 26%. In the granitic material, desorption increased progressively when pH increased from 4 to 6, contrary to what happened to mussel shell. Regarding the fractionation of the adsorbed As(V), most of it was in the soluble fraction (weakly bound). Globally, the granitic material did not show high As(V) retention capacity, which implies risks of water pollution and transfer to the food chain; however, the mussel shell amendment increased As(V) retention, making this practice recommendable.

Geothermal potential of Caledonian granites in Ireland and the Isle of Man: Implications from hydrothermal alteration

NASA Astrophysics Data System (ADS)

Fritschle, Tobias; Daly, J. Stephen; Whitehouse, Martin J.; Buhre, Stephan; McConnell, Brian; The Iretherm Team

2015-04-01

Ordovician to Devonian (Caledonian) granites are common in the Iapetus Suture Zone (ISZ) in Ireland and Britain. Some of these, e.g., the buried Kentstown and Glenamaddy granites, are situated beneath Upper Palaeozoic sedimentary basins, and hence are potential geothermal targets. Numerous granites of similar age and related origin (Fritschle et al., 2014) are exposed astride the ISZ. They are considered to be analogous to the buried ones, and their geochemical characteristics are used as a proxy for the buried granites as samples from deep drilling are naturally limited. The whole-rock geochemistry of nine granite intrusions (71 samples, including both hydrothermally altered and unaltered samples) varies significantly, but with no obvious geographical control. The granites are S- and I-Types with ASI (Aluminium Saturation Index) between 0.7 - 1.4. Average heat production rates range from 1.4 μW/m³ for the Leinster Granite to 4.9 μW/m³ for the Drogheda Granite (Fritschle et al., 2015). The heat-producing elements uranium (U), thorium (Th) and potassium (K) and calculated heat production rates generally correlate positively with niobium and rubidium concentrations. However, S-Type compared to I-Type granites show elevated abundances in rubidium (>130 ppm) and usually have a lower Th/U ratio. Altered samples tend to have a higher Th/U ratio compared to unaltered ones. Within individual plutons trends of decreasing heat production rates with increasing Th/U ratios were observed. This trend is attributed to the hydrothermal redistribution of the mobile heat-producing element uranium. This is also implied by uranium-enrichment in hydrothermally generated Ca and Si-veinlets. Metasomatic processes such as hydrothermal alteration appear capable of significantly redistributing mobile elements such as uranium. Hence, these processes may act as a major mechanism controlling the granite's heat production budget, often shaping a pluton's geothermal exploitation potential

Petrography and physicomechanical properties of rocks from the Ambela granitic complex, NW Pakistan.

PubMed

Arif, Mohammad; Bukhari, S Wajid Hanif; Muhammad, Noor; Sajid, Muhammad

2013-01-01

Petrography and physicomechanical properties of alkali granites, alkali quartz syenite, and nepheline syenite from Ambela, NW Pakistan, have been investigated. Whereas the alkali quartz syenite and most of the alkali granites are megaporphyritic, the nepheline syenite and some of the alkali granites are microporphyritic. Their phenocryst shape and size and abundance of groundmass are also different. The values of unconfined compressive strength (UCS) are the lowest and highest for megaporphyritic alkali granite and alkali quartz syenite, respectively. However, all the four rock types are moderately strong. Correspondingly, their specific gravity and water absorption values are within the permissible range for use as construction material. The UCS for the alkali quartz syenite is the highest, most probably because (i) it has roughly equal amounts of phenocryst and groundmass, (ii) it displays maximum size contrast between phenocryst and groundmass, (iii) its phenocrysts are highly irregular, and (iv) it contains substantial amounts of quartz.

Intrusion of basaltic magma into a crystallizing granitic magma chamber: The Cordillera del Paine pluton in southern Chile

NASA Astrophysics Data System (ADS)

Michael, Peter J.

1991-10-01

The Cordillera del Paine pluton in the southernmost Andes of Chile represents a deeply dissected magma chamber where mafic magma intruded into crystallizing granitic magma. Throughout much of the 10x15 km pluton, there is a sharp and continuous boundary at a remarkably constant elevation of 1,100 m that separates granitic rocks (Cordillera del Paine or CP granite: 69 77% SiO2) which make up the upper levels of the pluton from mafic and comingled rocks (Paine Mafic Complex or PMC: 45 60% SiO2) which dominate the lower exposures of the pluton. Chilled, crenulate, disrupted contacts of mafic rock against granite demonstrate that partly crystallized granite was intruded by mafic magma which solidified prior to complete crystallization of the granitic magma. The boundary at 1,100 m was a large and stable density contrast between the denser, hotter mafic magma and cooler granitic magma. The granitic magma was more solidified near the margins of the chamber when mafic intrusion occurred, and the PMC is less disrupted by granites there. Near the pluton margins, the PMC grades upward irregularly from cumulate gabbros to monzodiorites. Mafic magma differentiated largely by fractional crystallization as indicated by the presence of cumulate rocks and by the low levels of compatible elements in most PMC rocks. The compositional gap between the PMC and CP granite indicates that mixing (blending) of granitic magma into the mafic magma was less important, although it is apparent from mineral assemblages in mafic rocks. Granitic magma may have incorporated small amounts of mafic liquid that had evolved to >60% SiO2 by crystallization. Mixing was inhibited by the extent of crystallization of the granite, and by the thermal contrast and the stable density contrast between the magmas. PMC gabbros display disequilibrium mineral assemblages including early formed zoned olivine (with orthopyroxene coronas), clinopyroxene, calcic plagioclase and paragasite and later-formed amphibole

Generation of syntectonic calc-alkaline, magnesian granites through remelting of pre-tectonic igneous sources - U-Pb zircon ages and Sr, Nd and Pb isotope data from the Donkerhoek granite (southern Damara orogen, Namibia)

NASA Astrophysics Data System (ADS)

Schwark, L.; Jung, S.; Hauff, F.; Garbe-Schönberg, D.; Berndt, J.

2018-06-01

The 541 ± 4 Ma-old magnesian, weakly peraluminous, calc-alkalic Donkerhoek Onanis granite is part of the ca. 6000 km2 large Donkerhoek batholith in the Southern Zone of the Damara orogen of Namibia. Linear major and trace element variations and decreasing MgO, FeO, Al2O3, CaO, K2O, Na2O, Ba and Sr concentrations with increasing SiO2 indicate that this part of the batholith represent a coherent mass and underwent fractional crystallization processes. The Donkerhoek Onanis granites are isotopically evolved (initial εNd: -4.7 to -12.3, initial 87Sr/86Sr: 0.7099-0.7157) with moderately radiogenic Pb isotope ratios (206Pb/204Pb: 17.26-18.22; 207Pb/204Pb: 15.59-15.67; 208Pb/204Pb: 37.60-38.06). Beside heterogeneities imparted by the sources, an evaluation of LREE fractionation and Nd isotope data suggests that AFC processes also modified some samples. Based on the chemical and isotope data, the Donkerhoek Onanis granites cannot be derived by partial melting of Al- and Fe-rich metasedimentary rocks of the Kuiseb formation in which they intruded. Instead, melting of meta-igneous crustal sources with Proterozoic crustal residence ages is more likely. Three igneous to meta-igneous rock suites from the area (Matchless amphibolites, Proterozoic mafic to felsic gneisses from the southern Kalahari craton basement, syn-tectonic Salem granodiorites to granites) are potential sources. An evaluation of chemical and isotope data suggests that remelting of early syn-orogenic Salem-type granites is the most likely process which would also explain the existence of ca. 563 ± 4 Ma-old zircon in the Donkerhoek Onanis granites. Comparison of the Donkerhoek Onanis granites with experimentally derived melt compositions from an intermediate igneous parent indicates temperatures between 800 and 850 °C. It is suggested that the Pan-African igneous activity in this part of the Damara Belt was a moderate-temperature intra-crustal event. Although there are some compositional similarities with

Petrochemical evolution of the White Mfolozi Granite pluton: Evidence for a late Palaeoarchaean A-type granite from the SE Kaapvaal Craton, South Africa

NASA Astrophysics Data System (ADS)

Misra, Saumitra; Reinhardt, Jürgen; Wilson, Allan H.

2017-08-01

One of the major limitations in understanding the geochemical evolution of the Kaapvaal Craton, South Africa, is the scarcity of whole rock trace element data of the granitoid and other rocks compared to the vastness of this cratonic block. Here we present new XRF major oxide and ICP-MS trace element analyses of the White Mfolozi Granitoid (WMG) pluton, SE Kaapvaal Craton, which suggest that the 3.25 Ga (U-Pb zircon age) old WMG pluton is a peraluminous A-type granite and could be equivalent to the intrusive potassic granite phase of the Anhalt Granitoid suite, occurring to the North of the WMG pluton. The pluton was generated by batch partial melting of a pre-existing TTG source in two major phases under relatively anhydrous conditions, and the heat of partial melting could have been provided by a voluminous mantle-derived mafic magma, which intruded into mid-crustal levels (c. 17 km), perhaps during a period of crustal extension. The estimated pressure and temperature of generation of the WMG parent magma with average molar [or/(or + ab)] 0.48 could be 500 MPa and close to 1000 °C, respectively, when compared with the results of experimental petrology. Interstitial occurrence of relatively iron-rich biotite [Mg/(Mg + Fe) 0.41-0.45] suggests that the final temperature of crystallization of the pluton was close to 800 °C. An important magmatic event following the main phase of partial melting was limited mixing between the intrusive mafic magma and co-existing newly generated granitic melt. This magma mixing resulted in distinct variations in SiO2 and a low initial Sr isotopic ratio (0.7013) of the WMG pluton. Although both the models of partial melting of quartzo-feldspathic sources and fractional crystallization of basaltic magmas with or without crustal assimilation have been proposed for the origin of A-type granites, the model of magmatic evolution of the WMG pluton presented here can also be an alternative model for the generation of A-type granites. In

Ultrasonic characterization of granites obtained from industrial quarries of Extremadura (Spain).

PubMed

del Río, L M; López, F; Esteban, F J; Tejado, J J; Mota, M; González, I; San Emeterio, J L; Ramos, A

2006-12-22

The industry of ornamental rocks, such as granites, represents one of the most important industrial activities in the region of Extremadura, SW Spain. A detailed knowledge of the intrinsic properties of this natural stone and its environmental evolution is a required goal in order to fully characterize its quality. In this work, two independent NDT acoustic techniques have been used to measure the acoustic velocity of longitudinal waves in different prismatic granitic-samples of industrial quarries. A low-frequency transceiver set-up, based on a high-voltage BPV Steinkamp instrument and two 50 kHz probes, has been used to measure pulse travel times by ultrasonic through-transmission testing. In complementary fashion, an Erudite MK3 test equipment with an electromagnetic vibrator and two piezoelectric sensors has also been employed to measure ultrasonic velocity by means of a resonance-based method, using the same types of granite varieties. In addition, a comprehensive set of physical/mechanical properties have also been analyzed, according to Spanish regulations in force, by means of alternative methods including destructive techniques such as strength, porosity, absorption, etc. A large number of samples, representing the most important varieties of granites from quarries of Extremadura, have been analyzed using the above-mentioned procedures. Some results obtained by destructive techniques have been correlated with those found using ultrasonic techniques. Our experimental setting allowed a complementary characterization of granite samples and a thorough validation of the different techniques employed, thus providing the industry of ornamental rocks with a non-destructive tool that will facilitate a more detailed insight on the properties of the rocks under study.

Geochemistry of Cretaceous granites from Mianning in the Panxi region, Sichuan Province, southwestern China: Implications for their generation

NASA Astrophysics Data System (ADS)

Xu, Cheng; Huang, Zhilong; Qi, Liang; Fu, Pingqing; Liu, Congqiang; Li, Endong; Guan, Tao

2007-03-01

The Cretaceous granites of Mianning, located in the northern Panxi region, were emplaced after collision of the Tibetan Plateau and Yangtze Block. These granites have very high K 2O + Na 2O, Ga, Zr, Nb, Y, REE (except Eu), and very low MgO, CaO, P 2O 5, and Sr contents relative to M-, I- or S-type granites. Based on the chemical discrimination criteria of Whalen et al . [Whalen, J.B., Currie, K.L., Chappell, B.W., 1987. A-type granites: geochemical characteristics, distribution and petrogenesis. Contributions to Mineralogy and Petrology 95, 407-419], most of them are A-type granites. Moreover, the granites plot in the range of post-collision granites and belong to the A2 type. Elevated initial Sr isotopic ratios (>0.72) suggest their derivation dominantly from a crustal source. These features are consistent with granite formation in a post-orogenic setting, such as after subduction or collision between of the Tibetan Plateau and Yangtze Block. In addition, the granites are characterized by low abundances of Ba, Sr, P, Ti, and Eu, positive correlation between Ba and Eu anomalies, and negative correlation between Rb and K/Rb. Plots of Rb vs. Sr suggest that fractional crystallization affected the final compositions of these granites after melting from a dominantly crustal source. From the late Proterozoic to late Mesozoic, the crustal composition, compared to that of the mantle, appears to have increased in the Panxi region. While the mantle component played an important part in the generation of Cretaceous granites in southeastern China, its influence was relatively minor in the Panxi region. Thus, there was a significant difference in mantle evolution between southeastern China and the Panxi region, which led to different metallogenic processes.

Petrography and Physicomechanical Properties of Rocks from the Ambela Granitic Complex, NW Pakistan

PubMed Central

Arif, Mohammad; Bukhari, S. Wajid Hanif; Muhammad, Noor; Sajid, Muhammad

2013-01-01

Petrography and physicomechanical properties of alkali granites, alkali quartz syenite, and nepheline syenite from Ambela, NW Pakistan, have been investigated. Whereas the alkali quartz syenite and most of the alkali granites are megaporphyritic, the nepheline syenite and some of the alkali granites are microporphyritic. Their phenocryst shape and size and abundance of groundmass are also different. The values of unconfined compressive strength (UCS) are the lowest and highest for megaporphyritic alkali granite and alkali quartz syenite, respectively. However, all the four rock types are moderately strong. Correspondingly, their specific gravity and water absorption values are within the permissible range for use as construction material. The UCS for the alkali quartz syenite is the highest, most probably because (i) it has roughly equal amounts of phenocryst and groundmass, (ii) it displays maximum size contrast between phenocryst and groundmass, (iii) its phenocrysts are highly irregular, and (iv) it contains substantial amounts of quartz. PMID:23861654

GEOLOGY, SULFUR ISOTOPES AND THE ORIGIN OF THE HEATH STEELE ORE DEPOSITS, NEWCASTLE, N.B., CANADA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dechow, E.

The Heath Steele mine is located 35 miles northwest of Newcastle, New Brunswick, Canada. Middle Ordovician Tetagouche Group rocks, consisting of siliceous and basic volcanic rocks, and fine-grained quartz sericite schists and porphyry, have been folded into a steeply plunging recumbent anticline. The ore deposits of zinc, lead, and copper are associated with minor folding and/or sheared dilatent zones at or near the contact between porphyry and fine-grained senicitic schist. Mineralogically the sulfide bodies consist of early, euhedral arsenopyrite, magnetite, and pyrite, followed by interstitial pyrrhotite, sphalerite, chalcopyrite and galena. Minor minerals are ternantite-tetrahedrite, bismuthinite, marcasite, hematite, and some graphite.more » Supergene minerals consist of chalcocite, covellite, and marcasite with a little native silver. Little hypogene replacement has taken place between the minerals, which show a "porphyritic" texture. Sulfur isotope ratios were determined for over 150 sulfide and sulfate specimens from five of the seven ore bodies, and from granite, acid and basic volcanics, porphyry, and sediments. The results indicate that there is no detectable fractionation either during hypogene mineralization or supergene enrichment. The spread (21.82 to 22.02) covered by the ratios is narrow, and suggestive of a well homogenized source of mineral solutions. The enrichment of S/sup 34/ in the ore sulfides and the presence of graphite, evident from mineralographic studies and mass spectrometric analysis, suggests reduction of original sulfates (known to be enriched in S/sup 34/) by organic carbon at temperatures in excess of 500 deg C. A calculation based on the isotopic exchange reaction between sulfide and sulfate under equilibrium conditions and the spread of the ratios indicates a temperature of 700 to 800 deg C for the source. Finally the ratios determined for sulfides in a gneissic granite close to Heath Steele have the same ratio as the ore

Zircon U-Pb geochronology and geochemistry of granites in the Zhuguangshan complex, South China: Implications for uranium mineralization

NASA Astrophysics Data System (ADS)

Zhang, Long; Chen, Zhenyu; Li, Xiaofeng; Li, Shengrong; Santosh, M.; Huang, Guolong

2018-05-01

The Zhuguangshan complex, composed of Caledonian, Indosinian, and Yanshanian granites, and Cretaceous mafic dykes, is one of the most important granite-hosted uranium producers in South China. Here we present LA-ICP-MS zircon U-Pb and hornblende 40Ar/39Ar geochronology and whole-rock and biotite geochemistry for the granites in this complex to evaluate the magmatism and its constraints on uranium mineralization. Samples collected from the Fuxi, Youdong, Longhuashan, Chikeng, Qiling, and Sanjiangkou intrusions yield zircon weighted 206Pb/238U ages of 426.7 ± 5.4 Ma, 226.4 ± 3.5 Ma, 225.0 ± 2.7 Ma, 152.2 ± 3.0 Ma, 153.9 ± 2.1 Ma, and 155.2 ± 2.1 Ma, respectively. A new Ar-Ar dating of the hornblende of the diabase from the Changjiang uranium ore field yields a plateau age of 145.1 ± 1.5 Ma. These results coupled with published geochronological data indicate that six major magmatic events occurred in the study area at 420-435 Ma, 225-240 Ma, 150-165 Ma, 140 Ma, 105 Ma, and 90 Ma. Both U-bearing and barren granites occur in this complex, and they display differences in whole-rock and biotite geochemistry. The barren granites show higher Al2O3, CaO, TFMM, Rb, Zr, Ba, SI, Mg#, (La/Yb)N, and Eu/Eu*, but lower SiO2, ALK, Rb, DI, Rb/Sr, and TiO2/MgO than those of the U-bearing granites. Biotites in the U-bearing granites are close to the Fe-rich siderophyllite-annite end member with Fe/(Fe + Mg) ratios higher than 0.66, whereas those in the barren granites are relatively close to the Mg-rich eastonite-phlogopite end member with Fe/(Fe + Mg) ratios <0.66. The U-bearing granites were mainly derived from the partial melting of pelitic sedimentary source, whereas the psammitic source generated the barren granites. In addition, the barren granites show higher TFMM, Ba, and Eu/Eu* but lower SiO2, Rb/Sr and Al2O3/TiO2 ratios with higher zircon saturation temperatures relative to the U-bearing granites. These results indicate that the geochemical compositions of the U

Jurassic high heat production granites associated with the Weddell Sea rift system, Antarctica

NASA Astrophysics Data System (ADS)

Leat, Philip T.; Jordan, Tom A.; Flowerdew, Michael J.; Riley, Teal R.; Ferraccioli, Fausto; Whitehouse, Martin J.

2018-01-01

The distribution of heat flow in Antarctic continental crust is critical to understanding continental tectonics, ice sheet growth and subglacial hydrology. We identify a group of High Heat Production granites, intruded into upper crustal Palaeozoic metasedimentary sequences, which may contribute to locally high heat flow beneath the West Antarctic Ice Sheet. Four of the granite plutons are exposed above ice sheet level at Pagano Nunatak, Pirrit Hills, Nash Hills and Whitmore Mountains. A new Usbnd Pb zircon age from Pirrit Hills of 178.0 ± 3.5 Ma confirms earlier Rbsbnd Sr and Usbnd Pb dating and that the granites were emplaced approximately coincident with the first stage of Gondwana break-up and the developing Weddell rift, and 5 m.y. after eruption of the Karoo-Ferrar large igneous province. Aerogeophysical data indicate that the plutons are distributed unevenly over 40,000 km2 with one intruded into the transtensional Pagano Shear Zone, while the others were emplaced within the more stable Ellsworth-Whitmore mountains continental block. The granites are weakly peraluminous A-types and have Th and U abundances up to 60.7 and 28.6 ppm respectively. Measured heat production of the granite samples is 2.96-9.06 μW/m3 (mean 5.35 W/m3), significantly higher than average upper continental crust and contemporaneous silicic rocks in the Antarctic Peninsula. Heat flow associated with the granite intrusions is predicted to be in the range 70-95 mW/m2 depending on the thickness of the high heat production granite layer and the regional heat flow value. Analysis of detrital zircon compositions and ages indicates that the high Th and U abundances are related to enrichment of the lower-mid crust that dates back to 200-299 Ma at the time of the formation of the Gondwanide fold belt and its post-orogenic collapse and extension.

Laser versus scalpel cleaning of crustose lichens on granite

NASA Astrophysics Data System (ADS)

Rivas, T.; Pozo-Antonio, J. S.; López de Silanes, M. E.; Ramil, A.; López, A. J.

2018-05-01

This paper addresses the evaluation of the cleaning of crustose lichens developing on granite. The evaluation was performed considering the effectiveness of the cleanings and harmfulness exerted on the granite. The laser cleaning of lichen was compared with the most conventional procedure, scalpel. The combination of both procedures was also tested. The study, which was carried out with two different species of crustose lichen, was also focused on the influence of the intrinsic characteristics of the lichen on the effectiveness. The cleanings were evaluated by optic and electronic microscopies, FTIR and colour spectrophotometry. A previous characterization of the lichen and its interaction with the granite using those analytical techniques were also performed. The laser cleaning effectiveness depends on the coverage and the colour of the lichen; also, the prior mechanical weakening of the lichen by scalpel seemed to improve the laser cleaning. The darkest lichen was satisfactorily removed by laser and with the combined cleaning. Conversely, the lightest lichen was more difficult to extract with laser than the darkest lichen, being necessary to apply both methods sequentially. Despite laser and the combination of methods cleaned satisfactorily the surface, they were unable to eliminate the thalli into fissures.

Lower Granite Dam Smolt Monitoring Program, 2000 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrill, Charles; Ross, Doug; Mensik, Fred

2000-01-01

The 2000 fish collection season at Lower Granite was characterized by lower than average spring flows and spill, low levels of debris, cool water temperatures, increased unclipped yearling and subyearling chinook smolts, and 8,300,546 smolts collected and transported compared to 5,882,872 in 1999. With the continued release of unclipped supplementation chinook and steelhead above Lower Granite Dam, we can no longer accurately distinguish wild chinook, steelhead, and sockeye/kokanee in the sample. Although some table titles in this report still show ''wild'' column headings, the numbers in these columns for 1999 and 2000 include wild and unclipped hatchery origin smolts. Themore » increases over previous years reflect the increased supplementation. A total of 8,300,546 juvenile salmonids were collected at Lower Granite Dam. Of these, 187,862 fish were bypassed back to the river and 7,950,648 were transported to release sites below Bonneville Dam, 7,778,853 by barge and 171,795 by truck. A total of 151,344 salmonids were examined in daily samples. Nine research projects conducted by four agencies impacted a total of 1,361,006 smolts (16.4% of the total collection).« less

The Oldest Granites of Russia: Paleoarchean (3343 Ma) Subalkali Granites of the Okhotsk Massif

NASA Astrophysics Data System (ADS)

Kuzmin, V. K.; Bogomolov, E. S.; Glebovitskii, V. A.; Rodionov, N. V.

2018-02-01

The Paleoarchean age (3.34 Ga) of subalkali granite magmatism first established for the Kukhtui uplift of the Okhotsk Massif suggests a formation time of the mature continental K-rich crust in this region as early as the Paleoarchean. According to the geological structural, mineralogical-geochemical, geochronological, and isotopic-geochemical data, the Kukhtui uplift can be considered as the most ancient Paleoarchean province in Russia: the ancient consolidation core of the sialic protocrust of the Okhotsk-Omolon Craton.

Conventional U-Pb dating versus SHRIMP of the Santa Barbara Granite Massif, Rondonia, Brazil

USGS Publications Warehouse

Sparrenberger, I.; Bettencourt, Jorge S.; Tosdal, R.M.; Wooden, J.L.

2002-01-01

The Santa Ba??rbara Granite Massif is part of the Younger Granites of Rondo??nia (998 - 974 Ma) and is included in the Rondo??nia Tin Province (SW Amazonian Craton). It comprises three highly fractionated metaluminous to peraluminous within-plate A-type granite units emplaced in older medium-grade metamorphic rocks. Sn-mineralization is closely associated with the late-stage unit. U-Pb monazite conventional dating of the early-stage Serra do Cicero facies and late-stage Serra Azul facies yielded ages of 993 ?? 5 Ma and 989 ?? 13 Ma, respectively. Conventional multigrain U-Pb isotope analyses of zircon demonstrate isotopic disturbance (discordance) and the preservation of inherited older zircons of several different ages and thus yield little about the ages of Sn-granite magmatism. SHRIMP U-Pb ages for the Santa Ba??rbara facies association yielded a 207Pb/206Pb weighted-mean age of 978 ?? 13 Ma. The textural complexity of the zircon crystals of the Santa Ba??rbara facies association, the variable concentrations of U, Th and Pb, as well as the mixed inheritance of zircon populations are major obstacles to using conventional multigrain U-Pb isotopic analyses. Sm-Nd model ages and ??Nd (T) values reveal anomalous isotopic data, attesting to the complex isotopic behaviour within these highly fractionated granites. Thus, SHRIMP U-Pb zircon and conventional U-Pb monazite dating methods are the most appropriate to constrain the crystallization age of the Sn-bearing granite systems in the Rondo??nia Tin Province.

Identification and Description of Geophysical Techniques.

DTIC Science & Technology

1980-11-01

electrodes are used for voltage measurements with the potentiometer. Current elec- trodes may be stainless-steel or copper rods, buried copper screens, drill...steel in a borehole, or buried metal culverts. Potential elec- trodes may be stainless steel rods or porous containers filled with copper sulfate...Granite 28-2,700 Diorite 47 Gabbro 68-2,370 Porphyry 47 Diabase 78-1,050 Basalt 680 Olivine-Diabase 2,000 1. Peridotite 12,500 I (1)Adapted from C. A

FROGS (Friends of Granites) report

NASA Astrophysics Data System (ADS)

Miller, Calvin

This VGP News, which is devoted to petrology, is a good one for noting the existence of FROGS. FROGS is, as the name suggests, an informal organization of people whose research relates in one way or another to granitic rocks. Its purpose has been to promote communication among geoscientists with different perspectives and concerns about felsic plutonism. Initially, a major focus was experimental petrology and integration of field-oriented and lab-oriented viewpoints; now that there is the opportunity to communicate with the Eos readership, an obvious additional goal will be to bring together volcanic and plutonic views of felsic magmatism.FROGS first gathered in late 1982 under the guidance of E-an Zen and Pete Toulmin (both at U.S. Geological Survey (USGS), Reston, Va.), who saw a need for greater interaction among those interested in granites and for renewed, focused experimental investigations. They produced two newsletters (which were sent out by direct mail) and organized an informal meeting at the Geological Society of America meeting at Indianapolis, Ind., and then turned over the FROG reins to Sue Kieffer (USGS, Flagstaff, Ariz.) and John Clemens (Arizona State University, Tempe). They generated another newsletter, which was directly mailed to a readership that had grown beyond 200.

New contributions to granite characterization by ultrasonic testing.

PubMed

Cerrillo, C; Jiménez, A; Rufo, M; Paniagua, J; Pachón, F T

2014-01-01

Ultrasound evaluation permits the state of rocks to be determined quickly and cheaply, satisfying the demands faced by today's producers of ornamental stone, such as environmental sustainability, durability and safety of use. The basic objective of the present work is to analyse and develop the usefulness of ultrasound testing in estimating the physico-mechanical properties of granite. Various parameters related to Fast Fourier Transform (FFTs) and attenuation have been extracted from some of the studies conducted (parameters which have not previously been considered in work on this topic, unlike the ultrasonic pulse velocity). The experimental study was carried out on cubic specimens of 30 cm edges using longitudinal and shear wave transducers and equipment which extended the normally used natural resonance frequency range up to 500 kHz. Additionally, a validation study of the laboratory data has been conducted and some methodological improvements have been implemented. The main contribution of the work is the analysis of linear statistical correlations between the aforementioned new ultrasound parameters and physico-mechanical properties of the granites that had not previously been studied, i.e., resistance to salt crystallization and breaking load for anchors. Being properties that directly affect the durability and safety of use of granites, these correlations consolidate ultrasonics as a nondestructive method well suited to this type of material. Copyright © 2013 Elsevier B.V. All rights reserved.

Using the concentration-volume (C-V) fractal model in the delineation of gold mineralized zones within the Tepeoba porphyry Cu-Mo-Au, Balikesir, NW Turkey

NASA Astrophysics Data System (ADS)

Kumral, Mustafa; Abdelnasser, Amr; Karaman, Muhittin; Budakoglu, Murat

2016-04-01

The Tepeoba porphyry Cu-Mo-Au mineralization that located at the Biga peninsula (W Turkey) developed around the Eybek pluton concentrated at its southern contact. This mineralization that hosted in the hornfels rocks of Karakaya Complex is associated with three main alteration zones; potassic, phyllic and propylitic alterations along the fault controlled margins of the Eybek pluton and quartz stockwork veining as well as brecciation zones. As well as two mineralized zones were occurred in the mine area; hypogene and oxidation/supergene zone. The hypogene zone has differentiated alteration types; high potassic and low phyllic alteration, while the oxidation/supergene zone has high phyllic and propylitic alterations. This work deals with the delineation of gold mineralized zone within this porphyry deposit using the concentration-volume (C-V) fractal model. Five zones of gold were calculated using its power-law C-V relationship that revealed that the main phase of gold mineralization stated at 5.3083 ppm Au concentration. In addition, the C-V log-log plot shows that the highly and moderately Au mineralization zone developed in western part of deposit correlated with oxidation zone related to propylitic alteration. On the other hand, its weakly mineralization zone has a widespread in the hypogene zone related to potassic alteration. This refers to the enrichment of gold and depletion of copper at the oxidation/supergene zone is due to the oxidation/supergene alteration processes that enrich the deposits by the meteoric water. Keywords: Concentration-volume (C-V) fractal model; gold mineralized zone; Tepeoba porphyry Cu-Mo-Au; Balikesir; NW Turkey.

Origin, distribution and glaciological implications of Jurassic high heat production granites in the Weddell Sea rift, Antarctica

NASA Astrophysics Data System (ADS)

Leat, Phil T.; Jordan, Tom A. R. M.; Ferraccioli, Fausto; Flowerdew, Michael; R, Riley, Teal; Vaughan, Alan P. M.; Whitehouse, Martin

2013-04-01

The distribution of heat flow in Antarctic continental crust is critical to understanding ice sheet nucleation, growth and basal rheology and hydrology. We identify a group of High Heat Production granites intruded into Palaeozoic sedimentary sequences which may contribute to locally high heat flow beneath the central part of the West Antarctic Ice Sheet. Four of the granite plutons are exposed above ice sheet level at Pagano Nunatak, Pirrit Hills, Nash Hills and Whitmore Mountains. A new U-Pb zircon age from Pirrit Hills of 177.9 ± 2.3 Ma confirms earlier Rb-Sr dating that suggested an Early-Middle Jurassic age for the granites, coincident with the Karoo-Ferrar large igneous province and the first stage of Gondwana break-up. Our recently-acquired aerogeophysical data indicate that the plutons are distributed unevenly over 1000 km2 and were intruded into the actively extending, locally transcurrent, Jurassic Weddell Sea Rift [1]. In the NW part of the rift, the Pirrit Hills, Nash Hills and Whitmore Mountains granites form small isolated intrusions within weakly deformed upper crust. In the SE part of the rift, where granite intrusion was strongly structurally controlled within transtensional structures, the Pagano Nunatak granite is the only outcrop of a probably multiphase, ca 180 km long granite intrusion. The granites are weakly peraluminous, S-type and have Th and U abundances up to 61 and 19 ppm respectively. Heat production of analysed granite samples is ca. 2.9-9.1 µWm-3, toward the upper limit of values for High Heat Production granites globally. The granites are thought to have been generated during mafic underplating of the Weddell Rift during eruption of the contemporaneous Karoo-Ferrar magmatism [2]. The high Th and U abundances may be related to fractionation of the high Th-U Ferrar basaltic magmas combined with assimilation of pelitic sedimentary rocks. The granites correspond to an area of West Antarctica that may have heat flow significantly above

Studies on radon/thoron and their decay products in granite quarries around Bangalore city, India

NASA Astrophysics Data System (ADS)

Ningappa, C.; Sannappa, J.; Chandrashekara, M. S.; Paramesh, L.

2009-08-01

The radon survey was performed in granite quarries around Bangalore rural district and Bangalore city as part of a lung cancer epidemiological study. Long duration measurements of indoor and outdoor radon, thoron and their progenies concentrations were made around granite quarries of Bangalore rural district by using Solid State Nuclear Track Detector (SSNTD, LR-115, Type-II Plastic track detector) during summer and winter period (2006-07). The increase of radioactivity in granite quarries and inhalation dose to workers and populations near the quarries have been summarized. The higher concentrations of radon and thoron in granite quarries suggest radiation health effects on workers and public around the quarries is higher than permissible levels. The results are presented and analyzed with reference to ICRP limits.

Smolt Monitoring at the Head of Lower Granite Reservoir and Lower Granite Dam, 2003 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buettner, Edwin W.; Putnam, Scott A.

This project monitored the daily passage of Chinook salmon Oncorhynchus tshawytscha, steelhead trout O. mykiss, and sockeye salmon O. nerka smolts during the 2003 spring out-migration at migrant traps on the Snake River and Salmon River. In 2003 fish management agencies released significant numbers of hatchery Chinook salmon and steelhead trout above Lower Granite Dam that were not marked with a fin clip or coded-wire tag. Generally, these fish were distinguishable from wild fish by the occurrence of fin erosion. Total annual hatchery Chinook salmon catch at the Snake River trap was 2.1 times less in 2003 than in 2002.more » The wild Chinook catch was 1.1 times less than the previous year. Hatchery steelhead trout catch was 1.7 times less than in 2002. Wild steelhead trout catch was 2.1 times less than the previous year. The Snake River trap collected 579 age-0 Chinook salmon of unknown rearing. During 2003, the Snake River trap captured five hatchery and 13 wild/natural sockeye salmon and 36 coho salmon O. kisutch of unknown rearing. Differences in trap catch between years are due to fluctuations not only in smolt production, but also differences in trap efficiency and duration of trap operation associated with flow. The significant differences in catch between 2003 and the previous year were due mainly to low flows during much of the trapping season and then very high flows at the end of the season, which terminated the trapping season 12 days earlier than in 2002. Trap operations began on March 9 and were terminated on May 27. The trap was out of operation for a total of zero days due to mechanical failure or debris. Hatchery Chinook salmon catch at the Salmon River trap was 16.8% less and wild Chinook salmon catch was 1.7 times greater than in 2002. The hatchery steelhead trout collection in 2003 was 5.6% less than in 2002. Wild steelhead trout collection was 19.2% less than the previous year. Trap operations began on March 9 and were terminated on May 24 due

Smolt Monitoring at the Head of Lower Granite Reservoir and Lower Granite Dam, 2002 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buettner, Edwin W.; Putnam, Scott A.

This project monitored the daily passage of Chinook salmon Oncorhynchus tshawytscha, steelhead trout O. mykiss, and sockeye salmon smolts O. nerka during the 2002 spring out-migration at migrant traps on the Snake River and Salmon River. In 2002 fish management agencies released significant numbers of hatchery Chinook salmon and steelhead trout above Lower Granite Dam that were not marked with a fin clip or coded-wire tag. Generally, these fish were distinguishable from wild fish by the occurrence of fin erosion. Total annual hatchery Chinook salmon catch at the Snake River trap was 11.4 times greater in 2002 than in 2001.more » The wild Chinook catch was 15.5 times greater than the previous year. Hatchery steelhead trout catch was 2.9 times greater than in 2001. Wild steelhead trout catch was 2.8 times greater than the previous year. The Snake River trap collected 3,996 age-0 Chinook salmon of unknown rearing. During 2002, the Snake River trap captured 69 hatchery and 235 wild/natural sockeye salmon and 114 hatchery coho salmon O. kisutch. Differences in trap catch between years are due to fluctuations not only in smolt production, but also differences in trap efficiency and duration of trap operation associated with flow. The significant increase in catch in 2002 was due to a 3.1 fold increase in hatchery Chinook production and a more normal spring runoff. Trap operations began on March 10 and were terminated on June 7. The trap was out of operation for a total of four days due to mechanical failure or debris. Hatchery Chinook salmon catch at the Salmon River trap was 4.2 times greater and wild Chinook salmon catch was 2.4 times greater than in 2001. The hatchery steelhead trout collection in 2002 was 81% of the 2001 numbers. Wild steelhead trout collection in 2002 was 81% of the previous year's catch. Trap operations began on March 10 and were terminated on May 29 due to high flows. The trap was out of operation for four days due to high flow or debris. The

Bluish granites from Extremadura (Spain): a radiological evaluation.

NASA Astrophysics Data System (ADS)

Pereira, Dolores; Neves, Luís.; Peinado, Mercedes; Pereira, Alcides; Rodríguez, Leticia; António Blanco, José

2010-05-01

We have found in the area of Trujillo (Extremadura, Spain) a variety of striking bluish granites, outcropping within the Plasenzuela pluton. They are all quarried under different names and are characterized by leucocratic minerals such as quartz, feldspar (both potassium and plagioclase), sometimes giving a fenocrystic texture and muscovite, with some biotite. As accessory phases, idiomorphic tourmaline is found. Recently a bluish phosphate distributed in the whole rock was detected, included within most mineral phases and fillings from stressed structures that are cutting the rock. We attribute the bluish color of the granites to this phosphate. Although biotite is almost always transformed to chlorite, the rock gives an excellent response to be polished. Physico-mechanical properties make this bluish granite a perfect option for most applications. Absorption coefficient is rather low and alteration by thermal changes has not been observed. A secondary facies with yellow colour also occurs, spatially close to the topographic surface, and probably represents an alteration product of the original granite. This facies is also commercialized as ornamental stone. A radiological survey was carried out in the field, using a gamma ray spectrometer. The radiological background is quite homogeneous in the pluton, without significant differences between gamma ray fluxes of both facies (altered and non altered). The average contents of U, Th and K2O determined in situ with the spectrometer are 7.4 ppm, 0.8 ppm and 3.67%, respectively (n=15). Using U as a Ra proxy, the I index of the EU technical document 112 can be determined, and results in a value of 0.64 for the referred composition. This implies that the rock can be used without any restrictions for building purposes. However, a marked difference was observed in radon exhalation tests carried out in laboratorial facilities. The dominant blue variety shows radon exhalation rates comprised between 0.02 and 0.04 Bq.kg-1.h-1

Study of natural radioactivity in Mansehra granite, Pakistan: environmental concerns.

PubMed

Qureshi, Aziz Ahmed; Jadoon, Ishtiaq Ahmed Khan; Wajid, Ali Abbas; Attique, Ahsan; Masood, Adil; Anees, Muhammad; Manzoor, Shahid; Waheed, Abdul; Tubassam, Aneela

2014-03-01

A part of Mansehra Granite was selected for the assessment of radiological hazards. The average activity concentrations of (226)Ra, (232)Th and (40)K were found to be 27.32, 50.07 and 953.10 Bq kg(-1), respectively. These values are in the median range when compared with the granites around the world. Radiological hazard indices and annual effective doses were estimated. All of these indices were found to be within the criterion limits except outdoor external dose (82.38 nGy h(-1)) and indoor external dose (156.04 nGy h(-1)), which are higher than the world's average background levels of 51 and 55 nGy h(-1), respectively. These values correspond to an average annual effective dose of 0.867 mSv y(-1), which is less than the criterion limit of 1 mSv y(-1) (ICRP-103). Some localities in the Mansehra city have annual effective dose higher than the limit of 1 mSv y(-1). Overall, the Mansehra Granite does not pose any significant radiological health hazard in the outdoor or indoor.

Differential rates of feldspar weathering in granitic regoliths

USGS Publications Warehouse

White, A.F.; Bullen, T.D.; Schulz, M.S.; Blum, A.E.; Huntington, T.G.; Peters, N.E.

2001-01-01

Differential rates of plagioclase and K-feldspar weathering commonly observed in bedrock and soil environments are examined in terms of chemical kinetic and solubility controls and hydrologic permeability. For the Panola regolith, in the Georgia Piedmont Province of southeastern United States, petrographic observations, coupled with elemental balances and 87Sr/86Sr ratios, indicate that plagioclase is being converted to kaolinite at depths > 6 m in the granitic bedrock. K-feldspar remains pristine in the bedrock but subsequently weathers to kaolinite at the overlying saprolite. In contrast, both plagioclase and K-feldspar remain stable in granitic bedrocks elsewhere in Piedmont Province, such as Davis Run, Virginia, where feldspars weather concurrently in an overlying thick saprolite sequence. Kinetic rate constants, mineral surface areas, and secondary hydraulic conductivities are fitted to feldspar losses with depth in the Panola and Davis Run regoliths using a time-depth computer spreadsheet model. The primary hydraulic conductivities, describing the rates of meteoric water penetration into the pristine granites, are assumed to be equal to the propagation rates of weathering fronts, which, based on cosmogenic isotope dating, are 7 m/106 yr for the Panola regolith and 4 m/106 yr for the Davis Run regolith. Best fits in the calculations indicate that the kinetic rate constants for plagioclase in both regoliths are factors of two to three times faster than K-feldspar, which is in agreement with experimental findings. However, the range for plagioclase and K-feldspar rates (kr = 1.5 x 10-17 to 2.8 x 10-16 mol m-2 s-1) is three to four orders of magnitude lower than for that for experimental feldspar dissolution rates and are among the slowest yet recorded for natural feldspar weathering. Such slow rates are attributed to the relatively old geomorphic ages of the Panola and Davis Run regoliths, implying that mineral surface reactivity decreases significantly with

Petrogenesis of the Zheduoshan Cenozoic granites in the eastern margin of Tibet: Constraints on the initial activity of the Xianshuihe Fault

NASA Astrophysics Data System (ADS)

Lai, Shao-cong; Zhao, Shao-wei

2018-06-01

The Zheduoshan Miocene granitic pluton is exposed at the eastern margin of Tibet and along the strike-slip Xianshuihe Fault, and is the product of syn-tectonic magmatism closely related to this fault. This paper is focused on the petrogenesis of different granitic lithological units in the Zheduoshan composite intrusion, and the results of geochronology and lithology show that the Zheduoshan Miocene granitic pluton is incremental assembly by three stages of granitic magma influx and growth, represented by fine-grain biotite granite at 18.0 Ma, corase-grain and porphyraceous biotite monzogranite at 16.0 Ma and medium-grain two-mica monzogranite at 14.0 Ma. Combining with the geochemical signatures, these granitic rocks have high intial 87Sr/86Sr ratios, enriched Nd and Hf isotopic compositions, revealing that the sources of these granitic rocks are metabasatic rocks for fine-grain biotite granite, greywackes for coarse-grain biotite monzogranite and medium-grain monzogranite. These granites have high Sr/Y ratios, revealing that these granitic magma form at high pressure condition. The Sr/Y ratios and calculated crystallization pressure gradually decreased, implying the pressure gradually decreasing with the formation of these three stages of granites, which is probably caused by the tectonic mechanism transition from compression to strike-slip extension during the generation of these granites at 18.0-14.4 Ma. This tectonic mechanism change implied the initial activity of Xianshuihe Fault at least before 14.4 Ma.

Weathering-associated bacteria from the Damma glacier forefield: physiological capabilities and impact on granite dissolution.

PubMed

Frey, Beat; Rieder, Stefan R; Brunner, Ivano; Plötze, Michael; Koetzsch, Stefan; Lapanje, Ales; Brandl, Helmut; Furrer, Gerhard

2010-07-01

Several bacterial strains isolated from granitic rock material in front of the Damma glacier (Central Swiss Alps) were shown (i) to grow in the presence of granite powder and a glucose-NH(4)Cl minimal medium without additional macro- or micronutrients and (ii) to produce weathering-associated agents. In particular, four bacterial isolates (one isolate each of Arthrobacter sp., Janthinobacterium sp., Leifsonia sp., and Polaromonas sp.) were weathering associated. In comparison to what was observed in abiotic experiments, the presence of these strains caused a significant increase of granite dissolution (as measured by the release of Fe, Ca, K, Mg, and Mn). These most promising weathering-associated bacterial species exhibited four main features rendering them more efficient in mineral dissolution than the other investigated isolates: (i) a major part of their bacterial cells was attached to the granite surfaces and not suspended in solution, (ii) they secreted the largest amounts of oxalic acid, (iii) they lowered the pH of the solution, and (iv) they formed significant amounts of HCN. As far as we know, this is the first report showing that the combined action of oxalic acid and HCN appears to be associated with enhanced elemental release from granite, in particular of Fe. This suggests that extensive microbial colonization of the granite surfaces could play a crucial role in the initial soil formation in previously glaciated mountain areas.

Hydrothermal alteration of deep fractured granite: Effects of dissolution and precipitation

NASA Astrophysics Data System (ADS)

Nishimoto, Shoji; Yoshida, Hidekazu

2010-03-01

This paper investigates the mineralogical effects of hydrothermal alteration at depth in fractures in granite. A fracture accompanied by an alteration halo and filled with clay was found at a depth of 200 m in a drill core through Toki granite, Gifu, central Japan. Microscopic observation, XRD, XRF, EPMA and SXAM investigations revealed that the microcrystalline clays consist of illite, quartz and pyrite and that the halo round the fracture can be subdivided into a phyllic zone adjacent to the fracture, surrounded by a propylitic zone in which Fe-phyllosilicates are present, and a distinctive outer alteration front characterized by plagioclase breakdown. The processes that result in these changes took place in three successive stages: 1) partial dissolution of plagioclase with partial chloritization of biotite; 2) biotite dissolution and precipitation of Fe-phyllosilicate in the dissolution pores; 3) dissolution of K-feldspar and Fe-phyllosilicate, and illite precipitation associated with development of microcracks. These hydrothermal alterations of the granite proceed mainly by a dissolution-precipitation process resulting from the infiltration of hydrothermal fluid along microcracks. Such infiltration causes locally high mobility of Al and increases the ratio of fluid to rock in the alteration halo. These results contribute to an understanding of how granitic rock becomes altered in orogenic fields such as the Japanese island arc.

Petrogenesis and tectonic setting of the Devonian Xiqin A-type granite in the northeastern Cathaysia Block, SE China

NASA Astrophysics Data System (ADS)

Cai, Da-wei; Tang, Yong; Zhang, Hui; Lv, Zheng-Hang; Liu, Yun-long

2017-06-01

Most Silurian-Devonian granites in South China are S- or I-type granites, which are suggested to be petrogenetically related to the Wuyi-Yunkai orogeny. In this paper, we present the detailed LA-ICP-MS zircon U-Pb dating, major and trace element geochemical, and Nd-Hf isotopic data for Xiqin A-type granites in the northeastern Cathaysia Block, SE China. Zircon U-Pb dating results show that the Xiqin granites were emplaced at about 410 Ma, indicating that they were generated at the end of Wuyi-Yunkai orogeny. These granites are high in K2O + Na2O (6.31-8.79 wt%), high field strength elements (Zr + Nb + Ce + Y = 427-699 ppm), rare earth elements (total REE = 221-361 ppm) as well as high Ga/Al ratios (10,000 Ga/Al = 2.50-3.10), and show characteristics typical of A-type granites. εHf(t) values of the Xiqin granites mainly vary from -0.4 to -3.1 and yield Mesoproterozoic T2DM(Hf) (mainly ranging from 1.29 to 1.45 Ga). The εNd(t) values are from -1.23 to -2.11 and T2DM(Nd) vary from 1.25 to 1.32 Ga. These isotopic data suggest that the Xiqin granites were generated by partial melting of metavolcanic rocks with minor metasedimentary rocks in the lower crust. Our data on the Xiqin granites, coupled with previous studies of Silurian-Devonian magmatism, suggest that the tectonic regime had changed to a strongly post-collisional extension environment in the Wuyi-Yunkai orogen at least since 410 Ma, and that delamination, which accounts for the change in stress from the compression to extension and asthenospheric upwelling during the early Paleozoic, plays a significant role in the generation of Xiqin A-type granites.

Geology and reconnaissance stable isotope study of the Oyu Tolgoi porphyry Cu-Au system, South Gobi, Mongolia

USGS Publications Warehouse

Khashgerel, B.-E.; Rye, R.O.; Hedenquist, J.W.; Kavalieris, I.

2006-01-01

The Oyu Tolgoi porphyry Cu-Au system in the South Gobi desert, Mongolia, comprises five deposits that extend over 6 km in a north-northeast-oriented zone. They occur in a middle to late Paleozoic are terrane and are related to Late Devonian quartz monzodiorite intrusions. The Hugo Dummett deposits are the northernmost and deepest, with up to 1,000 m of premineral sedimentary and volcanic cover rock remaining. They are the largest deposits discovered to date and characterized by high-grade copper (>2.5% Cu) and gold (0.5-2 g/t) mineralization associated with intense quartz veining and several phases of quartz monzodiorite intruded into basaltic volcanic host rocks. Sulfide minerals in these deposits are zoned outward from a bornite-dominated core to chalcopyrite, upward to pyrite ?? enargite and covellite at shallower depth. The latter high-sulfidation-state sulfides are hosted by advanced argillic alteration mineral associations. This alteration is restricted mainly to dacitic ash-flow tuff that overlies the basaltic volcanic rock and includes ubiquitous quartz and pyrophyllite, kaolinite, plus late dickite veins, as well as K alunite, Al phosphate-sulfate minerals, zunyite, diaspore, topaz, corundum, and andalusite. A reconnaissance oxygen-hydrogen and sulfur isotope study was undertaken to investigate the origin of several characteristic alteration minerals in the Oyu Tolgoi system, with particular emphasis on the Hugo Dummett deposits. Based on the isotopic composition of O, H, and S (??18O(SO4) = 8.8-20.1???, ??D = -73 to -43???, ??34S = 9.8-17.9???), the alunite formed from condensation of magmatic vapor that ascended to the upper parts of the porphyry hydrothermal system, without involvement of significant amounts of meteoric water. The isotopic data indicate that pyrophyllite (??18O = 6.5-10.9???, ??D = -90 to -106???) formed from a magmatic fluid with a component of meteoric water. Muscovite associated with quartz monzodiorite intrusions occurs in the core

REE enrichment in granite-derived regolith deposits of the southeast United States: Prospective source rocks and accumulation processes

USGS Publications Warehouse

Foley, Nora K.; Ayuso, Robert A.; Simandl, G.J.; Neetz, M.

2015-01-01

The Southeastern United States contains numerous anorogenic, or A-type, granites, which constitute promising source rocks for REE-enriched ion adsorption clay deposits due to their inherently high concentrations of REE. These granites have undergone a long history of chemical weathering, resulting in thick granite-derived regoliths, akin to those of South China, which supply virtually all heavy REE and Y, and a significant portion of light REE to global markets. Detailed comparisons of granite regolith profiles formed on the Stewartsville and Striped Rock plutons, and the Robertson River batholith (Virginia) indicate that REE are mobile and can attain grades comparable to those of deposits currently mined in China. A REE-enriched parent, either A-type or I-type (highly fractionated igneous type) granite, is thought to be critical for generating the high concentrations of REE in regolith profiles. One prominent feature we recognize in many granites and mineralized regoliths is the tetrad behaviour displayed in REE chondrite-normalized patterns. Tetrad patterns in granite and regolith result from processes that promote the redistribution, enrichment, and fractionation of REE, such as late- to post- magmatic alteration of granite and silicate hydrolysis in the regolith. Thus, REE patterns showing tetrad effects may be a key for discriminating highly prospective source rocks and regoliths with potential for REE ion adsorption clay deposits.

Rapakivi Granite: An architectural emblem of St Petersburg and its utilisation in other world cities

NASA Astrophysics Data System (ADS)

Bulakh, Andrey; Gavrilenko, Vladimir; Panova, Helen

2015-04-01

The wide-ranging utilisation of Rapakivi Granite in St Petersburg is typified by the the famous Alexander Column, and 114 stone columns of St Isaac's Cathedralas well as the pedestal of the Nicholas I monument, and portals and basements of buildings of the Admiralty, General Staff, Senate and Synod. The stone is also frequently seen among pavement slabs and in parapets of embankments and bridges around the city. This list of examples where Rapakivi Granite has been used could be expanded further. All Rapakivi Granites used in the buildings of St.Petersburg were quarried from the so-called Vyborg massif. At present it has been found that the massif occupies an area of about 18 000 km2. In the past granite of the Vyborg massif was worked from several quarries in the vicinity of Fredrikshamn (Hamina) in Finland for use in St Peterburg. The best known granite quarries are at Piterlaks (Piuterlahti) and Gimmekyul (Hämeenkylä). Sometimes Rapakivi Granite form Finland differs in appearance from typical varieties. Thus columns of a classical portal in the house at N 7 in Pochtamtskaya Street are hewn from this greyish variety. Other examples are the plinth of the General Staff and Trade Store buildings. After the 1960s varieties from the Leningrad district, and Korosten (Ukraine) massifs were used in St Petersburg. Today it is possible to find examples of Rapakivi Granite from Finland in cities in the USA, South Africa, United Kingdom and Germany. It is a long used stone as demonstrated by its cultural heritage. It is also used as an ornamental or decorative stone in modern architecture. References: 1) Bulakh, A.G., Abakumova, N.B., and Romanovsky, J.V. St Petersburg: a History in Stone. 2010. Print House of St Petersburg State University. 173 p. (In English). 2) Tutakova, A.Ya., Romanovskiy, A.Z., Bulakh, A.G., and Leer, V.I. Dimension Stone of the Leningrad Region. Granites of the Karelia Isthmus in Architecture of the Modern St Petersburg. 2011. St Petersburg. 78 p

Geochemistry and fluid characteristics of the Dalli porphyry Cu-Au deposit, Central Iran

NASA Astrophysics Data System (ADS)

Zarasvandi, Alireza; Rezaei, Mohsen; Raith, Johann; Lentz, David; Azimzadeh, Amir-Mortaza; Pourkaseb, Hooshang

2015-11-01

The Miocene Dalli porphyry Cu-Au deposit in the central part of Urumieh-Dokhtar magmatic arc is the first reported Au-rich porphyry Cu deposit in the Zagros orogenic belt. The Cu-Au mineralization is mainly hosted in diorite and quartz diorite intrusions, presenting as numerous veinlets in the altered wall rocks, with potassic, phyllic, and propylitic alteration developed. Based on the mineral assemblages and crosscutting relations of veinlets, hydrothermal mineralization-alteration occurred in at least three stages, characterized by veinlets of (1) Qtz + Kfs + Mag ± Ccp, (2) Qtz + Py + Ccp ± Bn ± Cv ± Cc and, (3) Qtz + Chl + Bt. The ore-bearing intrusions exhibit typical geochemical characteristics of subduction zone magmas, including LREE fractionated pattern, strong enrichment in LILE (Cs, Rb, Ba, Pb, and U), and depletion of HFSE, with marked negative Ti and Nb anomalies. The adakite-like ore-hosting porphyry intrusions are characterized by a systematic gradual decreasing and increasing of Y and Eu/Eu∗ with increasing SiO2 content, respectively. Moreover, they exhibit a significant increasing trend of Sr/Y with decreasing of Y, which indicates progressive hornblende fractionation and suppression of plagioclase fractionation during the evolution toward high water content of parental magma. A relatively flat HREE pattern with low Dyn/Ybn and Nb/Ta values may represent that amphibole played a more important role than garnet in the generation of the adakitic melts in the thickened lower crust. Based on the phase assemblages confirmed by detailed laser Raman spectroscopy analyses and proportion of solid, liquid, and gaseous components, five types of fluid inclusions were recognized, which are categorized as; (1) liquid-rich two phase (liquidH2O + vaporH2O) (IIA), (2) vapor-rich two phase (vaporH2O/CO2 + liquidH2O) (IIB), (3) high saline simple fluids (IIIA; liquidH2O + vaporH2O + Hl), (4) high saline opaque mineral-bearing fluids (IIIB; liquidH2O + vaporH2O

An exploration hydrogeochemical study at the giant Pebble porphyry Cu-Au-Mo deposit, Alaska, USA, using high-resolution ICP-MS

USGS Publications Warehouse

Eppinger, Robert G.; Fey, David L.; Giles, Stuart A.; Kelley, Karen D.; Smith, Steven M.

2012-01-01

A hydrogeochemical study using high resolution ICP-MS was undertaken at the giant Pebble porphyry Cu-Au-Mo deposit and surrounding mineral occurrences. Surface water and groundwater samples from regional background and the deposit area were collected at 168 sites. Rigorous quality control reveals impressive results at low nanogram per litre (ng/l) levels. Sites with pH values below 5.1 are from ponds in the Pebble West area, where sulphide-bearing rubble crop is thinly covered. Relative to other study area waters, anomalous concentrations of Cu, Cd, K, Ni, Re, the REE, Tl, SO42− and F− are present in water samples from Pebble West. Samples from circum-neutral waters at Pebble East and parts of Pebble West, where cover is much thicker, have anomalous concentrations of Ag, As, In, Mn, Mo, Sb, Th, U, V, and W. Low-level anomalous concentrations for most of these elements were also found in waters surrounding nearby porphyry and skarn mineral occurrences. Many of these elements are present in low ng/l concentration ranges and would not have been detected using traditional quadrupole ICP-MS. Hydrogeochemical exploration paired with high resolution ICP-MS is a powerful new tool in the search for concealed deposits.

Geological model of supercritical geothermal reservoir related to subduction system

NASA Astrophysics Data System (ADS)

Tsuchiya, Noriyoshi

2017-04-01

Following the Great East Japan Earthquake and the accident at the Fukushima Daiichi Nuclear power station on 3.11 (11th March) 2011, geothermal energy came to be considered one of the most promising sources of renewable energy for the future in Japan. The temperatures of geothermal fields operating in Japan range from 200 to 300 °C (average 250 °C), and the depths range from 1000 to 2000 m (average 1500 m). In conventional geothermal reservoirs, the mechanical behavior of the rocks is presumed to be brittle, and convection of the hydrothermal fluid through existing network is the main method of circulation in the reservoir. In order to minimize induced seismicity, a rock mass that is "beyond brittle" is one possible candidate, because the rock mechanics of "beyond brittle" material is one of plastic deformation rather than brittle failure. Supercritical geothermal resources could be evaluated in terms of present volcanic activities, thermal structure, dimension of hydrothermal circulation, properties of fracture system, depth of heat source, depth of brittle factures zone, dimension of geothermal reservoir. On the basis of the GIS, potential of supercritical geothermal resources could be characterized into the following four categories. 1. Promising: surface manifestation d shallow high temperature, 2 Probability: high geothermal gradient, 3 Possibility: Aseismic zone which indicates an existence of melt, 4 Potential : low velocity zone which indicates magma input. Base on geophysical data for geothermal reservoirs, we have propose adequate tectonic model of development of the supercritical geothermal reservoirs. To understand the geological model of a supercritical geothermal reservoir, granite-porphyry system, which had been formed in subduction zone, was investigated as a natural analog of the supercritical geothermal energy system. Quartz veins, hydrothermal breccia veins, and glassy veins are observed in a granitic body. The glassy veins formed at 500-550 �

Raman spectroscopic study of alunite occurrences in the Sapes porphyry-epithermal deposit, NE Greece

NASA Astrophysics Data System (ADS)

Papazotos, Panagiotis; Perraki, Maria; Voudouris, Panagiotis; Skliros, Vasilios

2017-04-01

The Sapes area, Northeastern Greece, represent a deeply eroded Oligocene volcanic edifice built up of post-collisional intermediate-to-acidic intrusives and their volcanic equivalents. The area hosts a telescoped porphyry-epithermal system and associated high-sulfidation epithermal Au-Ag-Cu-Bi-Te mineralization within advanced argillic alteration lithocaps (Voudouris, 2014). Alunite is a common mineralogical constituent among the advanced argillic alteration assemblages and it is a hydrated aluminium potassium sulfate mineral with a general formula KAl3(SO4)2(OH)6. The objective of this work is to study the alunites samples in the Sapes porphyry-epithermal deposit by means of Raman spectroscopy, as it has been shown to be a useful tool in studying the alunite structure, either natural or synthetic (Frost et al., 2006; Maubec et al., 2012). Raman spectra were excited employing a 532 nm laser at a resolution of 2 cm-1 in the range of 100-4000 cm-1. Raman spectra exhibit distinguished bands at 162 cm-1, attributed to translational mode of cations and or librational and translational modes of SO42-, at 235 cm-1 suggesting framework deformations including the SO42- entities as a whole or attributed to OH/O hydrogen bond stretching mode, a weak band at 385 cm-1 may corresponding to Al-OH stretching vibrations, a moderate band at 564 cm-1 assigned to Al-O and OH deformation modes, bands at 484 and 653 cm-1 respectively due to v2(SO42-) and v4(SO42-) bending modes, a very strong vibration at 1025 cm-1 that is ascribed to the v1 stretching vibration of the SO42- bands located at 1080 and 1186 cm-1 due to v3(SO42-) stretching modes and finally two bands at 3480 cm-1 and 3502 cm-1 that are assigned to the OH stretching vibrations (Breitinger et al., 1997; Frost et al., 2006; Maubec et al., 2012 and references therein). A Raman and FTIR spectroscopic future work will focus on the comparative study among the alunites occurrences in Greece (Sapes, Limnos, Lesvos and Milos), so

Threshold Differences on Figure and Ground: Gelb and Granit (1923)

PubMed Central

Kinateder, Max

2017-01-01

In 1923, Gelb and Granit, using a method of adjustment for a small red light, reported a lower threshold for the target when presented on a ground region than on an adjacent figural region. More recent work in perceptual organization has found precisely the opposite—a processing advantage seems to go to items presented on the figure, not the ground. Although Gelb and Granit continue to be cited for their finding, it has not previously been available as an English translation. Understanding their methodology and results is important for integrating early Gestalt theory with more recent investigations. PMID:28286640

Threshold Differences on Figure and Ground: Gelb and Granit (1923).

PubMed

Kinateder, Max; Nelson, Rolf

2017-01-01

In 1923, Gelb and Granit, using a method of adjustment for a small red light, reported a lower threshold for the target when presented on a ground region than on an adjacent figural region. More recent work in perceptual organization has found precisely the opposite-a processing advantage seems to go to items presented on the figure, not the ground. Although Gelb and Granit continue to be cited for their finding, it has not previously been available as an English translation. Understanding their methodology and results is important for integrating early Gestalt theory with more recent investigations.

Determining heterogeneous deformation for granitic rocks in the northern thrust in Wadi Mubarak belt, Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Kassem, Osama M. K.

2011-05-01

Finite-strain was studied in the mylonitic granitic and metasedimentary rocks in the northern thrust in Wadi Mubarak belt to show a relationship to nappe contacts between the old granitic and metavolcano-sedimentary rocks and to shed light on the heterogeneous deformation for the northern thrust in Wadi Mubarak belt. We used the Rf/ϕ and Fry methods on feldspar porphyroclasts, quartz and mafic grains from 7 old granitic and 7 metasedimentary samples in the northern thrust in Wadi Mubarak belt. The finite-strain data shows that old granitic rocks were moderate to highly deformed and axial ratios in the XZ section range from 3.05 to 7.10 for granitic and metasedimentary rocks. The long axes (X) of the finite-strain ellipsoids trend W/WNW and E/ENE in the northern thrust in Wadi Mubarak belt. Furthermore, the short axes (Z) are subvertical associated with a subhorizontal foliation. The value of strain magnitudes mainly constants towards the tectonic contacts between the mylonitic granite and metavolcano-sedimentary rocks. The data indicate oblate strain symmetry (flattening strain) in the mylonitic granite rocks. It is suggested that the accumulation of finite strain was formed before or/and during nappe contacts. The penetrative subhorizontal foliation is subparallel to the tectonic contacts with the overlying nappes and foliation was formed during nappe thrusting.

Porphyry copper assessment of the Central Asian Orogenic Belt and eastern Tethysides: China, Mongolia, Russia, Pakistan, Kazakhstan, Tajikistan, and India: Chapter X in Global mineral resource assessment

USGS Publications Warehouse

Mihalasky, Mark J.; Ludington, Stephen; Hammarstrom, Jane M.; Alexeiev, Dmitriy V.; Frost, Thomas P.; Light, Thomas D.; Robinson, Gilpin R.; Briggs, Deborah A.; Wallis, John C.; Miller, Robert J.; Bookstrom, Arthur A.; Panteleyev, Andre; Chitalin, Andre; Seltmann, Reimar; Guangsheng, Yan; Changyun, Lian; Jingwen, Mao; Jinyi, Li; Keyan, Xiao; Ruizhao, Qiu; Jianbao, Shao; Gangyi, Shai; Yuliang, Du

2015-01-01

The U.S. Geological Survey collaborated with international colleagues to assess undiscovered resources in porphyry copper deposits in the Central Asian Orogenic Belt and eastern Tethysides. These areas host 20 known porphyry copper deposits, including the world class Oyu Tolgoi deposit in Mongolia that was discovered in the late 1990s. The study area covers major parts of the world’s largest orogenic systems. The Central Asian Orogenic Belt is a collage of amalgamated Precambrian through Mesozoic terranes that extends from the Ural Mountains in the west nearly to the Pacific Coast of Asia in the east and records the evolution and final closure of the Paleo-Asian Ocean in Permian time. The eastern Tethysides, the orogenic belt to the south of the Central Asian Orogenic Belt, records the evolution of another ancient ocean system, the Tethys Ocean. The evolution of these orogenic belts involved magmatism associated with a variety of geologic settings appropriate for formation of porphyry copper deposits, including subduction-related island arcs, continental arcs, and collisional and postconvergent settings. The original settings are difficult to trace because the arcs have been complexly deformed and dismembered by younger tectonic events. Twelve mineral resource assessment tracts were delineated to be permissive for the occurrence of porphyry copper deposits based on mapped and inferred subsurface distributions of igneous rocks of specific age ranges and compositions. These include (1) nine Paleozoic tracts in the Central Asian Orogenic Belt, which range in area from about 60,000 to 800,000 square kilometers (km2); (2) a complex area of about 400,000 km2 on the northern margin of the Tethysides, the Qinling-Dabie tract, which spans central China and areas to the west, encompassing Paleozoic through Triassic igneous rocks that formed in diverse settings; and (3) assemblages of late Paleozoic and Mesozoic rocks that define two other tracts in the Tethysides, the 100

Assessing exposure to granite countertops--Part 2: Radon.

PubMed

Allen, Joseph G; Minegishi, Taeko; Myatt, Theodore A; Stewart, James H; McCarthy, John F; Macintosh, David L

2010-05-01

Radon gas ((222)Rn) is a natural constituent of the environment and a risk factor for lung cancer that we are exposed to as a result of radioactive decay of radium ((226)Ra) in stone and soil. Granite countertops, in particular, have received recent media attention regarding their potential to emit radon. Radon flux was measured on 39 full slabs of granite from 27 different varieties to evaluate the potential for exposure and examine determinants of radon flux. Flux was measured at up to six pre-selected locations on each slab and also at areas identified as potentially enriched after a full-slab scan using a Geiger-Muller detector. Predicted indoor radon concentrations were estimated from the measured radon flux using the CONTAM indoor air quality model. Whole-slab average emissions ranged from less than limit of detection to 79.4 Bq/m(2)/h (median 3.9 Bq/m(2)/h), similar to the range reported in the literature for convenience samples of small granite pieces. Modeled indoor radon concentrations were less than the average outdoor radon concentration (14.8 Bq/m(3); 0.4 pCi/l) and average indoor radon concentrations (48 Bq/m(3); 1.3 pCi/l) found in the United States. Significant within-slab variability was observed for stones on the higher end of whole slab radon emissions, underscoring the limitations of drawing conclusions from discrete samples.

The adsorption behavior of U(VI) on granite.

PubMed

Fan, Q H; Hao, L M; Wang, C L; Zheng, Z; Liu, C L; Wu, W S

2014-03-01

The effects of pH, counter ions and temperature on the adsorption of U(VI) on Beishan granite (BsG) were investigated in the presence and absence of fulvic acid (FA) and humic acid (HA). The adsorption edge of U(VI) on BsG suggested that U(VI) adsorption was mainly controlled by ion exchange and outer-sphere complexation at low pH, whereas inner-sphere complex was the dominant adsorption species in the pH range of 4.0-9.0. Above pH 9.0, Na2U2O7 might play an important role in the rise of U(VI) adsorption again. Counter ions such as Cl(-), SO4(2-) and PO4(3-) can provoke U(VI) adsorption on BsG to some extent, which was directly correlated to the complexing ability of U(VI)-ligand. More noticeably, the large enhancement of U(VI) adsorption in the presence of phosphate can be attributed to the ternary complex formation (BsG-PO4-UO2), precipitation ((UO2)3(PO4)2(s)) and secondary phase (Na-autunite). Both FA and HA can slightly increase U(VI) adsorption at low pH, whereas they strongly inhibited U(VI) adsorption at high pH range. Artificial synthesized granite (AsG) prepared in the laboratory is impossible to use as an analogue of natural granite because of the large difference in the adsorption and surface properties.

Reutilization of granite powder as an amendment and fertilizer for acid soils.

PubMed

Barral Silva, M T; Silva Hermo, B; García-Rodeja, E; Vázquez Freire, N

2005-11-01

The properties of granite powders--a granite manufacturing waste product-were analyzed to assess their potential use as amendments and fertilizers on acid soils. Two types of powders were characterized: one produced during cutting of granite with a diamond-edged disc saw, comprising only rock powder, the other produced during cutting with a multi-blade bandsaw, containing calcium hydroxide and metal filings added during the cutting procedure. The acid neutralizing capacity of the granite powders was assessed in short- (2-3 h) and medium-term (1-30 d) experiments. The powders showed a buffering capacity at around pH 8, which corresponded to the rapid dissolution of basic cations, and another buffering effect at pH<4.5, attributable to the dissolution of Fe and Al. The acid neutralizing capacity (ANC) determined in the short-term experiments, to a final pH of 4.5, varied between 5 and 61 cmol H+kg(-1) powder. The ANC to pH 4.5 obtained in the medium-term experiments was much higher than that obtained in the short-term experiments, reaching a maximum ANC value of 200 cmol H+kg(-1) powder. There was no great difference in the neutralizing capacity determined at between 1 and 30 d. The most abundant elements in acid solutions obtained at the end of medium-term experiments were Mg and Ca for disc saw powders, whereas Ca and Fe (at pH<5) were the most soluble elements in the bandsaw powders. The rapid release of these cations suggests the possible effective use of the granite powders as a source of nutrients on being added to acid soils.

Porphyry-copper ore shells form at stable pressure-temperature fronts within dynamic fluid plumes.

PubMed

Weis, P; Driesner, T; Heinrich, C A

2012-12-21

Porphyry-type ore deposits are major resources of copper and gold, precipitated from fluids expelled by crustal magma chambers. The metals are typically concentrated in confined ore shells within vertically extensive vein networks, formed through hydraulic fracturing of rock by ascending fluids. Numerical modeling shows that dynamic permeability responses to magmatic fluid expulsion can stabilize a front of metal precipitation at the boundary between lithostatically pressured up-flow of hot magmatic fluids and hydrostatically pressured convection of cooler meteoric fluids. The balance between focused heat advection and lateral cooling controls the most important economic characteristics, including size, shape, and ore grade. This self-sustaining process may extend to epithermal gold deposits, venting at active volcanoes, and regions with the potential for geothermal energy production.

Porphyry-Copper Ore Shells Form at Stable Pressure-Temperature Fronts Within Dynamic Fluid Plumes

NASA Astrophysics Data System (ADS)

Weis, P.; Driesner, T.; Heinrich, C. A.

2012-12-01

Porphyry-type ore deposits are major resources of copper and gold, precipitated from fluids expelled by crustal magma chambers. The metals are typically concentrated in confined ore shells within vertically extensive vein networks, formed through hydraulic fracturing of rock by ascending fluids. Numerical modeling shows that dynamic permeability responses to magmatic fluid expulsion can stabilize a front of metal precipitation at the boundary between lithostatically pressured up-flow of hot magmatic fluids and hydrostatically pressured convection of cooler meteoric fluids. The balance between focused heat advection and lateral cooling controls the most important economic characteristics, including size, shape, and ore grade. This self-sustaining process may extend to epithermal gold deposits, venting at active volcanoes, and regions with the potential for geothermal energy production.

Charnockites and granites of the western Adirondacks, New York, USA: a differentiated A-type suite

USGS Publications Warehouse

Whitney, P.R.

1992-01-01

Granitic rocks in the west-central Adirondack Highlands of New York State include both relatively homogeneous charnockitic and hornblende granitic gneisses (CG), that occur in thick stratiform bodies and elliptical domes, and heterogeneous leucogneisses (LG), that commonly are interlayered with metasedimentary rocks. Major- and trace-element geochemical analyses were obtained for 115 samples, including both types of granitoids. Data for CG fail to show the presence of more than one distinct group based on composition. Most of the variance within the CG sample population is consistent with magmatic differentiation combined with incomplete separation of early crystals of alkali feldspar, plagioclase, and pyroxenes or amphibole from the residual liquid. Ti, Fe, Mg, Ca, P, Sr, Ba, and Zr decrease with increasing silica, while Rb and K increase. Within CG, the distinction between charnockitic (orthopyroxene-bearing) and granitic gneisses is correlated with bulk chemistry. The charnockites are consistently more mafic than the hornblende granitic gneisses, although forming a continuum with them. The leucogneisses, while generally more felsic than the charnockites and granitic gneisses, are otherwise geochemically similar to them. The data are consistent with the LG suite being an evolved extrusive equivalent of the intrusive CG suite. Both CG and LG suites are metaluminous to mildly peraluminous and display an A-type geochemical signature, enriched in Fe, K, Ce, Y, Nb, Zr, and Ga and depleted in Ca, Mg, and Sr relative to I- and S-type granites. Rare earth element patterns show moderate LREE enrichment and a negative Eu anomaly throughout the suite. The geochemical data suggest an origin by partial melting of biotite- and plagioclase-rich crustal rocks. Emplacement occurred in an anorogenic or post-collisional tectonic setting, probably at relatively shallow depths. Deformation and granulite-facies metamorphism with some partial melting followed during the Ottawan phase

Granite School District First Grade Reading Study.

ERIC Educational Resources Information Center

Castner, Myra H.; And Others

A comparative study of first-grade reading instructional methods was undertaken with the support of the Granite School District Exemplary Center for Reading Instruction. This study was conducted in 19 schools of the district and involved approximately 1,295 students. Nine hypotheses concerning the various approaches used in reading instruction…

Landslides and the weathering of granitic rocks

Treesearch

Philip B. Durgin

1977-01-01

Abstract - Granitic batholiths around the Pacific Ocean basin provide examples of landslide types that characterize progressive stages of weathering. The stages include (1) fresh rock, (2) corestones, (3) decomposed granitoid, and (4) saprolite. Fresh granitoid is subject to rockfalls, rockslides, and block glides. They are all controlled by factors related to...

Geochemistry and statistical analyses of porphyry system and epithermal veins at Hizehjan in northwestern Iran

NASA Astrophysics Data System (ADS)

Radmard, Kaikhosrov; Zamanian, Hassan; Hosseinzadeh, Mohamad Reza; Khalaji, Ahmad Ahmadi

2017-12-01

Situated about 130 km northeast of Tabriz (northwest Iran), the Mazra'eh Shadi deposit is in the Arasbaran metallogenic belt (AAB). Intrusion of subvolcanic rocks, such as quartz monzodiorite-diorite porphyry, into Eocene volcanic and volcano-sedimentary units led to mineralisation and alteration. Mineralisation can be subdivided into a porphyry system and Au-bearing quartz veins within andesite and trachyandesite which is controlled by fault distribution. Rock samples from quartz veins show maximum values of Au (17100 ppb), Pb (21100 ppm), Ag (9.43ppm), Cu (611ppm) and Zn (333 ppm). Au is strongly correlated with Ag, Zn and Pb. In the Au-bearing quartz veins, factor group 1 indicates a strong correlation between Au, Pb, Ag, Zn and W. Factor group 2 indicates a correlation between Cu, Te, Sb and Zn, while factor group 3 comprises Mo and As. Based on Spearman correlation coefficients, Sb and Te can be very good indicator minerals for Au, Ag and Pb epithermal mineralisation in the study area. The zoning pattern shows clearly that base metals, such as Cu, Pb, Zn and Mo, occur at the deepest levels, whereas Au and Ag are found at higher elevations than base metals in boreholes in northern Mazra'eh Shadi. This observation contrasts with the typical zoning pattern caused by boiling in epithermal veins. At Mazra'eh Shadi, quartz veins containing co-existing liquid-rich and vapour-rich inclusions, as strong evidence of boiling during hydrothermal evolution, have relatively high Au grades (up to 813 ppb). In the quartz veins, Au is strongly correlated with Ag, and these elements are in the same group with Fe and S. Mineralisation of Au and Ag is a result of pyrite precipitation, boiling of hydrothermal fluids and a pH decrease.

Modeling of lung cancer risk due to radon exhalation of granite stone in dwelling houses.

PubMed

Abbasi, Akbar

2017-01-01

Due to increasing occurrences of lung cancer, radon exhalation rates, radon concentrations, and lung cancer risks in several types of commonly used granite stone, samples used for flooring in buildings, have been investigated. We measured the radon exhalation rates due to granite stones by means of an AlphaGUARD Model PQ2000 in a cube container with changeable floor by various granite stones. The lung cancer risk and percentage of lung cancer deaths (LCRn) due to those conditions were calculated using Darby's model. The radon exhalation rates ranged from 1.59 ± 0.41 to 9.43 ± 0.74 Bq/m 2/h. The radon concentrations in the standard room with poor and normal ventilation were calculated 20.10-71.09 Bq/m 3 and 16.12-47.01 Bq/m 3, respectively. The estimated numbers of lung cancer deaths attributable to indoor radon due to granite stones in 2013 were 145 (3.33%) and 103 (2.37%) for poor and normal ventilation systems, respectively. According to our estimations, the values of 3.33% and 2.37% of lung cancer deaths in 2013 are attributed to radon exhalation of granite stones with poor and normal ventilation systems, respectively.

The Coast Artillery Journal. Volume 77, Number 6, November-December 1934

DTIC Science & Technology

1934-12-01

The Tsingtau peninsula, between Lau schan and Kiautschou Bays, is a rocky headland of granite and porphyry , but to the north of the Pai scha ho the...has un- dergone a rather complete overhaul since its first water trials, receiving a coat of anti-fouling paint, a copper ex- haust pipe and a bronze...and rate it as excellent. No filters or chlorinators are used. Every 48 hours five pounds of copper sulphate are placed in a perforated can in front

Early Neoarchaean A-type granitic magmatism by crustal reworking in Singhbhum craton: Evidence from Pala Lahara area, Orissa

NASA Astrophysics Data System (ADS)

Topno, Abhishek; Dey, Sukanta; Liu, Yongsheng; Zong, Keqing

2018-04-01

Several volumetrically minor ˜ 2.8 Ga anorogenic granites and rhyolites occur along the marginal part of the Singhbhum craton whose origin and role in crustal evolution are poorly constrained. This contribution presents petrographic, geochemical, zircon U-Pb and trace element, and mineral chemical data on such granites exposed in the Pala Lahara area to understand their petrogenesis and tectonic setting. The Pala Lahara granites are calc-alkaline, high-silica rocks and define a zircon U-Pb age of 2.79 Ga. These granites are ferroan, weakly metaluminous, depleted in Al, Ca and Mg and rich in LILE and HFSE. They are classified as A2-type granites with high Y/Nb ratios. Geochemical characteristics (high SiO2 and K2O, very low MgO, Mg#, Cr, Ni and V, negative Eu anomaly, flat HREE and low Sr/Y) and comparison with melts reported by published experimental studies suggest an origin through high-temperature, shallow crustal melting of tonalitic/granodioritic source similar to the ˜ 3.3 Ga Singhbhum Granite. Intrusion of the Pala Lahara granites was coeval with prominent mafic magmatism in the Singhbhum craton (e.g., the Dhanjori mafic volcanic rocks and NNE-SSW trending mafic dyke swarm). It is suggested that the ˜ 2.8 Ga A-type granites in the Singhbhum craton mark a significant crustal reworking event attendant to mantle-derived mafic magmatism in an extensional tectonic setting.

The Pikes Peak batholith, Colorado front range, and a model for the origin of the gabbro-anorthosite-syenite-potassic granite suite

USGS Publications Warehouse

Barker, F.; Wones, D.R.; Sharp, W.N.; Desborough, G.A.

1975-01-01

This study of the Pikes Peak batholith includes the mineralogy and petrology of quartz syenite at West Creek and of fayalite-bearing and fayalite-free biotite granite near Mount Rosa; major element chemistry of the batholith; comparisons with similar postorogenic, intracratonic, sodic to potassic intrusives; and genesis of the batholith. The batholith is elongate in plan, 50 by 100 km, composite, and generally subalkalic. It was emplaced at shallow depth 1,040 m. y. ago, sharply transects its walls and may have breached its roof. Biotite granite and biotite-hornblende granite are predominant; quartz syenite, fayalite granite and riebeckite granite are present in minor amounts. Fayalite-bearing and fayalite-free quartz syenite, fayalite-biotite granite and riebeckite granite show a well-defined sodic differentiation trend; the less sodic fayalite-free granites exhibit a broader compositional range and no sharp trends. Crystallization was largely at PH2O < Ptotal; PH2O approached Ptotal only at late stages. Aplite residual to fayalite-free biotite granite in the north formed at about 1,500 bars, or 5 km depth. Feldspar assemblages indicate late stages of crystallization at about 720??C. In the south ilmenite and manganian fayalite indicate fO2 of 10-17 or 10-18 bars. Biotite and fayalite compositions and the 'granite minimum' imply completion of crystallization at about 700??C and 1,500 bars. Nearby fayalite-free biotite granite crystallized at higher water fugacity. All types of syenite and granite contain 5-6% K2O through a range of SiO2 of 63-76%. Average Na2O percentages in quartz syenite are 6.2, fayalite granite 4.2, and fayalite-free granite 3.3 MgO contents are low, 0.03-0.4%; FeO averages 1.9-2.5%. FeO/Fe2O3 ratios are high. Fluorine ranges from 0.3 to 0.6%. The Pikes Peak intrusives are similar in mode of emplacement, composition, and probably genesis to rapakivi intrusives of Finland, the Younger Granites of Nigeria, Cape Ann Granite and Beverly Syenite

Petrogenesis of ore-bearing porphyry in non-subduction setting: a case study of the Eocene potassic intrusions in the western Yangtze Block

NASA Astrophysics Data System (ADS)

Liu, Zheng; Liao, Shi-Yong; Zhou, Qing; Zhang, Xin

2018-05-01

In the western Yangtze Block, abundant Eocene ( 38-34 Ma) potassic adakite-like intrusions and associated porphyry copper deposits are exposed in non-subduction setting, including Machangjing, Beiya, Binchuan, Habo and Tongchang intrusions. All these ore-bearing porphyries share many geochemical characteristics of adakite such as depletion in heavy rare earth elements (HREEs), enrichment in Sr and Ba, absence of negative Eu anomalies, high SiO2, Al2O3, Sr/Y, La/Yb and low Y, Yb contents. They also exhibit affinities of potassic rocks, e.g., alkali-rich, high K2O/Na2O ratios and enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILEs). Their Sr-Nd isotopic ratios are similar to coeval shoshonitic lamprophyres. Geochemical data indicate that they were probably produced by partial melting of newly underplated potassic rocks sourced from a modified and enriched lithospheric mantle. These underplated rocks have elevated oxygen fugacity, water and copper contents, with high metallogenic potential. We propose that all the studied potassic rocks were emplaced in a post-collisional setting, associated with the local removal of lithospheric mantle.

Questioning the Sedimentary Paradigm for Granites

NASA Astrophysics Data System (ADS)

Glazner, A. F.; Bartley, J. M.; Coleman, D. S.; Boudreau, A.; Walker, J. D.

2007-12-01

A critical question regarding volcano-pluton links is whether plutons are samples of magma that passed through on its way to eruption, or residues left behind after volcanic rocks were extracted. A persistent theme of recent work on granites sensu lato is that many are sedimentary accumulations of crystals that lost significant volumes of magmatic liquid. This view is based on observations of structures that clearly seem to reflect deposition on a magma chamber floor (e.g., flows of chilled mafic magma into silicic magma) and on the inference that many other structures, such as modal layering, truncated layering, and crystal accumulations, reflect crystal sedimentation on such chamber floors. There are significant physical and geochemical reasons to question this view, based on observations in the Sierra Nevada of California and similar results from other batholiths. First, few granites show the enrichments in Ba, Sr, and relative Eu that feldspar accumulation should produce. Second, sedimentary features such as graded bedding and cross-bedding form in highly turbulent flows, but turbulence is unachievable in viscous silicic liquids, where velocities on the order of 104 m/s would be required to induce turbulence in a liquid with η=104 Pa s. Third, tabular modally layered domains commonly cut surrounding modal layering on both sides, and orientations of modal layering and of the troughs of "ladder dikes" commonly scatter widely within hectare-sized areas; it is difficult to reconcile these features with gravity-driven settling. Fourth, accumulations of K-feldspar megacrysts are typically inferred to be depositional, but this is precluded by crystallization of most K- feldspar after rheologic lock-up occurs. Finally, accumulations of K-feldspar and hornblende are typically packed too tightly to be depositional. With analogy to layered mafic intrusions, many features attributed to crystal sedimentation in granites may be better explained by crystal aging and other in

Estimation of the indoor radon and the annual effective dose from granite samples

NASA Astrophysics Data System (ADS)

Sola, P.; Srinuttrakul, W.; Kewsuwan, P.

2015-05-01

Inhalation of radon and thoron daughters increases the risk of lung cancer. The main sources of indoor radon are building materials. The aim of this research is to estimate the indoor radon and the annual effective dose from the building materials. Eighteen granite samples bought from the markets in Thailand were measured using an ionization chamber (ATMOS 12 DPX) for the radon concentration in air. Radon exhalation rates were calculated from the radon concentration in chamber. The indoor radon from the granite samples ranged from 10.04 to 55.32 Bq·m-2·h-1 with an average value of 20.30 Bq·m-2·h-1 and the annual effective dose ranged from 0.25 to 1.39 mSv·y-1 with an average value of 0.48 mSv·y-1. The results showed that the annual effective doses of three granite samples were higher than the annual exposure limit for the general public (1 mSv·y-1) recommended by the International Commission on Radiological Protection (ICRP). In addition, the relationship between the colours and radon exhalation rates of granite samples was also explained.

Predicted indoor radon concentrations from a Monte Carlo simulation of 1,000,000 granite countertop purchases.

PubMed

Allen, J G; Zwack, L M; MacIntosh, D L; Minegishi, T; Stewart, J H; McCarthy, J F

2013-03-01

Previous research examining radon exposure from granite countertops relied on using a limited number of exposure scenarios. We expanded upon this analysis and determined the probability that installing a granite countertop in a residential home would lead to a meaningful radon exposure by performing a Monte Carlo simulation to obtain a distribution of potential indoor radon concentrations attributable to granite. The Monte Carlo analysis included estimates of the probability that a particular type of granite would be purchased, the radon flux associated with that type, the size of the countertop purchased, the volume of the home where it would be installed and the air exchange rate of that home. One million countertop purchases were simulated and 99.99% of the resulting radon concentrations were lower than the average outdoor radon concentrations in the US (14.8 Bq m(-3); 0.4  pCi l(-1)). The median predicted indoor concentration from granite countertops was 0.06 Bq m(-3) (1.59 × 10(-3) pCi l(-1)), which is over 2000 times lower than the US Environmental Protection Agency's action level for indoor radon (148 Bq m(-3); 4 pCi l(-1)). The results show that there is a low probability of a granite countertop causing elevated levels of radon in a home.

Weathering-Associated Bacteria from the Damma Glacier Forefield: Physiological Capabilities and Impact on Granite Dissolution ▿

PubMed Central

Frey, Beat; Rieder, Stefan R.; Brunner, Ivano; Plötze, Michael; Koetzsch, Stefan; Lapanje, Ales; Brandl, Helmut; Furrer, Gerhard

2010-01-01

Several bacterial strains isolated from granitic rock material in front of the Damma glacier (Central Swiss Alps) were shown (i) to grow in the presence of granite powder and a glucose-NH4Cl minimal medium without additional macro- or micronutrients and (ii) to produce weathering-associated agents. In particular, four bacterial isolates (one isolate each of Arthrobacter sp., Janthinobacterium sp., Leifsonia sp., and Polaromonas sp.) were weathering associated. In comparison to what was observed in abiotic experiments, the presence of these strains caused a significant increase of granite dissolution (as measured by the release of Fe, Ca, K, Mg, and Mn). These most promising weathering-associated bacterial species exhibited four main features rendering them more efficient in mineral dissolution than the other investigated isolates: (i) a major part of their bacterial cells was attached to the granite surfaces and not suspended in solution, (ii) they secreted the largest amounts of oxalic acid, (iii) they lowered the pH of the solution, and (iv) they formed significant amounts of HCN. As far as we know, this is the first report showing that the combined action of oxalic acid and HCN appears to be associated with enhanced elemental release from granite, in particular of Fe. This suggests that extensive microbial colonization of the granite surfaces could play a crucial role in the initial soil formation in previously glaciated mountain areas. PMID:20525872

Elemental analysis of granite by instrumental neutron activation analysis (INAA) and X-ray fluorescence analysis (XRF).

PubMed

El-Taher, A

2012-01-01

The instrumental neutron activation analysis technique (INAA) was used for qualitative and quantitative analysis of granite samples collected from four locations in the Aswan area in South Egypt. The samples were prepared together with their standards and simultaneously irradiated in a neutron flux of 7×10(11)n/cm(2)s in the TRIGA Mainz research reactor. Gamma-ray spectra from an hyper-pure germanium detector were analyzed. The present study provides the basic data of elemental concentrations of granite rocks. The following elements have been determined Na, Mg, K, Fe, Mn, Sc, Cr, Ti, Co, Zn, Ga, Rb, Zr, Nb, Sn, Ba, Cs, La, Ce, Nd, Sm, Eu, Yb, Lu, Hf, Ta, Th and U. The X-ray fluorescence (XRF) was used for comparison and to detect elements, which can be detected only by XRF such as F, S, Cl, Co, Cu, Mo, Ni, Pb, Se and V. The data presented here are our contribution to understanding the elemental composition of the granite rocks. Because there are no existing databases for the elemental analysis of granite, our results are a start to establishing a database for the Egyptian granite. It is hoped that the data presented here will be useful to those dealing with geochemistry, granite chemistry and related fields. Copyright © 2011 Elsevier Ltd. All rights reserved.

An orientation soil survey at the Pebble Cu-Au-Mo porphyry deposit, Alaska

USGS Publications Warehouse

Smith, Steven M.; Eppinger, Robert G.; Fey, David L.; Kelley, Karen D.; Giles, S.A.

2009-01-01

Soil samples were collected in 2007 and 2008 along three traverses across the giant Pebble Cu-Au-Mo porphyry deposit. Within each soil pit, four subsamples were collected following recommended protocols for each of ten commonly-used and proprietary leach/digestion techniques. The significance of geochemical patterns generated by these techniques was classified by visual inspection of plots showing individual element concentration by each analytical method along the 2007 traverse. A simple matrix by element versus method, populated with a value based on the significance classification, provides a method for ranking the utility of methods and elements at this deposit. The interpretation of a complex multi-element dataset derived from multiple analytical techniques is challenging. An example of vanadium results from a single leach technique is used to illustrate the several possible interpretations of the data.

Porphyry copper deposit model: Chapter B in Mineral deposit models for resource assessment

USGS Publications Warehouse

Ayuso, Robert A.; Barton, Mark D.; Blakely, Richard J.; Bodnar, Robert J.; Dilles, John H.; Gray, Floyd; Graybeal, Fred T.; Mars, John L.; McPhee, Darcy K.; Seal, Robert R.; Taylor, Ryan D.; Vikre, Peter G.; John, David A.

2010-01-01

This report contains a revised descriptive model of porphyry copper deposits (PCDs), the world's largest source (about 60 percent) and resource (about 65 percent) of copper and a major source of molybdenum, gold and silver. Despite relatively low grades (average 0.44 percent copper in 2008), PCDs have significant economic and societal impacts due to their large size (commonly hundreds of millions to billions of metric tons), long mine lives (decades), and high production rates (billions of kilograms of copper per year). The revised model describes the geotectonic setting of PCDs, and provides extensive regional- to deposit-scale descriptions and illustrations of geological, geochemical, geophysical, and geoenvironmental characteristics. Current genetic theories are reviewed and evaluated, knowledge gaps are identified, and a variety of exploration and assessment guides are presented. A summary is included for users seeking overviews of specific topics.

Geochemical behavior of rare earth elements of the hydrothermal alterations within the Tepeoba porphyry Cu-Mo-Au deposits at Balikesir, NW Turkey

NASA Astrophysics Data System (ADS)

Doner, Zeynep; Abdelnasser, Amr; Kiran Yildirim, Demet; Kumral, Mustafa

2016-04-01

This work reports the geochemical characteristics and behavior of the rare earth elements (REE) of the hydrothermal alteration of the Tepeoba porphyry Cu-Mo-Au deposit located in the Anatolian tectonic belt at Biga peninsula (Locally Balikesir province), NW Turkey. The Cu-Mo-Au mineralization at this deposit hosted in the hornfels rocks and related to the silicic to intermediate intrusion of Eybek pluton. It locally formed with brecciated zones and quartz vein stockworks, as well as the brittle fracture zones associated with intense hydrothermal alteration. Three main alteration zones with gradual boundaries formed in the mine area in the hornfels rock that represents the host rock, along that contact the Eybek pluton; potassic, propylitic and phyllic alteration zones. The potassic alteration zone that formed at the center having high amount of Cu-sulfide minerals contains biotite, muscovite, and sericite with less amount of K-feldspar and associated with tourmalinization alteration. The propylitic alteration surrounds the potassic alteration having high amount of Mo and Au and contains chlorite, albite, epidote, calcite and pyrite. The phyllic alteration zone also surrounds the potassic alteration containing quartz, sericite and pyrite minerals. Based on the REE characteristics and content and when we correlate the Alteration index (AI) with the light REEs and heavy REEs of each alteration zone, it concluded that the light REEs decrease and heavy REEs increase during the alteration processes. The relationships between K2O index with Eu/Eu* and Sr/Sr* reveals a positive correlation in the potassic and phyllic alteration zones and a negative correlation in the propylitic alteration zone. This refers to the hydrothermal solution which is responsible for the studied porphyry deposits and associated potassic and phyllic alterations has a positive Eu and Sr anomaly as well as these elements were added to the altered rock from the hydrothermal solution. Keywords: Rare

Quantum states of neutrons in the gravitational and centrifugal potentials in a new GRANIT spectrometer

ScienceCinema

Nesvizhevsky, Valery

2018-05-14

We will discuss the scientific program to be studied in a new gravitational spectrometer GRANIT in a broad context of quantum states (quantum behaviour) of ultracold neutrons (UCN) in gravitational [1] and centrifugal [2] potentials, as well as applications of these phenomena/spectrometer to various domains of physics, ranging from studies of fundamental short-range interactions and symmetries to neutron quantum optics and reflectometry using UCN. All these topics, as well as related instrumental and methodical developments have been discussed during dedicated GRANIT-2010 Workshop [3]. The GRANIT spectrometer has been recently installed at the Institut Laue-Langevin, Grenoble, France [4] and could become operational in near future. 1. V.V. Nesvizhevsky et al (2002), Nature 415, 297. 2. V.V. Nesvizhevsky et al (2010), Nature Physics 6, 114. 3. GRANIT-2010, Les Houches, 14-19 february 2010. 4. M. Kreuz et al (2009), NIM 611, 326.

Peralkaline and peraluminous granites and related mineral deposits of the Arabian Shield, Kingdom of Saudi Arabia

USGS Publications Warehouse

Elliott, James E.

1983-01-01

Existing geochemical and geologic data for many parts of the Arabian Shield were compiled as a basis for evaluating the resource potential of the granites of the Shield. Commodities associated with granites that have potential for economic mineral deposits include tin, tungsten, molybdenum, beryllium, niobium, tantalum, zirconium, uranium, thorium, rare-earth elements, and fluorite. Prospecting methods useful in discriminating those granites having significant economic potential include reconnaissance geologic mapping, petrographic and mineralogic studies, geochemical sampling of rock and wadi sediment, and radiometric surveying.

Phase equilibrium modelling of granite magma petrogenesis: B. An evaluation of the magma compositions that result from fractional crystallization

NASA Astrophysics Data System (ADS)

Garcia-Arias, Marcos; Stevens, Gary

2017-04-01

Several fractional crystallization processes (flow segregation, gravitational settling, filter-pressing), as well as batch crystallization, have been investigated in this study using thermodynamic modelling (pseudosections) to test whether they are able to reproduce the compositional trends shown by S-type granites. Three starting compositions comprising a pure melt phase and variable amounts of entrained minerals (0, 20 and 40 wt.% of the total magma) have been used to study a wide range of likely S-type magma compositions. The evolution of these magmas was investigated from the segregation from their sources at 0.8 GPa until emplacement at 0.3 GPa in an adiabatic path, followed by isobaric cooling until the solidus was crossed, in a closed-system scenario. The modelled magmas and the fractionated mineral assemblages are compared to the S-type granites of the Peninsula pluton, Cape Granite Suite, South Africa, which have a composition very similar to most of the S-type granites. The adiabatic ascent of the magmas digests partially the entrained mineral assemblage of the magmas, but unless this entrained assemblage represents less than 1 wt.% of the original magma, part of the mineral fraction survives the ascent up to the chosen pressure of emplacement. At the level of emplacement, batch crystallization produces magmas that only plot within the composition of the granites of the Peninsula pluton if the bulk composition of the original magmas already matched that of the granites. Flow segregation of crystals during the ascent and gravitational settling fractional crystallization produce bodies that are generally more mafic than the most mafic granites of the pluton and the residual melts have an almost haplogranitic composition, producing a bimodal compositional distribution not observed in the granites. Consequently, these two processes are ruled out. Filter-pressing fractional crystallization produces bodies in an onion-layer structure that become more felsic

Sorption of Eu(III) on granite: EPMA, LA-ICP-MS, batch and modeling studies.

PubMed

Fukushi, Keisuke; Hasegawa, Yusuke; Maeda, Koushi; Aoi, Yusuke; Tamura, Akihiro; Arai, Shoji; Yamamoto, Yuhei; Aosai, Daisuke; Mizuno, Takashi

2013-11-19

Eu(III) sorption on granite was assessed using combined microscopic and macroscopic approaches in neutral to acidic conditions where the mobility of Eu(III) is generally considered to be high. Polished thin sections of the granite were reacted with solutions containing 10 μM of Eu(III) and were analyzed using EPMA and LA-ICP-MS. On most of the biotite grains, Eu enrichment up to 6 wt % was observed. The Eu-enriched parts of biotite commonly lose K, which is the interlayer cation of biotite, indicating that the sorption mode of Eu(III) by the biotite is cation exchange in the interlayer. The distributions of Eu appeared along the original cracks of the biotite. Those occurrences indicate that the prior water-rock interaction along the cracks engendered modification of biotite to possess affinity to the Eu(III). Batch Eu(III) sorption experiments on granite and biotite powders were conducted as functions of pH, Eu(III) loading, and ionic strength. The macroscopic sorption behavior of biotite was consistent with that of granite. At pH > 4, there was little pH dependence but strong ionic strength dependence of Eu(III) sorption. At pH < 4, the sorption of Eu(III) abruptly decreased with decreased pH. The sorption behavior at pH > 4 was reproducible reasonably by the modeling considering single-site cation exchange reactions. The decrease of Eu(III) sorption at pH < 4 was explained by the occupation of exchangeable sites by dissolved cationic species such as Al and Fe from granite and biotite in low-pH conditions. Granites are complex mineral assemblages. However, the combined microscopic and macroscopic approaches revealed that elementary reactions by a single mineral phase can be representative of the bulk sorption reaction in complex mineral assemblages.

Petrographic and geochemical characterization of the granitic rocks of the Araguainha impact crater, Brazil

NASA Astrophysics Data System (ADS)

Silva, Dailto; Lana, Cristiano; Souza Filho, Carlos Roberto

2016-03-01

Petrographic and geochemical data obtained on the Araguainha impact crater (Goiás/Mato Grosso States, Brazil) indicate the existence of several molten products that originated during impact-induced congruent melting of an alkali-granite exposed in the inner part of the central uplift of the structure. Although previous studies have described these melts to some extent, there is no detailed discussion on the petrographic and geochemical variability in the granite and its impactogenic derivatives, and therefore, little is known about the geochemical behavior and mobility of trace elements during its fusion in the central part of the Araguainha crater. This paper demonstrates that the preserved granitoid exposed in the core of the structure is a magnesium-rich granite, similar to postcollisional, A-type granites, also found in terrains outside the Araguainha crater, in the Brasília orogenic belt. The molten products are texturally distinct and different from the original rock, but have very similar geochemical composition, making it difficult to separate these lithotypes based on concentrations of major and minor elements. This also applies for trace and rare earth elements (REE), thus indicating a high degree of homogenization during impact-induced congruent melting under high pressure and postshock temperature conditions. Petrographic observations, along with geochemical data, indicate that melting occurs selectively, where some of the elements are transported with the melt. Simultaneously, there is an effective dissolution of the rock (granite), which leads to entrainment of the most resistant solid phases (intact or partially molten minerals) into the melt. Minerals more resistant to melting, such as quartz and oxides, contribute substantially to a chemical balance between the preserved granite and the fusion products generated during the meteoritic impact.

Fe isotopes and the contrasting petrogenesis of A-, I- and S-type granite

NASA Astrophysics Data System (ADS)

Foden, John; Sossi, Paolo A.; Wawryk, Christine M.

2015-01-01

We present new Fe isotope data of 42 S-, I- and A-type (ferroan) granites from the Cambrian Delamerian orogen in South Australia, the Palaeozoic Lachlan Fold Belt and Western USA. Interpretation of these data, together with modelling suggests that magmatic processes do result in quite complex Fe-isotopic differentiation trends and can lead to granites with isotopically heavy iron with δ57Fe > 0.35‰. By comparison Mid-Ocean Ridge Basalts (MORBs) have δ57Fe = 0.15‰ (Teng et al., 2013). These variations are similar to those previously reported (Poitrasson and Freydier, 2005; Heimann et al., 2008; Telus et al., 2012), but, contrary to some interpretations (Beard and Johnson, 2006; Heimann et al., 2008), heavy values are not necessarily the product of late-stage hydrothermal fluid loss, though this process is undoubtedly also an important factor in some circumstances. A-type (ferroan) granites reach very heavy δ57Fe values (0.4-0.5‰) whereas I-types are systematically lighter (δ57Fe = 0.2‰). S-type granites show a range of intermediate values, but also tend to be isotopically heavy (δ57Fe ≈ 0.2-0.4‰). Our results show that the iron isotopic values and trends are signatures that reflect granite generation processes. A modelling using the Rhyolite-MELTS software suggests that contrasting trajectories and end-points in Fe isotope evolution towards granite depend on: oxidation state of the evolving magma and, whether or not the system is oxygen-buffered. Iron isotopic evolution supports an origin of ferroan A-type granite from protracted, closed magma chamber fractionation of moderately reduced mafic magmas. In these systems magnetite saturation is delayed and the ferric iron budget is finite. I-type systems originate with the supply of relatively oxidised, hydrous, subduction-related magmas from the mantle wedge to the upper plate crust. These then experience oxygen-buffered open-system AFC processes in lower crustal hot-zones. S-type magmas are crustal

Chronology and petrogenesis of a 1.8 g lunar granitic clast:14321,1062

NASA Technical Reports Server (NTRS)

Shih, C.-Y.; Bansal, B. M.; Wiesmann, H.; Nyquist, L. E.; Bogard, D. D.; Wooden, J. L.

1985-01-01

Geochronological, isotopic, and trace element data for a pristine granite clast from Apollo 14 breccia 14321 obtained using Rb-Sr, Sm-Nd, and (Ar-39)-(Ar-40) methods are presented. Trace element data for a possibly related evolved rock, the quartz-monodiorite clast from breccia 15404 are also presented, and the relationship between these two rock types is discussed. The concordancy of the Rb-Sr and Sm-Nd internal isochron ages and especially the Rb-Sr model age strongly suggest that the granite clast formed 4.1 AE ago. It probably crystallized slowly in the crust and was later excavated and brecciated about 3.88 AE ago, as indicated by the Ar-Ar age. A two-stage model involving crystal fractionation followed by silicate liquid immiscibility is proposed for the lunar granite genesis.

Sources of granite magmatism in the Embu Terrane (Ribeira Belt, Brazil): Neoproterozoic crust recycling constrained by elemental and isotope (Sr-Nd-Pb) geochemistry

NASA Astrophysics Data System (ADS)

Alves, Adriana; Janasi, Valdecir de Assis; Campos Neto, Mario da Costa

2016-07-01

Whole rock elemental and Sr-Nd isotope geochemistry and in situ K-feldspar Pb isotope geochemistry were used to identify the sources involved in the genesis of Neoproterozoic granites from the Embu Terrane, Ribeira Belt, SE Brazil. Granite magmatism spanned over 200 Ma (810-580 Ma), and is dominated by crust-derived relatively low-T (850-750 °C, zircon saturation) biotite granites to biotite-muscovite granites. Two Cryogenian plutons show the least negative εNdt (-8 to -10) and highest mg# (30-40) of the whole set. Their compositions are strongly contrasted, implying distinct sources for the peraluminous (ASI ∼ 1.2) ∼660 Ma Serra do Quebra-Cangalha batholith (metasedimentary rocks from relatively young upper crust with high Rb/Sr and low Th/U) and the metaluminous (ASI = 0.96-1.00) ∼ 630 Ma Santa Catarina Granite. Although not typical, the geochemical signature of these granites may reflect a continental margin arc environment, and they could be products of a prolonged period of oceanic plate consumption started at ∼810 Ma. The predominant Ediacaran (595-580 Ma) plutons have a spread of compositions from biotite granites with SiO2 as low as ∼65% (e.g., Itapeti, Mauá, Sabaúna and Lagoinha granites) to fractionated muscovite granites (Mogi das Cruzes, Santa Branca and Guacuri granites; up to ∼75% SiO2). εNdT are characteristically negative (-12 to -18), with corresponding Nd TDM indicating sources with Paleoproterozoic mean crustal ages (2.0-2.5 Ga). The Guacuri and Santa Branca muscovite granites have the more negative εNdt, highest 87Sr/86Srt (0.714-0.717) and lowest 208Pb/206Pb and 207Pb/206Pb, consistent with an old metasedimentary source with low time-integrated Rb/Sr. However, a positive Nd-Sr isotope correlation is suggested by data from the other granites, and would be consistent with mixing between an older source predominant in the Mauá granite and a younger, high Rb/Sr source that is more abundant in the Lagoinha granite sample. The

Lower Granite Dam Smolt Monitoring Program, 1999 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verhey, Peter; Morrill, Charles; Mensik, Fred

1999-01-01

The 1999 fish collection season at Lower Granite was characterized by high spring flows and spill, low levels of debris, cool water temperatures, increased hatchery chinook numbers, and an overall decrease in numbers of smolts collected and transported. A total of 5,882,872 juvenile salmonids were collected at Lower Granite. Of these, 5,466,057 were transported to release sites below Bonneville Dam, 5,232,105 by barge and 233,952 by truck. An additional 339,398 fish were bypassed back to the river. A total of 117,609 salmonids were examined in daily samples. Nine research projects conducted by four agencies impacted a total of 440,810 smoltsmore » (7.5% of the total collected) of which 247,268 were PIT tagged and 572 were recorded as incidental mortalities.« less

The 131-134 Ma A-type granites from northern Zhejiang Province, South China: Implications for partial melting of the Neoproterozoic lower crust

NASA Astrophysics Data System (ADS)

Hu, Qinghai; Yu, Kaizhang; Liu, Yongsheng; Hu, Zhaochu; Zong, Keqing

2017-12-01

Although Mesozoic granites are widely distributed in the Gan-Hang Belt in Southeast China, their petrogenesis and geodynamic settings are still matters of dispute. Here, the major and trace elements, Sr-Nd isotopic compositions, zircon U-Pb dating and Hf isotopes of three late Mesozoic granite plutons from Machebu, Shenzhongwu and Daixi in northern Zhejiang Province were analyzed to investigate their petrogenesis. These granite plutons are featured by an A2-type granite geochemical signature (e.g., high SiO2 (71 to 78 wt.%), total alkalis (Na2O + K2O = 7.57 to 9.12 wt.%), rare earth elements (total REE = 174 to 519 ppm) and HFSE contents, with mostly high FeOT/(FeOT + MgO) (0.82 to 0.93) and Ga/Al ratios (2.49 to 5.07) and low Ce4 +/Ce3 + ratios in zircons (1 to 90)), suggesting they were formed in an extensional tectonic setting. Combining whole rock Zr contents, mineral assemblages and the An content of plagioclase, it was suggested that these granites could have formed at a high temperature (> 850 °C) with a low H2O content ( 2.5 wt.%). Assuming the granite with the lowest SiO2 and high CaO contents as the "primary granite melt", the melting pressure was estimated to be 2.5 kbar based on model calculations using MELTs. Taking into account the effect of plagioclase fractional crystallization during the granite emplacement into shallow crustal levels, the initial melting pressure could be > 2.5 kbar at the stable field of plagioclase. This agrees well with the very low and variable Sr and Eu contents of these granite plutons. Zircon U-Pb dating yields a weighted mean 206Pb/238U age of 130.9 ± 1.0 Ma for the Machebu granite, 134.4 ± 2.1 Ma for the Shenzhongwu granite and 131.9 ± 1.2 Ma for the Daixi granite. The εHf(t) values of the zircons in these plutons gradually increase from southwest to northeast, i.e., from - 14.5 - 3.5 for the Machebu granite to - 1.5 - 0.2 for the Shenzhongwu granite and from 5.1 8.6 for the Daixi granite, suggesting the origin of

Health assessment of natural radioactivity and radon exhalation rate in granites used as building materials in Lebanon.

PubMed

Kobeissi, M A; El-Samad, O; Rachidi, I

2013-03-01

Measurements of specific activities (Bq kg(-1)) of gamma-emissions from radioactive nuclides, (238)U, (226)Ra, (214)Bi, (232)Th, (212)Pb and (40)K, contained in 28 granite types, used as building materials in indoors in Lebanon, were performed on the powdered granites. The concentration of the nuclides, (226)Ra, (232)Th and (40)K, in the granites varied from below detection level (BDL) to 494 Bq kg(-1), BDL to 157.2 Bq kg(-1) and BDL to 1776 Bq kg(-1), respectively. (226)Ra concentration equivalents, C(Raeq), were obtained and ranged between 37 and 591 Bq kg(-1), with certain values above the allowed limit of 370 Bq kg(-1). Calculated annual gamma-absorbed dose in air, D(aR), varied from 17.7 to 274.5 (nGy h(-1)). Annual effective dose, E (mSv y(-1)), of gamma radiations related to the studied granites and absorbed by the inhabitants was evaluated. E (mSv y(-1)) ranged from 0.09 to 1.35 mSv y(-1). Some granite types produced E above the allowed limit of 1 mSv y(-1) set by ICRP. Values of (222)Rn mass exhalation rate, E(M) (mBq kg(-1)h(-1))(,) in granite powder were obtained using the CR-39 detector technique. Diffusion factors, f, in 23 granite types were calculated with f ranging between (0.1 ± 0.02)×10(-2) and (6.6 ± 1.01)×10(-2).

Lift Off (Granite City C. U. School District 9)

ERIC Educational Resources Information Center

Goodall, Robert C.; And Others

1970-01-01

Describes and evaluates the ESEA Title I program in Granite City (Illinois) target area schools which provide preschool classes, remedial reading, and supportive health and counseling services. The programs are considered to be efficient. (DM)

Timing of multiple hydrothermal events in the iron oxide-copper-gold deposits of the Southern Copper Belt, Carajás Province, Brazil

NASA Astrophysics Data System (ADS)

Moreto, Carolina P. N.; Monteiro, Lena V. S.; Xavier, Roberto P.; Creaser, Robert A.; DuFrane, S. Andrew; Melo, Gustavo H. C.; Delinardo da Silva, Marco A.; Tassinari, Colombo C. G.; Sato, Kei

2015-06-01

The Southern Copper Belt, Carajás Province, Brazil, hosts several iron oxide-copper-gold (IOCG) deposits, including Sossego, Cristalino, Alvo 118, Bacuri, Bacaba, Castanha, and Visconde. Mapping and U-Pb sensitive high-resolution ion microprobe (SHRIMP) IIe zircon geochronology allowed the characterization of the host rocks, situated within regional WNW-ESE shear zones. They encompass Mesoarchean (3.08-2.85 Ga) TTG orthogneiss, granites, and remains of greenstone belts, Neoarchean (ca. 2.74 Ga) granite, shallow-emplaced porphyries, and granophyric granite coeval with gabbro, and Paleoproterozoic (1.88 Ga) porphyry dykes. Extensive hydrothermal zones include albite-scapolite, biotite-scapolite-tourmaline-magnetite alteration, and proximal potassium feldspar, chlorite-epidote and chalcopyrite formation. U-Pb laser ablation multicollector inductively coupled mass spectrometry (LA-MC-ICP-MS) analysis of ore-related monazite and Re-Os NTIMS analysis of molybdenite suggest multiple Neoarchean (2.76 and 2.72-2.68 Ga) and Paleoproterozoic (2.06 Ga) hydrothermal events at the Bacaba and Bacuri deposits. These results, combined with available geochronological data from the literature, indicate recurrence of hydrothermal systems in the Southern Copper Belt, including 1.90-1.88-Ga ore formation in the Sossego-Curral ore bodies and the Alvo 118 deposit. Although early hydrothermal evolution at 2.76 Ga points to fluid migration coeval with the Carajás Basin formation, the main episode of IOCG genesis (2.72-2.68 Ga) is related to basin inversion coupled with Neoarchean (ca. 2.7 Ga) felsic magmatism. The data suggest that the IOCG deposits in the Southern Copper Belt and those in the Northern Copper Belt (2.57-Ga Salobo and Igarapé Bahia-Alemão deposits) do not share a common metallogenic evolution. Therefore, the association of all IOCG deposits of the Carajás Province with a single extensive hydrothermal system is precluded.

The Influence of Temperature on Time-Dependent Deformation and Failure in Granite: A Mesoscale Modeling Approach

NASA Astrophysics Data System (ADS)

Xu, T.; Zhou, G. L.; Heap, Michael J.; Zhu, W. C.; Chen, C. F.; Baud, Patrick

2017-09-01

An understanding of the influence of temperature on brittle creep in granite is important for the management and optimization of granitic nuclear waste repositories and geothermal resources. We propose here a two-dimensional, thermo-mechanical numerical model that describes the time-dependent brittle deformation (brittle creep) of low-porosity granite under different constant temperatures and confining pressures. The mesoscale model accounts for material heterogeneity through a stochastic local failure stress field, and local material degradation using an exponential material softening law. Importantly, the model introduces the concept of a mesoscopic renormalization to capture the co-operative interaction between microcracks in the transition from distributed to localized damage. The mesoscale physico-mechanical parameters for the model were first determined using a trial-and-error method (until the modeled output accurately captured mechanical data from constant strain rate experiments on low-porosity granite at three different confining pressures). The thermo-physical parameters required for the model, such as specific heat capacity, coefficient of linear thermal expansion, and thermal conductivity, were then determined from brittle creep experiments performed on the same low-porosity granite at temperatures of 23, 50, and 90 °C. The good agreement between the modeled output and the experimental data, using a unique set of thermo-physico-mechanical parameters, lends confidence to our numerical approach. Using these parameters, we then explore the influence of temperature, differential stress, confining pressure, and sample homogeneity on brittle creep in low-porosity granite. Our simulations show that increases in temperature and differential stress increase the creep strain rate and therefore reduce time-to-failure, while increases in confining pressure and sample homogeneity decrease creep strain rate and increase time-to-failure. We anticipate that the

Timing of Multiple Stages of Granitic Magmatisms: Constraints on Shearing along the Ailao Shan-Red River Shear Zone

NASA Astrophysics Data System (ADS)

Chen, W.; Liu, J.; Fan, W.; Feng, J.; DAO, H.; Yan, J.

2017-12-01

The Ailao Shan-Red River (ASRR) shear zone is a large scale shear zone resulted from collision between India and Euro-Asia Plates in Cenozoic. Magmatisms related to the shear zone evolution took place before, during or after shearing process that contributes to pre-, syn- and post- granitic emplacement. Combined structure, fabric and geochronology analyses of granitic rocks within sheared Proterozoic country rocks along the ASRR shear zone offer important clues on timing of shearing activity and constraining on transformation of types of the shearing. Zircon U-Pb dating results indicate that the granitic intrusions within the ASRR shear zone are broadly grouped into two stages: Permo-Triassic (256.0±6.0 Ma, 244.0±7.6 Ma and 234.0±9.3 Ma) and Cenozoic (27.1±1.5 Ma, 26.34±0.62 Ma and 25.10±0.61 Ma). The Permo-Triassic intrusions show evidences for intensive mylonitization. The older Cenozoic granitic rocks were also strongly sheared, but the younger Cenozoic granites were weakly sheared and they cut across early intrusions (e.g. the Permo-Triassic and older Cenozoic intrusions). Petrographic microscope observations suggest that the Permo-Triassic granitic intrusions show prominent superimposition of high temperature mylonization by low temperature mylonization. Quartz c-axis fabrics of the granites demonstrate that there are multiple maxima due to the superimposition. The older Cenozoic granitic intrusion of 27.1±1.5 Ma shows weak mylonization and possess four symmetrical point maxima in their quartz c-axis fabrics. The EBSD data indicate that the intrusion experienced pure shearing. Intrusions of 26.34±0.62 Ma and 25.10±0.61 Ma show evidences for very weak mylonization. The quartz c-axis patterns of the rocks dominantly resulted from low temperature deformation by simple shearing. It is concluded, in summary, that: (1) Permo-Triassic granitic intrusions experienced superimposed shearing of high and low temperatures; (2) Evidences for both early pure

Laboratory grown subaerial biofilms on granite: application to the study of bioreceptivity.

PubMed

Vázquez-Nion, Daniel; Silva, Benita; Troiano, Federica; Prieto, Beatriz

2017-01-01

Simulated environmental colonisation of granite was induced under laboratory conditions in order to develop an experimental protocol for studying bioreceptivity. The experimental set-up proved suitable for producing subaerial biofilms by inoculating granite blocks with planktonic multi-species phototrophic cultures derived from natural biofilms. The ability of four different cultures to form biofilms was monitored over a three-month growth period via colour measurements, quantification of photosynthetic pigments and EPS, and CLSM observations. One of the cultures under study, which comprised several taxa including Bryophyta, Charophyta, Chlorophyta and Cyanobacteria, was particularly suitable as an inoculum, mainly because of its microbial richness, its rapid adaptability to the substratum and its high colonisation capacity. The use of this culture as an inoculum in the proposed experimental set-up to produce subaerial biofilms under laboratory conditions will contribute to standardising the protocols involved, thus enabling more objective assessment of the bioreceptivity of granite in further experiments.

Pattern of elemental release during the granite dissolution can be changed by aerobic heterotrophic bacterial strains isolated from Damma Glacier (central Alps) deglaciated granite sand.

PubMed

Lapanje, Aleš; Wimmersberger, Celine; Furrer, Gerhard; Brunner, Ivano; Frey, Beat

2012-05-01

Colonisation and weathering of freshly deglaciated granite are key processes in initial soil formation and development. We have obtained 438 isolates from granite sand covering glacial toe, 284 isolates at 22°C and 154 at 4°C incubation temperatures, respectively, to obtain cultures for the investigation of their weathering capabilities under laboratory conditions. The isolation of bacteria from granite sand was performed on rich-, intermediate- and low-nutrient-content solid media. Isolates were identified by 16S rRNA gene sequencing. According to the genera-associated weathering capabilities described in the literature and according to their abundance in our culture collection, we selected eight strains to analyse their effects on the weathering dynamics of granite sand during the batch culture experiment. Analysis of culturable bacteria showed higher species richness among isolates from 22°C than from 4°C incubations. In the R2A and 1/100 Ravan media, we observed the highest species richness of isolates obtained at 22°C and 4°C incubation temperatures, respectively. The obtained 16S rRNA sequences revealed the presence of alpha-, beta- and gamma-proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. The most numerous group of isolates was distantly related to Collimonas representatives, and according to the sequences of the 16S rRNA genes, they can form a new genus. Isolates from this group had the capability of causing increased dissolution rates for Fe, W, Ni and Rb. In general, at each sampling during the 30-day experiment, every strain showed a unique weathering profile resulting from differential rates of the dissolution and the precipitation of different minerals in the batch culture. Consequently, the presence of different strains, their growth stage and changes in proportions of strains in the bacterial community can affect further soil development and the successive colonisation by plants.

A-type granites and related rocks: Evolution of a concept, problems and prospects

NASA Astrophysics Data System (ADS)

Bonin, Bernard

2007-08-01

Although A-type granites have long been recognized as a distinct group of granites, the term A-type was coined first less than thirty years ago. A-type suites occur in geodynamic contexts ranging from within-plate settings to plate boundaries, locations and times of emplacement are not random. Rare in the lower crust, as some charnockite suites, they are fairly common at shallower depths, especially at the subvolcanic level where they form ring complexes rooting caldera volcanoes. Characteristic features include hypersolvus to transsolvus to subsolvus alkali feldspar textures, iron-rich mafic mineralogy, bulk-rock compositions yielding ferroan, alkali-calcic to alkaline affinities, high LILE+HFSE abundances, and pronounced anomalies due to high degrees of mineral fractionation. Isotopic features evidence sources containing a large mantle input. Experimental data show that A-type magmas contain dissolved OH F-bearing fluids, crystallised under reduced and oxidized conditions, and yield high-temperature liquidus, favouring early crystallisation of anhydrous iron minerals, such as fayalite. Though many petrogenetic models imply solely crustal derivation, no convincing A-type liquids were produced experimentally from crustal materials, nor have any leucosomes of A-type composition been detected within migmatitic terranes. As it occurs in association with mafic igneous rocks in continents as well as on the ocean floor, A-type granite is likely to come from mantle-derived transitional to alkaline mafic to intermediate magmas. Rare felsic materials found in the meteoritic and lunar record yield dominantly A-type features. Contrary to the more common types of granite, A-type granite is, therefore, not typical of Earth and was produced in planetary environments differing from those prevailing on Earth.

Zircon dating and mineralogy of the Mokong Pan-African magmatic epidote-bearing granite (North Cameroon)

NASA Astrophysics Data System (ADS)

Tchameni, R.; Sun, F.; Dawaï, D.; Danra, G.; Tékoum, L.; Nomo Negue, E.; Vanderhaeghe, O.; Nzolang, C.; Dagwaï, Nguihdama

2016-09-01

We present the mineralogy and age of the magmatic epidote-bearing granite composing most of the Mokong pluton, in the Central Africa orogenic belt (North Cameroon). This pluton intrudes Neoproterozoic (~830 to 700 Ma) low- to high-grade schists and gneisses (Poli-Maroua group), and is crosscut or interleaved with bodies of biotite granite of various sizes. The pluton is weakly deformed in its interior, but solid-state deformation increases toward its margins marked by narrow mylonitic bands trending NNE-SSW. The magmatic epidote granitic rocks are classified as quartz monzodiorite, granodiorite, monzogranite, and syenogranite. They are medium- to coarse-grained and composed of K-feldspar + plagioclase + biotite + amphibole + epidote + magnetite + titanite + zircon + apatite. In these granites, the pistacite component [atomic Fe+3/(Fe3+ + Al)] in epidote ranges from 16 to 29 %. High oxygen fugacity (log ƒO2 - 14 to -11) and the preservation of epidote suggest that the magma was oxidized. Al-in hornblende barometry and hornblende-plagioclase thermometry indicate hornblende crystallization between 0.53 and 0.78 GPa at a temperature ranging from 633 to 779 °C. Zircon saturation thermometry gives temperature estimates ranging from 504 to 916 °C, the latter being obtained on samples containing inherited zircons. U/Pb geochronology by LA-ICP-MS on zircon grains characterized by magmatic zoning yields a concordia age of 668 ± 11 Ma (2 σ). The Mokong granite is the only known occurrence magmatic epidote in Cameroon, and is an important milestone for the comparison of the Central Africa orogenic belt with the Brasiliano Fold Belt, where such granites are much more abundant.

Fertility of Rare-Metal Peraluminous Granites and Formation Conditions of Tungsten Deposits

NASA Astrophysics Data System (ADS)

Syritso, L. F.; Badanina, E. V.; Abushkevich, V. S.; Volkova, E. V.; Terekhov, A. V.

2018-01-01

The tungsten distribution in rocks of the Kukulbei Complex in eastern Transbaikal region results in a high potential of rare-metal peraluminous granites (RPG) for W mineralization and displays a different behavior of W in Li-F and "standard" RPG. These subtypes differ in the behavior of W in melt, spatial localization of mineralization, and the timing of wolframite crystallization relative to the age of the parental granitic rocks. The significant of W concentration is assumed to be due to fractionation of the Li-F melt; however, wolframite mineralization in Li-F enriched granite is not typical in nature. The results of experiments and our calculations of W solubility in granitic melt show that wolframite hardly ever crystallizes directly from melt; it likely migrates in the fluid phase and is then removes from the magma chamber to the host rocks, where secondary concentration takes place in exocontact greisens and quartz-cassiterite-wolframite veins. At the same time, the isotopic age of accessory wolframite (139.5 ± 2.1 Ma) within the Orlovka massif of Li-F granite is close to the formation age of the massif (140.6 ± 2.9 Ma). A different W behavior is recorded in the RPG subtype with a low lithium and fluorine concentration, exemplified by the Spokoininsky massif. There is no significant W gain in the melt. All varieties of wolframite mineralization in the Spokoininsky massif are derived from greisens, veins, and pegmatoids yielding the same crystallization ages (139.5 ± 1.1 Ma), which are 0.9-1.8 Ma later (taking into account the mean-square weighted deviation) than the Spokoininsky granite formation (144.5 ± 1.4 Ma). Perhaps this period corresponds to the time of transition from the magmatic stage to hydrothermal alteration. Comparison of the isotope characteristics (Rb-Sr and Sm-Nd isotope systems) of rocks and the associated ore minerals (wolframite, cassiterite) from all examined deposits shows a depletion in ɛNd values for ore minerals relative to the

A Study on Tribological Behavior of Glass-Epoxy Composite Filled with Granite Dust

NASA Astrophysics Data System (ADS)

Ray, Subhrajit; Rout, Arun Ku; KuSahoo, Ashok

2017-08-01

Granite powder is one of the solid wastes generated from stone processing industry used as organic filler replacing the conventional ceramic fillers in polymer matrix composite to increase the mechanical properties. The present work investigates the addition of granite powder on erosion wear properties of epoxy-glass fiber composite. The solid particle erosion wear rates of these hybrid composites are recorded considering various control parameters as impingement angles, erodent sizes and impact velocities following erosion resistance test in an air erosion test device at room temperatures. The test was conducted as per the Taguchi experimental design to minimize the erosion loss of material. The SEM views show the surface resistivity for the granite added specimens. The microscopic study also indicates various methods of material removal, crater wear and other subjective allocation during erosion experiment of the samples.

Petrogenesis of the Bosworgey granitic cusp in the SW England tin province and its implications for ore mineral genesis

NASA Astrophysics Data System (ADS)

Ball, T. K.; Basham, I. R.

1984-01-01

The Bosworgey granite cusp forms an apical portion of the concealed northern extension of the Tregonning-Godolphin granite ridge. It is characterised by unusually high values of B, P, Mn, Fe, As, Cu, Nb, Ta, Bi, Sn, W, U and S which are present largely as tourmaline, apatite, pyrite, arsenopyrite, chalcopyrite, bismuth, columbite, cassiterite, wolframite and uraninite; and low levels of Zr, Hf, Ti and REE present in zircon, ilmenite and monazite. The granite is classified as Sn and W “specialised” (Tischendorf, 1974) and it belongs to the ilmenite series of Japanese workers. The classification of Chappell and White (1974) (“S” and “I” type granites) is shown to be inapplicable to Cornubian rocks although the Bosworgey samples show characteristics of “S” type granites. The accessory mineral assemblages are typical of high temperature lodes (cassiterite, wolframite, arsenopyrite, chalcopyrite) and the assamblage is concluded to be the cusp analogue of hypothermal lodes produced by extreme differentiation and concentration of volatiles. It is speculated that such granites could provide the parent material for the mesothermal crosscourse mineralisation (pitchblende, bismuth, pyrite, galena, sphalerite).

The origin of granites and related rocks

USGS Publications Warehouse

Brown, Michael; Piccoli, Philip M.

1995-01-01

This Circular is a compilation of abstracts for posters and oral presentations given at the third Hutton symposium on the Origin of granites and related rocks. The symposium was co-sponsored by the Department of Geology, University of Maryland at College Park; the U.S. Geological Survey, Reston, Virginia; and the Department of Terrestrial Magnetism and Geophysical Laboratory, Carnegie Institution of Washington.

Petrochemistry and zircon U-Pb geochronology of granitic rocks in the Wang Nam Khiao area, Nakhon Ratchasima, Thailand: Implications for petrogenesis and tectonic setting

NASA Astrophysics Data System (ADS)

Fanka, Alongkot; Tsunogae, Toshiaki; Daorerk, Veerote; Tsutsumi, Yukiyasu; Takamura, Yusuke; Sutthirat, Chakkaphan

2018-05-01

Carboniferous biotite granite, Late Permian hornblende granite, and Triassic biotite-hornblende granite, all of which belong to the Eastern Granite Belt, expose in the Wang Nam Khiao area, Nakhon Ratchasima, northeastern Thailand. The Carboniferous biotite granite is dominated by quartz, K-feldspar, plagioclase, and biotite. The Late Permian hornblende granite contains dominant assemblages of plagioclase, quartz, K-feldspar, hornblende, and minor amount of biotite, while the Triassic biotite-hornblende granite consists of quartz, plagioclase, K-feldspar with small amounts of biotite, and hornblende. The REE patterns with steep decrease from light to heavy REE together with the LILE (e.g. K, Sr) enrichment and depletion of some particular HFSE (e.g. Nb, Ti) indicate low degree of partial melting. Mineral chemistry of biotite and hornblende in the granites reflects crystallization from hydrous calc-alkaline arc-derived magmas possibly formed by subduction. Amphibole-plagioclase thermometry and Al-in-hornblende barometry indicate that the Late Permian hornblende granite and the Triassic biotite-hornblende granite may have equilibrated at 3.0-5.8 kbar/700-820 °C and 2.0-3.2 kbar/600-750 °C, respectively, in the middle-upper crust (about 10-15 km depth). Zircon U-Pb geochronology of the Carboniferous biotite granite, Late Permian hornblende granite and Triassic biotite-hornblende granite yielded intrusion ages of 314.6-284.9 Ma, 253.4 Ma, and 237.8 Ma, respectively, which implies multiple episodes of arc-magmatism formed by Palaeo-Tethys subduction beneath Indochina Terrane during Late Carboniferous/Early Permian, Late Permian and Middle Triassic.

Flow Chart for Mineral Separation from Granitic Rocks.

ERIC Educational Resources Information Center

Mursky, Gregory

1987-01-01

Provided is a flow chart for the separation and purification of major, minor, and accessory minerals from granitic rocks. With careful use of heavy liquids, and a Franz Isodynamic Magnetic Separator, it is possible to obtain mineral concentrates with a purity of 95 percent or better. (Author/RH)

Indoor radon risk associated to post-tectonic biotite granites from Vila Pouca de Aguiar pluton, northern Portugal.

PubMed

Martins, L M O; Gomes, M E P; Teixeira, R J S; Pereira, A J S C; Neves, L J P F

2016-11-01

At Vila Pouca de Aguiar area, northern Portugal, crops out a post-tectonic Variscan granite pluton, related with the Régua-Vila Real-Verín fault zone, comprising three types of biotite granites. Among these granites, PSG granite yield the highest average contents of U, probably due to its enrichment in accessory U-bearing minerals such as zircon. In the proximity of faults and joints, these granites are often affected by different degrees of hydrothermal alteration, forming reddish altered rocks, commonly known as "episyenites". These altered rocks are probably associated to the occurrence of hydrothermal processes, which led to uranium enrichment in the most advanced stages of episyenitization. In these granites, both average gamma absorbed dose rates in outdoor and indoor air are higher than those of the world average. Furthermore, even in the worst usage scenario, all these granites can be used as a building material, since their annual effective doses are similar to the limit defined by the European Commission. The geometric mean of radon activity of 91 dwellings located at the Vila Pouca de Aguiar pluton is 568Bqm(-3), exceeding that of other northern Portuguese granites. Measurements carried out during a winter season, indicate that 62.6% of the analysed dwellings yield higher indoor radon average values than the Portuguese legislation limit (400Bqm(-3)), and annual effective doses due higher than the world's average value (1.2mSvy(-1)). The interaction of geogenic, architectural and anthropogenic features is crucial to explain the variance in the geometric mean of radon activity of dwellings from Vila Pouca de Aguiar pluton, but the role of geologic faults is probably the most important decisive factor to increase the indoor radon concentration in dwellings. Hence, the development of awareness campaigns in order to inform population about the incurred radiological risks to radon exposure are highly recommended for this specific area. Copyright © 2016

Geologic map of the Mount Sherman 7.5' quadrangle, Lake and Park Counties, Colorado

USGS Publications Warehouse

Bohannon, Robert G.; Ruleman, Chester A.

2013-01-01

The Mount Sherman 7.5- minute quadrangle is located along the crest of the Mosquito Range in between Leadville and Fairplay, Colorado. There are eleven 13,000-foot peaks and one fourteener, Mount Sherman, within the quadrangle. General elevations range from 10,400–14,036 feet (3,200–4,278 meters). The western half of the quadrangle primarily consists of Proterozoic granitic rocks reverse faulted over Paleozoic sedimentary rocks during the Laramide orogeny of late Cretaceous and Paleocene time. Coeval to this contractional event, sills and laccoliths of the White porphyry group (which probably includes rocks equivalent to the Pando Porphyry) were emplaced in the surrounding country rocks. Igneous activity continued into the Late Eocene with the emplacement of the Sacramento Porphyry (about 43.9 Ma) and the Gray porphyry group (about 36.7 Ma), and as young as 29 Ma to the north within the Climax quadrangle. With the inception of the Rio Grande rift within the region, the Paleozoic sedimentary rocks and Late Cretaceous to early Oligocene igneous rocks were extensionally faulted and tilted to the east. This resulted in the present 20–30 degree dip-slope of these rocks on top of Proterozoic basement rocks within the eastern half of the quadrangle. This extensional regime has continued well into the Pliocene. Within the southwestern quadrant, suspicious lineaments, alignment of springs, and continuous, measureable escarpments provide reasonable evidence for Quaternary tectonic activity along the western flank of the range. Pleistocene glaciers have dramatically sculpted the region, providing exceptional exposure of the region’s bedrock and structure.

Cesium adsorption and distribution onto crushed granite under different physicochemical conditions.

PubMed

Tsai, Shih-Chin; Wang, Tsing-Hai; Li, Ming-Hsu; Wei, Yuan-Yaw; Teng, Shi-Ping

2009-01-30

The adsorption of cesium onto crushed granite was investigated under different physicochemical conditions including contact time, Cs loading, ionic strength and temperature. In addition, the distribution of adsorbed Cs was examined by X-ray diffraction (XRD) and EDS mapping techniques. The results showed that Cs adsorption to crushed granite behaved as a first-order reaction with nice regression coefficients (R(2) > or = 0.971). Both Freundlich and Langmuir models were applicable to describe the adsorption. The maximum sorption capacity determined by Langmuir model was 80 micromol g(-1) at 25 degrees C and 10 micromol g(-1) at 55 degrees C. The reduced sorption capacity at high temperature was related to the partial enhancement of desorption from granite surface. In general, Cs adsorption was exothermic (DeltaH<0, with median of -12 kJ mol(-1)) and spontaneous (DeltaG<0, with median of -6.1 at 25 degrees C and -5.0 kJ mol(-1) at 55 degrees C). The presence of competing cations such as sodium and potassium ions in synthetic groundwater significantly reduces the Cs adsorption onto granite. The scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM/EDS) mapping method provided substantial evidences that micaceous minerals (biotite in this case) dominate Cs adsorption. These adsorbed Cs ions were notably distributed onto the frayed edges of biotite minerals. More importantly, the locations of these adsorbed Cs were coincided with the potassium depletion area, implying the displacement of K by Cs adsorption. Further XRD patterns displayed a decreased intensity of signal of biotite as the Cs loading increased, revealing that the interlayer space of biotite was affected by Cs adsorption.

Deep drilling at the Siljan Ring impact structure: oxygen-isotope geochemistry of granite

USGS Publications Warehouse

Komor, S.C.; Valley, J.W.

1990-01-01

The Siljan Ring is a 362-Ma-old impact structure formed in 1700-Ma-old I-type granites. A 6.8-km-deep borehole provides a vertical profile through granites and isolated horizontal diabase sills. Fluid-inclusion thermometry, and oxygen-isotope compositions of vein quartz, granite, diabase, impact melt, and pseudotachylite, reveal a complex history of fluid activity in the Siljan Ring, much of which can be related to the meteorite impact. In granites from the deep borehole, ??18O values of matrix quartz increase with depth from near 8.0 at the surface to 9.5??? at 5760 m depth. In contrast, feldspar ??18O values decrease with depth from near 10 at the surface to 7.1??? at 5760 m, forming a pattern opposite to the one defined by quartz isotopic compositions. Values of ??18O for surface granites outside the impact structure are distinct from those in near-surface samples from the deep borehole. In the deep borehole, feldspar coloration varies from brick-red at the surface to white at 5760 m, and the abundances of crack-healing calcite and other secondary minerals decrease over the same interval. Superimposed on the overall decrease in alteration intensity with depth are localized fracture zones at 4662, 5415, and 6044 m depth that contain altered granites, and which provided pathways for deep penetration of surface water. The antithetic variation of quartz and feldspar ??18O values, which can be correlated with mineralogical evidence of alteration, provides evidence for interaction between rocks and impact-heated fluids (100-300?? C) in the upper 2 km of the pluton. Penetration of water to depths below 2 km was restricted by a general decrease in impact-fracturing with depth, and by a 60-m-thick diabase sill at 1500 m depth that may have been an aquitard. At depths below 4 km in the pluton, where water/rock ratios were low, oxygen isotopic compositions preserve evidence for limited high-temperature (>500?? C) exchange between alkali feldspar and fluids. The high

76 FR 40722 - Granite Reliable Power, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-11

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER11-3941-000] Granite Reliable Power, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket Section 204 Authorization This is a supplemental notice in the above-referenced proceeding of Granite...

Crystal Cargo Characterization: Unravelling Granite Petrogenesis through Combined MicroXRF Imaging and In-situ Analyses.

NASA Astrophysics Data System (ADS)

McLeod, C. L.; Brown, K.; Brydon, R.; Haley, M.; Hill, T.; Shaulis, B.; Tronnes, R. G.

2017-12-01

Advances in the capabilities of microanalysis over the past several decades have promoted a redefinition of traditional petrological terminology. This has allowed a more accurate evaluation of a samples petrogenetic history. For example, the term "phenocryst", specifically describes crystals that grew from the liquid that solidified into the groundmass. Evolving from this idea is the term xenocryst, referring to crystals that did not originate in the magma but were gathered by it, and antecrysts, which crystallized from a progenitor of the magma that solidified into the groundmass. Through identification of a magmas different, and distinct, crystal populations, the petrogenetic history of a magmatic rock can therefore be unraveled. This approach has been widely applied to terrestrial volcanic systems throughout the past several decades. This study presents results from a combined microimaging and in-situ microanalytical investigation of granitic magmas crystal cargoes in order to unravel how granitic batholiths are constructed. 27 lithological units from two granite batholiths in the Oslo Rift, Norway form the basis of this investigation. Micro X-Ray Fluorescence (µXRF) mapping of major elements and selected trace elements is used in order to chemically map each granitic unit, identify any characteristic growth zoning, and compare the crystal cargoes of the different units. Major and trace elemental abundances of the major phases (feldspars, biotite, amphibole) and minor phases (apatite and titanite) are to be quantified through electron microprobe analysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) respectively. Through chemically fingerprinting the crystal cargoes of these Oslo Rift granitic magmas, the open vs. closed nature of granitic, intrusive, magmatic systems will be investigated. Within the context of the Oslo Rift, this study also offers an opportunity to evaluate the processes inherent to granitoid magmatism

Geochronology and tectonic significance of Middle Proterozoic granitic orthogneiss, North Qaidam HP/UHP terrane, Western China

USGS Publications Warehouse

Mattinson, C.G.; Wooden, J.L.; Liou, J.G.; Bird, D.K.; Wu, C.L.

2006-01-01

Amphibolite-facies para- and orthogneisses near Dulan, in the southeast part of the North Qaidam terrane, enclose minor ultra-high pressure (UHP) eclogite and peridotite. Field relations and coesite inclusions in zircons from paragneiss suggest that felsic, mafic, and ultramafic rocks all experienced UHP metamorphism and a common amphibolite-facies retrogression. Ion microprobe U-Pb and REE analyses of zircons from two granitic orthogneisses indicate magmatic crystallization at 927 ?? Ma and 921 ?? 7 Ma. Zircon rims in one of these samples yield younger ages (397-618 Ma) compatible with partial zircon recrystallization during in-situ Ordovician-Silurian eclogite-facies metamorphism previously determined from eclogite and paragneiss in this area. The similarity between a 2496 ?? 18 Ma xenocrystic core and 2.4-2.5 Ga zircon cores in the surrounding paragneiss suggests that the granites intruded the sediments or that the granite is a melt of the older basement which supplied detritus to the sediments. The magmatic ages of the granitic orthogneisses are similar to 920-930 Ma ages of (meta)granitoids described further northwest in the North Qaidam terrane and its correlative west of the Altyn Tagh fault, suggesting that these areas formed a coherent block prior to widespread Mid Proterozoic granitic magmatism. ?? Springer-Verlag 2006.

Zircon geochronology and Hf-O isotope geochemistry from granites in the Iapetus Suture Zone in Ireland and the Isle of Man

NASA Astrophysics Data System (ADS)

Fritschle, Tobias; Daly, J. Stephen; Whitehouse, Martin J.; McConnell, Brian; Buhre, Stephan

2014-05-01

Late Caledonian syn- to post-orogenic granites located in the Iapetus Suture Zone (ISZ) in Ireland and Britain have been related to A-type subduction and possible slab breakoff [1] following the Laurentia-Avalonian collision. Lack of reliable age data (especially in Ireland) has inhibited petrogenetic investigations of these rocks. Hence, ion microprobe U-Pb and oxygen isotope analyses as well as LA-MC-ICPMS Lu-Hf isotopic measurements on zircons from Irish and Isle of Man granites have been undertaken to provide better constraints on this enigmatic episode of the Caledonian Orogeny. Four stages of Late Caledonian granitic magmatism (c. 435, 417, 410 and 394 Ma) are indicated by U-Pb dating of oscillatory-zoned magmatic zircons. The Crossdoney, Kentstown, Drogheda and Ballynamuddagh granites together with a rhyolite from Glenamaddy have yielded U-Pb concordia ages, interpreted as intrusion-ages, between 419.9 ± 4.3 Ma (Glenamaddy) and 415.8 ± 2.0 Ma (Crossdoney) with a weighted average of 417.5 ± 0.9 Ma (MSWD = 1.3). The Glenamaddy Granite - which intruded the Glenamaddy Rhyolite - yielded an age of 410 ± 2.1 Ma. In addition, the Rockabill Granite yielded a younger age of 393.9 ± 1.9 Ma, whereas the Carnsore Granite yielded an older age of 434.6 ± 1.9 Ma. Inherited zircons (487 to 453 Ma) occur in several of the granites, and are interpreted to have been derived from Ordovician arc magmatic rocks accreted within the ISZ. A younger group of c. 440 Ma inherited zircons occurs in the c. 417 Ma Crossdoney and Ballynamuddagh granites. These grains could be related to continued or renewed Silurian arc magmatism. Hf-O isotopic measurements on the dated zircon grains range between -2 and +7 ɛHfi units and 5.5 to 8.5 o δ18O. These are interpreted to indicate the contribution of juvenile mantle melts - possibly derived from the Ordovician arc - to some of the granites. Significant heterogeneities in zircon oxygen isotopes in at least four of the granites further

Porphyry copper assessment of the Mesozoic of East Asia: China, Vietnam, North Korea, Mongolia, and Russia: Chapter G in Global mineral resource assessment

USGS Publications Warehouse

Ludington, Steve; Mihalasky, Mark J.; Hammarstrom, Jane M.; Robinson, Giplin R.; Frost, Thomas P.; Gans, Kathleen D.; Light, Thomas D.; Miller, Robert J.; Alexeiev, Dmitriy V.

2012-01-01

This report includes an overview of the assessment results and summary tables. Descriptions of each tract are included in appendixes, with estimates of numbers of undiscovered deposits, and probabilistic estimates of amounts of copper, molybdenum, gold, and silver that could be contained in undiscovered deposits for each permissive tract. A geographic information system that accompanies the report includes tract boundaries and a database of known porphyry copper deposits and prospects.

Petrogenesis and tectonic implications of the Early Paleozoic granites in the western segment of the North Qilian orogenic belt, China

NASA Astrophysics Data System (ADS)

Wang, Nan; Wu, Cai-Lai; Lei, Min; Chen, Hong-Jie

2018-07-01

Early Paleozoic granitic magmatism in the North Qilian orogenic belt records a complete Wilson cycle and provides critical geological clues for unraveling the regional tectonic history. In this study, we report the results of zircon U-Pb ages, Hf isotopic analysis and systematic whole-rock geochemical data for the Late Ordovician Hongliuhe granite and Early Silurian Qingshan monzogranite in the western segment of the North Qilian orogenic belt to constrain their emplacement ages, petrogenesis, and regional evolution history. U-Pb dating reveals that the Hongliuhe granite was emplaced around 453-452 Ma, and the Qingshan monzogranite was emplaced about 440-438 Ma. A geochemical study shows that the two granites belong to the calc-alkaline to high-K calc-alkaline series. The Hongliuhe granite shows adakitic and peraluminous features, while the Qingshan monzogranite belongs to metaluminous to weak peraluminous granites. Zircons in the Hongliuhe granite show εHf(t) values ranging from -15.1 to +11.7 with two-stage Hf model ages (tDM2) of 687-2398 Ma, whereas zircons in the Qingshan monzogranite show εHf(t) values ranging from +5.7 to +11.0 with two-stage Hf model ages from 814 to 1057 Ma. The geochemical characteristics indicate that the Hongliuhe granite was a transitional I/S-type granite and was generated from a thickened lower crust with the addition of minor Paleo- to Mesoproterozoic crustal materials, which left a rutile + garnet + pyroxene ± plagioclase residue. The Qingshan monzogranite formed from the partial melting of mafic crust with minor mantle-derived materials, and the fractionation of Ti-bearing phases, apatite and pyroxene occurred during the magma's evolution, which left an amphibole and plagioclase residue. We infer that the Hongliuhe granite formed during the northward subduction of the North Qilian Ocean, while the Qingshan monzogranite was generated during the post-collision stage between the Qilian and Alxa blocks. This observation indicates

GRANITE PEAK ROADLESS AREA, CALIFORNIA.

USGS Publications Warehouse

Huber, Donald F.; Thurber, Horace K.

1984-01-01

The Granite Peak Roadless Area occupies an area of about 5 sq mi in the southern part of the Trinity Alps of the Klamath Mountains, about 12 mi north-northeast of Weaverville, California. Rock and stream-sediment samples were analyzed. All streams draining the roadless area were sampled and representative samples of the rock types in the area were collected. Background values were established for each element and anomalous values were examined within their geologic settings and evaluated for their significance. On the basis of mineral surveys there seems little likelihood for the occurrence of mineral or energy resources.

Geology and mineralization of the Jabalat alkali-feldspar granite, northern Asir region, Kingdom of Saudi Arabia

NASA Astrophysics Data System (ADS)

Al Tayyar, Jaffar; Jackson, Norman J.; Al-Yazidi, Saeed

The Jabalat post-tectonic granite pluton is composed of albite- and oligoclase-bearing, low-calcium, F-, Sn- and Rb-rich subsolvus granites. These granites display evidence of late-magmatic, granitophile- and metallic-element specialization, resulting ultimately in the development of post-magmatic, metalliferous hydrothermal systems characterized by a Mo sbnd Sn sbnd Cu sbnd Pb sbnd Zn sbnd Bi sbnd Ag sbnd F signature. Two main types of mineralization are present within the pluton and its environs: (1) weakly mineralized felsic and aplitic dikes and veins enhanced in Mo, Bi, Ag, Pb and Cu; and (2) pyrite—molybdenite—chalcopyrite-bearing quartz and quartz—feldspar veins rich in Mo, Sn, Bi, Cu, Zn and Ag. A satellite stock, 3 km north of the main intrusion, is composed of fine-grained, miarolitic, muscovite—albite—microcline (microperthite) granite. The flanks of this intrusion and adjacent dioritic rocks are greisenized and highly enriched in Sn, Bi and Ag. Quartz veins which transect the satellite stock contain molybdenite and stannite.

The discovery and geophysical response of the Atlántida Cu-Au porphyry deposit, Chile

NASA Astrophysics Data System (ADS)

Hope, Matthew; Andersson, Steve

2016-03-01

The discovery of the Atlántida Cu-Au-Mo porphyry deposit, which is unconformably overlain by 25-80 m of gravels, is a recent example of exploration success under cover in a traditional mining jurisdiction. Early acquisition of geophysics was a key tool in the discovery, and in later guiding further exploration drilling throughout the life of the project. Detailed review of the geophysical response of the deposit, with respect to the distribution of lithologies and alteration, coupled with their petrophysical properties has allowed full characterisation, despite no exposure at the surface of host rock nor porphyry-style mineralisation. Data acquired over the project include induced polarisation, magnetotellurics, ground and airborne magnetics, ground-based gravimetry, and petrophysical sampling. The distribution of the key geological features of the deposit has been inferred via acquisition of petrophysical properties and interpretation of surface geophysical datasets. Magnetic susceptibility is influenced strongly by both alteration and primary lithology, whilst density variations are dominated by primary lithological control. Several studies have shown that electrical properties may map the footprint of the hydrothermal system and associated mineralisation, via a combination of chargeability and resistivity. These properties are observed in geophysical datasets acquired at surface and allow further targeting and sterilisation at the deposit and project scale. By understanding these geophysical characteristics in a geological context, these data can be used to infer distribution of lithological units, depth to exploration targets and the potential for high grade mineralisation. Future exploration will likely be increasingly reliant on the understanding of the surface manifestations of buried deposits in remotely acquired data. This review summarises the application and results of these principles at the Atlántida project of northern Chile. Geophysical data can be

Characterization of cesium diffusion behavior into granite matrix using Rutherford backscattering spectrometry

NASA Astrophysics Data System (ADS)

Tsai, Shih-Chin; Lee, Chuan-Pin; Tsai, Tsuey-Lin; Yu, Yueh-Chung

2017-10-01

The characterization of radionuclide diffusion behavior is necessary for performance assessment of granite as a geological barrier for high-level radioactive waste disposal. Rutherford backscattering spectrometry (RBS), a novel nuclear ion-beam technique, was selected in this study because it is suitable for analyzing the concentration gradients of heavy elements in a well-defined matrix and allows measuring diffusion coefficients on a micrometer scale. In this study Cs was selected to represent Cs-135 (a key radionuclide in high-level waste) diffusion in granite. The Cs energy spectrum and concentration deep profile were analyzed and the diffusion coefficient of Cs in granite for three different locations were determined, which were 2.06 × 10-19m2 s-1, 3.58 × 10-19m2 s-1, and 7.19 × 10-19m2 s-1-19m2 s-19m2 s-1, respectively, which were of a similiar order of magnitude. Results from other studies are also compared and discussed in this paper.

Yield Scaling of Frequency Domain Moment Tensors from Contained Chemical Explosions Detonated in Granite

NASA Astrophysics Data System (ADS)

MacPhail, M. D.; Stump, B. W.; Zhou, R.

2017-12-01

The Source Phenomenology Experiment (SPE - Arizona) was a series of nine, contained and partially contained chemical explosions within the porphyry granite at the Morenci Copper mine in Arizona. Its purpose was to detonate, record and analyze seismic waveforms from these single-fired explosions. Ground motion data from the SPE is analyzed in this study to assess the uniqueness of the time domain moment tensor source representation and its ability to quantify containment and yield scaling. Green's functions were computed for each of the explosions based on a 1D velocity model developed for the SPE. The Green's functions for the sixteen, near-source stations focused on observations from 37 to 680 m. This study analyzes the three deepest, fully contained explosions with a depth of burial of 30 m and yields of 0.77e-3, 3.08e-3 and 6.17e-3 kt. Inversions are conducted within the frequency domain and moment tensors are decomposed into deviatoric and isotropic components to evaluate the effects of containment and yield on the resulting source representation. Isotropic moments are compared to those for other contained explosions as reported by Denny and Johnson, 1991, and are in good agreement with their scaling results. The explosions in this study have isotropic moments of 1.2e12, 3.1e12 and 6.1e13 n*m. Isotropic and Mzz moment tensor spectra are compared to Mueller-Murphy, Denny-Johnson and revised Heard-Ackerman (HA) models and suggest that the larger explosions fit the HA model better. Secondary source effects resulting from free surface interactions including the effects of spallation contribute to the resulting moment tensors which include a CLVD component. Hudson diagrams, using frequency domain moment tensor data, are computed as a tool to assess how these containment scenarios affect the source representation. Our analysis suggests that, within our band of interest (2-20 Hz), as the frequency increases, the source representation becomes more explosion like

Source constraints on the genesis of Danubian granites in the South Carpathians Alpine Belt (Romania)

NASA Astrophysics Data System (ADS)

Duchesne, Jean-Clair; Laurent, Oscar; Gerdes, Axel; Bonin, Bernard; Liégeois, Jean-Paul; Tatu, Mihai; Berza, Tudor

2017-12-01

The pre-Alpine basement of the Lower Danubian nappes in the South Carpathians is made up of two Precambrian terranes (Drăgşan and Lainici-Păiuş) that were intruded by Pan-African/Cadomian and Variscan granitoid massifs. We focus on the major and trace element geochemistry (1) in the Drăgşan terrane, of the Variscan Retezat and Parâng intrusions; (2) in the Lainici-Păiuş terrane, of the Variscan Furcǎtura, Petreanu and Frumosu intrusions and of the Pan-African Vârful Pietrii, Şuşiţa and Olteţ granites and granitic leucosomes of migmatites; and (3) in the Upper Danubian nappes basement, of the Variscan Muntele Mic, Sfârdin, Cherbelezu and Ogradena intrusions. For each intrusion, in which a range of composition is observed, we decipher the differentiation mechanisms (fractional crystallization, hybridization, melt laden with restite minerals, etc.) in order to define the parental liquid compositions. The latter are calc-alkaline to alkali-calcic (except Olteţ that is calcic) and medium to high-K in composition. With [La/Yb]N > 10 and Sr/Y > 15, most melts display the so-called "continental adakite" affinities. The parental melt compositions are compared with experimental data to determine the melting conditions and the nature of the source rock. When the P-T conditions can be estimated, the temperatures range between 850 °C and 875 °C and the pressure between 5 and 15 kbar regardless of the ages of the granites and the terrane in which they have intruded. The source rock composition is dominated by a variety of mafic igneous compositions or metasediments rich in volcanic components. Clay-rich (pelitic) protoliths have not been identified. We confirm a Variscan age (c. 300 Ma) for the Frumosu intrusion granite and inherited Precambrian ages (c. 1.7-1.9 and 2.6-2.9 Ga) for the Motru dyke swarm. Thus, both Drăgşan and Lainici-Păiuş together with the Upper Danubian basement terranes were affected by Variscan post-collisional granitic plutonism. In

Porphyry copper assessment of East and Southeast Asia: Philippines, Taiwan (Republic of China), Republic of Korea (South Korea), and Japan: Chapter P in Global mineral resource assessment

USGS Publications Warehouse

Hammarstrom, Jane M.; Bookstrom, Arthur A.; Demarr, Michael W.; Dicken, Connie L.; Ludington, Stephen; Robinson, Gilpin R.; Zientek, Michael L.

2014-01-01

Descriptions of the geologic basis for delineating each tract, the data used, the geologic criteria and rationale for the assessment, and results of the assessment are included in appendixes along with the description of a geographic information system (GIS) that includes tract boundaries, known porphyry copper deposits and significant prospects, and assessment results.

Doses from radon 222 irradiation for workers of the granite mining industry.

PubMed

Сrygorieva, L; Tomilin, Yu

2017-12-01

determining the integral value of annual effective dose from 222Rn for workers of the granite mining industry and assessment for the expected life effective dose from 222Rn. Materials were the results of measurements of external exposure dose of radiation measurements equiv alent equilibrium volume activity of 222Rn in workrooms and workplaces of major groups of granite quarry workers Mykolaiv region, studies EROA 222Rn air premises of these workers, research content 222Rn in drinking water. Granite quarry workers receive double radiation exposure of 222Rn due to exposure in the workplace and at home. The load in the workplace due to inhalation of 222Rn the air was (2.1 ± 0.2) mSv / year (vari ation 0.9-5.9) in a residential area - (4,1 ± 0,2) mSv/year (variation 1.8-5.9). The total annual effective dose from internal exposure from air flow and working premises and drinking water was on average (6,5 ± 0,2) mSv/year, equal to a maximum value of 20 mSv/year. The expected life for the chronic exposure dose of technological naturally occurring radioactive sources for people who work in the granite quarries and, while living in high risk from radon is in the range of 0.16-1.12 Sv. The research results indicate that in assessing the effects associated with exposure due to radon 222 contingents persons such surveys must take into account all sources of this radionuclide dose. L. Сrygorieva, Yu. Tomilin.

Geochronology, geochemistry, and tectonic environment of porphyry mineralization in the central Alaska Peninsula

USGS Publications Warehouse

Wilson, Frederic H.; Cox, Dennis P.

1983-01-01

Porphyry type sulfide systems on the central Alaska Peninsula occupy a transition zone between the Aleutian island magmatic arc and the continental magmatic arc of southern Alaska. Mineralization occurs associated with early and late Tertiary magmatic centers emplaced through a thick section of Mesozoic continental margin clastic sedimentary rocks. The systems are of the molybdenum-rich as opposed to gold-rich type and have anomalous tungsten, bismuth, and tin, attributes of continental-margin deposits, yet gravity data suggest that at least part of the study area is underlain by oceanic or transitional crust. Potassium-argon age determinations indicate a variable time span of up to 2 million years between emplacement and mineralization in a sulfide system with mineralization usually followed by postmineral intrusive events. Finally, mineralization in the study area occurred at many times during the time span of igneous activity and should be an expected stage in the history of a subduction related magmatic center.

Quantifying Textures of Rapakivi Granites and Mantle Formation Insights

NASA Astrophysics Data System (ADS)

Ashauer, Z.; Currier, R. M.

2017-12-01

Rapakivi texture, the mantling of plagioclase on alkali feldspar, is a common occurrence in granitoids derived from crustal melting. Presented here, are several textural analyses that quantify mantle thickness and the overall distribution of crystal populations. Analyses were performed on outcrops and slabbed samples from the Wolf River Batholith, Wisconsin, USA and the Wiborg Batholith, Finland. Both localities are "classical" rapakivi granites of Proterozoic age associated with incipient rifting of the supercontinent Nuna/Columbia. Mantle thickness analysis reveals a relationship between the characteristic size of the mantle and the size of the core. The thickest mantles tend to be on relatively small cores while relatively large cores display thin mantles. This relationship is consistent with a replacement origin as a result of alkali feldspar dissolution with concomitant reprecipitation of plagioclase, due to disequilibrium between crystal and melt. If this is the case then crystal size distributions should be similar between unmantled and mantled megacrysts. Preliminary results confirm this supposition: rapakivi mantle formation in these classical systems appear to be the result of replacement. These textural analyses immediately call into question the viability of epitaxial growth models. A certain amount of disequilibrium is required to drive the replacement reaction. Two potential mechanisms are 1) mechanical transfer of crystals into a magma of more mafic composition (i.e., magma mixing), and 2) the production of a heterogeneous melt during rapid melting of granitic rock and reaction between unmelted crystals and partial melt. The classical rapakivi granites are associated with prolonged bimodal magmatism, and so there is clear potential to drive either of these mantling mechanisms.

Mineralogy maketh mountains: Granitic landscapes shaped by dissolution

NASA Astrophysics Data System (ADS)

Eggleton, Richard A.

2017-05-01

In tectonically quiet regions, the shape of the landscape is controlled by the erosion resistance of the rocks. Erosion largely depends on the release of particles from the weathering rock, which in turn requires a degree of dissolution of the more soluble grains. The rate of dissolution of the common rock forming minerals allows the construction of a numerical Rock Weatherability Scale (RWS) based on the rock's modal mineralogical analysis. Applied regionally to three granitic landscape regions of the Bega Valley of southern New South Wales, the Tate Batholith and Featherbed Volcanics of north Queensland, and granitoids in the Beaufort region of Victoria, the mean elevation of the larger plutons in each region correlates highly (r = 0.83-0.93) with their RWS. Variation in composition within a pluton also shows there is a clear connection between changes in RWS and relief within the pluton. From these results it is apparent that the landscape of such granitic terrains is determined very largely by mineral dissolution rates, with plagioclase composition and content being a major factor.

The Early Jurassic Bokan Mountain peralkaline granitic complex (southeastern Alaska): geochemistry, petrogenesis and rare-metal mineralization

USGS Publications Warehouse

Dostal, Jaroslav; Kontak, Daniel J.; Karl, Susan M.

2014-01-01

The Early Jurassic (ca. 177 Ma) Bokan Mountain granitic complex, located on southern Prince of Wales Island, southernmost Alaska, cross-cuts Paleozoic igneous and metasedimentary rocks of the Alexander terrane of the North American Cordillera and was emplaced during a rifting event. The complex is a circular body (~3 km in diameter) of peralkaline granitic composition that has a core of arfvedsonite granite surrounded by aegirine granite. All the rock-forming minerals typically record a two-stage growth history and aegirine and arfvedsonite were the last major phases to crystalize from the magma. The Bokan granites and related dikes have SiO2 from 72 to 78 wt. %, high iron (FeO (tot) ~3-4.5 wt. %) and alkali (8-10 wt.%) concentrations with high FeO(tot)/(FeO(tot)+MgO) ratios (typically >0.95) and the molar Al2O3/(Na2O+K2O) ratio Nd values which are indicative of a mantle signature. The parent magma is inferred to be derived from an earlier metasomatized lithospheric mantle by low degrees of partial melting and generated the Bokan granitic melt through extensive fractional crystallization. The Bokan complex hosts significant rare-metal (REE, Y, U, Th, Nb) mineralization that is related to the late-stage crystallization history of the complex which involved the overlap of emplacement of felsic dikes, including pegmatite bodies, and generation of orthomagmatic fluids. The abundances of REE, HFSE, U and Th as well as Pb and Nd isotopic values of the pluton and dikes were modified by orthomagmatic hydrothermal fluids highly enriched in the strongly incompatible trace elements, which also escaped along zones of structural weakness to generate rare-metal mineralization. The latter was deposited in two stages: the first relates to the latest stage of magma emplacement and is associated with felsic dikes that intruded along the faults and shear deformations, whereas the second stage involved ingress of hydrothermal fluids that both remobilized and enriched the initial

CO2-rich and CO2-poor ore-forming fluids of porphyry molybdenum systems in two contrasting geologic setting: evidence from Shapinggou and Zhilingtou Mo deposits, South China

NASA Astrophysics Data System (ADS)

Ni, P.

2017-12-01

Porphyry deposits are the world most important source of Mo, accounting for more than 95% of world Mo production. Porphyry Mo deposits have been classified into Climax type and Endako type. The Climax type was generally formed in an intra-continental setting, and contain high contents of Mo (0.15-0.45 wt.%) and F (0.5-5 wt.%). In contrast, the Endako type was generated in a continental arc setting and featured by low concentrations of Mo (0.05-0.15 wt.%) and F (0.05-0.15 wt.%). The systematic comparison of ore fluids in two contrasting tectonic environments is still poorly constrained. In this study, the Shapinggou and Zhilingtou Mo deposits in South China were selected to present the contrasting ore-forming fluid features. The fluid inclusion study of Shapinggou Mo deposit suggest: Early barren quartz veins contain fluid inclusions with salinities of 7.9-16.9 wt% NaCl equiv . CO2 contents are high enough to be detected by Raman. Later molybdenite-quartz veins contain vapor-type fluid inclusions with lower salinities (0.1-7.4 wt% NaCl equiv) but higher CO2-contents, coexisting with brine inclusions with 32.9-50.9 wt% NaCl equiv. The fluid inclusion study on Zhilintou Mo deposit suggest : Early barren quartz veins contain mostly intermediate density fluid inclusions with salinities of 5.3-14.1 wt% NaCl equiv, whereas main-stage quartz-molybdenite veins contain vapor-rich fluid inclusions of 0.5-6.2 wt% NaClequiv coexisting with brine inclusions of 38.6-44.8 wt% NaCl equiv. In contrast to the Shapinggou Mo deposit, the fluid inclusions at Shizitou contain only minor amounts of CO2. This study suggests the two porphyry molybdenum deposits experienced a similar fluid evolution trend, from single-phase fluids at the premineralization stage to two-phase fluids at the mineralization stage. Fluid boiling occurred during the ore stage and probably promoted a rapid precipitation of molybdenite. Intensive phyllic alteration, CO2-poor ore-forming fluids, and continental arc

Geochemical constraints on genesis of Paleoproterozoic A-type granite in the south margin of North China Craton

NASA Astrophysics Data System (ADS)

Xue, Shuo; Xu, Yang; Ling, Ming-Xing; Kang, Qing-Qing; Jiang, Xiao-Yan; Sun, Sai-Jun; Wu, Kai; Zhang, Zhe-Kun; Luo, Ze-Bin; Liu, Yu-Long; Sun, Weidong

2018-04-01

Paleoproterozoic A-type granites are widely outcropped in the North China Craton (NCC), particularly in the Trans-North China Orogen. However, their genesis and tectonic significance remain obscure. Here we report systematic studies on geochronology and geochemical characteristics of A-type granite in Huayangchuan, south margin of the NCC. The samples are enriched in total alkali (K2O + Na2O > 8.97 wt%), and depleted in MgO (0.84-0.93 wt%), CaO (1.28-1.90 wt%) and P2O5 (0.18-0.20 wt%), with high FeOT/MgO (5.69-6.67). They are characterized by high Zr + Y + Nb + Ce values (1293-1392 ppm) and 10,000 × Ga/Al ratios (3.14-3.35), which are typical characteristics of A-type granite. The Huayangchuan A-type granite can be further classified as A1-type subgroup based on particular geochemical features, e.g., low Y/Nb (0.87-1.00) and Yb/Ta (0.88-1.10). High precision zircon U-Pb dating of the A-type granite by secondary ion mass spectrometry (SIMS) yields Paleoproterozoic 207Pb/206Pb ages of 1829.5 ± 2.5 Ma. The low zircon ɛHf(t) values (-6.97 to -10.45), along with zircon Hf model age of 2.7-2.9 Ga, indicate that the Huayangchuan A-type granite was derived from partial melting of the ancient continental crust with contribution of enriched mantle components. The low zircon δ18O composition (4.00 to 6.78‰) indicates that the zircons were crystallized from low δ18O magmas, which derived from the crust metasomatized by low δ18O mantle fluids or melts. The E-W trend A1-type granitic plutons in the NCC are generally outcropped in a rift tectonic regime, which is consistent with the development of the mantle plume in the Xiong'er district. The large volume of basaltic magmas, generated by mantle plume head, underplated the lower continental crust and formed the Huayangchuan A-type granite.

Initiation and propagation of mixed mode fractures in granite and sandstone

NASA Astrophysics Data System (ADS)

Rück, Marc; Rahner, Roman; Sone, Hiroki; Dresen, Georg

2017-10-01

We investigate mixed mode fracture initiation and propagation in experimentally deformed granite and sandstone. We performed a series of asymmetric loading tests to induce fractures in cylindrical specimens at confining pressures up to 20 MPa. Loading was controlled using acoustic emission (AE) feedback control, which allows studying quasi-static fracture propagation for several hours. Location of acoustic emissions reveals distinct differences in spatial-temporal fracture evolution between granite and sandstone samples. Before reaching peak stress in experiments performed on granite, axial fractures initiate first at the edge of the indenter and then propagate through the entire sample. Secondary inclined fractures develop during softening of the sample. In sandstone, inclined shear fractures nucleate at peak stress and propagate through the specimen. AE source type analysis shows complex fracturing in both materials with pore collapse contributing significantly to fracture growth in sandstone samples. We compare the experimental results with numerical models to analyze stress distribution and energy release rate per unit crack surface area in the samples at different stages during fracture growth. We thereby show that for both rock types the energy release rate increases approximately linearly during fracture propagation. The study illuminates how different material properties modify fracture initiation direction under similar loading conditions.

Pioneering fungi from the Damma glacier forefield in the Swiss Alps can promote granite weathering.

PubMed

Brunner, I; Plötze, M; Rieder, S; Zumsteg, A; Furrer, G; Frey, B

2011-05-01

Fungi were isolated from fine granitic sediments, which were collected at 15 sampling points within a 20 m × 40 m area in front of the Damma glacier in the central Swiss Alps. From the 45 fungal isolates grown on nutrient-rich agar media at 4 °C, 24 isolates were selected for partial sequencing and identification based on the small subunit ribosomal DNA. Sequencing data revealed that the isolated fungi represented three fungal phyla and 15 species. The weathering potential of 10 of the 15 fungal species was tested with dissolution experiments using powdered granite material (<63 μm). The results showed that the zygomyceteous species Mucor hiemalis, Umbelopsis isabellina and Mortierella alpina dissolved the granite powder most efficiently due to the release of a variety of organic acids, mainly citrate, malate and oxalate. In particular, the high concentrations of Ca, Fe, Mg and Mn in the solutions clustered well with the high amounts of exuded citrate. This is the first report on fungi that were isolated from a non-vegetated glacier forefield in which the fungi's capabilities to dissolve granite minerals were examined. © 2011 Blackwell Publishing Ltd.

8. July, 1970 DETAIL OF BRICK SIDEWALK AND GRANITE CURB, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

8. July, 1970 DETAIL OF BRICK SIDEWALK AND GRANITE CURB, LOOKING EAST ON NORTH SIDE OF INDIA STREET FROM DRIVEWAY OF 31 INDIA STREET - India Street Neighborhood Study, 15-45 India Street, Nantucket, Nantucket County, MA

7. July, 1970 DETAIL OF BRICK SIDEWALK AND GRANITE CURB, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

7. July, 1970 DETAIL OF BRICK SIDEWALK AND GRANITE CURB, LOOKING EAST ON NORTH SIDE OF INDIA STREET FROM DRIVEWAY OF 31 INDIA STREET - India Street Neighborhood Study, 15-45 India Street, Nantucket, Nantucket County, MA

Effects of slip, slip rate, and shear heating on the friction of granite

USGS Publications Warehouse

Blanpied, M.L.; Tullis, T.E.; Weeks, J.D.

1998-01-01

The stability of fault slip is sensitive to the way in which frictional strength responds to changes in slip rate and in particular to the effective velocity dependence of steady state friction ????ss/?? ln V. This quantity can vary substantially with displacement, temperature and slip rate. To investigate the physical basis for this behavior and the possible influence of shear heating, we slid initially bare granite surfaces in unconfined rotary shear to displacements of hundreds of millimeters at normal stresses, ??n, of 10 and 25 MPa and at room temperature. We imposed step changes in slip rate within the range 10-2 to 103.5 ??m/s and also monitored frictional heating with thermistors embedded in the granite. The transient response of ?? to slip rate steps was fit to a rate- and state-dependent friction law using two state variables to estimate the values of several parameters in the constitutive law. The first 20 mm of slip shows rising friction and falling ????ss/?? ln V; further slip shows roughly constant friction, ????ss/?? ln V and parameter values, suggesting that a steady state condition is reached on the fault surface. At V ??? 10 ??m/s, ????ss/?? ln V = -0.004 ?? 0.001. At higher rates the response is sensitive to normal stress: At ??n = 25 MPa granite shows a transition to effective velocity strengthening (????ss/?? ln V = 0.008 ?? 0.004) at the highest slip rates tested. At 10 MPa granite shows a less dramatic change to ????ss/?? ln V ??? 0 at the highest rates. The maximum temperature measured in the granite is ???60??C at 25 MPa and 103.5 ??m/s. Temperatures are in general agreement with a numerical model of heat conduction which assumes spatially homogeneous frictional heating over the sliding surface. The simplest interpretation of our measurements of ????ss/?? ln V is that the granite is inherently veocity weakening (?????ss/??? In V 0 mimics velocity strengthening. These results have implications for the frictional behavior of faults during

A Bibliography on the Chemical Weathering of Granitic Rocks

DTIC Science & Technology

1988-09-01

of granite by salt action: from field to laboratory. Universitat Amsterdam FysischGeografischBoden Kwndig Laboratorium , vol. 16, pp. 67-80. Laforge, L...E. 1963. Biologische Ursachen der Wistenlackbildung. Zeitschrift fur Geornorphologie, vol. 7, pp. 112-119. Scott, G. A. J. and Street, J. M. 1976

Granitoid magmatism of Alarmaut granite-metamorphic dome, West Chukotka, NE Russia

NASA Astrophysics Data System (ADS)

Luchitskaya, M. V.; Sokolov, S. D.; Bondarenko, G. E.; Katkov, S. M.

2009-04-01

Main tectonic elements of West Chukotka are Alazey-Oloy, South-Anyui and Anyui-Chukotka fold systems, formed as a result of collision between structures of North-Asian continent active margin and Chukotka microcontinent [1-3]. South-Anyui fold system, separating Alazey-Oloy and Anyui-Chukotka systems, is considered as suture zon, formed as a result of oceanic basin closing [4-6]. Continent-microcontinent collision resulted in formation of large orogen with of northern and southern vergent structures, complicated by strike-slip deformations [7, 8]. Within Anyui-Chukotka fold system several rises, where most ancient deposits (crystalline basement and Paleozoic cover of Chukotka microcontinent) are exposed, were distinguished [2, 9-11]. Later they were considered as granite-metamorphic domes [12-14]. Alarmaut dome is located at West Chukotka to the north from Bilibino city and is traced from south to north in more than 120 km. General direction of structure is discordant to prevailing NW extensions of tectonic elements of the region. Paleozoic-Triassic deposits are exposed within the Alarmaut dome: 1) D3-C1 - crystalline schists, quartz-feldspar metasandstones, quartzites, marbles (700 m) [11]; 2) C1 - marblized limestones, quartz-feldspar metasandstones, quartzites, amphibole-pyroxene crystalline schists. Limestones contain corals, indicating Visean age of deposits [11]. Metamorphism reaches amphibolite facies, maximum P-T conditions are 660°С and 5 kbar. Migmatites, indicating in situ partial melting, are observed. Intensity of deformations of Paleozoic rocks increases at the boundary with Triassic deposits [11]; in the western part of dome slices of Pz rocks are separated by blastomylonite horizons [14]. Within Alramaut dome granitoids of Lupveem batholith (central part of dome), Bystrinsky pluton (southeastern part), and small Koyvel' and Kelil'vun plutons were studied. New U-Pb SHRIMP zircon data indicate Early Cretaceous (117-112 m.a.) age of granitoids [15

Rubidium-strontium date of possibly 3 billion years for a granitic rock from antarctica.

PubMed

Halpern, M

1970-09-04

A single total rock sample of biotite granite from Jule Peaks, Antarctica, has been dated by the rubidium-strontium method at about 3 billion years. The juxtaposition of this sector of Antarctica with Africa in the Dietz and Sproll continental drift reconstruction results in a possible geochronologic fit of the Princess Martha Coast of Antarctica with a covered possible notheastern extension of the African Swaziland Shield, which contains granitic rocks that are also 3 billion years old.

Preserved magnetic fabrics vs. annealed microstructures in the syntectonic recrystallised George granite, South Africa

NASA Astrophysics Data System (ADS)

Ferré, E. C.; Améglio, L.

2000-08-01

The Saldanian basement of the Cape Fold Belt of South Africa outcrops in the Kaaimans inlier with granite plutons intruded in low-grade pelitic and quartzitic metasediments around 535 Ma. New field data support a ubiquitous Saldanian top-to-the-north thrust kinematics coeval with granite emplacement with no substantial Cape tectonic overprint. The granites and their contact aureoles display both synkinematic and post-kinematic fabrics. This and the high strain zone commonly observed all along the contact between the Kaaimans inlier and the Cape Fold Belt, suggest a structural decoupling between the basement and its cover. Microstructures in the Kaaimans inlier and in the George pluton establish a post-kinematic, pervasive and thermal overprint of Saldanian age. Granites and country rocks record a medium-temperature/high-strain deformation phase followed by a strong low-temperature/static recrystallisation. Two sets of andalusite porphyroblasts occur systematically in the contact aureoles of the studied plutons and cannot be explained by successive magmatic pulses. The granites, studied by the Anisotropy of Magnetic Susceptibility (AMS) technique, are paramagnetic (20< Km<300 μSI). Biotite is mostly at the origin of the bulk rock susceptibility although minor contributions of tourmaline or ferromagnetic phases may occur. The contribution of biotite alone to the bulk magnetic susceptibility is supported by two quantitative models based, respectively, on whole rock compositions (Curie-Weiss law) and on intrinsic mineral susceptibilities. The magnetic foliations and lineations are homogeneous throughout the George pluton and are consistent with field structures. The AMS results mainly from the magneto-crystalline anisotropy of biotite and from its lattice preferred orientation (LPO) in the rock. The magnetic fabric reveals the biotite subfabrics that had been acquired before static recrystallisation and which was not modified by the subsequent thermal metamorphic

Weathering Grade Classification of Granite Stone Monument Using Reflectance Spectroscopy

NASA Astrophysics Data System (ADS)

Hyun, C.; Roh, T.; Choi, M.; Park, H.

2009-05-01

Stone monument has been placed in field and exposed to rain and wind. This outdoor environment and air pollution induced weathering of stone monument. Weathering grade classification is necessary to manage and conserve stone monuments. Visual interpretation by geologist and laboratory experiments using specimens fallen off from the monument to avoid damage on the monument have been applied to classify weathering grade conventionally. Rocks and minerals absorb some particular wavelength ranges of electromagnetic energy by electronic process and vibrational process of composing elements and these phenomena produce intrinsic diagnostic spectral reflectance curve. Non-destructive technique for weathering degree assessment measures those diagnostic absorption features of weathering products and converts the depths of features related to abundance of the materials to relative weathering degree. We selected granite outcrop to apply conventional six folded weathering grade classification method using Schmidt hammer rebound teste. The correlations between Schmidt hammer rebound values and absorption depths of iron oxides such as ferric oxide in the vicinity of 0.9 micrometer wavelength and clay minerals such as illite and kaolinite in the vicinity of 2.2 micrometer wavelength, representative weathering products of granite, were analyzed. The Schmidt hammer rebound value decreased according to increase of absorption depths induced from those weathering products. Weathering grade classification on the granite stone monument was conducted by using absorption depths of weathering products This research is supported from National Research Institute of Cultural Heritage and we appreciate for this.

δ30Si systematics in a granitic saprolite, Puerto Rico

USGS Publications Warehouse

Ziegler, Karen; Chadwick, Oliver A.; White, Arthur F.; Brzezinski, Mark A.

2005-01-01

Granite weathering and clay mineral formation impart distinct and interpretable stable Si isotope (δ30Si) signatures to their solid and aqueous products. Within a saprolite, clay minerals have δ30Si values ∼2.0‰ more negative than their parent mineral and the δ30Si signature of the bulk solid is determined by the ratio of primary to secondary minerals. Mineral-specific weathering reactions predominate at different depths, driving changes in differing δ30Sipore watervalues. At the bedrock-saprolite interface, dissolution of plagioclase and hornblende creates δ30Sipore water signatures more positive than granite by up to 1.2‰; these reactions are the main contributor of Si to stream water and determine its δ30Si value. Throughout the saprolite, biotite weathering releases Si to pore waters but kaolinite overgrowth formation modulates its contribution to pore-water Si. The influence of biotite on δ30Sipore water is greatest near the bedrock where biotite-derived Si mixes with bulk pore water prior to kaolinite formation. Higher in the saprolite, biotite grains have become more isolated by kaolinite overgrowth, which consumes biotite-derived Si that would otherwise influence δ30Sipore water. Because of this isolation, which shifts the dominant source of pore-water Si from biotite to quartz, δ30Sipore water values are more negative than granite by up to 1.3‰ near the top of the saprolite.

Ore-forming adakitic porphyry produced by fractional crystallization of oxidized basaltic magmas in a subcrustal chamber (Jiamate, East Junggar, NW China)

NASA Astrophysics Data System (ADS)

Hong, Tao; Xu, Xing-Wang; Gao, Jun; Peters, Stephen G.; Zhang, Di; Jielili, Reyaniguli; Xiang, Peng; Li, Hao; Wu, Chu; You, Jun; Liu, Jie; Ke, Qiang

2018-01-01

Adakitic intrusions are supposed to have a close genetic and spatial relationship to porphyry Cu deposits. However, the genesis of adakitic intrusions is still under dispute. Here, we describe newly discovered intrusive complex rocks, which are composed of ore-bearing, layered magnetite-bearing gabbroic and adakitic rocks in Jiamate, East Junggar, NW China. These Jiamate Complex intrusions have diagnostic petrologic, geochronologic and geochemical signatures that indicate they were all generated from the same oxidized precursor magma source. Additionally, these layered rocks underwent the same fractional crystallization process as the ore-bearing adakitic rocks in the adjacent Kalaxiangar Porphyry Cu Belt (KPCB) in an oceanic island arc (OIA) setting. The rocks studied for this paper include layered magnetite-bearing gabbroic intrusive rocks that contain: (1) gradual contact changes between lithological units of mafic and intermediate rocks, (2) geochemical signatures that are the same as those found in oceanic island arc (OIA) rocks, (3) typical adakitic geochemistry, and (4) similar characteristics and apparent fractional crystallization relationships of ultra-basic to basic rocks to those in the nearby Beitashan Formation and to ore-bearing adakitic rocks in the KPCB. They also display similar zircon U-Pb and zircon Hf model ages. The Jiamate Complex intrusions contain intergrowths of magnetite and layered gabbro, and the intermediate-acidic intrusions of the Complex display typical adakitic affinities. Moreover, in conjunction with previously published geochronological and geochemistry data of the mafic rocks in the Beitashan Formation and in the KPCB area, additional data generated for the Jiamate Complex intrusions rocks indicate that they were formed from fractional crystallization processes. The Jiamate Complex intrusions most likely were derived from a metasomatized mantle wedge that was underplated at the root of the Saur oceanic island arc (Saur OIA

Ore-forming adakitic porphyry produced by fractional crystallization of oxidized basaltic magmas in a subcrustal chamber (Jiamate, East Junggar, NW China)

USGS Publications Warehouse

Hong, Tao; Xu, Xing-Wang; Gao, Jun; Peters, Stephen; Zhang, Di; Jielili, Reyaniguli; Xiang, Peng; Li, Hao; Wu, Chu; You, Jun; Liu, Jie; Ke, Qiang

2018-01-01

Adakitic intrusions are supposed to have a close genetic and spatial relationship to porphyry Cu deposits. However, the genesis of adakitic intrusions is still under dispute. Here, we describe newly discovered intrusive complex rocks, which are composed of ore-bearing, layered magnetite-bearing gabbroic and adakitic rocks in Jiamate, East Junggar, NW China. These Jiamate Complex intrusions have diagnostic petrologic, geochronologic and geochemical signatures that indicate they were all generated from the same oxidized precursor magma source. Additionally, these layered rocks underwent the same fractional crystallization process as the ore-bearing adakitic rocks in the adjacent Kalaxiangar Porphyry Cu Belt (KPCB) in an oceanic island arc (OIA) setting. The rocks studied for this paper include layered magnetite-bearing gabbroic intrusive rocks that contain: (1) gradual contact changes between lithological units of mafic and intermediate rocks, (2) geochemical signatures that are the same as those found in oceanic island arc (OIA) rocks, (3) typical adakitic geochemistry, and (4) similar characteristics and apparent fractional crystallization relationships of ultra-basic to basic rocks to those in the nearby Beitashan Formation and to ore-bearing adakitic rocks in the KPCB. They also display similar zircon U-Pb and zircon Hf model ages.The Jiamate Complex intrusions contain intergrowths of magnetite and layered gabbro, and the intermediate-acidic intrusions of the Complex display typical adakitic affinities. Moreover, in conjunction with previously published geochronological and geochemistry data of the mafic rocks in the Beitashan Formation and in the KPCB area, additional data generated for the Jiamate Complex intrusions rocks indicate that they were formed from fractional crystallization processes. The Jiamate Complex intrusions most likely were derived from a metasomatized mantle wedge that was underplated at the root of the Saur oceanic island arc (Saur OIA). The

The late Variscan ferroan granite magmatism of southern Sardinia: inferences from Mo metallogenesis

NASA Astrophysics Data System (ADS)

Naitza, Stefano; Conte, Aida Maria; Cuccuru, Stefano; Fadda, Sandro; Fiori, Maddalena; Oggiano, Giacomo; Secchi, Francesco

2017-04-01

Metallogeny is a powerful tool to investigate crustal evolution; a good example is offered by the Variscan basement of Sardinia and its Mo deposits. Mo ores are poorly represented in Variscan metallogenic provinces of Europe: however, in Sardinia, numerous small Mo deposits, often associated to Sn, W and F ores, are present, invariably related to an early Permian intrusive peak bracketed at about 290 Ma (Fadda et al., 2015; Naitza et al., 2017). In Sardinia, two main magmatic peaks have been schematized at pre-300 and 290 Ma. In southern Sardinia, the 290 magmatic peak is made up of several intrusive F-bearing rock-suites (Conte et al., 2016), belonging to ilmenite series, showing a slight peraluminous character and mostly classifiable as ferroan granites (sensu Frost and Frost, 2011). Mo-bearing granites form a distinct suite of relatively small plutons, emplaced at very shallow depth (about 1kb) in an exhumed Variscan low-grade basement. Peculiar characters of Mo-bearing granites are the occurrence of greisenized microgranite and granophyre cupolas, with fayalite-bearing pegmatites, and ilmenite, xenotime-(Y), monazite, fluorite, and local topaz as accessory phases. Recently, Conte et al. (2016) interpreted these granites as originated by partial melting of low crustal felsic metaigneous photoliths enriched in granophiles (Mo, Sn, W). Mo ores occur as: a) endo- and exo- quartz-muscovite greisens with molybdenite±Fe-Cu sulphides, and b) quartz-molybdenite±wolframite±Fe-Cu-Zn sulphides±fluorite±topaz hydrothermal veins and stockworks, hosted in granites or in country rocks. Redox state of magmas exerts a strong control on Mo metallogeny, as in Mo districts worldwide ores are usually hosted by high-fO2 magnetite series intrusions (Ishihara, 1981). The close field association of Sardinian Mo mineralization with ferroan, low-fO2 ilmenite-series granites may be explained in terms of Mo-enriched crustal sources of magmas, and very efficient geochemical

Geochemical characteristics of Proterozoic granite magmatism from Southern Granulite Terrain, India: Implications for Gondwana

NASA Astrophysics Data System (ADS)

Yellappa, T.; Rao, J. Mallikharjuna

2018-03-01

Granitoid intrusions occur widely in the Southern Granulite Terrain (SGT) of India, particularly within the Cauvery Suture Zone (CSZ), which is considered as the trace of the Neoproterozoic Mozambique ocean closure. Here we present the petrological and geochemical features of 19 granite plutons across the three major tectonic blocks of the terrain. Our data show a wide variation in the compositions of these intrusions from alkali feldspathic syenite to granite. The whole rock geochemistry of these intrusions displays higher concentrations of SiO2, FeO*, K2O, Ba, Zr, Th, LREE and low MgO, Na2O, Ti, P, Nb, Y and HREE's. The granitoids are metaluminous to slightly peraluminous in nature revealing both I-type and A-type origin. In tectonic discrimination plots, the plutons dominantly show volcanic arc and syn-collisional as well as post-collisional affinity. Based on the available age data together with geochemical constrains, we demonstrate that the granitic magmatism in the centre and south of the terrain is mostly associated with the Neoproterozoic subduction-collision-accretion-orogeny, followed by extensional mechanism of Gondwana tectonics events. Similar widespread granitic activity has also been documented in the Arabian Nubian shield, Madagascar, Sri Lanka and Antarctica, providing similarities for the reconstruction of the crustal fragments of Gondwana supercontinent followed by Pan-African orogeny.

Laser ablation of iron-rich black films from exposed granite surfaces

NASA Astrophysics Data System (ADS)

Delgado Rodrigues, J.; Costa, D.; Mascalchi, M.; Osticioli, I.; Siano, S.

2014-10-01

Here, we investigated the potential of laser removal of iron-rich dark films from weathered granite substrates, which represents a very difficult conservation problem because of the polymineralic nature of the stone and of its complex deterioration mechanisms. As often occurs, biotite was the most critical component because of its high optical absorption, low melting temperature, and pronounced cleavage, which required a careful control of the photothermal and photomechanical effects to optimize the selective ablation of the mentioned unwanted dark film. Different pulse durations and wavelengths Nd:YAG lasers were tested and optimal irradiation conditions were determined through thorough analytical characterisations. Besides addressing a specific conservation problem, the present work provides information of general valence in laser uncovering of encrusted granite.

Magmatic evolution and controls on rare metal-enrichment of the Strange Lake A-type peralkaline granitic pluton, Québec-Labrador

NASA Astrophysics Data System (ADS)

Siegel, Karin; Vasyukova, Olga V.; Williams-Jones, Anthony E.

2018-05-01

Although it is well known that A-type granites are enriched in the rare earth elements (REE) and other high field strength elements (HFSE), the magmatic processes that concentrate these elements are still poorly understood. The 1.24 Ga Strange Lake pluton in northern Québec-Labrador provides an extraordinary example of hyper-enrichment in the REE, Zr, and Nb in a peralkaline A-type granite. The pluton consists of two hypersolvus granite units (southern and northern) and a transsolvus granite, all of which contain perthitic alkali feldspar as the earliest major mineral; the transsolvus granite also contains separate albite and microcline crystals. Arfvedsonite, a sodic amphibole, occurs exclusively as phenocrysts in the transsolvus granite, whereas in the hypersolvus granite it is present as a late, interstitial phase. The primary HFSE minerals are zircon, monazite-(Ce), gagarinite-(Ce) and the pyrochlore group minerals. Magma evolution was monitored by the alumina content in the bulk rock, which decreases from the southern to the northern hypersolvus granite and is lowest in the transsolvus granite. Alkalinity indices and bulk Si, Fe, Rb, REE, Zr, Nb concentrations show the opposite trend. Alkali feldspar compositions mirror the trend shown by the bulk rock, i.e., decreasing Al contents are accompanied by increasing Si, Fe3+, REE, Zr and Nb contents. The major driving forces for the evolution of the hypersolvus magma prior to emplacement were the early separation of a fluoride melt from the silicate melt and the crystallization of alkali feldspar and HFSE-rich phases (zircon, monazite-(Ce), pyrochlore group). An alkali feldspar-rich crystal-mush containing LREE-fluoride melt droplets was emplaced as the least evolved southern hypersolvus granite. Massive fractionation of alkali feldspar led to a sharp increase in ƒH2O and F- activity in the magma chamber that triggered the crystallization of arfvedsonite and was followed by emplacement of the northern hypersolvus

Cambro-Ordovician post-collisional granites of the Ribeira belt, SE-Brazil: A case of terminal magmatism of a hot orogen

NASA Astrophysics Data System (ADS)