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Sample records for adakitic intrusive rocks

  1. Late Jurassic sodium-rich adakitic intrusive rocks in the southern Qiangtang terrane, central Tibet, and their implications for the Bangong-Nujiang Ocean subduction

    NASA Astrophysics Data System (ADS)

    Li, Yalin; He, Juan; Han, Zhongpeng; Wang, Chengshan; Ma, Pengfei; Zhou, Aorigele; Liu, Sheng-Ao; Xu, Ming

    2016-02-01

    The lack of magmatic records with high-quality geochronological and geochemical data in the central segment of the southern Qiangtang subterrane in central Tibet inhibits a complete understanding of the subduction polarity of the Bangong-Nujiang Ocean lithosphere during the Mesozoic. In this study, we present the zircon U-Pb age as well as geochemical and Sr-Nd-Pb isotopic data for the Late Jurassic pluton from the Kangqiong area in the central segment of the southern Qiangtang subterrane. The Kangqiong pluton primarily consists of granodiorites (SiO2 = 62.87-65.17 wt.%) and was emplaced in the Late Jurassic (147.6 ± 2.4-149.9 ± 2.1 Ma). The granodiorites display high Na2O numbers (Na2O/K2O = 1.75-2.24) as well as high MgO (2.21-3.14 wt.%) and Mg-numbers (53-58), are characterized by a low abundance of heavy rare earth elements (e.g., Yb = 1.05-1.92 ppm) and Y (12.63-17.52 ppm), and high Sr/Y (29-61) and La/Yb (14-18) ratios, which are comparable in composition to those of slab-derived adakitic rocks. The Kangqiong adakitic granodiorites have initial (87Sr/86Sr)i ratios of 0.70611 to 0.70669, negative εNd(t) values (- 1.06 to - 0.25), (206Pb/204Pb)t ratios of 18.42 to 18.47, (207Pb/204Pb)t ratios of 15.62 to 15.63, and (208Pb/204Pb)t ratios of 38.50 to 38.60. These geochemical signatures indicate that the magmas were most likely derived from the partial melting of the subducted Bangong-Nujiang oceanic crust and minor contaminants from the accretionary complex. Our results, in combination with the coeval magmatism in the western segment of the southern Qiangtang subterrane, indicate that the Bangong-Nujiang oceanic lithosphere was subducted northward beneath the Qiangtang Terrane, forming a west-east magmatic arc over 800 km during the Late Jurassic.

  2. Partial melting of subducted paleo-Pacific plate during the early Cretaceous: Constraint from adakitic rocks in the Shaxi porphyry Cu-Au deposit, Lower Yangtze River Belt

    NASA Astrophysics Data System (ADS)

    Deng, Jianghong; Yang, Xiaoyong; Li, Shuang; Gu, Huangling; Mastoi, Abdul Shakoor; Sun, Weidong

    2016-10-01

    A large porphyry Cu-Au deposit associated with early Cretaceous intrusive rocks has been discovered and explored in the Shaxi area, Lower Yangtze River Belt (LYRB), eastern China. We studied two types of intrusive rocks in the Shaxi area: Cu-Au mineralization related diorites and quartz-diorites (adakitic rocks), and newly found high Sr/Y ratio biotite-gabbros. They were formed almost simultaneously with crystallization ages of ca. 130 to 129 Ma, younger than the early stage shoshonitic rocks (Longmenyuan, Zhuanqiao and Shuangmiao Fm.) in the Luzong volcanic basin, ~ 10 km south of the Shaxi area. These intrusive rocks show similar distribution patterns of trace elements (enriched in LILEs and depleted in HFSEs) and REEs (enriched in LREEs and depleted in HREEs, no Eu negative anomaly, flat HREE patterns). The diorites and quartz-diorites are adakitic rocks with calc-alkaline affinity, distinguished from other adakitic rocks in the LYRB which are high-K calc-alkaline series. The biotite-gabbros are not adakitic rocks, although they are characterized by high Sr/Y ratios. Shaxi adakitic rocks show positive zircon εHf(t) values, which may be attributed to the contribution of subducted oceanic crust, while the εHf(t) values of the biotite-gabbros are mostly negative, indicating the involvement of old crustal materials. Although Sr-Nd-Pb isotopes of Shaxi adakitic rocks are more depleted than those of other adakitic rocks in the LYRB, they are still slightly enriched, similar to continental arc adakites in the Andean Austral Volcanic Zone. The Shaxi adakitic rocks are characterized by high Sr contents and Sr/Y ratios, medium (La/Yb)N, MgO contents and Mg#, and low K2O/Na2O ratios, decoupling of Sr/Y and (La/Yb)N, low Th/U values, exhibiting characteristics of slab-derived adakitic rocks. They were not produced by fractional crystallization of basaltic magmas like adakitic rocks in Edong-Jiurui and Tongling but originally generated from partial melting of subducted

  3. Spatial and temporal distribution of Mesozoic adakitic rocks along the Tan-Lu fault, Eastern China: Constraints on the initiation of lithospheric thinning

    NASA Astrophysics Data System (ADS)

    Gu, Hai-Ou; Xiao, Yilin; Santosh, M.; Li, Wang-Ye; Yang, Xiaoyong; Pack, Andreas; Hou, Zhenhui

    2013-09-01

    The Mesozoic tectonics in East China is characterized by significant lithospheric thinning of the North China Craton, large-scale strike-slip movement along the Tan-Lu fault, and regional magmatism with associated metallogeny. Here we address the possible connections between these three events through a systematic investigation of the geochemistry, zircon geochronology and whole rock oxygen isotopes of the Mesozoic magmatic rocks distributed along the Tan-Lu fault in the Shandong province. The characteristic spatial and temporal distributions of high-Mg adakitic rocks along the Tan-Lu fault with emplacement ages of 134-128 Ma suggest a strong structural control for the emplacement of these intrusions, with magma generation possibly associated with the subduction of the Pacific plate in the early Cretaceous. The low-Mg adakitic rocks (127-120 Ma) in the Su-Lu orogenic belt were formed later than the high-Mg adakitic rocks, whereas in the Dabie orogenic belt, most of the low-Mg adakitic rocks (143-129 Ma) were generated earlier than the high-Mg adakitic rocks. Based on available data, we suggest that the large scale strike-slip tectonics of the Tan-Lu fault in the Mesozoic initiated cratonic destruction at the south-eastern margin of the North China Craton, significantly affecting the lower continental crust within areas near the fault. This process resulted in crustal fragments sinking into the asthenosphere and reacting with peridotites, which increased the Mg# of the adakitic melts, generating the high-Mg adakitic rocks. The gravitationally unstable lower continental crust below the Tan-Lu fault in the Su-Lu orogenic belt triggered larger volume delamination of the lower continental crust or foundering of the root.

  4. Early Cretaceous continental delamination in the Yangtze Block: Evidence from high-Mg adakitic intrusions along the Tanlu fault, central Eastern China

    NASA Astrophysics Data System (ADS)

    Jia, Liqiong; Mo, Xuanxue; Santosh, M.; Yang, Zhusen; Yang, Dan; Dong, Guochen; Wang, Liang; Wang, Xinchun; Wu, Xuan

    2016-09-01

    Early Cretaceous high-Mg adakitic rocks from central Eastern China provide important insights into the thinning mechanism of the over-thickened lithosphere in the Yangtze Block (YB) as well as the North China Block (NCB). The Tanlu fault (TLF), located between the North China and Yangtze Blocks, and has been considered as a prominent pathway of magmas and fluids that resulted in lithosphere thinning of the YB during the Mesozoic-Cenozoic. Here we report the petrology, whole-rock geochemistry, zircon U-Pb geochronology, in situ Hf isotopes, and whole-rock Sr-Nd-Pb isotopes of four high-Mg adakitic intrusions along the TLF in northeastern Langdai. These adakitic intrusions consist of monzodiorite, quartz monzonite porphyry, and quartz monzodiorite. Zircon LA-MC-ICPMS analyses of five samples yield weighted mean 206Pb/238U ages of 127.58 ± 0.80, 126.90 ± 0.81, 120.71 ± 0.64, 122.75 ± 0.57, and 129.2 ± 1.1 Ma, indicating their emplacement during the Early Cretaceous. The intrusions have intermediate SiO2 (53.18-65.48 wt%) and high potassium (K2O = 3.07-3.95 wt%; Na2O/K2O = 1.02-1.26) and are classified as shoshonitic to high-K calc-alkaline series. They are characterized by high MgO (1.80-7.35 wt%), Mg# (50-65), Sr (591-1183 ppm), Ni (20.3-143.0 ppm), and Cr (51.40-390.0 ppm) contents, high (La/Yb)N (11.60-28.33) and Sr/Y (27.9-113.5) ratios, and low Y (7.79-22.4 ppm) and Yb (0.60-2.01 ppm) contents, comparable with high-Mg adakites. The samples are enriched in light rare earth elements but depleted in heavy rare earth elements and high field strength elements with slightly negative to positive Eu anomalies (δEu = 0.81-1.30), resembling the features of high-Mg adakitic rocks. Their whole-rock εNd(t) = -16.2 to -15.0, initial (87Sr/86Sr)i = 0.7060-0.7074, low radiogenic Pb (206Pb/204Pb(t) = 16.208-16.509, 207Pb/204Pb(t) = 15.331-15.410, and 208Pb/204Pb(t) = 36.551-36.992), and zircon εHf(t) = -36.6 to -16.6 suggest magma derivation from a continental crustal

  5. Thickened juvenile lower crust-derived ~ 90 Ma adakitic rocks in the central Lhasa terrane, Tibet

    NASA Astrophysics Data System (ADS)

    Sun, Gao-Yuan; Hu, Xiu-Mian; Zhu, Di-Cheng; Hong, Wen-Tao; Wang, Jian-Gang; Wang, Qing

    2015-05-01

    The questions of why the Late Cretaceous magmatism generated and how the nature of the lower crust evolves in central Tibet remain poorly constrained. In this paper, we report the presence of early Late Cretaceous adakitic rocks from the Azhang area, northern edge of the central Lhasa subterrane, central Tibet. These rocks are rhyodacites/dacites in composition and have geochemical characteristics of adakitic rocks, e.g., high Sr (554-836 ppm), Sr/Y (66-100), and (La/Yb)N (20-21), low Y (7.96-8.96 ppm) and heavy rare earth elements (HREE). In situ zircon U-Pb dating for two samples yields an early Late Cretaceous age (90 ± 1 Ma and 87 ± 1 Ma). The low MgO (1.4-1.9 wt.%) contents and compatible element abundances (e.g., Cr = 22-30 ppm; Ni = 19-25 ppm) indicate that these rocks were most likely derived from the partial melting of a garnet-bearing amphibolite under a thickened lower crust condition. The positive whole-rock εNd(t) (+ 2.5 to + 5.6) and zircon εHf(t) (+ 8.9 to + 16.0) values suggest that this thickened lower crust was juvenile. The crust beneath the central Lhasa subterrane may have been significantly thickened due to tectonic shortening in response to the Lhasa-Qiangtang collision and magma underplating before the emplacement of Azhang adakitic rocks (~ 90 Ma). We argue that regional lithospheric delamination at ~ 90 Ma triggered the partial melting of the lowermost garnet-bearing crust that is still attached to the middle crust to generate the Azhang adakitic rocks. The presence of the ~ 90 Ma Azhang adakitic rocks provides valuable constraints on the origin of the early Late Cretaceous magmatism in the central Lhasa subterrane and on the crustal evolution beneath the Lhasa-Qiangtang collisional zone prior to the Cenozoic India-Asia collision.

  6. Adakite-like rocks of the Central Andean Jurassic arc: composition and tectonic setting

    NASA Astrophysics Data System (ADS)

    Kramer, W.; Seifert, W.

    2003-04-01

    During the last few years the suggestion on pre-Miocene adakite generation have been arosen. We draw attention to adakite-like Jurassic Central Andean volcanic rocks from a study area between 18 o30' and 24o latitude S. They occur intercalated with Sinemurian and Middle Oxfordian shallow marine sediments and mark the onset and terminating stages of the Jurassic arc volcanic activity, respectively. The investigated rocks meet the criteria of adakites according to Defant et al. (1991), except for low La/Yb ratios (La/Yb = 8 to 12). The most of them display >55% SiO_2, >17% Al_2O_2, 2 to 5% MgO, <14 ppm Y, <1.6 ppm (0.9 to 1.6) Yb, >400 ppm Sr, <0.7040 87Sr/86Sr_i and bear tschermakite or magnesiohornblende. However, comparison of the N-Chilean adakite-like andesites and dacites with adakites from the Philippine arc and Mt. Burney adakites, South Andes, in the incompatible element spider diagrams and in a Mg# vs. SiO_2 diagram show a far-reaching overlap with our samples. These in part have a slightly elevated level for HREE. According to experimental work by Rapp et al. (1999), Mg-rich adakite-like rocks as from the Lower Jurassic may result from slab melt hybridization due to reaction with peridotite in the mantle wedge. The Lower Jurassic volcanic association with adakite-like volcanic rocks occurs in the eastern Coastal Cordillera, whereas the intensive Middle Jurassic basaltic andesitic volcanism of the convergent plate-margin type spreads around the modern coast line on a broad front. In this context we envisage a westward shift of the magma sources and of the slab hinge, connected with slab steepening during the Early Bajocian between 18o30' and 21 oS. Defant, M.J. et al., 1991. Contrib. Mineral. Petrol. 106, 309-324. Rapp, R.P. et al., 1999. Chemical Geology 160, 335-356.

  7. Southeastward lower crustal channel flow beneath southern Tibet: geochemical evidences from Miocene adakitic rocks

    NASA Astrophysics Data System (ADS)

    Xu, J.; Chen, J.; Zhao, W.; Dong, Y.; Wang, B.; Kang, Z.; Tethyan Tectonic Evolution

    2010-12-01

    It is generally believed that the Miocene adakitic rocks in the Lhasa Block (Terrane), southern Tibet, were derived from a thickened lower crust (e.g. Chung et al., 2003; Hou et al., 2004; Guo et al., 2007), and that their compositions will therefore reflect the geochemical characteristics of their lower crustal source(s). Here we present new geochemical and dating data for the adakitic rocks in eastern and western part of the Lhasa Block, which, when combined with previous geochemical data on south sides of the Indus-Yalu suture (IYS), allow us to assess different possible sources between western and eastern part of the Lhasa block as well as on both sides of the IYS. These adakitic rocks in the Lhasa block and on the south side of the IYS were emplaced in Miocene (12-26 Ma), but they show different geochemical characteristics. Adakitic rocks in the western part of the Lhasa Block have geochemical and Sr-Nd isotopic compositions that clearly differ from those in the east. For example, the western rocks are more enriched in Nd-Sr isotopes and have older model ages than the eastern rocks, hinting that the compositions of the lower crust under western and eastern Lhasa also differ. In addition, it should be noted that adakitic rocks on the south side of the IYS have the same geochemical characteristics as adakitic rocks in western Lhasa, but differ from those of eastern Lhasa. Moreover, geochemical and Sr-Nd isotopic compositions of the adakitic rocks on the south side of the IYS indicate that they were probably not generated by partial melting of crust beneath the Himalayas. We suggest that the lower crustal material beneath western Lhasa extends to the southern side of the IYS, and that its presence there can be explained by channel flow. Previous study (King et al., 2007) proposed southward ductile flow of Asian crust below eastern part of the Lhasa Block in southern Tibet, but our data lead us to believe the southeastward-moving of lower crustal material from

  8. Petrogenesis of Cretaceous adakite-like intrusions of the Gangdese Plutonic Belt, southern Tibet: Implications for mid-ocean ridge subduction and crustal growth

    NASA Astrophysics Data System (ADS)

    Zheng, Yuan-chuan; Hou, Zeng-qian; Gong, Ying-li; Liang, Wei; Sun, Qing-Zhong; Zhang, Song; Fu, Qiang; Huang, Ke-Xian; Li, Qiu-Yun; Li, Wei

    2014-03-01

    least 70% of the magma source region was juvenile materials. Combined with the presence of HT (high temperature) charnockitic magmatism, HT granulite facies metamorphism, and large volumes of Late Cretaceous batholiths, the oceanic-slab-derived Nuri adakitic rocks indicate a substantial high heat flux in the Gangdese batholith belt during the Late Cretaceous, which may have been related to subduction of a Neo-Tethyan mid-ocean ridge system. According to this model, hot asthenosphere would rise up through the corresponding slab window, and come into direct contact with both the oceanic slab and the base of the overlying plate. This would cause melting of both the oceanic slab and the overlying plate by the addition of heat that was ultimately linked with peak magmatism and the significant growth and chemical differentiation of juvenile crust in southern Tibet during the Late Cretaceous (105-76 Ma). In addition, the petrogenesis of the Langxian adakite-like two-mica granite indicates that the southern Tibetan crust was still of normal thickness prior to the emplacement of these intrusions at ca. 76 Ma. This probably means that large parts of southern Tibet were not very highly elevated prior to the Indian-Asian collision.

  9. Petrogenesis and tectonic significance of the Eocene adakite-like rocks in western Yunnan, southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Ding, Huixia; Hou, Qingye; Zhang, Zeming

    2016-02-01

    Eocene magmatic rocks are widespread in western Yunnan, southeastern Tibetan Plateau. However, their petrogenesis and tectonic significance remain controversial. In this paper, we report geochemical and geochronological data of adakite-like rocks from the eastern part of western Yunnan. Zircon U-Pb dating reveals that they were emplaced at ca. 35 Ma. A geochemical study shows that these rocks have high SiO2 (68.97-72.44 wt.%), K2O (4.35-5.87 wt.%) and low MgO (0.61-1.16 wt.%), Y (6.65-12.6 ppm) and Yb (0.58-1.02 ppm) contents as well as high Sr/Y (74-228) and La/Yb (59-131) values, belonging to high-K calc-alkaline to shoshonitic adakite-like rocks. These rocks have high (87Sr/86Sr)i (0.70623-0.70653), low εNd(t) (- 4.5 to - 7.5) and slightly low radiogenic Pb isotopic compositions with (206Pb/204Pb)i = 18.042-18.179. Zircons of these rocks show εHf(t) values ranging from - 6.3 to + 1.2 and model ages (TDM2) of 1513-1035 Ma. The geochemical characteristics indicate that the Eocene adakite-like rocks from the eastern part of western Yunnan were derived from the partial melting of Neoproterozoic mafic rocks underplated in the lower crust of the western margin of the Yangtze Plate with input of mantle-derived potassic-ultrapotassic melt. Integration of published geochemical data clearly shows that zircon εHf(t) and whole-rock εNd(t) values of Eocene adakite-like rocks from the whole western Yunnan exhibit a trend of westward increase. We infer that the adakite-like rocks from the western part of western Yunnan were derived from the partial melting of late Paleozoic-Mesozoic mafic rocks formed as the lower crust of a continental magmatic arc during eastward subduction of the Paleo-Tethyan Ocean, and the Eocene magmatic rocks in western Yunnan were generated during the removal of thickened continental lithosphere triggered by the India and Asia collision.

  10. Evidence From Adakitic Rocks For Lithosphere Recycling At The U.S. East Coast Volcanic Rifted Margin

    NASA Astrophysics Data System (ADS)

    Meyer, R.; Van Wijk, J. W.

    2014-12-01

    Magmatism at magmatic rifted margins is dominated by asthenospheric melts generated during decompression melting from the upwelling asthenosphere. However reported magma compositions are diverse, giving clues about additional processes during rifting and continental rupture. We report here on adakites from the U.S. East Coast that are related to breakup of the North Atlantic. The sampled adakites are bi-modal, and show a clear high-Si and low-Si major and trace element chemistry. During the closure of the proto-Atlantic and its related back-arc basins, the Appalachian lithosphere sampled an ophiolitic mélange within major sutures. Subsequent metamorphic events in the Blue Ridge province of the U.S. East Coast increased the rock density of the ophiolites (eclogite) and partly hydrated these mafic to ultramafic rocks. Such a preconditioned lithosphere will likely develop gravitational instabilities at the asthenosphere-lithosphere boundary during rifting. We use geodynamic models to show when gravitational instabilities form below the East Coast margin, and how they eventually delaminate mantle lithosphere and lower crust material. After foundering, the delaminated lithosphere undergoes metamorphism, heats up, and interacts with fluids and melts in the surrounding convecting mantle. Partial melting of this metamorphic lithology produces high-Si adakitic melts. These melts percolated upwards through the mantle and were partially injected into the Valley and Ridge province. Where melt-to-peridotite (asthenosphere) ratios were small, the melts and fluids leaving the sinking lithospheric block became fixed within the peridotites. Geochemical modeling suggests, that 5 to 10% melting degrees of such a metasomatically overprinted and fertile asthenosphere produced the low-Si adakitic rocks of the Virginia adakites.

  11. Contrasting zircon Hf-O isotopes and trace elements between ore-bearing and ore-barren adakitic rocks in central-eastern China: Implications for genetic relation to Cu-Au mineralization

    NASA Astrophysics Data System (ADS)

    Wang, Fangyue; Liu, Sheng-Ao; Li, Shuguang; He, Yongsheng

    2013-01-01

    The petrogenesis of Early Cretaceous adakitic intrusions in the Lower Yangtze River belt (LYRB), central-eastern China, and their genetic association with Cu-Au mineralization have recently been debated. This study presented integrated in-situ zircon U-Pb-Hf-O isotopic and trace elemental data for the LYRB adakites, and a comparison with ore-barren adakites from the south Tan-Lu fault (STLF) adjacent to the LYRB. Magmatic zircons from these two series of intrusions have U-Pb ages of 145-132 Ma and 136-132 Ma respectively. The STLF zircons have δ18O ranging from 5.6 to 6.7‰ and ɛHf(t) from - 28.8 to - 16.4, plotted within the range of global lower crustal metabasaltic xenoliths, consistent with low-radiogenic Pb of the host adakitic rocks. In contrast, both Hf and O isotopic compositions of zircons from the LYRB are greatly variable with heavier δ18O (4.7 to 9.6‰) and higher ɛHf(t) values (- 25.5 to + 2.0) compared with the STLF series. The co-variations of Hf-O isotopes in the LYRB series reflect source heterogeneity as a result of mixing of basaltic oceanic crust with sediments (10-20%), consistent with high-radiogenic Pb and enriched Sr-Nd isotopic compositions of the host adakites. The high La, U and low Ti concentrations in the LYRB zircons also imply a volatile (perhaps, CO32 --rich, carbonatite-like) source. Combined with whole-rock geochemical data, the new results further suggest contrasting origins of the LYRB and STLF adakites from subducted oceanic crust and foundering lower continental crust, respectively. The LYRB zircons have much higher ratios of Ce4 +/Ce3 + (avg.417) and Eu/Eu* (avg. 0.67) than the STLF zircons (avg. 84 and 0.44). This difference confirms that the ore-bearing adakitic magmas are more oxidized relative to the ore-barren ones. There is roughly a positive correlation between zircon Ce4 +/Ce3 + and δ18O in the LYRB series, probably indicating that the elevated fO2 was related to components enriched in heavy oxygen isotopes. A

  12. High-Mg adakitic rocks and their complementary cumulates formed by crystal fractionation of hydrous mafic magmas in a continental crustal magma chamber

    NASA Astrophysics Data System (ADS)

    Ma, Qiang; Xu, Yi-Gang; Zheng, Jian-Ping; Sun, Min; Griffin, William L.; Wei, Ying; Ma, Liang; Yu, Xiaolu

    2016-09-01

    Understanding how adakitic magmas form is important for understanding the formation of the continental crust. Generating such high-Sr/Y rocks by crystal fractionation of basalts/basaltic andesites in magma chambers has been proposed in a wide range of tectonic settings. However, the complementary cumulates predicted by this scenario have rarely been observed. The late Triassic (~ 227 Ma) Ningcheng complex from the North China Craton is composed of a websterite - (Ol -/Hbl-) pyroxenite - gabbro unit and a quartz-diorite unit. They are interpreted as the products (cumulates and derivative melts, respectively) of fractionation from hydrous mafic magmas at mid- to lower-crustal pressures (4.9 ~ 8.3 kbar). The quartz diorites are high-Mg intermediate rocks with moderate SiO2 (57.0 ~ 62.9 wt%), high Mg# (> 49) and adakitic trace element signatures, such as high Sr (≥ 636 ppm) and light rare earth elements (REEs), low Y (≤ 17 ppm) and heavy REEs (Yb ≤ 1.8 ppm), lack of obvious Eu anomalies, and high Sr/Y (≥ 31) and La/Yb (≥ 24)). These adakitic signatures reflect differentiation of hydrous mantle-derived magmas in the deep crust, leaving behind a plagioclase-free residual solid assemblage in the early stages, which is represented by the coeval websterite-pyroxenite complex. This study therefore not only demonstrates that hydrous crystal fractionation is an important mechanism to form adakitic rocks, but also presents an example of a preserved fractionating system, i.e. high-Sr/Y rocks and their complementary cumulates. A geochemical comparison is made between representative adakitic rocks formed by fractionation of hydrous magmas and Archean TTGs. It is suggested that crystal fractionation is an efficient process for making Phanerozoic high Sr/Y rocks but was not responsible for the formation of Archean granitoids.

  13. Slab melting and the origin of gold in Au and Au-Cu deposits: geochemical clues from recent adakites.

    NASA Astrophysics Data System (ADS)

    Polve, M.; Maury, R.; Joron, J. L.

    2003-04-01

    Understanding the genetic processes responsible for the common occurrence of Au and Au-Cu deposits in subduction environments is a fairly "hot" question nowadays, as it is clear that most subduction-related magmatic rocks are barren. Studies of space and time relationships between magmatic intrusions, hydrothermal episodes and Au deposits have shown that, very often, Au deposits are associated with adakitic intrusions (Thieblemont et al, 1997, Sajona and Maury, 1998). Adakites are here understood as being generated by melting of the subducting oceanic crust. This study aims to check wether or not magmas derived from melted oceanic crust do contain significantly more Au than regular calc-alkaline magmas by measuring directly Au concentrations in fresh (and barren) adakites and equivalent calc-alkaline andesites. There is a lack of reliable data on Au content in unaltered adakites and andesites, because Au analyses are generally done on hydrothermalized rocks in connection with Au deposits and also because old measurements may give overestimated Au contents, due to technical limitations. Therefore we compiled recent literature data on gold contents of fresh calc-alkaline rocks, and measured Au on a selection of 40 well studied and dated adakites from different localities (Philippines, Baja California). Analyses have been performed either by INAA or by ICP-MS after Au extraction with aqua regia, following the method described by Terashima (1988). Preliminary results show that, for equivalent Si02 contents, adakites are systematically enriched in Au compared to regular dacites, even if regional trends also exist. Moreover, Au seems to behave as an incompatible element in adakitic magmas, whereas in calc-alkaline dacites it is controlled by sulfide crystallization. Our data suggest that, not excluding any other processes related to the hydrothermal phase in the deposit generation, adakites may indeed represent the source of Au, a possible explanation for the adakite

  14. Early Cretaceous low-Mg# adakitic rocks in the southern margin of the central North China Craton: Partial melting of thickened lower continental crust and tectonic implications

    NASA Astrophysics Data System (ADS)

    Yang, D.

    2015-12-01

    This paper reports new whole-rock geochemical, Sr-Nd-Pb isotopic, and zircon U-Pb and Hf isotopic data for Early Cretaceous intrusive rocks in the Sanmenxia-Houma area of central China, and uses these data to constrain the petrogenesis of low-Mg adakitic rocks (LMAR) and the spatial extent of the influence of the deeply subducted Yangtze slab during the Triassic evolution of this region. New zircon LA-ICP-MS U-Pb data indicate that the early- and late-stage southern Quli, Qiligou, and Gaomiao porphyritic quartz diorites, the Canfang granodiorite, and the northern Wangmao porphyritic quartz monzodiorite were emplaced during the Early Cretaceous (~130 Ma) and the late Early Cretaceous (116 Ma). These rocks are characterized by high Na2O/K2O, Sr/Y, and (La/Yb)n ratios as well as high Sr concentrations, low Mg# values, and low heavy rare earth element and Y concentrations, all of which indicate an LMAR affinity. The samples have relatively high initial 87Sr/86Sr ratios (0.7054-0.7095), and low eNd(t) (-11.90 to -22.20) and eHf(t) (-16.7 to -32.7) values, indicative of a lower continental crust origin. The presence of Neoproterozoic (754-542 Ma) and inherited Late Triassic (220 Ma) metamorphic zircons within the late Early Cretaceous LMAR and the relatively high 206Pb/204Pb ratios of these rocks suggest that they formed from primary magmas derived from partial melting of Yangtze Craton (YC) basement material that had undergone ultrahigh-pressure metamorphism. In contrast, the presence of Paleoproterozoic and Archean inherited zircons within early Early Cretaceous LMAR in this area and the relatively low 206Pb/204Pb ratios of these rocks are indicative of derivation from primary magmas generated by partial melting of the thickened lower continental crust of the North China Craton (NCC). These rocks may have formed in an extensional environment associated with the upwelling of asthenospheric mantle material. The presence of YC basement material within the NCC in the

  15. Adakite-like geochemical signature produced by amphibole-dominated fractionation of arc magmas: An example from the Late Cretaceous magmatism in Gangdese belt, south Tibet

    NASA Astrophysics Data System (ADS)

    Xu, Wang-Chun; Zhang, Hong-Fei; Luo, Bi-ji; Guo, Liang; Yang, He

    2015-09-01

    Late Cretaceous (~ 106-76 Ma) adakite-like intrusive rocks in the middle-eastern Gangdese belt occur in an E-W trending belt paralleling the Indus-Yarlung suture, south Tibet. Their petrogenesis and geodynamic processes have been a subject of debate. We report here U-Pb zircon ages, geochemical and Sr-Nd-Hf isotopic data for adakite-like intrusive rocks as well as the normal arc rocks (gabbros and gabbroic diorites) in the middle Gangdese belt. LA-ICPMS U-Pb zircon analyses yielded an identical age of ~ 88 Ma for two adakite-like rocks, which are slightly younger than the gabbro and gabbroic diorite (ca. 94-90 Ma). Both the adakite-like rocks and the normal arc rocks have similar whole-rock Sr-Nd and zircon Hf isotope compositions, indicating that they have been derived from a common source. Similarly, the adakite-like and normal arc intrusive rocks in the eastern Gangdese belt also show similar Sr-Nd-Hf isotope compositions. In the middle-eastern Gangdese belt, the > 85 Ma Late Cretaceous intrusive rocks consist of a magma series from gabbro to granodiorite, including both normal arc rocks and adakite-like rocks. These rocks overlap in space and time that conform to a normal arc differentiation trend. In terms of major and trace elements, they also show a clear evolution from the normal arc magmatic into adakitic field. Thus, we suggest that these > 85 Ma Late Cretaceous intrusive rocks were ultimately derived from melting of the hydrated mantle wedge and the adakite-like rocks can be generated in normal arc magmas by amphibole-dominated fractionation. Taking into accounting for the spatial and temporal distribution of the Cretaceous magmatic rocks in the Lhasa terrane, we prefer a model of early Late Cretaceous rollback following Early Cretaceous low-angle oceanic slab subduction. At intermediate pressure and H2O-rich conditions, fractionation of amphibole changes the major and trace element compositions of arc magmas, and will efficiently drives basaltic

  16. Geochemistry of eclogite xenoliths in Mesozoic adakitic rocks from Xuzhou-Suzhou area in central China and their tectonic implications

    NASA Astrophysics Data System (ADS)

    Xu, Wen-Liang; Gao, Shan; Yang, De-Bin; Pei, Fu-Ping; Wang, Qing-Hai

    2009-02-01

    Detailed geochemical (major and trace elements, Sr-Nd isotope) and new zircon U-Pb dating data for eclogite and garnet-clinopyroxenite xenoliths within the Mesozoic adakitic rocks from the Xuzhou-Suzhou area in central China provide insight into origin of their protolith and the Mesozoic tectonic evolution of the eastern North China Craton (NCC). The eclogite xenoliths have a basaltic bulk composition with SiO 2 = 44.44-52.30 wt.%, Al 2O 3 = 11.72-20.90 wt.%, FeO total = 7.35-17.28 wt.%, and MgO = 4.35-10.62 wt.%, CaO = 7.80-12.96 wt.%. They are characterized by enrichment in large ionic lithophile elements, depletion in high field strength elements (such as Nb, Ta, Zr, Hf, and Ti) and transitional elements (Ni and Cr), and variable Sr-Nd isotopic compositions (initial 87Sr/ 86Sr ratios and the ɛ Nd (t) values ranging from 0.7041 to 0.7139 and from 3.03 to - 17.19, respectively), suggesting that their protoliths could have been formed in an island arc setting. The zircon age spectrum suggests that the majority of the eclogite xenoliths have a NCC affinity and that few show characteristics of the Yangtze Craton (YC) basement. The existence of the YC basement beneath the NCC in the Xuzhou-Suzhou area, together with the discovery of the early Mesozoic metamorphic and Neoproterozoic magmatic inherited zircons in the Mesozoic granites from the eastern NCC, implies that the eclogite-facies metamorphism of the eastern NCC basement might be attributed to the early Mesozoic subduction of the YC beneath the NCC along the Tan-Lu fault zone oriented in a north-westward (NW) direction. The subsequent YC clockwise rotation with respect to the NCC, the large-scale lateral extrusion and uplift of the Tongbai-Dabie Mountains in eastern China after the Triassic collision, as well as the early Cretaceous strike-slip in the Tan-Lu fault zone, played the major role in formation of the present tectonic architecture of the Dabie-Sulu belts.

  17. Early Carboniferous adakitic rocks in the area of the Tuwu deposit, eastern Tianshan, NW China: Slab melting and implications for porphyry copper mineralization

    NASA Astrophysics Data System (ADS)

    Wang, Yin-Hong; Xue, Chun-Ji; Liu, Jia-Jun; Wang, Jian-Ping; Yang, Jun-Tao; Zhang, Fang-Fang; Zhao, Ze-Nan; Zhao, Yun-Jiang; Liu, Bin

    2015-05-01

    Existing geochronological and geochemical data for the Early Carboniferous magmatic rocks in the eastern Tianshan, Xinjiang, have been interpreted in a variety of theories regarding petrogenesis and geodynamic setting. The proposed settings include rift, back-arc basin, passive continental margin, island arc, ridge subduction, and post-collisional environment. To evaluate these possibilities, we present new SHRIMP zircon U-Pb geochronology and geochemical data, whole-rock geochemical, Hf isotope, and S isotope data for tonalitic rocks and ores associated with the Tuwu porphyry copper deposit located in the center of the late Paleozoic Dananhu-Tousuquan arc, eastern Tianshan. SHRIMP zircon U-Pb dating indicates that the magmatic activity and thus associated copper mineralization occurred ca.332 Ma. The tonalitic rocks are calc-alkaline granites with A/CNK values ranging from 1.16 to 1.58; are enriched in K, Rb, Sr, and Ba; and are markedly depleted in Nb, Ta, Ti, and Th. They show geochemical affinities similar to adakites, with high Sr, Al2O3, and Na2O contents and La/Yb ratios; low Y and Yb contents; and slight positive Eu anomalies. In situ Hf isotopic analyses of zircons yielded positive initial εHf(t) values ranging from 6.9 to 17.2. The δ34S values of the ore sulfides range from -3.0‰ to +1.7‰, reflecting a deep sulfur source. Our results indicate that the paleo-Tianshan oceanic slab was being simultaneously subducted northward beneath the Dananhu-Tousuquan arc, and southward beneath the Aqishan-Yamansu arc during the Early Carboniferous. The Tuwu adakitic tonalitic rocks were derived from the partial melting of the subducted paleo-Tianshan oceanic slab, which was subsequently hybridized by mantle wedge peridotites. The slab-derived magmas have considerably high copper contents and are highly oxidized, thus leading to porphyry copper mineralization. Such Early Carboniferous tonalitic rocks that are widespread in the eastern Tianshan define a province

  18. Slab-derived adakites and subslab asthenosphere-derived OIB-type rocks at 156 ± 2 Ma from the north of Gerze, central Tibet: Records of the Bangong-Nujiang oceanic ridge subduction during the Late Jurassic

    NASA Astrophysics Data System (ADS)

    Li, Shi-Min; Zhu, Di-Cheng; Wang, Qing; Zhao, Zhidan; Zhang, Liang-Liang; Liu, Sheng-Ao; Chang, Qing-Song; Lu, Ying-Huai; Dai, Jin-Gen; Zheng, Yuan-Chuan

    2016-10-01

    This paper reports zircon U-Pb age and Hf isotope, whole-rock major and trace element, and whole-rock Sr-Nd-Hf isotope data of the dacites from Rena Tso and mafic rocks (diabases and basalts) from Duobuza, north of Gerze, central Tibet. These data reveal the presence of a distinct rock association of slab-derived adakites (154 ± 1 Ma) and subslab asthenosphere-derived OIB-type (oceanic island basalt) mafic rocks (157.6 ± 1.4 Ma). The medium-K calc-alkaline dacites (SiO2 = 66-69 wt.%) from Rena Tso are enriched in Sr (520-1083 ppm) and depleted in heavy rare earth elements (HREEs) and Y (9.8-10.8 ppm), resembling adakites. These adakitic dacites have low whole-rock initial 87Sr/86Sr ratios of 0.7043-0.7046, positive εNd(t) (+ 1.0 to + 3.4), εHf(t) (+ 6.4 to + 7.0), and zircon εHf(t) (+ 1.9 to + 7.6) values, indicating an oceanic slab origin (crust and sediment). Considering the low Mg# (32-53) and (La/Yb)N (19-23), the adakitic dacites are most likely derived from the partial melting of the subducting slab at shallow depths and the subsequent interaction with peridotite in a thin mantle wedge during magma ascent. The diabases and basalts (SiO2 = 49-53 wt.%) from Duobuza show an alkali signature with enrichment of high field strength elements (HFSEs) (e.g., Zr = 213-285 ppm) and exhibit positive Nb-Ta-Ti anomalies that are geochemically comparable to those of OIB. These samples show positive whole-rock εNd(t) values of + 3.3 to + 3.7, εHf(t) values of + 4.7 to + 5.7, and negative to positive zircon εHf(t) values of - 1.5 to + 5.2. These OIB-type mafic samples are interpreted as the products of low-degree decompression melting of the upwelling subslab asthenosphere with a minor contribution from the sub-continental lithospheric mantle (SCLM). Our new data indicate the presence of a distinct rock association of coeval slab-derived adakites and subslab asthenosphere-derived OIB-type rocks. Such an association along with the normal arc rocks further to the north

  19. Intrusive Rock Database for the Digital Geologic Map of Utah

    USGS Publications Warehouse

    Nutt, C.J.; Ludington, Steve

    2003-01-01

    Digital geologic maps offer the promise of rapid and powerful answers to geologic questions using Geographic Information System software (GIS). Using modern GIS and database methods, a specialized derivative map can be easily prepared. An important limitation can be shortcomings in the information provided in the database associated with the digital map, a database which is often based on the legend of the original map. The purpose of this report is to show how the compilation of additional information can, when prepared as a database that can be used with the digital map, be used to create some types of derivative maps that are not possible with the original digital map and database. This Open-file Report consists of computer files with information about intrusive rocks in Utah that can be linked to the Digital Geologic Map of Utah (Hintze et al., 2000), an explanation of how to link the databases and map, and a list of references for the databases. The digital map, which represents the 1:500,000-scale Geologic Map of Utah (Hintze, 1980), can be obtained from the Utah Geological Survey (Map 179DM). Each polygon in the map has a unique identification number. We selected the polygons identified on the geologic map as intrusive rock, and constructed a database (UT_PLUT.xls) that classifies the polygons into plutonic map units (see tables). These plutonic map units are the key information that is used to relate the compiled information to the polygons on the map. The map includes a few polygons that were coded as intrusive on the state map but are largely volcanic rock; in these cases we note the volcanic rock names (rhyolite and latite) as used in the original sources Some polygons identified on the digital state map as intrusive rock were misidentified; these polygons are noted in a separate table of the database, along with some information about their true character. Fields may be empty because of lack of information from references used or difficulty in finding

  20. Crustal processes cause adakitic chemical signatures in syn-collision magmatism from SE Iran

    NASA Astrophysics Data System (ADS)

    Allen, Mark; Kheirkhah, Monireh; Neill, Iain

    2015-04-01

    We report new elemental and Nd-Sr isotopic analyses for Late Cenozoic intrusive and extrusive rocks emplaced in SE Iran as part of the wider syn-collision magmatic province within the Turkish-Iranian Plateau. The sample sites are near the town of Dehaj in Kerman Province. Most of the rocks are from stocks and batholiths, interpreted as the roots of central volcanoes. Age controls are not precise, but the rocks are likely to be Late Miocene-Quaternary in age. Basaltic to andesitic lavas crop out nearby; their relationships to the intrusive rocks are uncertain. Geochemically, the entire range of rocks from basalt lavas through to rhyolitic intrusives ranges from 51-71 wt.% silica and isotopic signatures are similar to Bulk Earth, without any clear evidence for large-scale crustal contamination. The basaltic to andesitic lavas appear to have variable and often high La/Yb and Sr/Y such that they range from calc-alkaline arc-like rocks to adakitic compositions depending on the degree of fractionation. The intrusive rocks seem to form a separate suite, with clear indications of increasing Sr/Y and Dy/Yb with fractionation. Previous interpretations relate adakitic magmatism to Tethyan oceanic slab break-off and slab melting beneath the collision zone. However, as the 'adakitic signature' is increasingly apparent in more evolved magmas, at least in the intrusives, adakite generation is more likely to have occurred during melt evolution from an initial low Sr/Y and low La/Yb parent. This parental melt may have been similar in starting composition to proposed non-adakitic basaltic melts from elsewhere in the collision zone. The high Sr/Yb and La/Yb signatures are best explained by the suppression of plagioclase fractionation by high magmatic water contents, promoting incompatible behaviour of Sr. Conversely, Y and Yb are compatible during amphibole and garnet fractionation at crustal or uppermost mantle levels. Rather than a localised slab break-off or melting effect, the

  1. Eocene high-Mg adakitic rocks of the northern Qiangtang terrane, central Tibet: possible delamination of lower crust and early uplift in the central plateau?

    NASA Astrophysics Data System (ADS)

    Xu, J.; Chen, J.; Zhao, W.; Dong, Y.; Wang, B.; Kang, Z.

    2011-12-01

    Details of the timing and mechanisms of uplift of the Tibetan Plateau have long been debated, such as whether the earliest uplift occurred at ~45 Ma in northern and northeastern Tibet (Turner et al. 1996; Chung et al. 1998; Guo et al. 2006; Wang et al. 2008), or if the whole plateau was instead formed by one stage or more stages of uplift (Turner et al. 1996; Williams et al. 2001; Tapponnier et al. 2001; Chen et al., 2009). It is generally believed that changes at the surface and in tectonic regime are typically marked by changes in the composition of associated magmatic products. Eocene high-Mg adakitic rocks (45-36 Ma) from the Qiangtang terrane provide important insights into the possible delamination of lower crust and/or underlying lithospheric mantle with a thickened keel, as well as early uplift processes of the central Tibetan plateau. We report new geochemical data for the Luanqinshan, Yuejinla and Dongyuehu Eocene lavas from the northern Qiangtang terrane. Analysis of a Meiriqiecuo lava yielded a 40Ar/39Ar plateau age of 43.35 ± 0.22 Ma, this result together with previously published ages indicate that the Eocene lavas in the northern Qiangtang terrane were mainly erupted from 45 to 36 Ma. The lava from the northern Qiangtang terrane have high Al2O3 and Sr contents, as well as high Sr/Y, La/Yb, and Mg# (43-69), but low Y and Yb concentrations. The same samples have low 87Sr/86Sr(t)(0.7062-0.7075) and low ɛNd(t) (-6.3 to -2.9). These geochemical features, combined with other characteristics of Tibetan Cenozoic lavas, indicate that they did not result from slab melting of a young oceanic crust, assimilation and fractional crystallization (AFC) of a mafic magma, or from either underplated or thickened continental crust. Instead, they were derived from partial melting of delaminated lower continental crust, which subsequently reacted with surrounding mantle peridotites during ascent to crustal depths. The high-Mg and low-Mg adakitic rocks (45-36 Ma), north

  2. The calc-alkaline and adakitic volcanism of the Sabzevar structural zone (NE Iran): Implications for the Eocene magmatic flare-up in Central Iran

    NASA Astrophysics Data System (ADS)

    Moghadam, Hadi Shafaii; Rossetti, Federico; Lucci, Federico; Chiaradia, Massimo; Gerdes, Axel; Martinez, Margarita Lopez; Ghorbani, Ghasem; Nasrabady, Mohsen

    2016-04-01

    A major magmatic flare-up is documented along the Bitlis-Zagros suture zone in Eocene-Oligocene times. The Cenozoic magmatism of intraplate Central Iran is an integrant part of this tectono-magmatic scenario. The Cenozoic magmatism of the Sabzevar structural zone consists of mostly intermediate to felsic intrusions and volcanic products. These igneous rocks have calc-alkaline and adakitic geochemical signatures, with nearly coincident zircon U-Pb and mica Ar-Ar ages of ca. 45 Ma. Adakitic rocks have quite low HREE and high Sr/Y ratio, but share most of their geochemical features with the calc-alkaline rocks. The Sabzevar volcanic rocks have similar initial Sr, Nd and Pb isotope ratios, showing their cogenetic nature. Nd model ages cluster tightly around ~ 0.2-0.3 Ga. The geochemistry of the Sabzevar volcanic rocks, along with their isotopic signatures, might strangle that an upper mantle source, metasomatized by slab-derived melts was involved in generating the Sabzevar calc-alkaline rocks. A bulk rock trace element modeling suggests that amphibole-plagioclase-titanite-dominated replenishment-fractional crystallization (RFC) is further responsible for the formation of the middle Eocene Sabzevar adakitic rocks. Extensional tectonics accompanied by lithospheric delamination, possibly assisted by slab break-off and melting at depth was responsible for the Eocene formation of the Sabzevar magmatic rocks and, more in general, for the magmatic "flare-up" in Iran.

  3. The large Bystrinskoe Cu-Au-Fe deposit (Eastern Trans-Baikal Region): Russia's first example of a skarn-porphyry ore-forming system related to adakite

    NASA Astrophysics Data System (ADS)

    Kovalenker, V. A.; Abramov, S. S.; Kiseleva, G. D.; Krylova, T. L.; Yazykova, Yu. I.; Bortnikov, N. S.

    2016-06-01

    The Bystrinskoe skarn-porphyry Cu-Au-Fe deposit (Eastern Trans-Baikal Region) is confined to skarn zones, which were formed along the contact of granitoids referred to the Shakhtama intrusive complex (J2-3), with terrigenous-carbonate sedimentary rocks. Commercial (Cu-Au-Fe ± W, Mo) mineralization was formed due to the regional postcollision development involving the intrusion of porphyritic granitoids, the derivatives of oxidized adakite highly magnesian magmas enriched in water, sulfur, and metals, which could develop under melting of garnet-bearing amphibolite in the mafic lower crustal arc.

  4. Pan-African adakitic rocks of the north Arabian-Nubian Shield: petrological and geochemical constraints on the evolution of the Dokhan volcanics in the north Eastern Desert of Egypt

    NASA Astrophysics Data System (ADS)

    Obeid, Mohamed A.; Azer, Mokhles K.

    2015-04-01

    The Precambrian basement of Egypt is part of the Red Sea Mountains and represents the north-western part of the Arabian-Nubian Shield (ANS). Five volcanic sections are exposed in the Egyptian basement complex, namely El Kharaza, Monqul, Abu Had, Mellaha and Abu Marwa. They are located in the north Eastern Desert (ED) of Egypt and were selected for petrological and geochemical studies as they represent the Dokhan volcanics. The volcanics divide into two main pulses, and each pulse was frequently accompanied by deposition of immature molasse type sediments, which represent a thick sequence of the Hammamat group in the north ED. Compositionally, the rocks form a continuum from basaltic andesite, andesite, dacite (lower succession) to rhyodacite and rhyolite (upper succession), with no apparent compositional gaps. These high-K calc-alkaline rocks have strong affinities to subduction-related rocks with enriched LILEs (Rb, Ba, K, Th, Ce) relative to high field strength elements (Nb, Zr, P, Ti) and negative Nb anomalies relative to NMORB. The lower succession displays geochemical characteristics of adakitic rocks with SiO2 >53 wt%, Al2O3 >15 wt%, MgO >2.5 wt%, Mg# >49, Sr >650 ppm, Y <17 ppm, Yb <2 ppm, Ni >25 ppm, Cr >50 ppm and Sr/Y >42.4. They also have low Nb, Rb and Zr compared to the coexisting calc-alkaline rhyodacites and rhyolites. The highly fractionated rhyolitic rocks have strong negative Eu anomalies and possess the geochemical characteristics of A-type suites. Trace element geochemical signatures indicate a magma source consistent with post-collisional suites that retain destructive plate signatures associated with subduction zones. The adakitic rocks in the northern ANS are generated through partial melting of delaminated mafic lower crust interacting with overlying mantle-derived magma. The Dokhan volcanics were likely generated by a combination of processes, including partial melting, crystal fractionation and assimilation.

  5. Dykes, cups, saucers and sills: Analogue experiments on magma intrusion into brittle rocks

    NASA Astrophysics Data System (ADS)

    Mathieu, L.; van Wyk de Vries, B.; Holohan, Eoghan P.; Troll, Valentin R.

    2008-07-01

    Magma is transported in the crust by blade-like intrusions such as dykes, sills, saucers, and also collects in thicker laccoliths, lopoliths and plutons. Recently, the importance and great number of shallow (< 5 km) saucer-shaped intrusions has been recognized. Lopoliths and cup-shaped intrusions have also been reported in many geological contexts. Our field observations indicate that many intrusions, especially those emplaced into breccias or fractured rocks, have bulging, lobate margins and have shear faults at their bulbous terminations. Such features suggest that magma can propagate along a self-induced shear fault rather than a hydraulic tension-fracture. To investigate this we use analogue models to explore intrusion propagation in a brittle country rock. The models consist of the injection of analogue magma (honey or Golden syrup) in a granular material (sand or sieved ignimbrite) that is a good analogue for brittle or brecciated rocks. These models have the advantage (over other models that use gelatin) to well represent the properties of brittle materials by allowing both shear-faults and tension fractures to be produced at suitable stresses. In our experiments we mainly obtain vertical dykes and inverted-cone like structures that we call cup-shaped intrusions. Dykes bifurcate into cup-shaped intrusions at depths depending on their viscosity. All cup-shaped intrusions uplift a central block. By injecting against a vertical glass plate we obtain detailed observations of the intrusion propagation style. We observe that dykes commonly split and produce cup-shaped intrusions near the surface and that shear zone-related intrusions develop at the dyke tip. We conclude that many dykes propagate as a viscous indenter resulting from shear failure of host rock rather than tensional hydraulic fracturing of host rocks. The shear propagation model provides an explanation for the shape and formation of cup-shaped intrusions, saucer-sills and lopoliths.

  6. Rapid intrusion of magma into wet rock: groundwater flow due to pore pressure increases.

    USGS Publications Warehouse

    Delaney, P.T.

    1982-01-01

    Analytical and numerical solutions are developed to simulate the pressurization, expansion, and flow of groundwater contained within saturated, intact host rocks subject to sudden heating from the planar surface of an igneous intrusion. For most rocks, water diffuses more rapidly than heat, assuring that groundwater is not heated along a constant-volume pressure path and that thermal expansion and pressurization adjacent to the intrusion drives a flow that extends well beyond the heated region. -from Author

  7. The Basal Onaping Intrusion in the North Range: Roof rocks of the Sudbury Igneous Complex

    NASA Astrophysics Data System (ADS)

    Anders, Denise; Osinski, Gordon R.; Grieve, Richard A. F.; Brillinger, Derek T. M.

    2015-09-01

    The 1.85 Ga Sudbury impact structure is one of the largest impact structures on Earth. Igneous bodies—the so-called "Basal Onaping Intrusion"—occur at the contact between the Sudbury Igneous Complex (SIC) and the overlying Onaping Formation and occupy ~50% of this contact zone. The Basal Onaping Intrusion is presently considered part of the Onaping Formation, which is a complex series of breccias. Here, we present petrological and geochemical data from two drill cores and field data from the North Range of the Sudbury structure, which suggests that the Basal Onaping Intrusion is not part of the Onaping Formation. Our observations indicate that the Basal Onaping Intrusion crystallized from a melt and has a groundmass comprising a skeletal intergrowth of feldspar and quartz that points to simultaneous cooling of both components. Increasing grain size and decreasing amounts of clasts with increasing depth are general features of roof rocks of coherent impact melt rocks at other impact structures and the Basal Onaping Intrusion. Planar deformation features within quartz clasts of the Basal Onaping Intrusion are indicators for shock metamorphism and, together with the melt matrix, point to the Basal Onaping Intrusion as being an impact melt rock, by definition. Importantly, the contact between Granophyre of the SIC and Basal Onaping Intrusion is transitional and we suggest that the Basal Onaping Intrusion is what remains of the roof rocks of the SIC and, thus, is a unit of the SIC and not the Onaping Formation. We suggest henceforth that this unit be referred to as the "Upper Contact Unit" of the SIC.

  8. Origin of adakite-like plutons in southern Korea

    NASA Astrophysics Data System (ADS)

    Oh, Jeong-Im; Choi, Sung Hi; Yi, Keewook

    2016-10-01

    We present Sr-Nd-Pb isotopic compositions for two adakite-like intrusions in southern Korea (Jindong and Bongnae), including major and trace element concentrations, and the sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb age. Our aim is to constrain the origin and tectonomagmatic processes that gave rise to the plutons. A SHRIMP U-Pb zircon age of 88.7 ± 0.7 Ma was obtained from a Jindong granodiorite sample. The Jindong plutons belong to the medium-K calc-alkaline series, and have an overall enrichment in large ion lithophile elements (LILE), such as K, Rb, Ba, and Pb, and a relative depletion in high field strength elements, such as Nb, Ta, and Ti, compared with the neighboring elements in the primitive mantle-normalized multi-trace element variation diagram. It was found that (87Sr/86Sr)i = 0.70475-0.70596, (143Nd/144Nd)i = 0.512547-0.512604, [(εNd)i = + 0.4 to 2.2], and (206Pb/204Pb)i = 18.19-18.37, which fall within the field of the arc-type Cretaceous to Tertiary Bulguksa intrusive rocks in the Sr-Nd and Pb-Pb isotopic correlation diagrams. The elevated Sr/Y (17-40), but low La/Yb (3.7-8.8) ratios of the Jindong plutons, together with their coherent geochemical trends and U-shaped rare earth element (REE) patterns, indicate that they were not formed by slab melting, but by amphibole-dominated fractional crystallization of the Bulguksa-like arc magma. A SHRIMP U-Pb zircon age of 226.5 ± 2.5 Ma was obtained from a Bongnae tonalite sample. The Bongnae plutons belong to the shoshonitic series. Their trace element patterns resemble the Jindong samples, but are characterized by significantly negative U anomalies in mafic rocks. They also have elevated MgO, Ni, Co, Cr, Rb, Ba, Sr, and low Al2O3 and Na2O contents at a given SiO2 concentration compared with the Jindong plutons, and are typified by highly radiogenic Sr and unradiogenic Nd and Pb isotopic compositions: [(87Sr/86Sr)i = 0.71096-0.71290, (143Nd/144Nd)i = 0.511641-0.511681, (εNd)i = - 13

  9. Geochemical Database for Intrusive Rocks of North-Central and Northeast Nevada

    USGS Publications Warehouse

    du Bray, Edward A.; Ressel, Michael W.; Barnes, Calvin G.

    2007-01-01

    North-central and northeast Nevada contains numerous large plutons and smaller stocks but also contains many small, shallowly emplaced intrusive bodies, including dikes, sills, and intrusive lava dome complexes. Decades of geologic investigations in the study area demonstrate that many ore deposits, representing diverse ore deposit types, are spatially, and probably temporally and genetically, associated with these igneous intrusions. However, despite the number and importance of igneous intrusions in the study area, no synthesis of geochemical data available for these rocks has been completed. This report presents a synthesis of geochemical data for these rocks. The product represents the first phases of an effort to evaluate the time-space-compositional evolution of Mesozoic and Cenozoic magmatism in the study area and identify genetic associations between magmatism and mineralizing processes in this region.

  10. Time, space, and composition relations among northern Nevada intrusive rocks and their metallogenic implications

    USGS Publications Warehouse

    duBray, E.A.

    2007-01-01

    Importantly, modal composition, age, and geochemical characteristics of intrusions associated with large mineral deposits along the trends, are indistinguishable from non-mineralized intrusions in northern Nevada and thus do not identify intrusions associated with significant deposits. Moreover, intrusion age and composition show little correlation with mineral-deposit type, abundance, and size. Given the lack of diagnostic characteristics for intrusions associated with deposits, it is uncertain whether age, modal composition, and geochemical data can identify intrusions associated with mineral deposits. These findings suggest that associations between northern Nevada intrusions and mineral deposits reflect superimposition of many geologic factors, none of which was solely responsible for mineral-deposit formation. These factors might include intrusion size, efficiency of fluid and metal extraction from magma, prevailing redox and sulfidation conditions, or derivation of metals and ligands from host rocks and groundwater. The abundance and diversity of mineral deposits in northern Nevada may partly reflect geochemical inheritance, for example, along the mineral trends rather than the influence of petrologically unique magma or associated fluids.

  11. LANDSAT and radar mapping of intrusive rocks in SE-Brazil

    NASA Technical Reports Server (NTRS)

    Parada, N. D. J. (Principal Investigator); Dossantos, A. R.; Dosanjos, C. E.; Moreira, J. C.; Barbosa, M. P.; Veneziani, P.

    1982-01-01

    The feasibility of intrusive rock mapping was investigated and criteria for regional geological mapping established at the scale of 1:500,00 in polycyclic and polymetamorphic areas using the logic method of photointerpretation of LANDSAT imagery and radar from the RADAMBRASIL project. The spectral behavior of intrusive rocks, was evaluated using the interactive multispectral image analysis system (Image-100). The region of Campos (city) in northern Rio de Janeiro State was selected as the study area and digital imagery processing and pattern recognition techniques were applied. Various maps at the 2:250,000 scale were obtained to evaluate the results of automatic data processing.

  12. Layering in the wall rock of Valles Marineris: intrusive and extrusive magmatism

    NASA Astrophysics Data System (ADS)

    Williams, Jean-Pierre; Paige, David A.; Manning, Craig E.

    2003-06-01

    High-resolution images of the walls exposed in Valles Marineris reveal variations in appearance and degree of layering indicating various lithologies comprise the Tharsis plateau. The layered wall rock has been proposed to result from effusive flood basalt volcanism or interbedded sediments and volcanics. We present observations of unlayered rock that indicate layering extends to a greater depth in the western half of Valles Marineris and is confined to the Tharsis plateau, a region of thickened, uplifted crust resulting from prolonged intrusive activity. Consistent with this view, we propose that the observed layering may be a manifestation of intrusive rocks resulting from crystal fractionation of intruded basaltic magmas. Terrestrial layered plutons provide analogs for comparison such as those of the North Atlantic Igneous Province (NAIP) a large igneous province associated with crustal rifting and exposures of thick sequences of layered flood basalts and intruded layered cumulates.

  13. Intrusive rocks viewed from fitness landscape diagrams: Evolution and immiscibility

    NASA Astrophysics Data System (ADS)

    Vigneresse, J. D.

    2011-12-01

    We introduce the hard-soft acid-base concepts to magma evolution. Those concepts and their derived chemical parameters provide a new insight into mantle- and continental-derived magmas. Hence magma evolution represents a free suite of chemical reactions, thus showing natural chemical trends. They should be controlled by the principles of maximum hardness and minimum electrophilicity that rule chemical reactions. When plotting into a fitness landscape diagram, rocks suites define two major tendencies. Mantle-derived rocks present all character of an closed chemical system. Conversely, rocks contaminated within the continental crust define two other trends, depending on whether they have affinities toward a silica pole or an alkaline one. They both show the character of an open chemical system. When plotting major igneous minerals onto that diagram shows the importance of olivine, silica and alkali-bearing oxides. It points to the development of immiscibility, depending on the path along which magmas evolve. It thus provides explanation to experimentally observed immiscibility.

  14. The occurrence of microdiamonds in Mesoproterozoic Chapada Diamantina intrusive rocks--Bahia/Brazil.

    PubMed

    Battilani, Gislaine A; Gomes, Newton S; Guerra, Wilson J

    2007-06-01

    The origin of diamonds from Serra do Espinhaço in Diamantina region (State of Minas Gerais) and in Chapada Diamantina, Lençóis region (State of Bahia) remains uncertain, even taking into account the ample research carried out during the last decades. The lack of typical satellite minerals in both districts makes a kimberlitic source for these diamonds uncertain. In mid 18th century the occurrence of a metamorphosed igneous rock composed of martite, sericite and tourmaline was described in Diamantina region and named hematitic phyllite, considered by some researchers as a possible diamond source. Similar rocks were found in Lençóis and examined petrographically and their heavy mineral concentration was investigated by means of scanning electron microscopy (SEM). Petrographic analyses indicated an igneous origin for these rocks and SEM analyses showed the discovery of microdiamonds. Geochronological studies using the Ar/Ar technique in muscovites yielded minimum ages of 1515+/-3 Ma, which may correlate with 1710+/-12 Ma from U-Pb method in igneous zircons from the hematitic phyllites. Both rock types also have the same mineral and chemical composition which leads to the conclusion that the intrusive rocks were protolith of the hematitic phyllites. This first discovery of microdiamonds in intrusive rocks opens the possibility of new investigation models for diamond mineralization in Brazilian Proterozoic terrains. PMID:17625685

  15. The occurrence of microdiamonds in Mesoproterozoic Chapada Diamantina intrusive rocks--Bahia/Brazil.

    PubMed

    Battilani, Gislaine A; Gomes, Newton S; Guerra, Wilson J

    2007-06-01

    The origin of diamonds from Serra do Espinhaço in Diamantina region (State of Minas Gerais) and in Chapada Diamantina, Lençóis region (State of Bahia) remains uncertain, even taking into account the ample research carried out during the last decades. The lack of typical satellite minerals in both districts makes a kimberlitic source for these diamonds uncertain. In mid 18th century the occurrence of a metamorphosed igneous rock composed of martite, sericite and tourmaline was described in Diamantina region and named hematitic phyllite, considered by some researchers as a possible diamond source. Similar rocks were found in Lençóis and examined petrographically and their heavy mineral concentration was investigated by means of scanning electron microscopy (SEM). Petrographic analyses indicated an igneous origin for these rocks and SEM analyses showed the discovery of microdiamonds. Geochronological studies using the Ar/Ar technique in muscovites yielded minimum ages of 1515+/-3 Ma, which may correlate with 1710+/-12 Ma from U-Pb method in igneous zircons from the hematitic phyllites. Both rock types also have the same mineral and chemical composition which leads to the conclusion that the intrusive rocks were protolith of the hematitic phyllites. This first discovery of microdiamonds in intrusive rocks opens the possibility of new investigation models for diamond mineralization in Brazilian Proterozoic terrains.

  16. Petrology, composition, and age of intrusive rocks associated with the Quartz Hill molybdenite deposit, southeastern Alaska.

    USGS Publications Warehouse

    Hudson, T.; Smith, James G.; Elliott, R.L.

    1979-01-01

    A large porphyry molybdenum deposit (Quartz Hill deposit) was recently discovered in the heart of the Coast Range batholithic complex about 70 km E of Ketchikan, SE Alaska. Intrusive rocks associated with the mineral deposit form two composite epizonal to hypabyssal stocks and many dikes in country rocks. All observed metallization and alteration is within the Quartz Hill stock. Molybdenite forms fracture coatings and occurs in veins with quartz. Alteration is widespread and includes development of secondary quartz, pyrite, K-feldspar, biotite, white mica, chlorite, and zeolite. Field relations indicate that the stocks were emplaced after regional uplift and erosion of the Coast Range batholithic complex, and K-Ar data show that intrusion and alteration took place in late Oligocene time, about 27 to 30 Ma ago. Data from the Ketchikan quadrangle indicate that porphyry molybdenum metallization in the Coast Range batholithic complex is associated with regionally extensive but spotty, middle Tertiary or younger, felsic magmatism. -from Authors

  17. Adakitic-like magmatism in western Ossa-Morena Zone (Portugal): Geochemical and isotopic constraints of the Pavia pluton

    NASA Astrophysics Data System (ADS)

    Lima, S. M.; Neiva, A. M. R.; Ramos, J. M. F.

    2013-02-01

    Granitic rocks are a major component of the Earth's continental crust and occur in a wide variety of tectonic settings. Their chemical and isotopic characterization is crucial to the recognition of the potential sources and mechanisms involved in their generation. In this study, we present the first whole rock chemical and isotopic (Sr-Nd-O) data for the Pavia pluton (328-317 Ma), located near the western border of the Ossa-Morena Zone (Évora Massif, Portugal). Major and trace element geochemistry suggests that the different granitic phases composing this intrusive body (enclaves, granites (s.l.) and crosscutting dikes) represent independent magma pulses and the majority is similar to TTGs and adakites. The little Sr-Nd-O isotopic variation, with (87Sr/86Sr)328 = 0.70428-0.70560, ɛNd328 ranging between - 3.4 and + 0.4 and δ18O varying from + 5.6‰ to + 8.4‰ implies an isotopically similar protolith for all phases. The most viable mechanism for the generation of the Pavia pluton adakitic-like magmatism is assimilation-fractional crystallization of a mantle-derived magma. This mechanism was also invoked to explain the genesis of other plutons within the Évora Massif but they have a distinct chemistry (typical arc calc-alkaline rocks). The chemical differences between them and the Pavia pluton granitic rocks are interpreted as the result of lower degrees of crustal assimilation and higher degrees of contamination of mantle-derived magmas by the sinking slab (after subduction blocking and subsequent slab break-off).

  18. Emplacement of multiple magma sheets and wall rock deformation: Trachyte Mesa intrusion, Henry Mountains, Utah

    NASA Astrophysics Data System (ADS)

    Morgan, Sven; Stanik, Amy; Horsman, Eric; Tikoff, Basil; de Saint Blanquat, Michel; Habert, Guillaume

    2008-04-01

    A detailed structural and rock magnetic study of the Trachyte Mesa intrusion and deformed sedimentary wall rocks, Henry Mountains, Utah, indicates that the intrusion grew vertically and horizontally by the accumulation of multiple horizontal magma sheets. 2-3 cm thick shear zones recognized by intensely cataclasized plagioclase phenocrysts define the contact between sheets. Sheets have bulbous and / or steep frontal terminations and are flat on top. The foliation within the interior of the sheets, near the frontal termination, is subvertical. This steep foliation rotates into the subhorizontal shear zones near the top and bottom contacts and provides a magma flow direction indicator. Away from the frontal termination, the interior foliation rotates to become subhorizontal, similar to the fabric in recent analog experimental studies. Sheets are interpreted as being emplaced as plug flows. Both the field fabric and the rock magnetic data collected from 103 locations on the top of the intrusion and from 73 locations along a vertical cross section exposed in a stream gorge support a multi-stage model of intrusion growth. Emplacement begins as narrow magma channels and magma spreads radially outward from the channels to form sheets. Sheets are stacked upon one another and stop at the same lateral termination. The deformation of the sandstones at the margin of the intrusion, which are rotated upward from the margin to become the roof, is partitioned into layer parallel extension, shearing and layer-parallel shortening components. Bulk strain within the thickest sandstone layer indicates ˜20% thinning and microstructures indicate that the thinning was accommodated by grain-scale fracture-induced porosity collapse. Extension occurred as the layer was stretched over the margin of the rising intrusion. Shearing and layer-parallel shortening are a result of coupling with the underlying sheets as they advanced and accommodated through numerous faults parallel to bedding and

  19. Petrogenesis of adakite and high-Nb basalt association in the SW of Sabzevar Zone, NE of Iran: Evidence for slab melt-mantle interaction

    NASA Astrophysics Data System (ADS)

    Mazhari, Seyed Ali

    2016-04-01

    Adakitic rocks appear in close association with high Nb basaltic (HNB) rocks in the SW of Sabzevar ophiolitic belt. Adakites are calc-alkaline and include trachy-andesite, teachy-dacite and dacite. These rocks are rich in Na2O, Al2O3 and Sr and show depletion in MgO, Y and Yb. Adakitic samples are defined by high Sr/Y (88-128) and La/Yb (20-45) ratios; as well as a lack of Eu anomaly (Eu/Eu∗ = 0.92-0.99) in REE patterns. Geochemical composition indicates that adakites were generated from slab melting in a high pressure-high heat flow subducting setting. Different adakitic rocks have been formed by various slab partial melting degrees and reaction of adakitic magma with heterogeneous mantle wedge rocks. HNB rocks are alkaline, nepheline normative and sodic (Na2O/K2O = 2.7-3.4) with high concentration of Al2O3, TiO2, MgO, P2O5, LILE and HFSE, especially Nb (30-56 ppm). These basalts show fractionated REE patterns with elevated LREE/HREE (LaN/YbN = 20-25) and trace elements contents suggest their generation by low partial melting degrees (<2%) from garnet-peridotite origin which have already metasomatized by adakitic melts.

  20. Zircon U-Pb ages, geochemistry, and Sr-Nd-Pb-Hf isotopes of the Nuri intrusive rocks in the Gangdese area, southern Tibet: Constraints on timing, petrogenesis, and tectonic transformation

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Qin, Ke-Zhang; Li, Guang-Ming; Li, Jin-Xiang; Xiao, Bo; Zhao, Jun-Xing; Fan, Xin

    2015-01-01

    Abundant magmatic rocks of various ages are exposed in Gangdese, southern Tibet. These rocks play an important role in understanding the tectonic transformation from the subduction of Neo-Tethyan oceanic crust to the collision of the Indian and Asian continents. Based on zircon U-Pb ages, geochemistry, and Sr-Nd-Pb-Hf isotopic data of the Late Cretaceous to early Oligocene (~ 96-30 Ma) intrusive rocks in the Nuri Cu-W-Mo deposit, we discuss the Late Cretaceous to early Oligocene tectonic transformation of the region and the origin of Oligocene Cu-W-Mo mineralization in southern Gangdese. The Nuri intrusive rocks represent three magmatic episodes: 96-91, 56-52, and 33-30 Ma. The 96-91 and 56-52 Ma rocks have relatively low (87Sr/86Sr)i (0.7041 to 0.7060), and high εNd(t) (+ 3.1 to + 3.5) and εHf(t) values (+ 3.7 to + 15); the 33-30 Ma rocks have relatively high (87Sr/86Sr)i (0.7061 to 0.7063) and Pb isotopes, and low εNd(t) (- 3.8 to - 1.8) and εHf(t) values (+ 0.6 to + 10.1). The three stages of intrusive rocks have geochemical characteristics that are similar to those of coeval rocks in Gangdese. The 96-91 and 33-30 Ma rocks are adakitic, whereas the 56-52 Ma rocks have characteristics of arc calc-alkaline magmatic rocks. The 96-91 Ma rocks were produced by the partial melting of Neo-Tethyan basaltic oceanic crust and minor sediments, whereas the 56-52 Ma rocks were generated by the partial melting of juvenile crust and the 33-30 Ma rocks were formed by the melting of Indian plate lower crust contaminated with overlying mantle materials. On the basis of the regional tectonic and magmatic characteristics, we suggest that Neo-Tethyan oceanic slab subduction and slab roll-back occurred from ~ 100 to 65 Ma, collision between the Indian and Asian continents occurred at 65 to 40 Ma, Neo-Tethyan oceanic slab break-off took place at ~ 50 Ma, and the Indian continent subducted northwards beneath the Asian continent at ~ 30 Ma. From the Late Cretaceous (96-91 Ma) to

  1. Paleomagnetism of Eocene Intrusive Rocks, Black Hills of South Dakota and Wyoming

    NASA Astrophysics Data System (ADS)

    Housen, B. A.; Fawcett, T. C.; Gregiore, P.

    2003-12-01

    The Black Hills of South Dakota and Wyoming are a large Precambrian-cored Laramide uplift. Intruding the Black Hills are a diverse suite of igneous rocks, which include phonolites, trachytes, latites, garnet-bearing rhyolites, and pyroxenites. These intrusive bodies range in size from several meter outcrop-scale bodies, to several 10s of km wide intrusive complexes. New geochronology (40Ar-39Ar) data indicate many of these intrusive rocks are between 58 and 45 Ma in age (Duke at al, 2002). As part of a larger paleomagnetic study aimed at Jurassic strata surrounding the Black Hills, a collection of 20 sites and 145 samples of the Eocene intrusive rocks was made. A combination of alternating field, thermal, and liquid nitrogen step-wise demagnetization revealed that, with a few exceptions, these rocks have two well-defined magnetization components. The first-removed component is interpreted to be a present (dipole) field magnetization, and is removed by 10 to 30 mT a.f., or 200 C thermal demagnetization steps. The second-removed components have either positive or negative inclinations, and are defined by demagnetization steps between 30 and 200 mT a.f., or 300 to 630 C thermal demagnetization steps. These components are interpreted to be ancient, presumably Eocene, magnetizations. A preliminary mean of the normal-polarity sites is D=352, I=59.3, k=26.7, a95=18.2, N=4, and of the reverse-polarity sites is D=154.9, I=-61.3, k=23.1, a95=18.2, N=4. The combined mean direction is D=344.9, I=60.3, k=28.8, a95=10.5, N=8. Two sites of rhyolites at Mt. Theodore Roosevelt have well-defined magnetization components, but either mixed polarity (Site 99Trr1), or reverse-polarity with what might be a transitional-field direction (D=27.7, I=-37.4, k=18.0, a95=18.6, n=5), and are not included in the calculation of means. The magnetizations recorded by these Eocene rocks are essentially identical to the expected direction for the Black Hills calculated from the Diehl et al., 1983

  2. Amphibole-rich intrusive mafic and ultramafic rocks in arc settings: implications for the H2O budget

    NASA Astrophysics Data System (ADS)

    Tiepolo, M.; Langone, A.; Morishita, T.; Esna-Ashari, A.; Tribuzio, R.

    2011-12-01

    Although amphibole is rarely a phenocryst of arc lavas, many intermediate and silicic magmas in arc settings are considered residual after cryptic amphibole crystallization at mid-low crustal levels (e.g., Davidson et al., 2007). Amphibole-rich mafic and ultramafic intrusive rocks (hornblendites, amphibole-gabbros to amphibole-diorites) are reported worldwide in orogenic settings. These amphibole-rich plutonics could be the "hidden" amphibole reservoir invoked in the arc crust. They usually possess chemical and textural heterogeneities recording the magmatic processes occurring in the mid to low crust (e.g., Tiepolo et al., 2011). Being amphibole-rich, these intrusive rocks are an important source of information on the possible role played by amphibole in arc magma petrogenesis. In particular, for the capability of amphibole to incorporate H2O and elements with a marked affinity for the fluid phase, these rocks are also useful to track the origin and evolution of subduction related fluids. We present here geochemical and geochronologic data on amphibole-rich ultramafic intrusive rocks from different localities worldwide: i) Alpine Orogen (Adamello Batholith and Bregell intrusions); ii) Ross Orogen (Husky Ridge intrusion - Antarctica); iv) Japan Arc (Shikanoshima Island intrusion); v) Sanandaj-Sirjan Zone, Central Iran (Aligoordaz granitoid complex). The coupling of textural information, micro-chemical data and "in situ" zircon geochronology has allowed us to show that these ultramafic intrusive rocks share striking petrologic and geochemical similarities. They are thus the expression of a common magmatic activity that is independent from the age and from the local geological setting and thus related to a specific petrogenetic process. Amphibole-rich mafic and ultramafic intrusive rocks are retained a common feature of collisional-systems worldwide. Amphibole is thus expected to play a major role in the differentiation of arc magmas and in particular in the H2O

  3. Late Paleozoic intrusive rocks from the southeastern Lhasa terrane, Tibetan Plateau, and their Late Mesozoic metamorphism and tectonic implications

    NASA Astrophysics Data System (ADS)

    Dong, Xin; Zhang, Zeming; Liu, Feng; He, Zhenyu; Lin, Yanhao

    2014-06-01

    The Lhasa terrane in southern Tibet experienced Late Paleozoic and Mesozoic-Cenozoic composite orogenesis. This work reports a study on the petrology, geochemistry, zircon U-Pb chronology and Hf isotopes of Late Paleozoic and Late Mesozoic intrusive rocks from the southeastern Lhasa terrane. The Late Paleozoic intrusive rocks crystallized in the Late Devonian-Early Carboniferous of 371 to 355 Ma, representing a bimodal igneous association formed in the back-arc extensional setting. The mafic end-member originated from the enriched mantle and experienced contamination of crustal materials, characterized by a slight enrichment of LREE, positive anomalies of U, K and Pb and negative anomalies of Th, Nb, Ta and Ti. The felsic end-member was derived from the partial melting of the ancient continental crust, characterized by metaluminous, positive anomalies of Th, Zr and Hf, negative anomalies of Ba, Sr, Nb, Ta and Ti and negative εHf(t) values of zircon with TDM2 ages from 1.90 to 1.40 Ga. The Late Cretaceous (ca. 107 Ma) mafic intrusions, along with the Late Paleozoic intrusive rocks, underwent nearly syn-intrusion amphibolite-facies metamorphism under P-T conditions of 0.56 to 0.69 GPa and 692 to 735 °C during the Andean-type orogeny correlated with the subduction of the Neo-Tethyan oceanic slab beneath the Lhasa terrane. This study provides a new insight into the pre-Cenozoic tectonic evolution of the Lhasa terrane.

  4. Geochemical Characteristics and Petrogenesis of Adakites in Sikhote-Alin, Russian Far East

    NASA Astrophysics Data System (ADS)

    Wu, Jeremy Tsung Jui; Jahn, Bor-ming; Nechaev, Victor; Chashchin, Alexander; Yokoyama, Kazumi; Tsutsumi, Yukiyasu

    2016-04-01

    The Sikhote-Alin orogenic belt and late Precambrian Khanka block are two major tectonic units in the southernmost Russian Far East. The Sikhote-Alin belt comprises several tectonostratigraphic terranes, including late Precambrian nappes, and Mesozoic accretionary prisms and turbidite basins. These terranes are overlain by Cretaceous to Paleocene felsic to intermediate volcanic rocks and intruded by granitoids. The magmatic rocks are collectively known as "the East Sikhote-Alin volcano-plutonic belt" (ESAVPB), and mainly characterized by acid-to-intermediate compositions. In this work we study the petrogenesis of adakitic rocks and discuss the possible tectonic implications. Adakitic rocks of the Sikhote-Alin orogen were emplaced in two main periods: Early Cretaceous (132-98 Ma) and Eocene (46-45 Ma). They mainly occur in the Khanka block, with a subordinate amount in the ESAVPB. The adakites show a large range of chemical composition: SiO2 = 57-74%, Al2O3 = 15-18%, Na2O = 3.5-6.1%, K2O = 0.7-3.2%, Na2O/K2O = 1.1-3.9, Sr/Y = 33-145, and (La/Yb)N = 11-53. HREE and HFSE are remarkably depleted. The Early Cretaceous adakites show eNd(T) = -1.0 to +3.2; ISr = 0.7040 - 0.7090, and the Eocene adakites have eNd(T) = -2.0 to +2.2; ISr = 0.7042 - 0.7058. Thus, the Cretaceous and Eocene adakites show rather similar Sr-Nd isotopic compositions, but their Nd isotopic signatures (slightly negative to positive eNd(T) values) may distinguish them from the granitoids of the ESAVPB (only negative eNd(T) values). Adakites may have different modes of generation, but partial melting of meta-basic rocks in a subduction zone is considered the most likely mode for the present case. The two periods of adakites have probably formed in the following scenario. The early Cretaceous emplacement ages for the adakites and the oldest granitoids of the ESAVPB, is considered as the time of initiation of the Paleo-Pacific subduction in NE Asia. The Eocene adakites were also generated in subduction

  5. Adakites from collision-modified lithosphere

    NASA Astrophysics Data System (ADS)

    Haschke, M.; Ben-Avraham, Z.

    2005-08-01

    Adakitic melts from Papua New Guinea (PNG) show adakitic geochemical characteristics, yet their geodynamic context is unclear. Modern adakites are associated with hot-slab melting and/or remelting of orogenic mafic underplate at convergent margins. Rift-propagation over collision-modified lithosphere may explain the PNG adakite enigma, as PNG was influenced by rapid creation and subduction of oceanic microplates since Mesozoic times. In a new (rift) tectonic regime, decompressional rift melts encountered and melted remnant mafic eclogite and/or garnet-amphibolite slab fragments in arc collisional-modified mantle, and partially equilibrated with metasomatized mantle. Alternatively, hot-slab melting in a proposed newborn subduction zone along the Trobriand Trough could generate adakitic melts, but recent seismic P-wave tomographic models lack evidence for subducting oceanic lithosphere in the adakite melt region; however they do show deep subduction zone remnants as a number of high P-wave anomalies at lithospheric depths, which supports our proposed scenario.

  6. Intrusive rocks northeast of Steamboat Springs, Park Range, Colorado, with a section on geochronology

    USGS Publications Warehouse

    Snyder, George L.; Hedge, Carl E.

    1978-01-01

    Major Precambrian and minor Tertiary intrusive rocks northeast of Steamboat Springs in the Park Range between 40?30' and 40?45' N. lat. are described and compared with related rocks elsewhere in Colorado and Wyoming. The Precambrian intrusives were emplaced in a sequence of high-grade interlayered felsic gneisses, amphibolites, and pelitic schists of sedimentary and volcanic origin. These rocks are cut by a major northeast-trending Precambrian shear zone where mainly left lateral movement of 1/ 2 to 1 mile is certain. Cumulative movement of many miles is possible. The Precambrian intrusives consist of a batholith, the Mount Ethel pluton, a smaller Buffalo Pass pluton, and small dikes or lenses of fine-grained porphyry, pegmatites, and ultramafics. The Mount Ethel pluton is an oval shaped body 7 miles wide by about 40 miles long (shown by geophysical data to extend beneath younger sediments in North Park). Outer batholithic contacts are sharp and dip steeply outward at about 85?. Five mappable internal variants consist, in order of decreasing age, of granodiorite, quartz monzonite porphyry of Rocky Peak, quartz monzonite of Roxy Ann Lake, granite and quartz monzonite, and. leucogranite. Internal contacts between these plutonic variants are sharp, and evidence of liquid-solid relationships abounds; despite this, all rocks except the granodiorite contribute to an Rb-Sr whole-rock isochron indicating emplacement about 1.4 b.y. (billion years) ago. The most important variants volumetrically are: the quartz monzonite porphyry of Rocky Peak, which forms an irregular 2-mile-thick carapace or mapped band around the west edge of the pluton and is lithologically similar to nearby Sherman Granite, and the quartz monzonite of Roxy Ann Lake, which forms most of the rest of the pluton and is lithologically similar to Silver Plume Granite. An apparent Sherman -Silver Plume dichotomy with similar rock types and similar relative ages is noted throughout Colorado plutons of that age

  7. Underplating of basaltic magmas and crustal growth in a continental arc: Evidence from Late Mesozoic intermediate-felsic intrusive rocks in southern Qiangtang, central Tibet

    NASA Astrophysics Data System (ADS)

    Hao, Lu-Lu; Wang, Qiang; Wyman, Derek A.; Ou, Quan; Dan, Wei; Jiang, Zi-Qi; Wu, Fu-Yuan; Yang, Jin-Hui; Long, Xiao-Ping; Li, Jie

    2016-02-01

    Phanerozoic growth of continental crust has widely been considered as an important geological phenomenon and mainly occurs in an arc setting. However, the crustal growth models (mantle-derived basalt underplating or accretion of island or intra-oceanic arc complexes or oceanic plateau) have been disputed. Here we present new zircon LA-ICPMS U-Pb age, whole-rock major and trace element, Sr-Nd and zircon Hf isotopic data for Late Mesozoic intermediate-felsic intrusive rocks in the Rena Co area in southern Qiangtang, central Tibet. LA-ICP-MS zircon U-Pb dating for two granodiorite and three diorite samples and one granodiorite porphyry sample gives ages of ca. 150 Ma, ca. 112 Ma, respectively, indicating they were generated in the Late Jurassic-Early Cretaceous. All rocks are sub-alkaline in composition and belong to the high-K cal-alkaline series. The ~ 150 Ma diorites (SiO2 = 57.9-61.2 wt.%) exhibit relatively high MgO (3.13-3.88 wt.%) and Cr (52.4-282 ppm) contents and Mg# (47-51) values, similar to magnesian diorites. They are geochemically characterized by uniformly low εNd(t) (- 5.5 to - 5.2), high (87Sr/86Sr)i (0.7071 to 0.7078) and Th/La (0.22-0.32), and variable zircon εHf(t) (- 8.7 to + 4.8) values. They were probably generated by melting of oceanic sediment diapirs, followed by interaction with the surrounding mantle during the northward subduction of Bangong-Nujiang Oceanic lithosphere. The ~ 150 Ma granodiorites and ~ 112 Ma granodiorite porphyries are characterized by low MgO (< 3 wt.%) contents and Mg# (< 45) values, high Al2O3 (> 15% wt.%) and Sr (> 400 ppm) and low Y (< 18 ppm) and Yb (< 1.9 ppm) contents, and high Sr/Y and La/Yb ratios, which are similar to those of typical adakites. The granodiorites have low εNd(t) (- 7.6 to - 3.7) and zircon εHf(t) (- 9.8 to + 0.2) and high (87Sr/86Sr)i (0.7069 to 0.7086) values, and were likely produced by partial melting of a thickened and heterogeneous ancient lower continental crust. The relatively

  8. The influence of igneous intrusions on the peak temperatures of host rocks: Finite-time emplacement, evaporation, dehydration, and decarbonation

    NASA Astrophysics Data System (ADS)

    Wang, Dayong; Song, Yongchen; Liu, Yu; Zhao, Minglong; Qi, Tian; Liu, Weiguo

    2012-01-01

    Using a 13-m-thick basic sill and its limestone host rocks of the Permian Irati Formation from the Parana Basin, South America, as an example, this paper presents a numerical investigation based on heat conduction models on the effect of the emplacement mechanism of igneous intrusions, pore-water evaporation, and dehydration and decarbonation of host rocks on the peak temperature ( Tpeak) of host rocks. Our results demonstrate that: (1) the finite-time intrusion mechanism of magma can lower the predicted Tpeak of host rocks by up to 100 °C relative to the instantaneous intrusion mechanism, and although pore-water evaporation together with dehydration and decarbonation reactions can also depress the thermal effect of the sill on its host rocks, the maximum effect of these mechanisms on Tpeak only reaches approximately 50 °C. (2) The effect of pore-water evaporation on Tpeak is obviously greater than that of the dehydration and decarbonation reactions: the former can cause a maximum deviation of 40 °C in the predicted Tpeak, whereas the deviation due to the latter is less than 20 °C. Further, the effect of the dehydration and decarbonation reactions on Tpeak is less than 10 °C if pore-water evaporation is allowed simultaneously in the models and can hence be ignored in thermal modeling. (3) The finite-time intrusion mechanism of magma probably represents the natural condition of the sill. Pore-water evaporation and dehydration and decarbonation of host rocks are also likely to play important roles in lowering the thermal effect of the sill.

  9. Niobium-enriched basalts from the Wabigoon subprovince, Canada: evidence for adakitic metasomatism above an Archean subduction zone

    NASA Astrophysics Data System (ADS)

    Wyman, D. A.; Ayer, J. A.; Devaney, J. R.

    2000-06-01

    Late Archean niobium-enriched basalts from the Central Sturgeon Lake assemblage and Neepawa group of the western Wabigoon subprovince have mantle-normalized Nb/La between 0.8 and 1.3 and Zr/Y between 4 and 7. They are compositionally similar to basalts attributed to adakite metasomatism of mantle wedge regions in Cenozoic subduction zones [Sajona et al., J. Petrol. 37 (1996) 693-726]. In detail, their Sc-REE systematics suggest the Archean basalts were generated above the garnet stability field. An association with adakite-like volcanic rocks, an absence of komatiites and the arc-like attributes of their host sequences suggest a subduction-related origin for the basalts. If current models of adakite and Niobium-enriched basalt genesis are valid, then additional examples of these rocks should be relatively common in other Archean greenstone belts.

  10. Transition from adakitic to bimodal magmatism induced by the paleo-Pacific plate subduction and slab rollback beneath SE China: Evidence from petrogenesis and tectonic setting of the dike swarms

    NASA Astrophysics Data System (ADS)

    Xia, Yan; Xu, Xisheng; Liu, Lei

    2016-02-01

    The late Mesozoic magmatic record of SE China is dominated by felsic volcanics and intrusions. However, this magmatism mainly occurred in coastal areas at 110-80 Ma, in contrast to poorly researched dike swarms that were emplaced inland at 165-120 Ma. Here, we focus on Early Cretaceous mafic and felsic dike swarms that provide new insights into the tectono-magmatic evolution of SE China. The swarms were intruded into Neoproterozoic plutons and include granodioritic porphyry, granitic porphyry, and diabase dikes. The granodioritic porphyry (128 ± 2 Ma) dikes are geochemically similar to adakitic rocks, suggesting that inland adakitic magmatism occurred between ca. 175 and ca. 130 Ma. The majority of these adakitic rocks are calc-alkaline and have Sr-Nd-Hf-O isotopic compositions that are indicative of derivation from a Neoproterozoic magmatic arc source within the lower crust. The granitic porphyry and diabase dikes were emplaced coevally at ca. 130 Ma, and the former contain high alkali and high field strength element (HFSE; e.g., Zr, Nb, Ce, and Y) concentrations that together with their high Ga/Al and FeOT/(FeOT + MgO) ratios imply an A-type affinity. The widespread ca. 130 Ma magmatism that formed the A-type granites and coeval diabase dikes defines a NE-SW trending inland belt of bimodal magmatism in SE China. The presence of mafic enclaves in some of the A-type granites, and the Sr-Nd-Hf isotopic compositions of the latter are indicative of inadequate mixing between the basement sediment-derived and coeval mantle-derived basaltic melts that define the bimodal magmatism. The transition from adakitic rocks to bimodal magmatism in the inland region of SE China indicates a change in the prevailing tectonic regime. This change was associated with an increase in the dip angle of the northwestward-subducting paleo-Pacific Plate beneath SE China between the Middle Jurassic and the Early Cretaceous. This resulted in a transition from a local intra-plate extensional

  11. Re-Os isotope studies of Mindanao adakites: Implications for sources of metals and melts

    NASA Astrophysics Data System (ADS)

    Dreher, Scott T.; MacPherson, Colin G.; Pearson, D. Graham; Davidson, Jon P.

    2005-12-01

    Whether the downgoing slab in modern subduction zones is able to melt is an important unresolved aspect of plate tectonics. Rare arc lavas with high Sr/Y ratios and low Y and heavy rare earth element concentrations, called adakites, are often attributed to melting of young subducted crust in subduction zones. Osmium isotopic data obtained for 13 adakite samples from Mindanao, Philippines, conflict with the slab-melting model. Ten of the samples have unradiogenic 187Os/188Os ratios inconsistent with partial melting of the ca. 50 Ma Philippine Sea lithosphere subducting beneath Mindanao. The Os isotope signatures are similar to those of young mid-oceanic-ridge basalts and normal arc rocks, consistent with a mantle source. In addition to implications for mass transfer in subduction zones, the apparent association of adakites with Cu-Au deposits makes understanding their origin, and that of the associated metals, economically interesting. This study suggests that a reevaluation is required of the slab-melting hypothesis in general, and that the metals associated with the Mindanao adakites come from the mantle.

  12. Stable isotopic constraints on fluid-rock interaction and Cu-PGE-S redistribution in the Sonju Lake intrusion, Minnesota

    USGS Publications Warehouse

    Park, Y.-R.; Ripley, E.M.; Miller, J.D.; Li, C.; Mariga, J.; Shafer, P.

    2004-01-01

    The Sonju Lake intrusion, part of the 1.1 Ga Midcontinent rift-related Beaver Bay Complex, is a 1,200-m-thick, strongly differentiated, layered sequence of mafic cumulates located in northeastern Minnesota. Basal melatroctolite and dunite layers are overlain by troctolite, gabbro, Fe-Ti oxide-rich gabbro, apatite diorite, and monzodiorite. Stratigraphic intervals rich in Pt + Pd, Cu, and S occur over ???500 m in the Fe-Ti oxide-rich gabbro and apatite diorite units. Peak concentrations show offsets that are similar to those found in other tholeiitic layered intrusions. Concentrations of Pd in excess of 100 ppb are confined to the lowermost 25 m of the interval. Copper shows a sharp increase to 630 ppm above the Pd-rich interval. Sulfur contents are low (<375 ppm) in the Cu-rich interval, but they increase to values as high as 3,150 ppm above in the apatite diorite. Disseminated sulfides in the intrusion have ??34S values that range from -2.2 to 3 per mil Vienna-Canyon Diablo Troilite (V-CDT) and suggest that contamination by country rock sulfur was not an important process in the formation of the metal-rich interval. ??18O values of plagioclase from the intrusion range from 5.6 to 12.0 per mil (V-SMOW) and indicate that a relatively low-18O fluid (??18O ???3-5 ???) interacted with the rocks of the intrusion at temperatures less than ???275??C. Clinopyroxene and Fe-Ti oxides (ilmenite with minor amounts of titanomagnetite) show much more restricted ranges in ??18O values (4.6-5.7 and 5.5-6.7 per mil, respectively) and attest to the kinetic control of the oxygen isotope exchange process. The externally derived fluid that interacted with rocks now enriched in platinum group elements (PGE) + Cu- and Fe-sulfide minerals locally liberated sulfur and replaced chalcopyrite and pyrite with goethite. In the Cu-rich zone, goethite that replaces chalcopyrite may contain up to 8.5 weight percent Cu. It is evident that hydrothermal alteration resulted in a decoupling of copper

  13. Experimental investigation of reservoir rocks by spontaneous imbibition and mercury intrusion porosimetry

    NASA Astrophysics Data System (ADS)

    Gao, Z.; Hu, Q.

    2013-12-01

    Spontaneous imbibition (SI), one of the important processes affecting hydrocarbon recovery from fractured reservoirs, is a capillary-force controlled process. The properties of displacing and displaced fluids, pore structure of porous media and their interactions are the main factors affecting the SI process. Many studies have been conducted to investigate these factors and among them scaling of SI is a widely used approach to predicting the oil/gas production behavior in the field based on laboratory imbibition tests. We have conducted SI experiments on different reservoir rocks, including Barnett shale (from different depths), dolomite and Indian sandstone. Because of the layered characteristic of Barnett shale, we also conducted imbibition experiments, with upward imbibition direction parallel or transverse to the shale bedding plane, to investigate its directional dependency. Two imbibing fluids, n-decane and water, were used during SI experiments to displace air, which is always treated as the non-wetting phase in the SI process. Mercury intrusion porosimetry (MIP) is a powerful tool of characterizing the pore-throat size distribution of porous media, and many important parameters (e.g. permeability and tortuosity) could be derived from MIP data. The median pore-throat diameter (D50), defined as the pore-throat diameter corresponding to 50% mercury saturation, is an important pore-structural parameter and has been used to predict permeability and tortuosity. Our results showed that Barnett shale (from different depths), dolomite and Indiana sandstone exhibited different SI behaviors. Wettability information was obtained by comparing scaled imbibition curves. Values of D50 obtained from MIP were also used to improve the existing scaling method. Low pore connectivity of Barnett shale was confirmed by both SI and MIP results.

  14. Intrusive rocks and plutonic belts of southeastern Alaska, U.S.A.

    USGS Publications Warehouse

    Brew, David A.; Morrell, Robert P.; Roddick, J.A.

    1983-01-01

    About 30 percent of the 175,000-km2 area of southeastern Alaska is underlain by intrusive igneous rocks. Compilation of available information on the distribution, composition, and ages of these rocks indicates the presence of six major and six minor plutonic belts. From west to east, the major belts are: the Fairweather-Baranof belt of early to mid-Tertiary granodiorite; the Muir-Chichagof belt of mid-Cretaceous tonalite and granodiorite; the Admiralty-Revillagigedo belt of porphyritic granodiorite, quartz diorite, and diorite of probable Cretaceous age; the Klukwan-Duke belt of concentrically zoned or Alaskan-type ultramafic-mafic plutons of mid-Cretaceous age within the Admiralty-Revillagigedo belt; the Coast Plutonic Complex sill belt of tonalite of unknown, but perhaps mid-Cretaceous, age; and the Coast Plutonic Complex belt I of early to mid-Tertiary granodiorite and quartz monzonite. The minor belts are distributed as follows: the Glacier Bay belt of Cretaceous and(or) Tertiary granodiorite, tonalite, and quartz diorite lies within the Fair-weather-Baranof belt; layered gabbro complexes of inferred mid-Tertiary age lie within and are probably related to the Fairweather-Baranof belt; the Chilkat-Chichagof belt of Jurassic granodiorite and tonalite lies within the Muir-Chichagof belt; the Sitkoh Bay alkaline, the Kendrick Bay pyroxenite to quartz monzonite, and the Annette and Cape Fox trondhjemite plutons, all interpreted to be of Ordovician(?) age, together form the crude southern southeastern Alaska belt within the Muir-Chichagof belt; the Kuiu-Etolin mid-Tertiary belt of volcanic and plutonic rocks extends from the Muir-Chichagof belt eastward into the Admiralty-Revillagigedo belt; and the Behm Canal belt of mid- to late Tertiary granite lies within and next to Coast Plutonic Complex belt II. In addition, scattered mafic-ultramafic bodies occur within the Fairweather-Baranof, Muir-Chichagof, and Coast Plutonic Complex belts I and II. Palinspastic

  15. Study project of intrusive rocks: States of Espirito Santo and Rio de Janeiro, south and east of Minas Gerais and southeast of the state of Sao Paulo. [Brazil

    NASA Technical Reports Server (NTRS)

    Dejesusparada, N. (Principal Investigator); Dossantos, A. R.; DOSANJOS; Barbos, M. P.; Veneziani, P.

    1981-01-01

    The feasibility of mapping intrusive rocks in polycyclic and polymetamorphic areas using the logic method for photointerpretation of LANDSAT and radar imagery was investigated. The resolution, scale and spectral characteristics of the imagery were considered. Spectral characteristics of the intrusive rock units mapped using image 100 were investigated. It was determined that identification of acidic and basic intrusive bodies and determination of their relationships with principal structural directions using the logic method was feasible. Tectonic compartments were subdivided into units according to their predominant lithographic types, ignoring stratigraphy. The principal directions of various foliations, faults, megafolds, and fractural systems were defined. Delineation of the boundaries of intrusive bodies mapped using the spectral characteristics of Image 100 imagery ws determined to be more accurate than visual analysis. A 1:500,000 scale map of intrusions in the areas studied was generated.

  16. Geochemistry of intrusive rocks associated with the Latir volcanic field, New Mexico, and contrasts between evolution of plutonic and volcanic rocks

    USGS Publications Warehouse

    Johnson, C.M.; Czamanske, G.K.; Lipman, P.W.

    1989-01-01

    Plutonic rocks associated with the Latir volcanic field comprise three groups: 1) ???25 Ma high-level resurgent plutons composed of monzogranite and silicic metaluminous and peralkaline granite, 2) 23-25 Ma syenogranite, and alkali-feldspar granite intrusions emplaced along the southern caldera margin, and 3) 19-23 Ma granodiorite and granite plutons emplaced south of the caldera. Major-element compositions of both extrusive and intrusive suites in the Latir field are broadly similar; both suites include high-SiO2 rocks with low Ba and Sr, and high Rb, Nb, Th, and U contents. Moreover, both intermediateto siliciccomposition volcanic and plutonic rocks contain abundant accessory sphene and apatite, rich in rare-earth elements (REE), as well as phases in which REE's are essential components. Strong depletion in Y and REE contents, with increasing SiO2 content, in the plutonic rocks indicate a major role for accessory mineral fractionation that is not observed in volcanic rocks of equivalent composition. Considerations of the rheology of granitic magma suggest that accessory-mineral fractionation may occur primarily by filter-pressing evolved magmas from crystal-rich melts. More limited accessory-mineral crystallization and fractionation during evolution of the volcanic magmas may have resulted from markedly lower diffusivities of essential trace elements than major elements. Accessory-mineral fractionation probably becomes most significant at high crystallinities. The contrast in crystallization environments postulated for the extrusive and intrusive rocks may be common to other magmatic systems; the effects are particularly pronounced in highly evolved rocks of the Latir field. High-SiO2 peralkaline porphyry emplaced during resurgence of the Questa caldera represents non-erupted portions of the magma that produced the Amalia Tuff during caldera-forming eruption. The peralkaline porphyry continues compositional and mineralogical trends found in the tuff. Amphibole

  17. Assessing the Compositional Diversity of Intrusive Rocks on the Moon Using Near-Infrared Spectroscopic Data

    NASA Astrophysics Data System (ADS)

    Klima, R. L.

    2016-05-01

    Near-infrared, gamma-ray and neutron, and thermal-infrared observations have advanced our understanding of the compositional diversity, including minor components such as thorium and hydroxyl, of intrusive lithologies exposed on the lunar surface.

  18. Intrusive rocks of the Holden and Lucerne quadrangles, Washington; the relation of depth zones, composition, textures, and emplacement of plutons

    USGS Publications Warehouse

    Cater, Fred W.

    1982-01-01

    The core of the northern Cascade Range in Washington consists of Precambrian and upper Paleozoic metamorphic rocks cut by numerous plutons, ranging in age from early Triassic to Miocene. The older plutons have been eroded to catazonal depths, whereas subvolcanic rocks are exposed in the youngest plutons. The Holden and Lucerne quadrangles span a -sizeable and representative part of this core. The oldest of the formations mapped in these quadrangles is the Swakane Biotite Gneiss, which was shown on the quadrangle maps as Cretaceous and older in age. The Swakane has yielded a middle Paleozoic metamorphic age, and also contains evidence of zircon inherited from some parent material more than 1,650 m.y. old. In this report, the Swakane is assigned an early Paleozoic or older age. It consists mostly of biotite gneiss, but interlayered with it are scattered layers and lenses of hornblende schist and gneiss, clinozoisite-epidote gneiss, and quartzite. Thickness of the Swakane is many thousands of meters, and the base is not exposed. The biotite gneiss is probably derived from a pile of siliceous volcanic rocks containing scattered sedimentary beds and basalt flows. Overlying the Swakane is a thick sequence of eugeosynclinal upper Paleozoic rocks metamorphosed to amphibolite grade. The sequence includes quartzite and thin layers of marble, hornblende schist and gneiss, graphitic schist, and smaller amounts of schist and gneiss of widely varying compositions. The layers have been tightly and complexly folded, and, in places, probably had been thrust over the overlying Swakane prior to metamorphism. Youngest of the supracrustal rocks in the area are shale, arkosic sandstone, and conglomerate of the Paleocene Swauk Formation. These rocks are preserved in the Chiwaukum graben, a major structural element of the region. Of uncertain age, but possibly as old as any of the intrusive rocks in the area, are small masses of ultramafic rocks, now almost completely altered to

  19. Thermo-physical rock properties of greywacke basement rock and intrusive lavas from the Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Mielke, P.; Weinert, S.; Bignall, G.; Sass, I.

    2016-09-01

    Greywacke of the Waipapa and Torlesse (Composite) Terrane form the basement of the Taupo Volcanic Zone (TVZ), New Zealand. Together with inferred buried lavas, domes and igneous complexes they are likely to be the dominant rock type prevailing at depths > 4 km beneath the TVZ. A fundamental understanding of the rock properties of the deep formations is of utmost importance for the exploration of deep unconventional geothermal resources. An outcrop analogue study was conducted to improve the understanding of the thermo-physical rock properties of likely deep buried rock formations beneath the TVZ. A total of 145 core samples were taken at 10 locations inside and outside the TVZ and their grain and bulk density, porosity, matrix permeability, bulk thermal conductivity and specific heat capacity, and the compressional and shear wave velocities measured on oven-dry samples. Additional tests of the unconfined compressive strength were conducted for selected greywacke samples to quantify their mechanical rock strength. The obtained data indicates that the thermo-physical rock properties are mainly controlled by porosity, and minor by mineralogy, texture and grain size. Samples from Waipapa-type and Torlesse-type greywacke exhibit minor rheological differences, with Waipapa-type greywacke having lowest porosity (about 1% vs. 3%) and highest bulk thermal conductivity (2.5 W m- 1 K- 1 vs. 1.7 W m- 1 K- 1) and specific heat capacity (0.8 kJ kg- 1 K- 1 vs. 0.7 kJ kg- 1 K- 1). Matrix permeability is < 1E-16 m2 for all greywacke samples. Tested lavas exhibit heterogeneous rock properties due to their wide range of porosity (< 1% up to 32%). The thermo-physical rock properties were tested at laboratory conditions (ambient temperature and pressure), which do not reflect the in situ conditions at greater depth. With depth, thermal conductivity and acoustic wave velocity are likely to decrease caused by micro fractures resulting from thermal cracking of the rock, while specific

  20. New KAr age determinations of intrusive rocks from the Cordillera Occidental and Altiplano of central Peru: Identification of magmatic pulses and episodes of mineralization

    NASA Astrophysics Data System (ADS)

    Soler, P.; Bonhomme, M. G.

    The post-Albian evolution of the Andes of central Peru is characterized by igneous activity, both effusive and intrusive, and by at least six distinct episodes of compressional tectonics. New KAr age determinations have been made of intrusive rocks from the Cajatambo-Oyón-Cerro de Pasco area. In conjunction with already published information, these new data permit a better estimate of the ages and the lateral extent of successive Cenozoic magmatic arcs. Metallogenetic implications of the 26.3-29.3 Ma age of mineralized Milpo-Atacocha intrusions are also discussed.

  1. Metasomatized and hybrid rocks associated with a Palaeoarchaean layered ultramafic intrusion on the Johannesburg Dome, South Africa

    NASA Astrophysics Data System (ADS)

    Anhaeusser, Carl R.

    2015-02-01

    The Johannesburg Dome occurs as an inlier of Palaeoarchaean-Mesoarchaean granitic rocks, gneisses and greenstones in the central part of the Kaapvaal Craton, South Africa. In the west-central part of the dome a large greenstone remnant is surrounded and intruded by ca. 3114 Ma porphyritic granodiorites. Referred to locally as the Zandspruit greenstone remnant, it consists of a shallow-dipping ultramafic complex comprised of a number of alternating layers of harzburgite and pyroxenite. The ultramafic rocks are metamorphosed to greenschist grade and have largely been altered to serpentinite and amphibolite (tremolite-actinolite). In the granite-greenstone contact areas the porphyritic granodiorite has partially assimilated the greenstones producing a variety of hybrid rocks of dioritic composition. The hybrid rocks contain enclaves or xenoliths of greenstone and, in places, orbicular granite structures. Particularly noteworthy is an unusual zone of potash-metasomatized rock, occurring adjacent to the porphyritic granodiorite, consisting dominantly of biotite and lesser amounts of carbonate, quartz and sericite. Large potash-feldspar megacrysts and blotchy aggregated feldspar clusters give the rocks a unique texture. An interpretation placed on these rocks is that they represent metasomatized metapyroxenites of the layered ultramafic complex. Field relationships and geochemical data suggest that the rocks were influenced by hydrothermal fluids emanating from the intrusive porphyritic granodiorite. The adjacent greenstones were most likely transformed largely by the process of infiltration metasomatism, rather than simple diffusion, as CO2, H2O as well as dissolved components were added to the greenstones. Element mobility appears to have been complex as those generally regarded as being immobile, such as Ti, Y, Zr, Hf, Ta, Nb, Th, Sc, Ni, Cr, V, and Co, have undergone addition or depletion from the greenstones. Relative to all the rocks analyzed from the greenstones

  2. Two types of ultrapotassic plutonic rocks in the Bohemian Massif — Coeval intrusions at different crustal levels

    NASA Astrophysics Data System (ADS)

    Kotková, Jana; Schaltegger, Urs; Leichmann, Jaromír

    2010-03-01

    We present U-Pb zircon age determinations of two Variscan ultrapotassic plutonic rocks from the Moldanubian Zone (Bohemian Massif). Equant, multifaceted zircons without inherited cores from a two-pyroxene-biotite quartz monzonite of the Jihlava Pluton yielded a precise age of 335.12 ± 0.57 Ma, interpreted as dating magma crystallization. The majority of both tabular and prismatic grains from the amphibole-biotite melagranite ("durbachite") from the Třebíč Pluton plot along a discordia intersecting the concordia at 334.8 ± 3.2 Ma; prismatic zircon grains commonly contain inherited cores and yield an upper intercept age of 2.2 Ga, indicating early Proterozoic inheritance. We therefore suggest that both types of the ultrapotassic plutonic rocks from the Bohemian Massif crystallized at ca 335 Ma, and the previously published ages higher than ca 340 Ma for "durbachites" were biased by a small amount of unresolved inheritance. The ultrapotassic magma emplacement in the middle crust was related to rapid exhumation of a deep crustal segment, considered as isothermal decompression between high-pressure (˜ 340 Ma) and medium-pressure (˜ 333 Ma) stages recorded in granulites. Mineral assemblages as well as external and internal zircon morphology suggest that the Jihlava intrusion was deep and dry, whereas the Třebíč intrusion was shallow and wet. Low ɛHf values of zircons (- 4.4 to - 7.5) in both rock types suggest a similar source with a predominant crustal component. However, inherited grains in the Třebíč melagranite indicate its contamination with crustal material during emplacement, and thus possibly a slower rate of exhumation and/or of magma ascent through the crust.

  3. Fluorian garnets from the host rocks of the Skaergaard intrusion: implications for metamorphic fluid composition

    USGS Publications Warehouse

    Manning, C.E.; Bird, D.K.

    1990-01-01

    Zoned, silica-deficient, calcic garnets containing up to 5 mol% F substitution for O formed during contact metamorphism of basalts by the Skaergaard intrusion in East Greenland. Fluorian calcic garnets occur as a retrograde alteration of prograde wollastonite and clinopyroxene that fills vesicles and vugs in lavas 30-70 m from the intrusion. The F content of garnet is extremely sensitive to minor changes in fluid composition. The calculations show that a decrease in pH or an increase in log aF- of 0.3 at constant pressure and temperature will decrease the F concentration in garnet from 5 to 0 mol%. The results of this study show that fluorian hydrous grandites provide a mineralogical record of the activities of F species in coexisting metamorphic and hydrothermal fluids. -from Authors

  4. Investigation of rock samples using X-ray-microcomputer-tomography before and after mercury intrusion porosimetry

    SciTech Connect

    Klobes, P.; Riesemeier, H.; Meyer, K.; Goebbels, J.; Siitari-Kauppi, M.; Hellmuth, K.H.

    1997-12-31

    A new method for the physical characterization of rock matrices for use in site investigations of nuclear waste repositories has been developed. The method can provide information needed in the assessment of the performance of the geosphere working as a natural barrier retarding the migration of radionuclides by diffusion into the rock matrix. Most conventional methods for the physical characterization of rocks give only bulk information. The combination of mercury porosimetry and computer tomography can give 3-D data on mineral-specific porosity distributions with additional pore size information. Additionally, limits for mineral-specific internal surface areas can be estimated, which is essential for the assessment of water-rock interaction and reactive interaction with radionuclides (sorption). Results of measurements on granitic rock (granodiorite) from the Baltic shield are discussed and integrated with results by complementary methods.

  5. Coupling fluid dynamics and host-rock deformation associated with magma intrusion in the crust: Insights from analogue experiments

    NASA Astrophysics Data System (ADS)

    Kavanagh, J. L.; Dennis, D. J.

    2014-12-01

    Models of magma ascent in the crust tend to either consider the dynamics of fluid flow within intrusions or the associated host-rock deformation. However, these processes are coupled in nature, and so to develop a more complete understanding of magma ascent dynamics in the crust both need to be taken into account. We present a series of gelatine analogue experiments that use both Particle Image Velocimentry (PIV) and Digital Image Correlation (DIC) techniques to characterise the dynamics of fluid flow within intrusions and to quantify the associated deformation of the intruded media. Experiments are prepared by filling a 40x40x30 cm3 clear-Perspex tank with a low-concentration gelatine mixture (2-5 wt%) scaled to be of comparable stiffness to crustal strata. Fluorescent seeding particles are added to the gelatine mixture during its preparation and to the magma analogue prior to injection. Two Dantec CCD cameras are positioned outside the tank and a vertical high-power laser sheet positioned along the centre line is triggered to illuminate the seeding particles with short intense pulses. Dyed water (the magma analogue) injected into the solid gelatine from below causes a vertically propagating penny-shaped crack (dike) to form. Incremental and cumulative displacement vectors are calculated by cross-correlation between successive images at a defined time interval. Spatial derivatives map the fluid flow within the intrusion and associated strain and stress evolution of the host, both during dike propagation and on to eruption. As the gelatine deforms elastically at the experimental conditions, strain calculations correlate with stress. Models which couple fluid dynamics and host deformation make an important step towards improving our understanding of the dynamics of magma transport through the crust and to help constrain the tendency for eruption.

  6. Composition, age, and petrogenesis of Late Cretaceous intrusive rocks in the central Big Belt Mountains, Broadwater and Meagher counties, Montana

    USGS Publications Warehouse

    Du Bray, E.A.; Snee, L.W.

    2002-01-01

    Cretaceous intrusions hosted by the Proterozoic Newland Formation. The northern intrusion, centered on Boulder Baldy, consists of outer, intermediate, and core zones composed of aegirine-augite quartz monzonite, hornblende quartz monzodiorite, and biotite granodiorite, respectively. The southern intrusion, north of Mount Edith, is compositionally indistinguishable from the intermediate zone of the northern intrusion.

  7. Geochronology and correlation of Tertiary volcanic and intrusive rocks in part of the southern Toquima Range, Nye County, Nevada

    USGS Publications Warehouse

    Shawe, Daniel R.; Snee, Lawrence W.; Byers, Frank M.; du Bray, Edward A.

    2014-01-01

    Extensive volcanic and intrusive igneous activity, partly localized along regional structural zones, characterized the southern Toquima Range, Nevada, in the late Eocene, Oligocene, and Miocene. The general chronology of igneous activity has been defined previously. This major episode of Tertiary magmatism began with emplacement of a variety of intrusive rocks, followed by formation of nine major calderas and associated with voluminous extrusive and additional intrusive activity. Emplacement of volcanic eruptive and collapse megabreccias accompanied formation of some calderas. Penecontemporaneous volcanism in central Nevada resulted in deposition of distally derived outflow facies ash-flow tuff units that are interleaved in the Toquima Range with proximally derived ash-flow tuffs. Eruption of the Northumberland Tuff in the north part of the southern Toquima Range and collapse of the Northumberland caldera occurred about 32.3 million years ago. The poorly defined Corcoran Canyon caldera farther to the southeast formed following eruption of the tuff of Corcoran Canyon about 27.2 million years ago. The Big Ten Peak caldera in the south part of the southern Toquima Range Tertiary volcanic complex formed about 27 million years ago during eruption of the tuff of Big Ten Peak and associated air-fall tuffs. The inferred Ryecroft Canyon caldera formed in the south end of the Monitor Valley adjacent to the southern Toquima Range and just north of the Big Ten Peak caldera in response to eruption of the tuff of Ryecroft Canyon about 27 million years ago, and the Moores Creek caldera just south of the Northumberland caldera developed at about the same time. Eruption of the tuff of Mount Jefferson about 26.8 million years ago was accompanied by collapse of the Mount Jefferson caldera in the central part of the southern Toquima Range. An inferred caldera, mostly buried beneath alluvium of Big Smoky Valley southwest of the Mount Jefferson caldera, formed about 26.5 million years

  8. The petrogenesis of Early Eocene non-adakitic volcanism in NE Turkey: Constraints on the geodynamic implications

    NASA Astrophysics Data System (ADS)

    Aydınçakır, Emre

    2014-11-01

    Whole-rock geochemistry, mineral chemistry, the 40Ar-39Ar age, and Sr-Nd isotopic data are presented for the Early Eocene non-adakitic volcanic rocks on the eastern corner of the Eastern Pontides orogenic belt (NE Turkey). The tectonic setting of the Eastern Pontides during the Late Mesozoic to Early Cenozoic remains a topic of debate. Here, for the first time, we describe the Early Eocene non-adakitic volcanic rocks from the Eastern Pontides. These rocks contain plagioclase, hornblende phenocrysts, and magnetite/titanomagnetite and apatite microphenocrysts. Geochronology studies based on the 40Ar-39Ar ratio of the amphibole separates reveal that the non-adakitic porphyritic volcanic rocks have a crystallization age of 50.04 ± 0.10 to 50.47 ± 0.22 Ma (Ypresian). The volcanic rocks show tholeiitic to calc-alkaline affinities and have low-to-medium K contents. They are also enriched in large-ion lithophile elements (LILE), light rare-earth elements (LREE), and depleted in high field strength elements (HFSE), with a no negative Eu anomaly (Eun/Eu* = 1.03-1.08) in mantle-normalized trace element spidergrams. The samples (Lacn/Lucn = 2.60-4.28) show low-to-medium enrichment in LREEs relative to HREEs, in chondrite-normalized REE patterns indicating similar sources for the rock suite. These rocks display a range of ISr (50 Ma) values from 0.70451 to 0.70485, and ƐNd (50 Ma) 2.9 and 3.7. The main solidification processes involved in the evolution of these volcanics consist of fractional crystallization, with minor amounts of crustal contamination. All of our evidence supports the conclusion that the parental magma of the rocks probably derived from an enriched mantle, previously metasomatized by fluids derived from the subducted slab, in a post-collisional, geodynamic setting.

  9. Arc-magmatism and subduction history beneath the Zagros Mountains, Iran: A new report of adakites and geodynamic consequences

    NASA Astrophysics Data System (ADS)

    Omrani, Jafar; Agard, Philippe; Whitechurch, Hubert; Benoit, Mathieu; Prouteau, Gaëlle; Jolivet, Laurent

    2008-12-01

    The Zagros Mountains were formed by convergence between Eurasia and Africa/Arabia. Compared to the wealth of recent studies on the external Zagros fold and thrust belt, the internal Sanandaj-Sirjan and Urumieh-Dokhtar magmatic arcs (SSMA, UDMA) remain poorly studied, despite being some of the best-preserved active margins within the greater Alpine-Himalayan convergent system. We focus on the key geodynamic constraints provided by the subduction-related magmatism of the upper plate, which shifted ~ 300 km inward from the SSMA to the UDMA at the end of the Mesozoic. Major and trace element data show that all studied magmatic rocks display the characteristics of subduction-related calc-alkaline magmas. Rare-earth element (REE) systematics for Mesozoic (SSMA) and Eocene (UDMA) volcanic and plutonic rocks suggest a similar mantle wedge source. In contrast, major and trace element data for volcanic rocks postdating the Late Miocene reveal a typical adakitic signature along part of the UDMA. The amphibole and SiO 2-rich (59-72 wt.%) Zagros adakites have very low Y and HREE contents. Adakitic magmas are likely to result from the melting of mafic material at depth (i.e., subducted oceanic crust from the slab and/or earlier obducted ophiolites) under unusually high temperature thermal conditions, in response to the regional-scale thermal re-equilibration accompanying collision or, to slab break-off. The fact that the distribution of these adakites is spatially restricted to the central parts of the UDMA (i.e. 200-300 km along strike) supports the slab break-off hypothesis, as do preliminary tomographic images. The timing of this event is coeval with slab-break-off below southern Turkey, which supports the view that slab detachment propagated laterally in the Neotethyan slab, both to the west (Turkey) and to the south (Iran), during the last 10-5 Ma.

  10. Frontier Mountain meteorite specimens of the acapulcoite-lodranite clan: Petrography, pairing, and parent-rock lithology of an unusual intrusive rock

    NASA Astrophysics Data System (ADS)

    Burroni, Alessandro; Folco, Luigi

    2008-04-01

    In this paper we reconstruct the heterogeneous lithology of an unusual intrusive rock from the acapulcoite-lodranite (AL) parent asteroid on the basis of the petrographic analysis of 5 small (<8.3 g) meteorite specimens from the Frontier Mountain ice field (Antarctica). Although these individual specimens may not be representative of the parent-rock lithology due to their relatively large grain size, by putting together evidence from various thin sections and literature data we conclude that Frontier Mountain (FRO) 90011, FRO 93001, FRO 99030, and FRO 03001 are paired fragments of a medium- to coarse-grained igneous rock which intrudes a lodranite and entrains xenoliths. The igneous matrix is composed of enstatite (Fs13.3 ± 0.4 Wo3.1 ± 0.2), Cr-rich augite (Fs6.1 ± 0.7 Wo42.3 ± 0.9), and oligoclase (Ab80.5 ± 3.3 Or3.2 ± 0.6). The lodranitic xenoliths show a fine-grained (average grain size 488 ± 201 μm) granoblastic texture and consist of olivine Fa9.5 ± 0.4 and Fe,Ni metal and minor amounts of enstatite Fs12.7 ± 0.4 Wo1.8 ± 0.1, troilite, chromite, schreibersite, and Ca-phosphates. Crystals of the igneous matrix and lodranitic xenoliths are devoid of shock features down to the scanning electron microscope scale. From a petrogenetic point of view, the lack of shock evidence in the lodranitic xenoliths of all the studied samples favors the magmatic rather than the impact melting origin of this rock. FRO 95029 is an acapulcoite and represents a separate fall from the AL parent asteroid, i.e., it is not a different clast entrained by the FRO 90011, FRO 93001, FRO 99030, and FRO 03001 melt, as in genomict breccias common in the meteoritic record. The specimen-to-meteorite ratio for the AL meteorites so far found at Frontier Mountain is thus 2.5.

  11. Occurrence of uranium in rocks of the intrusive complex at Ekiek Creek, western Alaska

    USGS Publications Warehouse

    Wallace, Alan R.

    1979-01-01

    Uranium in the Ekiek Creek Complex of western Alaska is related to a niobium-rich pyrochlore in the nepheline syenite of the complex. The complex consists of an aegirine-phlogopite pyroxenite that has been intruded and partly replaced by nepheline syenite. The contact zone between the two igneous units varies from a sharp contact to a diffuse zone where the pyroxenite has been metasomatically replaced by the syenite. The entire complex was intruded into an older Cretaceous monzonite. The pyrochlore occurs as an accessory mineral in the syenite, and is visible in rocks containing over 50 ppm uranium. Chemical analyses indicate that, in all samples of syenite, there is a positive correlation between uranium and niobium; this suggests that the uranium-pyrochlore association persists even when pyrochlore is not readily visible in thin section. The small amount of pyrochlore, and its refractory nature, make the complex an unfavorable source for secondary uranium leaching or heavy-mineral concentration.

  12. Uniaxial creep as a control on mercury intrusion capillary pressure in consolidating rock salt

    SciTech Connect

    Dewers, Thomas; Heath, Jason E.; Leigh, Christi D.

    2015-09-01

    The nature of geologic disposal of nuclear waste in salt formations requires validated and verified two - phase flow models of transport of brine and gas through intact, damaged, and consolidating crushed salt. Such models exist in oth er realms of subsurface engineering for other lithologic classes (oil and gas, carbon sequestration etc. for clastics and carbonates) but have never been experimentally validated and parameterized for salt repository scenarios or performance assessment. Mo dels for waste release scenarios in salt back - fill require phenomenological expressions for capillary pressure and relative permeability that are expected to change with degree of consolidation, and require experimental measurement to parameterize and vali date. This report describes a preliminary assessment of the influence of consolidation (i.e. volume strain or porosity) on capillary entry pressure in two phase systems using mercury injection capillary pressure (MICP). This is to both determine the potent ial usefulness of the mercury intrusion porosimetry method, but also to enable a better experimental design for these tests. Salt consolidation experiments are performed using novel titanium oedometers, or uniaxial compression cells often used in soil mech anics, using sieved run - of - mine salt from the Waste Isolation Pilot Plant (WIPP) as starting material. Twelve tests are performed with various starting amounts of brine pore saturation, with axial stresses up to 6.2 MPa (%7E900 psi) and temperatures to 90 o C. This corresponds to UFD Work Package 15SN08180211 milestone "FY:15 Transport Properties of Run - of - Mine Salt Backfill - Unconsolidated to Consolidated". Samples exposed to uniaxial compression undergo time - dependent consolidation, or creep, to various deg rees. Creep volume strain - time relations obey simple log - time behavior through the range of porosities (%7E50 to 2% as measured); creep strain rate increases with temperature and applied stress as

  13. Implications for the Upper Cycladic Unit: petrological, mineralogical and structural study of intrusive rocks from the Late-Cretaceous volcanic-arc in Anafi Island, Cyclades, Greece

    NASA Astrophysics Data System (ADS)

    Koutsovitis, P.; Soukis, K.; Lozios, S.

    2012-04-01

    Anafi Island is located at the southeastern edge of the Attic-Cycladic complex and is one of the few Cycladic islands composed solely by upper plate units, which are now found in the form of scattered relics in the central Aegean. The structure of the island consists of a series of thrust sheets which include from bottom to top: a non-metamorphosed flysch of partly Eocene age; greenschist facies metabasites; massive to plate amphibolites; a sequence of upper amphibolite facies meta-sediments and ophiolitic rocks, intruded by intermediate magmatic rocks; marbles and large bodies of felsic intrusive magmatic rocks. The age of the intrusive rocks within the two uppermost thrust sheets is late Cretaceous, (~85 Ma[1]). Mineral chemistry analyses of the intermediate and felsic rocks show that they include quartz, plagioclases (andesines, oligoclases and rarely labradorites), K-feldspars, amphiboles (magnesiohornblendes rarely tremolite), and biotite. The presence of quartz and biotite increases in the most felsic rocks while hornblendes less often appear. These rocks present subophitic textural features, between amphiboles and plagioclases, but also granitic textures in rocks where quartz is in a relatively high modal percentage. Structural observations reveal minor or no ductile deformation (rare undulose extinction in quartz). Based on CIPW and whole-rock chemistry results intrusive rocks are classified as quartz monzodiorites and granodiorites of calc-alkaline affinity[2]. They present subparallel REE patterns, enriched in LREE [(La/Yb)CN=6.1-20.3], with slight to moderate negative Eu anomalies (EuCN/Eu*=0.75-0.97). Their primitive mantle normalized patterns are also subparallel, enriched in LILE elements, such as Cs, Rb, Ba and K. Their Nb and Ta normalized values are lower than the normalized Th, U, K and La. Positive anomalies are noticed for Pb, negative for Ti and slightly negative to none for Zr. These features, along with their high Th/Yb ratios relative to Nb

  14. New African Lower Carboniferous paleomagnetic pole from intrusive rocks of the Tin Serririne basin (Southern border of the Hoggar, Algeria)

    NASA Astrophysics Data System (ADS)

    Derder, M. E. M.; Henry, B.; Bayou, B.; Ouabadi, A.; Bellon, H.; Djellit, H.; Khaldi, A.; Amenna, M.; Baziz, K.; Hemmi, A.; Guemache, M. A.

    2006-06-01

    A paleomagnetic study has been conducted on intrusive doleritic rocks cropping out within Devonian horizontal tabular formations of the Saharan craton (Tin Serririne basin, South of Hoggar shield). The 40K/ 40Ar dating of the dolerites gave an age of 347.6 ± 8.1 Ma, i.e. Tournaisian. The paleomagnetic data present three different directions. The first has a paleomagnetic pole close to the previous African poles of Permian age. This direction is therefore interpreted as a Permian remagnetization. The second direction, which is defined by both linear regression and remagnetization circles analysis, is considered as the primary magnetization. It yields a new African Tournaisian paleomagnetic pole ( λ = 18.8° S, ϕ = 31.2° E, K = 29, A95 = 7.5°) very close to the Ben Zireg Tounaisian pole [Aifa, T., Feinberg, H., Pozzi, J.P., 1990. Devonian/Carboniferous paleopoles for Africa. Consequences for Hercynian geodynamics. Tectonophysics, 179, 288-304]. The third direction has intermediate orientation between those of the first or second directions and that of the Upper Cenozoic field. It is interpreted as related to a composite magnetization. This new Tin Serririne pole improves the APWP of Gondwana, for this key period of the evolution of the Pangea. This APWP confirms the previous paleogeographic reconstruction which shows that the pre-Hercynian ocean between Gondwana and Laurussia is still not close during the beginning of the Carboniferous.

  15. U-Pb and K-Ar geochronology in Paleozoic and Mesozoic intrusive rocks of the Coastal Cordillera, Valparaiso, Chile

    USGS Publications Warehouse

    Gana, Paulina; Tosdal, Richard M.

    1996-01-01

    The U-Pb and K-Ar geochronology applied to intrusive rocks from the Coastal Batholith of Central Chile, demonstrates the existence of a basement block of the Mirasol Unit, with a crystallization age of 299??10 Ma, exposed in the northern block of the Melipilla Fault. The age of 214??1 Ma obtained in the 'Dioritas Gne??isicas de Cartagena Unit', indicates that a Late Triassic magmatism took place in this region; it coincides with the end of an extensive crustal melting period, proposed for northern Chile. The ages of the Jurassic plutonic units (Laguna Verde, Sauce, Pen??uelas and Limache) are restricted to the 156-161 Ma interval, showing in certain cases, inherited zircons from an unknown source. The difference between ages obtained using both chronological methods is a few million years, indicating that a short time passed between the crystallization and the cooling of the plutonic bodies, as well as a fast magmatic differentiation process. The Laguna Verde and Sauce Units, experienced a fast uplift, probably as a result of an extensional tectonic process in the magmatic arc, or induced by the magmatic pressure through fracture zones during Middle Jurassic.

  16. Syn-collisional adakitic granodiorites formed by fractional crystallization: Insights from their enclosed mafic magmatic enclaves (MMEs) in the Qumushan pluton, North Qilian Orogen at the northern margin of the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Chen, Shuo; Niu, Yaoling; Li, Jiyong; Sun, Wenli; Zhang, Yu; Hu, Yan; Shao, Fengli

    2016-04-01

    The Qumushan (QMS) syn-collisional granodiorite, which is located in the eastern section of the North Qilian Orogen at the northern margin of the Greater Tibetan Plateau, has typical adakitic characteristics and also contains abundant mafic magmatic enclaves (MMEs). This recognition offers an unprecedented insight into the petrogenesis of both the adakitic host granodiorite and the enclosed MMEs. The MMEs and their host granodiorites share many characteristics in common, including identical crystallization age (~ 430 Ma), same mineralogy, similar mineral chemistry and whole-rock isotopic compositions, indicating their genetic link. The MMEs are most consistent with being of cumulate origin formed at earlier stages of the same magmatic system that produced the QMS adakitic granodiorite. Subsequent replenishment of adakitic magmas could have disturbed the cumulate piles as "MMEs" dispersed in the adakitic granodiorite host during emplacement. The geochemical data and petrogenetic modeling of trace elements suggest that the QMS adakitic host granodiorite is most consistent with fractional crystallization dominated by the mineral assemblage of the MMEs. The parental magma for the QMS granodiorite is best explained as resulting from partial melting of the ocean crust together with recycled terrigenous sediments during continental collision, which may have also experienced interaction with mantle peridotite during ascent.

  17. Petrogenetic connections between volcanic rocks and intrusive suites in the California arc - toward an integrated model for upper-crustal magma system evolution

    NASA Astrophysics Data System (ADS)

    Barth, A. P.; Riggs, N.; Walker, J. D.; Andrew, J.; Jacobson, C. E.; Miller, D. M.; Robert, J.

    2014-12-01

    Volcanic and clastic sedimentary rocks in deeply eroded, predominantly plutonic arcs provide records of arc development and the links between volcanic and plutonic processes. We are analyzing existing and new geochronologic and petrologic data from volcanic breccias, ignimbrites and intrusive suites in the Sierra Nevada and Mojave Desert sectors of the Mesozoic California arc, in an effort to construct an integrated volcano-plutonic model for silicic magmatism in arc upper crust. SIMS and TIMS U-Pb zircon ages, immobile element abundances in whole rocks, and trace element abundances in zircons allow us to interpret the magmatic heritage of ignimbrites and components of underlying granodioritic to granitic intrusive suites. Preliminary results suggest several conclusions: (1) first-order magma production was episodic, with plutonic, forearc and retro-arc detrital zircons defining three magmatic pulses of ~40-60 m.y. duration that are largely mimicked by the more limited record of zircons in ignimbrites; (2) in the Triassic and Jurassic, second-order pulses on 2-10 m.y. time scales are recorded in both the intrusive and ignimbrite records, suggesting that eruption of ignimbrites was synchronous at the shortest resolvable time scales with assembly of underlying incrementally emplaced intrusive suites; (3) ignimbrites range from dacite to rhyolite in bulk composition, and are petrographically similar to modern "monotonous intermediate" dacite or phenocryst-poor low-silica rhyolite; (4) these tuffs are as fractionated as intrusive rocks, and commonly, though not always, contain zircons with similarly complex, multi-stage growth histories. Thus ignimbrites and felsic granodiorites in this arc are complementary elements recording lengthy and episodic evolutionary histories in cool and hydrous upper-crustal arc magma systems.

  18. Geochemical constraints on adakites of different origins and copper mineralization

    USGS Publications Warehouse

    Sun, W.-D.; Ling, M.-X.; Chung, S.-L.; Ding, X.; Yang, X.-Y.; Liang, H.-Y.; Fan, W.-M.; Goldfarb, R.; Yin, Q.-Z.

    2012-01-01

    The petrogenesis of adakites holds important clues to the formation of the continental crust and copper ?? gold porphyry mineralization. However, it remains highly debated as to whether adakites form by slab melting, by partial melting of the lower continental crust, or by fractional crystallization of normal arc magmas. Here, we show that to form adakitic signature, partial melting of a subducting oceanic slab would require high pressure at depths of >50 km, whereas partial melting of the lower continental crust would require the presence of plagioclase and thus shallower depths and additional water. These two types of adakites can be discriminated using geochemical indexes. Compiled data show that adakites from circum-Pacific regions, which have close affinity to subduction of young hot oceanic plate, can be clearly discriminated from adakites from the Dabie Mountains and the Tibetan Plateau, which have been attributed to partial melting of continental crust, in Sr/Y-versus-La/Yb diagram. Given that oceanic crust has copper concentrations about two times higher than those in the continental crust, whereas the high oxygen fugacity in the subduction environment promotes the release of copper during partial melting, slab melting provides the most efficient mechanism to concentrate copper and gold; slab melts would be more than two times greater in copper (and also gold) concentrations than lower continental crust melts and normal arc magmas. Thus, identification of slab melt adakites is important for predicting exploration targets for copper- and gold-porphyry ore deposits. This explains the close association of ridge subduction with large porphyry copper deposits because ridge subduction is the most favorable place for slab melting. ?? 2012 by The University of Chicago.

  19. Double-layer mode of acid intrusive rocks from Xiuwacu Porphyry Mo deposit, Northwestern Yunnan SW China: U-Pb geochronology evidence

    NASA Astrophysics Data System (ADS)

    Yu, Haijun; Li, Wenchang

    2016-04-01

    Recent research infer that, the south-north extension of the Xiuwacu-Tongchanggou acidic intrusive belt along the Geza island arc have been developed of intense molybdenum-mutimetallic mineralization(Li et al., 2012, 2013; Yu et al., 2015). The northern section of this intrusive belt exposed widly and occur much monzonitic granite, biotite-granite, granodiorite, biotite-monzogranite; while in southern section, intrusions are cocealed. The Tongchanggou district in south section have been obtained large breakthrough of porphyry-skarn type molybdenum-multimetallic deposits exploration recent years(Yu et al., 2014), the Mo-W mineral resources also increased year after year in north section of the belt. The Mo-mineral resouree potential of porphyry-skarn type Mo-mutimetallic deposits in whole area are tremendous. Xiuwacu Porphyry molybdenum deposit was explored in Geza island arc, and widespread Biotite granite and monzonitic granite that is closely related to mineralization. We have understood poorly about this ore deposit for the harsh geographical circumstance, through, some referential result in chronology have accumulated, it still lack of systematic lithogeochemical study and reliable chronology data about intrusions. We yield biotite granite and monzonitic zircons U-Pb ages(200.93±0.65Ma, 83.57±0.32Ma, respectively) of Xiuwacu. There are two periods of intermediate-acid intrusive rocks of Xiuwacu area. Indosinian Biotite granite and Yanshanian monzonitic granite were formed as superposition phenomenon.

  20. Hydrothermal alteration and tectonic setting of intrusive rocks from East Brawley, Imperial Valley: an application of petrology to geothermal reservoir analysis

    SciTech Connect

    Keskinen, M.; Sternfeld, J.

    1982-01-01

    A geothermal well near East Brawley intersected a series of thin (3 to 35m) diabasic to dioritic intrusives. The petrology and chemistry of these meta-igneous rocks can provide insight into the thermal and fluid chemical characteristics of the reservoir and into the processes of magma generation at depth. A description of the rock types and their hydrothermal alteration is presented in order to increase the petrologic data base relating to this important facet of the geothermal potential of the Salton Trough and to provide a case study illustrating how detailed petrologic examination of well cuttings can provide important input in the construction of a geothermal reservoir model.

  1. The questa magmatic system: Petrologic, chemical and isotopic variations in cogenetic volcanic and plutonic rocks of the latir volcanic field and associated intrusives, northern New Mexico

    SciTech Connect

    Johnson, C.M.

    1986-01-01

    Field, chemical and isotopic data demonstrate that nearly all igneous rocks at Questa resulted from interactions between mantle-derived parental magmas and the crust. Strontium, neodymium and lead isotope ratios of early andesites to rhyolites (28 to 26 Ma) indicate that these magmas assimilated > 25% lower crust. Injection of basaltic magmas extensively modified the strontium and neodymium but not the lead isotope compositions of the lower crust. Eruption of comendite magmas and the peralkaline Amalia Tuff 26 Ma is correlated with inception of regional extension. Lead isotope ratios identify different sources for the metaluminous granites and the peralkaline rocks. 26 Ma metaluminous granite to granodiorite intrusions have chemical and isotopic compositions to those of the precaldera intermediate-composition rocks, and are interpreted as representing the solidified equivalents of the precaldera magmatic episode. However, both conventional and ion-microprobe isotopic data prohibit significant assimilation of crustal rocks at the level of exposure, suggesting that the plutons were emplaced a relatively crystal-rich mushes which did not have sufficient heat to assimilate country rocks. This suggest that in some cases plutonic rocks are better than volcanic rocks in representing the isotopic compositions of their source regions, because the assimilation potential of crystal-rich magmas is significantly less than that of largely liquid magmas.

  2. Intrusive rocks in the ophiolitic mélange of Crete - Witnesses to a Late Cretaceous thermal event of enigmatic geological position

    NASA Astrophysics Data System (ADS)

    Langosch, Alexander; Seidel, Eberhard; Stosch, Heinz-Günter; Okrusch, Martin

    The ophiolitic mélange in the uppermost tectonic unit of the Cretan nappe pile contains crystalline slices which consist of a low-pressure/high-temperature metamorphic sequence and synmetamorphic intrusions, ranging in composition from diorite to granite. The plutonic rocks conform to two different igneous suites, dominated by diorites in eastern, and granites in central Crete, displaying I-type and A-type characters, respectively. Some of the granites from central Crete are classified as transitional I/S-type. They are closely associated with migmatitic paragneisses. Based on major and trace element, REE, Sr- and Nd-isotope geochemistry, the mafic members of both suites are derived from a depleted mantle source. The higher concentrations of P and Ti in the mafic members of the igneous suite in central Crete and the deviant trend of the whole suite may be explained by a different mantle source or a lower degree of partial melting. In both suites, magmatic evolution was governed by fractional crystallization of amphibole/clinopyroxene, plagioclase and minor phases. In addition, mixing or mingling of compositionally different magmas is indicated for the intrusive suite of eastern Crete whereas in central Crete the magma composition was at least partially modified through assimilation of (meta)pelites. The geochemical results suggest that the plutonic rocks formed in a supra-subduction zone setting. However, a formation during continental lithospheric extension cannot be ruled out. Published and new Rb-Sr and K-Ar dates on amphiboles and biotites from intrusive rocks and their metamorphic country rocks show that the peak of the low-P/high-T metamorphism and the intrusion of the two igneous suites testify to the same thermal event of Late Cretaceous age. A similar Late Cretaceous association of metamorphic and plutonic rocks has been described from the uppermost tectonic unit in the Attic-Cycladic Crystalline Complex. Together with the Cretan occurrences, they form a

  3. Formation of low-δ18O magmas of the Kangerlussuaq Intrusion by addition of water derived from dehydration of foundered basaltic roof rocks

    NASA Astrophysics Data System (ADS)

    Riishuus, Morten S.; Harris, Chris; Peate, David W.; Tegner, Christian; Wilson, J. Richard; Brooks, C. Kent

    2015-05-01

    The Kangerlussuaq Intrusion in East Greenland is concentrically zoned from quartz nordmarkite (quartz syenite) at the margin, through pulaskite, to foyaite (nepheline syenite) in the centre, with no apparent intrusive contacts. The δ18O values of coexisting minerals are consistent with oxygen isotope equilibrium at magmatic temperatures. Most of the intrusion formed from low-δ18O magma; magma δ18O values generally increased upwards from about 3.3 ‰ in the quartz nordmarkites to 5.6 ‰ in the foyaites. The lowest magma δ18O value of about -1.0 ‰ is from the upper part of the nordmarkites, where there is a high concentration of foundered basaltic xenoliths (stoped from the roof of the intrusion). The amphiboles in the syenites have δD values that range from those typical of hydrous mantle-derived minerals to much lower values (-86 to -157 ‰), as do whole-rock samples of xenolith and country rock (-125 to -148 ‰). The low magma δ18O and δD values are consistent with continuous incorporation, exchange and upward escape of low-δ18O and δD fluids released from stoped basaltic roof material. Mass balance suggests that the integrated amount of water involved was 7 wt% of the volume of the magma, but locally reached 30 wt% water. The requirement for large amounts of water with low δ18O value is satisfied only if the foundered basalt contained most of its water in cavities as opposed to hydrous minerals. Even with this requirement, the volume of stoped basalt would have been equal to the volume of the magma. Repeated recharge of the residual magma with progressively less contaminated silica undersaturated melt resulted in a gradual shift across the low-pressure thermal divide. Crystallisation was suppressed by the depression of the liquidus due to water saturation of the residual magma (pH2O ~1 kbar).

  4. New paleomagnetic results from Middle and Late Proterozoic intrusive rocks of the central and southern Rocky Mountains

    SciTech Connect

    Harlan, S.S. )

    1993-04-01

    Paleomagnetic results from Proterozoic intrusive rocks from the central and southern Rocky Mountains yield data that provide definition to the North American APW path. Results from the ca. 1420 Ma Laramie anorthosite (LA) and Sherman Granite (SG) yield dual polarity magnetizations; a combined pole (7[degree]S, 215[degree]E, A[sub 95] = 4[degree]) is essentially identical to 1400 Ma poles from elsewhere in North America. Group A dikes from the Tobacco Root (TR) Mtns, MT, along the southern margin of the Belt Basin, have a dual-polarity remanence with a pole at 10[degree]N, 222[degree]E (A[sub 95] = 11[degree]) that plots slightly north of the LA/SG and other poles of ca. 1450 Ma. Comparison of Belt Supergroup poles, assuming coherence of the Belt terrane and interior Laurentia, with 1400 Ma poles and those of the well-defined western arm of the Logan Loop of the N. American APW path, would seem to indicate that the age of most Belt poles are in the range of 1300--1400 Ma, although this age assignment conflicts with available geochronologic data. Results from 1100 Ma diabase sheets from central AZ yield two distinct, normal and reverse polarity magnetizations: ADn and ADr. ADn gives a pole at 23[degree]N, 181[degree]E (A[sub 95] = 8[degree]) that overlaps poles of ca. 1100 Ma from the midcontinent rift (MR). Pole ADr is located at 38[degree]N, 248[degree]E (A[sub 95] = 39[degree]); the large uncertainty of this pole precludes its use in defining the APW path. All dikes are of WNW trend and several from the TR Mtns and the Christmas Lake dike from the Beartooth uplift give hornblende [sup 40]Ar/[sup 39]Ar ages of 760--770 Ma. The data are interpreted to provide evidence for Late Proterozoic mafic magmatism along the W and SW margin of the Wyoming Province, possibly related to crustal extension accompanying deposition of the Windermere Group in the northern part of the Cordillera and volcanism and sedimentation in SE Idaho and NE Washington.

  5. Geochronology and geochemistry of Eocene potassic felsic intrusions in the Nangqian basin, eastern Tibet: Tectonic and metallogenic implications

    NASA Astrophysics Data System (ADS)

    Xu, Yue; Bi, Xian-Wu; Hu, Rui-Zhong; Chen, You-wei; Liu, He-qing; Xu, Lei-luo

    2016-03-01

    The Jinshajiang-Ailaoshan copper belt is the most significant porphyry copper belt in eastern Tibet. In the northern segment of this belt within the Nangqian basin, which occurs 100 km east of the Yulong porphyry copper deposit, several felsic intrusions have been recently discovered. The Yulong porphyry copper deposit is one of the largest porphyry copper deposits in China, and it is associated with peraluminous adakitic rocks formed in a post-collisional setting. The Nangqian felsic intrusions vary from syenite porphyry to monzonite porphyry in rock types. No significant Cu-Au mineralization has been found in the Nangqian felsic intrusions despite extensive exploration in recent years. LA-ICP-MS zircon U-Pb dating reveals that the Nangqian syenite porphyry and monzonite porphyry were emplaced at ~ 35.6±0.3 Ma and from 39.5±0.3 to 37.4±0.3 Ma, respectively, similar to the age of the Yulong porphyry copper deposit. The Nangqian felsic intrusions are characterized by metaluminous compositions (A/CNK = 0.82-1.01), and they share some common features with shoshonites such as high K2O contents (4.58-5.58 wt.%), high K2O/Na2O ratios (0.92-1.28), LREE-LILE enrichments and negative Nb-Ta-Ti-P anomalies, as well as with adakites derived from an eclogite-facies source with high Al2O3 (14.98-15.74 wt.%), Sr (954-2190 ppm), Sr/Y (68-132) and La/Yb (53-85), and low Y and Yb contents. The Nangqian felsic intrusions have high initial 87Sr/86Sr (0.7050-0.7055), variable εNd(t) (- 0.31-1.43) and small variations in (206Pb/204Pb)i (18.68-18.74), (207Pb/204Pb)i (15.53-15.62) and (208Pb/204Pb)i (38.51-38.80). Zircon crystals from both syenite and monzonite porphyries are characterized by positive εHf(t) from 5.2 to 8.5. The results suggest that the syenite and monzonite magmas were differentiated from parental shoshonitic melts by fractional crystallization of olivine, clinopyroxene and minor feldspar. The parent magmas originated from a lithospheric mantle metasomatized by slab

  6. Contrasting fluid/rock interaction between the Notch Peak granitic intrusion and argillites and limestones in western Utah: evidence from stable isotopes and phase assemblages

    USGS Publications Warehouse

    Nabelek, P.I.; Labotka, T.C.; O'Neil, J.R.; Papike, J.J.

    1984-01-01

    The Jurassic Notch Peak granitic stock, western Utah, discordantly intrudes Cambrian interbedded pure limestones and calcareous argillites. Contact metamorphosed argillite and limestone samples, collected along traverses away from the intrusion, were analyzed for ??18O, ??13C, and ??D. The ??13C and ??18O values for the limestones remain constant at about 0.5 (PDB) and 20 (SMOW), respectively, with increasing metamorphic grade. The whole rock ??18O values of the argillites systematically decrease from 19 to as low as 8.1, and the ??13C values of the carbonate fraction from 0.5 to -11.8. The change in ??13C values can be explained by Rayleigh decarbonation during calcsilicate reactions, where calculated {Mathematical expression} is about 4.5 permil for the high-grade samples and less for medium and low-grade samples suggesting a range in temperatures at which most decarbonation occurred. However, the amount of CO2 released was not anough to decrease the whole rock ??18O to the values observed in the argillites. The low ??18O values close to the intrusion suggest interaction with magmatic water that had a ??18O value of 8.5. The extreme lowering of ??13C by fractional devolatilization and the lowering of ??18O in argillites close to the intrusion indicates oxgen-equivalent fluid/rock ratios in excess of 1.0 and X(CO2)F of the fluid less than 0.2. Mineral assemblages in conjunction with the isotopic data indicate a strong influence of water infiltration on the reaction relations in the argillites and separate fluid and thermal fronts moving thru the argillites. The different stable isotope relations in limestones and argillites attest to the importance of decarbonation in the enhancement of permeability. The flow of fluids was confined to the argillite beds (argillite aquifers) whereas the limestones prevented vertical fluid flow and convective cooling of the stock. ?? 1984 Springer-Verlag.

  7. The Relationship Between Amphibole Cumulates and Adakite Magma

    NASA Astrophysics Data System (ADS)

    Rooney, T. O.

    2009-12-01

    Amphibole, while uncommon as a primary fractioning phase is increasingly recognized as a key constituent in the petrogenesis of arc magmas. Fractional crystallization of water-saturated arc magmas in the lower crust can yield substantial volumes amphibole cumulates that, depending on the pressure of crystallization, may also contain garnet. Fractionation of this higher pressure assemblage has been invoked as a possible mechanism in the production adakite magmas. The origin of adakites, defined by their heavy REE and Y depletion and Sr enrichments, have vigorously debated since their re-discovery in Panama two decades ago. In addition to widespread modern adakitic volcanism, the Panamanian portion of the Central American Arc preserves the magmatic record of arc development in close spatial association with younger magmatism. Late-Oligocene hypabyssal crystal-rich andesites from Cerro Patacon are preserved near the Panama Canal region. These contain nodules of amphibole cumulates, and may be used to examine the amphibole-fractionation model for adakite origin. The cumulate nodules are ~6 cm in diameter and are almost entirely composed of 5-10mm amphibole crystals (dominantly ferri-tschermakite), and are accompanied in the host andesites by amphibole phenocrysts, antecrysts and megacryts. Cerro Patacon andesites have REE concentrations that plot at the most depleted end of the array defined by similarly differentiated (58-60% SiO2) Central American Arc magmas, and exhibit a distinctive depletion in the middle REE. These geochemical and petrographic observations strongly support significant amphibole fractionation during formation of the Cerro Patacon andesite. Sr/Y which is used as a geochemical tool for discriminating adakites from other arc magams, is transitional in the Cerro Patcon andesites. However La/Yb is within the range for ‘normal’ arc magmas and shows that amphibole fractionation alone is insufficient to generate adakite magmas - some garnet

  8. Late Carboniferous adakitic granodiorites in the Qiongkusitai area, western Tianshan, NW China: Implications for partial melting of lower crust in the southern Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Yin, Jiyuan; Chen, Wen; Xiao, Wenjiao; Yuan, Chao; Long, Xiaoping; Cai, Keda; Zhang, Bin

    2016-07-01

    Carboniferous granitic rocks are wide spread in the western Tianshan, but their tectonic contexts remain controversial. We present zircon U-Pb age, major element, trace element, and in situ zircon Hf isotopic data for the Qiongkusitai granodiorites from the southern part of the Yili block in the western Tianshan. The granodiorites were emplaced in the Late Carboniferous (ca. 314 Ma) and are characterized by high SiO2 (62.1-65.7 wt.%), high Sr (376-485 ppm), low Y (13.7-17.7 ppm) and low Yb (1.34-1.81 ppm) with Sr/Y ratios of 23-34. Such characteristics imply adakitic affinities. Their low concentrations of Cr (3.85-6.75 ppm), Co (7.63-10.7 ppm) and Ni (2.94-6.80 ppm) suggest little, if any, interaction with a mantle source. Compared to the thickened lower crustal-derived adakitic rocks, the relatively low Nb/Ta ratios of the Qiongkusitai adakitic granodiorites indicate that they were probably generated by partial melting of amphibolite facies rocks, but not eclogite facies rocks. The Qiongkusitai adakitic granodiorites have positive zircon εHf(t) values of +0.7 to +5.1 and TDM2 of 1.28-1.68 Ga, and they are interpreted as being derived from remelting of amphibolite facies Mesoproterozoic basement with an input of juvenile material. Late Carboniferous magmatism in the western Tianshan was possibly triggered by asthenospheric upwelling as a result of the roll-back of the subducted southern Tianshan oceanic lithosphere.

  9. Zircon U-Pb geochronology of the basement rocks and dioritic intrusion associated with the Fushan skarn iron deposit, southern Taihang Mountains, China

    NASA Astrophysics Data System (ADS)

    Shen, Jun-Feng; Li, Sheng-Rong; Santosh, M.; Dong, Guo-Chen; Wang, Yan-Juan; Liu, Hai-Ming; Peng, Zi-Dong; Zhang, Zhao-Yu

    2015-12-01

    The Fushan iron ores, located in the southern part of the Taihang Mountains (TM) within the Trans-North China Orogen, is among the medium-sized skarn iron deposits in China. In this paper we report U-Pb age data on zircon grains from the magmatic intrusion related with the skarn formation and from the Neoarchean metamorphic basement in the area. The results show that the dioritic intrusion which generated the skarn mineralization was emplaced at 128.8 ± 1.9 Ma. Zircon grains from the basement rocks and xenoliths, as well as inherited zircon in the dioritic intrusion show Neoarchean to Paleoproterozoic ages, corresponding to similar ages reported from elsewhere in the North China Craton. Our results and those from previous studies suggest that the continental lower crust was the major source of Mesozoic magmatism and associated ore mineralization. The Mesozoic magmatism and metallogeny in the Fushan region correlate with the peak of lithospheric destruction of the North China Craton.

  10. The Quaternary adakite distribution of Kyushu Island, Ryukyu Arc, Japan

    NASA Astrophysics Data System (ADS)

    Shibata, T.; Yoshikawa, M.; Takemura, K.

    2011-12-01

    The Quaternary volcanoes are widely distributed in Kyusu Island, Japan. Philippine Sea plate is subducting beneath Kyushu. Clear distribution of deep seismic foci is observed below the Quaternary volcanoes in southern area, but not in northern area. Notsu et al. (1990, JVGR) examined the contribution of subduction to the magma source, and emphasized that no slab derived material is observed in northern area from Sr isotopic compositions. Volcanic activity similar to the within-plate type volcanism has been also emphasized for the magma genesis of this area (e.g. Kita et al, 2001, JVGR). However, we found adakitic rocks, which show high Sr/Y ratios and low Y concentrations (e.g. Defant and Drummond, 1990, Nature) from some Quaternary volcanoes in north Kyushu on the basis of published data (Otha et al, 1990, GANKO; Itoh, 1990, GANKO). Therefore, the magma genesis is still controversial. We studied lateral variations of Sr, Nd and Pb isotopic and trace element compositions for Quaternary volcanics from Kyushu to investigate the magma genesis. From the results, a clear variation of Sr/Y ratio, decreasing from north to south, is observed along the volcanic front. Some of the Sr/Y ratio of the most northern part of Kyusu shows the value >100. The all analyzed Pb isotope compositions show a single liner trend in 208Pb/204Pb v.s. 206Pb/204Pb diagram. The liner trend of Pb isotope ratios can be explained by the binary mixing of the Shikoku Basin basalt and tereginious sediment which might be a constituent of the subducting slab. The similar binary mixing relationships are found in Sr and Nd isotopic systematics. The isotopic characteristics of the Quaternary magma in Kyushu can be explained by the magma generation process of island arc, in spite of the lack of deep seismic foci in northern area. It is considered that high and low Sr/Y ratios suggest the contributions of partial melt in the north and aqueous fluid derived from subducting slab in the south, respectively. If

  11. Implications of Late Cretaceous U-Pb zircon ages of granitic intrusions cutting ophiolitic and volcanogenic rocks for the assembly of the Tauride allochthon in SE Anatolia (Helete area, Kahramanmaraş Region, SE Turkey)

    NASA Astrophysics Data System (ADS)

    Nurlu, Nusret; Parlak, Osman; Robertson, Alastair; von Quadt, Albrecht

    2016-01-01

    An assemblage of NE-SW-trending, imbricate thrust slices (c. 26 km E-W long × 6.3 km N-S) of granitic rocks, basic-felsic volcanogenic rocks (Helete volcanics), ophiolitic rocks (Meydan ophiolite) and melange (Meydan melange) is exposed near the Tauride thrust front in SE Anatolia. The volcanogenic rocks were previously assumed to be Eocene because of associated Nummulitic limestones. However, ion probe U-Pb dating of zircons extracted from the intrusive granitic rocks yielded ages of 92.9 ± 2.2-83.1 ± 1.5 Ma (Cenomanian-Campanian). The Helete volcanic unit and the overlying Meydan ophiolitic rocks both are intruded by granitic rocks of similar age and composition. Structurally underlying ophiolite-related melange includes similar-aged, but fragmented granitic intrusions. Major, trace element and rare earth element analyses coupled with electron microprobe analysis of the granitic rocks show that they are metaluminus to peraluminus and calc-alkaline in composition. A magmatic arc setting is inferred from a combination of tectonomagmatic discrimination, ocean ridge granite-normalized multi-element patterns and biotite geochemistry. Sr-Nd-Pb isotope data further suggest that the granitoid rocks were derived from variably mixed mantle and crustal sources. Granitic rocks cutting the intrusive rocks are inferred to have crystallized at ~5-16 km depth. The volcanogenic rocks and granitic rocks originated in a supra-subduction zone setting that was widely developed throughout SE Anatolia. Initial tectonic assembly took place during the Late Cretaceous probably related to northward subduction and accretion beneath the Tauride continent (Keban and Malatya platforms). Initial tectonic assembly was followed by exhumation and then transgression by shelf-depth Nummulitic limestones during Mid-Eocene, as documented in several key outcrops. Final emplacement onto the Arabian continental margin took place during the Early Miocene.

  12. Geochronology and geochemistry of Late Pan-African intrusive rocks in the Jiamusi-Khanka Block, NE China: Petrogenesis and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Yang, Hao; Ge, Wen-chun; Zhao, Guo-chun; Dong, Yu; Bi, Jun-hui; Wang, Zhi-hui; Yu, Jie-jiang; Zhang, Yan-long

    2014-11-01

    To constrain the early Paleozoic tectonic evolution of the Jiamusi-Khanka Block and its relationship to the Late Pan-African event in Gondwana, we undertook zircon U-Pb dating and geochemical analyses (major and trace elements, and Hf isotopic compositions) of early Paleozoic intrusive rocks in the Jiamusi-Khanka Block, NE China. LA-ICP-MS zircon U-Pb age data demonstrate that these intrusive rocks were emplaced at three stages during the Late Pan-African event, represented by ~ 540 Ma syenogranite, ~ 515 Ma quartz syenite, and ~ 500 Ma monzogranite and gabbro. Geochemically, the ~ 500 Ma gabbros in the Jiamusi-Khanka Block have low SiO2 (50.26-51.21 wt.%), relatively high MgO (4.08-5.67 wt.%), Ni (13.1-14.1 ppm) and Cr (28.4-56.0 ppm), and are slightly enriched in LILEs (e.g., Ba, K) and LREEs, and depleted in Zr, Hf, Nb, Ta and P. The εHf(t) values of zircons in the gabbro range from + 2.6 to + 6.4. All these geochemical features indicate that the gabbros were likely produced by the partial melting of a depleted mantle that had been metasomatized by fluids derived from a subducted slab. In contrast, the ca.540-500 Ma granites and quartz syenites contain high SiO2 (64.49-72.20 wt.%) and low MgO (0.40-0.75 wt.%), Cr (1.69-6.88 ppm) and Ni (1.26-3.26 ppm). They have relatively low 176Hf/177Hf ratios of 0.282247-0.282599 with Hf two-stage model ages of 1173-2280 Ma, and most of the magmatic zircons have positive εHf(t) values varying from + 0.2 - + 4.8, indicating that these granites and quartz syenites were probably derived from a dominantly Paleo-Mesoproterozoic "old" crustal source with possible different degrees of addition of juvenile materials. According to the geochemical data and global geological investigations, we propose that the 541-498 Ma intrusive rocks in the Jiamusi-Khanka Block formed in a post-collisional or post-orogenic extensional setting linked to the collapse of a Late Pan-African orogen associated within the Gondwana.

  13. New isotopic dating of intrusive rocks in the Sierra de San Luis (Argentina): implications for the geodynamic history of the Eastern Sierras Pampeanas

    NASA Astrophysics Data System (ADS)

    von Gosen, W.; Loske, W.; Prozzi, C.

    2002-06-01

    U-Pb datings of zircons from intrusions in the metamorphic complex of the Sierra de San Luis (Eastern Sierras Pampeanas, Argentina) suggest that the depositional, tectonic, metamorphic, and magmatic history in this part of the Pampean Terrane spans the Proterozoic through Early Paleozoic time interval. The Paso del Rey Granite intruded a clastic succession at 608+26/-25 Ma and, afterward, was deformed together with the country rocks. The intrusions of the Rı´o Claro Granite and La Escalerilla Granite at 490±15 and 507±24 Ma, respectively, mark the onset of Famatinian arc plutonism due to east-directed subduction beneath the Eastern Sierras Pampeanas. The new data, along with structural analyses and published results of isotopic dating, allow an interpretation of the history in this segment of the Pampean Terrane. After basement formation, Late Proterozoic turbiditic sedimentation in a passive margin setting was accompanied by block faulting and continued at least to the Early Cambrian. It is assumed that the Pampean Terrane represents a detached fragment of the Rı´o de La Plata Craton in the east. The first deformation in the Micaschist Group was an effect of an early stage of the compressive Pampean event, which is related to the collision of the Pampean Terrane with the Rı´o de La Plata Craton. The Early Cambrian is recorded by injections of acid magmatic sills and dykes, probably under overall crustal extension. This also indicates an age of the turbiditic sediments comparable to that of the Puncoviscana Formation s.l. of northwest Argentina. After cessation of Famatinian arc plutonism, compression and regional metamorphism affected the intrusives, clastic succession, and older basement units. The related amalgamation of the Cuyania (Precordillera) Terrane with the Eastern Sierras Pampeanas was completed during the Early Devonian.

  14. Age and origin of earliest adakitic-like magmatism in Panama: Implications for the tectonic evolution of the Panamanian magmatic arc system

    NASA Astrophysics Data System (ADS)

    Whattam, Scott A.; Montes, Camilo; McFadden, Rory R.; Cardona, Agustin; Ramirez, Diego; Valencia, Victor

    2012-06-01

    40-20 Ma marks a fundamental interval in the evolution of the 70-0 Ma Panamanian magmatic arc system. During this period, there is no evidence of Panamanian magmatic arc activity to the east of the Panama Canal Basin while to the west and in localized regions to the east of the Panama Canal Basin a phase of intrusive-only activity is recorded. Fundamentally, geochemical and geochronological evidence presented herein indicate that this intrusive activity was predominantly 'adakitic-like' and becomes younger from west to east along an approximately W-E striking lineament. Granodiorites of the Petaquilla batholith, western Panama yield LAM-ICP-MS 206Pb/238U zircon ages of 29.0 + 0.7, - 0.6 Ma, 28.5 + 0.7, - 0.5 Ma, 28.3 + 0.5, - 0.4 Ma and 26.2 + 0.5, - 0.9 Ma. To the east of the Panama Canal Basin zircons from a hypabyssal diorite of the mainly intermediate Majé subvolcanic suite, cedes a mean 206Pb/238U age of 18.9 + 0.4 Ma. Relative to other 70-5 Ma Panamanian magmatic arc lavas and intrusives, Majé and Petaquilla intrusives yield adakitic-like major and trace element abundances (e.g., > 15 wt.% Al2O3, generally > 3.5 wt.% Na2O, > 400 ppm Sr, < 1.9 ppm Yb, < 18 ppm Y, Sr/Y that ranges to > 120) and strongly fractionated HREE patterns. These 30-26 Ma (Petaquilla) and 19 Ma (Majé) suites are also compositionally similar to a subvolcanic suite of rare, circa 25 Ma adakitic-like, andesitic intrusives which occur within the Panama Canal Basin midway between Petaquilla and Majé and at the same approximate latitude as Petaquilla and Majé. Collectively, the geochemical and geochronological data for the adakitic-like intrusives arc consistent with formation via partial melting of lowermost, mafic crust above a sub-horizontal slab tear that propagated from the west (Petaquilla) to the east (Majé) between 30 and 19 Ma. Our new tectonic model postulates that collision between the Panamanian magmatic arc system and an 'indentor' (e.g., a tract of thickened buoyant

  15. Genesis of adakitic granitoids by partial melting of thickened lower crust and its implications for early crustal growth: A case study from the Huichizi pluton, Qinling orogen, central China

    NASA Astrophysics Data System (ADS)

    Qin, Zhengwei; Wu, Yuanbao; Siebel, Wolfgang; Gao, Shan; Wang, Hao; Abdallsamed, Mohammed. I. M.; Zhang, Wenxiang; Yang, Saihong

    2015-12-01

    Adakitic rocks are often considered as a key to deciphering the genesis of Archean TTGs and the early crustal growth. Granites from the Huichizi pluton in the North Qinling (NQ) unit have high Sr/Y and (La/Yb)N ratios similar to adakites. Their relatively high SiO2, K2O, and Na2O and very low MgO, Cr, and Ni contents are in the range of high-SiO2 adakites and early Archean TTGs and are compositionally similar to experimental melts derived from metabasalt sources. New SIMS zircon U-Pb dating constrains the emplacement age of the Huichizi pluton at 422 ± 5 Ma. Rock samples from the Huichizi pluton have εNd(t) and zircon εHf(t) values similar to the Neoproterozoic metabasalts in the NQ unit. In combination with their normal mantle-like δ18Ozir values, these adakites are best explained by partial melting of the Neoproterozoic mafic crustal root due to subduction of the Shangdan ocean. Regional geological data suggest that the crust was probably thickened by a ca. 490 Ma arc-collision process prior to the emplacement of the Huichizi pluton. Our results confirm that underplating of mafic magma and its subsequent fusion triggered by slab subduction under high pressure conditions could be an important mechanism for the formation of early continental crust.

  16. Acid-neutralizing potential of minerals in intrusive rocks of the Boulder batholith in northern Jefferson County, Montana

    USGS Publications Warehouse

    Desborough, George A.; Briggs, Paul H.; Mazza, Nilah; Driscoll, Rhonda

    1998-01-01

    Experimental studies show that fresh granitic rocks of the Boulder batholith in the Boulder River headwaters near Basin, Montana have significant acid-neutralizing potential and are capable of neutralizing acidic water derived from metal-mining related wastes or mine workings. Laboratory studies show that in addition to the acidneutralizing potential (ANP) of minor amounts of calcite in these rocks, biotite, tremolite, and feldspars will contribute significantly to long-term ANP. We produced 0.45 micrometer-filtered acidic (pH = 2.95) leachate for use in these ANP experiments by exposing metal-mining related wastes to deionized water in a waste:leachate ratio of 1:20. We then exposed these leachates to finely-ground and sized fractions of batholith rocks, and some of their mineral fractions for extended and repeated periods, for which results are reported here. The intent was to understand what reactions of metal-rich acidic water and fresh igneous rocks would produce. The reactions between the acidic leachates and the bulk rocks and mineral fractions are complex. Factors such as precipitation of phases like Fe-hydroxides and Alhydroxides and the balance between dissolved cations and anions that are sulfate dominated complicate analysis of the results. Research by others of acid neutralization by biotite and tremolite attributed a rise in pH to proton (H+) adsorption in sites vacated by K, Mg, and Ca. Destruction of the silicate framework and liberation of associated structural hydroxyl ions may contribute to ANP. Studies by others have indicated that the conversion of biotite to a vermiculite-type structure by removal of K at a pH of 4 consumes about six protons for every mole of biotite, but at a pH of 3 there is pronounced dissolution of the tetrahedral lattice. The ANP of fresh granitic rocks is much higher than anticipated. The three bulk Boulder igneous rock samples studied have minimum ANP equivalent to about 10-14 weight percent calcite. This ANP is in

  17. Origin of co-existing basalts, high-Mg andesites, and adakites in the SW Japan hot subduction system

    NASA Astrophysics Data System (ADS)

    Kimura, J.; Kunikiyo, T.; Osaka, I.; Shimoshioiri, Y.; Katakuse, M.; Kakubuchi, S.; Nagao, T.; Furuyama, K.; Kamei, A.; Nakajima, J.; Stern, R. J.; Gill, J. B.

    2012-12-01

    In response to subduction of the young, hot Shikoku Basin of the Philippine Sea Plate (PSP) slab, arc magmas have been active throughout the late Cenozoic (<13 Ma) in the SW Japan arc. Extremely variable magma types occurred including oceanic island-type basalt (OIB), shoshonitc to mildly alkalic to sub-alkalic basalts with arc signatures, high-Mg andesites (HMAs), and adakitic andesites and dacites. The OIB-type basalts preceded the arc-type magmas. Therefore, the transition from OIB- to arc-types was related to opening of the Japan of Sea back-arc basin and subsequent re-initiation of PSP subduction. However, both the origin and tectonic implications of this magmatism are debated. Consequently, we analyzed the bulk rock geochemistry of 340 lava samples from seven Quaternary volcanoes and investigated their sources and melting conditions using a geochemical mass balance model, Arc Basalt Simulator version 4 (ABS4). Comparison to basement granitoids precludes adakite genesis in the lower crust. Instead, the ABS4 model suggests that the adakites are mostly slab melts plus minor interaction with mantle wedge peridotite (PERID). Increasing involvement of PERID during slab melt-fluxed mantle melting explains fairly well the geochemical variations of the shoshonites, mildly alkalic to sub-alkalic basalts, and HMAs. We propose that the generation of various magma types in the late Cenozoic SW Japan arc originated simply by "slab melt-fluxed mantle melting" with large variations in melting conditions including depth, temperature, degree of melting, and flux fractions. Such volcanism has been continuous from 13 Ma (Setouchi HMA) to the present, so that the hot subduction system, involving subduction of the Shikoku Basin spreading ridge, should be continuous since 13 Ma beneath the SW Japan arc. Our results further suggest that this atypically hot system generated diverse primary arc magmas from various degrees of flux melting even though the slab source components and sub

  18. 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

  19. Geochemical studies of mafic and other low silica, Precambrian intrusive rocks in the Adirondack lowlands, New York

    SciTech Connect

    Antibus, J.; Carl, J.D. . Dept. of Geology)

    1993-03-01

    Mafic metaigneous rocks in the Adirondack Lowlands include gabbros, amphibolites and diorites that are associated with, and hard to distinguish from, a host of dark colored, low-silica, alkali feldspar-bearing rocks that include syenogabbros, syenites and monzonites. All rocks intrude metasedimentary and metavolcanic host rocks and occur as isolated, pre- to syn-metamorphic bodies, generally with elongate, sheet-like form. Some occur within or marginal to deformation zones. Lacking are the massive igneous complexes of the Highlands where anorthosites, charnockites and mangerites comprise a common field association. Amphibolites vary from mappable sheets that are hundreds of meters thick to thin (<1 m) layers within the host gneisses. Gabbros and diorites vary from circular to oval-shaped bodies, generally <2 km across, that may be infolded with the host rocks. Pervasive shear in Lowland granitic rocks (Hyde School Gneiss) that resulted in major sheath folds, as proposed by Tewksbury, extends into the mafic bodies whose margins show strong gneissic textures and grain size reduction, but the cores are less deformed. The Balmat gabbro varies inwardly and systematically from monzonitic to gabbroic composition in decreasing Si, Na, K, Rb, Zr and Ba, and in increasing Ca, Mg, Fe, Ti, P, Sr, Cr, V and Ni content. Y/Nb ratios remain constant at 3-4. Among explanations of assimilation and metasomatism, the authors tentatively prefer an hypothesis of exclusion of alkali material during crystallization of mafic magma. Calc alkali and low potassium tholeiites are indicated in plots of the Balmat and other mafic bodies on Ti/100-Zr-Yx3 and Ti-Zr discrimination diagrams, although there is much scatter of data. Within-plate basalts are lacking, and ocean floor basalts are indicated for some amphibolites.

  20. Catastrophic erosion of Hellas basin rim on Mars induced by magmatic intrusion into volatile-rich rocks

    USGS Publications Warehouse

    Tanaka, K.L.; Kargel, J.S.; MacKinnon, D.J.; Hare, T.M.; Hoffman, N.

    2002-01-01

    Malea and Hesperia Plana form large sectors of the rim of Hellas basin that display partly eroded volcanic shields and plains. These regions have topographic profiles that appear to be several hundred meters lower than those of adjacent rim sectors and lack prominent massifs of remnant basement that would be expected to stand above the lava plains. We interpret that before the volcanic edifices were constructed, these regions were denuded by an early stage of voluminous sill intrusion into friable, volatile-rich impact breccia. Magma-volatile interactions may have resulted in catastrophic generation of debris flows deposited into the adjacent basin, particularly if CO2 were involved. Later, lavas covered the eroded terrain; in turn, the lavas were eroded locally by volatile interactions. Across Mars, huge channel systems, erosional features in volcanic terranes, and vast layered deposits may be due to magma-volatile interactions.

  1. Origin and evolution of the granitic intrusions in the Brusque Group of the Dom Feliciano Belt, south Brazil: Petrostructural analysis and whole-rock/isotope geochemistry

    NASA Astrophysics Data System (ADS)

    Hueck, Mathias; Basei, Miguel Angelo Stipp; Castro, Neivaldo Araújo de

    2016-08-01

    In the southern Brazilian state of Santa Catarina the Dom Feliciano Belt, formed by the tectonic juxtaposition of different crustal blocks during the Brasiliano-Pan African Orogenic cycle, can be divided into three domains. In the central domain, three granitic suites intrude the metavolcanosedimentary sequence of the Brusque Group: São João Batista (SJBS), Valsungana (VS) and Nova Trento (NTS), from the oldest to the youngest. This extensive magmatism, here referred to as granitic intrusions in the Brusqe Group (GIBG), is coeval with the thermal peak in the host metamorphic successions, but postdates its main foliation. A progressive deformation starting from the magmatic stage throughout the cooling history points to the influence of the late stages of deformation recorded in the Brusque Group. The SJBS consists of gray to white leucocratic, equigranular granites, with aluminous minerals such as muscovite, garnet and tourmaline. The porphyritic VS is the largest of the suites and is characterized by its cm-sized K-feldspar megacrysts in a coarse-grained biotite-rich matrix. The granites from the NTS are equigranular, light gray to pink in color and have biotite as the main mafic mineral, but magmatic muscovite, tourmaline and hornblende can occur as well. Geochemically, the GIBG are mildly peraluminous and show a calc-alkaline affinity. Most intrusions have a high REE fractionation, but some SJBS granites show a characteristic pattern with no fractionation and strong negative Eu anomalies ("seagull pattern"). Elevated Sr(i) values, between 0.707 and 0.735, and negative εNd values as low as -24 points to the melting of old evolved crust. The Nd (TDM) ages are scattered between 1.54 and 2.76 Ga, with a predominance of values around 2.0 Ga. The GIBG have a strong crustal signature that most closely connects, within the regional units, to that of the metasedimentary rocks of the Brusque Group and its crystalline basement, the Camboriú Complex. All three suites

  2. Geochronological and geochemical implications of Early to Middle Jurassic continental adakitic arc magmatism in the Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Kim, Sung Won; Kwon, Sanghoon; Ko, Kyoungtae; Yi, Keewook; Cho, Deung-Lyong; Kee, Weon-Seo; Kim, Bok Chul

    2015-06-01

    Sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb ages and whole-rock chemical compositions of Early to Middle Jurassic plutons from the central to southern Korean Peninsula are reported to investigate the effect of paleo-Pacific plate subduction preserved along the continental margin. Twenty-one plutonic rocks from the Yeongnam massif (i.e., Sunchang and Namwon plutons), the Okcheon belt (Jeongup, Boeun, and Mungyeong plutons), the northeast (Gangreung pluton), and the Gyeonggi massif (Gonam, Anheung, and Ganghwa plutons) have age ranges from ca. 189-186 Ma to 177 Ma, 177-166 Ma, and 177-173 Ma, respectively. Most plutonic rocks have chemical compositions similar to adakites, showing high SiO2 (45.62-74.96 wt.%), low MgO (0.01-2.84 wt.%), high Na2O (2.65-4.83 wt.%), high Sr/Y and La/Yb, low Y and Yb, as well as low HFSEs (Nb and Ta), but initial Sr ratios (0.7048-0.7262), K2O (0.50-5.88 wt.%), and K2O/Na2O (0.34-2.1) were unlikely to have been formed by melting of either a thickened and/or delaminated lower continental crust, or an altered oceanic crust. These suggest that the "adakitic" plutonic rocks in this region resulted from partial melting of an enriched mantle source metasomatized by dewatering from a delaminated flat-slab. The spatial distributions of this continental adakitic plutonic belt, based on the present study, together with previously reported geochronological results, indicate that magmatic pulses gradually migrated toward the continent across the Korean Peninsula as a result of slab shallowing caused by periodic slab buckling. The similar geochronological and geochemical characteristics, petrogenesis and tectonic setting of the plutonic belt spanning the Korean Peninsula, Japan, eastern China, and eastern Russia indicate a possible link to an active subduction system that existed during the Early to Middle Jurassic, although the products of the plate subduction might differ in different locations along the East Asian continental

  3. Deformation of host rocks and flow of magma during growth of minette dikes and breccia-bearing intrusions near Ship Rock, New Mexico

    USGS Publications Warehouse

    Delaney, Paul T.; Pollard, David D.

    1981-01-01

    We have studied a small group of minette dikes and plugs that crop out within a flat-lying sequence of siltstone and shale near Ship Rock, a prominent volcanic throat of tuff breccia in northwestern New Mexico. Seven dikes form a radial pattern about Ship Rock we describe in detail the northeastern dike, which has an outcrop length of about 2,900 m, an average thickness of 2.3 m, and a maximum thickness of 7.2 m. The dike is composed of 35 discrete segments arranged in echelon; orientation. of dike segments ranges systematically from N. 52? E. to N. 66? E. A prominent joint set strikes parallel to the segments and is localized within several tens of meters of the dike. Regional joint patterns display no obvious relation to dike orientation. Small offsets of segment contacts, as well as wedge-shaped bodies of crumpled host rock within segments mark the sites of coalescence of smaller segments during dike growth. Bulges in the dike contact, which represent a nondilational component of growth, indicate that wall rocks were brecciated and eroded during the flow of magma. Breccias make up about 9 percent of the 7,176-m 2 area of the dike, are concentrated in its southwest half, and are commonly associated with its thickest parts. We also describe three subcircular plugs; each plug is smaller than 30 m in diameter, is laterally associated with a dike, and contains abundant breccias. Field evidence indicates that these plugs grew from the dikes by brecciation and erosion of wallrocks and that the bulges in the contact of the northeastern dike represent an initial stage of this process. From continuum-mechanical models of host-rock deformation, we conclude that dike propagation was the dominant mechanism for creating conduits for magma ascent where the host rock was brittle and elastic. At a given driving pressure, dikes dilate to accept greater volumes of magma than plugs, and for a given dilation, less work is done on the host rocks. In addition, the pressure required

  4. Rocks.

    ERIC Educational Resources Information Center

    Lee, Alice

    This science unit is designed for limited- and non-English speaking students in a Chinese bilingual education program. The unit covers rock material, classification, characteristics of types of rocks, and rock cycles. It is written in Chinese and simple English. At the end of the unit there is a list of main terms in both English and Chinese, and…

  5. Zircon age range and sources of alkaline rocks from the Kurgusul intrusion, Kuznetsk Alatau: The first U-Pb (SHRIMP II) and Sm-Nd isotope data

    NASA Astrophysics Data System (ADS)

    Vrublevskii, V. V.; Gertner, I. F.; Tishin, P. A.; Bayanova, T. B.

    2014-12-01

    U-Pb isotope analysis of basic feldspathoid rocks (juvites) of the Kurgusul intrusion, NE Kuznetsk Alatau, revealed three generations of zircons of various ages (˜1.3-1.5 Ga; 484.3 ± 5.5 and 393.6 ± 9.2Ma). This suggests several stages of regional alkaline basic magmatism in the Middle Cambrian-Early Ordovician and Early-Middle Devonian and melting of the Mesoproterozoic continental crust, which form part of the basement of the Kuznetsk Alatau terrane. The trace element geochemical data indicate a continental margin setting characterized by the complex interaction of a plume-related, supra-subduction zone and crustal materials. A possible model of the magmatic evolution assumes that the ascent of a plume at the Cambrian-Ordovician boundary induced generation of the initial alkaline basaltic magmas and metasomatism and erosion of the lower lithosphere. Repeated partial melting of the lower crust after a 100 Myr period produced new magma batches of alkaline composition, which inherited zircons from the preceding episode of magma generation. The inherited juvenile magmatic source (PREMA + E-type MORB + EM) is confirmed by similarities in the Sm-Nd isotopic signatures (ɛNd( T) ≈ +4.5 to +5.7, T(Nd)DM ≈ 0.8-0.9 Ga) of derivatives of regional alkaline basic complexes of different ages.

  6. Geochemistry and petrogenesis of intrusions at the Golden Pride gold deposit in the Nzega greenstone belt, Tanzania

    NASA Astrophysics Data System (ADS)

    Kwelwa, Shimba; Manya, Shukrani; Vos, Ivo M. A.

    2013-10-01

    The greenstone sequence at Golden Pride gold deposit in Nzega greenstone belt of northern Tanzania is cross-cut by several intrusions whose geochemistry and petrogenesis is unknown. We present major and trace elements geochemistry of the Golden Pride igneous intrusions with the aim of constraining their petrogenesis and their ancient tectonic setting. The Golden Pride intrusions are geochemically categorized into two main rock suites: the granodiorites (which include the porphyries) and the lamprophyres (formerly intermediate intrusions). The granodiorites are characterized by SiO2 contents of 54.5-69.9 wt%, elevated MgO (1.22-3.59 wt%) Cr (up to 54 ppm), Mg# (35-55) pointing to a mantle component in the source. Compared to the TTG and adakites, the granodiorites are characterized by higher K2O (1.52-4.30 wt%), medium HREE (Gd/ErCN = 2.13-3.77) and marked enrichment in Ba and Sr (Ba + Sr = 819-2922 ppm) and are in these respects similar to Archean high Ba-Sr sanukitoids. The rocks in this suite are interpreted to have formed by partial melting of an enriched mantle wedge through two metasomatic events: subduction-related fluids/melts and by metasomatism related to asthenospheric mantle upwelling caused by slab break-off. Compared to the granodiorites, the lamprophyres have higher MgO contents (2.37-3.81 wt%), Cr (60-298 ppm), Co (31-57 ppm) and Mg# (32-40). They also show slight enrichment of the LREE relative to HREE (La/YbCN = 3.3-7.1), moderate Nb-Ti depletion and sub-chondritic Zr/Hf ratios (34-41). These geochemical features are attributed to derivation of the Golden Pride lamprophyres by partial melting of the amphibole-rich metasomatized mantle by slab derived hydrous fluids. Both of the Golden Pride intrusion suites show strong affinity to subduction related magmas and we interpret that the entire greenstone sequence and the associated intrusions at Golden Pride gold deposit formed in a late Archaean convergent margin.

  7. Carboniferous magmatism in the Evora Massif (southwest Portugal, Ossa-Morena Zone): from typical arc calc-alkaline to adakitic-like magmatism

    NASA Astrophysics Data System (ADS)

    Lima, Selma M.; Neiva, Ana M. R.; Ramos, Joao M. F.

    2014-05-01

    The Evora Massif is one of the subdivisions of western Ossa-Morena Zone. It is a dome-like structure mainly composed of Ediacaran, Cambrian and Ordovician country rocks, affected by medium- and high-grade metamorphism coeval with the emplacement of several mafic to felsic intrusive bodies. The last magmatic event recorded in this area (Carboniferous) consists of calc-alkaline volcanism and voluminous plutonism (mainly composed by tonalites, gabbros, diorites and late-orogenic granodiorites and granites) [1]. Detailed chemical and isotopic studies from Evora Massif plutons were performed in the last few years. Whole-rock chemical and isotopic data suggest that the Hospitais tonalite (HT), Alto de Sao Bento area (ASB) and Reguengos de Monsaraz pluton (RM) resulted from fractional crystallization of mantle-derived magmas followed by mixing with variable proportions of crustal melts [2-4]. U-Pb ID-TIMS data indicate an age of 337-335 for the RM [4]. The Pavia pluton is a multiphase granitic body constructed incrementally by the episodic emplacement of several batches of magma (at 328 Ma, ca. 324 Ma and 319-317 Ma) [5]. The main granitic phases range from tonalite to two-mica granite that contain rare surmicaceous and fine-grained enclaves, and granitic and amphibolitic xenoliths. On the other hand, they are cut by abundant rhyodacite porphyries, microgranites (s.l.) and pegmatite dikes, predominantly oriented NE-SW and NW-SE. Although each phase seems to represent a distinct batch of magma, whole-rock Sr-Nd isotopic data suggest a similar and fairly homogenous source for all the constituent phases. Initial 87Sr/86Sr varies between 0.70428 and 0.7058 and ɛ Ndt ranges from -3.4 to +0.4, pointing towards a mantle or juvenile crust origin. A higher variation is observed in whole-rock δ18O (5.6-9.6 o), consistent with assimilation of crust. The PP was interpreted as the result of assimilation-fractional crystallization of a basaltic magma. Substantial differences between

  8. Geochronology, geochemistry, and deformation history of Late Jurassic-Early Cretaceous intrusive rocks in the Erguna Massif, NE China: Constraints on the late Mesozoic tectonic evolution of the Mongol-Okhotsk orogenic belt

    NASA Astrophysics Data System (ADS)

    Tang, Jie; Xu, Wen-Liang; Wang, Feng; Zhao, Shuo; Li, Yu

    2015-09-01

    This paper presents new zircon and sphene U-Pb ages, biotite and hornblende 40Ar/39Ar ages, Hf isotopic data, and geochemical data for five Mesozoic plutons in the Erguna Massif of NE China. These data are used to constrain the late Mesozoic tectonic evolution of the Mongol-Okhotsk orogenic belt. This new dating, when combined with previously published ages, indicates that the Late Jurassic-Early Cretaceous (J3-K1) intrusive rocks can be subdivided into three stages that represent periods of magmatism during the Late Jurassic (~ 155 Ma), early Early Cretaceous (~ 137 Ma), and late Early Cretaceous (~ 123 Ma). In addition, the rocks have undergone later deformation recorded by peak ages of ~ 137 and ~ 123 Ma. The Late Jurassic and early Early Cretaceous intrusive rocks in the study area are dominantly syenogranites and are either A-type granites or are classified as alkaline series, suggesting that they formed in an extensional environment. The late Early Cretaceous intrusive rocks in this area are generally monzogranitic and were emplaced as dikes in an extensional environment, along with coeval bimodal volcanics. These data, combined with the presence of regional unconformities in the northern part of Hebei Province and western part of Liaoning Province, and the spatial distribution of coeval volcanic rocks in NE China, suggest the Late Jurassic and early Early Cretaceous magmatisms and the early Early Cretaceous deformation in this area occurred in an extensional environment related to the delamination of a thickened part of the crust after closure of the Mongol-Okhotsk Ocean. In comparison, the late Early Cretaceous deformation and magmatism occurred in an extensional environment related to either delamination of the previously thickened crust related to the Mongol-Okhotsk tectonic regime or the subduction of the Paleo-Pacific Plate, or the combined influence of these two tectonic regimes.

  9. New age and geochemical constraints on the origin of Quaternary adakite-like lavas in the Arabia-Eurasia collision zone

    NASA Astrophysics Data System (ADS)

    Pang, Kwan-Nang; Chung, Sun-Lin; Zarrinkoub, Mohammad Hossein; Li, Xian-Hua; Lee, Hao-Yang; Lin, Te-Hsien; Chiu, Han-Yi

    2016-11-01

    Adakite-like lavas from the Iranian segment of the Arabia-Eurasia collision zone have been considered as partial melts derived from a subducted Neotethyan slab, a hypothesis that cannot be further evaluated due to the lack of systematic age and radiogenic isotopic data. Here, we revisit the Anar region, Iran where such lavas were reported by providing these data to examine their probable origin as slab melts. New SIMS zircon U-Pb ages attest to eruption at ca. 1 to 2 Ma, postdating the Arabia-Eurasia collision. The lavas are characterized by dacitic to rhyolitic, metaluminous to slightly peraluminous and trondhjemitic compositions, and incompatible element patterns similar to continental crustal rocks. Extreme depletion in Nb, Ta, Y and the heavy REE relative to the light and middle REEs reflects control by garnet and rutile. Except one sample presumably affected by secondary gain of radiogenic Sr, the depleted Sr-Nd-Hf isotopic compositions relative to the Bulk Silicate Earth [(87Sr/86Sr)i = 0.7040 to 0.7043; εNd(t) = + 3.2 to + 5.3; εHf(t) = + 10.5 to + 11.3] indicate magma genesis from juvenile source rocks. A slab melt origin for the Anar lavas is very unlikely and the reason is twofold. First, the Y and HREE of the source rocks estimated by inversed batch melting models assuming garnet pyroxenite residue are far too low compared with MORB-like lithologies and subducted sediments. Second, the low MgO, Ni and Cr of the lavas point to limited interaction with peridotites in a mantle wedge. Fractionation-related models are also unlikely due to the apparent lack of broadly coeval, mafic precursor magmas without adakitic signature. The low-Y and low-HREE source rocks revealed by the melting models, together with the low MgO, Ni and Cr of the Anar lavas, can be explained by lower crustal melting under eclogite-facies conditions. These source rocks were most likely high-pressure cumulates in the root of the Urumieh-Dokhtar magmatic arc, a Neotethyan arc that was

  10. Decoupling of whole-rock Nd-Hf and zircon Hf-O isotopic compositions of a 284 Ma mafic-ultramafic intrusion in the Beishan Terrane, NW China

    NASA Astrophysics Data System (ADS)

    Su, Ben-Xun; Qin, Ke-Zhang; Lu, Ying-Huai; Sun, He; Sakyi, Patrick Asamoah

    2015-10-01

    Abundant Permian mafic-ultramafic intrusions in the Beishan Terrane, NW China, are parts of the Tarim large igneous province. Among these intrusions, Luodong intrusion is composed of dunite, wehrlite and gabbro. These rocks have whole-rock Sr-Nd-Hf and zircon Hf-O isotope compositions that display significant decoupling. The decoupling of these generally well-correlated systems demonstrates contrasting evolving trends. Systematic compositional and mineralogical controls on decoupling have been investigated. Wehrlites and gabbros show MORB-like trace element patterns with negligible crustal contamination. They have high initial 143Nd/144Nd [ɛNd(t) = +6.6 to +11.2] and 176Hf/177Hf [ɛHf(t) = +12.2 to +16.9] and low initial 87Sr/86Sr [(87Sr/86Sr)i = 0.702949-0.704098] ratios and plot within the MORB field, indicating that their parental magmas were derived from a depleted mantle source. The enrichment features are present in the zircon crystals separated from the gabbro. These homogeneously unzoned zircon crystals have high U concentrations, low Th/U ratios and a U-Pb age of 284.0 ± 2.3 Ma. They are therefore interpreted as having formed rapidly in a highly fractionated/evolved magma. Their ɛHf(t) and δ18O values range from -9.3 to -6.7 and +10.25 ‰ to +11.42 ‰, respectively. The decoupling is linked with crustal contamination by ancient crust (probably Proterozoic schist in the Beishan Terrane) that occurred during zircon crystallization. However, the contamination signature in the whole-rock composition was soon overprinted by magma mixing process. The inference is evidenced by zoning textures preserved in plagioclase, clinopyroxene, spinel and particularly olivine, and the presence of coeval diabase dykes cutting through the intrusion. The isotope decoupling observed in this mantle-plume-related mafic-ultramafic intrusion supports the idea that Nd-Hf decoupling and Lu/Hf and Sm/Nd parent/daughter variations exist only on a small hand-size scale in a

  11. Petrogenesis and economic potential of the Erhongwa mafic-ultramafic intrusion in the Central Asian Orogenic Belt, NW China: Constraints from olivine chemistry, U-Pb age and Hf isotopes of zircons, and whole-rock Sr-Nd-Pb isotopes

    NASA Astrophysics Data System (ADS)

    Sun, Tao; Qian, Zhuang-Zhi; Li, Chusi; Xia, Ming-Zhe; Yang, Su-Hong

    2013-12-01

    The Erhongwa mafic-ultramafic intrusion is located in the southern margin of the Central Asian Orogenic Belt in northern Xinjiang where many early-Permian mafic-ultramafic intrusions host important Ni-Cu sulfide deposits. In this paper we report zircon U-Pb age, olivine chemistry and integrated whole-rock chemical and isotopic compositions for the Erhongwa mafic-ultramafic intrusion. This intrusion is composed of lherzolites and gabbroic rocks. The U-Pb age of zircon from a large olivine gabbro sample from the intrusion is 283.1 ± 1.5 Ma, which indicates that the Erhongwa intrusion is contemporaneous with the early-Permian sulfide ore-bearing mafic-ultramafic intrusions in the central Tianshan region. Olivine from the Erhongwa intrusion contains up to 89.5 mol% Fo and 3000 ppm Ni, which are the highest among all known early-Permian mafic-ultramafic intrusions in the region. The occurrence of small sulfide inclusions in the most primitive olivine and significant Ni depletion in more fractionated olivine in the Erhongwa intrusion indicate that sulfide segregation took place during olivine fractional crystallization. The Erhongwa intrusive rocks are characterized by light REE enrichment relative to heavy REE, negative Nb anomalies, positive εNd (t = 283 Ma) values from + 6.3 to + 7.7, low initial 87Sr/86Sr ratios from 0.7034 to 0.7036, initial 206Pb/204Pb ratios from 17.8 to 17.9 and zircon εHf values from 8.0 to 15.5. The Erhongwa mafic-ultramafic rocks and coeval A-type granites in the region have similar isotopic compositions but the former have lower Th/Nb ratios than the latter. These similarities and differences are consistent with the interpretation that the Erhongwa magma formed by the mixing of a mafic magma derived from a depleted mantle with a granitic melt derived from a juvenile arc crust. It is deduced that sulfide saturation in the Erhongwa magmatic system was related to the magma mixing event at depth. More significant sulfide mineralization may

  12. Important role of magma mixing in generating the Mesozoic monzodioritic-granodioritic intrusions related to Cu mineralization, Tongling, East China: Evidence from petrological and in situ Sr-Hf isotopic data

    NASA Astrophysics Data System (ADS)

    Chen, C. J.; Chen, B.; Li, Z.; Wang, Z. Q.

    2016-04-01

    The Mesozoic ore-bearing high-Mg monzodioritic-granodioritic rocks in the Tongling mining district (East China) have been described as having adakitic affinities, and their origin has been attributed to partial melting of delaminated eclogite at depth in the mantle, followed by interaction of the resultant granitic magma with mantle peridotite. Here we present petrological data and in situ Sr isotopic data for zoned plagioclase that are inconsistent with the eclogite-derived model and instead propose a model that involves magma mixing of siliceous crustal melts and basaltic magma that was derived from metasomatized mantle in a back-arc extensional regime. The principal geochemical signatures of these Mesozoic rocks include a high-K calc-alkaline affinity, high values of Mg#, high Sr-Ba abundances, high Sr/Y and La/Yb ratios, εNd(t) = - 13.1 to - 9.0, and ISr = 0.70707-0.70824. The magma mixing model is supported by (1) the common existence of mafic microgranular enclaves (MMEs) and the disequilibrium textures of plagioclase and amphibole, (2) the 87Sr/86Sr ratios of embayed high-Ca cores of plagioclase that are distinctly lower than in the euhedral low-Ca overgrowth rims, (3) the negative correlations between whole-rock Nd and Sr isotopic ratios, and (4) the significant differences in the values of εHf(t) (- 9.5 to - 26) within different zircons from the same intrusion.

  13. Effect of ultramafic intrusions and associated mineralized rocks on the aqueous geochemistry of the Tangle Lakes Area, Alaska: Chapter C in Studies by the U.S. Geological Survey in Alaska, 2011

    USGS Publications Warehouse

    Wang, Bronwen; Gough, Larry P.; Wanty, Richard B.; Lee, Gregory K.; Vohden, James; O’Neill, J. Michael; Kerin, L. Jack

    2013-01-01

    Stream water was collected at 30 sites within the Tangle Lakes area of the Delta mineral belt in Alaska. Sampling focused on streams near the ultramafic rocks of the Fish Lake intrusive complex south of Eureka Creek and the Tangle Complex area east of Fourteen Mile Lake, as well as on those within the deformed metasedimentary, metavolcanic, and intrusive rocks of the Specimen Creek drainage and drainages east of Eureka Glacier. Major, minor, and trace elements were analyzed in aqueous samples for this reconnaissance aqueous geochemistry effort. The lithologic differences within the study area are reflected in the major-ion chemistry of the water. The dominant major cation in streams draining mafic and ultramafic rocks is Mg2+; abundant Mg and low Ca in these streams reflect the abundance of Mg-rich minerals in these intrusions. Nickel and Cu are detected in 84 percent and 87 percent of the filtered samples, respectively. Nickel and Cu concentrations ranged from Ni <0.4 to 10.1 micrograms per liter (mg/L), with a median of 4.2 mg/L, and Cu <0.5 to 27 mg/L, with a median of 1.2 mg/L. Trace-element concentrations in water are generally low relative to U.S. Environmental Protection Agency freshwater aquatic-life criteria; however, Cu concentrations exceed the hardness-based criteria for both chronic and acute exposure at some sites. The entire rare earth element (REE) suite is found in samples from the Specimen Creek sites MH5, MH4, and MH6 and, with the exception of Tb and Tm, at site MH14. These samples were all collected within drainages containing or downstream from Tertiary gabbro, diabase, and metagabbro (Trgb) exposures. Chondrite and source rock fractionation profiles for the aqueous samples were light rare earth element depleted, with negative Ce and Eu anomalies, indicating fractionation of the REE during weathering. Fractionation patterns indicate that the REE are primarily in the dissolved, as opposed to colloidal, phase.

  14. Petrogenesis of the Kuangshancun and Hongshan intrusive complexes from the Handan-Xingtai district: Implications for iron mineralization associated with Mesozoic magmatism in the North China Craton

    NASA Astrophysics Data System (ADS)

    Sun, Yi; Xiao, Long; Zhan, Qiongyao; Wu, Jianxun; Zhu, Dan; Huang, Wan; Bai, Ming; Zhang, Yanhai

    2015-12-01

    The Handan-Xingtai district in eastern China exposes numerous late Mesozoic intrusions. Among these, the Kuangshancun intrusive complex is one of the major ore-related intrusions whereas the Hongshan complex is barren, although both intrusions display similar geochemical characteristics. The Kuangshancun complex consists of diorite and monzonite, with zircon LA-ICP-MS U-Pb age of 133.7 ± 1 Ma. The Hongshan complex mainly consists of syenite and shows zircon U-Pb age of 134.5 ± 1 Ma. The mineral chemistry of plagioclase from both complexes reveals normal zoning, consistent with the fractional crystallization process. Rocks of the Kuangshancun complex show SiO2 in the range of 58.92-63.84 wt.%, Na2O of 4.63-8.81 wt.%, and Al2O3 of 16.14-18.18 wt.%, together high Sr/Y (14-54) and high LaN/YbN (8.30-16.18) ratios. They show enrichment in LREE and depletion in HREE and HFSE, with no remarkable Eu anomalies, similar to the features of adakites. The whole rock initial 87Sr/86Sr ratios range from 0.706661 to 0.706722 and εNd (t = 134 Ma) between -15.26 and -15.12, which are consistent with zircon 176Hf/177Hf ratios of 0.281940-0.282059 and εHf (t) values of -27.0 to -22.7. Samples of the Hongshan complex show SiO2 in the range of 56.57-68.16 wt.%, high Sr/Y (19-112) and high LaN/YbN (11.39-16.82) ratios. The zircon εHf (t) values are in the range of -15.9 to -12.8 and εNd (t = 134 Ma) is between -9.82 and -8.62. The Kuangshancun complex was derived through partial melting of an enriched lithospheric mantle contaminated by lower continental crust components. The Hongshan complex was also derived from the EM I-like mantle source. However, the calculated zircon Ce4+/Ce3+ and Eu/Eu∗ ratios indicate that the source magma of the Kuangshancun complex were characterized by higher oxygen fugacity as compared to that the Hongshan complex. The high oxidation states and high water contents are considered as possible key factors that led to the iron mineralization in the

  15. Sr-Nd isotope geology and tectonomagmatic setting of the Dehsalm intrusives (Lut Block, Eastern Iran)

    NASA Astrophysics Data System (ADS)

    Arjmandzadeh, Reza; Francisco Santos, Jose; Ribeiro, Sara

    2013-04-01

    The Dehsalm porphyritic shallow intrusives belong to the Lut Block volcanic-plutonic belt (central eastern Iran). Previous research on alteration, mineralization and hydrothermal fluids indicates that a Cu-Mo porphyry type mineralization system is related with these intrusives (Arjmandzadeh et al., 2012). The rocks studied in this work range in composition from gabbro-diorite to granite, with dominance of monzonites and quartz monzonites, and have geochemical features of high-K calc alkaline to shoshonitic volcanic arc suites. The trends of major element oxides on Harker diagrams, together with textural evidence, point to the crystal fractionation of clinopyroxene, Ca - plagioclase, hornblende, apatite and oxide minerals. Primitive mantle - normalized trace element spider diagrams display strong enrichment in LILE, such as Rb, Ba and Cs, and depletions in some high field strength elements (HFSE), such as Nb, Ti, Y and HREE. Chondrite-normalized plots show significant LREE enrichments, high LaN/YbN (21.5 to 31.0) and the lack of Eu anomaly. Sr/Y and La/Yb ratios of Dehsalm intrusives are respectively 31.6-72.2 and 21.5-33.5, which reveals that, despite their K-rich composition, these rocks also have some adakitic affinity. A Rb-Sr whole rock-feldspar-biotite age of 33.4±1 Ma was obtained in a quartz monzonite sample; this date may be interpreted as close to the intrusion age, considering that the chosen sample is almost unaltered and should have suffered fast cooling. The obtained age coincides, within error, with a previous geochronological result in a similar rock from the Chah-Shaljami area (Arjmandzadeh et al., 2011), further northwest along the eastern border of the Lut Block. 87Sr/86Sr(33Ma) and ɛNd(33Ma) values range from 0.70481 to 0.70508 and from +1.5 to +2.5, respectively, which fits into a supra-subduction mantle wedge source for the parental melts and indicates that crustal contribution for magma diversification was not relevant. Sr and Nd isotope

  16. Timing, petrogenesis and tectonic setting of the Late Paleozoic gabbro-granodiorite-granite intrusions in the Shalazhashan of northern Alxa: Constraints on the southernmost boundary of the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Shi, Xingjun; Wang, Tao; Zhang, Lei; Castro, Antonio; Xiao, XuChang; Tong, Ying; Zhang, Jianjun; Guo, Lei; Yang, Qidi

    2014-11-01

    The Late Paleozoic tectonic setting and location of the southernmost boundary of the Central Asian Orogenic Belt (CAOB) with respect to the Alxa Block or Alxa-North China Craton (ANCC) are debated. This paper presents new geochronological, petrological, geochemical and zircon Hf isotopic data of the Late Paleozoic intrusions from the Shalazhashan in northern Alxa and discusses the tectonic setting and boundary between the CAOB and ANCC. Using zircon U-Pb dating, intrusions can be broadly grouped as Late Carboniferous granodiorites (~ 301 Ma), Middle Permian gabbros (~ 264 Ma) and granites (~ 266 Ma) and Late Permian granodiorites, monzogranites and quartz monzodiorites (254-250 Ma). The Late Carboniferous granodiorites are slightly peraluminous and calcic. The remarkably high zircon Hf isotopes (εHf(t) = + 6-+ 10) and characteristics of high silica adakites suggest that these granodiorites were mainly derived from "hot" basaltic slab-melts of the subducted oceanic crust. The Middle Permian gabbros exhibited typical cumulate textures and were derived from the partial melting of depleted mantle. The Middle Permian granites are slightly peraluminous with high-K calc-alkaline and low εHf(t) values from - 0.9 to + 2.9. These granites were most likely derived from juvenile materials mixed with old crustal materials. The Late Permian granodiorites, monzogranites and quartz monzodiorites are characterized as metaluminous to slightly peraluminous, with variable Peacock alkali-lime index values from calc-alkalic to alkali-calcic. These rocks were mainly derived from juvenile crustal materials, as evidenced by their high εHf(t) values (+ 3.3 to + 8.9). The juvenile sources of the above intrusions in the Shalazhashan are similar to those of the granitoids from the CAOB but distinct from the granitoids within the Alxa Block. These findings suggest that the Shalazhashan Zone belongs to the CAOB rather than the Alxa Block and that its boundary with the Alxa block can be

  17. Zircon U-Pb age, Hf isotope and geochemistry of Carboniferous intrusions from the Langshan area, Inner Mongolia: Petrogenesis and tectonic implications

    NASA Astrophysics Data System (ADS)

    Liu, Min; Zhang, Da; Xiong, Guangqiang; Zhao, Hongtao; Di, Yongjun; Wang, Zhong; Zhou, Zhiguang

    2016-04-01

    Late Paleozoic was a critical period for the tectonic evolution of the northern margin of the Alxa-North China craton, but the evolutionary history is not well constrained. The Carboniferous intrusions in the Langshan area in the western part of the northern margin of the Alxa-North China craton are mainly composed of tonalite, quartz diorite, olivine gabbro and pyroxene peridotite. Zircon LA-ICP-MS U-Pb dating indicates that the Langshan Carboniferous intrusions were emplaced at ca. 338-324 Ma. The quartz diorites are characterized by high amounts of compatible trace elements (Cr, Ni and V) and high Mg# values, which may suggest a significant mantle source. The positive Pb and negative Nb-Ta-Ti anomalies, the variable εHf(t) (-6.9 to 2.0) values and the old Hf model ages (1218-1783 Ma) imply some involvement of ancient continental materials in its petrogenesis. The tonalite has relatively high Sr/Y ratios, low Mg#, Yb and Y contents, features of adakite-like rocks, negative εHf(t) values (-9.8 to -0.1) and older Hf model ages (1344-1953 Ma), which suggest significant involvement of ancient crust materials and mantle-derived basaltic component in its petrogenesis. The high Mg# values, high Cr and Ni contents, and low Zr and Hf contents of the mafic-ultramafic rocks show evidence of a mantle source, and the relatively low zircon εHf(t) values (-5.9 to 3.2) might point to an enriched mantle. The trace element characteristics indicate the influence of subducted sediments and slab-derived fluids. In the tectonic discrimination diagrams, all the rocks plot in subduction-related environment, such as volcanic arc and continental arc. Considering the regional geology, we suggest that the Carboniferous intrusions in the Langshan area were likely emplaced during the late stage of the southward subduction of the Paleo-Asian Ocean plate, which formed a continental arc along the northern margin of the Alxa-North China craton.

  18. A Review on Forearc Ophiolite Obduction, Adakite-Like Generation, and Slab Window Development at the Chile Triple Junction Area: Uniformitarian Framework for Spreading-Ridge Subduction

    NASA Astrophysics Data System (ADS)

    Bourgois, Jacques; Lagabrielle, Yves; Martin, Hervé; Dyment, Jérôme; Frutos, Jose; Cisternas, Maria Eugenia

    2016-10-01

    This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45°-48°S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics associated with a comprehensive review of geologic, geochemical, and geophysical data provide new constraints on the geodynamics of this puzzling area. We discuss: (1) the emplacement mode for the Pleistocene Taitao Ridge and the Pliocene Taitao Peninsula ophiolite bodies. (2) The occurrence of these ophiolitic complexes in association with five adakite-like plutonic and volcanic centers of similar ages at the same restricted locations. (3) The inferences from the co-occurrence of these sub-coeval rocks originating from the same subducting oceanic lithosphere evolving through drastically different temperature-pressure ( P- T) path: low-grade greenschist facies overprint and amphibolite-eclogite transition, respectively. (4) The evidences that document ridge-jump events and associated microplate individualization during subduction of the SCR1 and SCR-1 segments: the Chonos and Cabo Elena microplates, respectively. The ridge-jump process associated with the occurrence of several closely spaced transform faults entering subduction is controlling slab fragmentation, ophiolite emplacement, and adakite-like production and location in the CTJ area. Kinematic inconsistencies in the development of the Patagonia slab window document an 11- km westward jump for the SCR-1 spreading segment at ~6.5-to-6.8 Ma. The SCR-1 spreading center is relocated beneath the North Patagonia Icefield (NPI). We argue that the deep-seated difference in the dynamically sustained origin of the high reliefs of the North and South Patagonia Icefield (NPI and SPI) is asthenospheric convection and slab melting, respectively. The Chile Triple Junction area provides the basic constraints to define the basic signatures for spreading-ridge subduction beneath an Andean

  19. A Review on Forearc Ophiolite Obduction, Adakite-Like Generation, and Slab Window Development at the Chile Triple Junction Area: Uniformitarian Framework for Spreading-Ridge Subduction

    NASA Astrophysics Data System (ADS)

    Bourgois, Jacques; Lagabrielle, Yves; Martin, Hervé; Dyment, Jérôme; Frutos, Jose; Cisternas, Maria Eugenia

    2016-05-01

    This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45°-48°S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics associated with a comprehensive review of geologic, geochemical, and geophysical data provide new constraints on the geodynamics of this puzzling area. We discuss: (1) the emplacement mode for the Pleistocene Taitao Ridge and the Pliocene Taitao Peninsula ophiolite bodies. (2) The occurrence of these ophiolitic complexes in association with five adakite-like plutonic and volcanic centers of similar ages at the same restricted locations. (3) The inferences from the co-occurrence of these sub-coeval rocks originating from the same subducting oceanic lithosphere evolving through drastically different temperature-pressure (P-T) path: low-grade greenschist facies overprint and amphibolite-eclogite transition, respectively. (4) The evidences that document ridge-jump events and associated microplate individualization during subduction of the SCR1 and SCR-1 segments: the Chonos and Cabo Elena microplates, respectively. The ridge-jump process associated with the occurrence of several closely spaced transform faults entering subduction is controlling slab fragmentation, ophiolite emplacement, and adakite-like production and location in the CTJ area. Kinematic inconsistencies in the development of the Patagonia slab window document an 11- km westward jump for the SCR-1 spreading segment at ~6.5-to-6.8 Ma. The SCR-1 spreading center is relocated beneath the North Patagonia Icefield (NPI). We argue that the deep-seated difference in the dynamically sustained origin of the high reliefs of the North and South Patagonia Icefield (NPI and SPI) is asthenospheric convection and slab melting, respectively. The Chile Triple Junction area provides the basic constraints to define the basic signatures for spreading-ridge subduction beneath an Andean

  20. Geochemical characteristics of the Shujiadian Cu deposit related intrusion in Tongling: Petrogenesis and implications for the formation of porphyry Cu systems in the Middle-Lower Yangtze River Valley metallogenic belt, eastern China

    NASA Astrophysics Data System (ADS)

    Wang, Shiwei; Zhou, Taofa; Yuan, Feng; Fan, Yu; Cooke, David R.; Zhang, Lejun; Fu, Bin; White, Noel C.

    2016-05-01

    Porphyry Cu deposits can form in intracontinental or post-collision settings; however, both the genesis of fertile magmas and the mechanism of metal enrichment remain controversial. The Shujiadian porphyry Cu deposit is located in the Tongling area of the Middle-Lower Yangtze River Valley metallogenic belt. It is hosted by the Shujiadian complex, which mainly consists of quartz diorite porphyry (143.7 ± 1.7 Ma) and pyroxene diorite (139.8 ± 1.6 Ma). They both belong to the calc-alkaline series, with enrichment in large-ion lithophile elements (LILE) and light rare earth elements (LREE), depletion in high field-strength elements (HFSE) and heavy rare earth elements (HREE), and slightly negative Eu anomalies. Both quartz diorite porphyry and pyroxene diorite have geochemical affinities with adakite, and their low MgO (1.5-3.7 wt%), and Ni (3.7-6.9 ppm), Cr (2.0-44 ppm), and Th/Ce contents (0.06-0.11) indicate that the intrusive rocks have some characteristics of adakite-like rocks derived from thickened lower crust and melts from metabasaltic rocks and eclogites. Plagioclases from the quartz diorite porphyry are andesine (An value = 31.8-40.5) and from the pyroxene diorite are felsic albite and oligoclase with large-scale zones and variable An value (An value = 8.9-18.3), Fe and Sr contents, which indicate that mixing of mafic and felsic magma may have occurred in the shallow magma chamber. Compared to the barren quartz diorite porphyry, relatively lower SiO2 contents (49.5-55.2 wt.%), higher εNd(t) values (- 7.4 to - 6.9), εHf(t) values (- 11.0 to - 9.1) compositions, Ti-in-zircon temperatures (714-785 °C), and variations of HREE contents of the mineralization-related pyroxene diorite suggest mixing with high-temperature mafic magma. Calculated Ce4 +/Ce3 + values of pyroxene diorite plot between the Ni-NiO buffer (NNO) and magnetite-hematite buffer (MH), and barren quartz diorite porphyry samples plot below the Ni-NiO buffer (NNO). Geochemical features of

  1. Adakites, a key to understanding lile depletion in the lower continental crust

    NASA Astrophysics Data System (ADS)

    Rollinson, H.; Tarney, J.

    2003-04-01

    There are now powerful arguments, which indicate that LILE depletion of felsic lower crust during granulite facies metamorphism can no longer be sustained as a mechanism of intra-crustal element fractionation. Instead we propose that LILE depletion of the lower continental crust relates to the process of crust formation. We have taken as our starting position two observations (a) evidence from experimental studies, that through much of the early part of earth history new crust was formed through the partial melting of a basaltic source. In this we include the felsic granulites of the lower continental crust the majority of which are TTG in composition; (b) the suite of elements which is depleted in the lower continental crust overlaps with the suite of elements enriched in island arc magmas, and is thought to have been removed from a subducting slab by dehydration. We argue that the observed element depletion in felsic lower crustal granulites relates to the depletion of the source from which the parent TTG melts were derived. We propose an incremental melting model for a subducting slab in which there is a progression from dehydration to partial melting and adakite-TTG production. Experimental studies show that slab dehydration will produce a residue which is depleted in Rb, which on melting will yield a Rb-depleted adakitic/TTG melt. Different slabs with contrasting thermal histories will experience different dehydration-melting histories. In this way, we seek to explain contrasting K-Rb and U-Th fractionation in slab melts through a combination of dehydration and melting equilibria. Adakites show very variable K/Rb ratios, similar to that found in felsic granulites, although Th-U concentrations are less extreme. Adakites from the Austral volcanic zone (Stern and Killian, CMP, 1996; Sigmarsson et al. Nature 1998) are have high K/Rb ratios comparable to felsic granulites and are depleted in U, a process which can be related to (a) the large slab melt component in

  2. Petrogenesis of Early-Middle Jurassic intrusive rocks in northern Liaoning and central Jilin provinces, northeast China: Implications for the extent of spatial-temporal overprinting of the Mongol-Okhotsk and Paleo-Pacific tectonic regimes

    NASA Astrophysics Data System (ADS)

    Zhang, Hai-Hong; Wang, Feng; Xu, Wen-Liang; Cao, Hua-Hua; Pei, Fu-Ping

    2016-07-01

    The Mesozoic tectonic evolution of NE China was controlled mainly by the Mongol-Okhotsk and Paleo-Pacific tectonic regimes. However, the extent of the spatial and temporal overprinting of these two regimes is poorly understood. Here, we report new zircon LA-ICP-MS U-Pb dating and geochemical analyses of Jurassic intrusive rocks in northern Liaoning and central Jilin provinces, northeast China, to discuss their petrogenesis and outline the extent of spatial and temporal overprinting of these two tectonic regimes. Dating results indicate that Jurassic magmatism occurred in two stages during the Early (ca. 175 Ma) and Middle Jurassic (170-163 Ma). These rocks represent two-stage typical bimodal igneous rock associations composed mainly of olivine gabbro, gabbro, and gneissic granitoids. The Early and Middle Jurassic gabbros have low rare earth element (REE) abundances, positive Eu anomalies, depletion in high field strength elements (HFSEs), and positive εHf(t) values (+ 4.0 to + 10.3, except for one value of - 17.8), suggesting that the primary magma was derived from partial melting of depleted lithospheric mantle metasomatized by subducted-slab-derived fluids. The Early Jurassic monzogranite exhibit high REE abundances (195-201 ppm), weak negative Eu anomalies (δEu = 0.63-0.64), and negative εHf(t) values (- 11.9 to - 8.2), suggesting a primary magma that was derived from partial melting of lower continental crust of the NCC. The Middle Jurassic granodiorites are enriched in light REEs (LREEs) and large ion lithophile elements (LILEs), and are depleted in heavy REEs (HREEs) and HFSEs, as well as high Sr/Y (29-132) and (La/Yb)N (15-44) ratios. In addition, the Middle Jurassic granitoids near or within the NCC exhibit negative εHf(t) values (- 18.9 to + 0.2), whereas those within the Xing'an-Mongolia Orogenic Belt (XMOB) have generally positive εHf(t) values (- 0.6 to + 6.4), suggesting their origin from partial melting of thickened ancient NCC and newly accreted

  3. Hydrothermal alteration and Cu–Ni–PGE mobilization in the charnockitic rocks of the footwall of the South Kawishiwi intrusion, Duluth Complex, USA

    PubMed Central

    Benkó, Zsolt; Mogessie, Aberra; Molnár, Ferenc; Krenn, Kurt; Poulson, Simon R.; Hauck, Steven; Severson, Mark; Arehart, Greg B.

    2015-01-01

    In the Neoarchean (~ 2.7 Ga) contact metamorphosed charnockitic footwall of the Mesoproterosoic (1.1 Ga) South Kawishiwi intrusion of the Duluth Complex, the primary metamorphic mineral assemblage and Cu–Ni–PGE sulfide mineralization is overprinted by an actinolite + chlorite + cummingtonite + prehnite + pumpellyite + quartz + calcite hydrothermal mineral assemblage along 2–3 cm thick veins. In calcite, hosted by the hydrothermal alteration zones and in a single recrystallized quartz porphyroblast, four different fluid inclusion assemblages are documented; the composition of these fluid inclusions provide p–T conditions of the fluid flow, and helps to define the origin of the fluids and evaluate their role in the remobilization and reprecipitation of the primary metamorphic sulfide assemblage. Pure CO2 fluid inclusions were found as early inclusions in recrystallized quartz porphyroblast. These inclusions may have been trapped during the recrystallization of the quartz during the contact metamorphism of the footwall charnockite in the footwall of the SKI. The estimated trapping pressure (1.6–2.0 kbar) and temperature (810–920 °C) conditions correspond to estimates based on felsic veins in the basal zones of the South Kawishiwi intrusion. Fluid inclusion assemblages with CO2–H2O–NaCl and CH4–N2–H2O–NaCl compositions found in this study along healed microfractures in the recrystallized quartz porphyroblast establish the heterogeneous state of the fluids during entrapment. The estimated trapping pressure and temperature conditions (240–650 bar and 120–150 °C for CO2–H2O–NaCl inclusions and 315–360 bar and 145–165 °C for CH4–N2–H2O–NaCl inclusions) are significantly lower than the p–T conditions (> 700 °C and 1.6–2 kbar) during the contact metamorphism, indicating that this fluid flow might not be related to the cooling of the Duluth Complex and its contact aureole. The presence of chalcopyrite

  4. Sr-Nd-Hf isotopes of the intrusive rocks in the Cretaceous Xigaze ophiolite, southern Tibet: Constraints on its formation setting

    NASA Astrophysics Data System (ADS)

    Zhang, Liang-Liang; Liu, Chuan-Zhou; Wu, Fu-Yuan; Zhang, Chang; Ji, Wei-Qiang; Wang, Jian-Gang

    2016-08-01

    The Cretaceous Xigaze ophiolite is best exposed at the central part of the Yarlung-Zangbo Suture Zone, Tibet Plateau. It consists of a thick section of mantle peridotites, but a relatively thin mafic sequence. This study presents geochronological and geochemical data for intrusive dykes (both mafic and felsic) and basalts to revisit the formation setting of the Xigaze ophiolite. The rodingites are characterized by high CaO and low Na2O contents relative to mafic dykes and show big variations in trace element compositions. Both gabbros and diabases have similar geochemical compositions, with MgO contents of 6.42-11.48 wt% and Mg# of 0.56-0.71. They display REE patterns similar to N-MORB and are variably enriched in large ion lithophile elements. Basalts have fractionated compositions and display LREE-depleted patterns very similar to N-MORB. They do not show obvious enrichment in LILE and depletion in high-field-strength elements, but a negative Nb anomaly is present. The studied plagiogranites have compositions of trondhjemite to tonalite, with high Na2O and low K2O contents. They have low TiO2 contents less than 1 wt%, consistent with melts formed by anatexis of gabbros rather than by differentiation of basalts. Zircons from seven samples, including three rodingites, three plagiogranites, and one gabbro, have been dated and yielded U-Pb ages of 124.6 ~ 130.5 Ma, indicating the Xigaze ophiolite was formed during the Early Cretaceous. They have mantle-like δ18O values of + 4.92 ~ + 5.26‰ and very positive εHf(t) values of + 16 ~ + 13.3. Ages of the rodingites and less altered gabbros indicate that serpentinization was occurred at ~ 125 Ma. Occurrence of both gabbroic and diabase dykes within the serpentinites suggests that the mantle lithosphere of the Xigaze ophiolite was rapidly exhumed. Both mafic and felsic dykes have slightly more radiogenic 87Sr/86Sr ratios relative to MORB, but depleted Hf-Nd isotpe compositions. They have a limited range of ε

  5. 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

  6. Paleoposition of the northern margin of Armorica in Late Devonian times: Paleomagnetic and rock magnetic results from the Frankenstein Intrusive Complex (Mid-German Crystalline Rise)

    NASA Astrophysics Data System (ADS)

    Zwing, Alexander; Bachtadse, Valerian

    2000-09-01

    A detailed rockmagnetic and paleomagnetic study of the Frankenstein Intrusive Complex (FIC, 363±7 Ma in age), southwestern Germany, has been carried out in order to test whether the paleomagnetic declinations within the internal parts of the European Variscides follow a common trend controlled by the structural grain of the orogen or whether the distribution of declinations follows a random pattern. In addition, new paleomagnetic data will contribute to further refine the drift history of the Armorican Terrane Assemblage during late Paleozoic times. The unmetamorphosed Frankenstein Igneous Complex forms part of the Mid-German Crystalline Rise within the Armorican Terrane Assemblage, amalgamated to Avalonia and Baltica during the Variscan orogeny, Stepwise thermal and alternating field (AF) demagnetization experiments identify four components (A, B, Cn, and Cr) of magnetization. Component A is a recent viscous overprint that parallels the present-day geomagnetic field. The high unblocking temperatures of A in some samples can be explained by the presence of multidomain magnetite. Component B is carried by hematite and is considered to be a late Carboniferous remagnetization. Components Cr and Cn, found in 110 samples from 20 sites, are antiparallel and pass a class C reversal test. Their primary origin is further supported by a contact test. Cr and Cn have maximum unblocking temperatures of up to 580°C and occasionally above over 600°C, indicating magnetite and hematite to carry the characteristic remanent magnetization. Ore microscopy revealed that primary hematite lamellae in ilmenite carry Cr and Cn and that a secondary generation of hematite is the carrier of B. The overall site mean direction of Cr and Cn (20 sites) based on endpoints and remagnetization circle analysis of 198°/40° (declination/inclination) with a 95% confidence limit (α95) of 4.9° and a precision parameter (k) of 45.0 defines a paleopole at 15°S, 9°W. When comparing to the apparent

  7. Adakitic volcanism in the eastern Aleutian arc: Petrology and geochemistry of Hayes volcano, Cook Inlet, Alaska

    NASA Astrophysics Data System (ADS)

    McHugh, K.; Hart, W. K.; Coombs, M. L.

    2012-12-01

    Located in south-central Alaska, 135 km northwest of Anchorage, Hayes volcano is responsible for the most widespread tephra fall deposit in the regional Holocene record (~3,500 BP). Hayes is bounded to the west by the Cook Inlet volcanoes (CIV; Mt. Spurr, Redoubt, Iliamna, and Augustine) and separated from the nearest volcanism to the east, Mount Drum of the Wrangell Volcanic Field (WVF), by a 400 km-wide volcanic gap. We report initial results of the first systematic geochemical and petrologic study of Hayes volcano. Hayes eruptive products are calc-alkaline dacites and rhyolites that have anomalous characteristics within the region. Major and trace element analyses reveal that the Hayes rhyolites are more silicic (~74 wt. % SiO2) than compositions observed in other CIV, and its dacitic products possess the distinctive geochemical signatures of adakitic magmas. Key aspects of the Hayes dacite geochemistry include: 16.03 - 17.54 wt. % Al2O3, 0.97 - 2.25 wt. % MgO, Sr/Y = 60 - 78, Yb = 0.9 - 1.2 ppm, Ba/La = 31 - 79. Such signatures are consistent with melting of a metamorphosed basaltic source that leaves behind a residue of garnet ± amphibole ± pyroxene via processes such as melting of a subducting oceanic slab or underplated mafic lower crust, rather than flux melting of the mantle wedge by dehydration of the down-going slab. Additionally, Hayes tephras display a distinctive mineralogy of biotite with amphibole in greater abundance than pyroxene, a characteristic not observed at other CIV. Furthermore, Hayes rhyolites and dacites exhibit little isotopic heterogeneity (87Sr/86Sr = 0.70384 - 0.70395, 206Pb/204Pb = 18.866 - 18.889) suggesting these lavas originate from the same source. Hayes volcano is approximately situated above the western margin of the subducting Yakutat terrane and where the dip of the Pacific slab beneath Cook Inlet shallows northward. Due to its position along the margin of the subducting Yakutat terrane, it is plausible that Hayes magmas

  8. Trace element behavior and P-T-t evolution during partial melting of exhumed eclogite in the North Qaidam UHPM belt (NW China): Implications for adakite genesis

    NASA Astrophysics Data System (ADS)

    Zhang, Guibin; Niu, Yaoling; Song, Shuguang; Zhang, Lifei; Tian, Zuolin; Christy, Andrew G.; Han, Lei

    2015-06-01

    We have studied trace element behavior and timing of decompression melting of UHP rocks during exhumation recorded in the magmatic products, i.e., the melt phase (leucosomes), cumulate (garnetite) and residue (amphibolitized eclogite) from a single outcrop in the south Dulan area, North Qaidam UHPM belt, NW China. Two distinct episodes of partial melting are recognized. First, Grt-free tonalitic-trondhjemitic leucosome melts with higher silica crystallized at 424.0 ± 2.7 Ma. Garnets grew in the leucosome melt but fractionated out to form garnetite cumulates along with Ti-rich phases (rutile and titanite), strengthening the adakitic signature of the leucosome. Later Grt-bearing leucosome melts with an age of 412.4 ± 2.9 Ma cross-cut boudins and layers of amphibolitized eclogite. Geochemical investigation of bulk-rocks and in situ minerals verifies the genetic relationship between the amphibolitized eclogite and the tonalitic-trondhjemitic melts. Zircons from the amphibolitized eclogite have older (> 700 Ma) protolith ages, with subsequent eclogite-facies metamorphism, retrograde granulite-facies overprinting and partial melting. Phase modeling and Zr-in-rutile thermometry calculations in combination with zircon geochronology reveal the evolution P-T-t path for the exhumation and the partial melting of the deeply subducted continental crust at the North Qaidam subduction zone in the Early Paleozoic.

  9. SHRIMP U-Pb dating and geochemistry of the Cretaceous plutonic rocks in the Korean Peninsula: A new tectonic model of the Cretaceous Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Kim, Sung Won; Kwon, Sanghoon; Park, Seung-Ik; Lee, Changyeol; Cho, Deung-Lyong; Lee, Hong-Jin; Ko, Kyoungtae; Kim, Sook Ju

    2016-10-01

    The Cretaceous tectonomagmatism of the Korean Peninsula was examined based on geochemical and geochronological data of the Cretaceous plutonic rocks, along with distribution of volcano-sedimentary nonmarine N- to NE-trending fault bounded sedimentary basins. We conducted sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb ages and whole-rock geochemical compositions of 21 Cretaceous plutonic rocks, together with previously published data, from the central to southern Korean Peninsula. Four age groups of plutonic rocks were identified: Group I (ca. 119-106 Ma) in the northern to central area, Group II (ca. 99-87 Ma) in the central southern area, Group III (ca. 85-82 Ma) in the central to southern area, and Group IV (ca. 76-67 Ma) in the southernmost area. These results indicate a sporadic trenchward-younging trend of the Cretaceous magmatism in the Korean Peninsula. The Group I, II, and III rocks are dominated by high-K calc-alkaline I-type rocks with rift-related A-type granitoids. In contrast, the Group IV rocks are high-K calc-alkaline I-type plutonic rocks with no A-type rocks. The geochemical signatures of the entire groups indicated LREEs (light rare earth elements) enrichments and negative Nb, Ta, and Ti anomalies, indicating normal arc magmatism. A new tectonic model of the Cretaceous Korean Peninsula was proposed based on temporal and spatial distribution of the Cretaceous plutons represented by four age groups; 1) magmatic quiescence throughout the Korean Peninsula from ca. 160 to 120 Ma, 2) intrusions of the I- and A-type granitoids in the northern and central Korean Peninsula (Group I plutonic rocks from ca. 120 to 100 Ma) resulted from the partial melting of the lower continental crust due to the rollback of the Izanagi plate expressed as the conversion from flat-lying subduction to normal subduction. The Gyeongsang nonmarine sedimentary rift basin in the Korean Peninsula and adakite magmatism preserved in the present-day Japanese Islands

  10. Petrogenesis and geodynamic setting of Early Cretaceous mafic-ultramafic intrusions, South China: A case study from the Gan-Hang tectonic belt

    NASA Astrophysics Data System (ADS)

    Qi, Youqiang; Hu, Ruizhong; Liu, Shen; Coulson, Ian M.; Qi, Huawen; Tian, Jianji; Zhu, Jingjing

    2016-08-01

    A study using whole-rock major-trace elements and Sr-Nd isotopes as well as zircon U-Pb dating has been carried out on Early Cretaceous mafic-ultramafic intrusions from the Gan-Hang tectonic belt (GHTB), South China, to understand the origin of mantle sources and the sequential evolution of the underlying Late Mesozoic lithospheric mantle of this area. The study focused on two intrusions, one at Quzhou and the other at Longyou (see Fig. 1). They are primarily composed of mafic-ultramafic rocks with wide range of chemical compositions. The Quzhou mafic rocks have relatively narrow ranges of SiO2 (48.94-51.79 wt%), MgO (6.07-7.21 wt%), Fe2O3 (10.48-11.56 wt%), CaO (8.20-8.81 wt%), and Mg# (51.7-56.5) with relatively low K2O (0.56-0.67 wt%) and Na2O (3.09-3.42 wt%). By contrast, the ultramafic rocks from Longyou have distinct lower SiO2 (41.50-45.11 wt%) and higher MgO (9.05-9.90 wt%), Fe2O3 (12.14-12.62 wt%), CaO (8.64-10.67 wt%), and Mg# (59.5-61.1) with relatively higher K2O (1.32-1.75 wt%) and Na2O (4.53-5.08 wt%). They are characterized by Ocean Island Basalts (OIB)-type trace element distribution patterns, with a significant enrichment of light rare earth elements (LREE), large ion lithophile elements (LILE, i.e., Rb, Ba, K, and Sr) and high field strength elements (HFSE, i.e., Nb, Ta), and slight depletion of Th, U, Ti, and Y. The intrusions exhibit relatively depleted Sr-Nd isotope compositions, with (87Sr/86Sr)i range of 0.7035 to 0.7055 (143Nd/144Nd)i of 0.51264 to 0.51281 and εNd(t) values of + 3.0 to + 6.6. Zircon U-Pb dating of Longyou and Quzhou intrusions yields consistent magma emplacement ages of 129.0 ± 3.9 to 126.2 ± 2.4 Ma, respectively. The dating results are consistent with the peak of extension in Early Cretacerous throughout the Gan-Hang tectonic belt. Their magmas were principally derived from near-solidus partial melting of pyroxenites with different content of silica, and the pyroxenites were resulted from a juvenile SCLM peridotite

  11. Short-term and localized plume-slab interaction explains the genesis of Abukuma adakite in Northeastern Japan

    NASA Astrophysics Data System (ADS)

    Lee, Changyeol; Lim, Chungwan

    2014-06-01

    The pulse-like adakite eruption in Mt. Abukuma, northeastern Japan at ∼16 Ma has been considered peculiar because the subducting Pacific slab was too old to have been melted. Recent studies suggested that the injection of hot asthenospheric mantle as a temporal temperature anomaly into the corner of the mantle wedge was responsible for partial melting of the subducting slab, producing adakitic magma. However, the pulse-like and localized eruption of the Abukuma adakite poses a problem to the above model because rollback of the Pacific plate for ∼10 Myr should have resulted in injection of the hot asthenospheric mantle into the corner of the mantle wedge along northeastern Japan, Sikhote-Alin, and Sakhalin. In addition, no quantitative examination of the interaction between the hot asthenospheric mantle and cold subducting Pacific plate has been performed. In this study, we used a series of two-dimensional kinematic-dynamic numerical subduction models to evaluate slab melting by the injection of a short-term temperature anomaly into the mantle wedge. Our model calculations show that injection of the short-term temperature anomaly into the corner of the mantle wedge resulted in slab melting at ∼17 Ma, but that the duration of injection should be <5 Myr to comply with the pulse-like eruption of the Abukuma adakite at ∼16 Ma. The localization of the Abukuma adakite, which excludes other areas of northeastern Japan, as well as Sikhote-Alin and Sakhalin, implies that the short-term temperature anomaly existed as a blob, which may have resulted from the penetration of the mantle plume through a neck in the subducting Pacific plate. The rising hot blob of the mantle plume from the slab neck was entrained to the corner flow of the mantle wedge and arrived at the slab surface at ∼17 Ma. The pulse-like and localized Abukuma adakite was thus the consequence of short-term and localized plume-slab interaction in the Abukuma region.

  12. Interior intrusion detection systems

    SciTech Connect

    Rodriguez, J.R.; Matter, J.C. ); Dry, B. )

    1991-10-01

    The purpose of this NUREG is to present technical information that should be useful to NRC licensees in designing interior intrusion detection systems. Interior intrusion sensors are discussed according to their primary application: boundary-penetration detection, volumetric detection, and point protection. Information necessary for implementation of an effective interior intrusion detection system is presented, including principles of operation, performance characteristics and guidelines for design, procurement, installation, testing, and maintenance. A glossary of sensor data terms is included. 36 figs., 6 tabs.

  13. Brine and Gas Flow Patterns Between Excavated Areas and Disturbed Rock Zone in the 1996 Performance Assessment for the Waste Isolation Pilot Plant for a Single Drilling Intrusion that Penetrates Repository and Castile Brine Reservoir

    SciTech Connect

    ECONOMY,KATHLEEN M.; HELTON,JON CRAIG; VAUGHN,PALMER

    1999-10-01

    The Waste Isolation Pilot Plant (WIPP), which is located in southeastern New Mexico, is being developed for the geologic disposal of transuranic (TRU) waste by the U.S. Department of Energy (DOE). Waste disposal will take place in panels excavated in a bedded salt formation approximately 2000 ft (610 m) below the land surface. The BRAGFLO computer program which solves a system of nonlinear partial differential equations for two-phase flow, was used to investigate brine and gas flow patterns in the vicinity of the repository for the 1996 WIPP performance assessment (PA). The present study examines the implications of modeling assumptions used in conjunction with BRAGFLO in the 1996 WIPP PA that affect brine and gas flow patterns involving two waste regions in the repository (i.e., a single waste panel and the remaining nine waste panels), a disturbed rock zone (DRZ) that lies just above and below these two regions, and a borehole that penetrates the single waste panel and a brine pocket below this panel. The two waste regions are separated by a panel closure. The following insights were obtained from this study. First, the impediment to flow between the two waste regions provided by the panel closure model is reduced due to the permeable and areally extensive nature of the DRZ adopted in the 1996 WIPP PA, which results in the DRZ becoming an effective pathway for gas and brine movement around the panel closures and thus between the two waste regions. Brine and gas flow between the two waste regions via the DRZ causes pressures between the two to equilibrate rapidly, with the result that processes in the intruded waste panel are not isolated from the rest of the repository. Second, the connection between intruded and unintruded waste panels provided by the DRZ increases the time required for repository pressures to equilibrate with the overlying and/or underlying units subsequent to a drilling intrusion. Third, the large and areally extensive DRZ void volumes is a

  14. Petrography and petrology of Smoky Butte intrusives, Garfield County, Montana

    USGS Publications Warehouse

    Matson, Robert E.

    1960-01-01

    The Smoky Butte intrusives are located in T. 18 N., R. 36 E. Garfield County, Montana on the extreme eastern edge of the petrographic province of Central Montana. They consist of dikes and plugs arranged in linear, en-echelon pattern with a northeast trend and intrude the Tullock member (Paleocene age) of the Fort Union formation. Extrusive rocks are absent. The rocks are potassium-rich volcanic types showing a disequilibrium mineral assemblage consisting of sanidine, leucite, biotite, olivine, pyroxene, magnetite plus. ilmenite, apatite, calcite, quartz, and a yellowish to dark greenish glassy groundmass. Two chemical analyses of Smoky Butte rocks show high magnesium, potassium, titanium, and phosphorous and low aluminum and sodium content. The two norm calculations show that the rocks are oversaturated with 1.3 and 3.1 per-cent excess silica. Because of the peculiar nature of the Smoky Butte rocks, descriptive names have been applied to them. They are divided into six different types. Three periods of intrusion are proposed for Smoky Butte quarry where three rock types crop out. Other evidence for multiple injection occurs in several multiple dikes. The upper contact of the intrusion is visible on a few plugs and dikes. Smoky Butte rocks show some similarities to the undersaturated potassium-rich rocks of the Highwood and Bearpaw Mountains of Montana, the rocks of the Leucite Hills of Wyoming, and the oversaturated rocks of the West Kimberly District of Australia.

  15. Igneous intrusions in coal-bearing sequences

    SciTech Connect

    Gurevich, A.B.; Shishlov, S.B.

    1987-08-01

    Intrusions of various compositions, sizes, and shapes have been observed in 115 out of 620 coal basins or deposits on all the continents. They are mainly subvolcanic and hypabyssal, with depths of emplacement estimated as ranging from a few hundred meters to 6 km, but usually 3-4 km. Compositionally, 42% are basic, 31% intermediate, 23% acid, and 4% ultrabasic. Mafic (and related) rock types include dolerites, trachydolerites, gabbro-dolerites, gabbro-monzonites, monzonites, diabases, gabbrodiabases, and less often gabbros and basalts (subvolcanic bodies). These mafic intrusions occur in coal formations of various ages from Carboniferous through Neogene, but predominate in Paleozoic (47%) and Cenozoic beds (45%). They also occur in coal formations of all genetic types, apart from those on ancient stable platforms, where there are no signs of intrusive activity. The mafic intrusions are almost everywhere associated with comagmatic lavas and tuffs (mainly in the younger strata), and the coal beds themselves are to some extent enriched in pyroclastic material, particularly in the upper horizons. This paper gives a worldwide review of igneous intrusions in coal beds. 24 references.

  16. Important role of magma mixing in generating the Mesozoic monzodioritic-granodioritic intrusions related to Cu mineralization, Tongling, East China: evidence from petrological and in situ Sr-Hf isotopic data

    NASA Astrophysics Data System (ADS)

    Chen, Bin; Chen, ChangJian

    2016-04-01

    The Mesozoic ore-bearing high-Mg monzodioritic-granodioritic rocks in the Tongling mining district (East China) have been described as having adakitic affinities, and their origin has been attributed to partial melting of delaminated eclogite at depth in the mantle, followed by interaction of the resultant granitic magma with mantle peridotite. Here we present petrological data and in situ Sr isotopic data for zoned plagioclase that are inconsistent with the eclogite-derived model, and instead propose a model that involves magma mixing of siliceous crustal melts and basaltic magma that was derived from metasomatized mantle by subduction zone fluids in an extensional regime. The principal geochemical signatures of these Mesozoic rocks include a hydrous and high-K calc-alkaline affinity, high values of Mg#, high Sr abundances, high Sr/Y and La/Yb ratios, ɛNd(t)=-13.1 to -9.0, and ISr=0.70707-0.70824. The magma mixing model is supported by (1) the common existence of mafic microgranular enclaves (MMEs) and the disequilibrium textures of plagioclase and hornblende, (2) the increase in Ti and Al(IV) from hornblende cores to rims, and the overgrowths of high-Ca pyroxene around hornblende grains as well, indicative of episode of heating and rejuvenation of the magma chamber as a result of recharge of mafic magma, (3) the 87Sr/86Sr ratios of embayed high-Ca cores of plagioclase that are distinctly lower than in the euhedral low-Ca overgrowth rims, (4) negative correlations between whole-rock Nd and Sr isotopic ratios, and (5) the significant differences in the values of ɛHf(t) (-9.5 to -26) within different zircons from the same intrusion. We propose that underplating of hydrous basaltic magma from the metasomatized lithospheric mantle in the lower crust resulted in partial melting of the lower crustal rocks (Precambrian TTG gneisses and amphibolite/granulite) under water-saturated conditions, during which plagioclase decomposed, leaving hornblende-rich restites and

  17. Bro Intrusion Detection System

    SciTech Connect

    Paxson, Vern; Campbell, Scott; leres, Craig; Lee, Jason

    2006-01-25

    Bro is a Unix-based Network Intrusion Detection System (IDS). Bro monitors network traffic and detects intrusion attempts based on the traffic characteristics and content. Bro detects intrusions by comparing network traffic against rules describing events that are deemed troublesome. These rules might describe activities (e.g., certain hosts connecting to certain services), what activities are worth alerting (e.g., attempts to a given number of different hosts constitutes a "scan"), or signatures describing known attacks or access to known vulnerabilities. If Bro detects something of interest, it can be instructed to either issue a log entry or initiate the execution of an operating system command. Bro targets high-speed (Gbps), high-volume intrusion detection. By judiciously leveraging packet filtering techniques, Bro is able to achieve the performance necessary to do so while running on commercially available PC hardware, and thus can serve as a cost effective means of monitoring a site’s Internet connection.

  18. Computer Intrusions and Attacks.

    ERIC Educational Resources Information Center

    Falk, Howard

    1999-01-01

    Examines some frequently encountered unsolicited computer intrusions, including computer viruses, worms, Java applications, trojan horses or vandals, e-mail spamming, hoaxes, and cookies. Also discusses virus-protection software, both for networks and for individual users. (LRW)

  19. Water-saturated magmas in the Panama Canal region: a precursor to adakite-like magma generation?

    NASA Astrophysics Data System (ADS)

    Rooney, Tyrone O.; Franceschi, Pastora; Hall, Chris M.

    2011-03-01

    Amphibole, while uncommon as a phenocryst in arc lavas, is increasingly recognized as a key constituent in the petrogenesis of arc magmas. Fractional crystallization of water-saturated arc magmas in the lower crust can yield substantial volumes of amphibole cumulates that, depending on the pressure of crystallization, may also contain garnet. Fractionation of this higher pressure assemblage has been invoked as a possible mechanism in the production of magmas that contain an adakitic signature. This study examines newly dated Late-Oligocene (25.37 ± 0.13 Ma) hypabyssal amphibole-rich andesites from Cerro Patacon in the Panama Canal region. These andesites contain nodules of amphibole cumulates that are ~4-6 cm in diameter and are almost entirely composed of 5-10-mm amphibole crystals (dominantly ferri-tschermakite). Geochemical variations, optical and chemical zoning of the Cerro Patacon amphiboles are consistent with their evolution in a crystal mush environment that had at least one recharge event prior to entrainment in the host andesite. Amphiboles hosted within the cumulate nodules differ from those hosted in the Cerro Patacon andesite and contain consistently higher values of Ti. We suggest these nodules represent the early stages of fractionation from a water-saturated magma. Cerro Patacon andesites have REE concentrations that plot at the most depleted end of Central American Arc magmas and exhibit a distinctive depletion in the middle REE. These geochemical and petrographic observations strongly support significant amphibole fractionation during formation of the Cerro Patacon andesite, consistent with the petrographic evidence. Fractionation of water-saturated magmas is a mechanism by which adakitic compositions may be produced, and the Cerro Patacon andesites do exhibit adakite-like geochemical characteristics (e.g., elevated Sr/Y; 28-34). However, the relatively elevated concentrations of Y and HREE indicate garnet was not stable in the fractionating

  20. Scanning Seismic Intrusion Detector

    NASA Technical Reports Server (NTRS)

    Lee, R. D.

    1982-01-01

    Scanning seismic intrusion detector employs array of automatically or manually scanned sensors to determine approximate location of intruder. Automatic-scanning feature enables one operator to tend system of many sensors. Typical sensors used with new system are moving-coil seismic pickups. Detector finds uses in industrial security systems.

  1. Intrusive STM imaging

    NASA Astrophysics Data System (ADS)

    Boulanger-Lewandowski, Nicolas; Rochefort, Alain

    2011-03-01

    An interactive scanning tunneling microscopy (STM) simulator has been designed to efficiently compute the effects of chemical and structural modifications of adsorbed species on resulting STM images. Our general approach is based on first-order perturbation theory that takes into account different tip geometries. In our intrusive STM imaging strategy, we consider small variations such as substitutions, vacancies, functionalizations, and molecular reorganizations from a reference system. First, we show that our perturbation theory approach can provide STM images that are qualitatively similar to those of a more rigorous electron scattering technique based on the Landauer-Büttiker formalism for the case of adsorbed tetracyanoethylene on a Cu(100) single crystal. Second, we demonstrate that the efficiency of Bardeen and Tersoff-Hamann approaches to generate STM images can be substantially improved by exploiting different algorithms to evaluate the tunnel current and to deal with large-scale eigenvalue problems. Following our general intrusive strategy, we have reduced the computing time to generate an STM image of a modified system by about an order of magnitude with respect to the reference image. The shape and position of the contrasts of the STM image evaluated in the context of intrusion are virtually identical to an image computed without intrusive features but within a considerably smaller computing time.

  2. Bro Intrusion Detection System

    2006-01-25

    Bro is a Unix-based Network Intrusion Detection System (IDS). Bro monitors network traffic and detects intrusion attempts based on the traffic characteristics and content. Bro detects intrusions by comparing network traffic against rules describing events that are deemed troublesome. These rules might describe activities (e.g., certain hosts connecting to certain services), what activities are worth alerting (e.g., attempts to a given number of different hosts constitutes a "scan"), or signatures describing known attacks or accessmore » to known vulnerabilities. If Bro detects something of interest, it can be instructed to either issue a log entry or initiate the execution of an operating system command. Bro targets high-speed (Gbps), high-volume intrusion detection. By judiciously leveraging packet filtering techniques, Bro is able to achieve the performance necessary to do so while running on commercially available PC hardware, and thus can serve as a cost effective means of monitoring a site’s Internet connection.« less

  3. Magma mixing in a zoned alkalic intrusion

    SciTech Connect

    Price, J.G.; Henry, C.D.; Barker, D.S.; Rubin, J.N.

    1985-01-01

    The Marble Canyon stock is unique among the alkalic intrusions of the Trans-Pecos magmatic province in being zoned from a critically silica-undersaturated rim of alkali gabbro (AG) to a silica-oversaturated core of quartz syenite (QS). Hybrid rocks of intermediate chemical and mineralogical compositions occur between the rim and core. Nepheline-syenite dikes occur only within the AG. Silica-rich dikes of quartz trachyte, pegmatite, and aplite cut the AG, QS, and hybrid rocks. Thermodynamic calculations of silica activity in the magmas illustrate the presence of two trends with decreasing temperature: a silica-poor trend from AG to nepheline syenite and a silica-rich trend from hybrid rocks to QS. Least-square modeling of rock and mineral compositions suggests 1) the nepheline syenites were derived by crystal-liquid fractionation from nearly solidified AG at the rim of the stock, 2) AG magma farther from the rim mixed with a small proportion of granitic magma, and 3) the mixture then differentiated to produce the hybrid rocks and QS. Zirconium dioxide inclusions in plagioclase crystals of the hybrid rocks and QS indicate that the AG magma contained some crystals before it mixed with the granitic magma. Two origins for the granitic magma are possible: 1) a late-stage differentiate of a mantle-derived hypersthene-normative magma and 2) melting of crustal material by the AG magma. Recognition of magma mixing might not have been possible if the AG had been hypersthene-normative.

  4. Petrochemistry of igneous rocks of the California-Vetas mining district, Santander, Colombia: Implications for northern Andean tectonics and porphyry Cu (-Mo, Au) metallogeny

    NASA Astrophysics Data System (ADS)

    Bissig, Thomas; Mantilla Figueroa, Luis Carlos; Hart, Craig J. R.

    2014-07-01

    Porphyry Mo and Cu mineralization in the California-Vetas mining district is contemporaneous with 10.9 to 8.4 Ma granodiorite porphyry stocks and overprinted by Au-Ag mineralization of epithermal affinity. Mineralization is hosted by Grenvillian aged paragneisses (Bucaramanga Gneiss of the Santander Massif) and late Triassic to early Jurassic granitic rocks. All intrusive rocks are high-K calc-alkaline. Late Triassic to early Jurassic rocks include peraluminous granites with more than 70 wt.% SiO2 as well as metaluminous diorites, tonalites and granodiorites with SiO2 between 54.9 and 60.4 wt.%. Late Miocene rocks are weakly peraluminous granodiorite porphyries with SiO2 between 61 and 67 wt.% SiO2. Late Miocene rocks share some characteristics with adakite-like rocks which are widely associated with porphyry and epithermal style mineralization elsewhere in the Andes. They have high Ba (930 to 1500 ppm) and high Ba/La (28 to 50), high Sr (850 to 1100 ppm) and Sr/Y (48-78) and depleted middle rare earth elements (MREE) compared to the Mesozoic granites, which have 400 to 700 ppm Ba (Ba/La 14 to 25) and 80 to 150 ppm Sr (Sr/Y 2.5 to 14), and Mesozoic diorites and tonalites, which have ~ 900 to 1200 ppm Ba (Ba/La 20 to 32) and ~ 610 to 750 ppm Sr (Sr/Y 22 to 25). Miocene granodiorite porphyries, in contrast to Mesozoic intrusive rocks have only weak negative Eu anomalies. The Miocene rocks have 87Sr/86Sr ratios of 0.7052 to 0.7067 and εNd of - 1.9 to - 5.4 and are significantly more isotopically primitive than all other rocks in the study area including the Mesozoic diorites to tonalites (87Sr/86Sr = 0.7082 and 0.7092; εNd = - 6.7 and - 7.2), granites (87Sr/86Sr = 0.730 (n = 2); εNd = - 8.2 and - 8.3) and Bucaramanga Gneiss (0.718 to 0.743; εNd = - 10.8 to - 14.1). Lead isotope data are broadly consistent with the Sr and Nd isotope data and the Miocene porphyries have the lowest 207Pb/204Pb ratios but overlap with the Mesozoic diorites to tonalites in their 206Pb

  5. Lithologic mapping of mafic intrusions in East Greenland using Landsat Thematic Mapper data

    NASA Technical Reports Server (NTRS)

    Naslund, H. Richard; Birnie, R. W.; Parr, J. T.

    1989-01-01

    The East Greenland Tertiary Igneous Province contains a variety of intrusive and extrusive rock types. The Skaergaard complex is the most well known of the intrusive centers. Landsat thematic mapping (TM) was used in conjunction with field spectrometer data to map these mafic intrusions. These intrusions are of interest as possible precious metal ore deposits. They are spectrally distinct from the surrounding Precambrian gneisses. However, subpixel contamination by snow, oxide surface coatings, lichen cover and severe topography limit the discrimination of lithologic units within the gabbro. Imagery of the Skaergaard and surrounding vicinity, and image processing and enhancement techniques are presented. Student theses and other publications resulting from this work are also listed.

  6. Petrology of the igneous rocks

    NASA Technical Reports Server (NTRS)

    Mccallum, I. S.

    1987-01-01

    Papers published during the 1983-1986 period on the petrology and geochemistry of igneous rocks are discussed, with emphasis on tectonic environment. Consideration is given to oceanic rocks, subdivided into divergent margin suites (mid-ocean ridge basalts, ridge-related seamounts, and back-arc basin basalts) and intraplate suites (oceanic island basalts and nonridge seamounts), and to igneous rocks formed at convergent margins (island arc and continental arc suites), subdivided into volcanic associations and plutonic associations. Other rock groups discussed include continental flood basalts, layered mafic intrusions, continental alkalic associations, komatiites, ophiolites, ash-flow tuffs, anorthosites, and mantle xenoliths.

  7. The vernon supersuite: Mesoproterozoic A-type granitoid rocks in the New Jersey highlands

    USGS Publications Warehouse

    Volkert, R.A.; Drake, A.A.

    1998-01-01

    Abundant Mesoproterozoic A-type granitoid rocks of two intrusive suites underlie approximately 50 percent of the New Jersey Highlands. These rocks, the Byram Intrusive and Lake Hopatcong Intrusive Suites, consist of granite, alaskite, quartz monzonite, monzonite, and minor pegmatite. Byram and Lake Hopatcong rocks, although different mineralogically, are similar geochemically and contain overlapping abundances of most major and trace elements. Petrographic relationships, geochronology, field relationships, and geochemical similarities support a comagmatic origin for both suites. They constitute the here named Vernon Supersuite.

  8. Lamprophyre dike intrusion and the age of the Alpine fault, New Zealand

    SciTech Connect

    Cooper, A.F.; Barreiro, B.A.; Kimbrough, D.L.; Mattinson, J.M.

    1987-10-01

    The orientations of intrusive rocks from a carbonatitic lamprophyre dike swarm and the history of emplacement relative to country-rock schist structures are compatible with intrusion into tension fractures and Riedel shears formed during initiation of the dextral wrench system of the Alpine fault. New U-Pb and Rb-Sr dates indicate a late Oligocene-early Miocene time of intrusion which, in turn, suggests a mid-Tertiary history for propagation of the Alpine fault plate boundary through South Island, New Zealand.

  9. Geochemistry and stratigraphic relations of middle Proterozoic rocks of the New Jersey Highlands

    USGS Publications Warehouse

    Volkert, Richard A.; Drake, Avery Ala

    1999-01-01

    Middle Proterozoic rocks of the New Jersey Highlands consist of a basement of dacitic, tonalitic, trondhjemitic, and charnockitic rocks that constitute the Losee metamorphic suite. These rocks are unconformably overlain by a layered supracrustal sequence of quartzo-feldspathic and calcareous rocks. Abundant sheets of hornblende- and biotite-bearing rocks of the Byram intrusive suite and clinopyroxene-bearing rocks of the Lake Hopatcong intrusive suite were synkinematically emplaced at about 1,090 Ma. These intrusive suites constitute the Vernon Supersuite. The postorogenic Mount Eve Granite has been dated at 1,020?4 Ma and is confined to the extreme northern Highlands.

  10. Acoustic emission intrusion detector

    DOEpatents

    Carver, Donald W.; Whittaker, Jerry W.

    1980-01-01

    An intrusion detector is provided for detecting a forcible entry into a secured structure while minimizing false alarms. The detector uses a piezoelectric crystal transducer to sense acoustic emissions. The transducer output is amplified by a selectable gain amplifier to control the sensitivity. The rectified output of the amplifier is applied to a Schmitt trigger circuit having a preselected threshold level to provide amplitude discrimination. Timing circuitry is provided which is activated by successive pulses from the Schmitt trigger which lie within a selected time frame for frequency discrimination. Detected signals having proper amplitude and frequency trigger an alarm within the first complete cycle time of a detected acoustical disturbance signal.

  11. Hybrid network intrusion detection

    NASA Astrophysics Data System (ADS)

    Tahmoush, David

    2014-05-01

    We report on a machine learning classifier that can be used to discover the patterns hidden within large networking data flows. It utilizes an existing intrusion detection system (IDS) as an oracle to learn a faster, less resource intensive normalcy classifier as a front-end to a hybrid network IDS. This system has the capability to recognize new attacks that are similar to known attack signatures. It is also more highly scalable and distributable than the signature-based IDS. The new hybrid design also allows distributed updates and retraining of the normalcy classifier to stay up-to-date with current threats.

  12. Thermal aureoles of igneous intrusions: some possible indications of hydrothermal convective cooling

    SciTech Connect

    Parmentier, E.M.; Schedl, A.

    1981-01-01

    The size and shape of metamorphic aureoles is investigated as a possible indicator of hydrothermal convective cooling of epizonal igneous intrusions. A simple family of numerical models illustrates the effect of convective cooling on maximum temperatures attained in the country rock surrounding an intrusion. Boundary layer approximations have also been applied to describe convection of vaporizing groundwater near the contact of an intrusion early in its cooling history. Maximum temperature isotherms are taken to reflect the width and shape of thermal aureoles defined by preserved mineral assemblages as appears to be reasonable based on several well-studied conductively cooled intrusions. The thermal aureoles of intrusions for which oxygen and hydrogen isotope data indicate convective groundwater circulation have been examined on the basis of the simple numerical and boundary layer models. The shape of the low temperature alteration aureole of the well-mapped El Salvador porphyry copper deposit suggests convective cooling of a permeable intrusion. The width of the low temperature (greenschist) aureole of the Mull intrusive complex can be explained by convective cooling of permeable intrusive rock. The narrow high temperature (amphibolite) aureole of the Cuillin gabbro on Skye can be explained by strong convective cooling; but the low temperature (greenschist) aureole is wide enough to be consistent with conductive cooling, thus suggesting decreasing permeabilities during the cooling history. This is consistent with oxygen isotope sampling and other geologic observations.

  13. Intrusion detection sensor testing tools

    SciTech Connect

    Hayward, D.R.

    1994-08-01

    Intrusion detection sensors must be frequently tested to verify that they are operational, and they must be periodically tested to verify that they are functioning at required performance levels. Concerns involving this testing can include: The significant amount of manpower required, inconsistent results due to variability in methods and personnel, exposure of personnel to hazardous environments, and difficulty in obtaining access to the areas containing some of the intrusion sensors. To address these concerns, the Department of Energy directed Sandia National Labs. to develop intrusion detection sensor testing tools. Over the past two years Sandia has developed several sensor testing tool prototypes. This paper describes the evolution of an exterior intrusion detection sensor tester and automatic data logger, and also describes various interior intrusion detection sensor test fixtures that can be remotely activated to simulate an intruder.

  14. Rapid deployment intrusion detection system

    SciTech Connect

    Graham, R.H.

    1997-08-01

    A rapidly deployable security system is one that provides intrusion detection, assessment, communications, and annunciation capabilities; is easy to install and configure; can be rapidly deployed, and is reusable. A rapidly deployable intrusion detection system (RADIDS) has many potential applications within the DOE Complex: back-up protection for failed zones in a perimeter intrusion detection and assessment system, intrusion detection and assessment capabilities in temporary locations, protection of assets during Complex reconfiguration, and protection in hazardous locations, protection of assets during Complex reconfiguration, and protection in hazardous locations. Many DOE user-need documents have indicated an interest in a rapidly deployable intrusion detection system. The purpose of the RADIDS project is to design, develop, and implement such a system. 2 figs.

  15. UThPb age of Apollo 12 rock 12013

    USGS Publications Warehouse

    Tatsumoto, M.

    1970-01-01

    A UThPb isotopic study of three chips from lunar rock 12013 indicates that parental material of the intrusion breccia formed quite early in the moon's history, possibly 3.9 to 4.3 by ago. The UThPb characteristics of the rock are distinctly different from those of other Apollo 12 igneous rocks and suggest a different origin. ?? 1970.

  16. Syn-collision Hairhan layered intrusion, Lakes Zone, Western Mongolia

    NASA Astrophysics Data System (ADS)

    Vishnevskiy, A. V.; Izokh, A. E.; Kalugin, V. M.; Gertner, I. F.

    2012-04-01

    In the structure of the Lakes Zone of Western Mongolia, which is reconstructed as the Early Cambrian island arc (Lakes island arc terrane), there are several groups of contiguous space gabbroic intrusions, merged in Hirgisnuur complex. The largest (70 km2) is Hairhan intrusion, located in the central part of the Lake Zone in the Bumbat-Hairhan ridge. The structure of the intrusion disturbed by later tectonic movements and the subsequent formation of Cambrian granitoids Tohtoginshil complex. The structures of the body are two groups of rocks: layered series and marginal facies, fragmentary spread to the periphery of intrusion. Gabbronorites of marginal facies have intrusive contacts with the sedimentary rocks of Early Cambrian age Burgastay formation. The marginal facies, apparent thickness which is 1.5 km, is composed primarily of non-olivine gabbronorites in which there is trachytoid and sometimes bedding. Layered series composes the central part of the Hairhan intrusion, the direction of layering has a northwest strike, coaxial with the long axis of the intrusion. The lower part of the layered series consists mainly troctolites with minor olivine gabbroids. The upper part of the layered series consists mainly of olivine gabbro, troctolite occur here less frequently also observed small schlieren anorthosites. Of particular interest is the horizon taxitic gabbro and being above it - the horizon orbicular gabbro at the top of the layered series. The rocks are widely manifested magmatic disruptive and plastic deformation - both macro and micro levels. They are expressed in the collapse of layering of elements in small folds of varying amplitude (typically to a few tens centimeters), often passing into areas and zones taxitic disruption. The greatest number of these structural elements characteristic of the upper part of the layered series, including the orbicular gabbro and troctolites taxitic horizons. These features indicate intensive tectonic processes that

  17. The petrogenesis of late Neoproterozoic mafic dyke-like intrusion in south Sinai, Egypt

    NASA Astrophysics Data System (ADS)

    Azer, M. K.; Abu El-Ela, F. F.; Ren, M.

    2012-08-01

    New field, petrographical and geochemical studies are presented here for the late Neoproterozoic Rimm intrusion (˜15 km long) exposed in the southern Sinai Peninsula, Egypt in the northernmost Arabian-Nubian Shield (ANS). Field relations indicate that the Rimm intrusion is younger than the surrounding metamorphic rocks and calc-alkaline syn-tectonic granodiorite and it was not affected by regional metamorphism. The anorogenic peralkaline granite of Gebel Serbal crosscuts the Rimm intrusion. The Rimm intrusion is made up of several consanguineous rock types with gradational contacts. It is composed chiefly of pyroxene-hornblende gabbro, hornblende gabbro and minor quartz diorite. The chemical composition of the mafic minerals indicated that the studied rocks derived from calc-alkaline mafic magma. Geochemically, the studied rocks are characterized by enrichment in LILE relative to HFSE and LREE relative to HREE [(Ce/Yb)N = 4.50-6.36]. Quartz diorite display slightly concave HREE pattern and slightly negative Eu-anomaly [(Eu/Eu*)n = 0.91] which may be the result of fractionation of amphibole and plagioclase from the source melt, respectively. The Rimm intrusion evolved from mafic mantle magma into different type rocks by fractional crystallization with minor crustal contamination. The initial magma corresponds to pyroxene-hornblende gabbro and the crystallization of hornblende was caused by slight H2O increase in magma after crystallization of near-liquidus clinopyroxene and Ca-rich plagioclase. Amphiboles geobarometer indicate that the gabbroic rocks of the Rimm intrusion crystallized at pressures between 4.8 and 6.4 Kb, while quartz diorite crystallized at 1.3-2.1 Kb. Crystallization temperatures range between 800 and 926 °C for the gabbros and between 667 and 784 °C for the quartz diorite. The Rimm intrusion represents a post-orogenic phase formed during the crustal thinning and extension of the Arabian-Nubian Shield.

  18. Episodic intrusion, internal differentiation, and hydrothermal alteration of the miocene tatoosh intrusive suite south of Mount Rainier, Washington

    USGS Publications Warehouse

    du Bray, E.A.; Bacon, C.R.; John, D.A.; Wooden, J.L.; Mazdab, F.K.

    2011-01-01

    The Miocene Tatoosh intrusive suite south of Mount Rainier is composed of three broadly granodioritic plutons that are manifestations of ancestral Cascades arc magmatism. Tatoosh intrusive suite plutons have individually diagnostic characteristics, including texture, mineralogy, and geochemistry, and apparently lack internal contacts. New ion-microprobe U-Pb zircon ages indicate crystallization of the Stevens pluton ca. 19.2 Ma, Reflection-Pyramid pluton ca. 18.5 Ma, and Nisqually pluton ca. 17.5 Ma. The Stevens pluton includes rare, statistically distinct ca. 20.1 Ma zircon antecrysts. Wide-ranging zircon rare earth element (REE), Hf, U, and Th concentrations suggest late crystallization from variably evolved residual liquids. Zircon Eu/Eu*-Hf covariation is distinct for each of the Reflection-Pyramid, Nisqually, and Stevens plutons. Although most Tatoosh intrusive suite rocks have been affected by weak hydrothermal alteration, and sparse mineralized veins cut some of these rocks, significant base or precious metal mineralization is absent. At the time of shallow emplacement, each of these magma bodies was largely homogeneous in bulk composition and petrographic features, but, prior to final solidification, each of the Tatoosh intrusive suite plutons developed internal compositional variation. Geochemical and petrographic trends within each pluton are most consistent with differential loss of residual melt, possibly represented by late aplite dikes or erupted as rhyolite, from crystal-rich magma. Crystal-rich magma that formed each pluton evidently accumulated in reservoirs below the present level of exposure and then intruded to a shallow depth. Assembled by episodic intrusion, the Tatoosh intrusive suite may be representative of midsized composite plutonic complexes beneath arc volcanoes. ?? 2011 Geological Society of America.

  19. Geologic and geophysical investigations of Climax stock intrusive, Nevada

    SciTech Connect

    1983-12-31

    This document contains three parts of a survey of Climax stock intrusive, Nevada by the US Geological Survey. The first contains the results of a conventional survey of the site and an investigation of rock composition. The second contains the results of a gravity survey and the third contains the results of a magnetic aerial survey. Each of the three documents contains a separate abstract.

  20. Human intrusion in geologic disposal

    SciTech Connect

    Not Available

    1993-12-31

    This report discusses the possibility of human intrusion into the WIPP facility, an undergound disposal facility for alpha-bearing wastes. The probability of exploratory drilling occurring at the site is described.

  1. Modal Composition and Age of Intrusions in North-Central and Northeast Nevada

    USGS Publications Warehouse

    du Bray, Edward A.; Crafford, A. Elizabeth Jones

    2007-01-01

    Introduction Data presented in this report characterize igneous intrusions of north-central and northeast Nevada and were compiled as part of the Metallogeny of the Great Basin project conducted by the U.S. Geological Survey (USGS) between 2001 and 2007. The compilation pertains to the area bounded by lats 38.5 and 42 N., long 118.5 W., and the Nevada-Utah border (fig. 1). The area contains numerous large plutons and smaller stocks but also contains equally numerous smaller, shallowly emplaced intrusions, including dikes, sills, and endogenous dome complexes. Igneous intrusions (hereafter, intrusions) of multiple ages are major constituents of the geologic framework of north-central and northeast Nevada (Stewart and Carlson, 1978). Mesozoic and Cenozoic intrusions are particularly numerous and considered to be related to subduction along the west edge of the North American plate during this time. Henry and Ressel (2000) and Ressel and others (2000) have highlighted the association between magmatism and ore deposits along the Carlin trend. Similarly, Theodore (2000) has demonstrated the association between intrusions and ore deposits in the Battle Mountain area. Decades of geologic investigations in north-central and northeast Nevada (hereafter, the study area) demonstrate that most hydrothermal ore deposits are spatially, and probably temporally and genetically, associated with intrusions. Because of these associations, studies of many individual intrusions have been conducted, including those by a large number of Master's and Doctoral thesis students (particularly University of Nevada at Reno students and associated faculty), economic geologists working on behalf of exploration and mining companies, and USGS earth scientists. Although the volume of study area intrusions is large and many are associated with ore deposits, no synthesis of available data that characterize these rocks has been assembled. Compilations that have been produced for intrusions in Nevada

  2. Gas intrusion into SPR caverns

    SciTech Connect

    Hinkebein, T.E.; Bauer, S.J.; Ehgartner, B.L.; Linn, J.K.; Neal, J.T.; Todd, J.L.; Kuhlman, P.S.; Gniady, C.T.; Giles, H.N.

    1995-12-01

    The conditions and occurrence of gas in crude oil stored in Strategic Petroleum Reserve, SPR, caverns is characterized in this report. Many caverns in the SPR show that gas has intruded into the oil from the surrounding salt dome. Historical evidence and the analyses presented here suggest that gas will continue to intrude into many SPR caverns in the future. In considering why only some caverns contain gas, it is concluded that the naturally occurring spatial variability in salt permeability can explain the range of gas content measured in SPR caverns. Further, it is not possible to make a one-to-one correlation between specific geologic phenomena and the occurrence of gas in salt caverns. However, gas is concluded to be petrogenic in origin. Consequently, attempts have been made to associate the occurrence of gas with salt inhomogeneities including anomalies and other structural features. Two scenarios for actual gas intrusion into caverns were investigated for consistency with existing information. These scenarios are gas release during leaching and gas permeation through salt. Of these mechanisms, the greater consistency comes from the belief that gas permeates to caverns through the salt. A review of historical operating data for five Bryan Mound caverns loosely supports the hypothesis that higher operating pressures reduce gas intrusion into caverns. This conclusion supports a permeability intrusion mechanism. Further, it provides justification for operating the caverns near maximum operating pressure to minimize gas intrusion. Historical gas intrusion rates and estimates of future gas intrusion are given for all caverns.

  3. Paleomagnetic record of a geomagnetic field reversal from late miocene mafic intrusions, southern nevada.

    PubMed

    Ratcliff, C D; Geissman, J W; Perry, F V; Crowe, B M; Zeitler, P K

    1994-10-21

    Late Miocene (about 8.65 million years ago) mafic intrusions and lava flows along with remagnetized host rocks from Paiute Ridge, southern Nevada, provide a high-quality paleomagnetic record of a geomagnetic field reversal. These rocks yield thermoremanent magnetizations with declinations of 227 degrees to 310 degrees and inclinations of -7 degrees to 49 degrees , defining a reasonably continuous virtual geomagnetic pole path over west-central Pacific longitudes. Conductive cooling estimates for the intrusions suggest that this field transition, and mafic magmatism, lasted only a few hundred years. Because this record comes principally from intrusive rocks, rather than sediments or lavas, it is important in demonstrating the longitudinal confinement of the geomagnetic field during a reversal. PMID:17816684

  4. Talking Rocks.

    ERIC Educational Resources Information Center

    Rice, Dale; Corley, Brenda

    1987-01-01

    Discusses some of the ways that rocks can be used to enhance children's creativity and their interest in science. Suggests the creation of a dramatic production involving rocks. Includes basic information on sedimentary, igneous, and metamorphic rocks. (TW)

  5. Cup-shaped Intrusions, Morphology and Emplacement Mechanism Investigate Through Analogue Modelling

    NASA Astrophysics Data System (ADS)

    Mathieu, L.; van Wyk de Vries, B.

    2007-12-01

    We investigate the morphology of large-scale shallow-depth magma intrusions and sub-volcanic complexes with analogue models. Intrusions of analogue magma are done in a granular material that can contain a ductile layer. The model surface is flat to model the formation of plutonic intrusions and it is overlain by a cone when modelling late sub-volcanic complexes. For flat-top models, we obtain cup-shaped intrusions fed by dykes. Cup-shaped intrusions are inverted-cone like bodies. They are different from saucer-shaped intrusions as they possess neither a well developed sill-base, nor an outer rim. However, like saucers, cups are shallow depth intrusions that dome the country rocks. They initiate from an advancing dyke and first develop an inverted-cone like morphology. Then, the central thickness increases and thrusts form at the edge of the domed country rocks. At this stage, the intrusions progressively involve toward a lopolith shape. By using analogue magma of various viscosities we have been able to constrain key relationships: higher intrusion viscosity causes deeper initiation and the deeper they initiate, the larger is the intrusion diameter. A natural example of such intrusion might by the circles of volcanoes like the Azufre-Lastaria (Peru) that might be overlain be a large-scale cup-shaped intrusion. When adding a cone at the surface of the model and, sometimes, a thin ductile layer in the substratum, the morphology of cup-shaped intrusions vary. Note that the ductile layer of our models is not thick enough to induce the gravitational spreading of the cone. Generally, cup-shaped intrusions are asymmetric in cross section and elliptical in plan view. Their formation creates extension structures in the cone (croissant-shaped rift, straight rift or normal fault) and thrusts in some sectors below the cone. Both types of structures are bordered by strike-slip faults. Cups and saucers share many similarities, but differ probably in the fact that saucers are

  6. Deformation structures associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: Implications for sill and laccolith emplacement mechanisms

    NASA Astrophysics Data System (ADS)

    Wilson, Penelope I. R.; McCaffrey, Ken J. W.; Wilson, Robert W.; Jarvis, Ian; Holdsworth, Robert E.

    2016-06-01

    Deformation structures in the wall rocks of igneous intrusions emplaced at shallow crustal depths preserve an important record of how space was created for magma in the host rocks. Trachyte Mesa, a small Oligocene age intrusion in the Henry Mountains, Utah, is composed of a series of stacked tabular, sheet-like intrusions emplaced at 3-3.5 km depth into sandstone-dominated sedimentary sequences of late Palaeozoic-Mesozoic age. New structural analysis of the spatial distribution, geometry, kinematics and relative timings of deformation structures in the host rocks of the intrusion has enabled the recognition of distinct pre-, syn-, and late-stage-emplacement deformation phases. Our observations suggest a two-stage growth mechanism for individual sheets where radial growth of a thin sheet was followed by vertical inflation. Dip-slip faults formed during vertical inflation; they are restricted to the tips of individual sheets due to strain localisation, with magma preferentially exploiting these faults, initiating sill (sheet) climbing. The order in which sheets are stacked impacts on the intrusion geometry and associated deformation of wall rocks. Our results offer new insights into the incremental intrusion geometries of shallow-level magmatic bodies and the potential impact of their emplacement on surrounding host rocks.

  7. 1420 Ma diabasic intrusives from the Mesoproterozoic Singhora Group, Chhattisgarh Supergroup, India: Implications towards non-plume intrusive activity

    NASA Astrophysics Data System (ADS)

    Das, Priyabrata; Das, Kaushik; Chakraborty, Partha Pratim; Balakrishnan, S.

    2011-04-01

    Besides offering significant clues towards tracking the geochemical evolution of the mantle and architectural reconstruction of different `supercontinent', geochronological and geochemical appraisal of igneous inputs are also important to bracket the depositional time frame of any lithopackage, particularly, the unfossiliferous sedimentary successions. The present study deals with diabasic intrusive within Mesoproterozoic Saraipalli Formation, which is an argillaceous constituent present at the basal part of nearly 400 m thick four-tiered unmetamorphosed but deformed sedimentary succession of Singhora Group, Chhattisgarh Supergroup, central India. The SE-NW trending intrusive comprises mainly of plagioclase and augite together with minor orthopyroxene, biotite and opaque minerals. Though some plagioclase laths are partially sericitized, the ophitic-to-subophitic texture of the rock is well preserved. Major and trace element geochemical data indicate that this intrusive is basalt-to-basaltic andesite in character and of subalkaline basalt affinity. Multi-element plot shows overall LILE-enrichment and enrichment of Pb and slight depletion of Nb and P, coupled with moderate La/Nb and Th/Nb ratios. Zr, Y and Nb ternary diagrams plot in the fields of within plate basalt. Selected HFSE ratios indicate a non-plume source with crustal assimilation/sediment mixing. Sm-Nd and Rb-Sr isotope data show that the intrusive has Srinitial and Ndinitial of 0.709377-0.706672 and 0.510919-0.510815, respectively. Positive ɛ t Nd [ t = 1420 Ma] values (+0.3 to + 2.3) indicate depleted isotopic nature of their protolith. The calculated T DM age is 1.7-1.9 Ga. The mineral-whole rock isochron data (Sm-Nd systematics) of the intrusive implies an emplacement age of ca. 1420 Ma. Considering synchronous terrain boundary shear zone development in Bastar craton on the southeastern part of the Singhora basin, mafic magmatism in Eastern Ghats and large-scale basic intrusion in Sausar mobile belt

  8. Fusion of arkosic sand by intrusive andesite

    USGS Publications Warehouse

    Bailey, Roy A.

    1954-01-01

    An andesite dike in the Valles Mountains of northern New Mexico has intruded and partly fused arkosic sediments for a distance of 50 feet from its contacts. The dike is semi-circular in form, has a maximum width of about 100 feet, and is about 500 feet long. Small associated arcuate dikes are arranged in spiral fashion around the main dike, suggesting that they were intruded along shear fractures similar to those described by Burbank (1941). The fused rocks surrounding the andesite dike are of three general types: 1) partly fused arkosic sand, 2) fused clay, and 3) hybrid rocks. The fused arkosic sand consists of relict detrital grains of quartz, orthoclose, and plagioclase, imbedded in colorless glass containing microlites of tridymite, cordierite, and magnetite. The relict quartz grains are corroded and embayed by glass; the orthoclase is sanidinized and partly fused; and the plagioclase is inverted to the high temperature form and is partly fused. The fused clay, which was originally a mixture of montmorillonite and hydromica, consists primarily of cordierite but also contains needle-like crystals of sillimanite (?) or mullite (?). The hybrid rocks originated in part by intermixing of fused arkosic sediments and andesitic liquid and in part by diffusion of mafic constituents through the fused sediments. They are rich in cordierite and magnetite and also contain hypersthene, augite, and plagioclase. The composition of pigeonite in the andesite indicates that the temperature of the andesite at the time of intrusion probably did not exceed 1200?C. Samples of arkosic sand were fused in the presence of water in a Morey bomb at 1050?C. Stability relations of certain minerals in the fused sand suggest that fusion may have taken place at a lower temperature, however, and the fluxing action of volatiles from the andesite are thought to have made this possible.

  9. Data Mining for Intrusion Detection

    NASA Astrophysics Data System (ADS)

    Singhal, Anoop; Jajodia, Sushil

    Data Mining Techniques have been successfully applied in many different fields including marketing, manufacturing, fraud detection and network management. Over the past years there is a lot of interest in security technologies such as intrusion detection, cryptography, authentication and firewalls. This chapter discusses the application of Data Mining techniques to computer security. Conclusions are drawn and directions for future research are suggested.

  10. Petrogenesis of the Ni-Cu-PGE sulfide-bearing Tamarack Intrusive Complex, Midcontinent Rift System, Minnesota

    NASA Astrophysics Data System (ADS)

    Taranovic, Valentina; Ripley, Edward M.; Li, Chusi; Rossell, Dean

    2015-01-01

    The Tamarack Intrusive Complex (TIC, 1105.6 ± 1.2 Ma) in NE Minnesota, was emplaced during the early stages of the development of the Midcontinent Rift System (MRS, "Early Stage": 1110-1106 Ma). Country rocks of the TIC are those of the Paleoproterozoic Thomson Formation, part of the Animikie Group including sulfide-bearing metasedimentary black shale. The magmatic system is composed of at least two principal mafic-ultramafic intrusive sequences: the sulfide-barren Bowl Intrusion in the south and the "dike" area intrusions in the north which host Ni-Cu-Platinum Group Elements (PGE) mineralization with up to 2.33% Ni, 1.24% Cu, 0.34 g/t Pt, 0.23 g/t Pd and 0.18 g/t Au. Two distinct intrusive units in the "dike" area are the CGO (coarse-grained olivine-bearing) Intrusion, a sub-vertical dike-like body, and the overlying sub-horizontal FGO (fine-grained olivine-bearing) Intrusion. Both intrusions comprise peridotite, feldspathic peridotite, feldspathic pyroxenite, melatroctolite and melagabbro. Massive sulfides are volumetrically minor and mainly occur as lenses emplaced into the country rocks associated with both intrusions. Semi-massive (net-textured) sulfides are distributed at the core of the CGO Intrusion, surrounded by a halo of the disseminated sulfides. Disseminated sulfides also occur in lenses along the base of the FGO Intrusion. Olivine compositions in the CGO Intrusion are between Fo89 and Fo82 and in the FGO Intrusion from Fo84 to Fo82. TIC intrusions have more primitive olivine compositions than that of olivine in the sheet-like intrusions in the Duluth Complex (below Fo70), as well as olivine from the smaller, conduit-related, Eagle and East Eagle Intrusions in Northern Michigan (Fo86 to Fo75). The FeO/MgO ratios of the CGO and FGO Intrusion parental magmas, inferred from olivine compositions, are similar to those of picritic basalts erupted during the early stages of the MRS formation. Trace element ratios differ slightly from other intrusions in the

  11. Composite synvolcanic intrusions associated with Precambrian VMS-related hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Galley, Alan G.

    2003-06-01

    Large subvolcanic intrusions are recognized within most Precambrian VMS camps. Of these, 80% are quartz diorite-tonalite-trondhjemite composite intrusions. The VMS camps spatially associated with composite intrusions account for >90% of the aggregate sulfide tonnage of all the Precambrian, intrusion-related VMS camps. These low-alumina, low-K, and high-Na composite intrusions contain early phases of quartz diorite and tonalite, followed by more voluminous trondhjemite. They have a high proportion of high silica (>74% SiO2) trondhjemite which is compositionally similar to the VMS-hosting rhyolites within the volcanic host-rock successions. The quartz-diorite and possibly tonalite phases follow tholeiitic fractionation trends whereas the trondhjemites fall within the composition field for primitive crustal melts. These transitional M-I-type primitive intrusive suites are associated with extensional regimes within oceanic-arc environments. Subvolcanic composite intrusions related to the Archean Sturgeon Lake and Noranda, and Paleoproterozoic Snow Lake VMS camps range in volume from 300 to 1,000 km3. Three have a sill morphology with strike lengths between 15 and 22 km and an average thickness between 1,500 and 2,000 m. The fourth has a gross stock-like shape. The VMS deposits are principally restricted to the volcanic strata above the strike length of the intrusions, as are areally extensive, thin exhalite units. The composite intrusions contain numerous internal phases which are commonly clustered within certain parts of the composite intrusion. These clusters underlie eruptive centers surrounded by areas of hydrothermal alteration and which contain most of the VMS deposits. Early quartz-diorite and tonalite phases appear to have intruded in rapid succession. Evidence includes gradational contacts, magma mixing and disequilibrium textures. They appear to have been emplaced as sill-dike swarms. These early phases are present as pendants and xenoliths within later

  12. Pre-Elsonian mafic magmatism in the Nain Igneous Complex, Labrador: the bridges layered intrusion

    USGS Publications Warehouse

    Ashwal, L.D.; Wiebe, R.A.; Wooden, J.L.; Whitehouse, M.J.; Snyder, Diane

    1992-01-01

    Decades of work on the pristine, unmetamorphosed, and well exposed anorthositic, mafic and granitic rocks of the Nain igneous complex, Labrador, have led to the conclusion that all plutonic rocks in that area were emplaced in a short time intercal at about 1300 ?? 10 Ma). We report here new isotopic data for mafic intrusive rocks that appear to have crystallized several hundred Ma earlier than the bulk of the plutonic activity in the Nain complex. The Bridges layered intrusion (BLI) is a small (15-20 km2) lens of layered mafic rocks about 1.5 km thick, surrounded and intruded by anorthositic, leuconoritic and leucotroctolitic plutons in the middle of the coastal section of the Nain igneous complex. BLI shows very well developed magmatic structures, including channel scours, slump structures, and ubiquitous modally graded layering. Most rocks, however, show granular textures indicative of recrystallization, presumably caused by emplacement of younger anorthositic rocks. BLI contains cumulate rocks with slightly more primitive mineral compositions (An60-83, Fo66-71) than those of other mafic intrusions in the Nain igneous complex, including Kiglapait. SmNd isotopic data for 7 BLI whole-rocks ranging in composition between olivine melagabbro and olivine leucogabbro yield an age of 1667 ?? 75 Ma, which we interpret as the time of primary crystallization. The internal isotopic systematics of the BLI have been reset, probably by intrusion of adjacent anorthositic plutons. A SmNd mineral isochron (plag, whole-rock, mafics) for a BLI olivine melagabbro gives an age of 1283 ?? 22 Ma, equivalent within error of a mineral array (plag, whole-rock, opx, cpx) for an adjacent, igneous-textured, leuconorite vein (1266 ?? 152 Ma). The initial Nd ratio for BLI corresponds to ??{lunate}Nd = -3.18 ?? 0.44. Other whole-rock samples, however, some with vein-like alteration (Chlorite, serpentine, amphiboles), show ??{lunate}Nd values as low as -9.1, suggesting variable contamination by

  13. Aeromagnetic and radio echo ice-sounding measurements over the Dufek intrusion, Antarctica.

    USGS Publications Warehouse

    Behrendt, John C.; Drewry, D.J.; Jankowski, E.; Grim, M.S.

    1981-01-01

    Comparisons of the magnetic and subglacial topographic profiles illustrate the usefulness of this combination of methods in studying bedrock geology beneath ice-covered areas. Rocks are exposed in only 3% of the inferred area of the intrusion.-from Authors

  14. Collecting Rocks.

    ERIC Educational Resources Information Center

    Barker, Rachel M.

    One of a series of general interest publications on science topics, the booklet provides those interested in rock collecting with a nontechnical introduction to the subject. Following a section examining the nature and formation of igneous, sedimentary, and metamorphic rocks, the booklet gives suggestions for starting a rock collection and using…

  15. Rock Finding

    ERIC Educational Resources Information Center

    Rommel-Esham, Katie; Constable, Susan D.

    2006-01-01

    In this article, the authors discuss a literature-based activity that helps students discover the importance of making detailed observations. In an inspiring children's classic book, "Everybody Needs a Rock" by Byrd Baylor (1974), the author invites readers to go "rock finding," laying out 10 rules for finding a "perfect" rock. In this way, the…

  16. Rock Art

    ERIC Educational Resources Information Center

    Henn, Cynthia A.

    2004-01-01

    There are many interpretations for the symbols that are seen in rock art, but no decoding key has ever been discovered. This article describes one classroom's experiences with a lesson on rock art--making their rock art and developing their own personal symbols. This lesson allowed for creativity, while giving an opportunity for integration…

  17. Adaptive Intrusion Data System (AIDS)

    SciTech Connect

    Corlis, N. E.

    1980-05-01

    The adaptive intrusion data system (AIDS) was developed to collect data from intrusion alarm sensors as part of an evaluation system to improve sensor performance. AIDS is a unique data system which uses computer controlled data systems, video cameras and recorders, analog-to-digital conversion, environmental sensors, and digital recorders to collect sensor data. The data can be viewed either manually or with a special computerized data-reduction system which adds new data to a data base stored on a magnetic disc recorder. This report provides a synoptic account of the AIDS as it presently exists. Modifications to the purchased subsystems are described, and references are made to publications which describe the Sandia-designed subsystems.

  18. Petrogenesis of the Middle Jurassic Yinshan volcanic-intrusive complex, SE China: Implications for tectonic evolution and Cu-Au mineralization

    NASA Astrophysics Data System (ADS)

    Wang, Guo-Guang; Ni, Pei; Zhao, Kui-Dong; Wang, Xiao-Lei; Liu, Ji-Qiang; Jiang, Shao-Yong; Chen, Hui

    2012-10-01

    Volcanic-subvolcanic rocks and associated Cu-Au deposits in Yinshan are located in the eastern part of the Neoproterozoic Jiangnan orogenic belt between the Yangtze and Cathaysia blocks, constituting a large metallogenic district in southeastern China. This paper presents new laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U-Pb dating, element and Sr-Nd-Hf isotopic data for Yinshan igneous rocks in the Dexing region. Our results show that the Yinshan igneous rocks were produced during the Middle Jurassic (ca. 176-166 Ma). Geochemically, the Yinshan igneous rocks are characterized by calc-alkaline and show some adakitic affinities with high Sr contents (up to 903 ppm), Sr/Y (up to 93.2) and LaN/YbN ratios (12.4 to 65.1) and low Y (2.53 to 15.8 ppm) and Yb contents (0.22 to 1.39 ppm). The absence of a negative Eu anomaly, extreme depletion in Y and Yb, relatively low MgO contents (0.2 to 2.9 wt.%), and relatively high 207Pb/204Pb ratio (15.555-15.575), indicate that Yinshan igneous rocks were likely derived from the partial melting of thickened lower continental crust. In addition, the Yinshan igneous rocks show similar element characteristics to arc-derived igneous rocks with bulk Earth-like ɛNd (t) values (- 1.1 to + 1.8) and initial 87Sr/86Sr (0.7036-0.7090), relatively depleted ɛHf (t) values (- 1.5 to + 5.8), and Hf model ages of 0.8-1.2 Ga. However, there is no arc-related evidence in the study area in the Middle Jurassic, which indicates that these arc-related elemental and isotopic compositions are possibly inherited from Meso- to Neo-Proterozoic juvenile continental crust formed by the Neoproterozoic oceanic crust subduction along the Jiangnan Orogen. The geodynamic environment responsible for the development of the Middle Jurassic Yinshan igneous rocks is probably a localized intra-continental extensional environment along the NE Jiangxi Deep Fault, as a tectonic response to far-field stress at the margins of South China

  19. Geologic and geophysical investigations of Climax Stock intrusive, Nevada

    USGS Publications Warehouse

    ,

    1983-01-01

    The Climax stock is a composite granitic intrusive of Cretaceous age, composed of quartz monzonite and granodiorite, which intrudes rocks of Paleozoic and Precambrian age. Tertiary volcanic rocks, consisting of ashflow and ash-fall tuffs, and tuffaceous sedimentary rocks overlie the sedimentary rocks and the stock. Erosion has removed much of the Tertiary volcanic rocks. Hydrothermal alteration of quartz monzonite and granodiorite is found mainly along joints and faults and varies from location to location. The Paleozoic carbonate rocks have been thermally and metasomatically altered to marble and tactite as much as 457 m (1,500 ft) from the contact with the stock, although minor discontinuous metasomatic effects are noted in all rocks out to 914 m (3,000 ft). Three major faults which define the Climax area structurally are the Tippinip, Boundary and Yucca faults. North of the junction of the Boundary and Yucca faults, the faults are collectively referred to as the Butte fault. The dominant joint sets and their average attitudes are N. 32? W., 22? NE; N. 60? W., vertical and N. 35? E., vertical. Joints in outcrop are weathered and generally open, but in subsurface, the joints are commonly filled and healed with secondary mineral s. The location of the water table and the degree of saturation of the granitic rocks are presently unknown. Measurement from drill holes indicated that depth to perched water levels ranges from 30 to 244 m (100-800 ft). Recent field investigations have shown the contact between the Pogonip marble and the granodiorite is a contact rather than a fault as previously mapped. The thickness of the weathered granodiorite is estimated to be 8 to 46 m (25 to 150 ft).

  20. Platinum-group element geochemistry of zoned ultramafic intrusive suites, Klamath Mountains, California and Oregon.

    USGS Publications Warehouse

    Gray, F.; Page, N.J.; Carlson, C.A.; Wilson, S.A.; Carlson, R.R.

    1986-01-01

    Analyses for platinum-group elements of the varied rock suites of three Alaskan-type ultramafic to mafic multi-intrusive bodies are reported. Ir and Ru are less than analytical sensitivities of 100 and 20 ppb; Rh is less than or near 1 ppb. Average Pd assays vary among the rocks within intrusive complexes and between the three complexes (6.3, 13.7, 36.4 ppb); average Pt assays vary little among the same samples (27.9, 60.9, 34.0 ppb). Statistically adjusted Pt/(Pt + Pd) ratios increase in each suite from gabbro through clinopyroxenite to olivine-rich rocks, possibly owing to Pd fractionation.-G.J.N.

  1. Triggers on sulfide saturation in Fe-Ti oxide-bearing, mafic-ultramafic layered intrusions in the Tarim large igneous province, NW China

    NASA Astrophysics Data System (ADS)

    Cao, Jun; Wang, Christina Yan; Xu, Yi-Gang; Xing, Chang-Ming; Ren, Ming-Hao

    2016-08-01

    Three Fe-Ti oxide-bearing layered intrusions (Mazaertag, Wajilitag, and Piqiang) in the Tarim large igneous province (NW China) have been investigated for understanding the relationship of sulfide saturation, Platinum-group element (PGE) enrichment, and Fe-Ti oxide accumulation in layered intrusions. These mafic-ultramafic layered intrusions have low PGE concentrations (<0.4 ppb Os, <0.7 ppb Ir, <1 ppb Ru, <0.2 ppb Rh, <5 ppb Pt, and <8 ppb Pd) and elevated Cu/Pd (2.2 × 104 to 3.3 × 106). The low PGE concentrations of the rocks are mainly attributed to PGE-depleted, parental magma that was produced by low degrees of partial melting of the mantle. The least contaminated rocks of the Mazaertag and Wajilitag intrusions have slightly enriched Os isotopic compositions with γOs(t = 280 Ma) values ranging from +13 to +23, indicating that the primitive magma may have been generated from a convecting mantle, without appreciable input of lithospheric mantle. The Mazaertag and Wajilitag intrusions have near-chondritic γOs(t) values (+13 to +60) against restricted ɛ Nd(t) values (-0.4 to +2.8), indicating insignificant crustal contamination. Rocks of the Piqiang intrusion have relatively low ɛ Nd(t) values of -3.1 to +1.0, consistent with ˜15 to 25 % assimilation of the upper crust. The rocks of the Mazaertag and Wajilitag intrusions have positive correlation of PGE and S, pointing to the control of PGE by sulfide. Poor correlation of PGE and S for the Piqiang intrusion is attributed to the involvement of multiple sulfide-stage liquids with different PGE compositions or sulfide-oxide reequilibration on cooling. These three layered intrusions have little potential of reef-type PGE mineralization. Four criteria are summarized in this study to help discriminate between PGE-mineralized and PGE-unmineralized mafic-ultramafic intrusions.

  2. Fracture mode analysis and related surface deformation during dyke intrusion: Results from 2D experimental modelling

    NASA Astrophysics Data System (ADS)

    Abdelmalak, M.; Mourgues, R.; Bureau, D.

    2012-04-01

    The analysis of surface deformation in response to approaching intrusion is important for assessing volcanic hazards. In this paper, we present results from 2D scaled models of magma intrusion, in which we discuss the propagation mode and related surface deformation during dyke growth. Our experiments consist in the injection of analogue magma (Golden syrup) into cohesive fine-grained silica powder, simulating the brittle upper crust. Using an optical image correlation technique (Particle Imaging Velocimetry), we were able to follow the surface deformation, the displacements within the country rock and to calculate strains induced by the magma emplacement. We identified two kinds of intrusion morphologies resulting from different interactions between the dyke and plastic deformations occurring in the country rock near the surface. In both morphologies, the dyke is vertical at depth. Our analysis demonstrates that both hydraulic tensile opening and shear-related propagation operate during this first stage of vertical growth. At the same time, the surface lifted up and formed a smooth symmetrical dome. Both types of morphologies differ in the upper part. During a second stage of evolution, the first type of intrusion inclined at a dip between 45 to 65°. This inclination is not caused by shear deformations and is attributed to stress rotation near the tip. Closer to the surface, the growth of the inclined sheet creates shear bands which conduct the fluid toward the surface. The surface uplift becomes asymmetric. The second type of intrusion does not rotate at depth and continues its vertical propagation by catching vertical tensile cracks. The intrusion of magma in these cracks creates horizontal stresses which are responsible for the closure of fractures and the formation of reverse faults. At the surface the dome remains symmetrical. For both intrusions, the surface uplift accelerates during the second stage and it is strongly influenced by the presence or the

  3. Stratigraphic and geophysical evidence for a Tertiary intrusion near Beaufort, S. C

    SciTech Connect

    McCartan, L.; Gettings, M.E.

    1985-01-01

    A mafic intrusion about 10 km in diameter at 1.5 km depth is indicated by strong positive gravity and magnetic anomalies and a closed structural high is overlying upper Eocene limestone near Beaufort, S.C. Sediments of Oligocene age northeast of Beaufort and of Miocene age to the west and southwest indicate that the Beaufort high divided the Southeast Georgia Embayment into two sub-basins by late Oligocene time. The stratigraphic relations and elevated geothermal gradients suggest an age of 20-30 Ma for the intrusion. Maintenance of the Beaufort high through time despite several marine incursions implies continued uplift, probably due to effects of the intrusion and Tertiary compressional warping. Intrusions with similar geophysical signatures are commonest in the southeast but are also present elsewhere along the Atlantic continental margin. Seismic profiles across the anomalies at the Clubhouse Crossroads deep corehole, 60 km north of Beaufort, show a flat Jurassic reflector, so the intrusive rocks there are Jurassic or older. However, 175 km northeast of Beaufort, a seismic line crossing one of the offshore anomalies shows an intrusion doming up Cenozoic sediments. Substantiation of a Tertiary age for the Beaufort pluton would significantly change the current models of the Tertiary tectonic history of the Southeast Georgia Embayment.

  4. Saline and particle-driven interfacial intrusions

    NASA Astrophysics Data System (ADS)

    de Rooij, Frans; Linden, P. F.; Dalziel, Stuart B.

    1999-06-01

    This paper presents a theoretical and experimental investigation into saline and particle-driven intrusions along the interface between two layers of different densities. The conditions at the nose of an intrusion are described in an analysis similar to that applied by Benjamin (1968) to boundary gravity currents. Equations for propagation velocity and front position as functions of relative density are derived. These are used in an integral model for intrusions, which also includes the effects of sedimentation of particles and detrainment of interstitial fluid. The model describes the time-evolution of the length of the intrusion and the sediment distribution it produces. Laboratory experiments were carried out with lock-releases of a fixed volume of saline or particle-laden fluid into a two-layer stratification. Measurements were taken of the intrusion propagation, intrusion position and sediment distribution, and are found to be in good agreement with the solutions of the integral model.

  5. Science Rocks!

    ERIC Educational Resources Information Center

    Prestwich, Dorothy; Sumrall, Joseph; Chessin, Debby A.

    2010-01-01

    It all began one Monday morning. Raymond could not wait to come to large group. In his hand, he held a chunk of white granite he had found. "Look at my beautiful rock!" he cried. The rock was passed around and examined by each student. "I wonder how rocks are made?" wondered one student. "Where do they come from?" asked another. At this moment, a…

  6. Effect of permeability on cooling of magmatic intrusion in a goethermal reservoir

    SciTech Connect

    Lau, K.H.

    1980-09-01

    Transient cooling of magmatic intrusion in a geothermal reservoir due to conduction and convection is studied. The effects of overlying cap rock and different horizontal and vertical permeability of the reservoir are considered. Results are compared to the data from Salton Sea Geothermal Field. It is also observed that multiple layers of convection cells exist when horizontal permeability is much larger than the vertical permeability. The sharp dropoff of surface heat flow observed at Salton Sea Geothermal Field is confirmed by numerical results. Based on these numerical results, it is possible to speculate that the age of the intrusive body is about 8000 to 12,000 years.

  7. Rock flows

    NASA Technical Reports Server (NTRS)

    Matveyev, S. N.

    1986-01-01

    Rock flows are defined as forms of spontaneous mass movements, commonly found in mountainous countries, which have been studied very little. The article considers formations known as rock rivers, rock flows, boulder flows, boulder stria, gravel flows, rock seas, and rubble seas. It describes their genesis as seen from their morphological characteristics and presents a classification of these forms. This classification is based on the difference in the genesis of the rubbly matter and characterizes these forms of mass movement according to their source, drainage, and deposit areas.

  8. An international perspective on Facebook intrusion.

    PubMed

    Błachnio, Agata; Przepiorka, Aneta; Benvenuti, Martina; Cannata, Davide; Ciobanu, Adela Magdalena; Senol-Durak, Emre; Durak, Mithat; Giannakos, Michail N; Mazzoni, Elvis; Pappas, Ilias O; Popa, Camelia; Seidman, Gwendolyn; Yu, Shu; Wu, Anise M S; Ben-Ezra, Menachem

    2016-08-30

    Facebook has become one of the most popular social networking websites in the world. The main aim of the study was to present an international comparison of Facebook intrusion and Internet penetration while examining possible gender differences. The study consisted of 2589 participants from eight countries: China, Greece, Israel, Italy, Poland, Romania, Turkey, USA. Facebook intrusion and Internet penetration were taken into consideration. In this study the relationship between Facebook intrusion and Internet penetration was demonstrated. Facebook intrusion was slightly negatively related to Internet penetration in each country. PMID:27347649

  9. An international perspective on Facebook intrusion.

    PubMed

    Błachnio, Agata; Przepiorka, Aneta; Benvenuti, Martina; Cannata, Davide; Ciobanu, Adela Magdalena; Senol-Durak, Emre; Durak, Mithat; Giannakos, Michail N; Mazzoni, Elvis; Pappas, Ilias O; Popa, Camelia; Seidman, Gwendolyn; Yu, Shu; Wu, Anise M S; Ben-Ezra, Menachem

    2016-08-30

    Facebook has become one of the most popular social networking websites in the world. The main aim of the study was to present an international comparison of Facebook intrusion and Internet penetration while examining possible gender differences. The study consisted of 2589 participants from eight countries: China, Greece, Israel, Italy, Poland, Romania, Turkey, USA. Facebook intrusion and Internet penetration were taken into consideration. In this study the relationship between Facebook intrusion and Internet penetration was demonstrated. Facebook intrusion was slightly negatively related to Internet penetration in each country.

  10. Linking magnetic fabric and cumulate texture in layered mafic-ultramafic intrusions (Invited)

    NASA Astrophysics Data System (ADS)

    O Driscoll, B.; Stevenson, C.; Magee, C.

    2013-12-01

    Research on the magnetic fabrics of igneous rocks, pioneered by Balsley and Buddington[1] and Khan[2], has greatly contributed to our understanding of magma dynamics in lava flows, sheet intrusions and plutons over the past five decades. However, considerably few magnetic fabric studies have focused on layered mafic-ultramafic intrusions, particularly ';lopolithic' intrusions, despite the fact that such rocks may preserve a large range of small-scale kinematic structures potentially related to important magma chamber processes. This may be partly due to the fact that mafic-ultramafic cumulates commonly exhibit visible planar fabrics (mineral lamination), as well as compositional layering, in contrast to the frequent absence of such features in granite bodies or fine-grained mafic lava flows. Indeed, debates in the 1970s and 1980s on the development of layering and mineral fabrics in mafic-ultramafic intrusions, focused around the crystal settling versus in situ crystallisation paradigms, are classic in the subject of igneous petrology. Central to these debates is the notion that a wide range of magma chamber processes occur in layered mafic-ultramafic intrusions that are not frequently considered to occur in their relatively viscous granitic counterparts; in essence, the latter have historically been viewed as much more likely to ';freeze-in' a primary magma flow fabric whilst mafic-ultramafic intrusions are subjected to a more protracted solidification history. This wide array of potential initial sources for layering and mineral fabrics in layered mafic-ultramafic intrusions, together with the possible modification of textures at the postcumulus stage, demands a cautious application of any fabric analysis and presents a problem well-suited to interrogation by the AMS technique. The purpose of this contribution is to provide specific context on the application of AMS to elucidating the formation of cumulates in layered mafic-ultramafic intrusions. Examples of AMS

  11. Potassium-Argon and Lead-Alpha Ages of Plutonic Rocks, Bokan Mountain Area, Alaska.

    PubMed

    Lanphere, M A; Mackevett, E M; Stern, T W

    1964-08-14

    Most of the granitic rocks in the Bokan Mountain area, southeastern Alaska, are early Paleozoic (probably Ordovician) judged by potassium-argon and lead-alpha age measurements. The Bokan Mountain Granite, the youngest intrusive unit in the area, belongs to a Mesozoic plutonic episode. These age measurements are the first direct evidence for the emplacement of early Paleozoic granitic intrusive rocks close to the Pacific margin of North America.

  12. Potassium-argon and lead-alpha ages of plutonic rocks, Bokan Mountain area, Alaska

    USGS Publications Warehouse

    Lanphere, M.A.; MacKevett, E.M., Jr.; Stern, T.W.

    1964-01-01

    Most of the granitic rocks in the Bokan Mountain area, southeastern Alaska, are early Paleozoic (probably Ordovician) judged by potassium-argon and lead-alpha age measurements. The Bokan Mountain Granite, the youngest intrusive unit in the area, belongs to a Mesozoic plutonic episode. These age measurements are the first direct evidence for the emplacement of early Paleozoic granitic intrusive rocks close to the Pacific margin of North America.

  13. Zircon U-Pb age, Lu-Hf isotope, mineral chemistry and geochemistry of Sundamalai peralkaline pluton from the Salem Block, southern India: Implications for Cryogenian adakite-like magmatism in an aborted-rift

    NASA Astrophysics Data System (ADS)

    Renjith, M. L.; Santosh, M.; Li, Tang; Satyanarayanan, M.; Korakoppa, M. M.; Tsunogae, T.; Subba Rao, D. V.; Kesav Krishna, A.; Nirmal Charan, S.

    2016-01-01

    The Sundamalai peralkaline pluton is one among the Cryogenian alkaline plutons occurring in the Dharmapuri Rift Zone (DRZ) of the Salem Block in the Southern Granulite Terrane (SGT) of India. Here we present zircon U-Pb age and Lu-Hf isotopic composition, mineral chemistry and geochemistry of the pluton to explore the petrogenesis and geodynamic implications. Systematic modal variation of orthoclase, Na-plagioclase, Ca-amphibole (ferro-edenite and hastingsite) and quartz developed quartz-monzonite and granite litho units in the Sundamalai pluton. Thermometry based on amphibole-plagioclase pair suggests that the pluton was emplaced and solidified at around 4.6 kbar pressure with crystallization of the major phases between 748 and 661 °C. Estimated saturation temperature of zircon (712-698 °C) is also well within this range. However, apatite saturation occurred at higher temperatures between 835 and 870 °C, in contrast with monazite saturation (718-613 °C) that continued up to the late stage of crystallization. Estimated oxygen fugacity values (log fO2: -14 to -17) indicate high oxidation state for the magma that stabilized titanite and magnetite. The magmatic zircons from Sundamalai pluton yielded a weighted mean 206Pb/238U age of 832.6 ± 3.2 Ma. Geochemically, the Sundamalai rocks are high-K to shoshonitic, persodic (Na2O/K2O ratio > 1), silica-saturated (SiO2:65-72 wt.%), and peralkaline in composition (aluminum saturation index, ASI < 1; Alkalinity index, AI < 0). The initial magma was mildly metaluminous which evolved to strongly peralkaline as result of fractional crystallization (plagioclase effect) controlled differentiation between quartz-monzonite and granite. Both rock types have high content of Na2O (5.1-6.3 wt.%), Ba (350-2589 ppm) and Sr (264-1036 ppm); low content of Y (8.7-17 ppm) and Yb (0.96-1.69 ppm); elevated ratios of La/Yb (11-46) and Sr/Y (46-69) and are depleted in Ti, with a positive Sr anomaly suggesting an adakite-like composition and

  14. Non-intrusive speed sensor

    NASA Technical Reports Server (NTRS)

    Wyett, L.

    1986-01-01

    In Phase I of the Non-Intrusive Speed Sensor program, a computerized literature search was performed to identify candidate technologies for remote, non-intrusive speed sensing applications in Space Shuttle Main Engine (SSME) turbopumps. The three most promising technologies were subjected to experimental evaluation to quantify their performance characteristics under the harsh environmental requirements within the turbopumps. Although the infrared and microwave approaches demonstrated excellent cavitation immunity in laboratory tests, the variable-source magnetic speed sensor emerged as the most viable approach. Preliminary design of this speed sensor encountered no technical obstacles and resulted in viable and feasible speed nut, sensor housing, and sensor coil designs. Phase II of this program developed the variable-source magnetic speed sensor through the detailed design task and guided the design into breadboard fabrication. The speed sensor and its integral speed nut were evaluated at both unit and system level testing. The final room-temperature and cryogenic spin testing of the hardware demonstrated that the sensor was capable of generating sufficient output signal to enable remote speed sensing from 1500 to 40000 rpm over a speed nut/sensor separation of 3.5 inches.

  15. Intrusive Images in Psychological Disorders

    PubMed Central

    Brewin, Chris R.; Gregory, James D.; Lipton, Michelle; Burgess, Neil

    2010-01-01

    Involuntary images and visual memories are prominent in many types of psychopathology. Patients with posttraumatic stress disorder, other anxiety disorders, depression, eating disorders, and psychosis frequently report repeated visual intrusions corresponding to a small number of real or imaginary events, usually extremely vivid, detailed, and with highly distressing content. Both memory and imagery appear to rely on common networks involving medial prefrontal regions, posterior regions in the medial and lateral parietal cortices, the lateral temporal cortex, and the medial temporal lobe. Evidence from cognitive psychology and neuroscience implies distinct neural bases to abstract, flexible, contextualized representations (C-reps) and to inflexible, sensory-bound representations (S-reps). We revise our previous dual representation theory of posttraumatic stress disorder to place it within a neural systems model of healthy memory and imagery. The revised model is used to explain how the different types of distressing visual intrusions associated with clinical disorders arise, in terms of the need for correct interaction between the neural systems supporting S-reps and C-reps via visuospatial working memory. Finally, we discuss the treatment implications of the new model and relate it to existing forms of psychological therapy. PMID:20063969

  16. Intrusive images and intrusive thoughts as different phenomena: two experimental studies.

    PubMed

    Hagenaars, Muriel A; Brewin, Chris R; van Minnen, Agnes; Holmes, Emily A; Hoogduin, Kees A L

    2010-01-01

    According to the dual representation theory of PTSD, intrusive trauma images and intrusive verbal thoughts are produced by separate memory systems. In a previous article it was shown that after watching an aversive film, participants in non-movement conditions reported more intrusive images than participants in a free-to-move control condition (Hagenaars, Van Minnen, Holmes, Brewin, & Hoogduin, 2008). The present study investigates whether the experimental conditions of the Hagenaars et al. study had a different effect on intrusive thoughts than on intrusive images. Experiment 2 further investigated the image-thoughts distinction by manipulating stimulus valence (trauma film versus neutral film) and assessing the subsequent development of intrusive images and thoughts. In addition, both experiments studied the impact of peri-traumatic emotions on subsequent intrusive images and thoughts frequency across conditions. Results showed that experimental manipulations (non-movement and trauma film) caused higher levels of intrusive images relative to control conditions (free movement and neutral film) but they did not affect intrusive thoughts. Peri-traumatic anxiety and horror were associated with subsequent higher levels of intrusive images, but not intrusive thoughts. Correlations were inconclusive for anger and sadness. The results suggest intrusive images and thoughts can be manipulated independently and as such can be considered different phenomena. PMID:20391178

  17. 'Tetl' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image, taken by the panoramic camera on NASA's Mars Exploration Rover Spirit during the rover's trek through the 'Columbia Hills' at 'Gusev Crater,' shows the horizontally layered rock dubbed 'Tetl.' Scientists hope to investigate this rock in more detail, aiming to determine whether the rock's layering is volcanic or sedimentary in origin. If for some reason this particular rock is not favorably positioned for grinding and examination by the toolbox of instruments on the rover's robotic arm, Spirit will be within short reach of another similar rock, dubbed 'Coba.' Spirit took this image on its 264th martian day, or sol (Sept. 29, 2004). This is a false-color composite image generated from the panoramic camera's 750-, 530-, and 430-nanometer filters.

  18. The Eagle and East Eagle sulfide ore-bearing mafic-ultramafic intrusions in the Midcontinent Rift System, upper Michigan: Geochronology and petrologic evolution

    NASA Astrophysics Data System (ADS)

    Ding, Xin; Li, Chusi; Ripley, Edward M.; Rossell, Dean; Kamo, Sandra

    2010-03-01

    The Eagle and East Eagle intrusions are small, subvertical dike-like mafic-ultramafic bodies that cut Proterozoic sedimentary strata in the Baraga Basin in northern Michigan. The Eagle intrusion hosts a newly discovered magmatic Ni-Cu-PGE deposit. The nearby East Eagle intrusion also contains sulfide mineralization, but the extent of this mineralization has yet to be determined by further drilling. Both intrusions contain olivine-bearing rocks such as feldspathic peridotite, melatroctolite, and olivine melagabbro. Sulfide accumulations range from disseminated at both Eagle and East Eagle to semimassive and massive at Eagle. U-Pb baddeleyite dating gives a crystallization age of 1107.2 ± 5.7 Ma for the Eagle intrusion, coeval with eruption of picritic basalts at the base of the volcanic succession in the Midcontinent Rift System (MRS). The Fo contents of olivine cores in the Eagle and East Eagle intrusions vary between 75 and 85 mol %, higher than those of olivine in larger layered intrusions in the MRS such as the Duluth Complex. The FeO/MgO ratios and Al2O3 contents of the parental magmas for the Eagle and East Eagle intrusions inferred from olivine and spinel compositions are similar to those of picritic basalts in the base of the MRS volcanic succession. These petrochemical data suggest that the Eagle and East Eagle intrusions are the intrusive equivalents of high-MgO basalts that erupted in the early stages of continental magmatism associated with the development of the rift. Variations in mineral compositions and incompatible trace element ratios suggest that at least three major pulses of magmas were involved in the formation of low-sulfide rocks in the Eagle intrusion. Lower Fo contents of olivine associated with semimassive sulfides as compared to that of olivine in low-sulfide rocks suggest that the magma associated with the semimassive sulfide was more fractionated than the parental magmas of the low-sulfide rocks in the Eagle intrusion. Accumulation of

  19. Magmatic intrusions and hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Gulick, Virginia Claire

    1993-01-01

    This dissertation investigates the possible role of hydrothermally driven ground-water outflow in the formation of fluvial valleys on Mars. Although these landforms have often been cited as evidence for a past warmer climate and denser atmosphere, recent theoretical modeling precludes such climatic conditions on early Mars when most fluvial valleys formed. Because fluvial valleys continued to form throughout Mars' geological history and the most Earth-like stream valleys on Mars formed well after the decline of the early putative Earth-like climate, it may be unnecessary to invoke drastically different climatic conditions for the formation of the earliest stream valleys. The morphology of most Martian fluvial valleys indicates formation by ground-water sapping which is consistent with a subsurface origin. Additionally, many Martian fluvial valleys formed on volcanoes, impact craters, near fractures, or adjacent to terrains interpreted as igneous intrusions; all are possible locales of vigorous, geologically long-lived hydrothermal circulation. Comparison of Martian valley morphology to similar features on Earth constrains valley genesis scenarios. Volumes of measured Martian fluvial valleys range from 1010 to 1013 m3. Based on terrestrial analogs, total water volumes required to erode these valleys range from approximately 1010 to 1015 m3. The clustered distribution of Martian valleys within a given terrain type, the sapping dominated morphology, and the general lack of associated runoff valleys all indicate the importance of localized ground-water outflow in the formation of these fluvial systems. An analytic model of a conductively cooling cylindrical intrusion is coupled with the U.S. Geological Survey's numerical ground-water computer code SUTRA to evaluate the magnitude of ground-water outflow expected from magmatically-driven hydrothermal systems on Mars. Results indicate that magmatic intrusions of several 102 km3 or larger can provide sufficient ground

  20. Legal Vs. Psychological Aspects of Intrusiveness.

    ERIC Educational Resources Information Center

    Binder, Virginia L.

    Court decisions stressing the rights of mental patients have necessitated a radical revision in the management of behavioral treatment programs. The client's rights to the least intrusive procedures to achieve treatment goals have become important in case law. Factors which identify intrusiveness include: (1) the extent to which the "new mental…

  1. Reduction of Attrition Through Intrusive Advising.

    ERIC Educational Resources Information Center

    Glennen, Robert E.; Baxley, Dan M.

    1985-01-01

    Examines the effects of an intrusive advising program on the attrition rate of college freshmen and sophomores. Identifies reasons students drop out and outlines an advising program used at Western New Mexico University. Results showed the intrusive advising program to be effective in reducing attrition rates. (BH)

  2. Emotional and Behavioral Reaction to Intrusive Thoughts

    ERIC Educational Resources Information Center

    Berry, Lisa-Marie; May, Jon; Andrade, Jackie; Kavanagh, David

    2010-01-01

    A self-report measure of the emotional and behavioral reactions to intrusive thoughts was developed. The article presents data that confirm the stability, reliability, and validity of the new seven-item measure. Emotional and behavioral reactions to intrusions emerged as separate factors on the Emotional and Behavioral Reactions to Intrusions…

  3. Vapour Intrusion into Buildings - A Literature Review

    EPA Science Inventory

    This chapter provides a review of recent research on vapour intrusion of volatile organic compounds (VOCs) into buildings. The chapter builds on a report from Tillman and Weaver (2005) which reviewed the literature on vapour intrusion through 2005. Firstly, the term ‘vapour intru...

  4. Art Rocks with Rock Art!

    ERIC Educational Resources Information Center

    Bickett, Marianne

    2011-01-01

    This article discusses rock art which was the very first "art." Rock art, such as the images created on the stone surfaces of the caves of Lascaux and Altimira, is the true origin of the canvas, paintbrush, and painting media. For there, within caverns deep in the earth, the first artists mixed animal fat, urine, and saliva with powdered minerals…

  5. Magnetic Fabrics in the Bjerkreim Sokndal Layered Intrusion

    NASA Astrophysics Data System (ADS)

    Biedermann, Andrea R.; Jackson, Mike; McEnroe, Suzanne A.; Michels, Alexander

    2016-04-01

    The Bjerkreim Sokndal (BKSK) layered intrusion in Southern Norway covers 230 km2 and was emplaced 930 Ma ago by several pulses of jotunitic magma. It forms a syncline with strong foliation on the limbs. The rocks consist of plagioclase-pyroxene cumulates, and contain two magnetic minerals, magnetite and hemo-ilmenite. Earlier studies suggest that the remanent magnetization in the rocks is carried by lamellar hemo-ilmenite. Hemo-ilmenite displays a strong anisotropy of magnetic susceptibility and therefore we are interested in the magnetic fabrics of the rocks from the BKSK intrusion. Magnetic fabrics have been characterized for 60 sites, with a main focus on the so-called MCU IVe' unit, which generates a strong negative aeromagnetic anomaly. In order to define the carriers of the magnetic fabrics, anisotropy of anhysteretic remanent magnetization (AARM), anisotropy of isothermal remanent magnetization (AIRM) and anisotropy of thermal remanent magnetization (ATRM) were measured in addition to low-field anisotropy of magnetic susceptibility (LF-AMS). AIRM and ATRM were partially demagnetized in an attempt to isolate the magnetic fabrics due to high-coercivity hemo-ilmenite. Initial results show a strong AARM which is coaxial to the LF-AMS. Partially demagnetized AIRM and ATRM are not significant. This indicates a strong contribution of a low-coercivity phase such as magnetite. The high-coercivity hemo-ilmenite anisotropy could not be isolated in samples that contain both magnetite and hemo-ilmenite. Samples that are free of magnetite show a strong LF-AMS, but anisotropy of remanent magnetization is in general not significant. This suggests that higher fields would be needed to isolate the hemo-ilmenite fabric. Mineral fabric data will be used to determine whether the magnetite anisotropy is influenced by the orientation of hemo-ilmenite lamellae.

  6. Prediction of sea water intrusion for mining activity in close precincts of sea shore.

    PubMed

    Singh, Awanindra Pratap; Gupta, Prem Kumar; Khandelwal, Manoj

    2013-01-01

    The mining lease area of Surka [District Bhavnagar, Gujarat (India)] is located within 6-12 km horizontal distance of sea shore of Gulf of Cambay. Whenever, there will be onset of lignite extraction, there will be always a threat of sea water intrusion into the mining lease area due to its close proximity to seashore. This article describes the prediction of sea water intrusion into the lease area of whole mining block using Ghyben-Herzberg relation between fresh and saline water, Remote Sensing, Ground Truth verification, Electrical Resistivity Survey and groundwater table monitored during the year 2004. As per the Ghyben-Herzberg relation, results show that there will not be sea water intrusion. If there is excess pumping of water then also the basement rock below the lignite seam will put hindrance to any possible upconing of saline water interface. PMID:24083098

  7. Petrogenesis of the Late Triassic volcanic rocks in the Southern Yidun arc, SW China: Constraints from the geochronology, geochemistry, and Sr-Nd-Pb-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Leng, Cheng-Biao; Huang, Qiu-Yue; Zhang, Xing-Chun; Wang, Shou-Xu; Zhong, Hong; Hu, Rui-Zhong; Bi, Xian-Wu; Zhu, Jing-Jing; Wang, Xin-Song

    2014-03-01

    Studies on zircon ages, petrology, major and trace element geochemistry, and Sr-Nd-Hf-Pb isotopic geochemistry of intermediate volcanic rocks from the Southern Yidun arc, Sanjiang-Tethyan Orogenic Belt, SW China have been undertaken in this paper. They are used to discuss the petrogenesis of these rocks and to constrain the tectonic setting and evolution of the Yidun arc. These intermediate volcanic rocks were erupted at ca. 220 Ma (U-Pb zircon ages). Trachyandesite is the dominant lithology among these volcanic rocks, and is mainly composed of hornblende and plagioclase, with minor clinopyroxene and biotite. A hornblende geobarometer suggests that the stagnation of magma in the lower crust, where plagioclase crystallization was suppressed while hornblende crystallized, giving rise to high Sr/Y ratios that are one of the distinguishing features of adakites, after the primary magma originated from the lithospheric mantle wedge. Steeply right-inclined Rare Earth Element (REE) pattern combined with high La/Yb ratios suggests adakitic affinity of these volcanic rocks, implying that slab-melt from the subducting oceanic crust is a necessary component in the primary magma. Besides, trace element geochemistry and isotopic geochemistry also indicate that partial melting of pelagic sediments in the subduction zone and noticeable contamination with the lower crust were involved in the evolution of parental magma of these volcanic rocks. Based on previous work on the Northern Yidun arc and this study, we propose that the subduction was initiated in the Northern Yidun arc and extended to the southern part and that the Northern Yidun arc is an island arc while the Southern Yidun arc represents a continental arc, probably caused by the existence of the Zhongza Massif, that was invoked to be derived from Yangtze Block, as a possible basement of the Southern Yidun arc.

  8. Terby's Rocks

    NASA Technical Reports Server (NTRS)

    2006-01-01

    27 January 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the light-toned, layered, sedimentary rock outcrops in northern Terby Crater. Terby is located along the north edge of Hellas Planitia. The sedimentary rocks might have been deposited in a greater, Hellas-filling sea -- or not. Today, the rocks are partly covered by dark-toned sediment and debris.

    Location near: 27.2oS, 285.3oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  9. The Torres del Paine intrusion as a model for a shallow magma chamber

    NASA Astrophysics Data System (ADS)

    Baumgartner, Lukas; Bodner, Robert; Leuthold, Julien; Muntener, Othmar; Putlitz, Benita; Vennemann, Torsten

    2014-05-01

    The shallow magmatic Torres del Paine Intrusive Complex (TPIC) belongs to a series of sub-volcanic and plutonic igneous bodies in Southern Chile and Argentina. This trench-parallel belt is located in a transitional position between the Patagonia Batholith in the West, and the alkaline Cenozoic plateau lavas in the East. While volumetrically small amounts of magmatism started around 28 my ago in the Torres del Paine area, and a second period occurred between 17-16 Ma, it peaked with the TPIC 12.59-12.43 Ma ago. The spectacular cliffs of the Torres del Paine National park provide a unique opportunity to study the evolution of a very shallow magma chamber and the interaction with its host rocks. Intrusion depth can be estimated based on contact metamorphic assemblages and granite solidus thermobarometry to 750±250 bars, corresponding to an intrusion depth of ca. 3km, ca. 500m above the base of the intrusion. Hornblende thermobarometry in mafic rocks agrees well with these estimates (Leuthold et al., 2014). The TPIC is composed of a granitic laccolith emplaced over 90ka (Michel et al., 2008) in 3 major, several 100m thick sheets, forming an overall thickness of nearly 2 km. Contacts are sharp between sheets, with the oldest sheet on the top and the youngest on the bottom (Michel et al., 2008). The granitic laccolith is under-plated by a ca. 400m thick mafic laccolith, built up over ca. 50ka (Leuthold et al. 2012), constructed from the bottom up. Granitic and mafic sheets are themselves composed of multiple metric to decametric pulses, mostly with ductile contacts between them, resulting in outcrop patterns resembling braided stream sediments. The contact of the TPIC with the Cretaceous flysch sediments document intrusion mechanism. Pre-existing sub-horizontal fold axes are rotated in the roof of the TPIC, clearly demonstrating ballooning of the roof; no ballooning was observed in the footwall of the intrusion. Extension during ballooning of the roof is indicated by

  10. Intrusion detection using secure signatures

    DOEpatents

    Nelson, Trent Darnel; Haile, Jedediah

    2014-09-30

    A method and device for intrusion detection using secure signatures comprising capturing network data. A search hash value, value employing at least one one-way function, is generated from the captured network data using a first hash function. The presence of a search hash value match in a secure signature table comprising search hash values and an encrypted rule is determined. After determining a search hash value match, a decryption key is generated from the captured network data using a second hash function, a hash function different form the first hash function. One or more of the encrypted rules of the secure signatures table having a hash value equal to the generated search hash value are then decrypted using the generated decryption key. The one or more decrypted secure signature rules are then processed for a match and one or more user notifications are deployed if a match is identified.

  11. Intrusion-Aware Alert Validation Algorithm for Cooperative Distributed Intrusion Detection Schemes of Wireless Sensor Networks

    PubMed Central

    Shaikh, Riaz Ahmed; Jameel, Hassan; d’Auriol, Brian J.; Lee, Heejo; Lee, Sungyoung; Song, Young-Jae

    2009-01-01

    Existing anomaly and intrusion detection schemes of wireless sensor networks have mainly focused on the detection of intrusions. Once the intrusion is detected, an alerts or claims will be generated. However, any unidentified malicious nodes in the network could send faulty anomaly and intrusion claims about the legitimate nodes to the other nodes. Verifying the validity of such claims is a critical and challenging issue that is not considered in the existing cooperative-based distributed anomaly and intrusion detection schemes of wireless sensor networks. In this paper, we propose a validation algorithm that addresses this problem. This algorithm utilizes the concept of intrusion-aware reliability that helps to provide adequate reliability at a modest communication cost. In this paper, we also provide a security resiliency analysis of the proposed intrusion-aware alert validation algorithm. PMID:22454568

  12. The fate of mafic and ultramafic intrusions in the continental crust

    NASA Astrophysics Data System (ADS)

    Roman, Alberto; Jaupart, Claude

    2016-11-01

    Geochemical and petrological data indicate that the bulk continental crust results from the fractionation of basaltic magmas followed by the foundering of residual mafic cumulates. Structural and geological evidence for foundering has been elusive and it is argued that it lies in the shapes of mafic intrusions that have been preserved in the crust. Numerical calculations of visco-elasto-plastic deformation induced by a dense intrusive body in continental crust have been carried out for a wide range of physical conditions. Three regimes are defined on the basis of the amount of dense material that remains at the original emplacement level as well as on the shape of the residual body. With strong encasing rocks, the intrusion deforms weakly in a sagging regime characterized by downwarping of the floor. At the other extreme, the intrusion sinks through weak surroundings, leaving behind a very small volume of material. In an intermediate regime, the intrusion does not sink wholesale and undergoes a dramatic change of shape. A residual body is preserved with a shape that depends on the aspect ratio of the initial intrusion. For aspect ratios of order one, the residual body is funnel-shaped above a thin and deep vertical extension. For the small aspect ratios that typify large igneous complexes such as the Bushveld, South Africa, the residual body is characterized by thick peripheral lobes with inward-dipping igneous layers and a thinner central area that has lost some of the basal cumulates. The transitions between these regimes depend on the rheology and temperature of encasing rocks.

  13. Rock Garden

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This false color composite image of the Rock Garden shows the rocks 'Shark' and 'Half Dome' at upper left and middle, respectively. Between these two large rocks is a smaller rock (about 0.20 m wide, 0.10 m high, and 6.33 m from the Lander) that was observed close-up with the Sojourner rover (see PIA00989).

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

  14. Enhanced rock discrimination using Landsat-5 Thematic Mapper (TM) data

    NASA Technical Reports Server (NTRS)

    Blodget, H. W.; Andre, C. G.; Marcell, R. F.

    1985-01-01

    The application of TM data to rock discrimination is discussed. Sixteen specific terrains derived from geologic maps are examined on TM images of the Arabian shield obtained on Apr. 14, 1984; visual enhancement procedures are applied to the images. The rock types observed in the test site are described; the major sedimentary formations in the test area are laterite and sandstone. The data reveal that the layered rocks in the outcrop consist of a variety of metamorphosed volcanics, metamorphosed sediments, and amphibolite, and the intrusive complex is composed of several classes of mafic and acidic rocks.

  15. 'Lutefisk' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Figure 1

    NASA's Mars Exploration Rover Spirit used its panoramic camera to take this image of a rock called 'Lutefisk' on the rover's 286th martian day (Oct. 22, 2004). The surface of the rock is studded with rounded granules of apparently more-resistant material up to several millimeters (0.1 inch) or more across. The visible portion of Lutefisk is about 25 centimeters (10 inches) across.

  16. Dynamics of tectonic nappes: Thrusting versus intrusion or dynamic pressure versus lithostatic pressure

    NASA Astrophysics Data System (ADS)

    Markus Schmalholz, Stefan; Podladchikov, Yuri; Medvedev, Sergei

    2014-05-01

    Despite extensive research, the dynamics of tectonic nappes exhibiting high and ultra-high pressure ((U)HP) rocks is still debated. We classify existing models for nappe formation into two types, and refer to them as thrust and intrusion model. Thrust models approximate the orogen as wedge with a rigid buttress behind and a subducting lithospheric slab beneath. The dominant process of nappe formation is thrusting (brittle and/or ductile) that generates a dominant top-to-the-foreland shear sense. Rocks remain within crustal depth (<~60 km). Uplift and exhumation of (U)HP rocks is explained by underplating accompanied by isostatic uplift, extension in higher levels of the wedge and erosion. Thrust models can explain the imbricate nappe stacking and first-order structural observations in the Western Alps. However, in the last decades (U)HP rocks were found in nappes, and it is usually assumed that metamorphic pressure is a good indicator of maximum burial. This assumption represents a fundamental problem for the thrust model, namely to account for the large burial depth of (U)HP rocks indicating depths >100 km. Nappe formation at such mantle depths cannot be explained by the thrust model. In intrusion models (U)HP rocks are subducted to mantle depths and return to crustal depths by buoyancy driven or tectonically forced flow. Nappes are formed during the return flow with an opposite shear sense at the bottom and top of the nappe. Intrusion models could reproduce the first-order patterns of P-T-time paths of the Western Alps. However, there are problems with intrusion models. First, the intrusion scenario requires a major extensional shear zone in the hanging wall of the exhuming (U)HP unit. However, for most (U)HP units of the Western Alps the earliest coherent structures recorded along the upper boundary are top-to-the-foreland shear zones (consistent with thrust models). Second, dynamic intrusion models are usually unable to generate an imbricate nappe stack. The

  17. The Patuki intrusive suite: closed-system fractionation beneath a slow-spreading ridge

    NASA Astrophysics Data System (ADS)

    Sivell, W. J.; Waterhouse, J. B.

    A wide range of mafic and ultramafic rock types, together with cogenetic silicic plagiogranites, form a structurally coherent intrusive sequence within the Patuki Volcanics at south D'Urville Island, New Zealand. In addition, gabbroic rocks comprise abundant tectonic inclusions in highly-sheared, concordant serpentinite bands which intrude the Patuki suite. Chemical evidence suggests many of the gabbros, including those in which recrystallization has obliterated original textures, represent magmatic cumulates and indicates extensive closed-system fractionation analogous to that known to occur beneath slow-spreading mid-oceanic ridges. Dyke intrusion occurred throughout the generation of the suite. An early stage of spreading is suggested by the anomalously low thickness of the sequence, the non-sheeted nature of the dyke suite and chemical characteristics of the lavas which comprise the extrusive component of the ophiolite.

  18. Geophysical Survey and Detailed Geologic Mapping of an Eroded Stratovolcano's Central Intrusive Complex, Summer Coon, Co.

    NASA Astrophysics Data System (ADS)

    Harp, A.

    2015-12-01

    Eroded volcanoes expose plumbing systems that provide important information on intrusive geometries, magma propagation directions, and the effects of host rock types and heterogeneities. Summer Coon Volcano, CO, is an Oligocene stratovolcano where erosion has removed much of the original edifice, revealing the intrusive stocks of the central intrusive complex (CIC). Surrounding the CIC are hundreds of radial dikes ranging from basaltic to rhyolitic in composition. Published geologic maps indicate most radial dikes do not connect to the intrusive stocks, supporting published theories that most did not emanate from the central intrusions. However, much of the area surrounding the CIC is covered by alluvium, suggesting that the lack of connection might be an artifact of exposure. We completed a ground magnetic survey and detailed geological mapping to determine if the dikes continue beneath the alluvium and into the intrusive stocks. Linear magnetic anomalies indicate four NW-SE trending rhyodacite dikes continue beneath the alluvium for up to 250 m, and mapping indicates that at least two of the rhyodacite dikes do extend into the CIC. Shorter linear anomalies are attributed to seven NW-SE trending basaltic dikes ~100-500-m-long which are sparsely exposed in the alluvium. Mapping shows that three rhyodacite dikes extend into the CIC and to within 200 m of their possible source, an 800-m-wide granodiorite stock. Additionally, three rhyolitic dikes extend to within several meters of a 200×500-m-wide tuff breccia zone of similar composition, likely their source. In summary, magnetic data and detailed mapping indicate that radial dikes do extend into the central intrusive complex in contrast to some model predictions.

  19. Self-report may underestimate trauma intrusions.

    PubMed

    Takarangi, Melanie K T; Strange, Deryn; Lindsay, D Stephen

    2014-07-01

    Research examining maladaptive responses to trauma routinely relies on spontaneous self-report to index intrusive thoughts, which assumes people accurately recognize and report their intrusive thoughts. However, "mind-wandering" research reveals people are not always meta-aware of their thought content: they often fail to notice shifts in their attention. In two experiments, we exposed subjects to trauma films, then instructed them to report intrusive thoughts during an unrelated reading task. Intermittently, we asked whether they were thinking about the trauma. As expected, subjects often spontaneously reported intrusive thoughts. However, they were also "caught" engaging in unreported trauma-oriented thoughts. The presence and frequency of intermittent probes did not influence self-caught intrusions. Both self-caught and probe-caught intrusions were related to an existing tendency toward intrusive cognition, film-related distress, and thought suppression attempts. Our data suggest people may lack meta-awareness of trauma-related thoughts, which has implications for theory, research and treatment relating to trauma-related psychopathology. PMID:24993526

  20. Evaluation of geologic materials to limit biological intrusion into low-level radioactive waste disposal sites

    SciTech Connect

    Hakonson, T.E.

    1986-02-01

    This report describes the results of a three-year research program to evaluate the performance of selected soil and rock trench cap designs in limiting biological intrusion into simulated waste. The report is divided into three sections including a discussion of background material on biological interactions with waste site trench caps, a presentation of experimental data from field studies conducted at several scales, and a final section on the interpretation and limitations of the data including implications for the user.

  1. Association rule mining in intrusion detection systems

    NASA Astrophysics Data System (ADS)

    Zhao, Dong; Lu, Yan-sheng

    2004-04-01

    In a modern computer system, intrusion detection has become an essential and critical component. Data mining generally refers to the process of extracting models from large stores of data. The intrusion detection system first apply data mining programs to audit data to compute frequent patterns, extract features, and then use classification algorithms to compute detection models. The most important step of this process is to determine relations between fields in the database records to construct features. The standard association rules have not enough expressiveness. Intrusion detection system can extract the association rule with negations and with varying support thresholds to get better performance rather than extract the standard association rule.

  2. Advanced technologies for perimeter intrusion detection sensors

    SciTech Connect

    Williams, J.D.

    1995-03-01

    The development of integrated circuit fabrication techniques and the resulting devices have contributed more to the advancement of exterior intrusion detectors and alarm assessment devices than any other technology. The availability of this technology has led to the improvements in and further development of smaller more powerful computers, microprocessors, solid state memories, solid state cameras, thermal imagers, low-power lasers, and shorter pulse width and higher frequency electronic circuitry. This paper presents information on planning a perimeter intrusion detection system, identifies the site characteristics that affect its performance, and describes improvements to perimeter intrusion detection sensors and assessment devices that have been achieved by using integrated circuit technology.

  3. Oxygen- and strontium-isotopic studies of the skye intrusive complex, northwest Scotland

    SciTech Connect

    Smith, B.M.

    1981-01-01

    This dissertation is comprised of three parts, each of which addresses some aspect of the meteoric-hydrothermal fluid/rock interaction which affected the rocks within and near the Skye intrusive complex. Part 1 was undertaken to determine the scale and magnitude of hydrothermal Sr contamination in the Coire Uaigneich Granophyre (CUG). Sr- and O-isotopic and electron microprobe results show that Sr was mobile in the low-/sup 18/O meteoric-hydrothermal fluids, that Sr-exchange between these fluids and the CUG was limited to thin (less than or equal to 1 cm) zones of bleached and albitized granophyre adjacent to fractures, and that the scale of O-exchange was much larger. Part 2 focuses on the stable isotopic and mineralogical compositions of the Beinn an Dubhaich Granite and its Durness Limestone host rocks. Part 3 is an attempt to discriminate between magmatic and subsolidus /sup 18/O depletions in porphyritic felsitic dikes from two widely separated regions of the intrusive complex. Eastern Red Hills felsites, collected approximately 9 km from the exposed margin of the Cuillins intrusion, probably crystallized from O-isotopically normal magmas. Empirical and experimental data on the kinetics of volume diffusion of oxygen in feldspar minerals and quartz (in the presence of H/sub 2/O) suggest that the /sup 18/O depletion in quartz and feldspar from the SPF may be attributed to very high-temperature (>600/sup 0/C) subsolidus exchange with circulating low-/sup 18/O fluids.

  4. The age and origin of felsic intrusions of the Thetford Mines ophiolite, Quebec.

    USGS Publications Warehouse

    Clague, D.A.; Frankel, C.S.; Eaby, J.S.

    1985-01-01

    This ophiolite was obducted in the early Ordovician during the closing of the proto-Atlantic. The tectonized peridotite of the lower unit of the ophiolite is intruded by felsic dykes and pods, including isolated lenses of massive rodingite, small bodies of strongly deformed diorite, and younger, less deformed monzonite. These intrusions are found only near the base of the ophiolite, and are considered to have been emplaced before the ophiolite reached its present position. The young group of intrusions consists of biotite-muscovite quartz monzonite and leuco-quartz monzonite. Analysed samples have high K2O, high (K2O X 100)/Na2O + K2O) ratios, and high initial Sr ratios, indicating that the magma source was continental and that these felsic rocks formed by partial melting of continental sediments. Whole-rock and mineral isochron ages suggest that the felsic intrusions are approx 456 + or - 4 m.y. old and that they were metamorphosed approx 418 + or - 7 m.y. ago. The detachment of the ophiolite occurred approx 491 + or - 3 m.y. ago. The felsic dykes were intruded approx 35 m.y. later, during the Taconic orogeny. The lengthy time between detachment and final nappe emplacement recorded by the felsic dykes may be a requirement for formation of abundant asbestiform chrysotile. Whole-rock analyses (16) and Rb, Sr and 87Sr/86Sr data from the Colline de Granite, King Mts., Vimy Ridge and Black Lake samples are presented.-P.Br.

  5. AIDE - Advanced Intrusion Detection Environment

    SciTech Connect

    Smith, Cathy L.

    2013-04-28

    Would you like to know when someone has dropped an undesirable executable binary on our system? What about something less malicious such as a software installation by a user? What about the user who decides to install a newer version of mod_perl or PHP on your web server without letting you know beforehand? Or even something as simple as when an undocumented config file change is made by another member of the admin group? Do you even want to know about all the changes that happen on a daily basis on your server? The purpose of an intrusion detection system (IDS) is to detect unauthorized, possibly malicious activity. The purpose of a host-based IDS, or file integrity checker, is check for unauthorized changes to key system files, binaries, libraries, and directories on the system. AIDE is an Open Source file and directory integrity checker. AIDE will let you know when a file or directory has been added, deleted, modified. It is included with the Red Hat Enterprise 6. It is available for other Linux distros. This is a case study describing the process of configuring AIDE on an out of the box RHEL6 installation. Its goal is to illustrate the thinking and the process by which a useful AIDE configuration is built.

  6. 3D-Seismic images reveal the external structure of igneous intrusions, off-shore New Zealand

    NASA Astrophysics Data System (ADS)

    Christiansen, E. H.; Luke, J.; Keach, R. W., II

    2011-12-01

    Several volcano-plutonic complexes are imaged in a 3D seismic survey by Pogo New Zealand/Plains Exploration. The data provide insight into the sizes, shapes, and wall rock deformation associated with emplacement of plutons. The magmatic rocks are part of the Mohakatino Volcanic Centre (15 to 1.6 Ma) that intrudes and partially fills the Taranaki graben. Imaged plutons range from >1 to 12 km across. The large intrusions are steep-sided and do not resemble sills, but their bases are poorly resolved. The top of the complex is sharply delineated and marked by multiple apophyses as much as 2 km across and hundreds of meters high. Deformation along the sides of the intrusion is dominated by highly attenuated dipping strata with apparent dips >45°. Dips decrease away from the intrusion but doming extends several hundred meters from the margins. High-angle faults fan out from the margin of the pluton and cut the folded strata along the margin. These faults terminate against the intrusion, extend as much as 1 pluton diameter away from the margin, and then merge with regional normal faults that are part of the graben. Offset along these faults is on the order of a few hundred meters. Strata on the top of the complex are thinned and deformed into a faulted dome with an amplitude of about 1 km. Steep, dip-slip faults form a semi-radial pattern in the roof rocks but their orientations are strongly controlled by the regional stress field as many of the faults are sub-parallel to those that form the graben. The longest roof faults are about the same length as the diameter of the pluton and cut through approximately 1 km of overlying strata, but offset gradually diminishes vertically away from the top of the intrusion. The pluton appears to be composite and formed from multiple, steep-sided intrusions as evidenced by the complex margins, roof domes, and multiple apophyses. Small sills are apparent several hundreds of meters above the top of the main complex. Multiple episodes of

  7. Autonomous Rule Creation for Intrusion Detection

    SciTech Connect

    Todd Vollmer; Jim Alves-Foss; Milos Manic

    2011-04-01

    Many computational intelligence techniques for anomaly based network intrusion detection can be found in literature. Translating a newly discovered intrusion recognition criteria into a distributable rule can be a human intensive effort. This paper explores a multi-modal genetic algorithm solution for autonomous rule creation. This algorithm focuses on the process of creating rules once an intrusion has been identified, rather than the evolution of rules to provide a solution for intrusion detection. The algorithm was demonstrated on anomalous ICMP network packets (input) and Snort rules (output of the algorithm). Output rules were sorted according to a fitness value and any duplicates were removed. The experimental results on ten test cases demonstrated a 100 percent rule alert rate. Out of 33,804 test packets 3 produced false positives. Each test case produced a minimum of three rule variations that could be used as candidates for a production system.

  8. How Jurassic Folds Control the Geometry of a Tertiary Intrusion: Trachyte Mesa, Henry Mountains, Utah

    NASA Astrophysics Data System (ADS)

    Kiyosugi, K.; Connor, C.; Wetmore, P. H.; Roman, D. C.

    2009-12-01

    Mechanisms of igneous intrusion are important to understand for improving forecasts of volcanic activity and to interpret geophysical results gathered on volcanoes. An igneous intrusion in the Henry Mountains, Utah was mapped and found to have remarkable features: First, the magma was more dense than the surrounding host rocks and therefore injected under pressure, rather than buoyantly ascending. Second, it intruded along the axis of a syncline and in between beds of Entrada sandstone. Thus, the intrusion of dense magma was strongly controlled by pre-existing structure and magma pressure or rigidity contrasts in the host rock. We attempted to simulate the conditions of this intrusion with analog experiments in blocks of gelatin solidified in 15 cm x 15 cm x 15 cm plastic tanks. Two types of gelatin block were used: The first consisted of two layers, with a more rigid upper layer and a layer boundary molded into folds. To simulate magma intrusion, air was injected into the gelatin block from a hole in the bottom of the tank with a syringe. The air crack then ascended buoyantly in the gelatin block. The second type of gelatin block had uniform rigidity but a fold was precut in the upper part of gelatin block. In this case, both air and dyed sugar water, more dense than the gelatin block, were injected into the base of the tank. Because of the lack of buoyancy, continuous injection pressure was applied to extend the water crack upward in the gelatin block. In the first experiment, the rigidity contrast worked as a barrier to upward air crack ascent, but did not simulate fluid concentration along the axis of a syncline as observed in the Trachyte Mesa intrusion. Experiments with the precut gelatin block showed two different results based on the density contrast between the injected fluid and gelatin: When air was injected into a gelatin block, the air crack arrested in the anticline after arriving at the precut fold. However, when denser sugar water was injected into

  9. A General Model for Shallow Magmatic Intrusions

    NASA Astrophysics Data System (ADS)

    Thorey, C.; Michaut, C.

    2015-12-01

    Shallow magmatic intrusions make room for themselves by upward bending of the elastic overburden. Previous studies have shown that the bending of the overlying layer first controls the dynamics. Then, when the radius reaches a few times the flexural wavelength of the overburden, it transitions to a gravity current regime. This model predicts the appropriate geometry for both terrestrial laccoliths and large mafic sills. However, it underestimates the absolute dimensions of these magmatic intrusions; in particular, it requires abnormally high viscosity to reconcile both observations and predictions. To get some insights into the effective flow viscosity, we develop a model that account for the cooling of such elastic-plated gravity currents. We show that the coupling between the temperature field and the flow itself leads to the formation of a highly viscous region at the tip that slows down the spreading in both regimes. The intrusions are predicted to be thicker and their dimensions, especially in the bending regime, are now consistent with observations. By introducing the potentially complex structure of the overburden, we also show that the topography largely contributes to constrain the final intrusion morphology. For instance, in the case of an intrusion centered below a circular depression, the model predicts that the lithostatic increase at the crater rim prevents the magma from spreading laterally and enhances the thickening of the intrusion. This model has already proven successful in reproducing the deformations observed on potential intrusion centered below lunar impact craters. Caldera complexes often exhibit ground deformations that might be associated to the formation of shallow magmatic intrusions. InSAR imaging and GPS measurements now provide efficient tools to monitor these deformations. We conclude this study by examining the ability of the model to reproduce the deformation observed in several caldera complexes.

  10. [Intrusive care and the nursing approach].

    PubMed

    Bécu, Anays Vaplet; Viltart, Valérie

    2015-04-01

    All caregivers who listen to patients will hear them tell their experience of the intrusive nature of care, whether it be basic, technical, educational or relational. The relational approach implemented by nurses enables them to identify organisational and behavioural methods which favour the establishment of a climate of trust. It helps them appropriate this interdisciplinary approach to caregiving, limiting as much as possible the intrusion felt by the patient during their hospital stay. PMID:26043629

  11. 10 CFR 63.322 - Human intrusion scenario.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 2 2011-01-01 2011-01-01 false Human intrusion scenario. 63.322 Section 63.322 Energy... REPOSITORY AT YUCCA MOUNTAIN, NEVADA Postclosure Public Health and Environmental Standards Human Intrusion Standard § 63.322 Human intrusion scenario. For the purposes of the analysis of human intrusion, DOE...

  12. 10 CFR 63.322 - Human intrusion scenario.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 2 2013-01-01 2013-01-01 false Human intrusion scenario. 63.322 Section 63.322 Energy... REPOSITORY AT YUCCA MOUNTAIN, NEVADA Postclosure Public Health and Environmental Standards Human Intrusion Standard § 63.322 Human intrusion scenario. For the purposes of the analysis of human intrusion, DOE...

  13. 10 CFR 63.322 - Human intrusion scenario.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 2 2014-01-01 2014-01-01 false Human intrusion scenario. 63.322 Section 63.322 Energy... REPOSITORY AT YUCCA MOUNTAIN, NEVADA Postclosure Public Health and Environmental Standards Human Intrusion Standard § 63.322 Human intrusion scenario. For the purposes of the analysis of human intrusion, DOE...

  14. 10 CFR 63.322 - Human intrusion scenario.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 2 2012-01-01 2012-01-01 false Human intrusion scenario. 63.322 Section 63.322 Energy... REPOSITORY AT YUCCA MOUNTAIN, NEVADA Postclosure Public Health and Environmental Standards Human Intrusion Standard § 63.322 Human intrusion scenario. For the purposes of the analysis of human intrusion, DOE...

  15. Field Observation of Joint Structures in Various Types of Igneous Rocks

    NASA Astrophysics Data System (ADS)

    Kano, Shingo; Tsuchiya, Noriyoshi

    2006-05-01

    In this study, field observations of natural fracture network systems in some intrusive and extrusive rocks were undertaken, to clarify the fracturing mechanism in the rocks. Shallow intrusives, whose depth of emplacement was less than several hundred metres, include the Momo-iwa Dacite dome on Rebun Island (Hokkaido), and Jodogahama Rhyolite in Iwate prefecture. Extrusive complexes studied include the Tojinbo Andesite and Ojima Rhyodacite in Fukui prefecture. Rocks of `granitic' composition were collected from the Takidani (Japan Alps) and Hijiori (Yamagata prefecture) plutons. The joint structure in Hijiori Granite was evaluated by analysis of core samples extracted from the HDR-3 geothermal production well. Based on detailed field observation, joint structures related to thermal contraction of a rock mass could be classified according to their inferred depth of formation. Joints from a near surface setting, such as shallow intrusive rocks and extrusives, tend to form pentagonal — hexagonal columnar structures (for a variety of rock types), whilst granitic rocks (from a deeper setting) typically exhibit a parallelepiped structure. The apparent differences in joint form are inferred to be dependent on the confining pressure, which acts on joint generation and propagation. In cases of non-confining pressure, such as the near-surface (shallow intrusive/extrusive) setting, joint networks typically form a columnar structure. On the contrary, confining pressure is considerably greater for deeper rock masses, and these form a parallelepiped joint structure.

  16. Cenozoic rocks of the Santa Rita Mountains, southeast of Tucson, Arizona

    USGS Publications Warehouse

    Drewes, Harald

    1972-01-01

    the interpretations of the geologic record of the rocks themselves. The rocks of the greatest potential economic interest are the Greaterville intrusives of the Helvetia and Greaterville mining districts and the quartz vein swarm of the Tyndall and Wrightson mining districts.

  17. A system for distributed intrusion detection

    SciTech Connect

    Snapp, S.R.; Brentano, J.; Dias, G.V.; Goan, T.L.; Heberlein, L.T.; Ho, Che-Lin; Levitt, K.N.; Mukherjee, B. . Div. of Computer Science); Grance, T. ); Mansur, D.L.; Pon, K.L. ); Smaha, S.E. )

    1991-01-01

    The study of providing security in computer networks is a rapidly growing area of interest because the network is the medium over which most attacks or intrusions on computer systems are launched. One approach to solving this problem is the intrusion-detection concept, whose basic premise is that not only abandoning the existing and huge infrastructure of possibly-insecure computer and network systems is impossible, but also replacing them by totally-secure systems may not be feasible or cost effective. Previous work on intrusion-detection systems were performed on stand-alone hosts and on a broadcast local area network (LAN) environment. The focus of our present research is to extend our network intrusion-detection concept from the LAN environment to arbitarily wider areas with the network topology being arbitrary as well. The generalized distributed environment is heterogeneous, i.e., the network nodes can be hosts or servers from different vendors, or some of them could be LAN managers, like our previous work, a network security monitor (NSM), as well. The proposed architecture for this distributed intrusion-detection system consists of the following components: a host manager in each host; a LAN manager for monitoring each LAN in the system; and a central manager which is placed at a single secure location and which receives reports from various host and LAN managers to process these reports, correlate them, and detect intrusions. 11 refs., 2 figs.

  18. The neural representation of intrusive thoughts

    PubMed Central

    Schmiedek, Florian; Brose, Annette; Schott, Björn H.; Lindenberger, Ulman; Lövden, Martin

    2013-01-01

    Based on the philosophical notion that language embodies thought we investigated whether a habitual tendency for intrusive thought that younger and older participants report over a period of 100 sessions, spread out over about 6 months, is associated with brain regions related to language production. In favour of this hypothesis, we found that individual differences in habitual intrusive thoughts are correlated with activity in the left inferior frontal gyrus (IFG, Broca’s area) as well as the cingulate cortex (CC) during a two-choice reaction-time task in fMRI. Participants who habitually tended to experience intrusive thoughts showed greater activity during task-free (baseline) compared to task periods in brain regions involved in language production. Task performance was unrelated to individual differences in intrusive thoughts. We conclude that intrusive thoughts may be represented in a language-like format and that individuals reporting a habitually higher tendency for intrusive thoughts may have stronger and more habitual inner speech processes. PMID:22563007

  19. Oxygen isotope geochemistry of The Geysers reservoir rocks, California

    SciTech Connect

    Gunderson, Richard P.; Moore, Joseph N.

    1994-01-20

    Whole-rock oxygen isotopic compositions of Late Mesozoic graywacke, the dominant host rock at The Geysers, record evidence of a large liquid-dominated hydrothermal system that extended beyond the limits of the present steam reservoir. The graywackes show vertical and lateral isotopic variations that resulted from gradients in temperature, permeability, and fluid composition during this early liquid-dominated system. All of these effects are interpreted to have resulted from the emplacement of the granitic "felsite" intrusion 1-2 million years ago. The {delta}{sup 18}O values of the graywacke are strongly zoned around a northwest-southeast trending low located near the center of and similar in shape to the present steam system. Vertical isotopic gradients show a close relationship to the felsite intrusion. The {delta}{sup 18}O values of the graywacke decrease from approximately 15 per mil near the surface to 4-7 per mil 300 to 600 m above the intrusive contact. The {delta}{sup 18}O values then increase downward to 8-10 per mil at the felsite contact, thereafter remaining nearly constant within the intrusion itself. The large downward decrease in {delta}{sup 18}O values are interpreted to be controlled by variations in temperature during the intrusive event, ranging from 150{degree}C near the surface to about 425{degree}C near the intrusive contact. The upswing in {delta}{sup 18}O values near the intrusive contact appears to have been caused by lower rock permeability and/or heavier fluid isotopic composition there. Lateral variations in the isotopic distributions suggests that the effects of temperature were further modified by variations in rock permeability and/or fluid-isotopic composition. Time-integrated water:rock ratios are thought to have been highest within the central isotopic low where the greatest isotopic depletions are observed. We suggest that this region of the field was an area of high permeability within the main upflow zone of the liquid

  20. Rock Paintings.

    ERIC Educational Resources Information Center

    Jones, Julienne Edwards

    1998-01-01

    Discusses the integration of art and academics in a fifth-grade instructional unit on Native American culture. Describes how students studied Native American pictographs, designed their own pictographs, made their own tools, and created rock paintings of their pictographs using these tools. Provides a list of references on Native American…

  1. Contact relations and petrography of the Solarya intrusive complex (NW Turkey)

    NASA Astrophysics Data System (ADS)

    Nur Güraslan, Işıl; Ünal, Alp; Altunkaynak, Şafak

    2016-04-01

    Solarya pluton is a N-S trending intrusive body exposed in the North of the Balikesir city in NW Anatolia. It is Early Miocene in age and intruded into the Nilüfer and Hodul unit of Karakaya complex representing Triassic metamorphic and non-metamorphic basement of Sakarya Continent. Solarya plutonic complex consists of three granitic rock members: Porphyritic granodiorite with K-feldspar (orthoclase) megacrystals, microgranite-microgranodiorite and haplogranite. Coarse grained porphyritic granodiorite is common in northern part of the pluton while the southern part of the pluton is formed from microgranite-microgranodiorite. Haplogranite was emplaced between the pluton and the metamorphic country rocks and surrounds the pluton as a thin light coloured outer zone along northern half of the border. Haplogranitic envelope zone display graphic and granophyric textures. Main plutonic body also contains mafic enclaves and syn-plutonic mafic dykes. Along the southern border, the fine grained chilled margin of Solarya pluton gradually passes into the hypabyssal and volcanic rocks. At the western border of the pluton, a young fault separates the pluton from non-metamorphic Hodul Unit of Karakaya complex. Along the northern and eastern margin, Solarya pluton intruded into metamorphic rocks of Nilüfer Unit which consist mainly of marbles, metapelites and metabasites. Solarya intrusive complex developed contact metamorphism in a narrow zone (150-200 m) around its eastern margin between the marbles which reaches to hornblende-hornfels facies conditions. The grain sizes of the marbles grow towards the margin of the pluton. Contact metamorphic rocks surrounding the intrusive body are common with granoblastic texture and display calcite + plagioclase + tremolite + diopside + garnet ± quartz mineral paragenesis dominantly. This mineral paragenesis suggest that the contact metamorphic aureole has developed under 500-550 C° and 2-3 kbar temperature and pressure conditions, which

  2. Age, field, and petrological relationships of the Hyde School Gneiss, Adirondack lowlands, New York: Criteria for an intrusive igneous origin

    SciTech Connect

    McLelland, J. ); Perham, A. ); Chiarenzelli, J.

    1992-01-01

    Alaskitic and tonalitic rocks constituting Hyde School Gneiss (HSG) occur in 14 domical bodies in the Adirondack lowlands. Recent models have interpreted these bodies as metamorphosed rhyolitic and dacitic ash-flow deposits forming the basal member of a regional stratigraphic package. In contrast, this paper presents criteria and evidence for an intrusive origin for HSG. Field evidence includes intrusion breccias and complex crosscutting relationships involving mafic layers resembling synplutonic dikes. Petrologic constraints supporting an intrusive origin include: (1) the common occurrence of quartz-mesoperthite hypersolvus assemblages; (2) magmatic features in tonalitic, trondhjemitic, and alaskitic facies, (3) local occurrences of orthopyroxene in all facies of HSG; and (4) the development of marginal garnet-sillimanite gneiss with corundum-spinel-garnet-sillimanite assemblages yielding paleotemperatures of 780-810C and interpreted as restite remaining after anatexis of country rock metapelite by intrusions of hypersolvus granitoids. U-Pb zircon ages reported here suggest that the majority of the HSG was intruded at ca. 1230 Ma, contemporaneous with high-grade metamorphic activity in the Adirondacks and elsewhere in the SW sector of the Grenville Province. Geochronological evidence from a leucogranitic rock crosscutting metasediments on Wellesley Island suggest that these metasediments are older than 1416 {plus minus} 5 Ma.

  3. 916 Ma Pole for southwestern Baltica: palaeomagnetism of the Bjerkreim-Sokndal layered intrusion, Rogaland Igneous Complex, southern Norway

    NASA Astrophysics Data System (ADS)

    Brown, Laurie L.; McEnroe, Suzanne A.

    2015-10-01

    The Rogaland Igneous Complex (RIC) in southern Norway intruded into post-Sveconorwegian granulite facies crust ˜930 Ma. It includes three massif anorthosites, several small leuconorite bodies and the ˜7 km thick norite-quartz mangerite layered Bjerkreim-Sokndal (BKS) intrusion. The intrusion consists of five rhythmic megaunits created by repeated magma influxes topped by a transition zone and more evolved mangerites and quartz mangerites. Over 70 palaeomagnetic sites have been collected in the BKS, sampling all the megacyclic subunits and overlying mangerites. Remanence within the BKS is held in hemo-ilmenite-only rocks (lower parts of the megacyclic units), mixed hemo-ilmenite and magnetite rocks (upper parts of the lower megacyclic units) and magnetite only rocks in the upper highest megacyclic unit and overlying mangerites. Due to the different oxides present magnetic susceptibility varies over four orders of magnitude with a bimodal distribution (mean susceptibility of 6.4 × 10-3 SI for hemo-ilmenite rocks, and 8.7 × 10-2 SI for magnetite rocks). NRM values do not show a strong bimodal distribution as many of the rocks lacking magnetite have hemo-ilmenite with strong lamellar magnetism; average NRM for the entire suite is 8.83 A m-1. All sites within the cyclic part of the intrusion have stable remanence and produce well-clustered site means. Samples from the upper mangerite rocks, dominated by MD magnetite, are commonly unstable and not all sites provide acceptable data. Mean directions for 66 sites spanning the entire intrusion are I = -73.5°, D = 303.4°, with α95 = 3.7° and k = 24. The resulting pole position is at 35.9°S and 217.9°E, with a palaeolatitude for this part of Baltica of -59.4°. Examination of the magnetic mineralogy combined with geochronology for RIC rocks and cooling rates for the region yields an age of magnetization of 916 Ma. Metamorphic country rocks yield similar directions at least 10 km from the contact, confirming the

  4. Isotopic variation in the Tuolumne Intrusive Suite, central Sierra Nevada, California

    USGS Publications Warehouse

    Kistler, R.W.; Chappell, B.W.; Peck, D.L.; Bateman, P.C.

    1986-01-01

    Granitoid rocks of the compositionally zoned Late Cretaceous Toulumne Intrusive Suite in the central Sierra Nevada, California, have initial87Sr/86Sr values (Sri) and143Nd/144Nd values (Ndi) that vary from 0.7057 to 0.7067 and from 0.51239 to 0.51211 respectively. The observed variation of both Sri and Ndi and of chemical composition in rocks of the suite cannot be due to crystal fractionation of magma solely under closed system conditons. The largest variation in chemistry, Ndi, and Sri is present in the outer-most equigranular units of the Tuolumne Intrusive Suite. Sri varies positively with SiO2, Na2O, K2O, and Rb concentrations, and negatively with Ndi, Al2O3, Fe2O3, MgO, FeO, CaO, MnO, P2O5, TiO2, and Sr concentrations. This covariation of Sri, Ndi and chemistry can be modeled by a process of simple mixing of basaltic and granitic magmas having weight percent SiO2 of 48.0 and 73.3 respectively. Isotopic characteristic of the mafic magma are Sri=0.7047, Ndi=0.51269 and ??18O=6.0, and of the felsic magma are Sri=0.7068, Ndi=0.51212 and ??18O=8.9. The rocks sampled contain from 50 to 80% of the felsic component. An aplite in the outer equigranular unit of the Tuolumne Intrusive Suite apparently was derived by fractional crystallization of plagioclase and hornblende from magma with granudiorite composition that was a product of mixing of the magmas described above. Siliceous magmas derived from the lower crust, having a maximum of 15 percent mantle-derived mafic component, are represented by the inner prophyritic units of the Tuolumne Intrusive Suite. ?? 1986 Springer-Verlag.

  5. White Rock

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 19 April 2002) The Science 'White Rock' is the unofficial name for this unusual landform which was first observed during the Mariner 9 mission in the early 1970's. As later analysis of additional data sets would show, White Rock is neither white nor dense rock. Its apparent brightness arises from the fact that the material surrounding it is so dark. Images from the Mars Global Surveyor MOC camera revealed dark sand dunes surrounding White Rock and on the floor of the troughs within it. Some of these dunes are just apparent in the THEMIS image. Although there was speculation that the material composing White Rock could be salts from an ancient dry lakebed, spectral data from the MGS TES instrument did not support this claim. Instead, the White Rock deposit may be the erosional remnant of a previously more continuous occurrence of air fall sediments, either volcanic ash or windblown dust. The THEMIS image offers new evidence for the idea that the original deposit covered a larger area. Approximately 10 kilometers to the southeast of the main deposit are some tiny knobs of similarly bright material preserved on the floor of a small crater. Given that the eolian erosion of the main White Rock deposit has produced isolated knobs at its edges, it is reasonable to suspect that the more distant outliers are the remnants of a once continuous deposit that stretched at least to this location. The fact that so little remains of the larger deposit suggests that the material is very easily eroded and simply blows away. The Story Fingers of hard, white rock seem to jut out like icy daggers across a moody Martian surface, but appearances can be deceiving. These bright, jagged features are neither white, nor icy, nor even hard and rocky! So what are they, and why are they so different from the surrounding terrain? Scientists know that you can't always trust what your eyes see alone. You have to use other kinds of science instruments to measure things that our eyes can

  6. Meridiani Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    16 September 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the complex surfaces of some of the light- and intermediate-toned sedimentary rock exposed by erosion in eastern Sinus Meridiani. Similar rocks occur at the Mars Exploration Rover, Opportunity, site, but they are largely covered by windblown sand and granules. The dark feature with a rayed pattern is the product of a meteor impact.

    Location near: 0.8oN, 355.2oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  7. Terby's Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    25 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered, sedimentary rock outcrops in the crater, Terby. The crater is located on the north rim of Hellas Basin. If one could visit the rocks in Terby, one might learn from them whether they formed in a body of water. It is possible, for example, that Terby was a bay in a larger, Hellas-wide sea.

    Location near: 27.9oS, 285.7oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Winter

  8. Magmatic intrusions and deglaciation at mid-latitude in the northern plains of Mars

    NASA Astrophysics Data System (ADS)

    Michaut, Chloé; Baratoux, David; Thorey, Clément

    2013-07-01

    On Earth, igneous rocks are generally affected by magmatic differentiation and the volume of intrusive bodies is considered to be 5-10 times larger than the volume of volcanic rocks. In contrast, in the case of Mars, the occurrence of olivine-phyric basalts at Gusev crater (McSween, H.Y. [2006]. J. Geophys. Res. (Planets) 111(E10), E02S10), the primitive nature of at least four picritic shergottites (Grott, M. [2013]. Planet. Space Sci. 174, 49-111) and the chemical composition of major volcanic provinces (Baratoux, D., Toplis, M.J., Monnereau, M., Gasnault, O. [2011]. Nature 472, 338-341) suggest that primary melts of the mantle may have commonly reached the surface. These observations, together with sparse morphologic evidence of intrusions in comparison with other terrestrial planets, raise the issue of the conditions for the formation and occurrence of sub-surface zones of magma storage on Mars. In this respect, a series of two types of young (Amazonian) domes located at mid-latitudes in western Arcadia Planitia, East of Phlegra Montes, previously interpreted as surface expressions of intrusive bodies (Farrand, W.H., Lane, M.D., Edwards, B.R., Yingst, R.A. [2011]. Icarus 211, 139-156), are examined here. A fraction of the domes consist of upraised plain material, whereas others, distinguished by a massive core and a large aspect ratio, could be partially exhumed intrusions or extrusions of viscous differentiated magma. The latter interpretation is however not compatible with the mafic compositions inferred from orbital visible and near infrared spectroscopic observations. The thicknesses and radii of both types of domes appear to be related through a power-law relationship with exponents close to 1 or 5/4. These exponent values are not compatible with extrusive morphologies but are characteristic of intrusions magma below an elastic layer (Michaut, C. [2011]. J. Geophys. Res. 10.1029/2010JB008108). We conclude that all types of domes are intrusive bodies. The

  9. Lead-alpha age determinations of granitic rocks from Alaska

    USGS Publications Warehouse

    Matzko, John J.; Jaffe, H.W.; Waring, C.L.

    1957-01-01

    Lead-alpha activity age determinations were made on zircon from seven granitic rocks of central and southeastern Alaska. The results of the age determinations indicate two periods of igneous intrusion, one about 95 million years ago, during the Cretaceous period, and another about 53 million years ago, during the early part of the Tertiary. The individual ages determined on zircon from 2 rocks from southeastern Alaska and 1 from east-central Alaska gave results of 90, 100, and 96 million years; those determined on 4 rocks from central Alaska gave results of 47, 56, 58, and 51 million years.

  10. Debris avalanche triggered by sill intrusions in basaltic volcanoes (Piton des Neiges, La Réunion Island)

    NASA Astrophysics Data System (ADS)

    Berthod, C.; Famin, V.; Bascou, J.; Michon, L.; Ildefonse, B.

    2014-12-01

    Debris avalanches derived from the flanks of volcanic islands are among the largest on Earth. Debris avalanches are rare, catastrophic destabilizations that still keep geologists debating about the mechanisms that initiate them and make them travel huge runout distances. To shed light on the trigger of such destabilizations, we studied the inland scar of a debris avalanche deposit cropping out at Piton des Neiges, a dormant and eroded basaltic volcano of La Réunion Island. The avalanche deposit rests on a pile of 50-70 sill intrusions with a shallow northward dip, i.e. toward the sea. We measured the anisotropy of magnetic susceptibility in a transect across the uppermost sill of the pile in contact with the avalanche deposit. This transect reveals a strongly asymmetric magnetic fabric, consistent with a north-directed shear movement of the upper intrusion wall. This suggests that the upper sill induced a co-intrusive shear displacement of the volcano flank toward the sea. The upper sill margin in contact with the avalanche is striated, showing that this intrusion is older than the avalanche. Striae indicate a northward direction of avalanche runout. The upper sill margin also displays a magmatic lineation consistent with a magma flow in the intrusion toward the north. There is thus a striking kinematic consistency between the directions of intrusion propagation and avalanche runout, both oriented toward the sea. From the above results, we propose that repeated sill intrusions, such as observed on Piton des Neiges, increase the instability of a volcanic edifice. Each injection induces an incremental slip of the overlying rock mass, which may eventually end up into a landslide. Sill intrusions associated with seaward displacements of volcano flank, such as inferred for the April 2007 eruption of Piton de la Fournaise (also in La Réunion), should therefore be considered as a potential trigger of debris avalanches.

  11. Monoclinal bending of strata over laccolithic intrusions

    USGS Publications Warehouse

    Koch, F.G.; Johnson, A.M.; Pollard, D.D.

    1981-01-01

    Sedimentary strata on top of some laccolithic intrusions are nearly horizontal and little deformed, but are bent into steeply dipping monoclinal flexures over the peripheries of these intrusions. This form of bending is not explained by previous theories of laccolithic intrusion, which predict either horizontal undeformed strata over the center and faulted strata around the periphery, or strata bent continuously into a dome. However, a slight generalization of these theories accomodates the observed form and contains the previous forms as special cases. A critical assumption is that the strength of contacts within a multilayered overburden is overcome locally by layer-parallel shear. If this strength is less than the strength of the layers themselves, then layers over the center remain bonded together and display negligible bending, whereas layers over the periphery slip over one another and are readily bent into a monoclinal flexure. ?? 1981.

  12. Origin of the Lyme Dome and implications for the timing of multiple Alleghanian deformational and intrusive events in southern Connecticut

    USGS Publications Warehouse

    Walsh, G.J.; Aleinikoff, J.N.; Wintsch, R.P.

    2007-01-01

    Geologic mapping, structural analysis, and geochronology in the area of the Lyme dome, southern Connecticut provides constraints on the origin of the rocks in the core of the dome, the absolute timing of the principal deformational and thermal events attributed to Alleghanian orogenesis, and the processes that generated the dome. Detrital zircon geochronology in combination with ages on intrusive rocks brackets the deposition of quartzite in the core of the dome sometime between ca. 925 and 620 Ma. Granite and granodiorite intruded the Neoproteorozic metasedimentary rocks in the core of the dome at ca. 620 to 610 Ma. Four major early Permian events associated with the Alleghanian orogeny affected the rocks in the Lyme dome area. Syn-tectonic migmatization and widespread penetrative deformation (D1, ca. 300 - 290 Ma) included emplacement of alaskite at 290 ?? 4 Ma during regional foliation development and aluminosilicate-orthoclase metamorphic conditions. Rocks of the Avalon terrane may have wedged between Gander cover rocks and Gander basement in the core of the Lyme during D1. Limited structural evidence for diapiric uplift of the Lyme dome indicates that diapirism started late in D1 and was completed by D2 (ca. 290 - 280 Ma) when horizontal WNW contractional stresses dominated over vertical stresses. Second sillimanite metamorphism continued and syn-tectonic D2 granite pegmatite (288 ?? 4 Ma) and the Joshua Rock Granite Gniess (284 ?? 3 Ma) intruded at this time. North-northwest extension during D3 (ca. 280 - 275 Ma) led to granitic pegmatite intrusion along S3 cleavage planes and in extensional zones in boudin necks during hydraulic failure and decompression melting. Intrusion of a Westerly Granite dike at 275 ?? 4 Ma suggests that D3 extension was active, and perhaps concluding, by ca. 275 Ma. Late randomly oriented but gently dipping pegmatite dikes record a final stage of intrusion during D4 (ca. 275 - 260 Ma), and a switch from NNW extension to vertical

  13. Dating Intrusions in the Salinian Block Using Single Zircon U-PB CA-TIMS Analysis

    NASA Astrophysics Data System (ADS)

    DeNicola, S.; Mundil, R.; Wang, C. Y.; Sprain, C. J.; Manga, M.

    2015-12-01

    The Salinian block (SB) consists largely of metasedimentary basement intruded by suites of compositionally heterogeneous Early to Late Cretaceous rocks. Exposed throughout Central and Northern California, it is bordered to the northwest by the Naciemiento fault, to the southwest by the Big Pine fault and to the east by the San Andreas Fault. These faults are thought to have caused a dextral offset of the SB; however, its original position is still debated. Published radioisotopic ages from various techniques on SB intrusives suggest that the initial magmatic activity of the Salinian arc began at around 100 Ma and concluded some 40 myr later, but the timing of individual magmatic pulses are yet to be fully understood because arguably most of the available geochronological data are compromised with respect to precision and accuracy. Previous studies include U-Pb zircon ages from different lithologies and areas using multi-crystal TIMS as well as ICPMS, and SIMS techniques. Whereas the former technique is now known to be prone to producing inaccurate, although precise, ages due to averaging effects from older inheritance and open system behavior, the latter are often associated with analytical uncertainty at the several percent level as well as unrecognized open system behavior, making the interpretation of age data notoriously difficult. Complementary geochemical, petrological and structural studies have been conducted, but are also difficult to interpret in absence of precise and accurate geochronological data because geochemical trends and intrusion rates cannot be reconstructed. Here, we examine a group of intrusive rocks from the Northern California SB that include a biotite-hornblende granodiorite host rock which is intruded by a complex array of igneous dikes of varying lithology ranging from ~5% to ~50% mafic components. We perform closed system single zircon U-Pb CA-TIMS analysis and obtain 206Pb/238U ages of ~98 Ma and ~92 Ma (with permil level resolution

  14. Computationally Efficient Neural Network Intrusion Security Awareness

    SciTech Connect

    Todd Vollmer; Milos Manic

    2009-08-01

    An enhanced version of an algorithm to provide anomaly based intrusion detection alerts for cyber security state awareness is detailed. A unique aspect is the training of an error back-propagation neural network with intrusion detection rule features to provide a recognition basis. Network packet details are subsequently provided to the trained network to produce a classification. This leverages rule knowledge sets to produce classifications for anomaly based systems. Several test cases executed on ICMP protocol revealed a 60% identification rate of true positives. This rate matched the previous work, but 70% less memory was used and the run time was reduced to less than 1 second from 37 seconds.

  15. Magmatic intrusions in the lunar crust

    NASA Astrophysics Data System (ADS)

    Michaut, C.; Thorey, C.

    2015-10-01

    The lunar highlands are very old, with ages covering a timespan between 4.5 to 4.2 Gyr, and probably formed by flotation of light plagioclase minerals on top of the lunar magma ocean. The lunar crust provides thus an invaluable evidence of the geological and magmatic processes occurring in the first times of the terrestrial planets history. According to the last estimates from the GRAIL mission, the lunar primary crust is particularly light and relatively thick [1] This low-density crust acted as a barrier for the dense primary mantle melts. This is particularly evident in the fact that subsequent mare basalts erupted primarily within large impact basin: at least part of the crust must have been removed for the magma to reach the surface. However, the trajectory of the magma from the mantle to the surface is unknown. Using a model of magma emplacement below an elastic overlying layer with a flexural wavelength Λ, we characterize the surface deformations induced by the presence of shallow magmatic intrusions. We demonstrate that, depending on its size, the intrusion can show two different shapes: a bell shape when its radius is smaller than 4 times Λ or a flat top with small bended edges if its radius is larger than 4 times Λ[2]. These characteristic shapes for the intrusion result in characteristic deformations at the surface that also depend on the topography of the layer overlying the intrusion [3].Using this model we provide evidence of the presence of intrusions within the crust of the Moon as surface deformations in the form of low-slope lunar domes and floor-fractured craters. All these geological features have morphologies consistent with models of magma spreading at depth and deforming an overlying elastic layer. Further more,at floor-fractured craters, the deformation is contained within the crater interior, suggesting that the overpressure at the origin of magma ascent and intrusion was less than the pressure due to the weight of the crust removed by

  16. Convective, intrusive geothermal plays: what about tectonics?

    NASA Astrophysics Data System (ADS)

    Santilano, A.; Manzella, A.; Gianelli, G.; Donato, A.; Gola, G.; Nardini, I.; Trumpy, E.; Botteghi, S.

    2015-09-01

    We revised the concept of convective, intrusive geothermal plays, considering that the tectonic setting is not, in our opinion, a discriminant parameter suitable for a classification. We analysed and compared four case studies: (i) Larderello (Italy), (ii) Mt Amiata (Italy), (iii) The Geysers (USA) and (iv) Kizildere (Turkey). The tectonic settings of these geothermal systems are different and a matter of debate, so it is hard to use this parameter, and the results of classification are ambiguous. We suggest a classification based on the age and nature of the heat source and the related hydrothermal circulation. Finally we propose to distinguish the convective geothermal plays as volcanic, young intrusive and amagmatic.

  17. Complete Analytical Data for Samples of Jurassic Igneous Rocks in the Bald Mountain Mining District, Nevada

    USGS Publications Warehouse

    du Bray, Edward A.

    2009-01-01

    This report presents all petrographic, major oxide, and trace element data for a set of 109 samples collected during an investigation of Jurassic igneous rocks in the Bald Mountain mining district, Nevada. Igneous rocks in the district include the Bald Mountain stock, quartz-feldspar porphyry dikes, basaltic andesite dikes, aplite sills, and rare lamprophyre dikes. These rocks, although variably altered near intrusion-related mineral deposits, are fresh in many parts of the district. Igneous rocks in the district are hosted by Paleozoic sedimentary rocks.

  18. Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    6 November 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows outcrops of sedimentary rocks in a crater located just north of the Sinus Meridiani region. Perhaps the crater was once the site of a martian lake.

    Location near: 2.9oN, 359.0oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  19. Thermal Inertia of Rocks and Rock Populations

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Jakosky, B. M.; Mellon, M. T.

    2001-01-01

    The effective thermal inertia of rock populations on Mars and Earth is derived from a model of effective inertia versus rock diameter. Results allow a parameterization of the effective rock inertia versus rock abundance and bulk and fine component inertia. Additional information is contained in the original extended abstract.

  20. SW U. S. diabase province: A 1. 1-Ga intrusion event of middle Grenville and middle Keweenawan age

    SciTech Connect

    Conway, C.M.; Elston, D.P. ); Wrucke, C.T. )

    1993-02-01

    Diabase in the southwestern US intrudes Middle Proterozoic stratified rocks as sills and Early and Middle Proterozoic crystalline rocks as subhorizontal sheets and subvertical dikes. It is discontinuous in a broad belt extending from western Texas to southeastern California. The best known intrusions are sills in Middle Proterozoic strata in Death Valley, Grand Canyon, and central Arizona. Sparse to rare dikes in some of these strata trend mostly north but range from north-northeast to west-northwest. Diabase dikes widespread in crystalline rocks in western Arizona and adjacent parts of southeastern California strike from north to west-northwest, but are predominantly northwesterly. Dikes and sheets are also present in crystalline rocks in the southern Pinaleno Mountains, southeastern Arizona, where dikes strike west-northwest. The northwest trend of the diabase province and prevalent northwesterly trend of dikes in crystalline rocks suggest that intrusion was controlled by an approximately horizontal least compressive stress field roughly parallel to the Grenville Front. Radiometric ages of Arizona and California diabase indicate emplacement at [approximately]1,100 Ma. Paleomagnetic poles from diabase sills and enclosing stratified rocks in Arizona correlate with poles reported from middle and early-late Keweenawan rocks of Lake Superior. Emplacement of the diabase coincides with: (1) the middle Keweenawan eruptive and intrusive episode of the Midcontinent Rift System; (2) a major episode of (middle) Grenville thrusting and deformation documented in the Van Horn area; and (3) a time of abrupt reversal in North American apparent polar wander. These interrelated manifestations presumably arose in response to a major episode of plate interaction and collision between North American and a plate that encroached from the southeast.

  1. Calcic myrmekite in anorthositic and gabbroic rocks

    SciTech Connect

    Schiffries, C.M.; Dymek, R.F.

    1985-01-01

    Myrmekite is a common feature of granitic plutonic rocks and quartzo-feldspathic gneisses, but it is rarely reported in anorthositic and gabbroic rocks. The authors have identified myrmekitic intergrowths of quartz and calcic plagioclase in a variety of plagioclase-rich cumulate rocks, including samples from a number of massif anorthosites and layered igneous intrusions. It appears that calcic myrmekite has been frequently overlooked, and is a common accessory feature in these rock types. Chemical and textural characteristics of myrmekite in the St-Urbain massif anorthosite (Quebec) and the Bushveld Igneous Complex (South Africa) have several features in common, but this myrmekite appears to be fundamentally different from that described by most previous investigators. Whereas myrmekite typically consists of a vermicular intergrowth of sodic plagioclase and quartz that occurs adjacent to alkali feldspar, the intergrowths in these rocks contain highly calcic plagioclase and lack the intervening alkali feldspar. In addition, the plagioclase in the myrmekite is more calcic than that in the surrounding rock. The boundary between the myrmekite and the host material is generally extremely sharp, although reverse zoning of host plagioclase may obscure the contact in some cases. The textural and chemical evidence is consistent with a replacement origin for these intergrowths; the proportion of quartz in the myrmekite is in close agreement with the predicted amount of silica that is generated by the theoretical replacement reaction. It appears that water played a key role in the replacement process.

  2. Rock Driller

    NASA Technical Reports Server (NTRS)

    Peterson, Thomas M.

    2001-01-01

    The next series of planetary exploration missions require a method of extracting rock and soil core samples. Therefore a prototype ultrasonic core driller (UTCD) was developed to meet the constraints of Small Bodies Exploration and Mars Sample Return Missions. The constraints in the design are size, weight, power, and axial loading. The ultrasonic transducer requires a relatively low axial load, which is one of the reasons this technology was chosen. The ultrasonic generator breadboard section can be contained within the 5x5x3 limits and weighs less than two pounds. Based on results attained the objectives for the first phase were achieved. A number of transducer probes were made and tested. One version only drills, and the other will actually provide a small core from a rock. Because of a more efficient transducer/probe, it will run at very low power (less than 5 Watts) and still drill/core. The prototype generator was built to allow for variation of all the performance-effecting elements of the transducer/probe/end effector, i.e., pulse, duty cycle, frequency, etc. The heart of the circuitry is what will be converted to a surface mounted board for the next phase, after all the parameters have been optimized and the microprocessor feedback can be installed.

  3. Sulfur Isotopic Composition and Behavior in Granitoid Intrusions, southwestern New Brunswick, Canada

    NASA Astrophysics Data System (ADS)

    Yang, X.; Lentz, D. R.

    2004-05-01

    Bulk sulfur isotopic composition and sulfur content were determined for 12 granitoid intrusions (48 samples) associated with various types of mineralization (e.g., Au, Sb-W-Mo-Au, W-Sn-In-Zn-Pb-Cu) and the pertinent wallrocks (7 samples), in southwestern New Brunswick, Canada. This data together with data from field relations, magnetic susceptibility, sulfide mineralogy, petrology, and geochemistry, were used to characterize these intrusions. Two distinct groups can be established, although both show some features of I-type grantiods: (1) a Late Devonian granitic series (GS) including the Mount Pleasant, True Hill, Beech Hill, Pleasant Ridge, Kedron, Sorrel Ridge granites, and (2) a Late Silurian to Early Devonian granodioritic to monzogranitic series (GMS) including the Magaguadavic, Bocabec, Utopia, Tower Hill, Evandale, and Lake George intrusions. The former occur along the northwestern flank of the Saint George Batholith as satellite plutons, and the later form parts of this batholith and the Pokiok Batholith to the north. The GS rocks show the attributes of evolved I-type with some A-type features, whereas the GMS rocks are either reduced I-type (ilmenite-series), or normal I-type (magnetite-series). Strong assimilation and contamination by local metasedimentary rocks lead to the Tower Hill granite resembling S-type, e.g., the presence of muscovite and garnet. The GS type rocks have δ 34S values between -7.1 and +13 per mil with bulk-S content ranging from 33 to 3434 ppm. The GMS type rocks have relatively narrower variation in δ 34S values (-4.4 to +7.3 per mil), but with larger ranges of bulk-S content (45 to 11100 ppm). The granite samples with S contents much higher than its solubility in felsic melts are interpreted to be affected either by local metasedimentary rocks or by late stage hydrothermal alteration. The metasedimentary rocks contain variable S contents (707 to 14000 ppm) with δ 34S values of -10.6 to 0.1 per mil. In terms of mass balance, a

  4. Paleomagnetism of the Miocene intrusive suite of Kidd Creek: Timing of deformation in the Cascade arc, southern Washington

    USGS Publications Warehouse

    Hagstrum, J.T.; Swanson, D.A.; Snee, L.W.

    1998-01-01

    Paleomagnetic study of the intrusive suite of Kidd Creek in the southern Washington Cascades (23 sites in dikes and sills) was undertaken to help determine if these rocks are comagmatic and whether they postdate regional folding of the volcanic arc. Fission track and 40Ar-39Ar age determinations indicate an age of ???12.7 Ma (middle Miocene) for these rocks. The similarity of normal-polarity characteristic directions for most samples corroborate the available geochemical data indicating that these rocks are most likely comagmatic. Reversed-polarity directions for samples from four sites, however, show that emplacement of Kidd Creek intrusions spanned at least one reversal of the geomagnetic field. The paleomagnetic directions for the dikes and sills fail a fold test at the 99% confidence level indicating that the Kidd Creek rocks postdate regional folding. The mean in situ direction also indicates that the Kidd Creek and older rocks have been rotated 22?? ?? 6?? clockwise about a vertical or near-vertical axis from the expected Miocene direction. Compression and regional folding of the Cascade arc in southern Washington therefore had ended by ???12 Ma prior to the onset of deformation resulting in rotation of these rocks.

  5. Assessment of the long-term risks of inadvertent human intrusion

    SciTech Connect

    Wuschke, D.M. )

    1993-01-01

    Canada has conducted an extensive research program on the safe disposal of nuclear fuel wastes. The program has focused on the concept of disposal of spent fuel in durable containers in an engineered facility, or vault, 500 to 1000 m deep in intrusive igneous rock in the Canadian Shield. An essential goal of this program has been to develop and demonstrate a methodology to evaluate the performance of the facility against safety criteria established by Canada's regulatory agency, the Atomic Energy Control Board (AECB). These criteria are expressed in terms of risk, where risk is defined as the sum over all significant scenarios of the product of the probability of the scenario, the magnitude of the resultant dose, and the probability of a health effect per unit dose. This paper describes the methodology developed to assess the long-term risk from inadvertent human intrusion into such a facility and the results of its application to a conceptual design of such a facility.

  6. 3D Seismic Studies of Igneous Intrusions, Taranaki Basin, off-shore west New Zealand

    NASA Astrophysics Data System (ADS)

    Harbor, R. L.; Chrisitiansen, E. H.; Keach, R. W.

    2008-12-01

    Several off-shore volcano-plutonic complexes are imaged in a detailed 3D seismic survey acquired by Pogo New Zealand/Plains Exploration. The new data provide insight into the sizes, shapes, and wall rock deformation associated with the emplacement of plutons. The seismic survey, conducted in 2005, covers 1700 km2 and was processed with modern techniques used in hydrocarbon exploration. The images and structures have to be interpreted with care because of distortions caused by "velocity pull ups" created by the large seismic wave velocity contrast between sediment and igneous rock. The magmatic rocks may be part of the Mohakatino Volcanic Centre (15 to 1.5 Ma) that intrudes and partially fills the Taranaki graben, which began to form in the Cretaceous. Imaged plutons range from less than 1 to as much as 12 km across. The intrusions are steep-sided and do not resemble sills, but their bases are poorly resolved. The top of the largest complex is sharply delineated and marked by multiple apophyses as much as 2 km across and hundreds of meters high. Deformation along the sides of the intrusion is dominated by of a faulted rim anticline, with apparent dips of 45° or higher. Dips decrease rapidly away from the intrusion but doming extends several hundred meters from the margins. A series of high-angle faults fan out from the margin of the pluton and cut the folded strata along the margin. These faults terminate against the margins of the intrusion, extend as much as 1 pluton diameter away from the margin, and then merge with "regional" faults that are part of the Taranaki graben. Offset along these radiating faults is on the order of a few hundred meters. Strata on the top of the complex are thinned but are deformed into a faulted dome with an amplitude of about 1 km. Steep, dip-slip faults form a semi-radial pattern in the roof rocks but are strongly controlled by the regional stress field as many of the faults are sub-parallel to those that form the graben. The longest

  7. Intrusion of Soil Water through Pipe Cracks

    EPA Science Inventory

    This report describes a series of experiments conducted at U.S. EPA’s Test and Evaluation Facility in 2013-2014 to study the intrusion of contaminated soil water into a pipe crack during simulated backflow events. A test rig was used consisting of a 3’ x 3’ x 3’ acrylic soil bo...

  8. Chemical Observations of a Polar Vortex Intrusion

    NASA Technical Reports Server (NTRS)

    Schoeberl, M. R.; Kawa, S. R.; Douglass, A. R.; McGee, T. J.; Browell, E.; Waters, J.; Livesey, N.; Read, W.; Froidevaux, L.

    2006-01-01

    An intrusion of vortex edge air in D the interior of the Arctic polar vortex was observed on the January 31,2005 flight of the NASA DC-8 aircraft. This intrusion was identified as anomalously high values of ozone by the AROTAL and DIAL lidars. Our analysis shows that this intrusion formed when a blocking feature near Iceland collapsed, allowing edge air to sweep into the vortex interior. along the DC-8 flight track also shows the intrusion in both ozone and HNO3. Polar Stratospheric Clouds (PSCs) were observed by the DIAL lidar on the DC-8. The spatial variability of the PSCs can be explained using MLS HNO3 and H2O observations and meteorological analysis temperatures. We also estimate vortex denitrification using the relationship between N2O and HNO3. Reverse domain fill back trajectory calculations are used to focus on the features in the MLS data. The trajectory results improve the agreement between lidar measured ozone and MLS ozone and also improve the agreement between the HNO3 measurements PSC locations. The back trajectory calculations allow us to compute the local denitrification rate and reduction of HCl within the filament. We estimate a denitrification rate of about lO%/day after exposure to below PSC formation temperature. Analysis of Aura MLS observations made

  9. Intrusive [r] and Optimal Epenthetic Consonants

    ERIC Educational Resources Information Center

    Uffmann, Christian

    2007-01-01

    This paper argues against the view of intrusive [r] as a synchronically arbitrary insertion process. Instead, it is seen as a phonologically natural process, which can be modelled within the framework of Optimality Theory (OT). Insertion of [r] in phonologically restricted environments is a consequence of a more general theory of consonant…

  10. ON-LINE CALCULATOR: VAPOR INTRUSION MODELING

    EPA Science Inventory

    Migration of volatile chemicals from the subsurface into overlying buildings is called vapor intrusion (VI). Volatile organic chemicals in contaminated soils or groundwater can emit vapors, which may migrate through subsurface soils and may enter the indoor air of overlying build...

  11. An Adaptive Database Intrusion Detection System

    ERIC Educational Resources Information Center

    Barrios, Rita M.

    2011-01-01

    Intrusion detection is difficult to accomplish when attempting to employ current methodologies when considering the database and the authorized entity. It is a common understanding that current methodologies focus on the network architecture rather than the database, which is not an adequate solution when considering the insider threat. Recent…

  12. BTSC VAPOR INSTRUSION PRIMER "VAPOR INTRUSION CONSIDERATION FOR REDEVELOPMENT"

    EPA Science Inventory

    This primer is designed for brownfields stakeholders concerned about vapor intrusion, including property owners, real estate developers, and contractors performing environmental site investigations. It provides an overview of the vapor intrusion issue and how it can impact the ap...

  13. Comparative petrogenesis of anorthositic and troctolitic series rocks of the Duluth Complex, Minnesota

    SciTech Connect

    Miller, J.D. Jr.; Weiblen, P.W.

    1985-01-01

    Results of new mapping in the NW part of the Middle Proterozoic Duluth Complex in NE Minnesota reinforces the view that the Complex consists dominantly of two major lithostratigraphic units: an Anorthositic Series (AS) and a Troctolitic Series (TS) dominated by troctolite and olivine gabbro. Consistent intrusive and inclusive relationships confirm that AS rocks are older than TS. Interpretations of field, petrographic, and petrochemical data imply that the petrogenesis of the two rock series differed in at least four significant ways: 1) While parent magmas to both rock series could have been derived from high-Al olivine tholeiite primary magmas by fractional crystallization of Pl+Ol+Cpx+Sp in lower to intermediate crustal (40-15 km) chambers, AS parent magmas were generally more evolved than TS magmas upon their introduction into the Duluth Complex. 2) As magmas were intruded as plagioclase crystal muses (less than or equal to50% crystals), whereas later TS intrusions contained rare or minor intratelluric plagioclase and olivine. Periodic intrusions of viscous AS mushes probably caused much of the structural complexity ubiquitous to these rocks. 3) Although parent magmas to both rock series were saturated in plagioclase upon intrusion, AS magmas were less often saturated in olivine than were TS magmas. 4) TS rocks record fractional crystallization within Duluth Complex chambers; however, the extent and pattern of differentiation often reflects repeated replenishment of more primitive magmas.

  14. Multiple magma evolution and ore-forming processes of the Hongge layered intrusion, SW China: Insights from Sr-Nd isotopes, trace elements and platinum-group elements

    NASA Astrophysics Data System (ADS)

    Liao, Mingyang; Tao, Yan; Song, Xieyan; Li, Yubang; Xiong, Feng

    2015-12-01

    The Hongge layered intrusion (259 Ma), which is located in the inner zone of the Emeishan large igneous province (ELIP), is one of the most typical Fe-Ti-V ore deposits in the Pan-Xi area. Mafic-ultramafic layered intrusions of the ELIP have attracted a lot of attention lately because these intrusions host world class Fe-Ti-V oxide deposits plus interesting Cu-Ni-(PGE) mineralization which may have economic potential. This paper, reports new whole-rock major and trace element compositions, PGE abundances and Sr-Nd isotopic data for selected cumulate rocks and basalts. We use these data to investigate the nature of parental magmas and the controls on its evolution from the source mantle en route to the surface involving the Hongge ore-bearing intrusion. Two abrupt changes in Mt/Ilm and trace element ratios such as Ba/Th with depths in the Hongge layered intrusion indicate that this intrusion formed by at least two pluses of relatively primitive magma. The whole rock Sr-Nd isotopic data of basaltic and intrusive rocks plot in the region of Emeishan low-Ti basalts and the compositions of residual liquid (at ∼1260 °C and 1155 °C) calculated by MELTS are similar to our actual high-Ti (BFQ-2) and low-Ti (BC-1) basltic samples, indicate they are co-magmatic rather than derivation from a distinct source. Total PGE abundances in the Hongge samples are extremely low, ranging from 0.5 to 10 ppb. Sulfide-bearing rocks in the Hongge intrusion and the nearby coeval Banfangqing and Baicao basalts have similar mantle-like Pd/Pt ratios (2-6) and extremely high Cu/Pd ratios (3 × 104 to 4 × 105), indicating that sulfide segregation took place at depth prior to emplacement at Hongge and eruption in this region. Sulfide saturation in the Hongge magma may have resulted from such crustal contamination event. Crystallization of silicate minerals under the anhydrous magma, magma hydration plus Fe-Ti enrichments in the parental magma are three critical factors for the formation of Fe

  15. NADIR (Network Anomaly Detection and Intrusion Reporter): A prototype network intrusion detection system

    SciTech Connect

    Jackson, K.A.; DuBois, D.H.; Stallings, C.A.

    1990-01-01

    The Network Anomaly Detection and Intrusion Reporter (NADIR) is an expert system which is intended to provide real-time security auditing for intrusion and misuse detection at Los Alamos National Laboratory's Integrated Computing Network (ICN). It is based on three basic assumptions: that statistical analysis of computer system and user activities may be used to characterize normal system and user behavior, and that given the resulting statistical profiles, behavior which deviates beyond certain bounds can be detected, that expert system techniques can be applied to security auditing and intrusion detection, and that successful intrusion detection may take place while monitoring a limited set of network activities such as user authentication and access control, file movement and storage, and job scheduling. NADIR has been developed to employ these basic concepts while monitoring the audited activities of more than 8000 ICN users.

  16. Insight into Vent Opening Probability in Volcanic Calderas in the Light of a Sill Intrusion Model

    NASA Astrophysics Data System (ADS)

    Giudicepietro, Flora; Macedonio, G.; D'Auria, L.; Martini, M.

    2016-05-01

    The aim of this paper is to discuss a novel approach to provide insights on the probability of vent opening in calderas, using a dynamic model of sill intrusion. The evolution of the stress field is the main factor that controls the vent opening processes in volcanic calderas. On the basis of previous studies, we think that the intrusion of sills is one of the most common mechanism governing caldera unrest. Therefore, we have investigated the spatial and temporal evolution of the stress field due to the emplacement of a sill at shallow depth to provide insight on vent opening probability. We carried out several numerical experiments by using a physical model, to assess the role of the magma properties (viscosity), host rock characteristics (Young's modulus and thickness), and dynamics of the intrusion process (mass flow rate) in controlling the stress field. Our experiments highlight that high magma viscosity produces larger stress values, while low magma viscosity leads to lower stresses and favors the radial spreading of the sill. Also high-rock Young's modulus gives high stress intensity, whereas low values of Young's modulus produce a dramatic reduction of the stress associated with the intrusive process. The maximum intensity of tensile stress is concentrated at the front of the sill and propagates radially with it, over time. In our simulations, we find that maximum values of tensile stress occur in ring-shaped areas with radius ranging between 350 m and 2500 m from the injection point, depending on the model parameters. The probability of vent opening is higher in these areas.

  17. Constraints on the magmatic evolution of the oceanic crust from plagiogranite intrusions in the Oman ophiolite

    NASA Astrophysics Data System (ADS)

    Haase, Karsten M.; Freund, Sarah; Beier, Christoph; Koepke, Jürgen; Erdmann, Martin; Hauff, Folkmar

    2016-05-01

    We present major and trace element as well as Sr, Nd, and Hf isotope data on a suite of 87 plutonic rock samples from 27 felsic crustal intrusions in seven blocks of the Oman ophiolite. The rock compositions of the sample suite including associated more mafic rocks range from 48 to 79 wt% SiO2, i.e. from gabbros to tonalites. The samples are grouped into a Ti-rich and relatively light rare earth element (LREE)-enriched P1 group [(Ce/Yb) N > 0.7] resembling the early V1 lavas, and a Ti-poor and LREE-depleted P2 group [(Ce/Yb) N < 0.7] resembling the late-stage V2 lavas. Based on the geochemical differences and in agreement with previous structural and petrographic models, we define phase 1 (P1) and phase 2 (P2) plutonic rocks. Felsic magmas in both groups formed by extensive fractional crystallization of olivine, clinopyroxene, plagioclase, apatite, and Ti-magnetite from mafic melts. The incompatible element compositions of P1 rocks overlap with those from mid-ocean ridges but have higher Ba/Nb and Th/Nb trending towards the P2 rock compositions and indicating an influence of a subducting slab. The P2 rocks formed from a more depleted mantle source but show a more pronounced slab signature. These rocks also occur in the southern blocks (with the exception of the Tayin block) of the Oman ophiolite implying that the entire ophiolite formed above a subducting slab. Initial Nd and Hf isotope compositions suggest an Indian-MORB-type mantle source for the Oman ophiolite magmas. Isotope compositions and high Th/Nb in some P2 rocks indicate mixing of a melt from subducted sediment into this mantle.

  18. Crystallization conditions in the lherzolite-gabbronorite Suoi Cun intrusion (Northeastern Vietnam)

    NASA Astrophysics Data System (ADS)

    Izokh, A. E.; Svetlitskaya, T. V.; Tolstykh, N. D.; Phuong, N. T.

    2012-04-01

    Crystallization conditions in the lherzolite-gabbronorite Suoi Cun intrusion (Northeastern Vietnam) Suoi Cun intrusion refers to the Late Permian Cu-Ni-PGE ultramafic-mafic complex (Cao Bang complex) of the Song Hiem rift zone of the northeastern Vietnam. The lower part of the intrusion is composed of plagiolherzolite, and the upper part consists of olivine gabbronorite and gabbronorite. The most magnesian olivines are in ultramafic rocks (Mg # = 86), less magnesian olivines are in gabbronorites (Mg # = 70). Clinopyroxene are represented by magnesium diopside-augite. Plagioclase composition varies from anorthite (An90) in plagiolherzolite to labradorite (An55) in gabbronorites. Interstitial sulphide inclusions (pyrrhotite + chalcopyrite + pentlandite) occur in plagiolherzolite. Richest sulfide zone is located near contact zone of inversion.The presence of sulphide droplets in liquidus olivine and in Cr-spinel inclusions in olivine indicates the saturation of the sulfur of the parent picrobasalt melt in the intermediate chamber.The presence of an early liquidus orthopyroxene in plagiolherzolite not consistent with the theoretical calculations by the program «Comagmat», but may be explained by early sulfurization of the melt. Data of zircons from plagiolherzolite and gabbronorites show considerable degree of crustal contamination. Geochemical features of sulfides, including the distribution of platinum group elements (PGE), suggest that the sulfide liquid was segregated from the primary PGE-enriched picrobasalt melt. Based on the calculated concentrations of ore-forming elements (Ni, Cu, PGE) in the parental melts, the ratio of the mass of sulfide liquid to the total mass of the equilibrium silicate melt (N factor) for the Suoi Cun intrusion is 500-2000. Thus, geochemical features of sulfide of the Suoi Cun intrusion indicate that sulfurization of picrobasalt melt occurred in the deep intermediate chamber.

  19. Evaluation of Seawater Intrusion Potential into a Coastal Underground Oil Storage Cavern in Korea

    NASA Astrophysics Data System (ADS)

    Lee, E.; Lim, J.; Moon, H.; Lee, K.

    2010-12-01

    Underground oil storage caverns have been operated in Korea since 1990s, and the facility at Yeosu, south coast of Korea, is one of the largest underground oil storage facilities in Korea. Hydrologic and water quality monitoring of the facility has been performed to find out whether the facility maintains secure containment condition and long-term stability. Recently, seawater intrusion into the base of the storage cavern was suspected based on the long-term monitoring of water levels and chemical analyses of seepage water pumped out from cavern bottom. The sudden decrease of water pressure during the construction of storage tunnel seems to cause the inland movement of saline water. In this study, numerical analysis was performed to estimate the potential of seawater intrusion into underground oil storage cavern using a three dimensional groundwater simulation model, FEFLOW (Diersch, 2005). The geometry of the cavern and water curtain was represented by using the implemented functions. The groundwater flow field and seawater intrusion in response to construction activity was also estimated. The simulation results were validated by comparing EC and salinity of seepage water monitoring data. Sensitivity analyses on hydraulic conductivity and water pressure from the water curtain or injection well were also conducted. Relatively high groundwater level was observed at this site due to the low hydraulic conductivity of base rock and high altitude of the mountains. Therefore, the amount of intruded seawater does not seem to be significant. However, apparent decrease of water level was observed along the main fracture zone and seawater could be intruded along these paths. Simulation results show that the seawater intrusion to the cavern is mainly controlled by the fracture zone, which would be the main channel of groundwater movement. The injection of fresh water to the injection wells along the coast may retard the intrusion of seawater.

  20. Magmatic Cu-Ni sulfide mineralization of the Huangshannan mafic-untramafic intrusion, Eastern Tianshan, China

    NASA Astrophysics Data System (ADS)

    Zhao, Yun; Xue, Chunji; Zhao, Xiaobo; Yang, YongQiang; Ke, Junjun

    2015-06-01

    The Huangshannan Ni-Cu (-PGE) sulfide deposit, a new discovery from geological prospecting in Eastern Tianshan, is in a belt of magmatic Ni-Cu (-PGE) sulfide deposits along the southern margin of the Central Asian Orogenic Belt. The host intrusion of the Huangshannan deposit is composed of a layered ultramafic sequence and a massive gabbro-diorite unit. The major sulfide orebodies occur mainly within websterite and lherzolite in the layered ultramafic sequence. In-situ zircon U-Pb dating analyses yielded a crystallization age of 282.5 ± 1.4 Ma, similar to the ages of the Permian Tarim mantle plume. Samples from the Huangshannan intrusion are characterized by nearly flat rare earth elements patterns, negative Zr, Ti and Nb anomalies, arc-like Th/Yb and Nb/Yb ratios, and significantly lower rare earth element and immobile trace element contents than the Tarim basalts. These characteristics suggest that the Huangshannan intrusion was not generated from the Tarim mantle plume. The primary magma for the Huangshannan intrusion and its associated sulfide mineralization were formed from different pulses of picritic magma with different degrees of crustal contamination. The first pulse underwent an initial removal of 0.016% sulfide in the deep magma chamber. The evolved magma reached sulfide saturation again in the shallow magma chamber and formed sulfide ores in lherzolite. The second pulse of magma reached a level of 0.022% sulfide segregation at staging chamber before ascending up to the shallow magma chamber. In the shallow conduit system, this sulfide-unsaturated magma mixed with the first pulse of magma and with contamination from the country rocks, leading to the formation of sulfide ores in websterite. The third magma pulse from the deep chamber formed the unmineralized massive gabbro-diorite unit of the Huangshannan intrusion.

  1. Estimation of preferential recharge and saltwater intrusion to a coastal groundwater system in central Vietnam by means of 3D stratigraphic modeling

    NASA Astrophysics Data System (ADS)

    Thanh Tam, Vu; Batelaan, Okke; Thanh Le, Tran

    2013-04-01

    Saltwater intrusion is worldwide regarded as a major threat to groundwater resources. Mostly, saltwater intrusion problems are related to sea water level rise or induced intrusion due to excessive groundwater extraction in coastal aquifers. However, the hydrogeological heterogeneity of the subsurface might play an important role in (non-)intrusion as well. We study local (hydro)geological conditions for preferential recharge as well as saltwater intrusion to a coastal groundwater system in Vietnam where geological formations exhibit highly heterogeneous lithologies. A cluster analysis technique combined with a chronographic marker is used to distinguish and map well-log intervals of similar lithological properties in different geological formations. The cluster analysis is carried out on lithological composition, distribution depth and thickness of each lithological distinctive drilling interval of well-logs of 43 groundwater investigation boreholes carried out within the study area. The chronographic marker is a layer of clay originated from weathered basalt rocks, whose color and lithological properties can be distinguished from the other formations. Detailed to coarse 3D stratigraphic models, based on the above analysis, are constructed and used as a tool to estimate preferential recharge paths and saltwater intrusion to the groundwater system under study. Chemical analysis of groundwater water samples is also used to support the estimation. Result of this research work contributes to the interpretation of why the aquifer system of the study area is almost uninfluenced by saltwater intrusion which is relatively common in coastal aquifers of Vietnam.

  2. Intrusive Memories in Perpetrators of Violent Crime: Emotions and Cognitions

    ERIC Educational Resources Information Center

    Evans, Ceri; Ehlers, Anke; Mezey, Gillian; Clark, David M.

    2007-01-01

    The authors investigated factors that may determine whether perpetrators of violent crime develop intrusive memories of their offense. Of 105 young offenders who were convicted of killing or seriously harming others, 46% reported distressing intrusive memories, and 6% had posttraumatic stress disorder. Intrusions were associated with lower…

  3. Geochemical reconnaissance for uranium occurrences in the Notch Peak intrusive area, House Range, Millard County, Utah

    USGS Publications Warehouse

    Cadigan, R.A.; Robinson, Keith

    1982-01-01

    Samples collected from the contact metamorphic zone of the Notch Peak intrusive area, House Range, Millard County, Utah, indicate the occurrence of low-grade uranium and thorium ore. Maximum abundances in the altered mineralized rocks in the contact zone are 450 ppm uranium and 480 ppm thorium. Interpretation of factor analysis of the spectrochemical and delayed neutron analytical data suggests the presence of five geological factors which account for 82 percent of element covariance of 34 elements in 61 samples. The factors are identified as (1) limestone source rock reactions; (2) monzonite source rock reactions; (3) hydrothermal element group 1; (4) rare earth group; and (5) hydrothermal element group 2. The last factor effects the distribution of, primarily, beryllium, uranium, copper, molybdenum, tungsten, niobium, and secondarily, thorium, tin, and zinc; it is identified as the prime mineralization factor. The Notch Peak intrusive area has been a tungsten producing area since before the 1940's and the location of small-scale gold placer operations. This reconnaissance study was a 'follow-up' of uranium anomaly data which were developed during the U.S. Dept. of Energy National Uranium Resource Evaluation (NURE) program in 1978-80.

  4. High-precision temporal constraints on intrusive magmatism of the Siberian Traps

    NASA Astrophysics Data System (ADS)

    Burgess, Seth; Bowring, Sam; Pavlov, Volodia E.; Veselovsky, Roman V.

    2014-05-01

    The broad temporal coincidence between large igneous province magmatism and some of the most severe biotic/environmental crises in Earth history has led many to infer a causal connection between the two. Notable examples include the end-Permian mass extinction and eruption/emplacement of the Siberian Traps large igneous province (LIP) and the end-Triassic mass extinction and the Central Atlantic Magmatic Province. In models proposing a causal connection between LIP magmatism and the environmental changes that lead to mass extinction, gases and particulates injected into the atmosphere are thought to cause abrupt changes in climate and ocean chemistry sufficient to drive mass extinction of marine and terrestrial biota. Magmatism has been proposed to cause voluminous volatile release via contact metamorphism of the sedimentary rocks. In the case of the Siberian Traps LIP, the compositions of sedimentary rocks (carbonates, evaporates, organic-rich shales) that host sills and dikes are ideal for greenhouse gas generation. When coupled with the enormous volume of Siberian LIP intrusive rocks, there is the potential for volatile generation on a scale necessary to drive environmental changes and mass extinction. This model must be tested by comparing the timing of intrusive magmatism with that of the mass extinction. Coupled high-precision geochronology and astrochronology have constrained the timing of biotic crisis and associated environmental perturbations from the deca-millennial to sub-millennial timescale, suggesting that the biotic crisis was abrupt, occurring over < 100 ka. Published geochronology on sills and dikes from the LIP are sparse and lack the necessary precision to resolve the relative timing of the two events outside of age uncertainty. We present new high-precision U-Pb zircon geochronology on seventeen gabbroic sills from throughout the magmatic province. This includes samples from the mineralized and differentiated intrusions in the Noril'sk region

  5. Decimeter Scale Ultra-Fine Fault Rocks (Possible Pseudotachylites) in an Ancient Subduction Thrust Zone

    NASA Astrophysics Data System (ADS)

    Rowe, C. D.; Moore, J. C.; Meneghini, F.; McKiernan, A. W.

    2004-12-01

    Large bodies of ultrafine fault rock (possible pseudotachylite or frictional melt) occur within cataclastic thrust zones in the Ghost Rocks Formation, Kodiak Accretionary Complex, Alaska. The Paleocene Ghost Rocks Formation includes map-scale mélange belts formed by flattening and shearing of seafloor sediments and volcanic rocks at about 250 degrees C and 325 MPa (~13 km depth) during subduction between 65-60Ma. Ten to 15-meter thick cataclastite zones crosscut the mélange fabric at a low angle, representing a stage of increasingly localized shear during subduction thrusting. Ultrafine fault rocks occur as thick (10-25cm) continuous planar beds along the boundaries of cataclastites, or in discontinuous accumulation bodies within cataclastite zones. The boundaries of the ultrafine fault rocks are intrusive, sharp but irregular and deform the cataclastite host fabric. Single pulse intrusions of the ultrafine fault rock range up to 0.5m in intrusive dimension and form complex morphologies resembling both upward and downward directed flame structures and dike-sill complexes, as well as sheath folds and disharmonic flow banding and folding. These field characteristics indicate fluidization and perhaps frictional melting of the ultrafine fault rocks. Ultrafine fault rock bodies can be traced laterally for meters to tens of meters at individual outcrops and occur for about 2 km along strike. Preliminary SEM analysis reveals that the primary matrix material is physically and chemically homogenous down to few-micron scale, consistent with the field identification of pseudotachylite. Thin sections show rounded remnant quartz aggregates, typical of pseudotachylytes. Although some thin sections show suggest melting others may represent ultracataclastite. Some ultrafine fault rock material is rebrecciated and cataclastized to a fine scale, indicating reactivation of previous fault rock generation surfaces. These ultrafine fault rock zones represent the most highly deformed

  6. How to build a mid-crustal intrusive suite: geologic mapping, U-Pb geo-/thermochronology, and thermal modeling of the Bergell Intrusion, Central Alps

    NASA Astrophysics Data System (ADS)

    Samperton, K. M.; Schoene, B.; Annen, C.

    2015-12-01

    Insights into the characteristic rates and processes of crustal magmatic systems can best be made through the integration of observational, analytical and modeling perspectives. We present such an approach in reconstructing the emplacement, differentiation and cooling history of the Bergell Intrusion (N Italy/SE Switzerland), a normally-zoned pluton preserving a ~10 km mid-crustal transect. U-Pb zircon, titanite and allanite geo-/thermochronology of Bergell granitoids provide key empirical constraints for informing numerical simulations of pulse-wise, incremental assembly. Protracted zircon crystallization histories, representing the time between magma zircon saturation and cooling to the solidus, provide a direct petrologic link to forward models of magma emplacement, both of which can be used to derive quantitative magmatic cooling rates for the middle crust. Titanite and allanite dates provide additional constraints on the timing of solidification. Geochronology and modeling are performed in the context of detailed field and structural observations, including those previously interpreted as evidence of upward, pluton-scale melt migration via floor convergence/roof ballooning. Combined Bergell data and modeling demonstrate that pulsed assembly can lead to the formation of substantial melt reservoirs in the middle crust: this finding is largely in contrast to similar models of shallow crustal plutons, highlighting the importance of factors such as ambient country rock temperature in affecting melt residence timescales. This work emphasizes the importance of implementing joint data/modeling studies to intrusive rocks across the full range of spatial scales, emplacement levels and tectonic settings observed on Earth.

  7. Magnetic anomalies in Bahia Esperanza: A window of magmatic arc intrusions and glacier erosion over the northeastern Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Galindo-Zaldívar, Jesús; Ruiz-Constán, Ana; Pedrera, Antonio; Ghidella, Marta; Montes, Manuel; Nozal, Francisco; Rodríguez-Fernandez, Luis Roberto

    2013-02-01

    Bahia Esperanza, constituting the NE tip of the Antarctic Peninsula, is made up of Paleozoic clastic sedimentary rocks overlain by a Jurassic volcano-sedimentary series and intruded by Cretaceous gabbros and diorites. The area is located along the southern part of the Pacific Margin magnetic anomaly belt. Field magnetic researches during February 2010 contribute to determining the deep geometry of the intermediate and basic intrusive rocks. Moreover, the new field data help constrain the regional Pacific Margin Anomaly, characterized up to now only by aeromagnetic and marine data. Field magnetic susceptibility measurements of intrusive intermediate and basic rocks, responsible for magnetic anomalies, ranges from 0.5 × 10- 3 SI in diorites to values between 0.75 × 10- 3 SI and 1.3 × 10- 3 SI in gabbros. In addition, a significant remanent magnetism should also have contributed to the anomalies. The regional magnetic anomaly is characterized by a westward increase from 100 nT up to 750 nT, associated with large intrusive diorite bodies. They probably underlie most of the western slopes of Mount Flora. Gabbros in the Nobby Nunatak determine local residual rough anomalies that extend northwards and westwards, pointing to the irregular geometry of the top of the basic rocks bodies below the Pirámide Peak Glacier. However, the southern and eastern boundaries with the Buenos Aires Glacier are sharp related to deep glacier incision. As a result of the glacier dynamics, magnetic anomalies are also detected north of the Nobby Nunatak due to the extension of the anomalous body and the presence of gabbro blocks in the moraines. The Bahia Esperanza region is a key area where onshore field geological and magnetic research allows us to constrain the shape of the crustal igneous intrusions and the basement glacier geometry, providing accurate data that complete regional aeromagnetic research.

  8. Mapping faults and intrusions onshore Disko Island by use of Vibroseismic data, shallow marine seismic data and electromagnetic observations

    NASA Astrophysics Data System (ADS)

    Clausen, Ole R.; Nørmark, Egon; Gulbrandsen, Pelle; Sabra, Henrik

    2014-05-01

    The west Greenland margin is characterized by sedimentary basins containing high density of intrusions (dikes and sills) originating from the Cenozoic breakup and separation of Greenland and North American. The magmatic rocks have lately attracted interest due to observations of hydrocarbons associated to the intrusions but here due to the ore potential associated to the same intrusions. In 2000 a marine seismic campaign by GEUS in the coastal areas of West Greenland showed that it is possible to identify magmatic intrusions in the sedimentary succession as well as map normal faults, and that the intrusions are heterogeneous distributed and probably related to the normal faults. The presence of normal faults is known from the regional onshore geological mapping campaigns performed by GEUS. However, the marine seismic data indicate a much more complicated structural pattern than presented in the onshore maps, which is a well-known phenomenon (Marcussen et al., 2002). In 2012 and 2013 seismic data were acquired onshore on the northern coast of Disko as part of a research project funded by Avannaa Resources . The objective was initially to test whether it is possible to acquire data of a quality enabling the observation and mapping of intrusions in the subsurface. Later it was followed by a more extensive survey where it was attempted to map the depth to and geometry of the intrusions. The relatively dense seismic grid onshore -compared to the marine seismic data offshore west Greenland- enable the identification and more important the mapping of several intrusions. They show some of the same characteristics as intrusions observed at e.q. the Norwegian margin of the North Atlantic (Hansen et al., 2004). The preliminary results which integrate both marine and onshore seismic data revise the structural understanding of the area and indicate a close relation between the intrusions and the rift related normal faults. The results are consistent with remote sensing methods

  9. Petrogenesis of postcollisional magmatism at Scheelite Dome, Yukon, Canada: Evidence for a lithospheric mantle source for magmas associated with intrusion-related gold systems

    USGS Publications Warehouse

    Mair, John L.; Farmer, G. Lang; Groves, David I.; Hart, Craig J.R.; Goldfarb, Richard J.

    2011-01-01

    The type examples for the class of deposits termed intrusion-related gold systems occur in the Tombstone-Tungsten belt of Alaska and Yukon, on the eastern side of the Tintina gold province. In this part of the northern Cordillera, extensive mid-Cretaceous postcollisional plutonism took place following the accretion of exotic terranes to the continental margin. The most cratonward of the resulting plutonic belts comprises small isolated intrusive centers, with compositionally diverse, dominantly potassic rocks, as exemplified at Scheelite Dome, located in central Yukon. Similar to other spatially and temporally related intrusive centers, the Scheelite Dome intrusions are genetically associated with intrusion-related gold deposits. Intrusions have exceptional variability, ranging from volumetrically dominant clinopyroxene-bearing monzogranites, to calc-alkaline minettes and spessartites, with an intervening range of intermediate to felsic stocks and dikes, including leucominettes, quartz monzonites, quartz monzodiorites, and granodiorites. All rock types are potassic, are strongly enriched in LILEs and LREEs, and feature high LILE/HFSE ratios. Clinopyroxene is common to all rock types and ranges from salite in felsic rocks to high Mg augite and Cr-rich diopside in lamprophyres. Less common, calcic amphibole ranges from actinolitic hornblende to pargasite. The rocks have strongly radiogenic Sr (initial 87Sr/86Sr from 0.711-0.714) and Pb isotope ratios (206Pb/204Pb from 19.2-19.7), and negative initial εNd values (-8.06 to -11.26). Whole-rock major and trace element, radiogenic isotope, and mineralogical data suggest that the felsic to intermediate rocks were derived from mafic potassic magmas sourced from the lithospheric mantle via fractional crystallization and minor assimilation of metasedimentary crust. Mainly unmodified minettes and spessartites represent the most primitive and final phases emplaced. Metasomatic enrichments in the underlying lithospheric mantle

  10. Igneous layering in the peralkaline intrusions ,Kola Peninsula :leading role of gravitational differentiation

    NASA Astrophysics Data System (ADS)

    Kogarko, L. N..

    2012-04-01

    In the center of Kola Peninsula there are two large layered intrusions of agpaitic nepheline syenites - Khibina and Lovozero. . The Khibina alkaline massif (Kola Peninsula,Russia) hosts the world's largest and economically most important apatite deposit. The Khibina massif is a complex multiphase body built up from a number of ring-like and conical intrusions. The apatite bearing intrusion is ring-like and is represented by a layered body of ijolitic composition with a thickness of about 1 - 2 km. The upper zone is represented by different types of apatite ores. These rocks consist of 60-90% euhedral very small (tenths of mm)apatite crystals. The lower zone has mostly ijolitic composition. The lower zone grades into underlying massive urtite consisting of 75-90% large (several mm) euhedral nepheline. Our experimental studies of systems with apatite demonstrated the near-eutectic nature of the apatite-bearing intrusion, resulting in practically simultaneous crystallization of nepheline, apatite and pyroxene. The mathematical model of the formation of the layered apatite-bearing intrusion based on the processes of sedimentation under the conditions of steady state convection taking account of crystal sizes is proposed. Under the conditions of steady-state convection large crystals of nepheline continuously had been settling forming massive underlying urtite whereas smaller crystals of pyroxenes, nepheline and apatite had been stirred in the convecting melt. During the cooling the intensity of convection decreased causing a settling of smaller crystals of nepheline and pyroxene and later very small crystalls of apatite in the upper part of alkaline magma chamber. The Lovozero massif, the largest of the Globe layered peralkaline intrusion, comprises super-large rare-metal (Nb, Ta, REE) deposit. The main ore mineral is loparite (Na, Ce, Ca)2 (Ti, Nb)2O6 which was mined during many years. The composition of cumulus loparite changed systematically upward through the

  11. Research on IPv6 intrusion detection system Snort-based

    NASA Astrophysics Data System (ADS)

    Shen, Zihao; Wang, Hui

    2010-07-01

    This paper introduces the common intrusion detection technologies, discusses the work flow of Snort intrusion detection system, and analyzes IPv6 data packet encapsulation and protocol decoding technology. We propose the expanding Snort architecture to support IPv6 intrusion detection in accordance with CIDF standard combined with protocol analysis technology and pattern matching technology, and present its composition. The research indicates that the expanding Snort system can effectively detect various intrusion attacks; it is high in detection efficiency and detection accuracy and reduces false alarm and omission report, which effectively solves the problem of IPv6 intrusion detection.

  12. A Rock Encyclopedia That Includes Rock Samples.

    ERIC Educational Resources Information Center

    Laznicka, Peter

    1981-01-01

    Described is a rock encyclopedia combining rock sample sets and encyclopedic word and picture entries which can be used as a realistic information resource for independent study or as a part of a course. (JT)

  13. Mineralogical, petrological, and geochemical studies of the Limahe mafic-ultramatic intrusion and associated Ni-Cu sulfide ores, SW China

    NASA Astrophysics Data System (ADS)

    Tao, Yan; Li, Chusi; Song, Xie-Yan; Ripley, Edward M.

    2008-11-01

    The Limahe Ni-Cu sulfide deposit is hosted by a small mafic-ultramafic intrusion (800 × 200 × 300 m) that is temporally associated with the voluminous Permian flood basalts in SW China. The objective of this study is to better understand the origin of the deposit in the context of regional magmatism which is important for the ongoing mineral exploration in the region. The Limahe intrusion is a multiphase intrusion with an ultramafic unit at the base and a mafic unit at the top. The two rock units have intrusive contacts and exhibit similar mantle-normalized trace element patterns and Sr-Nd isotopic compositions but significantly different cumulus mineralogy and major element compositions. The similarities suggest that they are related to a common parental liquid, whereas the differences point to magma differentiation by olivine crystallization at depth. Sulfide mineralization is restricted to the ultramafic unit. The abundances of sulfides in the ultramafic unit generally increase towards the basal contacts with sedimentary footwall. The δ 34S values of sulfide minerals from the Limahe deposit are elevated, ranging from +2.4 to +5.4‰. These values suggest the involvement of external S with elevated δ 34S values. The mantle-normalized platinum-group element (PGE) patterns of bulk sulfide ores are similar to those of picrites associated with flood basalts in the region. The abundances of PGE in the sulfide ores, however, are significantly lower than that of sulfide liquid expected to segregate from undepleted picrite magma. Cr-spinel and olivine are present in the Limahe ultramafic rocks as well as in the picrites. Mantle-normalized trace element patterns of the Limahe intrusion generally resemble those of the picrites. However, negative Nb-Ta anomalies, common features of contamination with the lower or middle crust, are present in the intrusion but absent in the picrites. Sr-Nd isotopes suggest that the Limahe intrusion experienced higher degrees of

  14. Non-intrusive refrigerant charge indicator

    DOEpatents

    Mei, Viung C.; Chen, Fang C.; Kweller, Esher

    2005-03-22

    A non-intrusive refrigerant charge level indicator includes a structure for measuring at least one temperature at an outside surface of a two-phase refrigerant line section. The measured temperature can be used to determine the refrigerant charge status of an HVAC system, and can be converted to a pressure of the refrigerant in the line section and compared to a recommended pressure range to determine whether the system is under-charged, properly charged or over-charged. A non-intrusive method for assessing the refrigerant charge level in a system containing a refrigerant fluid includes the step of measuring a temperature at least one outside surface of a two-phase region of a refrigerant containing refrigerant line, wherein the temperature measured can be converted to a refrigerant pressure within the line section.

  15. Distributed fiber optic moisture intrusion sensing system

    DOEpatents

    Weiss, Jonathan D.

    2003-06-24

    Method and system for monitoring and identifying moisture intrusion in soil such as is contained in landfills housing radioactive and/or hazardous waste. The invention utilizes the principle that moist or wet soil has a higher thermal conductance than dry soil. The invention employs optical time delay reflectometry in connection with a distributed temperature sensing system together with heating means in order to identify discrete areas within a volume of soil wherein temperature is lower. According to the invention an optical element and, optionally, a heating element may be included in a cable or other similar structure and arranged in a serpentine fashion within a volume of soil to achieve efficient temperature detection across a large area or three dimensional volume of soil. Remediation, moisture countermeasures, or other responsive action may then be coordinated based on the assumption that cooler regions within a soil volume may signal moisture intrusion where those regions are located.

  16. A simplified approach to true molar intrusion

    PubMed Central

    2012-01-01

    Background Orthodontic management of anterior open bites is a demanding task for orthodontists. Molar intrusion as a primary means of open bite correction entails the need for appropriate anchorage. Orthodontic mini implants can provide the required mechanical support. The suggested procedure aims to reduce the risk of complications such as root damage or soft tissue irritations while minimizing overall complexity. Methods Three female patients aged 14, 18 and 19 years who decided against a surgical correction were treated with a device consisting of mini implants in the palatal slope, a palatal bar and intrusion cantilevers. Results In all three patients, an open bite reduction of more than a millimeter occurred within four months. An anterior overbite of 2 mm or more could be established within 6 to 9 months. Conclusions The method presented in this article enables the practitioner to use mini implants in an easily accessible insertion site. A lab-side procedure is optional but not required. PMID:23134693

  17. A Survey on Intrusion Detection in MANETs.

    NASA Astrophysics Data System (ADS)

    BakeyaLakshmi, P.; Santhi, K.

    2012-10-01

    A mobile ad hoc network is an infrastructureless network that changes its links dynamically, which makes routing in MANET a difficult process. As Mobile Ad-Hoc Network (MANET) has become a very important technology, research concerning its security problem, especially, in intrusion detection has attracted many researchers. Feature selection methodology plays a vital role in the data analysis process. PCA is used to analyze the selected features. This is because, redundant and irrelevant features often reduce performance of the intrusion detection system. It performs better in increasing speed and predictive accuracy. This survey aims to select and analyze the network features using principal component analysis. While performing various experiments, normal and attack states are simulated and the results for the selected features are analyzed.

  18. Palaeoproterozoic porphyry Cu-Au, intrusion-hosted Au and ultramafic Cu-Ni deposits in the Fennoscandian Shield: Temporal constraints using U-Pb geochronology

    NASA Astrophysics Data System (ADS)

    Bejgarn, Therese; Söderlund, Ulf; Weihed, Pär; Årebäck, Hans; Ernst, Richard E.

    2013-08-01

    The Skellefte district, northern Sweden, is known for the occurrence of 1.89 Ga Palaeoproterozoic volcanogenic massive sulphide (VMS) deposits. The deposits are hosted by the older part of a volcanosedimentary succession, which was intruded at 1.88-1.86 Ga by multiple phases of the syn-volcanic, early orogenic Jörn intrusive complex (JIC). The oldest phase of the JIC hosts different styles of mineralisation, among them porphyry Cu-Mo-Au, intrusion-related Au, and mafic-hosted Fe and Cu-Ni deposits. To discriminate between the different intrusive and ore related events, U-Pb ages of zircons have been obtained for nine intrusive phases and from Na-Ca alteration spatially related to mineralisation, while U-Pb ages of baddeleyite (ZrO2) have been used to constrain intrusive ages of three mineralised and barren mafic-ultramafic intrusive rocks. The two main JIC intrusive phases of a granodioritic-tonalitic composition in the southern study area intruded at 1887 ± 3 Ma and 1886 ± 3 Ma, respectively, and were succeeded by the intrusion of layered mafic-ultramafic intrusive rocks in the northern and southern study area at 1879 ± 1 Ma and 1884 ± 2 Ma, respectively. Emplacement of porphyry dykes took place at ca. 1877 Ma in the southern, western and northern JIC. The dykes are spatially and temporally associated with formation of porphyry style mineralisation, alteration and Au-mineralisation, as inferred from 1879 ± 5 Ma zircons in adjacent Na-Ca alteration zones. High SiO2 and Al2O3 contents together with high Sr/Y ratios, mingling structures, mafic xenoliths and hornblende phenocrysts in the porphyry dykes suggest that the magma originated from hydrated partial melts, possibly from the base of the crust at a mature stage of subduction. Local extension resulted in intrusion of mafic-ultramafic rocks around 1.88 Ga prior to and after, the porphyry dykes and associated mineralisation, approximately 10 Ma after the formation of the spatially related 1.89 Ga VMS deposits

  19. Non-intrusive appliance monitor apparatus

    DOEpatents

    Hart, George W.; Kern, Jr., Edward C.; Schweppe, Fred C.

    1989-08-15

    A non-intrusive monitor of energy consumption of residential appliances is described in which sensors, coupled to the power circuits entering a residence, supply analog voltage and current signals which are converted to digital format and processed to detect changes in certain residential load parameters, i.e., admittance. Cluster analysis techniques are employed to group change measurements into certain categories, and logic is applied to identify individual appliances and the energy consumed by each.

  20. Non-intrusive appliance monitor apparatus

    DOEpatents

    Hart, G.W.; Kern, E.C. Jr.; Schweppe, F.C.

    1989-08-15

    A non-intrusive monitor of energy consumption of residential appliances is described in which sensors, coupled to the power circuits entering a residence, supply analog voltage and current signals which are converted to digital format and processed to detect changes in certain residential load parameters, i.e., admittance. Cluster analysis techniques are employed to group change measurements into certain categories, and logic is applied to identify individual appliances and the energy consumed by each. 9 figs.

  1. [Approaching intrusive care in nursing education].

    PubMed

    Flament, Nathalie; Godon, Guillaume; Henon, Nathalie; Witzak, Elisabeth; Grousset, Sylvie

    2015-04-01

    The initial representations of the profession and of proper care of student nurses beginning their training, will, throughout their course, come up against the reality of nursing practice. At the heart of the complexity of potentially intrusive care procedures and the relational approach in which they are players or witnesses, their practical work experience becomes a modelling tool for their career. This is facilitated when the teaching team structures the reflexive analysis through pedagogical approaches favouring expression and objectivity between peers.

  2. An Intrusion Detection Algorithm Based On NFPA

    NASA Astrophysics Data System (ADS)

    Anming, Zhong

    A process oriented intrusion detection algorithm based on Probabilistic Automaton with No Final probabilities (NFPA) is introduced, system call sequence of process is used as the source data. By using information in system call sequence of normal process and system call sequence of anomaly process, the anomaly detection and the misuse detection are efficiently combined. Experiments show better performance of our algorithm compared to the classical algorithm in this field.

  3. Intrusion detection using rough set classification.

    PubMed

    Zhang, Lian-hua; Zhang, Guan-hua; Zhang, Jie; Bai, Ying-cai

    2004-09-01

    Recently machine learning-based intrusion detection approaches have been subjected to extensive researches because they can detect both misuse and anomaly. In this paper, rough set classification (RSC), a modern learning algorithm, is used to rank the features extracted for detecting intrusions and generate intrusion detection models. Feature ranking is a very critical step when building the model. RSC performs feature ranking before generating rules, and converts the feature ranking to minimal hitting set problem addressed by using genetic algorithm (GA). This is done in classical approaches using Support Vector Machine (SVM) by executing many iterations, each of which removes one useless feature. Compared with those methods, our method can avoid many iterations. In addition, a hybrid genetic algorithm is proposed to increase the convergence speed and decrease the training time of RSC. The models generated by RSC take the form of "IF-THEN" rules, which have the advantage of explication. Tests and comparison of RSC with SVM on DARPA benchmark data showed that for Probe and DoS attacks both RSC and SVM yielded highly accurate results (greater than 99% accuracy on testing set).

  4. Intrusion detection using pattern recognition methods

    NASA Astrophysics Data System (ADS)

    Jiang, Nan; Yu, Li

    2007-09-01

    Today, cyber attacks such as worms, scanning, active attackers are pervasive in Internet. A number of security approaches are proposed to address this problem, among which the intrusion detection system (IDS) appears to be one of the major and most effective solutions for defending against malicious users. Essentially, intrusion detection problem can be generalized as a classification problem, whose goal is to distinguish normal behaviors and anomalies. There are many well-known pattern recognition algorithms for classification purpose. In this paper we describe the details of applying pattern recognition methods to the intrusion detection research field. Experimenting on the KDDCUP 99 data set, we first use information gain metric to reduce the dimensionality of the original feature space. Two supervised methods, the support vector machine as well as the multi-layer neural network have been tested and the results display high detection rate and low false alarm rate, which is promising for real world applications. In addition, three unsupervised methods, Single-Linkage, K-Means, and CLIQUE, are also implemented and evaluated in the paper. The low computational complexity reveals their application in initial data reduction process.

  5. Decoding low dihedral angles in gabbroic layered intrusions

    NASA Astrophysics Data System (ADS)

    Holness, M. B.; Humphreys, M.; Veksler, I. V.

    2010-12-01

    Texturally equilibrated rocks are granular with a unimodal grain size, smoothly curved grain boundaries, and angles at three-grain junctions of 110-140°. Gabbros are not texturally equilibrated: primocrysts commonly have planar faces whereas later-formed phases fill in the interstitial spaces. Augite-plagioclase-plagioclase dihedral angles (Θcpp) rarely attain the equilibrium value in gabbros and the population of disequilibrium angles preserves otherwise inaccessible information about rock history. The Θcpp population varies significantly between different basaltic bodies. In a rapidly cooled dolerite Θcpp has a low median (60-70°) and a high standard deviation (20-25°). The plagioclase-augite grain boundaries are generally planar. In more slowly cooled gabbros in layered intrusions, the angle populations have a higher median (80-110°) with a low standard deviation (10-15°). The plagioclase-augite grain boundaries are generally planar far from the triple junction, but curve within 10 microns of the junction. This curvature is commonly asymmetric. The angle population in solidified gabbros infiltrated by low-temperature melts is similar to that in dolerites, although the low angles are associated with cuspate interstitial grains. The dihedral angle is a function of both the original solidification process and subsequent high-temperature (melt-absent) grain boundary migration. Infilling of a melt pocket by overgrowth of the bounding solid phases necessitates supersaturation, and this is easier to attain for planar faces, resulting in inhibition of augite growth into pores bounded by planar plagioclase grains and an asymmetry of the initial augite-plag-plag junction. If the solidified gabbro is kept sufficiently hot these initial junction geometries can change during textural equilibration. In the Skaergaard, Rum and Bushveld intrusions, the median Θcpp varies with liquidus assemblage, increasing step-wise on the addition of a new liquidus phase. Locally

  6. Lower-crustal intrusion on the North Atlantic continental margin.

    PubMed

    White, R S; Smith, L K; Roberts, A W; Christie, P A F; Kusznir, N J; Roberts, A M; Healy, D; Spitzer, R; Chappell, A; Eccles, J D; Fletcher, R; Hurst, N; Lunnon, Z; Parkin, C J; Tymms, V J

    2008-03-27

    When continents break apart, the rifting is sometimes accompanied by the production of large volumes of molten rock. The total melt volume, however, is uncertain, because only part of it has erupted at the surface. Furthermore, the cause of the magmatism is still disputed-specifically, whether or not it is due to increased mantle temperatures. We recorded deep-penetration normal-incidence and wide-angle seismic profiles across the Faroe and Hatton Bank volcanic margins in the northeast Atlantic. Here we show that near the Faroe Islands, for every 1 km along strike, 360-400 km(3) of basalt is extruded, while 540-600 km(3) is intruded into the continent-ocean transition. We find that lower-crustal intrusions are focused mainly into a narrow zone approximately 50 km wide on the transition, although extruded basalts flow more than 100 km from the rift. Seismic profiles show that the melt is intruded into the lower crust as sills, which cross-cut the continental fabric, rather than as an 'underplate' of 100 per cent melt, as has often been assumed. Evidence from the measured seismic velocities and from igneous thicknesses are consistent with the dominant control on melt production being increased mantle temperatures, with no requirement for either significant active small-scale mantle convection under the rift or the presence of fertile mantle at the time of continental break-up, as has previously been suggested for the North Atlantic Ocean.

  7. Fracture fillings and intrusive pyroclasts, Inyo Domes, California

    SciTech Connect

    Heiken, G.; Wohletz, K.; Eichelberger, J.

    1988-05-10

    Fractures containing juvenile magmatic pyroclasts were encountered during drilling into a 600-year-old feeder dike beneath the Inyo Domes chain, California. The Inyo Domes consist of a north-south trending, 10-km-long chain of domes, rhyolitic tuff rings, and phreatic craters. Boreholes were cored through the 51-m-diameter conduit of Obsidian Dome, the largest of the Inyo Domes, and through an unvented portion of the intrusion (dike) 1 km to the south. Pyroclast-bearing fractures were intersected in both holes: (1) 7- to 40-cm-thick fractures in welded basaltic scoria and quartz monzonite country rock are adjacent to the conduit at depths of 400--411 m and 492--533 m; they contain gray, clastic deposits, which show truncated cross bedding and convolute bedding; (2) adjacent to the dike, massive fracture fillings occur at depths of 289--302 m (129 m east of the dike) and 366--384 m (95--87 m east of the dike).

  8. Lower-crustal intrusion on the North Atlantic continental margin.

    PubMed

    White, R S; Smith, L K; Roberts, A W; Christie, P A F; Kusznir, N J; Roberts, A M; Healy, D; Spitzer, R; Chappell, A; Eccles, J D; Fletcher, R; Hurst, N; Lunnon, Z; Parkin, C J; Tymms, V J

    2008-03-27

    When continents break apart, the rifting is sometimes accompanied by the production of large volumes of molten rock. The total melt volume, however, is uncertain, because only part of it has erupted at the surface. Furthermore, the cause of the magmatism is still disputed-specifically, whether or not it is due to increased mantle temperatures. We recorded deep-penetration normal-incidence and wide-angle seismic profiles across the Faroe and Hatton Bank volcanic margins in the northeast Atlantic. Here we show that near the Faroe Islands, for every 1 km along strike, 360-400 km(3) of basalt is extruded, while 540-600 km(3) is intruded into the continent-ocean transition. We find that lower-crustal intrusions are focused mainly into a narrow zone approximately 50 km wide on the transition, although extruded basalts flow more than 100 km from the rift. Seismic profiles show that the melt is intruded into the lower crust as sills, which cross-cut the continental fabric, rather than as an 'underplate' of 100 per cent melt, as has often been assumed. Evidence from the measured seismic velocities and from igneous thicknesses are consistent with the dominant control on melt production being increased mantle temperatures, with no requirement for either significant active small-scale mantle convection under the rift or the presence of fertile mantle at the time of continental break-up, as has previously been suggested for the North Atlantic Ocean. PMID:18368115

  9. Count out your intrusions: effects of verbal encoding on intrusive memories.

    PubMed

    Krans, Julie; Naring, Gerard; Becker, Eni S

    2009-11-01

    Peri-traumatic information processing is thought to affect the development of intrusive trauma memories. This study aimed to replicate and improve the study by Holmes, Brewin, and Hennessy (2004, Exp. 3) on the role of peri-traumatic verbal processing in analogue traumatic intrusion development. Participants viewed an aversive film under one of three conditions: counting backwards in 3s ("verbal interference"), verbalising emotions and thoughts ("verbal enhancement"), or without an extra task. A dual-process account of PTSD would predict that verbal interference would increase intrusion frequency compared to no task, whereas verbal enhancement would lead to a decrease. In contrast, mainstream memory theory predicts a decrease in intrusion frequency from any concurrent task that diverts attention away from the trauma film. The main finding was that the verbal interference task led to a decrease in intrusive memories of the film compared to the other two conditions. This finding does not support a dual-process account of PTSD, but is in line with general theories of memory and attention.

  10. Saline intrusion in partially mixed estuaries

    NASA Astrophysics Data System (ADS)

    Prandle, D.

    2004-03-01

    Restricting interest to partially mixed estuaries, earlier studies of tidally averaged linearised theories relating to the vertical structure of salinity and velocities (accompanying saline intrusion) are extended to take account of tidal straining and associated convective overturning. The applicability of these theories is evaluated by reference to a 'single-point' numerical model in which the time-varying cycle of depth-averaged tidal current amplitude, Û, and a (temporally and vertically) constant saline gradient, S x, are specified. This model highlights the importance of convective overturning in counteracting unstable density structures introduced by tidal straining. By omitting overturning in the model, results agree closely with linearised theoretical derivations. However, incorporating overturning substantially increases tidally averaged surface-to-bed differences for both residual currents, δ u, and salinity, δ s. The vertical structure of tidal currents is a maximum, and hence the effect of tidal straining, in shallow macro-tidal estuaries. The propagation of tidal elevations and currents remains insensitive to saline intrusion in partially mixed estuaries. The applicability of the model was evaluated by simulation of recent measurements by Rippeth et al. (J. Phys. Oceanogr. 31 (2001) 2458). To explore the generality of estuarine responses, the model was run for a wide range of values of saline intrusion lengths, L, and water depths, D. Additional sensitivity analyses were made for changes in Û and bed stress coefficient, k. Response frameworks are shown for: δ u, δ s, potential energy anomaly φ, work done by bed friction and internal shear, rates and efficiency of saline mixing and ratios of relative mixing by diffusion to overturning. By equating the rate of mixing associated with vertical diffusion with river flow, Q, an expression for saline intrusion length L∝D 2/k ÛU o ( Uo river flow velocity) was derived. This formulation agrees with

  11. Workshop on Pristine Highlands Rocks and the early History of the Moon

    NASA Technical Reports Server (NTRS)

    Longhi, J. (Editor); Ryder, G. (Editor)

    1983-01-01

    Oxide composition of the Moon, evidence for an initially totally molten Moon, geophysical contraints on lunar composition, random sampling of a layered intrusion, lunar highland rocks, early evolution of the Moon, mineralogy and petrology of the pristine rocks, relationship of the pristine nonmore rocks to the highlands soils and breccias, ferroan anorthositic norite, early lunar igneous history, compositional variation in ferroan anosthosites, a lunar magma ocean, deposits of lunar pristine rocks, lunar and planetary compositions and early fractionation in the solar nebula, Moon composition models, petrogenesis in a Moon with a chondritic refractory lithophile pattern, a terrestrial analog of lunar ilmenite bearing camulates, and the lunar magma ocean are summarized.

  12. Broad accommodation of rift-related extension recorded by dyke intrusion in Saudi Arabia

    USGS Publications Warehouse

    Pallister, J.S.; McCausland, W.A.; Jonsson, Sigurjon; Lu, Zhiming; Zahran, H.M.; El, Hadidy S.; Aburukbah, A.; Stewart, I.C.F.; Lundgren, P.R.; White, R.A.; Moufti, M.R.H.

    2010-01-01

    The extensive harrat lava province of Arabia formed during the past 30 million years in response to Red Sea rifting and mantle upwelling. The area was regarded as seismically quiet, but between April and June 2009 a swarm of more than 30,000 earthquakes struck one of the lava fields in the province, Harrat Lunayyir, northwest Saudi Arabia. Concerned that larger damaging earthquakes might occur, the Saudi Arabian government evacuated 40,000 people from the region. Here we use geologic, geodetic and seismic data to show that the earthquake swarm resulted from magmatic dyke intrusion. We document a surface fault rupture that is 8 km long with 91 cm of offset. Surface deformation is best modelled by the shallow intrusion of a north-west trending dyke that is about 10 km long. Seismic waves generated during the earthquakes exhibit overlapping very low- and high-frequency components. We interpret the low frequencies to represent intrusion of magma and the high frequencies to represent fracturing of the crystalline basement rocks. Rather than extension being accommodated entirely by the central Red Sea rift axis, we suggest that the broad deformation observed in Harrat Lunayyir indicates that rift margins can remain as active sites of extension throughout rifting. Our analyses allowed us to forecast the likelihood of a future eruption or large earthquake in the region and informed the decisions made by the Saudi Arabian government to return the evacuees.

  13. River Valley pluton, Ontario - A late-Archean/early-Proterozoic anorthositic intrusion in the Grenville Province

    NASA Technical Reports Server (NTRS)

    Ashwal, Lewis D.; Wooden, Joseph L.

    1989-01-01

    This paper presents Nd, Sr, and Pb isotopic data indicating a late-Archean/early-Proterozoic age for the River Valley anorthositic pluton of the southwestern Grenville Province of Sudbury, Ontario. Pb-Pb isotopic data on 10 whole-rock samples ranging in composition from anorthosite to gabbro yield an age of 2560 + or - 155 Ma. The River Valley pluton is thus the oldest anorthositic intrusive yet recognized within the Grenville Province. The Sm-Nd isotopic system records an age of 2377 + or - 68 Ma. High Pb-208/Pb-204 of deformed samples relative to igneous-textured rocks implies Th introduction and/or U loss during metamorphism in the River Valley area. Rb-Sr data from igneous-textured and deformed samples and from mineral separates give an age of 2185 + or - 105 Ma, indicating substantial disturbance of the Rb-Sr isotopic system.

  14. Episodic growth of a Late Cretaceous and Paleogene intrusive complex of pegmatitic leucogranite, Ruby Mountains core complex, Nevada, USA

    USGS Publications Warehouse

    Howard, K.A.; Wooden, J.L.; Barnes, C.G.; Premo, W.R.; Snoke, A.W.; Lee, S.-Y.

    2011-01-01

    Gneissic pegmatitic leucogranite forms a dominant component (>600 km3) of the midcrustal infrastructure of the Ruby Mountains-East Humboldt Range core complex (Nevada, USA), and was assembled and modified episodically into a batholithic volume by myriad small intrusions from ca. 92 to 29 Ma. This injection complex consists of deformed sheets and other bodies emplaced syntectonically into a stratigraphic framework of marble, calc-silicate rocks, quartzite, schist, and other granitoids. Bodies of pegmatitic granite coalesce around host-rock remnants, which preserve relict or ghost stratigraphy, thrusts, and fold nappes. Intrusion inflated but did not disrupt the host-rock structure. The pegmatitic granite increases proportionally downward from structurally high positions to the bottoms of 1-km-deep canyons where it constitutes 95%-100% of the rock. Zircon and monazite dated by U-Pb (sensitive high-resolution ion microprobe, SHRIMP) for this rock type cluster diffusely at ages near 92, 82(?), 69, 38, and 29 Ma, and indicate successive or rejuvenated igneous crystallization multiple times over long periods of the Late Cretaceous and the Paleogene. Initial partial melting of unexposed pelites may have generated granite forerunners, which were remobilized several times in partial melting events. Sources for the pegmatitic granite differed isotopically from sources of similar-aged interleaved equigranular granites. Dominant Late Cretaceous and fewer Paleogene ages recorded from some pegmatitic granite samples, and Paleogene-only ages from the two structurally deepest samples, together with varying zircon trace element contents, suggest several disparate ages of final emplacement or remobilization of various small bodies. Folded sills that merge with dikes that cut the same folds suggest that there may have been in situ partial remobilization. The pegmatitic granite intrusions represent prolonged and recurrent generation, assembly, and partial melting modification of a

  15. Frequency of intrusive luxation in deciduous teeth and its effects.

    PubMed

    Carvalho, Vivian; Jacomo, Diana Ribeiro; Campos, Vera

    2010-08-01

    The aims of this study were three-fold: First, to determine the prevalence of partial and total intrusion of the primary anterior teeth. Second, to investigate the sequelae of total and partial intrusive luxation in the primary anterior teeth and in their successors and finally, to establish whether the sequelae on both deciduous and permanent teeth were related to the child's age at the time of the intrusion. Data collected from records of 169 boys and 138 girls, all between the ages of zero and 10 years, who were undergoing treatment during the period of March 1996 to December 2004. The sample was composed of 753 traumatized deciduous teeth, of which 221 presented intrusive luxation injury. Children with ages ranging from one to 4 years were the most affected with falls being the main cause of intrusion. Of all intruded teeth 128 (57.9%) were totally intruded and 93 (42.1%) partially. Pulp necrosis/premature loss and color change were the most frequent sequelae in both total and partial intrusions. Concerning permanent dentition, the most common disturbances were color change and/or enamel hypoplasia. Both types of intrusion caused eruption disturbance. Total intrusion was the most frequent type of intrusive luxation. There was no significant correlation between the child's age at the time of intrusion and the frequency of subsequent sequela on primary injured teeth (P = 0.035), between the age at the time of injury and the developmental disturbances on permanent teeth (P = 0.140).

  16. Geophysical Exploration of Disseminated and Stockwork deposits associated with plutonic intrusive: A Case study in the eastern flank of the western Cordillera, Colombia

    NASA Astrophysics Data System (ADS)

    Hernandez, O.; Alexander, G. C.; Pintor, I. M.

    2011-12-01

    Disseminated deposit exploration in the tropics suffers from difficult geological mapping due to thick vegetation, lack of rock outcrop, and extensive but variable saprolitic weathering. Geophysical exploration of these deposits normally includes magnetic, induced polarization and gamma ray spectrometry surveys. The largest RTP Total field magnetic anomaly highs are usually associated with the diorite porphyry intrusive bodies. Normally, diorites are less magnetic than the basaltic rocks. Therefore, where the magnetic anomaly highs are related to the intrusions they can be explained by the intensive mineralization of basic metals including magnetite that are associated with the porphyry intrusions. Regularly, the magnetic anomaly gradients help to delineate local discontinuities that can be interpreted as local faults and joints that can be mineralized. The gamma ray spectrometry is useful to determine the anomalous concentration of Potassium, Uranium and Thorium that can be interpreted in terms of alteration halos and linear discontinuities. The statistical analysis of the data also can determine the intermediate intrusive / extrusive nature of the porphyry intrusions. The use of gamma ray spectrometry helps to determine the concentration of elemental potassium, regardless of the associated potassium mineral species, enabling alteration mapping in a geological setting related to volcanic-associated massive sulphide base metals and gold. The induced polarization survey is useful in outlining sulphide distribution in porphyry deposits related to chargeability anomaly highs. The preliminary results of the geophysical exploration program of the eastern flank of the Western Cordillera in the Andes Mountains of Colombia are discussed.

  17. Mafic dykes intrusive into Pre-Cambrian rocks of the São Luís cratonic fragment and Gurupi Belt (Parnaíba Province), north-northeastern Brazil: Geochemistry, Sr-Nd-Pb-O isotopes, 40Ar/39Ar geochronology, and relationships to CAMP magmatism

    NASA Astrophysics Data System (ADS)

    Klein, Evandro L.; Angélica, Rômulo S.; Harris, Chris; Jourdan, Fred; Babinski, Marly

    2013-07-01

    Dykes of diabase and microgabbro intruded into Pre-Cambrian rocks of the São Luís cratonic fragment and Gurupi Belt, which are tectonic and erosive windows of the Parnaíba Basin in north-northeastern Brazil. Ar-Ar ages were determined, and major, trace element, and Nd-Sr-Pb-O isotopic compositions of these dykes were measured to provide insights into their age, and into the nature of their mantle sources and petrogenetic processes. The data have also been used to compare the chemical and isotopic signatures of the dykes with those of the Central Atlantic Magmatic Province (CAMP). Four chemical groups of mafic dykes have been identified. These comprise two subtypes of high-Ti rocks (i) HTi-1 (TiO2 < 2.3 wt.%; SiO2 > 47 wt.%), (ii) HTi-2 (TiO2 > 2.7 wt.%; SiO2 > 47 wt.%), in addition to (iii) evolved high-Ti (TiO2 > 4 wt.%; SiO2 of ~ 46 wt.%) and (iv) low-Si (TiO2 > 2.2 wt.%; SiO2 < 45 wt.%) rocks. 40Ar/39Ar geochronology of plagioclase returned ages of 201 ± 4 Ma and 193 ± 10 Ma for the HTi-2 subtype, and of 201 ± 2 Ma and 207 ± 9 Ma for the evolved high-Ti group. The HTi-1 and low-Si groups presented highly disturbed age spectra, and did not allow the definition of their emplacement ages. The Argon data indicate an age > 200 Ma for the low-Si group and are dubious with respect to the age of theHTi-1 subtype, if coeval with (i.e., ~ 200 Ma), or older than, the HTi-2 and evolved high-Ti types. All groups present δ18O values of pyroxene that are compatible with uncontaminated mantle-derived magmas. The HTi-1 subtype (average 143Nd/144Nd200 = 0.512644; 87Sr/86Sr200 = 0.7035; 206Pb/204Pb of 17.86) shows the less enriched and less fractionated (more primitive) trace element distribution of all groups. The HTi-2 subtype shows enriched trace element pattern and depleted Nd-Sr signature (143Nd/144Nd200 = 0.512610; 87Sr/86Sr200 = 0.7037) and average 206Pb/204Pb ratios of 17.23. The evolved high-Ti chemical group shows average ratios of 143Nd/144Nd200 = 0.512558, 87Sr

  18. Uranium and other element analyses of igneous rocks of Arkansas

    SciTech Connect

    Steele, K.F.

    1982-05-01

    Seventy-six samples of igneous rocks representing a variety of rock types and locations in Arkansas were analyzed by neutron activation analysis for the elements U, Th, Na, Al, Sc, Ti, V, Mn, Fe, La, Ce, Sm, Eu, Dy, Yb, Lu, and Hf. Samples were collected from the major igneous intrusions at Granite Mountain, Bauxite, Magnet Cove, Potash Sulfur Springs, and Murfreesboro, representing various syenites, lamprophyres, carbonatite, kimberlite, and periodotite. To make the data available for public use without further delay, this report is being issued without the normal technical and copy editing.

  19. Isotopic Studies of processes in mafic magma chambers: III. The Muskox intrusion, Northwest Territories, Canada

    NASA Astrophysics Data System (ADS)

    Stewart, Brian W.; DePaolo, Donald J.

    We report the results of a neodymium and strontium isotopic investigation of magma sources and magma chamber processes in the Proterozoic Muskox layered mafic intrusion. Our internal Sm-Nd isochron age of 1258±40 Ma from a two-pyroxene gabbro agrees well with previous U-Pb age determinations for the Muskox intrusion and Mackenzie igneous events. The preservation of a pre-Muskox Sm-Nd isochron age in a sample of stoped wall rock has allowed us to place constraints on the duration of the Muskox magma system; models for diffusive equilibration suggest a time scale of 103-104 years for crystallization of the upper 10% of the magma chamber. The liquids injected into the magma chamber had ɛNd(1258 Ma) values in the range of -3 to +1, indicating that they were derived from an undepleted mantle source. Large differences in 87Sr/86Sr and 143Nd/144Nd between the Muskox parent magma and a zone of wall rock-derived silicic magma that existed at the roof of the chamber make these isotopes sensitive indicators of interaction between the components of the system. Modeling of isotopic variations within individual cyclic units (where each cyclic unit represents crystallization of a single influx of magma into the chamber) suggests that the rate of assimilation of silicic wall rock by mafic magma was <5% of the crystallization rate, in spite of the proximity of the basaltic liquid to the overlying molten wall rock. We attribute this lack of significant assimilation to large differences in buoyancy and viscosity between mafic and silicic magmas. Variations in 87Sr/86Sr and 143Nd/144Nd among cyclic units within the layered series most likely resulted from mixing between mafic magma and molten silicic wall rock during injection of new magma pulses, or from variations in the magma source feeding the Muskox intrusion. We suggest that the successive cyclic units moved toward more evolved compositions as the vigor of the magmatic system decreased, allowing increased mixing between new

  20. Rollerjaw Rock Crusher

    NASA Technical Reports Server (NTRS)

    Peters, Gregory; Brown, Kyle; Fuerstenau, Stephen

    2009-01-01

    The rollerjaw rock crusher melds the concepts of jaw crushing and roll crushing long employed in the mining and rock-crushing industries. Rollerjaw rock crushers have been proposed for inclusion in geological exploration missions on Mars, where they would be used to pulverize rock samples into powders in the tens of micrometer particle size range required for analysis by scientific instruments.

  1. 900 Ma Pole from the Bjerkreim-Sokndal Layered Intrusion, Rogaland Igneous Complex, Norway: Where Was Baltica in the Early Neoproterozoic?

    NASA Astrophysics Data System (ADS)

    Brown, L. L.; McEnroe, S. A.

    2014-12-01

    The southern Norwegian Rogaland Igneous Complex (RIC) intruded into post-Sveconorwegian granulite facies crust between 930 and 920 Ma. It includes three massif anorthosites, several small leuconorite bodies and the ~7km thick norite-quartz mangerite layered Bjerkreim-Sokndal (BKS) intrusion. The intrusion consists of five rhythmic mega-units created by repeated magma influxes capped by a transition zone and a thick sequence of more evolved mangerites and quartz mangerites. Over 70 paleomagnetic sites have been collected in the BKS, sampling all the mega-cyclic subunits and overlying mangerites. Remanence within the BKS is held in hemo-ilmenite-only rocks (lower parts of the mega-cyclic units), mixed hemo-ilmenite and magnetite rocks (upper parts of the lower mega-cyclic units) and magnetite only rocks in the upper highest mega-cyclic unit and overlying mangerites. Due to the different oxides present magnetic susceptibility varies over four orders of magnitude with a bimodal distribution (mean susceptibility of 6.4 x 10-3 SI for hemo-ilmenite rocks, and 8.9 x 10-2 SI for magnetite rocks). NRM values do not show a strong bimodal distribution as many of the rocks lacking magnetite have hemo-ilmenite with strong lamellar magnetism; average NRM for the entire suite is 8.83 A/m. All sites within the cyclic part of the intrusion have stable remanence and produce well-clustered site means. Samples from the upper mangerite rocks, dominated by MD magnetite, are often unstable and not all sites provide acceptable data. Mean directions for 66 sites spanning the entire intrusion are I = -73.7°, D = 303.7°, with α95 = 3.6° and k = 24. The resulting pole position is at 36.1°S and 217.5°E, with a paleolatitude for this part of Baltica of 59.7°S. Examination of the magnetic mineralogy combined with geochronology for RIC rocks yields an age of magnetization of ~900 Ma. Metamorphic country rocks yield similar directions at least 10 km from the contact, confirming the presence

  2. Platinum-Group Element Mineralization in the Fedorovatundra layered intrusion, Kola Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Groshev, Nikolay; Subbotin, Victor; Korchagin, Alexey

    2016-04-01

    The 2526 to 2485 Ma Fedorovatundra layered mafic intrusion in the central part of the Kola Peninsula, Russia, is the western massif of the Fedorova-Pana Complex (2526-2446 Ma), which is situated along the northern contact of the Early Proterozoic Imandra-Varzuga rift and Archean granite gneiss. The Fedorovatundra intrusion of approximately 4 km thick has two major parts: (1) located at the bottom of the intrusion Taxitic series (10 to 900 m) and composing the main volume of the massif Layered series (4000 m). The Taxitic series is distinctive, due to its predominant vary-textured often quartz-saturated norites and gabbronorites (with fewer amounts of leucogabbro, melanorite and Ol-gabbronorite) and abundant pyroxenite, less harzburgite xenoliths. Medium to coarse-grained mottled or massive leucocratic gabbronorite and leucogabbro prevails in the Layered series with mesocratic gabbronorite, pyroxenite and troctolite as subordinate rocks. Depending on its localization, geochemical features, mineral composition and economic value platinum-group element (PGE) mineralization of the Fedorovatundra intrusion is divided into 'marginal' (basal, contact) and 'reef' types. 'Marginal' type of mineralization is presented by irregular disseminated interstitial sulfides (1-2 vol. %) of pentlandite-pyrrhotite-chalcopyrite association (Cu/Ni = 1.8) in the Taxitic series. Less sulfides occur as uniformly disseminated aggregates, thin massive lenses and nests. PGE and base metals are concentrated in several ore horizons of 3.5 km long complicated structure. Thickness of ore horizons varies generally within 10-150 m, but it can rise up to 280 m in bulges. In the most common ore-bearing rock (taxitic gabbronorite) average Pt + Pd content is 1.6 ppm (Pd/Pt 4.5). The pyroxenite xenoliths occurring within the Taxitic series are practically barren of sulfide and can dilute higher PGE and base metal grades in the gabbronorite matrix. 'Marginal' mineralization of the Fedorovotundrovsky

  3. Bald Mountain gold mining district, Nevada: A Jurassic reduced intrusion-related gold system

    USGS Publications Warehouse

    Nutt, C.J.; Hofstra, A.H.

    2007-01-01

    The Bald Mountain mining district has produced about 2 million ounces (Moz) of An. Geologic mapping, field relationships, geochemical data, petrographic observations, fluid inclusion characteristics, and Pb, S, O, and H isotope data indicate that An mineralization was associated with a reduced Jurassic intrusion. Gold deposits are localized within and surrounding a Jurassic (159 Ma) quartz monzonite porphyry pluton and dike complex that intrudes Cambrian to Mississippian carbonate and clastic rocks. The pluton, associated dikes, and An mineralization were controlled by a crustal-scale northwest-trending structure named the Bida trend. Gold deposits are localized by fracture networks in the pluton and the contact metamorphic aureole, dike margins, high-angle faults, and certain strata or shale-limestone contacts in sedimentary rocks. Gold mineralization was accompanied by silicification and phyllic alteration, ??argillic alteration at shallow levels. Although An is typically present throughout, the system exhibits a classic concentric geochemical zonation pattern with Mo, W, Bi, and Cu near the center, Ag, Pb, and Zn at intermediate distances, and As and Sb peripheral to the intrusion. Near the center of the system, micron-sized native An occurs with base metal sulfides and sulfosalts. In peripheral deposits and in later stages of mineralization, Au is typically submicron in size and resides in pyrite or arsenopyrite. Electron microprobe and laser ablation ICP-MS analyses show that arsenopyrite, pyrite, and Bi sulfide minerals contain 10s to 1,000s of ppm Au. Ore-forming fluids were aqueous and carbonic at deep levels and episodically hypersaline at shallow levels due to boiling. The isotopic compositions of H and O in quartz and sericite and S and Pb in sulfides are indicative of magmatic ore fluids with sedimentary sulfur. Together, the evidence suggests that Au was introduced by reduced S-bearing magmatic fluids derived from a reduced intrusion. The reduced

  4. Edifice and substrata deformation induced by intrusive complexes and gravitational loading in the Mull volcano (Scotland)

    NASA Astrophysics Data System (ADS)

    Mathieu, Lucie; Vries, Benjamin Van Wyk De

    2009-12-01

    It is likely that the structure of a volcanic edifice can be significantly modified by deformation caused by large, shallow intrusions. Such deformation may interact with that caused by volcano loading. We explore such intrusion-related and loading-related deformation with field evidence and analogue models. To do this we have chosen the eroded Palaeogene Mull volcano (Scotland) that had a major edifice, has well exposed intrusions and significant deformation. There are thin Mesozoic sedimentary rocks forming ductile layers below the volcano, but their thickness is insufficient to allow the gravitational spreading of the volcanic edifice, especially when considering that a thick lava pile covers them. Thus intrusive push may have been the driving force for deformation. The Mull activity migrated toward the northwest, forming three successive intrusive complexes (Centres 1, 2 and 3). Our detailed fieldwork reveals that deformation due to these was accommodated on three levels; along thrust planes in lava sequences, along a décollement located in a thin clay-rich sediment succession and in basement schists. A relative chronology has been established between different groups of structures using dyke and sill cross-cutting relationships. Centre 1 is surrounded by a fold and thrust belt leading to radial expansion. In contrast, Centre 2 and 3 are connected to thrusts located to the south and east, bounded by strike-slip faults, leading to expansion to the southeast. The migration of centres and the directed sliding of the edifice may be related to the presence to the southeast of low-resistance Dalradian basement that failed significantly during growth of Centres 2 and 3. To study the observed relationships we have carried out scaled analogue models. Models are made with fine powder intruded by a viscous magma analogue. The models show an intimate relationship between intrusion growth, uplift of the volcano and subsequent flank sliding. The structures produced can be

  5. Corticostriatal circuitry in regulating diseases characterized by intrusive thinking

    PubMed Central

    Kalivas, Benjamin C.; Kalivas, Peter W.

    2016-01-01

    Intrusive thinking triggers clinical symptoms in many neuropsychiatric disorders. Using drug addiction as an exemplar disorder sustained in part by intrusive thinking, we explore studies demonstrating that impairments in corticostriatal circuitry strongly contribute to intrusive thinking. Neuroimaging studies have long implicated this projection in cue-induced craving to use drugs, and preclinical models show that marked changes are produced at corticostriatal synapses in the nucleus accumbens during a relapse episode. We delineate an accumbens microcircuit that mediates cue-induced drug seeking becoming an intrusive event. This microcircuit harbors many potential therapeutic targets. We focus on preclinical and clinical studies, showing that administering N-acetylcysteine restores uptake of synaptic glutamate by astroglial glutamate transporters and thereby inhibits intrusive thinking. We posit that because intrusive thinking is a shared endophenotype in many disorders, N-acetylcysteine has positive effects in clinical trials for a variety of neuropsychiatric disorders, including drug addiction, gambling, trichotillomania, and depression. PMID:27069381

  6. Corticostriatal circuitry in regulating diseases characterized by intrusive thinking.

    PubMed

    Kalivas, Benjamin C; Kalivas, Peter W

    2016-03-01

    Intrusive thinking triggers clinical symptoms in many neuropsychiatric disorders. Using drug addiction as an exemplar disorder sustained in part by intrusive thinking, we explore studies demonstrating that impairments in corticostriatal circuitry strongly contribute to intrusive thinking. Neuroimaging studies have long implicated this projection in cue-induced craving to use drugs, and preclinical models show that marked changes are produced at corticostriatal synapses in the nucleus accumbens during a relapse episode. We delineate an accumbens microcircuit that mediates cue-induced drug seeking becoming an intrusive event. This microcircuit harbors many potential therapeutic targets. We focus on preclinical and clinical studies, showing that administering N-acetylcysteine restores uptake of synaptic glutamate by astroglial glutamate transporters and thereby inhibits intrusive thinking. We posit that because intrusive thinking is a shared endophenotype in many disorders, N-acetylcysteine has positive effects in clinical trials for a variety of neuropsychiatric disorders, including drug addiction, gambling, trichotillomania, and depression.

  7. Evaluation of vapor intrusion using controlled building pressure.

    PubMed

    McHugh, Thomas E; Beckley, Lila; Bailey, Danielle; Gorder, Kyle; Dettenmaier, Erik; Rivera-Duarte, Ignacio; Brock, Samuel; MacGregor, Ian C

    2012-05-01

    The use of measured volatile organic chemical (VOC) concentrations in indoor air to evaluate vapor intrusion is complicated by (i) indoor sources of the same VOCs and (ii) temporal variability in vapor intrusion. This study evaluated the efficacy of utilizing induced negative and positive building pressure conditions during a vapor intrusion investigation program to provide an improved understanding of the potential for vapor intrusion. Pressure control was achieved in five of six buildings where the investigation program was tested. For these five buildings, the induced pressure differences were sufficient to control the flow of soil gas through the building foundation. A comparison of VOC concentrations in indoor air measured during the negative and positive pressure test conditions was sufficient to determine whether vapor intrusion was the primary source of VOCs in indoor air at these buildings. The study results indicate that sampling under controlled building pressure can help minimize ambiguity caused by both indoor sources of VOCs and temporal variability in vapor intrusion.

  8. Periodontal changes following molar intrusion with miniscrews

    PubMed Central

    Bayani, Shahin; Heravi, Farzin; Radvar, Mehrdad; Anbiaee, Najmeh; Madani, Azam Sadat

    2015-01-01

    Background: With the introduction of skeletal anchorage system, recently it is possible to successfully intrude molar teeth. On the other hand, there have been concerns about periodontal changes associated with intrusion and there are few studies on this topic, especially for posterior teeth. Materials and Methods: Ten female patients were enrolled in this study. Maxillary molar intrusion was achieved by inserting two miniscrews and a 17 × 25 titanium molybdenum alloy spring. Crestal height changes were evaluated at three intervals including: Baseline (T0), end of active treatment (T1) and 6 months after retention (T2). Other variables including probing depth, gingival recession, attachment level and bleeding on probing were evaluated by clinical measurements in the three above mentioned intervals. One-sample Kolmogrov-Smirnov test ascertained the normality of the data. For all patients, the changes in tooth position and crestal height were evaluated using one-sample t-test. (P < 0.05) Results: Supra-erupted molars were successfully intruded a mean of 2.1 ± 0.9 mm during active treatment (T0-T1). A mean bone resorption of 0.9 ± 0.9 mm in mesial crest and 1 ± 0.8 mm in distal crest had occurred in total treatment (T0-T2). A mean of 0.6 ± 1.4 mm bone was deposited on mesial crest during the retention period (T1-T2) following tooth relapse. On average, 0.8 ± 0.4 mm attachment gain was obtained. Gingival margin coronalized a mean of 0.8 ± 0.6 mm throughout the entire treatment. Probing depth showed no significant change during treatment. Conclusion: Within the limitations of this study, these results suggest that not only periodontal status was not negatively affected by intrusion, but also there were signs of periodontal improvement including attachment gain and shortening of clinical crown height. PMID:26288629

  9. Eddy flow and associated particle dynamics during magma intrusion: the Basement Sill, Antarctica

    NASA Astrophysics Data System (ADS)

    Petford, Nick; Mirhadizadeh, Seyed

    2014-05-01

    The McMurdo Dry Valleys magmatic system Antarctica forms part of the Ferrar dolerite Large Igneous Province. The intrusions comprise a vertical stack of four interconnected sills linked to surface flows of the Kirkpatrick flood basalts. Together the complex provides a world-class example of pervasive lateral flow of magma on a continental scale. In addition the Basement Sill offers unprecedented two and three dimensional sections through the now frozen particle macrostructure of a congested magma slurry. Using image-based numerical modelling (the intrusion geometry defines its unique finite element mesh) it is possible to simulate aspects of the flow regime and rheology that have bearing on the formation of mesostructures including compositional layering. A distinction between structures formed during flow, where the shearing regime dominates, and post-emplacement features due to local crystal-melt segregation constrained by thermal modeling, is made. In the former regime we describe a potentially novel crystal-liquid segregation that may have been overlooked because it is so simple. The critical boundary condition is an undulating base or roof in the intrusion where magma eddies can develop during low Reynolds Number flow. Numerical particle tracing is used to show that wall eddies can either trap (and ultimately freeze) crystals in-situ or retain and eject them back into the flow at a later time according to their mass density. The mechanism has potential to develop local variations in magma chemistry and structure that would not otherwise arise where the contact between magma and country rock is linear. We refer to this local fluid dynamical effect as 'slingshot' fractionation and are not aware of any previous quantitative description of this effect in igneous rocks.

  10. Clinical Evaluation of Efficacy of CIA and CNA Intrusion Arches

    PubMed Central

    Vora, Sambhav; Pandey, Vinisha

    2015-01-01

    Background and Objectives Excessive overbite is one of the most common problems that confront the orthodontist. Deep bite can be due to infraocclusion of posterior teeth, supraocclusion of anterior teeth or a combination of the two. Correction of same can be carried out by extrusion of molars, intrusion of incisors or by a combination of both respectively. Various intrusion arches are recommended for correcting deep bite by true intrusion of anterior teeth, Utility arches, Segmental arch, Connecticut Intrusion Arch (CIA) and Connecticut New Arch (CNA). The purpose of this study was to evaluate clinical efficacy of CIA and CNA intrusion arches. Materials and Methods Tracings recorded from pre and post-treatment lateral cephalograms of 25 patients treated by CIA (Group I) and another 25 patients treated by CNA (Group II) intrusion arches in deep bite cases after four months of treatment were analysed and findings were recorded. Statistical Analysis Paired t-test was used to compare pre and post-treatment changes within Groups I and II and unpaired t-test was used to compare treatment changes between Group I and Group II. A P-value of < 0.05 was set for statistical significance. Results Findings of this study demonstrate that an average of 1mm of intrusion takes place with CIA intrusion arch and 1.3mm with CNA intrusion arch in a period of 4 months. Both intrusion arches do not affect the position of molar in vertical or anteroposterior plane. Interpretation & Conclusion Both CIA and CNA intrusion arches are effective in bringing about intrusion of lower incisors. PMID:26501008

  11. The architecture of a network level intrusion detection system

    SciTech Connect

    Heady, R.; Luger, G.; Maccabe, A.; Servilla, M.

    1990-08-15

    This paper presents the preliminary architecture of a network level intrusion detection system. The proposed system will monitor base level information in network packets (source, destination, packet size, and time), learning the normal patterns and announcing anomalies as they occur. The goal of this research is to determine the applicability of current intrusion detection technology to the detection of network level intrusions. In particular, the authors are investigating the possibility of using this technology to detect and react to worm programs.

  12. Late Neoproterozoic post-collisional mafic magmatism in the Arabian-Nubian Shield: A case study from Wadi El-Mahash gabbroic intrusion in southeast Sinai, Egypt

    NASA Astrophysics Data System (ADS)

    Khalil, A. E. S.; Obeid, M. A.; Azer, M. K.

    2015-05-01

    Late Neoproterozoic gabbroic intrusion of Wadi El-Mahash lays in the northwestern sector of the Arabian-Nubian Shield (ANS) which is exposed in the Sinai Peninsula, Egypt. It occurs as small undeformed mafic body intruding metamorphic rocks and truncated by alkali granites. Field relations, mineralogical characteristics and chemical data indicate that Wadi El-Mahash mafic intrusion is unmetamorphosed. The intrusion consists of medium- to coarse-grained gabbroic rocks. The medium-grained one (hornblende gabbro) formed nearly simultaneous with, or slightly later than, the coarse-grained rock (pyroxene-hornblende gabbro). Geochemically, the gabbroic samples are characterized by enrichment in LILE relative to HFSE and LREE relative to HREE [(La/Yb)n = 4.52-6.35]. They show geochemical signature similar to other post-collisional gabbroic intrusions of south Sinai. The subduction-related geochemical characteristic of the gabbroic intrusion of Wadi El-Mahash can be explained by partial melting of a relatively enriched lithospheric mantle source following a previous subduction process in the ANS. The gabbroic rocks crystallized at pressures between 6.2 and 6.5 kbar (∼15-20 km depth) with crystallization temperature ranging from 750 to 970 °C. Lithospheric delamination model is suggested for the mafic magma of Wadi El-Mahash since delamination of lithospheric mantle allowed asthenosphere to rise rapidly causing partial melting and generating gabbroic melts. The produced melts then infiltrated the base of the crust to induce the post-collisional magmatism in south Sinai.

  13. Diabetes Intrusiveness and Wellness among Elders: A Test of the Illness Intrusiveness Model

    ERIC Educational Resources Information Center

    DeCoster, Vaughn A.; Killian, Tim; Roessler, Richard T.

    2013-01-01

    Using data collected from 147 predominately African American senior citizens in Arkansas, this research examined the Illness Intrusiveness Model (Devins, 1991; Devins & Seland, 1987; Devins & Shnek, 2000) to explain variations in wellness specifically related to participants' adaptation to diabetes. The theoretical model hypothesized…

  14. Kontay intrusion (Polar Siberia)- an example of strong magmatic differentiation in the single magmatic body

    NASA Astrophysics Data System (ADS)

    Zaitsev, Victor

    2016-04-01

    Kontay intrusion is located in the north-west part of Maimecha-Kotuy province, (part of Siberian Large Igneous Province) in the northern part of the Siberian Platform. Intrusion is fully overlaid and practically not studied before. Geophysical data evident that intrusion has form of laccolite with diameter ˜7.5 km and thickness ˜ 2.5 km [1]. Initially lower part of intrusion was described as "gabbro-anortozite and anortositic gabbro" and higher part - as "leucocratic granophyric anortosites" [2]. Complex mineralo-petrological-geochemical study allow to divide intrusion section on three zones: Lower zone (below 1100 m) - layered sequence of leucocratic and melanocratic of biotite- and ortopyroxene-bearing gabbro, with minor alkaline feldspar, Middle zone (1100-700m) - biotite- and K-feldspar bearing gabbro and monzonotes, interstitial space often contain micrographical structures. Biotite corroded clinopyroxene and form interstitial crystals and Upper zone (700-214 m) - petrographically monotone porthyric quartz-monzonites and granosyenites with rare phenocrysts of plagioclase, magnetite, clinopyroxene and biotite. The main secondary minerals are albite, amphibole (edenite-feroedenite), secondary biotite, chlorite, and F,Al-bearing titanite. Rocks of the all parts fall in the same trends on the binary petrochemical diagrams, they belong to the High-K calc-alkaline seria. They are clearly more alkaline then intrusions of Norilsk district and less alkaline then alkaline-ultramafic intrusions of Maymecha-Kotuy province. Volcanic rocks of Norilsk and Maymecha-Kotuy area was subdivided for four geochemical types, mainly by the Ti-content, Th/U, Gd/Yb and Sm/Yb ratio: Low-Ti-1 (predominated), Low-Ti-2 (well -developed in Norilsk region), Moderate-Ti (developed only in the lower part of volcanic formation in Norilsk region), High-Ti (rare in Norilsk region, but widely spread in Mailecha-Kotuy area) [3]. Kontay intrusion rocks belong to Moderate-Ti group. The closest

  15. Relationships between volcano gravitational spreading and magma intrusion

    NASA Astrophysics Data System (ADS)

    Delcamp, Audray; van Wyk de Vries, Benjamin; James, Mike R.; Gailler, L. S.; Lebas, E.

    2012-04-01

    Volcano spreading, with its characteristic sector grabens, is caused by outward flow of weak substrata due to gravitational loading. This process is now known to affect many present-day edifices. A volcano intrusive complex can form an important component of an edifice and may induce deformation while it develops. Such intrusions are clearly observed in ancient eroded volcanoes, like the Scottish Palaeocene centres, or in geophysical studies such as in La Réunion, or inferred from large calderas, such as in Hawaii, the Canaries or Galapagos volcanoes. Volcano gravitational spreading and intrusive complex emplacement may act simultaneously within an edifice. We explore the coupling and interactions between these two processes. We use scaled analogue models, where an intrusive complex made of Golden syrup is emplaced within a granular model volcano based on a substratum of a ductile silicone layer overlain by a brittle granular layer. We model specifically the large intrusive complex growth and do not model small-scale and short-lived events, such as dyke intrusion, that develop above the intrusive complex. The models show that the intrusive complex develops in continual competition between upward bulging and lateral gravity spreading. The brittle substratum strongly controls the deformation style, the intrusion shape and also controls the balance between intrusive complex spreading and ductile layer-related gravitational spreading. In the models, intrusive complex emplacement and spreading produce similar structures to those formed during volcano gravitational spreading alone (i.e. grabens, folds, en échelon fractures). Therefore, simple analysis of fault geometry and fault kinetic indicators is not sufficient to distinguish gravitational from intrusive complex spreading, except when the intrusive complex is eccentric from the volcano centre. However, the displacement fields obtained for (1) a solely gravitational spreading volcano and for (2) a gravitational

  16. Derivation of S and Pb in phanerozoic intrusion-related metal deposits from neoproterozoic sedimentary pyrite, Great Basin, United States

    USGS Publications Warehouse

    Vikre, P.G.; Poulson, S.R.; Koenig, A.E.

    2011-01-01

    The thick (???8 km), regionally extensive section of Neoproterozoic siliciclastic strata (terrigenous detrital succession, TDS) in the central and eastern Great Basin contains sedimentary pyrite characterized by mostly high d34S values (-11.6 to 40.8%, <70% exceed 10%; 51 analyses) derived from reduction of seawater sulfate, and by markedly radiogenic Pb isotopes ( 207Pb/204Pb <19.2; 15 analyses) acquired from clastic detritus eroded from Precambrian cratonal rocks to the east-southeast. In the overlying Paleozoic section, Pb-Zn-Cu-Ag-Au deposits associated with Jurassic, Cretaceous, and Tertiary granitic intrusions (intrusion-related metal deposits) contain galena and other sulfide minerals with S and Pb isotope compositions similar to those of TDS sedimentary pyrite, consistent with derivation of deposit S and Pb from TDS pyrite. Minor element abundances in TDS pyrite (e.g., Pb, Zn, Cu, Ag, and Au) compared to sedimentary and hydrothermal pyrite elsewhere are not noticeably elevated, implying that enrichment in source minerals is not a precondition for intrusion-related metal deposits. Three mechanisms for transferring components of TDS sedimentary pyrite to intrusion-related metal deposits are qualitatively evaluated. One mechanism involves (1) decomposition of TDS pyrite in thermal aureoles of intruding magmas, and (2) aqueous transport and precipitation in thermal or fluid mixing gradients of isotopically heavy S, radiogenic Pb, and possibly other sedimentary pyrite and detrital mineral components, as sulfide minerals in intrusion-related metal deposits. A second mechanism invokes mixing and S isotope exchange in thermal aureoles of Pb and S exsolved from magma and derived from decomposition of sedimentary pyrite. A third mechanism entails melting of TDS strata or assimilation of TDS strata by crustal or mantle magmas. TDS-derived or assimilated magmas ascend, decompress, and exsolve a mixture of TDS volatiles, including isotopically heavy S and radiogenic Pb

  17. Geomechanical rock properties of a basaltic volcano

    NASA Astrophysics Data System (ADS)

    Schaefer, Lauren; Kendrick, Jackie; Lavallée, Yan; Oommen, Thomas; Chigna, Gustavo

    2015-06-01

    In volcanic regions, reliable estimates of mechanical properties for specific volcanic events such as cyclic inflation-deflation cycles by magmatic intrusions, thermal stressing, and high temperatures are crucial for building accurate models of volcanic phenomena. This study focuses on the challenge of characterizing volcanic materials for the numerical analyses of such events. To do this, we evaluated the physical (porosity, permeability) and mechanical (strength) properties of basaltic rocks at Pacaya Volcano (Guatemala) through a variety of laboratory experiments, including: room temperature, high temperature (935 °C), and cyclically-loaded uniaxial compressive strength tests on as-collected and thermally-treated rock samples. Knowledge of the material response to such varied stressing conditions is necessary to analyze potential hazards at Pacaya, whose persistent activity has led to 13 evacuations of towns near the volcano since 1987. The rocks show a non-linear relationship between permeability and porosity, which relates to the importance of the crack network connecting the vesicles in these rocks. Here we show that strength not only decreases with porosity and permeability, but also with prolonged stressing (i.e., at lower strain rates) and upon cooling. Complimentary tests in which cyclic episodes of thermal or load stressing showed no systematic weakening of the material on the scale of our experiments. Most importantly, we show the extremely heterogeneous nature of volcanic edifices that arise from differences in porosity and permeability of the local lithologies, the limited lateral extent of lava flows, and the scars of previous collapse events. Input of these process-specific rock behaviors into slope stability and deformation models can change the resultant hazard analysis. We anticipate that an increased parameterization of rock properties will improve mitigation power.

  18. Characterizing and Improving Distributed Intrusion Detection Systems.

    SciTech Connect

    Hurd, Steven A; Proebstel, Elliot P.

    2007-11-01

    Due to ever-increasing quantities of information traversing networks, network administrators are developing greater reliance upon statistically sampled packet information as the source for their intrusion detection systems (IDS). Our research is aimed at understanding IDS performance when statistical packet sampling is used. Using the Snort IDS and a variety of data sets, we compared IDS results when an entire data set is used to the results when a statistically sampled subset of the data set is used. Generally speaking, IDS performance with statistically sampled information was shown to drop considerably even under fairly high sampling rates (such as 1:5). Characterizing and Improving Distributed Intrusion Detection Systems4AcknowledgementsThe authors wish to extend our gratitude to Matt Bishop and Chen-Nee Chuah of UC Davis for their guidance and support on this work. Our thanks are also extended to Jianning Mai of UC Davis and Tao Ye of Sprint Advanced Technology Labs for their generous assistance.We would also like to acknowledge our dataset sources, CRAWDAD and CAIDA, without which this work would not have been possible. Support for OC48 data collection is provided by DARPA, NSF, DHS, Cisco and CAIDA members.

  19. From Intrusion Detection to Self Protection

    SciTech Connect

    Frincke, Deb; Wespi, Andreas; Zamboni, Diego

    2007-04-11

    Modern computer systems have become so complex and interdependent that the traditional model of system defense, utilizing layers and including an intrusion detection system that provides alerts to a human who responds to them, is becoming unfeasible. Effective human-guided real-time responses are no longer a reasonable expectation for large scale systems--this is particularly troublesome because a failure to respond correctly and rapidly can have disastrous consequences. In an ideal world, our systems would automatically detect and respond to threats of all kinds, including but not limited to automated attacks, human-guided attacks, and the constant onslaught of unsolicited email (spam). Traditionally, these threats have been dealt with by separate communities--the anti-virus community, the intrusion-detection/firewall community, and the anti-spam community. Today however, we see an increasing need for integrating different technologies toward achieving a common goal. In this special issue, we surveyed the research community with the intent of identifying novel, multidisciplinary and integrated approaches to system defense that contribute towards development of true self-protecting and self-healing systems. The result is reflected in the articles we selected.

  20. Mafic intrusions triggering eruptions in Iceland

    NASA Astrophysics Data System (ADS)

    Sigmarsson, O.

    2012-04-01

    The last two eruptions in Iceland, Eyjafjallajökull 2010 and Grímsvötn 2011, were both provoked by an intrusion of more mafic magma into pre-existing magmatic system. Injection into the latter volcano, which is located in the main rift-zone of the island, above the presumed centre of the mantle plume and is the most active volcano of Iceland, has been gradual since the last eruption in 2004. In contrast, at Eyjafjallajökull volcano, one of the least active volcano in Iceland and located at the southern part of a propagating rift-zone where extensional tectonics are poorly developed, mafic magma intrusion occurred over less than a year. Beneath Eyjafjallajökull, a silicic intrusion at approximately 6 km depth was recharged with mantle derived alkali basalt that was injected into residual rhyolite from the penultimate eruption in the years 1821-23. The resulting magma mingIing process was highly complex, but careful sampling of tephra during the entire eruption allows the dynamics of the mingling process to be unravelled. Short-lived disequilibria between the gaseous nuclide 210Po and the much less volatile nuclide 210Pb, suggest that basalt accumulated beneath the silicic intrusion over approximately 100 days, or from early January 2010 until the onset of the explosive summit eruption on 14 April. Due to the degassing, crystal fractionation modified the composition of the injected mafic magma producing evolved Fe-and Ti-rich basalt, similar in composition to that of the nearby Katla volcano. This evolved basalt was intruded into the liquid part of the silicic intrusion only a few hours before the onset of the explosive summit eruption. The short time between intrusion and eruption led to the production of very heterogeneous (of basaltic, intermediate and silicic composition) and fine-grained tephra during the first days of explosive eruption. The fine grained tephra resulted from combined effects of magma fragmentation due to degassing of stiff magma rich in

  1. Platinum mineralization in the Kapalagulu Intrusion, western Tanzania

    NASA Astrophysics Data System (ADS)

    Wilhelmij, Harry R.; Cabri, Louis J.

    2016-03-01

    Low-grade copper and nickel mineralization was found near the eastern shore of Lake Tanganyika at Kungwe Bay in the early part of the twentieth century. The mineralization occurs in harzburgite at the base of a layered gabbro complex known as the Kapalagulu Intrusion, emplaced between the Paleoproterozoic Ubendian basement and overlying Neoproterozoic Itiaso Group metasediments. Several mining and exploration companies continued the geophysical and drilling exploration for base metals throughout the last century culminating in the discovery of high-grade platinum-group element (PGE) mineralization associated with chromitite and sulfide-bearing harzburgite within the southeastern extension of the Kapalagulu Intrusion (known as the Lubalisi Zone) that is covered by a layer of nickel-rich laterite regolith. The poorly layered southeastern harzburgite forms part of the >1500 m-thick Lower Ultramafic Sequence and resembles a dike-like body that flares upwards into a succession of well-layered gabbroic rocks of the Upper Mafic Sequence. No PGE mineralization has been found in the layered gabbro; all the mineralization is associated with the chromite- and sulfide-rich harzburgite of the Lower Ultramafic Sequence and the laterite regolith overlying the mineralized harzburgite. The Lubalisi Zone harzburgite is underlain by basal dunite and overlain by an interval of layered harzburgite and troctolite and this ultramafic sequence is folded into a syncline that plunges towards the northwest that has been modified by major dolerite-filled faults orientated subparallel to the fold axial surface. Extensive deep drilling in the Lubalisi Zone of the Kapalagulu Intrusion shows that the folded harzburgite can be subdivided into a lower feldspathic harzburgite, a harzburgite containing chromitite seams and intervals of sulfide and chromite mineralization known as the Main Chromite Sulfide Succession (MCSS), an overlying sulfide-rich harzburgite, and an upper feldspathic harzburgite

  2. Platinum mineralization in the Kapalagulu Intrusion, western Tanzania

    NASA Astrophysics Data System (ADS)

    Wilhelmij, Harry R.; Cabri, Louis J.

    2016-03-01

    Low-grade copper and nickel mineralization was found near the eastern shore of Lake Tanganyika at Kungwe Bay in the early part of the twentieth century. The mineralization occurs in harzburgite at the base of a layered gabbro complex known as the Kapalagulu Intrusion, emplaced between the Paleoproterozoic Ubendian basement and overlying Neoproterozoic Itiaso Group metasediments. Several mining and exploration companies continued the geophysical and drilling exploration for base metals throughout the last century culminating in the discovery of high-grade platinum-group element (PGE) mineralization associated with chromitite and sulfide-bearing harzburgite within the southeastern extension of the Kapalagulu Intrusion (known as the Lubalisi Zone) that is covered by a layer of nickel-rich laterite regolith. The poorly layered southeastern harzburgite forms part of the >1500 m-thick Lower Ultramafic Sequence and resembles a dike-like body that flares upwards into a succession of well-layered gabbroic rocks of the Upper Mafic Sequence. No PGE mineralization has been found in the layered gabbro; all the mineralization is associated with the chromite- and sulfide-rich harzburgite of the Lower Ultramafic Sequence and the laterite regolith overlying the mineralized harzburgite. The Lubalisi Zone harzburgite is underlain by basal dunite and overlain by an interval of layered harzburgite and troctolite and this ultramafic sequence is folded into a syncline that plunges towards the northwest that has been modified by major dolerite-filled faults orientated subparallel to the fold axial surface. Extensive deep drilling in the Lubalisi Zone of the Kapalagulu Intrusion shows that the folded harzburgite can be subdivided into a lower feldspathic harzburgite, a harzburgite containing chromitite seams and intervals of sulfide and chromite mineralization known as the Main Chromite Sulfide Succession (MCSS), an overlying sulfide-rich harzburgite, and an upper feldspathic harzburgite

  3. Ortigalita Peak gabbro, Franciscan complex: U-Pb dates of intrusion and high-pressure low-temperature metamorphism

    NASA Astrophysics Data System (ADS)

    Mattinson, James M.; Echeverria, Lina M.

    1980-12-01

    Paleontological and isotopic age data from the Franciscan complex in the Ortigalita Peak quadrangle, Diablo Range, California, provide new insight into the tectonic evolution of at least part of the Franciscan complex. Graywacke, shale, pillowed greenstone, and chert in the quadrangle were deposited in Late Jurassic (Tithonian) time, about 135 to 150 m.y. ago, on the basis of radiolaria. These rocks then were incorporated in an accretionary wedge prior to the intrusion of gabbroic magma 95 m.y. ago (U-Pb dating on zircons). Subduction (metamorphism of gabbro and surrounding sedimentary rocks to blueschist grade) closely followed intrusion at about 92 m.y. ago (U-Pb dating on metamorphic titanite and “plagioclase” = albite + pumpellyite ± quartz). The brief interval between intrusion and subduction confirms the idea that the gabbro was intruded into the accretionary wedge, essentially at the site of plate convergence. The much longer interval (about 40 to 55 m.y.) between deposition and subduction reveals that the Franciscan had a long presubduction history and provides a time frame within which more speculative concepts such as extensive northward translation of the Franciscan must be constrained.

  4. Periodicity of Kı¯lauea's Dike Intrusions

    NASA Astrophysics Data System (ADS)

    Montgomery-Brown, E. K.; Miklius, A.

    2015-12-01

    Magmatic intrusions commonly occur in the rift zones of Kı¯lauea Volcano. Individual dike intrusions observed by geodetic methods are usually 5 to 10 km long, and can occur repeatedly in the same region. Five such intrusions in Kı¯lauea's East Rift Zone, with inferred locations downrift of the bend where the NNW trending upper ERZ turns to the ENE trending ERZ, have occurred since the start of the ongoing ERZ eruption in 1983. The intrusions occur on one of two segments that correlate with seismic segments (Wright and Klein, USGS PP1806, 2014): Makaopuhi (1993 and 2007) and Nāpau (1983, 1997, and 2011). During each intrusion, the amount of dike opening was between 2 and 3 meters. Intrusions into the UERZ tend to be much smaller (~10 cm of dike opening) and occur more frequently. The time between ERZ intrusions for same-segment pairs are: 14.07 (1983-1997), 14.09 (1997-2011), and 13.95 (1993-2007) years, with the Nāpau segment becoming active about 3.5 years after the Makaopuhi segment in each case. The amount of modeled dike opening during each of these events roughly corresponds to the amount of seaward south flank motion and deep rift opening accumulated in the time between events, as was noted by Owen et al. (GRL, 2000) for the 1983 and 1997 intrusions. The recurrence interval of ~14 years appears to be unaffected by the magma surge of 2003-2007 (Poland et al., Nature, 2012), suggesting that flank motion, rather than magma supply, could be a controlling factor in the periodicity of intrusions. The long duration of the seismic catalog and the coincidence of repeated dike intrusions with the seismic segments suggest that on the timescale of decades, Kı¯lauea's East Rift Zone segments are persistent rather than ephemeral features related to single intrusion events.

  5. Parental magma composition and petrological modeling of the Muskox intrusion formation (Canada)

    NASA Astrophysics Data System (ADS)

    Borodina, E. V.

    2003-04-01

    The Muskox layered intrusion is an Proterozoic pluton, more then 5 km across, situated in the District of Mackenzie, Northwest territories. The layered series is composed of peridotit, pyroxenites, gabbro, troctolit, anorthositic gabbro and granophyre-bearing gabbro units. Mg-numbers (100*Mg/(Mg+Fe)) in the layered series rocks decrease from 86,9 in ultramafic rock suite (44,0 wt.% MgO) to 27,5 in granophyres (1,9 wt.% MgO) (Francis D., 1994). The order of crystallization of the parental magma changed from Ol; Cpx; Pl; Opx during the early stages of solidification to Ol; Opx; Cpx; Pl during later stages. The intermediate order Ol; Cpx; Opx; Pl is locally evident (Irvine T.N., 1970). The petrochemical features of the Muskox intrusion rocks are consistent with fractional crystallization of komatiitic parental magma with 30 wt.% MgO, 8,5 wt.% FeO (mg-number - 86,3). The compositions trend of model cumulates determined from a fractional crystallization simulation using the COMAGMAT 3,5 computer program (Ariskin A.A. et al., 1993) (42,2 - 4,4 wt.% MgO ; mg-numbers - 92,1 - 38,7) is similar to the compositions trend of observed cumulates. The supposed physical parameters of fractional crystallization are: total pressure of 2 kbar, oxygen buffer QFM, 0,5 wt.% H2O. According to this model the crystallization sequence is Ol (T - 1542oC) followed by Cpx (T - 1185oC), Pl (T - 1172oC) and finally Opx (T - 1168oC). CaO decrease and SiO2 increase in the parental magma less then 1 wt.% result in a change in the main crystallization sequence. The first Opx becomes the third (Ol (T - 1543oC), Cpx (T - 1183oC), Opx (T - 1174oC), Pl (T - 1170oC)) and then the second phase to crystallize (Ol (T - 1546oC), Opx (T - 1184oC), Cpx (T - 1175oC), Pl (T - 1167oC)). Depleted N-MORB - normalized HREE pattern and enriched HFSE pattern in the Muskox intrusion rocks indicate that the intrusion parental magma was derived from a garnet-bearing enriched mantle source. The primary mantle magma as a

  6. Salt Intrusion in the Tweed Estuary

    NASA Astrophysics Data System (ADS)

    Uncles, R. J.; Stephens, J. A.

    1996-09-01

    Results are presented from a 2-week field programme in the Tweed Estuary, U.K. Maximum values of the empirically based Estuarine Richardson Number, Ri E, occurred during neap tides, and minimum values occurred during spring tides. Estimated values of Ri Evaried between 0·3 and 2·3, suggesting the occurrence of partially mixed to stratified conditions, depending on tidal state and freshwater inflow. These relatively large values of Ri Ewere consistent with both observed strong salinity stratification and large salt fluxes due to vertical shear transport. Low values (<0·25) of the estimated gradient Richardson Number, Ri, generally occurred close to the bed on the flood, suggestive of tidal mixing there, and higher (>0·5) values in the halocline. A velocity maximum occurred within the halocline during the early flood. Wave-like spatial oscillations of the halocline occurred on the ebb. The oscillation troughs were situated above deep holes located just down-estuary of the rail and old road bridges. There was an indication that the constricted flow between the bridges' arches resulted in enhanced mixing of near-surface waters and a thickening of the halocline. It is also possible that these wave-like structures were stationary, near-critical internal lee waves, triggered by the deep holes. Trapping of high-salinity waters occurred on the ebb. Saline pools were isolated within a deep hole or deeper section of bed by the falling halocline. When the salt wedge moved further down-estuary, the ' trapped ' waters were subjected to strongly ebbing, overlying freshwater, and were subsequently entrained and flushed. The salinity intrusion was a strong function of spring-neap tidal state and a weaker function of freshwater inflow. The estimated salinity intrusion varied from about 4·7 to 7·6 km during the fieldwork period. The strong dependence on tidal range followed from the comparable lengths of the tidal excursion and salinity intrusion. Long excursion lengths were

  7. Chineysky Layered Intrusion with unique V and PGE-Cu ores (Siberia, Russia)

    NASA Astrophysics Data System (ADS)

    Gongalskiy, Bronislav; Krivolutskaya, Nadezda

    2010-05-01

    South of the Siberian platform is an extraordinary metallogenic province. Many giant deposits of different genetic types are concentrated here: Udokan (Cu), Chiney (Ti-Fe-V, Pd-Cu), Katugin (Ta, Nb), Sulumat (Fe) etc. It is his considered this massif is the largest component of the Proterozoic volcanic-plutonic system of the Kodar-Udokan district. Chineisky massif located among Cu-rich sedimentary rocks is represented by interlayering horizons of gabbronorite and titanomagnetite gabbro in its lower zone and gabbro and anorthosite in the upper zone.The intrusive rocks were proved to be genetically interrelated and show certain similar geochemical features: they have elevated TiO2 concentrations and have similar trace element patterns and (La/Sm)N and (Gd/Yb)N ratios (1.5-2.3 and 1.87-2.06, respectively). The Chineisky massif is thought to have been formed by the successive emplacement of genetically similar basic magmas, which produced four rock groups with fine and coarse layering and cyclicity of variable rank (micro-rhythms, rhythms, units, and series). The results of cluster analysis indicate that the rocks can be classified into 13 petrochemical types. The phase and chemical characteristics of the parental melts of these compositions were simulated with the use of the COMAGMAT-3.5 computer model, which was also applied to evaluate the composition of the most primitive initial magma of the whole Chineisky massif. Our results indicate that the primitive magma was heterogeneous (olivine + plagioclase titanomagnetite + melt) at a temperature of approximately 1130 C. The initial melt had a ferrobasaltic composition and was close to saturation with magnetite at ~NNO 0.5 The basic and ultrabasic rocks of the Luktur pluton are supposed to be the Mg-rich fraction of the parental melt. Gravimetric and magnetic geophysical data show that ultrabasic and basic rocks occur at shallow depths at the Chiney pluton and around it. These facts show the existence of huge magmatic

  8. Theory of wing rock

    NASA Technical Reports Server (NTRS)

    Hsu, C.-H.; Lan, C. E.

    1985-01-01

    Wing rock is one type of lateral-directional instabilities at high angles of attack. To predict wing rock characteristics and to design airplanes to avoid wing rock, parameters affecting wing rock characteristics must be known. A new nonlinear aerodynamic model is developed to investigate the main aerodynamic nonlinearities causing wing rock. In the present theory, the Beecham-Titchener asymptotic method is used to derive expressions for the limit-cycle amplitude and frequency of wing rock from nonlinear flight dynamics equations. The resulting expressions are capable of explaining the existence of wing rock for all types of aircraft. Wing rock is developed by negative or weakly positive roll damping, and sustained by nonlinear aerodynamic roll damping. Good agreement between theoretical and experimental results is obtained.

  9. The Rock Cycle

    ERIC Educational Resources Information Center

    Singh, Raman J.; Bushee, Jonathan

    1977-01-01

    Presents a rock cycle diagram suitable for use at the secondary or introductory college levels which separates rocks formed on and below the surface, includes organic materials, and separates products from processes. (SL)

  10. Rocks and Minerals.

    ERIC Educational Resources Information Center

    Naturescope, 1987

    1987-01-01

    Provides background information on rocks and minerals, including the unique characteristics of each. Teaching activities on rock-hunting and identification, mineral configurations, mystery minerals, and growing crystals are provided. Reproducible worksheets are included for two of the activities. (TW)

  11. Rocks in Our Pockets

    ERIC Educational Resources Information Center

    Plummer, Donna; Kuhlman, Wilma

    2005-01-01

    To introduce students to rocks and their characteristics, teacher can begin rock units with the activities described in this article. Students need the ability to make simple observations using their senses and simple tools.

  12. Intrusive Memories of Distressing Information: An fMRI Study

    PubMed Central

    Battaglini, Eva; Liddell, Belinda; Das, Pritha; Malhi, Gin; Felmingham, Kim

    2016-01-01

    Although intrusive memories are characteristic of many psychological disorders, the neurobiological underpinning of these involuntary recollections are largely unknown. In this study we used functional magentic resonance imaging (fMRI) to identify the neural networks associated with encoding of negative stimuli that are subsequently experienced as intrusive memories. Healthy partipants (N = 42) viewed negative and neutral images during a visual/verbal processing task in an fMRI context. Two days later they were assessed on the Impact of Event Scale for occurrence of intrusive memories of the encoded images. A sub-group of participants who reported significant intrusions (n = 13) demonstrated stronger activation in the amygdala, bilateral ACC and parahippocampal gyrus during verbal encoding relative to a group who reported no intrusions (n = 13). Within-group analyses also revealed that the high intrusion group showed greater activity in the dorsomedial (dmPFC) and dorsolateral prefrontal cortex (dlPFC), inferior frontal gyrus and occipital regions during negative verbal processing compared to neutral verbal processing. These results do not accord with models of intrusions that emphasise visual processing of information at encoding but are consistent with models that highlight the role of inhibitory and suppression processes in the formation of subsequent intrusive memories. PMID:27685784

  13. Intrusive and Withdrawn Depressed Mothers and Their Infants

    ERIC Educational Resources Information Center

    Field, Tiffany; Hernandez-Reif, Maria; Diego, Miguel

    2006-01-01

    This review of the literature on two different interaction styles of depressed mothers, intrusive and withdrawn, shows that withdrawn versus intrusive mothers typically have an EEG pattern that is associated with negative affect (i.e., greater relative right frontal EEG activation) as well as lower levels of the activating neurotransmitter,…

  14. Identification and Control of Pollution from Salt Water Intrusion.

    ERIC Educational Resources Information Center

    Environmental Protection Agency, Washington, DC. Office of Water Programs.

    This document contains informational guidelines for identifying and evaluating the nature and extent of pollution from salt water intrusion. The intent of these guidelines is to provide a basic framework for assessing salt water intrusion problems and their relationship to the total hydrologic system, and to provide assistance in developing…

  15. Young women's experiences of intrusive behavior in 12 countries.

    PubMed

    Sheridan, Lorraine; Scott, Adrian J; Roberts, Karl

    2016-01-01

    The present study provides international comparisons of young women's (N = 1,734) self-reported experiences of intrusive activities enacted by men. Undergraduate psychology students from 12 countries (Armenia, Australia, England, Egypt, Finland, India, Indonesia, Italy, Japan, Portugal, Scotland, and Trinidad) indicated which of 47 intrusive activities they had personally experienced. Intrusive behavior was not uncommon overall, although large differences were apparent between countries when women's personal experiences of specific intrusive activities were compared. Correlations were carried out between self-reported intrusive experiences, the Gender Empowerment Measure (GEM), and Hofstede's dimensions of national cultures. The primary associations were between women's experiences of intrusive behavior and the level of power they are afforded within the 12 countries. Women from countries with higher GEM scores reported experiencing more intrusive activities relating to courtship and requests for sex, while the experiences of women from countries with lower GEM scores related more to monitoring and ownership. Intrusive activities, many of them constituent of harassment and stalking, would appear to be widespread and universal, and their incidence and particular form reflect national level gender inequalities. PMID:26299620

  16. Prior-List Intrusions in Serial Recall Are Positional

    ERIC Educational Resources Information Center

    Osth, Adam F.; Dennis, Simon

    2015-01-01

    Henson (1996) provided a number of demonstrations of error patterns in serial recall that contradict chaining models. One such error pattern concerned when participants make intrusions from prior lists: Rather than originating from random positions in the prior list, intrusions tend to be recalled in the same position as their position in the…

  17. Parental Intrusiveness and Children's Separation Anxiety in a Clinical Sample

    ERIC Educational Resources Information Center

    Wood, Jeffrey J.

    2006-01-01

    In this article, a theoretical model of the role of parental intrusiveness in the development of childhood separation anxiety disorder is presented and tested. Parents who act intrusively tend to take over tasks that children are (or could be) performing independently, thereby limiting mastery experiences and inducing dependence on caregivers.…

  18. SAMPLING-BASED APPROACH TO INVESTIGATING VAPOR INTRUSION

    EPA Science Inventory

    Vapor intrusion is defined as the migration of volatile organic compounds (VOCs) into occupied buildings from contaminated soil or ground water. EPA recently developed guidance to facilitate assessment of vapor intrusion at sites regulated by RCRA and CERCLA. The EPA guidance e...

  19. Thermochronology and Cooling Histories of Intrusive Suites: Implications for Incremental Pluton Assembly

    NASA Astrophysics Data System (ADS)

    Davis, J.; Coleman, D.; Heizler, M.

    2007-12-01

    Debate persists about the timescales and mechanisms of pluton emplacement and batholith formation. An understanding of whether plutons accumulate as large masses of magma or as an incremental series of pulses, in which the active magma body is small relative to the final pluton, is important for understanding the relationship between volcanoes and plutons. If volcanic eruptions < 1000 km3 are the most common size and large ignimbrites are rare, it follows that most plutons should record accumulations of small volumes of melt that were emplaced over long time intervals (millions to tens of millions of years) and therefore preserve predictable, protracted thermal histories. Modeling predicts observable differences in thermal histories of plutons and their aureoles that can be tested through thermochronology. Application of multiple chronometers (zircon and titanite U-Pb TIMS; hornblende, biotite, and K-feldspar 40Ar/39Ar; zircon and titanite (U-Th)/He) combined with K-feldspar multiple diffusion domain (MDD) modeling were used to determine the thermal history and to calibrate thermal models of two eastern California, Sierra Nevada batholith intrusive suites; the dike-like John Muir Intrusive Suite (JMIS) and the laccolithic Mt. Whitney Intrusive Suite (MWIS), and their wall rocks. Preliminary results of (U-Th)/He zircon data from the JMIS and its wall rock (the Tinemaha granodiorite) show a tight cluster of dates ranging from 75.6 to 70.4 Ma. The JMIS is thought to be mesozonal (8 to 11 km) and these data are interpreted as resulting from exhumation and additional 40Ar/39Ar data are required to determine if the thermal history reflects incremental intrusions. In contrast to the JMIS, preliminary (U-Th)/He zircon data from the MWIS and its wall rock (the Bullfrog pluton) show a wide range in dates ranging from 91.4 to 74.6 Ma that are interpreted to reflect reheating events. Amphibole 40Ar/39Ar inverse isochron dates, K- feldspar age spectra, and (U-Th)/He zircon data

  20. Isotope-geochemical Nd-Sr evidence of Palaeoproterozoic plume magmatism in Fennoscandia and mantle-crust interaction on stages of layered intrusions formation

    NASA Astrophysics Data System (ADS)

    Serov, Pavel; Bayanova, Tamara; Kunakkuzin, Evgeniy; Steshenko, Ekaterina

    2016-04-01

    Palaeoproterozoic Fennoscandian layered intrusions belong to the pyroxenite-gabbronorite-anorthosite formation and spread on a vast area within the Baltic Shield. Based on isotope U-Pb, Sm-Nd, Rb-Sr and Re-Os data the duration of this formation can be to 100-130 Ma (2.53-2.40 Ga) [Serov et. al., 2008; Bayanova et. al., 2009]. We have studied rocks of layered PGE-bearing Fedorovo-Pansky, Monchetundra, Burakovsky, Olanga group intrusions and Penikat intrusion. According to recent and new complex Nd-Sr-REE data magma source of the vast majority of these intrusions was a mantle reservoir with unusual characteristics: negative values of ɛNd (from 0 to -4) and ISr = 0.702-0.706, flat spectra of REE (value of (La/Yb)N ~ 1.0-5.8) with positive Eu-anomalies [Bayanova et. al., 2009; Bayanova et. al., 2014]. However, the distribution of REE for ore-bearing gabbronorite intrusions Penikat (Sm-Nd age is 2426 ± 38 Ma [Ekimova et. al., 2011]) has a negative Eu-anomalies. This may be due to the formation of plagioclase and its removal from the magma chamber. One of the aims of isotope geochemical investigations is to establish the contribution of mantle components in the formation of layered intrusions rocks and the degrees of contamination of the magma source by crustal material. To calculate the proportion of mantle component model binary mixture was used [Jahn et. al., 2000]. As the mantle components we used data for CHUR: ɛNd = 0, [Nd] = 1.324 [Palm, O'Neil, 2003] and for crustal components were used host-rocks Nd-data. The proportion of mantle component for the studied intrusions was 77-99%. Also, data were obtained for the Monchetundra dike complex and amphibolized gabbro, for which the proportion of mantle material was 20-40%. For these rocks a significant crustal contamination is most likely. This process resulted in low values of ɛNd, a direct relationship between ɛNd and Nd concentration, and significant differences between the U-Pb and Sm-Nd model ages. A

  1. Principles of rock deformation

    SciTech Connect

    Nicolas, A.

    1987-01-01

    This text focuses on the recent achievements in the analysis of rock deformation. It gives an analytical presentation of the essential structures in terms of kinetic and dynamic interpretation. The physical properties underlying the interpretation of rock structures are exposed in simple terms. Emphasized in the book are: the role of fluids in rock fracturing; the kinematic analysis of magnetic flow structures; the application of crystalline plasticity to the kinematic and dynamic analysis of the large deformation imprinted in many metamorphic rocks.

  2. An empirical model for salinity intrusion in alluvial estuaries

    NASA Astrophysics Data System (ADS)

    Parsa, Javad; Etemad-Shahidi, Amir

    2011-10-01

    The main parameters that affect the salinity intrusion in estuaries are their geometric, hydrologic and hydrodynamic characteristics. The recognition of effective parameters and understanding their roles in the salinity intrusion are required for estuarine water management. In this study, the governing equations of the salinity intrusion processes were scaled to derive the effective dimensionless parameters. Then, a previously verified model, CE-QUAL-W2, was utilized as a virtual laboratory to investigate the effects of different governing parameters on the salinity intrusion. Analysis of the results showed that logarithmic functions can be used to describe the effect of dimensionless parameters obtained by scaling of governing equations. Finally, a formula was suggested to predict the salinity intrusion length based on geometrical and hydrodynamic characteristics of alluvial estuaries.

  3. Structural control on the shape of intrusions in the Koktokay ore district, Chinese Altai, north western China

    NASA Astrophysics Data System (ADS)

    Tian, Ye; Qin, Ke Zhang; Zhou, Qi Feng; Paterson, Greig

    2016-02-01

    The Koktokay pegmatite-type rare-metal-bearing ore district in the Altai orogen is famous for both its large scale and its diversity of rare metals. However, the emplacement mechanisms of the ore-bearing pegmatite intrusions in the Koktokay ore district are still unclear. Based on field observations, the emplacement of the ore-bearing pegmatite intrusions falls into two types. The first type is typical of the formation of dykes and sills, whereby they intruded into fan shaped, moderate dipping, joints within plutonic rocks. The second type involves the formation of a punched laccolith that was fed by a pegmatite sill. Magmatic stoping is the main mechanism of the laccolith emplacement. The peripheral faults played an important role in helping the emplacement of the laccolith. The trend of dykes and sills indicate two potential prospecting areas, which are located in the western and northern regions of the Koktokay ore district.

  4. Rock and Sexuality.

    ERIC Educational Resources Information Center

    Frith, Simon; McRobbie, Angela

    1978-01-01

    Discusses rock as a form of both sexual expression and control. Describes rock's representations of masculinity and femininity and considers the contradictions involved in the representations. Relates the effects of rock to its form--as music, as commodity, as culture, and as entertainment. (JMF)

  5. My Pet Rock

    ERIC Educational Resources Information Center

    Lark, Adam; Kramp, Robyne; Nurnberger-Haag, Julie

    2008-01-01

    Many teachers and students have experienced the classic pet rock experiment in conjunction with a geology unit. A teacher has students bring in a "pet" rock found outside of school, and the students run geologic tests on the rock. The tests include determining relative hardness using Mohs scale, checking for magnetization, and assessing luster.…

  6. Giant clastic intrusions primed by silica diagenesis

    NASA Astrophysics Data System (ADS)

    Davies, Richard J.; Huuse, Mads; Hirst, Philip; Cartwright, Joe; Yang, Yuesuo

    2006-11-01

    Postdepositional sediment mobilization is a common phenomenon that occurs over large areas of sedimentary basins, usually within mudstone-rich successions; however, defining the exact mechanism that initiates this process has proved elusive. Here we describe a number of large-scale clastic intrusions (injectites), 50 to >300 m in height, hosted within fine-grained biosiliceous upper Eocene to Pliocene strata in four sedimentary basins. Within these basins diagenetic conversion of opal A into opal CT (cristobalite and tridymite) causes a marked reduction in sediment porosity and the liberation of bound water, often at relatively shallow burial (<0.5 km). We propose that this occurs over geologically short time periods over large expanses of sedimentary basins, causing rapid pore fluid expulsion and overpressure buildup within interbedded sands. The liberated fluids primed these sands, rendering them susceptible to remobilization. This mechanism should have broad applicability.

  7. Coastal Marsh Monitoring for Persistent Saltwater Intrusion

    NASA Technical Reports Server (NTRS)

    Hall, Callie M.

    2008-01-01

    This viewgraph presentation reviews NASA's work on the project that supports the Gulf of Mexico Alliance (GOMA) Governors Action Plan to monitor the coastal wetlands for saltwater intrusion. The action items that relate to the task are: (1) Obtain information on projected relative sea level rise, subsidence, and storm vulnerability to help prioritize conservation projects, including restoration, enhancement, and acquisition, and (2) Develop and apply ecosystem models to forecast the habitat structure and succession following hurricane disturbance and changes in ecological functions and services that impact vital socio-economic aspects of coastal systems. The objectives of the program are to provide resource managers with remote sensing products that support ecosystem forecasting models requiring salinity and inundation data. Specifically, the proposed work supports the habitat-switching modules in the Coastal Louisiana Ecosystem Assessment and Restoration (CLEAR) model, which provides scientific evaluation for restoration management.

  8. Stress, intrusive imagery, and chronic distress.

    PubMed

    Baum, A

    1990-01-01

    Discusses the nature of stress in the context of problems with its definition and sources of confusion regarding its usefulness and specificity. Stress can be defined as a negative emotional experience accompanied by predictable biochemical, physiological, and behavioral changes that are directed toward adaptation either by manipulating the situation to alter the stressor or by accommodating its effects. Chronic stress is more complex than most definitions suggest and is clearly not limited to situations in which stressors persist for long periods of time. Responses may habituate before a stressor disappears or may persist long beyond the physical presence of the stressor. This latter case, in which chronic stress and associated biobehavioral changes outlast their original cause, is considered in light of research at Three Mile Island and among Vietnam veterans. The role of intrusive images of the stressor or uncontrollable thoughts about it in maintaining stress is explored. PMID:2286178

  9. 68. LITTLE ROCK AND PALMDALE IRRIGATION DISTRICT, LITTLE ROCK DAM: ...

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

    68. LITTLE ROCK AND PALMDALE IRRIGATION DISTRICT, LITTLE ROCK DAM: STRESS SHEET, SHEET 4; MAY, 1918. Littlerock Water District files. - Little Rock Creek Dam, Little Rock Creek, Littlerock, Los Angeles County, CA

  10. Emplacement of sandstone intrusions during contractional tectonics

    NASA Astrophysics Data System (ADS)

    Palladino, Giuseppe; Grippa, Antonio; Bureau, Denis; Alsop, G. Ian; Hurst, Andrew

    2016-08-01

    Sandstone injections are created by the forceful emplacement of remobilized sand in response to increases in overpressure. However, the contribution provided by horizontal compressive stress to the build-up in overpressure, and the resulting emplacement of sand injection complexes, is still to be substantiated by robust field observations. An opportunity to address this issue occurs in Central California where a large volume of sandstone intrusions record regionally-persistent supra-lithostatic pore-pressure. Detailed fieldwork allows sandstone-filled thrusts to be recognized and, for the first time, permits us to demonstrate that some sandstone intrusions are linked to contractional deformation affecting the western border of the Great Valley Basin. Fluidized sand was extensively injected along thrust surfaces, and also fills local dilatant cavities linked to thrusting. The main aims of this paper are to provide detailed descriptions of the newly recognized syn-tectonic injections, and describe detailed cross-cutting relationships with earlier sandstone injection complexes in the study area. Finally, an evolutionary model consisting of three phases of sand injection is provided. In this model, sand injection is linked to contractional tectonic episodes affecting the western side of the Great Valley Basin during the Early-Middle Cenozoic. This study demonstrates that sand injections, driven by fluid overpressure, may inject along thrusts and folds and thereby overcome stresses associated with regional contractional deformation. It is shown that different generations of sand injection can develop in the same area under the control of different stress regimes, linked to the evolving mountain chain.

  11. Coeval potassic and sodic calc-alkaline series in the post-collisional Hercynian Tanncherfi intrusive complex, northeastern Morocco: geochemical, isotopic and geochronological evidence

    NASA Astrophysics Data System (ADS)

    Ajaji, Tamimount; Weis, Dominique; Giret, André; Bouabdellah, Mohamed

    1998-12-01

    The post-collisional late Hercynian Tanncherfi intrusive complex (TIC) is part of a widespread intrusive episode in the Moroccan Meseta. The complex contains a wide range of rock types, from monzogabbros to monzogranites. Two distinct magmatic series are recognized: (1) a potassic (shoshonitic) series consisting of monzogabbros, quartz monzonites and monzogranites; and (2) a sodic (granodioritic) series represented by quartz monzodiorites and granodiorites. All the Tanncherfi plutonic rocks display similar spider-diagram profiles, with LILE and LREE enrichment and Nb, Ta, Ti depletion, which are typical of subduction-related magmas. Combined major, trace element compositions and Sr, Nd isotopic results indicate that the two series have been derived from a LILE- and LREE-enriched continental lithospheric mantle source, under different partial melting and/or depth conditions. Intrusion of the Tanncherfi rocks was not temporally related to subduction and the enrichment of their source is likely to be linked to preceding subduction events. The two series evolved by fractional crystallization, of clinopyroxene, plagioclase, hornblende, biotite, K-feldspar and accessories (Fe-Ti oxide minerals, titanite, apatite and zircon) for the potassic series while the sodic series combined fractional crystallization with assimilation of felsic magmas with lower Sr isotopic ratio than the more mafic term of the series, the quartz monzodiorite. The intrusion of the potassic magmas (344±6 Ma) marks a major change in the tectonic regime of eastern Meseta. These magmas intruded during post-thickening uplift and extension, both probably favored by convective thinning of the lithosphere. This model provides a reasonable mechanism for the genesis of other Hercynian intrusive complexes in Morocco.

  12. Strategy for radioactive waste disposal in crystalline rocks.

    PubMed

    Bredehoeft, J D; Maini, T

    1981-07-17

    A strategy for waste disposal is proposed in which the repository would be situated in a crystalline rock mass beneath a blanket of sedimentary rocks whose ground-water flow characteristics are well understood. Such an approach exemplifies the concept of multiple barriers to the isolation of radioactive wastes from the biosphere. This strategy has the advantages that (i) ground-water flow within the sedimentary rocks can be investigated and modeled by conventional, well-under-stood theory and technology; (ii) under favorable circumstances, the flow system operates as an active barrier, so that a long migration path and extremely low flow rate to the biosphere can be assured; and (iii) since, in many locations, ground water is nonpotable, the possibility of future human intrusion can be minimized.

  13. Rock Creek Tower Painting Project : Environmental Assessment.

    SciTech Connect

    United States. Bonneville Power Administration.

    1988-10-01

    Bonneville Power Administration (BPA) built a 500-kV line across Rock Creek, a Class I trout stream about 20 miles east of Missoula, MT. Two 190-foot towers rise on either side of the Rock Creek valley, and the line between is suspended 600 feet over the valley floor. The crossing poses a hazard to passing airplanes and disrupts the natural landscape. The area where the line crosses Rock Creek is prized for its scenic beauty. In response to public demand that BPA protect the visual beauty of this area, BPA painted the towers gray to blend them best in with their natural surroundings. The issue now is to decide between either two gray towers or two orange-and-white towers. The underlying need is to resolve the conflict of pilot safety against scenic intrusion. The proposed action is to paint the gray tower aeronautical orange and white. Alternatives are to paint the orange-and-white tower back to its original gray; or leave the dilemma unresolved (the ''no-action'' alternative). 9 refs., 3 figs.

  14. Elastic Properties of Sedimentary Rocks

    NASA Astrophysics Data System (ADS)

    Melendez Martinez, Jaime

    Sedimentary rocks are an important research topic since such rocks are associated to sources of ground water as well as oil, gas, and mineral reservoirs. In this work, elastic and physical properties of a variety of sedimentary samples that include glacial sediments, carbonates, shales, one evaporite, and one argillite from a variety of locations are investigated. Assuming vertical transverse isotropy, ultrasonic compressional- and shear-waves (at 1 MHz central frequency) were measured as a function of confining pressure on all samples with the exception of glacial samples which were tested assuming isotropy. Tensile strength tests (Brazilian test) were also carried out on selected glacial samples and, in addition, static-train measurements were conducted on shales and argillite samples. Lithological and textural features of samples were obtained through thin section techniques, scanning electron microscopy images and micro-tomography images. X-ray diffraction and X-Ray fluorescence provided the mineralogical oxides content information. Porosity, density, and pore structure were studied by using a mercury intrusion porosimeter and a helium pycnometer. The wide range of porosities of the studied samples (ranging from a minimum of 1% for shales to a maximum 45% for some glacial sediments) influence the measured velocities since high porosity sample shows an noticeable velocity increment as confining pressure increases as a consequence of closure of microcracks and pores, unlike low porosity samples where increment is quasi-lineal. Implementation of Gassmann's relation to ultrasonic velocities obtained from glacial samples has negligible impact on them when assuming water saturated samples, which suggests that state of saturation it is no so important in defining such velocities and instead they are mainly frame-controlled. On the other hand, velocities measured on carbonate and evaporite samples show that samples are at best weak anisotropic, thus the intrinsic

  15. Emplacement and geochemical evolution of eocene plutonic rocks in the Colville batholith

    SciTech Connect

    Holder, R.W.

    1986-01-01

    Eocene plutonic rocks in the Colville batholith are divided on the basis of field evidence and chemical composition into, in order of decreasing age, (1) several calc-alkalic biotite-hornblende monzodiorite to granodiorite intrusions referred to as the Devils Elbow suite, and (2) compositionally variable calc-alkalic to alkali-calcic intrusions referred to as the Herron Creek suite. These Eocene suites are distinct from older, more voluminous, leucocratic granite and granodiorite intrusions, designated the Keller Butte suite, which are calcic and characteristically lack hornblende. Results of qualitative and computer modeling of major element variation and quantitative models of trace element variation in the chemically coherent Bridge Creek intrusions, a member of the Herron Creek suite, are compatible with fractionation of plagioclase feldspar + hornblende + biotite + magnetite + apatite from a parent magma of andesitic composition to account for the observed variation. Strongly curved variation trends preclude mixing as the primary mechanism for the observed variation. It is suggested that parallel variation trends in the other Eocene intrusions are also the result of crystal fractionation. Lateral chemical variations including a decrease in silica saturation suggest the chemical characteristics of these rocks reflect those of parental magmas derived from the mantle, with an unknown amount of crustal contribution. Rotated and angular xenoliths, discordant contacts, and temporal and spatial proximity to graben structures indicate that the Eocene plutons were passively implaced into the upper crust along graben-bounding faults during graben formation, the earlier stages of which appear to have been contemporaneous with regional mylonitic deformation.

  16. Geochemistry of Rock Samples Collected from the Iron Hill Carbonatite Complex, Gunnison County, Colorado

    USGS Publications Warehouse

    Van Gosen, Bradley S.

    2008-01-01

    A study conducted in 2006 by the U.S. Geological Survey collected 57 surface rock samples from nine types of intrusive rock in the Iron Hill carbonatite complex. This intrusive complex, located in Gunnison County of southwestern Colorado, is known for its classic carbonatite-alkaline igneous geology and petrology. The Iron Hill complex is also noteworthy for its diverse mineral resources, including enrichments in titanium, rare earth elements, thorium, niobium (columbium), and vanadium. This study was performed to reexamine the chemistry and metallic content of the major rock units of the Iron Hill complex by using modern analytical techniques, while providing a broader suite of elements than the earlier published studies. The report contains the geochemical analyses of the samples in tabular and digital spreadsheet format, providing the analytical results for 55 major and trace elements.

  17. Post-intrusive south directed Deformation of the Serifos metamorhic Core Complex (western Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Rambousek, C.; Grasemann, B.; Petrakakis, K.; Zamolyi, A.; Iglseder, C.

    2003-04-01

    The Attic - Cycladic belt is part of the Alpine orogen in the eastern Mediterranean. It is located SE of the Greek mainland and trends parallel to the Hellenic volcanic arc. Since the Miocene the whole area of the southern Aegean region is characterized by a NS oriented extensional regime partly accommodated by crustal low-angle normal faults. Some of the islands in the eastern Cyclades (Naxos, Paros, Ios) have been suggested to represent metamorphic core complex (MCC) indicating an asymmetric extension partly to the N and to the S (e.g. Lister et al. 1984). This work focuses on the S directed detachment of a newly found MCC on Serifos, in the western Cyclades. The SE part of the island is dominated by an undeformed Hornbelende-Biotite granodiorite pluton in the core, which becomes with increasing intensity foliated towards higher structural levels transforming into S-dipping low-temperature mylonitic to ultra-mylonitic rocks with abundant SSW-directed kinematic indicators (scc´ fabrics, sigma- and delta-clasts, flanking fold structures and mica-fish). This zone forms the main detachment of the Serifos MCC. The northern contact of the granodiorite is mainly intrusive cross cutting amphibolite facies highly deformed marbles, metabasic and metapelitic rocks with typical Ca-Fe-Mg skarns (Salemink, 1985). On the peninsular in the SE most part of Serifos (E of Livadi) statically recristallized mylonitic marbles and amphibolite grade metabasic and metapelitic rocks with the typical Ca-Fe-Mg skarns occur in the hanging wall of the main detachment zone. These characteristic lithologies also occur as mega boudins (several tens of meters long) in the main detachment zone and are lithologically similar to the host rocks in the north of the intrusion. There, these rocks are structurally in the footwall of the main detachment and therefore a minimum dip-slip 6 km can be estimated for the post-intrusive deformation. Geochronological cooling ages of the granodiorite using

  18. Magmatism and tectonic evolution of the Chinese Altai, NW China: insights from the Paleozoic mafic and felsic intrusions

    NASA Astrophysics Data System (ADS)

    Cai, Keda; Sun, Min; Xiao, Wenjiao; Yuan, Chao; Zhao, Guochun; Long, Xiaoping

    2013-04-01

    The Chinese Altai, as a key segment of the Central Asian Orogenic Belt (CAOB), is dominated by variably deformed and metamorphosed sedimentary rocks, volcanic rocks and plutonic rocks. The plutonic rocks include extensive granites and relatively subordinate mafic intrusions. For instance, mafic dykes in the northwestern region (Habahe area) have an emplacement age of 375.5±4.8Ma and include gabbroic and doleritic dykes. The gabbroic dykes have chondrite-normalized REE patterns similar to N-MORB (La/YbN=0.86~1.1), together with their high ɛNd(t) values (+7.6~+8.1), indicating deriviation from a N-MORB-type depleted asthenospheric mantle. While the doleritic dykes resemble E-MORB (La/YbN= 1.12~2.28) with relatively low ɛNd(t) values (+3.4-+5.4) and high initial 87Sr/86Sr ratios (0.7057-0.7060), suggesting derivation from a mantle wedge metasomatized by slab-derived fluids and/or melts. In contrast, mafic intrusions in the southeastern region (Keketuohai area) occur as a zoned intrusion with an emplacement age of 409±5 Ma, consisting of dunite, olivine gabbro, hornblende gabbro and pyroxene diorite. Their ɛNd(t) values (0 to +2.7) suggest that the parental magma was produced by partial melting of the lithospheric mantle under a high geothermal regime. Zircon U-Pb ages demonstrate that voluminous granitoids were continuously emplaced over more than 30 % area of the Chinese Altai during the period from 447 Ma to 368 Ma with a climax at ca. 400 Ma. Positive ɛHf(t) values (0 to +9) of normal magmatic zircons suggest that the granitoid magmas were derived from juvenile sources. The extensive magmatism at ca. 400 Ma significantly changed the Hf isotopic composition of the magma source by substantial input of juvenile material in a relatively short period. Four representative large S-type granitic intrusions were emplaced from 419 to 393 Ma, consistent with a period of intensive magmatic activities. The S-type granitic magmas were generated by dehydration melting of

  19. New prospects of Sm-Nd sulphide dating of the PGE-bearing layered intrusions in the NE Fennoscandian Shield

    NASA Astrophysics Data System (ADS)

    Ekimova, N.; Bayanova, T.

    2009-04-01

    The Sm-Nd investigations steadily employ new minerals-geochronometers. Of these, sulphides of PGE-bearing layered intrusions are quite important in terms of dating the process of ore origin. Studying the REE distribution in the sulphides of MOR hydrothermal sources has shown possible REE presence in the suphide lattice [Rimskaya-Korsakova et. al., 2003]. The isotope Sm-Nd investigations of sulphides have for the first time been done in Russia. These are difficult to carry out because the concentrations of Sm and Nd isotopes in sulphides are much lower than those in chondrites [Rimskaya-Korsakova et. al., 2003]. This investigation was aimed at determining Sm-Nd concentrations and Nd isotope compositions for the purpose of dating the ore genesis process of the PGE-bearing intrusions. The geochronological samples were taken from the Pt intrusions of the Fennoscandian Shield. These are the Fedorov-Pana intrusion (Russia) and the Nottrask intrusion (Sweden). It is known that the economic Pt-Pd mineralization is associated with sulphides. The sulphides were chemically prepared for Sm-Nd dating using the following modified procedure: a portion of sulphides (~50 mg) mixed with a solution of 149Sm/150Nd tracer was dissolved in nitrohydrocloric acid sand then in hydrogen chloride until fully dissolved. Following the fractional acid decomposition, REEs were separated from the solution by cation exchange chromatography using cation exchange tar, Dowex 50x8 (200-400 mesh). Another minerals and rocks were decomposed in accordance with the standard procedure [Zhuravlev et al., 1987]. The variation of the Nd isotope composition and Sm and Nd concentrations using the isotope dilution method was carried out at the seven-channel solid phase mass-spectrometer, Finnigan - MAT 262 (PRQ) in a static two-band mode at the collectors with Re+Re and Ta+Re bands. The Pt-bearing Fedorov-Pana intrusion occurs in the NE Fennoscandian Shield, or in the centre of the Kola Peninsula, and referred

  20. Tertiary alkaline Roztoky Intrusive Complex, České středohoří Mts., Czech Republic: petrogenetic characteristics

    NASA Astrophysics Data System (ADS)

    Skála, Roman; Ulrych, Jaromír; Ackerman, Lukáš; Jelínek, Emil; Dostál, Jaroslav; Hegner, Ernst; Řanda, Zdeněk

    2014-07-01

    The České středohoří Mts. is the dominant volcanic center of the Ohře (Eger) rift zone. It hosts the Roztoky Intrusive Complex (RIC), which is made up of a caldera vent and intrusions of 33-28-Ma-old hypabyssal bodies of essexite-monzodiorite-sodalite syenite series accompanied by a radially oriented 30-25-Ma-old dike swarm comprising about 1,000 dikes. The hypabyssal rocks are mildly alkaline mostly foid-bearing types of mafic to intermediate compositions. The dike swarm consists of chemically mildly alkaline and rare strongly alkaline rocks (tinguaites). The geochemical signatures of the mildly alkaline hypabyssal and associated dike rocks of the RIC are consistent with HIMU mantle sources and contributions from lithospheric mantle. The compositional variations of essexite and monzodiorite can be best explained by fractional crystallization of parent magma without significant contributions of crustal material. On the other hand, the composition of monzosyenite, leuco-monzodiorite and sodalite syenite reflects fractional crystallization coupled with variable degrees of crustal assimilation. It is suggested that the parent magmas in the Ohře rift were produced by an adiabatic decompression melting of ambient upper mantle in response to lithospheric extension associated with the Alpine Orogeny.

  1. Welded tuff porosity characterization using mercury intrusion, nitrogen and ethylene glycol monoethyl ether sorption and epifluorescence microscopy

    USGS Publications Warehouse

    Reddy, M.M.; Claassen, H.C.; Rutherford, D.W.; Chiou, C.T.

    1994-01-01

    Porosity of welded tuff from Snowshoe Mountain, Colorado, was characterized by mercury intrusion porosimetry (MIP), nitrogen sorption porosimetry, ethylene glycol monoethyl ether (EGME) gas phase sorption and epifluorescence optical microscopy. Crushed tuff of two particle-size fractions (1-0.3 mm and less than 0.212 mm), sawed sections of whole rock and crushed tuff that had been reacted with 0.1 N hydrochloric acid were examined. Average MIP pore diameter values were in the range of 0.01-0.02??m. Intrusion volume was greatest for tuff reacted with 0.1 N hydrochloric acid and least for sawed tuff. Cut rock had the smallest porosity (4.72%) and crushed tuff reacted in hydrochloric acid had the largest porosity (6.56%). Mean pore diameters from nitrogen sorption measurements were 0.0075-0.0187 ??m. Nitrogen adsorption pore volumes (from 0.005 to 0.013 cm3/g) and porosity values (from 1.34 to 3.21%) were less than the corresponding values obtained by MIP. More than half of the total tuff pore volume was associated with pore diameters < 0.05??m. Vapor sorption of EGME demonstrated that tuff pores contain a clay-like material. Epifluorescence microscopy indicated that connected porosity is heterogeneously distributed within the tuff matix; mineral grains had little porosity. Tuff porosity may have important consequences for contaminant disposal in this host rock. ?? 1994.

  2. Structure, intrusion, and tectonic origin of the Independence dike swarm, eastern California

    NASA Astrophysics Data System (ADS)

    Carl, Brian Stewart

    2000-10-01

    The Jurassic (˜148 Ma) Independence dike swarm is exposed over a distance of >600 km and has served as a valuable temporal and structural marker across eastern California. This study investigates new structural, field, and compositional data associated with the swarm's tectonic origin, deformation and emplacement, and proposes models to explain these data. In addition, this study explores an enigmatic relationship between deformed mafic dikes and their undeformed granitic host. In the eastern Sierra, Independence dikes within Jurassic plutons cut and are themselves deformed by NNE-striking reverse-sense mylonitic shear zones, providing strong evidence for syndeformational dike intrusion. Many dikes contain a penetrative, solid-state ductile fabric which formed during sinistral shear across the dikes. Mylonitization and sinistral shear along Sierran dikes may have occurred along a Late Jurassic transpressional Cordilleran arc. Swarm intrusion likely occurred in response to a rapid change in North American plate motion rather than during rifting of the arc or in response to a collisional event. Composite Independence dikes may indicate the mode of dike emplacement and magma interaction at depth. Most Sierran composite dikes contain subparallel mafic intrusions but a few contain both mafic and felsic phases. Along more southerly portions of the swarm, in the Spangler Hills and in the Granite and Fry mountains, composite dikes contain abundant enclaves. These features may correlate with dike compositions. In the Sierra, composite dikes are dominantly either mafic or felsic, whereas more southerly composite dikes include intermediate phases. If dikes tapped plutons emplaced at similar paleodepths, then dike features and compositional variability may reflect different degrees of mixing along dike conduits. Rock mechanics experiments indicate that mafic rocks should be more competent than quartz-rich granite. Dikes which are strongly mylonitized along their margins

  3. The role of stress during memory reactivation on intrusive memories.

    PubMed

    Cheung, Jessica; Garber, Benjamin; Bryant, Richard A

    2015-09-01

    Intrusive memories are unwanted recollections that maintain distress in psychological disorders. Increasing evidence suggests that memories that are reactivated through retrieval become temporarily vulnerable to environmental or pharmacological manipulation, including changes in levels of circulating stress hormones. This study investigated the influence of stress during memory reactivation of an emotionally arousing trauma film on subsequent intrusive memories. Three groups of participants (N=63) viewed a trauma film depicting a serious car accident at baseline. Two days later (Time 2), one group received a reactivation induction following a socially evaluated cold pressor test (SECPT; Stress/Reactivation condition), whilst the second group reactivated the memory after a control procedure (Reactivation condition). A third group underwent the SECPT but was not asked to reactivate memory of the trauma film (Stress condition). Two days later (Time 3), all participants received a surprise cued memory recall test and intrusions questionnaire which they completed online. Results showed that those in the Stress/Reactivation group had higher intrusions scores than the other two groups, suggesting that acute stress promotes intrusive memories only when the memory trace is reactivated shortly afterwards. Increased cortisol predicted enhanced intrusive experiences in the Stress/Reactivation condition but not in the other conditions. This pattern of results suggests that acute stress during the reactivation of emotional material impacts on involuntary emotional memories. These findings suggest a possible explanation for the mechanism underlying the maintenance of intrusive memories in clinical disorders.

  4. Realistic computer network simulation for network intrusion detection dataset generation

    NASA Astrophysics Data System (ADS)

    Payer, Garrett

    2015-05-01

    The KDD-99 Cup dataset is dead. While it can continue to be used as a toy example, the age of this dataset makes it all but useless for intrusion detection research and data mining. Many of the attacks used within the dataset are obsolete and do not reflect the features important for intrusion detection in today's networks. Creating a new dataset encompassing a large cross section of the attacks found on the Internet today could be useful, but would eventually fall to the same problem as the KDD-99 Cup; its usefulness would diminish after a period of time. To continue research into intrusion detection, the generation of new datasets needs to be as dynamic and as quick as the attacker. Simply examining existing network traffic and using domain experts such as intrusion analysts to label traffic is inefficient, expensive, and not scalable. The only viable methodology is simulation using technologies including virtualization, attack-toolsets such as Metasploit and Armitage, and sophisticated emulation of threat and user behavior. Simulating actual user behavior and network intrusion events dynamically not only allows researchers to vary scenarios quickly, but enables online testing of intrusion detection mechanisms by interacting with data as it is generated. As new threat behaviors are identified, they can be added to the simulation to make quicker determinations as to the effectiveness of existing and ongoing network intrusion technology, methodology and models.

  5. A novel interacting multiple model based network intrusion detection scheme

    NASA Astrophysics Data System (ADS)

    Xin, Ruichi; Venkatasubramanian, Vijay; Leung, Henry

    2006-04-01

    In today's information age, information and network security are of primary importance to any organization. Network intrusion is a serious threat to security of computers and data networks. In internet protocol (IP) based network, intrusions originate in different kinds of packets/messages contained in the open system interconnection (OSI) layer 3 or higher layers. Network intrusion detection and prevention systems observe the layer 3 packets (or layer 4 to 7 messages) to screen for intrusions and security threats. Signature based methods use a pre-existing database that document intrusion patterns as perceived in the layer 3 to 7 protocol traffics and match the incoming traffic for potential intrusion attacks. Alternately, network traffic data can be modeled and any huge anomaly from the established traffic pattern can be detected as network intrusion. The latter method, also known as anomaly based detection is gaining popularity for its versatility in learning new patterns and discovering new attacks. It is apparent that for a reliable performance, an accurate model of the network data needs to be established. In this paper, we illustrate using collected data that network traffic is seldom stationary. We propose the use of multiple models to accurately represent the traffic data. The improvement in reliability of the proposed model is verified by measuring the detection and false alarm rates on several datasets.

  6. Experimental modelling of ground deformation associated with shallow magma intrusions

    NASA Astrophysics Data System (ADS)

    Galland, O.

    2012-04-01

    Active volcanoes experience ground deformation as a response to the dynamics of underground magmatic systems. The analysis of ground deformation patterns may provide important constraints on the dynamics and shape of the underlying volcanic plumbing systems. Nevertheless, these analyses usually take into account simplistic shapes (sphere, dykes, sills) and the results cannot be verified as the modelled systems are buried. In this contribution, I will present new results from experimental models of magma intrusion, in which both the evolution of ground deformation during intrusion and the shape of the underlying intrusion are monitored in 3D. The models consisted of a molten vegetable oil, simulating low viscosity magma, injected into cohesive fine-grained silica flour, simulating the brittle upper crust; oil injection resulted is sheet intrusions (dykes, sills and cone sheets). The initial topography in the models was flat. While the oil was intruding, the surface of the models slightly lifted up to form a smooth relief, which was mapped through time. After an initial symmetrical development, the uplifted area developed asymmetrically; at the end of the experiments, the oil always erupted at the steepest edge of the uplifted area. After the experiment, the oil solidified, the intrusion was excavated and the shape of its top surface mapped. The comparison between the uplifted zone and the underlying intrusions showed that (1) the complex shapes of the uplifted areas reflected the complex shapes of the underlying intrusions, (2) the time evolution of the uplifted zone was correlated with the evolution of the underlying intrusion, and (3) the early asymmetrical evolution of the uplifted areas can be used to predict the location of the eruption of the oil. The experimental results also suggest that complex intrusion shapes (inclined sheet, cone sheet, complex sill) may have to be considered more systematically in analyses of ground deformation patterns on volcanoes.

  7. Experimental modelling of ground deformation associated with shallow magma intrusions

    NASA Astrophysics Data System (ADS)

    Galland, Olivier

    2012-02-01

    Active volcanoes experience ground deformation as a response to the dynamics of underground magmatic systems. The analysis of ground deformation patterns may provide important constraints on the dynamics and shape of the underlying volcanic plumbing systems. Nevertheless, these analyses usually take into account simplistic shapes (sphere, dykes, sills) and the results cannot be verified as the modelled systems are buried. In this paper, I present new results from experimental models of magma intrusion, in which both the evolution of ground deformation during intrusion and the shape of the underlying intrusion are monitored. The models consisted of a molten vegetable oil, simulating low viscosity magma, injected into cohesive fine-grained silica flour, simulating the brittle upper crust; oil injection resulted is sheet intrusions (dykes, sills and cone sheets). The initial topography in the models was flat. While the oil was intruding, the surface of the models slightly lifted up to form a smooth relief, which was mapped through time. After an initial symmetrical development, the uplifted area developed asymmetrically; at the end of the experiments, the oil always erupted at the steepest edge of the uplifted area. After the experiment, the oil solidified, the intrusion was excavated and the shape of its top surface mapped. The comparison between the uplifted zone and the underlying intrusions showed that (1) the complex shapes of the uplifted areas reflected the complex shapes of the underlying intrusions, (2) the time evolution of the uplifted zone was correlated with the evolution of the underlying intrusion, and (3) the early asymmetrical evolution of the uplifted areas can be used to predict the location of the eruption of the oil. The experimental results also suggest that complex intrusion shapes (inclined sheet, cone sheet, complex sill) may have to be considered more systematically in the analyses of ground deformation patterns on volcanoes.

  8. Chemical and textural variations of plutons along the Wasatch intrusive belt, central Wasatch mountains, Utah

    SciTech Connect

    Hanson, S.L.; Nash, W.P. . Dept. of Geology and Geophysics)

    1993-04-01

    The Wasatch intrusive belt, located in the central Wasatch mountains, consists of 11 Tertiary plutons. Uplift and rotation of the Wasatch mountains has exposed the 11 km thick section which hosts these plutons. They include from west to east, the Little Cottonwood (LC), Alta (AS) and Clayton Peak (CP) stocks, the Park City Porphyries, and the Park Premier Porphyries which intrude the Keetley Volcanics. Stratigraphic and fluid inclusion studies suggest that depths of emplacement range from nearly 11 km in the west to less than 1 km in the east. Both textural and chemical variations within the Wasatch plutons are consistent with successively shallower depths of emplacement. The LC, AS and CP rocks are phaneritic with grain size decreasing eastward, whereas Park City and Park Premier rocks exhibit a porphyritic texture. Or content in zoned plagioclase from the phaneritic stocks remains constant (Or[sub 1.7]) with decreasing An content, whereas Or content from the porphyritic stocks increases (Or[sub 1.3] to Or[sub 5.1]). Equilibration pressures calculated from hornblende compositions correspond to depths of approximately 9.8 km and 6.8 km for the western portion of LC stocks as AS, respectively. Although ages of many of these plutons are poorly constrained, there does not appear to be a direct correlation between east-west location and age. However, whole rock major element analyses exhibit a typical calc-alkaline enrichment trend with the older plutons being more mafic than the younger.

  9. Titaniferous magnetite in the layered intrusive complex at Lakathah, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Martin, Conrad; Roberts, Ralph Jackson; Stoeser, D.B.

    1979-01-01

    The Lakathah layered intrusive complex about 90 km east of Qunfudhah contains significant resources of low-grade titanium-bearing rock. The complex is about 10 km in diameter and consists of three principal units: an outer syenite ring, an intermediate diorite-gabbro zone, and a central pyroxenite-hornblendite core. The principal mineralization zone is in the ultramafic core of the complex. The titanium is mainly in titaniferous magnetite, but some is in ilmenite intergrown with magnetite and in the titanium-bearing hornblende, kaersutite. The titaniferous magnetite is in concordant lenses and veinlets and is disseminated throughout the host rock. The lenses and veins range from a few centimeters to 3 m in width and are as much as 50 m long. The layered disseminated bodies contain as much as 25 percent magnetite. Exploratory drilling showed that an area 500 by 1000 m contains titaniferous rock averaging about 6.2 percent TiO2. This mineralized zone contains about 175,000,000 tons per 100 m depth. Material of this grade is not commercial at this time, but may be a future resource. Alluvial deposits along the Red Sea near Al Qunfudhah should be tested for possible deposits of titaniferous sand.

  10. Laboratory experiments of salt water intrusion

    NASA Astrophysics Data System (ADS)

    Crestani, Elena; Camporese, Matteo; Salandin, Paolo

    2015-04-01

    The problem of saltwater intrusion in coastal aquifers is dealt with by the proper setup of a sand-box device to develop laboratory experiments in a controlled environment. Saline intrusion is a problem of fundamental importance and affects the quality of both surface water and groundwater in coastal areas. In both cases the phenomenon may be linked to anthropogenic (construction of reservoirs, withdrawals, etc.) and/or natural (sea-level excursions, variability of river flows, etc.) changes. In recent years, the escalation of this problem has led to the development of specific projects and studies to identify possible countermeasures, typically consisting of underground barriers. Physical models are fundamental to study the saltwater intrusion problem, since they provide benchmarks for numerical model calibrations and for the evaluation of the effectiveness of solutions to contain the salt wedge. In order to study and describe the evolution of the salt wedge, the effectiveness of underground barriers, and the distance from the coast of a withdrawal that guarantees a continuous supply of fresh water, a physical model has been realized at the University of Padova to represent the terminal part of a coastal aquifer. It consists of a laboratory flume 500 cm long, 30 cm wide and 60 cm high, filled for an height of 45 cm with glass beads with a d50 of 0.6 mm and a uniformity coefficient d60/d10~= 1.5. The material is homogeneous and characterized by a porosity of about 0.37 and by an hydraulic conductivity of about 1.8×10-3 m/s. Upstream from the sand-box, a tank, continuously supplied by a pump, provides fresh water to recharge the aquifer, while the downstream tank, filled with salt water, simulates the sea. The volume of the downstream tank (~= 2 m3) is about five times the upstream one, so that density variations due to the incoming fresh water flow are negligible. The water level in the two tanks is continuously monitored by means of two level probes and is

  11. Is assimilation of country rocks in camera of crystallization an important factor for origin of the Noril'sk ores?

    NASA Astrophysics Data System (ADS)

    Krivolutskaya, Nadezhda; Kryazhev, Sergey; Svirskaya, Natalia

    2013-04-01

    In origin of the unique PGE-Cu Noril'sk deposits a great significance is attached to assimilation of country rocks by mafic melts in camera of crystallization for formation large-scale sulfide ore bodies. The main argument in favor of widespread assimilation is the enrichment of ore sulfides in the heavy sulfur isotope due to the participation of anhydrite from country rocks (Godlevsky, Grinenko, 1963). But real data demonstrated this process are almost absent in literature. We have studied geochemistry rocks of some sections from surrounding rocks to intrusive ones with sulfide ores. Two of them were done at the Southern Maslovsky deposit located in basalts and one was considered at Talnakh deposit (SW branch) that is situated among carbonate-terrigenouse rocks with evaporates (salt, anhydrite, gypsum). Ores at the Maslovsky deposit are characterized by δ34S = 6-11‰ while the host basalts of the Nadezhdinsky Formation have δ34S < +5 ‰ (Ripley et al., 2003). Hence, the latter could not been a source of heavy sulfur in sulfides. So basalts of the lower Nadezhdinsky subformation at the contact of the Southern Maslovsky intrusion are close to each other in major oxide contents, but basalts are enriched in LREE in comparison with normal REE concentrations in gabbro-dolerite. The La/Sm ratio is characteristic in this respect. At the upper intrusive contact an influence to country basalts on composition of intrusive rocks is not detected at all and revealed in a narrow zone (< 1 m) at the eastern end of the intrusion. The 50-m sill of the Talnakh intrusion with 11 m of massive ores is located in Devonian rocks. In cross section main, REE, Sr and Nd isotopes were determined. The assimilation of country rocks by magma must be reflected in change of chemical and modal composition of intrusive rocks, especially in contact zones of intrusions, but this effect is noted established. Line of component variations have sharp profile from sedimentary rocks to gabbro

  12. Gravity evidence for a mafic intrusion beneath a mineralized zone in the Bondy gneiss complex, Grenville Province, Quebec - Exploration implications

    NASA Astrophysics Data System (ADS)

    Dufréchou, Grégory; Harris, Lyal B.; Corriveau, Louise; Antonoff, Vladimir

    2011-09-01

    A ground gravity survey over the Bondy gneiss complex and its mineralized iron oxide- and copper-rich hydrothermal system(s) in the Grenville Province of SW Quebec was undertaken to aid mineral exploration in mapping subsurface intrusions. Several kilometric-scale positive Bouguer anomalies were identified that coincide with outcropping mafic and intermediate intrusive rocks of the post peak-metamorphic, 1.17-1.16 Ga mafic to intermediate Chevreuil suite intrusions and a 1.09-1.07 Ga Rolleau ultramafic stock. An additional 4 × 3 kilometre positive gravity anomaly indicates a mafic body underlies part of the metamorphosed hydrothermal system in the area of magnetite, pyrite, pyrrhotite, and chalcopyrite mineralization. Advanced argilic alteration associated with sulphide enrichment here is however indicative of an epithermal system with a felsic intrusion fluid source. As a felsic intrusion cannot explain the positive Bouguer gravity anomaly both felsic and mafic bodies must be present beneath the mineralized zone. Our preferred interpretation based on integrating gravity data and 2D forward gravity modelling with the results of field and geochemical studies is that this anomaly corresponds to a ca. 500 m deep mafic 1.17-1.16 Ga Chevreuil suite pluton that may have provided the source for hydrothermal fluids associated with late ductile shear- and fault-related mineralization or remobilization of early mineralization associated with a felsic pluton into late structures. This interpretation is compatible with gabbro xenoliths in the 1.07 Ga Rivard lamprophyre dyke on the NW margin of the gravity anomaly that bear significant similarities with those of the Chevreuil intrusive suite. The presence of both early felsic and late mafic intrusions beneath a group of three mineral occurrences in the Bondy gneiss complex strengthens their prospectivity in comparison to other mineral occurrences in the area. That early, pre-metamorphic mineralization was upgraded late in the

  13. Thermal and tectonic history of the Mineral Mountains intrusive complex

    SciTech Connect

    Evans, S.; Nielson, D.L.

    1982-10-01

    Study of the Mineral Mountains intrusive complex was undertaken to decipher interrelationships of intrusion, uplift rate and structural control as related to the Roosevelt Hot Springs geothermal system. Results of fission track and K-Ar dating show that different units of the intrusive complex underwent similar cooling histories. Uplift rates calculated for the north (0.25 mm/yr) and central (0.5 mm/yr) portions differ substantially. This difference in uplift rate may have accounted for the development of faulting which has been important as structural controls on the geothermal system.

  14. Mafic and felsic igneous rocks at Gale crater

    NASA Astrophysics Data System (ADS)

    Sautter, Violaine; Cousin, Agnès; Mangold, Nicolas; Toplis, Michael; Fabre, Cécile; Forni, Olivier; Payré, Valérie; Gasnault, Olivier; Ollila, Anne; Rapin, William; Fisk, Martin; Meslin, Pierre-Yves; Wiens, Roger; Maurice, Sylvestre; Lasue, Jérémie; Newsom, Horton; Lanza, Nina

    2015-04-01

    The Curiosity rover landed at Gale, an early Hesperian age crater formed within Noachian terrains on Mars. The rover encountered a great variety of igneous rocks to the west of the Yellow Knife Bay sedimentary unit (from sol 13 to 800) which are float rocks or clasts in conglomerates. Textural and compositional analyses using MastCam and ChemCam Remote micro Imager (RMI) and Laser Induced Breakdown Spectroscopy (LIBS) with a ˜300-500 µm laser spot lead to the recognition of 53 massive (non layered) igneous targets, both intrusive and effusive, ranging from mafic rocks where feldspars form less than 50% of the rock to felsic samples where feldspar is the dominant mineral. From morphology, color, grain size, patina and chemistry, at least 5 different groups of rocks have been identified: (1) a basaltic class with shiny aspect, conchoidal frature, no visible grains (less than 0.2mm) in a dark matrix with a few mm sized light-toned crystals (21 targets) (2) a porphyritic trachyandesite class with light-toned, bladed and polygonal crystals 1-20 mm in length set in a dark gray mesostasis (11 targets); (3) light toned trachytes with no visible grains sometimes vesiculated or forming flat targets (6 targets); (4) microgabbro-norite (grain size < 1mm) and gabbro-norite (grain size >1 mm) showing dark and light toned crystals in similar proportion ( 8 targets); (5) light-toned diorite/granodiorite showing coarse granular (>4 mm) texture either pristine or blocky, strongly weathered rocks (9 rock targets). Overall, these rocks comprise 2 distinct geochemical series: (i) an alkali-suite: basanite, gabbro trachy-andesite and trachyte) including porphyritic and aphyric members; (ii) quartz-normative intrusives close to granodioritic composition. The former looks like felsic clasts recently described in two SNC meteorites (NWA 7034 and 7533), the first Noachian breccia sampling the martian regolith. It is geochemically consistent with differentiation of liquids produced by low

  15. Structure and petrology of the La Perouse gabbro intrusion, Fairweather Range, southeastern Alaska.

    USGS Publications Warehouse

    Loney, R.A.; Himmelberg, G.R.

    1983-01-01

    The gabbro was intruded during the Middle Tertiary into a Mesozoic granulite-facies metamorphic environment dominated by strike-slip fault movement, compression and possible minor subduction. The asymmetric funnel form of the intrusion is due to subsidence from magmatic loading at high T, coupled with control from pre-existing structures, and not from tectonic compression. The intrusion is 12 X 27 km and has exposed cumulate layering of approx 6000 m. Probe analyses of olivines (24), Ca-poor pyroxenes (28), augites (22) and plagioclases (35) are tabulated. Cumulus mineral compositions in the basal cumulates are: olivine Fo86-71, plagioclase An81-63, bronzite Ca3Mg82Fe15 - Ca4Mg75Fe21, augite Ca45Mg47Fe8 - Ca42Mg48Fe10. The layered gabbro above the basal cumulates consists dominantly of lenticularly interlayered plagioclase-augite-orthopyroxene-olivine, plagioclase-augite- olivine and plagioclase-orthopyroxene-augite cumulates, the composition ranges being olivine Fo75-50, plagioclase An78-42, orthopyroxene and inverted pigeonite Ca2.8Mg76.4Fe20.8 - Ca1.4Mg31.0Fe67.6, augite Ca43.1Mg46.9Fe10.0 - Ca40.5Mg27.1Fe32.4. The most iron-rich pyroxene and albite-rich plagioclase occur in a zone near the margin of the intrusion and are probably related to exchange reactions with the country rock. It is considered that the gabbro did not accumulate by simple fractional crystallization of a single or even several large batches of magma, but by numerous influxes of previously fractionated magma from a deeper reservoir. Conditions of crystallization are interpreted as approx 1055oC, 5.4 kbar and fO2 near the wustite-magnetite buffer.-R.A.H.

  16. Re-Os isotopic evidence for an enriched-mantle source for the Noril'sk-type, ore-bearing intrusions, Siberia

    USGS Publications Warehouse

    Walker, R.J.; Morgan, J.W.; Horan, M.F.; Czamanske, G.K.; Krogstad, E.J.; Fedorenko, V.A.; Kunilov, V.E.

    1994-01-01

    Magmatic Cu-Ni sulfide ores and spatially associated ultramafic and mafic rocks from the Noril'sk I, Talnakh, and Kharaelakh intrusions are examined for Re-Os isotopic systematics. Neodymium and lead isotopic data also are reported for the ultramafic and mafic rocks. The Re-Os data for most samples indicate closed-system behavior since the ca. 250 Ma igneous crystallization age of the intrusions. There are small but significant differences in the initial osmium isotopic compositions of samples from the three intrusions. Ores from the Noril'sk I intrusion have ??Os values that vary from +0.4 to +8.8, but average +5.8. Ores from the Talnakh intrusion have ??Os values that range from +6.7 to +8.2, averaging +7.7. Ores from the Kharaelakh intrusion have ??Os values that range from +7.8 to +12.9, with an average value of +10.4. The osmium isotopic compositions of the ore samples from the Main Kharaelakh orebody exhibit minimal overlap with those for the Noril'sk I and Talnakh intrusions, indicating that these Kharaelakh ores were derived from a more radiogenic source of osmium than the other ores. Combined osmium and lead data for major orebodies in the three intrusions plot in three distinct fields, indicating derivation of osmium and lead from at least three isotopically distinct sources. Some of the variation in lead isotopic compositions may be the result of minor lower-crustal contamination. However, in contrast to most other isotopic and trace element data, Os-Pb variations are generally inconsistent with significant crustal contamination or interaction with the subcontinental lithosphere. Thus, the osmium and lead isotopic compositions of these intrusions probably reflect quite closely the compositions of their mantle source, and suggest that these two isotope systems were insensitive to lithospheric interaction. Ultramafic and mafic rocks have osmium and lead isotopic compositions that range only slightly beyond the compositions of the ores. These rocks also

  17. Development of a deep-crustal shear zone in response to syntectonic intrusion of mafic magma into the lower crust, Ivrea-Verbano zone, Italy

    USGS Publications Warehouse

    Snoke, A.W.; Kalakay, T.J.; Quick, J.E.; Sinigoi, S.

    1999-01-01

    A 1 to 1.5 km-thick, high-temperature shear zone is localized in wall rocks subparallel to the eastern intrusive contact of the Permian Mafic Complex of the Ivrea-Verbano zone (IVZ), Italy. The shear zone is characterized by concentrated ductile deformation manifested by a penetrative foliation subparallel to the intrusive contact and a northeast-plunging sillimanite lineation. Evidence of noncoaxial strain and transposition is widespread in the shear zone including such features as rootless isoclinal folds, dismemberment of competent layers, and scattered kinematic indicators. The metasedimentary rocks in the shear zone are migmatitic, and the accumulation of leucosome is variable within the shear zone. Near the intrusive contact with the Mafic Complex leucosome forms ~20 vol% of the wall rock, whereas leucosome concentrations may locally reach ~60 vol% of the wall rock near the outer limits of the shear zone. This variation in vol% leucosome suggests melt/magma migration from the inferred site of anatexis along the intrusive contact to lower-strain regions within and near the margins of the shear zone. The leucosome accumulations chiefly occur as layer-parallel concentrations, but are also folded and boudined, and locally are associated with tension gashes and fracture arrays. Networks of granitic dikes and small plutons in the eastern IVZ suggest that some magmas migrated out of the high-temperature shear zone. Some magma apparently migrated laterally along the strike of the shear zone and concentrated in areas of lower strain where the intrusive contact takes a major westward bend. The high-temperature shear zone is interpreted as a 'stretching fault' (or stretching shear zone) after Means [W.D. Means, Stretching faults, Geology 17 (1989) 893-896], whereupon the metasedimentary wall rocks and associated leucosome deformed synchronously with the multistage emplacement and deformation flow of the Mafic Complex. The recognition of a high-temperature shear zone

  18. Mafic intrusion remobilising silicic magma under El Hierro, Canary Islands

    NASA Astrophysics Data System (ADS)

    Sigmarsson, O.; Laporte, D.; Marti, J.; Devouard, B.; Cluzel, N.

    2012-04-01

    The 2011 submarine eruption at El Hierro, Canary Islands, has produced volcanic bombs that degas at sea surface, boil seawater and sink when cooled and degassed. At the beginning of the eruption white coloured pumices enveloped in darker coloured spatters floated on land. These composite pumices show evidence of magma mingling with folds and undulations of the darker coloured magma within the white pumice suggesting magma mingling in a viscous regime. The white pumice is highly vesicular and resembles foam. Most of the vesicular structure is made of tightly packed, polygonal bubbles of uniform size (˜ 100 μm), suggesting a single event of homogeneous bubble nucleation. An earlier event of heterogeneous bubble nucleation is indicated by the presence of a few large bubbles developed around tiny quartz crystals. Both the darker and lighter coloured pumices are almost aphyric. A few olivine crystals with perfect euhedral morphology occur within the darker part. Rare olivines of same composition are also found in the white pumice glass but then display somewhat rounded outlines and hopper-type structure. Melt inclusions in olivines of the darker pumice are of the same composition as the enveloping mafic glass, whereas olivines in the mixing boundary layer have melt inclusions of less mafic composition. The whole-rock composition and slightly more evolved glass composition are of basanitc and alkali rhyolitic composition (at the limit of the trachyte field) according to the TAS classification. Such rhyolitic compositions are rare in the Canaries. Analyses of residual volatile concentration in the glasses show that the silicic glass is highly degassed (F: 511 ±222; Cl: 202 ±58; S: below detection limit; values in ppm,1SD, n=10), whereas the basanitic glass still has very high halogene concentrations (F: 1354 ±151; Cl: 1026 ±47; S: 362 ±29; 1SD, n=10). In-situ analysis of trace element compositions of the dark glasses reveal typical basanitic compositions with

  19. Drilling the Bushveld Complex- the world's largest layered mafic intrusion

    NASA Astrophysics Data System (ADS)

    Ashwal, L. D.; Webb, S. J.; Trumbull, R. B.

    2013-12-01

    The fact that surprising new discoveries can be made in layered mafic intrusions (e.g., subtle 100-150 m cyclicity in apparently homogeneous cumulates over 1000s of m) means that we are still in the first-order characterization phase of understanding these objects. Accordingly, we have secured funding from ICDP for a planning workshop to be held in Johannesburg in early 2014, aimed at scientific drilling of the Bushveld Complex, the world's largest layered mafic intrusion. Science objectives include, but are not limited to: 1. Magma chamber processes & melt evolution. How many melts/magmas/mushes were involved, what were their compositions and how did they interact? What, if anything, is missing from the Complex, and where did it go? Did Bushveld magmatism have an effect upon Earth's atmosphere at 2 Ga? 2. Crust-mantle interactions & origin of Bushveld granitoids. Are Bushveld granites & rhyolites crustal melts, differentiates from the mafic magmas or products of immiscibility? How can the evolved isotopic signatures in the mafic rocks (e.g., epsilon Nd to -8) be understood? 3. Origin of ore deposits. What were the relative roles of gravity settling, magma mixing, immiscibility and hydrothermal fluid transport in producing the PGE, Cr and V deposits? We have identified 3 potential drilling targets representing a total of ~12 km of drill core. Exact locations of drill sites are to be discussed at the workshop. Target A- East-Central Bushveld Complex. We propose 3 overlapping 3 km boreholes that will provide the first roof-to-floor continuous coverage of the Rustenburg Layered Suite. These boreholes will represent a curated, internationally available reference collection of Bushveld material for present and future research. Target B- Southeastern Bushveld Complex. We propose a single borehole of ~2 km depth, collared in Rooiberg felsite, and positioned to intersect the Roof Zone, Upper Zone, Main Zone and floor of the Complex. Amongst other things, this site will

  20. Effects of magmatic and metamorphic volatiles on the evolution of fluid-rock interactions and fluid pressure during contact metamorphism

    SciTech Connect

    Hanson, R.B. )

    1992-01-01

    Finite difference models of hydrothermal flow around a cooling intrusion that include fluid production from the magma during crystallization and from wall rocks during heating are used to investigate the evolution of fluid pressure and fluid-rock interactions during the contact metamorphism. For a granodiorite intrusion with a width of 9 km and releasing just 1: H[sub 2]O linearly during crystallization, fluid production elevates fluid pressures to lithostatic values above and adjacent to the intrusion when permeabilities are less than 1 [mu]D (10[sup [minus]18] m[sup 2]). Alternatively, hydrofracturing resulting from fluid production would be sufficient to create and maintain a time-averaged permeability of 1 [mu]D for 50,000 years: permeability decreases gradually with time afterward until the magma crystallizes (350,000 years). In detail, the history depends strongly on how fluids are released from the crystallizing magma. The effect is comparable to that obtained for devolatilization of 5% H[sub 2]O by weight over heating of 400 C in adjacent wall rocks. Fluid production dominates other mechanisms for elevating fluid pressures such as thermal expansion of pore fluids or ductile strain. In models with both magmatic and metamorphic fluids, fluid flow is outward from the inner aureole for much of the cooling history at wall-rock permeabilities of [le]100 [mu]D. Extensive up-temperature flow is not predicted. The evolution of flow is such that magmatic fluids can initially dominate fluid-rock interactions in a plume above the intrusion, although the timing of interaction of magmatic and metamorphic waters is sensitive to the detailed devolatilization histories. Initial pore fluids rapidly become insignificant in the overall fluid budget. Surface or external fluids infiltrate only late in the cooling history, as rocks within a few kilometers of the intrusion are cooling.

  1. A Review of Vapor Intrusion Models

    PubMed Central

    Yao, Yijun; Suuberg, Eric M.

    2013-01-01

    A complete vapor intrusion (VI) model, describing vapor entry of volatile organic chemicals (VOCs) into buildings located on contaminated sites, generally consists of two main parts-one describing vapor transport in the soil and the other its entry into the building. Modeling the soil vapor transport part involves either analytically or numerically solving the equations of vapor advection and diffusion in the subsurface. Contaminant biodegradation must often also be included in this simulation, and can increase the difficulty of obtaining a solution, especially when explicitly considering coupled oxygen transport and consumption. The models of contaminant building entry pathway are often coupled to calculations of indoor air contaminant concentration, and both are influenced by building construction and operational features. The description of entry pathway involves consideration of building foundation characteristics, while calculation of indoor air contaminant levels requires characterization of building enclosed space and air exchange within this. This review summarizes existing VI models, and discusses the limits of current screening tools commonly used in this field. PMID:23360069

  2. A review of vapor intrusion models.

    PubMed

    Yao, Yijun; Shen, Rui; Pennell, Kelly G; Suuberg, Eric M

    2013-03-19

    A complete vapor intrusion (VI) model, describing vapor entry of volatile organic chemicals (VOCs) into buildings located on contaminated sites, generally consists of two main parts: one part describing vapor transport in the soil and the other describing its entry into the building. Modeling the soil vapor transport part involves either analytically or numerically solving the equations of vapor advection and diffusion in the subsurface. Contaminant biodegradation must often also be included in this simulation, and can increase the difficulty of obtaining a solution, especially when explicitly considering coupled oxygen transport and consumption. The models of contaminant building entry pathway are often coupled to calculations of indoor air contaminant concentration, and both are influenced by building construction and operational features. The description of entry pathway involves consideration of building foundation characteristics, while calculation of indoor air contaminant levels requires characterization of building enclosed space and air exchange within this. This review summarizes existing VI models, and discusses the limits of current screening tools commonly used in this field. PMID:23360069

  3. Intrusive Cognitive Content and Postdeployment Distress.

    PubMed

    Shipherd, Jillian C; Salters-Pedneault, Kristalyn; Matza, Alexis

    2016-08-01

    Although intrusive cognitions (ICs) are common posttrauma, little is known about trauma-related IC content, or associations between IC content and posttraumatic adjustment. A mixed-method cross-sectional approach was used in a secondary analysis of IC content and postdeployment distress. Participants were 1,521 U.S. Army soldiers 3-12 months postdeployment reporting their most distressing postdeployment ICs (mean number of ICs reported was 1.20). ICs were transcribed and content was categorized by 13 emergent themes. The most commonly reported ICs were of injury or death (48.2%) and combat (43.5%), and soldiers with probable posttraumatic stress disorder (PTSD; n = 187) were more likely to report the presence of these ICs, χ(2) s(1) = 35.27, ps < .001, φs < .16 than those without probable PTSD (n = 1,331). Other domains also emerged frequently, including ICs about friends (31.0%), family (15.8%), and leadership concerns (13.8%). IC content was a small, but significant correlate of distress after adjusting for combat exposure (ΔR(2) ≥ .02, ps ≤ .001). The presence of ICs of injury or death, combat, military sexual trauma, health, leadership, and family (βs > .06, ps < .02) were unique correlates of distress. Results suggested that ICs about a wide range of topics should be addressed in postdeployment interventions. PMID:27405098

  4. Intrusion signature creation via clustering anomalies

    NASA Astrophysics Data System (ADS)

    Hendry, Gilbert R.; Yang, Shanchieh J.

    2008-03-01

    Current practices for combating cyber attacks typically use Intrusion Detection Systems (IDSs) to detect and block multistage attacks. Because of the speed and impacts of new types of cyber attacks, current IDSs are limited in providing accurate detection while reliably adapting to new attacks. In signature-based IDS systems, this limitation is made apparent by the latency from day zero of an attack to the creation of an appropriate signature. This work hypothesizes that this latency can be shortened by creating signatures via anomaly-based algorithms. A hybrid supervised and unsupervised clustering algorithm is proposed for new signature creation. These new signatures created in real-time would take effect immediately, ideally detecting new attacks. This work first investigates a modified density-based clustering algorithm as an IDS, with its strengths and weaknesses identified. A signature creation algorithm leveraging the summarizing abilities of clustering is investigated. Lessons learned from the supervised signature creation are then leveraged for the development of unsupervised real-time signature classification. Automating signature creation and classification via clustering is demonstrated as satisfactory but with limitations.

  5. The Rock Physics Handbook

    NASA Astrophysics Data System (ADS)

    Mavko, Gary; Mukerji, Tapan; Dvorkin, Jack

    2003-10-01

    The Rock Physics Handbook conveniently brings together the theoretical and empirical relations that form the foundations of rock physics, with particular emphasis on seismic properties. It also includes commonly used models and relations for electrical and dielectric rock properties. Seventy-six articles concisely summarize a wide range of topics, including wave propagation, AVO-AVOZ, effective media, poroelasticity, pore fluid flow and diffusion. The book contains overviews of dispersion mechanisms, fluid substitution, and Vp-Vs relations. Useful empirical results on reservoir rocks and sediments, granular media, tables of mineral data, and an atlas of reservoir rock properties complete the text. This distillation of an otherwise scattered and eclectic mass of knowledge is presented in a form that can be immediately applied to solve real problems. Geophysics professionals, researchers and students as well as petroleum engineers, well log analysts, and environmental geoscientists will value The Rock Physics Handbook as a unique resource.

  6. The oxygen isotope composition of granitoid and sedimentary rocks of the southern Snake Range, Nevada

    USGS Publications Warehouse

    Lee, D.E.; Friedman, I.; Gleason, J.D.

    1982-01-01

    Six diverse intrusive igneous types are exposed as discrete outcrops within an area of 900 km2 in the southern Snake Range, White Pine County, Nevada. The previously recognized variety among these igneous types is reflected in the wide range of ??18O values (-1.1 to 13.4 permil) found in these rocks. This range of ??18O values probably results from differences in source material and post-crystallization history of the different intrusive types. The Jurassic intrusive of the Snake Creek-Williams Canyon area represents the chemical equivalent of a large part of a differentiation sequence, with the entire range of composition (63-76 percent SiO2) exposed over a horizontal distance of about five km. The rather regular increase of ??18O values from the most mafic to the most felsic parts of this pluton, together with ??18O values determined for constituent minerals recovered from five of the samples, supports a fractional crystallization model. The high ??18O values found (10.2-12.2 permil) indicate that the magma likely was derived from or assimilated sedimentary materials. Nine samples of the Cretaceous two-mica granite of the Pole Canyon-Can Young Canyon area have ??18O values in the range 10.6-12.1 permil. These high ??18O values, an initial87Sr/86Sr ratio of 0.7165, and the presence of muscovite along with an accessory mineral suite limited to monazite, apatite, zircon, and an allanite-like mineral, characterize this intrusive mass as an S-type granite. It probably formed through anatexis of late Precambrian pelitic rocks. The granitoid rock exposed in the Young Canyon-Kious Basin area is Tertiary (32 m.y.). Most of this intrusive has been cataclastically deformed as a result of late (18 m.y.) movement on the overlying Snake Range decollement. The undeformed portion of this intrusive has ??18O values of 8.7-10.0 permil. However, the deformed portion of this intrusive has ??18O values as low as -1.1 permil, apparently resulting from isotopic exchange between this

  7. Theoretical prediction of gold vein location in deposits originated by a wall magma intrusion

    NASA Astrophysics Data System (ADS)

    Martin, Pablo; Maass-Artigas, Fernando; Cortés-Vega, Luis

    2016-05-01

    The isotherm time-evolution resulting from the intrusion of a hot dike in a cold rock is analized considering the general case of nonvertical walls. This is applied to the theoretical prediction of the gold veins location due to isothermal evolution. As in previous treatments earth surface effects are considered and the gold veins are determined by the envelope of the isotherms. The locations of the gold veins in the Callao mines of Venezuela are now well predicted. The new treatment is now more elaborated and complex that in the case of vertical walls, performed in previous papers, but it is more adequated to the real cases as the one in El Callao, where the wall is not vertical.

  8. Luna 24 - Systematics in spinel mineral chemistry in the context of an intrusive petrogenetic grid

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E.

    1978-01-01

    Spinels in the Luna 24 gabbroic fragments have a restricted bimodal distribution of aluminum chromite and ulvospinel, whereas those in the Luna 24 basalts form a continuous sequence which defines a compositional variation from Al-Mg-chromites to ulvospinels containing 1 wt% Al2O3. A comparison of these spinel mineral chemistries with basaltic spinels from other mare regions and with spinels from other lunar intrusive rocks suggest that the Luna 24 gabbroic spinels lie at the low pressure end of a P-T spinel grid, and that titanium enrichment trends on Mg-Al-Cr rich spinel cores are related to extrusion and formed at the terminal stages of magmatic crystallization.

  9. A reconnaissance 40Ar/39Ar geochronologic study of ore-bearing and related rocks, Siberian Russia

    USGS Publications Warehouse

    Dalrymple, G.B.; Czamanske, G.K.; Fedorenko, V.A.; Simonov, O.N.; Lanphere, M.A.; Likhachev, A.P.

    1995-01-01

    40Ar/39Ar age spectra of biotite from a mineralized vein in the ore-bearing, Noril'sk I intrusion and from picritic-like gabbrodolerite from the weakly mineralized, Lower Talnakh intrusion show that these bodies were emplaced at 249 ?? 2 Ma, which is not significantly different from the age of the Permian-Triassic boundary. The ore-bearing intrusions postdate the lower third of the flood-basalt sequence in the Noril'sk area and, on the basis of geochemistry, can best be correlated with lavas slightly younger than those which they cut. Thus, flood basalt was erupted at the time of the Permian-Triassic mass extinction event, although its role in this event is, as yet, ill defined. Additional new 40Ar/39Ar age data for a group of intrusive and extrusive rocks on the western margin of the Siberian craton are discussed. -from Authors

  10. Sulfide mineralization associated with arc magmatism in the Qilian Block, western China: zircon U-Pb age and Sr-Nd-Os-S isotope constraints from the Yulonggou and Yaqu gabbroic intrusions

    NASA Astrophysics Data System (ADS)

    Zhang, Zhao-Wei; Li, Wen-Yuan; Gao, Yong-Bao; Li, Chusi; Ripley, Edward M.; Kamo, Sandra

    2014-02-01

    The sulfide-bearing Yulonggou and Yaqu mafic intrusions are located in the southern margin of the Qilian Block, Qinghai Province, western China. They are small dike-like bodies mainly composed of gabbros and diorites. Disseminated sulfides (pyrrhotite, pentlandite, and chalcopyrite) are present as concordant lenses within the intrusions. Precise CA-ID-TIMS zircon U-Pb dating yields the crystallization ages of 443.39 ± 0.42 and 440.74 ± 0.33 Ma for the Yulonggou and Yaqu intrusions, respectively. Whole rock samples from both intrusions show light rare earth element (REE) enrichments relative to heavy REE and pronounced negative Nb-Ta anomalies relative to Th and La, which are consistent with the products of arc basaltic magmatism. The Yulonggou intrusion has negative ɛ Nd values from -5.7 to -7.7 and elevated (87Sr/86Sr) i ratios from 0.711 to 0.714. In contrast, the Yaqu intrusion has higher ɛ Nd values from -4.1 to +8.4 and lower (87Sr/86Sr) i ratios from 0.705 to 0.710. The δ34S values of sulfide separates from the Yulonggou and Yaqu deposits vary from 0.8 to 2.4 ‰ and from 2 to 4.3 ‰, respectively. The γ Os values of sulfide separates from the Yulonggou and Yaqu deposits vary between 80 and 123 and between 963 and 1,191, respectively. Higher γ Os values coupled with higher δ34S values for the Yaqu deposit relative to the Yulonggou deposit indicate that external sulfur played a bigger role in sulfide mineralization in the Yaqu intrusion than in the Yulonggou intrusion. Mixing calculations using Sr-Nd isotope data show that contamination with siliceous crustal materials is more pronounced in the Yulonggou intrusion (up to 20 wt%) than in the Yaqu intrusion (<15 wt%). The distribution of sulfides in both intrusions is consistent with multiple emplacements of sulfide-saturated magmas from depth. The Yulonggou and Yaqu sulfide deposits are not economically valuable under current market condition due to small sizes and low Ni grades, which can be explained

  11. Heart rate, startle response, and intrusive trauma memories

    PubMed Central

    Chou, Chia-Ying; Marca, Roberto La; Steptoe, Andrew; Brewin, Chris R

    2014-01-01

    The current study adopted the trauma film paradigm to examine potential moderators affecting heart rate (HR) as an indicator of peritraumatic psychological states and as a predictor of intrusive memories. We replicated previous findings that perifilm HR decreases predicted the development of intrusive images and further showed this effect to be specific to images rather than thoughts, and to detail rather than gist recognition memory. Moreover, a group of individuals showing both an atypical sudden reduction in HR after a startle stimulus and higher trait dissociation was identified. Only among these individuals was lower perifilm HR found to indicate higher state dissociation, fear, and anxiety, along with reduced vividness of intrusions. The current findings emphasize how peritraumatic physiological responses relate to emotional reactions and intrusive memory. The moderating role of individual difference in stress defense style was highlighted. PMID:24397333

  12. Intrusive memories in perpetrators of violent crime: emotions and cognitions.

    PubMed

    Evans, Ceri; Ehlers, Anke; Mezey, Gillian; Clark, David M

    2007-02-01

    The authors investigated factors that may determine whether perpetrators of violent crime develop intrusive memories of their offense. Of 105 young offenders who were convicted of killing or seriously harming others, 46% reported distressing intrusive memories, and 6% had posttraumatic stress disorder. Intrusions were associated with lower antisocial beliefs before the assault, greater helplessness, fear, dissociation, data-driven processing and lack of self-referent processing during the assault, more disorganized assault narratives, and greater negative view of the self, negative interpretations of intrusive memories, perceived permanent change, and self-blame. In a logistic regression analysis, the cognitive and emotional variables explained substantial variance over and above demographic factors. The results suggest that cognitive factors that predict reexperiencing symptoms in victims of crime generalize to perpetrators. PMID:17295572

  13. An expert system application for network intrusion detection

    SciTech Connect

    Jackson, K.A.; Dubois, D.H.; Stallings, C.A.

    1991-01-01

    The paper describes the design of a prototype intrusion detection system for the Los Alamos National Laboratory's Integrated Computing Network (ICN). The Network Anomaly Detection and Intrusion Reporter (NADIR) differs in one respect from most intrusion detection systems. It tries to address the intrusion detection problem on a network, as opposed to a single operating system. NADIR design intent was to copy and improve the audit record review activities normally done by security auditors. We wished to replace the manual review of audit logs with a near realtime expert system. NADIR compares network activity, as summarized in user profiles, against expert rules that define network security policy, improper or suspicious network activities, and normal network and user activity. When it detects deviant (anomalous) behavior, NADIR alerts operators in near realtime, and provides tools to aid in the investigation of the anomalous event. 15 refs., 2 figs.

  14. Organizational coevolutionary classifiers with fuzzy logic used in intrusion detection

    NASA Astrophysics Data System (ADS)

    Chen, Zhenguo

    2009-07-01

    Intrusion detection is an important technique in the defense-in-depth network security framework and a hot topic in computer security in recent years. To solve the intrusion detection question, we introduce the fuzzy logic into Organization CoEvolutionary algorithm [1] and present the algorithm of Organization CoEvolutionary Classification with Fuzzy Logic. In this paper, we give an intrusion detection models based on Organization CoEvolutionary Classification with Fuzzy Logic. After illustrating our model with a representative dataset and applying it to the real-world network datasets KDD Cup 1999. The experimental result shown that the intrusion detection based on Organizational Coevolutionary Classifiers with Fuzzy Logic can give higher recognition accuracy than the general method.

  15. Water in evolved lunar rocks: Evidence for multiple reservoirs

    NASA Astrophysics Data System (ADS)

    Robinson, Katharine L.; Barnes, Jessica J.; Nagashima, Kazuhide; Thomen, Aurélien; Franchi, Ian A.; Huss, Gary R.; Anand, Mahesh; Taylor, G. Jeffrey

    2016-09-01

    We have measured the abundance and isotopic composition of water in apatites from several lunar rocks representing Potassium (K), Rare Earth Elements (REE), and Phosphorus (P) - KREEP - rich lithologies, including felsites, quartz monzodiorites (QMDs), a troctolite, and an alkali anorthosite. The H-isotope data from apatite provide evidence for multiple reservoirs in the lunar interior. Apatite measurements from some KREEP-rich intrusive rocks display moderately elevated δD signatures, while other samples show δD signatures similar to the range known for the terrestrial upper mantle. Apatite grains in Apollo 15 quartz monzodiorites have the lowest δD values measured from the Moon so far (as low as -749‰), and could potentially represent a D-depleted reservoir in the lunar interior that had not been identified until now. Apatite in all of these intrusive rocks contains <267 ppm H2O, which is relatively low compared to apatites from the majority of studied mare basalts (200 to >6500 ppm H2O). Complexities in partitioning of volatiles into apatite make this comparison uncertain, but measurements of residual glass in KREEP basalt fragments in breccia 15358 independently show that the KREEP basaltic magmas were low in water. The source of 15358 contained ∼10 ppm H2O, about an order of magnitude lower than the source of the Apollo 17 pyroclastic glass beads, suggesting potential variations in the distribution of water in the lunar interior.

  16. Opaque rock fragments

    SciTech Connect

    Abhijit, B.; Molinaroli, E.; Olsen, J.

    1987-05-01

    The authors describe a new, rare, but petrogenetically significant variety of rock fragments from Holocene detrital sediments. Approximately 50% of the opaque heavy mineral concentrates from Holocene siliciclastic sands are polymineralic-Fe-Ti oxide particles, i.e., they are opaque rock fragments. About 40% to 70% of these rock fragments show intergrowth of hm + il, mt + il, and mt + hm +/- il. Modal analysis of 23,282 opaque particles in 117 polished thin sections of granitic and metamorphic parent rocks and their daughter sands from semi-arid and humid climates show the following relative abundances. The data show that opaque rock fragments are more common in sands from igneous source rocks and that hm + il fragments are more durable. They assume that equilibrium conditions existed in parent rocks during the growth of these paired minerals, and that the Ti/Fe ratio did not change during oxidation of mt to hm. Geothermometric determinations using electron probe microanalysis of opaque rock fragments in sand samples from Lake Erie and the Adriatic Sea suggest that these rock fragments may have equilibrated at approximately 900/sup 0/ and 525/sup 0/C, respectively.

  17. Bounce Rock Dimple

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This panoramic camera image shows the hole drilled by the Mars Exploration Rover Opportunity's rock abrasion tool into the rock dubbed 'Bounce' on Sol 65 of the rover's journey. The tool drilled about 7 millimeters (0.3 inches) into the rock and generated small piles of 'tailings' or rock dust around the central hole, which is about 4.5 centimeters (1.7 inches) across. The image from sol 66 of the mission was acquired using the panoramic camera's 430 nanometer filter.

  18. Hungry for Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image from the Mars Exploration Rover Spirit hazard identification camera shows the rover's perspective just before its first post-egress drive on Mars. On Sunday, the 15th martian day, or sol, of Spirit's journey, engineers drove Spirit approximately 3 meters (10 feet) toward its first rock target, a football-sized, mountain-shaped rock called Adirondack (not pictured). In the foreground of this image are 'Sashimi' and 'Sushi' - two rocks that scientists considered investigating first. Ultimately, these rocks were not chosen because their rough and dusty surfaces are ill-suited for grinding.

  19. Geochemical signature variation of pre-, syn-, and post-shearing intrusives within the Najd Fault System of western Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Hassan, M.; Abu-Alam, T. S.; Hauzenberger, C.; Stüwe, K.

    2016-10-01

    Late Precambrian intrusive rocks in the Arabian-Nubian Shield emplaced within and around the Najd Fault System of Saudi Arabia feature a great compositional diversity and a variety of degrees of deformation (i.e. pre-shearing deformed, sheared mylonitized, and post-shearing undeformed) that allows placing them into a relative time order. It is shown here that the degree of deformation is related to compositional variations where early, usually pre-shearing deformed rocks are of dioritic, tonalitic to granodioritic, and later, mainly post-shearing undeformed rocks are mostly of granitic composition. Correlation of the geochemical signature and time of emplacement is interpreted in terms of changes in the source region of the produced melts due to the change of the stress regime during the tectonic evolution of the Arabian-Nubian Shield. The magma of the pre-shearing rocks has tholeiitic and calc-alkaline affinity indicating island arc or continental arc affinity. In contrast, the syn- and post-shearing rocks are mainly potassium rich peraluminous granites which are typically associated with post-orogenic uplift and collapse. This variation in geochemical signature is interpreted to reflect the change of the tectonic regime from a compressional volcanic arc nature to extensional within-plate setting of the Arabian-Nubian Shield. Within the context of published geochronological data, this change is likely to have occurred around 605-580 Ma.

  20. Palaeomagnetic study of the Derbyshire lavas and intrusions, central England: definition of Carboniferous apparent polar wander

    NASA Astrophysics Data System (ADS)

    Piper, J. D. A.; Atkinson, D.; Norris, S.; Thomas, S.

    1991-11-01

    The remanence in extrusive volcanic rocks of Lower Carboniferous (Visean) age in the Pennines of central England has been reinvestigated, employing detailed thermal demagnetisation and incorporating new geological knowledge of field relationships. Indications of primary remanence identified by early studies are supported and four successive reversals in the Asbian-Brigantian succession (about 335 Ma) recognised. A mean (reversed) direction of D/ I = 203/36° (10 sites, R = 9.75) yields a pole position at 336°E 14°S ( dp/ dm = 6/10°). Grouping improves slightly when correction is made for mild intra-Carboniferous folding and widespread uniformity of polarity is recognised within individual units. Sporadic Variscan overprinting increases in importance to the southeast. Intrusive dolerite bodies yield two contrasting directions of magnetisation: in the central part of the Derbyshire pericline mixed polarity directions (mean D/ I = 211/37° (4 sites, R = 3.92)) comparable to the lavas imply a Lower Carboniferous age of emplacement; in the SE Upper Permian (?) directions of reversed polarity (mean D/ I = 221/-23°) define a later intrusive event or comprehensive overprinting. The primary Lower Carboniferous pole positions accord with contemporaneous poles from the Midland Valley of Scotland and demonstrate that Carboniferous and younger tectonic movements are palaeomagnetically undetectable, at least between these two areas. Apparent polar wander (APW) movement is confirmed between Lower and Upper Carboniferous times at about 335-320 Ma. The Lower Carboniferous limestones have a remanence entirely younger than depositional ages and are therefore unreliable indicators of Carboniferous magnetostratigraphy and tectonics. Silicified limestones prove to have remanences closer to the primary Lower Carboniferous field and appear to have been shielded from the effects of later overprinting. The APW swathe identified from North American Carboniferous rocks coincides in

  1. 3D modeling of a dolerite intrusion from the photogrammetric and geophysical data integration.

    NASA Astrophysics Data System (ADS)

    Duarte, João; Machadinho, Ana; Figueiredo, Fernando; Mira, Maria

    2015-04-01

    The aims of this study is create a methodology based on the integration of data obtained from various available technologies, which allow a credible and complete evaluation of rock masses. In this particular case of a dolerite intrusion, which deployed an exploration of aggregates and belongs to the Jobasaltos - Extracção e Britagem. S.A.. Dolerite intrusion is situated in the volcanic complex of Serra de Todo-o-Mundo, Casais Gaiola, intruded in Jurassic sandstones. The integration of the surface and subsurface mapping, obtained by technology UAVs (Drone) and geophysical surveys (Electromagnetic Method - TEM 48 FAST), allows the construction of 2D and 3D models of the study local. The combination of the 3D point clouds produced from two distinct processes, modeling of photogrammetric and geophysical data, will be the basis for the construction of a single model of set. The rock masses in an integral perspective being visible their development above the surface and subsurface. The presentation of 2D and 3D models will give a perspective of structures, fracturation, lithology and their spatial correlations contributing to a better local knowledge, as well as its potential for the intended purpose. From these local models it will be possible to characterize and quantify the geological structures. These models will have its importance as a tool to assist in the analysis and drafting of regional models. The qualitative improvement in geological/structural modeling, seeks to reduce the value of characterization/cost ratio, in phase of prospecting, improving the investment/benefit ratio. This methodology helps to assess more accurately the economic viability of the projects.

  2. Management of aquifer recharge in Lebanon by removing seawater intrusion from coastal aquifers.

    PubMed

    Masciopinto, Costantino

    2013-11-30

    This study investigates the feasibility of management of aquifer recharge (MAR) in Lebanon by designing well barriers to remove seawater intrusion from the fractured carbonate aquifers. Groundwater flow and saltwater/freshwater 50% sharp interface have been modeled along the coastal area using the Ghyben-Herzberg theory. The groundwater flow simulations have been supported by field transmissivity estimations and depth measurements carried out on 44 wells during 2003. Results have shown the seawater intrusion in coastal aquifers at Jieh and Damour regions. Three well-injection barriers have been proposed. The water volumes for recharge and the barrier positions have been defined by means of groundwater flow simulations. MAR can provide a valuable contribution to colloid (even pathogen) removal from injectant water, although during water infiltration in subsoil the reduction of aquifer permeability causes clogging. A simple new model for estimating the soil-rock permeability reduction due to the well clogging has been presented. The MAR, including the soil aquifer treatment at Damour and Jieh regions, has been studied by considering aquifer transmissivity (and soil porosity) reduction caused by clogging. Furthermore, the appropriate mixing of the injectant water by using reclaimed water, groundwater and surface water can be simulated using the proposed models. The time required to achieve 5% of rock permeability reduction at the proposed well barriers ranged from 71 to 935 d, by changing water quality and flow rate for recharge. This study can assist regional governments with water management in areas affected by scarcity of freshwater by implementing appropriate well-barrier projects.

  3. SALTWATER INTRUSION IN A HIGHLY TRANSMISSIVE UNCONFINED AQUIFER.

    USGS Publications Warehouse

    Waller, Bradley G.

    1986-01-01

    Saltwater intrusion is particularly dynamic in coastal Dade County because of the high permeability of the Biscayne aquifer, because of the good interconnection between canals and the aquifer, and because of the seasonal rainfall. The problem is accentuated as urban growth continues to encroach on inland wetland areas which results in lowered inland water levels. This lowering reduces the seaward freshwater hydraulic gradient and the freshwater head at the coast, both of which govern the intrusion of saltwater.

  4. Saltwater intrusion in coastal regions of North America

    NASA Astrophysics Data System (ADS)

    Barlow, Paul M.; Reichard, Eric G.

    2010-02-01

    Saltwater has intruded into many of the coastal aquifers of the United States, Mexico, and Canada, but the extent of saltwater intrusion varies widely among localities and hydrogeologic settings. In many instances, the area contaminated by saltwater is limited to small parts of an aquifer and to specific wells and has had little or no effect on overall groundwater supplies; in other instances, saltwater contamination is of regional extent and has resulted in the closure of many groundwater supply wells. The variability of hydrogeologic settings, three-dimensional distribution of saline water, and history of groundwater withdrawals and freshwater drainage has resulted in a variety of modes of saltwater intrusion into coastal aquifers. These include lateral intrusion from the ocean; upward intrusion from deeper, more saline zones of a groundwater system; and downward intrusion from coastal waters. Saltwater contamination also has occurred along open boreholes and within abandoned, improperly constructed, or corroded wells that provide pathways for vertical migration across interconnected aquifers. Communities within the coastal regions of North America are taking actions to manage and prevent saltwater intrusion to ensure a sustainable source of groundwater for the future. These actions can be grouped broadly into scientific monitoring and assessment, engineering techniques, and regulatory approaches.

  5. Three Dimensional Vapor Intrusion Modeling: Model Validation and Uncertainty Analysis

    NASA Astrophysics Data System (ADS)

    Akbariyeh, S.; Patterson, B.; Rakoczy, A.; Li, Y.

    2013-12-01

    Volatile organic chemicals (VOCs), such as chlorinated solvents and petroleum hydrocarbons, are prevalent groundwater contaminants due to their improper disposal and accidental spillage. In addition to contaminating groundwater, VOCs may partition into the overlying vadose zone and enter buildings through gaps and cracks in foundation slabs or basement walls, a process termed vapor intrusion. Vapor intrusion of VOCs has been recognized as a detrimental source for human exposures to potential carcinogenic or toxic compounds. The simulation of vapor intrusion from a subsurface source has been the focus of many studies to better understand the process and guide field investigation. While multiple analytical and numerical models were developed to simulate the vapor intrusion process, detailed validation of these models against well controlled experiments is still lacking, due to the complexity and uncertainties associated with site characterization and soil gas flux and indoor air concentration measurement. In this work, we present an effort to validate a three-dimensional vapor intrusion model based on a well-controlled experimental quantification of the vapor intrusion pathways into a slab-on-ground building under varying environmental conditions. Finally, a probabilistic approach based on Monte Carlo simulations is implemented to determine the probability distribution of indoor air concentration based on the most uncertain input parameters.

  6. Configurable Middleware-Level Intrusion Detection for Embedded Systems

    SciTech Connect

    Naess, Eivind; Frincke, Deborah A.; McKinnon, A. D.; Bakken, David E.

    2005-06-20

    Embedded systems have become integral parts of a diverse range of systems from automobiles to critical infrastructure applications such as gas and electric power distribution. Unfortunately, research on computer security in general and intrusion detection in particular, has not kept pace. Furthermore, embedded systems, by their very nature, are application specific and therefore frameworks for developing application-specific intrusion detection systems for distributed embedded systems must be researched, designed, and implemented. In this paper, we present a configurable middleware-based intrusion detection framework. In particular, this paper presents a system model and a concrete implementation of a highly configurable intrusion detection framework that is integrated into MicroQoSCORBA, a highly configurable middleware framework developed for embedded systems. By exploiting the application-specific logic available to a middleware framework (e.g., object interfaces and method signatures), our integrated framework is able to autogenerate application-specific intrusion detection systems. Next, a set of configurable intrusion detection mechanisms suitable for embedded systems is presented. A performance evaluation of these mechanisms, run on two hardware platforms, is presented at the end of the paper.

  7. A New Intrusion Detection Method Based on Antibody Concentration

    NASA Astrophysics Data System (ADS)

    Zeng, Jie; Li, Tao; Li, Guiyang; Li, Haibo

    Antibody is one kind of protein that fights against the harmful antigen in human immune system. In modern medical examination, the health status of a human body can be diagnosed by detecting the intrusion intensity of a specific antigen and the concentration indicator of corresponding antibody from human body’s serum. In this paper, inspired by the principle of antigen-antibody reactions, we present a New Intrusion Detection Method Based on Antibody Concentration (NIDMBAC) to reduce false alarm rate without affecting detection rate. In our proposed method, the basic definitions of self, nonself, antigen and detector in the intrusion detection domain are given. Then, according to the antigen intrusion intensity, the change of antibody number is recorded from the process of clone proliferation for detectors based on the antigen classified recognition. Finally, building upon the above works, a probabilistic calculation method for the intrusion alarm production, which is based on the correlation between the antigen intrusion intensity and the antibody concen-tration, is proposed. Our theoretical analysis and experimental results show that our proposed method has a better performance than traditional methods.

  8. Evaluation of vapor intrusion using controlled building pressure.

    PubMed

    McHugh, Thomas E; Beckley, Lila; Bailey, Danielle; Gorder, Kyle; Dettenmaier, Erik; Rivera-Duarte, Ignacio; Brock, Samuel; MacGregor, Ian C

    2012-05-01

    The use of measured volatile organic chemical (VOC) concentrations in indoor air to evaluate vapor intrusion is complicated by (i) indoor sources of the same VOCs and (ii) temporal variability in vapor intrusion. This study evaluated the efficacy of utilizing induced negative and positive building pressure conditions during a vapor intrusion investigation program to provide an improved understanding of the potential for vapor intrusion. Pressure control was achieved in five of six buildings where the investigation program was tested. For these five buildings, the induced pressure differences were sufficient to control the flow of soil gas through the building foundation. A comparison of VOC concentrations in indoor air measured during the negative and positive pressure test conditions was sufficient to determine whether vapor intrusion was the primary source of VOCs in indoor air at these buildings. The study results indicate that sampling under controlled building pressure can help minimize ambiguity caused by both indoor sources of VOCs and temporal variability in vapor intrusion. PMID:22486634

  9. Intrusion Detection in Control Systems using Sequence Characteristics

    NASA Astrophysics Data System (ADS)

    Kiuchi, Mai; Onoda, Takashi

    Intrusion detection is considered effective in control systems. Sequences of the control application behavior observed in the communication, such as the order of the control device to be controlled, are important in control systems. However, most intrusion detection systems do not effectively reflect sequences in the application layer into the detection rules. In our previous work, we considered utilizing sequences for intrusion detection in control systems, and demonstrated the usefulness of sequences for intrusion detection. However, manually writing the detection rules for a large system can be difficult, so using machine learning methods becomes feasible. Also, in the case of control systems, there have been very few observed cyber attacks, so we have very little knowledge of the attack data that should be used to train the intrusion detection system. In this paper, we use an approach that combines CRF (Conditional Random Field) considering the sequence of the system, thus able to reflect the characteristics of control system sequences into the intrusion detection system, and also does not need the knowledge of attack data to construct the detection rules.

  10. The effects of nicotine on intrusive memories in nonsmokers.

    PubMed

    Hawkins, Kirsten A; Cougle, Jesse R

    2013-12-01

    Correlational research suggests that smoking increases risk of posttraumatic stress disorder (PTSD), though such research by nature cannot rule out third variable explanations for this relationship. The present study used an analogue trauma film design to experimentally test the effects of nicotine on the occurrence of intrusive memories. Fifty-four healthy nonsmokers were randomly assigned to ingest either a nicotine or placebo lozenge before viewing a film depicting motor vehicle accidents. Participants recorded intrusive memories immediately after the film and for a week via diary. Participants in the nicotine condition reported significantly more intrusive memories immediately after watching the film, yet no group differences emerged on intrusions or intrusion-related distress reported during the following week. Among participants low in dispositional rumination, those who had ingested a nicotine lozenge reported more intrusions in the subsequent week than those in the placebo condition. These findings provide novel experimental evidence for the role of nicotine in increasing risk of PTSD and suggest that nicotine may contribute to trauma-related rumination but not heightened reactivity to trauma cues. PMID:24099352

  11. Influence of seawater intrusion on microbial communities in groundwater.

    PubMed

    Unno, Tatsuya; Kim, Jungman; Kim, Yumi; Nguyen, Son G; Guevarra, Robin B; Kim, Gee Pyo; Lee, Ji-Hoon; Sadowsky, Michael J

    2015-11-01

    Groundwater is the sole source of potable water on Jeju Island in the Republic of (South) Korea. Groundwater is also used for irrigation and industrial purposes, and it is severely impacted by seawater intrusion in coastal areas. Consequently, monitoring the intrusion of seawater into groundwater on Jeju is very important for health and environmental reasons. A number of studies have used hydrological models to predict the deterioration of groundwater quality caused by seawater intrusion. However, there is conflicting evidence of intrusion due to complicated environmental influences on groundwater quality. Here we investigated the use of next generation sequencing (NGS)-based microbial community analysis as a way to monitor groundwater quality and detect seawater intrusion. Pristine groundwater, groundwater from three coastal areas, and seawater were compared. Analysis of the distribution of bacterial species clearly indicated that the high and low salinity groundwater differed significantly with respect to microbial composition. While members of the family Parvularculaceae were only identified in high salinity water samples, a greater percentage of the phylum Actinobacteria was predominantly observed in pristine groundwater. In addition, we identified 48 shared operational taxonomic units (OTUs) with seawater, among which the high salinity groundwater sample shared a greater number of bacterial species with seawater (6.7%). In contrast, other groundwater samples shared less than 0.5%. Our results suggest that NGS-based microbial community analysis of groundwater may be a useful tool for monitoring groundwater quality and detect seawater intrusion. This technology may also provide additional insights in understanding hydrological dynamics.

  12. Saltwater intrusion in coastal regions of North America

    USGS Publications Warehouse

    Barlow, Paul M.; Reichard, Eric G.

    2010-01-01

    Saltwater has intruded into many of the coastal aquifers of the United States, Mexico, and Canada, but the extent of saltwater intrusion varies widely among localities and hydrogeologic settings. In many instances, the area contaminated by saltwater is limited to small parts of an aquifer and to specific wells and has had little or no effect on overall groundwater supplies; in other instances, saltwater contamination is of regional extent and has resulted in the closure of many groundwater supply wells. The variability of hydrogeologic settings, three-dimensional distribution of saline water, and history of groundwater withdrawals and freshwater drainage has resulted in a variety of modes of saltwater intrusion into coastal aquifers. These include lateral intrusion from the ocean; upward intrusion from deeper, more saline zones of a groundwater system; and downward intrusion from coastal waters. Saltwater contamination also has occurred along open boreholes and within abandoned, improperly constructed, or corroded wells that provide pathways for vertical migration across interconnected aquifers. Communities within the coastal regions of North America are taking actions to manage and prevent saltwater intrusion to ensure a sustainable source of groundwater for the future. These actions can be grouped broadly into scientific monitoring and assessment, engineering techniques, and regulatory approaches.

  13. Mapping of hydrothermally altered rocks using airborne multispectral scanner data, Marysvale, Utah, mining district

    USGS Publications Warehouse

    Podwysocki, M.H.; Segal, D.B.; Jones, O.D.

    1983-01-01

    containing zeolites and some ash-fall tuffs containing montmorillonite were readily recognized on the color-coded density slice as having less intense 2.2-??m absorption than areas of highly altered rocks. The areas of most intense absorption, as depicted in the color-coded density slice, are dominated by highly altered rocks containing large amounts of alunite and kaolinite. These areas form an annulus, approximately 10 km in diameter, which surrounds a quartz monzonite intrusive body of Miocene age. The patterns of most intense alteration are interpreted as the remnants of paleohydrothermal convective cells set into motion during the emplacement of the central intrusive body. ?? 1983.

  14. Rock relationships in the Mogok metamorphic belt, Tatkon to Mandalay, central Myanmar

    NASA Astrophysics Data System (ADS)

    Mitchell, A. H. G.; Htay, Myint Thein; Htun, Kyaw Min; Win, Myint Naing; Oo, Thura; Hlaing, Tin

    2007-03-01

    The Mogok metamorphic belt (MMB), over 1450 km long and up to 40 km wide, consists of regionally metamorphosed rocks including kyanite and sillimanite schists and granites lying along the Western margin of the Shan Plateau in central Myanmar and continuing northwards to the eastern Himalayan syntaxis. Exposures in quarries allow correlation of Palaeozoic meta-sedimentary, early Mesozoic meta-igneous and late Mesozoic intrusive rocks within a 230 km long northerly-trending segment of the MMB, from Tatkon to Kyanigan north of Mandalay, and with the Mogok gemstone district 100 km to the northeast. Relationships among the metamorphic and intrusive rocks, with sparse published radiometric age controls, indicate at least two metamorphic events, one before and one after the intrusion of Late Jurassic to early Cretaceous calc-alkaline rocks. These relationships can be explained by either of two possible tectonic histories. One, constrained by correlation of mid-Permian limestones across Myanmar, requires early Permian and early Jurassic regional metamorphic events, prior to an early Tertiary metamorphism, in the western part of but within a Shan-Thai - western Myanmar block. The second, not compatible with a single laterally continuous Permian limestone, requires pre-Upper Jurassic regional metamorphism and orogenic gold mineralization in the Mergui Group and western Myanmar, early Cretaceous collision of an east-facing Mergui-western Myanmar island arc with the Shan Plateau, and early Tertiary metamorphism in the MMB related to reversal in tectonic polarity following the arc-Plateau collision.

  15. Emplacement and cooling history of a mafic intrusion into the deep crust of the Ivrea-Verbano Zone, NW Italy

    NASA Astrophysics Data System (ADS)

    Peressini, G.; Sinigoi, S.; Quick, J. E.; Hofmann, A. W.

    2003-04-01

    The Ivrea Zone represents a section of the lower crust, cropping out in a vertical orientation to the South of the Insubric Line, after tilting and obduction in the Alpine collision. Within this section, metapelitic schists and paragneiss, calc-silicate rocks and amphibolites of the Kinzigite Formation were intruded in Permian time by gabbroic to dioritic rocks of the Mafic Complex (MC). The MC is a pluton of mantle origin about 10 km thick per ca. 50 km wide; its structure and relationship to the country rock can be studied directly in cross section, due to the tilting of about 90°. Alpine tectonics, though, have not dismembered the section, leaving its original features basically undisturbed: the Mafic Complex has an internal arcuate structure, defined by high-T foliation and banding, that are discordant to the roof of the intrusion. Heat introduced by the mafic magma did not cause the regional granulite-facies metamorphism: rocks in the roof of the Mafic Complex attain upper-amphibolite grade. A large data-set of SHRIMP U-Pb ages has been produced on samples from the Mafic Complex and from anatectic granites within the Kinzigite Formation, with the aim of determining time and timing of their emplacement. Geochronologic constraints allow considerations on their relative time of emplacement and on the thermal impact of the mafic pluton on the lower crustal country rock. Intrusion of the MC in extending continental crust, suggested by pre-Triassic, high-T, extensional shear zones in the Ivrea Zone, is not directly constrained by the time of activity of these: the Anzola shear Zone in Val d'Ossola, prior to 280 Ma (Brodie, 1989), and the CMB, recently dated at 285 Ma (Mulch, 2002); from this study, we know the Mafic Complex intrusion had a main phase between 285 and 290 Ma. Following the mafic intrusion, partial melting of the country rock with extraction and transfer of anatectic granites to higher crustal levels was triggered, between 285±5 and 270±5 Ma. Due to

  16. Welcome to Rock Day

    ERIC Educational Resources Information Center

    Varelas, Maria; Benhart, Jeaneen

    2004-01-01

    At the beginning of the school year, the authors, a first-grade teacher and a teacher educator, worked together to "spice up" the first-grade science curriculum. The teacher had taught the unit Rocks, Sand, and Soil several times, conducting hands-on explorations and using books to help students learn about properties of rocks, but she felt the…

  17. Rock Bites into 'Bounce'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This panoramic camera image from the Mars Exploration Rover Opportunity features the 6.44 millimeter (0.25 inch) deep hole ground into the rock dubbed 'Bounce' by the rover's rock abrasion tool. The tool took 2 hours and 15 minutes to grind the hole on sol 66 of the rover's journey. A combination of limited solar power and the rock's jagged texture led the rock abrasion tool team to set very aggressive grinding parameters to ensure that the end result was a full circle, suitable for a thorough read from the rover's spectrometers.

    Bounce's markedly different appearance (when compared to the rocks that were previously examined in the Eagle Crater outcrop) made it a natural target for rover research. In order to achieve an ideal position from which to grind into the rock, Opportunity moved in very close with its right wheel next to Bounce. In this image, the panoramic camera on the rover's mast is looking down, catching the tip of the solar panel which partially blocks the full circle ground by the rock abrasion tool.

    The outer ring consists of the cuttings from the rock, pushed out by the brushes on the grinding instrument. The dark impression at the top of the outer circle was caused by the instrument's contact mechanism which serves to stabilize it while grinding.

  18. Rock Cycle Roulette.

    ERIC Educational Resources Information Center

    Schmidt, Stan M.; Palmer, Courtney

    2000-01-01

    Introduces an activity on the rock cycle. Sets 11 stages representing the transitions of an earth material in the rock cycle. Builds six-sided die for each station, and students move to the stations depending on the rolling side of the die. Evaluates students by discussing several questions in the classroom. Provides instructional information for…

  19. Session: Hard Rock Penetration

    SciTech Connect

    Tennyson, George P. Jr.; Dunn, James C.; Drumheller, Douglas S.; Glowka, David A.; Lysne, Peter

    1992-01-01

    This session at the Geothermal Energy Program Review X: Geothermal Energy and the Utility Market consisted of five presentations: ''Hard Rock Penetration - Summary'' by George P. Tennyson, Jr.; ''Overview - Hard Rock Penetration'' by James C. Dunn; ''An Overview of Acoustic Telemetry'' by Douglas S. Drumheller; ''Lost Circulation Technology Development Status'' by David A. Glowka; ''Downhole Memory-Logging Tools'' by Peter Lysne.

  20. Geochronology of the Voisey's Bay intrusion, Labrador, Canada, by precise U Pb dating of coexisting baddeleyite, zircon, and apatite

    NASA Astrophysics Data System (ADS)

    Amelin, Yuri; Li, Chusi; Naldrett, A. J.

    1999-06-01

    The emplacement history of the Voisey's Bay troctolite intrusion, that hosts the major Ni-Cu-Co sulfide deposit of the same name, has been studied using precise U-Pb geochronology of baddeleyite, zircon and apatite. The baddeleyite U-Pb ages of multiple drill core samples of troctolite and gabbro indicate that all of the mafic rocks studied from different components of the Voisey's Bay intrusion: Eastern Deeps, Discovery Hill Zone and Reid Brook Zone, and from the adjacent Red Dog area, were emplaced at 1332.7±1.0 Ma. On the basis of combined geological and geochronological evidence, it is suggested that the Voisey's Bay Ni-Cu-Co deposit was formed during the same period. The zircons coexisting with the ca. 1333 Ma baddeleyite show a diversity of ages. The zircons from normal troctolite and some of the olivine gabbro samples are coeval with the baddeleyite, while zircon from the varied textured troctolite and feeder olivine gabbro are much younger at 1305.0±0.8 Ma. The identical ages of the younger zircon population and the Voisey's Bay syenite that cuts the mafic rocks indicate a link between zircon growth in the mafic rocks and contact metamorphism, related to the emplacement of the syenite. Various mechanisms of zircon growth were probably involved, including reaction of the 1333 Ma baddeleyite with a silica-enriched fluid with formation of a secondary polycrystalline zircon, and zircon crystallization from syenite micro-veins in the mafic rocks. The mean 207Pb/ 206Pb age of 1303.5±2.6 Ma of the Voisey's Bay apatites is similar to the age of the younger zircon population. The apatite age may either be a result of resetting the U-Pb system in response to the syenite intrusion, or may reflect the closure of the system during regional cooling and cessation of fluid circulation. The presence of xenocrystic zircon in a Discovery Hill Zone feeder olivine gabbro indicates that the Voisey's Bay magmas were contaminated with 1.90 Ga crustal rocks.

  1. Layered Rocks in Crater

    NASA Technical Reports Server (NTRS)

    2004-01-01

    19 June 2004 Exposures of layered, sedimentary rock are common on Mars. From the rock outcrops examined by the Mars Exploration Rover, Opportunity, in Meridiani Planum to the sequence in Gale Crater's central mound that is twice the thickness of of the sedimentary rocks exposed by Arizona's Grand Canyon, Mars presents a world of sediment to study. This unusual example, imaged by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC), shows eroded layer outcrops in a crater in Terra Tyrrhena near 15.4oS, 270.5oW. Sedimentary rocks provide a record of past climates and events. Perhaps someday the story told by the rocks in this image will be known via careful field work. The image covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the left.

  2. Construction of the Vinalhaven Intrusive Complex, Maine, USA: the Plutonic Record of Evolving Magma Chambers Affected by Multiple Episodes of Replenishment, Rejuvenation, Crystal Accumulation and Eruption

    NASA Astrophysics Data System (ADS)

    Wiebe, R. A.; Hawkins, D. P.

    2004-12-01

    Increasingly, the plutonic roots of volcanic systems can be shown to contain temporal records of events inferred from the study of volcanic rocks. The Vinalhaven intrusive complex preserves evidence for multiple episodes of silicic and mafic replenishments, rejuvenation of granite, and probable eruptive events over a nominal time-span of 1.7 Ma (Hawkins and Wiebe, this volume). The complex is about 12 km in diameter and consists mainly of cg granite, a thick section of arcuate, inward-dipping gabbro-diorite sheets in the southeastern half of the complex, and a circular core of fg granite. Field relations demonstrate that the base of the intrusion is along the southeastern margin of the complex, and the top is along the northwestern margin where it intrudes coeval volcanic rocks. Aphyric basaltic and granitic dikes fed this essentially bimodal intrusion. When basaltic dikes intersected a silicic chamber, basalt spread across a floor of silicic crystal mush to form gabbro-diorite sheets in granite. Several extensive layers of angular blocks of country rock occur within the mafic rocks. Granitic dikes and the fg granitic core of the complex have sharp to gradational contacts with cg granite, and, locally, both granites are intimately mixed and commingled. These relations indicate that new silicic injections mixed into partly crystallized resident magma. Several irregular bodies of porphyry (0.2 to 0.5 km in average dimension) intrude cg granite with sharp, gradational, or commingled contacts. The porphyry has 5 to 40% corroded phenocrysts, identical in composition to crystals in the granite, and a variably quenched matrix. Some of these bodies formed when late injections of basalt remelted largely solid portions of cg granite. New silicic input may have contributed to other porphyry bodies. The matrix probably quenched because of a sudden decrease in pressure, possibly due to eruption of magma from the chamber. The cg granite and inter-layered mafic rocks preserve a

  3. Sandia Network Intrusion Detection Assessment Version 1.0

    SciTech Connect

    Bauer, Keith C.; Volkmer, Greg

    2002-09-20

    SNIDE Assess is a general-purpose software package for matching network event notifications from specialized sensors against on or more attack templattes. If a pattern of events matches an attack template, then SNIDE Assess can be configured to initate responses. SNIDE Assess provides a graphical user interface for configuring attack templates, and provides the required flexibility to define new event notification messages and responses. In general, SNIDE Assess is designed for event correlation for network intrusion detection systems. This version of SNIDE Assess is configured specifically for detection of control plane intrusions on Asynchronous Transfer Mode (ATM) networks. The SNIDE Assessment Engine is written in C. The SNIDE Assessment engine is a piece of the software that is responsible for receiving incoming messages from sensors, assimilating the information from the tripped sensors, and determining if the messages received constitute and intrusion, based on the rules specified by the system administrator. If it has been determined that a possible intrusion has occurred, the SNIDE Assessment engine will send a message to one or more response components to perform the action specified in the rule. The SNIDE Assessment engine is rule driven, that is, it's behavior is determined by specifying a set of text based rules. To provide flexibility, the definition of what constitutes an intrusion is left to the intrusion detection system administrator. a graphical rule editor is provided to allow the administrator to define what type of intrusions are to be monitored. The rules consist of combinations of sensors with boolean operators and filters. SNIDE Assessment rules can be made arbitrarily compled by using Operators and Filters. Operators allow for logic constructs to be created that combine incoming Sensor Notification events. When grouped together, they are referred to as solution sets. Each operator defnes on logic operation that is satisfied when a complete

  4. Number of Waste Package Hit by Igneous Intrusion

    SciTech Connect

    M. Wallace

    2004-10-13

    The purpose of this scientific analysis report is to document calculations of the number of waste packages that could be damaged in a potential future igneous event through a repository at Yucca Mountain. The analyses include disruption from an intrusive igneous event and from an extrusive volcanic event. This analysis supports the evaluation of the potential consequences of future igneous activity as part of the total system performance assessment for the license application (TSPA-LA) for the Yucca Mountain Project (YMP). Igneous activity is a disruptive event that is included in the TSPA-LA analyses. Two igneous activity scenarios are considered: (1) The igneous intrusion groundwater release scenario (also called the igneous intrusion scenario) considers the in situ damage to waste packages or failure of waste packages that occurs if they are engulfed or otherwise affected by magma as a result of an igneous intrusion. (2) The volcanic eruption scenario depicts the direct release of radioactive waste due to an intrusion that intersects the repository followed by a volcanic eruption at the surface. An igneous intrusion is defined as the ascent of a basaltic dike or dike system (i.e., a set or swarm of multiple dikes comprising a single intrusive event) to repository level, where it intersects drifts. Magma that does reach the surface from igneous activity is an eruption (or extrusive activity) (Jackson 1997 [DIRS 109119], pp. 224, 333). The objective of this analysis is to develop a probabilistic measure of the number of waste packages that could be affected by each of the two scenarios.

  5. Intrusion of incisors in adult patients with marginal bone loss.

    PubMed

    Melsen, B; Agerbaek, N; Markenstam, G

    1989-09-01

    Elongated and spaced incisors are common problems in patients suffering from severe periodontal disease. Thirty patients characterized by marginal bone loss and deep overbite were treated by intrusion of incisors. Three different methods for intrusion were applied: (1) J hooks and extraoral high-pull headgear, (2) utility arches, (3) intrusion bent into a loop in a 0.17 x 0.25-inch wire, and (4) base arch as described by Burstone. The intrusion was evaluated from the displacement of the apex, incision, and the center of resistance of the most prominent or elongated central incisor. Change in the marginal bone level and the amount of root resorption were evaluated on standardized intraoral radiographs. The pockets were assessed by standardized probing and the clinical crown length was measured on study casts. The results showed that the true intrusion of the center of resistance varied from 0 to 3.5 mm and was most pronounced when intrusion was performed with a base arch. The clinical crown length was generally reduced by 0.5 to 1.0 mm. The marginal bone level approached the cementoenamel junction in all but six cases. All cases demonstrated root resorption varying from 1 to 3 mm. The total amount of alveolar support--that is, the calculated area of the alveolar wall--was unaltered or increased in 19 of the 30 cases. The dependency of the results on the oral hygiene, the force distribution, and the perioral function was evaluated in relation to the individual cases. It was obvious that intrusion was best performed when (1) forces were low (5 to 15 gm per tooth) with the line of action of the force passing through or close to the center of resistance, (2) the gingiva status was healthy, and (3) no interference with perioral function was present.

  6. Deformation patters above intrusive complexes in strike-slip settings

    NASA Astrophysics Data System (ADS)

    Girard, G.; van Wyk de Vries, B.

    2003-04-01

    Long-lived intrusions below volcanic complexes are weak, ductile zones in the crust. In volcanic areas with strike-slip deformation pull-apart complexes are often associated with volcanoes, especially calderas. The Masaya-Las Sierras volcano in Nicaragua is a basaltic caldera complex situated in a developing pull-apart (Managua Graben). The pull-apart faults are responsible for highly damaging earthquakes (Managua 1931, 68, 72). We raise the hypothesis that pull-apart and caldera intrusive system are interrelated and that joint surveillance of faults and volcano could provide the best monitoring strategy. To test relationships between intrusive complex and tectonics we have run a series of ‘sand-box’ analogue models. Displacement is created by a motor on a basal discontinuity and computer-controlled. The models have a lower ductile crust (silicone layer), an upper brittle crust (sand and plaster), and an intrusion made of silicone or varying density and viscosity. Experiments show that a pull apart always forms around a ductile intrusion, irrespective of its density, however that a non-ductile intrusive complex has no significant influence. Whatever the shape of the intrusion, the fault pattern forms a typical rhombohedral pull-apart shape. Fault patterns spaying out from the models resemble closely the Managua fault pattern. With large displacements two zones of thrusting were observed in the system. Such deformation is not present at Masaya, but may be at other calderas with more active strike-slip activity. We provide one possible example in the Atacama, N Chile.

  7. The mineralogy and petrography of the ferruginous manganese rocks at Mankwadzi, Ghana

    NASA Astrophysics Data System (ADS)

    Dzigbodi-Adjimah, Komla

    2004-02-01

    Outcrops of a banded ferruginous manganiferous rock occur at Mankwadzi village 8 km west of Winneba, Ghana. The rock has variously been referred to as gondite and banded iron formation. The very fine-grained texture and the intense alteration of the rock make the resolution of its petrographic nature by ordinary transmitted and reflected light microscopy rather difficult. The present investigations provide petrologic and chemical data from microprobe analyses of the minerals within the manganiferous horizons and whole rock analyses of the country rocks. Mineral compositions were calculated and rock classifications determined from the data so obtained. The host rocks appear to have been deposited in a sub-aqueous environment during Birimian times. They include erosion products made up of siliceous material from terrigenous sources and mafic material probably of submarine volcanic origin. Chemically, the rock compositions suggest andesitic and tholeiitic basaltic parentage. The Mn/Fe ratio of 3:1 of the Mn horizons lies within the range (0.1 < Mn/Fe < 10), which is typical of "Sedex" deposits. Also, the contents of transitional metals (notably Co, Ni, and Zn) in the Mn horizons are high and point to probable derivation from marine sources. The Cu content is, however, low. The Fe content is constant in both the host rocks and the Mn horizons, whilst the Mn/Fe ratio rises from an average of less than 0.02 in the host rocks to over 3.00 in the manganiferous horizons indicating that while the Fe may be indigenous, the Mn appears foreign and was probably introduced from external source(s). Although regional metamorphism is up to garnet-amphibolite facies, the effects of retrograde metamorphism are recognised in all the rocks. The presence of pyroxene and pyroxmangite/rhodonite in the manganiferous rocks is enigmatic since these minerals could be either primary igneous precursor minerals or products of a higher temperature metamorphic event distinct from the pervasive

  8. Basement influences on dolomite-hosted vertical sedimentary intrusions in marine erg-margin deposits from the Pennsylvanian of Northern Wyoming (USA)

    NASA Astrophysics Data System (ADS)

    Blanchard, Sébastien; Frank, Tracy D.; Fielding, Christopher R.

    2016-06-01

    Understanding soft-sediment deformation structures and their triggers can help in assessing the influence of tectonics, climate, and diagenesis on the stratigraphic record. Such features commonly record processes that would not otherwise be preserved. The description of soft-sediment deformation in Pennsylvanian deposits of the western United States, characterized by orbitally driven alternations between eolian sandstones, marine dolomites, and shales, has been limited to contorted cross-beds. We document discordant, sheet-like sedimentary intrusions in three marine intervals over a 45-km-wide area. Intrusions consist of very well to moderately cemented, very fine to fine-grained quartz sandstone. Body widths range from 5 to 50 cm, and heights up to 2 m. The orientations of 103 vertical bodies were measured. Based on upward- and downward-tapering, and the presence of deformed, microfractured fragments of host rocks, these intrusions are interpreted to result from seismically induced fluidization of water-saturated sands. Their sheet-like morphology indicates injection through fractures. Two predominant directions (WNW-ESE and N-S) were recognized and interpreted as pre-injection fracture sets. Folding of surrounding layers around the intrusions suggests negligible compaction prior to injection, indicating penecontemporaneous or shallow burial fluidization. The intraplate location of Wyoming implies that seismicity did not originate at a plate boundary. The area within which intrusions are found is crossed by a zone characterized by localized development of thick eolian stories at the top of the formation, interpreted to reflect the rejuvenation of a basement lineament. The seismically active character of lineaments may explain overpressure and fluidization, substantiating the notion that Precambrian structures repeatedly affected Phanerozoic sedimentation. Similar intrusive features may be wrongly identified or overlooked in deposits of arid environments, but their

  9. Our World: The Rock Cycle

    NASA Video Gallery

    Find out how rocks brought to Earth by the Apollo astronauts have helped NASA learn more about the rock cycle. Compare igneous, sedimentary and metamorphic rocks found on Earth to three types of ro...

  10. STEFLUX: a tool for investigating stratospheric intrusions

    NASA Astrophysics Data System (ADS)

    Putero, Davide; Cristofanelli, Paolo; Sprenger, Michael; Škerlak, Bojan; Bonasoni, Paolo

    2016-04-01

    Stratosphere-to-Troposphere Exchange (STE) represents one of the natural processes that have substantial impacts on atmospheric chemistry and is an important aspect of global change. In particular, stratospheric intrusions (SI) are capable of changing the oxidation capacity of the troposphere and their contribution to ozone (O3) levels in the troposphere was estimated to be as large as the net photochemical production. SI is a topic of ongoing research, especially for what concerns its possible impact on long-term trends of tropospheric O3. In this work, a new tool called STEFLUX is presented. The main purpose of STEFLUX is to obtain a fast and reliable identification of the SI occurring at a specific location and during a selected time window, by using a set of Lagrangian trajectories. The database used as input is a compiled STE climatology, which makes use of the ERA-Interim reanalysis dataset from the ECMWF, as well as a refined version of a well-developed Lagrangian methodology. In this work, STEFLUX outputs were compared to the observations from two high-mountain stations in the Himalayas and in the Mediterranean basin, i.e. the Nepal Climate Observatory-Pyramid (NCO-P, 5079 m a.s.l.) and Mt. Cimone in the Italian northern Apennines (2165 m a.s.l.), which represent a suitable place for the occurrence of SI events. The STEFLUX performance was assessed by observing that it well represented the seasonal- and inter-annual variability of the frequency of SI events at the two measurement sites; then, by following both a "backward" and a "forward" approach, it was demonstrated that the tool is especially powerful in capturing long-lasting SI events (i.e. longer than one day). Then, by exploiting the fact that the ERA-Interim reanalysis extends back to 1979, STEFLUX was used to obtain a SI occurrence climatology for the two sampling sites. A trend evaluation study was performed for both cases, indicating no significant trends, except for the winter season.

  11. Late orogenic mafic magmatism in the North Cascades, Washington: Petrology and tectonic setting of the Skymo layered intrusion

    USGS Publications Warehouse

    Whitney, D.L.; Tepper, J.H.; Hirschmann, M.M.; Hurlow, H.A.

    2008-01-01

    The Skymo Complex in the North Cascades, Washington, is a layered mafic intrusion within the Ross Lake fault zone, a major orogen-parallel structure at the eastern margin of the Cascades crystalline core. The complex is composed dominantly of troctolite and gabbro, both with inclusions of primitive olivine gabbro. Low-pressure minerals in the metasedimentary contact aureole and early crystallization of olivine + plagioclase in the mafic rocks indicate the intrusion was emplaced at shallow depths (<12 km). The Skymo rocks have trace-element characteristics of arc magmas, but the association of Mg-rich olivine (Fo88-80) with relatively sodic plagioclase (An75-60) and the Al/Ti ratios of clinopyroxene are atypical of arc gabbros and more characteristic of rift-related gabbros. A Sm-Nd isochron indicates crystallization in the early Tertiary (ca. 50 Ma), coeval with the nearby Golden Horn alkaline granite. Mantle melting to produce Skymo magma likely occurred in a mantle wedge with a long history of arc magmatism. The Skymo mafic complex and the Golden Horn granite were emplaced during regional extension and collapse of the North Cascades orogen and represent the end of large-scale magmatism in the North Cascades continental arc. ?? 2008 Geological Society of America.

  12. Rapid dike intrusion into Sakurajima volcano on August 15, 2015, as detected by multi-parameter ground deformation observations

    NASA Astrophysics Data System (ADS)

    Hotta, Kohei; Iguchi, Masato; Tameguri, Takeshi

    2016-04-01

    We present observations of ground deformation at Sakurajima in August 2015 and model the deformation using a combination of GNSS, tilt and strain data in order to interpret a rapid deformation event on August 15, 2015. The pattern of horizontal displacement during the period from August 14 to 16, 2015, shows a WNW-ESE extension, which suggests the opening of a dike. Using a genetic algorithm, we obtained the position, dip, strike length, width and opening of a dislocation source based on the combined data. A nearly vertical dike with a NNE-SSW strike was found at a depth of 1.0 km below sea level beneath the Showa crater. The length and width are 2.3 and 0.6 km, respectively, and a dike opening of 1.97 m yields a volume increase of 2.7 × 106 m3. 887 volcano-tectonic (VT) earthquakes beside the dike suggest that the rapid opening of the dike caused an accumulation of strain in the surrounding rocks, and the VT earthquakes were generated to release this strain. Half of the total amount of deformation was concentrated between 10:27 and 11:54 on August 15. It is estimated that the magma intrusion rate was 1 × 106 m3/h during this period. This is 200 times larger than the magma intrusion rate prior to one of the biggest eruptions at the summit crater of Minami-dake on July 24, 2012, and 2200 times larger than the average magma intrusion rate during the period from October 2011 to March 2012. The previous Mogi-type ground deformation is considered to be a process of magma accumulation in preexisting spherical reservoirs. Conversely, the August 2015 event was a dike intrusion and occurred in a different location to the preexisting reservoirs. The direction of the opening of the dike coincides with the T-axes and direction of faults creating a graben structure.

  13. Petrological evidence for non-linear increase of magmatic intrusion rates before eruption at open vent mafic volcanoe

    NASA Astrophysics Data System (ADS)

    Ruth, D. C. S.; Costa Rodriguez, F.

    2015-12-01

    The most active volcanoes on earth erupt in a yearly to decadal time scales, typically erupt mafic magmas and are open-vent systems with prominent degassing plumes (e.g. Mayon, Arenal, Llaima, Etna). Here we investigate the plumbing systems, dynamics, and processes that drive eruptions at these systems. These are key questions for improving hazard evaluation, and better understanding the unrest associated with these types of volcanoes. The petrology and geochemistry from six historical eruptions (1947-2006) of Mayon volcano (Philippines) shows that all lavas are basaltic andesite with phenocrysts of plagioclase + orthopyroxene (Opx) + clinopyroxene. Opx crystals show a variety of compositions and zoning patterns (reverse, normal or complex) with Mg# (= 100 *Mg/[Mg+Fe]) varying from 67 to 81. The simplest interpretation is that the low Mg# parts of the crystals resided on an upper crustal and crystal rich reservoir that was intruded by more primitive magmas from which the high Mg# parts of the crystals grew. Modelling Mg-Fe diffusion in Opx shows that times since magma injection and eruption range from a few days up to 3.5 years in all of the investigated eruptions. The longest diffusion times are shorter than the repose times between the eruptions, which implies that crystal recycling between eruptive events is negligible. This is a surprising result that shows that for each eruption a different part of the evolved crystal-rich plumbing system is activated. This can be due to random intrusion location or an irreversibility of the plumbing system that prevents multiple eruptions from the same crystal-rich part. Moreover, we find that the number of intrusions markedly increases before each eruption in a non-linear manner. Such an increased rate of intrusions with time might reflect non-linear rheological properties of the crystal-rich system, of the enclosing rocks, or the non-linear evolution of crystal-melt reaction-dissolution fronts during magma intrusions.

  14. Plume-orogenic lithosphere interaction recorded in the Haladala layered intrusion in the Southwest Tianshan Orogen, NW China

    NASA Astrophysics Data System (ADS)

    He, Peng-Li; Huang, Xiao-Long; Xu, Yi-Gang; Li, Hong-Yan; Wang, Xue; Li, Wu-Xian

    2016-03-01

    The plume-orogenic lithosphere interaction may be common and important for the generation of large igneous provinces. The information regarding such a process is recorded by the Haladala gabbroic intrusion (~300 Ma), the largest layered ultramafic-mafic intrusion hosting V-Ti magnetite deposits in the Southwest Tianshan Orogen, NW China. The Haladala gabbros exhibit unfractionated chondrite-normalized rare earth element patterns with negative Nb and Ta anomalies and positive Pb anomaly on the primitive mantle-normalized multielement variation diagram. They are characterized by low initial Sr isotopes, slightly decoupled but high positive bulk rock ɛNd(t) and ɛHf(t), and high 207Pb/204Pb and 208Pb/204Pb relative to 206Pb/204Pb, delineating a DUPAL signature in the sources. The Haladala gabbros cannot be arc or postcollisional magmatism, given the lack of hydrous minerals and low K contents, respectively. This is further supported by the relatively low oxygen fugacity required for the gradual enrichment of V-Ti magnetite during the magma fractionation and by an overall anhydrous mantle source suggested by troctolite mineral assemblage (olivine + plagioclase). The emplacement age of the Haladala gabbros is identical to that of the Wajilitag kimberlites in the Tarim's interior, which have been interpreted as the first magmatic expression of the Tarim mantle plume. We thus propose that the Haladala gabbroic intrusion was generated in a hybrid geodynamic setting in which the Southwest Tianshan Orogen was impacted by an upwelling mantle plume. In this sense, the Haladala layered gabbroic intrusion records the early phase of magmatism of the Tarim plume, which was preferentially emplaced in a lithospheric weak zone.

  15. 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.

  16. Evidence for multiple pulses of crystal-bearing magma during emplacement of the Doros layered intrusion, Namibia

    NASA Astrophysics Data System (ADS)

    Owen-Smith, T. M.; Ashwal, L. D.

    2015-12-01

    The Doros Complex is a relatively small (maximum 3.5 km × 7.5 km) shallow-level, lopolithic, layered mafic intrusion in the early Cretaceous Paraná-Etendeka Large Igneous Province. The stratigraphy broadly comprises a minor, fine-grained gabbroic sill and a sequence of primitive olivine-cumulate melagabbros, with a basal chilled margin, an intermediate plagioclase-cumulate olivine gabbro, and a sequence of mineralogically and texturally variable, intermediate, strongly foliated, plagioclase-, olivine- or magnetite-cumulate gabbros. An evolved syenitic (bostonite) phase occurs as cross-cutting dykes or as enclaves within the foliated gabbros. Major element modelling of the liquid line of descent shows that the spectrum of rock types, including the bostonite, is consistent with the fractionation of a basaltic parental magma that crystallised olivine, clinopyroxene, plagioclase, magnetite, K-feldspar and apatite. However, the stratigraphic succession does not correspond to a simple progressive differentiation trend but instead shows a series of punctuated trends, each defined by a compositional reversal or hiatus. Incompatible trace element concentrations do not increase upwards though the body of the intrusion. The major units show similar, mildly enriched rare earth element patterns, with minimal Eu anomalies. Back-calculation of the rare earth element concentrations of these cumulate rocks produces relatively evolved original liquid compositions, indicating fractionation of this liquid from a more primitive precursor. Based on combined field, petrographic, geochemical and geophysical evidence, we propose an origin for the Doros Complex by a minimum of seven closely spaced influxes of crystal-bearing magmas, each with phenocryst contents between 5% and 55%. These findings represent a departure from the traditional single-pulse liquid model for the formation of layered mafic intrusions and suggest the presence of an underlying magmatic mush column, i.e., a large

  17. Space Weathering of Rocks

    NASA Technical Reports Server (NTRS)

    Noble, Sarah

    2011-01-01

    Space weathering discussions have generally centered around soils but exposed rocks will also incur the effects of weathering. On the Moon, rocks make up only a very small percentage of the exposed surface and areas where rocks are exposed, like central peaks, are often among the least space weathered regions we find in remote sensing data. However, our studies of weathered Ap 17 rocks 76015 and 76237 show that significant amounts of weathering products can build up on rock surfaces. Because rocks have much longer surface lifetimes than an individual soil grain, and thus record a longer history of exposure, we can study these products to gain a deeper perspective on the weathering process and better assess the relative impo!1ance of various weathering components on the Moon. In contrast to the lunar case, on small asteroids, like Itokowa, rocks make up a large fraction of the exposed surface. Results from the Hayabusa spacecraft at Itokowa suggest that while the low gravity does not allow for the development of a mature regolith, weathering patinas can and do develop on rock surfaces, in fact, the rocky surfaces were seen to be darker and appear spectrally more weathered than regions with finer materials. To explore how weathering of asteroidal rocks may differ from lunar, a set of ordinary chondrite meteorites (H, L, and LL) which have been subjected to artificial space weathering by nanopulse laser were examined by TEM. NpFe(sup 0) bearing glasses were ubiquitous in both the naturally-weathered lunar and the artificially-weathered meteorite samples.

  18. Contact zone permeability at intrusion boundaries: New results from hydraulic testing and geophysical logging in the Newark Rift Basin, New York, USA

    USGS Publications Warehouse

    Matter, J.M.; Goldberg, D.S.; Morin, R.H.; Stute, M.

    2006-01-01

    Hydraulic tests and geophysical logging performed in the Palisades sill and the underlying sedimentary rocks in the NE part of the Newark Rift Basin, New York, USA, confirm that the particular transmissive zones are localized within the dolerite-sedimentary rock contact zone and within a narrow interval below this contact zone that is characterized by the occurrence of small layers of chilled dolerite. Transmissivity values determined from fluid injection, aquifer testing, and flowmeter measurements generally fall in the range of 8.1E-08 to 9.95E-06 m2/s and correspond to various scales of investigation. The analysis of acoustic and optical BHTV images reveals two primary fracture sets within the dolerite and the sedimentary rocks - subhorizontal fractures, intersected by subvertical ones. Despite being highly fractured either with subhorizontal, subvertical or both fracture populations, the dolerite above and the sedimentary rocks below the contact zone and the zone with the layers of chilled dolerite are significantly less conductive. The distribution of the particular conductive intervals is not a function of the two dominant fracture populations or their density but rather of the intrusion path of the sill. The intrusion caused thermal fracturing and cracking of both formations, resulting in higher permeability along the contact zone. ?? Springer-Verlag 2005.

  19. Detached rock evaluation device

    DOEpatents

    Hanson, David R.

    1986-01-01

    A rock detachment evaluation device (10) having an energy transducer unit 1) for sensing vibrations imparted to a subject rock (172) for converting the sensed vibrations into electrical signals, a low band pass filter unit (12) for receiving the electrical signal and transmitting only a low frequency segment thereof, a high band pass filter unit (13) for receiving the electrical signals and for transmitting only a high frequency segment thereof, a comparison unit (14) for receiving the low frequency and high frequency signals and for determining the difference in power between the signals, and a display unit (16) for displaying indicia of the difference, which provides a quantitative measure of rock detachment.

  20. Rock Garden Mosaic

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image mosaic of part of the 'Rock Garden' was taken by the Sojourner rover's left front camera on Sol 71 (September 14). The rock 'Shark' is at left center and 'Half Dome' is at right. Fine-scale textures on the rocks are clearly seen. Broken crust-like material is visible at bottom center.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  1. Weird 'Endurance' Rock Ahead

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken by the Mars Exploration Rover Opportunity shows a bizarre, lumpy rock dubbed 'Wopmay' on the inner slopes of 'Endurance Crater.' Scientists say the rock's unusual texture is unlike any others observed so far at Meridiani Planum. Wopmay measures approximately 1 meter (3.3 feet) across. The image was taken by the rover's panoramic camera on sol 195 (Aug. 11, 2004). Opportunity will likely travel to this or a similar rock in coming sols for a closer look at the alien surface.

  2. Continental Basaltic Rocks

    NASA Astrophysics Data System (ADS)

    Farmer, G. L.

    2003-12-01

    During the past few decades, geochemical studies of continental basaltic rocks and their petrologic kin have become mainstays of studies of the continental lithosphere. These igneous rocks have taken on such an important role largely because the chemical and isotopic composition of continental basaltic rocks and their mantle (see Chapter 2.05) and crustal xenoliths (see Chapter 3.01) provide the best proxy record available to earth scientists for the chemical and physical evolution of the deep continental lithosphere and underlying mantle, areas that are otherwise resistant to direct study. Keeping this in mind, the primary goal of this chapter is to illustrate how geochemical data can be used both to assess the origin of these rocks and to study the evolution of the continental lithosphere.A complete overview of continental basaltic rocks will not be attempted here, because continental "basalts" come in too wide a range of compositions, and because of the sheer volume of geochemical data available for such rocks worldwide. The scope of the chapter is limited to a discussion of a select group of ultramafic to mafic composition "intraplate" continental igneous rocks consisting primarily of kimberlites, potassic and sodic alkali basalts, and continental flood basalts. Igneous rocks forming at active continental margins, such as convergent or transform plate margins, are important examples of continental magmatism but are not directly discussed here (convergent margin magmas are discussed in Chapters 2.11, 3.11, and 3.18). The geochemistry of intraplate igneous rocks of the ocean basins are covered in Chapters 2.04 and 3.16. Although basaltic magmatism has occurred throughout the Earths history, the majority of the examples presented here are from Mesozoic and Cenozoic volcanic fields due to the more complete preservation of younger continental mafic igneous rocks. While considerable effort has been expended in studying the chemical differentiation of mafic magmas

  3. Perception of the English intrusive stops by Korean listeners

    NASA Astrophysics Data System (ADS)

    Han, Jeong-Im

    2002-05-01

    This paper reports results of an experiment examining Korean listeners' perception of English intrusive stops in nasal-obstruent clusters. The experiment tests (1) how often intrusive stops are perceived; (2) how language-specific syllable structure constraints influence the perception, given the fact that Korean does not allow consonant clusters in syllable onsets and codas; (3) whether even the perception of phonetic variables like intrusive stops, not phonemes, could be improved by learning. Ninety English non-words with a monosyllable structure of CVC1C2 were created, where C1=/m,n,N/, and C2=/p,k,s/. The stimuli including additional 90 filler items were recorded by three native English speakers and one representative data among them was given to three groups of native Korean listeners in terms of their English proficiency. Each was asked to monitor the target sounds [Warner and Weber, J. Phonetics 29, 23-52 (2001)]. The preliminary results show that identification of intrusive stops in English is totally dependent on Korean syllable structure, so even stimuli with strong acoustic cues were misparsed. Nonetheless, there's a high correlation between perception of intrusive stops and listeners' English proficiency, showing the possibility of the improvement of perception by learning.

  4. Kuroshio intrusion into the South China Sea: A review

    NASA Astrophysics Data System (ADS)

    Nan, Feng; Xue, Huijie; Yu, Fei

    2015-09-01

    The Kuroshio carrying the northwestern Pacific water intrudes into the South China Sea (SCS) through the Luzon Strait, significantly affecting the temperature, salinity, circulation, and eddy generation in the SCS. Thus, the Kuroshio intrusion makes important contributions to the momentum, heat and salt budgets in the SCS. In the past decades, much work has been done on the Kuroshio intrusion. This paper reviews past efforts and summarizes our current understanding of the Kuroshio intruding processes from observational evidence, laboratory results, theoretical analyses, and a range of numerical model simulations. In addition, discrepancies between results simulated by models, as well as those between simulations and observations, are presented. Specifically, this paper addresses the following topics: (1) different types of the Kuroshio intrusion into the SCS and their identification, (2) vertical structure of the Kuroshio in the Luzon Strait, (3) an overview of the Luzon Strait transport resulting from observations and numerical model simulations, (4) seasonal and interannual variations of the Kuroshio intrusion, as well as eddy generation due to the Kuroshio path variation, and (5) dynamical mechanisms (e.g., wind forcing, interbasin pressure gradient, β effect and hysteresis, potential vorticity, eddy activity) controlling the Kuroshio intrusion into the SCS. Finally, several future research topics for gaining a better understanding of the Kuroshio intruding processes are suggested.

  5. Compositions of biotite from granitoids of the Sierra Nevada batholith: constraints on magmatic source rocks

    SciTech Connect

    Ague, J.J.; Brimhall, G.H.

    1985-01-01

    Two compositional types of biotite from the Cretaceous Sierra Nevada batholith occur in a systematic regional pattern which reflects magmatic source material and correlates with tungsten mineralization. Biotite from each group may be characterized in terms of F/OH and Mg/Fe as follows. Type I biotites generally coexist with hornblende and magnetite + sphene. Type II biotites coexist wit