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Sample records for ore deposit formation

  1. The Klyuchevskoe gold ore deposit (Eastern Transbaikalia): Formation conditions and petrogeochemical features of rocks and ores

    NASA Astrophysics Data System (ADS)

    Abramov, B. N.

    2015-09-01

    It was found that the magma chambers in the Amudzhikan complex (J3) were characterized by close degrees of their differentiation and occurred at depths corresponding to the lower continental crust. The formation of explosive breccias proceeded during each period of the ore-forming process. The magma chambers of early breccias occurred at great depths. The late breccias contain carbonate cement and are characterized by an increased REE content.

  2. Formation conditions of high-grade beryllium ore at the Snezhnoe deposit, Eastern Sayan

    NASA Astrophysics Data System (ADS)

    Damdinova, L. B.; Smirnov, S. Z.; Damdinov, B. B.

    2015-11-01

    The structure and formation conditions of beryllium ore, as well as the fluorite and fluorite-microcline bodies at the Snezhnoe deposit in Eastern Sayan have been revealed and studied using geological, mineralogical, petrographic, and thermobarogeochemical methods. It has been established that the stringer and breccia ores were largely formed as a result of filling of open cavities (voids and fissures) rather than of replacement of low-Ca host rocks. Three types of high-grade ore consist of almost the same set of minerals in different proportions. Calcium and fluorine necessary for fluorite formation in three main types of ore have been supplied with the near-neutral high-F solutions (type I) and the solutions of elevated alkalinity (II, III types) in the form of complex compounds like Na2CaF 4 0 , Ca2Cl3F0, etc. Beryllium minerals were deposited within a temperature interval from ≥340 to 230°C due to the cooling of the solution and binding of F into fluorite with the breakdown of Be fluorine complexes and intense deposition of Be minerals.

  3. Structural controls on the formation and transposition of the Malmberget apatite iron ore deposit, northern Sweden

    NASA Astrophysics Data System (ADS)

    Bauer, Tobias; Sarlus, Zimer; Andersson, Joel; Kearney, Thomas

    2015-04-01

    The Malmberget mine is the World's second largest underground iron ore operation. It is composed of approximately 20 apatite iron ore bodies, whereas 13 ore bodies with 5-245 Mt each are presently mined. The massive magnetite ore is hosted within volcanic and volcaniclastic rocks. Host rocks within the entire area were subject to intense hydrothermal alteration. The ore reserves at beginning of 2012 totalled 290 Mt at 44 percent iron. Together with Kiruna and Svappavaara these three deposits stands for more than 90 percent of the iron ore production in Europe. An on-going collaborative research project aims at unravelling the structural geometries, relationships and control on ore formation and ore body transposition at different scales in the Gällivare district in general and in the Malmberget mine in particular. Recent results show the three-dimensional crustal architecture of the Malmberget deposit which has undergone at least two separate deformation events. The first deformation event (D1) resulted in the formation of a strong and penetrative cleavage (S1) forming a varyingly intense banding within the volcanic rocks. The D1-event coincides with the amphibolite facies peak metamorphism in the area. Distinct, biotite-rich D1 shear zones are spatially related to the majority of the S1-parallel massive magnetite bodies. These D1 shear zones seem to be responsible for a strong strain partitioning during D1. A second compressional event (D2) resulted in open to close folding of the S1 fabric, the D1 shear zones and the related ore bodies. The result is an asymmetric F2-synform with moderately south-west-plunging fold axis. Furthermore, distinct D2 high strain zones are responsible for local transposition of S1 fabrics, tight to isoclinal folding and channeling or re-mobilization of hydrothermal alteration minerals. Both deformation events are accompanied by syn- and late-tectonic granitic intrusions forming both foliated and unfoliated and commonly boudinaged

  4. The formation of ore mineral deposits on the Moon: A feasibility study

    NASA Technical Reports Server (NTRS)

    Taylor, Lawrence A.; Lu, Fengxiang

    1992-01-01

    Most of the ore deposits on Earth are the direct result of formation by hydrothermal solutions. Analogous mineral concentrations do not occur on the Moon, however, because of the absence of water. Stratified ore deposits form in layered instrusives on Earth due to fractional crystallization of magma and crystal settling of high-density minerals, particularly chromium in the mineral chromite. We have evaluated the possibility of such mineral deposition on the Moon, based upon considerations of 'particle settling velocities' in lunar vs. terrestrial magmas. A first approximation of Stoke's Law would seem to indicate that the lower lunar gravity (1/6 terrestrial) would result in slower crystal settling on the Moon. However, the viscosity of the silicate melt is the most important factor affecting the settling velocity. The viscosities of typical lunar basaltic melts are 10-100 times less than their terrestrial analogs. These lower viscosities result from two factors: (1) lunar basaltic melts are typically higher in FeO and lower in Al2O3, Na2O, and K2O than terrestrial melts; and (2) lunar igneous melts and phase equilibria tend to be 100-150 C higher than terrestrial, largely because of the general paucity of water and other volatile phases on the Moon. Therefore, particle settling velocities on the Moon are 5-10 times greater than those on Earth. It is highly probable that stratiform ore deposits similar to those on Earth exist on the Moon. The most likely ore minerals involved are chromite, ilmenite, and native FeNi metal. In addition, the greater settling velocities of periodotite in lunar magmas indicate that the buoyancy effects of the melt are less than on Earth. Consequently, the possibility is considerably less than on Earth of deep-seated volcanism transporting upper mantle/lower crustal xenoliths to the surface of the Moon, such as occurs in kimberlites on Earth.

  5. Manganese deposits in northeastern European Russia and the Urals: Isotope geochemistry, genesis, and evolution of ore formation

    NASA Astrophysics Data System (ADS)

    Kuleshov, V. N.; Brusnitsyn, A. I.; Starikova, E. V.

    2014-09-01

    Based on new data on the lithology, mineralogy, chemistry, and isotopic composition of manganese carbonate ores and rocks at the deposits and occurrences in the Novaya Zemlya Archipelago, the Pai-Khoi, and the Urals, as well as using data from the literature, the main Phanerozoic basins of manganese deposition have been established in the geological history of Laurasia, Pangea, and Siberian paleocontinents. The formation conditions of manganese ore gradually changed from hydrothermal-sedimentary in the Middle Paleozoic to sedimentary-diagenetic in Mesozoic and Cenozoic. The ore was also formed under catagenetic conditions. Carbon of oxidized organic matter plays a substantial role in the formation of manganese carbonates.

  6. Tectonophysics of hydrothermal ore formation: an example of the Antei Mo-U deposit, Transbaikalia

    NASA Astrophysics Data System (ADS)

    Petrov, V. A.; Rebetsky, Yu. L.; Poluektov, V. V.; Burmistrov, A. A.

    2015-07-01

    The Antei deposit of the southeastern Transbaikalian region is one of the largest uranium mines in Russia. It is hosted by the Late Paleozoic granitic basement of the Streltsovskaya caldera and was formed as a result of Late Mesozoic tectonothermal activity. Vein and stockwork-disseminated molybdenum-uranium mineralization at this deposit is controlled by zones of intense hydrothermal alteration, cataclasis, brecciation, and intense fracturing along steeply dipping faults, which acted as conduits for mineralizing fluids and hosts to the ore bodies. The upper edge of the ore-bearing zone is located at a depth of 400 m, and its lower edge was intersected at a depth of 1300 m from the day surface. The conditions of ore localization were determined using structural-geological and petrophysical studies coupled with numerical modeling of the effects of gravitational body forces at purely elastic and postcritical elastoplastic deformational stages. The dynamics of the tectonic stress field in the rock massif was reconstructed using the results of mapping of morphogenetic and kinematic characteristics of fault and fracture systems, as well as data on petrography and mineralogy of rocks and vein-filling material. It was shown that the fault framework of the deposit was formed in four tectonic stages, three of which took place in the geologic past and one of which reflects recent geologic history. Each tectonic stage was characterized by different parameters of the tectonic stress-strain field, fault kinematics, and conditions of mineral formation. The following types of metasomatic rocks are recognized within the deposit: high-temperature K-feldspar rocks and albitites (formed during the Late Paleozoic as the primary structural elements of a granitic massif) and Late Mesozoic low-temperature preore (hydromicatized rocks), synore (hematite, albite, chlorite, and quartz) and postore (kaolinite-smectite) rocks. The following petrophysical parameters were determined for all

  7. Sulphur isotope constraints on formation conditions of the Luiswishi ore deposit, Democratic Republic of Congo (DRC)

    NASA Astrophysics Data System (ADS)

    Lerouge, C.; Cailteux, J.; Kampunzu, A. B.; Milesi, J. P.; Fléhoc, C.

    2005-07-01

    Luiswishi is a Congo-type Neoproterozoic sediment-hosted stratiform Cu-Co ore deposit of the Central Africa Copperbelt, located northwest of Lubumbashi (DRC). The ores form two main Cu-Co orebodies hosted by the Mines Subgroup, one in the lower part of the Kamoto Formation and the other at the base of the Dolomitic Shales Formation. Sulphides occur essentially as early parallel layers of chalcopyrite and carrolite, and secondarily as late stockwork sulphides cross-cutting the bedding and the early sulphide generation. Both types of stratiform and stockwork chalcopyrite and carrolite were systematically analyzed for sulphur isotopes, along the lithostratigraphic succession of the Mine Series. The quite similar δ 34S values of stratiform sulphides and late stockwork sulphides suggest an in situ recrystallization or a slight remobilization of stockwork sulphides without attainment of isotopic equilibrium between different sulphide phases (chalcopyrite and carrolite). The distribution of δ 34S values (-14.4‰ to +17.5‰) combined with the lithology indicates a strong stratigraphic control of the sulphur isotope signature, supporting bacterial sulphate reduction during early diagenesis of the host sediments, in a shallow marine to lacustrine environment. Petrological features combined with sulphur isotopic data of sulphides at Luiswishi and previous results on nodules of anhydrite in the Mine Series indicate a dominant seawater/lacustrine origin for sulphates, precluding a possible hydrothermal participation. The high positive δ 34S values of sulphides in the lower orebody at Luiswishi, hosted in massive chloritic-dolomitic siltite (known as Grey R.A.T.), fine-grained stratified dolostone (D.Strat.) and silicified-stromatolitic dolomites alternating with chloritic-dolomitic silty beds (R.S.F.), suggest that they were probably deposited during a period of regression in a basin cut off from seawater. The variations of δ 34S values (i.e. the decrease of δ 34S values

  8. Evolution of ore deposits on terrestrial planets

    NASA Technical Reports Server (NTRS)

    Burns, R. G.

    1991-01-01

    Ore deposits on terrestrial planets materialized after core formation, mantle evolution, crustal development, interactions of surface rocks with the hydrosphere and atmosphere, and, where life exists on a planet, the involvement of biological activity. Core formation removed most of the siderophilic and chalcophilic elements, leaving mantles depleted in many of the strategic and noble metals relative to their chondritic abundances. Basaltic magma derived from partial melting of the mantle transported to the surface several metals contained in immiscible silicate and sulfide melts. Magmatic ore deposits were formed during cooling, fractional crystallization and density stratification from the basaltic melts. Such ore deposits found in earth's Archean rocks were probably generated during early histories of all terrestrial planets and may be the only types of igneous ores on Mars. Where plate tectonic activity was prevalent on a terrestrial planet, temporal evolution of ore deposits took place. Repetitive episodes of subduction modified the chemical compositions of the crust and upper mantles, leading to porphyry copper and molybdenum ores in calc-alkaline igneous rocks and granite-hosted tin and tungsten deposits. Such plate tectonic-induced mineralization in relatively young igneous rocks on earth may also have produced hydrothermal ore deposits on Venus in addition to the massive sulfide and cumulate chromite ores associated with Venusian mafic igneous rock. Sedimentary ore deposits resulting from mechanical and chemical weathering in reducing atmospheres in Archean earth included placer deposits (e.g., uraninite, gold, pyrite ores). Chromite, ilmenite, and other dense unreactive minerals could also be present on channel floors and in valley networks on Mars, while banded iron formations might underlie the Martian northern plains regions. As oxygen evolved in earth's atmosphere, so too did oxide ores. By analogy, gossans above sulfide ores probably occur on Mars

  9. Seeking the mantle contribution for the formation of giant ore deposits: Contemporaneous alkaline lamproites and carbonatites in the Kalmakyr and Muruntau ore districts, Tienshan, Uzbekistan

    NASA Astrophysics Data System (ADS)

    Seltmann, Reimar; Choulet, Flavien

    2014-05-01

    various geological objects involved in both giant mineral systems. Upper Carboniferous lamproitic pipes have been recognized around the Kalmakyr ore deposit [1]; diamond-bearing lamproites occur near the Muruntau ore deposit and are contemporaneous to the Murun granite [2]. Indicator minerals of deep crustal and mantle origin have been identified within xenoliths hosted by the ore-bearing intrusions and the dikes and pipes spatially and temporally associated to the giants. SEM and CT scanning observations allow for revealing the shape and internal texture of indicator minerals and their relations (inclusion, interstitial or bulk minerals). Microanalysis (EPMA and LA-ICPMS) of indicator minerals is used to estimate the physico-chemical conditions of their formation and track the mantle involvement in magma fertilization. Results permit clues on the mantle contribution in ore formation during the late collisional to post-collisional stages of the Tienshan, and, based on complementary comparisons with other ore systems, to refine exploration models. References: [1] Yusupov, R.G.; Stanley, C.J.; Welch, M.D.; Spratt, J.; Cressey, G.; Rumsey, M.S.; Seltmann, R.; Igamberdiev, E., 2009: Mavlyanovite, Mn5Si3: a new mineral species from a lamproite diatreme, Chatkal Ridge, Uzbekistan. Mineralogical Magazine 73, 43-50. [2] Golovko, A. V.; Divaev, F. K., 2010: Ore mineralisation of the Karashokho diatreme, western Uzbekistan. Applied Earth Science 119.2: 100. [3] Dolgopolova, A.; Seltmann, R.; Armstrong, R.; Belousova, E.; Pankhurst, R.; Konopelko, D.; Koneev, R., 2013: Sr-Nd-Hf-Pb Isotope Mapping of Tien Shan in Uzbekistan. Mineralogical Magazine 77.5: 1001.

  10. Oil shales, evaporites and ore deposits

    NASA Astrophysics Data System (ADS)

    Eugster, Hans P.

    1985-03-01

    elevated temperatures and with carbonates as principal host rocks. The Pine Point deposits are cited for their close association with evaporites. Alkaline, metal-rich brines are postulated for the HYC deposit of McArthur River, Australia. Such brines are known from the Green River Formation and deposits formed from such brines constitute the GRT class. They can be recognized by the presence of Magadi-type cherts and zeolite-analcime-K-spar tuffs. The Cu-Co ore bodies of Outokumpu, Finland, might also belong to this type. A new classification of sedimentary ore deposits is proposed, based on their geochemical environment. KST and MVT are formed from acid ore fluids, while GRT and CT (Creede type) are derived from basic ore fluids. pH of the fluids is best evaluated not from the ores themselves, but from their effect on the host-rocks.

  11. Metalliferous black shales and related ore deposits

    SciTech Connect

    Grauch, R.I. ); Huyck, H.L.O. )

    1990-01-01

    This book comprises papers and extended abstracts dealing with a variety of topics including the geochemistry and organic geochemistry of several black shale formations: the nature of modern Black Sea sediments: metal- organic complexes in ore fluids; black shales related to disseminated gold deposits; vanadium concentrations and molybdenum-nickel deposits; and the problem of defining metalliferous black shales.

  12. Studies of disseminated gold deposits near Carlin, Nevada: Evidence for a deep geologic setting of ore formation

    SciTech Connect

    Kuehn, C.A.

    1989-01-01

    The Carlin gold deposit occurs in the upper 175 meters of the Siluro-Devonian Roberts Mountains Formation in Eureka County, Nevada. Pre-, syn- and post-gold episodes are distinguished by (1) hydrocarbon maturation, (2) gold mineralization and alteration and (3) subsequent oxidation. Mineralization post-dates Early Cretaceous dikes which cut zones of thermally mature petroleum residue. Preore P-T conditions of 155 {+-} 20 C and 0.6 to 1.4 kb are defined by coexisting saline aqueous and methane-rich fluid inclusions. Main Gold Ore Stage (MGOS) alteration of pyrite-bearing unaltered calcareous carbonaceous argillaceous siltstones progresses from K-feldspar silt and calcite destruction, then dolomite dissolution, and finally illite conversion to dickite/kaolinite in intensely altered silicified zones near hydrothermal conduits. MGOS fluids are acid from elevated CO{sub 2} contents (5-10 mole percent), and also contain appreciable H{sub 2}S, 3 {+-} 1 wt% NaCl and {delta}{sup 18}O{sub H2O} values +5{per thousand} to {gt} +9{per thousand}. CO{sub 2}-exsolution occurs at 215 {+-} 30{degree}C and 800 {+-} 400 bars during portions of MGOS time and constrains ore formation to minimum depths of 4.4 {+-} 2.2 km. Late Gold Ore Stage (LGOS) fluids are non-boiling and gas-poor with {lt}1.5 wt% NaCl and {delta}{sup 18}O{sub H2O} values {le}-4{per thousand} to -3{per thousand}. As LGOS fluids flood the system, calcite {delta}{sup 18}O values shift from near whole-rocks at +12 {+-} 3{per thousand} to 0 {+-} 1{per thousand} in veinlets containing unoxidized As {+-} Sb-phases. Gas-rich MGOS fluids may result from buried intrusions, contact aueroles, or deeper low-grade metamorphism. Deposition may occur in throttling zones where conditions change abruptly from lithostatic to hydrostatic.

  13. Ore formation in porphyry-type deposits during incrementally built magma chamber and fluid sparging

    NASA Astrophysics Data System (ADS)

    Vigneresse, J. L.; Bachmann, O.; Huber, C.; Parmigiani, A.; Dufek, J.; Campos, E.

    2012-04-01

    Porphyry-type mineralizations are commonly associated with an underlying magma chamber from which a volatile phase exsolves from the crystallizing magma. We suggest a model of fluid sparging during multiple successive intrusions yielding metals concentration within the gas phase. Metals enrichment by 3-4 orders of magnitude takes place during the magmatic stage prior to hydrothermal effects, resulting from a competition between diffusion and advection of the volatile phase. The model explains why a single intrusion is not efficient enough to lead to economically viable ore deposit, though it also involves a gas phase percolating within a crystalline mush. During multiple intrusions, metals segregate from the new melt to the gas phase by diffusion, as long as the gas has not overcome a critical saturation level (about 20 % gas). Adding gas exsolved, about 4 % at each new magma recharge, overcomes this level. Then, the diffusion process switches toward advection, since the bubbles get interconnected, enhancing the transport of a gas phase enriched in metals. Once advected, the enriched gas phase turns into hydrothermal circulation during which metals condensate. Two non-dimensional numbers, Péclet and Stefan numbers, respectively rule diffusion and advection of elements while heat is lost through cooling. The model also examines the total duration of the process that re-establishes after 4-6 recharges in magma. It also provides an explanation why intrusions are barren or enriched, although they result from similar conditions of magma genesis. Development of a zoned alteration pattern may serve as a guide for prospection.

  14. The world-class Jinding Zn-Pb deposit: ore formation in an evaporite dome, Lanping Basin, Yunnan, China

    NASA Astrophysics Data System (ADS)

    Leach, David L.; Song, Yu-Cai; Hou, Zeng-Qian

    2016-07-01

    The Jinding Zn-Pb sediment-hosted deposit in western Yunnan, China, is the fourth largest Zn deposit in Asia. Based on field observations of the ore textures, breccias, and the sandstone host rocks, the ores formed in a dome that was created by the diapiric migration of evaporites in the Lanping Basin during Paleogene deformation and thrust loading. Most of the ore occurs in sandstones that are interpreted to be a former evaporite glacier containing a mélange of extruded diapiric material, including breccias, fluidized sand, and evaporites that mixed with sediment from a fluvial sandstone system. A pre-ore hydrocarbon and reduced sulfur reservoir formed in the evaporite glacier that became the chemical sink for Zn and Pb in a crustal-derived metalliferous fluid. In stark contrast to previous models, the Jinding deposit does not define a unique class of ore deposits; rather, it should be classified as MVT sub-type hosted in a diapiric environment. Given that Jinding is a world-class ore body, this new interpretation elevates the exploration potential for Zn-Pb deposit in other diapir regions in the world.

  15. Ore formation at the Kupol epithermal gold-silver deposit in northeastern Russia deduced from fluid inclusion study

    NASA Astrophysics Data System (ADS)

    Volkov, A. V.; Prokof'ev, V. Yu.; Savva, N. E.; Sidorov, A. A.; Bayankin, M. A.; Uyutnov, K. V.; Kolova, E. E.

    2012-07-01

    The Kupol epithermal gold-silver deposit-the largest of this type of mineralization in northeastern Russia-is situated in the outer zone of the Okhotsk-Chukotka volcanic belt. The results of thermobarogeochemical study of fluid inclusions in quartz from ore veins at the Kupol deposit are compared with the data on the Dvoinoi and Arykvaam deposits. The study of aqueous extracts from fluid inclusions revealed that the chemical compositions of ore-forming fluids at the Dvoinoi and Kupol deposits are similar in most elements. The only substantial difference is that fluids from the Kupol deposit are considerably enriched in sulfate, as is characteristic of the alunite-subtype of epithermal high-sulfidation mineralization. The salinity of aqueous solutions filling inclusions in amethyst and quartz from ore veins at the Kupol and Dvoinoi deposits is two-three times higher than the salinity of fluid inclusions from the barren veins at the Arykvaam occurrence. The data obtained support the hypothesis put forward earlier that fumaroles and solfataras played a part in ore deposition at the Kupol deposit.

  16. Geochemistry of dispersed organic matter in gold-ore deposits of black shale formations

    NASA Astrophysics Data System (ADS)

    Budyak, A. E.; Goryachev, N. A.; Razvozzhaeva, E. A.; Spiridonov, A. M.; Sotskaya, O. T.; Bryukhanova, N. N.

    2015-08-01

    Bitumens from carbonaceous shales of various ages of the Baikal-Patom highlands and the Degdekan deposit (Yana-Kolyma folded system) were considered. It was determined that bitumens of the Bodaibo synclinorium are mainly represented by asphaltenes, asphaltogenic acids, and hydrocarbons; bitumens of the Degdekan field are represented predominantly by hydrocarbons.

  17. Sources of ore-forming fluids and formation environments of orogenic Au deposits in the Main Uralian Fault zone (Southern Urals)

    NASA Astrophysics Data System (ADS)

    Znamenskii, S. E.; Puchkov, V. N.; Michurin, S. V.

    2015-09-01

    The analysis of stable S, C, and O isotopes in minerals combined with the results of structural studies of orogenic gold deposits in carbonaceous shales of the Main Uralian Fault in the South Urals reveals that orogenic gold mineralization was formed during two stages of Late Paleozoic collisional deformations: early (thrust formation) and late (wrench faulting). The leading role in hydrothermal ore-forming systems of the first stage belonged to fluids of metamorphic origin, while at the second sage they were magmatogenic.

  18. Timing of the formation of the Changba-Lijiagou Pb-Zn ore deposit, Gansu Province, China: Evidence from Rb-Sr isotopic dating of sulfides

    NASA Astrophysics Data System (ADS)

    Hu, Qiaoqing; Wang, Yitian; Mao, Jingwen; Wei, Ran; Liu, Shengyou; Ye, Dejin; Yuan, Qunhu; Dou, Ping

    2015-05-01

    The giant Changba-Lijiagou Pb-Zn deposit is located in the north of the Xihe-Chengxian (abbreviated as "Xicheng") ore cluster in Gansu Province, China. The orebodies in the deposit are mainly hosted in the marble, dolomitic marble, and biotite-calcite-quartz schist of the Middle Devonian Anjiacha Formation. The genesis of the deposit has previously been argued to be of SEDEX type (sedimentary exhalative type) or of epigenetic hydrothermal type. This paper reports results of Rb-Sr isotopic dating on sphalerite and pyrite taken from the main orebody, which yield an isochron age of 222.3 ± 2.2 Ma for eight sphalerite samples, and 222.0 ± 3.0 Ma for the eight sphalerite samples combined with four pyrite samples, indicating that the deposit formed during the Late Triassic. The (87Sr/86Sri) value of the sphalerite is 0.71370 ± 0.00013, and that of the sphalerite and pyrite is 0.71371 ± 0.00014, which are identical within experimental error, suggesting that the ore metals are derived mainly from the continental crust. By integrating the present results with the regional geology, we propose that the Changba-Lijiagou Pb-Zn deposit is a product of regional hydrothermal mineralization processes, forced by tectono-magmatic activities, which took place in the Xicheng ore cluster during Triassic orogenic processes.

  19. Genesis and formation conditions of deposits in the unique Strel'tsovka Molybdenum-Uranium ore field: New mineralogical, geochemical, and physicochemical evidence

    NASA Astrophysics Data System (ADS)

    Aleshin, A. P.; Velichkin, V. I.; Krylova, T. L.

    2007-10-01

    The ambiguity of genetic interpretations of uranium ore formation at Mo-U deposits of the Strel’tsovka ore field led us to perform additional geochemical, mineralogical, and thermobarogeochemical studies. As a result, it has been established that closely related U and F were progressively gained in the Late Mesozoic volcanic rocks from the older basic volcanics (170 Ma) to the younger silicic igneous rocks (140 Ma). The Early Cretaceous postmagmatic hydrothermal epoch (140-125 Ma) is subdivided into preore, uranium ore, and first and second postore stages. The primary brannerite-pitchblende ore was formed in association with fluorite. At the first postore stage, this assemblage was replaced by a U-Si metagel, which was previously identified as coffinite. The metagel shows a wide compositional variation; its fine structure has been studied. The preore metasomatic alteration and related veined mineralization were formed under the effect of sodium (bicarbonate)-chloride solution at a temperature of 250-200°C. The uranium ore formation began with albitization and hematitization of rocks affected by supercritical fluid at 530-500°C; brannerite and pitchblende precipitated at 350-300°C. The chondrite-normalized REE patterns of pitchblende hosted in trachybasalt, trachydacite, and granite demonstrate a pronounced Sm-Nd discontinuity and a statistically significant tetrad effect of W type. These attributes were not established in REE patterns of rhyolites derived from the upper crustal magma chamber. This circumstance and a chronological gap of 5 Ma between silicic volcanism and ore formation do not allow us to suggest that uranium was derived from this magma chamber. According to the proposed model, the evolved silicic Li-F magma was a source of uranium. U4+, together with REE, was fractionated into the fluid phase as complex fluoride compounds. The uranium mineralization was deposited at a temperature barrier. It is suggested that hydromica alteration and the

  20. Mixing from below in hydrothermal ore deposits

    NASA Astrophysics Data System (ADS)

    Bons, Paul D.; Gomez-Rivas, Enrique; Markl, Gregor; Walter, Bejamin

    2014-05-01

    Unconformity-related hydrothermal ore deposits typically show indications of mixing of two end-member fluids: (a) hot, deep, rock-buffered basement brines and (b) colder fluids derived from the surface or overlying sediments. The hydromechanics of bringing these fluids together from above and below remain unclear. Classical percolative Darcy-flow models are inconsistent with (1) fluid overpressure indicated by fracturing and brecciation, (2) fast fluid flow indicated by thermal disequilibrium, and (3) strong fluid composition variations on the mm-scale, indicated by fluid inclusion analyses (Bons et al. 2012; Fusswinkel et al. 2013). We propose that fluids first descend, sucked down by desiccation reactions in exhumed basement. Oldest fluids reach greatest depths, where long residence times and elevated temperatures allow them the extensively equilibrate with their host rock, reach high salinity and scavenge metals, if present. Youngest fluids can only penetrate to shallower depths and can (partially) retain signatures from their origin, for example high Cl/Br ratios from the dissolution of evaporitic halite horizons. When fluids are released from all levels of the crustal column, these fluids mix during rapid ascent to form hydrothermal ore deposits. Mixing from below provides a viable hydromechanical mechanism to explain the common phenomenon of mixed shallow and deep fluids in hydrothermal ore deposits. Bons, P.D., Elburg, M.A., Gomez-Rivas, E. 2012. A review of the formation of tectonic veins and their microstructures. J. Struct. Geol. doi:10.1016/j.jsg.2012.07.005 Fusswinkel, T., Wagner, T., Wälle, M., Wenzel, T., Heinrich, C.A., Markl, M. 2013. Fluid mixing forms basement-hosted Pb-Zn deposits: Insight from metal and halogen geochemistry of individual fluid inclusions. Geology. doi:10.1130/G34092.1

  1. The Kharapeh orogenic gold deposit: Geological, structural, and geochemical controls on epizonal ore formation in West Azerbaijan Province, Northwestern Iran

    USGS Publications Warehouse

    Niroomand, Shojaeddin; Goldfarb, Richard J.; Moore, Farib; Mohajjel, Mohammad; Marsh, Erin E.

    2011-01-01

    The Kharapeh gold deposit is located along the northwestern margin of the Sanandaj–Sirjan Zone (SSZ) in the West Azerbaijan province, Iran. It is an epizonal orogenic gold deposit formed within the deformed zone between central Iran and the Arabian plate during the Cretaceous–Tertiary Zagros orogeny. The deposit area is underlain by Cretaceous schist and marble, as well as altered andesite and dacite dikes. Structural analysis indicates that the rocks underwent tight to isoclinal recumbent folding and were subsequently co-axially refolded to upright open folds during a second deformation. Late- to post-tectonic Cenozoic granites and granodiorites occur northeast of the deposit area. Mineralization mainly is recognized within NW-trending extensional structures as veins and breccia zones. Normal faults, intermediate dikes, and quartz veins, oriented subparallel to the axial surface of the Kharapeh antiform, indicate synchronous extension perpendicular to the fold axis during the second folding event. The gold-bearing quartz veins are >1 km in length and average about 6 m in width; breccia zones are 10–50 m in length and ≤1 m in width. Hydrothermal alteration mainly consists of silicification, sulfidation, chloritization, sericitization, and carbonatization. Paragenetic relationships indicate three distinct stages—replacement and silicification, brecciation and fracture filling, and cataclastic brecciation—with the latter two being gold-rich. Fluid inclusion data suggest mineral deposition at temperatures of at least 220–255°C and depths of at least 1.4–1.8 km, from a H2O–CO2±CH4 fluid of relatively high salinity (12–14 wt.% NaCl equiv.), which may reflect metamorphism of passive margin carbonate sequences. Ore fluid δ18O values between about 7‰ and 9‰ suggest no significant meteoric water input, despite gold deposition in a relatively shallow epizonal environment. Similarities to other deposits in the SSZ suggest that the deposit formed as

  2. Geochemical peculiarities of ores from the largest Natalka gold deposit in Northeastern Russia

    NASA Astrophysics Data System (ADS)

    Volkov, A. V.; Murashov, K. Yu.; Sidorov, A. A.

    2016-02-01

    This study of the behavior of trace and rare earth elements in ores from the Natalka gold deposit allows us to draw several conclusions. It is suggested that ore formation is related to the regional metamorphism of the host terrigenous carbonaceous rocks, which could be the major source for trace and rare earth elements. Minor enrichment of the Natalka ores in W is evidence of the contribution of magmatic fluid, which could be superimposed on early quartz veins, in ore formation. Our results support the metamorphic-magmatic model of formation of economic gold-quartz deposits of the Yana-Kolyma Belt. The similarity of metasomatites of the Natalka deposit with disseminated gold-sulfide refractory ores from the Nezhdaninskoe and Bakyrchik deposits points to the possible presence of such ores in the Natalka deposit. Our data are important for forecasting regional metallogenic reconstructions, search, and evaluation of gold deposits.

  3. Geochemical and Nd isotopic constraints on provenance and depositional setting of the Shihuiding Formation in the Shilu Fe-Co-Cu ore district, Hainan Province, South China

    NASA Astrophysics Data System (ADS)

    Yu, Liangliang; Zou, Shaohao; Cai, Jianxin; Xu, Deru; Zou, Fenghui; Wang, Zhilin; Wu, Chuanjun; Liu, Meng

    2016-04-01

    The Shihuiding Formation, a subordinate succession hosting the Fe-Co-Cu ores, is a suite of Neoproterozoic terrigenous clastic rocks occurring in the Shilu Fe-Co-Cu ore district of the Hainan Island, South China. Integrated petrographical, geochemical, and Nd isotopic analyses have been carried out on 23 sandstone specimens of the Shihuiding Formation in order to understand their provenance and the tectonic setting of their deposition. The samples can be divided into two groups, quartzose sandstones (13 samples) and ferruginous sandstones (10 samples). The ferruginous sandstones have average SiO2 and Fetotal contents of 77.23 wt.% and 18.09 wt.%, respectively, and this contrasts with the higher average SiO2 (94.04 wt.%) and lower Fetotal (2.67 wt.%) contents of the quartzose sandstones. The bivariant Th/Sc and Zr/Sc ratios indicate a predominantly recycled sedimentary provenance, and the low to medium degrees of weathering are commonly indicated by an average chemical index of maturity (CIM) of 81 and an average chemical index of alteration (CIA) of 68. The Shihuiding Formation sandstones have REE contents of 21-249 ppm, with LREE/HREE = 9.18 and δEu = 0.67. The εNd (970 Ma) values of -5.7 to -3.4, and model (TDM) ages of 2099-1773 Ma are compatible with a source mainly from the Paleo- to Mesoproterozoic Baoban Group, a suite of metamorphosed sedimentary rocks intruded by ca. 1450 Ma granites. Quantitative provenance modeling indicates that the Shihuiding Formation sandstones are best modeled with a mixture of 29% plagioclase-amphibole gneiss (29 P), 38% quartz-muscovite schist (38 Q), and 33% granite (33 G) detritus. Mixing the εNd values of the sandstones, calculated at 970 Ma, indicates that the sediment received 22-47% (average 34%) of its detritus from the Baoban Group quartz-muscovite schists. Components from hydrothermal fluids may also have been involved during deposition of the Shihuiding Formation sandstones, as revealed by a bivariant Al/(Al + Fe + Mn

  4. Early Permian stage of formation of gold-ore deposits of northeastern Transbaikalia: Isotope-geochronological (Rb-Sr and 39Ar-40Ar) data for the Uryakh ore field

    NASA Astrophysics Data System (ADS)

    Chugaev, A. V.; Nosova, A. A.; Abramov, S. S.; Chernyshev, I. V.; Bortnikov, N. S.; Larionova, Yu. O.; Goltsman, Yu. V.; Moralev, G. V.; Volfson, A. A.

    2015-08-01

    This work presents the first results of geochronological study of metasomatic rocks accompanying gold-bearing quartz veins of the Uryakh ore field (UOF). Based on the Rb-Sr and 39Ar-40Ar geochronological data, it is shown that hydrothermal metasomatic processes in the ore field occurred about 280 Ma ago (Early Permian) and they are correlated with the terminal phases of formation of the Angara-Vitim batholith.

  5. Application of low-temperature thermochronology to hydrothermal ore deposits: Formation, preservation and exhumation of epithermal gold systems from the Eastern Rhodopes, Bulgaria

    NASA Astrophysics Data System (ADS)

    Márton, István; Moritz, Robert; Spikings, Richard

    2010-03-01

    New low-temperature thermochronological data have been used to quantify the protracted, Eocene-Miocene cooling histories of upper and lower plate rocks of the Kesebir-Kardamos extensional dome, Eastern Rhodopes, Bulgaria. 40Ar/ 39Ar and apatite fission-track data reveal that the lower plate has experienced continuous cooling and exhumation, since the Late Eocene. Muscovite 40Ar/ 39Ar plateau ages of 36.90 ± 0.16 Ma and 37.28 ± 0.19 Ma (2 σ) from metamorphic rocks of the footwall reveal the approximate time span during which they cooled below ˜ 350 °C during exhumation caused by detachment faulting. The sedimentary rock-hosted gold mineralization, which represents a thermal event at ˜ 250-220 °C, developed during the early stage of basin formation between 34.71 ± 0.16 Ma and 35.36 ± 0.21 Ma (adularia 40Ar/ 39Ar plateau ages; 2 σ). The termination of hydrothermal mineral deposition at Ada Tepe occurred contemporaneously with the earliest phase of calc-alkaline type magmatism at Iran Tepe (33.97 ± 0.36 Ma to 34.62 ± 0.46 Ma, hornblende and biotite 40Ar/ 39Ar plateau ages, 2 σ). Thermal history modelling of apatite fission-track data shows that the lower plate rocks cooled through ˜ 120 °C at ˜ 18.3 ± 1.9 Ma (1 σ). A time-temperature model obtained from zircon and apatite fission-track data from the upper plate reveals that it was being buried during the late Eocene. At ˜ 33-30 Ma, a dramatic change of the time-temperature path was caused by the initiation of horst-graben structures, resulting in rapid exhumation of the upper plate. Our new thermochronological data reveal many aspects of the mechanisms of formation of sedimentary rock-hosted gold deposits. The heat accumulated during sedimentary burial of the upper plate is a plausible heat source to drive hydrothermal fluid circulation and ore formation. The development of large half-graben basins in the hanging walls of detachment faults, accompanied by a favourable climate, may have created a

  6. Exploration and local forecast of gold-ore deposits based on typomorphic properties of pyrite

    NASA Astrophysics Data System (ADS)

    Pshenichkin, A. Ya; Ananyev, Yu S.; Bushmano, A. I.; Abramova, R. N.

    2015-11-01

    The article describes the data in exploration and local forecast of gold-ore deposits based on typomorphic pyrite properties. The pyrite properties: crystal shape, impurity-elements and thermal EMF change in relation to the deposit formation conditions are consistent with the mineralogical and geochemical zoning of ore bodies and deposits. In this case, it is possible to evaluate the ore zone erosion, prospectivity and productivity of the ore bodies at depth and flanks. Mineralogical sampling on pyrite and gold should be conducted on the basis of other methods during exploration and mining.

  7. Textures, paragenesis and wall-rock alteration of lode-gold deposits in the Charters Towers district, north Queensland: implications for the conditions of ore formation

    NASA Astrophysics Data System (ADS)

    Kreuzer, Oliver P.

    2006-01-01

    Ore deposits of the Charters Towers Goldfield (CTGF) are mainly hosted by fault-fill veins. Extensional (˜8% of all veins) and stockwork-like (˜3%) veins are less common and of little economic significance. Crosscutting relationships and published structural and geochronological data indicate a Late Silurian to Early Devonian timing of gold mineralization, coincident with regional shortening (D4) and I-type magmatism. Paragenetic relationships, which are uniform in veins everywhere within the CTGF, suggest that vein formation commenced with the deposition of large volumes of buck quartz (stage I), followed by buck and comb quartz, and significant pyrite and arsenopyrite precipitation (stage II). Gold was introduced during stage III, after earlier sphalerite and coincident with galena and chalcopyrite. Narrow, discontinuous calcite veins of stage IV mark the waning of gold-related hydrothermal activity or a later unrelated episode. Ore zones within the veins are everywhere composed of comb and/or gray quartz, calcite and/or ankerite and bands or clusters of fractured pyrite that are spatially associated with galena, sphalerite or chalcopyrite. Low-grade or barren vein sections, on the other hand, are mainly composed of milky buck quartz with little evidence for modification, overprinting or interaction with later fluids. Gold-related hydrothermal wall-rock alteration is symmetrically zoned, displaying proximal sericite-ankerite and distal epidote-chlorite-hematite assemblages that may be taken to imply wall-rock interaction with near neutral fluids (pH 5-6). Isocon plots assuming immobile Al, P, Ti, Y and Zr consistently indicate As, K, Pb, S and Zn enrichment and Na, Si and Sr depletion in altered wall-rock specimens relative to the least altered rocks. Alteration assemblages, quartz textures, fault rocks and published fluid inclusion and stable isotope data imply that the veins were formed under conditions of episodic fluid overpressuring (˜0.9-3.8 kbar), at a

  8. Physical-chemical conditions of ore deposition

    USGS Publications Warehouse

    Barton, P.B., Jr.

    1981-01-01

    Ore deposits form under a wide range of physical and chemical conditions, but those precipitating from hot, aqueous fluids-i.e. the hydrothermal deposits-form generally below 700??C and at pressures of only 1 or 2 kbar or less. Natural aqueous fluids in rocks may extract metal and sulfur from a variety of rock types or may acquire them as a residual heritage from a crystallizing silicate magma. Ore-forming hydrothermal fluids never appear as hot springs (except in deep, submarine situations) because they boil, mix with surface waters, and cool, thereby losing their ore-bearing ability before reaching the surface. Mineral systems function as chemical buffers and indicators just as buffers and indicators function in a chemical laboratory. By reading the record written in the buffer/indicator assemblages of minerals one can reconstruct many aspects of the former chemical environment. By studying the record of changing conditions one may deduce information regarding the processes functioning to create the succession of chemical environments and the ore deposits they represent. The example of the OH vein at Creede, Colorado, shows a pH buffered by the K-feldspar + muscovite + quartz assemblage and the covariation of S2 and O2 buffered by the assemblage chlorite + pyrite + quartz. Boiling of the ore fluid led to its oxidation to hematite-bearing assemblages and simultaneously produced an intensely altered, sericitic capping over the vein in response to the condensation of vapors bearing acidic components. The solubility of metals as calculated from experimental and theoretical studies of mineral solubility appears too low by at least one or two powers of ten to explain the mineralization at Creede. In contrast to Creede where the mineral stabilities all point to a relatively consistent chemistry, the Mississippi Valley type deposits present a puzzle of conflicting chemical clues that are impossible to reconcile with any single equilibrium situation. Thus we must

  9. Magmatic-vapor expansion and the formation of high-sulfidation gold deposits: Structural controls on hydrothermal alteration and ore mineralization

    USGS Publications Warehouse

    Berger, B.R.; Henley, R.W.

    2011-01-01

    High-sulfidation copper-gold lode deposits such as Chinkuashih, Taiwan, Lepanto, Philippines, and Goldfield, Nevada, formed within 1500. m of the paleosurface in volcanic terranes. All underwent an early stage of extensive advanced argillic silica-alunite alteration followed by an abrupt change to spatially much more restricted stages of fracture-controlled sulfide-sulfosalt mineral assemblages and gold-silver mineralization. The alteration as well as ore mineralization stages of these deposits were controlled by the dynamics and history of syn-hydrothermal faulting. At the Sulfate Stage, aggressive advanced argillic alteration and silicification were consequent on the in situ formation of acidic condensate from magmatic vapor as it expanded through secondary fracture networks alongside active faults. The reduction of permeability at this stage due to alteration decreased fluid flow to the surface, and progressively developed a barrier between magmatic-vapor expansion constrained by the active faults and peripheral hydrothermal activity dominated by hot-water flow. In conjunction with the increased rock strength resulting from alteration, subsequent fault-slip inversion in response to an increase in compressional stress generated new, highly permeable fractures localized by the embrittled, altered rock. The new fractures focused magmatic-vapor expansion with much lower heat loss so that condensation occurred. Sulfide Stage sulfosalt, sulfide, and gold-silver deposition then resulted from destabilization of vapor phase metal species due to vapor decompression through the new fracture array. The switch from sulfate to sulfide assemblages is, therefore, a logical consequence of changes in structural permeability due to the coupling of alteration and fracture dynamics rather than to changes in the chemistry of the fluid phase at its magmatic source. ?? 2010.

  10. Morphostructural and constitutional features of titanomagnetite in iron ore of the Pudozhgorsky deposit

    NASA Astrophysics Data System (ADS)

    Bystrov, I. G.; Pirogov, B. I.; Yakushina, O. A.

    2015-11-01

    Ti-bearing iron ore of the Pudozhgorsky deposit has been studied in detail using laboratory mineralogical analytical methods in order to determine the morphostructural and constitutional features of titanomagnetite. The genesis of the ore and gangue mineral intergrowths has been established, as well as typomorphic attributes of three titanomagmetite varieties differing in degree of heterogeneity. The behavior of ore in technological processes is controlled by exsolution structures of titanomagnetite with ilmenite formation. The possibility of the complex development of this ore has been shown. Titanomagnetites of major mineral assemblages pertaining to various types of Tiand V-bearing iron ores are compared.

  11. A geochemical assessment of possible lunar ore formation

    NASA Technical Reports Server (NTRS)

    Haskin, Larry A.; Colson, Russell O.; Vaniman, David

    1991-01-01

    The Moon apparently formed without appreciable water or other relatively volatile materials. Interior concentrations of water or other volatile substances appear to be extremely low. On Earth, water is important to the genesis of nearly all types of ores. Thus, some have reasoned that only abundant elements would occur in ore concentrations. The definition and recognition of ores on the Moon challenge the imaginations and the terrestrial perceptions of ore bodies. Lunar ores included solar-wind soaked soils, which contain abundant but dilute H, C, N, and noble gases (including He-3). Oxygen must be mined; soils contain approximately 45 percent (wt). Mainstream processes of rock formation concentrated Si, Mg, Al, Fe, and Ca, and possibly Ti and Cr. The highland surface contains approximately 70 percent (wt) feldspar (mainly CaAl2Si2O8), which can be separated from some highland soils. Small fragments of dunite were collected; dunite may occur in walls and central peaks of some craters. Theoretical extensions of observations of lunar samples suggest that the Moon may have produced ores of trace elements. Some small fragments have trace-element concentrations 10(exp 4) times higher than the lunar average, indicating that effective geochemical separations occurred; processes included fractional crystallization, silicate immiscibility, vaporization and condensation, and sulfide metamorphism. Operations of these processes acting on indigenous materials and on meteoritic material in the regolith could have produced ores. Infalling carbonaceous meteorites and comets have added water and hydrocarbons that may have been cold-trapped. Vesicles in basalts, pyroclastic beads, and reported transient events suggest gag emission from the lunar interior; such gas might concentrate and transport rare elements. Large impacts may disperse ores or produce them through deposition of heat at depth and by vaporization and subsequent condensation. The main problem in assessing lunar

  12. Nickel dispersion and enrichment at the bottom of the regolith: formation of pimelite target-like ores in rock block joints (Koniambo Ni deposit, New Caledonia)

    NASA Astrophysics Data System (ADS)

    Cathelineau, Michel; Quesnel, Benoît; Gautier, Pierre; Boulvais, Philippe; Couteau, Clément; Drouillet, Maxime

    2016-02-01

    In New Caledonian Ni deposits, the richest Ni silicate ores occur in fractures within the bedrock and saprolite, generally several tens of meters to hundred meters below the present-day surface. Fracture-related Ni silicate ore accounts for high Ni grades, at least a few weight percent above the average exploited grade (2.5 %). These Ni-rich veins are affected by active dissolution-precipitation processes at the level of the water table. Ni in solution is precipitated as silicates in thin layer cementing joints. This mineralization is characterized by chemical and mineralogical concentric zoning with an outer green rim around an inner white zone composed, from the edge to the centre of the block, (i) a highly oxidized and altered zone, (ii) a green pure Ni-rich pimelite zone, (iii) a zone (limited to a few centimetres) with a mixture of Ni-poor kerolite and Ni-rich pimelite and intermediate colours and (iv) a large white Mg-kerolite mineralization zone. This study proposes that the concentric zonation results from evapo-precipitation process related to alternate periods of hydration and drying, induced by water table movements. This extensive dispersion of Ni in concentrically zoned ores can partly explain the rather monotonous Ni grade of the bulk exploitation at the base of the regolith with values between 2 and 3 wt%.

  13. Magnetic properties of the Bled El Hadba phosphate-bearing formation (Djebel Onk, Algeria): Consequences of the enrichment of the phosphate ore deposit

    NASA Astrophysics Data System (ADS)

    Bezzi, Nacer; Aïfa, Tahar; Merabet, Djoudi; Pivan, Jean-Yves

    2008-02-01

    To improve the enrichment of the Thanetian marine phosphate ore deposit from the quarry of Bled El Hadba (Djebel Onk, Algeria) before its exploitation, we first conducted a joint study using different techniques for comparison. These studies reveal that magnetic minerals play a significant role within the matrix of the central productive unit which is squeezed between two other units. Magnetic separation procedures show that there are some positive correlations between magnetic susceptibility and grain size fraction (80-250 μm). These dolomite-rich fractions are more clearly separated. Different tools were used to characterize the magnetic minerals (X-ray, microprobe, differential scanning calorimetry, thermogravimetric and thermomagnetic analyses). They show correlations between magnetic phases and the presence of associated magnetic minerals within the matrix or included in the phosphate ore deposit. They enabled us to distinguish a series of magnetic minerals (magnetite, hematite, maghemite, goethite, ilmenite, pyrite, iron-titanium oxide and titanium oxide sulphate) and to determine that Fe and Ti are prevalent in the separated fractions, following the same variation as Mg. The phosphorous (phosphate) rate is higher in the non-magnetic material, especially in the layers that are rich in dolomitic carbonates (upper and lower units), which could be trapped within the dolomitic matrix, while Magnesium (dolomite) is more important in the magnetic fraction. The separation of phosphate elements and dolomite carbonates is effective and therefore the ore can be enriched through magnetic procedures. Comparison between products enriched by magnetic separation, flotation and calcination showed important differences, chemically, economically and technically speaking.

  14. Mineralogical and geochemical characteristics of the Noamundi-Koira basin iron ore deposits (India)

    NASA Astrophysics Data System (ADS)

    Mirza, Azimuddin; Alvi, Shabbar Habib; Ilbeyli, Nurdane

    2015-04-01

    India is one of the richest sources of iron ore deposits in the world; and one of them is located in the Noamundi-Koira basin, Singhbhum-Orissa craton. The geological comparative studies of banded iron formation (BIF) and associated iron ores of Noamundi-Koira iron ore deposits, belonging to the iron ore group in eastern India, focus on the study of mineralogy and major elemental compositions along with the geological evaluation of different iron ores. The basement of the Singhbhum-Orissa craton is metasedimentary rocks which can be traced in a broadly elliptical pattern of granitoids, surrounded by metasediments and metavolcanics of Greenstone Belt association. The Singhbhum granitoid is intrusive into these old rocks and to younger, mid Archaean metasediments, including iron formations, schists and metaquartzites and siliciclastics of the Precambrian Iron Ore Group (Saha et al., 1994; Sharma, 1994). The iron ore of Noamundi-Koira can be divided into seven categories (Van Schalkwyk and Beukes 1986). They are massive, hard laminated, soft laminated, martite-goethite, powdery blue dust and lateritic ore. Although it is more or less accepted that the parent rock of iron ore is banded hematite jasper (BHJ), the presence of disseminated martite in BHJ suggests that the magnetite of protore was converted to martite. In the study area, possible genesis of high-grade hematite ore could have occurred in two steps. In the first stage, shallow, meteoric fluids affect primary, unaltered BIF by simultaneously oxidizing magnetite to martite and replacing quartz with hydrous iron oxides. In the second stage of supergene processes, deep burial upgrades the hydrous iron oxides to microplaty hematite. Removal of silica from BIF and successive precipitation of iron resulted in the formation of martite- goethite ore. Soft laminated ores were formed where precipitation of iron was partial or absent. The leached out space remains with time and the interstitial space is generally filled

  15. Relationship between metamorphism and ore formation at the Sukhoi Log gold deposit hosted in black slates from the data of U-Th-Pb isotopic SHRIMP-dating of accessory minerals

    NASA Astrophysics Data System (ADS)

    Yudovskaya, M. A.; Distler, V. V.; Rodionov, N. V.; Mokhov, A. V.; Antonov, A. V.; Sergeev, S. A.

    2011-02-01

    The formation conditions and age of the Sukhoi Log gold deposit are considered on the basis of new isotopic-geochemical data. The U-Pb isotopic study of zircon and monazite from high-grade ore and host black slates at the Sukhoi Log deposit was carried out with SIMS technique using a SHRIMP II instrument. Two generations of monazite are distinguished on the basis of optical and scanning electron microscopy, cathodoluminescence, and micro X-ray spectroscopy. Monazite I is characterized by black opaque porphyroblasts with microinclusions of minerals pertaining to metamorphic slates and structural attributes of pre- and synkinematic formation. Monazite II occurs only within the ore zone as transparent crystals practically free of inclusions and as rims around monazite I. The REE contents are widely variable in both generations. Porphyroblastic monazite I differs in low U and Th (0.01-0.7 wt % ThO2) contents, whereas transparent monazite II contains up to 4 wt % ThO2. The average weighted U-Pb isotopic age of monazite I is 650 ± 8.1 Ma (MSWD = 1.6; n = 9) and marks the time of metamorphism or catagenesis. The U-Pb age estimates of synore monazite II cover the interval of 486 ± 18 to 439 ± 17 Ma. Zircons of several populations from 0.5 to 2.6 Ga in age are contained in the ore. Most detrital zircon grains have porous outer rims composed of zircon and less frequent xenotime with numerous inclusions of minerals derived from slates. The peaks of 206Pb/238U ages in the most abundant zircon populations fall on 570 and 630 Ma and correspond to the age of newly formed metamorphic mineral phases. The discordant isotopic ages indicate that the U-ThPb isotopic system of ancient detrital zircons was disturbed 470-440 Ma ago in agreement with isotopic age of monazite II and the Rb-Sr whole -rock isochron age of black slates (447 ± 6 Ma). The new data confirm the superimposed character of the gold-quartz-sulfide mineralization at the deposit. Black shales of the Khomolkho

  16. Sedimentary carbonate-hosted giant Bayan Obo REE-Fe-Nb ore deposit of Inner Mongolia, China; a cornerstone example for giant polymetallic ore deposits of hydrothermal origin

    USGS Publications Warehouse

    Chao, E.C.T.; Back, J.M.; Minkin, J.A.; Tatsumoto, M.; Junwen, Wang; Conrad, J.E.; McKee, E.H.; Zonglin, Hou; Qingrun, Meng; Shengguang, Huang

    1997-01-01

    Detailed, integrative field and laboratory studies of the textures, structures, chemical characteristics, and isotopically determined ages and signatures of mineralization of the Bayan Obo deposit provided evidence for the origin and characteristics favorable for its formation and parameters necessary for defining giant polymetallic deposits of hydrothermal origin. Bayan Obo is an epigenetic, metasomatic, hydrothermal rare earth element (REE)-Fe-Nb ore deposit that is hosted in the metasedimentary H8 dolostone marble of the Middle Proterozoic Bayan Obo Group. The metasedimentary sequence was deposited on the northern continental slope of the North China craton. The mine area is about 100 km south of the suture marking Caledonian subduction of the Mongolian oceanic plate from the north beneath the North China craton. The mineralogy of the deposit is very complex, consisting of more than 120 different minerals, some of which are epigenetic minerals introduced by hydrothermal solutions, and some of which are primary and secondary metamorphic minerals. The major REE minerals are monazite and bastnaesite, whereas magnetite and hematite are the dominant Fe-ore minerals, and columbite is the most abundant Nb mineral. Dolomite, alkali amphibole, fluorite, barite, aegirine augite, apatite, phlogopite, albite, and microcline are the most widespread gangue minerals. Three general types of ores occur at Bayan Obo: disseminated, banded, and massive ores. Broad zoning of these ore types occurs in the Main and East Orebodies. Disseminated ores are in the outermost zone, banded ores are in the intermediate zone, and massive ores are in the cores of the orebodies. On the basis of field relations, host rocks, textures, structures, and mineral assemblages, many varieties of these three types of ores have been recognized and mapped. Isotopic dating of monazite, bastnaesite, aeschynite, and metamorphic and metasomatic alkali amphiboles associated with the deposit provides constraints

  17. Morphology of orebodies and genesis of uranium deposits in the Khiagda ore field

    NASA Astrophysics Data System (ADS)

    Kochkin, B. T.; Novgorodtsev, A. A.; Tarasov, N. N.; Martynenko, V. G.

    2014-11-01

    The localization controls of uranium lodes at deposits in the Khiagda ore field are considered in this paper on the basis of detailed documentation of borehole cores, geological sections, and maps. Detailed mapping has been carried out at four of eight deposits of the ore field; additionally, three deposits were studied fragmentary using separate sections and boreholes. We have shown that the idea of the lenticular shape of ore-bodies in section and their ribbonlike shape in plan view only partially corresponds to reality. The revealed morphological features of orebodies along with spatial relationships with epigenetic alteration of host rocks and faults indicate that mineralization was formed by mixing of the oxygen- and uranium-bearing subsurface water descending downdip the seam and the reductive subsurface water ascending from the basement along faults. The available data on the composition of subsurface water currently contained in the basement of ore field give grounds to assume that water similar in composition could have participated in uranium ore deposition. The special properties of this water, interacting for a long time with flows of formation water under conditions of the local geological setting, have imparted those features to the studied deposits, which differentiate them from other economic sandstone-hosted deposits, including those localized in paleovalleys.

  18. Evolution of volcanic and tectonic features in caldera settings and their importance in the localization of ore deposits

    USGS Publications Warehouse

    Rytuba, J.J.

    1994-01-01

    Many calderas are located along regionally important fault zones that are intermittently active before and after the caldera cycle. In mineralized calderas, the ore deposits are controlled by structures developed during caldera formation and by regional faults which intersect and reactivate the caldera-related structures. The paper discusses the importance of the different stages of caldera formation in connection with the localization of ore deposits. -from Author

  19. Mineralogical and geochemical characteristics of the Noamundi-Koira basin iron ore deposits (India)

    NASA Astrophysics Data System (ADS)

    Mirza, Azimuddin; Alvi, Shabbar Habib; Ilbeyli, Nurdane

    2015-04-01

    India is one of the richest sources of iron ore deposits in the world; and one of them is located in the Noamundi-Koira basin, Singhbhum-Orissa craton. The geological comparative studies of banded iron formation (BIF) and associated iron ores of Noamundi-Koira iron ore deposits, belonging to the iron ore group in eastern India, focus on the study of mineralogy and major elemental compositions along with the geological evaluation of different iron ores. The basement of the Singhbhum-Orissa craton is metasedimentary rocks which can be traced in a broadly elliptical pattern of granitoids, surrounded by metasediments and metavolcanics of Greenstone Belt association. The Singhbhum granitoid is intrusive into these old rocks and to younger, mid Archaean metasediments, including iron formations, schists and metaquartzites and siliciclastics of the Precambrian Iron Ore Group (Saha et al., 1994; Sharma, 1994). The iron ore of Noamundi-Koira can be divided into seven categories (Van Schalkwyk and Beukes 1986). They are massive, hard laminated, soft laminated, martite-goethite, powdery blue dust and lateritic ore. Although it is more or less accepted that the parent rock of iron ore is banded hematite jasper (BHJ), the presence of disseminated martite in BHJ suggests that the magnetite of protore was converted to martite. In the study area, possible genesis of high-grade hematite ore could have occurred in two steps. In the first stage, shallow, meteoric fluids affect primary, unaltered BIF by simultaneously oxidizing magnetite to martite and replacing quartz with hydrous iron oxides. In the second stage of supergene processes, deep burial upgrades the hydrous iron oxides to microplaty hematite. Removal of silica from BIF and successive precipitation of iron resulted in the formation of martite- goethite ore. Soft laminated ores were formed where precipitation of iron was partial or absent. The leached out space remains with time and the interstitial space is generally filled

  20. Complexity of Ore-controlling Fracture System of Dajishan Tungsten Deposit, China

    NASA Astrophysics Data System (ADS)

    LIU, Ningqiang; YU, Chongwen

    To understand the complexity of the development and evolution of ore-controlling fracture system in Dajishan tungsten deposit, Quannan County, Jiangxi Province, we collected rock samples in different depth of deposit and carried out experimental work on rock acoustic emission. Results show that the sequence of rock acoustic emission events follows a clear process of occurrence, quiescence, and burst. The onset and development of fracture system has a cascade of avalanches-punctuated equilibrium hierarchic fractal structure, and the breaking process is very discontinuous, the energy released is also discontinuous, and it becomes smaller with the increase of depth, which reflects the development of mineralization. The author applies the theory of complexity to study the ore-controlling fractures of the vein-type tungsten ore deposits in Dajishan. The following conclusions are drawn. The dynamics of the onset and development of fracture system is similar to the ore-forming system. That is, it consists of the self-organization arising from the coupling of random motion, the coherent behavior produced by interaction between subsystems, the realization of cooperative synchronization, the occurrence of critical transition point, and the attainment of self-organized criticality. These result from the coupling and interaction of physical movement of minerals, time, and space. The formation of vein-type tungsten ore deposit in Dajishan is closely related to critical rupture of ore-controlling fracture system and its avalanches-punctuated equilibrium cascade fractal growth, that is, metallogenic model of vein-type tungsten ore deposit in Dajishan follows generalized "five-storeyed type" metallogenic model.

  1. Analog Experiments on Sulfide Foams in Magmatic Ore Deposits

    NASA Astrophysics Data System (ADS)

    Leitch, A. M.; Dahn, D.; Zavala, K.

    2009-05-01

    Metal sulfides form as an immiscible phase from silicate magmas. Dynamic mingling and unmingling of the two phases is important for the development of economic deposits: mingling promotes enrichment of the sulfide in valuable metals, and subsequent unmingling generates massive sulfide. Analog experiments were carried out to investigate mingling processes in immiscible systems, using oil, water and small beads to represent magma, sulfide liquid and silicate crystals. Stirring or injection led to the formation of a foam of analog sulfide droplets within an analog silicate framework. We propose that the partial collapse of such a foam explains massive sulfide lenses at the Voisey's Bay magmatic sulfide deposit, and that crystallization of silicate crystals in the remaining foam walls generates 'net-textured' ores. In the experiments, solid particles had a profound effect on unmingling: analog sulfide droplets were stably contained within analog crystal-rich magma and did not coalesce. We therefore suggest that 'net' and 'leopard' textures in disseminated sulfides indicate mingling of sulfide with crystal-poor magma, whereas isolated disseminated patches of sulfide indicate mingling with a crystal-rich magma.

  2. Compositional Variability of Rutile in Hydrothermal Ore Deposits

    NASA Astrophysics Data System (ADS)

    Clark, J. R.; Williams-Jones, A. E.

    2009-05-01

    Rutile is a relatively common accessory phase in many geological environments, and although it is almost always composed dominantly of TiO2, it is also associated with a wide range of minor and trace element substitutions. The most prominent minor elements that occur in rutile are Fe, Cr, V, Nb and Ta. Like Ti, the latter two elements are essentially immobile in most non-magmatic metallic ore deposits, and their concentrations in rutile are largely influenced by precursor mineral compositions. Iron, Cr and V concentrations vary considerably in rutile hosted by ore deposits, and reflect combinations of precursor mineral composition and the bulk chemistry of the local mineralized or altered rock environment. However, in hydrothermal alteration zones, rutile compositions are clearly anomalous compared to those in unaltered host rocks, and have distinctive elemental associations and substitutions in different types of ore deposits. We have evaluated the mineral chemistry of rutile in >40 ore deposits worldwide. In general, rutile in volcanogenic massive sulfide deposits contains Sn (and locally W, Sb and/or Cu). Rutile from mesothermal and related gold deposits invariably contains W, and in some of the larger and more important deposits, also contains Sb and/or V. Tungsten-bearing detrital rutile grains from the Witwatersrand suggest that paleoplacer mineralization may have had a mesothermal/orogenic gold source. In some magmatic-hydrothermal Pd-Ni-Cu deposits, rutile contains Ni and Cu. Rutile associated with granite-related Sn deposits has strongly elevated concentrations of Sn and W, and granite-pegmatite W-Sn deposits contain rutile with these elements plus Nb and Ta. The Olympic Dam deposit hosts rutile that is enriched in W, Sn and Cu. Rutile associated with porphyry and skarn Cu and Cu-Au deposits tends to contain elevated W, Cu (and sometimes V). Although many ore deposits have well-defined and diagnostic rutile compositions, there are some compositional

  3. The Gas Hills uranium district and some probable controls for ore deposition

    USGS Publications Warehouse

    Zeller, Howard Davis

    1957-01-01

    Uranium deposits occur in the upper coarse-grained facies of the Wind River formation of Eocene age in the Gas Hills district of the southern part of the Wind River Basin. Some of the principal deposits lie below the water table in the unoxidized zone and consist of uraninite and coffinite occurring as interstitial fillings in irregular blanket-like bodies. In the near-surface deposits that lie above the water table, the common yellow uranium minerals consist of uranium phosphates, silicates, and hydrous oxides. The black unoxidized uraninite -coffinite ores show enrichment of molybdenum, arsenic, and selenium when compared to the barren sandstone. Probable geologic controls for ore deposits include: 1) permeable sediments that allowed passage of ore-bearing solutions; 2) numerous faults that acted as impermeable barriers impounding the ore -bearing solutions; 3) locally abundant pyrite, carbonaceous material, and natuial gas containing hydrogen sulfide that might provide a favorable environment for precipitation of uranium. Field and laboratory evidence indicate that the uranium deposits in the Gas Hills district are very young and related to the post-Miocene to Pleistocene regional tilting to the south associated with the collapse of the Granite Mountains fault block. This may have stopped or reversed ground water movement from a northward (basinward) direction and alkaline ground water rich in carbonate could have carried the uranium into the favorable environment that induced precipitation.

  4. Oligocene shoshonitic rocks of the Rogozna Mts. (Central Balkan Peninsula): Evidence of petrogenetic links to the formation of Pb-Zn-Ag ore deposits

    NASA Astrophysics Data System (ADS)

    Borojević Šoštarić, S.; Cvetković, V.; Neubauer, F.; Palinkaš, L. A.; Bernroider, M.; Genser, J.

    2012-09-01

    This study focuses on age and evolution of the Oligocene quartz latite of the Rogozna Mts. (Central Balkan Peninsula), in order to better understand the link between magmatism and formation of Pb-Zn ± Ag mineralization. New 40Ar/39Ar biotite and amphibole plateau ages suggest that the Rogozna Mts. quartz latite originated through a continuous volcanic episode from 27.3 ± 0.1 to 29.5 ± 0.1 Ma which was immediately followed by a hydrothermal phase. The quartz latites are hypocrystalline porphyritic with phenocrysts and microphenocrysts (~ 60 vol.%) of plagioclase (An37-49), biotite Mg# [100 × Mg / (Mg + Fetot)] < 50, calcic amphibole, quartz, sanidine clinopyroxene and phlogopite (Mg# = 79 to 84). The rocks display numerous disequilibrium textures, such as: sieved plagioclase phenocrysts, dissolution effects on quartz, phlogopitized biotite and amphibole crystals, and phlogopite microphenocrysts showing effects of incomplete growth (or dissolution?) and biotitization. The Rogozna Mts. quartz latites are shoshonitic in character with Na2O/K2O < 1, high LILE/HFSE ratios, strong depletions at Nb and Ti and K, Pb and U peaks on primitive mantle-normalized diagrams. They are similar to other potassic/ultrapotassic rocks in this region, in particular to those of Veliki Majdan and Rudnik (West Serbia), which are also related to Pb-Zn deposits. The evolution of the Rogozna Mts. quartz latite is modeled using a trace element binary mixing model adopting a lamproite magma and a dacite-like calc-alkaline melt as end-members. The model implies that a fractionating magma chamber (~ 4.5-9.5 km) undergoes cooling in the range of > 850 °C-~720 °C and injection of lamproite-like melts. The injection causes an increase of temperature and a decrease of viscosity of the resulting hybrid magma, facilitating its upwelling and triggering pyroclastic eruptions. The addition of new volatiles by lamproitic melts most probably established the conditions for a hydrothermal phase above the

  5. Application of natural analog studies to exploration for ore deposits

    SciTech Connect

    Gustafson, D.L.

    1995-09-01

    Natural analogs are viewed as similarities in nature and are routinely utilized by exploration geologists in their search for economic mineral deposits. Ore deposit modeling is undertaken by geologists to direct their exploration activities toward favorable geologic environments and, therefore, successful programs. Two types of modeling are presented: (i) empirical model development based on the study of known ore deposit characteristics, and (ii) concept model development based on theoretical considerations and field observations that suggest a new deposit type, not known to exist in nature, may exist and justifies an exploration program. Key elements that are important in empirical model development are described, and examples of successful applications of these natural analogs to exploration are presented. A classical example of successful concept model development, the discovery of the McLaughlin gold mine in California, is presented. The utilization of natural analogs is an important facet of mineral exploration. Natural analogs guide explorationists in their search for new discoveries, increase the probability of success, and may decrease overall exploration expenditure.

  6. The coupled geochemistry of Au and As in pyrite from hydrothermal ore deposits

    NASA Astrophysics Data System (ADS)

    Deditius, Artur P.; Reich, Martin; Kesler, Stephen E.; Utsunomiya, Satoshi; Chryssoulis, Stephen L.; Walshe, John; Ewing, Rodney C.

    2014-09-01

    The ubiquity of Au-bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of Au and As in this sulfide occurs under a wide range of physico-chemical conditions. Despite significant advances in the last 20 years, fundamental factors controlling Au and As ratios in pyrite from ore deposits remain poorly known. Here we explore these constraints using new and previously published EMPA, LA-ICP-MS, SIMS, and μ-PIXE analyses of As and Au in pyrite from Carlin-type Au, epithermal Au, porphyry Cu, Cu-Au, and orogenic Au deposits, volcanogenic massive sulfide (VHMS), Witwatersrand Au, iron oxide copper gold (IOCG), and coal deposits. Pyrite included in the data compilation formed under temperatures from ∼30 to ∼600 °C and in a wide variety of geological environments. The pyrite Au-As data form a wedge-shaped zone in compositional space, and the fact that most data points plot below the solid solubility limit defined by Reich et al. (2005) indicate that Au1+ is the dominant form of Au in arsenian pyrite and that Au-bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native Au. The analytical data also show that the solid solubility limit of Au in arsenian pyrite defined by an Au/As ratio of 0.02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal-chemical properties of pyrite and post-depositional alteration. Compilation of Au-As concentrations and formation temperatures for pyrite indicates that Au and As solubility in pyrite is retrograde; Au and As contents decrease as a function of increasing temperature from ∼200 to ∼500 °C. Based on these results, two major Au-As trends for Au-bearing arsenian pyrite from ore deposits are defined. One trend is formed by pyrites from Carlin-type and orogenic Au deposits where compositions are largely controlled by fluid-rock interactions and/or can be highly perturbed by changes in temperature and

  7. REE Mineralization in Kiruna-type Magnetite-Apatite Ore Deposits: Magmatism and Metasomatism

    NASA Astrophysics Data System (ADS)

    Harlov, D. E.

    2015-12-01

    Magnetite-apatite ore bodies of the Kiruna type occur worldwide and are generally associated with volcanic rocks or volcanism. They also show strong evidence of extensive metasomatism over a wide P-T range. Notable examples include the Kiirunavaara ore body, northern Sweden (Harlov et al., 2002, Chem. Geol., 191, 47-72); the Grängesberg ore body, central Sweden (Jonsson et al., 2010, NGF abstracts, vol 1, 88-89); the Mineville ore body, Adirondacks, New York, USA (McKeown and Klemc, 1956, U.S. Geol Sur Bull (1956), pp. 9-23); the Pea Ridge ore body, SE Missouri, USA (Kerr, 1998, MS Thesis, Univ. Windsor, Windsor, Ontario, Canada 113 pp); the Jurassic Marcona ore body in south-central Peru (Chen et al., 2010, Econ Geol, 105, 1441-1456); and a collection of ore bodies from the Bafq Region, central Iran (Daliran et al., 2010, Geol. Assoc. Canada, Short Course Notes, v. 20, p.147-159). In these ore bodies, low Th and U monazite, xenotime, allanite, REE carbonates, and/or REE fluorides are commonly associated with the apatite as inclusions, rim grains, or as independent grains in the surrounding mineral matrix. High contrast BSE imaging, coupled with EMPA and LA-ICPMS, indicates that the apatite has experienced fluid-induced alteration in the form of (Y+REE) + Na + Si + Cl depletion implying that it served as the source for the (Y+REE) (e.g. Kiirunavaara, northern Sweden; Harlov et al., 2002). Formation of monazite and xenotime associated with fluorapatite, as inclusions or rim grains, has experimentally been demonstrated to originate from the fluorapatite as the result of fluid-aided, coupled dissolution-reprecipitation processes (Harlov et al., 2005, Contrib. Mineral. Petrol. 150, 268-286). This is explains the low Th and U content of the monazite and xenotime. Fluid sources could range from 700-900 °C, residual, acidic (HCl, H2HSO4) grain boundary fluids, remaining after the last stages of ore body crystallization, to later stage, cooler (< 600 °C) (H2O-CO2-(Na

  8. Precambrian rift: genesis of strata-bound ore deposits.

    PubMed

    Kanasewich, E R

    1968-09-01

    Study of deep seismic reflections has detected a Precambrian rift valley below flat-lying sediments in southern Alberta. The anomalous magnetic and gravity trends show that the rift is continuous across Alberta and British Columbia (through the Kimberley lead-zinc field) and possibly the Coeur d'Alene mining district of Idaho. There is evidence that these ore bodies were deposited in a Precambrian rift under conditions similar to those prevailing in the hot-brine areas of the modern Red Sea. PMID:17812797

  9. Supergene processes and uranium ore formation in the Ronneburg ore field, Germany

    NASA Astrophysics Data System (ADS)

    Bolonin, A. V.; Gradovsky, I. F.

    2012-04-01

    The Ordovician-Lower Carboniferous sequence of slightly metamorphosed gray carbonate-terrigenous rocks contains the Silurian black cherty shales enriched in carbon (6-9%), pyrite (6-7%), and uranium (˜30 ppm). The uranium ore is localized at the pinch-out of areal and linear zones of the Early Permian supergene (exogenic) oxidation of rocks expressed in reddening (hematitization). U, As, Sb, Cu, Ni, Mo, and Ag have been removed from the oxidized black shales and concentrated in the cementation zone in form of pitchblende and sulfides in wall-rock disseminations and veinlets largely hosted in carbonate-bearing rocks. In the Late Permian, during deposition of the upper Rotliegende and Zechstein, the fractures in the basement were filled with carbonates and sulfates; uranium was partly redeposited along with enrichment in Pb and Zn. Mesozoic and Cenozoic supergene processes altered uranium ore insignificantly.

  10. Mineralogy and geochemistry of banded iron formation and iron ores from eastern India with implications on their genesis

    NASA Astrophysics Data System (ADS)

    Roy, Subrata; Venkatesh, A. S.

    2009-12-01

    The geological complexities of banded iron formation (BIF) and associated iron ores of Jilling-Langalata iron ore deposits, Singhbhum-North Orissa Craton, belonging to Iron Ore Group (IOG) eastern India have been studied in detail along with the geochemical evaluation of different iron ores. The geochemical and mineralogical characterization suggests that the massive, hard laminated, soft laminated ore and blue dust had a genetic lineage from BIFs aided with certain input from hydrothermal activity. The PAAS normalized REE pattern of Jilling BIF striking positive Eu anomaly, resembling those of modern hydrothermal solutions from mid-oceanic ridge (MOR). Major part of the iron could have been added to the bottom sea water by hydrothermal solutions derived from hydrothermally active anoxic marine environments. The ubiquitous presence of intercalated tuffaceous shales indicates the volcanic signature in BIF. Mineralogical studies reveal that magnetite was the principal iron oxide mineral, whose depositional history is preserved in BHJ, where it remains in the form of martite and the platy hematite is mainly the product of martite. The different types of iron ores are intricately related with the BHJ. Removal of silica from BIF and successive precipitation of iron by hydrothermal fluids of possible meteoric origin resulted in the formation of martite-goethite ore. The hard laminated ore has been formed in the second phase of supergene processes, where the deep burial upgrades the hydrous iron oxides to hematite. The massive ore is syngenetic in origin with BHJ. Soft laminated ores and biscuity ores were formed where further precipitation of iron was partial or absent.

  11. Analytical fingerprint for tantalum ores from African deposits

    NASA Astrophysics Data System (ADS)

    Melcher, F.; Graupner, T.; Sitnikova, M.; Oberthür, T.; Henjes-Kunst, F.; Gäbler, E.; Rantitsch, G.

    2009-04-01

    Kibaran age either show flat patterns for most tantalites, rising values from the LREE to the HREE, or trough-like patterns. Eu anomalies are strongly negative in columbite-tantalite from the Alto Ligonha Province in Mozambique, from the Namaqualand Province (Namibia, South Africa), and from Zimbabwe. Four main age populations of coltan deposits in Africa were revealed: (1) Archean (>2.5 Ga), (2) Paleoproterozoic (2.1-1.9 Ga), (3) early Neoproterozoic ("Kibaran", 1.0-0.9 Ga), and (4) late Neoproterozoic to early Paleozoic (Pan-African; ca. 0.6-0.4 Ga). Currently, we focus on the resolution of the fingerprinting system from region via ore province down to deposit scale, establishing a large and high-quality analytical data base, and developing fast-screening and low-cost methods. Analytical flow-charts and identification schemes for coltan ores will be presented at the Conference. The analytical results obtained so far indicate that a certification scheme including fingerprinting of sources of coltan ores is feasible. The methodology developed is capable to assist in the establishment of a control instrument in an envisaged certification of the production and trade chain of coltan.

  12. Characterization of U ore from a roll-front U deposit: Implications of dominant U-Ti mineral for ore genesis and post solution-mining U immobilization

    NASA Astrophysics Data System (ADS)

    Brown, S. T.; Basu, A.; Christensen, J. N.; Reimus, P. W.; Heikoop, J. M.; WoldeGabriel, G. W.; Hartmann, M.; DePaolo, D. J.

    2015-12-01

    Reductive immobilization of dissolved U(VI) is an important process that gives rise to roll-front U deposits as well as offers a remediation strategy after in situ recovery (ISR) mining of roll-fronts by oxidative dissolution of the U ore. About 25% of the global and over 90% of all U resources in the United States consist of roll-front deposits. Accordingly, ~50% of global U mining and almost all current U mining in the United States is ISR mining. Therefore, it is important to identify the U immobilization pathways for an improved understanding of the U ore genesis and postmining U(VI) remediation. Here, we characterize (XRD, XRF, SEM/EDS, QEMSCAN) the U ore from a roll-front U deposit and sediments downgradient of the ore from an ISR site at Rosita, TX, USA. The dominant U mineral in Rosita U ore is brannerite (nominally U4+Ti2O6, up to 0.032 wt%), followed by coffinite and U-oxides. The U mineralized sand is composed of quartz (41-53%), calcite (15-30%), plagioclase (11-19%), microcline (2-9%), clinoptilolite (0.5-7%) with minor amounts of pyrite/marcasite (2-7%) and clays/micas (1-4%), and very little organic C (<0.1%). Ore zone samples contain minor amounts (<2%) of hematite, V-oxides/V-Ti-Fe-oxides and sulfidized Fe-Ti oxides with variable Fe, Ti and S ratios locally hosting low levels of U. The dominant sulfide mineral is marcasite. We observe a complex relationship between U-Ti minerals and sulfide/silicate phases where U minerals occur as inclusions, irregularly developed veins or intergrowths. Except for the U concentrations, the downgradient sediments are compositionally similar to the ore and contain abundant smectite/illite (7-45%). The predominance of brannerite implies direct reduction of U(VI) on surfaces of reduced Fe-Ti oxides as a major ore-forming mechanism. Our results reveal an as yet unidentified mechanism of ore genesis that differs from the current model that presupposes the sulfidized Fe-Ti oxides as the main reductant of U

  13. Raman Spectroscopic Characterisation of Australian Banded Iron Formation and Iron Ore

    NASA Astrophysics Data System (ADS)

    Wells, M. A.; Ramanaidou, E. R.

    2012-04-01

    In Australia and world-wide over the past 5-10 years, declining reserves of premium, high-grade (>64% Fe), low-P bearing iron ore, have seen iron ore producers increase their utilisation of lower Fe-grade, higher P/Al/Si ore. In Australia, the channel iron deposits (CID), bedded iron deposits (BID) and, more recently, BIF-derived magnetite iron deposits (MID) have seen increased usage driven mainly by the increased demand from Chinese steel mills (Ramanaidou and Wells, 2011). Efficient exploitation and processing of these lower-grade iron ores requires a detailed understanding of their iron oxide and gangue mineralogy and geochemistry. The common Fe-bearing minerals (e.g., hematite, magnetite, goethite and kenomagnetite) in these deposits, as well as gangue minerals such as quartz and carbonates, are all strongly Raman active (e.g., de Faria et al., 1997). Their distinct Raman spectra enable them to be easily detected and mapped in situ in either unprepared material or samples prepared as polished blocks. In this paper, using representative examples of Australian CID ore, martite-goethite bedded iron deposit (BID) ore and banded iron formation (BIF) examined as polished blocks, we present a range of Raman spectra of the key iron ore minerals, and discuss how Raman spectroscopy can be applied to characterising iron ore mineralogy. Raman imaging micrographs, obtained using a StreamLine Plus Raman imaging system, clearly identified the main Fe-oxide and gangue components in the CID, BID and BIF samples when compared to optical micrographs. Raman analysis enabled the unequivocal identification of diamond in the CID ore as a contaminant from the polishing paste used to prepare the sample, and confirmed the presence of hematite in the BID ore in the form of martite, which can be morphologically similar to magnetite and, thus, difficult to otherwise distinguish. Image analysis of Raman mineral maps could be used to quantify mineral abundance based on the number of 'pixels

  14. Geological characteristics and ore-forming process of the gold deposits in the western Qinling region, China

    NASA Astrophysics Data System (ADS)

    Liu, Jiajun; Liu, Chonghao; Carranza, Emmanuel John M.; Li, Yujie; Mao, Zhihao; Wang, Jianping; Wang, Yinhong; Zhang, Jing; Zhai, Degao; Zhang, Huafeng; Shan, Liang; Zhu, Laimin; Lu, Rukui

    2015-05-01

    , changes of physico-chemical conditions resulted in fluid immiscibility that played a key role in gold and sulfide deposition. The geochemical and mineralogical characteristics of the Carlin-type deposits in the western Qinling region are similar to those in the Carlin trend, Nevada, USA. Gold deposits such as La'erma and Jinlongshan occur mostly in the southeastern margin of the western Qinling regionic region whereas some deposits occur in its eastern part. These deposits are hosted in slightly metamorphosed Cambrian to Triassic sedimentary rocks, showing structurally- and stratigraphically-controlled features. The deposits mainly contain submicroscopic and microscopic gold in arsenian pyrite and arsenopyrite, with characteristic ore-forming elements of Au-As-Sb-Ba. The ore-forming fluids are early-stocked formation water and later-recharged meteoric water. Meteoric water apparently evolved in ore-forming fluids by circulation, indicating the extensional setting, and led to the deposition of Au and other elements in cool reactive permeable rocks at shallow levels, forming the disseminated ores. Carlin-like gold deposits occur between the Shang-Dan suture and the Fengxian-Zhen'an fault. The host rocks are mainly sedimentary rocks that underwent reconstruction through reworking by structural metamorphism. These deposits are structurally controlled by brittle-ductile shear zone and occur adjacent to granitoid plutons. The most important characteristic that differ to the orogenic and Carlin-type gold deposits is the genetic relationship with the synchronous magmatism. Gold occurs mainly as microscopic gold. Pyrite and arsenian pyrite can be recognized as gold-bearing minerals. The ore-forming fluids are main magmatic water mixed with metamorphic and/or formation water. Similar to orogenic gold deposits, fluid immiscibility caused the deposition of gold Carlin-like gold deposits.

  15. Hybrid gravity survey to search for submarine ore deposit

    NASA Astrophysics Data System (ADS)

    Araya, A.; Kanazawa, T.; Fujimoto, H.; Shinohara, M.; Yamada, T.; Mochizuki, K.; Iizasa, K.; Ishihara, T.; Omika, S.

    2011-12-01

    Along with seismic surveys, gravity survey is a useful method to profile the underground density structure. We propose a hybrid gravity survey using gravimeters and gravity gradiometers to detect submarine ore deposits as density anomalies by towing the instruments using an AUV (Autonomous Underwater Vehicle) or an ROV (Remotely Operated Vehicle). Gravimeters measure the regional density structure below the seafloor, whereas gravity gradiometers are sensitive to localized mass distribution. A gravity gradiometer comprises two accelerometers arranged with a vertical separation, and a gravity gradient can be obtained from the acceleration difference. Compared to gravimeters, gravity gradiometers are insensitive to common disturbances such as parallel acceleration, thermal drift, and apparent gravity effect (Eötvös effect). We made two accelerometers using astatic pendulums, and obtained common acceleration reduction more than two orders of magnitude. With these pendulums of 500-mm separation, resolution of 7E (=7x10^{-9}(1/s^2)), enough to detect a typical ore deposit buried 50m below the seafloor, was evaluated. During measurements using a submersible mobile object, instrument orientation is required to be controlled to keep verticality and to reduce centrifugal force associated with rotation of the instrument. Using a gyro and a tiltmeter, angular rotation was shown to be controlled within 0.001deg/s which corresponds to 0.3E in effective gravity gradient due to the centrifugal force. In this paper, target of this research, details of the instruments and their performance, and development for the submarine gravity survey using an AUV will be presented.

  16. Palaeoproterozoic metavolcanic and metasedimentary succession hosting the Dannemora iron ore deposits, Bergslagen region, Sweden

    NASA Astrophysics Data System (ADS)

    Dahlin, P.

    2012-04-01

    The Dannemora inlier constitutes some of the best preserved primary structures and textures in the metavolcanic and metasedimentary rocks in the Bergslagen region. The aim for this study was to define and interpret the primary textures and deposition environment to obtain a better understanding of the palaeoenvironment in which the Dannemora iron ore deposit formed. In addition, the region has been subjected to at least two fold episodes therefore the establishment of stratigraphy and younging directions were crucial for structural interpretations. The Bergslagen region, located in the south-central Sweden, represents a back-arc setting active c. 1.9 Ga and consisted of numerous large calderas, that accommodated pyroclastic deposits of great thicknesses. The Dannemora inlier is composed of the supracrustal the Dannemora Formation, which is dominated by of metavolcanic rocks and subordinated by marble. The succession is 700-800 m and is divided into a lower and an upper member. The latter hosts the second largest iron ore deposit in the Bergslagen region. The ore is hosted by manganiferous skarn and dolomitic carbonate (marble) and is situated within uppermost part of the upper member positioned in an isoclinal syncline. From reflection seismic imaging and 3-D processing, the ore has been interpreted to reach depths of c. 2000 m. The presence of an anticline west of the ore bearing syncline is suggested by the geochemical similarities of rock units. Undisturbed layers of ash-siltstone with normal grading and fluid-escape structures, units of pyroclastic density currents and ash-fall in the eastern part of the Dannemora inlier indicate subaqueous deposition below wave base of the upper member. Reworking of the volcaniclastic deposits is evident in e.g. channels and cross-bedding, on the other hand, implies deposition above wave base of the upper member in the central part of Dannemora inlier. The thickness of the marble in the eastern part is c. 80 m and in the

  17. Paleomagnetic and mineral magnetic studies of zinc-lead ore deposits in the Metaline (Washington state, USA) and Midlands (Ireland) ore fields

    NASA Astrophysics Data System (ADS)

    Pannalal, Shanmugam Johari

    Carbonate-hosted Zn-Pb deposits of the Metaline (USA) and Irish Midlands (Ireland) ore fields exhibit features of both MVT and SEDER deposits, and therefore, play an important role in the debate over genetic models for MVT - SEDER deposits, including the structural controls on ore mineralization, syngenetic versus epigenetic models, and the origin and migration pathways for hydrothermal fluids. The genetic controversy arises largely because of the lack of direct dates on mineralization. Paleomagnetic analyses on samples of host rock and ore mineralization from 38 sites (400 specimens) in the Metaline Zn-Pb district, Washington (USA), using the known thermal history and the paleoarc method of paleomagnetic dating, indicate coeval postfolding magnetizations acquired during the Middle Jurassic (166+/-6 Ma), in the waning stages of the Nevadan Orogeny. The thermal (Th) and alternating field (AF) step demagnetization, saturation isothermal anaylses (SIRM), and artificial specimens' tests show that the characteristic remanent magnetizations (ChRM) is carried mostly by pseudosingle (PSD) to single domain (SD) pyrrhotite that records a primary chemical remanent magnetization (CRM) in ore and a secondary ChRM in host specimens. Furthermore, the paleomagnetic Middle Jurassic age suggests an epigenetic origin for ore formation of the Zn-Pb mineralization at the Pend Oreille Mine that coincides with the timing of cooling from the regional Nevadan orogenic heating episode. Paleomagnetic analyses of the least thermally affected (conodont alteration indices (CAI) of <3) Lower Carboniferous rocks at 18 sites (231 specimens) from Northern Ireland indicate posttilting ChRMs in magnetite and pyrrhotite that record a secondary CRM that was acquired ˜3 to 4 Ma after limestone deposition. Also, paleomagnetic analyses of host rock and ore specimens in 46 sites (705 specimens) from the Galmoy and Lisheen Zn-Pb deposits from the Irish Midlands give stable postfolding ChRM, that reside in

  18. The Role of Groundwater Flow and Faulting on Hydrothermal Ore Formation in Sedimentary Basins

    NASA Astrophysics Data System (ADS)

    Garven, G.

    2006-05-01

    Sediment-hosted ore formation is thought to occur as a normal outcome of basin evolution, due to deep groundwater flow, heat transport, and reactive mass transport ---all of which are intimately coupled. This paper reviews recent attempts to understand the hydrologic and geochemical processes forming some of the world's largest sediment-hosted ores. Several questions still dominate the literature (driving forces for flows, source and controls on metal acquisition, concentrations of ore-forming components, timing and duration, role of faults, effects of transient flows). This paper touches upon all of these questions. Coupled reactive transport models have been applied for understanding the genesis of sandstone-hosted uranium ores of North America and Australia, red-bed copper ores of North America and northern Europe, carbonate-hosted MVT lead-zinc ores of the U.S. Midcontinent and northwestern Canada, and the carbonate- hosted lead-zinc ores of Ireland and southeast France. Good progress has been made in using these computational methods for comparing and contrasting both carbonate hosted (MVT and Irish types) and shale- hosted (SEDEX type) Pb-Zn deposits. The former are mostly associated with undeformed carbonate platforms associated with distal orogenic belts and the later are mostly associated with extensional basins and failed rifts that are heavily faulted. Two giant ore provinces in extensional basins provide good examples of structural control on reactive mass transport: shale-hosted Pb-Zn ores of the Proterozoic McArthur basin, Australia, and shale-hosted Pb-Zn-Ba ores of the Paleozoic Kuna basin, Alaska. For the McArthur basin, hydrogeologic simulations of thermally-driven free convection suggest a strong structural control on fluid flow created by the north-trending fault systems that dominate this Proterozoic extensional basin. Brines appear to have descended to depths of a few kilometers along the western side of the basin, migrated laterally to the

  19. Geodynamically unusual settings of sedimentary rock and ore formation due to tectonic-decompression effects

    SciTech Connect

    Goryainov, P.M.

    1984-05-01

    The traditional views of terrigenous rocks as products of classical sedimentary cycle, ''mobilization-transport-deposition,'' are not universal. Detrital rocks are sometimes formed due to flaking and fracturation of rocks of rising blocks. The process is produced by tectonic-decompression mechanisms - the origination of a gradient of excessive stress and its discharge. It is incorrect to classify rocks created by this phenomenon with weathering crusts. The origins of certain terrigenous rocks, as well as products of low-temperature chemical processing, are connected with deep-volume decompression (brecciation, stockwork formation, formation of pipes and columns of igneous rocks, and chamber pegmatite and karst formation). The ore concentrations associated with such entities and appearing as stratiform deposits are most likely not exogenous, but they complete the endogenous history of the block concerned. The means and methods tested on typical endogenous deposits may therefore prove valuable in predicting certain varieties of stratiform deposits.

  20. Ore-fluid evolution at the Getchell Carlin-type gold deposit, Nevada, USA

    USGS Publications Warehouse

    Cline, J.S.; Hofstra, A.A.

    2000-01-01

    Minerals and fluid-inclusion populations were examined using petrography, microthermometry, quadrupole mass-spectrometer gas analyses and stable-isotope studies to characterize fluids responsible for gold mineralization at the Getchell Carlin-type gold deposit. The gold-ore assemblage at Getchell is superimposed on quartz-pyrite vein mineralization associated with a Late-Cretaceous granodiorite stock that intruded Lower-Paleozoic sedimentary rocks. The ore assemblage, of mid-Tertiary age, consists of disseminated arsenian pyrite that contains submicrometer gold, jasperoid quartz, and later fluorite and orpiment that fill fractures and vugs. Late ore-stage realgar and calcite enclose ore-stage minerals. Pre-ore quartz trapped fluids with a wide range of salinities (1 to 21 wt.% NaCl equivalent), gas compositions (H2O, CO2, and CH4), and temperatures (120 to >360??C). Oxygen- and hydrogen-isotope ratios indicate that pre-ore fluids likely had a magmatic source, and were associated with intrusion of the granodiorite stock and related dikes. Ore-stage jasperoid contains moderate salinity, aqueous fluid inclusions trapped at 180 to 220??C. Ore fluids contain minor CO2 and trace H2S that allowed the fluid to react with limestone host rocks and transport gold, respectively. Aqueous inclusions in fluorite indicate that fluid temperatures declined to ~175??C by the end of ore-stage mineralization. As the hydrothermal system collapsed, fluid temperatures declined to 155 to 115??C and realgar and calcite precipitated. Inclusion fluids in ore-stage minerals have high ??D(H2O) and ??18O(H2O) values that indicate that the fluid had a deep source, and had a metamorphic or magmatic origin, or both. Late ore-stage fluids extend to lower ??D(H2O) values, and have a wider range of ??18O(H2O) values suggesting dilution by variably exchanged meteoric waters. Results show that deeply sourced ore fluids rose along the Getchell fault system, where they dissolved carbonate wall rocks and

  1. The mechanism of formation of the seafloor massive sulfide ore body beneath the seafloor at HAKUREI Site in Izena Caldera, Middle Okinawa Trough

    NASA Astrophysics Data System (ADS)

    Yoshizumi, R.; Urabe, T.

    2012-12-01

    dominant at lower of the ore, relatively. The existence of "Black ore (sphalerite-galena ore)" at upper part and "Yellow ore (chalcopyrite-pyrite ore)" at lower part of the Lower ore indicate that the SMS ore beneath the seafloor has already the characteristic mineral assemblage of Kuroko ore deposit at the time of formation. Fe content in Sphalerite is over 6wt% in the Upper ore and under 1wt% in the Lower ore, respectively, which shows that the Lower ore is formed under high Sulfur and Oxygen fugacity than Upper ore if the temperature of formation is not very different each other. Barite occurs not only in the Upper ore, but also in the Lower ore and the crystal size becomes coarser downwards. These lines of evidence imply that the existence of the Lower ore indicates that the mineralization has been repeated in the HAKUREI site. This study is a part of "TAIGA" project funded by Grant-in-Aid program by Monbusho.t; t;

  2. Monzonitoid magmatism of the Glukhoe gold ore deposit (Primorye): U-Pb, SHRIMP dating, petrochemical and minor-element compositions, and peculiar features of noble metal mineralization

    NASA Astrophysics Data System (ADS)

    Sakhno, V. G.; Kovalenko, S. V.; Barinov, N. N.; Lyzganov, A. V.; Kuznetsov, Yu. A.

    2015-11-01

    Monzogabbrodiorites and monzodiorites from the Tatibin Group of Central Sikhote Alin (Primorye), which hosts the Glukhoe gold ore deposit, are considered with discussion of the most important data on the geological structure and composition of magmatic complexes and the results of U-Pb and SHRIMP dating. It is first established that mineral associations of the gold ore deposit include native Pt, Cu, and other compounds and mineral associations. Their formation conditions of both scientific and practical significance are analyzed.

  3. Modeling the formation of porphyry-copper ores

    USGS Publications Warehouse

    Ingebritsen, Steven E.

    2012-01-01

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

  4. Sulfur- and carbon-isotope composition of the ores and rocks of the lead-zinc deposits of the Sardana ore node (Southeastern Yakutia)

    SciTech Connect

    Grinenko, L.N.; Zairi, N.M.; Ponomarev, V.G.; Ruchkin, G.V.; Tychinskii, A.A.

    1980-10-01

    Variations in sulfur isotopes from the sulfides of ores and rocks, and also carbon isotopes of the carbonate rocks of the Sardana ore node were examined. The deposition of the ores probably took place from solutions (brines of subsurface waters), heated in the thermal field of dikes and rising along fault zones. During the reduction of the oxidized forms of sulfur and transportation of the ore-forming elements, carbon dioxide gases, associated with petroleum occurrences, played a probable role.

  5. The Granites gold deposits, Northern Territory, Australia: evidence for an early syn-tectonic ore genesis

    NASA Astrophysics Data System (ADS)

    Adams, G. J.; Both, R. A.; James, P.

    2007-01-01

    The ore deposits of The Granites goldfield are shear-hosted within Palaeoproterozoic amphibolite facies metasedimentary rocks in the Tanami Region, Northern Territory, Australia. The ore bodies are located within a 5- to 35-m thick sequence of steeply dipping unit of metamorphosed iron-rich metasedimentary rocks. Deformation at The Granites was complex and is characterized by five successive deformation phases (D1-5). Shear veins (central and oblique) are the dominant type of vein geometry, with minor development of extensional veins and reverse-fault related veins. Four generations of syn-tectonic veins, corresponding to D1, D3, D4, and D5, have been recognized and are comprised of quartz, quartz-carbonate, calc-silicate, and calcite. In addition, two generations of disseminated sulfide-arsenide mineralization, dominated by pyrrhotite, arsenopyrite, and loellingite, with minor pyrite, chalcopyrite and rare marcasite, formed syn-D1 and syn- to post-D3. Textural and structural evidence indicates deposition of gold was contemporaneous with the syn-D1 veins and sulfide-arsenide mineralization. Four hydrothermal phases are proposed for the formation of the veins and disseminated sulfide-arsenide assemblages. The first phase (D1) was responsible for transport and deposition of the majority of the gold. Minor remobilization and deposition of gold occurred during the D3 and D4 phases. Little is known about the nature of the D1 ore fluid, although a relatively low sulfur content is indicated by the assemblage pyrrhotite-arsenopyrite-loellingite+rare pyrite. The growth of amphibolite facies metamorphic minerals andalusite and almandine garnet during D1 indicates a high temperature for the fluid. The D3 hydrothermal phase coincided with peak metamorphism. D4 fluids were hypersaline, high temperature, CO2-poor, and H2S-poor.

  6. Age of uranium ores at Ranger and Jabiluka unconformity vein deposits, Northern Territory, Australia

    SciTech Connect

    Ludwig, K.R.; Grauch, R.I.; Nutt, C.J.; Frishman, D.; Nash, J.T.; Simmons, K.R.

    1985-01-01

    The Ranger and Jabiluka uranium deposits are the largest in the Alligator Rivers Uranium Field (ARUF), which contains at least 20% of the world's low-cost uranium reserves. Ore occurs in early Proterozoic metasediments, below an unconformity with sandstones of the 1.65 Ga Kombolgie Formation. This study uses U-Pb isotope data from over 60 whole-rock drill core samples that contained a variety of mineral assemblages and textures. Data for Ranger samples indicate a well-defined age of 1.74 +/-.02 Ga. This 1.74 Ga age is distinctly pre-Kombolgie, so the Ranger deposit cannot have been formed by processes requiring its presence. This Ranger age is consistent, however, with mineralization related to heating associated with either the emplacement of early post-metamorphic granites, or possibly with intrusion of the nearby Oenpelli Dolerite. In contrast, data for the least-altered Jabiluka ores yield a concordia-intercept age of 1.44 +/-.02 Ga--significantly younger than the Ranger age, and also younger than the Komobolgie. This age may correspond to a regional thermal event, as indicated both by mafic dikes of roughly this age and a zircon lower-intercept age from a nearby granite-gneiss. Thus, together with the well-defined approx.900 Ma age of ores at the Nabarlek deposit, there are at least 3 distinct periods of major U-mineralization in the ARUF. Data for both Ranger and Jabiluka indicate the same, profound isotopic disturbance at some time in the interval of 0.4-0.6 Ga. Possibly this time corresponds to the development of basins and associated basalt flows to the W and SW, a suggested by Crick et. al. (1980).

  7. Localization conditions and ore mineralogy of the Ulziit hydrogenic uranium deposit, Mongolia

    NASA Astrophysics Data System (ADS)

    Grechukhin, M. N.; Doinikova, O. A.; Ignatov, P. A.; Rassulov, V. A.

    2016-05-01

    Information on the speciation of uranium minerals in ore of the recently discovered Ulziit uranium deposit in Mongolia is given for the first time. The ore composition has been studied by analytical scanning electron microscopy and local laser luminescent spectroscopy. The ore formed as a result of epigenetic redox processes. Transition from permeable variegated fan sediments to poorly permeable gray-colored coalbearing lacustrine-boggy sediments is the main ore-controlling factor. High-tech uranium mining with borehole in-situ leaching is feasible.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  9. Rock-magnetism and ore microscopy of the magnetite-apatite ore deposit from Cerro de Mercado, Mexico

    NASA Astrophysics Data System (ADS)

    Alva-Valdivia, L. M.; Goguitchaichvili, A.; Urrutia-Fucugauchi, J.; Caballero-Miranda, C.; Vivallo, W.

    2001-03-01

    Rock-magnetic and microscopic studies of the iron ores and associated igneous rocks in the Cerro de Mercado, Mexico, were carried out to determine the magnetic mineralogy and origin of natural remanent magnetization (NRM), related to the thermo-chemical processes due to hydrothermalism. Chemical remanent magnetization (CRM) seems to be present in most of investigated ore and wall rock samples, replacing completely or partially an original thermoremanent magnetization (TRM). Magnetite (or Ti-poor titanomagnetite) and hematite are commonly found in the ores. Although hematite may carry a stable CRM, no secondary components are detected above 580°, which probably attests that oxidation occurred soon enough after the extrusion and cooling of the ore-bearing magma. NRM polarities for most of the studied units are reverse. There is some scatter in the cleaned remanence directions of the ores, which may result from physical movement of the ores during faulting or mining, or from perturbation of the ambient field during remanence acquisition by inhomogeneous internal fields within these strongly magnetic ore deposits. The microscopy study under reflected light shows that the magnetic carriers are mainly titanomagnetite, with significant amounts of ilmenite-hematite minerals, and goethite-limonite resulting from alteration processes. Magmatic titanomagnetites, which are found in igneous rocks, show trellis, sandwich, and composite textures, which are compatible with high temperature (deuteric) oxy-exsolution processes. Hydrothermal alteration in ore deposits is mainly indicated by martitization in oxide minerals. Grain sizes range from a few microns to >100 mm, and possible magnetic state from single to multidomain, in agreement with hysteresis measurements. Thermal spectra, continuous susceptibility measurements, and IRM (isothermal remanent magnetization) acquisition suggest a predominance of spinels as magnetic carriers, most probably titanomagnetites with low

  10. Relations between ore deposits and granites resulting from low degree of melting of the continental crust

    NASA Astrophysics Data System (ADS)

    Cuney, Michel

    2015-04-01

    Ore deposits present three major types of relations with granites: syn-magmatic mineralization disseminated in the granites themselves (such as rare metal granites or pegmatites), magmatic-hydrothermal mineralization occurring as veins within the granites or in enclosing rocks (such as porphyry type deposits), and deposits generated by hydrothermal fluids of variable origin and occurring within the granites or their vicinity soon or much later than granite emplacement (such as vein-type uranium deposits). Besides this diversity of relations between granites and mineral deposits there is also a large diversity of magma types which may in relation with mineral deposits. We will focus our contribution on magmas produced by moderate degree of partial melting within the continental crust leading to the formation of anatectic pegmatoids for very low rate of partial melting and peraluminous leucogranites for low rate of partial melting. The major processes controlling the solubility of the metals in these magmas will be reviewed. The role of metal enrichment: (i) in the sources lithologies, (ii) as external input by fluids liberated during granulitisation of metasediments by a carbonic wave, (iii) extraction from enclosing metamorphic rocks, will be discussed.

  11. Alunite in the Pascua-Lama high-sulfidation deposit: Constraints on alteration and ore deposition using stable isotope geochemistry

    USGS Publications Warehouse

    Deyell, C.L.; Leonardson, R.; Rye, R.O.; Thompson, J.F.H.; Bissig, T.; Cooke, D.R.

    2005-01-01

    the deposit and probably formed from oxidation of H2S during boiling of the magmatic ore fluids. Coarsely crystalline magmatic steam alunite (8.4 Ma) is restricted to the near-surface portion of Brecha Central. Postmineral alunite ?? jarosite were previosly interpreted to be supergene crosscutting veins and overgrowths, although stable isotope data suggest a mixed magmatic-meteoric origin for this late-stage alteration. Only late jarosite veinlets (8.0 Ma) associated with fine-grained pseudocubic alunite have a supergene isotopic signature. The predominanca of magmatic fluids recorded throughout the paragenesis of the Pascua system is atypical for high-sulfidation deposits, which typically envolve significant meteoric water in near-surface and peripheral alteration and, in some systems, even ore deposition. A Pascua, the strong magmatic signature of both alteration and main-stage (alunite-pyrite-enargite assemblage) ore is attributed to limited availability of meteoric fluids. This is in agreement with published data for the El Indio-Pascua belt, indicating an event of uplift and subsequent pediment incision, as well as a transition from semiarid to arid climatic conditions, during the formation of the deposit in the mid to late Miocene. ?? 2005 Society of Economic Geologists, Inc.

  12. First native silica findings in bismuth from garnet skarns of Ribny Log - 2 gold ore target in Topolninsk ore deposit (Gorny Altai)

    NASA Astrophysics Data System (ADS)

    Cherkasova, T.; Timkin, T.; Savinova, O.

    2015-02-01

    The nanomineralogic investigation results of ore minerals in metasomatites (garnet skarns) of Ribny Log- 2 gold ore in Topolninsk ore deposit (Gorny Altai) revealed the native silica impurities (Si) of 1 - 5 nm within the grains of native bismuth (Bi). Polished sections were examined by using Tescan Vega 3 scanning electron microscope (SEM) with Oxford energy-dispersive spectrometer at the Department of Geology and Mineral Exploration, Institute of Natural Resources, Tomsk Polytechnic University.

  13. Environmental Mineralogy of the Kursk Iron Ore Deposit

    NASA Astrophysics Data System (ADS)

    Posukhova, Tatiana V.; Riakhovskaya, Sofiya K.

    The development of new technologies is one of the most effective ways to solve environmental problems related to ore-dressing. Complex mineralogical investigations are able to help in improving this process. In collaboration with researchers from the IPKON institute, we have developed an electrochemical method to improve the properties of crushed ores prepared for the wet magnetic separation. This article studies the samples before and after application of the electrochemical method. Surfaces of mineral grains investigated by the scanning electron microscopy show differences in flocculation. Measured polarization curves showed unequal electrochemical processes on surfaces of magnetite, hematite, and martite particles. X-ray analysis and Mössbauer data also confirmed the changes in compositions of the ores before and after using the electrochemical method. Magnetic properties of the studied species to be compared before and after the application of method showed relevant increase in parameters such as magnetic viscosity (Svo), breaking saturation field (Hcr), magnetic susceptibility (χ), and specific magnetization (Is).

  14. Mineral-petrochemical wallrock alteration of rocks in Bericul gold-ore deposit (Kuznetsk Alatau)

    NASA Astrophysics Data System (ADS)

    Kucherenko, I.; Yuxuan, Zhang; Abramova, R.

    2015-11-01

    The distribution of mineral associations in near-veined zonal propylite-beresite metasomatic columns of mesothermal Bericul gold-ore deposit was analyzed. However, the polymineral composition in the inner (axial and adjacent with it rear) zones is inconsistent to the existing metasomatic column theoretical model. According to Korzhinskii metasomatic zoning theory, implied monomineral (quartz) and binary-mineral (quartz, sericite) compositions are characteristic of axial and rear zones, respectively. In common with above- mentioned facts, the zoning formation of differential component mobility is influenced by two additional factors: counter diffusion of components from fractured fluids into pores and diffusion mechanism of mass transfer it's from pores fluids into fractured of rock-fluid systems.

  15. Geochemical constraints on the origin of the Kicking Horse and Monarch Mississippi Valley-type lead-zinc ore deposits, southeast British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Vandeginste, Veerle; Swennen, Rudy; Gleeson, Sarah A.; Ellam, Rob M.; Osadetz, Kirk; Roure, François

    2007-11-01

    Two Mississippi Valley-type (MVT) ore deposits, Kicking Horse and Monarch, have been studied with the aim of comparing the ores at the two localities and to characterize the origin of the mineralizing fluids and the ore formation process(es). Both deposits are hosted by the Middle Cambrian Cathedral Formation carbonate host rocks, Kicking Horse on the north and Monarch on the south flank of the Kicking Horse valley near Field (SE British Columbia). The ore bodies are situated at the transition of (western) basinal to (eastern) shallow-water strata of the paleo-Pacific passive margin succession in the Cordilleran Foreland Province of the Western Canada Sedimentary Basin. Both deposits are related spatially to normal faults. In both localities, the ore minerals are dominated by pyrite, sphalerite, and galena. Dolomite, minor quartz, and calcite are also present in close association with the ores. The salinity (21-30 wt% NaCl eq.) and homogenization temperatures (63-182°C) measured in fluid inclusions in carbonate, quartz, and sphalerite lie within the typical range of MVT fluid conditions. The good stoichiometry (50-53 mol% CaCO3), low δ18O values (-21 to -14‰ Vienna Peedee belemnite) and relatively high homogenization temperatures (>95°C) of the dolomite suggest the dolomites were formed under burial diagenesis. The ore-forming fluids probably interacted with siliciclastic units, based on elevated Li contents and 87Sr/86Sr ratios, which are highest in the dolomite type after the main ore stage. We propose that the ores formed from the mixing of a downward-infiltrating, sulfur-bearing halite-dissolution fluid with an upward-migrating, metal-rich evaporated seawater fluid, which had already undergone minor mixing with a dilute fluid.

  16. Geology and ore deposits of the Monument Valley area, Apache and Navajo counties, Arizona: Part II

    USGS Publications Warehouse

    Witkind, I.J.; Thaden, R.E.

    1958-01-01

    In 1951 and 1952, the U.S. Geological Survey conducted a program of uranium investigations and geologic mapping in the Monument Valley area, Apache and Navajo Counties, Ariz. About 700 square miles were mapped on the Navajo Indian Reservation. A resource appraisal of the area was an inherent part of the program, and is detailed in this report. Production of vanadium and uranium is from two areas, the Monument No. 1 mine area in Navajo County, and the Monument No. 2 mine area in Apache County. In the period 1942-53 about 200,300 tons of ore was produced from these two areas. This ore yielded about 1,700,000 pounds of U3O8 and about 6,500,000 pounds of V2O5. The grade ranged from 0.15 percent U3O8 to 0.60 percent U3O8, and from 0.38 percent V2O5 to 3.02 percent V2O5. The vanadium-uranium ratio is about 4:1. The ore deposits are composed principally of the hydrous calcium-uranium vanadate tyuyamunite in basal channel sediments of the Shinarump member off the Chinle formation. Four types of ore bodies are present: (1) rods, (2) tabular ore bodies, (3) corvusite-type ore bodies, and (4) rolls. The reserves of uranium- and vanadium-bearing material are classed as measured, indicated, inferred, and potential. The reserves are further divided into three grade classes for material 1 foot or more thick: (1) 0.10 percent U3O8 and 1.00 percent V2O5 and above; (2) 0.05 percent U3O8 and 0.50 percent V2O5 and less than 0.10 percent U3O8 and 1.00 percent V2O5; and (3) 0.01 percent U3O8 and 0.10 percent V2O5 and less than 0.05 percent U3O8 and 0.05 percent V2O5. Measured reserves as of June 1953, in the Monument Valley area, Arizona, (all in the Monument No. 2 mine) total about 36,000 tons. Indicated reserves in the first grade class amount to about 62,000 tons. In this same grade class inferred reserves total about 3,000,000 tons. In the second grade class indicated and inferred reserves amount to about 2,000,000 tons. Inferred reserves in the third grade class total about 345

  17. Variations in the uranium isotopic compositions of uranium ores from different types of uranium deposits

    NASA Astrophysics Data System (ADS)

    Uvarova, Yulia A.; Kyser, T. Kurt; Geagea, Majdi Lahd; Chipley, Don

    2014-12-01

    precipitation in the form of U6+ minerals. The δ238U values of uranium ore minerals from a variety of deposits are controlled by the isotopic signature of the uranium source, the efficiency of uranium reduction in the case of UO2 systems, and the degree to which uranium was previously removed from the fluid, with less influence from temperature of ore formation and later alteration of the ore. Uranium isotopes are potentially superb tracers of redox in natural systems.

  18. Banded sulfide-magnetite ores of Mauk copper massive sulfide deposit, Central Urals: Composition and genesis

    NASA Astrophysics Data System (ADS)

    Safina, N. P.; Maslennikov, V. V.; Maslennikova, S. P.; Kotlyarov, V. A.; Danyushevsky, L. V.; Large, R. R.; Blinov, I. A.

    2015-05-01

    The results of investigation of metamorphosed sulfide-magnetite ores from the Mauk deposit located within the Main Ural Fault at the junction of Tagil and Magnitogorsk massive sulfide zones are discussed. The ore-hosting sequence comprises metamorphic rocks formed from basalt, carbonaceous and carbonaceous-cherty siltstone, and lenticular serpentinized ultramafic bodies. The ores of the deposit are represented by banded varieties and less frequent breccia. The clastic origin of the banded ore is indicated by load casts at the bottom of sulfide beds, alternation of sulfide and barren beds, and the truncation of the growth zones of pyrite crystals. Pyrite, pyrrhotite, chalcopyrite, sphalerite, and magnetite are the major minerals of the banded ores. The internal structure of the listed minerals testifies to the deep metamorphic recrystallization of primary hydrothermal-sedimentary ores accompanied with deformation. Cubanite, pyrrhotite, mackinawite, greigite, and gold are enclosed in metacrysts of pyrite, magnetite, and chalcopyrite. The accessory minerals of the Pb-Bi-Te, Bi-Te, and Ag-Te systems as well as uraninite have been found at the Mauk deposit for the first time. Magnetite predominantly replaces pyrite and less frequently chalcopyrite, pyrrhotite, and gangue minerals. It was established that the major carriers of As and Co are crystals of metamorphic pyrite. Chalcopyrite is the major carrier of Zn, Sn, Te, Pb, Bi, and Ag. Admixture of Fe and Cu is typical of sphalerite, and Se and Ni are characteristic of pyrrhotite. Ti, V, Mn, Sb, As, Ba, and U are concentrated in magnetite. The banded ores of the Mauk deposit are suggested as having been transformed in several stages: diagenesis, anadiagenesis, epidiagenesis ( t < 300°C), and amphibolite facies metamorphism ( t > 500°C).

  19. Massive deep-sea sulphide ore deposits discovered on the East Pacific Rise

    USGS Publications Warehouse

    Francheteau, Jean; Needham, H.D.; Choukroune, P.; Juteau, Tierre; Seguret, M.; Ballard, Richard D.; Fox, P.J.; Normark, William; Carranza, A.; Cordoba, D.; Guerrero, J.; Rangin, C.; Bougault, H.; Cambon, P.; Hekinian, R.

    1979-01-01

    Massive ore-grade zinc, copper and iron sulphide deposits have been found at the axis of the East Pacific Rise. Although their presence on the deep ocean-floor had been predicted there was no supporting observational evidence. The East Pacific Rise deposits represent a modern analogue of Cyprus-type sulphide ores associated with ophiolitic rocks on land. They contain at least 29% zinc metal and 6% metallic copper. Their discovery will provide a new focus for deep-sea exploration, leading to new assessments of the concentration of metals in the upper layers of the oceanic crust. ?? 1979 Nature Publishing Group.

  20. Geology and geochemistry of the Macheng Algoma-type banded iron-formation, North China Craton: Constraints on mineralization events and genesis of high-grade iron ores

    NASA Astrophysics Data System (ADS)

    Wu, Huaying; Niu, Xianglong; Zhang, Lianchang; Pirajno, Franco; Luo, Huabao; Qin, Feng; Cui, Minli; Wang, Changle; Qi, Min

    2015-12-01

    The Macheng iron deposit is located in the eastern Hebei province of the North China Craton (NCC). It is hosted in Neoarchean metamorphic rocks of Baimiaozi formation in the Dantazi Group, consisting of biotite-leptynite, plagioclase-gneiss, plagioclase-amphibolite, migmatite, migmatitic granite and quartz schist. Geochemical analyses of the host biotite leptynite and plagioclase amphibolites show that their protoliths are both volcanics, inferred to be trachytic basalt and basaltic andesite, respectively. Based on the geochemical signature of the host rocks, together with geology of the iron deposit, it is inferred that the Macheng BIF is an Algoma-type iron exhalative formation, formed in an arc-related basin in the Neoarchean. Post-Archean Australian Shale (PAAS)-normalized rare earth elements (REEs) plus yttrium (Y) concentrations of different BIF ores with gneissic, striated and banded structure in the Macheng deposit, show similar patterns with depletions in light rare earth elements (LREEs) and middle rare earth elements (MREEs) relative to heavy rare earth elements (HREEs) and with apparently positive La, Y and Eu anomalies. Y/Ho ratios of the gneissic, striated and banded BIF ores vary from 37 to 56. These geochemical features of the BIF ores reveal their affinity with the sea water and the presence of a high-temperature hydrothermal component, indicating that both the seawater and high temperature hydrothermal fluids derived from alteration of oceanic basalts and komatiites may contribute to formation of the Macheng BIF. Geological, mineralogical and geochemical studies of the Macheng deposit recognized two kinds of high-grade iron ores. One is massive oxidized high-grade ore (Fe2O3T = 74.37-86.20 wt.%), mainly consisting of hematite with some magnetite, which shows geochemical characteristics of the gneissic, striated and banded BIF ores. The other type is magnetite high-grade ore, also massive and consisting of magnetite, with distinct characteristics

  1. Mineralogy and fluid inclusions study of carbonate-hosted Mississippi valley-type Ain Allega Pb-Zn-Sr-Ba ore deposit, Northern Tunisia

    NASA Astrophysics Data System (ADS)

    Abidi, R.; Slim-Shimi, N.; Somarin, A.; Henchiri, M.

    2010-05-01

    The Ain Allega Pb-Zn-Sr-Ba ore deposit is located in the flysch zone on the Eastern edge of the Triassic diapir of Jebel Hamra. It is part of the extrusive Triassic evaporate formation along the Ghardimaou-Cape Serrat faults. The ore body consists of argilic-dolomite breccias surrounded by argilo-gypsum Triassic formation, which forms the hanging wall of the deposit, and rimmed by the Paleocene marls. The ore minerals show a cap-rock type mineralization with different styles particularly impregnation in dolomite, cement of breccias, replacement ore and open space filling in the dissolution cavities and fractures. Ore minerals include sphalerite, galena, marcasite and pyrite. Principal gangue minerals are composed of barite, celestite, calcite, dolomite and quartz. The ore minerals are hosted by the Triassic carbonate rocks which show hydrothermal alteration, dissolution and brecciation. X-ray - crystallographic study of barite-celestite mineral series shows that pure barite and celestite are the abundant species, whereas strontianiferous barite (85-96.5% BaSO 4) and barian-celestite (95% SrSO 4) are minor. Primary and secondary mono-phase (liquid only) fluid inclusions are common in celestite. Microthermometric analyses in two-phases (liquid and vapour) fluid inclusions suggest that gangue and ore minerals were precipitated by a low-temperature (180 °C) saline (16.37 wt.% NaCl equivalent) solution originated possibly from a basinal brine with some input from magmatic or metamorphic fluid. Based on geology, mineralogy, texture and fluid characteristics, the Ain Allega deposit is classified as a carbonate-hosted Mississippi valley-type deposit.

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

    PubMed

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

    2002-06-01

    Microanalysis of major and trace elements in sulfide and silicate melt inclusions by laser-ablation inductively coupled plasma mass spectrometry indicates a direct link between a magmatic sulfide liquid and the composition of porphyry-type ore deposits. Copper (Cu), gold (Au), and iron (Fe) are first concentrated in a sulfide melt during magmatic evolution and then released to an ore-forming hydrothermal fluid exsolved late in the history of a magma chamber. The composition of sulfide liquids depends on the initial composition and source of the magma, but it also changes during the evolution of the magma in the crust. Magmatic sulfide melts may exert the dominant direct control on the economic metal ratios of porphyry-type ore deposits. PMID:12052953

  3. Study of ore deposits by the dynamic systems investigation methods: 1. Calculation of the correlation dimension

    NASA Astrophysics Data System (ADS)

    Rodkin, M. V.; Shatakhtsyan, A. R.

    2015-05-01

    The method for calculating the fractal correlation dimension is applied for analyzing the data on the locations of large and extralarge ore deposits. The approach implemented in this study differs by a few of important points from that commonly used, e.g., in the calculations of the correlation dimension for a set of the epicenters (hypocenters) of the earthquakes. Firstly, we demonstrate the possibility and advisability of obtaining different dimension estimates for different spatial scales. Such a separation turned out to be useful in distinguishing between the regularities in the location of ore deposits on the scale of an ore cluster, ore province, and entire continent. Secondly, we introduce a new notion, a mixed correlation dimension, and use it for different types of the objects (e.g., Au and Ag). The standard formula for calculating the correlation dimension is trivially generalized on this case. It is shown that the values of the correlation dimension can be lower and higher than the dimension of the hosting medium. The cases when the correlation dimension is higher than that of the hosting medium are interpreted as a "mutual repulsion" of the deposits of the two mentioned types. In contrast, the small correlation dimensions indicate that the deposits of the corresponding types tend to have spatially close locations. The calculations are conducted for the spherical Earth. The method is applied to the data on the large and extralarge world-class ore deposits from the Largest Mineral Deposits of the World (LMDs) geoinformation system (GIS). Different patterns of the studied behavior are illustrated by the model examples.

  4. High-grade iron ore deposits of the Mesabi Range, Minnesota-product of a continental-scale proterozoic ground-water flow system

    USGS Publications Warehouse

    Morey, G.B.

    1999-01-01

    The Mesabi Range along the north edge of the Paleoproterozoic Penokean orogen in northern Minnesota has produced 3.6 billion metric tons of ore since its discovery in 1890. Of that amount, 2.3 billion metric tons were extracted from hematite- or geothite-rich deposits generally referred to as 'high-grade' ores. The high-grade ores formed as the Biwabik Iron-Formation was oxidized, hydrated, and leached by solutions flowing along open faults and fractures. The source of the ore-forming solutions has been debated since it was first proposed that the ores were weathering products formed by descending meteoritic ground-water flowing in late Mesozoic time. Subsequently others believed that the ores were better explained by ascending solutions, possbily hydrothermal solutions of pre-Phanerzoic age. Neither Wolff nor Gruner could reconcile their observations with a reasonable source for the solutions. In this paper, I build on modern mapping of the Mesabi Range and mine-specific geologic observations summarized in the literature to propose a conceptual model in which the high-grade ores formed from ascending solutions that were part of continent-scale topographic or gravity-driven ground-water system. I propose that the ground-water system was active during the later stages of the development of a coupled fold and thrust belt and foreland basin that formed during the Penokean orogen.

  5. Ore-forming processes in the Drazhnoe gold-quartz deposit (Eastern Yakutia, Russia)

    NASA Astrophysics Data System (ADS)

    Aristov, V. V.; Prokofiev, V. Yu.; Imamendinov, B. N.; Kryazhev, S. G.; Alekseev, V. Yu.; Sidorov, A. A.

    2015-09-01

    Themobarogeochemical investigations revealed that quartz from the Drazhnoe deposit was formed in mesothermal conditions at depths of 3-4 km from carbon dioxide-water fluids with wide salinity variations and an admixture of methane. Several types of fluids are distinguishable on the basis of the composition of extracts: hydrocarbonate-sodium, highly diluted, and late sulfate-hydrocarbonate-sodium with elevated salinity. Ore minerals precipitated in the thermostatic environments against the background of fluid heterogenization due to a probably significant pressure drop and mixing of different solutions. Metamorphic processes related to the early collision stage provided no substantial impact on the composition and potential of gold ore mineralization.

  6. Bio-mineralization and potential biogeochemical processes in bauxite deposits: genetic and ore quality significance

    NASA Astrophysics Data System (ADS)

    Laskou, Magdalini; Economou-Eliopoulos, Maria

    2013-08-01

    The Parnassos-Ghiona bauxite deposit in Greece of karst type is the 11th largest bauxite producer in the world. The mineralogical, major and trace-element contents and δ18O, δ12C, δ34S isotopic compositions of bauxite ores from this deposit and associated limestone provide valuable evidence for their origin and biogeochemical processes resulting in the beneficiation of low grade bauxite ores. The organic matter as thin coal layers, overlying the bauxite deposits, within limestone itself (negative δ12C isotopic values) and the negative δ34S values in sulfides within bauxite ores point to the existence of the appropriate circumstances for Fe bio-leaching and bio-mineralization. Furthermore, a consortium of microorganisms of varying morphological forms (filament-like and spherical to lenticular at an average size of 2 μm), either as fossils or presently living and producing enzymes, is a powerful factor to catalyze the redox reactions, expedite the rates of metal extraction and provide alternative pathways for metal leaching processes resulting in the beneficiation of bauxite ore.

  7. Discrimination of iron ore deposits of granulite terrain of Southern Peninsular India using ASTER data

    NASA Astrophysics Data System (ADS)

    Rajendran, Sankaran; Thirunavukkarasu, A.; Balamurugan, G.; Shankar, K.

    2011-04-01

    This work describes a new image processing technique for discriminating iron ores (magnetite quartzite deposits) and associated lithology in high-grade granulite region of Salem, Southern Peninsular India using visible, near-infrared and short wave infrared reflectance data of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Image spectra show that the magnetite quartzite and associated lithology of garnetiferrous pyroxene granulite, hornblende biotite gneiss, amphibolite, dunite, and pegmatite have absorption features around spectral bands 1, 3, 5, and 7. ASTER band ratios ((1 + 3)/2, (3 + 5)/4, (5 + 7)/6) in RGB are constructed by summing the bands representing the shoulders of absorption features as a numerator, and the band located nearest the absorption feature as a denominator to map iron ores and band ratios ((2 + 4)/3, (5 + 7)/6, (7 + 9)/8) in RGB for associated lithology. The results show that ASTER band ratios ((1 + 3)/2, (3 + 5)/4, (5 + 7)/6) in a Red-Green-Blue (RGB) color combination identifies the iron ores much better than previously published ASTER band ratios analysis. A Principal Component Analysis (PCA) is applied to reduce redundant information in highly correlated bands. PCA (3, 2, and 1 for iron ores and 5, 4, 2 for granulite rock) in RGB enabled the discrimination between the iron ores and garnetiferrous pyroxene granulite rock. Thus, this image processing technique is very much suitable for discriminating the different types of rocks of granulite region. As outcome of the present work, the geology map of Salem region is provided based on the interpretation of ASTER image results and field verification work. It is recommended that the proposed methods have great potential for mapping of iron ores and associated lithology of granulite region with similar rock units of granulite regions of Southern Peninsular India. This work also demonstrates the ability of ASTER's to provide information on iron ores, which is valuable

  8. Lead and zinc dust depositions from ore trains characterised using lead isotopic compositions.

    PubMed

    Kristensen, L J; Taylor, M P; Morrison, A L

    2015-03-01

    This study investigates an unusual source of environmental lead contamination - the emission and deposition of lead and zinc concentrates along train lines into and out of Australia's oldest silver-lead-zinc mine at Broken Hill, Australia. Transport of lead and zinc ore concentrates from the Broken Hill mines has occurred for more than 125 years, during which time the majority was moved in uncovered rail wagons. A significant amount of ore was lost to the adjoining environments, resulting in soil immediately adjacent to train lines elevated with concentrations of lead (695 mg kg(-1)) and zinc (2230 mg kg(-1)). Concentrations of lead and zinc decreased away from the train line and also with depth shown in soil profiles. Lead isotopic compositions demonstrated the soil lead contained Broken Hill ore in increasing percentages closer to the train line, with up to 97% apportioned to the mined Broken Hill ore body. SEM examination showed ceiling dusts collected from houses along the train line were composed of unweathered galena particles, characteristic of the concentrate transported in the rail wagons. The loss of ore from the uncovered wagons has significantly extended the environmental footprint of contamination from local mining operations over an area extending hundreds of kilometres along each of the three train lines. PMID:25627173

  9. Evaluation of feasibility of static tests applied to Küre VMS ore deposits

    NASA Astrophysics Data System (ADS)

    Demirel, Cansu; Çelik Balci, Nurgül; Şeref Sönmez, M.

    2015-04-01

    Küre volcanogenic massive sulfide (VMS) ore deposits have been mined for its copper content for over centuries. However, there is no published data on AMD around Küre VMS ore deposits. This study investigates the sources of acid producing mechanisms in Küre, using field and laboratorial approaches. Geochemical static tests to predict AMD generation are widely applied to mining sites for assessing potential environmental consequences. However, there are well known limitations of these methods particularly resulting from assumptions used for calculations. To test the feasibility of the methods to predict potential of AMD generation of Küre (VMS) copper deposits, for the first time, acid production and neutralization potential of various mine wastes of Küre (VMS) copper deposits were determined. To test our static test results, in situ and laboratory geochemical data were also obtained from the groundwater discharges from Bakibaba underground mining tunnels. Feasibility study showed that, despite a few inconsistencies, static tests were suitable for predicting generation of AMD around Küre copper mining site and reflected well the site conditions. The current study revealed that pulp density, defined as solid/liquid ratio and used for static tests, is an important limiting factor to predict reliable data for AMD generation. In this study, we also determined surface waters affected by AMD are predicted to have a pH value between 3 and 5, with an average of pH 4. Excessive concentrations of manganese, copper, cobalt and sulfate are also noted with considerable amounts of iron and zinc, which can reach to toxic levels. Moreover, iron and zinc were found to be the controlling the fate of metals by precipitation and co-precipitation, due to their relatively depleted concentrations at redox shifting zones. Key words: Küre pyritic copper ore, Bakibaba mining tunnels, volcanogenic massive sulfide ore deposits, acid production potential, neutralization potential

  10. Regularities of spatial association of major endogenous uranium deposits and kimberlitic dykes in the uranium ore regions of the Ukrainian Shield

    NASA Astrophysics Data System (ADS)

    Kalashnyk, Anna

    2015-04-01

    During exploration works we discovered the spatial association and proximity time formation of kimberlite dykes (ages are 1,815 and 1,900 Ga for phlogopite) and major industrial uranium deposits in carbonate-sodium metasomatites (age of the main uranium ore of an albititic formation is 1,85-1,70 Ga according to U-Pb method) in Kirovogradsky, Krivorozhsky and Alekseevsko-Lysogorskiy uranium ore regions of the Ukrainian Shield (UkrSh) [1]. In kimberlites of Kirovogradsky ore region uranium content reaches 18-20 g/t. Carbon dioxide is a major component in the formation of hydrothermal uranium deposits and the formation of the sodium in the process of generating the spectrum of alkaline ultrabasic magmas in the range from picritic to kimberlite and this is the connection between these disparate geochemical processes. For industrial uranium deposits in carbonate-sodium metasomatitics of the Kirovogradsky and Krivorozhsky uranium ore regions are characteristic of uranyl carbonate introduction of uranium, which causes correlation between CO2 content and U in range of "poor - ordinary - rich" uranium ore. In productive areas of uranium-ore fields of the Kirovogradsky ore region for phlogopite-carbonate veinlets of uranium ore albitites deep δ13C values (from -7.9 to -6.9o/oo) are characteristic. Isotope-geochemical investigation of albitites from Novokonstantynovskoe, Dokuchaevskoe, Partyzanskoe uranium deposits allowed obtaining direct evidence of the involvement of mantle material during formation of uranium albitites in Kirovogradsky ore region [2]. Petrological characteristics of kimberlites from uranium ore regions of the UkrSh (presence of nodules of dunite and harzburgite garnet in kimberlites, diamonds of peridotite paragenesis, chemical composition of indicator minerals of kimberlite, in particular Gruzskoy areas pyropes (Cr2O3 = 6,1-7,1%, MgO = 19,33-20,01%, CaO = 4,14-4,38 %, the content of knorringite component of most grains > 50mol%), chromites (Cr2O3 = 45

  11. Geology and ore deposits of the Mahd Adh Dhahab District, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Luce, Robert W.; Bagdady, Abdulaziz; Roberts, Ralph Jackson

    1976-01-01

    The principal ore minerals are pyrite, chalcopyrite, sphalerite, galena, and minor tetrahedrite, argentite, and native gold and silver. The gold and silver occurs finely disseminated in the veins and in the altered selvages of the veins. Widespread potassic and propylitic alteration accompanied the ore-forming processes. Potassium feldspar was introduced during an early stage of vein formation. Isotopic analyses of lead in vein potassium feldspar and galena yield a model age of about 900-1050 million years with the possibility of the original lead source having been remobilized about 600 million years ago. Chlorite and carbonate are also prominent vein minerals.

  12. Mineralogical study of sediment-hosted gold deposits in the Yangshan ore field, Western Qinling Orogen, Central China

    NASA Astrophysics Data System (ADS)

    Liang, Jinlong; Sun, Weidong; Zhu, Sanyuan; Li, He; Liu, Yulong; Zhai, Wei

    2014-05-01

    The Yangshan gold ore field is located in the southern subzone of the Western Qinling Orogen. Mineralization is confined by the east-west-striking Anchanghe thrust fault zone. These subparallel faults constitute a branch of the regional Mianlue structural zone, crosscutting Middle Devonian carbonaceous carbonate and clastic rock sequences, an ore-bearing unit locally named the Sanhekou Formation. The metasedimentary clastic and carbonate rocks containing fine-grained sulfides are the main host rocks of the deposit, with minor mineralization occurring as coarse-grained pyrite-quartz veinlets in black shale and as dissemination in some plagiogranite dykes. Electron microprobe (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses show that arsenian pyrite and arsenopyrite are the major hosts for gold with tens of ppm up to weight percent levels of Au, and the Au contents in arsenopyrite are one order of magnitude higher than those in pyrite. A negative correlation of As and S in arsenian pyrite is consistent with the substitution of As for S in the mineral. Both arsenian pyrite and arsenopyrite in the Yangshan ore field show chemical zonations with middle parts (mantle) enriched in As and Au relative to cores and the outermost rims, reflecting the chemical evolution of ore-forming fluids. High resolution transmission electron microscopy (HRTEM) analysis failed to identify any nanoparticle of native gold even in the highest Au parts of arsenopyrite. This observation combined with the relatively homogenous distribution of Au, a positive correlation of As and Au, and Au/As ratios below the solubility limit of gold in arsenian pyrite and arsenopyrite, suggests that invisible gold is likely present as structurally bound Au+1 in sulfides, although our work cannot exclude the existence of Au nanoparticles in arsenian pyrite as identified in American Carlin-type gold deposits. Submicron native gold may be much more easily found in

  13. Paragenetic link between organic matter and late-stage ore deposition in the Sweetwater mine, Viburnum Trend, southeast Missouri

    SciTech Connect

    Niewendorp, C.A. ); Clendenin, C.W.

    1993-03-01

    At the Sweetwater mine bitumen exudes from mine walls as a tacky liquid and is present as spherical blebs in vugs throughout the Bonneterre Formation. Bitumen blebs occur as overgrowths on older mineral phases and are frequently over-grown by late vug-filling sulfides. Slickensided bitumen interlayered with deformed galena occurs in Middle Bonneterre Formation collapse breccias. Anthraxolite, a coal-like bitumen, has also been identified in these collapse breccias and is commonly overgrown by cubic-form galena in vugs. Petrographic examination, verified by SEM analysis, reveals inclusions of dendritic-form galena intimately intergrown in such anthraxolite samples; pyrite and chalcopyrite also occur as inclusions. The presence of sulfide inclusions in anthraxolite establishes a direct paragenetic link between organic matter and ore deposition. Generation of bituminous material appears to correspond to a major period of solution-induced brecciation during main-stage mineralization. Observations indicate that precipitation of dendritic-form galena in anthraxolite coincides with subsequent deposition of cubic-form galena. Such a paragenetic link supports the proposal that nonbiologic sulfate reduction by organic matter has occurred and is a precipitation mechanism for sulfide ores in the Viburnum Trend.

  14. Volcanic environments of ore formation in the late Archaean Abitibi greenstone belt of Canada

    SciTech Connect

    Ludden, J.N.

    1985-01-01

    The tectonic and petrological evolution of the late Archaean Abitibi greenstone belt indicate both emergent and submergent volcanism played a role in its metallogenesis. At approximately 2700 m.y. the southern volcanic zone (SVZ) of the Abitibi belt was dominated by a rift-related tectonic and volcanic evolution in a transcurrent (wrench) fault regime. The tholeiitic and komatiitic magmas and associated differentiated volcanic rocks had access to shallow crustal levels allowing the development of submarine hydrothermal systems and syngenetic Cu-Zn (Noranda type) massive sulfide ore bodies. These deposits formed along a 300 km. axis in submerging, fault bounded, basins. In contrast, the northern volcanic zone (the Chibougamau-Chapais area) formed at 2720 m.y and was characterized by emergent volcanoes emplaced on a continental crust and cored by coeval diorite-tonalite plutons. Mafic magma was inhibited from the crust by fractionated and contaminated magmas. This resulted in the emplacement of hydrous calc-alkaline magmas and associated porphyry-type epigenetic Cu(Au) massive sulfides. Au-lode deposits are predominantly located near major shear-zones in the SVZ. The are forming solutions were released as a result of burial due to wrench faulting. The dynamic regime of the rifted SVZ may have resulted in the syngenetic massive sulfides, the Au-lode deposits, metamorphism and sedimentation being synchronous on a regional scale, whilst on a local scale, Au-lodes superimpose and replace massive sulfides, iron formation and metamorphic isograds.

  15. Triggers for the formation of porphyry deposits in magmatic arcs

    NASA Astrophysics Data System (ADS)

    Wilkinson, Jamie

    2014-05-01

    Porphyry ore deposits source much of the copper, molybdenum, gold and silver utilized by humankind. They typically form in magmatic arcs above subduction zones via a series of linked processes, beginning with magma generation in the mantle and ending with the precipitation of metals from hydrous fluids in the shallow crust. In this review, a hierarchy of four key "triggers" involved in the formation of porphyry deposits is outlined. Trigger 1 (100-1000 km scale) is a process of cyclic refertilization and enrichment of magmas in metals and volatiles in deep crustal sills trapped for long time periods in compressional tectonic settings. Trigger 2 (10 to 100 km scale) is the process of sulphide saturation in magmas that can both enhance and destroy ore-forming potential by stripping chalcophile metals from silicate melts, but also, in this way, pre-concentrating them. Trigger 3 (1-10 km scale) relates to the efficient transfer of metals into hydrothermal fluids exsolving from porphyry magmas, in particular the potential role of melt reduction in enhancing melt-volatile partitioning. Trigger 4 (1-5 km scale) identifies processes that are currently thought to be critical for the efficient precipitation of ore minerals in the deposit environment. Although all processes are required to a greater or lesser degree, it is argued that trigger 2, as an over-riding mechanism, can best explain the restriction of large porphyry deposits, highly enriched in chalcophile metals and sulphur, to specific arc segments and time periods. Consequently, recognition of the fingerprint of sulphide saturation in igneous rocks may help mineral exploration companies to identify parts of magmatic arcs particularly predisposed to porphyry ore formation.

  16. Prospecting For Magnetite Ore Deposits With A Innovative Sensor's of Unique Fundamentally New Magnetometer.

    NASA Astrophysics Data System (ADS)

    Emelianenko, T. I.; Tachaytdinov, R. S.; Sarichev, V. F.; Kotov, B. V.; Susoeva, G. N.

    After careful study of principles and abilities of all existing magnetmeters of all three revolutions in magnetic prospecting we have come to the conclusion that they cannot solve local guestions of the magnetic prospecting or determine centre coordinates of magnetite ore body before drilling Electromagnetism lows and achievents magnetprospectings and radioelectronics of all 20th century serve as a theoretical base of the "locator". While creating this cardinally new magnetmeter , we borrowed different things from radio-prospectors, magnetprospectors, wireless operators and combined all of them while creating the "locators''. The "locators' construction is bas ed on the "magnetic intensification" principle ,owing to which this "locators" are characterised by hight sensitiveness and ability to determine centers of even little commercial magnetite ore deposits with relatively weak magnetic anomalies. The main advantage of the "locators" over existing ones is that it can solve local questions determine centre coordinates. A remarkably simple locator construction determine direction of the on-surface measurings towards the ore body centre and gives approximate prognosis resourses before/withour/ drilling. The "locators" were worked out for the first time in history , they have 2 licences. The fundamental design and drawbacks of the existing magnetometers have been inherited from the original magnetometre dating back two or three hundred years. The developers of the existing magnetometres have all gone along the same well- beaten track of replacing the primitive sensor in the form of a piece of ore hung on a string at first by an arrow sensor and later by magnetically oriented protons and quanta, with amplification of the sensors' OUTPUT signal. Furthermore, all the existing magnetometres are imperfect in that they, lacking the directivity of the ground-level magnetic measurements, only record the overall magnetic vector field generated by all the ore bodies around the

  17. Lacustrine-humate model for primary uranium ore deposits, Grants uranium region, New Mexico.

    USGS Publications Warehouse

    Turner-Peterson, C. E.

    1985-01-01

    It is concluded that the primary ore formation in the Morrison formation of the San Juan basin, formed during late Jurassic and early Cretaceous, was related to humic-rich pore fluids. The fluids were derived from lacustrine mud-flat facies of the Brushy basin and 'K' shales. The fluids moved into the Westwater Canyon member and the Jackpile sandstone. -K.A.R.

  18. Metallogeny of the Great Basin: crustal evolution, fluid flow, and ore deposits

    USGS Publications Warehouse

    Hofstra, Albert H.; Wallace, Alan R.

    2006-01-01

    The Great Basin physiographic province in the Western United States contains a diverse assortment of world-class ore deposits. It currently (2006) is the world's second leading producer of gold, contains large silver and base metal (Cu, Zn, Pb, Mo, W) deposits, a variety of other important metallic (Fe, Ni, Be, REE's, Hg, PGE) and industrial mineral (diatomite, barite, perlite, kaolinite, gallium) resources, as well as petroleum and geothermal energy resources. Ore deposits are most numerous and largest in size in linear mineral belts with complex geology. U.S. Geological Survey (USGS) scientists are in the final year of a research project initiated in the fall of 2001 to increase understanding of relations between crustal evolution, fluid flow, and ore deposits in the Great Basin. Because of its substantial past and current mineral production, this region has been the focus of numerous investigations over the past century and is the site of ongoing research by industry, academia, and state agencies. A variety of geoinformatic tools was used to organize, reinterpret, and display, in space and time, the large amounts of geologic, geophysical, geochemical, and hydrologic information deemed pertinent to this problem. This information, in combination with concentrated research on (1) critical aspects of the geologic history, (2) an area in northern Nevada that encompasses the major mineral belts, and (3) important mining districts and deposits, is producing new insights about the interplay between key tectonic events, hydrothermal fluid flow, and ore genesis in mineral belts. The results suggest that the Archean to Holocene history of the Great Basin was punctuated by several tectonic events that caused fluids of different origins (sea water, basinal brine, meteoric water, metamorphic water, magmatic water) to move through the crust. Basement faults reactivated during these events localized deformation, sedimentation, magmatism, and hydrothermal fluid flow in overlying

  19. Investigation of LANDSAT imagery on correlations between ore deposits and major shield structures in Finland

    NASA Technical Reports Server (NTRS)

    Tuominen, H. V. (Principal Investigator); Kuosmanen, V.

    1977-01-01

    The author has identified the following significant results. Several regional lineaments appear to correlate with the distribution of ore deposits and showings. Combined study of LANDSAT summer and winter mosaics and color composites of geological, geomorphological, and geophysical maps makes the correlation more perceptible. The revealed pattern of significant lineaments in northern Finland is fairly regular. The most significant lineaments seen in LANDSAT mosaics are not detectable in single images.

  20. Constraints on the composition of ore fluids and implications for mineralising events at the Cleo gold deposit, Eastern Goldfields Province, Western Australia

    USGS Publications Warehouse

    Brown, S.M.; Johnson, C.A.; Watling, R.J.; Premo, W.R.

    2003-01-01

    The Cleo gold deposit, 55 km south of Laverton in the Eastern Goldfields Province of Western Australia, is characterised by banded iron-formation (BIF)-hosted ore zones in the gently dipping Sunrise Shear Zone and high-grade vein-hosted ore in the Western Lodes. There is evidence that gold mineralisation in the Western Lodes (which occurred at ca 2655 Ma) post-dates the majority of displacement along the Sunrise Shear Zone, but it remains uncertain if the ore in both structures formed simultaneously or separately. Overall, the Pb, Nd, Sr, C. O and S isotopic compositions of ore-related minerals from both the Western Lodes and ore zones in the Sunrise Shear Zone are similar. Early low-salinity aqueous-carbonic fluids and late high-salinity fluids with similar characteristics are trapped in inclusions in quartz veins from both the Sunrise Shear Zone and the Western Lodes. The early CO2, CO2-H2O, and H2O- dominant inclusions are interpreted as being related to ore formation, and to have formed from a single low-salinity aqueous-carbonic fluid as a result of intermittent fluid immiscibility. Homogenisation temperatures indicate that these inclusions were trapped at approximately 280??C and at approximately 4 km depth, in the deeper epizonal range. Differences between the ore zones are detected in the trace-element composition of gold samples, with gold from the Sunrise Shear Zone enriched in Ni, Pb, Sn, Te and Zn, and depleted In As, Bi, Cd, Cu and Sb, relative to gold from the Western Lodes. Although there are differences in gold composition between the Sunrise Shear Zone and Western Lodes, and hence the metal content of ore fluids may have varied slightly between the different ore zones, no other systematic fluid or solute differences are detected between the ore zones. Given the fact that the ore fluids in each zone have very similar bulk properties, the considerable differences in gold grade, sulfide mineral abundance, and ore textures between the two ore zones

  1. The origin of terrestrial pisoliths and pisolitic iron ore deposits: Raindrops and sheetwash in a semi-arid environment

    NASA Astrophysics Data System (ADS)

    Lascelles, Desmond F.

    2016-07-01

    Ooliths evidently form by chemical precipitation in limnic, paralic, fluvial and marine environments, pisoliths, however, appear to be restricted to terrestrial environments. Typically composed of iron, aluminium and manganese sesquioxides with minor admixtures of quartz and kaolinite, they are widely distributed in tropical to subtropical regions overlying deeply weathered soil profiles. Although iron-, aluminium- and manganese-rich end members are important sources of these metals, their genesis is still enigmatic; their formation has never been observed or produced experimentally and current models for their origin are little more than guesses. A new model is presented based on a unique personal observation in which pisoliths are formed by the action of charged raindrops during thunderstorms impacting on dry deeply weathered powdery soils. The pisoliths are transported across pediments by sheetwash, accumulating as thick deposits in the valley floors. Pisolites are characteristically unfossiliferous and typically clearly pedogenic. The absence of fine depositional layering, fossil seeds, leaves and pollen in pisolites is explained by bioturbation and the action of soil organisms during extended pedogenesis while the major coarse bedding features derive from erosional and depositional events in the evolution of the pediment. Pisolitic iron ores (aka channel iron deposits, CID) are a special case of transported pisolitic ferricrust that form an important resource of medium grade iron ore (57-60 wt% Fe) in the Pilbara Region of Western Australia. Apart from minor deposits in the northern Yilgarn Province of Western Australia, they have not been found elsewhere. They differ from normal transported ferricrust and terrestrial pisolites not only in the exceptionally high iron and low alumina and silica content but also in containing abundant fossilised wood particles.

  2. Ore petrology and geochemistry of Tertiary gold telluride deposits of the Colorado mineral belt

    SciTech Connect

    Saunders, J.A.; Romberger, S.B.

    1985-01-01

    Epithermal gold telluride deposits from the Colorado mineral belt share a number of similarities: relationship to alkalic stocks; high fluorine and CO/sub 2/ content; and similar paragenesis. Petrography of deposits in the Jamestown, Cripple Creek, and La Plata districts has resulted in a composite paragenesis: early Fe-Cu-Pb-Zn sulfides + hematite; tetrahedrite; high Te tellurides; low Te tellurides; late native gold. Fluid inclusion studies suggest telluride deposition occurred below 200/sup 0/C from low salinity. Gangue and alteration mineralogy indicates the ore fluids were near neutral pH during telluride deposition. The presence of hematite and locally barite suggest relatively oxidizing conditions. Evaluation of thermodynamic stabilities of tellurides and aqueous tellurium species indicates that progressive oxidation is consistent with the observed ore mineral paragenesis. Available data on gold bisulfide and chloride complexes suggest neither were important in the transport of gold in these systems. Thermodynamic data suggest the ditelluride ion (Te/sub 2//sup 2 -/) predominates in the range of inferred physiochemical conditions for the transport and deposition of gold in these systems. Inferred complexes such as AuTe/sub 2//sup -/ could account for the gold transport, and oxidation would be the most effective mechanism of precipitation of gold telluride or native gold. Published data suggest the associated alkalic stocks may be the ultimate source of the metals, since they are enriched in Au, Ag, Te, As, and Bi.

  3. Origin of high-grade gold ore, source of ore fluid components, and genesis of the Meikle and neighboring Carlin-type deposits, Northern Carlin Trend, Nevada

    USGS Publications Warehouse

    Emsbo, P.; Hofstra, A.H.; Lauha, E.A.; Griffin, G.L.; Hutchinson, R.W.

    2003-01-01

    The Meikle mine exploits one of the world's highest grade Carlin-type gold deposits with reserves of ca. 220 t gold at an average grade of 24.7 g/t. Locally, gold grades exceed 400 g/t. Several geologic events converged at Meikle to create these spectacular gold grades. Prior to mineralization, a Devonian hydrothermal system altered the Bootstrap limestone to Fe-rich dolomite. Subsequently the rocks were brecciated by faulting and Late Jurassic intrusive activity. The resulting permeability focused flow of late Eocene Carlin-type ore fluids and allowed them to react with the Fe-rich dolomite. Fluid inclusion data and mineral assemblages indicate that these fluids were hot (ca. 220??C),of moderate salinity (400 g/t. Petrographic observations, geochemical data, and stable isotope results from the Meikle mine and other deposits at the Goldstrike mine place important constraints on genetic models for Meikle and other Carlin-type gold deposits on the northern Carlin trend. The ore fluids were meteoric water (??D = -135???, ??18O = -5???) that interacted with sedimentary rocks at a water/rock ratio of ca. 1 and temperatures of ca. 220??C. The absence of significant silicification suggests that there was little cooling of the ore fluids during mineralization. These two observations strongly suggest that ore fluids were not derived from deep sources but instead flowed parallel to isotherms. The gold was transported by H2S (??34S = 9???), which was derived from Paleozoic sedimentary rocks. The presence of auriferous sedimentary exhalative mineralization in the local stratigraphic sequence raises the possibility that preexisting concentrations of gold contributed to the Carlin-type deposits. Taken together our observations suggest that meteoric water evolved to become an ore fluid by shallow circulation through previously gold- and sulfur-enriched rocks. Carlin-type gold deposits formed where these fluids encountered permeable, reactive Fe-rich rocks.

  4. Simulation of geochemical processes responsible for the formation of the Zhezqazghan deposit

    NASA Astrophysics Data System (ADS)

    Ryzhenko, B. N.; Cherkasova, E. V.

    2014-05-01

    Physicochemical computer simulation of water-rock systems at a temperature of 25-150°C and under a pressure of up to 600 bar has been carried out for quantitative description of the mineralization formation conditions at sandstone- and shale-hosted copper deposits. The simulation is based on geological and geochemical information concerning the Zhezqazghan deposit and considers (i) a source of ore matter, (ii) composition of the fluid that transfers ore matter to the ore formation zone, and (iii) factors of ore concentration. It has been shown that extraction of copper from minerals of rocks and its accumulation in aqueous solution are optimal at a high mass ratio of rock to water (R/W > 10), Eh of +200 to -100 mV, and an obligatory content of chloride ions in the aqueous phase. The averaged ore-bearing fluid Cl95SO44//Ca50(Na + K)30Mg19 (eq %), pH ˜ 4, mineralization of up to 400 g/L, is formed by the interaction of red sandstone beds with a sedimentogenic brine (a product of metamorphism of seawater in carbonate rocks enriched in organic matter). The ore concentration proceeds in the course of cooling from 150 to 50°C during filtration of ore-bearing fluid through red sandstone beds in the rock-water system thermodynamically opened with respect to the reductive components.

  5. Reconstructions of subducted ocean floor along the Andes: a framework for assessing Magmatic and Ore Deposit History

    NASA Astrophysics Data System (ADS)

    Sdrolias, M.; Müller, R.

    2006-05-01

    The South American-Antarctic margin has been characterised by numerous episodes of volcanic arc activity and ore deposit formation throughout much of the Mesozoic and Cenozoic. Although its Cenozoic subduction history is relatively well known, placing the Mesozoic arc-related volcanics and the emplacement of ore bodies in their plate tectonic context remains poorly constrained. We use a merged moving hotspot (Late Cretaceous- present) and palaeomagnetic /fixed hotspot (Early Cretaceous) reference frame, coupled with reconstructed spreading histories of the Pacific, Phoenix and Farallon plates to understand the convergence history of the South American and Antarctic margins. We compute the age-area distribution of oceanic lithosphere through time, including subducting oceanic lithosphere and estimate convergence rates along the margin. Additionally, we map the location and migration of spreading ridges along the margin and relate this to processes on the overriding plate. The South American-Antarctic margin in the late Jurassic-early Cretaceous was dominated by rapid convergence, the subduction of relatively young oceanic lithosphere (< 35 m.y. old) and extensive arc volcanism on the overriding plate. Additionally, our reconstructed position of the Farallon-Phoenix ridge during this period corresponds with the emplacement of several ore bodies in southern South America, similar to formation of Miocene to recent ore deposits in the northern Andes due to aseismic ridge subduction. A change in absolute motion of the Pacific plate after ~120 Ma, led to a significant decrease in the convergence rate and the southward migration of the Farallon-Phoenix ridge and this may have contributed to the cessation of back- arc spreading in the "Rocas Verdes" in southern South America. The speed of subduction increased again along the South American-Antarctic margin at ~105 Ma after another change in tectonic regime. Newly created crust from the Farallon-Phoenix ridge continued to be

  6. Isotopic evidence for organic matter oxidation by manganese reduction in the formation of stratiform manganese carbonate ore

    USGS Publications Warehouse

    Okita, P.M.; Maynard, J.B.; Spiker, E. C.; Force, E.R.

    1988-01-01

    Unlike other marine-sedimentary manganese ore deposits, which are largely composed of manganese oxides, the primary ore at Molango (Hidalgo State, Mexico) is exclusively manganese carbonate (rhodochrosite, Mn-calcite, kutnahorite). Stable isotope studies of the carbonates from Molango provide critical new information relevant to the controversy over syngenetic and diagenetic models of stratiform manganese deposit formation. Negative ??13C values for carbonates from mineralized zones at Molango are strongly correlated with manganese content both on a whole rock scale and by mineral species. Whole rock ??13C data fall into three groups: high-grade ore = -16.4 to -11.5%.; manganese-rich, sub-ore-grade = -5.2 to 0%.; and unmineralized carbonates = 0 to +2.5%. (PDB). ??18O data show considerable overlap in values among the three groups: +4.8 to -2.8, -5.4 to -0.3%., and -7.4 to +6.2 (PDB), respectively. Isotopic data for individual co-existing minerals suggest a similar separation of ??13C values: ??13C values from calcite range from -1.1 to +0.7%. (PDB), whereas values from rhodochrosite are very negative, -12.9 to -5.5%., and values from kutnahorite or Mn-calcite are intermediate between calcite and rhodochrosite. 13C data are interpreted to indicate that calcite (i.e. unmineralized carbonate) formed from a normal marine carbon reservoir. However, 13C data for the manganese-bearing carbonates suggest a mixed seawater and organic source of carbon. The presence of only trace amounts of pyrite suggests sulfate reduction may have played a minor part in oxidizing organic matter. It is possible that manganese reduction was the predominant reaction that oxidized organic matter and that it released organic-derived CO2 to produce negative ??13C values and manganese carbonate mineralization. ?? 1988.

  7. Characteristic features of ore gabbro formation in the third layer of the oceanic crust

    NASA Astrophysics Data System (ADS)

    Eskin, A. E.

    2009-07-01

    Peculiarities of ore gabbro formation in slow-spreading mid-ocean ridges exemplified by the non-transform Sierra Leone fault and Marathon fault areas are considered. The formation of ore gabbros is most often connected with the rheologically weakened oceanic lithosphere mainly with active fault zones, in which basic magmatic melts intruded. Those faults provide ways for migration of differentiated melts at different depth levels. When intruding and moving along fault zones, melts interacting with the mantle and crust host rocks are often already hydrated. Such interaction occurs largely in conditions of subsolidus deformations resulting in enrichment of melts with volatile components.

  8. Chemical Equilibrium of the Dissolved Uranium in Groundwaters From a Spanish Uranium-Ore Deposit

    SciTech Connect

    Garralon, Antonio; Gomez, Paloma; Turrero, Maria Jesus; Buil, Belen; Sanchez, Lorenzo

    2007-07-01

    The main objectives of this work are to determine the hydrogeochemical evolution of an uranium ore and identify the main water/rock interaction processes that control the dissolved uranium content. The Mina Fe uranium-ore deposit is the most important and biggest mine worked in Spain. Sageras area is located at the north part of the Mina Fe, over the same ore deposit. The uranium deposit was not mined in Sageras and was only perturbed by the exploration activities performed 20 years ago. The studied area is located 10 Km northeast of Ciudad Rodrigo (Salamanca) at an altitude over 650 m.a.s.l. The uranium mineralization is related to faults affecting the metasediments of the Upper Proterozoic to Lower Cambrian schist-graywacke complex (CEG), located in the Centro-Iberian Zone of the Hesperian Massif . The primary uranium minerals are uraninite and coffinite but numerous secondary uranium minerals have been formed as a result of the weathering processes: yellow gummite, autunite, meta-autunite, torbernite, saleeite, uranotile, ianthinite and uranopilite. The water flow at regional scale is controlled by the topography. Recharge takes place mainly in the surrounding mountains (Sierra Pena de Francia) and discharge at fluvial courses, mainly Agueda and Yeltes rivers, boundaries S-NW and NE of the area, respectively. Deep flows (lower than 100 m depth) should be upwards due to the river vicinity, with flow directions towards the W, NW or N. In Sageras-Mina Fe there are more than 100 boreholes drilled to investigate the mineral resources of the deposit. 35 boreholes were selected in order to analyze the chemical composition of groundwaters based on their depth and situation around the uranium ore. Groundwater samples come from 50 to 150 m depth. The waters are classified as calcium-bicarbonate type waters, with a redox potential that indicates they are slightly reduced (values vary between 50 to -350 mV). The TOC varies between <0.1 and 4.0 mgC/L and the dissolved

  9. Giant iron-ore deposits of the Hamersley province related to the breakup of Paleoproterozoic Australia: New insights from in situ SHRIMP dating of baddeleyite from mafic intrusions

    NASA Astrophysics Data System (ADS)

    Müller, Stefan G.; Krapež, Bryan; Barley, Mark E.; Fletcher, Ian R.

    2005-07-01

    Banded iron formations of the ca. 2770 2405 Ma Hamersley province of Western Australia were locally upgraded to high-grade hematite ores during the Early Paleoproterozoic by a combination of hypogene and supergene processes after the initial rise of atmospheric oxygen. Ore genesis was associated with the stratigraphic break between the Lower and Upper Wyloo Groups of the Ashburton province, and has been variously linked to the Ophthalmian orogeny, late-orogenic extensional collapse, and anorogenic continental extension. Small-spot in situ Pb/Pb dating of baddeleyite by sensitive high-resolution ion microprobe (SHRIMP) has resolved the ages of two key suites of mafic intrusions, constraining for the first time the tectonic evolution of the Ashburton province and the age and setting of iron-ore formation. Mafic sills dated as ca. 2208 Ma were folded during the Ophthalmian orogeny and then cut by the unconformity at the base of the Lower Wyloo Group. A mafic dike swarm that intrudes the Lower Wyloo Group and has a close genetic relationship to iron ore is ca. 2008 Ma, slightly younger than a new syneruptive 2031 ± 6 Ma zircon age for the Lower Wyloo Group. These new ages constrain the Ophthalmian orogeny to the period between ca. 2208 and 2031 Ma, before Lower Wyloo Group extension, sedimentation, and flood-basalt volcanism. The ca. 2008 Ma dikes pre s ent a new maximum age for iron-ore genesis and deposition of the Upper Wyloo Group, thereby linking ore genesis to a ca. 2050 2000 Ma period of continental extension similarly recorded by Paleoproterozoic terrains worldwide well after the initial oxidation of the atmosphere by ca. 2320 Ma.

  10. Genesis and Paleo-ecological Interpretation of Swamp Ore Deposits at Sahara Paleo-lakes of East Niger

    NASA Astrophysics Data System (ADS)

    Felix-Henningsen, Peter

    In formerly vegetated flat lake-shore areas of Pleistocene and Holocene paleo-lake depressions in the Sahara of East Niger (Ténéré, Tchigai mountains and in the Erg of Bilma), ancient dune sands are covered by rampart-like or flat beds of individual or networked rhizoconcretions. The massive goethite accumulation, which partly includes an outer fringe of lepidocrocite, impregnated the ancient dune sands. Apart from Fe, P, Ca, and Mg, other heavy metals were also concentrated. The formation and morphological differentiation of these swamp ores were generally bound at vegetated shallow water areas of paleo-lakes in ancient dune fields. Accordingly, the swamp ores of the Ténéré, which has flat to undulating relief, display a large dissemination. In contrast, in the Erg of Bilma the high altitude and steep slopes of ancient dune ridges led to steeper shore areas of the paleo-lakes, at which beds of rhizoconcretions were unable to develop. The oxides were formed by oxidation of Fe2 + -ions from the lake water and concentrated around the roots in the upper root zone of the swamp vegetation. The lack of oxygen in the warm lake water of the shore region, as well as the decomposition of vegetation residues, excluded high redox potentials within the deeper water near the subhydric soil surface. Hence, the formation of rhizoconcretions can only be explained by the specific physiological characteristics of the swamp vegetation, which was able to supply oxygen to the roots through an aerenchyma. The release of surplus oxygen from such roots obviously caused high redox potentials at the root surface and in the neighbouring root environment. As a result precipitation of Fe and Mn oxides occurred, which adsorbed nutrients and heavy metals from the soil solution. The redistribution of the ions from the reduced sediments of the lake basin into the root zone of the shore area resulted from diffusion and mass flow. Paleo-climatically, the swamp ore deposits denote humid periods

  11. Origin of the ore-forming fluids and metals of the Bangpu porphyry Mo-Cu deposit of Tibet, China: Constraints from He-Ar, H-O, S and Pb isotopes

    NASA Astrophysics Data System (ADS)

    Wang, Liqiang; Tang, Juxing; Cheng, Wenbin; Chen, Wei; Zhang, Zhi; Lin, Xin; Luo, Maocheng; Yang, Chao

    2015-05-01

    The Bangpu porphyry Mo-Cu deposit is a representative Mo-dominated deposit besides the Sharang porphyry Mo deposit in the Gangdese metallogenic belt. The Mo-Cu mineralization has a close relationship with the monzogranite porphyry and diorite porphyrite. We identify three stages during the ore formation: a pre-ore stage, a main-ore stage with Mo-Cu deposited dominantly, and a post-ore stage. In this study, He-Ar, H-O, S and Pb isotopic compositions of the Bangpu deposit were determined. Based on these determinations, integrated isotope geochemistry studies were performed to constrain the possible sources of the ore-forming fluids and metals. The 3He/4He and 40Ar/36Ar ratios of fluid inclusions exhibit a range of 0.12209-0.36370 Ra and 275.6-346.1, respectively. The 4He and 40Ar concentrations vary from 1.51 to 3.57 (10-7 cm3 STP g-1) and 0.49 to 9.31 (10-7 cm3 STP g-1), respectively. He-Ar isotopic compositions suggest dominantly crustal-derived fluid with minor amount of meteoric water in the main ore stage. The δ18Ofluid and δDfluid values vary from -1.3‰ to 3.9‰ and -140.5‰ to -73.7‰, respectively, indicating that magma fluids mixed with meteoric water. The average δ34S value of the sulfides (0.3‰) in the main-ore stage is close to the ore-forming porphyries, indicating a magmatic source. The lead isotopic components of ore sulfides exhibit restricted ranges with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 18.450-18.728, 15.602-5.672, and 38.715-39.211, respectively and μ values in the range of and 9.46-9.58, indicating ore-forming metals of primarily an upper crust source with a small amount of mantle materials. Compared to the Bangpu deposit, the ore metals derived from mantle are even greater in the Jiama and Qulong deposits, which leads to Cu being the dominant mineralization in the Jiama and Qulong deposit.

  12. Evidence for participation of microbial mats in the deposition of the siliciclastic ‘ore formation’ in the Copperbelt of Zambia

    NASA Astrophysics Data System (ADS)

    Porada, H.; Druschel, G.

    2010-10-01

    The Copperbelt of Zambia is the world's largest sediment-hosted stratiform copper province, hosted in siliciclastic sediments of the Roan Group, which forms the basal part of the Neoproterozoic-Paleozoic Katanga Supergroup. Much of the ore deposition occurred between 880 Ma and 780 Ma, on a rimmed platform consisting of a carbonate barrier, a lagoonal basin and tidal flats grading into sabkhas in the hinterland. Various sedimentary structures developed in the ore formation at the Mindola Open Pit mine, are herein considered to be microbially induced and are identified as microbial shrinkage cracks, wrinkle structures, mat deformation structures, petees, concentric microfaults, and microbial mat chips. The occurrence of these structures in all ore formation units at the Mindola Mine suggests microbial mats grew on the paleo-sediment surface throughout deposition of the cupriferous succession. As these structures require cohesive layers, the mats were likely of the cyanobacterial type, that grew in the well aerated intertidal to lower supratidal zones. Cyanobacterial mats typically consist of a surface layer of filamentous cyanobacteria underlain by anaerobic, heterotrophic sulfate reducing bacteria (SRB). A distinct sulfide mineral zonation, developed in all major deposits of the Copperbelt, ranges from barren supratidal (sabkha) sediments, through chalcocite in the lower supratidal zone, to bornite followed by chalcopyrite in the intertidal zone, and pyrite in the subtidal zone and anoxic lagoonal depotcentre. This sequence of minerals can be modelled as a paragenetic sequence of mineralization resulting from the progressive reduction of a source fluid, indicating that geochemical conditions of ore formation, at least, are produced by the activity of SRB.

  13. 3D Geological Model of Nihe ore deposit Constrained by Gravity and Magnetic Modeling

    NASA Astrophysics Data System (ADS)

    Qi, Guang; Yan, Jiayong; Lv, Qingtan; Zhao, Jinhua

    2016-04-01

    We present a case study on using integrated geologic model in mineral exploration at depth. Nihe ore deposit in Anhui Province, is deep hidden ore deposit which was discovered in recent years, this finding is the major driving force of deep mineral exploration work in Luzong. Building 3D elaborate geological model has the important significance for prospecting to deep or surround in this area, and can help us better understand the metallogenic law and ore-controlling regularity. A 3D geological model, extending a depth from +200m to -1500m in Nihe ore deposit, has been compiled from surface geological map, cross-section, borehole logs and amounts of geological inference. And then the 3D geological models have been given physical property parameter for calculating the potential field. Modelling the potential response is proposed as means of evaluating the viability of the 3D geological models, and the evidence of making small changes to the uncertain parts of the original 3D geological models. It is expected that the final models not only reproduce supplied prior geological knowledge, but also explain the observed geophysical data. The workflow used to develop the 3D geologic model in this study includes the three major steps, as follows: (1) Determine the basic information of Model: Defining the 3D limits of the model area, the basic geological and structural unit, and the tectonic contact relations and the sedimentary sequences between these units. (2) 3D model construction: Firstly, a series of 2D geological cross sections over the model area are built by using all kinds of prior information, including surface geology, borehole data, seismic sections, and local geologists' knowledge and intuition. Lastly, we put these sections into a 3D environment according to their profile locations to build a 3D model by using geostatistics method. (3) 3D gravity and magnetic modeling: we calculate the potential field responses of the 3D model, and compare the predicted and

  14. Understanding Cu release into environment from Kure massive sulfide ore deposits, Kastamonu, NW Turkey

    NASA Astrophysics Data System (ADS)

    Demirel, Cansu; Sonmez, Seref; Balci, Nurgul

    2014-05-01

    Covering a wide range on the earth's crust, oxidation of metal sulfide minerals have vital environmental impacts on the aquatic environment, causing one of the major environmental problems known as acid mine drainage (AMD). Located in the Kastamonu province of the Western Black Sea region, Kure district is one of the major copper mining sites in Turkey. Mining activities in the area heads back to ancient times, such that operation is thought to be started with the Roman Empire. Currently, only the underground mining tunnels of Bakibaba and Asikoy are being operated. Thus, mining heaps and ores of those pyritic deposits have been exposed to the oxidative conditions for so long. As a result of weathering processes of past and recent heaps of the Kure volcanic massive sulfide deposits in addition to the main ore mineral (chalcopyrite), significant amount of metals, especially Cu, are being released into the environment creating undesirable environmental conditions. In order to elucidate Cu release mechanisms from Kure pyritic ore deposits and mining wastes, field and laboratory approaches were used. Surface water and sediment samples from the streams around the mining and waste sites were collected. Groundwater samples from the active underground mining site were also collected. Physical parameters (pH, Eh, T°C, and EC) of water samples were determined in situ and in the laboratory using probes (WTW pH 3110, WTW Multi 9310 and CRISON CM 35). Metal and ion concentrations of the water samples were analysed using ICP-MS and DR 2800 spectrophotometer, respectively. High Cu, Co, Zn and Fe concentrations were determined in the water samples with pH values ranging from 2.9- 4. Cu concentrions ranges from 345 ppm to 36 ppm in the water samples. Consistent with the water samples, high Cu, Fe, Zn and Co were also determined in the sediment samples. Laboratory chalcopyrite oxidation experiments under the conditions representing the field site were set up as biological and

  15. Processes of ore genesis at the world-class Yuchiling molybdenum deposit, Henan province, China

    NASA Astrophysics Data System (ADS)

    Zhang, Juan; Ye, Hui-shou; Zhou, Ke; Meng, Fang

    2014-01-01

    The Yuchiling molybdenum deposit is one of the most significant porphyry molybdenum systems in the eastern Qinling of central China. The mineralization is mainly hosted by a porphyritic granite and associated cryptoexplosive breccia. Hydrothermal alteration minerals include K-feldspar, sericite, pyrite, chlorite, epidote, carbonate, kaolinite, fluorite, and gypsum. Ore minerals are dominated by molybdenite and pyrite, with lesser amounts of chalcopyrite, galena, scheelite, wolframite, ilmenite, leucoxene, native gold, sphalerite, and hematite. The δ34S compositions of sulfide minerals range from -6.0‰ to +4.0‰. The deposit is characterized by four hydrothermal stages: quartz-K-feldspar (stage I), molybdenite-quartz (stage II), pyrite-sericite-quartz (stage III), and quartz-carbonate (stage IV). Microthermometric studies of fluid inclusions show that the fluids evolved gradually during the ore-forming process. Homogenization temperatures, salinities, and minimum pressure estimates for the inclusions from each mineralization stage evolved as follows: (1) stage I: homogenization temperatures = 203.7-525.8 °C, salinities = 2.96-10.49 and 29.66 wt.% NaCl equiv., and minimum pressures = 101.9-196.2 MPa; (2) stage II: homogenization temperatures = 173.6-448.6 °C, salinities = 1.81-9.74 wt.% NaCl equiv., and minimum pressures = 93.1-172.0 MPa; (3) stage III: homogenization temperatures = 130.1-386.0 °C, salinities = 1.40-9.73 and 34.07 wt.% NaCl equiv., and minimum pressures = 95.5-142.5 MPa; (4) stage IV: homogenization temperatures = 170-230 °C and salinities = 0.18-5.71 wt.% NaCl equiv. Various fluid inclusions were observed to contain H2O, CO2, CH4, SO2, C2H2, C2H4, C2H6, and (or) H2S, as well as solids that include halite, sylvite, anhydrite, chalcopyrite, hematite, molybdenite, and jamesonite. The δ18O and δD of the hydrothermal fluids vary from -4.4‰ to +8.5‰ and -81‰ to -61‰, respectively. Microthermometric and stable isotope data indicate that

  16. Fluid mixing and ore deposition during the geodynamic evolution of the Sierra Almagrera (Betics, Spain)

    NASA Astrophysics Data System (ADS)

    Dyja, Vanessa; Tarantola, Alexandre; Hibsch, Christian; Boiron, Marie-Christine; Cathelineau, Michel

    2013-04-01

    Marine and continental intramountaineous basins developed during the Neogene orographic evolution of the Betico-rifan orogenic wedge, as well as the related uplifted ranges within the Sierra Almagrera Metamorphic Core Complexes (MCC). The NNE-SSW striking trans-Alboran transcurrent fault system crosscuts the MCC post-dating the extensional exhumation stages recorded in the metamorphic fabric. Iron ores (± Pb, Cu, Zn) are encountered either as stratabound ore deposits in the Neogene basins or as vein networks crosscutting the metamorphic fabric of graphitic phyllites from the Sierra Almagrera. These Late Miocene ore deposits are related to the activity of the N-S striking Palomares fault segment of the Trans-Alboran fault system. Three sets of quartz veins (Vα, Vαβ and Vβ) and one set of mineralized vein (Vγ, siderite, barite) are distinguished. The Vα and Vαβ respectively are totally or partially transposed into the foliation. The Vβ and Vγ veins are discordant to the foliation. The problem addressed in this study concerns the nature of the fluids involved in the metal deposits and their relationships with the main reservoir fluids, e.g. the deep metamorphic fluids, the basinal fluids, and eventually the recharge meteoric fluids. This study focuses thus on the evolution of the fluids at different stages of ductile-brittle exhumation of the metamorphic ranges (Sierras) and their role during the exhumation and later on in relation with the hydrothermalism and metal deposition at a regional scale. Paleofluids were studied as inclusions in quartz, siderite and barite from veins by microthermometry and Raman spectroscopy, and a stable isotope study is in progress. Earliest fluids recorded in (Vαβ) quartz veins are H2O- NaCl + CaCl2 (17 wt. %) - (traces of CO2, CH4, N2) metamorphic brines trapped at the ductile brittle transition at a minimum trapping temperatures (Th) of 340 °C. Older metamorphic fluids in (Vα) veins were lost during the complete

  17. Jasperoid float and stream cobbles as tools in geochemical exploration for hydrothermal ore deposits

    USGS Publications Warehouse

    Lovering, T.G.

    1981-01-01

    Fragments of silicified rocks that are associated with deposits of base and precious metals may be transported as cobbles and pebbles in alluvium far downstream from the source outcrop. These rocks commonly exhibit certain characteristics which distinguish them from other detrital siliceous material, and may thus serve as a useful tool in reconnaissance geochemical exploration. The predominant characteristics of jasperoid samples, classified according to genesis, type of host rock, and proximity to base and precious metal deposits have been tabulated from a large master file containing descriptive and analytical information on jasperoid samples representing more than a hundred areas in the United States. Jasperoid that is genetically and spatially associated with ore deposits is generally dark gray or brown in color, brecciated, phaneritic, and vuggy. Jasperoids associated with lead and zinc deposits exhibit extensive halos of lead and silver anomalies, and more restricted zinc and gold anomalies. Those related to copper deposits show extensive copper, silver, and gold anomalies, and more restricted bismuth and molybdenum anomalies. Jasperoid related to gold deposits tends to exhibit extensive gold and silver anomalies and more restricted titanium, barium, vanadium, molybdenum, and rare-earth element anomalies. ?? 1981.

  18. Hydrothermal alteration, ore fluid characteristics, and gold depositional processes along a trondhjemite-komatiite contact at Tarmoola, Western Australia

    USGS Publications Warehouse

    Duuring, P.; Hagemann, S.G.; Cassidy, K.F.; Johnson, C.A.

    2004-01-01

    studies and stage II mineral equilibria, gold deposited from a homogeneous, neutral to slightly alkaline (pH 5.1-5.5), reduced, low-salinity (<5.5 wt % NaCl equiv) fluid that had a bulk composition of 78 mole percent H2O and 21 mole percent CO2, and trace amounts of CH4, C2H6, H2, Ar, H2S, and He. Gold deposition occurred at 300?? ?? 50??C and 0.5 to 3.0 kbars. Assuming lithostatic fluid pressures, gold precipitated at a 2- to 10-km depth. Stage II gray quartz ??18Ofluid values range from 5.9 to 7.5 per mil, whereas ??Dfluid values calculated from the dehydration of muscovite grains and measured directly from bulk fluid inclusion analyses of stage II gray quartz have ranges of -9 to -35 and -27 to -28 per mil, respectively. Hydrothermal ore fluids were transported from greater crustal depths to the site of gold deposition during the district-scale D3 event by shallowly W dipping, reverse brittle-ductile shear zones in supracrustal rock and along the steeply east dipping trondhjemite contact. Associated subhorizontal east-west shortening caused the reactivation of the eastern trondhjemite margin and subparallel foliation, which facilitated the transport of hydrothermal fluids and the generation of gold-bearing veins and hydrothermal alteration zones in komatiite. East-west-striking fractures in trondhjemite aided the lateral migration of ore fluids away from trondhjemite margins and the formation of east-west-striking gold-bearing veins and broad alteration zones. Gold was most likely transported in the stage II fluid as bisulfide complexes. The sulfidation of trondhjemite and komatiite wall rock by the stage II fluid caused the destabilization of An bisulfide complexes and gold deposition. Potassium, Ca, and CO2 metasomatism of komatiite wall rock may have enhanced gold deposition via the acidification of the stage II fluid. The physicochemical characteristics of the Tarmoola ore fluid and relative timing of gold mineralization are consistent with the Yilgarn-wide,

  19. Environment of ore deposition in the Creede mining district, San Juan Mountains, Colorado: Part VI. Maximum duration for mineralization of the OH vein

    USGS Publications Warehouse

    Campbell, W.R.; Barton, P.B.

    2005-01-01

    The rate at which ore deposits form is one of the least well established parameters in all of economic geology. However, increased detail in sampling, improved technology of dating, and sophistication in modeling are reducing the uncertainties and establishing that ore formation, at least for the porphyry copper-skarn-epithermal base and precious metals deposit package, may take place in surprisingly brief intervals. This contribution applies another approach to examine the duration of mineralization. The degree to which compositional gradients within single crystals has flattened through solid-state diffusion offers a measure of the thermal dose (that is temperature combined with time) that the crystals have been subjected to since deposition. Here we examine the steepness of gradients in iron content within individual single sphalerite crystals from the epithermal silver-lead-zinc deposit in the OH vein at Creede, Colorado. Two initial textures are considered: growth-banded crystals and compositionally contrasting overgrowths that succeed crosscutting dissolution or fractured surfaces. The model used estimates the maximum possible time by assuming a perfectly sharp original compositional step, and it asks how long it would take at a known temperature for the gradient measured today to have formed. Applying the experimentally determined diffusion rates of Mizuta (1988a) to compositional gradients (ranging from 0.4-2.2 mol % FeS/??m) measured by the electron microprobe in 2-??m steps on banded sphalerite formed early in the paragenetic history yields a maximum duration of less than ???10,000 yr. Sphalerite from a solution unconformity in a position midway through the paragenetic sequence is indistinguishable from instantaneous deposition, supporting the conclusion of rapid ore formation. While this formation interval seems very brief, it is consistent with less well constrained estimates using entirely different criteria. ?? 2005 Society of Economic Geologists, Inc.

  20. The distribution of trace elements in a range of deep-sea sulphide ore deposits and their impact on seafloor mining

    NASA Astrophysics Data System (ADS)

    Fallon, E. K.; Scott, T. B.; Brooker, R. A.

    2015-12-01

    Acid rock drainage is a natural weathering process that is often exacerbated by mining activities, common in onshore sulphide ore deposits, that can lead to considerable environmental impact. A similar 'weathering process' occurs at seafloor massive sulphide (SMS) ore deposits. In contrast to the onshore situation, the expected consequence in the marine environment is often considered to be oxide formation, negligible metal release and minimal net acid generation due to the high buffering capacity of seawater and low solubility of iron at near neutral pH. However, no dissolution studies exist that emulate the true composition of sulphide ore deposits that either sit passively on the seafloor or are actively mined in this colder, more saline, and alkaline environment. In particular, these deposits will include a variety of minerals, and it is the interaction of these minerals and inclusions in regards to galvanic cells that can subsequently increase the dissolution of metals into the water column. Any heavy metal release that is not balanced by subsequent oxidation and precipitation, has the potential to produce toxicity for benthic ecosystems, bioaccumulation and dispersal through currents. The present work has sought to provide a pilot investigation on the deep sea weathering of sulphide minerals, by identifying the mineral phases, trace elements and potential galvanic couples that may arise in sulphide mineral samples collected from various tectonic settings. Samples have been analysed using EMPA and LA-ICPMS in order to identify the range of trace elements and toxins that may be contributed to the water column, especially heavy metals and environmental toxins (e.g. Fe, Cu, Zn, Pb, Co, Ni, Cd, As, Sb, Sn, Hg). Our observations raise important questions about which ore deposits could have more or less environmental impact during any mining activity. These observations will be used to design oxidative dissolution experiments at deep-sea conditions utilising the

  1. Mineral paragenesis, geochemistry and geochronology investigations of the Carlin-type gold deposits at the Goldstrike property, northern Nevada: Implications for ore genesis, igneous petrogenesis and mineral exploration

    NASA Astrophysics Data System (ADS)

    Almeida, Carolina Michelin De

    The Goldstrike property is located in northern Nevada and contains one of the largest and highest-grade Carlin-type gold deposits. The majority of the Eocene Au mineralization (e.g., Ore I) is hosted in intensely altered Paleozoic lower plate impure carbonate rocks, and is characterized by strong to moderate silicification, higher calculated pyrite and ore-related element concentrations (e.g., As, Cu, Hg, Ni, Tl, Sb, W, and Zn) than Ore II, which is weakly altered. However, both ore types contain similar Au concentration in whole rock and pyrite chemistry analyses. Lithogeochemical and microprobe data suggest that the Paleozoic sedimentary rocks may have been a major source of Cd, Mo, Ni, U, V, and Zn and minor As, Cu, Hg, and Se. The Jurassic lamprophyre dikes might have been a significant source of Ba, Co, and Se, and minor Au, and some of the Jurassic and Eocene intrusive rocks may have provided some Fe. Moreover, the Eocene magmas are interpreted to be the main source of auriferous mineralizing fluids. Trace element abundances and ratios of the Jurassic intrusive rocks suggest that they are shoshonitic and formed from a metasomatized mantle-derived magma, crystal fractionation, and crustal contamination. The Eocene dikes, also shoshonitic, are considerably more evolved and contaminated than the studied Jurassic rocks. Furthermore, Ar-Ar results show that the Jurassic rocks were negligibly affected by the Eocene thermal event, and that temperature of mineralizing fluids were below the closure temperature of biotite (< 350°C). A magmatic-related model is proposed to explain the formation of the Carlin-type gold deposits at the studied area. In this model, Au and the ore-related elements were exsolved along with volatiles by degassing of a deep and large plutonic complex during its early stage of crystallization. As these magmatic-hydrothermal fluids moved upward along major conduits (e.g., NNW-striking faults), they may have interacted with a Fe-rich fluid

  2. Origin and evolution of ore-forming fluids in the Hemushan magnetite-apatite deposit, Anhui Province, Eastern China, and their metallogenic significance

    NASA Astrophysics Data System (ADS)

    Luo, Gan; Zhang, Zhiyu; Du, Yangsong; Pang, Zhenshan; Zhang, Yanwen; Jiang, Yongwei

    2015-12-01

    The Middle-Lower Yangtze River Metallogenic Belt in the northern Yangtze Block is one of the most important economic mineral districts in China. The Hemushan deposit is a medium-class Fe deposit located in the southern part of the Ningwu iron ore district of the Middle-Lower Yangtze River Metallogenic Belt. The Fe-orebodies are mainly hosted in the contact zone between diorite and Triassic marble. The actinolite-phlogopite-apatite-magnetite ore shows metasomatic/filling textures and disseminated/mesh-vein structures. Based on evidences and petrographic observations, the ore-forming process can be divided into three distinct periods-the early metallogenic period (albite-diopside stage), the middle metallogenic period (magnetite stage and hematite stage), and the late metallogenic period (quartz-pyrite stage and carbonate stage). Fluid inclusion studies show four types of inclusions: type I daughter mineral-bearing three-phase inclusions (L + V + S), type II vapor-rich two-phase inclusions (L + V), type III liquid-rich two phase inclusions (L + V), and minor type IV liquid-phase inclusions (L). Apatites from the magnetite stage contain type I, type II and type III inclusions; anhydrites from the hematite stage mainly contain abundant type II inclusions and relatively less type I inclusions; quartz and calcite from the late metallogenic stage are mainly characterized by type III inclusions. Laser Raman spectroscopy and microthermometry of fluid inclusions show that the ore-forming fluids broadly correspond to unsaturated NaCl-H2O system. From the magnetite stage to the carbonate stage, the ore-forming fluids evolved from moderate-high temperature (average 414 °C), moderate salinity (average 25.01 wt.% NaCl equiv.) conditions to low temperature (average 168 °C), low salinity (average 6.18 wt.% NaCl equiv.) conditions. Hydrogen and oxygen isotopic studies indicate that the ore-forming fluid during the early stage of middle metallogenic period was mainly of magmatic

  3. Paragenesis and conditions of formation of ore minerals from metalliferous breccia pipes, N. Arizona

    SciTech Connect

    Wenrich, K.J.; Pratt, L.M.

    1985-01-01

    Ore deposits within N. Arizona breccia pipes are currently being exploited for U, but at various times during the past century Cu, Pb, Zn, and Ag were mined. These pipes formed as solution-collapses within the Mississippian Redwall Ls and stopped upward through overlying strata. The principal ore minerals are: uraninite, chalcopyrite, chalcocite, tennantite-tetrahedrite, galena, sphalerite, millerite, gersdorffite, siegenite, and molybdenite. Common gangue minerals are marcasite, pyrite, barite, dolomite, calcite and quartz. Marcasite and pyrite appear to have formed prior to the ore minerals, followed closely by chalcopyrite. The Ni and Co phases also appear to be early: gersdorffite crystals are rimmed by later galena. Tennantite-tetrahedrite formed later than both galena and sphalerite; uraninite, the latest ore mineral, consisting fills interstices. Primary fluid inclusions in dolomite, quartz, and sphalerite show filling temperatures from 80 to 145/degree/C and high salinities, averaging 15 wt% NaCl (eq). Secondary inclusions in sphalerite have consistently higher filling temperatures from 105 to 173/degree/C, but similar salinities. Rock-Eval pyrolysis of pyrobitumen yields little or no volatile hydrocarbons (S/sub 1/=0-0.2 mg/gm), but large amounts of pyrolytic hydrocarbons (S/sub 2/=105-216 mg/gm). Temperatures of maximum pyrolytic yield are relatively low (424-430/degree/C), suggesting temperatures did not exceed 150/degree/C following pyrobitumen emplacement. Except for uraninite, the breccia pipes are similar to Mississippi Valley-type (MVT) deposits in mineralogy, fluid-inclusion filling temperatures and salinities, and associated organic material. Because MVT deposits do not host U minerals, a possible two-stage mineralization history of the pipes is suggested, the first by a MVT brine and perhaps a second forming the uraninite.

  4. Ore petrography of a sedimentary uranium deposit, Live Oak County, Texas

    SciTech Connect

    Bomber, B.J.; Ledger, E.B.; Tieh, T.T.

    1986-01-01

    Samples from the McLean 5 open-pit uranium mine, a small high-grade deposit located along a normal fault in the Miocene Oakville sandstone of Live Oak County, Texas, have been studied for uranium abundance, distribution, and nature of occurrence on the microscopic level. The host sandstone is composed of quartz, feldspars, and volcanic rock fragments, cemented by sparry calcite. Authigenic minerals include iron disulfide minerals (dominantly pyrite and some marcasite) and small amounts of clays, Ti oxides, and opal. High-grade ore (to 3% U) occurs along the fault, decreasing to less than 1,000 ppm within 10 m from the fault. The ore mineral is amorphous pitchblende and exhibits botryoidal morphology. The microscopic occurrence of uranium, documented by fission-track mapping of petrographic thin sections, is presented in detail. Uranium occurs abundantly as grain coatings and fillings in intergranular spaces in samples with high uranium content, where calcite cement has been partially or totally leached as mineralization proceeded. Lesser amounts are adsorbed onto leucoxene (microcrystalline anatase), mud clasts, and altered igneous rock fragments. Adsorbed uranium is the major code of occurrence in samples, with lower uranium contents farther from the orebody. Textural relations indicate that iron sulfides formed both before and after mineralization. Initial mineralization was by adsorption onto aggregates of fine particles of Ti oxide and clay minerals of various origins. With dissolution of cement and continued uranium influx, uranium precipitated as grain coatings and pore fillings.

  5. Rhenium in ores of the Mikheevskoe porphyry Cu-Mo deposit, South Urals

    NASA Astrophysics Data System (ADS)

    Plotinskaya, O. Yu.; Grabezhev, A. I.; Seltmann, R.

    2015-03-01

    The distribution of Re in ores of the Mikheevskoe Mo-Cu deposit in the South Urals is studied. It is established that the grade of Re in the ores usually does not exceed 0.5 g/t. A positive correlation between concentrations of Re and Mo (correlation coefficient 0.94), and Re and Cu (correlation coefficient 0.52) is found. EMPA of individual flakes of molybdenite showed that a Re content higher than the detection limit has been measured in most flakes studied, as a rule as high as 0.4-0.5 wt %, but occasionally reaching 1.34 wt %. Re within flakes of molybdenite is irregularly distributed. Patchy, linear, and concentric-zoned patterns of zones with elevated Re content (usually 0.5-1 wt % Re, sometimes higher) are found against the lower content (up to 0.2 wt % Re) that is regularly distributed within the flake. Later hydrothermal processes and mechanical deformation of flakes result in epigenetic Re redistribution in molybdenite that leads to homogenization of molybdenite composition and smoothing of primary pattern, or removal of Re from molybdenite.

  6. Multiple Sulfate Isotopic Evidence on the Formation of Oxide Copper Ore at Spence, Atacama Desert, Northern Chile

    NASA Astrophysics Data System (ADS)

    Sun, T.; Bao, H.; Reich, M.; Palacios, C.

    2007-12-01

    In the Atacama Desert of northern Chile, one of the world's richest metallogenic provinces, porphyry copper deposits are characterized by the unique occurrence of atacamite in their oxidized zones. The origin and formation of the oxide zone of these copper deposits is, however, controversial. It was proposed that Cl-rich deep formation water pumping-up events along faults by earthquakes, after onset of the hyperaridity, were required (Cameron et al., 2007). Their model would imply that supplies of saline deep formation water from fractures to the surface should have left behind a homogeneous or fracture-controlled salt profile from surface down to the oxide zone. While no excluding the deep formation water model in other deposit, here we propose that, in our sampling region, the alternative saline source, which is critical for atacamite formation, could be locally evaporated groundwater, Cl-rich salts leached from arid surface by meteoric water, or brines from eastern salar basins at a time when the climate in northern Chile was changing from arid to hyperarid. At this climate transition, arid- requiring minerals such as atacamite in the oxide zone were formed and, more importantly, preserved upon evaporation beneath the surface alluvial deposits. Since salt accumulation at the surface remain active during hyperarid condition, our model would predict that water-soluble salt profile from surface to the oxide zone should have a characteristic pattern: salts with an atmospheric component on the surface gradually transitioning to salts of the oxide ore zone on the bottom and a mixing zone in between. To test these two alternative models, we focus on sulfate salts, one of the common water-soluble salts in arid environments. An added advantage is that sulfate accumulated on desert surface has a secondary atmospheric component that bears a unique triple oxygen isotope signature, easily distinguishable from sulfate formed by the oxidation of sulfide minerals at the oxide

  7. Precipitation of lead-zinc ores in the Mississippi Valley-type deposit at Treves, Cevennes region of southern France

    USGS Publications Warehouse

    Leach, D.; Macquar, J.-C.; Lagneau, V.; Leventhal, J.; Emsbo, P.; Premo, W.

    2006-01-01

    The Trèves zinc–lead deposit is one of several Mississippi Valley-type (MVT) deposits in the Cévennes region of southern France. Fluid inclusion studies show that the ore was deposited at temperatures between approximately 80 and 150°C from a brine that derived its salinity mainly from the evaporation of seawater past halite saturation. Lead isotope studies suggest that the metals were extracted from local basement rocks. Sulfur isotope data and studies of organic matter indicate that the reduced sulfur in the ores was derived from the reduction of Mesozoic marine sulfate by thermochemical sulfate reduction or bacterially mediated processes at a different time or place from ore deposition. The large range of δ34S values determined for the minerals in the deposit (12.2–19.2‰ for barite, 3.8–13.8‰ for sphalerite and galena, and 8.7 to −21.2‰ for pyrite), are best explained by the mixing of fluids containing different sources of sulfur. Geochemical reaction path calculations, based on quantitative fluid inclusion data and constrained by field observations, were used to evaluate possible precipitation mechanisms. The most important precipitation mechanism was probably the mixing of fluids containing different metal and reduced sulfur contents. Cooling, dilution, and changes in pH of the ore fluid probably played a minor role in the precipitation of ores. The optimum results that produced the most metal sulfide deposition with the least amount of fluid was the mixing of a fluid containing low amounts of reduced sulfur with a sulfur-rich, metal poor fluid. In this scenario, large amounts of sphalerite and galena are precipitated, together with smaller quantities of pyrite precipitated and dolomite dissolved. The relative amounts of metal precipitated and dolomite dissolved in this scenario agree with field observations that show only minor dolomite dissolution during ore deposition. The modeling results demonstrate the important control of the reduced

  8. A deposit model for Mississippi Valley-Type lead-zinc ores: Chapter A in Mineral deposit models for resource assessment

    USGS Publications Warehouse

    Leach, David L.; Taylor, Ryan D.; Fey, David L.; Diehl, Sharon F.; Saltus, Richard W.

    2010-01-01

    This report also describes the geoenvironmental characteristic of MVT deposits. The response of MVT ores in the supergene environment is buffered by their placement in carbonate host rocks which commonly results in near-neutral associated drainage water. The geoenvironmental features and anthropogenic mining effects presented in this report illustrates this important environmental aspect of MVT deposits which separates them from other deposit types (especially coal, VHMS, Cu-porphyry, SEDEX, acid-sulfate polymetallic vein).

  9. Significance of oil-like hydrocarbons in metamorphic and ore-deposit rocks

    SciTech Connect

    Price, L.C.

    1996-10-01

    Carbonaceous rocks (0.7-45.0% carbon content) from both greenschist metamorphism and hydrothermal-ore deposition were solvent-extracted and the resulting extracts characterized by standard analyses. Blank runs showed no contamination from laboratory procedures. The recovered HCS are in low, but significant, concentrations (0.5-50 ppm, rock weight). Moreover, the composition of these HCS (including biomarkers) resemble that of mature crude oils and do not have the ultra-mature characteristics expected from their high temperature environs. This strongly suggests that HCS will survive in even higher-rank rocks. These data contradict petroleum-geochemical paradigm regarding an inferred thermal instability of HCS and also bear on natural gas origins (e.g. - the hypothesized cracking of oil to gas), rock-water-HC interactions, petroleum-geochemical models, and other related topics.

  10. A Long-Lived Porphyry Ore Deposit and Associated Upper Crustal Silicic Magma Body, Bajo de la Alumbrera, Argentina

    NASA Astrophysics Data System (ADS)

    Harris, A. C.; Allen, C. M.; Reiners, P. W.; Dunlap, W. J.; Cooke, D. R.; Campbell, I. H.; White, N. C.

    2004-05-01

    Porphyry Cu deposits form within and adjacent to small porphyritic intrusions that are apophyses to larger silicic magma bodies that reside in the upper parts of the Earth's crusts. Centred on these intrusions are hydrothermal systems of exsolved magmatic fluid with a carapace of convectively circulating meteoric water. We have applied several different dating techniques to assess the longevity of the magmatic-hydrothermal system and to define the cooling history of porphyry intrusions at the Bajo de la Alumbrera porphyry Cu-Au deposit, Argentina. The closure temperatures of these techniques range from 800oC (zircon U-Pb) to ~70oC (apatite (U-Th)/He; Fig. 1). The resulting cooling history indicates that the magmatic-hydrothermal system cooled to ca. 200oC by ~1.5 m.y. after the last porphyry intrusion (i.e., 6.96±0.09 Ma; U-Pb zircon age). Based on (U-Th)/He apatite data (closure temperature ~60-70oC), exposure and cessation of the system occurred before 4 Ma. The longevity of the magmatic-hydrothermal system indicated by these results is inconsistent with accepted mechanisms for porphyry Cu deposit formation. Depending on wallrock permeability, depth and cooling method, a 2 km wide by 3 km high intrusion has been predicted to cool between 0.01 to 0.1 m.y. (marked as the grey interval; Cathles et al., 1997 Economic Geology). We have obtained numerous age determinations younger than the U-Pb zircon age of the last known intrusion at Bajo de la Alumbrera. These imply that simple cooling of the small, mineralized porphyries did not happen. For the magmatic-hydrothermal system to have been sustained for longer than 0.1 m.y., either 1) younger small intrusions have been episodically emplaced below the youngest known intrusions, thus prolonging heat flow, or 2) fluids derived from a deeper and larger parental intrusion have been episodically discharged through the ore deposit long after the porphyry intrusion had lost its available heat. In either case, the longevity of

  11. Geochronological U-PB zircon dating of two ore-bearing magma pulses: stratifrom and non-stratiform bodies in the Fedorov deposit (Kola Peninsula).

    NASA Astrophysics Data System (ADS)

    Nitkina, E.

    2009-04-01

    separated from fractions of different size; the age of the ore-bearing rocks has been estimated to be 2515+/-12 Ma. As a result, the isotope U-Pb dating of the upper and lower stratiform ore bodies yielded the following ages: 2518+/-9 Ma and 2515+/-12 Ma, respectively. The age of the non-stratiform ore body obtained earlier is 2485+/-9 Ma. The ages determined in this work confirm the concepts proposed by geologists about the presence of two ore-forming stages in the Fedorov block: stratiform or simultaneous to the formation of the overall layering (2.52 Ga) and later non-stratiform stage (2.48 Ga). The research is performed under the support of grants RFBR 07-05-00956 and ofi-a 05-05-08208, SciSchool -1413.2006.5, State contract with the Federal agency of science and innovations 02.445.11.7403. Bayanova T. - S.-Peterburg.: Nauka. 2004. P. 174 Zagorodniy V., Radchenko A. - L.: Nauka. 1988. P. 110 Mitrofanov F. - Smirnovskiy sbornik - 2005. Moscow. 2005. pp. 39-54. Nitkina E. - Reports of RAS. - 2006. - V. 40. V. 1 . pp. 87-91. Mitrofanov F.P., Korchagin A.U., Dudkin O.B., Rundkvist T.V. - Exploration for platinum-group elements deposits. Short Course delivered on behalf of the Mineralogical Association of Canada in Oulu, Finland, 6-7 August 2005. Short Course Series Volume 35. Chapter 15. 2005. - P. 343-357. Schissel D., Tsvetkov A. A., Mitrofanov F. P., Korchagin A. U. - Economic geology. Vol. 97. 2002. P. 1657-1677.

  12. Oxidation potential and state of some vanadium ores and the relation of woody material to their deposition

    USGS Publications Warehouse

    Pommer, Alfred Michael

    1956-01-01

    Oxidation potential studies with a multiple pH-potential recorder designed and constructed for this purpose demonstrated that some uranium-vanadium ores in the Colorado Plateau were in a reduced state when deposited. Any oxidation which took place occurred after deposition. Experimental and theoretical reducing studies on fresh wood, wood degraded by burial for 450 years, and lignite, indicate that such ores may have been deposited by reduction of oxidized vanadium solutions by woody material. A vanadium (III) mineral, V2O(OH)4, was prepared synthetically by reduction of a vanadium (V) solution with wood. This is the only reported synthesis of any reduced vanadium mineral by any method. It was shown that the origin of almost all vanadium deposits currently of commercial importance involves life processes and products.

  13. Structural characteristics of chalcopyrite from a Cu(Au) ore deposit in the Carajás Mineral Province, Brazil

    NASA Astrophysics Data System (ADS)

    Ribeiro, Andreza Aparecida; Lima, Diana Quintão; Duarte, Hélio Anderson; Murad, Enver; Pereira, Márcio César; de Freitas Suita, Marcos Tadeu; Ardisson, José Domingos; Fabris, José Domingos

    2011-11-01

    Mössbauer spectra and X-ray diffraction data show a chalcopyrite from the Cristalino Cu(Au) deposit in the Carajás Mineral Province in northern Brazil to consist of a single, tetragonal phase. This is in stark contrast to a previously described chalcopyrite from the Camaquã copper mine in southern Brazil, obviously reflecting differences in mineral (and thus ore deposit) genesis.

  14. Coupled Heat and Fluid Flow Modeling of the Earth's Largest Zinc Ore Deposit at Red Dog, Alaska: Implications for Structurally-Focused, Free Convection in Submarine Sedimentary Basins

    NASA Astrophysics Data System (ADS)

    Garven, G.; Dumoulin, J. A.; Bradley, D. A.; Young, L. E.; Kelley, K. D.; Leach, D. L.

    2002-12-01

    Crustal heat flow can provide a strong mechanism for driving groundwater flow, particularly in submarine basins where other mechanisms for driving pore fluid flow such as topography, compaction and crustal deformation are too weak or too slow to have a significant effect on disturbing conductive heat flow. Fault zones appear to play a crucial role in focusing fluid migration in basins, as inferred in ancient rocks by many examples of hydrothermal deposits of sediment-hosted ores worldwide. Many rift-hosted deposits of lead, zinc, and barite ore appear to have formed at or near the seafloor by focused venting of hot basinal fluids and modified seawater, although the geophysical nature of these systems is not so well known. For example, the upper Kuna Formation, a finely laminated, black, organic-rich siliceous mudstone and shale in the Western Brooks Range of northwest Alaska, is host to the largest resources of zinc yet discovered in the Earth's crust, containing ore reserves in excess of 175 Mt averaging about 16% Zn and 5% Pb. Although situated today in a highly-deformed series of structural allocthonous plates thrusted during the Jurassic to Cretaceous Brookian Orogeny, the stratiform ores are thought to have formed much earlier in the anoxic, mud-rich Carboniferous-age Kuna Basin when adjacent carbonate platforms were drowned by rifting and tectonic subsidence. Fluid inclusion studies of ore-stage sphalerite and gangue minerals indicate sub-seafloor mineralization temperatures less than 200oC and most likely between 120 to 150 oC, during a period of sediment diagenesis and extensional faulting. We have constructed fully-coupled numerical models of heat and fluid flow to test hydrologic theories for free convection, submarine venting and subsequent ore formation, as constrained by paleoheat flow and petrologic observations. A finite element grid was designed and adapted for a cross section of the Kuna Basin, geologically restored to latest Mississippian time

  15. Model of formation of the Khibiny-Lovozero ore-bearing volcanic-plutonic complex

    NASA Astrophysics Data System (ADS)

    Arzamastsev, A. A.; Arzamastseva, L. V.; Zhirova, A. M.; Glaznev, V. N.

    2013-09-01

    The paper presents the results of a study of the large Paleozoic ore-magmatic system in the northeastern Fennoscandian Shield comprising the Khibiny and Lovozero plutons, the Kurga intrusion, volcanic rocks, and numerous alkaline dike swarms. As follows from the results of deep drilling and 3D geophysical simulation, large bodies of rocks pertaining to the ultramafic alkaline complex occur at the lower level of the ore-magmatic system. Peridotite, pyroxenite, melilitolite, melteigite, and ijolite occupy more than 50 vol % of the volcanic-plutonic complex within the upper 15 km accessible to gravity exploration. The proposed model represents the ore-magmatic system as a conjugate network of mantle magmatic sources localized at different depth levels and periodically supplying the melts belonging to the two autonomous groups: (1) ultramafic alkaline rocks with carbonatites and (2) alkali syenites-peralkaline syenites, which were formed synchronously having a common system of outlet conduits. With allowance for the available isotopic datings and new geochronological evidence, the duration of complex formation beginning from supply of the first batches of melt into calderas and up to postmagmatic events, expressed in formation of late pegmatoids, was no less than 25 Ma.

  16. Ore genesis and fluid evolution of the Daheishan giant porphyry molybdenum deposit, NE China

    NASA Astrophysics Data System (ADS)

    Zhou, Ling-li; Zeng, Qing-dong; Liu, Jian-ming; Friis, Henrik; Zhang, Zuo-lun; Duan, Xiao-xia; Chu, Shao-xiong

    2015-01-01

    The Daheishan giant porphyry Mo deposit is located at the eastern segment of the CAOB, NE China. The ore-bearing intrusion of Daheishan deposit is a Jurassic granitic complex that includes Changgangling biotite granodiorite, Qiancuoluo seriate granodiorite, and Qiancuoluo granodioritic porphyry. Mineralization consists of disseminated, breccia and veined types. The hydrothermal fluids show significant magmatic signatures, as evidenced by the hydrogen and oxygen isotopic compositions of quartz and sulfur isotopic characteristics of ores. Consistence of lead isotopic compositions of the sulfides and the Daheishan intrusive complex further indicate a close relationship between the mineralization and magma. The fluid inclusions in quartz comprise of predominant aqueous two-phase as well as gas-rich fluid inclusions and a small number of daughter mineral-bearing inclusions. The gas species in the fluid inclusions are H2O, CO2, N2, CH4, C2H6, Ar∗ and minor H2S; the liquid compositions are SO42-, Cl-, Na+, K+, Ca2+ and Mg2+. Raman spectroscopy on individual fluid inclusions reveals a main gaseous composition of H2O, minor H2S and CO2. The fluid system in Daheishan Mo deposit can be described as NaCl-KCl-H2O type. Fluid inclusion microthermometry reveals subsolidus homogenization temperatures for fluid inclusions in the magmatic quartz phenocrysts (Th = 400-450 °C, salinities = ∼21 eq. wt.%), suggesting an obliteration of higher temperature history of the porphyry system by the superimposed processes. Most of the mineralization occurred at temperature range of 220-360 °C, or higher. The temperature and salinity decreased to 100-170 °C and 0-15 eq. wt.%, respectively, when the hydrothermal fluid activities were gradually ending. No distinct evolution pattern based on the homogenization temperature or stable isotopic analyses is observed among the different mineralization stages. Mineralization was supposed to be related to the multi-phased boiling of fluids, instead

  17. High-resolution acoustic mapping to understand the ore deposit in the Bayonnaise knoll caldera, Izu-Ogasawara arc

    NASA Astrophysics Data System (ADS)

    Honsho, Chie; Ura, Tamaki; Asada, Akira; Kim, Kangsoo; Nagahashi, Kenji

    2015-04-01

    We collected deep-sea multibeam, side scan, and subbottom profiler data using an autonomous underwater vehicle at the Bayonnaise knoll, a submarine caldera located in the rift zone of the Izu-Ogasawara arc. We aimed to reveal topographic and geological features and the origin of a hydrothermal field called the Hakurei site in the caldera. We performed seafloor classification by textural analysis using calibrated side-scan sonar data, which provided an effective means to understand the geology and to highlight potential areas of hydrothermal constructions. The high-resolution bathymetric map illustrates that the Hakurei hydrothermal field is distributed over a landslide landform in the caldera wall. The distribution of hydrothermal vents indicates that the slip surface has served as a major route of hydrothermal fluids. The radial alignment of chimneys and mounds indicates radial routes of hydrothermal fluid and/or belching along fragile lines in the landslide landform. Various postcaldera activities are inferred including the formation of a lava dome, a pyroclastic cone, and subsequent phreatic explosions. A general volcano-tectonic structure extending across the caldera in a NW-SE direction is interpreted as an inferred boundary fault of the North Myojin Rift. Analogous to the Hokuroku basin and land kuroko deposits, it is suggested that the main contributing factor in the formation of kuroko deposits was volcano-tectonic activity that dominated the margin of the back-arc rift basin. The intersections between the margin of a rift basin and the surrounding knolls have a high potential for ore-forming areas.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  19. Seismic response of ore deposits in Kevitsa and Outokumpu mining areas: new insights from data mining and seismic forward modeling

    NASA Astrophysics Data System (ADS)

    Hellqvist, Niina; Koivisto, Emilia; Komminaho, Kari; Tuomi, Hilkka; Malehmir, Alireza; Kukkonen, Ilmo; Heikkinen, Pekka; Voipio, Teemu; Wijns, Chris

    2015-04-01

    The Kevitsa Ni-Cu-PGE disseminated sulfide deposit is hosted by the Kevitsa mafic to ultramafic intrusion located within the Central Lapland Greenstone Belt in northern Finland. The Outokumpu semi-massive to massive polymetallic (Cu-Co-Zn-Ni-Ag-Au) sulfide deposits are hosted by ophiolite-derived altered ultramafic rocks within the Raahe-Ladoga Belt in eastern Finland. Extensive, excellent quality 2D reflection seismic data have been collected at both sites in the 2000s. In addition, there is a 3D seismic data set available from Kevitsa. The ore deposits of Kevitsa and Outokumpu have different mineralization styles, grades and scales and thus have different kinds of seismic responses as well. Imaging disseminated ore deposits with the reflection seismic method is complicated, as, for example, the Kevitsa disseminated ore itself does not have dimensions detectable with the method. However, it has been suggested that subtle localised magmatic layering within the Kevitsa intrusion controls the sub-horizontal layering and spatial extent of the disseminated sulfides, and that this magmatic layering is detectable with the reflection seismic method. Initial results from data mining via SOM (Self-Organizing Maps) analysis and seismic forward modeling of the magmatic layering within the Kevitsa intrusion are used to test these hypotheses. In the case of Outokumpu-type deposits seismic forward modeling results confirm that the semi-massive to massive ore could potentially be seen directly in the seismic data, if the deposits meet the size, thickness, and presentation constraints required for reflection or diffraction.

  20. Source of ore-forming fluids of the Tianbaoshan Pb-Zn deposit, Southwest China: constrains from C-O, S, and He-Ar isotopes

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Zhang, Jun; Zhong, Wenbin

    2016-04-01

    The Sichuan-Yunnan-Guizhou (SYG) metallogenic province is one of the most important areas for Pb-Zn resources in China. The metallogenic sources of these Pb-Zn deposits have long been debated. In this study, we provide integrated C-O-S-He-Ar isotopic data of the typical Tianbaoshan Pb-Zn deposit, with an aim to constrain the sources of ore-forming fluids. The Tianbaoshan deposit a large-sized Pb-Zn deposit in SYG metallogenic province, Southwest China. The proven resources include 2.6 Mt metals of Zn+Pb with average grades of 10.09% Zn and 1.50% Pb. The orebodies are hosted within the carbonates of the Ediacaran Dengying Formation. Ore minerals consist mainly of sphalerite, galena, chalcopyrite, and pyrite. Gangue minerals are dominated by calcite and dolomite. The calcite samples from the Tianbaoshan deposit yield homogeneous δ13CV ‑PDBvalues of -1.70‰ to -1.60‰ (average -1.63), with δ18OV ‑SMOW values ranging from 12.9‰ to 15.2‰ (average 14.4). The C-O isotopic data suggest the hydrothermal fluids may be originated from a mixed source involving both mantle and carbonate wall rocks. The δ34S values of the sphalerite, galena and chalcopyrite samples vary from 3.32‰ to 5.71‰ -0.36‰ to 1.31‰ and 4.5‰ to 4.7‰ respectively, indicating a magmatic source for sulfur. The 3He/4He ratios of chalcopyrite samples range from 0.01 to 0.32 Ra which is slightly higher than the crustal ratios (0.05 Ra), but obviously lower than that of mantle fluids (6 to 9 Ra). The 40Ar/36Ar ratios range from 345.0 to 669.1, which are slightly higher than that of air (298.5). The He-Ar isotopic compositions suggest that the ore-forming fluids are dominantly derived from the crust, with litter contamination from mantle-derived fluids. In combination with the C-O, S, and He-Ar isotopic data, we propose the ore-forming fluids of the Tianbaoshan deposit were derived by mixing of crustal and mantle fluids. And the metallogenic process may be genetically related to the

  1. Petrophysical zoning elements of Chertovo Koryto gold-ore deposit (Patom Upland, Eastern Siberia)

    NASA Astrophysics Data System (ADS)

    Sokolov, S. V.; Kolmakov, Y. V.; Terre, D. A.

    2015-11-01

    The paper considers magnetic susceptibility (χ) and electrode potentials (EP) of rocks in the Chertovo Koryto deposit. Carbon-bearing substance is found in all the studied samples, but in some cases, this substance supplies EP (-150 ÷ -400 mV). In these samples χ rarely exceeds 40·10-5 SI units, while, in other samples χ is 8-10 (up to 30) times higher. Less intensive EP (-20 ÷ -240 mV) is furnished due to the sulfides in this deposit. Rocks with polarized carbon-bearing substance do not contain magnetic pyrrhotine and are negative linear EP anomalies. Rocks in which carbon-bearing substance is associated with pyrrhotine are revealed as magnetic anomalies. The adjacent rocks determine petrophysical zoning of the Chertovo Koryto deposit. The combination of negative linear EP anomalies and magnetic anomalies is a potential indicator and can define the multi-stage formation of the deposit itself.

  2. SHRIMP U-Pb ages of xenotime and monazite from the Spar Lake red bed-associated Cu-Ag deposit, western Montana: Implications for ore genesis

    USGS Publications Warehouse

    Aleinikoff, John N.; Hayes, Timothy S.; Evans, Karl V.; Mazdab, Frank K.; Pillers, Renee M.; Fanning, C. Mark

    2012-01-01

    Xenotime occurs as epitaxial overgrowths on detrital zircons in the Mesoproterozoic Revett Formation (Belt Supergroup) at the Spar Lake red bed-associated Cu-Ag deposit, western Montana. The deposit formed during diagenesis of Revett strata, where oxidizing metal-bearing hydrothermal fluids encountered a reducing zone. Samples for geochronology were collected from several mineral zones. Xenotime overgrowths (1–30 μm wide) were found in polished thin sections from five ore and near-ore zones (chalcocite-chlorite, bornite-calcite, galena-calcite, chalcopyrite-ankerite, and pyrite-calcite), but not in more distant zones across the region. Thirty-two in situ SHRIMP U-Pb analyses on xenotime overgrowths yield a weighted average of 207Pb/206Pb ages of 1409 ± 8 Ma, interpreted as the time of mineralization. This age is about 40 to 60 m.y. after deposition of the Revett Formation. Six other xenotime overgrowths formed during a younger event at 1304 ± 19 Ma. Several isolated grains of xenotime have 207Pb/206Pb ages in the range of 1.67 to 1.51 Ga, and thus are considered detrital in origin. Trace element data can distinguish Spar Lake xenotimes of different origins. Based on in situ SHRIMP analysis, detrital xenotime has heavy rare earth elements-enriched patterns similar to those of igneous xenotime, whereas xenotime overgrowths of inferred hydrothermal origin have hump-shaped (i.e., middle rare earth elements-enriched) patterns. The two ages of hydrothermal xenotime can be distinguished by slightly different rare earth elements patterns. In addition, 1409 Ma xenotime overgrowths have higher Eu and Gd contents than the 1304 Ma overgrowths. Most xenotime overgrowths from the Spar Lake deposit have elevated As concentrations, further suggesting a genetic relationship between the xenotime formation and Cu-Ag mineralization.

  3. Hydrothermal zebra dolomite in the Great Basin, Nevada--attributes and relation to Paleozoic stratigraphy, tectonics, and ore deposits

    USGS Publications Warehouse

    Diehl, S.F.; Hofstra, A.H.; Koenig, A.E.; Emsbo, P.; Christiansen, W.; Johnson, Chad

    2010-01-01

    In other parts of the world, previous workers have shown that sparry dolomite in carbonate rocks may be produced by the generation and movement of hot basinal brines in response to arid paleoclimates and tectonism, and that some of these brines served as the transport medium for metals fixed in Mississippi Valley-type (MVT) and sedimentary exhalative (Sedex) deposits of Zn, Pb, Ag, Au, or barite. Numerous occurrences of hydrothermal zebra dolomite (HZD), comprised of alternating layers of dark replacement and light void-filling sparry or saddle dolomite, are present in Paleozoic platform and slope carbonate rocks on the eastern side of the Great Basin physiographic province. Locally, it is associated with mineral deposits of barite, Ag-Pb-Zn, and Au. In this paper the spatial distribution of HZD occurrences, their stratigraphic position, morphological characteristics, textures and zoning, and chemical and stable isotopic compositions were determined to improve understanding of their age, origin, and relation to dolostone, ore deposits, and the tectonic evolution of the Great Basin. In northern and central Nevada, HZD is coeval and cogenetic with Late Devonian and Early Mississippian Sedex Au, Zn, and barite deposits and may be related to Late Ordovician Sedex barite deposits. In southern Nevada and southwest California, it is cogenetic with small MVT Ag-Pb-Zn deposits in rocks as young as Early Mississippian. Over Paleozoic time, the Great Basin was at equatorial paleolatitudes with episodes of arid paleoclimates. Several occurrences of HZD are crosscut by Mesozoic or Cenozoic intrusions, and some host younger pluton-related polymetallic replacement and Carlin-type gold deposits. The distribution of HZD in space (carbonate platform, margin, and slope) and stratigraphy (Late Neoproterozoic Ediacaran-Mississippian) roughly parallels that of dolostone and both are prevalent in Devonian strata. Stratabound HZD is best developed in Ediacaran and Cambrian units, whereas

  4. Cesium and strontium tolerant Arthrobacter sp. strain KMSZP6 isolated from a pristine uranium ore deposit.

    PubMed

    Swer, Pynskhem Bok; Joshi, Santa Ram; Acharya, Celin

    2016-12-01

    Arthrobacter sp. KMSZP6 isolated from a pristine uranium ore deposit at Domiasiat located in North-East India exhibited noteworthy tolerance for cesium (Cs) and strontium (Sr). The strain displayed a high minimum inhibitory concentration (MIC) of 400 mM for CsCl and for SrCl2. Flow cytometric analysis employing membrane integrity indicators like propidium iodide (PI) and thiazole orange (TO) indicated a greater sensitivity of Arthrobacter cells to cesium than to strontium. On being challenged with 75 mM of Cs, the cells sequestered 9612 mg Cs g(-1) dry weight of cells in 12 h. On being challenged with 75 mM of Sr, the cells sequestered 9989 mg Sr g(-1) dry weight of cells in 18 h. Heat killed cells exhibited limited Cs and Sr binding as compared to live cells highlighting the importance of cell viability for optimal binding. The association of the metals with Arthrobacter sp. KMSZP6 was further substantiated by Field Emission-Scanning Electron Microscopy (FE-SEM) coupled with Energy dispersive X-ray (EDX) spectroscopy. This organism tolerated up to 1 kGy (60)Co-gamma rays without loss of survival. The present report highlights the superior tolerance and binding capacity of the KMSZP6 strain for cesium and strontium over other earlier reported strains and reveals its potential for bioremediation of nuclear waste. PMID:27620733

  5. Ore transport and deposition in the Red Sea geothermal system: a geochemical model

    USGS Publications Warehouse

    Shanks, Wayne C., III; Bischoff, J.L.

    1977-01-01

    Thermodynamic calculation of distribution of dissolved aqueous species in the Red Sea geothermal brine provides a model of ore transport and deposition in good agreement with observed accumulations of base metal sulfides, anhydrite, and barite. The Red Sea brine is recirculated seawater that acquires high salinity by low-temperature interaction with Miocene evaporites and is subsequently heated to temperatures in excess of 200??C by interaction with recent rift zone intrusive rocks. At temperatures up to 250??C, NaSO-4 and MgSO04 are the dominant sulfur-bearing species. H2S forms by inorganic sulfate reduction at the higher temperatures but is maintained at a uniform concentration of about 2 ppm by the strength of the sulfate complexes. Chloride complexes solubilize metals at the higher temperatures, and thus sulfide and metals are carried together into the Atlantis II Deep. Below 150??C, the brine becomes supersaturated with respect to chalcopyrite, sphalerite, galena, and iron monosulfide due to chloride-complex dissociation. Sulfide precipitation rates, based on the rate of brine influx, are in good agreement with measured sedimentation rates. Anhydrite precipitates as crystalline fissure infillings from high-temperature inflowing brine. Barite forms from partial oxidation of sulfides at the interface between the lower hot brine and the transitional brine layer. ?? 1977.

  6. Chapter C: Hydrothermal Enrichment of Gallium in Zones of Advanced Argillic Alteration-Examples from the Paradise Peak and McDermitt Ore Deposits, Nevada

    USGS Publications Warehouse

    Rytuba, James J.; John, David A.; Foster, Andrea; Ludington, Steven D.; Kotlyar, Boris

    2003-01-01

    Gallium is produced as a byproduct from bauxite and zinc sulfide ores and rarely from primary Ga ores. High Ga contents (>60 ppm) can occur in zones of advanced argillic alteration consisting of alunite+kaolinite+quartz associated with quartz-alunite (high sulfidation Au-Ag) deposits. In a magmatic-hydrothermal environment, the zones of advanced argillic alteration associated with quartz-alunite (high sulfidation) Au-Ag deposits have the highest Ga contents (max 120 ppm). In these Au deposits, Ga is enriched in the zone of alunite+kaolinite alteration and depleted in the zone of quartz-rich alteration within acid-leached rocks. Peripheral zones of argillic alteration have Ga contents and Al/Ga ratios similar to those in unaltered volcanic rocks. The zones of advanced argillic alteration that formed in a steam-heated environment in association with hot-spring-type Hg-Au deposits are not Ga enriched, and residual silicified zones have very low Ga contents. The McDermitt Hg and Paradise Peak Au-Hg deposits, Nev., have zones of advanced argillic alteration that are Ga enriched. At the Paradise Peak Au-Hg deposits, Ga is enriched in the zone of alunite+jarosite alteration that formed in a magmatic-hydrothermal environment. Ga is depleted in the zone of opal+alunite alteration formed in a steam-heated environment, in residual silicified zones formed in a magmatic-hydrothermal environment, and in zones of supergene jarosite alteration. At the McDermitt Hg deposit, Ga is enriched in the zone of alunite+kaolinite alteration below the zone of adularia-quartz alteration that coincides with the Hg ore body. The spatial relation of Ga enrichment to alunite-kaolinite alteration suggests that formation in a magmatic-hydrothermal environment. X-ray-absorption spectra of Ga-enriched samples from the McDermitt Hg deposit are similar to that of gallium sulfate and support the association of Ga enrichment with alunite alteration.

  7. Geodynamic and climate controls in the formation of Mio-Pliocene world-class oxidized cobalt and manganese ores in the Katanga province, DR Congo

    NASA Astrophysics Data System (ADS)

    Decrée, Sophie; Deloule, Étienne; Ruffet, Gilles; Dewaele, Stijn; Mees, Florias; Marignac, Christian; Yans, Johan; de Putter, Thierry

    2010-10-01

    The Katanga province, Democratic Republic of Congo, hosts world-class cobalt deposits accounting for ~50% of the world reserves. They originated from sediment-hosted stratiform copper and cobalt sulfide deposits within Neoproterozoic metasedimentary rocks. Heterogenite, the main oxidized cobalt mineral, is concentrated as “cobalt caps” along the top of silicified dolomite inselbergs. The supergene cobalt enrichment process is part of a regional process of residual ore formation that also forms world-class “manganese cap” deposits in western Katanga, i.e., the “black earths” that are exploited by both industrial and artisanal mining. Here, we provide constraints on the genesis and the timing of these deposits. Ar-Ar analyses of oxidized Mn ore and in situ U-Pb SIMS measurements of heterogenite yield Mio-Pliocene ages. The Ar-Ar ages suggest a multi-phase process, starting in the Late Miocene (10-5 Ma), when the metal-rich substratum was exposed to the action of meteoric fluids, due to major regional uplift. Further oxidation took place in the Pliocene (3.7-2.3 Ma) and formed most of the observed deposits under humid conditions: Co- and Mn-caps on metal-rich substrata, and coeval Fe laterites on barren areas. These deposits formed prior to the regional shift toward more arid conditions in Central Africa. Arid conditions still prevailed during the Quaternary and resulted in erosion and valley incision, which dismantled the metal-bearing caps and led to ore accumulation in valleys and along foot slopes.

  8. The composition of fluid inclusions in ore and gangue minerals from the Silesian-Cracow Mississippi Valley-type Zn-Pb deposits Poland: Genetic and environmental implications

    USGS Publications Warehouse

    Viets, J.G.; Hofstra, A.H.; Emsbo, P.; Kozlowski, A.

    1996-01-01

    The composition of fluids extracted from ore and gangue sulfide minerals that span most of the paragenesis of the Silesian-Cracow district was determined using a newly developed ion chromatographic (IC) technique. Ionic species determined were Na+, NH+4, Ca2+, Mg2+, K+, Rb+, Sr2+, Ba2+, Cl-, Br-, F-, I-, PO3-4, CO2-3, HS-, S2O2-3, SO2-4, NO-3, and acetate. Mineral samples included six from the Pomorzany mine and one from the Trzebionka mine which are hosted in the Triassic Muschelkalk Formation, and two samples of drill core from mineralized Upper Devonian strata. Nine paragenetically identifiable sulfide minerals occur throughout the Silesian-Cracow district. These include from earliest to latest: early iron sulfides, granular sphalerite, early galena, light-banded sphalerite, galena, dark-banded sphalerite, iron sulfides, late dark-banded sphalerite with late galena, and late iron sulfides. Seven of the minerals were sampled for fluid inclusion analysis in this study. Only the early iron sulfides and the last galena stage were not sampled. Although the number of analyses are limited to nine samples and two replicates and there is uncertainty about the characteristics of the fluid inclusions analyzed, the data show clear temporal trends in the composition of the fluids that deposited these minerals. Fluid inclusions in minerals deposited later in the paragenesis have significantly more K+, Br-, NH+4, and acetate but less Sr2+ than those deposited earlier in the paragenesis. The later minerals are also characterized by isotopically lighter sulfur and significantly more Tl and As in the solid minerals. The change in ore-fluid chemistry is interpreted to reflect a major change in the hydrologic regime of the district. Apparently, the migrational paths of ore fluids from the Upper Silesian basin changed during ore deposition and the fluids which deposited early minerals reacted with aquifers with very different geochemical characteristics than those that deposited

  9. Mineral-organic formations in Berezitovy deposit (the Amur region, Russia)

    NASA Astrophysics Data System (ADS)

    Vakh, E. A.; Vakh, A. S.; Petukhov, V. I.; Nikulina, T. V.; Tarasenko, I. A.

    2016-03-01

    The article examines the structure and composition of mineral-organic formations within the hypergenesis zone of Berezitovy deposit (the Amur region). The detailed study has shown that these recent formations are represented by algae identified as Trentepohlia jolithus (Linnaeus) Wallroth. The process of macro and micro element accumulation in these formations is likely to have a complex sediment-chemogenic-organogenic nature and results from the flow of the suspended and dissolved substances formed within the hypergenesis zone of sulphide ores. It is also assumed that some elements accumulated in the formations were previously absorbed by algae from the mineralized water environment.

  10. Boiling, colloid nucleation and aggregation, and the genesis of bonanza Au-Ag ores of the sleeper deposit, Nevada

    NASA Astrophysics Data System (ADS)

    Saunders, J. A.; Schoenly, P. A.

    1995-06-01

    A deep “parent” composition for bonanza oreforming fluids at the Sleeper deposit was calculated by the computer program SOLVEQ using fluid-inclusion microthermometric and gas data, and by assuming equilibrium with the following minerals present in vein samples below the bonanza zones: gold, chalcedony, adularia, pyrite, chalcopyrite, and acanthite. The calculated dissolved gold content of 295 ppb is approximately 2 orders of magnitude higher than that assumed for typical geothermal systems. Thus, a gold-enriched fluid appears to have been a principal factor in the genesis of bonanza Au-Ag ores at the Sleeper deposit. Geochemical modelling of possible ore-forming processes using the computer program CHILLER, with the reconstructed ore-forming solution as a starting composition, indicates that boiling most closely reproduces observed minerals and their relative abundances in bonanza ores. The constraint imposed by the association of amorphous silica with gold precludes all of the mixing scenarios modelled, such as mixing with cold and steam-heated groundwaters (acid-sulfate, CO2-rich). Modelling indicates that boiling of a gold-rich deep solution leads to rapid gold precipitation, and that the amount of gold precipitated initially is large relative to other minerals. These factors apparently led to nucleation of colloidal gold particles instead of in-situ gold deposition or coprecipitation with other phases. Gold colloids apparently were entrained in the upward-flowing hydrothermal solutions and grew as they travelled. Upon reaching a critical size (10 100 nm?), they were deposited due to orthokinetic aggregation at an elevation and temperature at which amorphous silica was nucleating and aggregating.

  11. Dal'negosrk skarn deposit, Sikhote-Alin: Stages and sources of matter for borosilicate ores

    NASA Astrophysics Data System (ADS)

    Karas', O. A.; Ratkin, V. V.

    2014-04-01

    The danburite orebody at the northeastern wall of the open pit of the Dal'negorsk borosilicate deposit is studied. The comparative mineralogical-, isotopic-, and thermobarogeochemical analyses of danburite from the Levoberezhnyi area and datolite of the late skarn stage from the Tsentral'nyi open pit confirms that danburite is a result of the early borosilicate stage of formation of the deposit. Combined with previously published data, it is concluded that marine sedimentary rocks or Early Cretaceous arkose sandstones from the matrix of the Taukhin accretionary prism could be the source of boron.

  12. Structural controls and evolution of gold-, silver-, and REE-bearing copper-cobalt ore deposits, Blackbird district, east-central Idaho: Epigenetic origins

    USGS Publications Warehouse

    Lund, K.; Tysdal, R.G.; Evans, K.V.; Kunk, M.J.; Pillers, R.M.

    2011-01-01

    Textural data at all scales indicate that the host sites for veins and the tectonic evolution of both host rocks and mineral deposits were kinematically linked to Late Cretaceous regional thrust faulting. Heat, fluids, and conduits for generation and circulation of fluids were part of the regional crustal thickening. The faulting also juxtaposed metaevaporite layers in the Mesoproterozoic Yellowjacket Formation over Blackbird district host rocks. We conclude that this facilitated chemical exchange between juxtaposed units resulting in leaching of critical elements (Cl, K, B, Na) from metaevaporites to produce brines, scavenging of metals (Co, Cu, etc) from rocks in the region, and, finally, concentrating metals in the lower-plate ramp structures. Although the ultimate source of the metals remains undetermined, the present Cu-Co ± Au (± Ag ± Ni ± REE) Blackbird ore deposits formed during Late Cretaceous compressional deformation.

  13. Leaching of silica bands and concentration of magnetite in Archean BIF by hypogene fluids: Beebyn Fe ore deposit, Yilgarn Craton, Western Australia

    NASA Astrophysics Data System (ADS)

    Duuring, Paul; Hagemann, Steffen

    2013-03-01

    The ~2,752-Ma Weld Range greenstone belt in the Yilgarn Craton of Western Australia hosts several Fe ore deposits that provide insights into the role of early hypogene fluids in the formation of high-grade (>55 wt% Fe) magnetite-rich ore in banded iron formation (BIF). The 1.5-km-long Beebyn orebody comprises a series of steeply dipping, discontinuous, <50-m-thick lenses of magnetite-(martite)-rich ore zones in BIF that extend from surface to vertical depths of at least 250 m. The ore zones are enveloped by a 3-km-long, 150-m-wide outer halo of hypogene siderite and ferroan dolomite in BIF and mafic igneous country rocks. Ferroan chlorite characterises 20-m-wide proximal alteration zones in mafic country rocks. The magnetite-rich Beebyn orebody is primarily the product of hypogene fluids that circulated through reverse shear zones during the formation of an Archean isoclinal fold-and-thrust belt. Two discrete stages of hypogene fluid flow caused the pseudomorphic replacement of silica-rich bands in BIF by Stage 1 siderite and magnetite and later by Stage 2 ferroan dolomite. The resulting carbonate-altered BIF is markedly depleted in SiO2 and enriched in CaO, MgO, LOI, P2O5 and Fe2O3(total) compared with the least-altered BIF. Subsequent reactivation of these shear zones and circulation of hypogene fluids resulted in the leaching of existing hypogene carbonate minerals and the concentration of residual magnetite-rich bands. These Stage 3 magnetite-rich ore zones are depleted in SiO2 and enriched in K2O, CaO, MgO, P2O5 and Fe2O3(total) relative to the least-altered BIF. Proximal wall rock hypogene alteration zones in mafic igneous country rocks (up to 20 m from the BIF contact) are depleted in SiO2, CaO, Na2O, and K2O and are enriched in Fe2O3(total), MgO and P2O5 compared with distal zones. Recent supergene alteration affects all rocks within about 100 m below the present surface, disturbing hypogene mineral and the geochemical zonation patterns associated with

  14. The Sarylakh and Sentachan gold-antimony deposits, Sakha-Yakutia: A case of combined mesothermal gold-quartz and epithermal stibnite ores

    NASA Astrophysics Data System (ADS)

    Bortnikov, N. S.; Gamynin, G. N.; Vikent'eva, O. V.; Prokof'ev, V. Yu.; Prokop'ev, A. V.

    2010-10-01

    New mineralogical, thermobarometric, isotopic, and geochemical data provide evidence for long and complex formation history of the Sarylakh and Sentachan Au-Sb deposits conditioned by regional geodynamics and various types of ore mineralization, differing in age and source of ore matter combined in the same ore-localizing structural units. The deposits are situated in the Taryn metallogenic zone of the East Yakutian metallogenic belt in the central Verkhoyansk-Kolyma Fold Region. They are controlled by the regional Adycha-Taryn Fault Zone that separates the Kular-Nera Terrane and the western part of the Verkhoyansk Fold-Thrust Belt. The fault extends along the strike of the northwest-trending linear folds and is deep-rooted and repeatedly reactivated. The orebodies are mineralized crush zones accompanied by sulfidated (up to 100 m wide) quartz-sericite metasomatic rocks and replacing dickite-pyrophyllite alteration near stibnite veinlets. Two stages of low-sulfide gold-quartz and stibnite mineralization are distinguished. The formation conditions of the early milk white quartz in orebodies with stibnite mineralization at the Sarylakh and Sentachan deposits are similar: temperature interval 340-280°C, salt concentration in fluids 6.8-1.6 wt % NaCl equiv, fluid pressure 3430-1050 bar, and sodic bicarbonate fluid composition. The ranges of fluid salinity overlapped at both deposits. In the late regenerated quartz that attends stibnite mineralization, fluid inclusions contain an aqueous solution with salinity of 3.2 wt % NaCl equiv and are homogenized into liquid at 304-189°C. Syngenetic gas inclusions contain nitrogen 0.19 g/cm3 in density. The pressure of 300 bar is estimated at 189°C. The composition of the captured fluid is characterized as K-Ca bicarbonatesulfate. The sulfur isotopic composition has been analyzed in pyrite and arsenopyrite from ore and metasomatic zones, as well as in coarse-, medium-, and fine-grained stibnite varieties subjected to

  15. Microfracturing and fluid mixing in granites: W (Sn) ore deposition at Vaulry (NW French Massif Central)

    NASA Astrophysics Data System (ADS)

    Vallance, Jean; Cathelineau, Michel; Marignac, Christian; Boiron, Marie-Christine; Fourcade, Serge; Martineau, François; Fabre, Cécile

    2001-07-01

    The Vaulry W-(Sn) mineralisation, located at the eastern boundary of the Blond rare metal leucogranite, is contained in a set of subvertical quartz veins, locally with muscovite and minor quartz selvages. The sequence of deposition was: (1) milky quartz, predominantly as fracture filling, generally affected by subsequent ductile deformation; (2) hyaline quartz-wolframite-cassiterite; (3) minor sulphides. Other sets of quartz veinlets, although generally barren are observed in the Blond massif. Fluid migration at the microscopic scale within the granite and in the vicinity of quartz fractures was constrained by studying the geometry of fluid-inclusion planes and fluid-inclusion chemistry in and outside the mineralised area. Three major sets of subvertical fluid-inclusion planes are recognised: a N050°-060°E set, mostly developed in the veins and in the immediate vicinity, a N110°-130°E set, regionally developed in the granite and a N140-160°E set of local extent. As a whole, the density of FIP decreases from the mineralised zones toward the barren part of the pluton, except for the N140°-160°E set. These are locally abundant around quartz veinlets with similar orientations that form a broad "N-S" band near the Blond locality. Mineralising fluids observed as primary inclusions in cassiterite and in undeformed hyaline quartz are mostly aqueous, with moderate salinity and a minor volatile component, at variance with many other W-(Sn) deposits in the Variscan belt. Ore deposition occurred around 315°C, at an estimated depth of 5.5 km, under hydrostatic to slightly suprahydrostatic pressures. It resulted from fluid mixing, in the central part of a large hydrothermal system, between two end-members: (i) a hot (425-430°C) moderately saline fluid, that contained a diluted volatile component and, although Na-dominated, minor amounts of Li and Ca. The estimated δ18O indicates that this fluid was completely equilibrated with the tectono-magmatic pile (pseudo

  16. Kizilcaören ore-bearing complex with carbonatites (northwestern Anatolia, Turkey): Formation time and mineralogy of rocks

    NASA Astrophysics Data System (ADS)

    Nikiforov, A. V.; Öztürk, H.; Altuncu, S.; Lebedev, V. A.

    2014-02-01

    The results of isotope-geochronological and mineralogical studies of the rocks making up the Kizilcaören fluorite-barite-REE deposit, northwestern Anatolia, Turkey are discussed in the paper. The ore is a constituent of the subvolcanic complex localized in a large fault zone. The complex combines (from earlier to later rocks): (1) phonolite and trachyte stocks, (2) carbonatite and carbonate-silicate dikelike bodies; and (3) fluorite-barite-bastnaesite ore in the form of thick homogeneous veins and cement in breccia. The K-Ar dating of silicate igneous rocks and carbonatites shows that they were formed in the Chattian Age of the Oligocene 25-24 Ma ago. Mineralogical observations show that the ore is the youngest constituent in the rock complex. Supergene alteration deeply transformed ore-bearing rocks, in particular, resulting in leaching of primary minerals, presumably Ca-Mn-Fe carbonates, and in cementation of the residual bastnaesitefluorite framework by Fe and Mn hydroxides. Most of the studied rocks contain pyrochlore, LREE fluorocarbonates, Nb-bearing rutile, Fe-Mg micas, and K-feldspar. The genetic features of the deposit have been considered. In general, the ore-bearing rock complex is compared in the set of rocks and their mineralogy and geochemistry with deposits of the Gallinas Mountains in the United States, the Arshan and Khalyuta deposits in the western Transbaikalia region, and Mushugai-Khuduk deposit in Mongolia. The Kizilcaören deposit represents a variant of postmagmatic mineralization closely related to carbonatite magmatism associated with alkaline and subalkaline intermediate rocks.

  17. The importance of dissolved free oxygen during formation of sandstone-type uranium deposits

    USGS Publications Warehouse

    Granger, Harry Clifford; Warren, C.G.

    1979-01-01

    One factor which distinguishes t, he genesis of roll-type uranium deposits from the Uravan Mineral Belt and other sandstone-type uranium deposits may be the presence and concentration of dissolved free oxygen in the ore-forming. solutions. Although dissolved oxygen is a necessary prerequisite for the formation of roll-type deposits, it is proposed that a lack of dissolved oxygen is a prerequisite for the Uravan deposits. Solutions that formed both types of deposits probably had a supergene origin and originated as meteoric water in approximate equilibrium with atmospheric oxygen. Roll-type deposits were formed where the Eh dropped abruptly following consumption of the oxygen by iron sulfide minerals and creation of kinetically active sulfur species that could reduce uranium. The solutions that formed the Uravan deposits, on the other hand, probably first equilibrated with sulfide-free ferrous-ferric detrital minerals and fossil organic matter in the host rock. That is, the uraniferous solutions lost their oxygen without lowering their Eh enough to precipitate uranium. Without oxygen, they then. became incapable of oxidizing iron sulfide minerals. Subsequent localization and formation of ore bodies from these oxygen-depleted solutions, therefore, was not necessarily dependent on large reducing capacities.

  18. The Carlin-type gold deposits of the "golden triangle" of SW China: Pb and S isotopic constraints for the ore genesis

    NASA Astrophysics Data System (ADS)

    Chen, Maohong; Zhang, Zhiqiang; Santosh, M.; Dang, Yuan; Zhang, Wei

    2015-05-01

    The Yunnan-Guizhou-Guangxi "golden triangle" is considered as one of the important regions for Carlin-type (or Carlin-like) gold deposits in China. Gold deposits in this region can be grouped into lode type controlled by faults and layer-like type controlled by host strata. Arsenopyrite is one of the major gold-bearing minerals in these deposits. Here we report the S and Pb isotopic composition of arsenopyrites from the fault-controlled Lannigou and Jinya gold deposits and the stratabound Shuiyindong gold deposits, with a view to trace the sources of sulfur and lead, and to evaluate the genetic aspects of gold mineralization. The average δ34S values of arsenopyrites are 11.7‰ for Lannigou, 6.7‰ for Shuiyindong and -5.3‰ for Jinya, which are slightly lower to that of diagenetic pyrite in the host rocks of each deposit. The δ34S values of arsenopyrites show significant variation among the different deposits (-9.0‰ to +17.1‰), which indicate a sedimentary origin for sulfur, followed by local fluid-rock interaction. The Pb isotopic composition of arsenopyrites from these deposits shows a narrow range (206Pb/204Pb = 18.494-18.813, 207Pb/204Pb = 15.630-15.748, 208Pb/204Pb = 38.559-38.884), indicating that the different deposits have the same source of lead. Based on a comparison with Pb isotopic ratios of diagenetic pyrite, arsenopyrite and Late Cretaceous magmatic rocks from this region reported in previous studies, we infer that the lead was sourced from the sediments rather than from magmatic intrusions. The formation of the Carlin-type gold deposits are therefore correlated with the evolution of the Youjiang basin from rifting to closure, and involved four distinct stages leading to the concentration of the gold ores.

  19. [Physiological Properties of Acidithiobacillus ferrooxidans Strains Isolated from Sulfide Ore Deposits in Kazakhstan].

    PubMed

    Kanaeva, Z K; Bulaev, A G; Kanaev, A T; Kondrat'eva, T F

    2015-01-01

    Acidithiobacillus ferroxidans strains were isolated from acidophilic microbial communities of Kazakhstan sulfide ore deposits. Their biotechnologically important properties (optimal and maximal growth temperatures and resistance to NaCl) were determined. While temperature optima of the strains were the same (30-32 degrees C), temperature ranges were different. Thus, strain TFBK oxidized iron very poorly at 37 degrees C, while for strain TFV, the iron oxidation rate at this temperature was insignificantly lower than at lesser temperatures. NaCl inhibited the oxidative activity of both strains. Iron oxidation by strain TFV was inhibited at 5 g/L NaCl and was suppressed almost completely at 20 g/L. Iron oxidation by strain TFBK was inhibited by NaCl to a lesser degree, so that iron oxidation rate was relatively high at 10 g/L, while at 20 g/L NaCl the process was not suppressed completely, although the oxidation rate was low. Sulfur oxidation by these strains was less affected by NaCl than oxidation of ferrous iron. Sulfur oxidation by strain TFV was considerably inhibited only at 20 g/L NaCl, but was not suppressed completely. Sulfur oxidation by strain TFBK was more affected by NaCl. At 10 g/L NaCl the oxidation rate was much lower than at lower NaCl concentrations (sulfate concentrations after 6 days of oxidation at 5 and 10 g/L NaCl were -130 and -100 mM, respectively). While sulfur oxidation by strain TFBK was considerably inhibited at 10 and 20 g/L NaCl, similar to strain TFV it was not suppressed completely. Our results indicate the adaptation of the species A. ferrooxidans to a broad range of growth conditions. PMID:26263692

  20. Deposit formation in hydrocarbon rocket fuels

    NASA Technical Reports Server (NTRS)

    Roback, R.; Szetela, E. J.; Spadaccini, L. J.

    1981-01-01

    An experimental program was conducted to study deposit formation in hydrocarbon fuels under flow conditions that exist in high-pressure, rocket engine cooling systems. A high pressure fuel coking test apparatus was designed and developed and was used to evaluate thermal decomposition (coking) limits and carbon deposition rates in heated copper tubes for two hydrocarbon rocket fuels, RP-1 and commercial-grade propane. Tests were also conducted using JP-7 and chemically-pure propane as being representative of more refined cuts of the baseline fuels. A parametric evaluation of fuel thermal stability was performed at pressures of 136 atm to 340 atm, bulk fuel velocities in the range 6 to 30 m/sec, and tube wall temperatures in the range 422 to 811 K. Results indicated that substantial deposit formation occurs with RP-1 fuel at wall temperatures between 600 and 800 K, with peak deposit formation occurring near 700 K. No improvements were obtained when deoxygenated JP-7 fuel was substituted for RP-1. The carbon deposition rates for the propane fuels were generally higher than those obtained for either of the kerosene fuels at any given wall temperature. There appeared to be little difference between commercial-grade and chemically-pure propane with regard to type and quantity of deposit. Results of tests conducted with RP-1 indicated that the rate of deposit formation increased slightly with pressure over the range 136 atm to 340 atm. Finally, lating the inside wall of the tubes with nickel was found to significantly reduce carbon deposition rates for RP-1 fuel.

  1. The genesis of ores

    SciTech Connect

    Brimhall, G. )

    1991-05-01

    Human history and technology have been shaped by metals. How did they become concentrated in minable deposits located so conveniently near the earth's surface The author explains the mechanisms of fluid transport-by magma, water and even air and wind-responsible for the chemical and physical interactions that created bodies of metallic ores throughout geologic history. From their formation to their modification at the surface of the earth, ore deposits are geologically transitory and reflect dynamic processes within the earth as well as atmospheric and climatic influences on hydrologic systems. As highly reactive supracrustal systems, they then serve as geochemical sensors providing a powerful record and set of tracer elements for deducing the history, transport paths and forces operative in the crust.

  2. Origin of the giant Allard Lake ilmenite ore deposit (Canada) by fractional crystallization, multiple magma pulses and mixing

    NASA Astrophysics Data System (ADS)

    Charlier, Bernard; Namur, Olivier; Malpas, Simon; de Marneffe, Cédric; Duchesne, Jean-Clair; Vander Auwera, Jacqueline; Bolle, Olivier

    2010-06-01

    The late-Proterozoic Allard Lake ilmenite deposit is located in the Havre-Saint-Pierre anorthosite complex, part of the allochtonous polycyclic belt of the Grenville Province. Presently the world's largest Fe-Ti oxide deposit, it had a pre-mining amount in excess of 200 Mt at grades over 60 wt.% hemo-ilmenite. The main ore body is a funnel-shaped intrusion, measuring 1.03 × 1.10 km and 100-300 m-thick. Two smaller bodies are separated by faults and anorthosite. The ore is an ilmenite-rich norite (or ilmenitite) made up of hemo-ilmenite (Hem 22.6-29.4, 66.2 wt.% on average), andesine plagioclase (An 45-50), aluminous spinel and locally orthopyroxene. Whole-rock chemical compositions are controlled by the proportions of ilmenite and plagioclase ± orthopyroxene which supports the cumulate origin of the deposit. Ore-forming processes are further constrained by normal and reverse fractionation trends of Cr concentration in cumulus ilmenite that reveal multiple magma emplacements and alternating periods of fractional crystallization and magma mixing. Mixing of magmas produced hybrids located in the stability field of ilmenite resulted in periodic crystallization of ilmenite alone. The unsystematic differentiation trends in the Allard Lake deposit, arising from a succession of magma pulses, hybridisation, and the fractionation of hemo-ilmenite alone or together with plagioclase suggest that the deposit formed within a magma conduit. This dynamic emplacement mechanism associated with continuous gravity driven accumulation of Fe-Ti oxides and possibly plagioclase buoyancy in a fractionating ferrobasalt explains the huge concentration of hemo-ilmenite. The occurrence of sapphirine associated with aluminous spinel and high-alumina orthopyroxene (7.6-9.1 wt.% Al 2O 3) lacking exsolved plagioclase supports the involvement of a metamorphic overprint during the synchronous Ottawan orogeny, which is also responsible for strong textural equilibration and external granule of

  3. Formation and resulfidization of a South Texas roll-type uranium deposit

    USGS Publications Warehouse

    Goldhaber, Martin B.; Reynolds, Richard L.; Rye, Robert O.

    1979-01-01

    Core samples from a roll type uranium deposit in Live Oak County, south Texas have been studied and results are reported for Se, Mo, FeS2 and organic-carbon distribution, sulfide mineral petrology, and sulfur isotopic composition of iron-disulfide phases. In addition, sulfur isotopic compositions of dissolved sulfate and sulfide from the modern ground water within the ore bearing sand have been studied. The suite of elements in the ore sand and their geometric relationships throughout the deposit are those expected for typical roll-type deposits with well-developed oxidation-reduction interfaces. However, iron-disulfide minerals are abundant in the altered tongue, demonstrating that this interval has been sulfidized after mineralization (resulfidized or rereduced). Iron disulfide minerals in the rereduced interval differ mineralogically and isotopically from those throughout the remainder of the deposit. The resulfidized sand contains dominantly pyrite that is enriched in 34S, whereas the sand beyond the altered tongue contains abundant marcasite that is enriched in the light isotope, 32S. Textural relationships between pyrite and marcasite help to establish relative timing of iron disulfide formation. In reduced rock outside the altered tongue, three distinct generations of iron disulfide are present. The oldest of these generations consists largely of pyrite with lesser amounts of marcasite. A major episode of marcasite formation contemporaneous with ore genesis postdates the oldest pyrite generation but predates a younger pyrite generation. Resulfidization probably led to the final pyrite stage recognized beyond the altered tongue. Stable isotope data establish that the source of sulfur for the resulfidization was fault-leaked H2S probably derived from the Edwards Limestone of Cretaceous age which underlies the deposit. The deposit formed in at least two stages: (1) a pre-ore process of host rock sulfidization which produced disseminated pyrite as the dominant

  4. Enumeration and characterization of microorganisms associated with the uranium ore deposit at Cigar Lake, Canada; Informal report

    SciTech Connect

    Francis, A.J.; Joshi-Tope, G.; Gillow, J.B.; Dodge, C.J.

    1994-03-01

    The high-grade uranium deposit at Cigar Lake, Canada, is being investigated as a natural analog for the disposal of nuclear fuel waste. Geochemical aspects of the site have been studied in detail, but the microbial ecology has not been fully investigated. Microbial populations in an ore sample and in groundwater samples from the vicinity of the ore zone were examined to determine their effect on uranium mobility. Counts of the total number of bacteria and of respiring bacteria were obtained by direct microscopy, and the viable aerobic and anaerobic bacteria were assessed as colony forming units (CFUs) by the dilution plating technique. In addition, the population distribution of denitrifiers, fermenters, iron- and sulfur-oxidizers, iron- and sulfate-reducers, and methanogens was determined by the most probable number (MPN) technique.

  5. Ore mineralogy of the Serra Pelada Au-Pd-Pt deposit, Carajás, Brazil and implications for ore-forming processes

    NASA Astrophysics Data System (ADS)

    Berni, Gabriel V.; Heinrich, Christoph A.; Lobato, Lydia M.; Wall, Vic

    2016-01-01

    Serra Pelada is a world-class hydrothermal Au-Pd-Pt deposit located at the eastern border of the Amazon craton, northern Brazil. The rocks at Serra Pelada have experienced intense tropical weathering for about 70 Ma, but drill core samples preserve the primary mineralogy and hydrothermal alteration features, with extreme grades of Au, Pd and Pt individually reaching hundreds of parts per million (ppm) by weight. Mineralization at Serra Pelada occurs in hydrothermally altered metasiltstones and dolomitic metasandstones at the hinge zone of a recumbent syncline, comprising zones of hematite, chlorite-carbon, argillic, and siliceous alteration. The main hydrothermal gangue minerals are quartz, kaolinite, sericite, amesite, hematite, monazite, florencite and variable amounts of highly reflective carbonaceous matter. Hydrothermal carbon input is evident from precipitated carbon occurring along crenulation planes and veinlets associated with the precious metals. Ore and accessory minerals include a variety of sulphide, selenide, arsenide, sulphate and oxide minerals, including gold with variable metal contents, palladian gold, fischesserite, sudovikovite, sperrylite, selenian braggite, isomertieite, mertieite-II and secondary Au-Pt-Pd alloys. The composition of fischesserite varies from the ideal formula (Ag3AuSe2) towards a more Ag-rich composition, indicating a disordered solid solution form that is stable only above 260 °C, consistent with the high thermal maturity of associated carbonaceous matter approaching graphite. Primary ore and gangue minerals at Serra Pelada comprise a suite of elements that are best transported in oxidising conditions and precipitated upon reduction. This suggests that fluid mixing between a highly oxidised (metal carrier) and a reduced fluid was a key process for high-grade noble metal precipitation at Serra Pelada.

  6. Ore mineralogy of the Serra Pelada Au-Pd-Pt deposit, Carajás, Brazil and implications for ore-forming processes

    NASA Astrophysics Data System (ADS)

    Berni, Gabriel V.; Heinrich, Christoph A.; Lobato, Lydia M.; Wall, Vic

    2016-08-01

    Serra Pelada is a world-class hydrothermal Au-Pd-Pt deposit located at the eastern border of the Amazon craton, northern Brazil. The rocks at Serra Pelada have experienced intense tropical weathering for about 70 Ma, but drill core samples preserve the primary mineralogy and hydrothermal alteration features, with extreme grades of Au, Pd and Pt individually reaching hundreds of parts per million (ppm) by weight. Mineralization at Serra Pelada occurs in hydrothermally altered metasiltstones and dolomitic metasandstones at the hinge zone of a recumbent syncline, comprising zones of hematite, chlorite-carbon, argillic, and siliceous alteration. The main hydrothermal gangue minerals are quartz, kaolinite, sericite, amesite, hematite, monazite, florencite and variable amounts of highly reflective carbonaceous matter. Hydrothermal carbon input is evident from precipitated carbon occurring along crenulation planes and veinlets associated with the precious metals. Ore and accessory minerals include a variety of sulphide, selenide, arsenide, sulphate and oxide minerals, including gold with variable metal contents, palladian gold, fischesserite, sudovikovite, sperrylite, selenian braggite, isomertieite, mertieite-II and secondary Au-Pt-Pd alloys. The composition of fischesserite varies from the ideal formula (Ag3AuSe2) towards a more Ag-rich composition, indicating a disordered solid solution form that is stable only above 260 °C, consistent with the high thermal maturity of associated carbonaceous matter approaching graphite. Primary ore and gangue minerals at Serra Pelada comprise a suite of elements that are best transported in oxidising conditions and precipitated upon reduction. This suggests that fluid mixing between a highly oxidised (metal carrier) and a reduced fluid was a key process for high-grade noble metal precipitation at Serra Pelada.

  7. Multiphase origin of the Cu Co ore deposits in the western part of the Lufilian fold-and-thrust belt, Katanga (Democratic Republic of Congo)

    NASA Astrophysics Data System (ADS)

    Dewaele, S.; Muchez, Ph.; Vets, J.; Fernandez-Alonzo, M.; Tack, L.

    2006-12-01

    A multiphase origin of the Cu-Co ores in the western part of the Lufilian fold-and-thrust belt in Central Africa is proposed based on literature, satellite image interpretations and petrographic and fluid inclusion analyses on samples from the stratiform mineralization of Kamoto and Musonoi (DR Congo). The various mineral occurrences in the Katanga Copperbelt can be classified in distinct categories: stratiform, supergene enrichment and vein-type. The stratiform mineralization form the largest group and can be found mainly in Lower Roan (R-2) rocks, which can be identified as ridges on satellite imagery. Ore deposits outside the R-2 occur along lineaments and result often from supergene enrichment. The main phase of the stratiform mineralization in the Katanga Copperbelt occurred during diagenesis preceding the Lufilian orogeny. Petrographic observation identified various mineralizing phases, which played a role in the formation of these stratiform mineralization. Mineralization started during early diagenesis, but mainly occurred during further burial. After the formation of early diagenetic pyrite, the circulation of diagenetic Cu-Co-rich fluids resulted in the formation of the main mineralization. Preliminary microthermometric investigation of primary inclusions in authigenic quartz, associated with the main stage of stratiform mineralization, indicates that an H 2O-NaCl fluid with a minimum temperature between 80 and 195 °C and a salinity between 8.4 and 18.4 eq. wt% NaCl circulated during the main phase of mineralization. Numerous faults and fractures formed during the Lufilian orogeny cut the stratiform mineralization. They are, however, at Kamoto and Musonoi only associated with minor sulphides. Supergene alteration along faults and fractures resulted in an enrichment of the mineralization, with the formation of secondary Cu-oxides, -carbonates and -silicates. The importance of the interaction of various processes for the formation of economic Cu-Co ore

  8. Hydrothermal alteration and the chemistry of ore-forming fluids in an unconformity-type uranium deposit

    SciTech Connect

    Komninou, A.; Sverjensky, D.A.

    1995-07-01

    Compositions of hydrothermal chlorite and fine-grained white mica from the inner and outer alteration halos in the Koongarra U deposit were analyzed by electron microprobe and analytical electron microscopy. Analyses show that although chlorite and white mica compositions vary considerably outside the main ore zone, they are uniform inside the ore zone. Ore-zone chlorite has a ratio of Fe/(Fe + Mg) of 0.25 and low octahedral occupancy (average 5.5 per formula unit), which may represent a mixture of di- and trioctahedral chlorite. White mica has a typical K + Na atomic content of 0.85 per formula unit. These compositions were used to calculate the activity ratios a{sub Fe{sup +2}}/a{sub H{sup +}}{sup 2}, a{sub Mg{sup +2}}/a{sub H{sup +}}{sup 2}, a{sub K{sup +}}/a{sub H{sup +}}, and a{sub Na{sup +}}/a{sub H{sup +}} for the hydrothermal fluids associated with deposition of uraninite. Hydrothermal apatite analyses in conjunction with salinities suggested from fluid inclusion studies were used to calculate the pH of the fluids during the pre-ore alteration. The calculated pH values range from 4.8 to 6.0. Finally, the coexistence of chlorite with quartz and hematite was used to calculate oxygen fugacities. The calculated values are about 2 log units higher than for the hematite-magnetite buffer at 200{degrees}C. Consequently, the oxidation state of the fluid lay in the hematite field and U was probably transported as uranyl complexes.

  9. Metallogeny of the northeastern Pacific Rim: an example of the distribution of ore deposits along a growing continental margin

    USGS Publications Warehouse

    Goldfarb, R.J.; Hart, C.J.; Mortensen, J.K.

    1999-01-01

    The distribution of mineral deposits within northwestern North America (Alaska, Yukon, and northern British Columbia) allows for an in-depth examination of the metallogenic patterns of a growing continental margin. A more complete understanding of the tectonic evolution of this part of the Pacific Rim, achieved over the last 15 to 20 years, now allows for the placement of ore systems into a well-defined plate tectonic framework. Ore deposits older than about 185 Ma represent hydrothermal systems that were active in the platform/shelf environment of ancestral North America's miogeocline or hydrothermal systems developed in oceanic arcs and continental fragments more distal to the craton. These include important SEDEX, VMS, and pre-accretionary porphyry deposits. In contrast, most mineral deposits younger than about 185 Ma were formed within the growing Cordilleran orogen, as terranes were accreted to the continental margin during interactions between the North America and Pacific/Farallon/Kula plates. Such syn- to post-accretionary mineralised systems include many large lode gold and porphyry/skarn systems.

  10. Genesis of basalt-hosted massive sulphide deposits from the Trondheim and Sulitjelma districts, Norway: ore lead isotopic considerations

    NASA Astrophysics Data System (ADS)

    Fox, J. S.; Farquhar, R.; Rui, I.; Cook, N.

    1988-10-01

    Lead isotopic ratios of bulk sulphides from eleven stratigraphically equivalent deposits from the Köli Nappe sequence in the Trondheim district, and eleven from the Köli sequence at Sulitjelma Norway, have been determined. When plotted on 207Pb/204Pb-206Pb/204Pb diagrams, the data define a linear trend extending from the mantle to the upper crustal model growth curves of Doe and Zartman (1979). Moreover, the data from both districts lie on the same trend. This isotopic trend is interpreted as resulting from the mixing of lead from a mantle source (probably the host basalts) with that of an upper-crustal end member (either sialic basement or the terrigenous sediments surrounding the host basalts). It is also concluded that the deposits in both camps formed more or less contemporaneously. The isotopic mixing line is comparable with that obtained from Besshi ore pyrites in Japan, for which an aulacogenic depositional environment, similar to that found today in the Gulf of California, has been proposed (Fox 1984). It is concluded that a similar depositional environment was responsible for the Trondheim and Sulitjelma ores, although an ensialic back-arc basin, or other possible environments, cannot be entirely ruled out.

  11. Studies into the formation of PBDEs and PBDD/Fs in the iron ore sintering process.

    PubMed

    Drage, D S; Aries, E; Harrad, S

    2014-07-01

    Polybrominated diphenyl ethers (PBDEs) and polybrominated dibenzo-p-dioxins and furans (PBDD/Fs) were detected in stack emissions from UK sinter plants. The sum of 36 PBDE congeners was measured at a mean concentration of 295 ng/N m(3) with a standard deviation of 96 ng/N m(3). The mean PBDD/F concentrations were 0.14 ng WHO-TEQ/m(3) (range=0.03-0.39). PBDD/F emission concentrations were approximately ten times lower than their PCDD/F homologues. To understand the possible formation mechanisms of brominated organic species in iron ore sintering, both full-scale and laboratory experiments using an experimental sintering process were carried out. A complete PBDE mass balance was undertaken for a full scale sinter plant showing that PBDEs were already present in the raw materials such as iron ores and coke breeze and that a significant proportion of the PBDE inputs were actually destroyed during the process. A number of controlled experiments were conducted using a laboratory-scale sintering apparatus (sinter pot). These were designed to investigate: (a) mass balance of PBDEs during sintering, (b) the relationship between the availability of bromide (as KBr) and PBDE emissions, and (c) the influence of the availability of both bromide and PBDEs on PBDD/F formation. As observed in the full scale plant, the PBDEs already present in the raw materials were mostly destroyed during the process (79-96%) for all sinter pot experiments. Increasing amounts of KBr in the raw sinter mix did not result in a significant increase in PBDE formation suggesting that there was no PBDE formation in sintering via de novo synthesis. No relationship was observed between PBDE inputs and PBDD/F emissions indicating that PBDEs did not act as precursors for PBDD/Fs formation. Finally, PBDD/F formation was enhanced substantially with increasing amounts of KBr suggesting that their formation mechanism was similar to that of PCDD/Fs via de novo synthesis. PMID:24742560

  12. Mantle heat drives hydrothermal fluids responsible for carbonate-hosted base metal deposits: evidence from 3He/4He of ore fluids in the Irish Pb-Zn ore district

    NASA Astrophysics Data System (ADS)

    Davidheiser-Kroll, B.; Stuart, F. M.; Boyce, A. J.

    2014-06-01

    There is little consensus on whether carbonate-hosted base metal deposits, such as the world-class Irish Zn + Pb ore field, formed in collisional or extensional tectonic settings. Helium isotopes have been analysed in ore fluids trapped in sulphides samples from the major base metal deposits of the Irish Zn-Pb ore field in order to quantify the involvement of mantle-derived volatiles that require melting to be realised, as well as test prevailing models for the genesis of the ore fields. 3He/4He ratios range up to 0.2 R a, indicating that a small but clear mantle helium contribution is present in the mineralising fluids trapped in galena and marcasite. Sulphides from ore deposits with the highest fluid inclusion temperatures (~200 °C) also have the highest 3He/4He (>0.15 R a). Similar 3He/4He are recorded in fluids from modern continental regions that are undergoing active extension. By analogy, we consider that the hydrothermal fluids responsible for the carbonate-hosted Irish base metal mineralization circulated in thinned continental crust undergoing extension and demonstrate that enhanced mantle heat flow is ultimately responsible for driving fluid convection.

  13. Hydrodynamic modeling of magmatic-hydrothermal activity at submarine arc volcanoes, with implications for ore formation

    NASA Astrophysics Data System (ADS)

    Gruen, Gillian; Weis, Philipp; Driesner, Thomas; Heinrich, Christoph A.; de Ronde, Cornel E. J.

    2014-10-01

    Subduction-related magmas have higher volatile contents than mid-ocean ridge basalts, which affects the dynamics of associated submarine hydrothermal systems. Interaction of saline magmatic fluids with convecting seawater may enhance ore metal deposition near the seafloor, making active submarine arcs a preferred modern analogue for understanding ancient massive sulfide deposits. We have constructed a quantitative hydrological model for sub-seafloor fluid flow based on observations at Brothers volcano, southern Kermadec arc, New Zealand. Numerical simulations of multi-phase hydrosaline fluid flow were performed on a two-dimensional cross-section cutting through the NW Caldera and the Upper Cone sites, two regions of active venting at the Brothers volcanic edifice, with the former hosting sulfide mineralization. Our aim is to explore the flow paths of saline magmatic fluids released from a crystallizing magma body at depth and their interaction with seawater circulating through the crust. The model includes a 3×2 km sized magma chamber emplaced at ∼2.5 km beneath the seafloor connected to the permeable cone via a ∼200 m wide feeder dike. During the simulation, a magmatic fluid was temporarily injected from the top of the cooling magma chamber into the overlying convection system, assuming hydrostatic conditions and a static permeability distribution. The simulations predict a succession of hydrologic regimes in the subsurface of Brothers volcano, which can explain some of the present-day hydrothermal observations. We find that sub-seafloor phase separation, inferred from observed vent fluid salinities, and the temperatures of venting at Brothers volcano can only be achieved by input of a saline magmatic fluid at depth, consistent with chemical and isotopic data. In general, our simulations show that the transport of heat, water, and salt from magmatic and seawater sources is partly decoupled. Expulsion of magmatic heat and volatiles occurs within the first few

  14. Lead and Sulfur isotopic constraints on the origin of Pb-Zn ore deposits and tectonic evolution of the Central Tauride Belt, Turkey

    NASA Astrophysics Data System (ADS)

    Ghosh, N.; Ciftci, E.; Basu, A. R.

    2010-12-01

    source and evaporite horizons, respectively. The 206Pb/204Pb versus δ34S plot for the Galena samples show a distinctly negative trend from more positive δ34S values at lower 206Pb/204Pb ratios to δ34S ≈ 0 at 206Pb/204Pb = 19.06, the latter indicating the mantle component in the galenas. From the above geochemical data we suggest a large portion of the lead in the Pb-Zn ore deposits of the Central Taurides was sourced from the igneous activity associated with the oceanic crust formation in an island arc setting. The regional geological and tectonic setting of these massive sulfide deposits thus suggest a rifting process in the beginning, followed by ore deposition in an oceanic crust, and terminating with the closure of the ocean basin in the Upper Senonian by compressional tectonic activity.

  15. Boron isotope evidence for the involvement of non-marine evaporites in the origin of the Broken Hill ore deposits

    USGS Publications Warehouse

    Slack, J.F.; Palmer, M.R.; Stevens, B.P.J.

    1989-01-01

    IDENTIFYING the palaeogeographic setting and mode of origin of stratabound ore deposits can be difficult in high-grade metamorphic terranes, where the effects of metamorphism may obscure the nature of the protoliths. Here we report boron isotope data for tourmalines from the early Proterozoic Broken Hill block, in Australia, which hosts giant lead-zinc-silver sulphide deposits. With one exception the 11B/10B ratios are lower than those for all other tourmalines from massive sulphide deposits and tour-malinites elsewhere in the world. We propose that these low ratios reflect leaching of boron from non-marine evaporitic borates by convecting hydrothermal fluids associated with early Proterozoic continental rifting. A possible modern analogue is the Salton Sea geothermal field in California. ?? 1989 Nature Publishing Group.

  16. Spatial and temporal distribution of Cu-Au-Mo ore deposits along the western Tethyan convergent margin: a link with the 3D subduction dynamics

    NASA Astrophysics Data System (ADS)

    Menant, A.; Bertrand, G.; Loiselet, C.; Guillou-Frottier, L.; Jolivet, L.

    2012-12-01

    Emplacement conditions of mineralized systems in subduction and post-subduction environments and the sources of metals such as Cu, Mo and Au have been considered in the past. However, despite their importance in exploration strategies at the continental scale, interrelationships between distribution of ore systems and subduction dynamics are still partly unclear. Along the western Tethyan convergent margin, where Tertiary subduction history is well constrained, porphyry, epithermal and skarn ore deposits show a variable evolution of their spatial distribution. Using different and complementary database on European and Middle East ore deposits, three metallogenic episodes have been highlighted: (1) a late Cretaceous - Paleocene phase characterized by a copper mineralization within the Balkan chain and in the Kaçkar mountains (eastern Turkey), (2) an Eocene phase with a few copper ore deposits in eastern Turkey and small Caucasia and (3) an Oligocene - Neogene phase with a more southern distribution along the margin and mainly constituted by epithermal Au systems in the west (Carpathians, Rhodope, Aegean and western Turkey) and by porphyry copper deposits in the east (Zagros). These changes are suspected to be controlled by complex and evolving subduction dynamics. Using paleogeographic tools, it turned out that, in the eastern Mediterranean area, the late Cretaceous - Paleocene and Oligocene - Neogene metallogenic episodes are coeval with a significant decrease of the Africa - Eurasia convergence rate, from about 1.5 to 0.4 cm/yr. Indeed, compressional tectonics in the volcanic arc domain, associated with a high convergent rate, promote the storage of large volumes of metal-rich magma and the development of an extensive MASH (melting, assimilation, storage and homogenization) zone. When this convergence rate decreases, a stress relaxation occurs in the overriding crust, inducing the ascent of a sufficient flux of this fertile magma and allowing the formation of

  17. The Balmat-Edwards zinc-lead deposits-synsedimentary ore from Mississippi valley-type fluids.

    USGS Publications Warehouse

    Whelan, J.F.; Rye, R.O.; Delorraine, W.

    1984-01-01

    The Balmat-Edwards Zn-Pb district in New York is in Mid-Proterozoic Grenville marbles. Tabular to podiform, generally conformable massive sphalerite-galena orebodies occur at various horizons in the approx 1 km-thick marbles. Metamorphism obscured or obliterated most primary characteristics, whose reconstruction is attempted through detailed S, C, and O isotope studies of the Fowler orebody, and trace element and S isotope studies of sphalerite concentrates and composite ore samples from 22 orebodies. Sulphur isotope data reflect equilibration at near peak metamorphism with some indication of re-equilibration during retrograde metamorphism. The carbon and oxygen isotope composition of gangue carbonates suggests derivation from the host marbles. The oxygen isotope composition of gangue quartz is compatible with a chert origin or metamorphism-equilibration with other minerals. Sulphur and lead isotopes and sulphide mineralogy suggests that the ore fluids were evolved basin brines, chemically like those responsible for Mississippi Valley-type deposits. The large stratigraphic span (> 600 m) of the Balmat orebodies may be due to basin dewatering of million-year intervals. Stratigraphically increasing 34S values of evaporite-anhydrite are postulated to record hydrothermal events and to imply bacterial sulphate reduction on an unusually large scale. Such a stratigraphic increase may be a general exploration guide where sediment-hosted exhalative deposits or Mississippi Valley-type deposits occur.-G.J.N.

  18. Lead-isotopic, sulphur-isotopic, and trace-element studies of galena from the Silesian-Cracow Zn-Pb ores, polymetallic veins from the Gory Swietokrzyskie MTS, and the Myszkow porphyry copper deposit, Poland

    USGS Publications Warehouse

    Church, S.E.; Vaughn, R.B.; Gent, C.A.; Hopkins, R.T.

    1996-01-01

    Lead-isotopic data on galena samples collected from a paragenetically constrained suite of samples from the Silesian-Cracow ore district show no regional or paragenetically controlled lead-isotopic trends within the analytical reproducibility of the measurements. Furthermore, the new lead-isotopic data agree with previously reported lead-isotopic results (R. E. Zartman et al., 1979). Sulfur-isotopic analyses of ores from the Silesian-Cracow district as well as from vein ore from the Gory Swietokrzyskie Mts. and the Myszkow porphyry copper deposit, when coupled with trace-element data from the galena samples, clearly discriminate different hydrothermal ore-forming events. Lead-isotopic data from the Permian and Miocene evaporite deposits in Poland indicate that neither of these evaporite deposits were a source of metals for the Silesian-Cracow district ores. Furthermore, lead-isotopic data from these evaporite deposits and the shale residues from the Miocene halite samples indicate that the crustal evolution of lead in the central and western European platform in southern Poland followed normal crustal lead-isotopic growth, and that the isotopic composition of crustal lead had progressed beyond the lead-isotopic composition of lead in the Silesian-Cracow ores by Permian time. Thus, Mesozoic and Tertiary sedimentary flysch rocks can be eliminated as viable source rocks for the metals in the Silesian-Cracow Mississippi Valley-type (MVT) deposits. The uniformity of the isotopic composition of lead in the Silesian-Cracow ores, when coupled with the geologic evidence that mineralization must post-date Late Jurassic faulting (E. Gorecka, 1991), constrains the geochemical nature of the source region. The source of the metals is probably a well-mixed, multi-cycle molasse sequence of sedimentary rocks that contains little if any Precambrian metamorphic or granitic clasts (S. E. Church, R. B. Vaughn, 1992). If ore deposition was post Late Jurassic (about 150 m. y.) or later

  19. Geological, geochronological, and mineralogical constraints on the genesis of the Chengchao skarn Fe deposit, Edong ore district, Middle-Lower Yangtze River Valley metallogenic belt, eastern China

    NASA Astrophysics Data System (ADS)

    Yao, Lei; Xie, Guiqing; Mao, Jingwen; Lü, Zhicheng; Zhao, Caisheng; Zheng, Xianwei; Ding, Ning

    2015-04-01

    The Edong ore district is located within the westernmost Middle-Lower Yangtze River Valley metallogenic belt (MLYRB), and hosts the largest concentration of skarn Fe deposits in China, although the origin of these deposits remains controversial. The Chengchao deposit is the largest skarn Fe deposit so far discovered within the MLYRB, and provides a good opportunity to address the debate surrounding the origin of these skarn Fe deposits. Here, we present geological, geochronological, and mineralogical data from the Chengchao skarn deposit and associated intrusions, and discuss the relationships between granitoids and mineralization in the Chengchao deposit. The NW-SE-striking orebodies in the study area have porphyritic quartz monzonite and/or granite footwalls, and Triassic marble or diorite hangingwalls, indicating a spatial relationship between these intrusions and Fe mineralization. Zircon U-Pb data from the granite, porphyritic quartz monzonite, diorite, and porphyritic diabase dike within the deposit show ages of 129 ± 1, 128 ± 1, 140 ± 1, and 126 ± 1 Ma, respectively. These ages and the previously reported ages on the timing of mineralization suggest that the porphyritic quartz monzonite and granite are coeval with the formation of the skarn Fe deposit. Our data confirm that the granitic rocks are temporally associated with Fe mineralization. The prograde substage of skarn development is characterized by two stages of andradite (Adr98-38Grs61-2Prp2-0Sps1-0Alm1-0) and diopside (Di95-61Hd37-5Jo3-0), including an early stage of garnet and pyroxene formation that is genetically associated with the mineralization. The early stage garnets are more andradite-rich (Adr98-50Grs49-2Prp1-0Sps1-0Alm0) than the late veinlet garnets characterized by intermediate grandite compositions (Adr67-37Grs61-31Prp2-0Sps1-0Alm1-0). The early stage pyroxenes (Di95-74Hd26-5Jo1-0) are compositionally distinct from the late stage pyroxenes (Di84-61Hd37-16Jo3-0). Compositional

  20. Formation and mitigation of PCDD/Fs in iron ore sintering.

    PubMed

    Ooi, Tze Chean; Lu, Liming

    2011-10-01

    The sintering of iron ore is presently a significant industrial source of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) worldwide owing to the fundamental requirement of the operation of a high temperature process to pre-treat fines and to recycle plant by-products arising from the integrated iron and steelworks. The process is a noteworthy contributor of PCDD/F indirectly due to decreasing PCDD/F releases from municipal solid waste incineration. Commonly PCDD/F formation from the process is associated with the addition of oily mill scales although raw material containing a combination of C, Cl and specific metal catalyst has been shown to drastically increase PCDD/F formation in the process. The degenerate graphitic structure of carbon present in coke fuel and soot formed and the chemistry of catalytic metals and Cl are important factors. A review on PCDD/F emission in this process has been carried out, including examination of its formation mechanism, congener distribution, contributing factors and mitigation strategies, with emphasis on the use of inhibiting compound to achieve suppression. A detailed analysis of the de novo and precursor theories of formation and the contributing factor is given since the subject of PCDD/F formation is still controversial. The de novo formation pathway identified in sinter plants and controlled studies performed in the laboratory as well as at pilot-scale are discussed; where appropriate, a comparison is drawn between sintering and other thermal processes emitting PCDD/Fs. Summary of the latest developments in PCDD/F downstream abatement strategies presently employed in full scale industrial plants is provided. Potential inhibiting compounds are discussed in terms of their mode of action and merits under sintering conditions. PMID:21880347

  1. Ores and Climate Change - Primary Shareholders

    NASA Astrophysics Data System (ADS)

    Stein, Holly J.; Hannah, Judith L.

    2015-04-01

    Many in the economic geology community concern themselves with details of ore formation at the deposit scale, whether tallying fluid inclusion data to get at changes in ore-forming fluids or defining structures that aid and abet mineralization. These compilations are generally aimed at interpretation of events at the site of ore formation, with the goal being assignment of the deposit to a sanctioned ore deposit model. While providing useful data, this approach is incomplete and does not, by itself, serve present-day requirements for true interdisciplinary science. The ore-forming environment is one of chaos and disequilibrium at nearly all scales (Stein, 2014). Chaos and complexity are documented by variably altered rocks, veins or disseminated mineralization with multi-generational fluid histories, erratic and unusual textures in host rocks, and the bitumen or other hydrocarbon products entwined within many ore deposits. This should give pause to our drive for more data as a means to find "the answer". The answer lies in the kind of data collected and more importantly, in the way we interpret those data. Rather than constructing an ever-increasing catalog of descriptive mutations on sanctioned ore deposit models (e.g., IOGC or Iron-Oxide Copper Gold deposits), the way forward is to link source and transport of metals, sulfur, and organic material with regional and ultimately whole Earth chemical evolution. Important experimental work provides chemical constraints in controlled and behaved environments. To these data, we add imagination and interpretation, always tying back to field observations. In this paper, several key points are made by way of ore deposit examples: (1) many IOCG deposits are outcomes of profound changes in the chemistry of the Earth's surface, in the interplay of the atmosphere, hydrosphere, biosphere, and lithosphere; (2) the redox history of Fe in deep earth may be ultimately expressed in the ore-forming sequence; and (3) the formation of

  2. An overview of the geology and major ore deposits of Central Africa: Explanatory note for the 1:4,000,000 map “Geology and major ore deposits of Central Africa”

    NASA Astrophysics Data System (ADS)

    Milesi, J. P.; Toteu, S. F.; Deschamps, Y.; Feybesse, J. L.; Lerouge, C.; Cocherie, A.; Penaye, J.; Tchameni, R.; Moloto-A-Kenguemba, G.; Kampunzu, H. A. B.; Nicol, N.; Duguey, E.; Leistel, J. M.; Saint-Martin, M.; Ralay, F.; Heinry, C.; Bouchot, V.; Doumnang Mbaigane, J. C.; Kanda Kula, V.; Chene, F.; Monthel, J.; Boutin, P.; Cailteux, J.

    2006-04-01

    This paper is prepared within the frameworks of IGCP Project 470 and the associated BRGM scientific project "Africa 1999-2004" to accompany the 1:4,000,000 scale map "Geology and major ore deposits of Central Africa, presented at the 20th Colloquium of African Geology in Orleans in June 2004. It incorporates geological and metallogenic data from eight countries in Central Africa (Angola, Cameroon, Chad, Central African Republic, Congo Brazzaville, Democratic Republic of Congo (DRC), Equatorial Guinea and Zambia). The map is a harmonised and geo-referenced preliminary map, based on a GIS at 1:2,000,000 scale, and focusses on the spatial and temporal distribution of selected major deposits.

  3. Physicochemical formation conditions of silver sulfoselenides at the Rogovik deposit, Northeastern Russia

    NASA Astrophysics Data System (ADS)

    Zhuravkova, T. V.; Palyanova, G. A.; Kravtsova, R. G.

    2015-07-01

    The chemical compositions of acanthite, naumannite, and associated ore minerals have been studied from the samples of polychronous Au-Ag ores at the Rogovik deposit. The following admixtures have been detected: S in naumannite (0-2.9 wt %), Se in acanthite (0-7.45 wt %), argyrodite (~4.8 wt %), and galena (~3.1 wt %), and Fe in sphalerite (~1.2 wt %). The physicochemical parameters of ore formation have been reconstructed on the basis of mineralogical and geochemical data and thermodynamic calculations. Eh-pH (25°C, 1 bar), log fO2-pH, log fS2- T, log fSe2- T, and log fS2-log fSe2 (100-300°C, 1-300 bars) diagrams for the Ag-S-Se-H2O system with the stability fields of Ag sulfoselenides Ag2S1- x Se x of various composition (step x = 0.25, where 0 ≤ x ≤ 1) have been calculated for the first time. It has been established that Ag sulfoselenides of the naumannite series from polychronous ores of the Rogovik deposit precipitated below 70-133°C under reductive conditions (log fO2 =-65…-50) from near-neutral solutions containing elevated Se and relatively lowered S. It has been established that Ag sulfoselenides of acanthite series were formed later then naumannite but in the same range of log fO2 values at temperatures below 110-177°C from solutions with high S concentration and relatively lowered concentration of Se. The complex composition of the studied Au-Ag ores, whose characteristic feature is extremely variable mineralogy, is confirmed.

  4. Chalcophile element (Ni, Cu, PGE, and Au) variations in the Tamarack magmatic sulfide deposit in the Midcontinent Rift System: implications for dynamic ore-forming processes

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    correlation between Pt and Pd, and between individual IPGE. At a given Pt or Pd content, however, the semi-massive sulfide ores have higher IPGE contents than the disseminated sulfide samples. Modeling results show that the variations in PGE tenors (metals in recalculated 100 % sulfide) in the Tamarack magmatic sulfide deposit are mainly controlled by variable R factors (magma/sulfide-liquid mass ratios) during sulfide-liquid segregation and subsequent monosulfide solid solution (MSS) fractionation during cooling. The initial contents of Ir, Pt, and Pd in the parental magma, estimated from the metal tenors of the disseminated sulfides, are 0.2, 2, and 1.8 ppb, respectively, which are ˜1/5 of the values for the PGE-undepleted primitive basalts of the Midcontinent Rift System. The variations of PGE tenors in the semi-massive and massive sulfide ores can be explained by MSS fractional crystallization from sulfide liquids. Extreme variations in the PGE contents of the massive sulfides may also in part reflect metal mobility during post-crystallization hydrothermal processes. The higher PGE tenors for the disseminated sulfides in the CGO dike relative to those in the FGO Intrusion are consistent with formation in a dynamic conduit where the early sulfide liquids left in the conduit by the FGO magma were subsequently upgraded by the subsequent surge of the CGO magma. The relatively low PGE tenors for the semi-massive and massive sulfides can be explained by lack of such an upgrading process for the sulfide due to their distal locations in a migrating conduit.

  5. Evolution of volcanic rocks and associated ore deposits in the Marysvale volcanic field, Utah

    USGS Publications Warehouse

    Cunningham, Charles G.; Steven, Thomas A.; Rowley, Peter D.; Naeser, Charles W.; Mehnert, Harald H.; Hedge, Carl E.; Ludwig, Kenneth R.

    1994-01-01

    A geological account on the igneous activity and associated mineral deposition in the volcanic field of Marysvale in Utah is presented. Three episodes (34-22 Ma, 22-14 Ma and 9-5 Ma) involved in the volcanic rock eruption and associated mineralization are described. The first episode is believed to have occurred during the time of tectonic convergence when two contrasting suites of rocks, Mount Dutton Formation and Bullion Canyon Volcanics, erupted concurrently. Mineralization during this period was sparse. In the second episode, change from intermediate to bimodal volcanism occurred. During the third episode, basaltic compositions did not change. Although major element constituent had rhyolites similar to that of the second episode, rhyolites had a marked radiogenic isotope characteristic difference.

  6. Geophysical model of the Cu-Mo porphyry ore deposit at Copper Flat Mine, Hillsboro, Sierra County, New Mexico

    NASA Astrophysics Data System (ADS)

    Gutierrez, Adrian Emmanuel Gutierrez

    A 3D gravity model of the Copper Flat Mine was performed as part of the exploration of new resources in at the mine. The project is located in the Las Animas Mining District in Sierra County, New Mexico. The mine has been producing ore since 1877 and is currently owned by the New Mexico Copper Corporation, which plans o bringing the closed copper mine back into production with innovation and a sustainable approach to mining development. The Project is located on the Eastern side of the Arizona-Sonora-New Mexico porphyry copper Belt of Cretaceous age. Copper Flat is predominantly a Cretaceous age stratovolcano composed mostly of quartz monzonite. The quartz monzonite was intruded by a block of andesite alter which a series of latite dikes creating veining along the topography where the majority of the deposit. The Copper Flat deposit is mineralized along a breccia pipe where the breccia is the result of auto-brecciation due to the pore pressure. There have been a number of geophysical studies conducted at the site. The most recent survey was a gravity profile on the area. The purpose of the new study is the reinterpretation of the IP Survey and emphasizes the practical use of the gravity geophysical method in evaluating the validity of the previous survey results. The primary method used to identify the deposit is gravity in which four Talwani models were created in order to created a 3D model of the ore body. The Talwani models have numerical integration approaches that were used to divide every model into polygons. The profiles were sectioned into polygons; each polygon was assigning a specific density depending on the body being drawn. Three different gridding techniques with three different filtering methods were used producing ten maps prior to the modeling, these maps were created to establish the best map to fit the models. The calculation of the polygons used an exact formula instead of the numerical integration of the profile made with a Talwani approach. A

  7. Sulfur isotope and trace element data from ore sulfides in the Noranda district (Abitibi, Canada): implications for volcanogenic massive sulfide deposit genesis

    NASA Astrophysics Data System (ADS)

    Sharman, Elizabeth R.; Taylor, Bruce E.; Minarik, William G.; Dubé, Benoît; Wing, Boswell A.

    2015-06-01

    We examine models for volcanogenic massive sulfide (VMS) mineralization in the ~2.7-Ga Noranda camp, Abitibi subprovince, Superior Province, Canada, using a combination of multiple sulfur isotope and trace element data from ore sulfide minerals. The Noranda camp is a well-preserved, VMS deposit-rich area that is thought to represent a collapsed volcanic caldera. Due to its economic value, the camp has been studied extensively, providing a robust geological framework within which to assess the new data presented in this study. We explore previously proposed controls on mineralization within the Noranda camp and, in particular, the exceptional Au-rich Horne and Quemont deposits. We present multiple sulfur isotope and trace element compositional data for sulfide separates representing 25 different VMS deposits and "showings" within the Noranda camp. Multiple sulfur isotope data for this study have δ34SV-CDT values of between -1.9 and +2.5 ‰, and Δ33SV-CDT values of between -0.59 and -0.03 ‰. We interpret the negative Δ33S values to be due to a contribution of sulfur that originated as seawater sulfate to form the ore sulfides of the Noranda camp VMS deposits. The contribution of seawater sulfate increased with the collapse and subsequent evolution of the Noranda caldera, an inference supported by select trace and major element analyses. In particular, higher concentrations of Se occur in samples with Δ33S values closer to 0 ‰, as well as lower Fe/Zn ratios in sphalerite, suggesting lower pressures and temperatures of formation. We also report a relationship between average Au grade and Δ33S values within Au-rich VMS deposits of the Noranda camp, whereby higher gold grades are associated with near-zero Δ33S values. From this, we infer a dominance of igneous sulfur in the gold-rich deposits, either leached from the volcanic pile and/or directly degassed from an associated intrusion.

  8. A quantitative model of ground-water flow during formation of tabular sandstone uranium deposits

    USGS Publications Warehouse

    Sanford, R.F.

    1994-01-01

    Presents a quantitative simulation of regional groundwater flow during uranium deposition in the Westwater Canyon Member and Jackpile Sandstone Member of the Upper Jurassic Morrison Formation in the San Juan basin. Topographic slope, shoreline position, and density contrasts in the lake and pore fluids controlled the directions of flow and recharge-discharge areas. The most important results for uranium ore deposit formation are that regional groundwater discharged throughout the basin, regional discharge was concentrated along the shore line or playa margin, flow was dominantly gravity driven, and compaction dewatering was negligible. A strong association is found between the tabular sandstone uranium deposits and major inferred zones of mixed local and regional groundwater discharge. -from Author

  9. Genesis of sediment-hosted disseminated-gold deposits by fluid mixing and sulfidization: Chemical-reaction-path modeling of ore-depositional processes documented in the Jerritt Canyon district, Nevada

    NASA Astrophysics Data System (ADS)

    Hofstra, A. H.; Leventhal, J. S.; Northrop, H. R.; Landis, G. P.; Rye, R. O.; Birak, D. J.; Dahl, A. R.

    1991-01-01

    Integrated geologic, geochemical, fluid-inclusion, and stableisotope studies of the gold deposits in the Jerritt Canyon district, Nevada, provide evidence that gold deposition was a consequence of both fluid mixing and sulfidization of host-rock iron. Chemical-reaction-path models of these ore-depositional processes confirm that the combination of fluid mixing, including simultaneous cooling, dilution, and oxidation of the ore fluid, and wall-rock reaction, with sulfidization of reactive iron in the host rock, explains the disseminated nature and small size of the gold and the alteration zonation, mineralogy, and geochemistry observed at Jerritt Canyon and at many other sediment-hosted disseminated gold deposits.

  10. Paleomagnetism, rock magnetism and opaque mineralogy of iron ore deposits from southern Mexico and their implications for quantitative modelling of magnetometric data

    SciTech Connect

    Alva-Valdivia, L.M.; Fucugauchi, Urrutia, J.; Bohnel, H.; Moran Zenteno, D.J. )

    1990-06-01

    Paleomagnetism, Rock Magnetism and Opaque Mineralogy of Iron Ore Deposits from Southern Mexico and Their Implications for Quantitative Modelling of Magnetometric Data. The tectonic history of the Pacific continental margin is critical for understanding their mineral deposits. The margin presents intrusive and volcanic activity characteristic of magmatic arcs of subduction zones, which are genetically related with deposits of Cu, Fe, Mo, Au, and Ag. Although the tectonic history has been complex, involving oblique plate subduction, lateral movements, accretion of magmatic arcs and oceanic plateaux, and lateral displacements of major blocks, the mineral deposits are spatially distributed along elongated belts that roughly follow the margin. The authors have conducted paleomagnetic, rock magnetic, and petrological studies of the iron ore deposits to investigate genesis, magnetic mineralogy, stratigraphic relationships, metamorphism, and applications on quantitative modelling of magnetometric data. The remanent magnetization and susceptibility data are necessary for interpretation of magnetic anomalies. The results permit a comparison of the mineral deposits along the continental margin.

  11. Hydrothermal alteration of organic matter in uranium ores, Elliot Lake, Canada: Implications for selected organic-rich deposits

    SciTech Connect

    Mossman, D.J.; Nagy, B.; Davis, D.W.

    1993-07-01

    Organic matter in the uraniferous Matinenda Formation, Elliot Lake, is preserved in the forms of syngenetic kerogen and solid bitumen as it is in many of the Oklo uranium deposits and in the Witwatersrand gold-uranium ores. The Elliot Lake kerogen is a vitrinite-like material considered to be remnants of the Precambrian cyanobacterial mats. The kerogen at Elliot Lake has reflectances (in oil) ranging from 2.63-7.31% RO{sub max}, high aromaticity, relatively low (0.41-0.60) atomic H/C ratios, and it contains cryptocrystalline graphite. Bitumen, present primarily as dispersed globules (up to 0.5 mm dia.), has reflectances from 0.72-1.32% RO{sub max}, atomic H/C ratios of 0.71-0.81, and is somewhat less aromatic than the kerogen. Overall similarity in molecular compositions indicates that liquid bitumen was derived from kerogen by processes similar to hydrous pyrolysis. The carbon isotopic composition of kerogen ({minus}15.62 to {minus}24.72%), and the now solid bitumen ({minus}25.91 to {minus}33.00%) are compatible with these processes. Despite having been subjected to several thermal episodes, ca. 2.45 Ga old kerogen of microbiological origin here survived as testimony of the antiquity of life on Earth. U-Pb isotopic data from discrete kerogen grains at Elliot Lake form a scattered array intersecting concordia at 2130 {+-} 100 Ma, correspond to the Nipissing event. U-Pb systems were totally reset by this event. Uranium and lead show subsequently partial mobility, the average of which is indicated by the lower concordia intersect of 550 {+-} 260 Ma. The migrated bitumen contains virtually no uranium and thorium but has a large excess of {sup 206}Pb, which indicates that the once liquid bitumen must have acted as a sink for mobile intermediate decay products of {sup 238}U. Emplacement of the Nipissing diabase may have been responsible for producing the bitumen and, indirectly, for its enrichment in {sup 206}Pb as a result of outgassing of {sup 222}Rn.

  12. The source of phosphate in the oxidation zone of ore deposits: Evidence from oxygen isotope compositions of pyromorphite

    NASA Astrophysics Data System (ADS)

    Burmann, Fabian; Keim, Maximilian F.; Oelmann, Yvonne; Teiber, Holger; Marks, Michael A. W.; Markl, Gregor

    2013-12-01

    Pyromorphite (Pb5[PO4]3Cl) is an abundant mineral in oxidized zones of lead-bearing ore deposits and due to its very low solubility product effectively binds Pb during supergene alteration of galena (PbS). The capacity of a soil or near-surface fluid to immobilize dissolved Pb depends critically on the availability of phosphate in this soil or fluid. Potential phosphorus sources in soil include (i) release during biological processes, i.e. leaching from litter/lysis of microbial cells (after intracellular enzyme activity) in soil and hydrolysis from soil organic matter by extracellular enzymes and (ii) inorganic phosphate from the dissolution of apatite in the adjacent basement rocks. Intracellular enzyme activity in plants/microorganisms associated with kinetic fractionation produces an oxygen isotope composition distinctly different from inorganic processes in soil. This study presents the first oxygen isotope data for phosphate (δ18OP) in pyromorphite and a comprehensive data set for apatite from crystalline rocks. We investigated 38 pyromorphites from 26 localities in the Schwarzwald (Southwest Germany) and five samples from localities outside the Schwarzwald in addition to 12 apatite separates from gneissic and granitic host rocks. Pyromorphites had δ18OP values between +10‰ and +19‰, comparable to literature data on δ18OP in the readily available P fraction in soil (resin-extractable P) from which minerals potentially precipitate in soils. δ18OP values below the range of equilibrium isotope fractionation can be attributed either to apatites that formed geochemically (δ18OP of apatites:+6‰ to +9‰) or less likely to biological processes (extracellular enzyme activity). However, for most of our samples isotopic equilibrium with ambient water was indicated, which suggests biological activity. Therefore, we conclude that the majority of pyromorphites in oxidized zones of ore bodies formed from biologically cycled phosphate. This study highlights that

  13. Influence of gangue existing states in iron ores on the formation and flow of liquid phase during sintering

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-liang; Wu, Sheng-li; Chen, Shao-guo; Su, Bo; Que, Zhi-gang; Hou, Chao-gang

    2014-10-01

    Gangue existing states largely affect the high-temperature characteristics of iron ores. Using a micro-sintering method and scanning electron microscopy, the effects of gangue content, gangue type, and gangue size on the assimilation characteristics and fluidity of liquid phase of five different iron ores were analyzed in this study. Next, the mechanism based on the reaction between gangues and sintering materials was unraveled. The results show that, as the SiO2 levels increase in the iron ores, the lowest assimilation temperature (LAT) decreases, whereas the index of fluidity of liquid phase (IFL) increases. Below 1.5wt%, Al2O3 benefits the assimilation reaction, but higher concentrations proved detrimental. Larger quartz particles increase the SiO2 levels at the local reaction interface between the iron ore and CaO, thereby reducing the LAT. Quartz-gibbsite is more conductive to assimilation than kaolin. Quartz-gibbsite and kaolin gangues encourage the formation of liquid-phase low-Al2O3-SFCA with high IFL and high-Al2O3-SFCA with low IFL, respectively.

  14. Extraction and separation of nickel and cobalt from saprolite laterite ore by microwave-assisted hydrothermal leaching and chemical deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Yan; Gao, Jian-ming; Yue, Yi; Peng, Ben; Que, Zai-qing; Guo, Min; Zhang, Mei

    2013-07-01

    Extraction and separation of nickel and cobalt from saprolite laterite ore were studied by using a method of microwave-assisted hydrothermal leaching and chemical deposition. The effects of leaching temperature and time on the extraction efficiencies of Ni2+ and Co2+ were investigated in detail under microwave conditions. It is shown that the extraction efficiencies of Ni2+ and Co2+ from the ore pre-roasted at 300°C for 5 h were 89.19% and 61.89% when the leaching temperature and time were about 70°C and 60 min, respectively. For the separation process of Ni and Co, the separation of main chemical components was performed by adjusting the pH values of sulfuric leaching solutions using a NaOH solution based on the different pH values of precipitation for metal hydroxides. The final separation efficiencies of Ni and Co were 77.29% and 65.87%, respectively. Furthermore, the separation efficiencies of Fe of 95.36% and Mg of 92.2% were also achieved at the same time.

  15. Diversity, metal resistance and uranium sequestration abilities of bacteria from uranium ore deposit in deep earth stratum.

    PubMed

    Islam, Ekramul; Sar, Pinaki

    2016-05-01

    Metal resistance and uranium (U) sequestration abilities of bacteria residing in subsurface U ore was investigated using 122 pure culture strains isolated through enrichment. The cumulative frequencies of isolates resistant to each metal tested were as follows: As(V), 74%; Zn, 58%; Ni, 53%; Cd, 47%; Cr(VI), 41%; Co, 40%; Cu, 20%; and Hg, 4%. 16S rRNA gene analysis revealed that isolated bacteria belonged to 14 genera with abundance of Arthrobacter, Microbacterium, Acinetobacter and Stenotrophomonas. Cobalt did not interfere with the growth of most of the bacterial isolates belonging to different groups while U allowed growth of four different genera of which Stenotrophomonas and Microbacterium showed high U tolerance. Interestingly, tolerance to Ni, Zn, Cu, and Hg was observed only in Microbacterium, Arthrobacter, Paenibacillus¸ and Acinetobacter, respectively. However, Microbacterium was found to be dominant when isolated from other five different metal enrichments including U. Uranium removal study showed that 84% of the test bacteria could remove more than 50mgUg(-1) dry weight from 80 or 160mgL(-1) U within 48h. In general, Microbacterium, Arthrobacter and Acinetobacter could remove a higher amount of U. High resolution transmission electron microscopy (HRTEM) study of U exposed cells revealed that accumulated U sequestered mostly around the cell periphery. The study highlights that indigenous U ore deposit bacteria have the potential to interact with U, and thus could be applied for bioremediation of U contaminated sites or wastes. PMID:26796528

  16. The formation and evolution of the Bitincke nickel laterite deposit, Albania

    NASA Astrophysics Data System (ADS)

    Thorne, Robert; Roberts, Stephen; Herrington, Richard

    2012-12-01

    The Bitincke nickel laterite deposit, located in the south east of Albania, contains an estimated ore resource of 35.6 Mt of nickel ore with a grade of 1.2 % Ni. The deposit developed on peridotites within Late Jurassic ophiolites which were obducted in the Early Cretaceous and which form part of the Albanian Mirdita ophiolite zone. Limestones and conglomerates overlying the deposit delimit the minimum age of lateritization to the mid-Eocene. The laterite is composed of two distinct ore zones characterized by silicate nickel and iron oxide phases. Within the silicate zone, Ni concentrations reach a maximum of 1.5 wt% and although laterally and vertically variable this zone is typically characterized by olivine and serpentine at the base of the horizon which are gradually replaced by secondary silicates and iron oxides up section. The boundary between the silicate and the oxide zone above is normally sharp and characterized by an increase in Fe2O3 (from ~10 to 80 wt%), decreases in SiO2 (from ~30 to 5 wt%) and a dramatic reduction in MgO content (from ~10 to 0.1 wt%). The oxide horizon is dominated by goethite and displays relatively little variation in textural morphology or geochemistry. Nickel concentrations are greatest near the base of this zone, reaching a maximum of 2.3 wt%. Weathering profile formation and variation in the thickness of the deposit was controlled by the interaction between topography, faulting and protolith fracture density. The oxide zone formed on topographic highs was subject to increased rates of erosion, whereas the laterite profile within topographic lows, and in areas of relatively high fracture density, tends to be thicker due to increased permeability. The most substantive sections of the Ni laterite weathering profile developed in small fault controlled basins and were preserved by the deposition of a sequence of limestones and mudstones.

  17. Mechanism of unintentionally produced persistent organic pollutant formation in iron ore sintering.

    PubMed

    Sun, Yifei; Liu, Lina; Fu, Xin; Zhu, Tianle; Buekens, Alfons; Yang, Xiaoyi; Wang, Qiang

    2016-04-01

    Effects of temperature, carbon content and copper additive on formation of chlorobenzenes (CBzs) and polychlorinated biphenyls (PCBs) in iron ore sintering were investigated. By heating simulated fly ash (SFA) at a temperature range of 250-500°C, the yield of both CBzs and PCBs presented two peaks of 637ng/g-fly ash at 350°C and 1.5×10(5)ng/g-fly ash at 450°C for CBzs, and 74ng/g-fly ash at 300°C and 53ng/g-fly ash at 500°C. Additionally, in the thermal treatment of real fly ash (RFA), yield of PCBs displayed two peak values at 350°C and 500°C, however, yield of CBzs showed only one peak at 400°C. In the thermal treatment of SFA with a carbon content range of 0-20wt% at 300°C, both CBzs and PCBs obtained the maximum productions of 883ng/g-fly ash for CBzs and 127ng/g-fly ash for PCBs at a 5wt% carbon content. Copper additives also affected chlorinated aromatic formation. The catalytic activity of different copper additives followed the orders: CuCl2∙2H2O>Cu2O>Cu>CuSO4>CuO for CBzs, and CuCl2∙2H2O>Cu2O>CuO>Cu>CuSO4 for PCBs. PMID:26686523

  18. Stratification Studies with Sub Grade Iron Ore from Deposit No. 10 and 11A, Bacheli Complex, Bailadila, Chhattisgarh, India

    NASA Astrophysics Data System (ADS)

    Venkateswara Rao, Gottumukkala; Markandeya, Ravvala; Sharma, Satish Kumar

    2016-06-01

    Experiments were carried out with two different sizes of (-30 + 6 and -6 + 1 mm) sub grade iron ore sample from Deposit No. 10 and 11A, Bacheli Complex, Bailadila, India to study the stratification behaviour at optimised parameters in a under bed air pulsed jig at 1, 2, 5, 10, 15 and 20 minutes residence time. This paper deals with the rate at which stratification takes place and determines the optimum stratification time (residence time) for above two size fractions. Average apparent density along with Jig Stratification Index (JSI) of both the size fractions was calculated. It was observed that the stratification rate is high for fines (-6 + 1 mm) and stratification index was higher for lump (-30 + 6 mm) when compared with the other size fraction. The maximum JSI observed was 0.35 for lump (-30 + 6 mm) and 0.30 for fines (-6 + 1 mm).

  19. Deep magnetic anomaly sources interpreted as Otanmäki type Iron ore reserves

    NASA Astrophysics Data System (ADS)

    Korhonen, Juha; Kukkonen, Ilmo

    2013-04-01

    In Otanmäki ore province of Central Finland vertically integrated magnetization is estimated from two aeromagnetic coverages of different altitudes and by varying overall models of regional field. Petrophysically and geochemically determined magnetization of the mined deposits and correlation between it and ore concentration is used to evaluate iron ore reserves in the deeper part of known ore fields. Further, similar analysis is made to nearby magnetically anomalous areas covered by weakly magnetic metasediments, to estimate potential ore reserves at unexposed formations.

  20. Origin of sedimentary humic acids, potential carriers of ore-forming elements

    NASA Astrophysics Data System (ADS)

    Hatcher, P. G.

    Humic acids are complex, macromolecular organic components of sediments and are defined by their solubility in dilute alkali insolubility in dilute acid. Because of their general structural characteristics (for example, their high proportion of oxygen functional groups), humic acids can complex with inorganic cations and may be important in forming ore deposits. In some instances (such as uranium ores), ore bodies are believed to have originated by mobilization of an ore-forming element complexed with humic acids and subsequent precipitation. Knowledge of the mechanism for the formation of humic acids is being applied to two major ore deposits. Carlin-type gold ores from Nevada show that humic acids may have been precursors. This suggests that the humic acids could have played a major role in the transport and accumulation of the ore.

  1. Depositional environments of the uranium-bearing Cutler Formations, Lisbon Valley, Utah

    USGS Publications Warehouse

    Campbell, John A.; Steele-Mallory, Brenda A.

    1979-01-01

    The Cutler Formation in Lisbon Valley, San Juan County, Utah, is composed predominantly of fluvial arkosic sandstones, siltstones, shales, and mudstones that were deposited by meandering streams that flowed across a flood plain and tidal flat close to sea level. Two types of channel deposits are recognized from their sedimentary structures: meandering and distributary. The flood plain was occasionally transgressed by a shallow sea from the west, resulting in the deposition of several thin limestones and marine sandstones. The marine sandstones were deposited as longshore bars. Wind transported sand along the shoreline of the shallow sea, forming a coastal dune field. Marine sandstones and eolian sandstones are more common in the upper Cutler in the southern part of the area, whereas in the central and northern part of the area the formation is predominantly fluvial. Crossbed orientation indicates that Cutler streams flowed S. 67? W. on the the average, whereas marine currents moved sediment S. 36? E. and N. 24? W., and wind transported sand S. 800 E. The uranium in the Cutler is found in the central and northern part of the area, in the upper part of the formation, in small fluvial sandstone bodies that were deposited predominantly in a distributary environment. No uranium is known in the marine or eolian sandstones. Petrographically, the uranium-bearing sandstones are identical to other Cutler fluvial sandstones except that they contain less calcite and more clay and are slightly coarser grained. Ore formation has modified the host sandstones very little.

  2. The role of the Antofagasta-Calama Lineament in ore deposit deformation in the Andes of northern Chile

    NASA Astrophysics Data System (ADS)

    Palacios, Carlos; Ramírez, Luis E.; Townley, Brian; Solari, Marcelo; Guerra, Nelson

    2007-02-01

    During the Late Jurassic-Early Oligocene interval, widespread hydrothermal copper mineralization events occurred in association with the geological evolution of the southern segment of the central Andes, giving rise to four NS-trending metallogenic belts of eastward-decreasing age: Late Jurassic, Early Cretaceous, Late Paleocene-Early Eocene, and Late Eocene-Early Oligocene. The Antofagasta-Calama Lineament (ACL) consists of an important dextral strike-slip NE-trending fault system. Deformation along the ACL system is evidenced by a right-lateral displacement of the Late Paleocene-Early Eocene metallogenic belts. Furthermore, clockwise rotation of the Early Cretaceous Mantos Blancos copper deposit and the Late Paleocene Lomas Bayas porphyry copper occurred. In the Late Eocene-Early Oligocene metallogenic belt, a sigmoidal deflection and a clockwise rotation is observed in the ACL. The ACL is thought to have controlled the emplacement of Early Oligocene porphyry copper deposits (34-37 Ma; Toki, Genoveva, Quetena, and Opache), whereas it deflected the Late Eocene porphyry copper belt (41-44 Ma; Esperanza, Telégrafo, Centinela, and Polo Sur ore deposits). These observations suggest that right-lateral displacement of the ACL was active during the Early Oligocene. We propose that the described structural features need to be considered in future exploration programs within this extensively gravel-covered region of northern Chile.

  3. A precise 232Th-208Pb chronology of fine-grained monazite: Age of the Bayan Obo REE-Fe-Nb ore deposit, China

    USGS Publications Warehouse

    Wang, Jingyuan; Tatsumoto, M.; Li, X.; Premo, W.R.; Chao, E.C.T.

    1994-01-01

    We have obtained precise Th-Pb internal isochron ages on monazite and bastnaesite for the world's largest known rare earth elements (REE)-Fe-Nb ore deposit, the Bayan Obo of Inner Mongolia, China. The monazite samples, collected from the carbonate-hosted ore zone, contain extremely small amounts of uranium (less than 10 ppm) but up to 0.7% ThO2. Previous estimates of the age of mineralization ranged from 1.8 to 0.255 Ga. Magnetic fractions of monazite and bastnaesite samples (<60-??m size) showed large ranges in 232Th 204Pb values (900-400,000) and provided precise Th-Pb internal isochron ages for paragenetic monazite mineralization ranging from 555 to 398 Ma within a few percent error (0.8% for two samples). These results are the first indication that REE mineralization within the giant Bayan Obo ore deposit occurred over a long period of time. The initial lead isotopic compositions (low 206Pb 204Pb and high 208Pb 204Pb) and large negative ??{lunate}Nd values for Bayan Obo ore minerals indicate that the main source(s) for the ores was the lower crust which was depleted in uranium, but enriched in thorium and light rare earth elements for a long period of time. Zircon from a quartz monzonite, located 50 km south of the ore complex and thought to be related to Caledonian subduction, gave an age of 451 Ma, within the range of monazite ages. Textural relations together with the mineral ages favor an epigenetic rather than a syngenetic origin for the orebodies. REE mineralization started around 555 Ma (disseminated monazite in the West, the Main, and south of the East Orebody), but the main mineralization (banded ores) was related to the Caledonian subduction event ca. 474-400 Ma. ?? 1994.

  4. The source of phosphate in the oxidation zone of ore deposits: Evidence from oxygen isotope compositions of pyromorphite

    NASA Astrophysics Data System (ADS)

    Burmann, Fabian; Keim, Maximilian F.; Oelmann, Yvonne; Teiber, Holger; Marks, Michael A. W.; Markl, Gregor

    2013-12-01

    Pyromorphite (Pb5[PO4]3Cl) is an abundant mineral in oxidized zones of lead-bearing ore deposits and due to its very low solubility product effectively binds Pb during supergene alteration of galena (PbS). The capacity of a soil or near-surface fluid to immobilize dissolved Pb depends critically on the availability of phosphate in this soil or fluid. Potential phosphorus sources in soil include (i) release during biological processes, i.e. leaching from litter/lysis of microbial cells (after intracellular enzyme activity) in soil and hydrolysis from soil organic matter by extracellular enzymes and (ii) inorganic phosphate from the dissolution of apatite in the adjacent basement rocks. Intracellular enzyme activity in plants/microorganisms associated with kinetic fractionation produces an oxygen isotope composition distinctly different from inorganic processes in soil. This study presents the first oxygen isotope data for phosphate (δ18OP) in pyromorphite and a comprehensive data set for apatite from crystalline rocks. We investigated 38 pyromorphites from 26 localities in the Schwarzwald (Southwest Germany) and five samples from localities outside the Schwarzwald in addition to 12 apatite separates from gneissic and granitic host rocks. Pyromorphites had δ18OP values between +10‰ and +19‰, comparable to literature data on δ18OP in the readily available P fraction in soil (resin-extractable P) from which minerals potentially precipitate in soils. δ18OP values below the range of equilibrium isotope fractionation can be attributed either to apatites that formed geochemically (δ18OP of apatites:+6‰ to +9‰) or less likely to biological processes (extracellular enzyme activity). However, for most of our samples isotopic equilibrium with ambient water was indicated, which suggests biological activity. Therefore, we conclude that the majority of pyromorphites in oxidized zones of ore bodies formed from biologically cycled phosphate. This study highlights that

  5. Tertiary meteoric hydrothermal systems and their relation to ore deposition, northwestern United States and southern British Columbia

    NASA Astrophysics Data System (ADS)

    Criss, Robert E.; Fleck, Robert J.; Taylor, Hugh P., Jr.

    1991-07-01

    U-bearing Eocene "porphyry" plutons; and (6) Miocene epithermal deposits, most prominently the Au and Ag bearing veins at Silver City and DeLamar, Idaho, the Hg deposits at the McDermitt caldera, Nevada and Oregon, and at Weiser, Idaho, and Au deposits in the Western Cascade Range and Lake County, Oregon. A close spatial association has been demonstrated between ore deposits and rocks having anomalous δ18O values and low δD values. The most important deposits are associated with relatively small (generally 5-300 km2) zones of low δ18O values, and they are particularly closely linked with zones of very steep 18O/16O gradients in the altered rocks. These associations hold much promise for the use of δ18O and δD contour maps in future exploration efforts.

  6. In situ Sr isotope analysis of apatite by LA-MC-ICPMS: constraints on the evolution of ore fluids of the Yinachang Fe-Cu-REE deposit, Southwest China

    NASA Astrophysics Data System (ADS)

    Zhao, Xin-Fu; Zhou, Mei-Fu; Gao, Jian-Feng; Li, Xiao-Chun; Li, Jian-Wei

    2015-10-01

    Apatite is a ubiquitous accessory mineral in a variety of rocks and hydrothermal ores. Strontium isotopes of apatite are well known to retain petrogenetic information and have been widely used to investigate the origin of igneous rocks, but such attempts have rarely been made to constrain ore-forming processes of hydrothermal systems. We here report in situ LA-MC-ICPMS Sr isotope data of apatite from the ~1660-Ma Yinachang Fe-Cu-REE deposit, Southwest China. The formation of this deposit was coeval to the emplacement of regionally distributed doleritic intrusions within a continental-rift setting. The deposit has a paragenetic sequence consisting of sodic alteration (stage I), magnetite mineralization (stage II), Cu sulfide and REE mineralization (stage III), and final barren calcite veining (stage IV). The stage II and III assemblages contain abundant apatite, allowing to investigate the temporal evolution of the Sr isotopic composition of the ore fluids. Apatite of stage II (Apt II) is associated with fluorite, magnetite, and siderite, whereas apatite from stage III (Apt III) occurs intimately intergrown with ankerite and Cu sulfides. Apt II has 87Sr/86Sr ratios varying from 0.70377 to 0.71074, broadly compatible with the coeval doleritic intrusions (0.70592 to 0.70692), indicating that ore-forming fluids responsible for stage II magnetite mineralization were largely equilibrated with mantle-derived mafic rocks. In contrast, Apt III has distinctly higher 87Sr/86Sr ratios from 0.71021 to 0.72114, which are interpreted to reflect external radiogenic Sr, likely derived from the Paleoproterozoic strata. Some Apt III crystals have undergone extensive metasomatism indicated by abundant monazite inclusions. The metasomatized apatite has much higher 87Sr/86Sr ratios up to 0.73721, which is consistent with bulk-rock Rb-Sr isotope analyses of Cu ores with 87Sr/86Sri from 0.71906 to 0.74632. The elevated 87Sr/86Sr values of metasomatized apatite and bulk Cu ores indicate

  7. Trail formation based on directed pheromone deposition.

    PubMed

    Boissard, Emmanuel; Degond, Pierre; Motsch, Sebastien

    2013-05-01

    We propose an Individual-Based Model of ant-trail formation. The ants are modeled as self-propelled particles which deposit directed pheromone particles and interact with them through alignment interaction. The directed pheromone particles intend to model pieces of trails, while the alignment interaction translates the tendency for an ant to follow a trail when it meets it. Thanks to adequate quantitative descriptors of the trail patterns, the existence of a phase transition as the ant-pheromone interaction frequency is increased can be evidenced. We propose both kinetic and fluid descriptions of this model and analyze the capabilities of the fluid model to develop trail patterns. We observe that the development of patterns by fluid models require extra trail amplification mechanisms that are not needed at the Individual-Based Model level. PMID:22526837

  8. The formation of technic soil in a revegetated uranium ore waste rock pile (Limousin, France)

    NASA Astrophysics Data System (ADS)

    Boekhout, Flora; Gérard, Martine; Kanzari, Aisha; Calas, Georges; Descostes, Michael

    2014-05-01

    Mining took place in France between 1945 and 2001 during which time ~210 different sites were exploited and/or explored. A total of 76 Kt of uranium was produced, 52 Mt of ore was extracted, but also 200 Mt of waste rocks was produced, the majority of which, with uranium levels corresponding to the natural environment. So far, the processes of arenisation and technic soil formation in waste rock piles are not well understood but have important implications for understanding the environmental impact and long-term speciation of uranium. Understanding weathering processes in waste rock piles is essential to determine their environmental impact. The main objectives of this work are to assess 1) the micromorphological features and neo-formed U-bearing phases related to weathering and 2) the processes behind arenisation of the rock pile. The site that was chosen is the Vieilles Sagnes waste rock pile in Fanay (Massif Central France) that represents more or less hydrothermally altered granitic rocks that have been exposed to weathering since the construction of the waste rock pile approximately 50 years ago. Two trenches were excavated to investigate the vertical differentiation of the rock pile. This site serves as a key location for studying weathering processes of waste rock piles, as it has not been reworked after initial construction and has therefore preserved information on the original mineralogy of the waste rock pile enabling us to access post emplacement weathering processes. The site is currently overgrown by moss, meter high ferns and small trees. At present day the rock pile material can be described as hydrothermally altered rocks and rock fragments within a fine-grained silty clay matrix exposed to surface conditions and weathering. A sandy "paleo" technic soil underlies the waste rock pile and functions as a natural liner by adsorption of uranium on clay minerals. Post-mining weathering of rock-pile material is superimposed on pre-mining hydrothermal and

  9. Pattern Formation in Mississippi Valley-Type Deposits

    NASA Astrophysics Data System (ADS)

    Kelka, Ulrich; Koehn, Daniel

    2015-04-01

    Alternating, monomineralic dark and white bands are common features of ore hosting dolostones which are generally termed Zebra textures. These structures consist of coarse grained light and fine grained dark layers and accompany ore bodies of the Mississippi Valley-Type (MVT) worldwide. These deposits frequently develop in large hydrothermal systems, located in the flanks of foreland basins or in fold and thrust belts. The microstructural- and microchemical analysis in this study were performed on samples which were collected in the San Vicente mine. This large MVT deposit is hosted in Triassic/Jurassic Platform Carbonates located in an east-vergent fold and thrust belt of the Peruvian Andes. The thin sections were analyzed with petrographic- and scanning electron microscope. It is observed that one common striking feature is the high density of second-phase particles in the dark bands, whereas the coarser grained layers are virtually particle free. Furthermore, the particle distribution is found to be non-random. The highest particle densities in the samples occur on grain boundaries in the dark bands implying that grain boundaries can capture particles. Based on recent theories and the additional analytical findings, we developed a numerical simulation to study the pattern formation. The modelling is performed in 2D at the scale of a thin section, using a boundary-model coupled with a lattice-particle-code. During the simulation two processes are active, first a reaction takes place that replaces calcite with dolomite driven by a fluid that infiltrates the model, followed by a grain growth processes with an average grain size increase as a function of surface energy reduction. Fluid infiltration in the rock is modelled assuming Darcy Flow and an advection-diffusion equation coupled with a reaction which is a function of concentration. The reaction increases permeability of the solid and thus enhances infiltration. The reaction front in the model shifts particles

  10. Deep-Sea Magnetics on Active and Fossil Hydrothermal Sites: a Tool to Detect and Characterize Submarine Ore Deposits

    NASA Astrophysics Data System (ADS)

    Dyment, J.; Szitkar, F.; Fouquet, Y.; Choi, Y.

    2011-12-01

    Since the first discoveries of hydrothermal sites at mid-ocean ridges in the 70s, international efforts in the deep seafloor exploration have unravelled a wide variety of hydrothermal sites in terms of geological settings, physical parameters, and biological communities as well. Such efforts, coordinated in the InterRidge program since 1992, are becoming even more important when the increasing need in metals for developing economies makes the exploitation of metal sulfides accumulated at deep-sea hydrothermal sites a realistic target. The usual method to find hydrothermal sites is to detect the associated chemical plumes enriched in manganese, methane, hydrogen, helium 3, in the water column. How efficient it has been proven, such a method is limited to the search for active hydrothermal vents. Active vents, however, are not the best places for mining the seafloor, because (1) they host massive sulfides deposits in the making and may not represent the largest accumulation; (2) they are still very hot and would rapidly damage the mining tools; and, last but not the least, (3) they host fragile and precious ecosystem that could be dramatically affected by mining operations. Methods to find fossil hydrothermal sites (i.e. colder and devoid of specific ecosystems) include systematic rock sampling - a very tedious endeavour - and high resolution, near seafloor geophysical surveys. Existing magnetic surveys on basalt-hosted, peridotite-hosted and sediment-hosted sites revealed different types of signatures, which reflect the magnetizations of the host rock and the ore deposit, among others. Basalt-hosted sites exhibit negative magnetic anomalies, i.e. a deficit of magnetization, due to thermal demagnetization and hydrothermal alteration of the highly magnetic basalt, whereas both peridotite-hosted and sediment-hosted sites show positive anomalies, i.e. an excess of magnetization, clearly associated with the ore deposit. Results from recent cruises Serpentine (R

  11. The coupled geochemistry of Au and As in pyrite from ore deposits and geothermal fields: monitoring fluid evolution and external forcing factors in hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Reich, M.; Deditius, A.; Tardani, D.; Sanchez-Alfaro, P.

    2014-12-01

    Gold and arsenic incorporation into pyrite (FeS2) is strongly coupled in different types of ore deposits, including Carlin-type Au, porphyry Cu, epithermal Au, orogenic Au, volcanogenic massive sulphide (VMS) and iron-oxide Cu-Au (IOCG), among others. Despite significant advances in the last decades, the fundamental factors controlling Au and As partition in pyrite from hydrothermal systems formed under different tectonic settings and crustal levels remain poorly known. Furthermore, the complexity of pyrite microtextures and growth features suggest multi-stage growth that may be useful to monitor changes in fluid composition related to episodic pumping of fluids. Here we report a comprehensive database of EMPA, SIMS, LA-ICP-MS and micro-PIXE Au-As analyses that cover temperature conditions of pyrite formation from ~30ºC to ~600ºC. The global pyrite Au-As data form a wedge-shaped zone in compositional space, and show that the solid solubility limit of Au in arsenian pyrite is independent of the geochemical environment of pyrite formation and rather depends on its crystal-chemical properties and post-depositional alteration. Compilation of Au-As concentrations and formation temperatures for pyrite indicates that Au and As solubility is retrograde in this mineral, as Au and As contents decrease with increasing temperature from ~200-500ºC. Based on these results, we define one Au-As trend formed by pyrites from Carlin-type and orogenic Au deposits where compositions are largely controlled by fluid-rock-interactions and can be highly perturbed by changes of temperature or subsequent alteration. The second trend consists of pyrites from porphyry Cu, epithermal Au deposits and geothermal systems, which are characterized by compositions that preserve the Au/As signature of mineralizing magmatic-hydrothermal fluids. The well-developed oscillatory zoning in pyrite detected in these systems, where Cu-rich, Au-As-depleted growth zones alternate with Cu-poor, Au

  12. Sedimentary exhalative nickel-molybdenum ores in south China

    USGS Publications Warehouse

    Lott, D.A.; Coveney, R.M., Jr.; Murowchick, J.B.; Grauch, R.I.

    1999-01-01

    Unique bedded Ni-Mo ores hosted by black shales were discovered in localized paleobasins along the Yangzte platform of southern China in 1971. Textural evidence and radiometric dates imply ore formation during sedimentation of black shales that grade into readily combustible beds, termed stone coals, which contain 10 to 15 percent organic carbon. Studies of 427 fluid inclusions indicate extreme variation in hydrothermal brine salinities that were contained by Proterozoic dolostones underlying the ore zone in Hunan and Guizhou. Variations of fluid inclusion salinities, which range from 0.1 to 21.6 wt percent NaCl equiv, are attributed to differences in the compositions of brines in strata underlying the ore bed, complicated by the presence of seawater and dilute fluids that represent condensates of vapors generated by boiling of mineralizing fluids or Cambrian meteoric water. The complex processes of ore deposition led to scattered homogenization temperatures ranging from 100??to 187??C within the Hunan ore zone and from 65??to 183??C within the Guizhou ore zone. While living organisms probably did not directly accumulate metals in situ in sufficient amounts to explain the unusually high grades of the deposits, sulfur isotope ratios indicate that bacteria, now preserved as abundant microfossils, provided sufficient sulfide for the ores by reduction of seawater sulfate. Such microbiota may have depended on vent fluids and transported organic matter for key nutrients and are consistent with a sedex origin for the ores. Vent fluids interacted with organic remains, including rounded fragments of microbial mats that were likely transported to the site of ore deposition by the action of waves and bottom currents prior to replacement by ore minerals.

  13. Origin of stratiform sediment-hosted manganese carbonate ore deposits: Examples from Molango, Mexico, and TaoJiang, China

    USGS Publications Warehouse

    Okita, P.M.; Shanks, Wayne C., III

    1992-01-01

    Carbonate and sulfide minerals from the Molango, Mexico, and TaoJiang, China, Mn deposits display similar and distinctive ??34S and ??13C patterns in intervals of manganese carbonate mineralization. ??13C-values for Mn-bearing carbonate range from -17.8 to +0.5??? (PDB), with the most negative values occurring in high-grade ore zones that are composed predominantly of rhodochrosite. In contrast, calcite from below, within and above Mn-carbonate zones at Molango has ??13C???0??? (PDB). Markedly negative ??13C data indicate that a large proportion of the carbon in Mn-carbonates was derived from organic matter oxidation. Diagenetic reactions using MnO2 and SO2-4 to oxidize sedimentary organic matter were the principle causes of such 12C enrichment. Pyrite content and sulfide ?? 34S-values also show distinctive variations. In unmineralized rocks, very negative ??34S-values (avg. < -21??? CDT) and abundant pyrite content suggest that pyrite formed from diagenetic, bacteriogenic sulfate reduction. In contrast, Mn-bearing horizons typically contain only trace amounts of pyrite (e.g., <0.5 wt% S with ??34S-values 34S-enriched, in some cases to nearly the value for contemporaneous seawater. 34S-enriched pyrite from the Mn-carbonate intervals indicates sulfide precipitation in an environment that underwent extensive SO2-4 reduction, and was largely a closed system with regard to exchange of sulfate and dissolved sulfide with normal seawater. The occasional occurrence of 34S-depleted pyrite within Mn-carbonate zones dominated by 34S-enriched pyrite is evidence that closed-system conditions were intermittent and limited to local pore waters and did not involve entire sedimentary basins. Mn-carbonate precipitation may have occluded porosity in the surficial sediments, thus establishing an effective barrier to SO2-4 exchange with overlying seawater. Similar isotopic and mineralogic characteristics from both the Molango and TaoJiang deposits, widely separated in geologic time and

  14. Systematics of hydrothermal alteration at the volcanic-hosted Falun Zn-Pb-Cu-(Au-Ag) deposit - implications for ore genesis, structure and exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

    NASA Astrophysics Data System (ADS)

    Kampmann, Tobias C.; Jansson, Nils J.; Stephens, Michael B.; Majka, Jarosław

    2016-04-01

    The Palaeoproterozoic, volcanic-hosted Falun Zn-Pb-Cu-(Au-Ag) sulphide deposit was mined for base and precious metals during several centuries, until its closure in 1992. The deposit is located in a 1.9 Ga ore district in the Bergslagen lithotectonic unit, Fennoscandian Shield, south-central Sweden. Both the ores and their host rock underwent polyphase ductile deformation, and metamorphism under amphibolite facies and later retrograde conditions at 1.9-1.8 Ga (Svecokarelian orogenic system). This study has the following aims: (i) Classify styles and intensities of alteration in the hydrothermally altered zone at Falun; (ii) identify precursor rocks to hydrothermally altered rocks and their spatial distribution at the deposit; (iii) evaluate the chemical changes resulting from hydrothermal alteration using mass change calculations; and (iv) assess the pre-metamorphic alteration assemblages accounting for the observed metamorphic mineral associations in the altered rocks at Falun. Results will have implications for both the ore-genetic and structural understanding of the deposit, as well as for local and regional exploration. Metamorphic mineral associations in the altered rocks include biotite-quartz-cordierite-(anthophyllite) and, more proximally, quartz-anthophyllite-(biotite-cordierite/almandine), biotite-cordierite-(anthophyllite) and biotite-almandine-(anthophyllite). The proximal hydrothermally altered zone corresponds to intense chlorite-style alteration. Subordinate dolomite or calcite marble, as well as calc-silicate (tremolite, diopside) rocks are also present at the deposit. Metavolcanic rocks around the deposit are unaltered, weakly sericitized or sodic-altered. Immobile-element (e.g. Zr, TiO2, Al2O3, REE) systematics of the silicate-rich samples at and around the deposit suggest that the precursors to the hydrothermally altered rocks at Falun were predominantly rhyolitic in composition, dacitic rocks being subordinate and mafic-intermediate rocks

  15. The origin or the Archean Jardine iron formation-hosted lode gold deposit. Montana

    SciTech Connect

    Ping, Liu.

    1992-06-09

    While there is considerable controversy concerning the origin of greenstone-hosted lode gold deposits of Archean age, there is a general consensus that these deposits are epigenetic. By contrast, iron formation-hosted lode gold deposits of Archean or Proterozoic age are considered either epigenetic or syngenetic. At least three genetic models have been proposed for these gold deposits: a syngenetic model involving simultaneous deposition of gold and the iron formation; an epigenetic model involving a later introduction of gold, arsenic, and sulfur into the iron formation; and a multistage model involving primary concentration of gold during deposition of iron formation followed by remobilization and reconcentration of gold during later events. The Jardine district is one of only three Archean lode gold districts in the United States that have reserves of greater than 300,000 ounces of gold. The other two are the South Pass-Atlantic City district, Wyoming, and the Ropes mine, Michigan. The fact that two of the three districts are in the Wyoming province suggests that the province might be an Archean gold province similar to Archean provinces in Canada. Placer gold was discovered near Jardine in 1866, and gold quartz veins were mined in the 1880's at Mineral Hill. Exploration by the Jardine Joint Venture has concentrated on the Jardine area, including Crevasse Mountain, where minor lode gold mineralization occurs in quartz-biotite schists. In order to complement previous geochemical, mineralogical, petrological and structural studies, the present study has concentrated on fluid inclusion, stable isotope, and electron microprobe studies with the intention of determining: (1) the source of the ore-forming fluids and gold, and (2) the genetic relationship between gold mineralization and iron formation, alteration and metamorphism.

  16. The origin or the Archean Jardine iron formation-hosted lode gold deposit. Montana

    SciTech Connect

    Ping, Liu

    1992-06-09

    While there is considerable controversy concerning the origin of greenstone-hosted lode gold deposits of Archean age, there is a general consensus that these deposits are epigenetic. By contrast, iron formation-hosted lode gold deposits of Archean or Proterozoic age are considered either epigenetic or syngenetic. At least three genetic models have been proposed for these gold deposits: a syngenetic model involving simultaneous deposition of gold and the iron formation; an epigenetic model involving a later introduction of gold, arsenic, and sulfur into the iron formation; and a multistage model involving primary concentration of gold during deposition of iron formation followed by remobilization and reconcentration of gold during later events. The Jardine district is one of only three Archean lode gold districts in the United States that have reserves of greater than 300,000 ounces of gold. The other two are the South Pass-Atlantic City district, Wyoming, and the Ropes mine, Michigan. The fact that two of the three districts are in the Wyoming province suggests that the province might be an Archean gold province similar to Archean provinces in Canada. Placer gold was discovered near Jardine in 1866, and gold quartz veins were mined in the 1880`s at Mineral Hill. Exploration by the Jardine Joint Venture has concentrated on the Jardine area, including Crevasse Mountain, where minor lode gold mineralization occurs in quartz-biotite schists. In order to complement previous geochemical, mineralogical, petrological and structural studies, the present study has concentrated on fluid inclusion, stable isotope, and electron microprobe studies with the intention of determining: (1) the source of the ore-forming fluids and gold, and (2) the genetic relationship between gold mineralization and iron formation, alteration and metamorphism.

  17. Detrital zircon U-Pb ages of the Proterozoic metaclastic-sedimentary rocks in Hainan Province of South China: New constraints on the depositional time, source area, and tectonic setting of the Shilu Fe-Co-Cu ore district

    NASA Astrophysics Data System (ADS)

    Wang, Zhilin; Xu, Deru; Hu, Guocheng; Yu, Liangliang; Wu, Chuanjun; Zhang, Zhaochong; Cai, Jianxin; Shan, Qiang; Hou, Maozhou; Chen, Huayong

    2015-12-01

    The Shilu Fe-Co-Cu ore district, located at Hainan Province of South China, is well known for high-grade hematite-rich Fe ores and also two Precambrian host successions, i.e. the Shilu Group and the overlying Shihuiding Formation. This district has been interpreted as a banded iron formation (BIF) deposit-type, but its depositional time, source area and depositional setting have been in debate due to poor geochronological work. Detrital zircon U-Pb dating aided by cathodoluminescence imaging has been carried out on both the Shilu Group and Shihuiding Formation. Most of the zircon grains from both the successions are subrounded to rounded in morphology and have age spectra between 2000 Ma and 900 Ma with two predominant peaks at ca. 1460-1340 Ma and 1070 Ma, and three subordinate peaks at ca. 1740-1660 Ma, 1220 Ma and 970 Ma. The similar age distribution suggests the same depositional system for both successions. Linked to the geological and paleontological signatures, the Shihuiding Formation is better re-interpreted as the top, i.e. Seventh member of the Shilu Group, rather than a distinct Formation. The youngest statistical zircon age peaks for both successions, i.e. ca. 1070-970 Ma may define the maximum depositional time of the Shilu Group and interbedded BIFs. At least two erosional sources are required for deposition of the studied detrital zircons, with one proximal to provide the least abraded zircons and the other distal or recycled to offer the largely abraded zircons. The predominance of rounded or subrounded zircons over angular zircons probably implies a relatively stable tectonic setting during deposition. Given the Precambrian tectonics of Hainan Island, a retro-arc foreland basin is proposed for the deposition of the Shilu Group and interbedded BIFs. In comparison with those from the South China and other typical Grenvillian orogens, the detrital zircon age populations reveal that Hainan Island had crystalline basement similar to neither the Yangtze

  18. Formation of the enigmatic Matoush uranium deposit in the Paleoprotozoic Otish Basin, Quebec, Canada

    NASA Astrophysics Data System (ADS)

    Alexandre, Paul; Kyser, Kurt; Layton-Matthews, Daniel; Beyer, Steve R.; Hiatt, Eric E.; Lafontaine, Jonathan

    2015-10-01

    The Matoush uranium deposit is situated in the Paleoproterozoic Otish Basin, northern Quebec, Canada, and is hosted by the Indicator Formation sandstones. Its sheet-like ore bodies are closely associated with the steeply dipping Matoush Fracture, which hosts mafic dykes and minor quartz-feldspar-tourmaline pegmatites. Regional diagenesis, involving oxidizing basinal fluids (δ2H ˜-15‰, δ18O ˜8‰), produced mostly illite and possibly leached U from accessory phases in the Indicator Formation sandstones. The bimodal Matoush dyke intruded the Indicator Formation along the Matoush Fracture, and the related metasomatism produced Cr-rich dravite and muscovite in both the dyke and the proximal sandstones. Uraninite formed when U6+ in the basinal brine was reduced to U4+ in contact with the mafic dyke and by Fe2+ in Cr-dravite and Cr-muscovite, and precipitated together with eskolaite and hematite. Because of its unique characteristics, the Matoush deposit cannot be easily classified within the generally accepted classification of uranium deposits. Two of its main characteristics (unusual reduction mechanism, structural control) do not correspond to the sandstone-hosted group of deposits (unconformity type, tabular, roll front), in spite of uranium being derived from the Otish Group sandstones.

  19. Ore Petrology and Alteration of the West Ansil Volcanic-hosted Massive Sulphide Deposit of the Noranda Mining Camp, Rouyn-Noranda, Quebec

    NASA Astrophysics Data System (ADS)

    Boucher, Stephanie M.

    The West Ansil deposit was the first Cu discovery in 25 years in the Noranda Central Camp. It has a combined indicated and inferred resource of ˜1.2 Mt. Grades for the indicated resource are 3.4% Cu, 0.4% Zn, 1.4 g/t Au and 9.2 g/t Ag. The bulk of the resource is located in three massive sulphide lenses (Upper, Middle and Lower) that are entirely within the Rusty Ridge Formation above the Lewis exhalite. The mineralization in all three ore lenses consists of massive pyrrhotite + chalcopyrite +/- magnetite. Semi-massive sphalerite is restricted to the upper and lower parts of the Middle lens. Massive magnetite occurs at the center of the Upper and Middle lenses, where it replaces massive pyrrhotite. A striking feature of West Ansil is the presence of abundant colloform and nodular pyrite (+/-marcasite) in the massive sulphides. Late-stage replacement of massive pyrrhotite by colloform pyrite and marcasite, occurs mostly along the upper and lower contacts of the lenses.

  20. Beyond the obvious limits of ore deposits: The use of mineralogical, geochemical, and biological features for the remote detection of mineralization

    USGS Publications Warehouse

    Kelley, D.L.; Kelley, K.D.; Coker, W.B.; Caughlin, B.; Doherty, M.E.

    2006-01-01

    Far field features of ore deposits include mineralogical, geochemical, or biological attributes that can be recognized beyond the obvious limits of the deposits. They can be primary, if formed in association with mineralization or alteration processes, or secondary, if formed from the interaction of ore deposits with the hydrosphere and biosphere. This paper examines a variety of far field features of different ore deposit types and considers novel applications to exploration and discovery. Primary far field features include mineral and rock chemistry, isotopic or element halos, fluid pathways and thermal anomalies in host-rock sequences. Examples include the use of apatite chemistry to distinguish intrusive rocks permissive for iron oxide copper gold (IOCG) and porphyry deposits; resistate mineral (e.g., rutile, tourmaline) chemistry in exploration for volcanogenic massive sulfide (VMS), orogenic gold, and porphyry deposits; and pyrite chemistry to vector toward sedimentary exhalative (sedex) deposits. Distinctive whole-rock geochemical signatures also can be recognized as a far field feature of porphyry deposits. For example, unique Sr/Y ratios in whole-rock samples, used to distinguish barren versus fertile magmas for Cu mineralization, result from the differentiation of oxidized hydrous melts. Anomalous concentrations of halogen elements (Cl, Br, and I) have been found for distances of up to 200 m away from some mineralized centers. Variations in isotopic composition between ore-bearing and barren intrusions and/or systematic vertical and lateral zonation in sulfur, carbon, or oxygen isotope values have been documented for some deposit types. Owing to the thermal aureole that extends beyond the area of mineralization for some deposits, detection of paleothermal effects through methods such as conodont alteration indices, vitrinite or bitumen reflectance, illite crystallinity, and apatite or zircon thermochronology studies also can be valuable, particularly for

  1. The conjunction of factors that lead to formation of giant gold provinces and deposits in non-arc settings

    USGS Publications Warehouse

    Groves, David I.; Goldfarb, Richard J.; Santosh, M.

    2016-01-01

    In contrast to their province scale similarities, the different giant gold deposit styles show contrasting critical controls at the district to deposit scale. For orogenic gold deposits, the giants appear to have formed by conjunction of a greater number of parameters to those that control smaller deposits, with resultant geometrical and lithostratigraphic complexity as a guide to their location. There are few giant IRGS due to their inferior fluid-flux systems relative to orogenic gold deposits, and those few giants are essentially preservational exceptions. Many Carlin-type deposits are giants due to the exceptional conjunction of both structural and lithological parameters that caused reactive and permeable rocks, enriched in syngenetic gold, to be located below an impermeable cap along antiformal “trends”. Hydrocarbons probably played an important role in concentrating metal. The supergiant Post-Betze deposit has additional ore zones in strain heterogeneities surrounding the pre-gold Goldstrike stock. All unequivocal IOCG deposits are giant or near-giant deposits in terms of gold-equivalent resources, partly due to economic factors for this relatively poorly understood, low Cu-Au grade deposit type. The supergiant Olympic Dam deposit, the most shallowly formed deposit among the larger IOCGs, probably owes its origin to eruption of volatile-rich hybrid magma at surface, with formation of a large maar and intense and widespread brecciation, alteration and Cu-Au-U deposition in a huge rock volume.

  2. Sulfuric acid karst and its relationship to hydrocarbon reservoir porosity, native sulfur deposits, and the origin of Mississippi Valley-type ore deposits

    SciTech Connect

    Hill, C.A. , Albuquerque, NM )

    1993-03-01

    The Delaware Basin of southeastern New Mexico and West Texas contains hydrocarbons and native sulfur in the basin and sulfuric acid-formed caves and Mississippi Valley-type (MVT) ore deposits around the margins of the basin. Hydrocarbons reacting with sulfate evaporite rock produced hydrogen sulfide gas, which gas oxidized to native sulfur in the basin and which gas also migrated from basin to reef and accumulated there in structural and stratigraphic traps. In the reduced zone of the carbonate reef margin the H[sub 2]S combined with metal-chloride complexes to form MVTs, and in the oxidized zone later in time the H[sub 2]S formed sulfuric acid which dissolved out the famous caves of the region (e.g., Carlsbad Cavern, Lechuguilla Cave). Sulfuric acid karst can be recognized by the discontinuity, large size, and spongework nature of its cave passages, and by the presence of native sulfur, endellite, and large gypsum deposits within these caves. Sulfuric acid oilfield karst refers to cavernous porosity filled with hydrocarbons and can be produced by the mixing of waters of different H[sub 2]S content or by the oxidation of H[sub 2]S to sulfuric acid. Sulfur and carbon-oxygen isotopes have been used to establish and trace the sequence of related hydrocarbon, sulfur, MVT, and karst events in the Delaware Basin.

  3. Magmatic ore deposits in layered intrusions - Descriptive model for reef-type PGE and contact-type Cu-Ni-PGE deposits

    USGS Publications Warehouse

    Zientek, Michael L.

    2012-01-01

    Layered, ultramafic to mafic intrusions are uncommon in the geologic record, but host magmatic ore deposits containing most of the world's economic concentrations of platinum-group elements (PGE) (figs. 1 and 2). These deposits are mined primarily for their platinum, palladium, and rhodium contents (table 1). Magmatic ore deposits are derived from accumulations of crystals of metallic oxides, or immiscible sulfide, or oxide liquids that formed during the cooling and crystallization of magma, typically with mafic to ultramafic compositions. "PGE reefs" are stratabound PGE-enriched lode mineralization in mafic to ultramafic layered intrusions. The term "reef" is derived from Australian and South African literature for this style of mineralization and used to refer to (1) the rock layer that is mineralized and has distinctive texture or mineralogy (Naldrett, 2004), or (2) the PGE-enriched sulfide mineralization that occurs within the rock layer. For example, Viljoen (1999) broadly defined the Merensky Reef as "a mineralized zone within or closely associated with an unconformity surface in the ultramafic cumulate at the base of the Merensky Cyclic Unit." In this report, we will use the term PGE reef to refer to the PGE-enriched mineralization, not the host rock layer. Within a layered igneous intrusion, reef-type mineralization is laterally persistent along strike, extending for the length of the intrusion, typically tens to hundreds of kilometers. However, the mineralized interval is thin, generally centimeters to meters thick, relative to the stratigraphic thickness of layers in an intrusion that vary from hundreds to thousands of meters. PGE-enriched sulfide mineralization is also found near the contacts or margins of layered mafic to ultramafic intrusions (Iljina and Lee, 2005). This contact-type mineralization consists of disseminated to massive concentrations of iron-copper-nickel-PGE-enriched sulfide mineral concentrations in zones that can be tens to hundreds

  4. How metallic is the binding state of indium hosted by excess-metal chalcogenides in ore deposits?

    NASA Astrophysics Data System (ADS)

    Ondina Figueiredo, Maria; Pena Silva, Teresa; Oliveira, Daniel; Rosa, Diogo

    2010-05-01

    Discovered in 1863, indium is nowadays a strategic scarce metal used both in classical technologic fields (like low melting-temperature alloys and solders) and in innovative nano-technologies to produce "high-tech devices" by means of new materials, namely liquid crystal displays (LCDs), organic light emitting diodes (OLEDs) and the recently introduced transparent flexible thin-films manufactured with ionic amorphous oxide semiconductors (IAOS). Indium is a typical chalcophile element, seldom forming specific minerals and occurring mainly dispersed within polymetallic sulphides, particularly with excess metal ions [1]. The average content of indium in the Earth's crust is very low but a further increase in its demand is still expected in the next years, thus focusing a special interest in uncovering new exploitation sites through promising polymetallic sulphide ores - e.g., the Iberian Pyrite Belt (IPB) [2] - and in improving recycling technologies. Indium recovery stands mostly on zinc extraction from sphalerite, the natural cubic sulphide which is the prototype of so-called "tetrahedral sulphides" where metal ions fill half of the available tetrahedral sites within the cubic closest packing of sulphur anions where the double of unfilled interstices are available for further in-filling. It is worth remarking that such packing array is particularly suitable for accommodating polymetallic cations by filling closely located interstitial sites [3] as happens in excess-metal tetrahedral sulphides - e.g. bornite, ideally Cu5FeS4, recognized as an In-carrying mineral [4]. Studying the tendency towards In-In interactions able of leading to the formation of polycations would efficiently contribute to understand indium crystal chemistry and the metal binding state in natural chalcogenides. Accordingly, an X-ray absorption near-edge spectroscopy (XANES) study at In L3-edge was undertaken using the instrumental set-up of ID21 beamline at the ESRF (European Synchrotron

  5. Paragenetic and minor- and trace-element studies of Mississippi Valley-type ore deposits of the Silesian-Cracow district, Poland

    USGS Publications Warehouse

    Viets, J.G.; Leach, D.L.; Lichte, F.E.; Hopkins, R.T.; Gent, C.A.; Powell, J.W.

    1996-01-01

    Paragenetic and minor- and trace-element studies were conducted on samples of epigenetic ore and gangue minerals collected from mines and drill core in the Silesian-Cracow (S-C) district of southern Poland. Four discrete mineral suites representing four mineralizing stages can be identified throughout the district. The earliest epigenetic minerals deposited during stage 1 consist of a late dolomite cement together with minor pyrite and marcasite. Stage 2 was the first ore-forming stage and included repetitive deposition of sphalerite and galena in a variety of morphologies. Stage 3 abruptly followed the first ore stage and deposited marcasite and pyrite with variable amounts of late sphalerite and galena. In the samples studied, minerals deposited during stage 3 are predominately marcasite-pyrite with minor sphalerite and galena in the Pomorzany and Olkusz mines, whereas, at the Trzebionka mine, stage 3 mineralization deposited mostly galena and sphalerite with little marcasite or pyrite. Stage 4 minerals include contains barite, followed by calcite, with very minor pyrite and a rare, late granular sphalerite. Compared to other major Mississippi Valley-type (MVT) districts of the world, the Silesian-Cracow district contains sphalerite with the second largest range in Ag concentrations and the largest range in Fe and Cd concentrations of any district. Unlike in other districts, very wide ranges in minor- and trace-element concentrations are also observed in paragenetically equivalent samples collected throughout the district. This wide range indicates that the minor- and trace-element content of the ore-forming environment was highly variable, both spatially and temporally, and suggests that the hydrologic system that the ore fluids traversed from their basinal source was very complex. Throughout the district, a significant increase in Tl, Ge, and As concentrations is accompanied by a lightening of sulfur isotopes between stage 2 and stage 3 minerals. This change

  6. Relation of ERTS-1 detected geologic structure to known economic ore deposits

    NASA Technical Reports Server (NTRS)

    Rich, E. I.

    1973-01-01

    A preliminary analysis of ERTS-1 imagery of the Northern Coast Ranges and Sacramento Valley, California, has disclosed a potentially important fracture system which may be one of the controlling factors in the location of known mercury deposits in the Coast Ranges and which appears to be associated with some of the oil and gas fields within the Sacramento Valley. Recognition of this fracture system may prove to be an extremely useful exploration tool, hence careful analysis of subsequent ERTS imagery might delineate areas for field evaluation.

  7. Rock chemistry and fluid inclusion studies as exploration tools for ore deposits in the Sila batholith, southern Italy

    USGS Publications Warehouse

    de Vivo, B.; Ayuso, R.A.; Belkin, H.E.; Lima, A.; Messina, A.; Viscardi, A.

    1991-01-01

    The Sila batholith is the focus of an extensive petrogenetic research program, which includes an assessment of its potential to host granite-related ore deposits. Univariate and multivariate statistical techniques were applied to major- and minor-element rock geochemical data. The analysis indicates that the highest potential for mineralization occurs in corundum-normative, peraluminous, unfoliated, relatively late-stage plutons. The plutons are enriched in Rb, Nb, Ta and U, but depleted in Fe, Mg and Sr. The K/Rb, Ba/Rb, Rb/Sr and Rb3/Ba??Sr??K indices and high R-factor scores of Si-K-Rb are typical of mineralized granitic rocks. A reconnaissance fluid inclusion study indicates that the sub-solidus rock was infiltrated by solutions of widely different temperatures (50-416??C) and variable salinities (0 to ???26 wt.% NaCl equivalent). The higher-temperature solutions probably represent granite or magmatic-related Hercynian fluids, whereas the lower-temperature fluids may be either Hercynian or Alpine in age. Fluids with characteristics typical of mineralized "porphyry" systems have not been recognized. ?? 1991.

  8. The Reocín zinc-lead deposit, Spain: paleomagnetic dating of a late Tertiary ore body

    USGS Publications Warehouse

    Symons, David T. A.; Lewchuk, Michael T.; Kawasaki, Kazuo; Velasco, Francisco; Leach, David L.

    2009-01-01

    The Reocín mine in northern Spain’s Basque–Cantabrian basin exploited a world-class Mississippi Valley-type Zn–Pb deposit. Its epigenetic mineralization is in Urgonian 116 ± 1 Ma dolomitized limestones of the Santillana syncline, which was formed by Oligocene and mid Miocene pulses of the Pyrenean orogeny. Paleomagnetic results (22 sites, 274 specimens) in mineralization isolated a stable remanence (ChRM) in pyrrhotite and minor magnetite inclusions in ore specimens, Zn concentrate, and tailings. A fold test shows that the ChRM is substantially post-folding. The mineralization’s paleopole lies on the European apparent polar wander path and indicates that the mineralization was formed at 15 ± 10 Ma. We postulate that brines originated in underlying Triassic and Lower Cretaceous sedimentary rocks and were driven upward into the host rocks by the hydraulic gradient created by the nearby Asturian massif.

  9. Measurement of uranium series radionuclides in rock and groundwater at the Koongarra ore deposit, Australia, by gamma spectrometry

    SciTech Connect

    Yanase, Nobuyuki; Sekine, Keiichi

    1995-12-31

    Gamma spectrometry without any self-absorption correction was developed to measure low energy gamma rays emitted by uranium and actinium series radionuclides in rock samples and groundwater residues collected at the Koongarra ore deposit, Australia. Thin samples were prepared to minimize the self-absorption by uranium in the samples. The present method gave standard deviations of 0.9 to 18% for the measurements of concentrations of uranium and actinium series radionuclides. The concentrations of {sup 238}U, {sup 230}Th and {sup 235}U measured by gamma spectrometry were compared with those by alpha spectrometry that requires a complicated chemical separation procedure. The results obtained by both methods were in fairly good agreement, and it was found that the gamma spectrometry is applicable to rock and groundwater samples having uranium content sup to 8.1% (10{sup 3} B1/g) and 3 Bq/l of {sup 238}U, respectively. The detection limits were calculated to be of the order of 10{sup {minus}2} Bq/g for rock samples and 10{sup {minus}1} Bq/l for groundwater samples. The concentrations of uranium and actinium series radionuclides can be determined precisely in these samples using gamma spectrometry without any self-absorption correction.

  10. Genesis of sediment-hosted disseminated-gold deposits by fluid mixing and sulfidization: chemical-reaction-path modeling of ore- depositional processes documented in the Jerritt Canyon district, Nevada

    USGS Publications Warehouse

    Hofstra, A.H.

    1991-01-01

    Integrated geologic, geochemical, fluid-inclusion, and stable-isotope studies of the gold deposits in the Jerritt Canyon district, Nevada, provide evidence that gold deposition was a consequence of both fluid mixing and sulfidization of host-rock iron. Chemical-reaction-path models of these ore-depositional processes confirm that the combination of fluid mixing, including simultaneous cooling, dilution, and oxidation of the ore fluid, and wall-rock reaction, with sulfidization of reactive iron in the host rock, explains the disseminated nature and small size of the gold and the alteration zonation, mineralogy, and geochemistry observed at Jerritt Canyon and at many other sediment-hosted disseminated gold deposits. -Authors

  11. Alfred E. Bergeat (1866-1924): a distinguished volcanologist and ore deposit researching scientist at the mining academies of Freiberg (Saxony) and Clausthal (Harz mountains) in Germany

    NASA Astrophysics Data System (ADS)

    Pfaffl, Fritz A.

    2010-06-01

    Alfred E. Bergeat, originated from a family, who produced gold-glance in a factory (porcelain painting), studied mineralogy and geology at the University of Munich from 1886 to 1892. Due to the results of his habilitation work on the volcanism of island arcs, especially of the Stromboli volcanic island in the Tyrrhenian Sea, he became a recognized volcanologist and specialist in volcanic petrography. He further became an explorer of syngenetic, epigenetic and deuterogenic ore deposits at the mining academies (Bergakademien) of Freiberg (Saxony) and Clausthal (Harz mountains). He described these ore deposits in a two-volume manual (1904-1906) which was summarized again in 1913. After his early death in 1924, the two manuals “Die Vulkane” (1925) and “Vulkankunde” (1927) were posthumously published by his colleague and friend Karl Sapper (1866-1945).

  12. Ore geology and fluid inclusion geochemistry of the Tiemurt Pb-Zn-Cu deposit, Altay, Xinjiang, China: A case study of orogenic-type Pb-Zn systems

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zheng, Yi; Chen, YanJing

    2012-04-01

    The Tiemurt Pb-Zn-Cu deposit is hosted in a Devonian volcanic-sedimentary basin of the Altay orogenic belt, and is thus interpreted to have formed by sea-floor hydrothermal exhalation in previous studies. Our investigation discovered that the deposit is not stratiform or stratabound, but structure-controlled instead. The hydrothermal ore-forming process can be divided into the early, middle and late stage, represented by pyrite-quartz, polymetallic sulfide-quartz and carbonate-quartz veinlets, respectively. The early-stage veins and contained minerals are structurally deformed and brecciated, suggesting a compressional or transpressional tectonic regime. The middle-stage veinlets intrude and infill the fissures of the early-stage assemblages, and show no deformation, suggesting a tensional shear setting. The late-stage veinlets mostly infill open-space fissures that crosscut veins and replacements formed in the earlier stages. Four types of fluid inclusions (FIs), including aqueous (type W), carbonic-aqueous (type C), pure carbonic (type PC) and solid-bearing (type S), are identified at the Tiemurt deposit. The early-stage minerals contain the C- and W-type primary FIs that are totally homogenized at temperatures of 330-390 °C with low salinities of 0.8-11.9 wt.% NaCl eqv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 118-205 °C, and salinities of 1.4-3.4 wt.% NaCl eqv. This indicates that the ore fluid system evolved from CO2-rich, probably metamorphic to CO2-poor, meteoric fluids; and that a significant CO2-escape must have occurred. All the four types of FIs can be only observed in the middle-stage minerals, and even in a microscopic domain of a crystal, representing an association trapped from a boiling fluid system. These FIs homogenize at temperatures ranging from 270 to 330 °C, with two salinity clusters of 1.9-14.5 and 37.4-42.4 wt.% NaCl eqv., respectively. This implies that metal precipitation

  13. Host-rock controlled epigenetic, hydrothermal metasomatic origin of the Bayan Obo REEFe-Nb ore deposit, Inner Mongolia, P.R.C.

    USGS Publications Warehouse

    Chao, E.C.T.; Back, J.M.; Minkin, J.A.; Yinchen, R.

    1992-01-01

    Bayan Obo, a complex rare earth element (REE)FeNb ore deposit, located in Inner Mongolia, P.R.C. is the world's largest known REE deposit. The deposit is chiefly in a marble unit (H8), but extends into an overlying unit of black shale, slate and schist unit (H9), both of which are in the upper part of the Middle Proterozoic Bayan Obo Group. Based on sedimentary structures, the presence of detrital quartz and algal fossil remains, and the 16-km long geographic extent, the H8 marble is a sedimentary deposit, and not a carbonatite of magmatic origin, as proposed by some previous investigators. The unit was weakly regionally metamorphosed (most probably the lower part of the green schist facies) into marble and quartzite prior to mineralization. Tectonically, the deposit is located on the northern flank of the Sino-Korean craton. Many hypotheses have been proposed for the origin of the Bayan Obo deposit; the studies reported here support an epigenetic, hydrothermal, metasomatic origin. Such an origin is supported by field and laboratory textural evidence; 232Th/208Pb internal isochron mineral ages of selected monazite and bastnaesite samples; 40Ar/39Ar incremental heating minimum mineral ages of selected alkali amphiboles; chemical compositions of different generations of both REE ore minerals and alkali amphiboles; and evidence of host-rock influence on the various types of Bayan Obo ores. The internal isochron ages of the REE minerals indicate Caledonian ages for various episodes of REE and Fe mineralization. No evidence was found to indicate a genetic relation between the extensive biotite granitic rocks of Hercynian age in the mine region and the Bayan Obo are deposit, as suggested by previous workers. ?? 1992.

  14. Positive feedback between strain localization and fluid flow at the ductile-brittle transition leading to Pb-Zn-Fe-Cu-Ag ore deposits in Lavrion (Greece)

    NASA Astrophysics Data System (ADS)

    Scheffer, Christophe; Tarantola, Alexandre; Vanderhaeghe, Olivier

    2016-04-01

    At the crustal scale, the ductile-brittle transition (DBT) might correspond to a physical barrier that separates a deep reservoir of metamorphic and magmatic fluids from a shallow reservoir of surficial fluids. Rock rheology, and thus the location of the DBT, is mainly governed by lithology, temperature and the presence/absence of fluids. Accordingly, the position of the DBT potentially evolves during orogenic evolution owing to thermal evolution and fluid circulation. In turn rocks are transferred across it during burial and exhumation. These processes induce connections between fluid reservoirs which might play a role on ore deposition. In this contribution, we discuss the impact of lithological heterogeneities on deformation, fluid flow and ore deposition based on the example of the Lavrion low-angle top-to-the-SSW detachment accommodating gravitational collapse of the Hellenides orogenic belt in Greece. The Lavrion peninsula, localized along the western boundary of the Attic-Cycladic Metamorphic Core Complex, is characterized by Pb-Zn-Fe-Cu-Ag ore mineralization mainly concentrated along a lithological contact (marble/schists) below and within a detachment shear zone. The mylonitic marble below the detachment shear zone is composed of white layers of pure marble alternating with blue layers containing impurities (SiO2, Al2O3, organic matter…). Development of the mylonitic fabric in competent impure blue marble is associated with its preferred dolomitization related to focused fluid infiltration. This mylonitic marble is cross-cut by several cataclastic horizons preferentially developed within the more competent impure blue marble and newly-crystallized dolomitic horizon. These cataclasites are invaded by fluorite and calcite gangue minerals showing locally Mn, Pb, Zn, Fe oxides and/or hydroxides, sphalerite, Ag-galena, Ag-sulfur and native Ag. Oxygen and carbon stable isotopes performed on marble sections point out decarbonation with magmatic contribution and

  15. The Paleozoic Ozbak-Kuh carbonate-hosted Pb-Zn deposit of East Central Iran: Isotope (C, O, S, Pb) geochemistry and ore genesis

    NASA Astrophysics Data System (ADS)

    Ehya, Farhad

    2014-02-01

    Lead and zinc mineralization occurs in dolostones of the Middle Devonian Sibzar Formation at Ozbak-Kuh, which is located 150 km north of Tabas city in East Central Iran. The ore is composed of galena, sphalerite and calcite, with subordinate dolomite and bitumen. Wall-rock alterations include carbonate recrystallization and dolomitization. Microscopic studies reveal that the host rock is replaced by galena and sphalerite. The Pb-Zn mineralization is epigenetic and stratabound. The δ13C values of hydrothermal calcite samples fall in the narrow range between -0.3‰ and 0.8‰. The δ18O values in calcite display a wider range, between -14.5‰ and -11.9‰. The δ13C and δ18O values overlap with the oxygen and carbon isotopic compositions of Paleozoic seawater, indicating the possible important participation of Paleozoic seawater in the ore-forming fluid. The δ18O signature corresponds to a spread in temperature of about 70 °C in the ore-bearing fluid. The δ13C values indicate that the organic materials within the host rocks did not contribute significantly in the hydrothermal fluid. The δ34S values of galena and sphalerite samples occupy the ranges of 12.2‰-16.0‰ and 12.1-16.8‰, respectively. These values reveal that the seawater sulfate is the most probable source of sulfur. The reduced sulfur was most likely supplied through thermochemical sulfate reduction. The sulfur isotope ratios of co-precipitated sphalerite-galena pairs suggest that deposition of the sulfide minerals took place under chemical disequilibrium conditions. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of the galena samples represent average values of 18.08, 15.66, and 38.50, respectively. These ratios indicate that galena Pb likely originated from an orogenic source in which supracrustal rocks with high 238U/204Pb and 232Th/204Pb ratios are dominant. The average lead isotope model age portrays Cambrian age. This model age is not coeval with the host rocks, which are of middle

  16. Sulfur-containing particles emitted by concealed sulfide ore deposits: an unknown source of sulfur-containing particles in the atmosphere

    NASA Astrophysics Data System (ADS)

    Cao, J.; Li, Y.; Jiang, T.; Hu, G.

    2014-11-01

    Sources of sulfur dioxide, sulfates, and organic sulfur compounds, such as fossil fuels, volcanic eruptions, and animal feeding operations, have attracted considerable attention. In this study, we collected particles carried by geogas flows ascending through soil, geogas flows above the soil that had passed through the soil, and geogas flows ascending through deep faults of concealed sulfide ore deposits and analyzed them using transmission electron microscopy. Numerous crystalline and amorphous sulfur-containing particles or particle aggregations were found in the ascending geogas flows. In addition to S, the particles contained O, Ca, K, Mg, Fe, Na, Pb, Hg, Cu, Zn, As, Ti, Sr, Ba, Si, etc. Such particles are usually a few to several hundred nanometers in diameter with either regular or irregular morphology. The sulfur-containing particles originated from deep-seated weathering or faulting products of concealed sulfide ore deposits. The particles suspended in the ascending geogas flow migrated through faults from deep-seated sources to the atmosphere. This is a previously unknown source of the atmospheric particles. This paper reports, for the first time, the emission of sulfur-containing particles into the atmosphere from concealed sulfide ore deposits. The climatic and ecological influences of these sulfur-containing particles and particle aggregations should to be assessed.

  17. Sulfur-containing particles emitted by concealed sulfide ore deposits: an unknown source of sulfur-containing particles in the atmosphere

    NASA Astrophysics Data System (ADS)

    Cao, J. J.; Li, Y. K.; Jiang, T.; Hu, G.

    2015-06-01

    Sources of sulfur dioxide, sulfates, and organic sulfur compounds, such as fossil fuels, volcanic eruptions, and animal feeding operations, have attracted considerable attention. In this study, we collected particles carried by geogas flows ascending through soil, geogas flows above the soil that had passed through the soil, and geogas flows ascending through deep faults of concealed sulfide ore deposits, and analysed them using transmission electron microscopy. Numerous crystalline and amorphous sulfur-containing particles or particle aggregations were found in the ascending geogas flows. In addition to S, the particles contained O, Ca, K, Mg, Fe, Na, Pb, Hg, Cu, Zn, As, Ti, Sr, Ba, Si, etc. Such particles are usually a few to several hundred nanometres in diameter with either regular or irregular morphology. The sulfur-containing particles originated from deep-seated weathering or faulting products of concealed sulfide ore deposits. The particles suspended in the ascending geogas flow migrated through faults from deep-seated sources to the atmosphere. This is a previously unknown source of the atmospheric particles. This paper reports, for the first time, the emission of sulfur-containing particles into the atmosphere from concealed sulfide ore deposits. The climatic and ecological influences of these sulfur-containing particles and particle aggregations should be assessed.

  18. Magmatogenic manganese ores of the South Minusa Intermontane Trough

    NASA Astrophysics Data System (ADS)

    Kassandrov, E. G.; Mazurov, M. P.

    2009-10-01

    The first data on the mineral composition and formation conditions of manganese ore at the Chapsordag and Malosyrsky deposits in the Askiz ore district of Khakassia are integrated and systematized. The detailed mineralogical mapping of the deposits has been carried out. The identification of minerals and examination of the ore microstructure were performed with optical microscopy in transmitted and reflected light and using SEM/EDS, EMPA, XRD, IRS, and other methods. It was established that the ore mineralization is spatially and genetically related to the Early Devonian magmatism and accompanying hydrothermal activity and metasomatism. Syngenetic braunite was detected for the first time in elevated amounts reaching an economic level in the devitrified groundmass of volcanic rocks, in cement of lava breccia, and in fragments in pyroclastic rocks. By analogy with iron deposits, this magmatogenic type of manganese mineralization is regarded as ore lavas and tuffs combined with metasomatic and hydrothermal mineral assemblages into a strata-bound orebearing complex and as a source of hydrothermal metasomatic ore. The elevated Mn content in magmatic melts of the Early Devonian trachybasalt-trachyandesite-trachydacite association is caused by assimilation of Riphean and Lower Cambrian high-Mn carbonate sequences in crustal magma chambers. In contours of economic orebodies, the hydrothermal economic ore is recognized as sites of massive, patchy and impregnated, brecciated, stringer-disseminated, and disseminated varieties. High-grade massive ore occurs as stratiform and branching bodies up to 1.5 m thick and a few tens of meters long and as smaller pocketlike bodies. Braunite and pyrolusite (polianite) are major ore minerals varying in size, degree of crystallinity, and character of intergrowths with associating minerals. Gangue minerals include carbonates, sulfates, albite, quartz, chlorite, actinolite, piemontite, and okhotskite, a Mn-pumpellyite identified in Russia

  19. Geochronology, petrogenesis and tectonic settings of pre- and syn-ore granites from the W-Mo deposits (East Kounrad, Zhanet and Akshatau), Central Kazakhstan

    NASA Astrophysics Data System (ADS)

    Li, GuangMing; Cao, MingJian; Qin, KeZhang; Evans, Noreen J.; Hollings, Pete; Seitmuratova, Eleonora Yusupovha

    2016-05-01

    There is significant debate regarding the mineralization ages of the East Kounrad, Zhanet and Akshatau W-Mo deposits of Central Kazakhstan, and the petrogenesis and tectono-magmatic evolution of the granites associated with these deposits. To address these issues, we present molybdenite Re-Os dating, zircon U-Pb dating, whole rock geochemistry as well as Sr-Nd-Pb and zircon O-Hf isotopic analyses on the pre-mineralization and ore-forming granites. U-Pb dating of zircons from pre-mineralization granitic rocks yield Late Carboniferous ages of 320-309 Ma, whereas ore-forming granites have Early Permian ages of 298-285 Ma. Molybdenite Re-Os isotopic data indicate a mineralization age of ~ 296 Ma at East Kounrad, ~ 294 Ma at Akshatau and ~ 285 Ma at Zhanet. The pre-ore and ore-forming granites are high-K calc-alkaline, metaluminous to slightly peraluminous I-type granites. The pre-mineralization granites are relatively unfractionated, whereas the ore-forming granites are highly fractionated. The fractionating mineral phases are probably K-feldspar, apatite, Ti-bearing phases and minor plagioclase. The pre-mineralization and ore-forming rocks are characterized by similar Sr-Nd-Pb-Hf-O isotopic compositions ((87Sr/86Sr)i = 0.70308-0.70501, εNd (t) = - 0.5 to + 2.8, 207Pb/204Pb = 15.60-15.82, zircon εHf (t) = + 1.2 to + 15.6 and δ18O = + 4.6 to + 10.3‰), whole rock TDMC (Nd) (840-1120 Ma) and zircon TDMC (Hf) (320-1240 Ma). The isotopic characteristics are consistent with a hybrid magma source caused by 10-30% assimilation of ancient crust by juvenile lower crust. The geochronology and geochemistry of these granites show that the Late Carboniferous pre-mineralization granitic rocks formed during subduction, whereas the Early Permian ore-forming, highly fractionated granite probably underwent significant fractionation with a restite assemblage of K-feldspar, apatite, Ti-bearing phases and minor plagioclase and developed during collision between the Yili and Kazakhstan

  20. REE, trace elements, Sr, Pb, C, and O isotopes in a zoned skarn ore deposit

    SciTech Connect

    Langmuir, C.; LeHuray, A.; Fairbanks, R.; Meinert, L.

    1985-01-01

    The Groundhog skarn in the Central Mining District, New Mexico, is zoned along its >2km length adjacent to a dike swarm which trends NE toward the Santa Rita porphyry Cu deposit. Isotopes and trace elements in whole rocks and mineral separates from skarn and adjacent carbonate allow the study of the source of the metals and the systematics of trace element behavior in a skarn system. (1) /sup 87/Sr//sup 86/Sr ratios are uniform (.7083 +/- 1) in the carbonate host, but they range up to .714 in hydrothermal calcite and pyx from the skarn, values distinct from both Santa Rita (.706) and carbonate. (2) delta/sup 18/O (SMOW) in carbonate ranges from (+6.3 -+ 23) and is correlated positively with delta/sup 13/C (-5.6-+2.4) and negatively with /sup 87/Sr//sup 86/Sr. Several trace elements also correlate with delta/sup 18/O. (3) Pb isotopes in galenas lie on the regression line for southwestern New Mexico Proterozoic crust. PbS from the skarn closest to Santa Rita has isotope ratios identical to PbS from the Santa Rita pit. (4) Most of the REE are not in gar or pyx. REE abundances are <1X chondrites after HC1 leaches, but in unleached samples can be >20X chondrites. All pyx separates have deep negative Ce and very deep Eu anomalies. Sr isotopes show that neither Santa Rita magma nor carbonate is the sole source of Sr. Pb isotopes are consistent with a Santa Rita source. The Ce anomaly suggests a seawater source for the REE. The data show that many of the metals in the skarn are not derived from the Santa Rita porphyry, and suggest that different elements may be derived from different source rocks.

  1. Structural evolution of the Mount Wall region in the Hamersley province, Western Australia and its control on hydrothermal alteration and formation of high-grade iron deposits

    NASA Astrophysics Data System (ADS)

    Dalstra, Hilke J.

    2014-10-01

    The discovery of two relatively small but high-grade iron ore deposits near Mt Wall, an intensely faulted part of the southwestern Hamersley province provides unique insights into the structural control on ore formation in this region. The deposits have many geological features typical of the high grade microplaty hematite group which also contains the much larger Mt Tom Price, Paraburdoo and Mt Whaleback deposits. The deposits are structurally controlled along early normal faults and contain abundant microplaty hematite and martite, and are largely confined to the Dales Gorge member of the Brockman Iron Formation. In addition to the microplaty hematite-martite ore, there are martite-goethite ores and rare magnetite-goethite or magnetite-hematite ores. Below the modern weathering surface, hydrothermally altered zones in wallrock BIF from the Lower Dales Gorge member contain magnetite, hematite and carbonate/talc bearing mineral assemblages. A staged ore genesis model involving early extension and fluid circulation along normal faults, hypogene silica leaching and carbonate alteration, followed by deep meteoric oxidation with microplaty hematite formation and finally weathering can explain most features of the Mt Wall deposits. The role of deformation was to provide pathways for mineralising fluids and initiate the seed points for the mineralised systems. High grade iron in the Wellthandalthaluna deposit is situated between the NW to NNW trending Boolgeeda Creek fault and a synthetic joining splay, the Northern fault. Both are high angle normal faults and formed during early extension in this part of the province. Faults are characterised by localised small scale deformation and brecciation, deep carbonate alteration and oxidation. Recent weathering has penetrated deeply into the fault zones, converting the carbonate-rich assemblages into goethite. Mineralisation in the Arochar deposit is situated in the overlap or relay zone between two segments of the Mt Wall

  2. Evidence for microbial activity in the formation of carbonate-hosted Zn-Pb deposits

    NASA Astrophysics Data System (ADS)

    Kucha, H.; Raith, J.

    2009-04-01

    *Kucha H **Raith J *University of Mining and Metallurgy, Faculty of Geology, Geophysics and Environmental Protection, Mickiewicza 30, PL-30-059 Krakow, Poland. ** University of Leoben, Department of Applied Geosciences and Geophysics, A-8700 Leoben, Peter Tunner Str. 5, Austria Evidence for microbial activity in the formation of carbonate-hosted Zn-Pb deposits To date evaluation of bacterial processes in the formation of carbonate-hosted Zn-Pb deposits is largely based on sulphur isotope evidence. However, during a past few years, textural criteria, have been established, which support the bacterial origin of many of these deposits. This has received a strong support from micro-, and nano-textures of naturally growing bacterial films in a flooded tunnel within carbonates that host the Piquette Zn-Pb deposit (Druschel et al., 2002). Bacterial textures, micro- and nano textures found in carbonate-hosted Zn-Pb deposits are: i)wavy bacterial films up to a few mm thick to up to a few cm long composed of peloids, ii)semimassive agglomeration of peloids in the carbonate matrix, and iii)solitary peloids dispersed in the carbonate matrix. Peloids are usually composed of a distinct 50-90um core most often made up of Zn-bearing calcite surrounded by 30-60um thick dentate rim composed of ZnS. Etching of Zn-carbonate cores reveals 1 - 2um ZnS filaments, and numerous 15 to 90nm large ZnS nano-spheres (Kucha et al., 2005). In massive ore composite Zn-calcite - sphalerite peloids are entirely replaced by zinc sulphide, and form peloids ghosts within banded sulphide layers. Bacterially derived micro- and nano-textures have been observed in the following carbonate-hosted Zn-Pb deposits: 1)Irish-type Zn-Pb deposits. In the Navan deposit the basic sulphur is isotopically light bacteriogenic S (Fallick at al., 2001). This is corroborated by semimassive agglomerations of composite peloids (Zn-calcite-ZnS corona or ZnS core-melnikovite corona). Etching of Zn-calcite core reveals globular

  3. Formation conditions of paleovalley uranium deposits hosted in upper Eocene-lower Oligocene rocks of Bulgaria

    NASA Astrophysics Data System (ADS)

    Vinokurov, S. F.; Strelkova, E. A.

    2016-03-01

    The uranium deposits of Bulgaria related to the Late Alpine tectonomagmatic reactivation are subdivided into two groups: exogenic-epigenetic paleovalley deposits related to the basins filled with upper Eocene-lower Oligocene volcanic-sedimentary rocks and the hydrothermal deposits hosted in the coeval depressions. The geological and lithofacies conditions of their localization, the epigenetic alteration of rocks, mineralogy and geochemistry of uranium ore are exemplified in thoroughly studied paleovalley deposits of the Maritsa ore district. Argumentation of the genetic concepts providing insights into both sedimentation-diagenetic and exogenic-epigenetic mineralization with development of stratal oxidation zones is discussed. A new exfiltration model has been proposed to explain the origin of the aforementioned deposits on the basis of additional analysis with consideration of archival factual data and possible causes of specific ningyoite uranium ore composition.

  4. Complex, multiple ore fluids in the world class southeast Missouri Pb-Zn-Cu MVT deposits: Sulfur isotope evidence

    SciTech Connect

    Burstein, I.B.; Shelton, K.L. ); Gregg, J.M.; Hagni, R.D. . Dept. of Geology Geophysics)

    1993-03-01

    More than 625 sulfur isotope data from all of the mines in the Viburnum Trend Pb-Zn-Cu MVT district of southeast Missouri have identified large temporal variations of sulfur isotope composition within the complex mineral paragenesis of each mine as well as large spatial variations in sulfur isotope composition within and among mines. The general trend of [delta][sup 34]S values with increasing paragenetic time is: Early pyrite, [minus]9 to [minus]1[per thousand]; Early bornite-chalcopyrite, [minus]9 to +16[per thousand]; Massive chalcopyrite, [minus]14 to +9[per thousand]; Main sphalerite, +12 to +26[per thousand]; Cuboctahedral galena, +5 to +22[per thousand]; Main marcasite, [minus]19 to +9[per thousand]; Cubic galena, [minus]2 to +13[per thousand] Late sphalerite, +6 to +13[per thousand]; Late marcasite, +10 to +19[per thousand]; Late chalcopyrite, +2 to +33[per thousand]. Spatial correlation of [delta][sup 34]S values of the Main stages of sulfide mineralization in the West Fork mine may indicate that the cuboctahedral galena in this mine was precipitated from a Pb-rich, S-poor fluid that incorporated sulfur from reaction with earlier marcasite. In the rest of the district, ore precipitation may have occurred by mixing of Pb-rich, S-poor fluids with Pb-poor, S-rich fluids. Complex mineral parageneses and sulfur isotope systematics within the southeast Missouri Pb-Zn-Cu MVT deposits are compatible with multiple, metal-specific fluids and multiple precipitation mechanisms, as well as multiple sulfur sources.

  5. Metal surface effects on deposit formation in a flow reactor

    SciTech Connect

    Li, J.; Eser, S.

    1996-10-01

    The formation of carbonaceous deposits on metallic surfaces of the fuel system due to thermal degradation/pyrolysis of jet fuels is a major concern in the development of advanced jet aircraft in which the fuel is to be used to dissipate the heat loads. The effects of these surfaces on deposit formation at relatively high temperatures (> 400{degrees}C) are studied using a bench scale flow reactor by passing JP-8 fuel and a mixture of n-paraffins (NORPAR 13) on metal coupons (Ni, Cu, Ti, Stainless Steel) inserted inside the reactor. Gas phase reaction products are analyzed by an on-line GC attached to the reactor. Global kinetics for deposit formation is studied by the amount of deposit on the coupons. Carbonaceous deposits on the metal coupons are characterized with SEM, optical microscopy and FTIR. Nickel and copper surfaces are found active in incipient deposit formation. Deposit formed from gas phase with isotropic textures is also observed. The combined data help the understanding of the metal surface effects on deposit formation in comparison to those from tubing bomb reactor and those from actual engine fuel system.

  6. Introduction to ore geology

    SciTech Connect

    Evans, A.M.

    1987-01-01

    This textbook on ore geology is for second and third year undergraduates and closely parallels the undergraduate course given in this subject at England's University of Leicester. The volume covers three major areas: (1) principles of ore geology, (2) examples of the most important types of ore deposits, and (3) mineralization in space and time. Many chapters have been thoroughly revised for this edition and a chapter on diamonds has been added. Chapters on greisen and pegmatite have also been added, the former in response to the changing situation in tin mining following the recent tin crisis, and the latter in response to suggestions from geologists in a number of overseas countries. Some chapters have been considerably expanded and new sections added, including disseminated gold deposits and unconformity-associated uranium deposits. The author also expands on the importance of viewing mineral deposits from an economic standpoint.

  7. Photosynthesis and oxidative stress in the restinga plant species Eugenia uniflora L. exposed to simulated acid rain and iron ore dust deposition: potential use in environmental risk assessment.

    PubMed

    Neves, Natália Rust; Oliva, Marco Antonio; da Cruz Centeno, Danilo; Costa, Alan Carlos; Ribas, Rogério Ferreira; Pereira, Eduardo Gusmão

    2009-06-01

    The Brazilian sandy coastal plain named restinga is frequently subjected to particulate and gaseous emissions from iron ore factories. These gases may come into contact with atmospheric moisture and produce acid rain. The effects of the acid rain on vegetation, combined with iron excess in the soil, can lead to the disappearance of sensitive species and decrease restinga biodiversity. The effects of iron ore dust deposition and simulated acid rain on photosynthesis and on antioxidant enzymes were investigated in Eugenia uniflora, a representative shrub species of the restinga. This study aimed to determine the possible utility of this species in environmental risk assessment. After the application of iron ore dust as iron solid particulate matter (SPM(Fe)) and simulated acid rain (pH 3.1), the 18-month old plants displayed brown spots and necrosis, typical symptoms of iron toxicity and injuries caused by acid rain, respectively. The acidity of the rain intensified leaf iron accumulation, which reached phytotoxic levels, mainly in plants exposed to iron ore dust. These plants showed the lowest values for net photosynthesis, stomatal conductance, transpiration, chlorophyll a content and electron transport rate through photosystem II (PSII). Catalase and superoxide dismutase activities were decreased by simulated acid rain. Peroxidase activity and membrane injury increased following exposure to acid rain and simultaneous SPM(Fe) application. Eugenia uniflora exhibited impaired photosynthetic and antioxidative metabolism in response to combined iron and acid rain stresses. This species could become a valuable tool in environmental risk assessment in restinga areas near iron ore pelletizing factories. Non-invasive evaluations of visual injuries, photosynthesis and chlorophyll a fluorescence, as well as invasive biochemical analysis could be used as markers. PMID:19321190

  8. Geological, fluid inclusion and isotopic studies of the Yinshan Cu-Au-Pb-Zn-Ag deposit, South China: Implications for ore genesis and exploration

    NASA Astrophysics Data System (ADS)

    Wang, Guo-Guang; Ni, Pei; Wang, Ru-Cheng; Zhao, Kui-Dong; Chen, Hui; Ding, Jun-Ying; Zhao, Chao; Cai, Yi-Tao

    2013-09-01

    The Yinshan Cu-Au-Pb-Zn-Ag deposit is located in Dexing, South China. Ore bodies are primarily hosted in low-grade phyllite of the Neoproterozoic Shuangqiaoshan Group along EW- and NNW-striking fault zones. Pb-Zn-Ag mineralization is dictated by Jurassic rhyolitic quartz porphyries (ca. 172 Ma), whereas Cu-Au mineralization is associated with Jurassic dacite porphyries (ca. 170 Ma). The main ore minerals are pyrite, chalcopyrite, galena, sphalerite, tetrahedrite-tennatite, gold, silver, and silver sulphosalt, and the principal gangue minerals are quartz, sericite, calcite, and chlorite. Two-phase liquid-rich (type I), two-phase vapor-rich (type II), and halite-bearing (type III) fluid inclusions can be observed in the hydrothermal quartz-sulfides veins. Type I inclusions are widespread and have homogenization temperatures of 187-303 °C and salinities of 4.2-9.5 wt.% NaCl equivalent in the Pb-Zn-Ag mineralization, and homogenization temperatures of 196-362 °C and salinities of 3.5-9.9 wt.% NaCl equivalent in the Cu-Au mineralization. The pervasive occurrence of type I fluid inclusions with low-moderate temperatures and salinities implies that the mineralizing fluids formed in epithermal environments. The type II and coexisting type III inclusions, from deeper levels below the Cu-Au ore bodies, share similar homogenization temperatures of 317-448 °C and contrasting salinities of 0.2-4.2 and 30.9-36.8 wt.% NaCl equivalent, respectively, which indicates that boiling processes occurred. The sulfur isotopic compositions of sulfides (δ34S = -1.7‰ to +3.2‰) suggest a homogeneous magmatic sulfur source. The lead isotopes of sulfides (206Pb/204Pb = 18.01-18.07; 207Pb/204Pb = 15.55-15.57; and 208Pb/204Pb = 38.03-38.12) are consistent with those of volcanic-subvolcanic rocks (206Pb/204Pb = 18.03-18.10; 207Pb/204Pb = 15.56-15.57; and 208Pb/204Pb = 38.02-38.21), indicating a magmatic origin for lead in the ore. The oxygen and hydrogen isotope compositions (δ18O = +7.8

  9. Hydrothermal alteration, fluid inclusions and stable isotope systematics of the Alvo 118 iron oxide-copper-gold deposit, Carajás Mineral Province (Brazil): Implications for ore genesis

    NASA Astrophysics Data System (ADS)

    Torresi, Ignacio; Xavier, Roberto Perez; Bortholoto, Diego F. A.; Monteiro, Lena V. S.

    2012-03-01

    The Alvo 118 iron oxide-copper-gold (IOCG) deposit (170 Mt at 1.0 wt.% Cu, 0.3 g/t Au) lies in the southern sector of the Itacaúnas Shear Belt, Carajás Mineral Province, along a WNW-ESE-striking, 60-km-long shear zone, close to the contact of the ~2.76-Ga metavolcano-sedimentary Itacaiúnas Supergroup and the basement (~3.0 Ga Xingu Complex). The Alvo 118 deposit is hosted by mafic and felsic metavolcanic rocks and crosscutting granitoid and gabbro intrusions that have been subjected to the following hydrothermal alteration sequence towards the ore zones: (1) poorly developed sodic alteration (albite and scapolite); (2) potassic alteration (biotite or K-feldspar) accompanied by magnetite formation and silicification; (3) widespread, pervasive chlorite alteration spatially associated with quartz-carbonate-sulphide infill ore breccia and vein stockworks; and (4) local post-ore quartz-sericite alteration. The ore assemblage is dominated by chalcopyrite (~60%), bornite (~10%), hematite (~20%), magnetite (10%) and subordinate chalcocite, native gold, Au-Ag tellurides, galena, cassiterite, F-rich apatite, xenotime, monazite, britholite-(Y) and a gadolinite-group mineral. Fluid inclusion studies in quartz point to a fluid regime composed of two distinct fluid types that may have probably coexisted within the timeframe of the Cu-Au mineralizing episode: a hot (>200°C) saline (32.8‰ to 40.6 wt.% NaCl eq.) solution, represented by salt-bearing aqueous inclusions, and a lower temperature (<200°C), low to intermediate salinity (<15 wt.% NaCl eq.) aqueous fluid defined by two-phase (LH2O + VH2O) fluid inclusions. This trend is very similar to those defined for other IOCG systems of the Carajás Mineral Province. δ 18OH2O values in equilibrium with calcite (-1.0‰ to 7.5‰ at 277°C to 344°C) overlap the lower range for primary magmatic waters, but the more 18O-depleted values also point to the involvement of externally derived fluids, possibly of meteoric origin

  10. An investigation into heterogeneity in a single vein-type uranium ore deposit: Implications for nuclear forensics.

    PubMed

    Keatley, A C; Scott, T B; Davis, S; Jones, C P; Turner, P

    2015-12-01

    Minor element composition and rare earth element (REE) concentrations in nuclear materials are important as they are used within the field of nuclear forensics as an indicator of sample origin. However recent studies into uranium ores and uranium ore concentrates (UOCs) have shown significant elemental and isotopic heterogeneity from a single mine site such that some sites have shown higher variation within the mine site than that seen between multiple sites. The elemental composition of both uranium and gangue minerals within ore samples taken along a single mineral vein in South West England have been measured and reported here. The analysis of the samples was undertaken to determine the extent of the localised variation in key elements. Energy Dispersive X-ray spectroscopy (EDS) was used to analyse the gangue mineralogy and measure major element composition. Minor element composition and rare earth element (REE) concentrations were measured by Electron Probe Microanalysis (EPMA). The results confirm that a number of key elements, REE concentrations and patterns used for origin location do show significant variation within mine. Furthermore significant variation is also visible on a meter scale. In addition three separate uranium phases were identified within the vein which indicates multiple uranium mineralisation events. In light of these localised elemental variations it is recommended that representative sampling for an area is undertaken prior to establishing the REE pattern that may be used to identify the originating mine for an unknown ore sample and prior to investigating impact of ore processing on any arising REE patterns. PMID:26301831

  11. Formation and deposition of volcanic sulfate aerosols on Mars

    NASA Technical Reports Server (NTRS)

    Settle, M.

    1979-01-01

    The paper considers the formation and deposition of volcanic sulfate aerosols on Mars. The rate limiting step in sulfate aerosol formation on Mars is the gas phase oxidation of SO2 by chemical reactions with O, OH, and HO2; submicron aerosol particles would circuit Mars and then be removed from the atmosphere by gravitational forces, globally dispersed, and deposited over a range of equatorial and mid-latitudes. Volcanic sulfate aerosols on Mars consist of liquid droplets and slurries containing sulfuric acid; aerosol deposition on a global or hemispheric scale could account for the similar concentrations of sulfur within surficial soils at the two Viking lander sites.

  12. Evolution of Ore Deposits and Technology Transfer Project: Isotope and Chemical Methods in Support of the U.S. Geological Survey Science Strategy, 2003-2008

    USGS Publications Warehouse

    Rye, Robert O.; Johnson, Craig A.; Landis, Gary P.; Hofstra, Albert H.; Emsbo, Poul; Stricker, Craig A.; Hunt, Andrew G.; Rusk, Brian G.

    2010-01-01

    Principal functions of the U.S. Geological Survey (USGS) Mineral Resources Program are providing assessments of the location, quantity, and quality of undiscovered mineral deposits, and predicting the environmental impacts of exploration and mine development. The mineral and environmental assessments of domestic deposits are used by planners and decisionmakers to improve the stewardship of public lands and public resources. Assessments of undiscovered mineral deposits on a global scale reveal the potential availability of minerals to the United States and other countries that manufacture goods imported to the United States. These resources are of fundamental relevance to national and international economic and security policy in our globalized world economy. Performing mineral and environmental assessments requires that predictions be made of the likelihood of undiscovered deposits. The predictions are based on geologic and geoenvironmental models that are constructed for the diverse types of mineral deposits from detailed descriptions of actual deposits and detailed understanding of the processes that formed them. Over the past three decades the understanding of ore-forming processes has benefited greatly from the integration of laboratory-based geochemical tools with field observations and other data sources. Under the aegis of the Evolution of Ore Deposits and Technology Transfer Project (referred to hereinafter as the Project), a 5-year effort that terminated in 2008, the Mineral Resources Program provided state-of-the-art analytical capabilities to support applications of several related geochemical tools to ore-deposit-related studies. The analytical capabilities and scientific approaches developed within the Project have wide applicability within Earth-system science. For this reason the Project Laboratories represent a valuable catalyst for interdisciplinary collaborations of the type that should be formed in the coming years for the United States to meet

  13. Mineralogical and geochemical constraints on environmental impacts from waste rock at Taojiang Mn-ore deposit, central Hunan, China

    NASA Astrophysics Data System (ADS)

    Peng, Bo; Piestrzynski, Adam; Pieczonka, Jadwiga; Xiao, Meilian; Wang, Yaozhu; Xie, Shurong; Tang, Xiaoyan; Yu, Changxun; Song, Zhi

    2007-07-01

    The mineralogy and geochemistry of the waste rocks distributed at Taojiang Mn-ore deposit, central Hunan province, China, were studied using X-ray powder diffraction (XRD), electron microprobe analysis (EMPA) fitted with energy dispersive spectrometer (EDS) and inductively coupled plasma mass spectrum (atomic emission spectra) ICP-MS (AES), with the aim of predicting the environmental impacts of weathering of the waste rocks. The mineralogical results from microscope observation and XRD and EMPA studies show that the waste rock is composed of black shale and minor Mn carbonates. The oxidation of sulfide minerals such as galena, pyrite and chalcopyrite is accompanied by decomposition of Mn carbonates and K-feldspar during exposure to atmospheric O2. The geochemical characteristics of major, rare earth elements (REE) and trace elements of the waste rocks also show that the waste rock can be divided into black shale and Mn carbonate, and both of them are currently under chemical weathering. The major alkalies and alkaline elements (Ca, Mg, Na, K, Rb, Sr and Cs) and major elements (Fe, S and P) and heavy metals (Sc, V, Cr, Th, U, Sn, Co, Ni, Cu, Zn, Pb, Mo, Cd, Sb, an Tl) are being released during weathering. The mobility of alkalis and alkaline elements Ca, Mg, Na, K, Rb, Sr and Cs is controlled by decomposition of Mn carbonates. The dispersion of Cr, Sc and Th (U) might be related to weathering of K-feldspar, and the release of the heavy metals Co, Ni, Cu, Zn, Pb, Mo, Cd Sb and Tl is dominated by the breaking of sulfide minerals. The REE of the waste rocks and surrounding soils and the spidery distribution patterns of heavy metals in the waste rocks, the surrounding soils and the surface waters show that weathering of the waste rocks and bedrock might be the sources of heavy metal contamination for the surrounding soils and surface water system for the mining area. This is predicted by the mass-balance calculation by using Zr as an immobile element. Therefore, it is

  14. Recent massive sulfide deposits of the Semenov ore district, Mid-Atlantic Ridge, 13°31' N: Associated rocks of the oceanic core complex and their hydrothermal alteration

    NASA Astrophysics Data System (ADS)

    Pertsev, A. N.; Bortnikov, N. S.; Vlasov, E. A.; Beltenev, V. E.; Dobretsova, I. G.; Ageeva, O. A.

    2012-09-01

    The oceanic core complexes and large-offset detachment faults characteristic of the slow-spreading Mid-Atlantic Ridge are crucial for the structural control of large hydrothermal systems, including those forming sub-seafloor polymetallic sulfide mineralization. The structural-geological, petrographic, and mineralogical data are considered for the oceanic core complex enclosing the Semenov-1, -2, -3, -4, and -5 inactive hydrothermal sulfide fields recently discovered on the Mid-Oceanic Ridge at 13°31' N. The oceanic core complex is composed of serpentinized and talc-replaced peridotites and sporadic gabbroic rocks, however, all hydrothermal fields reveal compositional indications of basaltic substrate. The volcanic structures superposed on the oceanic core complex are marked by outcrops of pillow lavas with fresh quenched glass. Dolerites regarded as volcanic conduits seem to represent separate dike swarms. The superposed volcanic structures develop largely along the near-latitudinal high-angle tectonic zone controlling the Semenov-1, -2, -5, and -3 hydrothermal sulfide fields. The manifestations of hydrothermal metasomatic alteration are diverse. The widespread talcose rocks with pyrrhotite-pyrite mineralization after serpentinite, as well as finding of talc-chlorite metabasalt are interpreted as products of hydrothermal activity in the permeable zone of detachment fault. Chloritization and brecciation of basalts with superposed quartz or opal, barite, and pyrite or chalcopyrite mineralization directly related to the sub-seafloor sulfide deposition. The native copper mineralization in almost unaltered basalts at the Semenov-4 field is suggested to precipitate from ore-forming fluids before they reach the level of sub-seafloor sulfide deposition. Amphibolites with plagiogranite veinlets are interpreted as tectonic fragments of the highest-temperature portions of hydrothermal systems, where partial melting of basic rocks in the presence of aqueous fluid with

  15. Deposit formation in hydrocarbon rocket fuels: Executive summary

    NASA Technical Reports Server (NTRS)

    Roback, R.; Szetela, E. J.; Spadaccini, L. J.

    1981-01-01

    An experimental program was conducted to study deposit formation in hydrocarbon fuels under flow conditions that exist in high-pressure, rocket engine cooling systems. A high pressure fuel coking test apparatus was designed and developed and was used to evaluate thermal decomposition (coking) limits and carbon deposition rates in heated copper tubes for two hydrocarbon rocket fuels, RP-1 and commercial-grade propane. Tests were also conducted using JP-7 and chemically-pure propane as being representative of more refined cuts of the baseline fuels. A parametric evaluation of fuel thermal stability was performed at pressures of 136 atm to 340 atm, bulk fuel velocities in the range 6 to 30 m/sec, and tube wall temperatures in the range 422 to 811K. In addition, the effect of the inside wall material on deposit formation was evaluated in selected tests which were conducted using nickel-plated tubes. The results of the tests indicated that substantial deposit formation occurs with RP-1 fuel at wall temperatures between 600 and 800K, with peak deposit formation occurring near 700K. No improvements were obtained when de-oxygenated JP-7 fuel was substituted for RP-1. The carbon deposition rates for the propane fuels were generally higher than those obtained for either of the kerosene fuels at any given wall temperature. There appeared to be little difference between commercial-grade and chemically-pure propane with regard to type and quantity of deposit. The results of tests conducted with RP-1 indicated that the rate of deposit formation increased slightly with pressure over the range 136 atm to 340 atm. Finally, plating the inside wall of the tubes with nickel was found to significantly reduce carbon deposition rates for RP-1 fuel.

  16. Crustal and uppermost mantle velocity structure and its relationship with the formation of ore districts in the Middle-Lower Yangtze River region

    NASA Astrophysics Data System (ADS)

    Ouyang, Longbin; Li, Hongyi; Lü, Qingtian; Yang, Yingjie; Li, Xinfu; Jiang, Guoming; Zhang, Guibin; Shi, Danian; Zheng, Dan; Sun, Sanjian; Tan, Jing; Zhou, Ming

    2014-12-01

    and the amplitude is consistent with the fact that peak ages of magmatic events along the Middle-Lower Yangtze River Metallogenic Belt progressively become younger and younger from 148 Ma in the southwest to 125 Ma in the northeast. The observed low-velocity zone may represent the cooling hot upper mantle which was partially molten in the past resulting from partial melting of the paleo-Pacific plate or of an enriched mantle source induced by the westward subduction of the paleo-Pacific plate. The upwelling of the mantle-derived magmas may result in the formation of these granitic rocks and coeval ores deposits along the Middle-Lower Yangtze River Metallogenic Belt.

  17. Strontium isotope constraint on the genesis of crude oils, oil-field brines and Kuroko ore deposits from the Green Tuff region of northeastern Japan

    NASA Astrophysics Data System (ADS)

    Nakano, Takanori; Kajiwara, Yoshimichi; Farrell, Clifton W.

    1989-10-01

    Crude oils from Akita to northern Niigata oil fields in the Green Tuff region of northeastern Japan have distinctly uniform 87Sr/86Sr ratios (0.7080-0.7082), while those from the southern Niigata oil field contain more radiogenic strontium (0.7095-0.7102). The regional variation in the strontium isotopic composition of crude oils is also reflected in their sulfur contents and sulfur isotopic compositions, and may be attributed to the regional heterogeneity of marine organic sediments from which the crude oils were ultimately derived. The 87Sr/86Sr ratios of most oil-field brines (0.7061-0.7084), however, are different from and vary more locally than those of the accompanying crude oils. This finding supports the view that strontium, and by inference some other dissolved solutes in the brines, may have evolved during diagenesis by reaction of a connate and/or a meteoric water with rocks in the Green Tuff region. Barites in the sulfide ore and anhydrites and gypsums in the sulfate (sekko) ore from the Fukazawa and Kosaka Kuroko deposits in the Hokuroku district are divided by the 87Sr/86Sr ratio of 0.7081 (±0.0001), which is identical to that of crude oils from nearby oil fields. This similarity in ratios lends support to the conclusion that the Kuroko base metal deposits and crude oil deposits were ultimately derived from a common organic sediment named PUMOS (Primitive Undifferentiated Metalliferous Organic Sediments).

  18. Occurrence of copper, gold, silver,uranium, tungsten, tin ore deposits in the Late Proterozoic aulacogen mobile melt of southeast China

    SciTech Connect

    Ma, X.H.

    1985-01-01

    In the early period of the late Proterozoic Era (1100 m.y. +/-) an aulacogen mobile belt was formed in the southeast of China. It extends about 1000 km crossing the Yantze Platform and Jiangnan Foldbelt in NNE-NE direction and adjoins the south China geosyncline basement. This belt shows some features of geology and mineralization similar to the Adelaide geosyncline and the Zambia-Zaire Copper-uranium belt. Within the belt, there are about 9000 to 12,000 m polystratotype strata and continuous sediments of the Late Proterozoic Erathem, including alkaline and meta-alkaline volcanic products of 4 epochs of mainly marine facies. A great number of ore-forming elements, such as Cu, U, Pb, Zn, Au, Ag, Fe, Co, Ni, Mn, P, and W, Sn, TR etc., were deposited and enriched in the whole volcano-sedimentary sequency at various times and in various places. A few of them have become syngenetic deposits, but most of them have been transformed into large-scale ore deposits or mineralization fields or areas of copper and gold, lead-zinc and silver, uranium, tungsten, tin, and other metals.

  19. Sulfur isotope geochemistry of ore and gangue minerals from the Silesian-Cracow Mississippi Valley-type ore district, Poland

    USGS Publications Warehouse

    Leach, D.L.; Vets, J.G.; Gent, C.A.

    1996-01-01

    Studies of the sulfur isotopic composition of ore and gangue minerals from the Silesian-Cracow Zn-Pb district were conducted to gain insights into processes that controlled the location and distribution of the ore deposits. Results of this study show that minerals from the Silesian-Cracow ore district have the largest range of sulfur isotope compositions in sulfides observed from any Mississippi Valley-type ore district in the world. The ??34S values for sulfide minerals range from +38 to -32 per mil for the entire paragenetic sequence but individual stages exhibit smaller ranges. There is a well developed correlation between the sulfur isotope composition and paragenetic stage of ore deposition. The first important ore stage contains mostly positive ??34S values, around 5 per mil. The second stage of ore formation are lower, with a median value of around -5 to -15 per mil, and with some values as low as -32 per mil. Late stage barite contains isotopically heavy sulfur around +32 per mil. The range in sulfur isotope compositions can be explained by contributions of sulfur from a variety of source rocks together with sulfur isotope fractionations produced by the reaction paths for sulfate reduction. Much of the variation in sulfur isotope compositions can be explained by bacterial reduction of sedimentary sulfate and disequilibrium reactions by intermediate-valency sulfur species, especially in the late-stage pyrite and sphalerite. Organic reduction of sulfate and thermal release of sulfur from coals in the Upper Silesian Coal Basin may have been important contributors to sulfur in the ore minerals. The sulfur isotopic data, ore mineral textures, and fluid inclusion data, are consistent with the hypothesis that fluid mixing was the dominant ore forming mechanism. The rather distinct lowering of ?? 34S values in sulfides from stage 2 to stage 3 is believed to reflect some fundamental change in the source of reduced sulfur and/or hydrology of the ore

  20. New isotopic evidence bearing on bonanza (Au-Ag) epithermal ore-forming processes

    NASA Astrophysics Data System (ADS)

    Saunders, James A.; Mathur, Ryan; Kamenov, George D.; Shimizu, Toru; Brueseke, Matthew E.

    2016-01-01

    New Cu, S, and Pb isotope data provide evidence for a magmatic source of metal(loid)s and sulfur in epithermal Au-Ag deposits even though their ore-forming solutions are composed primarily of heated meteoric (ground) waters. The apparent isotopic discrepancy between ore metals and ore-forming solutions, and even between the ore and associated gangue minerals, indicates two different sources of epithermal ore-forming constituents: (1) a shallow geothermal system that not only provides the bulk of water for the ore-forming solutions but also major chemical constituents leached from host rocks (silica, aluminum, potassium, sodium, calcium) to make gangue minerals and (2) metals and metalloids (As, Te, Sb, etc.) and sulfur (±Se) derived from deeper magma bodies. Isotopic data are consistent with either vapor-phase transport of metal(loids) and sulfur and their subsequent absorption by shallow geothermal waters or formation of metallic (Au, Ag, Cu phases) nanoparticles at depth from magmatic fluids prior to encountering the geothermal system. The latter is most consistent with ore textures that indicate physical transport and aggregation of nanoparticles were significant ore-forming processes. The recognition that epithermal Au-Ag ores form in tectonic settings that produce magmas capable of releasing metal-rich fluids necessary to form these deposits can refine exploration strategies that previously often have focused on locating fossil geothermal systems.

  1. Timing and setting of skarn and iron oxide formation at the Smältarmossen calcic iron skarn deposit, Bergslagen, Sweden

    NASA Astrophysics Data System (ADS)

    Jansson, Nils F.; Allen, Rodney L.

    2013-03-01

    Abundant iron oxide deposits including banded iron formations, apatite iron oxide ores, and enigmatic marble/skarn-hosted magnetite deposits occur in the Palaeoproterozoic Bergslagen region, southern Sweden. During the last 100 years, the latter deposit class has been interpreted as contact metasomatic skarn deposits, metamorphosed iron formations, or metamorphosed carbonate replacement deposits. Their origin is still incompletely understood. At the Smältarmossen mine, magnetite was mined from a ca. 50-m-thick calcic skarn zone at the contact between rhyolite and stratigraphically overlying limestone. A syn-volcanic dacite porphyry which intruded the footwall has numerous apophyses that extend into the mineralized zone. Whole-rock lithogeochemical and mineral chemical analyses combined with textural analysis suggests that the skarns formed by veining and replacement of the dacite porphyry and rhyolite. These rocks were added substantial Ca and Fe, minor Mg, Mn, and LREE, as well as trace Co, Sn, U, As, and Sr. In contrast, massive magnetite formed by pervasive replacement of limestone. Tectonic fabrics in magnetite and skarn are consistent with ore formation before or early during Svecokarelian ductile deformation. Whereas a syngenetic-exhalative model has previously been suggested, our results are more compatible with magnetite formation at ca. 1.89 Ga in a contact metasomatic skarn setting associated with the dacite porphyry.

  2. Iron isotope and REE+Y composition of the Cauê banded iron formation and related iron ores of the Quadrilátero Ferrífero, Brazil

    NASA Astrophysics Data System (ADS)

    Mendes, Mônica; Lobato, Lydia M.; Kunzmann, Marcus; Halverson, Galen P.; Rosière, Carlos A.

    2016-04-01

    The Minas Supergroup banded iron formations (BIFs) of the Brazilian Quadrilátero Ferrífero (QF) mineral province experienced multiple deformational events synchronous with hypogene mineralization, which resulted in the metamorphism of BIFs to itabirites and their upgrade to high-grade iron ore. Here, we present rare earth element and yttrium (REE+Y) compositions together with iron isotope ratios of itabirites and their host iron orebodies from 10 iron deposits to constrain environmental conditions during BIF deposition and the effects of hypogene iron enrichment. The REE+Y characteristics of itabirites (positive Eu anomaly and LREE depletion) indicate hydrothermal iron contribution to the Minas basin. Iron isotope data and Ce anomalies suggest BIFs were precipitated by a combination of anoxic biological-mediated ferrous iron oxidation and abiotic oxidation in an environment with free oxygen (such as an oxygen oasis), perhaps related to increase in oxygen concentrations before the Great Oxidation Event (GOE). The similarity of the REE+Y composition of the itabirites from the different QF deformational domains, as well as to other Superior-type BIFs, indicates that the metamorphism and synchronous hydrothermal mineralization did not significantly affect the geochemical signature of the original BIFs. However, iron isotope compositions of iron ore vary systematically between deformational domains of the QF, likely reflecting the specific mineralization features in each domain.

  3. In-situ Pb isotope analysis of Fe-Ni-Cu sulphides by laser ablation multi-collector ICPMS: New insights into ore formation in the Sudbury impact melt sheet

    NASA Astrophysics Data System (ADS)

    Darling, J. R.; Storey, C. D.; Hawkesworth, C. J.; Lightfoot, P. C.

    2012-12-01

    Laser-ablation (LA) multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) is ideally suited to in situ determination of isotope ratios in sulphide minerals. Using samples of magmatic sulphide ore from the Sudbury impact structure, we test LA-MC-ICPMS analytical protocols that aim to meet a range of analytical challenges in the analysis of Pb isotopes. These include: potential matrix sensitive isotopic fractionation; interferences on Pb isotopes; low melting points of many sulphide minerals; the availability of standards. Magmatic sulphides of wide ranging mineralogy (pyrrhotite, pentlandite, chalcopyrite, pyrite and sphalerite) were analysed for Pb isotopic composition, using the silicate glass NIST SRM 610 as an external standard to correct for instrumental mass-fractionation. Despite matrix sensitive melting and re-deposition around ablation pits, several lines of evidence indicate that all analyses are accurate, within typical analytical uncertainties of 0.003-2% (2σ), and that the defined approach is insensitive to compositional diversity in sample matrix: (a) laser ablation and dissolution based measurements of sulphide powders are in agreement; (b) analyses from each sample define isochron ages within uncertainty of the known crystallization age (1850 Ma); (c) the results of sulphide measurements by laser ablation are consistent with age-corrected feldspar analyses from the same samples. The results have important implications for ore formation in Sudbury. The Pb isotope data regressions are consistent with age corrected feldspar analyses from each respective sample, which together with time integrated Th/U ratios that match whole rock values (3.1, 4.0 and 6.1 for the Worthington, Copper Cliff and Parkin Offset Dykes, respectively) indicate chemical equilibrium between the silicate and sulphide systems during ore formation. The sulphides within each respective sample have indistinguishable model initial Pb isotope ratios (207Pb/204Pbm

  4. Formation of the layered deposits in the Valles Marineris, Mars

    NASA Technical Reports Server (NTRS)

    Nedell, S. S.; Squyres, S. W.

    1987-01-01

    Evidence is presented for large standing bodies of water on Mars during past epochs. It is noted that the origin of the horizontally-layered deposits in the Valles Marineris can be best explained by formation in standing bodies of water. These lakes, if they existed, were most likely covered by ice. There are several geologically feasible mechanisms that could have led to formation to thick deposits in ice covered paleolakes in the Valles Marineris. Present data are insufficient to choose conclusively among the various possibilities.

  5. How two gravity-gradient inversion methods can be used to reveal different geologic features of ore deposit - A case study from the Quadrilátero Ferrífero (Brazil)

    NASA Astrophysics Data System (ADS)

    Carlos, Dionísio U.; Uieda, Leonardo; Barbosa, Valeria C. F.

    2016-07-01

    Airborne gravity gradiometry data have been recently used in mining surveys to map the 3D geometry of ore deposits. This task can be achieved by different gravity-gradient inversion methods, many of which use a voxel-based discretization of the Earth's subsurface. To produce a unique and stable solution, an inversion method introduces particular constraints. One constraining inversion introduces a depth-weighting function in the first-order Tikhonov regularization imposing a smoothing on the density-contrast distributions that are not restricted to near-surface regions. Another gravity-gradient inversion, the method of planting anomalous densities, imposes compactness and sharp boundaries on the density-contrast distributions. We used these two inversion methods to invert the airborne gravity-gradient data over the iron-ore deposit at the southern flank of the Gandarela syncline in Quadrilátero Ferrífero (Brazil). Because these methods differ from each other in the particular constraint used, the estimated 3D density-contrast distributions reveal different geologic features of ore deposit. The depth-weighting smoothing inversion reveals variable dip directions along the strike of the retrieved iron-ore body. The planting anomalous density inversion estimates a compact iron-ore mass with a single density contrast, which reveals a variable volume of the iron ore along its strike increasing towards the hinge zone of the Gandarela syncline which is the zone of maximum compression. The combination of the geologic features inferred from each estimate leads to a synergistic effect, revealing that the iron-ore deposit is strongly controlled by the Gandarela syncline.

  6. Formation of sulfide-calcite veinlets in the Kupferschiefer Cu-Ag deposits in Poland by natural hydrofracturing during basin subsidence

    SciTech Connect

    Jowett, E.C.

    1987-07-01

    Calcite and copper-(iron) sulfide veinlets in the Kupferschiefer ore deposits in southwestern Poland display many characteristics of antitaxial veinlets, including trails of wall-rock shards from wall to wall. Cross-cutting relationships demonstrate a change from sulfate to sulfide chemical stability and an evolution of stress orientation during ore-formation. Bedding-plane sulfate veinlets and later bedding-plane sulfide veinlets are superseded by vertical sulfide veinlets, suggesting tectonic extension during ore-formation. Thin bedding-plane calcite-(sulfide) veinlets record a return to pre-ore stress conditions after ore formation ceased. The vertical veinlets are thin and lens-shaped, typically 1-3 mm thick, 30-35 cm high, and 50-70 cm long, with orientations similar to Kimmerian-age (Triassic-Jurassic) directions. Sulfide replacement lenses cut across and are cut by vertical veinlets, suggesting contemporaneous formation after lithification. A mid-Triassic paleomagnetic age and cross-cutting Alpine-age faults and dikes suggest that the veinlets and other mineralization formed during rapid subsidence in the Triassic, and not during Alpine-age uplift. A genetic model is proposed whereby the fractures originated by natural hydrofracturing caused by (1) aquathermal pressuring and (2) generation of water, CO/sub 2/, and CH/sub 4/ from the coal organic matter in the Kupferschiefer, aided by over-pressured pore fluid. It is inferred that the mineralization was accompanied by natural-gas generation and by opening of the Tethys. 61 references.

  7. Lead isotope study of Zn-Pb ore deposits associated with the Basque-Cantabrian basin and Paleozoic basement, Northern Spain

    NASA Astrophysics Data System (ADS)

    Velasco, F.; Pesquera, A.; Herrero, J. M.

    1996-01-01

    A total of forty-three galena samples from syngenetic and epigenetic Pb-Zn mineralizations emplaced in the Lower Cretaceous Basque-Cantabrian basin and Paleozoic basement of the Cinco Villas massif in the western Pyrenees, have been analyzed for Pb-isotopic composition. Galena from sedex mineralizations hosted in Carboniferous clastic rocks in the Cinco Villas massif display an homogeneous lead isotopic signature (206Pb/2044Pb ≈ 18.43, 207Pb/204Pb ≈ 15.66, 208Pb/ 204Pb ≈ 38.69) suggesting a single lead reservoir. These values are slightly more radiogenic than lead from other European Hercynian deposits, possibly reflecting the influence of a more evolved upper crustal source. Underlying Paleozoic sediments are proposed as lead source for the Cinco Villas massif ores. Analyses from twenty-six galena samples from the four strata-bound ore districts hosted in Mesozoic rocks reveal the existence of two populations regarding their lead isotopic composition. Galena from the western Santander districts (e.g., Reocin) is characterized by more radiogenic isotope values (206Pb/204Pb ≈ 18.74, 207Pb/204Pb ≈ 15.67, 208Pb/ 204Pb ≈ 38.73) than those from the central and eastern districts (Troya-Legorreta, Central and Western Vizcaya, 206Pb/204Pb ≈ 18.59, 207Pb/204Pb ≈ 15.66, 208Pb/ 204Pb ≈ 38.73). In all districts, the most likely source for these mineralizations was the thick sequence of Lower Cretaceous clastic sediments. The existence of two separate lead isotopic populations could be the result of regional difference in the composition of the basement rocks and the clastic sediments derived of it or different evolution histories. In both sub-basins, isotopic ratios indicate an increase in crustal influence as the age of the ores decreases.

  8. Coke Deposition and Smoke Formation in Turbojet Engines

    NASA Technical Reports Server (NTRS)

    Hibbard, R. R.; Wear, J. D.

    1956-01-01

    In the early development of jet engines, it was occasionally found that excessive amounts of coke or other carbonaceous deposits were formed in the combustion chamber. Sometimes a considerable amount of smoke was noted in the-exhaust gases. Excessive coke deposits may adversely affect jet-engine performance in several ways. The formation of excessive amounts of coke on or just downstream of a fuel nozzle (figs. 116(a) and (b)) changes the fuel-spray pattern and possibly affects combustor life and performance. Similar effects on performance can result from the deposition of coke on primary-air entry ports (fig. 116(c)). Sea-level or altitude starting may be impaired by the deposition of coke on spark-plug electrodes (fig. 116(b)), deposits either grounding the electrodes completely or causing the spark to occur at positions other than the intended gap. For some time it was thought that large deposits of coke in turbojet combustion chambers (fig. 116(a)) might break away and damage turbine blades; however, experience has indicated that for metal blades this problem is insignificant. (Cermet turbine blades may be damaged by loose coke deposits.) Finally, the deposition of coke may cause high-temperature areas, which promote liner warping and cracking (fig. 116(d)) from excessive temperature gradients and variations in thermal-expansion rates. Smoke in the exhaust gases does not generally impair engine performance but may be undesirable from a tactical or a nuisance standpoint. Appendix B of reference 1 and references 2 to 4 present data obtained from full-scale engines operated on test stands and from flight tests that indicate some effects on performance caused by coke deposits and smoke. Some information about the mechanism of coke formation is given in reference 5 and chapter IX. The data indicate that (1) high-boiling fuel residuals and partly polymerized products may be mixed with a large amount of smoke formed in the gas phase to account for the consistency

  9. Processing Gold Quarry refractory ores

    NASA Astrophysics Data System (ADS)

    Hausen, D. M.

    1989-04-01

    The Gold Quarry deposit is the largest sediment-hosted gold deposit yet discovered on the Carlin trend in northern Nevada. However, despite the locale's vast reserves, the gold is difficult to extract from portions of the deposit. Detailed, ongoing mineralogical analyses assure proper treatment of the ore.

  10. Elemental imaging of organic matter and associated metals in ore deposits using micro PIXE and micro-EBS

    NASA Astrophysics Data System (ADS)

    Fuchs, S.; Przybylowicz, W. J.; Williams-Jones, A. E.

    2014-01-01

    Micro-PIXE and micro-EBS analyses were carried out on samples from the Au-U-bearing Carbon Leader Reef of the Witwatersrand in South Africa to investigate the role of organic matter in the formation of this deposit. Micro-PIXE and Micro-EBS shows a very complex metal distribution within the bitumen nodules and their interstitial spaces. The style of the gold distribution and its association with epigenetic minerals (REE phosphates, phyllosilicates) indicates that all observed gold migrated in aqueous solution and precipitated by reduction on the surfaces of the bitumen nodules. Uraninite occurrences are confined to the bitumen nodules, which supports the argument of a uraninite paleo-placer; however the pervasive distribution of uranium also supports the argument that uraninite is derived from organo-metallic complexes. This study shows that micro-PIXE is a powerful tool to characterize metals associated with hydrocarbons. However, the organic matrix, the complexity of the obtained spectra and the small size of the minerals have significant influence on the reliability of the quantitative data. Due to highly variable amounts of heavy metals (U, Au, Pb) the obtained micro-EBS results are of questionable quality.

  11. Organic matter diagenesis as the key to a unifying theory for the genesis of tabular uranium-vanadium deposits in the Morrison Formation, Colorado Plateau

    USGS Publications Warehouse

    Hansley, P.L.; Spirakis, C.S.

    1992-01-01

    Interstitial, epigenetic amorphous organic matter is intimately associated with uranium in the Grants uranium region and is considered essential to genetic models for these deposits. In contrast, uranium minerals are intimately associated with authigenic vanadium chlorite and vanadium oxides in amorphous organic matter-poor ores of the Slick Rock and Henry Mountains mining districts and therefore, in some genetic models amorphous organic matter is not considered crucial to the formation of these deposits. Differences in organic matter content can be explained by recognizing that amorphous organic matter-poor deposits have been subjected to more advanced stages of diagenesis than amorphous organic matter-rich deposits. Evidence that amorphous organic matter was involved in the genesis of organic matter-poor, as well as organic matter-rich, deposits is described. -from Authors

  12. Formation of metal oxides by cathodic arc deposition

    SciTech Connect

    Anders, S.; Anders, A.; Rubin, M.; Wang, Z.; Raoux, S.; Kong, F.; Brown, I.G.

    1995-03-01

    Metal oxide thin films are of interest for a number of applications. Cathodic arc deposition, an established, industrially applied technique for formation of nitrides (e.g. TiN), can also be used for metal oxide thin film formation. A cathodic arc plasma source with desired cathode material is operated in an oxygen atmosphere, and metal oxides of various stoichiometric composition can be formed on different substrates. We report here on a series of experiments on metal oxide formation by cathodic arc deposition for different applications. Black copper oxide has been deposited on ALS components to increase the radiative heat transfer between the parts. Various metal oxides such as tungsten oxide, niobium oxide, nickel oxide and vanadium oxide have been deposited on ITO glass to form electrochromic films for window applications. Tantalum oxide films are of interest for replacing polymer electrolytes. Optical waveguide structures can be formed by refractive index variation using oxide multilayers. We have synthesized multilayers of Al{sub 2}O{sub 3}/Y{sub 2}O{sub 3}/AI{sub 2}O{sub 3}/Si as possible basic structures for passive optoelectronic integrated circuits, and Al{sub 2-x}Er{sub x}O{sub 3} thin films with a variable Er concentration which is a potential component layer for the production of active optoelectronic integrated devices such as amplifiers or lasers at a wavelength of 1.53 {mu}m. Aluminum and chromium oxide films have been deposited on a number of substrates to impart improved corrosion resistance at high temperature. Titanium sub-oxides which are electrically conductive and corrosion resistant and stable in a number of aggressive environments have been deposited on various substrates. These sub-oxides are of great interest for use in electrochemical cells.

  13. Depositional systems distribution of the lower Oligocene Vicksburg Formation, TX

    SciTech Connect

    Coleman, J.; Galloway, W.E. )

    1990-05-01

    The lower Oligocene Vicksburg Formation of Texas is situated between the upper Eocene Jackson Group and the upper Oligocene Frio Formation. The paleogeography of the Texas Gulf coastal plain during the early Oligocene is typical of a progradational passive continental margin. However, a detailed regional depositional systems analysis of stratigraphic units, such as the Vicksburg, within a mature petroleum basin can yield results beneficial in both exploration and development. Stratigraphic plays are determined from the distribution of depositional systems, and reservoir characteristics are heavily influenced by conditions of sedimentation. Two primary depocenters (and exploration fairways) of the Texas Vicksburg were the Houston Embayment and the Rio Grande Embayment; they were separated by a deep-rooted structural nose in central Texas: the San Marcos arch. Within the embayments, deltaic depositional systems merged along strike with barrier/strand plain systems. Updip, fluvial systems traversed coastal plain units. On the seaward edge of the paralic systems, sand and mud deposits prograded across, and built up over, the relict Jackson shelf and shelf margin. Contemporaneous growth faulting controlled deltaic depositional patterns in the Rio Grande Embayment and, to a lesser degree, in the Houston Embayment. A barrier/strand plain system within an interdeltaic coastal bight extended across the northern flank of the San Marcos arch. Several minor wave-dominated delta complexes were interspersed within this regional setting. The southern flank of the arch was influenced by the fluvial systems of the Rio Grande Embayment that established another wave-dominated delta. Deposition of the Vicksburg progradational paralic sediments was initiated seaward of the Jackson coastal position. A brief, minor transgression interrupted the progradational pattern during middle Vicksburg deposition.

  14. Depositional setting and paleogeography of Ordovician Vinini Formation, central Nevada

    SciTech Connect

    Finney, S.C.; Perry, B.D. )

    1991-02-01

    The eugeoclinal strata of the Ordovician Vinini Formation composes most of the Roberts Mountains allochthon (RMA). Its stratigraphy, reconstructed in the Roberts Mountains, can be precisely correlated throughout much of the RMA and into coeval strata of the autochthonous miogeocline by means of graptolite and conodont biostratigraphy. The Vinini is a mixture of clastic lithologies with some limestone and greenstone. Coarse clastics, characterized by well-rounded and well-sorted sands derived from cratonic sources, occur in two separate intervals and provide critical data on depositional and paleogeographic setting. The lower interval, hundreds of meters thick, was deposited in the latest Ibexian-earliest Whiterockian and can be closely correlated throughout central Nevada. It is a mixture of quartz sandstone, siltstone, limestone, and calcareous sandstone, deposited by turbidity flows during a lowstand of sea level. Both eastern and western sources have been interpreted for these sands. The upper interval is a prominent, pure quartzite up to 20 m thick deposited as a prograding blanket of sand in the latest Whiterockian-earliest Mohawkian. It occurs in the Vinini in the northern Toquima Range and in a parautochthonous sequence of transitional strata in the southern Toiyabe Range. This interval represents the most basinward edge of the Eureka Quartzite, which was also deposited across the miogeocline. The presence of sand of the Eureka Quartzite in the RMA indicates that the basin in which the RMA strata were deposited was immediately adjacent to the margin of North America in the Ordovician.

  15. Deposits of the Peruvian Pisco Formation compared to layered deposits on Mars

    NASA Astrophysics Data System (ADS)

    Sowe, M.; Bishop, J. L.; Gross, C.; Walter, S.

    2013-09-01

    Deposits of the Peruvian Pisco Formation are morphologically similar to the mounds of Juventae Chasma at the equatorial region on Mars (Fig. 1). By analyzing these deposits, we hope to gain information about the environmental conditions that prevailed during sediment deposition and erosion, hence conditions that might be applicable to the Martian layered and hydrated deposits. Mariner 9 data of the Martian mid-latitudes have already shown evidence of the wind-sculptured landforms that display the powerful prevailing eolian regime [1]. In addition, [2] reported on similarities between Martian erosional landforms and those of the rainless coastal desert of central Peru from the Paracas peninsula to the Rio Ica. As indicated by similar erosional patterns, hyper-arid conditions and unidirectional winds must have dominated at least after deposition of the sediments, which are intermixed volcaniclastic materials and evaporate minerals at both locations. Likewise, variations in composition are displayed by alternating layers of different competence. The Pisco formation bears yardangs on siltstones, sandstones and clays with volcaniclastic admixtures [3] whereas the presence of sulphate minerals and the omnipresent mafic mineralogy has been reported for the layered mounds of Juventae Chasma equally [4]. Likewise, a volcanic airfall deposition and lacustrine formation have been proposed for the sulphate-rich deposits of Juventae Chasma [5,6]. In order to find out about potential spectral similarities, we performed a detailed spectral analysis of the surface by using LANDSAT and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) VNIR/ SWIR data (visible to near-infrared and shortwave infrared region).

  16. Deposit formation and heat transfer in hydrocarbon rocket fuels

    NASA Technical Reports Server (NTRS)

    Giovanetti, A. J.; Spadaccini, L. J.; Szetela, E. J.

    1984-01-01

    An experimental research program was undertaken to investigate the thermal stability and heat transfer characteristics of several hydrocarbon fuels under conditions that simulate high-pressure, rocket engine cooling systems. The rates of carbon deposition in heated copper and nickel-plated copper tubes were determined for RP-1, propane, and natural gas using a continuous flow test apparatus which permitted independent variation and evaluation of the effect on deposit formation of wall temperature, fuel pressure, and fuel velocity. In addition, the effects of fuel additives and contaminants, cryogenic fuel temperatures, and extended duration testing with intermittent operation were examined. Corrosion of the copper tube surface was detected for all fuels tested; however, plating the insides of the tubes with nickel reduced deposit formation and eliminated corrosion in most cases. The lowest rates of carbon deposition were obtained for natural gas, and the highest rates were obtained for propane. Forced-convection heat transfer film coefficients were satisfactorily correlated using a Nusselt-Reynolds-Prandtl number equation for all the fuels tested.

  17. Deposit formation and heat transfer in hydrocarbon rocket fuels

    NASA Technical Reports Server (NTRS)

    Giovanetti, A. J.; Spadaccini, L. J.; Szetela, E. J.

    1983-01-01

    An experimental research program was undertaken to investigate the thermal stability and heat transfer characteristics of several hydrocarbon fuels under conditions that simulate high-pressure, rocket engine cooling systems. The rates of carbon deposition in heated copper and nickel-plated copper tubes were determined for RP-1, propane, and natural gas using a continuous flow test apparatus which permitted independent variation and evaluation of the effect on deposit formation of wall temperature, fuel pressure, and fuel velocity. In addition, the effects of fuel additives and contaminants, cryogenic fuel temperatures, and extended duration testing with intermittent operation were examined. Parametric tests to map the thermal stability characteristics of RP-1, commercial-grade propane, and natural gas were conducted at pressures of 6.9 to 13.8 MPa, bulk fuel velocities of 30 to 90 m/s, and tube wall temperatures in the range of 230 to 810 K. Also, tests were run in which propane and natural gas fuels were chilled to 230 and 160 K, respectively. Corrosion of the copper tube surface was detected for all fuels tested. Plating the inside of the copper tubes with nickel reduced deposit formation and eliminated tube corrosion in most cases. The lowest rates of carbon deposition were obtained for natural gas, and the highest rates were obtained for propane. For all fuels tested, the forced-convection heat transfer film coefficients were satisfactorily correlated using a Nusselt-Reynolds-Prandtl number equation.

  18. Lead-isotopic compositions of diverse igneous rocks and ore deposits from southwestern New Mexico and their implications for early Proterozoic crustal evolution in the western United States.

    USGS Publications Warehouse

    Stacey, J.S.; Hedlund, D.C.

    1983-01-01

    Basement rocks in this area are 1750 m.y. old and extend northward through Colorado to Utah. Galena data show that the fraction of older sialic lead in these rocks increases toward the the Archaean craton in Wyoming. The crust apparently developed southward from Wyoming in stages at 2400 m.y. ago or before, 2100 m.y. ago and 1750 m.y. ago. The Laramide alkali to calc-alkaline rocks and their associated porphyry Cu and massive replacement deposits have similar 206Pb/204Pb ratios and are the least radiogenic in the region; their 206Pb/204Pb ratios are all 18.0. Pb isotopes in this region offer some criteria for prospecting purposes. The 206Pb/204Pb values for the larger ore deposits related to Laramide activity are all <18.0, particularly for the larger ones. Within the mid- Tertiary group, the same criteria apply - i.e. the largest deposits have the lowest 206Pb/204Pb ratios. -L.C.H.

  19. Formation of the giant Chalukou porphyry Mo deposit in northern Great Xing'an Range, NE China: Partial melting of the juvenile lower crust in intra-plate extensional environment

    NASA Astrophysics Data System (ADS)

    Li, Zhen-Zhen; Qin, Ke-Zhang; Li, Guang-Ming; Ishihara, Shunso; Jin, Lu-Ying; Song, Guo-Xue; Meng, Zhao-Jun

    2014-08-01

    monzogranite formed by partial melting of thickened lower crust in a collisional setting caused by closure of Mongol-Okhotsk Ocean. The post-ore feldspar porphyry shares a similar magma source with ore-forming porphyry, but the quartz monzonite porphyry has a relatively deeper magma source region and has not experienced as much fractional crystallization. The transformation from middle Jurassic compression to late Jurassic extension created favorable conditions for the generation and emplacement of the ore-forming magma. The juvenile lower crust provided the main source of molybdenum for Chalukou deposit. Enrichment of Mo by fractional crystallization played an important role in concentrating Mo during formation of the Chalukou Mo deposit. The age (~ 147 Ma), high fluorine, and associated Pb-Zn deposits are all different from other major porphyry Mo deposits in NE China; Chalukou is a new mineral deposit type in the Great Xing'an Range.

  20. Quantifying fat, oil, and grease deposit formation kinetics.

    PubMed

    Iasmin, Mahbuba; Dean, Lisa O; Ducoste, Joel J

    2016-01-01

    Fat, oil, and grease (FOG) deposits formed in sanitary sewers are calcium-based saponified solids that are responsible for a significant number of nationwide sanitary sewer overflows (SSOs) across United States. In the current study, the kinetics of lab-based saponified solids were determined to understand the kinetics of FOG deposit formation in sewers for two types of fat (Canola and Beef Tallow) and two types of calcium sources (calcium chloride and calcium sulfate) under three pH (7 ± 0.5, 10 ± 0.5, and ≈14) and two temperature conditions (22 ± 0.5 and 45 ± 0.5 °C). The results of this study displayed quick reactions of a fraction of fats with calcium ions to form calcium based saponified solids. Results further showed that increased palmitic fatty acid content in source fats, the magnitude of the pH, and temperature significantly affect the FOG deposit formation and saponification rates. The experimental data of the kinetics were compared with two empirical models: a) Cotte saponification model and b) Foubert crystallization model and a mass-action based mechanistic model that included alkali driven hydrolysis of triglycerides. Results showed that the mass action based mechanistic model was able to predict changes in the rate of formation of saponified solids under the different experimental conditions compared to both empirical models. The mass-action based saponification model also revealed that the hydrolysis of Beef Tallow was slower compared to liquid Canola fat resulting in smaller quantities of saponified solids. This mechanistic saponification model, with its ability to track the saponified solids chemical precursors, may provide an initial framework to predict the spatial formation of FOG deposits in municipal sewers using system wide sewer collection modeling software. PMID:26599432

  1. Krasnotur'insk Skarn copper ore field, Northern Urals: The U-Pb age of ore-controlling diorites and their place in the regional metallogeny

    NASA Astrophysics Data System (ADS)

    Grabezhev, A. I.; Ronkin, Yu. L.; Puchkov, V. N.; Gerdes, A.; Rovnushkin, M. Yu.

    2014-06-01

    The Krasnotur'insk skarn copper ore field known from the theoretical works of Academician K.S. Korzhinskii is located in the western part of the Tagil volcanic zone (in the area of the town of Krasnotur'insk). The ore field is composed of layered Devonian (Emsian) volcanosedimentary rocks intruded by small plutons of quartz diorites, diorites, and gabbrodiorites. Widespread pre-ore and intra-ore dikes of similar composition control the abundance of the andradite skarns formed after limestones and the magnetitesulfide and sulfide ore bodies formed after skarns. The LA-ICP-MS U-Pb concordant age of zircon from the quartz diorite of the Vasil'evsko-Moskalevskii pluton calculated by 16 analyses (16 crystals) is 407.7 ± 1.6 Ma (MSWD = 1.5). Taking into account the geological and petrogeochemical similarity of diorites of small plutons and intra-ore dikes, it is assumed that this age corresponds to the period of formation of the ore-magmatic system of the Krasnotur'insk skarn copper ore field. It was probably formed somewhat earlier than the Auerbakh montzonitic pluton and the accompanying skarn magnetite deposits in the south.

  2. Reduction kinetics of aqueous U(VI) in acidic chloride brines to uraninite by methane, hydrogen or C-graphite under hydrothermal conditions: Implications for the genesis of unconformity-related uranium ore deposits

    NASA Astrophysics Data System (ADS)

    Dargent, Maxime; Truche, Laurent; Dubessy, Jean; Bessaque, Gilles; Marmier, Hervé

    2015-10-01

    The formation of hydrothermal uranium ore deposits involves the reduction of dissolved U(VI)(aq) to uraninite. However, the nature of the reducing agent and the kinetics of such a process are currently unknown. These questions are addressed through dedicated experiments performed under conditions relevant for the genesis of unconformity-related uranium (URU) deposits. We tested the efficiency of the following potential reductants supposed to be involved in the reaction: H2, CH4, C-graphite and dissolved Fe(II). Results demonstrate the great efficiency of H2, CH4 and C-graphite to reduce U(VI)(aq) into uraninite in acidic chloride brines, unlike dissolved Fe(II). Times needed for H2 (1.4 bar), CH4 (2.4 bar) and C-graphite (water/carbon mass ratio = 10) to reduce 1 mM of U(VI)(aq) in an acidic brine (1 m LiCl, pH ≈ 1 fixed by HCl) to uraninite at 200 °C are 12 h, 3 days and 4 months, respectively. The effects of temperature (T) between 100 °C and 200 °C, H2 partial pressure (0.14, 1.4, and 5.4 bar), salinity (0.1, 1 and 3.2 m LiCl) and pH at 25 °C (0.8 and 3.3) on the reduction rate were also investigated. Results show that increasing temperature and H2 partial pressure increase the reaction rate, whereas increasing salinity or pH have the reverse effect. The reduction of uranyl to uraninite follows an apparent zero-order with respect to time, whatever the considered electron donor. From the measured rate constants, the following values of activation energy (Ea), depending on the nature of the electron donor, have been derived: EaC-graphite = 155 ± 3 kJ mol-1, EaCH4 = 143 ± 6 kJ mol-1, and EaH2 = 124 ± 15 kJ mol-1 at T < 150 °C and 32 ± 6 kJ mol-1 at T > 150 °C. An empirical relationship between the reaction rate, the hydrogen partial pressure, the uranyl speciation, and the temperature is also proposed. This allows an estimation of the time of formation of a giant U ore deposit such as McArthur River (Canada). The duration of the mineralizing event is

  3. Scheelite geochemical signatures by LA-ICP-MS and potential for rare earth elements from Hutti Gold Mines and fingerprinting ore deposits

    NASA Astrophysics Data System (ADS)

    Raju, P. V. S.; Hart, Craig J. R.; Sangurmath, P.

    2016-02-01

    Scheelite (CaWO4), with gold and REE enrichments, is found in appreciable concentrations in the world class Hutti Gold deposit, Eastern Dharwar Craton (EDC), India. We used in situ Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) to determine the rare earth elements in scheelite and utilize results to fingerprint the extensions/continuity of auriferous ore shoots/lodes/reefs. The Hutti Gold deposit is briefly compared to southern African gold deposits and corroborates in terms of geochemistry, structural, chemical alterations and REE contents in scheelite etc… The scheelite samples from Hutti are enriched in light rare earth elements (LREE) up to 11 ppm and depleted in heavy rare earth elements(HREE) up to 6.50 ppm with positive to negative europium anomaly. The total REE (∑ REE + Y) of the scheelite samples is up to 35 ppm. The ratio of LREE/HREE values is 1.80. The results for the REEs indicate: (1) considerable differences in the ΣREEs amongst the sample suite (2) most samples are dominated by a single chondrite-normalized (CN) pattern, but rarely a second pattern is present; 3) although the type of CN REE patterns vary (e.g., convex MREE, LREE enrichment), there is a similarity among deposit types; and 4) both positive and negative 'Eu' anomalies are observed; 5) positive correlations between MREE and HREE suggesting a strong influence of magmatic fluids. These initial results suggest that the minor and trace-element chemistry of scheelite may offer the potential to discriminate and identify deposit types based on its geochemical fingerprinting.

  4. Field Vectors to Metamorphosed Ores: A Prelude to Finding Currently Concealed Volcano-Plutonic Arc Settings and Their Mineral Deposits in The Grenville Province

    NASA Astrophysics Data System (ADS)

    Corriveau, L.; Bonnet, A.; van Breemen, O.

    2004-05-01

    Recent mineral deposits synthesis highlights the largely barren nature of the high-grade metamorphic terrains of the Canadian Shield in terms of large mining camps. No where is the gap most startling than in the Grenville Province even though a lot of its Paleo- to Mesoproterozoic crust consists of magmatic arcs renown worldwide to host IOCG, VHMS and Porphyry Cu deposits. All these deposit types have significant alteration halos that can serve as vectors to ore. The use of such vectors forced a complete reinterpretation of the nature of the La Romaine domain in the eastern Grenville Province. Mapped in the 70's as being a metasedimentary basin with >500 km2 of meta-arkose and minor pelite, quartzite, conglomerate and marble, the domain is herein reassessed as a major 1.5 Ga Pinwarian continental magmatic arc fertile in Cu-sulphides and Fe-oxides mineralizing systems. The original markers used to prognosticate a sedimentary origin can now be demonstrated to be a series of rhyolitic to dacitic lapillistone, sericitized tuff with Al nodules and veins, Al gneiss locally with lapilli textures, garnetite, ironstones and calc-silicate rocks. The distribution, paragenesis and mode of the Al-, Fe- and Ca-rich units significantly depart from those of normal metasediments but are very diagnostic of metamorphosed hydrothermal alteration zones and meta-exhalites. Mapping alteration vectors provided clues to search for and find the volcanic rocks concealed among the composite granitic gneiss, the zones of hydrothermal leaching (e.g., sericitic, argillic and advanced argillic alterations) and discharge, the cap rocks, and the Cu mineralization. Spatial and stratigraphic relationships provided a means to compare their settings with ore deposit models. Roof pendants of Ba-rich meta-exhalite in surrounding 1.5 Ga granitic plutons and intrusion of 1495 Ma Qtz-Kfs porphyry across hydrothermally altered 1500 Ma tuffs attest to coeval hydrothermal activity and sub-volcanic plutons. The

  5. Influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel films

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Anderoglu, O.; Misra, A.; Wang, H.

    2007-04-01

    The authors have studied the influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel thin films. Transmission electron microscopy shows that the volume fraction of twinned grains increases with increasing deposition rate, whereas the average columnar grain size and twin spacing stay approximately unchanged. These experimental results agree qualitatively with their analytical model that predicts deposition rate dependent formation of growth twins. The film hardness increases monotonically with increasing volume fraction of twinned grains.

  6. Influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel films

    SciTech Connect

    Zhang, X.; Anderoglu, O.; Misra, A.; Wang, H.

    2007-04-09

    The authors have studied the influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel thin films. Transmission electron microscopy shows that the volume fraction of twinned grains increases with increasing deposition rate, whereas the average columnar grain size and twin spacing stay approximately unchanged. These experimental results agree qualitatively with their analytical model that predicts deposition rate dependent formation of growth twins. The film hardness increases monotonically with increasing volume fraction of twinned grains.

  7. Comparison of the chemical characteristics of the uranium deposits of the Morrison Formation in the Grants uranium region, New Mexico

    USGS Publications Warehouse

    Spirakis, C.S.; Pierson, C.T.

    1983-01-01

    Statistical treatment of the chemical data of samples from the northeast Church Rock area, Ruby deposit, Mariano Lake deposit, and the Ambrosia Lake district indicates that primary ore-forming processes concentrated copper, iron, magnesium, manganese, molybdenum, selenium, vanadium, yttrium, arsenic, organic carbon, and sulfur, along with uranium. A barium halo that is associated with all of these deposits formed from secondary processes. Calcium and strontium were also enriched in the ores by secondary processes. Comparison of the chemical characteristics of the redistributed deposits in the Church Rock district to the primary deposits in the Grants uranium region indicates that calcium, manganese, strontium, yttrium, copper, iron, magnesium, molybdenum, lead, selenium, and vanadium are separated from uranium during redistribution of the deposits in the Church Rock area. Comparisons of the chemical characteristics of the Church Rock deposits and the secondary deposits at Ambrosia Lake suggest some differences in the processes that were involved in the genesis of the redistributed deposits in these two areas.

  8. An evaporated seawater origin for the ore-forming brines in unconformity-related uranium deposits (Athabasca Basin, Canada): Cl/Br and δ 37Cl analysis of fluid inclusions

    NASA Astrophysics Data System (ADS)

    Richard, Antonin; Banks, David A.; Mercadier, Julien; Boiron, Marie-Christine; Cuney, Michel; Cathelineau, Michel

    2011-05-01

    Analyses of halogen concentration and stable chlorine isotope composition of fluid inclusions from hydrothermal quartz and carbonate veins spatially and temporally associated with giant unconformity-related uranium deposits from the Paleoproterozoic Athabasca Basin (Canada) were performed in order to determine the origin of chloride in the ore-forming brines. Microthermometric analyses show that samples contain variable amounts of a NaCl-rich brine (Cl concentration between 120,000 and 180,000 ppm) and a CaCl 2-rich brine (Cl concentration between 160,000 and 220,000 ppm). Molar Cl/Br ratios of fluid inclusion leachates range from ˜100 to ˜900, with most values between 150 and 350. Cl/Br ratios below 650 (seawater value) indicate that the high salinities were acquired by evaporation of seawater. Most δ 37Cl values are between -0.6‰ and 0‰ (seawater value) which is also compatible with a common evaporated seawater origin for both NaCl- and CaCl 2-rich brines. Slight discrepancies between the Cl concentration, Cl/Br, δ 37Cl data and seawater evaporation trends, indicate that the evaporated seawater underwent secondary minor modification of its composition by: (i) mixing with a minor amount of halite-dissolution brine or re-equilibration with halite during burial; (ii) dilution in a maximum of 30% of connate and/or formation waters during its migration towards the base of the Athabasca sandstones; (iii) leaching of chloride from biotites within basement rocks and (iv) water loss by hydration reactions in alteration haloes linked to uranium deposition. The chloride in uranium ore-forming brines of the Athabasca Basin has an unambiguous dominantly marine origin and has required large-scale seawater evaporation and evaporite deposition. Although the direct evidence for evaporative environments in the Athabasca Basin are lacking due to the erosion of ˜80% of the sedimentary pile, Cl/Br ratios and δ 37Cl values of brines have behaved conservatively at the basin

  9. Zircon U-Pb ages and Sr-Nd-Hf isotopes of the highly fractionated granite with tetrad REE patterns in the Shamai tungsten deposit in eastern Inner Mongolia, China: Implications for the timing of mineralization and ore genesis

    NASA Astrophysics Data System (ADS)

    Jiang, Si-Hong; Bagas, Leon; Hu, Peng; Han, Ning; Chen, Chun-Liang; Liu, Yuan; Kang, Huan

    2016-09-01

    The Shamai tungsten deposit is located in the eastern part of the Central Asian Orogenic Belt (CAOB). Tungsten mineralization is closely related to the emplacement of fine- to medium-grained biotite monzogranite (G1) and porphyritic biotite monzogranite (G2) in the Shamai Granite. NW-trending joints and faults host orebodies in the Shamai Granite and Devonian hornfels. The mineralization is characterized by a basal veinlet zone progressing upwards to a thick vein zone followed by a mixed zone, a veinlet zone, and a thread vein zone at the top. The ore-related alteration typically consists of muscovite, greisen, and hornfels. In order to constrain the timing of the Shamai mineralization and discuss the ore genesis, muscovite Ar-Ar, molybdenite Re-Os, and zircon U-Pb geochronological, geochemical, and Sr-Nd-Hf isotopic studies were completed on the deposit. The U-Pb zircon dating yielded weighted mean ages of 153 ± 1 Ma for G1 and 146 ± 1 Ma for G2. Muscovite from a wolframite-bearing quartz vein yielded an Ar-Ar plateau age of 140 ± 1 Ma, whereas two molybdenite samples yielded identical Re-Os model ages of 137 ± 2 Ma. These two ages are younger than the two monzogranites, suggesting a prolonged magmatic-hydrothermal interaction during tungsten mineralization. Major and trace element geochemistry shows that both G1 and G2 are characterized by high SiO2 and K2O contents, high A/CNK values (1.08-1.40), a spectacular tetrad effect in their REE distribution patterns, and non-CHARAC (charge-and-radius-controlled) trace element behavior. This suggests that both G1 and G2 are highly differentiated peraluminous rocks with strong hydrothermal interaction. The Nd-Hf isotope data for the Shamai Granite (εNd(t) between - 1.9 and + 7.4, ɛHf(t) from 5.2 to 12.8) are largely compatible with the general scenario for much of the Phanerozoic granite emplaced in the CAOB. It is here suggested that the Shamai Granite originated from partial melting of a juvenile lower crust with

  10. Inkjet printing of aqueous rivulets: Formation, deposition, and applications

    NASA Astrophysics Data System (ADS)

    Bromberg, Vadim

    early-time dynamics during rivulet formation in determining the nature of subsequent particle convection and deposition. New flow and deposition phenomena have also been identified and leveraged to develop novel processes for deposition of micron-scale electrically conducting lines of silver nanoparticles. Low-temperature processing of printed silver nitrate lines with environmentally benign Ar plasma to improve electrical properties has also been investigated and will be discussed.

  11. Gas-exchange chamber analysis of elemental mercury deposition/emission to alluvium, ore, and mine tailings.

    PubMed

    Miller, Matthieu B; Gustin, Mae Sexauer

    2015-07-01

    Deposition of mercury (Hg) from the atmosphere is an important source of this contaminant to terrestrial ecosystems. Once deposited, all forms of Hg can be retained or emitted back to the atmosphere. Distinguishing between volatilization of geogenic or indigenous Hg and that deposited from the atmosphere is difficult. Field flux measurements in the general area of two industrial scale gold mining operations, showed local deposition of Hg emitted from point and nonpoint sources, and subsequent re-emission. The work presented in this paper investigated deposition/emission of elemental Hg to and from alluvium and two mine materials before, during, and after exposure to high air concentrations, for both wet and dry conditions, using a laboratory gas exchange chamber and a Hg permeation source. In general, results showed a range in mean elemental Hg deposition velocities ranging from 0.13 to 0.46 cm s(-1) that varied with material. A significant influence of atmospheric ozone (O3) on flux was observed that depended on the material and whether wet or dry. A synergistic relationship existed between O3 and light promoting Hg flux, and flux was also influenced by material grain size, chemistry, and primary mineralogy. PMID:25880343

  12. Fat, oil and grease deposits in sewers: characterisation of deposits and formation mechanisms.

    PubMed

    Williams, J B; Clarkson, C; Mant, C; Drinkwater, A; May, E

    2012-12-01

    Fat, oil and grease deposits (FOG) in sewers are a major problem and can cause sewer overflows, resulting in environmental damage and health risks. Often simplistically portrayed as cooling of fats, recent research has suggested that saponification may be involved in FOG formation. However there are still questions about the mechanisms effecting transformations in sewers and the role and source of metal cations involved in saponification. This study characterises FOG deposits from pumping stations, sewers and sewage works from different water hardness zones across the UK. The sites all had previous problems with FOG and most catchments contained catering and food preparation establishments. The FOG deposits were highly variable with moisture content ranging from 15 to 95% and oil content from 0 to 548 mg/g. Generally the pumping stations had lower moisture content and higher fat content, followed by the sewers then the sewage works. The water in contact with the FOG had high levels of oil (mean of about 800 mg/L) and this may indicate poor kitchen FOG management practices. FOG fatty acid profiles showed a transformation from unsaturated to saturated forms compared to typical cooking oils. This seems to relate to ageing in the sewer network or the mechanism of formation, as samples from pumping stations had higher proportions of C18:1 compared to C16. This may be due to microbial transformations by bacteria such as Clostridium sp. in a similar process to adipocere formation. There was an association between water hardness and increased Ca levels in FOG along with harder deposits and higher melting points. A link between FOG properties and water hardness has not been previously reported for field samples. This may also be due to microbial processes, such as biocalcification. By developing the understanding of these mechanisms it may be possible to more effectively control FOG deposits, especially when combined with promotion of behavioural change. PMID:23039918

  13. Origin of marcasite and its implications regarding the genesis of roll-front uranium deposits

    USGS Publications Warehouse

    Goldhaber, Martin B.; Reynolds, Richard L.

    1979-01-01

    Study of five roll-type uranium deposits (three in Texas and two in Wyoming) has resulted in the recognition of ore-stage marcasite in each deposit. Ore-stage marcasite is identified by its close association with uranium- and vanadium-bearing phases in the ore zones; by its close association with ferroselite at and near the redox boundary in some deposits; by its abundance and distribution across deposits; and by its textural relationships with identifiable pre-ore iron disulfide minerals (primarily pyrite). In deposits that are essentially devoid of fossil vegetal debris, marcasite is the dominant ore-stage sulfide and occurs in a large volume of rock beyond the ore zones. In deposits that contain organic matter, ore-stage pyrite is at least as abundant as ore-stage marcasite. Many factors and processes may lead to the formation of either marcasite or pyrite as an ore-stage mineral in roll-type deposits. One of the dominant factors is the complex interrelationship of pH and sulfur species that are precursors of iron-disulfide minerals. Experimental work and study of geochemical environments analogous to those governing the formation of roll-type deposits indicate that relatively low pH (less than about six) and the presence of elemental sulfur favor marcasite, whereas higher pH and the presence of polysulfide ions favor pyrite. Conditions that favor marcasite as the dominant ore-stage iron disulfide are likely to arise during uranium deposition in host rock without fossil vegetal matter. In host rock containing carbonaceous debris, the presence of polysulfide ions and pH buffering any anaerobic bacterial metabolic processes apparently lead to the formation of ore-stage pyrite.

  14. Geophysical Investigations of the Uranium Mineralized Formation in the Coaly Black Shale Deposits in Korea

    NASA Astrophysics Data System (ADS)

    Kim, C.; Son, J.; Yoon, H.; Park, S.

    2011-12-01

    , two locations of concern with low resistivity anomalies and with high IP response were selected to drill down to 300-500m depth, based on the geological, geochemical, and geophysical investigations. The drilling operation has penetrated two formations of uranium-bearing coaly black slate at the different depths. The integrated geophysical investigation techniques including the construction of the conceptual geophysical model and the selection of appropriate geophysical methods, based on the geological and geochemical results, were useful for the uranium exploration in this study and can be applied to other sites of uranium-bearing ore deposits with similar geologic conditions.

  15. Influence of deposit architecture on intrastratal deformation, slope deposits of the Tres Pasos Formation, Chile

    NASA Astrophysics Data System (ADS)

    Auchter, Neal C.; Romans, Brian W.; Hubbard, Stephen M.

    2016-07-01

    Slope sediments on passive and active margins deform and fail across a broad range of scales ranging from loading and sediment remobilization near the sediment-water interface to submarine landslides and mass movements that incorporate significant volumes of slope deposits. Deformational styles are characterized by updip extension and downdip compressional features that occur above a detachment surface. Conditions for failure and deformation include the presence of weak layer(s) that serve as a detachment surface, competency contrasts that allow for detachment and downslope movement, deformation above a detachment surface, and a triggering mechanism(s) that initiates failure. Slope failure processes and products are well documented at scales resolvable by seismic-reflection surveys and in instances of extensive downslope failure, but the processes and products associated with intermediate-scale slope deformation are poorly understood. Intrastratal deformation is defined as stratigraphically isolated zones of deformation bounded above and below by concordant and undeformed strata. In this study, outcrop examples of intrastratal deformation from the Upper Cretaceous Tres Pasos Formation are used to elucidate the influence of depositional architecture on slope deformation. The facies distribution associated with compensational stacking of lobe deposits is shown to have a first-order control on the location and style of deformation. Detachment planes that form in mudstone deposits associated with lobe fringe and interlobe deposits are spatially limited and deformation is restricted to interbedded sandstone and mudstone associated with off-axial lobe positions. Downslope translation was arrested by stratigraphic buttresses associated with more sandstone-prone axial deposits. Emplacement of a regionally extensive mass transport deposit is interpreted as the triggering mechanism for contemporaneous intrastratal deformation of > 60 m of underlying stratigraphy. A vertical

  16. The formation of basal-type uranium deposits in south central British Columbia

    SciTech Connect

    Boyle, D.R.

    1982-08-01

    The basal-type uranium deposits in south central British Columbia occur within unconsolidated, late Miocene fluvial paleochannel sediments that overlie major fault zones within the Okanagan Highlands Intrusive Complex. Five uranium deposits have been outlined to date, of which the Blizzard (4,020 metric tons U) and Tyee (650 metric tons U) are the largest. The basement intrusive complex underlying the deposits varies in age from early Cretaceous to Eocene and is comprised of quartz monzonite, granodiorite, Coryell monzonite, porphyritic granite, and pegmatite. Uranium mineralization is present in the form of uranous (ningyoite) or uranyl (saleeite, autunite) phosphates coating clastic grains and filling voids. Because of very strong reducing conditions related to large concentrations of marcasite and organic material, ningyoite is the only uranium mineral in the Tyee deposit, whereas the Blizzard deposit contains a more complex assemblage of minerals (saleeite, autunite, ningyoite). The observed paragenetic sequence of mineral precipitation in the Blizzard deposit (autunite-saleeite-ningyoite) indicates that the uranyl minerals, saleeite and autunite, are primary. Investigations of the source of the ore-forming elements (U, Ca, Mg, PO/sub 4/) showed the deposits to be formed by the infiltration into fluvial sediments of deep-seated, structurally controlled, ground waters that migrated in a well-developed regional hydrologic system within the Complex. Research indicates that the ore-forming ground waters were cold, slightly bicarbonated (150-400 ppm), highly uraniferous (10-50 ppb), and slightly oxidizing (dissolved oxygen = 2-4 ppm).

  17. Geographical Coincidence of High Heat Flow, High Seismicity, and Upwelling, with Hydrocarbon Deposits, Phosphorites, Evaporites, and Uranium Ores

    PubMed Central

    Libby, L. M.; Libby, W. F.

    1974-01-01

    Oil deposits occur in deep sediments, and appear to be organic matter that has been transformed through the action of geothermal heat and pressure. Deep sediments, rich in biological remains, are created by ocean upwelling, caused in part by high geothermal heat flow through the sea bottom. Such regions correlate with enhanced seismic activity. We look for correlations of seismicity, high heat flux, petroleum, uranium, phosphates, and salts, deposited from abundant plant life. These may be useful in discovering more petroleum and coal. We estimate that the known world reserves of petroleum and coal are about 10-4 of the total of buried biogenic carbon. Images PMID:16592185

  18. Oxidation and formation of deposit precursors in hydrocarbon fuels

    NASA Technical Reports Server (NTRS)

    Mayo, F. R.; Lan, B.; Cotts, D. B.; Buttrill, S. E., Jr.; St.john, G. A.

    1983-01-01

    The oxidation of two jet turbine fuels and some pure hydrocarbons was studied at 130 C with and without the presence of small amounts of N-methyl pyrrole (NMP) or indene. Tendency to form solid-deposit precursors was studied by measuring soluble gum formation as well as dimer and trimer formation using field ionization mass spectrometry. Pure n-dodecane oxidized fastest and gave the smallest amount of procursors. An unstable fuel oil oxidized much slower but formed large amounts of precursors. Stable Jet A fuel oxidized slowest and gave little precursors. Indene either retarded or accelerated the oxidation of n-dodecane, depending on its concentration, but always caused more gum formation. The NMP greatly retarded n-dodecane oxidation but accelerated Jet A oxidation and greatly increased the latter's gum formation. In general, the additive reacted faster and formed most of the gum. Results are interpreted in terms of classical cooxidation theory. The effect of oxygen pressure on gum formation is also reported.

  19. Correspondence of ores of silver and gold with basement terranes in the American southwest

    NASA Astrophysics Data System (ADS)

    Titley, S. R.

    1991-04-01

    The ratios of silver to gold produced from epigenetic ore districts of the American southwest reveal a consistency of value ranges, differing by an order of magnitude, that may be identified with either one or the other of two geologic terranes in which the ores occur. A discriminating value of the ratio is about 17.5∶1, the ratio of crustal abundance given by Ahrens (1965). (No further significance is attributed to this value, at this time, beyond the fact that it appears to establish a reasonable separation of values on the basis of geographic occurrence.) Ores relatively enriched in Ag occur in terranes floored by thick Proterozoic clastic and Paleozoic marine successions, and ores relatively enriched in Au lie above or within a Proterozoic basement dominated by maficfelsic volcanic (arc) successions. Proterozoic granites occur in each region. The values of the ratio are broadly consistent within each terrane, irrespective of the age of ore formation, the ore deposit style, associated igneous rocks, structural control, differing interpreted styles of subduction, and weathering histories. These characteristics and associations support a hypothesis that metallogenic signatures of ore districts in this region are fundamentally related to the crust in which the ores occur.

  20. Helium isotope data from the Goldfield epithermal system, Nevada: Evidence for volatile input from a primitive mantle source during ore formation

    NASA Astrophysics Data System (ADS)

    Hofstra, A. H.; Manning, A. H.

    2013-12-01

    crust. This exceptional volatile plumbing system may be an important ingredient in the formation of large, high sulfidation gold deposits. The ascent of mantle-sourced volatiles may be related to the coeval transition from transpression to transtension within the western North American plate caused by microplate capture along the San Andreas transform.

  1. Formation of Acid Mine Drainage Water at Sb (Au) Deposit Pezinok

    NASA Astrophysics Data System (ADS)

    Rusko, Miroslav; Andráš, Peter; Kušnierová, Mária; Aschenbrenner, Štefan; Krnáč, Jozef; Dubiel, Ján

    2011-01-01

    The article presents the results of leaching experiments regarding the comparison of chemical and biological-chemical leaching of ores from the Sb-(Au-) base metal deposit Pezinok (Malé Karpaty., the Western Carpathians) under the same conditions in solution. Discussed are the differences between chemical and biological-chemical leaching activity. The extent and the kinetics of the biological-chemical leaching of the technogenous sediments from the setting-pits are significantly higher than those without bacteria.

  2. Origin of the ore-forming fluids of the Tongchang porphyry Cu-Mo deposit in the Jinshajiang-Red River alkaline igneous belt, SW China: Constraints from He, Ar and S isotopes

    NASA Astrophysics Data System (ADS)

    Xu, Leiluo; Bi, Xianwu; Hu, Ruizhong; Tang, Yongyong; Jiang, Guohao; Qi, Youqiang

    2014-01-01

    The Jinshajiang-Red River alkaline igneous belt with abundant Cu-Mo-Au mineralization, in the eastern Indian-Asian collision zone, is an important Cenozoic magmatic belt formed under an intra-continental strike-slip system in southwestern (SW) China. The Tongchang deposit is a representative porphyry Cu-Mo deposit in southern segment of the Jinshajiang-Red River alkaline igneous belt, with 8621 t Cu @ 1.24 wt.% and 17,060 t Mo @ 0.218 wt.%. In this study, He, Ar and S isotopic compositions of the Tongchang deposit were determined. He and Ar isotopic compositions suggest that the ore-forming fluids, with 3He/4He ratios varying from 0.17 to 1.50 Ra and 40Ar/36Ar ratios from 299.1 to 347.3 for the deposit, are a mixture between a crust-derived fluid (MASW) with near atmospheric Ar and crustal He, and a mantle-derived fluid. However, the δ34S values of the hydrothermal pyrite samples ranging from 1.0‰ to 1.5‰ with an average of 1.2‰, indicate that the sulfur in the ore-forming fluids of the Tongchang deposit was primarily derived from the magma or indirectly mantle-derived without assimilation of crustal sulfur. In combination with previously published He and Ar isotopic data of the Yulong and Machangqing deposits in northern and central segments of the Jinshajiang-Red River alkaline igneous belt, respectively, the ore-forming fluids of the Yulong and Machangqing deposits are obviously richer in 3He and 40Ar, and poorer in 36Ar in comparison with the Tongchang deposit, implying that more mantle-derived fluids were involved in the ore-forming fluids of the Yulong and Machangqing deposits than those for the Tongchang deposit. This might be one of the most important factors producing larger scales of mineralization in the Yulong and Machangqing deposits than the Tongchang deposit.

  3. Depositional Environment of Permian Tak Fa Formation, Nakhonsawan, Northern Thailand

    NASA Astrophysics Data System (ADS)

    Ketwetsuriya, Chatchalerm; Nützel, Alexander; Kanjanapayont, Pitsanupong

    2016-04-01

    The carbonate rocks of the study area at Amphoe Tak Fa and Amphoe Takhli, Changwat Nakhon Sawan belong to the Tak Fa Formation, Saraburi Group. This formation crops out in the Khao Khwang Platform and consists of late Palaeozoic carbonate platform deposits. It reaches a thickness of 900 meters and crops out in a vast area. The exposures have been measured and samples were collected for petrographic study. The rock consists of limestones, argillaceous limestones, mudstones and dolomites with nodular and banded cherts, which comprise many invertebrate fossils such as fusulinids, ammonoid, pelecypod, gastropod, coral and bryozoa. Many of the fossils are silicified. The gastropod assemblage is currently under study and represents one of the most diverse faunas reported from SE Asia. The age of the rock is Yakhtashian or Artinskian (late Early Permian) to Midian or Capitanian (late Middle Permian). The study of carbonate facies and fauna indicates that the depositional environment was on shelf lagoon within the carbonate platform varying from shallow marine to barrier bar.

  4. Ash formation, deposition, corrosion, and erosion in conventional boilers

    SciTech Connect

    Benson, S.A.; Jones, M.L.

    1995-12-01

    The inorganic components (ash-forming species) associated with coals significantly affect boiler design, efficiency of operation, and lifetimes of boiler parts. During combustion in conventional pulverized fuel boilers, the inorganic components are transformed into inorganic gases, liquids, and solids. This partitioning depends upon the association of the inorganic components in the coal and combustion conditions. The inorganic components are associated as mineral grains and as organically associated elements, and these associations of inorganic components in the fuel directly influence their fate upon combustion. Combustion conditions, such as temperature and atmosphere, influence the volatility and the interaction of inorganic components during combustion and gas cooling, which influences the state and size composition distribution of the particulate and condensed ash species. The intermediate species are transported with the bulk gas flow through the combustion systems, during which time the gases and entrained ash are cooled. Deposition, corrosion, and erosion occur when the ash intermediate species are transported to the heat-transfer surface, react with the surface, accumulate, sinter, and develop strength. Research over the past decade has significantly advanced understanding of ash formation, deposition, corrosion, and erosion mechanisms. Many of the advances in understanding and predicting ash-related issues can be attributed to advanced analytical methods to determine the inorganic composition of fuels and the resulting ash materials. These new analytical techniques have been the key to elucidation of the mechanisms of ash formation and deposition. This information has been used to develop algorithms and computer models to predict the effects of ash on combustion system performance.

  5. Silico-ferrite of Calcium and Aluminum (SFCA) Iron Ore Sinter Bonding Phases: New Insights into Their Formation During Heating and Cooling

    NASA Astrophysics Data System (ADS)

    Webster, Nathan A. S.; Pownceby, Mark I.; Madsen, Ian C.; Kimpton, Justin A.

    2012-12-01

    The formation of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore sinter phases during heating and cooling of synthetic iron ore sinter mixtures in the range 298 K to 1623 K (25 °C to 1350 °C) and at oxygen partial pressure of 5 × 10-3 atm has been characterized using in situ synchrotron X-ray diffraction. SFCA and SFCA-I are the key bonding phases in iron ore sinter, and an improved understanding of their formation mechanisms may lead to improved efficiency of industrial sintering processes. During heating, SFCA-I formation at 1327 K to 1392 K (1054 °C to 1119 °C) (depending on composition) was associated with the reaction of Fe2O3, 2CaO·Fe2O3, and SiO2. SFCA formation (1380 K to 1437 K [1107 °C to 1164 °C]) was associated with the reaction of CaO·Fe2O3, SiO2, and a phase with average composition 49.60, 9.09, 0.14, 7.93, and 32.15 wt pct Fe, Ca, Si, Al, and O, respectively. Increasing Al2O3 concentration in the starting sinter mixture increased the temperature range over which SFCA-I was stable before the formation of SFCA, and it stabilized SFCA to a higher temperature before it melted to form a Fe3O4 + melt phase assemblage (1486 K to 1581 K [1213 °C to 1308 °C]). During cooling, the first phase to crystallize from the melt (1452 K to 1561 K [1179 °C to 1288 °C]) was an Fe-rich phase, similar in composition to SFCA-I, and it had an average composition 58.88, 6.89, 0.82, 3.00, and 31.68 wt pct Fe, Ca, Si, Al, and O, respectively. At lower temperatures (1418 K to 1543 K [1145 °C to 1270 °C]), this phase reacted with melt to form SFCA. Increasing Al2O3 increased the temperature at which crystallization of the Fe-rich phase occurred, increased the temperature at which crystallization of SFCA occurred, and suppressed the formation of Fe2O3 (1358 K to 1418 K [1085 °C to 1145 °C]) to lower temperatures.

  6. Evolutionary and geological factors controlling endogenic uranium mineralization and the potential for the discovery of new ore districts

    NASA Astrophysics Data System (ADS)

    Mashkovtsev, G. A.; Miguta, A. K.; Shchetochkin, V. N.

    2015-03-01

    The exhaustion of known surface and near-surface high-grade uranium deposits poses the serious problem of prospecting and exploration of new large endogenic deposits. A comparison of large data sets for endogenic deposits from the world's major uranium districts allowed the authors to develop an evolutionary geological model of large-scale uranium ore genesis, which reflects the succession and nature of preore, ore-forming, and post-ore processes. The study reveals a combination of general (recurrent) factors controlling the formation of ore districts with large-scale uranium mineralization regardless of the genesis and timing of the mineralization. At the same time, these factors depend on the regional setting and can vary considerably among deposits of the same type localized in different tectonic blocks with different characteristics and structural evolution. In connection with this, the exploration of major genetic types of deposits requires the application of specified criteria. Along with the consideration of the evolutionary geological model of ore formation, the study discusses a variety of tectono-magmatic, mineralogical, geochemical, radiogeochemical, and physicochemical factors and indications in three uranium districts (the Streltsovskoe, Elkon, and Central Ukrainian districts), which can form the basis for further uranium prospecting and exploration. Using a combination of favorable prerequisite conditions the study compares the possibilities for the discovery of large endogenic uranium deposits in several regions of Russia.

  7. Pattern, age, and origin of structural features within the Ozark plateau and the relationship to ore deposits

    NASA Technical Reports Server (NTRS)

    Arvidson, R. E.

    1981-01-01

    Topography and gravity anomaly images for the continental United States were constructed. Evidence was found based on gravity, remote sensing data, the presence, trend, and character of fractures, and on rock type data, for a Precambrian rift through Missouri. The feature is probably the failed arm of a triple junction that existed prior to formation of the granite-rhyolite terrain of southern Missouri.

  8. Local natural electric fields - the electrochemical factor of formation of placers and the criterion of prospectings of oil and gas deposits on the Arctic shelf

    NASA Astrophysics Data System (ADS)

    Kholmiansky, Mikhail; Anokhin, Vladimir; Kholmianskaia, Galina

    2014-05-01

    On the basis litologo-facial, geo- and hydrochemical characteristics of a cross-section lito - and shelf hydrospheres, the estimation of structural features modern and paleostatic local electric fields and their influence on transportation of the suspended mineral material is made. The formula of dynamic carrying over of the ore material which is in a subcolloidal condition under the influence of natural electric field of a shelf is deduced. On a structure of a friable cover and its features on G.I. Teodorovicha's method position of oxidation-reduction border, sign Eh was reconstructed. On the basis of the established dependence between Eh and local substatic electric field of a shelf it was reconstructed paleostatic a field and its influence on the weighed mineral particles was estimated. Influence of local electric field on lithodynamic moving of ore minerals is estimated for a shelf of the Arctic seas of Russia. On the basis of this estimation and data on structure of a friable cover the map of influence of local electric field on sedimentation and transportation of ore minerals for water area of the East Arctic seas of Russia is constructed. For Laptev seas and East-Siberian the areas in which limits local electric field promoted are revealed and promotes formation Holocene placers of an ilmenite, a cassiterite and gold. For Chukchi and the Bering Seas such estimation is made for all friable cover. hydrocarbonic deposits located on water area of the Arctic shelf of the Russian Federation, initiate occurrence of jet auras of dispersion of heavy metals in ground deposits and in a layer of the sea water, blocking these deposits. Intensity of auras and their spatial position is caused by a geological structure of deposits of breeds containing them, lithodynamic and oceanologic factors. On the basis of the theoretical representations developed by M.A.Holmjansky and O.F.Putikova (Holmjansky, Putikov, 2000, 2006, 2008) application of electrochemical updating of

  9. Estimating gold-ore mineralization potential within Topolninsk ore field (Gorny Altai)

    NASA Astrophysics Data System (ADS)

    Timkin, T.; Voroshilov, V.; Askanakova, O.; Cherkasova, T.; Chernyshov, A.; Korotchenko, T.

    2015-11-01

    Based on the results of ore and near-ore metasomatite composition analysis, the factors and indicators of gold-ore mineralization potential were proposed. Integration of the obtained data made it possible to outline magmatic, structural, and lithological factors, as well as direct and indirect indicators of gold-ore mineralization. Applying multidimensional analysis inherent to geochemical data, the spatial structure was investigated, as well as the potential mineralization was identified. Based on the developed and newly-identified mineralization, small (up to medium-sized) mineable gold-ore deposits in skarns characterized by complex geological setting was identified.

  10. A mixture of mantle and crustal derived He-Ar-C-S ore-forming fluids at the Baogutu reduced porphyry Cu deposit, western Junggar

    NASA Astrophysics Data System (ADS)

    Cao, MingJian; Qin, KeZhang; Li, GuangMing; Evans, Noreen J.; He, HuaiYu; Jin, LuYing

    2015-02-01

    Most large to huge porphyry Cu deposits (PCDs) are oxidized, making the Baogutu reduced porphyry Cu deposit (RPCD) a relative rarity. CH4-bearing ore-forming fluids formed at several hydrothermal stages, however, their source is still unclear. To address this issue, isotopic investigations of sulfide He-Ar-S and calcite C were conducted. Fluid inclusions hosted in sulfides (arsenopyrite, chalcopyrite and pyrite) showed 3He/4He ratios of 0.06-0.30 Ra (Ra is the 3He/4He ratio of air = 1.39 × 10-6), 40Ar/36Ar of 311-405, 40Ar∗/4He of 0.06-1.01, and F4He ratios of 902-11,074 (sample BGT-Py 2 yielded a ratio of 100), indicating a predominantly crustal source for the fluids with minor mantle input (less than 5%). The δ13C values of carbonate yielded a value of -7.8‰ (n = 3), implying that CO2 was probably sourced from mantle or juvenile lower crust. According to the restricted sulfide δ34S values, the total S isotopic composition of the hydrothermal system was estimated to be 0.0-0.5‰, suggesting that the sulfur was derived from mantle or lower crust magmatic source. According to the published granitoids Nd isotopic compositions at the Baogutu RPCD, fairly young TDM model ages (450-650 Ma) suggest that the granitoids were derived from partial melting of a juvenile basaltic lower crust. Thus, we propose that small proportion of mantle-derived fluids (less than 5%), probably rise up and then mix with the fluids of juvenile lower crust under an extensional tectonic setting, forming the mantle-derived Sr-Nd-Pb-S-C but crustal He-Ar isotopic compositions.

  11. Selective copper diffusion into quartz-hosted vapor inclusions: Evidence from other host minerals, driving forces, and consequences for Cu-Au ore formation

    NASA Astrophysics Data System (ADS)

    Seo, Jung Hun; Heinrich, Christoph A.

    2013-07-01

    Recent experimental studies have raised concerns that Cu concentrations in quartz-hosted fluid inclusions from magmatic-hydrothermal ore deposits do not represent pristine concentrations in the trapped fluids, but are modified by post-entrapment diffusional exchange through the host quartz. New microanalyses of fluid inclusions hosted in topaz show significantly lower Cu concentrations in vapor inclusions, compared to otherwise identical inclusions hosted by coexisting quartz, whereas coeval brine (hypersaline liquid) inclusions are very similar independent of host mineral in one sample. Sulfur is present as a major component in all vapor inclusions, as in most porphyry-related vapor inclusions, and Cu never exceeds S, but commonly matches the S content at a molar ratio of Cu:S ⩽ 2 in vapor inclusions hosted by quartz. Univalent ions with a radius smaller than ˜1 Å are known to diffuse rapidly through the channels of the quartz structure, parallel to its crystallographic c axis. Since only Cu concentrations differ between topaz- and quartz-hosted inclusions, we hypothesize that Cu+ and H+ re-equilibrate by diffusional ion exchange through these channels, while all other element concentrations remain essentially unchanged. A thermodynamic model considering charge-balanced Cu+H+ exchange and diffusive H2 re-equilibration of an initially Cu-poor but S-rich vapor inclusion with a typical rock-buffered fluid environment outside the host crystal demonstrates a strong chemical driving force for Cu+ to migrate from the surrounding rock into the fluid inclusion during cooling of the system. The driving force for Cu diffusion, against the gradient in total Cu concentration, is the abundant H+ liberated inside the inclusion by dissociation of HCl and particularly by the precipitation of CuFeS2 by reaction with the initially trapped H2S and/or SO2. Gold is not only a much larger ion, but is subject to an opposing driving force, suggesting that high concentrations of this

  12. Mineralogical, fluid inclusion, and stable isotope constraints on mechanisms of ore deposition at the Samgwang mine (Republic of Korea)—a mesothermal, vein-hosted gold-silver deposit

    NASA Astrophysics Data System (ADS)

    Yoo, Bong Chul; Lee, Hyun Koo; White, Noel C.

    2010-02-01

    The Samgwang mine is located in the Cheongyang gold district (Cheonan Metallogenic Province) of the Republic of Korea. It consists of eight massive, gold-bearing quartz veins that filled NE- and NW-striking fractures along fault zones in Precambrian granitic gneiss of the Gyeonggi massif. Their mineralogy and paragenesis allow two separate vein-forming episodes to be recognized, temporally separated by a major faulting event. The ore minerals occur in quartz and calcite of stage I, associated with fracturing and healing of veins. Hydrothermal wall-rock alteration minerals of stage I include Fe-rich chlorite (Fe/(Fe+Mg) ratios 0.74-0.81), muscovite, illite, K-feldspar, and minor arsenopyrite, pyrite, and carbonates. Sulfide minerals deposited along with electrum during this stage include arsenopyrite, pyrite, pyrrhotite, sphalerite, marcasite, chalcopyrite, galena, argentite, pyrargyrite, and argentian tetrahedrite. Only calcite was deposited during stage II. Fluid inclusions in quartz contain three main types of C-O-H fluids: CO2-rich, CO2-H2O, and aqueous inclusions. Quartz veins related to early sulfides in stage I were deposited from H2O-NaCl-CO2 fluids (1,500-5,000 bar, average 3,200) with T htotal values of 200°C to 383°C and salinities less than about 7 wt.% NaCl equiv. Late sulfide deposition was related to H2O-NaCl fluids (140-1,300 bar, average 700) with T htotal values of 110°C to 385°C and salinities less than about 11 wt.% NaCl equiv. These fluids either evolved through immiscibility of H2O-NaCl-CO2 fluids as a result of a decrease in fluid pressure, or through mixing with deeply circulated meteoric waters as a result of uplift or unloading during mineralization, or both. Measured and calculated sulfur isotope compositions (δ34SH2S = 1.5 to 4.8‰) of hydrothermal fluids from the stage I quartz veins indicate that ore sulfur was derived mainly from a magmatic source. The calculated and measured oxygen and hydrogen isotope compositions (δ18OH2O

  13. El Paso Formation - a Lower Ordovician platform carbonate deposit

    SciTech Connect

    Clemons, R.E.

    1987-05-01

    The eastward-transgressive Lower Ordovician El Paso Formation conformably overlies Bliss Sandstone in southern New Mexico. Locally, lower El Paso was deposited on low hills of plutonic and volcanic rocks. The region subsided gradually throughout Canadian time, receiving the El Paso carbonate rock blanket up to 460 m thick. Lithologic and chronologic correlative rocks were deposited over most of the southwestern US as the first Paleozoic carbonate platform sequence. The El Paso Formation contains four members, listed here in ascending order: Hitt Canyon, Jose, McKelligon, and Padre. Gradually decreasing sand content upward through the Hitt Canyon indicates deepening water and/or greater distance to shore. Girvanella(.) oncolites are locally abundant. Stromatolite mounds near the top of the Hitt Canyon, combined with an influx of sand, ooids, and rounded bioclasts in the Jose Member, recorded a shoaling phase. The overlying McKelligon Member contains little or no sand, and sponge-Calathium mounds are prominent at some locales. Stromatolite mounds are interbedded with sponge-Calathium mounds in a few sections. Lower Padre Member beds are typically silty to sandy and locally contain thinly-laminated zones. The Padre contains more restricted fauna that includes traces of ostracods. Pervasive bioturbation of El Paso beds and fauna consisting of echinoderms, sponges, gastropods, trilobites, Nuia, Calathium, cephalopods, and algae plus minor brachiopods and Pulchrilamina indicate predominating shallow-subtidal environments. Low-energy platform environments, in which a large volume of micritic muds accumulated, were disturbed thousands of times by storms producing abundant thin, poorly washed biosparite, intrasparite, and intrasparrudite lenses.

  14. LA-ICP-MS analyses of minor and trace elements and bulk Ge isotopes in zoned Ge-rich sphalerites from the Noailhac - Saint-Salvy deposit (France): Insights into incorporation mechanisms and ore deposition processes

    NASA Astrophysics Data System (ADS)

    Belissont, Rémi; Boiron, Marie-Christine; Luais, Béatrice; Cathelineau, Michel

    2014-02-01

    sphalerite varies from -2.07 ± 0.37‰ to +0.91 ± 0.16‰ (2σ SD) and positively correlates with bulk Ge content. This indicates considerable Ge isotopic fractionation within sphalerite during low-T hydrothermal deposition and zoning processes, associated with possible microscale open system fluid mixing. The trace element features in sphalerite from Saint-Salvy compared with those of other deposits confirm their use as discriminators among genetic types of ores (e.g., high In contents for magmatic-related deposits, and Ge for low-temperature deposits). The LA-ICP-MS technique is revealed to be a powerful tool to measure in situ trace and minor elements occurring as solid solutions in sphalerite. The 74Ge isotope is most relevant for Ge analysis using the LA-ICP-MS, as this isotope shows the lowest isobaric interferences. Principal component analysis (PCA) of LA-ICP-MS dataset revealed an antithetic distribution of element clusters in sphalerite: Cu and trace elements Ge, Sb, Ag, and As are enriched and positively correlated in sector zoning whereas Fe, Cd, In and Sn are enriched in dark brown rhythmic bands. This distribution implies crystallographic controls on the incorporation of trace elements. Regardless of the zoning type, all spots considered, notable coupled substitutions have been suggested from binary scatter plots: 2Zn2+ ↔ Cu+ + Sb3+ and 3Zn2+ ↔ Ge4+ + 2Ag+. Also, the data suggest the substitution 3Zn2+ ↔ In3+ + Sn3+ + □ although Sn oxidation state needs verification using appropriate methods (e.g., XAS, μ-XANES/EXAFS). Fe and Cd are mainly involved in direct Zn2+ ↔ (Fe2+, Cd2+) substitutions. Noticeably, in all spots, Cu content approaches the sum of all available tri- and tetravalent cations. In this way, Cu (occurring as Cu+) could provide charge-balance for the entire broad set of coupled substitution mechanisms responsible for incorporation of the whole range of trace elements in Saint-Salvy sphalerite, especially Ge, Ga and Sb. Germanium

  15. Depositional environments of Fort Union Formation, Bison Basin, Wyoming

    SciTech Connect

    Southwell, E.H.; Steidtmann, J.R.; Middleton, L.

    1983-08-01

    The Paleocene Fort Union Formation crops out in the vicinity of the Bison basin, approximately equidistant from the southeast terminus of the Wind River Range and the southwestern edge of the Granite Mountains uplift in central Wyoming. Early Laramide tectonic activity produced a series of uplifts north of the area forming a platform separating the Wind River and Great Divide basins. During middle to late Paleocene, aggrading fluvial systems flowing southward, rapidly deposited a sequence of thin, lenticular conglomerates and medium to coarse-grained planar-bedded sandstones in braided and anastomosing stream channels and carbonaceous overbank silt and claystones. Subaerially exposed interchannel areas developed cyclic pedogenic horizons. Early diagenetic cementation preserved tubular burrows and rhizoliths as well as impressions of fruits, nuts, leaves, and wood. Anomalous silicic cementation of mudstone, sandstone, and conglomerates probably are silcrete soil horizons developed in a warm temperature to subtropical humid climate. The sandstones are multicyclic containing fragments of preexisting siliceous sedimentary rocks (e.g., Tensleep Sandstone, Mowry Shale, and cherts from the Madison, Morrison, and Phosphoria Formations). Reworked glauconite is locally abundant in some Fort Union sandstones, reflecting the proximity of Paleozoic sources. Altered and embayed feldspars are present in trace amounts throughout most of the section, but significant accumulations of fresh feldspar are present near the top, indicating unroofing of Precambrian source before the Eocene.

  16. Composition and origin of Early Cambrian Tiantaishan phosphorite-Mn carbonate ores, Shaanxi Province, China

    USGS Publications Warehouse

    Hein, J.R.; Fan, D.; Ye, J.; Liu, T.; Yeh, H.-W.

    1999-01-01

    The Tiantaishan phosphorite-Mn carbonate ores occur in the Early Cambrian Tananpo Formation in complexly folded and faulted rocks located in southern Shaanxi Province. About 65 x 106 tonnes of 17% P2O5 ore reserves exist and Mn-ore reserves are about 8.3 x 106 tonnes of +18% Mn. The stratigraphic sequence in ascending order consists of black phyllite, black to gray phosphorite ore, black phyllite, rhodochrostone ore, Mn mixed-carbonates, and dolostone. Data are presented from microprobe mineral chemistry, whole-rock chemistry, stable isotopes of carbonates, X-ray mineralogy, petrographic and SEM observations, and statistical analysis of chemical data. The dominant ore-forming minerals are hydroxy- and carbonate fluorapatite and Ca rhodochrosite, with Mg kutnahorite and dolomite comprising the Mn mixed-carbonate section. Pyrite occurs in all rock types and alabandite (MnS) occurs throughout the rhodochrostone section. The mean P2O5 content of phosphorite is 31% and argillaceous phosphorite is 16%, while the mean MnO content of rhodochrostone ore is 37%. Phosphorite ores are massive, spheroidal, laminated, and banded, while rhodochrostone ores have oolitic, spheroidal, and granular fabrics. The most distinguishing characteristics of the ores are high total organic carbon (TOC) contents (mean 8.4%) in the phosphorite and high P2O5 contents (mean 2.7%) in the rhodochrostone ore. The atypically high TOC contents in the Tiantaishan phosphorite probably result from very strong productivity leading to high sedimentation rates accompanied by weak reworking of sediments; poor utilization of the organic matter by bacteria; and/or partial replacement of bacterial or algal mats by the apatite. The depositional setting of the ores was the margin of an epicontinental seaway created as a direct consequence of global processes that included break-up of a supercontinent, formation of narrow seaways, creation of extensive continental shelves, overturn of stagnant, metal-rich deep

  17. Stable isotope study of water-rock interaction and ore formation, Bayhorse base and precious metal district, Idaho

    USGS Publications Warehouse

    Seal, R.R., II; Rye, R.O.

    1992-01-01

    Whole-rock ??18O and ??D values from the Garden Creek Phyllite define an isotopically depleted zone (60 km2) around the Nevada Mountain stock and are the result of high-temperature interactions with ancient meteoric waters at water/rock ratios ranging from 0.002 to 0.09. Comparison of the ore fluid ??18OH2O and ??DH2O values with hypothetical waters equilibrated with the Garden Creek Phyllite indicates that the hydrothermal fluids must have also interacted with the basal dolomite of Bayhorse Creek, which underlies the phyllite. The ?? 13CCO2 values for the hydrothermal fluids also record a transition from early water/rock interactions that were dominated by the Garden Creek Phyllite to later interactions that were influenced significantly by the basal dolomite of Bayhorse Creek. The range of ??34S values may be interpreted as either a heterogeneous sedimentary source or mixed sedimentary-magmatic sources. -from Authors

  18. Metal organic chemical vapor deposition of environmental barrier coatings for the inhibition of solid deposit formation from heated jet fuel

    NASA Astrophysics Data System (ADS)

    Mohan, Arun Ram

    Solid deposit formation from jet fuel compromises the fuel handling system of an aviation turbine engine and increases the maintenance downtime of an aircraft. The deposit formation process depends upon the composition of the fuel, the nature of metal surfaces that come in contact with the heated fuel and the operating conditions of the engine. The objective of the study is to investigate the effect of substrate surfaces on the amount and nature of solid deposits in the intermediate regime where both autoxidation and pyrolysis play an important role in deposit formation. A particular focus has been directed to examining the effectiveness of barrier coatings produced by metal organic chemical vapor deposition (MOCVD) on metal surfaces for inhibiting the solid deposit formation from jet fuel degradation. In the first part of the experimental study, a commercial Jet-A sample was stressed in a flow reactor on seven different metal surfaces: AISI316, AISI 321, AISI 304, AISI 347, Inconel 600, Inconel 718, Inconel 750X and FecrAlloy. Examination of deposits by thermal and microscopic analysis shows that the solid deposit formation is influenced by the interaction of organosulfur compounds and autoxidation products with the metal surfaces. The nature of metal sulfides was predicted by Fe-Ni-S ternary phase diagram. Thermal stressing on uncoated surfaces produced coke deposits with varying degree of structural order. They are hydrogen-rich and structurally disordered deposits, spherulitic deposits, small carbon particles with relatively ordered structures and large platelets of ordered carbon structures formed by metal catalysis. In the second part of the study, environmental barrier coatings were deposited on tube surfaces to inhibit solid deposit formation from the heated fuel. A new CVD system was configured by the proper choice of components for mass flow, pressure and temperature control in the reactor. A bubbler was designed to deliver the precursor into the reactor

  19. The sources of our iron ores. II

    USGS Publications Warehouse

    Burchard, E.F.

    1933-01-01

    In this instalment** the iron ore deposits of the Lake Superior States, which normally furnish about 80 per cent, of the annual output of the United States, are described together with historical notes on discovery and transportation of ore. Deposits in the Mississippi Valley and Western States are likewise outlined and the sources of imported ore are given. Reviewing the whole field, it is indicated that the great producing deposits of the Lake Superior and southern Appalachian regions are of hematite in basin areas of sedimentary rocks, that hydrated iron oxides and iron carbonates are generally found in undisturbed comparatively recent sediments, and that magnetite occurs in metamorphic and igneous rocks; also that numerical abundance of deposits is not a criterion as to their real importance as a source of supply. Statistics of production of iron ore and estimates of reserves of present grade conclude the paper.

  20. Late-Variscan rare metal ore deposition and plume-related magmatism in the eastern European Variscides (D, CZ)

    NASA Astrophysics Data System (ADS)

    Seifert, Thomas

    2014-05-01

    Located at the northwestern border of the Bohemian Massif in the eastern part of the European Variscides, the Erzgebirge-Krušné hory is one of the most important metallogenic provinces in Europe with a 800-year history of mining. The following rare metal resources are associated with late-Variscan (315 - 280 Ma), postmagmatic mineralization pulses in the Erzgebirge-Krušné hory and surrounded areas: 900 kt Sn, 230 kt W, 10 kt Mo, 1 kt Ta, 300 kt Li, 200 kt Rb, 2 kt Cs, 1.5 kt In, 230 t Ge, 320 t Sc, 14 kt Sb, 10 kt Bi, and 3 kt Ag. At the end of the Variscan Orogeny the regional tectonic regime in Central Europe changed, indicating the beginning of the break-up of the supercontinent. The Late Carboniferous-Early Permian in Europe was a period of widespread basin formation that was associated in many areas with mantle-derived magmatic activity. 300 Ma-old dike swarms in NE England and the Scottish Midland Valley, the Oslo Graben and Scania, radiate from a triple junction in the northernmost part of Jutland. This triple junction marked the axis of a deep-mantle plume centered in this area. In this context it is important to note that the mantle plume center is surrounded by significant lamprophyre intrusions which show in some districts spatial-time relationships to Sn-W-polymetallic, Ag-base metal, and U mineralization. During the Late Carboniferous and Early Permian an extensive magmatic province developed within the present northern and central Europe, intimately with extensional tectonics, in an area stretching from southern Scandinavia, through the North Sea, into Northern Germany. Peak magmatic activity was concentrated in a narrow time-span from 300 to 280 Ma. Simultaneously in Stephanian-Early Permian an intensive bimodal magmatism associated with intra-continental extensional setting occurs in the European Variscides. Permo-Carboniferous volcanism in the Spanish Central System, Iberian Ranges, Cantabrian Chain, Pyrenees and the French Massif Central

  1. Environment of ore deposition in the creede mining district, San Juan Mountains, Colorado: Part V. Epithermal mineralization from fluid mixing in the OH vein

    USGS Publications Warehouse

    Hayba, D.O.

    1997-01-01

    Detailed fluid inclusion studies on coarse-grained sphalerite from the OH vein, Creede, Colorado, have shown that the abrupt color changes between growth zones correspond to abrupt changes in the nature of the ore fluids. Within each growth zone, however, the composition of the fluids remained constant. The base of a distinctive orange-brown growth zone marks a sharp increase in both temperature and salinity relative to the preceding yellow-white zone. The orange-brown growth zone can be correlated along much of the vein and is believed to represent a time-stratigraphic interval. Along the vein, temperatures and salinities of fluid inclusions within this interval show a systematic decrease from about 285??C and 11.5 wt percent NaCl equiv near the base of the vein to about 250??C and 8 wt percent NaCl equiv, respectively, near the top of the vein. The iron concentration of this sphalerite growth zone shows a similar pattern, decreasing from about 2.8 to 1.2 mole percent FeS. When plotted on an enthalpy-salinity diagram, the fluid inclusion data define a spatial trend indicating the progressive mixing of deeply circulating hydrothermal brines with overlying, dilute ground waters. The hydrothermal brines entered the OH vein from below at a temperature, salinity, and density of approximately 285??C, 11.5 wt percent NaCl equiv, and 860 kg/m3, respectively, whereas the overlying ground waters appear to have been preheated to roughly 150??C and had an assumed salinity of 0 wt percent and a density of 920 kg/m3. The greater density of the heated ground water promoted mixing with the hydrothermal brine within the open fractures, causing sphalerite deposition. Although there were also episodes of boiling during vein mineralization, boiling appears unimportant for this sphalerite. Isotopic evidence and geochemical modeling studies also indicate that mixing was the depositional mechanism for sphalerite. An important aspect of the mixing hydrology of the Creede system involves

  2. Constraints of mineralogical characterization of gold ore: Implication for genesis, controls and evolution of gold from Kundarkocha gold deposit, eastern India

    NASA Astrophysics Data System (ADS)

    Sahoo, P. R.; Venkatesh, A. S.

    2015-01-01

    Gold mineralization in Kundarkocha gold deposit occurs in the eastern Indian Craton that is hosted by sheared quartz-carbonate-sulfide veins emplaced within the graphitic schist, carbonaceous phyllite and talc-chlorite-serpentine schist belongs to Gorumahisani-Badampahar schist belt of Iron Ore Group. Gold mineralization exhibits both lithological and structural controls in the study area, albeit the stratigraphic control is more ubiquitously observed. Detailed mineralogical characterization coupled with electron probe microanalysis of the sulfide phases reveal the occurrences of gold in three distinct forms (i) as lattice-bound form within sulfides especially enriched in arsenopyrite, loellingite, pyrite, pyrrhotite and chalcopyrite in decreasing order of abundance; (ii) as micro inclusions or nano-scale gold inclusions within pyrite and arsenopyrite especially along the growth zones and micro-fractures as substrates and (iii) as free milling nugget gold grains either along the grain boundaries of sulfides or within the host rocks. Three generations of pyrite (Py-I, Py-II and Py-III) and arsenopyrite (Asp-I, Asp-II, Asp-III) have been identified based on textural, morphological characteristics and mineral chemistry. The lattice-bound gold content in pyrite and arsenopyrite varies from 600 to 2700 ppm and 900 to 3600 ppm respectively and increase in concentration of such refractory gold is seen in the order of chalcopyrite > pyrrhotite > pyrite > loellingite/arsenopyrite. The evolutionary stages of different forms of gold include remobilization of the lattice-bound grains in pyrite and arsenopyrite (Py-I and Asp-I) and re-concentration along the zoned-pyrite and arsenopyrite (Py-II and Asp-II) and ultimately as native gold/nuggets surrounding the sulfides as well as within the main mineralized zone. Lattice-bound gold distribution could have resulted due to metamorphic devolatilization reactions which are further aided by the influx of hydrothermal fluids. These

  3. Formation of amorphous metal alloys by chemical vapor deposition

    DOEpatents

    Mullendore, A.W.

    1988-03-18

    Amorphous alloys are deposited by a process of thermal dissociation of mixtures of organometallic compounds and metalloid hydrides,e.g., transition metal carbonyl, such as nickel carbonyl and diborane. Various sizes and shapes of deposits can be achieved, including near-net-shape free standing articles, multilayer deposits, and the like. Manipulation or absence of a magnetic field affects the nature and the structure of the deposit. 1 fig.

  4. Formation of amorphous metal alloys by chemical vapor deposition

    DOEpatents

    Mullendore, Arthur W.

    1990-01-01

    Amorphous alloys are deposited by a process of thermal dissociation of mixtures or organometallic compounds and metalloid hydrides, e.g., transition metal carbonyl such as nickel carbonyl, and diborane. Various sizes and shapes of deposits can be achieved, including near-net-shape free standing articles, multilayer deposits, and the like. Manipulation or absence of a magnetic field affects the nature and the structure of the deposit.

  5. Porosity formation and gas bubble retention in laser metal deposition

    NASA Astrophysics Data System (ADS)

    Ng, G. K. L.; Jarfors, A. E. W.; Bi, G.; Zheng, H. Y.

    2009-11-01

    One of the inherent problems associated with laser metal deposition using gas-assisted powder transfer is the formation of porosity, which can be detrimental to the mechanical properties of the bulk material. In this work, a comprehensive investigation of porosity is carried out using gas atomised Inconel 718 powder. In the analysis, a clear distinction is made between two types of porosity; namely lack of fusion and gas porosity. The results show that the two types of porosity are attributed by different factors. The gas porosity, which is more difficult to eliminate than the lack of fusion, can be as high as 0.7%. The study shows that the gas porosity is dependent on the process parameters and the melt pool dynamics. The flotation of entrapped gas bubbles was analysed, showing that in a stationary melt pool the gas would be retained by Marangoni-driven flow. The overall Marangoni-driven flow of the melt pool is in the order of five times higher than the flotation effect, and this is the reason why the melt pool geometry would tend to dominate the flow direction of the gas bubbles. Through optimisation, the gas porosity can be reduced to 0.037%.

  6. Environment of deposition of Clear Fork Formation: Yoakum County, Texas

    SciTech Connect

    Moore, B.K.

    1987-05-01

    The Clear Fork Formation is Permian (Leonardian) in age and constitutes a major oil-bearing unit in the Permian basin of west Texas. In Yoakum County, west Texas, the upper Clear Fork carbonates record a subtidal upward-shoaling sequence of deposition. A small bryozoan-algal patch reef is situated within these carbonates near the southern edge of the North Basin platform. The reef is completely dolomitized, but paramorphic replacement has facilitated a study of the paleoecology, lateral variations, and community succession within this buildup. Build-ups of this type are scarcely known in strata of Permian age. The reef was apparently founded on a coquina horizon at the base of the buildup. The reef apparently had a low-relief, dome-shaped morphology. The trapping and binding of sediment by bryozoa appear to have been the main constructional process. A significant role was also played by encrusting forams and the early precipitation of submarine cements, both of which added rigidity to the structure. The reef also contains a low-diversity community of other invertebrates. Algal constituents predominate at the basinward edge of the buildup. The reef was formed entirely subaqueously on a broad, relatively shallow tropical marine carbonate shelf environment. An understanding of the lithofacies distribution and paragenesis within this sequence will provide information on porosity variations and the nature and distribution of permeability barriers. Such information is useful in reservoir modeling studies and for secondary recovery techniques in shelf-edge carbonate reservoirs of this type.

  7. Neoproterozoic Cana Brava chrysotile deposit (Goiás, Brazil): Geology and geochemistry of chrysotile vein formation

    NASA Astrophysics Data System (ADS)

    Biondi, João Carlos

    2014-01-01

    The Cana Brava chrysotile asbestos deposit of Goiás, Brazil, contains approximately 150 Mt of ore with an average of 3.5 wt.% of cross-fiber chrysotile and lies in the differentiated, mafic-ultramafic Neoproterozoic Cana Brava complex. This complex was formed at approximately 0.79 Ga and metamorphosed at 0.77 to 0.76 and 0.63 Ga. The 0.77 to 0.76 Ga metamorphic event was a high-grade one that transformed the mafic and ultramafic rocks into meta-peridotites and meta-pyroxenites. The low-grade 0.63 Ga metamorphism allowed the formation of black, red and brown serpentinite, graphitic, magnesite-rich talc serpentinite, and rodingite, which became folded and foliated. At the end of the 0.63 Ga metamorphism, black serpentinites were oxidized to form red serpentinites, the main type of serpentinite that outcrops today at the Cana Brava mineralized region. Post-metamorphic fluids reactivated the process of serpentinization, thereby generating massive green serpentinite from the red. Green formed on the most fractured zones, and double red and green reaction rims formed on the sides of the veins located outside the green serpentinite zones. This process did not cause significant variation in the volume of the rocks and resulted in a strongly reducing system thanks to the loss of Fe2O3 and iron and the subsequent crystallization of magnetite within veinlets and altered rocks. Low angle shear, developed under brittle conditions, caused hydraulic fracturing and the generation of oversaturated, oxidizing fluids that crystallized the cross-fiber chrysotile inside open fractures. Very densely fractured zones with fractures filled with cross-fiber chrysotile constitute the ore that is mined at present.

  8. Fluid inclusion and stable isotope studies of the Mesloula Pb-Zn-Ba ore deposit, NE Algeria: Characteristics and origin of the mineralizing fluids

    NASA Astrophysics Data System (ADS)

    Laouar, Rabah; Salmi-Laouar, Sihem; Sami, Lounis; Boyce, Adrian J.; Kolli, Omar; Boutaleb, Abdelhak; Fallick, Anthony E.

    2016-09-01

    In the Saharan Atlas (NE Algeria), the Triassic evaporitic formation was brought to the surface through the thick Cretaceous and Tertiary sedimentary cover as diapirs due to the effect of Atlasic tectonic events. The diapir piercing began in the Jurassic and has continued through present day. Many outcrops of several square kilometres are distributed in a large area (approximately 80 km wide) that extends northeasterly over 300 km towards Tunisia. The diapiric evaporitic formation is often accompanied by the emplacement of Pb-Zn-Ba-F mineralization. The Mesloula massif is an example of these deposits. Fluid inclusion and sulphur, carbon and oxygen isotope studies were carried out on Pb-Zn-Ba mineralization and associated gangue carbonates. Gypsum of the Triassic formation was also analysed for its sulphur isotope composition to show the role of evaporates in the generation of this typical peridiapiric deposit. Gypsum from the Triassic formation showed a narrow range of δ34SVCDT values, ranging from +14.6 to +15.5‰ (n = 8). This range is comparable to that of Triassic seawater sulphates. Sulphide minerals yielded δ34SVCDT values between 0 and + 11.7‰ (n = 15), indicating that sulphide sulphur was likely derived from Triassic sulphates through thermochemical sulphate reduction (TSR) because fluid inclusion microthermometric measurements yielded a mean temperature of 150 °C. Residual sulphate in such a system would have been enriched in 34S; this is reflected in the barite δ34SVCDT values, which range from +21.1 to +33.5‰ (n = 5). The δ13CVPDB values of calcite minerals, ranging from +2.1 to +6.3‰ (n = 4), indicate an inorganic carbon origin, likely from the host carbonate rocks. δ18OVSMOW values were between +21.9 and + 24.9‰, indicating that the most likely source of mineralizing fluids was formation water.

  9. Mechanisms of Fat, Oil and Grease (FOG) Deposit Formation in Sewer Lines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    FOG deposits in sewer systems recently have been shown to be metallic salts of fatty acids. However, the fate and transport of FOG deposit reactant constituents and the complex interactions during the FOG deposit formation process are still largely unknown. Batch tests were performed to elucidate ...

  10. Evidence for fat, oil and grease (FOG) deposit formation mechanisms in sewer lines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The presence of hardened and insoluble fats, oil, and grease (FOG) deposits in sewer lines is a major cause of line blockages leading to sanitary sewer overflows (SSOs). Despite the central role that FOG deposits play in SSOs, little is known about the mechanisms of FOG deposit formation in sanitary...

  11. Lithofacies and the depositional history of the Tessey Formation, Frenchman Hills, West Texas

    USGS Publications Warehouse

    Haneef, Mohammad; Wardlaw, B.R.

    2000-01-01

    The Tessey Formation in the Frenchman Hills, northwest Glass Mountains, represent deposition in a basinal setting. The formation consists of at least two shallowing-upward sequences of carbonate and evaporite deposition marked by two episodes of subaerial exposure, meteoric water dissolution, and collapse brecciation.

  12. Formation of the Wiesloch Mississippi Valley-type Zn-Pb-Ag deposit in the extensional setting of the Upper Rhinegraben, SW Germany

    USGS Publications Warehouse

    Pfaff, Katharina; Hildebrandt, Ludwig H.; Leach, David L.; Jacob, Dorrit E.; Markl, Gregor

    2010-01-01

    The Mississippi Valley-type (MVT) Zn-Pb-Ag deposit in the Wiesloch area, Southwest Germany, is controlled by graben-related faults of the Upper Rhinegraben. Mineralization occurs as vein fillings and irregular replacement ore bodies consisting of sphalerite, banded sphalerite, galena, pyrite, sulfosalts (jordanite and geocronite), barite, and calcite in the Middle Triassic carbonate host rock. Combining paragenetic information, fluid inclusion investigations, stable isotope and mineral chemistry with thermodynamic modeling, we have derived a model for the formation of the Wiesloch deposit. This model involves fluid mixing between ascending hot brines (originating in the crystalline basement) with sedimentary formation waters. The ascending brines originally had a near-neutral pH (around 6) and intermediate oxidation state, reflecting equilibrium with granites and gneisses in the basement. During fluid ascent and cooling, the pH of the brine shifted towards more acidic (around 4) and the oxidation state increased to conditions above the hematite-magnetite buffer. These chemical characteristics contrast strongly with those of the pore and fracture fluid residing in the limestone aquifer, which had a pH between 8 and 9 in equilibrium with calcite and was rather reduced due to the presence of organic matter in the limestone. Mixing between these two fluids resulted in a strong decrease in the solubility of silver-bearing sphalerite and galena, and calcite. Besides Wiesloch, several Pb-Zn deposits are known along the Upper Rhinegraben, including hydrothermal vein-type deposits like Badenweiler and the Michael mine near Lahr. They all share the same fluid origin and formation process and only differ in details of their host rock and fluid cooling paths. The mechanism of fluid mixing also seems to be responsible for the formation of other MVT deposits in Europe (e.g., Reocin, Northern Spain; Treves, Southern France; and Cracow-Silesia, Poland), which show notable

  13. The formation of Qulong adakites and their relationship with porphyry copper deposit: Geochemical constraints

    NASA Astrophysics Data System (ADS)

    Hu, Yong-bin; Liu, Ji-qiang; Ling, Ming-xing; Ding, Wei; Liu, Yan; Zartman, Robert E.; Ma, Xiu-feng; Liu, Dun-yi; Zhang, Chan-chan; Sun, Sai-jun; Zhang, Li-peng; Wu, Kai; Sun, Wei-dong

    2015-04-01

    Qulong porphyry Cu deposit is the largest Cu deposit in China so far discovered, with total reserves of 10.6 Mt Cu@0.5% and 0.5 Mt Mo@0.03%. The petrogenesis of the Miocene intrusion and its genetic association with Cu mineralization have been debated. This study presents new results on whole rock major and trace elements, Sr-Nd isotopes, zircon U-Pb dating, Hf-O isotopic compositions of the Qulong ore-bearing and barren adakites. All the Qulong adakites studied here have low MgO (< 2 wt.%), high K2O (between 2 wt.% and 6 wt.%), with K2O/Na2O ratios ranging from 0.2-2.0. The SiO2 contents are mostly higher than 64 wt.%. These are dramatically different from ore-forming adakites in the circum-Pacific region and other places in general. Ore-bearing adakites have systematically higher SiO2 and K2O compared with barren ones, likely due to the addition of Si and K during alteration and mineralization. Magmatic zircons from these two series of intrusions have U-Pb ages of 16.6 ± 0.5-17.0 ± 0.6 Ma and 16.7 ± 0.3-17.4 ± 0.4 Ma, respectively, which are identical to each other within analytical errors but are systematically older than although marginally overlap with the Re-Os isochron ages of 15.36 ± 0.21-16.41 ± 0.48 Ma. The Qulong porphyries have geochemical characteristics of typical adakites, with Sr = 259-1195 ppm, Y = 1.91-9.12 ppm, Yb = 0.2-0.92 ppm, Sr/Y = 49-202 ppm, and (La/Yb)n = 13-49 for both ore-bearing and barren adakites. In a Sr/Y versus (La/Yb)n diagram, most of the samples plot in the low part of circum-Pacific field, close to the field defined by Dabie adakites. Some of the ore-bearing adakites even plot in the Dabie adakite field, indicating that both slab melts and lower continental crust melts have been involved. Zircons from the ore-bearing adakites have δ18O ranging from 5.1 to 7.3‰ (average 6.4‰) and εHf(t) from 1.9 to 10.4‰, which plot close to MORB. Similarly, zircons from the barren adakite have δ18O ranging from 4.0 to 7.4

  14. Iron deposits in relation to magmatism in China

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaochong; Santosh, M.; Li, Jianwei

    2015-12-01

    China has a rich reserve of iron ores, and hosts most of the major types of iron deposits recognized over the world. However, most of these deposits are low-grade ores (<50% Fe), and the high-grade iron ores only account for ˜1% of the total iron ore resources (Zhang et al., 2014a). During 50s to 70s of the last century, two major research and exploration programmes were implemented on national level in China, focusing on the high-grade iron ores of banded iron formation (BIF) deposits. However, apart from several small deposits, no large high-grade iron deposits under the BIF category were discovered. Thus, the exploration and scientific studies on iron deposits came to a dead-end during 1980's to 2005. In the recent years, however, there has been an increasing demand for iron resources due to China's rapid industrialization and economic development. Thus, a new surge of studies and prospecting of high-grade iron deposits started, which resulted in many advances in our understanding of the formation and exploration of iron deposits.

  15. A Paleozoic anorthosite massif related to rutile-bearing ilmenite ore deposits, south of the Polochic fault, Chiapas Massif Complex, Mexico

    NASA Astrophysics Data System (ADS)

    Cisneros, A.; Ortega-Gutiérrez, F.; Weber, B.; Solari, L.; Schaaf, P. E.; Maldonado, R.

    2013-12-01

    The Chiapas Massif Complex in the southern Maya terrane is mostly composed of late Permian igneous and meta-igneous rocks. Within this complex in southern Mexico and in the adjacent San Marcos Department of Guatemala, south of the Polochic fault, several small outcrops (~10 km2) of a Phanerozoic andesine anorthosite massif were found following an E-W trend similar to the Polochic-Motagua Fault System. Such anorthosites are related to rutile-bearing ilmenite ore deposits and hornblendite-amphibolite bands (0.1-3 meters thick). The anorthosites show recrystallization and metamorphic retrogression (rutile with titanite rims), but no relicts of high-grade metamorphic minerals such as pyroxene or garnet have been found. In Acacoyagua, Chiapas, anorthosites are spatially related to oxide-apatite rich mafic rocks; in contrast, further to the west in Motozintla, they are related to monzonites. Zircons from these monzonites yield a Permian U-Pb age (271.2×1.4 Ma) by LA-MC-ICPMS. Primary mineral assemblage of the anorthosites include mostly medium to fine-grained plagioclase (>90%) with rutile and apatite as accessory minerals, occasionally with very low amounts of quartz. Massive Fe-Ti oxide lenses up to tens of meters in length and few meters thick are an ubiquitous constituent of these anorthosites and their mineralogy include ilmenite (with exsolution lamellae of Ti-magnetite), rutile, magnetite, clinochlore, ×spinel, ×apatite, ×zircon and srilankite (Ti2ZrO6, first finding of this phase in Mexico). Rutile occurs within the massive ilmenite in two morphological types: (1) fine-grained (5-40 μm) rutile along ilmenite grain boundaries or fractures, and (2) coarse-grained rutile (<5 mm) as discrete grains, whereas magnetite and srilankite only appear as small grains along ilmenite boundaries. Zircon is present as discontinuously aligned small grains (10-40 μm) forming rims around many rutile and ilmenite grains. Attempts to date zircon rims by U-Pb using LA

  16. Genetic implications of regional and temporal trends in ore fluid geochemistry of Mississippi Valley-type deposits in the Ozark region

    USGS Publications Warehouse

    Viets, J.G.; Leach, D.L.

    1990-01-01

    Fluids extracted from aqueous fluid inclusions in epigenetic gangue and ore minerals record the migration of huge volumes of highly saline fluids throughout the stratigraphic section of the Ozark region. The extracted fluids share many similarities regionally, but there are significant temporal differences which define two geochemically distinct end-member ore-forming fluids, referred to as the Viburnum Trend main stage or Viburnum Trend type and the Tri-State type. Possible explanations for the origins of these two end-member fluids are discussed. -from Authors

  17. Uranium mill ore dust characterization

    SciTech Connect

    Knuth, R.H.; George, A.C.

    1980-11-01

    Cascade impactor and general air ore dust measurements were taken in a uranium processing mill in order to characterize the airborne activity, the degree of equilibrium, the particle size distribution and the respirable fraction for the /sup 238/U chain nuclides. The sampling locations were selected to limit the possibility of cross contamination by airborne dusts originating in different process areas of the mill. The reliability of the modified impactor and measurement techniques was ascertained by duplicate sampling. The results reveal no significant deviation from secular equilibrium in both airborne and bulk ore samples for the /sup 234/U and /sup 230/Th nuclides. In total airborne dust measurements, the /sup 226/Ra and /sup 210/Pb nuclides were found to be depleted by 20 and 25%, respectively. Bulk ore samples showed depletions of 10% for the /sup 226/Ra and /sup 210/Pb nuclides. Impactor samples show disequilibrium of /sup 226/Ra as high as +-50% for different size fractions. In these samples the /sup 226/Ra ratio was generally found to increase as particle size decreased. Activity median aerodynamic diameters of the airborne dusts ranged from 5 to 30 ..mu..m with a median diameter of 11 ..mu..m. The maximum respirable fraction for the ore dusts, based on the proposed International Commission on Radiological Protection's (ICRP) definition of pulmonary deposition, was < 15% of the total airborne concentration. Ore dust parameters calculated for impactor duplicate samples were found to be in excellent agreement.

  18. Paragenesis and chemistry of multistage tourmaline formation in the sullivan Pb-Zn-Ag deposit, British Columbia

    USGS Publications Warehouse

    Jiang, S.-Y.; Palmer, M.R.; Slack, J.F.; Shaw, D.R.

    1998-01-01

    /rock conditions, rather than control by the chemical composition of the original host sediments. Rare Fe-rich schorl within the bedded Pb-Zn-Ag ores is believed to have formed on the sea floor by reaction of an Fe-rich brine pool with detrital aluminous sediments. Postore emplacement of gabbro sills and local dikes in the footwall produced Fe-rich hydrothermal fluids, which were responsible for formation of minor Fe-rich dravite-schorl which overprinted earlier dravite. Postore, but synsedimentary, hydrothermal alteration involving entrained seawater was responsible for deposition of dravite and uvite in the hanging wall and for dravite in the brown tourmalinites of the shallow footwall. Mg-rich dravite-uvite associated with chlorite and in discordant rims on schorl in the bedded ores formed by sulfide-silicate reactions during greenschist facies regional metamorphism.

  19. Fundamental studies of the mechanisms of slag deposit formation: Final report

    SciTech Connect

    Austin, L.G.; Benson, S.; Rabinovich, A.; Tangsathitkulchai, M.; Schobert H.H.

    1987-07-01

    The kinetics of ash deposition on utility boilers have been studied. A heated tube furnace system was used in the study. Areas of consideration in the deposition mechanics were: close space knowledge of chemical composition and distribution of inorganic constituents in coal, transformations and reactions of the inorganic constituents in the flame, ash transport mechanisms, initial adhesion of ash particles to heat transfer surfaces and subsequently to each other to form a deposit, and further interactions of the deposited ash to grow a strong deposit. Interactions of deposited ash that cause changes in physical and chemical properties in an aged deposit are due to processes such as sintering, chemical reactions, and melting. The degree of these changes increases as the deposit grows from the heat transfer surfaces where it forms. All of these changes during the deposit formation process are coal-specific and are strongly dependent on the boiler configuration and operating conditions. 18 refs., 55 figs., 42 tabs.

  20. 2.8-Ma ash-flow caldera at Chegem River in the northern Caucasus Mountains (Russia), contemporaneous granites, and associated ore deposits

    USGS Publications Warehouse

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

    1993-01-01

    Diverse latest Pliocene volcanic and plutonic rocks in the north-central Caucasus Mountains of southern Russia are newly interpreted as components of a large caldera system that erupted a compositionally zoned rhyolite-dacite ash-flow sheet at 2.83 ?? 0.02 Ma (sanidine and biotite 40Ar/39Ar). Despite its location within a cratonic collision zone, the Chegem system is structurally and petrologically similar to typical calderas of continental-margin volcanic arcs. Erosional remnants of the outflow Chegem Tuff sheet extend at least 50 km north from the source caldera in the upper Chegem River. These outflow remnants were previously interpreted by others as erupted from several local vents, but petrologic similarities indicate a common origin and correlation with thick intracaldera Chegem Tuff. The 11 ?? 15 km caldera and associated intrusions are superbly exposed over a vertical range of 2,300 m in deep canyons above treeline (elev. to 3,800 m). Densely welded intracaldera Chegem Tuff, previously described by others as a rhyolite lava plateau, forms a single cooling unit, is > 2 km thick, and contains large slide blocks from the caldera walls. Caldera subsidence was accommodated along several concentric ring fractures. No prevolcanic floor is exposed within the central core of the caldera. The caldera-filling tuff is overlain by andesitic lavas and cut by a 2.84 ?? 0.03-Ma porphyritic granodiorite intrusion that has a cooling age analytically indistinguishable from that of the tuffs. The Eldjurta Granite, a pluton exposed low in the next large canyon (Baksan River) 10 km to the northwest of the caldera, yields variable K-feldspar and biotite ages (2.8 to 1.0 Ma) through a 5-km vertical range in surface and drill-hole samples. These variable dates appear to record a prolonged complex cooling history within upper parts of another caldera-related pluton. Major W-Mo ore deposits at the Tirniauz mine are hosted in skarns and hornfels along the roof of the Eldjurta Granite

  1. Main types of gold ore forming systems and their relationship with the paleogeodynamic settings on the Taimyr Peninsula and the Severnaya Zemlya Archipelago

    NASA Astrophysics Data System (ADS)

    Proskurnin, Vasiliy; Anatoly, Gavrish; Aleksandra, Bagaeva; Petrushkov, Boris; Shneider, Alexey; Saltanov, Vasily; Stepunina, Maria; Proskurnina, Alina

    2014-05-01

    carbonate-terrigenous carbonaceous deposits and tectonic-hydrothermal (propylite-beresite) in plutonic-volcanic complexes (Malinovsky, Gagarinsky, Svetlinsky ore zones). Late Paleozoic - Early Mesozoic manifestations of plutonic - hydrothermal ore-forming systems are associated: for gold - (sulphide) - quartz formation - with development of early deuterogenic diorite- granitoids of the diorite-granodiorite formation (I - type) and confinement to the remote from granites exocontact areas of greenschist facies (Osnovnoy Creek, Lagerninsky ore zones); for gold-bearing copper-molybdenum-porphyry formation - with development of late deuterogenic subalkaline granites of A-type and confinement to the apical areas of massifs (Oleninsky, Shirokinsky, Uboyninsky ore clusters).

  2. Tectonic breccias--conduits for ore-bearing and metasomatic fluids in the Jabiluka unconformity-type uranium-gold deposit, Northern Territory, Australia

    SciTech Connect

    Nutt, C.J.; Grauch, R.I.

    1985-01-01

    The distribution of strata-bound uranium ore in the highly chloritized Early Proterozoic metasedimentary rocks at Jabiluka, Australia, is controlled by shear zones associated with repeated episodes of brittle deformation. Based on extensive study of drill-hole core, the authors proposed tectonic control of ore distribution contrasts with most previous Jabiluka models that emphasize carbonate solution and collapse as the primary cause of brecciation. The strata-bound character of the ore, which is predominantly in chlorite, chlorite+graphite, and siliceous breccias, is a function of the susceptibility of specific rock types to shear and fracture. The siliceous breccias, which may in part be preferentially brecciated and silicified magnesite and dolomite, commonly contain fragments of sheared and strained quartz in recrystallized quartz matrix. Mineralized schist fragments and broken uraninite veins in breccias indicate that some of the brecciation occurred after a major mineralizing event. Brecciated zones and fractures are cemented and filled by quartz and by Mg-rich chlorite and 7A amesite. The presence of at least three generations of quartz in siliceous breccias and a number of optically, and in some cases chemically, distinguishable chlorites in chlorite breccias indicates that repeated pulses of fluids moved through the broken rocks. The circulation of these fluids redistributed and possibly further concentrated preexisting ore.

  3. Modeling of formation of deposited layer by plasma spray process

    NASA Astrophysics Data System (ADS)

    Lee, Joo-Dong; Ra, Hyung-Yong; Hong, Kyung-Tae; Hur, Sung-Kang

    1992-03-01

    An analytical model is developed to describe the plasma deposition process in which average solidified thickness and coating and substrate temperatures are obtained. During the deposition process, the solidification rate is periodically varied, due to the impingement of liquid splats, and the amount of liquid in the coating layer increases. Periodical variation of the solidification rate causes temperature fluctuation in coating and substrate. The nature of interfacial structure of plasma-sprayed NiCrBSi MA powder is compared with the result predicted using the model, which indicates that the liquid deposited at the coating surface during deposition causes discontinuous boundaries within the coating. The spraying rate and the solidification rate reverse periodically with spraying process.

  4. Trace elements in magnetite from massive iron oxide-apatite deposits indicate a combined formation by igneous and magmatic-hydrothermal processes

    NASA Astrophysics Data System (ADS)

    Knipping, Jaayke L.; Bilenker, Laura D.; Simon, Adam C.; Reich, Martin; Barra, Fernando; Deditius, Artur P.; Wälle, Markus; Heinrich, Christoph A.; Holtz, François; Munizaga, Rodrigo

    2015-12-01

    Iron oxide-apatite (IOA) deposits are an important source of iron and other elements (e.g., REE, P, U, Ag and Co) vital to modern society. However, their formation, including the namesake Kiruna-type IOA deposit (Sweden), remains controversial. Working hypotheses include a purely magmatic origin involving separation of an Fe-, P-rich, volatile-rich oxide melt from a Si-rich silicate melt, and precipitation of magnetite from an aqueous ore fluid, which is either of magmatic-hydrothermal or non-magmatic surface or metamorphic origin. In this study, we focus on the geochemistry of magnetite from the Cretaceous Kiruna-type Los Colorados IOA deposit (∼350 Mt Fe) located in the northern Chilean Iron Belt. Los Colorados has experienced minimal hydrothermal alteration that commonly obscures primary features in IOA deposits. Laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) transects and electron probe micro-analyzer (EPMA) wavelength-dispersive X-ray (WDX) spectrometry mapping demonstrate distinct chemical zoning in magnetite grains, wherein cores are enriched in Ti, Al, Mn and Mg. The concentrations of these trace elements in magnetite cores are consistent with igneous magnetite crystallized from a silicate melt, whereas magnetite rims show a pronounced depletion in these elements, consistent with magnetite grown from an Fe-rich magmatic-hydrothermal aqueous fluid. Further, magnetite grains contain polycrystalline inclusions that re-homogenize at magmatic temperatures (>850 °C). Smaller inclusions (<5 μm) contain halite crystals indicating a saline environment during magnetite growth. The combination of these observations are consistent with a formation model for IOA deposits in northern Chile that involves crystallization of magnetite microlites from a silicate melt, nucleation of aqueous fluid bubbles on magnetite surfaces, and formation and ascent of buoyant fluid bubble-magnetite aggregates. Decompression of the fluid-magnetite aggregate

  5. Ramp-style deposition of Oligocene Marine Vedder formation, San Joaquin Valley, California

    SciTech Connect

    Bloch, R.B.

    1986-04-01

    The Oligocene Vedder formation consists of well-sorted medium to fine-grained marine sand and shale in the subsurface of the eastern San Joaquin Valley. Updip, this formation interfingers with nonmarine/lagoonal facies known as the Walker Formation. This relationship appears to be transgressive because the marine Vedder generally overlies the Walker Formation. Downdip, the Vedder sands interfinger with middle to lower bathyal shale in a progradational manner, forming upward-coarsening patterns in well logs. Depositional water depths for the shale were determined from benthic foraminifera assemblages. The Vedder formation is approximately 750 ft thick along its updip part, and gradually thickens to 1500 ft downdip. Overall deposition geometry, determined from well-log correlations and seismic data, is generally parallel and downlapping. A prominent shelf-slope break is not evident. Rather, depositional surfaces are tabular or broadly lobate, with a depositional slope of 5/sup 0/-10/sup 0/. This geometry of constant slope between nonmarine and deep marine water depth is termed a ramp. The depositional style and geometry are similar to that of the Oligocene upper Pleito Formation, which crops out in the San Emigdio Mountains on the southern margin of the San Joaquin Valley. The Vedder formation was deposited subsequent to a period of rapid subsidence (about 50 cm/1000 years), as determined from geohistory analysis of well data on the Bakersfield arch. This rapid subsidence may have induced deposition in a ramp geometry, rather than a shelf-slope configuration.

  6. The characteristics of coignimbrite deposits and inferences for their formation

    NASA Astrophysics Data System (ADS)

    Engwell, S. L.; Eychenne, J.; Wulf, S.; De'Michieli Vitturi, M.

    2014-12-01

    Coignimbrite deposits form as fine-grained ash (< 250 microns) is lofted into the atmosphere from the top of pyroclastic density currents, producing convective plumes. Such material can be transported over continental sized areas and the fine-grained nature of this ash means that it poses great hazard, in respect to health, infrastructure and air traffic. To date, few coignimbrite deposits have been studied in detail, mainly due to their poor preservation potential, and difficulty distinguishing these deposits from Plinian deposits. As such, there is little in the published record regarding the physical characteristics of coignimbrite deposits. Deposits from Lago Grande di Monticchio, a maar lake 120 km east of the Campanian Volcanic Zone, Italy were analysed for this study. These lake sediments contain more than 340 distinct tephra layers, of which more than 300 are thought to have originated from the Campanian region. The physical characteristics of deposits from eruptions from within the past 50 kyrs are studied with particular emphasis placed on those with a known pyroclastic density current phase. Results show that in most cases, stratigraphy is comparable to proximal stratigraphy, and in the case of the Campanian Ignimbrite (Phlegrean Fields, 39.3 ka) and Monte Epomeo Green Tuff (Ischia, 55 ka) particularly, the coignimbrite contribution is easily identified. These coignimbrite deposits are composed of glass shards, with very small lithic and expanded pumice contents. Grainsize data from these coignimbrite events show remarkably similar characteristics, typically described by a very fine-grained mode (~50 microns), and poor sorting. This fine grain size implicates aggregation as the dominant process by which this ash is deposited. Similar trends are identified in the literature, for different types and scales of eruptions indicating the grainsize of these deposits is controlled by current dynamics rather than primary eruptive conditions at the vent. The

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  8. Reactive flow models of the Anarraaq Zn-Pb-Ag deposit, Red Dog district, Alaska

    USGS Publications Warehouse

    Schardt, C.; Garven, G.; Kelley, K.D.; Leach, D.L.

    2008-01-01

    The Red Dog ore deposit district in the Brooks Range of northern Alaska is host to several high-grade, shale-hosted Zn + Pb deposits. Due to the complex history and deformation of these ore deposits, the geological and hydrological conditions at the time of formation are poorly understood. Using geological observations and fluid inclusion data as constraints, numerical heat and fluid flow simulations of the Anarraaq ore deposit environment and coupled reactive flow simulations of a section of the ore body were conducted to gain more insight into the conditions of ore body formation. Results suggest that the ore body and associated base metal zonation may have formed by the mixing of oxidized, saline, metal-bearing hydrothermal fluids (<200??C) with reducing, HS-rich pore fluids within radiolarite-rich host rocks. Sphalerite and galena concentrations and base metal sulfide distribution are primarily controlled by the nature of the pore fluids, i.e., the extent and duration of the HS- source. Forward modeling results also predict the distribution of pyrite and quartz in agreement with field observations and indicate a reaction front moving from the initial mixing interface into the radiolarite rocks. Heuristic mass calculations suggest that ore grades and base metal accumulation comparable to those found in the field (18% Zn, 5% Pb) are predicted to be reached after about 0.3 My for initial conditions (30 ppm Zn, 3 ppm Pb; 20% deposition efficiency). ?? Springer-Verlag 2008.

  9. Comparison of the native antimony-bearing Paiting gold deposit, Guizhou Province, China, with Carlin-type gold deposits, Nevada, USA

    NASA Astrophysics Data System (ADS)

    Xie, Zhuo-Jun; Xia, Yong; Cline, Jean S.; Yan, Bao-Wen; Wang, Ze-Peng; Tan, Qin-Ping; Wei, Dong-Tian

    2016-03-01

    The Paiting gold deposit, Guizhou Province, China, has been regarded as a Carlin-type gold deposit by several researchers. Alteration and ore-related minerals from the Paiting deposit were examined, and results were compared with the Cortez Hills Carlin-type gold deposit, Nevada, USA. Similarities include the structural and stratigraphic controls on the orebodies in both deposits and the occurrence of invisible gold ionically bound in arsenian pyrite. Significant differences include the following: (1) The gold-bearing mineral in Nevada is arsenian pyrite. However, gold-bearing minerals in the Paiting deposit include arsenopyrite, arsenian pyrite, and trace pyrrhotite. Also, euhedral or subhedral gold-bearing arsenian pyrite at Paiting contains significantly less As, Cu, and Hg than gold-bearing pyrite from Nevada. (2) Alteration in the Paiting deposit displays significantly less decarbonatization. Instead, dolomite precipitation, which has not been described in Nevada deposits, is associated with deposition of gold-bearing sulfide minerals. (3) Stibnite and minor native antimony typify Paiting late-ore-stage minerals, whereas in Nevada, realgar, orpiment, and calcite are common late-ore-stage minerals. Precipitation of native antimony in the Paiting deposit reflects the evolution of a late-ore fluid with unusually low sulfur and oxygen fugacities. Some characteristics of the Paiting gold deposit, including formation of ore-stage dolomite and precipitation from CO2-rich ore fluids at temperatures in excess of 250 °C, are more typical of orogenic deposits than Nevada Carlin deposits. The presence of similarities in the Paiting deposit to both Carlin type and orogenic deposits is consistent with formation conditions intermediate to those typical of Carlin type and orogenic systems.

  10. Ash Deposit Formation and Deposit Properties. A Comprehensive Summary of Research Conducted at Sandia's Combustion Research Facility

    SciTech Connect

    Larry L. Baxter

    2000-08-01

    This report summarizes experimental and theoretical work performed at Sandia's Combustion Research Facility over the past eight years on the fate of inorganic material during coal combustion. This work has been done under four broad categories: coal characterization, fly ash formation, ash deposition, and deposit property development. The objective was to provide sufficient understanding of these four areas to be able to predict coal behavior in current and advanced conversion systems. This work has led to new characterization techniques for fuels that provide, for the first time, systematic and species specific information regarding the inorganic material. The transformations of inorganic material during combustion can be described in terms of the net effects of the transformations of these individual species. Deposit formation mechanisms provide a framework for predicting deposition rates for abroad range of particle sizes. Predictions based on these rates many times are quite accurate although there are important exceptions. A rigorous framework for evaluating deposit has been established. Substantial data have been obtained with which to exercise this framework, but this portion of the work is less mature than is any other. Accurate prediction of deposit properties as functions of fuel properties, boiler design, and boiler operating conditions represents the single most critical area where additional research is needed.

  11. The origin of manganese-rich metasediments and their relationship to iron formation and base metal deposits, western Georgia piedmont

    SciTech Connect

    Wonder, J.D.

    1987-08-01

    Manganiferous metasediments (coticules), banded iron-formation, and tourmaline-quartz rocks (tourmalinites) are found in close spatial association to each other and to volcanogenic base metal sulfide and gold deposits in the Northern Piedmont of western Georgia. Coticules, which consist of up to 90% garnet and contain from 1 to 15 weight % MnO and 14 to 37 % Fe/sub 2/O/sub 3/, are often hosted by metabasalt. Tourmalinites occur as poorly-bedded aggregates or disseminations and are also found locally associated with metabasalt. Trace element analyses of coticules yield conflicting results. Cu + Co + Ni values and Zr/Cr ratios are low and indicate a hydrothermal origin. Alumina concentrations, Y/P/sub 2/O/sub 5/% ratios, and Th values indicate the probable presence of pelagic sediments in the protolith. Rare earth element patterns are enriched in the light elements and have slight negative Eu anomalies, resembling the patterns of pelagic clays most closely. The protolith of coticules was apparently a hydrothermal sediment with pelagic and/or terrigenous input. Tourmaline in tourmalinites is chemically similar to stratabound sulfide-related examples. Both coticules and tourmalinites are interpreted as metamorphosed seafloor exhalative sediments and thus indicate the potential for the presence of genetically related ore mineralization.

  12. The connection between iron ore formations and "mud-shrimp" colonizations around sunken wood debris and hydrothermal sediments in a Lower Cretaceous continental rift basin, Mecsek Mts., Hungary

    NASA Astrophysics Data System (ADS)

    Jáger, Viktor; Molnár, Ferenc; Buchs, David; Koděra, Peter

    2012-09-01

    In the Early Cretaceous, the continental rift basin of the Mecsek Mts. (Hungary), was situated on the southern edge of the European plate. The opening of the North Atlantic Ocean created a dilatational regime that expanded to the southern edge of the European plate, where several extensional basins and submarine volcanoes were formed during the Early Cretaceous epoch. Permanent seaquake activity caused high swell events during which a large amount of terrestrial wood fragments entered into submarine canyons from rivers or suspended woods which had sunk into the deep seafloor. These fragments created extended wood-fall deposits which contributed large-scale flourishing of numerous burrowing thalassinid crustaceans. Twelve different thalassinid coprolite ichnospecies can be found in the Berriasian-Hauterivian volcano-sedimentary formations. According to the seladonitic crustacean burrows which associated with framboidal pyrite containing Zoophycos and Chondrites ichnofossils (i.e. a "fodinichnia" trace fossil association), the bottom water was aerobic and the pore water was anaerobic; in the latter sulfate reduction occurred. The preservation of wood fragments around thalassinid burrows can be explained by rapid sedimentation related to turbidity currents. Due to the low temperature hydrothermal circulations of seawater, large amounts of iron were released from intrusive, pillowed basaltic sills; these sills intruded into soft, water-saturated sediments containing large amounts of thalassinid excrement. In the coprolites can be found idiomorphic mineral particles originating from the basalts, and coprolites can often be found in peperitic interpillow sediments. This indicates that the life-activity of the decapoda crustaceans in many Lower Cretaceous occurrences initially preceded the first magmatic eruptions. The paroxysm of the rift volcanism took place during the Valanginian age, when some submarine volcanoes emerged above sea level, reaching a maximum height of

  13. Application of LANDSAT satellite imagery for iron ore prospecting in the western desert of Egypt

    NASA Technical Reports Server (NTRS)

    Elshazly, E. M.; Abdel-Hady, M. A.; Elghawaby, M. A.; Khawasik, S. M. (Principal Investigator)

    1977-01-01

    The author has identified the following significant results. The delineation of the geological units and geological structures through image interpretation, corroborated by field observations and structural analysis, led to the discovery of new iron ore deposits. A new locality for iron ore deposition, namely Gebel Qalamun, was discovered, as well as new occurrences within the already known iron ore region of Bahariya Oasis.

  14. Quantifying fat, oil, and grease deposit formation kinetics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fat, oil, and grease (FOG) deposits formed in sanitary sewers are calcium-based saponified solids that are responsible for a significant number of nationwide sanitary sewer overflows (SSOs) across United States. In the current study, the kinetics of lab-based saponified solids were determined to un...

  15. Mass-movement deposits in the lacustrine Eocene Green River Formation, Piceance Basin, western Colorado

    USGS Publications Warehouse

    Johnson, Ronald C.; Birdwell, Justin E.; Brownfield, Michael E.; Mercier, Tracey J.

    2015-01-01

    The Eocene Green River Formation was deposited in two large Eocene saline lakes, Lake Uinta in the Uinta and Piceance Basins and Lake Gosiute in the Greater Green River Basin. Here we will discuss mass-movement deposits in just the Piceance Basin part of Lake Uinta.

  16. Factors That Influence Properties of FOG Deposits and Their Formation in Sewer Collection Systems.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the formation of Fat, Oil, and Grease (FOG) deposits in sewer systems is critical to the sustainability of sewer collection systems since they have been implicated in causing sewerage blockages, which eventually lead to sanitary sewer overflows (SSOs). Recently, FOG deposits in sewer ...

  17. Microfacies and depositional environment of the Paleocene-Eocene Jahrum Formation (SW Iran)

    NASA Astrophysics Data System (ADS)

    Noormohammadi, Zohreh; Vazirimoghadam, Hossein

    2010-05-01

    The Jahrum Formation a thick carbonate succession of the Paleocene-Eocene in Zagros Mountains (south west Iran), has been studied to determine its microfacies and paleoenvironments. Detailed petrograhic analysis of the deposits led to the recognition, four major depositional environments were identified in the Jahrum Formation. These include tidal flat, lagoon, barrier and open marine environmental setting and are interpreted as a carbonate platform developed in a homoclinal ramp situation.

  18. Oxidation and formation of deposit precursors in hydrocarbon fuels

    NASA Technical Reports Server (NTRS)

    Buttrill, S. E., Jr.; Mayo, F. R.; Lan, B.; St.john, G. A.; Dulin, D.

    1982-01-01

    A practical fuel, home heating oil no. 2 (Fuel C), and the pure hydrocarbon, n-dodecane, were subjected to mild oxidation at 130 C and the resulting oxygenated reaction products, deposit precursors, were analyzed using field ionization mass spectrometry. Results for fuel C indicated that, as oxidation was initially extended, certain oxygenated reaction products of increasing molecular weights in the form of monomers, dimers and some trimers were produced. Further oxidation time increase resulted in further increase in monomers but a marked decrease in dimers and trimers. This suggests that these larger molecular weight products have proceeded to form deposit and separated from the fuel mixture. Results for a dodecane indicated that yields for dimers and trimers were very low. Dimers were produced as a result of interaction between oxygenated products with each other rather than with another fuel molecule. This occurred even though fuel molecule concentration was 50 times, or more greater than that for these oxygenated reaction products.

  19. Formation of diamond nanoparticle thin films by electrophoretic deposition

    NASA Astrophysics Data System (ADS)

    Goto, Yosuke; Ohishi, Fujio; Tanaka, Kuniaki; Usui, Hiroaki

    2016-03-01

    Thin films of diamond nanoparticles were prepared by electrophoretic deposition (EPD) using 0.5 wt % dispersions in water, ethanol, and 2-propanol. The film growth rate increased with increasing voltage applied to the electrodes. However, an excessive increase in voltage caused the degradation of film morphology. The optimum voltage was 4 V with an electrode separation of 5 mm. The film growth rate was higher in organic solvents than in water. The deposited film had a smooth surface with an average surface roughness comparable to the size of primary particles of the source material. It is notable that the EPD films had a considerably higher physical stability than spin-coated and cast films. The stability was further improved by thermally annealing the films. IR analysis revealed that the diamond nanoparticles have carboxy and amino groups on their surfaces. It is considered that the stability of the EPD films originate from a chemical reaction between these functional groups.

  20. Supercritical fluid molecular spray film deposition and powder formation

    DOEpatents

    Smith, Richard D.

    1986-01-01

    Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. Upon expansion and supersonic interaction with background gases in the low pressure region, any clusters of solvent are broken up and the solvent is vaporized and pumped away. Solute concentration in the solution is varied primarily by varying solution pressure to determine, together with flow rate, the rate of deposition and to control in part whether a film or powder is produced and the granularity of each. Solvent clustering and solute nucleation are controlled by manipulating the rate of expansion of the solution and the pressure of the lower pressure region. Solution and low pressure region temperatures are also controlled.

  1. Genesis of Carlin-type gold deposits

    SciTech Connect

    Burton, J.C.; Lawler, J.P.; Ayres, D.E.

    1985-01-01

    Carlin-type deposits are large, disseminated, sediment-hosted gold ore bodies. They are of major economic interest to mining companies because they represent low-cost, bulk-mineable targets. To develop a genetic model for the Carlin-type deposits, the authors have employed a multidisciplinary research program on ten Carlin-type deposits in Nevada and Utah. Studies included rock geochemistry, alteration mineralogy, fluid inclusions, oxygen isotopes, incremental Ar/sup 40/-Ar/sup 38/ age dating, hydrothermal experiments on temperature-stability relationships of gold complexes, and physical properties of host rocks. Their studies demonstrate that Carlin-type deposits are formed at initial temperatures of approximately 250/sup 0/C by acidic, reducing, low salinity, Tertiary, meteoric fluids. Gold is transported as a chloride complex and deposition occurs in response to destabilization of this complex with decreasing temperature. Temperature is the major parameter controlling ore deposition. The physical properties of the host environment place major constraints on ore formation in addition to temperature. In the Carlin systems studied, high porosity host rocks are capped by structural or stratigraphic closures which trap the ore fluid. The deposits do not necessarily form near the surface, and models based solely on analogies to hot springs systems may be misleading.

  2. Formation of Deep Sea Umber Deposits Linked to Microbial Metal Oxidation at the South Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Peng, Xiaotong; Ta, Kaiwen; Chen, Shun; Zhang, Lijuan; Xu, Hengchao

    2015-04-01

    Umber deposits are important metalliferous deposits, which occur in off-axis half-graben structures at ancient and modern ocean floor. The genesis of umber deposits has remained controversial for several decades. Recently, microbial Fe(II) oxidation associated with low-temperature diffuse venting has been identified as a key process for the formation of umber deposits, but the exact biochemical mechanisms involved to the precipitation of Mn oxides and co-precipitation of Fe oxyhydroxides and Mn oxides in umber deposits still remain unknown. Here, we used nano secondary ion mass spectrometer, synchrotron-based X-ray absorption spectroscopy, electron microscopy, and molecular techniques to demonstrate the coexistence of two types of metal-oxidizing bacteria within deep-sea hydrothermal umber deposits at the South Atlantic Ridge, where we found unique spheroids composed of biogenic Fe oxyhydroxides and Mn oxides in the deposits. Our data suggest that Fe oxyhydroxides and Mn oxides are metabolic by-products of lithotrophic Fe(II)-oxidizing bacteria and heterotrophic Mn(II)-oxidizing bacteria, respectively. The hydrothermal vents fuel lithotrophic Fe(II)-oxidizing bacteria, which constitute a trophic base that may support the activities of heterotrophic Mn(II)-oxidizing bacteria. The biological origin of umber deposits underscore the importance of geomicrobiologcial interaction in triggering the formation of deep-sea deposits, with important implications for the generation of submarine Mn deposits and crusts.

  3. Magmatic-vapor expansion and the formation of high-sulfidation gold deposits: Chemical controls on alteration and mineralization

    USGS Publications Warehouse

    Henley, R.W.; Berger, B.R.

    2011-01-01

    Large bulk-tonnage high-sulfidation gold deposits, such as Yanacocha, Peru, are the surface expression of structurally-controlled lode gold deposits, such as El Indio, Chile. Both formed in active andesite-dacite volcanic terranes. Fluid inclusion, stable isotope and geologic data show that lode deposits formed within 1500. m of the paleo-surface as a consequence of the expansion of low-salinity, low-density magmatic vapor with very limited, if any, groundwater mixing. They are characterized by an initial 'Sulfate' Stage of advanced argillic wallrock alteration ?? alunite commonly with intense silicification followed by a 'Sulfide' Stage - a succession of discrete sulfide-sulfosalt veins that may be ore grade in gold and silver. Fluid inclusions in quartz formed during wallrock alteration have homogenization temperatures between 100 and over 500 ??C and preserve a record of a vapor-rich environment. Recent data for El Indio and similar deposits show that at the commencement of the Sulfide Stage, 'condensation' of Cu-As-S sulfosalt melts with trace concentrations of Sb, Te, Bi, Ag and Au occurred at > 600 ??C following pyrite deposition. Euhedral quartz crystals were simultaneously deposited from the vapor phase during crystallization of the vapor-saturated melt occurs to Fe-tennantite with progressive non-equilibrium fractionation of heavy metals between melt-vapor and solid. Vugs containing a range of sulfides, sulfosalts and gold record the changing composition of the vapor. Published fluid inclusion and mineralogical data are reviewed in the context of geological relationships to establish boundary conditions through which to trace the expansion of magmatic vapor from source to surface and consequent alteration and mineralization. Initially heat loss from the vapor is high resulting in the formation of acid condensate permeating through the wallrock. This Sulfate Stage alteration effectively isolates the expansion of magmatic vapor in subsurface fracture arrays

  4. Geochemical and stable isotopic data on barren and mineralized drill core in the Devonian Popovich Formation, Screamer sector of the Betze-Post gold deposit, northern Carlin trend, Nevada

    USGS Publications Warehouse

    Christiansen, William D.; Hofstra, Albert H.; Zohar, Pamela B.; Tousignant, Gilles

    2011-01-01

    The Devonian Popovich Formation is the major host for Carlin-type gold deposits in the northern Carlin trend of Nevada. The Popovich is composed of gray to black, thin-bedded, calcareous to dolomitic mudstone and limestone deposited near the carbonate platform margin. Carlin-type gold deposits are Eocene, disseminated, auriferous pyrite deposits characterized by acid leaching, sulfidation, and silicification that are typically hosted in Paleozoic calcareous sedimentary rocks exposed in windows through siliceous sedimentary rocks of the Roberts Mountains allochthon. The Carlin trend currently is the largest gold producer in the United States. The Screamer ore zone is a tabular body on the periphery of the huge Betze-Post gold deposit. Screamer is a good place to study both the original lithogeochemistry of the Popovich Formation and the effects of subsequent alteration and mineralization because it is below the level of supergene oxidation, mostly outside the contact metamorphic aureole of the Jurassic Goldstrike stock, has small, high-grade ore zones along fractures and Jurassic dikes, and has intervening areas with lower grade mineralization and barren rock. In 1997, prior to mining at Screamer, drill core intervals from barren and mineralized Popovich Formation were selected for geochemical and stable isotope analysis. The 332, five-foot core samples analyzed are from five holes separated by as much as 2000 feet (600 meters). The samples extend from the base of the Wispy unit up through the Planar and Soft sediment deformation units into the lower part of the upper Mud unit of the Popovich Formation.

  5. Copper-silver deposits of the Revett Formation, Montana and Idaho: origin and resource potential

    USGS Publications Warehouse

    Frost, Thomas P.; Zientek, Michael L.

    2006-01-01

    The Revett Formation of northern Idaho and western Montana contains major stratabound copper-silver deposits near Troy, Rock Creek, and Rock Lake, Montana. To help the U.S. Forest Service (USFS) meet its goal of integrating geoscience information into the land-planning process, U.S. Geological Survey (USGS) scientists recently completed a compilation of regional stratigraphy and mineralogy of the Revett Formation and a mineral resource assessment of Revett-type copper-silver deposits. The USGS assessment indicates that a large area of USFS-administered land in northwestern Montana and northern Idaho may contain significant undiscovered Revett-type copper-silver deposits.

  6. Clay mineralogy of the Greenvale Ore Body, Queensland, Australia: Implications for the interpretation of paleoclimate

    SciTech Connect

    Lev, S.; Anderson, K.; Ramirez, B.; Sun, H.; Swank, R.; Yost, D.; Huff, W.; Maynard, J.B. . Dept. of Geology)

    1994-03-01

    A 3--5% nickel enriched laterite in the Greenvale Ore Body of Queensland, Australia, is the result of weathering a serpentinized ultramafic intrusion. Variations in solubilities and drainage, typical of laterite deposits, resulted in the formation of three primary zones: (1) the Saprolite zone, (2) the Intermediate zone, and (3) the Limonite zone. Within these zones, clay mineral species with distinct chemistries and/or mineralogies have been identified, including: Ni-rich Smectite, Halloysite, and Palygorskite. Clay minerals were analyzed using powder X-ray diffraction and SEM. Bulk chemistry was determined by X-ray fluorescence in an attempt to better constrain the chemical conditions at the time of formation of the clay minerals. Results indicate a complex drainage system and history for the Greenvale Ore Body. Based on the distribution of ore grade material, it is apparent that the deposit was initially characterized by fracture controlled drainage. Owing to precipitation of Ni-rich smectite, halloysite, and palygorskite, subsequent alteration of the ore body drainage network and/or local climate can be inferred.

  7. Tephrostratigraphy and depositional environment of young (<2.94 Ma) Hadar Formation deposits at Ledi-Geraru, Afar, Ethiopia

    NASA Astrophysics Data System (ADS)

    DiMaggio, Erin N.; Arrowsmith, J. Ramón; Campisano, Christopher J.; Johnson, Roy; Deino, Alan L.; Warren, Mark; Fisseha, Shimeles; Cohen, Andrew S.

    2015-12-01

    The Pliocene Hadar Formation, exposed throughout the lower Awash Valley, Ethiopia, chronicles the evolution and paleoenvironmental context of early hominins. Deposition of the Hadar Formation continued until at least 2.94 Ma, but what transpired in the Hadar Basin after this time remains poorly documented due to an erosional event that truncated the formation throughout much of the valley. Here we present geologic mapping and stratigraphic analysis of a 26 m-thick section of sedimentary rocks and tephras exposed in the Ledi-Geraru project area in the region of Gulfaytu. The section contains Hadar Formation strata younger than 2.94 Ma, and sediments that we interpret are Busidima Formation in age, <2.7 Ma. We use this record to place additional constraints on depositional environments and the tectonic and paleogeomorphic history of the region. The lower ∼20 m of section contains lacustrine deposits that conformably overly a 2.94 Ma marker bed (BKT-2U) that previously served as the uppermost dated tephra in the Hadar Formation. We identified seven post-BKT-2U tephras; three were analyzed for glass chemistry, and one yielded an 40Ar/39Ar age of 2.931 ± 0.017 Ma (1σ). Based on these analyses, the newly mapped deposits at Gulfaytu extend the top of the Hadar Formation, representing ca. 20 kyr of post-BKT-2 sedimentation. The Hadar Basin remained depositional following the BKT-2 eruptions, and paleolake Hadar was present at Gulfaytu at this time. An erosional surface marked by a conglomerate truncates the Hadar strata suggesting that the Gulfaytu region was also was influenced by significant changes to basin architecture well-documented elsewhere in the lower Awash Valley. In addition, geophysical models suggest that central Ledi Geraru hosts a thick subsurface lacustrine sedimentary record within the Hadar Basin. The results of this paper provide the outcrop and near surface characterization for the Hominin Sites and Paleolakes Drilling Project (HSPDP) effort at

  8. Environment of ore deposition in the Creede mining district, San Juan Mountains, Colorado; Part IV, source of fluids, from oxygen, hydrogen, and carbon isotope studies

    USGS Publications Warehouse

    Bethke, P.M.; Rye, R.O.

    1979-01-01

    The hydrogen isotopic composition of fluids responsible for formation of the near-surface silver-base metal vein deposits at Creede was measured by direct analysis of inclusion fluids in sphalerite, quartz, and rhodochrosite and was estimated from analyses of illite and chlorite. The oxygen isotopic composition was determined directly on inclusion fluids in sphalerite and was estimated from analyses of quartz, illite, rhodochrosite, siderite, and adularia. The carbon isotopic composition was estimated from analyses of rhodochrosite and siderite. The ranges in isotopic composition for water and CO2 in the fluids associated with the formation of each of the minerals is given below (number of determinations given in parentheses):Mineral delta D (sub H2) O ppm delta 18 O (sub H2) O ppm delta 13 C (sub CO2) ppmSphalerite -81 to -54 (4) -10.1 to -4.5 (4)Quartz -97 to -86 (4) -5.9 to 1.8 (18)Illite -62 to -50 (8) -1.6 to 1.2(7)Chlorite -64 to -55 (10) -2.2 to 0.8 (10)Adularia 4.2 (1)Rhodochrosite -82 to -78 (2) 4.2 to 9.4 (9) -5.7 to -4.2 (9)Siderite 4.9 to 9.9 (6) -6.9 to -2.7 (6)The delta D (sub H2) O and delta 18 O (sub H2) O values of fluids associated with the formation of sphalerite, quartz, illite/chlorite, and carbonate minerals differ substantially from one another, and these differences appear to have been maintained throughout the depositional history, regardless of the positions of the minerals in the paragenetic sequence.The data suggest that waters from three coexisting reservoirs fed the vein system alternately and episodically during vein formation, and apparently there was little mixing of the fluids from the different reservoirs. The hydrogen, oxygen, and carbon isotope data suggest that the carbonate waters were deep seated, probably dominantly magmatic, in origin. The sphalerite and illite/chlorite waters must have been dominantly meteoric in origin and substantially oxygen shifted by exchange with the volcanic country rocks. The quartz waters were

  9. Depositional environments of Permian Phosphoria Formation and related rocks, Leach Mountains, northeast Nevada

    SciTech Connect

    Martindale, S.G. )

    1991-02-01

    In the Leach Mountains, northeastern Nevada, the Phosphoria Formation is represented by phosphatic rocks of the late Leonardian Meade Peak Phosphatic Shale Tongue. The Meade Peak is overlain by dolomitic siltstones and chert, including black bedded chert, of the upper Leonardian( ) to lower Guadalupian Murdock Mountain Formation. The black bedded chert is related to the Rex Chert Member of the Phosphoria Formation. There is little consensus regarding depositional environments of the Meade Peak. Also, little work has been presented on the origin of the black bedded cherts such as in the Murdock Mountain and Rex Chert. Locally, a shallow subtidal to perhaps partly intertidal depositional model for the Meade Peak is based upon characteristics of reworked phosphatic clasts, a crowded and mixed shallow-water fauna, oolite beds, and stratigraphic position between shallow subtidal to supratidal rocks. Supratidal deposition of dolomitic siltstones and units of black bedded chert in the Murdock Mountain is based largely on abundant cauliflower-shaped blebs of chalcedony with shapes resembling modern anhydrite nodules. Also, zebraic chalcedony in the black bedded chert is interpreted as a replacement product of evaporite deposits. The setting in this southwestern part of the depositional basin of the Phosphoria Formation, in the late Leonardian, during the deposition of the Meade Peak, is interpreted as a network of shallow to very shallow marine basins and intervening, perhaps periodically merged shoals. Subsequently, during the late Leonardian( ) to early Guadalupian, there was a marine regression and the supratidal environment of the Murdock Mountain Formation was established.

  10. [Infrared Spectra Characteristics of the Silicate Nickel Ores: A Comparison Study on Different Ore Samples from Indonesia and China].

    PubMed

    Yang, Meng-li; Fu, Wei; Wang, Bao-hua; Zhang, Ya-qian; Huang, Xiao-rong; Niu, Hu-jie

    2015-03-01

    The silicate nickel ores developed in the lateritic nickel deposit, from Kolonodale, Sulawesi Island, Indonesia, and Yuanjiang, Yunnan province, China, were selected for the present study. The X-ray diffraction and Fourier infrared spectra were used to analyze the mineralogical attribute of laterite nickel ores from two different places. The results show that these two different silicate nickel ores have unique infrared spectra characteristics individually, which contributes to the ore classification. The silicate nickel ores from Kolonodale deposit, Indonesia, can be classified as the serpentine type, the montmorillonite + serpentine type, and the garnierite type. While, the silicate nickel ores from Yuanjiang deposit, China, can be classified as the serpentine type and the talc + serpentine type. Moreover, the mineral crystallinity of Yuanjiang nickel ores is generally better than Kolonodale nickel ores. According to the advantage of infrared absorption spectra in distinguishing mineral polytypes, it can be determined that lizardite is the main mineral type in the silicate nickel ores of the two deposits, and there is no obvious evidence of chrysotile and antigorite's existence. The characteristic of infrared absorption spectra also shows that frequency change of OH libration indicates Ni (Fe) replacing Mg in the serpentine type nickel-bearing mineral, that is, OH libration of serpentine moves to higher frequency, with the proportion of Ni (Fe) replacing Mg increasing. PMID:26117869

  11. Gold in the Brunswick No. 12 volcanogenic massive sulfide deposit, Bathurst Mining Camp, Canada: Evidence from bulk ore analysis and laser ablation ICP-MS data on sulfide phases

    NASA Astrophysics Data System (ADS)

    McClenaghan, Sean H.; Lentz, David R.; Martin, Jillian; Diegor, Wilfredo G.

    2009-07-01

    The 329-Mt Brunswick No. 12 volcanogenic massive sulfide deposit (total resource of 163 Mt at 10.4% Zn, 4.2% Pb, 0.34% Cu, and 115 g/t Ag) is hosted within a Middle Ordovician bimodal volcanic and sedimentary sequence. Massive sulfides are for the most part syngenetic, and the bulk of the sulfide ore occurs as a Zn-Pb-rich banded sulfide facies that forms an intimate relationship with a laterally extensive Algoma-type iron formation and defines the Brunswick Horizon. Zone refining of stratiform sulfides is considered to have resulted in the development of a large replacement-style Cu-rich basal sulfide facies, which is generally confined between the banded sulfide facies and an underlying stringer sulfide zone. Complex polyphase deformation and associated lower- to upper-greenschist facies regional metamorphism is responsible for the present geometry of the deposit. Textural modification has resulted in a general increase in grain size through the development of pyrite and arsenopyrite porphyroblasts, which tend to overprint primary mineral assemblages. Despite the heterogeneous ductile deformation, primary features have locally been preserved, such as fine-grained colloform pyrite and base and precious metal zonation within the Main Zone. Base metal and trace element abundances in massive sulfides from the Brunswick No. 12 deposit indicate two distinct geochemical associations. The basal sulfide facies, characterized by a proximal high-temperature hydrothermal signature (Cu-Co-Bi-Se), contains generally low Au contents averaging 0.39 ppm ( n = 34). Conversely, Au is enriched in the banded sulfide facies, averaging 1.1 ppm Au ( n = 21), and is associated with an exhalative suite of elements (Zn-Pb-As-Sb-Ag-Sn). Finely laminated sulfide lenses hosted by iron formation at the north end of the Main Zone are further enriched in Au, averaging 1.7 ppm ( n = 41) and ranging up to 8.2 ppm. Laser ablation inductively coupled plasma-mass spectrometry (ICP-MS) analyses of

  12. Fundamental studies of the mechanisms of slag deposit formation: Studies on initiation, growth and sintering in the formation of utility boiler deposits: Topical technical report

    SciTech Connect

    Tangsathitkulchai, M.; Austin, L.G.

    1986-03-01

    Three laboratory-scale devices were utilized to investigate the mechanisms of the initiation, growth and sintering process involved in the formation of boiler deposits. Sticking apparatus investigations were conducted to study deposit initiation by comparing the adhesion behavior of the ash drops on four types of steel-based heat exchanger materials under the conditions found in a utility boiler and an entrained slagging gasifier. In addition, the adhesion behavior of the ash drops on a reduced steel surface were investigated. All the ash drops studied in this investigation were produced from bituminous coals.

  13. Formation of aluminum films on silicon by ion beam deposition: A comparison with ionized cluster beam deposition

    SciTech Connect

    Zuhr, R.A.; Haynes, T.E.; Galloway, M.D. ); Tanaka, S.; Yamada, A.; Yamada, I. . Ion Beam Engineering Lab.)

    1990-01-01

    The direct ion beam deposition (IBD) technique has been used to study the formation of oriented aluminum films on single crystal silicon substrates. In the IBD process, thin film growth is accomplished by decelerating a magnetically-analyzed ion beam to low energies (10--200 eV) for direct deposition onto the substrate under UHV conditions. The energy of the incident ions can be selected to provide the desired growth conditions, and the mass analysis ensures good beam purity. The aluminum on silicon system is one which has been studied extensively by ionized cluster beam (ICB) deposition. In this work, we have studied the formation of such films by IBD with emphasis on the effects of ion energy, substrate temperature, and surface cleanliness. Oriented films have been grown on Si(111) at temperatures from 40{degree} to 300{degree}C and with ion energies from 30 to 120 eV per ion. Completed films were analyzed by ion scattering, x-ray diffraction, scanning electron microscopy, and optical microscopy. Results achieved for thin films grown by IBD are compared with results for similar films grown by ICB deposition. 15 refs., 3 figs.

  14. Formation of ultrasmooth thin silver films by pulsed laser deposition

    SciTech Connect

    Kuznetsov, I. A.; Garaeva, M. Ya.; Mamichev, D. A. Grishchenko, Yu. V.; Zanaveskin, M. L.

    2013-09-15

    Ultrasmooth thin silver films have been formed on a quartz substrate with a buffer yttrium oxide layer by pulsed laser deposition. The dependence of the surface morphology of the film on the gas (N{sub 2}) pressure in the working chamber and laser pulse energy is investigated. It is found that the conditions of film growth are optimal at a gas pressure of 10{sup -2} Torr and lowest pulse energy. The silver films formed under these conditions on a quartz substrate with an initial surface roughness of 0.3 nm had a surface roughness of 0.36 nm. These films can be used as a basis for various optoelectronics and nanoplasmonics elements.

  15. Types and geological characteristics of iron deposits in China

    NASA Astrophysics Data System (ADS)

    Li, Hou-Min; Li, Li-Xing; Yang, Xiu-Qing; Cheng, Yan-Bo

    2015-05-01

    Valley. Sedimentary-type iron deposits are dominantly hosted in Devonian clastic marine formations in southern China and in Mesoproterozoic marine strata in northern China, with hematite as main ore mineral. All of the weathering-leaching iron deposits in China are small in scale, and they have little economic value.

  16. Formation of polymer thin films and interface control by physical vapor deposition

    NASA Astrophysics Data System (ADS)

    Usui, Hiroaki

    2009-08-01

    Some strategies of physical vapor deposition (PVD) of polymer thin films have been proposed. Direct vapor deposition can be applied for simple polymers like polyethylene and Teflon. Coevaporation of bifunctional monomers can be achieved to deposit polyimide, polyurea etc., while chain polymerization assisted by ultraviolet or electron irradiation can be used to form vinyl or acryl polymers from single evaporation source. Surface-initiated deposition polymerization, which combines the self-assembled monolayer and vapor deposition, is another unique method to grow polymer thin films that are chemically bound to the substrate surface. The last method is also effective in controlling the interface between polymer films and inorganic substrates. The solvent-free nature of PVD is convenient for the formation of nanometer-thick films and especially multilayers that are required for device fabrication. Application of vapor deposition polymerization for fabrication of organic light-emitting diode is also described.

  17. A new model for tabular-type uranium deposits

    USGS Publications Warehouse

    Sanford, R.F.

    1992-01-01

    Tabular-type uranium deposits occur as tabular, originally subhorizontal bodies entirely within reduced fluvial sandstones of Late Silurian age or younger. This paper proposes that belts of tabular-type uranium deposits formed in areas of mixed local and regional groundwater discharge shortly after deposition of the host sediments. The general characteristics of tabular-type uranium deposits indicate that their essential feature was the formation at a density-stratified ground-water interface in areas of local and regional ground-water discharge. Reconstruction of the paleohydrogeology is the key to understanding the formation of these deposits. Geologic ground-water controls that favor discharge, such as the pinch-out of major aquifers, are also favorable for uranium ore. The combination of topographic and geologic features that both cause discharge is most favorable for ore deposition. -from Author

  18. Geochronology and isotopic-geochemical characteristics of magmatic complexes of gold-silver ore-magmatic structures in the Chukotka sector of the Russian Arctic coast

    NASA Astrophysics Data System (ADS)

    Sakhno, V. G.; Grigoriev, N. V.; Kurashko, V. V.

    2016-05-01

    The first results of SHRIMP dating of magmatic complexes and associated gold-silver deposits and ore occurrences (Kupol, Dvoinoe, Moroshka, and others) in the Chukotka sector of the Russian Arctic coast are discussed. The petrological and isotopic-geochronological data are used for reconstructing their formation conditions.

  19. Metamorphic mineral assemblages of the Hemlo and Big Bell gold deposits: design or accident

    SciTech Connect

    Stanton, R.L.

    1985-01-01

    The Superior Province of Canada and the Yilgarn Province of Australia are well-known to exhibit remarkable similarities in their petrological nature and constitution, and in their tectonic histories. Not only does this apply to the grosser features of petrogenetic and structural analogy, which are well established, but also to many of the finer elements, the recognition of which has been more recent. Among these smaller-scale analogies is a series of remarkably similar ore types: the small Archean iron formations; the Kirkland Lake/Kalgoorlie precious metal telluride ores and environments; the stratiform, volcanic-associated Cu-Zn-(Pb) sulfide deposits; and the nickel sulfide occurrences of basic/ultrabasic lava association. Recently there has emerged what appears to be yet another of these small-scale but important analogies: the Big Bell-Hemlo stratabound pyritic gold-molybdenum ore type. The recently-discovered deposits of Hemlo, Ontario, seem remarkably similar to the well-known occurrence of the Big Bell Mine in Western Australia. Not only are these two deposits very similar in their volcano-sedimentary environments and ore metal mineralogy, but also in their locally-developed metamorphic mineral assemblages. The two ore bodies exemplify a distinctive ore type which is characterized by an overall sulfide-native metal-sulfate-silicate assemblage. A corollary of the latter is that this ore type, whatever its genetic history, provides yet another example of the potential importance of metamorphic silicates to mineral exploration for stratiform ores in metamorphosed terrains.

  20. Formation of Deposits on the Cathode Surface of Aluminum Electrolysis Cells

    NASA Astrophysics Data System (ADS)

    Allard, François; Soucy, Gervais; Rivoaland, Loig

    2014-12-01

    The efficiency of electrolysis cells for aluminum production is reduced when deposits are formed on the cathode block surface. Overfeeding of alumina or excessive heat loss in industrial cells leads to the formation of highly resistive deposits. In this study, the chemical composition of sludge, ledge toe, and thin deposits was investigated at the bottom of both industrial and experimental electrolysis cells. The formation of deposits in laboratory experiments was demonstrated in acidic, neutral, and basic electrolytic bath. A gradient of chiolite (Na5Al3F14) and α-Al2O3 was observed in the deposits. The bath at the bottom of the experimental electrolysis cell had a higher cryolite ratio implying a higher liquidus temperature. The sludge formed at the bottom of the cell can lift the aluminum metal resulting in an important reduction of the contact surface between the aluminum and the cathode block. Moreover, the deposits disturb the current path and generate horizontal current components in the metal which enhance the motion and lower the current efficiency. A thin film of bath supersaturated in alumina was observed under the metal. This work provides clarification on the formation mechanisms of the various deposits responsible for the deterioration of the cathode surface.

  1. Tourmaline as a recorder of ore-forming processes

    USGS Publications Warehouse

    Slack, J.F.; Trumbull, R.B.

    2011-01-01

    Tourmaline occurs in diverse types of hydrothermal mineral deposits and can be used to constrain the nature and evolution of ore-forming fl uids. Because of its broad range in composition and retention of chemical and isotopic signatures, tourmaline may be the only robust recorder of original mineralizing processes in some deposits. Microtextures and in situ analysis of compositional and isotopic variations in ore-related tourmaline provide valuable insights into hydrothermal systems in seafl oor, sedimentary, magmatic, and metamorphic environments. Deciphering the hydrothermal record in tourmaline also holds promise for aiding exploration programs in the search for new ore deposits.

  2. 3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

    NASA Astrophysics Data System (ADS)

    Kampmann, Tobias C.; Stephens, Michael B.; Weihed, Pär

    2016-06-01

    Altered and mineralized rocks at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit, situated in the Palaeoproterozoic Bergslagen ore district in the south-western part of the Fennoscandian Shield, have been metamorphosed at low-pressure, amphibolite-facies conditions and affected by ductile deformation. Using combined surface mapping of lithology and structure, drill core logging and microstructural work, the polyphase (D1 and D2) ductile deformation is demonstrated and a 3D model for the deposit created. Mineral associations include quartz, biotite, cordierite, anthophyllite, and minor almandine, andalusite and chlorite in silicate-rich altered rock, calcite or dolomite in marble and tremolite-actinolite or diopside-hedenbergite in skarn. The silicate minerals show varying growth patterns during the different phases of the tectonothermal evolution, with considerable static grain growth occurring between D1 and D2, and even after D2. F2 sheath folding along axes that plunge steeply to the SSE, parallel to a mineral stretching lineation and the dip direction of the S2 foliation, is suggested as a key deformation mechanism forming steeply plunging, cone- to rod-shaped mineralized bodies. This contrasts with a previous structural model invoking fold interference. A major shear zone with talc-chlorite-(quartz-biotite) mineral association separates the northern and southern structural domains at the deposit and bounds the polymetallic massive sulphides to the north.

  3. 3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

    NASA Astrophysics Data System (ADS)

    Kampmann, Tobias C.; Stephens, Michael B.; Weihed, Pär

    2016-01-01

    Altered and mineralized rocks at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit, situated in the Palaeoproterozoic Bergslagen ore district in the south-western part of the Fennoscandian Shield, have been metamorphosed at low-pressure, amphibolite-facies conditions and affected by ductile deformation. Using combined surface mapping of lithology and structure, drill core logging and microstructural work, the polyphase (D1 and D2) ductile deformation is demonstrated and a 3D model for the deposit created. Mineral associations include quartz, biotite, cordierite, anthophyllite, and minor almandine, andalusite and chlorite in silicate-rich altered rock, calcite or dolomite in marble and tremolite-actinolite or diopside-hedenbergite in skarn. The silicate minerals show varying growth patterns during the different phases of the tectonothermal evolution, with considerable static grain growth occurring between D1 and D2, and even after D2. F2 sheath folding along axes that plunge steeply to the SSE, parallel to a mineral stretching lineation and the dip direction of the S2 foliation, is suggested as a key deformation mechanism forming steeply plunging, cone- to rod-shaped mineralized bodies. This contrasts with a previous structural model invoking fold interference. A major shear zone with talc-chlorite-(quartz-biotite) mineral association separates the northern and southern structural domains at the deposit and bounds the polymetallic massive sulphides to the north.

  4. Research of Geochemical Associations of Nephelin Ores

    NASA Astrophysics Data System (ADS)

    Vulf, M.; Simonov, K.; Sazonov, A.

    The instant paper concerns research of distribution petrogenic chemical members in urtit ore body of Kia-Shaltyrsk deposit. Rocks of the deposit are ore for producing alum earth. Actuality of the subject based on outlooks of detection noble metal ore-bearing (Au, Pt, Pd, Rh, Ru) in alkaline rocks of Siberia, including rocks of Kia-Shaltyrsk deposit (Kuznetsk Alatau). The main purpose of analysis of distribution of members is directed to detection of a non-uniformity of distribution of substance and segments enriched with alum earth and noble members. The basic solved problems are following: o Creation regression models of ore body; o Definition of cumulative distribution functions of members in a contour of ore body; o The analysis of the obtained outcomes in geologic terms. For construction regression models the full-scale data was used, which was presented by the results of the spectral and silicate analyses of gold and petrogenic members containing 130 assays arranged in ore body. A non-linear multiparameter model of the ore body based on components of nephelin ore using neural net approach was constructed. For each member the corresponding distribution function is produced. The model is constructed on the following members: Au, Al2O3, SiO2, Fe2O3, CaO, MgO, SO3, R2O ((Na2O+K2O) -1) and losses of burning. The error of model forecasting membersS concentrations was from 0.02 up to 20%. Large errors basically connected with assays located near contact of ore body and ad- jacent strata or with very high concentrations of members; also they can be connected with different genesis of rocks or superposition of other processes. The analysis of concentrations of members and normalised absolute errors of the fore- cast has shown, that all members can be sectioned into two groups: first: Al2O3, SiO2, R2O, Fe2O3 and second: Au, losses of burning, CaO, MgO, SO3. The distribution of 1 gold is tightly connected with calcium and losses of burning and spatially linked with zones

  5. Formation damage prevention through the control of paraffin and asphaltene deposition

    SciTech Connect

    Newberry, M.E.; Barker, K.M.

    1985-03-01

    Formation damage caused by the precipitation and deposition of paraffin or asphaltene particles has been a recurrent problem in the production of crude oil. A number of well established oilfield operations have been found to aggravate these organic deposition problems. Laboratory testing of crudes and chemical additives has led to a number of solutions to these problems. Case history information on testing, chemical application, and subsequent field results are presented.

  6. National uranium resource evaluation. Geology and recognition criteria for sandstone uranium deposits of the salt wash type, Colorado Plateau Province. Final report

    SciTech Connect

    Thamm, J.K.; Kovschak, A.A. Jr.; Adams, S.S.

    1981-01-01

    The uranium-vanadium deposits of the Salt Wash Member of the Morrison Formation in the Colorado Plateau are similar to sandstone uranium deposits elsewhere in the USA. The differences between Salt Wash deposits and other sandstone uranium deposits are also significant. The Salt Wash deposits are unique among sandstone deposits in that they are dominantly vanadium deposits with accessory uranium. The Salt Wash ores generally occur entirely within reduced sandstone, without adjacent tongues of oxidized sandstone. They are more like the deposits of Grants, which similarly occur in reduced sandstones. Recent studies of the Grants deposits have identified alteration assemblages which are asymmetrically distributed about the deposits and provide a basis for a genetic model for those deposits. The alteration types recognized by Shawe in the Slick Rock district may provide similar constraints on ore formation when expanded to broader areas and more complete chemical analyses.

  7. Playa lake and sheetflood deposits of the Upper Cretaceous Jindong Formation, Korea: Occurrences and palaeoenvironments

    NASA Astrophysics Data System (ADS)

    Paik, I. S.; Kim, H. J.

    2006-05-01

    Lake model of the Upper Cretaceous Jindong Formation in Korea was established on the basis of sedimentological and palaeobiological records of the playa lake and sheetflood deposits and their palaeoenvironmental implications. The playa lake and sheetflood deposits of the Jindong Formation are characterized by the common presence of traces of vanished evaporites, complicated polygonal desiccation cracks and rainprints, the pedogenic carbonate development, and the preservation of invertebrate traces and dinosaur and bird tracks. The traces of vanished evaporites including halite and sulphate evaporite occur as evaporite pseudopmorphs and moulds. The occurrence of all of the evaporite minerals as traces suggests that flooding stages persisted much longer than evaporation and desiccation stages. Invertebrates, birds, and dinosaurs inhabited the playa lake environment of the Upper Cretaceous Jindong Lake. The Jindong Lake formed by the combination of humid source area and arid depositional site due to an orographic effect in fault-bounded basin. Extensive development of the playa lake and sheetflood deposits with evaporite mineral casts and very limited association of shoreline deposits in the Jindong Formation are characteristic of closed lake, and the Jindong Lake is compared to a lake formed in partly drained closed basin. The aggradation of mudflat deposits indicates continued subsidence of the basin and continuation of an underfilled lake basin. The Jindong Lake expanded and stabilized as a playa lake surrounded by dry to saline mudflats, and palaeoclimate and subsidence rates changed little throughout the period of the Jindong Lake development.

  8. Deposition, diagenesis, and porosity relationships in the Glorieta formation, Keystone (Holt) field, Winkler County, Texas

    SciTech Connect

    Haack, R.C.; Jacka, A.D.

    1984-04-01

    Production of hydrocarbons from the Chevron 7C H.E. Lovett well, Keystone (Holt) field, is from the upper part of the Glorieta formation (Leonardian). The field is located near the western margin of the Central Basin platform (Permian basin) on a present-day structural high. The 116-ft (35.4-m) core contains at least 7 cycles of deposition, which consist, upward from the base, of progradational subtidal, intertidal and supratidal deposits. Supratidal deposits predominantly consist of dolostones with fenestral cavities; sabkha deposits are not represented. Scattered nodules of nonevaporitic anhydrite have been emplaced within subtidally deposited carbonates after dolomitization. Intrabiopelgrapestone grainstones, oointrabiopelgrainstones, intrabiopelpackstones and wackestones, and intrapelpackstones and wackestones are the predominant lithofacies. Dolostone is the predominant lithology.

  9. Depositional environments as a guide to uranium mineralization in the Chinle Formation, San Rafael Swell, Utah

    USGS Publications Warehouse

    Lupe, Robert

    1976-01-01

    Uranium deposits in the San Rafael Swell are related to sedimentary depositional environments in the Triassic Chinle Formation. The sedimentary textures resulting from depositional processes operating in lower energy environments appear to have influenced uranium mineralization. The Chinle consists of three fining-upward, fluvial-lacustrine sequences. Uranium mineralization is concentrated in the lower part of the lowest sequence in areas where sediments of lower energy environments are complexly interbedded with sediments of other environments. Areas favorable for uranium exploration exist in the subsurface to the north, west, and south of the Chinle outcrop in the Swell. This determination is based on the spatial distribution of depositional environments and the pattern of Chinle deposition through time.

  10. Tsunami characteristics and formation potential of sandy tsunami deposit in Sanriku Coast: implications from numerical modeling

    NASA Astrophysics Data System (ADS)

    Sugawara, D.; Haraguchi, T.; Takahashi, T.

    2013-12-01

    Geological investigation of paleotsunami deposit is crucial for knowing the history and magnitude of tsunami events in the past. Among various kinds of grain sizes, sandy tsunami deposit has been best investigated by previous studies, because of its potential for identification in the sedimentary column. Many sandy tsunami deposits have been found from coastal plains, which have sandy beach and low-lying wetlands. However, sandy tsunami deposits in narrow valleys at rocky ria coast have rarely been found. It may be presumed that formation potential of sandy tsunami layer in the rocky coasts is generally lower than coastal plains, because of the absence of sandy beach, tsunami run-up on steeper slope and stronger return flow. In this presentation, characteristics of the 2011 Tohoku-oki earthquake tsunami in Sanriku Coast, a continuous rocky ria coast located in the northeast Japan, is investigated based on numerical modeling. In addition, the formation potential of sandy tsunami deposit is also investigated based on numerical modeling of sediment transport. Preliminary result of tsunami hydrodynamics showed that the waveform and amplification of the tsunami are clearly affected by the local bathymetry, which is associated with submerged topography formed during the last glacial stage. Although the tsunami height in the offshore of each bay is around 8.0 m, the tsunami height at the bay head was increased in different way. The amplification factor at the bay head was typically 2.0 among most of V-shaped narrow embayments; meanwhile the amplification factor is much lower than 1.0 at some cases. The preliminary result of the modeling of sediment transport predicted huge amount of sediments may be suspended into the water column, given that sandy deposit is available there. Massive erosion and deposition of sea bottom sediments may commonly take place in the bays. However, formation of onshore tsunami deposit differs from each other. Whether the suspended sediments

  11. The F'derik-Zouerate iron district: Mesoarchean and Paleoproterozoic iron formation of the Tiris Complex, Islamic Republic of Mauritania

    USGS Publications Warehouse

    Taylor, Cliff D.; Finn, Carol A.; Anderson, Eric D.; Bradley, Dwight C.; Joud, Mohamed; Taleb Mohamed, Ahmed; Horton, John D.; Johnson, Craig A.

    2016-01-01

    High-grade hematitic iron ores (of HIF, containing 60-65 wt%Fe) have been mined in Mauritania since 1952 from Superior-type iron deposits of the F'derik-Zouerate district.  Depletion of the high-grade ores in recent years has resulted in new exploration projects focused on lower-grade magnetite ores occurring in Algoma-type banded iron formation (of BIF, containing ca. 35 wt% Fe).  Mauritania is the seventeenth largest iron producer in the world and currently has about 1.1 Gt of crude iron ore reserves. 

  12. Antimony ore in the Fairbanks district, Alaska

    USGS Publications Warehouse

    Killeen, Pemberton Lewis; Mertie, John B., Jr.

    1951-01-01

    Antimony-bearing ores in the Fairbanks district, Alaska, are found principally in two areas, the extremities of which are at points 10 miles west and 23 miles northeast of Fairbanks; and one of two minor areas lies along this same trend 30 miles farther to the northeast. These areas are probably only local manifestations of mineralization that affected a much broader area and formed antimony-bearing deposits in neighboring districts, the closest of which is 50 miles away. The ores were exposed largely as a result of lode gold mining, but at two periods in the past, high prices for antimony ore warranted an independent production and about 2500 tons of stibnite ore was shipped. The sulfide deposits occupy the same fractures along which a gold-quartz mineralization of greater economic importance occurred; and both are probably genetically related to igneous rocks which intrude the schistose country rock. The sulfide is in part contemporaneous with some late-stage quartz in which it occurs as disseminated crystals; and in part the latest filling in the mineralized zones where it forms kidney-shaped masses of essentially solid sulfide. One extremely long mass must have contained nearly 100 tons of ore, but the average of the larger kidneys is closer to several tons. Much of the ore is stibnite, with quartz as a minor impurity, and assays show the tenor to vary from 40 to 65 percent antimony. Sulphantimonites are less abundant but likewise occur as disseminated crystals and as kidney-shaped bodies. Antimony oxides appear on the weathered surface and along fractures within the sulfide ore. Deposits containing either stibnite or sulphantimonite are known at more than 50 localities, but only eighteen have produced ore and the bulk of this came from the mines. The geology of the deposit, and the nature, extent, and period of the workings are covered in the detailed descriptions of individual occurrences. Several geologic and economic factors, which greatly affect

  13. A systematic approach for the prevention and treatment of formation damage caused by asphaltene deposition

    SciTech Connect

    Leontaritis, K.J.; Amaefule, J.O.; Charles, R.E. )

    1994-08-01

    Asphaltene plugging is a known cause of near-wellbore formation damage. Deposited asphaltenes can reduce effective hydrocarbon mobility by (1) blocking the pore throats; (2) adsorbing onto the rock, thereby altering the formation wettability from water-wet to oil-wet; and (3) increasing hydrocarbon viscosity by nucleating water-in-oil emulsions. Asphaltene flocculation and deposition can be avoided in some, but not all, cases. Some formation damage resulting from asphaltene plugging is permanent and hence must be prevented rather than treated. Prevention of asphaltene-induced formation damage should be started in the early stages of drilling and well completion, once the oil is known to be asphaltenic. This paper presents a systematic approach to successful diagnosis, prevention, and mitigation of asphaltene problems during recovery of asphaltenic oils. A mechanism of asphaltene flocculation and deposition is proposed and analyzed, and the previously defined concept of asphaltene deposition envelope is further refined. Diagnostic technology is presented that can test the compatibility of drilling and completion fluids with any asphaltenic oil. Important issues that need to be considered in the design of treatments for asphaltene removal are discussed. Finally, the paper presents a methodology for restoring unfavorable wettability changes caused by asphaltene deposition.

  14. Porphyry copper deposit formation by sub-volcanic sulphur dioxide flux and chemisorption

    NASA Astrophysics Data System (ADS)

    Henley, Richard W.; King, Penelope L.; Wykes, Jeremy L.; Renggli, Christian J.; Brink, Frank J.; Clark, David A.; Troitzsch, Ulrike

    2015-03-01

    Porphyry copper deposits--the primary source of the world’s copper--are a consequence of the degassing of intrusion complexes in magmatic arcs associated with ancient subduction zones. They are characterized by copper and iron sulphides, commonly found with anhydrite (CaSO4), over scales of several kilometres through intensely altered and fractured rocks. The magmatic source of the metals is broadly understood, but the processes that transport and deposit the metals at the megaton scale are unclear. The hydrogen sulphide necessary for metal deposition is commonly assumed to form by a reaction between sulphur dioxide and water, but this reaction is inefficient and cannot explain the formation of economic-grade deposits. Here we use high-temperature laboratory experiments to show that a very rapid chemisorption reaction occurs between sulphur dioxide gas, a principal component of magmatic gas mixtures, and calcic feldspar, an abundant mineral in the arc crust. The chemisorption reaction generates the mineral anhydrite and hydrogen sulphide gas, and triggers deposition of metal sulphides. We use thermodynamic calculations to show that as magmatic gas cools and expands the concentration of hydrogen sulphide gas increases exponentially to drive efficient deposition of metal sulphides and consequent formation of economic-grade porphyry copper deposits.

  15. Deposit formation due to instability and contamination of raw materials in alkali-treated light distillates

    SciTech Connect

    Hessam, K.

    1986-01-01

    Alkali treating of petroleum distillates is carried out to obtain the advantages of the product purity and to improve performance. The use and quality of alkaline solutions must be controlled since metal ions present as impurities can catalyze low temperature oxidation and polymerization of olefinic compounds; leading to formation of heavy emulsions which tend to deposit in hydrocarbon phases and eventually to block the handling systems. The effects of the variable factors ''time, temperature, antioxidant and anticorrosion additives'' were studied. The addition of a small amount of methanol was found to retard the deposit formation.

  16. Fundamental study of ash formation and deposition: Effect of reducing stoichiometry

    SciTech Connect

    Helble, J.J.; Bool, L.E.; Kang, S.G.

    1995-11-01

    This project is designed to examine the effects of combustion stoichiometry on the fundamental aspects of ash formation and ash deposit initiation. Emphasis is being placed on reducing stoichiometries associated with low-NOx combustion, although a range of oxidant/fuel ratios are being considered. Previous work has demonstrated that ash formation depends strongly upon coal mineralogy, including mineral type, size, amount, and the presence of organically associated inorganic species. Combustion temperature and the oxidation state of iron also play a significant role. As these latter items will vary with changes in stoichiometry, research to determine the net effect on deposition is required.

  17. Bog iron formation in the Nassawango Creek watershed, Maryland, USA

    USGS Publications Warehouse

    Bricker, O.P.; Newell, W.L.; Simon, N.S.

    2004-01-01

    The Nassawango bog ores in the modern environment for surficial geochemical processes were studied. The formation of Nassawango bog ores was suggested to be due to inorganic oxidation when groundwater rich in ferrous iron emerges into the oxic, surficial environment. It was suggested that the process, providing a phosphorus sink, may be an unrecognized benefit for mitigating nutrient loading from agricultural lands. It is found that without the effect of iron fixing bacteria, bog deposites could not form at significant rates.

  18. Two types of ore-bearing mafic complexes of the Early Proterozoic East-Scandinavian LIP and their ore potential

    NASA Astrophysics Data System (ADS)

    Mitrofanov, Felix; Zhirov, Dmitry; Bayanova, Tamara; Korchagin, Alexey; Chaschin, Victor

    2015-04-01

    magma generate single volcano-plutonic rock series. For intrusive ore bodies rock differentiation with the formation of syngenetic wehrlite-clinopyroxenite-gabbro- orthoclase gabbro sequence is typical. Upper mantle source of the depleted magma is characterized by the following isotope indicators: ɛNd(T) +0.5 to +4, ISr= 87Sr/86Sr 0.703-0.704. Ore-bearing intrusive bodies are injected in the upper part of the Early Palaeoproterozoic volcano-sedimentary cross-section. Ores are located in the basement of intrusions and in the redeposited veined bodies, including offset setting. Numerous Ni-Cu deposits with total reserves and resources of several million tons of Nickel equivalent (with an average grade ≥ 0,3%) have been explored, and some of them now is mining. As a result of our research, the complex of indicators and criteria is suggested for predicting the occurrence, for regional exploration target selection and for regional resource evaluation of PGE and base metals. The studies are supported by the Russian Foundation for Basic Research (project nos. 13-05-12055).

  19. Modeling of the fault-controlled hydrothermal ore-forming systems

    SciTech Connect

    Pek, A.A.; Malkovsky, V.I.

    1993-07-01

    A necessary precondition for the formation of hydrothermal ore deposits is a strong focusing of hydrothermal flow as fluids move from the fluid source to the site of ore deposition. The spatial distribution of hydrothermal deposits favors the concept that such fluid flow focusing is controlled, for the most part, by regional faults which provide a low resistance path for hydrothermal solutions. Results of electric analog simulations, analytical solutions, and computer simulations of the fluid flow, in a fault-controlled single-pass advective system, confirm this concept. The influence of the fluid flow focusing on the heat and mass transfer in a single-pass advective system was investigated for a simplified version of the metamorphic model for the genesis of greenstone-hosted gold deposits. The spatial distribution of ore mineralization, predicted by computer simulation, is in reasonable agreement with geological observations. Computer simulations of the fault-controlled thermoconvective system revealed a complex pattern of mixing hydrothermal solutions in the model, which also simulates the development of the modern hydrothermal systems on the ocean floor. The specific feature of the model considered, is the development under certain conditions of an intra-fault convective cell that operates essentially independently of the large scale circulation. These and other results obtained during the study indicate that modeling of natural fault-controlled hydrothermal systems is instructive for the analysis of transport processes in man-made hydrothermal systems that could develop in geologic high-level nuclear waste repositories.

  20. Tourmaline in the central Swedish ore district

    NASA Astrophysics Data System (ADS)

    Hellingwerf, R. H.; Gatedal, K.; Gallagher, V.; Baker, J. H.

    1994-06-01

    More than 40 recently discovered tourmaline occurrences have been investigated in the Mid-Proterozoic Bergslagen ore district of central Sweden. Some are spatially associated with ores, others with zones of leaching, remobilization and migmatization. Among the tourmaline-bearing ore deposits are the Dammberg ZnPb-Fe sulphide deposit, the Sala Pb-Zn-Ag deposit, the Dalkarlsberg, Pershyttan and Håksberg Fe oxide deposits, the Leja Cu deposit, and the Zinkgruvan Zn-Pb-Ag deposit. Tourmaline has been recorded a) as tourmalinites and tourmaline-bearing chemical sediments; b) in tourmaline-bearing skarns; c) in tourmaline-quartz veins; d) as disseminations along the foliation in schists; e) in tourmaline pegmatites; f) in tourmalinized haloes in metavolcanites along tourmaline pegmatites; and g) in late joints. Tourmalinites, tourmaline-bearing chemical sediments and tourmaline-bearing skarns are spatially associated with sulphide and oxide mineralizations. The dravite components in these tourmalines are proportional to the size of Zn-Pb sulphide mineralizations. Tourmalines from quartz veins close to and within ore deposits contain high Zr and Cr contents. With increasing distance away from these deposits, the Zr and Cr contents fall significantly. Tourmalines from pegmatites have inherited a number of trace element enrichments through partial melting and assimilation of volcaniclastic sediments into granitic melts. Despite magmatic homogenization, Zn contents in these tourmalines reflect the proximity of Zn-Pb-sulphide deposits, decreasing away from them. Tourmalines from late joints with Zn contents above the 100 ppm level are also indicative for the proximity of Zn-Pb sulphide mineralizations. Thus, some trace elements in these tourmalines may represent suitable exploration tools.

  1. Appraisal of the accuracy of U.S. Geological Survey ore reserve estimates for uranium-vanadium deposits on the Colorado Plateau

    USGS Publications Warehouse

    Bush, Alfred Lerner; Stager, Harold Keith

    1954-01-01

    The U.S. Geological Survey has made estimates of the reserves of uranium and vanadium in the carnotite deposits explored by Geological Survey drilling on the Colorado Plateau. This report presents an appraisal of the accuracy of the reserve estimates for deposits in the Uravan mineral belt, the causes of inaccuracy, and the significance of the estimates in terms of the total known reserves of the region.

  2. Alteration and ore distribution in the Proterozoic Mines Series, Tenke-Fungurume Cu-Co district, Democratic Republic of Congo

    NASA Astrophysics Data System (ADS)

    Fay, I.; Barton, M. D.

    2012-06-01

    Two sediment-hosted stratiform Cu-Co deposits in the Tenke-Fungurume district of the Central African Copperbelt were examined to evaluate the alteration history of the ore-hosting Mines Series and its implications for ore distribution and processing. Core logging and petrography, focused on lithology and timing relationships, outlined a complex alteration sequence whose earliest features include formation of anhydrite nodules and laths, followed by precipitation of dolomite. Later alteration episodes include at least two silica introductions, accompanied by or alternating with two dolomite introductions into the existing gangue assemblages. One introduction of Cu-Co sulfides accompanied the last episode of dolomite alteration, overprinting an earlier generation of ore whose gangue association was unidentifiable. Sulfides and some carbonates were subsequently modified by supergene oxidation, transport, and reprecipitation to 100-200 m depth. Present-day ore distribution resulted from these successive processes. Ore is concentrated in two shale-dominated units on either side of a cavernous silicified dolomite, which is interpreted as the main conduit for the mineralizing fluids. Sulfide ores precipitated at the redox or sulfidation contacts between this dolomite and the shales. Later, supergene fluids dissolved and moved some of the metals, redepositing them as oxides and carbonates. Solubility differences between Cu and Co in supergene conditions caused them to precipitate separately. Thus, modern ore distribution at Tenke-Fungurume results both from original hypogene lithology- and contact-related precipitation and from supergene oxidation, transport, and Cu-Co decoupling. The supergene fluid flow also redistributed gangue minerals such as dolomite, which has an economically important influence on the processing costs of supergene ores.

  3. Stratigraphy and depositional environments of Fox Hills Formation (Late Cretaceous), Williston basin

    SciTech Connect

    Daly, D.J.

    1986-08-01

    The Fox Hills Formation (Late Cretaceous, Maestrichtian) was investigated where it crops out along the southern flank of the Williston basin and in the subsurface over the central portion of the basin, using 300 well logs. The formation is conformable and gradational with the underlying Pierre formation and can be either conformable or unconformable with the overlying Hell Creek Formation. The Fox Hills Formation is younger, thicker, and stratigraphically more complex to the east and is comprised of marginal marine sediments deposited during the final Cretaceous regression. To the west, the Fox Hills Formation is an upward-coarsening unit generally 30 to 45 m thick and usually contains three members: from the base, Trail City, Timber Lake, and Colgate. The lower Fox Hills (Trail City, Timber Lake) is generally dominated by hummocky bedding and contains a variety of trace fossils, most notably Ophiomorpha. The upper Fox Hills (Colgate), where present, is characterized by cross-bedding. To the east, including the type area, the section is generally 80 to 100 m thick and contains four members: from the base, Trail City, Timber Lake, Iron Lightning (Colgate and Bullhead lithofacies), and Linton. In contrast to the section in the west, this section is as much as three times thicker, contains abundant body fossils, generally lacks hummocky bedding, and contains the Bullhead and Linton strata. In the west, the strata represent lower shoreface deposits, predominantly of storm origin (lower Fox Hills), overlain by upper shoreface and fluvial deposits (upper Fox Hills). In the east, the lower Fox Hills contains deposits of the lower shoreface (Trail City) and a barrier bar complex (Timber Lake), overlain by the deltaic deposits of the upper Fox Hills (Iron Lightning, Linton).

  4. Age and metamorphism of some massive sulflde deposits in Virginia, North Carolina and Tennessee

    USGS Publications Warehouse

    Kinkel, A.R., Jr.; Thomas, H.H.; Marvin, R.F.; Walthall, F.G.

    1965-01-01

    Isotopic ages of vein and wall-rock samples have been determined on five massive sulflde deposits of the southern Appalachians. Vein mineral ages of about 1100 m.y. indicate that some ore bodies formed at least as early as the Grenville metamorphism, and probably soon after the formation of the enclosing gneiss and schist. Present textures of the ore were formed during subsequent metamorphic periods at about 450 m.y. and 300 to 330 m.y. ago. ?? 1965.

  5. The role of microorganisms in the formation of calcitic moonmilk deposits and speleothems in Altamira Cave

    NASA Astrophysics Data System (ADS)

    Sanchez-Moral, S.; Portillo, M. C.; Janices, I.; Cuezva, S.; Fernández-Cortés, A.; Cañaveras, J. C.; Gonzalez, J. M.

    2012-02-01

    Bacteria are able to induce carbonate precipitation although the participation of microbial or chemical processes in speleothem formation remains a matter of debate. In this study, the origin of carbonate depositions such as moonmilk, an unconsolidated microcrystalline formation with high water content, and the consolidation of carbonate precipitates into hard speleothems were analyzed. The utilized methods included measurements of the composition of stable isotopes in these precipitates, fluorimetric determinations of RNA/DNA ratios and respirometric estimations in Altamira Cave. Results from isotope composition showed increases of the δ 18O and δ 13C ratios from moonmilk in the very first stages of formation toward large speleothems. Estimates of RNA/DNA ratios suggested an inactivation of microorganisms from incipient moonmilk toward consolidated deposits of calcium carbonate. Respiratory activity of microorganisms also showed a significant decrease in samples with accumulated calcite. These results suggest that bacterial activity induces the conditions required for calcium carbonate precipitation, initiating the first stages of deposition. Progressive accumulation of carbonate leads towards a less favorable environment for the development of bacteria. On consolidated speleothems, the importance of bacteria in carbonate deposition decreases and chemical processes gain importance in the deposition of carbonates.

  6. Field study and three-dimensional reconstruction of thrusts and strike-slip faults in the Central Andes: implications for deep-seated geothermal circulation and ore deposits exploration

    NASA Astrophysics Data System (ADS)

    Norini, Gianluca; Groppelli, Gianluca; Giordano, Guido; Baez, Walter; Becchio, Raul; Viramonte, Jose; Arnosio, Marcelo

    2014-05-01

    The Puna plateau (NW Argentina), located in the back-arc of the Central Andes, is a plateau characterized by both orogen-parallel and orogen-oblique deformation styles, extensive magmatic and geothermal activity, and the broad occurrence of igneous and hydrothermal ore-forming minerals. In this area, like in other convergent margins, the behaviour of the magma-tectonics interplay can affect the circulation of hydrothermal fluids, so that the full comprehension of the tectonic control on the magmas and fluids paths in the continental crust is crucial to plan the geothermal and ore exploration. In this study, we present a structural analysis of the back-arc portion of the orogen-oblique Calama-Olacapato-El Toro fault system and the surrounding orogen-parallel thrust faults in the central-eastern Puna Plateau, comprising the Cerro Tuzgle-Tocomar geothermal volcanic area, with high geothermal potential, and silicic calderas and domes associated with epithermal ore deposits. We also focused on the tectonic and volcanotectonic structures of the Chimpa and Tuzgle stratovolcanoes, two of the most important polygenetic volcanic centres of the plateau. Morphostructural analysis and field mapping reveal the geometry, kinematics and dynamics of the tectonic structures of the studied area. These data and the available stratigraphic and geophysical data have been integrated with the software MOVE and PETREL in a three-dimensional reconstruction of the main fault planes, showing their attitude and intersections at depth. As a result of our study, we show that despite different geometry and kinematics of the Calama-Olacapato-El Toro fault system and the thrust faults, they formed and evolved under the same progressive evolving dynamic state, forming a single tectonic system and accommodating crustal shortening of a thickened crust. In this frame, the crust underwent simultaneous deformation along both the low-angle thrust faults and the vertical transcurrent strike-slip faults

  7. Deposition of finely disseminated gold mineralization in black shales: A hypothesis of microstructural control

    NASA Astrophysics Data System (ADS)

    Pek, A. A.; Malkovsky, V. I.; Safonov, Yu. G.

    2011-06-01

    The deposition of finely disseminated gold in the deposits hosted in black shales is considered. It is suggested that gold deposition is controlled by microstructure of pore space in host rocks. The pore space structure of tight shales indicates that most pore volume is occupied by nanopores with hundredths of micrometers in characteristic dimension. The balance calculations show that deposition of native gold in nanopore channels of filtration is hampered by shortage of number of atoms necessary to overcome a nucleation threshold of the future gold crystal in the pore volume. When ore-transporting solution meets on its way the cavities (pores, micro- and macrofractures), whose volume is sufficient to overcome the nucleation threshold, the excess content of ore component, which exceeds equilibrium concentration, is released with formation of crystallization centers and further precipitation of gold. The conditions of ore deposition are exemplified in the reference Sukhoi Log deposit hosted in black shales. On the basis on the PT conditions of ore deposition and physical features of fluid heat and mass transfer, it is suggested that ore disseminations were deposited at the early high-temperature stage under a fluid pressure close to lithostatic and at a host rock permeability markedly exceeding its present-day value.

  8. Oxidized and reduced mineral assemblages in greenstone belt rocks of the St. Ives gold camp, Western Australia: vectors to high-grade ore bodies in Archaean gold deposits?

    NASA Astrophysics Data System (ADS)

    Neumayr, Peter; Walshe, John; Hagemann, Steffen; Petersen, Klaus; Roache, Anthony; Frikken, Peter; Horn, Leo; Halley, Scott

    2008-03-01

    Hydrothermal sulfide-oxide-gold mineral assemblages in gold deposits in the Archaean St. Ives gold camp in Western Australia indicate extremely variable redox conditions during hydrothermal alteration and gold mineralization in space and time. Reduced alteration assemblages (pyrrhotite-pyrite) occur in deposits in the southwest of the camp (e.g., Argo, Junction deposits) and moderately to strongly oxidized assemblages (magnetite-pyrite, hematite-pyrite) occur in deposits in the Central Corridor in the northeast (e.g., North Orchin, Revenge deposits). Reduced mineral assemblages flank the Central Corridor of oxidized deposits and, locally, cut across it along E-W trending faults. Oxidized mineral assemblages in the Central Corridor are focused on gravity lows which are interpreted to reflect abundant felsic porphyritic intrusions at about 1,000 m below present surface. Hydrothermal magnetite predates and is synchronous with early phases of gold-associated albite-carbonate-pyrite-biotite-chlorite hydrothermal alteration. Later-stage, gold-associated pyrite is in equilibrium with hematite. The spatial distribution and temporal sequence of iron sulfides and oxides with gold indicate the presence of at least two spatially restricted but broadly synchronous hydrothermal fluids with contrasting redox states. Sulfur isotope constraints support the argument that the different mineral assemblages reflect differences in redox conditions. The δ 34S values for pyrite for the St. Ives gold camp range between -8.4‰ and +5.1‰ with the negative values occurring in oxidized magnetite-rich domains and slightly negative or positive values occurring in reduced, pyrrhotitic domains. Preliminary spatial and paragenetic analysis of the distribution of iron sulfides and oxides in the St. Ives camp suggests that gold grades are highest where the redox state of the hydrothermal alteration assemblages switches from relatively reduced pyrrhotite-pyrite to relatively oxidized magnetite

  9. Influence of snow and ice crystal formation and accumulation on mercury deposition to the Arctic.

    PubMed

    Douglas, Thomas A; Sturm, Matthew; Simpson, William R; Blum, Joel D; Alvarez-Aviles, Laura; Keeler, Gerald J; Perovich, Donald K; Biswas, Abir; Johnson, Kelsey

    2008-03-01

    Mercury is deposited to the Polar Regions during springtime atmospheric mercury depletion events (AMDEs) but the relationship between snow and ice crystal formation and mercury deposition is not well understood. The objective of this investigation was to determine if mercury concentrations were related to the type and formation of snow and ice crystals. On the basis of almost three hundred analyses of samples collected in the Alaskan Arctic, we suggestthat kinetic crystals growing from the vapor phase, including surface hoar, frost flowers, and diamond dust, yield mercury concentrations that are typically 2-10 times higher than that reported for snow deposited during AMDEs (approximately 80 ng/L). Our results show that the crystal type and formation affect the mercury concentration in any given snow sample far more than the AMDE activity prior to snow collection. We present a conceptual model of how snow grain processes including deposition, condensation, reemission, sublimation, and turbulent diffusive uptake influence mercury concentrations in snow and ice. These processes are time dependent and operate collectively to affect the retention and fate of mercury in the cryosphere. The model highlights the importance of the formation and postdeposition crystallographic history of snow or ice crystals in determining the fate and concentration of mercury in the cryosphere. PMID:18441801

  10. Characterization of dynamic droplet impaction and deposit formation on leaf surfaces

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Elucidation of droplet dynamic impaction and deposition formation on leaf surfaces would assist to optimize application strategies, improve biological control efficiency, and minimize pesticide waste. A custom-designed system consisting of two high-speed digital cameras and a uniform-size droplet ge...

  11. Carbonate-shelf depositional environments of the Ordovician Viola formation in South-Central Kansas

    USGS Publications Warehouse

    Newell, K.D.

    2000-01-01

    The Upper Ordovician Viola Formation, an important petroleum reservoir in the Midcontinent, is a carbonate unit present over much of the subsurface in Kansas. The Viola is composed of two fining-upward sedimentary packages that are separated from each other by a minor karstic surface representing a brief period of exposure. Each package represents a third-order sedimentary cycle and consists of an echinoderm-rich packstone overlain by a thicker lime mudstone. The echinoderm-rich packstone was deposited nearshore in agitated waters, but subsequently was bioturbated. The overlying lime mudstone was deposited in deeper, quiet waters, and locally contains storm-deposited carbonate sands. Subtle growth of the Central Kansas Arch and Pratt Anticline (structures transecting the depositional shelf) is indicated by packstones and grainstones being thicker over these arches, whereas finer grained lithologies dominate in basinal areas on the arch flanks. Structureless lime mudstones, probably intensely bioturbated, grade into laminated lime mudstones farther basinward.

  12. On the deposition mechanisms and the formation of glassy Cu-Zr thin films

    NASA Astrophysics Data System (ADS)

    Almyras, G. A.; Matenoglou, G. M.; Komninou, Ph.; Kosmidis, C.; Patsalas, P.; Evangelakis, G. A.

    2010-04-01

    We report on molecular dynamics (MD) simulations and physical vapor deposition experimental results concerning the development of glassy and nanocrystalline Cu-Zr thin films. MD has revealed that when Cu and Zr are deposited sequentially, a thin film overlayer is formed that consists of nanocrystalline a-Zr and t-Zr2Cu, while if Cu and Zr are simultaneously deposited, amorphous CuZr thin film emerges, due to the formation of icosahedral-like clusters that impede nucleation. Thin films grown by pulsed laser deposition and magnetron sputtering techniques were analyzed by x-ray diffraction and high-resolution transmission electron microscopy and yielded unequivocal evidence that validates our MD predictions. These findings may indicate an alternative pathway for the growth of metallic nanocomposites or glassy films.

  13. The role of microbes in the formation of modern and ancient phosphatic mineral deposits

    PubMed Central

    Crosby, Chris H.; Bailey, Jake V.

    2012-01-01

    The formation of marine phosphatic mineral deposits remains incompletely understood, despite decades of research. The involvement of bacteria in this process has long been suspected, and both modern and ancient associations between bacteria and phosphorites have been recorded. Only recently has a specific bacterial metabolic process associated with the formation of phosphorites been discovered. Recent studies demonstrate that polyphosphate utilization by sulfide-oxidizing bacteria results in the rapid precipitation of apatite – providing at least a partial mechanism to explain the close spatial correlation between accumulations of sulfide-oxidizing bacteria and modern phosphorites. Possible fossilized bacteria are known from ancient phosphatic mineral deposits. Potentially, the fossilized cells represent the remains of bacteria that induced the formation of those phosphorites. However, robust criteria for the recognition of these bacteria have yet to be identified. PMID:22783245

  14. Effect of process conditions on the microstructural formation of dc reactively sputter deposited AlN

    SciTech Connect

    Ekpe, Samuel D.; Jimenez, Francisco J.; Dew, Steven K.

    2010-09-15

    Thin film aluminum nitride (AlN), because of its attractive properties, is a material with many applications. Its microstructure and hence properties are greatly influenced by the deposition process conditions. In this work, AlN was reactively deposited in a dc magnetron sputtering system at different proportions of nitrogen in the process gas mixture and at different process conditions. The microstructure and composition of the films were analyzed using x-ray diffraction data, energy dispersive spectroscopy, and scanning electron microscopy. Results show that for a process gas pressure of 0.67 Pa, a magnetron power of 100 W, and a substrate-target distance of 10 cm, a near stoichiometeric AlN can be prepared at nitrogen proportions as low as 20%. At these process conditions, (002) was the preferred crystal orientation. Dense fibrous structures were obtained, especially at low deposition rates with high proportions of nitrogen. Increase in magnetron power and decrease in distance result in a more porous structure. High kinetic energies (average) of the sputtered Al particles and high deposition rates tend to favor AlN(101) formation, while low kinetic energies of the Al particles and low deposition rates generally favor more of the AlN(100) formation.

  15. Architecture of the Sierra Ladrones Formation, central New Mexico. Depositional controls on the permeability correlation structure

    SciTech Connect

    Davis, J.M.; Lohmann, R.C.; Phillips, F.M.; Wilson, J.L. ); Love, D.W. )

    1993-08-01

    Statistical models of hydrogeological heterogeneity are often used in aquifer and reservoir characterization. The number of data required to estimate objectively the spatial correlation structure of permeability, however, is often prohibitive. The objective of this study was to develop a better understanding of how information about depositional processes can be used to characterize hydrogeological heterogeneity. An outcrop of the fluvial/interfluvial Sierra Ladrones Formation of New Mexico was studied for this purpose. On the basis of previous studies of paleogeography and our own field observations, deposits of the Sierra Ladrones Formation are interpreted as marginal ancestral Rio Grande flood-plain and tributary deposits. Architectural elements were mapped over a 0.16-km[sup 2] peninsular outcrop of Pliocene-Pleistocene deposits of the central Albuquerque Basin. Geostatistical analysis of the architectural-element map data indicates non-orthogonal anisotropy in the horizontal direction. The orientations of the strongest (N30[degree]W) and weakest (N90[degree]E) correlation correspond to the orientation of the tributary system and the ancestral Rio Grande flood plain, respectively. In the vertical direction, the correlation structure exhibits exponential behavior corresponding to the average-element thicknesses. The results demonstrate that information about depositional environment can be used to help to quantify statistically subsurface heterogeneity. 28 refs., 9 figs., 1 tab.

  16. The role of matrix proteins in the control of nacreous layer deposition during pearl formation

    PubMed Central

    Liu, Xiaojun; Li, Jiale; Xiang, Liang; Sun, Juan; Zheng, Guilan; Zhang, Guiyou; Wang, Hongzhong; Xie, Liping; Zhang, Rongqing

    2012-01-01

    To study the function of pearl oyster matrix proteins in nacreous layer biomineralization in vivo, we examined the deposition on pearl nuclei and the expression of matrix protein genes in the pearl sac during the early stage of pearl formation. We found that the process of pearl formation involves two consecutive stages: (i) irregular calcium carbonate (CaCO3) deposition on the bare nucleus and (ii) CaCO3 deposition that becomes more and more regular until the mature nacreous layer has formed on the nucleus. The low-expression level of matrix proteins in the pearl sac during periods of irregular CaCO3 deposition suggests that deposition may not be controlled by the organic matrix during this stage of the process. However, significant expression of matrix proteins in the pearl sac was detected by day 30–35 after implantation. On day 30, a thin layer of CaCO3, which we believe was amorphous CaCO3, covered large aragonites. By day 35, the nacreous layer had formed. The whole process is similar to that observed in shells, and the temporal expression of matrix protein genes indicated that their bioactivities were crucial for pearl development. Matrix proteins controlled the crystal phase, shape, size, nucleation and aggregation of CaCO3 crystals. PMID:21900328

  17. Factors that influence properties of FOG deposits and their formation in sewer collection systems.

    PubMed

    Iasmin, Mahbuba; Dean, Lisa O; Lappi, Simon E; Ducoste, Joel J

    2014-02-01

    Understanding the formation of Fat, Oil, and Grease (FOG) deposits in sewer systems is critical to the sustainability of sewer collection systems since they have been implicated in causing sewerage blockages that leads to sanitary sewer overflows (SSOs). Recently, FOG deposits in sewer systems displayed strong similarities with calcium-based fatty acid salts as a result of a saponification reaction. The objective of this study was to quantify the factors that may affect the formation of FOG deposits and their chemical and rheological properties. These factors included the types of fats used in FSEs, environmental conditions (i.e. pH and temperature), and the source of calcium in sewer systems. The results of this study showed that calcium content in the calcium based salts seemed to depend on the solubility limit of the calcium source and influenced by pH and temperature conditions. The fatty acid profile of the calcium-based fatty acid salts produced under alkali driven hydrolysis were identical to the profile of the fat source and did not match the profile of field FOG deposits, which displayed a high fraction of palmitic, a long chain saturated fatty acid. It is hypothesized that selective microbial metabolism of fats and/or biologically induced hydrogenation may contribute to the FOG deposit makeup in sewer system. Therefore, selective removal of palmitic in pretreatment processes may be necessary prior to the discharge of FSE wastes into the sewer collection system. PMID:24317022

  18. Liquid phase products and solid deposit formation from thermally stressed model jet fuels

    NASA Technical Reports Server (NTRS)

    Kim, W. S.; Bittker, D. A.

    1984-01-01

    The relationship between solid deposit formation and liquid degradation product concentration was studied for the high temperature (400 C) stressing of three hydrocarbon model fuels. A Jet Fuel Thermal Oxidation Tester was used to simulate actual engine fuel system conditions. The effects of fuel type, dissolved oxygen concentration, and hot surface contact time (reaction time) were studied. Effects of reaction time and removal of dissolved oxygen on deposit formation were found to be different for n-dodecane and for 2-ethylnaphthalene. When ten percent tetralin is added to n-dodecane to give a simpler model of an actual jet fuel, the tetralin inhibits both the deposit formation and the degradation of n-dodecane. For 2-ethylnaphthalene primary product analyses indicate a possible self-inhibition at long reaction times of the secondary reactions which form the deposit precursors. The mechanism of the primary breakdown of these fuels is suggested and the primary products which participate in these precursor-forming reactions are identified. Some implications of the results to the thermal degradation of real jet fuels are given.

  19. Sedimentology of the Ripogenus Formation, Maine: A Silurian carbonate-siliciclastic depositional system

    SciTech Connect

    Comrie, T.A.; Caldwell, D.W. . Dept. of Geology)

    1993-03-01

    The Ripogenus Formation of north-central Maine is shallow marine unit of probable Wenlockian age characterized by interbeds of sandstone and limestone less than 50 cm. in thickness and separated by sharp, often erosional, contacts. Reefal material with abundant stromatoporoids is exposed in the eastern part of the formation and is overlain locally by Silurian andesite and Siluro-Devonian redbeds. Sediment size and bed thickness decrease to the west, as does the relative amount of carbonate sediment. Common fossils also include stromatolites, brachiopods, gastropods, crinoids, and corals. Large fossils, notably the stromatoporoids and stromatolites, are often found in growth position, but smaller fossils are usually found to have been abraided and transported. The formation was deposited in an area shown by paleogeographic reconstructions to have been located just south of the equator (probably near one or more islands) in the lapetus Ocean prior to its closure. Although sedimentary structures are often not well preserved due to its closure. Although sedimentary structures are often not well preserved due to soft-sedimentary deformation and slight metamorphism, there is some evidence of storm-controlled deposition. Deposition of this unit and other Silurian carbonates found in Maine and the Maritime Provinces are unlike those found throughout N. America in that they are the product of localized deposition in an unstable tectonic environment.

  20. Invisible gold distribution on pyrite and ore-forming fluid process of the Huangshan orogenic-type gold deposit of Zhejiang, SE China: implications from mineralogy, trace elements, impurity and fluid inclusion studies

    NASA Astrophysics Data System (ADS)

    Sundarrajan, Vijay Anand; Li, Zilong; Hu, Yizhou; Fu, Xuheng; Zhu, Yuhuo

    2016-07-01

    The Huangshan orogenic-type gold deposit in Zhejiang of SE China occurred in quartz-pyrite veins. It is hosted by phyllonite that underwent greenschist-facies metamorphism along a large Jiangshan-Shaoxing tectonic belt with a NE-SW direction. Trace elemental characteristics, ore-forming process and invisible gold on different forms of pyrite and quartz are studied. The Au associated pyrite can be classified into two categories; recrystallized pyrite and euhedral pyrite. The precipitation of invisible Au on pyrite is mainly derived by Co and Ni with AuHS2 - complex in the mineralizing fluids in different events. The XPS results revealed that valence states of Au3+ replaced 2Fe2+ in the pyrite and Au0 replaced Si4+ in the quartz structure. The electron paramagnetic resonance and trace elemental results suggested that the element pairs of Ge-Li-Al in quartz and Mn-Co-Ni in pyrite have distinct impurities as identified. A fluid inclusion study showed that the auriferous quartz is characterized by low-saline and CO2-rich fluids. Coexistence of the type I-type III inclusions and same range of homogenization temperature with different mode are evidences of immiscible fluid process. The temperature-pressure values of ca. 250 °C/1250 bar and ca. 220 °C/780 bar for gold precipitation have been calculated by intersection of coexisting fluids during the entrapment. The Huangshan orogenic-type gold deposit may be associated with the Wuyi-Yunkai orogeny during the early Paleozoic, including an upper-mid greenschist-facies metamorphism (450-420 Ma). All the features suggest that the Huangshan gold deposit is probably a product linking with the early Paleozoic orogeny in South China.

  1. Provenance and depositional environments of middle Eocene Canoe Formation, Big Bend National Park, Brewster County, Texas

    SciTech Connect

    Rigsby, C.A.

    1984-04-01

    The middle Eocene Canoe Formation contains the first sedimentologic evidence of local volcanism in the Big Bend region. Sediments comprising the formation's lower member, the Big Yellow Sandstone, were deposited by sandy braided streams which were scoured by ancient carbonate highlands and volcanic terranes to the west. The unit represents a continuation of the depositional styles and compositional trends recorded in the Paleocene and early Eocene strata of the region. In contrast, sediments comprising the upper, unnamed member of the Canoe Formation were deposited as a volcanic sediment apron of the fringes of the newly forming Chisos Mountains volcanic center. The sandstones (feldspathic litharenites and lithic arkoses) are dominated by volcanic rock fragments and, as such, document an abrupt change in depositional style and sediment composition brought about by the onset of local volcanism. A comparison of Canoe Formation and earlier Tertiary sediment compositions results in the delineation of distinct petrologic trends which record the tectonic evolution of the early Tertiary sediment source area. The Paleocene sediments of the area were derived primarily from ancient magmatic arcs in northeastern Mexico. With the onset of the Laramide orogeny in late Paleocene-early Eocene, a new source of sediment - newly uplifted carbonate highlands - was added. Local volcanism in the middle Eocene produced yet another source of sediment, lava flows, ash flow tuffs, and sand-size pyroclastic materials from the Chisos Mountain volcanic center. Rapid erosion of these materials produced volcanic sediment aprons such as the one described here. As regional volcanic activity increased, typical Paleocene and early Eocene depositional styles may have been completely abandoned, especially in areas proximal to the volcanic centers.

  2. Manganese formations in the accretionary belts of Japan: Implications for subduction-accretion process in an active convergent margin

    NASA Astrophysics Data System (ADS)

    Nakagawa, M.; Santosh, M.; Maruyama, S.

    2011-08-01

    In the accretionary complexes of Japan, many bedded manganese and iron-manganese ore deposits occur, especially in the Jurassic complexes such as the Chichibu, Tamba, Mino, Ashio and Northern Kitakami belts. The manganese ores in these Jurassic accretionary complexes probably formed from manganese nodule/crust-bearing siliceous sediments on deep-sea floor and were subsequently converted to the manganese ores by metamorphism during the subduction-accretion process. Some of the deposits also show the signatures of younger granitic intrusions. The manganese formations now incorporated within these belts are marker beds of accretionary tectonics associated with plate tectonic processes in convergent margins.

  3. Formation of fine sediment deposit from a flash flood river in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Grifoll, Manel; Gracia, Vicenç; Aretxabaleta, Alfredo; Guillén, Jorge; Espino, Manuel; Warner, John C.

    2014-09-01

    We identify the mechanisms controlling fine deposits on the inner-shelf in front of the Besòs River, in the northwestern Mediterranean Sea. This river is characterized by a flash flood regime discharging large amounts of water (more than 20 times the mean water discharge) and sediment in very short periods lasting from hours to few days. Numerical model output was compared with bottom sediment observations and used to characterize the multiple spatial and temporal scales involved in offshore sediment deposit formation. A high-resolution (50 m grid size) coupled hydrodynamic-wave-sediment transport model was applied to the initial stages of the sediment dispersal after a storm-related flood event. After the flood, sediment accumulation was predominantly confined to an area near the coastline as a result of preferential deposition during the final stage of the storm. Subsequent reworking occurred due to wave-induced bottom shear stress that resuspended fine materials, with seaward flow exporting them toward the midshelf. Wave characteristics, sediment availability, and shelf circulation determined the transport after the reworking and the final sediment deposition location. One year simulations of the regional area revealed a prevalent southwestward average flow with increased intensity downstream. The circulation pattern was consistent with the observed fine deposit depocenter being shifted southward from the river mouth. At the southern edge, bathymetry controlled the fine deposition by inducing near-bottom flow convergence enhancing bottom shear stress. According to the short-term and long-term analyses, a seasonal pattern in the fine deposit formation is expected.

  4. Mineralogical characterization of the Nkamouna Co-Mn laterite ore, southeast Cameroon

    NASA Astrophysics Data System (ADS)

    Lambiv Dzemua, G.; Gleeson, S. A.; Schofield, P. F.

    2013-02-01

    The Nkamouna property is an oxide laterite deposit developed on serpentinized peridotite in southeast Cameroon. It is enriched in Co and Mn, has sub-economic Ni grades and will be mined primarily for Co. The ore zone is ca. 10 m thick and comprises the lower breccia (˜3 m thick) and ferralite (7-8 m thick) units sandwiched between an 8-m-thick ferricrete overburden and a barren hydrated Mg-silicate saprolite. The ore mineral assemblage includes Mn oxyhydroxides, magnetite, maghemite, ferritchromite, goethite, hematite, kaolinite and gibbsite. Lithiophorite is the most common Mn mineral and is the main host of Co, Mn and a significant proportion of Ni. It occurs as coatings in pores and on other mineral grains and as concretions and impregnations in the matrix. It is invariably associated with gibbsite in the lower breccia and with magnetite and ferritchromite in the ferralite. Although ore in the lower breccia is volumetrically less important than the ferralite, it has the highest grade and Co/Ni ratio. The lithiophorite in the ore zone is authigenic, and its formation was enhanced by influx of Al3+ from the overlying ferricrete. Magnetite and ferritchromite in the ferralite are relicts and contributed to mineralization by enhancing the permeability of the ferralite and providing substrates for the precipitation of the Mn oxyhydroxides. The structure and mode of occurrence of the lithiophorite makes Nkamouna ore amenable to physical beneficiation, producing a concentrate with Co grades 2.3-4.5 times higher than the run-of-mine ore.

  5. Enhancement effect of relative humidity on the formation and regional respiratory deposition of secondary organic aerosol.

    PubMed

    Yu, Kuo-Pin; Lin, Chi-Chi; Yang, Shang-Chun; Zhao, Ping

    2011-07-15

    In this study, we investigated the effect of relative humidity (RH) on the formation of secondary organic aerosol (SOA) generated from the ozonolysis of d-limonene in an environmental chamber. The mass yield and the number concentration of SOA increased seven and eight times, respectively, when the RH increased from 18% to 82%. The measured total loss rates (apparent loss rates) of the number and mass concentration of SOA in the chamber ranged from 1.70 to 1.77 h(-1) and from 2.51 to 2.61 h(-1), respectively, at a controlled ventilation rate of 0.72±0.04 h(-1). The wall-deposition-loss-rate coefficient observed (1.00±0.02 h(-1)) was approximate to the estimated value based on Zhao and Wu's model which includes the factors of turbulence, Brownian diffusion, turbophoresis and surface roughness. According to the ICRP (International Commission on Radiological Protection) model, the inhaled SOA particles are deposited primarily in the alveoli of the lung. The integrated alveolar deposited dose of the mass (surface area) of SOA over 3h accounted for 74.0-74.8% (74.3-74.9%) of the total deposited dose at the investigated RH. Raising the RH resulted in the growth of SOA particle sizes and increment of the deposition dose but did not cause significant changes in the ratio of regional to the total respiratory deposition of SOA. PMID:21570180

  6. A model for heavy mineral deposit formation within Pleistocene to Holocene shoreline sequences in Georgia

    SciTech Connect

    Cocker, M.D. )

    1993-03-01

    The forms and locations of heavy mineral (HM) deposits, and the geomorphologies and HM suites of the six major Pleistocene paleobarrier island complexes on the Georgia coastal plain and the Holocene shoreline deposits may be the result of physical conditions prevalent during the development of two distinct shoreline sequences. The older Wicomico, Penholoway and Talbot complexes are typified by large, linear, undissected sand bodies and long, linear HM deposits and may have been strongly influenced by a greater sediment supply, a wave-dominated energy regime, and a steeper continental shelf than the younger Pamlico, Princess Anne, Silver Bluff and Holocene complexes. The younger complexes which consist of small, stubby and complexly dissected sand bodies may be the result of a tidal dominated energy regime and a more restricted sediment source. In the younger complexes, HM deposits are short and stubby and are commonly located immediately south of a source river. These relations indicate that only a relatively minor amount of longshore transport has occurred. Location of the HM deposits in the older shoreline sequences at a considerably greater distance south of a source river indicates that a greater degree of transport was involved. The development of stronger and more consistent longshore currents and winds during the earlier part of the Pleistocene may account for the differences in sediment transport and HM deposit formation in the older shoreline sequences. These physical differences may be related to the steeper continental shelf and different climatic conditions during the warmer, interglacial period.

  7. Depositional history of the Lower Triassic Dinwoody Formation in the Wind River basin area, Wyoming

    SciTech Connect

    Paul, R.K.; Paull, R.A. )

    1993-04-01

    Thirty-three measured sections of the Dinwoody Formation, including five from the literature, provide information on thickness, lithology, paleontology, and stratigraphic relations within the Wind River basin and immediately adjacent areas of Wyoming. Most of these sections are in Fremont County, and some lie within the Wind River Indian Reservation. The Dinwoody becomes progressively thinner eastward, from a maximum thickness of 54.6 m in the northwestern Wind River Mountains to zero near the Natrona County line. The formation is characterized by yellowish-weathering, gray siltstone and silty shale. Variable amounts of limestone, sandstone, gypsum, and claystone are also present. Marine bivalves, gastropods, brachiopods (Lingula), and conodonts are common in the western part of the study area, but are absent to the northeast in gypsiferous strata, and near the eastern limit of Dinwoody deposition. The Dinwoody in the Wind River Basin area was deposited unconformably on the Upper Permian Ervary Member of the Park City Formation during the initial Mesozoic flood onto the Wyoming shelf during the Griesbachian, and represents the first of three Lower Triassic transgressive sequences in the western miogeocline. Conodonts of the Isarcica Chronozone document the rapid nature of this eastward transgression. The Permian surface underlying the Dinwoody rarely shows evidence of the long hiatus separating rocks of this age and earliest Triassic deposits. The Dinwoody transgression was followed by westward progradation of the Red Peak Formation of the Chugwater Group across the study area.

  8. Geologic map of Kundelan ore deposits and prospects, Zabul Province, Afghanistan; modified from the 1971 original map compilations of K.I. Litvinenko and others

    USGS Publications Warehouse

    Tucker, Robert D.; Peters, Stephen G.; Stettner, Will R.; Masonic, Linda M.; Moran, Thomas W.

    2015-01-01

    Elevations on the cross sections are derived from the original Soviet topography and may not match the Global Digital Elevation Model (GDEM) topography used on the redrafted map of this report. Most hydrography derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) has not been included on our redrafted version of the map because of a poor fit with alluvial deposits from the unmodified original Soviet map (graphical supplement no. 18; Litvinenko and others, 1971).

  9. Potash ore reserves in the proposed Waste Isolation Pilot Plant area, Eddy County, southeastern New Mexico

    USGS Publications Warehouse

    John, Charles B.; Cheeseman, R.J.; Lorenz, J.C.; Millgate, M.L.

    1978-01-01

    The proposed Waste Isolation Pilot Plant (WIPP) area includes about 18,960 acres in Tps. 22 and 23 S., Rs. 30 and 31 E., New Mexico Principal Meridian, Eddy County, southeastern New Mexico. It is located within the Carlsbad Mining District about 25 miles east of Carlsbad. The WIPP area is immediately south of the Capitan Limestone subcrop, which formed the northern margin of the Delaware basin in Permian time. During Late Permian (Ochoan) time, gypsum, anhydrite, and halite were deposited in the seas of the Delaware basin to form the Castile Formation. These deposits have a maximum thickness of about 2,000 feet and grade upward into the more argillaceous beds of the Salado Formation. The Salado Formation contains abundant sulfate minerals, notably anhydrite and polyhalite. The potash ore minerals, langbeinite and sylvite, occur in the upper part of the Salado Formation in the McNutt potash zone, a local name applied to a potassium-rich zone.

  10. PHASE ANALYSES OF URANIUM-BEARING MINERALS FROM THE HIGH GRADE ORE, NOPAL I, PENA BLANCA, MEXICO

    SciTech Connect

    M. Ren; P. Goodell; A. Kelts; E.Y. Anthony; M. Fayek; C. Fan; C. Beshears

    2005-07-11

    The Nopal I uranium deposit is located in the Pena Blanca district, approximately 40 miles north of Chihuahua City, Mexico. The deposit was formed by hydrothermal processes within the fracture zone of welded silicic volcanic tuff. The ages of volcanic formations are between 35 to 44 m.y. and there was secondary silicification of most of the formations. After the formation of at least part of the uranium deposit, the ore body was uplifted above the water table and is presently exposed at the surface. Detailed petrographic characterization, electron microprobe backscatter electron (BSE) imagery, and selected x-ray maps for the samples from Nopal I high-grade ore document different uranium phases in the ore. There are at least two stages of uranium precipitation. A small amount of uraninite is encapsulated in silica. Hexavalent uranium may also have been a primary precipitant. The uranium phases were precipitated along cleavages of feldspars, and along fractures in the tuff. Energy dispersive spectrometer data and x-ray maps suggest that the major uranium phases are uranophane and weeksite. Substitutions of Ca and K occur in both phases, implying that conditions were variable during the mineralization/alteration process, and that compositions of the original minerals have a major influence on later stage alteration. Continued study is needed to fully characterize uranium behavior in these semi-arid to arid conditions.

  11. Depositional environments of the Santa Margarita Formation in the Miocene Santa Maria basin, Huasna syncline

    SciTech Connect

    Phillips, R.L. )

    1991-02-01

    Preliminary investigation of the depositional environments of the middle sandstone member of the late middle Miocene Santa Margarita Formation in the Huasna syncline suggests a current-dominated shallow shelf environment. Progradation of coarse-grained clastic and bioclastic-rich sediment over siltstone documents the initial stage of deposition of this sand body. Overlying the basal intensely bioturbated bioclastic sediments are large-scale tabular cross-beds, up to 16 m thick, interbedded with tabular lag deposits of barnacles, oysters, and echinoids. The tabular fossil-rich beds, which form sequences up to 6 m thick between the large-scale cross-beds, represent either deposition of bottom set beds of the large-scale cross-beds or current swept lag deposits. Increasing energy conditions are recorded vertically by a decrease in the amount of bioturbation and by an increase in large-scale cross-bed sets and cosets. however, in the northern outcrop area subtidal channels are incised into the upper bioclastic sediments suggesting local shoaling conditions. Paleocurrent data record a unidirectional southwest-directed current trend normal to the basin axis and the East Huasna fault. The coarse clastic deposition terminates with deposition of siltstone as energy conditions decreased and water depth again increased. A current-swept shallow shelf containing extensive sandwaves comprises the major depositional environments. The paleocurrent data and large-scale cross-beds suggest that the shallow shelf extended to the east of the Huasna syncline and that the currents were most likely tidal in origin.

  12. Formation of circular crack pattern in deposition self-assembled by drying nanoparticle suspension.

    PubMed

    Jing, Guangyin; Ma, Jun

    2012-05-31

    Curved cracks widely exist in nanoparticle (NP) deposition produced by drying colloidal suspension. Circular cracks, for example, initiate and propagate along a circular trajectory. One feasible theoretical explanation of a circular crack is the Xia-Hutchinson model, in which a preexisting track (flaw loop) in the film is necessary for initiating and propagating the crack on the circular path. Here, we report the first experimental evidence of dried deposition to support this model. Our results indicate that cracks along the circular trajectory can surprisingly "pass" across a 180 μm air gap. Moreover, two arc-path cracks originate in different areas and propagate to meet, forming a circular trajectory. These unexpected crack initiation and propagation indicate that the crack propagates alone the "preformed" track, experimentally confirming the hypothesis proposed by the Xia-Hutchinson model. The transition of the circular crack to a radial one indicates that the deposition microstructure is the dominant factor for the crack formation. PMID:22577983

  13. Terrestrial radioisotopes in black shale hosted Mn-carbonate deposit (Úrkút, Hungary)

    NASA Astrophysics Data System (ADS)

    Vigh, Tamás; Kovács, Tibor; Somlai, János; Kávási, Norbert; Polgári, Márta; Bíró, Lóránt

    2013-08-01

    Previously, little attention has been paid to terrestrial radioisotopes (U, Th, 40K) occurring in manganese ores, despite the fact that the biogeochemical relationship between Mn and U is versatile. Occurrence of terrestrial radioisotopes in great amounts during mining on a long-term causes significant radiation exposure. It is important to inspect black shale-hosted manganese ores from this aspect, as black shales are typically potential U-rich formations. Despite the increased radon concentration in the mine, based on the detailed major elements, trace elements and gamma spectroscopy inspection of the rock types of deposit, the U, Th enrichment was undetectable. However, the U and Th content of about average terrestrial abundance of the great ore amount may be in the background of the increased radon concentration level. This Mn-carbonate ore deposit in spite of the low U content exhibit potential radon danger for miners, which can be eliminated with intensive air change only.

  14. Stratigraphy and depositional environments of Fox Hills Formation in Williston basin

    SciTech Connect

    Daly, D.J.

    1988-07-01

    The Fox Hills Formation (Maestrichtian), representing part of a regressive wedge deposited during the withdrawal of the sea from the Western Interior at the close of the Cretaceous, consists of marginal marine strata transitional between the offshore deposits of the underlying Pierre Shale and the terrestrial deltaic and coastal deposits of the overlying Hell Creek Formation. An investigation of outcrops of the Fox Hills Formation along the western and southern flanks of the Williston basin and study of over 300 oil and gas well logs from the central part of the basin indicate that the formation can be divided both stratigraphically and areally. Stratigraphically, the Fox Hills can be divided into lower and upper sequences; the lower includes the Trail City and Timber Lake Members, and the upper sequence includes the Colgate Member in the west and the Iron Lightning and Linton Members in the east. Areally, the formation can be divided into a northeastern and western part, where the strata are 30-45 m thick and are dominated by the lower sequence, and into a southeastern area where both the lower and upper sequences are well developed in a section 80-130 m thick. Typically, the lower Fox Hills consists of upward-coarsening shoreface or delta-front sequences containing hummocky bedding and a limited suite of trace fossils, most notably Ophiomorpha. In the southeast, however, these strata are dominated by bar complexes, oriented northeast-southwest, composed of cross-bedded medium to very fine-grained sand with abundant trace and body fossils. The upper Fox Hills represents a variety of shoreface, deltaic, and channel environments. The strata of the Fox Hills Formation exhibit facies similar to those reported for Upper Cretaceous gas reservoirs in the northern Great Plains.

  15. Geochemical signatures of possible deep-seated ore deposits in Tertiary volcanic centers, Arizona and New Mexico, U.S.A.

    USGS Publications Warehouse

    Watts, K.C., Jr.; Hassemer, J.R.

    1989-01-01

    A reconnaissance geochemical survey of stream drainages within 21,000 km2 of southeastern Arizona and southwestern New Mexico shows broad zones of low-level to moderate contrast anomalies, many associated with mid-Tertiary eruptive centers and Tertiary fault zones. Of these eruptive centers, few are known to contain metallic deposits, and most of those known are minor. This, however, may be more a function of shallow erosion level than an indication of the absence of mineralization, since hydrothermal alteration and Fe-Mn-oxide staining are widespread, and geochemical anomalies are pervasive over a larger part of the region than outcrop observations would predict. Accordingly, interpretations of the geochemical data use considerations of relative erosion levels, and inferred element zonalities, to focus on possible undiscovered deposits in the subsurface of base-, precious-, and rare-metal deposits of plutonic-volcanic association. In order to enhance the identification of specific deep targets, we use the empirically determined ratio: Ag+Mn+Pb+Zn+Ba Au+Mo+Cu+Bi+W This ratio is based on reported metal contents of nonmagnetic heavy-mineral samples from the drainage sediment, determined by emission spectrographic analysis. Before the ratio was computed for each sample site, the data were normalized to a previously estimated regional threshold value. A regional isopleth map was then prepared, using a cell-averaging computer routine, with contours drawn at the 25th, 50th, 75th, 80th, 90th, 95th and 99th percentiles of the computed data. ?? 1989.

  16. Origin of tuff deposits in the lower Miocene Lospe Formation, Santa Maria basin, California

    SciTech Connect

    Cole, R.B. ); Stanley, R.G. ); Johnson, S.Y. )

    1991-02-01

    The Lospe Formation contains at least five mappable tuff units (17-18 Ma) which were erupted during initial stages of Neogene Santa Maria basin subsidence. Individual tuff units are lenticular, as much as 15-20 m thick, and 1-3 km wide; they were deposited predominantly in a lacustrine setting. Subaqueous deposition is indicated by facies of the interbedded nonvolcanic Lospe Formation. The lowermost Lospe Tuff unit, however, which overlies Jurassic basement, is interpreted as a subaerial deposit. Each subaqueous tuff unit contains two or more eruption units. Each eruption unit consists of three zones which are, from base to top: (1) massive vitric tuff comprising about 50% of the eruption unit, (2) thin- to medium-bedded vitric tuff with pumice concentrations at the tops of beds and mud drapes between beds, and (3) a thin-bedded interval of massive to planar laminated tuffaceous siltstone-mudstone. The predominance of delicate cuspate vitric shards and pumice, and the near absence of nonvolcanic detritus indicates that little or no reworking of the ash occurred prior to deposition. The Lospe tuffs are predominantly distal pyroclastic flow (zones 1 and 2) and pyroclastic turbidite (zones 2 and 3) deposits, derived from subaerial magmatic eruptions. A possible source for the Lospe tuffs is located at Tranquillon Mountain, 30 km to the south in the westernmost Transverse Range, where 17-18 Ma proximal pyroclastic deposits of welded lithic tuff breccia and thick pumiceous fallout tuffs are present. The similar ages, stratigraphic positions, and petrology, as well as the lateral facies relations suggests a correlation between the Tranquillon volcanic center and the Lospe tuff units. The authors are currently testing this hypothesis on the basis of geochemical and isotopic analyses.

  17. 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.

  18. Synthrusting deposition of the Pennsylvanian and Permian Strathearn Formation, Northern Carlin Trend, Nevada

    NASA Astrophysics Data System (ADS)

    Theodore, Ted G.; Berger, Vladimir I.; Singer, Donald A.; Harris, Anita G.; Stevens, Calvin H.

    2004-03-01

    The middle Upper Pennsylvanian and middle Lower Permian Strathearn Formation belongs to the overlap assemblage of the Antler orogen in Nevada. At Beaver Peak, near the Carlin Trend of gold deposits, it contains synorogenic conglomerate deposits associated with emplacement of a regionally extensive, 1-km-thick tectonic wedge that is floored by the Coyote thrust. Normal marine conodont biofacies throughout the Strathearn Formation suggest middle shelf or deeper, depositional environments. The allochthon floored by the Coyote thrust has been thrust above a middle Upper Pennsylvanian, lower conglomerate unit of the Strathearn Formation. A middle Lower Permian upper conglomerate unit, the highest unit recognized in the Strathearn Formation, as well as similarly aged dolomitic siltstone, onlap directly onto Ordovician quartzarenite of the Vinini Formation that makes up most of the Coyote allochthon. Quartz grains and quartzarenite fragments of variable roundness and shape in the conglomerate units were derived from the presently adjoining tectonic lobe of mostly quartzarenite that advanced southeast (present geographic coordinates) during the late Paleozoic into the developing Strathearn basin. Chert fragments in the conglomerates probably were derived mostly from Devonian Slaven Chert, including a widespread thick mélange unit of the Slaven Chert in the footwall of the Coyote thrust. Lithologic and shape ratio data from approximately 4200 clasts at 17 sites of the two major conglomerate units in the Strathearn Formation at Beaver Peak are roughly similar in that they contain only chert and quartzarenite clasts, and chert clasts predominate in both units. They differ in the relative proportion of the two lithologies whereby quartzarenite clasts increase sixfold in the upper unit (middle Lower Permian) versus its content in the lower conglomerate unit. Relations at the unconformity between the upper conglomerate unit and its underlying quartzarenite shows quartzarenite

  19. Sedimentological study of sandy and shaly deposits (Beglia Formation) in Cap Bon area

    SciTech Connect

    Mahjoub, M.N.; Khessibi, M.

    1988-08-01

    Sedimentological study of sandy and shaly deposits of the Beglia formation has been made in Cap Bon (northeast of Tunisia) to define a sedimentological and paleogeographical model which could be extrapolated into the Gulf of Hammamet. The main results follow. (1) The Beglia formation is serravalian in age and has a migratory deltaic complex facies which includes river and marine affinities (flood plain and tidal). (2) Three intervals within the Beglia have been studied in detail and indicate a northwest-southeast depositional trend which the authors consider the main direction of the middle Miocene detrital deposits in northeastern Tunisia. (3) The fine and well-sorted sandstones which extend up to hectometric and kilometric size, observed in outcrop, are the distal zones of the migratory fans and bars. (4) These sandstone bodies, because of their relative small size within their deltaic model, do not extend to the Gulf of Hammamet. The sandstones offshore have produced hydrocarbons in several areas. They are the distal equivalent of the poorly sorted and coarse channel deposits studied in the outcrops.

  20. Influence of peat formation conditions on the transformation of peat deposit organic matter

    NASA Astrophysics Data System (ADS)

    Serebrennikova, O. V.; Strelnikova, E. B.; Preis, Yu I.; Duchko, M. A.

    2015-11-01

    The paper studies the individual composition of n-alkanes, polycycloaromatic hydrocarbons, steroids, bi-, tri-, and pentacyclic terpenoids of two peat deposits of rich fen Kirek located in Western Siberia. Considering the individual n-alkanes concentrations, some indexes were calculated to estimate the humidity during peat formation. It was shown that the pH of peat medium primarily affects steroids, tri- and pentacyclic terpenoids transformations.

  1. Carbonate deposition, Pyramid Lake subbasin, Nevada: 1. Sequence of formation and elevational distribution of carbonate deposits (Tufas)

    USGS Publications Warehouse

    Benson, L.

    1994-01-01

    During the late Quarternary, the elevation of terrace cutting and carbonate deposition in the Pyramid Lake subbasin were controlled by constancy of lake level imposed by spill to adjoining subbasins. Sill elevations are 1177-1183 m (Mud Lake Slough Sill), 1207 m (Emerson Pass Sill), and 1265 m (Darwin Pass Sill). Carbonate deposition was favored by: (1) hydrologic closure, (2) proximity to a source of calcium, (3) elevated water temperature, and (4) a solid substrate. The thickness and aspect of tufa are a function oflake-level dynamics. Relatively thin sheets and pendant sheets were deposited during a rising or falling lake. The upper parts of thick reef-form tufas have a horizontal aspect and were deposited in a lake which was stabilized by spill to the Carson Desert subbasin. The lower parts of the reef-form tufas are thinner and their outer surface has a vertical aspect, indicating that the lower part formed in a receding lake. The thickest and most complete sequences of tufa are mounds that border the Pyramid Lake shore. The tops of the tallest mounds reach the elevation of the Darwin Pass Sill and many mounds have been eroded to the elevations of the Mud Lake Slough Sill of the Emerson Pass Sill. The sequence of tufa formation (from oldest to youngest) displayed in these mounds is: (1) a beachrock containing carbonate-cemented volcanic cobbles, (2) broken and eroded old spheroids that contain thinolitic tufa and an outer rind of dense laminated tufa, (3) large cylindrical (tubular) tufas capped by (4) coatings of old dense tufas, and (5) several generations of old branching tufa commonly associated with thin, platy tufas and coatings of thinolitic tufa, (6) young spheroids that contain poorly oriented young thinolitic tufa in the center and several generations of radially oriented young thinolitic tufas near the outer edge, (7) a transitional thinolite-to-branching tufa, (8) two or more layers of young branching tufa, (9) a 0.5-cm-thick layer of fine

  2. Formation of Lamellar Heterolattices in Block Copolymer Thin Films by Sequential Electrospray Deposition

    NASA Astrophysics Data System (ADS)

    Choo, Youngwoo; Hu, Hanqiong; Toth, Kristof; Osuji, Chinedum

    Electrospray deposition (ESD) of block copolymers (BCPs) on a heated substrate provides precise control over the formation of BCP thin films. This continuous deposition process allows one to fabricate heterogeneously assembled thin films by altering the deposition materials. Here, we demonstrate such the sequential ESD of lamellae-forming poly(styrene- b-4-vinylpyridine) BCPs with differing molecular weights and explore the morphology of the composite films. The resulting structure of the heterolattice interface was a strong function of temperature. Sharp interfaces with abrupt changes in the lamellar period (L0) were observed at lower deposition temperatures (150 - 170 °C), while higher temperature (190 °C) produced a smooth variation in the lamellar period from one molecular weight to the next. Furthermore, the ordering kinetics of a secondary layer which was deposited onto the primary layer could be substantially enhanced depending on the molecular weight of the polyme