Direct evidence for the source of uranium in the Baiyanghe deposit from accessory mineral alteration in the Yangzhuang granite porphyry, Xinjiang Province, northwest China

2020 ◽  
Vol 105 (10) ◽  
pp. 1556-1571
Author(s):  
Long Zhang ◽  
Xiaofeng Li ◽  
Guo Wang ◽  
Mou Wang
Keyword(s):  
Direct Evidence ◽  
Volcanic Rocks ◽  
Primary Source ◽  
Northwest China ◽  
Ore Deposits ◽  
Granite Porphyry ◽  
Source Rocks ◽  
Accessory Mineral ◽  
Accessory Minerals ◽  
Ore Bodies

Abstract Circumstantial evidence for the sources of uranium in ore deposits may be drawn from the study of deposit geochemistry and mineralogy. However, direct evidence supporting uranium leaching from source rocks has rarely been found. This study investigates the source of uranium in the Baiyanghe deposit in the Xiemisitai Mountains, northwest China. The main uranium ore bodies occur as fracture-fillings along contact zones between the Yangzhuang granite porphyry and the Devonian volcanic rocks. Zircon, thorite, columbite-(Mn), and bastnäsite are the dominant accessory minerals that host uranium in the granite porphyry. In situ columbite-(Mn) LA-ICP-MS U-Pb dating yields a weighted mean 206Pb/238U age of 310 ± 4 Ma, suggesting that the Yangzhuang granite porphyry was emplaced during the Late Carboniferous. Backscattered electron (BSE) images reveal that various degrees of alteration of these same accessory minerals may be observed in the granite porphyry, and the altered domains of these minerals have lower BSE intensities compared to the unaltered domains. Results indicate that the altered domains of zircon grains have lower concentrations of Zr, Si, and U, and higher concentrations of Y, Fe, Ca, and P relative to the unaltered domains, and the altered domains of columbite-(Mn) grains are enriched in Ti and Fe and are depleted in Nb, Ta, Mn, U, and Zr. The altered domains of thorite grains have higher concentrations of Zr, Fe, Ca, Nb, and P, and lower Th and U compared to those of the relict domains. The petrochemical data indicate that the granite porphyry experienced losses in U, Be, F, Ba, Sr, Pb, Zr, Mo, Nb, Ta, and Hf during alteration. These results suggest that the past-magmatic hydrothermal fluids might be responsible for the mobilization of uranium form minerals in the granite porphyry. It is concluded that U-bearing accessory minerals in the granite porphyry were the primary source of uranium, and that post-magmatic hydrothermal processes caused remobilization and significant localized enrichment of the uranium to form high-grade ores as fracture-fillings along its contacts.

U - Th - REE Mobility and Diffusion in Granitic Environments During Alteration of Accessory Minerals and U - Ores: A Geochemical Analogue to Radioactive Waste Disposal

1988 ◽  
Vol 127 ◽  
Author(s):  
M. Cathelineau ◽  
M. Vergneaud
Keyword(s):  
Radioactive Waste Disposal ◽  
Granitic Rocks ◽  
Critical Parameters ◽  
Accessory Mineral ◽  
Accessory Minerals ◽  
Oxidation Reduction ◽  
Ore Bodies ◽  
Geological Barrier ◽  
Geochemical Studies ◽  
Ree Mobility

ABSTRACTU, Th and REE concentrations and distributions have been studied in granitic rocks, using a multidisciplinary approach involving fission-track micromapping of cracks in oriented samples, together with mineralogical and geochemical studies of the different U-Th-REE bearing phases. The behaviour of U, Th and Nd, considered as chemical analogue elements of the radiotoxic nuclides, was investigated either in the vicinity of microsites (accessory mineral environment) or along plurimetric sections around U-ore bodies. The different granite minerals, especially the accessory minerals (uraninite, monazite, thorite, apatite, xenotime), as well as U-ores, present different initial concentrations of U, Th and REE. Limitations to the analogy between these U-Th-REE concentrations and the radwastes is discussed as a function of their mineralogical features, chemical composition, size and solubilities. These primary concentrations present different behaviour when subjected to hydrothermal alteration, such as propylitization, phyllite type alteration, or clay alteration. Results show that in reduced media, in the temperature range 80–200°C, the rate of mobilization of U, Th, REE is relatively moderate. However, fluids enriched in fluorides, phosphates or carbonates may significantly solubilize and transport U and REE under specific conditions. In addition, the degree of opening of the microcracks and faults, as well as the oxidation-reduction processes, are critical parameters for the efficiency of the granitic geological barrier.

scholarly journals Radiogenic Pb Enrichment of Mississippi Valley-Type Metallic Ore Deposits, Southern Ozarks: Constraints Based on Geochemical Studies of Source Rocks and Their Diagenetic History

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 172
Author(s):  
Jonathan Chick ◽  
Sydney E. McKim ◽  
Adriana Potra ◽  
Walter L. Manger ◽  
John R. Samuelsen
Keyword(s):  
Linear Trend ◽  
Ore Deposits ◽  
Source Rocks ◽  
Mississippi Valley ◽  
Isotopic Signatures ◽  
Boone Formation ◽  
Tripolitic Chert ◽  
Geochemical Studies ◽  
Mississippi Valley Type ◽  
Valley Type

Southern Ozark Mississippi Valley-type ores are enriched in radiogenic Pb, with isotopic signatures suggesting that metals were supplied by two end-member components. While the less radiogenic component appears to be derived from various shale and sandstone units, the source of the more radiogenic component has not yet been identified. Analyses of cherts from the Early Ordovician Cotter Dolomite and tripolitic chert from the Early Mississippian Boone Formation contain highly radiogenic Pb, with isotopic ratios comparable to those of ores. However, most samples have lower 208Pb/204Pb and 207Pb/204Pb for a given 206Pb/204Pb compared to ores. These relationships demonstrate that the enriched Pb isotopic values of the ore array cannot be related to the host and regional lithologies sampled, suggesting that the source of high ratios may lay further afield. The slope of the linear trend defined by the Pb isotope ratios of ores corresponds to an age of about 1.19 Ga. Therefore, an alternative for the linear array is the involvement of Precambrian basement in supplying ore Pb. Rare earth element patterns show that diagenetic processes involving the action of groundwater and hydrothermal fluids affected the sampled lithologies to various degrees, with Cotter Dolomite having experienced the highest degree of alteration.

Constraints on the formation of the giant Daheishan porphyry Mo deposit (NE China) from whole-rock and accessory mineral geochemistry

2021 ◽  
Author(s):  
Kai Xing ◽  
Qihai Shu ◽  
David R Lentz
Keyword(s):  
High Water ◽  
Accessory Mineral ◽  
Ne China ◽  
Accessory Minerals ◽  
Slab Rollback ◽  
Continental Arc ◽  
Arc Setting ◽  
Porphyry Mo Deposit ◽  
T Values ◽  
Water Contents

Abstract There are more than 90 porphyry (or skarn) Mo deposits in northeastern China with Jurassic or Cretaceous ages. These are thought to have formed mainly in a continental arc setting related to the subduction of the Paleo-Pacific oceanic plate in the Jurassic and subsequent slab rollback in the early Cretaceous. The Jurassic Daheishan porphyry Mo deposit is one of the largest Mo deposits in NE China, which contains 1.09 Mt Mo with an average Mo grade of 0.07%. To better understand the factors that could have controlled Mo mineralization at Daheishan, and potentially in other similar porphyry Mo deposits in NE China, the geochemical and isotopic compositions of the ore-related granite porphyry and biotite granodiorite, and the magmatic accessory minerals apatite, titanite and zircon from the Daheishan intrusions, were investigated so as to evaluate the potential roles that magma oxidation states, water contents, sulfur and metal concentrations could have played in the formation of the deposit. Magmatic apatite and titanite from the causative intrusions show similar εNd(t) values from -1.1 to 1.4, corresponding to TDM2 ages ranging from 1040 to 840 Ma, which could be accounted for by a mixing model through the interaction of mantle-derived basaltic melts with the Precambrian lower crust. The Ce and Eu anomalies of the magmatic accessory minerals have been used as proxies for magma redox state, and the results suggest that the ore-forming magmas are highly oxidized, with an estimated ΔFMQ range of + 1.8 to + 4.1 (+2.7 in average). This is also consistent with the high whole-rock Fe2O3/FeO ratios (1.3–26.4). The Daheishan intrusions display negligible Eu anomalies (Eu/Eu* = 0.7–1.1) and have relatively high Sr/Y ratios (40–94) with adakitic signatures; they also have relatively high Sr/Y ratios in apatite and titanite. These suggest that the fractionation of amphibole rather than plagioclase is dominant during the crystallization of the ore-related magmas, which further indicates a high magmatic water content (e.g., >5 wt%). The magmatic sulfur concentrations were calculated using available partitioning models for apatite from granitoids, and the results (9–125 ppm) are indistinguishable from other mineralized, subeconomic and barren intrusions. Furthermore, Monte Carlo modelling has been conducted to simulate the magmatic processes associated with the formation of the Daheishan Mo deposit, and the result reveals that a magma volume of ∼280 km3 with ∼10 ppm Mo was required to form the Mo ores containing 1.09 Mt Mo in Daheishan. The present study suggests that a relatively large volume of parental magmas with high oxygen fugacities and high water contents is essential for the generation of a giant porphyry Mo deposit like Daheishan, whereas a specific magma composition (e.g., with unusually high Mo and/or S concentrations), might be less critical.

Platinum-group minerals from alluvial placers of the Kitoy river (south-east part of East Sayan, Russia)

2021 ◽  
Author(s):  
Olga Kiseleva ◽  
Yuriy Ochirov ◽  
Sergey Zhmodik ◽  
Brian Nharara
Keyword(s):  
Publishing House ◽  
Primary Source ◽  
Platinum Metal ◽  
Mineral Chemistry ◽  
Source Rocks ◽  
Tectonic Deformation ◽  
Platinum Group Minerals ◽  
Placer Deposits ◽  
Platinum Group ◽  
Eastern Sayan

<p>The studied area is in the southeastern region of Eastern Sayan. Several tectonically dissected ophiolite complexes were exposed along the margin of the Gargan block and tectonically thrust over this block. Placer nuggets of PGE alloys from the Kitoy river were examined using a scanning electron microscope. Platinum-group minerals (PGM's) in placer deposits provide vital information about the types of their primary source rocks and ores as well as the conditions of formation and alteration. The primary PGM's are Os-Ir-Ru alloys, (Os, Ru)S<sub>2</sub>, and (Os, Ir, Ru)AsS. (Os, Ru)S<sub>2</sub> form overgrowth around the Os-Ir-Ru alloys. The secondary, remobilized PGM's are native osmium, (Ir-Ru) alloys, garutite (Ir, Ni, Fe), zaccarinite (RhNiAs), selenides, tellurides (Os, Ir, Ru), and non-stoichiometric (Pd, Pt, Fe, Te, Bi) phases (Fig.1). Secondary PGM's (garutite and RhNiAs) form rims around Os-Ir-Ru alloys, intergrowth with them, or form polyphase aggregates. Such PGM's (identical in composition and microstructure) are also found in chromitites from Neoproterozoic ophiolite massifs of Eastern Sayan (Kiseleva et al., 2014; 2020). Platinum-metal minerals, exotic for ophiolites, are found among secondary PGM's such as selenides and tellurides (Os, Ir, Ru), (Pt, Pd)<sub>3</sub>Fe, Pd<sub>3</sub>(Te, Bi), (Au, Ag), and non-stoichiometric (Pd, Pt, Fe, Te, Bi) phases. They occur as inclusions in the Os-Ir-Ru alloys or fill cracks in crushed grains of primary PGM's. PGM's in placer deposits of the Kitoy river are similar to the mineral composition of PGE in chromitites of the Ospa-Kitoy ophiolitic massif, which contain Pt-Pd minerals and Pt impurities in Os-Ir-Ru alloys (Kiseleva et al., 2014). Selenides (Os-Ir-Ru) are rare within PGM's from ophiolite chromitites (Barkov et al., 2017; Airiyants et al., 2020) and also occur in chromitites of the Dunzhugur ophiolite massif (Kiseleva et al., 2016). Features of selenides and tellurides (Os, Ir, Ru) indicate their late formation as a result of the influence of magmatic and metamorphic fluids on primary PGE alloys. The filling of cracks in crushed (Os-Ir-Ru) alloys indicates that selenides and tellurides formed during tectonic deformation processes. The source of platinum-group minerals from the Kitoy river placer is the Ospa-Kitoy ophiolite massif, and primarily chromitites.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.eb9553e3c70065361211161/sdaolpUECMynit/12UGE&app=m&a=0&c=f3ccc1c7cf7d06094d2afaa34fe9d9a1&ct=x&pn=gepj.elif&d=1" alt=""></p><p>Figure 1. BSE microphotographs of PGM from from alluvial placers of the Kitoy river</p><p>Mineral chemistry was determined at the Analytical Centre for multi-elemental and isotope research SB RAS. This work supported by RFBR grants: No. 16-05-00737a,  19-05-00764а, 19-05-00464a and the Russian Ministry of Education and Science</p><p>References</p><p>Airiyants E.V., Belyanin D.K., Zhmodik S.M., Agafonov L.V., Romashkin P.A.  // Ore Geology Reviews. 2020. V. 120. P.  103453</p><p>Barkov A.Y., Nikiforov A.A., Tolstykh N.D., Shvedov G.I., Korolyuk V.N. // European J. Mineralogy. 2017. V.29(9). P.613-621.</p><p>Kiseleva O.N., Zhmodik S.M., Damdinov B.B., Agafonov L.V., Belyanin D.K. // Russian Geology and Geophysics. <strong>2014</strong>. V. 55. P. 259-272.</p><p>Kiseleva O.N., Airiyants E.V., Belyanin D.K., Zhmodik S.M., Ashchepkov I.V., Kovalev S.A. // Minerals. 2020. V. 10. N 141. P. 1-30.</p><p>Kiseleva O.N., Airiyants E.V., Zhmodik S.M., Belyanin D.K / Russian and international conference proceedings “The problems of geology and exploitation of platinum metal deposits” – St.Petersburg: Publishing house of St.Petersburg State University. 2016. 184 P.</p>

Distribution and source significance of 2-methylalkanes in coal-measure source rocks, northwest China

2019 ◽  
Vol 174 ◽  
pp. 257-267 ◽  
Author(s):  
Qingsong Cheng ◽  
Huang Guanghui ◽  
Min Zhang ◽  
Zhang Wenjun ◽  
Liu Xi
Keyword(s):  
Northwest China ◽  
Source Rocks ◽  
Coal Measure

scholarly journals Fluid geochemistry of the Jurassic Ahe Formation and implications for reservoir formation in the Dibei area, Tarim Basin, northwest China

2018 ◽  
Vol 36 (4) ◽  
pp. 801-819 ◽  
Author(s):  
Shuangfeng Zhao ◽  
Wen Chen ◽  
Zhenhong Wang ◽  
Ting Li ◽  
Hongxing Wei ◽  
...  
Keyword(s):  
Natural Gas ◽  
Tarim Basin ◽  
Oil And Gas ◽  
Northwest China ◽  
Source Rocks ◽  
Coal Measure ◽  
Hydrocarbon Generation ◽  
Gas Reservoirs ◽  
Isotopic Analyses ◽  
Jurassic Coal

The condensate gas reservoirs of the Jurassic Ahe Formation in the Dibei area of the Tarim Basin, northwest China are typical tight sandstone gas reservoirs and contain abundant resources. However, the hydrocarbon sources and reservoir accumulation mechanism remain debated. Here the distribution and geochemistry of fluids in the Ahe gas reservoirs are used to investigate the formation of the hydrocarbon reservoirs, including the history of hydrocarbon generation, trap development, and reservoir evolution. Carbon isotopic analyses show that the oil and natural gas of the Ahe Formation originated from different sources. The natural gas was derived from Jurassic coal measure source rocks, whereas the oil has mixed sources of Lower Triassic lacustrine source rocks and minor amounts of coal-derived oil from Jurassic coal measure source rocks. The geochemistry of light hydrocarbon components and n-alkanes shows that the early accumulated oil was later altered by infilling gas due to gas washing. Consequently, n-alkanes in the oil are scarce, whereas naphthenic and aromatic hydrocarbons with the same carbon numbers are relatively abundant. The fluids in the Ahe Formation gas reservoirs have an unusual distribution, where oil is distributed above gas and water is locally produced from the middle of some gas reservoirs. The geochemical characteristics of the fluids show that this anomalous distribution was closely related to the dynamic accumulation of oil and gas. The period of reservoir densification occurred between the two stages of oil and gas accumulation, which led to the early accumulated oil and part of the residual formation water being trapped in the tight reservoir. After later gas filling into the reservoir, the fluids could not undergo gravity differentiation, which accounts for the anomalous distribution of fluids in the Ahe Formation.

scholarly journals HERMIONE, EVOLUTION OF ATe-BEARING EPITHERMAL MINERALIZATION, ARGOLIS, HELLAS

2007 ◽  
Vol 40 (2) ◽  
pp. 996 ◽  
Author(s):  
S. Tombros ◽  
K. St. Seymour
Keyword(s):  
Sedimentary Rocks ◽  
Ore Deposits ◽  
Stage I ◽  
Stage Ii ◽  
Quartz Veins ◽  
Minor Contribution ◽  
Epithermal Mineralization ◽  
Ore Bodies ◽  
Calcite Veins ◽  
Sandstone Formation

The Cu-Te-bearing pyrite deposits of Hermione, Argolis are hosted in Miocenic ophiolites. The ophiolites are overlain by a shale-sandstone formation with intercalations of limestones and manganiferous sedimentary rocks. The ore deposits form irregular lenticular or stratiform ore bodies, and veins. These ore bodies are related to volcanic activity in an arc-related rift at the margins of a palaeocontinent. Late N- to NNE-trending, sinistral, milky quartz-pyrite-calcite veins cut the host ophiolites. Alteration haloes of quartz-calcite, albite-sericitechlorite, and chalcedony-epidote-clay minerals are developed in the lavas as concentric shells, or as envelops that parallel the quartz veins. The telluriumbearing mineralization is developed in two successive stages, characterized by the assemblages: pyrite-(pyrrhotite)-magnetite-chalcopyrite-sphalerite (Stage I) and galena-sphalerite-freibergite-marcasite-chalcocite (Stage II), followed by a supergene stage. The cobaltiferous pyrite-chalcopyrite geothermometer defined two ranges of last-equilibration temperatures: 220° to 250°Cfor Stage I, and 120° to 195°Cfor Stage II. The calculated δ18 Ο and SD compositions of the mineralizing fluids, at 200° and 250°C, reflect the dominance of a magmatic component. The calculated δ SH2S fluid values reveal a magmatic source for the sulphur, with minor contribution from submarine sediments, whereas tellurium is proposed to be derived from a mafic-ultramafic source.

scholarly journals Lower Moscovian limestones of the Bogdashan Range (NW China) as an indicator of cessation of arc magmatism in the Junggar region

2019 ◽  
Vol 27 (1) ◽  
pp. 57-78
Author(s):  
D. V. Alexeiev ◽  
Yu. S. Biske ◽  
A. V. Djenchuraeva ◽  
B. Wang ◽  
O. L. Kossovaya ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Foreland Basin ◽  
Northwest China ◽  
Island Arc ◽  
Tien Shan ◽  
Lower Permian ◽  
Carbonate Sediments ◽  
Tropical Zone ◽  
Middle Carboniferous ◽  
Marine Facies

The field revision of the Carboniferous and Lower Permian stratigraphy of the northern Bogdashan (South Junggar, Northwest China) shows that the Lower to Middle Carboniferous island arc volcanic rocks, widely developed in this region, are overlapped everywhere by carbonate and terrigenous-carbonate sediments, containing occasional lava flows and overlain up the section by thick terrigenous series practically devoid of volcanic rocks. The deposition of limestone occurred at the stage of dying off of a volcanic arc, and the question of their age is of fundamental importance for dating this event. Carbonates are represented by facies of lagoons, shoals, and bioherms that formed on the leveled surface of the arc and on the slopes of the last active volcanoes. Bioherms are Waulsortian mounds and are mainly composed of algal limestones and carbonate mud. There are no framestones composed of corals and sponges (chaetetids) typical of the tropical zone. The facies of shallow crinoid-fusulinid limestones typical of the adjacent territories of the Southern Tien Shan and Tarim are poorly represented. Paleogeographically, the position of bioherms corresponds to the northern boundary of the realm of Pennsylvanian reefs. On the basis of foraminifers, brachiopods, and corals, the age of carbonates is early Moscovian (ca. 315–310 Ma). Cessation of island-arc volcanism, followed by the accumulation of limestone in Bogdashan, occurred sub-synchronously with formation of the West Junggar (Bayingou) suture and may reflect docking of the Bogdashan arc to the Yili active margin of the Kazakhstan continent. Further subsidence of Bogdashan and adjacent regions of the Junggar and Turfan basins, which was somewhat slower at the end of the Carboniferous and more intense in the Early and Middle Permian, may reflect the development of the foreland basin that formed along the northern flank of the Tien Shan orogen. Marine facies were locally preserved in this basin until the Artinskian (ca. 285 Ma), and later the Junggar and Turfan basins lost connection to the ocean and developed in continental environments.

scholarly journals THERMOCHRONOLOGY AND MATHEMATICAL MODELING OF THE FORMATION DYNAMICS OF RARE‐METAL‐GRANITE DEPOSITS OF THE ALTAI COLLISION SYSTEM

2019 ◽  
Vol 10 (2) ◽  
pp. 375-404 ◽  
Author(s):  
N. G. Murzintsev ◽  
I. Yu. Annikova ◽  
A. V. Travin ◽  
A. G. Vladimirov ◽  
B. A. Dyachkov ◽  
...  
Keyword(s):  
Rare Metal ◽  
Ore Deposits ◽  
Event Correlation ◽  
Magmatic Differentiation ◽  
Collision System ◽  
Rare Metal Granite ◽  
Development History ◽  
Ore Bodies ◽  
Thermal Cooling

The article presents an event correlation of the Permian‐Triassic granites of the Altai collision system, which are associated with industrial ore deposits and occurrences (Mo‐W, Sn‐W, Li‐Ta‐Be). The multi‐system and multi‐mineral isotope datings of igneous rocks and ore bodies (U/Pb, Re/Os, Rb/Sr, Ar/Ar‐methods) suggest the postcollisional (intraplate) formation of ore‐magmatic systems (OMS), the duration of which depended on the crustmantle interaction and the rates of tectonic exposure of geoblocks to the upper crustal levels.Two cases of the OMS thermal history are described: (1) Kalguty Mo‐W deposit associated with rare‐metal granite‐leucogranites and ongonite‐ elvan dykes, and (2) Novo‐Akhmirov Li‐Ta deposit represented by topaz‐zinnwaldite granites and the contemporary lamprophyre and ongonit‐elvan dykes. For these geological objects, numerical modeling was carried out. The proposed models show thermal cooling of the deep magmatic chambers of granite composition, resulting in the residual foci of rare‐metal‐granite melts, which are known as the petrological indicators of industrial ore deposits (Mo‐W, Sn‐W, Li‐Ta‐Be). According to the simulation results concerning the framework of a closed magmatic system with a complex multistage development history, the magmatic chamber has a lower underlying observable massif and a reservoir associated with it. A long‐term magmatic differentiation of the parental melt (a source of rare‐metal‐granite melts and ore hydrothermal fluids) takes place in this reservoir.

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