scholarly journals In–Situ LA-ICP-MS Trace Elements Analysis of Pyrite and the Physicochemical Conditions of Telluride Formation at the Baiyun Gold Deposit, North East China: Implications for Gold Distribution and Deposition

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 129
Author(s):  
Chang-Ping Li ◽  
Jun-Feng Shen ◽  
Sheng-Rong Li ◽  
Yuan Liu ◽  
Fu-Xing Liu
Keyword(s):  
Gold Deposit ◽  
Hydrothermal Fluids ◽  
Coarse Grained ◽  
Late Triassic ◽  
Invisible Gold ◽  
Northern Margin ◽  
Compositional Evolution ◽  
Quartz Veins ◽  
North East ◽  
Icp Ms

The Baiyun gold deposit is located in the northeastern North China Craton (NCC) where major ore types include Si-K altered rock and auriferous quartz veins. Sulfide minerals are dominated by pyrite, with minor amounts of chalcopyrite, sphalerite and galena. Combined petrological observations, backscattered electron image (BSE) and laser ablation analysis (LA-ICP-MS) have been conducted on pyrite to reveal its textural and compositional evolution. Three generations of pyrite can be identified—Py1, Py2 and Py3 from early to late. The coarse-grained, porous and euhedral to subhedral Py1 (mostly 200–500 μm) from the K-feldspar altered zone is the earliest. Compositionally, they are enriched in As (up to 11541 ppm) but depleted in Au (generally less than 10 ppm). The signal intensity of Au is higher than background values by two orders of magnitude and shows smooth spectra, indicating that invisible gold exists as homogeneously or nanoscale-inclusions in Py1. Anhedral to subhedral Py2 grains (generally ranging 500–1500 μm) coexist with other sulfides such as chalcopyrite, sphalerite and galena in the early silicification stage (gray quartz). They have many visible gold grains and contain little amounts of invisible Au. Notably, visible gold has an affinity with micro-fractures formed due to late deformation, implying that native gold may have resulted from mobilization of preexisting invisible gold in the structure of Py2 grains. Subsequently Py3 occurs as very fine-grained disseminations of euhedral crystals (0.05–1 mm) in late silicification stage (milky quartz) and coexists with tellurides (e.g. petzite, calaverite and hessite). They contain the highest level of invisible gold with positive correlations between Au-Ag-Te. In the depth profiles of Py3, the smooth Au spectra mirror those of Te with high intensities, revealing that gold occurred as homogeneously/nanoscale-inclusions and submicroscopic Au-bearing telluride inclusions in pyrite grains. The high Te and low As in Py3, combined with high Au content, imply that invisible gold can be efficiently scavenged by Te. Abundant tellurides (petzite, calaverite and hessite) have been recognized in auriferous quartz veins. Lack of symbiosis sulfides with the tellurium assemblages indicates crystallization under low fS2 and/or high fTe2 conditions and coincides with the result of thermodynamic calculations. High and markedly variable Co (from 0.24 to 2763 ppm, average 151.9 ppm) and Ni (from 1.16 to 4102 ppm, average 333.1 ppm) values suggest that ore-forming fluid may originate from a magmatically-derived hydrothermal system. Combined with previous geochronological data, the textural and compositional evolution of pyrite indicates that the Baiyun gold deposit has experienced a prolonged history of mineralization. In the late Triassic (220,230 Ma), the magmatic hydrothermal fluids, which had affinity with the post-collisional extensional tectonics on the NCC northern margin, caused initial gold enrichment. Then, as a result of deformation or the addition of new hydrothermal fluids, visible gold-rich Py2 was formed. The upwelling of mantle–derived magma brought in a lot of Te-rich ore-forming hydrothermal fluids during the peak of the destruction of the NCC (~120 Ma). Amount of visible/invisible gold and Au-Ag-Te mineral assemblages precipitated from these mineralized fluids when the physical and chemical conditions changed.

CALCITE U-Pb DATING UNRAVELS THE AGE AND HYDROTHERMAL HISTORY OF THE GIANT SHUIYINDONG CARLIN-TYPE GOLD DEPOSIT IN THE GOLDEN TRIANGLE, SOUTH CHINA

2021 ◽  
Vol 116 (6) ◽  
pp. 1253-1265
Author(s):  
Xiao-Ye Jin ◽  
Jian-Xin Zhao ◽  
Yue-Xing Feng ◽  
Albert H. Hofstra ◽  
Xiao-Dong Deng ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Early Cretaceous ◽  
South China ◽  
Gold Deposits ◽  
Ore Deposits ◽  
Late Triassic ◽  
Gold Deposition ◽  
Golden Triangle ◽  
Icp Ms ◽  
Carlin Type Gold Deposits

Abstract The ages of Carlin-type gold deposits in the Golden Triangle of South China have long been questioned due to the general lack of minerals unequivocally linked to gold deposition that can be precisely dated using conventional radiogenic isotope techniques. Recent advances in U-Pb methods show that calcite can be used to constrain the ages of hydrothermal processes, but few studies have been applied to ore deposits. Herein, we show that this approach can be used to constrain the timing of hydrothermal activity that generated and overprinted the giant Shuiyindong Carlin-type gold deposit in the Golden Triangle. Three stages of calcite (Cal-1, Cal-2, and Cal-3) have been recognized in this deposit based on crosscutting relationships, cathodoluminescence colors, and chemical (U, Pb, and rare earth element [REE]) and isotope (C, O, Sr) compositions. Cal-1 is texturally associated with ore-stage jasperoid and disseminated Au-bearing arsenian pyrite in hydrothermally altered carbonate rocks, which suggests it is synmineralization. Cal-2 fills open spaces and has a distinct orange cathodoluminescence, suggesting that it precipitated during a second fluid pulse. Cal-1 and Cal-2 have similar carbonate rock-buffered chemical and isotopic compositions. Cal-3 occurs in veins that often contain realgar and/or orpiment and are chemically (low U, Pb, and REE) and isotopically (higher δ13C, lower δ18O and Sri values) distinct from Cal-1 and Cal-2, suggesting that it formed from a third fluid. U-Pb isotope analyses, by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for U-rich Cal-1 and Cal-2 and by LA-multicollector (MC)-ICP-MS for U-poor Cal-3, yield well-defined age constraints of 204.3 to 202.6, 191.9, and 139.3 to 137.1 Ma for Cal-1, Cal-2, and Cal-3, respectively. These new ages suggest that the Shuiyindong gold deposit formed in the late Triassic and was overprinted by hydrothermal events in the early Jurassic and early Cretaceous. Given the association of Cal-3 with orpiment and realgar, and previous geochronologic studies of several other major gold deposits in the Golden Triangle, we infer that the latest stage of calcite may be associated with an early Cretaceous regional gold metallogenic event. Combined with existing isotopic ages in the region, these new ages lead us to propose that Carlin-type gold deposits in the Golden Triangle formed during two metallogenic episodes in extensional settings, associated with the late Triassic Indochina orogeny and early Cretaceous paleo-Pacific plate subduction. This study shows that the calcite U-Pb method can be used to constrain the timing of Carlin-type gold deposits and successive hydrothermal events.

scholarly journals Origin of the Granite Porphyry and Related Xiajinbao Au Deposit at Pingquan, Hebei Province, Northeastern China: Constraints from Geochronology, Geochemistry, and H–O–S–Pb–Hf Isotopes

Minerals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 330 ◽  
Author(s):  
Qingquan Liu ◽  
Yongjun Shao ◽  
Zhongfa Liu ◽  
Jianguo Zhang ◽  
Cheng Wang
Keyword(s):  
Partial Melting ◽  
Gold Deposit ◽  
Late Jurassic ◽  
North China ◽  
Granite Porphyry ◽  
Late Triassic ◽  
Granitic Magma ◽  
Northern Margin ◽  
The North ◽  
North China Plate

The Xiajinbao gold deposit is a medium-sized gold deposit in the Jidong gold province. Ore bodies mainly occur within the Xiajinbao granite porphyry and along the contact zone between the intrusion and Archean plagioclase hornblende gneiss. The zircon LA-ICP-MS age of the Xiajinbao granite porphyry yields 157.8 ± 3.4 Ma, which reflects the metallogenic age of the gold mineralization. Its petrographic features, major and trace element contents, zircon Hf isotopic model ages and compositional features all demonstrate that the Xiajinbao granitic magma is derived from partial melting of the Changcheng unit. The results of H–O isotopic analyses of auriferous quartz veins indicate that the ore-forming fluids are derived from magmatic waters that gradually mixed with meteoric waters during the evolution of the ore-forming fluids. S–Pb isotopic data indicate that the ore-forming fluids were mainly provided by the magma and by plagioclase hornblende gneisses. The gold metallogeny of the Xiajinbao gold deposit is temporally, spatially, and genetically associated with the high-K calc-alkaline-shoshonitic granitic magma emplaced during the Yanshanian orogeny and intruding the Archean plagioclase hornblende gneisses. These magmatic events mainly occurred during the period of 223–153 Ma and comprise three peak periods in the late Triassic (225–205 Ma), the early Jurassic (200–185 Ma) and the middle–late Jurassic (175–160 Ma), respectively. The metallogenic events in this area mainly occurred during the period of 223–155 Ma with the peak periods during the late Triassic (223–210 Ma) and the middle–late Jurassic (175–155 Ma), respectively. Both mineralization and magmatism occurred in a post-collisional tectonic setting related to the collision between the Mongolian plate and the North China plate at the end of the Permian. The magmatism of the early Jurassic occurred during the collision between the Siberian plate and the Mongolian plate, which caused the thickening and melting of the northern margin of the North China plate. The middle and late Jurassic magmatism and metallogenic activities are products of crustal thickening and partial melting during the Yanshanian intra-continental orogeny at the northern margin of the North China plate.

scholarly journals LA-ICP-MS Trace-Element Analysis of Pyrite from the Huanxiangwa Gold Deposit, Xiong’ershan District, China: Implications for Ore Genesis

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 157
Author(s):  
Fuping Gao ◽  
Yangsong Du ◽  
Zhenshan Pang ◽  
Yilun Du ◽  
Fengpei Xin ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Inductively Coupled Plasma ◽  
Trace Element Analysis ◽  
Hydrothermal Activity ◽  
Coarse Grained ◽  
First Episode ◽  
Yangtze Craton ◽  
Element Analysis ◽  
The North ◽  
Icp Ms

The Huanxiangwa deposit is a major gold deposit in the Xiong’ershan district, which is the third-largest gold-producing district in China. Pyrites from the Huanxiangwa deposit were investigated using ore microscopy and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Pyrite is the dominant Au-bearing mineral in the Huanxiangwa deposit and can be divided into two types: medium- to fine-grained subhedral-anhedral pyrite (Py1) disseminated in altered rocks and coarse-grained subhedral-euhedral pyrite (Py2) hosted in auriferous quartz veins. LA-ICP-MS time-resolved depth profiles show that invisible gold occurs primarily as solid solution or as homogeneously distributed nanoparticles of native gold, electrum, or Au-Ag-Te minerals in Py1, whereas it is present mainly as nano- to submicron-sized inclusions of complex Au-Ag-Cu-Pb-Zn domains in Py2. The presented data indicate that the Huanxiangwa deposit resulted from two episodes of hydrothermal mineralization associated with two distinct source reservoirs. The first episode of mineralization was linked to the dehydration of deep-seated mafic-ultramafic metamorphic rock during the Triassic collision of the North China Craton with the Yangtze Craton. The second episode of mineralization was related to hydrothermal activity resulting from Early Cretaceous I-type granitic magmatism.

Low-temperature thermal history of the Gilmore Dome area, Fairbanks Mining District, Alaska

1993 ◽  
Vol 30 (4) ◽  
pp. 764-768 ◽  
Author(s):  
John M. Murphy ◽  
Arne Bakke
Keyword(s):  
Gold Deposit ◽  
Fission Track ◽  
Hydrothermal Fluids ◽  
Mining District ◽  
Cooling Path ◽  
Alteration Assemblage ◽  
Zircon Fission Track ◽  
History Of ◽  
Maximum Temperatures ◽  
Fission Track Ages

Eight apatite and two zircon fission-track ages provide evidence of complex Tertiary thermal overprinting by hydrothermal fluids in the Gilmore Dome area. Five ages on apatite from the Fort Knox gold deposit average 41 Ma, one from the Stepovich prospect is 80 Ma, and two from Pedro Dome average 67 Ma. Elevations of these samples overlap but their ages do not, indicating that each area experienced a different thermal history.Ages of apatite from the Fort Knox gold deposit decrease with elevation from 42 to 36 Ma but have data trends indicative of complex cooling. Two ~51 Ma ages on zircon indicate that maximum temperatures approached or exceeded ~180 °C. An alteration assemblage of chalcedony + zeolite + calcite + clay in the deposit resulted from deposition by a paleo-hydrothermal system. The data suggest that the system followed a complex cooling path from > 180 to < 110 °C between 51 and 36 Ma, and that final cooling to below 60 °C occurred after ~25 Ma.The 80 Ma age from Stepovich prospect either resulted from cooling after intrusion of the underlying pluton (~90 Ma) or records postintrusion thermal overprinting sometime after ~50 Ma. The 67 Ma samples from Pedro Dome may also have experienced partial age reduction during later heating. The differences in the data from the different areas and the presence of a late alteration assemblage at Fort Knox suggest that the fluids responsible for heating were largely confined to the highly fractured and porous Fort Knox pluton.

scholarly journals Re-Discussion on the Metallogenic Age of the Hadamengou Gold Deposit in Inner Mongolia, China

2016 ◽  
Vol 5 (2) ◽  
pp. 85
Author(s):  
Yu Zhang ◽  
Yangyang Chen
Keyword(s):  
Gold Deposit ◽  
Inner Mongolia ◽  
North China ◽  
Northern Margin ◽  
The North ◽  
Geological Evolution ◽  
Western Segment ◽  
Mineralization Age ◽  
Extensive Collection ◽  
Metallogenic Age

The Hadamengou gold deposit is located in the western segment of the northern margin of the North China Craton (NCC). The mineralization age of the Hadamengou gold deposit is a matter of controversy. Based on the extensive collection the results of previous research, we infer that the Hadamengou gold deposit is exposed to prolonged geological evolution. It was formed as early as the Middle Hercynian orogen. The metallization mainly took place in the Early Indosinian epoch.

scholarly journals Naked oat is promising raw material for deep grain processing

2019 ◽  
Vol 20 (5) ◽  
pp. 447-455
Author(s):  
N. R. Andreev ◽  
V. G. Goldstein ◽  
L. P. Nosovskaya ◽  
L. V. Adikaeva ◽  
E. O. Golionko
Keyword(s):  
Agricultural Research ◽  
Starch Content ◽  
Raw Material ◽  
Coarse Grained ◽  
Cellulolytic Enzymes ◽  
Technological Parameters ◽  
Naked Oat ◽  
Grain Processing ◽  
North East ◽  
The North

During the research conducted at the All-Russian Research Institute for Starch Products there has been developed a technological mode of using cellulolytic enzymes to reduce the viscosity of grain pulp obtained by grinding naked oat grains soaked in a sodium metabisulphite solution. As the experimental data had been processed, the optimum technological parameters of the process were determined: the consumption of the enzyme preparation Viscoferm was 200 g/t of grain and the dura-tion of fermentation by constant stirring for 2.5 hours at pH 4.6 and temperature 50°C. Under laboratory conditions there has been studied the possibility of starch processing of naked oat grain samples Vyatka, Percheron, 857h05, 766 h05 varieties grown in the Federal Agricultural Research Center of the North-East named N.V. Rudnitsky. Technological assessment based on grain processing in the laboratory using the “plant on the table” method has shown that the yield of coarse-grained starch A in the processing of naked oat using cellulolytic enzymes is 51.4-53.9%, i.e. higher than that of filmy oats, rye Falenskaya 4 and Vyatka 2, wheat and triticale. Low starch content in fiber (7.7-8.7% dry substances DS of fiber) was found in comparison with the results obtained from the processing of filmy oats, Falenskaya and Vyatka 2 rye varieties, wheat and triticale (11.2 - 13.9% DS of fiber). Fiber output by the processing of naked oats is 7.3 - 8.8% DS of grain, by the processing of other types of grain 10.3 - 17.5% DS of grain. The yield of small-grain starch B in the processing of the studied varieties of naked oat is 19.2 - 20.8% DS of grain, that is higher than this value obtained by processing of filmy oats and wheat, but lower than by pro-cessing of rye and triticale. Isolated carbohydrate-protein concentrate, including starch B and proteins, is recommended for use with the extract and fiber as a component for the production of feed.

Fluid flow and faulting history of the Iano tectonic window (Southern Tuscany, Italy).

2021 ◽  
Author(s):  
Paolo Fulignati ◽  
Martina Zucchi ◽  
Andrea Brogi ◽  
Enrico Capezzuoli ◽  
Domenico Liotta ◽  
...  
Keyword(s):  
Fluid Inclusions ◽  
Hydrothermal Fluids ◽  
Normal Faults ◽  
High Angle ◽  
Quartz Veins ◽  
History Of ◽  
Tectonic Window ◽  
Liquid Vapor

&lt;p&gt;In the Iano area (Southern Tuscany) a small tectonic window of Tuscan metamorphic units is observed. This belongs to the northernmost part of the so-called Mid-Tuscan ridge and, during Pliocene, formed a submarine high, now defining the easternmost shoulder of the Volterra Pliocene basin. The area gives the opportunity to investigate the complete cycle of negative inversion from crustal thickening to crustal thinning, which characterizes Southern Tuscany. Our new data focus on the western margin of the Iano ridge, and in particular on a system of high angle normal faults that represents the youngest structures of the investigated area. These structures, deformed low angle regional detachments locally juxtaposing the uppermost units of contractional nappe stack (the ophiolite-bearing Ligurian units), with the Tuscan metamorphic units, with an almost complete excision of at least 3.5 Km thick Mesozoic to Tertiary Tuscan nappe succession. The high angle normal faults show variable Plio-Quaternary vertical displacements from few meters to about 500 meters, and acted as pathways for the upwelling of hydrothermal fluids, as revealed by Pleistocene travertine deposits, hydrothermal alteration and occurrence of different generations of fluid inclusions in hydrothermal veins associated with these fault systems. Fluid inclusions were studied in quartz veins hosted in the Verrucano metasediments forming the top of the Tuscan metamorphic unit, as well as in some carbonate lithotypes (Cretaceous to Tertiary in age) of the overlying Tuscan Nappe. Two different kinds of fluid inclusions were documented. The Type 1 are multiphase (liquid + vapor + 1 daughter mineral) liquid-rich fluid inclusions whereas the Type 2 are two-phase (liquid + vapor) liquid-rich fluid inclusions. Type 1 fluid inclusions are primary in origin and were found only in quartz veins present in Verrucano metarudites, whereas Type 2 fluid inclusions occur in quartz veins present in both Verrucano phyllites and quartzites and in the carbonate units of the Tuscan Nappe. These are secondary and can be furthermore distinguished in two sub-populations (Type 2a and Type 2b) on the basis of petrographic observation and microthermometric data. Fluid inclusion investigation evidenced an evolution of the hydrothermal fluids from relatively high-T (~265&amp;#176;C) and hypersaline (35 wt.% NaCl&lt;sub&gt;equiv.&lt;/sub&gt;) fluids trapped at about 100 MPa, to lower temperature (~195&amp;#176;C) and salinity (~9.5 wt.% NaCl&lt;sub&gt;equiv.&lt;/sub&gt;) fluids, having circulated in the high-angle fault system. Based on the new data and a revision of the local tectonic setting a fluid-rock interaction history has been reconstructed with new hints and constraints for the Plio-Quaternary extensional history of the Volterra basin.&lt;/p&gt;

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