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Type: Journal article
Title: Mineralogical, textural, sulfur and lead isotope constraints on the origin of Ag-Pb-Zn mineralization at Bianjiadayuan, Inner Mongolia, NE China
Author: Zhai, D.
Liu, J.
Cook, N.
Wang, X.
Yang, Y.
Zhang, A.
Jiao, Y.
Citation: Mineralium Deposita, 2019; 54(1):47-66
Publisher: Springer
Issue Date: 2019
ISSN: 0026-4598
Statement of
Degao Zhai, Jiajun Liu, Nigel J. Cook, Xilong Wang, Yongqiang Yang, Anli Zhang, Yingchun Jiao
Abstract: The Bianjiadayuan Ag-Pb-Zn deposit (4.81 Mt. @157.4 g/t Ag and 3.94% Pb + Zn) is located in the Great Hinggan Range Pb-Zn-Ag-Cu-Mo-Sn-Fe polymetallic metallogenic belt, NE China. Vein type Pb-Zn-Ag ore bodies are primarily hosted by slate, adjacent to a Sn ± Cu ± Mo mineralized porphyry intrusion. The deposit is characterized by silver-rich ores with Ag grades up to 3000 g/t. Four primary paragenetic sequences are recognized: (I) arsenopyrite + pyrite + quartz, (II) main sulfide + quartz, (III) silver-bearing sulfosalt + quartz, and (IV) boulangerite + calcite. A subsequent supergene oxidation stage has also been identified. Hydrothermal alteration consists of an early episode of silicification, two intermediate episodes (propylitic and phyllic), and a late argillic episode. Silver mineralization primarily belongs to the late paragenetic sequence III. Freibergite is the dominant and most important Ag-mineral in the deposit. Detailed ore mineralogy of Bianjiadayuan freibergite reveals evidence of chemical heterogeneity down to the microscale. Silver-rich sulfosalts in the late paragenetic sequence III are largely derived from a series of retrograde and solid-state reactions that redistribute Ag via decomposition and exsolution during cooling, illustrating that documentation of post-mineralization processes is essential for understanding silver ore formation. Sulfur and lead isotope compositions of sulfides, and comparison with those of local various geological units, indicate that the ore-forming fluids, lead, and other metals have a magmatic origin, suggesting a close genetic association between the studied Ag-Pb-Zn veins and the local granitic intrusion. Fluid cooling coupled with decreases in fO2 and fS2 are the factors inferred to have led to a decrease of silver solubility in the hydrothermal fluid, and successively promoted extensive Ag deposition.
Keywords: Freibergite; sulfur isotopes; lead isotopes; Ag-Pb-Zn deposit; Bianjiadayuan; NE China
Rights: © Springer-Verlag GmbH Germany, part of Springer Nature 2018
RMID: 0030085903
DOI: 10.1007/s00126-018-0804-6
Appears in Collections:Geology & Geophysics publications

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