Genesis of the Bangbu Orogenic Gold Deposit, Tibet： Evidence from Fluid Inclusion, Stable Isotopes, and Ar-Ar Geochronology

The Bangbu gold deposit is a large orogenic gold deposit in Tibet formed during the AlpineHimalayan collision. Ore bodies（auriferous quartz veins） are controlled by the E-W-trending Qusong-Cuogu-Zhemulang brittle-ductile shear zone. Quartz veins at the deposit can be divided into three types： pre-me...

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Bibliographic Details
Published in:Acta geologica Sinica (Beijing) 2016-04, Vol.90 (2), p.722-737
Main Authors: Yingru, PEI, Qingzhong, SUN, Yuanchuan, ZHENG, Zhusen, YANG, Wei, LI, Kexian, HUANG
Format: Article
Language:English
Subjects:
Age
Ar-Ar dating
Bangbu deposit
Deposits
Fluid flow
fluid inclusions
Gold
Homogenizing
orogenic gold deposit
Pyrite
Quartz
southern Tibet
stable isotope
Tibet-Himalayan orogen
Veins
变质成因
含金石英脉
含金矿脉
喜马拉雅造山带
流体包裹体
稳定同位素
蚌埠
西藏
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Summary:The Bangbu gold deposit is a large orogenic gold deposit in Tibet formed during the AlpineHimalayan collision. Ore bodies（auriferous quartz veins） are controlled by the E-W-trending Qusong-Cuogu-Zhemulang brittle-ductile shear zone. Quartz veins at the deposit can be divided into three types： pre-metallogenic hook-like quartz veins, metallogenic auriferous quartz veins, and postmetallogenic N-S quartz veins. Four stages of mineralization in the auriferous quartz veins have been identified：（1） Stage S1 quartz＋coarse-grained sulfides,（2） Stage S2 gold＋fine-grained sulfides,（3） Stage S3 quartz＋carbonates, and（4） Stage S4 quartz＋ greigite. Fluid inclusions indicate the oreforming fluid was CO_2-N_2-CH_4 rich with homogenization temperatures of 170–261°C, salinities 4.34–7.45 wt% Na Cl equivalent. δ~（18）Ofluid（3.98‰–7.18‰） and low δDV-SMOW（-90‰ to-44‰） for auriferous quartz veins suggest ore-forming fluids were mainly metamorphic in origin, with some addition of organic matter. Quartz vein pyrite has δ~（34）SV-CDT values of 1.2‰–3.6‰（an average of 2.2‰）, whereas pyrite from phyllite has δ~（34）SV-CDT 5.7‰–9.9‰（an average of 7.4‰）. Quartz vein pyrites yield 206Pb/204 Pb ratios of 18.662–18.764, 207Pb/204 Pb 15.650–15.683, and ~（208）Pb/204 Pb 38.901–39.079. These isotopic data indicate Bangbu ore-forming materials were probably derived from the Langjiexue accretionary wedge. 40Ar/39 Ar ages for sericite from auriferous sulfide-quartz veins yield a plateau age of 49.52 ± 0.52 Ma, an isochron age of 50.3 ± 0.31 Ma, suggesting that auriferous veins were formed during the main collisional period of the Tibet-Himalayan orogen（-65–41 Ma）.
ISSN:1000-9515
1755-6724
DOI:10.1111/1755-6724.12700