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In situ Pb-Pb isotopic dating of sulfides from hydrothermal deposits: a case study of the Lala Fe-Cu deposit, SW China
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Wei Terry Chen; Mei-Fu Zhou; Xiaochun Li; Jian-Feng Gao; Zhian Bao; Honglin Yuan
2019
Source PublicationMineralium Deposita
Volume54Issue:5Pages:671-682
Abstract

Precisely dating different generations of mineralization is important for understanding the origin and tectonic environment of ore formation. In this study, we have dated two generations of sulfides from the Lala Fe-Cu deposit, SW China, using in situ Pb-Pb isotopic data obtained by the LA-MC-ICPMS technique. The Lala deposit is composed of Fe-Cu ore bodies hosted in sedimentary-volcanic rocks of the Paleoproterozoic Hekou Group. It has a paragenetic sequence of pre-ore banded pyrite (Stage I) and Na alteration (Stage II), followed by early Fe (Stage III) and late Cu (Stage IV) mineralization. The sulfides in the deposit have dominantly formed in two stages, including pyrite from stratiform pyrite bands in the host rocks (i.e., Stage I) and epigenetic pyrite-chalcopyrite in Fe-Cu ore (i.e., Stage IV). The sulfides of both stages have highly radiogenic Pb isotopic ratios which form linear trends in the 207Pb/204Pb versus 206Pb/204Pb diagram. The regression trend for Stage I pyrite grains defines an errorchron age of 1669 ± 110 Ma (MSWD = 32), undistinguishable from zircon LA-ICPMS U-Pb ages of volcanic rocks in the Hekou Group (i.e., ~ 1700 Ma). The regressions for Stage IV pyrite and chalcopyrite yield younger errorchron ages of 1088 ± 88 Ma (MSWD = 93) and 1053 ± 220 Ma (MSWD = 15), respectively. Taking pyrite and chalcopyrite together, an errorchron age of 1053 ± 75 Ma (MSWD = 108) is obtained. These errorchron ages agree well with the molybdenite Re-Os age of the Fe-Cu ore (1086 ± 8 Ma). Despite the large error and MSWD values that are interpreted to be related to the small variation of initial ratios, or post-ore open system behavior, the good agreement with the precise zircon U-Pb and molybdenite Re-Os ages indicates that the Pb-Pb errorchron ages for Stage I and IV sulfides are geologically meaningful. Therefore, this study shows that the in situ Pb isotopic analyses can yield geologically meaningful Pb-Pb ages for radiogenic Pb-rich sulfide minerals. We also propose that in situ Pb-Pb isotopic dating may be more promising for Precambrian deposits containing sulfides with ingrown Pb, particularly for those involving multiple mineralization/hydrothermal events but without relevant minerals for precise Re-Os or U-Pb dating.

KeywordSulfides fs-la-mc-icpms in Situ Pb Isotopic analyze Pb-Pb Errorchron Age lala Deposit
Indexed BySCI
Language英语
Document Type期刊论文
Identifierhttp://ir.gyig.ac.cn/handle/42920512-1/10869
Collection矿床地球化学国家重点实验室
Affiliation1.State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
2.Department of Earth Sciences, University of Hong Kong, Pokfulam Road, Hong Kong, China
3.State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China
Recommended Citation
GB/T 7714
Wei Terry Chen,Mei-Fu Zhou,Xiaochun Li,et al. In situ Pb-Pb isotopic dating of sulfides from hydrothermal deposits: a case study of the Lala Fe-Cu deposit, SW China[J]. Mineralium Deposita,2019,54(5):671-682.
APA Wei Terry Chen,Mei-Fu Zhou,Xiaochun Li,Jian-Feng Gao,Zhian Bao,&Honglin Yuan.(2019).In situ Pb-Pb isotopic dating of sulfides from hydrothermal deposits: a case study of the Lala Fe-Cu deposit, SW China.Mineralium Deposita,54(5),671-682.
MLA Wei Terry Chen,et al."In situ Pb-Pb isotopic dating of sulfides from hydrothermal deposits: a case study of the Lala Fe-Cu deposit, SW China".Mineralium Deposita 54.5(2019):671-682.
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