首页|A metamorphic devolatilization model for the genesis of the Baiyun gold deposit in the North China Craton: A novel Fe-S isotopes perspective
A metamorphic devolatilization model for the genesis of the Baiyun gold deposit in the North China Craton: A novel Fe-S isotopes perspective
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NSTL
Elsevier
The Mesozoic gold deposits in the North China Craton (NCC) were hosted by the Precambrian basement and Mesozoic intrusions. Thus, most researchers consider that these gold deposits were genetically linked to the Mesozoic intrusions. However, we suggest that a metamorphic devolatilization model provides an alternative based on a combined Fe and in-situ S isotopes study on auriferous pyrites from the Baiyun gold deposit in the NCC. The Triassic Baiyun gold deposit contains the quartz vein and altered rock ores that were developed in the Paleoproterozoic metavolcanic-sedimentary rocks (the Liaohe Group). Our insitu S isotopic analyses show that pyrites from the quartz vein ores are characterized by negative delta S-34 values (-10.7 similar to -5.5 parts per thousand), while those from the altered rock ores have two distinct groups of delta S-34 values, one being positive (+13.5 similar to +16.2 parts per thousand) and the other negative (-10.6 similar to -3.0 parts per thousand). We suggest that pyrite grains with positive delta S-34 values should be relicts from the host rocks, because they show comparable delta S-34 values with those from the host rocks schists (+3.3 similar to +16.1 parts per thousand). Thus, only the negative delta S-34 values of pyrites in ores (-10.7 similar to -3.0 parts per thousand) and the Fe isotopes of the quartz vein ores (delta Fe-56 = +0.30 similar to +0.48 parts per thousand) can represent the isotopic characteristics of ore-forming fluids at Baiyun. Our study shows that the sulfur were probably from the pyritic volcanic-sedimentary sequences of the Liaohe Group, rather than from magmas. The calculated delta Fe-56 values of the ore-forming fluids (-0.78 similar to -0.37 parts per thousand; pyrite-fluid isotope fractionation) could be modelled in a metamorphic devolatilization model with Fe-species (pyrite&magnetite) of the Liaohe Group as sources. Therefore, our combined S- and Fe- isotope data indicate that the metamorphic devolatilization of the Liaohe Group could account for the genesis of the Baiyun gold deposit. (C) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
Fe isotopeIn-situ S isotopeOrogenic gold depositsMetamorphic devolatilization modelBaiyun gold depositU-PB AGEOROGENIC GOLDLIAODONG PENINSULAJIAODONG PENINSULAH-OSECULAR CHANGESFENZISHAN GROUPSULFUR ISOTOPELIAOHE-GROUPSULU OROGEN
NSTL
Elsevier
