First Reliable Re–Os Ages of Pyrite and Stable Isotope Compositions of F e(‐ C u) Deposits in the H ami Region, E astern T ianshan O rogenic B elt, NW C hina

Abstract

Abstract TheEasternTianshanOrogenicBelt (ETOB) inNW China is composed of theDananhu–Tousuquanarc belt, theKanggurtag belt, theAqishan–Yamansubelt and theCentralTianshan belt from north to south. These tectonic belts have formed through arc–continent or arc–arc collisions during thePaleozoic. A number ofFe(‐Cu) deposits in theAqishan–Yamansubelt, including theHeifengshan,Shuangfengshan andShaquanziFe(‐Cu) deposits, are associated withCarboniferous–EarlyPermian volcanic rocks and are composed of vein‐type magnetite ores. Metallic minerals are dominated by magnetite and pyrite, with minor chalcopyrite. Calcite, chlorite, and epidote are the dominant gangue minerals. Pyrite separates of ores from those three deposits have relatively high and variableRe contents ranging from 3.7 to 184 ppb. All pyrite separates have very low commonOs, allowing us calculation of single mineral model ages for each sample. Pyrite separates from theHeifengshanFe deposit have an187Re–187Os isochron age of 310 ± 23 Ma (MSWD= 0.04) and a weighted mean model age of 302 ± 5 Ma (MSWD= 0.17). Those from the ShuangfengshanFe deposit have an isochron age of 295 ± 7 Ma (MSWD= 0.28) and a weighted mean model age of 292 ± 5 Ma (MSWD= 0.33). TheShaquanziFe‐Cu deposit has pyrite with an isochron age of 295 ± 7 Ma (MSWD= 0.26) and a weighted mean model age of 295 ± 6 Ma (MSWD= 0.23). Pyrite separates from theseFe(‐Cu) deposits have δ34SCDTranging from −0.41‰ to 4.7‰ except for two outliers. Calcite from theHeifengshanFe deposit andShaquanziFe‐Cu deposit have similarCandOisotope compositions with δ13CPDBand δ18OSMOWranging from −5.5‰ to −1.0‰ and from 10‰ to 12.7‰, respectively. These stable isotopic data suggest thatS,C,andOare magmatic‐hydrothermal in origin. The association of low‐Ti magnetite andFe/Cu‐sulfides resembles those ofIron–Oxide–Copper–Gold (IOCG) deposits elsewhere. Our reliableRe–Os ages of pyrite suggest that theFe(‐Cu) deposits in theAqishan–Yamansubelt formed at ∼296Ma, probably in a back‐arc extensional environment.

Cite this work

No public copy is stored for this record, so only the metadata is cited.

Stored only when both papers are in the corpus — 88 citations exist upstream.

Papers that cite the same references — the relational fallback while embeddings are still backfilling.