Iron isotope fractionation in reduced hydrothermal gold deposits: A case study of the Wulong gold deposit, Liaodong Peninsula, East China

Abstract

Iron isotope fractionation in hydrothermal systems is a useful diagnostic tool for tracing ore-forming processes. Here, we report on the Fe isotopic compositions of a suite of hydrothermal minerals from ores (pyrite, pyrrhotite, and quartz) from the Wulong gold deposit, Liaodong Peninsula, East China. Pyrites from quartz sulfide ores show a δ 56 Fe (56 Fe/ 54 Fe in the sample relative to IRMM-14) variation from +0.11 ± 0.03‰ to +0.78 ± 0.03‰ (2SD), and pyrrhotites from the same vein are isotopically lighter than the pyrite, varying between-0.85 ± 0.01‰ and-0.07 ± 0.00‰. This result is consistent with theoretical predictions of equilibrium fractionation and published mineral compositions. For the first time, to our knowledge, we report the Fe isotopes of hydrothermal quartz that record the isotopic compositions of the ore-This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

Genesis of the Beizhan Iron Deposit in Western Tianshan, China: Insights from Trace Element and Fe-O Isotope Compositions of Magnetite

“…Mineral assemblages and paragenetic relationships suggest that sulfides formed after magnetite precipitation. Platy magnetite often occurs together with pyrrhotite, which possesses the lightest Fe isotope composition in Fe skarn deposits [80]. The precipitation of pyrrhotite causes the fluid to become enriched in heavy Fe isotopes, and the subsequently precipitated platy magnetite thus has a heavier Fe isotopic composition.…”

Tianyu-Py pyrite: a new natural reference material for micro-beam determination of iron isotopic ratios

“…The iron isotope fractionation in low-temperature pyrite has been used to trace modern and ancient microbial metabolisms, redox evolution of the oceans and atmosphere, and iron sources and cycling in sedimentary environments. 19,22,34,35 More recently, the Fe isotopic composition of pyrite is suggested to shed light on the formation of various types of sulde ore deposits, including magmatic-hydrothermal Sn-W deposits, 36 hydrothermal Au deposits, [37][38][39] porphyry Cu (-Mo) deposits, [40][41][42][43] skarn Cu-Fe deposits, 44 epigenetic sediment-hosted Cu-Co deposits, 45 sediment-hosted stratiform sulde deposits, 46 and sulde deposits on the modern seaoor. [47][48][49] The chemical zoning of pyrite can record a wealth of information during magma evolution and metamorphic reaction (e.g., ref.…”