Iron isotope fractionation during skarn-type metallogeny: a case study of Xinqiao Cu–S–Fe–Au deposit in the Middle–Lower Yangtze valley

Wang, Yue, Zhu, Xiang-kun, Mao, Jing-wen, Li, Zhi-hong, and Cheng, Yanbo (2011) Iron isotope fractionation during skarn-type metallogeny: a case study of Xinqiao Cu–S–Fe–Au deposit in the Middle–Lower Yangtze valley. Ore Geology Reviews, 43 (1). pp. 194-202.

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Abstract

Fe isotope compositions of mineral separates and bulk samples from Xinqiao Cu–S–Fe–Au skarn type deposit were investigated. An overall variation in δ^57Fe values from − 1.22‰ to + 0.73‰ has been observed, which shows some regularity. The δ^57Fe values of endoskarn and the earliest formed Fe-mineral phase magnetite are ca.1.2‰ and ca. 0.3‰ lower, respectively, relative to the quartz–monzodiorite stock, indicating that fluid exsolved from the stock is enriched in light Fe isotopes. Moreover, spatial and temporal variations in δ^57Fe values are observed, which suggest iron isotope fractionation during fluid evolution. Precipitation of Fe-bearing minerals results in the Fe isotope composition of residual fluids evolving with time. Precipitation of Fe (III) minerals incorporating heavy iron isotopes preferentially leaves the remaining fluid enriched in light isotopes, while precipitation of Fe (II) minerals preferentially taking-up light iron isotopes, and makes the Fe isotopic composition of the fluid progressively heavier. The regularity of Fe isotope variations occurred during fluid exsolution and evolution indicates that the dominant Fe source of Xinqiao deposit is magmatic. Overall, this study demonstrates that Fe isotope composition has great potential in unraveling ore-forming processes, as well as constraining the metal sources of ore deposits.

Item ID: 40111
Item Type: Article (Research - C1)
ISSN: 1872-7360
Keywords: iron isotopes; isotope fractionation; xinqiao deposit; fluid exsolution; fluid evolution
Funders: State Key Fundamental Program (SKFP), MRL Public Benefit Research Foundation (MRL)
Projects and Grants: SKFP Project 2007CB411408, (MRL) 201011027
Date Deposited: 20 Aug 2015 03:16
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040307 Ore Deposit Petrology @ 100%
SEO Codes: 84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840199 Mineral Exploration not elsewhere classified @ 100%
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