地质科技通报 (Nov 2023)
Iron isotopic characteristics of the Xinmin Fe deposit in the Taershan-Erfengshan district, Shanxi Province: Implications for origin of Fe mineralization
Abstract
Objective The Xinmin contact-metasomatism iron deposit is one of the most representative achievements of resource surveys in recent years in the Taershan-Erfengshan area, southern Shanxi Province.Determining the metal source and Fe mineralization process of this deposit is of great significance for regional exploration in this area. Methods In this study, Fe isotopic compositions of the altered diorite, hosting limestone(dolomite) and different types of magnetite samples have been obtained. Results The results show that the altered diorite have δ56Fe values(0.23‰) significantly heavier than the average value of the upper crust (0.07‰), which may be related to fluid migration during skarn/albitization, as the light iron isotope is preferably leached from the intrusions. The Ordovician limestone/dolomite samples have δ56Fe values (0 to 0.19‰) obviously different from those of magnetite (-0.56‰ to 0.07‰), indicating that those sedimentary strata cannot be the major ore-metal source. Considering that magnetite samples have obviously light Fe isotopic ratios which also exhibit an obviously increasing trend from centre to margin of a specific ore body, we propose that the ore-forming fluid may have once interacted with the intrusions during fluid migration, followed by precipitation in the limestone stratum. This interpretation is also supported by the remarkable negative correlation between δ56Fe and Fe content. Conclusion Our study is consistent with previous studies on Fe isotopes of skarn iron deposits, which provides important evidence for the origin of contact metasomatism. Furthermore, this study may also indicate that altered diorite with heavy δ56Fe ratios in the Taershan-Erfengshan area may be potential targets for iron prospect.
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