In situ geochemistry and Fe–O isotopic composition of iron oxides from the Pha Lek Fe deposit, northwest Truong Son orogenic belt, Laos: implications for ore-forming processes

Hou, Lin; Guo, Lei; Xu, Siwei; Zhang, Qiming; Zeng, Xiang‐ting

doi:10.1007/s00126-020-01028-x

Cited by 6 publications

(1 citation statement)

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“…Considerable research has focused on the variability in δ 18 O values of magnetite from different ore types of iron deposits, indicating the potential for using δ 18 O values to distinguish deposit types and infer their genesis [17,56,59,85,86]. Magnetite formed through magmatism typically exhibits a relatively narrow range of δ 18 O values, usually falling between +1‰ and +4‰ [5,59,70,83,87].…”

Section: Source Of Ore Componentsmentioning

confidence: 99%

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

Li,

Jiang,

Wang

et al. 2024

Minerals

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The Beizhan iron deposit (468 Mt at an average grade of 41% Fe) is the largest iron deposit in the Awulale iron metallogenic belt of Western Tianshan, northwest China. The high-grade magnetite ores are hosted in the Carboniferous volcanic rocks with extensive development of skarn alteration assemblages. While considerable progress has been made in understanding the characteristics of Beizhan and its genetic association with volcanic rocks, the genetic models for ore formation are poorly constrained and remain controversial. This study combines detailed petrographic investigations with in situ LA-ICP-MS analyses of trace elements and Fe-O isotope compositions of magnetite to elucidate the origin of magnetite and the conditions of ore formation. The trace element concentrations in magnetite unveil intricate origins for various ore types, implying the precipitation of magnetite from both magmatic and hydrothermal fluids. The application of the Mg-in magnetite thermometer (TMg-mag) reveals a notable temperature divergence across different magnetite varieties, spanning from relatively higher temperatures in magmatic brecciated magnetite (averaging ~641 and 612 °C) to comparatively lower temperatures in hydrothermal platy magnetite (averaging ~552 °C). The iron isotopic composition in massive and brecciated magnetite grains, characterized by lighter δ56Fe values (ranging from −0.078 to +0.005‰ and −0.178 to −0.015‰, respectively), suggest a magmatic or high-temperature hydrothermal origin. Conversely, the heavier δ56Fe values observed in platy magnetite (+0.177 to +0.200‰) are attributed to the influence of pyrrhotite, signifying late precipitation from low-temperature hydrothermal fluids. Additionally, the δ18O values of magnetite, ranging from +0.6 to +4.6‰, provide additional evidence supporting a magmatic–hydrothermal origin for the Beizhan iron deposit. Overall, the identified genetic associations among the three magnetite types at Beizhan provide valuable insights into the evolution of ore-forming conditions and the genesis of the deposit. These findings strongly support the conclusion that the Beizhan iron deposit underwent a process of magmatic–hydrothermal mineralization.

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