Iron isotope fractionation during fenitization:a case study of carbonatite dykes from Bayan Obo,Inner Mongolia,China

作     者：Zongyi Wu Jian Sun Xiaowei Li Xiangkun Zhu Zongyi Wu;Jian Sun;Xiaowei Li;Xiangkun Zhu

作者机构：Institute of GeologyMNR Key Laboratory of Deep-Earth DynamicsChinese Academy of Geological Sciences MNR Key Laboratory of Isotope Geology100037 BeijingPR China State Key Laboratory of Geological Processes and Mineral ResourcesSchool of Earth Science and ResourcesUniversity of Geosciences100083 BeijingChina 

出 版 物：《Acta Geochimica》 (地球化学学报（英文）)

年 卷 期：2022年第41卷第5期

页      面：789-793页

核心收录：

学科分类：070902[理学-地球化学] 0709[理学-地质学] 07[理学] 070901[理学-矿物学、岩石学、矿床学] 0708[理学-地球物理学] 

基　　金：the National Key R&D Programmes of China(Nos.2019YFA0708604 and 2019YFA0708404) the National Natural Science Foundation of China(No.41773018) the Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources(No.J1901-29)。 

主　　题：Iron isotopes Fenitization Fluid exsolution Carbonatite Bayan Obo 

摘      要：As a powerful tracer in high-temperature geochemistry,Fe isotopes have been studied for their behaviour during fl uid exsolution and evolution related to felsic magma system,but that for carbonatite magma system remains unknown.Here we study the Fe isotope fractionation behaviour during fenitization–processes that widely occur associated with carbonatite or alkaline intrusions.Nine fenite/carbonatite samples from carbonatite dykes at Bayan Obo area are analyzed for their Fe isotope compositions as well as elemental compositions.Combined with previous reported carbonatite δ^(56)Fe data,the results show that carbonatites range from-0.35‰to 0.28‰,with an average of-0.10‰in δ^(56)Fe values,while fenites range from-0.17‰to 0.30‰,with an average of 0.11‰in δ^(56)Fe values.This indicates that fenitizing fl uids exsolved from carbonatite melts are enriched in heavier Fe isotopes.Such a Fe isotope fractionation trend is diff erent from that for fl uid exsolution from felsic magmatism.δ^(56)Fe values in fenites are negatively correlated with indicators of fenitization intensity such as(Na+K),Ti,Ba,Th,Nb,U or Pb abundances,likely refl ecting that Fe isotopes fractionate during the evolution of the fenitizing fl uids.Thus,Fe isotopes are a valuable tool for tracing fl uid exsolution and evolution relevant to carbonatite magmatism and related metal mineralization.