Trace element and Nd isotope analyses of apatite in granitoids and metamorphosed granitoids from the eastern Central Asian Orogenic Belt:Implications for petrogenesis and post-magmatic alteration  

作　　者：Xin-Yu Long Jie Tang Wen-Liang Xu Chen-Yang Sun Jin-Peng Luan Shuai Xiong Xiao-Ming Zhang 

机构地区：[1]College of Earth Sciences,Jilin University,Changchun 130061,China [2]Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources of China,Changchun 130061,China [3]State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an 710069,China [4]Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines,Northeastern University,Shenyang 110819,China [5]State Key Laboratory of Superhard Materials,Jilin University,Changchun 130012,China

出　　处：《Geoscience Frontiers》2023年第2期71-85,共15页地学前缘（英文版）

基　　金：supported by the National Natural Science Foundation of China(grant numbers 42072071,41772047).

摘　　要：We present in situ trace element and Nd isotopic data of apatites from metamorphosed and metasomatized(i.e.,altered)and unaltered granitoids in the Songnen and Jiamusi massifs in the eastern Central Asian Orogenic Belt,with the aim of fingerprinting granitoid petrogenesis,including both the magmatic and post-magmatic evolution processes.Apatites from altered granitoids(AG)and unaltered granitoids(UG)are characterized by distinct textures and geochemical compositions.Apatites from AG have irregular rim overgrowths and complex internal textures,along with low contents of rare earth elements(REEs),suggesting the re-precipitation of apatite during epidote crystallization and/or leaching of REEs from apatite by metasomatic fluids.eNd(t)values of the these apatites are decoupled from zircon eHf(t)values for most samples,which can be attributed to the higher mobility of Nd as compared to Sm in certain fluids.Apatites from UG are of igneous origin based on their homogeneous or concentric zoned textures and coupled Nd-Hf isotopic compositions.Trace element variations in igneous apatite are controlled primarily by the geochemical composition of the parental melt,fractional crystallization of other REEbearing minerals,and changes in partition coefficients.Sr contents and Eu/Eu^(*) values of apatites from UG correlate with whole-rock Sr and SiO2 contents,highlighting the effects of plagioclase fractionation during magma evolution.Apatites from UG can be subdivided into four groups based on REE contents.Group 1 apatites have REE patterns similar to the host granitoids,but are slightly enriched in middle REEs,reflecting the influence of the parental melt composition and REE partitioning.Group 2 apatites exhibit strong light REE depletions,whereas Group 3 apatites are depleted in middle and heavy REEs,indicative of the crystallization of epidote-group minerals and hornblende before and/or during apatite crystallization,respectively.Group 4 apatites are depleted in heavy REEs,but enriched in Sr,which are features of adakites.Som

关 键 词：Eastern CAOB Granitoid petrogenesis Apatite geochemistry Fluid-induced alteration Nd-Hf isotopic decoupling Crustal assimilation 

分 类 号：P542[天文地球—构造地质学] P588.121[天文地球—地质学]