The effects of the source composition on the origin of orthopyroxenebearing adakitic granitoid in West Qinling,Central China  

作　　者：Yuanhui Xie Xiaowei Li Xuanxue Mo Guochen Dong Yuqin Sun Wei Shan 

机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources,and School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China [2]Shandong Institute of Geological Sciences,and Key Laboratory of Gold Mineralization Processes and Resource Utilization,Jinan 250013,China

出　　处：《Geoscience Frontiers》2023年第3期180-200,共21页地学前缘（英文版）

基　　金：funded by the State Key Program of National Natural Science of China(Grant No.41730426);the National Natural Science Foundation of China(Grant Nos.41872066 and 41702069);the Fundamental Research Funds for the Central Universities of China(Grant No.2652018121);the Open Research Funds for GPMR(Grant No.GPMR201509).

摘　　要：Orthopyroxene-bearing granodiorite(sometimes referred to as‘charnockite’)with an adakitic affinity is a rare type of granitoid.It is generally accepted that the stabilization of orthopyroxene in igneous charnockites essentially requires low aH_(2)O and/or high temperatures in a closed system.However,orthopyroxene can be an antecryst in a trans-crustal magmatic system.In this regard,orthopyroxenebearing granitoids are somewhat analogous to pseudo-charnockites,where the orthopyroxene stems from a mafic reservoir.On the other hand,the source compositions of continental adakites can vary,which is often ignored in the interpretation of their contribution to the adakitic geochemical signature.In this study,we have investigated a rare orthopyroxene-bearing felsic pluton from the Zhuyuan area of West Qinling,Central China.The Zhuyuan pluton was emplaced in the Middle–Late Triassic(222–217 Ma)and is mainly composed of metaluminous to weakly peraluminous granodiorites belonging to the high-K calc-alkaline series.Moreover,they are characterized by high Mg#values(49.7–60.9)and Sr contents(471–697 ppm),low Y(12.2–15.4 ppm)and Yb(1.03–1.24 ppm)contents,high Sr/Y(33.2–46.2)and(La/Yb)_(N)(15.3–21.4)ratios,and weakly negative Eu anomalies(Eu/Eu^(*)=0.78–0.89).The Zhuyuan adakitic granodiorites exhibit fairly limited Sr–Nd–Pb isotopic ratios and variable zircon initial Hf isotopes,indicating a major contribution from the Neoproterozoic basement of the Qinling Orogenic Belt.There is no evidence of any formation through high-pressure magmatic processes,and we propose that the adakitic signature of the Zhuyuan pluton could have been inherited from its source rocks(i.e.,from the Neoproterozoic basement).The orthopyroxenes in the Zhuyuan granodiorites display poikilitic textures with high MgO,NiO and Cr_(2)O_(3) contents,indicating that they have an antecrystic origin.Studies of regional tectonic evolution have shown that the Zhuyuan granodiorites formed during the tearing stage of the A’nimaque–Mianlue oc

关 键 词：Qinling Orogenic Belt Adakitic rock Orthopyroxene-bearing granodiorite Pseudo-charnockite 

分 类 号：P618.51[天文地球—矿床学]