投稿时间：2017-03-28
修订日期：2017-10-10
网络发布日期：2017-12-28
中文摘要:厂坝及黄渚关岩体位于商丹缝合带和勉略缝合带之间的秦岭微板块，主要由花岗闪长岩及二长花岗岩组成。LA-MC-ICP-MS锆石U-Pb定年显示，黄渚关及厂坝岩体的演化可划分为中三叠世（229 Ma）和晚三叠世（215~209 Ma）2期。黄渚关中心部位的年龄（（229.2±1.0）Ma）老于边部岩体（（215.8±0.8）Ma），厂坝岩体中心部位年龄（（218.3±1.2）Ma），老于边部年龄（（209.4±0.8）Ma），结合岩体中心相和边缘相渐变的特征，说明2个岩体是由中心部位侵位，边部岩体的侵位冷却时间较晚造成的。黄渚关岩体的εHf（t）为-3.13~-14.51，集中于-10~-6；厂坝岩体的εHf（t）为-5.17~-14.51，集中于-12~-6。在εHf（t）-t图解中，εHf（t）均在球粒陨石之下和古元古地壳演化线之上；二阶段模式年龄黄渚关岩体主要集中在1.8~2.1 Ga，厂坝岩体主要集中在2.0~2.2 Ga，结合继承锆石年龄1932 Ma、2039 Ma，表明古元古代地层可能为岩体的源区之一，在黄渚关岩体发现的暗色包体说明岩浆在上升的过程中发生了壳-幔岩浆的混合。因此，笔者认为黄渚关、厂坝岩体起源于古老地壳重熔，并在上升的过程中与幔源岩浆发生一定比例混合。
Abstract:Changba and Huangzhuguan plutons are located in the Qinling microplate between the Shang-Dan and the Mian-Lue suture zones.The plutons consist of granodiorite and monzonitic granite. LA-ICP-MS zircon U-Pb dating suggests that the Changba and Huangzhuguan plutons formed in Early Mesozoic, and can be divided into two stages:Middle Triassic (229 Ma) and Late Triassic (215~209 Ma). Because of the cooling of the intrusion, the age of the middle part((229.2±1.0) Ma) of the Huangzhuguan pluton is older than that of the marginal part ((215.8±0.8) Ma), while the age of the middle part (218.3±1.2) Ma)of the Changba pluton is older than that of the marginal part ((209.4±0.8) Ma). The εHf(t) values of the Huangzhuguan pluton are -3.13~-14.51, mainly between -10 and -6, whereas the εHf(t) values of the Changba pluton are -5.17~-14.51, mainly between -12 and -6. On the εHf(t) versus age diagram, εHf(t) is above the evolution curve of chondrite and below the evolution curve of depleted mantle. Moreover, the age of stage (TDM2) in Changba pluton is mainly between 1.8 and 2.1 Ga, whereas the age of stage (TDM2) in Huangzhuguan pluton is mainly between 2.0 and 2.2 Ga. Combined with the inherited zircon ages of 1932 Ma, 2039 Ma, the dark enclaves in Huangzhuguan pluton might suggest that the rock-forming materials were mainly derived from the Palaeoproterozoic crustal partial melting with the addition of mantle material.
keywords:geochemistry zircon U-Pb age Hf isotope composition Changba pluton Huangzhuguan pluton LA-MC-ICP-MS West Qinling
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中图分类号：P597.3
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基金项目:中央级公益性科研院所基本科研业务费专项资金（编号：K1612）、国家自然科学基金项目（编号：41372089）和中国地质调查局地质调查项目（编号：121201103000150006）联合资助
引用文本：
魏然,王义天,胡乔青,黄诗康,袁群虎,柏全良,胡文荣,张湘君,蔡拓.2017.西秦岭厂坝、黄渚关岩体的锆石U-Pb年龄、Hf同位素组成及其地质意义[J].矿床地质,36(6):1367~1386WEI Ran,WANG YiTian,HU QiaoQing,HUANG ShiKang,YUAN QunHu,BAI QuanLiang,HU WenRong,ZHANG XiangJun,CAI Tuo.2017.Zircon U-Pb ages and Hf isotope compositions of Changba and Huangzhuguan plutons in West Qinling, and their geological significance[J].Mineral Deposits36(6):1367~1386
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