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孟繁聪,贾丽辉,任玉峰,刘强,段雪鹏. 2017. 东昆仑东段温泉地区片麻岩记录的岩浆和变质事件:锆石U-Pb年代学证据. 岩石学报, 33(12): 3691-3709
东昆仑东段温泉地区片麻岩记录的岩浆和变质事件:锆石U-Pb年代学证据
作者单位
孟繁聪 中国地质科学院地质研究所, 北京 100037 
贾丽辉 中国地质科学院地质研究所, 北京 100037 
任玉峰 中国地质科学院地质研究所, 北京 100037 
刘强 中国地质科学院地质研究所, 北京 100037 
段雪鹏 中国地质科学院地质研究所, 北京 100037 
基金项目:本文受国家自然科学基金项目(41272052)和中国地质调查局项目(12120114080101、12120115027001、121201102000150005-08)联合资助.
摘要:
      本文采用LA-ICP-MS方法对东昆仑东端温泉地区含榴辉岩的副片麻岩和花岗片麻岩进行了锆石U-Pb年代学研究。副片麻岩中锆石的年龄范围为2400~430Ma,峰值范围为2000~1200Ma,其中检测出少量新元古代(1.0~0.9Ga)和早古生代(430Ma)的变质锆石,进一步限定了原岩的最早沉积时代为中元古代末期-新元古代早期(Pt2-3),指示该沉积岩经历了新元古代早期和志留纪的变质作用。花岗片麻岩的原岩时代为900Ma,1件样品的锆石εHft)值为-7.0~+5.5,多数为负值,单阶段亏损地幔模式年龄为1.83~1.25Ga,指示它们主要是古老地壳(可能为金水口岩群变沉积岩)熔融的产物。新元古代早期的岩浆-变质事件与全球Rodinia超大陆的形成有关。虽然副片麻岩锆石只给出少量早古生代志留纪变质的信息,考虑到片麻岩中的榴辉岩形成于早古生代(450~430Ma)及邻区柴北缘高压-超高压变质带的演化历史,推测该地区片麻岩也经历了早古生代榴辉岩相变质作用,片麻岩与榴辉岩为原地关系。根据柴达木盆地南北两侧相似的早期构造演化可以推测柴达木盆地基底演化与其类似,至少经历了新元古代和早古生代两期构造活动,并非是元古代以来的稳定克拉通。
英文摘要:
      The geochronology of the detrital zircons of the eclogite-hosting paragneiss and granitic orthogneiss in the Wenquan region, eastern part of the East Kunlun Mountains was studied by using LA-ICP-MS method in this paper. The ages of the detrital zircons of the paragneiss vary in a range of 2400~430Ma, with a peak age value range from 2000Ma to 1200Ma, and minor metamorphic zircons of 1.0~0.9Ga (Neoproterozoic) and 430Ma (Early Paleozoic) also found, implying that the protolith of the paragneiss deposited from Late Mesoproterozoic to Early Neoproterozoic (Pt2-3) and underwere metamorphism in Early Neoproterozoic and Silurian. Zircons of the granitic orthogneiss yield magmatic crystallization ages at 900Ma, with εHf(t) values of zircons from one sample varying from -7.0 to +5.5, but most of them showing negative values, and their tDM values from 1.8Ga to 1.3 Ga, demonstrating that the granites sourced mainly from the older basement melting (maybe metasediments from the Jinshuikou Group). The Neoproterozoic magmatic and metamorphic events should be related to the formation of global Rodinia supercontinent. Although only minor zircons of the paragneiss contain the information of an Early Paleozoic metamorphic event, we infer this gneiss experienced Early Paleozoic eclogite-facies metamorphism, linking that the paragneisses bearing the eclogite formed in Early Paleozoic (450~430Ma) as well as the in situ relationship between the gneiss and the eclogite, and tectonic evolution of HP-UHP belt in northern margin of the Qaidam Basin (QB). Base on similar tectonic histories of both the southern and northern margins of the QB, we speculate that the basement of the QB suffered Neoproterozoic and Early Paleozoic tectonic events, and the basement itself was not a stable craton scince Proterozoic.
关键词:副片麻岩  花岗片麻岩  锆石  变质基底  东昆仑  柴达木盆地
投稿时间:2017-06-11  修订日期:2017-09-08
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