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    毕政家, 曾忠诚, 张昆昆, 曹同礼, 刘德民, 陈宁, 赵江林, 李琦, 李德威. 阿尔金南缘帕夏拉依档沟斜长角闪岩年代学、地球化学及其构造意义[J]. 中国地质, 2016, 43(4): 1149-1164. DOI: 10.12029/gc20160403
    引用本文: 毕政家, 曾忠诚, 张昆昆, 曹同礼, 刘德民, 陈宁, 赵江林, 李琦, 李德威. 阿尔金南缘帕夏拉依档沟斜长角闪岩年代学、地球化学及其构造意义[J]. 中国地质, 2016, 43(4): 1149-1164. DOI: 10.12029/gc20160403
    BI Zheng-jia, ZENG Zhong-cheng, ZHANG Kun-kun, CAO Tong-li, LIU De-min, CHEN Ning, ZHAO Jiang-lin, LI Qi, LI De-wei. Geochronology, geochemical characteristics and tectonic implications of the amphibolite from Paxialayidang area on the southern margin of Altun terrain[J]. GEOLOGY IN CHINA, 2016, 43(4): 1149-1164. DOI: 10.12029/gc20160403
    Citation: BI Zheng-jia, ZENG Zhong-cheng, ZHANG Kun-kun, CAO Tong-li, LIU De-min, CHEN Ning, ZHAO Jiang-lin, LI Qi, LI De-wei. Geochronology, geochemical characteristics and tectonic implications of the amphibolite from Paxialayidang area on the southern margin of Altun terrain[J]. GEOLOGY IN CHINA, 2016, 43(4): 1149-1164. DOI: 10.12029/gc20160403

    阿尔金南缘帕夏拉依档沟斜长角闪岩年代学、地球化学及其构造意义

    Geochronology, geochemical characteristics and tectonic implications of the amphibolite from Paxialayidang area on the southern margin of Altun terrain

    • 摘要: 阿尔金造山带南缘帕夏拉依档沟零星发育一些斜长角闪岩,主要呈透镜状或豆荚状产于阿尔金岩群大理岩中。文章对这些斜长角闪岩开展了岩相学、年代学以及地球化学方面的研究,获得斜长角闪岩LA-ICP-MS锆石U-Pb年龄为(857.4±7.1)Ma和(432.5±5)Ma,前者代表其形成年龄,后者代表其变质年龄。地球化学特征显示斜长角闪岩轻稀土微弱富集,轻重稀土分异不显著,并有部分消减带玄武岩地球化学特征,源区为古俯冲带再循环的富集地幔源区,并受到流体或熔体的改造。结合判别图解和区域构造演化,分析得出斜长角闪岩原岩形成于初始裂谷环境,是大陆拉张向裂谷转换机制下形成的过渡岩石类型,较新年龄(432.5±5)Ma为早志留世陆壳伸展和软流圈底辟作用引起的变质年龄。本次研究为新元古代中晚期阿尔金南缘基性岩浆活动提供了新的年代学和地球化学方面的证据,这期基性岩浆活动可能为Rodinia超大陆初始裂解事件在阿尔金南缘的响应。

       

      Abstract: Amphibolite is distributed sporadically in Paxialayidang area on the southern margin of Altun terrain. The amphibolite is ellipsoidal or lenticular in shape and is wrapped by marble of Altun terrain. In this paper, the authors studied petrology, geochronology and geochemistry of the amphibolites. LA-ICPMS zircon U-Pb dating yielded ages of (432.5±5) Ma and (857.4±7.1) Ma for metamorphic event and protolith respectively, and shows that the protolith was formed during Neoproterozoic Qingbaikou period. Amphibolite is slightly enriched in REE, and shows unnoticeable fractionation between light rare earth elements (LREE) and heavy rare earth elements (LREE) and the signatures of subduction zone basalt. The primary magma originated from an enriched mantle source, which was formed by the recirculation of subducted slab, and was modified by fluid or melt subsequently. Combined with the evolution of regional tectonic, the authors hold that the protolith of amphibolite was formed in an incipient continental rift and was a transitional type formed during the transition from continental extension to continental rift. The younger age of (432.5±5) Ma represents the time of metamorphic event, which was caused by the detachment of continental lower crust during Early Silurian. In this paper, the authors provide new geochronological and geochemical evidence about basic magmatic activity during middle-late stage of Neoproterozoicin on the southern margin of Altun terrain. The basic magmatic activity was the response to the Rodinia supercontinent breakup on the southern margin of Altun terrain.

       

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