PAK Sang Wan,马拓,盖永升,康磊,王超,廖小莹,刘良.南阿尔金尤努斯萨依高压花岗质片麻岩原岩的形成时代与地球化学特征:对南阿尔金陆壳深俯冲板片属性的进一步限定[J].西北地质,2019,52(4):76-97 PAK Sang Wan,MA Tuo,GAI Yongsheng,KANG Lei,WANG Chao,LIAO Xiaoying,LIU Liang.Geochronology and Geochemical Characteristics of the Protolith Rock of Younusisayi High Pressure Granitic Gneiss: a Further Study on the Properties of Continental Crust Subduction Plate in South Altyn Tagh[J].Northwestern Geology,2019,52(4):76-97
南阿尔金尤努斯萨依高压花岗质片麻岩原岩的形成时代与地球化学特征:对南阿尔金陆壳深俯冲板片属性的进一步限定
Geochronology and Geochemical Characteristics of the Protolith Rock of Younusisayi High Pressure Granitic Gneiss: a Further Study on the Properties of Continental Crust Subduction Plate in South Altyn Tagh
投稿时间:2019-03-08  修订日期:2019-05-21
DOI:
中文关键词:  高压花岗质片麻岩;原岩的形成时代;原岩的地球化学;新元古代;南阿尔金
英文关键词:high pressure granitic gneiss;age of protolith;geochemistry;Neoproterozoic;South Altyn Tagh
基金项目:国家自然科学重点基金(41430209),国家重点基础研究发展计划项目(2015CB856103),国家自然科学群体和面上基金(41421002、41602052、41672187),西北大学大陆动力学国家重点实验室自主研究重点课题联合资助
作者单位E-mail
PAK Sang Wan 西北大学地质学系, 大陆动力学国家重点实验室, 陕西 西安 710069  
马拓 西北大学地质学系, 大陆动力学国家重点实验室, 陕西 西安 710069  
盖永升 西北大学地质学系, 大陆动力学国家重点实验室, 陕西 西安 710069  
康磊 西北大学地质学系, 大陆动力学国家重点实验室, 陕西 西安 710069  
王超 西北大学地质学系, 大陆动力学国家重点实验室, 陕西 西安 710069  
廖小莹 西北大学地质学系, 大陆动力学国家重点实验室, 陕西 西安 710069  
刘良 西北大学地质学系, 大陆动力学国家重点实验室, 陕西 西安 710069 liuliang@nwu.edu.cn 
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中文摘要:
      南阿尔金尤努斯萨依地区出露的高压花岗质片麻岩的SiO2=71.01%~75.07%,Al2O3=12.31%~14.21%,全碱Na2O+K2O=7.44%~8.37%,MgO=0.26%~0.60%,TFeO=1.75%~2.62%,CaO=0.95%~1.70%,具有高硅、高铝、高碱性的特征,属于钙碱性过铝质花岗质岩石。其稀土总量为131.15×10-6~234.34×10-6,相对富集Rb、Th、La等大离子亲石元素而亏损Ba、Ta、Nb、Sr、Ti,∑LREE/∑HREE=5.07~7.67,(La/Yb)N=4.82~9.58,具有强烈的Eu亏损(δEu=0.42~0.63),显示出S型花岗岩的特征。岩石Sr/Ba值(0.11~0.15)较低,CaO/Na2O=0.44~0.75>0.3,显示原岩可能为陆壳沉积的杂砂质岩石。LA-ICP-MS锆石U-Pb定年表明该花岗质高压岩石原岩的形成时代约为900 Ma,指示其所代表的构造岩浆事件可能与阿尔金及其周缘广泛报道的新元古代Rodinia超大陆汇聚的地质事件相关,并进一步限定其侵入的阿尔金杂岩的形成时代主体应为早新元古代。该高压花岗质片麻岩原岩的形成时代(~900 Ma)远大于其发生高压变质的时代(~500 Ma),表明其原岩就位于地壳约400 Ma之后才发生俯冲遭受高压变质作用。显然,该高压岩石的形成是陆壳俯冲作用的产物,为进一步限定南阿尔金早古生代陆壳俯冲-深俯冲作用提供了新的依据。
英文摘要:
      The major elements of granite gneiss exhibit the following geochemical characteristics:SiO2=71.01%~75.07%, Al2O3=12.31%~14.21%, Na2O+K2O=7.44%~8.37%, MgO=0.26%~0.60%, TFeO=1.75%~2.62%, and CaO=0.95%~1.70%, which reveals a typical calc-alkali peraluminous granitic rock series. The granitic gneisses are simultaneously characterized by relative enrichment in Rb, Th, K, La and depletion in Ba, Ta, Nb, Sr, Ti, their ∑REE values range from 131.15×10-6 to 234.34×10-6, ∑LREE/∑HREE ratios are 5.07~7.67, (La/Yb)N ratios vary from 4.82 to 9.58, and δEu value are 0.42~0.63, showing the element distribution of collision-induced granite. Meanwhile, the geochemical results also show that the source rock of the gneiss may be mixed sand rock deposited by continental crust with Sr/Ba=0.11~0.15 and CaO/Na2O=0.44~0.75>0.3. LA-ICP-MS zircon U-Pb isotopic dating has acquired a Neoproterozoic age of 899.7±4.0Ma. Based on geochemistry and chronology research, it is rationally suggested that Younusisayi granitic was formed in a syn-collision tectonic setting as the result of the partial melting of upper crust sandy rocks, as the response of Rodinia supercontinent aggregation event in the south. Meanwhile, this granite gneiss further indicated that the formation time of whole Altyn complex rocks should be Early Neoproterozoic. Moreover, a metamorphic age of~500Ma has been obtained, which is much younger than the protolith age, and indicates that the protolith rock of this granitic gneiss was intruded and located in the continental crust for about~400Ma before subduction and high-pressure metamorphism. Thus, the granitic gneiss is obviously the product of continental subduction, which produces new evidence for further defining the subduction-deep subduction of the continental crust during Paleozoic of south Altyn Tagh.
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