摘要
摘要:西天山赛里木微地块北缘，哈尔达坂铅锌矿矿区中南部的石英二长岩，呈岩脉状就位于中元古界哈尔达坂群灰岩、白云质灰岩和微晶灰岩中。SHRIMP U-Pb法测得锆石²⁰⁶Pb/²³⁸U加权平均年龄378.8±7.2 Ma（MSWD=0.56），表明其形成于中泥盆世早期。岩石地球化学特征显示，其具有偏铝质—钙碱性（A/CNK=0.88～1.44）、富碱（K₂O+Na₂O=7.08%～8.49%）的特征，富集大离子亲石元素Rb、Cs、Th、K，贫Eu、Ba、Sr和Ti、Nb、Ta、P等高场强元素。轻稀土略富集，重稀土略亏损，配分模式为右倾海鸥型；且轻、重稀土内部分馏较弱，具弱负Eu异常（δEu=0.47～0.97）；锆石饱和温度为（841℃～913℃）；并具高10000*Ga/Al（～2.8，>2.6）和较高Y/Nb比值（3.03～3.81，>1.2）。指示哈尔达坂石英二长岩具有A₂型花岗岩的元素地球化学特征。综合前人研究：判断哈尔达坂石英二长岩形成于中泥盆世的岛弧环境，并可能与新疆北部泥盆纪的北天山洋脊俯冲有关，由洋脊俯冲造成板片窗作用使得软流圈地幔上涌，熔融下地壳并形成近似“板内伸展环境”特色的花岗质岩石。
关键词: A型花岗岩/
锆石U-Pb年代学/
赛里木微地块/
洋脊俯冲/
板片窗

Abstract:Quartz monzonite in the central and southern part of the Haerdaban Pb, Zn deposit in the northern margin of the Sayram micro block, West Tianshan, is in the form of dyke and is located in the limestone, dolomitic limestone and microcrystalline limestone of the Middle Proterozoic Haerdaban Group. The SHRIMP zircon U-Pb dating yielded a ²⁰⁶Pb/²³⁸U age of 378.8±42 Ma(MSWD=0.56), which is interpreted as the formation age of the Early-Middle Devonian. Geochemical characteristics of the rocks show that they are aluminous calc alkaline (A/CNK=0.88~1.44) and alkali rich (K₂O+Na₂O=7.08%~8.49%), rich in large ion lithophile elements Rb, Cs, th, K, and poor in Eu, Ba, Sr and high field strength elements such as Ti, Nb, Ta, P. The samples exhibit a slight enrichment of LREE as well as negative anomalies of Eu (δEu=0.47~0.97), Also present "Sea-gull" type rare earth element pattern. Finally, these samples are characterized by the high saturation temperature of zircons (841℃~913℃), high 10000*Ga/Al(~2.8, >2.6) and especially Y/Nb(3.03~3.81, >1.2). It indicates that the Haerdaban quartz monzonite have the elemental geochemical characteristics of type A₂ granites. Comprehensive petrology, petrogeochemistry and previous studies:It is believed that the Hardaban quartz monzonite veins were formed in the island arc environment of the Middle Devonian and may be related to the subduction of the Devonian ridges in northern Xinjiang. The subduction caused slab windows to upwell the asthenospheric mantle and melt the lower crust to form granite with characteristics similar to "intraplate extensional environment".
Key words:A-tpye granites/
Zircon U-Pb geochronology/
Sayram block/
Ocean ridge subduction/
Slab windows



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