Characteristics of Mesoproterozoic Granites and Their Geological Significances from Middle Tianshan Block,East Tianshan District,NW China
Characteristics of Mesoproterozoic Granites and Their Geological Significances from Middle Tianshan Block,East Tianshan District,NW China
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发表时间：
2010
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通讯作者：
Shi Wen-xiang
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作者：
Shi Wen-xiang
识别出一套深圳湾典型岩石组合：片麻状闪长岩、片麻状花岗闪长岩、片麻状二长花岗岩、片麻状钾长花岗岩，产于天山造山带中天山地块星星峡群变质岩中，采用SHRIMP U-Pb法测定了中天山片麻状花岗闪长岩中16个锆石的年龄，（1 453±15）-（1458 ±40）Ma（207 Pb/206 Pb），相当于中元古代晚期，代表片麻状花岗闪长岩源岩的结晶年龄，岩石化学和地球化学特征显示为高钾钙碱性I型花岗岩，SHRIMP U-Pb结果为元古宙天山洋的存在和闭合事件提供了岩浆作用证据，此外，残留锆石SHRIMP U-Pb年龄（2991 ±22）Ma的发现，表明中天山基底时代可追溯至中生代。
A suit of pluton is identified,consisting of the typical rock association: gneissic diorite,gneissic granodiorite,gneissic monzonite granite,gneissic K-feldspar granite,from metamorphic rocks of the Xingxingxia Group,Middle Tianshan Block,Tianshan Orogenic Belt,NW China.16 zircons from Middle Tianshan gneissic granodiorites were dated using SHRIMP U-Pb method.A weighted average apparent age of(1 453±15)—(1 458±40) Ma(207Pb/206Pb) attained,is equal to the late Mesoproterozoic era,which represents the crystal age of the source rocks of gneissic granodiorite.The petrochemical and geochemical characteristics of the intrusive rocks shows a high-K calc-alkaline and I type granites,formed in convergent environment.It is a magmatism evidence for the existence and the closing event of the Proterozoic Tianshan Ocean according to the results of the SHRIMP U-Pb,which gives a good minimum ceiling of the age of Xingxingxia Group.Besides,the discovery of a residual zircon SHRIMP U-Pb age of(2 991±22) Ma indicates the basement time of the Middle Tianshan may cast back to the Archaean era.