东昆仑昆中缝合带的活化:来自石炭纪花岗岩的证据  

Activation of the Central Kunlun Suture Zone,East Kunlun:Evidence from Carboniferous granites.

作　　者：董越 刘畅 曹伟伟 关力伟 段星星[3] 刘珉 DONG Yue;LIU Chang;CAO Weiwei;GUAN Liwei;DUAN Xingxing;LIU Min(Langfang Center for General Survey of Natural Resources,CGS,Langfang 065000,Hebei,China;Beijing Research Institute of Uranium Geology,Beijing 100029,China;Urumqi Comprehensive Survey Center on Natural Resources,China Geological Survey,Urumqi 830057,Xinjiang,China)

机构地区：[1]中国地质调查局廊坊自然资源综合调查中心,河北廊坊065000 [2]核工业北京地质研究院,北京100029 [3]中国地质调查局乌鲁木齐自然资源综合调查中心,新疆乌鲁木齐830057

出　　处：《地质通报》2023年第12期2060-2083,共24页Geological Bulletin of China

基　　金：中国地质调查局项目《新疆且末县阿克苏河一带(J45E015010、J45E016009、J45E016010)15万区域地质矿产调查》(编号:DD2016007907)、中国核工业地质局地勘费项目《川藏地区雅安-林芝段铀多金属资源评价研究》(编号:地GT2201)。

摘　　要：在东昆仑西段工作程度较低的阿克苏河地区,首次识别出石炭纪侵入岩浆活动。阿克苏复式岩体位于昆中断裂带西段,锆石LA-ICP-MS定年显示,花岗闪长斑岩结晶年龄为361±2.4 Ma,二长花岗岩结晶年龄为357.5±2.8 Ma,花岗闪长岩结晶年龄为354±4.3 Ma,代表这些岩体侵位于晚泥盆世—早石炭世(临近昆中缝合带西部),该阶段岩浆事件此前未见公开报道。主量元素分析显示,此套花岗闪长斑岩、二长花岗岩和花岗闪长岩具有富Si、Al、K的特征,为高钾钙碱性过铝质系列;微量和稀土元素分析显示,岩石具有轻、重稀土元素分馏和轻稀土元素富集及负Eu异常特征,富集大离子亲石元素(LILE)Th、U、Rb、K;亏损高场强元素(HFSE)Nb、P、Ti等。锶同位素分析显示,^(87)Sr/^(86)Sr初始值为0.70612~0.71009,εNd(t)为-7.1~-5.1,T DM2为1.51~1.69 Ga。综合岩石-矿物特征和地球化学分析,这些岩石应该属于I型花岗岩,主要为受幔源岩浆作用后地壳物质重熔的结果,指示东昆仑昆中缝合带在石炭纪处于拉张裂解的状态。结合区域岩相学和岩石学资料,推断这一裂解事件应该为古特提斯洋俯冲引起的弧后盆地初始扩张,并将前人认为的古特提斯洋俯冲开启时间为二叠纪提前到石炭纪。In this publication,we identified Carboniferous intrusions for the first time in the Aksu River area,which has been relatively poorly explored in the western part of the East Kunlun.The Aksu acidic complex is located in the west section of the Central Kunlun fault zone.Zircon LA-ICP-MS dating results reveal that the granodiorite porphyry was crystallized at 361±2.4 Ma,the monzogranite at 357.5±2.8 Ma,and the granodiorite at 354±4.3 Ma,indicating that these rocks were intruded during Late Devonian to Early Carboniferous(close to the west of Central Kunlun Suture Zone)and this stage of the magmatic event has not previously been publicly reported.Analysis of major elements classifies these rocks as belonging to the high potassium calc-alkaline to calc-alkaline and peraluminous series.Trace and rare earth elements indicate that all rocks are enriched in large ion lithophile elements(such as Th,U,Rb,K),light rare earth elements and depleted in high field strength elements(such as Nb,P,Ti).These granites have high initial ^(87)Sr/^(86)Sr(0.70612~0.71009),low whole-rockεNd(t)values(-7.1~-5.1)and relative ancient T DM2 model ages ranging from 1.51 Ga to 1.69 Ga,which is comparable to the composition of enriched mantle or crust in the East Kunlun Orogen.Mineralogical and geochemical analyses indicate that the rocks are I-type granites,formed by remelting of crustal material,suggesting that the Central Kunlun Suture Zone underwent extensional setting during the Carboniferous.Combined with the regional geology and available geochronological data,we propose that this extensional event should be the result of the initial expansion of a back-arc basin caused by subduction of the Paleo-Tethys Ocean,which also places the time of initial subduction of the Paleo-Tethys Ocean in the Carboniferous rather than the Permian.

关 键 词：花岗岩 地壳重熔 断裂活化 阿克苏河 东昆仑 早石炭世 地质调查工程 

分 类 号：P534.45[天文地球—古生物学与地层学] P588.121[天文地球—地质学]