南阿尔金迪木那里克花岗岩地球化学、锆石U-Pb年代学与Hf同位素特征及其构造地质意义  

Geochemistry,geochronology and zircon Hf isotopes of the Dimunalike granite in South Altyn Tagn and its geological significance

作　　者：杨文强[1] 刘良[1] 丁海波 校培喜[3] 曹玉亭[1] 康磊[1] 

机构地区：[1]大陆动力学国家重点实验室,西北大学地质学系,西安710069 [2]新疆地矿局第三地质大队,库尔勒841000 [3]中国地质调查局西安地质矿产研究所,西安710054

出　　处：《岩石学报》2012年第12期4139-4150,共12页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划"973"项目(2009CB825003);中国地质调查局项目(1212011085034);国家自然科学基金项目(40972128);西北大学大陆动力学国家重点实验室创新基金项目(10DZSY021)联合资助

摘　　要：迪木那里克花岗岩侵入到南阿尔金迪木那里克浅海相沉积地层中,岩性为钾长花岗岩。地球化学数据显示该花岗岩具有高SiO2、高钾、高铝的特征,富集Rb、Th、K、La、Zr,亏损Ba、Ta、Nb、Sr、P、Ti,属于弱过铝质高钾钙碱性系列,具有S型花岗岩的特征;其源岩为杂砂岩,熔融温度和压力约为>800℃与～10kbar。锆石εHf(t)介于-3.52～0.95,LA-ICP-MS锆石U-Pb定年确定其形成时代为452.8±3.1Ma。迪木那里克花岗岩的形成时代明显晚于南阿尔金高压-超高压变质岩的峰期变质时代(486～504Ma),而与超高压岩石的退变质时代(455Ma)基本一致,又与形成时代为467Ma的长沙沟-清水泉一带裂谷型层状镁铁质-超镁铁质杂岩体伴生,其成因可能是阿尔金深俯冲陆壳板片发生断离后,深部地幔物质上涌导致地壳杂砂岩熔融的产物,具有同折返岩浆作用的特点。结合以往研究,南阿尔金俯冲碰撞杂岩带中早古生代花岗岩的演化期次可初步划分为:1)约500Ma,与高压-超高压变质岩的峰期变质时代一致,形成于陆-陆碰撞造山作用过程中的陆壳相互叠置加厚阶段;2)为466～451Ma,与超高压岩石的退变质时代大致相当,形成于深俯冲陆壳断离后的伸展构造背景;3)为426～385Ma,形成于碰撞造山作用结束后的伸展减薄阶段。The Dimunalike moyite intruded the Dimunalike shallow marine sedimentary strata in the South Altyn Tagh.Geochemical data shows that,this granite is high in SiO2,K2O and Al2O3,enriched in Rb,Th,K,La,Zr,depleted in Ba,Ta,Nb,Sr,P,Ti,and belongs to weakly peraluminous high-K calc-alkaline series.The Dimunalike moyite has characteristics of S-type granite.The magma of this granite might be derived from melting of greywacke under the temperature of 〉800℃ and pressure -10kbar.Variations of εHf（t） are-3.52-0.95.Zircon LA-ICP-MS U-Pb dating yields a weighted average age of 452.8±3.1Ma.The crystallization age of the Dimunalike granite was consistent with the retrograde metamorphic age of the UHP rocks and significantly younger than the peak metamorphic age of the HP-UHP rocks.The Dimunalike granite occurred associated with the Changshagou-Qingshuiquan rifting-related banded mafic-ultramafic intrusion.A possibly reason for this is that,after break-off of the Altyn deep subducted continantal slab,the upwelling material and heat from the deep mantle triggered partial melting of the greywacke unit in the crust.The genesis of the Dimunalike granite displays characteristics of syn-exhumation magmatism.Combined with previous studies,tectonic setting evolution process of the Early Paleozoic granite plutons of the South Altyn continental subduction-collision complex can be subdivided into three stages：I） -500Ma,this period was dominated by continent-continent collision and crustal thickening,and the age constraint is consistent with the peak age of the HP-UHP metamorphism;II） 462-451Ma,the study area was within an extensional tectonic setting caused by break-off of deep subducted continental slab as indicated by the retrograde metamorphic age of the UHP rocks;III） 426-406Ma,the tectonic setting of this stage is dominated by post-collisional extension and crustal thinning.

关 键 词：LA-ICP-MS锆石U-PB年龄 S型花岗岩 同折返岩浆作用 迪木那里克 南阿尔金 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]