印尼西婆罗洲早白垩世Mensibau花岗岩类的成因及构造意义  

Petrogenesis and tectonic significance of the Early CretaceousMensibau granitoids in West Borneo, Indonesia

作　　者：郭东海 刘铁翊 朱俊宾[1] 姜冠哲 李舢 GUO Donghai;LIU Tieyi;ZHU Junbin;JIANG Guanzhe;LI Shan(Institute of Geology,Chinese Academy of Geological Sciences,Beijing,100037;Sinoprobe Center,Chinese Academy of Geological Sciences,Beijing,100037;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing,100049)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质科学院地球深部探测中心,北京100037 [3]中国科学院大学地球与行星科学学院,北京100049

出　　处：《地质论评》2023年第4期1249-1268,共20页Geological Review

基　　金：国家自然科学基金资助项目(编号:42161144007,41772232);中国科学院大学中央高校基本科研业务费专项资金资助项目(编号:E2EG0401X2,E2ET0410X2)的成果~~。

摘　　要：婆罗洲西部(印尼)在中生代期间处于特提斯构造域和古太平洋构造域交汇地带,是全球少有的多重板块动力学体制既有先后叠加又有同时复合的独特大地构造单元。因此,该区相关花岗岩类成因及构造背景的研究对揭示东南亚构造—岩浆演化历史及多重构造体制叠合造山作用下的岩浆演化机制至关重要。笔者等对西婆罗洲Mensibau岩基的花岗岩类进行了锆石U-Pb年代学、元素地球化学和Sr-Nd-Hf同位素分析。其中,石英二长岩和钾长花岗岩样品的LA-ICP-MS锆石U-Pb同位素年龄分别为126.9±2.1 Ma和141.8±2.6 Ma,表明岩体形成于早白垩世,岩浆活动至少持续了15 Ma。Mensibau花岗岩类具有高SiO2(67.5%~73.3%)、高K2O (4.3%~5.4%)和低P2O5(0.07%~0.14%)的元素含量特征,铝饱和指数(A/CNK)为0.92~1.06,并且含角闪石,属准铝质—弱过铝质I型花岗岩类。这些花岗岩类具有轻稀土元素(LREEs)富集和重稀土元素(HREEs)亏损,弱的负铕异常(δEu=0.65~1.00),以及富集大离子亲石元素(Rb、Th、U和K)和亏损高场强元素(Nb、Ta和Ti)特征,显示出岛弧花岗岩的地球化学特征。此外,Mensibau花岗岩类具有正的εNd(t)值(+3.14~+4.09)、低的[n(87Sr)/n(86Sr)]i值(0.70420~0.70424)和高的锆石εHf(t)值(+9.30~+13.87),表明岩浆来源于新生镁铁质地壳的部分熔融。综合区域地质背景研究表明,发育在俯冲—增生杂岩上的Mensibau花岗岩类可能为受两种构造体制(古太平洋和新特提斯洋)叠合俯冲作用下的新生地壳来源的增生弧岩浆岩,证实了西婆罗洲地区在早白垩世期间经历了重要的增生造山过程。The western Borneo (Indonesia) was located at the intersection of the Tethys and Paleo-Pacifictectonic domains during the Mesozoic, and is a unique tectonic unit in the world where multiple plate dynamicssystems were superimposed sequentially and simultaneously. Therefore, the study of the petrogenesis and tectonicsetting of granitoids in this region is crucial to reveal the tectonic-magmatic evolutionary history of Southeast Asiaand the magmatic evolutionary mechanism under the superposition of multiple tectonic systems of orogeny.In this study, zircon U-Pb chronology, geochemistry, and Sr-Nd-Hf isotope analyses of granitoids from theMensibau batholith in West Borneo were carried out. The LA-ICP-MS zircon U-Pb isotopic ages of 126. 9 ± 2. 1Ma and 141. 8 ± 2. 6 Ma for quartz monzonite and K-feldspar granite sample, respectively, indicate that the rocksformed in the Early Cretaceous and magmatism lasted at least 15 Ma. The Mensibau granitoids has high SiO2(67. 5% ~ 73. 3%), high K2O (4. 3% ~ 5. 4%) and low P2O5 (0. 07% ~ 0. 14%) content, aluminum saturationindex ( A/ CNK) of 0. 92 ~ 1. 06, and the presence of hornblende, belongs to the metaluminous - weaklyperaluminous I type granites. These granitoids are characterized by enrichment of light rare earth elements(LREEs) and depleted of heavy rare earth elements (HREEs), weak negative europium anomalies (δEu = 0. 65~ 1. 00), and enrichment of large ion lithophile elements (Rb, Th, U, and K) and depleted of high field strengthelements (Nb, Ta, and Ti), showing the typical geochemical characteristics of island arc granites. In addition, theMensibau granitoids has positive εNd(t) values (+3. 14~ +4. 09), low [n(87Sr) / n(86Sr)]i values (0. 70420~0. 70424), and high zircon εHf(t) values (+9. 30~+13. 87), indicating that the magma was derived from partialmelting of the juvenile mafic crust.A comprehensive regional geological background study indicates that the Mensibau granitoids developed onsubduction - accretionary complexs may be accretionary arc magmatism of juv

关 键 词：东南亚 婆罗洲 Mensibau岩基 白垩纪花岗岩类 SR-ND-HF同位素 

分 类 号：P534.53[天文地球—古生物学与地层学] P588.121[天文地球—地质学]