加里曼丹东南部梅拉图斯斜长花岗岩的锆石U-Pb年代学及其地质意义  

Zircon U-Pb Dating and Tectonic Significance of the Plagiogranite in the Meratus Ophiolitic Mélange of SE Kalimantan

作　　者：王逸文 陈新跃[1] 甘成势 WANG Yiwen;CHEN Xinyue;GAN Chengshi(School of Earth Sciences and Spatial Information Engineering,Hunan University of Science and Technology,Xiangtan 410201,Hunan,China;Guangdong Provincial Key Lab of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519082,Guangdong,China)

机构地区：[1]湖南科技大学地球科学与空间信息工程学院,湖南湘潭410201 [2]中山大学地球科学与工程学院,广东省地球动力作用与地质灾害重点实验室,广东珠海519082

出　　处：《大地构造与成矿学》2022年第3期622-632,共11页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(42002236)资助。

摘　　要：加里曼丹岛位于特提斯和太平洋构造域的交汇之处,是研究两大构造域演化、延伸及耦合的关键地区。梅拉图斯蛇绿混杂岩呈近S-N向分布于加里曼丹岛东南部,但该蛇绿混杂岩带的年代学、构造归属及其与特提斯和太平洋构造域的亲缘性存在争议。本文针对梅拉图斯蛇绿混杂岩带内的斜长花岗岩开展了岩相学、年代学、主量和微量元素、Sr-Nd同位素地球化学分析。LA-ICPMS锆石U-Pb年代学结果揭示斜长花岗岩的结晶年龄为143.2±0.5 Ma(MSWD=0.4)。斜长花岗岩样品具较高的Ab含量(74%~91%),属于奥长花岗岩,其SiO_(2)=62.95%~66.92%,Al_(2)O_(3)=17.81%~20.48%,MgO=0.09%~3.02%,Fe_(2)O_(3)<0.92%,Na_(2)O=8.62%~10.61%,K_(2)O=0.06%~0.22%和TiO_(2)<0.05%。样品A/CNK和A/NK值分别为0.82~1.03和1.11~1.43,属于准铝质‒弱过铝质花岗岩系列。斜长花岗岩富集大离子亲石元素和轻稀土元素,具显著的Ba、Sr和Eu正异常特征,具较低的(^(87)Sr/^(86)Sr)i值(0.70493)和较高的ε_(Nd)(t)值(+3.6),为基性岩部分熔融的产物。综合对比结果显示,梅拉图斯蛇绿混杂岩与爪哇岛卢克乌璐蛇绿混杂岩在年代学、岩石组合及地球化学特征上相近,二者都属于特提斯洋产物。Kalimantan is mainly surrounded by the Tethyan and Pacific tectonic domains,and it is an important place for exploring the tectonic evolution and interaction of the two domains.The N-S trending Meratus ophiolitic mélange is located in SE Kalimantan,but the formation time and tectonic nature of this mélange are poorly constrained.This study firstly presents the zircon U-Pb age and major element contents of the plagiogranite in the Meratus ophiolitic mélange.Our data show that the plagiogranite formed at 143.2±0.5 Ma.The plagiogranite samples are characterized by high Al_(2)O_(3)(17.81%-20.48%)and Na_(2)O(8.62%-10.61%)with SiO_(2)=62.95%-66.92%,MgO=0.09%-3.02%,Fe_(2)O_(3)<0.92%,K_(2)O=0.06%-0.22%and TiO_(2)<0.05%.They are metaluminous to weakly peraluminous with A/CNK=0.82-1.03 and A/NK=1.11-1.43.The plagioclase in the plagiogranite has high Ab(74%-91%),and thus the plagiogranite can be termed as trondhjemite.They are enriched in LILE and LREE with significant Ba,Sr and Eu positive anomalies.They have low initial ^(87)Sr/^(86)Sr ratio of 0.704927 and highε_(Nd)(t)value of+3.6,likely deriving from partial melting of metasomatized gabbro or amphibolites.In combination with other data,the Meratus ophiolitic mélange has geological and geochemical features similar to those of the Luk Ulo and Bantimala ophiolitic mélanges in Central Java and SW Sulawesi,suggestive of the Tethyan subduction initiating at the earliest Cretaceous.

关 键 词：斜长花岗岩 梅拉图斯蛇绿混杂岩 加里曼丹 特提斯构造域 

分 类 号：P581[天文地球—岩石学] P597[天文地球—地质学]