特提斯喜马拉雅东部早白垩世双峰式火山岩地球化学特征及地质意义  

GEOCHEMICAL CHARACTERISTICS AND GEOLOGICAL SIGNIFICANCE OF EARLY CRETACEOUS BIMODAL VOLCANIC ROCKS IN HEASTERN TETHYAN HIMALAYA

作　　者：蔡磊 霍艳[1] 丁枫 费光春[1,2] 范宇航[1] 田京京[3] 邹婧 张鹏浩 CAI Lei;HUO Yan;DING Feng;FEI Guangchun;FAN Yuhang;TIAN Jingjing;ZOU Jin;ZHANG Penghao(College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Key Laboratory of Tectonic Mineralization and Accumulation,Natural Resources Department,Chengdu University of Technology,Chengdu,Sichuan 610059,China;State Key Laboratory of Geological Hazard Prevention and Geological Environmental Protection,Chengdu University of Technology,Chengdu Sichuan 610059,China)

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]成都理工大学、自然资源部构造成矿成藏重点实验室,四川成都610059 [3]成都理工大学、地质灾害防治与地质环境保护国家重点实验室,四川成都610059

出　　处：《矿物岩石》2023年第1期42-60,共19页Mineralogy and Petrology

基　　金：冈底斯-喜马拉雅铜矿资源基地调查项目(编号:DD20160015-06);国家自然科学基金项目(批准号:41702074)。

摘　　要：东冈瓦纳大陆初始裂解时间的界定对古地理重建和地球动力学模型的关键约束具有重大意义,为了研究东冈瓦纳大陆裂解时间,本次研究以特提斯喜马拉雅东部索努地区桑秀组双峰式火山岩为研究对象,其岩石学特征、地球化学特征以及LA-ICP-MS锆石U-Pb定年的研究表明:酸性火山岩主要为英安斑岩和气孔杏仁状英安岩,具过铝质(A/CNK值为0.98~1.15)、钙碱性-碱性(AR值为2.15~2.71)的特征,微量元素Th,U,Ce,Zr,Nb,Y及轻稀土含量较高,Sr,P,Ti含量较低,10000Ga/Al比值较高(3.12~3.62),与A型花岗岩地球化学特征相似,为基性岩浆底侵导致的地壳部分熔融的产物,酸性火山岩的成岩年龄为138.0±1.3 Ma。基性火山岩主要为隐晶质和气孔杏仁状玄武岩,具准铝质(A/CNK值为0.67~0.91)、钙碱性(AR值为1.49~1.78)的特征,其TiO2,P2O5,Ba,Ta,Nb,Sm等元素及轻稀土含量较高,Rb,K等元素含量较低,与OIB型玄武岩特征较为接近,为Kerguelen地幔柱与大陆岩石圈地幔相互作用在大陆裂谷中形成的产物。基于以上研究,我们认为桑秀组双峰式火山岩记录了特提斯喜马拉雅的裂谷事件,裂谷的形成代表着东冈瓦纳大陆的裂解,东冈瓦纳大陆的裂解时间应早于138 Ma,即大印度板块与澳大利亚板块的裂解时间早于138 Ma。In this paper,the bimodal volcanic rocks of the Sangxiu Formation in the Sonu region of the eastern Tethyan Himalaya are studied aiming to reveal the breakup time of the eastern Gondwana continent and provide key constraints for its paleogeographic reconstruction and geodynamic model.The petrological and geochemical characteristics of the Sangxiu Formation volcanic rocks and LA-ICP-MS zircon UPb dating show that the Sangxiu Formation acid volcanic rocks are mainly composed of dacite porphyry,vesicular and almond-shaped dacite.LA-ICP-MS zircon U-Pb dating for the acid volcanic rock yields an age of 138.0±1.3 Ma.Geochemical analysis shows that the rocks are characteristic of peraluminous(A/CNK value=0.98-1.15),calc-alkaline and alkaline(AR value=2.15-2.71)series.The contents of trace elements Th,U,Ce,Zr,Nb,Y and light rare earth are high,while the contents of Sr,P and Ti are low.The ratio of 10000Ga/Al is high(3.12 to 3.62),similar to the geochemical characteristics of A-type granite,which is resulted from the partial melting of crust during basic-magmatic basement invasion.The basic volcanic rocks are mainly cryptocrystalline and almond-shaped basalts,with characteristics of quasi-aluminous(A/CNK value=0.67-0.91)and calc-alkaline(AR value=1.49-1.78)series.The basic volcanic rocks have high content of TiO2,P2O5,Ba,Ta,Nb,Sm and light rare earth,and low content of Rb,K,etc.,similar to OIB basalt,formed in the continental rift by the interaction between Kerguelen mantle plume and continental lithospheric mantle.The research indicates that the formation of bimodal volcanic rocks of Sangxiu Formation at 138 Ma records the rift event of Tethyan Himalaya,and represents the breakup of east Gondwana continent,that is,the breakup of the Great India Plate and Australia Plate is earlier than 138 Ma.

关 键 词：特提斯喜马拉雅 早白垩世 双峰式火山岩 地球化学特征 东冈瓦纳大陆裂解 

分 类 号：P595[天文地球—地球化学] P581[天文地球—地质学]