摘要
海南岛铺前-木兰头一带海边发现一套中深变质岩(木兰头杂岩),由混合岩、大理岩、片岩和透辉石岩组成,以混合岩为主。研究选取其中较为发育和典型的混合片麻岩为研究对象,对其开展了锆石U-Pb同位素测年、岩石学和岩石地球化学等系统研究。结果表明,木兰头混合片麻岩原岩为中基性火山岩,形成时代为276 Ma,具有活动大陆边缘的岛弧钙碱性玄武岩地球化学特征,指示古特提斯洋俯冲的构造环境;早期发生深熔变质作用时间为261 Ma,指示华南和印支地块碰撞的构造环境;后期变质作用时间为248 Ma,指示华南和印支地块碰撞后伸展的构造环境。因此,木兰头混合片麻岩完整记录了海南岛早二叠世—早三叠世的构造演化信息,是古特提斯洋俯冲至关闭、华南和印支地块碰撞等地质事件的产物,其发现为马江缝合带向东延伸的方向提供了新的思路。
In the coastal area of Pujian to Mulantou on Hainan Island,a set of medium to deep metamorphic rocks(Mulantou complex)has been discovered,composed of migmatite,dolomite,shale,and amphibolite,with migmatite being the predominant lithology.This study selected well-developed and typical migmatitic gneisses as the research focus and conducted systematic zircon U-Pb isotope dating and petrological and geochemical studies.The results indicate that the protolith of the Mulantou migmatitic gneisses was intermediate basic volcanic rock formed around 276 Ma.These rocks exhibit geochemical characteristics of island-arc calc-alkaline basalt,suggesting a tectonic setting related to the subduction of the Paleo-Tethys Ocean.Early anatectic metamorphism occurred around 261 Ma,indicating a tectonic environment related to the collision between the South China Block and the Indochina Block.Later metamorphism took place around 248 Ma,signifying a tectonic environment associated with extension following the collision between the South China Block and the Indochina Block.Therefore,the Mulantou migmatitic gneisses preserve a comprehensive record of the tectonic evolution in Hainan Island from the Early Permian to the Early Triassic.They represent the geological consequences of events such as the closure of the Paleo-Tethys Ocean,the collision between the South China Block and the Indochina Block,and the subsequent extension.The discovery of these rocks provides new insights into the eastern extension of the Song Ma suture zone.
作者
胡在龙
赵小明
王勇
魏昌欣
吕昭英
吕嫦艳
HU Zailong;ZHAO Xiaoming;WANG Yong;WEI Changxin;LYU Zhaoying;LYU Changyan(Hainan Geological Survey Institute,Haikou 570206,Hainan,China;Hainan Key Laboratory of Marine Geological Resources and Environment,Haikou 570206,Hainan,China;Institute of Karst Geolegy,CAGS,Guilin 541004,Guangxi,China;School of Geosciences and Info-physics,Central South University,Changsha 410083,Hu’nan,China)
出处
《地质力学学报》
CSCD
北大核心
2023年第5期720-735,共16页
Journal of Geomechanics
基金
中国地质调查局地质调查项目(12120113065900)
海南省自然科学基金项目(420RC744)。
