海南岛高峰、保城地区花岗岩年代学、地球化学特征及构造意义  

Geochronology,Geochemistry and Tectonic Significance of Gaofeng and Baocheng Granite Batholiths in Hainan Island

作　　者：袁晓博[1] 方念乔[1] 董海龙 YUAN Xiaobo;FANG Nianqiao;DONG Hailong(School of Ocean Sciences,China University of Geosciences,Beijing 100083,China;Nonferrous Geological Exploration Bureau of Inner Mongolia Autonomous Region,Hohhot,Inner Mongolia 016043,China)

机构地区：[1]中国地质大学(北京)海洋学院,北京100083 [2]内蒙古自治区有色地质勘查局,内蒙古呼和浩特016043

出　　处：《现代地质》2019年第1期85-97,共13页Geoscience

基　　金：国家自然科学基金项目(41276047;41572207;41030853)

摘　　要：海南岛南部地区遍布晚中生代花岗岩,高峰、保城岩体即为其中的典型代表。应用同位素地质年代学和岩石地球化学分析方法,测得两岩体的年龄分别为(105. 4±3. 7) Ma和(105. 8±2. 4) Ma,岩石硅、碱含量中等,铝饱和指数分别为0. 95～1. 03和1. 05～1. 30,轻稀土富集,重稀土亏损,轻重稀土分馏程度较高,高场强元素亏损,大离子亲石元素富集。斜长石含量> 19%,角闪石含量> 3%,石英含量﹤32%,P2O5与Si O2呈负相关,表明高峰、保城花岗岩体属于Ⅰ型花岗岩。海南岛南部晚中生代花岗岩的大量形成并非孤立现象,该地区早白垩世安山岩-流纹岩组合和白垩纪沉积序列与花岗岩一起构建起较为完整的安第斯型大陆边缘弧体系,而且这一活动陆缘体系在岩石组合、展布和演化特征上与时代大体相当的浙闽地区活动陆缘体系存在明显区别,在区域构造意义的研究中值得给予特别关注。Magmatism in Hainan Island was intense during the late Mesozoic.Studies on the granites on the island can improve our understanding on the Cretaceous tectonic setting of the northern margin of the South China Sea.The Gaofeng and Baocheng batholiths on the island are zoned complexes,which contain mainly fine-medium-grained biotite monzogranite and minor granodiorite.These granitoids are classified as I-type.LA-ICP-MS zircon U-Pb dating of the Gaofeng and Baocheng granitoids yielded(105.4±3.7)Ma and(105.8±2.4)Ma,respectively.In terms of major element compositions,the Gaofeng and Baocheng granitoids contain medium SiO2 and total alkali contents.Light and heavy rare earth elements are highly fractionated in these rocks,and they are enriched in LREEs but depleted in HREEs.The granitoids are also enriched in large ion lithophile elements(LILEs)and depleted in high field strength elements(HFSEs).Hence,the petrographic and geochemical features of these rocks indicate that the late Mesozoic tectonic setting of Hainan Island was a marginal arc.Additionally,this arc was significantly different from the coeval Western Pacific magmatic arc in the Zhejiang and Fujian regions.The topic deserves special attention in regional tectonic studies.

关 键 词：海南岛 晚中生代 Ⅰ型花岗岩 俯冲 陆缘弧体系 

分 类 号：P548[天文地球—构造地质学] P595[天文地球—地质学]