海南岛儋州地区两期A型花岗岩的岩石成因与地质意义  

Petrogenesis study of two stages A-type granite and its geological significance in Danzhou area of Hainan Province

作　　者：吕昭英[1,2] 陈沐龙 傅杨荣 袁勤敏[1,2] 魏昌欣 常振宇[1,2] 胡在龙 LYU Zhaoying;CHEN Mulong;FU Yangrong;YUAN Qinmin;WEI Changxin;CHANG Zhenyu;HU Zailong(Hainan Geological Survey Institute,Haikou 570206,Hainan,China;Key Laboratory of Marine Geological Resources and Environment of Hainan Province,Haikou 570206,Hainan,China;Hainan Resources Environment Survey Institute,Haikou 570206,Hainan,China)

机构地区：[1]海南省地质调查院,海南海口570206 [2]海南省海洋地质资源与环境重点实验室,海南海口570206 [3]海南省资源环境调查院,海南海口570206

出　　处：《矿产与地质》2019年第4期660-669,共10页Mineral Resources and Geology

基　　金：中国地质大调查项目“海南1∶5万加来市、多文市、儋县、中兴镇幅区域地质调查”（编号：1212011220524）资助

摘　　要：海南岛儋州地区发育两期A型花岗岩,早期为发美村石英碱长正长岩,岩石具有中等的SiO2含量(63.44%~63.99%)和相对较高的碱含量[w(Na2O+K2O)=10.73%~10.74%],低钾高钠的特征;晚期为红岭正长花岗岩,岩石具有高的SiO2含量(73.97%~74.95%)和相对较高的碱含量[w(Na2O+K2O)=8.02%~8.32%]。发美村石英碱长正长岩的Mg^#为38~41,为碱性低钾系列,属于准铝质花岗岩,红岭正长花岗岩的Mg^#为29~34,具高钾钙碱性的特征,属于准铝质—弱过铝质花岗岩。结合地球化学数据、Sr-Nd同位素数据及实验岩石学的证据,判断发美村石英碱长正长岩以及红岭正长花岗岩均为长英质地壳物质部分熔融产生的,可能有极少量的幔源物质的加入,且早期的发美村石英碱长正长岩侵位深度应该比晚期的红岭正长花岗岩更深。研究表明:海南岛儋州地区在早三叠世(约247 Ma)已经处于伸展的构造背景下,结合区域地质资料判断,早期的发美村石英碱长正长岩岩体形成于后碰撞环境向板内环境转换的伸展环境,而红岭正长花岗岩岩体的出现,标志着儋州地区中三叠世(237 Ma)已经处于后造山环境下全面伸展体制下。There are two-stage A-type granites in Danzhou area,Hainan island.The early stage is Fameicun quartz-alkali syenite with moderate SiO2 content(63.44%-63.99%)and relatively high alkali content(Na2O+K2O=10.73%-10.74%),low potassium and high sodium.The late stage is Hongling syenite granite with high SiO 2 content(73.97%-74.95%)and relatively high alkali content(Na2O+K2O=8.02%-8.32%).The Mg^# of Fameicun Rock is 38-41,and the Mg^# of Hongling Rock is 29-34.Faimicun rock type is alkaline low potassium series,which belongs to quasi-aluminous granite.Hongling syenite granite has the characteristics of high potassium calc-alkalinity and belongs to quasi-aluminous-weak peraluminous granite.On the basis of geochemical data,Sr-Nd isotopic data and experimental petrology evidence,it is suggested that both Fameicun quartz alkali syenite and Hongling syenite granite are produced by partial melting of felsic crustal material.A small amount of mantle-derived material might be added up,and the emplacement depth of the early-stage Faimicun rock body should be greater than that of the late-stage Hongling rock body.The study in this paper shows that the Danzhou area of Hainan Island has already been in an extensional tectonic setting around the early Triassic period(247 Ma).Combined with the basis of regional and geological data,the early-stage Fameicun quartz-alkali syenite is formed in the extensional environment from post-collision environment to intra-plate environment,and the appearance of Hongling syenite granite indicates that Danzhou area has been under an all-around extension system under post-orogenic environment in Middle Triasic period(237 Ma).

关 键 词：A型花岗岩 早三叠世 中三叠世 后造山 儋州地区 海南岛 

分 类 号：P588.12[天文地球—岩石学]