摘要
凭祥地区位于滇-琼缝合带东段,是研究古特提斯东部闭合史的重要区域。对凭祥伏波山花岗岩进行了岩石学、地球化学、年代学、Nd及锆石Hf同位素分析研究:LA-ICP-MS锆石U-Pb定年结果显示,^(206)Pb/^(238)U加权平均年龄为244.7±0.9 Ma(MSWD=0.45),其形成于三叠世早期;样品具高硅(SiO_(2)含量73.88%~75.88%)、中铝(Al_(2)O_(3)为11.61%~12.03%)、中碱(Na_(2)O+K_(2)O为6.89%~7.25%)等特征,属高钾钙碱性系列,A/CNK值为1.08~1.39,属于强过铝质A_(2)型花岗岩;富集Rb、Th等大离子亲石元素,相对亏损Nb、Ta、Ti等高场强元素,并且有较低的ε_(Nd)(t)值(-10.9~-10.2),反映其具有俯冲消减作用形成的岛弧岩浆岩地球化学特征;ε_(Hf)(t)值(-12.9~-7.2)具有地壳同位素特征,反映其岩浆源区为地壳物质。凭祥地区A_(2)型碱长花岗岩可能是在俯冲的构造背景下,由华南板块产生局部拉张导致古老的长英质地壳物质减压熔融所形成,该结果为华南板块中三叠世早期构造-岩浆演化提供了新的证据。
Pingxiang area located in the eastern part of the Dian-Qiong suture zone,is important to address the history of closure of the Paleo-Tethys Ocean.The petrology,geochemistry,chronology,Nd and zircon Hf isotopic analysis of the Pingxiang Fuboshan granite are studied.LA-ICP-MS zircon U-Pb dating shows that the ^(206)Pb/^(238)U weighted average age of zircon from the Pingxiang Fuboshan granite is 244.7±0.9 Ma(MSWD=0.45),indicating that it belongs to the early Middle Triassic granite.The Pingxiang granits have high SiO_(2) content(73.88%-75.88%),medium Al_(2)O_(3) content(11.61%-12.03%)and medium alkalinity(Na_(2)O+K_(2)O=6.89%-7.25%)with A/CNK ratios(1.08-1.39),belonging to peraluminous A_(2)-type granite.The granites,belonging to a typical high-K calc-alkaline series,are characterized by relative enrichment in LILEs(e.g.,Rb,Th)and pronounced depletion HFSEs(e.g.,Nb,Ta and Ti),with lowε_(Nd)(t)(-10.9--10.2).Such signatures display geochemical characteristics of typical subduction-related arc magmatic rock.The ε_(Hf)(t)values(-12.9--7.2)have crustal characteristics,indicating that the magma source area is crustal material.The A_(2)-type alkali-feldspar granites in Pingxiang area may have been formed by decompression and ancient felicitic crustal materials melting by local extension of South China plate under subduction tectonic background,which provides new evidence for the tectonic-magmatic evolution of South China plate in the early Middle Triassic.
作者
黄雯敏
刘希军
李政林
韦艳玲
郭静涟
韩怡颖
赵兵
HUANG Wen-min;LIU Xi-jun;LI Zheng-lin;WEI Yan-ling;GUO Jing-lian;HAN Yi-ying;ZHAO Bing(Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin University of Technology,541006,China;Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi,Guilin University of Technology,541006,China;Xinjiang Research Center for Mineral Resources,Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Urumqi 830011,China)
出处
《桂林理工大学学报》
CAS
北大核心
2022年第2期281-294,共14页
Journal of Guilin University of Technology
基金
国家自然科学基金项目(92055208)
广西自然科学基金杰出青年科学基金项目(2018GXNSFFA281009)
广西科技创新基地建设项目(桂科ZY21195031)
广西八桂学者项目(2018,有色金属成矿理论与勘查技术)
广西中青年教师科研基础能力提升项目(2019KY0272)
广西研究生教育创新计划项目(YCBZ2021063)。
关键词
花岗岩
年代学
地球化学
凭祥
桂西南
granites
geochronology
geochemistry
Pingxiang
southwest Guangxi
