摘要
文章对桂东南糯垌—安平地区出露的阳起石化斜长角闪岩(变质基性岩)和中—基性火山角砾岩进行了锆石U-Pb年代学和全岩地球化学分析研究,结果表明,糯垌地区岩体的形成时代晚于123 Ma,安平地区火山角砾岩记录了两期重要的岩浆活动,一组为燕山期(或之后),年龄上限为~138 Ma,一组为早古生代加里东期(452~450 Ma)。两地(变质)中-基性岩均出现有大量中太古代—古元古代(3076~1806 Ma)、中-新元古代及早古生代的捕获锆石,指示研究区存在中太古代—古元古代的古老物质,记录了中元古代、新元古代和早古生代的岩浆事件。全岩地球化学分析显示,糯垌变质基性岩表现为平坦—亏损型的稀土配分模式,相对富集Th、U和Pb等大离子亲石元素,高场强元素Nb、Ta、Zr、Hf、Ti呈平坦—略亏损的特征;而安平中-基性火山角砾岩则表现为轻稀土元素富集,重稀土元素亏损,富集Rb、Ba、Th、U和Pb等大离子亲石元素,明显亏损Nb、Ta、P和Ti等高场强元素的特征。地球化学特征与前人在研究区的加里东期(变质)基性岩相似,表明岩石地球化学特征在判定岩石形成时的构造背景时具有一定的局限性,也具有多解性。
Zircon U-Pb dating and geochemical data are reported for actinolitization amphibolites(metamorphic basic rocks) and intermediate-basic volcanic breccias of Nuodong-Anping plutons, southeastern Guangxi. The data show that the formation age of the Nuodong pluton is later than 123 Ma, and the Anping pluton record two important magmatic activities. One was in Yanshanian period(or later) with the youngest age of ~138 Ma, and the other was in Early Paleozoic(452-450 Ma). A large number of captured zircons ranging from Middle Archean-Paleoproterozoic(3076-1806 Ma), Mesoproterozoic-Neoproterozoic to Early Paleozoic in both plutons indicate the existence of the Middle Archean-Paleoproterozoic basement materials and the Mesoproterozoic,Neoproterozoic and Early Paleozoic magmatism. Geochemical data exhibit that the Nuodong pluton is characterized by a flat or slightly loss rare earth elements(REEs) distribution model, with relatively enriched in large-ion lithophile elements(LILEs)(Th,U and Pb) and depleted in high-field-strength elements(HFSEs)(Nb, Ta, Zr, Hf and Ti). The Anping pluton is also enriched in LILEs(Rb, Ba, Th, U and Pb) and depleted in HFSEs(Nb, Ta, P and Ti), but they show enrichment in light REEs and depletion in heavy REEs contents. The geochemical characteristics are similar to the Caledonian(metamorphic) basic rocks in the study area,indicating that the geochemical characteristics of rocks have limitations and multiple solutions in determining the tectonic setting.
作者
庞超伟
时毓
唐远兰
梁任鑫
刘希军
PANG Chaowei;SHI Yu;TANG Yuanlan;LIANG Renxin;LIU Xijun(Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin University of Technology,Guilin 541004,China;Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources,Guilin University of Technology,Guilin 541004,China;State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China)
出处
《高校地质学报》
CAS
CSCD
北大核心
2022年第2期177-198,共22页
Geological Journal of China Universities
基金
国家自然科学基金项目(41862003,41562005)
广西自然科学基金杰出青年基金项目(2019GXNSFFA245005,2018GXNSFFA281009)
内生金属矿床成矿机制研究国家重点实验室(南京大学)开放基金项目(2020-LAMD-K09)联合资助。
关键词
(变质)中—基性岩
年代学
地球化学
糯垌—安平岩体
桂东南
华南板块
(metamorphic)intermediate-basic rocks
zircon geochronology
geochemistry
the Nuodong and Anping plutons
Southeastern Guangxi
South China Block
