摘要
桂东南地区晚中生代岩浆活动广泛发育,其形成构造背景以及动力学机制仍存在争议.本文对桂东南新州塘、大业地区火山岩进行了年代学、全岩地球化学和Sr-Nd-Hf同位素研究.结果显示新州塘、大业火山岩主体分别为安山岩和英安岩,锆石U-Pb年龄分别为98.5~100.5 Ma、99.2 Ma,均形成于早白垩世晚期.两者均具有低TiO_(2)(平均值<1%)、高Al_(2)O_(3)(平均值>15%)的特点,属于高钾钙碱性-钾玄系列,均富集LILE、亏损HFSE,在稀土元素配分模式上均表现为轻稀土富集右倾型,无明显的Eu异常.新州塘样品与大业样品相比具有较低的SiO_(2)含量、更高的Mg#值以及更高的Cr、Ni的含量,属于高镁安山岩.Sr-Nd-Hf同位素结果显示新州塘安山岩样品相对大业英安岩样品具有更加亏损的特征ε_(Nd)(t)值(分别为-6.26~-7.11、-9.35~-9.37)和ε_(Hf)(t)值(分别为-6.47~-8.95、-8.70~-14.08).综上所述,桂东南地区新州塘高镁安山岩应该是由富集地幔部分熔融形成,而大业英安岩是同期古元古代地壳物质部分熔融所形成,它们的形成与晚中生代华南大陆的拉张伸展构造密切相关.
The late Mesozoic magmatism was widely developed in southeastern Guangxi,and its formation background and dynamic mechanism are still controversial.Chronological,whole-rock geochemistry and Sr-Nd-Hf isotope studies were carried out on the volcanic rocks in Xinzhoutang and Daye areas in southeast Guangxi.The results show that the main bodies of the Xinzhoutang and Daye volcanic rocks are andesite and dacite,respectively,and the zircon U-Pb ages are 98.5 to 100.5 Ma and 99.2 Ma,respectively,which were formed in the late Early Cretaceous.Both have the characteristics of low TiO_(2)(average value1%) and high Al_(2)O_(3)(average value15%).They belong to the high potassium calcium-alkaline-potassium series.Both are enriched in LILE and depleted in HFSE,in the rare earth element distribution mode The above all showed the light rare earth enrichment right-leaning type,without obvious Eu anomaly.Compared with the Daye sample,the Xinzhoutang sample has a lower SiO_(2) content,a higher Mg# value,and a higher Cr and Ni content,It belongs to high magnesium andesite.The Sr-Nd-Hf isotope results show that the Xinzhou Tang andesite samples are more depleted than the Daye dacite samples(ε_(Nd)(t) values are(-6.26~-7.11,-9.35~-9.37),ε_(Hf)(t) values are(-6.47~-8.95,-8.70~-14.08)).Comprehensive regional data The Xinzhoutang andesite should be formed by partial melting of the enriched mantle,while the Daye dacite was formed by partial melting of the Paleoproterozoic crustal material during the same period.Their formation is closely related to the extensional structure of the South China continent in the Late Mesozoic.
作者
李衣鑫
康志强
许继峰
杨锋
刘冬梅
刘珊珊
单纯希
Li Yixin;Kang Zhiqiang;Xu Jifeng;Yang Feng;Liu Dongmei;Liu Shanshan;Shan Chunxi(College of Earth Sciences,Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi,Guilin University of Technology,Guilin 541006,China;School of Earth Science and Resources,China University of Geosciences,Beijing 100083,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2023年第8期2872-2887,共16页
Earth Science
基金
国家自然科学基金资助项目(Nos.42173048,41863005)
广西八桂学者项目(许继峰)
国家重点研发计划项目(No.2020YFA0714804)
第二次青藏高原综合科学考察项目(No.2019QZKK0703)。
关键词
白垩纪
火山岩
锆石U-PB定年
地球化学
桂东南
Cretaceous
volcanic rocks
zircon U-Pb dating
geochemistry
Southeast Guangxi.
