湖南嘉禾大窝岭剖面晚二叠世吴家坪期-长兴期之交长英质火山作用记录  

Felsic Volcanisms across the Wuchiapingian-Changhsingian Boundary(Late Permian) in the Dawoling Section, Jiahe Area, Hunan Province

作　　者：高秋灵 陈中强[3] 张宁[2] 夏雪飞 姜腾飞 王国庆[2] 肖明 陈晴 Gao Qiuling;Chen Zhong‐Qiang;Zhang Ning;Xia Xuefei;Jiang Tengfei;Wang Guoqing;Xiao Ming;Chen Qing(School of Environmental and Biological Engineering,Henan University of Engineering,Zhengzhou 451191,China;Faculty of Earth Science,China University of Geosciences,Wuhan 430074,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan 430074,China;Jianghan Oilfield Company,SINOPEC,Qianjiang 433124,China;Shandong Lunan Institute of Geo-Engineering Exploration,Jining 272100,China)

机构地区：[1]河南工程学院环境与生物工程学院,河南郑州451191 [2]中国地质大学地球科学学院,湖北武汉430074 [3]中国地质大学生物地质与环境地质国家重点实验室,湖北武汉430074 [4]中国石化江汉油田分公司,湖北潜江433124 [5]山东省鲁南地质工程勘察院(山东省地质矿产勘查开发局第二地质大队),山东济宁272100

出　　处：《地球科学》2022年第8期2925-2939,共15页Earth Science

基　　金：国家自然科学基金项目“陆相断陷盆地深部热流体活动及其成岩效应——以白音查干凹陷下白垩统腾格尔组为例”(No.42102168)。

摘　　要：在华南地区,中-晚二叠世之交和二叠纪-三叠纪之交的火山作用已成为地学研究的热点.相比较,地学界对晚二叠世内部的火山活动关注较少,以至对华南地区晚二叠世内部火山作用的喷发特征认识不够.湖南省嘉禾地区大窝岭剖面大隆组中下部,即吴家坪阶-长兴阶界线附近沉积了3层粘土岩,自下而上分别为HD08、HD12和HD20.对这3层粘土岩进行全岩地球化学,锆石U-Pb年代学、微量元素和Lu-Hf同位素测试工作表明,这些粘土岩源自蚀变的火山灰,代表吴家坪阶-长兴阶之交的三期火山作用.全岩和锆石微量元素特征显示火山灰来源于流纹质或流纹英安质火山作用,具有钙碱系列的亲属性,形成于汇聚大陆边缘的后碰撞构造环境.其中,HD08和HD20的ε_(Hf)(t)值为-6.4~7.1,范围变化较大,岩浆源于峨眉山/新元古代新生地壳物质和古老地壳物质的混合;HD12的ε_(Hf)(t)值为-12.0~-3.5,岩浆主要来源于古老地壳物质.这3层火山灰层的发现丰富了华南地区乐平统地层中火山作用的记录,综合前人研究成果,进一步证实了华南地块周边地区在晚二叠世中期发生强烈的、与Pangea超大陆汇聚有关的长英质火山作用.The volcanisms of the Guadalupian-Lopingian(also middle-late Permian) and Permian-Triassic boundaries in South China have attracted increasing attentions from geologists. In contrast, less studies concerned the volcanisms between the two.Here, we report geochemical studies on volcanisms near the Wuchiapingian-Changhsingian boundary within the late Permian from the Dawoling section of Jiahe Area, Hunan Province, South China, in which three layers of claystones, named as HD08,HD12 and HD20, are pronounced in the Wuchiapingian-Changhsingian boundary beds that are calibrated to the lower and middle Dalong Formation. The integrated analyses of whole-rock geochemistry, zircon U-Pb chronology, trace elements and Lu-Hf isotopes reveal that these three claystones originated from altered volcanic ashes, representing three episodes volcanism across the Wuchiapingian-Changhsingian boundary. The whole-rock and zircon trace element signatures indicate that the volcanic ashes originated from rhyolitic or rhyodacitic volcanism, with calc-alkaline affinities, and formed in post-collisional tectonic settings in the convergent continental margins. Among them, ε_(Hf)(t) values of HD08 and HD20 are-6.4 to 7.1, with a wide range of variability, and the magma originates from the mixing of Emeishan/Neoproterozoic neogenic crustal materials of and ancient crustal materials;ε_(Hf)(t) values of HD12 are-12.0 to-3.5, and the magma mainly originates from ancient crustal materials. These three volcanic ash layers, together with previous researches, further confirm the occurrence of intense felsic volcanisms related to the convergence of the Pangea supercontinent in the areas around the South China block during the middle of the Lopingian(late Permian).

关 键 词：晚二叠世 Pangea超大陆 火山作用 地球化学 锆石微量元素 锆石Lu-Hf同位素 

分 类 号：P597[天文地球—地球化学]