扬子地区奥陶纪-志留纪过渡期深时火山灰层发育特征及其对富有机质页岩沉积的影响  

Development characteristics of deep-time volcanic ash layers and its influence on deposition of organic-rich shale across Ordovician-Silurian transition in Yangtze area,south China

作　　者：杜学斌 贾冀新 赵珂 陆永潮[2] 谭超 陆扬博 吴岳恒 DU Xuebin;JIA Jixin;ZHAO Ke;LU Yongchao;TAN Chao;LU Yangbo;WU Yueheng(College of Marine Science and Technology,China University of Geosciences(Wuhan),Wuhan 430074,China;School of Earth Resources,China University of Geosciences(Wuhan),Wuhan 430074,China;School of Earth Sciences,China University of Geosciences(Wuhan),Wuhan 430074,China)

机构地区：[1]中国地质大学(武汉)海洋学院,湖北武汉430074 [2]中国地质大学(武汉)资源学院,湖北武汉430074 [3]中国地质大学(武汉)地球科学学院,湖北武汉430074

出　　处：《中南大学学报（自然科学版）》2022年第9期3509-3521,共13页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(42072137);国家科技重大专项项目(2016ZX05034002,2016ZX05060004)。

摘　　要：系统总结扬子地区奥陶纪−志留纪过渡期深时火山灰层的相关研究成果。首先,总结深时火山灰层的鉴定特征并概括了深时火山灰层的时空分布规律;其次,总结深时火山灰层的来源及其年龄;最后,总结深时火山灰对扬子地区富有机质页岩形成的影响。研究结果表明:深时火山灰层具有平面上分布范围广、垂向上分布不均一的特征;垂向上可进一步划分出密集段、稀疏段和零星段,代表了火山活动强度逐渐减弱;深时火山灰层可能来自扬子板块的南北两侧,存在3个潜在的来源:北侧的秦岭古洋壳在华北地块之下向北俯冲和扬子地块南缘地块内的伸展和拆离以及南侧的冈瓦纳大陆碎片向华南地块的西北向俯冲碰撞,这是华南地块复杂构造活动响应证据之一。深时火山灰层的锆石年龄指示了华南地区的构造运动可能与全球其他地区的并不同步,大约推迟了5.4 Ma。此外,火山灰可能通过提高古海洋生产力和营造有利保存环境2个方面来促进富有机质页岩的沉积,但对此仍存在一定的争议。为解决争议,建议今后从微观分析和定量研究2个方向开展研究。Relevant researches of deep-time volcanic ash layers in Yangtze area across Ordovician—Silurian transition were systematically summarized.Firstly,identification characteristics and temporal and spatial distribution of deep-time volcanic ash layers were summarized.Secondly,source and age of deep-time volcanic ash layers were summarized.Finally,influence of deep-time volcanic ash on the formation of organic-rich shale in Yangtze area was summarized.The results show that deep-time volcanic ash layers have the characteristics of wide distribution range on plane and uneven vertical distribution.Vertically,these can be further divided into dense interval,sparse interval and sporadic interval,representing the gradual weakening of the intensity of volcanic activities.Deep volcanic ash layers may come from the north and south margins of Yangtze Block,with three reliable sources:Qinling paleooceanic crust subducted northward under North China Block,and extension and detachment within the southern margin block of Yangtze Block,as well as northwest subduction−collision of Gondwana continental fragment to South China Block.It is one of the evidences of complex tectonic activities response of South China Block.Zircon age of deep-time volcanic ash layers indicates that tectonic activity in South China may not be synchronized with that in the world,which is delayed by about 5.4 Ma.In addition,volcanic ash can promote deposition and development of organic-rich shale from two aspects:improving paleomarine productivity and creating a favorable preservation environment,but there is still some controversy.In order to solve the dispute,it is suggested to carry out study in two directions of micro analysis and quantitative research in the future.

关 键 词：深时火山灰 发育特征 富有机质页岩 扬子地区 

分 类 号：P534.4[天文地球—古生物学与地层学]