摘要
四川盆地西南缘的沐川生基坪剖面(PTB)是研究海陆交互相二叠系-三叠系界线的关键。本次研究对研究区P-T界线地层的岩石学与地球化学特征进行研究,探讨了研究区的岩石组合特征、沉积环境、风化作用、古气候及物源特征。还原环境的宣威组中叶肢介化石、煤线和水平层理的出现,反映了近缘的滨浅湖相沉积特征;氧化环境的飞仙关组中双向交错层理、透镜状层理和脉状层理、波痕印模和干裂构造等特征的出现,反映了浅海相沉积特征。通过研究四川盆地晚二叠世-早三叠世岩相古地理可知,研究区宣威组的浅湖相和飞仙关组的潮间-潮下相沉积环境与前人所得出的海陆交互相和滨浅海相沉积环境基本吻合,反映了海水的持续入侵,与晚二叠世-早三叠世的海平面升降事件一致,表现了峨眉山玄武岩喷发之后伴随的海侵。高CIA、CIW和PIA值和A-CN-K和A-C-N图解共同指示了沉积岩物源区经历了强烈的风化作用,并暗示宣威组与飞仙关组沉积时期可能处于温暖潮湿的沉积气候环境。根据研究区宣威组、飞仙关组岩石组合中的玄武岩碎屑特征,并结合稀土元素特征、La/Yb-ΣREE、Co/Th-La/Sc源岩判别关系可推测沐川生基坪二叠系-三叠系界线处沉积岩的物质来源主要可能为宣威组底部的峨眉山玄武岩。
In this paper, the petrological and geochemical characteristics of the Permian-Triassic boundary(PTB) in the Muchuan County, the southwest margin of Sichuan Basin are studied, and the characteristics of rock assemblage, sedimentary environment, weathering, paleoclimate and provenance are discussed. The results show that the conchostracan fossils, coal streak and horizontal bedding in the Upper Permian Xuanwei Formation were formed in a reductive environment, reflecting the sedimentary characteristics of nearby shore-shallow lacustrine facies. The bi-modal cross-bedding, lenticular bedding and vein bedding, ripple imprint and dry crack structure in Lower Triassic Feixiguan Formation were the products of oxidizing environment, reflecting the sedimentary characteristics of shallow marine facies. Late Permian to early Triassic lithofacies palaeogeographic research in the Sichuan basin shows that in the study area, Upper Permian Xuanwei Formation belongs to shallow lake facies and Lower Triassic Feixianguan Formation belongs to intertidal-subtidal facies sedimentary environment, which is basically in accordance to the continental-oceanic interaction facies and littoral and shallow sea facies sedimentary environment proposed by previous researchers. It indicates that the continuous marine ingression following the Late Permian Emeishan basalt eruption is consistent with the Late Permian-Early Triassic sea level rise and fall event. The high CIA, CIW and PIA values and A-CN-K and A-C-N diagrams indicate that the sedimentary provenance of the P-T boundary rocks in the Muchuan area experienced strong weathering, and it also suggests that the Xuanwei and Feixiguan Formations were likely in a warm and humid sedimentary climate. Based on the basaltic characteristics of rock assemblages of Xuanwei and Feixianguan Formations in the study area, combined with the REE characteristics, La/Yb-ΣREE, Co/Th-La/Sc source rock discrimination relationship, it can be inferred that the material source of the sedimentary rocks along the Per
作者
刘丰良
董树义
程文斌
赵兵
赵红
王涌
展望
Liu Fengliang;Dong Shuyi;Cheng Wenbin;Zhao Bing;Zhao Hong;Wang Yong;Zhan Wang(College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu,Sichuan610059,China;Sichuan Zili Architectural Survey and Design Co.,Ltd.,Chengdu,Sichuan 610000,China;Regional Geological Survey Team of Sichuan Geology and Mineral Bureau,Chengdu,Sichuan 610213,China;China Petroleum&Chemical Cor poration Ex ploration Branch,Chengdu,Sichuan 610000,China)
出处
《矿物岩石》
CAS
CSCD
北大核心
2022年第3期20-33,共14页
Mineralogy and Petrology
基金
四川乌蒙山区1:5万马边县、沐川县、靛兰坝、新市镇4幅区域地质调查(项目编号:121201010000150002-11)。
关键词
P-T界线
沉积学特征
地球化学特征
峨眉山玄武岩
四川沐川
southwest margin of Sichuan Basin
Mabian-Muchuan area
P-T boundary
sedimentary characteristics
geochemical characteristics
Emeishan basalt.
