峨眉地幔柱构造对四川盆地栖霞期沉积格局的影响  

Effect of Emeishan Mantle Plume over the Sedimentary Pattern of Mid-Permian Xixia Period in Sichuan Basin

作　　者：张廷山[1,2] 陈晓慧[2] 刘治成[2] 魏国齐 杨巍[2] 闵华军[2] 张奇[4] 杨雨[4] 

机构地区：[1]油气藏地质与开发工程国家重点实验室,成都610500 [2]西南石油大学,成都610500 [3]中国石油与天然气股份公司科学技术研究院廊坊分院,河北廊坊065007 [4]西南油气田分公司勘探开发研究院,成都610051

出　　处：《地质学报》2011年第8期1251-1264,共14页Acta Geologica Sinica

基　　金：国家油气重大专项课题"四川盆地大型天然气田富集规律;目标评价与勘探配套技术"(编号2008ZX05007-004);四川省重点学科建设项目(编号SZD0414)资助成果

摘　　要：一系列地质分析表明,上升的地幔柱通常能造成大规模的地壳抬升以及形成穹窿状隆起地貌,并控制区域古地理格局和沉积相带展布。根据四川盆地内钻遇栖霞组的井下资料,以及盆地内部和周边栖霞组野外露头剖面的岩性、古生物组合及沉积构造特征,并结合前人对峨眉山大火成岩省及峨眉地幔柱的研究资料,本文系统讨论了峨眉地幔柱活动对该区中二叠世栖霞期沉积古地理格局特征及沉积相展布的控制。因峨眉地幔柱活动而造成的穹窿状水下隆起影响了栖霞期古地理特征,进而控制了其沉积相及其展布。由于中二叠世栖霞期时峨眉地幔柱的活动,在研究区内表现为西南部地区古地貌较高,并平缓地向东及东北方向降低的水下古地貌特征,不发育较陡的斜坡和明显的斜坡转折带。此种古地貌格局与区域海平面升降一起,直接控制了栖霞期沉积相带分布和地层厚度,形成了特殊的缓坡型碳酸盐台地沉积格局。根据本区穹窿状水下隆起不同部位所沉积的岩性及发育的沉积构造特征、古生物组合,可分划分出开阔台地亚相、浅缓坡亚相、深缓坡亚相及相应的微相。研究区西南部位于穹窿状水下隆起的较高处,为开阔台地亚相发育区,并逐渐向东及东北方向古地貌变低的缓坡亚相发育区过渡。本区栖霞期古地理格局特征及沉积相带的展布可视为碳酸盐缓坡逐渐向台地演化的早期阶段,并为峨眉地幔柱的活动提供了部分佐证。A number of geological examinations indicate that ascending mantle plume can often cause the large-scale crust doming and dome-shaped landform and control the regional paleogeographic pattern and sedimentary distribution.Based on the data obtained from underground drilling cutting the Xixia Formation,lithological features,paleontological assemblages and sedimentary structures of the Xixia Formation outcrops in and around the Basin,and previous research results,this study discussed effects of the Emeishan plume activity on sedimentary paleographical features and sedimentary-facies distribution during the Xixia period of mid-Permian.The doming uplift resulting from the Emeishan mantle plume controlled the paleogeomorphic features and further influenced the sedimentary facies and its distribution.Due to activity of the Emei mantle plume during the Qixia period of the middle Permian,the studying area was characterized by high relief in the southwestern part of the Upper Yangtze platform,flat paleogeomorphic features eastward and northeastward,and poorly-developed steep slope and distinct slope transition zone.The paleogeographical pattern of this kind,and local sea level change directly controlled the Qixia period sedimentary facies distribution and strata thickness,forming a unique pattern of carbonate ramp platform.According to the sedimentary lithology,structure features and paleotogical assemblages in various parts of submarine doming in this area,three subfacies and corresponding microfacies can be recogized： open platform subfacies,shallow ramp subfacies,and deep ramp subfacies.The studying area is a sub-facies open-platform developing area,located at the higher part of the submarine dome-shaped area in the southwestern Upper Yangtze platform,and gradually transformed eastward and northeastward into the ramp-facies developing area.The paleogeographical pattern and sedimentary facies distribution during the Xixia period in this area can be regarded as the early developing stage from carbonate ramp to platform,

关 键 词：峨眉地幔柱 地壳抬升 古地理特征 沉积相 栖霞期 

分 类 号：P618.13[天文地球—矿床学]