米仓山—大巴山前缘上三叠统须家河组四段砾岩特征及其对物源的指示  

The Conglomerate Composition of the Fourth Member of Xujiahe Formation, Upper Triassic, in the Front of Micang—Daba Mountains, Sichuan,China:Implication for Provenance Analysis

作　　者：淡永[1,2] 林良彪[3] 钟怡江[3] 范昱[3,4] 

机构地区：[1]中国地质科学院岩溶地质研究所,广西桂林541004 [2]国土资源部/广西岩溶动力学重点实验室,广西桂林541004 [3]成都理工大学沉积地质研究院,成都610059 [4]中国石化西北油田分公司勘探开发研究院,乌鲁木齐830011

出　　处：《地质论评》2013年第1期15-23,共9页Geological Review

基　　金：国家自然科学基金重点项目(编号40739901);中国地质科学院岩溶地质研究所基本科研业务费项目(编号2012001)的成果

摘　　要：米仓山—大巴山前缘上三叠统须家河组四段(须四段)中广泛发育一套砾岩,根据野外剖面和钻井剖面研究,发现砾岩为一套冲积扇砾岩,分选较差,磨圆相对较好,厚度为0～70m并由北东向南西减薄。偏光显微镜鉴定发现须四段砾岩以硅质岩砾石为主,含碳酸盐岩砾石、沉积石英岩砾石、(变)粉砂岩砾石及火山岩砾石,对火山岩砾石研究认为,南秦岭地区奥陶系—志留系火山岩为其母源。在结合硅质岩、(变)粉砂岩等砾石母源探讨后,认为须四段砾岩应来源于南秦岭地区,而砾石沉积时其母源区至少存在南华系—志留系地层。物源方向及母岩的确定可能对研究晚三叠世时期四川盆地演化、沉积环境及川东北地区须家河组有利油气储层展布等问题有重要意义。The conglomerate in the Fourth Member of Xujiahe Formation, Upper Triassic, is widely developed in the front of the Micang--Daba Mountains. Based on the outcrops and wells analysis of these conglomerates, it is showed that the conglomerate of the 4th Member of Xujiahe Formation, Upper Triassic, is an alluvial fan--fluvial sedimentary gravels, whose thickness is between 0 to 70m and decrease from northeast to southwest. The gravels is generally poor sorted, sub-rounded to rounded. We made a microcosmic analysis of conglomerate composition in the front of the Micang--Daba Mountains by polarizing microscope, it is found that the conglomerate consists of siliceous gravels, carbonate gravels, sedimentary quartzite gravels, sihstone gravels and volcanic gravels. However, the chert gravels is the main composition. We study individually volcanic gravels in detail, the results suggest that the Ordovieian to Silurian volcanic rocks in Southern Qinling Mountains should be its source rocks. Combined with the discussion on source rocks of chert gravels, sihstone gravels and other gravels, it is believed that the conglomerate＇ s source rocks in the front of the Micang--Daba Mountains is the Sinian to Silurian strata in Southern Qinling Mountains. It is proposed that the source rocks which have been presumed have potential significances for understanding evolution of Sichuan Basin, sedimentary environment in the Late Triassic, and favorable reservoir distribution of the Xujiahe Formation.

关 键 词：川东北 四川盆地 上三叠统须家河组 火山岩砾石 南秦岭 

分 类 号：P588.3[天文地球—岩石学]