川北米仓山山前带碎屑锆石U-Pb年代学及盆山演化意义  

Detrital Zircon U-Pb Geochronology of Micang Mountain Piedmont Zone, Northern Sichuan Basin and its Significance to Basin-Mountain Evolution

作　　者：李双建[1,2] 孙冬胜 蔡立国 高平 李天义[1,2] 袁玉松[1] 郑孟林 邱登峰 LI Shuangjian;SUN Dongsheng;CAI Liguo;GAO Ping;LI Tianyi;YUAN Yusong;ZHENG Menglin;QIU Dengfeng(Structural Geology and Reservoir Laboratory,SINOPEC,Beijing 100083,China;State Key Laboratory of Shale Oil and Gas Accumulation Mechanism and the Effective Development,Beijing 100083,China)

机构地区：[1]中国石化构造与储层实验室,北京100083 [2]页岩油气富集机理与有效开发国家重点实验室,北京100083

出　　处：《大地构造与成矿学》2018年第6期1087-1107,共21页Geotectonica et Metallogenia

基　　金：国家科技重大专项(2017ZX05005-001);国家自然科学基金重点支持项目(91755211);国家重点基础研究发展计划(2012CB412800)联合资助

摘　　要：米仓山前缘的碎屑岩沉积记录了四川盆地北缘造山带的构造演化信息,是研究四川盆地与北缘和西缘造山带盆-山耦合关系的理想对象。本文根据米仓山南缘中生界陆相地层中的碎屑锆石定年,分析了晚三叠世以来米仓山南缘碎屑岩物源的变化,并探讨了米仓山及其邻区印支期以来的构造演化过程。研究表明,上三叠统的碎屑锆石存在221～438Ma、732～959Ma、1618～2192Ma和2210～2526Ma四组年龄峰值,其中后两组年龄峰值所占比例最大,推测其物源主要来自华北板块南缘和北秦岭,指示华北与华南板块碰撞初期,秦岭造山带未完全阻挡北部物源。从下侏罗统开始碎屑锆石出现720～820Ma的年龄峰值,而且比例越来越高,推测其物源主要来自南秦岭和扬子北缘,指示此时秦岭已经隆起成山,阻隔了北部物源,同时汉南-米仓和龙门山成为川北地区的主要物源区。下白垩统碎屑锆石存在155～600Ma、725～910Ma、1716～1982Ma和2389～2779四组年龄峰值,总体表现比较分散,是典型多物源混合的结果,推测主要物源来自南秦岭和龙门山地区的古生代-中生代的再旋回沉积岩。根据物源变化,结合沉积中心迁移和其他构造年代学证据,可以看出四川盆地北缘的汉南-米仓山在晚三叠世未隆升出地表,早侏罗世开始由南秦岭向南前展式隆升,隆升一直延续到晚侏罗世,早白垩世随着四川盆地周缘造山带强烈的陆内造山,米仓山前缘接受了包括南秦岭、扬子北缘早期沉积岩和龙门山、松潘褶皱带在内的多物源沉积物供给。The clastic rocks in the piedmont zone of the Micang Mountain recorded the tectonic evolution of the orogenic belt and the northern margin of the Sichuan Basin, which is an ideal object for studying basin-mountain coupling relationship between the Sichuan Basin and the northern and western margins of the orogenic belt. Based on detrital zircon dating of the Mesozoic strata on the southern margin of the Micang Mountain, the provenance change of clastic rocks since the Late Triassic has been analyzed, and the tectonic evolution of the Micang Mountain and its adjacent areas since Indosinian has been studied. Our results showed four peak ages for detrital zircon from the upper Triassic, including 221 – 438 Ma, 732 – 959 Ma, 1618 – 2192 Ma, and 2210 – 2526 Ma. Among them, the last two peak ages accounted for the largest proportion, indicative of a provenance of the southern margin of the North China Craton and the North Qinling terrain. A North China Craton provenance indicates that rise of the Qinling orogenic belt did not completely stop the northern source at the beginning of the collision between the South and North China Blocks. Since the beginning of the Early Jurassic, detrital zircon with peak age of 720 – 820 Ma appears and its proportion gradually increases, implying that the sediments sourced mainly from the South Qinling and the northern margin of the Yangtze Block, which means that uplift of the Qinling Orogenic Belt blocked the northern provenance. At the same time, the Hannan-Micang and Longmen Mountains became the main provenance areas for the Northern Sichuan Basin. Four groups of detrital zircon peak age in the Lower Cretaceous can be recognized, including 155 – 600 Ma, 725 – 910 Ma, 1716 – 1982 Ma and 2389 – 2779 Ma. The peak age distribution is relatively scattered, which is the typical result of multi provenance hybrid. The main source comes from the Paleozoic and Mesozoic recycled sedimentary rocks in the South Qinling and Longmen Mountain. Based on the provenance change, as wel

关 键 词：四川盆地 米仓山 中生代 碎屑锆石 物源 盆山演化 

分 类 号：P541[天文地球—构造地质学] P597[天文地球—地质学]