贺兰山中南段米钵山组沉积特征及其物源分析  

Depositional Characteristics and Provenance Analysis of the Miboshan Formation,Helan Mountain

作　　者：黄喜峰[1] 钱壮志[1] 逯东霞 吴文奎 陆彦俊 白生明 

机构地区：[1]国土资源部成矿作用及其动力学重点实验室长安大学地球科学与资源学院,西安710054 [2]陕西省地质矿产局,西安710054 [3]宁夏地质环境监测总站,银川750021

出　　处：《沉积学报》2010年第3期426-433,共8页Acta Sedimentologica Sinica

基　　金：国家重点基础研究发展规划项目(编号:2003CB214600);1:25银川幅区域地质大调查项目(编号:J48C002003)资助

摘　　要：贺兰山中南段米钵山组地层岩性主要为钙质角砾岩、砾岩、互层状的砂岩或含砾砂岩以及页岩、含砾页岩、颗粒灰岩等,是一套区域浅变质、厚度巨大、具不同程度变形和深水陆源浊积岩组合的斜坡沉积,发育有复理石韵律层理及典型的浊积岩鲍马序列。研究表明中奥陶统米钵山组沉积期是贺兰"冷"裂谷活跃的时期,该时期的沉积特征对探讨贺兰山早古生代的构造格局及岩相古地理方面尤为重要。对米钵山组的地球化学分析结果表明,稀土元素La、Ce、∑REE、δEu等特征值与大陆岛孤和活动大陆边缘构造环境相似。综合该组沉积的矿物特征、构造环境及区域背景,其物源应来源于其南部的祁连造山带及邻区阿拉善地块,具有二元物源供给的近源沉积特征。Miboshan Formantion in the southern Helan Mountain mainly consisted calcareous breccia,conglomerate,interbedded sandstone or pebbled sandstone,and shale,pebbled shale and grain limestone,and it is very thick Slope facies that is regionally low-grade metamorphic terrigenous turbidite in deep water,which has experienced different degree deformation and the flysch rhythmic layering and typical Bouma sequence are well developed.Our results shows that the deposition duration of the Middle Ordovician Miboshan Formation is corresponding to the active stage of Helan cold rift,which is particularly important to understand the early Paleozoic tectonic framework and lithofacies paleogeography of Helan Mountain.Our geochemical analysis found that eigenvalue of La,Ce,∑REE and δEu are similar to that of continental island-arc and active continental margin setting.With further information from the tectonic environment and local background,it is concluded that the source of Miboshan Formation is from its southern region of Qilian orogenic belt and its adjacent area of Alashan massif,which is a near source sedimentation that is binary provenance.

关 键 词：贺兰山 米钵山组 地球化学 沉积环境 物源分析 

分 类 号：P512.2[天文地球—地质学]