摘要
青藏高原北部基础地质调查与研究工作中,在昆仑山地区测得志留纪(S),奥陶纪—志留纪(O-S)剖面39条,剖面厚度从169m到8260m不等,地层的上下接触关系多为断层和角度不整合。从沉积环境、物质组成等方面,反映出昆仑地区从西向东古地理环境为滨浅海-深海-滨浅海-深海的分布特征。西昆仑温泉沟群(S1W)在英吉莎县西,以砂岩、板岩为主,沉积环境为浅海陆棚;在麻扎一带,主要为砂岩、粉砂岩、板岩及硅质岩等,麻扎附近的石英片岩、砂板岩及灰岩中,含拉斑玄武岩,为活动大陆边缘环境下,深海相(俯冲带海沟沉积环境,麻扎一带),斜坡相浊积岩沉积(麻扎东、西一带),在麻扎一带叠复厚度8260m,向北西、南东方向变薄;东昆仑在木孜塔格峰北,该群为一套深海-半深海复理石沉积,由灰色、浅灰色浅变质各种岩屑砂岩、粉砂岩、泥岩组成。中晚志留世达坂沟群(S2-3D)在西昆仑为半深海到滨浅海沉积环境,在东昆仑沉积一套碳酸盐岩夹碎屑岩地层,以浅海环境为主。在若羌南的白干湖组(S1b)发育深海浮游生物——笔石,为深海相浊积岩,从下到上浊积扇向海推进,水体逐渐变深,属拉张环境下的深海弧后盆地沉积环境。在格尔木西南志留系赛什腾组(Ss)自下而上由大陆斜坡至陆隆和深海沉积到浅海的沉积环境演化,具有非扇大陆斜坡沉积类型,以远源浊积岩、半远洋沉积为特征,代表古海盆收缩到残留海盆阶段的沉积。布咯达坂峰东,加里东晚期(S3)同碰撞型二长花岗岩体锆石的LA-ICP-MSU-Pb年龄(421±3)Ma、(423±16)Ma。在格尔木东南的纳赤台群(OSN)超镁铁岩-辉绿岩墙-玄武岩-深水硅质岩构成早古生代的洋壳组合,具有蛇绿岩套特征。基性变玄武岩显示为洋中脊或洋岛环境。硅质岩的地球化学指标也显示为洋中脊或大洋盆地的远洋深水环境,超镁铁岩是古洋壳残片的地幔岩部分,变碎�
In the research work conducted in the Kunlun Mountain area,the authors measured 39 Silurian（S） and Ordovician-Silurian（O-S） geological sections,whose thicknesses range from 169 m to 8260 m,mostly with fault and angular unconformities between various strata.Littoral（shallow sea）-abyssal-littoral（shallow sea）-abyssal paleogeographic sedimentary environments characterize the study area,as shown by these sections.In West Kunlun,Wenquangou Group（S1W）is dominated by sandstone and slate,assuming a shallow sea（shelf sea）sedimentary environment,in west Yingjisha,and by silicalite,sandstone,siltstone and slate in Mazha area,with the existence of tholeiite,demonstrating a deep sea sedimentary environment（subduction zone ocean trench） in this area,a clinoform sedimentary environment in the west and east of Mazha,and thinning of strata northwestward and southeastward.In East Kunlun,Wenquangou Group（S1W）is composed of epimetamorphic rock,sandstone and mudstone,assuming abyssal-bathyal flysch facies in north Muzitage Peak.In middle and late Silurian（S2-3）,Dabangou Group（S2-3D） was bathyal-littoral（shallow sea） in the west and shallow sea sediments such as carbonate and fragmental rock in the east.In East Kunlun,the Baiganhu Formation（S1b）in south Ruoqiang is characterized by abyssal turbidite aggradation with graptolites as the mark of the deep sea basin environment under the tensile tectonic condition.The Saishiteng Formation（S3）in south Geermu City shows the upward evolution from clinoform through continental rise and shallow sea to abyssal facies,characterized by turbidite and semi-pelagic aggradation in relict sea basin,with the zircon LA-ICP-MS U-Pb ages of monzonitic granite being 421±3 Ma and 423±16 Ma.The Nachitai Group（OSN）strata in southeast Geermu City possess ultramafite-diabase-basalt-deep sea silicalite,derived from ocean crust substance.Ultramafite is a part of ocean crust relic fragments,metamorphic basalt marks midoceanic ridge and ocean island arc,silic
出处
《中国地质》
CAS
CSCD
北大核心
2010年第5期1284-1304,共21页
Geology in China
基金
中国地质调查局"青藏高原前寒武纪地质古生代构造-古地理综合研究"项目(1212010610102)资助
关键词
志留纪
昆仑山地区
构造-古地理环境
成矿与找矿
Silurian
Kunlun Mountain area
tectonic-paleogeographic environment
mineralization and ore prospecting
