阿尔金断裂东端酒西盆地古近系物源分析及意义

探讨酒西盆地古近纪沉积与阿尔金左行走滑断裂的关系。通过对酒西盆地西部红柳峡剖面古近系火烧沟组、白杨河组进行系统的沉积学和年代学分析表明:火烧沟组的砾石成分主要以中-低级变质岩和沉积岩为主,到了白杨河组则转变为以岩浆岩为主;古水流方向主体来自西部-西北部;室内砂岩碎屑鉴定结果显示古近系砂岩的碎屑成分全部落入再旋回造山带物源区;碎屑锆石U-Pb年龄测定结果表现出新元古代和中元古代2个主要的年龄峰值。综合对比酒西盆地周缘的物源区,初步认为阿尔金地体为火烧沟组和白杨河组主要的物源供给区。结合前人对阿尔金左行走滑断裂的研究,表明自渐新世以后阿尔金地体才离开酒西盆地,进一步确定阿尔金断裂带最大左行走滑量450km。

Provenance analysis of Paleogene in the Jiuxi basin on eastern Altyn Tagh fault and its implication

Sedimentology and geochronology of Paleogene sequences (including the Huoshaogou and Baiyanghe Formations) in the Hongliuxia section of Jiuxi basin are studied so as to explore the relation between the Paleogene sediments with left strike slip Altyn Tagh fault.It shows that the conglomerates in the formations are mainly composed of low-middle grade metamorphic rocks and sedimentary rocks in the Huoshaogou Formation,and of magmatic rocks in the Baiyanghe Formation.Study of these conglomerates reveals that the main paleocurrents are west and northwest direction.The sandstones from the Huoshaogou and Baiyanghe Formations belong to the recycled orogeny environment based on the Q-F-L diagram.Detrital zircons of the four Eocene sandstones obtained two Precambrian characteristic age populations,Neoproterozoic and Mesoproterozoic.Contrasting with periphery provenance sources,it is showed that the provenance of Huoshaogou Formation was mainly from the Altyn Tagh terrane.On the basis of geochronology data,along with the regional stratigraphic and paleocurrent studies,it is considered that the Altyn Tagh terrane is departed from Jiuxi basin after Oligocene,and the maximum left strike slip for Altyn Tagh fault is over 450 km.