摘要
多年来,对北天山冰达坂—后峡一带古生代地层的划分归属争论较大。通过1∶5万区调填图,在原划上石炭统奇尔古斯套组内发现一套火山岩系。对岩石组合、同位素测年、底砾岩、沉积环境的详细研究表明,这套火山岩属中二叠统阿尔巴萨依组,为一套陆相紫红色中基性—酸性火山岩组合,以安山岩、英安岩、流纹岩为主,多见角砾岩、角砾熔岩、火山集块岩、火山角砾岩等。与下伏后峡组和上覆三叠系小泉沟群均呈角度不整合接触。单颗粒锆石SHRIMPU-Pb测年值为272Ma±4Ma,时代厘定为中二叠世。构造环境为早中二叠世造山后期深部热力塌陷火山喷发环境。此研究成果为东、西天山地层单元的对比和构造区划提供了重要依据。
For many years there has been much controversy over the stratigraphic division of the Paleozoic in the Bingdaban- Houxia area, North Tianshan. Through the 1：50000 regional geological mapping, a suite of volcanic rocks was discovered in the original Upper Carboniferous Qirgustaw Formation. Intensive study of the rock association, isotope ages, basal conglomerate and sedimentary environment indicates that this suite of volcanic rocks belong to the Middle Permian Arbasay Formation, being an association of continental purplish red intermediate-basic-acid volcanic rocks. It consists predominantly of andesite, dacite and rhyolite and breccia, and in addition, breccia, brecciated lava, volcanic agglomerate and volcanic breccia are often seen. It has an unconformable contact with both the underlying Houxia Formation and the overlying Triassic Xiaquangou Group. The single-zircon SHRIMP U-Pb dating of the volcanic rocks yielded an age of 272±4 Ma, indicating a Middle Permian age. The volcanic rocks formed in a tectonic environment of deep thermal collapse eruption in the Early-Mid Permian late-orogenic phase. This study offers an important basis for the correlation of the stratigraphic units and tectonic division of the East and West Tianshan.
出处
《地质通报》
CAS
CSCD
北大核心
2006年第8期969-976,共8页
Geological Bulletin of China
基金
新疆维吾尔自治区1:5万区域地质矿产调查项目(XJQDZ2003-15)
国家重点基础研究发展计划项目(2003CB214601)资助。
