西准噶尔谢米斯台地区中泥盆统呼吉尔斯特组砂岩源区示踪

摘要

泥盆纪是西准噶尔南部洋陆转换的关键时期,以往研究多从火山岩角度分析该区构造演化过程,对本区中泥盆统呼吉尔斯特组砂砾岩沉积建造研究较少.本文以呼吉尔斯特组为研究重点,通过岩相学及锆石U-Pb年代学分析,研究呼吉尔斯特组沉积环境、物质来源,推测物源区所处大地构造背景,讨论西准噶尔地区古生代构造演化过程.结果表明,呼吉尔斯特组砂岩岩性主要为长石岩屑砂岩和岩屑砂岩,具高火山碎屑、斜长石,低多晶石英特征;锆石U-Pb同位素年代学获4组年龄:415～442 Ma、450～486 Ma、494～507 Ma、519～548 Ma.综合分析认为呼吉尔斯特组沉积物质源区主要有3个,即西准噶尔南部古造山带、火山碎屑沉积地层再风化剥蚀和西准噶尔北部火山岛弧带.%The key period of ocean continent conversion was Devonian in South West Junggar.Many previous researches on the tectonic evolution of this area used volcanic rocks generally and used clastic rocks of Middle Devonian Hujiersite Group rarely.This paper chose Hujiersite Group as the research focus studied the sedimentary environment,material source and tectonic background of Hujiersite Group through petrography and zircon U-Pb chronology analysis which provided important information for the discussion on Paleozoic tectonic evolution process in West Junggar from another angle.The results showed that Hujiersite Group sandstone were mainly feldspar lithic sandstone and lithic sandstone,and characterized by high percentage of volcanic debris and plagioclase,low percentage of quartz.Four sets of ages was obtained by the zircon U-Pb isotopic chronology:415Ma～442Ma,450Ma～486Ma,494Ma～507Ma,519Ma～548Ma,which implied there were three sediment source areas:the paleo-orogenic belt in the south of the west Junggar,the recycling of the volcano clastic sediments denudation and the volcanic island arc belt in thenorth of west Junggar.