摘要
新疆东准地区晚古生代地层出露广泛,其沉积时限的精确限定对理解中亚造山带的增生和拼贴过程、确立该地区构造框架及油气开发具有深远意义.然而,目前的研究主要集中于岩浆岩方面,对于晚古生代地层时代及其空间展布的研究则相对缺乏,特别是石炭系和泥盆系沉积地层标定较为模糊.为此,本文选取了3个原泥盆系砂岩进行了细致的野外剖面测制、岩石学观测和碎屑锆石U-Pb年代学分析.研究显示：原泥盆纪砂岩的最年轻碎屑锆石年龄为346～312 Ma;碎屑锆石年龄谱图分为：380～310 Ma（晚泥盆世—早石炭世,71.8％）、445～385 Ma（志留纪—早-中泥盆世,11.7％）、480～450 Ma（奥陶纪,3.9％）、540～485 Ma（寒武纪,4.5％）和前寒武纪年龄段（8.1％）;碎屑锆石年龄谱图区域上具有由南向北、由西向东呈简单化趋势且晚古生代年龄比重增加.结合该区岩浆岩年代学研究成果,将研究区原泥盆系沉积时代重新厘定到晚石炭系早-中期;认为东准地区的碰撞拼贴时间应发生于晚石炭世,并非是不同期次碰撞拼贴之产物.
Late Paleozoic strata are widely exposed in the area of East Junggar,Xinjiang. The correct chronological division of its depositional age is not only important to establish the tectonic framework, but also to develop oil and gas. Nowadays, the research of magmatic rock and ophiolite suite has yielded fruitful results. However, the research degree on some problems is relatively low, such as the distribution of the Late Paleozoic strata, contact relationship of strata and so on. The division of Carboniferous and Devonian strata is not clear is one of the main research problems. Therefore, this study selects detrital zircon from three typical sedimentary strata to date analysis by using zircon U-Pb isotope dating method, which is the correct division of its depositional age from the perspective of chronology. The result indicates the youngest age of detrital zircons from Devonian sandstone ranges from 346 Ma to 312 Ma; detrital zircon age spectra show five age ranges of 380 - 310 Ma （71.8%） , 445 - 385 Ma （11.7%）, 480- 450 Ma（3.9%）, 540- 485 Ma（4.5%）, and Precambrian （8. 1%）. Combined with the research results of intrusive geochronology of this area,the depositional age of those strata can be identified to Carboniferous but not Devonian.
出处
《地质科学》
CAS
CSCD
北大核心
2014年第2期695-717,共23页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
国家科技重大专项(编号:2011ZX05008-001)资助
关键词
东准噶尔
沉积地层
碎屑锆石
锆石U-PB定年
East Junggar, Sedimentary strata, Detrital zircon, Zircon U-Pb isotopedating
