【作者】 张吉衡；

【导师】 吴福元； 葛文春；

【作者基本信息】 吉林大学 ， 地球化学， 2006， 硕士

【摘要】 本文详细报道了大兴安岭地区中生代火山岩同位素年代学研究结果,初步建立了大兴安岭地区中生代火山岩的年代学格架。高精度的锆石U-Pb定年以及全岩40Ar/39Ar定年结果表明,大兴安岭中生代火山作用开始于中-晚侏罗世(～160Ma),而主要形成于早白垩世期间,主体时代范围在148±2Ma～111±1Ma之间。这些年龄结果具有明显的阶段性,可以划分为两个不同的阶段,而统计分析结果表明火山作用的高峰在130Ma～120Ma之间,并且与区内晚中生代侵入岩的年代学格架一致。大兴安岭南部与北部具有一致的时代特征,在岩浆作用的高峰时期内,同时形成了大量的中基性火山岩与酸性火山岩。大兴安岭地区中生代火山岩与整个中国东部中生代大火成岩带具有一致的年代学格架和相似的岩石组合特征。晚中生代中国东部火成岩的年代学结构、岩石组合特征以及空间分布特征表明,该区在晚中生代期间发生了大规模的岩石圈减薄事件,其中太平洋板块俯冲作用所诱发的大规模岩石圈拆沉和软流圈物质上涌,是造成大规模岩石圈减薄作用的主要原因。更多还原

【Abstract】 In this thesis, detailed geochronological data are reported for theLate Mesozoic volcanic rocks in the Great Xing’an Range, NE China.And a primary geochronological frame is founded based on these data.Results of high precise zircon U-Pb dating and whole rock 40Ar/39Ardating indicate that the volcanism in the Great Xing’an Range started inMiddle-Late Jurassic (~160Ma), whereas, the volcanic rocks weremainly erupted in the Early Cretaceous, with an age range between148±2Ma and 111±1Ma. And two episodes can be recognized based onthese age data. In the relative probability density diagram, peak of theseages appears at about 130Ma-120Ma, consistent with the Mesozoicintrusive rocks in the same area. The volcanic rocks both in the northand south Great Xing’an Range have the same geochronological frames.During the peak period of the volcanism, voluminous mafic and felsicvolcanic rocks were erupted contemporaneously. Mesozoic volcanicrocks in the Great Xing’an Range have the same geochronological frameand rock assemblages with the rocks in the large igneous belt in theeastern China, and they formed in a uniform extensional environment.The geochronological frame, feature of the rock assemblage and thespatial distribution of Mesozoic igneous rocks in the eastern Chinaindicate that the large scale lithospheric thinning also happened in thenortheastern China. Delamination and the subsequent upwelling of theasthenosphere, which were caused by the subduction of the Pacific plate,were the main causing of the lithospheric thinning in the eastern Chinaduring the period. As the result of the thinning, the voluminous igneousrocks formed in the eastern China.更多还原