摘要
为了探讨西秦岭舒家坝地区太阳寺岩组的物源特征及形成时代,本文选取该套地层中碎屑锆石作为研究对象,采用LA-ICP-MS锆石U-Pb同位素年代学方法,界定舒家坝地区太阳寺岩组的形成时代,并探讨其物质来源.结果表明,太阳寺岩组的沉积下限为（437±4）Ma,结合前人对周边地质体研究情况,其主体形成时代为志留纪.舒家坝地区太阳寺岩组碎屑锆石年龄谱明显分为4个年龄组段：（1）437～526Ma,峰值为458Ma,年龄较为集中,呈现最为强烈峰值特征,指示其物源可能来自于西秦岭北缘构造带和北祁连造山带;（2）601～978Ma,可细分为601～651Ma、738～978Ma 2个亚组,峰值分别为650Ma、814Ma,年龄也相对比较集中,这一时期受新元古代Rodinia超大陆汇聚和裂解的影响,在秦岭造山带和祁连造山带产生了一系列的构造岩浆活动,为研究区提供物源奠定了可能性;（3）1032～1245Ma,峰值为1092Ma,这组年龄反映其物源主要来自于北祁连造山带;（4）1668～2546Ma,该组可细分为1668～2019Ma、2304～2546Ma 2个亚组,其峰值分别为1920Ma、2418Ma,反映了西秦岭北缘构造带和北祁连造山带二者的结晶基底以及华北板块结晶基底都存在为研究区提供物源的可能性.综合分析显示太阳寺岩组碎屑沉积物质来源比较复杂,具有明显的多元性,有西秦岭北缘构造带、北祁连造山带和华北板块基底3个物源区,其中西秦岭北缘构造带和北祁连造山带为主要物源区,二者相比,北祁连造山带应为最主要物源区.
With elastic rocks of Taiyangsi Rock Group in Shujiaba area of West Qinling Mountains as the research object,the authors used the LA-ICP-MS zircon U-Pb isotopic geochronologic methods to study the formation age and material source of Taiyangsi Rock Group in.Shujiaba area.The results show that the lower limit of the deposition of Taiyangsi Rock Group is （437±4） Ma,suggesting that it was formed during the Silurian,as also evidenced by the previous research on the surrounding geological setting.Detrital zircon age spectra of Taiyangsi Rock Group in Shujiaba area can be clearly divided into four age segments：（1） 437-526 Ma,with the peak value of 458 Ma,characterized by relatively concentrated ages and a strong peak,indicating that the source might have come from the northern margin of West Qinling tectonic zone and North Qilian orogenic belt; （2） 601-978 Ma,which can be divided into two subgroups of 601-651 Ma and 738-978 Ma,with the peak values of 650 Ma and 814 Ma,assuming concentrated ages.During this period,due to the influence of the aggregation and breakup of the Neoproterozoic super-continent Rodinia,a series of orogenic magmatic activities occured in the Qinling and Qilian orogenic belts,which resulted in a possibility for providing source materials for the area; （3） 1032-1245 Ma,with the peak value of 1092 Ma,suggesting that the material source was probably mainly derived from the North Qilian orogenic belt; （4） 1668-2546 Ma,which can be divided into two subgroups of 1668-2019 Ma and 2304-2546 Ma,with the peak values being 1920 Ma and 2418 Ma respectively,implying that the crystalline basement of both the northern margin of West Qinling tectonic zone and the North Qilian tectonic belt and the crystalline basement of the North China plate were present in the study area to provide the possibility of provenance.A comprehensive analysis shows that the material sources of Taiyangsi Rock Group is much more complicated and characterized by obvious diversity.Its material sources might have com
出处
《中国地质》
CAS
CSCD
北大核心
2014年第3期741-755,共15页
Geology in China
基金
国家自然科学基金项目(41172186
40972136
40572121)
教育部高等学校博士学科点专项科研基金项目(20110205110004)
中央高校基本科研业务费专项资金项目(CHD2011TD020
2013G1271091
2013G1271092)联合资助
