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选取西秦岭两当地区太阳寺岩组的变质碎屑岩为研究对象,依据CL图像,采用LA-ICP-MS锆石U-Pb同位素定年方法,探讨两当地区太阳寺岩组的形成时代与物源。两当地区太阳寺岩组的锆石U-Pb年龄及与邻近地层的变质变形关系和时代对比表明,太阳寺岩组的沉积时代为426~420Ma,为晚志留世—末志留世。太阳寺岩组的碎屑锆石年龄谱可分为4组:500~420Ma、955~550Ma、1866~1227Ma和3039~2132Ma。早古生代年龄组呈现最强的烈峰值特征,峰值为438Ma,该组锆石物源以西秦岭北缘构造带为主;新元古代年龄组的碎屑锆石物源为西秦岭北缘构造带和北祁连造山带;中元古代和古元古代—新太古代年龄组的碎屑锆石物源主要来自于北祁连造山带和西秦岭北缘构造带基底岩系。综合分析认为,西秦岭北缘构造带为天水两当地区太阳寺岩组碎屑沉积物的主要源区。
The metamorphic clastic rocks of the Taiyangsi rock group in the two areas of West Qinling were selected as the research objects. Based on the CL images and the LA-ICP-MS zircon U-Pb zircon dating method, Source. The zircon U-Pb ages of the Taiyangsi-Tertiary Formation in the two areas and their relationship with the metamorphic deformation of the adjacent strata show that the depositional age of the Taiyangsianyan Formation is 426-420 Ma, which is Late Silurian-Late Silurian. The age distribution of detrital zircons in the Taiyangsi Formation can be divided into four groups: 500 ~ 420Ma, 955 ~ 550Ma, 1866 ~ 1227Ma and 3039 ~ 2132Ma. The Early Paleozoic age group showed the strongest peak-peak value with a peak value of 438Ma. The source rocks of this group are dominated by the tectonic belt in the northern margin of the western Qinling. Neoproterozoic detrital zircons are derived from the northern margin of the West Qinling And the North Qilian orogenic belt. The Mesoproterozoic and Paleoproterozoic-detrital zircons originated mainly from the North Qilian orogenic belt and the structural belt basement rocks in the northern margin of West Qinling. According to a comprehensive analysis, the tectonic belt in the northern margin of the West Qinling Mountains is the main source of clastic sediments in the Taiyangsi Rock Formation in the Tianshui area.