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东昆仑地区小庙岩组的形成时代长期存在争议,且缺少精确的年代学证据。以东昆仑东段塔妥地区小庙岩组变质碎屑岩为研究对象,采用LA-ICP-MS锆石U-Pb同位素定年方法,探讨其形成时代。结果显示,锆石具有较宽的年龄谱(1551~2624Ma),可划分为2624~2603Ma、2501~2290Ma、2196~2036Ma和1921~1551Ma年龄组,最后一组可进一步划分为1921~1690Ma和1641~1551Ma两个亚组。其中1921~1690Ma代表了物源区强烈的变质岩浆热事件,具有最强峰值特征(峰值年龄为1783Ma),而2501~2290Ma代表了源区一次变质事件,并有少量2196~2036Ma年龄记录,个别2600Ma的碎屑锆石暗示东昆仑地区存在新太古代的陆核。1641~1551Ma(加权平均年龄为1597Ma)代表了小庙岩组发生变质的时间,而物源区最晚变质年龄为1690Ma,从而确定小庙岩组形成于1690~1597Ma,属中元古代。对比碎屑锆石年龄频谱和东昆仑地区较老变质基底记录的构造-热事件信息,小庙岩组主要沉积物源可能来自于古元古界白沙河岩组,而东昆仑与华北在古元古代末—中元古代早期构造事件的对比揭示,在这一时期二者具有相似的构造演化特征。
The formation of the Xiao Miao-Yan Formation in the East Kunlun area has long been in dispute and lacks accurate chronological evidence. Taking the metamorphic clastic rocks in Xiaomiaoankou Formation of Datu area in the eastern Kunlun Mountains as the research object, the formation age was discussed by LA-ICP-MS zircon U-Pb isotopic dating. The results show that zircon has a wide spectrum of age (1551 ~ 2624Ma), can be divided into 2624 ~ 2603Ma, 2501 ~ 2290Ma, 2196 ~ 2036Ma 1921 ~ 1551Ma and age groups, the last group may be further divided into 1641 and 1921 ~ 1690Ma ~ 1551Ma two subgroups. 1921 ~ 1690Ma wherein represents strong metamorphic event magmatic source area, characterized in having the strongest peak (peak age 1783Ma), and 2501 ~ 2290Ma represents a metamorphic event source region, and a small amount of 2196 ~ 2036Ma Age recorded individual The 2600Ma detrital zircons suggest the presence of Neoarchean continental nuclei in the eastern Kunlun area. 1641 ~ 1551Ma (weighted average age of 1597Ma) represents the metamorphic time of the Xiaomiao Formation, and the latest metamorphic age of the provenance area is 1690Ma, which confirms that the Xiaomiaoyan Formation formed from 1690 to 1597Ma and belongs to Mesoproterozoic. Comparing the age spectrum of detrital zircons with the tectonic-thermal event information of older metamorphic basement records in the East Kunlun Mountains, the main sedimentary source of the Xiao-Miao-Rock Formation may come from the Baishahe Formation in Paleoproterozoic, A comparison of tectonic events at the end of the Proterozoic to the Mesoproterozoic reveals that both had similar tectonic evolution characteristics during this period.