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笔者以东秦岭商丹地区武关岩群毛坪长英质片岩单元中黑云石英片岩为研究对象,进行碎屑锆石LA-ICP-MS U-Pb年代学研究,探讨其沉积时代及物质来源。结果显示,碎屑锆石年龄可以划分为4个年龄谱段:早古生代年龄谱段416.8~590.5Ma,峰值为449Ma;新元古代年龄谱段731.5~1055.8Ma,峰值为830Ma;中元古代—古元古代年龄谱段1606.9~1 816.9Ma,峰值为1804Ma;古元古代—新太古代年龄谱段2434.6~2690.3Ma,峰值为2 687Ma。综合研究认为,武关岩群毛坪长英质片岩单元的沉积岩形成时代不早于420Ma,形成于顶志留世商丹洋闭合阶段,是构造混杂并卷入原有的裂谷型火山-沉积岩系之中的时代较新的沉积地层,其碎屑物质可能由北秦岭构造带和南秦岭构造带共同提供。
In this paper, the biotite-quartz schist from the Maopinghang-Changying-quality schist unit in the Shanguan area, Shangqin, Qinling, Qinling, is studied by LA-ICP-MS dating of detrital zircons and the sedimentary age and source of matter. The results show that the ages of detrital zircons can be divided into four age bands: the Paleozoic age band 416.8-590.5Ma, the peak value 449Ma; the Neoproterozoic age band 731.5-105.5.8Ma with a peak value of 830Ma; Paleoproterozoic age spectrum 1606.9 ~ 1816.9Ma, peak 1804Ma; Paleoproterozoic - neo-Archean age spectrum 2434.6 ~ 2690.3Ma, the peak value of 2 687Ma. According to the comprehensive study, the sedimentary rocks of the Maoping-Chang-Changying-type schist unit in the Wu-Guan-Yan Group were formed no earlier than 420 Ma, forming during the closure of the Upper Silurian Merchant-Danang Formation and were structurally mixed and entangled in the original rift-type volcanic- Among the newer sedimentary strata of the time, the detrital material may be provided by the North Qinling structural belt and the South Qinling structural belt.