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汝阳群分布在华北克拉通西南缘,位于河南-陕西-山西交界地区,主要为一套未变质的碎屑岩及碳酸盐岩地层,不整合于熊耳群火山岩系之上,其上被洛峪群整合覆盖。长期以来,其地质时代一直存有较大的争议。本文通过对汝阳群下部白草坪组4个石英砂岩样品中的碎屑锆石进行LA-ICP-MS U-Pb年龄测定,获得的~(207)Pb/~(206)Pb年龄分布范围为3 000~1 800 Ma,主要集中在2 600~2 400 Ma之间(约占67%),年龄主峰值为2 550~2 500 Ma,说明其沉积物质主要来源于新太古代末以及古元古代的地质体。其中,最年轻锆石的~(207)Pb/~(206)谐和年龄值分别为1 817±22 Ma、1 838±23Ma、1 924±17 Ma和1 829±28 Ma,说明汝阳群沉积时代不老于1 800 Ma,与其上覆洛峪群中近期获得1 611±8 Ma的年龄相吻合,因此其形成时代应为中元古代早期。
Ruyang group distributes in the southwestern margin of North China Craton, and is located in the junction of Henan-Shaanxi-Shanxi region. It is mainly composed of a set of unmodified clastic rocks and carbonate rocks that are not integrated with the Xiong’er Group volcanic rocks. Luoyu group integration coverage. For a long time, there has been much controversy over its geological history. In this paper, LA-ICP-MS U-Pb ages of detrital zircon from four quartz sandstone samples from the Baiyangtiao Formation in the Ruyang Group were determined. The age distribution of 207 Pb / 206 Pb was 3 000 ~ 1 800 Ma, mainly concentrated in the range of 2600 ~ 2400 Ma (about 67%) with the main age peak of 2 550 ~ 2 500 Ma, indicating that the sediments mainly come from the Late Neo-Archean and the Paleoproterozoic Of the geological body. The ~ (207) Pb / ~ (206) harmonic age values of the youngest zircons were 1817 ± 22 Ma, 1838 ± 23Ma, 1924 ± 17 Ma and 1829 ± 28 Ma, respectively. The sedimentary age is not older than 1 800 Ma, which coincides with the recent age of 1 611 ± 8 Ma overlying the Luoyu Group. Therefore, the age of its formation should be Early Mesoproterozoic.