New chronological constraints on Neoarchean gneisses, Proterozoic cover sediments, and Triassic granite, Jixian, China
New chronological constraints on Neoarchean gneisses, Proterozoic cover sediments, and Triassic granite, Jixian, China
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DOI：
10.1016/j.palaeo.2016.07.008
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发表时间：
2016-10
期刊：
影响因子：
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通讯作者：
Y. Sawaki;Yibing Li;H. Asanuma;S. Sakata;Kazue Suzuki;T. Hirata;B. Windley
中科院分区：
文献类型：
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作者：
Y. Sawaki;Yibing Li;H. Asanuma;S. Sakata;Kazue Suzuki;T. Hirata;B. Windley
在北中国克拉通东部，基底片麻岩被晚古元古代至新元古代早期的沉积所覆盖。本文报道了蓟县地区新的锆石资料，以确定基底正片麻岩的原岩年龄、盖层碎屑沉积物的碎屑年龄和构造后侵入花岗岩的年龄。正片麻岩中的大多数锆石在阴极发光图像中具有深色的核心和明亮的边缘。暗色岩芯的207Pb206Pb峰年龄为2520 Ma，这限制了正片麻岩的最小原岩年龄。与之相反，明亮的边缘具有宽广的207Pb/206Pb年龄范围，沿康科迪亚曲线分布，其年龄范围约为2500~1800 Ma，反映了北中国克拉通基底上的古元古代叠置。上复碎屑沉积主要含有来自基岩的2.5-2.7亿Ga锆石。2200 Ma的碎屑振荡带状锆石，特别是下马岭基性砾岩中的锆石，无疑来自2200 Ma的火成岩，可能来自北中国克拉通南部。侵入花岗岩中含有正面体锆石颗粒，具有明显的振荡带，其谐和年龄为205.6 Ma±11.1 Ma，可能形成于北中国克拉通东部中生代早期的拆沉作用。
In the eastern North China Craton, basement gneisses are covered by poorly dated Late Paleoproterozoic to Early Neoproterozoic sediments. This study reports new zircon data from the Jixian area to constrain the protolith age of basement orthogneisses, the detrital ages of cover clastic sediments, and the age of a post-tectonic intrusive granite. Most zircons in orthogneisses have dark cores and bright rims in cathodoluminescence images. The dark cores have207Pb/206Pb peak ages at 2520 Ma that constrain the minimum protolith age of the orthogneiss. In contrast, the bright rims have a wide207Pb/206Pb age range fromca.2500 Ma to 1800 Ma that is distributed along the Concordia curve, which reflect a Paleoproterozoic overprint on the basement of the North China Craton.Overlying clastic sediments mainly contain 2.5–2.7 Ga zircons derived from the basement rocks. 2200 Ma detrital oscillatory-zoned zircons, especially in a basal conglomerate of the Xiamaling Fm., were no doubt derived from 2200 Ma igneous rocks, probably from the southern North China Craton. The intrusive granite contains euhedral zircon grains with clear oscillatory zones that yield a Concordia age of 205.6 ± 1.1 Ma, and was likely generated during early Mesozoic delamination of the eastern North China Craton.