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对五台地区滹沱群底部四集庄组砾岩进行了详细研究,并选择其中花岗岩和石英岩砾石进行了锆石U-Pb和Hf同位素分析.2个花岗岩砾石中锆石207Pb/206Pb年龄分别为(2513±8)和(2527±8)Ma,与五台地区王家会灰色相花岗岩和光明寺/石佛花岗岩的侵位时代一致;2个石英岩砾石中锆石207Pb/206Pb年龄主要集中于2550~2490Ma,峰值为~2.5Ga,与五台群高凡亚群石英岩锆石年龄谱特征相似.砾石特征及年龄结果表明,滹沱群底部砾岩的沉积物源区为五台群和五台地区新太古代花岗岩.结合滹沱群底部玄武安山岩的时代((2140±14)Ma),限定滹沱群初始沉积时代为早元古代中期.豆村-东冶亚群中变质玄武岩(2200~2100Ma)具有裂谷火山岩地球化学特征,同时豆村-东冶亚群中碎屑岩和碳酸盐岩沉积于伸展构造环境中.因此,滹沱群豆村-东冶亚群火山沉积岩系与华北克拉通中部早元古代中-晚期(2200~2100Ma)裂谷活动有关,而郭家寨群沉积于裂谷闭合过程或之后.四集庄组砾岩中,花岗岩和石英岩砾石的锆石大多具有正的Hf(t)值,少量锆石的Hf(t)值与同期亏损地幔值相近,多数锆石的亏损地幔模式年龄与锆石U-Pb年龄相差200~100Ma.花岗岩和石英岩的源区为滞留时间较短的地壳(~2.7Ga)部分熔融形成的,同时存在新生地壳或亏损地幔物质的添加.研究进一步表明,华北克拉通经历了多期地壳生长并在新太古代末期初步完成克拉通化.
The conglomerates in the Shijiazhuang Formation at the bottom of the Yutuo Group in the Wutai area were studied in detail, and the zircon U-Pb and Hf isotopic analyzes of the granites and quartzite gravels were selected. The 207Pb / 206Pb zircon ages of the two granite gravels (2513 ± 8) and (2527 ± 8) Ma, which are consistent with emplacement times of Wangjiahui gray-phase granite and Guangmingsi / Shifang granite in Wutai area. The 207Pb / 206Pb ages of zircons from two quartzite gravels are mainly concentrated in 2550 ~ 2490Ma and peak ~ 2.5Ga, which are similar to those of the Gaofan sub-group quartzite in the Wutai Group.The gravel characteristics and age results show that the sedimentary source areas of the conglomerate in the bottom of the Hutuo Group are Wutai Group and Wu (2140 ± 14 Ma) in the bottom of the Basaluo Group, limiting the initial sedimentary age of the Hutuo Group to the Early Early Mesozoic. The metamorphic basalts in the Beocun-Dongye sub-group (2200 ~ 2100 Ma ) Have the geochemical characteristics of rift volcanic rocks, while the clastic rocks and carbonate rocks in the Beocun-Dongye sub-group are deposited in the extensional tectonic setting.Thus, the volcanic sedimentary rock series of the Tuotuo Group-Dongye sub-group volcanic sedimentary rocks and the North China Craton Middle Central Early Early Proterozoic mid-late (2200 ~ 2100Ma) rift While the Guozhaizhai group is deposited during or after the closure of the rift. Most of the zircons from the granites and quartzite gravels in the Shijiazhuang group have a positive Hf (t) value, and a small amount of zircon Hf (t) The values of depleted mantle are similar to the depleted mantle over the same period, and the majority of zircons have a depleted mantle age ranging from 200 to 100 Ma with zircon U-Pb ages. The source regions of granites and quartzites are partially melted (~ 2.7 Ga) in the short-lived crust , With the addition of new crust or depleted mantle material.The study further shows that North China craton experienced multi-stage crustal growth and initially completed cratonization in the late Neo-Archean.