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本文报道了冀东青龙地区新太古代朱杖子群和单塔子群变质岩的锆石SHRIMP U-Pb定年结果。朱杖子群底部张家沟组砾岩中的TTG砾石、花岗岩砾石和基质的岩浆锆石207Pb/206Pb加权平均年龄分别为2515±9Ma(MSWD=1.9)、2510±10Ma(MSWD=1.6)和2512±7Ma(MSWD=1.0),朱杖子群底部张家沟组黑云斜长片麻岩碎屑锆石207Pb/206Pb加权平均年龄为2540±6Ma(MSWD=1.6),朱杖子群桲罗台组变质酸性火山岩岩浆锆石207Pb/206Pb加权平均年龄为2516±8Ma(MSWD=1.1),单塔子群鲁杖子组黑云变粒岩碎屑锆石207Pb/206Pb加权平均年龄为2504±7Ma(MSWD=1.8),另有一个数据点的207Pb/206Pb年龄为3.04Ga。根据本文定年结果和前人资料,获得主要结论如下:朱杖子群和单塔子群形成于新太古代晚期,很可能为岛弧环境的产物;朱杖子群与下伏单塔子群之间虽存在角度不整合关系,但时间间断不长,朱杖子群底部张家沟组砾岩不具有底砾岩性质;③绿片岩相—角闪岩相的朱杖子群和单塔子群与角闪岩相—麻粒岩相的遵化深变质绿岩带—三屯营—太平寨—迁安岩浆杂岩区变质程度差异很大,但形成时代相同,是后期构造作用把它们置于同一地壳平面。
This paper reports the zircon SHRIMP U-Pb zircon dating of the Neoarly Archean Zhuzizi Group and the Danzai Group metamorphic rocks in the Qinglong area of eastern Hebei. The 207Pb / 206Pb magmatic zircons of TTG gravels, granite gravel and matrix in the conglomerates of Zhangjiagou at the bottom of Zhuzizi Group have a weighted mean age of 2515 ± 9Ma (MSWD = 1.9), 2510 ± 10Ma (MSWD = 1.6) and 2512 ± 7Ma (MSWD = 1.0). The weighted average age of detrital zircon 207Pb / 206Pb in the Zhangjiagou biotite gneiss at the bottom of Zhuzizi Group was 2540 ± 6Ma (MSWD = 1.6) The 207Pb / 206 Pb weighted average age of metamorphic acidic volcanic zircons was 2516 ± 8Ma (MSWD = 1.1). The weighted average age of detrital zircon 207Pb / 206Pb in the Zhitizi Formation of the Zhuanzizi Formation was 2504 ± 7Ma (MSWD = 1.8), and another data point 207Pb / 206Pb age of 3.04Ga. According to the results of this paper and previous data, the main conclusions are as follows: The Zhuzizi Group and the single tower form in the late Neo-Archean, which is probably the product of the island arc environment. Although there exists between the Zhuzhang subgroup and the underlying single sub-subgroup But the time interval is not long, the conglomerate in Zhangjiagou Formation at the bottom of Zhuzizi Group does not have the characteristics of base conglomerate. ③ The Zhuzhangzi Group and Danzazi Group of greenstone facies-amphibolite facies and amphibolite facies - The metamorphic greenstone belt of the Zunhua Deep metamorphic greenstone belt of the granulite facies - Sandun camp - Taipingzhai - Qian’an magmatic complex varies greatly in degree of metamorphism, but the formation ages are the same and are later tectonism putting them in the same crustal plane.