Magnetically stratified continental lower crust preserved in the North China Craton
Magnetically stratified continental lower crust preserved in the North China Craton
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DOI：
10.1016/j.tecto.2014.12.012
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发表时间：
2015-03
期刊：
影响因子：
2.9
通讯作者：
Zhiyong Li;Jianping Zheng;Qingsheng Liu;W. Griffin;Xiangyun Hu
中科院分区：
文献类型：
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作者：
Zhiyong Li;Jianping Zheng;Qingsheng Liu;W. Griffin;Xiangyun Hu
下地壳捕虏体和出露麻粒岩的磁性特征表明，华北北方东部下地壳存在磁性层状构造。上层（约24-33 km）为强磁性麻粒岩相地体，其中镁铁质麻粒岩具有最高的磁化率（κ，平均67.92 × 10−3SI）和自然反射磁化（NRM，平均0.59 A m−1）。相比之下，最低层（约33-42 km）主要由镁铁质麻粒岩和辉石岩组成，它们是弱磁性的，κ和NRM分别为0.9-1.5 × 10−3SI和0.04-0.1 Am−1。弱磁化地壳最低层的形成与晚中生代至新生代幔源玄武质岩浆在先存壳幔边界的持续底侵作用有关。我们认为这种磁层结下地壳可能广泛存在于华北板块之下。
The magnetic properties of lower crustal xenoliths, and outcropping granulites suggest that magnetically stratified lower crust is preserved in the northern North China Craton. The upper layer (~ 24–33 km) is represented by strongly magnetic granulite-facies terrains, in which the mafic granulites have the highest susceptibility (κ, mean 67.92 × 10−3SI) and natural remanent magnetization (NRM, mean 0.59 A m−1). In contrast, the lowermost layer (~ 33–42 km) is mainly composed of mafic granulites and pyroxenites sampled as xenoliths, which are weakly magnetic withκand NRM of 0.9–1.5 × 10−3SI and 0.04–0.1 Am−1, respectively. The formation of the weakly magnetized lowermost crustal layer is associated with continuous underplating of mantle-derived basaltic magmas at the pre-existing crust–mantle boundary from the late Mesozoic to Cenozoic. We suggest that this magnetically stratified lower crust may be widespread beneath the North China Craton.