华北克拉通中生代拆沉陆壳物质对岩石圈地幔的改造:来自橄榄岩捕虏体中角闪石的成分制约

对鲁西和太行山南段早白垩世高镁闪长岩中橄榄岩捕虏体中的角闪石进行了主量元素和痕量元素分析,并讨论了角闪石成分与改造岩石圈地幔熔体的性质与来源之间的关系。研究结果表明,橄榄岩类捕虏体中的角闪石主要为交代成因。在化学上,它们属于钙质角闪石。太行山南段符山橄榄岩捕虏体中的角闪石属于镁质普通角闪石和浅闪石或浅闪石质普通角闪石;鲁西铁铜沟橄榄岩捕虏体中的角闪石为韭闪石质普通角闪石、浅闪石质普通角闪石和镁绿钙闪石质普通角闪石。与板内橄榄岩捕虏体中的角闪石相比,鲁西和太行山南段早白垩世高镁闪长岩橄榄岩捕虏体中的角闪石具有相对高的Mg#(鲁西:86.0~90.8;太行山:90.7~94.2)和SiO2(鲁西:44.04%~46.98%;太行山:47.09%~49.79%)以及相对低的Na2O(1.92%~2.51%)、TiO2(0.01%~1.46%)、Nb(0.29×10-6~1.98×10-6)和Zr(1.61×10-6~5.34×10-6),这与来自俯冲带之上地幔楔橄榄岩捕虏体中的角闪石相类似。综合橄榄岩捕虏体的地球化学特征,可以判定华北克拉通早白垩世岩石圈地幔遭受了起源于拆沉陆壳物质熔融熔体的改造。

Mesozoic Lithospheric Mantle Modified by Delaminated Lower Continental Crust in the North China Craton:Constraints from Compositions of Amphiboles from Peridotite Xenoliths

Major and trace element analyses of amphiboles from the peridotite xenolith entrained by early Cretaceous high-Mg# diorites in western Shandong and southern Taihang Mountains(Mts.) were carried out with the aim of constraining the nature and derivation of the melt modifying lithospheric mantle.The results indicate that these amphiboles within the peridotite xenoliths are of metasomatic origin.Chemically,they belong to calcic amphibole group.The amphiboles from the peridotite xenoliths in the Fushan intrusio...