Geochemistry and petrogenesis of Wengen mafic-ultramafic layered intrusions, Inner Mongolia, China

摘要

Wengen mafic-ultramafic layered intrusion locates in central part of Central Asian Orogenic Blet. The intrusion is 6 kilometers in length, and 3 kilometers in width, it is composed of leucogabbro, melagabbro, anorthosite, olivine-gabbro, gabbronotite, norite, troctolite and bojite (Fig.1). The zircon SHRIMP age of anorthosite is 285 Ma.Anorthite of plagioclase is between 72 to 84, and Mg# of olivine is 0.62 to 0.83. the crystallization sequence of the intrusion is Ol-(Chr)→Ol-Pl-(Chr) →Ol-Pyx-Pl→Pyx-Pl and Hbl. The rocks are enriched LREE in relative to HREE, and exhibit strong positive 5Eu anomaly (+1.43 to +2.68). Rocks are depleted in Th, Nb and relatively enriched in Ba, U, Sr, Ti.