Geochemical constraints on the tectonic environment of the Late Paleoproterozoic mafic dyke swarms in the North China Craton

Abstract

Late Paleoproterozoic mafic dyke swarms are widespread in the Shanxi Province in the Western Block and Central Orogenic Zone, and also in the Shandong Province of the Eastern Block of the North China Craton (NCC). Both of the mafic dyke swarms in Shandong and Shanxi plot mainly in the field of continental rift environment. The trace element spidergrams and the rare-earth element (REE) graphs of both mafic dyke swarms show similar geochemical features to data from the lavas (Xiong'er Group) in the Zhongtiao-Yanliao aulacogens. This suggests that the origin of the mafic dyke swarms is related to the aulacogens. The trace elements and isotopic data from the mafic dykes and lavas in the aulacogens suggest that the mafic magma is derived from partial melting of the subcontinental lithospheric mantle, and contaminated by lower crust, then intruded the pre-existing fractures to form mafic dyke swarms in a rifting environment. The mafic dyke swarms and aulacogens represent a continuous extension event from 1.84-1.77 Ga in response to the breakup of the supercontinent Columbia.