Please use this identifier to cite or link to this item:
Scopus Web of Science® Altmetric
Type: Journal article
Title: Geochronology and geochemistry of mafic dykes in the Helanshan complex: implications for Mesozoic tectonics in the North China Craton
Author: Li, Z.
Liu, X.
Dong, Y.
Santosh, M.
Zhang, F.
Xu, J.
Citation: Geoscience Frontiers, 2018; 9(6):1711-1724
Publisher: Elsevier
Issue Date: 2018
ISSN: 1674-9871
Statement of
Zhenghui Li , Xiaoming Liu, Yunpeng Dong, M. Santosh, Feifei Zhang, Jie Xu
Abstract: The Helanshan tectonic belt (HTB) is a major tectonic divide between the Alxa and Ordos blocks in the North China Craton. The geochronology and petrogenesis of the mafic dykes in the northern HTB are keys to understanding the tectonic evolution of this belt. The mafic dykes, intruded into the Neoarchean–Paleoproterozoic metamorphic basement, are mainly composed of diabase with a mineral assemblage of plagioclase (45%–60%), pyroxene (25%–35%), minor quartz and Fe–Ti oxides. The LA-ICPMS U–Pb analysis of zircon grains from representative dykes yield a weighted mean age of 206 ± 1.9 Ma, which represents the crystallization age of the dyke. The diabases show high contents of Fe2O3T (11.88–17.55 wt.%), low contents of SiO2 (45.65–50.95 wt.%) and MgO (3.31–5.50 wt.%) with low Mg# (=100 × MgO/(MgO + FeO) atomic ration) of 33–44. They are characterized by enrichment of light rare earth elements (LREEs) and large ion lithophile elements (LILEs) (e.g., Rb, Ba and Pb), and slight depletion of high field strength elements (HFSEs). These features suggest that the magma has undergone extensive fractionation of olivine and pyroxene but only minor crustal contamination during its evolution. Their high Sm contents and La/Sm ratios, and low Sm/Yb ratios indicate that magma from which the dykes formed was derived from low degree (about 5%) partial melting of an enriched garnet + spinel lherzolite mantle source. Together with regional geology, these geochemical and geochronological data suggest that the mafic dykes in the HTB were formed in an intracontinental extensional setting during the late Triassic.
Keywords: Mafic dykes; geochemistry; zircon U–Pb geochronology; Hf isotope; Helanshan Tectonic Belt; North China Craton
Rights: © 2017, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY -NC-ND license ( licenses/by-nc-nd/4.0/).
DOI: 10.1016/j.gsf.2017.09.006
Published version:
Appears in Collections:Aurora harvest 8
Geology & Geophysics publications

Files in This Item:
File Description SizeFormat 
hdl_116086.pdfPublished Version4.92 MBAdobe PDFView/Open

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.