Geochemical, Sr-Nd isotopic, and zircon U-Pb geochronological constraints on the petrogenesis of Late Paleoproterozoic mafic dykes within the northern North China Craton, Shanxi Province, China
Journal
Precambrian Research
Journal Volume
236
Pages
182-192
Date Issued
2013
Author(s)
Abstract
The ages and source of Precambrian mafic dolerite dykes of the North China Craton (NCC) were determined using geochronological, geochemical, and whole-rock Sr-Nd isotopic data. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb analysis of zircons yielded consistent ages of 1621±6 and 1621±7Ma for two mafic dykes (SYG01 and SYG02) within the NCC. The dykes are classified as the sub-alkaline series according to their K2O+Na2O concentrations (2.5-2.9wt%), and as the calc-alkaline series according to their K2O concentrations (0.05-0.72wt%). These dykes also contain low concentrations of the light rare earth elements [(La/Yb)N=1.5-2.4], with negligible Eu anomalies (δEu=0.9-1.1), positive Ba, Pb, and K anomalies, and depletions in Th, U, and high field strength elements (P and Ti). In addition, the dykes contain relatively low amounts of radiogenic Sr[(87Sr/86Sr)i=0.7025-0.7035] and have high e{open}Nd(t) values (5.6-5.8). These data suggest that the dykes were derived from a depleted mantle source that was hybridized during interaction with foundered lower crustal material. The parental mafic magmas underwent the fractionation of olivine, pyroxene, hornblende, and Fe-Ti oxides (e.g. rutile, ilmenite, titanite) during ascent, with negligible evidence for crustal contamination prior to emplacement at a high crustal level. The NCC extension was related to foundering of lower crust, and there were three episodes of lithosphere extension during Proterozoic time (i.e. 1.8-1.6Ga, 1.3-1.2Ga, and 0.8-0.7Ga). © 2013 Elsevier B.V.
SDGs
Type
journal article