Late Neoarchean charnockite in Daqingshan terrane, North China Craton: petrogenesis and implications for continental crustal evolution

Abstract

<p>Modern analogues of Archaean charnockite are important because they facilitate investigations into processes of early crustal formation and tectonic transition. Herein, we present the results of the petrography, geochemistry, and isotope geochronology of Late Neoarchean charnockites in the Daqingshan terrane at the northern margin of the North China Craton. The sources, petrogenesis, and tectonic implications of the samples obtained are determined based on their geochemical characteristics. Charnockites mainly exhibit magnesian and calc-alkaline characteristics; furthermore, they contain high amounts of light rare-earth elements, with slightly positive Eu anomalies. Analysis of zircon U-Pb dating using a sensitive high-resolution ion microprobe reveals that Hademengou-Xiwulanbulang (HDMG-XWLBL) charnockites were emplaced during the (i) Late Neoarchean (ca. 2500 Ma), with zircon & epsilon;Hf(t) values ranging from 1.57 to 7.81; (ii) single-stage model ages (T-DM1) from 2529 to 2637 Ma; and (iii) two-stage model ages (T-DM2) from 2710 to 2820 Ma. A comparative study has performed on the petrography, geochemistry, and geochronology of charnockite and granulite shown that the parent magma of the charnockites is the product of the partial melting of granulite. Combining our results with geological data pertaining to the Archaean structural evolution of the Daqingshan terrane, we speculate that the Late Neoarchean HDMG-XWLBL charnockite was formed during a subduction-related thermo-tectonic event in the northern margin of the North China Craton.<br></p>