New chronological constraints on Neoarchean gneisses, Proterozoic cover sediments, and Triassic granite, Jixian, China

摘要

In the eastern North China Craton, basement gneisses are covered by poorly dated Late Paleoproterozoic to Early Neoproterozoic sediments. This study reports new zircon data from the Jixian area to constrain the protolith age of basement orthogneisses, the detrital ages of cover clastic sediments, and the age of a post -tectonic intrusive granite. Most zircons in orthogneisses have dark cores and bright rims in cathodoluminescence images. The dark cores have (207)pb/Pd-206 peak ages at 2520 Ma that constrain the minimum protolith age of the orthogneiss. In contrast, the bright rims have a wide Pd-207/Pb-206 age range from ca. 2500 Ma to 1800 Ma that is distributed along the Concordia curve, which reflect a Paleoproterozoic overprint on the basement of the North China Craton. Overlying clastic sediments mainly contain 2.5-2.7 Ga zircons derived from the basement rocks. 2200 Ma detrital oscillatory -zoned zircons, especially in a basal conglomerate of the Xiamaling Fm., were no doubt derived from 2200 Ma igneous rocks, probably from the southern North China Craton. The intrusive granite contains euhedral zircon grains with clear oscillatory zones that yield a Concordia age of 205.6 +/- 1.1 Ma, and was likely generated during early Mesozoic delamination of the eastern North China Craton. (C) 2016 Elsevier B.V. All rights reserved.