Jurassic ca. 160 Ma crustal remelting and Paleoproterozoic intrusive rock residues in the Liaodong Peninsula, East China: Evidence from in situ zircon U–Pb dating and Lu–Hf isotopic analysis

Abstract

The Liaodong Peninsula is an important component of the eastern North China Craton which underwent a transition from an orogenic stage to extension and lithospheric thinning in the Mesozoic era. This transition resulted in large‐scale magmatism and gold mineralization. In this paper, we report findings on Paleoproterozoic intrusive rock residues in the Mesozoic Wulong pluton. To analyse the chronology, magma source, and petrogenetic relationships between the Mesozoic and Paleoproterozoic intrusives, we performed SHRIMP U–Pb isotopic dating and in situ micro‐area Lu–Hf isotopic analysis of zircons. The results show that the crystallization age of the large‐scale Mesozoic intrusive rock is 158 ± 2 Ma, which is in the Late Jurassic. The εHf(t) values of the zircons are between −29.3 and −22.1, and their tDM2 values are between 2,606 and 3,064 Ma, which indicates that the magma source of materials is the Archean supracrust. The zircons of the Paleoproterozoic intrusive rock residues have a typical core–mantle–rim texture. The cores of the zircons have an age range from 1,851 to 2,528 Ma, εHf(t) from −12.2 to +4.0, and tDM2 between 2,519 and 3,437 Ma, reflecting characteristics of multiple sources for the inherited zircons. The mantles of the zircons have an upper intercept age of 1,862 ± 13 Ma, εHf(t) values between −11.9 and −2.2, and tDM2 between 2,644 and 3,241 Ma representing the age of the source rocks. The new growth rims of the zircons have a concordia age of 157.1 ± 2.2 Ma, εHf(t) values from −30.8 to −26.1, and tDM2 between 2,852 and 3,150 Ma representing the metamorphic recrystallization age and characteristics of the upper crustal magma source. The findings of this work suggest that the Wulong pluton, which occupies a large area in the Liaodong Peninsula, recrystallized from Paleoproterozoic granites that were affected by Late Jurassic (ca. 160 Ma) crustal remelting. The incompletely remolten residues are the direct result of the delamination and remelting during the Mesozoic era of Palaeoproterozoic intrusive rocks in the northern margin of the eastern North China Craton.