Paleoproterozoic tectono-metamorphic evolution of the southernmost North China Craton: New insights from the metamorphic evolution and geochronology of the Taihua complex at Lushan area

Abstract

The Taihua metamorphic complex along the southern margin of the North China Craton (NCC) mainly consists of tonalite–trondhjemite–granodiorite (TTG) gneisses, amphibolites, metapelites, marbles, quartzites, and banded iron formations (BIFs). The region has been subjected to upper amphibolite–granulite facies metamorphism and intense deformation, with NWW–SEE striking gneissosity. Garnet porphyroblasts from metapelites of the Lushan area are chemically zoned. Based on petrological and geochemical analyses, quantitative phase equilibria modeling, and traditional geothermobarometry, a clockwise pressure–temperature (P–T) path with a nearly isothermal decompression (ITD) segment was retrieved from the Lushan metapelites. The peak metamorphic conditions of ~770 °C and 11.7 kbar were recorded in sample L93, which reached to the upper amphibolite–granulite facies. High-resolution secondary ion mass spectrometry (SIMS) zircon U–Pb dating demonstrated that the metapelites record a peak or near-peak metamorphic age of ~1.93 Ga. Hornblende 40Ar/39Ar dates from amphibolite illustrated that the Taihua metamorphic complex have cooled to 500–600 °C by ~1.84 Ga. Accordingly, a prolonged Paleoproterozoic continental collision event is supported.