Clockwise P-T-t path for Paleoproterozoic metamorphism in the Huoqiu Metamorphic Complex of the southeastern North China Craton

Abstract

The Huoqiu Metamorphic Complex in the southeastern part of the North China Craton (NCC) is mainly composed of a meta-sedimentary rock series with minor meta-granitoids. The meta-sedimentary rocks contain metapelites, leptynite, amphibolite, marble, and banded iron formations (BIFs). The ages of the protoliths of the metapelites were constrained at 2.75–1.84 Ga according to detrital and metamorphic zircon ages. Based on microstructural observations, geochemical analyses, conventional thermobarometry, and phase equilibria modeling, clockwise pressure–temperature (P–T) paths with near isothermal decompression (ITD) segments were constructed from the metapelites. Peak metamorphic conditions of ~590 °C and 9.4–9.7 kbar were recorded in samples 20190408-1 and 20190408-3, which are ascribed to the lower amphibolite facies. Monazite laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb data from the Huoqiu metapelites indicate that the regional peak metamorphism of the Huoqiu area likely occurred at ~1.82–1.83 Ga. The P–T paths retrieved from the Huoqiu Metamorphic Complex are similar to high-grade metamorphic rocks in the northern, middle, and southern sections of the Jiao-Liao-Ji/Jiaoliao Mobile Belt. Based on these observations, the Huoqiu Metamorphic Complex can be considered part of the Jiao-Liao-Ji/Jiaoliao Mobile Belt, which records a complex collision event during the late Paleoproterozoic.