Magmatism and thermal effect of the Late Paleoproterozoic layered complex in the Jining terrane, North China Craton: Evidence from magmatic cooling duration and crust-mantle interaction

Abstract

The Paleoproterozoic Khondalite Belt from the northwestern North China Craton (NCC) is characterized by a wide distribution of high-temperature/ultrahigh-temperature (UHT) metamorphism and extensive magmatic events in its eastern segment, the Jining terrane. Although it has been proven that UHT metamorphism is related to large-scale thermal perturbation at the crustal level, the ultimate heat source has been kept unclear and the reliable interrelationship between the formation of UHT metamorphism and mantle-derived magmatism has not been established yet. We report data of two-layered complexes emplaced in duration over 100 Ma, as the candidates of the heat source of the UHT metamorphism. The samples include 1929 ± 23 Ma Sanchakou amphibole-gabbro (ZK0-3) and 1824 ± 2 Ma Hulu norite-gabbro(HL1517). Based on the published geochronological data of basic intrusive rocks in the Jining terrane, it is found that the Late Paleoproterozoic magmatism appears as two stages of ∼1.95 Ga (M1) and ∼1.85 Ga (M2). We calculated that the duration of M1-magmatism can reach ∼71 Myr through Monte Carlo simulation. The sample ZK0-3 is formed in M1-magmatism, coupled with the peak period of metamorphism and the slow cooling process of UHT pelitic granulite/gneiss. We used the “Magma Chamber Simulator (MCS_PhaseEQ_2019AC)” to simulate the genesis of these basic intrusive rocks. It is found that they have experienced the magmatic process of assimilationand fractional crystallizationunder energy constraints(EC-AFC). The augite, pargasite, and zircon record the crystallization temperatures during the slow cooling process of magma. Therefore, mantle-derived magmatism might have supplied heat to generate the UHT metamorphism in the Jining terrane.