Controlling factors of granite chemical diversity and implications for crustal evolution: A case of migmatites from the Daqingshan Complex, North China Craton Available to Purchase

Crustal evolution and the genesis of granite are closely linked to anatexis in the lower or middle crust, followed by the ascent of granitic magmas to the upper crust. The Daqingshan complex in the North China Craton is characterized by the extensive development of Precambrian migmatites and granites resulting from crustal anatexis. Understanding the controls on the geochemical diversity of these granitic magmas during their formation and extraction would enhance our understanding of crustal evolution from the late Neoarchean to early Proterozoic. In this study, we investigated the diverse types of migmatite and granitic rock related to partial melting in the Daqingshan complex using systematic petrographic, whole-rock geochemical and Sr−Nd isotopic compositions, and zircon U−Pb−Hf isotope analyses. Our new results, combined with data from the literature, allow reconstruction of the complete process of magma formation, extraction, and evolution for migmatites in the study area. The following new insights are obtained. (1) The Daqingshan migmatites record two main periods of metamorphism (at ca. 2.45 Ga and ca. 2.37 Ga) and one period of anatexis (at ca. 2.37 Ga). (2) The migmatites originated from the Daqingshan supracrustal rocks via dehydration melting of biotite. (3) During magma extraction, decomposition of the magma was controlled predominantly by the entrainment of residuum; incongruent melting of plagioclase and its early-stage crystallization and compaction led to the fractionation of plagioclase and K-feldspar within the in situ to semi in situ magmatic accumulation site. (4) Factors such as protolith composition, rock and mineral melting mechanisms, residuum entrainment, fractional crystallization, compaction, and the assimilation of surrounding rocks played crucial roles from initial melting to magmatic evolution and collectively contributed to the chemical diversity of migmatites and granitoids in the southwestern margin of the Daqingshan complex. (5) From the late Neoarchean to early Paleoproterozoic, substantial fractionation of plagioclase and K-feldspar during dehydration melting of metasedimentary rocks can resulted in the efficient migration of K-rich melt from the anatectic source. This migration may have provided the source magma for K-rich granite in the upper crust and contributed to the differentiation of continental crust from Plagioclase-rich to K-feldspar-rich components.