Geochemistry, geochronology, and geodynamic implications of mafic‐felsic dykes from the Hadamengou area, north‐western North China Craton

Abstract

Occurrences of multistage dykes provide a critical opportunity to constrain the nature of geological setting in the Daqingshan region during the Late Neoarchean to Middle Palaeoproterozoic. In this article, we present the results of zircon U–Pb ages and whole‐rock geochemical data from mafic‐felsic dykes in the Hadamengou area in order to constrain their ages and tectonic significance. Based on their zircon U–Pb ages, these dykes can be divided into four types: 2.52 Ga metadiabase, 2.45 Ga K‐feldspar granite, 2.44 Ga granitic pegmatite, and 1.99 Ga metagabbro. Geochemically, the 2.52 Ga metadiabase rocks have low SiO2, high MgO, and Na2O/K2O ratios, with enrichment in LILE and depletion in HFSE, which suggests these rocks originated from melting of the lithosphere mantle components metasomatised by subducted slab‐derived fluids. The 2.45 Ga K‐feldspar granite and the 2.44 Ga granitic pegmatite are characterised by high SiO2 and Na2O + K2O contents, low MgO, Ni and Cr contents, and high A/CNK ratios, similar to typical features of strongly peraluminous granites. Additionally, these rocks show a variation of Eu anomalies and strong depletion of Th, U, Nb, and Ta elements, which characteristics are considered as a feature of anatectic origin. The 1.99 Ga metagabbro rocks belong to calc‐alkaline rock series, and contain low SiO2 contents, high MgO, Cr and Ni contents, negative Nb, Ta, and Ti anomalies, and high LILE abundances without Eu anomalies. Geological features of the metagabbro dykes indicate that they are likely derived from partial melting of the subduction‐related metasomatised lithospheric mantle. Combined with the evidence of mafic‐felsic dykes in the Hadamengou and magmatism in the adjacent area, a complex tectonic evolution history during Late Neoarchean to Middle Palaeoproterozoic is presented in the Daqingshan region, which is associated with the amalgamation of micro‐blocks within the North China Craton (NCC), regional extension after cratonisation and subduction of the old ocean between the Yinshan Block and the Ordos Block.