A ca. 1.33 Ga mafic dyke identified from the Liaodong Peninsula, northeastern North China Craton: Implications for eastward extension of the Yanliao large igneous province

Abstract

Diabase sills (1.33–1.30 Ga) in the northern North China Craton (NCC) represent a large igneous province (Yanliao LIP) extending > 600 km from west to east. The Yanliao LIP in the NCC and the Derim Derim–Galiwinku LIP in Northern Australian Craton (NAC) are interpreted as fragmented parts of the same LIP, supporting a close connection between the northeastern margin of the NCC and the northern margin of the NAC during the Mesoproterozoic at ca. 1.32 Ga. However, the eastern edge and original size of the Yanliao LIP are less-constrained. Here, we present geochronological and geochemical data of a newly identified ca. 1.33 Ga dolerite dyke intruding the Paleoproterozoic Liaohe Group in the Liaodong Peninsula, northeastern NCC, and conclude a substantially broader extent of the Yanliao LIP than previously proposed. The dyke shows ophitic textures and contains mainly plagioclase, clinopyroxene and hornblende. LA–ICP–MS U–Pb dating of zircons from four dolerite samples yields a mean age of ∼1.33 Ga. The samples have 48.24–49.77 wt% SiO2, 12.41–13.75 wt% Fe2O3T, 4.61–7.18 wt% MgO and 2.54–3.51 wt% total alkalis (K2O + Na2O), exhibiting tholeiitic basalt compositions. In addition, the dolerites feature enrichments in light rare earth elements ((La/Yb)N = 3.00–3.61) and large ion lithophile elements (e.g., Rb and Pb) but depletions in some high field strength elements (e.g., Nb and Ta), with affinities to within-plate basalts. The dolerite samples have εNd(t) values of –0.6 to +1.0, Th/Nb (0.40–0.45) and Pb/Nb (0.49–1.59) ratios distinctly higher than those of E-MORB and OIB, consistent with derivation from a metasomatized subcontinental lithospheric mantle with insignificant crustal contamination. Our work and available investigations reveal spatial changes in the emplacement style of mafic sills in the central and mafic dykes in the eastern and western parts of the updated Yanliao LIP. The recognition of the ca. 1.33 Ga dolerite dyke in the Liaodong Peninsula reveals ∼500 km eastward extension for the Yanliao LIP to the northeastern margin of the NCC, which further supports the close link between the NCC and the NAC.