A new 1.32 Ga Tianshui mafic sill in the Liaodong area and its relations to the Yanliao large igneous province in the northern North China Craton

• A Mesoproterozoic (∼1.32 Ga) mafic sill within host limestone layers is identified in Liaodong area. • The 1.32 Ga Tianshui mafic sill shows similar geochemical features with the Yanliao LIP. • The 1.32 Ga mafic sill may indicate the existence of the Mesoproterozoic strata in Liaodong area. A new 1.32 Ga Tianshui mafic sill was identified in the Liaodong area, which enlarges the scale of the Yanliao large igneous province (LIP, extending >600 km) in the North China Craton. It intrudes concordantly into limestone layers and is overlain by Neoproterozoic strata. SIMS baddeleyite Pb-Pb dating on two coarse-grained gabbros yields weighted mean 207 Pb/ 206 Pb ages of 1324 ± 2 Ma (n = 20, MSDW = 1.5) and 1326 ± 5 Ma (n = 9, MSDW = 1.3), similar to those of mafic sills in the Yanliao LIP. The Tianshui mafic sill shows a similar E-MORB geochemical character as the mafic sills in the Yanliao LIP, including tholeiitic composition, enriched light rare earth elements (La/Yb N = 2.45–3.77), and large ion lithophile elements, but depleted high field strength elements, positive baddeleyite εHf t values of 3.59–10.96, with a peak of 6.07, and negative whole-rock εNdt values of −1.8 to −0.6, with an average of −1.3, indicative of an enriched mantle source. The host limestone layers are 800 m thick and possibly contemporaneous with the Mesoproterozoic Gaoyuzhuang Formation of the Liaoxi area. The 1.32 Ga Yanliao mafic sills underwent extensive crystallization differentiation controlled by olivine, clinopyroxene, and plagioclase. They were generated at a high primary temperature of ∼1550 °C and crystallized at ∼1140 °C at 0.24 kbar, which could be related to the mantle plume magmatism.