Long duration of Permian mafic intrusions in the northern Tarim Basin (northwestern China) and implications for the geodynamic evolution of the Tarim large igneous province

The mafic intrusions represent one of the key factors contributing to an improved understanding of the characteristics of the Tarim large igneous province (LIP) of northwestern China and the geodynamic processes. The Awati-Manjar transition zone in the northern Tarim Basin contains extensive mafic intrusions, predominantly composed of diabases, making it a critical region for strengthening our understanding of the evolution and dynamics of the Tarim LIP. In this paper, we conducted an integrated analysis of the newly identified diabase intrusions in the Awati-Manjar transition zone of the northern Tarim Basin, including seismic and drilling data interpretation, petrographic observations, U-Pb isotopic dating, and whole-rock elemental and Sr-Nd isotopic analyses. Seismic and drilling data reveal two distinct occurrence models for the diabase intrusions: sill-shaped and saucer-shaped. Apatite U-Pb dating indicates that the diabases range in age from ca. 308 Ma to 266 Ma, with two distinguishable emplacement episodes identified within analytical uncertainty of 308−299 Ma and 286−266 Ma. The diabases from the earlier episode are sparsely distributed across the study area, whereas those from the later episode are widespread and constitute the majority of the diabase intrusions in the region. Geochemically, the diabases belong to an alkaline, sodium-rich, and high-Ti series. They exhibit consistent chondrite-normalized rare earth element and primitive mantle−normalized trace element patterns, marked by pronounced enrichment in light rare earth elements and highly incompatible elements, respectively. Notably, no Eu anomaly is observed, while distinct positive anomalies are present at Ba and Pb. Whole-rock Sr-Nd isotopic analyses reveal relatively depleted signatures, with (87Sr/86Sr)i ratios ranging from 0.7049 to 0.7074 and εNd(t) values from +0.60 to +2.75. Both elemental and isotopic data indicate that the diabases are compositionally analogous to oceanic-island basalt, implying a genetic link to a mantle plume. That is, they were likely formed through partial melting of a mantle plume source, followed by variable degrees of crustal assimilation and fractional crystallization. More significantly, our newly acquired geological data reveal that the mafic intrusions within the Tarim LIP actually exhibit a longer emplacement duration (spanning the entire lifespan of the Tarim LIP) and a broader spatial distribution (extending beyond the craton margins into its interior) than previously considered. To account for these observed characteristics, a new integrated crust-mantle interaction model has been developed.