Control mechanism of Late Jurassic-Early Cretaceous magmatic activities on helium accumulation in the northern Ordos Basin

By integrating helium volume fraction data from gas-bearing strata with geochemical and geochronological analyses of peripheral magmatic rocks, we systematically examined the spatiotemporal coupling between magmatism and helium distribution. A dynamic model was established to elucidate the influence of magmatic activity on helium enrichment, emphasizing key factors including helium sources, migration pathways, reservoir conditions, and accumulation episodes. This study focuses on investigating the controlling effects of Late Jurassic-Early Cretaceous magmatic activity on helium enrichment, migration, and preservation in the Ordos Basin, aiming to provide theoretical foundations and innovative insights for helium resource exploration. Significant helium enrichment was identified in the northern Ordos Basin, particularly in the Qingyang, Yichuan, Dongsheng, and Shixi areas, where average helium fractions exceed 0.09%. The spatial pattern exhibits an annular differentiation trend, transitioning from low-value zones in sedimentary depressions to high-value belts along the basin margins. Magmatic activity in the basin periphery (160~100 Ma, Late Jurassic-Early Cretaceous) demonstrates spatiotemporal synchronization with helium-rich zones and critical accumulation episodes. This correlation suggests that mantle-derived magma upwelling likely enhanced helium enrichment through thermo-fluid-mechanical coupling processes. Helium enrichment in the Ordos Basin is governed by multi-scale effects of Late Mesozoic mantle-derived magmatism, manifesting as systematic regulation of helium source activation, migration channel development, and trap formation by magmatic thermal events. Accordingly, we propose that helium-rich reservoir exploration should prioritize areas surrounding Late Jurassic-Early Cretaceous pluton emplacement centers, adopting a target prioritization strategy of "radiating outward from pluton cores" to identify favorable gas reservoirs.