Linking deep-time magmatism to present-day lithospheric architecture through isotopic and elemental mapping

Probing the deep lithosphere remains a key objective in earth sciences. The present-day lithosphere architecture is a terminal, time-integrated image shaped by long-term geological processes, among which magmatism plays a crucial role. Consequently, a causal relation exists between deep-time magmatism and present-day lithospheric architecture. This study employs multi-proxy isotopic and elemental mapping of Late Carboniferous to Middle Permian magmatic rocks in West Tianshan, SW Central Asian Orogenic Belt. The mapping unravels two distinct lithospheric domains, i.e., an isotopically depleted domain in the north and an isotopically enriched domain in the south. Seismic and gravity data suggest significant differences in geophysical properties across different domains. By integrating phase equilibrium modeling, we further indicate that the present-day geophysical disparities can be attributed to deep-time magmatism involving differential mantle sources and infracrustal differentiation. The lower crust of the northern part was built by magmatic processes starting from intermediate magmas ultimately derived from a subduction-modified mantle. In contrast, the lower crust of the southern part was constructed through the interaction between ancient crust-metasomatized mantle-derived magmas and supracrustal relaminant. Our findings suggest a novel methodological approach for utilizing geochemical data from deep-time magmatic rocks to decipher present-day deep lithospheric architecture.