Spatiotemporal Variability of the Tibetan Plateau Uplift Revealed by Paleo‐Crustal Thickness Estimates From Igneous Rock Geochemistry

The tectonic evolution and growth of the Tibetan Plateau are closely linked to the India‐Asia collision. However, the timing and patterns of crustal thickening and surface uplift remain debated. Recent studies have calibrated the geochemical composition of magmatic rocks formed in convergent settings to estimate crustal thickness at the time of magmatism. This study applies whole‐rock trace‐element proxies from subduction settings and our recalibrations of existing proxies for collisional settings to quantify crustal thickness variations across the plateau. The results from different proxies show a consistent trend. Crustal thickness estimates from subduction‐related Sr/Y‐La/Yb proxies best match the current Moho depth and perform well in collisional settings, providing robust constraints for reconstructing crustal thickness in the past. Our findings reveal spatial and temporal variations in crustal thickening, which may reflect heterogeneous uplift across the Tibetan Plateau. From 60 to 45 Ma, crustal thickening and uplift mainly occurred in the eastern Gangdese and northern Qiangtang. Between ∼45 and 30 Ma, thickening and uplift extended to the central and southeastern plateau. The plateau had expanded both northward and southward, with thickening reaching the northern plateau and western Gangdese by ∼15 Ma. In the eastern Pamir, crustal thickness had reached present extent by ∼12–10 Ma. The mismatch between our estimated thick crust in the past and present thin crust in the southeastern plateau suggests lithospheric delamination and crustal thinning.