Crustal Thickness Inversion From Magmatic Geochemistry Reveals Spatiotemporal Evolution and Two‐Stage Uplift of the Iranian Plateau

The Cenozoic topographic growth of the Iranian Plateau, situated at the Arabia‐Eurasia collision front, provides insights into continental collision dynamics. However, the relative contributions of tectonic shortening versus deep mantle processes to crustal thickening remain debated because systematic quantitative constraints on paleo‐crustal thickness evolution are limited. Here, from a compiled data set of 2,525 Eocene to Quaternary volcanic rocks across the Alborz Magmatic Belt and Urumieh‐Dokhtar Magmatic Arc, we utilized 1,198 rigorously filtered samples to reconstruct crustal thickness since ∼56 Ma. Using Sr/Y and (La/Yb) N ratios as pressure‐sensitive proxies, we propose a two‐stage model of crustal thickening and surface uplift. Results indicate a relatively thin Eocene crust (∼37 km), corresponding to near‐sea‐level paleotopography. During the Oligocene–Miocene, continental collision drove diachronous, northwest‐to‐southeast crustal thickening. This established a unified thick crust (∼54 km) and regional isostatic uplift of 1.5–3.2 km, representing the first stage of primary tectonic shortening. Since the Pliocene (<5 Ma), localized secondary uplift has occurred in northwestern Iran and central Alborz, resulting in paleoelevation approaching ∼4 km. This secondary uplift was driven by deep geodynamic processes (slab break‐off and lithospheric delamination) superimposed on the Arabia‐Eurasia convergence. This two‐stage model is consistent with two discrete episodes of accelerated exhumation recorded by thermochronological data during the Oligocene and at 6–3 Ma. Our quantitative evidence supports the plateau's role as a topographic barrier enhancing the Miocene South Asian Summer Monsoon. This study highlights the Iranian Plateau's significance for linking deep geodynamics, crustal thickening, and surface‐environmental change.