Geothermal implications of the lithosphere’s thermal structure in northern Pakistan

Abstract. Conventional geothermal resources are typically associated with volcanically active plate boundaries, yet collisional orogens can also sustain elevated heat flow through radiogenic enrichment, crustal thickening, and rapid exhumation. Northern Pakistan, encompassing the Himalaya, Kohistan, and Karakoram terranes, hosts numerous hot springs aligned with major fault zones despite the absence of active volcanism. The origin of this anomalous heat remains debated, reflecting the lack of surface heat flow measurements and limited geophysical constraints on the lithosphere. To address this gap, we apply 1D steady-state, 1D transient, and 2D advective–conductive thermal models to the Nanga Parbat Massif (NPM), Kohistan arc, and Karakoram terrane resulting from translation of heat conduction due to exhumation of blocks. Steady-state results show strong dependence of geotherms on crustal radiogenic heat production (RHP): in the NPM, upper-crustal enrichment (4–5 μWm⁻³) yields surface heat flow of 85–120 mW m⁻², whereas Kohistan produces lower values (50–85 mW m⁻²) due to its mafic-dominated crust. Karakoram yields intermediate heat flow (65–103 mW m⁻²), with RHP concentrated in the batholith and metamorphic complexes. ID transient exhumation models demonstrate that uplift rates of 2–3 mm y⁻¹ in the NPM can further amplify geotherms, producing surface heat flow up to 220–250 mW m⁻² and inverting deep geotherms at 20 km when RHP is high. Two-dimensional thermal simulations capture the combined effects of radiogenic enrichment, exhumation, and rugged topography. Isotherms are compressed beneath valleys and expanded beneath peaks, with the strongest thermal anomalies localized in the NPM and Karakoram. Surface heat flow patterns reflect these contrasts, ranging from ~120 mW m⁻² (moderate scenarios) to nearly 180 mW m⁻² (high exhumation). Crustal differentiation indices further indicate strong upper-crustal enrichment in the NPM and Karakoram, indicating the redistribution of heat-producing elements during crustal thickening and partial melting. The models demonstrate that the region can sustain anomalously high heat flow through the interplay of RHP, exhumation, and crustal differentiation. For northern Pakistan, this provides a robust geoscientific basis for understanding the origin of widespread hydrothermal activity and underscores the region’s significant geothermal potential, positioning it as a promising target for future exploration and sustainable energy development.