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Heat-producing granitoids of North Pakistan as potential geothermal prospects

Subject Area Geology
Term from 2021 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 494793953
 
Final Report Year 2024

Final Report Abstract

This project was aimed at establishing a scientific basis for geothermal projects in the high mountains of northern Pakistan where numerous hot springs indicate elevated heat flow and, locally, some of the highest active exhumation rates on earth have been inferred. The size of the area, its rugged topography, limited road infrastructure, and harsh climate hinder largescale exploration on the ground. We found that remote sensing of surface thermal anomalies from spectral data alone is not a promising technique, but ground truthing suggests that a combination with remote mapping of lineament density and hydrothermal alteration from mineral spectra constrains promising areas reasonably well. We have demonstrated by in-situ and laboratory analyses that granitoids and gneisses commonly exposed in the western Himalaya and Karakorum have elevated contents of radiogenic elements and, hence, high heat production. Modelling shows that radiogenic heat production substantially contributes to local and regional geothermal gradients and should be considered in geothermal exploration. These bedrock-related effects on geothermal gradients are of similar magnitude but spatially more extensive than those caused by fast exhumation. Modelling also suggests that strong enrichment of radiogenic elements and high heat production must be limited to the upper crust. Using measured surface values for entire crustal profiles in the models results in excessive surface heat flow and unrealistic geothermal gradients. The correlation of hot springs with increased fracture density and alteration indicative of exhumed hydrothermal systems strongly suggests an important role of deeply circulating fluids in creating local heat anomalies. Our multi-scale and multi-method study has revealed the Nanga Parbat region and central-eastern Karakoram as potential geothermal target regions with hydrothermal and hot-dry rock geothermal play types that warrant more detailed and site-specific investigations. Our work provides new key data for understanding the region’s geothermal regime on a larger scale and lays the groundwork for future geothermal exploration. The execution of this project has benefitted enormously from combining a DAAD scholarship to an early career scientist with a modest amount of additional DFG funding that supported field work, sampling, sample transport and laboratory analyses.

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