The Himalaya, Kohistan, and Karakoram ranges comprise Proterozoic to Cenozoic crystalline complexes exposed in northern Pakistan. Numerous hot springs in the area indicate high subsurface temperatures, prompting a need to evaluate the local contribution of radiogenic heat to the general orogenic-related elevated geothermal gradients. The current study employed a portable gamma spectrometer to estimate the in-situ radiogenic heat production in the Nanga Parbat Massif, Kohistan–Ladakh batholith, and the Karakoram batholith. Heat production in the Nanga Parbat Massif is high, with a range from 0.2 to 10.8 µWm−3 and mean values of 4.6 ± 2.5 and 5.9 ± 1.9 µWm−3 for gneisses and granites, respectively. By contrast, the heat production is low in the Kohistan–Ladakh batholith, ranging from 0.1 to 3.1 µWm−3, with the highest mean of 2.0 ± 0.5 µWm−3 in granites. The Karakoram batholith shows a large variation in heat production, with values ranging from 0.4 to 20.3 µWm−3 and the highest mean of 8.4 ± 8.3 µWm−3 in granites. The in-situ radiogenic heat production values vary in different ranges and represent considerably higher values than those previously used for the thermal modeling of Himalaya. A conductive 1D thermal model suggests 93–108 °C hotter geotherms, respectively, at 10 and 20 km depths due to the thick heat-producing layer in the upper crust, resulting in a surface heat flow of 103 mWm−2. The present study provides first-order radiogenic heat production constraints for developing a thermal model for geothermal assessment.

中文翻译：

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原位伽马能谱法在巴基斯坦北部喜马拉雅山西部、科希斯坦和喀喇昆仑地区放射性产热估算中的应用

喜马拉雅山脉、科希斯坦山脉和喀喇昆仑山脉由暴露在巴基斯坦北部的元古代至新生代晶体杂岩组成。该地区的许多温泉表明地下温度很高，因此需要评估放射热对一般造山相关的地温梯度升高的局部贡献。目前的研究采用便携式伽马能谱仪来估计南迦帕尔巴特地块、科希斯坦-拉达克岩基和喀喇昆仑岩基的原位放射热产生量。南迦帕尔巴特地块的产热量很高，片麻岩和花岗岩的产热范围为 0.2 至 10.8 µWm−3，平均值分别为 4.6 ± 2.5 和 5.9 ± 1.9 µWm−3。相比之下，科希斯坦-拉达克岩基的产热量较低，范围为 0.1 至 3.1 µWm−3，花岗岩中的最高平均值为 2.0 ± 0.5 µWm−3。喀喇昆仑岩基的产热量变化很大，其值范围为 0.4 至 20.3 µWm−3，花岗岩中的最高平均值为 8.4 ± 8.3 µWm−3。现场放射热产生值在不同范围内变化，并且比以前用于喜马拉雅热模拟的值要高得多。传导一维热模型表明，由于上地壳较厚的产热层，10 公里和 20 公里深处的地温温度分别为 93–108 °C，导致表面热流为 103 mWm−2。本研究为开发地热评估热模型提供了一阶放射热产生约束。