Curie Point Depth Map for Western Afghanistan Deduced from the Analysis of Aeromagnetic Data

Abstract

The geologic setting of Afghanistan has the potential to contain natural resources such as mineral and petroleum as well as geothermal resources. Although, much of the country’s potential remains unknown due to lack in exploration. In that regards, a joint project between USGS and Afghanistan Geological Survey (AGS) to implement aeromagnetic survey over the country. In the present work, aeromagnetic data will be used to estimate the Curie Point Depth (CPD) in order to evaluate the geothermal resources within the country. CPD is an isothermal surface at which magnetic minerals lose their magnetization (580 oC). In order to achieve this goal, spectral analysis technique will be used for the aeromagnetic data to estimate the CPD and linked them to the geothermal activities in Afghanistan where there are for well know geothermal fields spreading out in the western portion of the country. The results show that, there are four regions can be characterized by CPD: 1) Shallow curie depths (~16 – 21 km) are located at Helmand basin. 2) Intermediate curie depths (~21 – 27 km) are located at south of Helmand basin (Baluchistan geothermal field associated with carbonatitic post-volcanic processes) and southeast of Helmand basin (Helmand-Arghandab geothermal field associated with Arghandab granitoid massifs). 3) Deep curie depths (~25 – 35 km) are located at Farad block (Farahrud geothermal field associated with Pasavand deep-seated fault and fracture system) and Helmand block. 4) Very deep curie depths (~35 – 40 km) are located at western part of north Afghanistan platform along the Herat fault system. Our results imply geothermal gradient ranging from 14.50 oC/km to 36.25 oC/km and heat-flow values ranging from 36.25 to 90 mW/m2 for the study area. The hot springs discharge mainly along deep-seated major faults bordering the tectonic blocks in Afghanistan. The deduced thermal structure in western Afghanistan has relationship with the collision of the continental Indian and Eurasian plates. The shallow CPDs values are related to the Kandahar arc.