Geochemical and Petrographic Analysis of Metamorphic Rocks in Aliabad Mountain, Kabul Block, Afghanistan

Abstract

The Kabul Block, a key geological feature in Afghanistan, comprises sedimentary, metamorphic, and volcanic rocks, including those of Aliabad Mountain. Despite its significance, Aliabad Mountain has received limited geochemical study. This research characterizes the lithological variations, chemical composition, and mineralogical properties of its metamorphic rocks to elucidate their protolith nature and tectonothermal history. X-ray fluorescence (XRF) and petrographic analyses were conducted on 15 rock samples collected from five localities across Aliabad Mountain. Samples were powdered, pelletized, and analyzed using a calibrated XRF spectrometer. Results indicate a silicate-rich composition, with SiO₂ ranging from 60–72 wt%. One lithological unit shows elevated Fe (5.0–6.5 wt%), Ti (0.3–0.5 wt%), Mn (0.05–0.08 wt%), and Zr (0.015–0.02 wt%), suggesting a mafic or hydrothermally altered protolith. Another unit is enriched in phosphorus (0.1–0.5 wt%) and contains apatite and trace Cu (0.001–0.003 wt%), indicating a felsic, phosphate-bearing origin. Ni (0.002–0.004 wt%) and Co (0.008–0.012 wt%) were detected only in the oxide-rich lithology, while Au, Ag, Pd, Nb, and W were below detection limits, ruling out metallic mineralization. Petrographic analysis reveals biotite gneisses and amphibolites with sedimentary textures, supporting a paragneiss origin. These findings enhance understanding of the Proterozoic Kabul Block’s geological evolution and suggest potential for construction material sourcing due to the rocks’ stable mineralogy, despite limited economic mineral potential