Himalayan Geology, Vol. 44 (2), 2023, pp. 36-56, Printed in India

Structural Controlled Metallic Mineralization in Lower Swat, NW Pakistan

MUHAMMAD IDREES¹, ASGHAR ALI², NIMATULLAH KHATTAK¹, RAFIQUE AHMAD³*, ASAD KHAN⁴

¹National Centre of Excellence in Geology, University of Peshawar, Khyber Pakhtunkhwa 25120, Pakistan

²Department of Geology, University of Peshawar, Khyber Pakhtunkhwa 25120, Pakistan

³Department of Geology, Bacha Khan University Charsadda, Khyber Pakhtunkhwa, 24420, Pakistan

⁴Department of Geology, FATA University, Akhurwal, Darra Adam Khel, District Kohat, Pakistan

*Email (Corresponding author): rafique.ahmad@bkuc.edu.pk

Abstract: The study presents the results of structural, hydrothermal, magmatic, and metamorphic control on metallic mineralization across the Kashala syncline, Loe Sar Dome, Kotah Dome, and the Main Mantle thrust mélange zone in Lower Swat, NW Pakistan. Lower Swat rocks preserved three well defined D₁, D₂ and D₃ deformation and metamorphic events. S₁ foliations related to D₁, preserved in garnet are truncated by the main S₂ crenulation cleavage. D₂ related S₂ and L²₂ that dominates the Swat valley predated the Kotah and Loe Sar domes/metamorphic core complexes culmination because the latter controls the dip pattern of the D₂ related structures. D₃ and L³₂ intersection lineation microscopically and mesoscopically overprint D₂. These multiple structures are constrained to gain insight into the structural traps in the form of shear zones, faults, boudinage necks, fold limbs, saddle reefs, contacts and veins to drop fluids laden Au, Ag, Cd, Co, Cr, Ni, Zn, Pb and Cu metallic ores. These ores are noticed along four zones of concentration. The Marghazar Concentration Zone 2 lies at the Nawagai Overturned Anticline saddle reef, the Marghazar Concentration Zone 2, lies at the Ilam Overturned Syncline. Similarly, Intrusive contacts of the Tertiary Swat Tourmaline Granite (STG) with the Marghazar Formation and Swat Granitic Gneisses (SGG) contain high concentration of Cr, Ni, Zn, and Cu with moderate Ag, Cd, Pb and Co. A quartz vein at the Ilam Overturned Syncline and a mineralized zone south of the Loe Sar Dome (LSD) at the Ghundai anticline contain the highest concentration of gold. Metals data collected from the shear zone within the Marghazar Formation is markedly depleted in Co, Zn, Cr, Ni, Cu and Pb as compared to the average concentration of these metals in the remaining Marghazar Formation.

Keywords: Multiple deformed-metamorphosed rocks,Micro‒mesoscopic structures,Kotah and Loe Sar domes, Metals concentration zones, MMT Melange zone