Petrographic characterization and classification of alteration zones using a spreadsheet-based system in the Kingking Porphyry Cu-Au Deposit, Barangay Kingking, Pantukan, Davao de Oro

University of Southeastern Philippines, BS in Geology Program, Davao City, Philippines

Abstract

Porphyry copper-gold deposits (PCDs) are globally significant sources of copper, molybdenum, and gold, characterized by hydrothermal alteration zoning that constrains ore-forming processes and assists mineral exploration. Despite the well-established Lowell-Guilbert model, classification of alteration sub-facies remains subjective, reliant on qualitative petrographic observations. This study introduces a spreadsheet-based classification system that applies point-count modal data to automate subzone assignment in the Kingking Cu-Au deposit, Pantukan, Davao de Oro. Twenty rock samples were collected, with eight representative thin sections subjected to 500-point modal counts using transmitted and reflected light petrography. Classification thresholds, informed by global porphyry models (Lowell & Guilbert, 1970; Sillitoe, 2010; Seedorff et al., 2005) and site-specific petrography, were encoded into a VBA-driven spreadsheet. Results delineate potassic (biotite-rich and K-feldspar-rich), phyllic (quartz-sericite-clay and sericite-chlorite-clay), and propylitic (epidote-and chlorite-dominant) subzones. Overprinting textures and mineral assemblages demonstrate a classic porphyry architecture, concordant with independent descriptions of the Kingking deposit. The approach improves reproducibility and transparency in petrographic classification while highlighting the need for calibration across deposits.