Band processing of Landsat 8-OLI multi-spectral images as a tool for delineating alteration zones associated with porphyry prospects: A case from Suyoc, Benguet, Philippines

Abstract

The Mankayan Mineral District in Luzon is marked by several porphyry and epithermal mineralizations. The possibility of blind porphyry mineralization in Mangga, Basig, and Palidan was forwarded based on the results of recent ground magnetic surveys in Suyoc, Mankayan, Benguet. These areas exhibited the diagnostic magnetic anomaly patterns expected of porphyry copper deposits. This signature, a magnetic core surrounded by a non-magnetic rim, is due to the alteration haloes common to porphyry systems. The magnetic core corresponds to the potassic zone dominated by iron-oxide-bearing minerals (e.g., magnetite). Meanwhile, the abundance of non-magnetic clay minerals at the periphery of the mineralized region corresponds to propylitic-argillic alteration zones. Delineation of alteration zones using remote sensing was done to further support the suggested mineralization prospects. Mixture tuned matched filtering (MTMF) was carried out to reduce the effects of vegetation cover from Landsat 8 data. Principal Components Analysis (PCA) was applied to generate bands exploiting the greatest difference between the clay and magnetite alterations with background earth materials. A classified composite map depicts the altered regions. The three sites previously identified from magnetic anomalies also display the expected alterations. Another prospect in the Lapangan area is being proposed based on magnetic anomalies and mapped alterations.