Summary:
The Poboya Prospect lies along the North Northwest - South Southeast Palu-Koro Fault Zone in the central part of the West Sulawesi Arc. The geology of the area consists of the Palu Metamorphic Complex overlain by the Paleogene-Neogene Tinombo Formation of volcanosedimentary rocks, the Celebes Molasse sediment, and Late Cenozoic granitic rocks.
Textures of quartz-carbonate veins in the River Reef Zone include massive micro-comb, moss, colloform, crustiform, mosaic, feathery, flamboyant, lattice bladed, ghost bladed, parallel bladed, and saccharoidal textures representing primary growth, recrystallization, and replacement.
River Reef Zone, Hill Reef Zone 1, and Hill Reef Zone 2 extend in a NW-SE strike, along with the occurrences of schist unit, biotite gneiss, granite, molasse, and alluvium sediments.
From the vein zone outward, hydrothermal alteration assemblages are chlorite-illite-chlorite/smectite-illite/smectite-calcite, chlorite-epidote-calcite-illite/smectitesmectite, and chlorite-illite/smectite-smectite.
The veins observed in the RRZ have an individual thickness of less than 1 cm up to approximately 10 m. The veins are mainly composed of quartz and calcite with variable grain size and mineral habits. Quartz was observed as cryptocrystalline [hereafter referred to as chalcedony], microcrystalline, and crystalline in terms of its size, while calcite was observed as platy and irregular, coarse grains.