Indications of Placer Gold Deposits Based on River Sediment and Pan Concentrate Analyses in Senggi District, Keerom Regency, Papua

Abstract

Placer gold occurrence is controlled by the interaction between geological processes, sediment transport, and depositional environments. This study assesses the indications of placer gold in the Senggi District, Keerom Regency, Papua, through integrated geological mapping, sedimentological analysis, and heavy mineral characterization. Field investigations involved structural measurements of the Miocene Makats Formation and the collection of three (n = 3) representative stream sediment grab samples (dry weights: 187.51 g, 215.65 g, and 297.70 g). Heavy mineral pan-concentrate analysis was verified under a binocular microscope with a calibrated eyepiece micrometer and micro-stylus malleability tests. A total of 21 fine-grained gold particles (0.125 mm to 0.063 mm) were physically recovered: sample H2.3 yielded 19 grains (mass-normalized abundance of 88.11 grains/kg), H2.4 yielded 2 grains (6.72 grains/kg), and H2.1 showed no gold. Sedimentological and structural results reveal that gold accumulation is highly localized, hydro-structurally trapped by sub-vertically dipping strata (up to 86°) acting as natural bedrock riffles. The probable provenance points to the upstream volcanic rocks of the Auwea Formation. While these preliminary results confirm secondary gold indications, the evidence is insufficient to define an economically significant deposit. The primary significance of this work lies in providing the first formal geological verification in Senggi and demonstrating the methodological value of integrating indigenous community panning knowledge with systematic, mass-normalized laboratory verification. This integrated workflow offers a highly reproducible, low-cost screening template for initial gold exploration in similarly data-scarce and geologically complex tropical settings globally.