An integrated mineral exploration programme in the Takengon tenement, Aceh magmatic arc, north Sumatra

Abstract

A multidisciplinary approach led to the discovery of several gold and base metal occurrences during the 1996–1998 exploration campaign in the Takengon tenement of the Aceh magmatic arc, north Sumatra. Mineralization types included: (i) Au + base metal-bearing quartz veins; (ii) porphyry Cu-style mineralization; (iii) skarn-like Au and Cu-sulphide mineralization; and (iv) granite-hosted molybdenite veins. Regional structural interpretation of synthetic aperture radar and Landsat Thematic Mapper satellite images revealed prominent NNW–SSE and NNE–SSW trending fault zones that cross-cut the region and that were later shown to be spatially related to mineralization. Results from stream sediment analyses delineated several areas that were anomalous in Au±Cu, Pb, Zn, Mo and As, and mineralized bedrock was encountered in some of these areas during a subsequent lithogeochemical survey. An airborne geophysical survey defined a broad region characterized by a low magnetic response with locally high magnetic relief, and moderate to high potassium (K) but low thorium (Th) counts. In addition, the geophysical signals outlined smaller isolated areas that exhibit moderate magnetic anomalies and variable low to high K values. An integrated map with superimposed geological, geochemical and geophysical data demonstrates that results from the various prospecting techniques were generally complementary. Where mineralized and altered rocks occur, the adjacent sediments are metal-bearing (Au±Cu±Pb±As) and the geophysical responses are magnetic, and moderately to highly radioactive (K). In one case in which stream sediments were not auriferous, the discovery of Au- and base-metal-bearing quartz veins was possible through a combined exploration approach consisting of pathfinder elements (As and Pb), elliptical magnetic lineament, moderate to high K anomalies, and regional structures.