The geology and mineralisation of the area around the disused Mangani gold mine have been investigated, in order to discover the m9de of formation of the deposits. 2 Mangani lies in an eastern, inactive part of the dextral Sumatra Fault System (SFS), which formed as a result of oblique subduction of the Indian plate under the Asian plate. Mineralisation occurs in or near a graben, which in the NE joins with an active strand of the SFS. Veins are located in faults related to movement along the SFS, and to extensional movement in the Mangani Graben. The geology of the area consists of marginal facies of the Central Sumatra Basin in the north, and a sedimentary breccia (Brani conglomerate) to the south. Basic to acid volcanics fill the graben, and lie on top of the sedimentary units, some volcanism being post mineralisation. Small intrusive bodies may be the exposed parts of a larger acid pluton. Geological mapping and stream and soil geochemistry have resulted in the discovery of several new mineralised areas. One area has been examined in detail using soil geochemistry and geophysics (VLF, S.P, Turam, magnetics). The most important discovery has been a large area of completely unexposed lead/zinc mineralisation. The suitability of the different exploration methods for use in tropical mountain terrain is discussed. Mineralogical examination and ~hemical analysis of specimens has revealed a complex history of fault controlled mineralisation. The vein mineralisation can be divided into a number of different groups, partly related to the geographical location and host rock type. Vertical zonation in veins is considered to be responsible for the spatial zonation. Other mines in Sumatra appear to be similar to Mangani (hosted in volcanics, in faults related to the SFS, with s-imilar suites of minerals), and a model for the formation for such deposits is proposed