Massive sulphide deposits and their possible significance to other ores in Southeast Asia

Broad and multi-faceted studies during the past 15 years have shown that all massive base metal sulphide deposits were formed on the sea floor by chemical precipitation from discharged metalliferous hydrothermal fluids. The fluids were generated within the sub-area floor rock column by reactions between connate, or convectively circulated sea water and the rocks themselves. Differing rock columns in various tectono-stratigraphic environments give rise to differing fluids and varieties ofdeposits. Nevertheless, because of their common genetic process, all massive sulphides share a set of common identifying primary geologic characteristics. Later metamorphism of various ranks, types and episodes inevitably reshapes, partially to completely, all these primary characteristics including fundamental geochemical relationships. Many of the geological characteristics of the massive base metal sulphides are duplicated in certain barite, manganese, iron-tin, iron skarn and base metal deposits of the central and eastern belts in Peninsular Malaysia, and their extensions northward and southward into Thailand and Indonesia. Some of the characteristics may also be present in the podiform chromite deposits of the Phillipines. These similarities suggest that many of the genetic and metamorphic processes involved in massive sulphide formation may have also contributed to formation of these southeast Asian deposits. Thus, the geology of massive sulphides may be significant to, and might enhance our understanding of such enigmatic deposits as complex tin-iron and podiform chromite ores. Some of the problems of these ores, whose genesis has been traditionally explained by concepts derived from other, less enigmatic tin and chromite ores, might be elucidated by an approach utilizing the concepts, principles and relationships established in studies of the massive sulphide deposits. Objective studies to determine the extent to which massive sulphide geology is applicable to these ores should be undertaken.