CRUSTAL EVOLUTION OF EARTH AND ITS CONTROL ON GLOBAL SCALE OROGENIC GOLD METALLOGENY

Crustal scale evolutionary processes are operating right from the very beginning of the evolutionary history of the earth. The implication of these processes in terms of crust mantle interaction has been the subject of research and discussion and has gained considerable importance among the geoscientists. However their implications on global scale metallogeny have been an issue of serious debate among the geoscientist for last few decades. The role of crustal evolution is being exclusively studied for their metallogenetic significance. Now a day’s most of the ore deposits are being exclusively correlated with the plate margin activities where tectono-magmatic processes have operated to mobilize and enrich the mineral deposits. Since the activities along the plate boundary may be classified as occurring at crustal scale, it has a very important role to first bring the economically important element like gold from deep inside the earth along these crustal scale shear zone on an initial basis .Later on this process might have been repeated several times and further supplemented by various geological processes, operating at regional scale to from workable deposits. This paper deals with the Global scale crustal evolutionary processes and its role on the spatial and temporal distribution of gold mineralization on a province/deposit scale. It has been observed that almost all the global Precambrian/ Paleaeozoic/ Mesozoic and Cenozoic gold provinces can be spatially correlated to plate margins. It is also well evident that the gold deposits associated with a specific plate margin were formed during the time, when that particular region/plate margin was active. There is sufficient reason to believe that the mobilization of gold in more that one phase was operative till the area was tectonically active on a crustal scale. The possibility of subsequent phase of mobilization can be held for the further enrichment of gold deposits.