ENDOGENIC GEOCHEMICAL ANOMALIES OF GOLD-ORE FIELDS OF PALEOZOIC FOLDED STRUCTURES

Abstract

By the example of the Siberian and West Kalba (Kazakhstan) gold-ore fields, the peculiarities of geochemical-anomaly manifestation in ore fields formed in various folded structures of the Earth's crust are considered. These ore fields belong to rift-like apofolded structures with widespread metasomatism. The gold deposits (often bearing platinoids) of these ore fields are typical hydrothermal-metasomatic deposits, which originated within ophiolite belts. They formed as a result of fluid flows in the zones of deep faults in the Earth's crust and upper mantle. It is shown that the complex interior structure of the regional geochemical fields is caused by the combination of negative, lowered, and positive geochemical aureoles and by the unequal erosion cross-section of individual structural blocks. The negative aureoles characterize blocks of rocks subjected to the processes of early alkaline metasomatism, and the positive aureoles correspond to the zones of late hydrothermal acidic leaching and sulfidization of rocks. The first-order geochemical fields, as a whole, represent a system of two types of the Earth's crust matter - regional tectonomagmatic and local metasomatic bodies as the products of decomposition of deep magma-fluid systems in the upper layers of the Earth's crust. The largest ore fields and deposits are most often localized along the boundaries of the negative and positive aureoles of chalcophile elements.