Gold Mineralization At Ouro Fino Mine Brazil Structure And Alteration

Within the last decade, the high and continuing demand for precious and base metals, as well as critical elements, has prompted a global rush on a scale never before seen. This eventually resulted in the demand for considerable innovation and improvement in mineral deposit genetic modelling and ore formation regimes for the many different types of gold deposits, now recognized, and paralleled by the wide employment of exploration techniques and a rapid expansion of geological databases. This Special Issue will show case studies of porphyry polymetal systems, orogenic gold formations, water–rock reaction, ore-forming structure evolution, mineralogy and petrology of ore deposit, ore formation regime, geochronology and geochemistry of ore deposit, ore-forming evolution, mineral exploration and cutting-edge technology in ore deposit study.

The Middle Zone ore body of the Cortez Hills Deposit, located in Lander County, NV, hosts gold mineralization in the Roberts Mountains Formation (Silurian) and the Wenban Limestone (Devonian). This study used drillhole data to create a structural model of the Middle Zone and determine controls on gold mineralization and possible visual indicators of said mineralization. Gold mineralization is located throughout the Middle Zone, but higher grades appear to be concentrated at the base of the Middle Zone in a structurally complex area with thrust faults, listric normal faults and high angle faults. The thrust faults extend throughout the entire Middle Zone and generally strike S45°E and dip between 40°SW-40°NE. The listric faults show at least 50 meters of apparent stratigraphic offset and strike N30°W and dip from near horizontal to 40°SW. The normal faults in the Middle Zone offset stratigraphy between seven and thirteen meters vertically and strike between N30°W and N50°W and dip between 25°SW-35°SW. The evolution of these structures is complex beginning to the northeast of the Middle Zone with a thrust fault and continuing with thrusting to the southwest with the last thrust overprinting the Middle Zone with units 4 and 5 of the Roberts Mountains Formation and all units of the Wenban Limestone. Alteration present in the Middle Zone includes decarbonatization, silicification, sulfidation and oxidation. All types of alteration other than silicification are associated with gold in the Middle Zone, with decarbonatization being most closely associated based upon a preliminary statistical analysis. Gold and alteration are spatially associated with both high angle faults and shallowly dipping thrust and listric normal faults indicating strong structural controls on gold mineralization. Identification of structural features and decarbonatization will assist in determining the distribution of ore during mining of the Middle Zone.