In a recent review article, Groves et al. (1998) suggested that lode-gold deposits worldwide, which have been variously termed mesothermal, turbidite-hosted, slate-belt hosted, greenstone-hosted, Mother lode-type or gold-only deposits, are a coherent group of gold deposits with a common origin.
На основе обобщения и анализа материалов томов I—4 монографии «Золоторудные месторождения СССР», с привлечением данных по новым типам оруденения и зарубежным объектам, уточнена систематика золоторудных формаций и их соотношения с геолого-промышленными типами месторождений. В целях геолого-генетического моделирования условий рудообразования выделены рудоносные структурно-вещественные парагенезисы. Рассмотрены поисковые критерии и принципы прогнозирования ведущих и перспективных типов золоторудных месторождений в различных геотектонических обстановках. Показано прогнозирующее значение формационной систематики золоторудных месторождении.
An orogenic gold deposit is a structurally controlled gold occurrence formed during one of the major stages of an orogeny by orogenic fluids. Any rock type within a greenstone or schist belt, a metamorphosed supracrustal rock, dyke, or intrusion within or intrusion bounding such belt may host an orogenic gold deposit.
The Sari Gunay epithermal gold deposit is located within a mildly alkaline latitic to trachytic volcanic complex in central-northwest Iran. Intrusive and volcanic rocks that host the deposit have been dated at between 11.7 and 11.0 Ma (with one younger sample at 8.0 Ma; 40Ar/39Ar dating of igneous biotite and hornblende), whereas sericitic alteration associated with an early stage of hydrothermal activity occurred between ~10.8 and ~10.3 Ma (the best age estimate is 10.7 Ma obtained by 40Ar/39Ar dating of sericite).
Epithermal gold (± Cu & Ag) deposits form at shallower crustal levels than porphyry Cu-Au systems, and are primarily distinguished as low and high sulphidation using criteria of varying gangue and ore mineralogy, deposited by the interaction of different ore fluids with host rocks and groundwaters. Low sulphidation deposits are in turn further divided according to mineralogy related to the depth and environment of formation, while high sulphidation systems vary with depth and permeability control, and are distinguished from several styles of barren acid alteration.
There are two main issues stemming from Vallée’s (2002) comments on Dominy et al. (2001b). First, he raises the importance of quality assurance/quality control (QA/QC) during resource estimation programs, and second, he indicates that the resolution and understanding of continuity (grade and geological) issues are paramount in the classification of resources. In particular, continuity is critical at the boundary between the Inferred and Indicated Mineral Resource categories.
The often complex, erratic, and localized nature of gold is a common feature of many vein-style gold deposits. This style of mineralization is often referred to as being nuggety or possessing a high-nugget effect. As a result of these complexities resource estimation is difficult and in general, only Exploration Results can be provided or an Inferred Mineral Resource estimated from surface drilling data alone. Underground development, further drilling, and probably bulk sampling will be required to delineate Indicated and Measured Resources.
The status of sampling practices in the Gold Mining Industry in Africa was determined as an initial step in a process to standardise sampling practices in the Mining Industry. Several mines, metallurgical plants and laboratories were visited and the status of equipment, standards and procedures were rated to determine the potential influence of the relevant sampling errors on each component of the particular sampling system.
Предложены прогнозно-поисковые комплексы (ППК) на три ведущие группы геолого-промышленных типов золоторудных и золото-серебряных месторождений (в терригенных комплексах подвижных поясов земной коры, в вулкано-плутонических поясах и зонах тектоно-магматической активизации, в вулканогенных эвгеосинклиналях), направленные на выявление месторождений благородных металлов. Приведены примеры применения комплексов при различных обстановках на различных стадиях геологоразведочного процесса, проанализированы их основные и сокращенные варианты.
