The so-called ‘mesothermal’ gold deposits are associated with regionally metamorphosed terranes of all ages. Ores were formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and collisional orogens. In both types of orogen, hydrated marine sedimentary and volcanic rocks have been added to continental margins during tens to some 100 million years of collision.

This book will address three primary metals and their associated metals. The primary metals are Platinum Group of Elements or Metals (PGE or PGM), nickel, and chromium. The associated metals include copper, gold, silver, and cobalt. The platinum group consists of six metals and occurs naturally in close association with one another as well as with nickel, chromium, copper, and cobalt. The group of metals represents a unique geological process having a common source of metal supply and a genetic model. The PGM is among the least abundant group of elements of the Earth’s element family.

History and Genesis of Deposits is the product of an effort by the Society of Economic Geologists to publish materials that will expand knowledge concerning timely, specific topics important to the study of economic geology and to economic geologists. A volume on gold was selected for a general review-type publication because of the importance of the gold mining industry in the 1980s. The officers and council of the Society of Economic Geologists authorized the preparation of this book on gold in 1981, and Dr. Robert W. Boyle was selected as its author. 

In the last 15 years the concept of mineral systems approach to understanding orogenic gold systems has been developed. The orogenic gold model, as defined by Groves et al. (1998) argues for gold to be deposited during compressional deformation in accretionary orogens, from hydrothermal fluids derived from the metamorphism of greenstones. These deposits are typically found in late Archaean or in Palaeoproterozoic greenstone belts (Groves et al., 2007) and include the world class gold provinces of Yilgarn Craton, Superior Province, the Birimian of West Africa and the Tanzania Craton.

Orogenic gold deposits have formed over more than 3 billion years of Earth’s history, episodically during the Middle Archean to younger Precambrian, and continuously throughout the Phanerozoic. This class of gold deposit is characteristically associated with deformed and metamorphosed mid-crustal blocks, particularly in spatial association with major rustal structures. A consistent spatial and temporal association with granitoids of a variety of compositions indicates that melts and fluids were both inherent products of thermal events during orogenesis.

A new promising ore province, the Gold Line, southwest of the well-known Skellefte District, northern Sweden, is currently under exploration. This province hosts, so far, one operating mine, the Svartliden Au mine, and the recently closed Blaiken Zn-Pb-Au-Ag mine. The largest known gold deposit, the hypozonal Fäboliden orogenic gold deposit, in the area was recently granted mining permits. The deposit holds c. 54 Mt at 1.2 g/t Au, with a planned production of 4.6 Mt of ore/year.

This Open-File report is complemented by a poster-size geological map of the world, Open-File report 4893: Gold deposits and gold districts of the world, showing locations and sizes of all gold deposits and gold districts spread across the globe. It also displays enlargements of key goldproducing areas (such as the Abitibi Belt and Western Australia) and detailed economic figures current to at least the end of December 2002. 
These products are companions to the Open-File report 4896: Gold deposits of Canada, a database comprising referenced and detailed geological, geographical and economical information on 128 gold deposits, and to the Open-File report 4894: Gold deposits and gold districts of Canada, a poster-size map of Canada showing the location and size of all important gold deposits, as well as enlargements of key gold districts. 

Связанные материалы - База данных месторождений