THÔNG TIN TÀI LIỆU
ECONOMIC GEOLOGY 439 Figure This map, showing the sites of tin production, is an example of the uneven global distribution of several mineral commodities Modified from World Mineral Statistics (2003) by permission of the British Geological Survey ß NERC All rights reserved IPR/46 28CW great energy resources in sedimentary basins within ancient shield areas of Archaean rocks The converse applies for the great banded iron formations (BIF) in Precambrian sedimentary basins that are host to most of the world’s high-grade Fe ore deposits (see Sedimentary Rocks: Banded Iron Formations) Similarly, large and highly productive porphyry copper deposits are strongly grouped in the mountain chains made up of volcanic rocks and granitic intrusions along the western margins of the Americas This pattern has been more readily understood over the past 40 years in the light of geological mapping and plate tectonic theory Empirical associations between mineral deposits and their host rocks have long been noted and put to use by miners, and the list is still growing as geological knowledge of Earth’s physico-chemical systems advances Concepts have developed of mineral provinces and mineral epochs, and in recent decades regional patterns of mineralization have been related to the various kinds of tectonic plate boundaries (Figure 7) (see Plate Tectonics) Economic Geology and the Extractive Minerals Industries Every producing mineral deposit is a non-renewable resource with a finite life In order to continue to meet world demand, the extractive industries are geared to a life cycle of activities as shown in Table These four activities are very briefly outlined below, and the reader is referred to specific topics for more comprehensive information The State of Relevant Geological Knowledge Economic geologists are widely employed in the many specialized areas of the extractive industries All, however, rely on the quality and appropriate application of their geological knowledge of mineral deposits (see Mineral Deposits and Their Genesis) Great advances have been made in the geological understanding of the 4500 million year history of the earth, and of the igneous, sedimentary and metamorphic processes in which the genesis of mineral deposits is an integral part Concentrations of valuable minerals into economic deposits are no longer seen as special, isolated events, but as the result of processes, often sequential and superimposed, that operate in geological environments of every kind and in every age from the Archaean to the present Advancing views on regional patterns of mineral deposition related to space and time (i.e., in mineral provinces and mineral epochs) were dramatically boosted through definition of crustal tectonic regimes by the theory of plate tectonics The scientific overview of mineral deposits has moved away from worthy attempts at genetic classification, notably that of Lindgren, towards development of ‘mineral
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