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Research about South America

Source-linked reports with geographic coverage including South America.

28 records · Page 2Linked to original sources
USGS1998

Glaciers of South America

Landsat images, together with maps and aerial photographs, have been used to produce glacier inventories, define glacier locations, and study glacier dynamics in the countries of South America, along with the Andes Mountains. In Venezuela, Colombia, Ecuador, and Bolivia, the small glaciers have been undergoing extensive glacier recession since the late 1800's. Glacier-related hazards (outburst floods, mud flows, and debris avalanches) occur in Colombia, in Ecuador, and associated with the more extensive (2,600 km 2 ) glaciers of Peru. The largest area of glacier ice is found in Argentina and Chile, including the northern Patagonian ice field (about 4,200 km 2 ) and the southern Patagonian ice field (about 13,000 km 2 ), the largest glacier in the Southern Hemisphere outside Antarctica.

Professional Paper↗
USGS1978

The metallogenic role of east-west fracture zones in South America with regard to the motion of lithospheric plates (with an example from Brazil)

The role of east-west fracture zones in South America is discussed with regard to global fracturing and the motion of lithospheric plates. A set of major NW-trending lineaments has been derived which show a tendency to be spaced equidistantly and may correspond to a set of east-west fractures in the "pre-drift" position of the South American plate. Statistical analysis of linears in the ERTS-mosaics shows that NW-fractures are also among the most important ones in the Andes region, suggesting that the above major lineaments extend into the basement of the Andes. Some of the old major fractures, trending east-west in the present orientation of South America, are discussed and their NE orientation in the pre-drift position of the plate is considered. An example of structural control of ore deposition in the Brazilian Shield is presented, using the maps of the RADAM Project. It is concluded that the small tin-bearing granitic bodies concentrated in the region of Sao Felix do Xingu in the state of Para represent upper parts of an unexposed granitoid massif which is controlled by the intersection of a major east-west fracture zone probably represents westward extension of the Patos Lineament of the easternmost part of Brazil, connected with the east-west fracture zone of the Para state through the basement of the Maranhao Basin (Sineclise do Maranhao-Piaui). It is expected that the proposed "Patos-Para Lineament" extends further westward and may similarly control, at intersections with fractures of other trends, some mineralization centers in the western part of the state of Para and in the state of Amazonas.

South America↗
USGS1973

Iron-formation in South America

Except for recent studies by certain South American governmental and quasi-governmental companies and agencies, little effort has been devoted to study of the iron-formations from which the great iron ore deposits of South America formed. Great gaps in basic information exist. Iron-formation is found in the Guayana and Brazilian Precambrian Shields as a common rock type and also occurs in Chile and astride the Bolivian-Brazilian border. Only the carbonate and oxide facies are known, the former being quite rare. The dominant oxide facies occurs in major units averaging more than 100 m in thickness and extending over hundreds of square kilometers, generally in a miogeosynclinal or intra-cratonic basin environment. The relation of such deposits with volcanism is tenuous and obscure, if indeed there is any direct relation. Smaller units of oxide facies iron-formation occur in many minor beds from widely varying geologic environments. The carbonate facies is found in a eugeosynclinal suite in Minas Gerais, Brazil, and is of the Algoma type. The deposits range in age from about 3,200 m.y. to late Precambrian or early Paleozoic; although the major epoch of deposition is debatable, it probably was about 2,000 m.y. ago. The South American oxide facies iron-formations are richer than many in the Northern Hemisphere, those of early and middle Precambrian age averaging about 40 percent in Fe and the same in SiO 2 . Younger iron-formations are still richer, averaging perhaps 50 percent Fe. Scanty trace element data do not indicate volcanic affiliations. The iron is present as magnetite, hematite, and martite; most rocks have been metamorphosed, and accordingly it is not known how much of the magnetite is metamorphic and how much is diagenetic or depositional in origin. Hematite and martite are dominant in most iron-formations. South American iron-formations are quite similar in lithology and occurrence to the major deposits in Africa and India and possibly formed when these continents were contiguous. These formations differ from those in the Northern Hemisphere in having a narrower range in lithologic facies and a generally higher iron content. In few areas can any direct relation with volcanism be demonstrated. © 1973 Society of Economic Geologists, Inc.

Economic Geology↗