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George Edward Ericksen

Publications and source records attributed to George Edward Ericksen.

11 recordsLinked to original sources
USGS1975

Metallogenic provinces of the southeastern Pacific region

Metalliferous mineral deposits of the southeastern Pacific region include: (1) hydrothermal, magmatic, and sedimentary deposits of the Andean region, one of the great mineral belts of the world; 2) Scattered hydrothermal mineral occurrences in the Antarctic Peninsula; and 3) metal-enriched pelagic sediments, ferromanganese nodules, and volcanic rocks(?) in the southeast Pacific basin. Andean metalliferous deposits, the chief concern of this report, are for the most part spatially and genetically related to calc-alkaline plutons, sub-volcanic intrusions, and volcanic rocks emplaced during the Andean orogeny of Late Triassic to Quaternary age. These deposits are components of a single metallogenic province superimposed on two or more pre-Andean metallogenic provinces that are indicated by scattered deposits of Paleozoic and Precambrian(?) age. Occurrences in the Antarctic Peninsula are of age and origin similar to the deposits in the Andes and are considered to belong to the Andean province. The Andean metallogenic province may be divided into several subprovinces, each parallel to the Andes and the continental margin and each having a dominant metal or suite of metals. The central Andes of Peru, northern Chile, and Bolivia, which contain the greatest concentration of exploitable deposits and the greatest variety of ore types, have as many as five linear partly overlapping subprovinces. These sub-provinces, from west to east (Pacific coast to the eastern Andean front), are characterized, respectively, by deposits of : 1) iron; 2) copper, with or without associated gold; 3) polymetallic base metals (zinc, lead, copper), generally containing silver; 4) tin; and 5) gold. Iron deposits chiefly are near the coast in central to northern Chile and in southern Peru. The copper and polymetallic provinces are characterized by abundant deposits in the central Andean region but comparatively few scattered deposits in the north (Ecuador, Colombia, and Venezuela) and in southern Chile and Argentina. Scattered gold-rich veins and placers occur along the western Andean front and coastal region, the general area of the copper province, from central Chile to northern Colombia. Similar deposits occur along a discontinuous belt in the eastern Andes from Bolivia to Ecuador and in the central Andes of Colombia. Tin deposits are almost wholly restricted to the eastern Andes of Bolivia. The position and age distribution of plutonic and volcanic rocks and associated metalliferous deposits of the Andes indicate presence of an active subduction zone in this region since at least Late Triassic time. Magmas of the calc-alkaline igneous rocks are believed to have formed chiefly by partial melting of mantle, oceanic sediments, and oceanic crust along the Benioff zone at depths of 100 to 200 km. Plutonic and volcanic rocks show a general though nonuniform progression of decreasing age from west to east. Rocks of Jurassic and Cretaceous age are most abundant near the coast, whereas those of Tertiary and Quaternary age dominate in the Andes. Locally, intrusive rocks and ore deposits of widely different ages are juxtaposed. Metals of the ore deposits associated with the calc-alkaline rocks were supplied by the source rocks in the Benioff zone, some of which probably had been previously enriched in certain metals at the ancestral East Pacific Rise and were mobilized or assimilated from metal-rich zones in the overlying mantle and continental crust by magmas rising from the Benioff zone.

Open-File Report↗
USGS1974

Metallogenic provinces of southeastern Pacific region

Metalliferous mineral deposits of the southeastern Pacific region include: (1) hydrothermal, magmatic, and sedimentary deposits of the Andean region, one of the great mineral belts of the world; (2) scattered hydrothermal deposits in the Antarctic Peninsula; and (3) metal-enriched pelagic sediments and ferromanganese nodules on the seafloor. Andean metalliferous deposits, the chief topic of this report, are for the most part spatially and genetically related to calc-alkaline plutons, subvolcanic intrusions, and volcanic rocks emplaced during the Andean orogeny of Late Triassic to Quaternary age. They are components of a single metallogenic province superimposed on two or more pre-Andean metallogenic provinces of Paleozoic and Precambrian(?) age. Deposits in the Antarctic Peninsula are similar in age and origin to the deposits in the Andes and are considered to belong to the Andean province. The Andean metallogenic province may be divided into several subprovinces, each parallel with the Andes and the continental margin and each having a dominant metal or suite of metals. The central Andes of Peru, northern Chile, and Bolivia, which contain the greatest concentration of exploitable deposits and the greatest variety of ore types, have as many as five linear, partly overlapping subprovinces. These subprovinces, from west to east (Pacific coast to the eastern Andean front), are characterized, respectively, by deposits of iron, copper, polymetallic base metals, tin, and gold. Calc-alkaline plutonic and volcanic rocks of the Andes, which probably originated by partial melting in the Benioff zone, show a general, though nonuniform progression of decreasing age from west to east. Igneous rocks of Jurassic and Cretaceous age are most abundant near the coast, whereas those of Tertiary and Quaternary age dominate in the Andes. Locally, intrusive rocks and associated ore deposits of widely different ages are juxtaposed. Several sources of the metals are probable; they include oceanic crust and pelagic sediments in the Benioff zone, some of which may have been enriched previously in certain metals at the ancestral East Pacific Rise, and metal-rich zones in the overlying mantle and continental crust.

AAPG Memoir↗
USGS1971

Computer studies of the composition of Chilean nitrate ores: Data reduction, basic statistics and correlation analysis

Electronic computer studies were made on a suite of 815 chemical analyses of soluble salines in nitrate ores, representing monthly averages of ores treated by the two largest nitrate plants in Chile from 1932 to 1967. A package statistical program, STATPAC, of the U.S. Geological Survey was utilized: 1) to estimate the abundance of sodium not reported in the analyses, 2) to determine the soluble-insoluble ratio, 3) to calculate the basic statistics, and4) to investigate the correlation between the saline constituents. The statistical average composition of the soluble salines in these nitrate ores, estimated to be a close approximation of the average of Chilean ores as a whole, is as follows (in weight percent; the standard deviation is given in parenthesis): NO 3 6.29(+0.60), CZ 4.58(+1.26), SO 4 10(+3.16), IO 3 0.060(+0.012), CZO 4 0.028(+0.012), B 5 0 9 0.50(+0.11), Na 6.90(+1.19), K 0.73(+0.36), Ca 1.81(+0.55), Mg 0.46(+0.28), percentage of solubles 31.36(+5.69). The analyses do not give the true abundance of salines of low solubility such as anhydrite, which commonly makes up several percent of the nitrate ore, nor of several other saline ions occurring in minor or trace amounts which together generally do not make up more than a percent or two. Tables are presented for the significant correlations between relative abundances of the constituents, which give a clue to the mineralogical composition of the nitrate ore. However, the analysis of these correlation studies has not yet been completed.

Open-File Report↗
USGS1963

Geology of the salt deposits and the salt industry of northern Chile

The study of the salt deposits of northern Chile is a cooperative project of the Institute de Investigaciones Geologicas (IIG) of Chile and the United Nations Special Fund and is part of a mineral resources survey, undertaken by these two organizations, of selected regions of northern Chile, during 1960-1963. The writer, an employee of the United States Geological Survey, worked in cooperation with the IIG and its predecessor organization, the Seccion Geologica of the Corporacion de Foment de la Produccion, during the period December 1954-March 1962, under the auspices of the United States Technical Aid program (AID). The work on salt deposits, which was started during 1961, has been under the auspices of the United Nations since April 1962, during completion of field work and preparation of this report. This report summarizes the data gathered during the field investigation, including information on reserves, production, and composition of salts supplied by private companies and government bureaus. As such, it is in the nature of a progress report, lacking: 1) a comprehensive review of the literature which, at least in regard to the well-known nitrate deposits, is extensive; 2) completion of laboratory investigations of chemical, mineralogical, and isotopic composition; and 3) a review of theories of origin of the salts, mainly nitrate. The salt deposits of northern Chile comprise the well-known nitrate deposits as well as salars that have been exploited principally for sodium chloride, sodium sulfate, and borate; bedded salt deposits and salt domes, and secondary salt deposits formed in the oxidation zone of metalliferous sulfide deposits. This report will discuss the nitrate deposits and associated sodium sulfate deposits, salars, and those secondary deposits, such as aluminum-magnesium sulfates or iron sulfates, which have been exploited for chemical use. Bedded salt deposits and salt domes, consisting mainly of halite and evidently restricted to one small area, were not studied. The numerous and important secondary copper deposits, as well as other metalliferous salt deposits, are beyond the scope of the report.

northern Chile↗