Geology topics

Research about Colombia

Source-linked reports with geographic coverage including Colombia.

22 records · Page 2Linked to original sources

USGS1972

Evaporite deposits of Bogota area, Cordillera Oriental, Colombia

Four evaporite-bearing stratigraphic zones are known in Cretaceous strata of the Cordillera Oriental of Colombia north and east of Bogota. The easternmost and oldest zone is probably of Berriasian to Valanginian age. The next oldest is probably late Barremian to early Aptian in age. The third appears to be Aptian. The westernmost and best known sequence in the Sabana de Bogota is Turonian to early Coniacian in age. This youngest sequence contains the thickest salt deposits known in Colombia and is probably the most widespread geographically. Most of the rock salt exposed in the three accessible mines (at Zipaquira, Nemocon, and Upin) has a characteristic lamination of alternating slightly argillaceous and highly argillaceous salt layers of varied but moderate thickness. Black, calcareous claystone, commonly very pyritic, is interbedded conformably with the laminated salt in many places throughout the deposits. Fragments of black claystone derived from the thinner interbeds are ubiquitous in all deposits, both as concordant breccia zones and as isolated clasts. Anhydrite is scarce at Zipaquira and apparently even rarer at Nemocon and Upin. Gypsum is produced at three small deposits in the oldest evaporite zone where it probably was concentrated by leaching of salt initially associated with it. The two intervening evaporite zones are not exposed, but their existence and distribution are indicated by brine springs and locally by "rute," a distinctive black, calcareous mud formed by the leaching of salt beds. Fossils show that the youngest salt-claystone zone, in the Sabana de Bogota, is contemporary with associated hematitic sandstone and siltstone, and with carbonaceous and locally coaly claystone. Although evidence is poor, this same facies relation probably exists within the other three evaporite zones. All salt deposits in this study probably are associated with anticlines, a relation best exemplified by the deposits on the Sabana de Bogota. Within these anticlines the salt deposits appear to be contained stratigraphically in fault-bound crestal, claystone cores that have not been mobilized over great vertical distances. The deposits of this study are not salt domes.

Bogota↗

USGS1971

Detrital serpentinite from the Guajira Peninsula, Colombia

Small lenses of detrital serpentinite, completely surrounded by massive serpentinite, occur within a sequence of Mesozoic phyllites and metasiltstones in the Cerros de Parashi area, Guajira Peninsula. These lenses, which are as much as 30 m thick, consist of poorly sorted breccias that grade irregularly upward into bedded serpentinite sandstone and shale. Graded bedding is well developed in the sandstones, and channel structures and cross-bedding are also common. Two chemical analyses of serpentinite sandstone and shale show them to be of normal serpentinite composition. The original detrital serpentine minerals in these rocks were lizardite and chrysotile, but they have been partially replaced by antigorite during a period of upper greenschist facies metamorphism. The detrital serpentinites were formed by large submarine turbidity currents or mudflows, and the massive serpentinites surrounding them are believed to have been emplaced by gravity sliding.

Cerros de Parashi, Guajira Peninsula↗

USGS1971

Phosphate investigations in Colombia, 1969 a progress report; with a note on the aluminous laterite deposits of the Department of Cauca

About 10 weeks were spent in Colombia from January through March 1970 examining the progress of the phosphate investigations. Field work was done in the Sogamoso area, where detailed mapped by geologists of the Instituto Nacional de Investigaciones Geologico-Mineras has shown a large area where structures are gentle and not too complex, and as a consequence, the phosphorite beds are in a potentially minable situation. The beds in the Sogamoso area are in the sandy facies of the late Cretaceous miogeosyncline, and weathered surface rocks are deficient in CaO, so that a part of the P 2 O 5 in these rocks is present as wavellite. No unweathered samples have been collected, but it is thought that fresh material may contain some calcite. Drilling to confirm structure and to obtain unweathered samples started in March 1970. This area is promising economically. Resources of phosphorite in the southern part of the country, in the Departments of Huila and Tolima, are not as promising as are the resources in the Sogamoso area. The southern area is at or close to the linebetween the sandy and the calcareous facies of the miogeosyncline, andthus much of the material contains excess CaO. The structure is more complex, and the phosphorite beds are thinner than in the Sogamoso area, and much of the area is covered by a thick section of continental Tertiary sediments. A very short visit was made to the sulfur mine on Purace volcano. The ore is native sulfur impregnating very recent tuffs. Sulfur was deposited by fumaroles. Although known reserves are small, much of Purace volcano has not been explored, and there is potential for additional reserves. Other volcanoes in the southern part of Colombia should also be investigated to determine their potential as a source of sulfur. A few days were spent examining the aluminous laterite deposits in the Department of Cauca. The deposits are formed from intense lateritic weathering of Plio-Pleistocene tuff beds. The tuffaceous material is completely destroyed in the weathering,leaving a soft, very fine grained, very wet clay-like material. On drying, aggregates of gibbsite are formed and these are stable. It is thought that Al 2 O 3 , Fe 2 O 3 , and a part of the SiO 2 in the clayey material may be non-crystalline. Reserves of the material are very large, and further work is definitely indicated.

Open-File Report↗

USGS1950

Mineral resources of Colombia (other than petroleum)

The following report summarizes data acquired during 1942-45, in Colombia, by geologists and engineers of the Foreign Economic Administration, with whom the United States Geological Survey cooperated. Twenty-nine mineral commodities are considered, but the data for five of them are scant because they were of no interest to FEA personnel. Petroleum is not considered. Preliminary to a review of individual mineral commodities, resumes are given of the general geography and geology of Colombia and of the country's mining laws. The principal mineral commodities, besides petroleum, produced in Colombia are (1) emeralds, gold, platinum, and silver, mainly for export, and (2) barite, cement, clay, coal, gypsum, salt, sand and gravel, silica, and stone, mainly for the domestic market. A large number of other mineral commodities are known in "raw" prospects, some of which may eventually become productive. Their distribution and apparent potentialities, as of 1945, are given. Factors unfavorable to mining are the ruggedness of the terrain, the scarcity of outcrops, and the very high transportation costs.

Bulletin↗