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Frank S. Simons

Publications and source records attributed to Frank S. Simons.

16 recordsLinked to original sources
USGS1977

Geochemistry of amphibolites from the central Beartooth Mountains, Montana-Wyoming

Trends of variation of major- and minor-element contents in amphibolites from the central Beartooth Mountains strongly suggest that these rocks of andesitic composition are derived from a tholeiitic, mafic igneous parent and not from a sedimentary parent. Discriminant functions based on minor-element content also indicate igneous parentage, whereas functions based on major-element content indicate a sedimentary parent, suggesting that the general assumption that the regional metamorphism is isochemical may not be entirely valid. Furthermore, chemical data on the amphibolites do not fit the fractionation curves of average Beartooth metadolerites, the most likely precursor. If, however, it is assumed that regional metamorphism and formation of amphibolites were accompanied by potassium metasomatism, then the higher concentrations of SiO 2 , Al 2 O 3 , K 2 O, and potassium-related minor elements in the amphibolites relative to metadolerite can be explained.

Montana, Wyoming↗
USGS1976

High-level plateaus of the southeastern Beartooth Mountains, Montana and Wyoming: remnants of an exhumed sub-Cambrian marine plain

The Beartooth Mountains of south-central Montana and northwestern Wyoming are a northwesterly trending high rugged range made up mainly of Precambrian metamorphic rocks. The southeastern part of the range is characterized by extensive high-altitude flat or gently rolling plateaus separated by deep glaciated canyons. The plateaus along the crest of the range are at altitudes of more than 3,350 metres (11,000 ft), whereas those on the flanks of the range are much lower. They are almost entirely on Precambrian rocks, and only small patches of Cambrian sedimentary rocks still remain at a few places in the high mountains. Topographic profiles across the southeastern Beartooth Mountains show that: (1) plateaus bearing the sedimentary remnants lie very close to the position of the sub-Cambrian depositional surface as projected from known occurrences of that surface along the south side of the mountains; (2) other plateaus on the crest and southwest flank also lie near this projected position; and (3) high plateaus and other summits on the northeast slope in areas distant from known or projected positions of the sub-Cambrian surface are markedly accordant. We believe the plateaus along the crest and southwest flank of the range to be remnants of an exhumed marine plain of Early Cambrian or Precambrian age, and those on the northeast flank may possibly have a similar origin. The sub-Cambrian depositional surface was protected until early Tertiary time by a cover of Paleozoic sedimentary rocks, and parts of it probably were covered until Pliocene time by Eocene volcanic rocks. The surface subsequently has been profoundly modified by fluvial and glacial erosion and by mass wasting.

Montana, Wyoming↗
USGS1975

Cylindrical jointing in mafic dikes, central Beartooth Mountains, Montana

Cylindrical joints are well displayed in two Precambrian mafic dikes that cut granitic gneiss in the central Beartooth Mountains, Mont. The dikes are vertical and about 23 m (75 ft) and 23 to 46 m (75-150 ft) thick, respectively. The cylindrical joints are perpendicular to the dike walls, and the cylinders defined by the joints are as much as 5 m (16 ft) in diameter. No petrographic, textural, or other features related to or possibly responsible for the joints are recognized. The dikes are chemically and petrographically similar to quartz dolerite dikes found throughout the Beartooth Mountains. Some of these dikes show typical polygonal columnar joints; a few others have cylindrical jointing, but in most dikes neither kind of jointing was observed. The orientation of the cylindrical joints normal to the walls of the dikes indicates that they probably formed by thermal contraction during post-crystallization cooling of the dikes and are thus genetically related to the much more common polygonal jointing. However, the model proposed to explain the cylindrical joints suggests that their origin is partly dependent on the geometric relation between the orientation of the dikes and that of the predike fracture pattern in the host rock.

Montana, Wyoming↗
USGS1963

Composite dike of andesite and rhyolite at Klondyke, Arizona

A composite dike of probable Tertiary age intrudes Precambrian granodiorite 6 miles north of Klondyke , Arizona . The dike is exposed discontinuously for about 1500 feet along the strike and has a core of porphyritic rhyolite 15-20 feet thick flanked by coarsely porphyritic andesite 1-2 feet thick. Field evidence indicates that the rhyolite is later than the andesite but that the core of the original andesite dike was still hot and unconsolidated at the time of intrusion of the rhyolite . Chemically, the rhyolite is nearly identical to a large alkali granite pluton of Tertiary age exposed 1 mile east. The andesite component is similar both petrographically and chemically to lavas exposed in the region, but a direct relationship could not be established. Meager evidence suggests that the two dike components were derived from separate magma bodies rather than being differentiates of a single magma.

Arizona↗
USGS1958

Geology of the manganese deposits of Cuba

Deposits of manganese ore have been found in five of the six provinces of Cuba and have been reported from the sixth. Only Oriente and Pinar del Rio provinces have more than a few known deposits and only the deposits of Oriente have yielded any appreciable amount of ore.

Bulletin↗