The ore deposits of the Sunlight mining region, Park County, Wyoming

Parsons, Willard H.

doi:10.2113/gsecongeo.32.6.832

Cited by 5 publications

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“…The depth to the top of the batholith ranges from less than 2 km to 7 km beneath the surface. In the Sunlight mining district, Wyoming (Parsons, 1937) ., 1975, fig. 27).…”

Section: H Koide 4nd S Bh4tt4ch4rjimentioning

confidence: 99%

Formation of fractures around magmatic intrusions and their role in ore localization

Koide¹,

Bhattacharji²

1975

Economic Geology

100

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An exact solution of three-dimensional theory of elasticity in an infinite elastic rock medium around magma reservoirs of various aspect ratios and the criteria of rock fracturing provide an important tool for the interpretation of the origin and nature of distribution of many ore-bearing fracture systems around magmatic bodies in the world. Theoretical analyses suggest the conditions and regions of formation of (1) dominant radial fractures, (2) dominant concentric fractures or combination of radial and concentric fractures, and (3) central subsidence (or graben) in domal uplift related to intrusions of magma bodies of various shapes and sizes. The relations of these fracture systems to the deposition of ore-bearing fluids are discussed in the light of excess magma and hydrothermal fluid pressures. Caldera subsidence and dominant concentric fractures, such as in the San Juan Mountains mining district in Colorado, are, according to our analyses and interpretations, related to intrusion(s) of vertically elongated magma cupolas and high magma and hydrothermal fluid pressures. This differs from Anderson's original contention (1936) that caldera subsidence and outward-dipping ring fractures are due to lower relative magma pressure than lithostatic pressure. Wedging action of magma immediately above a vertically elongated prolate magma body is suggested as a cause of central graben bounded by funnel-shaped normal faults over wide domal uplift. Displacement along normal faults causes underground subsidence above magma cupolas. Extension of such faults close to the surface and displacement along them can produce surface caldera subsidence. Vein-type deposits commonly associated with funnel-shaped felsic (rhyolitic) bodies may be related to near-surface caldera subsidence. The origin of arcuate zones of breccia pipes such as in Silverton cauldron, Colorado, appears to be related to axial symmetric stress condition (s) due to vertically elongated magma body at depth. Estimation of stress distribution around spheroidal and prolate magma bodies suggests development of possible zonal distribution of fractures from the periphery of the magma outward in the order of (1) continuous tension fracture zone, (2) brittle fault zone, (3) ductile fault zone followed by no fault zone. Brittle fault and continuous tension fracture zones provide excellent sites for ore mineral localization. The zonal distribution of fractures also suggests, in a general way, mode of origin and possible extent of distribution of various fracture types, hydrothermal zoning, and their alterations.

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“…The depth to the top of the batholith ranges from less than 2 km to 7 km beneath the surface. In the Sunlight mining district, Wyoming (Parsons, 1937) ., 1975, fig. 27).…”

Section: H Koide 4nd S Bh4tt4ch4rjimentioning

confidence: 99%

Formation of fractures around magmatic intrusions and their role in ore localization

Koide¹,

Bhattacharji²

1975

Economic Geology

100

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“…This has been discussed by Wisser (1941). SOURCES FOR SUNLIGHT : Parsons (1937; KIRWIN, WYOMING REGIONAL SETTING, ROCK FORMATIONS, STRUCTURE, METALLIZATION: The Kirwin district, 60 miles south-southwest of Sunlight (PI. 1) and near the south end of the Absaroka volcanic range, is mineralogically and structurally similar to Sunlight.…”

mentioning

confidence: 99%

Relation of Ore Deposition to Doming in the North American Cordillera

Wisser

1960

Geological Society of America Memoirs

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Many structural domes and anticlines rise from undeformed surroundings; the general crust of the earth is neither shortened nor extended by these local swells or blisters, but the area of the plate upfolded is increased. With plastic material the increase is effected largely by flow; with brittle material, largely by fracture.Many mining districts are associated with upfolds of this type. Districts here described fall into two categories: (1) those whose structural frame is a dome, and (2) those whose structural frame is an anticline.Domes may show fractures which radiate from the apex, or concentric fractures which are segments of circles, of varying diameters but with a common center, the apex of the dome. Both types may appear on the same dome; the fractures of each type aid enlargement of the plate during doming.Sunlight and Kirwin, Wyoming, are minor districts with dominant radial fracture patterns. Vein matter was deposited while the walls of the vein fractures were being pulled apart. With a radial vein system the only way in which all the vein walls could be simultaneously pulled apart is by stretching of the fabric of an expanding dome.The structural setting of the Ophir, Utah, lead-silver district, and of the Matehuala, Mexico, copper district is that of a half dome truncated by a normal fault with downthrow away from the domical apex. Displacement on the fault is greatest opposite the apex and decreases progressively in both directions, becoming zero at the spring line. No part of the dome ever existed on the downthrown side of the fault, which was a fracture before doming. Maximum uplift was centered on one side of the fault and there produced the half dome; but the pre-existing fracture offered locally an easier mode of uplift by rise of the footwall block.At Ophir ore shoots followed intersections on the half dome of radial fractures with limestone beds. At Matehuala stretching during doming was effected largely by flow of limestone, but a monzonite stock intruded in the half dome was too brittle to flow. The limestone pulled away from the unyielding stock; fractures concentrated around the periphery of the stock localized the Dolores copper ore bodies.In the Silverton-Telluride district, Colorado, fractures radiate from a relatively large, roughly circular graben, along whose margin monzonitic stocks were intruded. Evidence suggests that this fracture pattern resulted from domical uplift, with the graben at the apex. Transfer of volcanic material from depth to the surface in the central area produced a sag which has eliminated the upward bulge of the dome.Mineralization advanced outward from the graben step by step with the outward growth of the radial fractures. Copper-silver pipes within the fault zone bounding the graben were formed first, followed successively outward by basemetal deposits as veins, which were reopened to admit gold and silver, and by precious-metal vein deposits in the outermost zone.The structural setting of La Plata, Colorado, is that of a dome, truncated, south of its apex,...

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“…Sample widths or representative tonnages were not reported. Parsons (1937) reported three assays from claims within the Winona group. He stated that the assays "indicate a relative order of magnitude but the figures are not accurate enough for commercial use."…”

Section: Historymentioning

confidence: 99%

“…5 m) from the junction of the two crosscuts. Parsons (1937) reported an assay of a "sample taken from the ore vein outcrop" at the Evening Star property to be 0.02 ounce (7 ppm) gold and 91.44 ounces (3,136 ppm) silver per ton, 1.40 percent copper, and 1.30 percent lead. Inasmuch as its silver content was high, this was probably a selected sample.…”

Section: Novelty Claimmentioning

confidence: 99%

Geology and mineral resources of the North Absaroka Wilderness and vicinity, Park County, Wyoming, with sections on mineralization of the Sunlight mining region and geology and mineralization of the Cooke City mining district, and a section on aeromagnetic interpretation

Nelson¹,

Prostka²,

Williams³

et al. 1980

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Under the Wilderness Act (Public Law 88-577, Sept. 3, 1964) certain areas within the National forests previously classified as "wilderness," "wild," or "canoe" were incorporated into the National Wilderness Preservation System as wilderness areas. The act provides that the Geological Survey and the Bureau of Mines survey these wilderness areas to determine the mineral values, if any, that may be present. The act also directs that results of such surveys are to be made available to the public and submitted to the President and Congress. This bulletin reports the results of a mineral survey of the North Absaroka Wilderness, Park County, Wyoming, and some adjoining national forest lands that may be considered for wilderness designation.

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The ore deposits of the Sunlight mining region, Park County, Wyoming

Cited by 5 publications

References 0 publications

Formation of fractures around magmatic intrusions and their role in ore localization

Formation of fractures around magmatic intrusions and their role in ore localization

Relation of Ore Deposition to Doming in the North American Cordillera

Geology and mineral resources of the North Absaroka Wilderness and vicinity, Park County, Wyoming, with sections on mineralization of the Sunlight mining region and geology and mineralization of the Cooke City mining district, and a section on aeromagnetic interpretation

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