Geology of the Harney Peak Granite, Black Hills, South Dakota

Redden, Jack A.; Norton, J.J.; McLaughlin, Robert J.

doi:10.3133/ofr82481

Cited by 21 publications

(7 citation statements)

References 5 publications

(5 reference statements)

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“…Several of the larger laccoliths cited above were emplaced as numerous, thin sills or sheets, rather than as a single large intrusion (Brown et al, 1981;Redden et al, 1985;Nabelek et al, 1992;Guillot et al, 1993;Simony and Halwas, 1993). The Solitario laccolith may also have been emplaced as a series of sheets, and the rim sills definitely constitute a thin version of the "granitic sheets" cited by these authors.…”

Section: Comparison With Other Laccoliths and Plutonsmentioning

confidence: 99%

“…In contrast, the Solitario is comparable in size to many major intrusions that are demonstrably laccoliths, sills, or otherwise floored, tabular bodies. The shape of these intrusions is indicated both from geophysical data for intrusions where the base is not exposed (Bott and Smithson, 1967;Sweeney, 1976;Carrier and Chapman, 1981;Lynn et al, 1981;Carle, 1988;Hodge et al, 1982;Vejmelek and Smithson, 1995;Lyons et al, 1996) and from exposed cross sections (Hamilton and Myers, 1967;Bridgwater et al, 1974;Sides, 1980;Brown et al, 1981;Hildebrand, 1984;Redden et al, 1985;John, 1988;Hogan and Sinha, 1989;Hogan et al, 1992;Hildebrand et al, 1990;Hutton and Ingram, 1992;Guillot et al, 1993;Simony and Halwas, 1993;Scaillet et al, 1995). These examples range from individual plutons a few kilometers to 50 km across and 1 to 5 km thick to batholiths many hundreds of kilometers across and 10 or more km thick.…”

Section: Comparison With Other Laccoliths and Plutonsmentioning

confidence: 99%

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Henry

Kunk

Muehlberger

et al. 1997

Geological Society of America Bulletin

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The Solitario is a large, combination laccolith and caldera (herein termed "laccocaldera"), with a 16-km-diameter dome over which developed a 6 × 2 km caldera. This laccocaldera underwent a complex sequence of predoming sill, laccolith, and dike intrusion and concurrent volcanism; doming with emplacement of a main laccolith; ash-flow eruption and caldera collapse; intracaldera sedimentation and volcanism; and late intrusion. Detailed geologic mapping and 40 Ar/ 39 Ar dating reveal that the Solitario evolved over an interval of approximately 1 m.y. in three distinct pulses at 36.0, 35.4, and 35.0 Ma. The size, duration, and episodicity of Solitario magmatism are more typical of large ash-flow calderas than of most previously described laccoliths. Small volumes of magma intruded as abundant rhyolitic to trachytic sills and small laccoliths and extruded as lavas and tuffs during the first pulse at 36.0 Ma. Emplacement of the main laccolith, doming, ash-flow eruption, and caldera collapse occurred at 35.4 Ma during the most voluminous pulse. A complex sequence of debris-flow and debris-avalanche deposits, megabreccia, trachyte lava, and minor ash-flow tuff subsequently filled the caldera. The final magmatic pulse at 35.0 Ma consisted of several small laccoliths or stocks and numerous dikes in caldera fill and along the ring fracture. Solitario rocks appear to be part of a broadly cogenetic, metaluminous suite. Peralkaline rhyolite lava domes were emplaced north and west of the Solitario at approximately 35.4 Ma, contemporaneous with laccolith emplacement and the main pulse in the Solitario. The spatial and temporal relation along with sparse geochemical data suggest that the peralkaline rhyolites are crustal melts related to the magmatic-thermal flux represented by the main pulse of Solitario magmatism. Current models of laccolith emplacement and evolution suggest a continuum from initial sill emplacement through growth of the main laccolith. Although the Solitario laccocaldera followed this sequence of events, our field and 40 Ar/ 39 Ar data demonstrate that it developed through repeated, episodic magma injections, separated by 0.4 to 0.6 m.y. intervals of little or no activity. This evolution requires a deep, long-lived magma source, well below the main laccolith. Laccoliths are commonly thought to be small, shallow features that are not representative of major, silicic magmatic systems such as calderas and batholiths. In contrast, we suggest that magma chambers beneath many ashflow calderas are tabular, floored intrusions, including laccoliths. Evidence for this conclusion includes the following: (1) many large plutons are recognized to be laccoliths or at least tabular, (2) the Solitario and several larger calderas are known to have developed over laccoliths, and (3) magma chambers beneath calderas, which are as much as 80 km in diameter, cannot be as deep as they are wide or some would extend into the upper mantle. The Solitario formed during a tectonically neutral period following Laramide deformation and prece...

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Section: Comparison With Other Laccoliths and Plutonsmentioning

confidence: 99%

Section: Comparison With Other Laccoliths and Plutonsmentioning

confidence: 99%

Untitled

Henry

Kunk

Muehlberger

et al. 1997

Geological Society of America Bulletin

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show abstract

“…The pegmatite bodies are spatially related to the Harney Peak Granite: the density of bodies decreases away from the main body of the granite to the north, east, and west, but remains rather constant on the south (Norton, 1975b;Redden, Norton, and McLaughlin, 1982). Some pegmatite intruded the foliation of the country schist, but many bodies are concordant with the layering in the schist.…”

Section: Structural Controlmentioning

confidence: 99%

“…1), a coarse-grained to pegmatitic peraluminous muscovite granite containing accessory garnet, biotite, and tourmaline (Huang and Wylie, 1981;Redden, Norton, and McLaughlin, 1982). The granite occupies a 40-sq-mi area between Custer and Keystone in which hundreds of dikes and sills coalesce into a coherent, but compositionally and texturally variable, intrusive body.…”

Section: Plutonic Rocksmentioning

confidence: 99%

“…Area EGHI1 therefore has a high potential for small pegmatite bodies that contain all pegmatite commodities except tin and beryllium. Deposits in this area would be predominantly potassium feldspar-mica bodies (H) such as the Dakota Feldspar, Greene, Elkhorn, and Bull Moose pegmatite bodies (Norton, 1975b;Redden, Norton, and McLaughlin, 1982). Large pegmatite bodies that contain significant beryllium, such as the Smith and Black Diamond-Beecher Number 3, border the area on the south and west, respectively.…”

Section: Assessmentmentioning

confidence: 99%

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