Geology, age, and tectonic setting of the Cretaceous Sliderock Mountain Volcano, Montana

Bray, Edward A. du; Harlan, Stephen S.

doi:10.3133/pp1602

Cited by 5 publications

(7 citation statements)

References 20 publications

(29 reference statements)

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“…Brooker (1992) differentiated autoclastic breccia, matrix-supported breccia (lahars and hyperconcentrated floodflows), clast-to-matrix-supported breccia (lahar deposits), and clast-supported breccia (lahar deposits). We note that similar approaches have been taken at other volcanoes where abundant breccia in the absence, or near absence, of coherent lava has led to the interpretation of cone-forming deposits comprised to a large extent by "laharic" breccia of inferred sedimentary origin (e.g., Lydon 1968;du Bray and Harlan 1998). We suggest that thick autoclastic breccias are more likely components of cone-forming facies than are reworked sedimentary deposits.…”

Section: Comparison To Previous Studiesmentioning

confidence: 81%

Nature and origin of cone-forming volcanic breccias in the Te Herenga Formation, Ruapehu, New Zealand

Smith¹,

Grubensky²,

Geissman³

1999

Bulletin of Volcanology

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Volcanic breccias form large parts of composite volcanoes and are commonly viewed as containing pyroclastic fragments emplaced by pyroclastic processes or redistributed as laharic deposits. Field study of cone-forming breccias of the andesitic middle Pleistocene Te Herenga Formation on Ruapehu volcano, New Zealand, was complemented by paleomagnetic laboratory investigation permitting estimation of emplacement temperatures of constituent breccia clasts. The observations and data collected suggest that most breccias are autoclastic deposits. Five breccia types and subordinate, coherent lava-flow cores constitute nine, unconformity-bounded constructional units. Two types of breccia are gradational with lava-flow cores. Red breccias gradational with irregularly shaped lava-flow cores were emplaced at temperatures in excess of 580 7C and are interpreted as aa flow breccias. Clasts in gray breccia gradational with tabular lava-flow cores, and in some places forming down-slope-dipping avalanche bedding beneath flows, were emplaced at varying temperatures between 200 and 550 7C and are interpreted as forming part of block lava flows. Three textural types of breccia are found in less intimate association with lava-flow cores. Matrix-poor, well-sorted breccia can be traced upslope to lava-flow cores encased in autoclastic breccia. Unsorted boulder breccia comprises constructional units lacking significant exposed lavaflow cores. Clasts in both of these breccia types have paleomagnetic properties generally similar to those of the gray breccias gradational with lava-flow cores; they indicate reorientation after acquisition of some, or all, magnetization and ultimate emplacement over a range of temperatures between 100 and 550 7C. These breccias are interpreted as autoclastic breccias associated with block lava flows. Matrix-poor, well-sorted breccia formed by disintegration of lava flows on steep slopes and unsorted boulder breccia is interpreted to represent channel-floor and levee breccias for block lava flows that continued down slope. Less common, matrixrich, stratified tuff breccias consisting of angular blocks, minor scoria, and a conspicuously well-sorted ash matrix were generally emplaced at ambient temperature, although some deposits contain clasts possibly emplaced at temperatures as high as 525 7C. These breccias are interpreted as debris-flow and sheetwash deposits with a dominant pyroclastic matrix and containing clasts likely of mixed autoclastic and pyroclastic origin. Pyroclastic deposits have limited preservation potential on the steep, proximal slopes of composite volcanoes. Likewise, these steep slopes are more likely sites of erosion and transport by channeled or unconfined runoff rather than depositional sites for reworked volcaniclastic debris. Autoclastic breccias need not be intimately associated with coherent lava flows in single outcrops, and fine matrix can be of autoclastic rather than pyroclastic origin. In these cases, and likely many other cases, the alternation of coherent lava flows and fragm...

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Section: Comparison To Previous Studiesmentioning

confidence: 81%

Nature and origin of cone-forming volcanic breccias in the Te Herenga Formation, Ruapehu, New Zealand

Smith¹,

Grubensky²,

Geissman³

1999

Bulletin of Volcanology

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“…Thin-skinned thrust faults in the frontal fold-thrust belt locally modified the edges of preexisting foreland basement uplifts Ruppel & Lopez, 1984). The basement rocks that form the Laramide uplifts were structurally elevated along roughly north trending foreland arches in the hanging walls of west and southwest dipping thrust faults and in the hanging walls of northwest striking, northeast dipping, highangle reverse faults of Precambrian ancestry ( Figure 2; DeCelles et al, 1987;Garihan et al, 1983;Schmidt & Hendrix, 1981;Schmidt & O'Neill, 1982;Schmidt et al, , 1993 Harlan, 1998;Lund et al, 2002;Foster et al, 2002Foster et al, , 2012; magmatism continued to the east until ca. 55 Ma (Constenius et al, 2003, and references therein).…”

Section: Geologic Setting Of Southwest Montana Laramide Upliftsmentioning

confidence: 99%

Early Inception of the Laramide Orogeny in Southwestern Montana and Northern Wyoming: Implications for Models of Flat‐Slab Subduction

2019

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Timing and distribution of magmatism, deformation, exhumation, and basin development have been used to reconstruct the history of Laramide flat‐slab subduction under North America during Late Cretaceous‐early Cenozoic time. Existing geodynamic models, however, ignore a large (~40,000‐km2) sector of the Laramide foreland in southwestern Montana. The Montana Laramide ranges consist of Archean basement arches (fault‐propagation folds) that were elevated by thrust and reverse faults. We present new thermochronological and geochronological data from six Laramide ranges in southwestern Montana (the Beartooth, Gravelly, Ruby and Madison Ranges, and the Tobacco Root and Highland Mountains) that show significant cooling and exhumation during the Early to mid‐Cretaceous, much earlier than the record of Laramide exhumation in Wyoming. These data suggest that Laramide‐style deformation‐driven exhumation slightly predates the eastward sweep of magmatism in western Montana, consistent with geodynamic models involving initial strain propagation into North American cratonic rocks due to stresses associated with a northeastward expanding region of flat‐slab subduction. Our results also indicate various degrees of Cenozoic heating and cooling possibly associated with westward rollback of the subducting Farallon slab, followed by Basin‐and‐Range extension.

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“…Thus, it would not be unreasonable to have another intrusion along the same NW-trending lineament that formed because of low-angle subduction of the Farallon plate. The igneous products of the Sliderock Mountain stratovolcano were interpreted to be the products of arc-related magmatism based on geochemistry [90]. The inferred intrusion may account for the Si, Ba, Au, and other metals present in the minerals of the PMD and not present in the LMD.…”

Section: Mineral Paragenesis Pmdmentioning

confidence: 99%

“…It may have formed in a similar timeframe to the Sliderock volcano and the Lodgepole intrusive, part of an extensive NW-trending volcanic field that lies astride the folds and faults of the Nye-Bowler lineament [90,91] (Figure 3, laccoliths). The alignment of these volcanic intrusives along the Nye-Bowler lineament strongly suggests the fault zone controlled the emplacement of the volcanic centers of the field [90]. Thus, it would not be unreasonable to have another intrusion along the same NW-trending lineament that formed because of low-angle subduction of the Farallon plate.…”

Section: Mineral Paragenesis Pmdmentioning

confidence: 99%

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Possible Involvement of Permian Phosphoria Formation Oil as a Source of REE and Other Metals Associated with Complex U-V Mineralization in the Northern Bighorn Basin?

Moore-Nall

Tsosie

2017

Minerals

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Abstract:The origin of V, U, REE and other metals in the Permian Phosphoria Formation have been speculated and studied by numerous scientists. The exceptionally high concentrations of metals have been interpreted to reflect fundamental transitions from anoxic to oxic marine conditions. Much of the oil in the Bighorn Basin, is sourced by the Phosphoria Formation. Two of the top 10 producing oil fields in Wyoming are located approximately 50 km west of two abandoned U-V mining districts in the northern portion of the basin. These fields produce from basin margin anticlinal structures from Mississippian age reservoir rock. Samples collected from abandoned U-V mines and prospects hosted in Mississippian aged paleokarst in Montana and Wyoming have hydrocarbon residue present and contain anomalous high concentrations of many metals that are found in similar concentrations in the Phosphoria Formation. As, Hg, Mo, Pb, Tl, U, V and Zn, often metals of environmental concern occur in high concentrations in Phosphoria Formation samples and had values ranging from 30-1295 ppm As, 0.179-12.8 ppm Hg, 2-791 ppm Mo, <2-146 ppm Pb, 10-490 ppm Tl, 907-86,800 ppm U, 1240-18,900 ppm V, and 7-2230 ppm Zn, in mineralized samples from this study. The REE plus Y composition of Madison Limestone-and limestone breccia hosted-bitumen reflect similar patterns to both mineralized samples from this study and to U.S. Geological Survey rock samples from studies of the Phosphoria Formation. Geochemical, mineralogical and field data were used to investigate past theories for mineralization of these deposits to determine if U present in home wells and Hg content of fish from rivers on the proximal Crow Indian Reservation may have been derived from these deposits or related to their mode of mineralization.

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Geology, age, and tectonic setting of the Cretaceous Sliderock Mountain Volcano, Montana

Cited by 5 publications

References 20 publications

Nature and origin of cone-forming volcanic breccias in the Te Herenga Formation, Ruapehu, New Zealand

Nature and origin of cone-forming volcanic breccias in the Te Herenga Formation, Ruapehu, New Zealand

Early Inception of the Laramide Orogeny in Southwestern Montana and Northern Wyoming: Implications for Models of Flat‐Slab Subduction

Possible Involvement of Permian Phosphoria Formation Oil as a Source of REE and Other Metals Associated with Complex U-V Mineralization in the Northern Bighorn Basin?

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