The origin of the silica of the bedrock hypogene ore deposits

Schmitt, Harrison Ashley

doi:10.2113/gsecongeo.49.8.877

Cited by 3 publications

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“…There are two distinct dike types in the Groundhog mine, both of which are considered to be Tertiary in age (Jones et al, 1967). The granodiorite porphyry dikes (Table 2) ] Groundhog mine, Vanadium area; L. Entwistle, analyst (Schmitt, 1954) g Groundhog mine, 1634 drift; L. D. Trumbull, analyst (Jones et al, 1967) 3 Analyses by X-ray fluorescence, Department of Geology, Washington State University (Meinert, 1983); analyses are normalized on a volatile-free basis with the oxidation state of iron set at the arbitrary ratio of Fe203/FeO = 0.87 size and the extent or intensity of skarn-endoskarn alteration. However, the amount of skarn and number of dikes is greater toward the northeast part of the system.…”

Section: Introductionmentioning

confidence: 99%

Skarn zonation and fluid evolution in the Groundhog Mine, Central mining district, New Mexico

Meinert¹

1987

Economic Geology

118

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The Groundhog mine contains one of the largest and best exposed Zn-Pb-Cu-Ag skarn deposits in the United States. Skarn is formed in Carboniferous limestones spatially associated with a nearly vertical swarm of Early Tertiary granodiorite porphyry dikes. Metal ratios, mineralogy, composition, and fluid inclusion characteristics of the skarn are systematically zoned from northeast to southwest along the >3-km strike length of the system and relative to the original dike-limestone contact. Zn/Cu, Zn/Ag, Pb/Cu, Pb/Zn, and Pb/Ag ratios all increase toward the distal southwest end of the mine where highest Zn, Pb, and total metal grades also occur. Endoskarn is zoned in terms of the relative proportions and manganese content of epidote and chlorite. In the Northeast zone, skarn is zoned away from dikes in the sequence: garnet to pyroxene to pyroxenoid to marble. In the Central skarn zone, garnet is absent and pyroxene begins the zonation sequence at the dike contact. In the Southwest zone, pyroxene is less abundant and pyroxenoid locally begins the zonation sequence. Sphalerite-galena-pyrite-quartzcarbonate are present in all skarn zones and in carbonate replacement mantos and chimneys beyond skarn. Distal mineralogical zones (e.g., pyroxenoid and manto) are more extensive to the southwest. In general, the skarn zonation sequence is wider and more fully developed in pure, coarse-grained limestone than in silty, carbonaceous, or fine-grained limestone. High permeability and water/rock ratio are considered the dominant controls on skarn size. Most skarn minerals, including garnet, pyroxene, pyroxenoid, ilvaite, amphibole, chlorite, carbonate, and sphalerite, are enriched in manganese. Pyroxene becomes more manganese rich (up to 85 mole % johannsenite):(1) toward marble, (2) along strike to the southwest, (3) at higher elevations, and (4) in coarser grained, cleaner limestones. The more manganese-rich pyroxenes formed from fluids which are distal in the overall zonation sequence. In contrast, pyroxene formed in proximal locations (dike contact, Northeast skarn zone, low elevation, fine-grained, impure limestone) is enriched in magnesium. Pyroxene-forming fluids are depleted first in Mg, then in Fe, and finally in Mn, as proposed by Burt (1977). Fluid inclusion homogenization temperatures are lower than for most zinc skarns. In the Northeast skarn zone the average homogenization temperature is 337øC and salt daughter minerals are present in garnet and pyroxene (inclusions without daughter minerals average 8.5 wt % NaCI), whereas salt daughter minerals are absent in the Central and Southwest skarn zones and average homogenization temperatures and salinities are 320øC, 7.3 wt percent NaC1, and 293øC, 6.2 wt percent NaC1, respectively. Pressure estimates from rare clusters of fluid inclusions with evidence for boiling are between 155 and 175 bars. Skarn thermal gradients calculated from fluid inclusion homogenization temperatures are 35øC from dike to marble front and 50øC from dike to the limit of alteration (carbonate repla...

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Section: Introductionmentioning

confidence: 99%

Skarn zonation and fluid evolution in the Groundhog Mine, Central mining district, New Mexico

Meinert¹

1987

Economic Geology

118

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“…126 Ontwerpers van constituties moeten niet denken dat ze dit probleem makkelijk kunnen vermijden. 127 Hierin vinden we de derde aanwijzing voor het belang van 'openheid' bij Schmitts parlementsanalyse. 128 Wederom zien we Schmitts fascinatie voor de versluierde, aan het oog ontsnappende, werkelijke macht terugkomen (denk aan: de arcana, de geheime staatspolitiek uit zijn analyse van het parlement) -en cruciaal daarbij is de figuur van de 'voorkamer', die nu ook weer door Schmitt wordt ingezet.…”

Section: Een Alternatieve Interpretatie Van Schmitts Parlementstheseunclassified

De waarde van het parlement: Van der Pot bij de VWR, Schmitt en het parlement als architectonisch-ordeningsprincipe

Rijpkema¹

2019

Netherlands Journal of Legal Philosophy

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Laramide Igneous Rocks and Related Porphyry Copper Occurrences of Southwest Romania

Gunnesch

1982

Ore Genesis

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The origin of the silica of the bedrock hypogene ore deposits

Cited by 3 publications

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Skarn zonation and fluid evolution in the Groundhog Mine, Central mining district, New Mexico

Skarn zonation and fluid evolution in the Groundhog Mine, Central mining district, New Mexico

De waarde van het parlement: Van der Pot bij de VWR, Schmitt en het parlement als architectonisch-ordeningsprincipe

Laramide Igneous Rocks and Related Porphyry Copper Occurrences of Southwest Romania

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