The Pewabic Mine

Schmitt, Harrison Ashley

doi:10.1130/gsab-50-777

Cited by 9 publications

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“…The Hanover limestone is a very pure white, coarse-grained (0.2-2 mm) crinoidal limestone, whereas the Upper, Middle, and Lower Blue limestones are fine-grained (<0.01-0.2 mm), black, carbonaceous, silty, slightly argillaceous limestones. The magnesium (and presumably iron and manganese) content of the Hanover, Upper, Middle, and Lower Blue limestones does not vary significantly, being respectively: 0.19, 0.14, 0.10, and 0.44 wt percent MgO (Schmitt, 1939). Although skarn has formed in all of these units, the bulk of the economic skarn and carbonate replacement mineralization in the Groundhog mine occurs in the Hanover limestone.…”

Section: Introductionmentioning

confidence: 95%

“…In the Groundhog mine ilvaite occurs sporadically as euhedral crystals at the marble front, relict carbonate patches in skarn, and as unaltered crystals in zones of intense chlorite-pyrite retrograde alteration along dike contacts. It is richer in manganese (Table 7) than ilvaite from the zinc skarns at the Pewabic mine, New Mexico (Schmitt, 1939) and South Mountain, Idaho (Sorenson, 1927), but there are too few published ilvaite analyses in the literature for a systematic review.…”

Section: Mineral Composition and Zonationmentioning

confidence: 99%

“…1) approximately 25 km east of Total Groundhog mine production to September 1977: 2,987,340 tons averaging 12.3% Zn, 3.6% Pb, 1.3% Cu, and 2.5 oz/ton Ag (data from Lasky, 1936;Lasky and Hoagland, 1950;and T. Dalla Vista, pers. commun., 1980) Abbreviations: P --production, R = reserves deposits with related copper skarn occur at Continental , Copper Flat (Hernon and Jones, 1968), and Santa Rita (Nielson, 1968;Amad and Rose, 1980;Reynolds and Beane, 1985); (2) iron and zinc skarn deposits occur in a broad zone around the Hanover-Fierro pluton, including the Pewabic (Schmitt, 1939), Empire, Kearney, and Oswaldo mines (Hernon and Jones, 1968), and also along several north-and northeast-trending dike swarms, including the Groundhog and Grant County mines; and (3) lead-zinc-silver veins and replacements occur at the Bullfrog, Georgetown, upper Groundhog, Slate, and Three Brothers mines (Lasky, 1942;Hernon and Jones, 1968). Most workers consider the ore deposits in the Central mining district to be the result of a single prolonged mineralization event related to a complex series of granitic stocks and dikes (Hernon and Jones, 1968).…”

Section: Introductionmentioning

confidence: 99%

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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: 95%

Section: Mineral Composition and Zonationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Meinert¹

1987

Economic Geology

118

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“…In many cases, the clinopyroxenes are partially replaced by these sulfides and oxides. Such replacement of silicates by oxide and sulfide minerals is a common feature of skarn deposits (Schmitt, 1959;Hernon and Jones, 1968;Burt, 1972a).…”

Section: Some Of the Clinopyroxenes Have Undergone Ret-mentioning

confidence: 99%

“…Early formed skarn silicates, such as clinopyroxenes, normally predate ore minerals and may well exert chemical controls on later ore are largely members of the hedenbergite-diopside-iohannsenite solid solution series and the garnets are commonly referred to as andradite or grossular. Compositional characterization of these silicates has been based largely on older wet chemical analyses (Allen and Fahey, 1957;Zharikov, 1970), as well as X-ray and optical properties of these minerals (Schmitt, 1959). Only recently have electron microprobe analyses of clinopyroxenes and garnets from a number of skarn deposits been published (Huckenholz and Yoder, 1971;Morgan, 1975;Einaudi, 1977;Shimazaki, 1977;Shimazaki and Bunno, 1978;Kwak, 1978a, b).…”

Section: Introductionmentioning

confidence: 99%

The f O2 -T and f S2 -T stability relations of hedenbergite and of hedenbergite-johannsenite solid solutions

Burton

Taylor

1982

Economic Geology

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Clinopyroxene in mineralized skarns appears to place local chemical controls on ore mineral precipitation by entering into oxygen-and sulfur-buffering reactions in which garnet is an end product. Prior to investigating these reactions experimentally, the compositions of clinopyroxenes and garnets from ten polymetallic (Zn, Cu-Pb-Zn, Fe-Cu, Zn-Cu, and Fe) skarp. s in the southwestern United States, Japan, and Italy were analyzed with an electron microprobe. The clinopyroxenes are members of the hedenbergite (CaFeSi206)-diopside (CaMgSi206)-johannsenite (CaMnSi206) solid solution series with the hedenbergite component dominating and ranging from 36 to 95 mole percent, the diopside component from 0 to 41 mole percent, and the johannsenite component from 2 to 31 mole percent. The garnets are predominantly andradite (CaaFe2SiaO•2) with traces of Mn (0.3 to 2.6 wt %). The oxygen-and sulfur-buffering reactions involving pure hedenbergite in skarns have been studied at 800 ø, 700 ø, and 600øC and Ptotal = 2 kb, utilizing the hydrogen fugacity sensor technique of Chou and Eugster (1976). The terminal oxidation reaction for hedenbergite is: hedenbergite + O2 = andradite + magnetite + quartz. The general equation for log fo2 for this reaction at T and Ptotal is: 26,457 0.087(P-1) log 0Coz)T.e(-4-0.12) -4-12.12 + T T Experiments were also performed utilizing the same sensor technique to evaluate the effect of Mn on the hedenbergite oxygen-buffering reaction. The microprobe compositional analyses of naturally occurring skarn clinopyroxenes were used to constrain the starting material chemistry of the hedenbergitic phase. Addition of 15 mole percent johannsenite to the clinopyroxene raises the stability field of hedenbergite by about 1 log fo• over the temperature range of interest.Sulfur fugacities for the analogous sulfur-buffering reaction, hedenbergite + Sa = andradite + pyrite and/or pyrrhotite + quartz, were determined graphically from log fs2-1og fo• diagrams utilizing the experimental fo•-T data for hedenbergite. At Ptotal = 2 kb, pure hedenbergitc can coexist stably with pyrite below 288 ø + 16øC and with pyrrhotite at higher temperatures. With decreasing temperature hedenbergite containing 15 mole percent johannsenite first enters the pyrite stability field at 587 ø + 87øC and Ptotal = 2 kb.Results of this study support theoretical models proposed by Burr (1972a, b) for the stability of clinopyroxene in Ca-Fe-Si skarn deposits.

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Manganiferous pyroxenes and pyroxenoids from three Pb-Zn-Cu skarn deposits

Abrecht

1985

Contrib Mineral and Petrol

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The Pewabic Mine

Cited by 9 publications

References 0 publications

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

The f O2 -T and f S2 -T stability relations of hedenbergite and of hedenbergite-johannsenite solid solutions

Manganiferous pyroxenes and pyroxenoids from three Pb-Zn-Cu skarn deposits

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