Oxygen-Isotope Fractionations in Systems Containing Dolomite

Northrop, D.A.; Clayton, Robert N.

doi:10.1086/627153

Cited by 388 publications

(164 citation statements)

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“…Sulfur isotopic equilibrium fractionation factors for the zinc sulfide sulfide ion and lead sulfide sulfide ion pairs were studied by the partial exchange technique (NORTHROP and CLAYTON, 1966). Sulfides used in this isotopic fractionation experiment were prepared and ana lyzed as follows:…”

Section: Experimental and Resultsmentioning

confidence: 99%

“…The fractionation factors for the zinc sulfide HS and lead sulfide HS pairs were estimated from the results given in Tables 2 and 3, respectively, by the partial exchange method (NORTHROP and CLAYTON, 1966), on the assumption that isotopic exchange reaction between metallic sulfide and HS ions approaches equilibrium at a constant rate at a given temperature.…”

Section: Isotopic Analysesmentioning

confidence: 99%

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Sulfur isotopic fractionation among sphalerite, galena and sulfide ions

Kiyosu¹

1973

Geochem. J.

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Section: Experimental and Resultsmentioning

confidence: 99%

Section: Isotopic Analysesmentioning

confidence: 99%

Sulfur isotopic fractionation among sphalerite, galena and sulfide ions

Kiyosu¹

1973

Geochem. J.

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“…The 6 0 values for the secondary carbonates range from 16.0-19,2 per mil. Presuming an alteration temperature of 225°C, and using the dolomite-water fractionation 18 curve of Northrop and Clayton (1966), the <5 0 values of the 18 altering fluid varied between +4.6 and +7.8 per mil. The 6 0 values from two samples collected immediately adjacent to and 10 18 cm from the 18-1 vein demonstrate an increase in the 6 0 value of the altering fluid away from the vein as it reacted with the metamorphic rocks.…”

Section: Unaltered and Altered Wall Rocksmentioning

confidence: 99%

Alteration and vein mineralization, Schwartzwalder uranium deposit, Front Range, Colorado

Wallace¹

1983

Open-File Report

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The Schwartzwalder uranium deposit, in the Front Range west of Denver, Colorado, is the largest vein-type uranium deposit in the United States. The deposit is situated in a steeply dipping fault system that cuts Proterozoic metamorphic rocks. The host rocks represent a submarine volcanic system with associated chert and iron-and sulfide-rich pelitic rocks. Where faulted, the more competent garnetiferous and quartzitic units behaved brittlely and created a deep, narrow conduit.The ores formed 70-72 m.y. ago beneath 3 km of Phanerozoic sedimentary rocks. Mineralization included two episodes of alteration and three stages of vein mineralization. Early carbonatesericite alteration pseudomorphically replaced mafic minerals, whereas the ensuing hematite-adularia episode replaced only the earlier alteration assemblage. Early vein mineralization produced a minor sulfide-adularia-carbonate assemblage. Later vein mineralization generated the uranium ores in two successive stages. Carbonates, sulfides, and adularia filled the remaining voids. Clastic dikes composed of fault gouge and, locally, ore were injected into new and existing fractures.Geologic and chemical evidence suggest that virtually all components of the deposit were derived from major hornblende gneiss units and related rocks. The initial fluids were evolved connate/metamorphic water that infiltrated and resided along the extensive fault zones. Complex fault movements in the frontal zone of the eastern Front Range caused the fluids to migrate to the most permeable segments of the fault zones. Heat was supplied by increased crustal heat flow related to igneous activity in the nearby Colorado mineral belt. Temperatures decreased from 225°C to 125°C during later mineralization, and the pressure episodically dropped from 1000 bars. The CO^ fugacity was initially near 100 bars, and uranium was carried as a dicarbonate complex. Sudden decreases in confining pressure during fault movement caused evolution of 009 and a consequent increase in pH. Uranium was released with destruction of the uranyl complexes; it was subsequently reduced by aqueous sulfur species, thereby leading to the precipitation of pitchblende. ACKNOWLEDGMENTS

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“…At equilibrium, the 80 18 of dolomite is greater than that of calcite by about 4 per mil at 25°C (O'Neil and Epstein, 1966;Northrup and Clayton, 1966;Sheppard and Schwarcz, 1970), but the two minerals occurring together in nature often show (Clayton and others, 1968) , so they are not iso topically comparable. Because of these uncertainties, we do not consider the equilibrium fractionation between the two minerals to explain the oxygen compositions shown in figure 3.…”

Section: General Features Of the Isotopic Compositionmentioning

confidence: 99%

Geological Survey research 1972

1972

Professional Paper

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Oxygen-Isotope Fractionations in Systems Containing Dolomite

Cited by 388 publications

References 17 publications

Sulfur isotopic fractionation among sphalerite, galena and sulfide ions

Sulfur isotopic fractionation among sphalerite, galena and sulfide ions

Alteration and vein mineralization, Schwartzwalder uranium deposit, Front Range, Colorado

Geological Survey research 1972

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