Rb-Sr dating of sphalerites from Mississippi Valley-type (MVT) ore deposits

Journal Article · Fri Jan 01 00:00:00 EST 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90440-8· OSTI ID:6669603

Nakai, S; Halliday, A N; Kesler, S E; Jones, H D ^[1]; Kyle, J R ^[2]; Lane, T E ^[3]

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1. Univ. of Michigan, Ann Arbor (United States)
2. Univ. of Texas, Austin (United States)
3. Memorial Univ. of Newfoundland, St. John's (Canada)

Mississippi Valley-type (MVT) ore deposits are epigenetic carbonate-hosted Pb-Zn deposits that contain galena, sphalerite, fluorite, barite, dolomite, calcite, and quartz. Although they are thought to form from basinal brines, their exact origins are still unclear, partly because of the scarcity of reliable geochronological data. Rb-Sr dating of sphalerites has recently been shown to be a promising technique for the direct dating of ore minerals in MVT deposits. This paper reports the results of a reconnaissance study of sphalerites, their fluid inclusions, and associated minerals from MVT deposits of North America. Sphalerites from Immel mine, Mascot-Jefferson City district, east Tennessee, define a Rb-Sr age of 347 [plus minus] 20 Ma consistent with a Rb-Sr age of 377 [plus minus] 29 Ma for sphalerites from Coy mine in the same district, but inconsistent with models that ascribe their genesis to the effects of the late Paleozoic Alleghenian orogeny. Rb-Sr isotopic analyses of K-feldspar from Immel mine preclude the possibility that the Rb-Sr data reflect feldspar inclusions. Sphalerites from the main ore zone of Daniel's Harbour mine, Newfoundland, do not form a linear isochron and open behavior of the Rb-Sr system is suspected. Sphalerites from the Pine Point district, Northwest Territories, Canada, define a Rb-Sr age of 361 [plus minus] 13 Ma, indicating that the mineralization took place shortly after the deposition of the middle Devonian host carbonate rocks. These results are not compatible with mineralization models based on regional fluid migration related to early Tertiary Cordilleran deformation. Sphalerites from northern Arkansas have very low Rb and Sr concentrations (less than 0.1 ppm). The Rb-Sr data do not form isochrons and the sphalerites have higher [sup 87]Sr/[sup 86]Sr ratios than expected, given their Rb/Sr ratios and reasonable constraints on their ages. 58 refs., 7 figs., 2 tabs.

• OSTI ID: 6669603
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 57:2; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
58 GEOSCIENCES
RUBIDIUM
ISOTOPE RATIO
SPHALERITE
ISOTOPE DATING
STRONTIUM
ARKANSAS
BARITE
BRINES
CALCITE
CANADA
CARBONATE ROCKS
DEFORMATION
DEPOSITION
DEPOSITS
DOLOMITE
FLUORITE
GALENA
INCLUSIONS
MIGRATION
MINERALIZATION
NEWFOUNDLAND
NORTH AMERICA
NORTHWEST TERRITORIES
QUARTZ
TENNESSEE
AGE ESTIMATION
ALKALI METALS
ALKALINE EARTH METALS
CARBONATE MINERALS
DEVELOPED COUNTRIES
ELEMENTS
HALIDE MINERALS
ISLANDS
METALS
MINERALS
OXIDE MINERALS
ROCKS
SEDIMENTARY ROCKS
SULFATE MINERALS
SULFIDE MINERALS
USA
400100* - Analytical & Separations Chemistry
580000 - Geosciences