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Effects of Mississippi Valley-Type Mineralization on REE Patterns of Carbonate Rocks and Minerals, Viburnum Trend, Southeast Missouri

Joseph L. Graf Jr.
The Journal of Geology
Vol. 92, No. 3 (May, 1984), pp. 307-324
Stable URL: http://www.jstor.org/stable/30069402
Page Count: 18
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Effects of Mississippi Valley-Type Mineralization on REE Patterns of Carbonate Rocks and Minerals, Viburnum Trend, Southeast Missouri
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Abstract

The lead-zinc ores of the Viburnum Trend were deposited as replacements and open space fillings within the Cambrian Bonneterre Formation. The shapes of rare earth element (REE) patterns of unmineralized limestones and dolostones of the Bonneterre Formation (host rocks) are similar to each other and to shale REE patterns, regardless of facies or of insoluble residue content. In mineralized zones, recrystallized and mineralized dolostones (mean La/Sm = 2.6), vug dolomites (mean La/Sm = 1.6), and vug calcites (mean La/Sm = 0.9) have La/Sm ratios that are significantly lower than those of host rocks (mean La/Sm = 5.7). Vug calcites have lower Sm/Lu (mean = 6.7) and vug dolomites have higher Sm/Lu (mean = 22.5) than host rocks (mean Sm/Lu = 11.5). Preliminary partitioning experiments and estimates of the effects of complexing suggest that the observed REE patterns of carbonate minerals could not have developed from a solution with a REE distribution like that of host rocks or by dissolution and reprecipitation of REE from immediate host rocks. The Sm/Lu ratios of vug dolomites and vug calcites may be explained by precipitation zoning, but the low La/Sm values are best explained if the Viburnum Trend ore solutions had very low La/Sm ratios. Mixing of host-rock and ore solution REE took place during ore deposition; host rock REE became much less important during deposition of vug carbonates. When more is known about the distribution of REE in rocks along possible solution paths and about the partitioning behavior of REE between solutions and these rocks, REE studies may provide additional information regarding paths of solution flow and possible source rocks for the lead-zinc deposits in the Viburnum Trend and in other Mississippi Valley Type ore districts.

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