The geochemistry of manganese carbonate in Panama Basin sediments |
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| Authors: | TF Pedersen NB Price |
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| Institution: | Department of Oceanography, The University of British Columbia, 6270 University Boulevard, Vancouver, B.C., Canada, V6T 1W5;Grant Institute of Geology, University of Edinburgh, West Mains Road, Edinburgh, Scotland, EH9 3JW |
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| Abstract: | The Mn distribution in Panama Basin area sediments and interstitial waters is discussed. Striking surficial Mn enrichments produced by a well-known diagenetic recycling process characterize the sediments of the region. Thermodynamic solubility calculations indicate that in at least one core interstitial waters approach saturation with respect to MnCO3. A mixed carbonate phase of composition (Mn48 Ca47 Mg5)CO3 was recovered from an ash band in the same core. The association of this material with the coarse volcaniclastic debris is thought to result from facile manganous carbonate precipitation in sediment horizons of coarser mean grain size. Since sulphate reduction in the upper two metres of Panama Basin sediments is fairly minor, little increase in alkalinity is observed, and it is postulated that significant production of carbonate alkalinity is not a prerequisite for manganous carbonate generation in hemipelagic sediments. A more important factor appears to be the availability of Mn oxides for solution during early diagenesis. Stable C isotopic analyses indicate that little C of organic origin is used in the precipitation reaction in either Panama Basin or Loch Fyne (Scotland) sediments. |
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