Relationship between Paleotemperatures of Metamorphic Dolomites and ESR Determined Mn(II) Partitioning Ratios
An Electron Spin Resonance (ESR) study of the distribution of Mn(II) between Mg sites and Ca sites in 28 contact metamorphic dolomite samples suggests that the distribution is temperature sensitive. The data can be modelled by alternative interpretations. In the first a polynomial equation approximates the trend of the data suggesting an exponential relation with Mn(II) ratios decreasing to a stable value of 10 with increasing temperature (to near 900°C). The second suggests two groups of dolomites. One group, close to the intrusion ( < 100 m), has a low partitioning ratio (10 to 30), possibly increasing linearly with increasing distance from the intrusive contact. The second group (100 to 400 m) increases in scatter and distribution ratio (20 to 215) with increasing distance. Whatever the detailed relationship, we conclude that Mn partitioning is related to the thermal halo of the intrusion and that lower ratios result from higher temperatures. Mn(II) partitioning ratios may yield absolute paleotemperature data when calibrated against other techniques.
R. Lloyd et al., "Relationship between Paleotemperatures of Metamorphic Dolomites and ESR Determined Mn(II) Partitioning Ratios," Geochimica et Cosmochimica Acta, vol. 49, no. 12, pp. 2565-2568, Elsevier, Dec 1985.
The definitive version is available at http://dx.doi.org/10.1016/0016-7037(85)90125-5
Geosciences and Geological and Petroleum Engineering
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