Loss of metals from pelites during regional metamorphism |
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Authors: | U Haack H Heinrichs M Boneß A Schneider |
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Institution: | (1) Geochemisches Institut der Universität, Goldschmidtstr. 1, D-3400 Göttingen, Germany |
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Abstract: | In aluminous metapelites the ratio H2O+/K2O decreases with increasing metamorphic grade and degree of reaction. This ratio is a very practical indicator for the progress of the mineral reconstitution during progressive metamorphism. With decreasing values of the ratio H2O+/ K2O the Cu concentration and the following element ratios also decrease either continuously or in stepwise fashion: Tl/K2O, Ba/K2O, Pb/K2O, Bi/K2O, Hg/K2O, Sr/Na2O, Zn/(Fe2++Mg), Cd/(Fe2++Mg); Rb/K2O remains approximately constant. In the aluminous metapelites of the Damara Orogen in Namibia the following losses occur between the biotite isograd and anatexis: 61% Cu, 20% Tl, 34% Ba, 59% Pb, 86% Bi, 46% Hg, 30% Sr, 25% Zn, 31% Cd. Thus the potential of regional metamorphism to form hydrothermal deposits in the low grade environment should not be neglected. |
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