Metamorphic Grade and Iron-Magnesium Distribution between Co-Existing Garnet-Biotite and Garnet-Hornblende
- 1 October 1962
- journal article
- Published by Cambridge University Press (CUP) in Geological Magazine
- Vol. 99 (5) , 427-438
- https://doi.org/10.1017/s0016756800059690
Abstract
It is shown that in the two mineral pairs discussed the metamorphic grade can be estimated from the atomic ratios (Xa = Mg/Mg + Fe + 0·175 Mn + 0·360 Ca) in garnet and Xb = Mg/(Mg + Fe) in the other mineral. The standard error of the estimation is about one-third of the temperature range of the amphibolite facies.Where M is the metamorphic grade on an arbitrary scale, in which the lower boundary of the amphibolite facies is at 4·2 and the upper at 5·1, and K is the distribution coefficient (Xb—XaXb)/(Xa—XaXb), then the estimating equation is M = 5·6 — 1·5 log10 K.Keywords
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