Chemical variations in clinopyroxene and garnet from eclogites of the Vara Valley (Voltri Group, Italy)
European Journal of Mineralogy Volume 7 Number 1 (1995), p. 103 - 118
published: Feb 8, 1995
manuscript accepted: Sep 22, 1994
manuscript received: Oct 26, 1993
ArtNo. ESP147050701008, Price: 29.00 €
Abstract Co-existing clinopyroxene-garnet pairs from 7 eclogite samples in a single body cropping out in the Vara Valley (Voltri Group, Italy) were examined by microprobe and X-ray powder diffraction. Both minerals show marked heterogeneities implying a broad scatter of chemical compositions, as well as variations in the oxidation state of clinopyroxene. Such features strongly affect the calculation of the distribution coefficient (KD), so the application of any exchange thermometry based on the garnet/clinopyroxene pair is rendered inaccurate or even effectively useless.