Abstract

Some metacarbonate rocks from the Nevado-Filabride Complex (Betic Cordilleras, southern Spain) contain unusual quantities of Cr-rich minerals. These occur in very thin layers concentrated in beds a few meters thick, interbedded with other lithologies (metapelites and metacarbonates) devoid of chromium. Cr 2 O 3 contents reported here reach values (in wt.%) of 5.74 in epidote, 5.09 in phengitic muscovite, 1.37 in paragonite, 2.19 in chlorite, 2.24 in amphibole, 1.15 in garnet, 0.72 in titanite, and 1.30 in rutile. The distribution of Cr in the samples is very irregular, even at the scale of a single crystal. In all silicates, Cr enters octahedral sites replacing VI Al. In epidote, Cr is mainly located at the M1 site, and in most samples epidote preferentially incorporates Cr over Al in comparison to other silicates. Rare, small inclusions of chromian spinel with anomalously high Zn contents (up to 15.14 wt.% ZnO) are found in some of the silicate phases. We consider chromian spinel to be the source of Cr in these metasediments, which were deposited as beach placers. The conservation of the original, sedimentary heterogeneity in Cr distribution as well as the zoning pattern of Cr in epidote suggest very limited mobility of this element during metamorphism. The high concentration of Zn in relict inclusions of chromian spinel is interpreted as a passive enrichment.

First Page Preview

First page PDF preview
You do not currently have access to this article.