Origin of eclogite and garnet pyroxenite from the Moldanubian Zone of the Bohemian Massif, Czech Republic and its implication to other mafic layers embedded in orogenic peridotites

Summary The granulite terrane of the Czech part of the Gf?hl unit includes numerous small bodies of mantle derived peridotite, some of which contain layers or lenses of eclogite and garnet pyroxenite. These eclogitic rocks have generally been considered to be high-pressure crystal cumulates formed in the upper mantle. We present new analyses of whole-rock major and trace element contents for three kynanite-quartz eclogite samples taken from the Nové Dvory garnet peridotite body. Integrating these data with previously published analyses from the literature on eclogitic rocks from this terrane, we demonstrate that a magnesian group of eclogites, including these three new samples, were originally formed as cumulus gabbros, which were later transformed to eclogites in the mantle. A gabbroic origin for some mafic layers (Type II) has been advocated for other orogenic peridotites, such as Beni Bousera (Morocco), Ronda (Spain), and Horoman (Japan). By comparing these sets of data with those from the Bohemian Massif, we propose a simple method of identifying groups of metagabbros by utilizing MgO-normalization in oxide ratio plots for whole-rock major element analyses.