Comments on “Garnet-bearing ultramafic rocks from the Dominican Republic: Fossil mantle plume fragments in an ultra high pressure oceanic complex?” by Gazel et al. [Lithos 125 (2011) 393-404

Abstract

The Rio San Juan Complex in the Dominican Republic hosts a suite of enigmatic corundum-bearing garnet peridotite rocks. Two hypotheses for their origin exist, an ultrahighpressure (UHP) hypothesis, in which corundum, spinel and garnet crystallised simultaneously at UHP magmatic conditions (>3.2 GPa and >1500°C), and a low pressure (LP) hypothesis, in which the rocks are metamorphosed equivalents of low-pressure plagioclase-bearing cumulates. Distinction between the two is hampered by extensive metamorphic recrystallisation of the rocks under UHP conditions. In a recent paper, Gazel et al. [Gazel, E., Abbott, R.N., Draper, G., 2011, ultramafic rocks from the Dominican Republic: Fossil mantle plume fragments in an ultra high pressure oceanic Lithos 125, 393-404] reported trace element data for minerals from a garnet clinopyroxenite rock and used garnet-clinopyroxene partitioning coefficients to demonstrate an ultrahigh formation temperature of the rock, thus supporting the UHP hypothesis. However, the interpretations contained many unwarranted assumptions and were not consistent even with their own new data. This Comment addresses the shortcomings of the paper and demonstrates that (1) the authors’ temperature estimates are invalid, (2) their garnet compositional data are best explained by its formation by metamorphic recrystallisation after plagioclase. Therefore, an UHP igneous origin of the rocks is highly unlikely. Author Final Draft or ‘Post-Print’ Versionthe final version was subsequently published in Lithos copyright of Elsevier (2012) available online. Cite As: De Hoog, C-J 2012, 'Comments on Garnet-bearing ultramafic rocks from the Dominican Republic: Fossil mantle plume fragments in an ultra high pressure oceanic complex? by Gazel et al. [Lithos 125 (2011) 393-404]' Lithos, vol 134-135, pp. 330-334.