The Case for UHP Conditions in the Cuaba Terrane, Río San Juan Metamorphic Complex, Dominican Republic
Keywords:
Ultra high pressure, Garnet-bearing ultramafic rock, Eclogite, Dominican RepublicAbstract
This paper is essentially a review of previously published data and interpretations for ultramafic and eclogitic rocks from the Cuaba terrane in northern Dominican Republic. Ultrahigh pressure (UHP) conditions are indicated for the Cuaba terrane on the basis of phase relationships in garnet-bearing ultramafic rock. Dikes and orthocumulate textures indicate a magmatic origin. Mineral assemblages define a line of descent controlled by fractional crystallization. The original estimate of the magmatic conditions (P>3.4GPa, T>1550°C) was inferred previously from available high-P melting experiments in the CMAS system and high-P experimental determination of the sapphirine-out reaction in the MAS system. Revised estimates of magmatic conditions (P>3.2GPa, T>1500°C) take into account the influence of other components, especially Fe. We propose an origin in the mantle-wedge above a subduction zone. The rock was delivered to the subduction zone by forced convection in the mantle wedge (corner-flow), coupled with erosion of the hanging wall. Thermobarometry indicates >850°C and >3.4GPa when the ultramafic rock was incorporated into eclogite (deep-subducted oceanic crust). Evidence for UHP conditions in the retrograded eclogite is not obvious. Two types of symplectic intergrowths, plagioclase + clinopyroxene (Sym-I) and plagioclase + epidote (Sym-II), are interpreted as the products of the decomposition of two types of omphacite, Omp-I and Omp-II. Theoretically, Omp-II formed as the result of a retrograde reaction of the form, Omp-II + coesite = Omp-I + kyanite + /- garnet, according to which the maximum pressure for Omp-II is between ~2.8GPa (~850°C) and ~4.2GPa (~950°C), consistent with subsolidus conditions for the garnet-bearing ultramafic rocks. For eclogite, the highest-pressure mineral assemblage would have been Omp-I + kyanite + garnet + coesite.
Downloads
Issue
Section
License
Copyright
The commercial rights of the printed and online versions of Geologica Acta are property of the UB, ICTJA, IDAEA and UAB, and Geologica Acta must be cited for any partial or full reproduction.
The opinions and conclusions stated in each article are the exclusive responsability of the authors and do not necessarily coincide with those of the above mentioned institutions UB, ICTJA, IDAEA and UAB.
Author Rights
Authors retain the copyright on their papers (accepted manuscript, uncorrected proof and published paper) and are authorized to post them on their own Web page or their institutional repositories. In all cases, the complete citation and a link to the Digital Object Identifier (DOI) of the article must be included.
The authors can use excerpts or reproduce illustrations of their papers in other works without prior permission of Geologica Acta provided the source of the paper including the complete citation is fully acknowledged.
Papers are distributed under the Attribution-Share Alike Creative Commons License. This license allows others to alter, remix or build upon a paper and the resulting work may be distributed under the same or similar license to this one.