RT Journal Article
T1 Petrografía y condiciones de formación de las rocas ultramáficas con granate asociadas a las eclogitas de Cabo Ortegal
T1 Petrography and conditions of formation of garnet-bearing ultramafic rocks related to the Cabo Ortegal eclogites
A1 Mendia, M.
A1 Gil Ibarguchi, José Ignacio
AB Garnet-bearing ultramafic rocks forming a decametric outcrop occur associated to the eclogites of theupper catazonal unit of the Cabo Ortegal Complex. These ultramafites are included within variablymylonitized amphibole-pyroxene gneisses located between the eclogite band on top and the so-called‘banded gneisses’ formation below. They are harzburgites with orthopyroxene, olivine and amphibole asmain phases and spinel, garnet and ilmenite as minor phases. Serpentine and chlorite are the mainsecondary minerals. The absence of pervasive deformational features, lack of anisotropy and poikilitictexture of pyroxene and amphibole are noteworthy and point to a possible magmatic/mantle origin ofthese rocks. However, a detailed petrographic study has shown the existence of discrete domains made ofaggregates of minute pyrope-rich garnet, orthopyroxene and olivine with subgrain recrystallization. Themineralogical and textural features thus reveal a metamorphic origin for, at least part, of the presentmineral association. Calculated P-T conditions for the orthopyroxene-garnet assemblages are ca. 760 °Cand 19 kbar. The rocks studied bear important textural and, to some extent, mineralogical similarities toultramafic rocks elsewhere within the complex along major tectonic contacts (e.g. Carreiro Zone of TectonicMovement), although, in view of the relatively Mg-poor olivine and orthopyroxene compositions, an originthrough recrystallization of serpentinite protoliths appears unlikely. Instead, an origin through partialrecrystallization of mantle fragments related to the subduction and tectonic stacking processes that gaverise to the Complex is proposed
PB Sociedad Geológica de España
YR 2004
FD 2004
LK http://hdl.handle.net/10272/8888
UL http://hdl.handle.net/10272/8888
LA spa
DS Repositorio Institucional de la Universidad de Huelva
RD 1 jun 2026