Evolución metamórfica de los esquistos con Grt-St-Ky del antiforme de Arinteiro (Complejo de Órdenes, noroeste del Macizo Ibérico)

  1. Castiñeiras García, Pedro
  2. Arenas Martín, Ricardo
  3. Martínez Catalán, José Ramón
  4. González del Tánago del Río, José
Journal:
Geogaceta

ISSN: 0213-683X

Year of publication: 2002

Issue: 32

Pages: 107-110

Type: Article

More publications in: Geogaceta

Abstract

The Órdenes Series in the Arinteiro anti form are generally Grt-St-Ky schists which exhibit a regional schistosity (SJ and a metamorphic peak mineral assemblage with Qtz-Pl-Ms-Bt-Grt-Ky-Rt-llm. Some garnets show a distinctive pétrographie zoning which correlates with compositional zoning patterns. Kyanite occurs as stretched aggregates, usually surrounded by a shimmer aggregate of muscovite. Staurolite is scarce and develops allotriomorphic crystals partially replaced by garnet and kyanite. Mineral analyses were undertaken in six samples of Grt-St-Ky schists to obtain mineral chemistry and PT determinations, with special attention given to the characterization of garnet and plagioclase zoning, and avoiding later reequilibration between Fe-Mg minerals. PT conditions were calculated using the TWEEQU method with core and rim compositions of garnet and, plagioclase, and an average composition of matrix biotite. Peak metamorphic conditions can be divided into a baric and a thermal peak. The obtained PT path is interpreted to be a consequence of crustal thickening occurred in Lower Ordovician times. This evolution is clearly different from that registered in the underlying high-P and high-T units