Caracterización de los minerales del dique gabroideo de Messejana - Plasencia en su sector nor-oriental

Abstract

In the gabbroic Messejana–Plasencia dyke we have distinguished three types of pyroxenes: enstatite, pigeonite and augite. Enstatite and augite have been the first minerals that have crystallized at high T (1100ºC – 1150ºC). Pigeonites (@1000ºC) are later and finally appear symplectic two-pyroxene intergrowths around the orthopyroxene. Plagioclase have a continuous zonation with cores of An75 towards rims of An18. Occasionally, there is a micrographic intergrowth of orthoclase–quartz or albite-quartz interstitially to the plagioclase and pyroxene framework. Three types of amphibole have been distinguished: ferroedenite, magnesiohornblende and ferroactinolite. The estimated temperature range of amphibole crystallization is low suggesting that most amphiboles are subsolidus. Finally, biotite are FeO and TiO2 rich, its crystallization being late when residual liquids were enriched in those elements.