The trachytic lobe-hyaloclastite complex of the Caldera of Taburiente (La Palma, Canary Islands).
Monday, 30 January 2017
Marina/Gretel (Hobart Function and Conference Centre)
Ramón Casillas Sr.1, Julio de La Nuez Pestana Sr.1, Juan Ramón Colmenero Navarro Sr.2, Carlos Fernandez3 and Marisa Quesada Alvarez Sr.1, (1)University of La Laguna, Biología Animal, Edafología y Geología, La Laguna, Spain, (2)University of Salamanca, Geología, Salamanca, Spain, (3)University of Huelva, Ciencias de la Tierra, Huelva, Spain
Abstract:
In the submarine volcanic rocks that appear in the Basal Complex of La Palma we can distinguish an older felsic formation, and a more modern basaltic-trachybasaltic sequence,resting on the first according to a conformable contact with stratigraphic continuity. In the felsic formation, coherent facies (in the form of trachytic lobes, consisting of porphyritic, aphanitic or glass trachytes); autoclastic facies (hyaloclastites and autobreccias); and syn-eruptive resedimented facies (mono and polymictic, massive or graded breccias and volcaniclastic sands and gravels), can be found. The architecture and structure that define the different described facies seem to correspond to a trachytic lobe-hyaloclastite complex, older than the outcropping submarine basaltic-trachybasaltic formation, and, possibly related to the evolution of a former basaltic magma that would have led to the formation of a basaltic submarine shield, which does not currently crop out in the surface of the island. This paper first describes a lobe-hyaloclastite felsic complex on an oceanic island of intraplate environment.A geochemical characterization of felsic submarine rocks of the La Palma island has been carried out. These felsic rocks are forming a lobe-hyaloclastite complex in the Caldera de Taburiente and they are classified as trachytes, although due to their hydrothermal alteration they should be considered as metatrachytes. By the incompatible trace element behaviour the variety of these trachytic rocks (porphyritic or aphanitic terms) could be explained as a crystal fractionation process. On the other hand, the incompatible trace element and rare earth features indicate that these trachytes are not cogenetic with the submarine basaltic and trachybasaltic rocks of the Basal Complex of La Palma, but the trachytic magmas responsible of the lobe-hyaloclastite complex formation would have been resulted in the late evolution of a basaltic magma whose edifice does not currently crop out.
