Temperatura de emplazamiento de las ignimbritas Roque Nublo (Gran Canaria, Islas Canarias) mediante técnicas paleomagneticas

Abstract

The main characteristic of the Pliocene volcanic phase of Gran Canaria. the Cycle 11 or Roque Nublo. is the building of a central stratovolcano. probably reaching more than 2.500 m aboye sea level. Among the most relevant deposits associated to this volcanic edifice are the pyroclastic breccia-type deposits. generally known as «Roque Nublo agglomerates or breccias». These deposits have been gene rally interpreted as pyroclastic flows. However, their emission. transport and depositional mechanisms are hitherto poorly understood. In the present work. the analysis of the paleomagnetic characteristics of the lithic and juvenile fragments and the matrix of these pyroclastic deposits have provide sorne important constraints in their evolution and depositional temperatures. The Roque Nublo ignimbrites seem to have been deposited at temperatures below 300 ºC. In such circumstances. hot water originated by the condensation of interstitial water vapor reacted with the cineritic glass fraction, giving place to zeolite neomineralizations. The relatively fast cooling experimented by the ignimbrites after their emission. as deduced from the paleomagnetic analysis, can be explained by the high proportion of lithics and the intcraction of water as an important factor in the triggering of the eruptions in which the ignimbrites were originated.