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The NE Rift of Tenerife: towards a model on the origin and evolution of ocean island rifts
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2009 (Engelska)Ingår i: Estudios Geologicos, Vol. 65, nr 1, s. 5-47Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The NE Rift of Tenerife is an excellent example of a persistent, recurrent rift, providing important evidence of the origin and dynamics   of these major volcanic features. The rift developed in three  successive, intense and relatively short eruptive stages (a few hundred   ka), separated by longer periods of quiescence or reduced activity: A  Miocene stage (7266 +/- 156 ka), apparently extending the central Miocene shield of Tenerife towards the Anaga massif; an Upper Pliocene   stage (2710 +/- 58 ka) and the latest stage, with the main eruptive   phase in the Pleistocene. Detailed geological (GIS) mapping, geomagnetic reversal mapping and stratigraphic correlation, and radioisotopic (K/Ar) dating of volcanic   formations allowed the reconstruction of the latest period of rift   activity. In the early phases of this stage the majority of the   eruptions grouped tightly along the axis of the rift and show reverse polarity (corresponding to the Matuyama chron). Dykes are of normal and   reverse polarities. In the final phase of activity, eruptions are more   disperse and lavas and dykes are consistently of normal polarity   (Brunhes chron). Volcanic units of normal polarity crossed by dykes of   normal and reverse polarities yield ages apparently compatible with   normal subchrons (M-B Precursor and Jaramillo) in the Upper Matuyama   chron. Three lateral collapses successively mass-wasted the rift: The   Micheque collapse, completely concealed by subsequent nested volcanism,   and the Guimar and La Orotava collapses, that are only partially   filled. Time occurrence of collapses in the NE rift apparently   coincides with glacial stages, suggesting that giant landslides may be   finally triggered by sea level changes during glaciations. Pre-collapse   and nested volcanism is predominantly basaltic, except in the Micheque   collapse, where magmas evolved towards intermediate and felsic   (trachytic) compositions.   Rifts in the Canary Islands are long-lasting, recurrent features,   probably related to primordial, plume-related fractures acting   throughout the entire growth of the islands. Basaltic volcanism forms   the bulk of the islands and rift zones. However, collapses of the   flanks of the rifts disrupt their established fissural feeding system,   frequently favouring magma accumulation and residence at shallow   emplacements, leading to differentiation of magmas, and intermediate to felsic nested eruptions. Rifts and their collapse may therefore act as an important factor in providing petrological variability to oceanic   volcanoes. Conversely, the possibility exists that the presence of  important felsic volcanism may indicate lateral collapses in oceanic shields and ridge-like volcanoes, even if they are concealed by post-collapse volcanism or partially mass-wasted by erosion.

Ort, förlag, år, upplaga, sidor
2009. Vol. 65, nr 1, s. 5-47
Nyckelord [en]
Rifts, NE Rift of Tenerife, Canary Islands, K/Ar ages, sector collapses, lateral collapses and geochemical evolution, central felsic volcanoes and lateral collapses
Nationell ämneskategori
Geovetenskap och miljövetenskap
Forskningsämne
Geovetenskap med inriktning mot mineralogi, petrologi och tektonik
Identifikatorer
URN: urn:nbn:se:uu:diva-119280DOI: 10.3989/egeol.39755.056ISI: 000267844600001OAI: oai:DiVA.org:uu-119280DiVA, id: diva2:299979
Tillgänglig från: 2010-02-24 Skapad: 2010-02-24 Senast uppdaterad: 2016-05-12Bibliografiskt granskad

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