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Cone sheet formation and intrusive growth of an oceanic island—The Miocene Tejeda complex on Gran Canaria (Canary Islands)

¹ GEOMAR Forschungszentrum, Wischhofstrasse 1-3, D-24148 Kiel, Germany

More than 500 trachytic to phonolitic cone sheet dikes, hypabyssal syenite stocks, and subordinate radial dikes form a 20-km-diameter intrusive complex in the volcaniclastic fill of the Miocene Tejeda caldera (20 x 35 km) on Gran Canaria (Canary Islands). The dikes intruded concentrically around a central axis of radial symmetry and dip uniformly an average of 41° toward the center. Single-crystal ⁴⁰Ar/³⁹Ar ages of dikes and syenite stocks ranging from 12.3 ± 0.1 to 7.32 ± 0.05 Ma suggest more or less continuous intrusive activity during both volcanically active and inactive phases. Intrusions were emplaced at average intervals of 5–10 k.y., while explosive eruptions took place at >50 k.y. intervals. The estimated aggregate volume of evolved cone sheet magma added at shallow level (<2000 m below sea level) amounts to 250 km³ compared to 500 km³ of evolved extrusive volcanics erupted during the same period.

Formation of the Tejeda cone sheets most likely resulted from deformation processes due to resurgent doming, initiated by the recurrent replenishment of a flat, laccolith-like shallow magma chamber. Magma supply exceeding the volume that could be compensated for by updoming of the overlying caldera fill resulted in the formation of cone-shaped fractures.

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