Page 155 - Caldera Volcanism Analysis, Modelling and Response

130 A. Pittari et al.

Figure 14 Schematic representation of the substrate geology and the superimposed active
volcanic system just prior to the climactic destructive Abrigo eruption. Abbreviation: DH,
Diego Herna Ł ndez.

Mafic cumulate body(s) have been identified from geophysical studies at depths
of 5–14 km below central Tenerife (Ablay and Kearey, 2000; Aran ˜a et al., 2000) and
are probably the source of the very rare syeno-gabbroid and gabbroid lithic clasts
within the Abrigo ignimbrite. It is likely that syenite was a more dominant wall
rock lithology. Mafic plutonic lithic clasts within the Abrigo ignimbrite are more
common on the eastern flanks of the edifice and could be evidence for a higher
abundance of syeno-gabbro/gabbros at the eastern end of the Abrigo chamber wall.

3.6.2. Ancient hydrothermal systems
The abundance of hydrothermally altered lithic clasts within the Abrigo ignimbrite
(often up to 40%) indicates that a large subsurface region of hydrothermally altered
rock was sampled during the eruption (Figure 14). Hydrothermal altered rocks are
locally exposed along the margin of the caldera wall (Aran ˜a, 1971) and may be the