dacitic

Volcanic ash of Guagua Pichincha is a thin material (<2 mm in diameter), and the main products found are dacitic, andesitic, and high-Rb acid [4] including sulfur dioxide, silicon oxide (Si[O.sub.2]), and aluminum oxide ([Al.sub.2][O.sub.3]) [5].

Formed during the Pleistocene to Holocene, the volcano consists of andesitic and dacitic lavas.

1) include mafic flows and tuffs of the Long Reach Formation and conformably overlying, fine-grained, feldspathic sandstone, siltstone, dacitic flows, and minor mafic tuffs of the Jones Creek Formation.

To the east lies the dacitic and adakitic Sahand Volcano and it is possible that the Bezow dome of similar affinity (Modjarrad, 2015 a; 2015b) is part of the volcanic complex (Fig.

These sapphires are believed to have a metamorphic origin followed by transport to the surface in rhyolitic to dacitic volcanic eruptions.

The collected rock samples lie in Volcanic Formation" which consists of dolerites, andesite, dacites, dacitic tuff, rhyolites and rhyolitic tuff.

The geometry of this structure is masked and obliterated by many dacitic and andesitic subvolcanic bodies and pyroclastic flows (Leveratto, 1968), their ages ranging from 18 to 7 Ma (Leveratto, 1976; Bercowski et al., 1986, 1993; Verges et al., 2001).

The explosive products consist in pyroclastic deposits (Brecha Pirociastica Cantimplora; thickness = 1-4 m), conformed by dacitic blocks (20-30 cm), pumice clasts (<15 cm), and ash, that occurred intercalated with the lava flows.