Browsing by Author "Wolff, John A."
Now showing 1 - 1 of 1
Results Per Page
Sort Options
- Heterogeneity of phonolitic pumice deposits from Tenerife, Canary IslandsPublication . Wolff, John A.The island of Tenerife has an extensive Quaternary phonolitic pyroclastic series, comprising plinian pumice-fall deposits, ignimbrites, and pyroclastic surges. The dominant petrological feature of these pumice deposits is their geochemical and petrographical heterogeneity. Evidence is presented for three causes of heterogeneity: assimilation of roof-rock by the magma, resulting in less evolved compositions of the first erupted pumice; zonation of the magma chamber, causing a change to intermediate compositions among the last products of an eruption; and magma mixing, where mafic and banded tephra are distributed more or less randomly through a particular pumice deposit.