Two-mica rhyolitic tephra in the East Pisco Basin (Peru): new age and dispersion constraints for the eruptions of the Eastern Cordillera of Central Andes

Bosio, Giulia; Gioncada, Anna; Di Celma, Claudio; Villa, Igor Maria; Pichavant, Michel; Urbina, Mario; Bianucci, Giovanni (2020). Two-mica rhyolitic tephra in the East Pisco Basin (Peru): new age and dispersion constraints for the eruptions of the Eastern Cordillera of Central Andes. Bulletin of volcanology, 82(6), pp. 1-22. Springer-Verlag 10.1007/s00445-020-1373-y

Text Bosio2020-BullVolc.pdf - Published Version Restricted to registered users only until 12 May 2024. Available under License Publisher holds Copyright. Download (6MB) | Request a copy

Two-mica—biotite and muscovite—volcanics are particularly rare in the geological record. One of the several dozen volcanic ash layers from Central Andes volcanoes found in the upper Miocene marine succession of the Pisco Formation (Ica Desert, Peru) contains juvenile biotite and muscovite, sillimanite/andalusite, feldspars, and rhyolitic glass. 39Ar–40Ar dating on biotite and muscovite concordantly constrain an age of 7.96 Ma for this two-mica ash layer. A second tephra in the Pisco Formation has a similar biotite composition and an age between 7.45 and 6.93 Ma. The peculiar mineral assemblage and the chemical composition of biotite indicate a strongly peraluminous composition of the erupted magmas and, together with the 39Ar–40Ar ages, suggest to consider a correlation of these ash layers to the eruptions of the Miocene Macusani (Peru) or Morococala (Bolivia) volcanic complexes in the Eastern Cordillera of Central Andes. The major and trace element composition of glass supports the correlation with Macusani. A prove- nance from Morococala seems less likely given the large distances involved. These results provide new data on the volcanic activity of the Eastern Cordillera revealing ash that dispersed to over 500 km to the west, in the forearc marine basins. This finding highlights that the exhumed forearc East Pisco Basin is highly promising as an archive of distal ash for the reconstruction of the volcanic activity of Central Andes during the Miocene silicic flare-ups.

Interest & Impact

Downloads

2 since deposited on 15 Apr 2021
0 in the past 12 months

Citations

5 Citations in Web of Science ®
6 Citations in Scopus

Search

in Google Scholar™

Services

Actions (login required)

Edit item

Actions (login required)

Edit item