Fitful and protracted magma assembly leading to a giant eruption, Youngest Toba Tuff, Indonesia

Mary Reid, Jorge A. Vazquez

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The paroxysmal eruption of the 74 ka Youngest Toba Tuff (YTT) of northern Sumatra produced an extraordinary 2800 km3 of nonwelded to densely welded ignimbrite and coignimbrite ashfall. We report insights into the duration of YTT magma assembly obtained from ion microprobe U-Th and U-Pb dates, including continuous age spectra over >50% of final zircon growth, for pumices and a welded tuff spanning the compositional range of the YTT. A relatively large subpopulation of zircon crystals nucleated before the penultimate caldera-related eruption at 501 ka, but most zircons yielded interior dates 100–300 ka thereafter. Zircon nucleation and growth was likely episodic and from diverse conditions over protracted time intervals of >100 to >500 ka. Final zircon growth is evident as thin rim plateaus that are in Th/U chemical equilibrium with hosts, and that give crystallization ages within tens of ka of eruption. The longevity and chemical characteristics of the YTT zircons, as well as evidence for intermittent zircon isolation and remobilization associated with magma recharge, is especially favored at the cool and wet eutectoid conditions that characterize at least half of the YTT, wherein heat fluxes could dissolve major phases but have only a minor effect on larger zircon crystals. Repeated magma recharge may have contributed to the development of compositional zoning in the YTT but, considered together with limited allanite, quartz, and other mineral dating and geospeedometry, regular perturbations to the magma reservoir over >400 ka did not lead to eruption until 74 ka ago.

Original languageEnglish (US)
Pages (from-to)156-177
Number of pages22
JournalGeochemistry, Geophysics, Geosystems
Volume18
Issue number1
DOIs
StatePublished - Jan 1 2017

Fingerprint

Indonesia
tuff
volcanic eruptions
magma
zircon
volcanic eruption
assembly
calderas
igneous rocks
dating
rims
crystals
chemical equilibrium
heat flux
recharge
plateaus
isolation
quartz
minerals
nucleation

Keywords

  • compositional zoning
  • geochronology
  • supervolcano
  • zircon

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Cite this

Fitful and protracted magma assembly leading to a giant eruption, Youngest Toba Tuff, Indonesia. / Reid, Mary; Vazquez, Jorge A.

In: Geochemistry, Geophysics, Geosystems, Vol. 18, No. 1, 01.01.2017, p. 156-177.

Research output: Contribution to journalArticle

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