Rapid generation of both high- and low-δ18O, large-volume silicic magmas at the Timber Mountain/Oasis Valley caldera complex, Nevada

Bindeman, I. N.; Valley, John W.

doi:10.1130/0016-7606(2003)115<0581:rgobha>2.0.co;2

Cited by 72 publications

(33 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The generation of low ␦ 18 O magmas will be enhanced in areas of glaciation where large reservoirs of low ␦ 18 O water are available (Bindeman et al, 2001b). Rapid generation of both low and high ␦ 18 O, large-volume magmas is favored in extensional environments, where low ␦ 18 O magmas would readily be produced by nearly total remelting of hydrothermally altered roof rocks (Bindeman and Valley, 2003).…”

Section: Genesis Of Low ␦ 18 O Zirconsmentioning

confidence: 99%

Zircon U-Pb and oxygen isotope evidence for a large-scale 18O depletion event in igneous rocks during the Neoproterozoic

Zheng

Chen

et al. 2004

Geochimica et Cosmochimica Acta

490

277

View full text Add to dashboard Cite

Section: Genesis Of Low ␦ 18 O Zirconsmentioning

confidence: 99%

Zircon U-Pb and oxygen isotope evidence for a large-scale 18O depletion event in igneous rocks during the Neoproterozoic

Zheng

Chen

et al. 2004

Geochimica et Cosmochimica Acta

490

277

View full text Add to dashboard Cite

“…Employing a crystal-melt fractionation factor (Δ 18 O quartz-rhyolite ) of 0.5‰ (e.g., ref. 31), the δ 18 O value of the Toba magma(s) can be calculated from the derived crystal data. The average calculated δ 18 O magma value is 8.3 ± 0.4‰ (n = 191, 1σ) for SIMS data and 8.4 ± 0.2‰ (n = 13, 1σ) for the LF data.…”

Section: Resolving Crustal Differentiation Processes At Tobamentioning

confidence: 99%

“…( b ) Binary mixing relationship between average YTT quartz core δ 18 O magma (SIMS) value (n = 78) and a high silica hydrothermally-altered contaminant with δ 18 O = 0‰ (assumed value as a result of high-temperature alteration, cf. refs 7, 9 and 31). Approximately 25% mixing and assimilation with a low-δ 18 O component is required to bring the average core δ 18 O values (representing the ambient magma) to the lowest measured quartz rim value, reflecting a mixture of ambient magma and low-δ 18 O material for those portions of the YTT system that crystallised the low δ 18 O quartz rims.…”

Section: Figurementioning

confidence: 99%

Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz

Budd

Troll

Deegan

et al. 2017

Sci Rep

Self Cite

View full text Add to dashboard Cite

Quartz is a common phase in high-silica igneous rocks and is resistant to post-eruptive alteration, thus offering a reliable record of magmatic processes in silicic magma systems. Here we employ the 75 ka Toba super-eruption as a case study to show that quartz can resolve late-stage temporal changes in magmatic δ18O values. Overall, Toba quartz crystals exhibit comparatively high δ18O values, up to 10.2‰, due to magma residence within, and assimilation of, local granite basement. However, some 40% of the analysed quartz crystals display a decrease in δ18O values in outermost growth zones compared to their cores, with values as low as 6.7‰ (maximum ∆core−rim = 1.8‰). These lower values are consistent with the limited zircon record available for Toba, and the crystallisation history of Toba quartz traces an influx of a low-δ18O component into the magma reservoir just prior to eruption. Here we argue that this late-stage low-δ18O component is derived from hydrothermally-altered roof material. Our study demonstrates that quartz isotope stratigraphy can resolve magmatic events that may remain undetected by whole-rock or zircon isotope studies, and that assimilation of altered roof material may represent a viable eruption trigger in large Toba-style magmatic systems.

show abstract

“…Bacon and Druitt, 1988;de Silva, 1991;Hildreth, 2004). Although mixing of different magma batches remains popular as the cause of geochemical and isotopic heterogeneities in magma reservoirs (see also Bindeman and Valley, 2003;Sumner and Wolff, 2003), the importance of in-situ differentiation processes in generating and maintaining chemical and physical gradients, has been recently reiterated (Bachmann and Bergantz, 2008;Medlin et al, 2015;Sliwinski et al, 2015). In a fractional crystallization-dominated scenario, crystal-liquid separation occurs most efficiently at an intermediate crystallinity stage (∼50-70% crystals), when convection in the magma chamber has ceased (Bachmann and Bergantz, 2004).…”

Section: Introductionmentioning

confidence: 97%

The origin of a zoned ignimbrite: Insights into the Campanian Ignimbrite magma chamber (Campi Flegrei, Italy)

Forni

Bachmann

Mollo

et al. 2016

Earth and Planetary Science Letters

View full text Add to dashboard Cite

Caldera-forming eruptions, during which large volumes of magma are explosively evacuated into the atmosphere from shallow crustal reservoirs, are one of the most hazardous natural events on Earth. The Campanian Ignimbrite (CI; Campi Flegrei, Italy) represents a classical example of such events, producing a voluminous pyroclastic sequence of trachytic to phonolitic magma that covered several thousands of squared kilometers in the south-central Italy around 39 ka ago. The CI deposits are known for their remarkable geochemical gradients, attributed to eruption from a vertically zoned magma chamber. We investigate the relationships between such chemical zoning and the crystallinity variations observed within the CI pyroclastic sequence by combining bulk-rock data with detailed analyses of crystals and matrix glass from well-characterized stratigraphic units. Using geothermometers and hygrometers specifically calibrated for alkaline magmas, we reconstruct the reservoir storage conditions, revealing the presence of gradients in temperature and magma water content. In particular, we observe a decrease in crystallinity and temperature and an increase in magma evolution and water content from the bottom to the top of the magma chamber. We interpret these features as the result of protracted fractional crystallization leading to the formation of a cumulate crystal mush at the base of the eruptible reservoir, from which highly evolved, crystal-poor, water-rich and relatively cold melts were separated. The extracted melts, forming a buoyant, easily eruptible cap at the top of the magma chamber, fed the initial phases of the eruption, until caldera collapse and eruption of the deeper more crystalline part of the system. This late-erupted, crystal-rich material represents remobilized portions of the cumulate crystal mush, partly melted following hotter recharge. Our interpretation is supported by: 1) the positive bulk-rock Eu anomalies and the high Ba and Sr contents observed in the crystal-rich units, implying feldspar accumulation; 2) the positive Eu anomalies in the matrix glass of the crystal-rich units, testifying to the presence of liquid derived from partial melting of low temperature mineral phases within the crystal mush (mostly feldspars); 3) the Ba and Sr-rich rims in the feldspars and positive Eu anomalies in clinopyroxene rims, suggesting late rim growth from a locally enriched melt following cumulate mush remelting and 4) the occurrence of An-rich plagioclase, relict from a more mafic recharge, which acted as a heat source. Our model reconciles many observations made over the years on zoned deposits of such high-magnitude explosive eruptions, and provides a framework to understand magma chamber processes leading up to cataclysmic events.

show abstract

Rapid generation of both high- and low-δ18O, large-volume silicic magmas at the Timber Mountain/Oasis Valley caldera complex, Nevada

Cited by 72 publications

References 55 publications

Zircon U-Pb and oxygen isotope evidence for a large-scale 18O depletion event in igneous rocks during the Neoproterozoic

Zircon U-Pb and oxygen isotope evidence for a large-scale 18O depletion event in igneous rocks during the Neoproterozoic

Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz

The origin of a zoned ignimbrite: Insights into the Campanian Ignimbrite magma chamber (Campi Flegrei, Italy)

Contact Info

Product

Resources

About