From mush to eruption in centuries: assembly of the super-sized Oruanui magma body

Allan, Aidan S. R.; Morgan, D. J.; Wilson, C. J. N.; Millet, Marc-Alban

doi:10.1007/s00410-013-0869-2

Cited by 164 publications

(412 citation statements)

References 67 publications

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“…In orthopyroxene, BSE brightness is controlled largely by changing Fe-Mg content. Ca can have a minor effect, but this can be neglected in this case (see Electronic Appendix 3 and Allan et al 2013). All crystals were imaged completely and any zoning identified, before high-resolution images of the boundaries in the crystal were acquired to give improved spatial resolution across boundaries of interest.…”

Section: Bse Imagingmentioning

confidence: 99%

“…Diffusion anisotropy was considered small for Ti in quartz, and Ba and Sr in sanidine, as previous studies have not noted marked anisotropy in these systems (Cherniak 2002(Cherniak , 2010Cherniak and Watson 1992;). The modelling parameters used for each species are presented in (Ganguly and Tazzoli 1994), the formula of Ganguly and Tazzoli (1994) modified as in Allan et al (2013) is used to calculate D Fe-Mg :…”

Section: Imagingmentioning

confidence: 99%

“…In order to then model a timescale, finite difference methods were used, as detailed in Allan et al (2013). We revisit the potential accuracy of this expression in the discussion.…”

Section: Imagingmentioning

confidence: 99%

“…Morgan et al 2004;Ginibre et al 2007;Wark et al 2007;Martin et al 2008;Humphreys et al 2009;Allan et al 2013). However, two factors make interpretation complex.…”

Section: Introductionmentioning

confidence: 99%

“…Although diffusion modelling of single or 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 multiple elements has been frequently utilised to explore timescales of crystal residence in magma chambers (e.g. Zellmer et al 1999;Costa et al 2003;Morgan et al 2004;Costa and Dungan 2005;Wark et al 2007;Gualda et al 2012a;Saunders et al 2012;Till et al 2012;Allan et al 2013), multiple phases from the same sample have not been routinely investigated. Here we compare and contrast the timescales inferred from Fe-Mg interdiffusion in orthopyroxene, Ti diffusion in quartz (cf.…”

Section: Introductionmentioning

confidence: 99%

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Timescales of mixing and mobilisation in the Bishop Tuff magma body: perspectives from diffusion chronometry

Chamberlain

Morgan

Wilson

2014

Contrib Mineral Petrol

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Abstract:We present two-feldspar thermometry and diffusion chronometry from sanidine, orthopyroxene and quartz from multiple samples of the Bishop Tuff, California, to constrain the temperature stratification within the pre-eruptive magma body and the timescales of magma mixing prior to its eruption. Two-feldspar thermometry yields estimates that agrees well with previous Fe-Ti oxide thermometry and gives a ~80 °C temperature difference between the earlier-and later-erupted regions of the magma chamber. Using this thermometry, we model diffusion of Ti in quartz, and Ba and Sr in sanidine as well as Fe-Mg interdiffusion in orthopyroxene to yield timescales for the formation of overgrowth rims on these phenocryst phases. Diffusion profiles of Ti in quartz and Fe-Mg in orthopyroxene diffusion both yield timescales of <150 years for the formation of overgrowth rims. In contrast, both Ba and Sr diffusion in sanidine yield nominal timescales 1-2 orders of magnitude longer than these two methods. The main cause for this discrepancy is inferred to be an incorrect assumption for the initial profile shape for Ba and Sr diffusion modelling (i.e., growth zoning). Utilising the divergent diffusion behaviour of Ba and Sr, we place constraints on the initial width of the interface and can refine our initial conditions considerably, bringing Ba and Sr data into alignment, and yielding timescales closer to 500 years, the majority of which are then within uncertainty of timescales modelled from Ti diffusion in quartz. Care must be thus taken when using Ba-in-sanidine geospeedometry in evolved magmatic systems where no other phases or elements are available for comparative diffusion profiling. Our diffusion modelling reveals piecemeal rejuvenation of the lower parts of the Bishop Tuff magma chamber at least 500 years prior to eruption. Timescales from our mineral profiling imply either that diffusion coefficients currently used are uncertain by 1-2 orders of magnitude, or that the minerals concerned did not experience a common history, despite being extracted from the same single pumice clasts. Introduction of the magma initiating crystallization of the contrasting rims on sanidine, quartz, orthopyroxene and zircon was prolonged, and may be a marker of other processes that initiated the Bishop Tuff eruption rather than the trigger itself. 2 AbstractWe present two-feldspar thermometry and diffusion chronometry from sanidine, orthopyroxene and quartz from multiple samples of the Bishop Tuff, California, to constrain the temperature stratification within the pre-eruptive magma body and the timescales of magma mixing prior to its eruption. Twofeldspar thermometry yields estimates that agree well with previous Fe-Ti oxide thermometry and gives a ~80 °C temperature difference between the earlier-and later-erupted regions of the magma chamber. Using this thermometry, we model diffusion of Ti in quartz, and Ba and Sr in sanidine as well as Fe-Mg interdiffusion in orthopyroxene to yield timescales for the formation of overgrowth rims on th...

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Section: Bse Imagingmentioning

confidence: 99%

Section: Imagingmentioning

confidence: 99%

“…In order to then model a timescale, finite difference methods were used, as detailed in Allan et al (2013). We revisit the potential accuracy of this expression in the discussion.…”

Section: Imagingmentioning

confidence: 99%

“…Morgan et al 2004;Ginibre et al 2007;Wark et al 2007;Martin et al 2008;Humphreys et al 2009;Allan et al 2013). However, two factors make interpretation complex.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Timescales of mixing and mobilisation in the Bishop Tuff magma body: perspectives from diffusion chronometry

Chamberlain

Morgan

Wilson

2014

Contrib Mineral Petrol

Self Cite

133

173

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Processes and time scales of dacite magma assembly and eruption at Tauhara volcano, Taupo Volcanic Zone, New Zealand

Millet

Tutt

Handler

et al. 2014

Geochem Geophys Geosyst

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[1] Magma mixing plays a prominent role in the origins of intermediate magmas in subduction zones. However, the conditions and time scales of magma mixing and how these are linked to subsequent eruption are unclear. Mount Tauhara is the largest dacitic volcanic complex in the Taupo Volcanic Zone, New Zealand. Dacites from Tauhara volcano have a complex petrography (Qtz 1 Plag 1 Amph 1 OPx 1 CPx 1 Oxi 6 Oli) that can only have been produced by magma mixing and offer an ideal opportunity to investigate the processes and time scales involved in assembling dacite magmas in a continental subduction zone. Here, we present whole-rock and mineral-specific major and trace element and isotopic data for the Tauhara dacites in order to identify the magma mixing end-members, constrain the physical conditions of mixing, and estimate the time scales and relationships between magma mixing, ascent, and eruption. These data reveal that four separate mixing events between crystal-rich rhyolites (77-80 wt % SiO 2 ; 40 ppm Sr) and crystal-poor mafic magmas of basaltic (48 wt % SiO 2 ; 1340 ppm Sr) to andesitic (55-59 wt % SiO 2 ; 490-580 ppm Sr) composition occurred to produce the Tauhara dacites. Mixing took place in well-stirred magma chambers located at midcrustal depths (8-13 km) at temperatures from 840 to 900 C. The time scales of magma mixing obtained from Ti diffusion in quartz appear to be largely dependent on the temperature and viscosity contrast between the end-members as andesite and rhyolite magma mixed on time scales of 2-7 months, whereas basalt and rhyolite magmas mixed on time scales of 1-2 years. The short magma mixing time scales, combined with the physical properties (e.g., viscosity and density) of the mixed dacite magmas, as compared with those of the end-member magmas, facilitated the ascent and eruption of dacite magmas at Tauhara volcano.

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Comb layering monitors decompressing and fractionating hydrous mafic magmas in subvolcanic plumbing systems (Fisher Lake, Sierra Nevada, USA)

McCarthy

Müntener

2016

JGR Solid Earth

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Understanding the dynamics of volcanic eruptions requires constraints on the processes of melt extraction in shallow magma reservoirs. This study focuses on the formation of intraplutonic igneous layering known as comb layers and orbicules within the Fisher Lake Pluton, Sierra Nevada. Comb layers are mineralogically and texturally diverse, ranging from plagioclase‐amphibole comb layers to plagioclase‐pyroxene and olivine comb layers. The majority of individual layers are related to the initiation of plagioclase nucleation and growth on preexisting host rocks and remobilized xenoliths. We use simple phase diagrams to illustrate the formation of comb layers through crystal fractionation along conduit walls and xenoliths, with plagioclase as the liquidus phase. Near‐adiabatic ascent of water‐undersaturated melts through the crust will lead to superheating and crystal resorption, which upon saturation of volatiles at shallow depth can induce heterogeneous nucleation of plagioclase. The rarity of orbicules and comb layers worldwide suggests that adiabatic decompression of crystal‐poor, moderately hydrous melts through the crust is rare. Most melts in intermediate/silicic volcanoes crystallize in multiple reservoirs within the crust prior to emplacement at shallow depth as crystal‐bearing melts. Comb layers and orbicules preserve evidence of multiple melt injections where a sequence of texturally and mineralogically similar comb layers and orbicules reflect the timescale of an individual melt pulse. Short timescales on the order of months to years for the growth of these sequences are estimated using experimental plagioclase growth rates and are interpreted as representing the lifetime of a melt injection within a long‐lived, subvolcanic melt extraction zone.

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From mush to eruption in centuries: assembly of the super-sized Oruanui magma body

Cited by 164 publications

References 67 publications

Timescales of mixing and mobilisation in the Bishop Tuff magma body: perspectives from diffusion chronometry

Timescales of mixing and mobilisation in the Bishop Tuff magma body: perspectives from diffusion chronometry

Processes and time scales of dacite magma assembly and eruption at Tauhara volcano, Taupo Volcanic Zone, New Zealand

Comb layering monitors decompressing and fractionating hydrous mafic magmas in subvolcanic plumbing systems (Fisher Lake, Sierra Nevada, USA)

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