Compositional Zoning of the Bishop Tuff

Hildreth, Wes; Wilson, C. J. N.

doi:10.1093/petrology/egm007

Cited by 468 publications

(611 citation statements)

References 115 publications

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“…All inclusions measured are within BSE-'dark' cores of crystals, showing that the temperature stratification of ~80 °C calculated by two-feldspar thermometry was present prior to any mixing with the contrasting magma composition that gave rise to the BSE-bright crystal rims. The 'bright-rim' forming magma is inferred to have been of slightly higher temperature than the 'normal' Bishop Tuff magma due to its less-evolved melt composition and as indicated by increases in Fe-Ti oxide and oxygen-isotope model temperatures with inferred depth in the system (Hildreth 1979;Wallace et al 1999;Bindeman and Valley 2002;Hildreth and Wilson 2007).…”

Section: Two-feldspar Thermometrymentioning

confidence: 95%

“…Over 600 km 3 of magma was erupted to generate fall deposits and ignimbrite, along with voluminous infill from the formation of Long Valley caldera ( Fig. 1; Bailey et al 1976;Hildreth 1979Hildreth , 2004Wilson and Hildreth 1997;Hildreth and Wilson 2007). The volume of rhyolite erupted as the Bishop Tuff is greater than all other felsic eruptions combined in the Long Valley area before or since (Hildreth 2004), and so questions arise as to how, and over what time period, such a large body of magma was accumulated and what the triggering processes were for the eruption.…”

Section: Geological Settingmentioning

confidence: 99%

“…1). Pumice clasts are categorised within two spectra: the 'normal' crystal-poor (xp) to crystal-rich (xr) scale, and the 'variant' types, following Hildreth and Wilson (2007). The latter are of particular interest because they often show evidence of physical mixing on millimetre to centimetre scales, and so eight samples of the 'swirly' and 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 'chocolate' variant pumice types of Hildreth and Wilson (2007) were inspected from packages Ig1Eb through to Ig2Nb.…”

Section: Geological Settingmentioning

confidence: 99%

“…We then use these temperature results, in consideration with previously published Fe-Ti oxide thermometry (Hildreth and Wilson 2007), to estimate temperatures at which diffusion occurred (Table 3). Samples from units Ig2Na yield cooler temperatures than those of the overlying Ig2Nb and Ig2Nc packages ( preserved Ti zonation, and this diffusion was modelled at 753 °C, that is, an average of Ig2E and Ig2Na modelled temperatures.…”

Section: Two-feldspar Thermometrymentioning

confidence: 99%

“…Whilst the Bishop Tuff has been the subject of many volcanological and geochemical investigations (see Hildreth and Wilson 2007, for review), the timescales associated with magma chamber assembly, residence and pre-eruptive mobilisation remain controversial. For example, early radiogenic isotopic studies on crystal and glass separates from the Bishop Tuff pointed to a long residence time for the magma (300 -1300 kyr: Christensen and Halliday 1996; Davies and Halliday 1998), apparently supported by theoretical models of felsic magma genesis (Fowler and Spera 2010).…”

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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135

173

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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: Two-feldspar Thermometrymentioning

confidence: 95%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Two-feldspar Thermometrymentioning

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

135

173

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Structural controls on the emission of magmatic carbon dioxide gas, Long Valley Caldera, USA

2015

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We present a degassing study of Long Valley Caldera that explores the structural controls upon emissions of magmatic carbon dioxide gas. A total of 223 soil gas samples were collected and analyzed for stable carbon isotopes using a field-portable cavity ring-down spectrometer. This novel technique is flexible, accurate, and provides sampling feedback on a daily basis. Sampling sites included major and minor volcanic centers, regional throughgoing faults, caldera-related structures, zones of elevated seismicity, and zones of past and present hydrothermal activity. The classification of soil gases based on their δ 13 C and CO 2 values reveals a mixing relationship among three end-members: atmospheric, biogenic, and magmatic. Signatures dominated by biogenic contributions (~4 vol %, À24‰) are found on the caldera floor, the interior of the resurgent dome, and areas associated with the Hilton Creek and Hartley Springs fault systems. With the introduction of the magmatic component (~100 vol %, À4.5‰), samples acquire mixing and hydrothermal signatures and are spatially associated with the central caldera and Mammoth Mountain. In particular, they are concentrated along the southern margin of the resurgent dome where the interplay between resurgence-related reverse faulting and a bend in the regional fault system has created a highly permeable fracture network, suitable for the formation of shallow hydrothermal systems. This contrasts with the south moat, where despite elevated seismicity, a thick sedimentary cover has formed an impermeable cap, inhibiting the ascent of fluids and gases to the surface.

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Origins of felsic magmas in Japanese subduction zone: Geochemical characterizations of tephra from caldera‐forming eruptions <5 Ma

Kimura

Nagahashi

Satoguchi

et al. 2015

Geochem Geophys Geosyst

120

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Dacitic to rhyolitic glass shards from 80 widespread tephras erupted during the past 5 Mys from calderas in Kyushu, and SW, central, and NE Japan were analyzed. Laser ablation inductively coupled plasma mass spectrometry was used to determine 10 major and 33 trace elements and A few tephras from SW Japan were identified as adakite and alkali rhyolite and were regarded to have originated from slab melt and mantle melt, respectively. The Pb isotope ratios of the tephras are comparable to those of the intermediate lavas in the source areas but are different from the basalts in these areas. The crustal assimilants for the intermediate lavas were largely from crustal melts and are represented by the rhyolitic tephras. A large heat source is required for forming large volumes of felsic crustal melts and is usually supplied by the mantle via basalt. Hydrous arc basalt formed by cold slab subduction is voluminous, and its heat transfer with high water content may have melted crustal rocks leading to effective felsic magma production. Coincidence of basalt and felsic magma activities shown by this study suggests caldera-forming eruptions are ultimately the effect of a mantle-driven cause.

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Compositional Zoning of the Bishop Tuff

Cited by 468 publications

References 115 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

Structural controls on the emission of magmatic carbon dioxide gas, Long Valley Caldera, USA

Origins of felsic magmas in Japanese subduction zone: Geochemical characterizations of tephra from caldera‐forming eruptions <5 Ma

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