Mixing and mingling in the evolution of andesite–dacite magmas; evidence from co-magmatic plutonic enclaves, Taupo Volcanic Zone, New Zealand

Cole, Jim; Gamble, J. A.; Burt, R. M.; Carroll, L.D; Shelley, David

doi:10.1016/s0024-4937(01)00056-1

Cited by 33 publications

(26 citation statements)

References 22 publications

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“…Given the absence of primary melt inclusions in the ferromagnesian minerals, the chemistry of the mafic end‐members can be examined with two approaches. First, microcrystalline comagmatic enclaves and xenoliths present within the host dacites [ Worthington , ; Cole et al ., ] can potentially record the chemistry of the intruding mafic magma. However, although these samples generally have andesitic compositions that could be consistent with a mafic end‐member, their Sr and REE contents are too low and have been interpreted to represent fragments of crystal mush representing assimilated magma chamber wall rock [ Cole et al ., ].…”

Section: Discussionmentioning

confidence: 99%

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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Section: Discussionmentioning

confidence: 99%

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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“…In some granitoid plutons, MMEs from different origins coexist and have provided important constraints on formation processes of the granitoid plutons in continental crust (e.g., Grout, 1937;Tindle and Pearce, 1983;Didier, 1987;Didier and Barbarin, 1991;Fornelli, 1994;Stimac et al, 1995;Elburg, 1996b;Schödlbauer et al, 1997;Yang et al, 2004;Barbarin, 2005;Ilbeyli and Pearce, 2005;Esna-Ashari et al, 2011;Clemens and Elburg, 2013). Using MMEs as one of the most important indicators of mixing and/or mingling between mantle-derived mafic and crustal-derived felsic magmas, most researchers considered magma mixing as a common phenomenon in generation of intermediate magmatic rocks such as andesites and diorites (e.g., Cantagrel et al, 1984;Ussler and Glazner, 1989;Castro et al, 1990a;Cole et al, 2001;Janoušek et al, 2004;Alpaslan et al, 2005;Kawabata and Shuto, 2005). However, recent results show that andesites are dominantly produced by crystal-liquid fractionation, and crystal-liquid segregation appears to be the dominant process in generating intermediate magmas, with mixing playing a secondary role (Lee and Bachmann, 2014).…”

Section: Introductionmentioning

confidence: 99%

Cogenetic origin of mafic microgranular enclaves in calc-alkaline granitoids: The Permian plutons in the northern North China Block

Zhang

Zhao

2017

Geosphere

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Mafic microgranular (microgranitoid) enclaves (MMEs) with fineto medium-grain-size igneous microstructures are abundant in Permian gran itoid plutons in the northern North China Block (NCB). They are mainly dioritic in composition with SiO 2 contents from 51.0 wt% to 62.7 wt% and are contiguous with their host granitoids (SiO 2 = 60.4-68.4 wt%). Their main mineral assemblage of plagioclase (oligoclase and andesine), hornblende, biotite, K-feldspar, and quartz is similar to that of their host granitoids but with different mineral proportions. Zircon laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) U-Pb dating, hornblende-plagioclase thermobarometry, and Ti-in-zircon thermometry results show that the crystallization ages and pressure-temperature (P-T) conditions of the MMEs in each Permian granitoid pluton are very similar to those of their host granitoids, indicating simultaneous crystallization at the middle to upper crustal levels. Petrographical, geochemical, and Sr-Nd-Hf isotopic data show that the source areas of the Permian granitoid plutons in the northern NCB are temporally and spatially different and magma mixing was likely involved during formation of some granitoid plutons. However, the whole-rock Sr-Nd and zircon Hf isotopic compositions of the MMEs in each pluton are very similar to those of their host granitoids, indicating complete isotopic equilibration between the host granitoids and their enclaves. Combined with similar mineral assemblage and mineral chemistry between the MMEs and their host granitoids and absence of coeval mantle-derived rocks in or nearby the plutons, we confirm that the MMEs were crystallized from a coeval magma that gave rise to the host granitoids, and not by mixing and/or mingling between mantle-derived mafic and crustal-derived felsic magmas or by synplutonic injections of mafic magma into the host granitoid magma. We conclude that magma isotopic equilibration between host granitoids and their enclaves was achieved prior to emplacement and the magma mixing process during formation of some Permian granitoid plutons occurred mainly in the melting, assimilation, storage, and homogenization (MASH) zone in the lowermost crust or mantle-crust transition, not in the magma conduits or chambers at middle to upper crustal levels. A two-stage model that includes rapid cooling within the cogenetic host granitoid magma operating at pluton margins to form solid to sub-solid dioritic rocks and crystal accumulations of the host granitoid magma at the bottom of the pluton to form cumulates, and dioritic rocks and cumulates then fragmentated and interacted with progressive evolved host granitoid magma to change their shapes and orientations is proposed for origin of the MMEs in the Permian granitoid plutons in the northern NCB. This model may be more widely applicable to the generation of many MMEs in granitic rocks, especially where no direct evidence exists for the presence of mafic magmas coeval with granitoids and where there is a lack of isotopic contrast between...

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“…Mandeville et al 1996;Wolf and Eichelberger 1997;Coombs et al 2000;Cole et al 2001) suggest that andesitic magmas commonly involve mixing of acid and mafic melts. This mixing can lead to magmatic volatile saturation, which can potentially trigger volcanic eruptions (Hattori 1993) and may play a decisive role in the formation of magmatichydrothermal ore deposits (Dietrich et al 1999).…”

Section: Introductionmentioning

confidence: 99%

“…The mixing process may occur by injection of basic melt into an evolved magma reservoir where the distinct melts mix prior to eruption (Wolf and Eichelberger 1997;Venezky and Rutherford 1997). It may also occur during eruption of a structured magma chamber containing compositionally distinct regions (Sigurdsson and Sparks 1981;Druitt and Bacon 1989;Jaupart and Tait 1990;Mandeville et al 1996;Cole et al 2001), or by continued supply of distinct magmas without formation of a major magma chamber (Dungan et al 2001). Distinguishing these processes is essential for a better understanding of the genesis of andesitic rocks in general, for predicting the causes and mechanisms of eruption and emplacement of subvolcanic stocks (Tait et al 1989;Kress 1997;Matthews et al 1997;Stix et al 1997;Murphy et al 2000), and for identifying the specific conditions required for the formation of magmatic-hydrothermal ore deposits (Dilles 1987;Cline and Bodnar 1991).…”

Section: Introductionmentioning

confidence: 99%

Laser-ablation ICP-MS analysis of silicate and sulfide melt inclusions in an andesitic complex II: evidence for magma mixing and magma chamber evolution

Halter

Heinrich

Pettke

2004

Contrib Mineral Petrol

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Laser-ablation microanalysis of a large suite of silicate and sulfide melt inclusions from the deeply eroded, Cu-Au-mineralizing Farallo´n Negro Volcanic Complex (NW Argentina) shows that most phenocrysts in a given rock sample were not formed in equilibrium with each other. Phenocrysts in the andesitic volcano were brought together in dominantly andesitic-dacitic extrusive and intrusive rocks by intense magma mixing. This hybridization process is not apparent from macroscopic mingling textures, but is clearly recorded by systematically contrasting melt inclusions in different minerals from a given sample. Amphibole (and rare pyroxene) phenocrysts consistently contain inclusions of a mafic melt from which they crystallized before and during magma mixing. Most plagioclase and quartz phenocrysts contain melt inclusions of more felsic composition than the host rock. The endmember components of this mixing process are a rhyodacite magma with a likely crustal component, and a very mafic mantle-derived magma similar in composition to lamprophyre dykes emplaced early in the evolution of the complex. The resulting magmas are dominantly andesitic, in sharp contrast to the prominently bimodal distribution of mafic and felsic melts recorded by the inclusions. These results severely limit the use of mineral assemblages to derive information on the conditions of magma formation. Observed mineral associations are primarily the result of the mixing of partially crystallized magmas. The most mafic melt is trapped only in amphibole, suggesting pressures exceeding 350 MPa, temperatures of around 1,000°C and water contents in excess on 6 wt%. Upon mixing, amphibole crystallized with plagioclase from andesitic magma in the source region of porphyry intrusions at 250 MPa, 950°C and water contents of 5.5 wt%. During ascent of the extrusive magmas, pyroxene and plagioclase crystallized together, as a result of magma degassing at low pressures (150 MPa). Protracted extrusive activity built a large stratovolcano over the total lifetime of the magmatic complex (>3 m.y.). The mixing process probably triggered eruptions as a result of volatile exsolution.

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Mixing and mingling in the evolution of andesite–dacite magmas; evidence from co-magmatic plutonic enclaves, Taupo Volcanic Zone, New Zealand

Cited by 33 publications

References 22 publications

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

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

Cogenetic origin of mafic microgranular enclaves in calc-alkaline granitoids: The Permian plutons in the northern North China Block

Laser-ablation ICP-MS analysis of silicate and sulfide melt inclusions in an andesitic complex II: evidence for magma mixing and magma chamber evolution

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