Micro-textures in plagioclase from 1994–1995 eruption, Barren Island Volcano: Evidence of dynamic magma plumbing system in the Andaman subduction zone

Renjith, M.L.

doi:10.1016/j.gsf.2013.03.006

Cited by 75 publications

(73 citation statements)

References 57 publications

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“…Thus, the LLC may have grown due to crystallization from a homogeneous magma under equilibrium conditions between crystal and melt. In contrast, oscillatory zoning in the mineral may have developed either by an extrinsic mechanism: crystallization from a melt that was undergoing rhythmic changes in temperature or pressure or composition or by an intrinsic mechanism: local incremental diffusion-controlled kinetic growth at the crystal-melt interface in response to near-equilibrium conditions (Shore and Fowler, 1996;Hoskin, 2000;Fowler et al, 2002;Renjith, 2014). Extrinsic mechanisms involve physical or chemical changes within the bulk system that are partially or wholly independent of any local crystallization mechanism (Shore Table 3.…”

Section: Clarifying the Different Events In Zircon Crystallizationmentioning

confidence: 99%

“…In the absence of magmatic zonation developed in the major axis (c-axis), the width of magmatic zonal area along the minor axis is represented as number in parentheses. and Fowler, 1996), such as crystal settling in a magma chamber (e.g., Igarashi et al, 2007), large-scale convection in a magma chamber (e.g., Singer et al, 1995), or magma mixing and reservoir replenishment (e.g., Edwards and Russell, 1996;Wallace and Bergantz, 2002;Renjith, 2014). Fowler et al (2002) suggest that the OZ formation arose from an intrinsic crystal growth mechanism rather than any extrinsic or bulk system-scale fluctuations.…”

Section: *4mentioning

confidence: 99%

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Zircon growth in a granitic pluton with specific mechanisms, crystallization temperatures and U–Pb ages: Implication to the ‘spatiotemporal’ formation process of the Toki granite, central Japan

Yuguchi

Iwano²,

Kato

et al. 2016

Journal of Mineralogical and Petrological Sciences

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Zircons collected from a granitic pluton provide evidence of serial growth events with specific mechanisms, crystallization temperatures and U-Pb ages, revealing details of the sequential formation process from intrusion through emplacement to crystallization/solidification. The events have been identified by: 1) the study of the internal structure of zircon using cathodoluminescence, 2) deriving crystallization temperatures using Ti-inzircon thermometry of the internal structure and 3) U-Pb age dating of the internal structure. The magmatic zircons from the Toki granite, central Japan, show two kinds in their internal structure: a low luminescence core (LLC) and oscillatory zonation (OZ). The LLC was produced by interfacial reaction-controlled growth in the granitic magma with cooling from about 910 to 760°C. The formation of OZ occurred by diffusion-controlled growth in a cooling magma chamber from about 850 to 690°C. The U-Pb ages derived from the LLC ranges from 74.7 ± 4.2 to 70.5 ± 1.3 Ma, indicating the incipient intrusion timing of the magma into the shallow crust. The OZ ages distribute from 72.7 ± 0.6 to 70.4 ± 1.7 Ma, which mean the timing from emplacement to crystallization/solidification of the granite pluton. Thus, the serial processes from intrusion through emplacement to crystallization/solidification occurred within a few million years. The old LLC and OZ ages are recognized in the western margins of the Toki granite, implying that the magma forming the western margins was the first to intrude, emplace and crystallize/solidify. The western margins with initial intrusion may accompany the crustal assimilation in order to create sufficient magma reservoir space, which is consistent with larger SrI and ASI values found in the western margins of the granite.

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Section: Clarifying the Different Events In Zircon Crystallizationmentioning

confidence: 99%

Section: *4mentioning

confidence: 99%

Zircon growth in a granitic pluton with specific mechanisms, crystallization temperatures and U–Pb ages: Implication to the ‘spatiotemporal’ formation process of the Toki granite, central Japan

Yuguchi

Iwano²,

Kato

et al. 2016

Journal of Mineralogical and Petrological Sciences

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“…Minerals that form in magma systems are highly sensitive to local thermodynamic conditions and can record the changing thermodynamic properties of the system in their textures and compositional zoning (Jerram and Martin, ). The textural and compositional zoning of plagioclase phenocrysts is particularly useful for exploring the evolution of magma systems (Renjith, ), as plagioclase is common in magmatic rocks, crystallizes over a wide range of temperatures and persists as a stable crystal phase throughout cooling and emplacement. Compositional variations, especially in the concentrations of Fe, Mg, Sr and Ba and the contents of anorthite [An; Ca/(Ca + N + K)], and textural zoning patterns that develop during primary growth are preserved in plagioclase, on account of the slow rates of CaAl–NaSi diffusion (Morse, ; Smith et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Back‐arc magma processes in the Okinawa Trough: new insights from textural and compositional variations of plagioclase in basalts

et al. 2016

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The evolution of magma during ascent through the crust in the region of the Okinawa Trough is recorded by its mineralogy. In this study, we utilized the characteristics of plagioclase minerals in basaltic magma to deduce magma generation processes, by examining (via back‐scattered electron images) the compositional features of plagioclase phenocrysts in basalts dredged from the middle and southern portions of the Okinawa Trough, which provided a detailed account of the evolution and crystallization of the magma. The crystallization and evolutionary histories of magmas from the middle Okinawa Trough are distinct from those in the southern Okinawa Trough. In the middle Okinawa Trough, we identified seven textural varieties of plagioclase: homogeneous‐core, fine oscillatory‐zoned, core‐sieved, mantle‐sieved, patchy‐core, glomerocrystic and microlitic. Anorthite (An) contents in the cores of plagioclase crystals are 80–87%, while concentrations of Fe, Mg and Sr vary more strongly, especially in patchy‐core plagioclase. The homogeneous‐core, fine oscillatory‐zoned and glomerocrystic plagioclase crystallized in deep‐seated chambers. In contrast, the core‐sieved, mantle‐sieved and patchy‐core textures developed when magmas ascended slowly and were injected into shallow chambers, during which plagioclase was resorbed and dissolved due to decompression. In the southern Okinawa Trough, homogeneous‐core plagioclase crystallized when magma ascended rapidly through deep conduits and was injected into a shallow chamber; under these conditions, only homogeneous‐core and core‐sieved plagioclase phenocrysts crystallized in the shallow chamber. The core of homogeneous‐core plagioclase (An86–An93) was partially resorbed and contaminated by crustal material. Degassing and undercooling promoted the rapid crystallization of microlitic plagioclase, especially in the outermost rims, during and after the extraction of magma from shallow chambers, in both the middle and southern Okinawa Trough. Copyright © 2016 John Wiley & Sons, Ltd.

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“…The textural and compositional zoning of plagioclase is particularly useful for deciphering magma processes in modern volcanic systems (Anderson, ; Berlo, Blundy, & Turner, ; Hattori & Sato, ; Renjith, ), as well as for reconstructing the cooling history of plutonic rocks (Pietranik, Koepke, & Puziewicz, ; Wiebe, ), on account of the slow rate of CaAl–NaSi diffusion. As known, a decrease of anorthite content with fractional crystallization is well characterized in plagioclase (Ginibre et al, ), but the same trend is not observed in the studied samples, since GAG plagioclases display reverse and oscillatory zoning.…”

Section: Discussionmentioning

confidence: 99%

Role of magma mixing in generating of the Gheshlagh–Aftabrow intrusions, SW Buin Zahra, Iran: Evidence for a juvenile origin from geochemical and Sr–Nd isotopic data

et al. 2018

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In this paper, we investigate host granodiorites and associated mafic microgranular enclaves (MMEs), including gabbroic to quartz diorite enclaves from the Middle Eocene Gheshlagh-Aftabrow granitoid, to assess magma mixing and crust-mantle interaction in the Urumieh-Dokhtar magmatic arc. The host granodiorites yield zircon U-Pb ages of ca. 40 Ma. Geochemical and bulk rock Nd-Sr isotopic modelling, together with the widespread occurrence of mafic microgranular enclaves with ellipsoidal and spherical shapes and chilled margins, K-feldspar and plagioclase megacrysts in the enclaves, and the presence of acicular apatite, ocellar quartz, plagioclase with oscillatory zoning and resorption surfaces, suggests that the mafic microgranular enclaves are globules of a more mafic magma derived from the mantle that was injected into and mixed/mingled with the magma derived from partial melting of a lower crust. Geochemically, the granitoid rocks are high-K calc-alkaline and metaluminous (A/CNK = 0.87-0.92) and belong to I-type suite. These granitoid host rocks have much higher SiO 2 (65.4-67.3 wt%) and relatively low Fe 2 O 3 (1.8-2.1 wt%) and MgO (1-1.58 wt%), so compared with the host rocks, the mafic microgranular enclaves have much lower SiO 2 contents (50.5-55 wt%), considerably higher Fe 2 O 3 (3.4-4.2 wt%) and MgO (3.9-4.8 wt%). Both the host intrusion and enclaves are enriched in LREE relative to HREEs (LREE/HREE = 3.1-4.1; (La/Yb) N = 2.1-4.1) and show slightly negative Eu anomalies (δEu = 0.75-0.90) and nearly flat HREE patterns ((Gd/Yb) N = 0.86-1.26). Analyses of Sr-Nd isotopes in the host granodiorites and associated enclaves show ( 87 Sr/ 86 Sr) i host = 0.705070-0.705174, εNd (t) host = 0.21-2.31, T DM1 host = 782-983 Ma, ( 87 Sr/ 86 Sr) i enclave = 0.704997-0.705170, εNd (t) enclave = 2.15-2.17, and T DM1 enclave = 874-980 Ma, indicating of juvenile nature for these granites. This characteristic together with similar trace-element compositions indicates intense magma mixing and a high degree of geochemical equilibration between the host granodiorites and their enclaves.A binary mixing model based on Sr-Nd isotopic compositions of the GAG indicates that rocks were mostly generated by mixing of 7-12% melts produced by partial melting of meta-igneous old lower crust rocks with 88-93% contribution of mantlederived juvenile basaltic magmas.The Gheshlagh-Aftabrow granodiorites (GAG) in central Urumieh-Dokhtar magmatic arc (UDMA) are characterized by the presence of mafic-intermediate microgranular enclaves (MMEs). In this paper, we present field relationships, petrographic descriptions, major-and trace-element compositional and textural disequilibrium features of some minerals (e.g., plagioclase), with geochemical and Rb-Sr isotopic data for the granodiorite hosts and associated MMEs of the Gheshlagh-Aftabrow intrusive rocks in order to unravel their respective source characteristics and petrogenesis and to contribute to a better understanding of magma mixing/mingling processes.

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Micro-textures in plagioclase from 1994–1995 eruption, Barren Island Volcano: Evidence of dynamic magma plumbing system in the Andaman subduction zone

Cited by 75 publications

References 57 publications

Zircon growth in a granitic pluton with specific mechanisms, crystallization temperatures and U–Pb ages: Implication to the ‘spatiotemporal’ formation process of the Toki granite, central Japan

Zircon growth in a granitic pluton with specific mechanisms, crystallization temperatures and U–Pb ages: Implication to the ‘spatiotemporal’ formation process of the Toki granite, central Japan

Back‐arc magma processes in the Okinawa Trough: new insights from textural and compositional variations of plagioclase in basalts

Role of magma mixing in generating of the Gheshlagh–Aftabrow intrusions, SW Buin Zahra, Iran: Evidence for a juvenile origin from geochemical and Sr–Nd isotopic data

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