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Camejo-Harry M, Melekhova E, Aufrère S, McCarthy A, Blundy J. Early arc crust formation preserved in the Grenadines archipelago, southern Lesser Antilles arc. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231914. [PMID: 39076803 PMCID: PMC11285511 DOI: 10.1098/rsos.231914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 03/08/2024] [Accepted: 03/11/2024] [Indexed: 07/31/2024]
Abstract
Intra-arc diversity in volcanic activity and composition is ubiquitous, but its underlying causes remain largely unresolved in many settings. In this work, we examine such variability in the Grenadines archipelago, southern Lesser Antilles arc. Here, juxtaposed volcanic centres exhibit eruptive longevities and chemistries distinct from northern counterparts in the same arc. Our goal is to explain this deviation by investigating variations in magmatic processes using petrological data from erupted crustal xenoliths and lavas, and interpreting these findings within the context of the archipelago's tectonic history and geophysical structure. Textural analyses of xenoliths reveal crystallization over a wide range of pressure-temperature-melt composition conditions in the crust. Mineral phases display discrete compositional trends pointing towards significant inter-island variability in underlying plumbing systems. The geochemical variety of erupted magmas is reminiscent of the entire arc. We speculate that the Grenadines represents the early onset of subduction forming the modern-day Lesser Antilles arc. Extrusive volcanism initiated as submarine activity. Subsequent uplift eroded the original topography of these volcanic centres following the eventual cessation of volcanism in the Neogene. The positioning of the Grenadines on an elevated platform provides rare modern insight into early arc crust formation not commonly preserved in established active arcs.
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Affiliation(s)
| | - Elena Melekhova
- Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK
| | - Sarah Aufrère
- Department of Earth Sciences, Simon Fraser University, , British ColumbiaV5A 1S6, Canada
| | - Anders McCarthy
- Department of Earth Sciences, ETH Zurich, Zurich, Switzerland
| | - Jon Blundy
- Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK
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Zanon V, D’Auria L, Schiavi F, Cyrzan K, Pankhurst MJ. Toward a near real-time magma ascent monitoring by combined fluid inclusion barometry and ongoing seismicity. SCIENCE ADVANCES 2024; 10:eadi4300. [PMID: 38324686 PMCID: PMC10849590 DOI: 10.1126/sciadv.adi4300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 01/08/2024] [Indexed: 02/09/2024]
Abstract
Fluid inclusion microthermometry on olivines, clinopyroxenes, and amphiboles was used during a volcanic eruption, in combination with real-time seismic data and rapid petrographic observations, for petrological monitoring purposes. By applying this approach to the study of 18 volcanic samples collected during the eruption of Tajogaite volcano on La Palma Island (Canary Islands) in 2021, changes in the magma system were identified over time and space. Magma batches with distinct petrographic and geochemical characteristics emerged from source zones whose depth progressively increased from 27 to 31 kilometers. The rise of magma of deeper origin is attested by fluid inclusions made of N2 and CO, markers of mantle outgassing. Magma accumulation occurred over different durations at depths of 22 to 27 and 4 to 16 kilometers. Time-integrated magma ascent velocities (including ponding times) were estimated at between 0.01 and 0.1 meters per second. This method is cost-effective and quickly identifies changes in the magma system during an eruption, enhancing petrological monitoring procedures.
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Affiliation(s)
- Vittorio Zanon
- Instituto de Investigação em Vulcanologia e Avaliação de Riscos (IVAR), Universidade dos Açores, Rua Mãe de Deus, 9500-123 Ponta Delgada, Portugal
| | - Luca D’Auria
- Instituto Tecnológico y de Energías Renovables (ITER), 38600 Granadilla de Abona, Tenerife, Canary Islands, Spain
- Instituto Volcanológico de Canarias (INVOLCAN), 38400 Puerto de la Cruz, Tenerife, Canary Islands, Spain
| | - Federica Schiavi
- Laboratoire Magmas et Volcans, CNRS, IRD, OPGC, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France
| | - Klaudia Cyrzan
- Instituto de Investigação em Vulcanologia e Avaliação de Riscos (IVAR), Universidade dos Açores, Rua Mãe de Deus, 9500-123 Ponta Delgada, Portugal
| | - Matthew J. Pankhurst
- Instituto Tecnológico y de Energías Renovables (ITER), 38600 Granadilla de Abona, Tenerife, Canary Islands, Spain
- Instituto Volcanológico de Canarias (INVOLCAN), 38400 Puerto de la Cruz, Tenerife, Canary Islands, Spain
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Grondahl C, Zajacz Z. Sulfur and chlorine budgets control the ore fertility of arc magmas. Nat Commun 2022; 13:4218. [PMID: 35864119 PMCID: PMC9304346 DOI: 10.1038/s41467-022-31894-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 07/07/2022] [Indexed: 11/17/2022] Open
Abstract
Continental arc magmas supply the ore-forming element budget of most globally important porphyry-type ore deposits. However, the processes enabling certain arc segments to preferentially generate giant porphyry deposits remain highly debated. Here we evaluate the large-scale covariation of key ore-forming constituents in this setting by studying silicate melt inclusions in volcanic rocks from a fertile-to-barren segment of the Andean Southern Volcanic Zone (33–40 °S). We show that the north-to-south, fertile-to-barren gradient is characterized by a northward increase in S and Cl concentrations and a simultaneous decrease in Cu. Consequently, we suggest that the concentration of S and Cl rather than the concentration of ore metals regulates magmatic-hydrothermal ore fertility, and that the loss of volatiles prior to arrival in the upper crust impacts ore-forming potential more than magmatic sulfide saturation-related ore metal scavenging. Earth’s largest copper deposits form in continental arcs, yet it is not well understood what determines whether a magmatic system generates economic mineralization or not. Here the authors show that the abundance of chlorine and sulfur, rather than the abundance of ore metals controls magmatic ore fertility.
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Affiliation(s)
- Carter Grondahl
- Department of Earth Sciences, University of Toronto, Toronto, Canada
| | - Zoltán Zajacz
- Department of Earth Sciences, University of Toronto, Toronto, Canada. .,Department of Earth Sciences, University of Geneva, Geneva, Switzerland.
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Richter M, Nebel O, Schwindinger M, Nebel-Jacobsen Y, Dick HJB. Competing effects of spreading rate, crystal fractionation and source variability on Fe isotope systematics in mid-ocean ridge lavas. Sci Rep 2021; 11:4123. [PMID: 33603040 PMCID: PMC7893168 DOI: 10.1038/s41598-021-83387-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 01/11/2021] [Indexed: 11/24/2022] Open
Abstract
Two-thirds of the Earth is covered by mid-ocean ridge basalts, which form along a network of divergent plate margins. Basalts along these margins display a chemical diversity, which is consequent to a complex interplay of partial mantle melting in the upper mantle and magmatic differentiation processes in lower crustal levels. Igneous differentiation (crystal fractionation, partial melting) and source heterogeneity, in general, are key drivers creating variable chemistry in mid-ocean ridge basalts. This variability is reflected in iron isotope systematics (expressed as δ57Fe), showing a total range of 0.2 ‰ from δ57Fe = + 0.05 to + 0.25 ‰. Respective contributions of source heterogeneity and magma differentiation leading to this diversity, however, remain elusive. This study investigates the iron isotope systematics in basalts from the ultraslow spreading Gakkel Ridge in the Arctic Ocean and compares them to existing data from the fast spreading East Pacific Rise ridge. Results indicate that Gakkel lavas are driven to heavier iron isotope compositions through partial melting processes, whereas effects of igneous differentiation are minor. This is in stark contrast to fast spreading ridges showing reversed effects of near negligible partial melting effects followed by large isotope fractionation along the liquid line of descent. Gakkel lavas further reveal mantle heterogeneity that is superimposed on the igneous differentiation effects, showing that upper mantle Fe isotope heterogeneity can be transmitted into erupting basalts in the absence of homogenisation processes in sub-oceanic magma chambers.
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Affiliation(s)
- Marianne Richter
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, 3800, Australia.
| | - Oliver Nebel
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, 3800, Australia
| | - Martin Schwindinger
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, 3800, Australia
| | - Yona Nebel-Jacobsen
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, 3800, Australia
| | - Henry J B Dick
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543-1539, USA
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Bennett EN, Jenner FE, Millet MA, Cashman KV, Lissenberg CJ. Deep roots for mid-ocean-ridge volcanoes revealed by plagioclase-hosted melt inclusions. Nature 2019; 572:235-239. [PMID: 31391560 DOI: 10.1038/s41586-019-1448-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 05/28/2019] [Indexed: 11/09/2022]
Abstract
The global mid-ocean ridge system is the most extensive magmatic system on our planet and is the site of 75 per cent of Earth's volcanism1. The vertical extent of mid-ocean-ridge magmatic systems has been considered to be restricted: even at the ultraslow-spreading Gakkel mid-ocean ridge under the Arctic Ocean, where the lithosphere is thickest, crystallization depths of magmas that feed eruptions are thought to be less than nine kilometres2. These depths were determined using the volatile-element contents of melt inclusions, which are small volumes of magma that become trapped within crystallizing minerals. In studies of basaltic magmatic systems, olivine is the mineral of choice for this approach2-6. However, pressures derived from olivine-hosted melt inclusions are at odds with pressures derived from basalt major-element barometers7 and geophysical measurements of lithospheric thickness8. Here we present a comparative study of olivine- and plagioclase-hosted melt inclusions from the Gakkel mid-ocean ridge. We show that the volatile contents of plagioclase-hosted melt inclusions correspond to much higher crystallization pressures (with a mean value of 270 megapascals) than olivine-hosted melt inclusions (with a mean value of 145 megapascals). The highest recorded pressure that we find equates to a depth 16.4 kilometres below the seafloor. Such higher depths are consistent with both the thickness of the Gakkel mid-ocean ridge lithosphere and with pressures reconstructed from glass compositions. In contrast to previous studies using olivine-hosted melt inclusions, our results demonstrate that mid-ocean-ridge volcanoes may have magmatic roots deep in the lithospheric mantle, at least at ultraslow-spreading ridges.
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Affiliation(s)
- Emma N Bennett
- School of Earth and Ocean Sciences, Cardiff University, Cardiff, UK.
| | - Frances E Jenner
- School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes, UK
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Bennett EN, Lissenberg CJ, Cashman KV. The significance of plagioclase textures in mid-ocean ridge basalt (Gakkel Ridge, Arctic Ocean). CONTRIBUTIONS TO MINERALOGY AND PETROLOGY. BEITRAGE ZUR MINERALOGIE UND PETROLOGIE 2019; 174:49. [PMID: 31178598 PMCID: PMC6530810 DOI: 10.1007/s00410-019-1587-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Accepted: 04/26/2019] [Indexed: 06/09/2023]
Abstract
Textures and compositions of minerals can be used to infer the physiochemical conditions present within magmatic systems. Given that plagioclase is an abundant phase in many magmatic systems, understanding the link between texture and process is vital. Here, we present a database of textural and compositional data for > 1800 plagioclase crystals in mid-ocean ridge basalt from the Gakkel Ridge (Arctic Ocean) to investigate the physiochemical conditions and processes that govern the formation of plagioclase textures and compositions. The Gakkel basalts have high modal crystal contents (up to 50%). The crystal cargo is complex, with both individual plagioclase and glomerocrysts showing large variations in crystal habit, zoning and resorption. The most common types of zoning are reverse and patchy; we attribute patchy zoning to infilling following either skeletal growth or resorption. Resorption is abundant, with multiple resorption events commonly present in a single crystal, and results from both magmatic recharge and decompression. Periods of strong undercooling, distinct to quench crystallisation, are indicated by matured skeletal crystals and thin normally zoned melt inclusion-rich bands following resorption. Individual samples often contain diverse textural and compositional plagioclase groups. Furthermore, most plagioclase is not in equilibrium with its host melt. Finally, the porous open structures of some glomerocrysts suggest that they represent pieces of entrained disaggregated mush. We interpret this to indicate that the crystal cargo is not generally phenocrystic in origin. Instead, plagioclase crystals that formed in different parts of a mush-dominated plumbing system were entrained into ascending melts. The textures of individual crystals are a function of their respective histories of (under)cooling, magma mixing and decompression. The morphologies of melt inclusion trapped in the plagioclase crystals are associated with specific host crystal textures, suggesting a link between plagioclase crystallisation processes and melt inclusion entrapment. The database of plagioclase presented herein may serve as a template for the interpretation of plagioclase textures in magmatic systems elsewhere.
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Affiliation(s)
- Emma N. Bennett
- School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff, CF10 3AT UK
| | - C. Johan Lissenberg
- School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff, CF10 3AT UK
| | - Katharine V. Cashman
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol, BS8 1RJ UK
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Edmonds M, Cashman KV, Holness M, Jackson M. Architecture and dynamics of magma reservoirs. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2019; 377:20180298. [PMID: 30966933 PMCID: PMC6335485 DOI: 10.1098/rsta.2018.0298] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/16/2018] [Indexed: 06/01/2023]
Abstract
This introductory article provides a synopsis of our current understanding of the form and dynamics of magma reservoirs in the crust. This knowledge is based on a range of experimental, observational and theoretical approaches, some of which are multidisclipinary and pioneering. We introduce and provide a contextual background for the papers in this issue, which cover a wide range of topics, encompassing magma storage, transport, behaviour and rheology, as well as the timescales on which magma reservoirs operate. We summarize the key findings that emerged from the meeting and the challenges that remain. The study of magma reservoirs has wide implications not only for understanding geothermal and magmatic systems, but also for natural oil and gas reservoirs and for ore deposit formation. This article is part of the Theo Murphy meeting issue 'Magma reservoir architecture and dynamics'.
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Affiliation(s)
- Marie Edmonds
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
| | - Katharine V. Cashman
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Clifton BS8 1RJ, UK
| | - Marian Holness
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
| | - Matthew Jackson
- Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK
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