Petrology

  • Article
    | Open Access

    Chemically variable primitive basalts undergo mixing during ascent from the mantle. Here the authors show observations from magma–magma reaction experiments which demonstrate how isothermal mixing between chemically variable basalts creates and modifies crystal cargoes erupted in oceanic settings.

    • David A. Neave
    • , Philipp Beckmann
    •  & François Holtz
  • Article
    | Open Access

    Ultramafic olivine-rich achondrites provide insight into the missing mantle problem in the asteroid belt. The petrology and geochemistry of these samples suggests they are related to Vesta or the Vestoids.

    • Zoltan Vaci
    • , James M. D. Day
    •  & Andreas Pack
  • Article
    | Open Access

    Episodic magmatism of the early Andes is the result of a complex interplay between mantle, crust, slab and sediment contributions that can be traced using zircon chemistry. An external (tectonic) model is argued for the episodic plutonism in this extensional continental arc.

    • José Joaquín Jara
    • , Fernando Barra
    •  & Diego Morata
  • Perspective
    | Open Access

    Vast, ancient impact basins scattered mantle materials across the lunar surface. We review lunar evolution models to identify candidate mantle lithologies, then assess orbital observations to evalutae the current distribution of these materials and implications for fundamental planetary processes.

    • Daniel P. Moriarty III
    • , Nick Dygert
    •  & Noah E. Petro
  • Article
    | Open Access

    Experiments and buoyancy calculations reveal that subduction of limestone results in massive carbon storage in arc lithosphere, forming an important carbon reservoir in convergent margins. Remobilization of this carbon reservoir during arc magma ascent may dominate carbon emissions at volcanic arcs.

    • Chunfei Chen
    • , Michael W. Förster
    •  & Yongsheng Liu
  • Article
    | Open Access

    Arc olivines are commonly explained through a paradigm of core-to-rim sequential growth and oscillatory zoning is interpreted to represent magma mixing. Here the authors show Fo–Ni–P oscillatory zoned olivines can grow as out-of-sequence crystal frames and complex zoning can occur in closed systems.

    • Pablo Salas
    • , Philipp Ruprecht
    •  & Osvaldo Rabbia
  • Article
    | Open Access

    Subduction zone volcanoes are underlain by extensive magma plumbing systems, which can obscure original mantle source signals. Here, the authors show that intra-crystal oxygen isotope analysis of clinopyroxenes from the Sunda arc (Indonesia) reveal the δ18 O value of the sub-arc mantle.

    • Frances M. Deegan
    • , Martin J. Whitehouse
    •  & Osvaldo González-Maurel
  • Article
    | Open Access

    Diamonds encapsulate the deep Earth fluids that form them, providing windows to deep mantle processes. This study constrains their ages, based on uranium-thorium-to-helium radioactive decay in the fluids and helium diffusivity in diamond, and relates diamond formation to geological events in Southern Africa.

    • Yaakov Weiss
    • , Yael Kiro
    •  & Steven L. Goldstein
  • Article
    | Open Access

    Phase equilibrium modelling combined with Ca isotope measurements in ancient granitoids demonstrates that subduction of oceanic crust occurred repeatedly throughout the Archaean and that carbonate sediments were present in early Eoarchaean oceans (>3.8 billion years).

    • Michael A. Antonelli
    • , Jillian Kendrick
    •  & Frédéric Moynier
  • Article
    | Open Access

    Chlorine behaviour during complex, polybaric arc magma degassing is poorly understood. Here, the authors show that chemical feedbacks during coeval magma differentiation and degassing account for the Cl record at both volcanoes and ore deposits, and quantify the role of Cl in efficient copper extraction during degassing.

    • B. Tattitch
    • , C. Chelle-Michou
    •  & R. R. Loucks
  • Article
    | Open Access

    Here, the authors identify that magnetotelluric conductive anomalies commonly observed on the trenchward-side of volcanic arcs in subduction zones can be explained by subducted sediments. High-pressure experiments show that these sediment melts will react with the overlying mantle wedge to produce electrically conductive phlogopite pyroxenites.

    • M. W. Förster
    •  & K. Selway
  • Article
    | Open Access

    Subduction of oceanic crust and sediments contributes to heterogeneities in the mantle, which are sampled by mantle plumes. Here, the authors find that extreme isotopic heterogeneity in Samoan clinopyroxenes can help constrain the composition of mantle sources containing sediment recycled into the Earth’s mantle.

    • Jenna V. Adams
    • , Matthew G. Jackson
    •  & John M. Cottle
  • Article
    | Open Access

    The Rustenburg Layered Suite of the Bushveld Complex, South Africa, has long been regarded as a textbook result of fractional crystallization from a melt-dominated magma chamber. Here, the authors find that the Rustenburg Layered Suite can be derived from crustal assimilation by komatiitic magma to form magmatic mushes without requiring the existence of a magma chamber by using thermodynamic models.

    • Zhuosen Yao
    • , James E. Mungall
    •  & M. Christopher Jenkins
  • Article
    | Open Access

    The fate of subducted CO2 remains debated, with estimates mainly from numerical predictions varying from wholesale decarbonation of the shallow subducting slab to massive deep subduction of CO2. Here, the authors present field-based data and show that ~40% to ~65% of the CO2 in subducting crust is released via metamorphic decarbonation reactions at forearc depths.

    • E. M. Stewart
    •  & Jay J. Ague
  • Article
    | Open Access

    This study makes use of the total spread of zircon ages and trace elements to study the thermal evolution of magmatic systems. Applied to Nevado de Toluca, the authors determine the size of its subvolcanic magma reservoir and assess its potential of re-activation.

    • Gregor Weber
    • , Luca Caricchi
    •  & Axel K. Schmitt
  • Article
    | Open Access

    Pegmatite crystals are thought to grow rapidly, yet their growth rates and conditions are not well constrained. Here, the authors find that the trace element distributions of pegmatitic quartz crystals indicate rapid growth in highly dynamic environments, suggesting that large meter-scale crystals can be formed within days.

    • Patrick R. Phelps
    • , Cin-Ty A. Lee
    •  & Douglas M. Morton
  • Article
    | Open Access

    Transport properties of melts in the deep Earth have dictated the evolution of the early Earth’s magma oceans and also govern many modern dynamic processes, such as plate tectonics. Here, the authors find there is a reversal in the trends of transport properties of basaltic melts at pressures near 50 GPa, with implications for the timescales of early Earth’s magma oceans.

    • Arnab Majumdar
    • , Min Wu
    •  & John S. Tse
  • Article
    | Open Access

    Magmatic systems play a crucial role in enriching the crust with volatiles and elements that reside primarily within the Earth’s mantle. Here, the authors show that carbon, as a buoyant supercritical CO2 fluid, could be a covert agent that may promote the physical transport of sulfides across the mantle-crust transition.

    • Daryl E. Blanks
    • , David A. Holwell
    •  & Elena Ferrari
  • Article
    | Open Access

    Plate tectonics necessitates mantle recycling throughout Earth’s history, yet direct geochemical evidence for mantle reprocessing remains elusive. Here, the authors present evidence of recycled supra-subduction zone mantle wedge peridotite dredged from the Mid-Atlantic Ridge near 16°30′N.

    • B. M. Urann
    • , H. J. B. Dick
    •  & J. F. Casey
  • Article
    | Open Access

    In this study the authors show that monotonous basaltic volcanoes can host a range of melts in their sub-volcanic systems, extending to rhyolitic compositions. The study implies that volcanoes which have produced monotonous basaltic lavas on long timescales could transition to more explosive, silica-rich eruptions in the future.

    • Michael J. Stock
    • , Dennis Geist
    •  & John Maclennan
  • Article
    | Open Access

    Magma storage zones are debated to either be crystal-dominated mush zones or large liquid-dominated magma chambers. Here, the authors discover fossilized solidification fronts of magnetitite in the Bushveld pluton, which indicate nucleation and crystal growth occurred at the magma chamber floor, precluding the existence of a thick crystal mush zone in this region.

    • Willem Kruger
    •  & Rais Latypov
  • Article
    | Open Access

    Feldspars are stable at pressures up to 3 GPa along the mantle geotherm, but they can persist metastably at higher pressures at colder conditions. Here, above 10 GPa the authors find  new high-pressure polymorphs of feldspars that could persist at depths corresponding to the Earth’s upper mantle, potentially influencing the dynamics and fate of cold subducting slabs.

    • Anna Pakhomova
    • , Dariia Simonova
    •  & Leonid Dubrovinsky
  • Article
    | Open Access

    Many major mass extinction events have been associated with large volcanic eruption events, with the argument that large volumes of volcanic degassing could trigger past global climate changes. Here, the authors find that during the end-Triassic extinction event volcanic pulses emitted large amounts of CO2 comparable to projected anthropogenic emissions for the 21st century in the future 2 °C warming scenario.

    • Manfredo Capriolo
    • , Andrea Marzoli
    •  & Csaba Szabó
  • Article
    | Open Access

    The authors here analyse the petrology of the meteorite NWA 8321 (parent body Vesta). They find sulfidation processes of olivine suggesting metasomatism in the Vestan interior and a partial melting origin for the host noritic diogenite.

    • Ai-Cheng Zhang
    • , Noriyuki Kawasaki
    •  & Hisayoshi Yurimoto
  • Article
    | Open Access

    Sulfur is one of the key volatiles in Earth’s chemical cycles; however, sulfur speciation, isotopic composition, and flux during the subduction cycle remain unclear. Here, the authors provide direct constraints on subduction zone sulfur recycling from high-pressure rocks and explore implications for arc magmatism.

    • Ji-Lei Li
    • , Esther M. Schwarzenbach
    •  & Xin-Shui Wang
  • Article
    | Open Access

    The ~70 km-diameter Yarrabubba impact structure in Western Australia has previously been regarded as among Earth’s oldest meteorite craters, but has hitherto lacked absolute age constraints. Here, the authors determine a precise impact age of 2229 ± 5 Ma, which extends the terrestrial cratering record back in time by > 200 million years and establishes Yarrabubba as the oldest recognised meteorite impact structure on Earth.

    • Timmons M. Erickson
    • , Christopher L. Kirkland
    •  & Thomas M. Davison
  • Article
    | Open Access

    Porphyry copper and gold deposits are the dominant natural suppliers of these metals to our society, yet the large variations in metal endowments of porphyry Cu–Au deposits remain obscure. Here, the author shows that Cu-rich porphyries require large amounts of magma and water to be formed, while Au-rich porphyries are the result of a better efficiency of Au precipitation.

    • Massimo Chiaradia
  • Article
    | Open Access

    Olivine crystals with prominent intracrystalline distortions have previously been used to quantify deformational processes within the mantle. Here, the authors show that similar techniques can be applied to deformed volcanic olivine crystals, providing quantitative constraints on the geometry of melt-rich mush piles within magmatic plumbing systems.

    • Penny E. Wieser
    • , Marie Edmonds
    •  & John Wheeler
  • Article
    | Open Access

    The increasingly prevalent view of magmatic systems as mush-dominated challenges the common assumption that melt inclusions record the pre-eruptive storage and processing of the melts they were erupted with. Here, the authors show that melt inclusions from Kīlauea Volcano, Hawai'i exhibit extreme compositional diversity, consistent with the accumulation of inclusion-bearing crystals in magmatic mush zones for >170 years before their eventual eruption in unrelated carrier melts.

    • Penny E. Wieser
    • , Marie Edmonds
    •  & Barbara E. Kunz
  • Article
    | Open Access

    The authors here perform experiments to investigate the dihedral angle of olivine-H2O and olivine-H2O-NaCl systems. The observed effect of NaCl to decrease dihedral angles allows fluids to percolate through forearc mantle wedge and to accumulate in the overlying crust, accounting for the high electrical conductivity anomalies in forearc regions.

    • Yongsheng Huang
    • , Takayuki Nakatani
    •  & Catherine McCammon
  • Article
    | Open Access

    The links between plate tectonics and deep mantle structure remain unclear. Here, the authors demonstrate that transition elements (Ni, Cr, and Fe/Mn) in basaltic rocks can be used as a tool to trace plume-related magmatism through Earth history, and their results indicate the presence of a direct relationship between the intensity of plume magmatism and the supercontinent cycle.

    • Hamed Gamal EL Dien
    • , Luc S. Doucet
    •  & Ross Mitchell
  • Article
    | Open Access

    Chromian-spinel from mafic-ultramafic rocks is used as a reliable geotectonic and mantle melting indicator. Here, the authors argue that this only works partially – it can be used to assess information on mantle metasomatic processes but not petrogenesis.

    • Hamed Gamal El Dien
    • , Shoji Arai
    •  & Mohamed Hamdy
  • Article
    | Open Access

    Diamonds can give us clues to the processes regulating deep carbon transport within the Earth. Here, the author discovers evidence from diamond coatings that organic compounds exist at great depth in Earth’s interior, and furthermore, that organic molecules may provide scaffolds for diamond nucleation and growth.

    • Maria Luce Frezzotti
  • Article
    | Open Access

    This study seeks to tackle the question of why intermediate magmatic rock compositions are poorly represented on the Earth’s surface. The authors do so by tracking the evolution of the physical behaviour of immiscible Fe-rich liquids within a sample suite from the lava lake on the Kilauea Iki volcano, Hawaii.

    • Victoria C. Honour
    • , Marian B. Holness
    •  & Marlon M. Jean
  • Article
    | Open Access

    The geodynamic evolution of mountain ranges can be reconstructed using the pressure recorded by minerals in metamorphic rocks, under the key assumption that rock pressure is lithostatic. Here, the authors challenge the lithostatic pressure paradigm by showing that there can be significant outcrop-scale pressure gradients due to compression- and reaction-induced stress.

    • Cindy Luisier
    • , Lukas Baumgartner
    •  & Torsten Vennemann
  • Article
    | Open Access

    Tectonic plate motions are often reconstructed based on the assumption that mantle plumes are fixed within the mantle. Here, the authors provide geochemical and geodynamic evidence to suggest that the asymmetry of the Azores thermal anomaly can be explained by northward motion of the Azores plume.

    • Maëlis Arnould
    • , Jérôme Ganne
    •  & Xiaojun Feng
  • Article
    | Open Access

    Recycling of Earth’s crust through subduction and delamination contributes to mantle heterogeneity. Here, the authors measure coupled Sr-Nd-Pb isotope compositions of melt inclusions in Italian potassium-rich lavas, they suggest their results indicate a potential ancient lower crustal component in the mantle source.

    • Janne M. Koornneef
    • , Igor Nikogosian
    •  & Gareth R. Davies
  • Perspective
    | Open Access

    The primary causes of dramatic variations in volcanic flux and composition along strike in subduction zones remain largely unknown. Here we use a promising new approach to show that along-strike volcanic variability in the Quaternary Cascades Arc is primarily due to variations in the flux of basalt into the base of the crust, rather than crustal magma storage.

    • C. B. Till
    • , A. J. R. Kent
    •  & B. W. Pitcher
  • Article
    | Open Access

    The amount of carbon stored in closed hidden reservoirs is unknown. Here the authors use a computational approach to study the evolution of carbon species and observe polymerization of carbon atoms at high pressures, illustrating the potential for a significant carbon reservoir in the Earth’s deep interior.

    • Natalia V. Solomatova
    • , Razvan Caracas
    •  & Craig E. Manning
  • Article
    | Open Access

    The solubility of sulfur in basaltic melt has important implications for the formation of magmatic ore deposits. Here, the authors show that magma ascent and sulfur-degassing influence the degree to which basaltic magmas are enriched in economically-important chalcophile and siderophile elements.

    • C. D. J. Reekie
    • , F. E. Jenner
    •  & H. M. Williams
  • Article
    | Open Access

    Thermodynamic calculations suggest that condensed carbonaceous matter should be the dominant product of abiotic organic synthesis during serpentinization of the oceanic crust at Mid-Ocean Ridges. Here the authors report natural occurrences of such carbonaceous matter formed during low temperature alteration.

    • Marie Catherine Sforna
    • , Daniele Brunelli
    •  & Bénédicte Ménez
  • Article
    | Open Access

    Boron is one of the main proxies for seawater-derived fluids in subduction zone volcanics and it is vital to characterise the location and concentration of boron in the oceanic lithosphere. Here the authors show that boron concentration in the mantle of downgoing slabs has been overestimated, because boron is strongly decoupled from water in the hydration process.

    • Andrew M. McCaig
    • , Sofya S. Titarenko
    •  & Samuele Agostini
  • Article
    | Open Access

    Crustal melting may play a fundamental role in orogenic processes, but quantifying crustal melt remains difficult. Here, the authors combine pressure-temperature paths, electrical conductivity and geophysical data to elucidate the melting conditions in Tibet since the Miocene.

    • Jinyu Chen
    • , Fabrice Gaillard
    •  & Guillaume Richard
  • Article
    | Open Access

    The oxidised nature of arc magmas is either attributed to recycling from the slab or magma differentiation. Here, the authors show that oxidised iron and sulfur, respectively in sub-arc mantle spinel and glass inclusions with elevated U/Th, Pb/Ce, Sr/Nd and δ34S, trace dehydration products of slab serpentinites.

    • Antoine Bénard
    • , Kevin Klimm
    •  & Dmitri A. Ionov