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| Open AccessKinetics and detectability of the bridgmanite to post-perovskite transformation in the Earth's D″ layer
The D\({}^{{\prime\prime} }\) layer in the Earth’s lower mantle involves a seismic discontinuity which is often assigned to a mineral phase transition to post-perovskite, however, as this phase transition occurs over broad region the assignment of seismic boundaries remains unclear. Here, the authors find that due to the kinetics of the bridgmanite to post-perovskite transformation, thick transition layers can be detected by seismic reflections, unlike previously thought.
- Christopher Langrand
- , Denis Andrault
- & Sébastien Merkel
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Article
| Open AccessSaline aqueous fluid circulation in mantle wedge inferred from olivine wetting properties
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
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Article
| Open AccessA general orientation distribution function for clay-rich media
A reference function for describing the orientation of clay platelets in clay-rich materials is still lacking, but is necessary for applications such as prediction of water and solute transfer and designs of innovative materials. Here, the authors determine a reference orientation function of clay platelets, and validate their function for both engineered and natural clay-rich media.
- Thomas Dabat
- , Fabien Hubert
- & Eric Ferrage
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Article
| Open AccessExposed soil and mineral map of the Australian continent revealing the land at its barest
In this study, the authors combine Landsat images spanning 30 years with a new statistical estimator to produce a soil and mineral spectra map of the Australian continent largely unobscured by vegetation or clouds.
- Dale Roberts
- , John Wilford
- & Omar Ghattas
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Article
| Open AccessCr-spinel records metasomatism not petrogenesis of mantle rocks
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
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Article
| Open AccessSemiarid climate and hyposaline lake on early Mars inferred from reconstructed water chemistry at Gale
Gale Crater on Mars has been demonstrated to have once hosted water, but its chemistry is still under debate. Here the authors use mineralogical rock compositions and show the once saline character of Gale Crater—a result of warmer climate periods during the Hesperian period.
- Keisuke Fukushi
- , Yasuhito Sekine
- & Robin Wordsworth
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Article
| Open AccessMolybdenum systematics of subducted crust record reactive fluid flow from underlying slab serpentine dehydration
Fluid liberation and migration from subducted oceanic slabs play a critical role in arc magmatism but the volume and origin of the released fluids is unclear and difficult to trace. Here, the authors use Molybdenum isotope ratios to tackle these problems.
- Shuo Chen
- , Remco C. Hin
- & Tim Elliott
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Article
| Open AccessSulphur isotopes of alkaline magmas unlock long-term records of crustal recycling on Earth
Sulphur isotopes track recycling of subducted crustal material, yet few igneous rocks preserve these signals over Earth history. Here, the authors investigate a billion-year-old alkaline province in Greenland and are able to reconstruct a recycled mantle source, thus alkaline rocks can be used to reveal crustal recycling through geological time.
- William Hutchison
- , Rainer J. Babiel
- & Nicola J. Horsburgh
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Article
| Open AccessTemperature-induced amorphization in CaCO3 at high pressure and implications for recycled CaCO3 in subduction zones
Subduction of oceanic crust introduces huge amounts of carbonates into Earth’s mantle, contributing to the global carbon cycle. Here, based on high-pressure-temperature experiments, the authors present a reversible temperature-induced transition from aragonite to amorphous CaCO3.
- Mingqiang Hou
- , Qian Zhang
- & Yingwei Fei
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Article
| Open AccessCarbon sequestration during core formation implied by complex carbon polymerization
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
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Article
| Open AccessRipplocations provide a new mechanism for the deformation of phyllosilicates in the lithosphere
Phyllosilicate minerals are critical components of seismogenic fault, shear and subduction zones. Here, the authors provide a new deformation mechanism for phyllosilicates, based on newly discovered crystallographic defects in biotite (ripplocations), affecting our understanding of fault zone processes.
- Joe Aslin
- , Elisabetta Mariani
- & Michel W. Barsoum
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Article
| Open AccessNb/Ta systematics in arc magma differentiation and the role of arclogites in continent formation
It is unclear why the crust among many arcs is so silica rich when there is a missing mafic component. Here the authors compile a global evaluation of Nb/Ta and examine xenoliths from Arizona to derive a model of why Nb/Ta fractionation is favored in the crust.
- Ming Tang
- , Cin-Ty A. Lee
- & Hehe Jiang
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Correspondence
| Open AccessReply to 'No substantial long-term bias in the Cenozoic benthic foraminifera oxygen-isotope record'
- S. Bernard
- , D. Daval
- & A. Meibom
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Article
| Open AccessThe Medusae Fossae Formation as the single largest source of dust on Mars
Martian dust is globally enriched in S and Cl and has a distinct mean S:Cl ratio. Here the authors identify that the largest potential source region for Martian dust based on analysis of elemental abundance data may be the Medusae Fossae Formation.
- Lujendra Ojha
- , Kevin Lewis
- & Mariek Schmidt
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Article
| Open AccessMineral dissolution and reprecipitation mediated by an amorphous phase
Fluid-mediated mineral dissolution is a key mechanism for mineral reactions in the Earth. Here, the authors show that element transport during mineral dissolution and reprecipitation reactions can be mediated by an amorphous phase, which can contain significant amounts of metals.
- Matthias Konrad-Schmolke
- , Ralf Halama
- & Franziska D. H. Wilke
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Article
| Open AccessValence and spin states of iron are invisible in Earth’s lower mantle
Bridgmanite is the most abundant mineral in the lower mantle and therefore is crucial to interpreting geophysical observations and models. Here, the authors show that ferric-iron-only bridgmanite Fe3+ undergoes a spin transition at 43–53 GPa at 300 K and therefore has implications for mantle structure and dynamics.
- Jiachao Liu
- , Susannah M. Dorfman
- & E. Ercan Alp
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Article
| Open AccessCompositional heterogeneity near the base of the mantle transition zone beneath Hawaii
Seismic discontinuities near 410 and 660 km depth have often been used to map lateral variations in mantle temperature. Here, the authors apply array analysis to SS reflections off these discontinuities under Hawaii and find evidence of lateral variations in mantle composition at 660 km, but not at 410 km.
- Chunquan Yu
- , Elizabeth A. Day
- & Robert D. van der Hilst
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Article
| Open AccessPeridotite weathering is the missing ingredient of Earth’s continental crust composition
The concentration of Ni and Cr of the continental crust cannot be explained by formation models involving differentiated magmatic rocks. Here, the authors show that hydrothermal alteration and chemical weathering of ultramafic rock compensates for the low Ni and Cr concentrations of island arc-type magmatic rocks.
- Andreas Beinlich
- , Håkon Austrheim
- & Andrew Putnis
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Article
| Open AccessViscosity jump in the lower mantle inferred from melting curves of ferropericlase
Viscosity increase in the mantle may cause slab stagnation and plume deflection, but the cause has been unclear. Here, the authors perform experiments showing that the viscosity of ferropericlase increases by 10–100 times from 750 to 1250 km depth indicating a single mechanism for these observations.
- Jie Deng
- & Kanani K. M. Lee
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Article
| Open AccessGeochemical and mineralogical evidence that Rodinian assembly was unique
The supercontinent Rodinia has been hypothesised to have formed in a different manner from other supercontinents. Here, the authors report geochemical and mineralogical evidence for prevalence of non-arc magmatism and enhanced erosion of volcanic arcs and orogens during Rodinian assembly.
- Chao Liu
- , Andrew H. Knoll
- & Robert M. Hazen
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Article
| Open AccessCrystal plasticity as an indicator of the viscous-brittle transition in magmas
The rheological behaviour of magma in shallow conditions may help determine a volcano’s eruptive style. Here, the authors perform deformation experiments on lava from Volcán de Colima to demonstrate that crystal plasticity may preclude failure at certain shallow magmatic conditions.
- J. E. Kendrick
- , Y. Lavallée
- & N. R. Varley
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Article
| Open AccessPlanktic foraminifera form their shells via metastable carbonate phases
Understanding foraminifera mineralisation pathways is essential to correctly decipher the geochemical climate signals recorded in their shells. Here, the authors identify a non-classical crystallization pathway via metastable phases for Orbulina universa and Neogloboquadrina dutertrei.
- D. E. Jacob
- , R. Wirth
- & S. M. Eggins
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Article
| Open AccessClay mineral formation under oxidized conditions and implications for paleoenvironments and organic preservation on Mars
In the Gale Crater on Mars, organic matter has been detected, but in much lower concentrations than expected. Here, the authors conduct clay mineral synthesis experiments which suggest that clay minerals may rapidly form under oxidized conditions and thus explain the low organic concentrations in Gale Crater.
- Seth R. Gainey
- , Elisabeth M. Hausrath
- & Courtney L. Bartlett
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Article
| Open AccessPlume-subduction interaction forms large auriferous provinces
The lithospheric controls on giant gold deposits remain unclear. Here, the authors show evidence for native gold in the mantle from the Deseado Massif in Patagonia demonstrating that refertilisation of the lithospheric mantle is key in forming metallogenic provinces.
- Santiago Tassara
- , José M. González-Jiménez
- & Alexandre Corgne
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Article
| Open AccessArchaean and Proterozoic diamond growth from contrasting styles of large-scale magmatism
Dating of inclusions within diamonds is used to reconstruct Earth’s geodynamic history. Here, the authors report isotope data on individual garnet inclusions within diamonds from Venetia, South Africa, showing that two suites of diamonds define two isochrons, showing the importance of dating individual inclusions.
- Janne M. Koornneef
- , Michael U. Gress
- & Gareth R. Davies
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Article
| Open AccessAncient hydrothermal seafloor deposits in Eridania basin on Mars
The Eridania basin on Mars was once the site of a vast inland sea. Here, the authors show that the most ancient materials in the Eridania basin were formed in a deep-water hydrothermal setting and may be an analogue for early environmental conditions on Earth.
- Joseph R. Michalski
- , Eldar Z. Noe Dobrea
- & Javier Cuadros
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Article
| Open AccessCompressional pathways of α-cristobalite, structure of cristobalite X-I, and towards the understanding of seifertite formation
The presence of α-seifertite and seiferite in shocked meteorites are used to determine shock pressures. Here, using high-pressure experiments, the authors find that the presence of α-cristobalite does not exclude high-pressure transformation and seifertite does not necessarily indicate high pressures.
- Ana Černok
- , Katharina Marquardt
- & Leonid Dubrovinsky
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Article
| Open AccessEnd-Triassic mass extinction started by intrusive CAMP activity
The cause of the end-Triassic extinction remains controversial. Here, the authors present U-Pb age data showing that magmatic activity occurred 100 kyr before the earliest known eruptions, which links to changes in climate and biotic records indicating the importance of understanding the intrusive record.
- J.H.F.L. Davies
- , A. Marzoli
- & U. Schaltegger
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Article
| Open AccessDehydration-driven stress transfer triggers intermediate-depth earthquakes
Intermediate-depth earthquakes (30-300 km) occur in subducting oceanic slabs, but their generation mechanism remains enigmatic. Here, the authors show through high-pressure and dehydration experiments of antigorite that dehydration-driven stress transfer triggers intermediate-depth earthquakes.
- Thomas P. Ferrand
- , Nadège Hilairet
- & Alexandre Schubnel
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Article
| Open AccessSeismic anisotropy of the D″ layer induced by (001) deformation of post-perovskite
The source of the anisotropic layer (D'' layer) at the bottom of the lower mantle remains unclear. Here, using high pressure and temperature experiments, the authors find that seismic anisotropy observed at the D'' layer is caused by 50% deformation of the minerals post-perovskite and ferropericlase.
- Xiang Wu
- , Jung-Fu Lin
- & Vitali B. Prakapenka
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Article
| Open AccessMassive production of abiotic methane during subduction evidenced in metamorphosed ophicarbonates from the Italian Alps
Alteration of ultramafic rocks plays a role in hydrocarbon production, but little is known about this process at depth. Here, the authors provide evidence that alteration of carbonated ultramafic rocks at high-pressures are an important source of abiotic methanogenesis with implications for deep C mobility.
- Alberto Vitale Brovarone
- , Isabelle Martinez
- & Imène Esteve
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Article
| Open AccessMineral inclusions in diamonds may be synchronous but not syngenetic
Trapped mineral inclusions in diamonds give information on diamond crystallization and ages, under the assumption that they are syngenetic (formed simultaneously). Here, the authors show evidence that many mineral inclusions are protogenetic (formed at different times) thus undermining previous diamond ages.
- Fabrizio Nestola
- , Haemyeong Jung
- & Lawrence A. Taylor
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Article
| Open AccessZinc isotope evidence for sulfate-rich fluid transfer across subduction zones
During subduction, fluids are released into the mantle wedge, but the exact compositions of these fluids are unclear. Ponset al. by analysing zinc isotopes from serpentinite provide evidence that oxidized, sulphate rich fluids are released to the mantle wedge during subduction.
- Marie-Laure Pons
- , Baptiste Debret
- & Helen Williams
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Article
| Open AccessSilica deposits on Mars with features resembling hot spring biosignatures at El Tatio in Chile
Hydrothermal deposits on Mars may provide the best opportunity to find Martian biosignatures. Ruff and Farmer report that silica structures created by biotic and abiotic process in hot springs at El Tatio, Chile resemble those found in Gusev crater, thus making it an ideal location for future missions.
- Steven W. Ruff
- & Jack D. Farmer
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Article
| Open AccessPre-eruptive magmatic processes re-timed using a non-isothermal approach to magma chamber dynamics
Zoned crystals may reflect magma chamber dynamics, where changes in temperature, pressure and timescale before volcanic eruption may be measured. Petrone et al. develop a new Non-Isothermal Diffusion Incremental Step model to reconstruct crystal lifetime histories to constrain pre-eruptive magmatic processes.
- Chiara Maria Petrone
- , Giuseppe Bugatti
- & Simone Tommasini
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Article
| Open AccessMolecular preservation of 1.88 Ga Gunflint organic microfossils as a function of temperature and mineralogy
Thermal diagenesis is generally seen as detrimental to the preservation of organic biosignatures. Using synchrotron-based XANES data, Alleon et al.find preservation of the molecular signatures of organic microfossils from the 1.88 Ga Gunflint cherts.
- Julien Alleon
- , Sylvain Bernard
- & François Robert
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Article |
Nanoscale infrared spectroscopy as a non-destructive probe of extraterrestrial samples
Infrared spectral mapping offers the non-destructive analyses of samples; however, the spatial resolution is restricted to >10 microns. Here, the authors present a new infrared technique capable of sub-micron scale mineral identification, demonstrated using a chondrule and a cometary dust grain.
- Gerardo Dominguez
- , A. S. Mcleod
- & D. N. Basov
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Lonsdaleite is faulted and twinned cubic diamond and does not exist as a discrete material
Lonsdaleite has been used as a marker of asteroid impacts and is thought to have mechanical properties superior to diamond; however, pure lonsdaleite has not been described or fabricated. Here, the authors show that it does not exist as a discrete material and is in fact faulted and twinned cubic diamond.
- Péter Németh
- , Laurence A. J. Garvie
- & Peter R. Buseck
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Tracing carbonate–silicate interaction during subduction using magnesium and oxygen isotopes
Carbon fluxes between the Earth’s surface and its interior are ultimately controlled by subduction of carbonated eclogites and carbonates, although the processes are not well understood. Here, the authors demonstrate that coupled Mg and O isotopic studies may help us to trace deep carbon recycling.
- Shui-Jiong Wang
- , Fang-Zhen Teng
- & Shu-Guang Li
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Article
| Open AccessVisualized effect of oxidation on magnetic recording fidelity in pseudo-single-domain magnetite particles
Magnetite provides a valuable record of the Earth's geomagnetic history. Here, Almeida et al. combine electron microscopy and energy-loss spectroscopy to study the effects of in situoxidation on the magnetization fidelity and crystalline phase of pseudo-single domain magnetite grains.
- Trevor P. Almeida
- , Takeshi Kasama
- & Rafal E. Dunin-Borkowski
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Article |
Formation of recent Pb-Ag-Au mineralization by potential sub-surface microbial activity
Studies suggest almost the same amount of biomass is present in subterranean settings as on Earth’s surface. Here, the authors propose that a large intraterrestrial microbial system was responsible for mineralization in southern Spain, and that microbes may play a major role in sub-surface ore-forming processes.
- Fernando Tornos
- , Francisco Velasco
- & Juan Manuel Escobar
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Article
| Open AccessClinopyroxene precursors to amphibole sponge in arc crust
Studies have suggested amphibole to be a major phase in the lower crust based on trace element geochemistry of volcanic suites, although the formation of these lithologies remains cryptic. Here, the author suggests a reaction-replacement mechanism to explain how this cryptic fractionation may occur.
- Daniel J. Smith
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Article
| Open AccessElastic anisotropy of experimental analogues of perovskite and post-perovskite help to interpret D′′ diversity
Seismological observations of the D′′ layer near the core–mantle boundary are difficult to interpret and the minerals present are unstable at ambient conditions. Yoneda et al.present experiments using analogues, suggesting the observations are due to preferred crystal orientations.
- Akira Yoneda
- , Hiroshi Fukui
- & Alfred Q. R. Baron
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Article
| Open AccessGreenhouse conditions induce mineralogical changes and dolomite accumulation in coralline algae on tropical reefs
Ocean acidification is affecting the stability of coral reefs, but the exact mineralogical response is poorly understood. Diaz-Pulido et al.show that, under warming conditions, the relative abundance of dolomite increases by as much as 200% and could therefore slow the climate-induced break-up of coral reefs.
- Guillermo Diaz-Pulido
- , Merinda C. Nash
- & Ulrike Troitzsch
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The discovery of kimberlites in Antarctica extends the vast Gondwanan Cretaceous province
Kimberlite, an igneous rock in which the majority of the world’s diamonds are found, has been reported on all major continents barring Antarctica. Yaxley et al. present mineralogical and chemical data that confirms the first bona fidediscovery of kimberlite in the Antarctic.
- Gregory M. Yaxley
- , Vadim S. Kamenetsky
- & Marc Norman
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Article
| Open AccessNatural gold particles in Eucalyptus leaves and their relevance to exploration for buried gold deposits
The discovery of new gold deposits has declined by 45% over the past 10 years. Lintern et al.present new evidence for the occurrence of particulate gold in trees growing above buried mineral deposits, and propose vegetation sampling as a mineral exploration method.
- Melvyn Lintern
- , Ravi Anand
- & David Paterson
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Biological carbon precursor to diagenetic siderite with spherical structures in iron formations
The role of bacteria in the origin of iron formations (IF) remains unclear because no direct evidence for their involvement exists. This study shows that spherical siderite in deep-water IF represents a biosignature for photoferrotrophy, whereas massive siderite reflects high cyanobacterial biomass in shallow-water.
- Inga Köhler
- , Kurt O Konhauser
- & Andreas Kappler
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The Tissint Martian meteorite as evidence for the largest impact excavation
High-pressure minerals in meteorites reflect the conditions prevailing when they were excavated and launched from their parent bodies. Tissint—a recent Martian meteorite—contains an unusual number of large high-pressure minerals, suggesting excavation from an impact of larger magnitude than for previous Martian samples.
- Ioannis P. Baziotis
- , Yang Liu
- & Lawrence A. Taylor
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New silica clathrate minerals that are isostructural with natural gas hydrates
Clathrates are minerals with cage-like structural voids that can be filled by guest species; three types are plausible but only one has been observed in nature. Mommaet al. have discovered the remaining two types in Japanese marine sediments, and determined their structural similarity to natural gas hydrates.
- Koichi Momma
- , Takuji Ikeda
- & Yasuhiro Kudoh