1
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Tian X, Behn MD, Ito G, Schierjott JC, Kaus BJP, Popov AA. Magmatism controls global oceanic transform fault topography. Nat Commun 2024; 15:1914. [PMID: 38429287 PMCID: PMC10907720 DOI: 10.1038/s41467-024-46197-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 02/16/2024] [Indexed: 03/03/2024] Open
Abstract
Oceanic transform faults play an essential role in plate tectonics. Yet to date, there is no unifying explanation for the global trend in broad-scale transform fault topography, ranging from deep valleys to shallow topographic highs. Using three-dimensional numerical models, we find that spreading-rate dependent magmatism within the transform domain exerts a first-order control on the observed spectrum of transform fault depths. Low-rate magmatism results in deep transform valleys caused by transform-parallel tectonic stretching; intermediate-rate magmatism fully accommodates far-field stretching, but strike-slip motion induces across-transform tension, producing transform strength dependent shallow valleys; high-rate magmatism produces elevated transform zones due to local compression. Our models also address the observation that fracture zones are consistently shallower than their adjacent transform fault zones. These results suggest that plate motion change is not a necessary condition for reproducing oceanic transform topography and that oceanic transform faults are not simple conservative strike-slip plate boundaries.
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Affiliation(s)
- Xiaochuan Tian
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA, USA.
| | - Mark D Behn
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA, USA
| | - Garrett Ito
- Department of Earth Sciences, University of Hawaii, Honolulu HI, USA
| | - Jana C Schierjott
- Department of Earth Sciences, University of Hawaii, Honolulu HI, USA
| | - Boris J P Kaus
- Institute of Geosciences, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Anton A Popov
- Institute of Geosciences, Johannes Gutenberg University Mainz, Mainz, Germany
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2
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Yu C, Goes S, Day EA, van der Hilst RD. Seismic evidence for global basalt accumulation in the mantle transition zone. SCIENCE ADVANCES 2023; 9:eadg0095. [PMID: 37256943 PMCID: PMC10413675 DOI: 10.1126/sciadv.adg0095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Accepted: 04/21/2023] [Indexed: 06/02/2023]
Abstract
The mantle's compositional structure reflects the thermochemical evolution of Earth. Yet, even the radial average composition of the mantle remains debated. Here, we analyze a global dataset of shear and compressional waves reflecting off the 410- and 660-km discontinuities that is 10 times larger than any previous studies. Our array analysis retrieves globally averaged amplitude-distance trends in SS and PP precursor reflectivity from which we infer relative wavespeed and density contrasts and associated mantle composition. Our results are best matched by a basalt-enriched mantle transition zone, with higher basalt fractions near 660 (~40%) than 410 (~18-31%). These are consistent with mantle-convection/plate-recycling simulations, which predict that basaltic crust accumulates in the mantle transition zone, with basalt fractions peaking near the 660. Basalt segregation in the mantle transition zone also implies that the overall mantle is more silica enriched than the often-assumed pyrolitic mantle reference composition.
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Affiliation(s)
- Chunquan Yu
- Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen 518055, China
- Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology, Southern University of Science and Technology, Shenzhen 518055, China
| | - Saskia Goes
- Department of Earth Science and Engineering, Imperial College London, London SW7 2BP, UK
| | - Elizabeth A. Day
- Department of Earth Science and Engineering, Imperial College London, London SW7 2BP, UK
| | - Robert D. van der Hilst
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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3
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Pierru R, Andrault D, Manthilake G, Monteux J, Devidal JL, Guignot N, King A, Henry L. Deep mantle origin of large igneous provinces and komatiites. SCIENCE ADVANCES 2022; 8:eabo1036. [PMID: 36322665 PMCID: PMC9629742 DOI: 10.1126/sciadv.abo1036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 08/17/2022] [Indexed: 06/16/2023]
Abstract
Large igneous provinces (LIPs) resulted from intraplate magmatic events mobilizing volumes of magma up to several million cubic kilometers. LIPs and lavas with deep mantle sources have compositions ranging from komatiites found in Archean greenstone belts to basalts and picrites in Phanerozoic flood basalt and recent oceanic islands. In this study, we identify the mantle conditions appropriate to each type of lava based on an experimental study of the melting of pyrolite. The depth of the mantle source decreases from 600 to 700 km for the oldest komatiites to 100 to 300 km for picrites and basalts, and the extent of mantle melting ranges from 10 to 50%. We develop a geodynamical model that explains the origin of the hot mantle plumes capable of generating these melting P-T conditions. Within a superadiabatic temperature gradient persisting in the deep mantle, the ascent of hot mantle plumes creates excess temperatures up to 250 to 300 K by adiabatic decompression.
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Affiliation(s)
- Rémy Pierru
- Université Clermont Auvergne, CNRS, IRD, OPGC, LMV, F-63000 Clermont-Ferrand, France
| | - Denis Andrault
- Université Clermont Auvergne, CNRS, IRD, OPGC, LMV, F-63000 Clermont-Ferrand, France
| | - Geeth Manthilake
- Université Clermont Auvergne, CNRS, IRD, OPGC, LMV, F-63000 Clermont-Ferrand, France
| | - Julien Monteux
- Université Clermont Auvergne, CNRS, IRD, OPGC, LMV, F-63000 Clermont-Ferrand, France
| | - Jean Luc Devidal
- Université Clermont Auvergne, CNRS, IRD, OPGC, LMV, F-63000 Clermont-Ferrand, France
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4
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Audhkhasi P, Singh SC. Discovery of distinct lithosphere-asthenosphere boundary and the Gutenberg discontinuity in the Atlantic Ocean. SCIENCE ADVANCES 2022; 8:eabn5404. [PMID: 35714195 PMCID: PMC9205597 DOI: 10.1126/sciadv.abn5404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 05/04/2022] [Indexed: 06/15/2023]
Abstract
The plate tectonic theory requires a rigid lithosphere floating over a weak asthenosphere, separated by the lithosphere-asthenosphere boundary, which has been sometimes interpreted as the Gutenberg discontinuity. Using a deep seismic reflection technique, we report the presence of two continuous reflections covering 27 Ma to 58 Ma oceanic lithosphere in the Atlantic Ocean. We find that the upper reflection deepens with age and follows the ~1250°C isotherm, whereas the deeper reflection lies at a constant depth of ~75 km. We suggest that the upper reflection represents the thermally controlled lithosphere-asthenosphere boundary, whereas the lower reflection is the Gutenberg discontinuity, a frozen-in dehydration boundary separating the dry mantle melting region above from the hydrated mantle below formed at the ridge axis. We also find that thermal mantle anomalies rejuvenate the lithosphere, uplift the lithosphere-asthenosphere boundary, and destroy the Gutenberg discontinuity.
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5
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Zhao SY, Yang AY, Langmuir CH, Zhao TP. Oxidized primary arc magmas: Constraints from Cu/Zr systematics in global arc volcanics. SCIENCE ADVANCES 2022; 8:eabk0718. [PMID: 35319995 PMCID: PMC8942352 DOI: 10.1126/sciadv.abk0718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 02/01/2022] [Indexed: 06/14/2023]
Abstract
Arc volcanics are more oxidized than mid-ocean ridge basalts (MORB), but it is debated whether this is a mantle feature or a result of magmatic evolution. Copper, a sulfur-loving element, has been used to trace the behavior of redox-sensitive sulfur during mantle melting and infer similar redox states of sub-arc and sub-ridge mantle. Previous studies, however, neglected elevated sulfur contents in the sub-arc mantle, leading to underestimation of oxygen fugacities, and did not recognize systematic Cu variations in arc volcanics. Here, we show that the Cu/Zr ratio is a sensitive indicator that responds to sulfur content, oxygen fugacity, and extent of melting of the mantle. Because of higher mantle S contents, Cu systematics of arc magmas require one log unit higher oxygen fugacities of sub-arc than sub-ridge mantle. Low Cu contents of thick-crusted arc volcanics result from low extents of melting of sulfur-rich mantle, obviating the need for deep crustal sulfide fractionation, with substantial implications for the origin of porphyry-Cu deposits.
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Affiliation(s)
- Si-Yu Zhao
- State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- CAS Center for Excellence in Deep Earth Science, Guangzhou, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
- University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Alexandra Yang Yang
- State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- CAS Center for Excellence in Deep Earth Science, Guangzhou, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | | | - Tai-Ping Zhao
- CAS Center for Excellence in Deep Earth Science, Guangzhou, China
- Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
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6
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Bao X, Lithgow-Bertelloni CR, Jackson MG, Romanowicz B. On the relative temperatures of Earth's volcanic hotspots and mid-ocean ridges. Science 2022; 375:57-61. [PMID: 34990241 DOI: 10.1126/science.abj8944] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Volcanic hotspots are thought to be fed by hot, active upwellings from the deep mantle, with excess temperatures (Tex) ~100° to 300°C higher than those of mid-ocean ridges. However, Tex estimates are limited in geographical coverage and often inconsistent for individual hotspots. We infer the temperature of oceanic hotspots and ridges simultaneously by converting seismic velocity to temperature. We show that while ~45% of plume-fed hotspots are hot (Tex ≥ 155°C), ~15% are cold (Tex ≤ 36°C) and ~40% are not hot enough to actively upwell (50°C ≤ Tex ≤ 136°C). Hot hotspots have an extremely high helium-3/helium-4 ratio and buoyancy flux, but cold hotspots do not. The latter may originate at upper mantle depths. Alternatively, the deep plumes that feed them may be entrained and cooled by small-scale convection.
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Affiliation(s)
- Xiyuan Bao
- Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095, USA
| | | | - Matthew G Jackson
- Department of Earth Science, University of California, Santa Barbara, CA 93106, USA
| | - Barbara Romanowicz
- Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA
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7
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Vaddineni VA, Singh SC, Grevemeyer I, Audhkhasi P, Papenberg C. Evolution of the Crustal and Upper Mantle Seismic Structure From 0-27 Ma in the Equatorial Atlantic Ocean at 2° 43'S. JOURNAL OF GEOPHYSICAL RESEARCH. SOLID EARTH 2021; 126:e2020JB021390. [PMID: 35865731 PMCID: PMC9285972 DOI: 10.1029/2020jb021390] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 06/04/2021] [Accepted: 06/08/2021] [Indexed: 06/15/2023]
Abstract
We present seismic tomographic results from a unique seismic refraction and wide-angle survey along a 600 km long flow-line corridor of oceanic lithosphere ranging in age from 0 to 27 Ma in the equatorial Atlantic Ocean at 2° 43'S. The velocities in the crust near the ridge axis rapidly increase in the first 6 Myr and then change gradually with age. The upper crust (Layer 2) thickness varies between 2 and 2.4 km with an average thickness of 2.2 km and the crustal thickness varies from 5.6 to 6 km along the profile with an average crustal thickness of 5.8 km. At some locations, we observe negative velocity anomalies (∼-0.3 km/s) in the lower crust which could be either due to chemical heterogeneity in gabbroic rocks and/or the effects of fault related deformation zones leading to an increase in porosities up to 1.6% depending on the pore/crack geometry. The existence of a low velocity anomaly beneath the ridge axis suggests the presence of partial melt (∼1.3%) in the lower crust. Upper mantle velocities also remain low (∼7.8 km/s) from ridge axis up to 5 Ma, indicating a high temperature regime associated with mantle melting zone underneath. These results suggest that the evolution of the crust and uppermost mantle at this location occur in the first 10 Ma of its formation and then remains unchanged. Most of the structures in the older crust and upper mantle are fossilized structures and could provide information about past processes at ocean spreading centers.
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Affiliation(s)
| | - Satish C. Singh
- Université de ParisInstitut de Physique du Globe de ParisCNRSParisFrance
| | - Ingo Grevemeyer
- GEOMAR Helmholtz Centre of Ocean Research KielRD4‐Marine GeodynamicsKielGermany
| | - Pranav Audhkhasi
- Université de ParisInstitut de Physique du Globe de ParisCNRSParisFrance
| | - Cord Papenberg
- GEOMAR Helmholtz Centre of Ocean Research KielRD4‐Marine GeodynamicsKielGermany
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8
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Ball PW, White NJ, Maclennan J, Stephenson SN. Global influence of mantle temperature and plate thickness on intraplate volcanism. Nat Commun 2021; 12:2045. [PMID: 33824348 PMCID: PMC8024351 DOI: 10.1038/s41467-021-22323-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 03/04/2021] [Indexed: 11/24/2022] Open
Abstract
The thermochemical structure of lithospheric and asthenospheric mantle exert primary controls on surface topography and volcanic activity. Volcanic rock compositions and mantle seismic velocities provide indirect observations of this structure. Here, we compile and analyze a global database of the distribution and composition of Neogene-Quaternary intraplate volcanic rocks. By integrating this database with seismic tomographic models, we show that intraplate volcanism is concentrated in regions characterized by slow upper mantle shear-wave velocities and by thin lithosphere (i.e. <100 km). We observe a negative correlation between shear-wave velocities at depths of 125–175 km and melt fractions inferred from volcanic rock compositions. Furthermore, mantle temperature and lithospheric thickness estimates obtained by geochemical modeling broadly agree with values determined from tomographic models that have been converted into temperature. Intraplate volcanism often occurs in regions where uplifted (but undeformed) marine sedimentary rocks are exposed. Regional elevation of these rocks can be generated by a combination of hotter asthenosphere and lithospheric thinning. Therefore, the distribution and composition of intraplate volcanic rocks through geologic time will help to probe past mantle conditions and surface processes. Here, the authors compile a global geochemical database of Neogene-Quaternary intraplate volcanism. By comparing the distribution and composition of these rocks with tomographic models they show that intraplate volcanism can be used to constrain upper-mantle structure at the time of eruption.
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Affiliation(s)
- P W Ball
- Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Rise, Cambridge, UK. .,Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia.
| | - N J White
- Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Rise, Cambridge, UK.
| | - J Maclennan
- Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Rise, Cambridge, UK
| | - S N Stephenson
- Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Rise, Cambridge, UK.,Department of Earth Sciences, University of Oxford, Oxford, UK
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9
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A thin mantle transition zone beneath the equatorial Mid-Atlantic Ridge. Nature 2021; 589:562-566. [PMID: 33505039 DOI: 10.1038/s41586-020-03139-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 11/03/2020] [Indexed: 01/30/2023]
Abstract
The location and degree of material transfer between the upper and lower mantle are key to the Earth's thermal and chemical evolution. Sinking slabs and rising plumes are generally accepted as locations of transfer1,2, whereas mid-ocean ridges are not typically assumed to have a role3. However, tight constraints from in situ measurements at ridges have proved to be challenging. Here we use receiver functions that reveal the conversion of primary to secondary seismic waves to image the discontinuities that bound the mantle transition zone, using ocean bottom seismic data from the equatorial Mid-Atlantic Ridge. Our images show that the seismic discontinuity at depths of about 660 kilometres is broadly uplifted by 10 ± 4 kilometres over a swath about 600 kilometres wide and that the 410-kilometre discontinuity is depressed by 5 ± 4 kilometres. This thinning of the mantle transition zone is coincident with slow shear-wave velocities in the mantle, from global seismic tomography4-7. In addition, seismic velocities in the mantle transition zone beneath the Mid-Atlantic Ridge are on average slower than those beneath older Atlantic Ocean seafloor. The observations imply material transfer from the lower to the upper mantle-either continuous or punctuated-that is linked to the Mid-Atlantic Ridge. Given the length and longevity of the mid-ocean ridge system, this implies that whole-mantle convection may be more prevalent than previously thought, with ridge upwellings having a role in counterbalancing slab downwellings.
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10
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Marjanović M, Singh SC, Gregory EPM, Grevemeyer I, Growe K, Wang Z, Vaddineni V, Laurencin M, Carton H, Gómez de la Peña L, Filbrandt C. Seismic Crustal Structure and Morphotectonic Features Associated With the Chain Fracture Zone and Their Role in the Evolution of the Equatorial Atlantic Region. JOURNAL OF GEOPHYSICAL RESEARCH. SOLID EARTH 2020; 125:e2020JB020275. [PMID: 33282617 PMCID: PMC7685155 DOI: 10.1029/2020jb020275] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 07/31/2020] [Accepted: 09/01/2020] [Indexed: 06/12/2023]
Abstract
Oceanic transform faults and fracture zones (FZs) represent major bathymetric features that keep the records of past and present strike-slip motion along conservative plate boundaries. Although they play an important role in ridge segmentation and evolution of the lithosphere, their structural characteristics, and their variation in space and time, are poorly understood. To address some of the unknowns, we conducted interdisciplinary geophysical studies in the equatorial Atlantic Ocean, the region where some of the most prominent transform discontinuities have been developing. Here we present the results of the data analysis in the vicinity of the Chain FZ, on the South American Plate. The crustal structure across the Chain FZ, at the contact between ∼10 and 24 Ma oceanic lithosphere, is sampled along seismic reflection and refraction profiles. We observe that the crustal thickness within and across the Chain FZ ranges from ∼4.6-5.9 km, which compares with the observations reported for slow-slipping transform discontinuities globally. We attribute this presence of close to normal oceanic crustal thickness within FZs to the mechanism of lateral dike propagation, previously considered to be valid only in fast-slipping environments. Furthermore, the combination of our results with other data sets enabled us to extend the observations to morphotectonic characteristics on a regional scale. Our broader view suggests that the formation of the transverse ridge is closely associated with a global plate reorientation that was also responsible for the propagation and for shaping lower-order Mid-Atlantic Ridge segmentation around the equator.
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Affiliation(s)
- Milena Marjanović
- Université de Paris, Institut de Physique du Globe de Paris, CNRSParisFrance
| | - Satish C. Singh
- Université de Paris, Institut de Physique du Globe de Paris, CNRSParisFrance
| | - Emma P. M. Gregory
- Université de Paris, Institut de Physique du Globe de Paris, CNRSParisFrance
| | - Ingo Grevemeyer
- GEOMAR Helmholtz Centre of Ocean Research Kiel, RD4—Marine GeodynamicsKielGermany
| | - Kevin Growe
- Applied Geophysics ProgramTU Delft, ETH Zürich, RWTH AachenAachenGermany
| | - Zhikai Wang
- Université de Paris, Institut de Physique du Globe de Paris, CNRSParisFrance
| | - Venkata Vaddineni
- Université de Paris, Institut de Physique du Globe de Paris, CNRSParisFrance
| | - Muriel Laurencin
- Université de Paris, Institut de Physique du Globe de Paris, CNRSParisFrance
| | - Hélène Carton
- Université de Paris, Institut de Physique du Globe de Paris, CNRSParisFrance
| | | | - Christian Filbrandt
- GEOMAR Helmholtz Centre of Ocean Research Kiel, RD4—Marine GeodynamicsKielGermany
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11
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Recycled arc mantle recovered from the Mid-Atlantic Ridge. Nat Commun 2020; 11:3887. [PMID: 32753577 PMCID: PMC7403410 DOI: 10.1038/s41467-020-17604-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 05/11/2020] [Indexed: 12/02/2022] Open
Abstract
Plate tectonics and mantle dynamics necessitate mantle recycling throughout Earth’s history, yet direct geochemical evidence for mantle reprocessing remains elusive. Here we present evidence of recycled supra-subduction zone mantle wedge peridotite dredged from the Mid-Atlantic Ridge near 16°30′N. Peridotite trace-element characteristics are inconsistent with fractional anhydrous melting typically associated with a mid-ocean ridge setting. Instead, the samples are best explained by hydrous flux melting which changed the melting reactions such that clinopyroxene was not exhausted at high degrees of melting and was retained in the residuum. Based on along-axis ridge depth variations, this buoyant refractory arc mantle is likely compensated at depth by denser, likely garnet-rich, lithologies within the mantle column. Our results suggest that highly refractory arc mantle relicts are entrained in the upper mantle and may constitute >60% of the upper mantle by volume. These highly refractory mantle domains, which contribute little to mantle melting, are under-represented in compilations of mantle composition that rely on inverted basalt compositions alone. 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.
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12
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High H 2O Content in Pyroxenes of Residual Mantle Peridotites at a Mid Atlantic Ridge Segment. Sci Rep 2020; 10:579. [PMID: 31953494 PMCID: PMC6969183 DOI: 10.1038/s41598-019-57344-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 12/29/2019] [Indexed: 11/08/2022] Open
Abstract
Global correlations of mid-ocean-ridges basalt chemistry, axial depth and crustal thickness have been ascribed to mantle temperature variations affecting degree of melting. However, mantle H2O content and elemental composition may also play a role. How H2O is distributed in the oceanic upper mantle remains poorly constrained. We tackled this problem by determining the H2O content of orthopyroxenes (opx) and clinopyroxenes (cpx) of peridotites from a continuous lithospheric section created during 26 Ma at a 11°N Mid-Atlantic Ridge segment, and exposed along the Vema Transform. The H2O content of opx ranges from 119 ppm to 383 ppm; that of cpx from 407 ppm to 1072 ppm. We found anomalous H2O-enriched peridotites with their H2O content not correlating inversely with their degree of melting, although H2O is assumed to be incompatible during melting. Inverse correlation of H2O with Ce, another highly incompatible component, suggests post-melting H2O enrichment. We attribute a major role to post-melting temperature-dependent diffusion of hydrogen occurring above the melting region, where water-rich melt flows faster than residual peridotites through dunitic conduits cross-cutting the uprising mantle. Accordingly, estimates of the H2O content of the MORB mantle source based on H2O in abyssal peridotites can be affected by strong uncertainties.
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13
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Arnould M, Ganne J, Coltice N, Feng X. Northward drift of the Azores plume in the Earth's mantle. Nat Commun 2019; 10:3235. [PMID: 31324813 PMCID: PMC6642178 DOI: 10.1038/s41467-019-11127-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 06/21/2019] [Indexed: 11/19/2022] Open
Abstract
Mantle plume fixity has long been a cornerstone assumption to reconstruct past tectonic plate motions. However, precise geochronological and paleomagnetic data along Pacific continuous hotspot tracks have revealed substantial drift of the Hawaiian plume. The question remains for evidence of drift for other mantle plumes. Here, we use plume-derived basalts from the Mid-Atlantic ridge to confirm that the upper-mantle thermal anomaly associated with the Azores plume is asymmetric, spreading over ~2,000 km southwards and ~600 km northwards. Using for the first time a 3D-spherical mantle convection where plumes, ridges and plates interact in a fully dynamic way, we suggest that the extent, shape and asymmetry of this anomaly is a consequence of the Azores plume moving northwards by 1-2 cm/yr during the past 85 Ma, independently from other Atlantic plumes. Our findings suggest redefining the Azores hotspot track and open the way for identifying how plumes drift within the mantle.
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Affiliation(s)
- Maëlis Arnould
- Laboratoire de Géologie, École Normale Supérieure, CNRS UMR 8538, PSL Research University, 75005, Paris, France.
- Laboratoire de Géologie de Lyon, Terre, Planètes, Environnement, École Normale Supérieure de Lyon, Université de Lyon, Université Claude Bernard, CNRS UMR 5276, 2 rue Raphaël Dubois, 69622, Villeurbanne, France.
- EarthByte Group, School of Geosciences, Madsen Building F09, University of Sydney, Sydney, 2006, NSW, Australia.
| | - Jérôme Ganne
- IRD, CNRS, GET, Université Toulouse III, 14 Avenue Edouard Belin, 31400, Toulouse, France
| | - Nicolas Coltice
- Laboratoire de Géologie, École Normale Supérieure, CNRS UMR 8538, PSL Research University, 75005, Paris, France
| | - Xiaojun Feng
- School of Safety Engineering, China University of Mining and Technology, Jiangsu, 221116, China
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14
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The causes of spatiotemporal variations in erupted fluxes and compositions along a volcanic arc. Nat Commun 2019; 10:1350. [PMID: 30902993 PMCID: PMC6430768 DOI: 10.1038/s41467-019-09113-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 02/18/2019] [Indexed: 11/08/2022] Open
Abstract
Decades of study on volcanic arcs have provided insight into the overarching processes that control magmatism, and how these processes manifest at individual volcanoes. However, the causes of ubiquitous and dramatic intra-arc variations in volcanic flux and composition remain largely unresolved. Investigating such arc-scale issues requires greater quantitative comparison of geophysical and geochemical data, linked through sets of common intensive variables. To work towards these goals, we use observed lava compositions to estimate the heat budget associated with Quaternary volcanism in the Cascades Arc and compare this to the heat required to produce the observed geophysical properties of the crust. Here we show that along-strike volcanic variability in the Quaternary Cascades Arc is primarily related to variations in the flux of basalt into the crust, rather than variations in their crustal storage history. This approach shows promise for studying other large-scale frontier geologic problems in volcanic arcs. 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.
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15
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Tschauner O, Huang S, Greenberg E, Prakapenka VB, Ma C, Rossman GR, Shen AH, Zhang D, Newville M, Lanzirotti A, Tait K. Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle. Science 2018; 359:1136-1139. [DOI: 10.1126/science.aao3030] [Citation(s) in RCA: 128] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 01/19/2018] [Indexed: 11/02/2022]
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16
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Sarafian E, Gaetani GA, Hauri EH, Sarafian AR. Experimental constraints on the damp peridotite solidus and oceanic mantle potential temperature. Science 2017; 355:942-945. [DOI: 10.1126/science.aaj2165] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 01/25/2017] [Indexed: 11/02/2022]
Affiliation(s)
- Emily Sarafian
- Massachusetts Institute of Technology–Woods Hole Oceanographic Institution Joint Program in Oceanography/Applied Ocean Science and Engineering, Cambridge, MA 02139, USA
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Glenn A. Gaetani
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Erik H. Hauri
- Department of Terrestrial Magnetism, Carnegie Institute for Science, 5241 Broad Branch Road, NW, Washington, DC 20015, USA
| | - Adam R. Sarafian
- Massachusetts Institute of Technology–Woods Hole Oceanographic Institution Joint Program in Oceanography/Applied Ocean Science and Engineering, Cambridge, MA 02139, USA
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
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Machida S, Kogiso T, Hirano N. Petit-spot as definitive evidence for partial melting in the asthenosphere caused by CO 2. Nat Commun 2017; 8:14302. [PMID: 28148927 PMCID: PMC5296659 DOI: 10.1038/ncomms14302] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 12/15/2016] [Indexed: 11/29/2022] Open
Abstract
The deep carbon cycle plays an important role on the chemical differentiation and physical properties of the Earth's mantle. Especially in the asthenosphere, seismic low-velocity and high electrical conductivity due to carbon dioxide (CO2)-induced partial melting are expected but not directly observed. Here we discuss the experimental results relevant to the genesis of primitive CO2-rich alkali magma forming petit-spot volcanoes at the deformation front of the outer rise of the northwestern Pacific plate. The results suggest that primitive melt last equilibrated with depleted peridotite at 1.8–2.1 GPa and 1,280–1,290 °C. Although the equilibration pressure corresponds to the pressure of the lower lithosphere, by considering an equilibration temperature higher than the solidus in the volatile–peridotite system along with the temperature of the lower lithosphere, we conclude that CO2-rich silicate melt is always produced in the asthenosphere. The melt subsequently ascends into and equilibrates with the lower lithosphere before eruption. The genesis of primitive CO2-rich alkali magma at petit-spot volcanoes is still poorly understood. Here, the authors perform high pressure and temperature experiments to show that the CO2-rich melt is derived from the asthenosphere.
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Affiliation(s)
- Shiki Machida
- Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology, Natsushima-cho 2-15, Yokosuka, Kanagawa 237-0061, Japan.,School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8654, Japan
| | - Tetsu Kogiso
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsu, Sakyo, Kyoto 606-8501, Japan
| | - Naoto Hirano
- Center for Northeast Asian Studies, Tohoku University, Kawauchi 41, Aoba-ku, Sendai 980-8576, Japan
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Record of massive upwellings from the Pacific large low shear velocity province. Nat Commun 2016; 7:13309. [PMID: 27824054 PMCID: PMC5105175 DOI: 10.1038/ncomms13309] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 09/20/2016] [Indexed: 11/09/2022] Open
Abstract
Large igneous provinces, as the surface expression of deep mantle processes, play a key role in the evolution of the planet. Here we analyse the geochemical record and timing of the Pacific Ocean Large Igneous Provinces and preserved accreted terranes to reconstruct the history of pulses of mantle plume upwellings and their relation with a deep-rooted source like the Pacific large low-shear velocity Province during the Mid-Jurassic to Upper Cretaceous. Petrological modelling and geochemical data suggest the need of interaction between these deep-rooted upwellings and mid-ocean ridges in pulses separated by ∼10-20 Ma, to generate the massive volumes of melt preserved today as oceanic plateaus. These pulses impacted the marine biota resulting in episodes of anoxia and mass extinctions shortly after their eruption.
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19
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Affiliation(s)
- Katherine A. Kelley
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA
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