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Shi Y, Morgan JP. Gondwanan flood basalts linked seismically to plume-induced lithosphere instability. Proc Natl Acad Sci U S A 2024; 121:e2320054121. [PMID: 38470921 PMCID: PMC10962961 DOI: 10.1073/pnas.2320054121] [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: 11/14/2023] [Accepted: 02/06/2024] [Indexed: 03/14/2024] Open
Abstract
Delamination of the continental lithospheric mantle is well recorded beneath several continents. However, the fate of the removed continental lithosphere has been rarely noted, unlike subducted slabs reasonably well imaged in the upper and mid mantle. Beneath former Gondwana, recent seismic tomographic models indicate the presence of at least 5 horizontal fast-wavespeed anomalies at ~600 km depths that do not appear to be related to slab subduction, including fast structures in locations consistent with delamination associated with the Paraná Flood Basalt event at ~134 Ma and the Deccan Traps event at ~66 Ma. These fast-wavespeed anomalies often lie above broad slow seismic wavespeed trunks at 500 to 700 km depths beneath former Gondwana, with slow wavespeed anomalies branching around them. Numerical experiments indicate that delaminated lithosphere tends to stagnate in the transition zone and mid-mantle above a mantle plume where it shapes subsequent plume upwelling. For hot plumes, the melt volume generated during plume-influenced delamination can easily reach ~2 to 4 × 106 km3, consistent with the basalt eruption volume at the Deccan Traps. This seismic and numerical evidence suggests that observed high-wavespeed mid-mantle anomalies beneath the locations of former flood basalts are delaminated fragments of former continental lithosphere, and that lithospheric delamination events in the presence of subcontinental plumes induced several of the continental flood basalts associated with the multiple breakup stages of Gondwanaland. Continued upwelling in these plumes can also have entrained subcontinental lithosphere in the mid-mantle to bring its distinctive geochemical signal to the modern mid-ocean spreading centers that surround southern and western Africa.
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Affiliation(s)
- Yanan Shi
- Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen518055, China
| | - Jason P. Morgan
- Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen518055, China
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Gianni GM, Likerman J, Navarrete CR, Gianni CR, Zlotnik S. Ghost-arc geochemical anomaly at a spreading ridge caused by supersized flat subduction. Nat Commun 2023; 14:2083. [PMID: 37045842 PMCID: PMC10097660 DOI: 10.1038/s41467-023-37799-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 03/27/2023] [Indexed: 04/14/2023] Open
Abstract
The Southern Atlantic-Southwest Indian ridges (SASWIR) host mid-ocean ridge basalts with a residual subduction-related geochemical fingerprint (i.e., a ghost-arc signature) of unclear origin. Here, we show through an analysis of plate kinematic reconstructions and seismic tomography models that the SASWIR subduction-modified mantle source formed in the Jurassic close to the Georgia Islands slab (GI) and remained near-stationary in the mantle reference frame. In this analysis, the GI lies far inboard the Jurassic Patagonian-Antarctic Peninsula active margin. This was formerly attributed to a large-scale flat subduction event in the Late Triassic-Early Jurassic. We propose that during this flat slab stage, the subduction-modified mantle areas beneath the Mesozoic active margin and surrounding sutures zones may have been bulldozed inland by >2280 km. After the demise of the flat slab, this mantle anomaly remained near-stationary and was sampled by the Karoo mantle plume 183 Million years (Myr) ago and again since 55 Myr ago by the SASWIR. We refer to this process as asthenospheric anomaly telescoping. This study provides a hitherto unrecognized geodynamic effect of flat subduction, the viability of which we support through numerical modeling.
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Affiliation(s)
- Guido M Gianni
- Instituto Geofísico Sismológico Ing. Fernando Volponi (IGSV), Universidad Nacional de San Juan, San Juan, Argentina
- National Scientific and Technical Research Council (CONICET), Capital Federal, Argentina
| | - Jeremías Likerman
- National Scientific and Technical Research Council (CONICET), Capital Federal, Argentina
- Instituto de Estudios Andinos Don Pablo Groeber, Universidad de Buenos Aires, Capital Federal, Argentina
| | - César R Navarrete
- National Scientific and Technical Research Council (CONICET), Capital Federal, Argentina
- Laboratorio Patagónico de Petro-Tectónica, Universidad Nacional de la Patagonia "San Juan Bosco", Comodoro Rivadavia, Chubut, Argentina
| | - Conrado R Gianni
- Instituto Geofísico Sismológico Ing. Fernando Volponi (IGSV), Universidad Nacional de San Juan, San Juan, Argentina
| | - Sergio Zlotnik
- Laboratori de Cálcul Numéric, Escola Técnica Superior d'Enginyers de Camins, Canals i Ports, Universitat Politécnica de Catalunya, Barcelona, Spain.
- Centre Internacional de Métodes Numérics a l'Enginyeria (CIMNE), Barcelona, Spain.
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Xiong Q, Dai HK, Zheng JP, Griffin WL, Zheng HD, Wang L, Reilly SYO. Vertical depletion of ophiolitic mantle reflects melt focusing and interaction in sub-spreading-center asthenosphere. Nat Commun 2022; 13:6956. [PMCID: PMC9663536 DOI: 10.1038/s41467-022-34781-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 11/02/2022] [Indexed: 11/16/2022] Open
Abstract
AbstractDecompressional melting of asthenosphere under spreading centers has been accepted to produce oceanic lithospheric mantle with vertical compositional variations, but these gradients are much smaller than those observed from ophiolites, which clearly require additional causes. Here we conduct high-density sampling and whole-rock and mineral analyses of peridotites across a Tibetan ophiolitic mantle section (~2 km thick), which shows a primary upward depletion (~12% difference) and local more-depleted anomalies. Thermodynamic modeling demonstrates that these features cannot be produced by decompressional melting or proportional compression of residual mantle, but can be explained by melt-peridotite reaction with lateral melt/rock ratio variations in an upwelling asthenospheric column, producing stronger depletion in the melt-focusing center and local zones. This column splits symmetrically and flows to become the horizontal uppermost lithospheric mantle, characterized by upward depletion and local anomalies. This model provides insights into melt extraction and uppermost-mantle origin beneath spreading centers with high melt fluxes.
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Liu CZ, Dick HJ, Mitchell RN, Wei W, Zhang ZY, Hofmann AW, Yang JF, Li Y. Archean cratonic mantle recycled at a mid-ocean ridge. SCIENCE ADVANCES 2022; 8:eabn6749. [PMID: 35648865 PMCID: PMC9159695 DOI: 10.1126/sciadv.abn6749] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Accepted: 04/15/2022] [Indexed: 05/26/2023]
Abstract
Basalts and mantle peridotites of mid-ocean ridges are thought to sample Earth's upper mantle. Osmium isotopes of abyssal peridotites uniquely preserve melt extraction events throughout Earth history, but existing records only indicate ages up to ~2 billion years (Ga) ago. Thus, the memory of the suspected large volumes of mantle lithosphere that existed in Archean time (>2.5 Ga) has apparently been lost somehow. We report abyssal peridotites with melt-depletion ages up to 2.8 Ga, documented by extremely unradiogenic 187Os/188Os ratios (to as low as 0.1095) and refractory major elements that compositionally resemble the deep keels of Archean cratons. These oceanic rocks were thus derived from the once-extensive Archean continental keels that have been dislodged and recycled back into the mantle, the feasibility of which we confirm with numerical modeling. This unexpected connection between young oceanic and ancient continental lithosphere indicates an underappreciated degree of compositional recycling over time.
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Affiliation(s)
- Chuan-Zhou Liu
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China
- CAS Center for Excellence in Deep Earth Sciences, Guangzhou 510640, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Henry J.B. Dick
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Ross N. Mitchell
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
| | - Wu Wei
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhen-Yu Zhang
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | | | - Jian-Feng Yang
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
| | - Yang Li
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
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Mineralogy, Geochemistry and Tectonic Setting of the Raobazhai Ultramafic Complex, North Dabie. MINERALS 2022. [DOI: 10.3390/min12030286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Raobazhai ultramafic complex is located in the north of the Dabie Mountains and is composed of spinel peridotites accompanied by a few lenticular mafic metamorphic rocks. The spinel peridotites are mostly harzburgite, along with minor dunite and lherzolite. This study reports the petrological, geochemical, and Re-Os isotopic data of spinel and chromite harzburgites from Raobazhai. The major and trace whole-rock geochemistry characteristics indicate that the rocks are remnants of partial melting to different degrees (6–17%). Both mineral and whole-rock geochemistry showed typical abyssal peridotite affinity. Due to the presence of water-bearing minerals, the Sr, Ba, and U were enriched, and the Nb, Zr, and Hf were depleted, which can be attributed to the strong metasomatism of the boninitic melting/fluid in the fore-arc domain. The flat distribution of platinum group elements (PGE) and the decoupling of Pt-Pd were also the result of the fore-arc melting/fluid interaction. The 187Os/188Os ratios (0.1149–0.1266) were generally lower than the recommended value of the primitive mantle and fell within the abyssal peridotite isotope range. This indicated that the Raobazhai harzburgites were likely mantle peridotites with oceanic characteristics that underwent a fore-arc boninitic melting/fluid transformation event.
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Liu CZ, Wu FY, Liu T, Zhang C, Zhang WQ, Zhang ZY, Zhang Z, Wei W, Lin YZ. An origin of ultraslow spreading ridges for the Yarlung-Tsangpo ophiolites. FUNDAMENTAL RESEARCH 2022; 2:74-83. [PMID: 38933911 PMCID: PMC11197761 DOI: 10.1016/j.fmre.2021.07.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 06/20/2021] [Accepted: 07/13/2021] [Indexed: 11/20/2022] Open
Abstract
As relics of ancient ocean lithosphere, ophiolites are the most important petrological evidence for marking the sutures and also play a key role in reconstructing plate configuration. They also provide valuable windows for studying crustal accretion and mantle processes occurring at modern ocean ridges. Abundant ophiolites are distributed along the Yarlung-Tsangpo suture and represent the relics of ocean lithosphere of the Neo-Tethys. They are characterized by an incomplete litho-stratigraphy, of which the mantle section is much thicker than the crustal section. Ocean crustal rocks outcropped in the Yarlung-Tsangpo ophiolites are much thinner than normal ocean crusts (~ 7 km) or even absent. Tectonic settings from which the Yarlung-Tsangpo ophiolites originated remain highly controversial, although an origin of the supra-subduction zone is prevailing. Moreover, their incomplete litho-stratigraphy has been commonly attributed to tectonic dismemberment during the late-stage emplacement after their formation. Nevertheless, such an incompleteness resembles the ocean lithosphere generated at modern ultraslow spreading ridges, such as the Southwest Indian Ridge (SWIR). In this paper, we present several lines of evidence that support the formation of the Yarlung-Tsangpo ophiolites at ultraslow spreading ridges, during which detachment faults were developed. This suggests that the Yarlung-Tsangpo ophiolites might represent the ocean core complexes (OCC) in the Neo-Tethys Ocean. The OCC with high topography in the seafloor were clogged in the trench and preserved as ophiolites through Indo-Eurasia collision. The clogging resulted in the demise of an old subduction and a new subduction was re-initiated beneath the clogged OCC.
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Affiliation(s)
- Chuan-Zhou Liu
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Fu-Yuan Wu
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Tong Liu
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
| | - Chang Zhang
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
| | - Wei-Qi Zhang
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhen-Yu Zhang
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhen Zhang
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wu Wei
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yin-Zheng Lin
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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Zhong Y, Zhang GL, Jin QZ, Huang F, Wang XJ, Xie LW. Sub-basin scale inhomogeneity of mantle in the South China Sea revealed by magnesium isotopes. Sci Bull (Beijing) 2021; 66:740-748. [PMID: 36654448 DOI: 10.1016/j.scib.2020.12.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 11/30/2020] [Accepted: 11/30/2020] [Indexed: 01/20/2023]
Abstract
The South China Sea (SCS) is the largest extensional basin in the western Pacific and was formed after rifting of the Euro-Asian continental margin. The nature of its underlying mantle remains enigmatic due to the lack of sampling of the seafloor's igneous crust. The International Ocean Discovery Program Expedition 349 cored seafloor basalts of the southwestern (Site U1433) and eastern (Site U1431) SCS sub-basins. The recovered basalt samples exhibit different source lithologies and geochemistries. The Mg isotopic compositions of seafloor basalts from these sites were investigated to elucidate the origin of this large-scale mantle inhomogeneity. Results indicate that the Site U1431 basalts have a mantle-like average δ26Mg value of -0.27‰ ± 0.06‰ (2SD; n = 10). Together with inhomogeneous Sr-Nd-Pb-Hf isotopic compositions, the Site U1433 basalts have an average δ26Mg value (-0.20‰ ± 0.06‰; 2SD; n = 8) higher than those of the Site U1431 basalts and normal mantle. Their heavier Mg isotopic compositions and low 206Pb/204Pb ratios (~17.7) indicate that the Site U1433 basalts were affected by the re-melting of detached continental-arc lithosphere in the sub-ridge mantle. The coupling of Mg and Sr-Nd isotopes provides robust evidence that the mantle-like δ26Mg values of the Site U1431 basalts resulted from mixing between detached continental arc lithosphere and the nearby Hainan plume, with respective supra- and sub-normal δ26Mg values. From the perspective of Mg isotope, the mantles of the southwestern and eastern sub-basins are compositionally inhomogeneous, with their mantle evolutionary histories being distinct.
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Affiliation(s)
- Yuan Zhong
- Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
| | - Guo-Liang Zhang
- Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Geology, National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China.
| | - Qi-Zhen Jin
- CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
| | - Fang Huang
- CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
| | - Xiao-Jun Wang
- State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Lie-Wen Xie
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
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