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Hernández-Uribe D. A re-evaluation of the peak P-T conditions of eclogite-facies metamorphism of the Paleozoic Acatlán Complex (Mexico) reveals deeper subduction. Sci Rep 2022; 12:21399. [PMID: 36496529 PMCID: PMC9741601 DOI: 10.1038/s41598-022-25992-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 12/07/2022] [Indexed: 12/13/2022] Open
Abstract
Eclogites in the Acatlán Complex, southern Mexico, record the subduction history of the complex. Previous studies indicate that the proto-Acatlán Complex reached < 50 km depth during subduction. Yet, a recent study reported higher pressures for a single eclogite, questioning the maximum depth reached by the complex during subduction. In this work, I re-calculate eclogite pressure and temperature (P-T) conditions using thermobarometric methods applicable to eclogite-facies mafic rocks to a set of eclogites cropping out throughout the high-pressure belt of the Acatlán Complex-the Piaxtla Suite. I find that Acatlán eclogites record substantially-and systematically-greater pressures than previously reported. Calculations show that eclogites from the central part of the Piaxtla Suite (in the Piaxtla area) record consistent pressures of ~ 2.0 GPa and temperatures ranging between 460 and 675 °C. Eclogites from the northern part of the Piaxtla Suite (Mimilulco and Santa Cruz Organal areas) lack phengite, thus pressures were not calculated; temperatures calculated for these rocks at a fixed pressure (2.0 GPa) yield contrasting temperatures (511 °C and 870 °C, respectively). Mimilulco eclogite likely records similar pressures (~ 2.0 GPa) to other Piaxtla eclogites, whereas the pressures of Santa Cruz Organal eclogites might have been different, and likely experiencing a different thermal history compared to the rest of the eclogites from the Piaxtla Suite. Overall, these results indicate that the Acatlán Complex subducted to greater depths than previously thought implying a faster burial-exhumation cycle of the proto-Acatlán Complex.
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Affiliation(s)
- D Hernández-Uribe
- Department of Earth and Environmental Sciences, University of Illinois Chicago, Chicago, IL, 60607, USA.
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Metasediments Covering Ophiolites in the HP Internal Belt of the Western Alps: Review of Tectono-Stratigraphic Successions and Constraints for the Alpine Evolution. MINERALS 2021. [DOI: 10.3390/min11040411] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Ophiolites of the Alpine belt derive from the closure of the Mesozoic Tethys Ocean that was interposed between the palaeo-Europe and palaeo-Adria continental plates. The Alpine orogeny has intensely reworked the oceanic rocks into metaophiolites with various metamorphic imprints. In the Western Alps, metaophiolites and continental-derived units are distributed within two paired bands: An inner band where Alpine subduction-related high-pressure (HP) metamorphism is preserved, and an outer band where blueschist to greenschist facies recrystallisation due to the decompression path prevails. The metaophiolites of the inner band are hugely important not just because they provide records of the prograde tectonic and metamorphic evolution of the Western Alps, but also because they retain the signature of the intra-oceanic tectono-sedimentary evolution. Lithostratigraphic and petrographic criteria applied to metasediments associated with HP metaophiolites reveal the occurrence of distinct tectono-stratigraphic successions including quartzites with marbles, chaotic rock units, and layered calc schists. These successions, although sliced, deformed, and superposed in complex ways during the orogenic stage, preserve remnants of their primary depositional setting constraining the pre-orogenic evolution of the Jurassic Tethys Ocean.
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Behr WM, Bürgmann R. What's down there? The structures, materials and environment of deep-seated slow slip and tremor. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2021; 379:20200218. [PMID: 33517877 PMCID: PMC7898123 DOI: 10.1098/rsta.2020.0218] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/27/2020] [Indexed: 05/26/2023]
Abstract
Deep-seated slow slip and tremor (SST), including slow slip events, episodic tremor and slip, and low-frequency earthquakes, occur downdip of the seismogenic zone of numerous subduction megathrusts and plate boundary strike-slip faults. These events represent a fascinating and perplexing mode of fault failure that has greatly broadened our view of earthquake dynamics. In this contribution, we review constraints on SST deformation processes from both geophysical observations of active subduction zones and geological observations of exhumed field analogues. We first provide an overview of what has been learned about the environment, kinematics and dynamics of SST from geodetic and seismologic data. We then describe the materials, deformation mechanisms, and metamorphic and fluid pressure conditions that characterize exhumed rocks from SST source depths. Both the geophysical and geological records strongly suggest the importance of a fluid-rich and high fluid pressure habitat for the SST source region. Additionally, transient deformation features preserved in the rock record, involving combined frictional-viscous shear in regions of mixed lithology and near-lithostatic fluid pressures, may scale with the tremor component of SST. While several open questions remain, it is clear that improved constraints on the materials, environment, structure, and conditions of the plate interface from geophysical imaging and geologic observations will enhance model representations of the boundary conditions and geometry of the SST deformation process. This article is part of a discussion meeting issue 'Understanding earthquakes using the geological record'.
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Affiliation(s)
- Whitney M. Behr
- Geological Institute, Department of Earth Sciences, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
| | - Roland Bürgmann
- Department of Earth and Planetary Science and Berkeley Seismological Laboratory, University of California, Berkeley, CA, USA
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Nishiyama T, Ohfuji H, Fukuba K, Terauchi M, Nishi U, Harada K, Unoki K, Moribe Y, Yoshiasa A, Ishimaru S, Mori Y, Shigeno M, Arai S. Microdiamond in a low-grade metapelite from a Cretaceous subduction complex, western Kyushu, Japan. Sci Rep 2020; 10:11645. [PMID: 32669632 PMCID: PMC7363827 DOI: 10.1038/s41598-020-68599-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 06/30/2020] [Indexed: 11/25/2022] Open
Abstract
Microdiamonds in metamorphic rocks are a signature of ultrahigh-pressure (UHP) metamorphism that occurs mostly at continental collision zones. Most UHP minerals, except coesite and microdiamond, have been partially or completely retrogressed during exhumation; therefore, the discovery of coesite and microdiamond is crucial to identify UHP metamorphism and to understand the tectonic history of metamorphic rocks. Microdiamonds typically occur as inclusions in minerals such as garnet. Here we report the discovery of microdiamond aggregates in the matrix of a metapelite from the Nishisonogi unit, Nagasaki Metamorphic Complex, western Kyushu, Japan. The Nishisonogi unit represents a Cretaceous subduction complex which has been considered as an epidote–blueschist subfacies metamorphic unit, and the metapelite is a member of a serpentinite mélange in the Nishisonogi unit. The temperature condition for the Nishisonogi unit is 450 °C, based on the Raman micro-spectroscopy of graphite. The coexistence of microdiamond and Mg-carbonates suggests the precipitation of microdiamond from C–O–H fluid under pressures higher than 2.8 GPa. This is the first report of metamorphic microdiamond from Japan, which reveals the hidden UHP history of the Nishisonogi unit. The tectonic evolution of Kyushu in the Japanese Archipelago should be reconsidered based on this finding.
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Affiliation(s)
- Tadao Nishiyama
- Department of Earth and Environmental Science, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.
| | - Hiroaki Ohfuji
- Geodynamics Research Center (GRC), Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790-8577, Japan
| | - Kousuke Fukuba
- Geodynamics Research Center (GRC), Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790-8577, Japan
| | - Masami Terauchi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
| | - Ukyo Nishi
- Department of Earth and Environmental Science, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Kazuki Harada
- Department of Earth and Environmental Science, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Kouhei Unoki
- Department of Earth and Environmental Science, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Yousuke Moribe
- Department of Earth and Environmental Science, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Akira Yoshiasa
- Department of Earth and Environmental Science, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Satoko Ishimaru
- Department of Earth and Environmental Science, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Yasushi Mori
- Kitakyushu Museum of Natural History and Human History, 2-4-1, Higashida, Yahatahigashi-ku, Kitakyushu, 805-0071, Japan
| | - Miki Shigeno
- Kitakyushu Museum of Natural History and Human History, 2-4-1, Higashida, Yahatahigashi-ku, Kitakyushu, 805-0071, Japan
| | - Shoji Arai
- Institute of Liberal Arts and Science, Kanazawa University, Kakuma, Kanazawa, 920-1164, Japan
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Pons ML, Debret B, Bouilhol P, Delacour A, Williams H. Zinc isotope evidence for sulfate-rich fluid transfer across subduction zones. Nat Commun 2016; 7:13794. [PMID: 27982033 PMCID: PMC5171646 DOI: 10.1038/ncomms13794] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 10/31/2016] [Indexed: 11/09/2022] Open
Abstract
Subduction zones modulate the chemical evolution of the Earth's mantle. Water and volatile elements in the slab are released as fluids into the mantle wedge and this process is widely considered to result in the oxidation of the sub-arc mantle. However, the chemical composition and speciation of these fluids, which is critical for the mobility of economically important elements, remain poorly constrained. Sulfur has the potential to act both as oxidizing agent and transport medium. Here we use zinc stable isotopes (δ66Zn) in subducted Alpine serpentinites to decipher the chemical properties of slab-derived fluids. We show that the progressive decrease in δ66Zn with metamorphic grade is correlated with a decrease in sulfur content. As existing theoretical work predicts that Zn-SO42- complexes preferentially incorporate heavy δ66Zn, our results provide strong evidence for the release of oxidized, sulfate-rich, slab serpentinite-derived fluids to the mantle wedge.
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Affiliation(s)
- Marie-Laure Pons
- Department of Earth Sciences, Cambridge University, Downing St, Cambridge CB2 3EQ, UK.,Department of Earth Sciences, Durham University, Elvet Hill, Durham DH1 3LE, UK
| | - Baptiste Debret
- Department of Earth Sciences, Cambridge University, Downing St, Cambridge CB2 3EQ, UK.,Department of Earth Sciences, Durham University, Elvet Hill, Durham DH1 3LE, UK
| | - Pierre Bouilhol
- Department of Earth Sciences, Durham University, Elvet Hill, Durham DH1 3LE, UK
| | - Adélie Delacour
- Université de Lyon, UJM-Saint-Etienne, Laboratoire Magmas et Volcans, UMR 6524, CNRS, UBP, IRD, F-42023 Saint-Etienne, France
| | - Helen Williams
- Department of Earth Sciences, Cambridge University, Downing St, Cambridge CB2 3EQ, UK.,Department of Earth Sciences, Durham University, Elvet Hill, Durham DH1 3LE, UK
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