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Hu J, Sharp TG. Formation, preservation and extinction of high-pressure minerals in meteorites: temperature effects in shock metamorphism and shock classification. PROGRESS IN EARTH AND PLANETARY SCIENCE 2022; 9:6. [PMID: 35059281 PMCID: PMC8732827 DOI: 10.1186/s40645-021-00463-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 12/18/2021] [Indexed: 05/21/2023]
Abstract
The goal of classifying shock metamorphic features in meteorites is to estimate the corresponding shock pressure conditions. However, the temperature variability of shock metamorphism is equally important and can result in a diverse and heterogeneous set of shock features in samples with a common overall shock pressure. In particular, high-pressure (HP) minerals, which were previously used as a solid indicator of high shock pressure in meteorites, require complex pressure-temperature-time (P-T-t) histories to form and survive. First, parts of the sample must be heated to melting temperatures, at high pressure, to enable rapid formation of HP minerals before pressure release. Second, the HP minerals must be rapidly cooled to below a critical temperature, before the pressure returns to ambient conditions, to avoid retrograde transformation to their low-pressure polymorphs. These two constraints require the sample to contain large temperature heterogeneities, e.g. melt veins in a cooler groundmass, during shock. In this study, we calculated shock temperatures and possible P-T paths of chondritic and differentiated mafic-ultramafic rocks for various shock pressures. These P-T conditions and paths, combined with observations from shocked meteorites, are used to constrain shock conditions and P-T-t histories of HP-mineral bearing samples. The need for rapid thermal quench of HP phases requires a relatively low bulk-shock temperature and therefore moderate shock pressures below ~ 30 GPa, which matches the stabilities of these HP minerals. The low-temperature moderate-pressure host rock generally shows moderate shock-deformation features consistent with S4 and, less commonly, S5 shock stages. Shock pressures in excess of 50 GPa in meteorites result in melt breccias with high overall post-shock temperatures that anneal out HP-mineral signatures. The presence of ringwoodite, which is commonly considered an indicator of the S6 shock stage, is inconsistent with pressures in excess of 30 GPa and does not represent shock conditions different from S4 shock conditions. Indeed, ringwoodite and coexisting HP minerals should be considered as robust evidence for moderate shock pressures (S4) rather than extreme shock (S6) near whole-rock melting.
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Affiliation(s)
- Jinping Hu
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 USA
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 USA
| | - Thomas G. Sharp
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 USA
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Abstract
Feldspars are rock-forming minerals that make up most of the Earth’s crust. Along the mantle geotherm, feldspars are stable at pressures up to 3 GPa and may persist metastably at higher pressures under cold conditions. Previous structural studies of feldspars are limited to ~10 GPa, and have shown that the dominant mechanism of pressure-induced deformation is the tilting of AlO4 and SiO4 tetrahedra in a tetrahedral framework. Herein, based on results of in situ single-crystal X-ray diffraction studies up to 27 GPa, we report the discovery of new high-pressure polymorphs of the feldspars anorthite (CaSi2Al2O8), albite (NaAlSi3O8), and microcline (KAlSi3O8). The phase transitions are induced by severe tetrahedral distortions, resulting in an increase in the Al and/or Si coordination number. High-pressure phases derived from feldspars could persist at depths corresponding to the Earth upper mantle and could possibly influence the dynamics and fate of cold subducting slabs. Feldspars are stable at pressures up to 3 GPa along the mantle geotherm, but they can persist metastably at higher pressures at colder conditions. Here, above 10 GPa the authors find new high-pressure polymorphs of feldspars that could persist at depths corresponding to the Earth’s upper mantle, potentially influencing the dynamics and fate of cold subducting slabs.
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Green HW. Phase-transformation-induced lubrication of earthquake sliding. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2017; 375:rsta.2016.0008. [PMID: 28827426 PMCID: PMC5580448 DOI: 10.1098/rsta.2016.0008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/28/2017] [Indexed: 06/07/2023]
Abstract
Frictional failure is not possible at depth in Earth, hence earthquakes deeper than 30-50 km cannot initiate by overcoming dry friction. Moreover, the frequency distribution of earthquakes with depth is bimodal, suggesting another change of mechanism at about 350 km. Here I suggest that the change at 30-50 km is from overcoming dry friction to reduction of effective stress by dehydration embrittlement and that the change at 350 km is due to desiccation of slabs and initiation by phase-transformation-induced faulting. High-speed friction experiments at low pressure indicate that exceeding dry friction provokes shear heating that leads to endothermic reactions and pronounced weakening. Higher-pressure studies show nanocrystalline gouge accompanying dehydration and the highest pressure experiments initiate by exothermic polymorphic phase transformation. Here I discuss the characteristic nanostructures of experiments on high-speed friction and high-pressure faulting and show that all simulated earthquake systems yield very weak transformation-induced lubrication, most commonly nanometric gouge or melt. I also show that phase-transformation-induced faulting of olivine to spinel can propagate into material previously transformed to spinel, apparently by triggering melting analogous to high-speed friction studies at low pressure. These experiments taken as a whole suggest that earthquakes at all depths slide at low frictional resistance by a self-healing pulse mechanism with rapid strength recovery.This article is part of the themed issue 'Faulting, friction and weakening: from slow to fast motion'.
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Affiliation(s)
- Harry W Green
- Department of Earth Sciences, University of California, Riverside, CA 92521, USA
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Bindi L, Chen M, Xie X. Discovery of the Fe-analogue of akimotoite in the shocked Suizhou L6 chondrite. Sci Rep 2017; 7:42674. [PMID: 28198399 PMCID: PMC5309820 DOI: 10.1038/srep42674] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 01/11/2017] [Indexed: 11/30/2022] Open
Abstract
We report the first natural occurrence of the Fe-analogue of akimotoite, ilmenite-structured MgSiO3, a missing phase among the predicted high-pressure polymorphs of Fe-pyroxene, with the composition (Fe2+0.48Mg0.37Ca0.04Na0.04Mn2+0.03Al0.03Cr3+0.01)Σ=1.00Si1.00O3. The new mineral was approved by the International Mineralogical Association (IMA 2016-085) and named hemleyite in honour of Russell J. Hemley. It was discovered in an unmelted portion of the heavily shocked L6 Suizhou chondrite closely associated to olivine, clinoenstatite and Fe-bearing pyroxene with a composition nearly identical to that of hemleyite. We also report the first single-crystal X-ray diffraction study of a Si-bearing, ilmenite-structured phase. The fact that hemleyite formed in a meteorite exposed to high pressures (<20 GPa) and temperatures (<2000 °C) during impact-induced shocks indicates that it could play a crucial role at the bottom of the Earth’s mantle transition zone and within the uppermost lower mantle.
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Affiliation(s)
- Luca Bindi
- Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Florence, Italy.,CNR-Istituto di Geoscienze e Georisorse, Via La Pira 4, I-50121 Florence, Italy
| | - Ming Chen
- State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.,Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou 510640, China
| | - Xiande Xie
- Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou 510640, China.,Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
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Solomatov VS, Reese CC. Grain size variations in the Earth's mantle and the evolution of primordial chemical heterogeneities. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007jb005319] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Persh SE, Houston H. Deep earthquake rupture histories determined by global stacking of broadbandPwaveforms. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003jb002762] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Steven E. Persh
- Department of Earth and Space Sciences; University of California; Los Angeles California USA
| | - Heidi Houston
- Department of Earth and Space Sciences; University of California; Los Angeles California USA
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Zhang J, Green HW, Bozhilov K, Jin Z. Faulting induced by precipitation of water at grain boundaries in hot subducting oceanic crust. Nature 2004; 428:633-6. [PMID: 15071590 DOI: 10.1038/nature02475] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2003] [Accepted: 03/04/2004] [Indexed: 11/09/2022]
Abstract
Dehydration embrittlement has been proposed to explain both intermediate- and deep-focus earthquakes in subduction zones. Because such earthquakes primarily occur at shallow depths or within the core of the subducting plate, dehydration at relatively low temperatures has been emphasized. However, recent careful relocation of subduction-zone earthquakes shows that at depths of 100-250 km, earthquakes continue in the uppermost part of the slab (probably the former oceanic crust that has been converted to eclogite) where temperatures are higher. Here we show that at such pressures and temperatures, eclogite lacking hydrous phases but with significant hydroxyl incorporated as defects in pyroxene and garnet develops a faulting instability associated with precipitation of water at grain boundaries and the production of very small amounts of melt. This new faulting mechanism satisfactorily explains high-temperature earthquakes in subducting oceanic crust and could potentially be involved in much deeper earthquakes in connection with similar precipitation of water in the mantle transition zone (400-700 km depth). Of potential importance for all proposed high-pressure earthquake mechanisms is the very small amount of fluid required to trigger this instability.
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Affiliation(s)
- Junfeng Zhang
- Institute of Geophysics and Planetary Physics and Department of Earth Sciences, University of California, Riverside, California 92521, USA
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Tibi R, Bock G, Wiens DA. Source characteristics of large deep earthquakes: Constraint on the faulting mechanism at great depths. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002jb001948] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Rigobert Tibi
- GeoForschungsZentrum Potsdam; Potsdam Germany
- Department of Earth and Planetary Sciences; Washington University; St. Louis Missouri USA
| | | | - Douglas A. Wiens
- Department of Earth and Planetary Sciences; Washington University; St. Louis Missouri USA
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Koper KD, Wiens DA, Dorman LM, Hildebrand JA, Webb SC. Modeling the Tonga slab: Can travel time data resolve a metastable olivine wedge? ACTA ACUST UNITED AC 1998. [DOI: 10.1029/98jb01517] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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McGuire JJ, Wiens DA, Shore PJ, Bevis MG. The March 9, 1994 (Mw7.6), deep Tonga earthquake: Rupture outside the seismically active slab. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/96jb03185] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Chen M, Sharp TG, Goresy AE, Wopenka B, Xie X. The Majorite-Pyrope + Magnesiowüstite Assemblage: Constraints on the History of Shock Veins in Chondrites. Science 1996. [DOI: 10.1126/science.271.5255.1570] [Citation(s) in RCA: 188] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Ming Chen
- M. Chen, Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany, and Guangzhou Institute of Geochemistry, Academia Sinica, 510640 Guangzhou, China
| | - Thomas G. Sharp
- T. G. Sharp, Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
| | - Ahmed El Goresy
- A. El Goresy, Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany
| | - Brigitte Wopenka
- B. Wopenka, Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA
| | - Xiande Xie
- X. Xie, Guangzhou Institute of Geochemistry, Academia Sinica, 510640 Guangzhou, China
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Abstract
Although enstatite is a major constituent of the Earth's upper mantle and subducting lithosphere, most kinetic studies of olivine phase transformations have typically involved single-phase polycrystalline aggregates. Transmission electron microscopy investigations of olivine to spinel and modified spinel (beta phase) reactions in the (Mg, Fe)(2)SiO(4)-(Mg,Fe)SiO(3) system show that transformation of olivine in the stability field of spinel plus phase begins with coherent nucleation of spinel on high-clinoenstatite grains. These observations demonstrate that high clinoenstatite can catalyze the transformation by enhancing nucleation kinetics and therefore imply that secondary phases can influence reaction kinetics during high-pressure mineral transformations.
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