ALBERT

Description: Recent evidence suggests that a portion of the Canary plume travelled northeastwards below the lithosphere of the Atlas Mountains in North Africa towards the Alboran domain and was captured ~10 Ma ago by the Gibraltar subduction system in the Western Mediterranean. The capture would have been associated with the mantle return flow induced by the westward-retreating slab that would have dragged and trapped a portion of the plume material in the mantle wedge of the Gibraltar subduction zone. Such material eventually contaminated the subduction related volcanism in the Alboran region. In this work, we use scaled analogue models of slab–plume interaction to investigate the plausibility of the plume capture. An upper-mantle-scaled model combines a narrow (400 km) edge-fixed subduction plate with a laterally offset compositional plume. The subduction dominated by slab rollback and toroidal mantle flow is seen to increasingly impact on the plume dynamics as the area of influence of the toroidal flow cells at the surface is up to 500 x 1350 km 2 . While the plume head initially spreads axisymmetrically, it starts being distorted parallel to the plate in the direction of the trench as the slab trench approaches the plume edge at a separation distance of about 500 km, before getting dragged towards mantle wedge. When applied to the Canary plume–Gibraltar subduction system, our model supports the observationally based conceptual model that mantle plume material may have been dragged towards the mantle wedge by slab rollback-induced toroidal mantle flow. Using a scaling argument for the spreading of a gravity current within a channel, we also show that more than 1500 km of plume propagation in the sublithospheric Atlas corridor is dynamically plausible.

Description: Strong evidence exists that water is carried from the surface into the upper mantle by hydrous minerals in the uppermost 10-12 km of subducting lithosphere, and more water may be added as the lithosphere bends and goes downwards. Significant amounts of that water are released as the lithosphere heats up, triggering earthquakes and fluxing arc volcanism. In addition, there is experimental evidence for high solubility of water in olivine, the most abundant mineral in the upper mantle, for even higher solubility in olivine's high-pressure polymorphs, wadsleyite and ringwoodite, and for the existence of dense hydrous magnesium silicates that potentially could carry water well into the lower mantle (deeper than 1,000 km). Here we compare experimental and seismic evidence to test whether patterns of seismicity and the stabilities of these potentially relevant hydrous phases are consistent with a wet lithosphere. We show that there is nearly a one-to-one correlation between dehydration of minerals and seismicity at depths less than about 250 km, and conclude that the dehydration of minerals is the trigger of instability that leads to seismicity. At greater depths, however, we find no correlation between occurrences of earthquakes and depths where breakdown of hydrous phases is expected. Lastly, we note that there is compelling evidence for the existence of metastable olivine (which, if present, can explain the distribution of deep-focus earthquakes) west of and within the subducting Tonga slab and also in three other subduction zones, despite metastable olivine being incompatible with even extremely small amounts of water (of the order of 100 p.p.m. by weight). We conclude that subducting slabs are essentially dry at depths below 400 km and thus do not provide a pathway for significant amounts of water to enter the mantle transition zone or the lower mantle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Green, Harry W 2nd -- Chen, Wang-Ping -- Brudzinski, Michael R -- England -- Nature. 2010 Oct 14;467(7317):828-31. doi: 10.1038/nature09401. Epub 2010 Oct 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Geophysics and Planetary Physics and Department of Earth Sciences, University of California, Riverside, California 92521, USA. harry.green@ucr.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20927105" target="_blank"〉PubMed〈/a〉

Description: How black holes accrete surrounding matter is a fundamental yet unsolved question in astrophysics. It is generally believed that matter is absorbed into black holes via accretion disks, the state of which depends primarily on the mass-accretion rate. When this rate approaches the critical rate (the Eddington limit), thermal instability is supposed to occur in the inner disk, causing repetitive patterns of large-amplitude X-ray variability (oscillations) on timescales of minutes to hours. In fact, such oscillations have been observed only in sources with a high mass-accretion rate, such as GRS 1915+105 (refs 2, 3). These large-amplitude, relatively slow timescale, phenomena are thought to have physical origins distinct from those of X-ray or optical variations with small amplitudes and fast timescales (less than about 10 seconds) often observed in other black-hole binaries-for example, XTE J1118+480 (ref. 4) and GX 339-4 (ref. 5). Here we report an extensive multi-colour optical photometric data set of V404 Cygni, an X-ray transient source containing a black hole of nine solar masses (and a companion star) at a distance of 2.4 kiloparsecs (ref. 8). Our data show that optical oscillations on timescales of 100 seconds to 2.5 hours can occur at mass-accretion rates more than ten times lower than previously thought. This suggests that the accretion rate is not the critical parameter for inducing inner-disk instabilities. Instead, we propose that a long orbital period is a key condition for these large-amplitude oscillations, because the outer part of the large disk in binaries with long orbital periods will have surface densities too low to maintain sustained mass accretion to the inner part of the disk. The lack of sustained accretion--not the actual rate--would then be the critical factor causing large-amplitude oscillations in long-period systems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kimura, Mariko -- Isogai, Keisuke -- Kato, Taichi -- Ueda, Yoshihiro -- Nakahira, Satoshi -- Shidatsu, Megumi -- Enoto, Teruaki -- Hori, Takafumi -- Nogami, Daisaku -- Littlefield, Colin -- Ishioka, Ryoko -- Chen, Ying-Tung -- King, Sun-Kun -- Wen, Chih-Yi -- Wang, Shiang-Yu -- Lehner, Matthew J -- Schwamb, Megan E -- Wang, Jen-Hung -- Zhang, Zhi-Wei -- Alcock, Charles -- Axelrod, Tim -- Bianco, Federica B -- Byun, Yong-Ik -- Chen, Wen-Ping -- Cook, Kem H -- Kim, Dae-Won -- Lee, Typhoon -- Marshall, Stuart L -- Pavlenko, Elena P -- Antonyuk, Oksana I -- Antonyuk, Kirill A -- Pit, Nikolai V -- Sosnovskij, Aleksei A -- Babina, Julia V -- Baklanov, Aleksei V -- Pozanenko, Alexei S -- Mazaeva, Elena D -- Schmalz, Sergei E -- Reva, Inna V -- Belan, Sergei P -- Inasaridze, Raguli Ya -- Tungalag, Namkhai -- Volnova, Alina A -- Molotov, Igor E -- de Miguel, Enrique -- Kasai, Kiyoshi -- Stein, William L -- Dubovsky, Pavol A -- Kiyota, Seiichiro -- Miller, Ian -- Richmond, Michael -- Goff, William -- Andreev, Maksim V -- Takahashi, Hiromitsu -- Kojiguchi, Naoto -- Sugiura, Yuki -- Takeda, Nao -- Yamada, Eiji -- Matsumoto, Katsura -- James, Nick -- Pickard, Roger D -- Tordai, Tamas -- Maeda, Yutaka -- Ruiz, Javier -- Miyashita, Atsushi -- Cook, Lewis M -- Imada, Akira -- Uemura, Makoto -- England -- Nature. 2016 Jan 7;529(7584):54-8. doi: 10.1038/nature16452.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, Graduate School of Science, Kyoto University, Oiwakecho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan. ; JEM Mission Operations and Integration Center, Human Spaceflight Technology Directorate, Japan Aerospace Exploration Agency, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505, Japan. ; MAXI team, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. ; The Hakubi Center for Advanced Research, Kyoto University, Kyoto 606-8302, Japan. ; Astronomy Department, Wesleyan University, Middletown, Connecticut 06459, USA. ; Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, AS/NTU No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan. ; Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, Pennsylvania 19125, USA. ; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA. ; Steward Observatory, University of Arizona, Tucson, Arizona 85721, USA. ; Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, New York 10003, USA. ; Department of Astronomy and University Observatory, Yonsei University, Seoul 120-749, South Korea. ; Institute of Astronomy and Department of Physics, National Central University, Chung-Li 32054, Taiwan. ; Max Planck Institute for Astronomy, Konigstuhl 17, 69117 Heidelberg, Germany. ; Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford University, 452 Lomita Mall, Stanford, California 94309, USA. ; Crimean Astrophysical Observatory, 298409 Nauchny, Crimea. ; Space Research Institute, Russian Academy of Sciences, 117997 Moscow, Russia. ; National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia. ; Leibniz Institute for Astrophysics, Potsdam, Germany. ; Fesenkov Astrophysical Institute, Almaty, Kazakhstan. ; Kharadze Abastumani Astrophysical Observatory, Ilia State University, Tbilisi, Georgia. ; Institute of Astronomy and Geophysics, Mongolian Academy of Sciences, Ulaanbaatar 13343, Mongolia. ; Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, Moscow, Russia. ; Departamento de Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, 21071 Huelva, Spain. ; Center for Backyard Astrophysics, Observatorio del CIECEM, Parque Dunar, Matalascanas, 21760 Almonte, Huelva, Spain. ; Baselstrasse 133D, CH-4132 Muttenz, Switzerland. ; 6025 Calle Paraiso, Las Cruces, New Mexico 88012, USA. ; Vihorlat Observatory, Mierova 4, Humenne, Slovakia. ; Variable Star Observers League in Japan (VSOLJ), 7-1 Kitahatsutomi, Kamagaya, Chiba 273-0126, Japan. ; Furzehill House, Ilston, Swansea SA2 7LE, UK. ; Physics Department, Rochester Institute of Technology, Rochester, New York 14623, USA. ; American Association of Variable Star Observers (AAVSO), 13508 Monitor Lane, Sutter Creek, California 95685, USA. ; Institute of Astronomy, Russian Academy of Sciences, 361605 Peak Terskol, Kabardino-Balkaria, Russia. ; International Center for Astronomical, Medical and Ecological Research of National Academy of Sciences of Ukraine (NASU), 27 Akademika Zabolotnoho street, 03680 Kiev, Ukraine. ; Department of Physical Science, School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan. ; Osaka Kyoiku University, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582, Japan. ; 1 Tavistock Road, Chelmsford, Essex CM1 6JL, UK. ; The British Astronomical Association, Variable Star Section (BAA VSS), Burlington House, Piccadilly, London W1J 0DU, UK. ; 3 The Birches, Shobdon, Leominster, Herefordshire HR6 9NG, UK. ; Polaris Observatory, Hungarian Astronomical Association, Laborc utca 2/c, 1037 Budapest, Hungary. ; 112-14 Kaminishiyama-machi, Nagasaki, Nagasaki 850-0006, Japan. ; Observatorio de Cantabria, Carretera de Rocamundo sin numero, Valderredible, Cantabria, Spain. ; Instituto de Fisica de Cantabria (CSIC-UC), Avenida Los Castros sin numero, E-39005 Santander, Cantabria, Spain. ; Agrupacion Astronomica Cantabra, Apartado 573, 39080 Santander, Spain. ; Seikei Meteorological Observatory, Seikei High School, Kichijoji-kitamachi 3-10-13, Musashino, Tokyo 180-8633, Japan. ; Center for Backyard Astrophysics (Concord), 1730 Helix Court, Concord, California 94518, USA. ; Kwasan and Hida Observatories, Kyoto University, Kitakazan-Ohmine-cho, Yamashina-ku, Kyoto 607-8471, Japan. ; Hiroshima Astrophysical Science Center, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima, Hiroshima 739-8526, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26738590" target="_blank"〉PubMed〈/a〉