Wouthuysen–Field coupling strength and application to high-redshift 21-cm radiation     

Christopher M. Hirata 《Monthly notices of the Royal Astronomical Society》2006,367(1):259-274

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Trace Element Composition and Classification of the Chinga Iron Meteorite     

K. D. Litasov  A. Ishikawa  I. S. Bazhan  D. S. Ponomarev  T. Hirata  N. M. Podgornykh  N. P. Pokhilenko 《Doklady Earth Sciences》2018,478(1):62-66

A complete microelement analysis of the Chinga meteorite was performed, and the possibility of attributing it together with a number of other iron meteorites into the IVC subgroup, which is transition between IVA and IVB is proposed.  相似文献   

Secular change in lifetime of granitic crust and the continental growth: A new view from detrital zircon ages of sandstones     

Hikaru Sawada  Yukio Isozaki  Shuhei Sakata  Takafumi Hirata  Shigenori Maruyama 《地学前缘(英文版)》2018,9(4):1099-1115

U-Pb ages of detrital zircons were newly dated for 4 Archean sandstones from the Pilbara craton in Australia, Wyoming craton in North America, and Kaapvaal craton in Africa. By using the present results with previously published data, we compiled the age spectra of detrital zircons for 2.9, 2.6, 2.3,1.0, and0.6 Ga sandstones and modern river sands in order to document the secular change in age structure of continental crusts through time. The results demonstrated the following episodes in the history of continental crust:(1) low growth rate of the continents due to the short cycle in production/destruction of granitic crust during the Neoarchean to Paleoproterozoic(2.9-23 Ga),(2) net increase in volume of the continents during Paleo-to Mesoproterozoic(2.3-1.0 Ga), and(3) net decrease in volume of the continents during the Neoproterozoic and Phanerozoic(after 1.0 Ga). In the Archean and Paleoproterozoic, the embryonic continents were smaller than the modern continents, probably owing to the relatively rapid production and destruction of continental crust. This is indeed reflected in the heterogeneous crustal age structure of modern continents that usually have relatively small amount of Archean crusts with respect to the post-Archean ones. During the Mesoproterozoic, plural continents amalgamated into larger ones comparable to modern continental blocks in size. Relatively older crusts were preserved in continental interiors, whereas younger crusts were accreted along continental peripheries.In addition to continental arc magmatism, the direct accretion of intra-oceanic island arc around continental peripheries also became important for net continental growth. Since 1.0 Ga, total volume of continents has decreased, and this appears consistent with on-going phenomena along modern active arc-trench system with dominant tectonic erosion and/or arc subduction. Subduction of a huge amount of granitic crusts into the mantle through time is suggested, and this requires re-consideration of the mantle composition and heterogeneity.  相似文献   

Age and associated stress field of middle Miocene back-arc basalt magmatism in Northeast Japan     

Jun Hosoi  Atsushi Yamaji  Hideki Iwano  Tohru Danhara  Takafumi Hirata 《Island Arc》2021,30(1):e12379

A large volume of middle Miocene basaltic rocks is widely distributed across the back-arc region of Northeast Japan, including around the Dewa Mountains. Petrological research has shown that basaltic rocks of the Aosawa Formation around the Dewa Mountains were generated as a result of the opening of the Sea of Japan. To determine the precise ages of the middle Miocene basaltic magmatism, we conducted U–Pb and fission-track (FT) dating of a rhyolite lava that constitutes the uppermost part of the Aosawa Formation. In addition, we estimated the paleostress field of the volcanism using data from a basaltic dike swarm in the same formation. The rhyolite lava yields a U–Pb age of 10.73 ±0.22 Ma (2σ) and a FT age of 10.6 ±1.6 Ma (2σ), and the paleostress analysis suggests a normal-faulting stress regime with a NW–SE-trending σ₃-axis, a relatively high stress ratio, and a relatively high magma pressure. Our results show that the late Aosawa magmatism occurred under NW–SE extensional stress and ended at ~ 11 Ma.  相似文献   

SPICES: spectro-polarimetric imaging and characterization of exoplanetary systems     

Anthony Boccaletti  Jean Schneider  Wes Traub  Pierre-Olivier Lagage  Daphne Stam  Raffaele Gratton  John Trauger  Kerri Cahoy  Frans Snik  Pierre Baudoz  Raphael Galicher  Jean-Michel Reess  Dimitri Mawet  Jean-Charles Augereau  Jenny Patience  Marc Kuchner  Mark Wyatt  Eric Pantin  Anne-Lise Maire  Christophe Vérinaud  Samuel Ronayette  Didier Dubreuil  Michiel Min  Michiel Rodenhuis  Dino Mesa  Russ Belikov  Olivier Guyon  Motohide Tamura  Naoshi Murakami  Ingrid Mary Beerer 《Experimental Astronomy》2012,34(2):355-384

SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) is a five-year M-class mission proposed to ESA Cosmic Vision. Its purpose is to image and characterize long-period extrasolar planets and circumstellar disks in the visible (450?C900 nm) at a spectral resolution of about 40 using both spectroscopy and polarimetry. By 2020/2022, present and near-term instruments will have found several tens of planets that SPICES will be able to observe and study in detail. Equipped with a 1.5 m telescope, SPICES can preferentially access exoplanets located at several AUs (0.5?C10?AU) from nearby stars (<25 pc) with masses ranging from a few Jupiter masses to Super Earths (??2 Earth radii, ??10 M_??) as well as circumstellar disks as faint as a few times the zodiacal light in the Solar System.  相似文献   

Permian Peri‐glacial Deposits from Central Mongolia in Central Asian Orogenic Belt: A Possible Indicator of the Capitanian Cooling Event     

Tatsuya Fujimoto  Shigeru Otoh  Yuji Orihashi  Takafumi Hirata  Takaomi D. Yokoyama  Masanori Shimojo  Yoshikazu Kouchi  Hokuto Obara  Yasuo Ishizaki  Kazuhiro Tsukada  Toshiyuki Kurihara  Manchuk Nuramkhan  Sersmaa Gonchigdorj 《Resource Geology》2012,62(4):408-422

A dropstone‐bearing, Middle Permian to Early Triassic peri‐glacial sedimentary unit was first discovered from the Khangai–Khentei Belt in Mongolia, Central Asian Orogenic Belt. The unit, Urmegtei Formation, is assumed to cover the early Carboniferous Khangai–Khentei accretionary complex, and is an upward‐fining sequence, consisting of conglomerates, sandstones, and varved sandstone and mudstone beds with granite dropstones in ascending order. The formation was cut by a felsic dike, and was deformed and metamorphosed together with the felsic dike. An undeformed porphyritic granite batholith finally cut all the deformed and metamorphosed rocks. LA‐ICP‐MS, U–Pb zircon dating has revealed the following ²⁰⁶Pb/²³⁸U weighted mean igneous ages: (i) a granite dropstone in the Urmegtei Formation is 273 ± 5 Ma (Kungurian of Early Permian); (ii) the deformed felsic dike is 247 ± 4 Ma (Olenekian of Early Triassic); and (iii) the undeformed granite batholith is 218 ± 9 Ma (Carnian of Late Triassic). From these data, the age of sedimentation of the Urmegtei Formation is constrained between the Kungurian and the Olenekian (273–247 Ma), and the age of deformation and metamorphism is constrained between the Olenekian and the Carnian (247–218 Ma). In Permian and Triassic times, the global climate was in a warming trend from the Serpukhovian (early Late Carboniferous) to the Kungurian long and severe cool mode (328–271 Ma) to the Roadian to Bajocian (Middle Jurassic) warm mode (271–168 Ma), with an interruption with the Capitanian Kamura cooling event (266–260 Ma). The dropstone‐bearing strata of the Urmegtei Formation, together with the glacier‐related deposits in the Verkhoyansk, Kolyma, and Omolon areas of northeastern Siberia (said to be of Middle to Late Permian age), must be products of the Capitanian cooling event. Although further study is needed, the dropstone‐bearing strata we found can be explained in two ways: (i) the Urmegtei Formation is an autochthonous formation indicating a short‐term expansion of land glacier to the central part of Siberia in Capitanian age; or (ii) the Urmegtei Formation was deposited in or around a limited ice‐covered continent in northeast Siberia in the Capitanian and was displaced to the present position by the Carnian.  相似文献   

Zircon U–Pb ages of plutonic rocks in the southern Abukuma Mountains: Implications for Cretaceous geotectonic evolution of the Abukuma Belt          下载免费PDF全文

Yutaka Takahashi  Masumi Mikoshiba  Kazuya Kubo  Hideki Iwano  Tohru Danhara  Takafumi Hirata 《Island Arc》2016,25(2):154-188

Plutonic rocks in the southern Abukuma Mountains include gabbro and diorite, fine‐grained diorite, hornblende–biotite granodiorite (Ishikawa, Samegawa, main part of Miyamoto and Tabito, Kamikimita and Irishiken Plutons), biotite granodiorite (the main part of Hanawa Pluton and the Torisone Pluton), medium‐ to coarse‐grained biotite granodiorite and leucogranite, based on the lithologies and geological relations. Zircon U–Pb ages of gabbroic rocks are 112.4 ±1.0 Ma (hornblende gabbro, Miyamoto Pluton), 109.0 ±1.1 Ma (hornblende gabbro, the Hanawa Pluton), 102.7 ±0.8 Ma (gabbronorite, Tabito Pluton) and 101.0 ±0.6 Ma (fine‐grained diorite). As for the hornblende–biotite granodiorite, zircon U–Pb ages are 104.2 ±0.7 Ma (Ishikawa Pluton), 112.6 ±1.0 Ma (Tabito Pluton), 105.2 ±0.8 Ma (Kamikimita Pluton) and 105.3±0.8 Ma (Irishiken Pluton). Also for the medium‐ to fine‐grained biotite granodiorite, zircon U–Pb ages are 106.5±0.9 Ma (Miyamoto Pluton), 105.1 ±1.0 Ma (Hanawa Pluton) and the medium‐ to coarse‐grained biotite granodiorite has zircon U–Pb age of 104.5 ±0.8 Ma. In the case of the leucogranite, U–Pb age of zircon is 100.6 ±0.9 Ma. These data indicate that the intrusion ages of gabbroic rocks and surrounding granitic rocks ranges from 113 to 101 Ma. Furthermore, K–Ar ages of biotite and or hornblende in the same rock samples were dated. Accordingly, it is clear that these rocks cooled down rapidly to 300 °C (Ar blocking temperature of biotite for K–Ar system) after their intrusion. These chronological data suggest that the Abukuma plutonic rocks in the southern Abukuma Mountains region uplifted rapidly around 107 to 100 Ma after their intrusion.  相似文献   

In situ Measurements of Tide Gauge Response and Corrections of Tsunami Waveforms from the Niigataken Chuetsu-oki Earthquake in 2007     

Yuichi Namegaya  Yuichiro Tanioka  Kuniaki Abe  Kenji Satake  Kenji Hirata  Masami Okada  Aditya R. Gusman 《Pure and Applied Geophysics》2009,166(1-2):97-116

Linear and nonlinear responses of ten well-type tide gauge stations on the Japan Sea coast of central Japan were estimated by in situ measurements. We poured water into the well or drained water from the well by using a pump to make an artificial water level difference between the outer sea and the well, then measured the recovery of water level in the well. At three tide gauge stations, Awashima, Iwafune, and Himekawa, the sea-level change of the outer sea is transmitted to the tide well instantaneously. However, at seven tide gauge stations, Nezugaseki, Ryotsu, Ogi, Teradomari, Banjin, Kujiranami, and Naoetsu, the sea-level change of the outer sea is not always transmitted to the tide well instantaneously. At these stations, the recorded tsunami waveforms are not assured to follow the actual tsunami waveforms. Tsunami waveforms from the Niigataken Chuetsu-oki Earthquake in 2007 recorded at these stations were corrected by using the measured tide gauge responses. The corrected amplitudes of the first and second waves were larger than the uncorrected ones, and the corrected peaks are a few minutes earlier than the uncorrected ones at Banjin, Kujiranami, and Ogi. At Banjin, the correction was significant; the corrected amplitudes of the first and second upward motion are +103 cm and +114 cm, respectively, while the uncorrected amplitudes were +96 cm and +88 cm. At other tide gauge stations, the differences between the uncorrected and corrected tsunami waveforms were insignificant.  相似文献   

http://dx.doi.org/10.1016/j.gsf.2016.06.013     

Tsuyoshi Komiya  Shinji Yamamoto  Shogo Aoki  Keiko Koshida  Masanori Shimojo  Yusuke Sawaki  Kazumasa Aoki  Shuhei Sakata  Takaomi D. Yokoyama  Kenshi Maki  Akira Ishikawa  Takafumi Hirata  Kenneth D. Collerson 《地学前缘(英文版)》2017,8(2):355-385

The Archean continental crusts account for ca.20% of the present volume,but the thermal history of the Earths' mantle suggests much more continental crusts were formed in the early Archean.Because the Archean continental crust underwent severe metamorphism,it is important to avoid influence by the later thermal events.We carried out a comprehensive geochronological work of Cathodoluminescence(CL) observation and U-Pb dating of zircons from orthogneisses and supracrustal rocks over the Saglek Block to obtain their protolith ages.The zircons were classified into three domains of core,mantle and rims,and the cores were further classified into three groups of inherited,altered and zoned cores based on the zonation on the CL images.We estimated the protolith ages from Pb-Pb ages of the zoned-cores of zircons with low U contents.We made a detailed sketch of a small outcrop in St.John's Harbour South(SJHS) area,and classified the orthogneisses and mafic enclaves into seven generations based on the geologic occurrence.The first and second generations comprise mafic rocks and lack magmatic zircons.We conducted CL imaging and U-Pb dating of zircons from the third,sixth and seventh generation of the orthogneisses to estimate the protolith ages at 3902 L 25,3892 ± 33 and 3897 ± 33 Ma for each,supporting the presence of the over 3.9 Ca Iqaluk Gneiss.The geological occurrence that the mafic rocks occur as enclaves within the 3.9 Ga Iqaluk Gneiss indicates that they are the oldest supracrustal rocks in the world.Our geochronological and geological studies show the Uivak Gneiss is quite varied in lithology and age from 3.6 to 3.9 Ga,and tentatively classified into six groups based on their ages.The oldest Uivak Gneiss components including the Iqaluk Gneiss are present around the SJHS area,and the orthogneisses become young as it is away.The lines of evidence of overprinting of younger granitoid on older granitoid in small outcrops and geological-map scale as well as presence of inherited zircons even in the oldest suite suggests that crustal reworking played an important role on erasing the ancient crusts.  相似文献   

Phosphorus and metals bound to organic matter in coastal sediments - An investigation of complexes of P,Cu, Zn,Fe, Mn,Ni, Co and Ti by inductively coupled plasma-atomic emission spectrometry with sephadex gel chromatography     

Shizuko Hirata 《Marine Chemistry》1985,16(1):23-46

Phosphorus and metals bound to organic matter were separated from coastal sediments of Harima Sound in Seto Inland Sea, Japan by extraction with NaOH and fractionated by Sephadex G-25 chromatography. Phosphorus and metals were determined in the eluates by a multi-channel, inductively coupled plasma-atomic emission spectrometer. Phosphorus and Cu, Zn, Fe, Mn, Ni, Cr, Co and Ti bound to organic matter with high molecular weights (OMHMW) (MW ? 5000) were found to be present in the sediments, but no Mo or V were found. The technique provides minimum estimates of the amounts of P and metals bound to organic matter. These organic complexes show surface enrichment in a sediment core (0–20 cm) and their contents decrease with depth. Also, the amounts of eighteen elements, namely: P, Fe, Mn, Zn, Cu, Si, Al, Ti, Pb, Co, Ni, Cr, Mo, V, Na, K, Ca and Mg, in H₂O, ammonium acetate at pH 7 and 5, hydrogen peroxide, hydroxylamine hydrochloride and hydrogen fluoric acid soluble fractions have been determined with a selective chemical leaching technique for the ²¹⁰Pb-dated sediment core sample. Considerable amounts of P (6–19%) and Cu (5–21%) were associated with organic matter, in contrast to other metals such as Fe, Mn, Zn, Ni, Cr, Co and Ti which were associated with sulfide and silicate.  相似文献