Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jafrearsci.2023.104855

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.chemer.2022.125945

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Publishing type：Research paper (scientific journal)  

With this Preface, we provide background information, a scientific overview of topics, and an annotated bibliography of the 63 papers published in the Journal of Geophysical Research (JGR) Special Issue on “Ophiolites and Oceanic Lithosphere, with a Focus on the Samail Ophiolite,” collected online at https://agupubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)2169-9356.SAMAIL1. Topics covered in the Special Issue include formation and alteration of igneous ocean crust at submarine spreading centers, subduction zone mass transfer at the leading edge of the mantle wedge, the tectonic emplacement and evolution of ophiolites, processes of alteration and weathering of tectonically exhumed mantle peridotite, and the subsurface biosphere in the peridotite weathering environment. The bibliography, in the form of a supplementary Excel spreadsheet with links to each paper, is organized by topic, but can be sorted by first author, order of publication, specific Oman Drilling Project boreholes, and other factors.

DOI： 10.1029/2023JB026677

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.gca.2022.09.041

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

The Wadi El-Hima Neoproterozoic I- and A-type granites in the Southern Eastern Desert of Egypt are rich in garnets (up to 30 vol%) and are cut by NW–SE strike-slip faults, as confirmed from structure lineament extraction maps. These mineralized granites and garnet mineralization zones can be successfully discriminated using remote sensing techniques. Spectral angle mapper and matched filtering techniques are highly effective for mapping garnet-rich zones and show that the highest garnet concentrations occur along the intrusive contact zone of NW–SE striking faults. El-Hima granites have high SiO₂ (73.5–75.1 wt%), Al₂O₃ (13.4–15.3 wt%) and total alkali (6.7–8.7 wt%) contents, suggesting that they were sourced from peraluminous (A/CNK > 1) parental magmas. Garnet-bearing trondhjemites are metasomatic in origin and formed after I-type tonalite-granodiorites, which originated in a volcanic arc tectonic setting. Garnet-rich syenogranites and alkali-feldspar granites are both post-collisional A-type granites: the syenogranites formed from peraluminous magmas generated by partial melting of lower crustal tonalite and metasedimentary protoliths during lithospheric delamination, and the alkali-feldspar granites crystallized from highly fractionated, felsic and alkali-rich peraluminous magmas in the upper crust. Garnets in El-Hima mineralized granites occur in three forms: (1) subhedral disseminated crystals, (2) vein-type crystals, and (3) aggregated subhedral crystals, reflecting different mechanisms of accumulation. All are dominantly almandine in composition (Alm₇₆Sps₁₀ Prp₇Grs₆Adr₁) and have high average concentrations of heavy rare earth elements (HREE) (ΣHREE = 1636 ppm), Y = (3394 ppm), Zn (325 ppm), Li (39.17 ppm) and Ga (34.94 ppm). Garnet REE patterns show strong negative Eu anomalies with HREE enriched relative to LREE, indicating a magmatic origin. These magmatic garnets are late-stage crystallization products of Al-rich hydrous magmas, and formed at low temperature (680–730 °C) and pressure (2.1–2.93 kbar) conditions in the upper continental crust. Peculiar garnet concentrations in syenogranites near and along contact zones with alkali feldspar granites are related to peraluminous parent hydrous magma compositions. These garnets formed by in situ crystallization from A-type granite melts, alongside accumulation of residual garnets left behind after partial melting of the host garnet-rich granites along the intrusive contact. Magmatic-fluid flow along the NW–SE striking fault of Najd system enhanced garnet accumulation in melts, which formed clots and veins of garnet.

DOI： 10.1007/s00531-022-02237-7

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Other Link： https://link.springer.com/article/10.1007/s00531-022-02237-7/fulltext.html

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jafrearsci.2022.104620

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/iar.12460

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/iar.12460

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.gca.2022.07.005

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.chemgeo.2022.120969

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jseaes.2022.105078

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Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1029/2021jb022694

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. The Oman Drilling Project (OmanDP), performed under theInternational Continental Scientific Drilling Program (ICDP), is aninternational scientific research project that undertook drilling at a range of sites in the Semail ophiolite (Oman) to collect core samples spanning the stratigraphy of the ophiolite, from the upper oceanic crust down to the basal thrust. The cores were logged to International Ocean Discovery Program (IODP) standards aboard the D/V Chikyu. During ChikyuOman2018 Leg 3 (July–August 2018), participants described cores from the crust–mantle transition (CM) sites. The main rock types recovered at these sites weregabbros, dunites and harzburgites, rocks typically forming the base of theoceanic crust and the shallow mantle beneath present-day spreading centres.In addition to the core description, selected samples were analysed by X-ray fluorescence spectrometry (XRF) for their chemical compositions, including major, minor and some trace elements. To complement these standard procedures, we developed newapproaches to measure ultra-trace element concentrations using a procedureadapted from previous works to prepare fine-grained pressed powder pelletscoupled with laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis using instrumentation aboard the D/V Chikyu. First, three (ultra)mafic reference materials were investigated to test and validate our procedure (BHVO-2, BIR-1a and JP-1), and then the procedure was applied to a selection of gabbro and dunite samples from the CM cores toexplore the limitations of the method in its current stage of development.The obtained results are in good agreement with preferred values for thereference materials and with subsequent solution replicate analyses of the same samples performed in shore-based laboratories following Leg 3 for theCM samples. We describe this procedure for the determination of 37 minor and (ultra-)trace elements (transition elements and Ga, Li and Large-Ion Lithophile Elements (LILE), Rare Earth Elements (REE), High-Field-Strength Elements (HFSE), U, Th, and Pb) in mafic and ultramafic rocks. The presented method has the major advantage that it allows the determination at sea of the(ultra-)trace element concentrations in a “dry”, safe way, without usingacid reagents. Our new approach could be extended for other elements ofinterest and/or be improved to be adapted to other rock materials duringfuture ocean drilling operations aboard the D/V Chikyu and other platforms.

DOI： 10.5194/sd-30-75-2022

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1029/2021jb022352

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2021JB022352

Publishing type：Research paper (scientific journal)  

Completely carbonated peridotites represent a window to study reactions of carbon-rich fluids with mantle rocks. Here, we present details on the carbonation history of listvenites close to the basal thrust in the Samail ophiolite. We use samples from Oman Drilling Project Hole BT1B, which provides a continuous record of lithologic transitions, as well as outcrop samples from listvenites, metasediments, and metamafics below the basal thrust of the ophiolite. 87Sr/86Sr of listvenites and serpentinites, ranging from 0.7090 to 0.7145, are significantly more radiogenic than mantle values, Cretaceous seawater, and other peridotite hosted carbonates in Oman. The Hawasina sediments that underlie the ophiolite, on the other hand, show higher 87Sr/86Sr values of up to 0.7241. δ13C values of total carbon in the listvenites and serpentinites range from −10.6‰ to 1.92‰. We also identified a small organic carbon component with δ13C as low as −27‰. Based on these results, we propose that during subduction at temperatures above >400°C, carbon-rich fluids derived from decarbonation of the underlying sediments migrated updip and generated the radiogenic 87Sr/86Sr signature and the fractionated δ13C values of the serpentinites and listvenites in core BT1B.

DOI： 10.1029/2021JB022704

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1029/2021jb022729

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2021JB022729

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.2021.0028

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Tokyo Geographical Society  

DOI： 10.5026/jgeography.130.507

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Mineralogical Sciences  

DOI： 10.2465/jmps.201130f

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Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Mineralogical Sciences  

DOI： 10.2465/jmps.201130c

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Mineralogical Sciences  

DOI： 10.2465/jmps.191008

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Nickel is a major element in the Earth. Due to its siderophile nature, 93% of Ni is hosted in the core and the Ni isotope composition of the bulk silicate Earth might inform on the conditions of terrestrial core formation. Whether Earth's mantle is fractionated relative to the chondritic reservoir, and by inference to the core, is a matter of debate that largely arises from the uncertain Ni isotope composition of the mantle. We address this issue through high-precision Ni isotope measurements of fertile- to melt-depleted peridotites and compare these data to chondritic meteorites. Terrestrial peridotites that are free from metasomatic overprint display a limited range in delta Ni-60/58 (deviation of Ni-60/Ni-58 relative to NIST SRM 986) and no systematic variation with degree of melt depletion. The latter is consistent with olivine and orthopyroxene buffering the Ni budget and isotope composition of the refractory peridotites. As such, the average Ni isotope composition of these peridotites (delta Ni-60/58 = 0.115 +/- 0.011 parts per thousand) provides a robust estimate of the delta Ni-60(/)58 of the bulk silicate Earth. Peridotites with evidence for melt metasomatism range to heavier Ni isotope compositions where the introduction of clinopyroxene appears to drive an increase in delta Ni-60(/)58. This requires a process where melts do not reach isotopic equilibrium with buffering olivine and orthopyroxene, but its exact nature remains obscure. Chondritic meteorites have variability in delta Ni-60(/)58 due to heterogeneity at the sampling scale. In particular, CD chondrites are displaced to isotopically lighter values due to sorption of Ni onto ferrihydrite during parent body alteration. Chondrites less extensively altered than the CII chondrites show no systematic differences in delta Ni-60(/)58 between classes and yield average delta Ni-60(/)58 = 0.212 +/- 0.013 parts per thousand, which is isotopically heavier than our estimate of the bulk silicate Earth. The notable isotopic difference between the bulk silicate Earth and chondrites likely results from the segregation of the terrestrial core. Our observations potentially provide a novel constraint on the conditions of terrestrial core formation but requires further experimental calibration. (C) 2019 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.gca.2019.10.017

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Oceanography Society  

DOI： 10.5670/oceanog.2019.139

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

DOI： 10.1016/j.egypro.2018.07.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Tectonic affinities of accreted basalts provide constraints on mass transport in convergent boundaries, improving our understandings on the evolution of regional geology. In this study, nineteen accreted basalts from the southernmost tip of Taiwan Island, which is on the convergent boundary between the Eurasian and Philippine Sea Plates, were analyzed for element concentrations as well as Sr, Nd, Hf, and Pb isotope ratios to investigate their tectonic affinities. All the samples contain > 3% LOI, reflecting post-magmatic alteration. LOI and Nb variation diagrams together with comparisons to oceanic basalt compositions indicated that the concentrations of most major elements and Rb, Sr, and Ba were modified by post-magmatic processes to varying extents, while P2O5, REE and HFSE remained immobile. Although some samples show Pb loss, most samples have Pb concentrations not affected by post-magmatic processes. Isotope ratios of Pb, Nd and Hf, generally reflect the mantle source characteristics. The epsilon(Nd)-epsilon(Hf) relationship and trace element abundance ratios indicated that the LREE-depleted samples were mostly scraped off the subducting South China Sea floor, reflecting the volumetric dominance of N-MORB on ocean floors. The overriding Philippine Sea Plate contributed both N-MORB and E-MORB to the accretionary prism. The tectonic affinities of the LREE-enriched samples, however, could not be unambiguously determined for the large geochemical variability of OIB from both subducting and overlying slabs. Based on our results, it is proposed that the tectonic affinity of the basalts in an accretionary prism can indicate the subduction polarity of the associated convergent boundary, providing a constraint for regional geology evolution.

DOI： 10.1016/j.jseaes.2018.02.015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEOCHEMICAL SOC JAPAN  

We examined quality of zircon U-Pb dating results by mean-of-ratios (MOR) reduction of time-resolved analysis acquired with quadrupole inductively coupled plasma mass spectrometer (ICPMS) and 213 nm YAG laser ablation system. Time-resolved MOR reduction has an advantage to enable statistic evaluation of stability of isotopic ratios and detect accidents in each measurement. We practically applied internal mean square weighted deviation (iMSWD) and correlation coefficient of linear regression to dating of five reference zircons. The MOR reduction provided reasonably accurate U-Pb ages with 2-3% errors of precision. However, their iMSWD suggested dispersion of isotopic ratios in excess of counting errors. The dispersion is inferably attributed to non-simultaneous measurements by quadrupole ICPMS, in addition to potential heterogeneity of samples. We also tested quality of age results from manually trimmed time profiles. The test suggested that ages from clipped profiles as short as 5 sec. are still useful if reduction of precision is acceptable. The method enables to extract meaningful ages from measurements containing accidents, when statistically stable parts out of accidents are properly clipped from the time profiles.

DOI： 10.2343/geochemj.2.0509

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Basic-oxygen furnace (BOF) slag is the second abundant by-product from the steel-making process. It is not readily recycled for high phosphorus content and volume instability. To eliminate its phosphorus-hosting dicalcium silicate (C2S) and volumetrically unstable free-lime, reductive heating experiments on BOF-slag are carried out at 1300-1600 degrees C using quartz-sand or serpentine as a basicity modifier. In the products, C2S and free-lime are consumed through reacting with CaO and MgO, which are produced by Ca-ferrite and Mg-wustite reduction, respectively, to formmerwinite and akermanite. The products are also characterized by silicatemetal segregation and the extent of that increases with increasing temperature and decreasing particle size of starting mixtures. Thermodynamic calculations show that phosphorus in C2S is mostly converted to Fe2P in the metal domain. Compared to the slag-serpentine experiments, the slag-quartz experiments resulted in higher extents of silicate-metal segregation with lower phosphorus contents of approximate to 0.1% in the silicate domain, which therefore is recyclable. To optimize silicate-metal segregation for recycling BOF-slag, it is suggested (i) bringing the BOF-slag composition within the low-temperature side of the C2S-merwinite-akermanite Alkemade triangle by adding quartz-sand; (ii) reductively heating to 1500-1600 degrees C; and (iii) cooling slowly then quenching to suppress C2S crystallization from melts.

DOI： 10.1002/srin.201500441

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

High arsenic abundance of 50-700 mu g/L in the groundwater from the Chianan Plain in southwestern Taiwan is a well-known environmental hazard. The groundwater-associated sediments, however, have not been geochemically characterized, thus hindering a comprehensive understanding of arsenic cycling in this region. In this study, samples collected from a 250 m sediment core at the centre of the Chianan Plain were analyzed for arsenic and TOC concentrations (N = 158), constituent minerals (N = 25), major element abundances (N = 105), and sequential arsenic extraction (N = 23). The arsenic data show a prevalence of >10 mg/kg with higher concentrations of 20-50 mg/kg concentrated at 60-80 and 195-210 m. Arsenic was extracted mainly as an adsorbate on clay minerals, as a co-precipitate in amorphous iron oxyhydroxide, and as a structural component in clay minerals. Since the sediments consist mainly of quartz, chlorite, and illite, the correlations between arsenic concentration and abundances of K2O and MgO pinpoint illite and chlorite as the major arsenic hosts. The arsenic-total iron correlation reflects the role of chlorite along with the contribution from amorphous iron oxyhydroxide as indicated by arsenic extraction data. Organic matter is not the dominant arsenic host for low TOC content, low arsenic abundance extracted from it, and a relatively low R-2 of the arsenic-TOC correlation. The major constituent minerals in the sediments are the same as those of the upriver metapelites, establishing a sink-source relationship. Composition data from two deep groundwater samples near the sediment core show Eh values and As(V)/As(III) ratios of reducing environments and high arsenic, K, Mg, and Fe contents necessary for deriving arsenic from sediments by desorption from clay and dissolution of iron oxyhydroxide. Therefore, groundwater arsenic was mainly derived from groundwater-associated sediments with limited contributions from other sources, such as mud volcanoes. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.scitotenv.2016.06.122

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PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN ASSOC MINERALOGICAL SCIENCES  

Chemically precipitated carbonate sediments directly record seawater composition that helps to decode the Earth's paleo-environment, the existence of paleo-oceans, and provide valuable clues on the paleo-tectonic position of continents through Earth's history. In addition, the geochemical and isotopic composition of carbonate rocks have a strong dependence on the depositional tectonic setting and surrounding source rock composition. This was particularly important in the Precambrian, during which biological activity was less prominent and vegetation was virtually absent. Here we present evidence for the existence of an extinct East Antarctic Ocean and its peripheral oceanic island arc system that preceded the formation of the East Antarctic continent in the Neoproterozoic before the final assembly of Gondwana. Applying a multi-element isotope geochemical approach on chemostratigraphically well-constrained metacarbonate rocks collected from the remote Sor Rondane Mountains in East Antarctica, we present a model on carbonate deposition surrounding an island arc system, mid-ocean volcanic islands and a shallow marine continental shelf of a yet unidentified interior Antarctic continent, all of which accreted in the late Neoproterozoic to early Paleozoic to form the present day East Antarctic continent prior to the final amalgamation of Gondwana supercontinent. Our results support the presence of an oceanic island arc system that might have separated the Mozambique ocean and East Antarctic ocean.

DOI： 10.2465/jmps.151029a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCIENCE PRESS  

Basic-oxygen furnace slag (BOF-slag) contains >35% CaO, a potential component for CO2 sequestration. In this study, slag-water-CO2 reaction experiments were conducted with the longest reaction duration extending to 96 hr under high CO2 pressures of 100-300 kg/cm(2) to optimize BOF-slag carbonation conditions, to address carbonation mechanisms, and to evaluate the extents of V and Cr release from slag carbonation. The slag carbonation degree generally reached the maximum values after 24 hr slag-water-CO2 reaction and was controlled by slag particle size and reaction temperature. The maximum carbonation degree of 71% was produced from the experiment using fine slag of <= 0.5 mm under 100 degrees C and a CO2 pressure of 250 kg/cm(2) with a water/slag ratio of 5. Vanadium release from the slag to water was significantly enhanced (generally >2 orders) by slag carbonation. In contrast, slag carbonation did not promote chromium release until the reaction duration exceeded 24 hr. However, the water chromium content was generally at least an order lower than the vanadium concentration, which decreased when the reaction duration exceeded 24 hr. Therefore, long reaction durations of 48-96 hr are proposed to reduce environmental impacts while keeping high carbonation degrees. Mineral textures and water compositions indicated that Mg-wustite, in addition to CaO-containing minerals, can also be carbonated. Consequently, the conventional expression that only considered carbonation of the CaO-containing minerals undervalued the CO2 sequestration capability of the BOF-slag by similar to 20%. Therefore, the BOF-slag is a better CO2 storage medium than that previously recognized. (C) 2015 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

DOI： 10.1016/j.jes.2015.06.012

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PubMed

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/petrology/egv073

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The whole-rock Hf, Sr and Nd isotope data of five high-Fe-Ti eclogites, nine high-Al edogites, and a garnetite from the Sulu ultrahigh pressure (UHF) metamorphic terrane at eastern China were analyzed to resolve the causes for the decoupling of the Lu-Hf, Sm-Nd, and Rb-Sr isotope systems in these UHP rocks and to infer their protolith characteristics. Seven of the nine high-Al eclogites define an Rb-87/Sr-86-Sr-87/Sr-86 errorchron age of 192 +/- 43 Ma (MSWD = 2.8), which is within the time span of retrograde metamorphism despite the large uncertainty. The high-Fe-Ti eclogites and garnetite, however, have low Rb-87/Sr-86 ratios of <0.031 with scattered Sr-87/Sr-86 ratios of 0.7042-0.7058. Accordingly, it is inferred that the Rb-Sr isotope system in the samples reflects the effects of processes postdating the UHP metamorphism. Despite having different constituent mineral assemblages and whole rock geochemistry, the samples, however, define a Sm-147/Nd-144-Nd-143/Nd-144 errorchron age of 232 +/- 36 Ma (MSWD = 4.6). Although the uncertainty of +/-36 Ma implies incomplete Nd isotope equilibrium among the samples, the large overlap between this errorchron age span and the mineral isochron ages of 245-210 Ma for the UHP metamorphism indicates the control of peak metamorphism on the Sm-Nd isotope system. The incomplete Nd isotope re-equilibration was accompanied by metamorphic modification on the Sm/Nd ratios as indicated by the U-shaped LREE patterns. The initial epsilon(Nd)(780) values of the protolith rocks calculated from the Sm/Nd ratios of the samples deviate from the igneous initial epsilon(Nd)(t)-epsilon(Hf)(t) trend to significantly lower values, consistent with the metamorphic increase in the Sm/Nd ratios. In contrast, the Lu/Hf ratios are generally within the range for basalts and do not vary systematically with the Hf-176/Hf-177 ratios. The protolith epsilon(Hf)(780) values calculated from the Lu/Hf ratios of the samples are nearly identical to the initial epsilon(Hf)(t) values of the -780 Ma magmatic zircon cores from the Yangtze craton, suggesting the dominance of protolith characteristics on the Lu-Hf isotope system, Being controlled by different processes, the Rb-Sr, Sm-Nd, and Lu-Hf isotope systems of the investigated samples are therefore decoupled. The epsilon(Nd)(220)-epsilon(Hf)(220) compositions of the samples deviate from the epsilon(Nd)(t)-epsilon(Hf)(t) trend of intraplate lavas to high epsilon(Hf)(220) at a given epsilon(Nd)(220) and are within the arc lava field. The protolith epsilon(Nd)(780)-epsilon(Hf)(780) compositions calculated from metamorphic initials using igneous Sm/Nd and Lu/Hf ratios show a similar distribution pattern, strengthening the arc affinity of the eclogites. These arc signatures together with the felsic-mafic bimodal geochemical features of the UHF rocks from the Sulu terrane are explained as the characteristics of protoliths generated by backarc rifting. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.lithos.2015.07.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

We have analysed the Li and Mg isotope ratios of a suite of samples from the Horoman Peridotite Massif. Our results show that most Li and all Mg isotopic compositions of the Horoman peridotites are constant over 100 metres of continuous outcrop, yielding values for pristine mantle of delta Li-7 = 3.8 +/- 1.4 parts per thousand (2SD, n = 9), delta Mg-25 = -0.12 +/- 0.02 parts per thousand and delta Mg-26 = -0.23 +/- 0.04 parts per thousand (2SD, n = 17), in keeping with values for undisturbed mantle xenoliths. However, there are also some anomalously low delta Li-7 values (-0.2 parts per thousand to 1.6 parts per thousand), which coincide with locations that show enrichment of incompatible elements, indicative of the prior passage of small degree melts. We suggest Li diffused from infiltrating melts with high [Li] into the low [Li] minerals and kinetically fractionated Li-7/Li-6 as a result. Continued diffusion after the melt flow had ceased would have resulted in the disappearance of this isotopically light signature in less than 15 Ma. In order to preserve this feature, the melt infiltration must have been a late stage event and the massif must have subsequently cooled over a maximum of similar to 0.3 Ma from peak temperature (950 degrees C, assuming the melts were hydrous) to Li closure temperature (700 degrees C), likely during emplacement. The constant delta Mg-26 values of Horoman peridotites suggest that chemical potential gradients caused by melt infiltration were insufficient to drive associated delta Mg-26 fractionation greater than our external precision of 0.03 parts per thousand. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.gca.2015.05.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

Eclogites from the Baijingsi area in the North Qilian orogen at NW China were analyzed for major and trace element abundances as well as Sr, Nd, and Hf isotope ratios to evaluate the impacts from subduction processes on these compositional parameters and to reveal the complexity in protolith characteristics. The major element compositions of the Baijingsi eclogites are within the ranges for basalts. However, the absence of systematic variations among major oxides indicates varying extents of metamorphic modifications. Seven samples are characterized by profound Nb and Ta depletions. Six of them form coherent trends in the La versus Th, HFSE, and LREE plots. They are classified as the Group 1 samples. Other eight samples, referred to as the Group 2 samples, define distinct La-Zr and La-Sm trends and have flat variation patterns with slight Th-Nb-Ta-LREE depletions in the primitive mantle-normalized multiple-element diagram. Group 1 dominates the Sr-87/Sr-86-Rb-87/Sr-86, Nd-143/Nd-144-Sm-147/Nd-144 and Hf-176/Hf-177-Lu-176/Hf-177 trends for relatively larger variations in the isotope and abundance ratios. Based on the errorchron ages from the samples, closure temperatures of the isotope systems, and isotope ratio versus 1/X plots (e.g., Sr-87/Sr-86-1/Sr), it is inferred that the Rb-Sr isotope system was subjected to metamorphic modification, whereas the Sm-Nd and Lu-Hf isotope systems mainly reflect protolith characteristics. In addition to the Nb and Ta depletions, the Group 1 samples generally have epsilon(Hf)(510) values (protolith initial at 510 Ma) higher than those of MORB at a given epsilon(Nd)(510), reflecting derivation from relatively high Lu/Hf ratio sources. They also plot within the fields for arc lavas in the Ta/Yb-Th/Yb and Th-Ta-Hf/3 diagrams. All these features are consistent with derivation from protoliths of an arc origin. In contrast, the Group 2 samples have eNd(510) values slightly higher than those of the Group 1 samples at a given epsilon(Hf)(510), plotting on the low epsilon(Nd)(510) margin of the MORB field. They also deviate from the Ta/Yb-Th/Yb trend defined by MORE and OIB toward higher Th/Yb values within the fields of back-arc basin basalts. Therefore, it is inferred that the protoliths of the Group 2 samples were generated as back-arc basin basalts possibly associated with the protoliths of the Group 1 samples in a common supra-subduction zone. The epsilon(Nd)(510)-epsilon(Hf)(510) relationship of the Baijingsi eclogites shows an affinity to the Indian ocean type mantle, implying protolith generation at the southern hemisphere on the margin or a fragment of the Gondwana continent, most likely in the Qilian Block. Based on the current tectonic configuration, a southward subduction is required for protolith generation and might eclogitize the arc protoliths by subduction erosion. Alternatively, the northward subduction in a bidirectional subduction system might become dominant during the amalgamation of the Qilian Block and the North China Craton to eclogitize the arc protoliths in the Qilian Block. Resolving these two possibilities requires more petrological, geochemical, and structural evidence from the North Qilian orogen. (C) 2014 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.gr.2014.06.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

The Oman ophiolite is one of the best preserved sections of oceanic crust and upper mantle worldwide, and consists of multiple massifs that lie along more than 400 km of the Arabian coast. In the northernmost massifs, the oceanic crust preserves a record of polygenetic magmatism from mid-ocean ridge to subduction-related stages. The lherzolites and clinopyroxene (Cpx)-rich harzburgites of the Fizh block are located a few tens to a hundred meters above the metamorphic sole of the ophiolite and the geochemistry of these Cpx-rich peridotites provides evidence of a genetic link between oceanic crust and mantle. These Cpx-rich peridotites contain olivine with a restricted range of forsterite contents (90-91), but variable Cr-spinel Cr# (Cr/(Cr + Al) atomic ratio) values (0.12-0.33), suggesting that these Cpx-rich peridotites have undergone variable degrees of melt extraction. Cpxs within the Cpx-rich peridotites have chondrite-normalised trace element variation patterns that slope either gently or steeply between the heavy rare earth elements (REEs) and the middle REEs ((Sm/Yb)(N) = 0.08-0.55, where N chondrite-normalised) and are enriched in highly incompatible elements such as Rb, Ba and Nb. This Cpx chemistry can be explained by a polygenetic evolution whereby an initial 4-12% of melt was extracted from the depleted mantle source before this mantle was metasomatised by interaction with fluids derived from dehydration of the metamorphic sole during subduction initiation and obduction. A comparison between Nd-143/Nd-144 versus Sm-147/Nd-144 for Cpx in the Fizh basal Cpx-rich peridotites and a mineral-whole rock Sm-Nd isochron for a gabbro from the same massif suggests a genetic link between crustal and mantle rocks in this area. In addition, Cpxs within the basal Cpx-rich peridotites have highly variable Sr isotopic compositions that are indicative of a significant contribution of seawater from the metamorphic sole, originally derived from subducted oceanic crustal material. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tecto.2014.12.004

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The southern part of Okushiri Island in the present-day back-arc margin of the NE Japan arc is one of the rare convergent plate boundaries where similar magma types (high-magnesian adakitic andesite (HMAA) and high-TiO2 basalt (HTB)) have been erupted concurrently at more than one time. Oligocene HMAA can be divided into two types: HMAA-I is characterized by high Sr/Y and low Y, and HMAA-II by relatively low Sr/Y and high Y. HMAA-I is primitive in terms of MgO (8.5 wt.%), Mg# (67), Ni (232 ppm) and Cr (613 ppm) contents, and the most Mg-rich olivine phenocrysts plot within the mantle olivine array in terms of Fo and NiO. The similar Cr versus Ni relations of types I and II HMAA indicate some interaction of slab-derived adaldtic melts with mantle peridotite, whereas Ni contents are higher than those of most boninites derived by partial melting of mantle peridotite at a given Cr content Types I and II HMAA have more enriched Stand Nd isotopic compositions than N-MORB. The petrography and geochemistry of these rocks, combined with published results on the genesis of high-magnesian andesite (HMA) indicate that types I and II HMAA could be produced by interaction of slab (N-MORB and sediment)derived adakitic melts with mantle peridotite. The comagmatism of HMAA and HTB is ascribed to the following model. A cool, less hydrous, adakite magma (spherical diapir) would rise from the subducting slab (Pacific Plate) and become more hydrous as a result of its interaction with overlying hydrous peridotite. This hydrated adakitic diapir further ascends and is heated on entering the overlying mantle wedge. Subsequently, the temperature and H2O gradients in the ascending adakitic diapir and surrounding mantle peridotite would have been established. The HTB magma segregated from the surrounding mantle peridotite region (high temperature and low H2O content) at a depth of 60 km or more, whereas the adakitic diapir (low temperature and high H2O content) continued to rise, with its chemical composition modified due to interaction with the surrounding mantle peridotite. Type I HMAA then segregated at about 50 km.The most attractive tectono-magmatic model to account for production of adakitic magma at two different periods in the same cool subduction zone region involves upwelling of depleted hot asthenosphere into the subcontinental lithosphere beneath the back-arc margin of the NE Japan arc, coincident with back-arc rifting which took place at the initiation of the Japan Sea opening. The unusually high temperature conditions established in the mantle wedge due to upwelling of depleted hot asthenosphere caused partial melting of a limited part of the cool oceanic crust subducting beneath the NE Japan arc, resulting in the generation of adakitic magma. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.lithos.2014.06.008

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Geological Society of London  

We report the major element compositions of constituent minerals in 278 harzburgites and of 101 whole rocks from the northern Fizh mantle section in the northern Oman Ophiolite to investigate the formation and evolution of oceanic lithospheric mantle. Olivine Fo varies from 90 to 92 whereas spinel Cr# (=Cr/(Cr + Al) atomic ratio) varies from 0.15 to 0.78. The Cr# of spinels in a large number of harzburgites exceeds 0.6, which is the upper bound for abyssal peridotites. In the northern Fizh mantle section, highly refractory harzburgites with spinel Cr# greater than 0.7 are distributed in a 3-km-wide band along a NW-SE-striking shear zone. We infer a two-stage depletion process in the northern Fizh mantle section. In the first stage, asthenospheric mantle was partially melted beneath a mid-ocean ridge, producing a harzburgitic residual column. In the second stage during detachment of oceanic lithosphere an H2O-rich fluid, released from the metamorphic sole due to thermal metamorphism of altered oceanic crust, extensively infiltrated the northern Fizh mantle section where the ridge segment boundary region was previously located. The residual harzburgites were subjected to flux melting, resulting in a highly refractory harzburgite zone with spinel Cr# greater than 0.7. © The Geological Society of London 2014.

DOI： 10.1144/SP392.12

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Language：Japanese   Publisher：Japan Association of Mineralogical Sciences  

Extensive lenticular-shaped ultramafic complexes that are composed of dominant amount of dunite associated with harzburgite and irregular-shaped pyroxenite cumulates, occur in the basal part of the Salahi mantle section in the northern Oman ophiolite. Petrologic characteristics such as rock types, textures and mineral compositions were examined to understand the origin of the ultramafic complex. Peridotites exhibit coarse-granular to very coarse-granular texture with grain size greater than five millimeters. The Cr#[=Cr/(Cr+Al) atomic ratio] of spinels in harzburgites ranges from 0.56 to 0.72, and is most frequent at 0.64-0.66 while spinel Cr# of dunites ranges from 0.61 to 0.84, and is most frequent at 0.76-0.82. The origin of voluminous dunite with high Cr# spinel can be explained by flux melting of residual harzburgite as a result of infiltration of large amount of fluid from the base of the ophiolite during oceanic thrusting. Dunites with very coarse-granular texture also support this hypothesis. The dunites in the central part of the complex tend to have both olivine Fo content and spinel Cr# greater than those in the host harzburgites. We speculate that not only orthopyroxene but also olivine were consumed during flux melting in this region resulted in the formation of voluminous dunites in the core of the complex. On the other hand, the dunites from the periphery of the complex have olivine with Fo content lower than those in the host harzburgites indicating precipitation of olivine from the melt. Moreover, crystallization of pyroxene formed numerous pyroxenites in this region. The southern part of the Salahi mantle section has been considered as a paleo-ridge segment end region. Our results support that the occurrence of highly refractory peridotites is spatially related to the segment end region in the northern Oman ophiolite.<br>

DOI： 10.2465/gkk.120624

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2204/iodp.sd.15.10.2013

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.118.11.IX_X

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Language：Japanese   Publisher：一般社団法人 日本鉱物科学会  

&amp;nbsp;&amp;nbsp;How much do we know the Earth&#039;s mantle? We would like to make clear what we want to know, what we can know and what we will be able to know the Earth&#039;s mantle. This special issue focuses on recent scientific advances in serpentinization, pressure-temperature paths including thermal history of the earth, tectono-magmatic processes, geochemical recycling, rheology and chemical compositions of the Earth&#039;s mantle based on analyses of mantle-derived materials including volcanic rocks. These topics provide useful information for a wide range of earth scientific communities.&lt;br&gt;

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The Oman ophiolite is a remnant of Neo-Tethyan oceanic lithosphere that has been modified by arc-related magmatism during oceanic thrusting prior to the obduction to the Arabian continent. To understand the formation of oceanic mantle lithosphere at a spreading ridge and subsequent modification at an incipient subduction zone a km-scale mineral chemical mapping of the mantle section was conducted in the Fizh and Salahi blocks in the northern Oman ophiolite. The range of spinel Cr#[= Cr/(Cr + Al) atomic ratio] in harzburgites becomes wider from the region of paleo-ridge segment center to the margin. In the northern part, where a paleo-ridge segment margin was inferred, refractory harzburgites with spinel Cr# greater than 0.7 are abundant and are distributed as a band (3 km in width) extending from the basal thrust to the Moho. Such high refractory harzburgites are associated with thick dunite bands in which spinel Cr# is also high (greater than 0.7). Dunites in the Fizh and Salahi mantle sections have spinel with Cr# ranging from 0.45 to 0.8 and tend to have higher spinel Cr# than the harzburgites. Moreover, the dunites with high Cr# spinel (greater than 0.7) are abundant in the basal part of the mantle section. The distribution of refractory har-zburgite and dunite in the northern Oman ophiolite can be modeled as follows. During oceanic thrusting the Oman ophiolite was displaced above an incipient subduction zone. The fluid released from metamorphic sole due to thermal metamorphism of altered oceanic crust in-iltrated into the mantle section. Dunite channels may have acted as pathways for luid in-iltration from the base of the ophiolite, which was instrumental for lux melting of wallrock harzburgite. The presence of the high refractory harzburgites in the northern Fizh mantle section implies that the iniltration of luid from the base of ophiolite was extensive in the ridge segment boundary region. © 2012, Japan Association of Mineralogical Sciences. All rights reserved.

DOI： 10.2465/gkk.120704

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DOI： 10.2204/iodp.sd.10.07.2010

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Language：English   Publisher：OXFORD UNIV PRESS  

DOI： 10.1093/petrology/egp098

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Geochemistry of kimberlites and associated carbonatites from the Snap Lake dyke system, Slave craton, Canada, shows that kimberlites are similar, but not identical to Group I kimberlites from South Africa and Siberia. Snap Lake kimberlites are enriched in most incompatible elements such as U, Th, Nb and LREE (up to 1400 times chondritic abundances), and are weakly differentiated relative to primitive mantle in their Sr and Nd isotope compositions. The Snap Lake carbonatites and kimberlites are enriched or depleted in certain trace elements relative to each other. Carbonatites are depleted in Cs, Rb, K, Ta and Ti but enriched in U, Sr, P, Zr, Hf, middle and heavy REEs relative to kimberlites. The observed element distributions are not consistent with experimental data on distribution of trace elements between immiscible carbonate and silicate liquids. However, the chemistry of these rocks shows a continuous systematic change from carbonatites to kimberlites, suggesting their genetic relationship. The range of major element concentrations from low SiO2 (3 wt.%) magmas to typical kimberlites are in excellent agreement with experimental data for melting of carbonated lherzolite at high pressure. Carbonatites have significantly superchondritic Nb/Ta (22-81) and Zr/Hf (57-128) ratios, which systematically decrease with increase of SiO2. Modeling of partial melting requires that the source for Snap Lake dyke rocks was enriched in incompatible elements but depleted in HREE relative to the primitive mantle. The most appropriate source rocks are metasomatically enriched peridotites of the deep lithospheric mantle roots. In the melting sequence of this source, the incipient magma was carbonatitic in composition but subsequently became kimberlitic as the degree of partial melting increased to 1%. Rocks of the Snap Lake dyke represent a natural example of primary melting process within a deep (&gt
250 km) lithospheric mantle. © 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chemgeo.2008.07.003

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.113.S167

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DOI： 10.1111/j.1440-1738.2006.00517.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In the Niigata region of the NE Japan arc, basaltic and intermediate to felsic volcanic rocks (silicic andesite, dacite and rhyolite) have been produced during the Early Miocene, Middle Miocene and Pliocene ages, spanning the pre-Japan Sea opening to post-opening stages. Early Miocene basaltic rocks are characterized by enriched Sr and Nd isotopic signatures (initial Sr-87/Sr-86 (SrI) = 0.70557 to 0.70592 and initial Nd-143/Nd-144 (NdI)=0.51255 to 0.51262), whereas Middle Miocene and Pliocene basaltic rocks are slightly enriched than MORB in terms of SrI (0.70314-0.70416) and NdI (0.51286-0.51310). Early Miocene basaltic rocks are also characterized by higher abundances of HFSE and LREE, and higher Zr/Y compared to Middle Miocene and Pliocene basaltic rocks. The geochemical features of Early Miocene basaltic rocks are almost identical to those of basaltic rocks found in continental rift zones, such as the Rio Grande rift. The different geochemical signatures of Early and Middle Miocene basaltic rocks can be ascribed to the geochemical differences in the mantle source. Apart from andesitic rocks of the Kakuda area, most of Early and Middle Miocene intermediate to felsic volcanic rocks from the Niigata region show significantly higher SrI values (0.70673-0.70773) and lower NdI values (0.51234-0.51254) than Early Miocene basaltic rocks, indicating a lower crustal origin for these more felsic volcanic rocks.

DOI： 10.1016/j.lithos.2005.06.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

A hypothetical model is proposed to explain the origin of compositional discontinuities in the layering observed in orogenic lherzolites. The observed collinearity of the whole-rock peridotite compositions is best explained in terms of partial melting and melt segregation. The presence of chemical discontinuities implies that melt segregation includes an abrupt and discontinuous process. A kg concept in the model is the topological transformation of melt geometry in partially molten rocks responding to the equality and inequality of the fluid pressure and solid pressure, which may be realized in a gravitational field. It is emphasized that the percolation threshold is a critical boundary, beyond which a rapid microstructural change occurs in response to the change of local fluid pressure, thus causing a rapid increase of permeability. The model implies that the mode of melting is closer to batch melting than to fractional melting in the upper mantle.

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2004.abst.0_265_1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

[1] Abundances of major and trace elements in whole rocks and minerals in lherzolites and harzburgites from the northern Oman ophiolite are used to understand the mantle processes creating compositional variation in oceanic lithospheric mantle. Detailed mapping shows that lherzolites occur near the base of a mantle section in the northern Fizh block. Geochemical analyses identify two types of basal lherzolite. The first type (Type I lherzolite) displays porphyroclastic microstructure and occurs sporadically in the basal mylonite zone. Whole rock and clinopyroxene are highly depleted in incompatible elements such as Na, Ti, Zr, and rare earth elements (REE). The chondrite-normalized patterns of Type I lherzolites show steep slopes from heavy REE (HREE) to light REE (LREE) that are ascribed to melt extraction, up to 12-18%, from a source containing a small amount of garnet. The chondrite-normalized patterns have slight enrichment in LREE relative to the patterns expected for residues of partial melting thereby indicating reaction with a LREE-enriched melt or fluid at a low melt/rock ratio. The second type (Type II lherzolite) shows mylonitic microstructure and only occurs at the contact between the mantle section and the metamorphic sole. Abundances of incompatible elements in whole rocks and clinopyroxenes are greater than those of Type I lherzolites, and clinopyroxenes in Type II lherzolites have high Na(2)O contents (&gt; 1 wt.%). To a first approximation, the high Na content of clinopyroxenes and whole rocks and the LREE-depleted, chondrite-normalized whole rock REE patterns are consistent with Type II lherzolite being in equilibrium with a midocean ridge basalt (MORB)-type melt at relatively high pressure (&gt; 2 GPa). However, the flatness of chondrite-normalized patterns for middle and heavy REE are inconsistent with residual garnet peridotite. The characteristics of Type II lherzolites are better explained by a mixing process in which residual peridotite was refertilized by addition of a LREE-depleted melt. The large compositional gradient near the basal thrust in the northern Fizh block may have recorded a transient state in which the degree of partial melting was progressively decreased as a result of reducing mantle temperature and upwelling rate. This scenario is consistent with the inferred failing ridge associated with a transform zone in the western side of the northern Fizh block proposed by Nicolas et al. [2000]. In the detachment stage of the Oman ophiolite, a small amount of ascending melt may have crystallized near the basal part of mantle section thereby forming Type II lherzolites. Basal lherzolites and their spatial chemical variations in the northern Fizh block may provide a key for understanding the processes of ridge segmentation and detachment at fast spreading ridges.

DOI： 10.1029/2001GC000232

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The Horoman peridotite complex exhibits a conspicuous layered structure. It is found, from the geological and petrological survey, that the pattern of layering has three characteristics: symmetry, asymmetry (subtly collapsed symmetry) and scale invariance. Especially, symmetric and asymmetric patterns clearly recognized in the sequence of mafic layers at the Northern ridge of Apoi-dake peak, and at the Western ridge of Bozu-yama peak are noticeable. We present a simple mathematical model describing stretching (thinning) and folding during deformation that accounts for the three characteristics. The model quantitatively reproduces the slope in cumulative frequency distribution of the width of mafic layers and indicates that the frequency distribution is strongly influenced by the spatial strain contrast. Applying the model result to the observational data for mafic layers, it is found that the strain contrast approximately ranges several to 10 times between regions with the highest and the lowest strain rates. © 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0012-821X(00)00382-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

Re-Os isotopic data for 20 samples from a well-characterized 140 m section across a layered sequence, ranging from plagioclase lherzolite through lherzolite to harzburgite, of the Horoman peridotite show: (1) a range in Os-187/Os-188 ratios (from 0.1158 to 0.1283) similar to that reported for other peridotitic massifs, thereby suggesting that the processes responsible for the Re-Os isotopic variation at the meter-scale and the whole-massif scale are similar; (2) that the Os isotopic ratio is controlled by the Re content through radiogenic ingrowth over a period of similar to0.9 Gy. The ultramafic and some of the mafic rocks (Type I layers)from the Horoman massif define an 'apparent age' of 1.12 +/- 0.24 Ga in the Re-OS isochron diagram, within error of the previously reported age of 833 +/- 78 Ma based on Sm-Nd isotopes. Although the Re-Os isotopic data do not define an isochron, the consistency of the similar to 900 Ma age defined by both isotopic systems suggests that this age has a geologic meaning and that mafic (Type I layers) and ultramafic rocks are genetically related, A plausible explanation for the genetic relationship between the mafic and ultramafic rocks, the meter-scale compositional variations from lherzolite to plagioclase lheriolite, the suprachondritic Re-187/Os-188 ratios in some fertile peridotites, and the oldest RE depletion model age of similar to1.86 Ga obtained for Horoman rocks is a refertilization process involving reaction of a mid-ocean ridge basalt-like magma with depleted lithospheric mantle at similar to 900 Ma.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Whole rock major and trace element abundances of the Horoman peridotites were used to understand processes forming lithological and compositional variations in the upper mantle. Similar to other orogenic peridotites, Horoman peridotites range from fertile lherzolites (3 to 4% Al(2)O(3) and CaO) to depleted harzburgites (similar to 0.5% Al(2)O(3) and CaO). Abundances of major oxides and compatible to moderately incompatible elements vary systematically with variations in MgO content. Such trends are commonly interpreted as indicating that the peridotites formed as residues from varying degrees of partial melting. The fertile end of these trends coincides with estimates of primitive mantle composition. Because of a mismatch between experimental melting trends for spinel peridotite, especially the Na(2)O-MgO trend, the compositional variations of Horoman peridotites are not consistent with formation as residues from partial melting of spinel peridotite. Non-Linear trends in minor and trace element versus major element abundance diagrams also preclude a two-component mixing model. Recent melting experiments on garnet peridotite demonstrate that at 3 GPa the near-solidus peridotite has a large amount of subcalcic clinopyroxene (ca. 27%) coexisting with small amount of garnet (ca. 2%). Residues from polybaric melting of such garnet peridotite are consistent with the abundance variations of major and moderately incompatible elements, such as Na and heavy rare-earth elements, in the Horoman peridotites. A similar conclusion is applicable to other orogenic peridotites such as the Ronda peridotite because their major element compositional variations are similar to the Horoman peridotite. Copyright (C) 2000 Elsevier Science Ltd.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本地質学会  

The following four brachiopod species are newly recognized from the Okutadami area, central Japan : Anemonaria sp., Yokovlevia sp., Spiriferella sp. and Attenuatella sp. These brachiopods indicate a late Middle Permian (Midian) in age. The Okutadami fauna, consisting of both the Boreal- and Bipolar-type genera, is the first documented Permian Boreal brachiopod fauna in Japan. The occurrence of the Boreal brachiopod fauna from the Okutadami area suggests that the fossil-bearing rocks were formed at the northernmost part of Japan in the Permian time.

DOI： 10.5575/geosoc.105.729

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The concentrations of the platinum-group elements (PGE) Ir, Ru, Pt and Pd were determined in 11 abyssal peridotites from ODP Sites 895 and 920, as well in six ultramafic rocks from the Horoman peridotite body, Japan, which is generally thought to represent former asthenospheric mantle. Individual oceanic peridotites from ODP drill cores are characterized by variable absolute and relative PGE abundances, but the average PGE concentrations of both ODP suites are very similar. This indicates that the distribution of the noble metals in the mantle is characterized by small-scale heterogeneity and large-scale homogeneity. The mean Ru/Ir and Pt/Ir ratios of all ODP peridotites are within 15% and 3%, respectively, of CI-chondritic values. These results are consistent with models that advocate that a late veneer of chondritic material provided the present PGE budget of the silicate Earth. The data are not reconcilable with the addition of a significant amount of differentiated outer core material to the upper mantle. Furthermore, the results of petrogenetic model calculations indicate that the addition of sulfides derived from percolating magmas may be responsible for the variable and generally suprachondritic Pd/Ir ratios observed in abyssal peridotites. Ultramafic rocks from the Horoman peridotite have PGE signatures distinct from abyssal peridotites: Pt/Ir and Pd/Ir are correlated with lithophile element concentrations such that the most fertile Iherzolites are characterized by non-primitive PGE ratios. This indicates that processes more complex than simple in-situ melt extraction are required to produce the geochemical systematics, if the Horoman peridotite formed from asthenospheric mantle with chondritic relative PGE abundances. In this case, the PGE results can be explained by melt depletion accompanied or followed by mixing of depleted residues with sulfides, with or without the addition of basaltic melt. (C) 1999 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press  

Two major types of mafic granulite layers occur within the Horoman peridotite, an 8 km x 10 km x 3 km orogenic lherzolite exposed in the high-T and low-P Hidaka metamorphic belt of Hokkaido, Japan. The mineral assemblages and textures of these layers reflect subsolidus reactions occurring during uplift from the upper mantle to the crust. Nevertheless, their whole-rock compositions can be used to infer the primary mineralogy of these layers, and a genetic relationship to melts geochemically similar to mid-ocean ridge basalts (MORB). The intralayer compositional variation of Type I layers (Al-Ti augite type mafic granulites) shows that the centers formed as garnet clinopyroxenites in equilibrium with an incompatible element depleted melt that crystallized to form the margins. In contrast, the Type II layers (Cr-diopside type mafic granulites) formed at relatively shallow depths and are much older, ~830 Ma, than the Type I garnet pyroxenites, which formed at ~80 Ma. The temporal sequence supports the hypothesis that the Horoman peridotite represents shallow MORB-related oceanic mantle that had subsided to deeper mantle depths before crustal emplacement.

DOI： 10.1093/petroj/40.12.1827

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier  

In order to investigate the mechanical properties of carbon nanotubes, dynamic shock wave pressures (≤50 GPa) were applied on arc-discharge-generated carbon nanotubes containing polyhedral nanoparticles. High-resolution transmission electron microscopy (HRTEM) studies of the shock-recovered samples reveal that: (i) layers of the outer shells of the nanotubes break and transform into curled graphitic structures and (ii) the inner tube walls and bulk material display structural defects. Further X-ray powder diffraction and HRTEM analyses exhibit the presence of diamond nanocrystals which are produced after the shock-wave compression of polyhedral particles (present in the starting material).

DOI： 10.1016/S0009-2614(98)00226-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Institute of Physics Inc.  

A radiation pyrometer in conjunction with a two-stage light gas gun has been used to measure shock temperatures of soda-lime glass in the pressure range 54-109 GPa. This pyrometer consists of two parts, i.e., an optical multichannel analyzer which measures the radiation spectrum over the visible range (∼450 nm window) and a four-channel photomultiplier tube system which records the time-varying behavior of shock temperatures. The measured radiation spectra are compared with the Planck function to estimate the shock temperatures and emissivities. Obtained spectra are well fit by the Planck function with moderate emissivities, indicating that relatively homogeneous thermal radiation is the main component of radiation. Obtained shock temperatures range from 2800 (100) to 5700 (300) K and they seem to represent shock temperatures of liquefied soda-lime glass (melt). The Hugoniot is well described by a linear relation, us = 0.14(21) + 1.92(5)up km/s. It is deduced that the radiation from liquids under shock compression, in contrast to the radiation from solids under shock compression, is more thermal and fits the Planck function well, even at lower temperatures. This is because the radiation spectrum of solids under compression often shows nonthermal radiation due to heterogeneous deformation, while the radiation spectrum of liquids under compression could not have such a nonthermal component. © 1995 American Institute of Physics.

DOI： 10.1063/1.366889

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Netherlands  

A series of recovery experiments was conducted using a propellant single-stage gun on starting materials of both α-SiC and β-S\\C. X-ray examination on the recovered samples indicated that obvious polytype transformations among 3C, 6H, and 15R took place. To the α-SiC starting material, 15R tends to increase and 6H tends to decrease, while a small amount of α-SiC form transforms to 3C type, along with increasing the shock temperature and pressure. X-ray diffraction analysis showed that the β-SiC polytype is transformed into rhombohedral forms. From results of both types of SiC samples, rhombohedral polytypes seem to be the favored shock modification. The effects of shock pressure and shock temperature and their heterogeneous distribution on these polytype transitions are discussed in detail. Analysis showed that these polytype transitions resulted from the stacking sequence changes of SiC atom layers. © 1998 Kluwer Academic Publishers.

DOI： 10.1023/A:1004482922441

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Processes occurring in the Earth's upper mantle are important in controlling evolution of the crust-mantle system. The effects of multiple igneous and metamorphic processes are recorded in upper-mantle peridotites, such as the Horoman Peridotite in Hokkaido, Japan. Geochemical studies of these peridotites and their minerals, combined with determination of the spatial geochemical variations, can be used to understand the sequence of processes that affected the peridotite. In this study we show that compositional zoning patterns of major and trace elements in clinopyroxene porphyroclasts reflect a sub-solidus, closed-system transition from garnet peridotite, equilibrated at 20-24 kbar and 1040-1160 degrees C, to plagioclase peridotite equilibrated at similar to 7 kbar and 850-950 degrees C. The preservation of compositionally zoned pyroxenes indicates that this transition was a relatively recent process that probably occurred as the Horoman Peridotite was emplaced into the Hidaka metamorphic belt, The clinopyroxene compositions also show that: (I) harzburgites and lherzolites reacted with a fluid/melt that resulted in relative enrichment of highly incompatible elements, such as the light rare-earth elements; and (2) this enrichment process preceded the sub-solidus breakdown of garnet.

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Publishing type：Research paper (scientific journal)  

DOI： 10.2138/am-1996-5-622

Scopus

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

THE segregation of melts from the Earth's upper mantle into the crust is an important process in the chemical evolution of the crust-mantle system. The processes of melt formation and migration in the upper mantle are inadequately understood, but some important characteristics of these processes can be inferred from upper-mantle rocks exposed at the Earth's surface. The Horoman peridotite body in northern Japan is a layered upper-mantle rock. The major-element compositions of the layers are consistent with their formation as residues from varying extents of melting; however, abundances of rare-earth elements (REE) require additional processes to have occurred1, such as post-melting enrichment (metasomatism) resulting from reaction with a migrating fluid phase. We report here that chondrite-normalized REE patterns in clinopyroxenes show abrupt changes in slope, which vary with stratigraphic position and rock type. These data can be modelled by chromatographic fractionation as melts migrated through and interacted with peridotite, creating compositional heterogeneities in the upper mantle. In the Horoman peridotite these heterogeneities occur on a scale length of tens of metres.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

The lower zone, similar to 2 km in thickness, of the similar to 8 km x 10 km Horoman peridotite is layered with several repetitive sequences of harzburgite-lherzolite-plagioclase lherzolite. Major and trace element abundances were determined in seven whole rocks and their minerals from a 200-m section that ranges from plagioclase lherzolite to harzburgite. The clinopyroxene- and plagioclase-rich (similar to 15-20%) lherzolites contain similar to 3-5-4% Al2O3, similar to 3-3-5% CaO, olivines of similar to Fo(89), and they have a relative light REE depletion, [(LREE)(N) similar to 06 and (HREE)(N) similar to 2 (N = chondrite-normalized)]. The variations in bulk-rock major element content and mineral composition from plagioclase lherzolite to harzburgite are consistent with control by melt-solid segregation. For example, a simple model of mixing between harzburgite, residual from partial melting, and a melt can explain most of the whole-rock compositional variations; i.e., abundances of major elements, compatible trace elements, and some incompatible trace elements. However, the whole-rock harzburgites and their constituent clinopyroxenes have anomalously high LREE/HREE ratios. These data require a more complex mantle process such as relative LREE enrichment caused by metasomatizing fluids. Evidence for a metasomatic process is the common occurrence of secondary phlogopite in some harzburgite layers (Arai & Takahashi, 1989).

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.95.241

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Other Link： https://jlc.jst.go.jp/DN/JALC/00224918327?from=CiNii

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Other Link： http://hdl.handle.net/10191/32236

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

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Event date： 1997

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Event date： 1995

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Event date： 1992

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Language：Japanese   Presentation type：Oral presentation (keynote)  

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Venue：Washington, D.C.  

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Venue：Washington D.C.  

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