Direct 40Ar/39Ar dating of Late Ordovician and Silurian brittle faulting in the southwestern Norwegian Caledonides          下载免费PDF全文

Thomas Scheiber  Giulio Viola  Camilla Maya Wilkinson  Morgan Ganerød  Øyvind Skår  Deta Gasser 《地学学报》2016,28(5):374-382

Structural data as well as U–Pb zircon and ⁴⁰Ar/³⁹Ar biotite and muscovite ages were collected from the Rolvsnes granodiorite in western Norway. The granodiorite intruded at c. 466 Ma, cooled quickly and escaped later viscous deformation. Brittle top‐to‐the‐NNW thrust faults (Set I) and WNW–ESE striking dextral strike‐slip faults (Set II) formed in a NNW–SSE transpressional regime. ⁴⁰Ar/³⁹Ar dating of synkinematic mica from both sets reveals a c. 450 Ma (Late Ordovician) age of faulting, which constrains early‐Caledonian brittle deformation. Set I and II faults are overprinted by a set of lower‐grade, variably oriented chlorite‐ and epidote‐coated faults (Set III) constraining WNW–ESE shortening. A lamprophyric dyke oriented compatibly with this stress field intruded at c. 435 Ma (Silurian), indicating that Set III formed at the onset of the Scandian Baltica–Laurentia collision. The preservation of Caledonian brittle structures indicates that the Rolvsnes granodiorite occupied a high tectonic level throughout the Caledonian orogeny.  相似文献   

Palynological characteristics of Kazakhstan Province of Carboniferous Euramerican Region     

Maya V． Oshurkova 《世界地质(英文版)》2012,15(1):1-12

The paper presents results of palynological studies of the coal-bearing Carboniferous in Central Ka-zakhstan.A quantitative dynamics of major genera of miospores reflects an overall succession of the Carbonifer-ous miospore assemblages.Viséan Serpukhovian assemblages are dominanted by Lophozonotriletes fuscatus,Ac-anthozonotriletes cristifer,A.inclusus,Punctatisporites glabratus,Crassispora ignorata,C.scrupea,Cyclobacu-lisporites trichacanthus,Lycospora breviapiculata,L.echinata and Vallatisporites decrescens.Rare Punctatis-porites bertschoguriensis,Stenozonotriletes marginellus,Vallatisporites appilicatus,Verrucosisporites scrobiculatus,Reticulatisporites cancellatus,Granulatisporites arcuatus are recorded,which are not found in assemblages from overlying sediments.Bashkirian--Moscovian assemblages are dominated by Lycospora subtriquetra,L.pusilla,Vallatisporites ciliaris,Apiculatisporis mollis,Cyclogranisporites testiculatus,Calamospora microrugosa,Schopfi-pollenites principalis,Psilohymena psiloptera,Florinites grandis and Granulatisporites piroformis miospores.Cris-tatisporites latispinus,Angulisporites didymus,Thymospora obscura and Torispora securis are also present,as well as single Apiculatisporis curvispinus,Raistrickia inordinata,Marsupipollenites retroflexus,Entylissa caperata,Potonieisporites grandis and Cordaitina sp.A similar succession of miospore assemblages is recorded in the Carboniferous deposits of Europe and North America,which allows carrying out correlations,despite an endemic characters of many species of Paleozoic miospores from the coal-bearing Carboniferous of the Kazakh-stan Province in the Euramerian Paleofloristic Region.  相似文献   

Spatial variations in chemical compositions along Langtang–Narayani river system in central Nepal     

Maya P. Bhatt  Toshiyuki Masuzawa  Mineko Yamamoto  Kevin H. Gardner 《Environmental Geology》2009,57(3):557-569

Surface water samples were collected from Langtang Lirung glacier outlet point to the Narayani river system in central Nepal in order to investigate the role of elevation in the variation of chemistry along the drainage networks. The chemistry of Langtang–Narayani river system was dominated by sulfide oxidation coupled with carbonate dissolution and weathering of silicate minerals. Calcium and magnesium concentrations were relatively higher than other cations and the sum of both species strongly correlated with alkalinity, supporting the dissolution of carbonate and dolomite as the dominant source for these ions. Aluminosilicate minerals primarily as albite and anorthite appeared as dominant silicate minerals within the drainage basin. Bisiallitization was the dominant type of weathering within the entire drainage system. Hydrogen ion concentration was lower in the low elevation sites than in high elevation sites reflecting the more consumption of carbon dioxide in the low elevation sites due to enhanced chemical weathering rates. Furthermore, major solutes like sum of base cations, silicon as well as alkalinity increased in concentration in the lower elevation sites. All regulating factors appeared to be directly related to elevation and hence elevation appeared to be the prime factor for the variation in chemical species along the Langtang–Narayani river system. Toshiyuki Masuzawa: deceased.  相似文献   

Regolith breccia Northwest Africa 7533: Mineralogy and petrology with implications for early Mars          下载免费PDF全文

Roger H. Hewins  Brigitte Zanda  Munir Humayun  Alexander Nemchin  Jean‐Pierre Lorand  Sylvain Pont  Damien Deldicque  Jeremy J. Bellucci  Pierre Beck  Hugues Leroux  Maya Marinova  Laurent Remusat  Christa Göpel  Eric Lewin  Marion Grange  Allen Kennedy  Martin J. Whitehouse 《Meteoritics & planetary science》2017,52(1):89-124

Northwest Africa 7533, a polymict Martian breccia, consists of fine‐grained clast‐laden melt particles and microcrystalline matrix. While both melt and matrix contain medium‐grained noritic‐monzonitic material and crystal clasts, the matrix also contains lithic clasts with zoned pigeonite and augite plus two feldspars, microbasaltic clasts, vitrophyric and microcrystalline spherules, and shards. The clast‐laden melt rocks contain clump‐like aggregates of orthopyroxene surrounded by aureoles of plagioclase. Some shards of vesicular melt rocks resemble the pyroxene‐plagioclase clump‐aureole structures. Submicron size matrix grains show some triple junctions, but most are irregular with high intergranular porosity. The noritic‐monzonitic rocks contain exsolved pyroxenes and perthitic intergrowths, and cooled more slowly than rocks with zoned‐pyroxene or fine grain size. Noritic material contains orthopyroxene or inverted pigeonite, augite, calcic to intermediate plagioclase, and chromite to Cr‐bearing magnetite; monzonitic clasts contain augite, sodic plagioclase, K feldspar, Ti‐bearing magnetite, ilmenite, chlorapatite, and zircon. These feldspathic rocks show similarities to some rocks at Gale Crater like Black Trout, Mara, and Jake M. The most magnesian orthopyroxene clasts are close to ALH 84001 orthopyroxene in composition. All these materials are enriched in siderophile elements, indicating impact melting and incorporation of a projectile component, except for Ni‐poor pyroxene clasts which are from pristine rocks. Clast‐laden melt rocks, spherules, shards, and siderophile element contents indicate formation of NWA 7533 as a regolith breccia. The zircons, mainly derived from monzonitic (melt) rocks, crystallized at 4.43 ± 0.03 Ga (Humayun et al. 2013 ) and a ¹⁴⁷Sm‐¹⁴³Nd isochron for NWA 7034 yielding 4.42 ± 0.07 Ga (Nyquist et al. 2016 ) defines the crystallization age of all its igneous portions. The zircon from the monzonitic rocks has a higher Δ¹⁷O than other Martian meteorites explained in part by assimilation of regolith materials enriched during surface alteration (Nemchin et al. 2014 ). This record of protolith interaction with atmosphere‐hydrosphere during regolith formation before melting demonstrates a thin atmosphere, a wet early surface environment on Mars, and an evolved crust likely to have contaminated younger extrusive rocks. The latest events recorded when the breccia was on Mars are resetting of apatite, much feldspar and some zircons at 1.35–1.4 Ga (Bellucci et al. 2015 ), and formation of Ni‐bearing pyrite veins during or shortly after this disturbance (Lorand et al. 2015 ).  相似文献   

The effect of mining and related activities on the sediment–trace element geochemistry of Lake Coeur d'Alene,Idaho, USA. Part III. Downstream effects: the Spokane River Basin     

Cecile A. Grosbois  Arthur J. Horowitz  James J. Smith  Kent A. Elrick 《水文研究》2001,15(5):855-875

During 1998/1999, surface and subsurface sediment samples were collected along the entire length of the Spokane River from its outlet at the northern end of Lake Coeur d'Alene (CDA), Idaho, to Lake Roosevelt on the Columbia River, Washington. The study was conducted to determine if the trace element enrichments observed in Lake CDA and on the floodplain and in the CDA River extend through the Spokane River Basin (SRB). As in Lake CDA, surface sediments in the SRB are enriched in Pb, Zn, As, Cd, Sb and Hg relative to local background levels. Pb, Cd and Zn are the most elevated, with maximum enrichment occurring in the upper Spokane River in close proximity to Lake CDA. On average, enrichment decreases downstream, apparently reflecting both increased distance from the inferred source (the CDA River Basin), as well as increased dilution by locally derived but unenriched materials. Only Cd and Zn display marked enrichment throughout the SRB. Pb, Zn and Cd seem to be associated mainly with an operationally defined iron oxide phase, whereas the majority of the As and Sb seem to be matrix‐held. Subsurface sediments also are enriched in Pb, Zn, As, Cd, Sb and Hg relative to background levels. Based on ¹³⁷Cs and excess ²¹⁰Pb dating, trace element enrichment began in the middle part of the SRB (Long Lake) between 1900 and 1920. This is contemporaneous with similar enrichments observed in Lake CDA, as well as the completion of Long Lake Dam (1913). In the most downstream part of the basin (Spokane River Arm of Lake Roosevelt), enrichment began substantially later, between 1930 and 1940. The temporal difference in enrichment between Long Lake and the River Arm may reflect the latter's greater distance from the presumed source of the enrichment (the CDA River Basin); however, the difference is more likely the result of the completion of Grand Coulee Dam (1934–1941), which formed Lake Roosevelt, backed up the Spokane River, and increased water levels in the River Arm by about 30 m.  相似文献   

Lower mantle diamonds from Rio Soriso (Juina area,Mato Grosso,Brazil)   总被引：4，自引：2，他引：2  

Patrick?C.?Hayman  Maya?G.?KopylovaEmail author  Felix?V.?Kaminsky 《Contributions to Mineralogy and Petrology》2005,149(4):430-445

The morphology, colour, fluorescence, cathodoluminescence, nitrogen content and aggregation state, internal structure and mineral inclusions have been studied for 69 alluvial diamonds from the Rio Soriso (Juina area, Mato Grosso State, Brazil). Nitrogen in most diamonds (53%) is fully aggregated as B centres, but there is also a large proportion of N-free stones (38%). A strong positive correlation between nitrogen and IR-active hydrogen concentrations is observed. The diamonds contain (in order of decreasing abundance) ferropericlase, CaSi-perovskite, magnetite, MgSi-perovskite, pyrrhotite, olivine, SiO₂, perovskite, tetragonal almandine-pyrope phase and some other minerals represented by single grains. The Rio Soriso diamond suite is subdivided into several subpopulations that originated in upper and lower mantle of ultramafic and mafic compositions, with the largest subgroup forming in the ultramafic lower mantle. Analysed ferropericlase grains are enriched in Fe (Mg#=0.43–0.89), which is ascribed to their origin in the lowermost mantle. The Juina kimberlites may be unique in sampling the material from depths below 1,700 km that ascended in a plume formed at the core–mantle boundary.Electronic Supplementary Material  Supplementary material is available for this article at

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Maya G. KopylovaEmail: Phone: +1-604-8220865Fax: +1-604-8226088

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Sequence and eruptive style of the 1783 eruption of Asama Volcano, central Japan: a case study of an andesitic explosive eruption generating fountain-fed lava flow, pumice fall, scoria flow and forming a cone     

Maya Yasui  Takehiro Koyaguchi 《Bulletin of Volcanology》2004,66(3):243-262

The 3-month long eruption of Asama volcano in 1783 produced andesitic pumice falls, pyroclastic flows, lava flows, and constructed a cone. It is divided into six episodes on the basis of waxing and waning inferred from records made during the eruption. Episodes 1 to 4 were intermittent Vulcanian or Plinian eruptions, which generated several pumice fall deposits. The frequency and intensity of the eruption increased dramatically in episode 5, which started on 2 August, and culminated in a final phase that began on the night of 4 August, lasting for 15 h. This climactic phase is further divided into two subphases. The first subphase is characterized by generation of a pumice fall, whereas the second one is characterized by abundant pyroclastic flows. Stratigraphic relationships suggest that rapid growth of a cone and the generation of lava flows occurred simultaneously with the generation of both pumice falls and pyroclastic flows. The volumes of the ejecta during the first and second subphases are 0.21 km³ (DRE) and 0.27 km³ (DRE), respectively. The proportions of the different eruptive products are lava: cone: pumice fall=84:11:5 in the first subphase and lava: cone: pyroclastic flow=42:2:56 in the second subphase. The lava flows in this eruption consist of three flow units (L1, L2, and L3) and they characteristically possess abundant broken phenocrysts, and show extensive "welding" texture. These features, as well as ghost pyroclastic textures on the surface, indicate that the lava was a fountain-fed clastogenic lava. A high discharge rate for the lava flow (up to 10⁶ kg/s) may also suggest that the lava was initially explosively ejected from the conduit. The petrology of the juvenile materials indicates binary mixing of an andesitic magma and a crystal-rich dacitic magma. The mixing ratio changed with time; the dacitic component is dominant in the pyroclasts of the first subphase of the climactic phase, while the proportion of the andesitic component increases in the pyroclasts of the second subphase. The compositions of the lava flows vary from one flow unit to another; L1 and L3 have almost identical compositions to those of pyroclasts of the first and second subphases, respectively, while L2 has an intermediate composition, suggesting that the pyroclasts of the first and second subphases were the source of the lava flows, and were partly homogenized during flow. The complex features of this eruption can be explained by rapid deposition of coarse pyroclasts near the vent and the subsequent flowage of clastogenic lavas which were accompanied by a high eruption plume generating pumice falls and/or pyroclastic flows.Editorial responsibility: T. Druitt  相似文献   

A Method for Simultaneous In Situ Measurement in the Vadose Zone of Field-Saturated Hydraulic Conductivity, Sorptivity and the Conductivity-Pressure Head Relationship   总被引：3，自引：0，他引：3  

W. Daniel Reynolds  David E. Elrick 《Ground Water Monitoring & Remediation》1986,6(1):84-95

The Guelph Permeameter (GP) method for simultaneous, in situ measurement in the vadose zone of field-saturated hydraulic conductivity (K_fS), sorptivity (S) and the conductivity-pressure head relationship [K(Ψ)] is described and discussed.
The method involves measuring the steady-state liquid recharge, Q, necessary to maintain a constant depth of water, H, in an uncased, cylindrical well of radius, a, finished above the water table. An "in-hole" Mariotte bottle device is used to maintain H and to measure Q.
Step-by-step procedures with example calculations are given for obtaining K_fS, S and K( Ψ ). Techniques for assessing the results are also given.
Although detailed field verification of the GP method is still incomplete, the studies conducted so far are quite encouraging.
Theoretical and practical advantages afforded by the GP method make it a desirable and cost-effective means for in situ measurement of K_fs, S and K( Ψ ), which are three of the most important parameters governing the flow of water and other wetting liquids in the vadose zone.  相似文献   

Geochemical appraisal of palaeovegetation and climate oscillation in the Late Miocene of Western Bulgaria     

Maya Stefanova  Dimiter A. IvanovTorsten Utescher 《Organic Geochemistry》2011,42(11):1363-1374

Palaeobotanical methods and geochemical techniques were used to assess plant contribution and palaeoenvironment for the Staniantsi Basin, Bulgaria. The aim was to connect palaeovegetation change and climate oscillation based on pollen and statistical analysis with organic geochemical proxies for a Late Miocene lacustrine to paludial sedimentary succession.Three samples from lignite/marl cycles were studied. The biomarker assemblage and bulk chemical data indicated that gymnosperms were not important in the palaeomire. The presence of des-A-triterpenoids, 17,21-seco-triterpenoids, hopanes, a high content of a D-ring monoaromatic hopane, and aromatized triterpenoids suggested that photochemical and microbial processes significantly contributed to the alteration of the organic matter (OM). A prolonged period of high water table and severe mechanical destruction promoted microbial activity prior to burial and enhanced decay. A geochemical appraisal of short term climate oscillation (ca. 21.7 kyr) was attempted within the limitations of the small number of samples studied. The cycles are expressed as lignite/marl-clay layers combined with cyclic changes in swamp vegetation related to cyclic changes in groundwater level and inundation of the basin. In periods of low water level (swamp phase) lignite accumulation took place. Preliminary results for selected samples suggest that the oscillation may be reflected in the content of friedelin vs. possible degradation products. The ratio of a chromatographic peak tentatively assigned as A-norfriedel-8-en-10-one to friedelin is proposed as a means of detecting short term environmental cycles, where values <1 represent the swamp phase and those >1 reflect periods of inundation. However, time-series analysis using densely sampled lignite-clay layer oscillations are needed to confirm the value of this biomarker ratio for environmental reconstruction.  相似文献   

Evaluation of Containment Performance from Viewpoints of Diffusion and Dispersion for Impervious Structures at Coastal Landfill Sites     

Shinya Inazumi  Maya Manabe  Ken-ichi Shishido 《Geotechnical and Geological Engineering》2017,35(5):2191-2203

The containment performance of impervious structures is considered the most important performance, which the toxic substances are enclosed in coastal landfill sites. The containment performance is evaluated generally by the hydraulic conductivity and the thickness of impervious structures to focus on an advection. However, the leakage of toxic substances is affected by a diffusion and a dispersion. The diffusion and the dispersion are considered to be easily distinguished on the impervious structure which has the low-hydraulic conductivity. Such phenomena should be considered due to evaluate the containment performance. This is because to improve the containment performance and comprehend leakage of the toxic substances. The containment performance is evaluated from the viewpoint of the diffusion and the dispersion in this research. Concretely, the influence which the toxic substances leaks from impervious structures on the diffusion and the dispersion is evaluated by the infiltration and advection–dispersion analysis on steel-made side impervious walls. In other word, The relation between the leaking amount of toxic substances and coefficient of molecular diffusion, the relation between the travel time or the flow velocity and the leaking amount and the change in the water-level difference are considered respectively. So, the leaking amount which is influenced by a diffusion and a dispersion is considered. Consideration about to secure the containment performance of impervious structure which is restrained leakage by a diffusion and a dispersion.  相似文献