A review of volatile compounds in tektites,and carbon content and isotopic composition of moldavite glass     

Karel ŽÁK  Roman SKÁLA  Zdeněk ŘANDA  Jiří MIZERA 《Meteoritics & planetary science》2012,47(6):1010-1028

Abstract– Tektites, natural silica‐rich glasses produced during impact events, commonly contain bubbles. The paper reviews published data on pressure and composition of a gas phase contained in the tektite bubbles and data on other volatile compounds which can be released from tektites by either high‐temperature melting or by crushing or milling under vacuum. Gas extraction from tektites using high‐temperature melting generally produced higher gas yield and different gas composition than the low‐temperature extraction using crushing or milling under vacuum. The high‐temperature extraction obviously releases volatiles not only from the bubbles, but also volatile compounds contained directly in the glass. Moreover, the gas composition can be modified by reactions between the released gases and the glass melt. Published data indicate that besides CO₂ and/or CO in the bubbles, another carbon reservoir is present directly in the tektite glass. To clarify the problem of carbon content and carbon isotopic composition of the tektite glass, three samples from the Central European tektite strewn field—moldavites—were analyzed. The samples contained only 35–41 ppm C with δ¹³C values in the range from ?28.5 to ?29.9‰ VPDB. This indicates that terrestrial organic matter was a dominant carbon source during moldavite formation.  相似文献   

A local spatial decision support system for developing countries based on MCA,fuzzy sets and OWA – case study of a municipality in Cuba     

Ricardo DELGADO TELLEZ  Ershun ZHONG  Yang ZUHU  Arisleydis PEÑA DE LA CRUZ 《地球空间信息科学学报》2013,16(2):120-129

This paper presents a Spatial Decision Support System for local governments of developing countries. It allows municipality government, enterprises, scientific community and civil society to address decision problems using GIS. The framework is supported by four modules of information technologies: Environmental Decision Support Database, Data Manipulation, Decision Support, and Mapping. A case study is presented covering the implementation of this framework in one municipality of Cuba. An example of land suitability planning for coconut crops is used to evaluate the system performance and usability. Results show local municipalities are able to use this framework to solve local decision problems using state of the art decision making even with low infrastructure development.  相似文献   

Chronological and palaeoenvironmental context of human occupations at the Buendía rockshelter (Central Spain) during the late Upper Pleistocene in inland Iberia          下载免费PDF全文

IGNACIO DE LA TORRE  ROSA MARÍA ALBERT  ETHEL ALLUÉ  ESTEBAN ÁLVAREZ‐FERNÁNDEZ  M.TERESA APARICIO  ADRIÁN ARROYO  ALFONSO BENITO‐CALVO  MARÍA JOSÉ GIL GARCÍA  ELÍAS LÓPEZ‐ROMERO  NORAH MOLONEY  M. BLANCA RUIZ ZAPATA  PALMIRA SALADIÉ 《第四纪科学杂志》2015,30(4):376-390

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Automicrite in a ‘nummulite bank’ from the Monte Saraceno (Southern Italy): evidence for synsedimentary cementation     

ADRIANO GUIDO  CESARE A. PAPAZZONI  ADELAIDE MASTANDREA  MICHELE MORSILLI  MAURO F. LA RUSSA  FABIO TOSTI  FRANCO RUSSO 《Sedimentology》2011,58(4):878-889

Following introduction of the term ‘nummulite bank’, there has been debate regarding interpretation of these types of deposits as autochthonous (automicrite) or allochthonous (detrital micrite). These banks are made up of large foraminifera and ill‐defined fine‐grained components. The fine‐grained components consist mainly of micrites. The recognition of automicrite has deep implications for the synsedimentary cementation and stabilization of the bank. In order to distinguish between automicrite and detrital micrite, the nanomorphology, geochemistry and organic matter remains in the microfacies of a nummulite bank in the Middle Eocene of Monte Saraceno (Gargano, Southern Italy) were analysed. Optical and scanning electron microscope investigations showed that the micrites have been recrystallized to aggrading microsparite. Epifluorescence observations on selected micrite/microsparite areas with peloidal texture revealed the presence of organic matter. Scanning electron microscope analyses on epifluorescent micrites showed that the microbial peloids have smaller crystal sizes than those in organic matter‐depleted areas. The geochemical characterization of extracted organic matter, performed through the functional group analyses by Fourier transform‐infrared spectroscopy, shows strong prevalence of the aromatic fraction over the aliphatic and carboxylic ones. These characteristics of organic compounds indicate both their thermal maturation and their likely derivation from degradation of bacterial communities. The local presence of peloidal anti‐gravity textures, bright epifluorescence and organic molecules in clotted peloidal areas suggest that the metabolic activity of microbial communities could have induced precipitation of these micrites and, consequently, the syndepositional cementation of the nummulite bank. This type of cementation can rapidly stabilize sediments and promote the depositional bank geometry.  相似文献   

SHORT COMMUNICATION THE USE OF TOPOLOGICAL MODELS IN ANALYTICAL CHEMISTRY     

M.DELAGUARDIA  J.L.CARRIóN  M.V.GALDú 《地理学报(英文版)》1988,(Z1)

In the present paper,the possible analytical applications of two topological models,the DARC modeland the group contribution model,are discussed.Both models are applied to obtain calibration laws,which relate UV and IR characteristics with the chemical structure of ethylene oxide condensates.The group contribution model is also applied to determine the contribution of each part of thedifferent compounds involved in a chemical interaction process,having established the sensitizationparameters of benzodiazepines and anionic surfactants from the micellar enhancement fluorescence.  相似文献   

The 410,000 year terrestrial age of eucrite Río Cuarto 001     

Jonathan LEVINE  Andrés ARAZI  Thomas FAESTERMANN  Jorge O. FERNáNDEZ NIELLO  Gunther KORSCHINEK  Ana María LA GAMMA  Agustín NEGRI  Georg RUGEL  Peter STEIER  Anton WALLNER 《Meteoritics & planetary science》2008,43(4):805-813

Abstract— We have measured a surprisingly long terrestrial age of 410,000 ±_45,00^20,000 yr (410 ±₂₀⁴⁵ka) for basaltic eucrite Río Cuarto 001 using accelerator mass spectrometry of ²⁶Al, ³⁶Cl, and ⁴¹Ca. Though many meteorites are known to have survived for tens or hundreds of ka in Antarctica or hot deserts, the mean annual precipitation of 815 mm in Río Cuarto, Cordoba Province, Argentina, makes the long survival of this meteorite remarkable. We propose two explanations for the exceptional preservation of Río Cuarto 001. First, the meteorite contains only trace amounts of metal, so the weathering and oxidation of metallic Fe, which commonly destroys chondrites, is ineffective in this case. Second, the meteorite was found in a relatively young deflation basin, and may have been exhumed only recently from beneath a protective layer of soil. Insofar as the survival on Earth of Río Cuarto 001 is due to environmental factors, there may be other meteorites with comparably long terrestrial ages still to be discovered in the vicinity.  相似文献   

Aqueous fluids and hydrous melts in high-pressure and ultra-high pressure rocks: Implications for element transfer in subduction zones   总被引：10，自引：0，他引：10  

Jrg Hermann  Carl Spandler  Alistair Hack  Andrey V. Korsakov 《Lithos》2006,92(3-4):399-417

High-pressure (HP) and ultra-high pressure (UHP) terranes are excellent natural laboratories to study subduction-zone processes. In this paper we give a brief theoretical background and we review experimental data and observations in natural rocks that constrain the nature and composition of the fluid phase present in HP and UHP rocks. We argue that a fluid buffered by a solid residue is compositionally well defined and is either an aqueous fluid (total amount of dissolved solids < 30 wt.%) or a hydrous melt (H₂O < 35 wt.%). There is only a small temperature range of approximately 50–100 °C, where transitional solute-rich fluids exist. A review of available experimental data suggest that in felsic rocks the second critical endpoint is situated at 25–35 kbar and  700 °C and hence must be considered in the study of UHP rocks. Despite this, the nature of the fluid phase can be constrained by relating the peak metamorphic conditions of rocks to the position of the wet solidus even if the peak pressure exceeds the pressure where the wet solidus terminates at the second critical endpoint. Transitional solute-rich fluids are expected in UHP terrains (P > 30 kbar) with peak temperatures of about 700 ± 50 °C. At higher temperatures, hydrous granitic melts occur whereas at lower temperatures aqueous fluids coexists with eclogite-facies minerals. This argument is complemented by evidence on the nature of the fluid phase from high-pressure terrains. We show that in the diamond-bearing, high-temperature UHP rocks from the Kokchetav Massif there are not only hydrous felsic melts, but probably also carbonate and sulfide melts present.

Hydrous quartzo-feldspathic melts are mainly produced in high temperature UHP rocks and their composition is relatively well constrained from experiments and natural rocks. In contrast, constraining the composition of aqueous fluids is more problematic. The combined evidence from experiments and natural rocks indicates that aqueous fluids liberated at the blueschist to eclogite facies transition are dilute. They contain only moderate amounts of LILE, Sr and Pb and do not transport significant amounts of key trace elements such as LREE, U and Th. This indicates that there is a decoupling of water and trace element release in subducted oceanic crust and that aqueous fluids are unable to enrich the mantle wedge significantly. Instead we propose that fluid-present melting in the sediments on top of the slab is required to transfer significant amounts of trace elements from the slab to the mantle wedge. For such a process to be efficient, top slab temperature must be at least 700–750 °C at sub-arc depth. Slab melting is likely to be triggered by fluids that derive from dehydration of mafic and ultramafic rocks in colder (deeper) portions of the slab.  相似文献   

ESSAI DE DETERMINATION AUTOMATIQUE DES VITESSES SISMIQUES PAR MESURES ENTRE PUITS*     

P. BOIS  M. LA PORTE  M. LAVERGNE  G. THOMAS 《Geophysical Prospecting》1971,19(1):42-83

Large memory computers create new possibilities for seismic interpretation in well-drilled areas, and more generally in problems involving deep sources. Records obtained by well-to-surface, surface-to-well and/or well-to-well propagation contain a large amount of information, owing to the great number of seismic rays travelling throughout the subsurface. This paper considers two successive steps: — direct case: computation of the first arrival times of seismic rays propagating through a two-dimensional subsurface with given vertical and horizontal velocity variations; — inverse case: computation of a two-dimensional velocity distribution, knowing the travel times of seismic rays through the subsurface. A computer program has been elaborated to solve both direct and inverse problems. There are no difficulties with the direct case; a certain number of uncertainties remain with the inverse case.  相似文献   

Significance of MORB-derived Amphibolites from the Aracena Metamorphic Belt, Southwest Spain   总被引：2，自引：0，他引：2  

CASTRO  ANTONIO; FERNANDEZ  CARLOS; DE LA ROSA  JESUS D.; MORENO-VENTAS  IAKI; ROGERS  GRAEME 《Journal of Petrology》1996,37(2):235-260

The Aracena metamorphic belt, in the southwest Iberian Massif,is characterized by the presence of MORB-derived amphibolitesand continental rocks deformed and metamorphosed during theHercynian orogeny. Geochemical relationships of these amphibolitesindicate the existence of a multiple fractionation process froma set of parental magmas, implying the existence of a multi-chambersystem beneath the ridge where the basalt protolith was extruded.Neodymium isotopic ratios are typical of MORB, and oxygen isotopesindicate that these amphibolites have been derived from theuppermost part of the oceanic crust. Thermal evolution, revealedfrom the study of chemical variations in the amphibole chemistry,is interpreted as resulting from subduction in a low-pressureregime in which the thermal structure of the continental hanging-wallplayed an important role. This continental wall was previouslyheated by subduction of a slab window resulting from migrationof a triple junction along the continental edge during plateconvergence. Three petrologic arguments support this tectonicmodel. These are: (1) the low-pressure inverted metamorphicgradient of amphibolites of the oceanic domain; (2) the high-temperature-low-pressure metamorphism of the continental hanging wall; (3)the early intrusion of boninites into the continental domain. ^*Corresponding author.  相似文献   

LINKING SEDIMENT EXPOSURE WITH EFFECTS: MODELING TECHNIQUES, ORGANIC AVAILABILITY AND UPTAKE     

Xiaoxia LU  Danny REIBLE 《国际泥沙研究》2003,(2)

1 INTRODUCTION Sediments are the ultimate sink for many hydrophobic contaminants and represent biologically important environmental habitats. Exposure of the sediment-associated contaminants is not only influenced by the fate and transport of sediment but also is influenced by a variety of physical, chemical, and biological processes that involve no net movement of sediments. These processes include pore water transport processes such as advection and diffusion, and sediment mixing process…  相似文献