The heat-capacity of ilmenite and phase equilibria in the system Fe-T-O     

Lawrence M. Anovitz  Allan H. Treiman  Eric J. Essene  Bruce S. Hemingway  Edgar F. Westrum  Victor J. Wall  Ramón Burriel  Steven R. Bohlen 《Geochimica et cosmochimica acta》1985,49(10):2027-2040

Low temperature adiabatic calorimetry and high temperature differential scanning calorimetry have been used to measure the heat-capacity of ilmenite (FeTiO₃) from 5 to 1000 K. These measurements yield S₂₉₈⁰ = 108.9 J/(mol · K). Calculations from published experimental data on the reduction of ilmenite yield Δ₂₉₈⁰(I1) = ?1153.9 kJ/(mol · K). These new data, combined with available experimental and thermodynamic data for other phases, have been used to calculate phase equilibria in the system Fe-Ti-O. Calculations for the subsystem Ti-O show that extremely low values of $\text{?O}{}_2$ are necessary to stabilize TiO, the mineral hongquiite reported from the Tao district in China. This mineral may not be TiO, and it should be re-examined for substitution of other elements such as N or C. Consideration of solid-solution models for phases in the system Fe-Ti-O allows derivation of a new thermometer/oxybarometer for assemblages of ferropseudobrookite-pseudobrookite_ss and hematite-ilmenite_ss. Preliminary application of this new thermometer/oxybarometer to lunar and terrestrial lavas gives reasonable estimates of oxygen fugacities, but generally yields subsolidus temperatures, suggesting re-equilibration of one or more phases during cooling.  相似文献   

Rb-Sr evidence for the presence of Ordovician gsranites in the deformed basement of the Badajoz-Córdoba belt,SW Spain     

J. L. García Casquero  N. A. I. M. Boelrijk  J. Chacón  H. N. A. Priem 《International Journal of Earth Sciences》1985,74(2):379-384

A Rb-Sr whole-rock investigation of suites of samples from two orthogneiss bodies in the Almendralejo area of the Oporto-Portalegre-Badajoz-Córdoba belt points to an Ordovician age for the granitic magmatism: about 470 Ma for the Almendralejo Gneiss (peralkaline metagranite) and about 425 Ma for the Ribera del Fresno Gneiss (leucocratic subaluminous metagranite), both with high initial⁸⁷Sr/⁸⁶Sr ratios. This points to a post-Ordovician (Hercynian) age for the metamorphism and tectonic deformation that affected the area, including the gneisses, and rules out the alleged Cadomian or even older age.

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Zusammenfassung Die Rb-Sr-Gesamtgesteinsanalysen von Probeserien zweier orthogneisischer Körper der Almendralejo-Region des Oporto-Portalegre-Badajoz-Córdoba-Gürtels weisen auf ein ordovizisches Alter des granitischen Magmas hin: rund 470 Ma für den Almendralejo-Gneis (peralkaliner Metagranit) und rund 425 Ma für den Ribera del Fresno-Gneis (leukokratischer Metagranit), beide bei einem hohen initialen⁸⁷Sr/⁸⁶Sr. Diese Ergebnisse deuten auf ein post-ordovizisches (herzynisches) Alter der Metamorphose und der tektonischen Deformation hin, die das Gebiet, einschließ-lich des Gneises, beeinflußt haben. Sie schließen ein vermeintliches kadomisches oder älteres Alter aus.

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Résumé Une étude par Rb-Sr sur roche totale de séries d'échantillons de deux massifs d'orthogneiss de la région d'Almendralejo, dans la ceinture Oporto-Portalegre-Badajoz-Cordoue, indique un âge ordovicien pour le magmatisme granitique: environ 470 Ma pour le gneiss d'Almendralejo (métagranite peralcalin) et environ 425 Ma pour le gneiss de Ribera del Fresno (métagranite leucocrate subalumineux), tous deux avec des rapports initiaux⁸⁷Sr/⁸⁶Sr élevés. Ces résultats indiquent un âge post-ordovicien (hercynien) pour le métamorphisme et la déformation tectonique qui ont affecté la région, y compris les gneiss, et éliminent l'hypothèse proposée par ailleurs d'un âge cadomien ou même plus ancien.

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— — — Rb/Sr : 425 -- ( ) 470 ( ) ⁸⁷Sr/⁸⁶Sr . - ( ) , , . , .

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Devonian-Carboniferous unconformity in Argentina and its relation to the Eo-Hercynian orogeny in southern South America     

O. R. López-Gamundí  E. A. Rossello 《International Journal of Earth Sciences》1993,82(1):136-147

The Devonian-Carboniferous contact in southern South America, characterized by a sharp unconformity, has been related to the Late Devonian-Early Carboniferous Eo-Hercynian orogeny. The Calingasta-Uspallata basin of western Argentina and the Sauce-Grande basin (Ventana Foldbelt) of eastern Argentina have been selected to characterize this unconformity. The Eo-Hercynian movements were accompanied in western Argentina by igneous activity related to a Late Devonian—Early Carboniferous magmatic arc mainly exposed today along the Andean Cordillera. This magmatic activity is partly reflected also in eastern Argentina (Ventana Foldbelt), where isotopic dates suggest a thermal event also related to the intrusions present to the west in the North Patagonian Massif and Sierras Pampeanas. The scarcity of Lower Carboniferous deposits in the stratigraphic record of southern South America suggests that the Early Carboniferous was a time interval dominated by uplift and erosion followed by widespread subsidence during the Middle and Late Carboniferous. The origin of the Eo-Hercynian orogeny can be linked with the convergence between the Arequipa Massif, and its southern extension, and the South American continent. Its effects are best represented along the Palaeo-Pacific margin, although distant effects are discernible in the cratonic areas of eastern South America. Correspondence to: O. R. López-Gamundí  相似文献   

Analysis of the complex solar particle event on April 29–30, 1973     

T. Gombosi  J. Kóta  A. J. Somogyi  V. G. Kurt  B. M. Kuzhevskii  Yu. I. Logachev 《Solar physics》1977,54(2):441-456

Based on the data of the high-apogee satellite Prognoz-3, the April 29–30, 1973 solar particle event is analysed. The event's complex energetic particle, interplanetary magnetic field and solar wind plasma properties are discussed. The unusual behaviour of solar particles up to energies 100 MeV can well be explained in terms of the interaction with an interplanetary shock wave system passing the Earth. Assuming that the structure of the interplanetary shock wave system is similar to that considered first by Parker (1961) and Gold (1959) and reviewed later by Hundhausen (1972) and Dryer (1974, 1975), the main characteristics of the energetic particle fluxes, solar wind and interplanetary magnetic field can be understood.  相似文献   

Static spherical configurations of cold matter in the Einstein-Cartan theory of gravitation     

M. Demiański  M. Prószyński 《Astrophysics and Space Science》1978,53(1):173-179

We investigate static, spherical configurations of cold catalized matter in the Einstein-Cartan theory of gravitation. Assuming that density of spin is proportional to the number density of baryonsn and using an equation of state of a degenerate, relativistic Fermi gas, we numerically integrated the relativistic equation of equilibrium. We have also studied the stability of those configurations. Configurations with central number densityn _c such that where is the effective pressure, are very similar to general relativistic configurations with the same central density. In the Einstein-Cartan theory there exists another disjoint family of equilibrium configurations for which but . Those configurations have very small masses 10^–6 g and raddi 10^–34 cm and are unstable.Supported in part by Research Grant MR-I-7.  相似文献   

Frequency Content Evolution of Snow Avalanche Seismic Signals     

Berta Biescas  François Dufour  Glória Furdada  Giorgi Khazaradze  Emma Suriñach 《Surveys in Geophysics》2003,24(5-6):447-464

Seismic signals generated by avalanches have been recorded by theavalanche team of the Universitat de Barcelona at theVallée de la Sionne experimental site (Switzerland) since 1998. During these years avalanches of varying size and flowwere recorded by two sensors located at different positions.In the present paper we show the general features of the running spectra of the seismicsignals for the different type of recorded avalanches. Using this method we are able not only to detect avalanches with low amplitude signals but also to distinguishbetween avalanches and other seismic sources (i.e., local earthquakes) which have thesame frequency content but a different frequency evolution.  相似文献   

Forging alliance with Russia: the example of a Green Investment Scheme     

Anna Korppoo 《Climate Policy》2003,3(1):67

Russian Kyoto related interests are economic and after the US withdrawal the mission of Russian actors has been to find new demand for Russian credits and allowances. Kyoto related benefits to Russia will be significantly smaller than earlier expected, however, the revenues are now more likely to be focused on climate change mitigation purposes. Competition in the Kyoto market has established buyers’ market and Russia has to accommodate the interests of investors in order to gain benefits. The Russian initiative ‘Green Investment Scheme’ to recycle revenues from International Emissions Trading (IET) to further environmental activities would convene demand for Russian AAUs but experience the same problems than the previous initiatives: inadequate institutional arrangement, unclear division of responsibilities between domestic actors, prolonged ratification process and lack of eligibility strategy. These problems have prevented implementation of GIS so far. Therefore, these problems have to be addressed by high-level Russian policy-makers if serious benefits from Kyoto are sought. Actors building alliances with Russia should focus on assisting with solving these problems.  相似文献   

Paleovegetation of marine isotope stages 4 and 3 in northern new zealand and the age of the widespread rotoehu tephra     

Phil Shane  Anna Sandiford 《Quaternary Research》2003,59(3):420-429

Paleolake sediment, constrained by tephrochronology, from Onepoto basin volcanic crater in Auckland, Northern New Zealand (36° 48′S), provides one of the few uninterrupted records of paleovegetation for marine oxygen isotope stages (MIS) 4 and 3 (76,000–26,000 yr B.P.) in the region. This period was characterized by cool temperate conifer-hardwood forest that lacked some of the warmer taxa typical of the Holocene. The period 64,400–60,500 yr B.P. was marked by opening of forest canopy and expansion of small trees and shrubs, and correlates to the thermal minima of MIS 4. However, the landscape was never as open as the forest-shrubland mosaic of the MIS 2. The beginning of MIS 3 (60,500–50,500 yr B.P.) was marked by the dramatic expansion and then decline of conifer-hardwood forest dominated by Dacrydium cupressinum, a species that prefers wetter conditions. This forest was succeeded by the typically montane Nothofagus at 50,500 yr B.P., corresponding to a thermal decline. Thus, MIS 3 began with an abrupt change to moist cool conditions that lasted about 5000 yr, followed by gradual cooling and dryer conditions. This supports some interpretations from other parts of the southwest Pacific region, that MIS 3 was a period of increased precipitation. The widespread and stratigraphically important Rotoehu tephra, erupted from Okataina Volcanic Centre, has been variously dated at 45,000–65,000 yr B.P. At Onepoto, sedimentation rate and paleovegetation reconstruction imply an age of c. 44,300 yr B.P. The tephra provides a correlation horizon in the marine and terrestrial realms during a period (MIS 3) difficult to date by radiometric methods.  相似文献   

Reply to Discussion on "Giant versus small porphyry copper deposits of Cenozoic age in northern Chile: adakitic versus normal calc-alkaline magmatism" by Oyarzun R,Márquez A,Lillo J,López I,Rivera S (Mineralium Deposita 36:794–798, 2001)     

Roberto Oyarzun  Alvaro Márquez  Javier Lillo  Ivan López  Sergio Rivera 《Mineralium Deposita》2002,37(8):795-799

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Visual discrimination of surface features of salt affected soils using satellite images in arid region of Rajasthan (India)     

D C Joshi  Tibor Tóth  Diana Sári 《Journal of the Indian Society of Remote Sensing》2002,30(1-2):33-38

The study has been carried for visual discrimination of natural salt affected soils on FCC images of IRS 1 B in Pali district of Rajasthan. The salt affected soils show wide variations in salinity (EC_2.53.7 to 28 dSm^-1), alkalinity (pH 8.5-9.8), cover ofP. juliflora (10-90%), salt tolerant grasses (10–55%) and gravelly surface (20–35%). ThoughP. juliflora and grasses were present at most of the observation points their cover decreased with soil EC_2.5 values more than 10 and 13 dSm^-1, respectively. Five darkness categories derived as the result of visual interpretation of FCCs; and ground and laboratory studies revealed that the darkness category 1 represented fewer plant community with high salinity (EC 28.7 dSm^-1) and gravelly surface, categories 2 and 3 were characterised by grass cover and moderate salt affected soils (EC 3-10 dSm^-1) whereas category 4 was dominated by thicket ofP. juliflora. The derived numerical darkness categories of the FCC images were slightly low for February images. The darkness values of observation pixel on February images correlated positively withP. juliflora cover and negatively with grass cover and soil pH indicating that surface features on FCC were related with the immediate observation pixels.  相似文献