Volatile Phase Separation in Silicic Magmas at Bajo de la Alumbrera Porphyry Cu-Au Deposit, NW Argentina   总被引：7，自引：0，他引：7  

Anthony C. Harris    Vadim S. Kamenetsky    Noel C. White  David A. Steele 《Resource Geology》2004,54(3):341-356

Abstract. At the Bajo de la Alumbrera porphyry Cu-Au deposit, NW Argentina, several key textural elements preserve evidence for volatile separation. Interconnected miarolitic cavities, while being studied extensively in granites, have now been recognized in intrusions related to porphyry Cu mineralization. Pods of saccharoidal quartz are connected by narrow, anastomosing zones of graphic quartz-alkali feldspar intergrowths and ragged biotite (with lesser apatite and magnetite). Their connectivity can be as much as 15 cm; however, more commonly, the interconnected miarolitic cavities are approximately 1 to 2 mm across and 5 cm or less, long. Features such comb-quartz layered textures and magmatic-hydrothermal veins (P veins), combined with aqueous fluid phase equilibria from fluid inclusions, better constrain physical models of exsolution. We interpret these textures in the context of vapour phase formation, coalescence and accumulation in an evolving silicic magma. Recognition of textures, such as the interconnected miarolitic cavities reported here, may provide a simple exploration tool for porphyry Cu deposits, helping explorers to recognize evidence for a potentially fertile intrusions.  相似文献   

Late Jurassic–Early Cretaceous closure of the Mongol-Okhotsk Ocean demonstrated by new Mesozoic palaeomagnetic results from the Trans-Baïkal area (SE Siberia)     

Jean-Pascal Cogné  Vadim A. Kravchinsky  Nadir Halim  Fatim Hankard 《Geophysical Journal International》2005,163(2):813-832

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Potassic primary melts of Vulsini (Roman Province): evidence from mineralogy and melt inclusions     

Vadim Kamenetsky  Nicole Métrich  Raffaello Cioni 《Contributions to Mineralogy and Petrology》1995,121(3):336-336

The online version of the original article can be found at  相似文献   

Quaternary high-Mg ultrapotassic rocks from the Qal’eh Hasan Ali maars,southeastern Iran: petrogenesis and geodynamic implications     

Kwan-Nang Pang  Sun-Lin Chung  Mohammad Hossein Zarrinkoub  Fei Wang  Vadim S. Kamenetsky  Hao-Yang Lee 《Contributions to Mineralogy and Petrology》2015,169(3):1-19

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On the determination of the effect of horizontal ionospheric gradients on ranging errors in GNSS positioning     

Ekaterina A. Danilogorskaya  Nikolay N. Zernov  Vadim E. Gherm  Hal J. Strangeways 《Journal of Geodesy》2017,91(5):503-517

An alternative approach to the traditionally employed method is proposed for treating the ionospheric range errors in transionospheric propagation such as for GNSS positioning or satellite-borne SAR. It enables the effects due to horizontal gradients of electron density (as well as vertical gradients) in the ionosphere to be explicitly accounted for. By contrast with many previous treatments, where the expansion of the solution for the phase advance is represented as the series in the inverse frequency powers and the main term of the expansion corresponds to the true line-of-sight distance from the transmitter to the receiver, in the alternative technique the zero-order term is the rigorous solution for a spherically layered ionosphere with any given vertical electron density profile. The first-order term represents the effects due to the horizontal gradients of the electron density of the ionosphere, and the second-order correction appears to be negligibly small for any reasonable parameters of the path of propagation and its geometry for VHF/UHF frequencies. Additionally, an “effective” spherically symmetric model of the ionosphere has been introduced, which accounts for the major contribution of the horizontal gradients of the ionosphere and provides very high accuracy in calculations of the phase advance.  相似文献   

Potassic primary melts of vulsini (Roman Province): evidence from mineralogy and melt inclusions   总被引：1，自引：1，他引：0  

Vadim Kamenetsky  Nicole Métrich  Raffaello Cioni 《Contributions to Mineralogy and Petrology》1995,120(2):186-196

The origin and the relationships between the high potassic (HKS) and potassic (KS) suites of the Roman Comagmatic Province and the nature of their primary magmas have been intensively debated over the past 35 years. We have addressed these problems by a study of mineralogy (olivine Fo_92-87, Cr-spinel and diopside) and melt inclusions in olivine phenocrysts from a scoria sample of Montefiascone (Vulsini area). This rock is considered as one of the most primitive (MgO=13.5 wt%, NiO=340 ppm; Cr=1275 ppm) in the northern part of the Roman Comagmatic Province. The compositions of both the olivine and their melt inclusions are controlled by two main processes. In the case of the olivine Fo<90.5, fractional crystallization (olivine + diopside + minor spinel) was the principal mechanism of the magma evolution. The olivine (Fo_92-90.5) and the Cr-spinel (Cr#=100. Cr/(Cr+Al)=63-73) represent a near-primary liquidus assemblage and indicate the mantle origin of their parental magmas. The compositions of melt inclusions in these olivine phenocrysts correspond to those of poorly fractionated H₂O-rich ( 1 wt%) primary melts (MgO=8.4-9.7 wt%,FeO^total=6-7.5 wt%). They evidence a wide compositional range (in wt%: SiO₂=46.5-50, K₂O=5.3-2.8, P₂O₅=0.4-0.2, S=0.26-0.12; Cl=0.05-0.03, and CaO/Al₂O₃= 0.8-1.15), with negative correlations between SiO₂ and K₂O, Al₂O₃ and CaO, as well as positive correlations between K₂O, and P₂O₅, S, Cl, with nearly constant ratios between these elements. These results are discussed in terms of segregation of various mantle-derived melts. The high and constant Mg# [100.Mg/(Mg+Fe²⁺)] 73-75 of studied melts and their variable Si, K, P, Ca, Al, S contents could be explained by the melting of a refractory lithospheric mantle source, heterogeneously enriched in phlogopite and clinopyroxene (veined mantle source).  相似文献   

Debris flows of 28 June 2014 near the Arshan village (Siberia,Republic of Buryatia,Russia)   总被引：1，自引：0，他引：1  

Alena V. Kadetova  Artem A. Rybchenko  Elena A. Kozireva  Vadim A. Pellinen 《Landslides》2016,13(1):129-140

On 28 June 2014, high intensity rainfall resulted in seven simultaneous debris flows going down the slopes of the Tunka Ridge in the vicinity of Arshan village, which is a balneological and alpine resort (51° 54′ 31″ N, 102° 25′ 44″ E). The debris flows caused one life loss and several injuries, 112 buildings were damaged, and 15 were completely destroyed. The total volume of the transported deposits amounted to 3?×?10⁶ m³. Debris flows’ formation began with the failure of weak sediments in the hanging cirques. Similar phenomena had not been recorded in the study area for over 40 years. The article presents a complete picture of the event and analysis of geological, geomorphological, and meteorological conditions for debris flows formation, for which extreme local rainfall was the major cause.  相似文献   

Carbonatite magmatism of the southern Siberian Craton 1 Ga ago: Evidence for the beginning of breakup of Laurasia in the early Neoproterozoic     

V. B. Savelieva  Yu. V. Danilova  E. P. Bazarova  A. V. Ivanov  V. S. Kamenetsky 《Doklady Earth Sciences》2016,471(1):1140-1143

Apatite and biotite from dolomite?ankerite and calcite?dolomite carbonatite dikes emplaced into the Paleoproterozoic metamorphic rock complex in the southern part of the Siberian Craton are dated by the U–Pb (LA-ICP-MS) and ⁴⁰Ar–³⁹Ar methods, respectively. Proceeding from the lower intercept of discordia with concordia, the age of apatite from calcite?dolomite carbonatite is estimated to be 972 ± 21 Ma and that for apatite from dolomite?ankerite carbonatite, as 929 ± 37 Ma. Values derived from their upper intercept have no geological sense. The ages obtained for biotite by the ⁴⁰Ar–³⁹Ar method are 965 ± 9 and 975 ± 14 Ma. It means that the formation of carbonatites reflects the earliest phases of the Neoproterozoic stage in extension of the continental lithosphere.  相似文献   

Potential and limits of double-difference tomographic methods     

Jean-Luc Got  Vadim Monteiller  Jean Virieux  Stéphane Operto 《Geophysical Prospecting》2008,56(4):477-491

Double-difference tomographic methods use directly accurate time delays computed between similar signals. Such methods are designed to image very heterogeneous media, such as volcanoes or fault zones. In seismological applications, similar signals are recorded at a given station from earthquakes sharing similar and close-by sources. In seismic exploration experiments, similar signals are often recorded at neighbouring receivers. After a brief presentation of the tomographic algorithm used, a seismological application is summarized. The potential and limits of double-difference tomographic methods are explored using various numerical experiments. They show that two effects are competing in double-difference tomography: (i) the degradation of the stability of the inversion due to the geometrical proximity of the rays used in the differentiation and (ii) the decrease in modelling error, which allows improving the stability of the inversion and using smaller quantities of a priori information when data are sufficiently accurate. The best resolution is obtained for an optimal value of the inter-source or inter-receiver distance. For optimal values of these distances and a priori information, tomography using traveltime differences provides significantly better resolved results than using traveltimes.  相似文献   

Distortions of EM transients in coincident loops at short time‐delays     

F. Kamenetsky  ChR. Oelsner 《Geophysical Prospecting》2000,48(6):983-993

Transient electromagnetic measurements with short time‐delays of transients are used for solving different problems within the upper part of a geoelectric section. However, it is necessary to take into consideration distortions connected with self‐transients within the transmitter–receiver system. From the practical point of view, it is important to estimate the minimum time‐delay after which these distortions may be neglected. We present such an estimation which uses a simple approximation method for a single‐loop (or coincident‐loop) configuration. For common values of the loop size (10 m × 10 m to 40 m × 40 m) and of the resistivity of a homogeneous half‐space (1–100 Ωm), the minimum time‐delay beyond which we can use a standard interpretation is in the range of 2–10 µs. This is equivalent to a minimum depth of investigation in the range of 1–30 m.  相似文献