排序方式： 共有17条查询结果，搜索用时 171 毫秒
1.
A series of experiments on the fluid-absent melting of a quartz-rich aluminous metagreywacke has been carried out. In this
paper, we report the chemical composition of the phases present in the experimental charges as determined by electron microprobe.
This analytical work includes biotite, plagioclase, orthopyroxene, garnet, cordierite, hercynite, staurolite, gedrite, oxide,
and glass, over the range 100–1000 MPa, 780–1025 °C. Biotites are Na- and Mg-rich, with Ti contents increasing with temperature.
The compositions of plagioclase range from An17 to An35, with a significant orthoclase component, and are always different from the starting minerals. At high temperature, plagioclase
crystals correspond to ternary feldspars with Or contents in the range 11–20 mol%. Garnets are almandine pyrope grossular
spessartine solid solutions, with a regular and significant increase of the grossular content with pressure. All glasses are
silicic (SiO2 = 67.6–74.4 wt%), peraluminous, and leucocratic (FeO + MgO = 0.9–2.9 wt%), with a bulk composition close to that of peraluminous
leucogranites, even for degrees of melting as high as 60 vol.%. With increasing pressure, SiO2 contents decrease while K2O increases. At any pressure, the melt compositions are more potassic than the water-saturated granitic minima. The H2O contents estimated by mass balance are in the range 2.5–5.6 wt%. These values are higher than those predicted by thermodynamic
models. Modal compositions were estimated by mass balance calculations and by image processing of the SEM photographs. The
positions of the 20 to 70% isotects (curves of equal proportion of melt) have been located in the pressure-temperature space
between 100 MPa and 1000 MPa. With increasing pressure, the isotects shift toward lower temperature between 100 and 200 MPa,
then bend back toward higher temperature. The melting interval increases with pressure; the difference in temperature between
the 20% and the 70% isotects is 40 °C at 100 MPa, and 150 °C at 800 MPa. The position of the isotects is interpreted in terms
of both the solubility of water in the melt and the nature of the reactions involved in the melting process. A comparison
with other partial melting experiments suggests that pelites are the most fertile source rocks above 800 MPa. The difference
in fertility between pelites and greywackes decreases with decreasing pressure. A review of the glass compositions obtained
in experimental studies demonstrates that partial melting of fertile rock types in the crust (greywackes, pelites, or orthogneisses)
produces only peraluminous leucogranites. More mafic granitic compositions such as the various types of calk-alkaline rocks,
or mafic S-type rocks, have never been obtained during partial melting experiments. Thus, only peraluminous leucogranites
may correspond to liquids directly formed by partial melting of metasediments. Other types of granites involve other components
or processes, such as restite unmixing from the source region, and/or interaction with mafic mantle-derived materials.
Received: 11 July 1995 / Accepted: 27 February 1997 相似文献
2.
A high sensitivity manifold for the determination of trace quantities (nanomolar concentrations) of nitrate+nitrite and nitrite alone is described. The method uses a classical Technicon AutoAnalyzer II usually employed for shipboard analysis. A reproducibility of ± 1 nmol dm−3 for nitrate plus nitrite and nitrite alone was obtained, with an analytical rate of 40 samples h−1. 相似文献
3.
J-Ph. Bernard P. Ade Y. André J. Aumont L. Bautista N. Bray P. de Bernardis O. Boulade F. Bousquet M. Bouzit V. Buttice A. Caillat M. Charra M. Chaigneau B. Crane J.-P. Crussaire F. Douchin E. Doumayrou J.-P. Dubois C. Engel P. Etcheto P. Gélot M. Griffin G. Foenard S. Grabarnik P. Hargrave A. Hughes R. Laureijs Y. Lepennec B. Leriche Y. Longval S. Maestre B. Maffei J. Martignac C. Marty W. Marty S. Masi F. Mirc R. Misawa J. Montel L. Montier B. Mot J. Narbonne J-M. Nicot F. Pajot G. Parot E. Pérot J. Pimentao G. Pisano N. Ponthieu I. Ristorcelli L. Rodriguez G. Roudil M. Salatino G. Savini O. Simonella M. Saccoccio P. Tapie J. Tauber J.-P. Torre C. Tucker 《Experimental Astronomy》2016,42(2):199-227
Future cosmology space missions will concentrate on measuring the polarization of the Cosmic Microwave Background, which potentially carries invaluable information about the earliest phases of the evolution of our universe. Such ambitious projects will ultimately be limited by the sensitivity of the instrument and by the accuracy at which polarized foreground emission from our own Galaxy can be subtracted out. We present the PILOT balloon project, which aims at characterizing one of these foreground sources, the polarized continuum emission by dust in the diffuse interstellar medium. The PILOT experiment also constitutes a test-bed for using multiplexed bolometer arrays for polarization measurements. This paper presents the instrument and its expected performances. Performance measured during ground calibrations of the instrument and in flight will be described in a forthcoming paper. 相似文献
4.
A. Didier V. Bosse P. Boulvais J. Bouloton J.-L. Paquette J.-M. Montel J.-L. Devidal 《Contributions to Mineralogy and Petrology》2013,165(6):1051-1072
Monazite is extensively used to date crustal processes and is usually considered to be resistant to diffusive Pb loss. Nevertheless, fluid-assisted recrystallisation is known to be capable of resetting the monazite chronometer. This study focuses on chemical and isotopic disturbances in monazite grains from two microgranite intrusions in the French Central Massif (Charron and Montasset). Petrologic data and oxygen isotopes suggest that both intrusions have interacted with alkali-bearing hydrothermal-magmatic fluids. In the Charron intrusion, regardless of their textural location, monazite grains are sub-euhedral and cover a large domain of compositions. U–Pb chronometers yield a lower intercept age of 297 ± 4 Ma. An inherited component at 320 Ma is responsible for the scattering of the U–Th–Pb ages. The Montasset intrusion was later affected by an additional F-rich crustal fluid with crystallisation of Ca-REE-fluorocarbonates, fluorite, calcite and chloritisation. Pristine monazite is chemically homogeneous and displays 208Pb/232Th and 206Pb/238U concordant ages at 307 ± 2 Ma. By contrast, groundmass monazite shows dissolution-recrystallisation features associated with apatite and thorite precipitation (Th-silicate) and strong chemical reequilibration. 208Pb/232Th ages are disturbed and range between 270 and 690 Ma showing that the Th/Pb ratio is highly fractionated during the interaction with fluids. Apparent U–Pb ages are older due to common Pb incorporation yielding a lower intercept age at 312 ± 10 Ma, the age of the pristine monazite. These results show that F-rich fluids are responsible for Th mobility and incorporation of excess Pb, which thus strongly disturbed the U–Th–Pb chronometers in the monazite. 相似文献
5.
Jean-Marc Montel 《Comptes Rendus Geoscience》2011,343(2-3):230-236
Safe storage of radioactive waste is a major challenge for the nuclear industry. Mineralogy is a good basis for designing ceramics, which could eventually replace nuclear glasses. This requires a new storage concept: separation-conditioning. Basic rules of crystal chemistry allow one to select the most suitable structures and natural occurrences allow assessing the long-term performance of ceramics in a geological environment. Three criteria are of special interest: compatibility with geological environment, resistance to natural fluids, and effects of self-irradiation. If mineralogical information is efficient for predicting the behaviour of common, well-known minerals, such as zircon, monazite or apatite, more research is needed to rationalize the long-term behaviour of uncommon waste form analogs. 相似文献
6.
A simplified mechanical model of a metamict crystal swelling in a host mineral shows that enough stress is generated in the host to trigger its failure and the appearance of radial fractures, in agreement with geological observations. The maximum stress, which combines radial compression and concentric tension, occurs along the host–inclusion interface and should create radial fractures. The maximum stress mainly depends on the amount of swelling, on the inclusion stiffness, and on the resistance to shearing of the host mineral. The external pressure, the host bulk modulus, and the inclusions/host radius ratio are parameters of minor relevance. The influence of the inclusion does not extend beyond about five times its radius. The application of published experimental data shows that a swelling metamict mineral may create significant fracturing in the host mineral. However, many parameters for both host and inclusion minerals are not available, even for the application of such a simple model. We think that in some circumstances, swelling of metamict mineral and fracturing of host mineral may significantly affect the physical properties of rocks at a larger scale by creating a network of fractures connecting metamict (i.e. uranium and thorium bearing) minerals to the geological environment. 相似文献
7.
We present a theoretical model for diffusive daughter isotope loss in radiochronological systems with increasing temperature.
It complements previous thermochronological models, which focused on cooling, and allows for testing opening and resetting
of radiochronometers during heating. The opening and resetting temperatures are, respectively,
where R is the gas constant, E and D
0 are the activation energy and the pre-exponential factor of the Arrhenius law for diffusion of the daughter isotope, a the half-size of the system (radius for sphere and cylinder and half-thickness for plane sheet) and τ the heating time constant, related to the heating rate by
For opening and resetting thresholds corresponding to 1 and 99% loss of daughter isotope, respectively, the retention parameters
for sphere, cylinder and plane sheet geometries are A
op = 1.14 × 105, 5.07 × 104 and 1.27 × 104 and A
rs = 2.40, 1.37 and 0.561. According to this model, the opening and resetting temperatures are significantly different for most
radiochronometers and are, respectively, lower and higher than the closure temperature.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Zorano Srgio de Souza Jean-Marc Montel Simone Maria Lima Costa Gioia Maria Helena Bezerra Maia de Hollanda Marcos Antonio Leite do Nascimento Emanuel Ferraz Jardim de S Venerando Eustquio Amaro Mrcio Martins Pimentel Jean-Marc Lardeaux Michelle Veschambre 《Gondwana Research》2006,9(4):441-455
The easternmost domain of the Borborema Province, northeastern Brazil, presents widespread, extensional-related high-temperature metamorphism during the Brasiliano (=Pan-African) orogeny. This event reached the upper amphibolite to granulite facies and provoked generalized migmatization of Proterozoic metapelitic rocks of the Seridó Group and tonalitic to granodioritic orthogneisses of the Archean to Paleoproterozoic basement. We report new geochronological data based on electron microprobe dating of monazite from metapelitic migmatite and leuconorite within the high-T shear zones that make up the eastern continuation of the huge E–W Patos shear belt. These data were also constrained by using the Sm–Nd isotopic systematic on garnet from a syntectonic alkaline granite and two garnet-bearing leucosomes. The results suggest an age of about 578 to 574 Ma for the peak of the widespread high-T metamorphism. This event is best recorded by Sm–Nd garnet-whole rock ages. The U–Th–Pb isotopes on monazite of the metapelitic migmatite show a younger thermal event at 553 ± 10 Ma. When compared to the Sm–Nd garnet-whole rock ages, the U–Th–Pb electron probe monazite ages seem to record an event of slightly lower temperatures after the peak of the high-T metamorphism. This may reflect the difference in the isotopic behavior of the geochronological methods employed. Otherwise, the U–Th–Pb ages on monazites could indicate an event not yet very well defined. In anyway, this paper reveals the partial or even complete re-opening and resetting of the U–Th–Pb isotopic system produced by the action of low-T Ca-rich fluid. 相似文献
9.
Franck Poitrasson Eric Oelkers Jean-Marc Montel 《Geochimica et cosmochimica acta》2004,68(10):2207-2221
The solubility of synthetic NdPO4 monazite end-member has been determined experimentally from 21 to 300°C in aqueous solutions at pH = 2, and at 21°C and pH = 2 for GdPO4. Measurements were performed in batch reactors, with regular solution sampling for pH measurement, rare earths and phosphorous analysis by inductively coupled plasma mass spectrometry (ICP-MS) coupled with a desolvation system. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to check that no reprecipitation of secondary phases occurred and that the mineral surfaces remained those of a monazite. Coupled with speciation calculations, measured solution compositions permitted the determination of NdPO4 and GdPO4 solubility products which are in general agreement with previous experimental determination on rhabdophane at 25°C, but showing that monazite is more than two orders of magnitude less soluble than inferred on the basis of previous thermodynamic estimates. The temperature evolution from 21 to 300°C of the equilibrium constant (K) of the NdPO4 monazite end-member dissolution reaction given by:
10.
Partial melting of metagreywackes. Part I. Fluid-absent experiments and phase relationships 总被引：28，自引：1，他引：27
Island arcs, active and passive margins are the best tectonic settings to generate fertile reservoirs likely to be involved in subsequent granitoid genesis. In such environments, greywackes are abundant crustal rock types and thus are good candidates to generate large quantities of granitoid magmas. We performed a series of experiments, between 100 and 2000 MPa, on the fluid-absent melting of a quartz-rich aluminous metagreywacke composed of 32 wt% plagioclase (Pl) (An22), 25 wt% biotite (Bt) (X
Mg45), and 41 wt% quartz (Qtz). Eighty experiments, averaging 13 days each, were carried out using a powder of minerals (5m) and a glass of the same composition. The multivariant field of the complex reaction Bt+Pl+QtzGrt/Crd/Spl+ Opx+Kfs+melt limited by the Opx-in and Bt-out curves, is located between 810–860°C at 100 MPa, 800–850°C at 200 MPa, 810–860°C at 300 MPa, 820–880°C at 500 MPa, 860–930°C at 800 MPa, 890–990°C at 1000 MPa, and at a temperature lower than 1000°C at 1500 and 1700 MPa. The melting of biotite+plagioclase+ quartz produced melt+orthopyroxene (Opx) +cordierite (Crd) or spinel (Spl) at 100, 200 and 300 MPa, and melt+orthopyroxene+garnet (Grt) from 500 to 1700 MPa (+Qtz, Pl, FeTi Oxide at all pressures). K-feldspar (Kfs) was found as a product of the reaction in some cases and we observed that the residual plagioclase was always strongly enriched in orthoclase component. The P-T surface corresponding to the multivariant field of this reaction is about 50 to 100°C wide. At temperatures below the appearance of orthopyroxene, biotite is progressively replaced by garnet with increasing P. At 850°C, we observed that (1) the modal proportion of garnet increases markedly with P; (2) the grossular content of the garnet increases regularly from about 4 mol% at 500 MPa to 15 mol% at 2000 MPa. These changes can be ascribed to the reaction Bt+Pl+Qtz Grt+Kfs+melt with biotite +plagioclase+quartz on the low-P side of the reaction. As a result, at 200 MPa, we observed the progressive disappearance of biotite without production of orthopyroxene. These experiments emphasize the importance of this reaction for the understanding of partial melting processes and evolution of the lower continental crust. Ca-poor Al-metagreywackes represent fertile rocks at commonly attainable temperatures (i.e. 800–900°C), below 700 MPa. There, 30 to 60 vol.% of melt can be produced. Above this pressure, temperatures above 900°C are required, making the production of granitoid magmas more difficult. Thin layers of gneisses composed of rothopyroxene, garnet, plagioclase, and quartz (±biotite), interbedded within sillimanite-bearing paragneisses, are quite common in granulite terrains. They may result from partial melting of metagreywackes and correspond to recrystallized mixtures of crystals (+trapped melt) left behind after removal of a major proportion of melt. Available experimental constraints indicate that extensive melting of pelites takes place at a significantly lower temperature (850°C±20) than in Al-metagreywackes (950°C±30), at 1000 MPa. The common observation that biotite is no longer stable in aluminous paragneisses while it still coexists commonly with orthopyroxene, garnet, plagioclase and quartz, provides rather tight temperature constraints for granulitic metamorphism.Abbreviations
Ab
albite
-
alm
almandine component in garnet
-
Als
aluminum silicate
-
An
anorthite
-
Ap
apatite
-
Bt
biotite
-
Cal
calcite
-
Crd
cordierite
-
Crn
corundum
-
En
enstatite
-
Fl
fluid phase
-
Fs
ferrosilite
-
Ged
gedrite
-
Gl
glass
-
Grs
Grossular
-
grs
grossular component in garnet
-
Grt
garnet
-
Hc
hercynite
-
Hem
hematite
-
Ilm
ilmenite
-
Kfs
K-feldspar
-
M
melt
-
Mag
magnetite
-
Ms
muscovite
-
Opx
orthopyroxene
-
Or
orthoclase
-
Phl
phlogopite
-
Pl
plagioclase
-
Po
Pyrrhotite
-
Prp
pyrope
-
prp
pyrope component in garnet
-
Otz
quartz
-
Rt
rutile
-
Sa
sanidine
-
Sil
sillimanite
-
Spl
spinel
-
St
staurolite
-
Ti-Mag
titano-magnetite
-
W
water 相似文献