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1.
Joel Sanchez-Bermudez Florentin Millour Fabien Baron Roy van Boekel Laurent Bourgès Gilles Duvert Paulo J. V. Garcia Nuno Gomes Karl-Heinz Hofmann Thomas Henning Jacob W. Isbell Bruno Lopez Alexis Matter J-Uwe Pott Dieter Schertl Eric Thiébaut Gerd Weigelt John Young 《Experimental Astronomy》2018,46(3):457-473
During the last two decades, the first generation of beam combiners at the Very Large Telescope Interferometer has proved the importance of optical interferometry for high-angular resolution astrophysical studies in the near- and mid-infrared. With the advent of 4-beam combiners at the VLTI, the u ? v coverage per pointing increases significantly, providing an opportunity to use reconstructed images as powerful scientific tools. Therefore, interferometric imaging is already a key feature of the new generation of VLTI instruments, as well as for other interferometric facilities like CHARA and JWST. It is thus imperative to account for the current image reconstruction capabilities and their expected evolutions in the coming years. Here, we present a general overview of the current situation of optical interferometric image reconstruction with a focus on new wavelength-dependent information, highlighting its main advantages and limitations. As an Appendix we include several cookbooks describing the usage and installation of several state-of-the art image reconstruction packages. To illustrate the current capabilities of the software available to the community, we recovered chromatic images, from simulated MATISSE data, using the MCMC software SQUEEZE. With these images, we aim at showing the importance of selecting good regularization functions and their impact on the reconstruction. 相似文献
2.
A. L. Perchuk M. Burchard H.-P. Schertl W. V. Maresch T. V. Gerya H.-J. Bernhardt O. Vidal 《Contributions to Mineralogy and Petrology》2009,157(5):573-592
We demonstrate the possibility of studying several diffusion couples in a single run, i.e. under almost similar P–T–t– conditions, allowing direct comparison of the diffusion rates in different diffusion couples. Thus the duration of experimental
study and the risk of failure of expensive experimental equipment can be decreased considerably. The diffusion experiments
were carried out in piston-cylinder apparatus. Gem-quality garnets of almandine, spessartine and grossular compositions together
with inclusion-rich eclogitic garnets were embedded in a powder of natural pyrope and annealed together under dry conditions
at P = 1.9–3.2 GPa and T = 1,070–1,400°C. Diffusion profiles were measured by electron microprobe and fitted numerically on the basis of multicomponent
diffusion theory. The datasets derived from different diffusion couples yields parameters of the Arrhenius equation for Ca,
Mg and Fe in natural eclogitic garnets and Mg, Mn and Fe in gem-quality garnets. We have also studied the effect of grain-boundary
diffusion in the sintered pyrope matrix on interdiffusion on the basis of 2D modeling. Under conditions analogous to those
of our experimental runs, we show that observed irregularities in some measured diffusion profiles (not applied for the diffusion
modeling) can be directly related to the superposition of local grain-boundary diffusion on dominant volume diffusion. 相似文献
3.
Shyh‐Lung Hwang Pouyan Shen Hao‐Tsu Chu Tzen‐Fu Yui Yoshiyuki Iizuka Hans‐Peter Schertl 《Journal of Metamorphic Geology》2019,37(8):1079-1098
Metamorphic garnet commonly contains needle‐like rutile inclusions as well as equant rutile inclusions that surround quartz inclusions and range in size from submicrometer to nanometer. Although the origin of these equant rutile inclusions, that is, exsolution or non‐exsolution, has important implications for petrological and tectonic processes, the crystallographic characteristics of these inclusions have rarely been studied because of the small sizes and analytical difficulties involved. Here, we report the crystallographic characteristics pertinent to the genetic origin of minute equant rutile inclusions in cloudy, nearly spherically shaped garnet domains with Ti‐depleted compositions surrounding quartz inclusions in ultrahigh‐pressure garnet from several diamondiferous Erzgebirge quartzofeldspathic gneissic rock samples. TEM analyses show that the equant rutile crystals in cloudy garnet domains are partially bounded by the low‐energy {100}rt ± {110}rt ± {101}rt facets and have rather random crystallographic orientation relationships (CORs) with the garnet host, with preferential alignment of low‐energy lattice planes, for example, {100}rt//{112}grt, for some rutile crystals. Although the rather random CORs are unlikely to be attributed to solid‐state exsolution subjected to the stringent topotactic garnet lattice constraints, the characteristic subhedral {100}rt ± {110}rt ± {101}rt crystal forms of rutile can be rationalized by a metasomatic dissolution‐reprecipitation mechanism via a fluid phase. In this scenario, the quartz+fluid inclusions in garnet were first subjected to decompression microcracking during rock exhumation, followed by dissolution of Ti‐bearing garnet matrix at the crack tips or along the crack surfaces and subsequent reprecipitation of rutile, apatite, gahnite, akdalaite, and Ti‐depleted garnet. The rapid coalescence between rutile and garnet crystals in fluid or direct attachment of rutile crystals onto the dissolving crack surfaces would then yield the rather random CORs as reported here. These results, along with previous work on rutile needles, indicate rather diverse genesis of rutile inclusions in various crystal forms, thus shedding light on the controversial exsolution origin for other inclusion suite/microstructure in minerals. 相似文献
4.
5.
A.L. Perchuk V.V. Davydova M. Burchard W.V. Maresch H.-P. Schertl V.O. Yapaskurt O.G. Safonov 《Russian Geology and Geophysics》2009,50(12):1153-1168
Samples of poikoblastic garnets from the Escambray (Cuba), Maksyutov (Russia), and Sambagawa (Japan) eclogite complexes were heated to 700–1100 ºC at 3 to 4 GPa (30–40 kbar). Epidote, amphibole, and chlorite inclusions in the garnets underwent dehydration melting over the entire experimental PT range, which is typical of ultrahigh-pressure (UHP) metamorphic complexes. In the presence of aqueous fluids, carbonate minerals in the inclusions began to melt at 800 ºC and 3 GPa. Melting gave rise to new garnet, with the composition controlled by the chemistry of the primary inclusions and by PT run conditions. Garnet either grew directly from the melt or formed by replacement of host garnet walls leaving residual melt at the substitution front in the latter case. Partial melting of inclusions decreased the mechanical strength of the garnet host and led to local shearing. The experimental results were used to interpret observed features in two samples of a diamond-bearing and a diamond-free carbonate-silicate rocks from the Kumdy-Kol deposit in the Kokchetav Massif. Multiphase inclusions in both samples contain newly formed garnet with morphologies and compositions consistent with those produced experimentally under the given PT conditions. Minerals in the inclusions are compositionally similar to those in matrix, thus suggesting that melting may have occurred on a large scale. 相似文献
6.
The pyrope-coesite rocks and their country rocks at Parigi,Dora Maira Massif,Western Alps: detailed petrography,mineral chemistry and PT-path 总被引：1，自引：0，他引：1
Both the coarse- and fine-grained varieties of the partly coesite-bearing pyrope-quartzites, their interlayered jadeite-kyanite rocks, and the biotite-phengite gneiss country rock common to all of them were subjected to detailed petrographic and textural studies in order to determine the sequence of crystallisation of their mineral constituents, which were also studied analytically by microprobe. Prior to pyrope and coesite growth, the Mg-rich metapelites were talc-kyanite-chlorite-rutile-ellenbergerite schists which — upon continued prograde metamorphism — developed first pyrope megacrysts in silica-deficient local environments at the expense of chlorite + talc + kyanite, and subsequently the smaller pyrope crystals with coesite inclusions from reacting talc + kyanite. Based on geobarometrically useful mineral inclusions as well as on experimentally determined phase relations, a prograde PT-path — simplified for water activity = 1 — is constructed which passes through the approximate PT-conditions 16 kbar and 560° C, 29 kbar and 720° C, and finally up to 37 kbar at about 800° C, where the Mg-rich metapelite was a pyrope-coesite rock with phengite, kyanite, and talc still present. During the retrograde path, pyrope was altered metasomatically either into phlogopite + kyanite + quartz or, at a later stage, to chlorite + muscovite + quartz. Both assemblages yield PT-constraints, the latter about 7–9 kbar, 500–600° C. The country rock gneisses have also endured high-pressures of at least 15 kbar, but they provide mostly constraints on the lowest portion of the uplift conditions within the greenschist facies (about 5 kbar, 450° C). Microprobe data are presented for the following minerals: pyrope, ellenbergerite, dumortierite (unusually MgTi-rich), jadeite, vermiculite (formed after Na-phlogopite?), paragonite, and for several generations of phengite, chlorite, talc, phlogopite, dravite, and glaucophane in the high-pressure rocks, as well as for biotite, chlorite, phengites, epidote, garnet, albite, and K-feldspar in the country rock gneisses. An outstanding open problem identified in this study is the preservation of minerals as inclusions within kyanite and pyrope beyond their PT-stability limits. 相似文献
7.
Using relevant geothermobarometric methods, P–T-data were collected for the reconstruction of the metamorphic evolution of 34 eclogite samples taken from small lenses and boudins within the ultrahigh-pressure (UHP) metamorphic coesite-bearing Brossasco-Isasca Unit (BIU) of the Dora-Maira Massif. The mineral phases used (clinopyroxene, garnet, phengite), or growth zones thereof, were identified as being coexistent for different stages of metamorphism on the basis of careful petrographic studies. Of several published geothermobarometers, the garnet–clinopyroxene thermometer of Powell [Powell, R., 1985. Regression diagnostics and robust regression in geothermometer/geobarometer calibration: the garnet–clinopyroxene geothermometer revisited. J. Metamorph. Geol., 3, pp. 231–243.] combined with the garnet–clinopyroxene–phengite barometer after Waters and Martin [Waters, D., Martin, H.N., 1993. The garnet–clinopyroxene–phengite barometer. Terra Abstr., 5, pp. 410–411.] was chosen here, because it provided the most reliable results. Nevertheless, the scatter of P–T-data points for the prograde (stage I), peak metamorphic (stage II), and retrograde (stage III) development of the eclogites is still considerable. Among the many possible reasons for this inconsistency discussed, a partial lack of equilibration of some of the eclogites during their metamorphic history should be taken into account. Despite the data scatter, an average P–T-path could be estimated, which includes the following coordinates: for stage I: 15 kbar/500°C; 25 kbar/570°C; 32 kbar/650°C; for stage II: 36 kbar/720°C; and for stage III: 24 kbar/680°C and 14 kbar/620°C. This is in fair agreement with P–T-paths derived earlier for other rock types of the BIU on the basis of other geothermobarometers. 相似文献
8.
N. V. Sobolev H.-P. Schertl J. W. Valley F. Z. Page N. T. Kita M. J. Spicuzza R. D. Neuser A. M. Logvinova 《Contributions to Mineralogy and Petrology》2011,162(5):1079-1092
Calcsilicate and garnet-pyroxene rocks with dolomite and Mg-calcite matrices occur with UHPM diamondiferous biotite gneisses
and schists of the Kokchetav Massif. The calcsilicates are characterized by high diamond grade, K-bearing diopside, and very
high Mg-garnets (Mg# > 77) with variable Ca contents (Ca# = 42.5–80). A rare calcsilicate sample with alternating layers of
different bulk compositions was selected for oxygen isotope and electron probe microanalysis of garnets and pyroxenes. A grain
of fresh garnet with a brownish-yellow luminescent inner domain (Mg# 94) and a non-luminescent outer part (Mg# 88) was selected
for in situ analysis of δ18O by ion microprobe (10 μm spot). The profile demonstrates a δ18O gradient of 1.5‰/200 μm, from 11.3 (rim) to 12.8‰ (core) VSMOW. Additional 2 mg samples of hand-picked garnet and clinopyroxene
fragments from different parts of the same sample (selected by color and chemical differences) were analyzed for δ18O by laser fluorination, yielding even larger differences in δ18O: 6.3–10.6‰ in garnets and 6.1–8.1 in clinopyroxenes. The zonation in δ18O among grains of the same mineral in different lithologies may in part reflect initial heterogeneities of the finely layered
sedimentary precursors. The δ18O values for the garnets are among the highest observed for UHP-origin (both for crustal or mantle rocks), confirming a sedimentary
origin for these carbonate-bearing rocks, and ruling out a primitive mantle-derived protolith. Oxygen diffusion in garnet
at peak metamorphism temperature (1,000°C) was arrested by rapid cooling. 相似文献
9.
We discuss recent results from near-infrared bispectrum speckle interferometry observations of the young outflow sources in the S140 and Mon R2 star forming regions. With spatial resolutions down to 0.075'', our data represent the highest resolution images obtained so far for these objects and exhibit previously unseen complex structures in the immediate vicinity of the young stellar objects. We discuss the relation of these structures to the jets and outflows. 相似文献
10.
Schertl Hans-Peter 《《地质学报》英文版》2015,89(Z2):81-83
<正>A geodynamical revolution in modern geosciences was initiated by Chopin(1984)and Smith(1984),who discovered metamorphic coesite in rocks of the Dora Maira Massif,Italy and the Western gneiss region,Norway,respectively.The term"UHP metamorphism"was born and such rocks which initially have been considered as products of an exotic process on a local scale, 相似文献