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In this work, the factors controlling the formation and preservation of high-pressure mineral assemblages in the metamorphosed orthopyroxene-bearing metagranitoids of the Sandmata Complex, Aravalli-Delhi Mobile Belt (ADMB), northwestern India have been modelled. The rocks range in composition from farsundite through quartz mangerite to opdalite, and with varying K2 O, Ca/(Ca + Na)rock and FeOtot + MgO contents. A two stage metamorphic evolution has been recorded in these rocks.
An early hydration event stabilized biotite with or without epidote at the expense of magmatic orthopyroxene and plagioclase. Subsequent high-pressure granulite facies metamorphism (∼15 kbar, ∼800 °C) of these hydrated rocks produced two rock types with contrasting mineralogy and textures. In the non-migmatitic metagranitoids, spectacular garnet ± K-feldspar ± quartz corona was formed around reacting biotite, plagioclase, quartz and/or pyroxene. In contrast, biotite ± epidote melting produced migmatites, containing porphyroblastic garnet incongruent solids and leucosomes.
Applying NCKFMASHTO T–M (H2 O) and P–T pseudosection modelling techniques, it is demonstrated that the differential response of these magmatic rocks to high-pressure metamorphism is primarily controlled by the scale of initial hydration. Rocks, which were pervasively hydrated, produced garnetiferous migmatites, while for limited hydration, the same metamorphism formed sub-solidus garnet-bearing coronae. Based on the sequence of mineral assemblage evolution and the mineral compositional zoning features in the two metagranitoids, a clockwise metamorphic P–T path is constrained for the high-pressure metamorphic event. The finding has major implications in formulating geodynamic model of crustal amalgamation in the ADMB. 相似文献
An early hydration event stabilized biotite with or without epidote at the expense of magmatic orthopyroxene and plagioclase. Subsequent high-pressure granulite facies metamorphism (∼15 kbar, ∼800 °C) of these hydrated rocks produced two rock types with contrasting mineralogy and textures. In the non-migmatitic metagranitoids, spectacular garnet ± K-feldspar ± quartz corona was formed around reacting biotite, plagioclase, quartz and/or pyroxene. In contrast, biotite ± epidote melting produced migmatites, containing porphyroblastic garnet incongruent solids and leucosomes.
Applying NCKFMASHTO T–M (H
3.
Hai-Ning LiNational Astronomical Observatories Chinese Academy of Sciences Beijing lhnDepartment of Astronomy Beijing Normal University Beijing 《中国天文和天体物理学报》2003,3(5)
We present a quantitative estimate of the relativistic corrections to the thermal SZ power spectrum produced by the energetic electrons in massive clusters. The corrections are well within 10% for current experiments with working frequencies below v < 100 GHz, but become non-negligible at high frequencies v > 350 GHz. Moreover, the corrections appear to be slightly smaller at higher l or smaller angular scales. We conclude that there is no need to include the relativistic corrections in the theoretical study of the SZ power spectrum especially at low frequencies unless the SZ power spectrum is used for precision cosmology. 相似文献
4.
C. Dickinson R. D. Davies R. J. Davis 《Monthly notices of the Royal Astronomical Society》2003,341(2):369-384
A full-sky template map of the Galactic free–free foreground emission component is increasingly important for high-sensitivity cosmic microwave background (CMB) experiments. We use the recently published Hα data of both the northern and southern skies as the basis for such a template.
The first step is to correct the Hα maps for dust absorption using the 100-μm dust maps of Schlegel, Finkbeiner & Davis. We show that for a range of longitudes, the Galactic latitude distribution of absorption suggests that it is 33 per cent of the full extragalactic absorption. A reliable absorption-corrected Hα map can be produced for ∼95 per cent of the sky; the area for which a template cannot be recovered is the Galactic plane area | b | < 5°, l = 260°–0°–160° and some isolated dense dust clouds at intermediate latitudes.
The second step is to convert the dust-corrected Hα data into a predicted radio surface brightness. The free–free emission formula is revised to give an accurate expression (1 per cent) for the radio emission covering the frequency range 100 MHz–100 GHz and the electron temperature range 3000–20 000 K. The main uncertainty when applying this expression is the variation of electron temperature across the sky. The emission formula is verified in several extended H ii regions using data in the range 408–2326 MHz.
A full-sky free–free template map is presented at 30 GHz; the scaling to other frequencies is given. The Haslam et al. all-sky 408-MHz map of the sky can be corrected for this free–free component, which amounts to a ≈6 per cent correction at intermediate and high latitudes, to provide a pure synchrotron all-sky template. The implications for CMB experiments are discussed. 相似文献
The first step is to correct the Hα maps for dust absorption using the 100-μm dust maps of Schlegel, Finkbeiner & Davis. We show that for a range of longitudes, the Galactic latitude distribution of absorption suggests that it is 33 per cent of the full extragalactic absorption. A reliable absorption-corrected Hα map can be produced for ∼95 per cent of the sky; the area for which a template cannot be recovered is the Galactic plane area | b | < 5°, l = 260°–0°–160° and some isolated dense dust clouds at intermediate latitudes.
The second step is to convert the dust-corrected Hα data into a predicted radio surface brightness. The free–free emission formula is revised to give an accurate expression (1 per cent) for the radio emission covering the frequency range 100 MHz–100 GHz and the electron temperature range 3000–20 000 K. The main uncertainty when applying this expression is the variation of electron temperature across the sky. The emission formula is verified in several extended H ii regions using data in the range 408–2326 MHz.
A full-sky free–free template map is presented at 30 GHz; the scaling to other frequencies is given. The Haslam et al. all-sky 408-MHz map of the sky can be corrected for this free–free component, which amounts to a ≈6 per cent correction at intermediate and high latitudes, to provide a pure synchrotron all-sky template. The implications for CMB experiments are discussed. 相似文献
5.
Abstract Zircons have been studied from different layers of migmatites (from Arvika, western Sweden and Nelaug, southern Norway) and from a paragneiss (from Arvika) associated with one of the migmatites. The main purpose of the investigation is to establish whether or not information about zircons can help in the elucidation of the parentage and rock-forming processes of migmatites.
The elongation ratio of zircons from all layers is small and characteristic of sedimentary zircons. Further, the absence of characteristic colours and the growth trends of the zircons (indicated by the reduced major axes) observed in the various samples both support a sedimentary parentage for these rocks. The zircons of all layers exhibit secondary growth (overgrowth, outgrowth and multiple growth) due to metamorphism. Compared with the zircons from the paragneiss, those of the migmatite layers are more clouded and less rounded, some of them becoming opaque or even skeletal; this is especially true of the zircons from the leucosomes. These observations indicate an alteration of the original sedimentary zircons in the migmatite, especially in the leucosomes, in response to the migmatization process, previously interpreted as partial melting. 相似文献
The elongation ratio of zircons from all layers is small and characteristic of sedimentary zircons. Further, the absence of characteristic colours and the growth trends of the zircons (indicated by the reduced major axes) observed in the various samples both support a sedimentary parentage for these rocks. The zircons of all layers exhibit secondary growth (overgrowth, outgrowth and multiple growth) due to metamorphism. Compared with the zircons from the paragneiss, those of the migmatite layers are more clouded and less rounded, some of them becoming opaque or even skeletal; this is especially true of the zircons from the leucosomes. These observations indicate an alteration of the original sedimentary zircons in the migmatite, especially in the leucosomes, in response to the migmatization process, previously interpreted as partial melting. 相似文献
6.
7.
Qinghai Wang Wenliang Xu Dongyan Wang Jingqian LinCollege of Earth Sciences Jilin University Changchun China 《东北亚地学研究》2003,(2)
1IntroductionAdakite has specially sense in the resuming structure background of rock formed,because of its distinctive geochemistry feature and implying partic-ular petrogenesis and ore genesis mechanism (De-fant and Drummond,1990),as a result,it arouses numerous researchers widely concern. After adakite conception was drawn by Chinese (Wang etal.,2000), it was widely concerned by domestic re-searchers (Wang etal.,2000,2001a,2001b;Xu etal.,2000;Pan etal.,2001;Qian,2001;Xu etal.,2001;X… 相似文献
8.
9.
Ignacio Ferreras Alessandro Melchiorri Domenico Tocchini-Valentini 《Monthly notices of the Royal Astronomical Society》2003,344(1):257-261
The age of the Universe has been increasingly constrained by different techniques, such as the observations of type Ia supernovae (SNIa) at high redshift or dating the stellar populations of globular clusters. In this paper, we present a complementary approach using the colours of the brightest elliptical galaxies in clusters over a wide redshift range ( z ≲ 1) . We put new and independent bounds on the dark energy equation of state parametrized by a constant pressure-to-density ratio w Q and by a parameter (ξ) which determines the scaling between the matter and dark energy densities. We find that accurate estimates of the metallicities of the stellar populations in moderate and high-redshift cluster galaxies can pose stringent constraints on the parameters that describe dark energy. Our results are in good agreement with the analysis of dark energy models using SNIa data as a constraint. Accurate estimates of the metallicities of stellar populations in cluster galaxies at z ≲ 2 will make this approach a powerful complement to studies of cosmological parameters using high-redshift SNIa. 相似文献
10.