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1.
Camille Dussaux Aude Gbelin Philippe Boulvais Vronique Gardien Stephen Grimes Andreas Mulch 《地学学报》2019,31(4):366-372
Variscan shear zones in the Armorican Massif represent sites of strong fluid‐rock interaction. The hydrogen isotope composition of muscovite (δDMs) from syntectonic leucogranite allows to determine the source of fluids that infiltrated the footwall of three detachment zones and the South Armorican Shear Zone. Using temperatures of hydrogen isotope exchange estimated from microstructural data, we calculate the hydrogen isotope ratios of water (δDwater) present within the shear zones during high‐temperature deformation. A ~40‰ difference in δDwater values from deep to shallow crustal level reveals a mixing relationship between deep crustal fluids with higher δD values that range from ?34 to ?33‰, and meteoric fluids with δD values as low as ?74‰ in the upper part of detachment footwalls. 相似文献
2.
The mass ratio of Charon to Pluto is a basic parameter describing the binary system and is necessary for determining the individual masses and densities of these two bodies. Previous measurements of the mass ratio have been made, but the solutions differ significantly (Null et al., 1993; Young et al., 1994; Null and Owen, 1996; Foust et al., 1997; Tholen and Buie, 1997). We present the first observations of Pluto and Charon with a well-calibrated astrometric instrument—the fine guidance sensors on the Hubble Space Telescope. We observed the motion of Pluto and Charon about the system barycenter over 4.4 days (69% of an orbital period) and determined the mass ratio to be 0.122±0.008 which implies a density of 1.8 to 2.1 g cm−3 for Pluto and 1.6 to 1.8 g cm−3 for Charon. The resulting rock-mass fractions for Pluto and Charon are higher than expected for bodies formed in the outer solar nebula, possibly indicating significant postaccretion loss of volatiles. 相似文献
3.
Lawrence M. Mayer Peter T. Rahaim William Guerin Stephen A. Macko Les Watling Franz E. Anderson 《Estuarine, Coastal and Shelf Science》1985,20(4):491-503
A variety of measures of organic matter concentration and quality were made on samples collected from the top few mm of intertidal mudflat sediment over the course of a year, in order to assess the relative importance of biological and sedimentological influences on sedimentary organic matter. Winter and summer were times of relatively fine-grained sediment accumulation, caused by biological deposition or stabilization processes and resulting in higher organic matter concentrations. Stable carbon isotope and Br:C ratios indicated a planktonic source of bulk organic matter. Ratios of organic carbon to specific surface area of the sediments were consistent with an organic monolayer coverage of sediment grains. Correction for changing grain size during the year showed no change in the organic concentration per unit surface area, in spite of organic matter inputs by in situ primary production, buildup of heterotroph biomass and mucus coatings, and biodeposition of organic-rich seston. There were also no indications of changes in bulk organic quality, measured as hydrolyzable carbohydrates and amino acids, in response to these biological processes. It is concluded that biological processes on a seasonal time scale affect the bulk organic matter of these sediments via a modulation of grain size rather than creation or decay of organic matter. 相似文献
4.
Arnold Gucsik Christian Koeberl Franz Brandsttter Eugen Libowitzky Wolf Uwe Reimold 《Meteoritics & planetary science》2003,38(8):1187-1197
Abstract— We studied unshocked and experimentally (at 12, 25, and 28 GPa, with 25, 100, 450, and 750°C pre‐shock temperatures) shock‐metamorphosed Hospital Hill quartzite from South Africa using cathodoluminescence (CL) images and spectroscopy and Raman spectroscopy to document systematic pressure or temperature‐related effects that could be used in shock barometry. In general, CL images of all samples show CL‐bright luminescent patchy areas and bands in otherwise nonluminescent quartz, as well as CL‐dark irregular fractures. Fluid inclusions appear dominant in CL images of the 25 GPa sample shocked at 750°C and of the 28 GPa sample shocked at 450°C. Only the optical image of our 28 GPa sample shocked at 25°C exhibits distinct planar deformation features (PDFs). Cathodoluminescence spectra of unshocked and experimentally shocked samples show broad bands in the near‐ultraviolet range and the visible light range at all shock stages, indicating the presence of defect centers on, e.g., SiO4 groups. No systematic change in the appearance of the CL images was obvious, but the CL spectra do show changes between the shock stages. The Raman spectra are characteristic for quartz in the unshocked and 12 GPa samples. In the 25 and 28 GPa samples, broad bands indicate the presence of glassy SiO2, while high‐pressure polymorphs are not detected. Apparently, some of the CL and Raman spectral properties can be used in shock barometry. 相似文献
5.
Andreas Just 《Astrophysics and Space Science》2003,284(2):727-730
There is a long term dynamical heating of stellar populations with age observed in the age – velocity dispersion – relation
(AVR). This effect allows a determination of the star formation history SFR(t) from local kinematical data of main sequence stars. Using a self-consistent disk model for the vertical structure of the
disk, we find from the kinematics of the stars in the solar neighbourhood that the SFR shows a moderate star burst about 10 Gyr ago followed by a continuous decline to the present day value consistent with the
observed number of OB stars. The gravitational potential of the gas component and of the Dark Matter Halo is included and
the effect of chemical enrichment, finite lifetime of the stars and mass loss of the stellar component are taken into account.
The scale heights for main sequence stars together with the SFR is then used to determine constistently the IMF from the observed local luminosity function. The main new result is that the power law break in the present day mass function
(PDMF) around 1 M
⊙ is entirely due to evolutionary effects of the disk and does not appear in the IMF.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
The integrated analysis of geological, seismological and field observations with lineament data derived from satellite images allows the identification of a possible seismogenic fault zone for an earthquake which occurred near Etne in southwestern Norway, on 29 February 1989. The hypocentre of the earthquake was located at the mid-crust at a depth of 13.8±0.9 km which is typical of small intraplate earthquakes. The Etne earthquake occurred as a result of normal faulting with a dextral strike-slip component on a NW–SE trending fault. Available geological and lineament data indicate correlation of the inferred seismogenic fault with the NW–SE trending Etne fault zone. An aeromagnetic anomaly related to the Etne fault zone forms a regional feature intersecting both Precambrian basement and allochthonous Caledonian rocks. Based on these associations the occurrence of the Etne event is ascribed to the reactivation of a zone of weakness along the Etne fault zone. Slope-instabilities developed in the superficial deposits during the Etne event demonstrate the existence of potentially hazardous secondary-effects of such earthquakes even in low seismicity areas such as southwestern Norway. 相似文献
7.
Martin M. Roth Thomas Fechner Dieter Wolter Andreas Kelz Thomas Becker 《Experimental Astronomy》2002,14(2):99-105
PMAS, the Potsdam Multi-Aperture Spectrophotometer, is a new integral field spectrograph in the optical, which is optimized
for good transmission and high image quality from 350 nm to 1 μm. We present our plan to implement a CCD charge-shuffle mode
to allow for beam switching with a very high degree of sky subtraction accuracy for faint object 3-D spectroscopy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Andreas Burkert 《Astrophysics and Space Science》2003,284(2):697-700
The puzzling correlation between the spin parameter λ of galactic disks and the disk-to-halo mass fraction f
disk is investigated. It is shown that such a correlation arises naturally from large uncertainties in determining the virial
masses of dark matter halos. This result indicates that halo properties derived from fits to observed rotation curves are
still very uncertain. An analysis of λ versus f
disk as function of the adopted halo virial mass shows that for reasonable halo concentrations f
disk ≈ 0.01 - 0.07 which is significantly smaller than the universal baryon fraction. Most of the available gas either never settled
into the galactic disks or was ejected subsequently.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Abstract— We report the results of dynamic crystallization experiments that were specifically designed to study the dependence of Ca and Al partitioning between forsterite and melt in rapidly cooling Caand Al‐rich melts. The partitioning of Ca between olivine and silicate melt is found to be independent of the cooling rate within the range of 1.5 to 1000°C/hr and at CaO contents of up to 25 wt%. Within analytical uncertainty, our data plot on the equilibrium partitioning curve obtained by Libourel (1999). The partitioning behavior of Al at high cooling rates is more complex. Aluminum is much more heterogenously distributed in the olivine and the co‐existing melt than Ca. But, no systematic trend of Al partition coefficient with cooling rate is observed. We apply the results of the experiments to the formation of meteoritic forsterites with relatively high contents of Ca and Al. Although these forsterites are found frequently inside chondrules, the Ca contents of their host chondrules are far too low to crystallize these high Ca‐forsterites. This is also true for very rapid cooling of chondrule melts. The parental melt of these forsterites requires CaO contents above 20 wt%. 相似文献
10.
Andreas G. Mueller Gregory C. Hall Alexander A. Nemchin Holly J. Stein Robert A. Creaser Douglas R. Mason 《Mineralium Deposita》2008,43(3):337-362
The Granny Smith (37 t Au production) and Wallaby deposits (38 t out of a 180 t Au resource) are located northeast of Kalgoorlie,
in 2.7 Ga greenstones of the Eastern Goldfields Province, the youngest orogenic belt of the Yilgarn craton, Western Australia.
At Granny Smith, a zoned monzodiorite–granodiorite stock, dated by a concordant titanite–zircon U–Pb age of 2,665 ± 3 Ma,
cuts across east-dipping thrust faults. The stock is fractured but not displaced and sets a minimum age for large-scale (1 km)
thrust faulting (D2), regional folding (D1), and dynamothermal metamorphism in the mining district. The local gold–pyrite
mineralization, controlled by fractured fault zones, is younger than 2,665 ± 3 Ma. In augite–hornblende monzodiorite, alteration
progressed from a hematite-stained alkali feldspar–quartz–calcite assemblage and quartz–molybdenite–pyrite veins to a late
reduced sericite–dolomite–albite assemblage. Gold-related monazite and xenotime define a U–Pb age of 2,660 ± 5 Ma, and molybdenite
from veins a Re–Os isochron age of 2,661 ± 6 Ma, indicating that mineralization took place shortly after the emplacement of
the main stock, perhaps coincident with the intrusion of late alkali granite dikes. At Wallaby, a NE-trending swarm of porphyry
dikes comprising augite monzonite, monzodiorite, and minor kersantite intrudes folded and thrust-faulted molasse. The conglomerate
and the dikes are overprinted by barren (<0.01 g/t Au) anhydrite-bearing epidote–actinolite–calcite skarn, forming a 600-m-wide
and >1,600-m-long replacement pipe, which is intruded by a younger ring dike of syenite porphyry pervasively altered to muscovite
+ calcite + pyrite. Skarn and syenite are cut by pink biotite–calcite veins, containing magnetite + pyrite and subeconomic
gold–silver mineralization (Au/Ag = 0.2). The veins are associated with red biotite–sericite–calcite–albite alteration in
adjacent monzonite dikes. Structural relations and the concordant titanite U–Pb age of the skarn constrain intrusion-related
mineralization to 2,662 ± 3 Ma. The main-stage gold–pyrite ore (Au/Ag >10) forms hematite-stained sericite–dolomite–albite
lodes in stacked D2 reverse faults, which offset skarn, syenite, and the biotite–calcite veins by up to 25 m. The molybdenite
Re–Os age (2,661 ± 10 Ma) of the ore suggests a genetic link to intrusive activity but is in apparent conflict with a monazite–xenotime
U–Pb age (2,651 ± 6 Ma), which differs from that of the skarn at the 95% confidence level. The time relationships at both
gold deposits are inconsistent with orogenic models invoking a principal role for metamorphic fluids released during the main
phase of compression in the fold belt. Instead, mineralization is related in space and time to late-orogenic, magnetite-series,
high-Mg monzodiorite–syenite intrusions of mantle origin, characterized by Mg/(Mg + FeTOTAL) = 0.31–0.57, high Cr (34–96 ppm), Ni (22–63 ppm), Ba (1,056–2,321 ppm), Sr (1,268–2,457 ppm), Th (15–36 ppm), and rare earth
elements (total REE: 343–523 ppm). At Wallaby, shared Ca–K–CO2 metasomatism and Th-REE enrichment (in allanite) link Au–Ag mineralization in biotite–calcite veins to the formation of the
giant epidote skarn, implicating a Th + REE-rich syenite pluton at depth as the source of the oxidized hydrothermal fluid.
At Granny Smith, lead isotope data and the Rb–Th–U signature of early hematite-bearing wall-rock alteration point to fluid
released by the source pluton of the differentiated alkali granite dikes. 相似文献