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1.
An evaluation of models of apatite compositional variability using apatite from the Middle Banded series of the Stillwater Complex,Montana 总被引：2，自引：0，他引：2
Apatite is a relatively common accessory mineral in the olivine-bearing zones (OB-III and OB-IV) of the Middle Banded series
of the Stillwater complex, occurring interstitial to cumulus grains, as monomineralic inclusions in cumulus grains, and in
polymineralic clusters which may or may not be included in the cumulus grains. Eighty-nine of 185 samples examined were found
to contain some apatite. The F-Cl-OH content of the apatite show distinct stratigraphic variations. XClAp (mole fraction Cl
in apatite) of interstitial apatite increases upsection in both OB-III and OB-IV with average values ranging from 0.15 to
0.85 in OB-III and from 0.03 to 0.60 in OB-IV. XFAp varies inversely with XClApwith average values ranging from 0.00 to 0.70, while XOHAp remains relatively constant near 0.40 or decreases slightly with
height. These variations are remarkable given that no appreciable stratigraphic variations in either the major or trace element
compositions of any of the cumulus minerals are found in the 800 m of section that comprise OB-III and OB-IV. Within-sample
variation of XClAp for samples containing Cl-rich apatite is substantially larger (up to 0.65 XClAp) than for samples with
more F-rich apatite (XClAp varies by approximately 0.15). Although interstitial apatite is found throughout OB-III and OB-IV,
apatite occurring as monomineralic inclusion in cumulus grains or in polymineralic clusters is almost exclusively found in
samples with Cl-rich apatite. The data are best explained by a model involving the degassing of a Cl-rich volatile phase from
the crystallizing interstitial liquid. The up-section migration of this fluid resulted in the crystallization of F-rich apatite
in the lower portion and progressive Cl-enrichment in the apatite with height. The presence of hornblende-bearing dikes, veins
and pegmatoids at the level of maximum Cl-enrichment is consistent with a fluid migration model.
Received: 5 October 1995 / Accepted: 19 March 1996 相似文献
2.
We present new results from the SINGG Hα survey of nearby galaxies, which show that starbursts have a lower fraction of diffuse, warm ionized gas than other star-forming galaxies. We discuss the possible causes of this effect, including a decrease in field-star contributions, absorption of ionizing radiation by dust, and the escape of ionizing radiation from the galaxies. 相似文献
3.
Apatite distributions and compositions from cumulates from the EPR at Hess Deep, the MAR at the Kane Transform, and the SWIR at ODP Hole 735B were determined to assess the variability at each setting and to evaluate the potential utility of apatite in understanding the evolution of the lower ocean crust. Apatite in cumulates with low P2O5 contents are heterogeneously distributed along linear arrays or in tight clusters suggesting they crystallized from planar or pipe-like channels of evolved liquid. Most of the variation in the apatite composition is in the halogen site. The XApF and XApCl are inversely correlated defining trends at near constant XApOH with EPR XApOH=0.25, MAR XApOH=0.45, and SWIR XApOH=0.65. These trends are defined both by sample averages and by the range of individual analyses in samples with large ranges in their F/Cl ratio. These trends are interpreted to reflect the reequilibration of apatite from variably evolved liquids/fluids that moved through the crystal mush. Comparison of the F–Cl–OH contents of apatite with the F–Cl–OH contents of glasses recovered from the same ridges show approximate correspondence: apatite and glasses from the EPR have the highest halogen contents while apatite and glasses from the MAR and SWIR have more OH. Some of the higher Cl contents in the apatite are interpreted to be produced by degassing of the cumulus pile while others reflect the assimilation of a seawater component. We suggest that systematic analysis of apatite from oceanic cumulates might allow cumulates that crystallized at shallow depths and assimilated seawater-derived components to be distinguished from those that crystallized below the level of seawater interaction. 相似文献
4.
Spatial distribution of metals in sediments of the Ribeira Bay, Angra dos Reis, Rio de Janeiro, Brazil 总被引：1，自引：0，他引：1
N.V. Freret-Meurer J.V. Andreata B.C. Meurer F.V. Manzano M.G.S. Baptista D.E. Teixeira M.M. Longo 《Marine pollution bulletin》2010,60(4):627-629
This study aims to analyze the spatial distributions of several metals in sediments from five sites in Ribeira Bay, Brazil. Ribeira Bay is a very important area to the local community, due to its artisan fishery, and it also has a biological relevance for many marine species that use mangroves as nursery and feeding sites. According to the results, the area was not considered a metal polluted area. Despite not having a significant source of metals inside the Bay nowadays, Ilha Grande Bay harbors a shipyard, an oil terminal, and a commercial port, as well as two thermonuclear power plants (Angra I e II), all of which indirectly influence the study area. 相似文献
5.
Grace Xingxin Gao Liang Heng Achim Hornbostel Holmer Denks Michael Meurer Todd Walter Per Enge 《GPS Solutions》2013,17(4):561-573
The Galileo E5a/E5b signals and the Global Positioning System (GPS) L5 signal lie within the aeronautical radionavigation services (ARNS) band. They suffer interference from the services in this frequency band, in particular, pulsed signals from distance measuring equipment (DME) and tactical air navigation (TACAN) systems. To maintain system accuracy and integrity, interference mitigation is beneficial and necessary. We first present the real DME/TACAN environment at Stanford, CA as an example to illustrate the need for mitigating DME/TACAN interference. We then propose a time and frequency joint mitigation algorithm—Hybrid Blanking and its simplified version, frequency domain adaptive filtering (FDAF) for hardware implementation. Finally, a flight measurements campaign was performed over a European DME/TACAN hotspot near Frankfurt, Germany, to record a worst-case DME interference environment. Recorded data from the flight tests mixed with injected GNSS signals verify the effectiveness of the proposed mitigation algorithm. 相似文献
6.
A multi-technique approach for characterizing the SVN49 signal anomaly, part 2: chip shape analysis 总被引：2，自引：1，他引：1
Steffen Thoelert Michael Meurer Stefan Erker Oliver Montenbruck André Hauschild Pat Fenton 《GPS Solutions》2012,16(1):29-39
Due to a satellite internal reflection at the L5 test payload, the SVN49 (PRN1) GPS satellite exhibits a static multipath
on the L1 and L2 signals, which results in elevation-dependent tracking errors for terrestrial receivers. Using a 30-m high-gain
antenna, code and carrier phase measurements as well as raw in-phase and quadrature radio frequency samples have been collected
during a series of zenith passes in mid-April 2010 to characterize the SVN49 multipath and its impact on common users. Following
an analysis of the receiver tracking data and the IQ constellation provided in Part 1 of this study, the present Part 2 provides
an in-depth investigation into chip shapes for the L1 and L2 signals. A single reflection model is found to be compatible
with the observed chip shape distortions and key parameters for an elevation dependent multipath model are derived. A good
agreement is found between multipath parameters derived independently from raw IQ-samples and measurements of a so-called
Vision Correlator. The chip shapes and their observed variation with elevation can be used to predict the multipath response
of different correlator types within a tracking receiver. The multipath model itself is suitable for implementation in a signal
simulator and thus enables laboratory testing of actual receiver hardware. 相似文献
7.
A multi-technique approach for characterizing the SVN49 signal anomaly, part 1: receiver tracking and IQ constellation 总被引：3，自引：1，他引：2
André Hauschild Oliver Montenbruck Steffen Thoelert Stefan Erker Michael Meurer Javad Ashjaee 《GPS Solutions》2012,16(1):19-28
A characterization of the signal anomaly of SVN49 is presented. A mathematical model is developed to relate the observed multipath
to the internal signal reflection. The analyses provided are based on measurements, which have been collected during a dedicated
tracking campaign with a 30-m dish antenna. Data on the L1 and L2 frequency have been collected with four different receivers.
In addition, IQ samples have been recorded directly with a spectrum analyzer. The multipath combination of the receiver measurements
on L1 and L2 is analyzed to demonstrate the effect of the signal reflections on different correlator spacing. The capability
to suppress the signal reflection with receiver multipath mitigation methods is demonstrated. Finally, preliminary estimates
of the attenuation, delay, and phase shift over elevation are obtained from an IQ sample analysis. 相似文献
8.
William P. Meurer S. Klaber Alan E. Boudreau 《Contributions to Mineralogy and Petrology》1997,130(1):81-92
Mineralogically zoned and unzoned discordant bodies composed predominately of plagioclase with up to 35% olivine, occur at
three different levels in Olivine-Bearing zones III and IV of the Middle Banded series of the Stillwater complex. The discordant
bodies are elongate perpendicular to the layering of the host cumulates with slender concordant apophyses. Although the host
olivine-gabbros are foliated with tabular plagioclase, the discordant bodies lack a discernible fabric and have blocky plagioclase.
Average olivine in the host rocks is slightly more magnesian than that of the discordant bodies (Mg#75.8 ± 0.7 versus Mg#74.6 ± 0.3 respectively) but plagioclase compositions are indistinguishable (An77.6 ± 2.0 versus An76.6 ± 4.3– average host and discordant bodies respectively). Whole-rock major- and trace-element compositions of the discordant bodies
are generally indistinguishable from cumulates with similar modal abundance. However, bulk compositions of anorthositic cores
from the discordant bodies are enriched in K, Na, Ba, Sr and P. We conclude that the discordant bodies formed when cooler
volatile fluids or fluid-rich silicate liquids moved upward and encountered a hotter undersaturated solid-plus-liquid assemblage.
Continued liquid/fluid fluxing increased the permeability along the flow path and focused the flow, allowing the original
bulk compositions to be modified and leaving plagioclase-rich troctolites and anorthosites. The shapes of the discordant bodies
suggest that the cumulus pile had anisotropic permeability during late-stage liquid/fluid flow. Chemical and mineralogical
evidence from other parts of Olivine-Bearing zones III and IV suggests that the processes that formed the discordant bodies
may have influenced other cumulates. In fact, it appears that the same processes that formed the discordant bodies operated
within an anorthositic layer, strongly modifying the chemistry of the rock but leaving no mineralogical or textural evidence.
Received: 10 December 1996 / Accepted: 12 August 1997 相似文献
9.
The size, paragenetic setting, distribution, and composition of apatite grains in 16 thin sections from one sample of an olivine
gabbro from the Stillwater Complex, Montana were documented to determine whether they grew from trapped interstitial liquid
or in an open system. The grains show extreme variability in cross-sectional area, ranging from <150 to >300,000 μm2. The apatite grains are not associated with quartz, Fe–Ti oxides, or evolved overgrowths on cumulus grains as expected for
the crystallization of a trapped liquid, which suggests that they grew in an open system. The grains are very irregularly
distributed, with a single cluster comprising almost 25% of the cumulative apatite cross-sectional area from all 16 slides.
The spatial patterns of the apatite indicate that the interstitial liquid moved in tubular channels during the final stages
of compaction. The trace-element composition of liquids calculated from apatite and silicate mineral compositions are similar,
indicating that the apatite crystallized from liquids that were not dramatically enriched in incompatible elements. We conclude
that the interstitial liquid never actually became trapped, that liquid was lost in an open system to essentially zero porosity,
and that the model of cumulates as a combination of cumulus grains and trapped liquid should be discarded. 相似文献
10.
Charles Paradis Nathan Van Ee Kendyl Hoss Cullen Meurer Aaron Tigar Paul Reimus Raymond Johnson 《Ground water》2022,60(4):565-570
A simple algebraic equation is presented here to estimate the magnitude of groundwater velocity based on data from a single-well injection-drift test thereby eliminating the time-consuming and costly extraction phase. A volume of tracer-amended water was injected by forced-gradient into a single well followed by monitoring of the conservative solute tracers under natural-gradient conditions as their upgradient portions drifted back through the well. The breakthrough curve data from the single well during the drift phase was analyzed to determine the mean travel times of the tracers. The estimated mean upgradient travel distance back through the single well and the mean travel times of the tracers were used in a simple algebraic equation to estimate groundwater velocity. The groundwater velocity based on the single-well injection-drift test was estimated to be approximately 0.64 ft per day. Two transects of observation wells were used to monitor the natural-gradient tracer transport downgradient of the injection well. The one-dimensional, or dual-well, transport of the tracer from the injection well to the nearest downgradient observation well indicated that the groundwater velocity was 0.55 ft per day. The two-dimensional, or multi-well, transport of the center of mass of the tracers indicated that the groundwater velocity was 0.60 ft per day; the dual- and multi-well results were in excellent agreement with those from the single-well and validated the simple algebraic equation. The new single-well method presented here is relatively simple, rapid, and does not require an extraction phase. 相似文献