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Charles?R.?SternEmail author Julien?M.?Allaz Markus?B.?Raschke G.?Lang?Farmer M.?Alexandra?Skewes Jeremy?T.?Ross 《Contributions to Mineralogy and Petrology》2018,173(8):65
Aplite dikes intruding the Proterozoic 1.42(±?3) Ga Longs Peak-St. Vrain Silver Plume-type peraluminous granite near Jamestown, Colorado, contain F, P, and rare earth element (REE)-rich globular segregations, with 40–46% REE, 3.7–4.8 wt% P2O5, and 5–8 wt% F. A combination of textural features and geochemical data suggest that the aplite and REE-rich globular segregations co-existed as two co-genetic liquids prior to their crystallization, and we propose that they are formed by silicate–fluoride?+?phosphate (+?S?+?CO2) melt immiscibility following ascent, cooling, and decompression of what was initially a single homogeneous magma that intruded the granite. The REE distribution coefficients between the silica-rich aplites and REE-rich segregations are in good agreement with experimentally determined distribution coefficients for immiscible silicate–fluoride?+?phosphate melts. Although monazite-(Ce) and uraninite U–Th–Pb microprobe ages for the segregations yield 1.420(±?25) and 1.442(±?8) Ga, respectively, thus suggesting a co-genetic relationship with their host granite, εNd1.42Ga values for the granites and related granitic pegmatites range from ??3.3 to ??4.7 (average ??3.9), and differ from the values for both the aplites and REE-rich segregations, which range from ??1.0 to ??2.2 (average ??1.6). Furthermore, the granites and pegmatites have (La/Yb)N <50 with significant negative Eu anomalies, which contrast with higher (La/Yb)N >100 and absence of an Eu anomaly in both the aplites and segregations. These data are consistent with the aplite dikes and the REE-rich segregations they contain being co-genetic, but derived from a source different from that of the granite. The higher εNd1.42Ga values for the aplites and REE-rich segregations suggest that the magma from which they separated had a more mafic and deeper, dryer and hotter source in the lower crust or upper mantle compared to the quartzo-feldspathic upper crustal source proposed for the Longs Peak-St. Vrain granite. 相似文献
13.
ABSTRACT Movement patterns of the Southern Rock Lobster Jasus edwardsii in Victoria, Australia were investigated from 8,533 tag-recapture events across a 20-year period (1992–2012). In total, 83% of lobsters were recaptured within 1?km of their tagging site and 93% within 5?km. While largely resident, elevated movements were observed within specific regions, with the overall direction of movement being from inshore to offshore areas. Movement was not impacted by lobster sex, size, or reproductive stage. The fishery for Southern Rock Lobster within Victoria is currently managed into two zones with separate total allowable commercial catches in each area. Given the high levels of site fidelity, our findings suggest that management of the resource at this spatial scale is appropriate and that consideration of significant movement between zones is not warranted in fishery stock assessment models. 相似文献
14.
Sergei V.Antipin Ignacio Becker AlexANDer A.Belinski Darya M.Kolesnikova Karim Pichara Nikolay N.Samus Kirill V.Sokolovsky Alla V.Zharova Alexandra M.Zubareva 《天文和天体物理学研究(英文版)》2018,(8)
Using 172 plates taken with the 40-cm astrograph of the Sternberg Astronomical Institute(Lomonosov Moscow University) in 1976–1994 and digitized with a resolution of 2400 dpi, we discovered and studied 275 new variable stars. We present the list of our new variables with all necessary information concerning their brightness variations. As in our earlier studies, the new discoveries show a rather large number of high-amplitude Delta Scuti variables, predicting that many stars of this type remain not detected in the whole sky. We also performed automated classification of the newly discovered variable stars based on the Random Forest algorithm. The results of the automated classification were compared to traditional classification and showed that automated classification was possible even with noisy photographic data. However, further improvement of automated techniques is needed, which is especially important when considering the very large numbers of new discoveries expected from all-sky surveys. 相似文献
15.
Alexandra Navrotsky David Ziegler Richard Oestrike Papu Maniar 《Contributions to Mineralogy and Petrology》1989,101(1):122-130
Transposed-temperature-drop calorimetry, using a Setaram HT 1500 calorimeter, was used to study directly the melting at 1773 K of mixtures of crystalline albite, anorthite, and diopside and of anorthite and forsterite. The enthalpy of albite at 1000–1773 K, starting with both crystalline and glassy samples, was also measured. The results confirm previously measured enthalpies of fusion of albite, diopside and anorthite (Stebbins et al. 1982, 1983; Richet and Bottinga 1984,1986). The new results use thermochemical cycles which completely avoid the glassy state by transforming crystals directly to melts. The enthalpy of fusion of forsterite is estimated to be 89±12 kJ/mol at 1773 K and 114±20 kJ/mol at its melting point of 2163 K. The data allow semiquantitative evaluation of heats of mixing in the molten silicates. Along the Ab-An join, enthalpies of mixing in the liquid at 773 K are the same or somewhat more negative than those in the glass at 986 K, whereas along Ab-Di and An-Di, enthalpies of mixing in the liquid are distinctly more positive than in the glass. These differences correlate with excess heat capacities in the liquids suggested by Stebbins et al. (1984). 相似文献
16.
Jaidong Ko Nancy E. Brown Alexandra Navrotsky Charles T. Prewitt Tibor Gasparik 《Physics and Chemistry of Minerals》1989,16(8):727-733
The phase boundary between MnTiO3 I (ilmenite structure) and MnTiO3 II (lithium niobate structure) has been determined by analysis of quench products from reversal experiments in a cubic anvil
apparatus at 1073–1673 K and 43–75 kbar using mixtures of MnTiO3 I and II as starting materials. Tight brackets of the boundary give P(kbar)=121.2−0.045 T(K). Thermodynamic analysis of this boundary gives ΔHo=5300±1000 J·mol−1, ΔSo = 1.98 ±1J·K−1· mol−1. The enthalpy of transformation obtained directly by transposed-temperature-drop calorimetry is 8359 ±2575 J·mol−1. Possible topologies of the phase relations among the ilmenite, lithium niobate, and perovskite polymorphs are constrained
using the above data and the observed (reversible with hysteresis) transformation of II to III at 298 K and 20–30 kbar (Ross
et al. 1989). The observed II–III transition is likely to lie on a metastable extension of the II–III boundary into the ilmenite
field. However the reversed I–II boundary, with its negative dP/ dT does represent stable equilibrium between ilmenite and lithium niobate, as opposed to the lithium niobate being a quench
product of perovskite. We suggest a topology in which the perovskite occurs stably at low T and high P with a triple point (I, II, III) at or below 1073 K near 70 kbar. The I–II boundary would have a negative P-T slope while the II–III and I–III boundaries would be positive, implying that entropy decreases in the order lithium niobate,
ilmenite, perovskite. The inferred positive slope of the ilmenite-perovskite transition in MnTiO3 is different from the negative slopes in silicates and germanates. These thermochemical parameters are discussed in terms
of crystal structure and lattice vibrations. 相似文献
17.
Alexandra Schmäh 《Journal of Paleolimnology》1993,9(2):99-108
In paleolimnology, subfossil head capsules of chironomids play an important role as ecological indicators of lake history. It is important to determine, therefore, whether fossil assemblages are representative of former biocoenoses. There is evidence that headcapsules washed in from other places can make up a significant percentage of the total. As interpretations are usually drawn from the examination of a single core, it is of special interest to know whether a fossil assemblage of a single site properly reflects limnological conditions of the whole lake. This study examined the taxonomic distribution of subfossil chironomids in the surficial sediments of the Bodensee-Untersee, with the aim of assessing the variability in chironomid assemblages. Apparently, most of the head capsules of the profundal fossil assemblages in the Untersee had been washed in from the littoral zone or from the slope. Although the Bodensee-Untersee is a rather large lake, variability is surprisingly low among all samples. Therefore a correct interpretation from a single core may be possible. 相似文献
18.
19.
Refraction effects of optical beams are generally caused by an inhomogeneous propagation medium and are a major source of systematic errors in the precise optical determination of angles and distances in the atmospheric surface layer. In this contribution a method for deriving vertical temperature and refractive index gradients from optical scintillation is presented. Knowledge of these gradients is required for the compensation of atmospherically induced errors for highly precise terrestrial geodetic measurements, like direct transfer and levelling. The advantage of the present optical method is, that temperature and refractive index gradients can be derived as line-averaged values over the propagation path, which is not possible by meteorological point measurements. Field observations have been carried out with a displaced-beam scintillometer over flat terrain and under different atmospheric conditions in order to verify this method. The experiments show, that this method allows to derive accurate correction values for precise terrestrial geodetic measurements. 相似文献
20.