177,169 research outputs found
The diamonds of South Australia
No full textConference proceedings published in Lithos, 2009; 112(Suppl. 2)Abstract not availableRalf Tappert, John Foden, Thomas Stachel, Karlis Muehlenbachs, Michelle Tappert, Kevin Will
Automated drill core logging using visible and near-infrared reflectance spectroscopy: A case study from the Olympic Dam IOCG deposit, South Australia
No full textReflectance spectrometers with automated scanning capabilities can gather compositional information directly from the surface of drill core. To showcase the usefulness of this analytical technique, 300 m of drill core from the Olympic Dam iron oxide copper-gold (IOCG) deposit, South Australia, were scanned using HyLogger. The reflectance spectra (400–2,500 nm) were analyzed to identify hematite and phengite, which are the most important alteration minerals at Olympic Dam. The results were plotted as a function of depth to produce a log that accurately identified ore-bearing and barren rocks. The position of the most intense absorption feature between 850 and 970 nm was found to correspond to iron concentration, and the intensity of the most intense absorption feature between 2,190 and 2,230 nm was found to correspond to aluminum concentration. In addition, phengite located near the ore-bearing zone was found to contain more aluminum than phengite located in the barren rocks, and this difference in phengite mineral chemistry was observable in the reflectance spectra between 2,190 and 2,230 nm.Michelle Tappert, Benoit Rivard, David Giles, Ralf Tappert and Alan Mauge
Spectroscopic Analysis of Tremendous-Outburst-Nova Candidates
No full textIn the course of a long-term project investigating classical novae with large outburst amplitudes, we have performed optical spectroscopy of several old-nova candidates. We here present the spectra of the candidates V630 Sgr, XX Tau, CQ Vel, V842 Cen, and V529 Ori, that hitherto lacked such classification.
While the first four show spectra typical of cataclysmic variables and can thus be identified as such, V529 Ori is probably misclassified. Of special interest are the two systems XX Tau and V842 Cen, which show signs of being low mass transfer systems. As such they can be used to judge the evolution scenarios for novae. In particular, given the rather young age of their outbursts, it appears more likely that these systems are not on their way into hibernation (i.e., cutting off mass transfer for a longer period of time), but are simply settling down towards their original configuration of comparatively low, but steady, mass transfer, such as for dwarf novae.
Based on observations collected at the European Southern Observatory, La Silla, Chile
Time-resolved Spectroscopy of Q Cyg
No full textA time-resolved optical spectroscopic study of the long-period (P=10.08h) old nova Q Cyg has revealed persistent yet erratic absorption features indicating the presence of a wind, while the system was rising to one of its stunded outbursts
The mineral chemistry, near-infrared, and mid-infrared reflectance spectroscopy of phengite from the Olympic Dam IOCG deposit, South Australia
No full textPhengite is the main potassic dioctahedral mica identified at the Olympic Dam iron oxide-copper-gold (IOCG) deposit, South Australia, where its mineral chemistry is quite variable. These differences can be explained by contrasting degrees of hydrothermal alteration. In the heavily-sericitized, ore-bearing rocks, the phengites display a lower-Si content, a higher-Al content, and a lower Mg-number than the phengites from the weakly-sericitized alteration halo that surrounds the deposit. Variations are also observed in the near- and mid-infrared reflectance spectra collected from phengite-bearing rocks. In the near-infrared, high-Al phengite produces a spectral absorption feature at 2.206. μm, and this feature is displaced to 2.213. μm for low-Al phengite. In the mid-infrared, high-Al phengite produces a strong reflectance peak at 9.59. μm, whereas this peak is observed at 9.57. μm in the spectra from low-Al phengite. Additional peaks were also identified at 10.98, 12.22, and 13.33. μm. These were most intense in the spectra from high-Al phengite. A drill core profile was produced using the results of the spectral analysis that shows the change in phengite mineral chemistry and phengite abundance as a function of depth. In general, near- and mid-infrared reflectance spectroscopy can be used to characterize the aluminum content of potassic dioctahedral micas like phengite, and this information can be used to infer the degree of sericitic alteration that has occurred as a result of hydrothermal fluid flow.Michelle C. Tappert, Benoit Rivard, David Giles, Ralf Tappert, Alan Mauge
Spectroscopy of old nova candidates
No full textWe present optical spectroscopy for several old nova candidates that hitherto lacked such observations. V842 Cen, V630 Sgr, XX Tau, CQ Vel, and V840 Oph show typical CV spectra, but V529 Ori is probably misclassified
A Carbon-Rich Nova V840 Oph
No full textWe present optical spectroscopy and multicolor photometry of the old nova V 840 Oph. As part of a long-term project to investigate novae with large outburst amplitudes, we identified this nova via its color characteristics and confirmed it spectroscopically. We find V840 Oph to be one of very few cataclysmic variables showing C IV emission at 580/1 nm. The study of the carbon lines suggests strongly that V 840 Oph contains a carbon-rich secondary star. So far, only the nova-like QU Car has been known to have such a companion. We also find spectroscopic evidence that V 840 Oph has a hot, dense accretion disc or stream and is probably a magnetic system
On the secondary star of the cataclysmic variable 1RXS J094432.1+035738
No full textWe present V and R-c-band photometry and optical near-infrared spectroscopy of the cataclysmic variable 1RXS J094432.1+035738. We detected features of a cool secondary star, which can be modeled with a red dwarf of spectral type M2(-1.0)(+0.5) V at a distance of 433 +/- 100 pc
Mineral inclusions in diamonds from the Panda kimberlite, Slave Province, Canada
No full textTappert, Ralf; Stachel, Thomas; Harris, Jeffrey W.; Shimizu, Nobumichi; Brey, Gerhard P
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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