Characterisation of gold from Fiji

This is a study of the variation in chemistry and inclusion mineralogy of bedrock and placer gold from Fiji. It forms part of a large project, undertaking gold characterisation from a wide range of geological environments in Ecuador, Zimbabwe, Malaysia and Fiji. The work was carried out under the Overseas Development AdministratiodBritish Geological Survey Technology Development and Research programme (Project R5549) as part of the British Government’s provision of technical assistance to developing countries. For the Fijian component of the project, samples were collected from river gravels, primary ore, and table concentrates. In total thirty-five samples from five localities were examined. Data collected from these samples are represented by over 100 point analyses of gold, identification of associated minerals, and microgeochemical maps of gold-mineral intergrowths. A framework for identifying possible sources of alluvial gold is given. This was achieved by characterising bedrock gold mineralisation from a variety of epithermal and porphyry environments. The environments studied included alkali (the Emperor Gold Mine), high-sulphidation (the Mount Kasi prospect) and telescoped (the Tuvatu prospect) systems. A study of placer gold from the Waimanu alluvial deposit, the only alluvial gold deposit in Fiji, showed two distinct sources of gold: one, a low-silver type, associated with Cu-Fe sulphides, can be related to the nearby Namosi porphyry copper deposit. The other source, a high-silver type with abundant tellurides, indicates an alkali epithermal association, suggesting a source similar in style to the mineralisation observed at Emperor Gold Mine. The identification of two bedrock sources for the Waimanu alluvials clearly shows that there must be a, yet unknown, alkali epithermal (Emperor) source within the Waimanu catchment. This demonstrates the power of alluvial gold characterisation and its role in gold exploration. An important implication of these results is that future exploration within the area should be focussed on locating this “Emperor type” source

Effects of gravity on contractile proteins

A method was established for the isolation and purification of nuclei in high yield from the microplasmodia of Physarum flavicomum. Purified nuclei were resistant to breakage by methods commonly employed for isolated plant and animal nuclei. Several methods for the extraction of nuclear protein were compared. Incubation of nuclear lysates with either 2 M NaCl, with or without 5 M urea, or 1 M CaCl2 resulted in the extraction of nuclear action together with histones. The histones were chemically fractionated into the 5 basic groups common to other eucaryotic tissue. Amino acid analyses of the total histone were also performed. Nuclear actin was found to have a molecular weight of 41,000 ? 4,000 daltons as determined by SDS polyacrylamide gel electrophoresis. The amino acid composition of the nuclear action was established

Pumping up the [N I] nebular lines

The optical [N I] doublet near 5200 {\AA} is anomalously strong in a variety of emission-line objects. We compute a detailed photoionization model and use it to show that pumping by far-ultraviolet (FUV) stellar radiation previously posited as a general explanation applies to the Orion Nebula (M42) and its companion M43; but, it is unlikely to explain planetary nebulae and supernova remnants. Our models establish that the observed nearly constant equivalent width of [N I] with respect to the dust-scattered stellar continuum depends primarily on three factors: the FUV to visual-band flux ratio of the stellar population; the optical properties of the dust; and the line broadening where the pumping occurs. In contrast, the intensity ratio [N I]/H{\beta} depends primarily on the FUV to extreme-ultraviolet ratio, which varies strongly with the spectral type of the exciting star. This is consistent with the observed difference of a factor of five between M42 and M43, which are excited by an O7 and B0.5 star respectively. We derive a non-thermal broadening of order 5 km/s for the [N I] pumping zone and show that the broadening mechanism must be different from the large-scale turbulent motions that have been suggested to explain the line-widths in this H II region. A mechanism is required that operates at scales of a few astronomical units, which may be driven by thermal instabilities of neutral gas in the range 1000 to 3000 K. In an appendix, we describe how collisional and radiative processes are treated in the detailed model N I atom now included in the Cloudy plasma code.Comment: ApJ in press. 8 pages of main paper plus 11 pages of appendices, with 13 figures and 12 table