The extended dust emission around the nova GK persei

We have applied maximum entropy reconstruction methods to the IRAS observations of the nova GK Persei to examine the spatial distribution of the far-IR emission. We have discovered discrete regions of emission in a co-linear structure extending to 17 arcmin on either side of the binary system, supporting a stellar origin for the structure. We postulate that the evolved secondary is the progenitor of the circumbinary envelope.     

Melt water chemistry and its impact on stream water quality

Samples of snowpack leachate were collected over a 60 day period of the spring melt season in 1988 and 1989 at a 10 km² upland catchment in the Cairngorm mountains of Scotland. These were analysed for major ions to assess snowpack chemistry dynamics through the spring and to assess the melt water influence on stream water chemistry. The data clearly show preferential elution of sulphate and nitrate over chloride and hydrogen over the other cations during the early melt of 1988. Following the addition of ions to the snow surface, either as snow or later in the season as rain, the elution sequence is reproduced. Comparison of leachate chemistry with stream chemistry samples taken at the basin outlet indicate that snow pack melt water contributes directly to stream water. The stream water chemistry signal is, however, noisy and the stream concentrations are considerably damped relative to the snowpack leachate. This is thought to be a consequence of differential melting within the catchment as the snowpack at lower altitudes is at a more advanced stage of melt and so holds fewer solutes and mixing with groundwater contributions. Temperature observations at different altitudes within the catchment support this interpretation.     

Dehydration melting and the granulite transition in metapelites from southern Namaqualand,S. Africa

In a prograde amphibolite-granulite transition zone in the Namaqualand Metamorphic Complex, metapelites show an interbanding of the amphibolite facies association biotite+sillimanite+quartz with the granulite facies association garnet+cordierite+K-feldspar. Relict graded bedding shows that compositional banding is of sedimentary origin. The garnet-cordierite-K-feldspar gneisses contain quartzofeldspathic segregations surrounding garnets, and have more Fe-rich bulk compositions than the biotite-sillimanite schists.The contrasting asemblages could have formed at the same pressure and temperature provided that a(H₂O) was systematically lower in the garnet-cordierite-K-feldspar layers. The a(H₂O) reduction resulted from the production of silicate melt by a vapour-absent continuous Fe-Mg reaction such as biotite+sillimanite+quartz=garnet+K-feldspar+liquid which affects Fe-rich compositions before vapour-absent melting occurs in more Mg-rich rocks. The segregations represent the solid and liquid products of the reaction.Such processes imply local control of a(H₂O), and indicate that this granulite transition did not result from a regional influx of metasomatising fluids.     

Geomorphic analysis of Hohokam settlement patterns on alluvial fans along the western Flank of the Tortolita Mountains,Arizona

Geoarchaeological investigations of the alluvial piedmont or bajada emanating from the Tortolita Mountains, Arizona, show that the distribution of Hohokam sites apparent from the surface is complete and undisturbed by geological processes. Late Holocene geomorphic processes and their resultant deposits on the bajada affected the location of prehistoric Hohokam agricultural settlements. Hohokam settlements were commonly situated on small alluvial fans dominated by sheetwash processes and deposition of fine-grained alluvium, where floodwater farming could be easily pursued with little modification of the natural surface. Large alluvial fans, dominated by channel processes and coarse-grained alluvium were avoided by the Hohokam farmer because these areas were less suitable for floodwater farming.