Evidence for lithium-aluminosilicate supersaturation of pegmatite-forming melts

New experimental data on the solubility of lithium (Li) at spodumene (LiAlSi₂O₆) and petalite (LiAlSi₄O₁₀) saturation at 500 MPa and 550–750 °C reveal evidence for lithium supersaturation of pegmatite-forming melts before the formation of Li-aluminosilicates. The degree of Li enrichment in granitic melts can reach ~11,000 ppm above the saturation value before the crystallization of Li-aluminosilicate minerals at lower temperatures. Comparison of the experimental results with the spodumene-rich Moblan pegmatite (Quebec) is consistent with extreme Li enrichment of the pegmatite-forming melt prior to emplacement, which cannot be explained with equilibrium crystallization of Li-aluminosilicates from a common granitic melt. The results of this study support the model of disequilibrium fractional crystallization through liquidus undercooling as the most plausible mechanism for the generation of such Li-rich ore resources.     

Hg and As Minerals in Fluid Inclusions from the Williams Mine,Hemlo,and Their Genetic Implications

The Hemlo mineralization is enigmatic compared to general Archean lode gold deposits based on the fact that is characterized by an exotic mineralogy containing elements such as As,Hg,Sb,Ba,V and Mo.The genetic concepts range from syngenetc to epigenetic types of mineralization.This reconnaissance study was designed to examine the relationshp of Hg-As minerals with respect of fluid inclusions in the Williams mine(formerly known as the Page Williams mine)covering the A and C ore zones.     

Determinations of focal depths of earthquakes associated with the bending of oceanic plates at trenches

The earthquakes examined in this paper are all within the oceanic lithosphere and are associated with the bending of plates before subduction. Accurate determinations of the depth of these earthquakes are needed to study the stress pattern within a bending plate. Routinely-determined depths of shallow sub-oceanic earthquakes published in bulletins are unreliable. The depths can be accurately determined to within a few kilometers if the original seismograms from these events are studied. In some cases, the reflected phases pP and pwP can be clearly identified. There exists the possibility that the wave reflected at the water-air interface, pwP, may be misidentified as pP, leading to erroneous estimates of depth. Additional methods of analysis, such as surface wave radiation patterns or the apparent frequency-dependence of reflection at the crust-water interface, can remove this possible source of confusion. One of the most powerful techniques for depth analysis is the modelling of long-period waveforms. The pattern of stresses within the bending oceanic lithosphere revealed by the depths and focal mechanisms of these intraplate earthquakes is one of horizontal, deviatoric tension down to a depth of about 25 km, with horizontal compression at greater depths.     

Permafrost science and secondary education: direct involvement of teachers and students in field research

Permafrost and periglacial geomorphology are absent from the science curriculum in most secondary schools in the United States. This is an unfortunate situation given the recent increases in development and environmental concerns in northern latitudes and high-mountain areas, and the interesting examples of basic scientific principles found in the history of research on periglacial geomorphology and permafrost. In 1997 and 1998, a University of Delaware research group studying permafrost and periglacial geomorphology in northern Alaska participated in the National Science Foundation's (NSF) Teachers Experiencing the Antarctic and Arctic (TEA) Program. In each of these years, a high school teacher and a student traveled as part of the research team to the North Slope of Alaska. They learned about the landscape, collected active-layer thickness and temperature measurements, and assisted in data analysis. Results from studies of active-layer thickness variability and ground temperature contributed to a series of long-term observations and international research on the impacts of global climate change. Since their expeditions, the teachers have shared their experiences with their classrooms and communities in several ways, including public lectures and the Internet. Classroom activities are available to the public through the TEA web site (http://tea.rice.edu). This experience may heighten public awareness of permafrost and contribute to it becoming a useful part of the secondary curriculum.     

Spitzer space telescope observations of SGR and AXP environments

Both Anomalous X-ray Pulsars (AXPs) and Soft Gamma Repeaters (SGRs) are thought to be manifestations of magnetars. However, the specific physical characteristics that differentiate the two classes of objects remain unclear. There is some evidence that the progenitors of these sources and/or the environment in which they form might influence the type of phenomena the resulting magnetar displays. Several of the AXPs appear to be associated with supernova remnants, while embedded clusters of massive stars have been found in the immediate vicinity of some SGRs. Since both AXPs and SGRs are distributed close to the Galactic plane, high extinction makes studies in the optical difficult. We present early results from our Spitzer program aimed at probing the environmental factors that might contribute to the difference in the observed characteristics between AXPs and SGRs.