ALBERT

Description: Hydrogen-tritium separation factors for determining mechanism of proton transfer across double layers

Description: A report is presented of detailed observations of electrons ranging in energy from 50 to 1000 keV in a relativistic electron precipitation event. The results shown were obtained with the aid of a sounding rocket that was launched at the Andoya rocket range in northern Norway in May 31, 1972. A graph is provided with the differential energy spectrum at a pitch angle of 30 deg for maximum and minimum values.-

Description: New rocket data on auroral electron energy spectra are presented. Two regions of the aurora are sharply defined: the peak energy region, called the beam, and a strongly altitude-dependent tail of slowed-down secondary and backscattered electrons. It is shown that the oscillating two-stream instability described by Papadopoulos and Coffey (1974) accounts for the observed features of the tail.

Description: Integral electron flux and current in retarding- potential plasma probes, considering application to nonconcave geometry and spacecraft probes

Description: The effects of mesoscale triggering on organized nonsevere convective cloud systems in the High Plains are considered. Two experiments were conducted to determine if a one-dimensional quasi-time dependent model could (1) detect soundings which were sensitive to mesoscale triggering, and (2) discriminate between cases which had mesoscale organized convection and those with no organized convection. The MESOCU model was used to analyze the available potential instability and thermodynamic potential for cloud growth. It is noted that lifting is a key factor in the release of available potential instability on the High Plains.

Description: Auroral band electron energy spectra, electron number density, ionization and luminosity obtained from rocket measurements

Description: The 2.67 Ga Hackett River volcanogenic massive sulfide (VMS) deposits located in the northeastern Slave province, Nunavut, Canada, are among the largest undeveloped massive sulfide resources in Canada and are silver rich compared to other such deposits of similar age, with Ag grades up to 3,000 g/t. The deposits are hosted by the Ignerit Formation of the felsic to intermediate calc-alkaline Hackett River Group metavolcanic rocks that are part of the province-wide supracrustal Yellowknife Supergroup. One of the most economically significant of the Hackett River deposits is the Hackett River Main zone (Main zone), which consists of two parts: a stratigraphically lower chalcopyrite-rich stringer zone and an upper massive to semimassive polymetallic sulfide lens. The mineralization is subdivided into five types based on mineralogy, textures, and approximate stratigraphic position: (1) disseminated footwall sulfides, (2) copper-rich stringer sulfides, (3) pyrite-poor sphalerite-pyrrhotite-chalcopyrite mineralization at the top of the stringer zone, (4) mineralization in calc-silicate–altered calcareous tuff units, and (5) sphalerite-pyrite massive sulfide. In type 1 mineralization, disseminated pyrite, pyrrhotite, and sphalerite contain negligible Ag and in type 2, Bi-Ag-(Pb) sulfides, Ag-Bi-Se–enriched galena and chalcopyrite are the dominant Ag hosts. Within type 3, Ag-rich tetrahedrite (freibergite) and galena are the main Ag hosts. In type 4, Ag is hosted in disseminated electrum and freibergite, and within type 5 mineralization, freibergite hosts 99% of the Ag. Overall within the Main zone, Ag-rich freibergite contains 79.4% of the Ag, whereas chalcopyrite hosts 6.3% and galena contains 1.8%. Trace minerals such as electrum host the remainder of the Ag, and these have a limited spatial distribution. Zone refining is the most important control on the distribution of Ag within the Main zone and the principal controls on Ag residence are mineralizing fluid temperature, deposit-scale relative redox conditions, sulfidation state, location of the mineralization relative to the hydrothermal conduit, and the ratio of Bi to Sb in the mineralizing fluid available for coupled substitution. Within the freibergite and chalcopyrite, Ag directly substitutes for Cu and replaces Pb in galena by coupled substitution with Bi and, to a lesser extent, Sb. Lower temperatures 〈ca. 250°C and more oxidizing conditions favored partitioning of Ag into freibergite and less oxidizing conditions favored galena as a host. At higher temperatures, 〉ca. 250°C, the most reducing conditions favored incorporation in Ag-Bi-rich galena (plus Se) and Bi-bearing sulfides or Ag-rich chalcopyrite under lesser reducing conditions.

Description: Sea-floor imagery, volcanic rock, massive sulfide, and hydrothermal plume samples (δ3He, pH, dissolved Fe and Mn, and particulate chemistry) have been collected from the Rumble II West volcano, southern Kermadec arc, New Zealand. Rumble II West is a caldera volcano with an ∼3-km-diameter summit depression bounded by ring faults with a resurgent central cone. Rocks recovered to date are predominantly mafic in composition (i.e., basalt to basaltic andesite) with volumetrically lesser intermediate rocks (i.e., andesite). On the basis of its size, geometry, volcanic products, and composition, Rumble II West can be classified as a mafic caldera volcano. Rumble II West has a weak hydrothermal plume signature characterized by a small but detectable δ3He anomaly (25%). Time-series light scattering data though, obtained from vertical casts and tow-yos, do show that hydrothermal activity has increased in intensity between 1999 and 2011. Massive sulfides recovered from the eastern caldera wall and eastern flank of the central cone are primarily comprised of barite and chalcopyrite, with lesser sphalerite, pyrite, and traces of galena. The weak hydrothermal plume signal indicates that the volcano is in a volcanic-hydrothermal quiescent stage compared to other volcanoes along the southern Kermadec arc, although the preponderance of barite with massive sulfide mineralization indicates higher temperature venting in the past. Of the volcanoes along the Kermadec-Tonga arc known to host massive sulfides (i.e., Clark, Rumble II West, Brothers, Monowai, Volcano 19, and Volcano 1), the majority (five out of six) are dominantly mafic in composition and all but one of these mafic volcanoes form moderate-size to large calderas. To date, mafic calderas have been largely ignored as hosts to sea-floor massive sulfide deposits. That 75% of the presently known massive sulfide-bearing calderas along the arc are mafic in composition (the dacitic Brothers volcano is the exception) has important implications for sea-floor massive sulfide mineral exploration in the modern oceans and ancient rock record on land.

Description: Volcanogenic massive sulfide (VMS) deposits typically contain significant proportions of magma-derived chalcophile (Cu affinity) and siderophile (Fe affinity) elements such as Au, Cu, V, Zn, Mo, Bi, Sb, and As that relate to the composition of associated (host) magmatic rocks. Here, we combine new and published trace element data for lavas recovered from 15 volcanic centers along the Kermadec arc. The data show that mafic back-arc and arc-front lavas are enriched in most of the chalcophile and siderophile elements when compared with mid-ocean ridge basalts (MORB). Elevated (Cu, Zn, V, Mo, Pb)/Yb, Ba/La, As/Ce, and Sb/Pr ratios indicate that the chalcophile and siderophile elements are either transported into the mantle wedge via hydrous fluids derived from the subducting slab, or are liberated from residual mantle wedge sulfides that are oxidized by hydrous fluids. Lower ratios of (Cu, Zn, Mo, Sb, and Pb)/(MREE, HREE) in basalts from the Kermadec back arc (Havre Trough) when compared to the arc front suggests decreasing slab-related input into the mantle source away from the arc front. Unusually high contents of LILE, Ag, Sn, Mo, Th, LREE, MREE, Nb, Zr, Hf, and positive trends in (Ag, Sn)/Yb with Th/Yb, Hf/Y, (La/Sm)N, but low Sr/Y, in dacites from the Brothers volcanic center, southern Kermadec arc, indicate the additional transport of Ag and Sn via a solute-rich supercritical fluid, or via a sediment-derived melt. Magmas generated through partial melting of a sub-arc mantle metasomatized by hydrous melts thus appear to play an important role in the formation of Cu-Au-Ag−rich arc-type VMS deposits.