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Jonelle Nikolai Crisostomo Jeddalyn Parian Daizo Ishiyama Redempta Baluda Sonia Eguia Jocelyn Galapon Gerry Comia Jessie Segura Maureen Laroco Noel Oliveros Victor B. Maglambayan 《Resource Geology》2007,57(2):241-247
Two ore and three alteration types were identified in the Lascogon Project of Philex Gold Philippines, in Surigao del Norte, Mindanao Island, Philippines. The jasperoid ore is the host to the Carlin‐like gold mineralization in the Lascogon and Danao prospects. The ore occurs in a decalcified and silicified horizon, with minor chlorite and goethite, stibnite, pyrite and quartz crystals ranging from cryptocrystalline to botryoidal. The stringer–stockwork type Cu‐Au mineralization in the Suyoc prospect is hosted in argillized andesitic rocks of the Mabuhay Formation. The primary ore minerals are chalcopyrite with minor amounts of sphalerite. The alteration types identified are propylitic alteration, argillic alteration and silicification. The propylitized basaltic and andesitic flows of the Bacuag Formation bound the jasperoid mineralization in the Lascogon prospect. Stratigraphically, the relationship between propylitized basalts and stringer–stockwork Cu‐Au is not clear but a lateral change can be inferred from jasperoid in the center and stringer–stockwork towards the east. 相似文献
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The human eye is an excellent, general-purpose airborne sensor for detecting marine debris larger than 10 cm on or near the surface of the water. Coupled with the human brain, it can adjust for light conditions and sea-surface roughness, track persistence, differentiate color and texture, detect change in movement, and combine all of the available information to detect and identify marine debris. Matching this performance with computers and sensors is difficult at best. However, there are distinct advantages over the human eye and brain that sensors and computers can offer such as the ability to use finer spectral resolution, to work outside the spectral range of human vision, to control the illumination, to process the information in ways unavailable to the human vision system, to provide a more objective and reproducible result, to operate from unmanned aircraft, and to provide a permanent record that can be used for later analysis. 相似文献
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John Krizmanic Brian Morgan Robert Streitmatter Neil Gehrels Keith Gendreau Zaven Arzoumanian Reza Ghodssi Gerry Skinner 《Experimental Astronomy》2005,20(1-3):299-306
Diffractive optics, such as Phase Fresnel Lenses (PFL's), offer the potential to achieve excellent imaging performance in the x-ray and gamma-ray photon regimes. In principle, the angular resolution obtained with these devices can be diffraction limited. Furthermore, improvements in signal sensitivity can be achieved as virtually the entire flux incident on a lens can be concentrated onto a small detector area. In order to verify experimentally the imaging performance, we have fabricated PFL's in silicon using gray-scale lithography to produce the required Fresnel profile. These devices are to be evaluated in the recently constructed 600-meter x-ray interferometry testbed at NASA/GSFC. Profile measurements of the Fresnel structures in fabricated PFL's have been performed and have been used to obtain initial characterization of the expected PFL imaging efficiencies. 相似文献
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We calculate chemical evolution models for 4 dwarf spheroidal satellites of the Milky Way (Carina, Ursa Minor, Leo I and Leo
II) for which reliable non-parametric star formation histories have been derived. We find that galaxies showing one single
burst of star formation (Ursa Minor and Leo II) require a dark halo slightly larger that the current estimates for their tidal radii for the gas heated by supernovae to be retained until the observed stellar population has formed. Systems showing extended
star formation histories however (Carina and Leo I), are consistent with the idea that their tidally limited dark haloes provide
the necessary gravitational potential wells to retain their gas.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
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Assessment of recharge to groundwater systems in the arid southwestern part of Northern Territory, Australia, using chlorine-36 总被引：1，自引：0，他引：1
Richard Cresswell John Wischusen Gerry Jacobson Keith Fifield 《Hydrogeology Journal》1999,7(4):393-404
The sustainability of community water supplies drawn from shallow aquifers in the arid southwest of the Northern Territory
has been evaluated using the radioactive isotope chlorine-36 (36Cl). These aquifers include fractured sandstones of the Ngalia Basin, fractured metamorphic rocks and Cainozoic sands and
gravels. 36Cl/Cl ratios for these shallow, regional groundwaters exhibit a bimodal distribution with peaks at 205 (±7) and 170 (±7)×10–15. The higher ratio probably represents modern (Holocene) recharge, diluted with windblown salts from local playa lakes, and
occurs mostly around the margin of the basin. The lower ratio corresponds to a 36Cl "age", or mean residence time, of 80–100 ka, implying that the last major recharge occurred during the last interglacial
interval (Oxygen Isotope Stage 5). These values are mainly observed in the interior of the Ngalia Basin. Lower values of the
36Cl/Cl ratio measured near playa lakes are affected by addition of chloride from remobilised salts. Finite carbon-14 (14C) data for the groundwaters are at variance with the 36Cl results, but a depth profile suggests low recharge, allowing diffusion of recent atmospheric carbon to the water table.
The 36Cl results have important implications for groundwater management in this region, with substantial recharge only occurring
during favourable, wet, interglacial climatic regimes; most community water supplies are dependent on these "old" waters.
Received, September 1997 · Revised, August 1998, March 1999 · Accepted, March 1999 相似文献
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Investigated herein are water and sediment geochemistry, and metal attenuation processes associated with natural acid rock drainage originating from black shale formations in the Macmillan Pass area, Clear Lake prospect and Engineer Creek by the Dempster Highway in the Yukon Territory, Canada. The most metalliferous water having pH 3.0, 150 mg/L Zn, 39 mg/L Ni, 2.8 mg/L Cu and 9.1 mg/L As was found in a tributary stream of Engineer Creek with no known mineral deposits occurring in the vicinity. For all three study areas, the water and sediment geochemistry is significantly affected by the local lithology and prevailing metal attenuation processes. Despite their anomalous acidity and metal contents, the natural acid streams contribute only a small fraction of the contaminant loadings to the major water courses because of their low flows. Dilution, neutralization, sorption and co-precipitation are identified as the major mechanisms attenuating aqueous transport of potentially deleterious metals. However, microbial mediation in metal attenuation is also evident in low-flow systems. The wide variation of water and sediment geochemistry along a flow path renders the establishment of background metal values difficult. In assessing environmental impacts, it may be more practical to consider metal loadings on a watershed scale than to rely on a comparison with operationally defined background concentrations. 相似文献