Evidence from fluid inclusions for a paleogeothermal gradient at the geothermal test well sites, Los Alamos, New Mexico

Homogenization temperatures of individual fluid inclusions from the geothermal test well sites near Los Alamos, New Mexico, systematically change as a function of depth in the cores. Inclusions in samples from depths between 1.5 and 3.0 km have re-equilibrated to thermal gradients higher than the present gradient of 50–60°C/km. The loci of maximum temperatures attained has a slope of about 70°C/km; the deepest sample has cooled to 200°C from a maximum of 230°C. The wide range of salinities (0.0 wt.% equivalent NaCl to more than 25 wt.% equivalent NaCl) observed in each sample indicates a large amount of pervasive fluid circulation had not occurred at the time of re-equilibration of these inclusions. The results are relevant to calculations for the thermal history of the test site.     

Morphology of seamounts in the western Pacific and Philippine Basin from multi-beam sonar data

New multi-beam bathymetric data from the Philippine Sea and northwest Pacific Basin reveal linear chains of small (less than 40 km³) domed-shaped volcanoes (Philippine) and coned-shaped volcanoes (Pacific) rising 100–1000 m above the 6 km deep ocean floor. Some appear to have well-developed collapsed calderas and spines. Their morphology suggest recent formation in supposedly stable mid-plate regions and their occurrence in linear chains approximately parallel to plate motion may suggest an origin by extrusion from “mini-hot spot” plumes.     

The porphyry molybdenum deposit of Compaccha,Peru, and its geologic setting

Compaccha, in Peru, is a zoned molybdenum, copper, zinc, lead, antimonyarsenic district which has historically been important because of tungsten production derived from all zones. Wolframite, the principal tungsten mineral, is zoned compatibly with the sulfides. Manganese tungstate occurs in the molybdenum zone, while iron replaces the manganese increasingly importantly as distance is gained away from this zone. The alteration zoning in and around the molybdenum zone is typical of that of a porphyry copper deposit, in that fluorite, topaz or other fluorine rich silicates are not common. The molybdenum zone does include a porphyry molybdenum deposit, however, and this is characterized by intense silicification and quartz veining (stockworks). Within the area of the deposit, east of the coastal batholith, no Mesozoic arc type or basic volcanics can be inferred. A cratonic setting is postulated for the deposit.     

The michiquillay porphyry copper deposit

Michiquillay is a mineralized intrusive quartz monzonite porphyry displaying typical porphyry copper alteration zones as found in metallized intrusives of that composition. From the interior outward these are the phyllic, argillic and propylitic zones. The potassic zone is not exposed at the surface. The intrusion and the center of mineralization coincide with the intersection of a major transverse fault and a cross fault. Mineralization appears dominantly to occur in fractures which may be related to each of these major structures, and is ascribed in origin to simultaneous movement on each fault during the period of hydrothermal activity. The stockwork developed at the fault intersection, and which is the locus of the ore body, fades as distance is gained away from its center. Coincidentally, intensity of mineralization also weakens.     

Overview of GIS Applications in Estuarine Monitoring and Assessment Research

Geographic information systems (GIS) tools are now considered integral in estuarine monitoring and assessment research. A synopsis is presented of our estuarine applications of GIS in the Northeast region of the U.S. The applications discussed cover sample site selection, support for field sampling activities, quality assurance of data, spatial display of geographic referenced information, quantitative spatial analysis of data, and communication of results.