Tertiary Meteoric Hydrothermal Systems and their Relation to Ore Deposition, Northwestern United States and Southern British Columbia

Tertiary meteoric hydrothermal systems have altered the rocks exposed over more than 5 % of the land surface of the northwestern United States and southern British Columbia, including at least 25,000 km^2 in Idaho. The systems typically involved convective circulation of fluid derived from ordinary meteoric groundwaters around crystallizing, calc-alkaline, epizonal plutons emplaced into coeval volcanic cover rocks. These individual systems had widely ranging “lifetimes” of 10^3 to 10^6 years and operated locally throughout the Cenozoic, although the most profound development of such activity occurred during Eocene time. Individual systems varied in size from a few tens of square kilometers (Yankee Fork, Idaho) or less to several thousand square kilometers (Sawtooth and Castro ring zones, Idaho) Typically, regional propylitization aacompanied the fluid circulation, although the higher-temperature alteration assemblages were developed locally, as were intense alteration effects (e.g., silicification, sericitization, etc.) near some veins and in mining districts. A significant amount, probably 25–50%, of the mineral production and potential in the region is closely related to Tertiary meteoric hydrothermal systems. Oxygen and hydrogen isotopic data clearly demonstrate the close geologic association of meteoric hydrothermal systems and mineralization in (1) the Paleocene, Cu-Zn-Pb-Mn Main Stage mineralization at Butte, Montana; (2) numerous Eocene epithermal deposits principally valued for Au and Ag but also including significant deposits of Cu, Pb, Zn, F, Sb, etc., as at Republic, Washington, and in several mining districts in the Idaho batholith and the Challis volcanic field; (3) several Eocene skarn deposits valued for W (Ima, Idaho) and Cu (Mackay, Idaho); (4) important lead-silver vein and replacement deposits of Tertiary (Bluebell, British Columbia) and of probable Cretaceous and early Tertiary age (Wood River, Idaho); (5) several potentially economic Mo-, Be-, and U-bearing Eocene “porphyry” plutons; and (6) Miocene epithermal deposits, most prominently the Au and Ag bearing veins at Silver City and DeLamar, Idaho, the Hg deposits at the McDermitt caldera, Nevada and Oregon, and at Weiser, Idaho, and Au deposits in the Western Cascade Range and Lake County, Oregon. A close spatial association has been demonstrated between ore deposits and rocks having anomalous δ^(18)O values and low δD values. The most important deposits are associated with relatively small (generally 5–300 km^2) zones of low δ^(18)O values, and they are particularly closely linked with zones of very steep ^(18)O/^(16)O gradients in the altered rocks. These associations hold much promise for the use of δ^(18)O and δD contour maps in future exploration efforts

New species of Hsunycteris.

26 pages : illustrations (some color), map ; 26 cm.A new species of the nectarivorous bat genus Hsunycteris is described from lowland Amazonian forest in northeastern Peru. The new species, H. dashe, can be distinguished from other congeners by its larger size; V-shaped array of dermal chin papillae separated by a wide basal cleft; metacarpal V longer than metacarpal IV; broad rostrum; lateral margin of infraorbital foramen not projecting beyond rostral outline in dorsal view; well-developed sphenoidal crest; large outer upper incisors; weakly developed lingual cusp on P5; and well-developed, labially oriented M1 parastyle. A phylogenetic analysis of cytochrome-b sequence data indicates that H. dashe is sister to a clade that includes all other species of the genus including H. cadenai, H. pattoni, and a paraphyletic H. thomasi. We provide a key based on craniodental and external characters of all four known species of Hsunycteris

A case control study examining the feasibility of using eye tracking perimetry to differentiate patients with glaucoma from healthy controls

Abstract To explore the feasibility of using Saccadic Vector Optokinetic Perimetry (SVOP) to differentiate glaucomatous and healthy eyes. A prospective case–control study was performed using a convenience sample recruited from a single university glaucoma clinic and a group of healthy controls. SVOP and standard automated perimetry (SAP) was performed with testing order randomised. The reference standard was a diagnosis of glaucoma based a comprehensive ophthalmic examination and abnormality on standard automated perimetry (SAP). The index test was SVOP. 31 patients with glaucoma and 24 healthy subjects were included. Mean SAP mean deviation (MD) in those with glaucoma was − 8.7 ± 7.4 dB, with mean SAP and SVOP sensitivities of 23.3 ± 0.9 dB and 22.1 ± 4.3 dB respectively. Participants with glaucoma were significantly older. On average, SAP sensitivity was 1.2 ± 1.4 dB higher than SVOP (95% limits of agreement = − 1.6 to 4.0 dB). SVOP sensitivity had good ability to differentiate healthy and glaucomatous eyes with a 95% CI for area under the curve (AUC) of 0.84 to 0.96, similar to the performance of SAP sensitivity (95% CI 0.86 to 0.97, P = 0.60). For 80% specificity, SVOP had a 95% CI sensitivity of 75.7% to 94.8% compared to 77.8% to 96.0% for SAP. SVOP took considerably longer to perform (514 ± 54 s compared to 267 ± 76 s for SAP). Eye tracking perimetry may be useful for detection of glaucoma but further studies are needed to evaluate SVOP within its intended sphere of use, using an appropriate design and independent reference standard

The Spectroscopic Footprint of the Fast Solar Wind

We analyze a large, complex equatorial coronal hole (ECH) and its immediate surroundings with a focus on the roots of the fast solar wind. We start by demonstrating that our ECH is indeed a source of the fast solar wind at 1AU by examining in situ plasma measurements in conjunction with recently developed measures of magnetic conditions of the photosphere, inner heliosphere and the mapping of the solar wind source region. We focus the bulk of our analysis on interpreting the thermal and spatial dependence of the non-thermal line widths in the ECH as measured by SOHO/SUMER by placing the measurements in context with recent studies of ubiquitous Alfven waves in the solar atmosphere and line profile asymmetries (indicative of episodic heating and mass loading of the coronal plasma) that originate in the strong, unipolar magnetic flux concentrations that comprise the supergranular network. The results presented in this paper are consistent with a picture where a significant portion of the energy responsible for the transport of heated mass into the fast solar wind is provided by episodically occurring small-scale events (likely driven by magnetic reconnection) in the upper chromosphere and transition region of the strong magnetic flux regions that comprise the supergranular network.Comment: 25 pages, accepted to appear in the Astrophysical Journal. Supporting movies can be found in http://download.hao.ucar.edu/pub/mscott/papers/ECH

Stripes in Doped Antiferromagnets: Single-Particle Spectral Weight

Recent photoemission (ARPES) experiments on cuprate superconductors provide important guidelines for a theory of electronic excitations in the stripe phase. Using a cluster perturbation theory, where short-distance effects are accounted for by exact cluster diagonalization and long-distance effects by perturbation (in the hopping), we calculate the single-particle Green's function for a striped t-J model. The data obtained quantitatively reproduce salient (ARPES-) features and may serve to rule out "bond-centered" in favor of "site-centered" stripes.Comment: final version as appeared in PRL; (c) 2000 The American Physical Society; 4 pages, 4 figure