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31.
32.
Donald L. Baker 《Ground water》1995,33(2):259-263
The “modified Picard” iteration method, which offers global mass conservation, can also be described as a form of Newton's iteration with lagged nonlinear coefficients. It converges to a time step with first-order discretization error. This paper applies second- and third-order diagonally implicit Runge Kutta (DIRK) time steps to the modified Picard method in one example. It demonstrates improvements over the first-order time step in rms error and error-times-effort model quality by factors ranging from two to over two orders of magnitude, showing that the “modified Picard” and DIRK methods are compatible. 相似文献
33.
Characteristics of hydrothermal plumes from two vent fields on the Juan de Fuca Ridge, northeast Pacific Ocean 总被引:1,自引:0,他引:1
Deep CTD/transmissometer tows and water bottle sampling were used during 1985 to map the regional distribution of the neutrally-buoyant plumes emanating from each of two major vent fields on the Southern Symmetrical Segment (SSS) and Endeavour Segment (ES) of the Juan de Fuca Ridge. At both vent fields, emissions from point and diffuse hydrothermal sources coalesced into a single 200-m-thick plume elongated in the direction of current flow and with characteristic temperature anomalies of 0.02–0.05°C and light-attenuation anomalies of 0.01–0.08 m−1 (10–80 μg/l above background). Temperature anomalies in the core of each plume were uniform as far downcurrent as the plumes were mapped (10–15 km). Downcurrent light-attenuation trends were non-uniform and differed between plumes, apparently because different vent fluid chemistries at each field cause significant differences in the settling characteristics of the hydrothermal precipitates. Vent fluids from the SSS are metal-dominated and mostly precipitate very fine-grained hydrous Fe-oxides that remain suspended in the plume. Vent fluids from the ES are sulfur-dominated and precipitate a high proportion of coarser-grained Fe-sulfides that rapidly settle from the plume. The integrated flux of each vent field was estimated from measurements of the advective transport of each plume. Heat flux was 1700 ± 1100 MW from the ES and 580 ± 351 MW from the SSS. Particle flux varied from 546 ± 312 g/s to 204 ± 116 g/s at the ES depending on distance from the vent field, and was 92 ± 48 g/s from the SSS. 相似文献
34.
Seepage from Oilfield Brine Disposal Ponds in Utah 总被引:1,自引:0,他引:1
35.
36.
Mg enrichment in diffusely bounded, schistose alteration zones occurring in Proterozoic submarine felsic volcanics NE of Hjulsjö, W. Bergslagen is shown to result from felsic rock-seawater interaction in a sub-seafloor hydrothermal system. The alteration is apparently in two stages, feldspar being altered first to a kaolinite-type clay which is then replaced by Mg-chlorite. Major and trace element data are presented for the schist and sheridanite (chlorite). Relative to the least altered felsic volcanics, and for negligible volume change, the schist shows strong addition of Mg and to a lesser extent Si; K, Al and Rb are apparently conserved, while most other elements are strongly depleted, including the REEs which are removed for ~75%, indicating a high degree of mobility. The chlorite, with its HREE enriched pattern, is considered to have equilibrated with the hydrothermal fluid, which consisted predominantly of seawater. Comparison with modern seawater leads to the tentative conclusion that the Proterozoic seawater HREE composition was not drastically different from that of modern seawater. 相似文献
37.
Air was injected through a well in a thin transparent tank filled with saturated glass beads to study how the size and air
saturation of air sparging plumes are affected by particle size and gradation; operational parameters such as injection pressure,
well depth, injection pressure pulsing; and well outlet configuration. V-shaped air plumes with an apex between 40° and 60°
were obtained for all tests. The air pressure required to initiate sparging agreed closely with the sum of the air entry pressure
and the hydrostatic pressure, with higher initiation pressures required in the fine and well-graded beads. Higher air flow
rates and air saturations were obtained in coarser beads at a given pressure, and the variation in flow rate was consistent
with estimated air permeabilities. Peak average air saturations were 28–56% for the coarse-medium beads, 10% for the well-graded
beads, and 8% for the fine beads. Air saturation and the radius of influence increased modestly (<40%) as the normalized injection
pressure exceeded 0.1. Radius of influence increased by approximately a factor of two as the well depth increased, but leveled
off once the ratio of radius of influence to well depth reached 0.60–1.05. Pulsing of injection pressure had no effect on
the initiation pressure, air flow rate, or air saturation, but increased the size of the air plume and the radius of influence
slightly (<15%). Well outlet configuration had only a slight affect the radius of influence (<10%), air saturation (<10%),
or air flow rate (<12%). Dye testing showed that water surrounding the air plume circulated during continuous and pulsed sparging.
However, pulsed sparging resulted in greater and more defined circulation of water within and adjacent to the air plume, which
should reduce mass transfer limitations during sparging. 相似文献
38.
39.
The Dublin Gulch intrusion-hosted gold deposit, Tombstone plutonic suite, Yukon Territory, Canada 总被引:1,自引:0,他引:1
The Dublin Gulch intrusion is a member of the Tombstone plutonic suite, a linear belt of middle Cretaceous intrusions that extend across the Yukon Territory. Like many of the intrusions in this suite, the Dublin Gulch intrusion is associated with several different zones of gold and tungsten mineralization, within and immediately adjacent to the intrusion. The Eagle zone (50.3 Mt @ 0.93 g/t gold), located in the southwestern part of the Dublin Gulch intrusion, hosts the most significant concentration of gold in the area. The gold occurs in a broadly east-west-striking, steeply south-dipping series of sheeted veins. The veins consist of early quartz-scheelite-pyrrhotite-pyrite-arsenopyrite, and are associated with K-feldspar-albite alteration envelopes. These grade out to and are overprinted by sericite-carbonate-chlorite alteration. The same assemblage also occurs in veinlets that refracture sheeted quartz veins and contain the majority of the gold. The gold occurs with molybdenite, lead-bismuth-antimony sulfosalts, galena, and bismuthinite. Gold correlates strongly with bismuth (r2=0.9), a relationship common to several intrusion-related gold deposits, but has a poor correlation with all other elements. Tungsten and molybdenum have a weak inter-element correlation (r2=0.55) and paragenetically pre-date the majority of gold precipitation. Lead, zinc, copper, silver, antimony, and arsenic have moderate to strong inter-element correlations (0.58 to 0.93). The change from tungsten-bearing mineralization through to gold-bismuth-rich ores with elevated syn- to post-ore lead, zinc, copper, silver, antimony, and arsenic can be grossly correlated with a change in hydrothermal fluid composition. Early scheelite-bearing quartz contains primary CO2-rich fluid inclusions, which are post-dated by secondary inclusions with higher salinities (up to 15 wt% NaCl equiv.) and less CO2. These latter inclusions are interpreted to coincide with the later gold-bismuth and base metal mineralization. The favored genetic model is one in which early CO2-rich fluids exsolved from a magma with an initially high CO2 content, but progressively became more saline and H2O-rich as the system evolved. 相似文献
40.
Arabia, a supposedly aseismic plate, has been the site of extensive alkalic volcanism during the past 10 m.y. The products of this activity, which extend intermittently from Syria to south central Saudi Arabia, are strongly alkalic and primarily basic in composition. Examination of specimens from the Jebel al Abyad area in Saudi Arabia, which displays a particularly wide variety of rock types, suggests the parental melt moved rapidly from depth to high level chambers where most of the chemical variation was produced by crystal fractionation. N-S dilational fissures of regional extent seem to have allowed the melt easy and rapid egress and a low degree of partial melting in the mantle could account for the high total alkalis content. The high K/Rb ratio, which also characterizes the granitic rocks of the underlying Precambrian basement, is thought to reflect a source mantle particularly low in rubidium. 相似文献