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1.
The Combined EMT/VES Geophysical Method for Siting Boreholes 总被引：2，自引：0，他引：2
2.
R. Beeson 《Journal of Geochemical Exploration》1984,22(1-3)
Partitioning of Cu, Pb, Zn, U, As and Mo between the minus 70 μm and minus 200 μm fractions of stream sediments from arid and semi-arid terrains is examined in the light of published case histories supplemented by new data. The advantages of selecting a particular fraction for routine sampling in such arid environments are assessed in terms of five criteria: (1) homogeneity of background population; (2) definition of threshold; (3) absolute element abundance levels; (4) contrast between anomalous and background populations; and (5) length of dispersion train. The most homogeneous background population distributions and improved definition of the threshold between background and anomaly occur in the very fine, minus 70 μm fraction of stream sediments for the majority of elements, in particular for Zn, Cu, U and As. Data for Pb and Mo do not consistently favour either size fraction in the case histories studied. Increased abundance levels of elements which are normally close to the analytical detection limit (U, Mo, As) occur most frequently in the minus 70 μm fraction, although Cu, Pb and Zn levels are commonly higher in the coarser fraction. In addition the finer size fraction better defines the anomalous population and provides the longer dispersion trains for Cu, Pb, Zn, U and As in the majority of case histories.The data examined indicate that the minus 70 μm fraction provides more useful information, in many instances, than the minus 200 μm fraction. The evidence suggests that problems expected with the use of the fine fraction — dilution through the abundance of wind blown material, and insufficient fine sediment — do not restrict the use of this fraction in stream sediment surveys in arid terrains. 相似文献
3.
4.
David A. Clague Jonathan T. Hagstrum Duane E. Champion Melvin H. Beeson 《Bulletin of Volcanology》1999,61(6):363-381
The tube-fed pāhoehoe lava flows covering much of the northeast flank of Kīlauea Volcano are named the 'Ailā'au flows. Their
eruption age, based on published and six new radiocarbon dates, is approximately AD 1445. The flows have distinctive paleomagnetic
directions with steep inclinations (40°–50°) and easterly declinations (0°–10°E). The lava was transported ∼40 km from the
vent to the coast in long, large-diameter lava tubes; the longest tube (Kazumura Cave) reaches from near the summit to within
several kilometers of the coast near Kaloli Point. The estimated volume of the 'Ailā'au flow field is 5.2±0.8 km3, and the eruption that formed it probably lasted for approximately 50 years. Summit overflows from Kīlauea may have been
nearly continuous between approximately AD 1290 and 1470, during which time a series of shields formed at and around the summit.
The 'Ailā'au shield was either the youngest or the next to youngest in this series of shields. Site-mean paleomagnetic directions
for lava flows underlying the 'Ailā'au flows form only six groups. These older pāhoehoe flows range in age from 2750 to <18,000
BP, and the region was inundated by lava flows only three times in the past 5000 years. The known intervals between eruptive
events average ∼1600 years and range from ∼1250 years to >2200 years. Lava flows from most of these summit eruptions also
reached the coast, but none appears as extensive as the 'Ailā'au flow field. The chemistry of the melts erupted during each
of these summit overflow events is remarkably similar, averaging approximately 6.3 wt.% MgO near the coast and 6.8 wt.% MgO
near the summit. The present-day caldera probably formed more recently than the eruption that formed the 'Ailā'au flows (estimated
termination ca. AD 1470). The earliest explosive eruptions that formed the Keanakāko'i Ash, which is stratigraphically above
the 'Ailā'au flows, cannot be older than this age.
Received: 10 October 1998 / Accepted: 12 May 1999 相似文献
5.
The large lead-zinc deposits of Middle Proterozoic age in northern Australia occur in sediments interpreted as having been deposited under saline, shallow-emergent conditions. Significant alkaline diagenesis is evident from the presence of abundant K-feldspar and locally albite. Alkali element compositions clearly distinguish the sediments of the mineralised shallow-emergent locations both from those of more permanent water cover (lacustrine or lagoonal), and from those close to basin margins. The key variables for identifying the geochemical contrasts are the levels of K, Rb and Na, and the ratios of K : Al and K : Rb. These geochemical parameters can be used in conjunction with the levels of the target and indicator elements to detect whether mineralisation may be present in a favourable geological environment. Two case studies of the application of whole rock geochemistry in base metal exploration are given for the Glyde River Sub-basin (McArthur Basin) and the Western Succession, Mt Isa Block. 相似文献
6.
The reliable yield of a water-supply well depends on many different factors, including the properties of the well and the
aquifer; the capacities of the pumps, raw-water mains, and treatment works; the interference effects from other wells; and
the constraints imposed by abstraction licences, water quality, and environmental issues. A relatively simple methodology
for estimating reliable yields has been developed that takes into account all of these factors. The methodology is based mainly
on an analysis of water-level and source-output data, where such data are available. Good operational data are especially
important when dealing with wells in shallow, unconfined, fissure-flow aquifers, where actual well performance may vary considerably
from that predicted using a more analytical approach. Key issues in the yield-assessment process are the identification of
a deepest advisable pumping water level, and the collection of the appropriate well, aquifer, and operational data. Although
developed for water-supply operators in the United Kingdom, this approach to estimating the reliable yields of water-supply
wells using operational data should be applicable to a wide range of hydrogeological conditions elsewhere.
Received, September 1998/Revised, May 1999, September 1999/Accepted, October 1999 相似文献
7.
Sea-floor sediment distribution in the Gulf of Mexico 总被引：1，自引：0，他引：1
William L. Balsam Jana Payne Beeson 《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(12):1421-1444
Carbonate content, smear-slide analysis and diffuse reflectance spectrophotometry were utilized to determine modern sediment composition and distribution throughout the Gulf of Mexico. In all, 186 core top and grab samples distributed throughout the Gulf were analyzed. Reflectance spectra were taken from thick smear slides from the near ultraviolet, through the visible, and into the near infrared. The first derivatives of the percent reflectance data were subjected to factor analysis producing factors that grouped covarying first-derivative wavelengths. Factors were interpreted by comparison to first-derivative curves for known sediment components and minerals. Interpretation was aided by the mapping of both calcium carbonate content and smear-slide sediment classes. The most easily interpreted factor solution was produced by analyzing only the visible region of the spectrum and extracting seven factors which explained 98% of the cumulative variance. These factors, in order of their relative importance, are interpreted as (1) marl and calcareous clay, (2) glauconite, (3) kaolinite, (4) organic matter, (5) phosphorite, (6) hematite, and (7) goethite. Some factor maps are consistent with known sources of fluvial sediment input; for example, kaolinite is deposited off rivers draining the southeastern US. Other factor maps are related to the origin of the material in the factor, glauconite, for example, being confined to low sedimentation regions of the outer shelf. The most unusual observation concerns the distribution of hematite, which appears to be transported from the rivers of south Texas, primarily the Rio Grande, across the shelf then eastward downslope along the base of the Sigsbee Escarpment. This eastward transport seems to be explainable only by transport in bottom currents flowing along the base of the Sigsbee Escarpment. 相似文献
8.
R. Beeson 《Journal of Geochemical Exploration》1980,13(1):9-25
Radiometrically anomalous tuffaceous rocks occur as conformable lenses in a volcano-sedimentary sequence of Neogene age near the village of Sarkhanlu, northwest Iran. The anomalous rocks have been extensively altered by hydrothermal fluids, and kaolinization and silicification are widespread. 250 samples of the anomalous and background tuffs and other sediments have been analyzed for Fe, Mn and 18 trace elements. Enhanced levels of Ag, As, Mo, Pb, Sn, Sr, Th, U, W and Zr indicate an alkaline volcanic origin of the tuffaceous material, and the elements of this association dominate the statistical analysis of the geochemical data. Maximum U and Th values are among the highest ever recorded in extrusive volcanic rocks. A zone of kaolinization contains increased levels of U, Th, Pb and Sr relative to the unaltered country rock, although nine other elements are depleted in the zone. This association of elements is recognized in the radiometrically anomalous lithologies, particularly in the kaolinized tuffs, and indicates the availability of U in the hydrothermal fluids causing the alteration. Although U mineralization has not yet been found at Sarkhanlu, comparisons with the similar geological environment in central Italy and elsewhere suggest possible exploration criteria for the future. Distinct sedimentary U associations have been defined in tuffs with only background radioactivity and in dark, calcareous shales. 相似文献
9.
A.M. Kudo S.E. Barker K. Keil Marvin H. Beeson 《Geochimica et cosmochimica acta》1982,46(12):2427-2434
Major and rare earth element (REE) data for basalts from Holes 483, 483B, and 485A of DSDP Leg 65, East Pacific Rise, mouth of the Gulf of California, support a simple fractional crystallization model for the genesis of rocks from this suite. The petrography and mineral chemistry (presented in detail elsewhere) provide no evidence for magma mixing, but rather a simple multistage cooling process. Based on its lowest TiO2 content (0.88%), ratio (0.95 with total Fe as FeO), and Mg# (100 ), sample 483-17-2-(78–83) has been selected as the most primitive primary magma of the samples analyzed. This is supported by the REE data which show this sample has the lowest total REE content, a (chondrite-normalized) = 0.36, and = 1.05. Because other samples analyzed have higher SiO2, lower Mg#, and a negative Eu anomaly ( as low as 0.89), they are most likely derivative magmas. Wright-Doherty and trace element modelling support fractional crystallization of 14.1% plagioclase (An88), 6.7% olivine (Fo86), and 4.7% clinopyroxene (Wo41En49Fs10) from 483-17-2-(78–83) to form the least differentiated sample with Mg# = 63. The of this derivative magma is almost identical to the parent magma (0.35 to 0.36), but the other samples have higher (0.45 to 0.51), more total REE, and lower Mg# (60 to 56). Both Wright-Doherty and trace element modelling indicate that the primary magma chosen cannot produce these more evolved samples. For the major elements, the TiO2 and P2O5 are too low in the calculated versus the observed (1.38 to 1.90; 0.11 to 0.17, respectively, for example). Rayleigh fractionation calculates a lower and requires about 60% crystal removal versus 40% for the Wright-Doherty. These more evolved samples must be derived from a parent magma different from the one selected here and, unfortunately, not sampled in this study. A magma formed by a smaller degree of partial melting with slightly more residual clinopyroxene left in the mantle than for sample 483-17-2-(78–83) is required. 相似文献
10.
R. Beeson 《Mineralium Deposita》1990,25(3):179-189
High grade lead-zinc-silver mineralisation occurs in metamorphosed carbonate and calc-silicate sequences at Wilcherry Hill, South Australia. Whole rock lithogeochemistry indicates that the host sequence of the mineralisation can be defined and contrasted from others at both prospect and exploration licence scales. Geochemical haloes are identified on the basis of Pb, Zn and Mn variations. A saline and possibly evaporitic environment of deposition distal from basin margins is proposed for the host sequence on the basis of alkali element compositions, iron formation facies, carbonate compositions, and comparisons with geochemically similar, less metamorphosed sequences with base metal mineralisation in the Middle Proterozoic of northern Australia. The combination of geochemical haloes and definition of the depositional environment provide additional criteria for the exploration geologist, even in metamorphosed and deformed terrains. 相似文献