Subsurface Imaging of an Abandoned Solid Waste Landfill Site in Norman, Oklahoma   总被引：6，自引：0，他引：6  

Joseph T. Zume  Aondover Tarhule  Scott Christenson 《Ground Water Monitoring & Remediation》2006,26(2):62-69

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Bashikaogong-Shimierbulake granitic complex, north Altun, NW China:Geochemistry and zircon SHRIMP ages   总被引：6，自引：0，他引：6  

Joseph L. Wooden  Frank K. Mazdab 《中国科学D辑(英文版)》2006,49(12):1233-1251

The Bashikaogong-Shimierbulake granitoid complex is about 30 km long and 2―6 km wide, with an area of 140 km2, located at the north margin of the Bashikaogong Basin in the north Altun terrain. It intruded into schist, metapelite and metatuff of Precambrian ages. This granitoid complex consists of darkish quartz diorite, grey granite, pink granite and pegmatite. Geochemically, the quartz diorite has I-type granite affinity and belongs to Calc-alkaline sereies, and the other gran- ites have S-type affinity and to high-K calc-alkaline series. Zircon SHRIMP U-Pb dating shows that the quartz diorite has a bigger age than those of other granites, which is 481.6±5.6 Ma for quartz diorite, 437.0±3.0 Ma―433.1±3.4 Ma for grey granite and 443±11 Ma―434.6±1.6 Ma for pink granite, re- spectively. Combined with regional geology, we think that the quartz diorite formed in tectonic envi- ronment related to oceanic crust subduction and the granites in post-collision.  相似文献   

Geology, Wall-rock Alteration and Vein Paragenesis of the Bilimoia Gold Deposit, Kainantu Metallogenic Region, Papua New Guinea     

Joseph Onglo Espi    Ken-Ichiro Hayashi    Kosei Komuro    Hiroyasu Murakami  Yoshimichi Kajiwara 《Resource Geology》2007,57(3):249-268

The Bilimoia deposit (2.23 Mt, 24 g/t Au), located in the eastern Central Mobile Belt of mainland Papua New Guinea, is composed of fault‐hosted, NW–NNW‐trending Irumafimpa–Kora and Judd–Upper Kora Au‐quartz veins hosted by Middle–Late Triassic basement that was metamorphosed to medium‐grade greenschist facies between Middle–Late Triassic and Early–Middle Jurassic. Mineralizing fluids were introduced during crustal thickening, rapid uplift, change of plate motions from oblique to orthogonal compression, active faulting and S₃ and S₄ events in an S₁–S₄ deformation sequence. The Bilimoia deposit is spatially and temporally related to I‐type, early intermediate to felsic and late mafic intrusions emplaced in Late Miocene (9–7 Ma). Hydrothermal alteration and associated mineralization is divided into 10 main paragenetic stages: (1) chlorite–epidote‐selvaged quartz–calcite–specularite vein; (2) local quartz–illite–pyrite alteration; (3) quartz–sericite–mariposite–fuchsite–pyrite wall‐rock alteration that delimits the bounding shears; (4) finely banded, colloform‐, crustiform‐ and cockade‐textured and drusy quartz ± early wolframite ± late adularia; (5) hematite; (6) pyrite; (7) quartz ± amethyst‐base metal sulfides; (8) quartz–chalcopyrite–bornite–Sn and Cu sulfides–Au tellurides and Te ± Bi ± Ag ± Cu ± Pb phases; (9) Fe ± Mn carbonates; and (10) supergene overprint. Fluid inclusions in stage 4 are characterized by low salinity (0.9–5.4 wt% NaCl equivalent), aqueous–carbonic fluids with total homogenization temperatures ranging from 210 to 330°C. Some of the inclusions that homogenized between 285 and 330°C host coexisting liquid‐ and vapor‐rich (including carbonic) phases, suggesting phase separation. Fluid inclusions in quartz intergrown with wolframite have low salinity (0.9–1.2 wt% NaCl equivalent), aqueous–carbonic fluids at 240–260°C, defining the latter’s depositional conditions. The ore fluids were derived from oxidized magmatic source initially contaminated by reduced basement rocks. Wall‐rock alteration and involvement of circulating meteoric waters were dominant during the first three stages and early part of stage 4. Stage 5 hematite was deposited as a result of stage 4 phase separation or entrainment of oxygenated groundwater. Gold is associated with Te‐ and Bi‐bearing minerals and mostly precipitated as gold‐tellurides during stage 8. Gold deposition occurred below 350°C due to a change in the sulfidation and oxidation state of the fluids, depressurization and decreasing temperature and activities of sulfur and tellurium. Bisulfides are considered to be the main Au‐transporting complexes. The Bilimoia deposit has affinities that are similar to many gold systems termed epizonal orogenic and intrusion‐related. The current data allow us to classify the Bilimoia deposit as a fault‐controlled, metamorphic‐hosted, intrusion‐related mesothermal to low sulfidation epithermal quartz–Au–Te–Bi vein system.  相似文献   

A Simple Reclassification Method for Correcting Uncertainty in Land Use/Land Cover Data Sets Used with Land Surface Models     

Joseph G. Alfieri  Dev Niyogi  Margaret A. LeMone  Fei Chen  Souleymane Fall 《Pure and Applied Geophysics》2007,164(8-9):1789-1809

With increasing computational resources, environmental models are run at finer grid spacing to resolve the land surface characteristics. The land use/land cover (LULC) data sets input into land surface models are used to assign various default parameters from a look-up tables. The objective of this study is to assess the potential uncertainty in the LULC data and to present a reclassification method for improving the accuracy of LULC data sets. The study focuses on the Southern Great Plains and specifically the Walnut River Watershed in southeastern Kansas, USA. The uncertainty analysis is conducted using two data sets: The National Land Cover Dataset 1992 (NLCD 92) and the Gap Analysis Program (GAP) data set, and a reclassification logic tree. A comparison of these data sets showed that they do not agree for approximately 27% of the watershed. Moreover, an accuracy assessment of these two data sets indicated that neither had an overall accuracy as high as 80%. Using the relationships between land-surface characteristics and LULC, a reclassification of the watershed was conducted using a logical model. This model iteratively reclassified the uncertain pixels according to their surface characteristics. The model utilized normalized difference vegetation index (NDVI) measurements during April and July 2003, elevation, and slope. The reclassification yielded a revised LULC dataset that was substantially improved. The overall accuracy of the revised data set was nearly 93%. The study results suggest: (i) as models adopt finer grid spacings, the uncertainty in the LULC data will become significant; (ii) assimilating NDVI into the land-surface models can reduce the uncertainty due to LULC assignment; (iii) the standard LULC data sets must be used with caution when the focus is on local scale; and (iv) reclassification is a valuable means of improving the accuracy of LULC data sets prior to applying them to local issues or phenomena.  相似文献   

Erosion and natural revegetation associated with surface land drains in upland peatlands     

Joseph Holden  Michelle Gascoign  Nick R. Bosanko 《地球表面变化过程与地形》2007,32(10):1547-1557

Open cut drains are the most frequently used drainage technique in peatlands and are common throughout the world. Land drains increase the drainage density and promote enhanced coupling of hillslope sediment sources with streams. They may be major sources of fine sediment to peatland stream systems but data on drain sediment production in peatlands are rare. Many drains are now being dammed by humans, yet some revegetate naturally. This paper presents a survey of the erosion and natural revegetation of peat drains related to variables such as slope, drainage area and shading. The paper also provides measured comparison of sediment flux from open drains, drains that have been blocked by peat dams, undisturbed subcatchments, and the catchment outlet. Natural infilling of drains was often found to occur on gentle slopes <4°. Drains on slopes <2° were rarely eroded, while drains on slopes >4° were rarely infilled. Nick‐point retreat at the confluence of drains was often observed. Revegetation of drains was uncommon where drains have been cut or incised into the underlying mineral substrate. Where the drain floor was peat‐based, revegetation was much more common. Revegetation of drain floors was affected by overhanging vegetation, which provided shading. Drain floors with less than 60% shading tended to have a greater vegetation cover than drains with 60–90% shading. However, drains that were almost totally shaded (>90%) had the greatest floor vegetation. The intact drains were found to be major sources of suspended sediment within the survey catchments, with 18·3% of the sediment originating from the unblocked drains which drained 7·3% of the area. The winter quarter of the year was more important than other seasons for producing suspended sediment, even though precipitation totals were not greatest during this period. Drains which had been dammed at intervals along their length using peat blocks had very low sediment yields. Even poorly dammed drains, where water could still flow along the full course of the drain, had 54 times less suspended sediment production than unblocked drains. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

A plea for more careful presentation of near‐surface air temperature data in geomorphology     

Joseph Holden 《地球表面变化过程与地形》2007,32(9):1433-1436

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Chemical “light meters” for photochemical and photobiological studies     

David J. Kieber  Dierdre A. Toole  Joseph J. Jankowski  Ronald P. Kiene  George R. Westby  Daniela A. del Valle  Doris Slezak 《Aquatic Sciences - Research Across Boundaries》2007,69(3):360-376

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The oceanic substratum of Northern Luzon: Evidence from xenoliths within Monglo adakite (the Philippines)   总被引：2，自引：0，他引：2  

Betchaida D.  Payot  Sebastien  Jego  Rene C.  Maury  Mireille  Polve  Michel  Gregoire  Georges  Ceuleneer  Rodolfo A.  Tamayo Jr  Graciano P.  Yumul Jr  Herve  Bellon  Joseph  Cotten 《Island Arc》2007,16(2):276-290

Abstract   A 8.65 Ma adakitic intrusive sheet exposed near Monglo village in the Baguio District of Northern Luzon contains a suite of ultramafic and mafic xenoliths including in order of abundance: spinel dunites showing typical mantle-related textures, mineral and bulk rock compositions, and serpentinites derived from them; amphibole-rich gabbros displaying incompatible element patterns similar to those of flat or moderately enriched back-arc basin basalt magmas; and amphibolites derived from metabasalts and/or metagabbros of identical affinity. A single quartz diorite xenolith carrying a similar subduction-related geochemical signature has also been sampled. One amphibolite xenolith provided a whole-rock K–Ar age of 115.6 Ma (Barremian). We attribute the origin of this suite to the sampling by ascending adakitic magmas of a Lower Cretaceous ophiolitic complex located at a depth within the 30–35 km thick Luzon crust. It could represent an equivalent of the Isabela-Aurora and Pugo-Lepanto ophiolitic massifs exposed in Northern Luzon.  相似文献   

Fourier packing ordinate: A univariate size-independent measurement of the polygonal packing variation in Paleozoic bryozoans     

Robert L. Anstey  Joseph F. Pachut 《Mathematical Geology》1980,12(2):139-156

The Fourier packing ordinate provides a highly sensitive, univariate, and size-independent measurement of the polygonal packing variation in Paleozoic bryozoan colonies. It is potentially useful in quantifying a wide variety of natural packing arrays or polygonal networks, and is preferable to counting the sides of polygons, the frequency of triple or quadruple junctions, the nearest-neighbor statistic, measurements of surface area per unit cell, or individual harmonic amplitudes. Fourier shape analysis provides exact measurements of the levels of two- to six-fold rotational symmetry in all natural packing gradients. In bryozoans these symmetries are intercorrelated because as each order of symmetry is increasing, the previous order is decreasing. Shapes in these packing arrays are normally hybrids of two or more orders of rotational symmetry. The levels of rotational symmetry involved in these packing gradients are significantly correlated with a single principal component, the Fourier packing ordinate, which is independent of both size and cell boundary phenomena. Spatial analysis of the Fourier packing ordinate within an Ordovician bryozoan colony reveals both variation in packing caused by subcolony budding, as well as large scale trends which vary from the colony center to the free-growing margin.  相似文献   

A PETROGRAPHIC AND MINERAL CHEMISTRY STUDY OF THE WESTON,CONNECTICUT, CHONDRITE     

Albert F. Noonan  Joseph A. Nelen 《Meteoritics & planetary science》1976,11(2):111-130

The Weston meteorite is a breccia containing mostly light-colored equilibrated chondritic xenoliths and less abundant highly un-equilibrated chondritic inclusions fixed in a dark grey host of chondrules, mineral and rock fragments. Many of the inclusions show evidence of shock. Unlike most xenolithic chondrites, the Weston host contains a large fraction of considerably more equilibrated silicates than is found in the unequilibrated inclusions, suggesting either that most host silicates retain the mineral chemistry of an equilibrated source indigenous to Weston, or represent a unique fraction which equilibrated separately, prior to final agglomeration. The host silicates are similar in composition to minerals in the common xenoliths, supporting the former possibility that host chondrules and mineral fragments are derived from the xenolithic material, probably by impact fragmentation and melting. Also mixed with Weston is a small but distinct carbonaceous component including the minerals fassaite, Fespinel, forsterite, magnetite and Ca-Al-rich inclusion which are normally associated with carbonaceous chondrites.  相似文献