Field Methods for Measurement of Ground Water Redox Chemical Parameters     

Katherine Walton-Day  Donald L. Macalady  Myron H. Brooks  Vernon T. Tate 《Ground Water Monitoring & Remediation》1990,10(4):81-89

An inexpensive, versatile, and portable system is presented, which facilitates rapid field determinations of redox potentials, pH, conductivity, ferrous and total iron, nitrite, specific conductance, dissolved oxygen, and temperature. Accuracy is facilitated by on-site measurements of most parameters using specially constructed flow-through cells and, for several analyses, sealed reagent ampoules, which can be broken and developed inside a flowing stream of ground water. Coupled with laboratory analyses of more stable ground water parameters, this system can provide accurate and relatively inexpensive determinations of redox conditions in ground water.  相似文献   

Book reviews     

James R. Rice  Mary Hubbard  Andrea Borgia  Göran Ekström  S. J. Gibowicz  Lev Truskinovsky  Yu. N. Korenkov  Vernon F. Cormier  Jacek Leliwa-Kopystyński 《Pure and Applied Geophysics》1992,138(1):155-179

  相似文献   

Discrete proterozoic structural terranes associated with low-P, high-T metamorphism, Anmatjira Range, Arunta Inlier, central Australia: tectonic implications     

W.J. Collins  R.H. Vernon  G.L. Clarke 《Journal of Structural Geology》1991,13(10)

Structural overprinting relationships indicate that two discrete terranes, Mt. Stafford and Weldon, occur in the Anmatjira Range, northern Arunta Inlier, central Australia. In the Mt. Stafford terrane, early recumbent structures associated with D_1a,_1b deformation are restricted to areas of granulite facies metamorphism and are overprinted by upright, km-scale folds F_1c), which extend into areas of lower metamorphic grade. Structural relationships are simple in the low—grade rocks, but complex and variable in higher grade equivalents. The three deformation events in the Mt. Stafford terrane constitute the first tectonic cycle (D₁-D₂) deformation in the Weldon terrane comprises the second tectonic cycle. The earliest foliation (S_2a) was largely obliterated by the dominant reclined to recumbent mylonitic foliation (S_2b), produced during progressive non-coaxial deformation, with local sheath folds and W- to SW-directed thrusts. Locally, (D_2d) tectonites have been rotated by N—S-trending, upright (F_2c) folds, but the regional upright fold event (F_2d), also evident in the adjacent Reynolds Range, rotated earlier surfaces into shallow-plunging, NW—SE-trending folds that dominate the regional outcrop pattern.The terranes can be separated on structural, metamorphic and isotopic criteria. A high-strain D₂ mylonite zone, produced during W- to SW-directed thrusting, separates the Weldon and Mt. Stafford terranes. 1820 Ma megacrystic granites in the Mt. Stafford terrane intruded high-grade metamorphic rocks that had undergone D_1a and D_1b deformation, but in turn were deformed by S_1c, which provides a minimum age limit for the first structural—metamorphic event. 1760 Ma charnockites in the Weldon terrane were emplaced post-D_2a, and metamorphosed under granulite facies conditions during D_2b, constraining the second tectonic cycle to this period.Each terrane is associated with low-P, high-T metamorphism, characterized by anticlockwise P—T—t paths, with the thermal peaks occurring before or very early in the tectonic cycle. These relations are not compatible with continental-style collision, nor with extensional tectonics as the deformation was compressional. The preferred model involves thickening of previously thinned lithosphere, at a stage significantly after (>50 Ma) the early extensional event. Compression was driven by external forces such as plate convergence, but deformation was largely confined to and around composite granitoid sheets in the mid-crust. The sheets comprise up to 80% of the terranes and induced low-P, high-T metamorphism, including migmatization, thereby markedly reducing the yield strength and accelerating deformation of the country rocks. Mid-crustal ductile shearing and reclined to recumbent folding resulted, followed by upright folding that extended beyond the thermal anomaly. Thus, thermal softening induced by heat-focusing is capable of generating discrete structural terranes characterized by subhorizontal ductile shear in the mid-crust, localized around large granitoid intrusions.  相似文献   

Neodymium and strontium isotopic characteristics of New Zealand granitoids and related rocks     

David A. Pickett  G. J. Wasserburg 《Contributions to Mineralogy and Petrology》1989,103(2):131-142

Initial ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd ratios of Phanerozoic granitoids and related intrusions of the New Zealand block display a mixing-type array indicative of the involvement in their sources of old continental crustal material, most likely of Proterozoic age. _Sr(T) values range from –4 to +273 (⁸⁷Sr/⁸⁶Sr=0.7041–0.7233), while _Nd(T) ranges from +2.7 to –11.0. Preexisting metasedimentary rocks have generally higher _Sr and lower _Nd (ranging to present-day values of +646 and –15.0, respectively), and, particularly for the Mesozoic intrusives, are isotopically appropriate mixing end-members. The widespread, early Paleozoic Greenland Group graywackes, which are derived from Proterozoic sources, are modeled as the source of the crustal end-member mixing with mantle-derived mafic magmas to produce the intrusive rocks. Four different types of models are applied to the isotopic and trace-element (Rb, Sr, Ba, REE) data: simple mixing; mixing with a partial melt of the metasedimentary rock, with or without isotopic equilibrium; and assimilation-fractional crystallization. Based on these models, some constraints may be applied on petrogenesis (e.g., the lack of high Rb concentrations points to the presence of biotite, and HREE depletion points to the presence of garnet); however, the models fail to adequately explain all the data. The New Zealand granitoids show similarities in isotopic character not only to rocks from offshore islands on the New Zealand block, but also to similar-aged granitoids in adjacent regions of Antarctica and Australia. This points to similarities in crustal character between continental blocks formerly proximal in Gondwanaland. We note an overall increase in _Nd and decrease in _Sr in felsic magmas from the Paleozoic to the Mesozoic to the Cenozoic in New Zealand, indicative of a decrease over time in the level of influence of recycled continental crust in subduction-related magmatism.Division Contribution No. 4538 (582)  相似文献   

Experimental deformation and recrystallization of a peristerite     

D. B. Marshall  R. H. Vernon  B. E. Hobbs 《Contributions to Mineralogy and Petrology》1976,57(1):49-54

Partial syntectonic recrystallization has been produced in an experimentally deformed plagioclase (peristerite An_4.5). The recrystallized grains are scattered through the strongly deformed matrix and appear to have developed by a nucleation and growth mechanism.  相似文献   

Origin of pyroxene-plagioclase aggregates in a rhyodacite     

R. H. Flood  R. H. Vernon  S. E. Shaw  B. W. Chappell 《Contributions to Mineralogy and Petrology》1977,60(3):299-309

Bodies of pyroxene-bearing rhyodacite in New England, New South Wales, previously considered to be intrusions, are reinterpreted as ignimbritic flows. Small aggregates of pyroxene and plagioclase are inferred to be either compositionally modified crystalline residuals from partial melting or crystal cumulates. An earlier hypothesis involving mixing of solid biotite-diorite with a rhyolitic liquid is questionable, and the origin of the rhyodacite can be explained in terms of recent experimental work on crystal-liquid equilibria under inferred crustal conditions.  相似文献   

SEM/microprobe study of some symplectic intergrowths replacing cordierite     

R.H. Vernon  G.D. Pooley 《Lithos》1981,14(1):75-82

Scanning electron microscopy (SEM), involving images produced by back-scattered electrons, reveals the microstructures of symplectic intergrowths replacing cordierite, which generally are too fine-grained and/or intricately intergrown for investigation using an optical microscope. Microprobe analysis, combined with the SEM technique, enables accurate identification of the intergrown minerals, and permits inference of equations for the local chemical changes involved in the formation of the intergrowths. Generally, the local replacement appears to have involved partial reactions taking place in a larger reactive system. Intergrowths forming partial pseudomorphs of cordierite in three metamorphic complexes consists of up to three minerals, only two of which comprise the intergrowth in any one domain. The following intergrown pairs of minerals have been identified: quartz-Al₂SiO₃, quartz-biotite, biotite-oligoclase, biotite-K-feldspar, muscovite-oligoclase, oligoclase-andalusite, K-feldspar-andalusite, aluminous orthopyroxene-Al₂SiO₃, and aluminous anthophylite-Al₂SiO₃.  相似文献   

Evidence of high sea level during isotope stage 5c in Queensland,Australia     

J.W. Pickett  C.H. Thompson  R.A. Kelley  D. Roman 《Quaternary Research》1985,24(1):103-114

Thirty-nine species of scleractinian corals have been recovered from under a high dune on the western (mainland) side of North Stradbroke Island, eastern Australia. The corals are associated with thin intertidal sediments and their good condition implies burial in situ and preservation in a saturated zone. Most likely this occurred as the coast prograded and a large dune advanced into the littoral zone, burying intertidal sediments and coral. The species assemblage indicates a sheltered environment but one open to the ocean without wide fluctuations in salinity. Three species yielded a mean ${}^{230}\text{Th}{}^{234}\text{U}$ age of 105,000 yr B.P. which is significantly younger than the nearest Pleistocene corals at Evans Head, New South Wales. The corals provide evidence of a sea stand near present sea level during isotope Stage 5c, which is considerably higher than previously suggested for this period. Their good condition implies that the overlying parabolic dune is of comparable age and formed during that high stand of sea level. Also, the isotope age provides a maximum period for the development of giant podzols in the podzol chronosequences on coastal dunes in southern Queensland.  相似文献   

Trace Element Geochemistry in Water from Selected Springs in Death Valley National Park, California   总被引：1，自引：0，他引：1  

David K. Kreamer  Vernon F. Hodge  Irving Rabinowitz  Kevin H. Johannesson  Klaus J. Stetzenbach 《Ground water》1996,34(1):95-103

  相似文献   

A hybrid approach to improving the skills of seasonal climate outlook at the regional scale     

Shuyan Liu  Julian X. L. Wang  Xin-Zhong Liang  Vernon Morris 《Climate Dynamics》2016,46(1-2):483-494

A hybrid seasonal forecasting approach was generated by the National Centers for Environmental Prediction operational Climate Forecast System (CFS) and its nesting Climate extension of Weather Research and Forecasting (CWRF) model to improve forecasting skill over the United States. Skills for the three summers of 2011–2013 were evaluated regarding location, timing, magnitude, and frequency. Higher spatial pattern correlation coefficients showed that the hybrid approach substantially improved summer mean precipitation and 2-m temperature geographical distributions compared with the results of the CFS and CWRF models. The area mean temporal correlation coefficients demonstrated that the hybrid approach also consistently improved the timing prediction skills for both variables. In general, the smaller root mean square errors indicated that the hybrid approach reduced the magnitude of the biases for both precipitation and temperature. The greatest improvements were achieved when the individual models had similar skills. The comparison with a North American multi-model ensemble further proved the feasibility of improving real-time seasonal forecast skill by using the hybrid approach, especially for heavy rain forecasting. Based on the complementary advantages of CFS the global model and CWRF the nesting regional model, the hybrid approach showed a substantial enhancement over CFS real-time forecasts during the summer. Future works are needed for further improving the quality of the hybrid approach through CWRF’s optimized physics ensemble, which has been proven to be feasible and reliable.  相似文献