Transfer and exchange equilibria in a portion of the pyroxene quadrilateral as deduced from natural and experimental data     

Ralph Kretz 《Geochimica et cosmochimica acta》1982,46(3):411-421

Differences in the chemical composition of metamorphic and igneous pyroxene minerals may be attributed to a transfer reaction, which determines the Ca content of the minerals, and an exchange reaction, which determines the relative Mg:Fe²⁺ ratios. Natural data for associated Ca pyroxene (Cpx) and orthopyroxene (Opx) or pigeonite are combined with experimental data for Fe-free pyroxenes, to produce the following equations for the Cpx slope of the solvus surface: $\text{> 1080°C: T =}\text{1000}\text{(0.468 + 0.246X}{}^{\mathrm{Cpx}}\text{? 0.123 ln (1–2 [Ca]))}$$\text{< 1080°C: T =}\text{1000}\text{(0.054 + 0.608X}{}^{\mathrm{Cpx}}\text{? 0.304 ln (1–2 [Ca]))}$, and the following equation for the temperature-dependence of the Mg-Fe distribution coefficient: $\text{T =}\text{1130}\text{(}\text{ln}\text{K}{}_{\mathrm{p}}\text{+ 0.505)}$, where T is absolute temperature, X is $\text{Fe}{}^{\mathrm{2+}}\text{(Mg + Fe}{}^{\mathrm{2+}}\text{))}$, [Ca] is $\text{Ca}\text{(Ca + Mg + Fe}{}^{\mathrm{2+}}\text{)}$ in Cpx, and K_D is the distribution coefficient, defined as $\text{X}{}^{\mathrm{Opx}}\text{/(1 ? X}{}^{\mathrm{Opx}}\text{) ÷ X}{}_{\mathrm{Cpx}}\text{/(1 ?}{}^{\mathrm{Cpx}}\text{)}$.The transfer and exchange equations form useful temperature indicators, and when applied to 9 sets of well-studied rocks, yield pairs of temperatures that are in good agreement. For example, temperatures obtained for the Bushveld Complex are 1020°C (solvus equation) and 980°C (exchange equation), based on 7 specimens. The uncertainty in these numbers, due to precision and accuracy errors, is estimated to be ±60°.  相似文献   

A petrologic method of analysis of nonmaceral microstructures in coal     

Ralph J. Gray 《International Journal of Coal Geology》1982,2(1):79-97

The petrographic maceral composition and vitrinoid reflectance of bituminous coals have been correlated with their carbonization characteristics and are widely used to predict how coals will perform in the coking process and to calculate the strength of the resulting coke. As a result, there is a growing dependence on coal petrographic data in characterizing coals for cokemaking. In addition, there is a growing awareness that there are other nonmaceral microstructures in coal such as material size, shape, association, fracturing, and weathering which should permit better characterization of coals when properly interpreted. These nonmaceral microstructures also give an insight into the metamorphic history and changes due to burial and exhumanation.To expand the use of coal petrologic and petrographic data, a new analytical procedure has been developed that requires the microscopic determination of such nonmaceral microstructures as normal coal, coal fines, pseudovitrinoids, microbrecciation, oxidation, coarse mineral matter, miscellaneous materials, and contamination. The occurrence of one or more of these microstructures in coal, depending on their kind and abundance, may have a significant effect on the coal performance in various processes. This work has resulted in formulation of a technique for determining the nonmaceral microstructures in coal and, if applied as a supplement to the routine maceral analysis of coals, should help in explaining the anomalous behavior of some coals.  相似文献   

Spherical earth gravity and magnetic anomaly analysis by equivalent point source inversion     

Ralph R.B. Von Frese  William J. Hinze  Lawrence W. Braile 《Earth and Planetary Science Letters》1981,53(1):69-83

To facilitate geologic interpretation of satellite elevation potential field data, analysis techniques are developed and verified in the spherical domain that are commensurate with conventional flat earth methods of potential field interpretation. A powerful approach to the spherical earth problem relates potential field anomalies to a distribution of equivalent point sources by least squares matrix inversion. Linear transformations of the equivalent source field lead to corresponding geoidal anomalies, pseudo-anomalies, vector anomaly components, spatial derivatives, continuations, and differential magnetic pole reductions. A number of examples using 1°-averaged surface free-air gravity anomalies and POGO satellite magnetometer data for the United States, Mexico and Central America illustrate the capabilities of the method.  相似文献   

Detecting rift basins in the Evans Ice Stream region of West Antarctica using airborne gravity data     

Philip C. Jones  Ashley C. Johnson  Ralph R. B. von Frese  Hugh Corr 《Tectonophysics》2002,347(1-3)

A total of 11,500 line km of aerogravity data have been used to construct an free-air gravity anomaly map for the Antarctic region that may contain the microplate boundary between the Haag Nunataks block and southern Antarctic Peninsula. Along-line free-air gravity anomaly data resolved wavelengths of 9 km or greater with better than 5 mGal accuracy. Coincident radio echo soundings provided data to construct a digital terrain model. The gravity effect of the terrain was calculated by Gauss–Legendre quadrature (GLQ) and spectrally correlated with the free-air gravity data. Terrain-correlated free-air anomalies related to possible isostatic imbalances of the crust were separated from terrain-decorrelated anomalies that may reflect intra-crustal density contrasts. Subtracting terrain-correlated free-air anomalies from the gravity effects of the terrain yielded compensated terrain gravity effects (CTGE) that were used to model the Moho by inversion. The results indicate moderate but significant crustal thinning below the Evans Ice Stream that is consistent with an extensional origin for the deep, wide, steep-sided trough that contains the ice stream as well as the continued elevation of the footwall flank of the basin. Changes along the axis of the rift, both in the gravity anomaly field and the distribution of Moho topography, can be explained by processes associated with continental lithospheric extension. Subsequently, many of the features produced by extension have been modified by glacial erosion and the sub-ice topography and gravity data reflect this.  相似文献   

Basement control on oblique thrust sheet evolution: seismic imaging of the active deformation front of the Central Andes in Bolivia     

Ralph Hinsch  Charlotte M. Krawczyk  Christoph Gaedicke  Raul Giraudo  Daniel Demuro 《Tectonophysics》2002,355(1-4)

In the area of the Bolivian Orocline, we examine the deformation pattern associated with the active development of a new thrust sheet. A dense grid of reprocessed 2-D seismic lines from hydrocarbon exploration industry is interpreted and a 3-D simplified structural and kinematic model is deduced. In the Boomerang Hills, onlapping Paleozoic and foredeep sediments are detached from the underlying S-dipping basement. They are thrust northeastwards by less than 2 km. Two zones can be differentiated along the Andean deformation front: (1) a W–E to NW–SE striking frontal segment of predominantly orthogonal shortening, comprising a thrust and anticline system; (2) a WSW–ENE striking lateral zone of oblique shortening within a complex system of thin-skinned strike–slip faults and minor folds. The deformation front always follows a pronounced edge in the topography of the top basement surface close to the boundary of the Paleozoic basin. The observed deformation pattern indicates intensified strain partitioning caused by the interaction of contraction direction and basement topography, which provides a near oblique ramp for the onlapping wedge of sediments. The SW–NE thrusting direction is divided into orthogonal and tangential components. These are accommodated by convergent and strike–slip structures, respectively, which sole into a common detachment horizon. The structural evolution of the new thrust sheet in the Bolivian Orocline is primarily controlled by the paleorelief of the Brazilian Shield because: (1) the shape of the basement affects the taper of the thrust wedge and localizes the deformation front and (2) small asperities in/close to the top of the basement promote fault localization. The coincidence of a relatively high basement position and a structural high of the Eastern Cordillera leads to the conclusion that the shape of the Brazilian Shield also controls the structural evolution of the pronounced eastern border of the Bolivian Orocline.  相似文献   

Questions and Answers for Environmental Professionals     

Daniel J. Gibby  Ralph E. Moon 《Ground Water Monitoring & Remediation》1997,17(2):56-58

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Spatial variation in delaware bay (U.S.A.) marsh creek fish assemblages     

Kenneth W. Able  David M. Nemerson  Ralph Bush  Phillip Light 《Estuaries and Coasts》2001,24(3):441-452

Delaware Bay is one of the largest estuaries on the U.S. eastern seaboard and is flanked by some of the most extensive salt marshes found in the northeastern U.S. While physicochemical and biotic gradients are known to occur along the long axis of the bay, no studies to date have investigated how the fish assemblage found in salt marsh creeks vary along this axis. The marshes of the lower portion of the bay, with higher salinity, are dominated bySpartina spp., while the marshes of the upper portion, with lower salinity, are currently composed primarily of common reed,Phragmites australis, S. alterniflora, or combinations of both. Extensive daytime sampling (n=815 tows) during May–November 1996 was conducted with otter trawls (4.9 m, 6 mm mesh) in six intertidal and subtidal marsh creek systems (upper and lower portions of each creek) where creek channel depths ranged from 1.4–2.8 m at high tide. The fish taxa of the marsh creeks was composed of 40 species that were dominated by demersal and pelagic forms including sciaenids (5 species), percichthyids (2), and clupeids (7), many of which are transients that spawn outside the bay but the early life history stages are abundant within the bay. The most abundant species wereMorone americana (24.3% of the total catch),Cynoscion regalis (15.4%),Micropogonias undulatus (15.3%),Anchoa mitchilli (12.0%), andTrinectes maculatus (10.8%). Non-metric Multi-Dimensional Scaling ordination of catch per unit effort (CPUE) data indicated two fish assemblages that were largely independent of the two major vegetation types, but generally corresponded with spatial variation in salinity. This relationship was more complex because some of the species for which we could discriminate different age classes by size had different patterns of distribution along the salinity gradient.  相似文献   

Design principles for individual transferable quotas     

Ralph E. Townsend  James McColl  Michael D. Young 《Marine Policy》2006

Individual transferable quota (ITQ) institutions should be designed to minimize two types of transaction costs. First, to minimize the costs of transferring ITQ rights among rights-holders and users, rights should be separated into three components: a permanent entitlement share, an annual catch allocation, and a license to fish. Second, ITQ rights can reduce the transactions costs for development of self-governance by owners both by specifying a non-unanimous voting rule (preferably one-share/one-vote) and also by delineating clear standards for devolution of responsibility from government. These same two principles for reduction of transactions costs can be applied, with slight variation, to individual transferable input systems.  相似文献   

Computers In Geography     

Ralph E. Olson 《The Professional geographer》1970,22(3):161-161

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Spectral analysis in geophysics,M. Bath,Developments in Solid Earth Geophysics, 7, Elsevier,Amsterdam (1974), p. 563, U.S. $46.20     

Ralph A. Wiggins 《Earth》1976,12(1):79-80

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