A first principles study of the distribution of iron in sphalerite   总被引：1，自引：0，他引：1  

Kate Wright  Julian D. Gale 《Geochimica et cosmochimica acta》2010,74(12):3514-3520

Quantum mechanical techniques, based on density functional theory, have been used to study the distribution of iron impurities in sphalerite (ZnS) at compositions ranging from 3.125 to 12.5 mol% FeS. Our results show that iron is most easily incorporated by direct substitution onto the zinc site and that energies for solution reactions involving FeS are exothermic when the system is zinc deficient. Furthermore, there appears to be a small driving force for the formation of bound Fe-Fe pairs at low iron concentrations, though there is no particular preference found for larger clusters of iron. The influence of iron on the sphalerite cell parameter is shown to be sensitive to the presence of Fe-Fe pairs and to the degree of sample non-stoichiometry.  相似文献   

Flows,Statistics And Maps: A Rejoinder     

C. Michael Costanzo  Nathan Gale 《The Professional geographer》1985,37(1):58-59

  相似文献   

Mechanical and hydraulic properties of rocks related to induced seismicity   总被引：1，自引：0，他引：1  

Paul A. Witherspoon  John E. Gale 《Engineering Geology》1977,11(1):23-55

Witherspoon, P.A. and Gale, J.E., 1977. Mechanical and hydraulic properties of rocks related to induced seismicity. Eng. Geol., 11(1): 23–55.The mechanical and hydraulic properties of fractured rocks are considered with regard to the role they play in induced seismicity. In many cases, the mechanical properties of fractures determine the stability of a rock mass. The problems of sampling and testing these rock discontinuities and interpreting their non-linear behavior are reviewed. Stick slip has been proposed as the failure mechanism in earthquake events. Because of the complex interactions that are inherent in the mechanical behavior of fractured rocks, there seems to be no simple way to combine the deformation characteristics of several sets of fractures when there are significant perturbations of existing conditions. Thus, the more important fractures must be treated as individual components in the rock mass.In considering the hydraulic properties, it has been customary to treat a fracture as a parallel-plate conduit and a number of mathematical models of fracture systems have adopted this approach. Non-steady flow in fractured systems has usually been based on a two-porosity model, which assumes the primary (intergranular) porosity contributes only to storage and the secondary (fracture) porosity contributes only to the overall conductivity. Using such a model, it has been found that the time required to achieve quasi-steady state flow in a fractured reservoir is one or two orders of magnitude greater than it is in a homogeneous system. In essentially all of this work, the assumption has generally been made that the fractures are rigid.However, it is clear from a review of the mechanical and hydraulic properties that not only are fractures easily deformed but they constitute the main flow paths in many rock masses. This means that one must consider the interaction of mechanical and hydraulic effects. A considerable amount of laboratory and field data is now available that clearly demonstrates this stress-flow behavior. Two approaches have been used in attempting to numerically model such behavior: (1) continuum models, and (2) discrete models. The continuum approach only needs information as to average values of fracture spacing and material properties. But because of the inherent complexity of fractured rock masses and the corresponding decrease in symmetry, it is difficult to develop an equivalent continuum that will simulate the behavior of the entire system. The discrete approach, on the other hand, requires details of the fracture geometry and material properties of both fractures and rock matrix. The difficulty in obtaining such information has been considered a serious limitation of discrete models, but improved borehole techniques can enable one to obtain the necessary data, at least in shallow systems. The possibility of extending these methods to deeper fracture systems needs more investigation. Such data must be considered when deciding whether to use a continuum or discrete model to represent the interaction of rock and fluid forces in a fractured rock system, especially with regard to the problem of induced seismicity. When one is attempting to alter the pressure distribution in a fault zone by injection or withdrawal of fluids, the extent to which this can be achieved will be controlled in large measure by the behavior of the fractures that communicate with the borehole. Since this is essentially a point phenomenon, i.e., the changes will propagate from a relatively small region around the borehole, the use of a discrete model would appear to be preferable.  相似文献   

The california poppy (eschscholtzia mexicana) as a copper indicator plant — a new example     

M.A. Chaffee  C.W. Gale III 《Journal of Geochemical Exploration》1976,5(1-2)

The abundance and distribution of the California poppy (Eschscholtzia mexicana) correlates closely with the copper-rich outcrop of a small porphyry-type deposit in Arizona. Chemical factors are probably more important than physical factors in determining why this species is sometimes found as a copper indicator plant.  相似文献   

The chronology of the Nakhla achondritic meteorite     

N.H. Gale  J.W. Arden  R. Hutchison 《Earth and Planetary Science Letters》1975,26(2):195-206

A well-defined internal RbSr isochron has been determined for the unbrecciated Nakhla achondrite, defining an age T = (1.24 ± 0.01) AE and an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.70254 ± 0.00003. The excellence of fit to the isochron shows that a very thorough Sr isotopic equilibration took place at this time between all phases of the meteorite. Recent petrological observations indicate that the age most probably represents the time of an igneous crystallization event on the parent body of Nakhla. The age shows that we may no longer assume that major chemical and physical differentiation processes took place only in early solar system history. The RbSr systematics are shown not to require late formation of the Nakhla parent body. Geochemical similarities between Nakhla and the earth are discussed.  相似文献   

Uranium-lead age of the Bruderheim L6 chondrite and the 500-Ma shock event in the L-group parent body     

N.H. Gale  J.W. Arden  M.C.B. Abranches 《Earth and Planetary Science Letters》1980,48(2):311-324

Measured Pb-Pb whole meteorite data for the Bruderheim L6 chondrite scatter slightly about a line passing above Can?on Diablo lead and yielding an age of 4.482 + 0.017 Ga, using the terrestrial²³⁸U/²³⁵U ratio of 137.88. The measured U isotopic composition for Bruderheim, using the dissolution procedures employed for these U-Pb studies, is near the terrestrial composition. In the concordia diagram the U-Pb data chiefly plot above the concordia curve and define a line which intersects the concordia curve at 4.536 + 0.006 Ga and 0.495 Ga, but the data for Bruderheim cannot be understood at all in terms of the more usual two- or three-stage episodic U-Pb models involving a fixed μ-value in the first stage. Most samples show an apparent excess of radiogenic lead for single-stage (closed system) evolution when Can?on Diablo troilite is used for the initial lead composition. Evidence is presented to show that the apparent excess radiogenic lead cannot be explained by terrestrial contamination alone.A different U-Pb model is presented which describes qualitatively and quantitatively most features of the U-Pb data for Bruderheim. If this model correctly describes the U-Pb evolution of Bruderheim then the “formation” age is given as 4.536 Ga by both U-Pb and Pb-Pb data, the meteorite U-Pb system was disturbed by a later (shock?) event at about 500 Ma ago, and the data are consistent with (though do not require) a Can?on Diablo initial lead composition. This interpretation suggests that the classical phenomenon of apparent excess radiogenic lead reflects the application of a single-stage model to a meteorite that has evidently experienced at least a two-stage history. The explanation of the observation that in the concordia diagram most meteorite samples (corrected for Can?on Diablo lead) plot in the lead excess region remains obscure, though this may be due to the wrong choice of initial lead for Bruderheim.  相似文献   

Discussion of a paper by McKerrow,Lambert and Chamberlain on the Ordovician,Silurian and Devonian time scales     

N.H. Gale  R.D. Beckinsale  A.J. Wadge 《Earth and Planetary Science Letters》1980,51(1):9-17

  相似文献   

Trace element geochemistry of Norwegian Lower Palaeozoic basic volcanics and its tectonic implications     

George H. Gale  David Roberts 《Earth and Planetary Science Letters》1974,22(4):380-390

The study of nearly 100 new trace element analyses of late Cambrian/early Ordovician greenstones from the Grong, Løkken, Støren and Stavenes areas of central and southern Norway indicates the presence of ocean floor type basalts in all four areas, and the presence of low-potassium tholeiites of island arc affinity in at least two of the areas. From this result an ocean floor-based Ordovician/early Silurian island arc complex and back-arc eugeosynclinal pile is recognised in the Trondheim region and its principal features described. This complex is considered to have been obducted during an early stage of the Middle Silurian orogeny upon an Eocambrian/Ordovician miogeosynclinal sedimentary succession which had developed on continental crust. During a later stage of the major folding and metamorphism of the juxtaposed sequences, further eastward thrusting took place such that total displacement of some allochthonous sheets may be in the order of several hundred kilometres.  相似文献   

SOME APPLICATIONS OF COMPUTER CARTOGRAPHY TO THE STUDY OF COGNITIVE CONFIGURATIONS     

Nathan Gale 《The Professional geographer》1982,34(3):313-321

Cartographic theory and techniques are applied to the study of environmental cognition in an urban setting. Cognitive configurations of Columbus, Ohio derived from nonmetric multidimensional scaling are analyzed by location. A distinction is made between the distortion, or average accuracy, and the fuzziness, or dispersion, of estimates associated with forty-nine location cues. Computer mapping techniques are used to portray the distortion and fuzziness of each of these cues individually, and then in the form of a composite map.  相似文献   

Invited comment on Wray & Gale's ‘The palaeoenvironment and stratigraphy of the Late Cretaceous Chalks’: Proceedings, Vol. 117, 2006, pp. 145-162     

Peter M. Hopson  Richard A. Ellison  Kathryn A. Booth  Andrew S. Gale 《Proceedings of the Geologists' Association. Geologists' Association》2006,117(2):163-171

  相似文献