Structural controls of lode-gold mineralization by mafic dykes in late-Paleozoic granitoids of the Kochkar district, southern Urals, Russia   总被引：2，自引：0，他引：2  

A. F. M. Kisters  F. M. Meyer  S. E. Znamensky  I. B. Seravkin  R. G. W. Ertl  A. M. Kosarev 《Mineralium Deposita》2000,35(2-3):157-168

The Kochkar gold district in the East Uralian Zone of the southern Urals is located in late-Paleozoic granite gneisses of the Plast massif. Gold mineralization is associated with tabular quartz lodes that are preferentially developed along the margins of easterly trending mafic dykes. Fabric development indicates that dykes had a profound influence on the development of shear zones in granitoids. ENE- and SE-trending dykes have been reactivated as dextral and sinistral oblique strike-slip shear zones, respectively, forming a set of approximately conjugate shear zones related to the Permian, regional-scale E-W directed shortening. Dyke-shear zone relationships in the Plast massif are the result of strain refraction due to the presence of biotite-rich, incompetent dykes in more competent granite-gneisses. Deformation and the formation of associated gold-quartz lodes occurred close to peak-metamorphic, upper-greenschist to lower-amphibolite facies conditions. Strain refraction has resulted in partitioning of the bulk strain into a component of non-coaxial mainly ductile shear in mafic dykes, and a component of layer-normal pure shear in surrounding granitoids where deformation was brittle-ductile. Brittle fracturing in granitoids has resulted in the formation of fracture permeabilities adjacent to sheared dykes, that together with the layer-normal dilational component, promoted the access of mineralizing fluids. Both ore-controlling dykes and gold-quartz lodes were subsequently overprinted by lower greenschist-facies, mainly brittle fault zones and associated hydrothermal alteration that post-date gold mineralization. Received: 15 October 1998 / Accepted: 18 August 1999  相似文献   

MANAGEMENT AND SUBSURFACE EFFECTS ON RUNOFF AND SEDIMENT YIELD FROM SMALL WATERSHEDS     

Dabney  S. M.  L. D. Meyer  C. E. Murphree 《国际泥沙研究》2000,(2)

lINTR0DUCTIONSoiler0si0ncanbeaseriousproblemonsl0pinguplands0fthes0uthemUnitedStatesthatareintensivelycr0pped.Conservati0nprovisionsofthel985U.S.FarmBillmandateddevelopmentofaconservati0nplanonhighlyer0diblelands.Researchwasinitiatedinl9870na28-haareaattheA-E.Nels0nFarrninn0rthernMississippit0determineiftheconservati0nprovisionscouldbeachievedwhileprofitablygr0wingrowcropsincludingcott0n(GosSyPiumhirsutumL.),soybean(GlyciDemax(L.)Merr.),sorghum(SOrghumbicolor(L.)Moench),c0rn(Zeam…  相似文献   

Author'Reply     

Solomon A. Isiorho  John H. Meyer 《Ground water》2000,38(3):327-328

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A novel sampling technique for image sharpening in infrared array cameras     

G. Finger  P. Biereichel  M. Meyer  A. F. M. Moorwood 《Experimental Astronomy》1994,3(1-4):185-187

A new nondestructive readout scheme of the array will be presented which allows first order wavefront corrections of images degraded by atmospheric seeing. During the stare time the integration ramp of the detector signal is sampled every 100 msec. A regressional fit of the sampled data points yields the slope of the integration ramp which is proportional to the flux received by a detector pixel. To this readout mode which is commonly used for IR arrays a small software module can be added to compensate the image motion of the observed object by shifting the nondestructively sampled images. This has the same effect as a tip tilt correction by an active optical element - but without the extra complexity of such a device. First results obtained at the telescope are presented.  相似文献   

The MAR-Vema Fracture Zone intersection surveyed by deep submersible Nautile     

Jean-Marie Auzende  Daniel Bideau  Enrico Bonatti  Mathilde Cannat  José Honnorez  Yves Lagabrielle  Jacques Malavieille  Vassilios Mamaloukas-Frangoulis  Catherine Mével 《地学学报》1990,2(1):68-73

One of the two objectives of the Vemanaute cruise of the French deep submersible Nautile, was the geological study of the eastern intersection area between the Mid-Atlantic Ridge (MAR) and the Vema Fracture Zone in the equatorial Atlantic. Fourteen dives were conducted that allowed detailed geological survey and sampling of the main morphostructural units of this area: the northern and southern walls of the fracture zone, the median ridge, the northern and southern troughs and the nodal basin. In situ observations of recent tectonic features such as furrows, ridges and circular depressions, concentrated within the southern trough, allowed us to establish the location and the size of the present-day displacement zone. Geological investigations have shown that the nodal basin is entirely floored by basalts thus contrasting with other equivalent areas such as the Kane and Oceanographer fracture zone-MAR eastern intersections. Finally, this study stresses the great opposition between the relatively old and tectonically inactive northern part of the fracture, and the southern part which shows active tectonics and recent volcanic activity.  相似文献   

Heavy-element abundances from a neutron burst that produces Xe-H     

W. Michael Howard  Bradley S. Meyer  Donald D. Clayton 《Meteoritics & planetary science》1992,27(4):404-412

Abstract— We examine quantitatively the suggestion that the heavy anomalous isotopes of Xe-HL found in meteoritic diamonds were produced by a short intense neutron burst and then implanted into the diamonds. Using a large nuclear reaction network we establish one (out of many) neutron irradiation histories that successfully reproduces the heavy isotopes of Xe-HL, and then evaluate what that same history would produce in every heavy element. This has become more relevant following recent measurement of anomalous Ba and Sr in those same diamond samples. Therefore we offer these calculations as a guide to the anomalies to be expected in all elements if this scenario is correct. We also discuss several other aspects of the problem, especially the established contradictions for Ba, the observed Kr pattern, the near normalcy of ¹²⁹Xe, and some related astrophysical ideas. In particular we argue from p-process theory that the observed deficit of ⁷⁸Kr in correlation with ^124–126Xe excess implicates Type II supernovae as the diamond sources. However, our more complete astrophysical conclusions will be published elsewhere. This present work is offered as computational expectation for this class of models and as a guide to considerations that may accelerate the digestion of new experimental results in the diamonds.  相似文献   

The pre-weichselian glaciations of North-West Europe     

Jürgen Ehlers  Klaus-Dieter Meyer  Hans-Jürgen Stephan 《Quaternary Science Reviews》1984,3(1):1-40

In North-West Europe no evidence has been found for glaciations older than the Elsterian. The Elsterian seems to consist of at least two separate ice advances with a minor interval in between. During the Elsterian in the area south of the Baltic Sea over 400 m deep channels were cut into the underlying substratum by a combination of glacial erosion and meltwater activity. The channels were active until the Late Elsterian and were subsequently filled with meltwater deposits and glaciolacustrine silt and clay. During the Saalian no comparative channels were being formed. Three different ice advances can be distinguished within the Saalian, the stratigraphical correlation of which is to be discussed. No convincing evidence was found for any interglacial within the Saalian sequence. There are good reasons to assume that the ice advances were only separated from each other by minor ice-free intervals.  相似文献   

THE USE OF CITATION INDICES IN COMPARING GEOGRAPHY PROGRAMS: AN EXPLORATORY STUDY*     

B. L. Turner  William B. Meyer 《The Professional geographer》1985,37(3):271-278

Citation information is discussed as a means for ranking the research and publication visibility of eleven graduate programs in geography. It is suggested that the ranks produced by this objective method correspond better to the peer-based ranks of the 1982 NRC survey of graduate programs than those derived from publication counts. Citation information also provides a means of evaluating the differences between programs' inter- and intradisciplinary visibility.  相似文献   

Methods to determine the angular resolution of the HEGRA extended air shower scintillator array     

M. Merck  A. Karle  S. Martinez  F. Arqueros  K. H. Becker  M. Bott-Bodenhausen  R. Eckmann  E. Faleiro  J. Fernandez  P. Fernandez  V. Fonseca  V. Haustein  G. Heinzelmann  I. Holl  F. Just  F. Krennrich  M. Kühn  E. Lorenz  H. Meyer  N. Müller  R. Plaga  J. Prahl  M. Probst  M. Rozanska  M. Samorski  H. Sander  K. Sauerland  C. Sesea  W. Stamm 《Astroparticle Physics》1996,5(3-4):379-392

A precise knowledge of the angular resolution of scintillator arrays used to observe extended air showers (EAS) is of key importance in the search for VHE/UHE γ point sources. Four independent methods have been used to determine the mean resolution for which a value of ΔΘ₆₃ of 0.8°(1.0°) at a proton threshold of 50 (40) TeV has been found for the HEGRA EAS-array.  相似文献   

The effect of low temperature on Antarctic endolithic green algae     

Meyer MA  Huang G-H  Morris GJ  Friedmann EI 《Polarforschung》1988,58(2-3):113-119

Laboratory experiments show that undercooling to about -5 degrees C occurs in colonized Beacon sandstones of the Ross Desert, Antarctica. High-frequency temperature oscillations between 5 degrees C and -5 degrees C or -10 degrees C (which occur in nature on the rock surface) did not damage Hemichloris antarctica. In a cryomicroscope, H. antarctica appeared to be undamaged after slow or rapid cooling to -50 degrees C. 14CO2 incorporation after freezing to -20 degrees C was unaffected in H. antarctica or in Trebouxia sp. but slightly depressed in Stichococcus sp. (isolated from a less extreme Antarctic habitat). These results suggest that the freezing regime in the Antarctic desert is not injurious to endolithic algae. It is likely that the freezing-point depression inside the rock makes available liquid water for metabolic activity at subzero temperatures. Freezing may occur more frequently on the rock surface and contribute to the abiotic nature of the surface.  相似文献