The Cone-in-Cone Structure and Its Origin   总被引：1，自引：0，他引：1  

Kolokol'tsev  V. G. 《Lithology and Mineral Resources》2002,37(6):523-535

Morphostructural investigation of carbonate cone-in-cone formations allows to conclude that they belong to self-organizing (dissipative, according to I. Prigogine's terminology) systems of the geological past formed in a thermogradient field at the expense of energy of heat and mass transfer (Prigogine and Stengers, 1984). First, the fluid-convective metasomatic hypothesis unites and reconciles the most well-known hypotheses that previously seemed to be incompatible and transforms them to rather consistent particular cases of a more intricate multistage geological phenomenon. Second, it helps to identify the morphologically and genetically analogous noncarbonate structures that mimic biogenic ones. The probable indicative role of cone-in-cone structure in the mapping of fluid-conducting systems is a consequence of the proposed hypothesis.  相似文献   

Isotope Evidences of the Paleozoic Stage of Epigenetic Transformation of Vendian Sediments of the Russian Platform     

V. I. Vinogradov  M. I. Bujakaite  V. I. Murav'ev  M. B. Burzin  A. F. Veis 《Lithology and Mineral Resources》2002,37(5):454-461

The Rb–Sr characteristics of whole-rock samples of Upper Vendian clayey rocks recovered by Gavrilov-Yam boreholes are studied. The Rb–Sr age versus sampling depth relationship has been revealed. Three sample assemblages are identified. The errorchron relationship of samples in the first interval (1760–2400 m) fits the age of 390 ± 40 Ma corresponding to the initial Hercynian history characterized by the transformation of platformal sediments. The other two assemblages (2410–2525 and 2528–2560 m) make up isochrons with slopes corresponding to 590 ± 50 and 690 ± 10 Ma, respectively. Their geochronological meaning is unclear.  相似文献   

The gravity method in groundwater exploration in crystalline rocks: a study in the peninsular granitic region of Hyderabad, India     

B. Murty  V. Raghavan 《Hydrogeology Journal》2002,10(2):307-321

The application of variations in the earth's gravity in groundwater exploration on a regional scale, especially in sedimentary basins, metamorphic terrains, valley fills, and for buried alluvial channels, is well established. However, its use in hard crystalline rocks is little known. In granite, for example, the upper weathered layer is a potential primary aquifer, and the underlying fractured rock can form a secondary aquifer. Fracturing and weathering increases the porosity of a rock, thereby reducing the bulk density. Changes in gravity anomalies of 0.1–0.7 mGal for granites, due to weathering or variations in lithology, can be detected. To test the use of gravity as a groundwater exploration tool for crystalline rocks, a gravity survey of the peninsular shield granites underlying Osmania University Campus, Hyderabad, India, was undertaken. At the site, gravity anomalies reflect variations in the lithology and in the thickness of weathered zones. These anomalies also define the position of intrusives and lineaments. Areas of more deeply weathered granite that contain wells of higher groundwater yield are represented by negative gravity values. In the weathered zone, well yield has an inverse relation to the magnitudes of residual gravity. The study confirms the feasibility of gravity as a tool for groundwater exploration in crystalline rocks. Electronic Publication  相似文献   

Equilibrium after violent relaxation in numerical dynamical models of open clusters     

V. M. Danilov 《Astronomy Reports》2002,46(6):443-450

Models of open clusters in a state of equilibrium in the space of the three parameters of the stellar motion and simultaneously far from virial equilibrium are analyzed. A formula for the phase-space stellar number density in such cluster models is derived, as well as formulas for the integrated and differential energy distributions of the phase-space volume occupied by cluster stars per unit stellar mass. These three quantities are computed for several times exceeding the time for violent relaxation of the cluster model. The phase-space density function obtained is used to compute the distribution of the absolute values of stellar velocities for the cluster model considered.  相似文献   

Structure of gas flows in Z And in quiescence and during outbursts     

D. V. Bisikalo  A. A. Boyarchuk  E. Yu. Kilpio  O. A. Kuznetsov 《Astronomy Reports》2002,46(12):1022-1029

A new mechanism is proposed to account for transitions between the quiescent and active states of symbiotic stars. A numerical study of the gas dynamics of the flows in the symbiotic star Z And shows that even small variations in the velocity of the wind from the cool giant can abruptly change the flow structure near the hot component. Such changes alter the accretion regime as the wind velocity increases: disk accretion makes a transition to accretion from the flow. Our calculations indicate that the accretion rate increases by a factor of several tens over a short time interval (～0.1 of the orbital period) during the rearrangement of the flow, when the accretion disk is destroyed.  相似文献   

Polarization of individual pulses of radio pulsars at the low frequencies 40, 60, and 103 MHz     

S. A. Suleimanova  V. D. Pugachev 《Astronomy Reports》2002,46(4):309-326

Measurements of the linear polarization of individual pulses at 40, 60, and 103 MHz are presented for ten pulsars. The degree and position angle of a linear polarization were measured with a temporal resolution of 1–7 ms, and the longitudinal distributions of these parameters were constructed for each pulsar at one or more of these frequencies. These are the first such measurements for pulsars B0031-07, B0320 + 39, B0628-28, and B2217 + 47. Apart from B0628-28, all the pulsars are characterized by the simultaneous presence of orthogonal polarization modes in at least one component of the integral profile. The secondary polarization mode increases at frequencies ≤100 MHz for pulsars whose integrated pulses contain pairs of conal components (B0031-07, B0329 + 54, B0834 + 06, B1133 + 16, B2020 + 28). This is manifested both as an expansion of the longitudinal range where the secondary polarization mode is observed and an increase in its contribution to the emission at a given longitude. New data confirming the dependence of the linear polarization of individual pulses on the intensity and mode of the pulsar emission have been obtained.  相似文献   

Color redshifts and the age of the stellar population of distant RC radio galaxies     

O. V. Verkhodanov  A. I. Kopylov  Yu. N. Pariiskii  N. S. Soboleva  A. V. Temirova  O. P. Zhelenkova 《Astronomy Reports》2002,46(7):531-542

BV RI data are presented for the majority of steep-spectrum objects in the RC catalog with m _R <23.5^m. Previously developed programs are applied to these data to estimate the redshifts and ages of the stellar systems of the host galaxies. Applying this program to the color data (BV RI JHK) for distant radio galaxies with spectroscopic redshifts indicates that this approach provides accurate estimates of the redshifts of such radio galaxies, close to those obtained using field galaxies (～20%). The age estimates are much less trustworthy, but a lower limit to the ages of objects that are not very distant (z<1.5) can be determined with certainty. We have identi fied several galaxies whose formal ages exceed the age of the Universe at the corresponding z in simple Cold Dark Matter models for the Universe. The possibility of using such objects to elucidate the role of “dark energy” is discussed. This paradox disappears in models with cosmological constants (Λ terms) equal to 0.6–0.8.  相似文献   

Mud Volcanoes, Their Distribution Regularities and Genesis: Communication 1. Mud Volcanic Provinces and Morphology of Mud Volcanoes     

V. N. Kholodov 《Lithology and Mineral Resources》2002,37(3):197-209

The article discusses regularities in the distribution of mud volcanoes and characterizes most important mud volcanic provinces of the world. A new morphogenetic classification of mud volcanoes substantiated by results of their study in the Crimean–Caucasian and West Turkmenian regions is proposed.  相似文献   

Ductile Thrusting Recorded by the Garnet Isograd from Blueschist-Facies Metapelites of the Ile de Groix, Armorican Massif, France   总被引：1，自引：1，他引：1  

BOSSE  V.; BALLEVRE  M.; VIDAL  O. 《Journal of Petrology》2002,43(3):485-510

Mineral assemblages in the blueschist-facies metapelites fromthe Ile de Groix (Armorican Massif, France) permit the distinctionof two main units. The Upper Unit is characterized by: (1) highmodal proportions of garnet; (2) larger grain size; (3) therarity of graphite-bearing layers; (4) a single, although composite,foliation S₁. A Lower Unit is defined by: (1) low modal proportionsof garnet; (2) smaller grain size; (3) an abundance of graphite-bearinglayers; (4) a pervasive crenulation cleavage S₂. In the UpperUnit, coexisting garnet and chloritoid are more magnesian andless manganiferous than in the Lower Unit. The differences inmodal proportions and chemistry of coexisting minerals reflectdifferent P–T conditions. The P–T history of theblueschist-facies metapelites is estimated using a simplifiedpetrogenetic grid in the NFMASH system and thermodynamic calculations,which suggest peak P–T conditions at about P = 16–18kbar, T = 450–500°C and P = 14–16 kbar, T =400–450°C in the Upper and Lower Units, respectively.Peak P–T conditions were followed by a nearly isothermaldecompression for both units at slightly different temperatures(of the order of 50°C). The contact between the two units,i.e. the garnet isograd, is interpreted as a greenschist-faciesductile thrust. Thrusting of the higher-grade unit, i.e. theUpper Unit, over the Lower Unit occurred after the high-pressureevent, i.e. during the exhumation of both units. The observedsuperposition of higher-grade rocks over lower-grade rocks arguesagainst models where the exhumation history is entirely controlledby crustal-scale vertical shortening (i.e. extension). KEY WORDS: Armorican Massif; blueschist facies; Ile de Groix; metapelites; P–T path; garnet isograd  相似文献   

Facies analysis of the Trypali carbonate unit (Upper Triassic) in central-western Crete (Greece): an evaporite formation transformed into solution-collapse breccias   总被引：1，自引：0，他引：1  

F. Pomoni-Papaioannou  V. Karakitsios 《Sedimentology》2002,49(5):1113-1132

The Trypali carbonate unit (Upper Triassic), which crops out mainly in central‐western Crete, occurs between the parautochthonous series (Plattenkalk or Talea Ori‐Ida series, e.g. metamorphic Ionian series) and the Tripolis nappe (comprising the Tripolis carbonate series and including a basal Phyllite–Quartzite unit). It consists of interbedded dolomitic layers, represented principally by algally laminated peloidal mudstones, foraminiferal, peloidal and ooidal grainstones, as well as by fine‐grained detrital carbonate layers, in which coarse baroque dolomite crystals and dolomite nodules are dispersed. Baroque dolomite is present as pseudomorphs after evaporite crystals (nodules and rosettes), which grew penecontemporaneously by displacement and/or replacement of the host sediments (sabkha diagenesis). However, portions of the evaporites show evidence of resedimentation. Pre‐existing evaporites predominantly consisted of skeletal halite crystals that formed from fragmentation of pyramidal‐shaped hoppers, as well as of anhydrite nodules and rosettes (salt crusts). All microfacies are characteristic of peritidal depositional environments, such as sabkhas, tidal flats, shallow hypersaline lagoons, tidal bars and/or tidal channels. Along most horizons, the Trypali unit is strongly brecciated. These breccias are of solution‐collapse origin, forming after the removal of evaporite beds. Evaporite‐related diagenetic fabrics show that there was extensive dissolution and replacement of pre‐existing evaporites, which resulted in solution‐collapse of the carbonate beds. Evaporite replacement fabrics, including calcitized and silicified evaporite crystals, are present in cements in the carbonate breccias. Brecciation was a multistage process; it started in the Triassic, but was most active in the Tertiary, in association with uplift and ground‐water flow (telogenetic alteration). During late diagenesis, in zones of intense evaporite leaching and brecciation, solution‐collapse breccias were transformed to rauhwackes. The Trypali carbonate breccias (Trypali unit) are lithologically and texturally similar to the Triassic solution‐collapse breccias of the Ionian zone (continental Greece). The evaporites probably represent a major diapiric injection along the base of the parautochthonous series (metamorphic Ionian series) and also along the overthrust surface separating the parautochthonous series from the Tripolis nappe (Phyllite–Quartzite and Tripolis series). The injected evaporites were subsequently transformed into solution‐collapse breccias.  相似文献