Dislocation Zone Research Articles

Recent dynamics and probable origin of the Tulva Upland in the Perm Foreurals

The Tulva Upland is a meridional neotectonic swell that complicates the eastern Russian Plate in its recent manifestation. The intense recent uplift is expressed in the rise and splitting of terraces of the Kama River and anomalously increasing lateral ruggedness of topography. Having a steep western and a gentle eastern limb, the swell is sharply asymmetric in cross section and additionally is complicated by a chain of local NE-trending uplifts. Several morphostructural indications testify to the substantial role of NW-trending strike-slip faulting in the structure of the swell, which was formed under conditions of latitudinal compression and conjugated meridional extension. Such a stress-strain field is confirmed by the study of mesotectonic structural elements in the western steep limb of the swell regarded as a flexure above a suggested reverse fault. Like many other zones of within-plate dislocations in the Russian Plate, the recent Tulva Swell was formed as a result of folding of sedimentary fill and inversion of long-lived platform trough. In our case, this trough inherited the Riphean Kaltasy Aulacogen. Together with the unilateral, probably, reverse-fault-line (?) Ufa Horst, the Tulva Swell is situated opposite to the area of maximum near-latitudinal compression of the recent Urals (the socalled Ufa amphitheater, or Central Ural pinch) and along with other within-plate arches similar in structure—Bugul’ma-Belebei and Obschii Syrt—marks a zone of neotectonic reactivation of the Russian Plate near the Urals.

Generation of radial and concentric melt-filled dislocation zones in the central uplift of the Vredefort Impact Structure, South Africa

Generation of radial and concentric melt-filled dislocation zones in the central uplift of the Vredefort Impact Structure, South Africa

The role of neotectonics in fluvial landscape development in the Western Mecsek Mountains and related foreland basins (SE Transdanubia, Hungary)

The paper presents an integrated application of geomorphological and geological methods to investigate the recent activity of a strike-slip fault system. Spatial analysis of Neogene and Quaternary sedimentary sequences through 3D basement and isopach maps based on surface geology, boreholes and sparse geophysical data revealed the evolutionary history of pull-apart basins linked to strike-slip faults. A model of a repeatedly branching and southward-shifting dislocation zone is proposed for the Cenozoic. Calculations from valley incision and sedimentation data resulted in estimations of minimum subsidence rates of 0.15–0.30 mm/y and 0.07–0.17 mm/y, respectively. Morphological analysis of the DEM including hillshade, aspect, slope and curvature calculations indicated a geological structure made up of several relatively small blocks showing contemporaneous, contrasting vertical movements. The continuity of Plio-Quaternary pediments and of palaeo-valleys has been broken by the neotectonic uplift or subsidence of some areas, these geomorphic features are thus indicators of vertical displacement of the blocks. River captures and rapid valley incisions refer to present-day basin subsidence. Several geomorphic features linked to tectonics – fault lines, ridges uplifted along these, triangular facets, valley deflections – support evidence suggesting activity of the fault system. The presence or absence of alluvial fans roughly correspond to more or less closed or open basins. These features together permitted the delineation of areas of ongoing uplift and subsidence. Neotectonic activity has been present during all periods since the Late Miocene, while the most important basin of the mountain foreland, the Pécs Basin, probably appeared as a morphological depression near the Middle–Late Pleistocene boundary.

Southern Perú coseismic subsidence: 23 June 2001 8.4-Mw earthquake

Abstract. The 23-June-2001 8.4-Mw magnitude earthquake partially filled the 1868-seismic-gap in southern Perú. This earthquake produced a thrust faulting dislocation with a rupture that started at about ~200 km SE from the 1996's Nazca earthquake epicenter, and stopped near Ilo, at about 300 km from the epicenter, near a positive gravity anomaly offshore Ilo. The 23-June-2001-earthquake dislocation zone is under the Arequipa sedimentary Basin. Pre- and post-seismic GPS measurements at Camaná and Ilo at SIRGAS-GPS points (SIRGAS: Sistema de Referencia Geocéntrico para América del Sur) and the average sea level pre- and post-seismic event at Mollendo tide gauge provide evidence of a regional subsidence of southern Perú, with 84 cm at Camaná, 16 cm at Ilo, and 15 cm at Mollendo. Field surveys post earthquake document significant subsidence in Camaná resort beaches. Results of a simple dislocation modelling of 23-June-2001 earthquake agree reasonably well with the observed data. However, the coseismic subsidence of southern Perú is at variance with the regional uplift of southern Perú based on Neotectonic studies. This fact, suggests that, in recent geological times, the magnitude of the secular uplift due to tectonic plate converge has been larger than the coseismic deformation recovery.

Detrital zircon constraints on terrane ages and affinities and timing of orogenic events in the San Juan Islands and North Cascades, Washington

Detrital zircon geochronology of this report pertains to Cretaceous orogeny in northwest Washington, an event that involved blueschist metamorphism and emplacement of nappes in the San Juan Islands – northwest Cascades thrust system and continental arc magmatism and associated Barrovian metamorphism in the neighboring Coast Plutonic Complex. Structurally low in the thrust system, quartzose gneiss of the Yellow Aster Complex yields an entirely Precambrian suite of detrital zircons, with an age pattern that is similar to that of Ordovician miogeoclinal rocks and the outboard Yukon–Tanana, Yreka, and Shoo Fly terranes elsewhere in the Cordillera. Midway in the nappe pile of the northwest Cascades, sandstone in the Bell Pass Mélange has a zircon age population of 110 Ma, an age that together with the spectrum of exotic materials associated with the sandstone suggests the mélange was a major zone of dislocation during mid-Cretaceous nappe emplacement. At a high level in the thrust system are nappes of the Fidalgo Complex, Lummi Formation, Constitution Formation, and Easton Metamorphic Suite, all with a prominent age peak in the range of 148–155 Ma. These units appear to be mutually related, represent inter-arc marginal basins, and are correlative with terranes in the western Klamath Mountains. The Nooksack Formation, footwall to nappes in the Cascades, has a zircon population at 114 Ma, providing a maximum age of nappe emplacement. The Tonga Formation of the Coast Plutonic Complex bears zircons that indicate a depositional age of <125 Ma, thus yielding a maximum age for the beginning of Barrovian metamorphism and continental arc plutonism in this region.

Isotopic and geochemical evidence of proterozoic episodic crustal reworking within the irumide belt of south-central Africa, the southern metacratonic boundary of an Archaean Bangweulu Craton

Whole-rock geochemistry and Sr–Nd isotopic data for granitoids and volcanic rocks of four main different igneous phases, the Usagaran phase (2.05–1.93 Ga), the Ubendian phase (1.88–1.85 Ga), the Lukamfwa phase (1.65–1.55 Ga) and the Irumide phase (1.05–0.95 Ga), recognised along the southern margin of the Congo Craton in the Bangweulu Block and Irumide Belt of Zambia, demonstrate a long history of crustal recycling of a cryptic Archaean basement complex. The isotopic record indicates that a largely similar crustal source can be assigned to all these magmatic phases, with subtle differences in isotopic and geochemical record reflecting varying distance to orogenic activity during each of these episodes, and varying, but always minor amounts of juvenile mantle input. T DM model ages, ranging between 3.3 and 2.8 Ga for the granitoids, and between 2.9 and 2.4 Ga for volcanic rocks, indicate preponderant Archaean crust within the Bangweulu Block and within the Irumide Belt. The corresponding initial ɛ Nd values vary between −6 and −15 for the granitoids, and between −2 and −7 for the felsic volcanic rocks. Only some of the ca. 1.85 Ga mafic volcanic units record a more juvenile character ( ɛ Nd( T) between −5 and 0 and T DM model ages between 3.2 and 2.4 Ga) but still with a significant old crust input. The geochemistry (major and trace elements) of the various magmatic groups shares many similarities indicating essentially similar crustal sources and conditions of melting. Only the anorogenic, 1.6 Ga, more alkaline granitoids, were generated through a lower degree of partial melting, but still from the same source. Combining all available constraints, we propose that the Irumide Belt corresponds to the recurrently destabilised (at 2, 1.85, 1.6 and 1 Ga) southern boundary of the Bangweulu Block, whose preserved nucleus appears to be an Archaean craton covered by Palaeoproterozoic sediments. There are no juvenile subduction-related rocks in the Irumide Belt s.s., but such rocks are reported to the south, across the Mwembeshi Dislocation Zone (MDZ), in a region referred to as the Southern Irumide Belt. Processes of endo-destabilisation in response to external forces (orogenies acting close or elsewhere), such as that recorded in the Bangweulu Block and the Irumide Belt s.s., correspond to a metacratonic evolution. Within the Irumide Belt itself, tectonic movements were mainly vertical, with horizontal movements restricted mainly to the supracrustal sequences.

TEM measurement of nanoindentation plastic zones in Ni3Al

Nanoindentation tests were performed on Ni3Al and the dense dislocation zones underneath the nanoindents were examined by transmission electron microscopy. The size of these dense dislocation zones was found to be significantly larger than the Oliver–Pharr contact size especially at small indentation depths. The results support an earlier suggestion that the densely dislocated core of a nanoindent relaxes to give rise to a reduction of the measured hardness from the simple Nix–Gao prediction.

Platinum-and gold-bearing rodingites of the Ust’-Dep ophiolite block (middle Amur region)

The Ust’-Dep ophiolite block, a part of the Selemdzha‐Zeya Belt, occupies an area of 350 km 2 and incorporates apoharzburgite serpentinite massifs intruded by numerous (>60) dikes of diabases and granitoids up to 100 m thick and more than 1 km long. Ophiolitic outcrops of this block make up a SW- to NW-trending band extending from the right bank of the Zeya River to the Gar River basin. Only small fragments of ophiolite massifs are preserved in spurs of the Tukuringr Ridge (Fig. 1). The Ust’-Dep and Gar protrusions in this area include dislocation zones with superimposed metasomatic alterations (development of listvenites and rodingites with gold mineralization). The majority of rodingite and listvenite occurrences are confined to outcrops of Lower Paleozoic‐Middle Cretaceous granitoid intrusions and dikes. Listvenites usually considered the source of placer gold are scrutinized in [1, 2]. However, data on the gold potential of rodingites in the Ust’-Dep block are lacking, although they are similar to rodingites in the Zolotaya Gora deposit (southern Urals) that was previously proposed as a holotype of the gold‐rodingite association [3]. Their similarity is manifested in the development of rodingites among listvenitized serpentinites. Therefore, the gold mineralization of Uralian rodingites is attributed to a younger process of listvenitization [4].

TEM Observation of Vacancy Clustering Process in FeAl Single Crystal

AbstractNanoporous surfaces are formed in B2-type FeAl single crystals by quenching into iced water, followed by surface treatment and aging heat treatment. From our previous works, it was indicated that the nanoporous phenomenon is caused by the clustering of supersaturated thermal vacancies. In this study, the clustering process of supersaturated thermal vacancies was systematically investigated by transmission electron microscopy (TEM). An irreversible exothermic peak was detected for as-quenched specimens by differential scanning calorimetry (DSC). The isochronal changes of surface morphology and substructure around the exothermic peak temperature were clarified by TEM observation. The average size of the surface pores monotonously increased with increasing the temperature. Dislocations whose Burgerse vectors are parallel to <100> existed in the isochronally-heated single crystals, and its density was changed with heat treatment temperature. On the other hand, there was no dislocation zone from surface to the depth of several tens nanometers. A growth model of the surface pores is discussed

Failure analysis of wear of main clutch separating ring of heavy vehicles

The severe wear of separating ring is considered to be a main reason which leads to the improper declutch of the main clutch of heavy vehicles. The wear mechanism of the separating ring is not well understood. Scanning electron microscopy and transmission electron microscopy were employed to analyze the surface features and dislocation characteristics of the separating ring. The typical features of furrows and rolled tongue-like metal were found on the surface of separating ring by scanning electron microscopy observation, which can be considered as a major indication of the grain-abrasion. A zone of high density dislocation was noted on the subsurface of the separating ring by transmission electron microscopy observation, which implies the contribution of the severe impact on the surface of the separating ring in the wear process. The influences of the structure of the separating ring, the service condition and the in-service stress distribution on the wear behavior, were also analyzed. The results show that the failure of separating ring results from the impact wear and grain-abrasion together with the plastic deformation.

Complex Isotopic and Hydrogeochemical Studies of Groundwater in the Kirov Region

Uranium-isotopic and multi-element hydrogeochemical methods are used to assess the natural pollution of fresh groundwater in horizons under development due to a modern intrusion of hypogene water with increased boron and fluorine contents in zones of old tectonic dislocations. The total index of the abovestandard (>MAC) pollution of groundwater in the region of the city of Kirov (“the Kirov area”) reaches 15. To reduce the effect of natural groundwater pollutants on the health of population, it is recommended that the groundwater intake should be regulated, purifiers should be used, and prospects revealed by the isotopic-and-hydrogeochemical data should be explored. The feasibility of modeling the groundwater formation and tracing the neotectonic dislocations in geological platforms is shown.

The magnetotelluric (MT) investigation of the Diósjenő dislocation belt

Firstly the authors give an overview on the geological, geophysical and tectonical features of the Diósjenő dislocation belt (or zone, according to some authors) around the river Ipoly near the Hungarian-Slovak border among great structural units: Vepor, Gemericum and formations of the Mid Hungarian Mts. The longest magnetic anomaly of the Pannonian Basin lies in this belt. It is assumed that it is due to ultrabasic magmatite of greenschist facies. The near-surface geoelectric soundings did not find any conductivity increase near Diósjenő (western part of the zone), but there are graphitic micaschists in the boreholes around Szécsény. There is some earthquake activitiy in the region with hypothetical depth of 7-8 km. Two deep magnetotelluric (MT) profiles cross the dislocation zone. The resistivity distribution from the surface to the conductive asthenosphere along these profiles was obtained by using instruments, operating in two different period ranges. After processing the measured data by 1D/2D inversion, it became obvious that the dislocation zone includes electrically conducting roots at a depth of 7-11 km. This result hints at the presence of fluid in the broken rocks having increased porosity in the dislocation zone. Another component that can increase the conductivity could be the graphite (carbon) originating from the Paleozoic crystalline rocks of the Gemericum (or Vepor). The ductile phase (fluid/graphite) observed by high conductivity in the centre of the dislocation zone can play an important role in the generation of the earthquakes according to the most recent statements of the international literature.

Remote sensing, field studies, petrography, and geochemistry of rocks in central Zambia: no evidence of a meteoritic impact in the area of the Lukanga Swamp

The Lukanga Swamp in central Zambia has previously been proposed as the site of a large (52 km diameter) impact structure on the basis of alleged observation of shock-diagnostic planar deformation features (PDFs) in quartz of breccia from the southern margin of the swamp. The southern margin of the swamp, marked by the Nyama Dislocation Zone, consists of quartzite and silicified meta-siltstone, shale, sedimentary quartz breccia, and fault breccia. Structures and textures in the meta-sediments are syn-sedimentary, whereas fault breccia displays tectonic fabrics. In thin section, quartz in sedimentary quartz breccia displays widely spaced, randomly oriented, subparallel, non-planar fluid inclusion trails, which were earlier misidentified to represent decorated PDFs formed by meteoritic impact. Siderophile element abundances (<105 ppm) in the rocks from around the swamp are normal for quartz-rich crustal rocks, and there are no relative enrichments in the breccias compared to other rocks to suggest extraterrestrial contributions. Aeromagnetic data do not reflect an impact crater signature. We analyzed regional structural and seismic data in an effort to account for the development of the swamp. From the structural synthesis it appears that reactivation of movements along the Nyama and Kapiri-Mposhi Dislocation Zones may have led to the development of the Lukanga Swamp, probably during the Cenozoic era.

Fatigue-cracking characteristics of a copper bicrystal when slip bands transfer through the grain boundary

We reported the fatigue cracking characteristics of a special copper bicrystal with a tilt ∑ 19b grain boundary (GB) and a coplanar primary slip system between the two grains. It is found that the primary slip bands of the two adjacent grains have a good continuation across the GB on the four surfaces of the bicrystal specimen in the axial plastic strain range of 1.5×10 −4–2.13×10 −3. It indicates that the surface slip bands had transferred through the GB during cyclic deformation. When cyclic plastic strain was continued to be applied on the bicrystal specimens, fatigue cracks always initiated and propagated along the GB at all the applied strain amplitudes. By using electron channeling contrast (ECC) technique in scanning electron microscopy (SEM), the dislocation patterns near the GB of the bicrystal were observed. The ladder-like persistent slip bands (PSBs) did not transfer through the GB continuously, no matter what the surface or the common primary slip plane of the bicrystal. Instead, a dislocation affected zone (DAZ) or piling-up of dislocations near the GB was observed. Based on the results above, the fatigue cracking mechanism of the bicrystal was discussed and the GB cracking was attributed to the difference in the slip directions of the two adjacent grains.

A TEM investigation on indentation plastic zones in Ni 3Al(Cr,B) single crystals

Nanoindentation has been carried out on (111) single crystals of Ni 3Al with the maximum applied load ranging from 800 to 8000 μN. The indentation plasticity fields are found to consist of two regions, namely, a core with a very high dislocation density and a surrounding region where the dislocation density is much lower. In the zone with lower dislocation density, individual dislocations were discernible, and three sets of dislocations, with Burgers vector of the 1 1 ̄ 0 type and parallel to the sample surface, were identified in all specimens. The dislocation segments were curvy at small loads but long and straight screw dislocations appeared at large loads. Measurements of the radii of the plasticity zones from TEM images indicate that the core and the surrounding low dislocation density zone did not evolve in a self-similar manner with increasing load. From the dislocation structure observed just after the pop-in in the load–displacement curve, the strain rate in the indent core during pop-in is estimated to be about 170 s −1. The nominal hardness calculated using the Oliver–Pharr scheme exhibits a sharp and negative dependence with respect to load, with the hardness dropping from ~12 GPa at 800 μN to about 6 GPa at 8000 μN. The value of P/ πc 2, where P is the load and c the radius of the surrounding dislocation zone, is however fairly constant with respect to load, with a variation of only about 10% in the same load range. The yield stress Y calculated from the equation Y=1.5 P/ πc 2 is about 356±32 MPa. These results suggest that, while nanohardness can still be expected to depend critically on the yield stress, there is an additional functional relationship that causes the hardness to vary with the indent size in the submicron regime.

The border of the East-European Craton in south-eastern Poland based on gravity and magnetic data

According to recent geological interpretations, the border of the East-European Craton (EEC) in SE Poland is located in the NE foreland of the Holy Cross Mts. Results of gravity and magnetic anomaly interpretations presented herein confirm this. According to 3D and 2D gravity and magnetic modelling, the EEC borders the SW flank of the regional crystalline feature with increased magnetic and density properties, which occur in the SE part of the Teisseyre–Tornquist Zone (TTZ). This flank rests near a deep fracture delimiting the TTZ on SW. The feature is a cause of the regional magnetic gradient observed there. Two SE–NW belts of residual gravity anomalies (dislocations) are also identified in the magnetic gradient zone, cutting Mesozoic and Palaeozoic formations. Results of geophysical and geological investigations show the importance of this dislocation zone and confirm that it occurs in all crustal complexes and the upper mantle.

Retention of ion-implanted deuterium in tungsten pre-irradiated with carbon ions

Deuterium (D) ion implantation and retention at room temperature was studied in pure and carbon (C) implanted tungsten single crystals. Pre-implantation with C was done at 40 keV and D implantation at 10 keV with the range confined in the carbon modified layer and at 100 keV with the range exceeding the carbon modified layer. The range distributions were investigated in situ using 1 MeV 3 He ions analysing the energy distributions of α particles from the D( 3 He, p) α reaction while the total amount of retained D was obtained from the p-integral. The range distribution of carbon was obtained from the backscattered 3 He energy distribution. C pre-impantation influences the D retention only if the range of the D ions is confined within the carbon modified surface layer. In this case, D diffusion beyond the ion range distribution does not occur and the retained D amount is smaller than in the pure W crystal. At D energies exceeding the carbon modified layer the retention occurs in the dislocation zone up to 1 μm and the total retained amount is the same for carbon implanted and pure W samples.

Estimating the radon emanation coefficient from crystalline rocks into groundwater

A simple method is proposed to estimate the coefficient of radon emanation from crystalline rocks into underground waters. In these cases, the crystalline rock seems as both the source and the reservoir of the radon. The calculations are based on a formula proposed by Maché for determining the concentration of radon in underground waters. Due to the inaccuracy of estimating some parameters (e.g. porosity), the results have a significant error. The advantage of this method is its simplicity and the possibility of obtaining results in a relatively short time. The estimated values of the emanation coefficient for selected crystalline rocks of the Sudety Mountains (SW Poland) vary from 7 to 41%, and after considering the error resulting from the estimation of rock porosity, saturation and density, the values range from 5 to 60%. The highest values of emanation coefficient (41, 33 and 21%) have been obtained for rocks in areas of tectonic dislocations and the lowest ones are for rocks outside dislocation zones (9 and 7%). The calculations imply that the emanation coefficient of rocks may have a greater influence on radon concentration in underground waters than the contents of radium in the reservoir rocks.

Origin of radon in medicinal waters of Lądek Zdrój (Sudety Mountains, SW Poland)

In this paper the origin of radon in the underground medicinal waters Lądek Zdrój is presented. This health resort is situated in the Polish part of the Sudety Mountains. The concentration of radon in these waters (exploited by five springs and one bore hole) range from 122 to 1284 Bq/dm 3, whereas the concentration of radium does not exceed 6.8 Bq/dm 3. In gneisses, through which the exploited waters flow, the amount of radium reaches about 34 Bq/kg and only locally rises to 50 Bq/kg. The increased concentration of 222Rn in the medicinal waters of Lądek Zdrój is not influenced by the time of contact of these underground waters with the rocks through which they flow. The concentration of 222Rn also does not depend on the concentration of 226Ra which is dissolved in these waters. Radon is dissolved as a gas in underground waters in the zone of their outflow to the surface. It is caused by the increase in the emanation coefficient of rocks in the weathering zone and in dislocation zones, through which the waters outflow to the surface. To a smaller extent, the genesis of radon in the thermal waters of Lądek Zdrój could also be related to a small admixture of shallow circulation waters containing enhanced amounts of dissolved radon. Much higher concentrations of radon in one of the intakes (Jerzy) should be attributed to its location in the area of a fork of a big dislocation zone and the increased quantity of 226Ra in gneisses of the intake region.

Effect of ultraprecision grinding on the microstructural change in silicon monocrystals

The effect of ultraprecision grinding on microstructural change in silicon monocrystals, such as surface roughness and dislocation structure, was investigated both experimentally and theoretically. The study found that there exists an additional concentration of oxygen and carbon in an amorphous layer for all investigated grinding regimes with their distributions dependent on the grinding variables. It showed that two atomic bonding configurations exist in the amorphous layer, i.e. silicon oxide in the surface region followed by amorphous silicon. The research established that the grinding table speed affects the thickness of the dislocation layer in the subsurface. Increase of the table speed leads to a thicker dislocation zone and created microcracks. The paper concludes that the ductile mode of material removal in the grinding of silicon monocrystals is due to the formation of the amorphous phase.