Tion Zone Research Articles

Textural-structural characteristics and mineral types of ores of the Aghlig-Filfilli mineralization area of the Duruja zone


 
 
 The black shale complex, which is organic carbon-bearing and characterized by syngenetic, epigenetic sulphidation and intense metamorphism in the Duruja structural-forma- tion zone of the southern slope of the Greater Caucasus, is the focus of geologists’ attention due to the mineralization areas, which are rich in significant non-ferrous, noble, radioactive metals, rare and rare earth elements. In order to determine the prospects of noble, non-ferrous, radioactive metals, rare and rare earth elements of the black shale of the Aghlig-Filfilli mineralization area of the Duruja zone, it is necessary to determine the mineralogical composition of the ores of the area, to study the textural-structural characteristics and to clarify whether the rocks of the zone are a source of complex ore raw materials. The object of the work is the mineragraphic and petrographic study of the numerous samples col- lected from the Aghlig-Filfilli mineralization area during the field expedition before the PhD admission period, during my post-graduate studies and currently in order to solve various important mineralogical and petrographic problems. In order to investigate the textural-structural characteristics and mineral types of the ores of the Aghlig-Filfilli mineralization area, thin sections and polished sections made from the samples were studied with the help of «Carl Zeiss» and «Polam-312» microscopes in transmitted and reflected rays. The composition, surface area and morphological characteristics of the monomineral samples were studied by the electron microscope «SEM». Accurate diagnosis of some minerals was carried out based on the results of their X-ray diffractometric analysis. According to the results of the research, the ores of the Aghlig-Filfilli mineralization area were formed in 3 stages: syngenetic, epigenetic and rem- ineralization as a result of strong metamorphism of syngenetic formations. At the same time, the origin of the ores of the Aghlıg-Filfilli mineralization area was studied. According to the results of the research, it was determined that epigenetic mineralization in contact with Aralig and Zangi deep faults in the north and south of the Aghlig-Filfilli area is of magmatogene origin (δ34S=1.6-4.6), and synge- netic mineralization in the black shales towards the center is of biogenic origin (δ34S= -18 – -22.6).
 
 

Comparison of the antimicrobial and antivirulence activities of Sidr and Tualang honeys with Manuka honey against Staphylococcus aureus.

Honey is one of the oldest traditional remedies that has been widely utilized to cure a variety of human ailments. The objective of this research was to test and compare the antibacterial activity of Sidr honey (SH) and Tualang honey (TH) to that of Manuka honey (MH) against Staphylococcus aureus. The antibacterial activity of MH, SH and TH against S. aureus was investigated by agar well diffusion, Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), time-kill curve, microtiter plate and RT-qPCR analysis. Agar inhibition assay showed that MH possess highest total antibacterial activity against S. aureus with an inhibition zone 25.1 mm compared with that of SH (22.2 mm) and TH (21.3 mm). The findings showed that when compared to SH and TH (MIC: 25% and MBC: 50%), MH honey had the lowest MIC (12.5%) and MBC (25%). After S. aureus was exposed to MH, SH, and TH, there was a decrease in colony-forming unit as seen by the time-kill curve. The lowest concentration 20% of MH, SH and TH was significantly found to inhibit S. aureus biofilm. The RT-qPCR results revealed that all the selected genes in S. aureus were downregulated in gene expression following exposure to each of the tested honeys. Comparing the total antibacterial, antibiofilm, and antivirulence activities of all the tested honeys, MH demonstrated the greatest levels of these properties. According to this study, various types of each evaluated honey have the capacity to effectively suppress and modify the virulence of S. aureus via a variety of molecular targets.

BONINITES THROUGH TIME AND SPACE: PETROGENESIS AND GEODYNAMIC SETTINGS

The article provides an overview of boninitic magmatism occurrences in space and time and shows that the boninite rock series were generated through the entire geological history of the Earth. In modern environments, the genesis of boninites is related to intra‐oceanic subduction initiation. Boninites are typical members of suprasubduc‐ tion zone ophiolite sequences in the Phanerozoic fold belts and also present in the early Precambrian greenstone belts. A comparative study on compositions of the early Precambrian and Phanerozoic boninites indicate their evolu‐ tion through time due to gradual transition from the early thick‐plate tectonics to the modern thin‐plate tectonics. A link between subduction initiation and mantle‐plume impingement at the oceanic lithosphere is discussed.

마찰 드럼 상에서의 집속체 꼬임 구조 특성

Frictional bundling of fibers is accompanied by twists that compel the bundle cohesion force to generate bundle strength. Twists generated by friction occur in two forms; one by fiber arrangement on the bundle layer and the other by torque due to the thickness distribution of the bundle on the friction surface. This study investigates the twists of a friction bundle that occur on the friction surface, and theoretical models of twists are applied to develop total twist and the twist characteristics by simulation. Results showed that the fiber arrangement twists are directionally opposite to the torque twists; fiber arrangement twists occur as S-twists and torque twists as Z-twists. In the steady state the bundle exiting the friction zone had S-twists finally and the twists per length was uni- form along the bundle radius. The steady state twists of the bundle at the exit of the fric- tion zone were determined by two model constants and a process variable. The two model constants were composed of model parameters such as slippage ratio, minimum thickness of the fleece for bundling, the density ratio of the bundle to the input fleece, and also of process variables such as friction ratio, the speed ratio of the fleece feeding to bundle take- up, and the thickness of the input fleece. The process variable acting directly on the bundle twist was the fleece feeding width. Thus, the twist angle of the bundle in the friction zone varied with the radial position inside the bundle. The twist angle was the lowest in the vicinity of the bundle axis. As the fiber layer approaches the bundle surface, the twist angle increases.

Modern geodynamically active zones in the Central East European Craton

To identify the modern geodynamic processes in the structures of the East European Craton (EEC), the complex approach is used. The results of visual and automated deciphering of the LANDSAT satellite images are analyzed combined with the data of preci� sion measurements for horizontal components of motion rates of GPS reference points. The approach used allowed us to consider the modern activity of geo� logical structures and to distinguish the zones of higher geodynamic instability. To analyze the morphostructures and geodynamic setting of the studied territory, we constructed a space� tectonic scheme of the central EEC using the LESSA software packet [1] and data on the deep structure of the Earth’s crust [2] (Fig. 1). In the scheme, the sys� tems of extended lineaments of different directions are marked; these lineaments shape the integrated struc� tural pattern describing the complex geological evolu� tion of the region. Deep faults in the basement are often expressed on the surface as localized deforma� tions and clustered cracking zones. The rheological properties of sedimentary rocks predetermine the “scatter” of boundaries (faults) between the basement blocks [3]. The orientation of extended lineaments and linea� ment forms in the central EEC reflects the block struc� ture of the basement and partially reveals the buried structures that were activated at the neotectonic stage. Figure 1 shows that the major lineaments are oriented in the SW–NE and SE–NW directions and are related with the primary regmatic division of the crust trans� formed by tectonic processes. Sublatitudinal and sub� meridional lineaments are of secondary value [4]. The distinguished extended Moscow–Ryazan lineament zone of SE–NW strike consists of a series of subparal� lel extended lineaments and corresponds to the transi� tion zone boundary at the layer of sedimentary cover

Experimental and theoretical simulation of the thermal and hydrodynamic structure of a subducting plate

The presented scenario of free convection flows in a subduction zone is based on experimental and theoretical simulation. The experimental simulation of free convection flows is carried out under various con� ditions of heat transfer that occurs between the oceanic and continental limbs of the subduction zone. The experiments show that to provide insights into subduction zones, it is necessary to estimate the horizontal forces acting on the left and right sides of the plunging plate, as well as the resulting horizontal force and its direction. The vector sum of horizontal and gravity forces of the subducting plate determines the slope angle of this plate at different depths. Heat transfer in the subducting plate has been considered. The y min coordi� nate of the temperature minimum in a plate and the value of minimum temperature have been estimated. The forces that arise due to phase transition and owing to the horizontal temperature gradient along the thickness of the descending lithosphere in the transitional mantle layer C are estimated as well. These forces are directed in opposite direction from the ymin coordinate and induce spreading of the subducting lithosphere along the boundary between the upper and lower mantle. Theoretical simulation of the hydrodynamics and heat trans� fer in combination with experimental simulation of convection flows in a subduction zone indicates that a sig� nificant part of the upper mantle material of the plunging plate circulates in the oceanic limb of the subduc� tion zone owing to spreading from the region of minimum temperature along a 670 km boundary.

Anti-Bacterial Effect of Different Fractionations of Acetic Acid Leaf Extract of Parinari curatellifolia

The research was aimed at determining the anti-bacterial effect of different fractions of acetic acid leaf extract of Parinari curatellifolia. The research was conducted in laboratory unit of peace specialist hospital, Yola, Nigeria between May and November, 2011. Different solvent extracts of the leaf were prepared using the soxhlet apparatus. Disc diffusion method was used to test for the anti-bacterial activities of the different solvent extracts. The Minimum Inhibitory Concentration (MIC) of the acetic acid extract which gave the highest zones of inhibition against the microbial isolates used revealed that the MIC for Streptococcus pyogenes and Pseudomonas sp is 5mg/ml while that for Klebsiella sp and Staphylococcus aureus is 50mg/ml The acetic acid extract was fractionated with different solvents using the column chromatography. Four fractions (TiA, TiB, TiC, and TiD) were obtained from the column. Fraction TiC gave the highest zone of inhibition ranging from 10.0±0.6 to 17.3±0.9 against the test organisms. This is significantly (P=0.5) different from the crude acetic acid extract with inhibition zones ranging from 20.0±0.6 to 28.3±0.3. Inhibition zones were measured using a metre rule. Fraction TiB did not have any anti-bacterial activity against all the test organisms. Fraction TiC gave three bands on thin layer chromatography with Rf values of 0.38, 0.36, and 0.23. The activities of the separated fractions were lower compared to the crude extract. This may be due to synergistic effect of various secondary metabolites present in the crude extract. Results were discussed in respect to the anti-bacterial effect of the different fractions.

Anti-Bacterial Effect of Different Fractionations of Acetic Acid Leaf Extract of Parinari curatellifolia

The research was aimed at determining the anti -bacterial effect of different fractions of acetic acid leaf extract of Parinaricuratellifolia. The research was conducted in laboratory unit of peace specialist hospital, Yola, Nigeria between May and November, 2011. Different solvent extracts of the leaf were prepared using the soxhlet apparatus. Disc diffusion method was used to test for the anti -bacterial activities of the different solvent extracts. The Minimum Inhibitory Concentration (MIC) of the acetic acid extract which gave the highest zones of inhibition against the microbial isolates use d revealed that the MIC forStreptococcus pyogenesand Pseudomonas sp is 5mg/ml while that for Klebsiella sp and Staphylococcus aureusis 50mg/ml The acetic acid extract was fractionated with different solvents using the column chromatography. Four fractio ns (TiA, TiB, TiC, and TiD) were obtained from the column. Fraction TiC gave the highest zone of inhibition ranging from 10.0±0.6 to 17.3 ±0.9 against the test organisms. This is significantly ( P=0.5) different from the crude acetic acid extract with inhibi tion zones ranging from 20.0±0.6 to 28.3±0.3. Inhibition zones were measured using a metre rule. Fraction TiB did not have any anti-bacterial activity against all the test organisms. Fraction TiC gave three bands on thin layer chromatography with Rf value s of 0.38, 0.36, and 0.23. The activities of the separated fractions were lower compared to the crude extract. This may be due to

Predicting earthquakes: The Mw9.0 Tohoku Earthquake and historical earthquakes in Northeastern Japan

A magnitude 7.3 foreshock occurred two days before the magnitude 9.0 Tohoku Earthquake. The energy release of earthquakes within two days after the M7.3 earth- quake is obviously different from the aftershocks of the Mw9.0 earthquake. But guided by historical earthquake experience, seismologists regarded the M7.3 earthquake as the main shock rather than a foreshock of another greater earthquake. Based on the analysis of historical earthquakes in coastal areas of northeastern Japan, the recurrence time of earth- quakes is in quasi-periods of decadal or centennial scale. These quasi-periods are related to fault rupture along subduc- tion zones located in marine environments adjacent to the coast. The probabilistic prediction for future earthquakes made by Japanese seismologists using historical earthquake data is based on a decadal scale quasi-period. It is difficult, however, to make relatively reliable predictions about the recurrence interval of rare great earthquakes based on historical earth- quakes due to the very long intervals between large magni- tude quakes and the limited historical and scientific records about their characteristics.

Microtexture and microstructure evolution during necking in a Zr-1% Nb alloy

plastic flow at a strainhardening exponent 0.5 < n < 0.2 and is accompanied by an oscillatory change in the local strain rate in the hardening-softening mode in the deformation zone. This is also accompanied by a periodical progressive decrease in the cross section of a sample and necking. In (3), we revealed the relation between an oscillatory change in the local strain rate and the cyclicity of microstructural evolution in the deformation zone, which is accompanied by a change in the size, elongation, and coarsening of structural elements; as a result, it can be related to texture forma� tion in a material. Indeed, the change in the specimen geometry induced by a change in the state of stress and flow localization in plastic anisotropy materials is inevitably accompanied by the appearance of texture heterogeneity (4). Although the deformation behavior of α�Zr and its alloys has been extensively studied, the mechanisms of their texture formation are still incom� pletely clear, which is caused by insufficient experi� mental data on the laws of crystallographic reorienta� tion of individual grains determined by shear stresses and the slip and twinning systems activated in them. The possibility of the operation of certain secondary slip systems during lowtemperature deformation and the role of basal slip and twinning in the formation and development of deformation textures are still being discussed (5, 6). Information on the relation between the activities of various slip systems in α�Zr and the development of a microstructure (structural dispersity, grain and subgrain morphology, grain misorientation spectrum) is absent. However, it is obvious that the microtexture and microstructure evolution in the materials with a pronounced anisotropy of elastic and plastic properties can determine the physical causes of the nonmonotonic deformation behavior. Therefore, the purpose of this work is to reveal the relation between the appearance of an unstable plastic flow during tension of hcp zirconium alloys and the mech� anisms of their texture formation and the relation between the evolution of a defect structure and the crystallographic orientation of a local deformed microvolume in a material. Abstract—The evolution of a microstructure and Schmid factors during tension under necking conditions are analyzed by electron backscatter diffraction. The oscillatory instability of the plastic flow in the deforma� tion zone in the hardening-softening mode is found to be related to geometrical hardening (softening) during the reorientation of easy slip planes in grains with respect to the loading axis. A relation between the activities of various slip systems and the evolution of quantitative microstructure parameters is revealed.

Luminescent properties of natural copper and silver iodides: Evidence for their composition and structure

Against the background of active investigation of luminescence of minerals from endogenous deposits, the luminescent properties of minerals from the oxida� tion zone of ore deposits have been studied insuffi� ciently, whereas information on the luminescence of natural iodides is scarce as a whole [1, 2]. This study concerns the luminescent spectroscopy of natural copper and silver iodides. Copper and silver iodides from the oxidation zone of the Rubtsovskoe polymetallic deposit located in the Northwestern Ore Altai (Russia) were selected as an object of investigation. They are represented by cubic minerals of the isomorphic series of marshite

Comparison of Point-to-Plane and Point-to-Point Corona Discharge for the Decontamination or Sterilization of Surfaces and Liquids

We studied the decontamination of surfaces and inactivation of bacteria and yeast in liquids by low-temperature plasma generated in the DC corona discharge of an open- air type in the point-to-plane or point-to-point arrangement. We found that the inactivation in liquid suspensions is slightly more ef fi cient with the point-to-plane discharge in comparison with the point-to-point one. In the case of agar surface decontamination, two types of inhibi- tion zones were observed, which indicates the different mechanism of action for the point-to- point and point-to-plane dicharges. This knowledge may be important in the future selection of microbicidal agents and in the development of ef fi cient methods for low-temperature plasma decontamination or sterilization.

Active and Passive Seismic as an Indicator of Large Equipment Interactions with the Oil Sand

The strain softening of oil sand in the underfoot of ultra class mobile mining equipment, due to the loading action of large mobile mining equipment such as trucks and shovels, yields a highly unstable condition for the operation of this ultra-class equipment. Soft ground conditions in oil sand, due to the low stiffness of the material a condition especially present in the summer, can cause high rack, pitch, and roll in trucks, leading to fatigue failure in structural compo- nents. For shovels, poor ground stability can cause twists in car bodies and undercarriages, resulting in major damages. Track and shovel frame failures due to this instability result in high maintenance costs. The authors carried out a geophysical study of the oil sand in order to evaluate the ground conditions under large mobile mining equipment. A geophysical investigation per- formed in summer 2001 encountered 6-8 m of thick soft material, commensurate with very low velocities, caused by the loosening of the surface material by heavy mining machinery and excavation; and a transi- tion zone of up to 25-26 m depth approaching the in situ oil sand below. The depth of the oil sand zones can be calculated by using the refraction analysis technique. Spectral Analysis of Surface Waves was used to estimate the ground stiffness. A new technique is proposed to evaluate the changing ground stiffness during the use of ultra-class mobile mining equipment.

Specific features of rainfall and snowfall radar in the millimeter-wave band

One way of measuring rainfall and snowfall zones is to use radars, which allow the sizes and locations of the pre� cipitation zones to be estimated. At present, meteorolog� ical radars usually use the centimeterwave band (1). The objective of the present study is to estimate the feasibility of rainfall and snowfall sensing with a millimeterwave radar and to determine what features of these precipita� tion zones can be discovered in the process of sensing. It is intuitively expected that the use of shorter wavelengths makes it possible (1) to shape radio beams with smaller divergence, a circumstance that implies a better spatial resolution and, thereby, a possibility of resolving the fine structure of zones with different rainfall and snowfall rates; (2) to record the signal reflected from zones with lower rainfall rate and snowfall rate than in the case of the cen� timeterwave band, the circumstance that allows the zones of these precipitations to be determined with greater accuracy; and (3) to use the techniques for retrieving profiles of the coefficient of the radiowave attenuation along the sens� ing path, which were developed for the lidar sensing in the optical band. It should be noted that the most familiar meteorologi� cal radars designed to analyze the rainfall zones operate on frequencies of about 3 GHz, and their antennas are 2.5 m (2) and 3.6 m (3) in diameter. Accordingly, the antennas with their rotators are rather cumbersome installations; in this respect, transition to the millimeter� wave band is also promising, since it results in a reduction in the radar mass and dimensions. The range of the abovementioned radars is 100- 150 km. An obvious drawback of the millimeterwave radar will be a certain decrease in its range. Since we have to deal with a volumedistributed target, the radar equation differs from the common one. The reflecting elements (raindrops or snowflakes), which are involved in the formation of the sum signal arriving at the radar receiver, are distributed over certain volume V. This volume can be approximated by a cylinder with base area Ω L 2 and height сτ/2, where L is the distance from the radar to the center of the desired volume, Ω is the antenna's solid angle (beam divergence), τ is the pulse duration, and с is the speed of light. In this case, it is assumed that the attenuation of radio waves in the illumi� nated volume is insignificant, and the precipitation parti� cles in the entire desired volume are identically illumi� nated. The antenna's solid angle is expressed in terms of its effective area А or directivity D:

Plant-to-plant direct competition for belowground resource in an overlapping depletion zone

In response to limited availability of soil resources in basal root zone, plant extends its roots into nearby resource-rich zones to fulfill essential resource demands for survival and repro- duction. This root proliferation into that enriched zones occupied by other plants constitutes inter- plant overlapping rooting zones and thereby the overlapping depletion zones, causing reduction in resource uptake by neighboring plants. By incorporating this mechanism into the classic resource competition model, we study interplant direct competition through their rooting system in an over- lapping depletion zone. The model results indicate an extension of Tilman's R* rule that has already been proved true when plants compete indirectly through their effect on shared resources. The results reveal that plant's direct competitive ability (i.e., the ability to occupy an overlapping deple- tion zone by excluding others) can be characterized by its R*-value, where a best competitor having lowest R*-value excludes others from an overlapping zone and occupies the zone by depleting the resource level to the lowest as in its non-overlapping depletion zone. By analyzing the model, we find a suite of traits that confers R* variation among directly competing plants. This suite of traits would be a useful proxy measure for R* that do not necessarily require to establish equilibrium field monoculture—a requirement for R* measurement in the field.

Petrophysical Properties Evaluation of Tight Gas Sand Resrvoirs Using NMR and Conventional Openhole Logs

Tight reservoir means reservoir of low porosity and low permeability. Many tight formations are extremely complex, produced from multiple layers with different permeability that is often enhanced by natural fracturing. The complicity of these reservoirs is attributed to a) Low porosity and low permeability reservoir, b) The presence of clay minerals like illite, kaolin and micas in pores, c) The heterogeneity of the reservoir in vertical and lateral directions. Evaluation of tight gas sand reservoirs represents difficult problems. Determination of petrophysical properties using only conventional logs is very complicated. Use of NMR in individual bases or in combination with conventional openhole logs and SCAL data leads to better determination of petrophysical properties of heterogeneous tight gas sand reservoirs. This paper focuses on determination of three petrophysical parameters of tight gas sand reservoirs: 1) Determination of detailed NMR porosity in combination with density porosity,  DMR, 2) NMR permeability, KBGMR, which is based on the dynamic concept of gas movement and bulk gas volume in the invaded zone and 3) Capillary pressure derived from re- laxation time T2 distribution and then it could be used for the saturation formation measurements especially in the transi- tion zone.

Co–CoO nanoparticles prepared by reactive gas-phase aggregation

The technique of gas-phase aggregation has been used to prepare partially oxidized Co nanoparticles films by allowing a controlled flow of oxygen gas into the aggregation zone. This method differs from those previously reported, that is, the passivation of a beam of preformed particles in a secondary chamber and the conventional (low Ar pressure) reactive sputtering of Co to produce Co-CoO composite films. Transmission electron microscopy shows that the mean size of the particles is about 6 nm. For sufficiently high oxygen pressures, the nanoparticles films become super-paramagnetic at room temperature. X-ray diffraction patterns display reflections corresponding to fcc Co and fcc CoO phases, with an increasing dominance of the latter upon increasing the oxygen pressure in the aggrega- tion zone, which is consistent with the observed reduction in saturation magnetization. The cluster films assembled with particles grown under oxygen in the condensation zone exhibit exchange-bias fields (about 8 kOe at 20 K) systematically higher than those measured for Co-CoO core-shell nanoparticles prepared by oxidizing preformed particles in the deposition chamber, which we attribute, in the light of results from annealing experiments, to a higher ferromagnetic-antiferromagnetic (Co-CoO) interface density.

Habitat overlap of Paralabrax humeralis (Cuvier & Valenciennes, 1828), Hemilutjanus macrophthalmos (Tschudi, 1845), and Acanthistiuspictus (Tschudi, 1845) (Pisces; Serranidae) in the rocky subtidal south of Iquique, Chile

A simple SCUBA diving survey was used to study the habitat use and coexistence of three spe- cies in the family Serranidae with sympatric distribution patterns along the rocky subtidal south of Iquique. Depth and microhabitat were recorded for each sampled individual. Samples were taken at 15 different beaches through SCUBA diving in the deepest areas of the first rocky fringe, herein referred to as the transi- tion zone. The data were analyzed according to depth and frequency of use (microhabitat, habitat) for each species and considering three size classes. Dendograms were created to interpret the similarities in the use of beaches, microhabitat, and habitat. The results showed the species to be independent in their use of the micro- habitat and habitat. The most abundant species was the roving Paralabrax humeralis whose habitat was mostly associated with Lessonia trabeculata. Hemiluthjanus macrophthalmos and Acanthistius pictus are cav- ity specialists, although their microhabitat use differed according to the size of the cavity: H. macrophthalmos occupied larger caves (> 0.5 m) and A. pictus mostly smaller cavities (< 0.5 m). The lack of juvenile A. pictus individuals seems to indicate the use of an alternative ecosystem. The distribution patterns of these Serranids varied throughout the study area, indicating a dependence on the geomorphology of the substrate and the pres- ence of the structural species L. trabeculata.

Characteristics of mantle fabrics beneath the south-central United States: Constraints from shear-wave splitting measurements

New shear-wave splitting measurements at permanent broadband seismic stations in the south-central United States reveal the orien- tation and degree of polarization of mantle fabrics, and provide constraints on models for the formation of these fabrics. For stations on the stable North American craton, correspon- dence between observed polarization direc- tion of the fast wave and the trend of Protero- zoic and Paleozoic structures associated with rifts and orogenic belts implies a lithospheric origin for the observed anisotropy. The larg- est splitting times (up to 1.6 s) are observed at stations located in the ocean-continent transi- tion zone, in which the fast directions are par- allel to the Gulf of Mexico continental margin. The parallelism and the geometry of the keel of the craton beneath the study area suggest that asthenospheric fl ow around the keel of the North American craton, lithospheric fab- rics developed during Mesozoic rifting, or a combination of these factors are responsible for the observed anisotropy on stations above the transitional crust.

Characteristics of Mineralization at the Main Zone of the Clarence Stream Gold Deposit, Southwestern New Brunswick, Canada: Evidence for an Intrusion-Related Gold System in the Northern Appalachian Orogen

Mineralization at the Main zone of the Clarence Stream gold deposit in southwestern New Brunswick occurs within a parallel series of quartz veins that occupy a NE-trending, steeply north-dip- ping, brittle-ductile shear zone related to the nearby terrane-bounding Sawyer Brook fault. This deforma- tion zone cuts volcaniclastic sedimentary and volcanic rocks of the Silurian Waweig Formation, and is intruded by mantle-derived East Branch Brook gabbroic dikes and a number of felsic dikes. Intermittent shear-zone reactivation during local magmatic activity induced heterogeneous deformation and alteration of the country rocks and dikes. The terminal phase of shearing is associated with narrow pegmatite-aplite dikes that grade laterally into granophyric granite, and into an auriferous quartz vein. Gold, aurostibite, and gold-antimony intergrowths, predominantly with vein quartz, are associated with a low ƒO2 sulfide mineral assemblage (pyrrhotite, arsenopyrite, and berthierite) that has a sulfur isotopic signature consistent with a magmatic source. Gold saturation and deposition occurred episodically between 300° and 360°C at low activity of sulfur, predominantly in response to pressure reduction during brittle failure combined with the effects of decreasing temperature and sulfidation reactions during fluid-wall-rock interaction. Geo - chronological studies demonstrate that the timing of the emplacement of the pegmatite-aplite dikes and associated auriferous veins overlap with that of the Early Devonian Magaguadavic granite. Moreover, the composition of the dikes is consistent with their derivation from this granite as late fractionates. The Main zone of the Clarence Stream deposit is therefore interpreted to be intrusion-related, with the Magaguad- avic granite being the ultimate source of the gold-bearing fluids. © 2008 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.