Schistose Rocks Research Articles

Stability Challenges and Remedial Practices in Himalayan Hydro-power Tunnels – A Review

The instability in tunnels is mainly affected by geological anomalies, rock mass quality, complex geological structures, active tectonics, and stress anisotropy. This review article presents challenges associated with stability and applied remedial measures prevailing in hydropower tunnels in the Himalayas. The review covers nine hydropower tunnels located in different parts of the Himalayas. The review found that rock bursting/spalling frequently occurs when the tunnel passes through a high overburden with good rock mass quality. On the other hand, plastic deformation (squeezing) occurs when a tunnel passes through the weak and schistose rock mass. It has been found through the review that the tunnel crew was able to successfully solve instability challenges. Effective planning, design, and selection of appropriate construction techniques help to complete tunneling projects in the Himalayas.

The Ediacaran metamorphosed banded iron formation (BIF) at Gohar Zamin mine (Gol-e-Gohar #3 anomaly), Sirjan (southeastern Iran): Perspective from ore structures, bulk ore-rock geochemistry and O-S-Pb isotopic signatures

Little is known about the occurrence of the Neoproterozoic banded iron formations (BIFs), except few cases of the glaciogenic Cryogenian BIFs. In this investigation, we describe an Ediacaran metamorphosed BIF interbedded with metamorphosed rocks. The Gohar Zamin iron deposit (643 Mt @ 54.3 % Fe, 2.04 % S, 0.12 % P) is hosted by mica schist, quartz schist and meta-basite that formed by metamorphism of the Fe-oxy-hydroxides, terrigenous (pelitic)-chemical (carbonate) sediments, silica gel and repeated phases of MORB-type submarine basic eruptions in shallow marine syn-rift basins. The sediments, basaltic eruptions and iron oxides were lithified to BIFs and then metamorphosed to greenschist facies during Cimmerian orogeny. The presence of macro-meso-microbandings in BIFs, coarse-grained quartz dropstones and magnetite clasts in the ores-host rocks, chemical index of alteration (CIA) (41.83 to 95.42 %) and positive correlation of Al2O3 against TiO2 and SiO2 values suggests a possible syn-glaciogenic BIF deposition. Fe/Ti-Al (Al + Fe + Mn), Fe-P, Co-Ni, V-Ti, V-Ni and Ni/ (Cr + Mn)-Ti + V diagrams suggest similarity to BIFs rather than the I-type granitoid magmatic-hydrothermal-skarn iron ores. REE + Y patterns display LREE depletion to slight enrichment, low-moderate Y/Ho ratios, HREE flat patterns, a nearly-zero to a seawater-like negative Ce anomaly and negative Eu anomaly. Such signatures may reflect low-T (300–200 °C) hydrothermal fluids for the origin of Fe-oxy-hydroxides formed by seawater-basaltic interaction and syn-glaciogenic meltwater influxes. Delta 18O values in magnetite-hematite (+3.3 to + 9.5 ‰) are in equilibrium with seawater and global BIFs. Delta 34S values in pyrite (+21.51 to + 26.59 ‰) reflect similarity to the Ediacaran pyrite composition formed by both thermal sulfate reduction (TSR) and bacterial sulfate reduction (BSR) processes. The radiogenic ratios of 206Pb/204Pb (19.228–25.105), 207Pb/204Pb (15.50–16.158) and 208Pb/204Pb (38.526–39.895) plot on the right side of 0.0 Ga geochron and were probably originated from the highly radiogenic zircon or galena clasts deposited by glaciogenic deposits. Geochemostratigraphy records zigzag elemental halos with the highest values of Fe (59.08 wt%) and Au (49.9 ppb). Exploration guides may be oriented to surficial sampling of the gossanized outcrops and heavy mineral surveys in drainage crosscutting the schistose rocks.

INVESTIGATING THE EFFECT OF LAYERING AND SCHISTOSITY ON THE MECHANICAL BEHAVIOR OF ROCKS USING THE DISCRETE ELEMENT METHOD

Anisotropy and deformation in rock material is mainly caused by the non-uniformity and irregular geometry of fracture systems. This factor is among the important problems in designing and evaluating the stability of engineering structures. In this research, the mechanical behavior of layered and schistose rocks is investigated by conducting compressive uniaxial and triaxial strength laboratory tests on rock samples from different directions and angles varying with respect to the loading axis. The tests were carried out on intact blocks of quartz schist rock with 0° layering and invisible schistosity. Next, numerical modelling was performed using the discrete element method (DEM) and calibrating numerical models by laboratory tests. In this process, three types of connections between the minerals (i.e. mica-mica, mica-quartz, and quartz-quartz), the growth of cracks, and the fracture mechanism of layered rocks with different layering angles were investigated. The results showed that unlike the arrangement of the rock particles, the layering angle of quartz schist has an important effect on the mechanical properties of the rock in such a way that uniaxial compressive strength, Young’s modulus, cohesion, and internal friction angle respectively have the greatest effect due to the change of the layering angle, while the tensile strength has the least effect.

Assessment of safe exploitability of undermined objects of the Underground Ore Mining Department of the Mine Management of the PJSC “ArcelorMittal Kryvyi Rih”

The article is devoted to monitoring surface displacement and the condition of monitored objects. The object of research is the process of displacement of the earth’s surface and the state of protected objects of the “United” deposit of the mine department for underground mining of ores of PJSC “ArcelorMittal Kryvyi Rih”. The displacement process is monitored based on long-lasting instrumental observations to determine surface deformations and assess the safety of exploitation of the monitored objects within the mining allotment. The study findings enable ascertaining that in the southern and central parts of the minefield, the displacement process has stopped, but in the northern part, it is still developing, and mining will have no impact on the technological objects of the Mine Management in the next two years. Over the recent two years, actual subsidence rates in the railway area have not exceeded 2.7 mm/month, and they are significantly lower than the permissible values (100 mm/month). The road sections shifting and the base for the removal of the road continue to develop. Mining operations at the deposit “Obiednanyi” have no hazardous impact on the “Schistose Rocks” natural geological reserve, the settlement of Karnavatka and the cemetery “Zakhidne”. Displacement on road and road base sections is in progress. In the vicinity of the settlement of Zhukivka, the maximum relative deformations (3.2 mm/m) are still much lower than the permissible one (6 mm/m), and they will not reach their maximum permissible values in the nearest two three years. In the last year, deformation rates decreased and reached the 2018 figure. Therefore, all the monitored objects within the mining allotment can be safely exploited.

Multiple episodes of hydrothermal alteration and uranium mineralization in the Singhbhum Shear Zone, eastern India: constraints from chemical and boron isotope composition of tourmaline

In this study, the chemical and B-isotope composition of tourmalines that coprecipitated with uraninite in schistose rocks of the Mohuldih and Bagjata uranium deposits along the Singhbhum Shear Zone are used to constrain the sources and the nature of the mineralizing fluids, along with the mechanism of primary uraninite precipitation. Three generations of tourmaline are identified, which can be correlated with three generations of uraninite in the host rocks. These correspond to three major episodes of hydrothermal alteration of the shear zone rocks at 1.8-1.9 Ga, 1.66-1.56 Ga, and ca. 1.0 Ga, synchronous with metamorphism/granitoid activity. The texturally earliest tourmaline with δ11B of 8.8 ± 0.3 ‰ precipitated together with primary uraninite from externally-sourced high saline fluids derived from subducting slab during the 1.8–1.9 Ga hydrothermal alteration event. The precipitation of uraninite can be linked to the decreasing salinity of the hydrothermal fluid as a consequence of fluid-rock interaction. Dissolution of chlorite/biotite and the precipitation of more Mg-rich tourmalines resulted in decrease of fluid salinity, which destabilized Fe-chloride and U-chloride complexes leading to the precipitation of Fe-rich tourmaline together with primary uraninite. The texturally later second and third generation tourmalines (δ11B = 2.5 to 6.3 ‰) and uraninites formed from mixed fluids derived from the slab and dehydration of pelitic assemblages during renewed episodes of hydrothermal alteration synchronous with metamorphism at 1.66-1.56 Ga and ca. 1.0 Ga. The δ11B of the tourmalines from the schists of the Singhbhum Shear Zone correspond to the range of values (–10.4 ‰ to +6.0 ‰) reported for IOCG-type deposits associated with metamorphic slab-derived fluid sources.

Hydrogeochemical Processes Regulating the Groundwater Quality and its Suitability for Drinking and Irrigation Purpose in Parts of Coastal Sindhudurg District, Maharashtra

Abstract The hydrochemistry of groundwater samples from the northern part of coastal Sindhudurg district, Maharashtra, India, was studied with an aim to comprehend its suitability for domestic and irrigation use. Groundwater samples were collected from 66 dug wells distributed over the study area, during the month of November 2017. The results of the chemical analysis indicate that the groundwater is alkaline in nature and are mainly characterized by Ca+-Mg+2-HCO3–, Ca+-Mg+2-Cl– and Na+-Cl– facies. The molar ratios of Na+/Cl–>1, both Mg2+/Na+ and Ca2+/Na+ ratios <1, (Ca2+ + Mg2+)/ (SO42– + HCO3–) = 1 suggest that the rock-water interaction of silicates / schistose rocks (quartz, chlorite, amphibolites, schist etc.) and ion exchange reaction are the major controlling factors of groundwater chemistry. Lower molar ratios of Cl–/ HCO3–< 0.5, NO3-/Cl-<0.3 observed reflect freshwater regime. Three samples which are in proximity to the Arabian Sea, deduce the effect of secondary contributions (saline water and anthropogenic sources). In order to determine the probable sources of groundwater contamination, principal component analysis was also carried out. The first three principal components with eigen value 1 or more are responsible for 71.31 %, 12.38% and 8.32% of the total variance in the data set, indicating major role of groundwater-rock interaction and marginal saltwater intrusion effect in the study area. Groundwater quality index computed for drinking purpose indicate that about 96% of the water samples lie within the permissible limits stipulated by the World Health Organization and Bureau of Indian Standards, and fall under the good to excellent category, suggesting its suitability for drinking purpose in the area. Water quality index indicates that most of the water is of excellent to good quality for irrigation, except for a few coastal samples.

Stone roofing in the Aosta Valley, Italy: Technical properties and durability of traditional Lithotypes

The Aosta Valley Region has promulgated in 1990 a law to partially finance stone roofs to the owners of houses in the historic centers of the valley, provided that the stone material chosen was suitable for this use. This suitability was certified by physical, mechanical and durability tests. More than twenty years ago, roofing slabs were extracted in north-western Alps mainly from schistose rocks. In recent time instead roofing slabs, according to global market, have an international origin. All the traditional stones tested showed excellent technical features according to the local legislation on roof slates. One of these traditional stones is a phyllite whose trade name is “Porfiroide” having the best physical and mechanical properties compared to the other kinds of traditional stones, but with a high standard deviation in the results of flexural strength performed after the freeze and thaw cycles. In the roofing installed 40 years ago, despite their best technical features, the “Porfiroide” roof slabs show a poor state of conservation with widespread detachments, fractures, growth of mosses and lichens, variations in colours. Otherwise, stones with a lower value of flexural strength and higher water absorption instead show good behaviour in the roofing in situ and also in terms of colour change.Evidently the only characterisation of the stone materials is not sufficient but it must be associated to a on-site verification, comparing each slab to be installed with a reference sample, part of the sample submitted to the tests, and to a control on site of the resistance of the stones to degradation.

Study of small-scale structures and their significance in unravelling the accretionary character of Singhbhum shear zone, Jharkhand, India

Localized strain within tabular ductile shear zones is developed from micro- to meso- to even large scales to form complex structures. They grow in width and length through linkage of segments with progressive accumulation of strain and displacement, and finally produce shear zone networks characterized by anastomosing patterns. Singhbhum shear zone (SSZ) represents a large composite zone characterized by a collage of different dismembered lithotectonic segments, with heterogeneous structural features, within a matrix typical of a shear zone. Structural features indicate that the material properties of protoliths have a great role in controlling the mechanics of deformation. Meso- and micro-scale structural studies of the east-central part of the SSZ reveal ‘tectonic complex like’ (? deeper level equivalent of melange type complex) assemblage of dismembered lithoteconic units. Shear-induced foliations, S, C and C′, were developed while the main mylonitic foliation is represented by C-plane. Apart from that, shear lenses are exceptionally well developed in both meso- and micro-scale in most of the units, particularly in schistose rocks. They were formed from different processes during progressive simple shear, which includes (1) anastomosing C-planes, (2) intersection between C- and C′-planes, (3) disruption of stretched out longer limbs of asymmetric folds, and (4) cleavage duplex. Fabrics recorded in rocks indicate that there was a progressive change in the development of predominantly flattening fabric (coaxial pure shear) in the northern part (outside the SSZ), to simple-shear non-coaxial type deformation producing shear fabric, dominating over the flattening fabric, in the southern part (within the SSZ) that is in close proximity with the Singhbhum Craton. Although an overall plane strain simple shear model is apparent, occasional presence of extensional features along two directions of the mylonitic foliation, demonstrative of three-dimensional deformation (simple shear and flattening: X > Y > 1 > Z), may indicate the stretching nature of the SSZ. From the orientation of oblique grain shape fabric [ISAmax (θ < 45°)], there is slight deviation from simple shear, i.e., a sub-simple nature of plane strain shear could be inferred. However, in conformity with simple shear model the ubiquitously developed stretching lineation shows consistency in orientation being parallel to the movement direction. There is no evidence of transpression. Shear sense indicators invariably indicate up-dip ductile thrust movement with vergence top-to-the south. Microstructural deformational characteristics indicate that peak temperature attained during the deformation in shear zone was ~600 °C. Prolonged period of metasomatism, induced by fluid influx, played an important role in strain softening during the development of SSZ.

A Modified Engineering Classification Method for Schistose Surrounding Rocks of Tunnel

For schistose surrounding rocks of tunnel, engineering classification of rock masses by the widely used BQ method in China are often inconsistent with the reality. In this study, microtests and uniaxial compression test were performed on three types of quartz mica schist. Microtests reveal that the schist is characterized by natural orientation and interbedded distribution of minerals and microfissures are prone to be distributed directionally along the smooth edge of flaky minerals. Mechanical test shows that the compressive strength of schist samples has U-shaped change with the varied loading direction. Moreover, the strength anisotropy degree of the schist is positively correlated with the development of schistosity planes, and the strength anisotropy increases significantly after saturation. When the direction of uniaxial load applied to the samples changes gradually, the splitting-tensile, shear-slip and shear failure occur respectively, indicating that the dominant factors affecting the strength of schist specimens are not uniform. In particular, the strength of specimens with transverse schistosity planes is less affected by the weak planes. Based on the experimental study, a new model considering the schistosity development degree was constructed, which is served as the evaluation of the basic quality of schistose rock mass. By regression analysis on 168 sets of practical data, an optimized BQ equation was further developed. Then a correction coefficient table was put forward based on numerical simulation, which is helpful to correctly determine the final engineering grade of surrounding rock. Case study shows that the improved BQ method is more reliable for classifying engineering grade of schistose surrounding rock.

Elemental substitutions and compositional evolution during tourmaline formation in metasomatic schistose rocks of Sikait area in the Southern Eastern Desert, Egypt

Tourmaline deposit in Sikait area (Southern Eastern Desert of Egypt [SEDE]) is closely associated with metapelitic schistose rocks that belong to Neoproterozoic time. The distribution of tourmaline was mostly controlled by Nugrus shearing, along with schist leucocratic rock varieties (leucogranite, pegmatite, and aplite dikes), which are syntectonically dissected by hydrothermal quartz veins. Local concentrations of tourmaline occur either as discontinuous tourmalinite bands/pockets or as disseminated isolated clusters of crystals within the metapelitic schistose rocks, pegmatites, and quartz veins. Chemical and mineralogical changes accompanying with tourmaline formation have been observed within the schistose rocks in contact with a pegmatitic bodies in Sikait area. Four mineral assemblages were identified on approaching to the pegmatite contact: (1) Quartz-Biotite-Potassium Feldspar-Chlorite assemblage (Q-B-K-C); (2) Quartz-Biotite-Tourmaline-Chlorite assemblage (Q-B-T-C); (3) Tourmaline-Quartz-Muscovite assemblage (T-Q-M); and (4) Tourmaline-Quartz assemblage (T-Q). Toward the pegmatite contact, K, Li, Rb, SiO2, CaO, MgO, Sr, and Ba are decreased, while Al2O3, B2O3, Na2O, Fe (tot), Zr, Y, and Th are moderately increased. Variations in the mineral assemblages and whole-rock chemistry within the four alteration zones appear to be controlled by boron metasomatism and potash leaching. The normalized rare earth element patterns of rock samples from the four alteration zones suggest a partial alteration of the original sedimentary patterns by the metasomatic-magmatic fluids. The alteration could be either a single phase of interactions between pegmatite fluid and schists with B-, Li-, Rb-carrying fluid or a couple of phases (B-, Mn-, Be-rich fluid and Rb-, Li-, K-rich fluid). In all cases, boron from the pegmatite-associated fluids reacts with the surrounding schistose rocks to breakdown of sheet silicate which acts as “traps” for Rb, Sr, Li, Ba, and K and hence leads to tourmaline-rich assemblages.

Geochemical and petrological studies of a magmatic carbonate-bearing metalamprophyre (spessartite) at Kalagalla - Evidence for shoshonitic calc-alkaline magmatism within auriferous Ramagiri-Penakacherla Schist Belt (2.5 Ga), Eastern Dharwar Craton, southern India

Geochemical and petrological characteristics of a lamprophyre dyke at Kalagalla intruded into the auriferous schistose rocks of the Ramagiri-Penakacherla Schist Belt, Anantapur district, Andhra Pradesh, India are presented here. The Kalagalla lamprophyre (KGL) is a melanocratic rock exhibiting typical knobbly or pustular texture on the rock surface. The micro-textures and mineralogy typical of lamprophyres are obscured by metamorphism; however, it exhibits porphyritic, nemato-granoblastic texture representating greenschist facies metamorphism. The rock is sheared and carbonatised possessing several globules formed by polycrystalline aggregates of calcite rimmed by coronitic subhedral plagioclase and biotite-phlogopite, evidencing its magmatic origin. The mineral assemblages noticed in thin-sections include amphibole, plagioclase, biotite-phlogopite with calcite ocelli as essential while apatite, zircon, magnetite, ilmenite and several opaque minerals as accessory phases. The SEM-EDS investigation on the opaque minerals revealed accessory sulphide and silicate phases like As-free pyrite, haematitised Ni-bearing chalcopyrite and Ni-As-Co- minerals indicative of sulphidation associated with greenstonevauriferous lodes; along with oxide phases like LREE-bearing titanite partially transformed into leucoxene and goethite. Presence of amphibole and dominance of plagioclase, it is presumably a spessartite variety. Based on its geochemistry, the rock is classified as a shoshonitic calc-alkaline lamprophyre. The LREE-bearing titanite appears to be the contributor of LREE enrichment. The high Mg# (77-79), Ni (153-162 ppm) and Cr (380-470 ppm) support a mantle source. The trace and REE patterns (ƩREE:326-343 ppm, LREE>HREE) indicate ivolvement of residual garnet at the source enriched in phlogopite in a ‘subduction-related’ environment. The absence of Eu anomaly reflects lack of plagioclase fractionation. The high Zr/Hf ratio (163-202) indicates carbonatite metasomatism and lack of crustal contamination. Further investigations are in progress.

Detrital zircon age studies of Haast Schist in western Otago and Marlborough, New Zealand: constraints on their protolith age, terrane ancestry and Au–W mineralisation

Detrital zircon U–Pb ages are reported from the Haast Schist in western Otago and Marlborough, South Island, New Zealand. The majority are from the Aspiring Lithological Association in Otago, which intervenes between Caples Terrane and Rakaia Terrane protoliths. These indicate provenances similar to those in established Jurassic and Late Triassic sandstones of the Waipapa Composite Terrane in the North Island. The populations are dominated (>60%) by Early Jurassic, Triassic and Permian zircons with only small proportions of pre-Permian zircons. In contrast, schists east of the Aspiring Lithological Association have substantial proportions (>20%) of early Paleozoic–Precambrian zircons and are thus assigned to the Triassic–Permian, Rakaia Terrane (Torlesse Composite Terrane), which is extensive across eastern Otago. However, three small areas of anomalous schist, with dominantly (80%) Carboniferous zircons, are considered the oldest level of the Rakaia Terrane protolith. Similar datasets from western Marlborough Schist confirm the correlation with western Otago Schist and are also assigned to the Waipapa Composite Terrane. The new Haast Schist datasets support a suspect terrane model in which both Rakaia and Waipapa Composite terrane protoliths have sediment provenances in eastern Australia and Au–W sources at their subsequent mineralisation sites. KEY POINTS Original protoliths are recognisable within the Haast Schist of New Zealand on the basis of distinctive detrital zircon age patterns. The Aspiring Lithological Association (Otago Schist) of western Otago, is correlated with a similar belt of schistose rocks (Marlborough Schist) in western Marlborough, and both are assigned to a Waipapa Composite Terrane protolith of Jurassic to Late Triassic age. The Jurassic-Late Triassic sandstones within Waipapa Composite Terrane are dominantly of granitoid provenance in eastern Australia. Detrital zircons of Carboniferous age in the Waipapa Composite Terrane support a possible New England Orogen provenance in northeastern NSW and southeastern Queensland, and also indicate possible primary sources for the gold and tungsten in the western Otago Schist and western Marlborough Schist. This result is in marked contrast to eastern Otago Schist where the protolith is Rakaia Terrane of Late Triassic age and whose provenance is in central-eastern Queensland.

On Applicability of Some Indirect Tests for Estimation of Tensile Strength of Anisotropic Rocks

The tensile strength of rocks plays a noteworthy role in their failure mechanism, and its determination can be beneficial in optimizing the design of the rock structures. Schistose rocks due to their inherent anisotropy in different foliation directions show a diverse strength at each direction. The purpose of this work was to compare and assess the tensile strength of phyllite, which was obtained in direct and indirect tensile tests in different foliation directions. To this end, several phyllite specimens with different foliation angles (0o, 30o, 45o, 60o, and 90o) related to the loading axis (β) were prepared. Finally, the direct tensile test, diametrical and axial point load tests, Brazilian test, and Schmidt hammer test were conducted on 188 samples. The results of the experimental tests revealed that the maximum and minimum tensile strengths in direct tensile testing tension were directly related to the angles of 0o and 90o. Also it was observed that the Brazilian tensile strength overestimated the tensile strength. Furthermore, an exponential correlation was introduced between the direct tensile strength and the Brazilian tensile strength.

Alteration of magmatic monazite in granitoids from the Ryoke belt (SW Japan): Processes and consequences

AbstractThe alteration of magmatic monazite and its consequences for monazite geochronology are explored in granitoids from the western part of the Ryoke belt (Iwakuni-Yanai area, SW Japan). Biotite-granite samples were collected in two plutons emplaced slightly before the main tectono-metamorphic event: the first one, a massive granite (Shimokuhara) adjoins schistose rocks affected by greenschist facies metamorphism; and the second, a gneissose granite (Namera) adjoins migmatitic gneiss that experienced upper-amphibolite facies conditions. Despite contrasting textures, the granite samples have similar mineral modes and compositions. Monazite in the massive granite is dominated by primary domains with limited secondary recrystallization along cracks and veinlets. It is variably replaced by allanite+apatite±xenotime±Th-U-rich phases. The outermost rims of primary domains yield a weighted average 206Pb/238U date of 102 ± 2 Ma while the Th-U phases show Th-U-Pb dates of 58 ± 5 and 15 to 14 ± 2–3 Ma. Monazite in the gneissose granite preserves sector- or oscillatory-zoned primary domains cross-cut by secondary domains enriched in Ca, Y, U, P, and containing numerous inclusions. The secondary domains preserve concordant 206Pb/238U dates spreading from 102 ± 3 to 91 ± 2 Ma while primary domain analyses are commonly discordant and range from 116 to 101 Ma.Monazite alteration textures in the two granites chiefly reflect differences in their post-magmatic histories. In the massive granite, monazite replacement occurred via a nearly stoichiometrically balanced reaction reflecting interaction with an aqueous fluid enriched in Ca+Al+Si±F during hydrothermal alteration of the granitic assemblage, likely below 500 °C. In the gneissose granite, a small amount of anatectic melt, probably derived from the neighboring metasedimentary rocks, was responsible for pseudomorphic recrystallization of monazite by dissolution-reprecipitation above 600 °C. Regardless of whether monazite underwent replacement or recrystallization, primary monazite domains preserve the age of magmatic crystallization for both plutons (102 ± 2 and 106 ± 5 Ma). Conversely, the age of monazite alteration is not easily resolved. Monazite replacement in the massive granite might be constrained using the Th-U-rich alteration products; with due caution and despite probable radiogenic Pb loss, the oldest date of 58 ± 5 Ma could be ascribed to chloritization during final exhumation of the granite. The spread in apparently concordant 206Pb/238U dates for secondary domains in the gneissose granite is attributed to incomplete isotopic resetting during dissolution-reprecipitation, and the youngest date of 91 ± 2 Ma is considered as the age of monazite recrystallization during a suprasolidus metamorphic event. These results reveal a diachronous, ca. 10 Ma-long high-temperature (HT) history and an overall duration of about 15 Ma for the metamorphic evolution of the western part of the Ryoke belt.

Late Miocene constrictional strain in the northern Apennines: A case study from the Barabarca metaconglomerate (Elba Island, Italy)

Finite strain analyses were performed on a deformed metaconglomerate from the Calamita Unit in the Island of Elba. The Calamita Unit is a synkinematic contact aureole that was shaped by Late Miocene contractional deformation coeval with high‐temperature metamorphism. The metaconglomerate occurs as an L‐tectonite in the footwall of a major thrust, entirely surrounded by S‐tectonites developed in schistose rocks. Object lineations, defined by the preferred orientation of clasts, trend subparallel to the stretching lineations in the associated rocks. Quartz microstructures registered ductile deformation of clasts by grain boundary migration to bulging recrystallization, suggesting temperature decrease during deformation. Rf/ϕ analyses were carried out on three metaconglomerate samples using quartzite clasts as markers. The finite strain data show that the metaconglomerates are strongly deformed in the constrictional field with K values between ~3 and ~7. The constrictional deformation registered by the metaconglomerate with respect to the surrounding metapelites, which likely deformed under plane strain, can be interpreted as the result of flow partitioning in rheologically heterogeneous sequences during deformation. These results suggest the presence of significant strain gradients in the Calamita Unit, strictly associated with heterogeneously distributed ductile shear zones.

Content analysis of literatures on Chinese massage (Tuina) for knee osteoarthritis

The present study describes a remote sensing approach for preparing lineament map that subsequently indicates the influence of lineament density in the severity of weathering development. In this study, SPOT-5 data, the integration of SPOT-ASTER and Digital Elevation Model (DEM) data were used and processed. The existence of an active fault system in the south of Mashhad city, NE Iran and presence of schistose rocks in this area result in the development of numerous lineament features. This region was selected for this research. Lineament features including fractures, bedding plane, cleavage, shear zones and schistosity were mapped in the study area. The results indicate that the highest concentration of lineaments occurred in the central-western and south-eastern parts of the study area, which coincide with metamorphic outcrops and NW-SE trending fault system. A comparison of lineament statistical analysis and field survey demonstrated that the structural discontinuities have a significant effect on forming and distribution of weathering profiles. It was observed that increasing the number, length and density of structural discontinuities led to strong severity in weathering, which can produce deep residual soils susceptible to landslide occurrence. The remote sensing approach developed in this study can be applicable for preparing lineament maps and evaluating the severity of weathering development in other active fault zones around the world.

Correlation of multiple deformation events in an area: Example from schistose rocks of Lesser Himalayas, NW Pakistan

Integrated micro-, meso- and macro-structural investigations were carried out in the multiply deformed rocks of the Mula Gori area, northeastern Khyber Agency, Lesser Himalayas. These investigations revealed an intricate history of deformation events that have not been formerly recognised. These structural examinations show four successive deformations. These events were identified in the field as well as in oriented vertical thin sections. The first deformation event \(\hbox {D}_{1}\) is preserved in the form of inclusion trails in garnet porphyroblasts of foliation intersection axis 1 (FIA 1) and the fold axis of the macroscopic fold indicates NW–SE orogeny-oblique shortening. The \(\hbox {D}_{2 }\) event produced N–S trending foliations, fold axes and mineral lineations indicating E–W shortening. The \(\hbox {D}_{3}\) is preserved as FIA 2 in garnet porphyroblast and E–W trending foliations, mineral lineations and fold axes in the field representing N–S shortening. The \(\hbox {D}_{4}\) created NNW–SSE fabrics, which post-dates the main mantle thrust and the main boundary thrust, and likely resulted from the ENE–WSW bulk shortening related to development of the Hazara–Kashmir syntaxis.

Lineament mapping and fractal analysis using SPOT-ASTER satellite imagery for evaluating the severity of slope weathering process

The present study describes a remote sensing approach for preparing lineament map that subsequently indicates the influence of lineament density in the severity of weathering development. In this study, SPOT-5 data, the integration of SPOT-ASTER and Digital Elevation Model (DEM) data were used and processed. The existence of an active fault system in the south of Mashhad city, NE Iran and presence of schistose rocks in this area result in the development of numerous lineament features. This region was selected for this research. Lineament features including fractures, bedding plane, cleavage, shear zones and schistosity were mapped in the study area. The results indicate that the highest concentration of lineaments occurred in the central-western and south-eastern parts of the study area, which coincide with metamorphic outcrops and NW-SE trending fault system. A comparison of lineament statistical analysis and field survey demonstrated that the structural discontinuities have a significant effect on forming and distribution of weathering profiles. It was observed that increasing the number, length and density of structural discontinuities led to strong severity in weathering, which can produce deep residual soils susceptible to landslide occurrence. The remote sensing approach developed in this study can be applicable for preparing lineament maps and evaluating the severity of weathering development in other active fault zones around the world.

Influence of TBM operational parameters on optimized penetration ratein schistose rocks, a case study: Golab tunnel Lot-1, Iran

TBM penetration rate is a function of intact rock properties, rock mass conditions and TBM operational parameters. Machine rate of penetrationcan be predicted by knowledge of the ground conditions and its effects on machine performance. The variation of TBM operational parameters such as penetration rate and thrust plays an important role in its performance. This study presents the results of the analysis on the TBM penetration rates in schistose rock types present along the alignment of Golab tunnel based on the analysis of a TBM performance database established for every stroke through different schistose rock types. The results of the analysis are compared to the results of some empirical and theoretical predictive models such as NTH and QTBM. Additional analysis was performed to find the optimum thrust and revolution per minute values for different schistose rock types.

2D geo-electrical imaging for groundwater exploration in Shika, along Zaria-Funtua Road north of Ahmadu Bello University main campus, Samaru, Zaria

A two dimensional (2D) geoelectrical tomography of Ahmadu Bello University Teaching Hospital Premises was carried out with the aim of identifying a suitable location for siting a borehole. This was sequel to the fact that a borehole drilled without proper geophysical investigation in the quarters for resident doctors did not produce water. State-of-the-art equipment was employed and 2D surveying proved a powerful geological mapping tool, for use in hydrogeological mapping including engineering and environmental applications. The 2D inversion results of the survey were correlated with the lithology information obtained from the boreholes in Jama’a village, and the hostels and the residential quarters of ABUTH. The stratigraphic structure of the study area is very complex and is a product of volcanic and magmatic activities of various ages. Based on the geo-electrical images obtained in the study area, three distinct layers were revealed, the overburden with an average thickness of about 16 m – 26 m. The overburden is immediately underlain by the weathered basement, 5 m – 14 m thick which consists of disintegrated schistose rock materials, sand and gravel. This layer has a relatively low resistivity due to the presence of water and clay, which reduces the permeability, so this layer is thus regarded as the aquifer. The fresh basement rock was encountered at a variable depth of between 21 m and &gt;30 m with resistivity 1223 Ωm up to 11918 Ωm. These results agree with the borehole logs. The complete set of borehole logs used in this research were obtained from the original hydro-geologic assessment report of the groundwater research department of the National Water Resources Institute (NWRI), Mando, Kaduna; Kaduna State, Nigeria.Keywords: Tomography, Inversion, Lithology, Geo-electrical, Aquifer, Borehole