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The Patearoa saline site in Maniototo basin has developed on variably clay-altered Otago Schist. Decomposition and sedimentary redistribution of schist outcrop components has led to formation of bare soil-free substrates (upper metre scale) with contrasting permeability to rain and shallow groundwater percolation. Relatively impermeable clay-rich substrates, with a surface crust (cm scale) of detrital clay and muscovite, are saline with electrical conductivity (EC) of 1–35 mS/cm and locally hyperalkaline (pH > 10), with evaporative mineral accumulations. These saline substrates are downslope of more permeable substrates consisting of coarse schist debris and fractured outcrops, which have lower salinity (EC < 1 mS/cm) and lower pH (<7). A salt line can be mapped at metre scale between these substrate types on hillsides. The geochemical contrasts across the salt line have strong effects on plant communities that are colonising bare ground. Initial colonisation of bare saline substrates by some plants changes the geochemical signatures of the surficial few centimetres to form proto-soil with lower EC and pH. Proto-soil development facilitates further colonisation by pasture grasses, but the underlying substrates remain saline and highly alkaline. Salt lines similar to the one at Patearoa are mappable elsewhere in the Otago area and constitute fundamental geoecological boundaries. [ABSTRACT FROM AUTHOR]

Controls on the physical and chemical architecture of the subsurface critical zone are somewhat controversial, with multiple hypotheses proposed to account for variations in the depth of weathering between sites, and with landscape position at a site. In the Piedmont region of the Mid‐Atlantic US weathering of crystalline bedrock has been observed to extend tens of meters below the surface and groundwater in a'bow‐tie' shape – i.e. weathering extends to lower elevations below ridges than below channels. The chemical and physical structure of a hillslope transect in the Maryland Piedmont was explored with a 45 m borehole in the ridge, as well as shallow bedrock boreholes at the toe of the slope and valley. Chemical weathering fronts were characterized using elemental abundances and mineralogical analysis. The ridge borehole did not extend deeper than the chemically and physically weathered rock. Surface and borehole geophysics and density measurements were used to characterize the weathered rock and saprolite. Na and Ca results suggest that plagioclase feldspar weathering is similar between samples collected from 45 m under the ridge and 2.2 m under the valley bottom. A narrow Fe oxidation garnet weathering front co‐insides with the transition from weathered bedrock to saprolite, suggesting that this reaction may generate initial saprolite porosity. Muscovite weathering co‐occurs with complete depletion of plagioclase a few meters above the Fe oxidation front. These nested weathering fronts in the saprolite appear to follow a subdued version of the surface topography. The location and shape of the nested saprolite weathering fronts may be controlled by the feedback between the transport of reactants and solutes and reaction‐generated porosity, consistent with the conceptual "valve" hypothesis. Differing dominant control mechanisms on deep bedrock weathering and saprolite initiating reactions may explain the thickness and structure of the critical zone at our site. [ABSTRACT FROM AUTHOR]

There are some persistent basic questions pertaining to the bedrock schist of New York City (NYC). How many mappable schist formations are exposed in NYC, and what was the sedimentary protolith of the Manhattan schists? Our proposed answers are based in part on a blending of published paleontological and radiometric dating results that constrain the timing of Taconic subduction and the best choice of a pelitic protolith for the schists of NYC. We have chemically analyzed some samples of schist and shales at key locations to evaluate the plausibility of our proposals. The compelling published evidence indicates that the Taconic Orogeny began about 475 Ma, when peri-Laurentian plates began the process of east-dipping subduction under the Moretown Terrane, resulting in a magmatic flareup of the Shelburne Falls arc that carried the Moretown Terrane west across NYC. East-dipping subduction accounts for early Ordovician metamorphism until an oceanic slab break-off event at about 466 Ma. Our review of the biostratigraphic data indicates a continuation of subduction and the deposition of pelitic sediments until about 455 Ma, during the transition to deep-water turbiditic sediment deposition. This disqualifies all post-455 Ma turbidites as viable protoliths for the NYC Manhattan schists but does include the Late Cambrian to lowermost Late Ordovician pelites of the Jutland Sequence that are exposed directly west of NYC in New Jersey. Our new chemical analyses of Jutland sediments and each of the three named schists from the NYC plot as a single geochemical population. We, therefore, propose that the schists of NYC could collectively be referred to as the Manhattan schist of the Late Cambrian to lower Late Ordovician. [ABSTRACT FROM AUTHOR]

The physical and mechanical characteristics of albitite and schist in Lala Copper mine, Liangshan, southwest China were taken as the research object, the variation of physical and mechanical characteristics with occurrence depth was studied. 54 engineering geological surveys were completed at elevations of + 1 890 ~ 1 760 m, 10 geostress tests were conducted at elevations of + 1 880 ~ 1 760 m, and samples of albitite and schist were sampled at elevations of + 1 984 ~ 1 760 m, and tests of physical properties, uniaxial compressive strength and uniaxial compression deformation of rock samples were completed. The density, porosity, uniaxial compressive strength, elastic modulus, Poisson's ratio of rock samples, joint spacing in-situ stress of rock mess of each elevation were obtained. The results show that the uniaxial compressive strength, elastic modulus, density and Poisson's ratio of albitic and schist increase with depth, porosity and joint spacing decrease with depth. With the increase of rock depth, the in-situ stress increases, which directly changes the stress environment of rock mass. The joint spacing of rock mass also reflects the change of stress environment. It also changes the porosity and density of rock mass. Then the mineral particles of the rock are squeezed, resulting in the gradual densification of the rock structure, and the improvement of the mechanical strength characteristics of rock. [ABSTRACT FROM AUTHOR]

Hydrogeochemical investigation as well as petrographic examination of rock samples was carried out in Enwan and environs, in Akoko Edo, South South Nigeria. Ten (10) water samples and two (2) rock samples were collected from study area for analyses. All of the samples collected were subjected to geochemical and petrographic analysis respectively, Physical parameters such as pH, TDS, Electrical conductivity and temperature were measured in-situ using standard equipments and the analysis for the chemical parameters was carried out with Atomic Absorption Spectrometer (AAS). The concentration of metals in the samples was determine through geochemical analysis the correlation of physical and chemical parameters. Ca 2+, Mg 2+, K +, Na 2+, Fe 2+ and Cu 2+ were the cations analyzed for while the anions included HCO3, NO3 - and Cl -. The results were compared with the world Health Organization (WHO) and Nigerian Industrial Standard (NIS) standards to determine the quality of the groundwater. ENW4 had the relatively highest calcium and magnesium ions concentration. ENW3 and ENW4 have the relatively highest chloride ion concentration, but all the samples have extremely high chloride concentration. The anthropogenic sources from which the high concentration of these parameters such as Chloride, Iron, Electrical conductivity and pH were found could either be as a result of the human activities in this study area or weathering of rock forming minerals such as Biotite, Quartz, plagioclase. The source of contamination of Iron in the groundwater is from weathering of surrounding rocks and subsequent leaching into the aquifer. During weathering, because feldspars are not resistant to weathering unlike quartz that are very resistant, it gives off Na+ and K+ which are then washed down into the groundwater through percolation. The Piper plot shows that the all the samples belong in the Ca2+-Mg2+-Cl-hydrochemical facies which results to an area of hardness because of the magnesium and chloride ions. [ABSTRACT FROM AUTHOR]

Halophytic plant communities have developed on exposed coastal landforms to form low-stature turf in several locations around New Zealand. We quantify the inorganic geochemistry, mineralogy and simulated ephemeral surface water composition of saline soil-free bare ground at a well-preserved site at Maori Head on Otago Peninsula, where halophytes have colonised from adjacent coastal turf. The community at this site is dominated by Leptinella dioica, Samolus repens, Disphyma australe and Selliera radicans. Maori Head substrates are dominated by clay-altered basalt colluvium and show a general trend from high electrical conductivity (EC > 10 mS/cm) and weakly acid pH (< 6) on bare ground to low EC (< 1 mS cm−1) and higher pH (> 7) in turf and adjacent pasture soils. High salinities on dry substrates and in simulated ephemeral surface waters result from surface evaporation of airborne sea spray and contain halite (NaCl) with some gypsum (CaSO4.2H2O). Chemical interactions with the substrate are minor. The high surface salinities were maintained despite a major winter rain event with strong onshore winds. However, surface salinity is frequently leached by rain and shallow groundwater, whereas inland saline sites (pH 8–11) have substantial salt accumulations driven by lower rainfall, high evaporation and chemical interaction with Otago Schist-derived substrates. [ABSTRACT FROM AUTHOR]

The Sutton Salt Lake is a rare occurrence of an inland evaporative saline lake on a small landmass with a temperate maritime climate. The lake lies on a bed of impermeable loess silt in a 2 ha depression between tor ridges of Otago Schist in inland east Otago. A rim of salt-tolerant plants (halophytes) occurs around parts of the lake margin. The vegetated lake margin has encroached laterally on to the lake bed by 5–30 m over the past 50 years. Salinity in the lake is dominated by Na and Cl (molar ratio ∼1) that has been concentrated by annual cycles of evaporation and replenishment by rain with marine aerosols. Drying lake margin sediments lose NaCl via rain-driven recycling back into the lake, with the formation of a salt crust that contains Ca, Mg and Na carbonate minerals, gypsum, and remnant halite. The lake and lake sediment chemistry are affected by carbonate dissolution and deposition, and more than 10-fold Ca–Mg carbonate supersaturation in lake waters contributes to elevated water pH (8.9–9.3). Geoecological evolution of the lake margin involves the encroachment of exotic weeds behind active halophytic habitats as dilute surface water lowers salinity. [ABSTRACT FROM AUTHOR]

Soil-free sodic salt pans with local pH >10 have formed on loess and schist-derived clay surfaces in the semi-arid climate of Central Otago. This study identifies evaporative mineral distributions and associated variations in surface geochemistry, and these results are relevant to survival of rare halophytic plants on some of the pans. Evaporative salts on pan surfaces are dominated by NaCl from marine aerosols, and Na-sulphates and Na-carbonates. Some of the Na in evaporites was derived from alteration of schist-derived albite and Na-bearing smectite formed from albite. The high pH pan surfaces result from a combination of long-term (decades to millennia) albite alteration and short-term (minutes to months) Na-carbonate dissolution and recrystallisation. This muscovite is variably cemented by evaporative salts, and some crusts have abundant salt-dissolution voids. High pH has facilitated dissolution of aluminium and silica from albite and smectite, with evaporative precipitation of Al-oxyhydroxide contributing to crust cementation. Different dissolution rates of evaporative minerals during rain events and damp seasons results in differential mobility of salt components downslope. The salt pans are physically and chemically dynamic features that have formed on time scales of decades to centuries. [ABSTRACT FROM AUTHOR]

Floor heave is a typical tunnel issue in tunnelling engineering. To gain deep insights into the deformation mechanism and failure processes of floor heave at the bottom of a tunnel in layered rock, biaxial step-loading tests were conducted on rock samples (including schist and sandstone) with and without prefabricated invert arches. The failure processes of the samples were observed by the three-dimensional digital image correlation technique (3D-DIC) during the test. The test results showed that the deformation evolution processes of the floor heave of the sample included the following steps: (1) crack initiation at the interlayer weak planes; (2) separation of the rock matrix into platy structures along the bedding planes and flexures; and (3) fracture and uplift of the platy structures in the middle part. As the stress redistributes on the bottom plate of the sample, and stress concentration zones shift toward locations far away from the arching surface, the deformation evolution shows a similar variation trend with the stress. Continuous buckling fracturing takes place progressively from the vicinity of the arch surface to certain distant regions. Based on the test results, the key location of internal surrounding rock deformation was determined, and the mechanism of floor heave was clarified. The schist sample SC-BI-10 began to experience floor heave at 1064.4 s, and the deformation curve (the relationship between Y and U) showed a convex shape in the range of 0–20 mm in the Y-coordinate. The displacement reached its maximum value at y = 11.7 mm, corresponding to the position where the rock slab was broken. In addition, the influence of the interlayer properties and cover depth of rocks on bottom uplift was also studied. The design of tunnel supports and the monitoring and prevention of floor heave can benefit from this study. [ABSTRACT FROM AUTHOR]

There are some persistent basic questions pertaining to the bedrock schist of New York City (NYC). How many mappable schist formations are exposed in NYC, and what was the sedimentary protolith of the Manhattan schists? Our proposed answers are based in part on a blending of published paleontological and radiometric dating results that constrain the timing of Taconic subduction and the best choice of a pelitic protolith for the schists of NYC. We have chemically analyzed some samples of schist and shales at key locations to evaluate the plausibility of our proposals. The compelling published evidence indicates that the Taconic Orogeny began about 475 Ma, when peri-Laurentian plates began the process of east-dipping subduction under the Moretown Terrane, resulting in a magmatic flareup of the Shelburne Falls arc that carried the Moretown Terrane west across NYC. East-dipping subduction accounts for early Ordovician metamorphism until an oceanic slab break-off event at about 466 Ma. Our review of the biostratigraphic data indicates a continuation of subduction and the deposition of pelitic sediments until about 455 Ma, during the transition to deep-water turbiditic sediment deposition. This disqualifies all post-455 Ma turbidites as viable protoliths for the NYC Manhattan schists but does include the Late Cambrian to lowermost Late Ordovician pelites of the Jutland Sequence that are exposed directly west of NYC in New Jersey. Our new chemical analyses of Jutland sediments and each of the three named schists from the NYC plot as a single geochemical population. We, therefore, propose that the schists of NYC could collectively be referred to as the Manhattan schist of the Late Cambrian to lower Late Ordovician.

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We investigate the influence of foliation orientation and fine-scale folding on the static and dynamic elastic properties and unconfined strength of the Poorman schist. Measurements from triaxial and uniaxial laboratory experiments reveal a significant amount of variability in the static and dynamic Young’s modulus depending on the sample orientation relative to the foliation plane. Dynamic P-wave modulus and S-wave modulus are stiffer in the direction parallel to the foliation plane as expected for transversely isotropic mediums with average Thomsen parameters values 0.133 and 0.119 for epsilon and gamma, respectively. Static Young’s modulus varies significantly between 21 and 117 GPa, and a peculiar trend is observed where some foliated sample groups show an anomalous decrease in the static Young’s modulus when the symmetry axis (x3-axis) is oriented obliquely to the direction of loading. Utilizing stress and strain relationships for transversely isotropic medium, we derive the analytical expression for Young’s modulus as a function of the elastic moduli E1, E3, ν31, and G13 and sample orientation to fit the static Young’s modulus measurements. Regression of the equation to the Young’s modulus data reveals that the decrease in static Young’s modulus at oblique symmetry axis orientations is directly influenced by a low shear modulus, G13, which we attribute to shear sliding along foliation planes during static deformation that occurs as soon as the foliation is subject to shear stress. We argue that such difference between dynamic and static anisotropy is a characteristic of near-zero porosity anisotropic rocks. The uniaxial compressive strength also shows significant variability ranging from 21.9 to 194.6 MPa across the five sample locations and is the lowest when the symmetry axis is oriented 45° or 60° from the direction of loading, also a result of shear sliding along foliation planes during static deformation.

To develop a more reactive pozzolan for supplementary cementitious materials (SCMs), the co-calcination of kaolinite and limestone was investigated for its contribution to hydration of blended cement. Kaolinite (with ~50 wt% quartz impurity) was calcined at 700 °C, and a mixture of kaolinite and limestone was calcined at 800 °C. These activated SCMs were added to ordinary Portland cement (OPC), replacing ca. 30 wt% of the OPC. The compressive strength of these blended cement paste samples was measured after 28 and 90 days, while the hydration products and microstructural development in these blended cement pastes were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results revealed that adding free lime to OPC, together with metakaolin, led to enhanced compressive strength. The compressive strength of this new blended cement paste reached 113% and 112% of the compressed strength of pure OPC paste after 28 and 90 days of hydration, respectively. Furthermore, this study showed that the improvement was due to the increased consumption of Portlandite (CH), the formation of calcium aluminosilicate hydrate (CASH), and the reduction of porosity in the sample containing free lime and metakaolin.

Copyright of Mineralia Slovaca is the property of State Geological Institute of Dionyz Stur and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Floor heave is a typical tunnel issue in tunnelling engineering. To gain deep insights into the deformation mechanism and failure processes of floor heave at the bottom of a tunnel in layered rock, biaxial step-loading tests were conducted on rock samples (including schist and sandstone) with and without prefabricated invert arches. The failure processes of the samples were observed by the three-dimensional digital image correlation technique (3D-DIC) during the test. The test results showed that the deformation evolution processes of the floor heave of the sample included the following steps: (1) crack initiation at the interlayer weak planes; (2) separation of the rock matrix into platy structures along the bedding planes and flexures; and (3) fracture and uplift of the platy structures in the middle part. As the stress redistributes on the bottom plate of the sample, and stress concentration zones shift toward locations far away from the arching surface, the deformation evolution shows a similar variation trend with the stress. Continuous buckling fracturing takes place progressively from the vicinity of the arch surface to certain distant regions. Based on the test results, the key location of internal surrounding rock deformation was determined, and the mechanism of floor heave was clarified. The schist sample SC-BI-10 began to experience floor heave at 1064.4 s, and the deformation curve (the relationship between Y and U) showed a convex shape in the range of 0–20 mm in the Y-coordinate. The displacement reached its maximum value at y = 11.7 mm, corresponding to the position where the rock slab was broken. In addition, the influence of the interlayer properties and cover depth of rocks on bottom uplift was also studied. The design of tunnel supports and the monitoring and prevention of floor heave can benefit from this study.

The occurrence of tourmaline in the metamorphic complex of the north of Golpayegan is observed within the granitoid mass and schists in contact with granitoid and marbles. Speaking of abundance, tourmaline is less frequently a minor mineral found in granites and granitic pegmatites as well as in low- to high-grade metamorphic rocks (Krmícek et al., 2020). The minerals of the tourmaline group can adjust their composition to adapt to varied settings, and therefore show a remarkable stability range in terms of pressure, temperature, fluid composition, and host rock composition (Van Hinsberg et al., 2011). Since tourmaline displays a negligible intra-crystalline diffusion, it can record the physical and chemical conditions of its setting and preserve this information in geological chronicles. Therefore, tourmaline accurately presents the composition of fluids and the melts from which it crystallized (Marks et al., 2013). Although tourmaline is common in many rocks, it is not common in metamorphosed carbonates (Krmícek et al., 2020). A petrographical and geochemical investigation of tourmalines in the north of Golpayegan was undertaken to know the formation mechanism of this mineral and to determine the differences between tourmalines crystallized at the contact, in granitoid and tourmaline in marbles. Regional Geology The Golpayegan Metamorphic Complex is located in the Sanandaj-Sirjan Zone and the occurrence of tourmaline in this complex is observed in two locations. The first location is on the west side of Ochestan farm where tourmaline is found in three forms: 1) In the granitoid mass (Gt); 2) In the amphibole schists (At) in contact with the granitoid mass, and 3) In the mica schists (Mt) in contact with the granitoid mass. The second area is in the north of Esfajerd where tourmaline occurs inside the marbles (Ct). Methodology With the completion of field reconnaissance and preparation of thin sections, a petrographic study was fulfilled to determine the texture and mineralogy of the minerals, and then, some samples were selected for electron microprobe analysis. Petrography The tourmaline in granitoid mass (Gt), appears as idiomorphic and coarse-grained without any inclusions. Micaschists (Mt) in contact with the granitoid mass are sieve-shaped or spongy. Inside the amphibole schists (At) in contact with the granitoid mass, it is idiomorphic without any inclusions. Tourmaline in marbles (Ct) is fine-grained and blue, which can be observed around biotites with corrosion marks, indicating its reaction with fluid. Tourmaline chemistry The tourmalines in Ochestan granite-pegmatite (Gt) are of alkali tourmaline variety with schorl composition, enriched in aluminum, and points to the replacement of Al in the Y (R2) position. The substitution type of these tourmalines is Al(NaFe+2)-1 owing to the high amount of Fe versus Mg, The tourmalines in amphibole schist (At) are alkali tourmaline with schorl-dravite composition and the tourmalines in mica schist (Mt) are alkali tourmaline with dravite composition, and both types are characterized by insignificant amounts of aluminum. This demonstrates the replacement of Al in the position of Y (R2) has not occurred. Due to the change in Mg and Fe content, the At-type tourmalines benefit from both Al(NaFe+2)-1 and Al(NaMg)-1 substitution varieties. However, the substitutions of Mt-type tourmalines are mainly Al(NaMg)-1 due to the high content of Mg versus Fe. Indeed, Fe+3Al-1 substitution can be observed in both types of tourmaline. Tourmalines in marble (Ct) are of the alkaline type of dravite composition and rich in aluminum, which indicates the replacement of Al in the Y (R2) position. Their substitution is Al(NaMg)-1 due to the high content of Mg versus Fe. Discussion The composition of tourmaline in Gt is of schorl type (Fe/Fe+Mg= 0.89-0.91) and has an aluminum replacement in the Y position. The composition of tourmaline in Mt type is of dravite type (Fe/Fe+Mg= 0.45-0.47) and the composition of tourmaline in At type is of schorl-dravite type (Fe/Fe+Mg= 0.49-0.51), which, replacement of aluminum in the Y position does not occur in both types of tourmaline in schists. Consequently, hydrothermal tourmalines have less aluminum (i.e. At and Mt-type tourmalines), and tourmalines in the granite-pegmatite mass have much more aluminum (i.e. Gt-type tourmalines). Based on the values of Fe# (FeO/FeO+MgO), it is possible to determine the formation site of tourmalines. If the amount of Fe# in tourmaline is >0.8, it indicates the closed magmatic system, lack of fluids interference, and their contamination with Al-rich sediments. Meanwhile, if the ratio is <0.6, it means that boron is metasomatic with sediments rich in Al and also is of an extrinsic origin. The Gt tourmaline samples in the range of Li-poor granitoids and related pegmatites and aplites related to them, the At and Mt tourmaline samples placed in the range of Ca-poor metapelites, metapsammites and quartz-tourmaline rocks not coexisting with an Al-saturating phase. The tourmalines in the marbles of the north Esfajard (Ct) are of dravite type with the ratio of Fe/Fe+Mg= 0.42-0.45. In these tourmalines, both aluminum replacement in the Y position and Al(NaMg)-1 substitution can be observed, which manifests the non-magmatic origin of these types of tourmalines. The Ct-type tourmalines in the range of metapelites and metapsammites coexist with an Al-saturating phase. The postmagmatic/residual-hydrothermal fluids related to alkali syenite magma of the north Esfajard along with the fluids from the progressive metamorphism in micaschists, have developed these tourmalines in marble. The discrepancy in the results of two types of thermometers (thermometry based on the amount of Ti in biotite and Mg-Fe exchange between tourmaline and biotite minerals) in meta-carbonates, highlights that at temperatures >566°C biotite, and lower temperatures, Ct-type tourmaline is composed of biotites. [ABSTRACT FROM AUTHOR]

To develop a more reactive pozzolan for supplementary cementitious materials (SCMs), the co-calcination of kaolinite and limestone was investigated for its contribution to hydration of blended cement. Kaolinite (with ~50 wt% quartz impurity) was calcined at 700 °C, and a mixture of kaolinite and limestone was calcined at 800 °C. These activated SCMs were added to ordinary Portland cement (OPC), replacing ca. 30 wt% of the OPC. The compressive strength of these blended cement paste samples was measured after 28 and 90 days, while the hydration products and microstructural development in these blended cement pastes were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results revealed that adding free lime to OPC, together with metakaolin, led to enhanced compressive strength. The compressive strength of this new blended cement paste reached 113% and 112% of the compressed strength of pure OPC paste after 28 and 90 days of hydration, respectively. Furthermore, this study showed that the improvement was due to the increased consumption of Portlandite (CH), the formation of calcium aluminosilicate hydrate (CASH), and the reduction of porosity in the sample containing free lime and metakaolin. [ABSTRACT FROM AUTHOR]

Landslides constitute one of the recurrent challenges in road infrastructure projects, whose proper management implies significant economic and safety gains. Thus, the prediction of this phenomenon constitutes an important opportunity to better anticipate any corrective or curative action. This work presents the results of a first attempt to propose a susceptibility map on the Taza-El-Hociema expressway (north-east of Morocco) based on five machine learning algorithms (artificial neural networks, random forest, k-nearest neighbors, support vector machines, and XGBoost) while considering 12 geomorphological, geological, neotectonic, and environmental parameters. The results allow an anticipatory mapping of the landslides over 98.00 km and evaluating the importance and contributions of the chosen parameters as inputs, as well as compare the accuracy of the considered algorithms. On average, it turns out that 42.47% of the studied corridor surface presents a medium or important susceptibility, which is mainly related to the topography aspects and the predominantly schistose and marly lithology known for its weathered character. In addition, the comparison of the accuracy indices allowed us to classify the used methods according to their precision while favoring the random forest algorithm, which has a Kappa index of 0.789 and an overall accuracy index of 0.901. Furthermore, the results of this study demonstrate well how selecting optimal machine learning techniques with proper conditioning selection methods can improve landslide susceptibility mapping and modeling. [ABSTRACT FROM AUTHOR]

The purpose of this article is to provide greater clarity on rockfall phenomena and the reasons for their occurrence. Rockfall are gravitational phenomena that occur in rocky terrain with a significant slope of more than 50 degrees. They are characterized by their instantaneous development, the complexity of their prediction and assessment. Rockfalls causes significant damage to buildings and infrastructure, as well as human casualties. This is also the case with the rockfall on the road I-1 Sofia-Botevgrad in the area of the village of Vrachesh at the foot of the Shuntova Chuka hill (652.3 m) in the Bilo Planina Mountain. The rockfall affected part of the electricity transmission network in the area, the road infrastructure and poses a potential danger to people who use the water of the spring at the base of the rock massif. [ABSTRACT FROM AUTHOR]

Determination of the straight down range of geologic formation between geographic latitude 8.30 °N to 9 °N and longitude 3.30 °E to 4.30 °E of the Igbeti schist belt became a thing of interest due to the on-going exploration in the region. Aeromagnetic field intensity anomaly data of the bound were then acquired, separated off regional field and a corresponding residual map obtained was later used applying Werner deconvolution method filtering tool. Three magnetic profiles were selected and labelled for the interpretation on the residual anomalies. The result shows that the depth to magnetic source has a maximum value of 1,000 m toward the subsurface in all the profiles selected, indicating the shallow nature of the magnetic source in the area. Based on the structural index shown, it further reveals solutions for contact and dyke which indicates that there are boundaries which separate rocks from one another and the presence of dyke formation. The implication of identical signature from all profiles is that the marble deposit is relative uniform extending to a great depth in the area. [ABSTRACT FROM AUTHOR]

Failures along cut road slopes are the main inconvenience for commuters and expressway planners as they put the human lives at considerable menace, worsen with monetary losses. Analysis of these vulnerable areas necessitates the evaluation of the suitable material mechanical properties taking into account a rigorous geological setting. The present work exposes the stability analysis of a 60-m-high schistose slope which was investigated to avoid a massive rock failure. Based on pathological field investigations, geological surveys, and a variety of laboratory tests, a finite element 3D simulation using the jointed rock model was chosen to analyze the rock hazard consistency, while several inclinometers were monitored for 6 months to better understand the kinematics of the noticed movement. Firstly, the results indicated a degradation of the mechanical qualities of the upper schistose layer, mainly due to the drainage and the drying-wetting cycle issues. Secondly, it is found that the safety factor taking into account the initial design remains insufficient and that the expressway platform can undergo significant displacements which were confirmed by the inclinometric observations. Finally, it was noted that the Jointed Rock Model offer a realistic representation of the Rifian schist by considering its anisotropic character. This paper recommended scaling, proceeding to the improvement of drainage conditions, and assuring the protection of the cut face. These recommendations would improve the safety factor and limit the displacement of the road platform. [ABSTRACT FROM AUTHOR]

Several physical parameters and anisotropy related to rock textural arrangements, schistosity and weakness planes such as cracks and joints affect the P-wave velocity (VP). First, VP anisotropy of quartz-mica schist as a common type of widespread metamorphic rock was compared with VP anisotropy of jointed homogeneous limestone specimens to clarify effect of these two different types of anisotropies. The results showed that the VP anisotropy of quartz-mica schist texture is stronger than the VP anisotropy of jointed limestone, because all body of quartz-mica schist specimens have VP anisotropy behavior. Many rocks are anisotropic and degree of anisotropy varies from one to another. Various investigations have been carried out on VP anisotropy but there is not a unique comprehensive relation to represent the influence of different degrees of anisotropy on the VP for different rocks. The relation between VP and angle (θ) between the axis of symmetry (perpendicular to weakness planes) with the wave propagation direction was analyzed for a wide range of anisotropy degrees using the results of nine different types of rocks including: Angouran quartz-mica schist, Golgohar mica schist, amphibole schist, mica-quart schist, Marcellus shale, Withby shale WUK47B, WUK70 and WUK2, and Veroia-Polymylos gneiss. A new simple empirical relation fitted to all groups of results was obtained to assess VP for different degrees of anisotropies with a good correlation of determination (R2 = 0.937), low RMSE (RMSE = 320 m/s) and low CV (CV = 7.0%). P wave velocity anisotropy can simply be predicted by the developed relation using only two parameters of VP0 and VP90 or ε that is the percentage change of VP0 with respect to VP90. A VP anisotropy classification diagram was also developed based on the different values of ε. [ABSTRACT FROM AUTHOR]

Clays are used in the general production of earthen tiles. In this study, the production and characterization of earthen tiles from schist, a clayey rock formed by metamorphism of mudstone or shale, was investigated. The impact of tiles on atmospheric temperature through their absorption of the visible, near-infrared and far-infrared wavelength regions is evaluated. In particular, the absorption of ultraviolet and infrared radiation by the tiles was evaluated, as this could have beneficial applications for human health and the environment. UV-A radiation (320-400 nm) is not absorbed by the atmosphere, but schist materials absorb UV-A, which can contribute to melanoma formation (i.e. cancer). Field-emission scanning electron microscopy, X-ray fluorescence spectrometry and X-ray diffraction were used for the analysis of the schist materials. The tile-production stages of schist materials (drying, firing, water absorption rate, etc.) were tested at Hatipoglu Gunes Tile and Brick Industry, Inc. (Turkey). The tiles fired at 950°C and 1000°C comply with the industry standard compressive strength values for fired tiles (when converted to industry production conditions) and were 156.15 and 123.20 kg cm-2, respectively. [ABSTRACT FROM AUTHOR]

Results of influence of mineralogy on physico-chemical and some geotechnical properties of soils developed over granite, schist, and migmatite gneiss around Minna in central Nigeria are presented. A region around Minna was studied to obtain the structure and petrography of the rocks. Three trial pits taken to depths of 5.0, 3.5, and 4.0m were dogged within region of granites, schists, and migmatite gneiss rocks, respectively, all of which belong to Basement Complex of northern Nigeria, to study the mineralogical, physico-chemical, and some geotechnical properties of overburden soils over these rocks. In each of the trial pits, soil samples were collected at interval of 0.5m depths to terminal depths of the pits. X-ray diffraction, index properties, and compaction tests were carried out the samples, and the results were analyzed to determine the influence of mineralogy on physico-chemical and some geotechnical properties of the soils. The result showed that rate of weathering is higher in granite rocks, where primary minerals altered to secondary minerals including smectite minerals. This is followed by overburden over schists, which was observed to alter to secondary minerals like illite and kaolinite. Overburden soil over migmatite gneiss did not showed alteration to secondary minerals but conversion of the carbon element to sodium carbonate salt. Higher fines content, cation exchange capacity, and Atterberg limits, recorded from soils developed over granite rocks, probably resulted from the smectite minerals recorded within this profile. The non-plastic nature of soils, on schist rocks, despite presence of secondary minerals, and judging from the low natural moisture content observed within this profile, indicated that the minerals developed under poor drainage condition. It was therefore concluded that mineralogy of overburden soils over basement complexes and the drainage condition during formation affect their geotechnical properties. [ABSTRACT FROM AUTHOR]

In this study, uniaxial compression testing was carried out to investigate the response of quartz mica schist to water in terms of strength and energy anisotropy. The micromechanism and water action mechanism of the anisotropic properties of the schist were further discussed based on microscopic observations of the rock fabric and analysis of the mineral composition of the solid precipitant after immersion. Mechanical tests reveal that both the failure strength and crack initiation strength of dry schist change in a U shape with the schistose angle; moreover, the strength anisotropy of schist generally increases with increasing immersion time. The specimen with α = 30° has the minimum energies, while that with α = 90° exhibits the maximum total and elastic energies. The total and elastic energies of dry specimens decrease significantly after saturation, but the influence degree of water on the energy of schist differs with the schistosity orientation. The energy response of specimens with α = 30° and 0° to water is more sensitive than that with α = 90°. The internal energy allocation of schist was found to be associated with the schistosity orientation and immersion time. Based on the analysis of microcrack propagation and macro-failure, it is concluded that the fabric of schist plays an essential controlling role in the strength and energy anisotropy. The response of anisotropy to water is closely dependent on the lubrication and disintegration of flaky minerals and the hydraulic action on the tips of voids in response to external compression. [ABSTRACT FROM AUTHOR]

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The exploitation of dimension stones, especially marble, has always been important for Greek economy. In the dimension stone market, granite and schist are also included. However, marble is by far the most important product of the dimension stone market of Greece. An attempt to highlight the trends of the last decade in the market of dimension stones in Greece is attempted. Several factors potentially affecting the demand are also assessed. Domestic demand for dimension stones seems to increase, but this is applied more to the general constructions sector rather than in private dwellings. The production and exports of marble and schist follow increasing patterns since 2011. The domestic market of granite is more complicated, due to the fact that there is no systematic exploitation of granite in Greece, even though the demand and therefore the imports increase steeply since 2017. [ABSTRACT FROM AUTHOR]

Combined laboratory and field research examining the possible alterations caused by herbicide treatments applied to the construction materials (schist and some granite, bound with mortar) in the Roman wall of Lugo (NW Spain), declared a World Heritage site by UNESCO in 2000, was performed in three separate studies in the past 20 years. In the summers of 1998 and 1999, the herbicides glyphosate, sulphosate and glufosinate–ammonium, as well as physical treatments (infrared and burning) were separately applied to different areas of the wall. In the spring of 2016, the oxyfluorfen herbicide Goal Supreme® was applied to test areas. In the winter of 2018, three essential oils, Origanum vulgare L., Thymus zygis Loefl. ex L., and Thymus vulgaris L., were each applied to test areas. Mineralogical modifications in the materials (determined by X-ray diffraction analysis), as well as visible physical changes, such as colour changes, and the appearance of saline residues were evaluated after the treatments. In the 1998/9 trial, glyphosate and both physical treatments triggered changes in the vermiculite clay minerals in the schists, and the physical treatments also caused changes in the kaolinite. None of the treatments caused highly perceptible colour changes. The oxyfluorfen herbicide did not cause any mineralogical alterations in the construction materials, but it did generate an increase in chloride, nitrate and sulphate contents of the granite and a slight darkening of this material. In the most recent study, the only deleterious effect observed was a perceptible increase in lightness and reduction in the yellow component after the application of Thymus zygis Loefl. ex L. essential oil to granite. [ABSTRACT FROM AUTHOR]

Xenolithic structures are considered to be natural defects in the igneous rocks that highly affect their physicochemical and mechanical properties. They are foreign rock fragments trapped in the magma or lava during the cooling process. They are totally unrelated to the igneous rocks, as they compose from different types of rock pieces that enclosed in the monumental granites during their emplacement. This paper aims to study and characterize the xenolith fragment trapped in the studied granitic obelisk. The analytical study was carried out using different techniques such as polarizing microscope, x-ray diffraction, scanning electron microscope, EDS elemental analysis and BET surface area. The results clarified that the studied xenolith fragment is classified as biotite schist xenolith. In addition, it was observed that the xenolith fragment not only affects the aesthetic appearance of the studied granitic obelisk but also it represents a serious weakness point in its structure. [ABSTRACT FROM AUTHOR]

Tourmaline is a common mineral in granites and metamorphic rocks in collisional orogens. This paper describes graphite-bearing, metasomatic tourmalinites in sillimanite-zone schists of the Proterozoic Black Hills Orogen, South Dakota. The tourmalinites bound quartz veins and beyond about 1 m grade into schists with disseminated tourmaline, and ultimately tourmaline becomes only a trace, intrinsic phase in the schists. Next to the quartz veins, tourmaline has almost completely replaced schist minerals, including biotite, muscovite, and plagioclase. The tourmaline is generally anhedral and follows the original foliation direction of the schist. However, tourmaline is euhedral in quartz veinlets cutting through the tourmalinites. Tourmaline is compositionally zoned from having about 22 to 2% of apparent Al occupancy on the Y sites. There are very good negative correlations of Y(Fe2++Mg2+), XCa2+, and YTi4+ with YAl3+, and a very good positive correlation of X-site vacancies with YAl3+. Mg# [molar Mg2+/(Mg2++Fe2+)] is fairly invariant at approximately 0.5, which is somewhat higher than that in the precursor biotite. This is in contrast to tourmaline in the neighboring peraluminous Harney Peak leucogranite where the range of Y site occupancy of Al is small at about 20%, but the Mg# ranges from 0.12 to 0.5. The compositional trends in the metasomatic tourmaline are dominated by the exchange Xo + 4 YAl3+ = XCa2+ + 3 Y(Fe2++Mg2+) + YTi4+. Mass-balance calculations suggest the metasomatizing fluid brought in H+ and B(OH)3 and removed K+, SiO2, and some Fe2+ during tourmalinization. Other elements in the tourmaline largely reflect the bulk composition of the replaced schist. The calculations show that silica in the quartz veins was locally derived, not brought in by the metasomatizing fluid. Interstitial graphite in the tourmalinites shows precipitation of carbon from the methane-bearing fluid. The study demonstrates an important effect of boron transfer by fluids during metamorphism and magmatism in the Earth's crust. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study, comprehensive laboratory experiments, such as thin-section and optical section analyses and P wave velocity and uniaxial compression tests, are performed on three types of quartz mica schist samples. The thin-section analysis reveals that the schist predominately consists of flaky mica and granular minerals, including quartz, feldspar, and calcite. The two types of minerals, both presenting a certain degree of orientation, are arranged to form a quasi-bedded structure as a whole, which essentially leads to macroscopic physicomechanic anisotropy. By means of optical section observation, directional microfissures are found to mainly be distributed alongside the edge of the oriented mica layer, while defects in other parts exhibit irregular orientation. Moreover, quantitative information is extracted from gray images by Image-Pro Plus (IPP), and then, relevant indicators are proposed to quantitatively analyze the differences in the content, morphology, and distribution characteristics of minerals and defects among the three types of samples. P wave velocity measurements of dry cylindrical specimens with different schistosity angles α show that the minimum value lies in the direction of the transverse schistosity planes (α = 90°) and that the P wave velocity increases with the decrease of the schistosity angle. There is an obvious linear positive correlation between the orientation coefficient of mica, which is adopted to indirectly reflect the orientation degree of microfissure, and the 0.5 power of the velocity anisotropy coefficient. The uniaxial compression test of specimens reveals the anisotropic characteristics of the peak strength, failure mode, and crack initiation and propagation for the schist samples. In particular, with the change of the schistosity angle, the peak strength and crack initiation strength have a U shape, characterized by a minimum value at α = 30° and maximum value at α = 0° or 90°. Directional microfissures and irregular defects with a dominant angle control the crack initiation of the specimens with 0° ≤ α ≤ 45° and 45° < α ≤ 90°, respectively. The weak edge of the directional mica layers has a more or less guiding effect on crack propagation when compressive loading is applied obliquely to the schistosity planes, while crack propagation is independent of weak edges when perpendicular to the planes. Three failure modes occur in the specimens with the change of the schistosity angle: tension-splitting failure, shear-slip failure, and shear failure. It is found that the mechanical anisotropy properties of the schist samples are closely associated with the content, morphology, and distribution characteristics of minerals and defects based on the analyses of the macro- and microquantitative data. [ABSTRACT FROM AUTHOR]

Abstract The Tekieh Bala iron index is located in the south east of Kordestan province in Sanandaj- Sirjan geotectonic zone. Exposed rocks at the study area are including granite, gabbro, diorite, quartzmonzonite, quartzmonzodiorite and actinolite schist to chlorite schist.Orebody is located in the fault-beratited zone. Magnetite, hematite, goethite, limonite and pyrite included iron minerals in this index. Epidotization, chloritization, sericitization, actinolitization and silicification are the main alteration around the orebody. Geochemical studies of major and trace elements from the magnetite ore and use of diagrams provided by the various researchers shows that this index placed in group of iron oxide deposits, IOA sub-type and IOCG-type. REE Studies have shown, patterns of these elements, and calculated differential parameters emphasize the similarity of this deposit and IOA-type. Ore forming fluids were formed in differentiation and crystalization of intermediate intrusions rocks as a iron-rich hydrothermal fluids, mixing with the meteoric waters has been led to change in the environmental conditions and deposition of orebody.

Territory Baltic shield is well understood and the identification of innovative geological formations rare stroke of luck. Thanks to the Russian Geographical Society in the summer of 2015 an integrated expedition to study the nature of the little-known islands of the Outer Gulf of Finland was carried out and found, much quartz rocks (SiO2 more than 90%) that compose most part of the island Bolhoy Tyuters. As a result of complex studies including petrogeochemical, microprobe, isotope, thermobarogeochemical investigations and chromatographic analysis of gases, it can be asserted that these rocks are secondary quartzites formed under the influence of carbon dioxide solutions. The presence of shadow structures of migmatites, as well as mineralogical features of quartzites, suggest that the initial rocks, on which secondary quartzites were formed, could be shales of the svecofennian complex. The temperature of homogenization of gas-liquid inclusions is 330-370°C, which indicates a high-temperature facies of secondary quartzites. The age of the dikes of the granite composition, which break through secondary quartzites, is close to 1660 and 1680 million years, which is somewhat older than the main phase of rapakivi granites (1650-1550 my) and coincides with the pre-Riphean weathering era, at the end of which the formation of the largest “type of disagreement” occurred. The formation of secondary quartzites of B. Tyuters, as well as for most classical manifestations of this type, we associate with the fluid-explosive activity of volcanoes preceded of rapakivi granites, whose products, in the form of basic and acidic lavas, were preserved as part of the Early Riphean strata located on the island Hogland. Considering the huge resources of these quartzites (more than 370 million tons), this manifestation is very promising for high purity quartz raw materials, close to the North-Western industrial area and St-Petersburg. The formation of a subhorizontal plane controlling the formation of a deposit of secondary quartzites and Early Riphean sediments and rapakivi granite intrusions, we associate with the tectonic activity of the marginal part of the Baltic Shield, known as the Polkanov lineament.

Acoustic emission (AE) location technique and moment tensor analysis were used to evaluate the temporal–spatial evolution and damage of micro-cracks of schist during true triaxial compression and strain burst tests. The results show that the AE locations coincide with the macroscopic cracks for true triaxial compression while they are scattered during unloading strain burst tests. A shearing concentration occurs at the bottom of ejection position, but a tensile zone is located in the fracture plane of the ejection block. The ratios of shear and mixed-mode micro-cracks to total micro-cracks for true triaxial compression are both larger than those for strain burst. However, the strain burst has more tensile micro-cracks. Additionally, the damage caused by tensile micro-cracks for a strain burst is larger than that for a true triaxial compression. Moreover, for strain burst, the difference of damage between shear and tensile micro-cracks is in direct proportion to the loading rates after unloading. [ABSTRACT FROM AUTHOR]

The anisotropy of schist usually has a complex influence on stability of tunnel surrounding rock. In this study, the schist anisotropy and its variation with the confining pressure are analyzed by the triaxial compression test. Then, geological models of tunnel under typical schistose angles α are established based on the highway tunnel project from Shiyan City to Fangxian County in China. Furthermore, the anisotropic failure mechanism, plastic zone distribution and displacement distribution of surrounding rock are investigated to understand its deformation and failure response pattern to the buried depth of tunnel and variable anisotropy. The results show that increased confining pressure weakens deformation anisotropy and weakly strengthens strength anisotropy of the schist. As the buried depth of tunnel changes from 60 to 140 m, the plastic morphology of surrounding rock with α = 0° presents a similar oval and it has a horizontal development trend. When α = 45°, it shows a spiral sector which has oblique extension as well as the increased angle θ between the long and short axis. While a cap shape with vertical development trend when α = 90°. With the weakening deformation anisotropy of surrounding rock, the anisotropic influence coefficient γ 1 decreases gradually, indicating that schistose plane engenders a diminishing effect on the anisotropic deformation of surrounding rock as buried depth of tunnel increases. [ABSTRACT FROM AUTHOR]

Placing foundation at different or variable levels below ground can easily be dealt with using renowned structural analysis programs which can work out moments and reaction loads. However, these software codes may not be equipped with constitutive models that realistically represent the behavior of specific subsurface formation and geological settings. This work presents a case study for a major education institute with many facilities constructed along the slope line of a Schist formation. Inspection of excavations prior to the placement of foundations was carried out. Driving forces and moments were found to pose a significant risk in some parts of the project site and extra safe conditions at other parts and locations. The geological survey and mapping can be a good tool for verifying the support conditions in rock containing laminations and extra thin layers. Physical and chemical properties provide a guide for better design and construction. Precautions and procedure measures to avoid potential slope failures are addressed and outlined. [ABSTRACT FROM AUTHOR]

Shiyan-Wudang area is located at the junction of South Qinling tectonic belt and Yangtze plate. Its metamorphism can provide important information for Indosinian orogenic process of Qinling orogenic belt. Based on the study of petrology and mineralogy of garnet-bearing schist in Shiyan-Wudang area, the metamorphic conditions were calculated by using garnet-biotite geothermometer and garnet-muscovite geothermometer. The results show that main metamorphism temperatures of metamorphic rocks from south and north parts of Fangtan-Wangjiashan section calculated by garnet-biotite geothermometer are 344 °C-410 °C and 368 °C-431 °C, which are in agreement with lower greenschist facies; meanwhile, main metamorphism temperatures of metamorphic rocks from south and north parts of Shiyan-Damu section calculated by garnet-muscovite geothermometer are 322 °C-440 °C and 535 °C-540 °C, agreeing with lower to higher greenschist facies condition. Combining with regional metamorphism and deformation data, it is suggested that metamorphic evolution of middle- and low-grade metamorphic rocks in Shiyan-Wudang area is related to the subduction-accretion process caused by the closure of ocean in South Qinling tectonic belt during Indosinian, which juxtaposes different grades of metamorphic rocks and makes them uplift together. [ABSTRACT FROM AUTHOR]

The theme of this paper are the Croatian terms for schist – škriljac, škriljevac or škriljavac, and for schistose – škriljav or škriljast. Linguistic and professional sources are not uniformed, so from the aspect of word formation, it is discussed which terms fit into the terminological system the best.