Schist Research Articles

GROUND WATER QUALITY AND ITS IMPACT ON HUMAN HEALTH IN DUNGARPUR DISTRICT OF RAJASTHAN, INDIA

Abstract. Dungarpur, one of the most backward districts of India, is a predominantly tribal region of Rajasthan state. Ground water is the major source of drinking water in the region. High concentrations of Fluoride (F) and Iron (Fe) have been reported in the region which poses high risk of rampant water-borne diseases. This study evaluates the ground water quality for drinking purpose in terms of 10 hydro-geochemical and two biological parameters in context of causative factors like land use and geology of the region. The occurrence of water borne diseases in resident population has been examined in association with quality of drinking water and priority areas for policy intervention have been identified. Water samples have been collected from 173 drinking water sources and 346 households consuming water from the selected sources have been surveyed for prevalence of water borne diseases. Water quality surfaces have been mapped in terms of F, Total Dissolved Solids (TDS), Hardness, Fe, alkalinity, Faecal Coliform (FC), E. Coli, and Water Quality Index (WQI) computed on the basis of 10 geochemical parameters, using Inverse Distance Weighted (IDW) method. Results reveal that the north-eastern part comprising Aspur, Sabla and part of Sagwara tehsils predominantly has ‘very poor’ to ‘unsuitable’ water quality. The western part has excessive faecal contamination. Entire district has high levels of TDS and hardness, while excessive Fe and F occur in specific regions. Disease incidence closely corresponds to the geochemical and microbial composition of water. Higher values of WQI correspond with occurrence of Phyllites and Mica Schists.

Geochemical characteristics and tectonic interpretation of garnet mica schists of Patharkhola area in Kumaun Lesser Himalaya, Uttarakhand Himalaya, India

The Patharkhola area is exposed in the core of the southern limb of the Dudhatoli syncline in the Kumaun Lesser Himalaya. Garnet mica schists of the Patharkhola occur in the folded outcrop pattern being located in between the limbs. They are dominantly composed of garnet, biotite, muscovite, chlorite, plagioclase and a subordinate amount of quartz. Garnet, both xenoblastic as well as idioblastic, is wrapped round by phyllosilicates minerals. These investigated rocks exhibits slightly LREE depleted patterns (LaN/SmN = 0.7, LaN/YbN = 0.64) with flat HREE patterns (SmN/YbN = 0.89). Field evidence along with geochemical characteristics suggests that the Patharkhola schists are peraluminous in nature, showing sedimentary sources having silt to silty clay protolith. They were formed in active continental margins in arc-type setting where the sediments were received both from arc and continental crust.

Microfabric, 3D-strain geometry and kinematic vorticity analysis of Au-bearing shear zone, Central Domain of the Borborema Province, NE Brazil

In the Central Domain of the Borborema Province, mineralized quartz veins type lode-gold deposits (orogenic gold deposits) occur hosted in shear zones. The gold mineralizations are associated with medium-grade metamorphic country rocks, mainly gneisses, and mica schists, consisting of several occurrences and small deposits closely related to the deformational fabric. The Itapetim Shear Zone (ISZ) is one of these shear zones hosting gold mineralizations, which is characterized by heterogeneous and asymmetric deformation fabric. Gold mineralizations occur in laminated quartz veins (shear veins), generally restricted to the innermost portion of the shear zone, extending along the strike for a few kilometers. The microstructures in mineralized quartz veins and mylonitic rocks show evidence of crystal plastic deformation and annealing, indicating that static recrystallization took place after deformation ceased. The strain magnitude, strain symmetry, and kinematic vorticity data show that the shear zone has experienced a deformation history of flattening to plane strain with contributions of both simple (Wm ≥ 0.9) and pure shear (Wm ≤ 0.6) deformation components. It is concluded that the partitioning of kinematic flow contributed to the localized occurrence of mineralized veins preferentially along a segment of the shear zone marked by a dominant simple shear deformation regime.

A Study on the Geological Characteristics and Genetic Types of Dashipo Andalusite Deposit in Yingjiang County, Yunnan Province

The Dashipo andalusite deposit in Yingjiang County, Yunnan Province is taken as an example in this article to discuss the geological characteristics of andalusite ore occurrence and to analyze the genesis of the deposit. The ore body is mainly found in the middle strata of the Upper segment of the Gaoligongshan Group in the Middle Proterozoic (Pt2gl2), with the ore-bearing layers consisting of Andalusite mica schist, Andalusite mica quartz schist, and Andalusite mica quartz schist. The main features of the deposit include its super-large scale, the medium to stable distribution of the ore layer, and the uniform grade changes. Most of the red feldspar in the deposit is composed of self-shaped to semi-self-shaped long columnar metamorphic crystals that are distributed along the schistosity of the ore layer. The ore material has a simple composition with relatively low content of harmful components, making it rare in China. Based on the location of the deposit, characteristics of the ore body, structural features of the ore, mineral associations, and chemical composition of the ore, it is preliminarily believed that the deposit belongs to the regional metamorphic type, which holds great significance for searching for similar types of deposits.

Characterizing rock transverse anisotropic spatial variations using digital drilling

Transverse anisotropy plays an important role in the engineering behavior of rock masses. This study examines the transverse anisotropic spatial variations and evaluates them using the coefficient of variation (CV) and anisotropy index (AI) through digital drilling tests. Four types of rocks, shale (SH), mudstone (MU), sandstone (SA), and schist (SC), are studied in four directions, revealing significant transverse anisotropy at the cutting point. The results demonstrate that the effect of the depth per rotation on the difference is weaker compared to the scaled weight and torque. The ranking of transverse anisotropy in the tested rocks is: MU > SA > SH > SC. Transverse anisotropy changes along the drilling depth vary across rock types. With the increase of drilling depth, SH experiences a decrease, rebound, and another decrease. MU shows an initial increase followed by a decrease. For SA, the degree of transverse anisotropy decreases and is sustained at a lower extent. SC exhibits slight fluctuations with the exception of the abrupt change. The time when the drilling bit is in perfect contact with the rock and the cutting efficiency in different drilling directions are the main factors causing the transverse anisotropy. The intricate evolution of transverse anisotropy should be worth investigating on a wider scale.

Strength and Microscopic Mechanism of Cement-Fly Ash-Slag-Desulfurization Gypsum Solidified Mica Schist Weathered Soil.

Mica schist weathered soil possesses a number of poor engineering characteristics, which make it difficult to use as a subgrade material for resource utilization. Therefore, in this study, a new type of curing agent, CFSD (cement-fly ash-slag-desulfurized gypsum), is proposed for this soil. The effects of different curing agent dosages, age of preservation, and confining pressure on the stress-strain curves were analyzed via the uniaxial compression test and triaxial compression test, while the micromorphological characteristics of cured soil were analyzed via X-ray diffraction analysis and the SEM test combined with Image J software. In this paper, we also establish a microscopic mechanism model to determine how curing agents increase the strength of mica schists. The results reveal that the compressive strength of solidified soil increases rapidly within 28 days; the CFSD dosage of 4% at 7 d increased by 103.23% by 28 d. After 28 d, the trend of compressive strength growth was flat. The CFSD dosage of 4% at 7 d increased by 128.34% by 90 d; with the increase in the dosage, the curve transformed from flat to steep. These results suggest that the CFSD dosage is positively correlated with the damage strain and damage bias stress of solidified soil. The curves for the strain softening type with a 4% dosage as the initial effective confining pressure increased from 50 kPa to 300 kPa; the failure stress and failure strain increased by 202.09% and 90.85%, respectively. With the increase in curing agent dosage and maintenance age, the pore size of 2~5 μm, >5 μm interval decreased from 56.46% to 27.92%, the porosity decreased from 12.51% to 4.6%, and the hydrate produced by the curing agent cemented and filled up the pore space between the loose particles of the soil body. Thus, the large pore space became microporous, and the pore structure densification was greatly improved.

In situ U-Pb dating of rutile and titanite from the Chaihulanzi lode gold deposit, northern North China Craton and its geological significance

The Chifeng-Chaoyang region, located along the northern margin of the North China Craton, is an important gold producer in China, with a proven gold reserve of about 500 tons. Most gold deposits are fault-controlled and formed in the Mesozoic, but the absolute ages of gold mineralization in this region have not been well constrained due to the lack of suitable dating minerals. This study presents in situ U-Pb ages of hydrothermal rutile and titanite for the Chaihulanzi gold deposit and obtains a distinctive age. The Chaihulanzi deposit (∼27 t Au) is located in the western portion of the Chifeng-Chaoyang region and mainly hosted in the carbonaceous mica schist of the Neoarchean-Paleoproterozoic Jianping Group along NW to NWW striking faults. It contains auriferous quartz veins and disseminated ores in hydrothermal alteration zones, with pyrite and pyrrhotite as the predominant ore minerals. Based on field and petrographic observations, four stages of mineralization process can be identified, involving stage I quartz-pyrite, stage II quartz-pyrite-pyrrhotite-chalcopyrite, stage III quartz-polymetallic sulfides, and stage IV quartz-calcite. Stage II represents the main gold stage and contains abundant hydrothermal rutile and titanite, which are intergrown with pyrite, pyrrhotite and native gold. Rutile grains have high contents of V, Nb, Fe, Cr, W and low contents of Zr and yield a Tera-Wasserburg lower intercept age of 285.4 ± 8.5 Ma (n = 37, MSWD = 3.9). Titanite grains show low Th/U and La/Yb ratios (0.03 to 0.66 and 0.26 to 3.98, respectively) and flat chondrite-normalized REE patterns (LREE/HREE = 0.88–5.72, Eu/Eu* = 0.71–1.71), with a Tera-Wasserburg lower intercept age of 282.3 ± 3.4 Ma (n = 20, MSWD = 2.1). Combined with the emplacement age of a post-ore mafic dyke (ca. 275.5 Ma), the timing of the Chaihulanzi deposit can be constrained to Early Permian, representing a new gold mineralization epoch in the Chifeng-Chaoyang region. On the basis of available geological and geochronological evidence, the Chaihulanzi deposit can be classified as an orogenic gold deposit formed during the southward subduction of the paleo-Asian Ocean. These new findings likely have important implications for future regional gold exploration.

Influence of Schistosity Orientation on Failure Mode and Indirect Tensile Strength of Mica Schist

Influence of Schistosity Orientation on Failure Mode and Indirect Tensile Strength of Mica Schist

Evolution of the Palaeozoic mafic-ultramafic Lizard Complex (SW England) from zircon and baddeleyite U-Pb-Hf isotopic constraints: New thoughts on the convergence of Avalonia and Armorica

The Palaeozoic Lizard Complex of southwestern England is composed of a peridotite body with gabbro and intruded by granitic rocks. The peridotites are bounded by amphibolite schists and metasedimentary rocks with those in the southern region also intruded by granodiorite sheets. These granodiorites sheets are coeval with the Man-of-War Gneiss on islets south of the Lizard headland. To the north, the Lizard Complex is in tectonic contact with the Devonian Gramscatho Group. Zircon and baddeleyite U-Pb-Hf isotopic data and zircon REE chemistry presented here provide more accurate resolution of the Lizard Complex's evolution. The Old Lizard Head Series at the southern point of the Lizard headland is intruded by granodiorite bodies with ages of 488 ± 11 and 499 ± 7 Ma, indistinguishable from the 498 ± 11 Ma age for the Man-of-War Gneiss. Thus the rocks bounding the Lizard Complex are interpreted as a Cambrian (Miaolingian or older) volcano-sedimentary and felsic intrusions package. The inital εHf(498Ma) values of the Man O'War Gneiss zircons range from +8.1 to +9; these values fall below depleted mantle estimates and are indicative of some older crustal components in the source region of the gneisses. The Landewednack and Traboe Hornblende Schists bounding the Lizard Complex carry prismatic oscillatory-zoned zircons that have U-Pb ages of ca. 490 Ma (Cambrian) and are interpreted as volcano-sedimentary in origin. Structureless zircons and rims on oscillatory zircon in these schists have U-Pb ages of 390–370 Ma and are interpreted as metamorphic in origin. The Crousa Downs Gabbro was intruded into the Lizard Complex peridotite at low pressure, and relict baddeleyite in it has a U-Pb age of 416 ± 17 Ma (Lower Devonian). The baddeleyite is variably recrystallised to zircon, and separate zircons have a U-Pb age of 393 ± 11 Ma, interpreted as indicating growth of zircon from igneous baddeleyite recrystallisation. The initial εHf(416 Ma) of the zircon grains is +13.4 to +15.6, indicating the gabbro has a depleted mantle source, uncontaminated by older continental crust. The new geochronology demonstrates that the Traboe Hornblende Schists are not genetically related to the Crousa Downs Gabbro, as was proposed in some previous studies. Pyroxene granulite felsic intrusions in the margin of the Lizard peridotite have magmatic zircons with U-Pb ages of 384 ± 11 and 396 ± 9 Ma, agreeing with the previously acquired zircon U-Pb ages on the Kennack Gneiss intrusions in the Lizard Complex. The pyroxene granulite magmatic zircon shows a lack of enrichment in the heavy REE, indicative of initial zircon growth in equilibrium with garnet. Like the Kennack Gneisses, these granulite felsic intrusions carry older inherited zircons, showing that by ca. 395 Ma, the Lizard peridotite and the juvenile Crousa Downs Gabbro were tectonically underlain by older quartzo-feldspathic crustal rocks. Early Palaeozoic inherited zircon in one of the pyroxene granulite sheets has an initial εHf value of ∼ + 8, similar to the Man O'War Gneiss magmatic zircons. The new data from the Lizard Complex are compatible with, and provide additional time constraints for previously expressed models that distal to subduction farther south, the Lizard Complex is part of a narrow, short-lived rift that during extension was invaded by a peridotite diapir and then an early Devonian gabbro intrusion. This rift was then inverted by northerly-directed thrusting starting shortly after 400 Ma, as a Normanian terrane thrust-nappe advanced to override progressively the Devonian Gramscatho Group to the north. Melting deep in the tectonically thickened crust, at least part in the stability field of garnet, had started by 390 Ma. Thus, although the Lizard Complex has some similarities with ophiolites, it is not the remnant of a broad domain of oceanic lithosphere.

Sulfidic schist release of As, Cu, and Pb in laboratory experiments and across eleven watersheds in central Massachusetts, USA.

Sulfidic schists are important rock formations due to their trace metal and metalloid (TMM) content and carry the potential for pyrite and pyrrhotite to hydrate and oxidize leading to acid-enhanced chemical weathering. The objectives of this study were to compare TMMs in sulfidic schists to other co-occurring bedrock, evaluate conditions that optimize TMM rock weathering, and examine streamwater TMMs in relation to bedrock lithology and human development in eleven streams across central Massachusetts. Sulfidic schists samples had the highest As (72 ± 46mgkg-1), Cu (63 ± 21mgkg-1), and Pb (63 ± 33mgkg-1) concentrations. Electron Probe Microanalysis (EPMA) images show As and Pb were widely distributed across silicate and sulfide minerals in both the mica schist and sulfidic schists, not exclusively hosted in sulfide minerals as hypothesized. Batch reactors had TMM dissolution rates an order of magnitude higher for sulfidic schists than granite and mica schists. Furthermore, TMM dissolution was greatest under pH 9 than pH 7 or pH 5 and dissolution rates were two times greater under anoxic conditions compared to oxic conditions. Streamwater concentrations of As (0.01 to 10.3μg L-1), Cu (0.2 to 206μg L-1), and Pb (0.001 to 8.3μg L-1) were below Massachusetts Surface Water Quality Standards. Across the eleven watersheds, % sulfidic schists were positively correlated with mean streamwater S and Cu concentrations and area-normalized annual export. Streamwater As and Pb concentrations were significantly correlated with %Developed land and %Mica schist, which strongly covaried. Our study confirmed the elevated abundance of TMMs in sulfidic schists but laboratory experiments suggest the precipitation of amorphous Fe oxyhydroxide phases decreased dissolved TMMs during oxic weathering. Future work will need to incorporate groundwater and stable isotope systems to separate anthropogenic and geogenic analyses.

Evaluation of asphalt concrete’s fatigue behavior using cyclic semi-circular bending test

Fatigue cracking in asphalt concrete (AC) is one of the major distresses that cause premature failure of flexible pavements. Fatigue tests are often lengthy, cumbersome, and expensive. Therefore, in the performance-related mix-design specifications, some static tests are recommended due to their simplicity. The monotonic semi-circular bending (SCB) test is among the most popular. Even though the SCB test is practical, the actual number of cycles to failure due to cyclic loads cannot be obtained. Implementing SCB testing under cyclic loading conditions for AC performance evaluation could be promising. This study aims to develop a cyclic SCB fatigue testing method. To this end, SCB specimens were produced, and static SCB fracture testing was first conducted to determine the loading levels of the cyclic SCB fatigue test. Then, cyclic SCB tests were conducted by varying load levels to obtain the S-N (stress-fatigue life) curves. To demonstrate the applicability of the proposed framework to differentiate fatigue behavior of mixtures, two AC mixtures were designed and subjected to the proposed protocol, varying the type of aggregate (gneiss and mica schist). Additionally, the S-N curves from cyclic SCB tests were compared to the ones from indirect tensile (IDT) fatigue tests. A considerable similarity in the results between the two approaches (SCB vs. IDT) under cyclic loading was observed, while SCB showed good test repeatability. The SCB configuration with a pre-notch allows fracture mechanics-based testing to monitor the cracking mechanisms and promote rapid cracking evolution, which can reduce testing time.

Multi-Scale Potential Field Data Integration Using Fuzzy C-Means Clustering for Automated Geological Mapping of North Singhbhum Mobile Belt, Eastern Indian Craton

Fuzzy C-Means (FCM) clustering is an unsupervised machine learning algorithm that helps to integrate multiple geophysical datasets and provides automated objective-oriented information. This study analyzed ground-based Bouguer gravity and aeromagnetic datasets using the FCM clustering algorithm to classify lithological units in the western part of the North Singhbhum Mobile Belt, a mineralized belt in the Eastern Indian Craton. The potential field signatures of clusters obtained using FCM correlate remarkably well with the existing surface geology on a broad scale. The cluster associated with the highest gravity signatures corresponds to the metabasic rocks, and the cluster with the highest magnetic response represents the mica schist rocks. The cluster characterized by the lowest gravity and magnetic responses reflects the granite gneiss rocks. However, few geological formations are represented by two or more clusters, probably due to the close association of similar rock types. The fuzzy membership scores for most of the data points in each cluster show above 0.8, indicating a consistent relationship between geophysical signatures and the existing lithological units. Further, the study reveals that integrating multi-scale geophysical data helps to disclose bedrock information and litho-units under the sediment cover.

Kinematics and geochronology of the Lancang metamorphic complex: Implications for the evolution of the Paleo-Tethys region

The Lancang metamorphic complex is a key component of the Three River Tethys Orogen in the SE Tibetan Plateau, with typical rock assemblages and deformation fabrics recording the subduction of the Paleo-Tethys Ocean and subsequent continental collision. In this study, we present new petrographic and structural observations, together with zircon U-Pb and mica 40Ar/39Ar geochronologic data, to reveal the deformation and kinematics of the Lancang metamorphic complex, thus providing insights into the Permian−Triassic evolution of the eastern Paleo-Tethys domain. The subduction of the Paleo-Tethys Ocean and subsequent collision resulted in a range of structural features, including penetrative regional foliations, thrusts, asymmetric folds at various scales, and ductile deformation fabrics such as asymmetric boudins and porphyroclasts. Zircon U-Pb dating of foliated gabbro and 40Ar/39Ar dating of mica schist and mylonite, which preserve shortening fabrics, suggest that the Paleo-Tethys Ocean was subducted during the Late Carboniferous to Permian−Early Triassic, and the collision of the Baoshan and Simao blocks mainly occurred during ca. 237−230 Ma in the SE Tibetan Plateau. Regional deformation likely shifted from shortening to extension ca. 230 Ma, as reflected by post-collision high-K calc-alkaline magmatism. Our results document regional structural patterns and place timing constraints on the evolution of the Paleo-Tethys Ocean.

High-grade iron ores in the laterite weathering crust after the banded iron formation in the Simandou mountain range, Republic of Guinea

In West Africa, in the southeastern Guinea, in the Simandou Range region underlain by the Archean gneiss-granite basement, a north–south synclinorium structure is extended, that is composed of the Lower Proterozoic series of metamorphic rocks. A thick sequence of the banded iron formation (itabirites) with interlayers of phyllites and mica schists is exposed in cores of the synclines. According to their composition, the itabirites are subdivided into quartz-magnetite and amphibole-quartz-magnetite varieties. High-grade iron ores (60–66% Fe) formed in a pseudomorphic manner after the itabirites in the Cenozoic lateritic weathering crust. At the North Simandou, Zogota, and Pic-de-Fon deposits, the rich ores compose mantle-shaped orebodies up to 150–350 m deep. The orebodies possess the following vertical zonality: primary magnetite itabirites – martitized itabirites – quartz-martite friable ore – martite friable ore and martite–limonite friable ore – goethite-hematite friable to solid ore – deluvial limonite ore (kanga and cuirass). All the types of the high-grade ores are dominated by hematite. The rich iron ores were formed from itabirites as a result of the oxidation of magnetite to martite, the almost complete removal of silica, and the subsequent additional supply of iron and its precipitation in the form of hydroxides. During the formation of the iron ores, kaolin clays and bauxites were formed after the phyllite interlayers.

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.

Quantitative Evaluation of the Fracturing State of Crystalline Rocks Using Infrared Thermography

The fracturing state of rocks is a fundamental control on their hydro-mechanical properties. It can be quantified in the laboratory by non-destructive geophysical techniques that are hardly applicable in situ, where biased mapping and statistical sampling strategies are usually exploited. We explore the suitabilty of infrared thermography (IRT) to develop a quantitative, physics-based approach to predict rock fracturing starting from laboratory scales and conditions. To this aim, we performed an experimental study on the cooling behaviour of pre-fractured gneiss and mica schist samples, whose 3D fracture networks were reconstructed using Micro-CT and quantified by unbiased fracture abundance measures. We carried out cooling experiments in both controlled (laboratory) and natural (outdoor) environmental conditions and monitored temperature with a thermal camera. We extracted multi-temporal thermograms to reconstruct the spatial patterns and time histories of temperature during cooling. Their synthetic description show statistically significant correlations with fracture abundance measures. More intensely fractured rocks cool at faster rates and outdoor experiments show that differences in thermal response can be detected even in natural environmental conditions. 3D FEM models reproducing laboratory experiments outline the fundamental control of fracture pattern and convective boundary conditions on cooling dynamics. Based on a lumped capacitance approach, we provided a synthetic description of cooling curves in terms of a Curve Shape Parameter, independent on absolute thermal boundary conditions and lithology. This provides a starting point toward the development of a quantitative methodology for the contactless in situ assessment of rock mass fracturing.

Landslides Triggered by the 2016 Heavy Rainfall Event in Sanming, Fujian Province: Distribution Pattern Analysis and Spatio-Temporal Susceptibility Assessment

Rainfall-induced landslides pose a significant threat to the lives and property of residents in the southeast mountainous area. From 5 to 10 May 2016, Sanming City in Fujian Province, China, experienced a heavy rainfall event that caused massive landslides, leading to significant loss of life and property. Using high-resolution satellite imagery, we created a detailed inventory of landslides triggered by this event, which totaled 2665 across an area of 3700 km2. The majority of landslides were small-scale, shallow and elongated, with a dominant distribution in Xiaqu town. We analyzed the correlations between the landslide abundance and topographic, geological and hydro-meteorological factors. Our results indicated that the landslide abundance index is related to the gradient of the hillslope, distance from a river and total rainfall. The landslide area density, i.e., LAD increases with the increase in these influencing factors and is described by an exponential or linear relationship. Among all lithological types, Sinian mica schist and quartz schist (Sn-s) were found to be the most prone to landslides, with over 35% of landslides occurring in just 10% of the area. Overall, the lithology and rainfall characteristics primarily control the abundance of landslides, followed by topography. To gain a better understanding of the triggering conditions for shallow landslides, we conducted a physically based spatio-temporal susceptibility assessment in the landslide abundance area. Our numerical simulations, using the MAT.TRIGRS tool, show that it can accurately reproduce the temporal evolution of the instability process of landslides triggered by this event. Although rainfall before 8 May may have contributed to decreased slope stability in the study area, the short duration of heavy rainfall on 8 May is believed to be the primary triggering factor for the occurrence of massive landslides.

Petrology and Geochemistry of Carbonate Metasediments from Pindwara-Aburoad Belt in the Southern Part of South Delhi Terrane: Implications for Protolith, Provenance and Tectonic Setting

Abstract The carbonate metasediments of Pindwara-AbuRoad Belt (PARB) in the Sirohi district belongs to the Kumbhalgarh Group of the South Delhi Terrane (SDT). The litho-assemblages associated are quartzite, carbonate, mica schist, phyllite, metavolcanics, and granitoids. The present study is made on impure marble and calc-silicates of the study area. The carbonates show mineralogical variations with indiscernible field boundaries. The carbonates composed of calcite, diopside, hornblende, tremolite, actinolite, biotite, muscovite, epidote, quartz, plagioclase with minor proportion of apatite, sphene, garnet, sericite, kyanite, zircon, opaque, and broadly may be termed as calc-silicates. The mineral chemistry, major, trace elements, and REE geochemistry of the carbonates reveal the nature of protolith, provenance, depositional environment, spatial and temporal constraints on metamorphism, and on going tectonic process. The study suggests that the PARB carbonate metasediments were derived from a varied proportion of terrigenous and quartzo-feldspathic felsic provenance and deposited in less saline shallow marine environment in an intracontinental rift setting. These exhibit amphibolite to green-schist facies metamorphism, accompanied by polyphase deformation. The metasediments of the region indicate the Meso-Neoproterozoic transition during the Delhi Orogeny in SDT.

Reworked Neoproterozoic sub-arc lithosphere beneath the Eastern Desert (Egypt): Evidence from geochemistry and geochronology of metabasites and granitoid gneisses, Gabal Um Gunud area

ABSTRACT High-grade granitoid gneisses (740–710 Ma) and elongate bodies of amphibolite and hornblende schist with cm-scale layers of garnet pyroxenite form an overturned fold in the Gabal Um Gunud area, South Eastern Desert of Egypt. Whole-rock geochemical data combined with zircon U-Pb-Hf isotope data suggest that the metabasites represent relics of oceanic crust with an N-MORB affinity, which has been derived from partial melting (2.0–1.4 GPa; ~65- ~ 45 km depth) of a depleted mantle source beneath an intra-oceanic, spreading forearc basin. Such increment of melting degree resulted in small basaltic melt batches with transitional tholeiitic to boninitic affinities. Progressive slab subduction and partial melting of the tholeiitic amphibolite produced high-Al and low HREE melts for trondhjemite at av. T = 854°C and low-Al and high HREE melts for tonalite at higher temperatures (av. 949°C). The low Mg# of the trondhjemite-tonalite rocks may be attributed to limited contamination of subduction components, as evidenced by the weak lanthanide tetrad effects (TE1,3~1) and near-chondritic Zr/Hf, Nb/Ta, and Y/Ho ratios, while the garnet pyroxenite was the residuum produced in equilibrium with the trondhjemite-tonalite melts.

Hydrogeochemical Assessment of Groundwater Quality and Geological Influence in Igarra and environs, Southwestern Nigeria

The impact of Geology on groundwater is not fully appreciated in many Nigerian groundwater quality literature. This study investigates the influence of Geology on the hydrogeochemical makeup of groundwater in Igarra and environs, Nigeria. Igarra and environs is underlain by metasediments intruded by Pan African Granites. Ten water samples were collected and analyzed in the laboratory to determine their chemical composition. The results revealed that the pH of most samples was slightly acidic to mainly alkaline, with high electrical conductivity (EC) and total dissolved solids (TDS) values. Correlation and regression analyses showed that the TDS, EC, salinity, chemical oxygen demand, dissolved oxygen, and major and minor constituents positively influenced the pH of the groundwater. Hierarchical cluster analysis demonstrated that the water samples had different compositions and concentrations based on local geological influences. The water samples from Granite, Quartzites, Migmatites and Gneiss rock types shared similar characteristics and had a lower concentration of minerals than the water samples taken from the Quartz Mica Schists and Metaconglomerates. The water in Igarra was predominantly Magnesium Bicarbonate type. However, some of the water samples exceeded the drinking standards for TDS, EC, Cl, Fe, Cr, Cd, and Pb. The study recommends the inclusion of biological parameters to gain a clearer picture of the water quality, particularly from the anthropogenic point of view.