Predominant Rock Research Articles

Morphotectonic Analysis in the Sombe Lewara Sub-Watershed in the Region of Palu City and Sigi Regency, Central Sulawesi Province

A study on the tectonic activity index (IAT) was conducted in the Sombe Lewara Sub-Watershed, encompassing the area of Palu City and Sigi Regency, Central Sulawesi Province. The objective of this research was to determine the level of tectonic activity in the Sombe Lewara Sub-Watershed. The analysis employed in this study was morphotectonic analysis, utilizing parameters such as Hypsometric Integral (HI), Basin Shape (BS), Asymmetry Factor (AF), Stream Length-gradient Index (SL), Area Factor (AF), and Valley floor width-to-height ratio (Vf ratio). The tectonic activity index (IAT) value in the Sombe Lewara Sub-Watershed was 1.6, which classifies it within the high tectonic activity category. This high level of tectonic activity in the research area influences the landscape conditions and the types of rocks present. The predominant rock types in the study area are sedimentary rocks such as conglomerate deposits, sandstone, siltstone, and claystone. These rocks form the character of an expansive alluvial fan landscape that nearly covers the entire plain. One of the primary factors contributing to liquefaction in the Balaroa Region is that the area is composed of sand sediment deposits and granite boulders that constitute the alluvial fan.

Deep Sandstone Reservoir Characteristics and Pore Structure Classification Based on Fractal Theory: A Case Study of the Bayingobi Formation in Guaizihu Sag, Yin'e Basin.

The paper focuses on deep oil and gas resources in the Bayingobi Formation of Guaizihu Sag in the Yin'e Basin. Previous studies overlooked the differences between the pores and throats, mainly focusing on pore analysis. This work aims to analyze the pore structure and petrophysical properties of the reservoir using various methods. The study utilized the constant velocity mercury intrusion method to quantify pores and throats separately. Scanning electron microscopy and casting thin section techniques characterize the pore and throat morphology. The analysis compares the pore structures in reservoirs with different petrophysical properties. Additionally, pore and throat types are classified based on fractal dimensions, and factors influencing their development are discussed. Results reveal feldspar lithic sandstone as the predominant rock type with a low compositional maturity. The sandstone reservoirs exhibit low porosity (10.23%) and ultralow permeability (0.99 mD). Primary reservoir pore spaces include intergranular pores, dissolution pores, and microfractures. Pore radius averages at 195.32 μm, while throat radius is 3.76 μm. Pore structures are categorized as micropore small-throat, small-pore small-throat, and large-pore coarse-throat types. The study area generally exhibits a high pore-to-throat ratio, impacting reservoir petrophysical properties significantly. Pore development is primarily influenced by early diagenesis, organic acid dissolution, and hydrocarbon filling. Weak compaction and cementation transformations provide a material and spatial basis for the subsequent dissolution. The presence of thick organic-rich mudstone above and below the reservoir contributes to organic acid dissolution and hydrocarbon filling.

Experimental characterization of damage during geothermal production of hot dry rocks: Comprehensive effects of the damage-elastic deformation on conductivity evolution

The development of hot dry rocks (HDRs) is of great significance to adjusting energy structure, alleviating energy shortage, reducing pollution, etc. Low-permeability granite is the predominant rock type in deep HDRs, making fractures the primary pathways for fluid circulation and heat extraction. The production of HDRs is significantly influenced by variable fracture conductivity, but current conductivity characterization primarily relies on the elastic deformation of the matrix, neglecting the impact of damage. Accordingly, we propose an experimental method and a supporting apparatus, which is used to unveil the conductivity evolution characteristics resulting from the comprehensive effects of damage and elastic deformation. The experimental results demonstrate that when subjected to confining force squeezing inward, the fracture conductivity experiences varying degrees of decrease compared to its initial state before the experiment. By utilizing the conductivity evolution rate as the evaluation criterion and conducting grey correlation analysis, it has been determined that temperature exerts the most significant influence on the conductivity evolution, followed by injection flow, and lastly, confining pressure. Moreover, rock particle types and production cycles also have different degrees of effect. After considering the comprehensive effects of damage-elastic deformation at the field-scale, the damage has a positive effect on conductivity enhancement. Our study provides a new approach for the characterization of fracture conductivity evolution for deep geothermal projects.

Analysis of the Morphology and Lithology of the Kisangani–Yangambi Section of the Congo River in the Democratic Republic of Congo

Vol. 19, Issue 1, 2024: 59–80 DOI: 10.15170/MG.2024.19.01.0459 Mawa Mukulia, Prométhée1 – Katembo Kasekete, Désiré2 – Makabu Kayembe, Gabriel3 – Muhindo Sahani, Walere 4 – Kahindo Muhongya, Jean-Marie5 Analysis of the Morphology and Lithology of the Kisangani–Yangambi Section of the Congo River in the Democratic Republic of Congo 6 ABSTRACT The Congo River, which is between 900 and 300 metres wide between the city of Kisangani and the town of Yangambi, is characterised by important socio-economic and conservation activities but also by a lack of knowledge on morphological and lithological matters. To fill the gaps, the lithology and the morphological dynamics of the riverbed were studied through a description of islands (between 1984 and 2017) and banks thanks to remote sensing and field work, respectively. With regard to the number of islands, the study revealed a loss of 5.13% and a recovery of 28.21% between 1984 and 2017. The direct factors of this dynamism are the erosion and landslides observed both on the banks and on the islands. The geological survey method allowed the collection of 4 samples of sound indurated rocks and 50 samples of loose rocks on the soil profiles of the islands and banks. The macroscopic description and sieving of the samples with 63 mm and 2 mm mesh size allowed the lithology map to be drawn up. The fine soil particles were analysed in the soil laboratory using the Robinson–Köhn pipette method to determine their texture. The USDA textural classification was used. The results of the analysis showed that sand is the predominant rock element in the area. Such a lithology would increase the sensitivity of the banks to mass movements observed here and there along the Kisangani–Yangambi river section.

Synthesis, Structural and Electrochemical Investigation of Disordered Rock Salt Compounds Based on Ni and Ti

Li-ion batteries achieved in the last 3 decades extremely high energy densities, making them the energy storage devices of choice for the electrification of our society. Despite this improvement, their energy density is still low as compared to gasoline, motivating further research towards materials with better performances. State of the art positive electrodes are nowadays layered materials with a ratio Li:M of 1:1, with M being one or multiple transition metals. Disordered rock salt (DRX) materials without a layered structure were thought to be electrochemically inactive. With the development of the percolation theory, 1(Urban, Lee, and Ceder) it was demonstrated that lithium-rich materials (Li:M>1) with a cation disordered rock-salt structure (DRX) can achieve high reversible specific capacities. The general formula of these lithium-rich compounds can be written Li1+y(MM′)1−yO2 where the Li content ranges usually from 1.05 to 1.33, essential to promote Li percolation pathways. With M is indicated a redox active specie (Mn, Ni, Fe, Cr, V) and M’ is typically a d0 element, which is redox inactive during charge and discharge and therefore stabilizes the disordered structure and acting as charge compensator.2 (Chen, Ahn, and Chen)In this work a class of Li-rich compounds with the chemical composition Li2yNiyTi2-3yO2 has been investigated (y = 0.50, 0.55, 0.60, 0.67). These samples were prepared via solid-state reaction at three different temperatures (700 °C, 800 °C, 900 °C). X-ray diffraction has been used to determine the crystal structure of the samples, revealing a predominant rock salt-type phase. However, by decreasing the synthesis temperature and increasing the Li content, phase separation occurs into a rock salt-type and a Li2TiO3 phase. The synthesis has been also verified by DFT and by in situ X-ray diffraction. Neutron diffraction experiment have been carried out to fully understand the cationic distribution in the samples. Finally, the electrochemical performances of the samples have been investigated in Li half cells, revealing a strong voltage hysteresis between charge and discharge.3 (Li et al.) Bibliography Urban, Alexander, Jinhyuk Lee, and Gerbrand Ceder. “The Configurational Space of Rocksalt-Type Oxides for High-Capacity Lithium Battery Electrodes.” Advanced Energy Materials 4, no. 13 (September 2014): 1400478. https://doi.org/10.1002/aenm.201400478.Chen, Dongchang, Juhyeon Ahn, and Guoying Chen. “An Overview of Cation-Disordered Lithium-Excess Rocksalt Cathodes.” ACS Energy Letters, March 17, 2021, 1358–76. https://doi.org/10.1021/acsenergylett.1c00203.Li, Biao, Khagesh Kumar, Indrani Roy, Anatolii V. Morozov, Olga V. Emelyanova, Leiting Zhang, Tuncay Koç, et al. “Capturing Dynamic Ligand-to-Metal Charge Transfer with a Long-Lived Cationic Intermediate for Anionic Redox.” Nature Materials 21, no. 10 (October 2022): 1165–74. https://doi.org/10.1038/s41563-022-01278-2

ASTER VNIR‐SWIR Based Lithological Mapping of Granitoids in the Western Junggar Orogen (NW Xinjiang): Improved Inputs to Random Forest Method

AbstractAlthough advanced spaceborne thermal emission and reflection radiometer multispectral analysis for lithological mapping has been widely applied, traditional methods such as band ratios (BR) and principal component analysis (PCA) are still hampered by cumbersome data processing and poor classification performance. In this study, we utilize improved data inputs for random forest (RF) to extract lithological information of granitoids, which are the predominant rock type for intrusion‐related polymetallic ore deposits in the western Junggar Orogen (NW Xinjiang). Based on spectral absorption features of minerals (e.g., orthoclase, K‐feldspar, hornblende, biotite, plagioclase, and oligoclase), image statistical information and textural features, we tested different combinations of bands, BR, PCA, and texture using RF method, and found that the combination of B13678 + T1 (Mean texture) achieved the highest weighted‐F1 score for granitoids, with an accuracy of 87.32%. Compared to the support vector machine, RF effectively distinguishes lithological differences between different types of granitoid and wallrocks, especially the granite, granodiorite, and alkali granite in the Akebasito intrusion, as well as the alkali granite, plagiogranite and biotite granite in the Karamay intrusions. Moreover, the large number of rare metal deposits (including Cu, Au, Mo, etc.) distributed near the granitoid intrusions in the western Junggar, our result facilitates the analysis of regional tectonic evolution and mineralization controlling.

Lithology-Controlled Hydrodynamic Behaviour of a Fractured Sandstone–Claystone Body in a Radioactive Waste Repository Site, SW Hungary

The fracture network modelling and hydrogeological assessment were performed in an 845 m deep borehole of the potential high-level waste repository formation and its caprock. The geometry of the fracture network was simulated using the discrete fracture network (DFN) modelling method, which is based on the geometric characteristics of the individual fractures. The hydrogeological evaluation was based on changes in porosity and permeability along the borehole using flow zone indicator (FZI) values that denote hydraulic flow units (HFU) within the rock body. Fracture network characteristics and hydrogeological features are mainly determined by the wellbore lithology, which can be divided into three zones. The sandstone body was intersected in the upper 300 m of the borehole, which forms a single HFU. The second zone was developed along with the transition zone between the sandstone and the underlying claystone bodies. Here the predominant rock type is claystone, but the characteristics of the fracture network are distinctly different from the deeper parts of this rock body. Below 400 m is the third zone, where distinct and extensive HFU-s could not form, probably due to different water–rock interaction processes that could have changed the porosity and permeability from point to point in the claystone.

Basement geology and its controls on the nucleation and growth of rift faults in the northern Campos Basin, offshore Brazil

AbstractThe rift phase of the Campos Basin developed during the Early Cretaceous on a heterogeneous crust comprising structures inherited from the Brasiliano‐Pan African tectonic events, mostly generated during the Neoproterozoic‐Cambrian amalgamation of western Gondwana blocks. The main rifting episode took place from the Hauterivian to the Barremian, then was succeeded by the transition and post‐rift (SAG) phases during the Aptian. Rift faults developed as a result of a progressive rotation of extension from E‐W to NW‐SE. The role of pre‐existing intra‐basement structures on the style and evolution of the rift faults was investigated using 3D high‐resolution seismic data, borehole logs and sidewall samples. Three seismic facies (SF1, SF2 and SF3) and three types of intra‐basement structures (Surfaces, Geobodies and Internal Reflections) were identified and mapped. They represent, respectively, contrasting levels of seismic anisotropy, interpreted as metamorphic foliation, and ductile shear zones that bound rock units with particular seismic facies signatures. Sidewall cores show that banded biotite‐gneiss is the predominant rock type in the eastern half of the study area, while more homogeneous granitoid is the dominant lithology on the west. Such a binary division of lithotypes is consistent with the distribution of mapped intra‐basement seismic facies and features. The contrasting basement heterogeneity across the study area is the major control in the strain distribution during rifting. Where the basement is highly heterogeneous, the pre‐existing fabric was selectively reactivated whenever its orientation was favourable, resulting in faults forming progressively as the extension direction rotates, whilst shallower low to very low angle basement fabric were cross‐cut by rift faults. Where the basement is homogeneous, only early formed faults remain active throughout the rifting.

Terrace formation and preservation: Santa Catalina Island and other California Channel Islands

ABSTRACT Uplifted coastal terraces are present on Santa Catalina Island, but so poorly preserved that researchers have debated for more than a century whether they even exist. Morphometric analyses of LIDAR-based topography on the California Channel Islands suggest that the poor expression of terraces on Catalina Island is due a combination of (1) geological conditions less conducive to terrace formation than on the other Channel Islands and (2) high landslide susceptibility around Catalina’s coastal margin that is erasing terrace morphology and deposits before they can reach the island's relatively un-dissected interior. Both of these factors seem to be related to the mechanical properties of the island’s predominant rock type, the Catalina Schist. Several of the other Channel Islands – such as Santa Barbara, San Clemente, Anacapa, and San Miguel Islands – have topography that is dominated by their terrace morphology, mostly by virtue of the small size of those islands. Of the large islands, Santa Rosa has the most extensive terraces, apparently driven by the prevalence of shallowly dipping sedimentary rock. Looking at terrace preservation generally, subhorizontal sedimentary units seem to represent an optimum between promoting the initial creation of wide terrace platforms and resistance to terrace erosion thereafter.

The Syenite–Carbonatite Complex of Ihouhaouene (Western Hoggar, Algeria): Interplay Between Alkaline Magma Differentiation and Hybridization of Cumulus Crystal Mushes

The 2 Ga-old Ihouhaouene alkaline complex (Western Hoggar, Algeria) is among the oldest known carbonatite occurrences on Earth. The carbonatites are calciocarbonatites hosted by syenites, the predominant rock type in the complex. Both rock types are characterized by medium-grained to pegmatitic textures and contain clinopyroxene, apatite, and wollastonite, associated with K-feldspar in syenites and a groundmass of calcite in carbonatites. The rock suite shows a continuous range of compositions from 57–65 wt.% SiO2and 0.1–0.4 wt.% CO2in red syenites to 52–58 wt.% SiO2and 0.1–6.5 wt.% CO2in white syenites, 20–35 wt.% SiO2and 11–24 wt.% CO2in Si-rich carbonatites (>10% silicate minerals), and <20 wt.% SiO2and 24–36 wt.% CO2in Si-poor carbonatites (<5% silicate minerals). Calculation of mineral equilibrium melts reveals that apatite and clinopyroxene are in disequilibrium with each other and were most likely crystallized from different parental magmas before being assembled in the studied rocks. They are subtle in the red syenites, whereas the white syenites and the Si-rich carbonatites bear evidence for parental magmas of highly contrasted compositions. Apatite was equilibrated with LREE-enriched (Ce/Lu = 1,690–6,182) carbonate melts, also characterized by elevated Nb/Ta ratio (>50), whereas clinopyroxene was precipitated from silicate liquids characterized by lower LREE/HREE (Ce/Lu = 49–234) and variable Nb/Ta ratios (Nb/Ta = 2–30). The Si-poor carbonatites resemble the Si-rich carbonatites and the white syenites with elevated REE contents in apatite equilibrium melts compared to clinopyroxene. However, apatite equilibrium melt in Si-poor carbonatite shows a majority of subchondritic values (Nb/Ta<10) and clinopyroxene has chondritic-to-superchondritic values (Nb/Ta = 15–50). Although paradoxical at first sight, this Nb-Ta signature may simply reflect the segregation of the carbonatite from highly evolved silicate melts characterized by extremely low Nb/Ta values. Altogether, our results suggest an evolutionary scheme whereby slow cooling of a silico-carbonated mantle melt resulted in the segregation of both cumulus minerals and immiscible silicate and carbonate melt fractions, resulting in the overall differentiation of the complex. This process was however counterbalanced by intermingling of partially crystallized melt fractions, which resulted in the formation of hybrid alkaline cumulates composed of disequilibrium cumulus phases and variable proportions of carbonate or K-feldspar.

The Influential Factors and Characteristics of Tight Sandstone Gas Reservoir: A Case Study in Ordos Basin in China

To analyze the impact of the factors on physical properties and the mechanism of tightness as well as favorable accumulation space of tight sandstone reservoir, comprehensive analysis is conducted using various kinds of experiments. The results show that the predominant rock type is medium-coarse grained lithic quartzarenite, and the main accumulating space is the dissolved secondary pores. Reservoir pore-throat structures can be divided into four categories. Based on morphologies and parameters which derived from capillary pressure curves, the physical properties rank in the following descending sequence: Type I > Type II > Type III > Type IV . The reservoir quality is influenced by both sedimentation and diagenesis synthetically. The underwater distributary channel is the dominant space for favorable reservoir. Compaction and cementation play dominant roles in the reduction of permeability. The loss of primary pores caused by both those diagenesis are 20.52% and 16.91%, respectively. Secondary pores formed by dissolution improve the reservoir quality by increase the porosity (2.68%). This suggests that weak diagenesis greatly contributes to the improvement of reservoir quality.

At the crossroads of the Lesser Caucasus and the Eastern Pontides: Late Cretaceous to early Eocene magmatic and geodynamic evolution of the Bolnisi district, Georgia

The Bolnisi district is a distinct tectonic zone of the Lesser Caucasus, which is considered to represent the eastern extremity of the Turkish Eastern Pontides. Late Cretaceous, low-K, calc-alkaline to high-K rhyolite of the Mashavera and Gasandami Suites is the predominant rock type of the district, and is accompanied by subsidiary dacite, and rare high-alumina basalt and trachyandesite of the Tandzia Suite. The Mashavera and Gasandami rhyolite and dacite have yielded U-Pb LA-ICP-MS and TIMS zircon ages between 87.14 ± 0.16 and 81.64 ± 0.94 Ma, which are in line with the Coniacan-Santonian ages of radiolarian fauna of the Mashavera Suite. The felsic rocks of the Mashavera and Gasandami Suites were deposited during a ~6.6 m.y.-long silicic magmatic flare-up event, which together with the Tandzia Suite mafic rocks, documents Late Cretaceous bimodal magmatism in an extensional tectonic setting. Trace element data indicate that high Y-Zr, low- to high-silica rhyolite and dacite, and low Y-Zr high-silica rhyolite have been erupted, respectively, from coeval deep and shallow crustal reservoirs. The rocks of the bimodal magmatic event are overlain by high-K volcanic rocks of the Campanian Shorsholeti Suite, which have been erupted during slab roll-back and steepening, from magmas produced by deep melting of a metasomatised mantle. Eocene postcollisional felsic intrusions crosscut the Late Cretaceous rock.The Coniacian to early Campanian bimodal magmatism, and the subsequent high-K magmatism of the Bolnisi district are contemporaneous and share geochemical characteristics with the Late Cretaceous magmatism of the Eastern Pontides. It documents the existence of a Late Cretaceous regional silicic magmatic province, and subsequent high-K magmatism during slab steepening. This regional magmatic evolution coincided with the opening of the Black Sea and the Adjara-Trialeti basins. This evolution was coeval with the wanning stages of northern Neotethyan subduction, after a ~40 m.y.-long magmatic lull along the southern Eurasian convergent margin. Early Eocene adakite-like magmatism affected both the Bolnisi district and the Eastern Pontides, demonstrating a common postcollisional magmatic evolution.

Visual Inspection of Geological Maps: an eye-tracking Study

Abstract. The paper describes the analysis of a visual inspection of paper geological maps by three groups of participants: geologists (GEOL), geographers (GEO) and geoinformaticians (GIS). The aim of the study was to identify the differences in how different groups of participants visually inspected geological maps.Geological maps show the distribution of different types of rock at the earth’s surface and are a fundamental tool for geologists. Geology as a distinct discipline is relatively young, and its origins date to the eighteenth century. In recent years, this otherwise relatively stable field has begun to incorporate new technology into its tools and methods. No study as yet has been published to assess geological maps using eye-tracking or cognitive cartography.Eye-tracking glasses SMI Eye Tracking Glasses 2 with a recording frequency of 60 Hz were used to record the eye-movements of participants during the experiment. Two maps at a scale of 1 : 25 000 produced by the Czech Geological Survey were used for the eye-tracking experiment. In the first part of the experiment, free viewing was analyzed. In the second part, participants solved six tasks with a map. The tasks were selected based on consultation with employees of the Czech Geological Survey.In the free viewing section, noticeable differences between groups were observed. The free viewing section revealed that the geoinformaticians group concentrated much less on the map itself and spent more time on the surrounding elements. The geographers and geologists mainly focused on the map field. The second part of the experiment comprised six tasks.The first task was the simplest and involved finding the coordinate system used in the map. The task caused no problems in any group, and completion times were balanced. The GIS group demonstrated the greatest experience in reading maps and was also the quickest to solve the task. The second task was to identify the geological units depicted in the map. The correct answer could be obtained either from the legend or by using the scheme of geological units. No statistically significant differences in time between the groups were recorded. In the third task, respondents were required to identify and mark the boundary between two geological units found in the previous task. The group of geologists was quickest to solve this task, and all other respondents found a solution with no great difficulty. The fourth task was to identify the predominant rock and determine its type according to the legend. The results suggest that ten respondents from GEO and GIS groups who concentrated on the lithostratigraphic scheme did not know where to look for the correct answer. In the fifth task, participants were required to mark an area with multiple landslides. The aim in this task was to find the landslide symbol in the legend and then identify the landslide area on the map. The differences between groups were most apparent in this task. The geologists were significantly quicker in finding the symbol in the legend. The other groups needed a much longer time to identify the symbol in the legend. In the final task, respondents were instructed to identify the predominant rock in the area with the highest amplitude of geomagnetic anomalies. To solve this task, using the diagram in the section at the bottom left was necessary. The GEOL group spent the least amount of time completing this task, indicating the respondents’ knowledge. The experiment and subsequent interviews revealed a different color reading strategy. When identifying a rock, the GEOL group compared colors mainly for quick orientation. However, the decisive factor for identification was the index, which was given for the rock in the map and legend.To conclude, the geologists group was quickest in solving the tasks and recorded the least wrong answers. The GIS and GEO groups achieved similar results in the experiment.

Localisation of the brittle Bathurst fault on pre-existing fabrics: a case for structural inheritance in the northeastern Slave craton, western Nunavut, Canada

The north–northwest-striking Bathurst fault in the northeastern Slave craton displaced the 1.9 Ga Kilohigok basin and the ca. 2.02–1.96 Ga Thelon tectonic zone, and projects beneath the 1.7 Ga Thelon basin where unconformity-associated uranium deposits are spatially associated with basement faults. Here we investigate the deformation–temperature–time history of the Bathurst fault rocks using structural and microstructural observations paired with U–(Th–)Pb and 40Ar/39Ar geochronology. Highly strained hornblende-bearing granitoid rocks, the predominant rock type on the northeastern side of the Bathurst fault in the study area, show ambiguous sense of shear suggesting flattening by coaxial deformation. Quartz and feldspar microstructures suggest ductile deformation occurred at ≥500 °C. Along the main fault trace, brittle features and hydrothermal alteration overprint the pervasive ductile flattening fabric. In situ U–Th–Pb dating of synkinematic monazite suggests ductile fabric formation at ca. 1933 ± 4 Ma and ca. 1895 ± 11 Ma, and zircon from a cross-cutting dyke constrains the brittle deformation to ≤1839 ± 14 Ma. 40Ar/39Ar dating of fabric-defining minerals yield cooling ages of ca. 1920–1900 Ma and ca. 1900–1850 Ma for hornblende and muscovite, respectively, and a maximum cooling age of ca. 1840 Ma for biotite. We suggest the ca. 1933–1895 Ma ductile flattening fabric developed during orthogonal collision and indentation of the Slave craton into the Thelon tectonic zone and Rae craton. Brittle deformation on the Bathurst fault was localised parallel to the ductile flattening fabric after ca. 1840 Ma and preceded Thelon basin deposition. Brittle deformation features in Bathurst fault rocks preserve evidence for fluid–rock interaction and enhanced basement permeability, suggesting the fault is a possible conduit structure for mineralising fluids.

Characterization of stone artifacts from the Middle and Late Neolithic to the Chalcolithic deposits of Drakaina Cave, Kephalonia, Ionian Islands: a mineralogical-geochemical approach for determination of local and “exotic” raw materials and their sources

This work presents the results of the mineralogical, petrographic, and geochemical study carried out on representative samples from the large assemblage of the Neolithic stone artifacts found in Drakaina Cave, at Kephalonia island, western Greece. The aim of this study is the determination of the raw materials used for the manufacture of lithic/stone implements, as well as their possible sources. Of the artifacts under study, the chipped stone tools were manufactured on cherts from local sources, while the ground stone edged tools on gabbro and the discoid stone beads on talc, both imported in the Ionian Islands. Geochemical analyses indicate that the most probable source for the gabbro artifacts is the Pindos Mountains. Limestones and sandstones, used by the Neolithic stone workers for the production of various ground stone tools, such as grinding slabs, grinders, abraders, polishers and hammer stones, were acquired exclusively from local sources, as they are the predominant rock types of the island. The raw material for the manufacture of a zoomorphic vessel of white marble was most probably originated from Naxos, an island of the Cyclades complex in the south Aegean Sea.

Petrogenesis of low-Ti and high-Ti basalt, adakite and rhyolite association in the Peddavuru greenstone belt, eastern Dharwar craton, India: A Neoarchean analogue of Phanerozoic-type back-arc magmatism

The petrogenetic record, available in the literature, illustrating Neoarchean arc magmatic processes in a back-arc setting is rare. In this contribution, we present a comprehensive account of field, petrography and geochemistry of the Neoarchean bimodal mafic – felsic metavolcanic rock association in the Peddavuru greenstone belt, eastern Dharwar craton, India.Basalt is the predominant rock type. Felsic volcanic rocks are interleaved with the basalts, in the central part. The basalts are fine grained, aphyric and essentially composed of amphibole and plagioclase with rutile, magnetite and ilmenite as accessory Fe-Ti oxide phases. The felsic volcanic rocks exhibit porphyritic texture. Based on the composition of the phenocryst type i.e. feldspar or quartz, two variants have been recognized. Biotite is present in subordinate amounts while, apatite and magnetite are the accessory phases.Basalts are tholeiitic in composition, whereas the felsic volcanic rocks are calc-alkaline in nature. On the basis of TiO2 contents, the basalts can be classified into low-Ti (< 1 wt. % TiO2) and high-Ti (> 1 wt. % TiO2) geochemical subgroups. The two subgroups, however, are consanguineous in nature. They display slightly depleted (La/Sm ∼ 0.89) and mildly enriched (La/Sm ∼ 1.44) chondrite normalized light rare earth element patterns (REE), and slightly depleted heavy REE (Gd/Yb ∼ 1.2). On a primitive mantle normalized trace element variation diagram, irrespective of low- or high-Ti, the basalts display negative Nb and Ti anomalies, and zero to negative Zr-Hf anomalies relative to the neighbouring REE.The felsic volcanic rocks are characterized by contrasting geochemical compositions. On the basis of high field strength element systematics, they are classified as dacites and rhyolites. Compared to the rhyolites, the dacites are characterized by high Mg# (39 ± 9 vs. 24 ± 5), low Nb (≤ 5 ppm vs. 14 ppm), Y (5.9 ± 1.8 ppm vs. 19 ppm) and Yb (0.47 ± 0.17 ppm vs. 1.72 ppm) contents. Further, the dacites exhibit comparatively steep chondrite normalized REE patterns (LaN/YbN ∼ 30 vs. 10) with negligible to slightly positive Eu anomaly (Eu/Eu* = 0.9–1.2 vs. 0.6). On a primitive mantle normalized trace element variation diagram they exhibit negative Nb and Ti anomalies, similar to the rhyolites, but contrasting positive Zr-Hf peaks and high Zr/Sm ratio (73 ± 18 vs. 24). The trace and rare earth element attributes of these dacites are identical to the adakitic rocks that have been recognized from the Phanerozoic intraoceanic arcs. On the contrary, rhyolites are the partial melt products involving minor plagioclase fractionation that are generated beneath the arc crust under extension.Overall, the chemical compositions of the mafic and felsic volcanic rocks in the Peddavuru belt indicate that interaction with the Archean upper continental crust, magma mixing and/or assimilation and fractional crystallization processes cannot be the cause of these geochemical patterns. The attributes instead reflect primary mantle source characteristics. MORB-like trace element signatures in combination with arc-like geochemical affinity in the Peddavuru basalts, provides compelling evidence of their origin in an intraoceanic back-arc setting. Accordingly, the Peddavuru greenstone belt presents a Neoarchean analogue of Phanerozoic-type back-arc magmatism.

Application of VLF-EM method for base metal exploration in Gwani area (Misau 107), Jigawa state, Nigeria

The Very Low Frequency (VLF) electromagnetic (EM) survey is a reliable technique for identifying network of fractures usually hidden by overburden materials that overlie the crystalline basement. The Gwaram area, Jigawa state of Nigeria is underlain by Older Granite of the basement complex of Nigeria, with predominant rock type being coarsely porphyritic biotite granite. The project is aimed at confirming the occurrence of sulphide mineralization within the study area, using both the geological information and VLF techniques. Measurements involving 10 profiles spaced 50 m interval were collected within the study area, using the transmitter of Le Blanc in France whose radio frequency is 18.3 kHz. Profiles 1-10 show the respective cross-over points (points of intersection) at 430, 460, 430, 470, 480, 500, 550, 560, 610, and 620 m with a positive in-phase response of 11.1, 7.3, 22.1, 23.7, 30.8, 36.2, 29.5, 17.6 and 20.8% respectively, the suspected fault occurred at respective depth of 45, 130, 150, 135, 150, 135, 140, 145, 145 and 125 m. The ratios of primary to secondary electromagnetic anomalies on the ten profiles are not constant and their profile shapes are never identical or consistent. Such anomalies at cross-over points have been used to infer the presence of fracture. All the profiles show one identical anomaly which is suspected to be a hydrothermal zone or mineralized fault. VLF-EM contour and 3D map were produced and indicate that there is high conductivity toward the southwest of the map. The results obtained in the survey inferred that the deposit is expected to be economically viable.

Assessment of heavy metals in the surface sediments and sediment-water interface of Lake Cajititlán, Mexico.

Lake Cajititlán is an endorheic tropical lake located in the state of Jalisco, Mexico, which has suffered the consequences of high levels of eutrophication. This study assessed the presence of heavy metals and metalloids in Lake Cajititlán to ascertain possible risks to its aquatic biota and the environment. Eleven monitoring sites were selected throughout the lake; from each site, one sample was taken from the sediments and another from the sediment-water interface by using an Ekman dredger and a Van Dorn bottle, respectively. The measured metals in each sample were As, Cd, Cr, Hg, Pb, Zn, Cu, Ni, Fe, Mn, and Al. The results showed the following sequence of heavy metal concentrations Al > Fe > Mn > Zn > Cu > Cr, wherein Al had the highest average concentration and Cr had the lowest. As, Cd, Hg, and Pb were practically undetectable. Because the predominant rock in the lake basin is volcanic tuff and the soil is vertisol, the high quantities of Al and Fe suggest the weathering of the basin's minerals. The analyses of the sediment-water samples contained small amounts of dissolved Al, Fe, and Mn. According to the Håkanson equations with Hg, Cd, As, Cu, Pb, Cr, and Zn, the calculations of the contamination degree and ecological risk revealed that the presence of metals and metalloids does not present a potential risk to the aquatic biota; nonetheless, the water is not suitable for local human consumption due to an unrelated factor associated with nutrient and bacteriological contamination. The results show that heavy metals in the sediments were dispersed throughout the lake mostly because of the weathering of minerals from the local basin and not because of the punctual discharges of the pollutants from the municipal wastewater treatment plants (WWTPs). However, to ensure that the small amounts of dissolved metals (Al, Fe, and Mn) do not affect the aquatic biota, the fish species and phytoplankton need to be internally analyzed.

Three-Dimensional Physical and Numerical Modelling of Fracturing and Deformation Behaviour of Mining-Induced Rock Slopes

Fracturing behaviour of jointed rock mass subjected to mining can significantly affect the stability of the rock structures and rock slopes. Ore mining within an open-pit final slope would lead to large-scale strata and surface movement of the rock slope. Rock mass structure, or more specifically, the strength, spacing and distribution of rock joints, are the controlling factors that govern the failure and deformation mechanisms of the final slope. Two-dimensional (2-D) physical modelling tests have been conducted in the literature, but in general, most of them have simplified the geological conditions and neglected some key features of rock mass structure in the field. In this study, new three-dimensional (3-D) physical modelling methods are introduced, with realistic modelling of mechanical behaviour of rock mass as well as identified properties of predominant rock joint sets. A case study of Yanqianshan iron mine is considered and the corresponding 1:200 model rock slope was created for studying the rock joint effects on the strata movement and the subsidence mechanism of the slope. The physical model test results are subsequently verified with 3-D discrete element numerical modelling. Due to the presence of the predominant joints, the observed well-shaped strata subsidence in Yanqianshan iron mine was successfully reproduced in the 3-D physical model. The failure mechanism of rock slopes differs from the trumpet-shaped subsidence observed in unconsolidated soil. Due to the formation of an arching mechanism within the rock mass, the strata deformation transferred gradually from the roof of the goaf to the slope surface.

Prediction of Flyrock in Mine Blasting: A New Computational Intelligence Approach

Blasting is the predominant rock fragmentation technique in civil constructions, underground and surface mines. Flyrock is the unwanted throw of rock fragments during blasting and is the major cause of considerable damage in and around the mines. The present research aimed to propose a new intelligence-based method to predict flyrock. In this regard, the recurrent fuzzy neural network (RFNN) combined with the genetic algorithm (GA) is proposed. For checking the suitability of the RFNN-GA model, artificial neural network (ANN), hybrid ANN and GA and a nonlinear regression model were also employed. To achieve the aims of the research, data for 70 blasting sites including four input parameters (spacing, burden, stemming and maximum charge per delay) and one output parameter (flyrock) were gathered from two quarry mines at the Shur River dam, Iran. The performance of the proposed prediction methods was then assessed with statistical evaluation criteria, i.e., R-square and root mean square error. The results indicate the proposed RFNN-GA model was more superior for prediction of flyrock than the GA-ANN, ANN and nonlinear regression models. According to a sensitivity analysis, the maximum charge per delay was the most influential parameter in flyrock prediction in this case.