Characteristics Of Rocks Research Articles

Fracture and fractal characteristics of high-temperature granite under confined space water jet impact

In the application of jet assisted deep drilling technology, the fracture mode and rock fragment characteristics of high-temperature rock in the confined space of jet drilling are not yet clear. We analyzed the fragmentation and debris distribution of high-temperature granite under confined space jet action using 3D reconstruction technology and statistical fractal theory to examine their fragmentation patterns and fractal characteristics. The results show that high-temperature rocks exhibit obvious thermal fracturing characteristics under the impact of confined water jet, and as the rock temperature increases, vertical compression shear cracks connect with radial tensile cracks. The maximum damage area is located near the bottom of the confined hole, and the distribution of cracks is more complex. As the degree of jet confinement decreases, the rock cracking form changes from radial tensile cracking to vertical compression shear cracking. As the rock temperature increases and the confined space size decreases, the total mass and large debris mass percentages of rock debris increase. The particle size distribution of rock debris follows an Rosin-Rammler (R-R) distribution and has obvious fractal characteristics. The fracture and fragmentation of high-temperature rocks under confined water jet impact are mainly caused by the combination of jet impact stress waves and thermal stress. The temperature difference of rocks affects the heat transfer between jet and rock, and the confined space size directly affects the heat transfer efficiency between jet and rock, which is manifested in different numbers of fracture cracks, internal damage area, and rock debris size distribution. These findings can provide a theoretical and parameter optimization basis for jet-assisted deep reservoir drilling applications.

Petrography and geochemistry of volcanic rocks of the Kulf-Amba area, in the Northwestern Ethiopian plateau: Implication for petrogenesis of felsic volcanic suites

The Kulf-Amba area, located on the Northwestern Ethiopian plateau, is primarily composed of Cenozoic volcanic rocks with minor intertrappean sediments. To understand the petrogenesis of these rocks, we conducted field investigations, petrographic studies, and geochemical analyses. The main volcanic products include basalt (upper and lower), rhyolite lava flows, rhyolitic ignimbrite, volcanic glass, and agglomeratic tuff. Basalts exhibit aphanitic, porphyritic, and glomerophyric textures, with phenocryst of olivine, Ca-rich plagioclase, clinopyroxene, and Fe-Ti oxides. Felsic rocks display porphyritic, aphyric, and glassy textures, with phenocryst of quartz, alkali feldspar, and Fe-Ti oxides. Geochemical data reveal a bimodal composition. The mafic rocks resemble high titaniferous (HT2) basalts of Northwestern Ethiopia and are classified as transitional to tholeiitic. Felsic rocks are primarily peralkaline comendites. The mafic rocks exhibit a depleted heavy rare earth element (HREE) pattern with (Dy/Yb)N = 1.75–2.02 and enriched light rare earth element (LREE) values with (Ce/Yb)N = 7.16–9.26, without a significant negative Eu anomaly. Enrichment in LREE with (Ce/Yb)N = 6.27–15.03 and flat HREE with (Dy/Yb)N = 1.23–1.79, with varying Eu negative anomaly are characteristics of the felsic volcanic rocks, indicating removal of plagioclase throughout their evolutionary process. The consistent Nb/Ta (17.29–23.67 ppm) and Zr/Hf (37.53–45.08 ppm) ratios in both mafic and felsic rocks suggest that fractional crystallization was the dominant process in their formation, with small crystal contamination. The primitive mantle-normalized variation diagram for the mafic rocks reveals LREE enrichment and HREE depletion, indicating garnet in the source. Melting models using primitive mantle normalized values of Sm/Yb vs. La/Sm ratios further confirm garnet's presence and suggest a low degree (2%) of partial melting a source with less than 2% of garnet. The trace element signatures and geochemical modelling of the mafic lavas indicate a plume-related origin, potentially related to the Afar mantle plume.

Contact metamorphism and dolomitization overprint on Cambrian carbonates from the Ossa-Morena Zone (SW Iberian Massif): implications to Sr-chronology of carbonate rocks

AbstractThe Cambrian Series 2 Carbonate Formation from the Alter do Chão Elvas-Cumbres Mayores unit (Ossa-Morena Zone, SW Iberian Massif) is composed of regionally metamorphosed marbles and marlstones that underwent chlorite zone metamorphism and preserve the primaeval limestone 87Sr/86Sr ratios (0.7083–0.7088). These are consistent with the established Lower Cambrian seawater curve, and therefore used for age constraints in formations lacking fossil contents. The regional mineralogical and Sr-isotopic features of the carbonate rocks are frequently overprinted by the effects of contact metamorphism induced by magmatic bodies emplaced during rift-related and synorogenic events of the Palaeozoic, as well as by post-metamorphic dolomitization processes. The development of calc-silicate minerals due to contact metamorphism is common in the rocks of the Carbonate Formation and apparently results from the interaction of the protolith with fluids of different origin: (i) internally produced fluids released by conductive heating (observed in external contact aureoles) and (ii) external intrusion-expelled fluids that, besides leading to the appearance of distinctive assemblages, also promote an influx of strontium content (observed in roof pendants). Calc-silicate mineralogy varies substantially throughout the region, likely due to the heterogeneous distribution of silicate minerals of the protolith, progression of intrusion-driven fluids, and the irregular effect of thermal gradients. Results suggest that high-grade contact metamorphism (hornblende facies or higher) and dolomitization processes imposed on the Carbonate Formation significantly influence the isotopic signatures of the carbonates, providing limitations in applying Sr-isotopic chronology. Graphical abstract

Influence of Engineering Properties on Radiation Shielding Characteristics of Some Egyptian Granitic Rocks as Potential Materials

Influence of Engineering Properties on Radiation Shielding Characteristics of Some Egyptian Granitic Rocks as Potential Materials

Rifting Basins at the Accretion-Collision Stage of Fold Belt Development: Eastern Slope of the Southern and Middle Urals in the Carboniferous

Research subject. Sedimentary basins within the Mississippian and Early Pennsylvanian (Middle Carboniferous of Russia) rift (sensu lato) structures on the eastern slope of the Southern and Middle Urals. Methods. An analysis of lithological characteristics of sedimentary rocks and relationships with volcanic complexes in order to clarify the evolution of rifting basins. Results. During the Mississippian and Early Pennsylvanian, several large rifting basins were common in this area. The Early Carboniferous rifting basins (Magnitogorsk-Bogdanovskoe graben and Alapaevsk-Kamensk rift) of accretionary margin of the East European craton were characterized by relatively shallow-water (in some places up to coastal-marine and continental) environments, caused by intensive (compensatory) filling of depressions with sedimentary material. In this case, volcanic rocks – those of fissure-type and stratovolcanoes lava flows – also played a significant role. In the Late Visean, the rifting process paused; a relatively shallow shelf basin regime was established throughout the entire area, which persisted until the end of the Early Carboniferous. In the Early Pennsylvanian, due to a hard oblique collision, the rifting process resumed. However, the rifting basins were already smaller in terms of area and most often deeper, whereas the occurring volcanic processes were less intensive. The characteristic feature of these basins was the presence of flysch complexes. The elongated shape of the rifting basins, large thicknesses of sedimentary strata, lateral facies variability, and the abundance of coarse clastic rocks, consisting largely of fragments of directly underlying sediments (Visean, Serpukhovian, Bashkirian), suggest that the Mississippian and Early Pennsylvanian rifts of the Southern and Middle Urals eastern slope had a strike-slip nature, i.e., the rifting basins were pull-apart type depressions.

Effect of geometric variations on the wing rock of blended wing–body aircraft

Blended wing–body configurations are anticipated to dominate future transport and military aerospace designs. The departure of the conventional tube-wing configuration has opened several areas of investigation. These designs are susceptible to lateral instability during landing, takeoff, and maneuvering flight despite having improved aerodynamics because of their tailless nature. One of these instabilities, Wing-Rock, poses significant performance and operational difficulties and can potentially cause crashes. Though experimental and numerical studies of the aerodynamics and stability of blended wing–body configurations have been conducted, wing-rock characteristics still need to be identified in the literature. This research aims to investigate these characteristics at low subsonic speeds with varying outboard sweep and geometric twist angles. The study includes a numerical approach based on the rigid body free-vibration method in single roll degree of motion, which uses three-dimensional unsteady Reynolds’ Average Navier Stokes equations, and an analytical approach based on the multiple time scale method, which captures the crucial aspect of the wing rock system. The findings show that the geometrical parameters significantly impact the wing rock characteristics, which are unique to such novel tailless designs.

Study of Soft Rock Anisotropy Based on Three-point Bending Experiments

Abstract Under the influence of its layered structure, soft rock exhibits significant non-homogeneity in its mechanical properties and a certain degree of anisotropy in its fracture characteristics. In this paper, we utilize GDEM-Pdyna to conduct numerical simulations of three-point bending experiments on soft rocks with various layered structures. The research focuses on examining the mechanical properties and anisotropic characteristics of soft rocks subjected to three-point bending tests with different prefabricated fracture angles and layered angles. The experimental results indicate that as the prefabricated crack angle increases, the peak strength required for the failure of the soft rock gradually increases. The load-displacement curves and deformation field maps for soft rocks with horizontal and vertical grain layers under three-point bending loading show a certain degree of consistency. Additionally, with an increase in the angle of the laminae, both the peak load and peak displacement during the loading process gradually decrease, along with a corresponding decrease in fracture toughness. This study provides valuable insights into the mechanical behavior and anisotropic characteristics of soft rocks, contributing to a better understanding of their response under different loading conditions and structural configurations.

Petrological, mineralogical, carbonate C-O and sulfide S isotope study of the Bayinqinggeli sandstone-hosted uranium deposit in the northern Ordos Basin

Many sandstone-hosted uranium deposits have been discovered in the northern Ordos Basin, including the Bayinqinggeli deposit, exhibiting tremendous potential for uranium exploration and prospecting. This region is characterized by complex fluid activities, yet unknowns or controversies still exist regarding the source and properties of the fluids and their influence on uranium mineralization. In this study, we employed optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), micro X-ray fluorescence (μ-XRF), C-O isotope of calcite, and in situ S isotope of pyrite, to investigate the genesis and evolution of the Bayinqinggeli deposit. Pyrite and calcite are closely associated with uranium minerals, and all exhibit distinct characteristics in rocks of varying grades. In high-grade mineralized rocks, ore-related pyrite, characterized by euhedral and colloidal forms, mainly predated uranium mineralization, evidenced by the extensive coffinite replacement. The mostly negative δ34S values with a broad range (−24.6 ‰ to 23.9 ‰; mean = −4.2 ‰) point to microbial sulfate reduction under restricted conditions. In low-grade and barren rocks, pyrite unrelated to mineralization, mainly as large granular or colloidal cement, shows generally positive δ34S values with a wide range (−49.5 ‰ to 67.4 ‰; mean = 15.3 ‰). This suggests the involvement of both biological and abiological processes during different stages, with the latter possibly associated with deep-sourced fluids. Considering the heterogeneous isotope compositions of sulfur in pyrite and carbon in calcite (δ13C ranging from −21.4 ‰ to −4.9 ‰), it can be deduced that the deposit was strongly affected by two types of fluids: (1) surface oxidizing fluids and (2) deep reducing fluids. The mineralizing fluids were derived from oxidizing surface water, which dissolved uranium ions, carbonates, and sulfates from weathered source rocks and during infiltration through the sandstone, resulting in the formation of abundant uranium minerals and associated pyrite and calcite. The presence of low δ13C calcite further corroborates the influence of deep hydrocarbon-bearing fluids, which played a protective role in post-ore stage preservation, corresponding to the widespread green alteration in the Lower Zhiluo formation. Overall, the development of sandstone-hosted uranium deposits is a continuous and progressive process, with early-formed mineralization being transformed by late-stage fluid events. Calcite has a significant impact on the formation, development, and extraction of uranium ores in the deposit, protecting the paleo-orebodies against remobilization and remigration. A significant portion of uranium ore is preserved by calcite cementation. Therefore, the careful management of carbonates during in situ leaching is essential for the effective extraction of uranium from the host sandstones.

Estimation of bearing capacity of bimsoils under shallow foundations

Bimsoils, consist of fine soil matrix and coarse rock aggregates, and are widespread as sedimentary soils. The bearing behavior of bimsoils are significantly affected by rock fraction. However, the mechanism governing the coarse fraction effect remains unclear. The traditional analysis methods are not effective in describing the rock fraction effect due to heterogeneous structure. To this end, 91 simulations have been performed to investigate the bearing capacity of bimsoils (mainly of two-dimensional, 2D) under shallow foundations using finite element method (FEM). It is found that the densified matrix bridge as well as the coarse aggregates forms a strong contact network which is responsible for the coarse fraction effect. A structure variable is introduced to quantify the reinforcing effect of rock aggregates. Then, a model incorporating the structural variable is proposed to evaluate the coarse fraction effect on the bearing capacity of bimsoils. Compared with the conventional method for pure soil matrix, only two additional parameters are required, and they can be readily calibrated by laboratory tests. The model is further validated by data available in literature, which can effectively estimate the bearing capacity of bimsoils under shallow foundations with a various of rock contents and rock characteristics.

Reconstruction of a granite structure composed of multiple irregular minerals

Accurately reconstructing rock structures using numerical methods is vital in rock mechanics research community, especially when obtaining rock samples is difficult and expensive. The reconstructed models must reflect the comprehensive characteristics of natural rock, including mineral content and spatial distributions. This study employs the bubbling method to reconstruct granite containing multiple minerals in both two- (2D) and three-dimensions (3D), proposing a general procedure for granite structure reconstruction. The bubbling method utilizes numerous bubbles (hemispheres or spheres) of varying sizes and gradually changing properties, which are randomly overlapped to create a heterogeneous plane (2D) or space (3D). The properties of these overlapped areas are adjusted based on the sum of neighboring bubbles' properties, allowing specific regions with extreme properties to be selected and intercepted to form the desired mineral shapes. The results demonstrate that the reproduced granite samples can accurately exhibit the mineral distributions and sizes of real granite, quantified by fractal dimension (D) and the hourglass parameter (). The proposed method is also suitable for reconstructing anisotropic granite models, with anisotropy described by a fitted elliptic curve derived from ratios between directional mineral sizes and cross-sectional dimensions. Based on these findings, a series of numerical granite models with similar structures were reconstructed and tested. Results indicate that different mineral distributions significantly impact the macroscopic mechanical behaviors, but variability in numerical simulation results decreases with increasing specimen size. The compressive and tensile strength values of the reconstructed numerical models show less variation than those of natural granite specimens. This suggests that, beyond mineral distribution, other factors such as internal defects within natural granite contribute to the observed discrepancies. Additionally, the bubbling method shows great potential for modeling porous structures and offers high computational efficiency.

Study on the impact damage behavior and infrared radiation evolution characteristics of rock under different drop hammer velocities

Infrared radiation effectively monitors rock deformation and failure, playing a significant role in monitoring dynamic disasters such as rockburst and mine tremors. This study investigates rock fracture modes, mechanical properties, and infrared radiation responses under different impact velocities through drop hammer impact tests. The infrared thermal imaging and infrared radiation anomaly area characteristics during rock impact failure were quantitatively analyzed using infrared radiation frequency distribution. The results show that as impact velocity increases, the maximum impact force initially rises then stabilizes with a slight decrease; the double peak of impact force gradually centers on the first peak; the degree of damage increases before decreasing, with failure cracks gradually aligning with the central axis. The energy conversion rate exhibits a threshold, reaching a maximum of 95.54 % when the initial impact energy reaches 70.68 J. Infrared thermal imaging analysis reveals that the average infrared temperature increment (ΔAIRT) lags behind the maximum infrared temperature increment (ΔMIRT), with ΔMIRT being 43.74 times higher than ΔAIRT at higher impact velocities, and ΔMIRT and ΔAIRT being 3.57 and 6.88 times higher than those at lower impact velocities, respectively. The proportion of infrared radiation anomaly areas increases with impact velocity. At higher impact velocities, the low temperature anomaly area Pl reaches 0.104 %, while the high temperature anomaly area Ph reaches 0.0627 % (Plmax is approximately 3.5 times Phmax). The research findings are significant for assessing rock stability and identifying impact failure.

Hydrocarbon generation potential of South Geisum Oilfield, Gulf of Suez, Egypt: Source rock evaluation and basin modeling for unconventional hydrocarbon prospects

This study aims to define the hydrocarbon generation potential of source rocks by assessing various factors including quantity of organic matter, types of kerogen, thermal maturity, and source of organic matter input. Depositional conditions of source rocks from Thebes, Brown Limestone, and Matulla formations in Well G-9, Well GA-2 and Well GW-6, are assessed through pyrolysis, vitrinite reflectance and 1D basin modeling. Results show the source rocks of Thebes and Brown Limestone formations exhibit favorable to excellent source rock characteristics with Type I–II kerogen and have the capacity to generate oil. Conversely, the source rocks of the Matulla Formation show fair to good source rock characteristics with Type II–III kerogen and have the capacity to produce both oil and gas. Thermal maturity shows the source rocks are at an immature stage. A 1D basin model is constructed for Well G-9 to simulate multi-tectonic episodes, burial events, and the history of thermal maturity. Sedimentation rates of Cretaceous to Eocene deposits are characterized by a low burial rate, which contrasts with the high burial and sedimentation rates for Miocene and post Miocene (Pliocene–Recent) strata. Overall, the South Geisum oilfield petroleum system is found to be immature based on integration of source rock evaluation and petroleum basin modelling.

Messages from the past: the petroglyphs of El Hierro Island, Canary Islands

Ancient cultures have frequently made use of stone surfaces to carve and engrave symbols, letters and messages for others. These petroglyphs usually have a lasting character and are frequently preserved well beyond the survival of the culture that produced the petroglyphs. In this article, we focus on the written and pictorial testimony of the pre‐Hispanic era of the island of El Hierro (Canary Islands, Spain), which exploited a series of volcanic rock features to create a written testimony of their presence and their way of life. This specific cultural heritage has been adapted to the specific geological features on the island and the emerging stone masonry skill of the aboriginal culture of the original islanders, creating a unique and lasting record of their ability to use geological elements for cultural development.

Source Rock Characteristics of Sargelu Formation in X Well, Northern Mesopotamian Zone, Iraq

Source Rock Characteristics of Sargelu Formation in X Well, Northern Mesopotamian Zone, Iraq

Mineralogical composition and strength characteristics of granite rocks

Mineralogical composition and strength characteristics of granite rocks

Source rock and petrophysical evaluation of the Late Cretaceous Haymana Formation, Haymana Basin, Central Anatolia, Turkey

This study investigates the petroleum potential of the mudstones of the Late Cretaceous Haymana Formation in the Haymana Basin, Turkey. Lithofacies, pore structure, and source rock characteristics of the mudstones are examined using stratigraphical, sedimentological, petrophysical, and organic geochemical methods along four stratigraphic sections and other sampling sites. The depositional model presents a facies distribution within a submarine fan system. According to bulk mineralogy, the identified lithofacies are mixed mudstone, mixed siliceous mudstone, marl, mixed carbonate mudstone, argillaceous/siliceous mudstone, and clay-rich siliceous mudstone. XRD and mercury intrusion measurements suggest that the macropores (> 50 nm) of the mudstones formed by dissolution of calcite, while mesopores (2 nm-50 nm) developed around the clay/quartz/feldspar. Of the analysed samples, no lithofacies class is distinct with any specific range of porosity or permeability, which suggests a strong heterogeneity in pore throat size, mineral content, and grain size. The black shale from the northwest of the basin with 1.19% TOC, 0.07 mg/g S 1 , 1.01 mg/g S 2 , and 441°C T max is a relatively more mature source rock although it still exhibits poor petroleum potential. Overall, the TOC values (avg. 0.38%) of the mudstones suggest organic-poor rock characteristics for the Haymana Formation in the studied parts of the Haymana Basin.

Investigation of Fatigue Mechanics and Crack Evolution Characteristics of Jointed Specimens Under Cyclic Uniaxial Compression

ABSTRACTNonpersistent joints are prevalent in engineering rock masses and are sensitive to cyclic loads induced by geological movements and engineering disturbances. Therefore, studying the fatigue mechanisms of rock masses with nonpersistent joints under cyclic compressive loads is crucial for ensuring the rational design and long‐term stability of rock engineering structures. Based on laboratory experiments, this study employed the discrete element method to create specimens with different nonpersistent joints, and uniaxial compressive cyclic loading tests were conducted on these specimens with different maximum cyclic stress levels. The results show that the joint inclination significantly affects the characteristics of jointed rock, such as deformation modulus, irreversible strain, energy evolution, and crack characteristics. Increasing the maximum stress in the stress path results in a rapid release of hysteretic energy in the jointed regions of the rock, which leads to an exponential decrease in fatigue life while an increase in initial irreversible strain, final irreversible strain, and hysteretic energy density. Additionally, the shear fracture zones on both sides of the model expand, and the propagation and merging of cracks between joints become more extensive and complex. The results are significant for studying rock fatigue instability and structure engineering design.

Evaluation of Wellbore Stability by Small Parameter Perturbation Nonlinear Elastoplastic Model

Abstract Wellbore instability is a frequent occurrence during drilling and a popular research topic among petroleum workers. Most of the previous studies simplified the hardening stage and ignored or classified it into the elastic stage. Engineering practice shows that the total stress–strain process of rock can more truly reflect the bearing and deformation characteristics of rock. This study establishes a total stress–strain constitutive model by combining the perturbation index equation with the linear elastic equation. Additionally, the physical model of rock around the well is presented using the total deformation theory for the plastic zone. The stress field of the rock surrounding the well is analyzed based on the physical model of the rock surrounding the well, taking into account the influence of rock strength and geostress state. The relationship between rock strength, geostress state, drilling fluid density, and plastic radius is given. The calculation method of drilling fluid density limit is also given. The practical application demonstrates that the stability of a borehole wall can be evaluated by analyzing the size and direction of the plastic radius, as well as the distribution of radial, tangential, and shear stress for various combinations of stress states and rock strengths. The maximum shear stress is always found in the softening zone, which is also the region where wellbore instability is most likely to happen. Therefore, the area within the softening radius is regarded as an unstable area, and the softening radius can be used to determine the range of wellbore instability.

Energy storage and fracture characteristics of brittle rock with rockburst proneness after microwave irradiation

Microwave irradiation has been considered a promising solution for high-temperature cracking rock. Most of the current researches are concentrated on investigating the effects of microwave irradiation on the physical and mechanical properties of rock. However, there is a paucity of reports on the application of microwave irradiation for controlling rockburst disasters. The novelty of this investigation lies in the utilization of microwave irradiation to modify the energy storage capacity and fracture characteristics of brittle rock with rockburst proneness. Based on the phenomenon of overheating in rock under microwave irradiation, the concept of progressive damage in granite was proposed for the first time. The weakening of energy storage capacity due to microwave irradiation was evaluated by defining an energy storage coefficient. A novel index for assessing the rockburst proneness of brittle rock was proposed. By combining this index with the strain energy release rate, the potential value of microwave irradiation in reducing the proneness and intensity of rockburst was explored. This study also introduced the concept of "sensitive stress level" which influences the closure state of cracks, and found that SSL and mechanical properties show high sensitivity to microwave power. A threshold power of 4.5 kW was identified, at which numerous parameters undergo significant changes.

A case study of crushed stone for road construction application: amphibolite and basalt varieties from Croatia

Crushed stone is one of the most exploited and important mineral raw material. Emphasis is given to determination of mineralogical and petrographic properties, of two genetically different rocks of silicate composition, commonly used as crushed stone for road constructions, as their physical properties depend on them. First is amphibolite from Vetovo, and second is basalt from Vratnik locality, both sourced from Croatia. Tests conducted according to European and Croatian norms evaluated the real and apparent density, open and total porosity, and water absorption of stones. The relationship between mineralogical and physical properties led to the following conclusions: the open porosity values of amphibolite samples are low, which is a consequence of the medium to high degree of metamorphism, (plagioclase and hornblenda), sosiritization, and undisturbed rock features. The total water saturation was achieved in a brief time, confirming this statement. The basalts have different porosity and water absorption values, which are consequences of differences their textural-structural properties (glassy, intersertal or intergranular groundmass), amount of amygdules, presence or absence of chlorite/volcanic glass. Furthermore, the percentage of plagioclase in the modal composition differs, and the plagioclase itself has been altered, and the amount of clay, sericite and calcite vary in two different varieties of basalt. Compared to amphibolites, basalts have notably higher water absorption values as well. Accordingly, the studied amphibolite has water absorption less than 0.5% and is suitable for use in a road construction application for wearing course in the asphalt pavement, and studied basalt is not.