Search Results (67)

Norite is a coarse-grained mafic igneous rock dominated by essential calcic plagioclase and orthopyroxene. Norite is known for its toughness, and it has a high compressive strength which makes it important in engineering. This paper examines the mechanical and petrographic properties of norite, including their relevance to geomechanical applications. Despite improvements in brittleness estimation, standardizing brittleness indices remains a challenge due to geological variability, incompatible petrographic techniques, and difficulties in relating mineral composition to mechanical behavior. Current brittleness models mainly rely on mechanical properties, often ignoring key petrographic factors like grain size, mineral composition, alteration, and porosity. This limits their accuracy, especially for complex rocks like norite. Few studies integrate both petrographic and mechanical data, creating a gap in fully understanding the geomechanical behavior of norite. This review was carried out by examining the origin, formation, and petrographic properties of norite, and a comparative analysis of its strength, flexibility, mineral structure, and fracture mechanics was conducted, highlighting their importance in the engineering and mining industries. The results of this study highlight how factors like strength, brittleness, and durability influence norite’s suitability for geomechanical applications in mining, tunneling, and construction. Furthermore, the results outline that the mineral composition of norite affects its strength, with quartz enhancing strength and altered minerals like feldspar, mica, and biotite weakening the rock and making it more prone to fracturing. These results are important for tunneling projects as they help predict how rocks will behave, ensuring tunnel stability and better design in underground support systems. Full article

Amphibole-rich cumulates provide crucial information pertaining to the petrogenetic history of suprasubduction zone ophiolites and are, therefore, helpful in constraining the evolution and closure of the Neo-Tethys during the late Cretaceous to the early Tertiary period. Following this, the present contribution examines the meta-hornblendite and meta-hornblende-gabbro lithologies in the Mayudia ophiolite complex (MdOC), NE Himalaya, based on their field and petrographic relations, constituent mineral compositions, whole rock major and trace element chemistry and bulk strontium (Sr)—neodymium (Nd) isotope systematics. MdOC cumulates potentially represent the fossilized record of an island arc root, where amphibole + titanite + magnetite was fractionally crystallized from a super hydrous magma (10.56–13.61 wt.% melt water content) prior to plagioclase in a stable physico-chemical condition (T: 865–940 °C, P: 0.8–1.4 GPa, logfO₂: −8.59–−11.19 unit) at lower crustal depths (30–38 km). Such extreme hydrous nature in the parental magma was generated by the flux melting of the sub-arc mantle wedge with aqueous inputs from the dehydrating slab. A super hydrous magmatic reservoir was, therefore, extant at sub-arc mantle depths in the eastern Neo-Tethys, which has likely modulated the composition of the oceanic crust during intraoceanic subduction. Full article

This study investigates the deterioration of granite graffiti at the Philae Archaeological Site on Bigeh Island (Aswan, Egypt), attributed to Khaemwaset (1281–1225 BCE, 19th Dynasty). These graffiti, despite being carved into durable Aswan granite, are experiencing progressive degradation due to environmental and hydrological factors. This research aims to analyze the mineralogical and chemical transformations affecting the graffiti to provide a comparative assessment of submerged and unsubmerged granite surfaces. A multi-analytical approach was employed, combining petrographical examination, X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) to identify compositional changes and deterioration patterns. The results indicate mineralogical transformations in submerged and periodically exposed surfaces. The granite primarily consists of quartz, feldspar, and biotite, with notable alterations including kaolinization and illitization and dissolution of feldspar minerals and biotite oxidation. These processes are directly linked to prolonged exposure to fluctuating water levels and recurrent wet–dry cycles, which accelerate granular disintegration, exfoliation, and surface loss. Additionally, salt crystallization, particularly halite, contributes to granite weathering, while sulfate interactions promote chemical weathering. In addition, biofilm colonization, facilitated by high moisture retention, further exacerbates surface deterioration by producing organic acids that weaken the mineral matrix. Finally, the results confirm the need for conservation interventions to mitigate ongoing damage. Full article

This paper aims to support stakeholders in the sustainable construction sector by exploring the potential of unexamined aggregates from five distinct origins: the Jandol River, the Swat River, the Panjkorha River, the Kitkot Drain, and the Shavey Drain situated in Malakand division, North Waziristan, Pakistan, concerning Alkali–Silica Reaction (ASR) prior to their incorporation into large-scale construction practices. Petrographic examination for the determination of the mineralogical composition of all collected aggregates revealed that aggregates stemming from the Swat River, Panjkorh River, Kitkot Drain, and Shavey Drain exhibited no reactive minerals. In contrast, those from the Jandol River showed reactive mineral content. Physical analysis of the aggregates revealed that Jandol River aggregates had superior resistance to impact, crushing, and abrasion, having values of 18.53%, 18.53%, and 20.10%, respectively. Moreover, the chemical analysis exhibited the highest silica content (SiO₂) in Jandol River aggregates, i.e., 94.7%, respectively. Samples in the form of cubes, prisms, and mortar bars were prepared to study both the mechanical properties and the expansion tendencies of specimens prepared from different aggregate sources. Validation of the reactive nature of the Jandol River aggregates was corroborated by the expansion results obtained from the mortar bars and the reduction in compressive strength and flexure strength by 8.2% and 9.2%, respectively, after 90 days, higher than that of aggregates exposed to ASR sourced from the other four origins. It can be asserted that aggregates from the Jandol River source are more susceptible to ASR as compared to other aggregates. To mitigate the potential of ASR, various strategies, such as using low reactivity, natural, or processed aggregates; low alkali-containing cement; inducing pozzolanic substances in concrete; etc., are recommended. Simultaneously, an economic feasibility study and environmental assessments are recommended as future developments. Full article

Reservoir evaluation in multi-source systems is challenging because studies generally follow single-source principles. This limitation has substantially hindered the understanding of reservoir and hydrocarbon accumulation processes in source–reservoir systems. This study examines the Dingbian area of the Ordos Basin, China, and investigates the key factors controlling hydrocarbon accumulation in the Chang 9 reservoir of the Triassic Yanchang Formation within a multi-source system. The study area spans approximately 0.9 × 10⁴ km². First, by comparing the biological markers in Chang 9 crude oil with those of potential source rocks, the oil source of the Chang 9 reservoir was identified. The study area was subsequently divided into three provenance zones—northeast, northwest, and central mixed source areas—based on heavy mineral content and the orientation of sedimentary sand bodies. Additionally, well logging data, oil production data, petrographic thin sections, scanning electron microscopy (SEM), and mercury injection porosimetry were used to investigate the reservoir characteristics, oil reservoir features, and crude oil properties across different source areas. The results indicate that the oil source of the Chang 9 reservoir in the Dingbian area is the Upper Chang 7 source rock. The northwest source area exhibits superior reservoir properties compared to the other two zones. In the northwest source area, lithology-structure oil reservoirs are predominant, whereas the central mixed source area is characterized by structural-lithology oil reservoirs, and the northeast source area predominantly features lithology-controlled reservoirs. From the northwest to the central mixed source areas, and finally to the northeast source area, crude oil density and viscosity increase gradually, while the degree of oil–water separation decreases correspondingly. Based on these findings, the study concludes that the distribution of structures, lithology, and source rocks significantly influences the Chang 9 reservoirs in the Dingbian area. The controlling factors of oil reservoirs differ across the various source zones. In multi-source systems, evaluating oil reservoirs based on source zones provides more precise insights into the characteristics of reservoirs in each area. This approach provides more accurate guidance for exploration and development in multi-source regions, as well as for subsequent “reserve enhancement and production increase” strategies. Full article

Rare metals such as lithium and beryllium are strategic mineral resources that play a highly significant role in the national aerospace, defense, and new energy industries. The western Kunlun–Songpan–Ganzi metallogenic belt is an important rare metal metallogenic belt in China that mainly consists of granite–pegmatite-type lithium–beryllium deposits with uncommon beryllium-only deposits. In the Jiulong area on the southeastern edge of this metallogenic belt, several deposits, including the Daqianggou lithium–beryllium, Luomo beryllium, Baitai beryllium, and Shangjigong beryllium deposits, have been identified. Unlike the northern areas of Jiajika, Ke’eryin, Zawulong, and the western regions of Dahongliutan and Bailongshan, this area contains beryllium-only deposits. In this paper, we examine representative beryllium deposits in the Jiulong area, including detailed petrographic observations and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb isotope dating of cassiterite and columbite–tantalite, to define the metallogenic age and summarize the spatiotemporal characteristics of the beryllium mineralization in this area. The research results show that the Daqianggou lithium–beryllium deposit is dominated by spodumene and beryl mineralization, while the Luomo and Baitai beryllium deposits primarily feature beryl mineralization. The dating results indicate that the U-Pb ages of the cassiterite and columbite–tantalite in the Daqianggou lithium–beryllium deposit are 157.3 ± 1.7 Ma and 164.1 ± 0.8 Ma, respectively. For the Luomo beryllium deposit, the U-Pb ages of the cassiterite and columbite–tantalite are 156.1 ± 1.5 Ma and 163.3 ± 0.8 Ma, respectively. For the Baitai beryllium deposit, the U-Pb age of the columbite–tantalite is 188.8 ± 1.1 Ma. Therefore, the Jiulong area experienced two pegmatite-type rare metal metallogenic events: a beryllium–niobium–tantalum–molybdenum event at 197~189 Ma and a lithium–beryllium–niobium–tantalum–rubidium event at 164~156 Ma. Based on the reported metallogenic ages, we suggest that the western Kunlun–Songpan–Ganzi rare metal metallogenic belt experienced three rare metal metallogenic events at 210~200 Ma, 200~180 Ma, and 170~150 Ma. Regarding exploration directions, early Yanshanian beryllium mineralization predominates in the Jiulong area along the southeastern edge of the belt, and deep exploration of the early Yanshanian rare metal mineralization within this belt should be strengthened to facilitate new breakthroughs. Full article

This study investigates the impact of the Emeishan Large Igneous Province (ELIP) on hydrocarbon formation within the Anyue gas field in the Sichuan Basin. As a major Middle to Late Permian large igneous province, the ELIP hosted intense mantle plume activity that reshaped regional tectonics and thermal structures, indirectly influencing hydrocarbon accumulation. This paper examines three primary factors in hydrocarbon evolution linked to the ELIP: its thermal influence, induced fluid activity, and role in hydrocarbon cracking. Data reveal that the thermal effects of the ELIP extend to the central Sichuan Basin, where an elevated paleogeothermal gradient has driven hydrocarbon evolution in the Anyue gas field. Petrographic characteristics, chronological data, fluid inclusion features, and C–O, S, and Pb isotopic signatures collectively indicate that around 260 Ma, a hydrothermal event occurred in the Sichuan Basin, closely aligned with a natural gas charging event. The combined effects of a heightened geothermal gradient and hydrothermal fluids (with temperatures up to 320 °C) suggest that paleo-oil reservoirs had already cracked into natural gas during the peak ELIP activity. Full article

The Carboniferous Benxi Formation in southern Shanxi of North China has significant bauxite resource potential; however, the source of its metallogenic material and its sedimentary environment remain unclear. The microscopy, X-ray diffraction, X-ray fluorescence spectroscopy, and inductively coupled plasma mass spectrometry methods were applied in this study to examine the mineralogical, petrographic, and geochemical characteristics. Geochemical proxies of La/Y, Sr/Ba, Al₂O₃/TiO₂, Zr/Sc, Th/Sc, La/Sc, and Th/Co were analyzed to investigate the paleo-depositional environment and provenance of the aluminum-bearing strata. The findings indicate that diaspores are the primary ore minerals in bauxite, while kaolinite and rutile are the predominant gangue minerals. Both the bauxite and claystone/aluminous rocks exhibit high enrichment in Li, Bi, and U, with relative enrichment in In, Sb, Th, Nb, and Ta. Li is notably concentrated in the claystone/aluminous rocks, reaching up to 1994.00 μg/g, primarily occurring in cookeite and boehmite, while U is highly concentrated in the bauxite. The aluminum-bearing strata were primarily formed under alkaline-reducing conditions, with changes in acidity and alkalinity of the environment during the sedimentary diagenetic process. Marine transgressions significantly impacted the sedimentary environment of the aluminum-bearing strata, and the paleoclimate was characterized as hot and humid. The principal factors contributing to enrichment of aluminum in the sedimentary basin were the in situ weathering of aluminum-rich source rocks and the transport of clastic materials from high-aluminum source rocks. The source rocks were closely associated with intermediate-acidic magmatic rocks and potentially related to the weathering of Ordovician carbonates. Full article

The Qiushuwan Cu-Mo deposit, situated in the East Qinling molybdenum belt, is a notable mining site renowned for its considerable quantities of medium-sized molybdenum. The goal of this study is to improve comprehension and identify additional mineral resources by conducting a thorough examination of the mine using the spread spectrum-induced polarization (SSIP) technique. Gathering SSIP data, conducting geological investigations, and examining the electrical characteristics of rock and mineral samples along Profile-80 led to significant discoveries. The investigation identified two significant ore bodies with high conductivity: C2, linked to granite porphyry and molybdenum veins, and C4, associated with a skarn deposit containing a concentrated amount of copper ore. This study used resistivity models created from SSIP data to find out how conductivity changed in different parts of the research area. Additional drill verifications validated these findings, indicating the presence of potential mineral resources. The petrographic analysis of core samples showed that minerals like pyrite, molybdenite, chalcopyrite, epidote, calcite, and garnet were present. Notably, the samples frequently contained both pyrite and molybdenite together. Sample 04-2 contained substantial quantities of molybdenite and pyrite; Sample 05-1 had occasional pyrite; and Sample 07-4 included both pyrite and chalcopyrite. These findings offer useful insights for evaluating the magnitude and economic feasibility of the mineral deposits; however, additional investigation is required to completely comprehend the scope of the resources. The integration of borehole data and the alignment of geological sections with inversion models confirmed the validity of the conclusions. The core samples that were retrieved show a lot of different minerals, including valuable ores and minerals that have been changed. Pyrite and molybdenite are always found together. These findings establish a solid basis for further investigation and the sustainable management of resources. This study contributes to the understanding of the Qiushuwan Cu-Mo deposit and advances exploration techniques using the spread spectrum-induced polarization (SSIP) method. It provides useful information for geologists, mining professionals, and stakeholders involved in resource usage. Full article

Bedrock geology is crucial in structuring alpine plant communities. Old studies mainly focused on the compositional differences between alpine plant communities on carbonate rocks and crystalline rocks, i.e., calcareous vs. siliceous vegetation. Increasing attention is being paid to bedrock types other than calcareous or siliceous ones, viz. those which have intermediate geochemical characteristics between pure calcareous and pure siliceous ones. Among these types of ‘intermediate’ bedrocks, calc-schists and serpentines are generally characterized by vegetation comprised of a mixture of basiphilous and acidophilous species. We selected several sites in alpine grasslands in the Western Italian Alps, on calc-schist and serpentine bedrocks, located at 2500 ± 100 m above sea level. X-ray fluorescence quantification of major and trace elements, combined with stereomicroscopic examination of bedrock samples with a petrographic approach, revealed a much broader range of bedrock types than recognized by inspection of geological maps. The vegetation investigated in our study was mostly composed of a set of species found more or less frequently in alpine silicicolous or calcicolous plant communities of the Alps and other European mountains. The carbonate content in the bedrock was one of the main drivers of variation in grassland vegetation, not necessarily related to soil pH. There were no distinctive species uniquely characterizing grassland vegetation on serpentines or calc-schists. Full article

Understanding the variations of the geomechanical properties of rocks in geotechnical projects from the perspective of their micro-structures and alteration conditions is crucial for ensuring the safety and long-term sustainability of rock engineering (e.g., tunnels, slopes, mining). This study was carried out on basaltic rocks from the Akcakale and Mersin vicinities in Trabzon City to investigate the geomechanical and mineralogical properties in comparison with the uniaxial compressive strength (UCS). This study was conducted in three different locations (A1, M2, and M3) where the basaltic rocks outcrop belongs to the same lithological formation. During this study, quite different results were obtained from the basalt samples taken from different sites and the reasons for these differences were examined by petrographic, SEM (Scanning Electron Microscopy), and EDS (Energy Dispersive Spectroscopy) analyses. Since the number of comprehensive studies on basalts is very limited, this study aims to investigate practical and useful equations in the estimation of the UCS for various alteration conditions. Statistically, significant relationships were observed between geomechanical properties with the UCS and serpentinization rate (SR). This study revealed that the serpentinization of the olivine mineral is the most important factor causing the differences in the experimental results. The proposed equations for estimating the UCS are particularly significant for geotechnical applications where direct sampling is challenging, such as in weak-rock environments. Full article

Archaeometry can help archaeologists in many ways, and one of the most common archaeometric objectives is provenance analysis. Volcanic rocks are often found in archaeological sites as materials used to make grinding tools such as millstones and mortars or as building materials. Petrographic characterization is commonly applied to identify their main mineralogical components. However, the provenance study of volcanic stones is usually undertaken by comparing geochemical data from reference outcrops using common descriptive statistical tools such as biplots of chemical elements, and occasionally, unsupervised multivariate data analysis like principal component analysis (PCA) is also used. Recently, the use of supervised classification methods has shown a superior performance in assigning provenance to archaeological samples. However, these methods require the use of reference databases for all the possible provenance classes in order to train the classification models. The existence of comprehensive collections of published geochemical analyses of igneous rocks enables the use of the supervised approach for the provenance determination of volcanic stones. In this paper, the provenance of volcanic grinding tools from two archaeological sites (Iulia Libica, Spain, and Sidi Zahruni, Tunisia) is attempted using data from the GEOROC database through unsupervised and supervised approaches. The materials from Sidi Zahruni have been identified as basalts from Pantelleria (Italy), and the agreement between the different supervised classification models tested is particularly conclusive. In contrast, the provenance of the materials from Iulia Libica remained undetermined. The results illustrate the advantages and limitations of all the examined methods. Full article

Salinized lacustrine shale (SLS) represents a frontier in the global quest for unconventional hydrocarbon resources. The impact of terrigenous input, which includes terrigenous organic matter (OM) and detrital matter, on the deposition and hydrocarbon potential of SLS is still controversial. Here, we examine this issue using the newly discovered SLS within the Paleogene Biyang Depression, employing a combination of organic petrographic and geochemical analyses. A high influx of terrigenous input (terrigenous OM and detrital matter) promotes the formation of SLS. On the one hand, terrigenous higher plants emerge as the primary source of OM in the SLS, as indicated by the dominance of terrigenous macerals (e.g., terrigenous liptinite) and the abundance of plant-derived biomarkers (e.g., tricyclic terpanes). Additionally, a portion of the OM may originate from bacteria. On the other hand, the rapid input of detrital matter improves the preservation of OM, resulting in the deposition of SLS with high total organic carbon (TOC) contents and low hydrogen index (HI) values. The findings of this study contribute to a deeper understanding of SLS deposition and provide guidance for regional hydrocarbon exploration. Full article

Feldspar alteration is among the most important processes in clastic rocks during diagenesis, but uncertainty remains about the factors that control feldspar diagenesis under subsurface conditions. Hence, the Upper Triassic Xujiahe formation of the Western Sichuan Basin were examined by an integrated petrographic, mineralogical and geochemical approach to unravel the causes and effects of feldspar diagenesis, with implication for mass transfer and openness of the geochemical system. The sandstones at various depths demonstrate three distinct, separate diagenetic behaviors of detrital feldspar within a single formation including (1) the complete dissolution of both plagioclase and K-feldspar in the upper member; (2) conservation of abundant detrital feldspar grains with minor albitization or overgrowths within the lower member of depths greater than 5 km; and (3) complete disappearance of K-feldspar within the uppermost horizons of the lower member, while plagioclase have survived in significant amounts. The exceptional disappearance of K-feldspar is the result of selective dissolution of K-feldspar during burial, accompanied by illite cementation and substantial K transfer at a scale of tens of meters. It is apparent that the clay diagenesis in the overlying mudstones, rather than porewater chemistry, is the major control of the reactivity of K-feldspar in adjacent deeply buried sandstones. Full article

The formation of chondrite materials represents one of the earliest mineralogical processes in the solar system. Phyllosilicates are encountered at various stages of the chondrule formation, from the initial stages (IDP agglomerates) to the final steps (chondrule internal alteration). While typically linked to aqueous alteration, recent studies reveal that phyllosilicates could precipitate directly from residual fluids in post-magmatic or deuteric conditions and under a wide range of temperatures, pressures, water/rock ratios, and H₂/H₂O ratio conditions. This study re-examined the formation of hydrated phyllosilicates in chondrules and associated fine-grained rims (FGRs) using published petrographical, mineralogical, and chemical data on carbonaceous chondrites. Given that chondrules originate from the melting of interplanetary dust particles, the water liberated by the devolatilization of primary phyllosilicates, including clay minerals or ice melting, reduces the melting temperature and leads to water dissolution into the silicate melt. Anhydrous minerals (e.g., olivine and diopside) form first, while volatile and incompatible components are concentrated in the residual liquid, diffusing into the matrix and forming less porous FGRs. Serpentine and cronstedtite are the products of thermal metamorphic-like mineral reactions. The mesostasis in some lobated chondrules is composed of anhydrous and hydrous minerals, i.e., diopside and serpentine. The latter is probably not the alteration product of a glassy precursor but rather a symplectite component (concomitant crystallization of diopside and serpentine). If so, the symplectite has been formed at the end of the cooling process (eutectic-like petrographical features). Water trapped inside chondrule porosity can lead to the local replacement of olivine by serpentine without external water input (auto-alteration). In the absence of water, hydrated phyllosilicates do not crystallize, forming a different mineral assemblage. Full article