Variety Of Rocks Research Articles

Petrochemical evaluation of gahnite from volcanogenic massive sulfide deposits in Betul belt, Central India: Insight from petrography and in‐situ trace element geochemistry

Gahnite occurs in diverse rock types and metamorphosed mineral deposits. The gahnite geochemistry is being used as an exploration tool for zinc sulfide deposits. In the present study, the geochemistry of gahnite and associated minerals viz. sphalerite, garnet, sillimanite, staurolite, anthophyllite, biotite, ilmenite, and chlorite, and their petrography have been used in studying the genesis, metamorphic evolution, deposit characterization, and exploration significance of seven Palaeoproterozoic volcanogenic massive sulfides (VMS) deposits in the Betul belt in the Central Indian Tectonic Zone, India. Different textural types of gahnites are recognized in the Betul belt. Field investigations of textural and geochemical characteristics suggest that the gahnites were formed by multiple geological processes: desulfidation of sphalerite, breakdown of almandine garnet, and zincian staurolite, and chloritization of zincian biotite corresponding with regional metamorphism. The temperature conditions of gahnite formation are estimated to be ~600–650°C using empirical Ti in biotite thermometry. The elemental concentrations in gahnites vary from Zn/Fe ratio 2–4; Co 1–30 ppm; Ga 14–573 ppm and Mn 126–3422 ppm, indicating that bimodal volcanics and volcano‐sedimentary rocks as protolith. High Mn content in gahnite suggests an influx of magmatic‐hydrothermal fluid in the protolith. Variations of trace elements (Mg vs. Al/V, Ti vs. Co/Mn, Co vs. V/Ga, Mn vs. Zn/Fe) and high‐temperature of gahnite formation attest to sensu stricto VMS type mineralization in Betul belt, which is entirely different from SEDEX, Broken Hill‐type, and non‐sulfide deposits. Principal component analysis of trace elements shows the geochemical variations at a few deposits and reveals that gahnites were formed as a result of the competing effect of fS2‐fO2 and governed by bulk rock composition.

Multivariate statistical analysis and geospatial approach for evaluating hydro-geochemical characteristics of meltwater from Shaune Garang glacier, Himachal Pradesh, India

The study focuses on the hydro-geochemistry of Shaune Garang glacier’s meltwater concerning glacial geomorphology. Seventy-nine water samples (53 in 2016 and 26 in 2017) of ablation season were analysed. The cations were dominant in the order Ca2+ > Mg2+ > Na+ > K+, and the anions in the order HCO3− > SO42− > Cl− > NO3−. The result demonstrated that HCO3− were the abundant ions, accounting for 41.03 and 34.84% of the total ionic budget (TZ). The high ionic proportions of (Ca2+ + Mg2+) versus TZ+ and (Ca2+ + Mg2+) versus (Na+ + K+) were identified as the primary factors influencing dissolved ion chemistry in meltwater. Piper diagram shows that Ca2+–HCO3– type water is the most common, followed by Mg2+–HCO3–. In addition, a remote sensing approach has been used to find the possible source of the chemical constituents in the meltwater. The catchment geology has been mapped on various scales, including diverse rocks and unconsolidated surface materials containing “quartz and carbonate minerals”. Layered silicates (LS) and “hydroxyl-bearing minerals” are not as common as they used to be, but their availability varies greatly in the area where they are found. The distribution of LS minerals within the catchment are majorly found at lower altitudes, which implies the weathering mechanism due to the interaction of meltwater and parental rock. Multivariate analysis revealed that CO3 and SiO2 weathering, sulphate dissolution, and pyrite oxidation dominate dissolved ion concentrations. Chemometric analysis of meltwater hydro-geochemistry through principal component analysis explains 72.1% of the total variance of four PCs. PCs 1, 2, 3, and 4 explain 39.21%, 12.91%, 10.24%, and 9.74% of variance, respectively, in 2016. Similarly, in 2017, four PCs explain 69.91% of the total variance. PC 1, 2, 3, and 4 can explain 26.62%, 20.12%, 12.64%, and 10.52% of variance.

Alkali-reactivity of Pernambuco east shear zone coarse concrete aggregates: An experimental discussion

Being the fifth largest country globally, Brazil has a wide variety of rocks used in concrete production. Due to their mineralogical characteristics, many Brazilian rocks present reactive alkali potential, mainly due to the strong presence of silica and/or silicates in their composition. Alkali silica reaction (ASR) was firstly public in Brazil in 1963 in the Jupiá dam. Since then, several ASR events have been reported, namely in Dam and electric power plants, which represent a concern, mainly due to those infrastructures' social, economic, and environmental impact. Even though the selection of the raw materials should consider the aggregate quality and adequacy for a certain application, it mostly depends on the local availability due to economic reasons. Thus, an effective way to evaluate ASR susceptibility on concrete aggregates and predict or prevent the in situ behaviour of the final concrete product properties is crucial. This is particularly important when aggregates sources are Shear Zones, such as Pernambuco East Shear Zone. International standards suggested evaluating aggregate susceptibility prone to ASR through petrographic analysis of aggregates in addition to expansion tests at mortar and/or concrete levels. Concrete prism tests (CPT) are considered the most reliable method for ASR potentially of concrete aggregates; however, CPT are very time consuming, and results might be available after one year. Thus, Brazilian Association for Standardisation suggested a new accelerated concrete test based on RILEM recommendation AAR-4.1, the NBR 15577-7.This work evaluated the behaviour of the coarse aggregate obtained from ZCPE, to prone ASR among different testing conditions proposed by most widespread international standards, namely, petrographic examination, ASTM C 1260, RILEM AAR-4.1, ASSTHO T 380 and NBR 15577-7. Then results were compared and discussed the applicability of the new national standard NBR 15577-7. According to petrographic examination, the coarse aggregate from Pernambuco East Shear Zone was potentially reactive. Expansion tests at mortar and concrete levels corroborated such results, and coarse aggregate was classified as potentially reactive among all standards followed. Thus, it can be concluded that the new NBR 15577-7 outputs similar results compared to other international standards and seems to be a faster way (20 weeks/140 days) to access the ASR potential of reactive aggregates.

Lithostratigraphy of the Bumbeni Complex and its associated subdivisions, South Africa

Abstract The Bumbeni Complex represents an Early Cretaceous volcanic complex that developed at the southern termination of the Lebombo mountain range in northern KwaZulu-Natal, South Africa. The volcano-sedimentary complex intrudes and disconformably overlies the Lebombo Group of the Karoo Large Igneous Province. The volcano-stratigraphy is defined by an assemblage of volcanic and volcaniclastic rocks as well as late stage quartz-syenite intrusions. Based on current geological and geophysical studies the complex is considered to represent the remnants of a collapsed cauldron structure. The stratigraphic succession is intricate and laterally discontinuous, comprising mafic and felsic lava flows, welded and non-welded tuffs, ignimbrites, lahar deposits, rhyolite domes and dykes and coarse-grained syenitic rocks. Rhyolite dome formation and collapse, and associated plinian eruptions and column collapse, were largely responsible for the variety of volcaniclastic rocks, including classic air-fall tuff deposits. The complex forms part of a northeast trending volcanic basement lineament known as the Bumbeni Ridge defined by aeromagnetic data.

The first identification of early Paleoproterozoic (2.46–2.38 Ga) supracrustal rocks in the Daqingshan area, northwestern North China Craton: Geology, geochemistry and SHRIMP U-Pb dating

Early Paleoproterozoic supracrustal rocks are relatively rare worldwide and only a few have been reported in the North China Craton (NCC). Daqingshan is a typical area of the Khondalite Belt, northwestern NCC, where early Precambrian supracrustal and intrusive rocks are widely distributed, although the precise age of all units remains unconfirmed. The Lower Wulashan Group is mainly composed of acidic to mafic volcanic and volcano-sedimentary rocks that have undergone amphibolite to granulite facies metamorphism; it was previously considered to be of Mesoarchean age. This study utilized integrated field and petrographic work, whole-rock geochemistry, and Nd whole-rock and zircon U-Pb-Hf isotopic analyses on the Lower Wulashan Group and related intrusive rocks. SHRIMP U-Pb dating of eight samples from the supracrustal rocks, interpreted as metavolcanics, yielded magmatic zircon ages of 2455–2382 Ma, thus for the first time identifying early Paleoproterozoic supracrustal rocks in the Daqingshan area. Thus it is of great importance for understanding the Precambrian evolution of the NCC as well as the Earth because this is within the period when magmatism was globally weak. Six samples from a variety of intrusive rocks have zircon U-Pb ages of 2436–2362 Ma, thus further confirming the depositional ages of the supracrustal rocks. These rocks include meta-alkali basalt, and are high in total rare earth element contents and have magmatic zircon εHf(t) values of −3.00 to +6.62 and crustal model ages of 3.12–2.52 Ga (38 analyses), and whole-rock εNd(t) of +1.0 to +2.6 with crustal model ages of 2.74–2.60 Ga (5 analyses). It is considered that the early Paleoproterozoic supracrustal rocks of the Lower Wulashan Group and related intrusive rocks formed in a continental environment, but more work is required to determine the tectonic regime (extension or subduction).

Geochronology and petrogenesis of granitoids and associated mafic enclaves from Ghohroud in the Urumieh–Dokhtar Magmatic Arc (Iran): Evidence for magma mixing during the closure of the Neotethyan Ocean

The Ghohroud granitoids (GG), containing mafic microgranular enclaves (MMEs) are located in the central part of the Urumieh‐Dokhtar Magmatic Arc (UDMA) in central Iran. They are associated with the subduction‐related magmatism in the Alpine‐Himalayan orogenic belt. The GG are comprised of a variety of intermediate and felsic rocks, including tonalite, granodiorite, granite, diorite porphyry and monzodiorite. The MMEs are gabbroic diorite and tonalite in composition and characterized by a fine‐grained hypidiomorphic microgranular texture with occasional chilled margins. They show rounded, sharp or irregular contact with the host granitoids. The occurrences of quartz, K‐feldspar and corroded plagioclase indicate that MMEs are the products of mixing between mantle and crust‐derived magmas. New ages of zircon U–Pb dating reveal that the GG in the Kashan area emplaced at ca. 19–17 Ma (Burdigalian). All the samples of MMEs and granitoid host rocks in this study are metaluminous and calc‐alkaline with I‐type affinities. They are enriched in light rare earth elements (LREEs) and show slight negative Eu anomalies (Eu/Eu* = 0.36–0.95). These features in a combination with the relative depletion in Nb, Ta, Ti and P, indicate the granitoids and MMEs are closely associated with subduction‐related magmas at an active continental margin. The host rocks yield relatively homogeneous isotopic compositions of initial 87Sr/86Sr ratios ranging from 0.706036 to 0.707055, εNd(t) values varying from −2.25 to 0.8, and the Nd model ages (TDM) vary in a limited range of 0.70–0.96 Ga. The MMEs show similar initial 87Sr/86Sr ratios (0.706420–0.707366), εNd(t) values (−1.32 to −0.27), TDM (0.68–1.09 Ga) and Pb isotopic compositions with host granitoids, which imply they attained isotopic equilibration during magma mingling and mixing. In combination with the petrographic, chemical and isotopic results, we suggest that the origin of MMEs and their host rocks were related to the interaction between crust‐derived melts and mantle‐derived mafic magmas. The magma‐mixing event possibly occurred during the transition from subduction to collision in the UDMA along with the closure of the Neotethyan ocean.

Discovery of Early Mesozoic Magmatism in the Northern Muglad Basin (Sudan): Assessment of Its Impacts on Basement Reservoir

The crystalline basement in the Central African Rift System (CARS) has been confirmed as a good unconventional reservoir in the surrounding basins of the Muglad area, Sudan. This study has recognized at least five Early Mesozoic intrusions for the first time at the northern margin of the Muglad Basin. Field and petrographic investigations show that they are mainly granite, syenite, diorite, and monzonite, with dominant alkali feldspar, plagioclase, quartz, and minor hornblende, biotite, and magnetite. Zircon internal structures, Th/U ratios, and rare earth element (REE) patterns indicate their magmatic origin. A total of 210 zircons from five samples were analyzed using LA-ICP-MS and they yielded U-Pb ages from 195.0 ± 6 to 225.0 ± 3 Ma, belonging to the Late Triassic-Early Jurassic. These results suggest that the Muglad Basin basement is not universally Precambrian as previously considered. The older basement was intruded and modified by Early Mesozoic magmas as evidenced by field contacts and our dating results. These magmatic events produced diverse Mesozoic igneous rocks prior to the formation of the Muglad Basin (Early Cretaceous), becoming new members of the crystalline basement. This composite basement then experienced prolonged weathering and fracturing for 65–95 Ma, resulting in porous and permeable weathered layers or fractured zones, making the basement a good unconventional reservoir for oil and gas.

Fracture Transmissivity in Prospective Host Rocks for Enhanced Geothermal Systems (EGS)

We experimentally determined the hydraulic properties of fractures within various rock types, focusing on a variety of Variscan rocks. Flow-through experiments were performed on slate, graywacke, quartzite, granite, natural fault gouge, and claystone samples containing an artificial fracture with a given roughness. For slate samples, the hydraulic transmissivity of the fractures was measured at confining pressures, pc, at up to 50 MPa, temperatures, T, between 25 and 100 °C, and differential stress, σ, acting perpendicular to the fracture surface of up to 45 MPa. Fracture transmissivity decreases non-linearly and irreversibly by about an order of magnitude with increasing confining pressure and differential stress, with a slightly stronger influence of pc than of σ. Increasing temperature reduces fracture transmissivity only at high confining pressures when the fracture aperture is already low. An increase in the fracture surface roughness by about three times yields an initial fracture transmissivity of almost one order of magnitude higher. Fractures with similar surface roughness display the highest initial transmissivity within slate, graywacke, quartzite and granite samples, whereas the transmissivity in claystone and granitic gouge material is up to several orders of magnitude lower. The reduction in transmissivity with increasing stress at room temperature varies with composition and uniaxial strength, where the deduction is lowest for rocks with a high fraction of strong minerals and associated high brittleness and strength. Microstructural investigations suggest that the reduction is induced by the compaction of the matrix and crushing of strong asperities. Our results suggest that for a given surface roughness, the fracture transmissivity of slate as an example of a target reservoir for unconventional EGS, is comparable to that of other hard rocks, e.g., granite, whereas highly altered and/or clay-bearing rocks display poor potential for extracting geothermal energy from discrete fractures.

Description and prospects of oil and gas potential of the Middle Devonian – Lower Frasnian complex of the south-east of the Timan-Pechora province

The article is devoted to the assessment of the petroleum potential of the deep Middle Devonian – Lower Frasnian oil and gas complex in the south-east of the Timan-Pechora oil and gas province. Within the Verkhnepechorskaya depression of the Pre-Ural foredeep and in the south of the Pechora-Kolvinsky aulakogen, several wells were drilled with a depth of more than 5 km, some of which opened deposits of the Lower Paleozoic. These strata are difficult to access and poorly studied, and the prospects for their oil and gas potential are unclear. The article describes the composition of the complex, gives geochemical characteristics, describes reservoir properties, and presents the results of 1 and 2D basin modeling. Models of the zoning of catagenesis are presented. The oil and gas complex includes a variety of oil and gas source rocks. It is possible to allocate collectors, as well as seals. In the Middle Devonian – Lower Frasnian sediments, the processes of oil, gas and gas condensate generation took place, which could ensure the formation of deposits both in the deep strata of the Middle Paleozoic, and in the overlying horizons. The generation and accumulation of hydrocarbons in deep-buried sediments occurred at a favorable time for the formation of deposits.

Transition in Thermal History and Recurring Burial-Exhumation Cycles along Colder Thermal Gradients at the Archaean-Proterozoic Boundary: New Insights from the Western Dharwar Craton, South India

Abstract The Hole Narsipur Greenstone Belt (HGB), in the Western Dharwar Craton, South India, preserves evidence for three cycles of metamorphism spanning the Archaean–Proterozoic transition. Changes in metamorphic style across the transition are investigated using integrated petrographic, mineral chemical, metamorphic evolutionary history, conventional geothermobarometry, and phase equilibria modeling studies of rocks of diverse bulk rock composition from the belt. These rocks record signatures of three overprinting metamorphic cycles (M2 → M3 → M4 in sequence), postdating a Mesoarchaean, M1 event in the craton. The M2 cycle represents characteristic LP–HT metamorphism along a counterclockwise (CCW) metamorphic P–T path, peak metamorphism at 4–5 kbar, 515–595°C, and high thermobaric ratios (T/P ~1050–1525°C/GPa) at the M2 peak. The intermediate M3 metamorphic cycle records a prograde burial of partially cooled M2 rocks to middle-lower crustal depths, peak metamorphism at P ~7.5–10.2 kbar, T ~630–655°C, and corresponding intermediate T/P ratios (T/P ~620–875°C/GPa) and a retrograde stage, marked by combined exhumation and cooling to P ~5.3–6.4 kbar, T ~530–575°C. The resultant P–T paths of evolution show variability of clockwise (CW) paths from classical hairpin type to two-stage prograde heating segments. During the M4 metamorphism (TMax ~630–640°C at ~8.9–10.3 kbar and with lower T/P ratios at ~610–720°C/GPa), the partially exhumed M3 crust is re-buried to lower crustal depths along an intermediate thermal gradient as during the M3 metamorphic cycle. We interpret the thermal transition, tectonic thickening along a cooler thermal gradient, repeated burial-exhumation cycles in the orogenic wedge, and tectonic mixing of the three metamorphic cycles in terms of a three-stage tectonic evolution of the HGB. These in a sequence are (a) the development of a hot and thinned crust (cf. M2 cycle), (b) the transition to a thickened crustal zone tectonic domain (cf. M3 cycle), with both the domains being part of the lithospheric peel-back driven convergence setting and (c) finally continental collision tectonics (cf. M4 cycle). The pulsating nature of orogenesis at the Archaean–Proterozoic boundary deduced here distinguishes the Western Dharwar Craton from other cratonic blocks globally at the same time frame.

The 1800-1770 Ma Colider silicic large igneous province in the Amazonian craton: crustal evolution using zircon in situ REE compositions, U-Pb ages and Hf isotope analyses

ABSTRACT This paper presents zircon U-Pb, REE and Hf data for Paleoproterozoic felsic volcanic rocks from the Colíder Group with outcrops in the southwestern Amazonian Craton. It is estimated that these rocks cover an area of 85,000 km2 with a volume of 2.7 × 106 km3. The Colíder volcanics are comprised of basalts, andesites and a variety of felsic rocks. The felsic rocks are characterized by rhyolite, andesite and dacite lavas with frequent intercalated pyroclastic and epiclastic deposits. Effusive and pyroclastic rocks are intruded in places by hypabyssal porphyritic rocks. The U-Pb ages obtained for the northeastern domain (1782–1776 Ma) are younger than the ages obtained for the southern domain (1800–1787 Ma). The NE volcanic facies show Hf TDM ages between 2.3 and 2.5 Ga (εHf from +1 to −3) and greater fractionation (Ce/Yb – 0.03–0.06) than the younger facies that has TDM from 2.4 to 2.7 Ga (εHf from −3 to −6) with Ce/Yb values of 0.025–0.030. The Hf isotope compositions, REE contents and U-Pb analyses suggest geographic (north-south) variations in composition, crystallization ages, and TDM age zonation during the generation of the Colíder large igneous province.

THE APPLICATION OF SCANNING ELECTRON MICROSCOPY USING ENERGY- AND WAVELENGTH DISPERSIVE SPECTROMETERS FOR CHEMICAL DATING OF URANIUM MINERALIZATION ON THE EXAMPLE OF CARBONACEOUS SHALES OF THE DABANZHALGA SUITE (EAST SAYAN)

On the one hand, the widespread use of electron microprobe analysis in the version of a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) and, on the other hand, the comparability of the metrological characteristics of the EDS and wavelength dispersive spectrometry (WDS) in the case of determining the major components of minerals are a favourable background for investigating the possibility of using SEM-EDS for chemical dating of uranium mineralization. Carbonaceous-siliceous formations of the Dabanzhalga suite are widespread in carbonate deposits of the Lower Paleozoic in the Oka structural-formational zone of the East Sayan and represent deep-water deposits of the back-arc basin. All varieties of carbonaceous-siliceous rocks of the Dabanzhalga suite are characterized by increased U, Au, Ag, Pt, Pd, Mo, V, P, Cu. Their amounts are 5–10 times higher than those for other black shale deposits of the Eastern Sayan. Uranium forms its minerals – uraninite and brannerite, in association with carbonaceous matter and sulfides, and is also part of anhydrous phosphates – xenotime, monazite. The paper presents data on the composition and dating of brannerite and uraninite in samples of carbonaceous-siliceous shale sampled at three sites: Uber-Zhadoy, Deed-Khara-Zhalga and Erye-Khara-Zhalga. The obtained estimates of the isochronous dates of uraninite and brannerite grains for these areas are 523±26, 506±10, and 511±17 Ma, respectively. It was shown that these dates could be compared with the age of metamorphism at the Sukhoi Log deposit, estimated using modern methods of isotope geochronology. It should be noted that the average estimates of the dates of uraninite and brannerite in all studied areas of the Dabanzhalga suite are lower than the corresponding estimates of the isochronous date, which is probably due to the partial loss of radiogenic lead. For the Uber-Zhadoy site, a comparison of the EDS and WDS data was carried out, and it was shown that when using the EDS data, there is an underestimation of the Pb content in uraninite, and, as a consequence, an underestimation of the age of uraninite.

Remote sensing-based mapping of the Wadi Sa’al-Wadi Zaghara basement rocks, southern Sinai, Egypt

The Wadi Sa'al-Wadi Zaghara area, southern Sinai, Egypt is a key geologic region within the framework of the Arabian-Nubian Shield (ANS). It almost documents the whole tectono-thermal evolution history of the Pan-African orogeny; hence it records the latest stages of Rodinia breakup (Late Mesoproterozoic) till the penultimate regional deformation event (D3) that impacted the northern tip of the ANS in the Late Neoproterozoic, i.e., before the Najd fault system. Since the metamorphosed volcano-sedimentary rock units in both Wadi Sa’al and Wadi Zaghara exhibit considerable differences in their geological evolution, they were dealt with as two distinct metamorphic belts. They cover a wide spectrum of basement rock varieties, which developed over a long period of time, from Late Mesoproterozoic (Wadi Sa’al metamorphosed volcano-sedimentary rocks) till Late Neoproterozoic Ediacaran period (post-collision granites). The different rock units of the study area were discriminated based on various image processing techniques such as Decorrelation Stretch (DS) Band Ratio (BR) and Principal Component (PC) of Sentinel-2, Landsat-8 and ASTER datasets. Remote sensing data analyses with the aid of petrography, previously published data and field verification enabled us to produce a new enhanced geological map of the study area. Advanced Land Observing Satellite (ALOS) digital elevation and enhanced Sentinel-2, Sobel directional filter images were successfully used for automatic lineaments extraction in the study area.

Strength of hard foundation rocks in the Southern Yakutian permafrost region (city of Neryungri)

This paper discusses the results of a statistical analysis of data from geotechnical surveys conducted in the mid-1970s in the city of Neryungri, southern Yakutia, located on sporadic, warm permafrost. The analysis included 162 laboratory determinations of uniaxial compressive strength of sandstone specimens. The test specimens were taken from core obtained boreholes. The study of the probabilistic distributions of sandstone strength values in the total sample population and in the formal groups divided into the rock strength categories has shown the following. In an unfavorable (artificially water-saturated) and favorable (frozen or air-dry) natural state, the Jurassic sandstone in the vast majority of cases is, according to the, a reliable and stable rock foundation for engineering structures. The range of average values for the rock varieties: sandstone of low strength and moderate strength together with sandstone of high strength in water-saturated and natural condition is 8.83–92.81 and 30.91–127.00 MPa. Comparison with the average dry strength values reported by Russian and foreign authors has shown that the Neryungri sandstone differs little in strength from sandstones southern Yakutia permafrost region (87.26 MPa), but also the territory of the former RSFSR, now Russia (84.53 MPa). On a regional scale, the proximity of a common measure of average strength and common territorial belonging, one of the sides of the natural essence of sandstone appears as a representative of the class of sedimentary rocks of the Eurasian continent.

Numerical modelling for geotechnical assessment of rock mass behaviour and performance of support system for diversion tunnels using optimized Hoek-Brown parameters

Purpose. Empirical and numerical methods play a vital role in assessing rock mass behaviour quantitatively and qualitatively to design underground structures/caverns and support systems. This research aims to assess and evaluate the rock mass be-haviour for safe, stable, efficient, and economical design of support system for underground structures especially tunnels in diverse rock mass conditions. Methods. In this research, such empirical design methods as Rock Mass Rating (RMR), Q-system and GSI were used to characterize and classify the rock mass environment along the tunnel for the preliminary design of twin tunnels and support systems. The geomechanical parameters, Hoek-Brown failure criterion, and its variants for assessing rock mass behaviour were optimized using multiple regression of Stewart, generalized and globalized variant of nonlinear regression method. The rock mass was classified for the selected section A-A. The excavation method and support system for the said section were designed based on the results obtained from empirical modelling. 2D elasto-plastic finite element method (FEM) was used for numerical analysis of rock mass behaviour and performance of the designed supports in section A-A. Findings. The major rock type encountered in the diversion scheme comprises gabbronorite (GN) and Ultramafic Association (UMA). Based on the quantification of RMR, Q-system, and GSI, section A-A’s rock mass ranges from very poor to poor. From the numerical analysis for the said rock mass environment both RMR and Q system support recommendations are equally efficient to support the rock mass surrounding the tunnel. However, keeping in view the yield zone, especially in the crown, the rock bolt’s length should not be less than 5 meters. Based on the analysis of results, both the tunnels are at a safe distance from each other. Originality. In this research, the design input parameters for numerical modeling were optimized by using different techniques to eliminate the chances of error in evaluating rock mass behaviour and designing an optimum support system in the said rock mass environment. Practical implications. The assessment of rock mass behaviour and the design of optimum support systems in heterogenous conditions is quite challenging and requires thorough investigation through different design techniques. This research provides a refined meth-od to be used for the safe, stable, and economical design of tunnels.

Kaizer Hill (Modi'in), a pre-pottery neolithic a quarry site - the terraced slopes.

The research of the Kaizer Hill site (the Hilltop and its Terraces), recognized as a Pre Pottery Neolithic A (PPNA) quarry site, involved studies of the rock damage associated with the quarrying activities as well as of the recovered material remains, mostly chipped stone artifacts. We present here the results of our on-site explorations (excavations, surveys and surface-collections), focusing on the findings deriving from the Terraces. Diverse rock damage patterns were identified and described, portraying systematic rock mass-exploitation through quarrying fronts, natural rock joints and fissures enlargement, drilling and chiseling. There are multiple indications that the local bedrock (Bi’na Formation, Turonian) comprising flint and limestone was quarried under a systematic quality evaluation, leaving residual flint unsuitable for exploitation. Of interest to note that nearly all of the flint artifacts excavated and collected on the Terraces were made on raw material transported from the Hilltop (Mishash Formation, Campanian), knapped in-situ, on the quarried rock surfaces of the slopes. The flint tools bear witness to intensive use involving mainly boring and drilling. The dominant tool type is the flint axe for which a variety of waste products related to its production were found in-situ, enabling the reconstruction of axe reduction sequence. Similar axes and waste products were found in many PPN sites indicating that there was a common, widely-used scheme of making flint axes during the PPN. Interestingly, besides the flint waste, there were also limestone waste products typical of the last shaping and thinning stages of axe production, indicating that limestone axes were shaped technologically similar to the flint ones, contrary to what has been assumed before. Rare findings, such as obsidian pieces, originating from much further a-field indicate ties with other PPN communities, near and/or far. Overall, this study provides unique and novel insights on Levantine PPN lifeways.

Hydrothermal – From Geology to Technology (Part 1)

Abstract The term hydrothermal is of geological origin. A great variety of crystals, minerals, ores and rocks have hydrothermal origin and occur as bulk, fine, ultrafine, and nanosized geologic materials. Hydrothermal refers to the action of water and other solvents at elevated temperature and pressure conditions in bringing about changes in the earth crust leading to the formation of rocks, minerals, crystals and ores. It also refers to the post-magmatic and pre-metasomatic stages. In the hydrothermal processes, a variety of volatiles also play an important role in the chemistry and geochemistry of hydrothermal solutions. The origin of a variety of metal deposits in deep-seated submarine hydrothermal ecosystems link with the origin of life on the earth. Today, hydrothermal has become one of the most important experimental methods of understanding the natural systems leading to the crystallization of rocks, minerals and ore deposits. Similarly, it has become one of the environmentally most benign techniques to synthesize a great variety of technological materials with desired functional properties. The technique has advanced so much that under laboratory conditions a wide range of pressure-temperature conditions can be created using specially designed hydrothermal autoclaves, PT sensors and controllers. In the present review, the authors discuss the evolution of hydrothermal process from geology to technology to develop technological materials in different sizes with specific functional properties. Also, the review describes some characteristic natural systems under hydrothermal conditions leading to the formation of some important geologic materials, the influence of different volatiles in the formation of various rocks and mineral deposits. Also the current trends in hydrothermal technology has been discussed with reference to the lowering of temperature and pressure conditions for the synthesis of high melting compounds like alkali rare earth tungstates, vanadates, diamond, etc. in this article.

Consumer Preference Survey of De Choice Fast Food in Uyo Metropolis, Akwa Ibom State, Nigeria

The purpose of this study was to provide a description of fast-food consumers, analyze their preferences, determine the adequacy of current packaging material, and recommend improvements in media vehicles and promotional strategy. A sample of 172 consumers entering De Choice Fast Food in Uyo Metropolis, were conveniently selected, while descriptive statistics was used in analyzing the data obtained. Findings showed that De Choice Fast Food consumers were predominantly resident in Uyo metropolis, singles, more males than females with some levels of education, relatively young people with average incomes. Of all the consumers, those who liked De Choice Fast Food products thought it was tasty, with great value while those who had complaints said their price was on the high side but that the foods/snacks were spicy. Furthermore, the findings showed that consumers prefer white transparent clear plastic packaging to other materials and that they consider De Choice Fast Food location, parking space and interior to be adequate. More so, they love a variety of music like gospels, pop, rock and traditional music and are mostly reached through De Choice bill boards. From these findings, we concluded that most of the consumers of De Choice Fast Food products were average income earners, quite young and enterprising men and women; the foods were of good taste and great value and billboards were the most effective means of reaching most of the consumers. Based on this, we recommended that a complete repackaging of their service strategy be revisited through process engineering of key service areas.

Quality Control of Nuclear Magnetic Resonance Measurements Using Pseudo-T2 Distributions

Summary Nuclear magnetic resonance (NMR) measurements are extremely valuable in the assessment of fluid-flow properties of rocks. However, inverted NMR transverse-relaxation time (T2) distributions are often biased by positivity constraints and the implementation of regularization (stabilization) methods. In some cases, it is difficult to determine whether the estimated pore-size distributions are reliable or byproducts of the inversion. On-site quality control of NMR inversion results is thus essential to avoid erroneous analyses based on nonphysical interpretations across conventional or unconventional rocks. It is also important to adjust the measurement acquisition process in real time in response to variable signal/noise conditions in the borehole environment. We introduce and compare three quality-control approaches; two of them are based on two different signal processing practices, namely the semilogarithmic derivative and the Hilbert transform, while the third is based on a nonlinear optimization technique. Validation of the inverted T2 distribution is performed by applying either method to the echo train decay of proton magnetization to estimate a pseudo-T2 distribution that is not affected by inversion artifacts. These three methods are data-driven processes for on-site, continuous quality control of borehole NMR measurements. In the first method, a pseudo-T2 distribution is constructed by taking the derivative of the echo train decay with respect to the natural logarithm of the relaxation time. For the second method, the Hilbert transform is applied to the raw proton magnetization decay to approximate the T2 distribution. The latter method consists of an approximation of the derivative of the time decay of magnetization using least-squares minimization. NMR laboratory measurements were performed on a wide variety of rocks, the associated T2 distributions were estimated using linear inversion, and the three quality-control methods were applied for comparison. The reliability of our quality-control procedures was verified by benchmarking them against the inverted T2 distributions. Furthermore, these quality-control methods, when applied continuously to borehole NMR measurements, enable the optimization of the measurements in real time to mitigate the effects of biasing noise. By verifying the location of the dominant mode of the T2 distribution during NMR measurement acquisition, the operator can determine whether (a) more stacking of proton magnetization decays is needed, or (b) longer- or shorter-time sampling is needed to attain a high-quality estimation of the pore-size distribution before performing the T2 inversion. Our work provides the basis of effective quality-control methods for NMR measurements for the petrophysical interpretation of rocks with complex pore-size distributions, especially in unconventional rocks, where noise present in the measurements (notably at early acquisition times), can mask the useful signal originating from pore-size distributions and fluids. The fast and reliable quality control of estimated T2 distributions is not affected by inversion artifacts, relying only on unfiltered, raw data.

Combined use of band shape algorithm, linear spectral un-mixing on Clementine & Moon Mineralogy Mapper data for identifying the imprints of magmatic differentiation – A study around Aristarchus Plateau

In this study, we have implemented a band shape algorithm (BSA) to identify the surface distribution of different minerals on parts of the Aristarchus Plateau using selected bands of Clementine and hyperspectral Moon Mineralogy Mapper (M3) data. BSA mineral maps derived using spectral bands of Clementine and M3 sensors could determine broadly similar surface distribution of minerals in the study area. Here we show that M3 based BSA mineral map could detect additional mineralogical details in selected places, especially around Vallis Schroteri, Aristarchus etc. areas. Therefore, we implemented linear spectral un-mixing (LSU) method on hyperspectral bands of M3 data using the reference spectra of Reflectance Experiment Laboratory (RELAB) to estimate the relative abundance of different minerals in above-mentioned areas. Based on the relative abundance of minerals in the LSU map, we could infer the presence of different rocks such as dunite/troctolite, norite, harzburgite, olivine-pyroxenite in those sites of the study area. The relative abundance of each mineral in a particular place was used as the basis for delineating specific rock in that place of the study area. These mineralogically diverse rocks with distinct proportions of mafic mineral and plagioclase content are exposed along a lunar structure that has been delineated using Gravity Recovery and Interior Laboratory (GRAIL) data. We hypothesize that some of these rocks might have formed by a magmatic differentiation process triggered by the structure by separating magma from the crystallized rocks and allowing the magma to compositionally evolve to produce different rocks under the influence of syn-magmatic structural activity.