Mineralogy Of Rocks Research Articles

A Bayesian Approach to End-Member Mixing Estimations in a Geological Nuclear Waste Repository in Sweden

The Swedish Nuclear Fuel and Waste Management Co. (SKB) has been searching for a site to construct a deep geological repository for spent nuclear fuel in Sweden. In 2012, Forsmark was selected as the location for the nuclear fuel repository and construction will start in 2027. An understanding of the chemical composition and evolution of the groundwaters at the site is an integral part of the long-term safety case. SKB’s traditional approach to describe a site has been to use M3 mixing of end-members as the main process controlling the groundwater composition. We propose a new approach using a Bayesian mixing model. Similarly to the traditional mixing approach, the fraction of each end-member for all samples in the dataset is calculated, with the exception of the deep saline end-member. Given the slow movement of the deep groundwaters, it is likely that they have reached equilibrium with the host rock and fracture minerals. Therefore, we introduce an additional step, consisting of a Phreeqc model to construct the theoretical composition of groundwater with an increasing Cl concentration in equilibrium with the mineralogy of the host rock. This is a way of introducing a geochemical explanation to deep saline waters found in the geosphere of the Forsmark site. The results indicated a higher fraction of glacial meltwater in deep groundwaters in Forsmark compared to previous models. This approach could be directly applied to other groundwater systems, with different mineralogy of the host rock, assuming slow moving groundwater in equilibrium.

Petrogenesis and tectonic setting of the mafic rocks from the Mfengou-Manki area, Central Cameroon Shear Zone: constraints from petrology and bulk-rock geochemistry

In the Central Cameroon Shear Zone, several studies were focused on granitoids and very few on mafic rocks. Here we report the petrography, geochemistry and mineralogy of the Mfengou-Manki mafic rocks in order to constrain their petrogenesis and tectonic settings and the role of lithospheric and asthenospheric mantle sources in their genesis. The studied mafic rocks are subdivided into columnar jointed basalts and mafic dykes. Clinopyroxene thermobarometry indicates that the mafic dykes crystallized at a temperature of 1071 to 1193 °C and a pressure of 4 to 12 kbar while the columnar jointed basalts emplaced at a temperature of 1064 to 1152 °C and 2 to 13 kbar pressure. The mafic dykes and columnar jointed basalts present high La/Sm, Sm/Yb, Nb/Yb and Th/Yb ratios, indicating garnet to spinel transition zone mantle source. The multi-element diagram of the mafic dykes display enrichment in Nb, Ta, Pb and Ti and depletion in Th, U, Ce and Zr compared to that of the columnar jointed basalts (slight depletion in Nb and Ta and pronounced depletion in U, Pb and Zr and enrichment in Cs, Ba and Rb) indicating the little involvement of the sub-continental lithospheric mantle to the formation of the columnar jointed basalts. The Nb/La ratio > 1 for the mafic dykes and < 1 for the columnar jointed basalts also suggest the derivation of the mafic dykes from the asthenospheric mantle and the columnar jointed basalts from the mixed lithospheric-asthenospheric mantle due to the sub-continental lithospheric mantle delamination under the Central Cameroon Shear Zone.

Mineralogy and Sr Isotope Characteristics of Dahua Stratified Tremolite Nephrite and Host Rocks, Guangxi Province, China

The tremolite nephrite deposit in Dahua county, Hechi City, Guangxi province, China is a new genetic type of nephrite deposit. It is hosed by Mg-poor limestone (~1.30 wt.% MgO) and intruded by diabase (~45 wt.% SiO2). The Mg and Si contents of these rocks are lower than those of the tremolite (58.18 wt.% SiO2, 13.18 wt.% CaO, 24.16 wt.% MgO), indicating an obviously insufficient source for the metallogenic material that generated the deposit. In particular, some tremolite nephrite ore bodies have no clear contact metamorphism between the host and intrusive rocks, which have the characteristics of stratified mineralization (stratified tremolite nephrite). The origin and mineralization of stratified tremolite nephrite remain poorly constrained. To address this shortcoming, the mineralogy, geochemistry and Sr isotopic of host rock, altered marble, stratified tremolite nephrite and intrusive rock in the Dahua stratified tremolite nephrite deposit were studied. The results show: stratified tremolite nephrite mainly consists of aggregates of microcrystalline-cryptocrystalline tremolites with content exceeding 95%. The in situ rare earth elements (REEs) distribution pattern of hydrothermal calcite in the contact position between stratified tremolite nephrite and marble is similar to that of marine carbonate rock, showing obvious enrichment of HREE, which is different from calcite in limestone and marble. 87Sr/86Sr of stratified tremolite nephrite is relatively uniform, with an average value of 0.7070, within the range of Permian seawater. The mean value of Y/Ho in the hydrothermal calcite is 51.24, indicating that the marine fluid has not been impregnated by terrigenous materials. In summary, the hydrothermal fluid rich in Ca and Si is formed after marine carbonate rocks are altered by marine fluids. Hydrothermal fluids alter diabase rocks formed by altered minerals like titanite, chamosite, zoisite, etc. This process leads to the formation of metallogenic hydrothermal fluids abundant in Si, Ca, Fe and Mg. The metallogenic hydrothermal fluids migrate in faults and fractures of marble and crystallize to form tremolite nephrite under suitable ore-forming conditions.

Identification of magnetic mineralogy and paleo-flow direction of the Miocene-quaternary volcanic products in the north of Lake Van, Eastern Turkey

Abstract One of the major challenges facing geochemistry, petrology, and volcanology researchers is the difficulty in determining the origin and paleo-flow directions of igneous and volcanic rocks. It is not possible to clearly determine origins and paleo-flow directions in areas with numerous volcanic centers. Anisotropy of magnetic susceptibility (AMS) is a valuable method that provides insights into the origins and paleo-flow directions of lavas that are complex to study. The presence of volcanic materials with thicknesses up to 1 km, coming from different sources at varied time intervals in the north of Lake Van, makes this area an ideal setting for implementing AMS in establishing paleo-flow directions. This study presents the magnetic mineralogy and AMS analysis of volcanic rocks from the Miocene to the Quaternary in the Lake Van region. We conducted isothermal remanent magnetization (IRM) and high-temperature susceptibility (HTS) studies to determine the magnetic mineralogy. IRM studies revealed that (titano)magnetite is responsible for the magnetization in most samples, while both (titano)magnetite and hematite are responsible for the rest. Alteration degrees and Curie temperatures of the rock samples were also determined through HTS measurements. There is good agreement between the anticipated directions of lava flow and our findings for nearly all volcanic rocks.

Nyatygran intrusive suite, Bureya massif: Petrography, geochemistry, and age

The proposed review and analytical article provides updated information on the geology, petrography, mineralogy, and chemical composition of rocks of the Precambrian Nyatygran intrusive suite. The article provides a geochemical interpretation of the chemical and trace element compositions and presents the most actual data on the uranium-lead isotopic age of the rocks. The igneous formations of the Nyatygran gabbro-granodiorite-granite complex make up small intrusive massifs of gabbroids and granitoids, located near the ore-bearing Mel’gin trough, in the basins of the Verkhny Mel’gin, Chepkan, and Bureya rivers and their tributaries. In the gabbroids, the main rock-forming minerals are labradorite, andesine, bluish-green hornblende, and biotite. The gneissic granitoids are dominated by cataclastic quartz and feldspars (andesine, oligoclase, microcline) and contain abundant micas (biotite, sericite). The subalkaline leucogranites are dominated by oligoclase, quartz, orthoclase, and microcline; they also contain significant amounts of biotite and aegirine and rare amphibole (hornblende). The gabbro and gabbrodiorites of normal and elevated alkalinity are assigned to the high-aluminous high-magnesian rocks. The gabbroids represent I-type igneous rocks. The gneissic granitoids of normal and elevated alkalinity are predominantly high-aluminous, more ferroan than magnesian rocks, and are represented by S- and I-type granitoids. The determined isotopic ages of the Nyatygran suite formations are confined to the three main ranges: 933 ± 12–916,3 ± 7,2 Ma (1st magmatic phase: gabbro, gabbrodiorites, amphibole-biotite granites), 909,0 ± 6,6–907,3 ± 5,5 Ma (2nd phase: granodiorites and granites), and 806,8 ± 6,6–789 ± 4,0 Ma (3rd phase: biotite granites and granite-porphyry dikes). The Nyatygran suite age is established as Neoproterozoic and corresponds to the early Neoproterozoic, or Tonian (1000–720 Ma), according to the International Chronostratigraphic Scale, 2018. On the 3rd generation 1:1 000 000-scale State geological maps of the Russian Federation, it is presented as Early Proterozoic.

Mineralogy of host rocks of the Osinovskoe gold-quartz deposit (Central Urals)

The paper describes the mineralogy of mica shales of the Osinovskoe gold deposit in the Central Urals. Our studies unraveled the role of dynamometamorphism in the transformation of primary rocks and allowed the characterization of their metasomatic alteration. We showed the relationship between plastic and brittle deformations and the formation of gold-bearing mineral assemblage with major pyrite, pyrrhotite and ilmenite and subordinate and rare sphalerite, chalcopyrite, marcasite, rutile, magnetite, molybdenum, galena, altaite, hessite, melonite, petzite, calaverite, volynskite, and sylvanite. The Ag content of native gold varies from 4 to 29 wt. %. Tellurides are associated with pyrite and pyrrhotite and also form monomineral grains and intergrowths in chlorite and mica with inclusions of REE minerals (xenotime-(Y), monazite-(Ce), hydroxylbastnesite-(Ce)), allanite-(Ce)), REE-bearing minerals (epidote, apatite, zircon), Th silicate (torite), and uraninite.

Rock Mineralogy Analysis of Airbenakat Formation to Map the Characteristics of the Reservoir Rocks in each Depositional Environment

The Airbenakat Formation is a sandstone reservoir which is one of the oil reservoirs located in Sumatra and is part of the South Sumatra Basin. The mineral composition of the sandstone reservoir in the Airbenakat Formation consists of quartz minerals as rock grains, clay as matrix and is often identified as cement, while carbonate as rock cement. Based on lithofacies observations, the depositional environment of the Airbenakat Formation consists of: Volcanic Alluvial Fan, Lake, Braid Bar, Braided Channel, Braid Deltaic Environment, Mud Flat, Tidal Sand Bar, Tidal Environment, Shallow Sea, and Deep Sea. This research was conducted on 2 (two) oil fields, namely MRP dan TPN which have different depositional environments but are included in the Airbenakat Formation as part of the South Sumatra Basin.The analyzes used in this study include X-Ray Diffraction (XRD) analysis, petrography, and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM/EDX). Analysis of the mineralogical content of the Airbenakat Formation will assist to determine the performance of chemical injections such as injection of anionic surfactant. The anionic surfactant used for chemical injection in Airbenakat Formations will be optimal if the content of smectite and calcite minerals can be ascertained. The presence of smectite and calcite minerals will affect the results of anionic surfactant injection. This research shows the results of anionic surfactant injection on the presence of smectite and carbonate in the injected core.

Accelerated weathering of silicate rock dusts predicts the slow-release liming in soils depending on rock mineralogy, soil acidity, and test methodology

The ongoing acidification of soil poses a significant threat to the proper functioning of various ecosystems worldwide. Silicate rock dusts (RD) are increasingly amended to acid soils to restore their pH, but the acid neutralising capacity (ANC) and dissolution rate of these products are highly variable and lack proper assessment protocols. It is expected that pH-dependent RD ANCs and dissolution rates dictate the pH increase in soils depending on the initial pH and pH buffer power of the soil. This study addressed these questions by comparing and validating three accelerated weathering tests for their capacity to predict the gradual liming effects in a two-year outdoor mesocosm. Five commercial RDs (two basalts, phonolite, foidite, and trachy-andesite) were tested in four acidified forest soils varying in initial pH, in texture and associated pH buffer power. First, RD dissolution was measured in aqueous batch renewal systems during one year at various starting pH (3.5, 4.5, and 5.5) and constant temperatures (20 °C, 37 °C, and 65 °C). These showed that the ANCs of RDs exhibit a fast fraction (half-life < 1 day) followed by a slower fraction. Second, titration tests of RDs at fixed solution pH, i.e., pHstat, performed between pH 3.5 and 4.5 revealed surface normalised dissolution rates that decreased factors 10–100 per unit pH increase, the slope depending on the RD’s mineralogy. Indeed, the rate ranking of observed surface area normalised dissolution rates confirmed that of literature-based values, weighed by the XRD-derived mineralogical fractions. Third, lime-calibrated agitated soil-RD suspension tests were conducted for two months, illustrating the dependency of RD ANC on soil context, and yielding ANCs that were factor 2–5 times larger than in the batch renewal test because of pH buffering effects of soil particulates. Finally, an outdoor soil mesocosm on the four acid soils amended with RDs at 12 Mg/ha and 340 Mg/ha was established and soil pH was monitored for 2 years. The observed pH trends corresponded well for both the low dose (R2a = 0.67) and the high dose (R2a = 0.93) with model predictions made using the pH- and temperature-dependent RD dissolution rates (pHstat test) and the soil pH buffer power and RD slow ANC-fraction (soil-RD suspension test). This model predicts half-lives of RD dissolution ranging between <1 month to >100 years depending on the starting pH of the soil, its pH buffer power, the RD mineralogy (XRD based) and its specific surface area. This study shows that the dissolution and ANC of RD can be most pragmatically predicted with a series of lime-calibrated soil-RD suspension tests of maximally two months.

The Thermal Structure of Central Te Riu a Māui/Zealandia Continent as Determined From the Depth to Base of Magnetic Sources

AbstractTo investigate the thermal structure of central Te Riu a Māui/Zealandia continent we estimate the depth to base of magnetic sources (DBMS), using an updated compilation of magnetic data. We calculate thousands of power spectral density estimates and solve an analytic solution for the fractal distribution of magnetization using a Bayesian method constrained by a sediment thickness model. Our DBMS results are broadly similar to a global model yet show complex relationships with independent models of crust and elastic thicknesses, and depth to base of seismicity (D90). Across central Zealandia, DBMS occurs above, coincident with, and below the Moho reflecting that factors additional to temperature influence DBMS. Away from subduction zones crustal thickness likely modulates DBMS while plate margins show varying influence dependent on margin characteristics. In the Taupō Volcanic Zone we interpret DBMS to reflect Curie point temperature at an average depth of 9–11 km. Error analysis shows that the choice of prior influences the posterior standard deviation and can result in counter intuitive error versus DBMS relationships. We use the DBMS as a basal temperature isotherm in heat flow models to compare with heat flow derived from borehole temperature measurements. Using the standard Curie point temperature of 580°C we find that DBMS derived heat flow models over estimate heat flow in areas underlain by plutonic rocks. We propose this reflects a higher titanomagnetite content in these rocks, although detailed studies of the magnetic mineralogy of Zealandia's plutonic rocks are required.

Weathering alterations of coal mining wastes geochemistry, petrography, and mineralogy, a case study from the Janina and Marcel Coal Mines, Upper Silesian Coal Basin (Poland)

Weathering-caused alterations in coal mining waste geochemistry, petrography, and mineralogy occurring in the known time span of 1998–2018 in the temperate climate of Poland were investigated. A series of coal mining waste rocks representing two parts of the Upper Silesian Coal Basin (USCB), differing in coalification stage, i.e., corresponding to sub-bituminous and bituminous coals, have been selected to find how the level of organic matter conditionates the weathering. Differences in organic matter content, petrographic composition, rock mineralogy and inorganic geochemistry were also taken into account. Whereas organic petrography, including vitrinite reflectance values, do not show significant weathering signs, apart from irregular cracks and, in very rare cases, paler in color oxidation rims, organic geochemistry has been affected due to low-temperature secondary processes, including increased oxygen index values, particularly in less mature coal mining wastes. Biomarker distribution has been changed to the largest extent, with partial removal of n-alkanes possibly due to biodegradation of organic matter and water-washing of lighter polycyclic aromatic hydrocarbons, including alkyl naphthalenes. Organic matter of lower maturity in coal mining wastes from the USCB eastern part, as more reactive, showed a higher level of secondary transformations. Minerals formed during weathering due to time and storage on dumps were mainly oxidation products of iron sulphides: goethite and jarosite; however, most of the minerals have not been altered. Thus, despite physical changes in coal mining wastes, such as increased brittleness, decreasing fragment size and surface color change, there are only limited changes in inorganic chemistry and mineralogy. This indicates that low-temperature processes do not favour the inorganic elements release to the environment and points out that measures to prevent self-heating within the dumps are the most vital part of post-mining activity leading to the best scenario - slow low-temperature weathering of coal mining wastes.

Uranium recovery from phosphate rocks/minerals – A comprehensive review

Although the use of nuclear energy is still viewed with caution due to various problems associated, such as the safe operation of 'aging' nuclear plants and the final disposal of nuclear waste, many countries in Europe are now increasingly considering nuclear energy as an alternative to reducing fossil fuel energy production. At the present stage primary sources of uranium are sufficient to meet uranium needs and secondary sources are becoming increasingly important in terms of their long-term availability and environmental friendliness. Mining/recovery of uranium from secondary sources (such as phosphate minerals) is considerably safer in terms of exposure to radiological radiation and therefore requires less stringent safety measures. Uranium is also present in waste produced from certain industrial processes such as fertilizer production industry (e.g. phoshogypsum) and in nuclear waste. This work refers to the extraction and recovery of uranium from phosphate rocks, which is directly related to the production of uranium-free phosphate fertilizers and aims to limit environmental pollution related to the use of phosphate fertilizers. Since the chemistry during the leaching step is critical to efficient uranium recovery, various investigations have been carried to study various parameters that play an important role in achieving an optimum uranium extraction from rocks. Uranium leaching is carried out under acidic or alkaline conditions and the choice of chemistry is determined by the mineralogy of the host rocks. Acid leaching yields a higher recovery than alkaline leaching because the matrix is often more resistant to alkali than to acid leaching. However, the alkaline leaching process has the advantage of leading to the precipitation of a comparatively purer product directly from the leaching liquid. In addition, the washing solutions can be regenerated for further use, making this method more environmentally friendly. Recently alternative methods have been proposed which make use of uranium complexing ligands (e.g. EDTA) to achieve more efficient and selective uranium recovery.

Adsorption behavior of surfactants on sandstone reservoir rocks with carbonate cements and its influence on wettability alteration

AbstractThis study investigates the adsorption behaviors of surfactants in sandstone reservoir rocks containing various amounts of carbonate cement/minerals and their impact on wettability alteration under low‐salinity conditions. Two types of rock samples from sandstone reservoirs of Assam oilfields in India are selected based on XRD results. These rock types are (i) high carbonate cement (HCC) core sample with higher carbonate cement (calcite 5.6% and dolomite 4.0%), and (ii) low carbonate cement (LCC) core sample with lower carbonate cement (calcite = 0.5% and dolomite 0%). The study reveals that the mineralogy of sandstone reservoir rocks especially the carbonate minerals affects the brine‐rock interactions including wettability alternation and surfactant adsorption. Notable differences (2° to 8°) in contact angles for the two rock types at different salinities revealed that carbonate cement in sandstone thus impacts brine‐rock interactions. Further, low salinity surfactant (LSS) could positively alter the wettability of both rock types to water‐wet conditions (contact angle &lt;60°). The most favorable wettability alterations (up to 30°) were achieved with cationic LSS solutions for both core types. Using LSS solutions also reduced the adsorption of anionic surfactant by around 40% and 33% for HCC and LCC rock samples, respectively. The study's novelty emanates from investigating the impact of sandstone reservoir rock mineralogy with varying amounts of carbonate cements on the adsorption behavior of surfactants under low‐salinity conditions. Moreover, this study provides a better understanding of the interrelationship existing between the degree of wettability alteration and the amount of surfactant adsorbed by sandstone rocks.

Mineralogy and geochemistry of trachytic rocks from the Lichi Volcanics, Eastern Himalaya: insights into the Kerguelen mantle plume activity in the Eastern Himalayan Region

Mineralogy and geochemistry of trachytic rocks from the Lichi Volcanics, Eastern Himalaya: insights into the Kerguelen mantle plume activity in the Eastern Himalayan Region

Primary Composition of Kimberlite Melt

The compositions (mineralogy, major- and trace-element chemistry of rocks and minerals, and Sr-Nd-Hf isotope systematics) of two kimberlite bodies, the Obnazhennaya pipe and the Velikan dyke from the Kuoika field, Yakutian kimberlite province (YaKP), which are close to each other (1 km distance) and of the same Upper Jurassic age, are presented. The kimberlites of the two bodies are contrastingly different in composition. The Obnazhennaya pipe is composed of pyroclastic kimberlite of high Mg and low Ti composition and is characterized by high saturation of clastic material of the lithospheric mantle (CMLM). The pyroclastic kimberlite contains rare inclusions of coherent kimberlite from previous intrusion phases. The Velikan dyke is represented by coherent kimberlite of relatively high Fe and high Ti composition, having neither mantle xenoliths nor olivine xenocrysts. The similarity of the isotopic geochemical characteristics for kimberlites from both bodies and their spatial and temporal proximity suggest that their formation is associated with the presence of a single primary magmatic source located in the asthenosphere. It is proposed that the asthenospheric melt differentiated into two parts: (1) a predominantly carbonate composition and (2) a carbonate–silicate composition, which, respectively, formed (a) low Fe and (b) Mg-Fe and high Fe-Ti petrochemical types of kimberlites. Both parts of the melt had different capabilities to capture the xenogenic material of the mantle rocks. The greater ability to destroy and, subsequently, capture CMLM belongs to the melt, which formed a high Mg type of kimberlite and which, according to the structural–textural classification, more often corresponds to the pyroclastic kimberlite. It is suggested that the primary kimberlite melt of asthenospheric origin is similar in composition to the high Fe, high Ti, coherent kimberlite from the Velikan dyke (in wt. %: SiO2–21.8, TiO2–3.5, Al2O3–4.0, FeO–10.6, MnO–0.19, MgO–21.0, CaO–17.2, Na2O–0.24, K2O–0.78, P2O5–0.99, CO2–12.6). It is concluded that the pyroclastic kimberlite contains only xenogenic Ol, whereas some of the Ol macrocrysts with high FeO content in the coherent kimberlite have crystallized from the melt. The similarity of Sr-Nd-Hf isotope systematics and trace element compositions for kimberlites of different ages (from Devonian to Upper Jurassic) in different parts of the YaKP (in the Kuoika, Daldyn and Mirny fields) indicates a single long-lived homogeneous magmatic asthenospheric source.

Thermal influence of sills on the chemostratigraphy and mineralogy of carbonate rocks from the Irati formation, Paraná basin

Carbonate rocks and shales are prominent lithologies in atypical petroleum systems. In these settings, the thermal effects of sills play a crucial role leading to mineralogical and geochemical alteration in the host rocks and in the maturation process of the associated organic matter. While extensive research has been conducted on shales within atypical systems, the understanding of the petrophysical and geochemical properties of carbonate rocks remains uncertain in numerous basins. In this study, we selected the Irati Formation (Paraná Basin) to investigate the thermal effects caused by diabase sills on the chemostratigraphic and lithologic features of carbonate rocks. We conducted mineralogical analyses, examined oxygen and carbon stable isotopes, and analyzed inorganic geochemical data from two distinct sections of the formation: one with diabase sills intruding the sequence and the other without identified intrusions in the area. Widespread recrystallization of minerals is observed throughout the studied rock wall, resulting in the formation of marbles and calc-silicate rocks, where dolomite is mainly replaced by calcite. The carbonate bank, located 5–7 m below the sill, is marked by brucite and chrysotile, while the rocks up to 1 m below and above the intrusion show the presence of tremolite, diopside, and antigorite. Substantial variations in elemental data are observed, including a significant increase in SiO2 and K2O below the sill, as well as elevated MgO levels within the carbonate bank. Additionally, stable isotopic signatures of oxygen and carbon display a negative shift influenced by decarbonation and intense fluid flow controlling the reactions. The contact aureole resulting from the intrusion is identified at least 7 m above and below the sill based on mineralogical and inorganic geochemical data.

Geology, Petrology, and Mineralogy of Hornfels-like Rocks (Beerbachite) in the Early Paleozoic Olkhon Collisional Orogen (West Baikal Area, Russia)

Geological, mineralogical, and petrological observations are reported for hornfels-like fine-grained granular mafic rocks in the Early Paleozoic Olkhon collisional orogen (West Baikal area, Russia). The rocks are composed of orthopyroxene, clinopyroxene, amphibole, plagioclase, and ilmenite; some samples also contain olivine, phlogopite, spinel, and titanomagnetite (Opx+Cpx+Amp+Pl+Ilm±Ol±Bt±Spl±Ti-Mag). There are three occurrences of these rocks in the area: a 500 m × 1000 m field in the Shirokaya Valley, another occurrence within the Tazheran Massif (a complex of igneous and metamorphic rocks), and dismembered dikes on the southern margin of the Birkhin gabbro intrusion. The Shirokaya field is located between two 500 Ma intrusions of the Birkhin gabbro; the Tazheran occurrence coexists with syenite, including nepheline syenite, subalkaline gabbro, and marble protrusions; and the dismembered dikes coexist with carbonates and display progressive alteration of dolerite through typical granular varieties. The dikes associated with granite and marble veins mark a part of a large arc-shaped shear zone that traverses the whole intrusive body produced by rotation of a rigid gabbro block during the peak of tectonic deformation at 470–460 Ma. All three occurrences of the hornfels-like rocks lack any evident source of heat that would be responsible for the thermal alteration of the igneous protolith. We hypothesize that the precursor, subvolcanic dolerite, may have undergone autometamorphism maintained by self-generated heat. Mafic magma intruded during high-rate strike–slip faulting, which caused rapid recrystallization of magmatic minerals and produced the observed metamorphic structures. Proceeding from the controversy in the formation mechanisms, with a heat source required for hornfels but lacking from the sampled occurrences of hornfels-like rocks, we suggest identifying the latter as beerbachite, though the term has mostly fallen into disuse. The reason is that the Olkhon rocks we study have a mineralogy, structure, and texture that are perfectly identical to those of beerbachites described in publications from the first half of the 20th century.

Middle Devonian Evandale porphyry Cu-Mo (Au) deposit, southwestern New Brunswick, Canada: Analysis of petrogenesis to potential as a source for distal intrusion-related epithermal gold mineralization

The 391.2 ± 3.2 Ma (U-Pb on zircon) Evandale Granodiorite of southwestern New Brunswick is quite a unique intrusive rock in the southern part of the northeastern Appalachians. This research examines the relationship between the porphyry Cu-Mo-(Au) and epithermal systems with Evandale Granodiorite and environs. This Middle Devonian multi-phase I-type granite intrudes along the northern boundary of the deformed Silurian sedimentary and mafic volcanic rocks of the Mascarene Basin. This granitoid is identified as an oxidized I-type system with adakitic geochemical signatures and associated porphyry Cu-Mo-(Au) mineralization, possibly linked to slab failure sourced from decompression melting of the lower crust caused by post-collisional uplift, similar to the Magaguadavic Granite to the southwest. The Evandale adakitic intrusion is divided into two phases that consist of (1) a calc-alkalic coarser phase ranging from medium- to coarse-grained, seriate to porphyritic granodiorite to monzogranite with metaluminous to peraluminous features, and (2) the later stage alkali-calcic fine-grained (to aplitic) locally porphyritic phase ranging from a monzogranite to syeno-granite with peraluminous characteristics. The primary mineralogy of the intrusive rocks consists of K-feldspar + albite + plagioclase + quartz + biotite + hornblende + apatite ± muscovite ± zircon, along with several alteration phases, such as biotite, chlorite, sericite, and calcite. Geochemical analyses (using INAA, ICP-MS, and XRF) indicate that both phases of the Evandale granodiorite show a high concentration of Cu (108 ppm) and Au (33 ppb) associated with the presence of pyrite, chalcopyrite, and arsenopyrite in the fine-grained dyke samples. Up to 6 ppm Mo was contained within the granitic phase, whereas lesser amounts of Mo were confined to the fine grained to aplite phases. Microprobe analyses of primary biotite as both phenocrysts and groundmass shows 0.55 avg. wt.% Cl and 0.21 avg. wt.% F, which are relatively concentrated compared to other high-grade porphyry deposits. Hydrothermally altered rocks, veins, and sulfides associated with the porphyritic suite result from buoyant magmatic-hydrothermal fluids from a deeper intrusion exsolving fluids (quenched porphyry related), depressurizing, and reacting with the host coarser grained granodiorite and even some of the dykes locally. Based on the geothermometry and geobarometry of amphibole (actinolite-magnesiohornblende), the crystallization temperature and pressure of the Evandale coarse-grained granite and aplite are 674–755 °C, 0.2–0.7 kbar (20–70 MPa) and 838 °C, 0.42–1.4 kbar (42–140 MPa), respectively. This is consistent with biotite formation at temperatures ranging from 670° to 760 °C, based on Ti-in-biotite thermometry. Also, zircon saturation temperatures of the earlier coarse-grained porphyritic granites and later fine-grained porphyry to aplitic dykes are 736 °C and 787 °C, respectively. Spatially and temporally associated gold deposits beside Evandale and within this region of southwestern New Brunswick suggests that these oxidized I-type intrusions are a potential source for distal, low sulfidation epithermal gold deposits in the region.

Accurate Petrophysical Interpretation of Carbonate using the Elemental Capture Spectroscopy (ECS)

Elemental capture spectroscopy (ECS) is an important tool in the petroleum industry for determining the composition and properties of rock formations in a reservoir. Knowledge of the types and abundance of different minerals in the reservoir is crucial for accurate petrophysical interpretation, reservoir engineering practices, and stratigraphic correlation. ECS measures the elemental content of the rock, which directly impacts several physical properties that are essential for reservoir characterization, such as porosity, fluid saturation, permeability, and matrix density. The ability to accurately determine these properties leads to better reservoir mapping, improved production, and more effective resource management. Accurately determining the mineralogy and porosity of carbonate rocks and other materials is the aim of this paper. Calcite, dolomite, quartz, clay (illite), anhydrite, and pyrite, in addition to water as a fluid, are taken into account in the computation. The formation's lithology and porosity can be ascertained from this data. When compared to the core descriptions in the geological report, the results demonstrated a distinct zone of unique lithology with good prediction accuracy.

P-T-H2O conditions during multistage fractional crystallization, magma replenishment and mixing through the nephelinitic–phonolitic series and their role on the eruptive styles on the Trindade Island (South Atlantic Ocean, Brazil)

Magmas are affected by several differentiation processes as they migrate through the lithospheric plate, which are recorded by mineralogy, textures and geochemistry in igneous rocks. These processes and their related physico-chemical conditions can be reconstructed by petrography and mineral geochemistry, providing a detailed magmatic history from magma source to crystallization. We present a detailed petrography coupled with single-spot and multiple-profile mineral chemistry and whole-rock geochemistry that allows the reconstruction of P-T–H2O–depth conditions that affected the nephelinite-phonolite magmatic series and influenced eruptive styles. Results on nephelinites and phonolites suggest their cogeneticity and led to the recognition of multistage fractional crystallization, magma replenishment and mixing during their storage and eruptive events. Our data allow us to reconstruct nephelinite magma storage within the oceanic crust (20-5 km depth) with higher H2O content, and chambers lodged below the volcanic centers (<5 km depth) with lower H2O contents, which represent pre-eruptive magma storage subjected to progressive boiling. On the other hand, the main phonolite magma storage, crystallization and mixing with nephelinitic pulses occurred within the lithospheric mantle at depths of 57–37 km, indicating that the main magmatic differentiation of this series occurred at this depth. This process is accompanied by H2O increase, which may be related to magma ascension from the mantellic depths to the volcanic environment and eruption controlled by volatile contents. These interpretations are consistent with Strombolian to Hawaiian eruptive styles reported previously for nephelinite episodes and Vulcanian eruptive styles for phonolite ones.

A Review of the Mineralogy, Petrography, and Geochemistry of Serpentinite from Calabria Regions (Southern Italy): Problem or Georesource?

Serpentinite rocks testify to the ocean-floor metamorphism that took place and transformed the original mineralogy and fabric of previous ultramafic rocks. Due to their tectonic and petrological importance, in recent decades, there has been increasing interest in serpentinites. From the economic point of view, it is worth noting that, due to their beauty and attractiveness, serpentinite rocks have been exploited and traded as building and ornamental stones since prehistorical times worldwide. In this work, we provide a comprehensive report of the petrographic, mineralogical, petrophysical, and geochemical features of the serpentinites cropping out in the northern sector of the Calabria–Peloritani Orogen (Italy), where the historical quarries are located. Since these serpentinite rocks have been traded for a long time and employed as an excellent building material, their detailed knowledge may provide a useful tool to understand their behavior when they are employed as building materials, to predict their performances upon emplacement in monuments, and to plan correct restoration by considering the provenance of the lithotypes employed. Moreover, comprehensive characterization is also particularly important because it has been reported that serpentinites from Calabria may contain asbestiform and other fibrous minerals, as testified by the occurrence of chrysotile, tremolite, and actinolite asbestos located within the veins, which could lead to health problems due to asbestos fiber exposure. Finally, serpentinite may be considered as an important potential CO2 sequestration sink.