Related Minerals Research Articles

Nutrition in open abdomen

Open abdomen is known as aserious consequence of various intra-abdominal pathologies. Initially, patients often have alife-threatening condition, sepsis or septic shock. Severe stress related malnutrition, mineral and fluid imbalance develop as metabolic consequences. Intestinal fistulas also occur as afrequent complication in patients with open abdomen. In such patients, acomprehensive approach is needed, including rehabilitation, nutritional support using optimal formulas, and local care for the open abdomen. Our case report presents apatient with open abdomen and enterocutaneous fistulation. Acomplex nutritional approach in the course of the disease is described and its importance is discussed. Finally, asummary of nutritional care for open abdomen patients is provided based on current recommendations.

Evaluation of component additive modelling approach for europium adsorption on 2:1 clays: Experimental, thermodynamic databases, and models

This study evaluates the component additive approach for Eu adsorption on mixtures of smectite and illite, which are the most common clays used as barriers for contaminant retention in waste repositories. A thorough set of Eu adsorption data for Na-exchanged smectite and illite that encompasses a wide range of pH values, ionic strengths, and Eu concentrations was provided. This database is likely one of the largest sorption databases available for Eu in 2:1 clays, making it appropriate for sorption model calibration.The main adsorption mechanisms considered were surface complexation, on weak and strong clay edge sites, and cation exchange. Further, the role of principal ions, which are naturally leached from clays, as competitive factors for Eu retention, was evaluated in the modelling calculations. The main uncertainties related to the modelling procedures and the use of different thermodynamic data on sorption modelling were outlined.The reactions and parameters successful in modelling Eu adsorption on individual clays were used without any modification to model Eu adsorption on illite/smectite mixtures, wherein only the relative mineral proportions were considered. The fit of the sorption data in the mixed clay system was satisfactory, indicating that, in 2:1 clays, Eu sorption is an additive process, which stresses the predictive capacity of the component additive approach in these systems. This is an important support for assessing the performance of barrier materials for contaminant migration under different geochemical conditions.

An Application of Simultaneous Stochastic Optimization at a Large Open-Pit Gold Mining Complex under Supply Uncertainty

The simultaneous stochastic optimization of mining complexes optimizes various components of the related mineral value chain jointly while considering material supply (geological) uncertainty. As a result, the optimization process capitalizes on the synergies between the components of the system while not only quantifying and considering geological uncertainty, but also producing strategic mine plans, maximizing the net present value. This paper presents an application of simultaneous stochastic optimization at a large gold mining complex. The complex contains three open-pit mines, three stockpiles, a waste dump, and a processing facility. Material hardness management is integrated at the processing facility. The case study generated production schedules for each mineral deposit considered, as well as an overall assessment of the project and related forecasts. It resulted in an 18 year life-of-asset and identified the semi-autogenous grinder (SAG) mill as the bottleneck of the operation.

The Mg/(Fe + Mg) ratio and the Ti and A site contents of tourmaline as promising indicators of granitic magma evolution

In the recent past, important research has shown how tourmaline can be used as a petrogenetic indicator in pegmatite rocks and related mineralization. Previous studies have demonstrated that tourmaline composition may be a useful guide to ascertain the degree of evolution and oxygen fugacity of host granitic rocks from the Variscan orogen in the Central Iberian Zone (CIZ). Following those promising preliminary conclusions, we have investigated whether these results hold for tourmaline-bearing granitic rocks from other geotectonic contexts, enlarging our scope to include whole-rock stable isotope analyses. The data collected so far has shown that, whereas most tourmaline components and component ratios seem essentially impervious to granitic magma composition and oxygen fugacity, there are a few exceptions, such as the Mg/(Mg + Fe) ratio and Ti contents of tourmaline that show clear variation with the degree of evolution and oxygen fugacity of the host granitic rocks. From both mineralogical and petrological points of view, it seems that these compositional features in tourmaline may be used as indicators of the degree of evolution and of specific characteristics of the granitic magmas that produced them.

Influence of Nutritive Value Quality on Chefs’ Food Preparation and Consumption

Nutritive value as part of food quality is the degree of a well-balanced vital nutrients of carbohydrates, protein, fat, vitamins and minerals in relation to the consumers’ nutrient requirements. Choosing the right preparation methods and ingredients that contain high nutritive value is an important aspect of healthy eating in daily food consumption. Within food industries, food quality is acquainted especially among the food handlers, food service staff and chefs. Many people believe that most chefs with knowledge and skills of culinary education have awareness and concern regarding food quality, nutritional value, safety and hygiene in their daily food preparation and consumption. Thus, this study empirically examined the importance and influence of food nutritive value quality in terms of ingredients and cooking methods on chefs’ daily food preparation and consumption. A descriptive research design using a quantitative approach was applied. A questionnaire-based survey was distributed to chefs who were directly involved in the food sectors within Klang Valley and had culinary educational background and experience. The findings showed that the quality of nutritive value in terms of ingredients and cooking methods played an important role in chefs’ daily food preparation and consumption. Hence, it is important for the chefs to enhance the quality and taste of the food by using fresh ingredients and practice healthy cooking method. Besides that, their skills and knowledge can help to convey the information and promote the awareness of good eating habits to the society.

Zones of PGE–Chromite Mineralization in Relation to Crystallization of the Pados-Tundra Ultramafic Complex, Serpentinite Belt, Kola Peninsula, Russia

The lopolithic Pados-Tundra layered complex, the largest member of the Serpentinite belt–Tulppio belt (SB–TB) megastructure in the Fennoscandian Shield, is characterized by (1) highly magnesian compositions of comagmatic dunite–harzburgite–orthopyroxenite, with primitive levels of high-field-strength elements; (2) maximum values of Mg# in olivine (Ol, 93.3) and chromian spinel (Chr, 57.0) in the Dunite block (DB), which exceed those in Ol (91.7) and Chr (42.5) in the sills at Chapesvara, and (3) the presence of major contact-style chromite–IPGE-enriched zones hosted by the DB. A single batch of primitive, Al-undepleted komatiitic magma crystallized normally as dunite close to the outer contact, then toward the center. A similar magma gave rise to Chapesvara and other suites of the SB–TB megastructure. Crystallization proceeded from the early Ol + Chr cumulates to the later Ol–Opx and Opx cumulates with accessory Chr in the Orthopyroxenite zone. The accumulation of Chr resulted from efficient cooling along boundaries of the Dunite block. The inferred front of crystallization advanced along a path traced by vectors of Ol and Chr compositions. Grains and aggregates of Chr were mainly deposited early after the massive crystallization of olivine. Chromium, Al, Zn and H2O, all incompatible in Ol, accumulated to produce podiform segregations or veins of chromitites. This occurred episodically along the moving front of crystallization. Crystallization occurred rapidly owing to heat loss at the contact and to a shallow level of emplacement. The Chr layers are not continuous but rather heterogeneously distributed pods or veins of Chr–Ol–clinochlore segregations. Isolated portions of melt enriched in H2O and ore constituents accumulated during crystallization of Ol. Levels of fO2 in the melt and, consequently, the content of ferric iron in Chr, increased progressively, as in other intrusions of the SB–TB megastructure. The komatiitic magma vesiculated intensely, which led to a progressive loss of H2 and buildup in fO2. In turn, this led to the appearance of anomalous Chr–Ilm parageneses. Diffuse rims of Chr grains, abundant in the DB, contain elevated levels of Fe3+ and enrichments in Ni and Mn. In contrast, Zn is preferentially partitioned into the core, leading to a decoupling of Zn from Mn, also known at Chapesvara. The sulfide species display a pronounced Ni-(Co) enrichment in assemblages of cobaltiferous pentlandite, millerite (and heazlewoodite at Khanlauta), deposited at ≤630 °C. The oxidizing conditions have promoted the formation of sulfoselenide phases of Ru in the chromitites. The attainment of high degrees of oxidation during crystallization of a primitive parental komatiitic magma accounts for the key characteristics of Pados-Tundra and related suites of the SB–TB megastructure.

Platinum mineralization and geochemistry of the Matysken zoned Ural-Alaskan type complex and related placer (Far East Russia)

Ural-Alaskan type complexes are the sources for unique placer platinum deposits and contain platinum-group minerals (PGM) within lodes. Such complexes occur along modern and ancient convergent tectonic margins and are comprised of dunite, wehrlite, clinopyroxenite and gabbro, which gradually interchange towards the marginal parts of the complex. In-situ PGM are largely restricted to chromitites, which are comprised of small veinlets and schlieren of chromian spinel in the dunite unit. PGM mineralization in chromitites can be extremely rich; however, their distribution is very sporadic, without any apparent regularity. Moreover, the role of accessory chromian spinel and post-magmatic overprinting of platinum group element (PGE) concentrations is poorly defined. Detailed studies of PGM assemblages, including those in chromitites, serpentine veinlets in dunites, and wehrlites, combined with PGE geochemistry could provide insights into the distribution and processes responsible for PGE accumulation.The Matysken complex in the Koryak Highlands (Far East Russia) is comprised of dunite, wehrlite, clinopyroxenite and gabbro units, and has a classic zoned structure, rendering it an excellent example of an Ural-Alaskan type complex, ideal for this case study. This locality contains mm-scale isoferroplatinum (Pt3Fe) nuggets that cement chromitites and occur as µm-scale euhedral inclusions in chromian spinel. Placer PGM assemblages in the nearby Matysken River consist of exactly the same assemblages of minerals that are found in dunites and chromitites but with larger compositional scatter, reflecting a complex history of alluvium accumulation, which was sourced from different eroded parts of the complex. Detailed textural investigations discovered a diverse array of hydrous silicate–related mineralization, including euhedral isoferroplatinum grains in chlorite matrix, isoferroplatinum–amphibole intergrowths, and a wide range of PGE, Fe and Cu alloys, sulfarsenides and antimonides, which formed in serpentine veinlets together with awaruite (Ni3Fe) and base metal sulfides. This provides further evidence that isoferroplatinum, which is widely accepted to be a magmatic mineral, may form under a wide range of conditions, including during serpentinization.Dunites have fractioned primitive mantle-normalized PGE patterns, typical of Ural-Alaskan type complexes, with strong enrichments in Pt and depletions in Ir, Ru and Pd. PGE, with an exception of Pd, are quite uniformly distributed in dunite containing accessory chromian spinel, with good correlations between PGE and Cr. This correlation, together with data from previous studies, allowed us to calculate the concentration of Pt in accessory chromian spinel (probably hosted as minute PGM inclusions), which is of the same grade as for chromitites (ppm levels). This suggests that the formation of chromitites does not concentrate PGE over Cr, but only assembles them into larger aggregates, causing the observed unevenness in the PGM distribution.

The Geology, Geochemistry, and Origin of the Porphyry Cu-Au-(Mo) System at Vathi, Serbo-Macedonian Massif, Greece

The Vathi porphyry Cu-Au ± Mo mineralization is located in the Serbo-Macedonian metallogenic province of the Western Tethyan Metallogenic Belt. It is mainly hosted by a latite and is genetically associated with a quartz monzonite intrusion, which intruded the basement rocks of the Vertiskos Unit and the latite, 18 to 17 Ma ago. A phreatic breccia crosscuts the latite. The quartz monzonite was affected by potassic alteration, whereas the latite was subjected to local propylitic alteration. Both styles of alteration were subsequently overprinted by intense sericitic alteration. M-type and A-type veins are spatially associated with potassic alteration, whereas D-type veins are related to the sericitic alteration. Three ore assemblages are associated with the porphyry stage: (1) pyrite + chalcopyrite + bornite + molybdenite + magnetite associated with potassic alteration; (2) pyrite + chalcopyrite related to propylitic alteration; and (3) pyrite + chalcopyrite + native gold ± tetradymite associated with sericitic alteration. A fourth assemblage consisting of sphalerite + galena + arsenopyrite + pyrrhotite + pyrite ± stibnite ± tennantite is related to an epithermal overprint. Fluid inclusion data indicate that the A-type veins and related porphyry-style mineralization formed at 390–540 °C and pressures of up to 646 bars (<2.6 km depth) from boiling hydrothermal fluids. A later condensation of vapor-rich inclusions resulted in a moderately saline fluid (8.4–11.2 wt % NaCl equiv) at temperatures between 311 and 392 °C, which were related to sericitic alteration, D-type veins, and associated metallic mineralization. Subsequent dilution of the moderately saline fluid at lower temperatures (205–259 °C) produced a less saline (1.4–2.9 wt % NaCl equiv.) fluid, which is likely associated with the late epithermal overprint.

РЕГУЛЮВАННЯ СОРБЦІЙНОЇ ЗДАТНОСТІ КОМБІНОВАНИХ ВОЛОКНИСТИХ МАТЕРІАЛІВ, НАПОВНЕНИХ ГЛИНИСТИМИ МІНЕРАЛАМИ

The results of determining the sorption properties of samples of combined fibrous materials impregnated with dispersions of water-soluble polymers of different types and concentrations filled with clay minerals in relation to the methylene blue dye are presented. The rational composition of dispersions of water-soluble polymers filled with clay minerals is determined. The obtained materials can be used as a reinforcing base of fibrous sorbents for their further use in the treatment of light industry wastewater from dyes and heavy metal ions.The aim of the work is to determine the kinetic regularities of sorption (by methylene blue) of combined fibrous materials impregnated with dispersions of water-soluble polymers of different types and concentrations filled with clay minerals. As a fibrous basis for the composite material used knitted fabric with a surface density of 240 g/m2, which was made of plaited weave using cotton yarn with a linear density of 25 Tex and polyethylene complex threads with a linear density of 16.5 Tex on a single-font circular knitting machine type MS. First, a dispersion of the clay mineral was prepared in an aqueous solution of a polymeric binder, which was then applied with a squeegee knife to the surface of the knitted material. The sorption properties of the samples were determined by the methylene blue dye, the change in optical density was measured on a UNICO 2150 E spectrophotometer, wavelength 600 nm, cuvette 10 mm. Calculated the degree of absorption of the dye from the solution after 24, 48 and 72 hours of treatment. It was determined that increasing the duration of sorption above 48 hours is not rational. The highest degree of absorption of MS is shown by samples of knitted material treated with 3% dispersions of PVA and starch,78.4 and 77.1%, respectively. This is probably due to the fact that these samples are characterized by the highest content of clay adsorbent, the weight gain for these samples after the introduction of clay adsorbent was 78.7 and 60.1%, respectively. In the case of the use of filled dispersions of CMC and CMS, a larger amount of clay adsorbent is characterized by samples treated with dispersions of CMC and CMC of lower concentration.

The Haidbach deposit in the Central Tauern Window, Eastern Alps, Austria: a metamorphosed orthomagmatic Ni-Cu-Co-PGE mineralization in the Polymetallic Ore District Venediger Nappe System – Hollersbach Complex

Abstract Cu-Ni-Co-PGE mineralization occurs at Haidbachgraben in the Early Palaeozoic, Subpenninic Hollersbach Complex of the Central Tauern Window, Austria. Massive sulfide ore formed from sulfide melt segregated from silicate melt during intrusion of pyroxenite into magmatic rocks formed in an MORB-type environment. Relics of magmatic minerals include chromian spinel and polyphase sulfide droplets composed of pyrrhotite, chalcopyrite and pentlandite preserved in recrystallized pyrite. Both ore and host rocks were multiply deformed and metamorphosed, leading to hornblendite carrying the ore, enveloped by chlorite-epidote schist. Conditions of – likely Variscan – amphibolite facies metamorphism are documented by relict pargasitic cores in hornblende and actinolite-tremolite, and by ternary sulfarsenide compositions in the Co-Ni-Fe solid solution series that are the most common accessory minerals found in the sulfide ore. Pyrrhotite, pentlandite, chalcopyrite and pyrite are the major sulfide minerals. Chalcopyrite is Cd-rich and retains a high-temperature magmatic signature. High Co/Sb and moderate Se/As ratios in pyrite also point to a magmatic environment of mineralization. The accessory mineral assemblage of small grain size (mostly <10 µm) comprises native Au-Ag alloy and petzite as Au-Ag minerals, sperrylite, a variety of Pd tellurides and bismuthotellurides with elevated Sb, irarsite, and Re sulfides such as tarkianite and a Pb-Re sulfide. In addition, minor molybdenite, bournonite, scheelite and selenides have been identified. Two precious metal assemblages are present in individual samples: (1) hessite associated with Pd tellurides, often accompanied by sphalerite and chalcopyrite; (2) tarkianite forming euhedral inclusions in pyrite. Sperrylite and Au-Ag native alloys are present throughout and were also detected in silicate matrix. Most of the precious metal-bearing phases must have formed during recrystallization of base metal sulfides after the magmatic, and probably during later metamorphic events terminating in the Neoalpine Tauern crystallization.

Accessing Legacy Phosphorus in Soils

Repeated applications of phosphorus (P) fertilizers result in the buildup of P in soil (commonly known as legacy P), a large fraction of which is not immediately available for plant use. Long-term applications and accumulations of soil P is an inefficient use of dwindling P supplies and can result in nutrient runoff, often leading to eutrophication of water bodies. Although soil legacy P is problematic in some regards, it conversely may serve as a source of P for crop use and could potentially decrease dependence on external P fertilizer inputs. This paper reviews the (1) current knowledge on the occurrence and bioaccessibility of different chemical forms of P in soil, (2) legacy P transformations with mineral and organic fertilizer applications in relation to their potential bioaccessibility, and (3) approaches and associated challenges for accessing native soil P that could be used to harness soil legacy P for crop production. We highlight how the occurrence and potential bioaccessibility of different forms of soil inorganic and organic P vary depending on soil properties, such as soil pH and organic matter content. We also found that accumulation of inorganic legacy P forms changes more than organic P species with fertilizer applications and cessations. We also discuss progress and challenges with current approaches for accessing native soil P that could be used for accessing legacy P, including natural and genetically modified plant-based strategies, the use of P-solubilizing microorganisms, and immobilized organic P-hydrolyzing enzymes. It is foreseeable that accessing legacy P will require multidisciplinary approaches to address these limitations.

Geology and genesis of vein-type corundum deposits in the Hafafit-Nugrus area, South Eastern Desert, Egypt

AbstractUnusual deposits formed by corundum are described from two separate pegmatitic veins in the Hafafit-Nugrus area of the South Eastern Desert of Egypt. Other related minerals are described too. The vein-type of corundum at Locality 1 (Vein 1) crosscuts through exposed rocks of an ophiolitic mélange, whereas at Locality 2 (Vein 2), it crosscuts through exposed serpentinised ultramafic rocks. The main minerals in Vein 1 are plagioclase, corundum, grossular, phlogopite, muscovite and clinochlore, while almandine, xenotime-(Y), allanite-(Ce), zircon, Cr-rich spinel, apatite, titanite, fergusonite-(Y), meta-ankoleite, U-rich thorite (uranothorite), carbonate and illite are the accessories. In Vein 2, the main minerals are plagioclase, corundum, phlogopite and chlorite, while clinochlore, euxenite-(Y), Nb-rich rutile, almandine, xenotime-(Y), allanite-(Ce), zircon, spinel, apatite, titanite, kasolite, dickite, illite, carbonate, antigorite and talc are accessories. The two types of corundum veins differ in their concentrations of Th, U, Zr, Nb, Ta, REE, Y and Li in whole-rock compositions. Field observations, mineralogy and chemical analyses of samples from the two veins of corundum deposits, as well as concentrations of chromophore elements in corundum crystals, suggest metasomatic origins. The present study suggests that the two types of corundum veins formed at different ages from different residual magmas that underwentin-situhybridisation with the host rocks.

MITIGATING SALT STRESS EFFECTS BY EXOGENOUS APPLICATION OF PROLINE AND YEAST EXTRACT ON MORPHO-PHYSIOLOGICAL, BIOCHEMICAL AND ANATOMICAL CHARACTERS OF CALENDULA PLANTS

To avoid the hazard effect of salinity on calendula (Calendula officinalis L.), two field experiments were carried out at Sahl El-Husseinieh Research Station, Al-Sharqia Governorate, Egypt during two successive winter seasons of 2017/2018 and 2018/2019 in silty clay soil to evaluate the effects of foliar spraying with yeast at 0, 4, 8 and 12 g l-1, proline at 0, 50, 75 and 100 mg l-1 and the interaction between them. The obtained results showed that foliar application of proline, yeast and their interactions led to improve and increase plant growth, floral, physiological and biochemical characters of calendula plants significantly more than those obtained by control, such as plant height, number of branches plant-1, plant fresh and dry weights, number of flowers plant-1, flowers fresh and dry weight, relative water content, carotenoid, total chlorophyll, proline content in plant leaves, as well as the activity of PPO, POX and CAT. Also, the above treatments led to improve calendula plant growth by reducing the activity of both superoxide and hydrogen peroxide and decreasing EL. Application of proline, yeast and their interactions increased the elements content of calendula plant for N, P, K, Ca and Mg %. In the contrary, they decreased Na % in the plant. Results showed that vegetative growth, floral parameters as well as anatomical characters of leaves were significantly decreased under salt stress conditions. The physiological and biochemical characters such as photosynthetic pigments content, relative water content (RWC %) and mineral elements (N, P, K, Ca and Mg %) in the leaves also significantly decreased. Whereas, Na %, proline concentration, the activity of (O-2 and H2O2) and electrolyte leakage (EL %) were increased. Moreover, available N, P and K (mg kg-1) in the soil is negatively affected by salt stress. The combined treatments of proline at 100 mg l-1 + yeast at 12 g l-1 followed by proline at 100 mg l-1 + yeast at 8 g l-1 gave the higher values of plant growth, biochemical and elemental content in plant besides improved the anatomical characters, consequently, increased the tolerance of calendula plants to salt stress under field conditions.

Calcimimetics Alter Periosteal and Perilacunar Bone Matrix Composition and Material Properties in Early Chronic Kidney Disease.

ABSTRACTChronic kidney disease (CKD) affects 15% of Americans and greatly increases fracture risk due to elevated parathyroid hormone, cortical porosity, and reduced bone material quality. Calcimimetic drugs are used to lower parathyroid hormone (PTH) in CKD patients, but their impact on bone matrix properties remains unknown. We hypothesized that tissue‐level bone quality is altered in early CKD and that calcimimetic treatment will prevent these alterations. To test this hypothesis, we treated Cy/+ rats, a model of spontaneous and progressive CKD‐mineral and bone disorder (CKD‐MBD), with KP‐2326, a preclinical analogue of etelcalcetide, early in the CKD disease course. To measure tissue‐level bone matrix composition and material properties, we performed colocalized Raman spectroscopy and nanoindentation on new periosteal bone and perilacunar bone using hydrated femur sections. We found that CKD and KP treatment lowered mineral type B carbonate substitution whereas KP treatment increased mineral crystallinity in new periosteal bone. Reduced elastic modulus was lower in CKD but was not different in KP‐treated rats versus CTRL. In perilacunar bone, KP treatment lowered type B carbonate substitution, increased crystallinity, and increased mineral‐to‐matrix ratio in a spatially dependent manner. KP treatment also increased reduced elastic modulus and hardness in a spatially dependent manner. Taken together, these data suggest that KP treatment improves material properties on the tissue level through a combination of lowering carbonate substitution, increasing mineral crystallinity, and increasing relative mineralization of the bone early in CKD. As a result, the mechanical properties were improved, and in some regions, were the same as control animals. Therefore, calcimimetics may help prevent CKD‐induced bone deterioration by improving bone quality in new periosteal bone and in bone tissue near osteocyte lacunae. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Nanoscale imaging of shale fragments with coherent X-ray diffraction.

Despite the abundance of shales in the Earth's crust and their industrial and environmental importance, their microscale physical properties are poorly understood, owing to the presence of many structurally related mineral phases and a porous network structure spanning several length scales. Here, the use of coherent X-ray diffraction imaging (CXDI) to study the internal structure of microscopic shale fragments is demonstrated. Simultaneous wide-angle X-ray diffraction (WAXD) measurement facilitated the study of the mineralogy of the shale microparticles. It was possible to identify pyrite nanocrystals as inclusions in the quartz-clay matrix and the volume of closed unconnected pores was estimated. The combined CXDI-WAXD analysis enabled the establishment of a correlation between sample morphology and crystallite shape and size. The results highlight the potential of the combined CXDI-WAXD approach as an upcoming imaging modality for 3D nanoscale studies of shales and other geological formations via serial measurements of microscopic fragments.

Remineralising effects of fluoride varnishes containing calcium phosphate on artificial root caries lesions with adjunctive application of proanthocyanidin

ObjectivesTo evaluate the remineralising effects of fluoride (F) varnishes containing bioavailable calcium-phosphate compound (Ca-P) based remineralisation systems and 5000 ppm F toothpaste (FTP) on root caries lesions (RCLs) and the potential effects of proanthocyanidin (PA) for the treatments of RCLs when used as an adjunct to F regimens. MethodsDemineralised root dentine and a pH-cycling model were used to mimic RCLs and the oral environment. Remineralising effects of MI VarnishTM (MIV) containing casein phosphopeptide–amorphous calcium phosphate (CPP-ACP) and Clinpro™ White Varnish (CPWV) containing tri-calcium phosphate (TCP) along with FTP and PA were evaluated regarding the birefringence, elemental composition, mechanical properties and mineral density of remineralised dentine with DuraphatTM as a comparison. ResultsMIV, CPWV and DuraphatTM promoted the incorporation of F into RCLs and increased mineral density but did not change microhardness of root dentine significantly. Surface microhardness increased significantly when MIV or CPWV was used with 5000 ppm FTP. Application of PA with F regimens significantly increased subsurface mineral density. When PA was applied with MIV or CPWV along with FTP, the highest ion uptake and relative mineral gain (%ΔZ) was achieved, and significant increase of microhardness was up to 30 μm depth. Generally, MIV was associated with a higher mineral content gain than CPWV. SignificanceTreatment of carious root surfaces remains challenging due to the complex pathological processes and difficulty in restoring the highly organised structure of root dentine. Treatment strategies targeting both remineralisation and preservation of the dentinal organic matrix have the potential to improve the fluoride-mediated remineralisation approaches.

Paragenesis of secondary Ca–Al silicates during hydrothermal alteration of Proterozoic granitic rocks (SE Sweden)

The texture and chemical compositions of secondary Ca–Al silicates (prehnite, pumpellyite, epidote, and titanite) and of related minerals (chlorite, sericite, K‐feldspar, albite, Fe‐oxides, fluorite, and calcite) are used to discuss their formation conditions during interaction of Proterozoic granitic rocks from SE Sweden with hydrothermal fluids. The paragenetic sequence of the Ca–Al silicates is suggested to have been accomplished at ca. 200–350°C and was controlled by small‐scale variations in the chemistry of the hydrothermal fluids, such as aCa2+/aH+ ratio and fO2 and fCO2. These variations in fluid chemistry occurred mostly in closed systems, which involved the redistribution of elements released from the alteration of the magmatic minerals, primarily plagioclase, biotite, and amphibole and inducing porosity modifications. Accordingly, results obtained in this study should have implications for the role of hydrothermal alterations on element redistribution in the continental crust and for suitability of granitic rocks as repositories for radioactive wastes.

Tracking the Deep Biosphere through Time

The oceanic and continental lithosphere constitutes Earth’s largest microbial habitat, yet it is scarcely investigated and not well understood. The physical and chemical properties here are distinctly different from the overlaying soils and the hydrosphere, which greatly impact the microbial communities and associated geobiological and geochemical processes. Fluid–rock interactions are key processes for microbial colonization and persistence in a nutrient-poor and extreme environment. Investigations during recent years have spotted microbial processes, stable isotope variations, and species that are unique to the subsurface crust. Recent advances in geochronology have enabled the direct dating of minerals formed in response to microbial activity, which in turn have led to an increased understanding of the evolution of the deep biosphere in (deep) time. Similarly, the preservation of isotopic signatures, as well as organic compounds within fossilized micro-colonies or related mineral assemblages in voids, cements, and fractures/veins in the upper crust, provides an archive that can be tapped for knowledge about ancient microbial activity, including both prokaryotic and eukaryotic life. This knowledge sheds light on how lifeforms have evolved in the energy-poor subsurface, but also contributes to the understanding of the boundaries of life on Earth, of early life when the surface was not habitable, and of the preservation of signatures of ancient life, which may have astrobiological implications. The Special Issue “Tracking the Deep Biosphere through Time” presents a collection of scientific contributions that provide a sample of forefront research in this field. The contributions involve a range of case studies of deep ancient life in continental and oceanic settings, of microbial diversity in sub-seafloor environments, of isolation of calcifying bacteria as well as reviews of clay mineralization of fungal biofilms and of the carbon isotope records of the deep biosphere.

Demineralization Inhibition by High-Speed Scanning of 9.3 µm CO2 Single Laser Pulses Over Enamel.

In vitro studies were conducted to evaluate the use of an automated system for high-speed scanning of single 9.3 µm CO2 laser pulses in the inhibition of caries-like lesion formation in the enamel of extracted human molars. The effect of the laser in generating an acid-resistant layer and the effect of the layer on inhibiting surface mineral loss during pH cycling was explored. Laser irradiation was performed with fluences of 0.6, 0.8, and 1.0 J/cm2 for single pulses of 1 mm diameter (1/e2 ), with pulse durations of 17, 22, and 27 microseconds, respectively. The laser was scanned at a 750 Hz pulse repetition rate in an automated pattern covering an area of 7 mm2 in 0.3 sec. Six treatment groups were investigated: three groups for each fluence for laser-only and three for laser irradiation with additional fluoride from a toothpaste slurry (sodium fluoride at 1100 ppm). Each group used non-irradiated areas, which included untreated controls for the laser-only groups and a fluoride-only treatment for the groups with additional fluoride. pH cycling was performed on both groups, followed by microhardness testing to determine the relative mineral loss (∆Z) from a caries-like formation and surface mineral loss (∆S). Laser irradiation with the 9.3 µm CO2 laser generated an acid-resistant layer of about 15 µm in depth. For the laser-irradiated samples with additional fluoride application, the relative mineral loss (∆Z) was 113 ± 63 vol%-µm, while for those with only fluoride application ∆Z was 572 ± 172 vol%-µm. At the highest fluence (1.0 J/cm2 ) used, an 80.2% inhibition of caries-like lesion was measured by ∆Z. Using only laser irradiation at the highest fluence resulted in an inhibition of caries-like lesion of 79.5% for the irradiated samples (∆Z = 374 ± 149 vol%-µm) relative to the control (∆Z = 1826 ± 325 vol%-µm). Surface microhardness tests resulted in an inhibition of surface softening, as measured by the Knoop Hardness Value (KHN) (108 ± 33 KHN for laser irradiated with additional fluoride, for non-irradiated controls with fluoride only 52 ± 16 KHN). Inhibition of surface loss was observed for all laser fluences, but the maximum surface loss for the untreated control group was only 2.2 ± 0.49 µm. The results demonstrate a significant benefit of the 9.3 µm CO2 laser at fluences of 0.6, 0.8, and 1.0 J/cm2 in caries-like lesion inhibition as measured by the relative mineral loss in depth and surface mineral loss, without significant damage to the enamel. Additionally, inhibition of surface softening and surface loss during pH cycling was observed. The surface loss was small compared with the overall lesion depth and thickness of the generated acid-resistant layer. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Oxygen Fugacity and Volatile Content of Syntectonic Magmatism in the Neoarchean Abitibi Greenstone Belt, Superior Province, Canada

Neoarchean syntectonic intrusions from the Chibougamau area, northeastern Abitibi Subprovince (greenstone belt), may be genetically related to intrusion related gold mineralization. These magmatic-hydrothermal systems share common features with orogenic gold deposits, such as spatial and temporal association with syntectonic magmatism. Genetic association with magmatism, however, remains controversial for many greenstone belt hosted Au deposits. To precisely identify the link between syntectonic magmas and gold mineralization in the Abitibi Subprovince, major and trace-element compositions of whole rock, zircon, apatite, and amphibole grains were measured for five intrusions in the Chibougamau area; the Anville, Saussure, Chevrillon, Opémisca, and Lac Line Plutons. The selected intrusions are representative of the chemical diversity of synvolcanic (TTG suite) and syntectonic (e.g., sanukitoid, alkaline intrusion) magmatism. Chemical data enable calculation of oxygen fugacity and volatile content, and these parameters were interpreted using data collected by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. The zircon and apatite data and associated oxygen fugacity values in magma indicate that the youngest magmas are the most oxidized. Moreover, similar oxygen fugacity and high volatile content for both the Saussure Pluton and the mineralized Lac Line intrusion may indicate a possible prospective mineralized system associated with the syntectonic Saussure intrusion.