Geochemistry of Calcite Veins: Records of Fluid Mixing and Fluid-Rock Interaction

AbstractDetailed geochemical investigations of calcite veins, genetically related to intrusions and vein-hosting bedrock, have been used to indicate fluid evolution during intrusion-related hydrothermal mineralization, involving fluid mixing and water rock interaction. The area of investigation is located in the southeast of Sweden. The 1.85 Ga granitoid country rocks and the 0.9 Ga dolerite vein-related intrusions differ in chemical, geochemical, and stable isotope composition. The variation in rare earth and stable isotope composition across calcite veins and the presence of two groups of fluid inclusions suggests mixing of two types of fluids. Light rare earth enrichment and increasing 87Sr/86Sr-ratios suggest water rock interaction of one/both fluids

Fractionation of rare earth elements in greisen and hydrothermal veins related to A-type magmatism

This study focuses on concentrations and fractionation of rare earth elements (REE) in a variety of minerals and bulk materials of hydrothermal greisen and vein mineralization in Paleoproterozoic monzodiorite to granodiorite related to the intrusion of Mesoproterozoic alkali- and fluorine-rich granite. The greisen consists of coarse-grained quartz, muscovite, and fluorite, whereas the veins mainly contain quartz, calcite, epidote, chlorite, and fluorite in order of abundance. A temporal and thus genetic link between the granite and the greisen/veins is established via high spatial resolution in situ Rb-Sr dating, supported by several other isotopic signatures (δ34S, 87Sr/86Sr, δ18O, and δ13C). Fluid-inclusion microthermometry reveals that multiple pulses of moderately to highly saline aqueous to carbonic solutions caused greisenization and vein formation at temperatures above 200–250°C and up to 430°C at the early hydrothermal stage in the veins. Low calculated ∑REE concentration for bulk vein (15 ppm) compared to greisen (75 ppm), country rocks (173–224 ppm), and the intruding granite (320 ppm) points to overall low REE levels in the hydrothermal fluids emanating from the granite. This is explained by efficient REE retention in the granite via incorporation in accessory phosphates, zircon, and fluorite and unfavorable conditions for REE partitioning in fluids at the magmatic and early hydrothermal stages. A noteworthy feature is substantial heavy REE (HREE) enrichment of calcite in the vein system, in contrast to the relatively flat patterns of greisen calcite. The REE fractionation of the vein calcite is explained mainly by fractional crystallization, where the initially precipitated epidote in the veins preferentially incorporates most of the light REE (LREE) pool, leaving a residual fluid enriched in the HREE from which calcite precipitated. Fluorite occurs throughout the system and displays decreasing REE concentrations from granite towards greisen and veins and different fractionation patterns among all these three materials. Taken together, these features confirm efficient REE retention in the early stages of the system and minor control of the REE uptake by mineral-specific partitioning. REE-fractionation patterns and fluid-inclusion data suggest that chloride complexation dominated REE transport during greisenization, whereas carbonate complexation contributed to the HREE enrichment in vein calcite

Incorporation of metals into calcite in a deep anoxic granite aquifer

Understanding metal scavenging by calcite in deep aquifers in granite is of importance for deciphering and modeling hydrochemical fluctuations and water–rock interaction in the upper crust and for retention mechanisms associated with underground repositories for toxic wastes. Metal scavenging into calcite has generally been established in the laboratory or in natural environments that cannot be unreservedly applied to conditions in deep crystalline rocks, an environment of broad interest for nuclear waste repositories. Here, we report a microanalytical study of calcite precipitated over a period of 17 years from anoxic, low-temperature (14 °C), neutral (pH: 7.4–7.7), and brackish (Cl: 1700–7100 mg/L) groundwater flowing in fractures at >400 m depth in granite rock. This enabled assessment of the trace metal uptake by calcite under these deep-seated conditions. Aquatic speciation modeling was carried out to assess influence of metal complexation on the partitioning into calcite. The resulting environment-specific partition coefficients were for several divalent ions in line with values obtained in controlled laboratory experiments, whereas for several other ions they differed substantially. High absolute uptake of rare earth elements and U(IV) suggests that coprecipitation into calcite can be an important sink for these metals and analogousactinides in the vicinity of geological repositories

Isotopic evidence for microbial production and consumption of methane in the upper continental crust throughout the Phanerozoic eon

Microorganisms produce and consume methane in terrestrial surface environments, sea sediments and, as indicated by recent discoveries, in fractured crystalline bedrock. These processes in the crystalline bedrock remain, however, unexplored both in terms of mechanisms and spatiotemporal distribution. Here we have studied these processes via a multi-method approach including microscale analysis of the stable isotope compositions of calcite and pyrite precipitated in bedrock fractures in the upper crust (down to 1.7 km) at three sites on the Baltic Shield. Microbial processes have caused an intriguing variability of the carbon isotopes in the calcites at all sites, with δ13C spanning as much as −93.1‰ (related to anaerobic oxidation of methane) to +36.5‰ (related to methanogenesis). Spatiotemporal coupling between the stable isotope measurements and radiometric age determinations (micro-scale dating using new high-spatial methods: LA-ICP-MS U–Pb for calcite and Rb–Sr for calcite and co-genetic adularia) enabled unprecedented direct timing constraints of the microbial processes to several periods throughout the Phanerozoic eon, dating back to Devonian times. These events have featured variable fluid salinities and temperatures as shown by fluid inclusions in the calcite; dominantly 70–85 °C brines in the Paleozoic and lower temperatures (<50–62 °C) and salinities in the Mesozoic. Preserved organic compounds, including plant signatures, within the calcite crystals mark the influence of organic matter in descending surficial fluids on the microbial processes in the fracture system, thus linking processes in the deep and surficial biosphere. These findings substantially extend the recognized temporal and spatial range for production and consumption of methane within the upper continental crust

Surface Covering of Downed Logs: Drivers of a Neglected Process in Dead Wood Ecology

Many species use coarse woody debris (CWD) and are disadvantaged by the forestry-induced loss of this resource. A neglected process affecting CWD is the covering of the surfaces of downed logs caused by sinking into the ground (increasing soil contact, mostly covering the underside of the log), and dense overgrowth by ground vegetation. Such cover is likely to profoundly influence the quality and accessibility of CWD for wood-inhabiting organisms, but the factors affecting covering are largely unknown. In a five-year experiment we determined predictors of covering rate of fresh logs in boreal forests and clear-cuts. Logs with branches were little covered because they had low longitudinal ground contact. For branchless logs, longitudinal ground contact was most strongly related to estimated peat depth (positive relation). The strongest predictor for total cover of branchless logs was longitudinal ground contact. To evaluate the effect on cover of factors other than longitudinal ground contact, we separately analyzed data from only those log sections that were in contact with the ground. Four factors were prominent predictors of percentage cover of such log sections: estimated peat depth, canopy shade (both increasing cover), potential solar radiation calculated from slope and slope aspect, and diameter of the log (both reducing cover). Peat increased cover directly through its low resistance, which allowed logs to sink and soil contact to increase. High moisture and low temperatures in pole-ward facing slopes and under a canopy favor peat formation through lowered decomposition and enhanced growth of peat-forming mosses, which also proved to rapidly overgrow logs. We found that in some boreal forests, peat and fast-growing mosses can rapidly cover logs lying on the ground. When actively introducing CWD for conservation purposes, we recommend that such rapid covering is avoided, thereby most likely improving the CWD's longevity as habitat for many species

An exploratory open-label multicentre phase I/II trial evaluating the safety and efficacy of postnatal or prenatal and postnatal administration of allogeneic expanded fetal mesenchymal stem cells for the treatment of severe osteogenesis imperfecta in infants and fetuses: The BOOSTB4 trial protocol

Introduction Severe osteogenesis imperfecta (OI) is a debilitating disease with no cure or sufficiently effective treatment. Mesenchymal stem cells (MSCs) have good safety profile, show promising effects and can form bone. The Boost Brittle Bones Before Birth (BOOSTB4) trial evaluates administration of allogeneic expanded human first trimester fetal liver MSCs (BOOST cells) for OI type 3 or severe type 4. Methods and analysis BOOSTB4 is an exploratory, open-label, multiple dose, phase I/II clinical trial evaluating safety and efficacy of postnatal (n=15) or prenatal and postnatal (n=3, originally n=15) administration of BOOST cells for the treatment of severe OI compared with a combination of historical (1-5/subject) and untreated prospective controls (≤30). Infants<18 months of age (originally<12 months) and singleton pregnant women whose fetus has severe OI with confirmed glycine substitution in COL1A1 or COL1A2 can be included in the trial. Each subject receives four intravenous doses of 3×10 6 /kg BOOST cells at 4 month intervals, with 48 (doses 1-2) or 24 (doses 3-4) hours in-patient follow-up, primary follow-up at 6 and 12 months after the last dose and long-term follow-up yearly until 10 years after the first dose. Prenatal subjects receive the first dose via ultrasound-guided injection into the umbilical vein within the fetal liver (16+0 to 35+6 weeks), and three doses postnatally. The primary outcome measures are safety and tolerability of repeated BOOST cell administration. The secondary outcome measures are number of fractures from baseline to primary and long-term follow-up, growth, change in bone mineral density, clinical OI status and biochemical bone turnover. Ethics and dissemination The trial is approved by Competent Authorities in Sweden, the UK and the Netherlands (postnatal only). Results from the trial will be disseminated via CTIS, ClinicalTrials.gov and in scientific open-access scientific journals. Trial registration numbers EudraCT 2015-003699-60, EUCT: 2023-504593-38-00, NCT03706482

Geochemistry of multiple sclerosis in Finland

Multiple sclerosis (MS) affects some 3 million people around the world and the prevalence is increasing. The MS incidence increases with distance from the equator forming a north-to-south gradient. The cause of this gradient and the cause of MS in general are largely unknown. Sulphide-bearing marine and lake sediments, when exposed to oxygen after drainage, form sulphuric acid resulting in the development of acid sulphate soils. From these soils major neurotoxic metals such as iron, aluminum and manganese and trace metals such as nickel, copper and cadmium are released into the surrounding environment. As these soils are largely used for farming, obvious routes to human metal exposure exist. Here we compare the distribution of acid sulphate soils in Finland to the geographic localisation of MS cases using data from a national acid sulphate soil mapping project and historical MS distribution data. Finland has among the highest MS prevalences in the world and several independent nationwide surveys have shown the highest prevalence in western Finland, stable over time. Acid sulphate soil distribution colocalizes with MS, both on a regional (nationwide) scale and local (proximity to rivers) scale. A toxicokinetic LADME model for MS pathogenesis is presented. We propose that neurotoxic metals leaching from acid sulphate soils contribute to the clustering of MS in Finland

Physical environmental hazards associated with the Swedish death care industry

In this study, the perceptions of Swedish funeral directors were elicited on physical environmental hazards associated with the five life stages of handling cadavers through interviews and questionnaires (The data was collected from 78 respondents across Sweden). We conclude that although the workers in the Swedish funeral industry are at high risk of developing health problems caused by exposure to various chemicals (e.g., formaldehyde ((FA)) based embalming fluids, heavy metals, pesticides, pathogens, insecticides, and fungicides) and the industry itself contaminating air, soil and groundwater, the health and environmental hazards are perceived low by the funeral directors. In the study, funeral homes are classified into four distinguished groups: (a) environmentally ardent and the epitome of sustainability-(G-1) (21 %); (b) environmental- and customer-oriented-(G-2) (64 %); (c) environmentally apathetic and customer-oriented-(G-3) (6 %); and (d) environmentally unconscious-(G-4) (8 %). Results show that most funeral directors under the G-1 &amp; G-2 (32 out of 43) are acquainted with generational environmental goals (GGs) set by the Swedish government and are aware of the choices that promote environmental wellbeing. On the other hand, G-4 is not acquainted with GGs and comprises only small funeral homes (&lt;10 employees). Poor safety culture, traditions, and prioritising economic returns hinder making environmentally sustainable funeral industry choices. The article provides a better understanding of the Swedish funeral industry and suggests appropriate short- and long-term strategies that could curtail the associated physical environmental hazards of the industry