Stable isotope ratios of carbon, oxygen and sulfur have been used since the 1950s to understand the formation of magmatic and hydrothermal ore deposits. They are particularly useful in tracing the origin and differentiation of phases involved in ore-forming processes. For many sulfide ore deposits, tracking the source of sulfur is important for decoding the genesis of a deposit and to understand the mineralizing systems regionally and globally. We studied the isotopic composition of carbon (delta 13C), oxygen (delta 18O) in wall rock carbonates, and sulfur (delta 33S and delta 34S) in sulfide ore and wall rock sulfates in the Paleoproterozoic Sakatti Cu-Ni-PGE sulfide deposit in the Central Lapland Greenstone Belt, northern Finland. The results suggest emplacement of a komatiitic olivine cumulate body into a c. 2.2-2.05 Ga evaporite sequence, which appears to have provided most of the crustal sulfur in the Sakatti sulfide ore body. Mechanisms of the incorporation of sulfate sulfur to mafic-ultramafic magmas have been recently advanced and recognized in many base-precious metal camps. Tracking the prior presence of evaporites can be cryptic, as they tend to be camouflaged in the geological record over lengthy time scales. Assimilation of sedimentary sulfur typically shifts sulfur isotope signatures away from mantle values towards the values of assimilated crustal sulfur. However, the shift in sulfur isotope signature of the resulting sulfides can be surprisingly subtle, only showing small deviations from mantle values. Sulfur isotopes can also be homogenized by the presence of coexisting fluids leading to a well-mixed delta 34S signature, as demonstrated by the limited range of the bulk of the delta 34S values (2-4 parts per thousand) measured from the Sakatti deposit. The assimilation of evaporitic material might also play an important role in the formation of Cu (+/- Pd +/- Au +/- Ag)-dominated ores in many other magmatic Ni-Cu-PGE deposits.

Finnish Meteorological Institute’s Climate Bulletin Research Letters is a recently established research-based publication that features short and easy-to-read research articles on climate and climate services. The issues are published as a supplement to the Climate Bulletin journal by the Finnish Meteorological Institute. Even though the articles may be short, each one is peer-reviewed and citeable with a unique DOI. Research Letters is published in English once or twice a year. All issues and articles are open access. No publication fees are charged either. The editorial and publication processes have been designed to facilitate swift publication. Couple of weeks review and revision times are imposed. Once approved for publication, an article is instantly published as online and preprint versions. After 7-8 articles have been published this way, they will be collected to a single issue and published online at ISSUU digital publication platform. Research Letters is a publication channel for short reports, results of projects or case studies that may not be suitable for a full-scale peer reviewed publication. It was established to satisfy a clear need for short research publications. The themes of the series revolve around climate, climate services, climate change, marine research and results of research projects. From time to time, theme issues present extreme weather phenomena or maritime themes, among other topics. Special emphasis of the publication is in introducing new climate services and tools for different target groups, such as cities and agricultural, forestry, tourism and energy sectors. Since the first issue in spring 2019, four regular issues and one special issue have been published with 39 articles in total. The first issue has now over 400 reads. It is possible to subscribe to receive email reminders when new issues of the Climate Bulletin (in Finnish with a short summary in English) or Research Letters are published. Subscribers will only receive reminders when new issues are published. Subscription data is not used for advertising or other purposes. Research Letters is available on the Climate Bulletin website: https://www.ilmastokatsaus.fi/category/research-letters/. Climate Bulletin editorial team can be reached via email: ilmastokatsaus@fmi.fi. The editor-in-chief of the Climate Bulletin is Hilppa Gregow, Head of Unit, Finnish Meteorological Institute, hilppa.gregow@fmi.fi.

Geochemical characteristics of precipitated fracture filling calcite and pyrite can provide much useful information about the deep bedrock environment at the time of their deposition. However, it has been difficult to identify fracture coatings precipitated from the present-day groundwater system. The aim of this study was to evaluate the relationship between the coexisting calcite and pyrite, and the groundwater present at the time of precipitation. Here we investigated fine-grained mineral precipitate deposited over a four-year period on the surface of groundwater monitoring equipment inserted into a drillhole at 530 m below sea level, at Olkiluoto, which is the planned site for a final repository of spent nuclear fuel. The experimental setting is also artificial in the sense that the drillholes have possibly affected groundwater circulation and a foreign object has been inserted into the drillhole. Combining the elemental and isotope geochemical composition of the precipitated calcite and pyrite with previously published compositional data on groundwater and evidence for microbial communities on this site, offered a possibility to get new insight of the precipitation and isotope fractionation processes taking place in deep crystalline bedrock. The concentration of the redox sensitive manganese in the precipitate gives supporting evidence for the influx of groundwater from overlying groundwater units. The delta C-13 (n = 13) and delta O-18 (n = 15) values of calcite vary from-13.2 to-9.7 parts per thousand and from-9.1 to-7.4 parts per thousand respectively. Comparison to the respective values in the local groundwater indicated that the precipitated calcite is in near isotopic equilibrium with its environment with respect to carbon and oxygen. The potential ultimate source of the carbon in the DIC and in the precipitate is likely in old fracture calcite coatings. The 834S values of pyrite (n = 9) show relatively small variation from-5.7 to 8.3 parts per thousand. This differs greatly from the huge span of 834S values from-50 to 80%o in fracture pyrites reported for the latest calcite fillings at Olkiluoto. The restricted range of 834S values is interpreted to result from open system conditions during precipitation, with new dissolved sulfate entering from the large brackish SO4-type groundwater unit above. The isotopic fractionation of sulfur between dissolved sulfate and sulfide is estimated to be 25 & PLUSMN; 10%o, which is in agreement with the results reported in laboratory experiments for bacterial sulfate reduction.

Bekker et al. (2020) and Philippot et al. (2018) discussed implications of the geological and geochemical records of the Turee Creek Basin in Western Australia with regards to the understanding of the Great Oxidation Episode (GOE). Whereas Bekker et al. (2020) inferred that, due to its deposition in a foreland basin with high sedimentation rates, the succession bears a high-resolution record leading to, and of, the early stage of the GOE, Philippot et al. (2018) maintained that it provides a detailed and continuous (i.e., stratigraphically unbroken) record spanning 2.45 Ga to 2.22 Ga. The disagreement is largely rooted in different readings of the geochronological data presented in Caquineau et al. (2018) and Philippot et al. (2018), but also in different views on the tectonostratigraphic evolution of the Turee Creek Basin, chemostratigraphic records of the succession, and correlation with other early Paleoproterozoic sequences. The disagreement has far-reaching implications for the GOE and its relationship to early Paleoproterozoic climate changes. Philippot et al. (2021) provided a detailed critique of our approach, allowing us to clarify our original interpretations. Based on the analysis provided below, we stand by our original reading, and provide a more nuanced view of the early Paleoproterozoic global correlations and events. By combining global records, we infer that the similar to 2.45-2.22 Ga time interval experienced so-far underappreciated large-scale swings in atmospheric oxygen level across the 10(-5) PAL threshold that were associated with, and likely led to, early Paleoproterozoic glaciations by impacting atmospheric levels of methane, a powerful greenhouse gas in an anoxic atmosphere.

The Turee Creek Basin of the Pilbara Craton is critical for timing onset of the early Paleoproterozoic Icehouse and the GOE. We establish correlation to the Koegas/Postmasburg Supersequence of the Kaapvaal Craton based on a common compressional basin, with the Pilbara succession deposited near the orogen and the Kaapvaal succession near the flexural arch. Whereas Turee Creek cyclicity was controlled by tectonic subsidence, glacioeustatic influence is discernible in the Koegas/Postmasburg Supersequence. Key features of the Turee Creek Basin are: the mid-Kungarra Formation glaciogenic Meteorite Bore Member; unconformity-bound sequences above the Kungarra Formation; and the basaltic Bubbawalyee Formation conformably above Quartzite 3. On the Kaapvaal Craton, the equivalent glaciogenic unit (Makganyene Formation), overlying the sedimentary Koegas Subgroup and underlying the basaltic Ongeluk Formation, is unconformity-bound. We correlate the sub-Ongeluk unconformity with the sub-Quartzite 3 unconformity, and propose tectonostratigraphic equivalence of the Ongeluk and Bubbawalyee formations. There are no equivalents of the post-Ongeluk, Hotazel and Mooidraai formations above the Bubbawalyee Formation on the Pilbara Craton, which is significant because the Hotazel Formation provides the earliest evidence for the GOE. Consequently, rather than spanning the GOE, the Turee Creek Basin provides a chemostratigraphy during its eve. All carbonate sediments deposited before and after the first global glaciation (Meteorite Bore/Makganyene) yield carbon isotope values close to 0‰, establishing that the first carbon isotope excursion occurred long after closure of the Turee Creek-Koegas/Postmasburg basin and onset of the GOE. It therefore appears that the carbon cycle responded to, rather than triggered, the GOE.

This study examines the effect of poly-aluminium chloride (PACl) pre-treatment on the biological purification process taking place during managed aquifer recharge (MAR). PACl treatment is used in waste and surface water treatment to remove organic material. PACl can decrease the organic carbon contents of water significantly. However, aluminium is toxic to microbes, which may be detrimental when the PACl treatment is followed by infiltration into an aquifer (MAR). In this study the effect of pre-treatment with PACl on the water purification process in MAR was examined, by using sediment from a MAR site in four test columns. Two columns were filled with PACl-treated water, and the remaining ones with river water without PACl. The residence time of water in the columns was raised from direct sampling gradually to 64 days. Among the parameters monitored were the pH of the water, microbial activity and the decomposition of dissolved organic carbon (DOC). The results showed active decomposition in all columns. Decomposition of organic matter, and the amount of living/active microbial cells, was marginally higher in the untreated water, which could imply a better functioning MAR system. However, this may also be due to higher DOC starting concentration.

Almost all evidence for the oldest traces of life on Earth rely on particles of graphitic carbon preserved in rocks of sedimentary protolith. Yet, the source of carbon in such ancient graphite is debated, as it could possibly be non-biological and/or non-indigenous in origin. Here we describe the co-occurrence of poorly crystalline and crystalline varieties of graphitic carbon with apatite in ten different and variably metamorphosed banded iron formations (BIF) ranging in age from 1,800 to >3,800 Myr. In Neoarchean to Palaeoproterozoic BIF subjected to low-grade metamorphism, 13C-depleted graphitic carbon occurs as inclusions in apatite, and carbonate and arguably represents the remineralisation of syngenetic biomass. In BIF subjected to high-grade metamorphism, 13C-depleted graphite co-occurs with poorly crystalline graphite (PCG), as well as apatite, carbonate, pyrite, amphibole and greenalite. Retrograde minerals such as greenalite, and veins cross-cutting magnetite layers contain PCG. Crystalline graphite can occur with apatite and orthopyroxene, and sometimes it has PCG coatings. Crystalline graphite is interpreted to represent the metamorphosed product of syngenetic organic carbon deposited in BIF, while poorly crystalline graphite was precipitated from C–O–H fluids partially sourced from the syngenetic carbon, along with fluid-deposited apatite and carbonate. The isotopic signature of the graphitic carbon and the distribution of fluid-deposited graphite in highly metamorphosed BIF is consistent with carbon in the fluids being derived from the thermal cracking of syngenetic biomass deposited in BIF, but, extraneous sources of carbon cannot be ruled out as a source for PCG. The results here show that apatite + graphite is a common mineral assemblage in metamorphosed BIF. The mode of formation of this assemblage is, however, variable, which has important implications for the timing of life's emergence on Earth.

6 Beijing SHRIMP Centre, Institute of Geology, Chinese Academy of Geological Sciences, China 12 Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, K1N 6N5 Canada 13 8 Department of Geosciences and Geography, University of Helsinki, P.O.Box 64 Finland 14 9 Department of Earth Sciences, Carleton University, Ottawa, ON K1S 5B6, Canada 15 Centre for Exploration Targeting, The University of Western Australia, 35 Stirling Highway, Crawley, WA 16 6009 Australia 17 18 19 Abstract 20 Almost all evidence for the oldest traces of life on Earth rely on particles of graphitic 21

The world's last population of woolly mammoths (Mammuthus primigenius) lived on Wrangel Island persisting well into the Holocene, going extinct at ca. 4000 cal BP. According to the frequency of 'radiocarbon dated mammoth remains from the island, the extinction appears fairly abrupt. This study investigates the ecology of the Wrangel Island mammoth population by means of carbon, nitrogen and sulfur isotope analyses. We report new isotope data on 77 radiocarbon dated mammoth specimens from Wrangel Island and Siberia, and evaluate them in relation to previously published isotope data for Pleistocene mammoths from Beringia and lower latitude Eurasia, and the other insular Holocene mammoth population from St. Paul Island. Contrary to prior suggestions of gradual habitat deterioration, the nitrogen isotope values of the Wrangel Island mammoths do not support a decline in forage quality/quantity, and are in fact very similar to their north Beringian forebears right to the end. However, compared to Siberian mammoths, those from Wrangel Island show a difference in their energy economy as judged by the carbon isotope values of structural carbonate, possibly representing a lower need of adaptive strategies for survival in extreme cold. Increased mid-Holocene weathering of rock formations in the central mountains is suggested by sulfur isotope values. Scenarios related to water quality problems stemming from increased weathering, and a possibility of a catastrophic starvation event as a cause of, or contributing factor in their demise are discussed. (C) 2019 The Authors. Published by Elsevier Ltd.

The cycling of iron and organic matter (OM) is thought to have been a major biogeochemical cycle in the early ferruginous oceans which contributed to the deposition of banded iron formations (BIF). However, BIF are deficient in OM, which is postulated to be the result of near-complete oxidation of OM during iron reduction. We test this idea by documenting the prevalence of OM in clays within BIF and clays in shales associated with BIF. We find in shales >80% of OM occurs in clays, but <1% occurs in clays within BIF. Instead, in BIF OM occurs with 13C-depleted carbonate and apatite, implying OM oxidation occurred. Conversely, BIF which possess primary clays would be expected to preserve OM in clays, yet this is not seen. This implies OM deposition in silicate-bearing BIF would have been minimal, this consequently stifled iron-cycling and primary productivity through the retention of nutrients in the sediments.

Studying the carbon balance in surface waters gives information on the annual cycles of photosynthesis and respiration. It also provides insight on the water body's capability to serve as a source or sink for atmospheric CO2, which may be essential in evaluating the effects of climate change. The target of this study was the Vantaanjoki River known to have a significant base flow component, located in a densely populated area in southern Finland. The aims of this study were firstly to study if human induced changes are evident in the inorganic carbon quality of the river, and secondly to determine whether the river releases carbon to the atmosphere. These aims were achieved by studying the isotopic composition and contents of dissolved inorganic carbon (DIC) in relation to river discharge. It was evident from the results that the human activities only have mild local and temporal effects on the quality of the DIC in the river. The most important contributors to the changes in the carbon balance are the annual changes in the proportion of the base flow and surface flow components and the escape of CO2 to the atmosphere.

It is generally accepted that carbon isotope variations in seawater were muted between c. 2.06 Ga, after the end of the Lomagundi carbon isotope excursion (LCIE), and c. 1.3 Ga. Evidence is presented here that c. 30 myr after the end of the LCIE, the biogeochemical cycle of carbon experienced a short-term ( c. 2 myr), high-amplitude (up to +8.4‰ V-PDB) perturbation, recorded in the Horseshoe rift basin, Western Australia. The basin was initiated at c. 2.03 Ga with deposition of fluvial and shallow-marine sandstones, followed by the eruption of flood basalt, and culminated with the deposition of platform carbonates, and accompanying volcaniclastic and siliciclastic sediments (Wooly Dolomite). The Horseshoe rift basin during deposition of the Wooly Dolomite was fault-compartmentalized but connected to an ocean. Six depositional sequences make up the Wooly Dolomite. Sequence 1 records establishment of a carbonate platform conformably on basalt and coevally with volcaniclastic sedimentation. All other sequences have dominant carbonate-platform deposits and are unconformity-bounded. Sequence 3 contains a c. 57 m thick section with 13 C-enriched carbonates bracketed between carbonates with close to 0‰ carbon isotope values. Further high-resolution chemostratigraphic studies may reveal a more complex pattern of carbon isotope variations during the ‘boring billion years’, but without precise geochronology similar short-term carbon isotope excursions in carbonate successions could be incorrectly correlated to the LCIE. Supplementary material: Table 2 including chemical and isotopic data, sample locations and their position in Figure 8 is available at https://doi.org/10.6084/m9.figshare.c.2868055.

The stable isotopic composition of two rivers, the Vantaanjoki River and the Kokemäenjoki River, in southern and southwestern Finland was studied to resolve the transit times and travel routes of the river water in the two different catchments. The Kokemäenjoki River is dominated by great lake basins whereas the Vantaanjoki River has been reported having a significant groundwater component. The mean residence time of the young surface flow component could be resolved by sine function fitting onto the annual fluctuations of the isotopic signal, and the amount of base flow was estimated by using the isotopic composition of the river and groundwater. In this study, we found that the methods work for simple two component catchments. In more complex cases with three different components mixing, the solution becomes increasingly difficult and requires more study.

Variation in 13C/12C-isotope ratios of fracture filling calcite was analyzed in situ to investigate carbon sources and cycling in fractured bedrock. The study was conducted by separating sections of fracture fillings, and analyzing the 13C/12C-ratios with secondary ion mass spectrometry (SIMS). Specifically, the study was aimed at fillings where previously published sulfur isotope data indicated the occurrence of bacterial sulfate reduction. The results showed that the δ13C values of calcite were highly variable, ranging from −53.8‰ to +31.6‰ (VPDB). The analysis also showed high variations within single fillings of up to 39‰. The analyzed calcite fillings were mostly associated with two calcite groups, of which Group 3 represents possible Paleozoic fluid circulation, based on comparison with similar dated coatings within the Baltic Shield and the succeeding Group 1–2 fillings represent late-stage, low temperature mineralization and are possibly late Paleozoic to Quaternary in age. Both generations were associated with pyrite with δ34S values indicative of bacterial sulfate reduction. The δ13C values of calcite, however, were indicative of geochemical environments which were distinct for these generations. The δ13C values of Group 3 calcite varied from −22.1‰ to +11‰, with a distinct peak at −16‰ to −12‰. Furthermore, there were no observable depth dependent trends in the δ13C values of Group 3 calcite. The δ13C values of Group 3 calcite were indicative of organic matter degradation and methanogenesis. In contrast to the Group 3 fillings, the δ13C values of Group 1–2 calcite were highly variable, ranging from −53.8‰ to +31.6‰ and they showed systematic variation with depth. The near surface environment of <30 m (bsl) was characterized by δ13C values indicative of degradation of surface derived organic matter, with δ13C values ranging from −30.3‰ to −5.5‰. The intermediate depth of 34–54 m showed evidence of localized methanotrophic activity seen as anomalously 13C depleted calcite, having δ13C values as low as −53.8‰. At depths of ∼60–400 m, positive δ13C values of up to +31.6‰ in late-stage calcite of Group 1–2 indicated methanogenesis. In comparison, high CH4 concentrations in present day groundwaters are found at depths of >300 m. One sample at a depth of 111 m showed a transition from methanogenetic conditions (calcite bearing methanogenetic signature) to sulfate reducing (precipitation of pyrite on calcite surface), however, the timing of this transition is so far unclear. The results from this study gives indications of the complex nature of sulfur and carbon cycling in fractured crystalline environments and highlights the usefulness of in situ stable isotope analysis.