Woody debris undergoes the same processes of deposition and diagenesis as its embedding sediments, making its fossilized products potentially good archives of basin evolution. We review this hypothesis by reconstructing the timelines, source and physicochemical conditions of mineralization in silicified Pennsylvanian wood from the Kyffhäuser, central Germany. Five stages of silicification are evidenced from quartz cathodoluminescence, fluid inclusions, triple-O and Si isotopes, Raman thermometry, electron-microprobe and scanning-electron analyses, and in situ U-Pb radiogenic isotope dating. (1) 304-299 Ma: permineralization of fluvial woody debris at near-surface conditions sourced from pedogenically altered pyroclasts; (2) 299-290 Ma: opal-quartz transformation during initial burial; (3) 257-260 Ma: quartz-hematite mineralization at 1 km depth related to thermal crustal relaxation; (4) c. 180 Ma: quartz formation from basinal brines upon maximum burial at 170-240°C and 3.5-5 km; and (5) 100 Ma: regional quartz-baryte mineralization following basin inversion before final exhumation in the Quaternary. The results expand the hitherto known timescales of wood mineralization, and reveal that fossil wood can record a basin's burial history and disclose the tectonic events on the hundred-million-year timescale.

Timing and dynamic processes forming eruptible magma in crustal magma systems that feed highly explosive volcanic eruptions are encoded in compositional variations of magmatic crystals. The ca. 40 ka Campanian Ignimbrite deposit, the product of the most voluminous explosive eruption in the Campi Flegrei volcanic field, contains a variety of compositionally zoned sanidine pheno- and antecrysts. Barium diffusion chronometry was applied to 79 zoned sanidine crystals from different units and types of pumice clasts from the deposit. We focused on the compositional boundaries at the outermost rims of sanidine crystals considered to indicate mingling/mixing and recharge processes shortly prior to the eruption. Grey-scale swath profiles extracted from accumulated back-scattered electron images across these compositional discontinuities return diffusion times of mostly < 60 years at 902 °C that is the most appropriate estimated temperature. At ca. 850 °C, most times are between ca. 380 and 8 years; at ca. 970 °C, most estimates result to be < 4 years till 1 month. Our results indicate that resident magmas even in large, long-lived reservoirs such as the one that fed the Campanian Ignimbrite at Campi Flegrei, can be activated and become eruptible in relatively short timescales, comparable to those obtained for similar large silicic eruptions.

The soda-based composition of the standard bulk glass of the 8th century in Europe was changed to a potash-based composition in the 9th century (Wedepohl 2010). This change in composition leads to a similar to 200 degrees C increase in furnace temperature required for melting from the similar to 1000 degrees C required to melt the sodium-rich glass. These are the temperatures required to produce a bubble-bearing melt after 30 min at temperature. Increasing these temperatures by 100 degrees C produces a bubble-free melt after 30 min. Similarly, increasing the amount of time at the lower temperatures would also produce bubble-free melts as the bubbles require more time to rise in more viscous melt. At a temperature of 1250 degrees C the viscosity of the potassium melt is 1.5 log(10) units higher than that of the sodium-based melt (10(1.5) to 10(0) Pa s). The difference in viscosity of the two melts changes from 2 log(10) units at 1100 degrees C (10(1) to 10(3) Pa s) to 3 log(10) units at 800 degrees C (10(4) to 10(7) Pa s). A consequence of the different viscosity/temperature relationship of the two melts is the shortening of the estimated "working time" from 30 s for the sodium melt to 20 s for the potassium melt, taking the working range to be 10(2)-10(6) Pa s. (If a maximum viscosity of 10(7) Pa s is taken for the working range, the working times vary from 40 s for the Na-rich glass to 25 s for the K-rich glass). The sodium melt was synthesized in air at 1100 degrees C, resulting in a transparent glass deep aubergine in colour. Heating the glass to 1400 degrees C produced a transparent pale blue-green glass as the Mn3+ atoms were presumably reduced to Mn2+ at higher temperature. As medieval furnaces were powered by wood burning and therefore operated at reducing conditions, the pale transparent Mn2+-sodium glass was the standard glass of the time. It was known at the time that adding oxygen to the furnace would produce the aubergine coloured glass (Dodwell, 1961; see also citations in Bidegaray et al., 2020). The potassium glass which was synthesized in air at 1400 degrees C is transparent and yellow-olive in colour.

Normally, volatiles in silicate melts are ephemeral components that escape as gases when the melt reaches fluid saturation. When fluid saturation occurs at elevated pressure, magmatic fluids may have large amounts of oxide solute dissolved, are less volatile, and may resemble viscous gels. In Cyprus we have the rare case that solutes of a magmatic fluid coexist with H 2 O saturated basaltic to boninitic glasses. Quenching of the melts and fluid solutes was induced by fluid segregation. When the fluids exsolved, the liquidus temperature was raised and the melts were left supercooled, while the system temperature remained ± constant. Quenching rates deduced from the morphologies and compositions of quench crystals were high. We analyzed coexisting glasses and fluid solutes for major and trace elements. The fluid mobile trace elements (Rb, K, Pb, Sr) are enriched in both the glasses and fluid solutes. Both endmembers (melt and fluid) have a common parentage and originated within a hydrous mantle source. The glasses have 2.5 ± 0.25 wt.% H 2 O and record residual H 2 O contents left after fluid exsolution was completed. Water contents in glasses correspond to an H 2 O partial pressure (pH 2 O) of 65 ± 10 MPa and an emplacement depth on the seafloor of 6500 ± 1000 m, provided equilibrium was reached between the pH 2 O imposed by the melts and the seawater column. Following fluid exsolution, the degree of supercooling ∆T of the melts relative to the dry MgO-in-melt liquidus temperature was – 65 ± 10 °C. The cooling rate ∆T/t at the time of crystallization of dendritic clinopyroxene crystals can be semi-quantified from the distribution of Al 2 O 3 between metastable clinopyroxene dendrites and melt, to at least – 50 °C h −1 . Toward the end of the article we speculate if other cases exist where quenching was triggered by fluid exsolution. A possible example are spinifex textures deep inside komatiite flows where quenching rates by conductive cooling did not exceed 0.3 to 1 °C h −1 . Our proposition assumes that many spinifex-textured komatiites were hydrous, that they contained H 2 O in quantities sufficient to reach fluid saturation at emplacement pressure, and that spinifex textures formed as a result of supersaturation by fluid loss.

Volcanic ash layers are important markers for the chronostratigraphy of paleoclimate and paleoenvironmental archives at the southern tip of South America. However, this requires that tephras are well-dated. We report geochemical data from stalagmite MA1 formed in a non-karst cave near Mt. Burney volcano in southernmost Patagonia (~53°S). High-resolution LA-ICP-MS analyses, SEM imagery, EPMA data, and NanoSIMS enable to identify volcanogenic signals during the last 4.5 kyrs from sub-annual trace element variations and tephra particles in distinct laminae. Our new 230 Th/U-chronology of MA1 provides precise dating of tephra from Mt. Burney (MB) and, probably, Aguilera (A) at 4,216 +93 / −193 yrs BP (MB 2 ), 2,291 ± 33 yrs BP (MB 3 ), 853 +41 / −60 yrs BP (MB 4 ) and 2,978 +91 / −104 yrs BP (A 1 ). This unique high-resolution record holds potential to date further eruptions from Southern Andean volcanoes for the tephrochronology in this critical region, and potentially also large-volume explosive volcanism off South America.

Arctic sea ice cover has been steeply declining since the onset of satellite observations in the late 1970s. However, the available annually resolved sea ice data before this time are limited. Here, we evaluated the suitability of annual trace element (Mg/Ca) ratios and growth increments from the long‐lived annual increment‐forming benthic coralline red alga, Clathromorphum compactum, as high‐resolution sea ice cover archive. It has previously been shown that the growth of C. compactum is strongly light controlled and therefore greatly limited during the polar night and underneath sea ice cover. We compare algal data from 11 sites collected throughout the Canadian Arctic, Greenland, and Svalbard, with satellite sea ice data. Our results suggested that algal growth anomalies most often produced better correlations to sea ice concentration than Mg/Ca ratios or when averaging growth and Mg/Ca anomalies. High Arctic regions with persistently higher sea ice concentrations and shorter ice‐free seasons showed the strongest correlations between algal growth anomalies and satellite sea ice concentration over the study period (1979–2015). At sites where ice breakup took place before the return of sufficient solar irradiance, algal growth was most strongly tied to a combination of solar irradiance and other factors such as temperature, suspended sediments, phytoplankton blooms, and cloud cover. These data are the only annually resolved in situ marine proxy data known to date and are of utmost importance to gain a better understanding of the sea ice system and to project future sea ice conditions.

To expand the newly developed ARM glasses as reference materials for in situ microanalysis of isotope ratios and iron oxidation state by a variety of techniques such as SIMS, LA‐MC‐ICP‐MS and EPMA, we report Li‐B‐Si‐O‐Mg‐Sr‐Nd‐Hf‐Pb isotope data and Fe2+/ΣFe ratios for these glasses. The data were mainly obtained by TIMS, MC‐ICP‐MS, IR‐MS and wet‐chemistry colorimetric techniques. The quality of these data was cross‐checked by comparing different techniques or by comparing the results from different laboratories using the same technique. All three glasses appear to be homogeneous with respect to the investigated isotope ratios (except for B in ARM‐3) and Fe2+/ΣFe ratios at the scale of sampling volume and level of the analytical precision of each technique. The homogeneity of Li‐B‐O‐Nd‐Pb isotope ratios at the microscale (30–120 μm) was estimated using LA‐MC‐ICP‐MS and SIMS techniques. We also present new EPMA major element data obtained using three different instruments for the glasses. The determination of reference values for the major elements and their uncertainties at the 95% confidence level closely followed ISO guidelines and the Certification Protocol of the International Association of Geoanalysts. The ARM glasses may be particularly useful as reference materials for in situ isotope ratio analysis.

Earth and Space Science Open Archive This work has been accepted for publication in Paleoceanography and Paleoclimatology. Version of RecordESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary. Learn more about preprints. preprintOpen AccessYou are viewing the latest version by default [v1]Suitability of the Coralline Alga Clathromorphum compactum as an Arctic Archive for Past Sea ice CoverAuthorsNatashaLeclerciDJochenHalfarSteffenHetzingerPhoebeChanWalterAdeyAlexandraTsayEricBrossierAndreasKronziDSee all authors Natasha LeclerciDCorresponding Author• Submitting AuthorUniversity of TorontoiDhttps://orcid.org/0000-0002-0570-4790view email addressThe email was not providedcopy email addressJochen HalfarUniversity of Toronto at Mississaugaview email addressThe email was not providedcopy email addressSteffen HetzingerUniversität Hamburgview email addressThe email was not providedcopy email addressPhoebe ChanUniversity of Bergen and Bjerknes Centre for Climate Researchview email addressThe email was not providedcopy email addressWalter AdeyDepartment of Botany, Smithsonian Institutionview email addressThe email was not providedcopy email addressAlexandra TsayUniversity of Genevaview email addressThe email was not providedcopy email addressEric BrossierAssociation Nord-Estview email addressThe email was not providedcopy email addressAndreas KronziDUniversitaet GoettingeniDhttps://orcid.org/0000-0001-5655-4633view email addressThe email was not providedcopy email address

Nickel is a strongly compatible element in olivine, and thus fractional crystallization of olivine typically results in a concave-up trend on a Fo-Ni diagram. 'Ni-enriched' olivine compositions are considered those that fall above such a crystallization trend. To explain Ni-enriched olivine crystals, we develop a set of theoretical and computational models to describe how primitive olivine phenocrysts from a parent (high-Mg, high-Ni) basalt re-equilibrate with an evolved (low-Mg, low-Ni) melt through diffusion. These models describe the progressive loss of Fo and Ni in olivine cores during protracted diffusion for various crystal shapes and different relative diffusivities for Ni and Fe-Mg. In the case when the diffusivity of Ni is lower than that for Fe-Mg interdiffusion, then olivine phenocrysts affected by protracted diffusion form a concave-down trend that contrasts with the concave-up crystallization trend. Models for different simple geometries show that the concavity of the diffusion trend does not depend on the size of the crystals and only weakly depends on their shape. We also find that the effect of diffusion anisotropy on trend concavity is of the same magnitude as the effect of crystal shape. Thus, both diffusion anisotropy and crystal shape do not significantly change the concave-down diffusion trend. Three-dimensional numerical diffusion models using a range of more complex, realistic olivine morphologies with anisotropy corroborate this conclusion. Thus, the curvature of the concave-down diffusion trend is mainly determined by the ratio of Ni and Fe-Mg diffusion coefficients. The initial and final points of the diffusion trend are in turn determined by the compositional contrast between mafic and more evolved melts that have mixed to cause disequilibrium between olivine cores and surrounding melt. We present several examples of measurements on olivine from arc basalts from Kamchatka, and published olivine datasets from mafic magmas from non-subduction settings (lamproites and kimberlites) that are consistent with diffusion-controlled Fo-Ni behaviour. In each case the ratio of Ni and Fe-Mg diffusion coefficients is indicated to be <1. These examples show that crystallization and diffusion can be distinguished by concave-up and concave-down trends in Fo-Ni diagrams.

Petrological and geochemical (major element, trace element, Sr-Nd isotope) data for recent (<5 kyr old) basalts that sporadically erupt on the western flank of Piton de la Fournaise (PdF), one of the most active volcanoes on Earth, allow the tracking of magma transfer and evolution from mantle to crustal depths. In the western peripheral area of PdF we document the broadly synchronous eruptions of (1) primitive olivine and olivine-clinopyroxene transitional basalts with tholeiitic affinity that are closely associated in space with (2) transitional olivine basalts with alkaline affinity, and (3) hybrid lavas, intermediate between the 'alkaline' and the 'tholeiitic' end-members. The composition of the latter overlaps with that of the lavas frequently erupted from the conduit system feeding the main summit cone. AlphaMELTS modelling, and fluid inclusion and clinopyroxene barometry, constrain the conditions of magma storage at 10-30 km, and the ascent of magma from the upper mantle to the shallow crustal plumbing system. Variable degrees of mantle melting, together with minor source heterogeneity and contamination with cumulate-derived partial melts, contribute to the diversity of PdF magmas. However, all these processes do not represent the dominant factors that produce the large variability we found in major element composition. Indeed, the composition of basalts erupted from PdF peripheral centers is strongly controlled by polybaric olivine-clinopyroxene fractionation at pressures higher than 3 kbar. Crystal textures and geochemical modelling suggest that fast magma ascent is critical to prevent clinopyroxene dissolution. Conversely, long-lasting magma stagnation promotes pyroxene resorption and magma differentiation. 'Central' eruptions occurring close to the PdF summit cone emit variably more evolved melts, which result from olivine-clinopyroxene-plagioclase differentiation at intermediate-shallow pressure (<3 kbar and in most cases <1 kbar). Deep and extensive magma mixing before injection into the crustal magma conduit system, located below the summit region, results in the apparent homogeneity of basalts erupted from the central area. As regards 'peripheral' eruptions, deep-seated stagnation of basaltic melts and differentiation at the mantle-crust transition zone (c. 4 kbar) produces a range of magma compositions. We demonstrate that rapid magma ascent from deep-seated reservoirs can bypass the central plumbing system. The eruptions of these magmas both in the central area and on the densely populated flanks have major consequences in terms of volcanic hazard at PdF.

Polycrystalline diamond aggregates occur in a few (but not all) kimberlite pipes in southern Africa (e.g.Venetia, Premier, Jwaneng, Orapa) and can make up several percent of the diamond production in a mine.They are classified by increasing grain size as framesite (Gurney and Boyd, 1982) or boart (Orlov, 1977) and typically have a porous structure that indicates formation from C-H-O fluids rather than from melts.The diamond aggregates can contain silicates of eclogitic and peridotitic affinity, similar (but not identical; Sobolev et al., 1975) to the inclusion suite found in gem-sized diamonds.The minerals occur mostly in interstices and are intimately intergrown with the diamonds, which, in addition to further structural and geochemical evidence (e.g.Jacob et al., 2000Jacob et al., , 2004;;Kurat and Dobosi, 2000) indicates contemporaneous crystallization within the diamond stability field in the Earth's mantle.In addition to silicates, rarer phases such as Fe-carbide can sometimes be found in framesites that record unusually low local oxygen fugacity at the time of their formation (Jacob et al. 2004).Furthermore, while most gem-sized diamonds have old, often Archaean formation ages, polycrystalline diamond aggregates from the Venetia Diamond Mine (South Africa) containing eclogitic minerals have been shown to form by very young remobilization processes within the cratonic lithosphere that directly preceded kimberlite eruption (Jacob et al., 2000).Thus, these samples may provide a unique source of information on the nature and timing of small scale processes that lead to diamond formation which complements evidence from gem-sized diamonds.

Introduction Commanditees par Theodulf pour orner l’oratoire de sa villa, les mosaiques de Germigny-des-Pres sont les seules de cette epoque conservees au nord des Alpes (fig. 1). Au ixe siecle, si plusieurs mosaiques ont ete realisees a Rome, celles de Germigny apparaissent bien isolees dans cette region de l’Empire carolingien. Cependant, elles ne devaient pas etre uniques, car beaucoup de mosaiques ont disparu, ce que prouvent les nombreux cubes decouverts en fouille sur des sites du haut ...

Three synthetic reference glasses were prepared by directly fusing and stirring 3.8 kg of high‐purity oxide powders to provide reference materials for microanalytical work. These glasses have andesitic major compositions and are doped with fifty‐four trace elements in nearly identical abundance (500, 50, 5 µg g−1) using oxide powders or element solutions, and are named ARM‐1, 2 and 3, respectively. We further document that sector‐field (SF) ICP‐MS (Element 2 or Element XR) is capable of sweeping seventy‐seven isotopes (from 7Li to 238U, a total of sixty‐eight elements) in 1 s and, thus, is able to quantify up to sixty‐eight elements by laser sampling. Micro‐ and bulk analyses indicate that the glasses are homogeneous with respect to major and trace elements. This paper provides preliminary data for the ARM glasses using a variety of analytical techniques (EPMA, XRF, ICP‐OES, ICP‐MS, LA‐Q‐ICP‐MS and LA‐SF‐ICP‐MS) performed in ten laboratories. Discrepancies in the data of V, Cr, Ni and Tl exist, mainly caused by analytical limitations. Preliminary reference and information values for fifty‐six elements were calculated with uncertainties [2 relative standard error (RSE)] estimated in the range of 1–20%.

Deep crustal felsic xenoliths from classic Scottish Midland Valley localities, carried to the surface by Permo-Carboniferous magmatism, are shown for the first time to include metaigneous varieties with dioritic and tonalitic protoliths. Four hypotheses regarding their origin have been evaluated: (1) Precambrian basement; (2) Permo-Carboniferous underplating; (3) 'Newer Granite' magmatism; (4) Ordovician arc magmatism. U-Pb zircon dating results rule out the Precambrian basement and Permo-Carboniferous underplating hypotheses, but establish that the meta-igneous xenoliths represent both 'Newer Granite' and Ordovician (to possibly Silurian) arc magmatism. The metadiorite xenoliths are shown to have protolith ages of c. 415Ma with epsilon Hf-t zircon values ranging from +0.1 to +11.1. These are interpreted to represent unexposed 'Newer Granite' plutons, based on age, mineralogical, isotopic and geochemical data. This shows that Devonian 'Newer Granite' magmatism had a greater impact on the Midland Valley and Southern Uplands crust than previously realized. Clinopyroxene-plagioclase-quartz barometry on the metadiorites from the east and west of the Midland Valley yielded a similar pressure range of c. 5-10 kbar, and a metadiorite from the east yielded a minimum two-feldspar temperature estimate of c. 793-816 degrees C. These results indicate that the metadiorites once resided in the middle-lower crust. In contrast, two metatonalite xenoliths have a Late Ordovician protolith age (c. 453 Ma), with zircon epsilon Hf-t values of +7.8 to +9.0. These are interpreted as samples of a buried Late Ordovician magmatic arc situated within the Midland Valley. Inherited zircons with similar Late Ordovician ages and epsilon Hf-t=453 values (+1.6 to +10.8) are present in the metadiorites, suggesting that the Devonian 'Newer Granites' intruded within or through this Late Ordovician Midland Valley arc. A younger protolith age of c. 430Ma from one of the metatonalites suggests that arc activity continued until Silurian times. This validates the long-standing 'arc collision' hypothesis for the development of the Caledonian Orogen. Based on U-Pb zircon dating, the metatonalite and metadiorite xenoliths have both experienced metamorphism between c. 400 and c. 391 Ma, probably linked to the Acadian Orogeny. An older phase of metamorphism at c. 411Ma was possibly triggered by the combined effects of heating owing to the emplacement of the 'Newer Granite' plutons and the overthrusting of the Southern Uplands terrane onto the southern margin of the Midland Valley terrane.

One of the most dramatic signs of ongoing global change is the mass loss of the Greenland Ice Sheet and the resulting rise in sea level, whereby most of the recent ice sheet mass loss can be attributed to an increase in meltwater runoff. The retreat and thinning of Greenland glaciers has been caused by rising air and ocean temperatures over the past decades. Despite the global scale impact of the changing ice sheet balance, estimates of glacial runoff in Greenland rarely extend past several decades, thus limiting our understanding of long‐term glacial response to temperature. Here we present a 42‐year long annually resolved red coralline algal Mg/Ca proxy temperature record from a southwestern Greenland fjord, with temperature ranging from 1.5 to 4 °C (standard error = 1.06 °C). This temperature time series in turn tracks the general trend of glacial runoff from four West Greenland glaciers discharging freshwater into the fjord (all p < 0.001). The algal time series further exhibits significant correlations to Irminger Sea temperature patterns, which are transmitted to western Greenland fjords via the West Greenland Current. The 42‐year long record demonstrates the potential of annual increment forming coralline algae, which are known to live up to 650 years and which are abundant along the Greenland coastline, for reconstructing time series of sea surface temperature.

Abstract. The shallow-marine benthic coralline alga Clathromorphum compactum is an important annual- to sub-annual-resolution archive of Arctic and subarctic environmental conditions, allowing reconstructions going back > 600 years. Both Mg content, in the high-Mg calcitic cell walls, and annual algal growth increments have been used as a proxy for past temperatures and sea ice conditions. The process of calcification in coralline algae has been debated widely, with no definitive conclusion about the role of light and photosynthesis in growth and calcification. Light received by algal specimens can vary with latitude, water depth, sea ice conditions, water turbidity, and shading. Furthermore, field calibration studies of Clathromorphum sp. have yielded geographically disparate correlations between MgCO3 and sea surface temperature. The influence of other environmental controls, such as light, on Mg uptake and calcification has received little attention. We present results from an 11-month mesocosm experiment in which 123 wild-collected C. compactum specimens were grown in conditions simulating their natural habitat. Specimens grown for periods of 1 and 2 months in complete darkness show that the typical complex of anatomy and cell wall calcification develops in new tissue without the presence of light, demonstrating that calcification is metabolically driven and not a side effect of photosynthesis. Also, we show that both light and temperature significantly affect MgCO3 in C. compactum cell walls. For specimens grown at low temperature (2 ∘C), the effects of light are smaller, with a 1.4 mol % MgCO3 increase from low-light (mean = 17 lx) to high-light conditions (mean = 450 lx). At higher (10 ∘C) temperature there was a 1.8 mol % MgCO3 increase from low to high light. It is therefore concluded that site- and possibly specimen-specific temperature calibrations must be applied, to account for effects of light when generating Clathromorphum-derived temperature calibrations.