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Accelerated warming and melting of Arctic sea-ice has been associated with significant increases in phytoplankton productivity in recent years. Here, utilizing a multiproxy approach, we reconstruct an annually resolved record of Labrador Sea productivity related to sea-ice variability in Labrador, Canada that extends well into the Little Ice Age (LIA; 1646 AD). Barium-to-calcium ratios (Ba/Ca) and carbon isotopes (δ13C) measured in long-lived coralline algae demonstrate significant correlations to both observational and proxy records of sea-ice variability, and show persistent patterns of co-variability broadly consistent with the timing and phasing of the Atlantic Multidecadal Oscillation (AMO). Results indicate reduced productivity in the Subarctic Northwest Atlantic associated with AMO cool phases during the LIA, followed by a step-wise increase from 1910 to present levels—unprecedented in the last 363 years. Increasing phytoplankton productivity is expected to fundamentally alter marine ecosystems as warming and freshening is projected to intensify over the coming century., Continued warming and melting of Arctic sea-ice have led to increases in Labrador Sea phytoplankton productivity in recent decades. Here, the authors utilize a novel annually resolved palaeoproxy and propose that the recently observed increase in surface ocean productivity is unmatched since the Little Ice Age.

The Birthday Reef was the most productive gold producer during historic mining of the Reefton goldfield on the west coast of the South Island of New Zealand. Deep exploration drill holes (up to 1.6 km long) intersected the mineralised quartz vein zone and adjacent hydrothermal alteration halo beneath the historic mine workings. The Paleozoic metasedimentary host rocks contain between 0.5 and 8 ppb Au and between 4 and 30 ppm As, and metamorphic pyrite typically contains 0.1 to 1 ppm Au in solid solution. The Au and As halo, above these background values, extends

Rutile (TiO2) is an important accessory mineral that, when present, offers a rich source of information about the rock units in which it is incorporated. It occurs in a variety of specific microstructural settings, contains significant amounts of several trace elements and is one of the classical minerals used for U–Pb age determination. Here, we focus on information obtainable from rutile in its original textural context. We do not present an exhaustive review on detrital rutile in clastic sediments, but note that an understanding of the petrochronology of rutile in its source rocks will aid interpretation of data obtained from detrital rutile. For further information on the important role of rutile in provenance studies, the reader is referred to previous reviews (e.g., Zack et al. 2004b; Meinhold 2010; Triebold et al. 2012). Coarse rutile is the only stable TiO2 polymorph under all crustal and upper mantle conditions, with the exception of certain hydrothermal environments (Smith et al. 2009). As such, we will focus on rutile rather than the polymorphs brookite, anatase and ultrahigh-pressure modifications. In this chapter, we first review rutile occurrences, trace element geochemistry, and U–Pb geochronology individually to illustrate the insights that can be gained from microstructures, chemistry and ages. Then, in the spirit of petrochronology, we show the interpretational power of combining these approaches, using the Ivrea Zone (Italy) as a case study. Finally, we suggest some areas of future research that would improve petrochronologic research using rutile. Rutile is a characteristic mineral in moderate- to high pressure metapelitic rocks, in high pressure metamorphosed mafic rocks, and in sedimentary rocks (e.g., Force 1980; Frost 1991; Zack et al. 2004b; Triebold et al. 2012). Rutile also occurs rarely in magmatic rocks, e.g., anorthosites, as well as in some hydrothermal systems. Coarse-grained …

The Palaeoproterozoic Transvaal and Olifantshoek Supergroups of South Africa contain some of the earliest hematite-rich sedimentary rocks (red-beds) and paleosols on record. The origin of these rocks has been variously attributed to surface processes under an oxygenated atmosphere that post-dated the ca. 2.3Ga Great Oxidation Event (GOE). Interpretations of their geochemical signatures, however, have been inconclusive with respect to the causes of the apparent K-enrichment that these rocks record. Here, we re-visit the basal Mapedi Formation of the Olifantshoek Supergroup and the unconformably underlying Drakenstein palaeo-weathering profile that develops against the Ongeluk Formation of the upper Transvaal Supergroup, and present new petrographic and geochemical data in an attempt to constrain the burial metasomatic history of these rocks. Apart from the strong hematitic nature and K-metasomatic overprint seen in both the Mapedi Formation and Ongeluk paleosol, a curious and hitherto unexplored enrichment in high-field strength elements (HFSEs: Ti, Nb, Y, Zr, REE, etc.) by several orders of magnitude higher than average shale characterizes the lower part of the Mapedi Formation as examined here. We show that such enrichments cannot be explained by normal source-to sink weathering processes, unless an unlikely provenance of special geochemical composition (i.e. alkali igneous rocks) is to be invoked. We conclude that the HFSE enrichment, K-metasomatism and evidently transgressive Fe-oxidation effects in the Mapedi shales can only be accounted for via post-depositional fluid-rock interaction, possibly involving F-bearing diagenetic brines. This opens the distinct possibility that such fluids may have also been implicated in alteration processes, enhanced Fe mobility and development of epigenetic hematitic iron-ores as seen at the Transvaal-Olifantshoek unconformity on regional scales. Copyright (c) 2017 John Wiley & Sons, Ltd.

An extensive microanalytical study of calcite precipitated from groundwater flowing into boreholes at >400 m depth in the Aspo Hard Rock Laboratory, Sweden, has been carried out. Hydrochemical variations in packed-off sections, isolating water-conducting fractures intersected by two boreholes, were documented over a period of 17 years. The extraction of the borehole equipment revealed calcite precipitation on the equipment. This mineral material enabled unique assessment of uptake of different trace elements by calcite during precipitation from granitoid fracture groundwater, at anoxic, low-temperature (c.a 14 °C), and neutral (pH: 7.4-7.7) conditions, under variable salinity (Cl: 2500-7000 mg/L) prevailing at these depths. Temporal hydrochemical variations could be traced by detailed micro-analytical transects in the calcites and the influence of metal speciation and complexation on partitioning into calcite could be assessed (e.g. explaining unexpectedly low incorporation of REEs). The resulting environment-specific partition coefficients for a large number of metals are relevant in models of radionuclide retention around proposed deep nuclear waste repositories in this kind of environment, particularly because 1) elements such as REEs act as natural analogues to actinides, and 2) existing coefficients established in laboratory or in other natural environments cannot be unreservedly applied to conditions in deep crystalline rocks.

In situ dating of K-rich minerals, e.g. micas and K-feldspar, by the Rb–Sr isotopic system is a new development made possible by the ICP-MS/MS technique. Online chemical separation of Rb and Sr is possible in an O2-filled reaction cell, wherein a portion of the Sr reacts to SrO+ while simultaneously no RbO+ is formed. O2 reactions provide stable analytical conditions sufficient for precise and accurate determination of Rb/Sr and Sr/Sr isotopic ratios using 80 micron laser ablation spots. However, to date 85% of Sr reacting with N2O and >70% Sr reacting with SF6; Rb does not react with either gas. As a result, the sensitivity for Sr reaction products is ∼10 times higher with N2O and ∼8 times higher with SF6 compared to O2. With these more reactive gases, the error of mica isochron ages, calibrated against a newly developed nano-particulate pressed powder tablet of mica–Mg, is ∼1% using a 50 μm laser spot. Our tests show that both N2O and SF6 form interfering reaction products, e.g., SrOH (N2O), SiF3 and TiF3 (SF6) that are difficult to handle using single mass spectrometer instruments, but which can be overcome using MS/MS. Using SF6 combined with H2, it is possible to measure 40Ca+ as 40Ca19F+, free from interference of 40Ar+ and 40K+. This facilitates the dating of micas by the K–Ca isotopic system; we present the first in situ K–Ca age determination.

Monazite is a common accessory phosphate mineral that occurs under a wide range of pressure and temperature conditions in sedimentary, metamorphic and igneous rocks. Monazite contains high amounts of Th and U, rendering single monazite grains suitable for in-situ U-Th/Pb dating using laser ablation inductively-coupled mass spectrometry (LA-ICP-MS). Two key aspects of monazite dating that are critical for accurate age data with maximum precision are (i) optimized instrumental conditions to minimize analytical scatter and (ii) a well characterized reference material to ensure the accuracy of the obtained aged. Here, we analyzed five monazite reference materials (USGS 44069, 94-222, MAdel, Moacir and Thompson Mine Monazite) for their U-Th/Pb ages using LA-ICP-MS technique and applied a variety of laser spot diameters and repetition rates to find the best operational conditions to achieve accurate age data while maintaining maximum precision. We find that a spot diameter of 10 &micro, m and a repetition rate of 10 Hz yield the most precise ages with a deviation of &plusmn, 2.0% from their respective high-precision U/Pb literature age data. Ages were reproduced in three different LA-ICP-MS laboratories using these parameters. Each reference material was tested for its suitability as a matrix-matched age reference material. For this, a rotating, iterative approach was adopted in which one reference monazite was used as calibration reference material against all others, which were treated as unknowns. The results reveal that USGS 44069, 94-222, Thompson Mine Monazite and MAdel all agree with their respective calculated ages and ID-TIMS reference ages and thus are suggested as suitable calibration reference materials. Moacir, however, appears slightly older than previously suggested (up to 4%), thus, caution is advised here when using Moacir as reference material for U-Th/Pb LA-ICP-MS dating in the absence of further absolute age calibration.

Volcanogenic massive sulfide deposits are enriched in metals that are either derived from hydrothermal alteration of the basement rocks or supplied by exsolution of metal-rich volatiles during magmatic differentiation. The extent to which each process contributes to metal enrichment in these deposits varies between different tectonic settings. Ocean Drilling Program Hole 786B recovered > 800 m of upper oceanic crust from a supra-subduction zone setting and includes a 30-m-thick mineralised zone. In situ S isotopic compositions of pyrite decrease from 5.9 ± 2.9‰ in the upper mineralised zone down to − 3.3 ± 2.1‰ in the extensively altered central mineralisation zone, potentially indicating strong magmatic fluid input in this area. Whole rock data and in situ trace element analyses in sulfide minerals show enrichment of Ag, As, Au, Bi, Mo, S, Se, Sb and Te in the mineralised zone. Evaluation of metal behaviour during magmatic differentiation and primary metal fertility of basement rocks suggests that degassing melt is the main source for the high Au, Se and S enrichment observed in the mineralised zone. Magmatic volatile exsolution occurred late during the magmatic differentiation (~ 2 wt.% MgO), concomitant with oxide crystallisation and metal depletion in the melt. Comparison of Ocean Drilling Program Hole 786B with volcanogenic massive sulfide deposits hosted by boninitic volcanic successions, such as in the Semail ophiolite, the Newfoundland Appalachians and the Flin Flon Belt, suggests that magmatic fluid exsolution could be a common mechanism for Au enrichment in bimodal mafic volcanogenic massive sulfide deposits.

This study presents the first combined S and Se isotope investigation of sulfide suited to explore differences in fractionation between these two redox sensitive isotope systematics as recorded in the same mineral. A case study of Cretaceous Navajun pyrite from the Mesozoic Cameros Basin, Spain, with known petrogenesis and geological context shows systematic decoupling at the microscale: Variable S isotope values within the analyzed pyrite coincide with rather constant Se isotope values and vice versa. These signatures were not generated during pyrite growth but record previous redox induced fractionations in fluids that each contributed both elements from two sources. It is likely that both S and Se isotope fractionation occurred during strong reduction from one fully oxidized source whereas only S but no Se isotope fractionation occurred during minor reduction following sulfide dissolution via H2O from another source. Subsequent mixing of these two H2S-H2Se fluids at different elemental S-Se ratios during incorporation into the pyrite can then explain the S-Se isotope variations in the investigated specimen. These inferences are in accordance with a larger range in the redox potential Eh of Se relative to S, resulting in coupled or decoupled Se and S isotope fractionation depending on the oxygen fugacity during the reduction process. If extended to other sulfides of diverse origin, for a given pH, combined Se and S isotope studies may allow to investigate the magnitude of redox variations and place more robust constraints on minimum and maximum oxygen concentrations in the source. We therefore suggest combined S-Se isotope analyses in sulfide as a new powerful proxy for studying Earth’s redox evolution beyond the bulk rock scale.

The Rb-Sr beta-decay dating system is one of the most attractive tools in geochronology, as Rb is sufficiently abundant in common K-bearing minerals like biotite, muscovite and K-feldspar. This allows dating of a wide variety of rocks (e.g., volcanic, magmatic, metamorphic, sedimentary and hydrothermal environments) without the need of preconcentration, as is often required for U-Pb dating of zircon. However, this advantage was to date negatively counteracted by the lack of a suitable in-situ technique, as beta decay systems by nature have isobaric interferences of the daughter isotope by their respective parent isotope. A reaction cell sandwiched between two quadrupoles within an inductively coupled plasma mass spectrometer (ICP-MS) allows exactly this, the online chemical separation of two different elements. Coupled to a laser ablation (LA) system, in-situ Rb-Sr dating is therefore possible if a suitable reaction gas within the reaction cell can be found that separates Sr from Rb. We present here a simple procedure in which Rb-Sr ages can be obtained from a suite of individual phases in regular thin sections. Using the most established reaction gas, oxygen (O 2 ), it is possible to react part of the ablated Sr to SrO + while no RbO + is formed. Measurements of feldspars and micas with a spot size of 80 μm were calibrated against glass standards NIST SRM 610, BCR-2G and biotite from La Posta (California; 91.6 Ma). Results are presented for a variety of magmatic rocks with well-established thermal records: a sample each from the Klokken syenodiorite (Greenland; 1161 Ma), the Ulvo alkaligabbro (Sweden; 1256 Ma) and a pegmatite from the Bohus granite (Sweden; 920 Ma). Obtained in situ Rb-Sr isochron ages are accurate 87 Sr/ 86 Sr ratios are accurate The methodology outlined in this study has significant implications for Rb-Sr studies due to the high spatial resolution: (1) quality of measurements can be better controlled by avoiding alterations and inclusions, (2) large sample numbers can be investigated simply by using regular thin sections, (3) several mineral generations can be targeted that would not be distinguishable in mineral separates, and (4) isotope zonation within single crystals can be revealed. This will open the Rb-Sr dating system to new fields of study. For example, thermochronologic studies can use 87 Sr/ 86 Sr and 87 Rb/ 86 Sr zonation within crystals to better work out cooling and/or reheating paths. Further applications are in the field of provenance studies and temporal evolution of shear zones.

The Palaeoproterozoic Hartley Formation in the Olifantshoek Group was deposited in one of the rift-related Waterberg (sensu lato) red bed basins which formed on the Kaapvaal Craton after the 2.05 Ga Bushveld intrusions and coeval thermal event. The age of these basins is not well constrained due to the shortage of directly dateable rock types. The Hartley Formation contains rare quartz-porphyry lavas interbedded with the dominant basalts and these provide the means to date the formation by analyses of zircon. In this work zircon from one sample has been dated by six Th-U-Pb methods, namely Laser Ablation ICP Quadrupole Mass Spectrometry, Laser Ablation ICP High-resolution Mass Spectrometry, Laser Ablation ICP Multicollector Mass Spectrometry U-Pb (also Lu-Hf), Nordsim Ion probe U-Pb and Th-Pb; and Krogh method ID-TIMS. Our precise ages give a combined age of 1915.2 ± 1.1 Ma. Including one published ion probe date from the only other known occurrence of quartz porphyry, the results only agree if the quoted analytical errors are increased by 20%, which gives a combined result of 1915.6 ± 1.4 Ma. This is considered a reliable, precise and accurate age for the Hartley Formation and supersedes the published Kober method 207Pb/206Pb age of 1928 ± 4 Ma. The new Lu-Hf zircon data, supported by published whole rock Sm-Nd and Rb-Sr data, suggests that both the dominant basalts and the rare quartz porphyries of the Hartley Formation were derived from mafic source rocks which had been in the crustal domain from Archaean times. By contrast with the intracratonic rifts of the other Waterberg Basins, the Olifantshoek Supergroup reflects the development of a western passive margin as the Archaean Kaapvaal Craton rifted and drifted. This was followed by accretion of the Rehoboth Province along the Kalahari Line, accompanied by the development of the east-vergent Kheis Province thrust complex. This created a larger cratonic block against which the 1.2 Ga collisions of Namaqua-Natal terranes impacted. The Kheis Province now yields ~1.17 Ma cooling ages, reflecting the Namaqua collisions, but the true age of the Kheis event is still enigmatic.

Experimental determination of the pressure and temperature controls on Ti solubility in quartz provides a calibration of the Ti-in-quartz (TitaniQ) geothermometer applicable to geological conditions up to ~ 20 kbar. We present a new method for determining 48Ti mass fractions in quartz by LA-ICP-MS at the 1 μg g−1 level, relevant to quartz in HP-LT terranes. We suggest that natural quartz such as the low-CL rims of the Bishop Tuff quartz (determined by EPMA; 41 ± 2 μg g−1 Ti, 2s) is more suitable than NIST reference glasses as a reference material for low Ti mass fractions because matrix effects are limited, Ca isobaric interferences are avoided, and polyatomic interferences at mass 48 are insignificant, thus allowing for the use of 48Ti as a normalising mass. Average titanium mass fraction from thirty-three analyses of low temperature quartz from the Czech Erzgebirge is 0.9 ± 0.2 μg g−1 (2s) using 48Ti as a normalising mass and Bishop Tuff quartz rims as a reference material. The 2s average analytical uncertainty for individual analyses of 48Ti is 8% for 50 μm spots and 7% for 100 μm spots, which offers much greater accuracy than the 21–41% uncertainty (2s) incurred from using 49Ti as an analyte.

Halogen contents for the widely distributed reference glasses BHVO-2G, BIR-1G, BCR-2G, GSD-1G, GSE-1G, NIST SRM 610 and NIST SRM 612 were investigated by pyrohydrolysis combined with ion chromatography, total reflection X-ray fluorescence analysis, instrumental neutron activation analysis, the noble gas method, electron probe microanalysis and laser ablation-inductively coupled plasma-mass spectrometry. Glasses BHVO-2G, GSD-1G and GSE-1G have halogen contents that can be reproduced at the 15% level by all bulk techniques and cover a significant range in halogen mass fractions for F (~ 20–300 μg g), Cl (~ 70–1220 μg g) and Br (~ 0.2–285 μg g) and I (~ 9–3560 ng g). The BIR-1G glass has low F (< 15 μg g), Cl (~ 20 μg g), Br (15 ng g) and I (3 ng g). The halogen contents for the silica-rich NIST SRM 610 and 612 glasses were poorly reproduced by the different techniques. The relatively high Cl, Br and I abundances in glasses GSD-1G and GSE-1G mean that these glasses are well suited for calibrating spatially resolved micro-analytical studies on silicate glasses, melt and fluid inclusions. Combined EPMA and laser ablation-inductively coupled plasma-mass spectrometry data for glass GSE-1G demonstrate homogeneity at the 10% level for Cl and Br.

In northwest Turkey, ophiolitic meta-gabbros are exposed on the Kazdag Massif located in the southern part of the Biga Peninsula. Trace element composition of rutile and Zr-in-rutile temperatures were determined for meta-gabbros from the Kazdag Massif. The Zr content of all rutiles range from 176 to 428 ppm and rutile grains usually have a homogeneous Zr distribution. The rutile grains from studied samples in the Kazdag Massif are dominated by subchondritic Nb/Ta (11–19) and Zr/Hf ratios (20–33). Nb/Ta and Zr/Hf show positive correlation, which is probably produced by silicate fractionation. The Nb/Ta and Zr/Hf ratios increase with a decrease in Ta and Hf contents. The core of rutile grains are generally characterized by low Nb/Ta ratios of 17–18 whereas the rims exhibit relatively high Nb/Ta ratios of 19–23. Trace element analyses in rutile suggest that these rutile grains were grown from metamorphic fluids. The P-T conditions of meta-gabbros were estimated by both Fe–Mg exchange and Zr-in-rutile thermometers, as well as by the Grt-Hb-Plg-Q geothermobarometer. The temperature range of 639 to 662 °C calculated at 9 kbar using the Zr-in-rutile thermometer is comparable with temperature estimates of the Fe-Mg exchange thermometer, which records amphibolite-facies metamorphism of intermediate P-T conditions. The P-T conditions of meta-ophiolitic rocks suggest that they occur as a different separate higher-pressure tectonic slice in the Kazdag metamorphic sequence. Amphibolite-facies metamorphism resulted from northward subduction of the Izmir-Ankara branch of the Neo-Tethyan Ocean under the Sakarya Zone. Metamorphism was followed by internal imbrication of the Kazdag metamorphic sequence resulting from southerly directed compression during the collision.

This provenance study focuses on detrital rutile grains from Jurassic sandstones of the Bayirkoy Formation in the central Sakarya Zone. Cr and Nb concentrations of detrital rutile grains in the Jurassic sandstones vary from 18 to 6855 μg/g and 70–13440 μg/g, respectively. Source area discrimination based on the Cr-Nb concentrations shows that 79 % of the detrital rutile grains originated from metapelitic and 21 % from metamafic rocks. The calculated rutile formation temperatures vary from 471 to 798 ℃ with an average temperature of 635 ℃ at P=10 kbar. Zr-in-rutile thermometer gives overlapping temperatures for all detrital rutile grains from both the metapelitic and metamafic sources. This demonstrates that most of the detrital rutiles sourced from metapelitic and metamafic rocks underwent similar metamorphic conditions and have similar metamorphic history. The U-Pb rutile dating yielded ages for the detrital rutiles in the time range of 346 to 319 Ma, which gives the age of metamorphism for the potential source rocks. Trace element compositions, Zr-in-rutile thermometer and U-Pb rutile geochronology show that detrital rutile grains were predominantly derived from early Carboniferous rocks that underwent metamorphism in amphibolite-facies conditions. Amphibolite-facies rocks of the Saricakaya Massif in the central Sakarya Zone seem to be the primary source lithologies for the detrital rutiles in the Jurassic Bayirkoy Formation as it comprises previously-mentioned source lithologies and has a close geographic position to the area studied. Carboniferous Variscan metamorphism was followed by emplacement of numerous post-collisional granitoids in the central Sakarya Zone.

Rare-earth elements play a crucial role in modern technologies and are necessary for a transition to a green economy. Potentially economic deposits of these elements are typically hosted in minerals such as monazite, bastnasite, and eudialyte (a complex Na-Ca-Fe-Zr silicate mineral with Cl), making these prime targets for geological research. Globally, rare-earth mineral deposits commonly show evidence of polyphase development and mineralisation processes, which need to be better understood to improve exploration strategies. The Norra Karr alkaline complex (Sweden) contains a globally significant deposit of rare-earth elements, hosted in the mineral eudialyte. In this study, we focussed on eudialyte crystals in undeformed, cross-cutting pegmatoid veins from Norra Karr. In order to determine their age, we refined an established micromilling method to enable sampling of minerals rich in rare-earth elements for precise analysis of major and trace elements, Nd isotope ratios, and Sm-Nd geochronology down to a scale of

The Western Dharwar Craton (WDC) and the Karwar Block (KB) in southern Peninsular India provide important windows to Earth’s early crustal evolution and continental growth as these domains likely represent fragments of the first landmass or supercontinent on our planet. Here we employ, for the first time, a coupled laser ablation zircon U-Pb dating and in-situ Rb-Sr dating of micas (biotite, muscovite) and feldspars to evaluate the Meso- to Neoarchean crustal evolution and Proterozoic magmatism/metamorphism in the Karwar Block. This novel approach based on integrated geochronological results show that the WDC and KB experienced (i) a major Mesoarchean continental growth event (c. 3.2 to 2.9 Ga), (ii) younger Neoarchean and Paleoproterozoic magmatism/migmatization (syn- and post-tectonic granite formation events at c. 2.8–2.6 Ga and 2.2 Ga, respectively), and (iii) Mesoproterozoic metamorphism/thermal imprint (as young as 1.2 Ga). The zircon eHf(t) values exhibit a range from +0.4 to +9.8 in amphibolite, hornblende gneiss and trondhjemite (3.28–3.08 Ga), as well as the +6.1 to +9.7 range for 2.96 Ga old zircons in porphyritic granite, which suggests juvenile source for the magmatism that constructed this crustal block. Overall, this study illustrates the benefits of using coupled zircon U-Pb and in-situ Rb-Sr mica and feldspar dating approaches, as the former (U/Pb) provides robust constraints or a ‘baseline age’ for initial crystallization of crustal sequences whereas the latter (Rb/Sr) is sensitive to younger magmatic and metamorphic events. Thus, the integration of these two laser ablation ICP-MS based geochronometers applied to crustal evolution studies, has the potential to provide more comprehensive insights into continental growth in the early Earth, and later magmatic and metamorphic history of the region.

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.

Finely acicular rutile intergrown with host quartz (rutilated quartz) is commonly found in hydrothermal veins, including the renown cleft mineral locations of the Swiss Alps. These Alpine cleft mineralizations reportedly formed between ~13.5 and 15.2 Ma (based on ages of rare hydrothermal monazite and titanite) at temperatures ( T ) of ~150–450 °C (based on fluid inclusions and bulk quartz-mineral oxygen isotope exchange equilibria), and pressures ( P ) of 0.5–2.5 kbar (estimated from a geothermal gradient of 30 °C/km). The potential of rutilated quartz as a thermochronometer, however, has not been harnessed previously. Here, we present the first results of age and T determinations for rutilated quartz from six locations in the Swiss Alps with vein country rocks that cover peak-metamorphic conditions between ~600 and with x = Zr ppm and R = 0.008314 (uncertainties scaled by the square root of the mean square of weighted deviates MSWD = 11; n = 9). This relationship supports previously recognized temperature-dependent Zr uptake in rutile, although widely used Zr-in-rutile thermometer calibrations based on high- T experiments are at variance with oxygen isotope exchange temperatures. By contrast, Ti-in-quartz lacks systematic relations with oxygen isotope temperatures. The discrepancy between low- T Ti-in-quartz thermometry on one side, and oxygen isotope and Zr-in-rutile thermometry on the other, suggests that Ti-in-quartz thermometry should be applied with caution for low- T (

We report homogeneity tests on large natural apatite crystals to evaluate their potential as U reference materials for apatite fission-track (AFT) thermochronology by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The homogeneity tests include the measurements of major element concentrations by electron probe microanalysis (EPMA), whereas for U concentration, isotope dilution (ID) ICP-MS and laser ablation (LA) ICP-MS were employed. Two apatite crystals are potential reference materials for LA-ICP-MS analysis: a 1 cm3 fraction of a Durango crystal (7.5 μg g−1 U) and a 1 cm3 Mud Tank crystal (6.9 μg g−1 U). The relative standard deviation (1 RSD) of the U concentration determined by ID-ICP-MS of both apatite crystals was ≤ 1.5%, whereas 1 RSD for the LA-ICP-MS results was better than 4%, providing sufficient homogeneity for fission-track dating. The results on the U homogeneity for two different apatite samples are an important step towards establishing in situ dating routines for AFT analysis by LA-ICP-MS. Nous restituons des tests d'homogeneite sur des grands cristaux d'apatite naturelle afin d’evaluer leur potentiel en tant que materiaux de reference pour l'U en vue d'une application dans le domaine de la thermochronologie par traces de fission sur apatite (AFT) par spectrometrie de masse a plasma induit couplee a l'ablation laser (LA-ICP-MS). Les tests d'homogeneite incluent des mesures des concentrations en elements majeurs par microsonde electronique (EPMA), alors que pour la concentration en U, la dilution isotopique (ID) ainsi que l'ablation laser (LA) ICP-MS ont ete employees. Deux cristaux d'apatite sont des materiaux de reference possibles pour les analyses LA-ICP-MS: une fraction d'1 cm3 d'un cristal de Durango (7,5 µg g−1 U) et un cristal d'1 cm3 de Mud Tank (6,9 µg g−1 U). L’ecart type relatif (1 RSD) de la concentration en U determinee par ID-ICP-MS des deux cristaux d'apatite est ≤ 1,5%, tandis que celui pour les resultats LA-ICP-MS est inferieur a 4%, offrant ainsi une homogeneite suffisante pour les datations par la methode des traces de fission sur apatite. Les resultats concernant l'homogeneite de l'U pour deux echantillons differents d'apatite sont une etape importante vers la possibilite d'envisager des datations AFT in situ en routine par LA-ICP-MS.

To facilitate the long term durability predictions of nuclear waste repositories, acceleration methods enhancing calcium leaching process from cementitious materials are needed, even though mechanisms not necessarily comparable to those predominant in a natural leaching process may be developed. In the previously published acceleration methods the samples are very small, which limits further physical or mechanical tests. In this paper, a new acceleration method based on electro-chemical migration is presented. The method although not driven with the same kinetics as in natural leaching, was designed in such a way that unnecessarily destructive by-effects could be minimized while promoting a higher leaching rate for a sample size suitable for further testing the mechanical and physical properties. It is shown that approximately 1x10^6 C of electrical charge per paste specimen of size O50 x 75 mm (approximately 230 g) is required to leach out the total amount of Portlandite. The chemical and mineralogical properties of leached samples are characterized by various techniques. It is concluded that aged samples are comparable to those leached in a natural leaching process as both are characterized by a layered system comprising an unaltered core delineated by total dissolution of Portlandite followed by a progressive decalcification of the calcium silicate hydrate gel.

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 (

In northwest Turkey, high-pressure metamorphic rocks occur as exotic blocks within the cetmi m lange located on the south of the Biga Peninsula. Rutile chemistry and rutile thermometry obtained from the eclogite and associated garnet-mica schist in the cetmi m lange indicate significant trace element behaviour of subducted oceanic crust and source-rock lithology of detrital rutiles. Cr and Nb contents in detrital rutile from garnet-mica schist vary from 355 to 1026 pzig and 323 and 3319 g/g, respectively. According to the Cr-Nb discrimination diagram, the results show that 85% of the detrital rutiles derived from metapelitic and 15% from metamafic rocks. Temperatures calculated for detrital rutiles and rutiles in eclogite range from 540 degrees C to 624 degrees C with an average of 586 degrees C and 611 degrees C to 659 degrees C with an average of 630 degrees C at P = 2.3 GPa, respectively. The calculated formation temperatures suggest that detrital rutiles are derived from amphibolite- and eclogite-facies metamorphic rocks. Amphibolite-facies rocks of the Kazdag Massif could be the primary source rocks for the rutiles in the garnet-mica schist from the cetmi m lange. Nb/Ta ratios of metapelitic and metamafic rutiles fall between 7-24 and 11-25, respectively. Nb/Ta characteristics in detrital rutiles may reflect a change in source-rock lithology. However, Nb/Ta ratios of rutiles in eclogite vary from 9 to 22. The rutile grains from eclogites are dominated by subchondritic Nb/Ta ratios. It can be noted that subchondritic Nb/Ta may record rutile growth from local sinks of aqueous fluids from metamorphic dehydration. (C) 2017 Elsevier GmbH. All rights reserved.

WOS: 000408588700008, The East Anatolian plateau (Turkey) is extensively covered by Neogene to Quaternary volcanic-sedimentary rocks, and is characterized by an attenuated lithospheric mantle. Its pre-Neogene basement is commonly considered to consist entirely of Late Cretaceous to Oligocene oceanic accretionary complexes, formed at the junction of several continental blocks. Here we report on three main exposures of the pre-Neogene basement in this region. The exposed areas consist mainly of amphibolite-to granulite-facies metamorphic rocks, including marble, amphibolite, metapelite, metagranite, and metaquartzite. An upper amphibolite-to granulitefacies domain is equilibrated at similar to 0.7 GPa and similar to 800 degrees C at 83 +/- 2 Ma (2 sigma). U-Pb dating of magmatic zircons from the metagranite yielded a Late Ordovician-early Silurian protolith age (444 +/- 9 Ma, 2 sigma). The detrital zircons from one metaquartzite point to a Neoproterozoic-early Paleozoic provenance. Ophiolitic rocks tectonically sit on the metamorphic rocks. Both the metamorphic and ophiolitic rocks are in turn unconformably covered by lower Maastrichtian clastic rocks and reefal limestones, suggesting that the whole exhumation process and juxtaposition with the ophiolitic rocks had occurred by the early Maastrichtian. Several lines of evidence, such as (1) the absence of any indication of a former high-pressure metamorphism in the metamorphic rocks, (2) the allochthonous nature of the ophiolitic rocks, (3) the presence of metagranite with a Late Ordovician-early Silurian protolith age, and (4) the Neoproterozoic- early Paleozoic provenance of detrital zircons in the metaquartzite (in contrast to the dominance of late Paleozoic-Mesozoic crystalline rocks in the adjacent continental blocks) indicate a substantial component of continental basement beneath the Neogene to Quaternary cover. Thus, the loss of the lithospheric mantle probably resulted from lithospheric foundering processes beneath the plateau, rather than just slab steepening and break-off., Scientific and Technological Research Council of Turkey [114Y226], We greatly benefited from lively discussions with C. Sengor, A. Okay, and O. Gogus, and constructive reviews by B. Wernicke and two anonymous reviewers. This work was financially supported by the Scientific and Technological Research Council of Turkey (grant 114Y226).

The Zr-in-rutile thermometer is well established for the determination of metamorphic temperatures, particularly in high-grade metamorphic terrains, and for sedimentary provenance studies. The robustness of the rutile thermometry has not been tested on hydrothermal systems. Unlike quartz, a common hydrothermal mineral with abundant fluid inclusions, it is difficult to find fluid inclusions in rutile that are suitable for fluid-inclusion microthermometry. Here, we report fluid-inclusion microthermometric measurements in rutile from the auriferous quartz–kaolinite–hematite vein that typifies the gold deposit of Mil Oitavas in the southern Serra do Espinhaco, Minas Gerais, Brazil. Primary fluid inclusions in the rutile record moderately saline (10–12 wt% NaCl equivalent), aqueous–carbonic fluids with a total homogenization temperature of ~250 °C, which were likely trapped at about 300 °C and 2.0 kbar. This temperature is approximately 200 °C lower than that predicted by the Zr-in-rutile thermometer. For hydrothermal conditions of relatively low temperature, direct measurements of homogenization temperatures in rutile-hosted fluid inclusions should be preferred to the Zr-in-rutile thermometer.

The Palaeoproterozoic Reynolds Range of the Arunta Region, central Australia, comprises a series of shallow marine clastic sediments (Reynolds Range Group) which overlies deeper water sequences of turbidites (Lander Rock Formation) and minor sandstones (“unnamed sandstone”). U–Pb age data collected from detrital rutile and zircon in these rocks indicates these sequences contain very similar age spectra, although with a notable and important shift to younger ages within the stratigraphically younger Reynolds Range Group. Detrital zircons from the “unnamed sandstone” directly underlying the unconformity with the Reynolds Range Group contain a major age component at ca. 1860 Ma, together with a wide spread of ages between ca. 3.2 and 2.0 Ga and a minor age component of 1830–1805 Ma. Detrital rutile from the same rock yield a unimodal age spectrum with a mean age of ca. 1840 Ma. The detrital zircon age spectrum from the Reynolds Range Group is similar, although the youngest cluster of ages is younger and dates to between 1800 Ma and 1780 Ma. Detrital rutile from these rocks yield a unimodal age spectrum with a mean age of ca. 1790 Ma. Although the observed differences in ages are subtle, we suggest these nevertheless mark a significant change in provenance. We attribute the predominance of 1860–1820 Ma detrital zircon and 1840 Ma detrital rutile within the “unnamed sandstone” and the characteristic ca. 1860 Ma detrital zircon age cluster in previously published provenance studies from the Lander Rock Formation to uplift and erosion of the Halls Creek–Pine Creek Orogen. This orogenic belt marks collision between the North Australian and Kimberley cratons, an event dated to between 1835 Ma and 1810 Ma and which incorporates marginally older rocks dating to 1860 Ma from the foreland of the Kimberley Craton. By contrast we attribute the influx of younger rutile and zircon, together with a distinct facies change observed with the onset of the deposition of the Reynolds Range Group, to a shift in provenance region to the Yapungku Orogen, which marks the collision between the West Australian and North Australian cratons and is dated to ca. 1800–1765 Ma. A change in provenance is additionally consistent with significant differences in rutile trace element composition. The Lander Rock Formation and the Reynolds Range Group are stratigraphically correlated with sedimentary rocks that overly large parts of the North Australian Craton. We suggest this indicates spatially continuous basinal conditions within the North Australian Craton between ca. 1840 Ma and 1780 Ma, although the erosion and drainage systems feeding this basin were strongly influenced by the collision and orogenesis along the northwest and southwest margins of the North Australian Craton.

The ability to quantify the rates at which metamorphic reactions occur is critical to assessing the extent to which equilibrium is achieved and maintained in a variety of dynamic settings. Here we investigate the kinetics of rutile replacement by titanite during amphibolite-facies overprinting of eclogite, garnet amphibolite and anorthosite from Catalina Island, CA, the Tromso Nappe, Norway, the North Qaidam terrane, China, and the Guichicovi Complex, Mexico. Trace element concentration profiles across rutile rimmed by titanite, as determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), reveal Nb zoning in rutile that we interpret as the result of Nb back-diffusion from the rutile–titanite boundary. We present new field-based reaction rates calculated from grain boundary velocities, which in turn were calculated using a 1-D diffusion model for Nb back-diffusion into rutile during titanite replacement over the temperature range 670–770 °C. Our data are consistent with or slightly faster than previous estimates of field-based reaction rates for regional metamorphism, and extend the temperature and compositional range over which regional metamorphic reaction rates are known.

We use thallium (Tl) concentrations, K/Rb, K/Tl and Rb/Tl ratios and Tl isotopes in minerals from the alkaline to peralkaline Ilimaussaq complex (South Greenland) to trace magmatic differentiation, crustal assimilation, magmatic degassing, ore precipitation and hydrothermal metasomatism. Closed-system magmatic differentiation is marked by a coherent decrease of K/Tl- and K/Rb-ratios, whereas crustal assimilation results in a strong Tl-enrichment, causing low K/Tl-ratios compared to K/Rb-ratios. Thallium isotopes show only slight changes during orthomagmatic differentiation and the assimilation of crustal material cannot be traced, since the isotopic composition of the average crust is within the range of the mantle and mantle-derived rocks. Magmatic degassing, however, increases Rb/Tl-ratios and changes the isotopic composition of Tl. The released fluids are enriched in Tl, characterized by high 205Tl/203Tl ratios and can precipitate Tl-rich sulfide and silicate minerals as indicated by some late-magmatic hydrothermal veins, which contain a conspicuous assemblage of Tl–Fe–Cu-sulfides (thalcusite, djerfisherite, chalcothallite). The oxidative alteration of these assemblages at high pH results in small-scale redistribution of Tl. Thallium released by this process is entrained into late-stage Tl-enriched astrophyllite.

The Early Miocene high-K I-type plutonic rocks constitute the early products of the Neogene to Quaternary magmatism, and the youngest exposed intrusions in the East Anatolian plateau. Here we deal with the petrogenesis of the Early Miocene Taslicay intrusion covering an area of similar to 62 km(2). The intrusion comprises leucogranite, and minor gabbro-monzodiorite and rhyolite porphyry. U-Pb dating of zircons from the leucogranite, monzodiorite and rhyolite porphyry yielded identical igneous crystallization ages of similar to 19 Ma (Early Miocene). According to the modified alkali-lime index, the leucogranite and the rhyolite porphyry are alkali-calcic, while the gabbro-monzodiorite is transitional calcic to calc-alkalic. On variation diagrams, the gabbro-monzodiorite and the leucogranite as well as rhyolite porphyry form distinct bimodal groupings, whereby the leucogranite display well-defined linear differentiation trends, in contrast to the gabbro-monzodiorite. The leucogranite has relatively fractionated rate earth element (REE) patterns with concave-upward shapes and significant negative Eu anomalies; middle REEs are hardly fractionated with respect to heavy REEs. The gabbro-monzodiorite is characterized by high abundances of incompatible elements, slightly fractionated chondrite-normalized REE patterns with feebly negative Eu anomaly. The rhyolite porphyry is compositionally similar to the leucogranite. The geochemical features imply a fractionating mineral assemblage of hornblende, plagioclase and biotite for the leucogranite, and hornblende and plagioclase for the gabbro-monzodiorite. All the rock types display a narrow Sr and Nd isotopic variation (initial Sr-87/Sr-86 = 0.7053 to 0.7065; initial epsilon Nd = -0.5 to -3.8). The leucogranite and rhyolite porphyry exhibit gradually slightly higher initial Sr-87/Sr-86 and lower initial Nd-143/Nd-144 ratios relative to the gabbro-monzodiorite. Similarly, delta O-18 and initial epsilon Hf values of zircons suggest slightly increasing amount of crustal component from the leucogranite to the rhyolite porphyry. The gabbro-monzodiorite is probably related to partial melts from the slightly enriched lithospheric mantle. The magmas of the leucogranite and the rhyolite porphyry, on the other hand, probably resulted from the remelting of a middle- to high-K basic to intermediate rocks, compositionally similar to the gabbro-monzodiorite, and assimilated gradually slightly increasing amount of old high-silica crustal material. Several lines of evidence such as (i) presence of the well-developed dike swarm of rhyolite porphyry at the north eastern margin of the intrusion, (ii) exhumation of the intrusion at the earth's surface by Middle Miocene, (iii) widespread apatite fission tract ages between 22 and 16 Ma from literature, and (iv) the absence of the exposed intrusions younger than the Early Miocene suggest that the Early Miocene represents probably a time of continental extension and exhumation in Eastern Anatolia and NW Iran. (C) 2019 Elsevier B.V. All rights reserved.

The timing of diamond crystallization is generally inferred from radiometric dating of individual or multiple mineral inclusions in diamond, where ages are derived from isochrons or isotopic evolution models. Resulting ages often significantly predate the emplacement ages of host kimberlites, but age information from both approaches can be ambiguous due to long-lived mantle heterogeneities where mixing can mimic isochrons or in-situ aging. Direct dating of accessory mineral inclusions in diamonds, by contrast, has rarely been attempted because of the scarcity of such inclusions, requiring careful high grading of large amounts of diamond concentrates. Here, we report secondary ionization mass spectrometry (SIMS) U–Pb ages from a suite of rare rutile inclusions which were extracted from diamond in an eclogitic paragenesis from the Mir kimberlite pipe, Siberia. One population of rutile inclusions shows diamond crystal-shapes and was petrographically identified as completely enclosed in diamond prior to host burning for inclusion extraction. These rutile inclusions were screened for U abundances (0.24–23 μg/g U) and those with the highest U contents were dated, yielding a uniform U–Pb concordia age of 375.5 ± 7.0 Ma (error 95% confidence; mean square of weighted deviates MSWD = 0.74; number of spots n = 19). This age is nearly coeval with, but significantly (at the 95% confidence level) older than combined U–Pb rutile ages for rutile intergrown with polycrystalline fibrous diamond (362.9 ± 9.5 Ma; MSWD = 0.96; n = 7) and rutile from the eclogitic xenolith matrix (369 ± 16 Ma; MSWD = 0.30; n = 5). Rutile ages are consistent with published ages for kimberlite emplacement (ca. 360 Ma), but much younger than Re–Os sulfide isochron ages between ca. 913 Ma and 2.1 Ga for groups of individual inclusions in diamond from the same location. When assuming the oldest Re–Os sulfide age as the timing of rutile entrapment, diffusive Pb-loss from rutile inclusions over ca. 2 Ga would require diffusivities of Pb in diamond of >10−22 m2/s, as well as Pb partitioning coefficients between diamond and rutile at near or greater unity. Alternatively, if Pb is immobile in diamond, ancient rutile ages could have been reset due to processes other than volume diffusion through diamond (e.g., due to fluid migration along cracks). However, in this scenario it remains difficult to explain why all rutile inclusions dated here would have been located along cracks, whereas sulfide inclusions investigated in other studies were not. Another explanation is that rutile inclusions were entrapped at the time of diamond formation, and that this event is recorded by U–Pb rutile ages, whereas sulfides predate diamond crystallization and their Re–Os systematics were incompletely reset. Trace element heterogeneity in rutile suggests that they originated in chemically different environments, and thus rutile likely predates diamond formation. However, due to rapid diffusion of Pb in rutile, radiogenic Pb accumulated only after entrapment in diamond (for inclusions) or eruptive quenching (for intergrown or matrix rutile). Overall, rutile geochronology indicates that at least some diamond from the Mir pipe formed briefly (within the ca. 20 Ma age difference between U–Pb rutile ages for inclusions and intergrown/matrix rutile) before kimberlite eruption, supporting models that link diamond formation with carbon-rich precursors of kimberlite magmas.

The Akcaabat gold deposit is mainly composed of massive arsenopyrite veins in strongly foliated augen gneisses of the Cine Sub-massif in western Turkey. K-bearing minerals from orogenic gold veins were dated by the in situ Rb-Sr method in order to determine the formation age of the Akcaabat gold deposit. Textural relationships between the vein minerals suggest that arsenopyrite, K-feldspar, quartz, and muscovite formed in one paragenetic stage. Native gold, native bismuth, scorodite, and galena were introduced in a later paragenetic stage. The isochron derived from K-feldspar and muscovite occurring in the veins yielded 31.3 ± 4.7 Ma. In situ Rb-Sr dating of the same assemblage (K-feldspar and muscovite) in the host rock gave an isochron age of 40.8 ± 3.8 Ma, 10 Ma older than the vein ages, and corresponding to peak metamorphism of the regional main Menderes metamorphism during the Alpine-Himalayan orogenic event. Biotite from the host rock gave an isochron age of 28.1 ± 2.2 Ma and probably reflects the cooling age. Homogenization temperatures from fluid inclusions in quartz show that quartz formed at 280–390 ℃ but has a dominant mode in the 350–360 ℃ temperature interval. The age of vein formation was successfully distinguished from the age of the Alpine-Himalayan orogenic event associated with main Menderes metamorphism. This study demonstrates that in situ Rb-Sr isotopic study can be applied to resolve absolute dating of orogenic deposits in metamorphic complexes.

We present a novel age-equation calibration for fission-track age determinations by laser ablation inductively coupled plasma mass spectrometry. This new calibration incorporates the efficiency factor of an internal surface, [ηq]is, which is obtained by measuring the projected fission-track length, allowing the determination of FT ages directly using the recommended spontaneous fission decay constant. Also, the uranium concentrations in apatite samples are determined using a Durango (Dur-2, 7.44 μg/g U) crystal and a Mud Tank (MT-7, 6.88 μg/g U) crystal as uranium reference materials. The use of matrix-matched reference materials allows a reduction in the uncertainty of the uranium measurements to those related to counting statistics, which are ca. 1 % taking into account that no extra source of uncertainty has to be considered. The equations as well as the matrix-matched reference materials are evaluated using well-dated samples from Durango, Fish Canyon Tuff, and Limberg as unknown samples. The results compare well with their respective published ages determined through other dating methods. Additionally, the results agree with traditional fission-track ages using both the zeta approach and the absolute approach, suggesting that the calibration presented in this work can be robustly applied in geological context. Furthermore, considering that fission-track ages can be determined without an age standard sample, the fission-track thermochronology approach presented here is assumed to be a valuable dating tool.

Provenance studies from Cambro-Ordovician sediments of the North Gondwana passive margin typically ascribe a North African source, a conclusion that cannot be reconciled with all observations. We present new U-Pb ages from detrital rutile and zircon from Late Ordovician sediments from Saxo-Thuringia, Germany. Detrital zircons yield age populations of 500–800 Ma, 900–1050 Ma and 1800–2600 Ma. The detrital rutile age spectra are unimodal with ages between 500 and 650 Ma and likely represent, together with the 500–800 Ma and 1800–2600 Ma zircon populations, detritus sourced predominantly from North Africa. In contrast, the c. 950 Ma zircons, which are persistently found in Cambro-Ordovician sediments of North Gondwana, have no obvious African source. We propose that these zircons are sourced from the Rayner Complex–Eastern Ghats regions of Antarctica and India. An Indo-Antarctic source indicates either continental-scale sedimentary transport from central Gondwana to its peripheries or multiple cycles of sediment reworking and redeposition.

The ca. 1.0–1.1 Ga Vijayan Complex (VC) of eastern and southeastern Sri Lanka is one of three high-grade metamorphic terranes making up the basement of the island and is in tectonic contact with the adjacent, older Highland Complex. It consists predominantly of granitoid gneisses ranging in composition from diorite to leucogranite, with a distinct calc-alkaline geochemical signature, and is interpreted as a magmatic arc. Strong ductile deformation has obliterated almost all original intrusive relationships. High-grade metamorphism during the Pan-African event at ca. 610–520 Ma has produced widespread granulite-facies assemblages that are now largely retrogressed and were affected by extensive late metamorphic K-metasomatism. In southern Sri Lanka the Vijayan gneisses are tectonically interlayered with rocks of the Highland Complex in a so-called mixed zone. We report zircon ages, whole-rock Nd and Hf-in-zircon isotopic systematics and geochemical data for a large selection of Vijayan gneissses in order to better characterize this complex and its tectonic setting. The zircon ages are predominantly in the range 1100–1000 Ma with a few early Neoproterozoic intrusions, and identify the VC as a Grenville-age magmatic arc. Many zircons experienced minor to significant lead-loss at about 580 Ma. The Nd and Hf isotopic data confirm a generally primitive origin for most Vijayan gneisses, but significant variations in both isotopic systems argue for source heterogeneities and the possible involvement of minor amounts of older continental material in their genesis. Immobile trace and rare earth element distributions favour an origin of the gneiss protoliths through melting at relatively shallow depth, and the chemical variation from diorite and tonalite via granodiorite to granite in the VC can be explained by increasing fractionation of plagioclase and biotite, accompanied by amphibole and accessory phases. The VC may be comparable, in some respect, to the composition and evolution of the Kohistan Arc in Pakistan. The unique composition, age and isotopic characteristics of the VC find no convincing counterpart in other fragments of the Gondwana supercontinent, and its origin therefore remains exotic and enigmatic.

The Plat Sjambok Anorthosite crops out near Prieska Copper Mines in the Namaqua–Natal Province of southern Africa. It is a massif-type anorthosite, previously regarded as a late-tectonic intrusion and part of the ca. 1100 Ma bimodal Keimoes Suite. Our new ion probe U–Pb zircon data show that the Plat Sjambok massif intruded at 1259 ± 5 Ma, before the 1220 Ma Namaqua collision events and is thus approximately 150 million years older than the Keimoes Suite. Despite the proximity to Prieska Mines, the anorthosite is located in the Kaaien Terrane close to the Brakbos Fault, which is the boundary with the Areachap Terrane in which Prieska Mines is situated. We dated the Nelspoortjie Tonalite, the main country rock of the Plat Sjambok Anorthosite, by laser ablation ICPMS at 1273 ± 13 Ma. Both intrusions thus originated concurrently with the 1286–1241 Ma volcanic rocks of the Areachap Group, which developed in a subduction-related arc setting, prior to its collision with the Kaaien Terrane and Kaapvaal Craton. M...

New analytical developments have made radiogenic helium ( 4 He) applicable to archeological gold artifacts for age determinations. Here we report the application of the U/Th– 4 He method to the direct dating of gold from the historically important gold deposit in Diamantina, Minas Gerais, Brazil. The U/Th– 4 He age of 515 ± 55 Ma for the Diamantina gold is corroborated by a new U/Pb age of 524 ± 16 Ma for rutile recovered from auriferous pockets. These ages tie the Diamantina gold mineralization to the Brasiliano orogenic event, in the context of the Gondwana amalgamation. Our results indicate that U/Th– 4 He dating of gold is possible, opening new perspectives for the dating of gold deposits without assuming contemporaneity between gold and datable hydrothermal minerals.

Rutile is a common accessory mineral in variousmetamorphic and igneous rocks. Although its formulais very simple, a number of elements may substitute forTi in rutile, including Al, V, Cr, Fe, Zr, Nb, Sn, Sb, Hf,Ta, W, and U [1]. The chemical characteristics of rutile(primarily, the character of HFSE distribution) arewidely used as geochemical indicators of mineralforming processes [1, 2]; Zr content in rutile was calibratedas a geothermometer [e.g., 3]; and rutile is a suitablemineral for the U–Pb dating of metamorphism andgeothermochronological reconstructions [4]. Theresults of the U–Pb dating of rutile and titanite from therocks of the Baltic shield were used for the reconstruction of the thermal history of the Karelian craton andBelomorian mobile belt (BMB) [5, 6]. The authorsestablished a significant difference between the U–Pbages of rutiles and titanites from the rocks of the Karelian craton (Archean) and BMB (Paleoproterozoic).However, the character of trace element distribution inrutile, which may potentially provide insight into theparameters controlling crystallization processes, wasnot previously explored in the rocks of the Baltic shield.This paper reports the results of an in situ LA–ICP–MS investigation of the geochemistry and U–Pb age ofrutile from metamorphic rocks of two areas within theBMB, the Shueretskoe deposit of garnet in its centralpart and the Salma eclogites from the northwesternBMB. Although the rocks of these complexes wereimprinted penecontemporaneously by the youngestSvecofennian metamorphism, they are significantlydifferent in the mineral and chemical composition ofrutilebearing rocks and the geologic history of theirtransformation.In the Shueretskoe deposit, rutile inclusions wereseparated from a garnet megacryst (sample 6). The ageof the metasomatic crystallization of this garnet wasdetermined as 1837 ± 14 Ma by the in situ SHRIMP IIdating of coexisting zircon and monazite inclusions atthe Center of Isotopic Investigations, Karpinskii AllRussia Geological Institute [7]. The deposit is locatedin the central part of the BMB, at the mouth of theShuya River and hosted by the metamorphic rocks ofthe Belomorian complex. Economically important aremetasomatic garnet gedritite and glimmerite in garnetbearing gneisses and amphibolites. Garnet occurs inthe metasomatic rocks as irregular nodules or, morerarely, faced crystals up to 25 cm across. The metasomatism that resulted in the formation of the garnetdeposit occurred under peak metamorphic conditions at a temperature of 650–680°C and a pressureof 7.8–8.5 kbar [7].The Salma eclogites were investigated in the pit ofthe KuruVaara deposit, where tonalite–trondhjemitegneisses with bodies and blocks of eclogites and eclogitelike

Zircon ages, mineral chemistry, whole-rock major and trace element compositions, as well as Sr–Nd isotopic ratios of basaltic (basanite, basalt, and hawaiite with MgO = 3.90–10.06 and SiO2 = 43.18–48.16) to andesitic (SiO2 = 50.86–61.27) and rhyolitic (SiO2 = 71.11–71.13) volcanic rocks (E-W emplaced Nall?han volcanics) in the Lower Eocene terrestrial sedimentary units in the Central Sakarya Zone were studied and compared with those of the northerly located E-W-trending Eocene volcanic rocks (the K?zderbent Volcanics with 52.7–38.1 Ma radiometric ages) that are thought to be related to slab break-off process following the continental collision in the NW Anatolia. Zircon U–Pb ages of the Nall?han volcanics vary from 51.7 ± 4.7 to 47.8 ± 2.4 Ma. Clinopyroxene from the basaltic and andesitic rocks record crystallization conditions from ~ 7–8 kbars (~ 23 km) and ~ 1210 °C, to 4.5–1.5 kbars (~ 14–1.5 km) and 1110–1010 °C crystallization conditions, respectively. The olivine-bearing, high-MgO (up to 10 wt%) basaltic rocks of the Nall?han volcanics have nepheline-normative and Na-alkaline compositions, while the andesitic to rhyolitic rocks show calc-alkaline affinity with mainly sodic character. This is the first time this type of volcanic rock has been described in this region. The initial Sr isotopic ratios of both basaltic and andesitic–rhyolitic samples from the Nall?han volcanics are similar (~ 0.7040–0.7045), indicating that fractional crystallization processes were not accompanied by crustal contamination and that the magma chambers were likely stored within ophiolitic units. Trace element ratios suggest that the Nall?han volcanics were derived from E-MORB- or OIB-like enriched mantle sources, while the K?zderbent volcanics had N-MORB-like depleted mantle sources. Both volcanic units were produced by partial melting of spinel-bearing (shallow) mantle sources that had undergone subduction-related enrichment processes, with the degree of enrichment having been greater for the K?zderbent volcanics. The geochemical features of both the Nall?han and K?zderbent volcanics are best explained as the result of slab break-off, in which the Nall?han volcanics (located closer to the original subduction front) were produced mainly by the melting of upwelling asthenospheric mantle. Further back from the subduction front, the upwelling interacted with more highly metasomatized sub-arc mantle that underwent partial melting to produce the K?zderbent volcanics. This geodynamic scenario can be used for understanding other post-collisional slab break-off-related magmatic activities.

Empirical and experimental calibration of single element solubility thermometers, such as Zr-in-rutile, Zr-in-titanite, Ti-in-zircon, and Ti-in-quartz, within the past 13 years has greatly expanded our ability to assess the pressure and temperature conditions of individual minerals associated with specific textures in metamorphic rocks. Combined with advances in in situ techniques for analyzing trace concentrations, this has led to an increase in the combined use of single element thermometers, geochronometers, and isotope ratios, often simultaneously, in metamorphic minerals. Here we review the calibration and application of single element thermometers at the pressure and temperature conditions of interest in metamorphic rocks. We discuss to what extent accessory phase equilibrium and trace element equilibrium are attained in metamorphic systems, and the thermodynamic and kinetic framework within which trace element equilibrium is assessed. As an example, we present a comprehensive study of trace element distribution during rutile replacement by titanite in rocks that experienced high-temperature amphibolite-facies overprinting and those that underwent low-temperature blueschist-facies overprinting from a variety of subduction-related terranes worldwide. We find that trace element distributions approach equilibrium partition coefficients in rocks from amphibolite-facies overprinted terranes, whereas trace element distributions do not approach equilibrium in rocks that experienced blueschist-facies overprinting. We caution that single element thermometers that rely upon slow-diffusing high field strength elements should not be applied to rocks equilibrated at

Cathodic prevention (CPre) technique is a promising method and has been used for the past two decades to prevent steel from corrosion in concrete structures. However, wide application of this technique has been restricted due to high costs of anode materials. In order to lower the cost and further improve this technique, carbon fiber composite anode has been introduced as an alternative anode material with affordable price and other outstanding properties. This paper presents the study of using carbon fiber mesh as anode material for long-term cathodic prevention system and the effect of accelerated current on macro- and microstructure of cementitious materials. In the study, electrochemically accelerated tests were developed for the purpose of shortening the experimental time into a manageable range. An estimation tool was used to predict the service life as well. Chemical and microstructure analyses were carried out by laser-ablation inductively-coupled-plasma mass-spectroscopy (LA-ICP-MS) and scanning electron microscope (SEM). Results indicate that calcium to silicon (Ca/Si) ratio and ion re-distribution in the current-affected zone around the anode were changed due to migration and electrochemical reactions. The predicted service life was in general longer than 100 years. Based on the results from this work, it can be concluded that carbon fiber mesh is suitable for the application as anode in long-term cathodic prevention system in cementitious materials.

We present a secondary ionization mass spectrometry (SIMS) technique for U–Pb geochronology of rutile at high spatial resolution and sensitivity using an O2+ primary ion beam coupled with surficial O2 gas deposition (O2 flooding). The O2+ beam is ~ 10 × more intense than conventionally applied O− or O2− beams at the same lateral resolution. Natural and synthetic rutile was determined to be conductive under O2+ bombardment, permitting higher excavation (sputter) rates than conventional SIMS using negatively charged O-beams without detrimental effects of sample charging. The main advantage of O2+ is rapid sputtering at shallow primary ion penetration depths. This minimizes the contribution of surface-derived common Pb, and generates a high secondary ion flux at high sensitivity with useful yields (UY = detected ions/atoms removed from target) for Pb in rutile of ~ 4 and 3% for O− and O2+, respectively. In addition, O2 flooding reduces spread in the Pb+/U+ vs. UO2+/U+ calibration by mitigating crystal orientation dependent variability of sputter yields. Calibrated against primary rutile standard R10b (1090 Ma), O2+-generated SIMS U–Pb and Pb–Pb age averages are accurate within

The metamorphic evolution of rocks cropping out near Stoer, within the Assynt terrane of the central region of the mainland Lewisian complex of NW Scotland, is investigated using phase equilibria modelling in the NCKFMASHTO and MnNCKFMASHTO model systems. The focus is on the Cnoc an t’Sidhean suite, garnet-bearing biotite-rich rocks (brown gneiss) with rare layers of white mica gneiss, which have been interpreted as sedimentary in origin. The results show that these rocks are polymetamorphic and experienced granulite facies peak metamorphism (Badcallian) followed by retrograde fluid-driven metamorphism (Inverian) under amphibolite facies conditions. The brown gneisses are inferred to have contained an essentially anhydrous granulite facies peak metamorphic assemblage of garnet, quartz, plagioclase and ilmenite (±rutile, K-feldspar and pyroxene) with biotite, hornblende, muscovite, chlorite and/or epidote as hydrous retrograde minerals. P–T constraints imposed by phase equilibria modelling imply conditions of 13–16 kbar at >900 °C for the Badcallian granulite facies metamorphic peak, consistent with the field evidence for partial melting in most lithologies. The white mica gneiss comprises a muscovite-dominated matrix containing porphyroblasts of staurolite, corundum, kyanite and rare garnet. Previous studies have suggested that staurolite, corundum, kyanite and muscovite all grew at the granulite facies peak, with partial melting and melt loss producing a highly aluminous residue. However, at the inferred peak P–T conditions, staurolite and muscovite are not predicted to be stable, suggesting they are retrograde phases that grew during amphibolite facies retrograde metamorphism. The large proportion of mica suggests extensive H2O-rich fluid-influx, consistent with the retrograde growth of hornblende, biotite, epidote and chlorite in the brown gneisses. P–T conditions of 5.0–6.5 kbar at 520–550 °C are derived for the Inverian event. In situ dating of zircon from samples of the white mica gneiss yield apparent ages that are difficult to interpret. However, the data are permissive of granulite facies (Badcallian) metamorphism having occurred at c. 2.7–2.8 Ga with subsequent fluid driven (Inverian) retrogression at c. 2.5–2.6 Ga, consistent with previous interpretations.

Apatite is ubiquitous in a wide range of magmatic rocks and its F–Cl–Br–S systematics can be used to decipher e.g., mixing processes within a magmatic complex and may give insights into fluid un-mixing and degassing processes during the emplacement and cooling of plutonic rocks. In this study, we analyzed a F-apatite (Durango, Mexico), a Cl-apatite (Odegarden, Norway) and apatites from five plutonic samples from the alkaline Mt. Saint Hilaire Complex (Canada) by means of Electron Microprobe Analysis (EPMA), Laser Ablation ICP-MS (LA-ICP-MS), Secondary Ion Mass Spectrometry (SIMS), pyrohydrolysis combined with ion chromatography, Fourier Transformed Infrared Spectroscopy (FTIR), Instrumental Neutron Activation Analysis (INAA) and Total Reflection X-ray Fluorescence Analysis (TXRF). The special focus of our study is Br, since the analytical possibilities for this element are especially in the low- to sub-μg/g range restricted and thus, reliable concentration data for Br in rock-forming minerals are scarce. We demonstrate here that TXRF, which is barely used in geosciences so far, is suitable for analyzing the bulk content of Br and Cl as well as of a range of important trace metals (e.g., Sr, Ce, Fe, Mn, As) in apatite simultaneously. The TXRF method combines the advantages of low to very low detection limits (μg/g- to sub-μg/g range), small sample amounts needed (mg range) and a relatively fast and inexpensive analytical procedure. Depending on the As content of apatite, reliable concentration data for Br can be produced with detection limits as low as 0.2 μg/g. Using the Durango apatite as an internal reference material, SIMS analyses give consistent results with EPMA, INAA and TXRF and allow for detailed insights into the F–Cl–Br–S systematics of apatites. The presented data set reveals significant heterogeneities within and between different apatite grains from a single sample.

Magmatic zircons from the basal part of an arc terrane in the accretionary complex NE of the Baydrag microcontinental block in central Mongolia were dated at 544 ± 7 Ma and reflect arc magmatism at the Ediacaran/Cambrian boundary. Detrital zircon ages for clastic metasediments of the adjacent Dzag zone suggest a depositional age

We have investigated the trace elemental composition in the skeleta of two specimens of attached-living coralline algae of the species Clathromorphum compactum from the North Atlantic (Newfoundland) and Clathromorphum nereostratum from the North Pacific/Bering Sea region (Amchitka Island, Aleutians). Samples were analyzed using Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) yielding for the first time continuous individual trace elemental records of up to 69 years in length. The resulting algal Mg/Ca, Sr/Ca, U/Ca, and Ba/Ca ratios are reproducible within individual sample specimens. Algal Mg/Ca ratios were additionally validated by electron microprobe analyses (Amchitka sample). Algal Sr/ Ca, U/Ca, and Ba/Ca ratios were compared to algal Mg/Ca ratios, which previously have been shown to reliably record sea surface temperature (SST). Ratios of Sr/Ca from both Clathromorphum species show a strong positive correlation to temperature-dependent Mg/Ca ratios, implying that seawater temperature plays an important role in the incorporation of Sr into algal calcite. Linear Sr/Ca-SST regressions have provided positive, but weaker relationships as compared to Mg/Ca-SST relationships. Both, algal Mg/Ca and Sr/Ca display clear seasonal cycles. Inverse correlations were found between algal Mg/Ca and U/Ca, Ba/Ca, and correlations to SST are weaker than between Mg/Ca, Sr/Ca and SST. This suggests that the incorporation of U and Ba is influenced by other factors aside from temperature