Seasonality is encoded in palaeoproxies of secondary cave mineral deposits (speleothems) and the ... more Seasonality is encoded in palaeoproxies of secondary cave mineral deposits (speleothems) and the code is becoming cracked. The petrology of calcite stalagmites from Obir, an Alpine (1100 m altitude), perennially wet cave, was characterized by optical and electron backscatter diffraction, and their chemistry by bulk ICP-MS analysis, ion microprobe and synchrotronbased micro-X-ray fluorescence. Vadose water penetrates 70 m through Triassic limestones (with some Pb-Zn mineralization) to the chamber Säulenhalle where the stalagmites were collected. Strong seasonal ventilation in the cave leads to low PCO 2 in winter associated with falls in speleothem sulphate S and increase in d 13 C values. All samples display autumnal event lamination defined by a narrow, optically visible zone with increases in trace element concentrations, within which synchrotron studies have resolved mm-scale enrichments of Pb and Zn. Small-scale (10 mm) lateral trace element variations reflect alternate flat faces and rough crystal edges, influenced by high Zn content. The elemental covariations are consistent with the transport of Pb, Zn, P, F, Br and I adsorbed onto organic colloids in dripwater, but the final deposition may have been from aerosols and we propose this as a new mechanism requiring further investigation. This study represents the most complete demonstration of how chemical variations are powerful expressions of seasonal cave physiology in humid temperate caves, including the contrast between summer and winter conditions, and the preservation of sub-weekly events during the autumn season.
Author(s) of this paper may load this reprint on their own web site or institutional repository p... more Author(s) of this paper may load this reprint on their own web site or institutional repository provided that this cover page is retained. Republication of this article or its storage in electronic databases other than as specified above is not permitted without prior permission in writing from the IUCr.
Recently, several techniques based on synchrotron radiation have been applied to environmental sc... more Recently, several techniques based on synchrotron radiation have been applied to environmental sciences giving the possibility for non-destructive investigations with micrometer spatial resolution. In particular, a combination of synchrotron methods (µ-XRF, µ-XRD, and µ-XAS) have been undertaken to investigate the metals speciation in mine wastes and soils.
Synchrotron radiation X-ray fluorescence (SR-XRF) was used to characterize As speciation within n... more Synchrotron radiation X-ray fluorescence (SR-XRF) was used to characterize As speciation within natural fluid inclusions from three deposits with different hydrogeochemical and geological settings. The studied samples represent different compositions of Au-bearing fluids: typical orogenic Au deposit (low-salinity, ~6 mol% CO 2 ± CH 4 ; Brusson, Western Italian Alps); brines from a Proterozoic (Fe)-Cu-Au deposit (Starra, Queensland, Australia); and an As-rich magmatic fluid with a bulk composition similar to that typical of orogenic gold (Muiane pegmatite, Mozambique). Arsenic K-edge X-ray absorption spectra (XAS) were obtained from fluid inclusions at temperatures ranging from 25 to 200 °C, and compared with spectra of aqueous As(III) and As(V) solutions and minerals. X-ray absorption near edge structure (XANES) data show that initially the fluid inclusions from all three regions contain some As in reduced form [As(III) at Brusson and Muiane; As-sulfide or possibly As(0) at Starra]. However, this reduced As is readily oxidized under the beam to As(V). Therefore, extended X-ray absorption fine structure (EXAFS) spectra for the As(III) aqueous complex could be collected only on the sample from the Muiane pegmatite containing large fluid inclusions with high As concentrations (>>1000 ppm). Analysis of these EXAFS data shows that As(OH) 3(aq) (coordination number of 3.0 ± 0.2 atoms, bond length of 1.76 ± 0.01 Å) is the dominant arsenic aqueous species in the Muiane fluid inclusions at 100 °C, in accordance with predictions based on studies conducted using autoclaves. The As(V) complex resulting from photooxidation in the Muiane inclusions was characterized at 200 °C; the As-O bond distance (1.711 ± 0.025 Å) corresponds to that found in the arsenate group in minerals, and to that measured for the (HAsO 4 ) 2complex at room temperature (1.700 ± 0.023 Å).
Barium, lanthanum, ytterbium, and yttrium partitioning experiments between fluid-saturated haplog... more Barium, lanthanum, ytterbium, and yttrium partitioning experiments between fluid-saturated haplogranitic melts and aqueous solutions were conducted at 750 to 950°C and 0.2 to 1 GPa to investigate the effects of melt and fluid composition, pressure, and temperature. Partition coefficients were determined using different experimental methods. On one hand quenched experiments were performed, and on the other hand, trace element contents in the aqueous fluid were determined directly using a hydrothermal diamondanvil cell and synchrotron radiation X-ray fluorescence microanalysis of K-lines. The latter required a high excitation energy of 50 keV due to the high energies necessary to excite the K-lines of the studied elements. The data from these two techniques showed good agreement for chloridic solutions, whereas quenching had a significant effect on results of the experiments with only water in the case of Ba. In Cl-free experiments, lanthanum and yttrium, trace element contents were even below detection limit in the quenched fluids, whereas small concentrations were detected in comparable in-situ experiments. This distinct difference is likely due to back reactions between fluid and melt upon cooling. The partitioning data of all elements show no dependence on the temperature and only small dependence on pressure. In contrast, the partitioning is strongly influenced by the composition of the starting fluid and melt. For chloridic fluids, there was a sharp increase in the Ba, La, Y and Yb partition coefficients with the alumina saturation index (ASI). The Ba partition coefficient increased from 0.002 at an ASI of 0.8 to 0.55 at an ASI of 1.07. At higher ASI, it decreased slightly to 0.2 at an ASI of ∼ 1.3. Likewise, it was one to two orders of magnitude higher in chloridic fluids compared to those found in H 2 O experiments. Fluid-melt partition coefficients of La and Y increased from 0.002 at an ASI of ∼ 0.8 to ∼ 0.1 at an ASI of 1.2. In the same ASI range, the Yb partition coefficient increased to a maximum value of 0.02. Even at high salinities all elements fractionate into the melt. The compositional dependence of the partitioning data imply that both melt composition and fluid composition have a strong influence on trace element behavior and that complexation of Ba, REE and Y tin the fluid is not only controlled by the presence of Cl − in the fluid. Instead, interaction of these elements with major melt components dissolved in the fluid is very likely.
Keywords: rutile solubility high-field-strength elements ti mobility fluid flow Rutile is an impo... more Keywords: rutile solubility high-field-strength elements ti mobility fluid flow Rutile is an important mineral host for high-field strength elements, so its solubility in geologic fluids at high pressure and temperature plays an important role in the crustal and mantle processes that control the terrestrial cycling of these elements. However, experimental measurements of rutile solubility are in conflict by a factor of more than 100 at most studied conditions. We performed new measurements of rutile solubility in H 2 O-albite and H 2 O-Na 2 Si 3 O 7 (NS3) fluids by in-situ synchrotron radiation X-ray fluorescence spectroscopy using modified Bassett-type hydrothermal diamond-anvil cells. Minimum detection limits were 1.9 and 2.3 ppm Ti by weight for the two cells. Three albite-H 2 O experiments at starting bulk compositions of 2.7, 6.7 and 10.3 wt.% albite involved spectral acquisition at rutile saturation in the presence of albite crystals, melt, or a single homogeneous fluid phase; after accounting for the additional phases, corrected fluid compositions were 0.6 to 7.5 wt.% dissolved silicate over the run conditions. At ≤2.7 wt.% albite, rutile dissolution rate was slow and steady state was not achieved at 600-800°C; however, at higher dissolved albite contents, constant solubility with time was observed. Rutile solubilities in the presence of a single fluid phase at 700°C, 0.79 GPa, 5.4 wt.% albite, and at 800°C, 1.10 GPa, 6.7 wt.% albite, were 37 ± 2 and 156 ± 6 ppm, respectively. These data agree with results acquired using hydrothermal piston-cylinder methods with long run times and suppression of new crystal growth, but not with data derived from visual observation in hydrothermal diamond-anvil cells. This discrepancy is likely due to lack of equilibrium in the latter approach. Two experiments in 10 and 30 wt.% NS3 at 660-800°C, 0.5 ± 0.1 GPa, show extreme concentration-dependent enhancement of rutile solubility to ∼ 4500 ppm. The data indicate a strong positive correlation between rutile solubility and Na/Al. Because (Na + K)/Al is likely to be greater than unity in aqueous fluids at high pressure and temperature due to incongruent dissolution of albite and micas, the increase in rutile solubility along the albite-NS3 join points to the possibility of significant Ti transport by silicate-bearing aqueous fluids in the lower crust and upper mantle.
available online at Abstract-A new olivine-pigeonite ureilite containing abundant diamonds and gr... more available online at Abstract-A new olivine-pigeonite ureilite containing abundant diamonds and graphite was found in the United Arab Emirates. This is the first report of a meteorite in this country. The sample is heavily altered, of medium shock level, and has a total weight of 155 g. Bulk rock, olivine ) and pyroxene (En 73.9-75.2 , Fs 15.5-16.9 , Wo 8.8-9.5 ) compositions are typical of ureilites. Olivine rims are reduced with Fo increasing up to Fo 96.1-96.8 . Metal in these rims is completely altered to Fehydroxide during terrestrial weathering. We studied diamond and graphite using micro-Raman and in situ synchrotron X-ray diffraction. The main diamond Raman band (LO=TO mode at ~1332 cm −1 ) is broadened when compared to well-ordered diamond single crystals. Full widths at half maximum (FWHM) values scatter around 7 cm −1 . These values resemble FWHM values obtained from chemical vapor deposition (CVD) diamond. In situ XRD measurements show that diamonds have large grain sizes, up to >5 µm. Some of the graphite measured is compressed graphite. We explore the possibilities of CVD versus impact shock origin of diamonds and conclude that a shock origin is much more plausible. The broadening of the Raman bands might be explained by prolonged shock pressure resulting in a transitional Raman signal between experimentally shock-produced and natural diamonds.
Synchrotron Radiation-induced X-Ray Fluorescence (SR-XRF) and X-ray Absorption Near Edge Structur... more Synchrotron Radiation-induced X-Ray Fluorescence (SR-XRF) and X-ray Absorption Near Edge Structure (XANES) experiments were performed on coexisting low density vapour and high density liquid inclusions from the Yankee Lode, Mole Granite, Australia. The chosen sample is a quartz crystal from a cassiterite-quartz-vein, showing a complex hydrothermal growth history characterized by successive pulses of fluid trapping from 600 to 200°C. The liquid and vapour inclusions analysed predated cassiterite precipitation and show a homogenisation temperature of about 450°C. In vapour inclusions, SR-XRF mapping showed that Cu is associated with S together with K, Mn, Fe, Zn and As, likely as a sulphide mineral. Elemental quantification deduced from XRF maps performed at room temperature on heterogeneous and on inclusions homogenised by heating indicate that Cu was concentrated in the low density vapour inclusions whereas Cl, K, Mn, Fe, Zn, Br and Rb were partitioned in the high density liquid phase. S and As show partition coefficients close to 1:1, with As displaying a stronger affinity for the liquid phase than S. Micro-XANES experiments at the Cu Kα edge show that Cl-ligand complexes dominate upon heating in both inclusion types up to 450°C. SR-XRF mapping during heating revealed that the vapour inclusion was not completely homogenised at 450°C. XANES analysis of the vapour inclusion showed that a new Cu-bearing phase formed above 450°C, which is not detectable in the liquid inclusion. To our knowledge, species detected in the XANES spectra acquired at 506°C do not correspond to any Cu-Cl complex published so far in the literature. We propose that a Cu 1+ complex of still unknown stoichimetry, including sulfur as a ligand and possibly Cl as well, could account for Cu complexation at high temperature. This observation supports the hypothesis that sulfur could play a central role for Cu-complexing in high temperature porphyry-type environments. Experimental data in the system Cu-S-Cl-CO 2 -H 2 O are needed to document fully this newly discovered Cu complex.
World class Cu resources are concentrated in porphyry and epithermal ore deposits. Their formatio... more World class Cu resources are concentrated in porphyry and epithermal ore deposits. Their formation remains partially understood, however, due to a lack of constraints on the partitioning properties of trace elements in general, and Cu in particular, between vapour and liquid phases evolved from boiling fluids at depth in the Earth's crust. Immiscible liquid and vapour fluid inclusions coexisting in a single quartz grain have been imaged in three dimensions by X-ray Fluorescence Computed Tomography (XFCT). Elemental spatial distributions confirm that Cu, and to a lesser extent As, partition into the vapour phase, whereas Mn, Fe, Zn, Br, Rb, Sr and Pb concentrate in the liquid inclusion. High resolution mapping of the vapour inclusions revealed that Cu is heterogeneously distributed at the scale of a single inclusion and is mostly concentrated as tiny daughter crystals.
Synchrotron hard X-ray microprobes have the capability to perform in situ measurements in high pr... more Synchrotron hard X-ray microprobes have the capability to perform in situ measurements in high pressure and temperature devices, including the versatile Diamond Anvil Cell. This represents a challenging analytical task with important repercussions on our understanding of fundamental processes in many fields. To illustrate these points, after developing quantification aspects inherent to X-ray microfluorescence and inherited from fluid inclusions analysis, two selected applications in experimental petrology and microbiology are presented
Fluid inclusions are studied using synchrotron radiation induced A-X-ray fluorescence (A-SR-XRF).... more Fluid inclusions are studied using synchrotron radiation induced A-X-ray fluorescence (A-SR-XRF). We analyse inclusions from the Brusson gold deposit, Italy. Several two-phase (liquid plus gas) inclusions of a single generation are used to compare a new standardless quantification procedure to previously published internal and external standardisation procedures. The three procedures are based on an infinite homogeneous plane layer and the calculations are performed with a non-iterative fundamental parameter method. Results show a good agreement between the average of the calculated concentrations obtained with the three procedures and the corresponding crush-leach analysis. Cl, K, Ca, Fe, Cu, Zn and As crush-leach concentrations are within error bars of the A-SR-XRF concentration estimates. Br crush-leach content is above A-SR-XRF estimates. Ti, Cr, Mn, Ni and Pb were detected with A-SR-XRF technique only. These elements show different concentrations from one inclusion to another, suggesting heterogeneous trapping of tiny, infra-microscopic solid phases. The good correspondence between the results obtained using the three calibration procedures show that accurate standardless quantitative analysis of individual fluid inclusions is achievable. Statistical error calculation of the three procedures shows that the standardless quantification method yields more accurate results than the internal or external standard procedures. Uncertainties on inclusion depths strongly affect calculated light element concentrations (Cl to Ca), whereas Mn and heavier elements concentration estimates are more sensitive to errors on fluid inclusion thickness. Uncertainties of F 1 Am or less on fluid inclusion thickness and depth yield statistical errors of~50% on Cl concentration estimates and lower than 20% on transition metals. This new standardless-A-SR-XRF based quantification procedure is more precise than the previously established ones and is efficiently applied to multielementary analysis (Cl to Pb) of diluted individual fluid inclusions. D
Microthermometry and Raman spectroscopy techniques are routinely use to constrain ore-fluids d 18... more Microthermometry and Raman spectroscopy techniques are routinely use to constrain ore-fluids d 18 O and molar proportions of anhydrous gas species (CO 2 , CH 4 , N 2 ). However, these methods remain imprecise concerning the ore-fluids composition and source. Synchrotron radiation X-ray fluorescence allows access to major and trace element concentrations (Cl, Br and K, Ca, Fe, Cu, Zn, As, Rb, Sr) of single fluid inclusion. In this paper, we present the results of the combination of these routine and newly developed techniques in order to document the fluids composition and source associated with a Mesoarchaean lode gold deposit (Warrawoona Syncline, Western Australia). Fluid inclusion analyses show that quartz veins preserved records of three fluid inclusion populations. Early fluids inclusions, related to quartz veins precipitation, are characterized by a moderate to high Br/Cl ratio relative to modern seawater, CO 2 ± CH 4 ± N 2 , low to moderate salinities and significant base metal (Fe, Cu, Zn) and metalloid (As) concentrations. Late fluid inclusions trapped in secondary aqueous fluid inclusions are divided into two populations with distinct compositions. The first population consists of moderately saline aqueous brines, with a Br/Cl ratio close to modern seawater and a low concentration of base metals and metalloids. The second population is a fluid of low to moderate salinity, with a low Br/Cl ratio relative to modern seawater and significant enrichment in Fe, Zn, Sr and Rb. These three fluid inclusion populations point to three contrasting sources: (1) a carbonic fluid of mixed metamorphic and magmatic origin associated with the gold-bearing quartz precipitation; (2) a secondary aqueous fluid with seawater affinity; and (3) a surface-derived secondary aqueous fluid modified through interaction with felsic lithologies, before being flushed into the syncline. Primary carbonic fluids present similar characteristics than those ascribed to Mesoarchaean lode gold deposits. This suggests similar mineralization processes for mid-and Mesoarchaean lode gold deposits despite contrasting fluid-rock interaction histories. However, in regard to the protracted history documented in the Warrawoona Syncline, we question the robustness of the epigenetic crustal continuum model, as ore-fluid characteristics equally support an epigenetic or a polyphased mineralization process.
The ID22 beamline is dedicated to hard X-ray microanalysis allowing the combination of fluorescen... more The ID22 beamline is dedicated to hard X-ray microanalysis allowing the combination of fluorescence, spectroscopy, diffraction and tomography techniques in a wide energy range from 6 to 70 keV. The recent installation of an in-vacuum undulator, a new sample stage and the adaptation of various focusing optics has contributed to a great improvement in the capabilities of the beamline, which is now accessed by a wide user community issued from medical, earth and environmental science, archaeology and material science. Many applications requiring low detection limits for localization/speciation of trace elements together with structural analysis have been developed at the beamline on the (sub)micrometer scale. The possibility of combining simultaneously different analytical probes offers the opportunity of a thorough study of a given sample or scientific problem. This paper presents a review of the recent developments of the beamline and a detailed description of its capabilities through examples from different fields of applications. A. Somogyi et al. Beamline ID22 at the ESRF 211 Figure 3
Fluid inclusions represent the only direct samples of ancient fluids in many crustal rocks; preci... more Fluid inclusions represent the only direct samples of ancient fluids in many crustal rocks; precise knowledge of their chemical composition provides crucial information to model paleofluid-rock interactions and hydrothermal transport processes. Owing to its nondestructive character, micrometer-scale spatial resolution, and high sensitivity, synchrotron radiation-induced µ-X-ray fluorescence has received great interest for the in situ multielement analysis of individual fluid inclusions. Major uncertainties associated with the quantitative analysis of single fluid inclusions arise from the inclusion depth and the volume of fluid sampled by the incident beam. While the depth can be extracted directly from the fluorescence spectrum, its volume remains a major source of uncertainty. The present study performed on natural and synthetic inclusions shows that the inclusion thickness can be accurately evaluated from transmission line scans. Experimental data matched numerical simulations based on an elliptical inclusion geometry. However, for one nonelliptical inclusion, the experimental data were confirmed using a computed absorption tomography reconstruction. Good agreement between the imaging and scanning techniques implies that the latter provides reliable fluid thickness values independent of the shape of the inclusion. Taking into consideration the incident angle, the incident beam energy, the inclusion fluid salinity, and the transmission measurement stability resulted in errors of 0.3-2 µm on calculated fluid inclusion thicknesses.
Seasonality is encoded in palaeoproxies of secondary cave mineral deposits (speleothems) and the ... more Seasonality is encoded in palaeoproxies of secondary cave mineral deposits (speleothems) and the code is becoming cracked. The petrology of calcite stalagmites from Obir, an Alpine (1100 m altitude), perennially wet cave, was characterized by optical and electron backscatter diffraction, and their chemistry by bulk ICP-MS analysis, ion microprobe and synchrotronbased micro-X-ray fluorescence. Vadose water penetrates 70 m through Triassic limestones (with some Pb-Zn mineralization) to the chamber Säulenhalle where the stalagmites were collected. Strong seasonal ventilation in the cave leads to low PCO 2 in winter associated with falls in speleothem sulphate S and increase in d 13 C values. All samples display autumnal event lamination defined by a narrow, optically visible zone with increases in trace element concentrations, within which synchrotron studies have resolved mm-scale enrichments of Pb and Zn. Small-scale (10 mm) lateral trace element variations reflect alternate flat faces and rough crystal edges, influenced by high Zn content. The elemental covariations are consistent with the transport of Pb, Zn, P, F, Br and I adsorbed onto organic colloids in dripwater, but the final deposition may have been from aerosols and we propose this as a new mechanism requiring further investigation. This study represents the most complete demonstration of how chemical variations are powerful expressions of seasonal cave physiology in humid temperate caves, including the contrast between summer and winter conditions, and the preservation of sub-weekly events during the autumn season.
Author(s) of this paper may load this reprint on their own web site or institutional repository p... more Author(s) of this paper may load this reprint on their own web site or institutional repository provided that this cover page is retained. Republication of this article or its storage in electronic databases other than as specified above is not permitted without prior permission in writing from the IUCr.
Recently, several techniques based on synchrotron radiation have been applied to environmental sc... more Recently, several techniques based on synchrotron radiation have been applied to environmental sciences giving the possibility for non-destructive investigations with micrometer spatial resolution. In particular, a combination of synchrotron methods (µ-XRF, µ-XRD, and µ-XAS) have been undertaken to investigate the metals speciation in mine wastes and soils.
Synchrotron radiation X-ray fluorescence (SR-XRF) was used to characterize As speciation within n... more Synchrotron radiation X-ray fluorescence (SR-XRF) was used to characterize As speciation within natural fluid inclusions from three deposits with different hydrogeochemical and geological settings. The studied samples represent different compositions of Au-bearing fluids: typical orogenic Au deposit (low-salinity, ~6 mol% CO 2 ± CH 4 ; Brusson, Western Italian Alps); brines from a Proterozoic (Fe)-Cu-Au deposit (Starra, Queensland, Australia); and an As-rich magmatic fluid with a bulk composition similar to that typical of orogenic gold (Muiane pegmatite, Mozambique). Arsenic K-edge X-ray absorption spectra (XAS) were obtained from fluid inclusions at temperatures ranging from 25 to 200 °C, and compared with spectra of aqueous As(III) and As(V) solutions and minerals. X-ray absorption near edge structure (XANES) data show that initially the fluid inclusions from all three regions contain some As in reduced form [As(III) at Brusson and Muiane; As-sulfide or possibly As(0) at Starra]. However, this reduced As is readily oxidized under the beam to As(V). Therefore, extended X-ray absorption fine structure (EXAFS) spectra for the As(III) aqueous complex could be collected only on the sample from the Muiane pegmatite containing large fluid inclusions with high As concentrations (>>1000 ppm). Analysis of these EXAFS data shows that As(OH) 3(aq) (coordination number of 3.0 ± 0.2 atoms, bond length of 1.76 ± 0.01 Å) is the dominant arsenic aqueous species in the Muiane fluid inclusions at 100 °C, in accordance with predictions based on studies conducted using autoclaves. The As(V) complex resulting from photooxidation in the Muiane inclusions was characterized at 200 °C; the As-O bond distance (1.711 ± 0.025 Å) corresponds to that found in the arsenate group in minerals, and to that measured for the (HAsO 4 ) 2complex at room temperature (1.700 ± 0.023 Å).
Barium, lanthanum, ytterbium, and yttrium partitioning experiments between fluid-saturated haplog... more Barium, lanthanum, ytterbium, and yttrium partitioning experiments between fluid-saturated haplogranitic melts and aqueous solutions were conducted at 750 to 950°C and 0.2 to 1 GPa to investigate the effects of melt and fluid composition, pressure, and temperature. Partition coefficients were determined using different experimental methods. On one hand quenched experiments were performed, and on the other hand, trace element contents in the aqueous fluid were determined directly using a hydrothermal diamondanvil cell and synchrotron radiation X-ray fluorescence microanalysis of K-lines. The latter required a high excitation energy of 50 keV due to the high energies necessary to excite the K-lines of the studied elements. The data from these two techniques showed good agreement for chloridic solutions, whereas quenching had a significant effect on results of the experiments with only water in the case of Ba. In Cl-free experiments, lanthanum and yttrium, trace element contents were even below detection limit in the quenched fluids, whereas small concentrations were detected in comparable in-situ experiments. This distinct difference is likely due to back reactions between fluid and melt upon cooling. The partitioning data of all elements show no dependence on the temperature and only small dependence on pressure. In contrast, the partitioning is strongly influenced by the composition of the starting fluid and melt. For chloridic fluids, there was a sharp increase in the Ba, La, Y and Yb partition coefficients with the alumina saturation index (ASI). The Ba partition coefficient increased from 0.002 at an ASI of 0.8 to 0.55 at an ASI of 1.07. At higher ASI, it decreased slightly to 0.2 at an ASI of ∼ 1.3. Likewise, it was one to two orders of magnitude higher in chloridic fluids compared to those found in H 2 O experiments. Fluid-melt partition coefficients of La and Y increased from 0.002 at an ASI of ∼ 0.8 to ∼ 0.1 at an ASI of 1.2. In the same ASI range, the Yb partition coefficient increased to a maximum value of 0.02. Even at high salinities all elements fractionate into the melt. The compositional dependence of the partitioning data imply that both melt composition and fluid composition have a strong influence on trace element behavior and that complexation of Ba, REE and Y tin the fluid is not only controlled by the presence of Cl − in the fluid. Instead, interaction of these elements with major melt components dissolved in the fluid is very likely.
Keywords: rutile solubility high-field-strength elements ti mobility fluid flow Rutile is an impo... more Keywords: rutile solubility high-field-strength elements ti mobility fluid flow Rutile is an important mineral host for high-field strength elements, so its solubility in geologic fluids at high pressure and temperature plays an important role in the crustal and mantle processes that control the terrestrial cycling of these elements. However, experimental measurements of rutile solubility are in conflict by a factor of more than 100 at most studied conditions. We performed new measurements of rutile solubility in H 2 O-albite and H 2 O-Na 2 Si 3 O 7 (NS3) fluids by in-situ synchrotron radiation X-ray fluorescence spectroscopy using modified Bassett-type hydrothermal diamond-anvil cells. Minimum detection limits were 1.9 and 2.3 ppm Ti by weight for the two cells. Three albite-H 2 O experiments at starting bulk compositions of 2.7, 6.7 and 10.3 wt.% albite involved spectral acquisition at rutile saturation in the presence of albite crystals, melt, or a single homogeneous fluid phase; after accounting for the additional phases, corrected fluid compositions were 0.6 to 7.5 wt.% dissolved silicate over the run conditions. At ≤2.7 wt.% albite, rutile dissolution rate was slow and steady state was not achieved at 600-800°C; however, at higher dissolved albite contents, constant solubility with time was observed. Rutile solubilities in the presence of a single fluid phase at 700°C, 0.79 GPa, 5.4 wt.% albite, and at 800°C, 1.10 GPa, 6.7 wt.% albite, were 37 ± 2 and 156 ± 6 ppm, respectively. These data agree with results acquired using hydrothermal piston-cylinder methods with long run times and suppression of new crystal growth, but not with data derived from visual observation in hydrothermal diamond-anvil cells. This discrepancy is likely due to lack of equilibrium in the latter approach. Two experiments in 10 and 30 wt.% NS3 at 660-800°C, 0.5 ± 0.1 GPa, show extreme concentration-dependent enhancement of rutile solubility to ∼ 4500 ppm. The data indicate a strong positive correlation between rutile solubility and Na/Al. Because (Na + K)/Al is likely to be greater than unity in aqueous fluids at high pressure and temperature due to incongruent dissolution of albite and micas, the increase in rutile solubility along the albite-NS3 join points to the possibility of significant Ti transport by silicate-bearing aqueous fluids in the lower crust and upper mantle.
available online at Abstract-A new olivine-pigeonite ureilite containing abundant diamonds and gr... more available online at Abstract-A new olivine-pigeonite ureilite containing abundant diamonds and graphite was found in the United Arab Emirates. This is the first report of a meteorite in this country. The sample is heavily altered, of medium shock level, and has a total weight of 155 g. Bulk rock, olivine ) and pyroxene (En 73.9-75.2 , Fs 15.5-16.9 , Wo 8.8-9.5 ) compositions are typical of ureilites. Olivine rims are reduced with Fo increasing up to Fo 96.1-96.8 . Metal in these rims is completely altered to Fehydroxide during terrestrial weathering. We studied diamond and graphite using micro-Raman and in situ synchrotron X-ray diffraction. The main diamond Raman band (LO=TO mode at ~1332 cm −1 ) is broadened when compared to well-ordered diamond single crystals. Full widths at half maximum (FWHM) values scatter around 7 cm −1 . These values resemble FWHM values obtained from chemical vapor deposition (CVD) diamond. In situ XRD measurements show that diamonds have large grain sizes, up to >5 µm. Some of the graphite measured is compressed graphite. We explore the possibilities of CVD versus impact shock origin of diamonds and conclude that a shock origin is much more plausible. The broadening of the Raman bands might be explained by prolonged shock pressure resulting in a transitional Raman signal between experimentally shock-produced and natural diamonds.
Synchrotron Radiation-induced X-Ray Fluorescence (SR-XRF) and X-ray Absorption Near Edge Structur... more Synchrotron Radiation-induced X-Ray Fluorescence (SR-XRF) and X-ray Absorption Near Edge Structure (XANES) experiments were performed on coexisting low density vapour and high density liquid inclusions from the Yankee Lode, Mole Granite, Australia. The chosen sample is a quartz crystal from a cassiterite-quartz-vein, showing a complex hydrothermal growth history characterized by successive pulses of fluid trapping from 600 to 200°C. The liquid and vapour inclusions analysed predated cassiterite precipitation and show a homogenisation temperature of about 450°C. In vapour inclusions, SR-XRF mapping showed that Cu is associated with S together with K, Mn, Fe, Zn and As, likely as a sulphide mineral. Elemental quantification deduced from XRF maps performed at room temperature on heterogeneous and on inclusions homogenised by heating indicate that Cu was concentrated in the low density vapour inclusions whereas Cl, K, Mn, Fe, Zn, Br and Rb were partitioned in the high density liquid phase. S and As show partition coefficients close to 1:1, with As displaying a stronger affinity for the liquid phase than S. Micro-XANES experiments at the Cu Kα edge show that Cl-ligand complexes dominate upon heating in both inclusion types up to 450°C. SR-XRF mapping during heating revealed that the vapour inclusion was not completely homogenised at 450°C. XANES analysis of the vapour inclusion showed that a new Cu-bearing phase formed above 450°C, which is not detectable in the liquid inclusion. To our knowledge, species detected in the XANES spectra acquired at 506°C do not correspond to any Cu-Cl complex published so far in the literature. We propose that a Cu 1+ complex of still unknown stoichimetry, including sulfur as a ligand and possibly Cl as well, could account for Cu complexation at high temperature. This observation supports the hypothesis that sulfur could play a central role for Cu-complexing in high temperature porphyry-type environments. Experimental data in the system Cu-S-Cl-CO 2 -H 2 O are needed to document fully this newly discovered Cu complex.
World class Cu resources are concentrated in porphyry and epithermal ore deposits. Their formatio... more World class Cu resources are concentrated in porphyry and epithermal ore deposits. Their formation remains partially understood, however, due to a lack of constraints on the partitioning properties of trace elements in general, and Cu in particular, between vapour and liquid phases evolved from boiling fluids at depth in the Earth's crust. Immiscible liquid and vapour fluid inclusions coexisting in a single quartz grain have been imaged in three dimensions by X-ray Fluorescence Computed Tomography (XFCT). Elemental spatial distributions confirm that Cu, and to a lesser extent As, partition into the vapour phase, whereas Mn, Fe, Zn, Br, Rb, Sr and Pb concentrate in the liquid inclusion. High resolution mapping of the vapour inclusions revealed that Cu is heterogeneously distributed at the scale of a single inclusion and is mostly concentrated as tiny daughter crystals.
Synchrotron hard X-ray microprobes have the capability to perform in situ measurements in high pr... more Synchrotron hard X-ray microprobes have the capability to perform in situ measurements in high pressure and temperature devices, including the versatile Diamond Anvil Cell. This represents a challenging analytical task with important repercussions on our understanding of fundamental processes in many fields. To illustrate these points, after developing quantification aspects inherent to X-ray microfluorescence and inherited from fluid inclusions analysis, two selected applications in experimental petrology and microbiology are presented
Fluid inclusions are studied using synchrotron radiation induced A-X-ray fluorescence (A-SR-XRF).... more Fluid inclusions are studied using synchrotron radiation induced A-X-ray fluorescence (A-SR-XRF). We analyse inclusions from the Brusson gold deposit, Italy. Several two-phase (liquid plus gas) inclusions of a single generation are used to compare a new standardless quantification procedure to previously published internal and external standardisation procedures. The three procedures are based on an infinite homogeneous plane layer and the calculations are performed with a non-iterative fundamental parameter method. Results show a good agreement between the average of the calculated concentrations obtained with the three procedures and the corresponding crush-leach analysis. Cl, K, Ca, Fe, Cu, Zn and As crush-leach concentrations are within error bars of the A-SR-XRF concentration estimates. Br crush-leach content is above A-SR-XRF estimates. Ti, Cr, Mn, Ni and Pb were detected with A-SR-XRF technique only. These elements show different concentrations from one inclusion to another, suggesting heterogeneous trapping of tiny, infra-microscopic solid phases. The good correspondence between the results obtained using the three calibration procedures show that accurate standardless quantitative analysis of individual fluid inclusions is achievable. Statistical error calculation of the three procedures shows that the standardless quantification method yields more accurate results than the internal or external standard procedures. Uncertainties on inclusion depths strongly affect calculated light element concentrations (Cl to Ca), whereas Mn and heavier elements concentration estimates are more sensitive to errors on fluid inclusion thickness. Uncertainties of F 1 Am or less on fluid inclusion thickness and depth yield statistical errors of~50% on Cl concentration estimates and lower than 20% on transition metals. This new standardless-A-SR-XRF based quantification procedure is more precise than the previously established ones and is efficiently applied to multielementary analysis (Cl to Pb) of diluted individual fluid inclusions. D
Microthermometry and Raman spectroscopy techniques are routinely use to constrain ore-fluids d 18... more Microthermometry and Raman spectroscopy techniques are routinely use to constrain ore-fluids d 18 O and molar proportions of anhydrous gas species (CO 2 , CH 4 , N 2 ). However, these methods remain imprecise concerning the ore-fluids composition and source. Synchrotron radiation X-ray fluorescence allows access to major and trace element concentrations (Cl, Br and K, Ca, Fe, Cu, Zn, As, Rb, Sr) of single fluid inclusion. In this paper, we present the results of the combination of these routine and newly developed techniques in order to document the fluids composition and source associated with a Mesoarchaean lode gold deposit (Warrawoona Syncline, Western Australia). Fluid inclusion analyses show that quartz veins preserved records of three fluid inclusion populations. Early fluids inclusions, related to quartz veins precipitation, are characterized by a moderate to high Br/Cl ratio relative to modern seawater, CO 2 ± CH 4 ± N 2 , low to moderate salinities and significant base metal (Fe, Cu, Zn) and metalloid (As) concentrations. Late fluid inclusions trapped in secondary aqueous fluid inclusions are divided into two populations with distinct compositions. The first population consists of moderately saline aqueous brines, with a Br/Cl ratio close to modern seawater and a low concentration of base metals and metalloids. The second population is a fluid of low to moderate salinity, with a low Br/Cl ratio relative to modern seawater and significant enrichment in Fe, Zn, Sr and Rb. These three fluid inclusion populations point to three contrasting sources: (1) a carbonic fluid of mixed metamorphic and magmatic origin associated with the gold-bearing quartz precipitation; (2) a secondary aqueous fluid with seawater affinity; and (3) a surface-derived secondary aqueous fluid modified through interaction with felsic lithologies, before being flushed into the syncline. Primary carbonic fluids present similar characteristics than those ascribed to Mesoarchaean lode gold deposits. This suggests similar mineralization processes for mid-and Mesoarchaean lode gold deposits despite contrasting fluid-rock interaction histories. However, in regard to the protracted history documented in the Warrawoona Syncline, we question the robustness of the epigenetic crustal continuum model, as ore-fluid characteristics equally support an epigenetic or a polyphased mineralization process.
The ID22 beamline is dedicated to hard X-ray microanalysis allowing the combination of fluorescen... more The ID22 beamline is dedicated to hard X-ray microanalysis allowing the combination of fluorescence, spectroscopy, diffraction and tomography techniques in a wide energy range from 6 to 70 keV. The recent installation of an in-vacuum undulator, a new sample stage and the adaptation of various focusing optics has contributed to a great improvement in the capabilities of the beamline, which is now accessed by a wide user community issued from medical, earth and environmental science, archaeology and material science. Many applications requiring low detection limits for localization/speciation of trace elements together with structural analysis have been developed at the beamline on the (sub)micrometer scale. The possibility of combining simultaneously different analytical probes offers the opportunity of a thorough study of a given sample or scientific problem. This paper presents a review of the recent developments of the beamline and a detailed description of its capabilities through examples from different fields of applications. A. Somogyi et al. Beamline ID22 at the ESRF 211 Figure 3
Fluid inclusions represent the only direct samples of ancient fluids in many crustal rocks; preci... more Fluid inclusions represent the only direct samples of ancient fluids in many crustal rocks; precise knowledge of their chemical composition provides crucial information to model paleofluid-rock interactions and hydrothermal transport processes. Owing to its nondestructive character, micrometer-scale spatial resolution, and high sensitivity, synchrotron radiation-induced µ-X-ray fluorescence has received great interest for the in situ multielement analysis of individual fluid inclusions. Major uncertainties associated with the quantitative analysis of single fluid inclusions arise from the inclusion depth and the volume of fluid sampled by the incident beam. While the depth can be extracted directly from the fluorescence spectrum, its volume remains a major source of uncertainty. The present study performed on natural and synthetic inclusions shows that the inclusion thickness can be accurately evaluated from transmission line scans. Experimental data matched numerical simulations based on an elliptical inclusion geometry. However, for one nonelliptical inclusion, the experimental data were confirmed using a computed absorption tomography reconstruction. Good agreement between the imaging and scanning techniques implies that the latter provides reliable fluid thickness values independent of the shape of the inclusion. Taking into consideration the incident angle, the incident beam energy, the inclusion fluid salinity, and the transmission measurement stability resulted in errors of 0.3-2 µm on calculated fluid inclusion thicknesses.
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Papers by Jean Cauzid