| 1. |
- Marks, Michael A. W., et al.
(författare)
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The F, Cl, Br and I Contents of Reference Glasses BHVO-2G, BIR-1G, BCR-2G, GSD-1G, GSE-1G, NIST SRM 610 and NIST SRM 612
- 2017
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Ingår i: Geostandards and Geoanalytical Research. - : Wiley. - 1639-4488 .- 1751-908X. ; 41:1, s. 107-122
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Tidskriftsartikel (refereegranskat)abstract
- 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−1), Cl (~ 70–1220 μg g−1) and Br (~ 0.2–285 μg g−1) and I (~ 9–3560 ng g−1). The BIR-1G glass has low F (< 15 μg g−1), Cl (~ 20 μg g−1), Br (15 ng g−1) and I (3 ng g−1). 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.
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| 2. |
- Pabst, Sonja, et al.
(författare)
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Evidence for boron incorporation into the serpentine crystal structure
- 2011
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Ingår i: American Mineralogist. - 0003-004X. ; 96:7, s. 1112-1119
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Tidskriftsartikel (refereegranskat)abstract
- Serpentinite mud volcanoes from the Mariana forearc comprise B-rich mantle wedge peridotites serpentinized by slab fluids. The major component of these rocks are serpentine group minerals [Mg(3)Si(2)O(5)(OH)(4)], showing highly variable textural and geochemical features. Micro-Raman spectroscopy reveals that the serpentine minerals are well-crystallized lizardite and chrysotile. In situ SIMS spot analyses and element mapping via ToF-SIMS show that B is evenly distributed across serpentine grains, suggesting that serpentine, both lizardite and chrysotile in different textural regions, can host significant amounts of B (up to similar to 200 mu g/g) into its crystal structure. As such structurally bound B can only be released during recrystallization or serpentine breakdown, our results have implications for modeling of the efficiency of cross-arc fluid mobile element recycling in subduction zones and stress the importance of the hydrated forearc mantle as a reservoir for fluid mobile elements.
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| 3. |
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| 4. |
- Andersson, Stefan S., et al.
(författare)
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Mineral paragenesis and sulphide trace element distribution in the metamorphosed Lovisa Zn-Pb deposit, Bergslagen (Sweden), as revealed by 3D X-ray tomography, ore petrography and LA-ICP-MS analysis
- 2022
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Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368 .- 1872-7360. ; 140
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Tidskriftsartikel (refereegranskat)abstract
- This study encompasses the ore mineralogy, textures and sulphide trace element chemistry of the Palaeoproterozoic Lovisa stratiform Zn-Pb deposit and the stratigraphically underlying Lovisa Fe Formation in the Bergslagen ore province (Sweden). We investigate the relative timing of formation and subsequent modifications of its ores in relation to the c. 1.87-1.80 Ga Svecokarelian orogeny. The Lovisa Zn-Pb deposit consists of several different ore types. The massive sphalerite-galena ore is distinctly deformed, exhibiting a multiple-scale "ball ore" texture with rounded silicate clasts within a deformed, fine-grained sulphide matrix. Underlying the massive ore is a locally folded, sphalerite-rich laminated ore, interpreted to represent a metamorphosed relict primary lamination. Several generations of sphalerite-galena fracture fillings and veins occur adjacent to the main ore zones and they cross-cut early ductile structures and metamorphic features. The trace element signatures of the sphalerite-galena infillings generally mimic those of the two main ore zones, thus supporting an origin by localised remobilisation of the primary sulphide ore and demonstrating limited trace element redistribution during this process. In contrast, discrete sulphosalt-rich fracture fillings cross-cutting earlier galena-chalcopyriterich fracture fillings and veinlets in the Lovisa Fe Formation suggest a significant but still relatively localised redistribution of metals. Trace element mapping of sulphides from the Lovisa Zn-Pb deposit reveals that inclusion-free overgrowths on pyrite crystals are locally Co-enriched compared to the cores, which resulted from the redistribution of Co during late metamorphic processes. Combined textural and geochemical evidence suggest that the originally syngenetic exhalative sulphide ore at Lovisa was locally strongly affected by polyphase deformation and remobilisation. This was initiated during the first stage of amphibolite facies grade regional metamorphism and deformation (D1, c. 1.87-1.85 Ga) but is mostly evident from the later stages (D2) and the evolution to retrograde and brittle conditions (c. 1.83-1.80 Ga and later).
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| 5. |
- Babaahmadi, Arezou, 1985, et al.
(författare)
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Development of an electro-chemical accelerated ageing method for leaching of calcium from cementitious materials
- 2016
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Ingår i: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 49:1-2, s. 705-718
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Tidskriftsartikel (refereegranskat)abstract
- 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 Ø50 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.
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| 6. |
- Baldermann, A., et al.
(författare)
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Impact of green clay authigenesis on element sequestration in marine settings
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Retrograde clay mineral reactions (reverse weathering), including glauconite formation, are first-order controls on element sequestration in marine sediments. Here, we report substantial element sequestration by glauconite formation in shallow marine settings from the Triassic to the Holocene, averaging 3 +/- 2 mmol.cm(-2).kyr(-1) for K, Mg and Al, 16 +/- 9 mmol.cm(-2).kyr(-1) for Si and 6 +/- 3 mmol.cm(-2).kyr(-1) for Fe, which is similar to 2 orders of magnitude higher than estimates for deep-sea settings. Upscaling of glauconite abundances in shallow-water (0-200 m) environments predicts a present-day global uptake of similar to <= 0.1 Tmol.yr(-1) of K, Mg and Al, and similar to 0.1-0.4 Tmol.yr(-1) of Fe and Si, which is similar to half of the estimated Mesozoic elemental flux. Clay mineral authigenesis had a large impact on the global marine element cycles throughout Earth's history, in particular during 'greenhouse' periods with sea level highstand, and is key for better understanding past and present geochemical cycling in marine sediments.
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| 7. |
- Barnes, Christopher J., et al.
(författare)
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Dating metamorphic processes and identifying 87Sr/86Sr inheritance using volume-coupled Rb/Sr geochronology and geochemistry of in situ white mica: A demonstration with HP/LT rocks from Syros, Greece
- 2024
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Ingår i: CHEMICAL GEOLOGY. - 0009-2541 .- 1872-6836. ; 660
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Tidskriftsartikel (refereegranskat)abstract
- High-pressure/low-temperature rocks from two well -studied outcrops of the Cycladic Blueschist Unit on Syros are used to demonstrate the advantages of volume -coupled 87 Rb/ 87 Sr geochronology and geochemistry of in situ white mica. Single -spot Rb/Sr dates are interpreted based on the microstructural position of white mica combined with its chemical information, and the results are discussed within the tectonic framework of the island. The first outcrop on Katerghaki cape exposes rigid blocks of foliated eclogite within well -foliated blueschist, whereas the second outcrop on Delfini peninsula comprises massive eclogitic blocks, likely of metasomatic origin, hosted within blueschist that are interlayered with white mica schists. The rheological contrasts exhibited in both outcrops preserve (near -)peak HP/LT metamorphism/metasomatism (eclogites) followed by retrogression and deformation in lower P -T conditions (blueschist, micaschist). The white mica in eclogite from both outcrops are in equilibrium with the HP/LT mineral assemblages, do not show chemical zoning nor systematic chemical variations, and yield uniform single -spot Rb/Sr dates. Weighted averages of the Rb/Sr dates are 48.2 +/- 3.7 Ma (MSWD: 0.9, n: 34; Katerghaki) and 44.5 +/- 3.1 Ma (MSWD: 0.7, n: 28; Delfini), interpreted as (near -)peak HP/LT metamorphism and metasomatism, respectively, overlapping with published garnet Lu - Hf and Sm - Nd geochronology of the corresponding outcrops. White mica in the Katerghaki blueschist and the Delfini micaschist exhibit significant chemical zoning and correlations of Ti with major and trace elements (Al, Fe, Mg, Rb, Sr, Zn, Ba, Nb). Weighted age averages were calculated from Rb/Sr dates corresponding to high -Ti and low -Ti white mica compositions. The blueschist yields ages of 56.0 +/- 10.6 Ma (MSWD: 2.2, n: 20/80) and 36.3 +/- 2.1 Ma (MSWD: 0.9, n: 20/80), whereas the micaschist produced ages of 43.7 +/- 3.5 Ma (MSWD: 0.5, n: 14/53) and 31.9 +/- 2.7 Ma (MSWD: 1.0, n: 13/53), respectively. These results are interpreted to resolve the timing of fluidmediated isotopic re -equilibration of white mica during deformation and retrogression (low -Ti), and reflect 87 Sr/ 86 Sr inheritance from the earlier HP/LT history (high -Ti). Overall, the results demonstrate that coupling 87 Rb/ 87 Sr geochronology with geochemistry of white mica in situ is advantageous for evaluating Rb/Sr datasets that may possess a single mica population (eclogites) or are affected by 87 Sr/ 86 Sr inheritance (blueschist, micaschist) in order to interpret geologically meaningful ages.
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| 8. |
- Barros, R., et al.
(författare)
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LA-ICP-MS Rb-Sr dating of LCT rare-element pegmatites and associated rocks of Leinster, Ireland
- 2017
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Ingår i: 14th SGA Biennial Meeting on Mineral Resources to Discover. 993-996. - 9782981689801
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Konferensbidrag (refereegranskat)abstract
- High technology metals such as lithium and tantalum are commonly hosted in pegmatites, leading to renewed interest in understanding their origin. Obtaining accurate and precise results from pegmatites can be challenging. We have applied a newly developed laser ablation Rb-Sr dating method using reaction gases in a quadrupole ICP-MS to spodumene pegmatites and country rocks, late Caledonian granodiorite and Ordovician schist, in southeast Ireland. Rb-Sr isochron ages and initial Sr-87/Sr-86 ratios obtained are: around 413 Ma and 0.7109 +/- 49 to 0.8348 +/- 82 for lithium pegmatites; around 413 Ma and 0.7054 +/- 50 to 0.7102 +/- 28 for barren pegmatites; 420.6 +/- 8.4 Ma and 0.7068 +/- 28 for granodiorite; 406.5 +/- 5.8 and 0.7160 +/- 58 for schist. The method is sufficiently accurate and precise to date pegmatites. Ages obtained are consistent with the emplacement age of the Leinster Granite. Age constraints from schist within a pegmatite exomorphic halo are shown to be a good tool to determine pegmatite age. Highly variable initial Sr-87/Sr-86 ratios in spodumene pegmatites emplaced near schists show evidence for country rock contamination.
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| 9. |
- Cabral, A. R., et al.
(författare)
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Distinguishing high-from low-temperature platinum nuggets through their trace-element pattern
- 2019
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Ingår i: Economic Geology and The Bulletin of the Society of Economic Geologists. - : Society of Economic Geologists. - 0361-0128. ; 114:2, s. 201-206
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Tidskriftsartikel (refereegranskat)abstract
- High- and lowerature platinum nuggets from two historical localities, Chocó in Colombia and Córrego Bom Sucesso in Brazil, are compared with respect to trace elements. Supergene platinum nuggets from Córrego Bom Sucesso are enriched in Se and Hg, but depleted in siderophile and chalcophile elements, and have fractionated platinum group element patterns, in comparison with magmatic platinum nuggets from Chocó. In particular, Se concentrations over ∼100 g/g Se and S/Se ratios above unity indicate Se recycling in a supergene environment with abundant organic matter. © 2019 Society of Economic Geologists; Economic Geology.
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| 10. |
- Cabral, A. R., et al.
(författare)
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Fluid-inclusion microthermometry and the Zr-in-rutile thermometer for hydrothermal rutile
- 2015
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Ingår i: International Journal of Earth Sciences. - : Springer Science and Business Media LLC. - 1437-3254 .- 1437-3262. ; 104:2, s. 513-519
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Tidskriftsartikel (refereegranskat)abstract
- 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 Espinha double dagger o, 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 similar to 250 A degrees C, which were likely trapped at about 300 A degrees C and 2.0 kbar. This temperature is approximately 200 A degrees 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.
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