1982 Compilation of Elemental Concentrations in Eleven United States Geological Survey Rock Standards

Elemental composition data on eight older (AGV-1, BCR-1, DTS-1, G-1, G-2, GSP-1, PCC-1 and W-1) and three newer (BIR-1, DNC-1 and W-2) USGS rock standards have been collected from institutional reports and journal articles from 1972–1981. This collection was combined with data from previous compilations and "consensus values" for up to 79 elements determined by comparing overall means, medians, and individual means based on analytical techniques.     

Molybdenum Concentrations Measured in Eleven USGS Geochemical Reference Materials by Isotope Dilution Thermal Ionisation Mass Spectrometry

Molybdenum concentrations in eleven USGS geochemical reference materials AGV-1, BCR-1, BHVO-1, BIR-1, DNC-1, DTS-1, G-2, GSP-1, MAG-1, PCC-1 and W-2 were measured by isotope dilution thermal ionisation mass spectrometry (ID-TIMS). In every case but one, the concentrations determined in this study were significantly lower than the current consensus values. Molybdenum concentrations determined by ID-TIMS are inherently more accurate and precisions may be up to an order of magnitude higher than those measured by other analytical techniques.     

Germanium Contents of USGS Standard Rocks by Flameless Atomic Absorption

Germanium in 13 USGS standard silicate rooks was determined by flameless atomic absoprtion using a procedure which permits the determination of 0.2 ppm of germanium in as little as 50 mg of sample. The mean germanium content found is (in ppm Ge) for the new USGS standards: BHVO-1, 1.60; SDC, 1. 51; STM-1, 1. 32; QLO-1, 1. 28; RGM-1, 1. 24; and for- the older USGS standards: W-l, 1.S3; BCR-1, 1.39; G-l, 1.19; GSP-1, 1.16; AGV-1, 1.06; G-2, 0.96; PCC-1, 0.80; DTS-1, 0.72.     

Precise determination of uranium in rocks and minerals by neutron activation analysis using 133I fission product

A radiochemical neutron activation technique for uranium determination in rock and mineral samples is presented. The method is based on an alkaline fusion, a selective oxidation of iodine by a sodium-nitrite solution, followed by an iodine distillation technique for the isolation of the ¹³³I produced in fission. The outlined scheme is rapid, sensitive and reliable. Determination of uranium in U.S. Geological Survey standard rocks (G-1, W-1, G-2, BCR-1, AGV-1, GSP-1), C.R.P.G. Nancy geochemical standards (GA, GH, BR, Mica-Fe, Mica-Mg), C.A.A.S. reference syenite rocks (SY-1, SY-2, SY-3) and other analysed rock samples are reported. These results are compared with those obtained by other methods.     

Determination of Scandium, Yttrium and Rare Earth Elements in Rocks by High Resolution Inductively Coupled Plasma-Mass Spectrometry

The high sensitivity, minimal oxide formation and single internal standard capability of high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS) is demonstrated in the direct determination of Sc, Y and REE in the international reference materials: basalts (BCR-1, BHVO-1, BIR-1, DNC-1), andesite (AGV-1) andultramafics (UB-N, PCC-1 and DTS-1). Time consuming ion exchange separation or preconcentration were found to be unnecessary. Smooth chondrite normalized plots of the REE in PCC-1 and DTS-1 were obtained in the range 0.8-50 ng g-1 (0.01-0.1x chondrite). Method precision was found to be digestion dependent with an average external repeatability of 2-4% for the basalts, AGV-1 and UB-N, and 10% for PCC-1 and DTS-1. The mass peak due to ⁴⁵Sc was completely resolved from ²⁹Si¹⁶O and ²⁸Si¹⁶O¹H spectral interferences using medium resolution, which casts doubt on the accuracy of Sc determinations using quadrupole ICP-MS. Literature values for Y in rock reference materials were found to be approximately 9% high after HR-ICP-MS and XRF analysis.     

Suppression of Matrix Effects in ICP-MS by High Power Operation of ICP: Application to Precise Determination of Rb, Sr, Y, Cs, Ba, REE, Pb, Th and U at ng g-1 Levels in Milligram Silicate Samples

We found that the suppression of signals for ⁸⁸Sr, ¹⁴⁰Ce and ²³⁸U in rock solution caused by rock matrix in ICP-MS (matrix effects) was reduced at high power operation (1.7 kW) of the ICP. To make the signal suppression by the matrix negligible, minimum dilution factors (DF) of the rock solution for Sr, Ce and U were 600, 400 and 113 at 1.1, 1.4 and 1.7 kW, respectively. Based on these findings, a rapid and precise determination method for Rb, Sr, Y, Cs, Ba, REE, Pb, Th and U using FI (flow injection)-ICP-MS was developed. The amount of the sample solution required for FI-ICP-MS was 0.2 ml, so that 1.8 mg sample was sufficient for analysis with a detection limit of several ng g^-1. Using this method, we determined the trace element concentrations in the USGS rock reference materials, DTS-1, PCC-1, BCR-1 and AGV-1, and the GSJ rock reference materials, JP-1, JB-1, -2, -3, JA-1, -2 and -3. The reproducibilities (RSD %) in replicate analyses (n=5) of BCR-1, AGV-1, JB-1, -2, -3, JA-1, -2, and -3 were < 6 %, and typically 2.5%. The difference between the average concentrations of this study for BCR-1 and those of the reference values were < 2%. Therefore, it was concluded that the method can give reliable data for trace elements in silicate rocks.     

Determination of Rb/Sr and 87Sr86Sr ratios of some standard rocks and evaluation of X-ray fluorescence spectrometry in Rb1bSr geochemistry

New isotope dilution results are presented for Rb and Sr concentrations in U.S.G.S. standard rocks and NBS-70a K-feldspar. The results (based on at least five analyses of each rock), are generally accurate to ± 0.5% and resolve discrepancies in previously published data. X-ray fluorescence analyses of the same samples yield Rb and Sr determinations which are only accurate to ± 5%, but Rb/Sr ratios which are as precise and in excellent agreement with the isotope dilution values. It is concluded that X.R.F. determination of Rb/Sr ratios is perfectly suitable for whole-rock Rb1bSr geochronology.${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratios have been determined on G-2, GSP-1, BCR-1 and AGV-1 as well as the Eimer and Amend SrCO₃ standard.     

The selenium content of U.S.G.S. standard rocks

Selenium was determined in duplicate portions from three bottles of six U.S.G.S. standard rocks by a spect rofluorimetric procedure. The following averages, as p.p.m. Se, were obtained: PCC-1, 0.031; GSP-1, 0.088; BCR-1, 0.12; SCo-1, 0.91; MAG-1, 1.3; and SGR-1, 3.7. One-way analysis of variance of the several sets of data showed no significant differences in the selenium content among bottles of any specific rock; these samples may be accepted as homogeneous for their selenium contents by this analytical method.     

Neutron-Capture Prompt Gamma-Ray Multielement Analysis of Twenty-Two Geochemical Reference Standards

Twenty-two geochemical reference standards obtained from the U.S. Geological Survey (AGV-1, PCC-1, G-2, GSP-1, BHVO-1, MAG-1, QLO-1, RGM-1, SCo-1, SDC-1, SGR-1, STM-1, BIR-1, DNC-1, W-2, Nod A-1, Nod P-1), the National Bureau of Standards (SRM 278 Obsidian, SRM 688 Basalt), the International Atomic Energy Agency (Soil-5, SL-1 Lake Sediment), and Batelle Pacific Northwest Laboratories (COS-1 Oil Shale) have been analyzed for up to twenty-one major, minor, and trace elements from the group of H, B, C, N, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Cd, Nd, Sm and Gd. The technique used, in-beam neutron-capture prompt γ-ray activation analysis (PGAA), is described and the data are compared to those from other studies.     

Determination of the REE in Geological Reference Materials DTS-1 (Dunite) and PCC-1 (Peridotite) by Ultrasonic and Microconcentric Desolvating Nebulisation ICP-MS

Inductively coupled plasma-mass spectrometry is well suited for the precise, accurate and rapid determination of rare earth elements in most geological samples. However, determination of rare earth elements in certain mantle-derived materials, without applying preconcentration techniques, remains problematical due to low natural concentrations (generally < 1 ng g⁻¹). Consequently, USGS reference materials DTS-1 (a dunite) and PCC-1 (a partially serpentinized harzburgite) have only suggested rather than recommended values for the rare earth elements in reference material compilations. We compared results obtained using two ICP-MS instruments: a U-5000AT ultrasonic nebuliser coupled to a PQ2+ quadrupole ICP-MS and an ELEMENT sector field ICP-MS equipped with a MCN-6000 microconcentric desolvating nebuliser, with the suggested literature values for these two reference materials. Precision and accuracy of analytical methods employed by both instruments were demonstrated by excellent relative standard deviations (< 2%) and inter-laboratory agreement (< 5%) for numerous analyses of BHVO-1 and BIR-1, which are well established with rare earth elements contents at the μg g⁻¹ level. Repeat analyses of DTS-1 and PCC-1 at each laboratory indicate that each method is generally precise to better than 5% at sub-g g⁻¹ levels. Furthermore, values from both instruments generally agree to within 10%. Our DTS-1 and PCC-1 values agree reasonably well with selected data reported in the literature (except for Ce and Sm in DTS-1) but exhibit poorer agreement with reported compilation values. With the demonstrated level of precision and accuracy, we contend that these new values for DTS-1 and PCC-1, generated by two different instruments, are the best estimates of the true whole-rock composition of these samples reported to date.     

Determination of Molybdenum, Antimony and Tungsten at sub μg g−1 Levels in Geological Materials by ID-FI-ICP-MS

We have developed a rapid and accurate method for the determination of Mo, Sb and W in geological samples using isotope dilution inductively coupled plasma-mass spectrometry with a flow injection system (ID-FI-ICP-MS). The chemical procedure requires HF digestion of the sample with a Mo-Sb-W mixed spike, subsequent evaporation and dissolution of Mo, Sb and W from Mg and Ca fluorides with HF. Recovery yields of Mo, Sb and W in the extraction were > 94% for samples of peridotite, basalt and andesite composition, with the exception of W in samples of peridotite composition for which recovery was 81%. No matrix effects were observed in the determination of the isotope ratios of Mo, Sb and W in solutions prepared from peridotite, basalt and andesite samples down to a dilution factor of 100. Detection limits of Mo, Sb and W in silicate materials were at the several ng g⁻¹ level. Analysis of the silicate reference materials PCC-1, DTS-1, BCR-1, BHVO-1, AGV-1 from the US Geological Survey and JP-1, JB-1, -2, -3, JA-1, -2, and -3 from the Geological Survey of Japan as well as the Smithsonian reference Allende powder yielded reliable Mo, Sb and W concentrations. The repeatability in the analysis of basalts and andesites was < 9%. This technique requires only 0.2 ml sample solution, and is therefore suitable for analyzing small and/or precious samples such as meteorites, mantle peridotites and their mineral separates.     

Determination of Zirconium, Niobium, Hafnium and Tantalum at ng g-1 Levels in Geological Materials by Direct Nebulisation of Sample HF Solution into FI-ICP-MS

We have developed a rapid and accurate method to determine Zr, Nb, Hf and Ta (denoted as HFSE) in geological samples by inductively coupled plasma-mass spectrometry fitted with a flow injection system (FI-ICP-MS). The method involves sample decomposition by HF followed by HF dissolution of HFSE coprecipitated with insoluble M and Ca fluoride residues formed during the initial HF attack. This HF solution was directly nebulized into an ICP mass spectrometer. An external calibration curve method and an isotope dilution method (ID) were applied for the determination of Nb and Ta, and of Zr and Hf, respectively. Recovery yields of HFSE were > 96% for peridotite, basalt and andesite compositions, apart from Zr and Hf for peridotite (> 85%). No matrix effects for either signal intensities of HFSE or isotope ratios of Zr and Hf were observed in basalt, andesite and peridotite solutions down to a dilution factor of 100. Detection limits in silicate rocks were 40, 2, 1 and 0.1 ng g-1 for Zr, Nb, Hf and Ta, respectively. This technique required only 0.1 ml of sample solution, and thus is suitable for analysing small and/or precious samples such as meteorites, mantle peridotites and their mineral separates. We also present newly determined data for the Zr, Nb, Hf and Ta concentrations in USGS silicate reference materials DTS-1, PCC-1, BCR-1, BHVO-1 and AGV-1, GSJ reference materials JB-1, -2, -3, JA-1, -2 and -3, and the Smithsonian reference Allende powder.     

A re-assessment of nickel-doping method in iron isotope analysis on rock samples using multi-collector inductively coupled plasma mass spectrometry

Element doping has been proved to be a useful method to correct for the mass bias fractionation when analyzing iron isotope compositions. We present a systematic re-assessment on how the doped nickel may affect the iron isotope analysis in this study by carrying out several experiments. We find three important factors that can affect the analytical results, including the Ni:Fe ratio in the analyte solutions, the match of the Ni:Fe ratio between the unknown sample and standard solutions, and the match of the Fe concentration between the sample and standard solutions. Thus, caution is required when adding Ni to the analyte Fe solutions before analysis. Using our method, the δ⁵⁶Fe and δ⁵⁷Fe values of the USGS standards W-2a, BHVO-2, BCR-2, AGV-2 and GSP-2 are consistent with the recommended literature values, and the long-term (one year) external reproducibility is better than 0.03 and 0.05‰ (2SD) for δ⁵⁶Fe and δ⁵⁷Fe, respectively. Therefore, the analytical method established in our laboratory is a method of choice for high quantity Fe isotope data in geological materials.

     

Stable W Isotope Measurements of Geological Reference Materials and Tungsten Ore Minerals by Double Spike MC-ICP-MS

This study presents high-precision W isotopic measurement results using the ¹⁸⁰W-¹⁸³W double spike technique with MC-ICP-MS. The effects of isobaric and polyatomic interferences on W isotopic measurements were evaluated. The δ^186/184W values were not significantly affected when the solution had Hf/W ≤ 3 × 10^-4, Ta/W ≤ 1, Os/W ≤ 0.06, Ce/W ≤ 0.0075, Nd/W ≤ 3.5 and Sm/W ≤ 5. The intermediate measurement precisions of both standard solutions (NIST SRM 3163 and Alfa Aesar W) and geological reference materials (NOD-A-1) were better than ±0.024‰ (2s). We also obtained a precision of 0.026‰ for a minimum sample loading mass of 5 ng, allowing the analysis of samples with low W contents. Replicated measurements of geological reference materials (AGV-2, BCR-2, BHVO-2, GSP-2, RGM-1, SDC-1, NOD-A-1 and NOD-P-1) yielded δ^186/184W values ranging from 0.017‰ to 0.144‰. The δ^186/184W values of two major tungsten ore minerals (scheelite and wolframite) were reported and compared herein. Scheelites had systematically slightly heavier W isotopic compositions than wolframites, which may reflect differences in the crystal structure. The resolvable variations of stable/mass-dependent W isotopic compositions in rocks and ore minerals make W isotopes a novel tool for studying hydrothermal mineralisation processes and the W cycle of geological reservoirs.     

Röntgenuntersuchung der wasserfreien Sulfate der dreiwertigen Metalle Eisen,Chrom und Gallium

Zusammenfassung Wasserfreies Eisen(III)sulfat, Fe₂(SO₄)₃, existiert in zwei Modifikationen. Nach Einkristallaufnahmen kristallisiert die eine wahrscheinlich in Raumgruppe (a_rh=8,791±0,004 Å, =55°52±2; Z=2), die andere in Raumgruppe C _2h ⁵ –P2₁/n (a=8,296±0,002 Å, b=8,515±0,002 Å, c=11,60±0,002 Å, =90°30; Z=4). Von Cr₂(SO₄)₃ und Ga₂(SO₄)₃ konnten für die rhomboedrischen Modifikationen, die isotyp zu jener von Fe₂(SO₄)₃ sind, aus Pulveraufnahmen die Gitterkonstanten bestimmt werden.

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Summary Anhydrous iron(III)sulfate exists in two modifications. From single-crystal work, one of the modifications crystallizes probably in space group (a_rh=8.791±0.004 Å, =55°52±2; Z=2), whereas the other in space group C _2h ⁵ –P2₁/n (a=8.296±0.002 Å, b=8.515±0.002 Å, c=11.60±0,002 Å, =90°30; Z=4). The lattice constants of the rhombohedral modifications of Cr₂(SO₄)₃ and Ga₂(SO₄)₃, which are isomorphous with rhombohedral Fe₂(SO₄)₃, have been determined from powder photographs.

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Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet.     

Determination of Fluorine and Chlorine by Pyrohydrolysis and Ion Chromatography: Comparison with Alkaline Fusion Digestion and Ion Chromatography

A method to determine F and Cl in silicate materials by employing pyrohydrolysis and ion chromatography (IC) is described. Pyrohydrolysis involved mixing a pulverised sample (∼ 40 mg) with V₂O₅ (∼ 160 mg) and heating to 1100 °C under a wet oxygen flow in a quartz tube. Recovery yields of F and Cl were ∼ 97% using a NaF + NaCl standard solution. Detection limits of the pyrohydrolysis-IC method for silicate samples were 0.36 and 0.69 μg g^-1 for F and Cl, respectively. Fluorine and Cl concentrations were determined in the reference materials JB-2, JB-3 and JA-1 from the GSJ; BCR-2, BHVO-1, BHVO-2, AGV-1 and AGV-2 from the USGS; and NIST SRM 610, 612 and 614 glasses. Precisions (RSD) for determinations of F were 1–13% (except NIST SRM 614) and 2–19% for Cl, and were dependent on the concentration and blank correction. Most results obtained in this study were in good agreement with those of previous studies. In comparison, the Na₂CO₃ + ZnO fusion method at 900 °C showed that the yields of F and Cl by alkaline fusion systematically decreased with fusion duration time. The yields were 84% and 83% for JB-3, inferring that F and Cl were lost in this alkaline fusion.     

Admontit,ein neues Boratmineral aus der Gipslagerstätte Schildmauer bei Admont in der Steiermark (Österreich)

Zusammenfassung Admontit ist ein neues Magnesiumborat, das in der Gipslagerstätte Schildmauer bei Admont in der Steiermark (Österreich) in Vergesellschaftung mit drei weiteren neuen borhaltigen Mineralien sowie Gips, Anhydrit, Hexahydrit, Löweit, Quarz und Pyrit auftritt.Das Mineral bildet undeutlich ausgebildete farblose Kristalle von monokliner Symmetrie, die zum Teil nachc gestreckt und tafelig nach {100} sind. Keine Spaltbarkeit, Bruch muschelig, Härte wahrscheinlich 2–3,D _gem .=1,82,D _x =1,875g·cm^–3;n =1,442±0,002,n =1,504±0,002, 2V 30°,r. AE(010),n c auf (010) ca. 45°. a ₀=12,68,b ₀=10,07,c ₀=11,32 Å (alle Werte±0,02 Å),=109,68° (±0,1°),Z=2, RaumgruppeP2₁/c. Stärkste Linien des Pulverdiagramms: 12,08(9), 7,60(10), 3,93(8), 2,68(9). Formel: 2 MgO·6 B₂O₃·15 H₂O. In Wasser wird Admontit langsam zersetzt. Erhitzungsversuche zeigten, daß das Gitter zwischen 100 und 200°C zerstört wird. Ein Teil des Wassers entweicht schon unterhalb 100°C, der Rest zwischen 150 und 350°C.

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Admontite, a new borate mineral from the gypsum deposit Schildmauer near Admont in Styria (Austria)

Summary Admontite is a new magnesium borate found in the gypsum deposit of Schildmauer near Admont in Styria (Austria) in association with three other new borium-containing minerals and with gypsum, anhydrite, hexahydrite, löweite, quartz and pyrite.The mineral occurs in poorly developed colourless crystals of monoclinic symmetry, which in part are elongated along thec axis and flattened on {100}. No cleavage, fracture conchoidal, hardness probably 2–3,D _meas .=1.82,D _x =1.875g·cm^–3.n =1.442±0.002,n =1.504±0.002, 2V 30°,r. AE(010),n c on (010) about 45°.a ₀=12.68,b ₀=10.07,c ₀=11.32 Å (all±0.02 Å), =109.68° (±0.1°),Z=2,space groupP2₁/c. Strongest lines of the powder pattern: 12.08(9), 7.60(10), 3.93(8), 2.68(9). Chemical composition: 2 MgO·6 B₂O₃·15 H₂O. Admontite is slowly decomposed in water. Investigations of the thermal behaviour show that the lattice breaks down between 100 and 200°C. Part of the water escapes already under 100°C, the rest between 150 and 350°C.

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Mit 1 Abbildung

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Herrn Univ. Prof. Dr.H. Meixner zum 70. Geburtstag gewidmet.     

Transition from eclogite to amphibolite-facies metamorphism in the Austroalpine Ulten Zone

Summary The Ulten Zone of the Austroalpine crystalline basement south-west of Meran (Italy) contains metapelitic schists and granoblastic paragneisses, leucocratic orthogneisses, migmatites (in both gneiss-lithologies), metabasites and ultramafic lenses. Metamorphic textures of the metapelitic schists and granoblastic paragneisses indicate two different metamorphic events, characterized by two mineral assemblages, which differ in mineral chemistry: (1) an eclogite facies mineral assemblage (M1) comprising Grt-Ky I-Bt. Ms-Kfs-PI-Qtz-Rt, and (2) an amphibolite facies mineral assemblage (M2) comprising Grt-KyII-Bt-Ms-PI-Qtz-Ilm±St. For the M1 event, pressures of at least 15kbar and temperatures of about 700°±50°C can be estimated. The later amphibolite facies overprint occurred at pressures of 6 to 8kbar and about 600°±50°C. The M1 and M2 assemblages belong to a continuous clockwise metamorphic evolution during the Variscan orogeny. Evidence for Alpine metamorphism can only be detected by sericite rims around kyanite and reset biotite ages. The migmatites, which contribute about 15–30vol.% of all rocks in the investigated area, were formed on the prograde path during the M1 event. Dissolution of H₂O in the melted part of the migmatites resulted in a CO₂dominated fluid, which was trapped in primary kyanite (M1) fluid inclusions. Secondary H₂O-rich fluid inclusions are found in quartz grains and may represent the fluid which enabled a pervasive equilibration during M2.

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Übergang von eklogit-zu amphibolitfazieller Matamorphose in der austroalpinen Ultenzone

Zusammenfassung Die Ulten Zone, ein Teil des ostalpinen kristallinen basements, südwestlich von Meran, wird aus Metapeliten and granoblastischen Paragneisen, leukokraten Orthogneisen, Migmatiten (in beiden Lithologien), Metabasiten and ultramafischen Linsen aufgebaut. Metamorphe Texturen der Metapelite und granoblastischen Paragneise lassen auf zwei verschiedene metamorphe Ereignisse schließen, die durch unterschiedliche Mineral-chemismen und Paragenesen charakterisiert sind: (1) eine eklogitfazielle Paragenese (M1), bestehend aus Grt-KyI-Bt-Ms-Kfs-P1-Qtz-Rt und (2) eine amphibolitfazielle Paragenese (M2), bestehend aus Grt-KyII-Bt-Ms-P1-Qtz-Ilm±St. Für M1 konnten Minimaldrucke von 15kbar und Temperaturen von 700°±50°C abgeleitet werden. Die spätere amphibolitfazielle Überprägung fand bei 6 bis 8kbar und 600°±50°C statt. M1 und M2 gehören einer kontinuierlichen Metamorphoseentwicklung während der variszischen Orogenese an.Die Migmatite, ungefähr 15–30vol.% der Gesteine im untersuchten Gebiet, wurden am prograden Pfad während des M1 Ereignisses gebildet. Aufgrund der höheren Löslichkeit von H₂0 in der Schmelze, blieb ein CO₂, reiches Fluid zurück, das im primären Kyanit (M1) eingeschlossen wurde. Wässrige Flüssigkeitseinschlüsse können in Quarzkörnern gefunden werden. Dieses Fluid ist wahrscheinlich für die Reequilibrierung zu amphibolitfaziellen Bedingungen verantwortlich.

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With 5 Figures     

Coexisting biotite and muscovite: An example from a Moinian mica schist at Glenfinnan,Scottish Highlands

Summary Moscovite-biotite intergrowths from Moinian mica schist at Glenfnnan probably represent a pair that grew under conditions of a thermodynamic equilibrium, at a temperature of 730 (± 50) °C and a pressure of 7.8 (± 1.0) kbar. Both micas and garnet are characterized by full chemical analyses and some physical data (density, unit-cell parameters). Precession photographs of five crystals show that there is a fxed crystallographic orientation between muscovite and biotite, with c* of both parallel and thehOl _MS net overlapping withh3hl _B1, 3hl _B1 orh0l _B1. Pairs of dioctahedral micas in association with trioctahedral deserve more attention, because they may help in understanding petrological histories of igneous and metamorphic rocks. The Fe²⁺ -(Li, Al)-Mg projection and a moscovite-phlogopite-annite plot appear useful in assessing whether or not pairs of coexisting micas came to a thermodynamic equilibrium.

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Koexistierender Biotit und Muskovit: ein Beispiel aus dem Moine-Glimmerschiefer von Glenfinnan, Schottisches Hochland

Zusammenfassung Muskovit-Biotit-Verwachsungen aus dem Moine-Glimmerschiefer von Glenfinnan stellen Paare dar, die unter Bedingungen thermodynamischen Gleichgewichtes bei 730 (± 50) °C und 7.8 (± 1.0) kbar kristallisierten. Glimmer und Granat werden mit chemischen Analysen und einigen physikalischen Daten (Dichte, Gitterkonstanten) dokumentiert. Präzessionsaufnahmen von fünf Kristallen zeigen, daß es eine gesetzmäßige kristallographische Orientierung zwischen Muskovit und Biotit gibt, wobei für beide c* parallel ist und dieh0l _MS Netze sich überlappen mith3hl _B1, 3hl_B1 oder Will. Paare von dioktaedrischen Glimmern in Assoziation mit trioktaedrischen Glimmern bedürfen größerer Aufmerksamkeit weil sie zum Verständnis der petrologischen Geschichte von magmatischen und metamorphen Gesteinen beitragen können. Die Fe²⁺-(Li, Al)-Mg Projektion und ein Muskovit-Phlogopit-Annit-Diagramm können dazu beitragen, die Frage zu klären, ob Paare koexistierender Glimmer in ein thermodynamisches Gleichgewicht gelangt sind.

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With 4 Figures     

First occurrence of the rare mineral Barylite in Greenland

Summary Barylite has been identified for the first time in Greenland in several specimens from the nepheline syenite pegmatite pockets at Narssârssuk. The crystals are orthorhombic, showing the forms {100}, {210} and {201}, and form thin plates parallel to {100}. Electron microprobe analysis and emission spectrography show a composition close to the ideal formula. The refined unit cell paramters are:a=9.835(2) Å,b=11.654(3) Å andc=4.673(1) Å. The barylite is biaxial negative, 2V =66^o±2^o,n =1.694,n = 1.697 andn _calc.=1.698.

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Das erste grönländische Vorkommen des seltenen Minerales Barylith

Zusammenfassung Der seltene Barylith wurde zum ersten Mal in Grönland in verschiedenen Proben aus Nephelin-Syenit-Pegmatit-Drusen bei Narssârssuk identifiziert. Die Kristalle sind orthorhombisch mit den Formen {100}, {210} und {201}, sie bilden dünne Tafeln nach {100}. Elektronensonden-Analyse und Emissions-Spektrographie ergeben eine chemische Zussammensetzung, die der Idealform nahekommt. Die verfeinerten Zellparameter sind folgende:a=9,835(2) Å,b=11,654(3) Å undc=4,673(1) Å. Barylith ist zweiachsig negativ, 2V =66^o±2^o,n =1,694,n =1.697 undn _calc.= 1,698.