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  • 1
    Electronic Resource
    Electronic Resource
    An analytical electron microscopic study of a pyroxene-amphibole intergrowth (1981)
    Springer
    Contributions to mineralogy and petrology 77 (1981), S. 115-120 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Samples of a garnet granulite from the mafic border units of the Lake Chatuge, Georgia alpine peridotite body were found to contain lamellar intergrowths of a pargastic amphibole in augite having the typical appearance of an exsolution feature. Single crystal X-ray diffraction, optical, electron microprobe and conventional and analytical electron microscopic studies have provided data limiting the compositions and structures of the coexisting phases. Individual lamellae of both materials are from 0.5 to 2.0 μm in width with the lamellar interface parallel to {0 1 0}. The formulae of the minerals, as determined by a combination of electron microprobe and analytical electron microscopy, are (Na0.1Ca1.0Mg0.6Fe3+ 0.3)(Si1.8Al0.2)O6 for the pyroxene and Na0.7Ca1.9(Mg2.1Fe2+ 1.4Fe3+ 0.5Ti0.1Cr0.1Al0.8)(Si5.9Al2.1) O22(OH)2 for the amphibole. Several other studies have described intergrowths similar to those observed in this work, in general favoring exsolution as the formation mechanism for the intergrowths. In the Lake Chatuge samples however, replacement of pyroxene by amphibole is in part indicated by continuous gradation of amphibole lamellae into amphiboles rimming the clinopyroxenes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00636515
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  • 2
    Electronic Resource
    Electronic Resource
    An evaluation of garnet-clinopyroxene geothermometry in granulites (1983)
    Springer
    Contributions to mineralogy and petrology 84 (1983), S. 191-198 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Four new formulations of the garnet-clinopyroxene geothermometer (Ellis and Green 1979; Ganguly 1979; Saxena 1979; Dahl 1980) have been evaluated in the Adirondacks and five other granulite terranes using results from 94 mineral pairs. The Saxena and Ganguly formulations give temperatures that are generally 100–150° C above those constrained by phase equilibria and other independent thermometry while the empirical calibration of Dahl gives widely scattered, erratic results. Despite some scatter in the data, the Ellis and Green calibration appears to be more accurate and precise than the others and is the most useful garnet-clinopyroxene thermometer currently available for quantitative thermometry in granulites. All four formulations are sensitive to large variations (〉70–80° C) in temperature suggesting that problems with accuracy and precision can be improved with further refinement of model-based aspects of the thermometers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371285
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  • 3
    Electronic Resource
    Electronic Resource
    A periclase-dolomite-calcite carbonatite from the Oka complex, Quebec, and its calculated volatile composition (1984)
    Springer
    Contributions to mineralogy and petrology 85 (1984), S. 149-157 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The eutectic mineral assemblage calcite-dolomite-periclase-apatite-forsterite-magnesioferrite-pyrrhotite-alabandite in a carbonatite dike within the Oka complex, Quebec, buffers the fugacities (and partial pressures) of all gas species in C-O-H-S-F, assuming vapor saturation. At the inferred eutectic (640° C, 1 kbar), the most important gas species and their partial pressures (bars) were: H2O, 882; CO2, 110; H2, 4.6; H2S, 2.7; CO, 0.5; and CH4, 0.1. Oxygen fugacity was near the QFM buffer, logf(O2)=−18.6, and sulfur fugacity was near the QFM-pyrrhotite buffer, logf(S2)=−5.9. Fluorine fugacity was low, logf(F2)=−43.9, consistent with the absence of fluoride minerals other than apatite. Presence of a water-rich gas phase is consistent with experiments on synthetic carbonatite systems (e.g. Fanelli et al. 1981), although compositions of the gas phase in published experiments cannot be determined exactly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371705
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  • 4
    Electronic Resource
    Electronic Resource
    Petrology of spinel harzburgite xenoliths from the Kishb Plateau, Saudi Arabia (1986)
    Springer
    Contributions to mineralogy and petrology 93 (1986), S. 335-346 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Two spinel harzburgite xenoliths from a Pleistocene alkali basalt unit erupted at the northwestern corner of the Tertiary Kishb Plateau (Saudi Arabia) are characterized by an incipient transition from protogranular to porphyroclastic texture. Vermicular and interstitial spinels are closely associated with neoblasts of olivine, enstatite, and diopside. Sparse exsolution lamellae of high-Ca pyroxene occur in all the enstatite porphyroblasts. Olivine neoblasts are, in many cases, in contact with one another, with the triple grain junctions rarely approaching 120°. Chemical zoning is undetectable by microprobe in spinel and olivine, whereas zoning of Al in enstatite and diopside indicates that chemical equilibrium was not attained. Clear, palegreen glasses occur as veinlets about 10 microns or less in width along grain boundaries and cracks. Consistent counting rates for Na in these glasses were obtained only at 5 kV with a sample current of about 6 namps and counting time of less than 7 s. These glasses are chemically homogeneous and are characterized by relatively high contents of SiO2 (55.8–58.7 wt%), Na2O (6.4–7.6 wt%), and Al2O3 (20.0–21.6 wt%), with inferred volatile contents of less than 1 wt%. The glass is suggested to be of upper mantle origin rather than having developed from the host basalt or by decompressional melting upon ascent. Geothermometry and geobarometry indicate that the lithospheric upper mantle beneath the Arabian Shield had been locally heated to higher than 1,050° C during Miocene/ Pliocene, resulting in some degree of partial melting. Spinel was formed by reaction between aluminous pyroxenes and olivine during subsequent cooling, and intercrystalline Mg-Fe exchange reached a steady state at about 800° C. The geotherm beneath the Arabian Shield since Miocene is estimated to be somewhat lower than that representing the present oceanic upper mantle. The thermal history established is consistent with the tectonic history of the Red Sea area and indicates a two-stage magmatism in the Arabian Shield since Miocene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389392
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  • 5
    Electronic Resource
    Electronic Resource
    Occurrence of wide-chain Ca-pyriboles as primary crystals in the Salton Sea Geothermal Field, California, USA (1986)
    Springer
    Contributions to mineralogy and petrology 94 (1986), S. 127-134 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Amphiboles and pyroxenes occurring in the Salton Sea Geothermal Field were found to contain coherent intergrowths of chain silicates with other than double and single chain widths by using transmission and analytical electron microscopy. Both occur in the biotite zone at the temperature (depth) interval of 310° C (1,060 m) to 330° C (1,547m) which approximately corresponds to temperatures of the greenschist facies. The amphiboles occur as euhedral fibrous crystals occupying void space and are composed primarily of irregularly alternating (010) slabs of double or triple chains, with rare quadruple and quintuple chains. Primary crystallization from solution results in euhedral crystals. Clinopyroxenes formed mainly as a porefilling cement and subordinately as prismatic crystals coexisting with fibrous amphiboles. Fine lamellae of double and triple chains are irregularly intercalated with pyroxene. AEM analyses yield formulae (Ca1.8Mg2.9Fe1.9Mn0.1) Si8O21.8(OH)1.8 (310° C) and (Ca2.0Fe2.5Mg2.3) Si8O21.8 (OH)2.0 (330° C) for amphiboles and (Ca1.1Fe0.6Mg0.3) Si2O6 for clinopyroxene. Thermodynamic calculations at Pfluid=100 bar of equilibrium reactions of (1) 3 chlorite +10 calcite + 21 quartz = 3 actinolite + 2 clinozoisite + 8 H2O + 10 CO2 and (2) actinolite+ 3 calcite+ 2 quartz = 5 clinopyroxene + H2O + 3 CO2 using Mg-end member phases indicate that formation of amphibole and pyroxene require very water-rich conditions $$(X_{CO_2 } 〈 0.06)$$ at temperatures below 330° C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371233
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  • 6
    Electronic Resource
    Electronic Resource
    Mantle eclogite and carbonate as sources of sodic carbonatites and alkalic magmas (1983)
    [s.l.] : Nature Publishing Group
    Nature 302 (1983), S. 700-703 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] At pressures above 25 kbar, partial melts in the system peridotite -f CO2 are rich in carbonate, and have been correlated with kimberlite or carbonatite magmas1'2. However, peridotite does not contain enough sodium to allow formation of most carbonatites and their associated sodic mafic magmas ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/302700a0
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  • 7
    Electronic Resource
    Electronic Resource
    Occurrence, chemistry, and origin of immiscible silicate glasses in a tholeiitic basalt: A TEM/AEM study (1986)
    Springer
    Contributions to mineralogy and petrology 94 (1986), S. 90-98 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The occurrence and chemistry of immiscible silicate glasses in a tholeiite mesostasis from the Umtanum formation, Washington, were investigated with transmission electron microscopy and analytical electron microscopy (TEM/AEM). TEM observation reveals isolated, dark globules (2.1 micron or less in diameter) randomly distributed in a transparent matrix glass interstitial to plagioclase laths. The globules less than 0.3 micron and larger than 0.8 micron fall beyond the linear relationship defined by the 0.3–0.8 micron globules in a plot of the logarithm of number versus size. Large globules (0.7 micron or larger in diameter) range from homogeneous to heterogeneous in optical properties and chemistry. Homogeneous globules are completely glassy, whereas heterogeneous globules contain crystalline domains. AEM analyses show that the globules have high Si, Fe, Ca, and Ti with subordinate Mg, Al, P, S, Cl, K, and Mn, which gives high normative fa, px, il, and ap. The matrix glass consists dominantly of Si with low Al and minor Na and K, yielding a high normative qz, or, ab, and an. It is proposed that the silicate liquid immiscibility occurs by reaction of network-modifying cations (NMCs) with dominantly chain-like anionic units in the parental melt to form less polymerized, NMC-bearing units and highly polymerized, Si-rich units. The globules nucleated metastably under supercooled conditions, and medium-size globules become either larger or smaller at lower temperatures. Internal nucleation of NMC-rich phases occurred in some larger globules upon cooling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371230
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  • 8
    Electronic Resource
    Electronic Resource
    Experimental investigation and application of the equilibrium rutile + orthopyroxene = quartz + ilmenite (1993)
    Springer
    Contributions to mineralogy and petrology 115 (1993), S. 18-35 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Equilibria in the Sirf (Silica-Ilmenite-Rutile-Ferrosilite) system: $${\text{SiO}}_{\text{2}} + ({\text{Mg,Fe}}){\text{TiO}}_{\text{3}} {\text{ + (Mg,Fe)SiO}}_{\text{3}} $$ have been calibrated in the range 800–1100° C and 12–26 kbar using a piston-cylinder apparatus to assess the potential of the equilibria for geobarometry in granulite facies assemblages that lack garnet. Thermodynamic calculations indicate that the two end-member equilibria involving quartz + geikielite = rutile + enstatite, and quartz + ilmenite = rutile + ferrosilite, are metastable. We therefore reversed equilibria over the compositional range Fs40–70, using Ag80Pd20 capsules with $$f_{{\text{O}}_{\text{2}} } $$ buffered at or near iron-wüstite. Ilmenite compositions coexisting with orthopyroxene are $$X_{{\text{MgTiO}}_{\text{3}} }^{{\text{Ilm}}} $$ of 0.06 to 0.15 and $$X_{{\text{Fe}}_{\text{2}} {\text{O}}_{\text{3}} }^{{\text{Ilm}}} $$ of 0.00 to 0.01, corresponding toK D values of 13.3, 10.2, 9.0 and 8.0 (±0.5) at 800, 900, 1000 and 1100° C, respectively, whereK D =(XMg/XFe)Opx/(XMg/XFe)Ilm. Pressures have been calculated using equilibria in the Sirf system for granulites from the Grenville Province of Ontario and for granulite facies xenoliths from central Mexico. Pressures are consistent with other well-calibrated geobarometers for orthopyroxeneilmenite pairs from two Mexican samples in which oxide textures appear to represent equilibrium. Geologically unreasonable pressures are obtained, however, where oxide textures are complex. Application of data from this study on the equilibrium distribution of iron and magnesium between ilmenite and orthopyroxene suggests that some ilmenite in deep crustal xenoliths is not equilibrated with coexisting pyroxene, while assemblages from exposed granulite terranes have reequilibrated during retrogression. The Sirf equilibria are sensitive to small changes in composition and may be used for determination of activity/composition (a/X) relations of orthopyroxene if an ilmenite model is specified. A symmetric regular solution model has been used for orthopyroxene in conjunction with activity models for ilmenite available from the literature to calculatea/X relations in orthopyroxene of intermediate composition. Data from this study indicate that FeSiO3−MgSiO3 orthopyroxene exhibits small, positive deviations from ideality over the range 800–1100°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712975
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  • 9
    Electronic Resource
    Electronic Resource
    Genesis and solvus relations of submicroscopically intergrown paragonite and phengite in a blueschist from northern California (1991)
    Springer
    Contributions to mineralogy and petrology 106 (1991), S. 367-378 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Electron microbeam techniques have been used to examine submicroscopically intergrown paragonite, phengite and chlorite from the South Fork Mountain Schist of the Franciscan Terrane of northern California, which was subjected to blueschist facies metamorphism. The sample also contains quartz, albite, lawsonite, and rutile. The subassemblage albite-lawsonite-rutile requires metamorphic conditions on the low-temperature side of the equilibrium albite+lawsonite+rutile=paragonite+sphene+quartz+H2O (T〈200° C and P〈7.4 kbars based on thermodynamic data of Holland and Powell 1990). The white micas appear to be optically homogeneous, but back-scattered electron images can distinguish two different micas by their slight difference in contrast. Electron microprobe analyses (EMPA) of micas show Na/(Na+K) ranging from 0.2 to 0.8. The two micas are resolved by transmission electron microscopy (TEM) as packets of phengite and paragonite that range from 20 to several hundred nm in thickness. The compositions, determined by analytical electron microscopy (AEM), constrain the limbs of the phengite-paragonite solvus to values of Na/(Na+K)=〈0.02 and 0.97, representing less mutual solid solution than ever reported by EMPA. The textural relations imply that the sheet silicates were derived from reactions between fluids and detrital clays and that they are in an intermediate stage of textural development. We caution that microprobe analyses of apparently homogeneous sheet silicates may yield erroneous data and lead to faulty conclusions using phengite barometry and paragonite-muscovite thermometry, especially in fine-grained rocks that formed at relatively low temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324564
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  • 10
    Electronic Resource
    Electronic Resource
    Erratum (1979)
    Springer
    Contributions to mineralogy and petrology 68 (1979), S. 441-441 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01164528
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