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  • 1
    Electronic Resource
    Electronic Resource
    Oxford : Blackwell Science Ltd
    Journal of metamorphic geology 14 (1996), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Raman spectral analyses of carbonaceous material (CM) extracted from pelitic samples along two sections traversing the metamorphic belt of Taiwan were carried out in the present study. The results show similar spectral variations of CM with metamorphic grade as those documented in the literature. However, continuous sampling from zeolite facies through prehnite–pumpellyite facies to greenschist facies metamorphic rocks in the present study does reveal some interesting features on the Raman spectra of CM that were not noted before. Both the Raman D (disordered-)/O (ordered-) peak area (i.e. integrated intensity) ratio and the D/O peak width (i.e. full width at half maximum, FWHM) ratio of the CM decrease with progressive metamorphism, but the most prominent change in the D/O peak area ratio occurs in samples of lower greenschist facies metamorphic grade, while the most significant decrease in the D/O peak width ratio occurs in samples near the boundary of prehnite–pumpellyite facies and greenschist facies. This phenomenon is interpreted as a result of the decoupling of the changing rates of in-plane crystallite size and degree of defects of CM with progressive metamorphism. It is postulated that the Raman spectrum of CM can serve as a metamorphic grade indicator to distinguish samples of prehnite–pumpellyite facies metamorphic grade from those of greenschist facies metamorphic grade.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 21 (2003), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract An analytical electron microscope study of almandine garnet from a metamorphosed Al–Fe-rich rock revealed detailed composition profiles and defect microstructures of resorption zoning along fluid-infiltrated veins and even into the garnet/ilmenite (inclusion) interface. This indicates a limited volume diffusion for the cations in substitution (mainly Ca and Fe) and an interface-controlled partition for the extension of a composition-invariant margin. A corrugated interface between the Ca-rich margin/zone and the almandine garnet core is characterized by dislocation arrays and recovery texture further suggesting a resorption process facilitated by diffusion-induced recrystallization, diffusion-induced dislocation migration and diffusion–induced grain boundary migration. Integrated microstructural and chemical studies are essential for understanding the underlying mechanisms of processes such as garnet zoning and its modification. Without this understanding, it will not be possible to reliably use garnet compositions for thermobarometry and other applications that rely on garnet chemical information.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Kyanite and staurolite occur in the Tananao Metamorphic Complex as submicron inclusions in almandine-rich garnet from a metamorphosed palaeosol weathering horizon, near Hoping, eastern Taiwan. Quartz, rutile/brookite and zircon are also found as associated submicron inclusions in garnet. Employing the reaction ilmenite+kyanite+quartz=almandine+rutile, and the breakdown of staurolite and quartz as thermobarometers, these submicron-scale minerals formed at 〉8.3–8.8 kbar and 〈 660–690 °C. This P–T estimate is different from that (i.e. 5–7 kbar and 530–550 °C) derived from matrix minerals, which include almandine-rich garnet, muscovite, chlorite, chloritoid, plagioclase, quartz and ilmenite. These results suggest that submicron inclusions in garnet-like materials may record portions of the otherwise undocumented prograde path or provide information about previous metamorphic events and thus yield new insights into orogenic belts.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1420-9136
    Keywords: Radon ; Groundwater ; Earthquakes ; Taiwan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Radon (222Rn) concentration in geothermal waters and CO2-rich cold springwaters collected weekly in duplicate samples from four stations in northern Taiwan were measured from July 1980 to December 1983. Seven spike-like radon anomalies (increases of 2 to 3 times the standard deviation above the mean) were observed at three stations. Following every anomaly except one, an earthquake ofM L above 4.6 occurred within 4 to 51 days, at an epicentral distance 14 to 45 km, and at a focal depth of less than 10 km. The distribution of the earthquakes preceded by radon anomalies is skewed in certain directions from the radon stations; the radon stations seem to be insensitive to earthquakes occurring in the other directions. At the fourth station, near a volcanic area, much gas (mainly CO2) is discharged from the well, together with hot water. A very high concentration of radon was detected in the discharged gas; therefore trapping of gas in the water can result in anomalously high radon contents. According to limited measurements, the radon concentration in water appears to be undersaturated with respect to that in gas. This suggests that hot water is very susceptible to radon loss, and monitoring of radon in gas is more desirable.
    Type of Medium: Electronic Resource
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