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111.
Subsolidus and melting reactions involving calcic plagioclase in pelitic assemblages in the K-Na-Ca model system occur at higher temperatures than their K-Na counterparts. For the most calcic plagioclase compositions observed in high-grade pelitic rocks (An25-An40) the equilibria are rarely extended by more than 30 ° C above those in KA1O2-NaAlO2-Al2O3-SiO2-H2O, although all discontinuities in facies inferred for the K-Na system are continuously displaced when they involve Ca-bearing plagioclase. The maximum pressure-temperature overlap between muscovite dehydration and initial melting reactions occurs in the pressure range of 4–6 kbar between about 640 ° and 720 ° C. This provides optimum conditions for anatectic melt generation in felsic rocks of the appropriate compositions progressively metamorphosed in kyanite-sillimanite facies series. Progressive regional metamorphism at pressures of 2–4 kbar, corresponding to andalusite-sillimanite facies series, shows little overlap between muscovite dehydration and initial melting reactions. Consequently anatectic melt generation in andalusite-sillimanite facies series would require the participation of biotite in dehydration-melting reactions. Felsic intrusive rock in andalusite-sillimanite terranes could have risen upward from their anatectic sites in high grade kyanite-sillimanite facies series at depth. Many andalusite-sillimanite facies series terranes culminating in migmatites could represent upward movement of kyanite-sillimanite facies series rocks to shallower depths with uplift rates faster than cooling rates. 相似文献
112.
Thomas H. Bolyard George M. Hornberger Robert Dolan Bruce P. Hayden 《Environmental Geology》1979,3(1):1-11
A multiple regression model was constructed for the purpose of predicting barrier island hydrology from easily measureable
island characteristics. The model was developed using data obtained from 17 sites on the Outer Banks of North Carolina. The
accuracy of the model for predicting key hydrologic variables was evaluated by statistical and graphic procedures. In general,
agreement between observed and predicted values of the hydrologic variables was very good, suggesting that the quantity of
potable water at various island sites can be estimated without resorting to extensive field investigations. The model was
then applied to Assateague Island, a barrier island located off the coasts of Maryland and Virginia. Results indicate that
the original model developed for the Outer Banks may be applied to other barrier islands but that errors involved may necessitate
corrections in detailed studies. Correction for bias in predictions for Assateague was shown to be possible with limited field
data from surface resistivity surveys. 相似文献
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Marine mussels accumulate the carcinogen benzo(a)pyrene from contaminated environments. Baseline studies in California indicate that levels of the carcinogen in mussels are at or near zero, except in areas of human activity. This finding runs counter to previous suggestions that benzo(a)pyrene is widely distributed in marine organisms. 相似文献
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The number of bacteria in sediments of a North Carolina salt marsh was determined by direct counts with epifluorescent illumination and acridine orange stain. Cell number decreased from 8.36–10.90×109 cells/cm3 of sediment at the surface to 2.19–2.58×109 cells/cm3 of sediment at a depth of 20 cm. No significant difference was found among four stations located on a transect which crossed the marsh and spanned subtidal to intertidal sediments. 相似文献
119.
A reevaluation of the entropy and Gibbs free energy of formation of Al3+(aq) yields ?308 ± 15 J/K·mol and 489.4 ± 1.4kj/mol for S0298 and respectively. The standard electrode potential for aluminum is 1.691 ± 0.005 volts. 相似文献
120.