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P. Imsland 《Contributions to Mineralogy and Petrology》1983,83(1-2):31-37
The volcanism in Iceland occurs on both rift zones and non-rifting zones. The rift zone volcanism produces rock suites of the tholeiitic series, ranging from primitive tholeiites (MORB) to highly silicic rocks. The non-rifting volcanic zones produce rock suites of transitional to mildly alkaline or even calc-alkaline composition, the basalts typically being FETI-basalts. Over 50 per cent of the rift zone production in Iceland is of the primitive MORB-type. The relative amount of the evolved rock types, as well as the total volcanic production increases inland along the rift zones. The rock types of the Icelandic rift zones are identical to those of the submerged oceanic rift zones, but the Icelandic production is somewhat offset towards a more voluminous evolved end. The skewness in volume relations of rock types, as compared to the oceanic rifts in general, is mainly caused by the products of the non-rifting volcanic zones of Iceland and only to a small degree by the rift zone products. 相似文献
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The Quaternary island Bouvetøya is situated near the triple junction on the South Atlantic Ridge. It is the top of a volcano of about 2000 km8, evolved beyond the stage of caldera collapse. Basic, intermediate and peralkaline silicic rocks of a transitional rock series are recorded. Major and trace element chemistry, model calculations and petrographic observations do not favour a closed system fractional crystallization from one parent. The rocks may have evolved from slightly different parents by fractional crystallization under varying P,T and PH2O conditions, or from one parent modified by crustal contamination and/or volatile transfer. 相似文献
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