Petrogenesis of metamorphic rocks within a subduction-accretion terrane, Signy Island, South Orkney Islands |
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| Authors: | B C STOREY A W MENEILLY |
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| Institution: | British Antarctic Survey, Natural Environment Research Council, Madingley Road, Cambridge CB3 0ET |
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| Abstract: | Abstract Whole-rock and mineral analyses of polydeformed mica-schist, quartzite, marble and amphibolite are presented from Signy Island, South Orkney Islands, part of the Scotia metamorphic complex. Whole-rock chemistry suggests that the amphibolites are the metamorphosed equivalent of enriched tholeiitic and alkali basalts of an oceanic intraplate basalt series. These, together with limestones and Mn-rich cherts of an oceanic island assemblage were tectonically mixed with trench or trench inner slope basin sediments in a subduction zone environment. Variation in mineral chemistry indicates an increase in temperature and decrease in pressure during metamorphism; pressures of 8 kbar and temperatures of approximately 545°C were reached during amphibolite facies metamorphism in the latter stages of deformation. These new data provide good evidence to support the previous interpretation of the Scotia metamorphic complex as a subduction complex. |
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| Keywords: | Key-words: amphibolite geochemistry oceanic intraplate basalt Scotia metamorphic complex thermobarometry |
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