Petrographical indicators of petrogenesis: Examples from Central Indian Ocean Basin basalts
Abstract
Petrographical features of the Central Indian Basin (CIOB) basalts were studied to understand their genetic significance. The fresh basaltic pillows show three textural zones from the top glassy (zone A) through the intermediate (zone B) to the holocrystalline interior (zone C), with each characterised by varying assemblages of plagioclase and olivine that form different textures. Based on the presence and morphotypes of the plagioclase and olivine, the CIOB basalts are classified as aphyric, plagioclase dominant, plagioclase+olivine bearing and rarely plagioclase+olivine+augite bearing. The mineral phases and the textures reflect the magmatic conditions under which the basalts crystallised from a tholeiitic magma.
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