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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
- IIT JAM
- Geology (GG)
21. among the different kinds of flood basalt, the sio, content is highest in: acontinental tholeiites b. oceanic tholeiites c. alkaline olivine basalts d) spil
21. Among the different kinds of flood basalt, the SiO, content is highest in: AContinental tholeiites B. Oceanic tholeiites C. Alkaline olivine basalts D) Spilites (AMU-2015)
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Saurabh 1![best-answer]()
I think it should be A. Continental tholeiites consist majorly of SiO2, K2O and are more evolved as compared to the one that belong to oceanic tholeiites. Alkali Olivine Basalt, as one can point out that it's quite silica-undersaturated, characterized by the absence of orthopyroxene, absence of quartz, presence of olivine, and typically contains some feldspathoid mineral. Spilites are altered basic to intermediate composition fine-grained igneous rock in which the feldspar is partially or completely composed primarily of albite. So as per former discussion, it should be A.
In case of spilites, what do u mean by altered igneous rock..is it metamorphosed??
You can somewhat say that they can be formed by low grade metamorphism of the oceanic basalt(cuz they are formed primarily due to hydrothermal alteration of oceanic basalt, in short a metasomatism can play a significant role in it's formation and thats why the plagioclase seems to be albitised in this case and you are bound to find ample amount of albitic plagioclase in spilites)