A potassium-rich Alkalic Suite from the Deccan Traps,Rajpipla, India |
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| Authors: | P Krishnamurthy K G Cox |
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| Institution: | (1) Grant Institute of Geology, King's Buildings, West Mains Road, Edinburgh, UK;(2) Department of Geology and Mineralogy, Parks Road, Oxford, UK;(3) Present address: Department of Atomic Energy, Atomic Minerals Division, Hyderabad, India |
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| Abstract: | The Rajpipla Alkalic Suite is the most potassium-enriched group of basaltic rocks so far described from the Deccan Traps. In the same area however early tholeiitic flows and late tholeiitic dykes show the potassium-poor nature characteristic of most Deccan Trap magmas. The rocks of the alkalic suite are highly porphyritic and their major element variation can be interpreted in terms of crystal fractionation dominated by clinopyroxene. Plagioclase, which is an important phenocryst phase, has fractionated only in relatively small amounts as a result of a lack of density contrast between it and the liquids. A dyke-like form for the magma chambers in which fractionation has taken place is postulated to account for the abundance of highly porphyritic types. The Rajpipla area is also notable as being one of the few Deccan localities where rhyolites are found.Abbreviations AB
ankaramitic basalt
- PB
porphyritic basalt
- PTB
porphyritic trachybasalt
- FPM
feldsparphyric mugearite
- M
mugearite
- TR
trachyte
- P. RHY
potassic rhyolite
- Th. B.
tholeiitic basalt
- Th. D.
tholeiitic dolerite
- Af
alkali feldspar |
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