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Two petrologically distinct alkali feldspar syenite bodies(AFS-1 and AFS-2) from Chhotaudepur area,Deccan Large Igneous Province are reported in the present work. AFS-1 is characterized by hypidiomorphic texture and consists of feldspar(Or55Ab43to Or25Ab71), ferro-pargasite/ferro-pargasite hornblende, hastingsite, pyroxene(Wo47, En5, Fs46), magnetite and biotite. AFS-2 exhibits panidiomorphic texture with euhedral pyroxene(Wo47-50, En22-39, Fs12-31) set in a groundmass matrix of alkali feldspar(Or99Ab0.77to Or1.33Ab98), titanite and magnetite. In comparison to AFS-1, higher elemental concentrations of Ba, Sr andPREE are observed in AFS-2. The average peralkaline index of the alkali feldspar syenites is w1 indicating their alkaline nature. Variation discrimination diagrams involving major and trace elements and their ratios demonstrate that these alkali feldspar syenites have a shoshonite affinity but emplaced in a within-plate and rifting environment. No evidence of crustal contamination is perceptible in the multi-element primitive mantle normalized diagram as well as in terms of trace elemental ratios. The enrichment of incompatible elements in the alkali feldspar syenites suggests the involvement of mantle metasomatism in their genesis.
Two petrologically distinct alkali feldspar syenite bodies (AFS-1 and AFS-2) from Chhotau depur area, Deccan Large Igneous Province are reported in the present work. AFS-1 is characterized by hypidiomorphic texture and consists of feldspar (Or55Ab43to Or25Ab71), ferro- AFS-2 exhibits panidiomorphic texture with euhedral pyroxene (Wo47-50, En22-39, Fs12-31) set in a groundmass matrix of The average peralkaline index of the alkali feldspar syenites is w1 indicating their alkali pentaerythritol (a). The average peralkaline index of the alkali feldspar syenites is w1 indicating their Alkaline nature. Variation of relation between significant and trace elements and their ratios demonstrate that these alkali feldspar syenites have a shoshonite affinity but emplaced in a within-plate and rifting environment. No evidence of crustal contaminati on is perceptible in the multi-element primitive mantle normalized diagram as well as in terms of trace elemental ratios. The enrichment of incompatible elements in the alkali feldspar syenites suggests the involvement of mantle metasomatism in their genesis.