Geochemistry and petrogenesis of lava flows around Linga, Chhindwara area in the Eastern Deccan Volcanic Province (EDVP), India

摘要

Based on systematic three-tier arrangement of vesicles, entablature and columnar joints, three distinct quartz normative tholeiitic lava flows (Ⅰ, Ⅱ and Ⅲ) were recognized in the area around Linga, in the Eastern Deccan Volcanic Province (EDVP). Each of the flows exhibits intraflow chemical variations marked by high Mg#-low Ti, and low Mg#-high Ti contents. The MgO (4.27-7.74 wt.%), Mg# (23.45-41.89) and Zr (161.5-246.3 ppm) of Linga flows suggest an evolved chemistry marked by fractional crystallization and crustal contamination processes. Positive Rb and Th anomalies, negative Nb anomalies, relative enrichment of LILE-LREE with respect to Nb, Nb/Th:3.71-6.77 indicate crustal contamination of magma by continental materials through magma-crust interaction during melt migration and contributions from sub-continental lithospheric mantle (SCLM). Negative K, Sr and Ti anomalies corroborate an intracontinental, rift-controlled tectonic setting for the genesis and evolution of Linga basalts. Chondrite-normalized REE patterns reflect low HREE abundances and prominent LREE/HREE, MREE/HREE fraction-ation thereby pointing towards partial melting of garnet peridotite mantle source. Nb, Zr, Y variations suggest 10-15% partial melting of mantle source for the derivation of parent tholeiitic melt that suffered crystal fractionation of phenocrystal phases and subsequent liquid immiscibility. Critical evaluation of Sr_(inltial) and Nd_(inltial) (65 Ma) isotopic compositions (~(87)Sr/~(86)Sr_(inltial) between 0.705656 and 0.706980 and ~(143)Nd/~(144)Nd_(inltial) between 0.512523 and 0.512598) suggests that these basalts were derived from an enriched mantle (～EM Ⅰ-EM Ⅱ) source. The ε_(Sr) (21.84-41.27) and ε_(Nd) (-0.28 to 1.10) isotopic signatures defined by higher ε_(Sr) and lower ε_(Nd) fingerprint a plume-related source. Positive and negative values of ε_(Nd) indicate an isotopically heterogeneous mantle source marked by mixing of depleted (DM) and enriched mantle (EM Ⅰ-EM Ⅱ) components at the source region and together with ~(87)Sr/~(86)Sr_(inltial) ranging from 0.705656 to 0.706980 suggest two stage contamination of parent magma which is much similar to that of Poladpur, Toranmal, Mhow, Chikaldara flows. Ba/Y versus ~(87)Sr/~(86)Sr and Nb/Y versus Rb/Y variations show an Ambenali-Poladpur contamination trend for the Linga basalts thereby suggesting the role of upper continental granitic crust as the contaminant of these flows through magma-crust interaction during melt migration. The lava flows of Linga are geochemically correlatable with the Poladpur flows of southwestern and Toranmal flows of northern Deccan and show genetic coherence with the basalts of Jabalpur, Seoni, Chakhla-Delakhari of eastern Deccan.