Chemical evolution, petrogenesis, and regional chemical correlations of the flood basalt sequence in the central Deccan Traps, India

Journal of Earth system science

Mario Barbieri2³  Leone Melluso1¹  Luigi Beccaluva3² 

[1] Dipartimento di Scienze della Terra, Universit`a di Napoli Federico II, via Mezzocannone 8, 80134 Napoli, Italy.$$;Dipartimento di Scienze Geologiche, Universit`a di Ferrara, Italy.$$;Dipartimento di Scienze della Terra, Universit`a di Roma “La Sapienza”, Italy.$$

关键词: Petrogenesis;    basalts;    basaltic andesites;    central Deccan Traps;    India.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

The lava sequence of the central-western Deccan Traps (from Jalgaon towards Mumbai) is formed by basalts and basaltic andesites having a significant variation in TiO2 (from 1.2 to 3.3 wt%), Zr (from 84 to 253 ppm), Nb (from 5 to 16 ppm) and Ba (from 63 to 407 ppm), at MgO ranging from 10 to 4.2 wt%. Most of these basalts follow a liquid line of descent dominated by low pressure fractionation of clinopyroxene, plagioclase and olivine, starting from the most mafic compositions, in a temperature range from 1220° to 1125°C. These rocks resemble those belonging to the lowermost formations of the Deccan Traps in the Western Ghats (Jawhar, Igatpuri and Thakurvadi) as well as those of the Poladpur formation. Samples analyzed for 87Sr/86Sr give a range of initial ratios from 0.70558 to 0.70621. A group of flows of the Dhule area has low TiO2 (1.2–1.5 wt%) and Zr (84–105 ppm) at moderate MgO (5.2–6.2 wt%), matching the composition of low-Ti basalts of Gujarat, low-Ti dykes of the Tapti swarm and Toranmal basalts, just north of the study area. This allows chemical correlations between the lavas of central Deccan, the Tapti dykes and the northwestern outcrops. The mildly enriched high field strength element contents of the samples with TiO2 < 1.5 wt% make them products of mantle sources broadly similar to those which generated the Ambenali basalts, but their high La/Nb and Ba/Nb, negative Nb anomalies in the mantle normalized diagrams, and relatively high 87Sr/86Sr, make evident a crustal input with crustally derived materials at less differentiated stages than those represented in this sample set, or even within the sub-Indian lithospheric mantle.

【 授权许可】

Unknown