Piyali Sengupta

Bio: Piyali Sengupta is an academic researcher from University of Calcutta. The author has contributed to research in topics: Cycloaddition & Aryl. The author has an hindex of 4, co-authored 14 publications receiving 63 citations.

Petrogenesis of flood basalts of the Narsingpur-Harrai-Amarwara-Lakhnadon section of eastern deccan province, India

Abstract: The present area of investigation falls in the Eastern Deccan segment where available field and geochemical data are rather limited. In the present study, five distinctive structural zones namely Lower Vesicular zone, Lower Colonnade Zone, Entablature Zone, Upper Colonnade Zone and Upper Vesicular Zone have been identified in different lava flows which are helpful for the purpose of stratigraphic correlation. All the lavas under investigation can be classified into three distinct geochemical groups (viz. Group I, Group 2 and Group 3) on the basis of their Mg′ number and TiO2 wt%. The Group 1 lavas are marked by low Mg′ No (0.39–0.45) and high TiO2 (2.9–3.6 wt%) while Group 2 lavas are characterized by moderate Mg′ No (0.45–0.50) and moderate TiO2 (2.4–2.9 wt%). On the other hand, high Mg′ No (0.49–0.54) and low TiO2 (1.91–2.31 wt%) characterize the Group 3 basalts. Interestingly, the basaltic flows corresponding to three distinct groups are intermixed with each other; in other words, lava flows belonging to several groups are juxtaposed with one another with increasing height.

Petrology of the Mafic Sill of Narshingpur-Lakhnadon Section, Eastern Deccan Volcanic Province

Abstract: Deccan volcanism with a tremendous burst of volcanic activity marks a unique episode in Indian geological history and covers nearly two third of Peninsular India. Occurrences of mafic sill in the continental basalts are rather rare throughout the flood basalt provinces and only few sporadic reports have been described from different Continental Flood Basalts of the world. In the present article, petrology of mafic sill from the Narshingpur-Lakhnadon section of Eastern Deccan province of India has been presented. The mafic sill in the field is found to occur in a relatively deep valley amidst Gondwana rocks, which occur as the basement of the extrusion. The sill is spatially associated with three initial flows viz. flow I, II and III of adjacent Narshingpur-Harrai-Amarwara section. The sill in its central part is a medium grained rock and petrographically corresponds to dolerite containing augite, plagioclase and rare olivine grains; the chilled facies of the sill is characterized by phenocrysts of olivine, plagioclase and augite that are set in groundmass consisting predominantly of plagioclase, olivine and glass. Mineral chemistry indicates that olivine phenocrystal phase is magnesian (Fo61). Plagioclase phenocrystal composition ranges from An 51 to An 71 whereas the same variation of the groundmass plagioclase composition corresponds to An 31 to An 62. The overlap in the compositions for groundmass and phenocrystal plagioclase may be explained due to fluctuating PH2O condition. The pyroxene compositions (both groundmass and phenocryst) in majority of the cases are clubbed well within the augite field, however, in a few cases, groundmass compositions are found to fall in the sub-calcic augite and pigeonite field. Some zoned pyroxene phenocrysts, characteristically display different types of zoning patterns. Opaque minerals in the mafic sill are found to be magnetite and ilmenite and this coexisting iron-oxide composition helps to constrain the prevalent fO2 condition in the parent magma. The geochemistry of the mafic sill and associated basaltic lava flows indicates close genetic link amongst them. Critical consideration of trace elements indicates a distinct enriched mantle source (EM-I/EM-II/HIMU) for the parental magma. Trace element modeling indicates that equilibrium batch-melting of plume source followed by fractionation of olivine, clinopyroxene and plagioclase and subsequent heterogeneous mixing of melt and settled crystals can very well explain the genesis of the mafic sill and the associated basaltic flows.

Isolation, Synthesis, and Evolutionary Ecology of Piper Amides

Abstract: The phytochemistry of the genus Piper is rich in terms of numbers of compounds discovered, but given the diversity of this genus and the intraspecific diversity of secondary metabolites in those species that have been examined, Piper chemistry has not been adequately investigated. The natural products chemistry that has been elucidated is well documented and has been the subject of extensive review (Sengupta and Ray 1987, Parmar et al. 1997). Since those reviews were published, 28 new species have been investigated (Benevides et al. 1999, Chen et al. 2002, Ciccio 1997, de Abreu et al. 2002, Dodson et al. 2000, dos Santos et al. 2001, Facundo and Morais 2003, Jacobs et al. 1999, Joshi et al. 2001, Martins et al. 1998, Masuoka et al. 2002, McFerren and Rodriquez 1998, Moreira et al. 1998, Mundina et al. 1998, Srivastava et al. 2000a, Stohr et al. 2001, Terreaux et al. 1998, Torquilho et al. 2000, Vila et al. 2001, 2003, Wu et al. 1997), and 69 compounds new to Piper have been discovered (Adesina et al. 2002, Alecio et al. 1998, Baldoqui et al. 1999, Banerji et al. 1993, 2002b, Boll et al. 1994, Chen et al. 2002, Ciccio 1997, Da Cunha and Chaves 2001, Das and Kashinatham 1998, daSilva et al. 2002, de Araujo-Junior et al. 1997, Dodson et al. 2000, Gupta et al. 1999, Jacobs et al. 1999, Joshi et al. 2001, Martins et al. 1998, Masuoka et al. 2002, Menon et al. 2000, 2002, Moreira et al. 1998, 2000, Mundina et al. 1998, Navickiene et al. 2000, Pande et al. 1997, Parmar et al. 1998, Santos and Chaves 1999a,b, Santos et al. 1998, Seeram et al. 1996, Siddiqui et al. 2002, Srivastava et al. 2000a,b, Stohr et al. 1999, Terreaux et al. 1998, Wu et al. 2002a,b, Zeng et al. 1997).