Kimberlites, lamproites and lamprophyres from the Indian shield: Highlights of researches during 2016-2019

The North Purulia Shear Zone that dissects the granulite basement of the Chotanagpur Granite Gneissic Complex of the East Indian Shield exposes a deformed and metamorphosed nepheline syenite. The studied ‘foid-monzosyenite’ shows high abundances of large ion lithophile elements and high field strength elements with low abundances of compatible elements. Trace-element signatures show negative U, Th, Zr, Ti and Pb and positive Sr, Ba and Eu anomalies with respect to the primitive mantle. The chondrite-normalized diagram shows strongly fractionated rare earth element patterns ((La/Lu)N ∼23–87). Geochemical fingerprints suggest that the basanitic protolith was formed by low-degree partial melting of garnet peridotite in the sub-continental lithospheric mantle. The enriched large ion lithophile, high field strength element and light rare earth element concentrations (relative to primitive mantle) can be explained by a mixed mantle source with components from a previously deformed alkaline rock/carbonatite. Geochemical data do not support any significant crustal contamination and suggest variable fractionation of clinopyroxene, ilmenite, titanite and apatite from the parental melt. Petrological data are consistent with the view that the nepheline syenite magma was emplaced in a rift setting with a minimum temperature of 800–900°C, low fO2 conditions (below the fayalite–magnetite–quartz buffer) at a mid-crustal depth between 950 and 900 Ma. The continental rift zone, however, did not lead to the formation of an open ocean basin. Subsequently, the studied rock and its basement was deformed and metamorphosed in a continent–continent collisional setting at ∼900 Ma. Combining information from the other Indian occurrences with this study, it is demonstrated that the deformed alkaline rocks and carbonatite are potentially valuable for tracing the birth and demise of the palaeo-supercontinents.

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Petrogenesis of a nepheline syenite from parts of the Chotanagpur Granite Gneissic Complex: implications for Neoproterozoic crustal extension in the East Indian Shield

Das

Sinha

Sanyal

et al. 2022

Geol. Mag.

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Mesoproterozoic ⁴⁰ Ar– ³⁹ Ar ages of some lamproites from the Cuddapah Basin and Eastern Dharwar Craton, southern India: implications for diamond provenance of the Banganapalle Conglomerates, age of the Kurnool Group and Columbia tectonics

Kumar

Talukdar

Rao

et al. 2021

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We report Mesoproterozoic 40Ar-39Ar (whole-rock) ages of lamproites from (i) the Ramadugu field (R4 dyke : 1434 ± 19 Ma and R5 dyke: 1334 ± 12 Ma) and the Krishna field (Pochampalle dyke: 1439 ± 3 Ma and Tirumalgiri dyke: 1256 ± 12 Ma) from the Eastern Dharwar Craton (EDC) and (ii) the Garledinne (1433 ± 8 Ma) and the Chelima (1373 ± 6 Ma) dykes from within the Paleo-Mesoproterozoic Cuddapah Basin, southern India. The ages reported for the Ramadugu and Tirumalgiri lamproites constitute their first radiometric dates. Ages of the Pochampalle and the Chelima lamproites from this study are broadly comparable to their previously reported 40Ar-39Ar (phlogopite) ages of c. 1500 Ma and 1418 ± 8 Ma, respectively. The ages of all these lamproites are much older than those of the (i) c. 1.1 Ga kimberlites from the Wajrakarur and Narayanpet fields of the EDC and (ii) c. 1.09 Ga lamproitic dykes at Zangamarajupalle which intrude the Cumbum Formation of the Cuddapah Basin. However, the age of the Tirumalgiri lamproite (c. 1256 Ma) is similar to that of the Ramannapeta lamproite (c. 1224 Ma) within the Krishna field. Our study provides evidence for protracted ultrapotassic (lamproitic) magmatism from c. 1.43 to 1.1 Ga over a widespread area (c. 2500 km2) in and around the Cuddapah Basin and the EDC. Implications of the obtained new ages for the diamond provenance of the Banganapalle Conglomerates, the age of the Kurnool Group and for the timing of break-up of the Paleo-Mesoproterozoic supercontinent of Columbia/Nuna are explored.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5289354

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Mineral chemistry of chrome-diopside bearing lamprophyre from Mesoproterozoic Settupalle igneous complex of Prakasam alkaline province: insights on the magma dynamics at shallow lithospheric mantle beneath the NE margin of the Cuddapah basin, Southern India

Sridhar,

Reddy,

Pandey

et al. 2024

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The Eastern Dharwar Craton (EDC) shows considerable variations in the activity of Kimberlite, lamproite, and lamprophyre and their related lithospheric thickness, thermal structure, and magmatic source characteristics from the innermost core to the margin. These variations have been revealed through seismic studies and the analysis of xenoliths, and xenocrysts carried in alkaline magmas, particularly kimberlites. This study reports the occurrence of chrome diopside phenocrysts from a lamprophyre of the Settupalle pluton, located on the northeastern margin of the Cuddapah basin, Prakasam Alkaline Province (PAP) in South India. Studied lamprophyre characterized by phenocrystic clinopyroxene (Cpx) and biotite, embedded in a groundmass of amphibole, biotite, opaques, calcite, feldspar, nepheline, and sodalite, with the latter minerals forming ocellar structures. Clinopyroxene displays normal zoning, with a high Mg-Cr rich diopside core (up to 1.92 wt%) and a Na 2 O, Al 2 O 3 , FeO, and TiO 2 -enriched salite rim. These chemical variations, along with elemental substitutions from core to rim, indicate the significant role of fractionation in the evolution of lamprophyre magma. The lack of chemical disparity among the studied Cpx, suggests closed-system fractionation, under high oxygen fugacity conditions. Thermobarometry results indicate polybaric crystallization for the Cpx (1206–1269 °C, 11.82–18.04 kbar) and biotite (825–856 °C, 3.49–6.94 kbar). The gradient inferred from the pressure of the Cpx suggests that its crystallization occurred at a depth of 43-66 km, implying shallow lithospheric magma contribution for the genesis of the lamprophyre magma. Supplementary material at https://doi.org/10.6084/m9.figshare.c.7249493

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Kimberlites, lamproites and lamprophyres from the Indian shield: Highlights of researches during 2016-2019

Cited by 4 publications

References 9 publications

Petrogenesis of a nepheline syenite from parts of the Chotanagpur Granite Gneissic Complex: implications for Neoproterozoic crustal extension in the East Indian Shield

Petrogenesis of a nepheline syenite from parts of the Chotanagpur Granite Gneissic Complex: implications for Neoproterozoic crustal extension in the East Indian Shield

Mesoproterozoic ⁴⁰ Ar– ³⁹ Ar ages of some lamproites from the Cuddapah Basin and Eastern Dharwar Craton, southern India: implications for diamond provenance of the Banganapalle Conglomerates, age of the Kurnool Group and Columbia tectonics

Mineral chemistry of chrome-diopside bearing lamprophyre from Mesoproterozoic Settupalle igneous complex of Prakasam alkaline province: insights on the magma dynamics at shallow lithospheric mantle beneath the NE margin of the Cuddapah basin, Southern India

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Kimberlites, lamproites and lamprophyres from the Indian shield: Highlights of researches during 2016-2019

Cited by 4 publications

References 9 publications

Petrogenesis of a nepheline syenite from parts of the Chotanagpur Granite Gneissic Complex: implications for Neoproterozoic crustal extension in the East Indian Shield

Petrogenesis of a nepheline syenite from parts of the Chotanagpur Granite Gneissic Complex: implications for Neoproterozoic crustal extension in the East Indian Shield

Mesoproterozoic 40 Ar– 39 Ar ages of some lamproites from the Cuddapah Basin and Eastern Dharwar Craton, southern India: implications for diamond provenance of the Banganapalle Conglomerates, age of the Kurnool Group and Columbia tectonics

Mineral chemistry of chrome-diopside bearing lamprophyre from Mesoproterozoic Settupalle igneous complex of Prakasam alkaline province: insights on the magma dynamics at shallow lithospheric mantle beneath the NE margin of the Cuddapah basin, Southern India

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Mesoproterozoic ⁴⁰ Ar– ³⁹ Ar ages of some lamproites from the Cuddapah Basin and Eastern Dharwar Craton, southern India: implications for diamond provenance of the Banganapalle Conglomerates, age of the Kurnool Group and Columbia tectonics