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Geochemical and Isotopic Constraints on Long-Lived Source Enrichment and Mantle Evolution in Paleoproterozoic Cratonic Lamprophyres

Naskar S, Pandey R, Baumann N, Chalapathi Rao NV, Mathew G, Amal Dev J, Tomson JK (2026)

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Publication Type: Journal article

Publication year: 2026

Journal

Book Volume: 27

Article Number: e2025GC012773

Journal Issue: 6

DOI: 10.1029/2025GC012773

Abstract

The cratonic lithospheric mantle records complex metasomatic processes and is frequently tapped by alkaline magmatism, offering a unique opportunity to trace the progressive evolution of the mantle. In the present contribution, we investigate a newly identified calc-alkaline lamprophyre field from the Neoarchean Jonnagiri Schist Belt, Eastern Dharwar Craton, southern India. Petrographic and mineralogical observations reveal reversely zoned amphibole phenocrysts, indicating magma mixing and recharge within a multi-level magma plumbing system. Amphibole cores, interpreted as antecrysts, crystallized in a deep-seated magma reservoir (∼20 km) and were later overgrown by rims equilibrated with a more mafic melt at shallower crustal levels (∼7 km), recording a dynamic history of magmatic evolution. ⁴⁰Ar/³⁹Ar age (2,200–2,400 Ma) of the lamprophyres cast a significantly distinct Paleoproterozoic calc-alkaline event that predates the widespread Mesoproterozoic (∼1,100 Ma) alkaline magmatism elsewhere in the craton. Whole-rock geochemistry characterized by negative Nb-Ta, Zr-Hf, and Ti anomalies in the spidergram, suggests derivation from a sub-continental lithospheric mantle source modified by slab-derived fluids during the Neoarchean subduction. The Th/Yb (5.3–2.5) and Nb/U (9.4–2.1) trace-element ratios, and the fractionated LREE/HREE pattern (LaN/YbN: 29–18) of the investigated lamprophyres are indistinguishable from those of lamprophyres from the Superior- and Yilgarn- Cratons. Near Chondritic εNdi signatures and enriched Archean mantle-like Sr isotopic signatures imply a short residence time of the generated magma after metasomatic modification. The geodynamic setup of the Jonnagiri schist belt reflects post-collisional reworking of the subduction-modified lithosphere, possibly triggered by the slab break-off and asthenospheric upwelling during the waning period of Neoarchean accretion. Partial melting of this enriched mantle during the Paleoproterozoic (∼2.3 Ga), likely related to Superia supercontinent break-up, contributed to the polychronous magmatic activity in this domain. The Jonnagiri lamprophyres record the prolonged influence of a subduction-enriched lithospheric domain tapped episodically during the Neoarchean to Mesoproterozoic.

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How to cite

APA:

Naskar, S., Pandey, R., Baumann, N., Chalapathi Rao, N.V., Mathew, G., Amal Dev, J., & Tomson, J.K. (2026). Geochemical and Isotopic Constraints on Long-Lived Source Enrichment and Mantle Evolution in Paleoproterozoic Cratonic Lamprophyres. Geochemistry Geophysics Geosystems, 27(6). https://doi.org/10.1029/2025GC012773

MLA:

Naskar, Sourav, et al. "Geochemical and Isotopic Constraints on Long-Lived Source Enrichment and Mantle Evolution in Paleoproterozoic Cratonic Lamprophyres." Geochemistry Geophysics Geosystems 27.6 (2026).

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