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Coupled trace element and Hf-isotope measurements of Hadean through Paleoarchean zircons from the Singhbhum Craton indicate derivation from a long-lived, mantle-derived protocrust.

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Title: Coupled trace element and Hf-isotope measurements of Hadean through Paleoarchean zircons from the Singhbhum Craton indicate derivation from a long-lived, mantle-derived protocrust.
Authors: Kirkpatrick, Heather1,2 (AUTHOR) heather.kirkpatrick@louisiana.edu, Stoll, Emily1 (AUTHOR), Drabon, Nadja1 (AUTHOR)
Source: Earth & Planetary Science Letters. Mar2026, Vol. 677, pN.PAG-N.PAG. 1p.
Subjects: Hadean, Zircon, Paleoceanography, Continental crust, Cratons, Trace elements, Hafnium isotopes, Plate tectonics
Geographic Terms: Singhbhum (India)
Abstract: • Older Metamorphic Tonalitic Gneiss grains > 3.7 Ga: derive from source heavily influenced by an enriched mantle and show little evidence for arc-like melting. • Grains < 3.7 Ga: dominantly mantle-like trace elements with minor arc-like trace elements and some evidence for crustal thickening. • 3.9 – 3.6 Ga: important period of local crustal reorganization with the Singhbhum Craton, but may have potentially also been an important period of global crustal reorganization. Due to the dearth of rock records during the Hadean, little is known about early crustal chemistry and geodynamics. Here, we present zircon trace and rare earth element and Lu-Hf measurements of zircons ∼ 3.3 Ga to ∼ 4.2 Ga from the Older Metamorphic Tonalitic Gneiss in the Singhbhum Craton to better understand geodynamic changes during the Hadean and Archean. We find decreasing, subchondritic zircon ε HfT among zircons > 3.7 Ga and no indication of addition of new crustal material during the Hadean after initial formation of this protocrust. Trace and rare earth element analyses of > 3.7 Ga grains indicate derivation from a source heavily influenced by the enriched mantle with little evidence for flux melting, and no clear evidence for deep melting. At ∼ 3.7 Ga, we observe an average ε HfT increase indicating new additions of juvenile felsic material. These zircons still show predominantly mantle-like trace elements, but with the appearance of some arc-like signatures and evidence for crustal thickening. This period of crustal reorganization speaks towards a shift in geodynamic regime characterized by the onset of communication between the mantle and the crust from which the zircons formed at this location. The presence of long-lived, mantle-derived protocrust in both India and South Africa appears to suggest the possibility of a local stagnant lid, albeit more data is necessary to confirm this. The presence of a transition of ε HfT data globally may point towards an important, diachronous period of crustal reorganization 3.9 – 3.6 Ga ago. [ABSTRACT FROM AUTHOR]
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Abstract:• Older Metamorphic Tonalitic Gneiss grains > 3.7 Ga: derive from source heavily influenced by an enriched mantle and show little evidence for arc-like melting. • Grains < 3.7 Ga: dominantly mantle-like trace elements with minor arc-like trace elements and some evidence for crustal thickening. • 3.9 – 3.6 Ga: important period of local crustal reorganization with the Singhbhum Craton, but may have potentially also been an important period of global crustal reorganization. Due to the dearth of rock records during the Hadean, little is known about early crustal chemistry and geodynamics. Here, we present zircon trace and rare earth element and Lu-Hf measurements of zircons ∼ 3.3 Ga to ∼ 4.2 Ga from the Older Metamorphic Tonalitic Gneiss in the Singhbhum Craton to better understand geodynamic changes during the Hadean and Archean. We find decreasing, subchondritic zircon ε HfT among zircons > 3.7 Ga and no indication of addition of new crustal material during the Hadean after initial formation of this protocrust. Trace and rare earth element analyses of > 3.7 Ga grains indicate derivation from a source heavily influenced by the enriched mantle with little evidence for flux melting, and no clear evidence for deep melting. At ∼ 3.7 Ga, we observe an average ε HfT increase indicating new additions of juvenile felsic material. These zircons still show predominantly mantle-like trace elements, but with the appearance of some arc-like signatures and evidence for crustal thickening. This period of crustal reorganization speaks towards a shift in geodynamic regime characterized by the onset of communication between the mantle and the crust from which the zircons formed at this location. The presence of long-lived, mantle-derived protocrust in both India and South Africa appears to suggest the possibility of a local stagnant lid, albeit more data is necessary to confirm this. The presence of a transition of ε HfT data globally may point towards an important, diachronous period of crustal reorganization 3.9 – 3.6 Ga ago. [ABSTRACT FROM AUTHOR]
ISSN:0012821X
DOI:10.1016/j.epsl.2025.119813