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1. U-Pb and Lu-Hf isotopic evolution of ∼3.6 Ga remnants in NE Brazil – Implications on Eo-Paleoarchean global crustal evolution

   https://doi.org/10.1016/j.chemgeo.2025.122646  

   Botero, Manuela; Vervoort, Jeffrey D; Meira, Vinicius T; Martins_de_Sousa, Daniel F; Santos, Ticiano JS (April 2025, Chemical Geology)

   NA (Ed.)

   Precambrian terrains preserving rocks older than 3.5 Ga contain an essential record of the crustal evolution of the primitive Earth. In this study, we investigated Eo-Paleoarchean rocks from the northern S˜ao Francisco Craton (NSFC) and the Borborema Province in northeastern Brazil to contribute to a more complete global isotopic record of this pivotal time in Earth’s history. Zircon U-Pb ages along with zircon Hf isotope compositions were obtained for migmatitic gneiss complexes in both terrains. Zircon U-Pb data from the NSFC yield well-defined populations with 207Pb/206Pb ages from 3.61 to 3.59 Ga and younger components at ~3.5 and ~3.4 Ga. Similarly, the Borborema Province gneiss yields a main zircon age population of 3.58 Ga and a younger ~3.5 Ga age component. The ~3.6 Ga zircon components yield consistently sub-chondritic Hf isotopic compositions with initial εHf between −1.9 and −3.1 for the NSFC and of εHf −0.5 for the Borborema Province. Gneisses from northeastern Brazil record a main crust forming period at 3.65–3.60 Ga with sub-chondritic Hf isotope compositions that indicate derivation from melting of a ~3.8 Ga source of broadly chondritic isotope composition, similar to that of many Eo-Paleoarchean gneisses worldwide. This Hf isotope record supports the existence of broadly chondritic mantle reservoir in the Eoarchean with development of depleted mantle and the appearance of evolved crust later in the Paleoarchean. 

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2. Tracking Archean crustal evolution of the Zimbabwe Craton through U-Pb geochronology and Hf isotopes

   https://doi.org/10.1016/j.gca.2026.05.026  

   Botero, Manuela; Vervoort, Jeffrey D; Hofmann, Axel (May 2026, Geochimica et Cosmochimica Acta)

   Not AvailableThe ancient history of the Earth is marked by pivotal times recorded in Precambrian terrains, providing crucial insight into the evolution of the crust-mantle system and the geodynamic processes operating in the evolving Earth. This research focuses on the Zimbabwe craton, an important ancient terrain where fundamental concepts of Archean tectonics were first defined and that remains largely uncharacterized by high-precision isotope studies. We integrate in-situ LA-ICPMS zircon U-Pb ages and Hf isotope compositions of magmatic samples and river sands to investigate the Paleo- and Meso-Neoarchean (∼3.6–3.3 Ga and ∼2.9–2.7 Ga) crustal evolution of the craton. Zircon U-Pb data from gneiss complexes and granites within the central part of the craton, which encompasses the Sebakwe proto-craton that experienced tectonic stability temporarily between 3.3 and 3.0 Ga ago, define a main magmatic event at 3.6–3.5 Ga and minor components at ∼3.3 Ga, ∼2.9 Ga, and 2.7 Ga. Outside of the central part of the craton within the Odzi-Mutare area the magmatic record is dominated by zircon U-Pb ages between 2.9 and 2.8 Ga. A similar age distribution is recorded by detrital zircon from modern sediments with age clusters in the Paleoarchean at 3.6–3.5 Ga and 3.4–3.3 Ga, with the latter being more prominent, and in the Meso-Neoarchean at 2.9–2.8 Ga and 2.6 Ga. The Paleoarchean magmatic components yield Hf isotope compositions within 4 epsilon units of CHUR (ƐHf(3.6-3.3Ga) + 2 to –4), similar to the isotope compositions of detrital zircons (ƐHf(3.6-3.3Ga) + 2 to –6). Meso-Neoarchean magmatic components yield Hf isotope compositions with ƐHf(i) between CHUR and +2 at ∼2.9–2.8 Ga, while detrital zircons range from ƐHf(i) + 4 to –9 at ∼2.9–2.6 Ga. Data from the Zimbabwe craton indicate crust formation in the Paleoarchean (3.6–3.3 Ga) that involved juvenile magma additions and a possible derivation from a ∼3.8 Ga chondritic source and craton-wide crust forming episodes between ∼2.9 and 2.6 Ga that involved crustal reworking in various degrees along with new additions of juvenile material. The Hf isotope record of the Zimbabwe craton aligns with the global isotope record—with chondritic to sub-chondritic Hf isotope compositions at ∼3.7–3.6 Ga, the appearance of juvenile additions after ∼3.5 Ga, and mixing trends after ∼3.0 Ga—supporting formation of a long-lived depleted mantle reservoir after ∼3.6 Ga. 

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3. Tracing primary signatures in Eo-Paleoarchean terranes: Mineral-scale constraints on disturbed bulk-rock isotope records

   https://doi.org/10.1016/j.epsl.2025.119668  

   Botero, Manuela; Vervoort, Jeffrey D; Meira, Vinicius T (December 2025, Earth and Planetary Science Letters)

   The Hf and Nd isotope records from Earth’s earliest history are essential for understanding the processes of crustmantle evolution in the early Earth. These records, however, have been largely obtained from bulk-rock samples that have often been compromised by post-crystallization processes. Complexities resulting from open-system behavior and mixing of different components are reflected in heterogeneous Eo-Paleoarchean bulk-rock Hf and Nd isotope records. In this study, we integrate in-situ Sm-Nd isotope analyses of REE-rich minerals with U-Pb titanite geochronology to assess the reliability of the bulk-rock isotope record in ~3.6 Ga gneisses from the northern S˜ao Francisco Craton (NSFC). Our results demonstrate that Nd isotope compositions of minerals controlling the elemental budget in rocks provide a more robust record of the early Earth. The NSFC mineral phases preserving primary signatures have chondritic ƐNd(i) (0.0 to +0.3) at their crystallization ages (~3.6 Ga). In contrast, bulk-rock Hf and Nd isotope compositions exhibit extreme heterogeneity (i.e. ƐNd(i) +4 to −12 ƐHf(i) +8 to −14) reflecting post-crystallization disturbances at 2.5–2.0 Ga. When mineral phases in these rocks have Sm- Nd isochron ages that agree with their U-Pb crystallization ages, their initial Nd isotope compositions are consistent with the zircon Hf isotope data. These findings align with global zircon Hf isotope data, which indicate a chondritic mantle reservoir until ~3.8 Ga, with evidence of significant mantle depletion and crustal differentiation emerging in the isotope record thereafter. This study underscores the importance of mineral-scale isotope investigations in refining interpretations of early crust-mantle evolution and the mechanisms affecting bulk-rock isotope records in Precambrian terranes. 

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4. Growth and evolution of Neoarchean−Paleoproterozoic crust in the NW Wyoming Province: Evidence from zircon U-Pb age and Lu-Hf isotopes of the Montana metasedimentary terrane

   https://doi.org/10.1130/B37160.1  

   Chen, Tsai-Wei; Vervoort, Jeffrey D; Baldwin, Julia A (October 2023, Geological Society of America Bulletin)

   The Montana metasedimentary terrane in the northern Wyoming Province provides valuable insight into crustal formation and reworking processes along the cratonic margin and offers a unique opportunity to decipher the complex Neoarchean−Paleoproterozoic terrane assembly in southwestern Laurentia. We report new zircon U-Pb dates and Hf isotopes from seven metaigneous samples in the northwestern Montana metasedimentary terrane. The internal textures of zircon in this study are complex; some lack inherited cores and metamorphic overgrowths, while others exhibit core-rim relationships. Based on the cathodoluminescence (CL) features, we interpret these grains to be magmatic populations. These data demonstrate discrete igneous pulses at 2.7 Ga, 2.4 Ga, and 1.7 Ga, which indicate significant crustal formation intervals in the Montana metasedimentary terrane. Zircons at 2.7 Ga have positive εHf values (+2.4 to +0.9) that indicate a depleted mantle source. Most 2.4 Ga and 1.7 Ga samples have negative εHf values (−1.6 to −15.5), which indicate significant contributions from preexisting crust. Two 1.7 Ga samples, however, have near-chondritic εHf values (+0.4 to +0.3) that indicate larger juvenile contributions. The time-integrated Hf isotope trend suggests that the Paleoproterozoic zircons were produced from a mixture of older crust and juvenile mantle inputs. Additionally, the isotopic age fingerprint of the Montana metasedimentary terrane suggests that it differs from northern-bounding terranes. Viewed more broadly, the 2.7 Ga and 1.7 Ga age peaks that the Montana metasedimentary terrane shares with the global zircon age spectrum suggest that the drivers of these events in the Montana metasedimentary terrane were common throughout the Earth and may be associated with the assembly of supercontinents Kenorland and Nuna. 

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5. Deciphering complex Hf-Nd records of polymetamorphic terranes through multiple isotope systems

   https://doi.org/10.1016/j.gca.2025.09.022  

   Chen, Tsai-Wei; Vervoort, Jeffrey D; Baldwin, Julia A (November 2025, Geochimica et Cosmochimica Acta)

   Understanding the history of polymetamorphic terranes requires integrating multiple analytical techniques to reveal different aspects of crustal evolution. This approach includes geochronological analyses to establish a timeline of geological events as well as isotopic analyses to understand the nature of source rocks. In this study, we analyze Sm-Nd isotopes in apatite and titanite and U-Pb ages in monazite and titanite from metaigneous samples in the northwest Wyoming Province. We integrate these new data with our previously published zircon U-Pb ages and Lu-Hf isotopes with garnet Lu-Hf and Sm-Nd dates from the same samples. This dataset allows us to reconstruct a complete history from magmatic crystallization through metamorphism to isotopic reequilibration. The U-Pb ages from monazite and titanite complement our existing garnet geochronology, constraining peak metamorphism and subsequent cooling at 1.78 Ga (billion years ago) and 1.71 Ga, respectively. Multi-phase Sm-Nd isotope data indicate that isotopic re-equilibration occurred between 1.82 Ga and 1.68 Ga, coinciding with the hypothesized occurrence of the Big Sky orogeny in the region. Notably, the Sm-Nd system reveals a bimodal initial isotopic composition—with one endmember with a near-chondritic composition (εNd(i) ~ −1.7) and the other with strongly subchondritic signatures (εNd(i) ~ −12)—indicating mixing between juvenile and reworked crustal components during orogenesis. The preservation of primary Hf isotopic signatures in zircon—in contrast to the disturbed and reset Nd isotopic compositions in other minerals (apatite, garnet, and titanite)—provides insights into the region’s tectonothermal evolution. These results demonstrate significant Sm- Nd re-equilibration during post-crystallization processes, similar to observations from other ancient terranes, highlighting the importance of multi-isotope approaches in unraveling early Earth evolution. 

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