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

   Botero, M; Vervoort, J; Meira, V; Martins_de_Sousa, Daniel F; Santos, T (October 2024, 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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3. 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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4. 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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5. What we can learn in the kitchen sink: an example from garnet granulite

   Stowell, H.H. (January 2021, America Geophysical Union)

   Interpretation of geochronological and petrological data from partially-melted granulite is challenging. However, integration of multiple chronometers and mineral assemblage diagrams (MAD) can be used to estimate the nature and duration of processes. Excellent lower-crustal exposures of garnet granulite from the Malaspina Pluton, Fiordland New Zealand provide an ideal place to employ this kitchen sink approach. We use zircon U-Pb ages from LA-ICPMS, SHRIMP-RG, and CA-TIMS, garnet Lu-Hf and Sm-Nd ages, and MAD in order to evaluate local partial melting vs. melt injection, equilibrium volumes, P-T conditions, and the duration of lower crustal thermal events. Host diorite (H), garnet-clinopyroxene reaction zones (GRZ), coarse garnet selvages, and tonalite veins provide a record of intrusion and granulite facies partial melting. Zircon U-Pb ages range from 123 to 107 Ma (all); LA-ICPMS ages contain the entire range; CA-TIMS ages range from 118.30±0.13 to 115.7±0.18 Ma; and SHRIMP-RG ages range from 121.4±2 to 109.8±1.8 Ma. The latter two techniques are interpreted to indicate primary igneous crystallization from ~119 to ~116 Ma and the youngest ~110 Ma ages are interpreted as metamorphic zircon growth. Garnet ages for ~1 cm grains are ~113 Ma (Lu-Hf & Sm-Nd) and record metamorphic growth, and <0.3 mm grains with Sm-Nd ages from 113 to 104 Ma reflect high temperature intracrystalline diffusion and isotopic closure during cooling to amphibolite facies. Zircon trace-element compositions indicate 2 distinct crystallization trends reflecting evolution of primary magma batches. MAD indicate that garnet was not in equilibrium with sampled rock compositions. Instead, garnet shows apparent equilibrium with a modeled mixture of the GRZ and the H and grew in equilibrium with an effective bulk composition that shifted toward the leucosome. This would produce the observed increase in garnet grossular content. We conclude that: Malaspina rocks from Crooked Arm preserve evidence for 2 igneous layers which evolved as discrete magmas, igneous crystallization lasted 2 to 3 m.y., granulite metamorphism peaked ~ 3 m.y. after intrusion, metamorphism lasted ≥3 m.y., cooling occurred at ~20°C/m.y., and granulite minerals equilibrated with a mixture of solid phases and melt at ~14 kbar and 920°C (based on garnet compositions and MAD). 

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