TY - JOUR

T1 - An isolated mildly depleted mantle source for the north atlantic craton

AU - Petersson, Andreas

AU - Waight, Tod

AU - Whitehouse, Martin

AU - Kemp, Anthony

AU - Szilas, Kristoffer

N1 - Funding Information: Financial support by the Danish Independent Research Fund, DFF-Research Project 2 \u2013 (grant number: 9040-0374B to T. Waight) is gratefully acknowledged. AK acknowledges an Australian Research Council Discovery Project (DP200103208). Hf isotope analysis at UWA was conducted with instrumentation funded by the Australian Research Council (LE100100203 and LE150100013). KS acknowledges financial support from Carlsbergfondet (CF18-0090) for the fieldwork to collect the sediment sample. The NordSIMS ion microprobe facility operates as Swedish infrastructure, partly funded by the Swedish Research Council (grant nos. 2017-00671 and 2021-00276). Insightful comments from Elis Hoffmann and Luc Doucet helped clarify and strengthen our interpretations. We appreciate the editorial guidance of Victoria Pease. This is Nordsim contribution #7XX. Publisher Copyright: © 2024 The Author(s)

PY - 2024

Y1 - 2024

N2 - Generation of continental crust during early Earth was a vital step towards stabilizing the cratonic lithosphere. How and when this happened is, however, still poorly understood. Radiogenic isotope data from the oldest crust, and minerals therein, provide a unique insight into the timing and processes that operated during Earth's earliest evolution. Using combined zircon U-Pb, O and Lu-Hf isotope data from a glacial stream-sediment within the Isukasia (Isua) terrane of southern West Greenland, we argue for an isolated mantle source for the ca. 1.3 Ga of initial stages of crustal growth in the North Atlantic Craton. Zircon Hf isotope data between 3939 and 2950 Ma yield strikingly homogeneous, near chondritic signatures, with the few analyses that deviate slightly being indicative of ancient Pb-loss. Combined with published data from carefully selected and well-characterized ca. 3.9–2.6 Ga magmatic rocks of the NAC, almost no indications of reworking of older crust can be detected, but all strongly sub-chondritic data rather fall on Pb-loss trends tracing back to chondritic sources. This long-lived and near-chondritic signature with negligible influence from a strongly depleted mantle, or from un-radiogenic sources, argues for protracted crust separation from an isolated mantle source. We suggest a scenario whereby primary melting to produce basaltic and komatiitic crust leaves an infertile harzburgitic residue, unlikely to re-melt, that becomes sequestered as mantle lithosphere. Hence, domains of primordial fertile mantle are continuously sourced from an undepleted mantle reservoir. Combined with small wavelength mantle convection, a near-chondritic to mildly depleted regional mantle is retained into at least the Mesoarchean.

AB - Generation of continental crust during early Earth was a vital step towards stabilizing the cratonic lithosphere. How and when this happened is, however, still poorly understood. Radiogenic isotope data from the oldest crust, and minerals therein, provide a unique insight into the timing and processes that operated during Earth's earliest evolution. Using combined zircon U-Pb, O and Lu-Hf isotope data from a glacial stream-sediment within the Isukasia (Isua) terrane of southern West Greenland, we argue for an isolated mantle source for the ca. 1.3 Ga of initial stages of crustal growth in the North Atlantic Craton. Zircon Hf isotope data between 3939 and 2950 Ma yield strikingly homogeneous, near chondritic signatures, with the few analyses that deviate slightly being indicative of ancient Pb-loss. Combined with published data from carefully selected and well-characterized ca. 3.9–2.6 Ga magmatic rocks of the NAC, almost no indications of reworking of older crust can be detected, but all strongly sub-chondritic data rather fall on Pb-loss trends tracing back to chondritic sources. This long-lived and near-chondritic signature with negligible influence from a strongly depleted mantle, or from un-radiogenic sources, argues for protracted crust separation from an isolated mantle source. We suggest a scenario whereby primary melting to produce basaltic and komatiitic crust leaves an infertile harzburgitic residue, unlikely to re-melt, that becomes sequestered as mantle lithosphere. Hence, domains of primordial fertile mantle are continuously sourced from an undepleted mantle reservoir. Combined with small wavelength mantle convection, a near-chondritic to mildly depleted regional mantle is retained into at least the Mesoarchean.

KW - Crustal growth

KW - Depleted mantle

KW - Isua

KW - Lu-Hf

KW - North Atlantic Craton

KW - Zircon

U2 - 10.1016/j.precamres.2024.107399

DO - 10.1016/j.precamres.2024.107399

M3 - Journal article

AN - SCOPUS:85191305079

VL - 407

JO - Precambrian Research

JF - Precambrian Research

SN - 0301-9268

M1 - 107399

ER -