How mafic was the Archean upper continental crust? Insights from Cu and Ag in ancient glacial diamictites

Chen, Kang; Rudnick, Roberta L.; Wang, Zaicong; Tang, Ming; Gaschnig, Richard M.; Zou, Zongqi; He, Tao; Hu, Zhaochu; Liu, Yongsheng

doi:10.1016/j.gca.2019.08.002

Cited by 43 publications

(35 citation statements)

References 65 publications

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“…Since many studies rely upon trace element ratios as proxies to infer major element concentration of the Archean crust [15,16,17,18], it is critical to understand the relationship be- that would result from mantle melting calculated using pMELTS-mode alphaMELTS simulations [46,47] tween such ratios and SiO 2 if we wish to infer Archean crustal silica content in this way. To quantify such relationships, and any potential variation therein over time, we calculate the mean (for single elements), median (for ratios) and the 95% credible interval thereof for several elements and ratios binned as a function of SiO 2 , for four age intervals 0-1 Ga, 1-2 Ga, 2-3 Ga, and 3-4 Ga.…”

Section: Secular Variation As a Function Of Silica Contentmentioning

confidence: 99%

“…In an attempt to avoid preservation bias, many estimates of the composition of the Archean crust are based on the composition of terrigenous sediments, rather than directly upon the concentration of Archean igneous rocks [16,17,18,26,27,28]. While such an approach has advantages, it also brings risks.…”

Section: Atmospheric Oxygenation and Trace Element Ratios In Terrigenmentioning

confidence: 99%

“…In the absence of any consensus on the subsequent formation and growth of Earth's continental crust [10,11], two competing conceptual endmember models have emerged. In the first, what Moorbath [12] characterized as the majority view of continental crust growth, Earth features predominantly mafic crust, no plate tectonics, and (presumably) a less well regulated climate until sometime in the mid-Archean [e.g., 13,14,15,16,17,18]. The second more uniformitarian view posits felsic continental crust (and thus subduction) and relatively equable climate since and possibly during the Hadean [19,10,20,21].…”

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confidence: 99%

“…In comparison to currently quiescent worlds like Mars [23] or our Moon [24], most of Earth's crust is geologically young [25]. While this first-order challenge is well known, recent estimates of the composition of Earth's Archean crust have nonetheless reached widely divergent results, from mafic [15,16,17,18] to felsic [26,27,28].…”

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confidence: 99%

“…44,45], yet many estimates of Archean crustal composition rely critically on redox-sensitive trace element ratios in terrigenous sediments [e.g. 16,17,18].…”

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confidence: 99%

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Constraining crustal silica on ancient Earth

Keller

Harrison

2020

Proc. Natl. Acad. Sci. U.S.A.

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Accurately quantifying the composition of continental crust on Hadean and Archean Earth is critical to our understanding of the physiography, tectonics, and climate of our planet at the dawn of life. One longstanding paradigm involves the growth of a relatively mafic planetary crust over the first 1 to 2 billion years of Earth history, implying a lack of modern plate tectonics and a paucity of subaerial crust, and consequently lacking an efficient mechanism to regulate climate. Others have proposed a more uniformitarian view in which Archean and Hadean continents were only slightly more mafic than at present. Apart from complications in assessing early crustal composition introduced by crustal preservation and sampling biases, effects such as the secular cooling of Earth’s mantle and the biologically driven oxidation of Earth’s atmosphere have not been fully investigated. We find that the former complicates efforts to infer crustal silica from compatible or incompatible element abundances, while the latter undermines estimates of crustal silica content inferred from terrigenous sediments. Accounting for these complications, we find that the data are most parsimoniously explained by a model with nearly constant crustal silica since at least the early Archean.

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Section: Secular Variation As a Function Of Silica Contentmentioning

confidence: 99%

Section: Atmospheric Oxygenation and Trace Element Ratios In Terrigenmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

“…44,45], yet many estimates of Archean crustal composition rely critically on redox-sensitive trace element ratios in terrigenous sediments [e.g. 16,17,18].…”

mentioning

confidence: 99%

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