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1. Radiogenic Power and Geoneutrino Luminosity of the Earth and Other Terrestrial Bodies Through Time

   https://doi.org/10.1029/2019GC008865  

   McDonough, W_F; Šrámek, O.; Wipperfurth, S_A (July 2020, Geochemistry, Geophysics, Geosystems)

   Abstract We report the Earth's rate of radiogenic heat production and (anti)neutrino luminosity from geologically relevant short‐lived radionuclides (SLR) and long‐lived radionuclides (LLR) using decay constants from the geological community, updated nuclear physics parameters, and calculations of theβspectra. We track the time evolution of the radiogenic power and luminosity of the Earth over the last 4.57 billion years, assuming an absolute abundance for the refractory elements in the silicate Earth and key volatile/refractory element ratios (e.g., Fe/Al, K/U, and Rb/Sr) to set the abundance levels for the moderately volatile elements. The relevant decays for the present‐day heat production in the Earth (19.9 ± 3.0 TW) are from⁴⁰K,⁸⁷Rb,¹⁴⁷Sm,²³²Th,²³⁵U, and²³⁸U. Given element concentrations in kg‐element/kg‐rock and densityρin kg/m³, a simplified equation to calculate the present‐day heat production in a rock isurn:x-wiley:ggge:media:ggge22244:ggge22244-math-0001 The radiogenic heating rate of Earth‐like material at solar system formation was some 10³to 10⁴times greater than present‐day values, largely due to decay of²⁶Al in the silicate fraction, which was the dominant radiogenic heat source for the first∼10 Ma. Assuming instantaneous Earth formation, the upper bound on radiogenic energy supplied by the most powerful short‐lived radionuclide²⁶Al (t_1/2= 0.7 Ma) is 5.5×10³¹ J, which is comparable (within a factor of a few) to the planet's gravitational binding energy. 

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2. Subaerial weathering drove stabilization of continents

   https://doi.org/10.1038/s41586-024-07307-1  

   Reimink, Jesse R; Smye, Andrew J (May 2024, Nature)

   Abstract Earth’s silica-rich continental crust is unique among the terrestrial planets and is critical for planetary habitability. Cratons represent the most imperishable continental fragments and form about 50% of the continental crust of the Earth, yet the mechanisms responsible for craton stabilization remain enigmatic¹. Large tracts of strongly differentiated crust formed between 3 and 2.5 billion years ago, during the late Mesoarchaean and Neoarchaean time periods². This crust contains abundant granitoid rocks with elevated concentrations of U, Th and K; the formation of these igneous rocks represents the final stage of stabilization of the continental crust^2,3. Here, we show that subaerial weathering, triggered by the emergence of continental landmasses above sea level, facilitated intracrustal melting and the generation of peraluminous granitoid magmas. This resulted in reorganization of the compositional architecture of continental crust in the Neoarchaean period. Subaerial weathering concentrated heat-producing elements into terrigenous sediments that were incorporated into the deep crust, where they drove crustal melting and the chemical stratification required to stabilize the cratonic lithosphere. The chain of causality between subaerial weathering and the final differentiation of Earth’s crust implies that craton stabilization was an inevitable consequence of continental emergence. Generation of sedimentary rocks enriched in heat-producing elements, at a time in the history of the Earth when the rate of radiogenic heat production was on average twice the present-day rate, resolves a long-standing question of why many cratons were stabilized in the Neoarchaean period. 

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3. What controlled the thickness of continental crust in the Archean?

   https://doi.org/10.1130/G50350.1  

   Mai, Vuong V.; Korenaga, Jun (June 2022, Geology)

   Abstract Exposed continents are one of Earth's major characteristics. Recent studies on ancient ocean volume and exposed landmasses suggest, however, that early Earth was possibly a water world, where any significant landmass was unlikely to have risen above sea level. On modern Earth, the thickness of continental crust seems to be controlled by sea level and the buoyancy of continental crust. Simply applying this concept to the Archean would not explain the absence of exposed continents, and we suggest that a third element that is currently insignificant was important during early Earth: the strength of continental upper crust. Based on the pressure imbalance expected at continent-ocean boundaries, we quantified the conditions under which rock strength controls the thickness of continental crust. With the level of radiogenic heat production expected for early Earth, continents may have been too weak to have maintained their thickness against a deep ocean. 

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4. A halogen budget of the bulk silicate Earth points to a history of early halogen degassing followed by net regassing

   https://doi.org/10.1073/pnas.2116083118  

   Guo, Meng; Korenaga, Jun (December 2021, Proceedings of the National Academy of Sciences)

   Halogens are important tracers of various planetary formation and evolution processes, and an accurate understanding of their abundances in the Earth’s silicate reservoirs can help us reconstruct the history of interactions among mantle, atmosphere, and oceans. The previous studies of halogen abundances in the bulk silicate Earth (BSE) are based on the assumption of constant ratios of element abundances, which is shown to result in a gross underestimation of the BSE halogen budget. Here we present a more robust approach using a log-log linear model. Using this method, we provide an internally consistent estimate of halogen abundances in the depleted mid-ocean ridge basalts (MORB)-source mantle, the enriched ocean island basalts (OIB)-source mantle, the depleted mantle, and BSE. Unlike previous studies, our results suggest that halogens in BSE are not more depleted compared to elements with similar volatility, thereby indicating sufficient halogen retention during planetary accretion. According to halogen abundances in the depleted mantle and BSE, we estimate that ∼87% of all stable halogens reside in the present-day mantle. Given our understanding of the history of mantle degassing and the evolution of crustal recycling, the revised halogen budget suggests that deep halogen cycle is characterized by efficient degassing in the early Earth and subsequent net regassing in the rest of Earth history. Such an evolution of deep halogen cycle presents a major step toward a more comprehensive understanding of ancient ocean alkalinity, which affects carbon partitioning within the hydrosphere, the stability of crustal and authigenic minerals, and the development of early life. 

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5. Protracted mantle heat conduction after lithospheric foundering beneath the Malagasy orogen

   https://doi.org/10.1130/G52316.1  

   Kaare-Rasmussen, Jonas; Horton, Forrest; Holder, Robert; Kylander-Clark, Andrew; Bouvier, Anne-Sophie; Müntener, Othmar; Rakotondrazafy, Michel (October 2024, Geology)

   Abstract Ultrahigh-temperature metamorphism (UHTM) is important for the evolution and long-term stability of continental crust. The Anosyen domain in southeastern Madagascar is a well-preserved UHTM terrane that formed during the amalgamation of Gondwana. The heat source(s) required to reach peak conditions is(are) a matter of debate. One potential cause of extreme crustal heating is the intrusion of mantle-derived melts into the crust. Foundering of the mantle lithosphere can also lead to increased heat flow. To assess the role of these heating mechanisms, we measured zircon δ18O, εHf(t) compositions, and U-Pb dates for plutonic rocks in the midcrustal UHTM domain. Our results indicate that pluton emplacement predated UHTM by as much as 40 m.y. and that all zircons have crustal O and Hf isotopic compositions. We propose that mantle lithosphere foundering caused melting in the lower crust, producing the magmas responsible for plutonism during the early stages of orogenesis. Prolonged conductive heating of the crust—combined with above-average radiogenic heating—may explain why UHTM occurred ∼40 m.y. after foundering. This suggests that foundering of the mantle lithosphere can swiftly lead to partial melting in the lower crust, as well as protracted heating of the middle crust that culminates tens of millions of years later. 

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