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Abstract Mantle plumes are responsible for the Earth’s largest volcanic provinces. In the prevailing paradigm, the deep mantle is less degassed than convecting shallow mantle, implying that plume-derived lavas have higher concentrations of primordial volatiles such as helium (He). Demonstrating this has led to explanations that question the established Earth model. Here, we show that the 3He/4He of basalts from the Red Sea display coherent relationships with trace elements, allowing the helium concentration of the Afar plume to be calculated. Contrary to the prevailing model it appears the helium concentration of the Afar plume is 10-25% of the upper mantle. This contradiction is resolved if the plume material itself is a mixture of helium-rich high-3He/4He deep mantle with helium-depleted low-3He/4He recently subducted oceanic crust. This implies that helium-depleted domains may exist in convecting mantle and that moderately high 3He/4He plumes likely do not contain a notable contribution of the deep mantle.

The Heimefrontfjella escarpment in Dronning Maud Land, East Antarctica divides inland precipitation-dominated ice dynamics from coastal dynamics dominated by grounding line migration, suggest inverse model simulations constrained by cosmogenic nuclide measurements.

Abstract The Atacama Desert is the driest and oldest desert on Earth. Despite the abundance evidence for long-term landscape stability, there are subtle signs of localised fluvial erosion and deposition since the onset of hyperaridity in the rock record. In the dry core of the Atacama Desert, pluvial episodes allowed antecedent drainage to incise into uplifting fault scarps, which in turn generated sinuous to meandering channels. Incision of ancient alluvial fan surfaces occurred during intermittent fluvial periods, albeit without signs of surface erosion. Fluvial incision during predominantly hyperarid climate periods is evident from these channels in unconsolidated alluvium. The absence of dense vegetation to provide bank stability and strength led us to investigate the potential role of regionally ubiquitous CaSO4-rich surface cover. This has enabled the preservation of Miocene surfaces and we hypothesize that it provided the required bank stability by adding strength to the upper decimetre to meter of incised alluvium to allow high sinuosity of stream channels to form during pluvial episodes in the Quaternary.

Testing feedbacks between climatic and geological processes are challenging. Here, the authors show that geomorphological features of the southern Red Sea margin are best interpreted by a feedback cycle between orographic precipitation, mid-ocean spreading and coastal magmatism, and that the feedback is enhanced by the trade wind.

Carbon capture and storage (CCS) is an industrial scale mitigation strategy for reducing anthropogenic CO2 from entering the atmosphere. However, for CCS to be routinely deployed, it is critical that the security of the stored CO2 can be verified and that unplanned migration from a storage site can be identified. A number of geochemical monitoring tools have been developed for this purpose, however, their effectiveness critically depends on robust geochemical baselines being established prior to CO2 injection. Here we present the first multi-well gas and groundwater characterisation of the geochemical baseline at the Carbon Management Canada Research Institutes Field Research Station. We find that all gases exhibit CO2 concentrations that are below 1%, implying that bulk gas monitoring may be an effective first step to identify CO2 migration. However, we also find that predominantly biogenic CH4 (∼90%–99%) is pervasive in both groundwater and gases within the shallow succession, which contain numerous coal seams. Hence, it is probable that any upwardly migrating CO2 could be absorbed onto the coal seams, displacing CH4. Importantly, 4He concentrations in all gas samples lie on a mixing line between the atmosphere and the elevated 4He concentration present in a hydrocarbon well sampled from a reservoir located below the Field Research Station (FRS) implying a diffusive or advective crustal flux of 4He at the site. In contrast, the measured 4He concentrations in shallow groundwaters at the site are much lower and may be explained by gas loss from the system or in situ production generated by radioactive decay of U and Th within the host rocks. Additionally, the injected CO2 is low in He, Ne and Ar concentrations, yet enriched in 84Kr and 132Xe relative to 36Ar, highlighting that inherent noble gas isotopic fingerprints could be effective as a distinct geochemical tracer of injected CO2 at the FRS.

Potentiating radiotherapy and chemotherapy by inhibiting DNA damage repair is proposed as a therapeutic strategy to improve outcomes for patients with solid tumors. However, this approach risks enhancing normal tissue toxicity as much as tumor toxicity, thereby limiting its translational impact. Using NU5455, a newly identified highly selective oral inhibitor of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) activity, we found that it was indeed possible to preferentially augment the effect of targeted radiotherapy on human orthotopic lung tumors without influencing acute DNA damage or a late radiation-induced toxicity (fibrosis) to normal mouse lung. Furthermore, while NU5455 administration increased both the efficacy and the toxicity of a parenterally administered topoisomerase inhibitor, it enhanced the activity of doxorubicin released locally in liver tumor xenografts without inducing any adverse effect. This strategy is particularly relevant to hepatocellular cancer, which is treated clinically with localized drug-eluting beads and for which DNA-PKcs activity is reported to confer resistance to treatment. We conclude that transient pharmacological inhibition of DNA-PKcs activity is effective and tolerable when combined with localized DNA-damaging therapies and thus has promising clinical potential., Introduction The activity of DNA-dependent protein kinase (DNA-PK) is essential to the repair of DNA double-strand breaks (DNA-DSBs) via canonical nonhomologous end joining (NHEJ) (1, 2). This repair mechanism involves [...]