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Funding: This study was supported by urgency funding from the U.K.’s Science and Technology Facilities Council (STFC) as part of the project “Curation and Preliminary Examination of the Winchcombe Carbonaceous Chondrite Fall.” Additional work was funded by STFC through grants ST/N000846/1, ST/T002328/1, ST/T506096/1, and ST/W001128/1 (to L.D., M.R.L., and L.J.Ha.); ST/V000675/1 (to K.H.J. and R.H.J.); ST/P005225/1 (to R.T.); ST/S000348/1 (to M.V.G., P.J.W., and M.J.B.); ST/R00143X/1 (to J.B. and L.J.Hi.); ST/S000615/1 (to G.S.C.); ST/V000799/1 (to P.G.); and ST/V000888/1 (to T.E.). A.J.K. and H.C.B. acknowledge funding support from UK Research and Innovation (UKRI) grant MR/T020261/1. P.L.C. acknowledges funding support from UKRI grant MR/S03465X/1. K.H.J. acknowledges funding support from the Royal Society, grant URF\R\201009. L.J.Ha. and M.R.L. acknowledge funding from Natural Environment Research Council (NERC) National Environmental Isotope Facility (NEIF) grant no. 2406.0321. L.D., M.R.L., and L.J.Ha. acknowledge COVID-19 funding support from the University of Glasgow, UK. D.V. was supported in part by NASA cooperative agreement 80NSSC21M0073. P.P. and I.Sy. acknowledge funding from the VEGA agency, project no.1/0421/20. A.J.T.J. acknowledges support from the European Union and the State of Hungary, cofinanced by the European Regional Development Fund in the project of GINOP-2.3.2-15-2016-00009 “ICER.” P.M.S. acknowledges support from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 945298. FRIPON was initiated by funding from ANR (grant N.13-BS05-0009-03), carried out by the Paris Observatory, Muséum National d’Histoire Naturelle, Paris-Saclay University, and Institut Pythéas (LAM-CEREGE). FRIPON data are hosted and processed at Institut Pythéas SIP (Service Informatique Pythéas). The Desert Fireball Network team and Global Fireball Observatory are funded by the Australian Research Council (DP200102073). Direct links between carbonaceous chondrites and their parent bodies in the solar system are rare. The Winchcombe meteorite is the most accurately recorded carbonaceous chondrite fall. Its pre-atmospheric orbit and cosmic-ray exposure age confirm that it arrived on Earth shortly after ejection from a primitive asteroid. Recovered only hours after falling, the composition of the Winchcombe meteorite is largely unmodified by the terrestrial environment. It contains abundant hydrated silicates formed during fluid-rock reactions, and carbon- and nitrogen-bearing organic matter including soluble protein amino acids. The near-pristine hydrogen isotopic composition of the Winchcombe meteorite is comparable to the terrestrial hydrosphere, providing further evidence that volatile-rich carbonaceous asteroids played an important role in the origin of Earth's water. Publisher PDF

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.

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 CaSO

Landscape evolution is modulated by the regional tectonic uplift, climate change, and river dynamics. However, how to distinguish these mechanisms through the research of surface exhumation and fluvial incision remains controversial. In this study, cosmogenic 10Be, 26Al, and 21Ne concentrations in quartz from cave deposits, modern river sediments, and bedrocks were measured to constrain the applicability of cosmogenic 21Ne and discuss Quaternary landscape evolution history in the Guizhou Plateau, southeast China. Using the 26Al-10Be and 21Ne-10Be pairs to distinguish the cosmogenic 21Ne concentration from the excess 21Ne, we found that the nucleogenic 21Ne produced by the U and Th decay in quartz is significant in the samples although there is the possibility of inherited cosmogenic 21Ne. Combining with previous studies, we suggest that the precise approach for applying the cosmogenic 21Ne could be reached by (1) estimating the contribution from nucleogenic 21Ne, (2) avoiding samples with complex burial histories to exclude inherited cosmogenic 21Ne, and (3) combining the 10Be-26Al-21Ne nuclides method for the Quaternary samples. In addition, both pre-burial basin denudation rates and burial ages derived from the 26Al-10Be pair were used to determine the different timescale surface denudation rate and fluvial incision rate in relation to previous work. The consistency of the different timescales pre-burial basin denudation rate, 36Cl surface denudation rate, and modern basin denudation rate indicates that the landscape-scale surface denudation has been likely stabilized since the Quaternary in the Guizhou Plateau area. The slightly higher river incision rates than the local surface denudation rate show that the river dynamics may not have reached a steady-state due to the regional tectonic uplift in the Guizhou Plateau.

International audience; Rifting of the Red Sea resulted in the formation of one of the highest escarpments on our planet: the Great Escarpment of southwestern Saudi Arabia. Published low-temperature geochronology ages are around the Paleogene-Neogene transition, but geomorphic features like the height, the steepness and the preservation of the escarpment may indicate a younger aspect to the exhumation history. Here we use apatite fission track (AFT) and (U-Th-Sm)/He (AHe) cooling ages in combination with a geomorphic analysis of the region from Jeddah to Jizan to test this idea. Pooled AFT ages range from to Ma (1σ). The base of the AFT partial annealing zone prior to rock uplift is at ∼200 m elevation in most of the studied area, but track length data show that the amount of exhumation is insufficient to affect all coastal plain samples. Consistent with earlier estimates in the literature, the total amount of rock uplift is estimated to be ∼4 km. Single grain AHe ages range from to Ma (1σ) and do not have a clear trend with distance from the escarpment. Overall, the distribution of data appears to indicate widespread downwearing of the elevated topography around the rift flank. In contrast, geomorphic analysis that indicates escarpment retreat including a flexural uplift response. We suggest that the conflict between geomorphological and geochronological data can be resolved by invoking a two-stage erosion model. The first stage involved dome-shaped rift flank uplift since initiation of the Afar plume, downwearing of this topography and cooling recorded by the AFT ages. The second stage involved the massive erosion that excavated the present day Saudi escarpment and reset the AHe ages. We suggest that this second stage is related to the formation of oceanic lithosphere since 13 Ma in the Red Sea, associated downwarping of the margin and flexural updoming of the eastern rift flank. The consequential orographic precipitation initiated asymmetric erosion and formation of a retreating escarpment. This model is consistent with the large age difference between Miocene AFT and Pliocene AHe ages and the geomorphic metrics.

Basalts from high flux intra-plate volcanism (Iceland, Hawaii, Samoa) are characterised by 3He/4He that are significantly higher than those from the upper mantle sampled at mid-ocean ridges. The prevailing paradigm requires that a largely undegassed deep Earth is enriched in primordial noble gases (3He, 20Ne) relative to degassed convecting upper mantle. However, the He concentration and 3He/20Ne ratio of high 3He/4He oceanic basalts are generally lower than mid-ocean ridge basalts (MORB). This so called ‘He paradox’ has gained infamy and is used to argue against the conventional model of Earth structure and the existence of mantle plumes. While the paradox can be resolved by disequilibrium degassing of magmas it highlights the difficulty in reconstructing the primordial volatile inventory of the deep Earth from partially degassed oceanic basalts.Basalts from 26 to 11°N on the Red Sea spreading axis reveals a systematic southward increase in 3He/4He that tops out at 15 Ra in the Gulf of Tadjoura (GoT). The GoT 3He/4He overlaps the highest values of sub-aerial basalts from Afar and Main Ethiopian Rift and is arguably located over modern Afar plume. The along-rift 3He/4He variation is mirrored by a systematic change in incompatible trace element (ITE) ratios that appear to define two-component mixing between E-MORB and HIMU. Despite some complexity, hyperbolic mixing relationships are apparent in 3He/4He-K/Th-Rb/La space. Using established trace element concentrations in these mantle components we can calculate the concentration of He in the Afar plume mantle. Surprisingly it appears that the upwelling plume mantle has 5-20 times less He than the convecting asthenospheric mantle despite the high 3He/4He (and primordial Ne isotope composition). This contradicts the prevailing orthodoxy but can simply be explained if the Afar mantle plume is itself a mixture of primordial He-rich, high 3He/4He (55 Ra) deep mantle with a proportionally dominant mass of He-poor low 3He/4He HIMU mantle. This is consistent with the narrow range of Sr-Nd-Os isotopes and ITE ratios of the highest 3He/4He Afar plume basalts, and is in marked contrast to high 3He/4He plumes (e.g. Iceland) that do not have unique geochemical composition. The HIMU signature of the Afar plume basalts implies origin in recycled altered oceanic crust (RAOC). Assuming that no He is recycled and using established RAOC U and Th concentrations, the low He concentration (< 5 x 1013 atoms/g He) of the He-poor mantle implies that the slab was subducted no earlier than 70 Ma and reached no more than 700 km before being incorporated into the upwelling Afar plume. We suggest that the Afar plume acquired its chemical and isotopic fingerprint during large scale mixing at the 670 km transition zone with the Tethyan slab, not at the core-mantle boundary.This study implies that large domains of essentially He-poor mantle exist within the deep Earth, likely associated with the HIMU mantle compositions. Further, it implies that moderately high-3He/4He (< 30 Ra) mantle plumes (e.g. Reunion) need not contain a significant contribution of deep mantle, thus cannot be used a priori to define primitive Earth composition.

Much of the interior of the Tibetan Plateau is characterized by internal drainage, low relief topography, and high altitude. How and when this landscape formed is controversial. In this study, we use new zircon U-Pb data and low-temperature thermochronological data (apatite and zircon [U-Th/He], apatite fission track [AFT]) from the Late Cretaceous to Cenozoic Nima Basin sedimentary rocks and Xiabie granite in the adjacent Muggar Thrust hanging wall (part of the regional Shiquanhe-Gaize-Amdo thrust system), to determine the paleodrainage and timing of exhumation in the region. Individual AHe and ZHe cooling ages range from 9 to 60 Ma and 58 to 118 Ma, and the AFT ages range from 30 to 90 Ma. The thermal history derived from the Northern Nima Basin sediments and Xiabie granite require a period of exhumation between 70 and 40 Ma in the thrust fault hanging wall, and 40 and 30 Ma in the Nima Basin. Across the region, this event was followed by low rates of exhumation and the deposition of locally sourced sediment, lacustrine, and evaporitic deposits that are indicative of an internal drainage system. We suggest that the exhumation event is associated with development of thrust-elevated relief that may have disrupted the drainage network favoring the development of an endorheic system. This system, sediment accumulation, and/or post-30 Ma tectonic quiescence led to the generation of low relief topography.

The Taiwan orogenic belt has high precipitation and high exhumation rates (3–6 km/Myr), making it a natural laboratory for understanding how erosion, tectonics, and climate interact. Understanding how rock exhumation rates have evolved since the late Miocene is key to unraveling climate–tectonic interactions. In this study, we present 8 new zircon fission track (ZFT) and (Usingle bondTh)/He (ZHe) cooling ages (including 2 unreset ages) from 5 samples from 1700 to over 3300 m elevation around the highly incised Dajia River in the core of the Hsuehshan Range (termed the mid-HR in this study) in central Taiwan. Two of the ZFT and ZHe ages (5.3 Ma and 2.6 Ma) are the oldest ages recorded in this region. These ages suggest that the cooling rate of the mid-HR is lower than that of the Backbone Range and Yushan. With these and previously published cooling ages, we modeled the exhumation and cooling history using a 2-D thermal diffusion equation with time-varying erosion. The ZFT and ZHe ages are best explained by a steadily increasing exhumation rate up to 3.4 + 0.5/−0.3 km/Myr from 6.5 to 1 Ma. The exhumation rate in the last million years is not as well constrained but appears to have increased at a slower rate. Our findings differ from those of previous studies that propose that the exhumation rate increased rapidly in the last 1–2 Myr. We propose that the steady increase in the exhumation rate in the mid-HR indicates increasing topographic relief, which is likely caused by progressive crustal thickening.

Air-derived neon is used for routine calibration of magnetic sector mass spectrometers, principally for determining sensitivity and mass discrimination for Ne isotope determinations. The commonly accepted 21Ne/20Ne ratio of air (0.002959 ± 0.000022; Eberhardt et al. (1965) does not take account of the contribution of 20NeH+ at m/z = 21. Honda et al. (2015) and Wielandt and Storey (2019) have recently re-determined the 21Ne/20Neair by resolving 20NeH+ from 21Ne+. The 21Ne/20Neair values of the two studies differ by 1.8%, beyond the uncertainty of the measurements (±

Geological storage of carbon dioxide (CO

We report the synthesis of aromatic germanimines [(HMDS)2Ge═NAr] (Ar = Ph, Mes, Dipp; Mes = 2,4,6-Me3C6H2, Dipp = 2,6-iPr2C6H3) and an investigation into their associated reactivity. [(HMDS)2Ge═NPh] decomposes above -30 °C, while [(HMDS)2Ge═NDipp] engages in an intramolecular reaction at 60 °C. [(HMDS)2Ge═NMes] was shown to rearrange via a 1,3-silyl migration to give [(HMDS){(SiMe3)(Mes)N}Ge(NSiMe3)] in a 1:7 equilibrium mixture at room temperature. These latter germanimines react with unsaturated polar substrates such as CO2, ketones, and arylisocyanate via a [2 + 2] cycloaddition pathway.

We have measured the He isotope composition in detrital native gold, copper, silver, Pt3Fe and OsIr alloy grains from placer deposits in order to assess the extent to which cosmogenic He can be quantified and used to determine the exposure history of grains in sedimentary systems. 3He/4He ratios (0.1–273 Ra) exceed values typical of radiogenic He. 4He is dominantly the result of the decay of U and Th, or 190Pt in the case of Pt-rich alloys. 3He concentrations in grains from alluvial deposits range from 0.05 to 2 × 108 at g−1 and appears to be dominantly cosmogenic in origin. The absence of significant nucleogenic or mantle-derived 3He in metals is tentatively confirmed by the analysis of grains from underground mine workings. The implantation of cosmogenic He is not the main source of 3He in alluvial metals but can be relatively important for small grains. New GEANT4-based calculations predict the production rate of 3He (including in precursor 3H) from Au and Pt to be approximately 25 at g−1 yr. Using this we determine that cosmogenic 3He concentrations in the detrital grains record minimum exposure times of between 0.5 and 7 million years that generally increase with distance from the putative source. Paired fragments from three large grains show that there is considerable heterogeneity in cosmogenic He concentrations that may reflect the complex origin of detrital metal grains. This work suggests that cosmogenic He in detrital metals and minerals may find use for providing the chronology of sedimentary processes.

The polar climate of Antarctica results in the lowest erosion rates on Earth. The low long-term erosion history of high elevation mountain tops that are exposed above the ice preserve a record of climate change that can be accessed using cosmogenic nuclides. However, unravelling the complexity of the long-term denudation histories of Antarctic summits is frequently hampered by intermittent ice cover. The aim of this work is to identify denudation rate changes in a surface that has been continuously exposed since the middle Miocene. We have measured stable (3He) and radioactive (10Be) cosmogenic nuclides in olivine from lherzolite xenoliths from the summit of the Mount Hampton shield volcano within the West Antarctic Ice Sheet. The peak (3200 m) has never been covered by the current ice sheet and local ice caps, consequently the data record the subaerial erosion history of a mountain top within the Antarctic interior. The 10Be concentrations in the olivines yield minimum exposure ages (33 to 501 ka) that are significantly younger than those derived from the cosmogenic 3He (90 to 1101 ka). The data reveal a complex exposure history that provide an integrated long-term erosion rate of between 0.2 and 0.7 m/My that is most likely caused by mechanical weathering. Inverse modelling shows that the data are readily explained by episodic erosion, consisting of one to five erosion pulses that may record major regional climatic changes.

Cosmogenic nuclide burial dating provides an alternative method for sediment dating, and the combination of radionuclide 10Be with noble gas isotope 21Ne would theoretically extend the burial dating range up to around 15 Ma ago, which endows 10Be/21Ne pair with huge potential in middle-Miocene sediment dating. Especially in the magnetostratigraphic studies of the Cenozoic sedimentary strata, the 10Be/21Ne pair could be expected to provide absolute age marker when the well-dated volcanic ash layer or bedded mammalian fossils are absent. However, the validity and accuracy of the 10Be/21Ne burial dating when used close to its limiting middle Miocene ages has not been assessed in case study. Here, we show our dating results of the sedimentary stratum samples, which deposited at the same bedding of the Vertebrate fossils of Platybelodon tongxinensis that offer an independent age constraint between 12 and 15 Ma. The 10Be/21Ne analyses yielded a mean burial age of 13.25 ± 0.33 Ma, which agrees well with the paleontological proxy, and the MSWD value of 0.66 indicates the good agreement of the apparent dispersion of six aliquots data with their individual measurement errors. In view of the extended applicable dating range of 10Be/21Ne pair, it is promising in providing absolute age marker or valuable chronological information for a variety of fields in Earth science and beyond.

The application of cosmogenic noble gases (3He and 21Ne) in detrital grains to quantify sediment transport rates and storage timescales is largely undeveloped. We have previously shown that cosmogenic He can be measured in single grains (Yakubovich et al. 2019). The low He diffusion rate and the chemical and/or physical robustness of metal alloys (eg Au, Ag, Cu, Pt, Fe) means the technique has potential to determine how critical metals accumulate at the Earth surface. In an effort to determine how long detrital Pt-alloy grains spend travelling to placer deposits we have measured cosmogenic3He concentrations in 60 (0.5–7 mg) grains of isoferroplatinum (Pt3Fe) from the world largest alluvial Pt placer deposits in the Kondyor-Uorgalan rivers in Khabarovsk region, and the Is-Turinsk and Nyas’ma river systems in Middle Urals, Russia.In both systems, there are no significant cosmogenic 3He in the grains from the low order streams that drain the source rock. 3Hecosconcentrations in Pt grains from distant placers (30 km) varies in order of magnitude from 0.3 to 30 x 107at g-1in grains in Uorgalan river, 5 to 40 x 107at g-1in Glubokinskoe placer deposit (Is river) and 20 to 70 x 107at g-1in the Generalka deposit (Nyas’ma river). Converting this to surface residence times (P = 25 at g y-1, Yakubovich et al., 2019) yields model exposure durations of0.1­–10, 3–20 and 13–38 Myr for grains from the Uorgalan, Glubokinskoe and Generalka deposits respectively. Assuming that all grains were extracted from shielded locations this exposure ages indicate the total time of transport and residence of the grains on river bed surface prior to final deposition.Pt grains are added to the river system constantly. If we assume that the average transport conditions are essentially identical for all grains, then the difference between the maximum and minimum exposure ages within the same location indicates the total duration of placer supply from the source rock. For the Urals it is equal for 17–25 Myr, while for Kondyor-Uorgalan placer it is 10 Myr. This is in a good agreement with geological observations. Within Kondyor-Uorgalan placer deposit the age of the alluvium varies from Neogene to Quaternary, while in the Urals Pt-bearing Jurassic, Neogene and Quaternary fluvial sediments are distinguished within the placers.Paleo peneplain surfaces are established nearby the Kondyor massif and pre-date the most productive platinum sands. Several stages of peneplenisation are evident in the Urals from thick weathering crusts. The exposure ages indicate10’s million-year scale of transport/deposition histories of detrital Pt alloys, which might result of multiple redeposition of material during long term accumulation of cosmogenic 3He during peneplenisation. Yakubovich O., Stuart F.M., Nesterenok A. and Carracedo A. (2019). Chem. Geol. 517, 22-33.

The Guizhou Plateau represents a geomorphic transition between the Tibetan Plateau and the Yangtze River Plain. It likely formed in response to the propagation of surface uplift in southeastern Tibet during India-Eurasia continental collision. However, the uplift history of the region is unclear largely due to a lack of datable material. The bedrock geology is dominated by carbonate rocks, which contains numerous multi-level caves in the main river valleys that are linked to the river incision history. Cosmogenic 26Al and 10Be burial dating of sediments in caves and river terraces from the northwestern and southern plateau reveals the fluvial chronology and provides the first direct determination of long-term river incision rates. The caves and terraces on the Liuchong River in NW Guizhou yield burial ages of between 0.41 ± 0.12 Ma and 2.85 ± 0.21 Ma, indicating an average incision rate of 57 ± 3 m/Ma. Four level caves at Libo in southern Guizhou yield burial ages of between 0.56 ± 0.16 Ma and 3.54 (+0.25/-0.22) Ma, indicating slightly slower incision rate (47 ± 5 m/Ma). These new results imply that the high elevation of the Guizhou Plateau had developed before the Late Pliocene, and that surface uplift during the Late Cenozoic was largely uniform across the region.

Coalbed methane (CBM) is an important energy source globally, thus understanding its origin and evolution is essential to the assessment of reserves and developing exploration strategies. This study aims to identify the origin of CBM in Liupanshui Coalfield (LPC) in southern China and evaluate the influence of basin exhumation on gas storage in different rank coals. Ten CBM samples were collected from four blocks that have different thermal histories and coal rank ranges. Based on the C1/(C2+C3) ratio (16-971), δ13CCH4 (-42.9 to -34.9‰) and δDCH4 (-206 to -140‰), the methane is mainly thermogenic in origin. Systematic compositional differences between the four blocks are consistent with coal maturity. Noble gases in LPC CBM are a mixture of air-derived gas dissolved in local groundwaters and radiogenic gases that were generated in the coals and diffused in from deeper crust. The radiogenic 4He/40Ar* and 21Ne*/40Ar* are lowest in CBM from Qingshan block, strong evidence of diffusive loss of light noble gases. 20Ne/36Ar (0.23-0.70) in all gases are higher than local air-saturated water (0.16) and are most easily explained by re-dissolution of noble gases that exsolved from groundwater during basin inversion. 84Kr/36Ar and 132Xe/36Ar ratios are higher than predicted from this process and likely reflect desorption of Xe and Kr that has been trapped on the coal matrix at the time of coal desorption. The noble gases are consistent with gas exsolution and loss from the reservoir during Mesozoic-Cenozoic basin inversion. Modelling the loss of both free and adsorbed gas during basin inversion we find that the Qingshan block has lost the highest proportion of free gas (77%), yet the total gas loss (free and adsorbed) is the lowest (25%) due to the strong adsorption capacity of the mature coals. The volume of groundwater that has interacted with the gas phase during the basin inversion is estimated according to the re dissolution process model to evaluate the role of groundwater in gas preservation and gas extraction. Combining gas production data for the four blocks, high gas content and efficient gas extraction in LPC are expected for the high maturity coals that have seen low groundwater during basin inversion but more at shallow depth.

Reconstructing past ice surface changes is key to test and improve ice-sheet models. Yet, data constraining the past behaviour of the East Antarctic Ice Sheet are sparse, limiting our understanding of its response to past and future climate changes. Here, we attempt to test whether the ice-sheet margin in western Dronning Maud Land has thinned since the last glacial maximum or whether it perhaps thickened in places due to increased precipitation associated with warmer climates. We report cosmogenic multi-nuclide (10Be, 26Al, 36Cl, 21Ne) data from bedrock and erratics on nunataks along Jutulstraumen ice stream and the Penck Trough in western Dronning Maud Land, East Antarctica. Spanning elevations between 751-2387 m above sea level, and between 5 and 450 m above the contemporaneous local ice sheet surface, the samples record apparent exposure ages between 2 ka and 5 Ma. The highest bedrock sample indicates (near-) continuous exposure since at least the Pliocene, with a very low apparent erosion rate of 15±3 cm Ma-1. However, there are also clear indications of a thicker-than-present ice sheet within the last glacial cycle, thinning ~35-120 m at several nunataks during the Holocene (~2-11 ka). Owing to difficulties in retrieving suitable sample material from the often rugged and quartz-poor mountain summits, and due to the presence of inherited nuclides in many of our samples, we are unable to present robust thinning estimates from elevational profiles. Nevertheless, the results clearly indicate ice-surface fluctuations of several hundred meters within the last glacial cycle in this sector of the EAIS, between the current grounding line and the edge of the polar plateau. Finally, inverse modelling of the cosmogenic multi-nuclide inventories in bedrock yields estimates of total erosion and ice cover across multiple glacial cycles. Our results show that the EAIS in western Dronning Maud Land was thicker than present during most of the Quaternary, covering sample sites up to 200 m above the present-day ice sheet for ~80 % of this period. Thinning of the ice since the last glacial maximum, combined with a long-term record of thicker-than-present ice, indicate that the ice sheet below the polar plateau in western Dronning Maud Land generally expands and thickens during climate cooling, despite decreasing precipitation associated with a cooler Southern Ocean.

Knowledge of the geological history of the Tibetan plateau is critical to understanding crustal deformation process, and the plateau’s influence on climate. However, the timing of Tibetan plateau development remains controversial. The Nima Basin along the Jurassic-Cretaceous Bangong Suture in central Tibet provides well-dated records of exhumation in this area. Here, we present detrital zircon U-Pb, apatite U-Th/He (AHe) and apatite fission track data (AFT) from upper Cretaceous and Oligocene red sandstones and conglomerates in the Nima Basin, as well as from the Xiabie granite in the hanging wall of the basin-bounding Muggar Thrust. 4 granite conglomerate clasts from the above yield zircon U-Pb ages ranging between 114-122 Ma, which likely come from the Xiabie granite. 7 granitoid/sandstone conglomerate clasts yield AHe ages ranging from 21-58 Ma, while AFT ages range from 34-83 Ma. Thermal history inversion modelling for five of the above samples show a consistent rapid cooling from 100 ℃ to 30 ℃ between 50-40 Ma, the cooling rate decreased significantly after 40 Ma. Implications of these data, integrated in the context of previously published data for the wider region (e.g. Rohrmann et al. 2012; Haider et al., 2013; Li et al., 2019) will be discussed. ReferenceRohrmann, A et al., 2012, Thermochronologic evidence for plateau formation in central Tibet by 45 Ma: Geology, v. 40, p. 187-190.Haider, V. L et al., 2013, Cretaceous to Cenozoic evolution of the northern Lhasa Terrane and the Early Paleogene development of peneplains at Nam Co, Tibetan Plateau: Journal of Asian Earth Sciences, v. 70-71, p. 79-98.Li, H. A et al., 2019, The formation and expansion of the eastern Proto-Tibetan Plateau: Insights from low-temperature thermochronology: Journal of Asian Earth Sciences, v. 183, 103975.

The source of metal and sulphur in porphyry and related epithermal deposits is a long debated issue. The role of mantle-derived magmas in providing the metals has proved particularly problematic. Here we report new He and Ar isotope determinations from ore fluids from the Zijinshan high sulfidation-epithermal Cu-Au deposit and Wuziqilong transitional Cu deposit from the giant Zijinshan porphyry-epithermal Cu-Au-Mo-Ag ore system (from 105 to 91 Ma), to decipher the contribution of mantle-derived volatiles and heat. Hydrothermal fluids in pyrite and digenite have 3He/4He up to 5.7 Ra, among the highest measured in ancient ore-forming fluids. A linear correlation between He and Ar isotopes indicate that the ore fluids were, to a first order, a mixture between a shallow crustal fluid, with low 3He/4He, and a dominantly mantle-derived fluid with high 3He/4He. The mantle 3He/4He is close to values typical of the upper mantle indicating the initial magmas that provided the heat for hydrothermal systems did not assimilate large volumes of continental crust. The ore-forming fluids have 3He/heat ratios that are 10 to 80 times higher than that of mid-oceanic ridge hydrothermal fluids, indicating that the metal-bearing fluids acquired heat and volatiles in a convective, rather than conductive, hydrothermal regime. It appears that mantle-derived volatiles, heat and probably metals have made a major contribution to the Cu-Au-Mo-Ag mineralization in the Zijinshan orefield.

The recent mineral exploration programme (2009–2014) in the Jiaodong gold province identified the new Guocheng-Liaoshang gold metallogenic belt which contains reserves of 92 tonnes (t) Au. In the main deposits the ore is fault-hosted in massive sulfides that make up to 25 to 95 vol%. The He-Ar isotope compositions of ore-forming fluids from 20 pyrite samples from the five main deposits are reported here. 3 He/ 4 He range between 0.41 and 2.39 R a , 40 Ar/ 36 Ar are 367 to 2112 and 40 Ar ⁎ / 4 He are 0.40–3.78. The data require four gas sources; a dominant mantle-derived component plus sub-ordinate crustal radiogenic, meteoric and basin brine components. The mantle end-member has 3 He/ 4 He (3.32–4.00 R a ). This is lower than most estimates for sub-continental lithospheric mantle (SCLM: 6–7 R a ), implying that it was probably refertilized by subduction-related fluid metasomatism. This is consistent with He-Ar isotopes reported for SCLM xenoliths from basalts in the Shandong Province. Within the mineralisation province, the mine Au reserve is positively correlated with the proportion of mantle-derived He in the ore-forming fluids. This implies that the fluids, and by inference the gold, was largely derived from mantle melts during lithospheric extension. Given the conspicuous association of gold ore deposits with mantle-derived magma in the Jiaodong Peninsula, we envisage that our genetic model can be applied, to some extent, to evaluate the potential of some mineral exploration targets.

Cosmogenic nuclide exposure dating of ancient shoreline terraces of the Quillagua-Llamara Soledad Lake in the central Atacama Desert of northern Chile provides new insights in the paleohydrology of the driest desert on Earth. The lake developed in a paleo-endorheic drainage system in the Central Depression prior to draining into the Pacific due to incision of the Rio Loa canyon. The durations of lake stages were sufficiently long to form wave-erosion induced shoreline terraces on the wind-exposed slopes of former islands. Successively younger shoreline levels are preserved over an elevation range of 250 m due to progressive uplift of the islands coeval with the lake stages. Cosmogenic 10Be- and 21Ne-derived exposure ages of the shorelines reveals that the hyperarid conditions in the Rio Loa catchment were interspersed by several pluvial stages during the Pliocene and Pleistocene, which generated a large and persistent lake in the Quillagua-Llamara basin. The exposure ages of the final lake stage provide the maximum age for the incision of the Rio Loa canyon (274 ± 74 ka) and the subsequent breaching of the Coastal Cordillera.

Noblesse multi-collector noble gas mass spectrometer is specially designed for multi-collection of Ar isotopes with different beam sizes, especially for small ion beams, precisely, and hence is perfectly suitable for 40Ar/39Ar geochronology. We have analyzed widely used sanidine, muscovite, and biotite standards with recommended ages of ~ 1.2–133 Ma, with the aim to assess the reliability of Noblesse for 40Ar/39Ar dating. An ESI MIR10 30W CO2 laser was used for total fusion or incremental heating samples. Extracted gases were routinely purified by four SAES NP10 getters (one at ~ 400 °C and others at room temperature). A GP50 getter and a metal cold finger cooled by liquid N (− 196 °C) were also attached for additional purification if necessary. The Ar isotopes were then measured by Noblesse using Faraday or multiplier according to the signal intensities. Over a period of 1.5 months 337 air calibrations produced a weighted mean 40Ar/36Ar of 296.50 ± 0.08 (2σ, MSWD = 4.77). Fish Canyon sanidine is used to calculate J-values, which show good linear relationship with position in irradiation. The age of four mineral standards (Alder Creek sanidine, Brione muscovite, Yabachi sanidine, and Fangshan biotite) are within error of the accepted ages. Five Alder Creek sanidine aliquots yielded an age range of 1.174–1.181 ± 0.013 Ma (2σ) which broadly overlaps the established age of the standard and the uncertainty approaches those of the foremost Ar/Ar laboratories in the world. The weighted mean ages of four Brione muscovite aliquots (18.75 ± 0.16 Ma, 2σ), five Yabachi sanidine aliquots (29.50 ± 0.19 Ma, 2σ), and three Fangshan biotite aliquots (133.0 ± 0.76 Ma, 2σ) are consistent with the recommended values of these standards, and the uncertainties are typical of modern Ar/Ar laboratories world-wide.

In order to unravel aspects of the Miocene landscape evolution of the eastern European Alps, we present geomorphic and isotopic data from the western Niedere Tauern region (Austria). The region is critical for such interpretations, because it is one of the few regions along the topographic axis of the Eastern Alps where the highest peaks (up to 2500 m a.s.l.) are dominated by limestone. As such, the region contains a record of Miocene landscape-forming events that survived the Pleistocene glaciations, not preserved elsewhere in the central Eastern Alps. This record includes karst caves, karstified planation surfaces and crystalline fluvial pebbles (Augenstein Formation) preserved on planation surfaces and in karst caves. Caves in the region occur in three distinct levels that correlate with well-known cave levels in the Northern Calcareous Alps, although they are somewhat higher in the Niedere Tauern. In part, these cave elevations also correlate with three planation surfaces and knickpoints of major streams draining the region, testifying their pre-glacial origin. We report details of a karst cave (Durchgangshohle) from the highest cave level located at 2340 m a.s.l. In this cave, allochthonous fluvial gravels are present, overgrown by speleothems. One speleothem yielded an early middle Pleistocene U-Pb age (682 ± 17 ka). We regard this as a minimum age for the erosion of the fluvial cave deposits during Marine Isotope Stages 17 or 16. Carbon and oxygen isotope data of these speleothems imply a climate that is consistent with this interpretation. Cosmogenic 21 Ne data of fluvial quartz clasts collected from the surface on plateaus of the Northern Calcareous Alps suggest minimum exposure durations of 115 and 262 ka. They probably reflect successive exposure since removal of the sediment cover of the Oligocene Augenstein Formation during the Pleistocene. While our geochronological data fail to record aspects of the earlier Miocene uplift history, they are consistent with the overall geomorphic history inferred from the geomorphic markers. This suggests that the Niedere Tauern share a common uplift history with the Northern Calcareous Aps and implies a moderate south-north topographic gradient that has been maintained since the Miocene.

The thermal evolution of distal domains along rifted margins is at present poorly constrained. In this study, we show that a thermal pulse, most likely triggered by lithospheric thinning and asthenospheric rise, is recorded at upper crustal levels and may also influence the diagenetic processes in the overlying sediments, thus representing a critical aspect for the evaluation of hydrocarbon systems. The thermal history of a distal sector of the Alpine Tethys rifted margin preserved in the Ligurian Alps (Case Tuberto-Calizzano unit) is investigated with thermochronological methods and petrologic observations. The studied unit is composed of a polymetamorphic basement and a sedimentary cover, providing a complete section through the prerift, synrift, and postrift system. Zircon fission track analyses on basement rocks samples suggest that temperatures exceeding~240 ± 25°C were reached before~150-160 Ma (Upper Jurassic) at few kilometer depth. Neoformation of green biotite, stable at temperatures of~350 to 450°C, was synkinematic with this event. The tectonic setting of the studied unit suggests that the heating-cooling cycle took place during the formation of the distal rifted margin and terminated during Late Jurassic (150-160 Ma). Major crustal and lithospheric thinning likely promoted high geothermal gradients (~60-90°C/km) and triggered the circulation of hot, deep-seated fluids along brittle faults, causing the observed thermal anomaly. Our results suggest that rifting can generate thermal perturbations at relatively high temperatures (between~240 and 450°C) at less than 3 km depth in the distal domains during major crustal thinning preceding breakup and onset of seafloor spreading.

The giant sediment-hosted Jinding zinc-lead deposit is located in the Lanping Basin, northwestern Yunnan Province, China. The genesis of the deposit has long been debated and the sources of the ore-forming fluids and metals are controversial. This study presents rare earth element (REE) and noble gas isotope data that constrain the origins of the ore fluids and the heat source driving the hydrothermal circulation. The early-stage sulfides are enriched in light REEs and have high ∑REE values (30.8–94.8 ppm) and weakly negative Eu (δEu 0.85–0.89) and Ce anomalies (δCe 0.84–0.95), suggesting that the fluids were likely derived from dissolution of Upper Triassic marine carbonates with input of REEs from aluminosilicate rocks in the basin. In contrast, the late-stage sulfides have irregular REE patterns, generally low ∑REE values (0.24–10.8 ppm) and positive Eu (δEu 1.22–10.9) and weakly negative Ce anomalies (δCe 0.53–0.90), which suggest that the ore-forming fluids interacted with evaporite minerals. The 3 He/ 4 He (0.01–0.04 R a ) and 40 Ar/ 36 Ar values (301–340) of the ore-forming fluids indicate crustal and atmospheric origins for these noble gases. These findings are in agreement with the published fluid inclusion microthermometry data and the results of H, O, C, S, Pb and Sr isotope studies. Our data, in combination with published results, support a two-stage hydrothermal mineralization model, involving early-stage basinal brines and late-stage meteoric water that acquired metals and heat from crustal sources.

Jeju Island, South Korea, is a Cenozoic intraplate volcano located in East Asia. The Jeju basalts display ocean island basalt (OIB)-like trace element patterns and enriched mantle type 2 (EM2) radiogenic isotope compositions, but the source that enriched the mantle remains unclear. Here we report new geochemical compositions of basalts and xenoliths, including the first helium isotope and element analysis of olivine phenocrysts to constrain the source of basalt. Olivines in the Jeju basalts have 3He/4He ratios of 3.5 to 7.3 Ra while olivines in the mantle xenoliths are 2.9 to 6.3 Ra. They provide no evidence of a lower mantle plume but overlap the range of the regional subcontinental lithospheric mantle (SCLM) and OIBs with low 3He/4He values. Olivine phenocrysts included in the basalts show variations in Mn, Ni, and Ca concentrations with forsterite (Fo) contents, similar to the trend for olivines crystallized from the pyroxenite-derived melts. Elemental ratios of Ca-Fe-Ni-Mg-Mn for the olivines also indicate the pyroxenite contribution. Considering our results, it is suggested that the main source of the Jeju basalts is the SCLM containing pyroxenite. In addition, the tomography image shows the low-velocity zone extending to the asthenosphere mantle beneath the central Jeju Island. This implies that the localized asthenospheric upwelling is caused by edge-driven convection, and the high-velocity zones exist around Jeju island indicating a thick cratonic lithosphere. Therefore, we propose that the interaction between the SCLM component containing pyroxenite and the rising asthenosphere is the main mechanism to generate enriched basaltic magmas for the Cenozoic intraplate volcanism in East Asia, including Jeju Island.

Extensive intraplate volcanism in the East Asia regions, including Dokdo and Ulleungdo (DU), occurred due to the extensional stress field during the Cenozoic era. However, the origin of magmatism is still controversial. Here we report new results of helium isotopes in olivine and clinopyroxene phenocrysts as well as major and trace element compositions from the DU basalts in order to determine the origin of the DU magmas and provide insights into Cenozoic mantle dynamics in East Asia. The DU volcanic islands were formed by magmatism after opening of the East Sea (Sea of Japan), a back-arc basin behind the Japanese arc, and are currently located in the Ulleung basin, one of sub-basins of the East Sea. The 3He/4He ratios range from 5.7 to 5.9 Ra for Dokdo and 4.5 to 6.0 Ra for Ulleungdo, respectively, similar to the sub-continental lithospheric mantle (SCLM) range of East Asia (4.6 to 7.7 Ra). Helium isotope compositions indicate that the depleted asthenosphere or the lower mantle plume might not be the direct source of the DU magmas. Also, there is no geochemical evidence that the DU magmas were influenced by subduction-derived components or the HIMU mantle source. Hence, we argue that SCLM provided enriched geochemical features in the DU basalts, contrary to basalts from other back-arc basins composed of the oceanic crust. In this respect, it is likely that the extended SCLM may still remain beneath the Ulleung basin. Our helium isotope and trace element mixing model shows the mixing trend between the metasomatized lithospheric melts and the asthenospheric melts. In addition, the presence of the low-velocity zone beneath the surface of the DU volcanoes in seismic tomography implies that the magmas were formed through the lithospheric melting due to the hot asthenospheric upwelling. Therefore, our study shows that the DU volcanism was mainly contributed by SCLM and that the lithosphere-asthenosphere interaction was the main mechanism that led to the Cenozoic magmatism in East Asia.

Cosmogenic Ne isotopes are stable and are routinely used for constraining the timing of events and the rate of surface change beyond the limit that can be studied with radionuclides 10Be, 26Al, and 36Cl. Cosmogenic Ne analysis can be used in quartz and in a range of other minerals. Analysis typically requires significantly less material than do cosmogenic 10Be and 26Al, opening up the technique for small samples—individual pebbles in river sediments, for example. Analysis is easier and faster than for radionuclides, not least because Ne measurements do not require significant chemical procedures. However, the presence of other sources of Ne in minerals tends to restrict the use of cosmogenic 21Ne to old landscapes and long exposure durations. In this review we briefly outline the background of cosmogenic Ne production in rocks and minerals at the Earth’s surface, then document the key uses of the technique by highlighting some earlier studies, and finish with a short perspective on the future of the technique.

The northern Central Indian Ridge (CIR) between 8°S and 17°S is composed of seven segments whose spreading rates increase southward from ∼35 to ∼40 mm/yr. During expeditions of R/V Onnuri to study hydrothermal activity on the northern CIR in 2009–2011, high-resolution multibeam mapping was conducted and ridge axis basalts were dredged. The major and trace element and Sr-Nd-Pb-He isotopic compositions of basaltic glasses dredged from the spreading axis require three mantle sources: depleted mantle and two distinct enriched mantle sources. The southern segments have Sr, Nd, and Pb that are a mix of depleted mantle and an enriched component as recorded in southern CIR MORB. This enrichment is indistinguishable from Reunion plume mantle, except for He isotopes. This suggests that the southern segments have incorporated a contribution of the fossil Reunion plume mantle, as the CIR migrated over hot-spot-modified mantle. The low 3He/4He (7.5–9.2 RA) of this enriched component may result from radiogenic 4He ingrowth in the fossil Reunion mantle component. Basalts from the northern segments have high 206Pb/204Pb (18.53–19.15) and low 87Sr/86Sr (0.70286–0.70296) that are distinct from the Reunion plume but consistent with derivation from mantle with FOZO signature, albeit with 3He/4He (9.2–11.8 RA) that are higher than typical. The FOZO-like enriched mantle cannot be attributed to the track of a nearby mantle plume. Instead, this enrichment may have resulted from recycling oceanic crust, possibly accompanied by small plume activity.

Industrial scale carbon capture and storage technology relies on the secure long term storage of CO2 in the subsurface. The engineering and safety of a geological storage site is critically dependent on how and where CO2 will be stored over the lifetime of the site. Hence, there is a need to determine how injected CO2 is stored and identify how injected CO2 interacts with sub-surface fluids. Since July 2008 ∼1 Mt of CO2 has been injected into the Cranfield enhanced oil recovery (EOR) field (MS, USA), sourced from a portion of the natural CO2 produced from the nearby Jackson Dome CO2 reservoir. Monitoring and tracking of the amount of recycled CO2 shows that a portion of the injected CO2 has been retained in the reservoir. Here, we show that the noble gases (20Ne, 36Ar, 84Kr, 132Xe) that are intrinsic to the injected CO2 can be combined with CO2/3He and δ13CCO2 measurements to trace both the dissolution of the CO2 into the formation water, and the interaction of CO2 with the residual oil. Samples collected 18 months after CO2 injection commenced show that the CO2 has stripped the noble gases from the formation water. The isotopic composition of He suggests that ∼0.2%, some 7 kt, of the injected CO2 has dissolved into formation water. The CO2/3He and δ13CCO2 values imply that dissolution is occurring at pH = 5.8, consistent with the previous determinations. δ13CCO2 measurements and geochemical modelling rule out significant carbonate precipitation and we determine that the undissolved CO2 after 18 months of injection (1.5 Mt) is stored by stratigraphic or residual trapping. After 45 months of CO2 injection, the noble gas concentrations appear to be affected by CO2-oil interaction, overprinting the signature of the formation water.

The timing and mechanisms involved in creating the elevated, low-relief topography of the South African plateau remains unresolved. Here we constrain the thermal history of the southwest African plateau since 300 Ma using apatite fission track (AFT) and (U-Th-Sm)/He (AHe) thermochronology. Archaean rocks from the centre of the Kaapvaal Craton yield AFT ages of 331.0 ± 11.0 and 379.0 ± 23.0 Ma and mean track lengths (MTL) of 11.9 ± 0.2 and 12.5 ± 0.3 µm. Towards the southwest margin of the craton and in the adjacent Palaeozoic mobile belt, AFT ages are significantly younger and range from 58.9 ± 5.9 to 128.7 ± 6.3 Ma, and have longer MTLs (>13 µm). The range of sampleAHe ages complements the AFT ages and single grain AHe ages for most samples are highly dispersed. Results from joint inverse modelling of these data reveal that the centre of the craton has resided at near surface temperatures (

Mantle plumes have been proposed to exert a first-order control on the morphology of Earth's surface. However, there is little consensus on the lifespan of the convectively supported topography. Here, we focus on the Cenozoic uplift and exhumation history of the British Isles. While uplift in the absence of major regional tectonic activity has long been documented, the causative mechanism is highly controversial, and direct exhumation estimates are hindered by the near-complete absence of onshore post-Cretaceous sediments (outside Northern Ireland) and the truncated stratigraphic record of many offshore basins. Two main hypotheses have been developed by previous studies: epeirogenic exhumation driven by the proto-Iceland plume, or multiple phases of Cenozoic compression driven by far-field stresses. Here, we present a new thermochronological dataset comprising 43 apatite fission track (AFT) and 102 (U–Th–Sm)/He (AHe) dates from the onshore British Isles. Inverse modelling of vertical sample profiles allows us to define well-constrained regional cooling histories. Crucially, during the Paleocene, the thermal history models show that a rapid exhumation pulse (1–2.5 km) occurred, focused on the Irish Sea. Exhumation is greatest in the north of the Irish Sea region, and decreases in intensity to the south and west. The spatial pattern of Paleocene exhumation is in agreement with the extent of magmatic underplating inferred from geophysical studies, and the timing of uplift and exhumation is synchronous with emplacement of the plume-related British and Irish Paleogene Igneous Province (BIPIP). Prior to the Paleocene exhumation pulse, the Mesozoic onshore exhumation pulse is mainly linked to the uplift and erosion of the hinterland during the complex and long-lived rifting history of the neighbouring offshore basins. The extent of Neogene exhumation is difficult to constrain due to the poor sensitivity of the AHe and AFT systems at low temperatures. We conclude that the Cenozoic topographic evolution of the British Isles is the result of plume-driven uplift and exhumation, with inversion under compressive stress playing a secondary role.

Apatite fission track (AFT) and (U-Th)/He (AHe) thermochronometry data are reported and used to unravel the exhumation history of crystalline basement rocks from the elevated (>1000 m a.s.l.), but low relief Tanzanian Craton. Coeval episodes of sedimentation documented within adjacent Paleozoic to Mesozoic basins of southern Tanzania and the Congo basin of the Democratic Republic of Congo (DRC) indicate that most of the cooling in the basement rocks in Tanzania was linked to erosion. Basement samples were from an exploration borehole located within the craton, and up to 2200 m below surface. Surface samples were also analysed. AFT dates range between 317 ± 33 Ma and 188 ± 44 Ma. Alpha (Ft)-corrected AHe dates are between 433 ± 24 Ma and 154 ± 20 Ma. Modelling of the data reveals two important periods of cooling within the craton; one during the Carboniferous-Triassic (340 -220 Ma) and a later, less well constrained episode, during the late Cretaceous. The later exhumation is well detected proximal to the East African Rift (70 Ma). Thermal histories combined with the estimated geothermal gradient of 9 °C/km constrained by the AFT and AHe data from the craton and a mean surface temperature of 20 °C, indicate removal of up to 9 ± 2 km of overburden since the end-Paleozoic. The correlation of erosion of the craton and sedimentation and subsidence within the Congo basin in the Paleozoic may indicate regional flexural geodynamics of the lithosphere due to lithosphere buckling induced by far-field compressional tectonic processes, and thereafter through deep mantle upwelling and epeirogeny tectonic processes.

The isotopic composition of the noble gases, in particular Ar, in samples of ancient atmosphere trapped in rocks and minerals provides the strongest constraints on the timing and rate of Earth atmosphere formation by degassing of the Earth's interior. We have re-measured the isotopic composition of argon in the Rhynie chert from northeast Scotland using a high precision mass spectrometer in an effort to provide constraints on the composition of Devonian atmosphere. Irradiated chert samples yield 40Ar/36Ar ratios that are often below the modern atmosphere value. The data define a 40Ar/36Ar value of 289.5 ± 0.4 at K/36Ar = 0. Similarly low 40Ar/36Ar are measured in un-irradiated chert samples. The simplest explanation for the low 40Ar/36Ar is the preservation of Devonian atmosphere-derived Ar in the chert, with the intercept value in 40Ar–39Ar–36Ar space representing an upper limit. In this case the Earth's atmosphere has accumulated only 3% ( 5.1 ± 0.4 × 10 16 mol ) of the total 40Ar inventory since the Devonian. The average accumulation rate of 1.27 ± 0.09 × 10 8 mol 40Ar/yr overlaps the rate over the last 800 kyr. This implies that there has been no resolvable temporal change in the outgassing rate of the Earth since the mid-Palaeozoic despite the likely episodicity of Ar degassing from the continental crust. Incorporating the new Devonian atmosphere 40Ar/36Ar into the Earth degassing model of Pujol et al. (2013) provides the most precise constraints on atmosphere formation so far. The atmosphere formed in the first ∼100 Ma after initial accretion during a catastrophic degassing episode. A significant volume of 40Ar did not start to accumulate in the atmosphere until after 4 Ga which implies that stable K-rich continental crust did not develop until this time.

A comprehensive petrological and geochemical dataset is reported in order to define the thermo-compositional characteristics of Ti (Fe)-enriched picrite–basalt lavas (HT2, TiO 2 3–7 wt%), erupted close to the axial zone of the inferred Afar mantle plume, at the centre of the originally continuous Ethiopian–Yemeni CFB plateau (ca. 30 Ma) which is zonally arranged with progressively lower Ti basalts (HT1, TiO 2 2–4 wt%; LT, TiO 2 1–3 wt%) toward the periphery. Integrated petrogenetic modelling based on major and trace element analyses of bulk rocks, minerals, and melt inclusions in olivines, as well as Sr–Nd–Pb–He–O isotope compositional variations enables us to make several conclusions. 1) The phase equilibria constraints indicate that HT2 primary picrites were generated at ca. 1570 °C mantle potential temperatures ( T p ) in the pressure range 4–5 GPa whereas the HT1 and LT primary melts formed at shallower level ( T p 1530 °C for HT1 and 1430 °C for LT). Thus, the Afar plume head was a thermally and compositionally zoned melting region with maximum excess temperatures of 300–350 °C with respect to the ambient mantle. 2) The HT2 primary melts upwelled nearly adiabatically to the base of the continental crust (ca. 1 GPa) where fractionation of olivine, followed by clinopyroxene, led to variably differentiated picritic and basaltic magmas. 3) Trace element modelling requires that the primary HT2 melts were generated—either by fractional or batch melting (F 9–10%)—from a mixed garnet peridotite source (85%) with 15% eclogite (derived from transitional MORB protoliths included in Panafrican terranes) that has to be considered a specific Ti–Fe and incompatible element enriched component entrained by the Afar plume. 4) The LT, HT1, and HT2 lavas have 143 Nd/ 144 Nd = 0.5131–0.5128, whereas Sr–Pb isotopes are positively correlated with TiO 2 , varying from 87 Sr/ 86 Sr 0.7032 and 206 Pb/ 204 Pb 18.2 in LT basalts to 87 Sr/ 86 Sr 0.7044 and 206 Pb/ 204 Pb 19.4 in HT2 picrite–basalts. High 3 He/ 4 He (15–20 R A ) ratios are exclusively observed in HT2 lavas, confirming earlier evidence that these magmas require a component of deep mantle in addition to eclogite, while the LT basalts may more effectively reflect the signature of the pre-existing mantle domains. The comparison between high-MgO (13–22%) lavas from several Phanerozoic CFB provinces (Karoo, Parana–Etendeka, Emeishan, Siberia, Deccan, North Atlantic Province) shows that they share extremely high mantle potential temperatures ( T p 1550–1700 °C) supporting the view that hot mantle plumes are favoured candidates for triggering many LIPs. However, the high incompatible element and isotopic variability of these high-MgO lavas (and associated CFB) suggest that plume thermal anomalies are not necessarily accompanied by significant and specific chemical effects, which depend on the nature of mantle materials recycled during the plume rise, as well as by the extent of related mantle enrichments (if any) on the pre-existing lithospheric section.

Measurements of Xe isotope ratios in ocean island basalts (OIB) suggest that Earth’s mantle accreted heterogeneously, and that compositional remnants of accretion are sampled by modern, high-3He/4He OIB associated with the Icelandic and Samoan plumes. If so, the high-3He/4He source may also have a distinct oxygen isotopic composition from the rest of the mantle. Here, we test if the major elements of the high-3He/4He source preserve any evidence of heterogeneous accretion using measurements of three oxygen isotopes on olivine from a variety of high-3He/4He OIB locations. To high precision, the Δ17O value of high-3He/4He olivines from Hawaii, Pitcairn, Baffin Island and Samoa, are indistinguishable from bulk mantle olivine (Δ17OBulk Mantle − Δ17OHigh 3He/4He olivine = −0.002 ± 0.004 (2 × SEM)‰). Thus, there is no resolvable oxygen isotope evidence for heterogeneous accretion in the high-3He/4He source. Modelling of mixing processes indicates that if an early-forming, oxygen-isotope distinct mantle did exist, either the anomaly was extremely small, or the anomaly was homogenised away by later mantle convection.\ud \ud The δ18O values of olivine with the highest 3He/4He ratios from a variety of OIB locations have a relatively uniform composition (∼5‰). This composition is intermediate to values associated with the depleted MORB mantle and the average mantle. Similarly, δ18O values of olivine from high-3He/4He OIB correlate with radiogenic isotope ratios of He, Sr, and Nd. Combined, this suggests that magmatic oxygen is sourced from the same mantle as other, more incompatible elements and that the intermediate δ18O value is a feature of the high-3He/4He mantle source. The processes responsible for the δ18O signature of high-3He/4He mantle are not certain, but δ18O–87Sr/86Sr correlations indicate that it may be connected to a predominance of a HIMU-like (high U/Pb) component or other moderate δ18O components recycled into the high-3He/4He source.

In his comment on our 2013 paper ‘A low-uncertainty measurement of the Boltzmann constant’ [1] Macnaughton claims that his re-analysis “…reveals systematic non-random patterns in residuals of the key fitted model equation”. He claims that “these patterns violate the assumptions underlying the analysis” and “raise questions about the validity of [our] estimate of kB”. He also claims that we deleted “troublesome” data in a “somewhat arbitrary” manner. While we are grateful to Macnaughton for his attention to our freely accessible data, we disagree with his conclusions. The dataset we analysed consists of 263 data points, while the ‘trends’ in the data to which he refers constitute at most 12 points. Concerning the improper removal of data points to which he alludes we note that all 324 data points that we acquired were included in the supplementary data, but some data were excluded from the analysis for the reasons stated in the original text. Macnaughton was able to determine the effect of including or excluding these data but did not do so. In this paper we demonstrate that none of the issues to which Macnaughton draws attention could conceivably have any significant effect on our final estimate for the Boltzmann constant or its uncertainty.

This study tests alternative models for the growth of the Tatry Mountains (Central Western Carpathians) by the application of low temperature thermochronology. Zircon (U + Th)/He ages from the north of the range are mostly between 48 to 37 Ma and indicate cooling prior to the onset of forearc sedimentation in the region (42–39 Ma). In contrast, zircon (U + Th)/He ages in the south of the range are around 22 Ma. Apatite fission track ages across the sampled sites range from 20 to 15 Ma. Apatite (U + Th)/He ages range from 18 to 14 Ma with little variation with elevation or horizontal location. Based on thermal modelling and tectonic reconstructions, these Miocene ages are interpreted as cooling in the hanging-wall of a northward dipping thrust ramp in the current location of the sub-Tatric fault with cooling rates of ~20 °C/Myr at ~22-14 Ma. Modeled cooling histories require an abrupt deceleration in cooling after ~14 Ma to

To determine the mechanisms responsible for mountain belt growth, it is important to accurately establish the timing of surface uplift. Here we exploit the altitude control on the production rate of in situ cosmogenic nuclides to test the hypothesis that the Andes was uplifted in the late Miocene. High concentrations of in situ cosmogenic 3He (3Hecos) have previously been measured in alluvial boulders on the western flank of the Central Andes, northern Chile (Evenstar et al. 2009). These are consistent with deposition soon after formation of the surface (13–14 Ma). We have modeled the accumulation of cosmogenic 3He in several different surface uplift scenarios and compared them to the measured concentrations. The measured 3Hecos concentrations are too high to be produced by late Miocene uplift and imply that the western flank of the Andean Cordillera attained a substantial part of its current elevation prior to 14 Myr ago.

Recycling of upper plate crust in subduction zones, or ‘subduction erosion’, is a major mechanism of crustal destruction at convergent margins. However, assessing the impact of eroded crust on arc magmas is difficult owing to the compositional similarity between the eroded crust, trench sediment and arc crustal basement that may all contribute to arc magma formation. Here we compare Sr–Nd–Pb–Hf and trace element data of crustal input material to Sr–Nd–Pb–Hf–He–O isotope chemistry of a well-characterized series of olivine-phyric, high-Mg# basalts to dacites in the central Mexican Volcanic Belt (MVB). Basaltic to andesitic magmas crystallize high-Ni olivines that have high mantle-like 3He/4He = 7–8 Ra and high crustal δ18Omelt = +6.3–8.5‰ implying their host magmas to be near-primary melts from a mantle infiltrated by slab-derived crustal components. Remarkably, their Hf–Nd isotope and Nd/Hf trace element systematics rule out the trench sediment as the recycled crust end member, and imply that the coastal and offshore granodiorites are the dominant recycled crust component. Sr–Nd–Pb–Hf isotope modeling shows that the granodiorites control the highly to moderately incompatible elements in the calc-alkaline arc magmas, together with lesser additions of Pb- and Sr-rich fluids from subducted mid-oceanic ridge basalt (MORB)-type altered oceanic crust (AOC). Nd–Hf mass balance suggests that the granodiorite exceeds the flux of the trench sediment by at least 9–10 times, corresponding to a flux of ⩾79–88 km3/km/Myr into the subduction zone. At an estimated thickness of 1500–1700 m, the granodiorite may buoyantly rise as bulk ‘slab diapirs’ into the mantle melt region and impose its trace element signature (e.g., Th/La, Nb/Ta) on the prevalent calc-alkaline arc magmas. Deep slab melting and local recycling of other slab components such as oceanic seamounts further diversify the MVB magmas by producing rare, strongly fractionated high-La magmas and a minor population of high-Nb magmas, respectively. Overall, the central MVB magmas inherit their striking geochemical diversity principally from the slab, thus emphasizing the importance of continental crust recycling in modern solid Earth relative to its new formation in modern subduction zones.

We have determined the acoustic and microwave frequencies of a misaligned spherical resonator maintained near the temperature of the triple point of water and filled with helium with carefully characterized molar mass g mol−1, with a relative standard uncertainty . From these data and traceable thermometry we estimate the speed of sound in our sample of helium at K and zero pressure to be m2 s−2 and correspondingly deduce the value J mol−1 K−1 for the molar gas constant. We estimate the value J K−1 for the Boltzmann constant using the currently accepted value of the Avogadro constant NA. These estimates of R and k, with a relative standard uncertainty of 1.06 × 10−6, are 1.47 parts in 106 above the values recommended by CODATA in 2010.