Noble gas geochemistry of fluid inclusions in South African diamonds: implications for the origin of diamond-forming fluids

Fibrous diamond growth zones often contain abundant high-density fluid (HDF) inclusions and these provide the most direct information on diamond-forming fluids. Noble gases are incompatible elements and particularly useful in evaluating large-scale mantle processes. This study further constrains the evolution and origin of the HDFs by combining noble gas systematics with δ13C, N concentrations, and fluid inclusion compositions for 21 individual growth zones in 13 diamonds from the Finsch (n = 3), DeBeers Pool (n = 7), and Koffiefontein (n = 3) mines on the Kaapvaal Craton. C isotope compositions range from −2.8 to −8.6‰ and N contents vary between 268 and 867 at.ppm, except for one diamond with contents of <30 at.ppm N. Nine of the thirteen studied diamonds contained saline HDF inclusions, but the other four diamonds had carbonatitic or silicic HDF inclusions. Carbonatitic and silicic HDFs yielded low He concentrations, R/Ra (3He/4Hesample/3He/4Heair) values of 3.2–6.7, and low 40Ar/36Ar ratios of 390–1940. Noble gas characteristics of carbonatitic-silicic HDFs appear consistent with a subducted sediment origin and interaction with eclogite. Saline HDFs are characterised by high He concentrations, with R/Ra mostly between 3.9 and 5.7, and a wide range in 40Ar/36Ar ratios (389–30,200). The saline HDFs likely originated from subducted oceanic crust with low He but moderate Ar contents. Subsequent interaction of these saline HDFs with mantle peridotite could explain the increase in He concentrations and mantle-like He isotope composition, with the range in low to high 40Ar/36Ar ratios dependent on the initial 36Ar content and extent of lithosphere interaction. The observed negative correlation between 4He contents and R/Ra values in saline HDFs indicates significant in situ radiogenic 4He production

Global distribution of sediment-hosted metals controlled by craton edge stability

Sustainable development and the transition to a clean-energy economy drives ever-increasing demand for base metals, substantially outstripping the discovery rate of new deposits and necessitating dramatic improvements in exploration success. Rifting of the continents has formed widespread sedimentary basins, some of which contain large quantities of copper, lead and zinc. Despite over a century of research, the geological structure responsible for the spatial distribution of such fertile regions remains enigmatic. Here, we use statistical tests to compare deposit locations with new maps of lithospheric thickness, which outline the base of tectonic plates. We find that 85% of sediment-hosted base metals, including all giant deposits (>10 megatonnes of metal), occur within 200 kilometres of the transition between thick and thin lithosphere. Rifting in this setting produces greater subsidence and lower basal heat flow, enlarging the depth extent of hydrothermal circulation available for forming giant deposits. Given that mineralization ages span the past two billion years, this observation implies long-term lithospheric edge stability and a genetic link between deep Earth processes and near-surface hydrothermal mineral systems. This discovery provides an unprecedented global framework for identifying fertile regions for targeted mineral exploration, reducing the search space for new deposits by two-thirds on this lithospheric thickness criterion alone.M.J.H. acknowledges support from the National Aeronautics and Space Administration (grant NNX17AE17G) and the Donors of the American Chemical Society Petroleum Research Fund (59062-DNI8). F.D.R. acknowledges support from the Schmidt Science Fellows program, in partnership with the Rhodes Trust. K.C. and D.L.H. publish with permission of the CEO of Geoscience Australia. Geoscience Australia eCat ID 132624

The Geology of the Argyle (AK1) Diamond Deposit,Western Australia

The Argyle (AK1) pipe in the Kimberley region of Western Australia is the world’s largest source of natural diamonds, and it has produced more than 835 million carats since mining began in 1983. The ~1.2 Ga olivine lamproite pipe lies within the Paleoproterozoic Halls Creek orogen at the southeastern margin of the Kimberley craton, and it was emplaced during a period of extension associated with large-scale, NNE-trending strikeslip faulting of the orogen. AK1 is composed of four coalesced, steep-sided diatremes aligned along an NNE-trending fault and tapering to narrow feeder zones at depth. The body is infilled by volcaniclastic olivine lamproite and cut by late olivine lamproite dikes. Two distinct groups of volcaniclastic rocks are present. The dominant type comprises mainly quartz-rich lapilli tuffs and coarse ash tuffs formed by numerous phreatomagmatic eruptions, when olivine lamproite magma was erupted through water-rich sands and silts of the Carr Boyd Group. In contrast, latestage olivine lamproite lapilli tuffs, devoid of accidental quartz grains, fill the center of the northern diatreme. Following emplacement, the body was tilted 30° to the north and extended north-south by the sinistral northnorthwest–south-southeast Gap fault system and east-northeast–west-southwest by the dextral Razor Ridge fault. The Razor Ridge fault offsets the most southerly diatreme (southern tail) from the main part of AK1. Reversal of structural offsets affecting AK1 reveals a geometry which closely resembles that of other ultramafic diatremes. Variations in diamond grade and quality within AK1 indicate that at least two distinct magmas with unique diamond contents have been emplaced at Argyle

Extracranial germ cell tumours: mature and immature (1990-2015) : first report by the South African Association of Paediatric Haematology Oncology (SAAPHO)

Abstract: Background and objectives: Outcomes of rare paediatric teratomas have not previously been reported nor treatment regimens standardised in low- and middle-income settings. We sought to evaluate treatment outcomes of children and adolescents with histologically confirmed extracranial germ cell tumours, both mature teratomas (MT) and immature teratomas (IT) in preparation for the development of the South African national treatment guideline.Methods: Retrospective data by folder review were collated from nine South African paediatric oncology units. Kaplan-Meier analysis with Cox regression was performed to determine 5-year overall survival (OS) and prognostic factors.Results: From January 1990 to December 2015, 60 patients were diagnosed with MTs; 14 males (median age 2 months; interquartile range [IQR]: 0-8.75 months) and 46 females (median age 9 months; IQR: 0-88.5 months). Forty patients were diagnosed with ITs; 10 males (median age less than 1 month; IQR: 0-1.75 months) and 30 females (median age 4.5 months; IQR: 1-162 months). There were high rates of upfront surgical resections in patients with MTs (58/60; 96.6%) and ITs (36/40; 90%), and similarly satisfactory rates of complete resection in patients with both MTs (55/60; 91.7%) and ITs (32/40; 80%). The 5-year OS for the whole group was 85.4%, significantly influenced by stage: Stage I (96.9%), Stage II (100%), Stage III (38.9%) (p < .001 [MT]; p = .013 [IT]). The event-free survival (EFS) ratio for the whole cohort was 78.7%.Conclusions: Five-year OS for those with low-stage disease was excellent, but was poorer for patients with advanced disease. The implementation of a national treatment guideline will facilitate the standardising of surgical approaches, indications for chemotherapy and specifications for follow-up to improve survival and to collect more robust late effects data

Efficacy of a postharvest treatment aiming at eradication of all developmental stages of Tecia solanivora in ware potatoes

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver a scientific opinion on the efficacy of a postharvest treatment aiming to eradicate all developmental stages of Guatemalan potato tuber moth Tecia solanivora (Lepidoptera: Gelechiidae) in ware potatoes. The Panel evaluated the scientific publication describing the elevated CO2 treatment, which was defined as: 10-day exposure to 30% CO2, 20% O2 and 50% N2 in controlled atmosphere at 17°C on the variety Negra Yema de Huevo (Papas Antiguas de Canarias, PDO potatoes, Solanum chaucha). In the scientific publication, the treatment was applied under semi-commercial and commercial conditions on artificially and field-infested tubers. The effect of the pest developmental stage on the treatment efficacy was investigated with artificial infestation of potato tubers with eggs, neonate and second instar larvae. Pupae and adults were placed in separate containers during the treatment. However, the third and fourth larval instars were not investigated. Further limitations were the sample size in the experiments, the mortality rate in the control group and the unknown level of infestation of the naturally infested potato tubers. It was not possible to evaluate the degree of pest freedom due to incomplete data on the conditions of production, i.e. the infestation level in the field. The Panel was able to conclude that although no surviving insects were observed in the performed experiments, the statistical evaluation of the presented results from the commercial trial indicate that it cannot be excluded that insects would survive the treatment. For example, based on the data provided the 95% confidence interval of the survival rate for eggs was: 0%-0.453%

Commodity risk assessment of Prunus domestica plants from Ukraine

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as ‘High risk plants, plant products and other objects’. This Scientific Opinion covers plant health risks posed by plants of Prunus domestica grafted on Prunus cerasifera imported from Ukraine, taking into account the available scientific information, including the technical information provided by Ukraine. All pests associated with the commodity were evaluated against specific criteria for their relevance for this opinion. One quarantine pest (Lopholeucaspis japonica), two protected zone quarantine pests (Erwinia amylovora and Xanthomonas arboricola pv. pruni) and one non-regulated pest (Eotetranychus prunicola) that fulfilled all relevant criteria were selected for further evaluation. For these four pests, the risk mitigation measures proposed in the technical dossier from Ukraine were evaluated taking into account the possible limiting factors. For the selected pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The degree of pest freedom varies among the pests evaluated, with Xanthomonas arboricola pv. pruni being the pest most frequently expected on the imported plants. The Expert Knowledge Elicitation indicated with 95% certainty that between 9,870 and 10,000 bundles (consisting of 10 plants each) per 10,000 would be free from Xanthomonas arboricola pv. pruni