Provenance Response to Rifting and Separation at the Jan Mayen Microcontinent Margin

Funding This research received no external funding. Acknowledgments We are grateful to John Still (University of Aberdeen) and Iain Macdonald (Cardiff University) for their assistance with acquisition of mineral chemical data, and to Mick Pointon (CASP) for running the “R” code to assign apatite provenance. This research was carried out as part of CASP’s Greenland-Norway Project. Our sponsors’ financial support is gratefully acknowledged. We are grateful for the reviewers comments, which significantly improved the manuscript.Peer reviewedPublisher PD

Challenge clusters facing LCA in environmental decision-making—what we can learn from biofuels

Purpose Bioenergy is increasingly used to help meet greenhouse gas (GHG) and renewable energy targets. However, bioenergy’s sustainability has been questioned, resulting in increasing use of life cycle assessment (LCA). Bioenergy systems are global and complex, and market forces can result in significant changes, relevant to LCA and policy. The goal of this paper is to illustrate the complexities associated with LCA, with particular focus on bioenergy and associated policy development, so that its use can more effectively inform policymakers. Methods The review is based on the results from a series of workshops focused on bioenergy life cycle assessment. Expert submissions were compiled and categorized within the first two workshops. Over 100 issues emerged. Accounting for redundancies and close similarities in the list, this reduced to around 60 challenges, many of which are deeply interrelated. Some of these issues were then explored further at a policyfacing workshop in London, UK. The authors applied a rigorous approach to categorize the challenges identified to be at the intersection of biofuels/bioenergy LCA and policy. Results and discussion The credibility of LCA is core to its use in policy. Even LCAs that comply with ISO standards and policy and regulatory instruments leave a great deal of scope for interpretation and flexibility. Within the bioenergy sector, this has led to frustration and at times a lack of obvious direction. This paper identifies the main challenge clusters: overarching issues, application and practice and value and ethical judgments. Many of these are reflective of the transition from application of LCA to assess individual products or systems to the wider approach that is becoming more common. Uncertainty in impact assessment strongly influences planning and compliance due to challenges in assigning accountability, and communicating the inherent complexity and uncertainty within bioenergy is becoming of greater importance. Conclusions The emergence of LCA in bioenergy governance is particularly significant because other sectors are likely to transition to similar governance models. LCA is being stretched to accommodate complex and broad policy-relevant questions, seeking to incorporate externalities that have major implications for long-term sustainability. As policy increasingly relies on LCA, the strains placed on the methodology are becoming both clearer and impedimentary. The implications for energy policy, and in particular bioenergy, are large

Achieving Deep Cuts in the Carbon Intensity of U.S. Automobile Transportation by 2050: Complementary Roles for Electricity and Biofuels

Passenger cars in the United States (U.S.) rely primarily on petroleum-derived fuels and contribute the majority of U.S. transportation-related greenhouse gas (GHG) emissions. Electricity and biofuels are two promising alternatives for reducing both the carbon intensity of automotive transportation and U.S. reliance on imported oil. However, as standalone solutions, the biofuels option is limited by land availability and the electricity option is limited by market adoption rates and technical challenges. This paper explores potential GHG emissions reductions attainable in the United States through 2050 with a county-level scenario analysis that combines ambitious plug-in hybrid electric vehicle (PHEV) adoption rates with scale-up of cellulosic ethanol production. With PHEVs achieving a 58% share of the passenger car fleet by 2050, phasing out most corn ethanol and limiting cellulosic ethanol feedstocks to sustainably produced crop residues and dedicated crops, we project that the United States could supply the liquid fuels needed for the automobile fleet with an average blend of 80% ethanol (by volume) and 20% gasoline. If electricity for PHEV charging could be supplied by a combination of renewables and natural-gas combined-cycle power plants, the carbon intensity of automotive transport would be 79 g CO2e per vehicle-kilometer traveled, a 71% reduction relative to 2013

Mantle heat drives hydrothermal fluids responsible for carbonate-hosted base metal deposits: evidence from 3He/4He of ore fluids in the Irish Pb-Zn ore district

There is little consensus on whether carbonate-hosted base metal deposits, such as the world-class Irish Zn+Pb ore field, formed in collisional or extensional tectonic settings. Helium isotopes have been analysed in ore fluids trapped in sulphides samples from the major base metal deposits of the Irish Zn-Pb ore field in order to quantify the involvement of mantle-derived volatiles, that require melting to be realised, as well as test prevailing models for the genesis of the ore fields. 3He/4He ratios range up to 0.2 Ra, indicating that a small but clear mantle helium contribution is present in the mineralising fluids trapped in galena and marcasite. Sulfides from ore deposits with the highest fluid inclusion temperatures (~200°C) also have the highest 3He/4He (> 0.15 Ra). Similar 3He/4He are recorded in fluids from modern continental regions that are undergoing active extension. By analogy we consider that the hydrothermal fluids responsible for the carbonate-hosted Irish base metal mineralization circulated in thinned continental crust, undergoing extension, and demonstrates that enhanced mantle heat flow is ultimately responsible for driving fluid convection

Sedimentology and geochemistry of Late Jurassic organic-rich shelfal mudstones from East Greenland: regional and stratigraphic variations in source-rock quality

Late Jurassic (Late Oxfordian–Early Volgian) sediments exposed across a wide area of East Greenland are dominated by organic-rich mudstones and sandy mudstones and reach a maximum thickness of 500 m. The facies are characterized by parallel-laminated, generally unbioturbated mudstones, in some cases containing thin sandstone laminae. Deposition occurred in an offshore shelf environment, with water depths difficult to constrain. In the northern sections, heterolithic, sandier units occur at the base of the mudstone succession, marking a gradual transition from the underlying shallow-marine sandstones. Mudstones in the south (Milne Land–Jameson Land) are more oil prone, with greater dilution by terrestrially derived Type III/IV kerogen in the north (Wollaston Forland–Kuhn Ø). In both areas there is an improvement in source-rock quality and oil proneness from proximal to distal settings, with the geochemical data in agreement with the palaeogeographical interpretation. In the south, the Late Kimmeridgian to Early Volgian marks the maximum westward transgression of source-rock facies and also represents the richest source interval. In the north there is a decrease in sand content through the Late Oxfordian–Kimmeridgian, although trends in source-rock quality are less clear. Whilst the northern sections are predominantly gas prone, some marginally oil-prone mudstones do occur. The Vøring and Møre basins were situated immediately to the east of Greenland in the Late Jurassic. The presence of a continuous blanket of potential source rocks in East Greenland and the eastward improvement in source-rock properties implies that good quality oil-prone source rocks of Late Jurassic age are likely to be present in the Vøring and Møre basins

Domain size as a parameter for studying the potential alkali-silica reactivity of chert-bearing aggregates

The presence of chert or flint in aggregates used for concrete manufacture has long been a source of concern in the context of alkali-silica reactivity. The global in-service performance of chert and flint-bearing aggregates, however, varies from innocuous to deleterious. This could be due to variations in the degree of crystallinity of the silica, which influences potential reactivity. Chert occurs in significant Irish sources of aggregate used for concrete, yet no cases of deleterious expansion have been reported in the Republic of Ireland to date. Many of these sources fail to conclusively demonstrate innocuous behaviour in the laboratory expansion tests despite satisfactory in-service behaviour. A previous X-ray diffraction study, employing quartz crystallinity index, had indicated a significant difference between Irish Carboniferous cherts and English Cretaceous flints. This paper reports a further study of crystallinity, correlated with mortar bar expansion tests, but employing both quartz crystallinity index and domain size in the characterisation of crystallinity. The influence of chert content was also studied. Twenty-three Irish aggregate sources were sampled, and petrographic analysis revealed that 17 of these contained chert. Three flint-bearing aggregates, from sources in England that had demonstrated alkali-silica reactivity, were also sampled. Chert and flint were extracted from the aggregate samples by a petrographer experienced in the field of concrete technology. Twenty-six distinct samples were successfully extracted from 13 of the Irish and the three English sources. X-ray diffraction testing confirmed the previous findings (using the quartz crystallinity indices) that the Irish cherts are,more crystalline than the English flints. Domain size determination, however, showed that the difference in crystallinity of the national sets was less than that anticipated. The influence of chert content is advanced as a hypothesis to explain the apparent reactivity of Irish cherts in screening tests. The potential value of combining domain size and chert content determination in helping to classify aggregate reactivity is advanced for cases where in-service behaviour is in significant conflict with findings from standard laboratory tests.Other funderIrish Cement Ltd"Full acknowledgement to source and publisher must be given. Please link to website: http://www.icevirtuallibrary.com/ ". Publiher version - http://www.icevirtuallibrary.com/content/article/10.1680/macr.2004.56.4.201. DG 29/07/10 au,ke.kpw25/8/1