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Tait J.,University of Edinburgh | Straathof G.,University of Edinburgh | Straathof G.,SGS Horizon BV | Soderlund U.,Lund University | And 7 more authors.

A precise U-Pb baddeleyite age of 2733. ±. 2. Ma has been obtained for the Ahmeyim Great Dyke of Mauritania that intruded into the Tasiast-Tijirit Terrane of the Reguibat Shield, NW Mauritania. This dyke is approximately 1500. m wide at the sampling area and extends for more than 150. km NNE/SSW. Major and trace element geochemistry of the dyke indicates that the magmas that formed this intrusive body were sub-alkaline, tholeiitic and boninitic, and the presence of a negative Nb anomaly indicates the involvement of subducted oceanic lithosphere during magma genesis, most likely an inherited signature from earlier subduction events and the Mesoarchaean collision of the Tasiast-Tijirit and Choum-Rag el Abiod Terranes. A palaeomagnetic study was also undertaken on samples collected from two different sections across the dyke. However, no within- or inter-site grouping of any palaeomagnetic directions could be identified, thus precluding any palaeographic interpretation. The Ahmeyim Great Dyke is interpreted to be part of the feeder system for a 2733. Ma Large Igneous Province (LIP); tholeiitic-komatiitic greenstone belts of this age are absent in the West African Craton (WAC) but are present on many other blocks. However, additional constraints are required to reliably link the Ahmeyim Great Dyke with any other such LIP-type greenstone belts in late Archaean supercontinent reconstructions. The magmas that formed the Ahmeyim Great Dyke were boninitic; this, combined with evidence of crustal contamination, the scale of the dyke and its potential link (as a feeder) to greenstone belts of tholeiitic-komatiitic affiliation within other crustal blocks suggests that it, and cogenetic magmatic units elsewhere, may be prospective for magmatic Ni-Cu-PGE sulphide exploration. © 2012. Source

Bergmann P.,Sintef | Chadwick A.,BGS
3rd Sustainable Earth Sciences Conference and Exhibition: Use of the Sub-Surface to Serve the Energy Transition

A method for volumetric estimation of subsurface fluid substitution is presented that relies on the analysis of 4D seismic time-shifts. Since time-shifts cannot resolve for fluid saturation and layer thickness simultaneously without additional constraints, mass estimates are derived from the complete set of possible fluid saturations and layer thicknesses. The method considers velocity-saturation relationships that range from uniform saturation to patchy saturation. Based on a generalized velocity-saturation relationship that is parameterized by the degree of patchiness, explicit upper and lower fluid mass bounds are provided. We show that the inherent ambiguity between fluid saturation and layer thickness has a severe impact on the convergence of these mass bounds. That is, roughly linear velocity-saturation relationships with patchy saturation tend to provide significantly better accuracy in a mass interpretation than the strongly non-linear velocity-saturation relationships associated with homogeneous saturation. The method is validated at the Sleipner storage site, where injected fluid masses are known. Moreover, a linear relationship between 4D time-shifts and injected mass is observed, suggesting that the evolving patterns of fluid saturation and fluid mixing in the CO2 plume at Sleipner have remained roughly constant with time. Source

Knox R.W.O.B.,BGS | Soliman M.F.,Assiut University | Essa M.A.,Assiut University

Improved methods of analysis and quantification of heavy mineral assemblages in Cambrian to Early Cretaceous sandstones of southwest Sinai have revealed successive changes in provenance that reflect both rejuvenation of the Arabian Shield and changes in the topographic configuration of the source area. Three mineral units have been identified in the Cambrian succession, at least three in the Carboniferous and three in the Cretaceous. It is predicted that the genetic units defined by these successive changes in mineralogy will be of regional extent and thus assist in elucidating the history of uplift of the Arabian-Nubian Shield and provide a better means of correlating sandstone units into adjacent areas. Variation in the abundance of apatite in the Cambrian succession is independent of provenance signature and is interpreted as reflecting alternating dry and humid climatic conditions. Source

Cobbing J.,Water Geosciences Consulting | Davies J.,BGS
Planet Earth

Jude Cobbing and Jeff Davies describe a new initiative to make data from old studies more accessible and improve scientific-cooperation and the availability of water in Africa. Groundwater is the main source of water for most Africans and makes up about a third of public-water supplies in England and Wales. There is no single-catalogue of African groundwater grey data, and many crucial details now exist only in the heads of the scientists who originally did the work. The Grey Data Project will catalogue and describe at least 2000 important grey items on groundwater in the southern African region held at BGS, in the process compiling a digital 'metadatabase.' The project is already yielding practical benefits. Martin Holland, a South African student at the University of Pretoria, is working on a PhD which reveals the reasons for varying yields of water from boreholes in different parts of the granitic 'basement' rocks. Source

Pearce J.M.,BGS | Delprat-Jannaud F.,French Institute of Petroleum | Akhurst M.,BGS | Nielsen C.,GEUS
Energy Procedia

The production of dry-run storage permit applications at two credible, if conceptual, CO2 storage sites allowed development of effective approaches to site characterization and identified the necessary levels of evidence required to assess the safety, containment and storage capacity of putative sites. This paper describes an exemplar permitting process and conclusions drawn from this experience for developing successful storage permits. © 2014 The Authors. Published by Elsevier Ltd. Source

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