We present the results of a detailed study of the volcanic geology of the median valley floor of the Mid-Atlantic Ridge in two adjacent but contrasting spreading segments immediately north of the Kane transform fault, based on a high-resolution deep-towed sidescan sonar (TOBI) survey, near-bottom photographic traverses, and geochemical analyses from 28 precisely sited sets of dredge samples. This has allowed us to assess the relative importance of small (intersegment) and large (transform) boundaries on magmatic processes at slow spreading ridges.We find that the petrological effect of the transform (so-called 'transform fault effect') is minor compared to the manifestation of the second-order segmentation. The southern, 'narrowgate'-type segment has a poorly developed neovolcanic zone, which tapers towards its bathymetric centre where continuous faulting causes rapid dismemberment. Flat-topped seamounts are preferentially located at the ends of the segment, particularly near the non-transform offset. There is a striking variation in the degree of fractionation along the length of this segment: primitive lavas were sampled at the centre, while more fractionated basalts, showing a greater range of parental compositions, form discrete volcanic edifices at the ends. In contrast, the northern segment has a wider inner valley, and syn-magmatic faults extend up to 15km along the crest of its robust axial volcanic ridge. The along-segment trend of increasing MgO towards the bathymetric crest of the axial volcanic ridge is similar to, but less well-defined than, that for the southern segment.There is no variation in the bulk degree of melting along the segments as determined from the major element geochemistry; hence, melt migration is favoured over focused mantle upwelling as the main cause of the crustal thickness variations which define second-order segmentation. Radiogenic isotopes show only very small variations with no systematic pattern emerging within or between the ridge segments. The isotopic irregularities are not related to the variations in incompatible elements, implying that the latter result from dynamic melting processes rather than from long-lived source heterogeneity. A model is developed which relates the volcanology, tectonic style and the geochemical trends to the episodicity of magma supply and eruption.

No abstract

Objective: There is limited evidence regarding effective smoking cessation interventions in deprived communities. This study explored what factors are considered most important in smoking cessation, from the perspective of a group of NHS Stop Smoking Service users from a deprived community. Design: A qualitative study. Setting: A deprived community in Brighton and Hove City, Southeast England. Methods: Fifteen adults who had used the local NHS Stop Smoking Service were recruited to the focus groups. Thematic analysis was used to identify key themes regarding factors that were considered most helpful during the smoking cessation attempt. Results: Factors deemed most important for a successful smoking cessation attempt were counsellors' attitude and knowledge, flexibility of appointments, personalized one-to-one support including additional support between sessions, all provided in an accessible local community setting. Individuals were most likely to decide to quit smoking for health reasons, and support from family and friends was important during the quit attempt. Conclusion: This study shows that smokers from deprived communities require more intensive, flexible and personalized support from a stop smoking service which should ideally be located in their community setting. A more innovative, tailored and less prescriptive approach to providing stop smoking services may help to improve cessation rates among smokers in deprived communities.

No abstract