Emplacement of the Nain anorthosite : diapiric versus conduit ascent

Estimation of settling velocities of large orthopyroxene megacrysts, found within anorthosite intrusions, are calculated and compared with ascent rates achieved by diapirism and conduit propagation. Calculations suggest that diapirism is far too slow to be an appropriate ascent mechanism for anorthositic crystal mush and favour conduit emplacement. The intrusions of the Nain Plutonic Suite (NPS) are located along the Abloviak shear zone, which marks the boundary between the Nain and Churchill provinces, and within the zone of juxtaposition of the Saglek and Hopedale blocks of the Nain Province. These crustal weaknesses have probably controlled the emplacement and distribution of the intrusions. Contact relations between intrusions of anorthosite and their gneissic host rock provide evidence for two emplacement styles within the NPS, the first typified by strongly deformed and recrystallized rocks, and the second by an outer border zone of mafic rocks. It is proposed that these differences in intrusive style are due to differences in ductility contrast between the magma and its surrounding host rocks, such that those intrusions emplaced into the thermally softened shear zone have deformed margins, whereas those intruded into the cooler Archaean crust have undeformed margins

The handling of hazard data on a national scale : a case study from the British Geological Survey

This paper reviews how hazard data and geological map data have been combined by the British Geological Survey (BGS) to produce a set of GIS-based national-scale hazard susceptibility maps for the UK. This work has been carried out over the last 9 years and as such reflects the combined outputs of a large number of researchers at BGS. The paper details the inception of these datasets from the development of the seamless digital geological map in 2001 through to the deterministic 2D hazard models produced today. These datasets currently include landslides, shrink-swell, soluble rocks, compressible and collapsible deposits, groundwater flooding, geological indicators of flooding, radon potential and potentially harmful elements in soil. These models have been created using a combination of expert knowledge (from both within BGS and from outside bodies such as the Health Protection Agency), national databases (which contain data collected over the past 175 years), multi-criteria analysis within geographical information systems and a flexible rule-based approach for each individual geohazard. By using GIS in this way, it has been possible to model the distribution and degree of geohazards across the whole of Britain

Can sustainable development be achieved if geology is ignored?

“Sustainable development” implies that a stable relationship between human activities and the natural world is possible such that the prospects of future generations do not diminish. Can this really be achieved in our urban centres where social and economic issues are often the driving force behind development? Geoscience information has traditionally been under-utilised in planning and development, because all too often its relevance and significance is misunderstood or underappreciated. However, this is starting to change. Using case studies from London and the Thames Gateway Development Zone, this paper discusses how technological developments, such as improvements in GIS technologies and 3D modelling software, are driving this turnaround. The paper also considers the impact of organisations not sharing ground investigation geodata and know-ledge about anomalous ground conditions across London, the huge benefits that data sharing can offer and how lessons learned in this study can be applied to other urban centres. The paper will show that within the environmental ecosystem, if one component part is misunderstood, then developing sustainably without compromising future needs will be difficult, if not impossible, to achieve. In London, difficult ground conditions cost developer's time and money through project overruns and expensive engineering solutions. A more sustainable solution is in improving our understanding of the relationship between the geology (lithology) and its properties (physical, chemical or hydrological characteristics). We will show that for the urban underground to be fully utilised throughout Europe, the lack of development policies for the subsurface needs to be addressed. For a subsurface development policy to be written, stakeholders will need to regard the urban underground as environmentally sensitive, just as it does for the surface

Combining numercial and cognitive 3D modelling approaches in order to determine the structure of the Chalk in the London Basin

In order to determine the structure of the Chalk in the London Basin, a combined cognitive and numerical approach to model construction was developed. A major difficultly in elucidating the structure of the Chalk in the London Basin is that the Chalk is largely unexposed. The project had to rely on subsurface data such as boreholes and site investigation reports. Although a high density of data was available problems with the distribution of data and its quality meant that, an approach based on a numerical interpolation between data points could not be used in this case. Therefore a methodology was developed that enabled the modeller to pick out areas of possible faulting and to achieve a geologically reasonable solution even in areas where the data was sparse or uncertain. By using this combined approach, the resultant 3D model for the London Basin was more consistent with current geological observations and understanding. In essence, the methodology proposed here decreased the disparity between the digital geological model and current geological Knowledge. Furthermore, the analysis and interpretation of this model resulted in an improved understanding of how the London Basin evolved during the Cretaceous period

U-Pb ages of syndeformational dykes associated with the Mesoproterozoic Nain Plutonic Suite, Labrador

Field and U-Pb zircon geochronological studies in a suite of crosscutting, deformed, and metamorphosed basic dykes show that they were emplaced in a syndeformational environment between 1328 ± 2 and 1316.5 ± 1.6 Ma. Earlier dykes in the suite are granulitic, commonly folded along north-south axes or strongly rotated into north-south-trending shear zones. Later dykes are metamorphosed to amphibolite grade. These sometimes retain igneous porphyritic textures and occasionally crosscut the granulite dykes. The amphibolite dykes were emplaced in a less ductile crustal environment and a structural environment less dominated by shear deformation. Both granulitic and to a lesser extent amphibolite dykes show evidence of synshear emplacement. The episode of emplacement is broadly coeval with the injection of the mid-Proterozoic Nain Plutonic Suite (NPS) and suggests that the dykes were injected as a series of leaks from NPS feeder chambers. If so, the granulite dykes may represent leaks intruded near the culmination of NPS activity, whereas the amphibolite dykes were probably injected during the waning phase of tectono-thermal conditions

The use of 3D geological models in the development of the conceptual groundwater model

The conceptual groundwater model is heavily dependent on the geological framework which is used to defi ne the aquifer being studied. In the past, two-dimensional datasets such as geological maps and cross-sections were used in coordination with site-specifi c point data to build a conceptual understanding at the site or catchment scale. This is then simplified and it is this simplifi ed version which is used to build the framework for the numerical groundwater fl ow model. Due to the way the geological framework model and the conceptual groundwater model were generated they could not be viewed together; this inevitably led to a signifi cant loss of information and understanding. With the current rapid developments in 3D modelling software and the increasing availability of digital geological data it is now possible to produce detailed 3D geological models of complex aquifer sequences. In this paper we will use two case studies (Chalk aquifer of the London Basin and the Jurassic limestone aquifer of the Cotswolds) to demonstrate that by developing a detailed 3D geological model signifi cant benefi ts are gained in the understanding and development of the conceptual groundwater model

Geology of London, UK

The population of London is around 7 million. The infrastructure to support this makes London one of the most intensively investigated areas of upper crust. However construction work in London continues to reveal the presence of unexpected ground conditions. These have been discovered in isolation and often recorded with no further work to explain them. There is a scientific, industrial and commercial need to refine the geological framework for London and its surrounding area. This paper reviews the geological setting of London as it is understood at present, and outlines the issues that current research is attempting to resolve

Women and property rights : a human rights and gender challenge to churches and society in Kenya (reference to the Meru community of Kenya)

In many developing countries like Kenya, issues of gender discrimination are evident in form of unequal inheritance and property rights. While there seems to be numerous campaigns for the advocacy of gender equality and human rights in all aspects, the practicability is something yet to be visualized. In Kenya for instance, customary law is quite dominant hence sabotaging any attempt to promote gender equality. In this paper, it has been noted that due to the impact customary law has especially on property rights, many have the feeling that security is more important than claiming for gender equality. Needless to say, this of course goes hand in hand with the primitive or traditional beliefs and practices that are still adored with high esteem. The question of women rights to property inheritance in Kenya is therefore not without suspicions and mixed feelings. Besides other aspects like poverty and illiteracy among many women, there is the challenge of some traditional beliefs and practices that can be harmful to their lives. Instead of empowering women with the rights to inherit family properties, especially after the death of their spouses, many have the traditional primitive view that a woman needs to be inherited together with other properties of the deceased; after all she too is part of the properties the deceased owned. A lot therefore needs to be done in order to improve the current situation of women’s rights to inherit properties in Kenya. Key words: Gender discrimination, customary law, Traditional beliefs and practices, poverty, and illiteracy