Combining fractal analysis of mineral deposit clustering with weights of evidence to evaluate patterns of mineralization: Application to copper deposits of the Mount Isa Inlier, NW Queensland, Australia

The clustering of mineral occurrences and their spatial associations with particular geological features are critical aspects of mineral distributions for exploration and understanding ore genesis. Variations in the degree of clustering of mineral occurrences or geological features can be measured by fractal dimensions, obtained from a shifting box counting method. Spatial associations between mineral occurrences and geological features can be quantified by the weights of evidence (WofE) method using the contrast value, which increases with the strength of the spatial relationship. A new method is proposed to evaluate mineral occurrence distributions by combining the power of fractal analysis of clustering with the WofE approach. The method compares the correlation between the variation in degree of clustering of mineral occurrences and a geological feature in a study area, with the contrast value of the same feature. The possible outcomes can be simplified into four scenarios, depending on whether the correlation in variation of clustering and the contrast are high or low, respectively. Each outcome has specific exploration implications. If either a high correlation in variation of clustering or a high contrast value is obtained, the geological feature can be used for exploration targeting.The integrated fractal and WofE approach is applied to copper occurrences in the Proterozoic Mount Isa Inlier, NW Queensland, Australia, which hosts large numbers of copper deposits (1,869 occurrences), including the world class Mount Isa copper deposit. Variation in clustering of copper occurrences has a positive correlation with variation in clustering of fault bends (R = 0.823), fault intersections (R = 0.862) and mafic rocks (R = 0.885). WofE results indicate that the copper occurrences are spatially associated with fault intersections and bends and with mafic rocks. Analyses were carried out separately for the two major lithostratigraphic sequences in the Inlier, the Eastern and Western Successions. The Western Succession copper occurrences are apparently more clustered than those of the Eastern Succession, which may reflect a lower degree of exploration and/or geological factors. The association of copper occurrences with mafic rocks compared with fault bends and intersections is greater in the Eastern Succession, which may reflect genetic factors. Correlations in the variation of clustering of mineral occurrences and geological features have a linear relationship with the contrast values, and the spatial association between all geological features and copper occurrences constitute high correlation/high contrast cases. The linear relationship suggests that the geological features that control the clustering of the copper occurrences could be the same features that control their localization.     

Feedback and late star formation in elliptical galaxies

We present a one-zone model of star formation in elliptical galaxies that includes thermal feedback from supernovae and a temperature dependent star formation efficiency. The modulation of feedback with the total mass results in the triggering of late episodes of star formation in low-mass galaxies. These small `bursts' can occur as late as at redshifts z ∼ 0.5 but they do not change significantly the optical and NIR color-magnitude relation (CMR) of cluster galaxies, both locally and out to moderate redshifts, in agreement with the observations. However, they introduce a large scatter at the faint end of the NUV-Optical CMR, as recently found in cluster Abell 851 (z = 0.41). This revised version was published online in August 2006 with corrections to the Cover Date.     

National-level factors affecting planned,public adaptation to health impacts of climate change

Our understanding of whether adaptive capacity on a national level is being translated into adaptation policies, programs, and projects is limited. Focusing on health adaptation in Annex I Parties to the UNFCCC, we examine whether statistically significant relationships exist between regulatory, institutional, financial, and normative aspects of national-level adaptive capacity and systematically measured adaptation. Specifically, we (i) quantify adaptation actions in Annex I nations, (ii) identify potential factors that might impact progress on adaptation and select measures for these factors, and (iii) calculate statistical relationships between factors and adaptation actions across countries. Statistically significant relationships are found between progress on adaptation and engagement in international environmental governance, national environmental governance, perception of corruption in the public sector, population size, and national wealth, as well as between responsiveness to health vulnerabilities, population size and national wealth. This analysis contributes two key early empirical findings to the growing literature concerning factors facilitating or constraining adaptation. While country size and wealth are necessary for driving higher levels of adaptation, they may be insufficient in the absence of policy commitments to environmental governance. Furthermore, governance and/or incentive frameworks for environmental governance at the national level may be an important indicator of the strength of national commitments to addressing health impacts of climate change.     

Resonance in rocks: Building a sustainable learning and engagement programme for the Jurassic Coast

World Heritage Sites have a duty, through educational and information programmes, to strengthen appreciation and respect by their peoples of the cultural and natural heritage of that site. The Jurassic Coast World Heritage Site (JCWHS) showcases nearly 185 million years of Earth’s history across 95 miles of coast and exemplifies some of the most spectacular rocks, fossils and landforms in the world. However, imparting these values to non-specialist audiences of all ages, abilities and needs provides unique challenges and opportunities. A critical factor for success in addressing such a wide audience is ensuring that content is relevant, meaningful and focused on the expectations of the end user. In this paper we present our learning framework that is based around two approaches. Firstly, we map out the needs and expectations of each of our four core audience groups and set out guidelines for who we should aim our content at and how that should be delivered. Secondly, we set out three pathways (Inspire, Curious and Motivated) through which a person may choose to engage with the Jurassic Coast. We argue that if our tailored content and experiences can resonate with a person at an emotional and intellectual level, they will ultimately become devoted to the Jurassic Coast. Through empowering a community of people who understand and appreciate the geoheritage of the Jurassic Coast, they can become advocates and champions for its protection and conservation in the future.     

Diffusion-creep modelling of fibrous pressure-shadows

Grain-scale deformation of a bimineralic composite by normal-stress-driven grain-boundary diffusive mass-transfer has been modelled using diffusion-creep software that, for the first time, allows different diffusion coefficients for interphase boundaries and grain-boundaries as well as for different components. By selecting suitable coefficients we have obtained a fully coupled mechanical and mass-transfer numerical solution for the formation of fibrous pressure-shadows or strain fringes at the interface between a rigid object and a deforming rock matrix of different compositions. The model is two-dimensional and run in pure-shear velocity mode to a stretch ratio of 1.4. The first results are reported, which show dissolution and face-controlled antitaxial growth of a soluble, polycrystalline, calcite matrix at the interface with a circular and relatively insoluble pyrite object.The ratio of CaCO₃ diffusion along calcite–pyrite versus calcite–calcite boundaries strongly influences the extent of pressure-shadow growth and the pattern of strains in the matrix. A low ratio produces little growth, significant perturbation, and deflection of total-strain axes around the pyrite. An intermediate ratio produces appreciable growth, little perturbation, and near-parallel total-strain axes. A high ratio produces larger pressure-shadows, and total-strain axes that bend in towards the pyrite as if it were a weak object. Sliding and rotation of matrix grains are also affected.These results differ fundamentally from purely physical models of ductile flow around a rigid object and demonstrate the influence of interface diffusional properties on the resulting behaviour. In particular, assumptions such as perturbation of the flow by the object, deflection of external foliation around pre-deformational porphyroblasts and relationships of pressure-shadow strain to bulk strain may need to be re-examined in the light of this finding.