Assessment of open boundary conditions on the elliptic formulation of the mild-slope equation

The performance of open boundaries in a finite differences scheme of the elliptic mild-slope equation is assessed. The wave propagation results show that lowest order parabolic radiation boundary conditions, unlike sponge layers combined with first order radiation boundary conditions, are an efficient alternative to first order radiation boundary conditions in order to improve the accuracy of the numerical solution of the problem.     

A Multistep Methodology for Building a Stochastic Model of Gold Grades in the Disseminated and Complex Deposit of Casas Novas in Alentejo,Southern Portugal

This paper proposes a multistep approach for creating a 3D stochastic model of gold grades in a complex disseminated auriferous deposit located in the Alentejo region, southern Portugal. The approach involves the following steps: (i) the creation of a 3D low‐resolution vector object model of two geological domains that better discriminate gold grades; (ii) the definition of three intervals for gold grades (low, intermediate, and high values); (iii) the estimation of the probability of each grid block belonging to each interval constrained by the geological domains; (iv) the calculation of local conditional cumulative distribution functions (CCDFs) of gold grades, for each block, taking into account the geological domains and the borehole data; and finally (v) the simulation of images of gold grades. The results demonstrate the usefulness and accuracy of the proposed procedure, as they are in compliance with the conceptual model, the distribution laws are conditioned by the geological domains, and the transition of grades between domains is continuous.     

Geochemistry of Famennian to Visean Metapelites from the Iberian Pyrite Belt: Implications for Provenance,Paleo-Redox Conditions and Vectoring to Massive Sulfide Deposits

Natural Resources Research - Massive sulfide deposits of the Iberian Pyrite Belt (IPB) document the progression of ore-forming processes in the SW Iberian Variscides, throughout uppermost Devonian...     

MPA as management tools for small-scale fisheries: The case study of Arrábida Marine Protected Area (Portugal)

Marine protected areas (MPA) have been widely suggested as a tool for both fisheries management and conservation goals. These multiple objectives are hard to achieve simultaneously as sustainable development implies the balance between the specific interests of conservation and economical activities. MPA success, namely for fisheries management, entails the implementation of restrictive measures that in a short-time frame may have negative effects on local fishermen communities. It is extremely important to evaluate their performance and effectiveness aiming at a quasi-optimal management, minimizing potential impacts on the social domain. In this study, a methodology for assessing the effectiveness of MPA as a small-scale fisheries management tool was developed, based on a set of indicators grouped in four dimensions (ecological, economic, social and management and governance). The indicators were scored individually according to an original score scale of five values and a median score was calculated for every dimension. Finally, the median overall score was calculated including the scores of the four dimensions. The scores were attributed for two distinct periods: before and after MPA implementation, in order to evaluate the performance of MPA. This methodology can be applied even with few scientific data available and taking into account experts and stakeholders’ judgements. The Arrábida MPA (Portugal) was used as a case study and it was found that with the implementation of the MPA social and economical aspects were impaired (median scores decreased near one value for the period after MPA implementation), while the other two dimensions showed an improvement trend. Thus, the overall score was the same before and after MPA implementation, an intermediate scale score. Results from the application of this method can give important indications about the state of an MPA and evaluate if the initial goals are being achieved through the implemented measures. The method is of easy communication and can be a useful tool for decision making and fisheries management processes.