Incorporação do conhecimento geológico em métodos de interpolação espacial: aplicação à prospeção geoquímica

Tese de mestrado, Geologia Aplicada (Geologia de Engenharia), Universidade de Lisboa, Faculdade de Ciências, 2016Portugal tem importantes recursos de matérias-primas minerais metálicas, em especial Cu e W. A diversidade geológica do território nacional tem suportado atividades de prospeção e exploração desde os tempos pré-romanos. De entre os principais tipos de sistemas mineralizantes existentes na Zona Centro Ibérica (ZCI) salientam-se os de W-Sn, de Au(-Ag), de U e de Li. Neste contexto, os sedimentos de corrente têm sido um dos meios de amostragem mais usados na cartografia geoquímica, servindo de referência à cartografia geológica, prospeção mineral e estudos metalogénicos. O principal objetivo desta dissertação é explorar a utilização de ferramentas de interpolação espacial (inverso da distância, krigagem e cokrigagem) para mapear os elementos e índices geoquímicos de amostras de sedimentos de corrente. A análise estatística univariada mostrou que a maioria dos elementos estudados apresenta concentrações com distribuição com simetria positiva e média superior à média da crosta continental. Através da análise estatística bivariada foi possível observar que a correlação entre os diversos elementos evidência a presença de litologias metasedimentares na área em estudo (SiO2 e Al2O3) e a presença de domínios mineralizados de W-Sn e Au-Ag. Realizaram-se diversos testes para validação dos modelos de interpolação utilizando 2 elementos com distribuições contrastantes: Cu e SiO2. Neste conjunto de testes, que se baseou num conjunto de amostras independente do conjunto utilizado na interpolação, foram determinadas várias estatísticas de erro, incluindo o erro quadrado médio, em mais de 10000 de ensaios. Nos testes realizados para o Cu observou-se que os resultados são relativamente independentes da densidade de amostragem (para uma distância média ao vizinho mais próximo superior a 1 km) e que os resultados obtidos com métodos do inverso da distância e da krigagem não são significativamente diferentes. Nos testes realizados para o SiO2 os resultados obtidos com o melhor modelo de krigagem e do inverso da distância com potência otimizada são virtualmente idênticos. Utilizando os dois modelos de interpolação otimizados, realizou-se a interpolação para a área em estudo dos elementos/índices. Em complemento à interpolação dos valores de concentração elementar, utilizaram-se índices geoquímicos, cuja qualidade de interpolação se revelou mais elevada, e permitiram obter mapas geoquímicos integrados e realistas. A distribuição espacial dos índices geoquímicos permitiu delimitar zonas anómalas e áreas com potencial para prospeção, nomeadamente: o Índice de Estanho e Tungsténio (ISW); o Índice de Metais Preciosos (IAA); e o Índice dos Metais básicos (IMB). O mapeamento dos Índices ISW, IAA e IMB procura condensar a informação de natureza mineralógica e geoquímica, sendo também úteis para uso como variáveis secundárias na estimação espacial de variáveis primárias. Muitas das zonas anómalas identificadas encontram-se na proximidade de zonas de falhas e/ou na proximidade de ocorrências minerais conhecidas e/ou jazidas exploradas no passado, demonstrando a fiabilidade dos resultados obtidos.Portugal has important resources of mineral raw materials metal, especially Cu and W. The geological diversity has supported prospection and exploration activities since pre-Roman times. Amongst the main mineralizing systems in the Central Iberian Zone (CIZ) it is possible to highlight the W-Sn, Au (-AG), U and Li. In this context, stream sediment sampling is commonly used in geochemical mapping, serving as a reference to geological mapping, mineral exploration and metallogenic studies. The main objective of this dissertation is to explore the use of spatial interpolation methods (inverse distance, kriging and cokriging) to map the elements and geochemical indexes of stream sediments samples. The univariate statistical analysis showed that most elements presents positive symmetry concentrations and an average that is higher than the continental crust average. Bivariate statistical analysis, through the computation of the correlation coefficient, put in evidence the presence of metasedimentary lithologies in the study area (SiO2 and Al2O3) and the presence of mineralized areas of W-Sn-Ag and Au. Validation of interpolation models was performed using 2 elements with contrasting distributions: Cu and SiO2. In this set of tests, which was based on a set of independent samples, various error statistics, including root mean square error, were determined in over 10,000 assays. In tests for Cu it was observed that the results are relatively independent of the sampling density (to an average distance to the nearest neighbor above 1 km), and the results obtained with the inverse distance and kriging methods are not significantly different. In tests for the SiO2 results obtained with the best kriging model and inverse distance with optimized power were virtually identical. Using the two optimized interpolation models the elements/ indexes were interpolation for the study area. The interpolation of geochemical indexes proved to be higher and enabled integrated and realistic geochemical maps. The spatial distribution of geochemical indices allows define anomalous areas with potential for exploration, including: the Tin and Tungsten Index (TTI); in Precious Metals Index (PMI); the basic metals index (MBI). The mapping of TTI Indices, PMI and MBI seek to condense the information mineralogical and geochemical nature, and is also useful for use as secondary variables to estimate primary variables. Many of the anomalous areas are identified in the vicinity of fault zones and / or in the vicinity of known mineral occurrences and / or deposits explored in the past, demonstrating the reality of the results

Brazilian Flora 2020: Leveraging the power of a collaborative scientific network

International audienceThe shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora

Growing knowledge: an overview of Seed Plant diversity in Brazil

Abstract An updated inventory of Brazilian seed plants is presented and offers important insights into the country's biodiversity. This work started in 2010, with the publication of the Plants and Fungi Catalogue, and has been updated since by more than 430 specialists working online. Brazil is home to 32,086 native Angiosperms and 23 native Gymnosperms, showing an increase of 3% in its species richness in relation to 2010. The Amazon Rainforest is the richest Brazilian biome for Gymnosperms, while the Atlantic Rainforest is the richest one for Angiosperms. There was a considerable increment in the number of species and endemism rates for biomes, except for the Amazon that showed a decrease of 2.5% of recorded endemics. However, well over half of Brazillian seed plant species (57.4%) is endemic to this territory. The proportion of life-forms varies among different biomes: trees are more expressive in the Amazon and Atlantic Rainforest biomes while herbs predominate in the Pampa, and lianas are more expressive in the Amazon, Atlantic Rainforest, and Pantanal. This compilation serves not only to quantify Brazilian biodiversity, but also to highlight areas where there information is lacking and to provide a framework for the challenge faced in conserving Brazil's unique and diverse flora