Estudo da morfologia, petrografia e análise da relevância científica, educativa e turística dos basaltos colunares de Matsequenha, Distrito de Namaacha para fins de geoconservação

Abstract

In Mozambique, there has recently been a growing trend in the number of studies on geological heritage for conservation purposes. As a result of these studies, the country currently has geosites classified as world geological heritage, given their representativeness and scientific interest. However, the quantification of the relevance of geosites in this field is a recent issue, and is a fundamental step towards understanding the heritage interest of the geosite, as well as defining strategies for its conservation. The columnar basalts of Matsequenha are the only known example of columnar disjunction in the country. These basalts occur to the north-east of Namaacha District, Maputo Province, a region characterised by geosites of enviable scientific, tourist and cultural interest. In this context, with the aim of understanding the scientific, educational and tourist relevance of these basalts, the elements that occur in this geosite were inventoried and quantified, followed by an analysis of their potential for geoconservation purposes. The methodology used to inventory and quantify the importance of the Matsequenha columnar basalts was adapted from the model for inventorying, characterising and evaluating geological heritage proposed by Cumbe (2007). The results showed that the columnar basalts of Matsequenha have regular columns, with a disjunction pattern that is mostly pentagonal and sometimes hexagonal, with an average diameter that varies from 21 to 35 cm and an average relative length of the small columns called colonnades of up to four metres. The columns studied show banding that accompanies the deformation of the columns into Chevron-type folds and show vesicles filled with a cryptocrystalline material of carbonate composition. The data obtained during the quantification show that the columnar basalts of Matsequenha have considerable scientific and educational relevance, calculated at [A = 0.56], associated with their morphological, petrographic and structural characteristics. As for tourist relevance, the calculated is low [U = 0.43], and the geosite is not very useful for tourism purposes, due to its poor relationship with other biotic and cultural elements, as well as its smaller area. In addition, the geosite has a high degree of vulnerability, calculated at [V = 0.66], due to its exploitation as a building material. From the qualitative and quantitative assessment carried out, it can be concluded that the columnar basalts of Matsequenha are of heritage interest, due to their rarity in the local and national geological context, their morphological, petrographic and structural features that make the geosite an ideal place to carry out petrological, mineralogical and tectonic studies. However, taking into account the risk of destruction that the geosite is in, there is an urgent need to protect this site in order to guarantee its prevalence for the development of scientific research, as well as in the training of geoscientists. (TRADUÇAO NOSSA)