ESTUDO PETROGRÁFICO DO SUPORTE ROCHOSO DO SÍTIO ARQUEOLÓGICO DA PEDRA DO INGÁ, PB

Resumo Este artigo apresenta o estudo do suporte rochoso do sitio arqueologico Pedra do Inga (PB).Os resultados do presente estudo visam contribuir prioritariamente para a adocao de medidas conservacionistas pautadas nas propriedades petrograficas desse sitio em face aos agentes exogenos. Nesse sentido, esta pesquisa estuda as caracteristicas petrograficas do suporte rochoso da Pedra do Inga. Essa caracterizacao foi realizada em amostras coletadas no entorno deste sitio. A analise das lâminas releva a existencia de Biotita-granodiorito, rocha ignea de textura compacta, granulacao fina, equigranular, isotropica de alta dureza. O quartzo ocorre com percentual de 30%, plagioclasios com 30%, feldspatos potassicos apresentam 24% o que e caracteristico de rochas igneas compostas por quartzo e feldspatos. A biotita e o principal mineral mafico e somados a ela ocorre, epidoto, zircao e minerais opacos. O plagioclasio mostra processo de alteracao para micas finas, denominado sericitizacao. A biotita apresenta alteracao para cloritas. Fatores intrinsecos (como composicao mineralogica, textura e porosidade) e extrinsecos (como quantidade de agua, temperatura, pH, potencial de oxi-reducao e forcas bioticas) contribuem para a degradacao e decomposicao da rocha. A presenca do Riacho Bacamarte fornece a agua, veiculo importante nas reacoes de hidratacao, hidrolise, oxidacao e tambem na dissolucao de minerais, alterando assim os minerais presentes no suporte, mas tambem atenua os efeitos da termoclastia que causa o desplacamento do suporte rochoso do referido sitio arqueologico. Palavras Chave: sitios arqueologicos; suporte rochoso; processos de alteracao Abstract PETROGRAPHIC STUDY OF THE ROCKY SUPPORT OF THE ARCHAEOLOGICAL SITE OF PEDRA DO INGA, PB. This paper presents the study for the rock support of the archaeological site Pedra do Inga (PB). The results of this study are intended to contribute primarily for the adoption of conservation measures guided by the petrographic properties of this site in face of exogenous agents. In this sense, this research studies the petrographic features of the rock support of Pedra do Inga. This characterization was performed on samples collected in the surrounding areas of this site. Slide analysis highlights the existence of biotite-granodiorite, igneous rock of compact texture, fine-grained, equigranular, high hardness isotropic. Quartz occurs with a percentage of 30%, plagioclase with 30%, potassic feldspar have 24% which is characteristic of igneous rocks composed by quartz and feldspar. The biotite is the main mafic mineral and added to thereareepidote, zircon and opaque minerals. The plagioclase shows alteration process for fine mica, called sericitization. The biotite shows alteration to chlorite. Intrinsic factors (such as mineral composition, texture and porosity) as well as extrinsic factors (such as the amount of water, temperature, pH, redox potential and biotic forces) contribute to the degradation and decomposition of the rock. The presence of Bacamarte Stream provides water, an important vehicle in the hydration reactions, hydrolysis, oxidation and also in the dissolution of minerals, thereby altering the minerals present in the support, but also mitigates the effects of termoclastia, which causes the peeling of the rock support of this archaeological site. Keywords : archaeological sites; Rock support; alteration processes