Marcos Antonio Leite do Nascimento

Augen gnaisses riacianos no Domínio Rio Piranhas-Seridó - Província Borborema, Nordeste do Brasil

Augen gneisses occurring at the Fazenda Genezare in the Serra da Formiga east of Caico, at the border of the Sao Vicente-Florânia (RN) nucleus, and in exposures SW and NW of Sao Jose do Serido (RN) were studied by geologic mapping, petrography, lithogeochemistry and U-Pb dating. These rocks consist of biotite augen gneisses, and granitic/granodioritic orthogneisses, with porphyro-granoblastic textures and light gray to pink colors. Their mineralogy consists of perthitic microcline, oligoclase, quartz, besides biotite and amphibole, with epidote, titanite, chlorite, opaque minerals, apatite, zircon and allanite as accessory minerals. Petrography indicates that these rocks were affected by amphibolite facies metamorphism, and a later greenschist facies retrometamorphism. They have a prominent low-angle NW-SE foliation containing a high rake stretching lineation. Lithogeochemistry indicates high-K, metaluminous to peraluminous and calc-alkaline geochemical signatures related to a collisional environment. U-Pb dating of zircon (LA-ICP-MS) provided an upper intercept age of 2252 ± 17 Ma and 2171 ± 20 Ma, for the rocks found north of Florânia (RN), and east of Genezare, respectively. In the latter values of 2.84 Ga TDM and ƐNd(0) of -20.76 were also obtained. The data allow attribution of the augen gneisses to the Rhyacian period, and are consequently associated with to the magmatism which formed the Caico Complex.

Valores de uso turístico dos geossítios de Sete Cidades (PI)

The National Park of Seven City (PN7C) was indicated by the Geological Survey of Brazil (CPRM), Geoparks under the Project in Brazil, as a potential area to create a Geopark because of the relevance of its geomorphological scenic beauty and paleoenvironmental. For the geotourism be promoted on this site, it is necessary advanced the adoption of measures geoconservation and beginning with the assessment of the geological heritage of the site visitation. In 2009, the CPRM started the report of the inventory of geological heritage PN7C, choosing eight Geosites, namely: Turtle Rock; Arc the Triomphe; Small Site; American Stone; Library; Lost City; and Canyons of Stone Waterfall the Riachao. In the measurement values are defined for Scientific Use; Conservation and Tourism, the latter being the main objective of this work establishing the potential of each geotouristic geosite from their values and Tourism of Use/Management, as defined in the first stage of the quantification. The highest values of tourist use, taking into account the overall average was 2.54, were assigned to Geosites Arc the Triomphe and Library, with values of 2, 8 and the lowest values for the Lost City Stone and Cannons, with 1,8 and 2,04, respectively. The cultural values of the Small Site and the Stone of the American are linked to the presence of archaeological graphics in sandstone cliffs that have not been dated. The Lost City, which was considered the seventh city of the park also features many graphics, but has no structure to the visitor and is open only for scientific research and the Stone of the American is vulnerable to visitors as they do not have the access control visitors. The methodology used in this study consisted of the literature review, field research for direct observation, photographic documentation and collection of points with the use of GPS for mapping the location of Geosites.

Geotouristic potential of waterfalls in igneous and metamorphic rocks: the case of the municipality of bonito, Pernambuco, northeast Brazil

The municipality of Bonito, located in the State of Pernambuco, northeast Brazil, has as its main touristic attraction several waterfalls embedded by a geodiversity characterized by igneous and metamorphic rocks. However, the tourism activity implemented in the area, does not use its full potential. The geologic information is not associated with geomorphologic features (waterfalls) and used to improve the knowledge and environmental education. This work has the goal to fulfill this gap with the implementation of tourism with geologic base. The main emphasis will be the educational and scientific values of these waterfalls hosted in igneous and metamorphic rocks. To accomplish this objective it is presented here a diagnosis of some waterfalls of Bonito. Geologic and geomorphologic analyses are associated with qualification and quantification of controlling parameters, followed by discussion of the main threads to geodiversity. A new method for quantification of geossites is presentend. This method was constructed based on that proposed by Brilha (2005). It attempts to give more reasonable mathematic meaning for the parameters analyzed; presenting graphics that will facilitate the interpretation of the values obtained by the quantification of geosites.

Definição de suítes magmáticas em corpos ediacaranos no extremo NE da Província Borborema (estado do Rio Grande do Norte): Plútons Pitombeira, Taipu e Gameleira

The Pitombeira, Taipu and Gameleira plutons, located in the northeasternmost portion of the Sao Jose do Campestre Domain within the Borborema Province (NE, Brazil), are subjects of lithogeochemical studies in the present work. The Pitombeira Pluton comprises a monzo- to syenogranitic facies defined by K-feldspar phenocrysts, and a quartz-dioritic to tonalitic facies, mainly as enclaves, with laths of plagioclase showing compositional zoning and chilled rims. The Taipu Pluton is made of equigranular, locally porphyritic, monzo- to syenogranites, whereas the Gamaleira Pluton encompasses tonalitic and granodioritic rocks with porphyritic textures and compositionally zoned plagioclase crystals. Geochemical discriminant diagrams reveal that the rocks forming the Gameleira Pluton are metaluminous, with a calc-alkaline signature and magnesian character, contrasting with the subalkaline (high-K calc-alkaline) signature and ferroan character of the Taipu and Pitombeira Plutons, where the former is highly peraluminous and the latter is metaluminous to slightly peraluminous. Rare Earth Elements patterns are similar to all plutons and register negative Eu anomalies and a relative enrichment of LREE over HREE, with LaN/YbN ratios between 9.38 to 16.20 (Gamaleira Pluton), 17.99 to 31.39 (granitic facies of the Pitombeira Pluton), 14.15 to 21.81 (dioritic facies of the Pitombeira Pluton) and 15.17 to 175.41 (Taipu Pluton). Based on the combined investigation of structural, textural and geochemical data, a late- to post-collisional tectonic environment is suggested for the plutons here studied.