Geologia e aspectos petrológicos das rochas intrusivas e efusivas mesozóicas de parte da borda leste da bacia do Paraná no estado de São Paulo

Abstract

The eastern edge of the Parana Basin in the State of Sao Paulo, shows a great number of sills and dikes, of basaltic composition, related to the Parana Magmatic Province (PMP), intruded mainly in the upper portion of the Tubarao Group, and also in the Irati and Corumbatai Formations. Petrographic analyzes of intrusive rocks and also of the lava flows indicated that they are constituted essentially by plagioclase, pyroxenes (augite and pigeonite), magnetite and mesostase (glass and/or microgranular), characterizing predominantly intergranular, subofitic and ofitic textures. On the other hand, the geochemical analyzes indicate that the rocks present basic nature, toleiitic affinity and can be classified in the group of high titanium (HTi) of the PMP. Moreover, the geochemical characteristics also indicate three distinct type of magmas (Urubici, Pitanga and Paranapanema), with a distinct occurrence for each one. Those of the Paranapanema type (1,7% 2,9% 350ppm) represent the majority of the intrusive bodies and lava flows (region of Jau and Franca), while the Urubici type (TiO 2 > 3,3% 550ppm) is intrusive in the region of Sao Sebastiao do Paraiso, Minas Gerais States, and lava flows of the northeast of the Sao Paulo State. Thus, in the investigated area, distinct processes of magmatic evolution are involved for the intrusives and extrusive basaltic rocks.