Litogeoquímica e química mineral das rochas félsicas e máficas aflorantes entre os Km 151-155 da BR 174, Município de Presidente Figueiredo (AM)

Abstract

The mafic and felsic rocks studied are located in the quarries Figueiredo, Javel, Manaus and Mercês, as well as in the vicinity of 151-155 km between the BR-174. These lithologies are inserted in Domínio Uaimiri, Province Tapajós-Parima, Craton Amazônico geotectonic unit. Through petrographic these rocks were classified as monzogranites the terms felsicdiorites and quartz diorites as the mafic terms. The monzogranites mainly consist of quartz crystals, alkali feldspar, plagioclase and biotite. Some samples also exhibit grenade. This assemble mineral presents aspects microtexturais as lamella deformation, grain boundaries migration and chessboard, indicating the presence of solid-state deformation. The diorites and quartz diorites are composed primarily of amphibole, biotite and plagioclase, which sometimes present themselves oriented in a preferred direction formed by magmatic flow. On a macroscopic scale are seen in front of the quarry mining Javel features indicating contemporaneity of mingling between the dikes diorite and quartz diorite, and thus can be characterized as syn-plutonic. The occurrence of a hydrothermal event is recorded in both lithologies, macroscopically evidenced by fractures filled by epidotes and sulfides as well as microscopically, since destabilization of crystals of plagioclase, alkali feldspar and biotite. Based on the degree of hydrothermal alteration more significant in diorites and quartz diorites separadados they were more altered and less altered. Mineral chemistry data show a dominant composition of plagioclases albite for monzogranites and a compositional variation for diorites and quartz diorites from labradorite to oligoclase, and quartz diorite to less altered diorites, labradorite and albite altered to have more. Chemically, the composition peraluminosa monzogranites present, affinities alkaline magmatism type a highly evolved generated in oxidized environments. ΣETR present between 126.1 to 293.8 and shows a LREE fractionation, represented by the ratio LaN / SmN between 7.01 to 14.53. Based on their chemical characteristics can be correlated to the Intrusive Suite granites belonging Mapuera mainly to São Gabriel Granite crops out in the vicinity of the study area. The diorites and quartz diorites are metaluminous, calc-alkaline geochemical affinities of high K and intermediate terms to evolve by fractional crystallization process. ΣETR present between 62.1 to 117 and changed over in accordance ΣETR between 66.8 to 123.3 under less altered. Their chemical characteristics do not show any correlation with mafic occurrence in the literature for the region and can treat yourself to a unit not yet mapped. The occurrence of an event subsequent deformation is recorded by reworking by shear zones with NE-SW monzogranites us diorites and quartz diorites and as well as by aspects microtexturais these rocks. This event is also responsible for the percolation of fluids and hydrothermal alteration that is less evident in diorites and quartz diorites. Based on microtexture as deformation lamella crystals of quartz and feldspar, by recrystallization migration of grain boundaries, formation of subgrains and forming tray chadrez shows that this event the temperature reached to 600 ° C.