Petrografia e química mineral de enclaves máficos microgranulares do Batólito Rio Jacaré, domínio Poço Redondo – Marancó, Sistema Orogênico Sergipano

Abstract

The Rio Jacaré Batholith (RJB) is an igneous intrusion at Poço Redondo migmatitic complex, Poço Redondo – Marancó Domain, Sergipano Orogenic System (SOS). It occurs in an elongated form, with NW-SE direction, with a total area of 167 km² and an age of 617 ± 4 My. In this study it was analyzed the petrography and mineral chemistry of mafic microgranular enclaves (MME), classified as monzodiorites (SOS-861-C and SOS-876-B), and quartz monzodiorito (SOS-871-B). The petrographic analysis was identified the porphyritic, inequigranular, hipidiomorfic and allotriomorfic textures in these rocks, and alterations in crystal of biotite, hornblende, plagioclase and potassium feldspar. The mineralogy is composed of plagioclase, biotite, potassium feldspar (orthoclase and microcline), hornblende, quartz, epidote, apatite, titanite, zircon and opaque minerals. The mineral chemistry identified the compositions of the plagioclase ranging from albite (Ab92 - An8) to labradorite (Ab48-50 - An52-50). The plagioclase crystals are zoned, varying between normal, reverse, oscillatory and patchy, it indicates different crystallization conditions, like decompression and mafic and felsic magmas mixing. The biotite is Mg-biotite, formed from calc-alkaline magma and later rebalanced. The magmatics amphibole are Mg-hornblend, endenite, magnesium-hastingsite and magnesium-sadanagaite. The epidote was formed from the magma and destabilization of plagioclase crystals. The apatite is fluorapatite and hydroxyapatite. With the mineralochemical analysis it was also possible to identify the opaque minerals as magnetite, besides indicating presence of torite associated with zircon.