Petrogenesis and tectonic of the Urucum granitic suite, Rio Doce Valley (Minas Gerais - Brazil): an example of syn to late collisional peraluminous magmatism associated with high-angle transcurrent shear zone

Petrogênese e tectônica da suíte granítica Urucum, Vale do Rio Doce (Minas Gerais - Brasil): um exemplo de magmatismo sin- a tardi-colisional associado a zonas de cisalhamento direcionais de alto ângulo

The Urucum suite (582 ± 2 Ma, zircon U-Pb age), situated in the Mid-Rio Doce Valley, eastern part of Minas Gerais State, is characterized by elongated, NW-SE and N-S trending granitic massifs associated with the Conselho Peña-Resplendor high-angle shear zone. It corresponds to a syn to late collisional magmatism that presents dominant solid-state foliation. Four facies are distinguished within the Urucum suite: (i) a porphyritic (Urucum); (ii) a medium- to coarse nequigranular (Palmital); (iii) a tourmaline-bearing; and (iv) a pegmatitic facies. These facies are peraluminous, with alumina saturation index varying from 0.98 to 1.38. SiO₂ contents vary from 70.7 to 73.7 wt%, with K₂O values ranging from 3.5 to 5.7 wt%, Na₂O from 1.9 to 4.4 wt%, MgO from 0.6 to 1.2 wt%, and CaO from 0.3 to 0.9%. Harker-type diagrams show rather continuous trends from the less-evolved Urucum facies to the more evolved tourmaline-bearing and pegmatitic facies. The behavior of several major oxides and trace elements (Fe₂O₃, MgO, MnO, CaO, TiO₂, Al₂O₃, K₂O, Rb and Ba) reflects the role played by fractionation of ferromagnesian minerals, feldspars and accessory minerals. Initial Sr⁸⁷/Sr⁸⁶ ratios vary from 0.711 to 0.716, with ε_{Nd (580 Ma)} values between -7.4 to -8.2, and Sm-Nd T_DM model ages ranging from 2290 to 1840 Ma.

Urucum suite; Geochemistry; Petrogenesis; Araçuaí belt