IDADE U-Pb DO DIORITO POSSELÂNDIA, HIDROLINA, GOIÁS

Abstract

The Posselândia Diorite intrudes Archean granite-greenstone terrains of the region of Hidrolina, Central Goiás, Brazil. U-Pb radiometric determinations in two fractions of zircon crystals from the diorite yield an age of 2,146 ±1.6 Ma, interpreted as the cristallization age of the intrusion. The lack of deformation in the intrusion demonstrates that condolidation of the granite-greenstone terrains in the Hidrolina-Pilar de Goiás-Crixás area took place before 2,146 Ma.

U–Pb SHRIMP and Sm–Nd geochronology of granite–gneiss complexes and implications for the evolution of the Central Brazil Archean Terrain

“…2.15 Ga metamorphic age of titanite from a flat-lying north-south foliation that crosscuts the metamorphic polydeformed compositional banding of the Crixás Açu gneisses (Queiroz, 2000). So, far, the metamorphic event was only followed by activity along shear-zones between 2.1 and 2.0 Ga, as indicated by a dioritic stock hosted by a northwest-trending shear zone that crosscuts the Hidrolina Complex (Jost et al, 1993), and by galena and felsic sills related to a gold-bearing shear zone at the eastern border of the Pilar de Goiás greenstone belt (Pulz, 1995;Queiroz, 2000). This indicates that during the Orosirian the crustal temperature was below the necessary to recycle the isotopic signature of magmatic Archean zircon crystals.…”

“…Additionally, Queiroz (2000) reports 2.15 Ga U-Pb SHRIMP titanite metamorphic age from the Crixás Açu tonalite gneiss. Magmatic activity is represented by 2.4-2.3 Ga Rb-Sr, Ar-Ar and Sm-Nd mafic dike swarm within the Caiçara and Anta complexes (Tomazzoli, 1997;Correa da Costa, 2003) and 2.15 Ga U-Pb SHRIMP diorite intrusion at the eastern portion of the Pilar de Goiás greenstone belt (Jost et al, 1993). In the Crixás greenstone belt, metamorphosed hydrothermal alteration paragenesis related to gold mineralization of Mina III yielded 600-550 Ma K-Ar, Rb-Sr and ArAr ages (Fortes, 1996).…”

The Paleoproterozoic Campinorte Arc: Tectonic evolution of a Central Brazil pre-Columbia orogeny

“…From bottom to top the greenstone belts sequence can be summarized as (a) basal metakomatiite; (b) metabasalts with local pillow structures and; (c) metasedimentary sequence with carbonaceous phyllite, metagraywacke, schist, metachert and gondites. Magmatism coeval with Paleoproterozoic basin formation is evidenced by 2.17 Ga mafic dikes cutting Crixás metagraywacke (Jost and Scandolara, 2010), ∼2.14 Ga metafelsic rock in the Pillar greenstone belt (Queiroz et al, 1999) and the ∼2.16 Ga Posselândia diorite east of the Hidrolina Complex (Jost et al, 1993). A provenance study of the Crixás and Guarinos greenstone belts upper metasedimentary rocks by Jost et al ( , 2012 provided a Paleoproterozoic sedimentation age of ∼2.15 Ga. Mixed mafic and felsic source contributions with Eu anomalies were determined by whole-rock geochemistry (Jost et al, 1996).…”

Polymetamorphic History of the Crixás-Açu Gneiss, Central Brazil: Shrimp Upb Evidence From Titanite and Zircon

“…The Archaean block is partially overthrusted by Proterozoic metasedimentary sequences. Previous Sm-Nd, Rb-Sr, Ar/ Ar, Pb/Pb, and U-Pb data (Tassinari and Montalvão 1980, Montalvão 1986, Arndt et al 1989, Vargas 1992, Jost et al 1993, Pulz 1995 P ro te ro zo ic Se q ue n ce s G r e en s to ne B e lt S u pra cru stals G ra nite -G n e iss ic Te rran es M ain T h ru st F a u lts M ain S h e ar Z o n es A ma zo n C raton São F ranci sco Craton…”