Titanite Crystal Chemistry and U-P Isotopic Data: A Petrogenetic Indicator for Precambrian Granitoid Plutons of the Eastern Brazilian Shield

Abstract

This paper presents crystal chemistry and U-Pb isotopic data for titanite (or sphene, CaTiSiO 5 ) from Precambrian granitoid plutons of distinct tectonic settings within the Eastern Brazilian shield. Despite the fact that most titanite ages are related to partial lead-loss, resetting or crystallization during metamorphic events, chemistry data reflect the magmatic history of the plutons, specially the Ti 4+ /Al+Fe 3+ ratio. It is demonstrated that for plutons of different crystallization ages (Archean, Paleoproterozoic and Neoproterozoic) the measured Ti 4+ /Al+Fe 3+ ratios of titanite grains are characteristic of the source region from which the magma was extracted, and the ratios remain unchanged during subsequent metamorphic events. Higher Ti 4+ /Al+Fe 3+ values (> 9) are found in predominantly mantle-derived granitoid plutons whilst crust-derived granitoid rocks have lower ratios. Therefore, titanite crystal chemistry may be used to discriminate magma sources of granitoid rocks regardless their age and metamorphic history.

Determinando a Duração Do Período Colisional Do Orógeno Araçuaí Com Base Em Geocronologia U-Pb De Alta Resolução Em Zircão: Uma Contribuição Para a História Da Amalgamação Do Gondwana Ocidental

“…ca. 528Ma, assim como a amostra de titanita de um ortognaisse mais velho (2867 ± 10 Ma, Silva et al 2002), mas do mesmo complexo, forneceu a idade de 506 ± 7 Ma (Piuzana et al 2008). Além disso, Oliveira (2002) obteve uma idade isocrônica Sm-Nd (rocha total-granada) de 521 ± 21 Ma para o metamorfismo de um gnaisse arqueano e Ribeiro-Althoff et al (1997) determinaram a idade Ar-Ar (de inclusões de flogopita em esmeralda) de 509 ± 2 Ma para o depósito de Capoeirana.…”

Geochemical evolution of a composite pluton: insight from major and trace element chemistry of titanite

“…8e) and high Sr, Zr and Nb contents. High Ti 4+ / Al + Fe 3+ ratio (>11) is indicative of mantle-related source regions (Piuzana et al 2008) and values >18 are demonstrated exclusively by LAM2 titanite (among all studied samples). High (Ce + Nd)/Y, La/Ce and low Nb/Zr, Y/Zr and Lu/Hf ratios have been documented in titanite from mafic rocks and MMEs of the Mangling granitoid pluton (Hu et al 2017) and from intermediate rocks and MMEs of the Ross of Mull granite (McLeod et al 2011), which both originated by mixing of mantle-and crust-derived sources.…”

“…Apart from rare earth elements, major and other trace element concentrations and ratios also show some affinity to the mafic mantle-related titanite. Ti 4+ /(Al + Fe 3+ ) ratios are usually >9 (and overlap with some of the LAM2 titanite grains) for FOJ titanite, suggesting significant mantle contribution Piuzana et al (2008) (Fig. 6).…”

“…Major elements and their ratios in titanite may also point to dominating origin of participating magmas. Ti 4+ /(Al + Fe 3+ ) ratio is indicative of mantle versus crustal origin (Piuzana et al 2008), while Al/Fe ratio can distinguish magmatic from hydrothermal/metamorphic titanite (Cao et al 2015;Rasmussen et al 2013).…”

Thermobarometry and electron-microprobe Th-U-Pb monazite dating in garnet metapelites from the Capelinha Formation, Araçuaí Orogen, Brazil

“…Fernandes (2001) presented the titanite age of ca.507 Ma (U-Pb TIMS) for the Statherian Borrachudos anorogenic granitoid. Piuzana et al, (2008) reported the titanite age of 506 ± 7 Ma for the trondhjemite gneiss of the Guanhães complex located south of the Capelinha region. Silva et al, (2011), for the biotite orthogneiss of the Guanhães complex situated at São João Evangelista town, presented the zircon age of 527 ± 45 Ma (U-Pb SHRIMP, inferior intercept).…”