Titanite (CaTiSiO5) is a common accessory mineral in orthoderived metamorphic rocks, calcsilicatic rocks, and calc-alkali granites. The closing temperature for Pb diffusion in titanite varies between 650-775°C. Furthermore, it tends to be more reactive than other petrochronometers such as zircon and monazite, as it is more susceptible to medium- to high-grade metamorphic reactions. Therefore, titanite is a geochronometer widely used in U–Pb dating of metamorphic, igneous, and hydrothermal events. This work consisted of the implementation of the experimental procedures of the U–Pb methodology in titanite by inductively coupled plasma source mass spectrometry and laser ablation microprobe (LA-ICP-MS) at the Isotope Geology Laboratory of the Federal University of Pará (Pará-Iso). The analytical routine was optimized based on analyzes of four reference titanites (Tory Hill, Khan, Mud Tank, and CHBK), to estimate the precision, reliability, and reproducibility of the data. The protocol was implemented based on procedures previously developed at the Pará-Iso Laboratory (U–Pb in zircon) and in other laboratories (U–Pb in titanite). The most suitable crystals for dating (those that are darker and without inclusions/fractures) were selected and fixed in epoxy resin mounts. Backscattered electron images helped to evaluate the internal features of the crystals and identify the domains for in situ analysis. The U–Pb analyses were performed with a quadrupole mass spectrometer (Q-ICP-MS) model iCAP Q from Thermo Fischer Scientific, with a solid-state Nd:YAG 213 nm laser microprobe model LSX-213 G2 from CETAC. The processing and reduction of the raw analytical data were performed with an in-house Excel spreadsheet, adapted to the specificities of iCAP Q and the U–Pb system in titanite, considering that titanite can incorporate large amounts of common Pb, which requires a careful evaluation and proper correction of the content of this Pb. Age calculation and Concordia diagrams were provided using the Isoplot/Excel software. To validate the U–Pb analysis protocol by LA-Q-ICP-MS, titanites from two reference materials (Khan and CKHB) and three samples (two orthogneisses and one tonalite) were also analyzed by SHRIMP IIe at the Center for Research in Geochronology and Isotopic Geochemistry at the University of São Paulo (CPGEO-USP). LA-Q-ICP-MS analyses on the Tory Hill and Khan titanites provided mean 206Pb*/238U ages of 1057.2 ± 2.5 Ma (n=79; MSWD=0.74) and 518.0 ± 4.9 Ma (n=26; MSDW=0.45), respectively, in agreement with the ID-TIMS age of 1059.7 ± 1.2 Ma from the literature for the Tory Hill titanite and with the SHRIMP age of 519.9 ±1, 8 Ma (n=18; MSWD=0.65) of the Khan titanite. The latter proved to be more suitable for use as a primary reference material (RM), as it showed a higher analytical signal, lower variance in isotopic ratios, and lower common Pb content. The Mud Tank and CKHB titanites, used as secondary RMs, provided, respectively, mean 206Pb*/238U ages of 318.4 ± 2.1 Ma (n=44; MSWD=0.30) and 93.9 ± 2.9 Ma (n=40; MSWD=0.05), identical to the ID-TIMS age of 319.20 ± 0.36 Ma from the literature for Mud Tank and the SHRIMP age of 93.8 ± 1.5 Ma (n=18; MSWD=0.10) of the CHKB titanite. SHRIMP ages demonstrate excellent interlaboratory reproducibility, certifying the implemented analytical protocol at the Pará-Iso Laboratory. As a geological application, titanites were dated from three metamorphic rocks, one Archean and two Paleoproterozoic from the southeastern Guiana Shield (SEGS) previously dated by U–Pb method in zircon: a granodioritic orthogneiss (JAP-02A, 2.69-2.60 Ga), the paleosome of a migmatized dioritic orthogneiss (STG-179B, 2139 ± 1 Ma) and tonalite (B107, 2139 ± 12 Ma). Titanites from sample JAP-02A yielded a mean 207Pb*/206Pb* age of 2051 ± 10 Ma, which records the late-Rhyacian metamorphic event that produced this orthogneiss from a Neoarchean protolith, in the northern portion of the Amapá Archean Block. Samples STG-179B and B107 crop out along the Oyapock River, on the border between Amapá and French Guiana. Titanites from these samples provided mean 207Pb*/206Pb* ages of 2111 ± 17 Ma and 2098 ± 29 Ma for the paleosome and tonalite, respectively. These ages record a regional metamorphism event associated with the collisional stage (2.11-2.09 Ga) of the Transamazonian orogeny (2.26-1.95 Ga), which built up the SEGS. Such findings reinforce the efficiency of the titanite U-Pb systematics on the record of metamorphic events. In addition, igneous titanites of a Neoproterozoic leucogranite (SOS-1257), from the Sergipe Orogenic System, in the southern sector of the Borborema Province were also analyzed. The mean 206Pb*/238U age of 639.1 ± 5.8 Ma was obtained and is considered the best estimate of the crystallization age of this leucogranite since U–Pb dating of zircons from this same sample failed as they are highly metamict crystals. The age obtained for this leucogranite illustrates the potential of titanite to provide crystallization ages for granitoids whose metamict zircons preclude the determination of a reliable age. The results obtained in this work demonstrate the feasibility of the U–Pb method on titanite by LA-Q-ICP-MS, which is now routinely used at the Pará-Iso Laboratory.
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