The Khan River (Namibia) and Bear Lake (Canada) titanites are investigated as potential reference materials (RM) for LA‐ICP‐MS applications. The Bear Lake titanite is texturally and compositionally homogeneous. The Khan River titanite is texturally heterogeneous and characterised by variable trace element compositions and total rare earth element contents. However, both titanites have consistent U‐Pb and Nd‐isotope ratios. U‐Pb isotope dilution‐thermal ionisation mass spectrometry analyses yielded Pbc‐uncorrected intercept ages of 516.3 ± 1.3 Ma (2s, n = 5, MSWD = 2.4) and 1067.81 ± 0.74 Ma (2s, n = 4, MSWD = 0.35) for Khan River and Bear Lake titanites, respectively. Multiple U‐Pb LA‐SF/MC‐ICP‐MS analyses gave consistent Pbc‐uncorrected intercept ages for both, Khan River (517 ± 1/5 Ma, 2s, n = 262, MSWD = 1.5) and Bear Lake (1070 ± 1/11 Ma, 2s, n = 325, MSWD = 0.88). U‐Pb SHRIMP analyses on the same material returned identical (within uncertainty) ages. Khan River and Bear Lake gave internally consistent solution MC‐ICP‐MS 143Nd/144Nd ratios of 0.511587 ± 0.000027 (2s, n = 2) and 0.512321 ± 0.000004 (2s, n = 2), respectively. The 143Nd/144Nd ratios via solution‐MC‐ICP‐MS and LA‐ICP‐MS all agree within uncertainty and suggest that both titanites can be used as RMs for Nd‐isotope analyses.
The Araçuaí orogen of SE Brazil consists of a suite of deformed, metamorphosed, and partly migmatitic sedimentary rocks and granitoid batholiths that predominantly formed during collision of the São Francisco and Congo cratons during West Gondwana assembly in the late Neoproterozoic. While widespread anatexis and a prolonged magmatic record are well-established, insufficient information exists about the extensive exposure of metamorphic rocks along the Araçuaí orogen. Combining information from a wide range of these metamorphic rocks is essential to reconstruct mountain-building processes and heat sources that operate in convergent tectonic settings. New petrographic observations, mineral chemistry, and phase equilibria modelling were used to constrain peak metamorphic conditions of amphibolite facies metasedimentary rocks from the central domain of the orogen at 580-620°C and 7-9 kbar. We applied in situ low-U (<1 µg/g) garnet U-Pb geochronology, which yielded ages in the range of 590-565 Ma, interpreted as the timing of bulk garnet growth during prograde metamorphism, and consistent with previously established monazite ages for the peak metamorphic event. Metamorphic zircon ages of c. 630 Ma are related to a cryptic terrane accretion event prior to the orogeny, whereas garnet U-Pb ages record the main orogenic event as revealed by disequilibrium rare earth element partitioning between the two minerals. A compilation of our results with previously
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