Titanite petrochronology of the southern Brasília Orogen basement: Effects of retrograde net-transfer reactions on titanite trace element compositions

Cioffi, Cauê Rodrigues; Neto, Mário da Costa Campos; Möller, Andreas; Rocha, Brenda Chung da

doi:10.1016/j.lithos.2019.06.035

Cited by 26 publications

(21 citation statements)

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“…In either case, it is apparent that the Zr concentrations in the titanite from this study do not reflect chemical equilibrium with zircon and rutile (e.g. Cioffi et al., 2019; Cruz‐Uribe et al., 2018; Holder & Hacker, 2019).…”

Section: Discussionmentioning

confidence: 69%

“…It is instead more likely that the elevated Zr concentrations reflect disequilibrium partitioning of Zr into titanite during crystal growth (e.g. Cioffi et al., 2019; Cruz‐Uribe et al., 2018; Holder & Hacker, 2019). Several factors appear to have contributed to the disequilibrium behaviour of Zr—and erroneously elevated Zr‐in‐titanite temperatures—in the studied samples including limited reactivity of refractory zircon and slow Zr diffusion relative to reaction rates.…”

Section: Discussionmentioning

confidence: 99%

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Delineation of multiple metamorphic events in the Himalayan Kathmandu Complex, central Nepal

Johnson

Cottle

Larson

2020

Journal Metamorphic Geology

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Quartz-inclusion geothermobarometry of texturally and chemically zoned garnet, together with U-(Th)-Pb accessory phase petrochronology, phase equilibria modelling, and major element thermobarometry delineates two metamorphic events withinthe Kathmandu Complex in central Nepal. Combined titanium-in-quartz thermometry (TitaniQ) and quartz-in-garnet barometry (QuiG) of quartz inclusions in garnet cores yields temperatures and pressures (555-580°C, 0.89-0.91 GPa) statistically higher than those estimated for both garnet rims and secondary garnet neoblasts (535-545°C, 0.81-0.84 GPa). Comparison of these temperatures and pressures with the results from phase equilibria modelling indicates that the garnet cores nucleated after overstepping the equilibrium garnet isograd. Estimation of the degree to which overstepping may have occurred, however, is complicated by uncertainty in the estimated reactive bulk compositions. Major element thermobarometry of the garnet rims returns temperatures and pressures lower than those preserved by the garnet cores but are consistent with previous estimates of Cenozoic metamorphism in the frontal portion of Kathmandu thrust sheet. Two generations of titanite are recognized on the basis of mineral morphology, chemical zoning, and U-Pb date (c. 500 Ma versus 29 ± 5 Ma). Trace-element systematics of the two titanite populations indicate varying co-stability with allanite and are consistent with Th-Pb dates of allanite growth (c. 489 Ma) and breakdown to clinozoisite (c. 30 Ma). Inclusion patterns within titanite indicate that the younger group formed following breakdown of rutile that originally coexisted with the older generation of titanite at pressures and temperatures similar to those determined from the garnet cores. Application of the Zr-in-titanite and Zr-in-rutile thermometers yields temperatures 100-150°C in excess of those indicated by both TitaniQ-QuiG and major element thermobarometry. This discrepancy is interpreted to reflect disequilibrium partitioning of Zr and limited zircon reactivity during metamorphism. Collectively, these observations are consistent with previous estimates of the timing and conditions of metamorphism associated with the Palaeozoic Bhimphedian and Cenozoic Himalayan orogenies in central Nepal. The estimated temperatures and pressures for growth of the garnet cores are consistent with rapid burial during thrust stacking.

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Section: Discussionmentioning

confidence: 69%

Section: Discussionmentioning

confidence: 99%

Delineation of multiple metamorphic events in the Himalayan Kathmandu Complex, central Nepal

Johnson

Cottle

Larson

2020

Journal Metamorphic Geology

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“…Trace element concentrations and ratios in accessory minerals can be used to (semi‐)quantitatively link accessory mineral growth to the growth and breakdown of major phases (e.g., Bea & Montero, 1999; Buick et al, 2006; Cioffi et al, 2019; Finger & Krenn, 2007; Foster et al, 2000, 2002; Garber et al, 2017; Hacker et al, 2019; Hermann & Rubatto, 2003; Hokada & Harley, 2004; Kelly et al, 2006; Kelly & Harley, 2005; Mottram et al, 2014; Pyle & Spear, 1999; Rubatto, 2002; Rubatto et al, 2006; Rubatto & Hermann, 2007; Taylor et al, 2015; Warren et al, 2019) (Figure 1). This approach—along with trace element thermobarometers (Ferry & Watson, 2007; Gratz & Heinrich, 1997; Hayden et al, 2008; Pyle et al, 2001; Seydoux‐Guillaume et al, 2002; Thomas et al, 2015; Tomkins et al, 2007; Wark & Watson, 2006) and modeling of accessory mineral stability (Janots et al, 2007; Kelsey et al, 2008; Kohn et al, 2015; Shrestha et al, 2019; Spear, 2010; Spear & Pyle, 2010; Yakymchuk, 2017; Yakymchuk et al, 2017; Yakymchuk & Brown, 2014)—can be combined with in situ U‐Pb geochronology to infer P‐T‐t‐d paths of crystalline rocks that underpin interpretations of their geodynamic significance (e.g., Engi, 2017; Kohn, 2017; Rubatto, 2017; Zack & Kooijman, 2017).…”

Section: Introductionmentioning

confidence: 99%

Accessory Mineral Eu Anomalies in Suprasolidus Rocks: Beyond Feldspar

Holder

Yakymchuk

Viete

2020

Geochem Geophys Geosyst

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Accessory mineral Eu anomalies (Eu/Eu*) are routinely measured to infer changes in the amount of feldspar over time, allowing accessory mineral U‐Pb dates to be linked to the progressive crystallization of igneous and metamorphic rocks and, by extension, geodynamic processes. However, changes in Eu/Eu* can reflect any process that changes the relative availability of Eu2+ and Eu3+. We constructed partitioning budgets for Sm, Eu2+, Eu3+, and Gd in suprasolidus metasedimentary rocks to investigate processes that can influence accessory mineral Eu anomalies. We modeled three scenarios: (1) closed‐system, equilibrium crystallization; (2) fractionation of Eu by feldspar growth during melt crystallization; and (3) removal of Eu by melt extraction. In the closed‐system equilibrium model, accessory mineral Eu/Eu* changes as a function of fO2 and monazite stability; Eu/Eu* changes up to 0.3 over a pressure‐temperature range of 4–12 kbar and 700–950°C. Fractionation of Eu by feldspar growth is modeled to decrease accessory mineral Eu/Eu* by ~0.05–0.15 per 10 wt% feldspar crystallized. Melt extraction has a smaller effect; removal of 10% melt decreases accessory mineral Eu/Eu* in the residue by ≤0.05. Although these models demonstrate that fractionation of Eu by feldspar growth can be a dominant control on a rocks u budget, they also show that the common interpretation that Eu/Eu* only records feldspar growth and breakdown is an oversimplification that could lead to incorrect interpretation about the duration and rates of tectonic processes. Consideration of other processes that influence Eu anomalies will allow for a broader range of geological processes to be investigated by petrochronology.

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“…600-560 Ma (Meira, Garcia-Casco, Hyppolito, et al, 2019). The older cluster of U-Pb SHRIMP ages from metamorphic zircons (~630-625 Ma) presented in Meira, Garcia-Casco, Hyppolito, et al (2019) is coeval with the metamorphic ages of different rocks of the Southern Brasilia Belt (SBB), which have been estimated by detailed petrochronologic studies, including U-Pb LA-ICP-MS dating of zircon and titanite (Cioffi et al, 2019;Rocha et al, 2017Rocha et al, , 2018Tedeschi et al, 2017Tedeschi et al, , 2018 and U-Th-Pb microprobe dating of monazite (Martins et al, 2009;Reno et al, 2012;Rocha et al, 2017). These results clearly correlate the chronology of metamorphism in both SBB and CRB (see also Duffles et al, 2016;Lobato et al, 2015;Trouw et al, 2013 for similar data within the Riberia Belt).…”

Section: Why Are the Costeiro And Embu Domains Key Areas To Test The mentioning

confidence: 80%

Reply to Comment by Heilbron and Valeriano on “Tectono Metamorphic Evolution of the Central Ribeira Belt, Brazil: A Case of Late Neoproterozoic Intracontinental Orogeny and Flow of Partially Molten Deep Crust During the Assembly of West Gondwana”

Meira

Garcia‐Casco

Hyppolito³

et al. 2020

Tectonics

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The exercise of paleogeographic/tectonic reconstruction of past orogenic belts is a complex task that includes the interpretation and integration of multi‐technique approaches such as basin tectonics, structural geology, petrology, geochemistry, geochronology, and geodynamics. Proterozoic geologic records are fragmented and incomplete, which make efforts to reconstruct paleogeography and orogenic processes even more challenging. Therefore, for our understanding of the tectonic evolution of past orogenic systems to advance, it is essential that any existing model, including the ones proposed by Heilbron and Valeriano (2020, https://doi.org/10.1029/2019tc005897), are repeatedly exposed to debate and testing. In this reply we address the points raised by Heilbron and Valeriano in order to clarify the scientific foundations of our tectonic interpretation for one of the Neoproterozoic Brasiliano/Pan‐African orogens in South America (the Central Ribeira Belt), presented in Meira, Garcia‐Casco, Hyppolito, et al. (2019, https://doi.org/10.1029/2018TC004959). We also evaluate the proposed paleogeographic reconstructions for this part of West Gondwana and conclude that an intracontinental model better explains the currently available data and observations, including the space problem pointed out in recent publications, and that existing geochemical and geochronologic data by themselves are not conclusive with respect to an unequivocal tectonic environment.

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Titanite petrochronology of the southern Brasília Orogen basement: Effects of retrograde net-transfer reactions on titanite trace element compositions

Cited by 26 publications

References 96 publications

Delineation of multiple metamorphic events in the Himalayan Kathmandu Complex, central Nepal

Delineation of multiple metamorphic events in the Himalayan Kathmandu Complex, central Nepal

Accessory Mineral Eu Anomalies in Suprasolidus Rocks: Beyond Feldspar

Reply to Comment by Heilbron and Valeriano on “Tectono Metamorphic Evolution of the Central Ribeira Belt, Brazil: A Case of Late Neoproterozoic Intracontinental Orogeny and Flow of Partially Molten Deep Crust During the Assembly of West Gondwana”

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