Reactive monazite and robust zircon growth in diatexites and leucogranites from a hot, slowly cooled orogen: implications for the Palaeoproterozoic tectonic evolution of the central Fennoscandian Shield, Sweden

Högdahl, Karin; Majka, Jarosław; Sjöström, Håkan; Nilsson, K.P.; Claesson, Stefan; Konečný, Petr

doi:10.1007/s00410-011-0664-x

Cited by 46 publications

(13 citation statements)

References 68 publications

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“…However, Th/U ratios <0.1 cannot, unfortunately, be used as a robust indicator of metamorphically-grown zircon, for the reason that the Th/U ratio is strongly controlled by the presence (and coexistence) of other Thbearing minerals such as monazite, allanite, xenotime and/or fluid/ melt (e.g. Kelly and Harley, 2005;Högdahl et al, 2012). If phases with a strong affinity for Th are present along with zircon, this will more probably result in low Th/U ratios in zircon, regardless of whether the zircon is of magmatic or metamorphic origin.…”

Section: Timescales and Geochronometersmentioning

confidence: 98%

“…Zircon is typically considered to be less reactive than monazite, including within melt-bearing rocks (e.g. Högdahl et al, 2012;Rubatto et al, 2013), suggesting that the concomitant use of the two geochronometers from the same rock has the potential to provide insight into the temporal evolution of a terrane that one geochronometer (zircon) in isolation may not provide (e.g. Kelsey et al, 2008).…”

Section: Timescales and Geochronometersmentioning

confidence: 99%

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On ultrahigh temperature crustal metamorphism: Phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings

Kelsey

Hand

2015

Geoscience Frontiers

370

285

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a b s t r a c tUltrahigh temperature (UHT) metamorphism is the most thermally extreme form of regional crustal metamorphism, with temperatures exceeding 900 C. UHT crustal metamorphism is recognised in more than 50 localities globally in the metamorphic rock record and is accepted as 'normal' in the spectrum of regional crustal processes. UHT metamorphism is typically identified on the basis of diagnostic mineral assemblages such as sapphirine þ quartz, orthopyroxene þ sillimanite AE quartz and osumilite in MgeAlrich rock compositions, now usually coupled with pseudosection-based thermobarometry using internally-consistent thermodynamic data sets and/or Al-in-Orthopyroxene and ternary feldspar thermobarometry. Significant progress in the understanding of regional UHT metamorphism in recent years includes: (1) development of a ferric iron activityecomposition thermodynamic model for sapphirine, allowing phase diagram calculations for oxidised rock compositions; (2) quantification of UHT conditions via trace element thermometry, with Zr-in-rutile more commonly recording higher temperatures than Ti-in-zircon. Rutile is likely to be stable at peak UHT conditions whereas zircon may only grow as UHT rocks are cooling. In addition, the extent to which Zr diffuses out of rutile is controlled by chemical communication with zircon; (3) more fully recognising and utilising temperature-dependent thermal properties of the crust, and the possible range of heat sources causing metamorphism in geodynamic modelling studies; (4) recognising that crust partially melted either in a previous event or earlier in a long-duration event has greater capacity than fertile, unmelted crust to achieve UHT conditions due to the heat energy consumed by partial melting reactions; (5) more strongly linking UePb geochronological data from zircon and monazite to PeT points or path segments through using Y þ REE partitioning between accessory and major phases, as well as phase diagrams incorporating Zr and REE; and (6) improved insight into the settings and factors responsible for UHT metamorphism via geodynamic forward models. These models suggest that regional UHT metamorphism is, principally, geodynamically related to subduction, coupled with elevated crustal radiogenic heat generation rates.Ó 2014, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

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Section: Timescales and Geochronometersmentioning

confidence: 98%

Section: Timescales and Geochronometersmentioning

confidence: 99%

On ultrahigh temperature crustal metamorphism: Phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings

Kelsey

Hand

2015

Geoscience Frontiers

370

285

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“…However, monazite has been shown experimentally to be a relatively reactive mineral, with resetting of the U-Th-Pb isotopic system being possible even under moderate P/T conditions (Williams et al, 2011). Previously obtained metamorphic monazite ages from the Svecokarelian orogen in the south-western part of the Fennoscandian Shield, Sweden, reflect both periods of metamorphism and demonstrate, in addition, the high reactivity of monazite during metamorphism in contrast to, for example, zircon (Högdahl et al, 2012).…”

Section: Timing Of Monazite Growth In a Regional Metamorphic Contextmentioning

confidence: 99%

“…1A), in the south-western part of the Fennoscandian Shield, using both U-Pb (zircon) and U-Pb (monazite) geochronology, have shown at least two episodes of high-grade metamorphism at around 1.86 Ga (M 1 ) and at 1.84-1.81 Ga (M 2 ), respectively (e.g. Andersson et al, 2006;Stephens et al, 2009;Högdahl et al, 2012;Stephens and Andersson, 2015). The U-Pb (monazite) ages obtained in this study (1831 ± 8 Ma and 1822 ± 5 Ma; Fig.…”

Section: Timing Of Monazite Growth In a Regional Metamorphic Contextmentioning

confidence: 99%

Time constraints on magmatism, mineralisation and metamorphism at the Falun base metal sulphide deposit, Sweden, using U–Pb geochronology on zircon and monazite

Kampmann

Stephens

Ripa

et al. 2016

Precambrian Research

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a b s t r a c t U-Th-Pb (zircon and monazite) ion probe data have provided constraints on the timing of emplacement and metamorphism of magmatic rocks close to the Palaeoproterozoic, Falun base metal sulphide deposit in the Bergslagen lithotectonic unit, Fennoscandian Shield, Sweden, and, thereby the timing of mineralisation. Hydrothermal alteration and mineralisation at Falun are constrained to a short interval of several million years between a 207 Pb/ 206 Pb weighted average age of 1894 ± 3 Ma for a rhyolitic sub-volcanic rock in the felsic volcanic to sub-volcanic host rock suite, and a 207 Pb/ 206 Pb weighted average age of 1891 ± 3 Ma for a post-sulphide, porphyritic dacite dyke. Magmatism also included the emplacement of granite plutons with igneous crystallization ages of 1894 ± 3, 1894 ± 2 Ma and 1893 ± 3 Ma. The felsic sub-volcanic to volcanic activity and the emplacement of dacite dykes and granite plutons overlap in age within their respective analytical uncertainties, indicating hydrothermal alteration and sulphide mineralisation inside a narrow time span of intense magmatic activity, and burial of the supracrustal rocks. Two distinct patchy and homogeneous metamorphic monazite types in a felsic volcanic rock around and hydrothermally altered rocks at the Falun deposit yield 207 Pb/ 206 Pb weighted average ages of 1831 ± 8 Ma and 1822 ± 5 Ma, respectively. These ages fall well within the temporal range of a younger 1.84-1.81 Ga (M 2 ) metamorphic episode during the 2.0-1.8 Ga Svecokarelian orogeny, with the older episode (M 1 ) inside the Bergslagen lithotectonic unit at around 1.86 Ga. This shows the major influence of the M 2 event in the north-western part of this unit, leading to a complete resetting of the U-Th-Pb isotope system in monazite.

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“…This software calculates dates following the methodology of Montel et al (1996). The analytical routine has previously been successfully applied for dating monazite (Hogdahl et al, 2012;Majka et al, 2012;Konečný et al, 2017). Pooled ages, construction of histograms and probability density curves were calculated by Isoplot 3.50.…”

Section: Monazitementioning

confidence: 99%

Peak to post-peak thermal history of the Saglek Block of Labrador: A multiphase and multi-instrumental approach to geochronology

et al. 2018

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A B S T R A C TThe Saglek Block of coastal Labrador forms the western margin of the North Atlantic Craton, where Archean gneisses and granulites have been reworked during the Paleoproterozoic. Previous work has established that the block is a composite of Eoarchean to Mesoarchean protoliths metamorphosed to upper amphibolite and granulite facies at around 2.8-2.7 Ga. New in-situ microbeam dating of accessory minerals in granoblastic gneisses reveals a complex peak to post-peak thermal history. Zircon growth at ca. 3.7-3.6 Ga provides the age of formation of the tonalitic protoliths to the gneisses. Further zircon growth in syn-tectonic granitic gneiss and monazite growth in a variety of orthogneisses confirm peak metamorphic conditions at ca. 2.7 Ga, but also reveal high-temperature conditions at ca. 2.6 Ga and 2.5 Ga. The former is interpreted as the waning stages of the 2.7 Ga granulite event, whereas the latter is associated with a younger phase of granitic magmatism. In addition, apatite ages of ca. 2.2 Ga may represent either cooling associated with the 2.5 Ga event or a previously unrecognized greenschist-facies metamorphism event that predates the Torngat Orogeny.

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Reactive monazite and robust zircon growth in diatexites and leucogranites from a hot, slowly cooled orogen: implications for the Palaeoproterozoic tectonic evolution of the central Fennoscandian Shield, Sweden

Cited by 46 publications

References 68 publications

On ultrahigh temperature crustal metamorphism: Phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings

On ultrahigh temperature crustal metamorphism: Phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings

Time constraints on magmatism, mineralisation and metamorphism at the Falun base metal sulphide deposit, Sweden, using U–Pb geochronology on zircon and monazite

Peak to post-peak thermal history of the Saglek Block of Labrador: A multiphase and multi-instrumental approach to geochronology

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