How long-lived is ultrahigh temperature (UHT) metamorphism? Constraints from zircon and monazite geochronology in the Eastern Ghats orogenic belt, India

Korhonen, Fawna J.; Clark, Chris; Brown, Michael; Bhattacharya, S.; Taylor, Richard

doi:10.1016/j.precamres.2012.12.001

Cited by 171 publications

(153 citation statements)

References 48 publications

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“…The evidence for the recording by zircon of multiple melt-related 'events' within longer G-UHT evolutions can be seen in migmatitic granulites from many terrains (Ashwal et al, 1999;Harley et al, 2001;Korhonen et al, 2013Korhonen et al, , 2014Clark et al, 2015;Johnson et al, 2015). Two examples of this behaviour are illustrated in Figure 6.…”

Section: Constraining Temperature and Time In Uht Metamorphismmentioning

confidence: 93%

“…Whilst many UHT granulites are typified by ITD and decompression-cooling paths, a smaller but significant number may be characterised by near-isobaric cooling (IBC) paths (Harley, 1989, 1998a, 2004, Brown, 2007Harley, 2008;Brown, 2009;Korhonen et al, 2013;Kelsey and Hand, 2015). These typically record long timescales of cooling (e.g., Ashwal et al, 1999), but like the UHT-ITD examples noted in the section on Large Hot Orogens, the duration of UHT itself, Δt 900 , is often elusive or poorly-constrained.…”

Section: Slow Granulites and Long Lived Uhtmentioning

confidence: 99%

“…Nevertheless, there are several examples where, on the basis of the collective age information obtained on zircons and monazites coupled with thermometry on the zircons and coexisting minerals, it is now possible to demonstrate long-lived UHT with Δt 900 durations of 30-100 Myr . For example, long-lived orogen residency under UHT or near-UHT conditions is inferred for central Eastern Ghats of India (Korhonen et al, 2013(Korhonen et al, , 2014, which record high-T metamorphic events from 1000 Ma through to 930-920 Ma and may have resided at >900°C for some 80 Myr. In this final section of this review two further examples of long-lived UHT, most likely developed within LHO settings and promoted by the burial of high heat-production crust, are presented.…”

Section: Slow Granulites and Long Lived Uhtmentioning

confidence: 99%

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A matter of time: The importance of the duration of UHT metamorphism

Harley

2016

Journal of Mineralogical and Petrological Sciences

145

110

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The duration of granulite (G) and ultra-high temperature (UHT) conditions in regional metamorphism is critical to arguments regarding the tectonic settings of granulites and their relationships to Supercontinent assembly. Analysis of zircon geochronology integrated with trace element (REE) constraints on the timing of zircon growth or modification and evidence for metamorphic temperatures from Ti-in-zircon reveals that zircon can form episodically at or near the metamorphic peak in long-lived UHT granulites. This reflects the segregation, transfer and stagnation or trapping of melts which leads to local melt-rock interactions that promotes zircon crystallisation. In contrast, although rutile can retain UHT information in short duration ('fast') G-UHT terrains it is afflicted by Zr loss in long duration ('slow') terrains and yields temperatures significantly lower than those preserved by zircons formed in the same G-UHT events. An assessment of the age-duration evidence from several well-documented G-UHT terrains reveals that most are 'slow', having durations of UHT, Δt 900 , in the range 30-100 Myr. Some UHT terrains previously considered to be short-lived (Δt 900 < 10 Myr) have longer durations of UHT in the light of recent geochronology and hence are also classed as 'slow'. Of the models proposed to account for UHT metamorphism, the 'large hot orogen' (LHO) model for collisional orogeny provides the best setting for the formation of such 'slow' UHT granulites. LHO models can account not only for the P-T paths, which can range from UHT with near-isothermal decompression (UHT-ITD) through to decompression-cooling and UHT followed by near-isobaric cooling (UHT-IBC), but also for residence times under UHT conditions. The Napier Complex, the Earth's premier UHT terrain, probably formed as trapped deep crust in the hot underbelly of a late-Archaean LHO. Shorter duration UHT and near-UHT granulites also exist, mostly with Δt 900 less than 10 Myr. A number of these are likely to have formed as a consequence of severe lithospheric thinning and crustal extension accompanied by voluminous magmatism, which could occur in arc and back-arc settings affected by subduction roll-back or, as advocated by previous workers, continental arcs undergoing extension. However, attaining long-lived UHT conditions in these settings is unlikely unless the crust has inherently high radioactive heat production in addition to the transient heat added during extension and magmatism.

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Section: Constraining Temperature and Time In Uht Metamorphismmentioning

confidence: 93%

Section: Slow Granulites and Long Lived Uhtmentioning

confidence: 99%

Section: Slow Granulites and Long Lived Uhtmentioning

confidence: 99%

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A matter of time: The importance of the duration of UHT metamorphism

Harley

2016

Journal of Mineralogical and Petrological Sciences

145

110

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“…However, in some granulite facies (> 900 °C) and (U) HT terranes (e.g. Rogaland: Möller et al 2003; Napier Complex: Kelly and Harley 2005; Eastern Ghats belt: Korhonen et al 2013), metamorphic zircon with Th/U ratios > 0.1 are well known. The trend towards higher Th/U ratios in zircon with increasing metamorphic grade reflects both an increase in Th and a decrease in U concentrations.…”

Section: Zircon Geochronology and Geochemistrymentioning

confidence: 99%

Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?

Kunz

Regis

Engi

2018

Contrib Mineral Petrol

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Granulite facies rocks frequently show a large spread in their zircon ages, the interpretation of which raises questions: Has the isotopic system been disturbed? By what process(es) and conditions did the alteration occur? Can the dates be regarded as real ages, reflecting several growth episodes? Furthermore, under some circumstances of (ultra-)high-temperature metamorphism, decoupling of zircon U-Pb dates from their trace element geochemistry has been reported. Understanding these processes is crucial to help interpret such dates in the context of the P-T history. Our study presents evidence for decoupling in zircon from the highest grade metapelites (> 850 °C) taken along a continuous high-temperature metamorphic field gradient in the Ivrea Zone (NW Italy). These rocks represent a well-characterised segment of Permian lower continental crust with a protracted high-temperature history. Cathodoluminescence images reveal that zircons in the mid-amphibolite facies preserve mainly detrital cores with narrow overgrowths. In the upper amphibolite and granulite facies, preserved detrital cores decrease and metamorphic zircon increases in quantity. Across all samples we document a sequence of four rim generations based on textures. U-Pb dates, Th/U ratios and Ti-in-zircon concentrations show an essentially continuous evolution with increasing metamorphic grade, except in the samples from the granulite facies, which display significant scatter in age and chemistry. We associate the observed decoupling of zircon systematics in high-grade non-metamict zircon with disturbance processes related to differences in behaviour of non-formula elements (i.e. Pb, Th, U, Ti) at high-temperature conditions, notably differences in compatibility within the crystal structure.

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“…Estimating the timing and duration of high-grade metamorphism through zircon and monazite dating can potentially place a very important constraint on the tectonic framework of lower crustal processes during continental collision events (e.g., Johnson and Harley, 2012;Rubatto et al, 2013;Korhonen et al, 2013). Recent advance in understanding the growth/recrystallization timing of zircon and monazite during metamorphic cycle, especially the roles of partial melting and fluid infiltration events in formation/dissolution/recrystallization of these minerals enable to reconstruct the lower crustal evolution in more detail (e.g., Rubatto et al 2001;Rubatto, 2002;Harley and Kelly, 2007;Rubatto et al, 2013;Kawakami et al, 2013;Korhonen et al, 2013;Harley and Nandakumar, 2014).…”

Section: Introductionmentioning

confidence: 99%

Possible polymetamorphism and brine infiltration recorded in the garnet–sillimanite gneiss, Skallevikshalsen, Lützow–Holm Complex, East Antarctica

Kawakami

Hokada

Sakata

et al. 2016

Journal of Mineralogical and Petrological Sciences

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Chlorine-rich (>0.3 wt%Cl) biotite inclusions in the core of garnet porphyroblasts in the garnet-sillimanite (Grt-Sil) gneiss from Skallevikshalsen, Lützow-Holm Complex (LHC), East Antarctica is estimated to be stable under >1.2 GPa, 820-850°C, coexisted with granitic melt as suggested by the nanogranite/felsite inclusions. Rare occurrence of matrix biotite, in spite of the common occurrence of biotite as inclusions in garnet, suggests almost complete consumption of pre-existed matrix biotite during the prograde to peak metamorphism. Brine infiltration during prograde to peak metamorphism in Skallevikshalsen is supported by Cl-rich scapolite described in previous studies. Brine infiltration and progress of continuous biotite-consuming melting reactions were probably responsible for elevating the Cl content of biotite in the studied sample.In situ electron microprobe U-Th-Pb dating of monazite and the in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb dating of zircon in the Grt-Sil gneiss revealed that both monazite and zircon has the 'older age population' with~650-580 Ma and the 'younger age population' with~560-500 Ma. The REE and trace element pattern of one of the P-rich patches in the garnet core is different from the Prich garnet rim. The isotope mapping of the same patch by LA-ICPMS revealed that the patch is also observed as a domain depleted in V concentration between the patch and the garnet rim suggests that this patch is not a continuous part from the garnet rim, but is likely a relic of preexisted garnet. Kyanite included in the patch suggests that the precursor rock was presumably a medium-to high-pressure type metamorphic rock. Presence of the older age population (~650-580 Ma) monazites in Skallevikshalsen and Skallen also suggest that rocks in these areas experienced polymetamorphism, and resetting by the~560-500 Ma metamorphic event was incomplete in these areas. Taking into account the presence of Cl-rich biotite inclusions in garnet, infiltration of brine accompanied by partial melting is one probable event that took place at~560-500 Ma in the Skallevikshalsen area, and part of the monazite possibly recrystallized by this brine infiltration.Detailed microstructural observation using trace element mapping combined with detailed petrography especially focusing on the Cl-bearing minerals as a tracer of brines would become a powerful tool for better interpreting the results of monazite and zircon dating and for investigating the fluid-related crustal processes.

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How long-lived is ultrahigh temperature (UHT) metamorphism? Constraints from zircon and monazite geochronology in the Eastern Ghats orogenic belt, India

Cited by 171 publications

References 48 publications

A matter of time: The importance of the duration of UHT metamorphism

A matter of time: The importance of the duration of UHT metamorphism

Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?

Possible polymetamorphism and brine infiltration recorded in the garnet–sillimanite gneiss, Skallevikshalsen, Lützow–Holm Complex, East Antarctica

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