Titanite petrochronology linked to phase equilibrium modelling constrains tectono-thermal events in the Akia Terrane, West Greenland

Kirkland, Chris; Yakymchuk, Chris; Gardiner, Nicholas J.; Szilas, Kristoffer; Hollis, Julie; Olierook, Hugo K.H.; Steenfelt, Agnete

doi:10.1016/j.chemgeo.2020.119467

Cited by 31 publications

(10 citation statements)

References 81 publications

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“…A first order expectation might be that igneous amphibole in cumulates would be relatively stable even with a granulite-facies overprint. This is considering a crystallisation temperature in the range of 850-1080°C, 4-10 kbar in modern basaltic-andesitic arc systems (Arculus and Wills, 1980;Martin, 2007) compared to peak Akia metamorphism of ∼800-850°C, perhaps higher, and ∼7.5-10 kbar (this study; Kirkland et al, 2018Kirkland et al, , 2020Yakymchuk et al, 2020). Indeed, amphibole-out in metabasite at moderate-to-high pressure (4-10 kbar) is expected to occur in the 850-970°C range (Green et al, 2016).…”

Section: Amphiboles Of the Amikoq Layered Complexmentioning

confidence: 72%

“…Metasedimentary rocks (pelites) of the Kangerluarsuk Supracrustal Belt in the W–NW part of Akia Majorqaq Belt (Dyck et al , 2015) were deposited between 2877–2857 Ma (Kirkland et al , 2018, 2020), and possibly as early as 2958 Ma (Gardiner et al , 2019). The presence of detrital zircon grains sourced from older Akia rocks demonstrate exhumation of at least part of Akia following peak granulite-facies conditions at 3010–2980 Ma (Dyck et al , 2015; Kirkland et al , 2018).…”

Section: Geological Settingmentioning

confidence: 99%

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The Mesoarchean Amikoq Layered Complex of SW Greenland: Part 1. Constraints on theP–Tevolution from igneous, metasomatic and metamorphic amphiboles

Aarestrup

Jørgensen

Armitage

et al. 2020

MinMag

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The metamorphic history of the Mesoarchean Amikoq Layered Complex within the Akia terrane of SW Greenland was characterised by electron microprobe mineral data and detailed petrography on 12 representative samples, integrated with zircon U–Pb geochronology and petrology. The complex intruded into a >3004 Ma supracrustal association now consisting of granoblastic metabasites with subordinate quartz-rich gneiss. Supracrustal host rocks contain a relict high-temperature assemblage of orthopyroxene–clinopyroxene (± pigeonite exsolution lamellae, exsolved at ~975–1010°C), which is interpreted to pre-date the Amikoq intrusion. Cumulate to granoblastic-textured rocks of the main Amikoq Layered Complex range modally from leuconorite to melanorite, orthopyroxenite to harzburgite/dunite and rare hornblende melagabbro. Observed mineralogy of main complex noritic lithologies is essentially relict igneous with orthopyroxene–biotite and hornblende–plagioclase thermometers yielding temperatures of ~800–1070°C. An anatectic zircon megacryst from a patchy quartzo–feldspathic leucosome hosted in an orthopyroxene-dominated Amikoq rock reflects local anatexis at peak metamorphic P–T conditions and yields an intrusion minimum age of 3004 ± 9 Ma. Field observations indicate local anatexis of orthopyroxene-dominated lithologies, possibly indicating a post-intrusion peak temperature of >900°C. The last preserved stages of retrogression are recorded in paragneiss plagioclase–garnet, biotite–garnet and host rock ilmenite–magnetite pairs (≤3 kbar and ~380–560°C). The Amikoq Complex intruded a MORB-like crustal section and the former remained relatively undisturbed in terms of modal mineralogy. Preservation of igneous textures and mineralogy are related to an anhydrous, high-grade metamorphic history that essentially mimics igneous crystallisation conditions, whereas local high-strain zones acted as fluid pathways resulting in hydrous breakdown of igneous minerals. There is no evidence of equilibration of the intrusion at sub-amphibolite-facies conditions.

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Section: Amphiboles Of the Amikoq Layered Complexmentioning

confidence: 72%

Section: Geological Settingmentioning

confidence: 99%

The Mesoarchean Amikoq Layered Complex of SW Greenland: Part 1. Constraints on theP–Tevolution from igneous, metasomatic and metamorphic amphiboles

Aarestrup

Jørgensen

Armitage

et al. 2020

MinMag

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“…On the other hand, Gao et al (2012) suggested >~800 °C from titanite samples which survived 800-850 °C metamorphism. Recent studies rather prefer such a high U-Pb closure temperature of > 830 °C (Hartnady et al, 2019;Kirkland et al, 2020). Even if U-Pb closure temperature of titanite is relatively low, our titanite crystals are large (3-5 mm in length), thus it is unlikely that coarse-grained titanite were influenced by intercrystalline Pb diffusion.…”

Section: Timing Of the Anatectic Event In The Hida Beltmentioning

confidence: 78%

Nature and timing of anatectic event of the Hida Belt (Japan): Constraints from titanite geochemistry and U-Pb age of clinopyroxene-bearing leucogranite

Harada¹,

Tsujimori²,

Kon³

et al. 2022

Preprint

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The Hida Belt, central Japan, is a continental fragment, which was once a part of the crustal basement of the East Asian continental margin. It consists mainly of Permo-Triassic granite-gneiss complexes with both syn-to-late-metamorphic migmatite or granite bodies. Clinopyroxene-bearing leucogranite, locally called as 'Inishi'-type migmatite, occurs characteristically in the migmatite zone associated with amphibolite and marble. The leucogranite is characterized by the presence of coarse-grained diopside-hedenbergite series clinopyroxene and titanite in plagioclase-dominated matrix. Clinopyroxene contains abundant calcite inclusions. Euhedral titanite with high Th/U ratios (~2.8-7.8) and REE contents (~4514-14069 μg/g) contains polycrystalline 'granitic' inclusions. Those mineralogical features indicate the involvement of carbonate during anatexis. Considering a nominal pressure of 0.4-0.7 GPa of the Hida gneiss, Zr-in-titanite thermometry yields a temperature of 730-810 °C and 770-850 °C at aTiO2 = 0.5 and 1, respectively. The titanites show highly variable U/Pb ( 238 U/ 206 Pb = 15.0-24.0) and Pb ( 207 Pb/ 206 Pb = 0.172-0.419) isotope ratios, and the scattered trend follows a discordia line with a lower intercept at 225.4 ± 1.9 Ma. This titanite age would represent the timing of regional anatexis that have occurred in a later stage of the regional metamorphism of the Hida Belt. A high apparent thermal gradient at middle crustal levels might have caused by regional extension.

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“…Further amphibolite-to granulite-facies metamorphism is recorded in the Alanngua Complex at 2.56 Ga (Dyck et al, 2015;Steenfelt et al, in review;Yakymchuk et al, in review) and the Akia terrane at 2.54 Ga (Kirkland et al, 2020). This coincides with minor granite intrusions in the northern Akia Terrane (Gardiner et al, 2019) and the intrusion of the Qôrqut Granite Complex along the southern margin of the Akia Terrane (Nutman et al, 2010;Naeraa et al, 2014), and has been associated with final cratonisation of the North Atlantic Craton (Yakymchuk et al, in review).…”

Section: The Akia Terranementioning

confidence: 99%

Geodynamic Implications of Synchronous Norite and TTG Formation in the 3 Ga Maniitsoq Norite Belt, West Greenland

et al. 2020

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Titanite petrochronology linked to phase equilibrium modelling constrains tectono-thermal events in the Akia Terrane, West Greenland

Cited by 31 publications

References 81 publications

The Mesoarchean Amikoq Layered Complex of SW Greenland: Part 1. Constraints on theP–Tevolution from igneous, metasomatic and metamorphic amphiboles

The Mesoarchean Amikoq Layered Complex of SW Greenland: Part 1. Constraints on theP–Tevolution from igneous, metasomatic and metamorphic amphiboles

Nature and timing of anatectic event of the Hida Belt (Japan): Constraints from titanite geochemistry and U-Pb age of clinopyroxene-bearing leucogranite

Geodynamic Implications of Synchronous Norite and TTG Formation in the 3 Ga Maniitsoq Norite Belt, West Greenland

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