Late-Neoproterozoic ultrahigh-temperature metamorphism in the Highland Complex, Sri Lanka

Dharmapriya, P.L.; Malaviarachchi, Sanjeewa P.K.; Santosh, M.; Tang, Li; Sajeev, K.

doi:10.1016/j.precamres.2015.10.010

Cited by 53 publications

(51 citation statements)

References 56 publications

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“…The detrital cores in zircons from the garnetbiotite gneiss in the SWHC preserved oscillatory zoning. Oscillatory zoned cores of zircons survived even under ultra-high temperature conditions have been reported by previous studies such as Sajeev et al (2010) and Dharmapriya et al (2015). In the sillimanite-bearing garnetbiotite gneiss (11-17GB), the detrital cores also preserve oscillatory zoning, but its abundance is extremely low, and all of those detrital cores show transgressive textures.…”

Section: Discussionsupporting

confidence: 69%

“…In the present study, the oscillatory zoned and transgressive detrital cores of zircons from the SWHC gave the oldest ages of 3380-3220 Ma, indicating the detrital zircons in the SWHC potentially originated from several Paleoarchean sources, similar to the case of the CHC (Kröner et al, 1987;Pram and Pohl 1994;Santosh et al, 2014;Dharmapriya et al, 2015;Takamura et al, 2015;He et al, 2016aHe et al, , 2016b.…”

Section: Discussionsupporting

confidence: 66%

“…In most of the zircon, the overgrowths in age range 6 shows Th/U ratio less than 0.1, which is reasonable to interpret them as product of the final metamorphic event (range 6; 630-500 Ma). The age range 6 has been also suggested by previous studies and considered as either parts of a single event or discrete thermal events (Kröner et al, 1987;Hölzl et al, 1991;Hölzl et al, 1994;Sajeev et al, 2010;Santosh et al, 2014;Dharmapriya, et al, 2015;Takamura et al, 2015;He et al, 2016aHe et al, , 2016b. Such thermal events may contribute to form peripheral thin layers of overgrowths observed in zircon grains (Figs.…”

Section: Formation Of Overgrowthssupporting

confidence: 61%

“…Sajeev et al (2010) has given evidence of 1.7 Ga age clusters, episodes of zircon growth at 1.04-0.83 Ga and two generations of overgrowths in zircon at 569 ± 5 and 551 ± 7 Ma in quartz-saturated granulites. Their results also indicate that the Archean sediments of the CHC have undergone repeated thermal events (Santosh et al, 2014;Dharmapriya et al, 2015;Takamura et al, 2015;He et al, 2016aHe et al, , 2016b.…”

Section: Introductionmentioning

confidence: 90%

“…According to studies by U-Pb zircon dating (Kröner et al, 1987;Santosh et al, 2014;Dharmapriya et al, 2015;Takamura et al, 2015;He et al, 2016aHe et al, , 2016b, Nd model ages (Milisenda et al, 1988(Milisenda et al, , 1994Pram and Pohl, 1994) and Sr model ages (Crawford and Oliver, 1969), the detritus of the metasediments in the CHC were derived from unidentified Archean to Proterozoic source terrains of 3.2-2.0 Ga in age, and peak metamorphism occurred around 610-550 Ma (Hölzl et al, 1991;Hölzl et al, 1994;Sajeev et al, 2010;Santosh et al, 2014;Dharmapriya et al, 2015;Takamura et al, 2015;He et al, 2016aHe et al, , 2016b. Baur et al (1991) and Hölzl et al (1994) obtained zircon upper intercept ages around 1900-1800 Ma for orthogneisses, which were interpreted as crystallization ages of the protoliths.…”

Section: Introductionmentioning

confidence: 99%

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Internal textures and U–Pb geochronology of zircons in metamorphic rocks from the Southwestern Highland Complex, Sri Lanka

Wanniarachchi

Akasaka

Hayasaka

et al. 2016

Journal of Mineralogical and Petrological Sciences

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Internal textures and U-Pb ages of zircons in garnet-biotite gneiss of the Southwestern Highland Complex (SWHC), Sri Lanka, were studied to clarify the repeated thermal events in the study area. The zircons from garnet-biotite gneiss consist of the detrital cores and overgrowths with two to five growth stages. The detrital zircon cores are rounded or euhedral to subhedral in shape, and show transgressive internal textures or oscillatory zoning.The rounded or subhedral to euhedral detrital core morphology suggests several major Archaean to Proterozoic sources of detritus zircons in the SWHC. Ages of the detrital cores are in a range of 3.3-1.7 Ga, and can be categorized into five ranges of 3380-3220, 2730-2660, 2550-2490, 2220-2170, and 1900-1700 Ma, implying the source rock ages. The detrital cores in the 3380-2170 Ma have Th/U-ratios of more than 0.3, suggesting igneous origin. The detrital cores in the range 1900-1700 Ma have Th/U of >0.3 or 0.3-0.1, suggesting an igneous or metamorphic origin. Some overgrowths with the ages in the ranges of 1900-1700 and 630-500 Ma have Th/U-ratios less than 0.1 implying that zircon growth corresponds to the thermal events. Zircons lacking detrital cores and having growth zones with characteristic metamorphic internal textures gave ages in a range of 630-500 Ma, implying the generation at the final granulite grade metamorphic event.

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Section: Discussionsupporting

confidence: 69%

Section: Discussionsupporting

confidence: 66%

Section: Formation Of Overgrowthssupporting

confidence: 61%

Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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Internal textures and U–Pb geochronology of zircons in metamorphic rocks from the Southwestern Highland Complex, Sri Lanka

Wanniarachchi

Akasaka

Hayasaka

et al. 2016

Journal of Mineralogical and Petrological Sciences

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Prolonged Neoproterozoic high‐grade metamorphism of the Wanni Complex, Sri Lanka: New insights from petrology, phase equilibria modelling, and zircon U–Pb geochronology of partially melted cordierite gneiss from Walpita

et al. 2020

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We report new petrological and geochronological data of garnet‐cordierite (Grt‐Crd) gneiss as well as two types of leucocratic rocks (garnet‐bearing and cordierite‐bearing leucosomes) crystallized during prograde and near‐peak metamorphisms of the Wanni Complex (WC) in Sri Lanka, and investigate the pressure–temperature–time evolution of granulite‐facies metamorphism for unravelling the timing and tectonics of the Neoproterozoic collisional processes related to Gondwana amalgamation. Grt‐Crd gneiss, garnet‐biotite (Grt‐Bt) gneiss, garnet‐bearing leucocratic rock (Grt‐L), and cordierite‐bearing leucocratic rock (Crd‐L) discussed in this study were collected from Walpita in the margin of the WC along the boundary with the Highland Complex (HC). Grt‐L occurs as thin layers parallel to the foliation of matrix Grt‐Bt and Grt‐Crd gneisses. The occurrences of porphyroblastic garnet in quartzo‐feldspathic matrix and crystallised melt inclusions within the garnet suggest that the Grt‐L could have formed by partial melting of host Grt‐Bt gneiss during prograde to peak metamorphism. Crd‐L is coarse‐grained and massive, lacks obvious foliation, and crosscuts the foliation of host Grt‐Bt gneiss. These observations suggest that the Crd‐L could have intruded after the crystallization of the Grt‐L. Application of phase equilibria modelling in the system NCKFMASHTO for the rocks yielded three discrete thermal events: 600–800°C/4.0–6.0 kbar (Stage 1 from Grt‐L), 700–840°C/5.5–7.0 kbar (Stage 2 from Grt‐Crd gneiss), and 840–880°C/4.5–5.5 kbar (Stage 3 from Crd‐L), suggesting a clockwise P–T evolution. LA‐ICP‐MS zircon U–Pb dating of the leucosomes yielded several metamorphic events: >577 Ma (partial melting of Grt‐L), ~562 Ma (crystallization of Grt‐L), 537 ± 14 Ma (peak metamorphism and crystallization of Crd‐L), and 507–503 Ma (post‐peak cooling event). The results of this study therefore confirmed prolonged (>70 Myr) high‐grade metamorphism of the WC, although the duration might be shorter than that of the HC (>100 Ma). The continuous heat supply necessary for such long‐lived high‐grade metamorphism is explained by a recent tectonic model of Sri Lanka. The model suggests double‐sided subduction and continent‐continent collision, which could have given rise to subsequent slab delamination and differential heating of lower to middle crust. Such complex subduction–collision processes possibly controlled the difference in the style of P–T path and the duration of high‐grade metamorphism between the HC and the WC.

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Tectonics of Sri Lanka

Jain

Banerjee

Kale

2020

Society of Earth Scientists Series

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Late-Neoproterozoic ultrahigh-temperature metamorphism in the Highland Complex, Sri Lanka

Cited by 53 publications

References 56 publications

Internal textures and U–Pb geochronology of zircons in metamorphic rocks from the Southwestern Highland Complex, Sri Lanka

Internal textures and U–Pb geochronology of zircons in metamorphic rocks from the Southwestern Highland Complex, Sri Lanka

Prolonged Neoproterozoic high‐grade metamorphism of the Wanni Complex, Sri Lanka: New insights from petrology, phase equilibria modelling, and zircon U–Pb geochronology of partially melted cordierite gneiss from Walpita

Tectonics of Sri Lanka

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