Peninsular India in Gondwana: The tectonothermal evolution of the Southern Granulite Terrain and its Gondwanan counterparts

Collins, Alan S.; Clark, Chris; Plavsa, Diana

doi:10.1016/j.gr.2013.01.002

Cited by 277 publications

(136 citation statements)

References 169 publications

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“…5), beginning with the cratonic margins in Africa and India, before discussing juvenile arcs, oceanic sutures, and reworked cratonic rocks within the orogen itself. Fritz et al (2013), Tucker et al (2014) and Collins et al (2014) provided detailed reviews of these relationships, with a focus on east Africa, Madagascar and India respectively, although some of their explanations for these relationships differ from those proposed here.…”

Section: Tectonic Architecture Of the East African Orogenmentioning

confidence: 80%

Pan–African granulites of Madagascar and southern India: Gondwana assembly and parallels with modern Tibet

Fitzsimons

2016

Journal of Mineralogical and Petrological Sciences

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Granulites of the southern East African Orogen formed by continental collision during Gondwana assembly. The highest metamorphic gradients of 25-50°C km −1 were attained at 0.58-0.53 Ga in a microcontinental block that was sandwiched between two collisional sutures and is now exposed in Madagascar and southern India. The 50 Myr duration of extreme pressure-temperature (P-T) conditions and lack of coeval mantle magmatism suggest that metamorphism was driven by radiogenic heat accumulation beneath a long-lived orogenic plateau. Bounding sutures most likely record transfer of this microcontinent across the Neoproterozoic Mozambique Ocean, analogous to Gondwanan terranes that crossed Tethys before final India-Asia collision and, like Tibet, these sutures mark the edges of a plateau that formed following terminal ocean closure and collision. Both sutures record moderate metamorphic gradients of 15-25°C km −1 but with quite different ages. Metamorphism along the western suture at 0.65-0.61 Ga followed the end of magmatism in an adjacent 0.85-0.65 Ga ocean-arc terrane. It has an anti-clockwise P-T path that reflects preferential thickening of the hot arc during early stages of collision, and dates ocean closure at the western suture. Metamorphism along the eastern suture at 0.53-0.51 Ga has a clockwise P-T path and is widely assumed to date terminal collision in the East African Orogen. However, this event was coeval with rapid exhumation of granulites in the adjacent plateau and is more likely to reflect reactivation of a much older eastern suture during plateau collapse. Great care should be taken when using metamorphism to date ocean closure in ancient orogens. Rocks with hot metamorphic gradients give poor age constraints on initial collision because peak T is attained >50 Myr after ocean closure if radioactivity is a major part of the heat budget. Suture zone rocks with moderate metamorphic gradients can provide more reliable estimates for the time of ocean closure but are also prone to later reactivation in orogens with protracted histories.

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Section: Tectonic Architecture Of the East African Orogenmentioning

confidence: 80%

Pan–African granulites of Madagascar and southern India: Gondwana assembly and parallels with modern Tibet

Fitzsimons

2016

Journal of Mineralogical and Petrological Sciences

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“…The timescales of UHT in the regional granulite belts of southern India and southern Madagascar are of considerable interest with respect to their implications for processes involved in the formation of the supercontinent of Gondwana from its constituent parts (Brown, 2009;Santosh et al, 2009;Santosh and Kusky, 2010;Collins et al, 2014;Clark et al, 2015), and also because in the compilation of Kelsey and Hand (2015) both regions are reported as having short duration UHT events (i.e. 'fast' granulites; 5-10 Myr: Kelsey and Hand, 2015, Fig.…”

Section: Long Duration Neoproterozoic-cambrian Uht In Southern India mentioning

confidence: 99%

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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“…The Mozambique Belt is one of the largest Neoproterozoic orogens associated with the assembly of the Gondwana supercontinent (e.g., Meert & Lieberman 2008;Santosh, Maruyama & Sato 2009;Collins et al 2014). One of the outstanding issues of the Mozambique Belt is its southern continuation into East Antarctica (Jacobs et al 1998).…”

Section: Southward Extension Of the Mozambique Beltmentioning

confidence: 99%

Electrical structure beneath Schirmacher Oasis, East Antarctica: a magnetotelluric study

Murthy

Veeraswamy²,

Harinarayana³

et al. 2013

Polar Research

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Maitri Station (70.76°S; 11.73°E) is located in Schirmacher Oasis, a coastal nunatak in north-central Dronning Maud Land covering an area of 35 km2. Here, we report results from the first magnetotelluric experiments and delineate the deep electrical conductivity structure under Schirmacher Oasis using the data acquired during the 24th Indian Antarctic Scientific Expedition. The magnetotelluric method has the advantage of shallow to deeper level coverage as the data acquisition covers a wide frequency band of 10−3–103 Hz, permitting different penetration depths depending on the frequency and conductivity of the layer under investigation. The modelling results indicate the presence of a highly resistive (8000–10 000 ohm m) upper crust, which shows a lateral variation in thickness from 20 km (below site 6) in the east to 10 km (between sites 1 and 2) in the west. It is underlain by a less resistive (500–600 ohm m) lower crust. The highly resistive upper crustal structure supports the existing notion that western Dronning Maud Land is a stable, cratonic platform. Results of free-air gravity, seismic, geomagnetic and surface wave dispersion investigations in East Antarctica also indicate a cratonic-type crust. The results of our study allow us to identify a westward thinning of the upper crust with a marked boundary between sites 1 and 2. We also find evidence for the continuity of the Mozambique mobile belt in East Antarctica on the western side of Schirmacher Oasis

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Peninsular India in Gondwana: The tectonothermal evolution of the Southern Granulite Terrain and its Gondwanan counterparts

Cited by 277 publications

References 169 publications

Pan–African granulites of Madagascar and southern India: Gondwana assembly and parallels with modern Tibet

Pan–African granulites of Madagascar and southern India: Gondwana assembly and parallels with modern Tibet

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

Electrical structure beneath Schirmacher Oasis, East Antarctica: a magnetotelluric study

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