From passive margin to volcano–sedimentary forearc: The Tonian to Cryogenian evolution of the Anosyen Domain of southeastern Madagascar

Boger, Steven D.; Hirdes, W.; Ferreira, Carlos; Schulte, B.; Jenett, T.; Fanning, C. Mark

doi:10.1016/j.precamres.2014.04.004

Cited by 49 publications

(59 citation statements)

References 104 publications

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“…Nor can it explain why the hottest thermal gradients are recorded in the Azania microcontinental block dominated by reworked Archean to Paleoproterozoic material, while adjacent arc terranes have cooler gradients. Jöns and Schenk (2011) suggested that UHT metamorphism in southern Madagascar was driven by charnockite plutons, which are most abundant in the Anosyen Domain where peak T is highest, but these 0.58-0.52 Ga syn-to late-tectonic plutons (now called the Ambalavao Suite; Boger et al, 2014;Tucker et al, 2014;Boger et al, 2015) are more likely a crustal re-sponse to high-T conditions than the cause of UHT metamorphism. Nicollet (1990) similarly used anorthosite and mafic-ultramafic complexes in southern Madagascar to argue that UHT conditions were driven by extension and delamination of mantle lithosphere, but these high-T magmatic rocks are now known to be much older than the UHT event.…”

Section: Discussionmentioning

confidence: 99%

“…Horton et al (2016) argued that peak T was >900°C in the south-central Anosyen Domain and decreased to the north and west, whereas earlier estimates of 0.3-0.5 GPa and 650-850°C for the Anosyen Domain (Nicollet, 1990;Martelat et al, 1999) are likely a retrograde overprint. These rocks yield a 0.63-0.51 Ga spread of metamorphic ages de Wit et al, 2001;Jöns and Schenk, 2011;Tucker et al, 2011b;Boger et al, 2014Boger et al, , 2015Horton et al, 2016) with a local overprint at 0.48-0.45 Ga (Giese et al, 2011). Although Boger et al (2015) suggested 0.63-0.60 Ga ages are restricted to the Androyen Domain, they also occur in the Anosyen Domain (Jöns and Schenk, 2011;Horton et al, 2016).…”

Section: Metamorphism Between the Suturesmentioning

confidence: 99%

“…Other igneous protoliths include~2.0, 1.7-1.6, and 1.0 Ga granite in the Nagercoil and northeastern and southern Madurai blocks of India (Plavsa et al, 2012;Brandt et al, 2014;Kröner et al, 2015), local 2.2-1.8 and~1.0 Ga mafic and felsic rocks in south-central Madagascar (Tucker et al, 2011b), and 0.94-0.90 Ga alkali granite and anorthosite in southern Madagascar (Boger et al, 2015). Most metasedimentary units in Madagascar and southern India contain abundant 2.7-2.4 and 2.2-1.8 Ga detrital zircons (Cox et al, 1998(Cox et al, , 2004Fitzsimons and Hulscher, 2005;Collins et al, 2007b;De Waele et al, 2011;Collins et al, 2012;Boger et al, 2014;Plavsa et al, 2014), but 1.1-0.9 Ga detritus dominates the Ikalamavony Domain of Madagascar (Tucker et al, 2011b) and southern Madurai Block and Achankovil Zone of India , and detritus in the Malagasy suture can have a mix of age populations including 3.3-3.1, 2.7-2.4, 2.2-1.8 and 0.84-0.70 Ga (Collins et al, 2003;Key et al, 2011).…”

Section: Reworked Crust Of the Southern East African Orogenmentioning

confidence: 99%

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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: Discussionmentioning

confidence: 99%

Section: Metamorphism Between the Suturesmentioning

confidence: 99%

Section: Reworked Crust Of the Southern East African Orogenmentioning

confidence: 99%

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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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“…However, even with a better understanding of the metamorphic ages, the paleo-position of Sri Lanka in Gondwana assembly with respect to southern India and eastern Antarctica is highly debated. Boger et al (2015) has recently proposed that a Neoproterozoic Gondwana suture extends from East Africa into Madagascar, Sri Lanka, and East Antarctica. This study suggested that the location of this suture in Sri Lanka is the tectonic boundary between the Highland Complex and Vijayan Complex (Fig.…”

Section: Tectonic Implicationsmentioning

confidence: 99%

“…8). According to Boger et al (2015), the Highland Complex of Sri Lanka is part of the Indian Crust, along with the Trivandrum Block of southern India, the Lützow-Holm Complex in East Antarctica, and much of central Madagascar, while the Vijayan Complex, along with the Sør Rondane Mountains of Antarctica and southwest Madagascar, are an extension of the Arabian-Nubian Shield and represent an ocean arc domain between Indian and African Crusts. However, this model does not agree with the some of the geochronological or geological evidence (e.g., Shiraishi et al, 1997;Dunkley et al, 2014), such as the type and timing of metamorphism (Neoproterozoic UHT metamorphism) and province/protolith ages (~2.5 Ga).…”

Section: Tectonic Implicationsmentioning

confidence: 99%

UHT granulites of the Highland Complex, Sri Lanka II: Geochronological constraints and implications for Gondwana correlation

Osanai

Sajeev²,

Nakano

et al. 2016

Journal of Mineralogical and Petrological Sciences

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The regional ultrahigh-temperature (UHT) metamorphism of the Highland Complex, Sri Lanka is well established and has an important role in our understanding of the tectonic history of the Gondwana supercontinent. U-Pb zircon dating of sapphirine-bearing Mg-Al granulites yielded two major metamorphic age populations at approximately 620-590 and 563-525 Ma with no evidence of older zircon cores. Pelitic granulite samples with a Grt-Sil-Spl-Crd assemblage have similar metamorphic ages with concordant data clusters at~602, 563, and 526 Ma and inherited zircon cores aged from 2040 to 1600 Ma. The pelitic granulites also underwent two stages of metamorphism (565-520 and 622-580 Ma). Some of these pelitic granulite samples have inherited zircon cores ranging from 3060 to 760 Ma. Zircons in mafic granulite samples have age ranges of 566-533 and 620-578 Ma. A calc-silicate granulite sample also has similar age populations at 591, 541, and 524 Ma. Combining these new results with previously published ages from Sri Lanka and formerly adjacent continental fragments of Gondwana, we propose that the terranes in southern Madagascar (south of Ranotsara Shear Zone), Northern and Southern Madurai and the Trivandrum Blocks of southern India, the Highland Complex of Sri Lanka, and the Skallen Group in the Lützow-Holm Complex of East Antarctica represent a unique metamorphic belt that regionally experienced the Ediacaran-Cambrian UHT event during the amalgamation of the Gondwana supercontinent.

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Focused radiogenic heating of middle crust caused ultrahigh temperatures in southern Madagascar

et al. 2016

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Internal heating can cause melting, metamorphism, and crustal weakening in convergent orogens.This study evaluates the role of radiogenic heat production (RHP) in a Neoproterozoic ultrahigh-temperature metamorphic (UHTM) terrane exposed in southern Madagascar. Monazite and zircon geochronology indicates that the Paleoproterozoic Androyen and Anosyen domains (i) collided with the oceanic Vohibory Arc at~630 Ma, (ii) became incorporated into the Gondwanan collisional orogen by~580 Ma, and (iii) were exhumed during crustal thinning at 525-510 Ma. Ti-in-quartz and Zr-in-rutile thermometry reveals that UHTM occurred over >20,000 km 2 , mostly within the Anosyen domain. Assuming that U, Th, and K contents of samples from the field area are representative of the middle to lower crust during orogenesis, RHP was high enough-locally >5 μW/m 3 -to cause regional UHTM in <60 Myr. We conclude that, due in large part to the stability and insolubility of monazite at high crustal temperatures, RHP was the principal heat source responsible for UHTM, obviating the need to evoke external heat sources. Focused RHP probably thermally weakened portions of the middle crust, gravitationally destabilizing the orogen and facilitating thinning via lateral extrusion of hot crustal sections.

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From passive margin to volcano–sedimentary forearc: The Tonian to Cryogenian evolution of the Anosyen Domain of southeastern Madagascar

Cited by 49 publications

References 104 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

UHT granulites of the Highland Complex, Sri Lanka II: Geochronological constraints and implications for Gondwana correlation

Focused radiogenic heating of middle crust caused ultrahigh temperatures in southern Madagascar

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