Madagascar occupied an important place in the amalgamation of Gondwana and preserves a record of several Neoproterozoic events that are linked to orogenesis of the East African Orogen. In this study, we integrate remote sensing, field data and thermochronology to unravel complex deformation in the Ikalamavony and Itremo domains of central Madagascar. The deformation sequence comprises a gneissic foliation (S 1 ), followed by south- to SW-directed, tight to isoclinal, recumbent folding (D 2 ). These are overprinted by north-trending upright folds that formed during an approximately east–west shortening event (D 3 ). Together these produced type 1 and type 2 fold interference patterns throughout the Itremo and Ikalamavony domains. We show that the Itremo and Ikalamavony domains were deformed together in the same orogenic system, which we interpret as the c . 630 Ma collision of Azania with Africa along the Vohibory Suture in southwestern Madagascar. In eastern Madagascar, deformation is syn- to post-550 Ma, and probably formed in response to final closure of the Mozambique Ocean along the Betsimisaraka Suture that amalgamated Madagascar with the Dharwar Craton of India. Apatite U–Pb and novel laser ablation triple quadrupole inductively coupled plasma mass spectrometry (LA-QQQ-ICP-MS) muscovite and biotite Rb–Sr thermochronology indicates that much of central Madagascar cooled through c . 500°C at c . 500 Ma. Supplementary material: A detailed geological map of central Madagascar (Supplementary A), detailed methods and geo- and thermochronology results (Supplementary B), isotopic data for geo- and thermochronology (Supplementary C) and Landsat images and structural interpretation examples (Supplementary D) are available at https://doi.org/10.6084/m9.figshare.c.4840575

Thermochronology

10.1144/jgs2019-132

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Citations (23)

MC-LA-ICP-MS zircon Hf isotope compositions. Stenian–Tonian arc magmatism in west–central Madagascar: the genesis of the Dabolava Suite

Figshare (2017)

Donnelly B. Archibald Alan S. Collins John Foden Justin L. Payne P.H. Macey

Table A.6: MC-LA-ICP-MS zircon Hf isotope compositions

10.6084/m9.figshare.5195593

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Citations (0)

Tectonic evolution of an Early Cryogenian late- magmatic basin in central Madagascar

Journal of African Earth Sciences (2021)

Raisa Costa Renata da Silva Schmitt Alan S. Collins Sheree Armistead Igor Vasconcelos Gomes

Detritus

Rodinia

10.1016/j.jafrearsci.2021.104205

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Citations (4)

Zircon standard data. Stenian–Tonian arc magmatism in west–central Madagascar: the genesis of the Dabolava Suite

Figshare (2017)

Donnelly B. Archibald Alan S. Collins John Foden Justin L. Payne P.H. Macey

Table A.1. Zircon standard data

10.6084/m9.figshare.5195596

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Two‐stage metamorphic evolution of the Bemarivo Belt of northern Madagascar: constraints from reaction textures and in situ monazite dating

Journal of Metamorphic Geology (2006)

Niels Jöns Volker Schenk Peter Appel Théodore Razakamanana

Abstract New results on the pressure–temperature–time evolution, deduced from conventional geothermobarometry and in situ U‐Th‐total Pb dating of monazite, are presented for the Bemarivo Belt in northern Madagascar. The belt is subdivided into a northern part consisting of low‐grade metamorphic epicontinental series and a southern part made up of granulite facies metapelites. The prograde metamorphic stage of the latter unit is preserved by kyanite inclusions in garnet, which is in agreement with results of the garnet (core)‐alumosilicate‐quartz‐plagioclase (inclusions in garnet; GASP) equilibrium. The peak metamorphic stage is characterized by ultrahigh temperatures of ∼900–950 °C and pressures of ∼9 kbar, deduced from GASP equilibria and feldspar thermometry. In proximity to charnockite bodies, garnet‐sillimanite‐bearing metapelites contain aluminous orthopyroxene (max. 8.0 wt% Al 2 O 3 ) pointing to even higher temperatures of ∼970 °C. Peak metamorphism is followed by near‐isothermal decompression to pressures of 5–7 kbar and subsequent near‐isobaric cooling, which is demonstrated by the extensive late‐stage formation of cordierite around garnet. Internal textures and differences in chemistry of metapelitic monazite point to a polyphasic growth history. Monazite with magmatically zoned cores is rarely preserved, and gives an age of c . 737 ± 19 Ma, interpreted as the maximum age of sedimentation. Two metamorphic stages are dated: M1 monazite cores range from 563 ± 28 Ma to 532 ± 23 Ma, representing the collisional event, and M2 monazite rims (521 ± 25 Ma to 513 ± 14 Ma), interpreted as grown during peak metamorphic temperatures. These are among the youngest ages reported for high‐grade metamorphism in Madagascar, and are supposed to reflect the Pan‐African attachment of the Bemarivo Belt to the Gondwana supercontinent during its final amalgamation stage. In the course of this, the southern Bemarivo Belt was buried to a depth of >25 km. Approximately 25–30 Myr later, the rocks underwent heating, interpreted to be due to magmatic underplating, and uplift. Presumably, the northern part of the belt was also affected by this tectonism, but buried to a lower depth, and therefore metamorphosed to lower grades.

Geothermobarometry

Isograd

Sillimanite

Cordierite

10.1111/j.1525-1314.2006.00641.x

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Citations (47)

S3: Zircon U–Pb, oxygen and hafnium isotopic characteristics of the Neoarchaean–Palaeoproterozoic Betsiboka Suite, Madagascar: tracing source to sink pathways in Proterozoic and Phanerozoic provenance studies

Figshare (2022)

Donnelly B. Archibald Alan S. Collins Sheree Armistead John Foden Justin L. Payne

Zircon U–Pb data

10.6084/m9.figshare.21501447