Evolving Marginal Terranes During Neoproterozoic Supercontinent Reorganization: Constraints From the Bemarivo Domain in Northern Madagascar. Issue 6 (22nd June 2019)

• Record Type: Journal Article
• Authors: Armistead, Sheree E.; Collins, Alan S.; Merdith, Andrew S.; Payne, Justin L.; Cox, Grant M.; Foden, John D.; Razakamanana, Théodore; De Waele, Bert
• Is Part Of: Tectonics. Volume 38:Issue 6(2019)
• Page Start: 2019
• Page End: 2035
• Publication Date: 2019-06-22
• Subjects: Rodinia -- Gondwana -- supercontinent -- Neoproterozoic -- Lu‐Hf -- zircon; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1029/2018TC005384
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: Madagascar is a key area for unraveling the geodynamic evolution of the transition between the Rodinia and Gondwana supercontinents as it contains several suites of c. 850–700 Ma magmatic rocks that have been postulated to correlate with other Rodinian terranes. The Bemarivo Domain of northern Madagascar contains the youngest of these units that date to c. 750–700 Ma. We present zircon Hf and O isotope data to understand northern Madagascar's place in the Neoproterozoic plate tectonic reconfiguration. We demonstrate that the northern component of the Bemarivo Domain is distinct from the southern part of the Bemarivo Domain and have therefore assigned new names—the Bobakindro Terrane and Marojejy Terrane, respectively. Magmatic rocks of the Marojejy Terrane and Anaboriana Belt are characterized by evolved εHf ( t ) signatures and a range of δ 18 O values, similar to the Imorona‐Itsindro Suite of central Madagascar. These magmatic suites likely formed together in the same long‐lived volcanic arc. In contrast, the Bobakindro Terrane contains juvenile εHf ( t ) and mantle‐like δ 18 O values, with no probable link to the rest of Madagascar. We propose that the Bobakindro Terrane formed in a juvenile arc system that included the Seychelles, the Malani Igneous Suite of northwest India, Oman, and the Yangtze Belt of south China, which at the time were all outboard from continental India and south China. The final assembly of northern Madagascar and amalgamation of the Bobakindro Terrane and Marojejy Terrane occurred along the Antsaba subduction zone, with collision occurring at c. 540 Ma. Key Points: New model links northern Madagascar, Seychelles, NW India, Oman, south China at c. 750 Ma New zircon Hf and O isotope data from northern Madagascar indicate that the Bobakindro Terrane (northern Bemarivo Domain) is juvenile The Marojejy Terrane (southern Bemarivo Domain) has evolved Hf isotope signatures and likely links with central Madagascar magmatic suites