Evidences for Neoproterozoic fragments with Indian origin in Oman and northern Madagascar

Newly obtained geochemical and geochronological data from the Saih Hatat Dome in northeastern Oman and the Betsiaka Group in northern Madagascar reveal compelling similarities in the Neoproterozoic geological evolution of these geographically distant regions. The Saih Hatat Dome serves as a tectonic window with a NW-SE extension of <95 km and an E-W extension of <50 km. It is encircled by the allochthonous Samail Ophiolite and the underlain nappes consisting of mostly sedimentary rocks from the Neo-Tethyan Hawasina Basin. The rocks within this window underwent Late Cretaceous high-pressure/low-temperature eclogite- and blueschist-facies metamorphism.

In contrast, the Betsiaka Group of northern Madagascar, located between the Neoproterozoic Bemarivo Belt (750-720 Ma) and the Permo-Mesozoic cover, includes amphibolites, garnet-sillimanite micaschists, quartzites, and rare calc-silicate rocks.

New U-Pb zircon LA-ICP-MS data from a quartzdiorite dyke, intruding the basal part of the Hatat schists of the Saih Hatat Dome, yielded a crystallization age of 845 +2/-4 Ma. Similarly, a U-Pb zircon age of 841 ± 5 Ma was determined from an orthogneiss within the Betsiaka Group. Both igneous suites exhibit a calc-alkaline geochemical signature characteristic of volcanic island arcs.

The quartzdiorite in the Saih Hatat intruded a volcanosedimentary sequence and is covered by Cryogenian to Ediacaran metasedimentary and metavolcanic formations. Two metatuffites contain igneous and detrital zircons with ages ranging from approximately 530 to 2872 Ma, featuring clusters around 750 to 850 Ma and 1010 to 1164 Ma. Ages exceeding 1.1 Ga are unprecedented from an Arabian Plate source. Conversely, a quartzite from the Betsiaka Group displays a youngest >90% concordant zircon age of 1771 ± 28 Ma, with age peaks at around 2.5, 2.4 Ga, 1.8 Ga, and 1.85 Ga, pointing towards a Late Paleoproterozoic deposition age. Zircon ages between 1.77 and 1.85 Ga are also absent from central Madagascan igneous rocks. We propose that these crustal fragments in Oman and Madagascar originated from an area previously proximate to the Aravalli Craton in NW India.