2 research outputs found
Provenance and tectonic significance of the Palaeoproterozoic metasedimentary successions of central and northern Madagascar
New detrital zircon U-Pb age data obtained from various quartzite units of three spatially
separated supracrustal packages in central and northern Madagascar, show that these units were
deposited between 1.8 and 0.8 Ga and have similar aged provenances. The distribution of detrital
zircon ages indicates an overwhelming contribution of sources with ages between 2.5 and 1.8 Ga.
Possible source rocks with an age of 2.5 Ga are present in abundance in the crustal segments
(Antananarivo, Antongil and Masora Domains) either side of a purported Neoproterozoic suture
("Betsimisaraka Suture Zone"). Recently, possible source rocks for the 1.8 Ga age peak have been
recognised in southern Madagascar. All three supracrustal successions, as well as the Archaean blocks
onto which they were emplaced, are intruded by mid-Neoproterozoic magmatic suites placing a
minimum age on their deposition. The similarities in detrital pattern, maximum and minimum age of
deposition in the three successions, lend some support to a model in which all of Madagascar's
Archaean blocks form a coherent crustal entity (the Greater Dharwar Craton), rather than an
amalgamate of disparate crustal blocks brought together only during Neoproterozoic convergence.
However, potential source terranes exist outside Madagascar and on either side of the Neoproterozoic
sutures, so that a model including a Neoproterozoic suture in Madagascar cannot be dispelled outright