Multiple Ediacaran tectono‐metamorphic events in the Adamawa‐Yadé Domain of the Central Africa Fold Belt: Insight from the zircon U–Pb LAM‐ICP‐MS geochronology of the metadiorite of Meiganga (Central Cameroon)

Abstract

One of the many orogeny cycles in Central Africa is the Pan‐African orogeny which took place during the Neoproterozoic era. In central Cameroon, the reworked materials are Archean to Palaeoproterozoic rocks of sedimentary and magmatic origin and subsequent granitoids. The metadiorite of Meiganga is a syntectonic magmatic rock, affected by three deformational phases. It is characterized by a schistosity highlighted by a banded structure related to migmatization and made up of green hornblende, biotite, plagioclase, quartz, chlorite, opaques minerals, apatite, zircon, and titanite. Zircon grains of the metadiorite are prismatic or roundish. Internally, they show oscillatory zonation, blurred oscillatory zonation, and sector zoning. Some grains portray an outer cathodoluminescence bright band with blurred oscillatory zonation and which transgress the inner oscillatory domain; zircons contain inclusions or are inclusion free. Laser‐ablation microprobe‐inductively coupled plasma‐mass spectrometry U–Pb data allow in relation with the internal structure of the zircon to decipher many tectono‐metamorphic steps in the Ediacaran phase of the Pan‐African Orogeny: (a) syntectonic emplacement of the dioritic protolith at 637 ± 5 Ma; (b) syn‐D2 melting process at 623 ± 2 Ma; (c) D3 time interval between 608 ± 2 and 562 ± 6 Ma; and (d) maximum age of the dextral movement of the regional shear zone at 570 ± 8 Ma. Ages founded in the studied metadiorite sample are recorded individually in different area of the Adamawa‐Yadé area of the Central African Fold Belt and the Borborema Province of NE Brazil, showing that the two domains underwent the same tectono‐metamorphic history during the Ediacaran period.