Rutile LA-ICP-MS U–Pb geochronology and implications for tectono-metamorphic evolution in the Yaoundé Group of the Neoproterozoic Central African Orogeny

Tectono-metamorphic evolution within the Cameroonian Yaoundé Group portion of the Central African Orogenic Belt (CAOB) was previously assessed from both metamorphic zircon, garnet and monazite and whole rock dates. In this contribution, and for the first time, robust rutile LA-ICP-MS U–Pb dates were obtained. As rutile is ubiquitous in the low-to high-grade metamorphic rocks therein, our new data allowed to refine the age of the Neoproterozoic metamorphism characterized by four main rutile growth events at 719 ± 32 Ma, 661 ± 21 Ma, 630 ± 6 Ma, and 561 ± 8 Ma in the Yaoundé Group. An age of 522 ± 6 Ma attributed to Pb loss during Ediacaran tectonism is also defined. It appears from these rutile ages that the metamorphic evolution of the Yaoundé Group occurred, not in the time span of ca. 616 Ma to ca. 540 Ma as previously considered, but between 719 Ma and ca. 561 Ma, as revealed by U–Pb rutile dating. A comparison between these rutile dates and mineral and whole rock ages at the regional scale suggests the same time span for Neoproterozoic metamorphism in the Cameroon segment of the CAOB. It follows that the latter resulted from a protracted (>150 Myr) tectono-metamorphic and magmatic event.