In-situ zircon and cassiterite LA-ICP-MS geochronology and implications for granite hosted Sn deposit models and exploration: insights from the Cameroon Line

Tin mineralization of significant economic importance occurs across the continental portion of the Cameroon Line (CL).Tin deposits therein occur as both primary and secondary (residual and alluvial) ore.Though the temporal, and by inference the genetic link between Sn mineralization and the host granite had long been modelled and widely accepted worldwide, in the CL however, the age of the granite hosting cassiterite is poorly constrained, preventing a robust assessment of the temporal and genetic relationship between the Sn mineralization and its host rock.Here, we present in-situ zircon and cassiterite laser ablation inductively coupled mass spectrometry (LA-ICP-MS) U-Pb data in order not only to constrain the age of the granitic rock hosting the primary Sn ore, but also to bracket the time frame of Sn mineralization, with respect to the magmatichydrothermal evolution of the parental magma of the host granite.Zircon from two greisenaltered, cassiterite-bearing granite samples yield overlapping and concordant ages of 64.21 ± 0.59 Ma and 65.46 ± 0.95 Ma, respectively, which are also overlapping with regional granite magmatism in the CL (ca.65-30 Ma).On the other hand, cassiterite that is spatially associated with the Paleocene zircon yields Lower Eocene ages of 54.99 ± 0.35 Ma and 56.08 ± 0.46 Ma.The ca. 10 Myr time gap between zircon and cassiterite suggests that the granite is a passive host not genetically related to the Sn mineralization, which may rather be linked to a younger, concealed intrusion of ca.55 Ma.This finding contrasts with the most widely accepted petrogenetic model of tin granite, according to which Sn mineralization and the host granite are co genetic.