Abstract: The results of ¹⁹⁰Pt–⁴He dating of placer-forming platinum-group minerals (PPMs) from the placer deposits of Mokhovoi Creek, its tributaries, and eluvial and proluvial deposits of the peneplain surface of dunites of the Chad alkaline-ultramafic massif (Aldan Shield, Ayan-Maya district of Khabarovsk krai) are presented. ¹⁹⁰Pt and ⁴He were measured in 27 samples. The statistical processing of the mineralogical and geochemical data allows us to separate three ¹⁹⁰Pt–⁴He age isochrones (Ma): 123 ± 6; 113 ± 6; and 107 ± 6, which is in good agreement with the geological observations and the mineralogy of the platinum group elements (PGEs) of the Chad massif. The range of ¹⁹⁰Pt–⁴He age isochrones indicates that platinum-metal ore formation occurred over 16 Myr. The geological and mineralogical data and the ¹⁹⁰Pt–⁴He isochrones of different ages allow us to conclude that the platinum-metal ore formation in the Chad massif was polycyclic during the Early Cretaceous. A comparison of the ¹⁹⁰Pt–⁴He ages of the PPMs of the Chad and Kondyor alkaline-ultramafic massifs indicates that there are temporal features between the platinum ore formation and the formation of these plutons during the Mesozoic tectonic–magmatic activation of the Aldan Shield.