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Since the Navigo Semaine package is valid throughout the Île-de-France zones 1-5, it could not be used for a direct trip to Château de Chantilly, which is located outside Zone 5.
SNCF shows it as a 50-minute journey from Paris Nord to Chantilly-Gouvieux for 8,70 €; the castle is about a 15-minute walk from the station.
Rome2Rio is also a useful tool to explore options and alternatives, and a map of your route. And @pnuts has thoughtfully provided this map of all your transport options within all of the Île-de-France zones.