ˈmother lode BrE AmE , moth‧er‧lode /ˈmʌðələʊd $ -ðərloʊd/ noun [countable usually singular] American English
1 . a mine that is full of gold, silver etc
2 . a place where you can find a lot of a particular type of object
mother lode of
The Sharper Image catalog is a mother lode of men’s gadgets and toys.
3 . hit the mother lode informal to produce or find something that will make you very rich, happy, or successful:
They hit the mother lode with their second album.