gold mine
noun uk/ˈɡəʊld ˌmaɪn/ us/ˈɡoʊld ˌmaɪn/
[ C ]金矿
a place where gold is taken from the ground
[ S ]宝库;宝藏;财源
something that produces wealth or information
The archive is a gold mine for historians. 这个档案馆对于历史学家来说就是一座宝库。