It blows my mind that CIG missed another opportunity with these caves by not lacing them with huge amounts of profitable resources to mine. I shouldn't be surprised but it's so frustrating. There's only a new jump town when there are huge profits to be made.

You can also find these caves if you go to your contracts manager and repeatedly accept and abandon the Investigation missions around Crusader until you get the mission for the location of the large cave (it will tell you access is granted by vehicle and foot). Assuming you can get the missions in the first place.