Beyonce & Mariah Carey -- Let's Talk Duets

Beyonce and Mariah Carey could be joining forces on a new track soon ... that is, if they go forward with plans made on Thursday.

The two divas were at a benefit in L.A. for the HeartView Global Foundation, and had tables beside each other. We're told when Bey and Mariah got a chance to talk, the possibility of a duet was brought up and the two agreed, it needs to happen.

At one point, they got in a bidding war over a portrait of Ray Charles and after throwing down thousands, the artist agreed to give them both a copy.

Our source says the girls share the same business manager, Jon Schwartz, who also runs the foundation, so it'd be easy to get them together in the studio.