Gold sold off on the headline that China halted reserves buying after an 18-month stretch. In my opinion, this has a lot more to do with the prevailing market narrative than a real fundamental reason. In fact, we've been hearing lots of talk about gold surging because of China and Russia buying, so the risk of that flow stopping triggered a negative reaction.
I would also point out that the selloff could have been exacerbated by algos and the price is now near the lower bound of the average daily range. Generally, the price doesn't extend much beyond these levels unless there's a very strong catalyst. Therefore, this might be a good opportunity for dip-buyers to fade the reaction.