I read a paper titled "Martian magmas contain abundant chlorine, but little water" in which it's mentioned that Mars could have up to 2.5 times more chlorine than Earth. Considering that Mars and Earth were created very close and at the same time, this is surprising.
This made me think about the mechanisms that could deposit large amounts of chlorine on a planet, so I tried to find information about it, but I did not find anything about it on the web.
So, how could a planet have large amounts of chlorine even though chlorine is much less abundant than other elements?
Even though chlorine is still not abundant, I think there might be enough for a chlorine planet to be created... only if enough chlorine can accumulate in a specific region of the protoplanetary disk.