A.T. Robertson Commentary Mark 10:11

"And he saith unto them, Whosoever shall put away his wife, and marry another, committeth adultery against her:" — Mark 10:11 (ASV)

Mark does not give the exception stated in Mt 19:9 "except for fornication" which see for discussion, though the point is really involved in what Mark does record. Mere formal divorce does not annul actual marriage consummated by the physical union. Breaking that bond does annul it.