If a spouse was sentenced to transportation beyond the seas then that effectively terminates the marriage. There are many threads explaining the statute English law dating back to early 1600s covering that, but basically it allowed re-marriage - so for example, 1800s England, a married woman with children committed a serious larcency, found guilty by the courts, sentenced to 7 years beyond the seas.
Say for instance she was sent to New South Wales. Ie beyond the seas... her husband was still in England with most of their children. He needed someone to be housekeeper while he continued to work (Ag lab or miner or shoemaker or yeoman or stonemason etc etc). He was free to marry another ... thus providing for someone to raise his children and give him more. The female convict arrives in NSW ... she was also free to marry, with permission of the Governor - the adminstrator appointed by the English Crown.
No need for any divorce, or any judicial separation,, or any fresh legal documents. The sentence of 7 years (or more) was sufficient ...
JM.