to become (formal)
to become; to get; to grow; to turn; to reach; to attain
開催が決定と相成った。
It has been decided that the event will be held.
合意に達することと相成っているようだ。
It appears that a conclusion of reaching agreement has been arrived at.
この度はご案内と相成る次第でございます。
I hereby have the occasion to inform you of this matter.