Two weeks after being briefed on the benefits and pitfalls of casinos in Massachusetts, Governor Deval Patrick and his administration are fighting to keep secret the completed studies that the governor is reviewing. On July 25, Patrick received a stack of studies on gambling to help him decide whether to support casinos. But in a sign that Patrick is treating the casino question with political caution, the administration declined Monday to provide copies of the records to the Globe, which filed a formal request for them July 26.