The first American sanctions on Iran since a moderate cleric won the presidential election there on June 14 went into effect on Monday, expanding the number of penalized industries and imposing rules that theoretically could halt all gold and currency trade by the country. Proponents of the latest round of sanctions said they could deprive the Iranians of billions of dollars of income that had evaded earlier rounds — particularly with the new prohibition on gold trade. Bullion dealers in other countries who flout the prohibition risk severe American penalties, including expulsion from the United States precious metals market.