The answer is synthesis reaction
The explanation:
when synthesis reaction or direct combination reaction is a type of chemical reaction in which two or more simple substances combine to form a more complex product. The reactants may be elements or compounds. The product is always a compound
and we here
Fe2O3 + 2SiO2 → Fe2Si2O7
Fe2O3 is combined with SiO2 and form a more complex product Fe2Si2O7
so this is a synthesis reaction.