There is a very large population of muslim in China. Many Chinese restaurants cater to the special needs of the muslim. A Chinese Islamic restaurant (清真菜館) is very similar to a Mandarin??? restaurant with a very obvious exception: no pork in the menu. Someone needs to confirm if the cuisine is really based on Mandarin! Obviously, lard is strictly forbidden in Islamic cooking. Another difference is that lamb and mutton are more available than in other Chinese restaurants.
In the US, Chinese Islamic restaurants are frequented by not just Chinese. Pakistanis and Arabics are also among the regular clientele.