A Quran Belt is a region where conservative Islamic values are strong. It is most commonly associated with an area where Islam has been historically influential in northwest China (Xinjiang, Ningxia, Gansu and Qinghai) along the borders of central Asia, Tibet and Mongolia.
Other parts of the world where Islam is or has historically been highly influential have also adopted this name, such as Kabul, Kandahar in Afghanistan, central Saudi Arabia, Southeastern Anatolia, Pakistan's Khyber Pakhtunkhwa and India's Jammu and Kashmir, Lakshadweep and Barak Valley region of Assam state.
References
Quran Belt Wikipedia(Text) CC BY-SA