Intrusive rocks –Consist of granodiorite (Tg),diorite (Tdi), syenite(Tsy),tonalite-trachyte(Tt),andesite (Ta),and dacite (Tda); assumed have intruded into the Middle Miocene rocks. The large intrusive body found in the middle of East Sumbawa is composed of rocks ranging from tonalite to trachyte ; characterized by feldspar a few mm to 2 cm in size . At some places the rocks surrounding the intrusive are fairly strong propylitized , silicified , and contain more quartz veins than in other areas.