The protolith of the plagioamphibolites in Middle Hainan is the metamorphosed Paleo-Mesoproterozoic basic volcanics.

• 琼中斜长角闪(片麻)岩为变质的古-中元古代基性火山岩,属于高铝和低钛的高钾钙碱性玄武岩系。