The protolith of the metavolcanic rocks is a volcanic-subvolcanic rock series composed chiefly of low-K tholeiite with subordinate low-K basaltic andesite formed in an oceanic extensional environment.

• 变质火山岩的原岩为大洋拉张环境下形成的以低钾拉斑玄武岩为主，低钾玄武安山岩次之的火山-次火山岩系，其物源为亏损地幔。