| 1 | Sumatra itself is part of an island arc. | |
| 2 | Silurian -Devonian island-arc volcanic formation may be hosted in rock full of porphyry copper deposits. | |
| 3 | Acid intrusions of Late Caledonian or Early Variscian Epoch result from island arc magmatism. | |
| 4 | Furthermore, the granite samples are located at volcanic arc granite area( VAG) in trace discrimination diagram. | |
| 5 | The result suggests that the protolith of amphibolite in Baoyintu Group was basalt which formed in the island-arc environment. |