A mid-ocean ridge basalt (MORB) is a basalt erupted at a mid-ocean ridge, the rock of the top of the oceanic crust. An ocean island basalt (OIB) is a basalt erupted at an oceanic volcano away from plate boundaries, such as those of Hawaii, commonly attributed to a mantle plume (Year 1 volume).
| oxide (wt %) | primitive mantle | MORB | OIB (BHVO-2) | upper cont. crust |
|---|---|---|---|---|
| 45.0 | 50.47 | 49.60 | 66.6 | |
| 0.201 | 1.68 | 2.731 | 0.64 | |
| 4.45 | 14.70 | 13.44 | 15.4 | |
| FeO (total) | 8.05 | 10.43 | 11.15 | 5.04 |
| MnO | 0.135 | 0.184 | 0.1690 | 0.10 |
| MgO | 37.8 | 7.58 | 7.257 | 2.48 |
| CaO | 3.55 | 11.39 | 11.40 | 3.59 |
| 0.36 | 2.79 | 2.219 | 3.27 | |
| 0.029 | 0.160 | 0.5130 | 2.80 | |
| 0.021 | 0.184 | 0.2685 | 0.15 |