| The dykes and sheets sharply truncate structures in the wall rock gneisses and greenstones, and large wall-rock xenoliths may be completely engulfed by the intrusive sheets. |
| Partial melting models, isotopic studies and the petrology of entrained ultramafic xenoliths suggest that many basanitic magmas are sourced in the asthenosphere. |
| None of the glass in these xenoliths can be directly related to metasomatism or any other process that occurred in situ in the mantle. |
| The basalt, inferred to be of Miocene age, appears to be an alkali basalt that contains xenoliths of ultramafic rocks up to a few centimeters in size. |
| However, rare xenoliths of sedimentary rocks occur in the granite. |
| If the magma has risen quickly from the source region of the volcano, the xenoliths may represent country rock from all levels of the crust through which it has travelled. |
