Figure 5. Embedded in the massive granite of Big Rock, there are several isolated masses of other rock types that look very different from the granite. These areas of other rock come in a variety of sizes, colors, and shapes, though most are small, dark gray, and rounded. Some dark patches, called enclaves, represent blobs of magma of a different composition from granite that mixed into the granite when they were both molten (Figure 5A, Figure 5B, Figure 5C). Other bits of foreign rock, called xenoliths, represent fragments of solid metamorphic rock that were engulfed by the granite magma when it rose through the earth's crust (Figure 5D). For some dark patches, it is not clear whether they are enclaves or xenoliths (Figure 5E). (Click on each photo for a larger view).
Last updated on November 20, 2012