| Description |
The diorite in the Mayflower Mine, Keetley, Utah, has assimilated to some extent the calcareous sediments with which it has come into contact during the process of intrusion. This assimilation is shown by an increase in grain size and a basification of the diorite at and near the contact. The increase in grain size and accompanying basification in a dioritic magma upon assimilation of calcareous sediments are effects to be expected. The banding that is shown on the 800 level of the mine is evident because of several factors: decrease in grain size, decrease in amount of plagioclase present, and increase in amount of dark minerals present. The symmetry of the petrographic diagrams of the plagioclase suggests that there was flow previous to and during solidification of the diorite, and that there is a relation of the magmatic flow with the contact. With the presence of flow structure, the banding is thought to be primary flow structure rather than relic structure. Alteration within the diorite is due to the action of hydrothermal solutions during several successive stages, and consists of chloritization, kaolinization-sericitization, and epidotization. The minerals that are present suggest that the alteration took place in a mesothermal environment of intermediate temperatures. |
