A TALE OF TWO APLITES – A COMPARATIVE STUDY
Aplite-2 is also a fine-grained equigranular rock and consists mainly of quartz and k-spar with high-Z oxide domains that include exotic trace minerals. However, unlike the first rock, there are small amounts of plagioclase and there are common occurrences of quartz/K-spar intergrowths that resemble graphic granite type intergrowths found in some pegmatites and other coarse-grained rocks.
Based on what we have observed thus far we offer the following provisional conclusions: (1) Aplites are late-phase phenomena (post plutonic rather than synplutonic); (2) All aplite dikes are not texturally and/or compositionally the same, even within the same intrusive body; (3) Aplites can provide some insight into the history of the pluton in which they occur. To attempt to explain why these aplites are different we offer the following hypotheses: (1) The two dikes were emplaced at different times; (2) The two were emplaced in different parts of the pluton - top to bottom, border to core; (3) The sizes (total volume) of the two dikes are different; (4) Two different sources provided the raw materials that crystallized into the two dikes.