Research Training Program

The Morefield pegmatite is a mineralogically complex, zoned, rare-element granitic pegmatite. The mineralogy of the pegmatite has been described in past literature, however studies have not been done involving the relationships among minerals, the crystallization of the minerals, and detailed descriptions of the internal zonation of the pegmatite. These topics are important in helping to determine exactly how the pegmatite developed. This research has established that the internal zonation of the pegmatite can be divided into five primary zones and two replacement units. The primary zones are defined as the wall zone, 1^st, 2^nd & 3^rd intermediate zones, and the core zone. The two replacement units (I & II) formed after the primary zones. Upon establishing the internal zonation, and by using the mineralogy from each zone, a crystallization history could be developed. The following three criteria were used to study the crystallization sequence of the pegmatite: the crystal shape of the minerals, the relationships between mineral phases, and cross-cutting relationships between minerals. The mineralogy from the crystallization history holds clues to the chemical evolution of the pegmatite melt. Elements like B, Li, Nb, Ta, Fe, Mn, and F in the minerals were studied in order to develop a preliminary chemical evolution of the pegmatite melt. These trace elements reveal that the pegmatite was B, Fe, and Nb enriched early in the stages of pegmatite crystallization, and that the melt became Li, Ta, F, and Mn enriched late in the crystallization of the pegmatite.