FLUID INCLUSION INVESTIGATION OF THE LORD HILL, BUMPUS AND COLE PEGMATITES

Pegmatites are commonly divided into two main categories depending on their rare earth element composition. These two groups are lithium-cesium-tantalum (LCT) pegmatites and niobium-yttrium-fluorine (NYF) pegmatites. The Lord Hill, Bumpus and Cole pegmatites, located in western Maine, are all known as LCT-type pegmatites. Melts from which these deposits crystallize from are commonly enriched in fluxing components such as water, phosphorus, fluorine and boron. The goal of this study is to characterize the fluids that form these deposits and to use this data in learning more about LCT type pegmatites and how they compare to NYF pegmatites. General petrography of fluid inclusions in various mineral phases was conducted in order to differentiate primary and secondary inclusions. Primary inclusions are the result of entrapped fluids during crystallization while secondary inclusions result commonly from fractures which were subsequently sealed. Fluid inclusion heating and freezing experiments were carried out using a Fluid Inc. stage at Stockton College in order to clearly relate the fluid inclusions to one another in a fluid inclusion assemblage and to characterize the general salinity of the fluid inclusions. The specific trace element geochemistry of these inclusions was determined using laser ablation-inductively coupled plasma mass spectrometry in the Fluids Research Laboratory at Virginia Tech. This data was then compared to similar fluid inclusion studies on other LCT-type pegmatites located in Maine and NYF-type pegmatites from Ontario in order to determine any differences or similarities between LCT and NYF pegmatites. In addition, a general model of formation for each pegmatite was determined.