| dc.description.abstract | Along the North Shore of Nova Scotia, Canada vesicular basalts in the McArras Brook
Formation are host to carbonate amygdules and veins. These basalts are interbedded within a
well characterized Devonian strata but have not been directly dated. Through previous studies
with U-Pb dating, the ages for calcite amygdules have been shown to form shortly after the
eruption of the host basaltic lava. Secondary processes lead to the formation of overgrowths on
existing calcite amygdules and low-T veins. These may form during tectonic emplacement and
thus, multiple generations of calcite can also be found in the same suite of basaltic rocks. Before
the U-Pb ages of both volcanism (amygdule formation) and later tectonic activity (secondary
calcite) can be accurately measured and used as a proxy for the age of the basalt flows, the
growth history of the calcite amygdules and viens must be carefully characterized. In this study
we have used basic textural relationships and UV fluorescence to examine calcite growth history,
both in the field and in collected samples. In-situ UV-fluorescence shows the growth of several
generations of calcite amygdules and veins in the basalts from McArras Brook. We will use the
UV characterization to help target analysis of different generations of calcite using a scanning
electron microscope (SEM) to analyse the relationships between the fluorescence and the major
elements. The results are expected to identify activator elements in the calcite which correspond
to the differences in fluorescence colour, and correlate element compositions to the growth
history. This will allow us to target the best areas for subsequent U-Pb dating of calcite to
determine the absolute (volcanic) ages of these basalts, and the ages of secondary processes. | en_US |
