| dc.description.abstract | The Deep Drill 1972 drill core of the Bermuda Islands provides a representative sampling of Bermuda’s volcanic basement lithologies. Although there have been studies of the two primary lithologies over the past 50 years, no published work has characterized the nature of geological veining found throughout the core. Veins are defined by the shape and chemistry of their minerals, which are representative of the physical and chemical conditions under which the veins developed. This work focuses on petrographic description and mineral chemistry of veins in a selection of 13 samples from the mafic units of Bermuda. Optical microscopy reveals that veins are predominantly blocky calcite. All sample veins are interpreted to be syntaxial. Wavelength-dispersive spectroscopy point analyses and element mapping shows that calcite across all samples is chemically homogenous, with zoning produced by varying manganese concentration occurring in just one sample. Laser ablation inductively coupled plasma mass spectrometry was carried out for rare earth element + yttrium analyses on select samples. Rare earth element + yttrium signatures indicate that most samples represent high-temperature hydrothermal fluid with possible remobilization, with the sample containing manganese-zoned calcite showing an ambiguous, mixed-fluid trend. These findings suggest that vein minerals in the Bermuda mafic units precipitated from a fluid which was low velocity or stagnant, above 250˚C, and did not undergo significant chemical change as calcite precipitation progressed. This work lays the basis for future study on the veins of the Deep Drill 1972 drill core which should produce a representative sample of veins and expand the suite of analytical tools.
Key Words: Calcite, Vein, Deep Drill 1972, Bermuda igneous basement, Petrography | en_US |
