TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

mm diameter tip (which also corresponds to the smallest measurable crystal size).
The tracings were digitized via high resolution scanning with a flatbed scanner.
Crystal intersection areas were shaded gray, detected, and measured according
to a best fit ellipse routine using the freeware program UTHSCSA ImageTool
(http://ddsdx.uthscsa.edu/dig/itdesc.html). The best fit ellipse major and minor
axis results were input into the spreadsheet program CSDslice written by Morgan
and Jerram [106] to estimate the three-dimensional crystal habit. The crystal
major axis data, the estimated 3D crystal habit, rock fabric, total area measured,
and an estimate of crystal roundness were input into the program CSDcorrections
version 1.37 written by Michael Higgins [68] to covert two-dimensional CSD data
to true three-dimensional CSDs as outlined by Marsh [96]. The areas and numbers
of crystals measured in each thin section are listed in table 3.1. Modal abundances
of plagioclase (and olivine for Site 1203 Units 11 and 16) were measured as the
percentage of the phase in the traced area, which Higgins [69] determined to be
an accurate method for estimation of modal abundance.
3.4.3 Electron Probe Microanalysis (EPMA) and Scanning Electron Microscopy
Backscatter electron images and major element analyses were performed us-
ing a JEOL JXA-8600 Superprobe electron microprobe at the University of Notre
Dame. Backscatter electron images were collected using a 1 µm beam, an acceler-
ating voltage of 20 kV, and a probe current of 25-50 nA. Microprobe analyses were
performed using a 10 µm defocused beam, accelerating voltage of 15 kV, a probe
current of 20 nA, 15 second on-peak counting time, and two background measure-
ments per peak. Sodium was measured first to minimize loss via volatilization.
Microprobe data were corrected for matrix effects using a ZAF correction rou-
95