Spectroscopic analyses were conducted on samples recovered from Holes 1188A, 1188F, 1189A, and 1191A. No onboard analyses were conducted on samples from Hole 1189B or powdered samples from Hole 1188F due to equipment malfunction.
The spectroscopic analyses were conducted using an Integrated Spectronics Portable Infrared Mineral Analyzer (PIMA) II, measuring the spectral range between 1300 and 2500 nm, in 2-nm increments.
The analyses were conducted on samples taken directly from the cores and on the powders produced for onboard X-ray diffraction (XRD) analyses. Core samples were analyzed after they were air-dried in the core trays. A 1-cm2 area of the core was analyzed where possible every 10 cm. Additional measurements were taken when features of additional interest such as vein material, alteration halos, and other areas of distinct alteration were observed. Powdered samples were measured in a petri dish with the PIMA calibrated to eliminate the effects of measurement through the glass.
Qualitative analyses of the spectra acquired were conducted using the "Integrated Spectronics PIMAView 3.1" software, combined with visual analysis of the sample spectra. Analysis of the spectra was carried out using hull-corrected data. All reflectance spectra were processed to remove the reflectance hull by applying a baseline "hull quotient" correction to the spectral data (Pontual et al., 1997). Relative abundance of each mineral identified was calculated applying the ratio of the hull-corrected depth of each mineral's diagnostic absorption feature and the overall range of the hull-corrected range for each spectra. More sophisticated methods for determining mineral abundance were not employed because of the generally poor quality of the spectral data. Illite composition was calculated by determining the position of the primary AlOH absorption feature occurring between 2180 and 2220 nm. AlOH absorptions occurring around 2180 nm in samples containing illite generally suggest a paragonitic illite composition, with absorptions around 2205 nm suggesting a "normal" potassic composition and absorptions around 2220 nm suggesting a more phengitic composition (Pontual et al., 1997).