Hydrothermal Alteration of the Ocean Crust and Patterns in Mineralization With Depth as Measured by Micro?Imaging Infrared Spectroscopy

Processes for formation, cooling, and altering Earth's ocean crust are not yet completely understood due to challenges in access sampling. Here, we use contiguous micro-imaging infrared spectroscopy develop complete-core maps of mineral occurrence investigate spatial patterns the hydrothermal alteration 1.2 km oceanic recovered from Oman Drilling Project Holes GT1A, GT2A, GT3A drilled Samail Ophiolite, Oman. The imaging spectrometer shortwave sensor measured reflectance light at wavelengths 1.0–2.6 ?m 250–260 ?m/pixel, resulting >1 billion independent measurements. We map distributions nine key primary secondary minerals/mineral groups—clinopyroxene, amphibole, calcite, chlorite, epidote, gypsum, kaolinite/montmorillonite, prehnite, zeolite—and find differences their occurrences pervasiveness. Accuracy spectral mapping is 68%–100%, established using X-ray diffraction measurements core description. sheeted dikes gabbros upper Hole show more pervasive dominated by epidote. foliated/layered GT2A intermediate crustal depths have similarly widespread chlorite but zeolite little amphibole layered lower (GT1A) remnant pyroxene 2X less extensive within surrounding major fault zones with amphibole. results indicate greater distribution higher temperature minerals relative deeper highlight importance convection crust.