Figure F115. Alteration of peridotite. A. Zone of green tremolite and pale talc replacing serpentinized harzburgite (interval 304-U1309B-11R-2, 25–50 cm) (field of view [FOV] = 25 cm). This zone has undergone reverse shear along talc-rich horizons, but the margin of talc alteration against serpentinite is unsheared, overprinting the preexisting serpentinite foliation defined by magnetite seams and serpentine ribbons. Boxes = location of B and D. B. Same as A; FOV = 4.4 cm. C. Collage showing the transition from the tremolite-rich core of the zone to talc-rich material replacing serpentinite. Relict bastites preserve serpentine + magnetite mineralogy (plane-polarized light; FOV = 9.6 cm). D. Detail of talc front against serpentinite. An orthopyroxene crystal within the serpentinite is pseudomorphed by talc + magnetite (cross-polarized light; FOV = 5.2 cm). E. Detail of lozenge-shaped carbonate (inferred to be magnesite) replacing interlithon microlithons in serpentinite ribbon texture (cross-polarized light; FOV = 4 cm). F. Tremolite vein cutting serpentinized harzburgite (Sample 304-U1309B-11R-2, 88–90 cm) (plane-polarized light; FOV = 5.3 cm). Vein is cut by chrysotile veins and zones of serpentine. G. Detail from F (cross-polarized light; FOV = 4.9 mm).
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