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Fig. 32 | Progress in Earth and Planetary Science

Fig. 32

From: The Atlantis Bank Gabbro Massif, Southwest Indian Ridge

Fig. 32

Selected samples collected from the eastern Atlantis Bank high-angle normal fault face at 57° 21′ E (Fig. 29): a Coarse-grained spinel-bearing troctolite with Mg# 88–90 augite. Approximately 50% of the olivine is replaced by actinolite and chlorite, and the rest by bright orange clay. b Amphibolite facies olivine gabbro with near 100% replacement of mafic minerals by undeformed black hornblende. c Porphyroclastic oxide-rich gabbro in an oxide-rich shear zone crosscutting a foliated troctolitic gabbro. Foliation traced by thin black lines whereas the contact is traced by the long-dashed white line. There is a ~ 2 cm-wide amphibole-albite alteration halo in the troctolitic gabbro around a crosscutting millimeter-thick black amphibole vein offsetting the foliation by ~ 1–2 mm. The olivine gabbro augite is the light gray to silvery mineral whereas the olivine is oxidized to orange clay. d Cataclasite consisting of angular fragments of gabbro amphibolite gneiss, with clasts ranging from protomylonite to mylonite, outlined by dashed white lines, in an undeformed recrystallized matrix of fine- to medium-grained amphibole and plagioclase replacing gabbro cataclasite from near the foot of the eastern, high-angle, normal fault face

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