11:00 AM - 11:15 AM
[SCG49-13] Petrophysical characteristics of serpentinized peridotites of Hole BA1B, BA3A and BA4A
Keywords:Oman Drilling Project, Peridotite, Crystal plastic fabric
Harzburgites in BA1B show variously deformed textures ranging from pophyroclastic to protomylonitic textures in dependent on the depth. In BA3A, harzburgites with protogranular texture were observed in relatively shallow sections (10-90 m), whereas porphyroclastic to strongly foliated textures were dominant in deeper sections. Most of hartzburgites in BA4A show porphyroclastic texture, partly clear foliation and protomylonitic textures by strongly elongated orthopyroxene grains. Dip angles of measured foliations in BA1B are mostly 0-20°, which are nearly horizontal. Most of dip angles in BA3A are at around 30°, up to 50°. In BA4A, dip angles of orthopyroxene grains take various values between 10-50°. In BA3A and BA4A show similar dip angles, but significantly steeper than those in BA1B. In each hole, dip angles were nearly constant independent on the depth.
Pyroxene and spinel grains in strongly foliated to protomylonitic peridotites are intensely elongated and aligned, exhibiting clear foliation at thin section scale. In protogranular peridotites, pyroxene and spinel grains have rounded shapes and are not elongated and aligned, and foliations are unclear. Elongated pyroxene and olivine grains in protomylonitic peridotites show kink bands and wavy extinction, whereas few rounded pyroxene grains in protogranular peridotites show these features.