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SUMMARY:Creeping gabbro: Mafic rock deformation from nature and experiment
 s - Amicia Lee (University of Tromso)
DTSTART:20211103T160000Z
DTEND:20211103T170000Z
UID:TALK161989@talks.cam.ac.uk
CONTACT:Sam Wimpenny
DESCRIPTION:Unaltered mafic rocks consist of mechanically strong minerals 
 (e.g. pyroxene\, plagioclase and garnet) that can be deformed by crystal p
 lastic mechanisms only at high temperatures (>800°C). Yet\, many mafic ro
 cks do show extensive deformation by non-brittle mechanisms when they have
  been subjected to lower temperature conditions. In such cases\, the defor
 mation typically is assisted by mineral reactions. In this seminar\, I wil
 l show results of microstructural and chemical analysis that indicate diss
 olution-precipitation creep (as a type of diffusion creep) plays a major r
 ole in deformation of gabbro lenses at upper amphibolite facies conditions
 . Synchronous deformation and mineral reactions of clinopyroxene suggest t
 hat mafic rocks can become mechanically weak during a general transformati
 on weakening process\, i.e. the interaction of mineral reaction and deform
 ation by diffusion creep. The weakening is directly connected to a fluid-a
 ssisted transformation process that facilitates diffusion creep deformatio
 n of strong minerals at far lower stresses and temperatures than dislocati
 on creep. Initially strong lithologies can become weak\, provided that rea
 ctions can proceed during deformation\; the transformation process itself 
 is an important weakening mechanism in mafic (and other) rocks\, facilitat
 ing deformation at low differential stresses and low stress exponents.
LOCATION:ONLINE - Details to be sent by email
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