Figure 39

Experimentally deformed feldspar aggregates

Figure caption

Experimentally deformed feldspar aggregates

Starting material / cataclastic flow / regime 1

39

TA pre-faulted at low P and T, then shortened 30% at 900°C, 10-6/sec, and 1200 MPa; regime 1 dislocation creep localized along former fault.

TA pre-faulted at 300°C, 10-4/sec, 400 MPa and then taken to 900°C and 1200 MPa and shortened 30% at
10-6/sec. The high temperature deformation has been almost entirely partitioned into the pre-existing thin zone of finer grain size. The fine-grained zone was able to rapidly undergo complete dynamic recrystallization (by the low T grain boundary migration mechanism), and then was significantly weaker than the coarser-grained material on either side. This is one process by which ductile shear zones may form. The fine-grained albite within the shear zone has in a general sense undergone 'superplastic flow' but the process was not predominantly grain boundary sliding with diffusion creep, as inferred from the strong crystallographic preferred orientation and the high dislocation densities observed in TEM. (W485)

		Experimentally deformed feldspar aggregates
		Figure caption

	Experimentally deformed feldspar aggregates	Starting material / cataclastic flow / regime 1


39		TA pre-faulted at low P and T, then shortened 30% at 900°C, 10-6/sec, and 1200 MPa; regime 1 dislocation creep localized along former fault. TA pre-faulted at 300°C, 10-4/sec, 400 MPa and then taken to 900°C and 1200 MPa and shortened 30% at 10-6/sec. The high temperature deformation has been almost entirely partitioned into the pre-existing thin zone of finer grain size. The fine-grained zone was able to rapidly undergo complete dynamic recrystallization (by the low T grain boundary migration mechanism), and then was significantly weaker than the coarser-grained material on either side. This is one process by which ductile shear zones may form. The fine-grained albite within the shear zone has in a general sense undergone 'superplastic flow' but the process was not predominantly grain boundary sliding with diffusion creep, as inferred from the strong crystallographic preferred orientation and the high dislocation densities observed in TEM. (W485)