Fault-zone weakening processes along the reactivated Outer Hebrides Fault Zone, Scotland

被引:83
作者
Imber, J [1 ]
Holdsworth, RE [1 ]
Butler, CA [1 ]
Lloyd, GE [1 ]
机构
[1] UNIV LEEDS,DEPT EARTH SCI,LEEDS LS2 9JT,W YORKSHIRE,ENGLAND
关键词
reactivation; phyllonites; fault zones; rheology;
D O I
10.1144/gsjgs.154.1.0105
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
The Outer Hebrides Fault Zone is a major reactivated structure cutting amphibolite-grade Lewisian basement gneisses in NW Scotland. During a regionally important phase of sinistral strike-slip movements, the influx of chemically active hydrous fluids along the fault zone was associated with the formation of a network of greenschist-facies phylionitic shear zones. Later ESE-directed extensional strain was preferentially focused into these pre-existing zones of weakness. The syn-tectonic alteration of a relatively strong, feldspar/hornblende-dominated load-bearing framework microstructure to an interconnected weak layer microstructure of fine-grained, strongly aligned phyllosilicate aggregates leads to the long-term weakening in the fault zone. Comparison with experimental data suggests that this produces a shallowing of the frictional-viscous creep ('brittie-ductile') transition and a substantial reduction in total crustal strength. Similar processes may account for the apparent weakness of many long-lived fault zones.
引用
收藏
页码:105 / 109
页数:5
相关论文
共 24 条
[2]   EVIDENCE FOR CALEDONIAN SINISTRAL STRIKE-SLIP MOTION AND ASSOCIATED FAULT ZONE WEAKENING, OUTER HEBRIDES FAULT ZONE, NW SCOTLAND [J].
BUTLER, CA ;
HOLDSWORTH, RE ;
STRACHAN, RA .
JOURNAL OF THE GEOLOGICAL SOCIETY, 1995, 152 :743-746
[3]  
BUTLER CA, 1995, THESIS U DURHAM
[4]   FRICTION, OVERPRESSURE AND FAULT NORMAL COMPRESSION [J].
BYERLEE, J .
GEOPHYSICAL RESEARCH LETTERS, 1990, 17 (12) :2109-2112
[5]   INTERNAL STRUCTURE AND WEAKENING MECHANISMS OF THE SAN-ANDREAS FAULT [J].
CHESTER, FM ;
EVANS, JP ;
BIEGEL, RL .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1993, 98 (B1) :771-786
[6]   STRAIN PATTERN IN THE AAR GRANITE (CENTRAL ALPS) - ORTHOGENESIS DEVELOPED BY BULK INHOMOGENEOUS FLATTENING [J].
CHOUKROUNE, P ;
GAPAIS, D .
JOURNAL OF STRUCTURAL GEOLOGY, 1983, 5 (3-4) :411-418
[7]   DEVELOPMENT OF PHYLLONITE FROM GRANODIORITE - MECHANISMS OF GRAIN-SIZE REDUCTION IN THE SANTA-ROSA MYLONITE ZONE, CALIFORNIA [J].
GOODWIN, LB ;
WENK, HR .
JOURNAL OF STRUCTURAL GEOLOGY, 1995, 17 (05) :689-&
[8]   THE SOLID-STATE FLOW OF POLYMINERALIC ROCKS [J].
HANDY, MR .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH AND PLANETS, 1990, 95 (B6) :8647-8661
[9]  
Hemley J.J., 1964, Econ. Geol, V59, P538, DOI [10.2113/gsecongeo.59.4.538, DOI 10.2113/GSECONGEO.59.4.538]
[10]   MICROSTRUCTURES AND C-AXIS FABRICS INDICATIVE OF QUARTZ DISSOLUTION IN SHEARED QUARTZITES AND PHYLLONITES [J].
HIPPERTT, JF .
TECTONOPHYSICS, 1994, 229 (3-4) :141-163