Emplacement conditions of igneous dikes in Ethiopian Traps

Research areas:
Year:
2008
Authors:
Journal:
JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH
Volume:
178
Number:
4
Pages:
683-692
Month:
DEC 30
ISSN:
0377-0273
BibTex:
Abstract:
The emplacement conditions for 39 igneous dikes cutting basalts in
northwestern Ethiopia are evaluated by analyzing their
displacement-length scaling relations. Maximum opening displacements and
lengths of the A dikes demonstrate displacement-length scaling of the
form D(max)=0.088L(0.48), consistent with other populations of dikes and
veins and different than the power-law scaling relation typically found
for faults. The dikes propagated through the thin Trap basalt sequence
tinder conditions of constant fracture toughness, with values corrected
for three-dimensional dike geometry of -77-273 MPa m(1/2). The large
values of fracture toughness are likely associated with (1) the
toughening effects of near-tip damage, (2) mixed-mode dike propagation,
as shown by magma flow fabric analysis through anisotropy of magnetic
susceptibility (AMS) and image analysis of thin sections, and (3)
elevated temperature within the blocky and ductile basaltic host rock,
evidence of which has been found in the field. (C) 2008 Elsevier B.V.
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