Abstract

Previous analyses of lineament orientation patterns in Alaska have been concerned with regions underlain by relatively undeformed or weakly deformed sedimentary rocks, or by batholiths. An analysis of lineament directions in southeastern Alaska was undertaken in an effort to extend the information on lineament patterns into a more intensely deformed terrain. The region investigated contains steeply tilted and partly metamorphosed Mesozoic and younger eugeosynclinal rocks and Mesozoic and Tertiary granitic plutons. Deformation apparently occurred as a consequence of eastward Mesozoic and Tertiary sea-floor spreading that piled the marine sediments against the unyielding craton to the east. Lineaments may be due in part to sedimentary bedding, metamorphic foliation, or dikes, but evidence indicates that most of them are major faults. Lineaments in the region comprise three major sets with much weaker complementary sets. Dominant is a northwest-trending set that parallels the structural grain of the region. A strong north-south trending set and a weaker north-northwest trending set are oblique to the structural grain. Ore deposits in the region occur in areas of relative structural complexity where oblique structures interrupt the northwest trend.