Abstract

In the Andes, major lineaments controlled sedimentation, vulcanicity, batholithic intrusions and mineralisation throughout the Mesozoic and Cenozoic. These lineaments represent major fault lines in an ancient crystalline basement. The magmas of the Coastal Batholith were emplaced along one such lineament and the emplacement of the individual plutons was closely controlled by transcurrent faults and by smaller scale joint patterns. Such structures were continuously exploited throughout the long emplacement history of the batholith. Exceptionally, plutons were forcefully emplaced along early lineaments and lifted roof blocks along shear zones coincident with pre-existing faults. More generally subsidence of large fracture-bound crustal blocks provided the space for the emplacement of magma in bell-jar and cauldron-subsidence structures while stoping along the regular, closely spaced joints resulted in a rectilinear pattern of contacts at outcrop scale.

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