The structure of SW Cornwall and its bearing on the emplacement of the Lizard Complex

Six phases of deformation can be recognized in the Devonian metasediments to the N of the Lizard Complex. The first two phases (D₁ & D₂) show a variety of orientations and styles, but with a general N or NW vergence. These phases, while respresenting regional deformation events, are considerably modified by the emplacement of the Lizard Complex. There is a general increase in intensity of both D₁ and D₂ structures towards the Lizard boundary. This is accompanied by variation in the orientation of both early phases of deformation, leading to a variety of interference patterns. Domains of oblique F₁ folds, with axes trending N-S, are developed in the rocks immediately to the NE and NW of the Lizard, and are considered to have formed by differential, NNW-directed thrusting of slabs of the complex during the early regional deformation. D₂ produced discrete shear zones ahead and below the Lizard rocks and may have resulted from the gravitational collapse of the D₁ nappes. The D₃ deformation post-dates the Lizard emplacement, being related to the Cornubian batholith. Subsequent phases represent essentially post-batholith, and hence post-Lizard emplacement, deformation.