Figure F60. Two-stage evolutionary tectonic model for the postmagmatic brittle structures observed in the dolerite intrusion (Section 180-1109D-47R-2). 1. Diagram illustrating the crosscutting relationships between successive generations of filled veins emplaced under horizontal tensile conditions (split core surface); V₂, V₃ = young master vertical veins (cristobalite, smectite, and chlorite) at right angles to ₃; V₁ = early shallow greigite-filled veins. Note evidence for horizontal shearing (S) along shallow V₂-type veins that also act as transfer structures (T) for earlier V₁ veinlets. Overlapping zone (O) between two greigite-filled veinlets. 2. Geometry of later extensional faulting as deduced from Figure F59 A and B. Note that the two successive events (emplacement of veins and faulting) are both consistent with almost horizontal extension. Symbols: = downward motion; = upward motion.