Control of strike-slip fault on dyke emplacement and morphology
By J. B. Spacapan, O. Galland, H. A. Leanza & S. Planke.
(a) Field photograph of Dyke 1 along an irregular fault zone (F1). Arrow shows the location of the fault plane with striation (C). (b) Interpreted drawing of the field photograph (a). Different grey shades of the layers are for clarity of the figure. Bold lines show measured strike-slip fault planes offsetting sedimentary layers. The dark grey Dyke 1 has a complex shape with several c. 1 m offshoots. (c) Detail of horizontal striations showing the relative displacement of the fault plane shown in (a). (d) Stereographic projection of measured fault planes (black lines) and dyke walls (grey).
Strike-slip faults are commonly assumed to influence magma transport and emplacement in the Earth’s crust. However, direct observations of magma conduits within strike-slip faults are lacking. Here we provide some of the first detailed field observations of dykes emplaced within strike-slip faults in the Neuquén Basin, Argentina. We show how fault planes within strike-slip fault zones affect the emplacement of dyke offshoots, resulting in complex dyke morphology. Our study also emphasizes the importance of pre-existing strike-slip fault array on the development of dyke swarms, showing that orientations of dyke swarms may not systematically relate to the principal tectonic stress axes.