Basalt dikes in the 1886 Tarawera Rift

Abstract

Basalt intruded into Tarawera Rift during the 1886 eruption occupies an en echelon pattern of dike-filled eruptive fissures. The leftstepping pattern of dilation fractures is consistent with dextral/normal movement on an underlying, older, master fault which appears to have influenced location of the earlier rhyolite eruptive vents of Tarawera Volcanic Complex, and controlled the orientation of deep basaltic intrusions. Although the Tarawera Rift was previously regarded as a pure normal fault, the 1886 dike pattern provides further geological evidence for the occurrence of dextral shear in the Taupo Volcanic Zone.