Form, mechanism, and control of dolerite intrusion near Hobart, Tasmania

Abstract

The Jurassic dolerites around Hobart were probably emplaced during four or five injection periods. Each period has produced a series of interlinked stepped sheets with the overall form of an axially flattened cone. Feeders were dyke‐like, although some were pipes or wedges from dykes. Dislocation by fracturing was followed by hydrostatic intrusion. Controls were imposed on the intrusion by roof load, magma pressure, and barrier formations. Early injections are believed to have been intruded low in the rock column, later ones at high levels.