Musgrave Block

The Musgrave Block is primarily exposed through the actions of the Petermann Orogeny at c. 535-550 Ma, which exhumed the orogenic belt along the Woodroffe Thrust.

The landforms of the area are primarily composed of wide calcrete plains, often covered by Pleistocene Age aeolian deposits of sand dunes, sometimes reworked into ephemeral sheetwash fans.

The most illustrating way of considering the Musgrave Block is as part of a time-space plot in which geological events are arrayed in time against rock units, stratigraphic relationships and for correlative purposes.

There are also significant granite caldera complexes, of many hundred square kilometres in area, which intrude the Musgrave Block.

The caldera is in two parts, an overlying volcanic edifice composed primarily of porphyritic rhyolite and dacite with occasional vent complex agglomerates, which shows prominent circular ring-complex faults, and the Winburn Granite which underlies the caldera and is primarily exposed in the east as a pink, potassium-feldspathic porphyry granite, the lower margins of which are weakly tectonised.

The Skirmish Hill Caldera is poorly exposed along the southern margin of the Musgrave Block and consists of granite and overlying?

Several other prominent gravity and magnetic highs are arranged along the Mugrave Block strike line, one of which was drilled by BHP in the 1990s through 300m of Permian glacial sediments.

This caldera is composed of highly tectonised, stretched felsic volcanic rocks, interleaved with a significant thickness of equally sheared titaniferous differentiated mafic sills.