Widgiemooltha Komatiite

The Widgiemooltha Komatiite is a formation of komatiite in the Yilgarn Craton of Western Australia.

The stratigraphy of the Widgiemooltha Komatiite is well known to be part of the regional komatiite magmatic event also seen at the Kambalda Dome, 50 kilometres (31 mi) to the north. There are comparisons which place the Widgiemooltha Komatiite as equivalent to the Silver Lake Komatiite. The Mt Edwards Basalt is correlated regionally with the Devon Consuls Basalt of Kambalda, and the Widgeimooltha Chert correlated with the Paringa Slate.

The structure of the Widgiemooltha Dome has three thrusted repetitions of the basal komatiite contact and komatiite sequence including footwall Mt Edwards Basalt and hangingwall sediments (Widgiemooltha Chert).

The Widgiemooltha Komatiite is exposed around the margins of a large, 450 square kilometres (174 sq mi) granite dome. The Widgiemooltha Granite is a coarse to medium, holocrystalline equigranlar granite with subordinate biotite and ferromagnesian minerals. It is mildly deformed, and is considered to have intruded concurrently with doming and uplift during late deformation. It is intrusive into the thrust repeated stratigraphy of the Widgiemooltha Komatiite and its sequence.

The Lake Zot Dolerite is similar to the Defiance Dolerite and other regionally important subvolcanic doleritic sill complexes throughout the Yilgarn Craton. Within the Widgiemooltha Dome area, the Lake Zot Dolerite can attain greater than 300 metres (984 ft) thickness and is intrusive into the hangingwall basalt and Widgiemooltha Chert above the Widgiemooltha Komatiite.

The dolerite is coarse grained in the main, often equigranular and holocrystalline although porphyritic areas are known and chilled margins and occasional compositional variations are noted. It is often epidotised, carbonated and sodium metasomatised in proximity to major structures. It can often be reasonably strained throughout its bulk and especially in the footwall contact with the Widgiemooltha Komatiite.

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