Jimberlana Intrusion, Norseman, Dundas Shire, Western Australia, Australiai

Regional Level Types
Jimberlana Intrusion	Intrusion
Norseman	Town
Dundas Shire	Shire
Western Australia	State
Australia	Country

Located near Norseman.
Bronzite cumulate and plagioclase-augite-hypersthene cumulate.


This entry is refering to a large funnel class dyke, which runs east-west from just east of Norseman to almost the wheatbelt, at 180 kilometres long and 2.5 kilometres wide. The merits of the many types of dykes get geologists excited and un-controllable. Unfortunately the space provided here does not allow us to go into that amount of detail about dykes.

Dykes or intrusions are a body of igneous rock created under intense heat, like being crystallised from molten magma. The Jimberlana Intrusion is viewed as being similar to the Great Dyke of Zimbabwe. It is classed as a funnel dyke which means it is an elongated outcrop with a V shaped cross-section, that narrows as you go downwards. Virtually all of the world's funnel dykes are very large.

The Jimberlana Intrusion shows eight canoe-shaped complexes along its length, and can be divided into three layers vertically. These are:
1. Lower Layer- which is the thickest, composed of repeated sequences of cyclic bronzite and olivine layers, overlain by thick plagioclase-augite-hypersthene layer.
2. Upper Layer- is viewed as recording a fresh injection of magma, and is similar to the lower layer, except the layering is smaller.
3. Marginal Layer- is the lowest part, and shows higher temperature mineral layers, overlying lower temperature mineral layers.

The intrusion is the type locality for loveringite, a rare metalic oxide mineral of the crichtonite group. It was discovered in 1978, and forms in the late stage of the residual melt of mafic layered intrusions.

Even by microscope, loveringite is difficult to detect, which is probably why no specimens have been seen for collectors. Annoyingly the reference does not mention the location along the dyke it obtained the samples it studied.

The species is most abundant in the bronzite cumulate, and trace amounts in the lower half of the plagioclase-augite-hypersthene cumulate. Loveringite from the bronzite cumulate shows a higher Cr content than the second unit mentioned. It occurs as isolated anhedral grains, and occasionally needles, closely associated with quartz-K feldspar intergrowths and phlogopite. It is a Ti-Fe and Cr oxide with several other minor elements including Ca, Zr, Mg, Ln, U, Th, V, and Ni.

The Jimberlana Intrusion contains two nickel mines : Maggie Hayes and Emily Ann. They are both 150 kilometres west of Norseman. Dodecahedral pyrite crystals to 20 cms are described from the mine. No specimens from the mines, or the intrusion have been seen on the market so far.

Other Regions, Features and Areas containing this locality

References