Comparing Perce and Luni, page-32

What age is the carbonatite at Luni/Emily/Crean etc?
Until good age dating is reported there are only some relative ages available.

The question is important as exploration will be constrained by where lithologies of such age can exist.

I pose the question because I was surprised to find that some 15 years of exploration by CGR and JV partners has been testing a field with some 300 magnetic targets. Some 70 kimberlite plugs/dykes found so far with more tests needed as only a small number of economic pipes are the norm in any field. Matter of luck to drill a good one, or more, early.
No micro diamonds in aircore/RC chips reported to date, but micro diamonds in surface soil sampling keeps them hopeful.




The "acne" spots on this first vertical derivative airmag image are the magnetic targets being tested for kimberlite and other magnetic features. The complex magnetics on the southern margin are older basement (>=1500 Mya), while the kimberlite plugs punch through rocks of the Amadeus Basin lithologies (<1000 Mya). CGR give the kimberlites a post Permian age (<250 Mya) which makes them very young, if correct.

Kimberlite pipes 2013 - an early example (haven't found a compilation of all pipes reported to date)


Going into this in detail is beyond the scope of a HC post.

Recent EIS drilling by CGR has also intersected mafic, and ultramafic lithologies (A138658) that intrude the Amadeus Basin lithologies which makes this igneous activity somewhat younger than the host rocks (c800-1000 My??). How much younger is yet to be established.
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Carbonatites, lamprophyres and kimberlites are sourced from deep in the mantle.

To date the carbonatites appear to intrude mid proterozoic age rocks but their age is not known. Dating at ENR's hole 1 is probably contemporaneous with carbonatite, but it was a dating of granitic intrusives and associated alteration that may not be the same.

The kimberlites CGR have drilled add a wrinkle that may be significant by being very young (apparently). If the carbonatites tapped the same source then they too could be "young" which opens nearology to the entire West Arunta.

LYN magnetics bear some similarities to CGR's though ga**broic and dioritic intrusives may explain some if not all the magnetics.

Other than the mantle sourcing there is no need for the carbonatites to be related to the kimberlites.
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However, there are these image from Araxa and surrounds.

Around Araxa and Tapira are distinctive small magnetic highs with some being kimberlite.
Araxa is c90 Mya with a scattering of kimberlitic pipes around it (?age for latter).


[Kamafugite intrusions??? New to me as one of many odd ball lithologies not regularly encountered outside certain geological fields.]

Rough correlation of K locations above with magnetics.


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