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I appreciated your post OFX and found it very helpful. I did...

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aubin

590 Posts.

702

03/09/22

12:07

Post #: 63500321
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Originally posted by UFX: ↑

Thanks oldgeo and aubin for your posts. Nothing like good schematics from both to get the grey mater thinking. This is just my opinion without at all checking past geological interpretations of the area.

Archean geology is often complex as is in this case. So far the story is that we start off with mafic and ultramafic suites, ie the basement basalt and the komatiite lava flows. The difference between the 2 are interpreted origins and chemistry but they can be relatively close. The komatiite interpreted to come from a deeper source. Interestingly enough given slower cooling at depth the basalt chemistry forms Pyroxenites and komatiites Peridotites. There lies a great relationship with these units but the complexity is in the environments in which these rock types form.

Then we have the black shales and cherts which are of sedimentary origin seeming deposited onto of mafic and ultramafic intrusives. An interpretation of that is uplift, erosion of lithologies above the the ultramafic intrusives, into to a watery environment and deposition of carbonaceous silicates hence the dark shales and chert. Then we have extrusives that have slowly cooled or metamorphized above to form the pyroxenites and peridotites at a later date.

At this stage the really complex part is the relationship between the metals, hydrothermal flows and the geological units. The underlying chemistry of the melts, often the deeper sourced komatiites- peridotites are sometimes endowed with Ni, Pd, Pt, and Cu. They can accumulate into the lowest sections of thick slow cooling ultra mafic and mafic units for example the bushveld igneous complex. These can form distinct bands of metal accumilation like the Merensky reef which is cms thick rich in Pt and other goodies. I don't think we have this although accumilation of Ni, Pt Pd to the lower sections of the cooling body has most likely occurred.

The hydothermal movements have mixed the metal mineralisation. The evidence of this is the accumilation of pentlandite and Chalcopyrite into the carbonaceous shales. Some talk is about feeder zones and no doubt there will be one or many. Hydrothermal fluids have either scavenged metals from existing units or have originally been enriched from a deeper source. It is obvious that these fluids have precipitated out a considerable load of Ni and Cu into the shale units. This is not uncommon.

So the events IMO in summary. Very fluid lava flows building to considerable thickness. An intrusive sill or sills forming and allowed to cool slowly and perhaps precipitation of Ni, and platinoids. Uplift, erosion, deposition, more volcanism in extrusives and intrusives forming. Pulses of hydrothermal fluids during those events and precipitation of metals mainly in the sedimentary units . Some tilting at some stages and finally erosion to the levels we have today.

The key IMO with what we know is the dark shale unit. It has to be reached with every drill hole and perhaps 30m deeper. I don't think it was reached in hole 1. Happy to be corrected and I'm sure this story will probably change after more information unfolds.

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I appreciated your post OFX and found it very helpful. I did some geology at varsity a long time ago but am very much a novice and your post was at the right level for me to understand.

GSR Price at posting: 6.7¢ Sentiment: Buy Disclosure: Held
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