TG6 has looked at the geology and ranked targets A and B ahead...

TG6 has looked at the geology and ranked targets A and B ahead of the larger C and D for a reason.

I haven't seen any past references to supergene effects for lithium in discussion threads. The Wiki references relate to copper which makes sense as a heavier metal. If I've understood correctly a supergene effect involves oxidised materials interacting with water tables to create a zone with elevated readings around or just below the water table level as oxidised material "falls" through the oxidised layer of material. This elevated level is then not reflective of the overall ore body once you get into fresh rock below it. If effects like erosion were to then remove this top layer of oxidised material, you could get near surface or at surface layer of over-representative grades. It would appear to be a key issue to watch out for re copper.

Lithium being the lightest metal and lighter than water would appear less likely to suffer from supergene effects. Weathering over millions of years has the potential to have the lithium release from its host rock and have lithium "float" upwards, rather than fall downwards through soils. Its common for weathered pegmatites to have lower lithium grades so that lithium has disappeared somewhere. I've never met references to it doing a "supergene" effect. I think what happens is if conditions are suitable for waterlogged soils and surface flooding then lithium will make it to the surface and "float" away. Lithium in soils grades are typically low at about 0.01% Li₂O. The grades only improve to the commercial zone of circa 1% when you get through heavily weathered material to lightly weathered or fresh rock. Lithium can shift easily as you have observed. If the lithium stayed in the area, even a modest sized weathered out pegmatite could create a large anomaly because if 10m of pegmatite were to release its lithium and became 1m of soils you have a 10:1 expansion. If you transition from 10,000ppm to 100ppm you have a 100:1 expansion potential. With a 1000:1 expansion potential a small weathered out lithium deposit could create a big anomaly. The billions of years since formation however have typically created conditions at least a few times that shift the lithium away so that a 100ppm anomaly does actually mean something.

You are correct that when talking about 0.01% Li₂O soils (100ppm), there is potential for this to come from either sub-commercial grades like <0.4% li₂O or from thin seams. There's been a heap of disappointments from lithium in soils anomalies in other locations and I think that is partly why the TG6 share price doesn't attribute much value yet to a large lithium in soils anomaly.