Depsotinal environment for 421 zone
appears to be fluid flow between the western limb of the clastic tuff antiform and the fault shown in figures 2 to 5. Notice that the fault is not shown in Figure 6. I think that a borehole drilled above 440 will show more mineralization. Hopefully those results will be coming out soon.
Also note that the alteration vertical section shown in Figure 7 is not the discrete cross-section at the eastern edge of the mineralization as shown on Figure 1, but is a composite of the 50 m wide alteration zone. Otherwise, the mineralisation pierce point for 440 should be right beside 442, based on the cross-section shown in Figure 6. That would show a very quick "pinching out" of the zone to the north. Instead, they appear to have placed the pierce point midway between the two mineralized intervals. I guess that's okay since they are describing it as an oblong ovoid or something, but it took me a while to see through what they did there.
My main takeaway is that the 421 zone has added confirmation to the model that the clastic tuff antiform is the controlling depositional feature for stardust. You can see this from analyzing the cross-sections in this zone and also by looking at the orientation of the mineralization zones outlined in Figure 1.
My thesis for continued investment is that even if they have come near the northern boundary of the 421 zone, all SUNM has to do is continue following the inclination of the clastic tuff antiform to find another zone where the fluids permeated into the surrounding limestone. In the meantime, they can also continue infill drilling to prove up an economic deposit at 421.