Share
10,573 Posts.
lightbulb Created with Sketch. 2804
clock Created with Sketch.
28/02/18
22:36
Share
Originally posted by Bigsky
↑
There needs to be more definition around exactly what the CSIRO program is and how it is funded. The One Big Hole (OBH) is unlikely to produce much information around the Wits 2 play. I predict the cong gold will be discovered at depth in this hole, as CRA have already demonstrated. The Pilbara Basin is after all an Archaean sedimentary basin, and this is geology not rocket science.
The holy grail of this is to locate the source of the watermelon seed nuggets. What is known is that they are widely distributed across the northern margin of the Basin, with finds from Comet Well/Purdys to Marble Bar and plenty of places between. Nuggets are in cong with the richest grades below the MRB with lower grades retransported (IMO) in the Hardey Fm.
Opinion (read QH) has the nuggets transported by water (but maybe deposited/accreted from acidic solution by microbial mats that oxygenated the water and precipitated out the gold, or perhaps actively precipitated gold using oxidation/reduction reactions).
IF these ideas hold it seems to me there may be a couple of scenarios to play out. If the gold was in acidic solution then it actually doesn't need a geological source. The primeval soup may just have been rich in the stuff and the Wits 2 holy grail source rock does not exist. There may however be potential to locate the source microbial beds which would be perhaps richer in grade.
If the alluvial concentration theory holds, then perhaps the gold source was from the microbial beds or erosion of sediments interbedded with extensive volcanics prior to 3bn yrs ago, and there may be gold rich volcanic/hydrothermal deposits sitting in the Archaean basement rocks under the basal MRB eg Honeyeater basalts? In this event perhaps finding the direction of transport for nuggets at Loudens, CW/Purdys, Egina, Wodgina, Marble Bar etc, and looking at likely basement rocks updip may be a way to go. Testing this theory would require detective work on site to delineate possible transport directions then I reckon a look at existing mines and prospects located updip in the Pilbara basement rocks for some clues to potential source rocks and drill these on tenement to see if the lucky dip pays off. This would require multiple holes across a number of tenements and not simply OBH.
This is an expensive undertaking and IMO not justified for ARV. Its like sampling oceanic trenches, lots of new scientific interest to CSIRO boffins but of questionable value to a mining going concern.
My view is that OBH is an expensive way to determine known Pilbara stratigraphy and repeat the work done by CRA but does not add to shareholder value. Locating and drilling targets on tenure to mine-able depths and sorting grades and extents of existing prospects should be the focus.
When SH have ridden this beast up to over 50c and back down again, the OBH does nothing to instill confidence. Get back to basics and execute them well ARV.
Cheers
BS
Expand
Great to have you posting here again mate - your detailed knowledge of the ground and the geology is unmatched. Please other readers, read carefully this blokes work.
The deep hole has nothing to do with day to day ARV programs - anything that we mine for maybe 10 years will be near surface, as is nearly all the minerals that come out of WA. But over time that will change. The deeper endowments will beckon.
IMO DL understands that, and this deep hole is a move to position ARV with invaluable knowledge for the long term. His thinking is a bit like the thinking BHP had when they searched for the lode on the west side of the mountain at Broken Hill, or that Rio Tinto had when they figured a way to mine at Rio Tinto in Southern Spain.
Last edited by
JandJ :
28/02/18