Hi Scobbydo,
Pretty sure the bedrock is the top weathered profile which is slightly softer than fresh rock but still considered bedrock!
I've read this announcement 3 times now and it seems pretty clear that they have gold mineralisation within the bedrock host rock which is indicated to be Saprolite.
This would explain why the aircore can get some penetration into the bedrock before it hits fresh rock and drill bit refusal.
"Saprolite is weathered bedrock which still retains the original lithic fabric. The nature of the saprolite is influenced by the type of rock from which it develops, and it determines the chemical and physical properties of the associated soils."
"Saprolite - Wikipedia
https://en.wikipedia.org › wiki › Saprolite
Saprolite is a chemically weathered rock. Saprolites form in the lower zones of soil profiles and represent deep weathering of the bedrock surface."
"Weathered bedrock Bedrock that is altered from its original state by chemical weathering processes (e.g. oxidation, hydrolysis).
I quote the following extracts from the announcement and highlight that they do make a distinction between the two with gold mineralisation in both.
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"The first traverse of deep angled holes (Line 5) was drilled across the A10 target. This encountered a broad zone of bedrock/cover interface gold mineralisation, bedrock gold mineralisation and bedrock hydrothermal alteration."
"These initial gold results are from 4m composite bedrock samples and single metre sediment/bedrock interface samples. They demonstrate that the drilling has intersected a 500m-wide zone of sediment/bedrock interface gold mineralisation overlying a 400m-wide zone of gold-mineralised bedrock alteration. This indicates that there is a significant gold mineralised system present at depth in the underlying bedrock"
"The bedrock/sediment interface gold mineralisation occurs within locally derived, extremely coarse grained, angular vein quartz gravels."
"The underlying gold-mineralised bedrock alteration zone occurs as intense chloritic and siliceous alteration, with variably developed quartz veins of up to 2m in width and traces of fresh pyrite and pyrrhotite."
"The drill holes were thus in sedimentary cover for most of their length, with only the final ten or so metres intersecting bedrock prior to blade bit refusal."
"Despite the minimal penetration into fresh bedrock and the lack of stratigraphic overlap, drilling successfully encountered alteration and gold mineralisation across the entire width of the target area."
"Figure 3: Line 5 cross section showing the notable depth of cover and the limited drilling coverage into bedrock. The bedrock presents visible variation in the chlorite alteration which is interpreted as being linked to the gold mineralisation. Importantly mineralisation is being intersected in bedrock as well as the covering sediments"
"Initial gold results have been received for the four-metre composite bedrock drill samples and single metre sediment/bedrock interface samples from Line 5. The results demonstrate that the drilling has intersected a 500m-wide zone of sediment/bedrock interface gold mineralisation, which overlies a 400m-wide zone of gold-mineralised bedrock alteration. It appears that there is a significant gold mineralised system present within the immediately underlying bedrock."
"Further drilling is also required to reach the mineralisation in the bedrock and define it"
"Each of the lines of shallow drilling also included one or two deep vertical holes, drilled to refusal at the centre of the interpreted target, to evaluate the depth of cover there and to collect geological information and bedrock gold assays at that point"
"One or more interface samples at the contact between the deep alluvial cover and saprolitic bedrock (one or more meters wide)."
", through the underlying paleo-alluvial sequence, and through the underlying bedrock to the end of the hole. These composite samples have been analysed for gold by fire assay, to identify broad zones of gold mineralisation in the drill holes"
"The host rock to the gold mineralisation is a Polymictic conglomerate
There is widespread gold in the altered bedrock and at the base of the overlying cover
Elevated bedrock gold values occur across an east-west width of at least 400m
The gold in the base of the overlying cover sequence occurs across an east-west width of 500m
It immediately overlies the zone of elevated bedrock gold values and intense alteration"
"Additional aircore drilling to map the extent of bedrock alteration and gold mineralisation
Diamond core drilling to determine the structural controls and configuration of the bedrock gold mineralisation so that it can be effectively explored along strike and at depth"
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Cheers
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- Ann: Significant Gold Discovery Under Lake Goongarrie
Ann: Significant Gold Discovery Under Lake Goongarrie, page-97
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