Some more data on Araxa to show why it is in a class of its own and give some context to Luni etc.
. In 2020, CBMM estimated the remaining Nb resource in the regolithic ore at 896 Mt, i.e., 1.49% Nb2O5. In 2017, the estimated resources of the other mineralization were 770 Mt containing 10.4% P2O5, 768 Mt having 20.1% BaSO4, and 352 Mt containing 5.6% REOs. Magnetite and barite are byproducts of pyrochlore and fluorapatite ore processing. BRAGA BIONDI 2023.
If the SG averaged 2.0 [1.82 for Sap, 2.5 for fresh in one paper, with laterite in between) and the ore is 50m thick the surface area would be a "square" with sides of 3Kms each. Obviously too simplistic a view but does put numbers like these into some context. At 100m thickness a rectangle of 3 x 1.5 Km would be the result at an SG of 2 = to the entire "whale" at Luni. These "dimensions" show the Tier 1 size and class of CBMM's Araxa.
Luni is in early exploration stage with hints that Nb grades in excess of 1% are present over an EW extent of some 3 Kms,, NS of perhaps 0.5 Km and thicknesses of 20-100m at bulk grades of 1+% [size and grade will be clarified with further assay results, a maiden MRE and more drilling into the future]. Smaller than CBMM's Araxa at this stage but likely to be number 2 in size.
This is 'only' the regolithic ore for CBMM with no categorising by JORC etc., and whether it is open or not. There are other land owners within the Araxa (formerly Barreiro) complex who have resources of Nb (+- REE/P205) albeit at lesser tonnages (E.G. Catalao 1 & 2 deposits/mines) so Nb REGOLITHIC resource is probably higher.
Finding useful data about 'Araxa' has been a bit like finding a needle in a haystack. If anything WA1/ENR/DRE/KFM's recent carbonatite exploration is a breeze by comparison. The "Araxa" data is out there but tucked away in company files and studies requiring payment for the most part. I did ante up for what turned out to be
an excellent report. Many of the figures are available in the
images associated with this google search [hope link works].
Images are available in the link above and come from the paper I acquired.
I have highlighted the collars for 6 holes (A-F) with grade histograms plus the location of the section on the Itafos deposit (Catalao1?).
Focusing in on sections A and B
I do not know how representative these holes are. Distinct differences between A and B and some of the others.
Some observations
- Nb extends to depth in 'fresh rock' albeit at a generally lower tenor than the Regolith and Saprolite zones.
- Regolith/Sap grades are higher in A than B. Coincidence or reflecting higher primary grades?
- host lithology appears to play a factor in Nb grades.
- Bulk Nb grades around the 1% level are likely to >500m below surface and possibly 1Km+
- other profiles (C-F) show the variation of Nb grades spatially and lithologically.
- While still early in exploration, the higher grade Nb in the weathered profile and the 'bouncy' Nb grades in the limited reported fresh rock drilling look like a pattern is emerging for Luni.
Itafos/Catalao1 was mined as a regolithic Nb deposit at a smaller scale than CBMMs. See image above for location.
Cordeiro etal 2011 Show mineralisation extending to depth. (Exactly what type is not totally clear - Mix of phosphate and Nb? + REEs.
Depth extensions - again. Grades not mentioned? Suspect less than regolith/saprolite.
Block model from different paper....
Higher grades near surface. Patchy at depth. REE and Phosphate also available for this area.
2008 table of deposits
Tapira is south of Araxa as a separate intrusive.
Moving further afield in Brazil there are distinct zones of carbonatite and alkaline complexes.
Such regional potential could auger well for additional discoveries in the West Arunta. How this would fit into an ?already tight market.....????
Zooming back in on CBMM's Araxa the geological history is complex with multiple intrusive and hydrothermal events over a c20 Million year period. Such complexity is probably one reason for the size and grade of the deposit though exploration and research would not happen without the economics. Chicken and egg?
[Age Araxa c80 Ma, Mt Weld c2100 Ma, Luni ??1580Mya. Processes and mineralisation show some surprising similarities even though there is such a disparity of ages. REE/Nb/Phosphate are common to all. Even DRE's carbonatite drilling shows variants of this. Could go on but that's another line of thought on an already long and complex post.]
Less than 2 years into exploring Luni so data are not readily available outside of the company regarding any complexities in the carbonatite intrusion. Variation in grades, and to a lesser extent, depths of weathering suggest there will be a combination of different lithologies and or structural controls. Too early to say much more other than the observation that Araxa, Mt Weld, and Phalabora show multiple lithologies and variation in grades across intrusives of significant dimensions.
(20min delay)