Delineation of core logging and assay results indicate that the orebody remains open in all directions with increasing thickness at depth highlighting a substantial resource increase. Pedra is the AVB’s second and LARGER copper development target....[clue]... Drilling is on schedule for a Pedra resource upgrade during 3rd Qtr where the current Pedra JORC Resource stands at 192,000t of Cu and 218,000oz of Au. Logging of drill core suggests the potential for significant growth....[clue]...Both ore zones remain open on depth/strike and where drilling is planned for the as yet “untested” central area, between the existing resources....[clue]
AVB believes results from the Eastern and Western Zones are as good as or better, than (historical Xstrata) holes up dip and on section...[clue]...Results from APBD-12-01, APBCD-12-03, APBCD-12-06 are definitively proving this. Interpretation of orebody geometry is reliable with 6 of the 7 holes drilled to date intersecting the continuation of mineralisation at depth where the two are drilling in mineralisation in APBD-12-07 and APBCD-12-11, with the latter hole having returned a 54m intersection of mineralisation1 supporting the interpretation that Pedra improves at depth with the deepest hole (APBD-12-12, 506.5m), collared down plunge and along strike on the Eastern zone intersected 28m averaging 3% Chalcopyrite. A new hole has commenced 120m down plunge...
These results provide compelling evidence toward increasing AVB’s resource base to +600,000t of contained copper [APBCD-12-07=Western Zone and APBCD-12-12=Eastern Zone]...Results have been received from the first holes at the Eastern and Western zones at Pedra. The Company believes these holes are comparable to or better than their corresponding holes up dip. As drilling now focuses on the deeper extensions of both zones, mineralisation appears to look better at depth. Results to date from, APBD-12-01, APBCD-12-03, APBCD-12-05, APBCD-12-06 prove this assessment. To date seven holes have been completed of which six have intersected the continuation of the Eastern or Western ore zones at depth. Three holes are in progress, two of which are currently in mineralised zones, as predicted by the new geology model. In the Eastern zone hole APBCD-12-11 has been collared below existing drilling, intersecting a 54m wide mineralised zone averaging 4% Chalcopyrite...
Interpreting this recent Pedro Announcement...
A key to understanding the significance of these acquisitions and IMO the consequent share purchase by the main directors at AVB is found in the 2012 Investor Presentation being, “...Pedro Branca is on one of the main Carajas geological trends, mineralogy similar to neighbouring world class deposits [i.e. Sossego]...with the Western Area with large open pit potential and the Eastern Area having Sub Vertical and higher Grade...” Pedro Branca and Sossego [355mt] being only 20km apart are found geographically south of the MAJOR Carajas Fault...I keep incorrectly discussing Pedro Branca’s epi-genesis as epithermal with a paragenetic hydro thermal primary oxidised region...After researching the regional geology myself...I think I understand why I made this mistake...
Exploring Major IOCG style deposites that are temporally associated with oxidized, potassic granitoids similar to those linked to major porphyry Cu–Au deposits. Evidence indicates fluids and ore components were likely sourced from magmatic intrusions. IOCG deposits form over a range of crustal levels because CO2-rich fluids separate from the magmas at higher pressures than in CO2-poor systems, thereby, promoting partitioning of H2O, Cl and metals to the fluid phase...At deep levels, the magma–fluid system cannot generate sufficient mechanical energy to fracture the host rocks as in porphyry systems and the IOCG deposits therefore form in a variety of fault-related structural traps where the magmatic fluids may mix with other fluids to promote ore formation. At shallow levels, the IOCG deposits form breccias and fracture-hosted mineralization styles similar to the hydrothermal intrusive breccias and sulphide vein systems that characterize many porphyry Cu–Au deposits...
The fluids associated with IOCG deposits are typically H2O–CO2–salt fluids that evolve by un-mixing of the carbonic phase and by mixing with fluids from other sources. In contrast, fluids in porphyry systems typically evolve by boiling of moderate salinity fluid to produce high salinity brine and a vapor phase commonly with input of externally derived fluids. These different fluid compositions and mechanisms of evolution lead to different alteration types and para geneses IOCG deposits. IOCG deposits typically evolve through sodic(–calcic), potassic and carbonate-rich stages, and at deeper levels, generally lack sericitic and argillic alteration. The common association of porphyry and IOCG Cu–Au deposits with potassic, oxidized intermediate to felsic granitoids, together with their contrasting fluid compositions, alteration styles and para-geneses suggest that they should be considered as part of the broad family of intrusion-related systems but that they are typically not directly related to each other... [sourced from Richard H. Sillitoe, 2002]
Now abbreviated from... “The Iron Oxide Copper-Gold Deposits of the Carajás Mineral Province, Brazil: An Updated and Critical Review”... by Roberto Perez Xavier, Lena Virgínia Soares Monteiro, Carlos Roberto de Souza Filho, Ignacio Torresi, Emerson de Resende Carvalho, André Luiz Silva Pestilho, Carolina Penteado N. Moreto, Instituto de Geociências, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil and Ana Maria Dreher, CPRM, Serviço Geológico do Brasil, Rio de Janeiro, RJ, Brazil. The Carajás Mineral Province, northern Brazil, represents an Archaean cratonic block that contains the world's largest concentration of large-tonnage IOCG deposits (e.g. Sossego, Salobo, Igarapé Bahia/Alemão, Cristalino, Alvo 118, Igarapé Cinzento/Alvo GT46). These deposits are hosted by 276 million year metavolcano-sedimentary units, 270 million gabbro/diorite, granitoids, and porphyry dykes within brittle-ductile and ductile shear zones. Geochronological data suggest that formation of the Carajás IOCG deposits may possibly be linked to three metallogenic events: 276 to 180million years old.... Carajás IOCG deposits display a hydrothermal alteration sequence characterised by early sodic and sodic-calcic assemblages, followed by potassic alteration, magnetite-(apatite) formation, chloritisation, copper-gold mineralisation and hydrolytic alteration. Silicification and carbonatisation are important in deposits formed in brittle-ductile conditions [eg....Sossego and Alvo 118). Extensive zones of scapolitisation (>20km2) represent sodic alteration around IOCG deposits (e.g., Sossego), reflecting high salinity and activity gradients in Cl in the early regional hydrothermal fluids...
Metal leaching from the host rocks was probably enhanced by the high salinity of fluids, driven by heat from the intrusive episodes recorded in the CarajásMineral Province. As a consequence, geochemical ore signatures defined by the Fe-Cu-Au-REE-(U-Y-Ni-Co-Pd-Sn-Bi-Pb-Ag-Te) association is variably developed in the Carajás IOCG deposits, and strongly dependent upon the chemistry of the leached host rocks...
Fluid inclusions in ore-related minerals point to a fluid regime in which hot brine (>30 wt% NaCl equiv.) solutions, represented by salt-bearing aqueous inclusions, were progressively cooled and diluted by lower temperature, low-salinity (<10 wt% NaCl equiv. aqueous fluids. This mixing process was likely responsible for a trend of salinity and temperature decrease (>550 to <300°C), accompanied by an O2 increase towards the mineralisation stages. This process tends to favour the predominance of hematite-bornite in more oxidised deposits (e.g., Alvo 118) over magnetite-chalcopyrite (e.g., Sossego)...
Extensive fluid-rock interactions, possibly involving basinal/evaporite and magmatic fluid components, result in 18O-enriched fluids typical of most Carajás IOCG deposits. In addition, calculated fluid isotopic compositions for shallow-emplaced deposits, such Sossego and Alvo 118 also reinforce the importance of the significant, structurally-controlled influx of meteoric fluids for ore deposition related to high fluid pressure release and brecciation. Chlorine and boron, combined with Cl/Br - Na/Cl systematic strongly suggest that fluid regimes responsible for the formation of the Carajás IOCG deposits involved a significant contribution from residual evaporative fluids (e.g. fluids generated by seawater evaporation) that may have mixed with magma-derived brines...
Now for the IMO interesting regional geological correlation between Sossego only 20km away and AVB’s Pedro and further clues to recent AVB director interest...
At SOSSEGO IOCG deposit..located approximately 80 km SE of Igarapé Bahia and Alemao, and 40 km west of_Cristalino and only 20 km from Pedro... Mineralisation is hosted along a regional WNW¬ESE-striking shear zone that defines the contact between the meta-volcano¬ sedimentary rocks of the ~276 million yr Itacaiúnas Supergroup and tonalitic to trondhjemitic gneisses and magmatites of the 280 million yr Xingu Complex...The deposit is hosted by granite, granophyric granite, gabbro and felsic metavolcanic rocks representing both suites. The ore is located in two adjacent centres, Sossego Hill (the Sossego Curral zones) and the larger Sequeirinho [The Pista Sequeirinho Baiano zones] which has a length of 1.6 km and thickness of 150 to 200 m in its central section. These two centres are separated by a major high angle fault....The Sequeirinho orebodies have been subjected to regional sodic and hematite alteration, overprinted by sodic calcic alteration accompanying with the formation of massive magnetite [apatite] bodies...Both alteration assemblages exhibit ductile to brittle-ductile fabrics and are cut by spatially restricted zones of potassic (biotite and potassium feldspar) alteration that grades outward to chlorite-rich assemblages...(Monteiro, et al., 2007)...
The Sossego Hill orebodies display only weakly developed early albitic and very poor subsequent calcic sodic alteration, although they have well-developed potassic alteration assemblages that were formed during brittle deformation that produced breccia bodies. The matrix of the breccias commonly displays coarse mineral infill suggestive of growth into open space...The sulphides of both groups of orebodies were initially accompanied by potassic alteration and a subsequent more important assemblage of calcite, quartz, epidote,chlorite...In the Sequeirinho orebodies, sulphides range from undeformed to deformed, while at the Sossego Hill orebodies they are undeformed...Very late stage, weakly mineralised hydrolytic alteration is present in the Sossego Hill orebodies...The dominant sulphides are chalcopyrite with subsidiary siegenite and millerite, and minor pyrrhotite and pyrite in the Sequerinho orebodies, although pyrite is relatively abundant in the Sossego-Hill-bodies...In early 2001 the total resource was quoted as 355 Mt @ 1.1% Cu, 0.28 g/t Au, encompassing a mineable reserve of 219 Mt @ 1.24% Cu, 0.33 g/t Au at a 0.4% Cu cut-off and stripping ratio of 3.3:1 waste:ore. [Also abbreviated from Porter, T.M. (ed.), 2010 - Hydrothermal Iron Oxide Copper-Gold & Related Deposits: A Global Perspective, volume 3, Advances in the Understanding of IOCG Deposits; PGC Publishing, Adelaide. pp. 285-306]...
So IMO Pedro is a Magmatic Intrusion Event...not a Surface or Basin derived, not Metamorphic [faulted] derived event and not epithermal in genesis...Just 2,531m of the planned 10,000m Pedra drill programme has been completed... Judging by the revised size of this deposit I would humbly suggest 50,000m of drilling minimum will be required to fully delineate the open both ends of strike, of over 1.5km and depth beyond 450 meters down to 750 meters and completed infill for a much larger JORC...At Pedro Branca being on a smaller scale to Sossego...the dioritic or aporitic hanging walls and pegmatite lenses and surrounding gneiss country rock may potentially be consistent with a Magmatic Hydro-Thermal Intrusion IOCG, not dissimilar to Sossego and the results of the deeper 450m holes etc, may provide compelling evidence for directors buying a this stage of AVB's development... Drawing rough comparisons with the size of Sossego...A deposit at Pedro IMO in the order of 50 to 100 million tonne is potentially not unrealistic or 500-750 million tonne to of CU equivalents...
I would appreciate any corrections or insights from of our more qualified Geo or Geo-phys Posters and happy to stand corrected if I'm wrong on any of the theoretical assumptions made here...
GLTA and DYOR...
AVB Price at posting:
6.9¢ Sentiment: LT Buy Disclosure: Held
