Sillitoe, 2010 - Avala Resources Ltd.

Thought on the porphyry poten-al beneath 

lithocap at Kuruga 

Prepared for Avala Resources d.o.o 

March 5, 2011 

Richard M. Tosdal, Ph.D., Pgeo 

Picacho Ex L.L.C.

KUDD-‐ 

034 

KUDD-‐ 

005 

KUDD-‐ 

009 

Map courtesy of Ivan Strambanovic, Avala Resources, March 2011 

Geology of the northern end of 

the Kuruga lithocap, Timok area, 

Serbia 

Area is underlain by a series of inferred 

supracrustal andesi@c volcanic, volcaniclas@c 

and tuffaceous rocks 

Extensive advanced argillic altera@on has 

converted much of the high topography to a 

silica±alunite±pyrophyllite lithocap. 

Significant hydrothermal breccia is present 

and the surface and in the historical drilling. 

3 drill holes were examined; KUDD-‐005 and 

KUDD-‐009 were drilled on the north into the 

mineralized part of a breccia complex; 

KUDD-‐034 explored the poten@al for a deep 

porphyry Cu system on the SW corner of the 

area.

Sillitoe, 2010 

What is seen in the Kuruga deep drill hole 

(KUDD-‐034)? 

Quartz – pyrophyllite?-‐kaolinite (supergene) 

at 33m 

Serici@zed gusano textured 

qtz-‐pyrophyrllite rock @ 57m


Sericite-‐chlorite overprint on 2nd Kuruga KUDD-‐034 

bio@te @213m 

Sericite-‐chlorite overprint on pervasive 2 nd 

bio@te-‐magne@te @285m


Kuruga KUDD-‐034 

Chlorite-‐sericite pyrite overprint 

on 2 nd bio@te-‐magne@te @288 m 

Anhydrite-‐pyrite vein with bleached 

chlorite-‐bearing selvage @330m


Kuruga KUDD-‐034 

Groundmass feldspar overprinted by 

anhydrite-‐pyrite-‐chlorite @428m 

Transi@on from pervasive 2 nd bio@te-‐magne@te to “unaltered” host 

hornblende diorite over 5 cm @460m


KUDD-‐034 

What part of a porphyry system might the deep 

Kuruga drill hole KUDD-‐034 have encountered? 

From top to ~462 m depth, the drill hole passed through rocks showing 

the typical hydrothermal silicate altera@on assemblage characteris@c of 

a porphyry Cu hydrothermal system. 

However, there was a remarkable lack of quartz veins as well as Cu-‐Fe 

sulfide minerals. The overall grade is likely low, perhaps in the 0.1+% Cu 

from the serici@c zone through the K silicate (potassic) altera@on zone. 

Pyrite where present is replacing Fe-‐bearing minerals (2 nd bio@te and 

magne@te) that form a pervasive replacement of mafic phases as well 

as veins 

Pyrite is also associated with anhydrite. 

The transi@on in the drill core from intensely altered to almost 

unaltered is very sharp (over 5 cm); sharp lateral gradients are expected 

as hydrothermal fluid flow on the margins will be largely ver@cal and in 

the case of the drill hole based on grain boundary diffusion due to the 

lack of significant veins. 

Taking all the observa@ons suggests that the drill hole KUDD-‐034 may 

have just cut the pervasive altera@on that extend outside the Cu shell 

(dashed line on cartoon to lej).

KUDD-‐034 

Loca-on of KUDD-‐034 with 

respect to soil Mo geochemistry 

Molybdenum forms a low grade shell (9 ppm 

Drill hole was collared at the southern end 

of the area of anomalous Mo and 

oriented easterly (shown approximately in 

pale green). 

Collec@vely, the soil geochemistry and the 

rocks in the drill hole suggest that the 

main por@on of a poten@ally mineralized 

porphyry may lie to the north of the 

KUDD-‐034. 

Map provided by Ivan Strambanovic, 

Avala Resources, 2011

Anatomy of a hydrothermal 

breccia 

In general, hydrothermal breccia show systema@c facies. 

There is a core of highly brecciated material. Where 

fluidiza@on has been intense, the matrix consists of rock flour 

(finely milled rock) with clasts of varying sizes. In a single 

stage breccia, clast sizes increase in size and angularity 

toward the margin. Rocks immediately outside of the breccia 

are crackled, that is fractured in place and essen@ally can be 

fit together as a jig-‐saw. Inter-‐clast displacement and 

rounding increases toward the breccia. 

Mul@-‐stage breccia have complex overprin@ng facies from the 

subsequent events. 

Breccia nucleate at depth and propagate upward un@l the 

energy is dissipated, thereby forming conical body. The roof 

rocks are cut by fingers of crackle breccia to rock flour breccia 

which represent the upward propaga@on of the larger body. 

Areas of maximum permeability are along breccia margins; 

complex when mul@ple breccia bodies present. 

Where they breach the surface, they form dis@nc@ve 

volcanic-‐like features (see next slide)

Anatomy of a hydrothermal breccia that vented to the surface 

Hydrothermal breccias that breach the 

surface some@mes are called diatremes. 

However that term is largely reserved to 

breccias formed from magma@c or 

phreato-‐magma@c processes whereby 

magma expands catastrophically to 

excavate a conical crater. In hydrothermal 

and magma@c-‐related breccias, the 

excavate cone is filled with material that 

was not ejected and that falls back into the 

crater. 

Breccia facies are similar to those in 

hydrothermal breccias but in magma@c 

breccias there is juvenile material in the 

form of irregular ameboidal shaped clasts. 

Permeability will be greatest along the 

breccia margins, or where mul@ple 

breccia@on events are superposed. 

The cri@cal criteria required to dis@nguish 

interac@on with magma is the presence of 

the juvenile clasts.

KUDD-‐009 

KUDD-‐ 

005 

Kuruga breccia facies placed in 

context of simple hydrothermal 

breccia 

Clas@c rock with 0.5 ppm Au; KUDD-‐009 

Tuffaceous horizon @32m; KUDD-‐009

KUDD-‐009 

KUDD-‐ 

005 

Auriferous crackle brecca forming feeder to 

overlying porous sediments; KUDD-‐009 

Low Au grade cap over rock flour matrix 

breccia; KUDD-‐009 @155 m

KUDD-‐009 

KUDD-‐ 

005 

Marginal crackle breccia; KUDD-‐005 

@ 23m with 1.93 ppm Au 

Alunite cemented rock flour 

breccia; KUDD-‐005 @ 195m

KUDD-‐009 

KUDD-‐ 

005 

Pyprite-‐enargite cemente breccia margin; 

KUDD-‐005 @ 70 m 

Mul@ple rebreccia@on with pyrite 

±enargite replacement of youngest rock 

flour; KUDD-‐005 @ 225 m

KUDD-‐009 

KUDD-‐ 

005 

Host Rocks to breccia 

Gusano (worm) texture in host 

rock — appears to be similar 

to many of the siliceous clasts 

in the hydrothermal breccia 

Relict igneous texture in rare clast 

sugges@ng breccia cuts plagioclase and 

hornblende phyric rocks at depth

What type of breccia underlies the northern part of the Kuruga 

property? 

Insufficient knowledge is available regarding the original style of breccia that forms the northern 

part of Kuruga. Drill hole KUDD-‐009 appears to have drilled into the top of a breccia body, 

whereas KUDD-‐005 was collared within a breccia margin. The laqer drill hole was collared at 

higher eleva@ons, and shows evidence of mul@stage breccia@on. An important observa@on is 

that the dominant clast in the breccia is silicified rocks, and thus essen@ally country rocks. 

Hence, trea@ng the breccia as a series of nested largely hydrothermal breccia lacking obvious 

magma@c input seems to be the most reasonable model at this date. 

Recognizing the mul@stage 

evolu@on of the breccia 

poten@ally is important, 

and should be clarified as it 

may play a role in 

mineraliza@on.

Some concluding thoughts 

1. Clearly there is evidence for considerable hydrothermal ac@vity at Kuruga. There is a deep porphyry 

evident as well as extensive hydrothermal breccia present. 

2. Gold in the lithocap is stratabound within a permeable tuffaceous horizon as well as within the 

crackle and jigsaw margins of the breccia. 

3. Copper in the lithocap is associated with a second (or third?) stage of breccia@on and is associated 

with enargite-‐pyrite cement. 

4. No evidence has been seen to date to indicate that the breccias have a magma@c component. If 

this is true, then they represent the catastrophic volume expansion of the hydrothermal fluid. If 

this is true, there is no need for them to be located over the top of a porphyry-‐style intrusion. 

Instead, they can be lateral to the intrusive center. 

5. The evidence for intense and pervasive K-‐silicate altera@on in the deep drill demands a porphyry 

center at depth, as would be expected. What is not know is whether it is mineralized as well. A drill 

hole into the main part of the likely porphyry is warranted. 

6. Judging from the depth of sulfide in drill core and in the nearby Lipa system, the sulfide in the 

porphyry center is likely to begin around depths of 650 m RL, and extend to depth. This depth 

approximately corresponds to the depth of extensive and not overprinted K silicate altera@on in 

KUDD-‐034.

Sillitoe, 2010 - Avala Resources Ltd.

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