Generalized Copper Porphyr System

7/27/2019 Generalized Copper Porphyr System

1/13


2/13

A copper porphyry system can generate up to six distinct and separate types of ore

deposits. The presence of carbonate bedrock is essential for the formation of skarns

around the intrusion. A particular copper porphyry does not necessarily generate all of

these deposit types, but multiple deposits generally occur in and around the porphyry

system.


3/13

One type of deposit formed by a copper porphyry system is zinc skarn, which occurs at the outer

edges of the mineralized area and typically hosts zinc-lead-silver mineralization. The skarns are

poddy, forming mantos (tabular bodies), pods and chimneys or pipes. They range from less than

1,000 tonnes to over 60,000 tonnes in a single body, but cumulatively they can form large tonnages

that are mineable from the same mine access. Deposits of several million tonnes have been mined

in other skarn districts. The Bolivar mine currently being operated as a pilot mine by Dia Bras is

this type of zinc skarn, although at Bolivar the zinc skarn is dominantly a zinc-copper rich and lead-

poor skarn because the Bolivar mineralization is copper rich. Grades of the massive sulfide

mantos and pods at Bolivar are very high, grading 30-40% zinc and 6-8% copper. Mill feed to DiaBras mill at Malpaso ranges between 12% and 16% combined copper-zinc because low-grade

(1-1.5% copper and 4-8% zinc) development rock from drifting of access tunnels to the various

high-grade pods is blended with the high-grade material. The Companys objective is to develop

more working faces in higher grade material so that mill feed will be maintained at higher levels.


4/13

If the carbonate rock around the intrusion contains a layer of permeable and porous

calcic limestone, the mineralizing fluids flowing through it will generate a copper skarn.

These skarns are stratabound and can extend laterally for several kilometers. The

largest copper skarns known contain up to one billion tonnes of mineralized rock

averaging 0.5% copper.


5/13

If the carbonate rock surrounding the intrusion contains a layer of permeable and

porous magnesian limestone (dolomite or dolostone), a copper-iron skarn is formed.

This skarn type can also occur over several kilometers length, either as a single

deposit or as multiple deposits in the same stratigraphic layer. The South Bolivar

skarn is this type of skarn. The list above shows the range of tonnages and grades

of copper-iron deposits just in the Yerington district (Nevada, USA) that weregenerated by a single porphyry system.


6/13

View of an old portal (Mina de Fierro) in the South Bolivar copper-iron skarn. The

skarn is about 30 meters thick in this area, which is located between the Bolivar mine

and El Gallo. Dia Bras has drilled this skarn over a 250 x 350 meter wide area, and it is

open down-dip and along strike. The copper-iron skarn has also been located by

drilling below the Level 6 of the Bolivar mine.

Old Portal in South Bolivar Cu-Fe Skarn


7/13

A view of El Gallo where the South Bolivar copper-iron skarn is exposed along a cliffwhere secondary copper (malachite, the green stain) occurs within the skarn. The

brown disturbed area at the center right view is the edge of the Increible mine, which is

a Cananea-type copper breccia pipe. The portal for Mina de Fierro is located over the

ridge (behind the house on the top of the ridge) and about 200 meters beyond it.

These exposures show the lateral continuity of the copper-iron skarn, which is typical

for this type of deposit. The down-dip extent of the skarn has not yet been determined,

but the Company is planning a 16,000 meter drilling program during 2006 to continue

defining the extent of this deposit.

Cu-Fe Mineralization in South Bolivar Skarn


8/13


9/13

View of the Increible breccia pipe deposit showing the strong relief of the area being

explored.

Mina Increble: Cananea-type breccia pipe


10/13

The top of the porphyry intrusion can become mineralized as a copper porphyry

deposit, where copper mineralization occurs in a large zone of quartz veining and

stockwork (cross-cutting quartz veinlets and veins) mineralization. Such a deposit is

the heart of the Bolivar mineralizing system but has not been located as of June 2006,

and it is a primary goal of the Company to search for this core intrusion during this

year.


11/13

The Bolivar area is within an extensive trend of copper porphyry deposits.


12/13

A compilation of the range of tonnes and grades found in various copper porphyrydeposits in this region. These list does not include the tonnes and grades of their

associated skarns and breccia pipes.


13/13

High-sulfidation gold deposits occur in the upper levels of the volcanic pile associatedwith the copper porphyry intrusion. The area around the Bolivar mine is eroded deeply

enough that the lateral and distal skarns are exposed, and any high-sulfidation gold

deposits in the immediate area have been eroded away or are covered by post-

mineralization volcanic ash flows.

Documents

Generalized Copper Porphyr System