Compania Minera Punitaqui - Copper and Gold
Compania Minera Punitaqui – Copper and Gold
The company holds leases of approximately 120km in area in the vicinity of Ovalle in Region IV, Northern Chile. All of the tenements are located on or adjacent to the Atacama Fault which is a major regional structure extending from the south of Santiago northwards into Peru, and has the majority of the giant copper deposits and many smaller copper and gold deposits of Chile along its length. The geology of the area consists of Cretaceous sediments and andesitic volcanics and older Jurassic granites.
LEASES
The leases can be divided into three areas (see figure 1) of differing geological affinity. In the northern most area, hydrothermal veins have historically been mined for copper since 1800. The central region includes the company’s Cinabrio mine which is currently producing around 0.35mt of copper ore per annum. This region contains stratiform Manto style mineralisation. The southernmost area contains the TMR mill and several small hydrothermal vein deposits which intermittently produce small quantities of gold. There is also copper mineralisation in this area in the form of hydrothermal veins in andesite.
1. Northern Area – Tamaya
This is the largest lease area covering approximately 90 square kilometres and is essentially the whole mountain with a steep topography. There are multiple small mines and one large underground mine in the area and the mineralisation is in veins 0.8m to 2m wide. The mines were worked from 1800 to 1995 at head grades of 12% to 20% copper with the vein sets extending for around 5km. The oxide material from the mine was dumped on the ground for 195 years and it has been estimated that the scattered surface dumps contain 300,000 to 500,000 tonnes of oxide copper ore at grades from 0.8% to 1.5%. There are a number of vein sets with the main mine located on the richest set and mining extending to around 300m below surface. The less rich veins have only been worked to relatively shallow levels and have grades to the order of 1% to 2% and are generally 0.5m to 1m wide.
Figure .1 – Compania Minera Punitaqui Active Exploration and Mining Areas
2. Central Area – Cinabrio, San Andres, Elvira, El Reloj
This is an area of Stratiform Manto style deposits. The host rock is lutitic (Lutum =Latin- Clay) shale with the hanging wall being a competent silicified volcanic Breccia and the footwall andesitic volcanics and occasional epiclastics. The area is a cluster of manto deposits with El Reloj in the north of the area then Juana and Satan owned by Chilean operators between El Reloj and Cinabrio.
El Reloj
There has been little work at El Reloj but the geology is known to be similar to Cinabrio. The mineralisation has been intersected by a small drive and 2 drill holes and is around 2m wide with a grade of 1.5% to 2% copper.
Juana and Satan
These are owned and mined by small Chilean operators. They are similar to Cinnabrio at the top, but the depth of these deposits is unknown as ore definition is only by underground development. Juana is the better of the deposits and trucks oxide and sulphide copper ore to a processing plant at Cocinera.
Cinabrio
Cinabrio is Tamaya’s current operating mine. The upper part of the deposit is oxide copper minerals and the lower part Chalcopyrite with lesser Bornite.
This deposit is currently being mined at a rate of 0.35Mt per annum. The production has been derived from a 5m to 40m wide mineralized, lutitic, sedimentary, sequence via a number of level developments between 470mRL to 330mRL. The lutite has been mapped on surface over a strike length of approximately 1km with the mineralisation dipping between 45 to 60 degreesand is broken up into a series of structural blocks by dipping cross faults (see figure2).
There are 62 drill holes (11,063m) that trace the lutite to a vertical depth of around 350m and define a steeply plunging copper – silver mineralized shoot over 300m of strike. At depth, the copper mineralogy is dominated by chalcopyrite, with lesser bornite, and copper oxides in the near surface. Copper – silver mineralization has also been intersected in a number of deep holes within the andesite underlying the lutite in the southern part of the mineralized shoot. A 3,000m drilling programme was completed in September 2006.
San Andres
This prospect has only recently been obtained by the company there has been no geological work on the tenement since 1998 (ie. before the discovery of the extent of Cinabrio). The geology of San Andres is identical to Cinabrio and it could be a fault offset of the same block. A site inspection of old workings confirmed that copper oxide mineralisation occurs in the same horizon as Cinabrio. The observed mineralisation was low grade but Cinabrio at the same level is also low grade. Figure 3 shows the relationship between Cinabrio and San Andrez.
A plan has been formulated for 3,000m of drilling to systematically test the tenement. The potential to find significant sulphide mineralisation is high. San Andres could be as large, or larger than Cinabrio.
Figure .2 – Cross Section of the Cinabrio Deposit at 480mN
Sta Elvira
The geology is not consistent with Manto style mineralisation and small pits on the prospect encountered very thin copper carbonate fracture filling in Andesite. There has been some drilling on the prospect that encountered 0.3m fracture filling by copper carbonates at < 0.5% Cu. This is a low priority exploration target.
Figure .3 – Spatial relationship between San Andres and Cinabrio
3. Southern Area – Vetas Tensionalles, Diatrema, Dalmacia
This is the area surrounding the Punitaqui concentrator (see figure 4). The dominant style of mineralisation is vein hosted gold with one copper prospect Dalmacia towards the southern part of the area. The Vestas Tensionalles is an area of four small, interconnected gold mines which are now flooded. Diatrema is vein gold deposit which is currently producing ore in small volumes for sale directly to Enami, or treatment at Punitaqui.
Figure .4 Southern Area Gold Prospects
Vetas Tensionalles
This prospect is also known as Los Mantos. It is essentially four interconnected mines each exploiting a separate 0.5 to 1.0m gold vein with average grades to the order of 5g/t. There appears to be some remaining resources attached to each of these veins. The mines until quite recently have produced small quantities of gold ore which have been blended with the copper ore feed into the Punitaqui Mill.
A detailed evaluation of the area is planned.
Diatrema
Diatrema is around 1km to the North of the Vestas Tensionalles (see figure 3). The deposit is essentially one gold vein with an average width of 2m. The maximum gold grades are to the order of 300g/t and the estimated resource potential at this point in time for this deposit is 50,000T @ 8.2g/t gold. The historical head grades are to the order of 20g/t and the underground drives are 3m x 3m. The operating mine is called Culebra and it mines part of the Diatrema deposit.
There is a decline currently in progress and a program of underground exploration drilling is being considered. The prospect will undergo a high level overview to assess the potential of the whole Diatrema deposit and also define resources by incremental steps at Culebra.
Dalmacia
This prospect is around 5km to the south West of the Punitaqui concentrator. It outcrops and is a potential open cut position (See figure 4). The mineralisation consists of copper rich lenses in andesite, however the exact nature of the mineralisation is not quite clear as all holes to date have been RC and the outcropping section is oxidised. The tenor of the mineralisation is 1% to 2% copper and the lenses are complex in their distribution. It is considered to be a very good open cut, copper oxide and copper sulphide target.
Figure 4 Surface Plan of Dalmacia
