Initial Project Evaluation of Tocllano Project, Province Castrovirreyna
Central Peru
September 2007
UTM WGS '56
0451740, 8502147
Photo shows view to the West with Cerro Tocllano
as the highest point and the alteration zone in the foreground.
An option agreement has been signed between the privately owned Peruvian company Minera Borboyona S.A.C. and Goldmark Minerals Ltd. on the 25th of July 2007 for the Huachac project/concessions. The option agreement covers a total of 10,600 hectares distributed over 21 different claims with the apparent potential for mineral deposits and was amended to include the Tocllano Project and another concession area 14 Km south of the Tocllano area. Goldmark has an exclusive option to purchase all or part of the concession open until January 31, 2008.
David Agostinelli, independent Peruvian consulting geologist, Gerhard Jacob of Goldmark Minerals, Juan Rosada a consulting geologist and Dayanara Hianojosa, Goldmark's general manager for Ecuador visited the property Tocllano in August 2007 and for a second more detailed investigation at the beginning of September 2007
The target area can be reached under normal circumstances in a 9 hour car drive from Lima. The highway southwards of Lima and the country road leading East of the coastal town of Pisco are in excellent condition. From the asphalted country road at Pampana Blanca a narrow, challenging dirt road via the villages of Huaca, Tricapo and Castrovirreyna might require 4x4 vehicles during the rain season (December- February), and took us in August 3:30 hours to get to a small settlement at E 0456320, S 8508827 at an elevation of around 3,100m. From there another 3 to 4 hours on foot along the steeply dipping slopes to the WSW are needed to reach the concession.
The Tocllano project area consists of a total of 4,200 hectares in an almost rectangular shape, which are distributed over 8 different claims (see attached map of concessions)
The national topographical grid applies the UTM WGS '56 on this topographical map.
The UTM coordinates are approximate and are for the center of the project area:
Zone 18 L, E: 0451700, S: 8502150.
The topography is steep to cliff like in an arid hot climate with elevations exceeding 3,490 m at the top of Mountain Cerro Tocllano and narrow river valleys with less than 1,800 m elevation. The ridge of the Cerro Tocllano is a local watershed dividing the creeks into a northerly drainage to the Rio Pisco and a southerly drainage into a E-W running feeder river into the Rio Pisco.
The latest edition of the metalogenetic map of Peru, 1: 2,000,000, subdivides the Andean Orogenic Belt into 18 different metallogenic provinces. It allocates the Tocllano target area along the eastern boundary of the NW-SE striking Cu-Mo (polymetallic) porphyritic belt of Cretaceous age with the bordering Tertiary volcanics to the East.
The geological sheets of Castrovirreyna, 27 m, and the next geological map to the South, 28 m, in the scale of 1:100,000 reflect the geology of the target area. The dominating rocks are andesitic and andesitic porphyritic metavolcanics of middle and Upper Cretaceous age and are labeled on the geological map as Kis-q. At the eastern boundary of the concession the intermediate dipping rock units of Cretaceous age are overlain by sub-horizontal to horizontal laying Tertiary lava sequences (described as Tim-s on the geological map). This unconformity is clearly visible in the field. No further attention was given to the lava flows at this stage, because the main vein disappeared underneath the lava flows and then continued on the other side of the hill. The author did not observe any geological indicators with the potential economical deposits in the lava flows.
Regional structural elements were observed and the regional geology suggests a anticline/syncline fold sequence. The dip-direction and dip of the Cretaceous volcanics around Cerro Tocllano is steep to the SE (160°) and NW (340°).
The target area, which is clearly visible in the field due to the four excavated trenches (additional trenches are being excavated at time of printing), is characterized by a topographical depression, a saddle situated between two hills, with Cerro Tocllano at the western end. The saddle is lined along an E-
W direction with steep slopes at its flanks, which finally drop into cliffs.
Two rock units are dominating the saddle and consist of a greenish grey, fine-grained porphyritic andesite with quartz and plagioclase crystals in its matrix. (Sensu strictu it might not be an andesite, it might well be a dacite or even a rhyolite. Please note this could only be answered with a microscopic investigation of thin sections). The other one is a reddish grey porphyritic andesite and lays concordant to the greenish andesite. They show an intermediate to steep dip to the SSE. Several lenses of grey marine carbonates, varying in size of the outcrop, were observed and are intercalated in the porphyritic andesites.
A approximately 40 m wide alteration zone, the lateral extension is most likely much wider, hosted in the porphyritic andesites marks the lowest areas of the depression and strikes in a N-S direction. In its center a 6 to 8m wide quartz-vein with jaspideous elements and portions showing tectonic breccias strikes on a 220°-040° direction for over 400 m to the south until the steep and inaccessible slopes at the northern portion of Cerro Tocllano.
The N-S strike of this hydrothermal quartz vein indicates a structural relationship. The strike is similar to the one of the veins at the Huachac project. They are both related with a high certainty to the same geological event, which was an intrusion related (doming-up-phase of the intrusion) placement of mineralized veins in sub-volcanic porphyritic andesites.
 Numerous highly altered quartz veins were observed, trenching exposed some of them. The smaller quartz veins show a varying thickness of several centimeters to over 1.00 m and run slightly oblique to the large quartz vein, which strikes along a 220° direction.
Sample of the strongly altered porphyritic andesite with a strongly mineralized quartz vein. The veins strike in a 250° direction. The hydrothermal veins are vuggy and show FeOxides and FeOOH. The free gold is expected to occur as small grains in the quartz veins. No visible gold has been observed so far. |
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The vein seems to be structurally controlled and appears to be syntectonic hosted in the subvolcanic porphyritic rocks related to a Pre-Tertiary and Post-Middle Cretaceous. Therefore it is most likely of an Upper Cretaceous event.
As a general and cost effective check for gold a total of 9 grab samples were collected during the first visit to Tocllano in August and submitted to ALS Chemex, Lima for the assay method ICP-41 (elements).
The first samples FA 01 to FA 06 were collected in the trenches.
The rocks sampled were from strongly weathered quartz-vein hosted in a regolithic dacitic or andesitic porphyritic rock.
Samples FA 07- FA 09 were randomly sampled rocks from the surface area in 20m to 30 m distance around up the slope from the trenching area.
Elevated gold values were detected in all samples. They range from 169 ppb to 17.15 ppm (14.30 ppm). The very encouraging assay results on gold clearly indicate the potential for gold.
The author recommends detailed mapping of different alteration halos, if they exist. Also further trenching should be executed for tracing the quartz veins and to be able to collect subsurface samples.
In general the Tocllano Project has a favorable geology for structurally controlled Au quartz-vein deposits hosted in marine volcanic and intercalated sedimentary sequences of Cretaceous age. There is also the possibility of disseminated gold being hosted in the porphyritic host rocks of andesitic chemistry. These particular models have to be investigated and confirmed by detailed mapping prior to a follow up program. Indicators of an expected underlying intrusive body, which were mentioned to be identified by Juan Rosado in the valley.
The observed, tracked and mapped continuous quartz-vein with elements of a tectonic breccia has the dimensions of at least 400m (length in N-S strike) and an average thickness of 6 to 8 m. The author suggests the geological model for the gold hosting Lepanto mine (Lepanto is about a 100 fold bigger) in the Phillipines may be applied to this geological gold target.
Tocllano has the possibility of a several hundered thousand tonne project with relatively good gold values over 5 gr Au /tonne and a high possibility for higher grades. If these grades are continuous or only restricted to pockets is uncertain at this stage. Detailed geological work will be essential.
The project is in a too early grass root stage to be able to comment on the mining potential for gold hosted in a porphyritic environment.
Two former producing mine sites are located in a 20 Km radius.
They are:
Mina Flores Torres @ 04485000, 8499500 about 4 Km south of Tocllano and just West of the concession boundary.
Mina Maria Elena @ 04495000, 8497000
The above mines are/were small Cu-Ag tonnage producers and semi to not mechanized.
Numerous remnants of historical sites such as foundations of small primitive buildings, the ruins of a fortress and several opened tombs were identified in the area and on the concession. Local people and Juan Rosado indicated some of the historical sites as to be pre Inca. Nevertheless, historical sites of pre Inca age and younger are common in the Andes of Peru and the involvement of the local population will definitely have a positive influence on the success of the continuation of the project.
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