秘鲁勘探报告模式

Anglo American Exploration Perú S.A. Document Reference No: 08-16-0033 Los Laureles 399, San Isidro, Lima 27, Perú Tel +51 1 422 7788 Fax +51 1 421 6199 FIRST YEAR EXPLORATION REPORT, PUCA CORRAL PROJECT, SOUTHERN PERU. ▲View north across main pyritic zone, Puca Corral. AUTHOR: Keenan Jennings DATE: March 2004 DISTRIBUTION: T.J. Beale C.J. Carlon G. Brown 2 LIST OF FIGURES AND APPENDICES ...................................................................................... 3 EXECUTIVE SUMMARY .............................................................................................................. 4 INTRODUCTION........................................................................................................................... 6 LOCATION AND ACCESS........................................................................................................... 7 GEOGRAPHICAL AND GEOLOGICAL FRAMEWORK ............................................................. 7 TENEMENT STATUS ................................................................................................................... 8 WORK COMPLETED ................................................................................................................... 8 Geological Mapping................................................................................................................. 8 Rock Chip Sampling.............................................................................................................. 10 Pima Studies .......................................................................................................................... 11 Ground Magnetics ................................................................................................................. 11 Drilling..................................................................................................................................... 12 PCD-01................................................................................................................................. 14 PCD-02................................................................................................................................. 15 PCD-03................................................................................................................................. 16 PCD-04................................................................................................................................. 17 PCD-05................................................................................................................................. 19 Downhole Susceptibility Modelling....................................................................................... 19 RESULTS.................................................................................................................................... 20 QUALITY ASSURANCE / QUALITY CONTROL....................................................................... 24 Field Replicates ..................................................................................................................... 24 Blanks ..................................................................................................................................... 24 Standards ............................................................................................................................... 24 PETROGRAPHY......................................................................................................................... 25 SAFETY, HEALTH, AND ENVIRONMENT ................................................................................ 25 Baseline Environmental Studies.......................................................................................... 25 Baseline Socio-Economic Studies....................................................................................... 26 Initiatives and Actions........................................................................................................... 27 EXPENDITURES ........................................................................................................................ 29 DISCUSSION .............................................................................................................................. 29 FUTURE PROGRAMME............................................................................................................. 30 3 LIST OF FIGURES AND APPENDICES Figure Title Scale Ref. No. 1 Puca Corral project location map Graphic 08-16-0015 2 Published geological map (INGEMET) 1:100,000 08-16-0016 3 Tenement status 1:100,000 08-16-0017 4 District-scale geological mapping (AAEP) 1:20,000 08-16-0018 4a Hydrothermal alteration mapping 1:20,000 08-16-0019 5 Prospect-scale geological mapping 1:5,000 08-16-0020 6 District-scale geochemical sample map 1:20,000 08-16-0021 7 Prospect-scale geochemical sample map 1:5,000 08-16-0022 8 Prospect-scale clay alteration map (PIMA) 1:5,000 08-16-0023 9 Ground magnetics (reduced to pole) 1:5,000 08-16-0024 10 Structural cartoon of Puca Corral area Graphic 08-16-0025 11 Location of diamond drill holes, Puca Corral prospect 1:2,500 08-16-0026 12 Geological section A-A´ (PCD01 – PCD02 – PCD04) 1:1,000 08-16-0027 13 Geological section B-B´ (PCD05 – PCD02 – PCD03) 1:1,000 08-16-0028 14 Geochemistry (Mo-Au), section A-A´ 1:1,000 08-16-0029 15 Geochemistry (Mo-Au), section B-B´ 1:1,000 08-16-0030 16 Downhole magnetic susceptibility modelling Graphic 08-16-0031 17 Schematic models, Puca Corral project Graphic 08-16-0032 Appendix Description Author 1 Rockchip descriptions AAEP 2 Rockchip geochemistry AAEP 3 PIMA Report AAEP 4 Geophysical Reports 4a Ground Magnetics, Data Acquisition Report Quantec Geofisica 4b Ground Magnetics Interpretation Report Dr. D. Cowan 4c Downhole Geophysics Assessment Dr. R. Morris 5 Summary Drill Logs AAEP 6 Field Drill Logs AAEP 7 Drill Hole geochemistry AAEP 8 Drill core photographs AAEP 9 Petrography Report Dr. G. Ocharan 4 EXECUTIVE SUMMARY The Puca Corral project has been systematically evaluated through a programme of detailed geological mapping, rock chip geochemistry, clay alteration mapping, ground magnetics, and drilling. The programme was carried out in order to determine the presence of significant porphyry copper mineralization at depth. Surface geological and clay alteration mapping demonstrated the presence of various generations of intrusives, with strong phyllic and locally potassic alteration. Stockwork A veins are also noted. Rock chip geochemistry adequately explain the results of regional drainage geochemistry, with a prominent Mo anomaly (up to 130 ppm) present over a wide area. In addition, elevated zinc values are reported zoned outward from the main area of interest. The ground magnetics programme reflected the presence of a large magnetic anomaly interpreted to be 150-200 m below the present ground surface. On the basis of these findings, a 5-hole drill programme was designed and executed to test for the presence of a buried potassic core associated with porphyry Cu mineralisation. Best results from the programme include 154 m @ 501 ppm Mo (PCD02), 5 m @ 270 ppb Au (PCD02), and 8 m @ 273 ppm Cu (PCD-03). The drilling demonstrated the presence of mineralised porphyry dykes with common Mo coatings on fractures, although no significant Cu mineralisation was intersected. A skarn-altered magnetite-silica-chlorite limestone unit underlying a thick quartzite sequence is considered the source of the magnetic anomaly, and may be a caprock to an underlying porphyry. Mineralisation patterns indicate a halo of molybendum ± gold mineralisation that appears dissociated from any copper mineralisation. Minor lead and zinc values suggest the outer shell of zoned porphyry Cu mineralisation. The working geological model for Puca Corral comprises an outcropping phyllic shell with minimal erosion of the roof zone of an underlying Eocene-aged porphyry. The thickness of an intervening limestone unit is equivocal, although geophysical modelling of downhole susceptibility data suggests a minimum thickness of 300 m. It is possible that underlying it is an intact potassically altered porphyry body. The presence of potassic-altered fragments within thin horizons of hydrothermal breccias cross-cutting the limestone reinforces this possibility. If the skarn alteration is around 200-300 m thick, any copper mineralisation is at least 400 m 5 below the current ground surface, and perhaps as deep as 600 m. Given the remoteness of the area and the depths of inferred mineralisation, it is considered unlikely that the economics of any operation would justify its development. No further technical work is recommended. A joint venture partner or third party option may allow AAEP to retain an interest in the project while continuing its exploration. Total expenditure incurred at Puca Corral during the 2003 exploration programme was US $242,879 against a success funding request of $242,500. 6 INTRODUCTION The first documented mention of the area around Puca Corral was during the fly-over survey completed by Minorco in 1998, with the identification of the “Huamanripa” colour anomaly. This was followed up with a series of 6 BLEG samples, and values of up to 14 ppm Mo were reported. No further follow-up was carried out. In 2000 (?) Minera Hochschild entered the area and carried out limited exploration, apparently focussing on a series of narrow gold-bearing epithermal veins located in the east of the property. Although rock chip sampling and small trenches were completed, there is no evidence of drilling, and they apparently did not carry out any systematic work within the area of the main colour anomaly. In 2002, the area (now known as Puca Corral) was nominated as a target for drainage follow-up by Ian Gendall on the basis of a prominent colour anomaly coincident with a potential dilational jog indicated by structural interpretation mapping. Subsequent drainage samples collected from the area immediately NW of the anomaly reported elevated Mo (up to 49 ppm; AEP0755), and other elements (peak values of 792 ppm Zn, 118 ppm Pb, and 674 ppb Ag). These were traced upstream to a large zone of pyritic alteration within quartzites of Cretaceous age. Small, previously unmapped bodies of weakly quartz-vein stockwork and sericitised tonalities were noted and sampled. Geochemical values from the tonalite reported maximum values of 714 ppb Ag, 17 ppm Mo, and 11.9 ppm Cu (AEP0756). A second sample from a narrow (1-2 m) brecciated quartz vein reported 0.8 g/t Au and 48 g/t Ag. Strontium values report low, consistent with previous empirical observations of Sr depletion in the vicinity of porphyry Cu deposits. The disseminated pyrite throughout the quartzites is the source of the colour anomaly originally noted, and is developed over an area of approximately 2km2. One age date was determined and reported 175 ± 4 Ma. The sample, a coarse grained porphyry of possible tonalitic composition, together with the surrounding diorite dykes, were expected to yield Eocene-Oligocene ages. In order to clarify this, a second sample from drillcore was submitted for age dating. This was determined to be 39.6 ± 1.8 Ma, which agrees very well with an Eocene age for the porphyry. It is likely that the previous sample was erroneous. 7 An initial exploration model envisaged a lithocap environment, and as a result the copper values could be expected to be low, while a molybdenum plume may explain the elevated Mo values in drainages. Other indications included a small outcrop approximately 3 km to the southwest that contained possible diaspore fragments within a breccia. On this basis, tenement was secured in March 2003 by AAEP following relinquishment of ground held previously by Hochschild. Work carried out during 2003 included geological mapping, clay mineralogy and petrology studies, ground magnetics, and drilling of 5 holes totalling 1286 m. The results of this exploration work are reported below. LOCATION AND ACCESS The Puca Corral project is located in an isolated area straddling the Departments of Arequipa and Abancay, approximately 300 km by road from Cuzco (Fig. 1). Travel time to the area is 1.5 days, as a stop in the nearest large town of Chalhuanca is necessary to ensure that all travel is made in daylight hours. The area is located at 4,800-5,200 m asl, and infrastructure is extremely poor. All supplies and fuel need to be shipped in from Cuzco and Chalhuanca, and accommodation has been variably in small fly camps or an old exploration hut owned by Hochschild located in the small village of Huarcaya, 40 minutes drive south of the zone of interest. Vehicle access to the village is relatively simple from Chalhuanca, west along the paved highway to the small village of Iscayhuaca. From here, the route tracks southeast, along well- formed dirt roads for 100 km until Huarcaya is reached. However, movement within the property is restricted to roughly formed tracks hand-built by AAEP in the central area. Elsewhere, access is chiefly by hiking, as there are few horses or pack animals available in the area. Several steep inclines present difficulties in gaining vehicular access, and precautions must be taken when transiting within the area. GEOGRAPHICAL AND GEOLOGICAL FRAMEWORK The general physiography of the Puca Corral area is characterised by mountainous terrain with small, and commonly elongate, intermontane plains and swamps. Owing to heavy precipitation of rain and snow during the summer months from December to March, little or no field work can be completed. From April to November, the climate is predominantly dry, although snow storms 8 occur perhaps twice a month. The temperature of the area is extremely cold, ranging from a minimum of –15° C at night to 12° C during the day. Owing to the altitude of the area, land use is restricted to grazing of llamas and alpacas. In general, the soil profile is poorly developed, and within the area of interest is largely devoid of vegetation. Swampy grasses and reeds are present in areas of stream confluence and in low- lying depressions, which both limit availability of outcrop and movement within the field. The geological setting of the area is characterised by extensive areas of mid-Tertiary Tacaza volcanics. The published geological map (Chulca; 30Q) shows outcropping Tacaza across significant areas of the tenement with Yura limestone outcropping in the northeastern part (Fig. 2). Mapping carried out by AAEP has demonstrated that in fact the Puca Corral area comprises a window through the volcanics to altered and weakly mineralised Cretaceous sediments and intrusives not apparent on the published map. The results of AAEP mapping are discussed more fully below. TENEMENT STATUS Anglo American Exploration Peru currently control 10 mining concessions over Puca Corral covering 8700 Ha. The tenement is centred on and surrounds the alteration system as seen at surface. Tenement payments are due at the end of June, 2004, and will cost $26,100 to maintain. The tenement status is shown in Figure 3. WORK COMPLETED Geological Mapping Initial geological mapping was carried out at 1:20,000 scale in order to determine the nature and extent of the principal rock types, alteration, and mineralisation present in the area. The results of the mapping demonstrate that Puca Coral comprises an inlier of Jurassic and ?Cretaceous sediments and intrusives within a windowed area of extensive Tertiary volcanics (tuffs and ignimbrites) of the Tacaza Group (Fig. 4). The sediments are dominated by sandstones and quartzites of the Yura Formation, with lesser greywackes, intercalated siltstones, and bituminous limestones. These sediments form a topographically high ring structure around a flat, swampy area with poor outcrop. Extensive pyrite mineralisation in the quartzites causes a significant colour anomaly. A prominent conglomeratic horizon present on the southern edge of the area of interest is interpreted as the Mesozoic paleosurface. No alteration or mineralisation 9 is observed in the Cenozoic volcanics in the immediate vicinity of the Puca Coral anomaly, indicating that all hydrothermal activity predates the emplacement of the volcanics. The mapping has confirmed the presence of an inlier of hydrothermally altered and mineralised quartzites and intrusives within an area of extensive post-mineral volcanics (Figs. 4, 4a). The inlier covers an area of approximately 3km2, and is developed within a northeast corridor mirroring several district-scale structures. This feature is not apparent on the published geological maps, and there is little evidence of previous work in the area. In order to further refine targeting, more detailed mapping at 1:5,000 scale was carried out over the central part of the inlier. The results are presented as Figure 5. The quartzite sequences are intruded by at least three phases of intrusives. The earliest (?) is a magnetic diorite most prominently outcropping in the east of the area, and somewhat removed from the main area of interest. This has developed a thin zone of hornfels along the contact with the host quartzites, but is generally unaltered. Intruding the diorite is a variably altered tonalite, cropping out sporadically as dykes (with a preferred NW trend) and small apophyses. The tonalite is characterised by small primary quartz grains within a fine, and typically clay-altered, matrix. In the central area, the tonalite is quartz- sericite altered and contains weak stringer pyrite veinlets within a localised poorly developed quartz-vein stockwork zone. The quartzites surrounding the tonalite bodies are extensively pyritised and form a topographically prominent arcuate ridge. A small block of fine-grained garnet-bearing skarn is also noted between the tonalite and the quartzite ridge. A third rhyolitic intrusive crosscuts the tonalite, and is characterized by coarse quartz eyes in a fine, glassy, and unaltered matrix, and appears to be late- or post-mineral. The results of this more detailed mapping suggested that the exposure level at Puca Corral may be immediately above a potassic core, within a zone of silica-sericite-illite alteration. Moreover, the presence of several generations of intrusive indicated that, although those observed at surface are barren of copper, one or more intrusives at depth may host economic copper grades. Mapped structures within the area are dominated by NE-trending features. A subsidiary fracture set trends NW through the area, and is marked by a series of tonalitic dykes. This is reflected in the ground magnetics data (see below), and a subtle E-W fracture set is also noted. The 10 principal area of interest appears to be focussed on the intersection of a major NE and NW discontinuity. Rock Chip Sampling A total of 70 rock chips samples were collected focused on the central area intruded by tonalite bodies. Copper and gold grades are generally poor, not exceeding 0.29ppm Au and 100ppm Cu. However a prominent Mo anomaly is present, with values >50ppm over an area 800m x 500m, with a peak value of 130ppm (Fig