EPITHERMAL SYSTEMS

The association of gold mineralization with volcanic and geothermal hot spring activity has long been recognized by prospectors and geologists. We now know that this association is a consequence of the hot magmas which not only produce volcanic eruptions and volcanic rocks but also are the source of the hot fluids that transport gold and other metals and may in fact be the source of gold itself. Fluids emanating from a molten magma are extremely hot and under high pressure deep below the surface. As these fluids rise, they mix with surface waters and change the composition of the rocks with which they come into contact. This process is known as alteration. Eventually the fluids breach the surface and form either acidic lakes known as fumaroles common in the craters of volcanoes or dilute, neutral hot springs like those at Yellowstone or the Geysers in California. These two different surface manifestations acidic lakes or neutral hot springs reflect two different fluid types that each result from the two different paths taken by the magma as it rises to the surface. Both form gold deposits and are known respectively as low- and high-sulphidation gold deposits. In both subtypes gold will largely be precipitated from 2.5 kilometers depth to surface.

Recognizing that gold precipitates near the surface in these systems, the great American geologist Waldemar Lindgren coined the term epithermal in 1933, epi meaning shallow and thermal referring to the heated fluid. The chemist Werner Giggenbach further subdivided epithermal gold deposits into low and high sulphidation types (illustrated right1). Low and high do not refer to each types relative amount of sulphide minerals (metal complexes of sulfur with metals). Rather the distinction is based on the different sulfur to metal ratio within the sulphide minerals of each subtype. While this discussion deals with high-sulphidation epithermal systems, it is worth mentioning that low-sulphidation systems also form economic gold deposits although they develop under vastly different chemical conditions.

HIGH-SULPHIDATION DEPOSITS

High-sulphidation deposits result from fluids (dominantly gases such as SO2, HF, HCl) channeled directly from a hot magma. The fluids interact with groundwater and form strong acids. These acids rot and dissolve the surrounding rock leaving only silica behind, often in a sponge-like formation known as vuggy silica. Gold and sometimes copper-rich brines that also ascend from the magma then precipitate their metals within the spongy vuggy silica bodies. The shape of these mineral deposits is generally determined by the distribution of vuggy silica. Sometimes the vuggy silica can be widespread if the acid fluids encountered a broad permeable geologic unit. In this case it is common to find large bulk-tonnage mines with lower grades.

The acidic fluids are progressively neutralized by the rock the further they move away from the fault. The rocks in turn are altered by the fluids into progressively more neutral-stable minerals the further away from the fault. As a result, definable zones of alteration minerals are almost always are formed in shell-like layers around the fault zone. Typically the sequence is to move from vuggy silica (the centre of the fault) progressing through quartz-alunite to kaolinite-dickite, illite rich rock, to chlorite rich rock at the outer reaches of alteration. Alunite (a sulphate mineral) and kalonite, dickite, illite and chlorite (clay minerals) are generally whitish to yellowish in colour. The clay and sulphate alteration (referred to as acid-sulphate alteration) in high-sulphidation systems can leave huge areas, sometimes up to 100 square kilometers of visually impressive coloured rocks.

ALTERATION IN A HIGH-SULPHIDATION SYSTEM:

In contrast, low-sulphidation veins are formed when the fluids interact with greater amounts of groundwater as they rise from the hot magma. The protracted boiling of the fluids in low-sulphidation systems produces high grade gold (greater than one ounce gold per ton) and silver deposits. The fluids interact with the surrounding rock for a much longer period of time than the quickly channeled high-sulphidation fluids. As a result, the fluids become dilute and neutralized and the silica dissolves. The silica is later precipitated in the veins as quartz, often sealing the fissure closed. When this occurs, the pressure of the gases underneath the sealed fault builds until the seal is ruptured, which provokes catastrophic boiling and the precipitation of gold. After this explosive boiling event, passive conditions return, and quartz precipitates once again. This cyclical process results in the well-known banded texture of the quartz-adularia veins typical of low-sulphidation vein systems. Quartz-adularia veins can contain high-grade gold (greater than one ounce gold per ton) and silver deposits, over vertical intervals of generally 300 to 600 metres. Within this vertical dimension, high gold grades can make for a large amount of easy to mine gold in a narrow compact area.ALTERATION IN A HIGH-SULPHIDATION SYSTEM:

HIGH-SULPHIDATION GOLD-SILVER DEPOSITS IN OR NEAR PRODUCTION TODAY

Yanacocha, Peru The Yanacocha deposit is operated by Newmont Gold Corp. It is one of if not the largest high-sulphidation deposit in the world and one of the largest gold deposits of any geologic type. Reserves stand at 128 Million Tonnes of 1.0 g/t or roughly 34.2 Million ounces of gold. The deposit is hosted by volcanic rocks, largely fine grained andesitic tuffs and flows. The figures below and on the following page illustrate a plan and cross section view respectively of the mineralized areas of the Yanacocha deposit. The cross section illustrates diamond drill intersection in grams per tonne (g/t) gold.2 Note how the gold is distributed within areas of vuggy silica and quartz-alunite alteration (red and pink colours) which are surrounded by clay alteration.

Pierina, Peru The Pierina gold deposit is located in Peru and is operated by Barrick Gold Corp. Gold is found in a succession of volcanic rock rocks that consist of andesite lavas overlain by rhyodacite pumice and lithic tuffs (permeable rocks). The gold and silver is predominantly found in the permeable pumice tuff, with lesser amounts in the overlying lithic tuff and the underlying andesite. The high-grade areas of the deposit are associated with vuggy silica alteration. This alteration type is surrounded by quartz-alunite and argillic alteration. Ore-grade mineralization in the pumice tuff occurs over intervals of more than 260 meters. The area of currently known mineralization at Pierina measures approximately 450 meters wide by 1,200 meters long and is presently open to the southeast. Over 95% of the known mineralization at Pierina is oxide. However, sulphide feeder zones have been intersected at the bottom of the deposit. At present Barrick Gold Corp. has defined reserves of over 65 Million Tonnes at an average grade of 1.3 g/t gold.

High-Sulphidation Epithermal Deposits in Mexico Mexico is particularly well endowed with epithermal low-sulphidation vein systems. In contrast, high-sulphidation gold deposits have not been as well developed. This is likely due in large part to the fact that high-sulphidation systems tend to occur as large bulk-tonnage deposits, which requires advanced technology to discover and mine, whereas the high-grade narrow veins typical of low-sulphidation deposits were more easily explored during Mexicos early mining history. However, in the last decade two significant high-sulphidation systems have been identified in Mexico and are entering production. Reserves are tabularized below.

THE CABALLO BLANCO HIGH-SULPHIDATION EPITHERMAL SYSTEM

The property is located 75 kilometers north-northwest of the city of Veracruz on the Gulf Coast of Mexico and is roughly 10 kilometers by 15 kilometers in size. Logistically, it is extremely well situated with the Pan-American highway running through the east end of the property and ready access to power (Laguna Verde Nuclear Power Plant) and ocean vessel port facilities. In January, 2003, Comaplex signed a Letter of Agreement with Almaden Minerals Corporation whereby Comaplex can earn a 60% interest in the Caballo Blanco gold property in eastern Mexico by incurring exploration expenditures of $2.0 million US over 4 years.

The property is largely underlain by a sequence of volcanic rocks consisting of andesitic to dacitic lithic tuffs, crystal tuffs and volcanic breccias. These volcanic centers are intruded by fine-grained, magnetic monzonite and diorite intrusions and dykes have been identified in several locations on the property. Large areas of clay and sulphate alteration cored by vuggy and massive silica have been identified on the property. Three main areas of alteration and mineralization have been mapped and are referred to as the Northern Zone, the Central Grid Zone and the Highway Zone. The Central Grid Zone is interpreted to represent an area of deeper erosion where copper porphyry style mineralization has been identified while the Northern and Highway Zones are interpreted to represent large, well preserved high-sulphidation epithermal systems.

Previous Work From 1995 to 1998, Almaden Minerals Ltd. completed extensive exploration that concentrated on porphyry Cu-Au and Au-Ag vein targets in the Central Grid Zone (CGZ). The 1998 work included 17 RC drill holes (2390 meters) that tested soil geochemical and IP geophysical anomalies spatially associated with mineralized float and outcrop. Preliminary surface work was completed in 1999 on the Highway and Northern Zones. Several zones of gold and silver mineralized quartz-barite veins were intersected. Two shallow drillholes into an intrusive in the Central Grid Area intersected 107 meters of 0.25 gmt gold and 0.18% copper in one hole and 40 meters averaging 0.39 gmt gold and 0.15% copper in another. Based on this work, it was interpreted that these holes were just touching the top of the system. In 2001, Noranda optioned the Caballo Blanco property from Almaden and drilled 7 diamond drillholes totaling 1,641 meters. No significant copper mineralization was intersected and despite significant alteration and anomalous gold mineralization in several holes, Noranda terminated its option in the fall of 2002. It is noteworthy that Noranda was singularly looking for a large copper deposit and their focus was not on gold.

Recent Exploration After optioning the property from Almaden, Comaplex completed three exploration programs on the property during the spring and summer of 2003. These programs concentrated on the Highway and Northern Zones and included detailed alteration mapping, aided by the use of Almadens portable infrared mineral analyzer (PIMA), rock sampling, an induced polarization-restivity (IP-R) survey and a magnetic survey. This work outlined two areas of extensive alteration and mineralization characteristic of high-sulphidation epithermal gold systems. Concurrent with this program, noted explorationist, Jeff Hedenquist visited the property on Comaplex's request to review the geology and alteration of the prospects and to assist Comaplex in best focusing their exploration efforts on the property.

ALTERATION AND MINERALIZATION Central Grid Zone The CGZ is mainly a zone of clay - silica alteration. Numerous zones of quartz vein float have been identified in the area in the past and the distribution of the vein float was mapped and sampled over the entire area, which is approximately 3km by 2 km. Comaplex completed additional sampling of the vein float with the vast majority of the samples assaying greater than 1 g/t and up to 25 g/t Au. Silver is locally present and most samples were highly anomalous in Cu, Pb and Zn. The mineralized quartz-vein float in the CGZ shares characteristics and settings that are typical of intermediate sulfidation veins, commonly associated with and adjacent to lithocaps of high-sulfidation deposits. The vein float may be indicative of a larger vein deposit at depth and their structural control and depth potential are being assessed.Highway Zone In the Highway Zone is a 3km x 4km area which exhibits a zone pattern of alteration and mineralization from innermost multiple silica core zones (vuggy quartz and silicified vuggy quartz), to quartz-alunite (advanced argillic), to kaolinite and/or dactite to illite (argillic), to propylitic margins. Rock samples from the Highway Zone are generally low (