The Parys Mountain Project

Geological Assessment

For the past three years Anglesey Mining has been carrying out a reassessment of the geology and structural setting of the Parys Mountain deposits. This program has included remapping of surface geology, a compilation and reinterpretation of historical drilling results as well as relogging much of the old drill core and a major study of the structural setting using lithogeochemical analysis and advanced scientific interpretation.

The work carried out is leading to a new understanding of the relationships between volcanic rocks of differing characteristics and the massive sulphide mineralisation and to the development of new stratigraphic models for the Parys Mountain area which demonstrate that there is potential for the identification of new mineral zones on the property which could add substantially to the existing mineral resource base. These conceptual models are being continuously refined as new information becomes available.

The Parys Mountain property is approximately 3 kilometres long (east - west) and about 1.5 kilometres wide (north - south). Only the western 1 kilometre of the east-west strike length has been subjected to any meaningful exploration and only the western fringe of this western kilometre itself has been subject to detailed assessment.

The reassessment work carried out to date, which is continuing, has demonstrated that there is considerable potential to identify and define new ore zones in the remaining 2 kilometres of the property to the east of the known Engine Zone (which was defined during the 1990-91 underground programme) and east of the existing Morris Shaft. It is believed that there is also potential for the discovery of new lenses of massive sulphide along the northern part of the property at depths of between 400 and 600 metres below surface.

Drilling

In 1997 Anglesey Mining initiated a new drilling programme at Parys Mountain with the objective of increasing the overall geological resource base and thus enhancing the viability of a new mining operation.

Between November 1997 and March 1998 three widely spaced vertical holes totalling
1,020 meters were drilled to explore the near surface updip portion of the central zone in areas which could be mined from the existing Morris Shaft. Although the holes did not hit economic mineralisation, drilling results are encouraging. The potential for massive sulphide lenses remains and further closely spaced drilling in this area is warranted however it would appear that the up-dip projection of the mineralisation in this area may be less extensive than had been hoped.

Hole AMC 12 located about 600 metres east of the Morris shaft was drilled to a depth of 450 metres where it intersected the target horizon. This hole was subsequently tested by a down-hole electromagnetic geophysical survey which showed a strong off-hole response at the target horizon between 360 and 400 metres deep. This has been interpreted to indicate a conductor of significant dimensions within 50 metres of the hole. The geophysical survey also showed a weaker response at an intermediate horizon of about 200 metres depth which could also indicate a significant conductor located further from the hole between 50 and 100 metres.

Hole AMC 11, located about 500 metres east of the Morris shaft and 300 metres southwest of AMC12, was drilled to a depth of 200 metres where it intersected the target horizon, but it is now believed the hole was drilled too far to the east of the projected zone. Hole AMC 13 was drilled 170 metres west of AMC 11 and again intersected the succession at the target horizon. Results of geophysical surveys carried out on holes 11 and 13 indicate possible minor mineralisation within ten metres of each hole at depths of 140 metres and 120 metres respectively.

The results of hole AMC 12 are particularly encouraging and indicate that the zone is present at the anticipated horizon. The low grade mineralisation, together with the geophysical results, indicate that a larger ore body may be close by. It is planned to drill a further hole, which would be about 500 metres deep, approximately 50 to 100 metres north-west of AMC 12.

The next part of the exploration programme commenced in May 1998 with the objective to test areas further to the northeast targeting down-dip zones. The projected location of these zones is based largely on geological interpretation as only one previous hole had been drilled in this area.  

Hole AMC 14 was located about 250 metres north of AMC 12 in the north central part of the Parys Mountain property and north of the open cast pits. The hole went to a depth of 620 metres and took almost two months to complete but deviated somewhat to the south-south-east with increasing depth. Although the hole did not intersect significant economic mineralisation it did intersect three horizons of interest.

At the first or highest horizon the hole intersected the northern shale/northern rhyolite contact where an interval of quartz rock plus locally copper rich sulphide vein mineralisation (Carreg-y-doll) was located at an interval between 180 metres and 193 metres below surface.

At a lower depth of approximately 390 metres, hole AMC 14 intersected a zone of weak mineralisation over an interval of about 10 metres. This interval contained disseminated sulphides, with rhyolite breccia and several polymetallic sulphide veins.

Finally at the bottom of hole AMC 14 an interval of black massive rock was intersected between 511 and 530 metres overlying a thin bed or vein of polymetallic sulphide. The black massive rock has been provisionally interpreted as strongly altered rhyolite indicating that this section has been subjected to intense hydrothermal alteration and may be close to a body of massive sulphide.

The preliminary results of AMC 14 provide ample evidence of both the potential and the complexity of Parys Mountain and are encouraging. Complete lithogeochemical analysis and geophysical surveys must be completed. However, it is clear that a "step-out hole" about 100 metres to the north is a very obvious follow up target.

The results of the ongoing geological assessment and the exploration programme carried out over the past year demonstrate clearly that the Parys Mountain property requires and justifies a major new drilling programme and that the potential for the discovery of substantial additional mineral resources in previously largely untested areas of the property is very significant. Geological assessment and advanced technological studies will be continued. The company has planned and laid out a drilling programme comprising a minimum of 10,000 metres in 10 to 15 holes.

 

New Exploration technologies

Major improvements in technology in recent years have had a significant impact on mineral exploration. Anglesey Mining has been at the forefront of the application and use of new methods and technologies and advanced instruments to help unravel the geological mysteries of Parys Mountain.

Lithogeochemistry

Over the past three years major lithogeochemical studies have been carried out at Parys Mountain. This work, which has been undertaken by Dr. Tim Barrett of Ore Systems Consulting of Vancouver in conjunction with Cardiff University of Wales and using the analytical laboratory at McGill University in Montreal, involved the re-examination of large quantities of drill core and outcrop. The work was significantly expanded during the year to include the current drilling and to extend to other parts of the property.

Lithogeochemistry depends on the observation that, although the chemical composition of rocks today may be very different to their original composition, certain of the elements within the rock are relatively immobile and do not change.

In order to apply lithogeochemistry it is necessary to accurately analyse rock using X-ray fluorescence and inductively-coupled-plasma mass-spectrometry or similar techniques.

Lithogeochemistry can not only identify rocks to the point where individual lava eruptions can be recognised, but the data can also provide information about the nature of the geological environment in which the volcanic activity occurred, such as a volcanic continental arc or rifted oceanic crust. Additionally lithogeochemical data allow hydrothermal alteration to be characterised and quantified accurately using mass-change techniques.

The goal of all this is to identify and follow volcanic units and their contacts with each other and with the surrounding shales as doing so will lead to the areas most likely to contain mineralisation.

Infrared Mineral Analysis

Mineral deposits are associated with hydrothermal alteration of the surrounding rocks. Such alteration commonly forms a halo around the mineralisation, providing an exploration target considerably larger than the deposit itself. The delineation and characterisation of hydrothermal alteration can therefore be of great value in mineral exploration for the identification and assessment of new targets.

Until recently, assessment of alteration assemblages was often difficult because of the fine grain-size of the minerals, and could only be accomplished by expensive and time consuming laboratory techniques. However, this problem can now be addressed using an instrument known as a PIMA (portable infrared mineral analyser), originally developed in Australia, which is a hand-held spectrometer which can provide important information on rocks, minerals and soils. The instrument is capable of detecting many of the minerals commonly found in hydrothermal alteration systems, such as clays, carbonates and sulphates

During the last year a joint project was carried out in conjunction with the British Geological Survey, supported by the Department of Trade and Industry, using the PIMA to examine the nature and distribution of alteration in the volcanogenic massive sulphide rocks at Parys Mountain.

The PIMA was successful in detecting distinctive mineral assemblages related to geology and formed by the alteration of the host rocks during interaction with mineralising fluids at Parys Mountain.

3D modelling

Anglesey has been working closely with the British Geological Survey in the application of 3-D visualisation and virtual-reality models to mineral exploration and mine development. BGS staff have worked with Anglesey on a project under the Technology Access Programme of the Department of Trade and Industry on a model of the geology and mineralisation at Parys Mountain so that the underground geology can be better understood and new exploration can be targeted. All the significant historic and new data from Parys Mountain has now been loaded into the BGS Vulcan 3D modelling system. Completing this process was time consuming because of the amount of data involved. It is planned to continue the examination and review of this data using Vulcan.

Radio isotope dating

The volcanogenic massive sulphide (VMS) deposits at Parys Mountain were originally formed in the vicinity of large submarine volcanic centres with associated hydrothermal systems.

In an effort to determine the age and duration of hydrothermal and volcanic activity at Parys Mountain where mineralisation occurs at three levels within the succession, a special project using radio isotope geochronology has been undertaken with the British Geological Survey. This project utilises the very high precision method of uranium/lead dating of the mineral zircon. Because of the unique attributes of the uranium/lead decay system, it is possible to date rocks to within approximately 500,000 years even when the rocks are as old as 2,700 million years.

This technique has been applied to the deposits at Parys Mountain only recently but if it is proved to be successful its impact might have far reaching consequences for the understanding of the formation of these orebodies.

Palaeontology

Palaeontology studies in conjunction with Leicester University were carried out in 1996 in order to help to determine the overall stratigraphic relationships at Parys Mountain. A review involving further evaluation of palaeontological data and examination of shale sequences has been completed in 1998. Determining the ages of the shale units at Parys Mountain will be very helpful in establishing the overall structural relations at the property. Systematic collections have not as yet been made from all of the property and a further phase of micro-paleontological dating forms part of the company’s plans.

The Parys Mountain property is the largest and the only undeveloped polymetallic mineral deposit in the United Kingdom. It contains an important identified geological resource of about 6.5 million tonnes with a grade of 5.3% zinc, 2.3% copper, 2.7% lead, 39 grams of silver and 0.32 grams of gold per tonne. A positive independent feasibility study was completed in 1990 and full planning permission obtained for a 1,000 tonne per day mine.

A complete geological reassessment of the property is being carried out and this has resulted in the development of new geological models which indicate that there is potential for the discovery of substantial additional mineral resources in areas east and north of the known resource largely unexplored to date.

A new exploration programme was launched in 1997 and four diamond drill holes were completed. The objective of the new exploration programme is to develop significantly larger mineral deposits at Parys Mountain.

 

Parys Mountain Project  -  Profile

Location

The Parys Mountain property is located in the northern part of the island of Anglesey in north Wales. The mineral property is about 3 kilometres in length and covers more than 2 square kilometres. The company owns the freehold, to about a half of this area and a leasehold of the other half and holds the mineral rights to the entire property. The company also has a mining lease from the Crown for gold and silver over a wider area.

The property is located 2 miles south of the town of Amlwch. The port of Holyhead is 18 miles to the west. Access to the property is excellent by road, rail and sea. All necessary services and resources including power, engineering, maintenance facilities and a skilled labour force are located nearby.

History

Parys Mountain has been the site of intermittent mining activity since at least Roman times. During the 1780s Parys Mountain was the largest copper mine in the world. Open pit and underground mining were carried out over a strike length of more than 3 kilometres and to depths of about 200 metres, the deepest then achievable by known technologies. Almost all activities ceased by the beginning of the 20th century.

In the 1960s the search for a new mine at Parys Mountain recommenced. Exploration in the 1960s and 1970s was focused on the extension of the old open pit workings and was directed towards copper. This exploration utilised a variety of geological, geophysical and geochemical methods together with approximately 285 diamond drill holes totalling about 60,000 metres of drilling.

The modern phase of exploration of Parys Mountain began in the early 1980s when a new important polymetallic zinc, lead, copper, silver, gold area was identified about 1 kilometre west of the old workings.

Between 1988 and 1990 a shaft was sunk to a depth of 300 metres. About 1,000 metres of lateral development were completed on the 280 metre level. Drilling and underground development work from 1988 to 1990 resulted in the identification of the Engine, White Rock and Chapel zones containing a resource of 6.5 million tonnes with a combined base metal grade (zinc, copper and lead) of 10.3%.

Approximately 2,000 tonnes of development ore were successfully hoisted and processed through a pilot plant constructed on the site for metallurgical testing and concentrate production of about 200 tonnes was sold to the smelter at Avonmouth.

Feasibility Study

In 1990 Kilborn Engineering completed an independent feasibility study of the project that confirmed the technical and economic viability of a 1,000 tonne per day (300,000 tonnes per year) mining and milling operation producing zinc, copper, lead and gold concentrates. Kilborn estimated the capital cost of the mine at £22 million. This study was based on a mineable reserve of 1,963,000 tonnes at a grade of 6.43% zinc, 1.30% copper, 3.32% lead, 75 grams of silver and 0.51 grams of gold per tonne and a mine life of seven years. This mineable reserve covered the shaft development area, being only a portion of the overall geological resource of 6.5 million tonnes.

Detailed mine and plant designs were prepared and planning permission obtained. At the same time an environmental protection programme was devised also giving attention to historical and archaeological concerns. Declining metal prices and weakening stock markets in 1991 and 1992 resulted in development of the project being placed on hold. The property has been maintained on a care and maintenance basis since that time. Reassessment of the geology commenced in 1995 and is continuing up to date.