Resource upgrade

RNS Number : 4685P

Griffin Mining Ld

02 October 2013

 

60 St James's Street, London SW1A 1LE, United Kingdom

Telephone: + 44 (0)20 7629 7772  Facsimile:  + 44 (0)20 7629 7773

E mail: [e-mail]

 

2nd October 2013

SIGNIFICANT RESOURCE UPGRADE AT CAIJIAYING ZINC-GOLD MINE

Griffin Mining Limited ("Griffin" or the "Company") is very pleased to announce the latest upgrade in resources for its Caijiaying Zinc-Gold Mine in the Hebei Province in the People's Republic of China, the highlights of which are outlined below:

·    A 215% increase in Measured Resources for the current mining area of Zone III

·    74% of the Zone III resource is now in the Measured & Indicated Categories

·    Zone III resource of 29.8 Mt @ 4.7% Zinc, 0.2% Lead, 23.4 g/t Silver & 0.7 g/t Gold

·    Total Resource 49.4 Mt @ 4.1% Zinc, 0.4% Lead, 23.9 g/t Silver & 0.5 g/t Gold

·    Total contained metal of:

·    2 million tonnes of Zinc

·    212,000 tonnes of Lead

·    37.9 million ounces of Silver

·    825,000 ounces of Gold

The success of the infill and extension drilling program, along with on-going mine development, has allowed for the reinterpretation and upgrade of the Zone III Mineral Resource.  A significant portion of the Mineral Resource is now confirmed in the higher Measured and Indicated categories and this material will underpin mining operations for many years to come.  Drilling is continuing and further drill access is being provided by new underground mine development. 

Griffin is currently working on a revised resource model for mine planning purposes.  In addition, the Company is also undertaking a major review of the data collection and management processes, grade control, mine planning and mine reconciliation to optimise production at Caijiaying.  This work will also allow the Company to adapt its plans to take advantage of a predicted increase in the zinc price due to pending market supply - demand issues.

The updated 2013 Mineral Resource estimate is reported at a zinc cut-off grade of 1%. No update was undertaken on the Zone II mineralisation.  The revised Caijiaying Mine resources are summarised below:

Caijiaying Zone III Remaining Mineral Resources June 2013 Grade Tonnage Reported above a Cut off Grade of 1.0% Zn
Zone	Category	Tonnes (Mt)	Zn (%)	Pb (%)	Ag (g/t)	Au (g/t)	Zn Metal (t)	Pb Metal (t)	Ag Metal (Oz)	Au Metal (Oz)
Zone III	Measured	14.0	5.0	0.3	26.6	0.8	701,000	42,000	11,986,000	359,000
	Indicated	8.1	4.5	0.2	22.5	0.7	362,000	14,000	5,835,000	173,000
	Inferred	7.7	4.2	0.2	18.5	0.5	323,000	12,000	4,560,000	129,000
	Sub-Total	29.8	4.7	0.2	23.4	0.7	1,386,000	68,000	22,381,000	661,000

Caijiaying Zone II Remaining Mineral Resources May 2012 Grade Tonnage Reported above a Cut off Grade of 1.0% Zn
Zone	Category	Tonnes (Mt)	Zn (%)	Pb (%)	Ag (g/t)	Au (g/t)	Zn Metal (t)	Pb Metal (t)	Ag Metal (Oz)	Au Metal (Oz)
Zone II	Measured	-	-	-	-	-	-	-	-	-
	Indicated	4.1	3.0	0.7	24.9	0.3	123,000	27,000	3,243,000	39,000
	Inferred	15.6	3.3	0.8	24.5	0.3	516,000	117,000	12,277,000	124,000
	Sub-Total	19.6	3.3	0.7	24.6	0.3	638,000	144,000	15,520,000	164,000

Caijiaying Global Remaining Mineral Resources Grade Tonnage Reported above a Cut off Grade of 1.0% Zn
Zone	Category	Tonnes (Mt)	Zn (%)	Pb (%)	Ag (g/t)	Au (g/t)	Zn Metal (t)	Pb Metal (t)	Ag Metal (Oz)	Au Metal (Oz)
Combined	Measured	14.0	5.0	0.3	26.6	0.8	701,000	42,000	11,986,000	359,000
	Indicated	12.1	4.0	0.3	23.3	0.5	485,000	41,000	9,078,000	212,000
	Inferred	23.2	3.6	0.6	22.5	0.3	839,000	129,000	16,837,000	253,000
	Total	49.4	4.1	0.4	23.9	0.5	2,024,000	212,000	37,901,000	825,000

Note: Zone II Mineral Resource includes 1.49 million tonnes at 3.09% zinc oxide material.

The Caijiaying Deposit is a polymetallic (Zn, Au, Pb, Ag, Au), multi-generational deposit hosted within deformed amphibolitic and calc-silicate gneisses and schists with minor marble. The Mineral Resource estimate is based on 2,470 underground diamond drill holes and 579 surface drill holes at Caijiaying. The underground drilling was carried out using nominal fan patterns of 20m by 20m, grading to a 40m by 40m pattern at depth. Resource wireframes were interpreted by CSA Global Pty Ltd ("CSA") in consultation with Griffin geologists.  The resource outlines were based on mineralisation envelopes prepared on cross-sections using a nominal 1% Zn cut-off grade.

Chairman's Statement

Chairman Mladen Ninkov commented, "With total contained metal at Caijiaying of a gross value of over $6.3 billion, Caijiaying continues to deliver on its promise as a world class, extensive, long life mineral system. Griffin, its joint venture partners, its shareholders, employees, contractors, local, provincial and central Chinese governments and local villagers should all be delighted with this continuing prosperity and, hopefully, even more to come."

Competent Persons Statement

The information in this report that relates to the Mineral Resource estimates is based on information compiled or reviewed by Dr. Bielin Shi, PhD, MSc (Geology), BSc (Geology), who is a Member of the Australian Institute of Geoscientists. Dr. Shi has more than 25 years' professional experience and is a Principal Resource Geologist and full time employee of CSA. Dr. Shi has sufficient experience (>5 years) which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he has undertaken to qualify as a Competent Person as defined in the 2004 Edition of the 'Australasian Code for Reporting of Exploration results, Mineral Resources and Ore Reserves' (the JORC Code).  Dr Shi consents to the inclusion in the report of the matters based on his information in the form and context which they appear.

 

Further information

Griffin Mining Limited

Mladen Ninkov - Chairman                               Telephone: [phone]

Roger Goodwin - Finance Director

Panmure Gordon (UK) Limited                                      Telephone: [phone]

             Dominic Morley

            Hannah Woodley

Griffin Mining Limited's shares are quoted on the Alternative Investment Market (AIM) of the London Stock Exchange (symbol GFM).  The Company's news releases are available on the Company's web site: www.griffinmining.com

Appendix A

Caijiaying Zone III Updated Resource Statement and Parameters

Zone III June 2013 Mineral Resources (1% Zn Cut-off)
Category	Tonnes (Mt)	Zn (%)	Pb (%)	Ag (g/t)	Au (g/t)	Zn Metal (t)	Pb Metal (t)	Ag Metal (Oz)	Au Metal (Oz)
Measured	14.0	5.0	0.3	26.6	0.8	701,000	42,000	11,986,000	359,000
Indicated	8.1	4.5	0.2	22.5	0.7	362,000	14,000	5,835,000	173,000
Inferred	7.7	4.2	0.2	18.5	0.5	323,000	12,000	4,560,000	129,000
Total	29.8	4.7	0.2	23.4	0.7	1,386,000	68,000	22,381,000	661,000

Note: Rounding errors may occur

The resource estimate was completed using the following parameters:

•           Drill holes used in the resource estimate included 2,470 underground diamond holes and 579 surface holes.  The underground drilling was carried out using nominal fan patterns of 20m x 20m, grading to a 40m x 40m patterns at depth.

•           The most recent site visit was conducted by Dr Bielin Shi (CSA) in April and May 2013.  General site procedures were reviewed as well as more detailed examinations (including underground inspection) of the local geology and mineralisation.

•           Core logging, sampling and assaying methods have been reviewed by CSA and are considered to be of a very high standard. 

•           Reviews of QA/QC data and procedures were completed by CSA in 2013 and 2011. CSA concluded the QA/QC of the assay data contained some bias and precision errors, however overall was acceptable for the resource reporting, with most components within acceptable limits.

•           Full database verification was not carried out by CSA at this time, however standard data audits were undertaken using Micromine software.

•           All drill hole collar coordinates in the resource have been accurately surveyed by qualified mine surveyors and tied into the local mine grid.

•          Wireframes were constructed using a nominal 1% Zn cut-off grade. 

•           Samples within the wireframes were composited to even 1.0m intervals based on analysis of the sample lengths in the database. 

•           For the resource estimation, the current model has individually assessed the high-grade outliers. Various top cuts were used to treat the high-grade outliers of the domains based on a review of the domain histogram, log probability plot.

•           A Micromine block model was created using 5.0mE × 5.0mN × 5.0mRL parent blocks. Sub-cells were generated down to 0.5mE × 0.5mN × 0.5mRL as appropriate to honour wireframe domains and geological interpretations during model construction.

•           Grade estimation was carried out using the linear Ordinary Kriging (OK) estimation method for Zn, Pb, Ag, Au and density. This OK method uses estimation parameters defined by the variography.  QKNA was undertaken on a subset of blocks in the main domains to establish optimum search and minimum/maximum composite parameters.

•           Bulk density values ranging between 2.78g/cc³ to 3.30g/cc³ (averaging 2.94g/cc³) for the mineralised zone were estimated using OK based on geostatistical analysis and the level of sample support.  These values compare favourably to the average 'measured' density of 2.91g/cc³.  Density values were provided in the project database and were recorded using the standard water immersion technique.

•           Validation of the block model was undertaken in three ways: visual on-screen assessment by slicing the model in positions coincident with drilling, statistical trend analysis by comparing the interpolated model grades to the raw data, and by validation plotting for northing, easting and elevation.  Overall, the assessment indicated that the trend of the modelled grade appeared consistent with the drill hole grades.

•           The resource model was depleted for underground mining (stopes and development) using wireframes provided by Caijiaying mine personnel as at the end of May 2013.

•           The Caijiaying Mineral Resource have been classified and reported in accordance with The 2004 Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (JORC Code). Resource classification is based on confidence in the QA/QC data analysis, geological interpretation, drill spacing and geostatistical measures. The initial classification process was based on an interpolation distance and minimum samples within the search ellipse.  The resource is classified as Measured, Indicated and Inferred Mineral Resource.  The Measured portion of the resource was defined for the main mineralised zones where there was extensive underground level development and drilling (less than 25m spacing).  The Indicated Mineral Resource was defined within areas of reasonably close spaced diamond drilling (between 25m and 50m) due to the good continuity and predictability of the lode positions.  Areas with larger drill spacing have been classified as Inferred Mineral Resource.

Glossary of key terms

amphibolitic	A metamorphic rock composed chiefly of amphibole with minor plagioclase and little quartz.
bedrock	Solid rock underlying surficial deposits
bulk density	The dry weight of soil or rock per unit volume of rock / soil. Bulk density considers both the solids and the pore space; whereas, particle density considers only the mineral solids.
calc-silicate	A metamorphic rock consisting mainly of calcium-bearing silicates, such as diopside and wollastonite, and formed by metamorphism of impure limestone or dolomite; associated with skarn-type mineral deposits.
Competent Person	A minerals industry professional who is a Member or Fellow of The Australasian Institute of Mining and Metallurgy, or of the Australian Institute of Geoscientists, or of a 'Recognised Professional Organisation' (RPO), as included in a list available on the JORC and ASX websites. These organisations have enforceable disciplinary processes including the powers to suspend or expel a member. A Competent Person must have a minimum of five years relevant experience in the style of mineralisation or type of deposit under consideration and in the activity which that person is undertaking.
CSA	CSA Global Pty Ltd.  A private consulting firm providing technical and management services to the global resources industry.
cross-section	A two dimensional geologic diagram which views the earth as if it were cut open and seen from the side.
cut-off	The lowest grade, or quality, of mineralised material that qualifies as economically mineable and available in a given deposit. May be defined on the basis of economic evaluation, or on physical or chemical attributes that define an acceptable product specification.
deposit	Natural accumulations of minerals in the earth crust, in form of one or several mineral bodies which can be extracted at the present time or in an immediate future.
diamond drill hole	Method of obtaining cylindrical core of rock by drilling with a diamond-set or diamond-impregnated bit
g/cc3	Grams per cubic centimetre - a unit for density measurement.
g/t	Grams per tonne - a unit of measurement used to express the concentration of an element within a mass of another (same as parts per million).
gneiss	A metamorphic rock form characterized by banding caused by segregation of different types of rock, typically light and dark silicates.
grade control	A mining process to quality check and control the grade and variability of an ore.
histogram	A graphical representation of the distribution of data. It is an estimate of the probability distribution of a continuous variable.
Indicated Mineral Resources	That part of a Mineral Resource for which quantity, grade (or quality), densities, shape and physical characteristics are estimated with sufficient confidence to allow the application of Modifying Factors in sufficient detail to support mine planning and evaluation of the economic viability of the deposit.
Inferred Mineral Resources	That part of a Mineral Resource for which quantity and grade (or quality) are estimated on the basis of limited geological evidence and sampling. Geological evidence is sufficient to imply but not verify geological and grade (or quality) continuity. It is based on exploration, sampling and testing information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes.
JORC	An acronym for Joint Ore Reserves Committee.  The 2004 JORC Code has been adopted by the Australasian Institute of Mining and Metallurgy (AusIMM) and the Australian Institute of Geoscientists (AIG), and is binding on their respective members.  It is endorsed by the Minerals Council of Australia (MCA) and the Securities Institute of Australia (SIA).  The Code has been adopted by and included in the listing rules of the Australian (ASX) and New Zealand (NZX) Stock Exchanges, the purpose of which is to set the regulatory enforceable standards or a Code of Practice for the reporting of Exploration Results, Mineral Resources and Ore Reserves.
log probability plot	A graphical technique for comparing two data sets, e.g. two sets of empirical observations, against each other.
marble	A non-foliated metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.
Micromine	Mining software
mineralisation	The concentration of metals and their chemical compounds within a body of rock
Measured Mineral Resources	That part of a Mineral Resource for which quantity, grade (or quality), densities, shape, and physical characteristics are estimated with confidence sufficient to allow the application of Modifying Factors to support detailed mine planning and final evaluation of the economic viability of the deposit.
Mineral Resources	A concentration or occurrence of solid material of economic interest in or on the Earth's crust in such form, grade (or quality), and quantity that there are reasonable prospects for eventual economic extraction. The location, quantity, grade (or quality), continuity and other geological characteristics of a Mineral Resource are known, estimated or interpreted from specific geological evidence and knowledge, including sampling. Mineral Resources are sub-divided, in order of increasing geological confidence, into Inferred, Indicated and Measured categories.
m3	Cubic metre
ordinary kriging	A geostatistical approach to modelling to interpolate spatial sample data and determining values between data points.
ounce	A unit of mass commonly used for gold deposits.  Also known as a troy ounce and equal to exactly 31.1034768 grams.
outlier	An observation that is numerically distant from the rest of the data.
polymetallic	A substance composed of a combination of different metals.
QA/QC	Quality Assurance / Quality Control
QKNA	Quantified Kriging Neighbourhood Analysis - a methodology for quantitatively assessing the suitability of a kriging neighbourhood.
RL	Reduced Level (same as elevation coordinate)
schist	A medium-grade metamorphic rock with medium to large grains of mica flakes in a preferred orientation (nearby mica flakes are roughly parallel).
stope	An underground space produced by stoping (mining).
tonne	A metric system unit of mass equal to 1,000 kilograms.
wireframe	A skeletal three-dimensional model in which only lines and vertices are represented.

 

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