Estimation and Reporting of Mineral Resources for Coarse Gold-bearing Veins

Dominy, Simon C.; Johansen, G.F.; Cuffley, Brian W.; Platten, I. M.; Annels, A. E.

doi:10.2113/0090013

Cited by 20 publications

(66 citation statements)

References 6 publications

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“…Underground development, closely spaced in-fill drilling and/or bulk sampling are needed to define local Indicated Mineral Resources and Probable Ore Reserves (Dominy et al, 2000b(Dominy et al, , 2003c. The definition of Measured Mineral Resources and Proven Ore Reserves is less likely, though is dependent upon the nature of the deposit, and data quality and density.…”

Section: Resource Reportingmentioning

confidence: 99%

Approaches to reporting grade uncertainty in high nugget gold veins

Dominy¹,

Edgar²

2012

Applied Earth Science

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High nugget effect gold veins are generally considered to be one of the most challenging of deposit types to evaluate and exploit. To potential investors and mining companies, they are viewed as high risk because of the associated uncertainties in the grade estimate and general paucity of reserves at production start-up. Despite the well-known risks, these deposits are often high grade and have a grade upside which makes them potentially attractive. The reporting of resource grade is of importance and perhaps even more so is the reporting of the associated uncertainty attached to the grade estimate. The quoting of the estimated grade within a grade range is recommended to achieve more complete and useful disclosure. The definition of the grade range can be somewhat subjective, ranging from opinion-based through to data-based estimates and geostatistical conditional simulation. Whichever approach is used, the over-riding issue must be the provision of enough data of appropriate quality and full disclosure to the public of relevant uncertainties.

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Section: Resource Reportingmentioning

confidence: 99%

Approaches to reporting grade uncertainty in high nugget gold veins

Dominy¹,

Edgar²

2012

Applied Earth Science

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“…Overview Coarse gold-bearing so-called nuggety deposits are generally characterized by the presence of localized and erratic high grades (Pelham, 1991(Pelham, , 1992Dominy et al, , 2000aDominy et al, , 2000bDominy et al, , 2000cDominy, 2001). Coarse gold is generally considered to be that in excess of 0.1 mm (100 µm) in size.…”

Section: Problem Of Resource Estimation In Coarse-gold Quartz Reef Symentioning

confidence: 99%

“…Carefully thoughtout sampling and preparation protocols are essential. The GNE must be controlled through careful interpretation of geology and grade distribution and by selecting the optimum sample size and density (Dominy et al, 2000b). This paper reports part of such a detailed investigation.…”

Section: Implications Of the Nugget Effectmentioning

confidence: 99%

“…Deposit evaluation has been aided in recent years by computerization, particularly 3D modelling, though is still challenging (Dominy et al, , 2000a(Dominy et al, , 2000b. A strong understanding of the geological controls of grade variation needs to accompany the resource estimation process.…”

Section: Introductionmentioning

confidence: 99%

“…Gold distribution in the quartz of the Gwynfynydd reefs is extremely erratic (Dominy et al, 1996(Dominy et al, , 2000a(Dominy et al, , 2000b. Localized rich pockets (sub-shoots), yielding up to 37 kg of gold, are sparsely distributed through the reef structures.…”

Section: Introduction To Gwynfynydd Minementioning

confidence: 99%

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The Occurrence of High-grade Gold Pockets in Quartz Reefs at the Gwynfynydd Mine, Wales, United Kingdom: A Geological Explanation for the Nugget Effect

Platten

Dominy

2001

Exploration and Mining Geology

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Gold-bearing quartz reefs commonly show extremely erratic and unpredictable grade variation, although gross geological continuity may be good. This type of variation is often described as being nuggety or having a high nugget effect and can be measured quantitatively using the semivariogram. Understanding of geological features such as reef texture and structure will provide improved models for the interpretation of assay data, drill core descriptions, etc. In this paper, a case study from the quartz-hosted gold occurrences in the Gwynfynydd mine, United Kingdom, is described. The work provides a starting point for models of lateral variation and demonstrates the types of structural and textural features that may be sought to give clues to the prediction of gold distribution in similar deposits.Gold deposition at Gwynfynydd is primarily associated with the reef footwall. The host veins form a discrete group of structures that may have been emplaced early in the sequence of quartz veins forming the reef. This potentially exposes them to a maximum number of dissection events during repeat dilations of the lode. Gold was deposited in the local porosity at extreme concentrations, equivalent to kg/t grades, when the host fissure had become filled with a porous framework of crystalline quartz and sulfides. Distribution of porosity varied laterally along the vein as the result of the formation of clump-like growths of minerals from the vein walls. The growth style is relevant to the distribution of gold although it may not be relevant to the occurrence of gold in a particular vein. The preservation of pores with some connectivity late in the vein fill sequence may be important in permitting continued but slow fluid flows. This facilitates effective fluid reaction with wall rock-derived methane, thus changing the relative rates of gold and quartz deposition in favor of gold.The textural studies explain the first-order control of nugget distribution at Gwynfynydd but do not allow for prediction and optimization of the resource estimation process. This is principally because of the very low geological continuity and poor predictability of the high-grade pockets. Nonetheless, the work does provide a clear geological explanation for the erratic nature of the gold. It indicates textures and structures that can be used to determine geological continuity of the goldbearing elements within the gross reef envelope.

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Using a Discrete Fracture Network and Spatial Point Processes to Populate Veins and Model Grade in a Coarse Gold Deposit

Mooney

Boisvert

2015

Nat Resour Res

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Estimation and Reporting of Mineral Resources for Coarse Gold-bearing Veins

Cited by 20 publications

References 6 publications

Approaches to reporting grade uncertainty in high nugget gold veins

Approaches to reporting grade uncertainty in high nugget gold veins

The Occurrence of High-grade Gold Pockets in Quartz Reefs at the Gwynfynydd Mine, Wales, United Kingdom: A Geological Explanation for the Nugget Effect

Using a Discrete Fracture Network and Spatial Point Processes to Populate Veins and Model Grade in a Coarse Gold Deposit

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