General considerations of sampling and assaying in a coarse gold environment

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

doi:10.1179/aes.2000.109.3.145

Cited by 31 publications

(59 citation statements)

References 10 publications

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“…These findings validate the use of large volume samples, 50 kg to 100 kg face samples and 30 t bulk development rounds, in grade control and evaluation methods at the mine (Dominy et al, 2000b(Dominy et al, , 2000c(Dominy et al, , 2001a. They also provide a clear geological explanation for the erratic nature of the gold.…”

Section: Applications In Resource Estimationsupporting

confidence: 70%

“…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: 98%

“…It is particularly problematic when dealing with coarse goldbearing material (Dominy et al, 2000c). In some instances, the SNE is the sole component of the total nugget effect and is nothing else than a reflection of the fundamental error or the short-range heterogeneity fluctuation error (Gy, 1982).…”

Section: The Role Of Geological Understanding During Resource Estimationmentioning

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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Section: Applications In Resource Estimationsupporting

confidence: 70%

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

confidence: 98%

Section: The Role Of Geological Understanding During Resource Estimationmentioning

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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“…There is generally a need for much larger field and sub-samples, and special preparation and assay methods (Dominy et al, 2000a(Dominy et al, , 2000b(Dominy et al, , 2001a(Dominy et al, , 2001b(Dominy et al, , 2003bRoberts et al, 2003). Within this style of mineralization, the application of bulk sampling has on numerous occasions showed its worth in providing a good estimate of likely mineable grade (Dominy et al, 2001a;Roberts et al, 2003;Johansen et al, 2003).…”

Section: Quality Assurance/quality Controlmentioning

confidence: 98%

Author's Reply to "Comments on Classification and Reporting of Mineral Resources for High-Nugget Effect Gold Vein Deposits," by M. Vallee

Dominy

2002

Exploration and Mining Geology

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“…primary gold-silver deposit. An outstanding characteristics possessed by almost of primary gold deposits is the presence of coarse gold grains which were randomly distributed (Dominy, 2000). This characteristic caused the erratic distribution for gold grade and abnormal distribution (high skewness).…”

Section: Introductionmentioning

confidence: 99%

Fractal Model and Classical Block Model in Ore Reserve Estimation: A Comparison

Prasetyo¹

2010

J.Ris.Geo.Tam

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The characteristic possessed by many gold deposits is the erratic distribution for gold grade and abnormal distribution (high skewness) which would restrain the application of certain estimation methods especially geostatistics. Another method proposed in order to handle high skewness distribution is fractal model. In this paper one of the models, the number-size model would be compared with block model in estimating ore tonnage and metal (Au-Ag) tonnage for deposit with complex and erratic data distribution. For this purpose, the data obtained from channel sampling program in Ciurug vein, block South 3, level 500 and 600, Pongkor mines would be used as study case. The results show that the number-size fractal model so far could be applied only to the deposits with continuous dimension and grade distribution. For deposits with erratic grade distribution the fractal model has only limited use, which powerful generally to estimate bulk volume or ore tonnage since the dimension i.e. thickness has relatively high continuity.Keywords: Fractal, number-size model, reserve estimation, Au-Ag, Pongkor

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General considerations of sampling and assaying in a coarse gold environment

Cited by 31 publications

References 10 publications

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

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

Author's Reply to "Comments on Classification and Reporting of Mineral Resources for High-Nugget Effect Gold Vein Deposits," by M. Vallee

Fractal Model and Classical Block Model in Ore Reserve Estimation: A Comparison

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