Morphological and compositional analysis of alluvial gold: The Fresnedoso gold placer (Spain)

Alves, Kelvin dos Santos; Sánchez, Santos Barrios; Barreiro, Juan Gómez; Palomares, Raúl Merinero; Prieto, José Manuel Compaña

doi:10.1016/j.oregeorev.2020.103489

Cited by 16 publications

(5 citation statements)

References 90 publications

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“…Grain size distribution in rocks usually follows a log-normal distribution [56,57,58,54]. Gold grain size distribution is expected to follow such law, a hypothesis that been verified in a few deposits by the author and other groups [55]. The current grain population approximates such distribution, with a log-average of 4.9 µm and a variation coefficient of 0.8.…”

Section: µMmentioning

confidence: 76%

Automated Gold Grain Counting. Part 1: Why Counts Matter!

Girard¹,

Trembaly²,

Néron³

et al. 2021

Preprint

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The quantitative and qualitative assessment of gold grains from samples of glacial till is a well-established method for exploring gold deposits hidden under glaciated cover. This method, widely used by the industry and which produced numerous successes in locating gold deposits in glaciated terrain, is still based on artisanal gravity separation techniques and visual identification. However, being artisanal, it is limited by inconsistent recoveries and the difficulty to visually identify the predominantly occurring small gold grains. These limitations hinder its capability to deceipher subtle or complex signal. To improve detection limits through recovery of small gold grains, a new approach has recently been introduced in the industry (commercially referred as “ARTGold” procedure) using an optimized miniature sluice box coupled with an automated scanning electron microscopy routine. The capabilities of this improved method are highlighted by comparing till surveys conducted around the Borden gold deposit (Ontario, Canada) using the conventional and improved methods at both local and regional scales. Relative to the conventional approach, the improved method recovered almost one order of magnitude more gold grains from samples (regional and down-ice mineralization), dominantly in small size fractions. Increasing the counts in low-abundance regional samples enables better discrimination between background signals and significant dispersions. The method offers an alternative to improve characterization of gold dispersal in glaciated terrain and the related gold deposit footprints.

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Section: µMmentioning

confidence: 76%

Automated Gold Grain Counting. Part 1: Why Counts Matter!

Girard¹,

Trembaly²,

Néron³

et al. 2021

Preprint

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show abstract

“…Studies of the morphology, chemical composition and mineral inclusions of gold grains have been widely used in gold exploration [28][29][30][31][32][33][34][35][36][37].…”

Section: Resultsmentioning

confidence: 99%

Typomorphic Features and Source of Native Gold from the Sykhoi Log Area Placer Deposits, Bodaibo Gold-Bearing District, Siberia, Russia

et al. 2023

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The Bodaibo gold-bearing district in the Lena gold province of Siberia is one of the largest and oldest placer gold-bearing provinces in the world. Approximately 1650 tons of gold has been extracted from the region. Precise studies on the source of these unique placer deposits are lacking and still controversial. Native gold from four different locations was gathered to investigate its morphology, chemical signatures, structure and inclusions. Some data on primary bedrock mineralization were obtained from the published literature. The linear weathering crusts developed along the zones of disjunctive dislocations near the Sukhoi Log gold deposit were researched. If they coincided with zones of low-grade veinlet-disseminated gold–quartz–sulphide mineralization with small gold grain sizes, a supergene replacement of primary mineralization was known to have occurred, accompanied by the formation of gold-rich rims and an increase in the size, content and purity of gold. Such mineralization associated with linear weathering crusts can be a source of local eluvial–proluvial placers, while placers of large valleys are formed due to low-sulphide gold–quartz lodes.

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“…About 40 km north of the torc cache, between the municipalities of Perales del Puerto and Moraleja (Cáceres), is the Fresnedoso stream, a paleoplacer‐type deposit resulting from the erosion of the surrounding reliefs (Santos et al . 2020; 2021a; 2021b). Somewhat closer, about 32 km away also to the north, exist the deposits of the Sierro de Coria (Coria, Cáceres), and again on the right bank of the Alagón river.…”

Section: The Torc: Description and Characteristicsmentioning

confidence: 99%

The Acehúche Gold Torc: Gold and Sacred Land on the Shores of the Tagus River (Cáceres, Western Spain)

Bravo¹,

Marcos

2023

Oxford J Archaeology

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This article describes the important discovery of a Late Bronze Age gold torc that was unearthed in a field of Acehúche (Cáceres, Spain). It was buried underneath some rocks at a site near a river crossing over the Tagus river. In its immediate vicinity, archaeological remains dating from the Copper Age to the Late Bronze Age have been found, which indicates the long use of this crossing. Until recently here, there existed a ferry and a chapel; and the place went by the toponym of the Dehesa de San Cristóbal. Legend too has it that the water from the river had curative properties. All of these components have maintained the sacred nature of the spot, otherwise transformed over the course of time, and reflect an earlier sacred landscape with quite ancient roots. THE TORC: DESCRIPTION AND CHARACTERISTICSThe Acehúche hoard consists of a plain bar torc of gold, given a deliberate ellipsoidal shape. The cross-section of the bar is circular: its maximum thickness is 10 mm in the central area, decreasing to 7 mm at the ends, whose very terminals are slightly sunken. It measures15.8 cm across

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Morphological and compositional analysis of alluvial gold: The Fresnedoso gold placer (Spain)

Cited by 16 publications

References 90 publications

Automated Gold Grain Counting. Part 1: Why Counts Matter!

Automated Gold Grain Counting. Part 1: Why Counts Matter!

Typomorphic Features and Source of Native Gold from the Sykhoi Log Area Placer Deposits, Bodaibo Gold-Bearing District, Siberia, Russia

The Acehúche Gold Torc: Gold and Sacred Land on the Shores of the Tagus River (Cáceres, Western Spain)

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