Integration of Detrital Gold Microchemistry, Heavy Mineral Distribution, and Sediment Geochemistry to Clarify Regional Metallogeny in Glaciated Terrains: Application in the Caledonides of Southeast Ireland

Moles, Norman; Chapman, Robert J.

doi:10.5382/econgeo.2019.4628

Cited by 18 publications

(17 citation statements)

References 27 publications

(36 reference statements)

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“…While ternary diagrams forms of curve generated by two distinct subpopulations where ranges are mutually exclusive (plot 1) and overlapping (plot 2). c: identification of distinct sub-populations using both alloy and inclusion data (adapted from Chapman et al 2000a, b, c) continue to be useful, spider diagrams ensure all data are presented, while clearly highlighting important aspects of inclusion mineralogy (Chapman et al 2017;Moles and Chapman 2019).…”

Section: Graphical Depiction Of Compositional Data Describing Populations Of Gold Particlesmentioning

confidence: 99%

“…Analysis of the primary alloy by EPMA involves selection of a site on the polished section chosen using the BSEimaging facility of the instrument and, consequently, the analysis of a site free from alloy heterogeneity or inclusions is assured. This approach results in high levels of reproducibility in the alloy analysis for Ag, either when samples are reanalyzed on a different EPMA system (e.g., Chapman et al 2000a), or when duplicate sample populations are collected and analyzed (Chapman et al 2000b;Moles and Chapman 2019). Conversely, spatial variation in the concentrations of minor, but measurable components such as Cu, Hg, and Pd, as revealed LA-ICP-(ToF)MS imaging (Fig.…”

Section: Analytical Proceduresmentioning

confidence: 99%

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Chemical and physical heterogeneity within native gold: implications for the design of gold particle studies

et al. 2021

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Studies of populations of gold particles are becoming increasingly common; however, interpretation of compositional data may not be straightforward. Natural gold is rarely homogenous. Alloy heterogeneity is present as microfabrics formed either during primary mineralization or by modification of pre-existing alloys by chemical and physical drivers during subsequent residence in either hypogene or surficial environments. In electron-probe-microanalysis (EPMA)-based studies, the combination of Cu, Hg, and Pd values and mineral inclusion suites may be diagnostic for source style of mineralization, but Ag alone is rarely sufficient. Gold characterization studies by laser-ablation-ICP mass spectrometry linked to both quadrupole and Time-of-Flight (ToF-MS) systems show that only Ag, Cu, and Hg form homogenous alloys with Au sufficiently often to act as generic discriminants. Where present, other elements are commonly distributed highly heterogeneously at the micron or submicron scale, either as mineral inclusions or in highly localized, but low concentrations. Drawing upon our own data derived from individual inspection and analyses of approximately 40,000 gold particles from 526 placer and in situ localities worldwide, we show that adequate characterization of gold from a specific locality normally requires study of a minimum of 150 particles via a two-stage approach comprising spatial characterization of compositional heterogeneity, plus crystallographic orientation mapping, that informs subsequent targeted acquisition of quantitative compositional data by EPMA and/or laser-ablation ICP-MS methods. Such data provide the platform to review current understanding of the genesis of gold particle characteristics, elevating future compositional studies from empirical descriptions to process-focused interpretations.

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Section: Graphical Depiction Of Compositional Data Describing Populations Of Gold Particlesmentioning

confidence: 99%

Section: Analytical Proceduresmentioning

confidence: 99%

Chemical and physical heterogeneity within native gold: implications for the design of gold particle studies

et al. 2021

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“…It is important to emphasize that metal finds of this size are very rare for placers in eastern Siberia, which is typically dominated by very small (−0.25 mm) gold grains, representing more than 95% [36]. Morphological features of native gold, such as a low ratio of roundness and a primary tubercular and dimpled surface, indicate its short stay in hydrodynamic environments and short-range water drift [37]. It should be noted that the studied gold of all grades was of a low roundness.…”

Section: Discussionmentioning

confidence: 99%

“…According to the researchers in [3,37], mineral inclusions in gold can serve as indicators to predict placer gold ore bodies. Mineral micro-inclusions of pyrrhotite, pyrite, hessite, chalcopyrite, sphalerite, arsenopyrite, quartz, and potash feldspar were identified in the placer gold using X-ray spectroscopic microanalysis.…”

Section: Discussionmentioning

confidence: 99%

Typomorphic Features of Placer Gold from the Billyakh Tectonic Melange Zone of the Anabar Shield and Its Potential Ore Sources (Northeastern Siberian Platform)

2020

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Precambrian shields and outcropped Precambrian rock complexes in the Arctic may serve as the most important sources of various types of mineral raw materials, including gold. The gold potential of the Anabar shield in the territory of Siberia has, thus far, been poorly studied. A number of primary and placer gold occurrences have been discovered there, but criteria for the prediction of and search for gold mineralization remain unclear. The main purpose of this paper was to study the typomorphic features of placer gold in the central part of the Billyakh tectonic mélange zone in the Anabar shield and to compare them to mineralization from primary sources. To achieve this, we utilized common methods for mineralogical, petrographic, and mineragraphic analyses. Additionally, geochemical data were used. As a result of this investigation, important prospecting guides were identified, and essential criteria for the prediction of and search for gold deposits were elucidated. The characteristics of the studied placer gold were specific for gold derived from a proximal provenance. These characteristics included the poor roundness of the native gold grains, a cloddy–angular and dendritic form, an uneven surface, and a high content of coarse-fraction native gold (0.5–2 mm), which was as high as 24% of the volume of analyzed native gold. In addition, we conducted a study on the mineralogical features of the gold-sulfide mineralization that was disseminated throughout a small exposure area of paleo-Proterozoic para- and orthogneisses in the Anabar shield basement. A comparison of mineral inclusions in the coarse-fraction native gold and mineral assemblages in the ore deposits showed that one of the possible primary sources for placer gold might be small bodies of metasomatically altered orthogneisses associated with large granitoid plutons.

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“…The reproducibility of such data has already been evidenced (Chapman et al, 2000b(Chapman et al, , 2010aMoles and Chapman, 2019) by resampling several aliquots at a given location but at different time (sometimes several years later). The obtained CDFs of the Ag content of these gold samples yield similar pattern, highlighting that (1) a gold sample can be considered as a representative aliquot of a population and (2) that results are reproducible.…”

Section: J O U R N a L P R E -P R O O F 21mentioning

confidence: 94%

Challenging the traceability of natural gold by combining geochemical methods: French Guiana example

Pochon

Desaulty

Bailly

et al. 2021

Applied Geochemistry

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Integration of Detrital Gold Microchemistry, Heavy Mineral Distribution, and Sediment Geochemistry to Clarify Regional Metallogeny in Glaciated Terrains: Application in the Caledonides of Southeast Ireland

Cited by 18 publications

References 27 publications

Chemical and physical heterogeneity within native gold: implications for the design of gold particle studies

Chemical and physical heterogeneity within native gold: implications for the design of gold particle studies

Typomorphic Features of Placer Gold from the Billyakh Tectonic Melange Zone of the Anabar Shield and Its Potential Ore Sources (Northeastern Siberian Platform)

Challenging the traceability of natural gold by combining geochemical methods: French Guiana example

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