Criteria for Determining the Genesis of Placers and Their Different Sources Based on the Morphological Features of Placer Gold

Zinaida Nikiforova

doi:10.3390/min11040381

Abstract

Based on the identified typomorphic features of placer gold, a set of determined morphogenetic criteria is proposed to identify the genesis of placer gold content and different sources in the platform areas, which allow more correctly selecting search methods and improving the efficiency of forecasting ore and placer gold deposits. Gold particles larger than 0.25 mm with signs of wind-worn processing indicate the formation of autochthonous aeolian placers. Gold particles with signs of wind-worn processing with a size of 0.1–0.25 mm, forming an extensive halo of dispersion, indicate the formation of allochthonous placers in Quaternary deposits. Deflationary (autochthonous) placers of native gold can be found by the halo of its distribution of toroidal and spherical hollow forms, which, of course, are the search morphogenetic criterion of aeolian placers. The presence of disc-shaped and lamellar gold particles with ridgelike edges in alluvial placers is typical for placers of heterogeneous origin, formed due to deflation of proluvial placers. The discovery of pseudo-ore gold in alluvial placers indicates the arrival of gold from intermediate gold-bearing sources of different ages and not from primary sources, which is a morphogenetic criterion for determining different sources of the placer. In modern gold placers, the presence of gold of a pseudo-ore appearance can serve as a search criterion for the discovery of gold-bearing conglomerates with high gold content. The developed method for diagnosing the genotype of placer gold by its morphological characteristics (alluvial, aeolian, pseudo-ore) can be successfully used by industrial geological organizations to search and explore ore and placer gold deposits.

Highlights

In the east of the Siberian Platform, unusual toroidal and spherical hollow gold particles were first discovered in Mesozoic–Cenozoic deposits [1,2,3]
It turned out to be possible to understand and explain the origin of the filamentous gold and the formation of the shell, which many researchers took for clots of redeposited gold. This morphological feature is due to the continuous “bombardment” of the edges of the flakes with grains of sand so that the thinnest threads were stretched from the edges of the flakes, which, overlapping each other, formed a shell; The presence of carbonaceous matter in the cavities of gold particles has led some researchers to associate the genesis of the studied forms with chemogenic processes
Lamellar and tabular shapes are transformed to disc-shaped forms; The formation of brittle aggregates of growth of native gold with quartz, ilmenite, zircon and other minerals is quite possible under the influence of the lithostatic pressure of the overlying strata; The appearance of scar furrows on the surface and through holes in the native gold occurs when simulating the processes of the effect of lithostatic pressure and tectonic displacements

Summary

Introduction

In the east of the Siberian Platform, unusual toroidal and spherical hollow gold particles were first discovered in Mesozoic–Cenozoic deposits [1,2,3]. The term “toroidal” form of gold particles was first proposed by Yablokova [3] It most successfully reflects the essence of the form. The toroid is considered as a “bagel”, but without a through-hole This term was later adopted by many researchers who studied similar forms of placer gold. When studying the spherical shape, Izbekov [2] distinguished it as “spherical hollow gold”. Many researchers, when describing similar forms of placer gold, use mainly the term “spherical gold”; some of them distinguish spherical gold with “blebs“ [22]. Later, when studying the considered forms of placer gold, it was proposed to use the terms “toroidal” according to Yablokova [3] and “spherical hollow” gold according to Izbekov [2]

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Discussion

Conclusion