Alluvial Gold Deposits Research Articles

Chapter 25 Gold deposits of Myanmar

This chapter presents a brief review of the gold deposits and occurrences in Myanmar and, where known, their resources. Many of these deposits are currently being or have recently been exploited, mostly on a small scale by licensed mining concerns. The smaller mining operations tend to be under-capitalized and hence geological data on the deposits being exploited are limited. In this sense the gold deposits in Myanmar remain underexplored and underdeveloped, but retain considerable future potential. Some of the gold deposits have been known for many years, and their earlier histories are mentioned in reviews by Chhibber (1934), Goossens (1978) and Bender (1983). More recent studies, including descriptions of individual deposits, can be found in Khin Zaw et al. (1993, 1999 a , b , 2014), Khin Zaw & Rice (1994), Mitchell et al. (1999, 2004), Ye Myint Swe et al. (2004 a , b ), Cho Cho Aye et al. (2007), Khin Zaw (2008), Cho Cho Aye & Ye Myint Swe (2014) and Tin Aung Myint et al. (2014). The main tectonic divisions of Myanmar and geological units containing gold deposits are shown in Figure 25.1, including an index of the gold deposits and prospects described in this chapter. Details of the primary gold deposits are summarized in Tables 25.1, 25.2, 25.3, 25.4, 25.5, 25.6. Other potentially significant hard-rock gold deposits are shown in Figure 25.2, and the distribution of some alluvial gold deposits is shown in Figure 25.3. Fig. 25.1. Major tectonic belts and location of major gold deposits and prospects in Myanmar (compiled after Mitchell et al. 1999; Khin Zaw et al. 1999 a , b , 2014, 2015; Ye Myint Swe et al. 2004 a , b ). Fig. 25.2. Locations …

A multi-analytical approach to gold in Ancient Egypt: Studies on provenance and corrosion

Recent results from a three-year multi-disciplinary project on Ancient Egyptian gold jewellery revealed that items of jewellery from the Middle Kingdom to the New Kingdom were manufactured using a variety of alluvial gold alloys. These alloys cover a wide range of colours and the majority contain Platinum Group Elements inclusions. However, in all the gold foils analysed, these inclusions were found to be absent. In this work a selection of gilded wood and leather items and gold foil fragments, all from the excavations by John Garstang at Abydos (primarily from Middle Kingdom graves), were examined using Scanning Electron Microscopy-Energy Disperse Spectroscopy (SEM-EDS), X-Ray Fluorescence (μXRF), Particle Induced X-Ray Emission (µPIXE) and Double Dispersive X-Ray Fluorescence (D2XRF). The work allowed us to characterise the composition of the base-alloys and also to reveal the presence of Pt at trace levels, confirming the use of alluvial gold deposits. Corrosion products were also investigated in the foils where surface tarnish was visually observed. Results showed that the differences in the colour of corrosion observed for the foils are related not only to the thickness of the corrosion layer but also to a multi-layer structure containing the various corrosion products.

Chinese Gold Miners and the "Chinese Question" in Nineteenth-Century California and Victoria

During the second half of the nineteenth century the largest gold deposits yet known in the world were discovered in the American West, Australasia, South Africa, and western Canada. From 1848 to 1891 a series of gold rushes—quick, short-term bonanzas (or failures) for individual miners—swept those regions, drawing hundreds of thousands of gold seekers from around the world. In fewer than fifty years miners and mining companies extracted from the earth some 435 million ounces of gold—more than the total that had been mined in the previous three thousand years. The sudden increase in world gold production in the late nineteenth century was produced by Anglo-American settler colonialism and capitalist development. Since ancient times gold has been valued for its beauty and purity. Indigenous populations on the settler-colonial frontiers were long aware of alluvial gold deposits in their midst, but they did not value gold as a money commodity. Thus, gold rushes furthered the dispossession of native peoples and transformed the Pacific worlds where gold was discovered, as well as the global economy. Sustained exploration and extraction required capital investment, deep-mining technology, mass labor migration, and long-distance transportation. Such activity accelerated the economic development of the gold-mining regions and strengthened the international financial power of Great Britain and the United States as creditor and investor nations.1

"Creating" Rural Informality: The Case of Artisanal Gold Mining in Sub-Saharan Africa

This paper offers a new perspective on the origin of informal artisanal and small-scale mining (ASM)—the low-tech, labor-intensive extraction and processing of mainly near-surface hard rock and alluvial gold deposits—in rural sub-Saharan Africa. It argues that the conditions that have fueled the sector’s recent rapid growth were brought about by policy changes made by host governments, multilateral organizations, and bilateral agencies. Over the past three decades, these actors have worked in partnership to promote industrial large-scale mineral exploration and excavation activity through increased foreign direct investment, and have simultaneously implemented regulatory frameworks for ASM industries. Previous scholarship has focused on the ASM sector’s sizable environmental footprint, including extensive land degradation and mercury pollution; the sector’s appalling health and safety record; and the many social ills commonly associated with communities where production takes place, such as prostitution and narcotics consumption. This paper will broaden understanding of the sector’s origins through a case study of Ghana’s informal mining economy.

Solution and laser ablationMC-ICP-MS lead isotope analysis of gold

A new approach is presented for the analysis of lead isotopes in gold using solution and laser ablation multi-collector inductively-coupled plasma mass-spectrometry (MC-ICP-MS). Repeat analyses of two gold reference materials (RAuGP3: 34.1 ± 0.5 ppm Pb and RAuGP5: 129 ± 4 ppm Pb, from SPEX CertiPrep Ltd) yield an external reproducibility of 20. Instrumental mass bias is corrected by standard sample bracketing, using NIST SRM981 for solution analyses and NIST SRM610 for laser ablation analyses. Both techniques agree within error, and they have been further demonstrated through the analyses of both geological and archaeological samples: multiple grains from two Irish alluvial gold deposits and samples of two Early Bronze Age Irish gold lunulae. The applicability of these techniques to studies concerning the sources and age of gold mineralisation, and the identification of gold sources exploited in antiquity, is highlighted.

3‐D tomographic seismic inversion of a paleochannel system in central New South Wales, Australia

Buried paleochannels are of significant interest for understanding hydrological mechanisms and their potential as alluvial gold deposits. Seismic tomographic methods are a suitable solution for resolving the vertical and horizontal structure of such features. We assess a method for seismic 3‐D tomographic inversion from refraction arrivals with reflection control over a suspected paleochannel adjacent to the Wyalong gold fields in the Lachlan fold belt of central New South Wales, Australia. A standard multichannel engineering seismic recording and cable–receiver system was used on a 3‐D field geometry of multiple linear arrays. More than 3000 P‐wave first‐arrival traveltime values were inverted using a regularized inversion scheme for which simplified 2‐D models served as initial velocity–depth models for the complete 3‐D inversion. Seismic reflection arrivals provided additional depth estimates to the bedrock and compensated for a lack of refraction phases at that depth. Correlating the 3‐D seismic velocity–depth data with existing drillhole and nonseismic geophysical data resulted in a detailed structural and compositional interpretation of the paleochannel and the incised regolith. The model suggests the presence of a system of deposits from meandering channels overlying a metasedimentary bedrock formation. The general paleodrainage deposit is relatively conductive in electromagnetic surveys, indicating a potential saline storage or transport mechanism.

Cratons and orogenic belts of the Brazilian Shield and their contained gold deposits

The Brazilian Shield extends over much of South America to the east of the Andean Chain, and is partly covered by Phanerozoic sedimentary rocks. The three major tectonic units (older than 900 Ma) of the shield are the Amazon, Sao Francisco, and Rio de la Plata Cratons, whereas rocks of the Neoproterozoic (900–550 Ma) Brasiliano Cycle belts surround the cratons in the eastern half of Brazil. Paleoarchean rocks occur as small cratonic nuclei in northeastern Brazil, but the cratons contain voluminous 3.0–2.6-Ga granitic and greenstone belts and a large volume of Paleoproterozoic rocks. Late Mesoproterozoic belts (~1.2 Ga) occur in the western and northwestern Amazon Craton and possibly in northeastern Brazil. There are voluminous Paleoproterozoic and Mesoproterozoic intrusive and volcanic rocks in the Amazon Craton. Belts of reworked crust are common, but the Amazon Craton grew to the north and west mainly during accretionary orogens. The Neoproterozoic Brasiliano Cycle belts contain 5% of juvenile crust in central and southern Brazil, but are dominantly derived from reworking of older crust. It is possible that the cratons were continuous in a super-continent during the Mesoproterozoic prior to the Brasiliano Cycle. Gold deposits are concentrated in the Archean and Paleoproterozoic terranes, including the Carajas and Quadrilatero Ferrifero gold provinces of the Amazon and Sao Francisco Cratons, respectively, but some also occur in younger terranes. Recent alluvial gold deposits and supergene deposits in the weathering zone are widespread in Brazil.

Tertiary and Quaternary alluvial gold deposits of Northwest Spain and Roman mining (NW of Duero and Bierzo Basins)

During the 1st and 2nd centuries AD, more than 500 gold mines were operating in the northwest (NW) of Spain. The region was then a part of the Roman Empire and known as Iberia. Corresponding excavations totaled 600million cubic meters (Mm3), with about 300Mm3 coming from alluvial mines. Miocene sediments (mainly alluvial fans) derived from the Cantabrian Mountain and León Mountain uplifts, and Quaternary deposits (principally regolith, fluvial terraces, moraines and fluvio-glacial fans) were exploited by the Roman miners, using hydraulic mining methods.The paper attempts to incorporate the following numerous themes. (a) The time-successive, global relationship of the auriferous deposits. (b) A brief geological overview of the Miocene and Quaternary placers in the NW Spain. (c) A description of the composition of the gold grains, both in the hardrock source and in the various alluvial placers. The latter is necessary to determine possible source areas. Pre-Miocene age of gold precipitation helps to understand the possible recycling processes. (d) The size, grade and gold grain size distribution of the studied deposits. (e) A brief description of Roman mining methods, including new viewpoints on how the operations were conducted. Special reference will be made to the Las Médulas mine (included in the World Heritage List in, the largest earth movement mining operation in Iberia up until the 20th century. (f) An update on earth moving techniques and gold recovery in Roman times.The present work draws heavily on data collected from some 6500m3 of alluvium washed from 300 trenches and drill holes on Miocene and Quaternary deposits, and the Las Médulas Archaeological Zone project.

Mercury Exposure and Murine Response to Plasmodium Yoelii Infection and Immunization

Malaria has re-emerged in Amazonia over the past two decades. Many factors have been proposed for this, among them changes in population distribution, failures of vector control and pharmacologic management, and local as well as global environmental changes. Among the latter factors, we have studied the potential role of increasing exposures to the immunotoxic metal mercury, which is widely used in Amazonia for artisanal extraction of alluvial gold deposits. We report here that Hg impairs host resistance to malaria infection at exo-erythrocytic stages. Hg exposed mice have higher parasitemia following infection with sporozoites, but not after transfusion of infected red cells. In mice inoculated with irradiated sporozoites, Hg blocks acquisition of immunity. In addition Hg affects immunologic parameters that are known to be involved in host response to malaria infection. These results have potential implications for the incidence and prevalence of malaria among populations exposed to mercury from artisanal goldmining and consumption of contaminated fish regions with high rates of malaria and other infectious diseases.

EPMA characterisation and geochemistry of gold deposits of Peninsular Malaysia- genetic implications

The highly automated electronprobe microanalyzer (EPMA) was used as a tool to characterise gold from the Raub-Tersang-Selinsing-Penjom, Rusila-Lubuk Mandi, and Jeli-Sokor areas in Peninsular Malaysia with the aim of characterising the various primary and alluvial gold deposits and tracing the alluvial gold grains to their primary sources. Gold from quartz-veins and their associated country rocks were sampled and studied in terms of . their morphology, size, inclusions, associated minerals and geochemistry. Alluvial gold and tailings in the surrounding areas were also sampled to study their association with the primary occurrences. The common mineral associated with gold in the quartz veins in all the areas sampled is pyrite. At Bukit Koman monazite was also found together with arsenopyrite and a Cu-Sb-S mineral in the gold veins. At TRA Mining, Selinsing, arsenopyrite together with a Pb-Fe-As-S mineral are associated with gold. At Specific Resources, Penjom, there is galena, chalcopyrite, sphalerite together with silver in the gold veins. At the limestone quarry at Kechau, galena is associated with chalcocite (Cu 2 S), and Cu-Sb- S and Cu-Zn-Sb-S minerals. - In Terengganu, at Rusila it was demonstrated that alluvial gold grain sizes nearest to the primary gold veins average 3.05 mm long and 2.5 mm wide while those furthest away tend to average to about 0.81 mm long and 0.7 mm wide. On the whole grains which are longer than 1 mm tend to be prismoidal in shape while those less than 1 mm are generally spherical. In the Raub-Tersang-Selinsing-Penjom area in P ahang, the alluvial samples from Sg. Ulu Tersang, a river in SE Selinsing and Sg. Terenggun and tailings samples from Kg. Pulai (Tersang) and NW Penjom generally show a bimodal distribution with dominant lengths averaging 0.4 mm for the major distribution and 1.0 mm for the minor. In Kelantan the-dominating sphericity of the alluvial samples collected in the Jeli area is prismoidal, and this differs from the samples in the Sokor area which have sphericity that ranges from subdiscoidal to discoidal. Gold grain size studies show that the samples from Sokor are fine grained which range from 0.1-0.3 mm for the lengths and the widths of the samples collected from Sg. Tui and Sg. Sokor, whereas the grain size of the samples from Jeli are bigger with an average length of 0.7 mm for samples from Sg. Pergau and an average particle size of 0.8 mm long and 0.4 mm wide for samples from Sg. Tadoh. In Terengganu, at Rusila the average Au content is 90.30% and silver is 10.46% for the gold from the veins (a fineness of 896.1889) while the alluvial gold average 88.52% Au and 10.32% Ag (a fineness of 895.5889). In Pahang, Primary gold at Bukit Koman, Raub has a fineness of 956.679, at TRA Mining, Selinsing the fineness is 881.7301, at Specific Resources, Penjom the fineness is 903.7245 and at the limestone quarry at Kechau, the fineness is 951.1200. The alluvial gold at Bukit Koman has a fineness of 982.8318, at a river in SE Selinsing the fineness is 930.9519 at Sg. Ulu Tersang the fineness is 944.0056 and at Sg. Terenggun (NW of Penjom) the fineness is 924.4767. The tailings at Kg. Pulai, Tersang show fineness of 976.5234 and those at NW Specific Resources have fineness of 891.8836. In Kelantan, EPMA studies show that the geochemistry ofthe gold grains are different for the 2 main areas. In the Jeli area, the 3 areas sampled in Sg. Pergau show average fineness of 922.9157, while the 2 areas in Sg. Tadoh average 923.7250. In the Sokor area, the fineness values are less than 900.000 and the average fineness values show a larger spread, the 2 areas in Sg. Tui average 845.1322, whereas the 2 areas in Sg. Sokor average 894.0914. Geochemical EPMA analysis of the gold grains revealed that silver is present in the gold in different amounts from different areas. It can be demonstrated that fineness is a useful character for tracing the primary sources of gold from the panned alluvial gold samples further downstream_ Preliminary results

Gold Deposits of Southern Ecuador

Research Article| October 01, 1992 Gold Deposits of Southern Ecuador Ilmars Gemuts; Ilmars Gemuts (SEG 1976) 1Consultant, Annapurna Exploration, Denver, CO, USA Search for other works by this author on: GSW Google Scholar Guillermo Lopez; Guillermo Lopez 2Prominex S.A. Quito, Ecuador Search for other works by this author on: GSW Google Scholar Franklin Jimenez Franklin Jimenez (SEG 1992) 2Prominex S.A. Quito, Ecuador Search for other works by this author on: GSW Google Scholar SEG Discovery (1992) (11): 1–16. https://doi.org/10.5382/SEGnews.1992-11.fea Article history first online: 27 Sep 2021 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation Ilmars Gemuts, Guillermo Lopez, Franklin Jimenez; Gold Deposits of Southern Ecuador. SEG Discovery 1992;; (11): 1–16. doi: https://doi.org/10.5382/SEGnews.1992-11.fea Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietySEG Discovery Search Advanced Search Ecuador is a prosperous tropical democratic country, about the size of Nevada (Fig. 1), led by architect Sixto Duran, who was elected President in July 1992. A new mining law was passed in 1991 and, although regulations are pending, foreign investment is welcomed. The gold mining tradition began in 1549 with the Portovelo mine, and many small silver and gold veins and alluvial gold deposits were subsequently exploited. Increasing gold prices spurred development of new precious metal properties in the 1980s, including the now-famous Nambija and the lesser-known Chinapintza, Bella Rica, La Playa, and Atlanta districts (... First Page Preview Close Modal You do not currently have access to this article.

Near‐surface secondary gold mobility and grain‐size enhancement, Barewood Mine, east Otago, New Zealand

Abstract Primary gold at Barewood, east Otago, New Zealand, occurs in quartz veins in the Otago Schist. The gold typically occurs as 1–3 pm grains enclosed in arsenopyrite, pyrite, or chalcopyrite. Secondary gold mobility occurred during formation of a zone of kaolinitisation (up to 20 m deep) in the Otago Schist immediately beneath an early Tertiary unconformity. Oxidation of the sulphides released the gold and allowed local migration, possibly as thiosulphate or reduced sulphur complexes. Silver was slightly more soluble than gold, and secondary gold has higher atomic fineness (930) than primary gold (870). Secondary gold is coarse grained (up to 1 mm), and was deposited in fractures, shears, and cavities in quartz veins and associated sheared schist. The secondary gold was precipitated with goethite and kaolinite, and locally with scorodite and/or pharmacosiderite. Dissolution, migration, and redeposition of gold is due to fluid composition evolution from local moderately reduced, sulphur rich, acid conditions at the site of decomposition of sulphides, to highly oxidised neutral pH conditions which prevailed elsewhere. There is no evidence for enrichment of gold in the alteration zone. Grain‐size enhancement of gold by secondary migration near the unconformity was important for formation of alluvial gold deposits in Otago when the unconformity was uplifted and eroded in the late Tertiary.

AS MINERALIZAÇÕES AURÍFERAS DA REGIÃO DE MARA ROSA (GO)

ln Mara Rosa region there is a number of gold mineralized areas that are being mined by prospectors. The main purpose of this work is to describe each mineralized area in order to define types and controls of gold mineralization. A generalized model for gold metallogenesis in the area is also proposed. The stratigraphy of the area comprises: Mara Rosa Supracrustals and Granite-Gneiss Complex, both of Archean to Early Proterozoic Age; Tertiary/Quaternary Lateritic Cover; and Quaternary Alluvial Deposits. Nine of the 14 gold occurrences studied are stratabound and occur in Mara Rosa Supracrustals; two are vein and pipe like quartz bodies in Mara Rosa Supracrustals and Granite-Gneiss Complex; and three are alluvial gold deposits overlying Mara Rosa Supracrustals. Although gold placer deposits have not been studied here, they have been mined in the area. It is proposed that syngenetic and low-grade gold mineralization are associated with interflow graphitic sediments, intermediate tuffs, and chert belonging to Mara Rosa Supracrustals. Folding and metamorphism resulted in local enrichments inside these source beds originating stratabound gold mineralization. Epigenetic and structurally controlled vein and pipe like ore bodies originated at least in part by remobilization of pre-existing singenetic mineralization. Elluvial gold mineralization was originated by weathering of weakly mineralized Mara Rosa Supracrustals rocks, whereas alluvial placer deposits were originated by reworking of all three pre-existing mineralization types.The studied area illustrates the permanence of gold mineralization in a given area by successive reworking of an early gold concentration both by endogenous and exogenic processes. ln fact, a NNE trending belt contains most of known gold mineralization of the area.

Effects of biological systems on metallic gold

Effects of biological systems on metallic gold

Geochemical and morphological characteristics of gold particles from recent river deposits and the fossil placers of the Witwatersrand

A relationship has been established between morphological features and fineness of gold particles and the distance over which they have been transported in recent alluvial placer deposits, such as the rivers of the Barberton Mountain Land, South Africa and the river Rhine in Germany. It was possible to show that most gold particles from the Witwatersrand conglomerates retained their detrital morphology and by comparing them with particles from recent alluvial gold deposits it was possible to estimate the distance of transport for the Witwatersrand gold, which in most cases ranged from 10 km to 30 km. Gold particles in recent placers show a characteristic increase in fineness with increasing distance of transport because of the leaching of the silver from them. The Witwatersrand gold particles on the other hand, have retained their primary fineness, because leaching of silver in the oxygen-deficient Precambrian atmosphere was not feasible chemically.

Fiscal Policy and Royal Sovereignty in Minas Gerais: The Capitation Tax of 1735

A study of the capitation tax of 1735 in Minas Gerais is interesting since it illustrates the way in which the Crown of Portugal succeeded in enforcing its will through the machinery of colonial administration in a newly incorporated, frontier society. It also tells something about the men of that administration and the political process in which they were involved.The collection of the tax on mineral wealth known as the quinto was one of the most enduring problems confronting Crown officials in Brazil during the eighteenth century. The king permitted his subjects to mine precious metals in his dominions in return for the payment of one fifth of the annual production. Rich alluvial gold deposits discovered in the closing years of the seventeenth century, lay beyond the territory effectively controlled by the governors of the littoral captaincies. Hidden in the shadows of Sabarabuçú, the shining mountain of Indian legends, the isolation of the mines and the tenuous control of the region by the royal administration made collection of the tax haphazard. As the eighteenth century progressed, the production of the gold mines increased, however the king's share failed to grow accordingly. The need for added revenue and the realization that the full amount due the Crown was not arriving at the customs house in Lisbon convinced the king that payment of the quinto should be rigorously enforced.

Mercury in some granitoid rocks of the yukon and its relation to gold-tungsten mineralization

Data for the mean mercury contents of some granitoid rocks of the Yukon are presented. A correlation of high mercury content with plutons postulated to be the sources, or genetically related to the sources, of the alluvial gold deposits of the McQuesten area is established. In addition a relation is indicated between high mercury content in one intrusion and high content in the Palaeozoic shale host rock. A limited amount of data is presented on the mercury content of the Proterozoic and Palaeozoic rocks of the sampled area.

Alluvial Gold Dredging in the Gold Coast Colony

AN interesting account is given in the G.E.C. Journal of February of the electrical equipment for the Bremang Gold Dredging Co., Ltd. This company dredges for alluvial gold on the Ankobra River, one of the larger rivers of the Gold Coast Colony, which flows roughly north and south and pours itself into the Gulf of Guinea. Many of the shallows of the river are sufficiently rich in alluvial gold deposits to warrant commercial development, and the Bremang Gold Dredging Co., Ltd., has installed equipment at two of these points for dredging mud and gravel from the river bed from which the gold is recovered. The dredges are electrically operated and are supplied from individual substations fed by a 55 kv. overhead transmission line from the power station of Ankobra Junction, a distance of about twenty miles.

The Mineral Wealth of Alaska

RECENT developments have shown that Alaska as a mining field stands in the front rank among the possessions of the United States. Its annual gold production represents a value of some 1,600,000l. It produces silver, copper, and coal in considerable quantities, and its recently discovered tin and petroleum deposits are of great promise. During the past year the investigation of the mineral resources of Alaska has been energetically carried on by the United States Geological Survey under adverse conditions, and the Bulletins (Nos. 259, 250, and 236) recently published by Mr. A. H. Brooks, Mr. G. C. Martin, and Mr. C. W. Wright afford striking evidence of the excellent work that is being done in this direction by officers of the survey. Attention has naturally been directed chiefly to the gold placers. The placers of the Seward Peninsula, a field embracing an area of 20,000 square miles, still hold the first place in gold production in Alaska. Seven distinct types of alluvial gold deposits are met with in Alaska:—