This document summarizes research characterizing gold in the Jinya Carlin-type gold deposit in China. Key findings include:
1) The majority (77%) of gold occurs as submicroscopic solid solution gold within arsenopyrite, with lesser amounts (16%) in arsenic-rich pyrite. Native gold accounts for 6% of gold.
2) Arsenopyritization and pyritization can be used as indicators for further exploration in the deposit district. However, the gold in sulfides is not amenable to direct cyanidation and requires pretreatment to recover.
3) A comprehensive study using various microscopy and analytical techniques was used to independently quantify each gold carrier and determine the
Gold is a transitional metal. In its purest form have reddish yellow color, soft, malleable, and ductile metal.
Atomic number : 79
Atomic mass : 196.9 u
Density : 19.32 g/cm3
Melting point : 1,064 °C
Boiling point : 2,700 °C
Founded in different form associated with different rock type in different tectonic setting.
Discovered from earlier time and used for multi purposes.
Formation of gold
The saying among prospectors that "gold is where you find it" suggests its occurrence is unpredictable, but there is some certain geological environments for the formation.
Because gold is very stable over a range of conditions, it is very widespread in the earth’s crust.
Gold dissolved in warm to hot salty water, the fluids are generated in huge volumes deep in the Earth’s crust as water-bearing minerals dehydrate during metamorphism.
Any gold present in the rocks being heated and squeezed is sweated out and goes into solution as complex ions.
In this form, dissolved gold, along with other elements such as silicon, iron and sulphur, migrates wherever fractures in the rocks allow the fluids to pass.
The direction is generally upwards, to cooler regions at lower pressures nearer the Earth’s surface.
Gold eventually becomes insoluble and begins to crystallize, most often enveloped by quartz.
The association of gold and quartz vein forms one of the most common types of "primary gold deposits".
India
In India, gold mineralization of economic importance is mainly restricted to Archean greenstone terranes of the Dharwar Craton (DC).
The eastern block of the DC has a high favorability for hosting major gold deposits such as Kolar, Hutti, and Ramagiri, whereas the western block hosts only a few smaller deposits such as Gadag, Ajjahanahalli, and Kempinkote.
Gold also discoverrd by GSI in the Singbhum Craton, Aravalli Craton, Bastar Craton and Southern Granulite Terrain (SGT).
India is the second-largest consumer of gold after China.
India currently holds about 558 tones of gold, representing 6.6% of its reserves, (World Gold Council, October 2016).
Kolar Gold Field, Hutti Gold Field and Ramgiri Gold Field are the most important gold fields.
Gold Demand and Use
The largest source of demand is the jewelry industry Gold’s workability, unique beauty, and universal appeal make this rare precious metal the favorite of jewelers all over the world.
Besides jewelry, gold has many applications in a variety of industries including aerospace, medicine, dentistry, and electronics for the manufacture of computers, telephones, televisions...
The third source of gold demand is governments and central banks that buy gold to increase their official reserves.
Private investors there are private investors. Depending upon market circumstances, the investment component of demand can vary substantially from year to year.
Gold is a transitional metal. In its purest form have reddish yellow color, soft, malleable, and ductile metal.
Atomic number : 79
Atomic mass : 196.9 u
Density : 19.32 g/cm3
Melting point : 1,064 °C
Boiling point : 2,700 °C
Founded in different form associated with different rock type in different tectonic setting.
Discovered from earlier time and used for multi purposes.
Formation of gold
The saying among prospectors that "gold is where you find it" suggests its occurrence is unpredictable, but there is some certain geological environments for the formation.
Because gold is very stable over a range of conditions, it is very widespread in the earth’s crust.
Gold dissolved in warm to hot salty water, the fluids are generated in huge volumes deep in the Earth’s crust as water-bearing minerals dehydrate during metamorphism.
Any gold present in the rocks being heated and squeezed is sweated out and goes into solution as complex ions.
In this form, dissolved gold, along with other elements such as silicon, iron and sulphur, migrates wherever fractures in the rocks allow the fluids to pass.
The direction is generally upwards, to cooler regions at lower pressures nearer the Earth’s surface.
Gold eventually becomes insoluble and begins to crystallize, most often enveloped by quartz.
The association of gold and quartz vein forms one of the most common types of "primary gold deposits".
India
In India, gold mineralization of economic importance is mainly restricted to Archean greenstone terranes of the Dharwar Craton (DC).
The eastern block of the DC has a high favorability for hosting major gold deposits such as Kolar, Hutti, and Ramagiri, whereas the western block hosts only a few smaller deposits such as Gadag, Ajjahanahalli, and Kempinkote.
Gold also discoverrd by GSI in the Singbhum Craton, Aravalli Craton, Bastar Craton and Southern Granulite Terrain (SGT).
India is the second-largest consumer of gold after China.
India currently holds about 558 tones of gold, representing 6.6% of its reserves, (World Gold Council, October 2016).
Kolar Gold Field, Hutti Gold Field and Ramgiri Gold Field are the most important gold fields.
Gold Demand and Use
The largest source of demand is the jewelry industry Gold’s workability, unique beauty, and universal appeal make this rare precious metal the favorite of jewelers all over the world.
Besides jewelry, gold has many applications in a variety of industries including aerospace, medicine, dentistry, and electronics for the manufacture of computers, telephones, televisions...
The third source of gold demand is governments and central banks that buy gold to increase their official reserves.
Private investors there are private investors. Depending upon market circumstances, the investment component of demand can vary substantially from year to year.
Mineral - naturally occurring, inorganic solid with orderly crystalline structure and a definite chemical composition.
These are the basic building blocks of rocks.
Studying Hand specimens & their Physical PropertiesAman Gupta
A slide prepared on the topic hand specimens and their physical properties. Gives an overview to help beginners to learn to ientify hand specimens easily.
Mineral - naturally occurring, inorganic solid with orderly crystalline structure and a definite chemical composition.
These are the basic building blocks of rocks.
Studying Hand specimens & their Physical PropertiesAman Gupta
A slide prepared on the topic hand specimens and their physical properties. Gives an overview to help beginners to learn to ientify hand specimens easily.
1-9 pages(Other pages are just infoblocs)
Gold as element.
in periodictable.
It's name and symbol.
Physical and other properties.
Chemical proporties.
Application.
End (9th page)
//Other pages include additional information that was not included in slide.
A Petrographical Approach to Study Mineral Phases Paragenesis of Gold Bearing...Premier Publishers
India hosts several world class gold prospects like Kolar Gold Fields (KGF), Hutti Gold Fields (HGF) and Gadag Gold Fields (GGF). Karnataka is the prime state for gold production since all of these gold deposits are located within. Apart from these world class gold deposits, several other gold prospects in India were identified and exploration activities are under progress. The present study aims to characterize the mineral assemblage and paragenetic phases of gold bearing Precambrian rocks around Hosur village in Gadag Schist Belt through detailed examination by Ore Microscopy. Gadag Schist Belt (GSB) is known by its significance of gold deposits for centuries. Gold mineralization in GSB is associated with tholeiitic meta-andesite, quartz porphyries and argillite greywacke assemblage. The Gadag Gold Field (GGF) constitutes one of the most important auriferous zones of the Archaean Greenstone terrains in Southern India. All known mineralization is in the form of structurally controlled vein systems. The occurrence of the gold is intimately associated with arsenopyrite. Representative samples were studied under polarizing reflected-light microscope to identify and to characterize the mineral phases of gold occurrences and its textural relationships. It has been observed that there are five phases of mineralization only in the third phase gold has formed along with arsenopyrite. Surface morphology of gold and sulphide mineralization was examined under SEM; whereas the elemental analysis of selected sample was carried out using EDS.The present work reveals the clear perception of gold occurrence and mineral phases paragenesis using ore microscopic approach.
Kalgutinskoye deposit - is the world-class tungsten-molybdenum-cooper deposit located in the the south-eastern part of Altai mountains in Kosh-Agach district of Altay Republic near the state boundaries of Mongolia, China and Kazakhstan.
Uranium Deposits
Uranium is a very dense metal which can be used as an abundant source of concentrated energy. It occurs in most rocks in concentrations of 2 to 4 parts per million and is as common in the earth's crust as tin, tungsten and molybdenum.
.
There are three main types of uranium deposits including 1. unconformity-type deposits, 2. paleoplacer deposits and 3. sandstone-type (roll front) deposits (Figure 1). Sandstone-type deposits are abundant in sedimentary rocks of the Colorado Plateau and found on the Navajo Nation. This type of uranium deposit is easier and cheaper to mine than the other types because the uranium is found near the surface of the Earth. These deposits formed when oxidized groundwater that had leached uranium from surface rocks flowed down into aquifers, where it was reduced to precipitate uraninite, the primary ore mineral of uranium. In some deposits, like those found on the Navajo Nation, reduction took place along curved zones know as roll-fronts, which represent the transition from oxidized to reduced conditions in the aquifer.
Artificial Reefs by Kuddle Life Foundation - May 2024punit537210
Situated in Pondicherry, India, Kuddle Life Foundation is a charitable, non-profit and non-governmental organization (NGO) dedicated to improving the living standards of coastal communities and simultaneously placing a strong emphasis on the protection of marine ecosystems.
One of the key areas we work in is Artificial Reefs. This presentation captures our journey so far and our learnings. We hope you get as excited about marine conservation and artificial reefs as we are.
Please visit our website: https://kuddlelife.org
Our Instagram channel:
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and write to us if you have any questions:
info@kuddlelife.org
UNDERSTANDING WHAT GREEN WASHING IS!.pdfJulietMogola
Many companies today use green washing to lure the public into thinking they are conserving the environment but in real sense they are doing more harm. There have been such several cases from very big companies here in Kenya and also globally. This ranges from various sectors from manufacturing and goes to consumer products. Educating people on greenwashing will enable people to make better choices based on their analysis and not on what they see on marketing sites.
WRI’s brand new “Food Service Playbook for Promoting Sustainable Food Choices” gives food service operators the very latest strategies for creating dining environments that empower consumers to choose sustainable, plant-rich dishes. This research builds off our first guide for food service, now with industry experience and insights from nearly 350 academic trials.
"Understanding the Carbon Cycle: Processes, Human Impacts, and Strategies for...MMariSelvam4
The carbon cycle is a critical component of Earth's environmental system, governing the movement and transformation of carbon through various reservoirs, including the atmosphere, oceans, soil, and living organisms. This complex cycle involves several key processes such as photosynthesis, respiration, decomposition, and carbon sequestration, each contributing to the regulation of carbon levels on the planet.
Human activities, particularly fossil fuel combustion and deforestation, have significantly altered the natural carbon cycle, leading to increased atmospheric carbon dioxide concentrations and driving climate change. Understanding the intricacies of the carbon cycle is essential for assessing the impacts of these changes and developing effective mitigation strategies.
By studying the carbon cycle, scientists can identify carbon sources and sinks, measure carbon fluxes, and predict future trends. This knowledge is crucial for crafting policies aimed at reducing carbon emissions, enhancing carbon storage, and promoting sustainable practices. The carbon cycle's interplay with climate systems, ecosystems, and human activities underscores its importance in maintaining a stable and healthy planet.
In-depth exploration of the carbon cycle reveals the delicate balance required to sustain life and the urgent need to address anthropogenic influences. Through research, education, and policy, we can work towards restoring equilibrium in the carbon cycle and ensuring a sustainable future for generations to come.
Characterization and the Kinetics of drying at the drying oven and with micro...Open Access Research Paper
The objective of this work is to contribute to valorization de Nephelium lappaceum by the characterization of kinetics of drying of seeds of Nephelium lappaceum. The seeds were dehydrated until a constant mass respectively in a drying oven and a microwawe oven. The temperatures and the powers of drying are respectively: 50, 60 and 70°C and 140, 280 and 420 W. The results show that the curves of drying of seeds of Nephelium lappaceum do not present a phase of constant kinetics. The coefficients of diffusion vary between 2.09.10-8 to 2.98. 10-8m-2/s in the interval of 50°C at 70°C and between 4.83×10-07 at 9.04×10-07 m-8/s for the powers going of 140 W with 420 W the relation between Arrhenius and a value of energy of activation of 16.49 kJ. mol-1 expressed the effect of the temperature on effective diffusivity.
1. Journal of Minerals & Materials Characterization & Engineering, Vol. 2, No.2, pp 83-100, 2003
http://www.jmmce.org, printed in the USA. All rights reserved
83
Gold in the Jinya Carlin-type Deposit: Characterization and Implications
Youqin (Joe) Zhou1)
and Kuiren Wang2)
1)
SGS Lakefield Research, P.O. Box 4300, 185 Concession Street, Lakefield, ON K0L 2H0, Canada
2)
Department of Earth & Space Sciences, University of Science & Technology of China, Hefei 230026, China
Gold in the Jinya Carlin-type deposit, assaying 6.27 g/t Au, was characterized
using a comprehensive mineralogical and analytical approach which includes
optical microscopy and several advanced microbeam techniques. Each gold carrier
was quantified independently. Gold in the Jinya ore occurred as microscopic gold
and submicroscopic gold. Submicroscopic gold, primarily in the form of solid
solution gold, was carried mainly by arsenopyrite (accounting for 77% of the gold
assay), and to a lesser extent (~16%) in arsenic-rich fine-grained and
microcrystalline pyrite. Native gold accounted for 6% of the gold assay. Gold
carried in cinnabar and rock minerals is insignificant. Gold deportment shows that
(1) arsenopyritization and pyritization can be used as indication of mineralization
for the further exploration in the Jinya district, and (2) gold in sulfides is not
amenable to direct cyanidation, but can be recovered by flotation of a sulfide
concentrate and then cyanidation with a pretreatment process.
Introduction
According to the mode of occurrence, gold can be classified into three categories: microscopic
gold, submicroscopic gold and surface-bound gold. Microscopic gold, also known as visible gold,
comprises native gold, electrum, gold alloys, gold tellurides, gold antimonide, gold bismuthite, gold
sulfides, gold selenides, gold sulfotellurides and gold sulfoselenides etc. Native gold (Au) and
electrum (Au, Ag), found in various types of gold deposits, are the two most common and most
important gold minerals. Other gold minerals with economic significance in some gold deposits
include kustelite (Ag, Au), auricupride (Cu3Au), tetraauricupride (CuAu), calaverite (AuTe2),
krennerite ((Au, Ag)Te2), aurostibite (AuSb2) and maldonite (Au2Bi) etc (Boyle, 1979; Healy et al.,
1990; Wang et al. 1994). Microscopic gold in primary ore occurs as pristine grains in varied size
and shape in fractures and microfractures, or as attachments to and inclusions in other minerals.
Gold that is invisible under optical microscope and scanning electron microscope is referred to as
submicroscopic gold or invisible gold. Submicroscopic gold, commonly occurs as discrete
particulate (<0.1 µm in diameter) within sulfide minerals (mainly in pyrite and arsenoppyrite), is
the major form of gold in the Carlin-type gold deposits and other refractory gold ores (Hausen,
1981; Radtke, 1985; Hausen et al., 1986; Cabri et al., 1989; Wang et al., 1992, 1994). Gold
concentration in pyrite can be several hundred ppm high, while that in arsenopyrite can be over
10,000 ppm (Chryssoulis et al., 1990). Other submicroscopic gold carriers include chalcopyrite
(Cook et al., 1990), loellingite (Neumayr et al., 1993), marcasite, FeOx (in oxidized ores or
calcines) and realgar (Wang et al., 1994), and clay minerals (Chao et al., 1987). Solid solution gold
and colloidal gold are the two major forms of submicroscopic gold. Surface-bound gold is the gold
that is adsorbed onto the surface of other minerals during the mineralization and subsequent
oxidation or metallurgical processing. Principal surface gold carriers in the ore include FeOx,
2. 84 Y.Zhou and K. Wang Vol.2, No.2
stained quartz, carbonaceous matter and clay minerals. Characterizing gold in an ore is important in
gold exploration and extraction metallurgy, particularly for the Carlin-type gold deposits. This is
because the majority of gold in Carlin-type deposits occurs as invisible gold in other minerals
which has to be characterized prior to metallurgical testwork.
Characteristics of Carlin-type Deposits
Unlike some widespread types of gold deposits, Carlin-type deposits only occur in certain
regions within the Pacific rim such as the western United States, southwest China and some other
locations (Radtke, 1985; Wang et al., 1994; Liu et al., 1994; Hofstra et al., 2000; Kerrich et al.,
2000; Yakubchuk, 2000; Teal et al., 2002; Peters et al., 2002). In the western United States, more
than 100 Carlin-type gold deposits and occurrences have been discovered since early 1960s with
some becoming major gold producers (e.g. Carlin, Betze, Meikle and Deep Post) (Kerrich et al.,
2000; Jory, 2002). They are restricted to a small part of the North American Cordillera, in northern
Nevada and northwest Utah, and formed over a short interval of time (42-30 Ma) in the Tertiary
(Hofstra et al., 2000). In the southwest China, including Yunnan, Guizhou, Guangxi, Hunan,
Sichuan, Shaanxi and Gansu provinces, over 20 medium-sized to large Carlin-type deposits have
been discovered in the past two decades. The gold mineralization in southwest China occurred
along the margin of the Yantze Craton, and is mainly distributed in the southwest border (also
known as the Dian-Qian-Gui Golden Triangle) and northwest border (also known as the Chuan-
Gan-Shaan Golden Triangle) of the Yantze Craton (Wang et al., 1994; Liu et al., 1994; Peters et
al., 2002).
Basically, Carlin-type gold deposits are characterized by (1) strong structural control of
mineralization by faults and folds, (2) calcareous sedimentary host rocks of diverse facies, ±igneous
rocks, (3) decarbonation, argillization, silicification and sulfidation alterations, (4) submicron gold
(<0.2 µm) in association with pyrite, arsenian pyrite and arsenopyrite, and (5) geochemical
signature of Au, As, Hg, Sb and Tl (Radtke, 1985; Wang et al., 1994; Liu et al., 1994; Hofstra et al.,
2000).
Mineralogically, Carlin-type gold ore consists of about 40 minerals, and the mineralogy is
basically the same in most deposits. Opaque minerals include native gold, pyrite, marcasite,
arsenopyrite, realgar, orpiment, stibnite, cinnabar, and pyrrhotite. Non-opaque minerals comprise
quartz, carbonates, clay minerals, albite, barite, carbonaceous matter and graphite. Lorandite
(TlAsS2) and ellisite (Tl3AsS3) are also observed in some Carlin-type deposits in the western United
States and southwest China, which are closely associated with gold mineralization (Radtke, 1985;
Liu et al., 1994).
The mode of occurrence of gold in the Carlin-type deposit has been an interesting and important
subject in gold mineralogy and extraction metallurgy, and extensively studied by numerous
researchers since those deposits were found in the western United States in early 1960s, and a great
deal of information on the occurrence of gold in various deposits has been acquired (Hausen, 1981,
1986; Chao et al., 1987; Hochella et al., 1987; Wang et al., 1992; Wang et al., 1994; Simon et al.,
1999; Hong et al., 2000). The most important characteristic of gold in Carlin-type deposits is that
the majority of gold in the ore occurs as submicroscopic gold, either in solid solution gold
(<0.01µm) or colloidal gold (0.01- 0.1 µm), or both, in pyrite and arsenopyrite. Pyrite is the most
common sulfide mineral and most important gold carrier in the Carlin-type deposits. The content of
pyrite in the ore is about 5% on average. Morphologically, pyrite commonly occurs as coarse-
grained, blastic, fine-grained and microcrystalline varieties (Figure 11). Coarse-grained pyrite often
3. Vol.2, No.2 Gold in the Jinya Carlin-type Deposit: Characterization and Implications 85
occurs as euhedral cubic or pyritohedron crystals, while fine-grained pyrite usually occurs as
irregular granule or framboids. Compositionally, pyrite is characterized by its high As content and
lower S/Fe (Wang et al., 1994). Zoned texture is observed in coarse pyrite in many Carlin-type gold
deposits. In zoned pyrite, As and Au concentrates in the outer zone (Wells et al., 1973), while in
fine-grained pyrite the distribution of As and Au is relatively homogeneous and a positive
correlation between Au and As is often observed (Simon et al., 1999; this paper). In addition, pyrite
in the Carlin-type deposits commonly contains high concentration of Hg, Sb and Tl (Wang et al.,
1994; Hofstra et al., 2000). In most Carlin-type deposits, pyrite is the major gold carrier,
particularly the fine-grained arsenian pyrite often contains high content of submicroscopic gold
(Bakken et al., 1991; Arehart et al., 1993; Wang et al. 1994). For example, fine-grained arsenian
pyrite (up to 2 µm in grain size) from Twin Creeks Carlin-type deposit contained 595-1,465 ppm
Au (Simon et al., 1999). Arsenopyrite and marcasite in the Carlin-type deposit refractory ores also
contain high concentration of gold. In certain Carlin-type deposits, such as the Jinya deposit in
southwest China, Au in arsenopyrite is as high as 1044 ppm, making arsenopyrite the principal gold
carrier in the ore (this paper). Comparable concentration of gold has been measured in arsenopyrite
from other types of gold deposits (Cabri et al., 1989). Other sulfide minerals, including realgar,
orpiment, stibnite and cinnabar, are often observed in the Carlin-type deposits, but no significant
amount of gold has been detected in these minerals (Wang et al., 1994; this paper).
Samples, Analytical Methods and Study Procedure
The ore from the Jinya mine, Guangxi in southwestern China was selected for the study. The
geology and mineralization were discussed by Wang et al. (1994). The Jinya mine is located in
Fengshan County, Guangxi Zhuang Autonomous Region and within the Yunnan-Guizhou-Guangxi
Golden Triangle. The orebodies at Jinya occur in sandstone, siltstone, and silty mudstone of the
upper Banna Group (Middle Triassic). Three types of ores were identified: pyrite ore, arsenopyrite
ore and pyrite-arsenopyrite ore. Alteration associated with gold mineralization included
pyritization, arsenopyritization, carnonatization, realgari-zation and silicification. The chemical and
mineralogical compositions of the Jinya ore were listed in Tables 1 and 2, respectively.
Table 1: Gold Assays and Head Analyses
Sample Name
Au
(g/t)
Fe (%) S (%) As (%)
J01 Feed 6.30 4.32 4.43 4.22
J02 Feed 6.24 - - -
J03 -5µm 4.57 - - -
J03 -5µm
CN Residue
3.82 - - -
4. 86 Y.Zhou and K. Wang Vol.2, No.2
Table 2: Mineralogical Composition
Mineral Name Chemical Formula
Abundance
(wt.%)
Arsenopyrite FeAsS 2.5
Pyrite FeS2 7.4
Realgar AsS 1.4
Quartz SiO2 45
Silicates - 40
Carbonates (Ca, Fe, Mg, Mn) (CO3)1-2 3.0
Sphalerite ZnS trace
Galena PbS trace
Chalcopyrite CuFeS2 trace
Covellite CuS trace
Pyrrhotite Fe1-xS trace
Stibnite Sb2S3 trace
Ilmenite FeTiO2 trace
Hematite Fe2O3 trace
Rutile TiO2 trace
Barite BaSO4 trace
Mative Arsenic As trace
A comprehensive mineralogical and analytical approach, including reflected light microscope and
several advanced microbeam techniques, was used for the current study. A reflected light
microscope was used to search for visible gold minerals and to determine the general mineralogical
composition. The model X-650 scanning electron microscope (SEM) equipped with two wavelength
dispersive spectrometers was used to search for micron-size gold particles. A JEOL 733 electron
microprobe (EMP) with wavelength-dispersion spectrometer was used to analyze gold particles and
the major sulfide minerals for their compositions. Polished blocks were examined under ore
microscope and interested areas were chosen for proton-induced X-ray emission (µ-PIXE) analysis
and mapping to determine the distribution of Au, As, S and Fe in individual sulfide minerals and
hosting silicates. Samples for secondary ion mass spectrometry (SIMS) analysis were prepared as
polished grain mounts in 22 mm diameter of epoxy with approximately 15 wt.% graphite added, and
were then examined under microscope to determine the abundance of pyrite and arsenopyrite
morphological types and to select target mineral particles. The quantitative analyses of Au197
, As75
,
S34
and Fe56
in different types of pyrite and arsenopyrite were performed on a CAMECA IMS-3f
SIMS with a cesium primary beam size of about 20 µm. The overall sampling depth of SIMS is 0.5-
1 µm and the minimum detection limit (MDL at 2?) is 0.3 ppm. Fe and S were also analyzed to
monitor SIMS instrumental conditions during the analysis. Analytical procedures and
standardization for gold in the SIMS analysis are given by Chryssoulis et al. (1987, 1989).
Calibration was done by external standardization using gold-implanted pyrite and arsenopyrite
(Chryssoulis et al., 1989). Time-of-flight resonance ionization mass spectrometry (TOF-RIMS) with
a minimum detection limit of 10 ppb for gold was used to detect and quantify gold in realgar.
5. Vol.2, No.2 Gold in the Jinya Carlin-type Deposit: Characterization and Implications 87
Intensive cyanidation was performed on –5µm fraction to determine the amount of cyanidable gold.
The procedure employed in the current study was depicted in Figure 1.
Figure 1: Study Procedure
Crushed ore
Assays for Au, Fe, S and As
Gravity separation of sized fractions
for gold and heavy minerals
Preparation of polished
sections from heavies,
middlings and lights
Assay for gold in
middlings and
lights fraction
Gold scans by optical
microscopy and SEM
Quantification of gold in
sulfide minerals by SIMS,
TOF-RIMS and PIXE
Mineralogical balance of gold
Preparation of mineral
particles for SEM
Gold search by SEM
Intensive cyanide
leaching
Assay for gold in
leach residue
6. 88 Y.Zhou and K. Wang Vol.2, No.2
Results
Microscopic examination
Several dozen polished sections made from concentrates, middlings and tails of sized fractions
were scanned under reflected light microscope at 500X. Four gold particles (Figure 2) less than 20
µm in size were found. Electron microprobe analysis showed that these gold particles are native
gold with 17.3 wt.% of Ag.
Figure 2: Microscopic gold particles (bright yellow). Pyrite: pale yellow; Arsenopyrite: greenish
white.
SEM examination
Systematic scans for fine-grained gold particles were conducted on both polished blocks and
individual pyrite, arsenopyrite and realgar particles selected from crushed samples under a binocular
microscope. No gold was found in 50 polished blocks. Forty micron-size gold particles (1-10 µm in
size) were observed on pyrite and arsenopyrite, occurring in microfissures, defect sites or detrital
materials on the surface of anhedral pyrite and arsenopyrite. Figure 3 shows that a micrograined
gold particle (1x2 µm) occurred in a void on the surface of an arsenopyrite particle. Figure 4 shows
two micrograined gold particles observed in the microfissures on pyrite. A gold particle with ~15
wt.% of Hg was shown in Figure 5. These micrograined gold particles are amenable to direct
cyanidation and will dissolve to completion during conventional cyanidation. Intensive cyanidation
conducted in the current study showed that approximately 6 wt% of gold in the Jinya ore is
leachable.
7. Vol.2, No.2 Gold in the Jinya Carlin-type Deposit: Characterization and Implications 89
Figure 3: Micron-size gold particle (1x2 um, in the centre of red circle) occurred in a void on
arsenopyrite.
Figure 4: Micron-size gold particles (left: 4x8 um, right: 3x3 um, in the centre of red circle)
occurred in fractures in pyrite.
8. 90 Y.Zhou and K. Wang Vol.2, No.2
Figure 5: Micron-size Hg-bearing gold particle (2x3 um, in the centre of red circle) on pyrite. The
EDS spectrum on the left is for Au, and that on the right is for Hg.
PIXE mapping
PIXE analysis is a multi-element and nondestructive technique with a small beam size (~5 µm)
and low detection limit for gold at ppm level. In addition to quantification capability, PIXE can also
be used to obtain two-dimension distribution images of gold and other elements in sulfide and rock
minerals. In the current study, PIXE mapping of Au, Fe, S and As were performed on numerous
polished blocks that contain pyrite, arsenopyrite and realgar in quartz and/or silicate. Figures 6-8
showed that the distribution and concentration of gold in the mapped area is closely associated with
that of arsenic, sulfur and iron, which indicates that gold was contained in pyrite, arsenopyrite and
realgar. No gold was detected in host rock minerals, which is consistent with fire assays of gravity
separated tails and binaries (Figure 9), implying that gold was contained in sulfides.
9. Vol.2, No.2 Gold in the Jinya Carlin-type Deposit: Characterization and Implications 91
Figure 6: PIXE element distribution map of pyrite, which shows gold distributed only in pyrite. No
gold was detected in host rock minerals. Scale bar on the right side represents the relative
concentration. From top to bottom, the concentration decreases.
Figure 7: PIXE element distribution map of arsenopyrite. Same as in pyrite, gold distributed only in
arsenopyrite. Scale bar on the right side represents the relative concentration. From top to bottom,
the concentration decreases.
10. 92 Y.Zhou and K. Wang Vol.2, No.2
Figure 8: PIXE element distribution map of realgar. Gold distributed only in realgar. Scale bar on
the right side represents the relative concentration. From top to bottom, the concentration decreases.
Gold in Binaries and Rocks
0.01
0.1
1
10
5-25 25-53 53-100 >100
Size Fractions (um)
Au
(g/t)
Rock Binaries
Figure 9: Gold assays of the sized rock mineral and rock/sulfide fractions. The systematic decrease
of gold concentration in the rock mineral fraction reflects increase of sulfide liberation. However,
gold is primarily concentrated in the rock/sulfide binaries, which constitute the second in importance
gold carrier in the Jinya ore.
11. Vol.2, No.2 Gold in the Jinya Carlin-type Deposit: Characterization and Implications 93
SIMS analysis
The Au content in arsenopyrite ranges from 0.10 to 1044 ppm (Table 3) with an average of 195
ppm. Arsenopyrite is one of the two principal “invisible” gold carrier-minerals in the Jinya ore; the
other one is arsenian pyrite, which ranges from 0.31 to 122 ppm (Table 4) and averages 13.2 ppm.
Among the four types of arsenopyrite, blastic and fine-grained particles are the two varieties that
contain high content of gold (Figure 10); while fine-grained and micro-crystalline pyrites are the
two major gold carriers among the pyrite varieties (Figure 11).
Using SIMS analysis, Cook et al. (1990) and Simon et al. (1999) demonstrated a positive
correlation between the concentration of “invisible” Au and As in arsenian pyrite. In the current
study, a positive correlation between Au and As in arsenian pyrite from Jinya ore was also indicated
by SIMS analyses (Figure 12), which is consistent with the distribution of gold and arsenic in pyrite
demonstrated by PIXE mapping (Figure 6).
Table 3: Submicroscopic Gold Content of Arsenopyrite
Grain # Morphological Type Au (ppm)
1 Coarse 0.44
2 1.64
3 0.17
4 0.89
5 1.54
6 0.64
Table 4: Submicroscopic Gold Content of Pyrite
Grain # Morphological Type Au (ppm)
As
(wt.%)
1 Coarse/Blastic 0.31 1.71
2 4.25 1.77
3 0.43 3.03
4 0.44 4.33
5 0.51 6.07
6 3.90 0.68
7 6.60 2.95
8 2.02 0.69
12. 94 Y.Zhou and K. Wang Vol.2, No.2
Figure 10: Morphological types of gold-bearing arsenopyrite. Coarse-grained arsenopyrite (top
three) contained very low content of gold, while blastic and fine-grained varieties (middle and
bottom rows) contained high content of gold. The deep color pit in the centre of each analyzed
particle is the analytical spot of SIMS, which is about 20 um in diameter.
17.6
ppm
1.6
ppm
0.1
ppm
545 ppm 521.5 ppm 173.1
ppm
982.6 ppm 775.5
ppm
401 ppm
60
13. Vol.2, No.2 Gold in the Jinya Carlin-type Deposit: Characterization and Implications 95
Au 0.51 ppm Au 5.60 ppm
Au 23.5 ppm Au 72.4 ppm
Figure 11: Morphological types of gold-bearing pyrite. Fine-grained and microcrystalline pyrites
are the two varieties which contained high content of gold. The deep color pit in the centre of each
analyzed particle is the analytical spot of SIMS.
0.1
1
10
100
0.1 1 10 100
As (wt%)
Au
(ppm)
Figure 12: Correlation between submicroscopic gold and arsenic in pyrite from Jinya ore.
40 um
40 um
15 um 15 um
14. 96 Y.Zhou and K. Wang Vol.2, No.2
TOF-RIMS analysis
TOF-RIMS is a microbeam analytical technique that allows for the identification and quantification
of atomic species in very small quantities, and has been demonstrated capable of providing
quantitative ultra trace element analysis of precious metals in minerals. The detection limit for gold
can be 10 ppb or even lower (Stamen et al., 1999). 13 realgar particles selected from Jinya ore were
analyzed by TOF-RIMS, ranges from 0.37-1.70 ppm Au with an average 0.68 ppm Au (Table 5).
TOF-RIMS analysis also showed that gold in realgar occurred as colloidal gold.
Table 5: Submicroscopic Gold Concentration of Realgar
Grain # Au (ppm)
1 0.44
2 0.51
3 0.65
4 0.65
5 0.85
6 0.37
7 0.65
8 0.72
9 0.72
10 0.37
11 0.44
12 0.72
13 1.70
Average 0.68
Discussion and Conclusions
Results from microscopic gold scans, SEM searching, PIXE mapping, and SIMS and RIMS
analyses demonstrated that there are two forms of gold occurring in the Jinya ore: microscopic gold
and submicroscopic gold. Microscopic gold, occurring as fine- to medium-grained native gold and
as micron-size gold particles, accounted for 6% of the gold assay. This part of gold can be
recovered by conventional cyanidation. Submicroscopic gold was mainly carried in sulfide minerals
(Figure 13), principally in arsenopyrite (accounting for 77% of the gold assay), and to a lesser
extent in pyrite (accounting for approximately 16% of the gold assay). Gold in realgar only
accounts for 0.2% due to its extremely low gold c
oncentration. Gold in rock minerals accounted for
1%. Gold deportment is depicted in Figure 14.
15. Vol.2, No.2 Gold in the Jinya Carlin-type Deposit: Characterization and Implications 97
0
5
10
15
20
25
30
35
40
45
50
0 0.2 0.4 0.6 0.8 1.0 3.0 6.0 10.0 30.0 60.0 100 300 600 >1000
Submicroscopic Au Concentration (ppm)
Relative
Abundance
(%)
Arsenopyrite
Pyrite
Realgar
Figure 13: Gold concentration: arsenopyrite (195 ppm) > pyrite (13.2 ppm) > realgar (0.68 ppm)
Figure 14: Deportment of gold in the Jinya ore. SS – solid solution. Apy – arsenopyrite; Py – pyrite;
Rg – realgar; Rock – rock minerals.
The systematic scans of a large number of polished blocks and grain mounts failed to prove the
occurrence of enclosed particulate gold in sulfide minerals from Jinya ore. Homogeneous
distribution of gold in arsenopyrite and pyrite indicated by PIXE mapping (Figures 6-8) and “flat”
SIMS in-depth concentration profiles (Figure 15) indicate that submicroscopic gold in arsenopyrite
and pyrite occurs as structurally bound solid solution gold. Except for realgar, no evidence was
found for the occurrence of colloidal gold in arsenopyrite and pyrite, such as has been reported by
Bakken et al. (1989) in several minerals from the Carlin gold deposit. Bakken et al. (1989) located
discrete native gold particles of 50-200 Å in diameter encapsulated in pyrite, cinnabar and more
rarely, quartz, as well as gold particles of 200-1000 Å in diameter associated with 1M illite.
16. 98 Y.Zhou and K. Wang Vol.2, No.2
Arsenopyrite
Au 775 ppm
Pyrite
Au 28.7 ppm
Figure 15: SIMS in-depth concentration profiles of pyrite (left) and arsenopyrite. “Flat” profiles of
gold (sky blue) show that gold in pyrite and arsenopyrite occurs as solid solution gold.
Occurrence of significant amount of gold in sulfides in the Jinya ore, particularly in arsenopyrite
and pyrite implies that arsenopyritization and pyritization can be used as indication of gold
mineralization and as a guide for the further exploration in the Jinya district. The implication of
structurally bound gold in the Jinya ore (and in other Carlin-type refractory ores) for gold
extraction is that finer grinding will improve the recovery of gold-bearing sulfides by flotation, but
will not improve the recovery of gold by conventional cyanidation because gold in sulfides is not
accessible to cyanide solution. The ore containing submicroscopic gold in pyrite structure needs to
be pretreated to make gold amenable to cyanide leaching. Roasting and pressure-oxidation
pretreatment processes are generally used for high-grade refractory ores, such as whole-ore
roasting and autoclaving pretreatment in Goldstrike, USA and whole-ore roasting in Minahasa,
Indonesia. Generally speaking, low-grade refractory ores containing 1 to 2.5 g/t (0.03 to 0.07 oz/st)
do not contain enough value to justify a milling pretreatment process (Wan, 2001). They can be
treated by biooxidation-heap leaching process. Therefore, it is very important to ascertain the mode
of occurrence of gold in the ore to be treated prior to process selection and flowsheet development.
Acknowledgements
We are grateful to Stephen Chryssoulis of AMTEL for his enthusiastic support with the SIMS,
RIMS and EPMA analyses, and to Fanqing Li of USTC for help with the SEM, and to Chigang
Ren and Shijun Zhou of Fudan University, China for help with the PIXE mapping. We are also
grateful to Dr. Jim Hwang, Editor-in-Chief for his helpful comments and suggestions.
17. Vol.2, No.2 Gold in the Jinya Carlin-type Deposit: Characterization and Implications 99
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