Mining Compliance, Geology, And Gold Mining Techniques In Ballarat

1.Assess the processes and procedures that would demonstrate compliance with relevant Australian Mining Acts and Regulations in a variety of mining contexts.

Review the Queensland Coal Mining Regulations 2017.

1. What are the basic elements that a coal mine’s safety management system must provide?
2. Provide a summary of what the site senior executive (SSE) for a coal mine must do to ensure they are complying with the regulations with regards to risk assessments?

2.Write a summary of the geology that describes the formation of the Ballarat goldfields. Your summary should include a description of alluvial deposits, the formation of turbidites and the formation of deep leads. You should also make mention of the gold bearing host rock and how the gold migrated.

3.Describe three different mining systems that have been used to mine gold in the Ballarat region.

How were the alluvial deposits mined in the early gold rush days of Victoria?

How was gold mined from the deep leads using steam power?

How is gold mined in Ballarat today?

4.The following problem is modified from the textbook, Introductory Mining Engineering, Hartman and Mutmansky. Develop a spreadsheet (MS excel) to calculate the ore reserves (tonnages and grade) for an open pit copper mine given the data in the following figures. Figure 1 shows the plan of a series of sections, E450, E1350, E2200 and E3300.  Figures 2 – 5 show the detail of the sections.

Assessing compliance with Australian Mining Acts and Regulations

1.1. Basic elements that a coal mine’s safety management system must provide

Queensland Coal Mining Regulation 2017 was made under the Coal Mining Safety and Health Act 1999 (The State of Queensland, 2017). The main objective of this regulation is to replace the Coal Mining Safety and Health Regulation 2001. According to Queensland laws, it is mandatory for these regulations to be updated after every ten years. The regulation plays a major role in safeguarding and enhancing the health and safety of workers in mining sector of Queensland. Application of this regulation started on September 1, 2017. According to the Queensland Coal Mining Regulations 2017, the basic elements that a coal mine’s safety management must provide are:

1.1.1. Risk identification and assessment

This element involves identifying the likelihood of different events that may cause may cause harm occurring in the processes of carrying out activities associated with coal mine operations. These risks or likelihoods are identified and assessed so as to prevent or minimize the possibility of their occurrence by bringing the risk level to acceptable limits.

1.1.2. Hazard analysis

This element entails investigating various causes of harm when undertaking coal mine activities. The main objective of this investigation is to develop measures of preventing these hazards from causing harm.

1.1.3. Hazard management and control

This element includes a wide range of strategies that are out in place so as to manage and control hazards on a coal mine site.

This element involves keeping records of all data and information related to health and safety on a coal mine. The documentation is mandatory for inspection by relevant agencies, reviewing the effectiveness of hazard management and control strategies applied, preventing more hazards and for the company’s future reference.

1.2. Responsibilities of the coal mine site senior executive (SSE)

In order to ensure that the SSE for a coal mine are complying with the Queensland Coal Mining Regulation 2017 with regards to risk assessment, the SSE must do the following:

1.2.1. Keep risk assessment data and information

Ensure to keep a copy of every risk assessment performed for the mine and details of the data and information that were the basis of the risk assessment. This copy must be kept until when the assessment is outdated or the hazard that was related to the assessment is no longer present at the mine.

1.2.2. Develop standard mine operating procedures 

Ensure that he/she consults with various workers on the coal mine site who are involved in performing a task so as to identify hazards that are related to the task and measures or strategies of managing or controlling these hazards.

Summary of the geology of Ballarat goldfields

Prepare a draft of standard operating procedure and share a copy with the coal mine workers that he/she consulted so that they can have a comprehensive understanding of the hazards and control measures. If the coal miner workers agree with the contents in the draft, the SSE must prepare the final document of the standard operating procedure. In case they disagree, the SSE must carry our further consultation, prepare a new draft and share it with the workers again. This should continue until the workers agree with the draft provided then the SSE prepares the final standard operating procedure.

1.2.3. Ensure easy access to copies of standard operating procedures

Ensure that he/she keeps a list of standard operating procedures of the mine at the mine and in a location that can be easily accessed by all workers at the mine, that all workers carrying out a particular activity can easily access a copy of standard operating procedure for the specific activity they are carrying out, and that these lists and copies are kept in a standard format that can be easily read and understood by the coal mine workers.

Ensure that he/she keeps a list of current recognized standards for the coal mining operations at the mine and in a location that can be easily accessed by all workers on site, that all workers carrying out a particular activity can easily access a copy of current recognized standards for the specific activity they are carrying out, and that these lists and copies are kept in a standard format that can be easily read and understood by the coal mine workers.

1.2.4. Manage overlapping areas

Immediately stop coal mining operations if he/she realizes that these operations are creating a safety risk to the workers at an adjacent petroleum facility that is in an overlapping area, or if the risk level is not acceptable (Queensland Government, 2018).

Stop the coal mining operations until an appropriate action is taken to reduce the risk level to an acceptable limit.

1.2.5. Compliance with the safety and health management system

Ensure that all requirements in the safety and health management system for the coal mine are adhered to.

2.This question involves writing a summary of how Ballarat goldfields formed. Ballarat area has a rich history in regards to gold. The city, which is located in Victoria, Australia, is known for a replica gold rush town called Sovereign Hill. This town has over 1850 streets, mines and shops. The Gold Museum, which is found in the city, has a wide range of gold artefacts and nuggets, demonstrating its mining history.

Various mining systems used in Ballarat region

Gold was first discovered in Australia by the California goldrushes veteran James Esmond in 1850. The following year, gold was discovered at Ballarat and resulted to the famous gold boom in Victoria. Ballarat goldfield became one of the world’s richest field. This gold field comprised of both alluvial deposits and deeper leads.

Gold deposits are formed through geological processes. The alluvial gold deposits (also known as secondary gold deposits) in Ballarat were formed from gold rushes that got deposited as they followed the course of Victorian rivers. These deposits formed as a result of primary gold deposits being exposed at the surface of the earth. As the Victorian rivers were flowing, they washed the exposed primary gold deposits down the stream and deposited them there in the soil and at the bottom of streams and creek beds. These rushes continued accumulating and after some time, they formed Ballarat goldfields. The alluvial deposits peaked between 1852 and 1853. Figure 1 below shows how primary and secondary/alluvial gold deposits form (Earth Resources, (n.d.)).

 

Figure 1: Primary and secondary/alluvial gold deposits (Earth Resources, (n.d.)) 

The alluvial deposits formed over time and they were a sign that the Victorian rivers were running through a ground that was rich in gold. As a result of the water’s erosive power, the surrounding rock got removed because of its relatively low density whereas the gold, which has a higher density, remained in place.

Turbidites are sedimentary rocks or fine-grained sediments that changes gradually from coarse- to fine-grained. Deposition of these sediments is by turbidity currents i.e. density flow. The heavier alluvial deposits in Ballarat area got deposited at the bottom of the rivers and covered by the lighter alluvial deposits. Since gold in Ballarat was mined using traditional methods and crude tools, the diggers could not good deep into the rivers to extract gold nuggets. As the heavier deposits moved slowly downstream, liquefaction took place causing a change to the water density. The moving water had a high percentage of suspended load comprising of fine-grained particles that formed a slurry. The density of slurry was almost the same as that of the gold deposits hence the gold moved downstream by density flow forming turbidites.    

Metamorphosis and folding of Ballarat turbidites took place under greenschist-facies conditions Devonian Tabberabberan Orogeny. It is believed that auriferous fluids were produced together with Cambrian greenstones’ devolatilization in the lower crust before or during Silurian Benambran Orogeny. Dilatant structures were formed from brittle deformation that caused the ore fluids to migrate into these structures. The faults sealed themselves causing fluid pressure to build up and later caused hydraulic fracture (Gao & Kwak, 1995).

Calculating ore reserves for an open pit copper mine

It is believed that turbidity currents in Ballarat were triggered by slope failure. There were many gold diggers in the area and the extensive mining activities cause failure of slope along the river banks. Extensive digging in the area also exposed it to numerous tremors and aftershocks that made it dangerous for diggers to mine gold. The slope failures, tremors and aftershocks triggered turbidity currents that transported sediment loads along the rivers and dropped them as the water and current slackers came to rest. These sediment deposits are the turbidites. The sequence of turbidites formation is referred as Bouma sequence.

Deep leads are basically alluvial deposits that are deeply buried and typically covered by Cainozoic basalts. The deep leads were mineral deposits that formed when alluvial deposits got buried by younger sediments or rocks through mechanical concentration by water action in river or stream beds. As the water flows through the river, it provides the necessary energy for sifting and sorting materials. In the process, gold sinks because of its higher density and gets concentrated at the bottom of the river. In Ballarat, the deep leads were covered with lava flows in the west of Yarrowee River, as shown in Figure 2 below.

 

Figure 2: Section of Ballarat goldfield (d'Auvergne, 2009)

The geographical map in Figure 3 below also shows the high concentration of deep leads in the West of Ballarat goldfields (indicated by the pink color). From the map, the depth of leads (indicated by the black stars) on the West was higher than the East. This is because the river systems’ energy was great on the West than the East.

 

Figure 3: Map showing deep leads in East and West of Ballarat (d''Auvergne, 2009)

After the gold was formed by being eroded from its source, it was transported by water in the Victorian rivers to new locales. The gold sediments together with other minerals and substances got deposited but since gold is heavier, it settled at the bottom of the river. Therefore miners had to dig and remove the top layers of soil and other lighter minerals before reaching the gold.

3.1. Three different mining systems that have been used to mine gold in the Ballarat region

The following are three different mining systems that were used to mine gold in the Ballarat region:

3.1.1. Digging and panning

This was the first technique that was used to mine gold in Ballarat region immediately it was discovered. The miners or diggers used shovels to dig up gold from very shallow depths. Other tools used in the process were a handmade cradle and gold pan. It was very easy to dig up gold using these tools because of the gently sloping hill and high rainfall in the area. This was a simple technique used to dig up alluvial deposits that were found in shallow depths or in creek beds. In this technique, miners placed a small amount of sand, gravel and/or soil into a pan and add water to it. They would then start swirling out the muddy water, as shown in Figure 4 below (Wikispaces.com, 2010). As a result, gold specks were left behind at the bottom of the pan. As the water was being swirled, the gold pecks sunk to the bottom of the pan due to their higher density.

 

Figure 4: Panning technique (Wikispaces.com, 2010)

3.1.2. Puddling

This technique was mainly used for separating clay and gold. In this technique, gold and clay would be mixed in a big container then water added to it. Miners then used a wooden stake to stir the mixture, as shown in Figure 5 below. As a result, the clay dissolved in water leaving sand and gold flecks at the bottom of the container. This was then followed by panning or cradling the remaining mixture to get gold. Some puddling machines were powered by horses.

 

Figure 5: Puddling technique (Wikispaces.com, 2010)

3.1.3. Shaft mining

This technique was used when gold started becoming scarce due to extensive mining. It became difficult for miners to get any gold at shallow depth. The miners had to dig shafts or holes deep into the surface (even up to 50m deep). To stop the shafts or holes from collapsing, timber was propped on the sides. A winch or windlass was then used to lift buckets full of soil onto the surface, as shown in Figure 6 below. This technique involved at least three miners. One of them miners would be shaft shoveling soil inside the hole into the bucket, another one would be at the top of the shaft winding the windlass to left the bucket, and another one would be washing the soil in a cradle.

 

Figure 6: Shaft mining technique (Wikispaces.com, 2010)

Other techniques included cradling technique, deep lead mining technique, quartz reef mining, water systems and sluicing, among others (The University of Melbourne, 2015).

3.2. How the alluvial deposits were mined in the early gold rush days of Victoria

Alluvial deposits (which were in form of nuggets, thin flakes and dust) in the early gold rush days of Victoria were mined using placer mining methods or also known as alluvial mining (Ballarat & District Genealogical Society Inc., (n.d.)). This method basically involved using simple tools, including shovels, pans and sieves, to dig up gold and sift it through mud, gravel and sand. Sometimes people could even use bare hands to do this (Barrera, 2017). The dredged river bed materials containing small sand, gold and other large mineral particles were separated mainly through physical separation methods, such as gravity and screening separation.

The alluvial mining comprised of various techniques, including use of tunneling equipment and surface excavating equipment. The various alluvial mining techniques used included: panning, sluicing, dry washing, cradling or use of rocker box, deep quartz mining, and deep lead mining, among others.

3.3. How gold was mined from the deep leads using steam power

In Ballarat region, water was a very important commodity in mining gold from the deep leads. The water was heated to produce steam. This steam powered plant and equipment that were used for the extraction and processing/manufacturing of gold. Water channels known as water races were constructed to create widespread water supply systems. The steam, which was water under high pressure, was fired against surfaces, such as riverbanks, where gold was. This highly pressurized water washed away loose rocks, soil and vegetation, and exposed gold deposits. Chemicals were then used for the extraction of finer gold particles (State Library Victoria, 2018).

3.4. How gold is mined in Ballarat today

Today, there are various modern techniques that are used to mine gold in Ballarat. These methods are more efficient, safe and environmentally friendly than the traditional ones. Some of them are just the improved versions of the old techniques, such as deep lead mining, water systems and quartz reef mining. Examples of methods used to mine gold in Ballarat today include the following:

3.4.1. Lode or hard rock mining

This method involves extracting gold from rocks where it was deposited originally. It involves drilling or blasting a tunnel to the ore source and transporting it to the surface for processing. The ore can be mined using different techniques, including block caving and drift-and-fill and cut-and-fill techniques. In some areas, large strips of surface rock and dirt are removed then the ore is extracted from the wide open pits. In most cases, the ore is removed using explosives, massive trucks and big power shovels. After the ore has been extracted, it gets processed to get the gold. In most cases, the ore is crushed into powder then it is initially separated from rock using a combination of gravity, froth floating and centrifugation methods. The remaining gold is then precipitated out through cyanide treatment.

3.4.2. Placer mining

The various placer mining techniques used today are more advanced than the traditional panning, sluicing and cradling techniques. The ones commonly used are dredging and hydraulic mining. These techniques use large river diversions and heavy equipment to extract native gold that has not yet chemically bonded with the rock. They use water and gravity to extract gold from the bedrock fissures or in between large rocks (Gold Truth Trekking, 2014).

4.This question entails calculating the tonnages and grade of the ore reserve for an open pit copper mine. The details of the sections of the 13 drill holes have been given. The calculations have been done in MS Excel spreadsheet. By definition tonnage is the total amount of ore mineral that can be mined or extracted from a particular ore reserve (H.W & Mutmansky, 2002). There are three factors that are considered when calculating tonnage: grade of the ore, volume of the ore reserve, and the ore mineral’s tenor. Tenor is simply the percentage of the actual ore mineral or metal that can be mined or extracted from the ore reserve. Grade is the percentage of the ore mineral or actual content of the metal that can be mined or extracted from the ore. The grade is expressed as a percentage while tonnage is expressed in tons. There is a relationship between these two elements (tonnage and grade) (Gerst, 2008), which has been demonstrated in the calculations in the Excel spreadsheet. Calculation of tonnage and grade is very important in mining engineering as it helps in determining the feasibility of mining projects or activities (Asad, 2006); (Hartman, 1992). Considering the demand for mineral resources and impacts of mining activities, it is very important to ensure that the tonnage ad grade values are determined accurately (Bickford, 2013); (Madani, 2012); (Noor, 2018).

Calculation of tonnages involve determining areas and volumes of sections of the ore reserve using methods such as triangular method, polygon method or sectional method, among others (Kau, 2017); (Kau, 2018); (Michaud, 2016). In this problem, the areas of the sections were given. Calculations can also be done using specialized models or software (Osanloo & Ataei, 2003). This depends on the unique characteristics of the ore reserve such as its location or prevailing conditions (Castanon, et al., 2017); (Daya, 2012).

The attached Excel spreadsheet contains all the calculations of each hole and section of the ore reserve. From the calculations, the total tonnage of the ore reserve is 29,390,519.19 tons while the average grade is 65.795% (to three decimal places).

References

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