Industrial index and technical economic analysis of a gold deposit

A gold deposit in Sichuan Province is a large-scale rock gold deposit discovered in recent years. The confirmation of the mineral industry index is the basis for providing the geological department with the circled ore body and submitting the gold exploration geology report.

I. Basis for the development of mineral industry indicators

(I) Construction conditions outside the mine The mining area is located in the southeastern part of the Qinghai-Tibet Plateau with a maximum elevation of 4 551 m and a minimum elevation of 3 670 m. The valley area is a farming area and the high mountain area is a pastoral area. The climate is cold, the highest temperature is 27 °C, the lowest temperature is -7.0 °C, and the annual frosty season is from October to March.

The highway from Chengdu to the county is about 800km, and the 80km forest road to the north of the county reaches 10km to the south side of the mining area.

The mining area and its vicinity are rich in water resources, and the production and living water can be basically satisfied. However, without the national grid power supply, it can be solved by self-built hydropower stations. The local economy is relatively backward and the social cooperation conditions are poor.

(2) Geological characteristics of the deposit

The mining area is located in the southern section of the Ganzi-Litang tectonic belt, the tectonic activity zone of the Yangtze continental margin and the intra-ocean rift zone. The exposed strata in the mining area are the Triassic Upper Qufu Temple and the Quaternary. The folds in the mining area are weak, and the fault structure is relatively complex. The main east-west fault (F1) is a main fault in which the ore-controlling, ore-mining, and ore-bearing are integrated. The magmatic rocks in the mining area are divided into three categories: (middle) basic volcanic rocks, diabase rocks and lamprophyre dykes.

The deposit is a hydrothermal gold deposit with fine dissemination type, shallow, medium and low temperature, and structural dynamics. Ore large scale, simple form, metallurgical ores containing ore is optionally arsenic, sulfur, or the like.

There are mines 1, 5, 7, 10, and 15 in the mining area. The ore bodies of No. 10 and No. 15 are the main ore bodies, and the form is layered and braided, accounting for 93.73% of the ore volume and 93.32% of the gold saturation. .

The geological map of the mining area is shown in the topographical geological map (Fig. 1).

Figure 1 Terrain geological map of the mining area

According to industrial utilization, gold ore can be divided into two types of oxidized ore and primary ore. The oxidized ore is mainly distributed in the depth range of 0 to 30 m of ore body, accounting for about 1/4 of the total ore of the ore.

Gold minerals are mainly natural gold, containing a small amount of silver and gold ore, gold and silver ore. The occurrence state of gold: occasionally natural gold in artificial heavy sand, the particle size is less than 0.1mm. Native ore pyrite and arsenopyrite are the major gold-bearing minerals, at least 90% of the gold is in pyrite and arsenopyrite occurrence of.

(3) Ore processing performance

Primary ore flotation test: the original ore grade is 4.93g/t, coarse grinding to -200 mesh content 58.2%, with a coarse, one fine, one sweep, the selection of tailings and sweeping concentrates back to the rough selection The flotation process is carried out by closed-circuit flotation, and a gold concentrate with a recovery rate of 96.43% and a concentrate grade of 56.6×10 ^-6 can be obtained.

The leaching test on the oxidized ore site is difficult: after mining, reactor, spray, adsorption, analysis, purification and other processes, the test results are shown in Table 1.

Table 1 Oxidation test data results

The test shows that under the conditions of gold extraction by cyanidation, the leaching rate of oxidized ore can reach more than 90%, and the recovery rate is above 70%.

(4) Technical conditions for mining

The mining area is a structural denudation (glacier eroding) alpine gorge landform. The topographical conditions are conducive to natural drainage. The groundwater is mainly replenished by atmospheric precipitation (snow), turbulent and reservoir by rock fissures (or dissolution gaps), and is discharged in the form of springs. The hydrogeological conditions are simple in the valleys and slopes.

There are Quaternary loose rock groups on the surface. The rocks on the roof of the ore body are weak. The F1 fault fracture zone between the ore body and the roof is soft. The oxidized ore on the shallow surface belongs to the strong weathering-soft rock. The primary ore and the inclusions belong to the medium-micro-weathering type-medium-hard rock. The direct floor physicochemical alteration of the ore body is a weak rock, and the surrounding rock properties of the ore body are complex.

Second, the determination of the main process parameters

(1) Mining process

Since the information currently provided by the geological department is mainly shallow ore body data, the scope of this certification is also the existing shallow ore body.

According to the characteristics of the ore body and the exposed surface of the ore body, it is planned to use open-pit mining. According to the available data, the open pit mining depth of the mining area in the future is about tens to more than 100 meters below the surface. The mining and stripping work of the mine is planned to adopt conventional perforated blasting, excavator shovel loading and automobile transportation.

In addition, the resource utilization factor is not considered at this stage.

(2) Selection and smelting process

Oxidized ore: using crushed ore, sieving, heap leaching, carbon adsorption, analysis, electrowinning, and finally the quality of gold. The heap leaching method not only saves costs, but also makes it easy to use the comprehensive recovery rate of resource gold to take 70%.

Primary ore: using flotation process, ie coarse, medium and fine crushed ore-sieving-grinding-one coarse, one fine, one sweep, finally gold concentrate, gold concentrate with gold grade 56×10 ^-6 , The recovery rate is 86%.

(III) Selection of industrial indicators

1, the cut-off grade

The cut-off grade is generally 2 to 4 times the grade of the tailings. The average grade of tailings in the leaching test on the oxidized ore site is 0.45×10 ^-6 ; the primary gold mine is subjected to closed-circuit flotation test: the tailing grade of YM1 tunneling test is 0.46×10 ^-6 , and the grade of tailings of YM4 is 0.19× 10 ^-6 . Referring to the boundary grade of the grassland gold mine in Jiuzhaigou County, Sichuan Province, 0.5×10 ^-6 , the Yinjiajin gold mine in Qingyang, Anhui Province is 0.5×10 ^-6 , and the Zijinshan gold deposit in Fujian is 0.5×10 ^-6 , due to the relatively stable construction conditions of the mine. Poor, oxidized ore and primary ore use the same cut-off grade, and the three scheme indicators are shown in Table 2.

Table 2 Industrial indicators of three types of ore bodies

2. Minimum industrial grade

The minimum industrial grade of the grassland gold mine in Jiuzhaigou County of Sichuan Province is 1.0×10 ^-6 , the Yinjiayan gold mine in Qingyang, Anhui Province is 1.0×10 ^-6 , and the Zijinshan gold deposit in Fujian is 1.0×10 ^-6 . According to the calculation, the oxidized ore product is a combined gold, the total recovery rate of the metallurgical process is 70%, the comprehensive cost of mining and metallurgy is 116.86 yuan/t, and the geological grade of the balance of income and expenditure is 1.41×10 ^-6 . The original ore product is gold concentrate, the total recovery rate of the metallurgical process is 86%, the comprehensive cost of mining and selection is 142.00 yuan/t, and the geological grade of the balance of income and expenditure is 1.73×10 ^-6 . The minimum industrial grade scheme determined by oxidized ore and primary ore is shown in Table 2.

3. Average grade of the deposit

The average grade of the Yinjiayu gold deposit in Qingyang, Anhui Province is 1.5×10 ^-6 , and the Fujian Zijinshan gold deposit is 1.5×10 ^-6 . Assume that the mine must obtain 10% of the profit. After calculation, when the mining and mining scale is 600,000 t/a, the total cost and cost of the oxidized mining enterprise is 1,658,500/t, and the primary ore is 174.03 yuan/t. The average grades of the deposits are 2.19×10 ^-6 and 2.33×10 ^{-6 respectively} . When the scale is 450,000 t/a, the sum of the total cost and cost of the oxidized ore enterprises is 201.17 yuan/t, and the primary ore is 206.96 yuan/t. The average grade of the deposits is 2.66×10 ^-6 and 2.76×10 ^{-6 respectively} . When the scale is 300,000 t/a, the sum of the total cost and cost of the oxidized ore enterprises is 260.40 yuan/t, and the primary ore is 255.61 yuan/t. The corresponding grades of the corresponding deposits are 3.45×10 ^-6 and 3.42×10 ^{-6 respectively} . Considering comprehensively, the average grade of the same ore deposit for oxidized ore and primary mines corresponds to different mining and selection scales, and the indicators are shown in Table 2.

4, the lowest recoverable thickness

Due to the steep appearance of the ore body, in order to make full use of the mineral resources, the lowest recoverable thickness is 2.0m in the open air. Take 1.0m for the part that should be used for underground mining without open pit mining.

5, stone removal thickness

According to the mining process, the thickness of the stone removed is 4.0m in the open air. Take 2.0m for the part that should be used for underground mining without open pit mining.

In addition, for the underground mining site, a non-mineral segment removal length index is proposed, and 20m is adopted uniformly.

Based on the above analysis, three sets of trial calculation schemes for industrial indicators of deposits were proposed.

In the above three schemes, when the ore body thickness is less than the lowest recoverable thickness and the gold grade is high, the m·g/t value is used to circle the ore body.

Third, resource comparison and technical and economic analysis

(1) Comparison of resources

According to the three sets of deposit industrial indicators listed in Table 2, the “Gold Mine Industry Index Recommendation” calculates the geological resources of the No. 1, 5, 7, 10, and 15 ore bodies in the mining area. The calculation results and comparison are shown in Table 3.

Table 3 Calculation results and comparison table of each program resource

It can be seen that with the decrease of industrial indicators, the amount of ore and metal in the ore body has increased, but the average grade is also low. If the industrial index is increased, the ore content and metal content of the ore body will decrease, but the average grade will also increase. .

(II) Comparison of ore body shape, occurrence, scale and integrity

Due to different industrial indicators, there are certain differences in the ore body's delineation and connection. In general, the ore body shape and occurrence are basically the same, but with the increase of industrial indicators, the ore body shape is slightly complicated, and branches appear, mainly shrinking inward. For example, the 0-line profile of No. 10 ore body (Fig. 2), with the increase of industrial indicators, the ore body area shrinks continuously. The area of ​​Oxidation Mine Scheme I, Scheme II and Scheme III are 1294m ² , 806m ² and 781m ^{2 respectively} . The areas of Scheme I, Scheme II and Scheme III are 3199m ² , 2010m ² and 1856m ^{2 respectively} .

Figure 2 Comparison of the industrial indicators of the No. 0 exploration line (10# ore body)

(III) Technical and economic analysis

The technical and economic benefits of each program are shown in Table 4.

Table 4 Comparison of technical and economic benefits of each program

It can be seen from Table 4 that the cost of the scheme I scheme has the scale advantage of the resources; the financial internal rate of return (after the income tax) of the entire investment scheme II is optimal, and the financial net present value of the scheme II is the largest after the investment income tax, indicating 3 Scheme II is the best among the schemes.

(4) Opinions on industrial indicators

The ore bodies and production patterns of the three industrial indicators are basically the same, and the integrity of the ore body in the section has a certain change, but the change is not big, mainly the increase or decrease of the ore body area. The scheme I is the most complete ore body. According to the calculation results, the amount of resources in the scheme I is the largest, and the scheme I is the best considering only the utilization of mineral resources. However, in terms of economic benefits, due to the weak local industrial base and relatively poor external construction conditions, the project investment is large and the production cost is high. Therefore, considering the economic benefits of enterprises and the rational use of mineral resources, in comparison, Scheme II Industrial indicators are better.

According to the above analysis, the industrial indicators for recommending gold ore to be exposed to the ore body and calculating the amount of resources are:

Boundary grade: 1.02×10 ^-6

Minimum industrial grade: oxidized ore 1.5×10 ^-6 , primary mine 2.0×10 ^-6

Average grade of deposit: 3.0×10 ^-6

Minimum recoverable thickness: 2m

Stone removal thickness: 4m

When the thickness of the ore body is less than the lowest recoverable thickness and the gold grade is higher, the m·g/t value is used to circle.

Fourth, there are problems and suggestions

The deep ore body is suitable for underground mining, but the deep ore body data has not been provided yet. In the future, the mineral industry index suitable for pit mining needs to be re-argued.