(Geological Team 403, Sichuan Bureau of Geology and Mineral Exploration and Development)

The Lala copper mine in Sichuan has experienced more than 50 years of exploration, and the development and utilization of geological data have played an important role in it. This paper introduces the general situation of Lala Copper Mine, summarizes the achievements of geological data development, and puts forward some ideas for further work.

Keywords Sichuan; Lala copper mine; Geological data; exploit

The copper ore field in Lala area, Huili County, Sichuan Province is a famous copper-iron ore producing area in the Sichuan-Yunnan copper-iron ore belt in China. It was discovered, surveyed, explored and developed by the 403 Geological Team of Sichuan Bureau of Geology and Mineral Exploration and Development (hereinafter referred to as the 403 Geological Team).

Lala copper mine experienced 55 spring and autumn periods from discovery to development, during which it experienced several ups and downs. After 2004, the scientific researchers of 403 Geological Team made a great breakthrough in prospecting in Lala area by sorting out historical materials and reusing cores, combining with new technologies and methods.

I. Overview of Lala Copper Mine

Lala copper ore field and its periphery are located in the eastern edge of the middle section of Kangdian axis and in the north of Panxi-Dongchuan aulacogen. It is a joint compound part of the east-west Jinsha River fold belt and the Sichuan-Yunnan meridian structural belt, with complex geological structure and frequent magmatic activity, which provides superior geological conditions for the formation of various minerals.

This area is based on siliceous crystals of pre-Sinian metamorphic rocks. The tectonic line formed by Jinning movement is nearly east-west, and then the Neoproterozoic Jinning island arc orogeny, SN- trending main fault and its supporting shear zone are formed. Different deposit types in this area are controlled by different tectonic periods, among which Lala copper polymetallic deposit is controlled by volcanic graben mineralization period in Hekou period.

Lala copper mine starts from Li Xi-Hekou in the north and reaches Li Hong at the junction of Yunnan and Sichuan in the south. It is about 30km long from north to south, 2-5km wide from east to west, and narrow from north to south, with an area of 107km2 (Figure 1). Submit the copper resources/reserves of 80× 104t, and the national mineral resources potential evaluation predicts the potential resources of 26×104t; ; Iron ore resources/reserves are 3000× 104t, and the national mineral resources potential evaluation predicts potential resources 16000× 104t.

Figure 1 Open pit of Lala Copper Mine

Lala copper deposit occurs in biotite schist, rhyolite schist and sodalite of Hekou Community Party Group. The deposit is roughly east-west in plan, with a length of 1900 m and a width of 900 m, and consists of 50 ore bodies, of which 24 ore bodies are more than 3 m thick. Among them, 1 ~ 5 ore body has the largest scale and a long extension, while other ore bodies are smaller. Orebodies are generally imbricated, and their shapes are mostly irregular layered and lenticular, with obvious expansion and contraction, bifurcation and recombination. The mineral composition is chalcopyrite, bornite, chalcopyrite, native gold, native copper, pyrite, magnetite and molybdenite. It is mainly granular structure, and the ore structure is disseminated, banded and banded. Lala copper deposit is a copper deposit with many beneficial associated components, including copper, cobalt, molybdenum, iron, sulfur, selenium, tellurium, rhenium, rare earth, gold, silver, phosphorus and nickel 13 elements.

The second is the secondary development of geological data and the prospecting results obtained.

1.2004 prospecting process

The third sub-team of 403 Geological Team began the general survey, detailed investigation and exploration of Luodang copper field in this area from 1956. 1956 to 1970, mainly looking for copper in small areas, mainly in Luodang mining area and its periphery. From 1970 to 1984, copper and iron are developed simultaneously, covering a large area, all directions, multiple arms and means, and teaching and scientific research are developed simultaneously. Concentrated a lot of material and financial resources, conducted copper-iron ore exploration in Lala, Li Xi and Maogu, and conducted surface prospecting in 1982. 1984 from 2004 to 2004, the work of 403 geological team fell into a trough, and the exploration in Lala mining area was stagnant.

2. Development and utilization of geological data and breakthrough in prospecting after 2004.

After 2004, the 403 Geological Team carried out the State Council's decision on strengthening geological work, and began to re-understand Lala copper-iron ore field, organized many professionals to repeatedly refer to the historical exploration reports, scientific research reports, papers and original engineering catalogues of Lala ore field, repeatedly visited drilling cores, analyzed the metallogenic mechanism, studied the ore source, transportation and storage of copper-iron ore deposits, and put forward new ideas for prospecting. See table 1 for the list of materials used.

Table 1 List of Geological Data in Lala Area

sequential

3. Data development forms a new prospecting idea.

Based on the comparative analysis of sodium volcanic rocks of Lala and Jiangyiluodang Formation, Li Hong Formation and manganese-bearing siderite of Tuanqing Formation in Yunnan, and combined with the occurrence of strata, a new understanding that Hongnipo is a compound syncline is put forward. Under the guidance of this idea, the 403 Geological Team has constructed four boreholes (Lala ZK764, Hongnipo CK743, Shilipai Zhibei ZK- 130 1, and Li Hongzk1) with a depth of more than 800 m between Lala and Li Hong, and determined the copper-bearing horizon and copper-bearing rocks in Lala Copper Mine. The determination of Hongnipo compound syncline has opened up a broad prospect for deep and peripheral prospecting (Figures 2 and 3).

Fig. 2 Geological experts look at the rock (ore) core.

Fig. 3 Comparison of physical geological data with original data and results of geological experts.

4. Using the test data to establish a sample database and dynamically evaluate the value of the deposit.

The industrial index grade of copper is a dynamic index. According to the dynamic relationship between market, grade and resource reserves, the Luodang copper mine sample database is established, and the reserves calculation profiles of different industrial indexes are compiled. Different industrial indexes are used to calculate the resource reserves of the deposit, the horizontal projection maps of No.I, No.II, No.III, No.IV and No.V orebodies in Lala Luodang mining area are compiled, and the mathematical model of grade-tonnage of Luodang copper mine is established. Workload completed: For Line 4 to Line 8, the reserves were calculated by using 30 1 borehole, 3 198 samples and 13 industrial indicators, and the topographic and geological map of 1 mining area and the horizontal projection map of 1 mining area reserves calculation 1: 2000 were compiled.

Using this model, the resources of Luodang mining area in 2006 were re-estimated, and the newly added copper resources were18.21×104t, which was equivalent to the discovery of a medium-sized copper deposit.

5. Estimation of porphyry iron ore resources

According to the mineral processing test, magnetite in volcanic rocks in Lala area can be recovered. According to the data analysis, the rocks of Tianshengba Formation, Xinqiao Formation, Luodang Formation, Datuanqing Formation, Xiaotongchang Formation and Baiyunshan Formation of the Pre-Sinian Hekou Group in Lala area all contain magnetic minerals, which are distributed between F27 fault (east boundary) and F 13 fault (west boundary). The estimated resources/reserves of the above six groups of low-grade porphyry iron ore are about 17× 108t (Table 2).

Table 2 Porphyry iron ore resources table

Third, promote the further development and utilization of geological data.

The reference room of 403 Geological Team strictly implements the system of handing in geological data according to law, carries out special cleaning of geological data, promotes the research and development of geological data, and makes it public and communicates with the society in accordance with relevant regulations. Accelerate the application of modern information technology, implement the "digital geology" project, establish a geological exploration graphic library, a professional database, a typical deposit metallogenic model and a deposit prediction model, establish a comprehensive analysis system, update the inquiry information system, solve the problems of scattered geological exploration and mineral resources information, backward preservation methods, inconvenient inquiry and so on, and improve the utilization efficiency and social enjoyment of geological and mineral information. Collect the geological and mineral information of various geological exploration industries and competent departments in Sichuan Province, provide basic geological and mineral information and other geological services to the whole society according to law, and let the whole society share the public achievements of geological work.