[China Geo University (Beijing)]
The 63-year development of exploration geochemistry in China is closely related to the construction of new China, which has gone through the process from initial establishment, exploration, development, prosperity to glory. Over the past 60 years, tens of thousands of geochemical prospectors in China have traveled over mountains and waters, had meals and slept in the open air, traveled all over Qian Shan and visited every inch of the motherland, and made great achievements. Exploration geochemistry is a branch of applied geology that closely serves social development and national economy. Its main task is to systematically observe the distribution, composition and concentration of chemical elements in rocks, river sediments, soil, water, atmosphere and crops in some cities with different accuracy, so as to provide the country with information on mineral resources, environment and ecology. In the early stage, the exploration of mineral resources was the main goal, and in the later stage, it developed into the demand for investigation and research involving people's living environment, regional ecology, agriculture, endemic diseases and so on. Geochemical mapping not only has the nature of land basic investigation, but also can find anomalies in time, provide all kinds of abnormal information about the environment and ecological conditions, and directly serve the national economic construction.
Exploration geochemistry, referred to as geochemical exploration for short, as an exploration technology, originated in the Soviet Union and Nordic countries in the 1930s, and geochemical exploration technology was listed as an advanced prospecting method by geological exploration departments in the 40s. At the beginning of the founding of New China, the demand for resource exploration for national economic construction was very urgent. China introduced geochemical exploration technology in time to explore for the construction of New China. As early as 195 1 year, the geochemical exploration team headed by Xie went to Yueshan, Anqing, Anhui Province to carry out the first exploration geochemical experiment in China, and found the copper indicator plant Elsholtzia Haizhou. It has attracted the attention of mineral exploration departments, and since then, geochemical exploration teams have been widely established in the national geological, metallurgical, nonferrous and later nuclear industries and gold systems to carry out geochemical exploration and prospecting. The history of exploration geochemistry in China can be divided into two stages according to the purpose of investigation, sampling media and application scope of results: the first stage is 1950 ~ 1998, and the second stage is 1999 ~ 20 13, that is, the first 50 years and the last 13 years.
1. The geochemical exploration stage with mineral resources as the main target ranges from 1950 to 1998.
These 50 years are the stage from introduction, exploration and perfection to success of exploration geochemistry in China. After 50 years' efforts and keeping pace with the advanced geochemical exploration theory and technology in the world, we have finally found an economical and efficient geochemical prospecting method suitable for China's geological landscape conditions, and achieved outstanding results. Many experts summarized and introduced the 50-year history of exploration geochemistry in China, and published papers and monographs. Here, only a few important events are summarized as follows.
1952 the department of geology and mineral resources of the Ministry of Geology established the geochemical exploration room, 1956 the metallurgical geochemical exploration group was established in the Ministry of Metallurgy. At first, the two geochemical exploration departments mainly carried out the effect tests of primary halo and secondary halo methods in some metal mining areas, and achieved initial results. Immediately, the first generation regional geochemical survey in China began. 1957, Institute of Geophysical and Geochemical Exploration (Xie, Shao Yue, etc. ) was established by the Ministry of Geology, and was established almost at the same time with the metallurgical and non-ferrous geochemical exploration departments (Ouyang Zongqi, etc. ), the primary halo and secondary halo prospecting methods of typical tungsten, tin and copper polymetallic deposits in China are systematically studied and developed, and the primary halo zoning model covering various hydrothermal deposit types is established, which has achieved obvious prospecting results. 1960 to 1977, set up geochemical exploration majors in Beijing Institute of Geology, Changchun Institute of Geology and Guilin Institute of Metallurgical Geology, and cultivate and strengthen geochemical exploration technical teams.
However, at this stage, due to lack of experience and immature technology, the first generation of regional geochemical exploration with soil metal measurement as the main method failed to achieve the expected results. Therefore, in order to explore the regional geochemical exploration methods and new technologies and ideas that adapt to the geological and geomorphological conditions in China, we have been exploring and gestating in the practice of 10 for many years.
1978, Xie proposed a national1:200,000 regional geochemical exploration plan. After summing up the experience and problems of regional geochemical exploration in the early stage and testing the sampling analysis method for more than two years, the Ministry of Geology officially released and organized the implementation of the second generation of national regional geochemical exploration scanning surface in 198 1. Technically, in view of the mountainous terrain in central and eastern China, river system sediment sampling with the scale of1:200,000 was carried out in the whole country except deserts and alluvial plains. 39 indexes such as mineralization, associated elements, trace elements and rock-forming element oxides were analyzed, and a national unified geochemical map of each element was compiled. 1990 inland and coastal areas have basically completed the plan. Remote provinces and regions such as arid desert grassland, forest swamp, loess plateau, karst and Qinghai-Tibet cold belong to special geochemical landscapes. A special sampling method (Ren Tianxiang et al. ) was developed and basically completed in 2000.
At the same time, the geochemical exploration of metallurgy and nonferrous metals with the metallogenic belt as the main target has been systematically carried out, and the investigation plan of regional water system sediments (12 key area, scale1:50,000 ~1:10000) has been carried out, with a total area of nearly 300,000 km2. A large number of large, medium and small gold, manganese, iron and copper deposits have been discovered, and the metallogenic regularity of major metallogenic belts and ore concentration areas in China has been studied, which has increased the reserve resources of mines in various places. In addition, the nuclear industry system and the gold forces have also carried out geochemical prospecting with various sampling media and scales in the metallogenic belt, the periphery of the mining area and the prospective area. China has a prosperous period of large-scale high-tech geochemical exploration.
1980 In May, the professional committee of exploration geochemistry in geological society of china was established. Since then, a national seminar on exploration geochemistry has been held about every four years. He has published professional journals such as geophysical exploration and geochemical exploration.
After nearly 20 years of nationwide systematic scanning survey, by the end of 1997, the national regional geochemical exploration scanning area of the Ministry of Geology and Minerals reached 5.75 million km2, accounting for 88% of the national 6.5 million km2 scannable area. During this period, the regional anomalies were verified, that is, geochemical survey and detailed investigation (1: 50,000 ~ 1: 1 10,000), and more than110,000 km2 was completed. According to (Mou Xuzan) statistics, by the end of 1997,1:200,000 geochemical scanning had found about 43,000 comprehensive anomalies of various elements, of which 1/3 had been checked for anomalies. The scanning surface of regional geochemical exploration has achieved rich prospecting results. During the three five-year plans of 198 1 ~ 1995, 569 large, medium and small deposits with industrial value were discovered through anomaly optimization verification and engineering verification, including more than 50 large ones. According to mineral types: 420 gold and silver mines, non-ferrous metal mines 140, and 9 others. According to the annual statistics, the number of deposits discovered by geochemical exploration is:1981~1985:114; 1986 ~1990: 204,1991~1995: 400. Among them, the potential value of gold mines alone exceeds 200 billion yuan. The minerals with outstanding geochemical exploration results are: gold, silver, copper, lead, zinc, tin, tungsten, molybdenum, nickel, mercury, cobalt, antimony, niobium, tantalum, rare earth and some nonmetallic minerals, totaling more than 20 kinds. Through regional geochemical exploration, new deposits and new types of deposits have been discovered in all provinces, and a large number of anomalies and prospective areas have not been proved, which provides prospecting targets and potential areas for geological exploration departments in all provinces in the next few years.
The regional geochemical exploration and scanning project has promoted the development and perfection of a series of exploration geochemical methods, techniques and theories, such as testing technology, quality control of laboratory analysis and making geochemical standard samples, and ensured the high quality of analytical data and the comparison of national data. For example, the improvement of the detection limit of Au and P t elements has made great contributions to the discovery of a large number of gold deposits: at that time, the detection limit of Au in China was 0.3× 10-9, while that in the United States and Canada was raised from 50× 10-9 to10-9 in the early 1990s. In addition, a large-scale and high-quality analytical data database has been established, a special calculation and drawing software has been developed, and 39 national geochemical maps with different scales have been drawn. On the basis of comprehensive analysis of regional geochemical maps and comparison with known ore concentration areas, Xie put forward the theory of geochemical block mineralization.
During this period, exploration geochemistry in China experienced an all-round prosperity in theory, thought and technology. In order to cope with the situation that outcrop mines will be exhausted, and the difficulty and depth of prospecting will increase, exploration geochemistry has carried out research on deep penetration geochemical prospecting technology, which is called non-traditional method, and has opened up new prospecting technology in coverage area and deep depth. Study on regional geochemistry and regional bedrock geochemical survey methods (Yu Chongwen, Zhang Benren, etc. ) has been paid attention to, and the direction of regional metallogenic potential prediction and evaluation based on the combination of metallogenic belt, ore concentration area and abnormal geological structure conditions has been opened up many times, which has promoted and deepened the research direction of the close combination of exploration geochemistry and metallogenic geological environment. The comprehensive information prospecting technology combining geophysics and remote sensing has been widely used in various provinces. In short, in the 1990s, the methods, techniques and theories of exploration geochemistry in China were improved in an all-round way, and the application effect was remarkable, which made the academic level of exploration geochemistry in China reach the leading position in the world.
1993 16 international conference on exploration geochemistry was held in Beijing. 1996-2006 undertook the task of providing ***8 international exploration technology training courses for developing countries in China. During the 23rd International Exploration Conference held in Spain in 2007, the International Association of Applied Geochemists awarded Academician Xie the "Gold Award of the Association of Applied Geochemists". China's exploration geochemistry has gone to the world and has been widely praised by international experts in this field.
2. 1999 to 20 10 is the applied geochemical stage of resources, environment, ecology and agricultural services.
The research and investigation of environmental geochemistry and agricultural geochemistry in China began in the early 1970s. With the country's reform and opening up and the rapid development of social economy, environmental problems and agricultural planting optimization need to be studied by applying geochemical theory and technology. Since 1980s, some geochemical exploration teams and technicians have turned to environmental or agricultural projects and achieved significant results. In China, the landmark event of the development of exploration geochemistry to applied geochemistry is the national "multi-objective regional geochemical survey" plan which started from 1999. Since then, exploration geochemistry has served the country and society in two aspects: mineral resources exploration and environmental ecology research.
1. Development and deepening of mineral resources exploration geochemistry
Since the 20th century, mineral exploration geochemistry in China has continued to make great strides. With the increase of demand for mineral resources and the difficulty of prospecting in the new period, the national investment has increased accordingly, and geochemical exploration has been strengthened. The general trend is to promote deep prospecting and prospecting in covered areas, and the technology is constantly improving. Outstanding achievements have been made in the following two aspects:
(1) The deepening of the theory and method of primary halo prospecting in mining areas and deep mines.
The comprehensive zoning model of primary abnormal elements in surrounding rocks of hydrothermal metal deposits and the laws of axial and vertical zoning are considered to be important scientific discoveries in the 20th century, which have an important guiding role in deeply understanding the hydrothermal mineralization process and tracking deep blind ore bodies. The primary halo method in mining area is the dominant field of geochemical exploration in China, and has made outstanding achievements in deep prospecting of hydrothermal deposits. For example, from 1970s to 2nd1century, Li Hui, Geophysical Exploration Institute of General Administration of Metallurgical Geology Exploration and Engineering of China, put forward the theory of "structural superimposed halo model" on the basis of years of gold prospecting practice. During their decades of geochemical exploration and prospecting, he and his group have studied and investigated more than 20 gold and other metal hydrothermal mining areas, and applied the structural superimposed halo model to predict more than 200 tons of gold metal. Through the engineering verification of some target areas, 65.9 tons of gold metal reserves have been obtained. A large number of gold mines have extended their mining life and achieved remarkable economic and social benefits.
(2) Exploration of deep penetration exploration technology in coverage area.
Coverage area is the main target of future resource exploration, and various deep-penetrating geochemical exploration methods have emerged, among which geogas method has the most potential. Since the end of the 20th century, Xie, Wang Xueqiu and others have initiated many projects around this topic, from the collection technology of geogas, high-precision analysis method to field sampling, and conducted multi-level experiments in mining areas and regions, which confirmed the existence of geogas and developed technical methods such as "nano-micron metal measurement" and "metal activity method". In recent years, the geogas method has been continuously exploring liquid adsorbent test and other technical methods, and has achieved prospecting results in copper, zinc, nickel and other deposit coverage areas. At the same time, the nuclear industry system has achieved many successes in the exploration of interlayer oxidation zone sandstone uranium deposits in the marginal coverage area of western basins in China.
In addition, geochemical methods have played an important role in the exploration and planning of reserve resources of crisis mines since the Eleventh Five-Year Plan. In recent 30 years, China's oil and gas geochemical exploration has been continuously explored and achieved practical results in some oil fields. In a word, mineral exploration has always been the key task of applied geochemistry, and geochemical exploration has always been in the front line of resource exploration, and it has been expanding to the depth of technology and the breadth of objectives with the needs of the task.
2. Investigation and evaluation of environmental ecological geochemistry
(1) Nature and Planning of Regional Multi-objective Survey
Eco-geochemistry originated in Russia in 1980s, and its basic idea is to include mapping and sampling of eco-geological and environmental geochemical information in addition to geological survey. In the 1990s, China put forward the national "multi-objective regional geochemical survey" plan, which was presided over by China Geological Survey. It was first tried out in Sichuan, Guangdong and Hubei provinces from 1999 to 200 1 year, and gradually rolled out throughout the country from 200 1 year (Xi small ring). The main task is to carry out geochemical surveys in densely populated areas such as plains, basins and river valleys, with soil survey as the main body and water medium sampling as the cooperation. Its goal is not only to detect new mineral resources information such as oil and gas, hot water, but also to include environment, ecology, agriculture, endemic diseases and so on closely related to human health. Multi-objective regional geochemical survey reflects human concern about environmental and ecological problems since the 20th century: pollution caused by the accumulation of harmful elements in natural and man-made soil/water environment, damage to human health caused by endemic diseases, and pollution of agriculture, animal husbandry and fruit and vegetable products. By finding abnormal pollution in the environment in time, put forward countermeasures; At the same time, investigate and delineate selenium-enriched areas in beneficial elements, and develop green pollution-free agriculture. Directly serve local economic development and people's health.
China plain valley area has a total measurable area of 4.5 million km2, which is planned to be completed within 1999 ~ 20 10 years. Multi-objective regional survey and eco-geochemical evaluation are large-scale national basic survey projects, and the survey scope is extended to lakes, wetlands and vast shallow sea and tidal flat areas, which can provide various environmental and ecological status information for national economic development and planning, including lakes, seawater, tidal flats, wetlands and other ecosystems, and have been basically completed as planned.
(2) Technical methods of multi-objective geochemical survey.
Measurement methods and sampling media (mainly soil measurement), including soil, Quaternary sediments and loess sampling; Measurement of water sediments: sampling of sediments from oceans, lakes, beaches, swamps and wetlands, rivers, etc. Water medium measurement: surface water, pore water, groundwater, precipitation and sewage sampling; Biomass measurement: sampling of plants, crops, grains, aquatic products, livestock products and human hair; Atmospheric measurement: industrial waste gas, dustfall, precipitation and acid rain sampling. Detection of harmful organic matter: 2 1 sample of persistent organic pollutants and pesticide residues.
Sampling grid: Double-grid soil measurement is adopted: soil sampling is divided into deep layer and surface layer, and the scale is1:250,000. A deep layer: native soil-unpolluted by human beings, sampling depth 1.5 ~ 2m, 1 piece/4km2; B Surface layer: the soil layer disturbed and polluted by human activities. Take the surface soil with a depth of 20cm, 1 unit /km2.
(3) observation index and analysis method
On the basis of 39 indexes of national geochemical exploration, ecological sensitive elements such as nitrogen, carbon and selenium have been added. After in-depth investigation and evaluation, pH, Eh, C organic matter, COD and persistent organic pollutants were added, and 54 observation indexes were added. A unified analysis method is established, which improves the test accuracy, detection limit and yield.
(4) Verification and evaluation of regional anomalies
It is divided into two levels: regional evaluation and local evaluation:
Regional eco-geochemical evaluation: the sampling grid and scale are1:50,000, and the grid is 6-8 samples /km2. According to the specific characteristics of abnormal ecological environment, the assessment work is divided into six types of geochemical ecosystems: farmland, basins and watersheds, lakes and wetlands, shallow beaches, industrial and mining areas and urban residential areas, and the assessment is carried out according to the national environmental and health standards for harmful elements. Local eco-geochemical assessment (assessment \ early warning \ restoration): It has the thematic nature of eco-environmental problems and should be investigated in detail or studied in profile on a larger scale. Besides evaluating and grading according to national standards, it is also necessary to find out the material sources of natural or human activities of pollution elements, conduct hazard risk assessment and put forward management countermeasures and governance measures.
(5) Achievements made
1) A large number of harmful elements, mainly heavy metals and persistent organic pollutants, are enriched in surface soil and water, and human activities and modern industry have caused pollution to soil, water, urban atmosphere and some crops.
2) Abnormal zones of heavy metals such as cadmium, mercury and lead have been found along the Yangtze River, Pearl River, Xiangjiang River and their tributaries, which may come from low-temperature and non-ferrous metal mineralization zones in southwest Yunnan, Guizhou, Sichuan, Hunan and Guangdong.
3) Due to the geographical and climatic differences between the Yangtze River and the Yellow River in the north and south of China, the supergene migration laws and ecological characteristics of elements are quite different. South China: Acid soil is seriously leached, but elements such as C, N and P are locally enriched or eutrophic in water/soil medium. North China: the soil moisture migration ability is weak in the areas with little rain or drought, and the endemic diseases such as harmful elements F and As are serious; Natural and man-made material sources of endemic diseases and harmful elements have been found in all provinces, and the regional geological background conditions and pathogenic mechanism have been identified through local regional evaluation.
4) Zhejiang, Guangdong, Jiangsu, Jiangxi, Fujian, Anhui, Sichuan and other provinces have circled many areas rich in agricultural nutrient elements such as selenium, molybdenum, boron, nitrogen and K2O, which provides a basis for rational planning of agricultural planting and development of green pollution-free agricultural areas.
Expected final result: regional geochemical maps of national \ provinces \ districts \ watersheds, etc. will be compiled, and the national soil element geochemical basic database and information data management system will be established to serve the economic development and planning of agriculture \ environment \ land \ ocean \ aquatic products \ cities. On the basis of finding out the distribution of beneficial and harmful elements, the development and control countermeasures are put forward, and an early warning and monitoring system is established through local evaluation and special research to solve the pollution/endemic disease problem and avoid the occurrence of ecological environment pollution incidents.
In a word, after 13, China has made new explorations, expanded the observation scope, and increased the experimental projects, which are closer to the field of serving social and economic development and people's health. The discipline of geochemistry has also found a new growth point, and the direction of applied geochemistry is booming. The regional multi-objective geochemical survey fills the blank of regional geochemical exploration in plain areas and makes the basic geochemical data cover the whole territory. China's exploration geochemistry has given full play to the advantages of socialist countries in attaching importance to basic surveys, so the national geochemical survey with large scale, multiple observation indexes, high precision and all-round social services is unique in the world, so it has the international leading level in technical level and application effect.
Third, the prospect of applied geochemistry in China in 2 1 century
With the development of China's modern society and economy, the tasks of resource development and environmental governance are getting heavier and heavier. Prospecting in coverage area and increasing storage of crisis mines are eternal themes of exploration geochemistry, and non-traditional deep-penetration geochemical exploration methods should give full play to their technical advantages. In terms of environment and eco-geochemistry, in recent years, the global carbon cycle and the creation of low-carbon environment, as well as persistent organic pollutants and other issues have become increasingly prominent, putting forward new requirements. Modern chemical and agricultural production, such as the expansion of the use of fossil fuels and organic compounds, emits a lot of greenhouse gases, such as carbon dioxide, which affects global change. Many heavy metal elements and persistent organic pollutants discharged by industry and mining have become strong harmful pollutants. For example, polycyclic aromatic hydrocarbons, nitrosamines and other organic pollutants are recognized as strong carcinogens, which constitute an important killer of occupational contact cancer and endemic cancer. Others, such as excessive chemical fertilizers and pesticide residues, are also harmful to crops and human health; Excessive fertilization and some natural factors * * * together lead to the increasingly serious problem of nitrogen and phosphorus eutrophication in soil and water. China's ecology, environment and agricultural geochemistry are facing severe situation and tasks. Facing the emerging new topics, applied geochemistry still has a long way to go. The authors of geochemical prospecting for miners in China should recognize the demand, seize the opportunity, identify the technical breakthrough, plan the development direction of the discipline, strengthen the team building, and explore new breakthroughs and innovations. In the process of building a well-off society in an all-round way and sustainable development in China in the 2 1 century, applied geochemistry will show new vitality and make greater contributions.
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