| Topics | Historical Overview | Analysis | Data Management | Current Exploration Challenges | Environmental Geochemistry | Contacts |
The Seminar on Regional Exploration Geochemistry sponsored by the Coordinating Committee for Coastal and Offshore Geoscience's Programmes in East and Southeast Asia (CCOP), Ministry of Land and Resources of China (MLR) and China Geological Survey (CGS) was held in Beijing, China on May 21-26, 2001.
The aims of the seminar were to have the CCOP member countries share their ideas, technology and experiences on geochemical exploration/mapping in China, to apply them in national geochemical mapping using different sampling media in different geographic environments in the CCOP member countries, to discuss the implementation of global geochemical mapping using flood-plain sediments as the sampling medium to quickly obtain an overview of the distribution of 71 elements in the CCOP member countries, and how to use a huge mass of information of geochemical data in mineral exploration, basic geology, environmental monitoring and agricultural production increase.
The 42 participants from 10 CCOP country members (Cambodia, China, Indonesia, Japan, Korea, Malaysia, Papua New Guinea, Philippines, Thailand, Vietnam) and from Argentina had an excellent opportunity to share and exchange ideas, standards, technology and experiences in geochemical exploration and geochemical mapping through 4 days of lectures and many hours of fruitful discussion, and a one-day visit to the Institute of Geophysical and Geochemical Exploration (IGGE) in Langfang.
The seminar focused on the following topics:
Exploration geochemistry was first used in the 1940s as a prospecting technique in mineral exploration. With this 60-year development exploration geochemistry has expanded its scope from mineral exploration to geochemical mapping and environmental geochemistry.
Since 1979 China's National Geochemical Mapping Project, the Regional Geochemistry - National Reconnaissance (RGNR) project has been implemented. During the past two decades, it has covered more than 6 million km2 of China's territory with stream sediment sampling and multi-element analysis for 39 major, minor, trace and ultra-trace elements. It has proven to be one of the most successful geochemical mapping projects in the world. It has made a magnificent contribution to mineral exploration in China. The discoveries of 579 ore deposits including precious metals (421), base metals (139), dispersed metals (12) and others (7) are due to this project. This project also provides a huge mass of information for basic geology, land use and environmental monitoring. The project is ongoing until China's entire territory is covered. The Geochemical Atlas of China with 39 elements will be published in the near future.
In the 1970s and '80s regional or national geochemical mapping projects were carried out in many countries. However, due to lack of standards the results were not satisfactory except in China. Thus standardization for geochemical mapping is particularly needed. The International Geochemical Mapping Project, whose main aim was to establish standards, was accepted as part of the International Geological Correlation Program (IGCP259) in 1988. The ideas, standards and methodology of China's National Geochemical Mapping Project contributed much to the IGCP259. In 1994 Global Geochemical Mapping Project using wide-spaced sampling in approximately 5000 GRN (Geochemical Reference Networks) cells to cover the whole earth surface to generate a global geochemical atlas was accepted as the IGCP360 entitled "Global Geochemical Baselines" in 1995. The Environmental Geochemical Monitoring Networks Project in China as the pilot study for the IGCP360 has demonstrated that flood-plain sediments from large basins are suitable a sampling medium for global geochemical mapping. The results of the two projects were summarized in a special UNESCO publication entitled " A Global Geochemical Data Base for Environmental and Resource Management".
To meet the requirements for the China's National Geochemical Mapping Project in the initiation stage of the late 1970s and early 1980s, more than 20 laboratories from all over China made a great effort to develop the analytical methods, prepare the standard materials, and design the quality control scheme. Today this analytical system and experiences have made a great contribution to the International Geochemical Mapping and the Global Geochemical Mapping.
To manage the huge set of data from the China's National Geochemical Mapping Project, software based on GIS for data management, processing and integrated interpretation of geochemical datasets has been developed and named the Regional Geochemical Database and Information System (GeoMDIS 2000). Since 1994 three versions have been released; it has become a basic tool for geochemical data management, data processing and map generation in China.
There are large diverse unexplored or under-explored overburden terrains in China and abroad that still remain to be covered by geochemical mapping. However, conventional geochemical methods are not suitable for or have limited application in searching for deposits hidden under cover of transported overburden or sequence of post-ore volcanic or sedimentary rocks. Development of low-cost and efficient methods is a real challenge for regional exploration of targets in such terrains. Deep-penetration geochemical methods have been developed and are being further exploited by use in regional survey in various overburden conditions such as alluvium, sand desert, grassland, loess and laterite terrains.
From the 1980s the search for giant ore deposits has been becoming the focus of the world mining industrial activities. Great efforts have been made in developing criteria for recognizing geological processes or settings favorable for the occurrence of giant ore deposits. However, such efforts have not led to encouraging results. This induced us to consider how to use the mass of high quality data obtained from China's Geochemical Mapping Projects to estimate the metal endowment (metal supply) necessary for the formation of large/giant ore deposits. A hierarchy of nested geochemical patterns was found in 1990s from the study on tungsten patterns in the whole of China. In 1995 further investigation recognized that the hierarchy of geochemical patterns are really the surface expressions of large rock mass with high contents of certain metal or metals. Total tonnage of metals in the rock mass could be calculated at given thickness of the rock mass (500 m or 1000 m), and its internal structure can be used to track the build-up of metal concentration toward the formation of an ore deposit. Such rock mass is termed a "geochemical block", whose area is equal or larger than the dimension of a geochemical province.
As a group of developed countries, Europe has its environmental problems. Dr. Shaun Reeder presented the progress of the Global Geochemical Baseline Project in Europe and used Europe as an example how to employ geochemical data to monitor and assess environmental problems. As a developing country, China (and other Asian countries) is also facing environmental problems. Multi-level environmental geochemical systems for monitoring regional, national and global environmental problems and the development of cost-effective bio/phytoremediation technology to clean "Delayed Geochemical Hazards" were proposed.
Resources, environments and population growth are the three main problems influencing the survival of human being. Mineral resources are composed of elements, while environmental problems in turn reflect the distribution and behavior of chemical elements in nature. Geochemistry studies chemical elements' distribution and behavior, and thus it can make a greater contribution to solving resource and environment problems in the new millennium.
The seminar has aroused wide interest to the participants from the CCOP member countries. Mr. Jiang Chengsong, Deputy Minister of MLR, Dr. Zhang Hongtao, Deputy Director-General of CGS, and Mr. Chen Shick Pei, director of the CCOP Technical Secretariat, have reached an agreement on further cooperation in the implementation of global and national geochemical mapping in East and Southeast Asian countries in the future.
Xueqiu Wang
Institute of Geophysical and Geochemical Exploration
Langfang, Hebei 065000
China
E-mail: xqwang@public.lfptt.he.cn
or geochemistry@sina.com