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Geochemical Exploration in Thailand

06 Jan 2021
23

Geochemical Exploration

Geochemical Exploration is a method for investigating the unusual elements existed in the nature applying chemical analysis to determine the amount or composition of compounds in rocks, soil, sediment, or plant.

Figure presents the distribution of elements in nature
Geochemical exploration can be conducted by the following 4 steps.

Orientation Survey is a preliminary survey surrounding the explored area to review the geological and geochemical condition applying for a guideline of the further survey.

Regional Geochemistry Survey is the exploration for preparing geology map in the large area by collecting sample of action stream and sieving for the major elements in the stream. The survey area is 1 to 10 square kilometer per sample. The collected data will be applied for specifying area for the further survey and being the beneficial information for agriculture and environmental quality control.

Semi-detail Geochemical Survey is the exploration in the small area that have the mineral potential by collecting sediment or soil sample. The distance between each sample is 200 to 500 meters.

Detail Geochemical Survey is the detail survey in specified area expecting to find the mineral site underneath by making trench exploration, digging the exploration hole, and collecting soil or rock sample. The distance between each sample is 10 to 100 meters.

  • To get the geochemical data presenting the distribution of metal elements for applying as the database for country development planning on agriculture and industries.
  • To apply as the database for preventing and mitigating the environmental impact that might occur due to the implementation of national development project.
  • Specify the area that might be impact from the contamination of elements and the suitable land use for the area.

Geochemical exploration in Thailand is the regional survey that has been implemented since 1985. Firstly, the major objective of the exploration is the mineral survey to prepare the mineral potential area information. Then the provincial geochemical exploration was conducted to provide the basic geology information of Thailand, survey the area that might be risk from the natural toxic, and prepare the basic geochemical for improving the quality of life. The provincial exploration covered 18 elements analysis meanwhile the preparation of the basic geochemical for improving the quality of life covered 34 elements analysis performed by the private company costing high budget which can afford for 2 year. However, the provincial geochemical exploration has been still implemented covering all provinces in Thailand to be applied as the importance basic national information on economy, environment, and quality of life.

Geochemical exploration comprises 4 steps:

step 1Collect the secondary data and study the geology characteristic of the site

1. Sample collection planning:Sediment sampling point must cover all site depending on:

  • Size of the area
  • Size of the area
  • Boundary of the potential area
  • Duration and budget

and specify the sampling referring to the above information.

step 2Collect geochemical sample and prepare sample for chemical analysis

2. Sediment sampling:separate as 2 steps e.g., sample collection and sample preparation for chemical analysis. The sample must be collected from the active sediment area.

Present points (red dot) of sediment sampling for regional exploration, distance of each point is about 2-5 kilometer

The collected sample must be air dry. In case of the sample is not completely dried, it must be dried in the oven at 60 decree Celsius for 45 minutes to 1 hour and left it cool down to room temperature. Mash the sample in a mortar (be careful to avoid cracking of stone or mineral grain) then sieve with no. 80 mesh to get at least 200 grams of sample, mix it, and divide the sample by coning and quartering method. Put 100 grams of sample into double layer plastic bag, label number of sample and submit for chemical analysis. Keep the remaining as the reference.

step 3Submit sample for chemical analysis to determine amount of elements

3. Chemical analysis:Depend on the efficiency of analytical tools. Tool that can analyze trace elements and identify many types of element is benefit for getting the information that can be applied efficiently.

Geochemical exploration can be analyzed as 2 types depending on budget of each project

1.analyze at Department of Mineral Resources: the sample will be analyzed for 18 elements comprising As, Ba, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Sb, Ti, V, and Zn using ICP-OES

2.analyze by private company: the sample will be analyzed for 34 elements comprising Ag, Al, As, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, La, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Sc, Sn, Sr, Ti, V, W, Y, Zn, and Zr using ICP-MS.

step 4Evaluate the result statistically to identify the amount of element that is unusually high and prepare the report

4. Evaluate and interpret the result:Identify background amount, maximum of background amount, the unusual high amount, and prepare geochemical map.

  • Evaluate that the area found high amount of element is significantly or not
  • Evaluate the cause of the unusual high amount
  • Study factors controlling the distribution of the element
  • Find the area expecting to involve with the mineral site for further exploration
Present the example of interpretation of lead (Pb) distribution in Singburi
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DMR

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Mineral Resources

Department of Mineral Resources

Ministry of Natural Resources and Environment
75/10 Rama VI Road, Ratchatewi, Bangkok
10400
+66 2 621 9500
+66 2 354 2504
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