1. Terrestrial and marine geochemical mapping project in Japan
Atsuyuki Ohta
Geological Survey of Japan, AIST

2. Contents 1. Introduction 2. Process of geochemical mapping
3. Influence of geology and mineral deposit on geochemical maps in terrestrial area
4. Comprehensive survey of multi-elements in coastal sea and stream sediments
5. Recent topics

3. Introduction
What is a geochemical map ?

4. Geochemical map Chemical information What is a geochemical map?
Topographic Map: Physical information
Vegetation Map: Biological informaiton
Geological Map: Geological information
Metamorphic rock
Sedimentary rocks
of accretionary complexes
Granitic rocks
Unconsolidated sediments
Geochemical map
Chemical information

5. Geochemical mapping in the world
1. Long history of use in mineral exploration.
China is actively making nationwide geochemical maps for mineral exploration
2. Application for environmental assessment
To know natural background level is important for contamination assessment
→ Nationwide geochemical maps have been made in Europe and America
England
Irland
Alaska
Porand
Lis et al. (1995); Weaver et al. (1983); Webb et al. (1978); Xie et al. (2001)

6. FOREGS Geochemical Baseline Mapping Programme
Geochemical mapping in cross boundary and sub-continental scale

7. https://gbank.gsj.jp/geochemmap/
Japanese geochemical mapping project

8. Japanese geochemical mapping project

9. 2. Process of geochemical mapping
1. Sample media, collection and preparation
2. Analytical method
3. Mapping procedure

10. Sample media Stream sediment Soil
　1. Most suitable material for surveying pollution
　2. Large heterogeneity of elemental concentrations
　3. Difficulty of collecting in Japan due to permission
Unsuitable for creating nationwide spatial distribution of elements
Surface water (river water)
　1. Suitable material for surveying pollution
　2. Large variation of elemental concentrations by the day
　3. Large variation of elemental concentrations by rainfall
Suitable for on-time monitoring (not for mapping)
Rock
　1. Hard work of sampling
　2. Large heterogeneity of elemental concentrations in the same lithology
　3. No information concerning pollution
Unsuitable for creating nationwide spatial distribution of elements
Stream sediment
　1. Easily-obtained materials
　2. High homogeneousness in respect to chemical compositions
　3. Representing a composite of materials derived from a widespread area

11. Why does a stream sediment sample represent a composite of materials derived from a widespread area?
A stream sediment is considered to consist of soil, sands and rocks in the catchment area (watershed) upstream from the sampling site.
Kaba Mountain
A sampling site is presumed to express the average chemical concentrations in a drainage basin.
Tsukuba Mountain
Koise River
The catchment area of Sakura River
Sakura River
A geochemical map can be obtained using a small number of samples (3,024 samples in Japan).
Kasumigaura Lake
GSJ, AIST
Here!
The watershed stream network is calculated from a 50 m mesh digital elevation model

12. Sample treatment A speedy and simple method of sample collection
Dried sample
1. Collecting stream sediments in the field (about 1-2 kg)
2. Drying samples in air for 2 weeks
3. Sieving samples with an 83-mesh (180 μm) screen.
4. Removing magnetic minerals from samples using a magnet
Sieving might change elemental concentrations from the bulk stream sediments?
Sieving with an 83-mesh (180 μm) screen hardly changes elemental concentrations from bulk stream sediments (Imai, 1987).

13. Survey of coastal sea sediments
Geological Survey of Japan has been conducting survey of coastal sea in Japan from 1980.
1. Coastal sea sediments around Japan were collected using a grab sampler in 1980–2007 （>4,000 samples）
2. Sediment samples in an inner bay were collected additionally （>500 samples）
１． The uppermost area of 0–3 cm of the sediments collected with the grab sampler was separated
（Rocky, cobble, pebble, and gravel sediments were not used for geochemical mapping. Alternatively, matrix sediments were collected from these samples.）
２． Dring samples in air (more than 2 weeks)
３． Grounding samples with an agate mortar and pestle (not seved)
Photos for collecting marine sediments

14. Sampling location A nationwide geochemical mapping
Land：3,024 samples (1 sample/80-120km2)　
Sea： 4,905 samples (1 sample/60-80km2)

15. 53 elements determined in geochemical mapping project
1 (1A)
2 (2A)
3 (3A)
4 (4A)
5 (5A)
6 (6A)
7 (7A)
   8    (8)
9 (1B)
10 (2B)
11 (3B)
12 (4B)
13 (5B)
14 (6B)
15 (7B)
16 (0) 1 H He 2 Li Be B C N O F Ne 3 Na Mg Al Si P S Cl Ar 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 6 Cs Ba L* Hf Ta W Re Os Ir Pt Au Hg Tl Pb BI Po At Rn 7 Fr Ra A* L* La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu A* Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Green : ICP-AES
Yellow : ICP-MS
Blue : AAS

16. Creating a geochemical map (a mesh map)
The study area is divided into 2 km cells
Five sediments were collected and analyzed for Ca. 1% 3%
1.5% 2%
2.5% 3%
2.5% 2%
1.5% 1%
Creating marine geochemical maps is more simple than terrestrial maps because a watershed is not needed.
A GIS software calculated the elemental concentrations of each cell node using Inverse Distance Weighted method.
The interval of each cell is 2 km
100 km2-wide watershed

17. Influence of geology and mineral deposits on geochemical maps in terrestrial area
What is a controlling factor?
1. Influence of geology
2. Influence of metalliferous deposit
3. Influence of anthropogenic activity
(4. Influence of hydrothermal activity)

18. (composed of rock materials)
Mean chemical compositions of Japanese upper crust, stream sediments and coastal sea sediments
Sediments (soil soil, and mud) cover the ground (a few m ～ 1,000 m)
Mountain
Valley
（river）
Sea
The earth crust
(composed of rock materials)
～10km
The earth’s surface is composed basically of rock materials.
Do stream and coastal sea sediments represent the chemical composition of the upper crust (rock materials) ?

19. Mean chemical compositions of Japanese upper crust, stream sediments and coastal sea sediments
The median elemental concentrations of the Japan upper crust (rock samples), stream and coastal sea sediments are normalized to continental upper crust data.

20. 1. Influence of geology on spatial distribution of elemental concentrations
Granite
Mafic volcanic rocks
Ultramafic rocks
Granite
Be, Na, K, Zr, Nb, rare earth elements, Ta, Hf, Th, U
Mafic volcanic rocks
Mg, P, Ca, 3d transition metals, Zn
Felsic volcanic rocks
alkali elements, Ba
Ultramafic rocks
Mg, Cr, Co, Ni
Accretionary complexes (mudstones and sandsones)
Li, K, Rb, Cs
Accretionary complexes
Felsic volcanic rocks

21. 2. Influence of mineral deposits on spatial distribution of elemental concentrations
Geochemical map of Pb
Geochemical map of Hg
Itomuka mine
Kamioka
mine
Cross symbol :
Zn-Pb type
deposit
Ogoya
mine
Active erosion resulting from high rainfall and steep mountains conceal the impact of mineral deposits on elemental abundance
Cross symbol :
Hg deposit

22. 3. Influence of anthropogenic activity on spatial distribution of elemental concentrations
Urban area
Urban area

23. Comprehensive Survey of Multi-Elements in Coastal Sea and Stream Sediments
Elemental transportation and diffusive process
from terrestrial areas
to coastal seas or in marine environments

24. Particle transfer from land to sea
Sediments are transported by a gravity flow (submarine landslide)
Funning out
Oceanic currents disperse sediments

25. Transfer of heavy metals from mining area and populated area to marine environment
Urban area ?

26. Recent Topics

27. Terrestrial γ-ray dose rates at a distance of 1 m above the ground (D)
D (nGy/h)
= 13.0CK (%) + 5.4CTh (mg/kg) + 2.7CU (mg/kg)
CK, CTh, and CU mean the concentrations of K, Th and U, respectively
(Beck et al., USAEC Report HASL-258; Minato, J. Geograph )
Fukushima dai-ichi
nuclear power plant

28. ? Map of Sr isotopic ratio 目的
Provenance study for archaeological samples and food products ?

29. Summary
1. Geological survey of Japan, AIST has conducted comprehensive geochemical mapping project in terrestrial and coastal sea regions
Many countries have produced national, cross-boundary and sub-continental geochemical atlases (only in terrestrial area), intended mainly for mineral exploration and environmental assessment
2. Geochemical variation occurring among terrestrial areas is explained conclusively in relation to the lithology and distribution of mineral deposits
3. Various kinds of horizontal particle transfer processes are found in the comprehensive geochemical maps
4. Geochemical maps are increased in application
Radiation risk estimation
Provenance study of archaeological samples and food products
Criminal investigation
Geoneutrino ···?