GEOBOTANICALTOOLS

forMineral

EXPLORATION

Introduction• Plants have close relationships with the

underlying regolith substrate.• Plant roots: extend tens and even hundreds of

metres.• Develop both physical and chemical

associations with subsurface regolith materials• Thus, ground organs of a plant may be

connected with underlying regolith materials.

• Expressed at the land surface by changesin plant communities, species distributionand abundance, biogeochemicalcharacteristics and morphology of plantsand plant organs (eg stunted tree growthassociated with shallow regoliththickness).

Geo-botanical Anomalies• Remote sensing has been utilized to map

geobotanical anomalies associated withmineral deposits.

• Bio-geochemical prospecting techniquesare useful for mapping geologic substrateand mineral anomalies.

• Bio geochemical techniques have alsobeen utilized to prove mineral uptake,including gold,in several species of plants.

• Soil –geochemical, bio-geochemical, andvegetal-spectral anomalies have beendetected in U.S.Certain elements are toxic to vegetationand their presence in underlying zones ofmineralization can cause stress, ifaccessed by the root system.The stress manifests morphological andmutational changes in the plant(geobotanical anomalies)

Geo-botanical guides and features revealing anomalies

• The observed structural and physiologicalexpressions may include dwarfism, gigantism,or chlorosis.

• Dwarfism and gigantism are relatively easy tospot in the field. On the other hand, chlorosisand other changes at the cellular level, maycause subtle changes not readily apparent to theunaided human eye.

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• Shift in the spectral position of chlorophyllbands have been found in the forestsaffected by metal induced stress.

• The metal affect causes the infraredchlorophyll edge to shift towards the shortwavelength end of the spectrum, (the blueshift).

• Salts of copper, zinc, and nickel inconcentrations of 100 ppm metal in thesoil appear to retard the development ofchlorophyll in the laboratory plants.

Geo-botanical sampling and mapping

• A particular plant species in the area ofmineralization works as a guide to locate ore.

• The growth and distribution of a particular plantis influenced by sub-surface geology.Geo-botanical survey involves-

• study of the nature of the vegetative cover,• plant distribution,• the presence of indicator plants,• mutational or morphological changes in species

due to mineral enrichment.

For mapping purpose:generally plots of 5 sq km are chosen.the plant species found in them, their

growth, density of growth, new species,rare species etc are marked.A species which shows special affinity to

the area is chosen by a process ofprogressive elimination.The association of these species with anyknown mineral occurrence in the area isestablished if such a correlation exists.This correlation can be used for searchingadjacent larger areas.

Indicator Plants• Two types of indicator plants are recognized

1. Universal indicators2. Local indicators

• Universal indicators grow only in a mineralizedterrain and are seen world over in similar setups.

• They are rare in their occurrence and distribution.• The local indicators are more common but are

important only locally. eg In North Kanara district ofKarnataka, local prospectors believe thatmanganese deposits show association with plantslike- ’nama’, ‘kundal’, ‘jamka’, and ‘karipatha’.However this association is yet to be scientificallyestablished.

Element Universal indicators Local indicators

1. Cobalt Crotalaria cobalticola,Silene cobalticola

--

2. Copper 1. Acrocephalus -robertii,

2. Astragalus –declinatus,

3. Becimum homblei,4. Gypsophila patrini,5. Merceya latifolia,6. Merceya lingulata,7. Mielichhoferia –

macrocarpa,

1. Armeria meritima,2. Elsholtzia –

haichowensis,3. Eschscholtzia –

mexicana,4. Polycarpaea glabra,5. Polycarpaea -

spriostylis,6. Polygonum posumbu

Element Universal indicators

Local indicators

Copper ….

1. Mielichhoferia -Mielichhoferia,

2. Tephrosia sp.,3. Viscaria alpina

--

3. Iron -- 1. Betula sp.,2. Clusia rosea,3. Dacrydium -caledonicum,4. Damnara ovata,5. Eutessa intermedia

Element Universal indicators

Local indicators

4. Lead -- 1. Baptisia - bracteata,2. Erianthus giganteus3. Tephrosia polyzyga

5. Manganese -- 1. Digitalis purpurea2. Fucus vesiculolus3. Trapa natans4. Zostera nana

6. Molybdenum -- 1. Astragalus - declinatus

Element Universal indicators

Local indicators

7. Nickel -- 1. Alyssum –bertolonii,2. Asplenium -adulterium,3. Pulsatilla - patens

8. Phosphorus

-- 1. Convolvulus -althaeoides

9. Selenium 1. Aster venusta,2. Asteragalus spp.,3. Oonopsis spp.4. Stanleya spp.

1. Neptunia -amplexicanlis

Element Universal indicators

Local indicators

10. Selenium & Uranium

1. Astragalus (certain spp.)

--

11. Silver -- 1. Eriogonum -ovalifolium,2. Lonicera -confusa

12. Vanadium 1. Astragalus-bisulcatus

Element Universal indicators Local indicators

13. Zinc 1. Thlaspi -calaminare,2. Thlaspi -cepaeacfolium,3. Viola -calaminaria,4. Viola lutea

1. Gomphrena -canescens,2. Matricaria -americana,3. Philadelphus sp.

• The presence of these plant species isindicative of the corresponding elements.

• Some mutational effects caused by certainelements on certain plants are also veryuseful in recognizing them.

• In multi-spectral aerial photography, themutational effects can be recognized.

• Thus they provide an indirect evidence ofthe possible presence of certain elementsin regional scale explorations.

Mutational effect and their causative elements

Element or mineral

Mutational effect

1. Chromium Chlorosis of leaves2. Cobalt Increase of chlorophyll in some

species and chlorosis in others3. Copper Chlorosis of leaves & dwarfism4. Iron Darkening of leaves5. Manganese Chlorosis of leaves with white

blotches6. Molybdenum Formation of abnormally coloured

shoot

Mutational effect and their causative elements

Element or mineral

Mutational effect

7. Nickel Chlorosis and nacrosis in leaves8. Serpentine Dwarfism, colour changes of flowers9. Uranium & radioactivity

Variation in flower colour, presence of abnormal fruits, increase in chromosomes of nucleus, stimulation

10. Zinc Chlorosis of leaves, symptoms of manganese deficiency

Geo-botanical prospecting in India

• Certain species of plants are seen inmineralized belt and metal content ofplants growing in these areas is richlyanomalous than those growing in barrentract.

• Some studies have been carried out usingcertain indicator plants for the search ofmineralization in the extension areas ofthe known mineralized belt.

Different indicator plants identified in various mineralized areas in India

• Luxuriant growth of Leucas aspera (family:Labiatae) on mine dumps, slag heaps andwaste dumps of the sampling shed in Rajpura-Dariba area.

• Samples of ashes prepared from the differentparts of the plant shows conspicuousconcentration of zinc and this plant can beused as a local indicator of zinc in the Rajpura-Dariba.

• A possible zinc indicator plant viz. Impatiensbalsania is identified in the Zawar Pb-Zn belt. Alarge population of such plant species is foundto grow selectively on zinc dumps and in areasof the mineralized belt.

• Growth of a species of plants with golden yellowflowers (similar to sun flower) as observed in mostparts of the auriferous tracts of Karnataka, has beennoticed in abundance, all along the auriferous tractsof Ramagiri- Penakacherla schist belt, Veligalluschist belt.

• This plant is identified as Pulicaria Angustifolia ofCompositae family.

• The samples collected from this plant speciesanalysed up to 200 ppb Au.

• Polycarpae cormybos Lamk is seen in thecupriferous area of Agnigundala. The same speciesis recognized in Singhbhum copper district.

• The absence of this species in neighbouring Pb-Znmineralized zone assumes significance and thegrowth shows preference for copper.

Gold colloids precipitated along a fungal hyphae isolated from soil samples from Gold

Mine, Australia

Fossilized colony of bacterial cells, Pedomicrobium sp. australiensis, on a gold flake panned from soil close to a gold mine, Australia