geo-vegetation mapping and soil geochemical ...en.earth-science.net/pdf/20140116105821.pdf · the...

Journal of Earth Science, Vol. 25, No. 1, p. 152–168, February 2014 ISSN 1674-487X Printed in China DOI: 10.1007/s12583-014-0409-7

Hewawasam, T., Fernando, G. W. A. R., Priyashantha, D., 2014. Geo-vegetation Mapping and Soil Geochemical Characteristics of In-dikolapelessa Serpentinite Outcrop, Southern Sri Lanka. Journal of Earth Science, 25(1): 152–168, doi:10.1007/s12583-014-0409-7

Geo-vegetation Mapping and Soil Geochemical Characteristics of the Indikolapelessa Serpentinite Outcrop,

Southern Sri Lanka

Tilak Hewawasam*1, 2, G W A R Fernando3, Danushka Priyashantha1 1. Department of Natural Resources, Sabaragamuwa University of Sri Lanka, Belihuloya, Sri Lanka

2. Department of Geography, University of Peradeniya, Peradeniya, Sri Lanka 3. Department of Physics, Open University of Sri Lanka, Nugegoda, Sri Lanka

ABSTRACT: The serpentinite blocks of Indikolapelessa, located along an identified litho-tectonic boundary between the Highland Complex (HC) and the Vijayan Complex (VC) of Sri Lanka, have undergone extensive lateralization with metal enrichment. Characteristic serpentinite vegetation with some endemic species was recognized in the soils and supergene deposits develop on serpentinite lithology. This type of geological and ecological relationship forms vegetation covers on serpentinite lithologies which are sharply demarcated from the surrounding metamorphic terrains. The aforesaid “geo-ecological phenomenon” can be used as a tool for geo-vegetation mapping in ultramafic terrains to trace the geological boundaries in landscapes where rock outcrops are virtually absent. We success-fully applied the concept of geo-vegetation mapping in order to demarcate the boundary of underlain serpentinite rocks from surrounding non-serpentinite metamorphic rocks (e.g. granitic gneiss). The hypothesis was supported by the geochemical variations of soils/supergene deposits found at serpen-tinite and non-serpentinite sites, especially immobile elements and some trace elements. Based on whole rock chemistry and soil chemical data obtained, we suggest that the Indikolapelessa serpentinite outcrop, together with the other four serpentinite outcrops, is more likely to represent the Mg-rich mantle fragments at the time of overthrusting of the two crustal blocks of HC and VC during the Pan-African event. KEY WORDS: serpentinite, serpentinite soil, geochemistry, geo-vegetation, ultramafic rock, Sri Lanka.

1 INTRODUCTION The growth of plants is very characteristic on serpentinite

soils and as indicator of the inherited soil properties, as evident from many plant studies carried out elsewhere in the world (Rajakaruna et al., 2009; Brady et al., 2005; Macnair and Gardner, 1998; Kruckeberg, 1984). Consequently, the flora on serpentinite soil is very typical, with specialized slow-growing species including some endemic varieties (Rajakaruna and Baker, 2004). Besides its uniqueness in composition, the areal covers of vegetation also greatly differ on serpentinite soils compared to soils develop on other geological formations. Therefore, a remarkable distinction exists between the vegeta-tion grown on serpentinite and non-serpentinite soils and the boundary between a serpentinite outcrop and the surrounding lithology should be easily detected based on the vegetation cover. Recognizing geological boundaries through vegetation, commonly referred to as “geo-vegetation mapping”, would be

*Corresponding author: [email protected] © China University of Geosciences and Springer-Verlag Berlin Heidelberg 2014 Manuscript received June 19, 2012. Manuscript accepted October 22, 2012.

an excellent alternative for the conventional method of geo-logical mapping which becomes a difficult task particularly in wet tropical regions where geology is mostly hidden by a cover of thick vegetation (Nash and Hernandez, 2001). In this context, vegetation cover on a landmass can be simply identified even remotely using aerial photographs and/or satellite images. Therefore, the concept of geo-vegetation mapping, which relies on differences in vegetation developed on serpentinite and non-serpentinite soils, is used in this study to demarcate the geo-logical boundaries at Indikolapelessa serpentinite outcrop in southern Sri Lanka. The reliability of geo-vegetation mapping was cross-checked by a detailed soil geochemical study with special emphasis on the boundary zones. This study may be the first approach of conducting such a geo-vegetation mapping in Sri Lanka to trace geology which otherwise remain obscured by vegetation.

Variations in the vegetation along geological boundaries between altered and unaltered rocks and zones of mineraliza-tion have been recognized by several studies world-wide during the last century and well-reviewed (Rajakaruna et al., 2009; Brady et al., 2005; Brooks, 1972). The reasons for the vegeta-tion changes, particularly across the serpentinite and non-serpentinite boundaries, should be attributed to the physical and chemical properties of soils that develop on serpentinite rocks

Geo-vegetation Mapping and Soil Geochemical Characteristics of Indikolapelessa Serpentinite Outcrop

153

which vary from those of soils develop on nearby non-serpentinite rocks. Previous analyses elsewhere in the world suggest that either physical or chemical properties individually or both physical and chemical factors together are the causes of the differences in vegetation. Such analyses are still scarce on serpentinite outcrops in Sri Lanka. Instead, Rajakaruna and Bohm (2002) conducted a floristic survey covering four serpen-tinite outcrops in Sri Lanka at Ginigalpellessa, Indikolapelessa, Ussangoda and Yodaganawa with a limited number of samples. They broadly suggested that chemical and physical features of the soil samples collected from the serpentinites in Sri Lanka were typical of such lithologies found in other parts of the world. Moreover, their study stimulated a detailed investigation to understand how the soil physical and chemical conditions adversely affect on the healthy growth of plants. Therefore, it is rational and significant to undertake a comprehensive soil study analyzing elemental concentrations, soil depths, and soil tex-ture covering a large number of samples. Hence, a detailed study on geochemical mapping simultaneously characterizing some soil chemical and physical properties was conducted at the Indikolapelessa site in order to verify the geo-vegetation boundaries and to understand the relationship between soil conditions and the existing vegetation.

Serpentinite outcrops found in Sri Lanka had been deeply weathered under tropical climate; with their upper part resem-bling a lateritic crust with a high content of Ni and Cr. For this reason, previous studies on serpentinites tend to address their economic potential to extract metals rather than to understand how they have been generated (Dissanayake, 1982; Dissanayake and Van Riel, 1978). Interestingly, all known serpentinite out-crops are located on the lithotectonic boundary of Highland Complex (HC) and Vijayan Complex (VC). Based on our soil geochemical data, we propose an initial hypothesis elucidating the emplacement of serpentinite outcrops along the lithotec-tonic boundary. Although this idea is supported by the geo-chemical discrepancies observed only in soils derived from the serpentinite outcrop and surrounding non-serpentinite rocks at Indikolapelessa, other known outcrops in the country were also visited for geological observations.

2 SERPENTINITE OUTCROPS IN SRI LANKA

The island of Sri Lanka is mainly underlain by Proterozoic high-grade rocks metamorphosed under granulite to amphibo-lites facies conditions. The Protorozoic basement rocks are subdivided into four crustal units based on Nd modal ages and geochemical characteristics (Cooray, 1994; Milisenda et al., 1994). They are identified as: (1) the Highland Complex (HC), (2) the Vijayan Complex (VC), (3) the Wanni Complex (WC) and (4) the Kadugannawa Complex (Fig. 1). The contact be-tween the HC and the VC is geologically distinct, being a su-tured boundary of two crustal fragments. So far, six serpentinite outcrops have been found in Sri Lanka viz. at Ussangoda, Indiko-lapelessa, Ginigalpellessa, Katupota, Yodaganawa and Rupaha. Five of them, except the one at Rupaha, occur in alignment with the contact between the HC and the VC (Fig. 1). These serpen-tinite outcrops contain large amounts of ultramafic minerals such as olivine, pyroxene and chromite. A mineralogical study con-ducted at the Udawalawa serpentinite outcrops covering both sites

80º 81ºE

Kadugannawa Complex

Miocene Wanni Complex

Highland Complex

Vijayan ComplexDolerite?

?

?

?

?

9ºN

7º

6º

8º

0 30 km

Colombo

Anuradhapura

Trincomalee

Jaffna

Sedimentary Metamorphic units

Intrusives

UssangodaGinigalpelessa

Katupotha

Rupaha

Yodaganawa

Indikolapellesa

N

Thermal spring

Figure 1. Geological subdivisions in Sri Lanka (Cooray, 1994) showing the locations of serpentinite outcrops. Note that five serpentinite outcrops are aligned along the litho-tectonic boundary between the Highland Complex (HC) and Vijayan complex (VC). at Ginigalpelessa and Indikolapelessa revealed that the rocks are composed with more than 90% of pyroxene and olivine, and the rest is made up with orthoclase, plagioclase, diopside and magnet-ite (Dissanayake, 1982; Dissanayake and Van Riel, 1978). The colour index is reported to be over 99%. Rupaha deposit is located toward the center of the island, far off from the litho-tectonic boundary, and referred to as a ‘metamorphosed serpentinite rock’ rather than an ultramafic rock (Fernando, 2001). It is pale green in color and mineralogically different from the other serpentinites because of extensive secondary carbonization. The rock is now interlayered with surrounding granulites (Fernando, 2001). The genesis of the other five serpentinite outcrops has not been dis-cussed anywhere. But, considering their northward orientation close to the litho-tectonic boundary, it is believed that these ser-pentinite outcrops have a deep-seated origin. A few exposures of another ultramafic or mafic rocks, commonly called as “dolorite dikes”, have been mapped in the eastern part of the country, but their genesis has not been discussed anywhere yet.

Tilak Hewawasam, G W A R Fernando and Danushka Priyashantha

154

3 METHODOLOGY A base map of the serpentinite outcrop at Indikolapelessa

was prepared demarcating the serpentinite and non-serpentinite boundary considering the vegetation pattern (Fig. 2a), based on satellite images. The demarcated boundary of this preliminary vegetation-map was verified at the field by means of re-tracing the vegetation boundaries based on visual observations and mapping all existing serpentinite exposures using a GPS.

This map was gridded into 100 m intervals and soil sam-pling was done to represent at least one sample from 0.01 km2 grid using the GPS. Sixty-four soil samples were collected at the depth of 10–25 cm from the surface in the serpentinite out-crop and surrounding non-serpentinite areas (Fig. 3). Moreover, 6 rock samples from the existing serpentinite outcrops at both Indikolapelessa and nearby Ginigalpellessa serpentinite bodies were obtained to determine their chemistry.

To determine the soil pH, 10 g of homogenized soil from each sample was mixed with 20 mL of 0.01 M CaCl2 solution. The suspension was stirred several times over a period of 30 minutes and allowed to stand for 1 h. After the complete set-tlement of the particulate material, pH of the supernatant solu-tion was measured using an Orion 4 star (thermo electron cor-poration) portable pH meter. The pH measurements were car-ried out at the Geological Survey and Mines Bureau (GSMB) of Sri Lanka.

All soil samples were air dried until complete dryness and were homogenized by mixing. Soil fraction of below 2 mm diameter was separated and powdered using a motor and pestle and, the fraction of less than 0.25 mm was taken for wet chemical analyses. Collected rock samples were powdered and the fraction less than 0.25 mm was taken for the wet chemical analyses. An accurate weight of 0.5 g of each homogenized sample was dissolved in 10.5 mL of HC1 (37% p.a.) and 3.5 mL of HNO3 (65% p.a.) in a 50 mL Teflon crucible. The sam-ple was left for digestion over 12 h and then placed on a sand bath at 160 °C over 3 h until a complete extraction was ob-tained. Then, the solution was allowed to cool and subse-quently diluted to 50 mL. Quantitative elemental analysis of the solution was carried out by Atomic Absorption Spectroscopy (AAS, GBC Avanta 933AAA), using the facility available at the Geological Survey and Mines Bureau of Sri Lanka, for Zn, Cd, Cu, Cr, Al, Mg, Ca, Ni, Mn and Fe. The spatial distribu-tions of elemental composition are illustrated in the Appendix (Figs. Sup-1 and Sup-2). The complete list of results is tabu-lated in Appendix-Table 1. Texture of soil samples collected from serpentinite bare lands and non-serpentinite surrounding was examined by a gradational analysis. An approximate weight of 200 g of soil was air dried until complete dryness and passed through a set of sieves of 4.75, 2.36, 1.18, 0.60, 0.30, 0.15, and 0.075 mm (Appendix-Table 2).

During the sampling and chemical analyses, quality con-trol methods were followed in order to collect the most repre-sentative samples and to maintain the accuracy and precision of the measurements. Samples were weighed carefully using an analytical balance and duplicate samples were run at every 10 samples to verify the precision. Standard reference samples were run in every sample batch to maintain the accuracy. Repe-titions were made at every 10 samples to check the precision of

data. Maximum care was taken to minimize random and sys-tematic errors. A calibration curve was obtained and all the tests were carried out in duplicates to establish confidence in the accuracy and reliability of data generated. 4 RESULTS AND DISCUSSION 4.1 Field Relationships at the Serpentinite Outcrop at In-dikolapelessa

In southern Sri Lanka, three serpentinite outcrops occur at Ussangoda (near Ambalantota), Ginigalpelessa (near Udawalawa) and Indikolapelessa (near Udawalawa), whilst Ginigalpelessa is the largest one spreading in an area about 1 km2. The outcrop at Ussangoda is relatively small covering an area of about 0.3 km2. The top of the serpentinite outcrop at Ussangoda is covered by a thin layer of red colored soil which is believed to be aeolian in origin. The Indikolapelessa serpen-tinite body, which is the focus of the present study, is situated close to the Ginigalpelessa outcrop and covers an area of ap-proximate 0.3 km2. The Indikolapelessa serpentinite outcrop is surrounded by crystalline rocks of migmatitic horrnblende-biotite gneisses and biotitic gneisses metamorphosed under upper amphibolite/granulite facies conditions. The said sur-rounding crustal rocks are granitic in composition. Within the serpentinite outcrop, several veins of quartz and feldspar show-ing graphic texture were observed as late pegmatitic intrusions formed from a residual melt of the ultramafic magma. These observations are clear indications for tectonically activeness of this block even in its uplifting stage.

The vegetation type at Ginigalpelessa and Indikolapelessa outcrops and in the vicinity of the deposits is evident of the un-derlying lithology. A detailed description of species found on the Indikolapelessa serpentinite outcrop is listed by Rajakaruna and Bohn (2002). Basically, three vegetation groups were recognized in the field as (i) bare-land or grass with some characteristic plants grown on serpentinite outcrops (Fig. 2), (ii) patches of thick vegetation grown on quartz-feldspathic pockets in the ser-pentinite outcrops, and (iii) thick vegetation grown on the sur-rounding rocks outside the serpentinite border (Fig. 2a). The said vegetation contrasts are visible in the field and even in the satel-lite images. Therefore, the sampling for the geochemical map-ping was conducted covering three types of soils.

1. Serpentinite soil (A)—reddish brown shallow soil, de-veloped on the serpentinite outcrop.

2. Boundary soil (B)—the soil at the contact between the serpentinite outcrop and the surrounding rocks.

3. Non-serpentinite soil (C)—the soil developed on the non-serpentinite rocks which are located around the serpen-tinite outcrop and occurring within the serpentinite outcrop as quartz-feldspathic pockets.

4.2 Chemistry of the Serpentinite Rock/Serpentinite and Non-serpentinite Soils

Concentrations of Zn, Cd, Cu, Cr, Al, Mg, Ca, Ni, Mn and Fe of 39 samples of serpentinite soil from the serpentinite out-crop, 11 samples from the boundary between the serpentinite outcrop and non-serpentinite rock and 15 samples of non-serpentinite soil from the surrounding area and within the out-crop are presented in this study (Fig. 3).


155

Figure 2. Photographs showing (a) the serpentinite exposure at Indikolapelessa illustrating a geo-vegetation boundary and (b) typical plant species found in the serpentinite outcrop.


156

Figure 3. Vegetation map of the Indikolapelessa outcrop showing serpentinite exposures, feldspathic patches and sampling locations.

Soil geochemical maps constructed for the cations of Mn, Ni, Mg, Fe, Zn and Cr illustrate an identical elemental distribu-tion pattern of higher concentration for serpentine soils (Figs. Sup-1 and Sup-2). For these elements, a significant difference in chemistry was noted between the serpentinite and non-serpentinite soils (Figs. 4 and 5). Statistically, the mean con-centrations of Mn, Ni, Mg, Fe, Zn and Cr in serpentinite soils are 2–5 times greater than the concentrations of those elements in the non-serpentinite soils (Table 1 and Figs. 4 and 5). The difference of Ca concentration between the serpentinite and the non-serpentinite soils is negligible. However, the Mg concen-tration in serpentinite soils (3.67%±2.53%) is significantly higher (4-fold increase) than that in the non-serpentinite soils (0.93%±0.57%). In contrast, a distribution of lower concentra-

tions of Al and lower ratios of Ca/Mg are shown in the geo-chemical maps for serpentine soils (Fig. Sup-2).

The Ca/Mg ratios are low (<1) in serpentinite soils than those in non-serpentinite soils; the fact is identical for soils derived from ultramafic rocks elsewhere in the world (Tables 1, 2). The ratio of Ca/Mg in serpentinite soils ranges from 0.03 to 0.90 whereas the ratio in non-serpentinite soil varies from 0.61 to 3.42. Therefore, these remarkable differences in Ca, Mg and Al concentrations in serpentinite and non-serpentinite soils as well as in serpentinite rocks suggest dissimilar origin for the serpentinite body in comparison to the surrounding rocks. These chemical discrepancies between the serpentinite and non-serpentinite soils may also reveal that serpentinite rocks are possibly derived from ultramafic rocks, an igneous


157

Table 1 Mean weight percentages of Mn, Ni, Mg, Fe, Cd, Cu and Zn measured in the different types of soils (n=64) and in the fresh rocks (n=6) within and in the vicinity of Indikolapelessa and Ginigalpelessa serpentinite outcrops at Udawalawe. Soils

were classified into three groups as: serpentinite soil (A), boundary soil (B) and non-serpentinite soil (C). Classification of soil is detailed in the text

Soil from Indikolapelessa Element Rock from Ginigalpellessa

(n=3)

Rock from Indikolapelessa

(n=3) Serpentinite soil

(n=39) Boundary soil

(n=11) Non-serpentinite soil

(n=13)

Mn (%) 0.06±0.00 0.06±0.02 0.20±0.06 0.14 ±0.04 0.10±0.03

Ni (%) 0.08±0.04 0.13±0.04 0.46±0.19 0.20±0.23 0.09±0.09

Mg (%) 20.72±0.26 19.5±1.46 3.67±2.53 1.30±1.43 0.93±0.57

Fe (%) 4.24±0.13 3.76±0.21 10.88±3.21 6.45±3.71 4.21±1.99

Cd (ppm) 1±1 2±1 3±4 3±3 3±3

Cu (ppm) 4±1 8±1 16±13 32±26 24±12

Zn (ppm) 18±4 22±9 54±65 42±17 34±12

Ca (%) 0.90±0.30 0.58±0.62 0.64±0.35 0.86±0.40 0.89±0.31

Al (%) 0.12±0.02 0.06±0.04 1.25±0.61 2.08±0.69 2.07±0.67

Cr (ppm) 232±23 194±25 710±419 294±254 230±186

Ca/Mg 0.026–0.054 0.007–0.062 0.03–0.90 0.22–0.74 0.61–3.42

Mg (

wt.

%)

10

15

20 Serpen. rock

Crustal rocks-SL

0

5

Fe

(wt.

%)

2

4

6

8

10

12

14

16

Ni

(wt.

%)

0.0

0.2

0.4

0.6

0.8

Mn

(wt.

%)

0.0

0.1

0.2

0.3

0.4

Serpen. soilBoundary soil

Non-serpen. soil

Metasedimentary

Charnockite-1

Charnockite-2

(a)

(c)

(b)

(d)

Figure 4. Elemental concentrations of Mg, Fe, Ni and Mn measured in serpentinite and non-serpentinite soils at Indikolape-lessa and serpentinite fresh rock at Indikolapelessa and Ginigalpelessa. Note that published whole rock chemistry of crustal rocks-pelitic rocks (Prame and Pohl, 1994), charnockite-1 (Hansen et al., 1987) and charnockite-2 (Kröner et al., 1994) are completely differ from whole rock chemistry of serpentinite. intrusive type of rocks, formed due to the solidification of magma derived from the mantle. Also, the abundance of Mg, Fe and Ni in serpentinite rocks, unlike in crustal rocks, is evi-dence for magma which is derived from the mantle.

Serpentinite is commonly formed as a result of an altera-tion of peridotite, an ultramafic rock rich in olivine, pyroxene

and chromite group minerals, and less than 45% silica (Evans, 1977). They are mainly exposed at the convergent plate mar-gins where plates are subducted into the lower crust or into the upper mantle. Occurrence of peridotite or altered serpentinite away from the subduction zones is very unlikely. Therefore, any occurrence of peridotite or altered serpentinite in a land-


158

mass reflects an existence of a paleo-subduction zone. Sri Lanka represents a stable fragment of Gondwanaland, which was not affected to any major tectonic event after the rifting which took place in the Early Cretaceous Period (Vanacker et al., 2007). Geologically, it is composed of more than 90% of crystalline rocks of crustal origin, metamorphosed at 455–610 Ma ago under the Pan-African orogeny (Cooray, 1994). In contrast, elemental concentrations of soil and rock of Indiko-lapelessa and Ginigalpelessa serpentinite deposits show that these outcrops are likely to have a mantle origin. This nature of origin appears to be the same for the other three serpentinite outcrops at Ussangoda, Katupota and Yodaganawa since they have also been located along the HC-VC litho-tectonic bound-ary (Fig. 1).

The tectonic nature of the HC-VC litho-tectonic boundary

can be explained on the basis of structural and metamorphic discontinuity, gravity and magnetic anomaly and occurrence of iron-rich mineral deposits (e.g., Buttala magnetite, in southern Sri Lanka close to the tectonic boundary) and the presence of thermal springs (Mahaoya, Mahapelessa, etc.) (Fig. 1). Previous studies suggest that the HC and VC have a tectonic boundary (Kleinschrodt, 1994; Hatherton et al., 1975). Initially, a plate tectonic collisional model was proposed for the evolution of the basements rocks of Sri Lanka, considering the nature on this tectonic boundary (Munasinghe and Dissanayake, 1982). Later studies indicate that the combined HC-WC unit was overthrusted onto the VC, similar to a subduction zone, during the amphibo-lite grade metamorphism, ca. 456–591 Ma ago (Kleinschrodt, 1994; Buchel, 1991). Presence of undeformed ultramafic and pegmatitic exposures observed at Indikolapelessa suggest the

Ca

(wt.

%)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Ca/M

g

0.0

1.0

2.0

3.0

4.0

5.0

Cr

(wt.

%)

0.00

0.05

0.10

0.15

0.20

Serpentine rock

Crustal rocks-SLA

l(w

t.%

)

0

2

4

6

8

10Serpentine soil

Boundary soil

Non-serpentine soil

Metasedimentary

Charnockite-1

Charnockite-2

(a) (b)

(c) (d)

Figure 5. Elemental concentrations of Cr, Al and Ca and Ca/Mg measured in serpentinite and non-serpentinite soils at In-dikolapelessa and serpentinite fresh rock at Indikolapelessa and Ginigalpelessa. Note that published whole rock chemistry of crustal rocks-pelitic rocks (Prame and Pohl, 1994), charnockite-1 (Hansen et al., 1987) and charnockite-2 (Kröner et al., 1994) are completely differ from whole rock chemistry of serpentinite.

Table 2 Ca/Mg ratio and pH of serpentinite soils worldwide

Serpentinite Deposit Reference Ca/Mg ratio pH

Jasper Ridge, California 0.27–0.52 6.74

Soldier’s Delight, Maryland 0.56 6.20

Little Deer Isle, Maine

(Oze et al., 2008)

0.42 6.50

Newfoundland, Canada 0.10 5.00

New Calidonia

(Roberts and Proctor, 1992)

0.04–0.40 6.10

Western Cuba (Reeves et al., 1999) 0.15

Natural Park, Mount Avic, Italy (Lazaro et al., 2006) 1.14

Meikle, Kilrannoch, Scotland (Johnston and Proctor, 1984) 0.06 6.38

Witwatersrand, Johannesberg, SA (Reddy et al., 2009) 0.56 5.88


159

derivation of serpentinite rich and ultramafic magma and intru-sion as isolated patches post-dating the subduction and over-thrusting events. Afterwards, the serpentinite patches were cooled through solidification and exposed along a paleo-subduction zone, which is now referred to as the HC-VC litho-tectonic boundary. 4.3 Effects of Soil Properties on Flora at Indikolapelessa Serpentinite Outcrop

Plants require nutrients at different levels for their growth: (i) macronutrients such as N, K, Ca, Mg, P and S in greater quantities and (ii) micronutrients such as Cl, Fe, B, Mn, Zn, Cu, Mo and Ni in smaller quantities. The basement ultramafic rock at Indikolapelessa is poor in nutrient-enriched minerals such as feldspar and mica. Therefore, the serpentinite soils derived at this location should be depleted with major macronutrients, so that prosperous growth of plants is halted on serpentinite soil. Micronutrients available in the soil also play a major role in the growth of plants. Ni, for instance, is an important micronutrient, which regulates the mineral metabolism, enzyme activity and several other metabolic processes in plants. The average Ni availability of plant is 0.1 ppm. However, high concentrations of Ni in plants are toxic causing severe chlorosis and necrosis and a host of other growth abnormalities and anatomical changes are incurred. Specific plants that grow on serpentinite soils have a capacity to tolerate and over accumulate of heavy metals at toxic levels, particularly Ni (Reeves, 2003). At In-dikolapelessa, the mean Ni content in the soil was found to be as high as 0.46%±0.19%. This high level of Ni is obviously toxic and can adversely affect plant growth.

Other heavy metals such as Cr, Mn, and Cd were also de-tected in excess levels in the serpentinite soils. Therefore, they also inflict toxicity. It has been shown that growth of plant is strongly affected by the concentration of exchangeable Ca and Mg ions in the soil, which is also reflected by the Ca/Mg ratio in the soil. There is remarkable difference between the Ca/Mg ratios in the serpentinite soil and the non-serpentinite soil at Indikolapelessa. The Ca/Mg ratio is very low and it varies from 0.03 to 0.90 in serpentinite soils whereas the ratio ranges from 0.61 to 3.42 in nearby non-serpentinite soil. This low ratio of Ca/Mg in serpentinite soil has constrained the plant growth only to serpentinite habitats.

In general, soil can be categorized into five groups based on their pH as; (i) strongly acidic (pH<5.5), (ii) moderately acidic (5.0<pH<6.5), (iii) neutral (6.5<pH<7.5), (iv) moder-ately alkaline (7.5<pH<8.5) and (v) strongly alkaline (pH>8.5). Soil pH outside the neutral range can influence the availability of specific nutrients to plants, as well as the activities of both beneficial and pathogenic micro-organisms. The pH of the serpentinite soil was measured by collecting 50 surface samples and the average pH is 6.34 (Table 3), which represents a mod-erately acidic condition.

Soil depths of 14 locations in the serpentinite outcrop and 4 locations in the non-serpentinite areas were determined using a steel rod and a hammer. Serpentinite soil is very shallow and the area is rocky and depth varies from 0 to 100 cm (Table 4). Several serpentinite outcrops are exposed within the body with a zero soil thickness. In contrast, depth of the non-serpentinite

soil close to the serpentinite body is greater than 150 cm (Table 4). Soil depth is an important factor in plant growth, which provides the necessary space for plant roots to spread. Very shallow soil layers and rock exposures prevailing in the serpen-tinite body at Indikolapelessa act as root barriers that limit the growth of shallow-rooted plants. Moreover, very shallow soil layers increase the soil temperature leading to the decrease of soil moisture. Shallow soil depths also decrease the water hold-ing capacity of soils. In short, the vegetation cover on the ser-pentinite soil at Indikolapelessa is mainly characterized by grass which is a typical shallow-rooted plant in the area.

Several soil properties such as water holding capacity, aeration, susceptibility to erosion, organic matter content, cation exchange capacity and pH buffering capacity of soil are influenced by its texture. The texture of a particular soil is de-scribed based on the relative proportion of different grain sizes in the soil. The texture of serpentinite soil was determined by analyzing 6 soil samples and it was compared with the texture of non-serpentinite soils by analyzing another 4 samples col-lected in the vicinity (Appendix Table 2). This comparison clearly indicates that serpentinite soil contains only 10%–55% of finer fractions (sum of clay, silt and fine sand) whereas non-serpentinite soils contain remarkably higher levels of finer fractions (68%–80%) (Fig. 6). It is now possible to explore a direct relationship between the soil chemistry and the soil tex-ture in serpentinite soil at Indikolapelessa. Clay minerals are formed as a secondary product through rock weathering and the element Al is an essential component in forming clay minerals in soil. According to the soil chemistry, the average Al content in the serpentinite soil at Indikolapelessa is very low when compared to Al concentration in other soils developed on gran-itic terrain. This low content of Al in the soil has limited the formation of clay minerals on the serpentinite soils. Instead, materials are bound with iron-rich binding material, which reflect the reddish colour in serpentinite soils. Generally, soil constituents are tightly bound by clay minerals due to their higher cohesion, which reduces the detachment of soil particles by raindrops thereby minimizing the rate of soil erosion. Since the clay content is very low in serpentinite soil at Indikolape-lessa, soil particles are readily disintegrated and a high rate of soil erosion is expected. As a result, shallow soil layers and rock exposures have been developed on the serpentinite out-crop. Moreover, by the action of surface runoff during the heavy rains, soil particles are selectively removed from the surface of the soil profile further enriching the coarse particles in the serpentinite soil.

Factors such as lack of macronutrients, presence of heavy metals at toxic levels, shallow soil thickness and presence of a little fraction of clays and silts have created an unfavorable environment for plants at the Indikolapelessa serpentinite out-crop thereby hindering their healthy growth. Several plant spe-cies, typical of and able to cope with a harsh environment, were observed on the serpentinite outcrop (Fig. 2b). These plants are capable of tolerating high concentrations of heavy metals pre-sent in the soil. A preliminarily taxonomical survey conducted by a group of ecologists in 2002 at the Indikolapelessa serpen-tinite deposit was able to identify 12 plant species, typical on serpentinite soils (Rajakaruna and Bohn, 2002). The authors


160

Table 3 Soil pH in the different types of soils. Serpentinite soil (A), boundary soil (B) and non-serpentinite soil (C) at Indikolapelessa deposit, Sri Lanka. Classification of soil is

detailed in the text

Serpentinite soil (A) Boundary soil (B) Non-serpentinite soil (C)

Sample pH Sample pH Sample pH Sample pH Sample pH

Ind-S-2 5.91 Ind-S-25 6.27 Ind-S-50 6.42 Ind-S-1 5.94 Ind-S-1 5.94










Ind-S-15 6.46 Ind-S-39 6.58 Ind-S-69 6.35 Ind-S-75 6.26

Ind-S-16 5.85 Ind-S-40 6.56 Ind-S-70 6.52

Ind-S-17 6.43 Ind-S-43 6.15 Ind-S-71 6.65

Ind-S-21 6.50 Ind-S-44 6.16 Ind-S-72 6.58

Ind-S-22 6.49 Ind-S-45 6.31 Ind-S-73 6.43

Ind-S-23 6.47 Ind-S-46 6.40 Ind-S-77 6.52

Ind-S-24 6.52 Ind-S-47 6.53

Mean=6.43±0.44

Mean=6.43±0.49 Mean=6.42±0.46

Table 4 Soil depth of serpentinite and non-serpentinite soils at Indikolapelessa deposit, Sri Lanka

Serpentinite soil (A) Non-serpentinite soil (B)

Sample Depth (cm) Sample Depth (cm) Sample Depth (cm) Sample Depth (cm)

Ind-S-2 105 Ind-S-16 22 Ind-S-38 60 Ind-S-1 90

Ind-S-3 90 Ind-S-17 105 Ind-S-40 150 Ind-S-6 >150

Ind-S-4 15 Ind-S-21 30 Ind-S-45 60 Ind-S-9 >150

Ind-S-5 65 Ind-S-34 30 Ind-S-46 75 Ind-S-10 > 150

Ind-S-7 30 Ind-S-37 60

Mean=60 Mean>150

highlighted the importance of conducting more taxonomic and physiological studies on the serpentinite outcrops in Sri Lanka to explore plant-microbe interactions. Further, a study con-ducted on the pharmacological properties of the Sri Lankan serpentinite plant species reveal that several of them are active against the microorganism tested (Rajakaruna et al., 2002). These findings imply that the dominant species may produce chemical compounds with important antimicrobial properties and hence further studies can be directed focusing on this as-pect. 5 CONCLUSIONS

This research successfully employed the novel approach of geo-vegetation mapping to demarcate the geological boundaries in ultramafic terrains with respect to serpentinite outcrop at Indikolapelessa in southern Sri Lanka. The demar-cated geo-vegetation boundaries were satisfactorily verified by soil geochemical mapping using several elements namely, Al,

Ca, Mg, Cr, Ni, Mn, Zn and Fe. Therefore, we conclude that vegetation can be used as concrete evidence of the underlying rocks and minerals in areas where geology is buried by vegeta-tion, which is very common in the wet tropical geographic setting.

This study further disclosed a remarkable difference in the composition of Fe, Ni, Cr, Mn and Mg as well as in Ca/Mg ratio between the serpentinite soil and nearby non-serpentinite soils. Metals like Fe, Ni, Cr and Mn could have been emplaced from the ultramafic magma, which solidifies and segregated in the serpentinite soils as supergene deposits. The elemental distribution pattern and Ca/Mg ratio in the serpentinite soil at Indikolapelessa are identical to those in serpentinite soils de-veloped on mantle rocks elsewhere in the world. This is evident in proposing that ultramafic rocks located along the HC-VC boundary bear a mantle origin. This concept of genesis is fur-ther supported by the geochemistry of fresh ultramafic rocks which recorded high contents of Mg, Fe and Ni and low values


161

Fine sand

0.01 0.1 1 10

0

10

20

30

40

50

60

70

80

90

100

Sieve size (mm)

Perc

en

tag

e p

ass

ing

0

10

20

30

40

50

60

70

80

90

100

Perc

en

tag

e p

ass

ing

Ind-s-18

Ind-s-53

Ind-s-42

Ind-s-56

Serpentine soil

Non-serpentine soil

Ind-s-6

Ind-s-3

Ind-s-24

Ind-s-30

Ind-s-45

Mean

Mean

Clay and silt Medium sand Coarse sand

Fine sandClay and silt Medium sand Coarse sand

Figure 6. Grain size distributions in serpentinite and non-serpentinite soils at Indikolapelessa.

of Al and Ca/Mg ratios, which is not typical in the crustal rocks. Moreover, the study area is characterized by undeformed intru-sions of ultramafic and pegmatitic rocks, as observed in the field, which also fortifies the concept of mantle origin. Therefore, based on all findings, it is possible to conclude that these ultramafic rocks were probably solidified during the cooling of magma de-rived from the mantle and injected through the paleo-subduction zone along the HC-VC litho-tectonic boundary.

The serpentinite body at Indikolapelessa is covered by occa-

sional bushes and serpentinite habitats, only such varieties can survive on the prevailing soil conditions. This study revealed that serpentinite soil at Indikolapelessa is characterized with high con-centrations of heavy metals such as Ni, Cd, Mn and Cr. Also, some ecological studies disclosed that the flora grown on serpen-tinite soil also contain heavy metals in excess levels. These heavy metals can directly contaminate the groundwater through rock weathering and also transfer into the human body via food chain leading to numerous health hazards. Therefore, more ecologic,


162

epidemiologic and socio-economic studies are needed to explore the true environmental impacts in this system.

ACKNOWLEDGMENTS

Special thanks go to Ms. Y P S Siriwardana, chief chemist, at the Geological Survey and Mines Bureau (GSMB) of Sri Lanka for providing facilities and support in chemical analyses. A re-search grant to TH by the Sabaragamuwa University of Sri Lanka (No. SUSL/RG/2006/05) is acknowledged for financial support. REFERENCES CITED Brady, K. U., Kruckeberg, A. R., Bradshaw, H. D., 2005. Evolu-

tionary Ecology of Plant Adaptation to Serpentine Soils. An-nual Rev. Ecol. Evol. Syst., 36: 243–266

Brooks, R. R., 1972. Geobotany and Biogeochemistry in Mineral Exploration. Harper & Row, New York

Buchel, G., 1991. Gravimetric Investigations along Tectonic Boundaries between the Highland/Southwestern Complex and the Vijayan Complex in Sri Laka. In: Kroner, A., ed., The Crystalline Crust of Sri Lanka, Part 1, Summary of the Research of the German-Sri Lankan Consortium. Geological Survey Department of Sri Lanka, Colombo. 89–93

Cooray, P. G., 1994. The Precambrian of Sri Lanka: A Historical Review. Precambrian Research, 66(1–4): 3–18

Dissanayake, C. B., 1982. The Geology and Geochemistry of the Uda Walawe Serpentinite, Sri Lanka. Journal of National Science Councial, Sri Lanka, 10(1): 13–34

Dissanayake, C. B., Van Riel, B. J., 1978. Petrology and Geo-chemistry of a Recently Discovered Nickeliferrous Serpen-tinite from Sri Lanka. Journal of Geological Society of India, 19: 464–471

Evans, B. W., 1977. Metamorphism of Alpine Peridotite and Serpentinite. Ann. Rev. Earth. Planet. Sci., 5: 397–447

Fernando, G. W. A. R., 2001. Genesis of Metasomatic Sapphirine-Corundum-Spinel-Bearing Granulites in Sri Lanka: An Integrated Field, Petrological and Geochemical Study: [Dissertation]. University of Mainz, Mainz. 175

Hansen, E. C., Janardhan, A. S., Newton, R. C., et al., 1987. Ar-rested Charnockite Formation in Southern India and Sri Lanka. Contributions to Mineralogy and Petrololgy, 96(2): 225–244

Hatherton, T., Pattiaratchi, D. B., Ranasinghe, V. V. C., 1975. Gravity Map of Sri Lanka, Professional Paper No. 3. Sri Lanka Geological Survey Department, Colombo. 39

Johnston, W. R., Proctor, J., 1984. The Effects of Magnesium, Nickel, Calcium and Micronutrients on the Root Surface Phosphatase Activities of a Serpentine and Non-Serpentine Clon of Festuca Rubra L. New Phytologist, 96: 95–101

Kleinschrodt, R., 1994. Large-Scale Thrusting in the Lower Crustal Basement of Sri Lanka. Precambrian Research, 66(1–4): 39–57

Kröner, A., Kehelpannala, K. V. W., Kriegsman, L. M., 1994. Origin of Compositional Layering and Mechanism of Crustal Thickening in the High-Grade Gneiss Terrain of Sri Lanka. Precambrian Research, 66(1–4): 21–37

Kruckeberg, A. R., 1984. California Serpentines: Flora, Vegeta-tion, Geology, Soils and Management Problems: [Disserta-

tion]. University of California, Berkeley Lazaro, J. D., Kidd, P. S., Martinez, C. M., 2006. A Photochemi-

cal Study of the Tras-Os-Montes Region (NE Portugal): Pos-sible Species for Plant Based Soil Remediation Technologies. Sciences of Total Environment, 354: 265–277

Macnair, M. R., Gardner, M., 1998. The Evolution of Edaphic Endemics. In: Howard, D. J., Berlocher, S. H., eds., Endless Forms: Species and Speciation. Oxford University Press, New York. 157–171

Milisenda, C. C., Liew, T. C., Hofmann, A. W., et al., 1994. Nd Isotopic Mapping of the Sri Lanka Basement: Update, and Additional Constrains from Sr Isotopes. Precambrian Re-search, 66(1–4): 95–110

Munasinghe, T., Dissanayake, C. B., 1982. A Plate Tectonic Model for the Geological Evolution of Sri Lanka. Journal of Geological Society of India, 23: 369–380

Nash, G. D., Hernandez, M. W., 2001. Cost-Effective Vegetation Anomaly Mapping for Geothermal Explorations, Twenty-Sixth Workshop on Geothermal Reservoir Engineering. 2001 SGP-TR-168, Stanford University, Stanford, California

Oze, C., Schroth, A. W., Coleman, R. G., 2008. Growing up Green on Serpentine Soils: Biogeochemistry of Serpentinite Vegetation in the Central Coast Range of California. Applied Geochmistery, 23: 3391–3403

Prame, W. K. B. N., Pohl, J., 1994. Geochemistry of Pelitic and Psammopelitic Precambrian Metasediments from South-western Sri Lanka: Implications for Two Contrasting Source-Terrains and Tectonic Settings. Precambrian Re-search, 66: 223–244

Rajakaruna, N., Baker, A. J. M., 2004. Serpentine: A Model Habi-tat for Botanical Research in Sri Lanka. Ceylon Journal of Science (Biological Science), 32: 1–19

Rajakaruna, N., Bohn, A. B., 2002. Serpentine and Its Vegetation: A Preliminary Study from Sri Lanka. Journal of Applied Botany, 76(1–2): 20–28

Rajakaruna, N., Harries, T. B., Alexander, E. B., 2009. Serpentine Geoecology of Eastern North America: A Review. Rhodora, 111(945): 21–108

Rajakaruna, N., Harris, C. S., Towers, G. H. N., 2002. Antimicro-bial Activity of Plants Collected from Serpentine Outcrops in Sri Lanka. Pharmaceutical Biology, 40: 235–244

Reddy, R. A., Balkwill, K., Mclellan, T., 2009. Plant Species Richness and Diversity of the Serpentine Areas on the Wit-watersrand. Plant Ecology, 201: 365–381

Reeves, R. D., 2003. Tropical Hyperaccumulators of Metals and Their Potential for Phytoextraction. Plant and Soil, 249: 57–65

Reeves, R. D., Baker, A. J. M., Borhidi, A., 1999. Nickel Hyper-accumulation in the Serpentine Flora of Cuba. Annals of Botany, 83: 29–38

Roberts, B. A., Proctor, J., 1992. The Ecology of Areas with Ser-pentinized Rocks: A World View. Kluwer Academic Pub-lishers, Nederlands. 420

Vanacker, V., Von Blanckenburg, F., Hewawasam, T., 2007. Constraining Landscape Development of the Sri Lankan Es-carpment with Cosmogenic Nuclides in River Sediment. Earth and Planetary Science Letters, 253: 402–414


163

Appendix

217.80 218.00 218.20 218.40 218.60

128.60

128.80

129.00

129.20

129.40

129.60

129.80

0.00.00.00.10.10.10.10.10.20.20.20.20.20.30.30.30.30.30.4

Mn (wt.%)

Mn

217.80 218.00 218.20 218.40 218.60

128.60

128.80

129.00

129.20

129.40

129.60

129.80

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

Mg (wt.%)

Mg

217.80 218.00 218.20 218.40 218.60

128.60

128.80

129.00

129.20

129.40

129.60

129.80

0.0

0.1

0.1

0.2

0.2

0.3

0.3

0.3

0.4

0.4

0.5

0.6

0.6

0.6

0.7

Ni (wt.%)

Ni

217.80 218.00 218.20 218.40 218.60

128.60

128.80

129.00

129.20

129.40

129.60

129.80

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

Fe (wt.%)

Fe

0.20

0.20

0.10

0.2

00.20

0.20

0.1

0

3.50

1.0

0

1.00

3.5

0

6.003.50

1.0

0

3.5

0

3.50

1.0

0

3.50

6.00

1.0

0

0.5

0

0.2

5

0.50

0.2

5

0.5

0

0.50

0.0

0

0.2

5

0.2

5

0.5

0

0.50

0.2

5

12.00

7.00

12

.007.0

0

7.0

0

12.00

12.00

7.0

02

.00

7.0

0

Figure Sup-1. Spatial distribution of Mn, Mg, Ni and Fe in soil of the serpentine outcrop and surrounding area at Idikolapel-lassa, near Embilipitiya, south of Sri Lanka. Yellow circles. serpentine fresh exposures; thick red line. boundary of the ser-pentine and non-serpentine areas demarcated by vegetation mapping; thick green line. boundary of the quartz feldspathic pockets; thick blue line. isolated non-serpentine habitats within the serpentine vegetation.


164

217.80 218.00 218.20 218.40 218.60

128.60

128.80

129.00

129.20

129.40

129.60

129.80

0.0000.0020.0040.0060.0080.0100.0120.0140.0160.0180.0200.0220.0240.0260.0280.0300.0320.0340.036

Zn (mg/kg)

Zn

217.80 218.00 218.20 218.40 218.60

128.60

128.80

129.00

129.20

129.40

129.60

129.80

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

Cr (mg/kg)

Cr

217.80 218.00 218.20 218.40 218.60

128.60

128.80

129.00

129.20

129.40

129.60

129.80

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

Al (wt.%)

Al

217.80 218.00 218.20 218.40 218.60

128.60

128.80

129.00

129.20

129.40

129.60

129.80

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

4.00

2.401.4

0

1.40

1.4

0

1.40

1.40

2.40

1.40

2.40

0.0

1

0.02

0.06

0.06

0.0

6

0.16

0.0

6

0.0

6

0.06

Ca/Mg

Figure Sup-2. Spatial distribution of Zn, Cr, Al, and Ca/Mg in soil of the serpentine outcrop and surrounding area at Idiko-lapellassa, near Embilipitiya, south of Sri Lanka. Yellow circles. serpentine fresh exposures; thick red line. boundary of the serpentine and non-serpentine areas demarcated by vegetation mapping; thick green line. boundary of the quartz feldspathic pockets; thick blue line. isolated non-serpentine habitats within the serpentine vegetation.

Appendix Table 1 Weight percentages of Mn, Ni, Mg, Fe, Ca, Al, Cr, Cd, Cu and Zn measured in the different types of soils (n=64 ) and in the fresh rocks (n= 06) within and in the vicinity of Indikolapelessa serpentinite deposit at Udawalawe

GPS location Sample number

Eastern (º) Northern (º)

Soil type Mn (wt.%)

Ni (wt.%)

Mg (wt.%)

Fe (wt.%)

Cd (ppm)

Cu (ppm)

Zn (ppm)

Ca (wt.%)

Al (wt.%)

Cr (ppm)

Ind-S-1 217.966 129.542 B 0.13 0.10 0.56 4.82 11 38 41 0.91 2.05 140

Ind-S-3 218.157 129.542 A 0.26 0.45 0.55 13.73 13 16 33 0.41 1.87 1 071

Ind-S-4 218.251 129.535 A 0.23 0.76 7.48 10.48 12 17 40 0.79 1.22 811

Ind-S-5 218.351 129.542 A 0.23 0.61 3.37 11.47 11 12 30 0.41 0.90 712

Ind-S-6 218.517 129.540 B 0.18 0.10 0.63 4.03 06 34 32 0.68 3.00 322

Ind-S-7 218.378 129.547 A 0.35 0.66 3.48 12.53 10 13 40 0.84 1.72 697

Ind-S-9 218.440 129.659 C 0.13 0.30 1.03 8.82 09 31 42 1.03 3.28 343

Ind-S-10 218.389 129.713 C 0.09 0.18 0.68 5.26 06 25 49 1.54 2.79 308

Ind-S-11 217.933 129.436 A 0.15 0.13 0.61 4.89 03 41 43 1.32 1.67 148

Ind-S-13 218.138 129.435 A 0.19 0.41 2.94 9.10 09 51 45 0.92 1.01 645

Ind-S-14 218.239 129.436 A 0.21 0.54 6.54 13.10 12 19 44 0.53 0.55 694

Ind-S-15 218.341 129.435 A 0.20 0.49 7.43 10.96 15 12 37 0.55 0.72 577

Ind-S-16 218.380 129.487 A 0.18 0.36 3.23 8.31 00 25 96 1.50 1.39 657

Ind-S-17 218.441 129.435 A 0.18 0.55 7.04 11.34 00 11 40 0.63 0.72 1 044

Ind-S-18 218.543 129.435 B 0.10 0.18 0.67 4.50 00 26 46 0.69 1.93 730

Ind-S-19 218.643 129.435 C 0.06 0.01 0.26 1.96 00 22 29 0.88 1.86 22

Ind-S-21 218.462 129.334 A 0.19 0.53 6.96 11.43 00 15 52 0.00 1.17 819

Ind-S-22 218.362 129.335 A 0.14 0.36 9.14 6.00 01 17 39 0.67 0.45 769

Ind-S-24 218.162 129.335 A 0.22 0.59 4.76 13.32 01 12 38 0.70 0.74 629

Ind-S-25 218.062 129.335 A 0.20 0.33 0.73 8.51 00 26 31 0.60 1.68 495

Ind-S-26 217.962 129.335 A 0.18 0.25 0.62 8.02 05 42 47 0.00 3.07 295

Ind-S-27 217.862 129.335 B 0.12 0.01 0.12 6.64 07 78 42 1.44 2.82 90

Ind-S-28 217.846 129.235 B 0.10 0.01 0.13 5.98 07 77 45 1.03 2.64 75

Ind-S-29 217.946 129.235 A 0.13 0.26 1.60 8.28 06 17 40 0.91 1.52 241

Continued



Soil type Mn (wt.%)

Ni (wt.%)

Mg (wt.%)

Fe (wt.%)

Cd (ppm)

Cu (ppm)

Zn (ppm)

Ca (wt.%)

Al (wt.%)

Cr (ppm)

Ind-S-31 218.146 129.235 A 0.19 0.60 1.88 13.95 06 18 44 1.03 1.77 856

Ind-S-32 218.246 129.236 A 0.22 0.68 2.95 13.43 01 21 42 0.51 0.92 1 032

Ind-S-33 218.346 129.235 A 0.19 0.60 0.91 16.19 00 13 44 0.84 1.15 2 152

Ind-S-34 218.446 129.235 A 0.24 0.60 3.57 13.51 03 12 37 0.90 1.01 1 815

Ind-S-35 218.544 129.235 C 0.11 0.06 0.80 3.19 05 25 37 1.17 2.15 176

Ind-S-37 218.311 129.135 A 0.21 0.42 2.87 14.86 00 54 38 0.93 1.61 657

Ind-S-38 218.211 129.135 A 0.18 0.72 5.12 8.79 00 07 35 0.84 0.82 524

Ind-S-39 218.111 129.135 A 0.39 0.52 2.75 13.30 00 08 37 0.54 1.23 649

Ind-S-40 218.011 129.135 A 0.17 0.27 5.94 8.66 00 05 31 0.76 0.39 319

Ind-S-41 217.911 129.135 C 0.16 0.02 1.59 5.36 00 12 48 1.35 1.14 160

Ind-S-42 217.811 129.135 B 0.14 0.02 0.56 4.21 00 49 36 1.11 2.38 66

Ind-S-43 217.998 129.047 A 0.22 0.46 1.15 11.17 00 12 32 0.54 1.41 335

Ind-S-45 218.198 129.047 A 0.24 0.68 4.01 14.04 00 06 77 0.40 0.93 679

Ind-S-46 218.298 129.047 A 0.26 0.00 2.38 16.07 00 03 76 0.36 0.78 1 252

Ind-S-47 218.398 129.047 A 0.21 0.64 2.49 13.06 00 05 122 0.61 1.68 1 275

Ind-S-48 218.498 129.047 C 0.08 0.03 0.40 1.76 01 13 40 0.85 1.01 69

Ind-S-49 218.450 128.947 C 0.07 0.12 0.58 3.76 02 19 24 0.38 1.92 129

Ind-S-50 218.350 128.947 A 0.22 0.55 1.96 13.83 02 10 31 0.29 1.47 800

Ind-S-51 218.250 128.947 A 0.20 0.63 4.98 12.24 02 01 65 0.36 1.00 726

Ind-S-53 218.168 128.847 B 0.17 0.49 3.28 10.64 02 13 78 1.30 1.76 514

Ind-S-54 218.268 128.847 A 0.15 0.36 1.86 9.04 03 04 36 1.67 1.04 498

Ind-S-55 218.368 128.847 B 0.10 0.03 0.19 1.79 04 03 10 0.24 0.93 97

Ind-S-56 218.355 128.753 C 0.07 0.03 0.56 3.36 04 33 23 0.69 1.98 66

Ind-S-58 217.898 129.049 C 0.12 0.20 2.45 6.25 03 07 26 0.64 2.07 174

Ind-S-59 217.754 129.029 C 0.08 0.01 0.74 3.53 03 47 19 0.74 1.91 88

Ind-S-60 217.939 129.963 C 0.17 0.49 6.23 9.91 03 01 28 0.35 1.04 692

Ind-S-61 217.891 128.967 A 0.12 0.19 1.22 4.76 03 12 22 0.33 1.26 230

Continued



Soil type Mn (wt.%)

Ni (wt.%)

Mg (wt.%)

Fe (wt.%)

Cd (ppm)

Cu (ppm)

Zn (ppm)

Ca (wt.%)

Al (wt.%)

Cr (ppm)

Ind-S-62 217.745 128.956 C 0.12 0.07 0.91 5.66 00 41 56 0.78 2.60 185

Ind-S-63 218.050 128.890 C 0.18 0.62 7.23 12.38 00 05 39 0.37 0.71 539

Ind-S-64 217.847 128.840 A 0.23 0.44 1.25 11.68 00 05 42 0.31 1.51 809

Ind-S-65 217.765 128.845 C 0.12 0.08 0.83 2.30 02 11 19 0.83 1.38 152

Ind-S-66 217.956 128.745 B 0.23 0.71 4.45 15.41 01 07 48 0.33 1.05 725

Ind-S-67 217.856 128.741 A 0.25 0.50 3.09 12.36 01 08 41 0.63 1.39 913

Ind-S-68 217.750 128.746 A 0.10 0.03 1.11 3.94 00 17 32 0.68 2.57 188

Ind-S-69 218.069 128.750 A 0.08 0.10 2.09 4.26 00 35 35 0.60 2.71 200

Ind-S-71 218.151 128.639 A 0.13 0.49 9.09 8.95 00 08 35 0.26 0.40 349

Ind-S-72 218.050 128.640 A 0.19 0.61 6.76 12.31 00 15 40 0.38 0.58 425

Ind-S-74 217.798 128.632 B 0.17 0.31 2.03 7.09 00 17 53 1.18 2.62 171

Ind-S-75 218.267 128.630 B 0.10 0.29 1.68 5.90 00 12 29 0.51 1.71 299

Ind-S-76 218.277 128.482 C 0.06 0.04 1.20 3.58 01 23 33 0.74 2.79 340

IK-R-1 Rock (Indikolapelessa) 0.04 0.17 17.96 3.79 01 03 24 0.12 0.02 170



GP-R-1 Rock (Ginigalpelessa) 0.06 0.04 20.47 4.31 00 04 21 1.10 0.10 206



Soils were classified into three groups as: serpentinite soil (A), boundary soil (B) and non-serpentinite soil (C), classification of soil is detailed in the text.

Appendix Table 2a Grain size distribution in serpentine and non-serpentine soils at Idikolapelassa as a weight (g)

Serpentine soil Non-serpentine soil Sieve size (mm)

Ind-S-3 Ind-S-6 Ind-S-24 Ind-S-30 Ind-S-45 Mean Ind-S-18 Ind-S-42 Ind-S-53 Ind-S-56 Mean

>4.75 0 8.27 0.56 0 5.78 2.92 0 0.25 0.2 1.01 0.37

4.75–2.36 0.75 77.3 30.89 9.32 36.03 30.86 1.48 4.39 1.36 2.98 2.55

2.36–1.18 16.85 38.11 29.74 25.14 30.69 28.11 14.69 21.77 24.95 17.41 19.71

1.18–0.6 32.3 17.02 38.2 31.04 32.92 30.30 23.84 20.73 25.73 18.62 22.23

0.6–0.3 67.3 27.34 52.87 64.81 48.67 52.20 52.93 49.01 56.47 55.14 53.39

0.3–0.15 58.06 20.06 35.49 43.38 34.02 38.20 76.64 64.83 56.31 71.98 67.44

0.15–0.075 16.8 7.42 8.17 13.16 6.76 10.47 16.3 25.01 20.51 22.47 21.07

<0.075 7.05 4.21 3.45 8.48 2.91 5.22 13.43 13.27 13.28 10.14 12.53

Total 199.11 199.73 199.37 195.33 197.78 198.28 199.31 199.26 198.81 199.75 199.28

Appendix Table 2b Grain size distribution in serpentine and non-serpentine soils at Idikolapelassa as a weight percentage (%)

Serpentine soil Non-serpentine soil Grain size (mm)

Ind-S-3 Ind-S-6 Ind-S-24 Ind-S-30 Ind-S-45 Mean Ind-S-18 Ind-S-42 Ind-S-53 Ind-S-56 Mean

>4.75 0 4.14 0.28 0 2.92 1.47 0 0.13 0.10 0.51 0.19

4.75–2.36 0.38 38.70 15.49 4.77 18.21 15.56 0.74 2.20 0.68 1.49 1.28

2.36–1.18 8.46 19.08 14.92 12.87 15.52 14.18 7.37 10.93 12.55 8.72 9.89

1.18–0.6 16.22 8.52 19.16 15.89 16.65 15.28 11.96 10.40 12.94 9.32 11.16

0.6–0.3 33.80 13.69 26.52 33.18 24.61 26.33 26.56 24.59 28.40 27.60 26.79

0.3–0.15 29.16 10.04 17.80 22.21 17.20 19.27 38.45 32.54 28.323 36.034 33.84

0.15–0.075 8.44 3.72 4.09 6.74 3.42 5.28 8.18 12.55 10.32 11.25 10.57

<0.075 3.54 2.11 1.73 4.34 1.47 2.63 6.74 6.66 6.68 5.08 6.29

geo-vegetation mapping and soil geochemical ...en.earth-science.net/pdf/20140116105821.pdf · the...

Documents