Geo-vegetation mapping and soil geochemical characteristics of the Indikolapelessa serpentinite outcrop, southern 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 successfully 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 serpentinite 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.

Keywords

serpentinite / serpentinite soil / geochemistry / geo-vegetation / ultramafic rock / Sri Lanka

References

[1] Brady K U, Kruckeberg A R, Bradshaw H D. Evolutionary Ecology of Plant Adaptation to Serpentine Soils. Annual Rev. Ecol. Evol. Syst., 2005, 36: 243-266.

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

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

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

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

[6] Dissanayake C B, Van Riel B J. Petrology and Geochemistry of a Recently Discovered Nickeliferrous Serpentinite from Sri Lanka. Journal of Geological Society of India, 1978, 19: 464-471.

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

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

[9] Hansen E C, Janardhan A S, Newton R C, . Arrested Charnockite Formation in Southern India and Sri Lanka. Contributions to Mineralogy and Petrololgy, 1987, 96(2): 225-244.

[10] Hatherton T, Pattiaratchi D B, Ranasinghe V V C. Gravity Map of Sri Lanka, 1975 Colombo: Sri Lanka Geological Survey Department, 39.

[11] Johnston W R, Proctor J. 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, 1984, 96: 95-101.

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

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

[14] Kruckeberg A R. California Serpentines: Flora, Vegetation, Geology, Soils and Management Problems, 1984 Berkeley: University of California

[15] Lazaro J D, Kidd P S, Martinez C M. A Photochemical Study of the Tras-Os-Montes Region (NE Portugal): Possible Species for Plant Based Soil Remediation Technologies. Sciences of Total Environment, 2006, 354: 265-277.

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

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

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

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

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

[21] Prame W K B N, Pohl J. Geochemistry of Pelitic and Psammopelitic Precambrian Metasediments from Southwestern Sri Lanka: Implications for Two Contrasting Source-Terrains and Tectonic Settings. Precambrian Research, 1994, 66: 223-244.

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

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

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

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

[26] Reddy R A, Balkwill K, Mclellan T. Plant Species Richness and Diversity of the Serpentine Areas on the Witwatersrand. Plant Ecology, 2009, 201: 365-381.

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

[28] Reeves R D, Baker A J M, Borhidi A. Nickel Hyperaccumulation in the Serpentine Flora of Cuba. Annals of Botany, 1999, 83: 29-38.

[29] Roberts B A, Proctor J. The Ecology of Areas with Serpentinized Rocks: A World View, 1992 Nederlands: Kluwer Academic Publishers, 420

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