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

作　　者：Tilak Hewawasam G W A R Fernando Danushka Priyashantha 

机构地区：[1]Department of Natural Resources,Sabaragamuwa University of Sri Lanka [2]Department of Geography,University of Peradeniya [3]Department of Physics,Open University of Sri Lanka

出　　处：《Journal of Earth Science》2014年第1期152-168,共17页地球科学学刊（英文版）

基　　金：by the Sabaragamuwa University of Sri Lanka(No.SUSL/RG/2006/05)is acknowledged for financial support

摘　　要：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.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.

关 键 词：SERPENTINITE serpentinite soil GEOCHEMISTRY geo-vegetation ultramafic rock Sri Lanka. 

分 类 号：P59[天文地球—地球化学]