*Durgalakshmi Durgalakshmi¹、Ian S Williams²、Satish Kumar M³、Sanjeewa Malaviarachchi⁴、Krishnan Sajeev⁵ (1.Department of Studies in Earth Science, University of Mysore, Mysuru, India、2.Research School of Earth Sciences, Australian National University, Canberra, Australia、3.Department of Geology, Niigata University, Niigata, Japan、4.Department of Geology, University of Peradeniya, Peradeniya, Sri Lanka、5.Centre for Earth Sciences, Indian Institute of Science, Bengaluru, India)