The surface texture features of volcanic glass shards inSakurajima, Japan
Mao Ziqiang1, 2Fang Xiaomin1 Song Chunhui3
CAS Center for Excellence in Tibetan Plateau Earth Sciences and Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101
University of Chinese Academy of Sciences, Beijing 100049
School of Earth Sciences & Key Laboratory of Western China??s Mineral Resources of Gansu Province, Lanzhou University, Lanzhou 730000
Volcanic ash chronology is the most simple and reliable approach to constrain stratigraphic age, leading to a wide utilization and common a key role in magnetostratigraphy, tectonic evolution, paleoclimatic environment change and archaeology, etc. However, a recognition of volcanic ash in stratigraphy often causes heated debate, hindering a reliable age determination and a resolution of many related scientific problems. Volcanic glass as a common and characteristic component in the ash is the key criteria to identity volcanic ash. In this paper, we try to use the surface texture features of the volcanic glass shards from the typical volcanic ashes in Sakurajima, Japan by using optical and scanning electron microscopes. The results show that the characteristics of volcanic glass are fractured shapes（long strip, sheet, granular, trihedral faces, etc.）with sharp edges, curved surfaces and various kinds of holes, pipe grooves, small round pits, oval pits and eye-like pits that are related to volcanic eruption. This provides an independent microscopic morphology approach to distinguish precisely andesitic and rhyolitic volcanic ash.