| dc.description.abstract | Cloud-to-ground lightning (CG lightning) is a common natural phenomenon which comes up with high energetic current and high pressure shock wave, and will form the associated geological evidence including melting and shock lamella on rocks, termed fulgurites. Because lightning strikes on different protolith. Our CG lightning event took place on granitic gneiss in Kimen county, Taiwan, on May. 7th, 2018. In the field, we found two strike points which are done by one lightning event. In our research, we used microanalytical methods including optical microscope, Field-Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscope (TEM), regular and synchrotron X-ray Diffraction (XRD), and Raman spectroscope, and built an energetic model of lightning. Our results show the fulgurites were characterized with a black-to-brown, roughly thin, and heterogeneous glassy crust with some vesicles covering on the host rock or injecting to cracks. Planar fractures derived from high pressures (up to several GPa) were found in k-feldspars suggesting the presence of shock waves. Also, we found some carbon and high reduced-state iron indicate that lightning made some reduction during the melting. Jarosite groups, were recognized to locally deposit on fulgurites, likely suggesting the presence of hydrothermal condition in near-surface exposures after the cessation of the CG lightning. These features which are easier to be weathered and disappear implies the fulgurites are formed recently by a high temperature and transient event. In addition, comparing the modelling result with the field observation (~9.5 m2 in area with the thickness of 50 μm), latter is much less than the former. Our study establishes a reference rock fulgurites data originated from CG lighting on granitic rocks set for future on-site drilling and presents an application of these data for studies of ancient rock fulgurite relicts. | en_US |