Lightning-induced high temperature and pressure microstructures in surface and subsurface fulgurites

Area of Science:

• Geology
• Mineralogy
• Physics

Background:

• Cloud-to-ground lightning induces high-temperature and high-pressure metamorphism in rocks.
• This process forms glassy rock structures known as fulgurites.

Purpose of the Study:

• To investigate microstructural features in surface and fracture-related fulgurites.
• To analyze the formation mechanisms of fracture-related fulgurites using numerical modeling.
• To broaden the understanding of near-surface environments affected by lightning.

Main Methods:

• Microstructural analysis of surface and fracture fulgurites.
• Comparison with granite reference samples.
• 1-D numerical modeling of electric current density in fractures.

Main Results:

• Fulgurites exhibit glass formation, K-feldspar phase transformation with plagioclase exsolution lamellae, and high residual stresses (up to 1.5 GPa).
• Fracture-related fulgurites were documented for the first time.
• Numerical models confirmed high electric current densities in fractures up to 40m from the strike point.

Conclusions:

• Lightning-induced metamorphism extends to subsurface fractures, creating unique geological records.
• Fracture-related fulgurites provide insights into extreme metamorphic events.
• The study expands the known occurrence of rock fulgurites in near-surface environments.