Variolite

Variolite is an extrusive igneous rock characterized by the presence of varioles – small, spherical or subspherical structures of radiating or concentric texture, typically lighter in color than the surrounding groundmass. These varioles are composed of feldspar, pyroxene, or other minerals. Variolites form in lavas, often pillow lavas, due to rapid cooling and sometimes, by liquid immiscibility. The presence and composition of varioles aid in distinguishing and classifying this distinctive rock type, alongside textural analysis and examination of associated geological context.

Variolite meaning with examples

• Geologists studying a newly discovered lava flow identified variolite by the distinctive spherical varioles embedded within the dark, fine-grained groundmass. These formations often indicate rapid cooling, which is common in underwater lava flows and can be used to determine eruptive conditions. The team used thin-section analysis to determine the composition of both the varioles and the host matrix and establish its composition and age to understand the volcanic history.
• The research focused on correlating the appearance of variolite with the geochemical signature of the associated lavas. By analyzing the chemical composition of the varioles and groundmass, they determined the source magma and the conditions under which it cooled. This approach aided in reconstructing the history of volcanic eruptions. Distinct types of variolites were identified based on the mineralogy, which led to better classification.
• Pillow lavas, where the external chilled surfaces often present variolitic textures, provided valuable information about subaqueous volcanism in the region. The size and density of the varioles varied depending on the eruption rate and the water-flow speed. The unique patterns within the variolitic structures have been correlated with the rate of heat exchange, which makes them excellent tools to interpret changes in the hydrothermal environment.
• During a field study of the ancient ocean floor, the team discovered variolite. Examination showed that the varioles' radial texture and mineralogy were indicative of rapid cooling from contact with cold seawater. Samples collected were subject to radiometric dating. This investigation expanded the knowledge of the evolution of the local geological landscape and supported the theory of plate tectonics and subduction zones in the area.