Basaltic magma chambers may grow catastrophically fast

An international group of researchers with geologists from Wits University (Prof. Rais Latypov and Dr. Sofya Chistyakova) in Johannesburg has come to the unexpected conclusion that basaltic magma chambers can grow extremely quickly – in months to years – making these chambers remarkable intrusive equivalents of caldera-forming eruptions associated with the Great Igneous Provinces. This research has been published as a paper in Scientific progress.

Professor Rais Latypov says that “the vertical rate at which magma chambers grow via magma placement is highly debated. Based on very accurate zircon dating and surface deformation measurements, it is currently thought that most plutons are deployed very slowly (several cm/year). However, such low velocities are difficult to reconcile with the existence of large, well-differentiated intrusions that seem to form only when the emplacement velocities are very high.An important question we were trying to answer is what degree of magma emplacement is required to completely melt the culture chamber? ”

To answer this question, the researchers took a new approach, using the classic Skaergaard intrusion in Greenland that only started to crystallize inward from all margins after it was completely filled with nearly crystal-free magma.

“This fundamental physical constraint provides a unique opportunity to estimate the minimal amount of magma placement required to maintain the Skaergaard magma body in a largely molten state (

The researchers used numerical simulations to determine the conditions needed to form such a large crystal-free magma chamber and found that the Skaergaard intrusion must have been set in less than a few decades, if not months/weeks. The vertical growth rate must have been of the order of several hundred to several 1000s m/year, corresponding to volumetric flow rates of 10s to 100s km3/yr. This makes the volumetric flow rate feeding Skaergaard several orders of magnitude higher than the currently accepted growth rates for basaltic magma chambers.

The researchers proposed that the Skaergaard and possibly other layered intrusions could be thought of as plutonic equivalents of super-eruptions (or catastrophic intrusions) that grow via extremely rapid magma deployment in the crust, producing completely molten magma chambers in a matter of weeks. . months to a maximum of tens/hundreds of years.

“In other words, we suggest that some stratified mafic invaders may be the plutonic analogs of the Great Igneous Provinces-related volcanoes responsible for erupting massive amounts of flood basalts on the Earth’s surface,” Latypov says.