The Magmatic Architecture of Continental Flood Basalts I: Observations From the Deccan Traps

Flood basalts are some of the largest magmatic events in Earth history, with intrusion and eruption of millions of km(3) of basaltic magma over a short time period (similar to 1-5 Ma). A typical continental flood basalt (CFB) is emplaced in hundreds of individual eruptive episodes lasting decades to centuries with lava flow volumes of 10(3)-10(4) km(3). These large volumes have logically led to CFB models invoking large magma reservoirs (> 10(4)-10(5) km(3)) within the crust or at Moho depth. Since there are currently no active CFB provinces, we must rely on observations of past CFBs with varying degrees of surface exposure to develop and test models. In the last few decades, significant improvements in geochronological, geochemical, paleomagnetic, volcanological, and paleo-proxy measurements have provided high-resolution constraints on CFB eruptive tempo - the volume, duration, and frequency of individual eruptive episodes. Using the well-studied Deccan Traps as an archetype for CFB systems, we compile multiple lines of evidence-geochronology, eruption tempo, dike spatial distribution, intrusive-extrusive ratio, geochemical variations, and volcanological observations-to assess the viability of previous models. We find that the presence of just a few large crustal magma reservoirs is inconsistent with these constraints. Although observations from the Deccan Traps primarily motivate our model, we discuss constraints from other CFBs to illustrate that this conclusion may be broadly applicable for CFB magmatic systems in general. Plain Language Summary Flood basalt eruptions are among the largest volcanic events in Earth history, erupting millions of cubic kilometers of lava over a geologically short time interval (similar to 1-5 Ma). Typically, continental flood basalt (CFB) eruptive sequences have hundreds of individual eruptions, each with a volume of thousands of km(3) of lavas. This is significantly larger than any volcanic eruption within human history. Because of the large size of the eruptions, it is usually assumed that the magma reservoir(s) feeding the eruption are also very large (> 10(4)-10(5) km(3)). In this study, we use the size, duration, and frequency of individual eruptions as known from several lines of evidence (geochronological, geochemical, paleomagnetic, volcanological, and paleo-proxy measurements) to investigate the properties of CFB magmatic systems. We find that the dynamics of these eruptions are inconsistent with just a few large magma reservoirs and instead require a network of smaller magma bodies feeding each eruption.

Automated summary

Flood basalt eruptions are some of the largest volcanic events in Earth history, erupting millions of cubic kilometers of lava over a geologically short time interval. Studies show that a network of smaller magma bodies is needed to explain the dynamics of these large eruptions, rather than just a few large magma reservoirs.