Here’s a new paper that proposes the biggest of big ideas: a 240 million year causal chain that runs from the Earth’s surface, to the core mantle boundary, and back again! Here’s how it supposedly goes:
1. Banded iron deposits form on the ocean floor.
2. After subduction, they slowly sink to the bottom of the mantle.
3. The presence of an iron-rich and conductive blob of subducted stuff on the core-mantle boundary boosts local heat flow, and triggers the formation of a mantle plume.
4. Once the plume rises to the base of lithosphere, vast amounts of magma forms by decompression melting, and a new Large Igneous Province is born.
A few quick thoughts on this:
- Most BIF formation occurs in the Proterozoic – most famously they are associated with the Great Oxygenation Event around 2.4 billion years ago, but even after that the ocean remained poorly oxygenated. Does this imply that Large Igneous Provinces were much more frequent in the Proterozoic (which would make the ‘Boring Billion‘ a mite less boring, IMHO)?
- There were episodes of BIF formation associated with the ‘Snowball Earth’/Cryogenian period at the end of the Proterozoic, which could be linked to Large Igneous Province formation in the Paleozoic (although the Siberian Traps is pushing the proposed time delay a bit).
- It assumes/requires that the Proterozoic was a time of active ‘modern’ subduction, which is somewhat disputed ground in the ‘When did plate tectonics start?’ debate…
- Although this is a cool idea, correlating events with such a large, and inherently noisy due to the details of subduction, lag time is something to do very carefully.
Nice plan for content warnings on Mastodon and the Fediverse. Now you need a Mastodon/Fediverse button on this blog.