The incredible life of Lara the lava!


We were recently asked to prepare a 180 seconds presentation of our PhD project so why leaving this in a random folder in my computer? I’ll try to walk you through my PhD project by presenting the story of Lara, the droplet of lava … with visual support!

Melt is formed by decompression melting of the upwelling mantle peridotites

“One day, Lara, a young droplet of melt, wakes up in her warm bed of peridotites.”

Melt travelling in the peridotite by porous flow

She decides that it is time to travel the Earth and go on an adventure! She grabs her bag and walks through the door, ready to discover everything the world has to offer.”

The reactive melt percolating in the mantle peridotites leads to the dissolution of mantle pyroxenes

“On her way she meets other travellers, just like her! They decide to hit the road together, but priorities first, they are hungry and decide to stop at their favourite restaurant: The Interaction, where they serve the best pyroxenes in town! Yummy!”

The melt-peridotite interaction also leads to the crystallization of olivine, whose constituent are then removed from the melt

“They pay with Olivines, the currency used down there, in the Oceanic Mantle”

The aggregation of melt fractions of various compositions forms MORB-type melt (for real it’s Mid Ocean Ridge Basalt)

“They get along so well that they decide, with other melt droplets they met on the way, to form a music band: The Mad Orchestra Ragga Bangsters, or MORB.”

Melts are travelling in high-porosity dunite channels

“For an increased efficiency on the music tour, they decide to hop on the Dunite bus, that will get them directly to the fancy parts of town, where they will perform their music everywhere!”

Melt impregnation at plagioclase-facies leads to crystallization of plagioclase into the percolated peridotite. The impregnation at decreasing melt-mass changes the composition of the remaining melt

“After an epic tour, a first member of the group decides to settle down to raise his new-born child, Plagioclase. The MORB group will never be the same without him!”

Melts reach the seafloor and crystallize as basalts, forming the oceanic upper crust

“Her friends finally decide to settle down one after the other, but Lara wants to see the seafloor and the fish everybody talks about downtown. When she finally reaches the end of her long adventure, she feels happier than ever, lies down and sleeps forever…”

This story could seem completely random but it is quite representative of my PhD thesis. The aim of my study is to “write” the biography of Lara, this droplet of melt: where did she go during her life, who did she meet and interact with, where did her friends stop and why?

These processes of melt transport, interaction with the percolated rock, and impregnation and crystallization at shallower levels take place constantly at mid-ocean ridges, where the oceanic crust is being formed by accretion of melts (next figure). These processes are important for the global understanding of the formation of the oceanic crust, the composition of Mid-Ocean Ridge melts and the dynamic of the Earth.

Mid-Atlantic Ridge segments, where the accretion of the oceanic crust takes place. Satellite image from Google Earth, Google©

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