Deciphering the mineral record at mid-ocean ridges: new perspectives on the dynamics of magmatic systems and their along-axis variability

The volcano-plutonic (dis)connection is a central question for a better understanding of magmatic systems in various settings. Studying this connection is essential at mid-ocean ridges, where basalts (MORB) are used to reconstruct the composition and structure of the mantle that produces the melts feeding crustal magmatic systems. The presence of mush-dominated reservoirs below the ridge axes questions the assumption that crustal differentiation mainly occurs by (fractional) crystallization. Here, I will present the characteristics of melt-mush reactions during the evolution of oceanic reservoirs, relying on high-resolution petro-geochemical studies of oceanic gabbros. The results show that the reactions are ubiquitous at various stages of reservoir formation, which advocates for their significant impact on differentiation. In addition, systematics found in the reaction signatures at different locations along mid-ocean ridges translate variability in the local reaction regimes (balance between assimilation and crystallization) and are likely caused by different melt fractions present in the mush during the reactions. The identification of reservoir dynamics (amount, location, and migration capacity of melts) during the formation of magmatic systems is thus potentially feasible through the mineral archive, provided a better quantification of “instantaneous” melt-mush reactions is available. This also paves the way for a more detailed understanding of MORB evolution prior to extraction, and a better reconstruction of the underlying mantle characteristics.

Zoom info:
https://cnrs.zoom.us/j/97483631268?pwd=bgubI1cEgCoYxjAx2U3ltbae9Gxn8S.1

Meeting ID: 974 8363 1268
Passcode: 3wf6au