ReversePetrogen: A Multiphase Dry Reverse Fractional Crystallization‐Mantle Melting Thermobarometer Applied to 13,589 Mid‐Ocean Ridge Basalt Glasses
Name
2020JB021292.pdf
Description
Published version
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5.2 MB
Format
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Checksum (MD5)
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Author(s)
Brown Krein, S.
Molitor, Z. J.
Grove, T. L.
Date Issued
July 2021
Journal
Journal of Geophysical Research: Solid Earth
Publisher
American Geophysical Union (AGU)
Citation
Brown Krein, S. et al. "ReversePetrogen: A Multiphase Dry Reverse Fractional Crystallization‐Mantle Melting Thermobarometer Applied to 13,589 Mid‐Ocean Ridge Basalt Glasses." Journal of Geophysical Research: Solid Earth 126, 8 (August 2021): e2020JB021292. © 2021 American Geophysical Union
Version
Final published version
Abstract
We present a new algorithm, ReversePetrogen (RevPet), to infer mantle melting conditions (pressure, temperature, source composition) using evolved basalts that have experienced multiphase fractional crystallization. RevPet measures and minimizes the compositional distance between experimentally predicted phase saturation boundaries and an erupted basalt and the more primitive liquids that return it to a primary melt. We use RevPet to investigate mantle melting conditions at mid-ocean ridges (MORs) using a global data set of 13,589 basaltic glasses. We find that their average apparent mantle potential temperature (TP*) is 1322°C ± 56°C with melting pressures of 13.0 ± 5 kbars. Inferring the true initial (pre-melted) TP from TP* requires knowing the style and degree of melting of the input basalts. If MORB glasses were entirely produced by near-fractional melting of a homogenous source, they would record the cooling of the mantle during melting from an initial TP = ∼1380°C (ΔTP = 0°C) down to TP = ∼1270°C. If, instead, they were all fully pooled near-fractional melts of the same source, they would record variations in ambient MOR TP from ∼1300°C to 1450°C (ΔTP = 150°C). However, because MOR basalts are thought to be both near-fractional and variably pooled melts of variable sources, MOR TP must be intermediate between these two extremes. Our best estimate, consistent with MOR crustal thickness, is that ambient MOR TP is homogenous (∼1350°C–1400°C) except near hotspots where TP reaches ∼1600°C. Some primitive glasses found near slow-spreading ridges and back-arcs record very low temperatures (TP* < 1250°C) and pressures of melting (<10 kbar) and reflect mantle cooling during melting and melt equilibration in the mantle lithosphere.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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DOI of Published Version
https://doi.org/10.1029/2020jb021292
