Deep-Diving Rocks Reveal a Subduction Zone’s Thermal Secrets
Rocks exhumed from a subduction zone in Papua New Guinea suggest that temperature changes with depth in ways not previously predicted, calling into question current models of subduction.
Deep-diving rocks in Papua New Guinea offer a rare glimpse into the thermal secrets of subduction zones, shedding light on the complex processes that lead to massive earthquakes and tsunamis. Researchers analyzed a rock from Goodenough Island, an eclogite characterized by its red and green coloration and high-pressure mineral composition.
This rock contained inclusions of coesite, a type of quartz that forms only under extreme pressure and temperature conditions. By examining the distribution of these minerals within the garnets of the eclogite, scientists discovered that the temperature increased more rapidly than expected in the shallow parts of the subduction zone before following a more usual gradient.
This finding suggests that the rock recorded two distinct moments in its subsurface journey, providing valuable data for refining models of subduction zones. The rapid journey of this rock, estimated to have traversed over 60 millimeters per year vertically, helped preserve its metamorphic history, offering a rare snapshot of conditions at two different depths within the Earth's mantle.
The researchers estimate that the rock experienced significantly higher heating at shallow depths compared to models of subduction, likely due to frictional heating from the movement of cold rock past one another. This discovery enhances our understanding of subduction zones and their thermal structures but further investigation across more samples is needed to confirm these findings.
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