Something’s off.A rock from Goodenough Island in eastern Papua New Guinea reportedly recorded an unexpected temperature history. Its minerals indicate it descended more than ninety kilometers in a subduction zone about 4.4 million years ago.
According to the report, the rock recorded roughly 700 °C at about 45 kilometers depth, then only about 100 °C more after descending beyond 90 kilometers. The reported pattern is unusual because the shallower stage was warmer than expected, while the deeper stage was cooler than expected by current subduction-zone models.
The researchers cited in the report suggest extra heat from intense shearing at shallow depth, or a young subduction system that had not yet cooled, as possible explanations.
UNVERIFIED
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