Xenolith Constraints on the Mantle Potential Temperature and Thickness of Cratonic Roots Through Time

Abstract

Abstract The temperature of the convecting mantle and thickness of the lithosphere control many of Earth's processes. However, there is disagreement regarding the evolution of these quantities through time. We use a global data set of mantle xenoliths and xenocrysts to construct paleogeotherms at different eruption ages (16–1,311 Ma) and estimate the temperature and depth of the lithosphere‐asthenosphere boundary (LAB) as a function of mantle potential temperature (Tp). We find that the maximum pressure and temperature (PT) of xenoliths matches the modeled LAB conditions when a Tp of 1,315°C is used. At higher Tp (1,450–1,550℃) we observe a gap between the maximum PT of xenoliths and the LAB conditions. Because this gap systematically increases with Tp, and the maximum PT of xenoliths has not changed over time, we suggest that there has actually been only minor (<50°C) changes in mantle Tp since the Meso‐Proterozoic.

Keywords

• potential temperature
• secular cooling
• Archean mantle
• cratonic Lithopshere
• mantle xenoliths
• kimberlite