A Tilted Broad Plume Underneath the Greenland Cratonic Keels

To advance our comprehension of the complex geological history and mantle dynamics in the North Atlantic region, we employ all available broadband seismic data recorded in Greenland to reveal an abnormal mantle transition zone (MTZ) structure. Central and eastern Greenland exhibits depressed 410 and 660 km discontinuities (d410 and d660, respectively) bordering the MTZ, indicative of a substantial thermal anomaly associated with an underlying plume, surpassing the 1,800 degrees C threshold for post-garnet phase transitions at the d660. Variations in MTZ thickness across Greenland stem from differing temperature anomalies at the d410 and d660, possibly linked to a tilted plume within the MTZ. These findings corroborate geodynamic models, elucidating the interaction between post-garnet phase transitions and upwelling plumes. The results shed light on the origin of the enigmatic Icelandic hotspot track and its influence on the thermal and lithospheric structures beneath Greenland. The physical and chemical processes responsible for producing the magnificent volcanic eruptions in Iceland and the North Atlantic region are debated issues in the geoscientific community despite numerous field and laboratory studies over the past several decades. One of the hypotheses for the formation of the volcanoes is that they originate from a column of hot rocks rising from the deep mantle, that is, a mantle plume. The geometry, depth extent, and temperature anomaly of the plume are not well defined but can be constrained using the topography of two phase-transition boundaries approximately at the globally averaged depths of 410 and 660 km, respectively. By analyzing P-to-S converted phases from the two discontinuities recorded by seismic stations, our results support the existence of a mantle plume that is broader than most other plumes on Earth beneath east Greenland. In addition, the results suggest that the nature of the phase transition across the 660 km discontinuity is different between the hottest core of the plume stem and the colder peripheral areas. The existence of the particular type of phase transition in the plume center can explain the large dimension of the plume, the excessive volcanism and other observations in the area. The central and east Greenland shows abnormal mantle transition zone (MTZ) thickness, indicating a deep-seated mantle plume Seismic data unveil the impact of post-garnet phase transition at the 660-km discontinuity on mantle dynamics Variations in MTZ thickness suggest the existence of a tilted plume and offer insights into the plume behavior