Australia: The Land Where Time Began

A biography of the Australian continent 

High Mantle Temperatures after Rifting Resulting from Continental Insulation

It is believed the temperature of the underlying mantle is influenced by the distribution of continents. A buildup of heat resulting from insulation effects that may lead to increased levels of magmatism (Anderson, 1982; Grigne & Labrosse, 2001; Lenardic, Moresi, Jellinek & Manga, 2005; Zhong & Gurnis, 1993) over geological time timescales, such as flood basalt volcanism (Coltice et al., 2007; Coltice et al., 2009), and ultimately to the rifting of continents, that leads to the new continents moving away as new ocean basins form. In this study the authors¹ used analyses of the major element chemistry of samples of lavas collected from oceanic crust in the Atlantic and Pacific Oceans to quantify the effects of continental insulation. Following continental rifting and break-up the lavas, that preserve upper mantle temperatures over about the last 170 My, formed at mid-ocean ridges, The results have shown that samples from the Pacific Ocean  - that were formed more than 2,000 km from the nearest margin of a continent, don't record mantle temperatures that are raised. Samples that formed in the Atlantic Ocean close to the margin of a rifted continent shows that temperatures of the upper mantle immediately after continental rifting are up to 150^o C higher than the average of the present, and these higher mantle temperatures remained high for 60-70 My. The authors¹ concluded that continental insulation led to the Atlantic thermal anomaly, that persisted in the mantle beneath the Atlantic Ocean long after the continental fragments had dispersed.

Sources & Further reading

1. Brandl, Philipp A., Marcel Regelous, Christoph Beier, and Karsten M. Haase. "High Mantle Temperatures Following Rifting Caused by Continental Insulation." Nature Geosci 6, no. 5 (05//print 2013): 391-94.