The hottest lavas of the Phanerozoic and the survival of deep Archaean reservoirs

• Published in: Nature geoscience Vol. 10; no. 6; pp. 451 - 456
• Main Authors: Trela, Jarek, Gazel, Esteban, Sobolev, Alexander V., Moore, Lowell, Bizimis, Michael, Jicha, Brian, Batanova, Valentina G.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.06.2017; Nature Publishing Group
• Subjects: 704/2151/210; 704/2151/598; 704/445/209; 704/445/431; Crystallization; Earth mantle; Earth science; Earth Sciences; Earth System Sciences; Geochemistry; Geology; Geophysics/Geodesy; Lava; Marine; Plumes; Provinces; Reservoirs; Volcanoes; Curacao; United States > US; Virginia; ASW, Caribbean Sea
• ISSN: 1752-0894; 1752-0908
• DOI: 10.1038/ngeo2954

Large igneous provinces and some hotspot volcanoes are thought to form above thermochemical anomalies known as mantle plumes. Petrologic investigations that support this model suggest that plume-derived melts originated at high mantle temperatures (greater than 1,500 °C) relative to those generated at ambient mid-ocean ridge conditions (about 1,350 °C). Earth’s mantle has also cooled appreciably during its history and the temperatures of modern mantle derived melts are substantially lower than those produced during the Archaean (2.5 to 4.0 billion years ago), as recorded by komatiites (greater than 1,700 °C). Here we use geochemical analyses of the Tortugal lava suite to show that these Galapagos-Plume-related lavas, which formed 89 million years ago, record mantle temperatures as high as Archaean komatiites and about 400 °C hotter than the modern ambient mantle. These results are also supported by highly magnesian olivine phenocrysts and Al-in-olivine crystallization temperatures of 1,570 ± 20 °C. As mantle plumes are chemically and thermally heterogeneous, we interpret these rocks as the result of melting the hot core of the plume head that produced the Caribbean large igneous province. Our results imply that a mantle reservoir as hot as those responsible for some Archaean lavas has survived eons of convection in the deep Earth and is still being tapped by mantle plumes. Earth’s mantle has cooled since the Archaean. Geochemical identification of anomalously hot lavas formed above the Galapagos Plume 89 million years ago, however, implies that a hot mantle reservoir may have persisted for billions of years.