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Published February 13, 2007 | public
Journal Article Open

Temperatures in ambient mantle and plumes: Constraints from basalts, picrites, and komatiites

Abstract

Several methods have been developed to assess the thermal state of the mantle below oceanic ridges, islands, and plateaus, on the basis of the petrology and geochemistry of erupted lavas. One leads to the conclusion that mantle potential temperature (i.e., TP) of ambient mantle below oceanic ridges is 1430°C, the same as Hawaii. Another has ridges with a large range in ambient mantle potential temperature (i.e., TP = 1300–1570°C), comparable in some cases to hot spots (Klein and Langmuir, 1987; Langmuir et al., 1992). A third has uniformly low temperatures for ambient mantle below ridges, ∼1300°C, with localized 250°C anomalies associated with mantle plumes. All methods involve assumptions and uncertainties that we critically evaluate. A new evaluation is made of parental magma compositions that would crystallize olivines with the maximum forsterite contents observed in lava flows. These are generally in good agreement with primary magma compositions calculated using the mass balance method of Herzberg and O'Hara (2002), and differences reflect the well-known effects of fractional crystallization. Results of primary magma compositions we obtain for mid-ocean ridge basalts and various oceanic islands and plateaus generally favor the third type of model but with ambient mantle potential temperatures in the range 1280–1400°C and thermal anomalies that can be 200–300°C above this background. Our results are consistent with the plume model.

Additional Information

© 2007 American Geophysical Union. Received: 16 June 2006; Revised: 10 October 2006; Accepted: 13 November 2006; Published: 13 February 2007. We are very grateful to Don Anderson, Fred Frey, Dave Green, Marc Hirschmann, Charles Langmuir, Keith Putirka, Mike Rhodes, and three anonymous reviewers for critical reviews. We also thank Michael Baker for sharing experimental information and Francis Albarède for numerous discussions. Auxiliary software calculates primary magma composition using melt fraction F as a constraint as discussed in section A1 of the main text.

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September 13, 2023
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