Book contents
- Frontmatter
- Contents
- Preface and Philosophy
- Abbreviations and acronyms
- Part I Planetary perspective
- Part II Earth: the dynamic planet
- Part III Radial and lateral structure
- Part IV Sampling the Earth
- Part V Mineral physics
- Part VI Origin and evolution of the layers and blobs
- Chapter 23 The upper mantle
- Chapter 24 The nature and cause of mantle heterogeneity
- Chapter 25 Crystallization of the mantle
- Part VII Energetics
- References and notes
- Appendix
- Index
Chapter 24 - The nature and cause of mantle heterogeneity
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface and Philosophy
- Abbreviations and acronyms
- Part I Planetary perspective
- Part II Earth: the dynamic planet
- Part III Radial and lateral structure
- Part IV Sampling the Earth
- Part V Mineral physics
- Part VI Origin and evolution of the layers and blobs
- Chapter 23 The upper mantle
- Chapter 24 The nature and cause of mantle heterogeneity
- Chapter 25 Crystallization of the mantle
- Part VII Energetics
- References and notes
- Appendix
- Index
Summary
The right to search for truth implies also a duty. One must not conceal any part of what one has discovered to be true.
Albert EinsteinOverview
The lithosphere clearly controls the location of volcanism. The nature and volume of the volcanism and the presence of ‘melting anomalies’ or ‘hotspots,’ however, reflect the intrinsic chemical and petrologic heterogeneity of the upper mantle. Melting anomalies – shallow regions of ridges, volcanic chains, flood basalts, radial dike swarms – and continental breakup are frequently attributed to the impingement of deep mantle thermal plumes on the base of the lithosphere. The heat required for volcanism in the plume hypothesis is from the core; plumes from the deep mantle create upper mantle heterogeneity. This violates the dictum of good Earth science: never go for a deep complex explanation if a shallow simple one will do.
Mantle fertility and melting point variations, ponding, focusing and edge effects, i.e. plate tectonic and near-surface phenomena, may control the volumes and rates of magmatism. The magnitude of magmatism may reflect the fertility and homologous temperature, not the absolute temperature, of the asthenosphere. The chemical and isotopic heterogeneity of the mantle is, in part, due to recycling and, in part, due to igneous processes internal to the mantle. The fertility and fertility heterogeneity of the upper mantle are due to subduction of young plates, aseismic ridges and seamount chains, and to delamination of the lower continental crust, as discussed in Part II.
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- New Theory of the Earth , pp. 312 - 317Publisher: Cambridge University PressPrint publication year: 2007
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