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The origin of electrical anomalies in the uppermost mantle

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Authors:Yang Xiaozhi
Author Affiliations:Primary:
Nanjing University, School of Earth Sciences and Engineering, Nanjing, China
Volume Title:Yanshi Kuangwuxue Zazhi Acta Petrologica et Mineralogica
Source:Yanshi Kuangwuxue Zazhi = Acta Petrologica et Mineralogica, 32(5), p.663-679. Publisher: Science Press, Beijing, China. ISSN: 1000-6524
Publication Date:2013
Note:In Chinese with English summary. 106 refs.; illus.
Summary:Anomalous zones of high electrical conductivity and pronounced electrical anisotropy have been detected by geophysical electromagnetic deep surveys in some regions of the uppermost mantle; nevertheless, their origin remains a long-standing controversial issue. Several conduction mechanisms have been proposed, such as the presence of partial melts, H-bearing olivine, graphite and sulfides in grain boundaries, Fe-rich garnet and hydrous minerals like micas. The differences between these models have significantly different impacts on the composition, structure and physical-chemical properties of the uppermost mantle, and even on the triggering of earthquakes and the styles of mantle convection and other dynamical processes. Based on recent studies of petrology, geochemistry, geophysics, numerical modeling and laboratory high-pressure and high-temperature experiments, this paper deals with various problems involved with the available models. The authors hold that electrical anomalies in some regions of the uppermost mantle may be related to its macro-scale heterogeneities, including the local enrichment of Fe3+-and H2O-rich augites(and other pyroxenite analogues) in the form of dykes/veins and/or the local presence of remnants from recycled crustal materials(e.g., conductive subduction-associated oceanic and continental crust and/or delaminated continental deep crust stretched into high aspect ratio bands/lenses due to mantle flow).Electrical anomalies in different regions of the uppermost mantle may have different origins, and thus eeking for a single unique explanation seems unnecessary.
Subjects:Anisotropy; Electrical anomalies; Electrical conductivity; Igneous rocks; Mantle; Physical properties; Plutonic rocks; Pyroxenite; Ultramafics; Upper mantle
Record ID:783798-8
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