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Modeling continental crust: Structural and chemical constraints
Author(s) -
Smithson Scott B.
Publication year - 1978
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl005i009p00749
Subject(s) - geology , crust , continental crust , adakite , geochemistry , oceanic crust , discontinuity (linguistics) , metamorphic rock , metamorphic core complex , felsic , petrology , geophysics , subduction , seismology , tectonics , mafic , mathematical analysis , mathematics , extensional definition
Seismic reflection studies reveal lateral and vertical heterogeneity of the deep crust that is comparable to that indicated by geologic observations. In a crust this heterogeneous, the concept of a “Conrad Discontinuity” has little meaning. Near‐horizontal reflectors in the deep crust are formed by horizontal movements in metamorphic rocks and magmatic crystallization within the earth’s gravity field. Supracrustal rocks in the lower crust suggest that much of the crust was built up as a supracrustal pile. Mean crustal composition is approximately quartz dioritic to granodioritic. This composition cannot be achieved by simply adding material through accretion of andesitic island arcs but must account for more felsic material.