Chapter 19: Breccia bodies in deformed Cambrian limestones, Heritage Range, Ellsworth Mountains, West Antarctica
Published:January 01, 1992
K. B. Spörli, Campbell Craddock, R. H. Rutford, John P. Craddock, 1992. "Chapter 19: Breccia bodies in deformed Cambrian limestones, Heritage Range, Ellsworth Mountains, West Antarctica", Geology and Paleontology of the Ellsworth Mountains, West Antarctica, G. F. Webers, C. Craddock, J. F. Splettstoesser
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Breccia bodies in the carbonate rocks of the Minaret Formation (Cambrian) of the Ellsworth Mountains were formed at depth by a combination of cavelike processes and contemporaneous low-temperature hydrothermal activity during the latest stages (early Mesozoic?) of compressive deformation in this fold belt. The breccia bodies consist of clasts of Minaret Formation limestone/marble with cleavage, embedded in a matrix of crystalline and detrital calcite; both clast shape alignments and the matrix locally show layering. Clast angularity and edge dissolution vary greatly as does the distance of clast transport (mainly downward). The boundaries between a breccia body and the adjacent country rock may be diffuse or sharp. Breccia body shapes, sizes, and orientations are varied; bodies are as high as approximately 250 m and as wide as 50 m. Many breccia bodies crosscut each other, showing that breccia body formation continued through a period of time. Fluid inclusions in calcite crystals from a vuggy vein yield a crystallization temperature of 160+ ± 5°C. That temperature and the inferred thickness of the overlying stratigraphic succession suggest that the breccia bodies may have formed at a depth as great as 5,000 m.