Ultrasonic Observation of the Calcite-Aragonite TransitionElastic-wave velocities were measured as a function of pressure by ultrasonic pulse Interferometry in Solenhofen and Manilus limestone specimens to pressures of 27 and 38 kb. Longitudinal velocities decrease sharply from 5.3 km/sec at a mean pressure of 4 kb to a minimum of 4.8 km/sec at 8 kb. Transverse velocities decrease from 3.1 to 2.9 km/sec. At the minimum bulk and rigidity moduli are 25 and 20 per cent below their 4-kb values. A density increase of 1.7 per cent is associated with this minimum. The observed effects are attributed to the calcite-aragonite transition, and they may be due to an inherent property of the material, a component of which undergoes a polymorphic transition, the low- and high-pressure phases coexisting over a considerable pressure range. This may be an additional mechanism to account for low-velocity zones in the earth?s interior.
Document ID
19630003648
Acquisition Source
Headquarters
Document Type
Other
Authors
Ahrens, T. J. (Rensselaer Polytechnic Inst. Troy, NY, United States)
Katz, S. (Rensselaer Polytechnic Inst. Troy, NY, United States)