A Caltech Library Service

The Calcite-Aragonite Transition Measured in the System CaO-CO_2-H_2O

Boettcher, A. L. and Wyllie, P. J. (1968) The Calcite-Aragonite Transition Measured in the System CaO-CO_2-H_2O. Journal of Geology, 76 (3). pp. 314-330. ISSN 0022-1376.

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item:


The study of melting reactions in the system CaO-CO_2-H_2O included redetermination of the calcite-aragonite transition boundary. The morphology of aragonite in equilibrium with the ternary liquid is distinct from that of calcite; the original shape of calcite or aragonite becomes frozen into the liquid during the quench and is preserved for microscopic examination regardless of the polymorphic changes that occur in quenching. The shape of the carbonate crystals in the quenched assemblage CaCO_3 + liquid + vapor was therefore used to bracket the calcite-aragonite transition boundary. Some original aragonite crystals inverted to biaxial calcite during the quench. The kinetics of the inversion are strongly influenced by crystal size. The transition boundary was extended below the solidus temperature (580° C. at 12.1 kb.) on the basis of microscopic examination of morphology of the quenched crystals, supplemented by X-ray diffraction patterns. The reaction was reversed at several points. The transition boundary changes slope at 480° C. and 9.4 kb., the triple point for aragonite + calcite I + calcite II. This change in slope is probably caused by ΔS for calcite I - calcite II, because ΔV is insignificant. The lowest point measured on the aragonite-calcite I curve is 400° C. at 8.3 kb., and the highest point measured on the aragonite-calcite II curve is 800° C. at 19.8 kb. These results are compared with a detailed review of previous experimental determinations. Geological applications of the calcite-aragonite geobarometer are discussed, as well as the possible use of biaxial calcite as a criterion for recognizing inverted aragonite.

Item Type:Article
Related URLs:
URLURL TypeDescription
Additional Information:© 1968 University of Chicago Press. Manuscript received June 29, 1967; revised September 1, 1967. We owe much to the assistance and advice of R.C. Newton in setting up and calibrating the piston-cylinder apparatus. R.C. Newton, J.C. Jamieson, and J.R. Goldsmith gave freely of their time and experience in many discussions about carbonates, and reviewed the manuscript. The authors alone are responsible for any errors that remain after its revision. The apparatus was supplied by Advanced Research Projects Agency contract SD-89, and the research was supported by National Science Foundation grant GP-4910.
Funding AgencyGrant Number
Advanced Research Projects Agency (ARPA)SD-89
Issue or Number:3
Record Number:CaltechAUTHORS:20160122-105328706
Persistent URL:
Official Citation:Boettcher, A. L., and P. J. Wyllie. “The Calcite-aragonite Transition Measured in the System CaO-CO_2-H_2O." The Journal of Geology 76.3 (1968): 314–330
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63888
Deposited By: Tony Diaz
Deposited On:22 Jan 2016 20:25
Last Modified:03 Oct 2019 09:32

Repository Staff Only: item control page