Quartz-coesite transition revisited; reversed experimental determination at 500-1200 degrees C and retrieved thermochemical properties

Other| April 01, 1995 Quartz-coesite transition revisited: Reversed experimental determination at 500–1200 °C and retrieved thermochemical properties Kunal Bose; Kunal Bose University of Arizona, Department of Geosciences, Tucson, AZ, United States Search for other works by this author on: GSW Google Scholar Jibamitra Ganguly Jibamitra Ganguly Search for other works by this author on: GSW Google Scholar American Mineralogist (1995) 80 (3-4): 231–238. https://doi.org/10.2138/am-1995-3-404 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Kunal Bose, Jibamitra Ganguly; Quartz-coesite transition revisited: Reversed experimental determination at 500–1200 °C and retrieved thermochemical properties. American Mineralogist 1995;; 80 (3-4): 231–238. doi: https://doi.org/10.2138/am-1995-3-404 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract We have determined the quartz-coesite transition by reversed experiments in a piston-cylinder apparatus in the range 500–1200 °C. The difference between the sample pressure and apparent pressure was calibrated by (1) studying the friction decay in the hysteresis loop defined by the relationship between apparent ("nominal") pressure and piston position in the compression and decompression cycles, and (2) determining the melting temperature of LiCl by DTA in pressure cells similar to those used in the reversal experiments and comparing the results with those determined in the gas apparatus. The equilibrium transition boundary can be expressed as P (kbar) = 21.945 (±0.1855) + 0.006901 (±0.0003)T (K). It is subparallel to, but ∼1.5 kbar higher than, the transition boundary determined by Bohlen and Boettcher (1982). We have also retrieved the entropy [39.56 ± 0.2 J/(mol·K)] and enthalpy of formation (−907.25 ± 0.007 kj/mol) from elements of coesite at 1 bar, 298 K, from our phase-equilibrium data and selected thermochemical data from the literature. From the characteristics of the hysteresis loop we conclude that the often-used practice of maintaining a constant nominal pressure by repeated pressure adjustment during an experiment leads to variation of pressure on the sample. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.