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Thermodynamic calculation of emplacement pressures for batholithic rocks, California: Implications for the aluminum-in-hornblende barometer

1997; Geological Society of America; Volume: 25; Issue: 6 Linguagem: Inglês

10.1130/0091-7613(1997)025 2.3.co;2

1943-2682

Jay J. Ague,

Geochemistry and Geologic Mapping

Research Article| June 01, 1997 Thermodynamic calculation of emplacement pressures for batholithic rocks, California: Implications for the aluminum-in-hornblende barometer Jay J. Ague Jay J. Ague 1Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, Connecticut 06520-8109 Search for other works by this author on: GSW Google Scholar Author and Article Information Jay J. Ague 1Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, Connecticut 06520-8109 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1997) 25 (6): 563–566. https://doi.org/10.1130/0091-7613(1997)025 2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Jay J. Ague; Thermodynamic calculation of emplacement pressures for batholithic rocks, California: Implications for the aluminum-in-hornblende barometer. Geology 1997;; 25 (6): 563–566. doi: https://doi.org/10.1130/0091-7613(1997)025 2.3.CO;2 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 SocietyGeology Search Advanced Search Abstract The aluminum-in-hornblende (AH) barometer has been widely used to estimate the emplacement pressure (P) of granitic rocks. Application of the barometer has remained controversial because the controls on the aluminum content of hornblende imposed by temperature (T), magma composition, and fluid composition remain incompletely understood. In this paper, the P-T conditions of equilibration for 19 rocks from the Mesozoic batholiths of California are estimated by simultaneous evaluation of (1) the P-sensitive reaction tremolite + phlogopite + 2 anorthite + 2 albite = 2 pargasite + 6 quartz + K-feldspar and (2) previously published amphibole-plagioclase thermometer equilibria. P estimates for the batholiths range from 1.2 to 7.4 kbar and are consistent with independent geologic evidence. The highest P samples (5.1–7.4 kbar) are located near the San Andreas fault. Furthermore, it appears that regional P gradients determined by previous AH barometry studies are valid, but that the absolute values of the P estimates will need to be revised somewhat (±1.5 kbar). I suggest that the method of this study provides a viable, thermodynamics-based alternative to conventional AH barometry that requires no a priori assumptions about T or bulk composition. 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.