Quartz-in-garnet inclusion barometry under fire: Reducing uncertainty from model estimates


Ashley, Kyle T.
Steele-MacInnis, Matthew
Bodnar, Robert J.
Darling, Robert S.

Quartz inclusions in garnet are suitable for barometry because quartz is highly compressible relative to garnet, and the garnet host can maintain large stress differences generated as pressure-temperature conditions change. However, experimental validation of the quartz-in-garnet approach has been limited, raising questions concerning the accuracy of calculated entrapment pressure. Here we test the results of quartz-in-garnet barometry by conducting in situ Raman analysis of natural inclusions over a range of temperatures (−175 to 600 °C). We assess the temperature (T) dependence of inclusion pressure (Pincl) at 1 bar and compare calculated entrapment pressures derived from measurements at different temperatures. Experiments used two quartz standards (oriented [c] and ) and fully encapsulated quartz inclusions from three different terranes, retaining different Pincl at room T (−444, 296, and 755 MPa). The stretched quartz inclusion (Pincl

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Figure 3. Calculated entrapment pressure from measured inclusion pressure, Pincl, at each heating step with linear regressions through the data (pure almandine garnet is assumed). Independently constrained entrapment conditions from Matthews and Schliestedt (1984) and Ashley et al. (2015b) are shown for reference. RMS—root mean square.

Publication Listing

Geology, v. 44, p. 699-702, doi: 10.1130/G38211.1