Carbonate Clumped Isotopes



Our 'Autoline', an automated system for extraction and purification of CO2 from carbonates and apatites for clumped-isotope thermometry, is shown to the left.  The system/process involves three main aspects (described in Passey et al., 2010):

1. Reaction of sample in H3PO4 under a vacuum environment, and simultaneous cryogenic removal of H2O and CO2.
2. Passage of the CO2 through a cold GC column (Porapak Q, -20C)
3. Removal of GC carrier gas (He), final in-vacuo cryogenic purification, and introduction to the mass spectrometer.

The system is fully automatic, and the user needs to be present only to refill the dewars with dry ice and liquid nitrogen, and to 'press start' on each run.  Processing time is ~45 minutes (solid carbonate to CO2 gas in the mass spec), with an additional ~120 minutes for analysis of the sample in the mass spectrometer.  About 4-5 unknowns and 1-2 standards can be analyzed each day.

As of October 2011 the system has processed over 1900 samples, about 1100 of which are unknowns and the remainder are equilibrium gas standards ('heated gases' and CO2-H2O 'equilibrated gases') and carbonate reference materials.  Our long-term external precision for carbonate reference materials is ~0.013 per mil (1-sigma for D47).

Projects so far include:
Cretaceous marine paleothermometry (G. Price, U. Plymouth, and B. Passey, JHU)
Clumped-isotope thermometry in recent mollusks (G. Henkes, B. Passey, JHU)
Studies of 13C-18O bond reordering at high temperature (B. Passey, JHU)
Holocene paleoclimate in Oaxaca, Mexico (R. Kraft, N. Levin, JHU)
Late Neogene paleoclimate in northern China (M. Suarez, B. Passey, JHU)
PETM temperature excursions in Utah (J. VanDeVelde, G. Bowen, Purdue)
Clumped-isotope speciation effects in DIC (W. Guo, Carnegie Geophysical Lab)