Thermobarometers

1. Common Thermometers

1) Garnet–Clinopyroxene thermometry (Powell 1985)

2) Garnet–Clinopyroxene thermometry (Ravna 2000)

3) Garnet–Phengite thermometry (Green and Hellman 1982).

2. Common Barometers

1) Garnet-omphacite-phengite geobarometer (GOP) (Waters and Martin 1996)

2) Empirical phengite geobarometer (Kamzolkin et al. 2016)

3. Common Thermobarometers

1) Muscovite–paragonite thermobarometry (Roux and Hovis 1996)

2) THERMOCALC AVE_PT mode thermobarometry (Powell and Holland 1994)

The P-T conditions are obtained by calculating the intersections of multiple thermobarometers (as the final resulting diagram below). Detailed instructions for building various thermobarometers can be found in the next section.

1. Common Thermometers

Most thermometers used in metabasites bases on the Fe(2+)-Mg exchange between mineral pairs. For instance, garnet–clinopyroxene thermometry (Powell 1985; Ravna 2000), garnet–phengite thermometry (Green and Hellman 1982).

Garnet–Clinopyroxene thermometry (Powell 1985)

Calculation using Tso Morari eclogite TM-15 as a sample (Click to download excel file)

Garnet–Clinopyroxene thermometry (Ravna 2000)

Calculation using Tso Morari eclogite TM-15 as a sample (Click to download excel file)

Garnet–Phengite thermometry (Green and Hellman 1982).

Calculation using Tso Morari eclogite TM-15 as a sample (Click to download excel file)

2. Common barometers

Garnet-omphacite-phengite geobarometer (GOP) (Waters and Martin 1996):

GOP calculates the pressure through the KMASH mode reaction equilibrium (Waters and Martin 1996):

Calculation using Tso Morari eclogite TM-15 as a sample (Click to download excel file)

Empirical phengite Geobarometer (Kamzolkin et al. 2016)

3. Common thermobarometers

Muscovite–paragonite thermobarometry (Roux and Hovis 1996)

Muscovite–paragonite thermobarometry was used to estimate P–T conditions based on K–Na exchange equilibria.

Pressure can be calculated by projecting the temperature and X(ms) in muscovite and paragonite into the diagram on right.

THERMOCALC AVE_PT mode thermobarometry (Powell and Holland 1994)

This function calculates an average P–T for a given mineral assemblage and bulk composition, as well as an associated model error estimate. For instance, calculating the average P–T conditions for phase assemblage: omp, grt, ms, tlc, lws, rt, coe, H2O, using the TC 3.33 version.

1) Open the THERMOCALC 3.33 and you will see the calculation types. For here you need to enter "2" for average pressure-temperature calculations, as below.

2) At this step, you need to enter the phase assemblage that you wan to calculate the average P and T, from the suggested phases. Here we can enter o, g, mu, ta, law, ru, coe, H2O.

3) At this step, the program asks you to enter which calculation type you want to enter. Here we will calculate the average P and T, so we enter "3: average PT"

4) At this step, you need to enter the P and T for calculating the activities of your endmember input. For this input, you need to have a certain background on your sample or the P-T range of the entered phase assemblage. For here, we enter 28 kbar for P and 610C for T.

5) At this step, you can see the calculated activities of entered endmembers. Next, you will be asked to enter whether the system has fluids, expected P-T range, and the fluid is H2O? Entering "1" for "yes" to continue.

6) At this step, you can see the results in the forms of average T and P, and their unccertainties.

7) The following is also part of the calculation results, which are the included equilibrium reactions that constrain the resulting average P and T. you must include these reactions in your result reporting.

8) Plot the result in the excel file as below.(Click to download excel file)