1. Clinopyroxene Group ABSi 2 O 6 Presented by Joyleen Desai Paul Sandlin

2. DiopsideHedenbergite Jadeite Acmite Spodumene

3. Chemical Composition ABSi 2 O 6 MineralAB DiopsideCa 2+ Mg 2+ HedenbergiteCa 2+ Fe 2+ JadeiteNa + Al 3+ AcmiteNa + Fe 3+ SpodumeneLi + Al 3+

4. Structural Cell Parameters Monoclinic Space Group: C2/c Point Group: 2/m Mineralabcρ (calc) Diopside9.7618.9265.2583.26 Hedenbergite9.8278.9945.2613.68 Jadeite9.4188.5625.2193.37 Acmite9.658.795.293.59 Spodumene9.528.325.253.17 Source: http://webmineral.com

5. Structure

6. Thermal Expansion MineralT Range (°C) α (x 10 -5 °C -1 ) Diopside24-10003.97 Hedenbergite24-10003.45 Jadeite24-8003.09 Acmite24-8002.78 Spodumene24-7602.83 Source: Cameron et al. (1973)

7. Compression MineralBulk Modulus (GPa) Shear Modulus (GPa) Diopside118.068.0 Hedenbergite119.063.9 Jadeite129.379.11 Source: http://www.ciw.edu/schutt/depletion/depletion_intro.html

8. Occurrences Clinopyroxenes are found in mafic and ultramafic igneous rocks They are also found in medium- to high- grade metamorphosed mafic rocks

9. Metamorphic Facies Source: Spear (1995)

10. Geothermobarometry Inferring T and P –Thermodynamic modeling and calculations, electron microprobe Assume equilibrium for sub-assemblages Possible to infer PT conditions at various stages in rock history –Can’t find ages, but can construct PT time path

11. Garnet-Cpx Thermobarometer Source: Spear (1995)

12. Diopside-Enstatite Geothermometer Below the solvus, a pyroxene of composition X will unmix to produce two pyroxenes The degree of unmixing is a function of temperature Source: Perkins (1998)

13. Crystal Structure

14. Hydrous Sodic Cpx in the Upper Mantle Source: Smyth et al. (1991)

15. Hydrous Importance Cpx in eclogites as mantle samples X-ray crystal structure refinement and analytical transmission electron microscopy (McCormick, 1996) –OH at dominant 3470 cm -1 band O2 site is underbonded according to Pauling bond strength –M2 site is the most likely candidate for OH, 250-1840 ppm by weight Cpx is stable at P=12 GPa, 30-400 km Cpx is 5-10 times more abundant in mantle rocks