Supplementary Materials

Size: px

Start display at page:

Download "Supplementary Materials"

Norah McCarthy
6 years ago
Views:

1 GSA Data Repository 2115 Behr et al., 21, Dehydration-induced rheological heterogeneity and the deep tremor source in warm subduction zones: Geology, Supplementary Materials Electron Backscatter Diffraction Methods EBSD measurements were collected on a Phillips/FEI XL3 Environmental Scanning Electron Microscope equipped with an Oxford Instruments Aztec EBSD detector. Post-processing of the data was conducted using Matlab-based freeware M-tex (Mainprice et al., 211). Garnet Inclusion Barometry Methods Raman Spectroscopy. Unpolarized Raman spectra of quartz inclusions in garnet were collected using the JY Horiba LabRam HR microprobe in the Department of Geosciences at Virginia Tech. Analyses were collected using a nm excitation (1 mw source laser power) argon laser with a high-resolution mm focal-length spectrometer (1 lines/mm grating). High spatial resolution ( 1 µm) is achieved using a 1x objective (NA =.9) and a confocal aperture set at, with a slit width of 15 µm. The collected spectra were centered on 36 cm 1 and covered a range of cm 1. This allowed for the simultaneous collection of the three main Raman bands of quartz: 6, 26 and 127 cm 1 at ambient conditions. Spectra were collected with a 6 s dwell over three iterations. All Raman lines were fitted using Peakfit v.12 from SYSTAT Software Inc., using the Pearson IV model which allows for asymmetric peak fitting. Electrical and environmental drift is linearly corrected through simultaneous collection of three Ar plasmalines (52.3, and 116. cm 1 ), achieving high spectral resolution of.1 cm 1 after peak fitting. Raman spectra frequency shifts were collected for two representative blueschists and two representative eclogites from Kini (Table S1). The quartz standard position used is /-.52 (2 sigma, after Ashley et al. 216). Inclusion and Encapsulation Pressure Determination. The frequency shift of the 6 cm 1 quartz band ( 6) was converted to inclusion pressure (Pincl) using the calibration of Ashley et al. (21), which is derived from the Schmidt and Ziemann (2) dataset. Neither the 26 shift or peak separation distances (e.g., Enami et al., 27) were considered for inclusion pressure estimation due to the low intensity of the 26 and 127 cm 1 lines and because of interference with the low-intensity garnet bands ( 2522 cm 1 ; Enami, 212). Additional issues with using the lower-frequency quartz bands for pressure determination are summarized 1

2 by Ashley et al. (215). Encapsulation pressures were determined using the computational approach of Ashley et al. (215). Here we implement the 1D elastic model of Guiraud and Powell (26) and calculate molar volumes of quartz and almandine garnet in the program PerpleX (Connolly, 29), which applies the P-V-T modified Tait equation of state of Holland and Powell (211). An almandine shear modulus of 921 kbar is taken from Wang and Ji (21). Calculated inclusion pressures and encapsulation pressures for the four samples are listed in Table S1 and shown in Figure 3 of the main text. Uncertainties are assuming an uncertainty in waveshift of ±.1 and are determined through squaring the quadratures of the regression. All modeling assumes pure almandine host and pure quartz inclusions. Table S1: Inclusion barometry data 2

$in blueschist matrix preserving the Ss foliation. White arrows point to shear fractures concentrated in the eclogite lens in the fold hinge.$ [B] Limb of open upright fold with axial planar crenulation cleavage (St) cutting the main Ss foliation. [C] Undeformed lawsonite pseudomorphs stamped across the Ss foliation.

[B] Limb of open upright fold with axial planar crenulation cleavage (St) cutting the main Ss foliation. [C] Undeformed lawsonite pseudomorphs stamped across the Ss foliation.

3 A B Ss St Ss S$_s$ C D N pi g irdl e Ss Poles to foliation (Ss) Fold axial planes Mineral lineations (Ls) Crenulation Cleavages (St) pi-point Figure S1: [A] Folded and brittlely deformed eclogite pod in blueschist matrix preserving the Ss foliation. White arrows point to shear fractures concentrated in the eclogite lens in the fold hinge. [B] Limb of open upright fold with axial planar crenulation cleavage (St) cutting the main Ss foliation. [C] Undeformed lawsonite pseudomorphs stamped across the Ss foliation. [D] Stereonet of structural data measured at Kini. A great-circle fit to primary foliation (Ss ) yields a fold axis orientation that is parallel to mineral lineations (Ls ). Crenulation cleavages (St ) are axial planar to more upright folds interpreted to represent early exhumation under blueschist facies conditions. E 1

4 2µm Δν6 = 7.53 cm-1 Herkimer quartz KCS53 Ar-plasmaline wavenumber (cm-1) Figure S2: [A] Example of measured quartz inclusions within a garnet crystal. [B] Raman spectra showing the spectral shift measured for blueschist sample KCS53 compared to Herkimer quartz. E 2

5 16 eclogite epidote-blueschist Phonolite A wt. % Na 2 O + K 2 O Foidite (a) Tephrite Basanite 5 Tephriphonolite Phono- Tephrite (1) Basalt Trachyandesite (2) Basaltic andesite Picrobasalt Andesite Trachyte Trachydacite wt. % SiO 2 Dacite Rhyolite WR Ocean Ridge Basalts (Gale et al., 213) (n=2261) (b) B 12 2 wt. % CaO wt. % Al 2 O eclogite (KCS3 & KCS55B) epidote-blueschist (KCS53 & KCS5B1) Whole-rock Ocean Ridge Basalts (Gale et al., 213) (n=2261) wt. % SiO 2 5 wt. % Na 2 O wt. % FeO 15 1 wt. % TiO wt. % MgO wt. % MgO Figure S3: [A] Chemical classification of volcanic rocks on Syros. Field 1 is trachy-basalt, Field 2 = basaltic trachy-andesite. [B] Major element bulk chemistry data from blueschists and eclogites on Syros. E 3

6 .6.5. Mg (apfu) Si (apfu) omphacite-rich lens in blueschist massive eclogite brittle vein in eclogite blueschist Figure S: Mg vs. Si concentrations from phengites grown in different microstructural contexts and metamorphic facies. Different Mg values on the y-axis likely reflect small differences in protolith bulk composition between samples. The overlap in Si composition among micas from a range of samples indicates that all of them formed at the same pressure conditions, including those grown in dilational fractures (green circles), which yield some of the highest Si atoms per formula unit (spfu). (Includes data from an equivalent fabric in metamafic rocks east of Kini at Agios Dimitrios.) E

7 References Cited in Supplementary Materials Ashley, K.T., Steele-MacInnis, M., Bodnar, R.J. and Darling, R.S., 216. Quartz-in-garnet inclusion barometry under fire: Reducing uncertainty from model estimates. Geology, (9), pp Ashley, K.T., Caddick, M.J., Steele MacInnis, M.J., Bodnar, R.J. and Dragovic, B., 21. Geothermobarometric history of subduction recorded by quartz inclusions in garnet. Geochemistry, Geophysics, Geosystems, 15(2), pp Connolly, J.A.D., 29. The geodynamic equation of state: what and how. Geochemistry, Geophysics, Geosystems, 1(1). Enami, M., Nishiyama, T. and Mouri, T., 27. Laser Raman microspectrometry of metamorphic quartz: A simple method for comparison of metamorphic pressures. American Mineralogist, 92(-9), pp Enami, M., 212. Influence of garnet hosts on the Raman spectra of quartz inclusions. Journal of Mineralogical and Petrological Sciences, 17(), pp Gale, A., Dalton, C.A., Langmuir, C.H., Su, Y. and Schilling, J.G., 213. The mean composition of ocean ridge basalts. Geochemistry, Geophysics, Geosystems, 1(3), pp Guiraud, M. and Powell, R., 26. P V T relationships and mineral equilibria in inclusions in minerals. Earth and Planetary Science Letters, 2(3-), pp Holland, T.J.B. and Powell, R., 211. An improved and extended internally consistent thermodynamic dataset for phases of petrological interest, involving a new equation of state for solids. Journal of Metamorphic Geology, 29(3), pp Mainprice, D., Hielscher, R. and Schaeben, H., 211. Calculating anisotropic physical properties from texture data using the MTEX open-source package. Geological Society, London, Special Publications, 36(1), pp Schmidt, C. and Ziemann, M.A., 2. In-situ Raman spectroscopy of quartz: A pressure sensor for hydrothermal diamond-anvil cell experiments at elevated temperatures. American Mineralogist, 5(11-12), pp Wang, Z. and Ji, S., 21. Elasticity of six polycrystalline silicate garnets at pressure up to 3. GPa. American Mineralogist, 6(1), pp

SUPPLEMENTARY MATERIALS FOR: Pressures of skarn mineralization at Casting Copper, Nevada, based on. apatite inclusions in garnet

GSA Data Repository 2017314 doi:10.1130/g39177.1 1 2 3 4 5 6 7 8 9 10 11 12 SUPPLEMENTARY MATERIALS FOR: Pressures of skarn mineralization at Casting Copper, Nevada, based on apatite inclusions in garnet