Microstructures associated with deep crustal subduction deformation in the Cycladic Blueschist belt, Syros, Greece

Transcription

1 Microstructures associated with deep crustal subduction deformation in the Cycladic Blueschist belt, Syros, Greece Gabriel J. Nelson Senior Integrative Exercise March 10, 2004 Submitted in partial fulfillment of the requirements for a Bachelor of Arts degree from Carleton College, Northfield, Minnesota

2 Table of Contents Abstract Introduction Tectonic Setting Geology of Syros Microstructures and Mineralogy of Blueschists Bimodal size distribution of glaucophane Mineral inclusions in garnet Garnet pressure shadows Discussion and Conclusions Acknowledgements References Cites Appendix Appendix

3 Microstructures associated with deep crustal subduction deformation in the Cycladic Blueschist belt, Syros, Greece Gabriel J. Nelson Senior Integrative Exercise March 2004 Cameron Davidson, advisor Abstract Pressure shadows and inclusion trails in garnet from Blueschist facies rocks on the Island of Syros, Greece reflect deformation events at blueschist facies conditions during Eurasia-Africa collision and subduction. Approximately 25% of all pressure shadows are asymmetric, and 44% of all thin sections contain garnet inclusions at high and low angles to foliation. To produce these microfabrics the deformation had a progressively changing (non-coaxial) maximum direction of compression during metamorphism. Keywords: Syros, blueschist, deformation, garnet, pressure shadows, inclusions

4 2 Introduction The island of Syros is in the Cycladic Blueschist belt of the Eastern Mediterranean (Figure 1). It is likely that the rocks of the Cycladic Blueschist have been the object of geologic study since early Phoenician influence in the region (Schumacher and Helffrich, 2001). These metamorphic rocks formed during subduction at deep crustal depths of 50 to 60 km and temperatures of Celsius (Gealey, 1988; Lister et al., 1984; Rosenbaum et al., 2002), and the exhumation of these rocks has been attributed to syn-orogenic and post-orogenic collapse processes (Jolivet and Faccenna, 2000; Lister and Raouzaios, 1996). Exhumation models typically employ low angle detachment faults producing non-coaxial shearing (Avigad et al., 1997; Lister and Raouzaios, 1996). These models typically use observations gathered from fabrics formed during deformation at shallow crustal levels (Rosenbaum et al., 2002). Deformation at deep crustal levels has on the other hand been interpreted as coaxial (Rosenbaum et al., 2002). Studies of deep crustal deformation have been done in part by the observation of high-pressure and lowtemperature fabrics preserved in blueschist facies rocks. These rocks typically have the assemblage garnet + omphacite + glaucophane + quartz (Rosenbaum et al., 2002). Rosenbuam et al. (2001) concluded that the blueschist facies rocks of Syros record multiple deformation events based on mineral inclusion trails in garnet and the geometry of pressure shadows. Over the past four years the Keck consortium has sent three teams of undergraduates to addresses geologic problems on the island of Syros. This paper is the result of the 2003 Keck project to Syros lead by Jack Cheney and Tekla Harms (Amherst College), John Brady (Smith College), and John Schumacher (Bristol University). This

5 Bulgaria Italy Albania Greece Turkey H H H H H H H H H H H H H H H H African Plate Syros Motion 36 inferred 36 extension: km OMC - M.Weinelt Hellenic Trench H H H H H H H Pliny/Strabo Trench Ultramafic rocks Granitic rocks Blueschist-facies carbonates Cycladic blueschist belt after Blake et al. (1984) Euboia 38 Andros 38 Kea Mykonos Kithnos Syros Paros Naxos Serifos Sifnos Amorgos Milos Tinos Ios C yc lades Ikaria km OMC - M.Weinelt GMT Jan 11 16: Figure 1. Geographic and Geologic of the Cyclades and Syros, from J.C. Schumacher (1999) 3

6 4 study is one project from the 2003 geology project to Syros with the support of the KECK consortium. This paper takes a fresh look at the fabrics recorded by the blueschist facies rocks of Syros. Microfabrics of glaucophane crystals suggest deformation occurred in isolated bands on the scale of a thin section. Garnet inclusion trails and pressure shadows around garnets suggest that deep crustal deformation was non-coaxial. The finding of non-coaxial deformation agrees with conclusions of shallow crustal deformation during the same exhumation event (Jolivet and Faccenna, 2000; Lister and Raouzaios, 1996), but contradict the conclusions of Rosenbaum et al. (2002) about deep crustal deformation in these rocks. Tectonic Setting The tectonic story of the lithologic package of the Cycladic Blueschist belt begins in the Triassic and Jurassic. The tensional forces responsible for the fragmenting Pangaea created rifting between what are today the African and Eurasian plates (Gealey, 1988). The rifting formed the Hellenides Platform and the Pindos-Cyclades ocean basin between the two plates (Papanikolaou, 1987). The sedimentary protoliths of the marbles, pelitic schists, and metabasites that compose the Cycladic Blueschist belt formed in the Pindos- Cycladic ocean basins. The extensional forces became compressional in the Late Cretaceous when the relative motions of the Africa and Eurasia plates changed (Jolivet and Faccenna, 2000). The ocean basin closed, ophiolites obducted, and subduction began northward along the Pindos Zone (Gealey, 1988). The collision and subduction date of this tectonic model fit with zircon ages of 78Ma, interpreted as the time of subduction metamorphism (Brocker and Enders, 2001). The magnitude of the plate collision slowed

7 5 the absolute motion of the African plate (Jolivet and Faccenna, 2000). The slowing of the African plate caused trench-rollback to the Hellenic Trench, changing plate boundaries between the African and Cycladic microplate (Gealey, 1988). The rollback lead to the back arch extension in the Aegean around 25-11Ma (Lister et al., 1984). Normal and some listeric faults were active in the region since at least the late Miocene (Papanikolaou, 1987) due to the positioning in the back arc of two trench systems (Avigad et al., 1997) (Figure 1). The extensional processes allowed for the exposure of the high-pressure metamorphic rocks formed during subduction before trench rollback. This sequence of events formed, subducted, and later exposed the Cycladic Blueschist belt rocks (Gealey, 1988; Jolivet and Faccenna, 2000). Geology of Syros The name Syros is derived from two Phoenician words meaning happy and rock (Schumacher and Helffrich, 2001). After Phoenician naming practices the island of Syros does not appear in significant geologic context until the late nineteenth century. In 1845 Hausmann first described glaucophane from the island of Syros. After Hausmann there was another break in the geologic consideration of this Aegean isle. Extensive studies of the geology of Syros did not appear in English language geologic papers until John Ridely s work in the late Syros is composed of alternating packages of shallow northeasterly dipping pelitic schists, marbles, and metabasites (Figure 2). Deformational features notable on a map scale include tectonic duplication represented by the alternating packages of rock types (Dixon, 1987), isoclinal folding on the kilometer scale (Papanikolaou, 1987), and several

8 Marbles Sample Locations with location names Total Samples San Michael Kastri Paradice Schists Metabasites 14 Windmill Hill Serpentinite Vari Gneiss North Ermopoli Kini Airport Charrasonis Perdiki N 0 3km N 0 3km Katerghaki Figure 2. Syros and its basic lithology, modified from Dixon and Ridley (1987). Figure 3. Names, locations, and thin sections from field sites on Syros. 6

9 7 fault zones cutting across the island (Figure 2). Faults are identified by zones of serpetintization and brecciation. The metamorphic rocks of Syros contain greenschist, eclogite, and blueschist. The eclogites, and blueschist facies rocks developed during high-pressure subduction metamorphism at Ma (Brocker and Enders, 2001; Lister and Raouzaios, 1996; Ridley and Dixon, 1984). The temperatures and pressures were approximately 14kbar and C (Dixon, 1976). During this metamorphism the blueschist developed foliation and lineation (Rosenbaum et al., 2002). These structures are represented by the preferential orientation of micas into the near horizontal foliation and preferred alignment of glaucophane into the lineation. The greenschist is a retrograding overprint of eclogite/blueschist and is more pervasive in the south of the island. It is identifiable by the chlorite overgrowth of garnet and glaucophane crystals. Greenschist metamorphism occurred at similar temperatures to the blueschist/eclogite metamorphism but at much shallower depths (Schiestedt and Matthews, 1987). The overprinting happened Ma (Lister et al., 1984; Schiestedt and Matthews, 1987). The preservation of some blueschist during exhumation required maintaining high subduction type pressures while lifting the blueschists to surface conditions without passing the low pressure phase of greenschist overprinting (Wijbrans et al., 1993). Wijbrans et al. (1993) proposed thrust faulting as a result of repeated delamination of lighter supercrustal rocks of the subducting plate. The story of metamorphism and subsequent exhumation is not a complete one. Continued work in this area is identifying further constraints on pressures, temperatures, timing, deformation, and chemical processes in the framework of subduction and exhumation processes.

10 8 Microstructures and Mineralogy of Blueschists Blueschist facies rocks on Syros have the mineral assemblage garnet + glaucophane + omphacite + epidote + white mica + quartz + sphene (Rosenbaum et al., 2002). Samples of blueschist were collected from around the island (Figure 3). Approximately eighty geochemical spot analyses were done on four thin sections of blueschist with a Scanning Electron Microscope (SEM) that has an Energy Dispersive X- ray Spectrometry (EDS) (Appendix 1). Results shows that garnet composition is 60%- 65% almandine and 16%-18% grossular with lesser components of pyrope and spessertine (Figure 4). Transects across garnet crystals show a reduction in magnesium corresponding to an increase in manganese from rim to core (Figure 5). These results are consistent with findings of Ridley and Dixon (1984). All glaucophane crystals have the chemical composition of true glaucophanes (Figure 6), and show a reduction in ferrous iron from rim to core (Figure 7). Variation in iron content from rim to core of glaucophane crystals has been noted by Ridley and Dixon (1984) and Schiestedt et al. (1987). The blueschists of Syros have a near horizontal foliation defined by the preferred orientation of mica crystals and a lineation within the plane of this foliation defined predominately by glaucophane crystals (Dixon, 1987). Garnet crystals have trails of mineral inclusions composed of white mica, quartz, and glaucophane. Pressure shadows around garnet crystals are composed of quartz, white mica, glaucophane, and chlorite.

11 9 50% Grossular + Spessartine (CaO+MnO) 100% Almandine (FeO) 50% Pyrope (MgO) Figure 4. Garnet chemical composition plot. Note that the Grossular + Spessartine and the Pyrope verticies are at 50% composition Rim XMg XMn Core Figure 5. Transects from rim to core of three garnets. Garnets show reduction in Mg and an increase in Mn toward the core. Average transect is 0.9 mm.

12 10 1 Fe +2 /(Fe +2 +Mg) 0.5 Ferro-Glaucophane Riebeckite Glaucophane Magnesio-Riebeckite Fe +3 /(Fe +3 +AL) Figure 6. Sodic amphibole composition plot. All glaucophane crystals analyzed plot as true glaucophane Ferrous Iron Rim Core Figure 7. Transects from rim to core of seven gaucophane crystals. Glaucophane shows a reduction in ferrous iron toward the core.

13 11 Bimodal Size Distribution of Glaucophane The size of glaucophane crystals in thin section remains within approximately 30% of an average glaucophane crystal size. There is the exception of a small population of thin sections (13 of 48) that show glaucophanes where crystal size is not uniform, but instead has a bimodal size distribution. In thin sections with bimodal size distribution, larger glaucophane crystals form bands parallel with foliation corresponding to areas of the highest concentration of garnet (Figure 8). Ten thin sections with bimodal size distribution of glaucophane are from one field location (Figure 9). Geochemical analyses from larger and smaller glaucophanes in thin sections with bimodal size distribution show no conclusive chemical difference between sizes of crystals (Figure 10). Mineral Inclusions in Garnet Roughly 97% of garnets observed in the thin sections contain mineral inclusions. The inclusions mainly consist of quartz, white mica, and glaucophane crystals. During garnet growth minerals are enveloped, which preserves crystal orientation (Davis and Reynolds, 1996). Consequently, textures present in the rock before or during garnet growth can be overgrown and preserved in the garnet. In the thin sections, garnet inclusions trails are straight (Figure 11) or curved (Figure 12, 13). Additionally, the trails are at high or low angles to the shallowly dipping foliation. Within individual thin sections, garnet inclusion trails exist that fit the four combinations of curved/straight and high/low angle types of trails. Trails that are at an angle of greater than 45 to foliation are considered at a high-angle to foliation (Figure 11), trails less than 45 to foliation are at a low-angle to foliation. Geographically, nine

14 12 area of larger glaucophanes Garnet Garnet Garnet Garnet Garnet area of smaller glaucophanes 1 mm Figure 8. Pictomicrograph photo of bimodal size distribution of glaucophane in association with garnets. Sample number North Ermopoli 1 Airport 2 Charrasonis Figure 9. Total thin-sections with bimodal size distribution of glaucophanes from locations across Syros. Locations are arranged from north to south on the island. Locations with no observed bimodal distribution were omitted.

15 Fe 2+ /(Fe 2+ + Mg) Fe +3 / (Fe +3 + Al) Large Glaucophanes Small Glaucophanes Figure 10. Composition plot of large and small glaucophane crystals on the glaucophane quadrant of a sodic amphibole plot. Variation in crystal size shows no correlation with respect to chemical composition. Figure 11. Pictomicrograph photo of straight garnet inclusions at high angle to foliation. Inclusion trend is marked with white arrow. Foliation is horizontal, sample number 16123

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17 15 out of ten field locations have inclusion trails at high and low angles to foliation, and all field locations have curved and straight inclusion trails. Forty-four percent of thin sections contain garnet inclusions at both high and low angles to foliation. High angle garnet inclusion trails are present in 6% more thin sections than low angle inclusion trails. (Figure 14). Garnet Pressure Shadows Sampling on Syros was restricted to blueschist with garnets likely to exhibit pressure shadows. Samples came from outcrops with deformation textures such as elongate boudens or garnet pressure shadows observable by hand-lens. Each set of garnet pressure shadows from oriented thin section was recorded (Appendix 2) as a sigma, delta, symmetric, or undetermined (Davis and Reynolds, 1996). The symmetry determination is made by imagining a line parallel to foliation through the center of the porphyroblast, which in this study is the center of garnet, and evaluating the position of the pressure shadows in relationship to the line (Figure 15) (Passchier and Simpson, 1986). Symmetric pressure shadows are centered on a line through the center of the porphyroblastic system (Figure 16). Sigma and delta porphyroblasts are both asymmetric (Figure 15, 16). Garnet pressure shadows with undetermined pressure shadows are of two types. One type lacks noticeable pressure shadows and the other has highly distorted pressure shadows. Highly distorted pressure shadows generally occur in close proximity to other garnets. Pressure shadows bend and distort around the large crystals, so that the tips do not represent deformation around one porphyroblast, but instead indicate significantly more complicated deformation associated with interaction of several porphyroblasts.

18 San Michael Kastri Paradice Windmill Hill North Ermopoli Kini Airport Charrasonis Perdiki Katerghaki Inclusions at low angle to Foliation Inclusions at High Angle to Foliation Figure 14. Total thin-sections, by location, with garnets containing inclusion trails at a high or low angle to the foliation. Locations are arranged from north to south on the island.

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20 18 Of the approximately 1200 garnet pressure shadows observed, 25% are asymmetrical and 40% are symmetrical (Figure 17). The asymmetric pressure shadows are less abundant than symmetric ones but constitute a significant proportion of total garnet pressure shadows. Asymmetric pressure shadows are also a substantial population of the pressure shadows observed from each field location (Figure 18). Discussion and Conclusions Lister and Raouzaios (1996) suggest that metamorphic mineral growth in the Cycladic Blueschist belt precedes tectonically driven deformational events. It would be possible, but unlikely, that bimodal size distribution is the result of one size of glaucophane crystals growing during an early metamorphic growth and the other size crystals forming in a later metamorphic growth. Preliminary tests show that the crystals of larger and smaller glaucophanes do not have a distinct chemistry (Figure 10). Ridley and Dixon (1984) concluded that chemical equilibrium changed progressively during the formation of high-pressure minerals. Additionally, The chemical zoning noted in transects across of crystals (Figure 5 and 7) within these blueschist facies rocks has been interpreted as prograde metamorphic mineral growth (Schiestedt et al., 1987), and a record of fluid-enhanced chemical exchange (Dixon, 1987). The progressive change in chemical equlibrium, and chemical zoning as a result of different crystal growth events would indicate that crystals forming at different times would have different chemistries reflecting the progressive change in chemical equilibrium of the rock. This is seemingly not true for the different sizes of glaucophanes in thin sections with bimodal size

21 Asymmetrical Symmetrical Undetermined Figure 17. Total of each type of porphyroblastic system observed in thin section San Michael Asymmetrical Symmetrical Undetermined Sample Locations North Ermopoli Kini Airport Charrasonis N 0 3km Katerghaki Figure 18. Syros with thin section analysis by sample location. Each graph shows relative proportions of garnet porphyroblastic systems. Only locations with more than one hundred porphyroblastic systems recorded are shown.

22 20 distribution, so the size variation is likely due to something other than glaucophanes from two blueschist metamorphic growth events. The variation in crystal size may instead be the result of the restrictive presence of fluids. If fluids favorable to the growth of glaucophane were concentrated in zones defined by garnet populations, the result would be larger glaucophanes in these zones. Fluids could also be concentrated as a result of movement to shielded areas and away from deformational shear bands. The pressure shadows around garnet porphyroblasts are a result of mineral recrystalization of reaction-softened material from the matrix in areas shielded from deformation, (for example quartz and white mica) (Passchier and Simpson, 1986). These shielded locations may also concentrate fluids favorable to glaucophane growth. The shield locations could also simply preserve larger glaucophane crystals. Ridley and Dixon (1984) found that larger glaucophanes from one growth event in one field location are broken into smaller polygonal crystals in other field locations. This breaking of glaucophane into smaller crystals may also be evident in bimodal glaucophane bands on the scale of a single thin section. Rosenbaum et al. (2002) concluded that there are three deformational events at blueschist facies conditions that are preserved in blueschist fabrics. The fabric from the earliest deformational event is preserved as inclusion trails in garnet porphyroblasts (Rosenbaum et al., 2002). The next deformation event is evidenced by the shallowly dipping foliation and symmetric features such as pressure shadows (Rosenbaum et al., 2002). Rosenbaum et al. (2002) found that garnet inclusions from the earlier deformational event are typically orthogonal to the near horizontal foliation that resulted in the later deformational event. They concluded that the porphyroblast inclusions are a

23 21 result of coaxial compression that was perpendicular to the later coaxial compression producing foliation and symmetric pressure shadows. Therefore the first deformation was during the African Eurasian continental collision resulting in deep crustal thickening. The later deformation was separate from the earlier one and signifies that deep crustal thinning in the horizontal direction was occurring during orogenic collapse (Rosenbaum et al., 2002). The third fabric and deformational event produced isolated non-coaxial shear bands (Rosenbaum et al., 2002). Shear bands, as noted by Rosenbaum et al. (2002), were not observed in this study. Sampling methods could have excluded blueschist with deformational fabrics obscuring clear pressure shadows from an earlier deformation, and thus representative shear bands of late blueschist deformation. It is also possible that the isolated shear bands noted by Rosenbaum et al. (2002) produced the bands of larger and smaller glaucophanes crystals (Figure 14). Microstructures described by Rosenbaum et al. (2002) as indicators of the two earliest blueschist metamorphic events were observed for this study, but the results and interpretations of this study differ from those of Rosenbaum et al. (2002). The inclusion trails in garnets were seen at high angle (greater than 45 ) (Figure 11) to foliation, including trails orthogonal to foliation. Inclusion trails were also often seen at low angles (less than 45 ) to foliation (Figure 12). The variation in inclusion angle is likely to be the cause of garnet rotation after overgrowth of the earlier blueschist fabric. In addition, the inclusion trails preserved in garnets are curved, (Figure 13) probably due to rotation of the garnet crystal during growth. Asymmetric pressure shadows are 10%-40% of the pressure shadows from each field location around the island (Figure 18). The asymmetric

24 22 pressure shadows (Figure 16) are likely the result of a non-coaxial deformation (Passchier and Simpson, 1986). The microfabrics of garnet inclusion trails and porphyroblastic systems indicated that blueschist deformational events were non-coaxial, similar to other studies on the Aegean island of Sifnos (Lister and Raouzaios, 1996). The implication is that maximum compressional directions change progressively during high-pressure subduction deformation, and that orogenic collapse was occurring during continental collision. Acknowledgments Thanks to all of the other undergraduate students on the 2003 Keck research trip to Syros. There are no others with whom I would rather toss back a Mythos and discuss beautiful blue rocks. I would like to thank John Brady, John Schumacher, Tekla Harms, and Jack Cheney for dedicating themselves to provide me and other students the amazing experience of Syros geology. Additional thanks to Jack Cheney for his never ending passion for discussion about rocks, to Tekla Harms for provide direction to my field work, and John Brady for the assistance and use of the Smith College SEM with EDS as well as feeding and housing me for my stay at Smith College. I would be remised to not thank Cameron Davidson for his help in the field, at the microscope, with drafts, papers, and ideas. This project would not have been possible without these people or the funding of the Keck consortium, the Charles W. Potts Endowment fund, and Thomas P. Cook Educational Trust. Without these sources of financial support I would not have been able to go to Greece, go to Amherst and Smith Colleges, ship rock samples home, have thin sections made, or complete any part of this project.

25 23 References Cited Avigad, D., Garfunkel, Z., Jolivet, L., and Azañón, J. M., 1997, Back arc extension and denudation of Mediterranean Eclogites: Tectonics, v. 16, no. 6, p Brocker, M., and Enders, M., 2001, Unusual bulk-rock composition in eclogite-facies rocks from Syros and Tinos (Cyclades, Greece): implications for U-Pb zircon geochronology: Chemical Geology, v. 175, p Davis, G. H., and Reynolds, S. J., 1996, Structural Geology: New York, John Wiley & Sons, Inc. Dixon, J. E., 1976, Glaucophane schists of Syros, Greece (abstract): Geologic Society Bulletin of France, v. 7, p Dixon, J. E. a. R., J., 1987, Syros (field trip excursion), in Helgeson, H. C., ed., Chemical transport in metasomatic processes: Nato Advanced Study Institutes: Dordrecht, D. Reidel Publishing Company, p. pp Gealey, W. K., 1988, Plate tectonic evolution of the Mediterranean-Middle East region: Tectonophysics, v. 155, p Jolivet, L., and Faccenna, C., 2000, Mediterranean extension and the Africa-Eurasia Collision: Tectonics, v. 19, no. 6, p Lister, G. S., Banga, G., and Feenstra, A., 1984, Metamorphic core complexes of Cordilleran type in the Cyclades, Aegean Sea, Greece: Geology, v. 12, p Lister, G. S., and Raouzaios, A., 1996, The tectonic significance of a porphyroblastic blueschist facies overprint during Alpine orogenesis: Sifnos, Aegean Sea, Greece: Journal of Structural Geology, v. 18, no. 12, p Papanikolaou, D. J., 1987, Tectonic Evolution of the Cycladic Blueschist Belt (Aegean Sea, Greece), in Helgeson, H. C., ed., Chemical Transport in Metasomatic Processes, D. Reidel Publishing Company, p Passchier, C. W., and Simpson, C., 1986, Porphyroclast systems as kinematic indicators: Journal of Structural Geology, v. 8, no. 8, p Ridley, J., and Dixon, J. E., 1984, Reaction pathways during the progressive deformation of a blueschist metabasite: the role of chemical disequilibrium and restricted range equilibrium: Journal of Metamorphic Geology, v. 2, p

26 24 Rosenbaum, G., Avigad, D., and Mario, S.-G., 2002, Coaxial flattening at deep levels of orogenic belts: evidence from blueschist and eclogites on Syros and Sifnos (Cyclades, Greece): Journal of Structural Geology, v. 24, no. 9, p Schiestedt, M., Altherr, R., and Matthews, A., 1987, Evolution of the Cycladic Crystalline Complex: Petrology, Isotope Geochemistry and Geochronolgy, in Helgeson, H. C., ed., Chemical Transport in Metasomatic Processes, D. Reidel Publishing Company, p Schiestedt, M., and Matthews, A., 1987, Transformation of blueschist to greenschist facies rocks as a consequence of fluid infiltration, Sifnos (Cycladed), Greece: Contributions to Mineralogy and Petrology, v. 97, p Schumacher, J. C., and Helffrich, G., 2001, Bristol Mapping Course: Syros and the Cyclades. Wijbrans, J. R., Wees, J., Stephenson, R., and Cloetingh, S. A. P. L., 1993, Pressuretemperature-time evolution of the high-pressure metamorphic complex of Sifnos, Greece: Geology, v. 21, p

27 Appendix 1. Table 1 SEM analyses of garnet crystals Garnet Data Sample # analysis # a 8b 8c 8d 1a 1b 1c 1d 2a 2b RIM CORE RIM CORE RIM Wt% oxide MgO Al2O SiO CaO MnO FeO total Stoichiometry [Cations based on 12 O] Mg Al Si Ca Mn Fe Pyrope Almandine Spessartine Grossular Mg/Fe Garnet Data Sample # analysis # 2c 2d 2e 2f a 14b 14c 14d 15 16a 16b CORE Wt% oxide MgO Al2O SiO CaO MnO FeO total Stoichiometry [Cations based on 12 O] Mg Al Si Ca Mn Fe Pyrope Almandine Spessartine Grossular Mg/Fe Note: Arrows from rim to core indicates mineral analyses along indivigual crystals transects 25

28 Appendix 1. Table 2 SEM analyses of glaucophane crystals Glaucophane Data Sample # analysis # Wt% oxide SiO2 Al2O3 FeO MgO CaO Na2O Total RIM CORE CORE RIM Stoichiometry [Cations Bases on 23 Oxygens] All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric Si Al Fe Fe Mg Ca Na Stoichiometry [Cations based Si + Al + Fe(total) + Mg = 13] Si Al Fe+3 Fe+2 Mg Ca Na Fe3/Fe3+Al Fe2/Fe2+Mg Glaucophane Data Sample # analysis # Wt% oxide SiO2 Al2O3 FeO MgO CaO Na2O Total a 3b RIM CORE CORE c 3d 3e 4 RIM Stoichiometry [Cations Bases on 23 Oxygens] All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric Si Al Fe Fe Mg Ca Na Stoichiometry [Cations based Si + Al + Fe(total) + Mg = 13] Si Al Fe+3 Fe+2 Mg Ca Na Fe3/Fe3+Al Fe2/Fe2+Mg Note: Arrows from rim to core indicates mineral analyses along indivigual crystals transects 26

29 Appendix 1. Table 3 SEM analyses of glaucophane crystals Glaucophane Data Sample # analysis # Wt% oxide SiO2 Al2O3 FeO MgO CaO Na2O Total RIM CORE a Stoichiometry [Cations Bases on 23 Oxygens] All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric Si Al Fe Fe Mg Ca Na Stoichiometry [Cations based Si + Al + Fe(total) + Mg = 13] Si Al Fe+3 Fe+2 Mg Ca Na Fe3/Fe3+Al Fe2/Fe2+Mg Glaucophane Data Sample # analysis # b 10c 10d 10e f Wt% oxide SiO2 Al2O3 FeO MgO CaO Na2O Total Stoichiometry [Cations Bases on 23 Oxygens] All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric Si Al Fe Fe Mg Ca Na Stoichiometry [Cations based Si + Al + Fe(total) + Mg = 13] Si Al Fe+3 Fe+2 Mg Ca Na Fe3/Fe3+Al Fe2/Fe2+Mg Note: Arrows from rim to core indicates mineral analyses along indivigual crystals transects

30 Appendix 1. Table 4 SEM analyses of glaucophane crystals Glaucophane Data Sample # analysis # Wt% oxide SiO2 Al2O3 FeO MgO CaO Na2O Total a 9b RIM c 10a 10b 10c CORE Stoichiometry [Cations Bases on 23 Oxygens] All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric Si Al Fe Fe Mg Ca Na Stoichiometry [Cations based Si + Al + Fe(total) + Mg = 13] Si Al Fe+3 Fe+2 Mg Ca Na Fe3/Fe3+Al Fe2/Fe2+Mg Glaucophane Data Sample # analysis # Wt% oxide SiO2 Al2O3 FeO MgO CaO Na2O Total d 11 12a 12b CORE c 12d RIM Stoichiometry [Cations Bases on 23 Oxygens] All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric All Ferrous All Ferric Si Al Fe Fe Mg Ca Na Stoichiometry [Cations based Si + Al + Fe(total) + Mg = 13] Si Al Fe+3 Fe+2 Mg Ca Na Fe3/Fe3+Al Fe2/Fe2+Mg Note: Arrows from rim to core indicates mineral analyses along indivigual crystals transects 28

31 29 Appendix 2. Prophyroblastic Systems Page in Field Date Collected Notes Location Thin Section Sigma Delta symetrical undetermined 6/9/03 26 Katergaki /9/03 26 Katergaki /10/03 31 Katergaki /10/03 32 Katergaki * /12/03 38 North Ermopoli /12/03 39 North Ermopoli /23/03 63 North Ermopoli /12/03 39 North Ermopoli 26122a /12/03 39 North Ermopoli * /12/03 39 North Ermopoli /12/03 39 North Ermopoli * /23/03 63 North Ermopoli /13/03 42 Airport /13/03 41 Airport /13/03 44 Airport /13/03 43 Airport /14/03 48 Charrasonis Hill * /14/03 45 Charrasonis Hill /14/03 47 Charrasonis Hill /14/03 47 Charrasonis Hill /14/03 48 Charrasonis Hill /14/03 48 Charrasonis Hill /17/03 50 Perdiki /17/03 51 Perdiki /19/03 52 Paradice /19/03 53 Paradice /19/03 52 Paradice /20/03 55 San Michael /20/03 55 San Michael /20/03 55 San Michael /21/03 57 Kini /21/03 57 Kini /21/03 56 Kini /21/03 56 Kini /22/03 58 Kastri /22/03 59 Kastri /22/03 59 Kastri /23/03 62 Windmill Hill /23/03 62 Windmill Hill totals Note: * Thin sections analyzed on Smith College's SEM with EDS