TECTONOMETAMORPHIC EVOLUTION OF CYCLADIC SUBDUCTION ZONE ROCKS: THE SYROS BLUESCHIST-ECLOGITE TERRANE III

TECTONOMETAMORPHIC EVOLUTION OF CYCLADIC SUBDUCTION ZONEROCKS: THE SYROS BLUESCHIST-ECLOGITE TERRANE III

FACULTY

John B. Brady, Smith CollegeJohn T. Cheney, Director, Amherst CollegeTekla A. Harms, Amherst CollegeJohn C. Schumacher, Bristol University, UK

STUDENTS

Scott J. Dougan, Amherst CollegeJessica M. Driscoll, Amherst CollegeNjoki W. Gitahi, Amherst CollegeElizabeth A. Holley, Pomona CollegeStacey K. Kepler, Amherst CollegeLaura Frye-Levine, Smith CollegeEli D. Lazarus, Williams CollegeGabriel J. Nelson Carleton CollegeEmily C. Pope, Colorado CollegeEric Purcell, Beloit College

VISITORS in Greece

Cameron Davidson, Carleton CollegeEmily Dubinsky, Amherst CollegeAndreas Magganas, University of AthensFrank Spear, Rensselaer Polytechnic Institute

EVOLUTION OF CYCLADIC SUBDUCTION ZONEROCKS: SYROS BLUESCHIST-ECLOGITE TERRANE III

JOHN T. CHENEYAmherst College

JOHN B. BRADYSmith College

TEKLA A. HARMSAmherst College

JOHN C. SCHUMACHERBristol University

REGIONAL INTRODUCTIONThe Cycladic islands, located in the AegeanSea (Figure 1), contain high-pressuremetamorphic rocks that are believed to be thedismembered roots of the mountain beltformed during Eurasia-Africa subduction(Lister and Raouzaios, 1996), which began inthe Eocene (Tomaschek et al., 2003) or lateMesozoic (Bröcker and Enders, 1999). TheCyclades are part of the Attic-Cycladiccomplex, an island belt of crystallineculminations linking continental Greece withTurkey. The complex consists of two maintectonic units. The upper unit contains variousintercalated fragments of ophiolites, Permiansedimentary rocks and high temperaturemetamorphic rocks. In contrast, the lower unitis polymetamorphic and consists of a series ofthrust sheets containing pre-Alpine basement,Mesozoic marble, metavolcanics andmetapelites. The polymetamorphic nature ofthis lower unit is manifest by: 1) high-pressure, blueschist facies metamorphism, 2)normal regional metamorphism, and 3) contactmetamorphism associated with the intrusion ofgranitic rocks (Schliestedt et al., 1987).

The high-pressure rocks are best preserved onthe islands of Sifnos and Syros. Mineralassemblages vary with protolith and include

metabasalts with clinopyroxene (omphacite) +garnet + glaucophane + epidote, felsicmetavolcanics with jadeite + quartz,metapelites with muscovite + glaucophane +garnet + epidote, marbles containing dolomite+ calcite ± quartz ± epidote ± phlogopite,ultramafic rocks, and quartzites (Schliestedt,1986; Ridley, 1984b: Dixon and Ridley,1987). Maximum metamorphic condition forthe high-P event of 460°C and 14 kilobars atSifnos (Schliestedt, 1986) are similar to the480°C and 16 kilobars proposed for Syros byTrotet et al. (2001a).

A younger metamorphic event has beenrelated to widespread late Oligocene/earlyMiocene extension throughout the Attic-Cycladic belt (Wijbrans et al., 1993). Thissecond event overprints the earlier blueschistsand eclogites, culminating at Naxos in amigmatite dome. On most islands and inparticular on Syros and Sifnos, this secondevent is recorded in the rocks as apervasive–yet localized– greenschist faciesoverprinting (Trotet et al., 2001b).Delamination of supracrustal rocks proximalto active subduction provided the coolingmechanism to preserve the blueschists andeclogites (Wijbrans et al., 1993) and may havebeen responsible for exhuming deeply buried(>50 km) rocks.

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Figure 1: Tectonic map of the Agean Sea with the location of Syros and the Cycladic Islands (top) and the important rock types in the Attic-Cycladic complex (bottom).

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The rocks on these islands are isoclinalyfolded and extensively sheared and flattened.Four generations of deformation have beenrecognized in terms of fabric andporphyroblast relations in rocks from Sifnosby Lister and Raouzaios (1996). Thus, rocksfrom Syros and Sifnos have been intenselydeformed and significantly recrystallized sothat most of the original igneous andsedimentary textures have been obliterated(Lister and Raouzaios, 1996; Dixon andRidley, 1987).

GEOLOGY OF SYROSThe rocks of Syros can be broadly divided intotwo tectono-stratigraphic units as shown onFigure 2 (Schumacher et al., 2000): (I)metasedimentary and metavolcanic rocks and(II) remnants of oceanic crust. The lowermostrocks of Unit I are metamorphosed felsic tuffs,mafic schists, marbles, and finely-laminatedmanganese cherts. These rocks give wayupwards to a section dominated by marbles.The two main lower marble horizons aretypically dolomitic, in part, and are separatedfrom each other by glaucophane-schists,greenschists (retrograde), and minor quartzitesand manganese cherts.

Unit II consists of several discrete, fault-bounded packages of blueschist/eclogite-faciesmafic rocks that contain minor serpentinite.The mafic rocks occur with a variety oftextures and modes but most are either finegrained, glaucophane-rich blueschists orcoarse-grained (>1cm), massive omphacite- orglaucophane-rich rocks. These rock types havebeen interpreted as metabasalt andmetagabbro, respectively (e.g. Dixon andRidley, 1987). This hypothesis has beenverified by 38 whole-rock XRF and INAAanalyses for 18 fine-grained and 20 coarse-grained samples reported by Brady et al.(2000) and Schumacher et al. (2001, 2004).These results show that the protoliths of thecoarse-grained mafic rocks are indeed gabbrosthat have been chemically differentiated byfractional crystallization, whereas theprotoliths of the fine-grained mafic rocks arelargely undifferentiated ocean floor basalts.This interpretation is consistent with the

conclusions of previous workers based onfield (Dixon, 1969), geochemical (Seck et al.,1996), and isotopic (Putlitz et al., 2000) data.This result raises the interesting question ofwhy a coarse-grained igneous protolith shouldlead to a coarse-grained metamorphic rockcontaining all new minerals. The massivecharacter of the original gabbros appears tohave had a strong influence on theirmetamorphism (coarse texture, littlehydration) and deformation (little fabric,coherent blocks) during subduction andexhumation.

The occurrence of multiple generations ofhigh-P minerals, hornblende as inclusions inglaucophane, intricate chemical zoning ofhigh-P minerals, and partial to complete"euhedral" pseudomorphs after lawsonite thatcontain inclusions of garnet all attest to thecomplexity of the PTt path that was followedby these rocks during subduction andexhumation. One constraint on this path isprovided by the occurrence of calcitepseudomorphs after aragonite that arewidespread in the marbles of Syros. Thesestriking features consist of polycrystallinebundles of calcite rods that are elongate andoriented at a high angle to the matrix foliation.Brady et al. (2004) have used the chemicalcomposition, shape, and occurrence topostulate that the aragonite grew in a preferredorientation during high-P metamorphism andthat it was subsequently topotacticaly replacedby calcite during exhumation.

According to Dixon and Ridley (1987), thereis but one penetrative fabric that affects nearlyall in the rocks of Syros. More recently,Rosenbaum et al. (2002) have identified atleast three phases of deformation associatedwith the high-pressure metamorphism. Theearliest fabric is preserved as inclusion trails ingarnet grains and it is commonly at an angle tothe matrix schistosity. High-pressure mineralsdefine the matrix schistosity, which is parallelto lithologic contacts. Some glaucophane, thelawsonite, and the pseudomorphs afterlawsonite appear to postdate the main fabric.There is some strain partitioning reflected bythe massive cores of the metagabbros andsome of the breccias. This dominantschistosity is the one identified by Dixon and

Ridley (1987) and glaucophane shear bandslocally cut it. Superimposed on these high-Pdeformation fabrics is a late locally-developedfabric associated with greenschistoverprinting.

Cheney et al. (2000) have reported 206Pb -238U ages from zircon in two blueschists. Ionmicroprobe spot ages were obtained fromthree zircon grains in sample SYR99-19A andone zircon grain in sample SYR-7A. Thezircon grains selected for dating are large,euhedral and their textual occurrence isconsistent with syn- to post-kinematic growth.Some of the euhedral zircon grains arepartially included in blue amphibole whereasothers crosscut the fabric. There are no grainsthat are wrapped by the fabric. Thus, thesezircons grains appear to have grown duringmetamorphism in accord with theinterpretation of Bröcker and Enders (1999)for a zircon in an omphacitite, also from thenorth end of Syros. The result of 83+/-10 Mafrom sample SYR99-19A is remarkablyconsistent with the 78+/-1 Ma TIMMS agereported by Bröcker and Enders (1999) andthey probably represent the true metamorphicage for all the rocks. Sample SYR-7A is aglaucophanite from the Kampos melange zoneand the zircon ages from one euhedral grainrange from 81+/-2 to 54+/-4. These dates mayindicate activation of the melange zone andcontinued metamorphism. Of interest is thatBröcker and Enders (1999) also reportedsimilar young ages of 60 Ma and 63 Ma zirconages in a jadeite rock on Tinos, which theyalso attributed to a younger "event". Theseresults lend credibility to the occurrence ofpre-Eocene high-pressure metamorphism inthe Aegean. This 80 Ma Cretaceous event mayrecord heating following the slowing of thesubducted slab. The younger Eocene datesreflect later lower pressure retrograding ofthese rocks and the continuing evolution of theaccretionary wedge. These ages are similar tozircon ages reported by Tomaschek et al.(2003). However, they interpret the 80 Ma.ages as magmatic ages of the zircon and thusthe ~80 Ma age is that of the ocean crust.Support for this hypothesis comes from theLu-Hf study of similar mafic rocks by Lagoset al. (2003). Tomaschek et al. (2003) argue

that the agreement between the 55 Ma U-Pbages and the ~ 55 Ma Ar-Ar ages of whitemicas from the same samples supports theconclusion that the metamorphism is Eocene.They do not, however, explain how zirconcrystallized from basaltic MORB-like magma.One likely source of Zr in a basalt is that itresides in augite. When augite breaks downduring hydration, either on the sea floor or inthe subduction zone, the Zr can beconcentrated to form zircon. Thus, the 80Maages of the zircons may well be recordingaugite breakdown and not magmaticprecipitation of zircon.

STUDENT PROJECTSThe 2004 student projects were conductedsolely on the island of Syros. The studentprojects were designed to build upon ourprevious results and to extend our coverage ofthe island in terms of both area coverage aswell as scope. These studies focused upon thestructural, mineralogical and texturalconsequences of the processes involved in theevolution of the Syros Blueschist-Eclogiteterrane.

Njoki Gitahi (Amherst) and Elizabeth Holly(Pomona) are studying one of the mostdistinctive and widespread rocks on Syros inorder to assess variation in metamorphicpressures and temperatures over the wholeisland. They are both focused upon thefabric, mineralogy and phase relationships ofthe eclogites that occur in the fault boundedmafic enclaves. They are using the newlycalibrated thermobaromter of Ravna and Terry(2004) for garnet + omphacite + phengite ±rutile ± quartz bearing rocks. Elizabeth isfocused upon eclogitic rocks from the east sideof Syros whereas Njoki is studying similarrocks from the west side of the island. EricPurcell (Beloit) is looking at blackwallreaction zones that have formed on these sameeclogites where they occur as exotic blocks insepentinite mélange. Eric is attempting todetermine the nature of metasomatism bothspatially and chemically. Laura Frye-Levine(Smith) is examining the graphitic schists thatare common on the north end of the island.These rocks typically contain a variety oflumps structures reminiscent of pseudomorph

after lawsonite and or garnet and thus providean interesting continuation of the lawsonitepseudomorph story initiated in our first project(e.g. Sperry 2000) and continued in phase II(e.g. Able, 2001).

The marbles of Syros are the focus of two verydifferent projects. Jessica Driscoll (Amherst)is using electron backscattered diffraction(EBSD) to determine in detail thecrystallographic orientation of calcitepsuedomorphs after aragonite that have beenrecently described by Brady et al. (2004).Jessica hopes to learn the extent anddistribution of calcite grains with acrystallographically-preferred orientation.Emily Pope (Colorado College) is usingCarbon and Oxygen isotopes to characterizethe metamorphic history and the nature ofmetamorphic fluids of the three differentmarbles on Syros. Emily is also studying theapplicability of calcite-dolomitegeothermometry in these blueschist faciesmarbles.

Stacey Kepler is continuing our efforts tocharacterize the protoliths of the variousmetamorphic rooks on Syros by studying themajor and trace element geochemistry of theglaucophane schist sequences that areassociated with the marbles in Unit I. Takentogether these schists and marbles comprisethe bulk of the island. These rocks are quitevariable in appearance ranging from light todark colored and thus in protolith, possiblyfrom felsic to mafic volcanic rocks, Ourearlier work (e.g. Sinitsin, 2001) has identifiedpossible calc-alkaline or arc related volcanicprotoliths on Syros. Volcanic protoliths fromthe nearby island of Sifnos reflect thesequential formation of a subduction zone, anisland arc and then a back arc basin (Mocek,2001).

Three of the students are studying elements ofthe structural evolution of Syros thatencompass the tectonic evolution fromsubduction to exhumation. Eli Lazurus(Williams) examined in the field three highangle faults associated with distinctive brecciazones that crop out along the west coast ofSyros. These post-metamorphic faults arepossibly synchronous with or younger than the

large-scale normal faults that exhumed theblueschist eclogite terrane of Syros. Fluidinclusion analysis of matrix minerals in theassociated fault breccias will help constrainthe context in which the faulting occurred. Thedetailed description and interpretation ofmicrofabrics are at the core of the studies ofScott Dougan (Amherst) and Gabe Nelson(Carleton). Gabe is studying the texturalrelationship between inclusion fabric withingarnet porphyroblasts in glaucophane schists,pressure shadows around the garnet (some ofwhich contain distinctive glaucophane “tails” )and the matrix foliation in schists from aroundthe island. Gabe will assess theserelationships in terms pure and simple shearduring high-pressure metamorphism. Scott isfocused upon the habits and textural variationsof white mica elements in micaceous schists.Scott is mining his samples for keyoccurrences of white mica that will allowstages in fabric development such ascrenulation and shearing to be dated by Ar-Arlaser techniques.

JANUARY WORKSHOPEight of the ten students and three of the fourfaculty participants in the 2004 Greece-SyrosKeck project assembled for a collaborativeworkshop at Amherst College over theweekend of 23-25 January, 2004. Theworkshop provided students and faculty withthe opportunity to exchange data and results,and to share experiences and problemsencountered in their endeavors. This wasparticularly useful as several of the studentprojects are interdependent in that they rely tosome extent on the results of each other’swork.

The group assembled Friday evening for apizza dinner followed by several hours ofslides of people, outcrops and views on Syros.On Saturday morning, each of the eightstudents in attendance gave a 15-minute oralpresentation. Varying materials includingphotomicrographs, projection of critical thin-sections, maps, chemical data, and mineralcomposition data accompanied these reports.The informal setting provided ampleopportunity for questions, discussion, andsharing of results, methods, problems and

concerns. During the afternoon, Tekla Harmsled a review and discussion of Mediterraneangeology. We then spent the rest of the dayreviewing and comparing minerals and fabricin our thin sections.

On Sunday, the workshop focused upon adetailed discussion of minerals we hadencountered in the rocks from Syros. Thisinvolved reviewing the crystal chemistry ofseveral important minerals includingomphacite, blue amphibole, phengitic micaand the epidote family. John Brady discussedferric iron corrections of SEM data for theseminerals as well as ways to representgraphically their compositions. Gabe Nelson(Carleton) stayed for several days followingthe workshop in order to complete the mineralanalysis portion of his study using theSEM/EDS system at Smith. Elizabeth Holly(Pomona) traveled to Amherst two weeksbefore our workshop in order to complete theanalytical part of her study using theSEM/EDS systems at Amherst.

RESULTSThe results of the 1999 and 2000 project weresummarized in the 2000 and 2001 KECKproceedings volumes. In addition, thesegroups have produced at least 8 studentabstracts that were presented at regional GSAmeetings, five abstracts jointly co-authored byproject faculty and students were presented atnational and international meetings and onepaper has been published. A list of these resultis appended below.

ACKNOWLEDGMENTSWe would like to acknowledge the wonderfulhospitality of the people of Syros. We werewelcomed as friends and treated as relatives.We especially want to thank Mr. GeorgiosRigoutsos and his family, the proprietors ofthe Hotel Olympia in Finikas, our home onSyros. Georgos with his friendly advice andknowledge of the island made our visit mostpleasurable with only the fondest of memories.We would also like to acknowledge thecompanionship of the Bristol University Year2 mapping class who as a group added aninteresting and most positive diversity to ourisland experience.

REFERENCES CITEDAvigad, D., 1993, Tectonic juxtaposition of blueschists

and greenschists in Sifnos Island (Aegean Sea)-implications for the structure of the Cycladicblueschist belt: Journal of Structural Geology, v.15, p. 1459-1469.

Brady, J.B., Shiver, H., Grandy, A, Cheney, J.T.,Schumacher, J.C., 2000, Whole- rock geochemistryand metamorphism of blueschist/eclogite-faciesmafic rocks on Syros, Cyclades, Greece:Geological Society of America, Abstracts withPrograms, v. 32, p. A152

Brady, J.B., Markley, M.J., Schumacher, J.C., Cheney,J. T., and Biancardi, G. A., 2004, Aragonitepseudomorphs in high-pressure marbles of Syros,Greece: Journal of Structural Geology, v. 26, p. 3-9.

Brocker, M. and Enders, M., 1999. U-Pb zircongeochronology of unusual eclogite-facies rocksfrom Syros and Tinos (Cyclades, Greece):Geological Magazine, v. 136, p. 111-118.

Cheney, J.T., Schumacher, J.C., Coath, C.D., Brady,J.B., DiFillipo, E.L., Argyrou, E.N., Otis, J.W.,Sable, J.E., Sperry, A.J., Skemer, P.A., 2000, IonMicroprobe ages of zircons from blueschists, Syros,Greece. Geological Society of America, Abstractswith Programs, v. 32, p. A152.

Dixon, J. E., and Ridley, J., 1987, Syros (field tripexcursion), in Helgeson, H. C., ed., Chemicaltransport in metasomatic processes, NATOAdvanced Study Institutes Series. Series C, pp. 489-500, D. Reidel Publishing Company, Dordrecht.

Höpfer, N., Schumacher, J.C., and Raith, M., 1994,Reaction paths in the high-pressure metamorphicrocks of Syros (Cyclades): Beihefte zur EuropeanJournal of Mineralogy, v. 6, p. 116.

Höpfer, N., and Schumacher, J.C., 1997, New fieldwork and interpretations of the sedimentarysequence, the position of the ophiolitic rocks andsubsequent deformation on Syros, Cyclades,Greece: Beihefte zur European Journal ofMineralogy, v. 9, p. 162.

Lagos, M., Munker, C., Tomaschek, F., Ballhaus, C.and Scherer, E., 2003, The age of oceanic crust andof HP/LT metamorphism on Syros (Cyclades,Greece) based on Lu-Hf geochronology andgeochemistry: Geophysical Research Abstracts, v.5, p. 12851.

Lieberman, J. and Matthews A., 1992, Stable isotopicsignatures and tectonic correlation: A new statisticalapproach and application to the Cyclades.Geological Society of America, Abstracts withPrograms, V24; p. 249.

Lister, G.S. and Raouzaios, A., 1996, The tectonicsignificance of a porphyroblastic blueschist faciesoverprint during Alpine orogenesis: Sifnos, Aegean

Sea, Greece: Journal of Structural Geology, v. 18, p.1417-1435.

Mocek, B., 2001, Geochemical evidence for arc-typevolcanism in the agean Sea: the blueschist unit ofSiphnos, Cyclades (Geece): Lithos, v. 57, p. 263-289.

Putlitz, B., Matthews, A., Valley, J.W., 2000, Oxygenand hydrogen isotope study of high-pressuremetagabbros and metabasalts (Cyclades, Greece):implications for the subduction of oceanic crust:Contributions to Mineralogy and Petrology, v. 138,p. 114-126.

Ravna, E.J. Krogh and Terry, M.P., 2004,Geothermobarometry of UHP and HP eclogites andschists–an evaluation of equilibria between garnet-clinopyroxene-kyanite-phengite-coesite/quartz:Journal of Metamorphic Geology, v. 22, in press.

Ridley, J., 1984a, The significance of deformationassociated with blueschist facies metamorphism onthe Aegean island of Syros, in Dixon, J. E. andRobertson, A. H. F., eds., The geological evolutionof the eastern Mediterranean, Geological SocietySpecial Publications, p. 545-550, BlackwellScientific Publications, Boston.

Ridley, J., 1984b. Evidence of a temperature-dependent''blueschist'' to ''eclogite'' transformation in high-pressure metamorphism of metabasic rocks: Journalof Petrology, v. 25, p. 852-870.

Rosenbaum, G., Avigad, D., and Sanchez-Gomez, M.,2001, Coaxial flattening at deep levels of orogenicbelts: evidence from blueschists and eclogites onSyros and Sifnos (Cyclades, Greece). Journal ofStructural Geology, V24, p.1451-1462.

Schliestedt, M., 1986. Eclogite-blueschist relationshipsas evidenced by mineral equilibrium in the high-pressure metabasic rocks of Sifnos, CycladicIslands, Greece: Journal of Petrology, v. 27, p.1437-1459.

Schliestedt, M., Altherr, R., and Matthews, A., 1987.Evolution of the Cycladic crystalline complex:petrology, isotope geochemistry and geochronology.in Helgeson, H. C., ed., Chemical transport inmetasomatic processes, NATO Advanced StudyInstitutes Series. Series C, pp. 389-428, D. ReidelPublishing Company, Dordrecht, Boston.

Schliestedt, M., and Matthews, A., 1987,Transformations of blueschist to greenschist faciesrocks as a consequence of fluid infiltration, Sifnos(Cyclades) Greece: Contributions to Mineralogy andPetrology, v. 97, p. 237-250.

Schumacher, J.C., Tonnsen, R., Cheney, J.T. and Brady,J.B., 2000, Glaucophane marbles and associatedhigh pressure rocks on the island Syros, Cyclades,Greece: Geological Society of America, Abstractswith Programs, v. 32, p. A114

Seck, H. A., Kotz, J., Okrusch, M., Seidel, E., andStosch, H.-G., 1996, Geochemistry of a meta-ophiolite suite: An association of metagabbros,eclogites and glaucophanites on the island of Syros,Greece: European Journal of Mineraogy, v. 8, p.607-623.

Tomaschek, F., Kennedy, A., Igore, V., Lagos, M., andBallhaus, C., 2003, Zircons from Syros, CycladesGreece-Recrystalization and mobilization of zirconduring high-pressure metamorphism: Journal ofPetrology, v. 44, p. 1977-2002.

Trotet, F., Vidal, O. and Jolivet, L., 2001a, Exhumationof Syros and Sifnos metamorphic rocks (CycladesGreece): European Journal of Mineralogy, v. 13, p.901-920.

Trotet, F., Jolivet, L. and Vidal, O., 2001b, Tectonometamorphic evolution of Syros and Sifnos islands(Cyclades Greece): Tectonophysics, v. 338, p. 179-206.

Wijbrans, J.R., van Wees, J.D., Stephenson, R.A., andCloetingh, S.A.P.L., 1993, Pressure-temperature-time evolution of the high-pressure metamorphiccomplex of Sifnos Greece: Geology, v. 21, p. 443-446.

PROJECT PUBLICATIONSin addition to KECK Symposium presentations.

Able, L., and Brady, J.B., 2001, Lawsonitepseudomorphs in the schists of Syros, Greece:Geological Society of America, Abstracts withPrograms, v. 33, p.A9.

Argyrou, E.N., Cheney, J.T. and Harms, T.A., 2000,Tectonometamorphic evolution of greenschist,blueschist and eclogite facies rocks, Ermoupoli,Syros, Greece: Geological Society of America,Abstracts with Programs, v. 32, p. A3.

Arsenault, M. and Brady, J.B., 2001, Calc-silicatemarbles of Syros, Greece: Geological Society ofAmerica, Abstracts with Programs, v. 33, p. A9.

Brady, J.B, Markley, M.J., Schumacher, J.C., Cheney,J. T. and Biancardi, G.A., 2004, Aragonitepseudomorphs in high pressure marbles, Syros,Greece: Journal of Structural Geology, v. 26, p. 3-9.

Brady, J.B., Able, L.M., Cheney, J.T., Sperry, A.J., andSchumacher, J.C., 2001, Prograde lawsonitepseudomorphs in blueschists from Syros Greece.Geological Society of America, Abstracts withPrograms, V33, p. 250-251.

Brady, J.B., Shiver, H., Grandy, A, Cheney, J.T.,Schumacher, J.C., 2000, Whole- rock geochemistryand metamorphism of blueschist/eclogite-faciesmafic rocks on syros, Cyclades, Greece: GeologicalSociety of America, Abstracts with Programs, v. 32,p. A152.

Cheney, J.T., Schumacher, J.C., Coath, C.D., Brady,J.B., DiFillipo, E.L., Argyrou, E.N., Otis, J.W.,Sable, J.E., Sperry, A.J., Skemer, P.A., 2000, IonMicroprobe ages of zircons from blueschists, Syros,Greece: Geological Society of America, Abstractswith Programs, v. 32, p. A152.

Breecker, D.O. and Cheney, J. T., 2001, Mineralassemblages of high-pressure quartz-mica schistsfrom Syros, Cyclades, Greece: Geological Societyof America, Abstracts with Programs, v. 33, p. A9.

Difilippo, E. L. and Brady, J.B., 2000, Metamorphicevolution of high-pressure, low-temperature maficrocks near Kini on the Island of Syros, Greece.:Geological Society of America, Abstracts withPrograms, v. 32, p. A14.

Holly, E.A., Ross, T., and Cheney, J. T., 2004,Pressure-temperature conditions of metamorphismin eclogites, Syros, Greece: Geological Society ofAmerica, Abstracts with Programs, v. 36, p. A

Otis, J.W., Cheney, J.T., and Harms, T.A., 2000,Petrologic and textural evolution of blueschist faciesmicaceous schists of Syros, Greece: GeologicalSociety of America, Abstracts with Programs, v. 32,p. A63.

Ratner, J.E. and Cheney, J. T., 2002, The evolution ofthe Cycladic subduction complex: constraining p-t-tpath geometry from compositional zoning andmineral inclusions within garnet in pelitic schistsfrom Syros, Cyclades, Greece: Geological Societyof America, Abstracts with Programs, v. 34, p. A67.

Richard, Jill E. and Markley, M.J., 2001, Origin ofblueschist brecia, Syros, Greece: GeologicalSociety of America, Abstracts with Programs, v. 33,p. A9.

Sable, J. E., Harms, T.A. and Cheney, J.T., 2000,Structural and petrologic character of mafic andsiliceous high-pressure rocks in southern Syros,Greece: Geological Society of America, Abstractswith Programs, v. 32, p. A71.

Schumacher, J. C., Brady, J.B., Prinkey, D, R, Walton,A, Able, L.M., Sinitsin, A.G. and Cheney, J.T.,2004, Geochemistry and metamorphism ofblueschist-eclogite facies rocks on the island ofSyros, Cyclades, Greece. EOS, vol XX, no. XX,pxxx.

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