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Neo-Tectonic and Rock Magnetic Study of the Circum Troodos Sedimentary Succession, Cyprus

Sutwnitîed in pafîial fulfilment of ttie requirements for the degree of

Supervisoc Dr. Gnham J. Bmdaik

ûepactment of Geology îaketuaâ University fhunôiw Bay, OMo Canada November, 1999 National Library Bibliotheque nationale du Canada uhitions and Acquisitions et "1Bib bgiaphic Senticem ssrvices bibliographiques

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Cana! The Ciram Trwdor Seâimentary Sucassion (Lata Cretaceous to Recent) overlies the Tmodos ophiolite of Cypnis, located in Vn, Eastern Witemnean. The pattern d neo-tedonic ddarmooon wm immtigated thmgh megnetic analysis of the t8donic ptdbrks. kiirobopy of maqidic mœpüôility (AM), anisotmpy of anhyWmüc remmema mognetization (AARM) and hysteresis bop parameters were detemu'ned in orckr to define the mgnetic faMc and the magnetic mineralogy.

The study amWmds oviw approximately 1ûûû km2 mainly to the south of the exposed TlOOdOs ophiolite. The ample suite indudes 432 oriented hand samples, predominantly of the Ll(kwr and Pakhna Formations.

Field measurementr indicatm Wingpredominantly dips less than 10' to the south, whik deavage, dips atmthan ôedding in various directions. The ôeddin@mmfp mlationthip yialds variable vei'@enœdirections suggemting gmity diding d the seâimmb tamûs kcil dmbasins. Southest of th Limassol Fmst Black abalplanar deavage msistmtly defines a SW vqpnœ . with impact to bedcâing due to r locally diit, Euly to Middle Miocem compression along NNE to NE - SSW to SW uzimuth.

The AMS fabric, in part tedmic, ir controlled by the pmfed mmy a##. AMS (blhtion pdémüdîy dipr rhsllowly to the east and wst. AMS linedion v- rqionelly, fmm west to eut rcmu the study ana, fiom a NNE to NNW tmh, ~*wty.Tb bdmk AMS tacngistem aithof a late Mim sprPrubducbjon extension regime due to -rd migration d the nadivation Cypman Arc or due to Pkiatocme gravity rliding due to uuplift of Vw, Troodos Ophiolite Cmplex.

The AARM ïakic ir amtmlled ecciwively by the preferred dim«uional orMathd pmAo ringk domrin magndite. Erckiding the ana in proximity to the Limasml Forslt Block, thr AARM fabric orientations are ragio~llyconsidont. AARM fdisüar phmm dig 45' to the NW mâ AARM limation is dimted NE and SW, almot orhogoml to AMS Iineatim. In som cases, in proximity to the Limassol Forest, the AARM linrdion mmb from the combined magnetic faMcs, pmlW to deavage and bedding nd is pmIW to the Wingclravage intwwdbn lhmtim. Th. .duil extension direction is to the WNW, ~~ed by the AARY, pfindoplaxes. SouWest d the Litnaud Fmst Blodc the AARM fabric mgisters the Evty to Middle MiiSW- NE campmrrion, and its tedonic expression ir conventibnal, with MAY, oriented NW and SE, parpmdiaikr to the mrnimwn comprsuion direction. iii

mir project waa funôad by a N.tunl Sciemas and Engim'ng Rem Council d Cnib(NSERC) grmt to Dr. Gnhvn J. BomQile. The rack magmücs lsborsQry at LaMmâ UrdwMy wir funûd throughout the yeam alw by NSERC. Nunerous people môe thir proje& pouibk and rhould k admwledge. Fint and bmmmt, rny supefviror, Dr. 0.J. Bonadaile for giving me the oppftunity to do thir projrct, for wuiching rny knorniledge of rodc msgneticr, and providing guidance and COC)S~~I~V~crilicirm throughorrt dl stages of this pmjact. I wwld like to awik Or. Xemphnt08 anâ his cdleagws 1th Oedogical Suwey of Cypnis for pmviding informational field examions Mile in Cyprus. Thanks to Gratuam Borndiile for cdIecüng a pnliminry oriented ample suite duhgthe199;1fidd~ndfahiorui~duingthe1998fiddseaon in cdkdingoww4WrpmpkrrdtJikigrmmmxnfldd~.Iwwld Jsa

takm by Pdw Puna.

6.3 AARM Rswlts ...... 94 5.3.1 Sh~peandECCdn~dAARMHIipsoid...... 94 6.4 Summary ...... 96

7.1 Bedding. Cbvage and Vwganœ ...... 97 7.1 .1 Olkntafbn mû Regim8/ DiStn'bmn ...... 97 7.1.2 InteqmtaIr'on ...... 107 7.2 Anirotropy of Magnetic Susmptibility (AMS) ...... 111 7.2.1 AMSFOlhtrOn ...... 111 7.2.2 AMSUitbn ...... 115 7.2.3 SummuyofAMSFabtfC ...... 119 7.3 Anirotropy of Anhystefetic Mignaic Remanence (AARM) .... 120 7.3.1 AARMFdhtbn ...... 120 7.3.2 AARMtimm ...... 124 7.3.3 Summaty of AAR# Fabk ...... 126 7.4 Chrorolo@opl Intwpmbtim ...... 126 7.5 Summsry ...... 131

AppmdixA - Wing and Cieavage Data ...... 145

AppemdixD . Hystemsis Loop anâ Cmcivity of R~~ Data ... 199 vii

Chaptew 1 Fig~f~1-1 TWmic terrains d Cyps ...... 2 Fig~m1-2 Pal-y at Pmin. friruic transition ...... 3 Figum 1-3 Blodc diagram of Mamociia Temin ...... 4 Figure 14 PaImgqmphy of EPrly and Late Cret~c~ous...... 6 Figure 1-5 Gmesis mcbl f6r ttm Troodos ophidite ...... 7 Figure 1.8 Riâge air and tmnrjami fault evoluüon dduig the fmimof the Traodor ophiolite ...... 9 Figun 1-7 Mi~lrtsrOtaim~l...... 11 Figure 1-8 Paleomagnotic dds of rotation ...... 12 F~~UVB1-9 ?ment plate tmtonic Mingof the Eastern Madit- ...... 16 Figum 1-10 Possible ndum tectonic cidivity ...... 18

ChPptw 2 Figure 2-1 p.c.0. devdopmnt by slip and rotation ...... 23 Figum 2-2 Ddmmation mechanim for a mo~nnimlicrock ..... 25 Figum 23 DefMnation mechmiun plot for quark and calcite ..... 29 Figure 24 Cleavage durification ...... 32 Figure 2-5 Pure ahem vems simple stiear ...... 40 Figure 26 Flinn diagram ...... 43

chaptcw 3 Figum 3-1 Types of ~katim...... 52 Figur~3-2 Jelinek plat ...... 65

. Chiptrr4 Figun 4-1 Histogmm of wwcivity (HJ ...... 70 Figum 4-2 Daypbtofdib ...... 71 Figura 4-3 HistoQmnd % ...... 73 Figure 44 FreqtJemy dktri'kiüari. OfIc,...... 75 viii

Chapter 6 Figure 6-1 AARM directions of samplem expad ...... Figure 6-2 Stemognghic proi#iim of AARM mrub ...... Figure 8-3 Contoumd Jdindc plot d AARM msults compared to AMSmwb ......

Chapter 7 Figure 7-1 Regional orientation variation of S. masurements ..... 9û Figm 7-2 Regions1 ori~*mvariation of S,, measurements ..... 99 Figub 7-3 Photognph of runpie FU8284 ...... 100 Figure74 MapdmPjorsüuctumIftusrofCyprus ...... 103 Figwo 7-5 Photograph d rniple FL98û31 ...... 104 Figure 74 Phdo~rsphof umpk FL9B117 ...... 105 Figure 7-7 Photograph of mploFM8167 ...... 06 Figure 78 Variation in cleavage vergema directions ...... 107 Figure 7-9 Sauthwvd bench migration modd ...... 109 Figure 7-1 0 Basin anâ high topognphy mode1 ...... 10 Figure 74 1 Regionsl vdBtiCon d AMS foliation ...... 12 Figure 7-1 2 Regional variation dAMS lineation ...... 13 Figure 7-1 3 Variation in AMS vergerics directions ...... 15 Figure744 Rateofmtfwtvm~eofsubduction ...... 118 Figure 7-1 5 Regional variation d AARM foliation ...... 121 Figure 7-1 6 Regionel vwidion of AARM limation ...... 122 Figure 7-1 7 Vwi*rüon in MRM vefgenœ dimcüons ...... 124 Figure 7-1 0 Schmatic illustration d the AARM composite fPbric ...125

Appndoc B Figue 6-1 Distribution d AMS foliation spatial averaging ...... 189 Figure 6-2 Distribution of AMS limation spatial averaging ...... 190 Appemdix C Figure C-1 Distribution d AARM foliation spatial avmging ...... 197 Figure C-2 Distribution d AARM lineation spatial avemging ...... 198

Chapter 1 - Tectonic Evolution of Cyp~s

Located in the eastem Mediterranean Sea, the island of Cypnis contains three tectonic terrains: the Kyrenia Temin, the Mamonia Terrain end th Tdos

Terrain (Figure 1-1). The purpose of this chapter is to outline chronologically the events which amalgamated these three Tenains to fom the present geological configuration of Cyprus. Tedonic events which would contribute to the evolution of Cyprus began during the Permian.

1.1 Pemlan

The palaeogeography during the Pennian places Gondwanaland to the

South and Laurasie to the nom separated by the Paleo-Tethys Seo (Figure 1-2).

Shallow water limeStones that aeaimulated on the norVmard dipping continental shelf of Gondwanaland are presently exposed in the eastem parts of the Kymnia

Terrains. These limestones fmpart d W KBntara F-on and represent the olded rocks in Cypnrs (Romton and Woodcdc, 1Q86). The transition from the

Permien to the Triassic was madced by th bfeaking up of th8 northem mrgin d

Gondwanaland driven by continental rifting and the opening of Neo-Tethys

(Robertson, 1990).

Figura 14 Propmd pa~~nphicrsconstfudion oîüte North Americin, Europian and African mnünents for the Pemian - Triassic transition psriod. Nu- wam pibssnl due to rllting, only r fw rra labelled hem. Tethys 1 in the diagram is quivalent to Pah-Tethys mntiomâ b the texl (fioni Oewsy et d., 1973).

of microcontinents separating the Paleo- and Neo- Tethys Seas. It is suggested

that the Mamonia Terrain originated as a rnictocontimntal margin. Whether aie

Kyrenia Terrain fomed as a rniaocontinent or fmed an independent platfm is

still unimwn (Robmbon, 1990). Today, these micrOcOrrtimnts wu pndomi~ntly

scatterd almg Ihe mthmawst of the Meditereman Sm. Evidenœ of Tri-ic

continental rifting is reen within the lithdogy d the Mamonia Tmin.

: Photios Gmup, doamcntr the eady stages of deposition within the continental rift, occumng in fault-bounded grab. The volcanic, Dhiwizor Oroup, records the

-5- volcanim related to the continental Ming initiatd during the Late Triassic

(Roktsm snd Wood- 1979). Figure 13rciconsm the mlatimship of th two rock groups of the Momonia Tmin within a continental rift system.

AllochthOM)ur material within the Ayios Photios seâimnts implies that sedimentatim ocairred on a muoin near one of the de!acheû microcontinents

(represented by the metamorphic terrain in Figure 13) (Robertson, 1990).

TbNeo-Tethys Sea continu4 to open throughaut the Jurassic and Eady

Cretaceous. The Afncan plate moveâ eastward in relation to the Eurasien plate and pmmted spmding and sttike-dip math within the Neo-Tethyan Sea (Figue

14). Duing aie MWk CfWmom ( aller 11 Ma ) plate motion changed and the

African plate veereâ northwcvd in relation to the Eurasian plate (Livermon, and

Smith, 1984) (Figure 14). Tbctuange in plate tedonia initiatd subduction,

core of Troodos, presents compelling evidence foi a spreading component to the

mode1 (Robinson et al., 1983).

Initially, wbdudion consumed rmall portions of young Cretaceous au&.

Denser Tn'auic mstenteting the trench caumâ the hinge of the subduction zone

. to migrate bachard (i.e., oceanward or southward)(Robertson, 1990). The

backward migration of the subduction ZOM hinge line imas8d the size of the

mantle wedge above the subduding plate. Decornpressing, melting and upwelling

of aie asthenosphem producad the spading fabric observeâ throughout ths

TrOOdos ophiolite (Robertson, 1990) (Figure 16). Alledon and Vine (1 987) defineâ

a spreading fabric fKwn a paleomagnetic sunmy of the Soke graben. in whidi the . . restoration of both dike remples to veftical and primary remamnt rnagmkatm to

a Wved strudurally cotreded remment magnetization diredim. ResuIts -8- indicated that dike rotations were consistent with the strudure developing through an axial process.

The ophiolite sequence, composed of harzburgite and diorite upper mrntle rocks, overlain by gabbro, sheeteâ dyke cornplex and pillow lavas sequence, began to fom 90-92 Ma ago and presently occupies about 213 of the island of Cyprus

(Bloome and Irwin, 1985; Staudigel et el., 1986). The tedonic setting of a supra- subduction zone is the most widely accepted view for the formation of the Troodos ophiolite. The Troodos Terrain preserved relids of the spreading axis as well as the transfom fault. The Arakapas fault zone, which runs E-W, represents aie remnant of a transform fault. The Solee Graben, oriented N-S and located north of

MtT~OO~OS, is thought to have been the spreading axis which cwitributed primarily to the formation of the Troodos ophiolite (Allerton and Vine, 1991). Younger crust fomied almg the Larnaca Graben, east of the Solea Graben, following an eastward jump of the ridge ais. The ridge migrated east after spreading ceased along the

Solea Graben and the Arakapas transform fault became inactive. Hawever, to accommodate spreading of the Lanarca Graben, a new transfom fault, with a slightly more northerly orientation, extendeâ et the eastem end of the Arakapas fault zone (Figure 14) (Allerton and Vine, 1991).

1.3.2 Mic8npf8t. RoCUon

The most significant tectonic adivity during the Late Cretac~ous,ir the initiation of microplate rotation. Figure 1-7 illustrates the tedonic kwng of the

Trooâos microplate and the sumnding Ambian, African and Turkish plates in

order to understand how the rotation began.

The African plate migratd northward. The Arabian plate or promontory, to

the east, then collided with the east-west striking subduction zone and spreading

centre that produced new oœan Roor. The initial collision obducted some -an

door onto the Arabian plate. The Hatay and Baer-Bassit ophiolites, exposed in

southem Turkey and northem Syria respedively, provide evidence of obdudion.

Furthermore, aie Hatay and BaerBassit ophiolite (pre-Upper Campanian) are of

similar age to the Troodos ophiolite (Santonian to Maastrichtian; Robertson, 1990;

Blome and Imin, 1985). Continuous northward motion of the African and Arabian

plates iniüated an anticlochvise rotation of the microplate around a pivot point.

Stable magnetization vectors with a uniform westerly azimuth retained fw the

Troodos ophiolite, the Arakapas transfomi fault, and the anti-Troodos plate

(Limassol forest) indicate these areas were al1 within the boundaries of the rotating

microplate. Similar preliminary analyds of rock samples ftom the Mamonia Terrain

. indicates that it was not within the boundaries of the rotating microplate and

consequently suffered a dincwent tedonic history (Clube and Roôertson, 19û6). It

is also suggested that the collision and onset of rotation halted the spreading above

the subduction zone (Robertson, 1990).

Palaeornagnetic studies provide the best evidence for microplate mtatian.

The stable characteristic part of the natuml rernanent rnagnethrn (NRM) veâofwas

isolateâ through thmal demagnetization and subsequent principal component

analysis (PCA) of samples from various stmtigraphic layers of the Tmdos terrain. These clearly illustrate the rotation. Tbpresent magnetic earth field (PEF) for

Cypnis has a dedination and inclination of 3' and 51 (calailated with the cornputer program Definitive International Geomagnetic Referenœ Field v. 1.4).

The olâest stmtigraphic layer within the Troodos Tmin is the Troodor pilluw lava sequema. Themal demigmtizatim of the lavas irolated stable NRM veston with dedinations of 274'. The Umm Formetion, intmbdûd with the

Troodor lava8 has a stable NRM -of declindion of 279'. Radiolarhs d the (paleomagmtic data: Club and Rokr(ron, 1988). Thmbm, by the end the

Ma, the TIoodor microplate unôerwW r 90 âegm ntidodwiso rotation to its pmmt dry geographical pooitkn (Figun 1-8).

-1 4-

motion of aie African plate coud mttnmrd underthrusting, which pouibly

mactivateâ zonas of weaûner Possibilities indudo the relid Cretaœ~w

subduction zone or the microplate boundary faulb or bdh (Robertson, 1990).

Whether or not an exiating zone d weakmss wm mdivated, wrderthfuaing oaamd in appdrnateiy the sam Oeogrephica! arwr as the pfei~mtCyprean Arc.

Umwas nevw axîmdve, (r5ûû km) because of aie daw movement of the Africen plate. In tum, major arc volcenism did not ocarr. Fu-,

underthrusting uplifted the froodor and the Msmonia Tarain8 to fmshallow mas and Iagooruil environments. To the mth of Troodos underthwsting causecl the

Kyreriia range to abside (Rohwbon, 1990). TbAnk0p.s fracture zari., locatd south dTroodos, openeâ and anisteâ southwarâ produdng the Yeresa fold and thnirt belt (Robertson, 1977).

Tho Mid to Late Miocrcw, v*odis rnarkeâ by extensia~lgrowai faulting parücuIa~Iyto the nwth and notthwast d TlOddOs (Followr adRobertson, 1990).

The Polis graben, in the IKWam)8stm ama of Cyp~snurlted from extenriond fBU)tjn~.Bebm th end dthe Miiperi*od suddm uplift niml mort of Cypn~s above ma Iewl (Robeftm, 1977).

During the Pliocme, a more locrlized uplift af Trwdos wbsidod the

Wmnnang areas (McCallum and 1990). ïha ovemll tactonic mime ftom the Pliocme priod to the psmt is extmiond in nature. The extmsim -15- direction ranges from NNW-SSE to NNE-SSW (Lapieire et al., 1988). North of

Troodos nomal faulting produced half-grabens, ruch as the Ovgos feult, rewlted

from the extensional tectonic regime. Follwing the faulting, the Ovgos graben

filled with 700 m of ophiolite derived dastiu. The Kymia mgenorth of the Ovgos

fault remains a law landmass during the Pliocene (Robertson, 1990).

1.8 Pleistocens

The Pleistocene hosted the last drastic uplift. For the first time, all three

tedonic terrains were uplifted as one unit. Even though the uplift was regional,

extending some 250 km offshore eastward, the Mount Olympus area was uplifted

more dramatically than anywhere else. This localized uplift is evident by the radial

pattern of alluvial fans around Mount Troodos (Roberlson, 1990).

The mechanism which could produor such a drastic localbd uplR ir stiII

debated. A popular mode1 suggests underthrusting of a microcontinent or

. seamount accompanied by serpentinite diapirism and upward movement of other

fluids emanating from the domigoing slab. Underthnisting would also have

readivated the TlOOdos-Kytenia boundary nsulting in compmrtion and uplift of the

Kyrenia range to its present elevation (Robertson, 1990).

1.8 Rocont

Presently the plate tectonic configuration around Cyprus has'the Cypreen

ke mningin an approximately east-west diredl*onsouth of Cyprus. Tha Cyprean

-1 7-

Afiican plate, it is suggested that the Eratosaiene seamount may collide with

Cyprus in the Mure (Kernpler and Ben-Avraham, 1987).

1.l O Futurs Tsctonics

The presenci, of aie Eratosthene seamount signifies Muretectonic instability for the Eastern Meditemean. Figure 1-1O illustrates two possible sanarios. In

(a), collision of the Eratostheno seamount with Cypu teminates the northward subduction and initiates a southward subduction where the Levant platforni would override (thrust over) the area norai of it. The second scenarïo (b) again results in a reversal of polarity of the subduction zone. However, subduction in this case would be initiated dong the North Aftican passive continental margin and the oceanic Levant platlwm would be rubducted beneath Africa (Kdmpler and Ben-

Avraham, 1987).

On a larger scale, nomof Cypius then, is located a tectonic block called the

îbatolian Block. Similarly to the microplate rotation of the Late Cretaceous, the

Anatolian Mo& is presently undergoing antidodwdse rotaüon and will continue into the Mure (Figure 18). The northwerd motion of the Ambian plate (to the souhast of the block) and the dextral movement of the Anatolian fauk (to th8 norai of the block) am the driving tec2onic mechanism of th. blodc rotation (Rotsein, 1984).

Therefore as long as these settings exist, antidockwjse rotation of the Anatolian

61- and conreqwntly of Cyprus, mldcmtinue.

-19- Chrpter 2- Review of putrofabrics and theIr nlationship to $train and bcbnlc klnemrtlo

The purpore of this chsptw is to Mdy wlline the various types of pebaakiclthdmeykmintholiddainbIibore(ory,aMhowthem fskicr am be nMbd to the theprindp.1 dirscücnr d min. Unfortunately, Ume am limitations to mventiond peWBkiC nelysis whm the purpose of the research is strain analysir. If eiüw the outcmp, hand qmcim or aiin section doets not exhibit observable min msrkm, stnin analysis is not passible.

Therefm, ansmitable for rtnin studiar wldk dictatd by the availability of markers auch as foorls, piIlam, pillw wlvagm, pebbks, sand dikes ac..

Momover,~~strahdrodacinnotbenrlywd.~~putdthis -20- define the megascqic ad miaolcopic study of rodc fabfic as a whde in its dation to the genesb dthe rodc Cowqmdy, pamlskic undyris ir ciwd out both m th8 field (megascopk) anâ the Iakxatary (microsapic). A fabric inclucks stnidures, textures and pfnsd orientations and1 mon, generelly, preferred orknteüon disbikrtions of mimlIatüces or grain hapes. These can conbol pattern of the extemal shape of tha rodc, for example its ability to rplit almg the rchistority or pencilcleavage limationr, as wll as the pattern of the interna1 elements. At th. grain levsl A ckraikr the pmdw -1 rprco lattice orientation diWkRion. VUhm r fabric ir repeated at a givm =le, a pattern is produad. îf the feature ir only abuwved once, it does not contribute to the fabric (Le. non- pmetmüve) (Hobbs et al., 1976). If the featum is obmed repeatedly it is called p.netfative anâ conrütutes a fOkiC. The sale 01 which one malces the obrenmtion will al#, didate wbthf or not a frkic is obmwed. Obviout~ly,

-22- Thordom the dislocation lim does not have to ôe wmtmimd itself to one rlip plane. A dislocation lins andimb to the next dislocation plam cruring the removal of an extra haIf plane of atms. lhe resuit d a dislocation dimb on the ayrtel is en ext8nsjOn or a shortening ml (pewpdiaik) to the extra haIf plane of the didocaticm (Nidm and Poirier, 1976). The w#king out d dislocations to the eôge of uystals, is an impoctnt mechaniun of their ching. in shap. New dislocations under plastic deformafion am bred by Fmnk-Remâ Sources (Nidas and Poirier, 1976).

Types d hniodirnensionsl W8ds indude sWngfaults, didocation wallr , grain bounderies and interface8 (Nicder and Poirier, 1976). All these involve a relative displacenmt of cryrtsl Iattiœ across a givrn plane. 21.2 PrafdCry,Wlognphlc on

PMmâcrystal- oWWcm (P.c.o.) my devebp a fabric by means of- rmchanim. These mechaniuns chpend prim*ipeon ttm tempetrature or strain rate of Wmtim. At low temperature8 or high min rate, dynamic mrysWliution is amaJt, ümwbm p.c.0. may &wIq due to rotation of inquant grains or di- within pin8cruring grain rotiaon, or plirtiarkb flaw dw to i- i- motion (Bocrsidei~,1981). Und« high tmpamt~ribor law strain rate conditions, whm mrydillizatii is eusior, the myrtillization pmœu will be assdateâ with th. dewlopmd of p.c.o. (Hom et a,1976).

21.a P.C. O. B Y SUP AND RûTATKMl

Thr dapnlknd œbWon vvhrn cfy8tallognphic rlip is the I Figun 2-1 me deve~opnenîof a pmremâ aysEsllognphic orientation by slip ori r cysiallognp)irc pkns BD uid consquent rotation of a lattice. Sm# tmâ for exphnation. (Modified from Hobbs et a/., 1918) only active mechanism is illustrated in Figure 2-1. The hypotheücal isolated grain is being shortened homogeneawly parallel to the A diredion and contains only one slippage plane parallel to the diagonal BD. Given that slip is the only mechanism of defonnation, the distance between BO or any grain dimension paralkl to the slip direction will remain constant during defonnation. Futhennore, a projection nmal to the slip plane will remain normal throughout defornation. Increasing degrees d deformation will rotate the projection nmalto the slip plane towards the shortening direction. We can transpose the concept of Figure 2-1 onto a quartz ml,when the plane BO represents the basal slip plane of a quartz grstal and the ml.the crystal -S. This explains the cornmon observation that quartz claxes am sub perpendicular to grain shape shistosity.

Realistically, grains within a rock are mt irolated. Therefore, in f# ductile behaviour to ocair, the grain boundaries must remain in constant contact or the rock will fail in a MttIe monnef (Homet d.,1976), or Wer iiaergerüde slip by psrticulate flow (Bonridaile, 1981). The von Mises condition states that if Cve -24- indepandent slip systemr dperate within each grain, üw rock mycontinwnidy

rtmin homogcw~aurly,meintainhg grain contid instead of bdiwing in a kittle

manrier, or dimggregating. Two slip systms are mid to be independent if the

shape chmue produad by rhrdong ori8 rystem cminot k pmduced by sbar

aknq the otk. The tmck is ieferred to Pattemon (1989) for a dbteiled dimssion

of ais von Misas condition. Unfortunatdy, few m@r rodc fming silicate8 do not

satisfy ths Von Mises criterion (Nicder and Poirier, 1976).

At hmtemperaturer crou slip of rcnnnr dirlociüorir, themally pdivateâ

dimb of edge dislocations (dirardearlier in section 2.1 -1) and diffusion miy

contribute to the devdopmcwit oipr&md ohmhüms. Un- these conditions the

requirement of five independent slip systern is modired by 8 dectease in the

=es an a stemogrsphic pmjectb. Diiwwit didri9bution pattms on r

steognphic mion cwi distinguirh k(wmn types of strain history

: defornaticm. fh. intdipn(.tkn of p.c.0. minthe tlw of atmin will k

fui(hrr discusmd ktm h thir chapte?. j cmvdla b:*m.::$$;:y z-- -7: 1 -- ,...... 1.1 1.1 ...... independent

1974; Hay and Evans, 1987). 0ththn nucldon, ümm u, r wick mgs d -26- mechanisms associated with recrystallization. These mechanism can k, relatedto

Woprocesses: grain boundary migrationand formation dnew grain boundaiy. The hoprocesses define three major types dmechanisms, which can be subsequently subdivided into three types of recrystallization mechanisms: rotation, migration, and a general recrystallization mechanisrn cnhich combines both rotation and migration. The subdivision of the types of mechanism charaderizes whether the transformation is continuous or discontinuous (Drury and Urai, 1990).

The process of grain boundary migration involves the transfer of material across Vie bomdary and only ocairs when diffusion rates are signifiant. CoMe creep and Nabarro-Herring aeep am mechanisms of ditlusion ocarrring along grain boundaries at high temperatures (T- = 4.6; Burton (1977) as reported by

McClay, 1977) and along lattices a slightly higher temperature (Tm = -0.9;

McClay, 1977) , respectively. At lower temperaturer, the transport of rnatter along gnin boundaries in a liquid film describes the pmssof pressure solution, which can be beated similarly to Coble aeep (Poirier, 1985). Pressure solution will be discussed in greater details in a later section.

The driving force of grain boundaiy migration can kto reduce stwd energy

(energy asrocibetedwith dislocatiks, point defects...), or chernical free emgy (Urai et al*, 1986). The formation of nw grain boundarier cm ocair either by plogresrive misorientation of a rtationary subgrain boundary or by migretion of a wbgrain boundery through an ama of cumulative lattiœ rotation (Dniry and Umi,

1990). The mechonim types are fi~fthersubdividd when the dogme dcontinuurn of the proces8 imrolved is assessed with mspect to time dufing static

reuyitaliization und strain during dynamic maystallization.

The madmim droblion mrysbllization primwily involver the processes

offomath d i#w Mgh mgk gmin boundary by either rotation of subgreins or by

wb-boundary migmtion (Drury and Urai, 1990). Rotational recrystallizatim

strsin at a grain-=le leva1 CHI ôe mlated to the failure to ritisfy the von Mima

criterion (i.8. not emugh slip ryrtrmr).

bowidsry migration. Unckr low nomiolizeâ stress or high temperature, aie

migration recrystallization is contimiow and no new grain or new grain bounduy

devdop (Dwy md Uni, 1990). Di- grain bomdary migration hm been

obsind. Hawever, in .II cases it is aswciatd with the procr,sr d famation of

combine boai gmin bwndmy migration and new gmin boundwy formation

piocesses for the tmWOrrmtjOn d mi~~ums.Numerou8 difhwt

: pooribilitim d the pmœmes. -28-

of the pmfwed aystallognphic orientation. The thme sbp~am as folloW8:

1- How do the processes of grain boummignüon adnew grain

baund#y formation combine to tmnsfom rnimstNdufes?

2- 1the tnnsformation involves rn gmh developmnt, ir it continuour w discontinuou?

3- if tfm transformation involves grain boundary migration, is it continuas

or disumtinuour, and what ir the physiml date d the bounâary (i.a

premnœ of fiuid-film auirting migration)?

Pressure solution is a pmœw âddliom the rodc ddamation medlanism of diffusive meu tronrfw, which involves shap msof individual grains by grain boundrry diffusion ruisted by îhe pmmnœ of 8 fluid film at the grain badwies (RW,1Q?6). RU#w (1 976) fWhw desuiôed pressure rduüon 8s the wmmation d üww basic procsssas:

1- trandw d mateda1 fmm the rdid phase into a solution prewmably

fming the intagmnulufluid film; of crystal growth, f the transported matefial stayr with the syaam, will be Iocatcbd almg the grain boundary normal to minimum compressive stress or the maximum tensile stress.

Coble wep and Naôawo-HSng cmep, as intmduœd in th pmviws

rdiilion, Cobk cmpad N-ng to minrates and grain rize for the minmals qusrtt and cilcite at ternpmûm of 2W°C and 350°C anâ r pmmm of 100 bur. Gsologically signi(icant strain rates able 10 pmducu natuml dudile stmctums mnges betwwn IV and 10'' sec1 (Pria, 1975). tt i8 d.wly -30-

chmmtmted that parure solution unôer low tempefatum deformation condition

ir the dominsting deformationil procorn, mors 80 in quwb than calcite, whefe

Coble crwp et tempemtums d 350°C (1- limit of greenschiat facies

metamphian) may acar at similar minrates and in rocks of dmilar grain size. The low stnin rater quirad for pmâucing pmuum solution somwhat

inhibit th0 dliciency of studying ~*mentallyte- multing from premm

solution. Hawever, then is much obac~vableevidenœ in the field for pssum solution as a Wngdefmatiml pmœss. Ramsay (1967) lists the rnost important ptmfmma Uluibrting pmu~wkrtion as followr: be seen in Chaptw 7, Figuras 7-3, 4, 6, and -7. The photogrsph d mple

FIS284 in Fii73 ddyillwtmtes a tectnic stylolite cross-cutting a bedding stylolite. Stylolites becam zones of accumulation, whm mmlyquartz phyllosiliCBfes and days are amcmtmted residues, giving the stylolite a da&w color.

21.3 FdIrMons nd Ck.vrgas

8omadaik et al. (1982) mcognize hnro definitions for foliations. The tint

vaneRiori. Secmdîy Mimay rko ôe ddkied as a penetrative pmferred aystal

(PCO) or dimensiorial (P Dû) o&tntation in a thin section, hand sample or outaop.

Tbcimage darock miy, in the majority of ~MS,be sepmted into hno

gnin (p.d.0. I sdikt~$@dmvrg~ 8ridlOf p.c.0.) IT 2 4m°C

the various types of deavqar and foliation to the debmatirn mechanian and

Slaty deavage typicslly ômmbp unôw low gnck metniorphism (Ww to

Table 24, in fine gminetd (< 0.5 mm) mdo (Borredsile et al., 1982). Sldy

- dwvsg. eamol k seen with the niksd w;huwever a rlata typically deaves into tabular thin plates. Micmmpimlly, rlaty cleavage appws as diwoidal to

lenticulr -tes of quwtz , bM8pu nd mia or chIofite sumnôod by

Phyllitic deavage and rchirlority am bmd in a similar way to slaty a/., 1982).

T)w~dQibCILI(etiorid.rv~isavidmœofa~phaamr latw phase of Monnation. CmuIation deavage de~opswhm an almdy foliated rock (i.e. a rock üut hm eithri a slaty clemvage, phylliüc cleavage, schistosity or an eailier muletion deavage) is f0IW (crcwiulated) on a miQdecale. The axial arfecl, al the mkfddds or muionam wbparalbl to ttm crwiulBiti*ondeavage. Typicaliy, the dmvogo domciin is very rich in mica whL the interveriing miQolithons, pmmwk'~th. micmfold hingo, ps8rvas the pmexisting foliation and commly hort quark and kldrpu.

Crenulatim deavage my k discmte or -1. Diswte mulation deavage appeam as naw miabfich kymrkuptly truntpüng the original foliation psefved in the quartz and fe#rpw ridi zones. Dimte crenulation

fiom the dirrdveâ matafial nmowd due to pmwm solution. Compwrtivdy, f

-35- During middle to high grade metamorphism, foliation is habitually expressed through gneissic structures (banding and layering). The banding or layering cm appear as differentiation in rnineralogy, colour andor texture. Commonly, the

differentiation results fram one of reuystallization, mechanical shearing and

dissolution mechanism. The most encountered type of banding takes the fmof

altemating mafic and felsic layen.

2.1 .36 FOUADON IN SEDlMENTARY ROCKS

Sdimentary rocks may develop textures related to the time of rock formation, such as bedding stylolites, or to a later deformational event, such as tedonic stylolites. Very Menthese are superimposed. These can be disthguished

in Vie field by careful observation, hmverduring magnetic fabric analysis special censiderations must be taken to effectively separate the primary (bedding) and secondary (tectonic) fabric components.

Bedding fabtics are usually observed in sedimentary rocks. Bedding is an

inherent fabric primarily because d the crystallagraphic shape of micas and becauw cwen less anisotmpic minerals inevitably have longer dimensions that preferentially lies flat. Consequently, inhercmt fabrics are not indicative of tectonics and tedonic strain csnnot be dediuced fram them.

Stylolitic cleavage produces a planar fabric due to the prefefential amangement of stylolites. Edbm stylolitic deavage is usdto suggest the principal

of min,we must distinguish ôetween diagemtic styklites and tectmic styîolites. Diagrnetic stylolitet are fmed due to gravitational loading anâ compaction. Furthemore, they are generally orientated paralle1 to subgarallel with bedding and cannol be used for strain analysis. On the other hand, tedonic stylolites form under tectonic stress and generally align perpendicular to the maximum compression or shortening direction (Ramsay and Huber, 1983). Alvarez et al. (1 978) pmposed a dasrrification schemo (see Table 2-2) in order ta dewibe~ the type of intensity of the stylolitic deavage and relate it to the amount of shortening represented by such an intensity. The intensity increases as the density of stylolites deavage increases (i.8. as the distance between deavage planes decreases).

This classificationscheme must be bereferred to with precaution. The @stance between stylolites (deavage planes) cannot indicate the amount of shortening the fock has undergone. Detemiining the amount of rock disolved mnrld ôe a qualitative indicator af shortening. The simple observation of a stylolitic deavage is a massutance that the rock in question has most likely experienced shoitening.

21.3~ FOUA~ONSRELAED to FAULTZONES

Two types of foliaüonr am rouüwly obmed within fault or shear zones. These were given aie tenof C-sufaces and S-surfaœs by Berthe et a/. (19779) and

together they fom an S-C fabric. The C-surlaces are shear planes of relative movement oriented parallel to the shear zone walls. S-sutfaces are planes of

flattening oriented initially at a 45' angle to the C-surfaces if there is porfect simple

shear (Ramsay, 1967). The angle wwld be les$ if th8 shear was not a perfed

simple shear. A non-simple shear zone results from a noncoaxial $train (as in

prfed simple shear) combined with a coaxial strain component This phenornemm

is also called a transpressive shear zone indicating that the area has been sheared

and compressed syntectonically. The compressive component produces an initial

angb of separation less than 45' between S- and C- surfaces in a nomsimple

shear zone.

Progressive shearing of the C-surfaces, rotates the S-surfaces as to reduœ

their angle with the C-surfaces. S-surfaces exîend between hmC-surfaces which

sandwich the S-surfaces. SC fabric con develop and k observed in a

hand-men, an outcrop or even at a regional scale where the C- and S-surfaces

can be traceâ for many kilometres. S-C fabrics anednmiely useM in regional

kinematic analysis as the relationship bewnthe two surfaces indicatm whether

the shear zone has a dexhl or sihistral sensa of motion.

21.4 Unertions

Lineations, likfoliations, are fie rwuk d strsin and myk observed in al1

rodctypet (i.0. metamorphic, seâimentary and igneous). A lineation may kfamd 1 136- lineationr, mineral limationo, grain shap lineations and crsnuldion lineations.

0th~lems commtypes indude slicIcm8ides 8triations.

21.4~ NON PENETRATNE UNEA-

Intersedm linedons wb the nrult d the intersedion of two planes. These two planes cm be two foliation planes, deavage plme and bedding plans, the cdmb(*natiOrissrr, endlem. These afe IlOn-P(MB1Tstivo fsbnc f88tures and am not relata dimdy to minar stma. The importint aspect for intwpfetations hourevw ir knowing wbt two types of plam am praducing the intersection limation.

Lineations indicating a relative movmmt are restrided to the surface of a phand do not pmbate the müm Sudi Iineation ars slickenride striations and goovr#. These can k obmed on fauit aufaces repremting the dindion of relative movement. Slickemides mry al- ocar on bedding Mfimsd folds formad by fie-l slip where individuil lrym glide on top of one amth.

that emenœd two (or more) epimdes of tedanic strain, causing S, to be mlated. \Miai kdwrg in the plem of the cmnulation cleavage, th. lineath is -39-

stress directions. This type of lineation is very common in metamorphic rocks. The

alignment of minerals fonn a preferred crystallographic orientation (p.c.0.) and the

alignment of the grains fotm a prefemd dimensional orientation (p.d.0.). As

pnrviously discussed, the preferred orientation is achieved by either

reaystalliration or minera! rotation. Commonly mineral lineation, in metamophic

rock, is found withnr oie foliation plane and together help define the strein ellipsoid

which will be diswssed later in this chapter.

2.2 Straln and Kinemrtlc Anrlyris

Kinernatic analysis refers to how rocks moved during their formation and

subsequent deformation, on a regional scale. Defornation d a rock is manifestai

through physical changes (strain) due to applied forces acting across or along an

area (stress). Strain analysis of smaller rtructures disperse amss a region leads

into the possible interpretations of kinernatic tectonics.

2.2.1 Theory of Stnln Analpis

'DefomWon' encompasses translation, rigid body rotation, dilation and

strain. At the outwp level, ws angenmlly concemsd with min. It is defined

as a change in shape d a body kulting from an applied sûess field. We can

schematically represent strain with r minellipsoid composed of thme mutually

perpendiwlat principal axes: X (maximum axis), Y (intermeâiate axis) and Z

, (minimum &s). These changes cui also be aocompanieâ by successiv~ incmmmts of min, applied in diflemt diredl'ons. in which case the minir raid 40- to be nonîoudal. îf the minirwmmts am 8dded in th same dimctimr, the

is coaxial. A nonIDspdJ min rignifh thut the principal minaxer change

on*emtatimwith mpedto the matefial thioughout the rb.in histoiy. An exampk

of rm-coWal strsin d vwy malmstrided conditions, is simple hear (Figum

25). A coaxial WnMins a constant ori*mtationd b mncil strain axes with

respect to the material. Such conditions define pufe rshear (Fi- 25). Most

'shsaM mcb actually msuk from trwispfession, a combination of shear strain

and pure sheaf.

îf stmin dhca a body unifomily, th. body is tmmgmmusly -id and consequently within the body straight lines will nmrin $Wight and psralkl liftes main paraIlel. If min vwim thmghout a body, the body is raid to k al- heterogeneously rtnined and msqrmitly straight lin88 becme curved and pralkl lim bewme norrpsnlkd. For pupasd rtnin analysir homgmwurly

bodiime W.Usmlly a body will be hettmgammusly stroined on e large scak but may k Wem doinnr into mallw homogeneourly rtrained domains for aie application of shin analysis techniques.

Thme are hwo mxhmbw type8 d min. Axially symmc extension is charaderird by a unifm extension dong tho X axis and wual shalening in dl diredians ppmûiailar to the X taxis (X > Y = 2). Tbnwlting strain ellipooid has a plate hapa (rod-like) prodming L48donitas. Mlly syrnmetrical shtening will have unifm thortening dong the Z ais and eqml extension in al1 directions peqmdicular to th Z mis (X = Y > Z) producing S- tedonites. In this case, the stnin dlipooid hsr an oblate shap (disdike). The intemiediate case ir pleiw *in, whethe Y romains unchartgeâ, üm X-ud*r is extended and the Z axis i8 hoftwd (X > Y = 1 Z and XP( = YIZ).

Tmditiondly, -8 minis gnphically mpmsented on a Flinn diagnm

(Figure 24) fw a rtNdural geologirt. On the diagrm. the ydsanâ x-axh are

Mneâ by Flinn'r nd b puuintm: 42- syrmebiml tlatteming is calkd the fidd dllattming strain. Th8 Flinn diagnm al80 relates to the shap of the eliproid, which ir Mnedby the pammeter k :

The greater the distance betW88CI a plotted point and the Mgin of the FIinn diagram, the pater the degreo d ecœnthdty of the msponding dliproid.

Hawevi~the hlinek plat is suprhlor bolh stwdural geology and magmtic fakic studies. lt expands the scale for weak stmins, buseof its logafithmic rcrle.

Moreover, the shpe parametew (Tl) is repremmted by rn and it is also syrnmetrical( +1 to -1), whereas Flinn's rhrpe paramter (8-1 )/(ô-1) nqpsfmm O to -.

Finalu, w lhauld ride that rtnin dwebpa in immmts. Wha a geologist observes and measures in the field ir a finb minthrt nrulteâ flmm the abject ddomation is the proces8 Mingftom an initial to r final aate of fin% min. / --(hPMng *T-

B-YK

Figun 24 me FWnn Oiagmm as a gmphical methoâ for prss4ntlng the shape and ûqm of anisotropy of an ellipsoid. For compatison, a Jelinek plot & illusû'ated iii FiQum3-2. direction of maximum extension; hence proof of progressive noncoa8alstrain.

This phenornenon may rlso be obsenmd miciorcopically in pnwsure rhedam.

A conduding remak on the thewy of stnin bringr attention b the relationship betw8en minand -8s. Stmin resultr fiom an applid stress field thecefore it is masonable to want to quantify this mlationdrip. For a cooUal min history, w can correlate the thme pfim'palstrsin axes with th8 Wee principal stress axes whem Z is paraIlel to a, (meximurn stress sxes), Y is pamIW to u2

(intermediate stress axis), and X is paralW to u3 (minimum stfess mis). For a non- Daimiining ü"m orientation of the principal stnin axes is r981~~18blyrccw if 11# srse miw obecnnoon Wôib a kliationI that is a planu flattening fahic (S- tedonites). S-lectmites, that are principal plam stnictwes, lia in the XY plam of th. -n dlipid mdthombre the Zdsorientation will k prpendiailu to the foliation or W plane. W a lineation ir prrnt in the plane of foliation, th8n the X- axis orientation is ddined by the olongated or stmtched dirudion of the limaticm.

Rodu which exhibit pavasive foliations (Sswfws) and linestions are calleâ L-S tedonites. mingon whith aspect of tfm fabric dominatas, the tedonite may k d.rrM u m L-tectonite, S-tectmite or an LS-taonite. 145-

However, in order to quantify the amount of $train, the extension (of shortmino) along eadi stmin axis must be measured. This requires the use of strain marken. Strain marken an, objedr that have been deformed but their original shape is kliown. Such objects include initially spherical abjects (ooids, redudion spots, vesiwles) conglomerates, pebbles, bilaterally symrnetfical fossilr, boudinaged layers and fold sets (Ramsay and Huber, 1983;~.197).

Measuing aie amount of strain can be achieveâ by considering the change in length of a line, change in angle between (wo lines and the change in volume.

The variation in length of a line can be rneasured and defined by the follahg

Wee parameten:

I Quadmtic elongaîbn ; A = = (1 + e)2 'a

Th. stretdi parameter (Means, 1976) is uS8hll when dealing with lwge scak austal deformation. The extension corretponds to an elmgation of ha mis when th8 oôtained value is positive, whemas a negative value indicetes a shorlening of the lais. ln tennr of extension, th. principal minaxes X, Y, and Zconssponû to (1

+ eJ,(1 + a&, and (1 + q)mspectively. Situations whem shear b rpFirnnt, shear min, y (gprnma), may k measumd and is definecl by the following quation: 46-

Eqn. 2-8

1 vvhere yi (pi) is the angular defidion of an original right angle. i I Very comonly straining is ampanied by a certain amwnt of volume

change. More often îhan not, the volume change is e volume loss (e.g. pressure

solution). If volume change is not accounted for Men detemining the amount d

minthe estimates will be misleading. The volume change, A (delta), is d8fined as:

where V, is the initial volume and V the obsewed volume. Howaver the change of

volume may be directly related to the principal strain axes and to the extension

suffered by each of the principal strain axes.

1 + A = (1 + eJ(1 + e,)(l + e,) Eqn. 24

The measurement of these parameten requim strain markers. Without uny

strain marken it becornes very dillicult to asress the $train state in the hld. We

mil now examine how strain may ba detemked from a variety of types of rtrain markers.

Elliptical objects that may have becm initially spherical cm k analyred by

imn redudion spots in metarnoiphic rocks and vesicules in volcanic rocks. The Rnl

48-

makem, for rtrain amlysis mquims th8 use of a diffmt graphicrl mahod. This

altemate mical mdhd&&es into accomt the final dlipticsl rhape obwwed in

the field as king a combination of ths pebbles original elliptical shape and the tedonic $train. ?lm graph plots the obmed stfain ratio (R), that is, the ratio

betwwn th. short sJOI anâ kng of th. pebMe, against the angle the long as

makm mth an arbitrary refere~~~~lino. The plotted data will eiüw yield a peaked didrikrüon indicaüw that R(strain) * R(initial) or a par-like distribution, in which case R(Wain) R(iniü91). The & and &, ratios unbe quiddy datennined fram a par-like distribution. The maxjmum and minimum ratios def~ne:

Eqn. 2-8

Eqn. 2-10 wtnm % is the original VIX reüo and R, is Ih. toctonic minYIX Mo. By dividing

equation 2-9 by equation 2-10 wa abtrin:

Eqn. 2-11

dimenrional mâ rlro for cases d initial norrurifomi putide rhip8 anâ non- 49- uniform particle orientation.

A more versatile method of analysing drain ir the selvage rim meaiod for certain closed loop markers with rims. This method can be usdon numerour type of strain markers: vesicles, lapilli, redudion spots, weathered pebbles, and even pillow lavas, which are a non-sphericai object. The method assumes that aie rims which foms on the outside of these objects are uniform. The ratio d the thickest rim width and the thinnest rirn widlh is equivalent to the strain ratio (Borradaile,

1987). Furthemiore, the mexi'mum extension diredion would be parallei to the direction of the thickness rim width. Som caution is needed when using this method with pillow lavas. \Mule pod-shaped pillow lavas will give strain ratios with

20% acwracy, the selvage rirn method predisd on tubular (tube-like) pillow lavas exposed on e (wo-dimensional outcrop surfaœ is unlikely to be a suitable candidate for strain analysis (Borradaile, 1985).

This outlines a few simple methods which can quantify the amount d strain a certain rock sMered by analysing field observable strain markers. However stmin markers annot very cornmon and consequently only the of $min thrwgh LSfabrics can k infemed. îf an outcrop is baiof strain marken and does not display any foliation or lineation, il was assumd the cvee wsr undefornieci. H0w8verI with the use of magnetic fakits it is possible to obbin the orientation of the principal strain axer even if the obmed outaop is banen of drain msrkers and oppan undefonnrd. 3.1 Magintlc FMa

The analysis of magnetic fabrics intmduces an extra dimension to the

magnetic minemlogy d th8 rock as wll w the magnetic properties of al1 typas of

minerals. Thmam two types uf magnatic fabric that can be investigated. The

susceptibility anirotropy define8 a faMc where the mirnwslogy of the whole rock

contributes; and the rmmanidotropy defines a fabric to which only

f&mmgnetic miwalr contribute. In ôoth cases the fabric msy be charactmomd

by an ellipsoid deaibing the shape and the orientation of the anisotmpy tenror.

In the bd sedion of thir mer, we will invedigate how cmventionsl petrofabrics

and magnetic fakics can k n(dd to str8in and tectonic kinemaücs.

Before diraissing how the anisotropy of various magmtic fakics tan k

analysd, we will rariew th fudmmtalr of mgnatiwn in the nalmr of

l All material have a certoin msgnet'iion because of the electms rotating

arwnd their spin mûs nd wound a nucleus. ln the pn,amœ d an applied ferromagnetic, antifenomagnetic or ferrimagnetic depending on how they mspond

Men a mgnetic field is applied and then subsequently removed (Figure 3-1).

A diamagnetic material in the pmsence of a magnetic field, Mll acquh a

small induced magnetization in the opposite direction to the applied field. Onœ the

magnetic field is removed, the diamagnetic material loses the induced

magnetization. All materials read diamagnetically, but a material dass9ed as

diamagnetic, has no other type of magnetic response because its electfon shells

are complete and thedore the atoms do not possess a magnetic moment (Butler,

1992). Pure quartz, calcite and feldspar ara examples of diamagnetic minerals and

are charedefizd by having negative magnetic susceptibilities, in the order of -101

SI vol. (Hrouda, 1966; Voight and Kinoshita, 1907; and Borradaile et el., 1987 as

reported by Bonadaile, 1988), which are indepandent of temperatun. However,

thew minerals are mmly pur@ as they commonly contain non-diamagnetic

inclusions.

Paramagnetic materialr will acquire an induced magneüz8tion paralkl to the

applied magnetic field. Theif atmdo possess a magnetic moment, but do nol

interad with adjacent atornic moments. However, like diamagnetic msponses,

: Paramagnetic material have rnagnetization equal to zero when the rpplied field ir

removed me atomic moments are randomly distributed causing th8 msuitant

: moment to equal zero. Most iron-baring carbonates and rilicetes am

: paramagnetic. The magnetic susœptibility is positive and generally ranges betweeri

le b IV SI vol., for cammon paramagnetic rock fming minerab (Dunlop anâ Figun 3-1 Diflemt types of magnetiulion. Thbold amto the kft of the kfhnd aolumn indm8 the direction of the rppîkd fkld. The ancm to the MMof the boxes inâicrta the mmand relative magnitude of rnagnuüzatio~~whrn i magnetic fieid is ipplbd (inducrd magnetizaüon) anâ thon mnoveâ (remanont mignaitsiuon). Refer to th. text for fu- expianation. (Modlfid Wm Twllng and Hmudr, 1993)

. ozdemir, 1997). Furthemore, paramagnetic minerals have susceptibilitks which

. depend on temperature; as temperature inmases, paramagnetic wsceptibility

decreases according to the Curie law d paramagnetic susœptibility (Butler, 1992).

i where x is the paramagnetic uisceptibility, J, magnetization, H, the applied field,

I N, the atomic moments per unit volume of the paramagnetic solid, M, magneüc moment, k, Boltzmann's constant, and T, the temperature.

The induced magnetizationof both diamagnetic and paremagnetic materials can be diredly related to the strength of the applied magnetic field. The relationship is linear and can be expresseci as:

M=KH Eqn. 3-2 whem M is the induced magnetization measuted in Alm, H is the strength d the applieû magnetic field in Nm and K is the rusceptibility which is useâ as the constant of proportionality.

Ferromagnetism an be defîned in hm ways. The first describes ferromagnetism in the general sense (i.e. sensu /ato),charadetized by a nmanent magnetization ( the ability of retaining a mangetization long aftw the removal of the extemal field), fhe umbrella term can k hrrthet divided into femagnetism, the specMc tenn (i.e. sensu stnbto), antifemmagnetiam and ferrimagnetism. hmagnetim (S./*) charaderizes dl materials that have strongly interading neighboring etomic magnetic moments. Fvthemore, ferromagnetic (SA)material can retain a magnetkation long &er the applid magnetic field is removedwith the acapüon d petfed antifammagnetic material. HOW~VW,the spin moments in an antifemmagnetic materiel are commonly canted resulting in retention d wne magnetization after the applkd field is removed. mese materislt can acquire a magnetization up to a maximum, called saturation magnetization. The saturation magnetization decnases with incnasing temperature until the satufatin -54- magnetization reaches zero. The comsponding temperature is termed the Curie temperature, a unique property for each femwnagnetic (S.).) material. Above their

Curie ternperatures, fenwnagnetic (S. 1.) minerals khave paramagnetically. if temperatures wen, to fall badc below the Curie temperature, the mineral would al that point regain its ferromagnetic (s.l.)propetdes-

The interadion between adjacent atomic magnetic moments can take the fom of one of two types of quantum-m&anical coupling forces: exchange or superexchange coupling forces (Tarling and Hrouda, 1993). Exchange force is common in the metallic transition dements (iron, nickel, cobalt and some of their compounds) and consist direct coupling with adjacent electron spins ofatoms. This results in having all magnetic vedors lying in the same diredion, charaderistic of ferromagnetim (S.S.). Magnetic moments of atoms within a single domain are al1 parallel.

More appropdately for compounds of Fe, Ni, T, etc is superexchange coupling, in which the coupling is done via an intmdiate atom. This is common in more cornplex compounds such as oxides, when the oxygen atoms (anion) will ad as a coupling bridge beniveen hno cations. Superexchange cwpling forces nsult in bving domains of atomic magnetic moments with opposing magnetic diredim. That is atomic magnetic moments within a Iayer are still parallel but betw8en layen them ir an snüparallelism. Ithemagneüzaüon is of equal stiength in rntigerellel layers th8 net magnaiun is zcwo and the material-is raid to k antifmagnetic. #the magnetization is not equal in antiparallel loyers, a net magnetic direction will iesult and the material is calld ferrimagnetic.

There ara numemus ferromagnetic (S.!.) minerals and the Fe-Ti oxides

account for the majority of them by far. OLher mineel groups or minerals exhibiting

ferromagnetic (S./.) properties include goethite (an iron hydroxide), pyrrhotite and

greigite (iron sulphides), and hydmted im sulphate (resulting most commonly from

the hydration of pyrite and marcasite which am very unstable when exposeci to air).

All these minerals have charaderistically high magnetic suscsptibilities (greater

than paramagnetic minerals) ranging anywhere from 10) SI vol. to 100 SI vol.

(Carnichael, 1982 as reported by Borradaile, 1988). More importantly for

paleomagnetism, they possess magnetic remanence.

3.1.2 Magnetic Anisotropy

The magnetic anisotropy of individus1 parücles depends on two fadon: the

anisotropy of the particles themselves and the degiee of the particles alignment

(Tarling and Hrouda, 1993). The particle anisotropy is composed d a aystalline

and a shape anisotmpy component.

A crystalline anisotmpy arises from lattiœ forces acting on the elecûon spin

configuration dthe particle. Psrücles (aystals) have certain crystallogmphicaxes

or planes in which dedron spin axes will pmfwmtially (mm mdily) align

; thmnselves, and magnetization will k grnatest in thse directions. These an temed easy axes or easy planes.

A shape anisotmpy fmfrom haaligmnt d el- spin axis cfeating

a mdh Md south magnetic pole at opporite points on th. sutface of the grain. The -56- magnetic poles are created by a net magnetization ,Ml which may k an inducd or a remanent magnetization. Internally, a demagnetking field, H,, is antiparallel to M. The magnetostatic energy, E,,,, results hmthe dipde moment (p) and the total intemal magnetic field of the grain. This may be expressed as follows;

Eqn. 34 where y is the extemal field, H, = -NM,and N is the demagnetization factor

(Dunlop and ozdemir, 1997). Grains thet are symmetrical will have poles that duster, enhancing the magnetostatic force of the grain. In non-symmetrical grains, the poles are scattered, weakening the mapnetostatic force of the grain (7arling and

Hrouda, 1993). Different minerals will have partide anisotropy controlled dominantly by their crydalline anisotmpy (e.~.hematite) and othen by theit rhape anisotropy (e.g. magnetite). The shape anisotmpy d ferromagnetic (S./.) grains depends entirely on grain size, as multidomain and single dornain grains behave differently. The susceptibility anirotropy is maxi*mized if the orientation of the uystalline easy axes and the shap long axer of the grain minci*des.

3.1.2~ Suscrmerrn AMWTROQV

The bulk susceptibility anisotmpy measured in a weak magneüc field (si mT) represents the sum of the susaptibility of al1 mimhpresent in the rock runple (diamagnetic, paramagrtetic and Ibnwnegnetic (al.)). HOW~VIKthe pnseme of a certain volume pemntqe of romo mirnwals can dominate the hlk susœpübüity. For example, if magna#o (susœptîbility d -1 û' PSI vol.) h prewnt 1 i in amounts exceeding 0.1 vol% of the total rock, it will , more Men than not,

dominate the bulk susœptibility of the sample. Where fmagnetic (S./*) minerals are absent, paramagnetic minerals (susc~ptibilitieo-1 0' - 1@ vSl vol.) will usually dominate the susœptibility anisotropy over e diamagnetic miricwalr

(suswptibilities of -10' uSI vol.), unless the paramagnetic amtent of the rock is less

than 1 vol%. In this latter case, the diamagnetic minerals will dominate th

susceptibility anisotropy and the rock will have a negative bulk susceptibility.

Measuring the anisotropy d magnetic susceptibility (AMS) in an applied

magnetic field of weak intensity (s 1 mT) yields thet susœptibility (K) in thm

principal orthogonal orientations: k, = maximum susœptibility direction, It, =

intemediate susceptibility direction and k3 = minimum susceptibility direction.

Together the thrw principal susœptibility directions defne the anisotropy d

exist for the analysis dthe AMS ellipsoid. These am listed in TaMe 3-1. Howevw

this extensive list of parameters in reality describes only two properües: th shape

and the degree of anisotmpy of the AMS dlipsoid (Jdinek, 1881). Tfaditionally, it

was suggested that the AMS ellipsoid had four propwtie8 (shap, foliation, lineaüon and degree of animtropy). However, foliation and Iineation am bsically th ml

, d rhape, and rhepe is synonyrnous with anisatropy degree. The analysis of the I 1' AMS dlipsoid anproduce insight for sûain and kinmtic evolution. Cardiil

conriderations am necesaiy for meanînglirl interpretatian and them will k

discuisad later. 3.1 .PB REMANENCEANISOTROPV

A magnetization which iemains aftw the removal of a magnetic field is called a remarient magnetism. This is a property displayed only by ferromagnetic (S./.) substances. Therefore the source of remanence anisotropy is much less variable than that of suscepübility anisotmpy. FurVismore, the key ferromagnetic (S./.) rninerals rnentioned in section 3.1-1 tend to fom under different conditions which translate very often to a monomineralic contribution to aie mgnetic remanence of a rock sample. The identification of the COTlfrjbuting mineral is very important when 1 interpretingthe remanence anisotropy. Not only mineral composition but also grain

' sire and time are important control factors for a rock sample acquiring a remanent

magnetization naturally or in the laboratory.

The concept of a remanent magnetization having a time dependency wm

developed by N6el(1955), and is expressed as

1 T = - exp (- Eqn. 34 C

where T is the relaxation time or the time required for the diredion of magnetization

of a magnetized grain to relax into the diredion of an applied magnetic field. Other

variables are: v, the volume of the grain, Bel the mmivity, J,, the spontaneous

magnetization, K, Boltzmann's constant, T,, the absdub temperature, and C, the

frquency factor estimated at 10' so1(Butler, 1992) or 10' swl(Dunlop and bzdemir,

1997). In a laboratory tetting, wtîich ir at room temperatus, the relaxation time ir

greater then the duration of the experiment, therefwe the temperature rspsents

the blocking temperatun, under cooling conditions, and the unblocking

temperature, under heating conditions, comparable to the duration of the

ercperiment. fhe maximum blocking temperatun, of al1 mmnence is the Curie

temperature discussed earlier. lt is n importMt tool in identming the minefai

contrikiangto the remanence, the nwninenœ is natmlly (NRM) occurring

or produœ in the laboratory. -60- Naturally ocwrring remanent magnetization include principally thermal,

chernical and depositional remanent magnetization. Isothemel remanent

magnetization may ocarr naturally only via a lightning strike. However, remamme

anisotropy studies generally reotrid themselves to the study of remanences

acquired in the laboratory.

The anisotropy of anhysteretic remanent magnetization (AARM) and

anisotropy of isothennal remnant magneüzation (AIRM) are both used extensively for the study of the remanence anisotropy ellipsoid. Understandingnatural remnant

magnetism (NRM) is key when axiduding a paleomagnetic study.

Both anhysteretic remanence magnetism (ARM) and isothemal remanence

magnetism (IRM) are remanences that an fabricated in the laboratory. The

acquisition of ARM in order to study the aniwtmpy requires subjeding smples to

a small direct field (0.1 mT) supsrimposed over a defined window of the altefnating field (usually less than or equal to 100 ml). On the other hand, the acquisition of

IRM subjeds the samples to a strong dired field (usually greoter thon 500 mT

depending on rock type and magnetic mimlogy). VVhen detmining tk AARM or AIRM, the rarnple mu& k completely demagnetized prior to imposing the

magnetic fabric, For aisrwionr rimpleswhem hmatite is the fwmmagmtic (al.) component, AARM and AlRM may not be determincd becausa them is currently no

instrument capable of completely demagnetizing a hematite karing romple.

For studies on sediments, ARM bettermagnetizesth8 fine partider that criy the stable remanence, than IRM, and therefm, ARM gives a Merappdmation of the remanence anisotropy (Jackson, 1991 ).

Similady to AMS, the masurement of the AARM (of AIRAII) in several

directions, yields threo principal directions wtrich correspond to an ellipsoid'r

maximum, intermediate and minimum axes. Again, the anisotropy elliproid is

characterized by L shape (Tj) and degree of anisotropy (Pj) which can owwi

perhaps be related to strein and tectonic kinematics.

3.2 Analyshg SWnliwn Magnetic Fabdcs

The use of magnetic fabrics as a minindicator was first ruggested by

Graham (1954), how8ver propar methods for the analysis wem not developeâ until

the 197Qs. Relating the orientation of the magnetic anisotropy ellipsoid to that d

the minellipsoids is qulstraightfmrd. Generally, the X, Y end Z direction of

principal strain conespond to th8 kq,It, anâ Ic, diredion of tho AMS ellipsoid or aiat

of the AARM or AlRM ellipsoids. This direct reprerentation is commonly

acceptable. Houmer, there are some cases where this relationship cannot k

. assumed.

The fint exception is whm tho AMS fakic do98 not completely erase th

primvy fabric (Borradaile and Henry, 1997). this is a common pmblem in weaWy

strained redimentary rodu where thb fabric acquired dwing deposition is diniait

Secondly, iodu Wich produo inversa anirotmpy will not have principal

orientation corresponâing to the equivalw principal strain oiimtatims (Bonsdrik

and Henry, 1997). Th. best k#m mineral which occisionslly exhibits thir -62- property is single domain (SD) magnetite, but tourmaline and Fwich calcite may also yield inverse fabrics when, the minimum wsœptibility axis is parallel to ha longest crystallographic axîs (Rochette et a/., 1992). Sinœ the anisotropy of mgnetite is mostly controlled by the shap8 d the grain, SD magnetite will have

AMS whmk, is parallel to the long axis of the grain, and k, is perprndicular to the long eus. The detemination of the AARM ellipsoid, will in this case yield a trw representation of the shape fabric d the SD magnetito grains and confimi the presenœ of SD magnetite by exhibiting a fabric which is orthogonal to tb AMS fabric. merrninerals such as tourmaline, carbonates and goethite, can produce an inverse fabric (Rochette et al., 1992).

Third, where the fabric accumulation was non-coaxial, dire relationship

ôetweetn the orientation of the magnetic anisotropy ellipsoid and that of the strain ellipsoid may not be assumed (Borradaik and Henry, 1997). This third exception is self-explanatory. Ouring a noncoaxkl strain history the orientation of the principal strain axes varies, therefore the orientation of tb AMS, AARM or AlRM ellipsoid will not be representative of the of the strain axes oirough the entire stfain history.

Fourth ancl lastly, whrn recrystallization fabricr dominate the pt9ncip.l diredioris of the AMS fabric will reveal the stress directions at the time of recrystalliration. Thesa directions will dilfw hmthe finite principal strain axes, unless the strain history, throughout the recrystallizatimevent, mmained ~narl'al.

Commonly, in metarnorphic rocks, the pcoducb d mcrystallization an, high 43- susceptibility minerals, such as magnetite, pyrrhotite and ilmenite. These later growing phases will commonly use silicate minerals as ternplates complmenting the principal AMS directions but possibly altering, unpredidably, the shape and degree of anisotropy of the susceptibility ellipsoid. Under these conditions, estimating strain magnitudes would be impossible (Borradaile and Henry, 1997).

Even though noncoaxial strain dws not permit the detemination d the orientation of strain, regional kinematics may still be interpreted. Non-coaxial strain means VHKe has been a rotation or shearing of the rock. In metamorphic rocks where minerals have grown at different times; genemlly quark and feldspar fm first, follawed by metamorphic phyllosilicates and lastly the late metamorphic magnetite, pyrrhotite and other remanence carrying minerals. The quartz and feldspar will give rise to schistosity, the phyllosilicate will dominate the AMS fabric and the remanence carrying minerab will pmduco the AARM fabric. The relationship behnieen the orientation of the foliations of these threb fabrics can define the sense of rotation or shear assodated with non~co~alstrain. This type of analysis as a regionel kinematic indicatw has been us& by Borradaik and

Spark (1gQl), Bonadaile and Dehls (1993), Bonadaile et al. (1993a) and Wem and Bonadaile (1996).

In section 3.1.2, il was raid that the magnetic anirdropy elliproid can k decriôd by two properties: the rhrpe Tj and the degme of anisotmpy (Pj)of th. ellipsoid. In that sedion, wr, wre refWng to the AMS rllipsoid; howevr, these hm promes also apply to th8 AARM anû th AlRM rllipaoids. Traditioricilly, the i ! hape of the magnetic ellipsoidwas graphically represented on a Flinndiagram, tho : sarne way the strain ellipsoid was plotted. The Flinn diagram plots a against b (for the strain ellipse) or L against F (for the magnetic enisotmpy ellipse)(sem Figwe 2-

6). lherefore, the Flim diagram Mes to cornlate two parameters which describe

the shape. Hrouda (1982) intrdud a graphical methoâ using the Pj and Tj

parameten of Jelinek (1981 ), which describes the degree of anisotmpy and shapa

of the anisotropy ellipsoid respedively. These two parameten are defined by

Hrouda (1982) by the following equations:

Eqn. 34

Eqn. 36

whem a, = In(4 / kb) for i= 1 to 3 and kb = (k, + ka + k3)/3. The result obtained fom

either d the kb definitions are acceptable as these do not Vary signifcantly for the

usuel range of k (Borradailr, 1991). The Pj parameter plots on the %a-sand

. originates et 1 where Pj = 1 describes a unit sphenr. The degm of anisotropy

inueases as Pj inmases. The y4s reprewnts the shap, fj, of aie anisotiopy

ellipsoid. The axis ranges from -1 to 1 whem Tj values above zero describe an

oblate elliproid and Tj values bekw zero describe a prolate ellipsoid (Figure 3-2).

l Unlike the fairly stiaightformird relationship betW88CI the orientation of the i strain ellipsoid and the magnetic nirotrqy elliproid, mlatingthe magnitude of

: the rnirotmpy elliproidwith the magnituâe d $train ir monatnbiguous. Borradeik

(1W1) shawed that using the Pj paramet81 to dedescri kth the magnetic Zone of oblateness

Zone of prolateness

Figun 3-2 Eumpk of the anatomy of r Jdinek piot. Thir gngNul meü~odis suplor to the Fiinn disgram for plotling Vis shap and dogme of inbotropy (Pj) of the magrieüc faMc ellipsoids. susceptibility anisotropy and sbain elliproids produced the strongest correlation between theif magnitudes. And, in expetifnent91 studies Bomdaile and Mard

(1987,1988) found strong power law agreements. Conelation studies between magnitudes of strain and of magnetic fabric have only investigated the relationship of strsin with AMS (Wood et al., 1976; Rathom, 1980; Bonadaile and Motherhill,

1984; Cogne and Pmd,1988; end many othem).

Conelation between Pj and min have only bwn wcœuful whmthe

shortening was in exœss of 3û96 and leuUwn 70% (Bomdsib anâ

Henry, 1997) (nde: #min is cdculaW by using equ8mn 3-5and subsditutr'ng k,, k, and kaby X, Y and 2). Beyond 3û96 shtming it is assumed ürst th primary fabric is completely overprinted and ôeyond 70% the mineral aligmnt is satuated and Pj has reached a plateau and no longer imaseswith increasing strain.

We must not forget that the uniquenesr of magnetic fabric was to estimate

strain orientation and intensity where minmarkers are absent In ordef to

correlate the AMS magnitude with strain each rample must contain strain marken.

Furthemore the stnin markers should minhomogenmusly at the same scak as

the AMS fabric. Pratically this mems that the strain markers should k

approxirnately of the same sin es a standard AMS sample core (10.55 cm3).

Larger strain marken record strain on a salewhich camot be easily related to th8

scale of a standard AMS core (Borradaile and Henry, 1997); because of aie larger

sale, strain would probaMy heterogeneous. Trying to cordate the magnitude d

AMS with strain seems to limit the potential of magnetic fabric analysis because of

the limited amount of outcrops which satisfy dl these conditions, and the additionai

problems of incomplete overprinting d primery fabric, saturation alignment near

high strain and tome fabrics causeâ by mystalliteüon and pqt strain, which must

- be considered.

Anelysing and comparing th msgnetic foliation, magnetic lineation and tha

degree of aniwtropy of AMS, ARM and IRM on a regional scak cen suggest

: kinematic sœnarios whem strain markers w conventibonalptrdabric analysis awld

not Th. main mason is the univenal property of magnetism. Every minml

possesses a magnetic pmpmty whe- it ir diamgnetic, paramagneüc or

ferromagnetic (S./.). 4.1 IntrocJuction

The magnetic mineralogy of sedimentary rocks, in this study predominantly pelagic chalks and maris and limestone, may be detemined by several methds, however, most present greater limitations than advantages. Any identification method requiringa concentrated separation of the ferromagnetic minerals (ie: Curie temperatures, X-Ray dimaction) is diffiwlt because it is rarely possible to separate enough of the ferramagnetic mineral to perfom, the test Separation by HCI and aœtic ecid is commonly used but also comrnonly digests most, if not al1 of the iron oxides as well as aie carbonates (Dunlop and ~zdernir,1997). the determination of blocûing temperaturer presents the complication of possibly producing hematite during demagnetization at temperatures above 310°C. Further discussion on limitations of other possible mineral identification methods cm k found in

Bonadaile et al. (1993b) and a complet0 mview in Lomie and Heller (1982).

For this study, the magnetic minemlogy was detemined by examining the hystensis loop parameters and the coercivity of remanenœ. This data set pennitr estimation of the ferromagnetic minenlogy and its domain structure, the determination of the susceptibility of the moba and the ferromagnetic content, a8 well as the degm d contribution of each phase to the total susceptibility.

lnsight on the contribution of diamagnetic, paramagnetic and femgnetic phases to the total sucepübility can alro k obtaid from the measured man susceptibility of the anisotropy of magnetic susœptibility (AhilS).

4.2 Hystemsls Loop Purmaten and Coamlvity of Remanence

An altemating gradient brce magnetometer (MiaoMag) was used to

determine the parameten of the hystemsis loop. The instrument war developed

commercially by Princeton Measurements Corpcraüon (Princeton, NJ, USA). The

sample size required is very small. Dimensions are no more than 2mm x 2mm x 1mm and its weight can not ex- much more than 50 mg - 100 mg. One limitation of this method becomas apparent when considering the sizb

of the sample testai. The mean weight of the cores for this study is 23 grams,

theMore, at the most the tested sample is repreoentative of 0.04% of the arefrom

which it is taken. If there is any heterogeneity within the are, which is most oRen

the case, the tested sample may not rspnsent the actual mean hysteresis loop

parameter values of the are. Forlunately, the rodu ttudied are both fineqmineâ

. and homogeneous ro that the srnall samples are representative.

From the hysteresis loop auva, the followhg parameters wore detennined:

maûix suamptibility (h) femgnetic rusqübility ()G) totai susceptibility (x) saturation rmgnetiz8tion (y) remnent magnetizatibn (M,) malizedas M, I M, CCH~~V~(He) mcivity of mmmœ (Hm)alro nomislized a8 H, 1 He

A complete Iist of the data for aach masudwnpk cm k founâ iri &PEMO( O. 4.21 ldmtlfication of the Ferromgnetlc Mineml

the review by Lowie and Heller (1982) on the magnetic properties of marine

limestones shows that the main contributor to the natural remanent magnetization

of non-red marine sediments is magnetite. Goethite, pynhotite and maghemite may

aiso have a minor contribution where goethite is the cornmonest of üie the, Ming

the only iron oxide in chernical equilibrium (regarding eHlpH) in seawater. Table

4-1 list some of the published data of the propefties for both of single domain (SD)

and multi domain (MD) magnetite.

Tabk 4-1 List of pubîisheâ paramden for single domain and mulü domain magnetite. Source: Dunlop (1968) Pannntir Singk Oomrin MuM Oomrin 4 10 -40 mT 2.5 - 4 mT

if we compare these published values with the averages obtained ftom this study - listd in Table 4-2, WB obse~ethat the studies values for the magnetization ratio

and the coercivity ratio faIl betweeri the ranges of SD and MD magnetite. The

average coemivity (He) valu8 i8 I-ed in Ulb loww limit d the SD range, îmwaver

teking into accwnt the standard deviation, the cornivity al80 straddles the SD and

: MD ases (Figure Cl ). \ These mid rang8 valmbebm SD and MO magnetite dearly conesponds

to pseudo-single domain (PSD) magnetite. By plotting the maunetkation ratio Day et al. (1 977), it is evident the data points fall within the field of PSD rnagnetite

(Figure 4-2).

Tabk 4-2 List of rvenges and standard deviation of measureâ mnmeten of this Jtudy% sarnpîes ~ammatar 1 Awngo 1 Standard Devktion 1 Standard Em h t 4.50 mT 13.23 ml 1.O2 mT

St. Dev. = 4.89 n= 170

Coercivily (Hc)

Fiaun Cl Frequency hhtgnrn ofthe coerdvity values (in ml') of th8 murund sampbs. Rmbrn chamderistic for mrgnetite. O 1 2 3 4 5 Hcr I Hc

the matrix and th. percent contribution of the mat& and the f&mmgnetic -72-

susceptibility of the matrix ranges from 6.87 x 1pta 4.00 x 1@ m31kg, where the

average and standard emr is 0.92 î 0.09 x 10' m3/kg. This indicates that the

matrix is cornposeci of a mixture of diamagnetic rninerals like calcium caRxmates

and quartz, which have negative susceptibilities, and pararnagnetic rninerals which

have positive but generally low wsceptibilities.

The suswptibilily of the of the ferromagnetic content ranges from 0.001 x 10

'to 15.9 x 10' m'kg, where the average and standard emor is 2.54 î 0.1 8 x le m'kg. By cornbining these two components, we obdained total susceptib~lities

rmging from 0.34 x 1O4 to 17.9 x 1pm'kg, where the average and standard emr

is 3.46 & 0.20 x 101 m31kg. By dividing the susœptibility of the ferromagnetic

cantent by the total susceptibility for each sample we can detemine the percent

contribution of each component to the total susceptibility.

The interpretation of the plot in Figum 4-3 #mmarlles the observation that

can k made about the magnetic natum of the matrix and the contribution each

- component brings to the total susceptibility. Figure 4-3 expresses the foIlowing

relationship:

A ratio greatw than 1 (1 1.8 % of the samples) indicates that the

matrix is diamagnetic. Samples included withnr the field of O to 0.5 '(17%) have

pararnagnetic matru and the paramagnetic component contributes mon, than 50 96 tigun CS Fmquency histwmm of îhe percent swaptibility of the femmegnetk conteiit dlvided by the toîal rusce@biüly. Sœtext krexpianation of each wMividd fieid.

of the total susceptibility. Similarly, samples included within the field of 0.5 to 1

(71.2% of Vie samples) also have paramagnetic matrix but the paramgnetic

rninerals contribute less Vian 50% to the total susceptibility.

These are positive results for undertaking remanence studies because the

femmagnetic content semr to have a dominant presence within the tested

samples. However we must keep in mind the limitationof this identificationme-

- diswssed in sedion 4.2. The sample sites are so mll that they may not always

represent the entire specirnen. For this mason the bulk susceptibility

measurements should give a better mpresentation since the entin con, is

4.3 Mem or Bulk Y agndc Susceptibllity

Tha anisottopy of magnetic rueceptibility (AMS) measures the ~usceptibilit~ of the diamagnetic, paramgnetic and femmagnetic components of a corn -74-

spedmen. The bulk susceptibility of a specirnen depends not only on the

mineralogid content of the specimen, but more importantly on the volum

pemntage of the mineral content. Table 4-3 outlines two boundary cases of how

volume percent of magnetite (a ferromagnetic mineral) and clays (paramagnetic

rninerals) can dictate the bulk susceptibility.

Table 4-3 Outline of boundary setting postibiliües when considering the volume percent of mapneîite and days in a diamapneîic mat& K of magnetic content + K of maûix - Tml K (WO~Ok i-10 x 10" SI)

-- - - 0.1 % magneüte x SOaOOO x 101 99.- mmx 40 x 1C SI = 490.01 x IVSI SI (average K for magneüte) = 9.99 x 1VSI r 500 x 101SI I 1W days (pinmrgnetic) x 1000 ûû% mrlrbr x -10 x 101 SI - x 101SI (average k for days) - 9.9 x 101 SI 10 x 1PSI

The mean susceptibility, obtained during the AMS study, for the 11 70 cores

rneasured ranged from -33 to 4145 SI x 1Q' (Figure 44) of which 83% d the

samples are within the range of -15 to 40 SI x lû? Negative bulk susceptibilities

were obtained in 37% of the ares. Therefore, it can be deduced that those

samples are composed d much less Vian 0.1 vol% magnetite and of leuthan 1

vol% paramagnetic rninenls. The majority d the cores yielding positive

susceptibilities have mean values les$ than 1W Si x IV (61.5%), indicating that

paramagnetic clays dominant the AMS signal by virtue of their rlrwrqer anirotropy.

The cores producing mean values greater than 100 SI x IV(1 -5%) sugged

, a gmater importarice of msgmtib. HOW~VW,th. abundam of rnagnetite within racofâed ir 440 SI x le Snipk FL98344 ir the only exception with its thnn, cons racding mcwi wsœpübility values of slightly mors than 4000 SI x 10'. -76- study hduckd 1170 O~C~S,whem th. Min conr ir measured. Conseqwntly, the man susœptibilities obtaimd through the AMS analysis are a better indicatw of the magnetic minoralogy pm,conbibuting to the magnetic faMc.

The diamagnatic contributom am predominantly calcite and quartz. measumd negaive man wgceplibility values cwelate to published mem

MOBptibilities for natunl, slightly impure calcite and quark of -1 3.8 SI x 101and

-9.29 SI x 101, nspdively (8ombilo et d., 1987).

of the ophiolitic Troodos Temin and the metmwphic Mamonia Temin. In semples with positive man susœptibilities (6696 d those meauned), these penmPqiebic mineral8 e#ittd the nisoûupydm wsceptibility. Therefore, Chapter S - Anirotropy of Magnetlc Susceptibility (AMS)

6.1 Introduction

The anisotropy of magnetic susceptibility (AMS), in this study, was measured in a weak magnetic field (0.05 mT) using a Sapphire Instrument Si-2. ihe weak magnetic field is important because it is comparable to th8 Earai's magnetic field.

A solenoidal coi1 produces the Iw-field intensity with an extemal field ftequency of

19 200 HL The older SI-2 usd75û Hz. Measuing at 19 200 Hz enhances the sensitivity but still retains a wbstantially inghase component, ~~ing susceptibility rather than electrical condudivity.

AMS measurements detemine the bulk magnetic susceptibility (K) which represents how easily a rock magnetizes in the presem of an extemal field. An anisotropic sample subjected to a week field will acquire an induced magnetirrition

(M) in a direction generally not parallel to the applied field (H). The acquired induced rnagnetization is defined by thme orthogonal components

Eqn. 6-1

Eqn. û-2 These nine parameters define six independent wmponents which define the anisotropy of magnetic susceptibility ellipsoid. The measuring schem8, us4 for this study, follomr Nye's 7 orientation prOCBdure outlimd in Figure 5-1 (Bonadaile and Stupasky, 1995). The computer program S1298.sxe designed by Dr. O. J.

Bonadaile cornputes the data of the seven orienWonmd yields the magnitude and orientation of the three orthogonal axes defining the AMS ellipoid.

Since the k,, are 30, the tensor can k reprewnteâ by an AMS elliproid, characterized by the length and orientation d Q thma principal axes K, (maximum axk) s K, (intermediate axis) z & (minimm a's). These in tum may may be useâ to give charaderistic anisotropy parameters which are listed in Table 3-1. From thir list, the following parameten were eorwidered in this study: mem susaptibility

Nye's seven orlentdons

6.2 AMS R~ulb

The AMS results am sepenteci into thesections. The fimt analyses the mean CUEcBptibility in order to Mmthe iwqiaic mineram d the samples. This discussion can be found in the previow chepter in sections 4.3 anâ 4.4. The second considem the orientation d the dlipsoids' principal directions in order to define the AMS foliation and lineatim. A detailed discussion of the mgionel variation of the AMS fakic can be found in Chapter 6. Lastly, the rhqe and degr- of anirampy of th AMS ellipooid is descriw using the Pl and Tl pammtws d Jelineîc (1981 ). Thme as domîy linked to the magnetic minwalogy nd mil a premtw below.

The AMS study induded 1170 m,maswing 25 mm in diameter and 22 mm in lmgth, drilleci (i#n 434 orientrd rniples (2 to 4 cons paf rnple). Plotteâ in Figure 52 sis the stemgmphic pmirdion of the principal axes of the AMS dlipmid. Peak contouring bwid uid pl- of the minima, intemediate and maxima axer rr Srs, 27m Md 1- mrprdively. Maximum and

to the minime axes.

circukr-nomal distribution d the minima axes ~inations(pokr to foliation) in

FiWa ilb&&e8ai. pnhmd dip dindkn dthe AMS foliation pianos. The Minimum 4

ciiailar-romisl distribution of the indinations for both minime and mima are

pWin Fii W. Th. indinrüm d(h.minima axes cmœnûata 1th 70 to

: expression d the thecontraaihg Circularml distribution d minimum and

1 mobnm ocrr hdintion cm k rnn in thr st-ic prolictions of Figure Figura Mb Hidogram of the percent frequency disûiôuüon of the AM8 maxima and minima axes inclinations (n = 1170). distribution express a partial girdle on the stereographic projection.

The AMS lineaüon, repremted by the direction dthe maxima axes, duster more and give a higher modal frequency than the minima axes. Histogmms d the dedination and inclination (Figure 5-3a and b) of th mw'*ma thow that the lineation predominantly pkinges 18ssthan 20° ancl ttends N-NNE and S-SSW.

ln chepter 7, the oiigin of the partly tedonic AMS fskic will be discumd and interpreted on a regional $cale.

6.21 Shaw and Ecc«rtncity of AMS Blipsoid

The anisotrupy of the magnetic suscaptibility elliproids ank âefineâ by hno

-84-

parameters, its shape (oblateness or prdatenerrs) and its degree of eccenbicity.

The Jelinek (1981) shape parameten Tj and eccentncity parameter P, will be used

in this study and the plot can be seen in Figure 5-4. The number of data points is

418,each representing the mean Pj and Tj values fiom several cores of raeh

sample. The S1298.exe cornputer program which contours tb Jelinek plot cwently

allcnm only a maximum number of data points of 500,vutiich explains the use of the

sarnple means.

The AMS ellipsoid is slightly oblate with a shape parametet, Tj, of mean and

standard error of 0.12 î 0.01 and an eccentricity, P, of 1.41 k 0.06. Thes8 are the

mean parameter values for the sample mean data set (n = 418). The mean and

standard enor of T, an P, for the entire con data set (n = 1170) are 0.12 t 0.01 and

1.66 i O. 13, respedively. The tendency of the AMS febric toward obfeteness may

also indicate that a primary sedimentary fabric remainr, whem oblatenesr results

from compaction preferentiallyflattening the mineral content within a cornmon plane

pamllel to bedding (S-tectonite). The ruperimposed tectonic fabric, where the L-

fabric is well developeâ, has reduœd the oblateness of- AMS ellipsoid, l~ring

' Ti value, and producing a fabric when S(dominantly nwment of the primary fabric)

component is slightly larger than th L(tectonic fabric) cornponent.

6.3 Summuy dAMS

The complete list of the AMS data, orientation and magnituded prindpal

axes, mean susœptibility, P, ancl Ti, can be found in APPENW B. The AMS fakic -85-

is prHy tbdonic, as will be argued ktsr in Chapter 7. Magnetic foliation planes dip

moderately to rhJlowly east and wst, inclimd to bedding, Mile the magnetic

lineation pndanimntly trends N to NNE mâ S to SSW with a gentle plunge of

abwt O' to 2û0. The dlipooid is siiioblate end modmtely eccentric, no doubt

' a mît of the mining primwy sedi- frkic dm to compaction. Chapter 6 - hiaotiopy of Anhystenüt Remanent Magnetlmüon (AARM)

6.1 Infrodwtlori

The rniwtropy of anhysteretic r#niridnt m8gmtization (AARM) Usa

dimension to the anilysis of a magnetic fabric by isololaang üie fabn'c of the

femnnagnetic mineraIr: those able to acquin a magnetic mm.

A sarnpk acquims an mhystmtic nmisnent migrntization (ARM) by

aposing it to a decaying altemating field (AF) that mdomizer the spin moments.

Simttmwdy, ovcw at k#1put d th AF range, a unell direct wrmt (OC) field

is imposed. This ir samtimes alld the bias field. Meawremenfs for mis atm

were dmusing a Sapphim Insûummts SI4 norrtumMing altemating field

ôefnagnetizer. In this sUy, using th. Iabat~spmviow 0-8, aie AF

decayed fiom a peak intemity d 100 mT Md a DC fidd of 0.1 mT was opplid

dving the demy window ofha AF between 60 to O ml. The mlationship between . . - mm- md üm applied OC field ir expssed by the following 6.2 Maasunmont Procdw,

The mmwing procsdvb #kwn the same Nye'r mven orientation sdwm

usdfor th AMmeawmmt8 (Figure 5-1). Fint, the sample is demagmtized

by an AF decBying from a pak value of 100 mito zero (AFlm) in the first thrw

ofthog~mlpb d the Nye's s&ma. Subsequcmtly the sample is axposed to the AF,, supwimposeâ on r OC field in al1 men orientations and the ARM ' intmsity is measumd mer each orientation. The ARM intensity is masured with

a JR6 rpignn0rmagnetometer, which has an Mxrracy d 0.001 mAîrn. The sevm

orientations of the ARM meawrernents are coll8ded by the cornputer program

Spin98.axe design by Dr. O. J. Borrsdeik. The data is then transfemed to the

S1298.exe cornputer pmgram, alm deigr#d by Dr. O. J. Borradaile, which

calculates the thm prWlaxes of the anisotfopy of ARM ellipsoid, AARM,

6.21 8niplm &n«ilng Pcocoames

ths rmaammdprocudm foc detmining the AARM is time consuming,

with an average time pef mmpk of 20 to 25 min. Far this mason, it is mm ' efficient to devalop a rcirnwiing pmœw to idontify the umples which will yield a -88- susceptibility, indicating a diamagnetic bulk msponso due to calcite, it is unlikly the femagnetic concentfation will be suffident, that is if femmagnetic minerals are even present. Thus, 430 cores were rejected (37% of total cores, leaving 740 meawrable cores for the AARM study).

A cornmon way of further aweening for an AARM dudy is to determine the intensity of their natuml remanent magnetization (NRM). îithe sample yields an

NRM intensity greater than 1 Wrn the sample was acœpted. This meWd rcreening was used for 20 samples , al1 of which wre accepted. However thir process is also time consuming (- 5 minutes per sample).

Theremfore, a more rapid rcreening pfocess used isothemal remanent magnetitation(IRM) as a potential tool for quiMy iemoving unsuitable samples for the AARM stuây. The procedure entaited applying an IRM of 100 mT (IRM,d in the

-x direction (horizontal to the top of the corn) using a SI6 pulse magnetizer and then measuring the intensity of the IRM in that direction with a Molspin spinner magnetometer. A total of 42 samples ware given IRM,, and producd intensities ranging from 35 to 4269 rnAlm. By trial and enor it wmdetemined that a minimum

IRM, af 40 mAlm wsr needed in ordrr to produœ a uiniciently masurable ARM.

Proœssing the data mvealed suspidow AARM principal directions wtm compared to AARM piinciil directions obtairnid fr#n 20 ramples not oxpomâ to the IW,, but mlecteâ by th, much Iengthier NRM intensity telection criterim. Figun Cl Stenognphic projedm of the riapldous MRM pindpni diWmof the 37 urnpkr apcwd to M in thr suwning procrir. Cides - minima axas, triangles + intemdi8te urr, uid rquwrr - mudm axes. Their AARM minima axes dustend about an axis trending in the x diredion and dipping approximately 20 ckgrees in the lowef hemisphm of the stereographic projection (Figure 6-1). AM-ma and intmdiate axes directions fumed a girdte striking in the y direction and dipping approximately 70 degreer to the -x direction. These msults sugoest that the AF,, applied in the -x direction is not adequate to dean an applied IRM,, along the rame diredion.

Two samples, FL98237B and FL982380, wero chosen to test what AF maximum peak intmity (AF,) was needed to clean IRM,from Oiese radu. Fi* the NRM was measued with a JR4a spinnef magnetometer. Semndly, an IRM,, mis applied in aie x diredion followed by a Vvea axes AF, demagnetizatim and finally measuring the temanent magnetization intensity and direction with Vie JR5r spinner magnetometer. This second step was repeated for AF pealc intensities of

1W, 1SI, l6O,ltO, l8O,lQO,and 200 mT (Table 6-1 ; ateps 1 Ihrargh 9). Sampk

FL98238D was deaned of its IRMjmby an AF AFWn 190 and 200 mT. ln sample

FL98237B, an AF field of 200 ml (the maximum AF field geneiated by the SI4 AF demagnetizer) was able to scatter the IRM direction. Since the SI4 AF demagnetirer could not confidently dean al1 $amples of the irnposed IRM, mis method was mt used.

T8bk 6-1 hisuniril8iits ofmrgI8etk mmMettœ cuknlstiori idintenrily of ample FLBû23ûO in ofder to de811 an rpOlkd IRM of 100 mT in the x dimdhn (3(KU00) (stops 1 - lô) and thon ckrnhg of the tnmlly acquired seIf rnagnetüation o#rid in #op 10 (stop 11 - 12).

1 none (NRM) 2 AF de- 50 mT 3 AF demrg 100 mT 4 AFdemig 150 mT S AFdMniglWmT 6 AF dmag 170 mT 7 AF de- 1ûO mT 8 AFdomrg 180 mT B AF demig 200 mT f0 Tn~fQ9'C 11 AFdeq50mT 12 AFdemeg2ûOmT -91 - Finally, the rrmples wem scmmd by rimply applying an ARM in the om, direction and mesuring the rcquireâ intmsity in the given dimon with aie

Moispin rpi*mmsgnetomoter. The ARM oonrirtd of an AF,, superimposeKi on the DC field of 0.1 mf through the Af window of 60 to O mT. The sample was mj8ded if the aquirsd intwsity wir lem aien 1 mAhn. Thir scmming pmœss was performed on 289 sampks, of which 81 wwe rejected. ûf course, rince the

AARM prî~*ldirections am unknonni, the one-step MMcwld have been applied in a IwlrARM direction. Thir probrbly kad to the mjection of some samples for which AARM cwld have been adequately measumâ.

The total amntd axes that satisfied my critaria far the MMstudy is

201.

6.22 A Casa of ThmwWIy Acquind 8rlf=ù~müzaüon

An altemate mrthod to dom the remples of thIRM ir by themal demagmtization. Smple FLW238D (the same r~mplefrom rbow which was cWWofibIRM bymAFd200mT) mrugain~dtonIRM,,in~x direction. The mmpk was then Weâ to 1100 OCin a thrmul &mgnatuer and war miintained at that tmpmtm For 5 minutes kfon slawly oooling dami.

Aftenmds, the nmsrmd mrgnetizaüon wu rneasumd rmh th JRSr rpim -92- fable 6-1). Such an intensity h# not been rcnm in these mmples with AF demagnetization, in tact the lafgast intensity wr 28 mAhn measumâ on sample

FL9823ûD Bfter AF, demagnetization.

Remsgnetization duing thermal ckmigmtization cwld result ibn contemination due to inadquate shidding of the hanace from tb extemal earüi msgnetic field. Hwver, I do not believe this to be the cauw of the presemt obmation. The lhemal- mdha8 a fa* layer mumetal shield, non- indudivdy w#nd bma~with ammic wallr and AllOj wool insulation. It is a well testai instrwmt that ha8 produgd vefy good nsub on nummur other sarnples of variow rock types. Moreover, tham h# been no evidence of contamination in cona~nentMine palmagnetic rhrdier.

in samples contsining pawdo-single domiin magnetite. P-8, in this cese, thmal demagnetization does dean the within the poeudo-single

tmatmmt TI#. &l(rkpr 11 and 12) rhom that

-94- expected results were abtained. Consequently, therg is evidence to believe

magnetite present in these rocks has a high mrcivity of remanenœ (mean ad

standard error of H, is 29.70 î 1.40; tee chapter 3), mat the grains are pseudo

single domain and they can selfiemagnetize when themally treated.

6.3 AARM Resulk

The AARM study included 201 cores located throughout the study area. A discussion and interpretation of AARM regional variation is found in Chapter 7.

Presented hem, will be the overall orientation and magnitude of the three principal axes of the AARM ellipsoid, as well as its shape and eccentricity.

The orientations of the thrw principal axes are plotted on stereographic projections in Figure 6-2. Peak contouring trend and plunge of the minima, intemediate and maxima axes an, 145/4û, 279/25 and 022124 raspectively. TIMI

AARM, axes an the poles to the AARM foliation, while usually the AARM, represents the orientation of the AARM lineaüon. We will see in section 7.3.2 that in some areas the AARM fabric is a composite result of the So and the pattially overprinted magnetic foliation planes. In these amas. the AARM lineation is mpresented by th0 AARM, axes.

6.3.1 8- uid ECC~tltd~ityof th8 MMElliprdd

The AARM elliproid is chamderized in th meman- orW the AMS ellipsoid was desmbbeû. The Jelinek plot is illustrated in Figure 6-3. ïhe distribution is dearly bimodal. One mode, defined by 114 data points. decri*ber

-96-

a nadtsl allipoidwtmb P,. 1.13 k0.01 andTi = 0.10 10.02. Tha second mode,

dained by 67 data points, ~besnextmnely oblate elliproid, where P, = 1.12

î 0.01 and T, = 0.93 î 0.02. Regimlly, bth f.kia am twqpmmurly

distributed. A low# ûegm of ecœntMty reflectr the absent contribution of the

platy day mineials and the primuy wdimmhry fakic which dominateci the non-

tLYjnnic cmponmt d hoAMS WC.Msgnetite, the fammgmtic tontnbutor to

the AARM Mcis typically msiâered to have grain8 thit are dimensionally and

th- magnetically plate. Therefore, an Mateffskic, mybe interpmted due to

tectonic control scattdq groin proiste elliproids to give an orientation distribution

thot genemtes a more strongiy oblate AARM fatuic.

6.4 Summwy

A complrte lirt d th AARM data, Orientation and magnitud. of prWpal

mean intmsities , Pl and Ti, cn be found in &PENDIX C. The minime axas

dudw to define a fdid#n piam which dipr about 40' to the NE. It will be argued

luter in Ch.pter 7 thrt the AARM liinraon ir mpsmted in rocrn cases by the

AARM mimi anâ elwwbm by the AARM intamadiate axes. The AARM

ellipids are more Mate nd ku ocœntrk than the AMS elliproid pwhp8 due

to tectonic mntmlr scattering prokte -te grain (th lkrormgmtic miml

, whmm a piimwy fikic of dry mimrkcontrolr th. AMS fabric. - Chapter 7 - Interpretaion and Discussion

This chapter will diswss the interpt'etation of the orientation of cleavage (S,),

AMS and AARM. First, each data set will be approadied individually. Secondly,

reiationships between data sets and tedonic ngimes wiii be examined

chronologically.

7.1 Bedding (SJ, Cleavage (SI) and Vergencr

7.1.1 0rlent.tion and Regionrl Mstributlon

A complete list of the bedding and deavage measurernents cen be found in

APFENOIXAThe regional variation of the styloliüc deavage orientations measured

in the field are presented in Figure 7-1. Plotted are the mean measurernent at eedr

outcrop Men, deavage was present (total of 171 outcrops). Tbfint observation

is thet S, is not paraIlel to the bedding planes (S,,), which dip gently to the narth and

. south (Figure 7-2). The angular didance of S, and S, confim thet the

cleavage was not due to diagenetic compadion and cementation. Furalemwx8, the photogmph and line diagram in Figure. 7-3 dearly demonstrates bedding stylolites being cut by tedonic stylolites. Note that whem S, stylolite cuts across the &,

rtylolite, the S,, stylolite ir displaω by 1.42 cm,indicciting that this thickneu of

limeStone was removed on a single tedonic (S,) Sty10Iite. Note that the thicknem

of insoluble residue on the S, rtylolite belwoc#i its intasectionswith the S, stylolite

is of 0.9 mm and the thickmss of the S, stylolite outside this zone is 0.25 mm.

Figun 7-3 Photognph of sampk FL982û4 and lin8 diagnm. The rmpkwas mdented and a veücsl face was cut pmklto 345" rdmuUi. me tectonic stylolites aoorait the bedding or diagenettic styloliîes. the vergence Q souaierly. 70% of the scwmulateâ insoluble msiâue b due totectonlc pnswn solution and only 30 % to diagenetic pressura solution. Fudhemon a dispîaament of 14.66 mm ocwrfeâ along S, due to dissolution. Outmp Idionmay bs fourid on MAP SHEET A at the back. -1 01- Therefore 70% of the insoluble residue was amulated during the S, tectonic pressure solution event. This defines a ratio d accumulated insoluble residue resulting from tectonic pressure solution relative to diagenetic pressure solution of

2.3 : 1.

The stereographic projections of the poles to the cleevage planes in Zones

1 through 6 illustrates that S, has a stwper dip than bedding. Table 7-1 lists tho calarlated contouring peaks for each zone. All zones have more than one ciuster, generally two dustem am present and in Zone 2 there are 4 dusten identifid. The dips of the cleavage planes consistently range behnreen 12' and 29'. ln Zone 4, there is an additional peak which corresponds to a cleavage dipping et 56'. This cleavage is an exception related to an Eady to Middle Miooene compressive tectonic regime which produω the Yemsa fold and thnid bell dong with 3 of the -1 02-

compressive lineament (Figure 74). For the following discussion, the

tedonic compression deavage in Zone 4 will be put aside and considerd

later in the chapter.

The consistency of the deavage dips suggests that the strain

producing S, was approximately coaxial in individual subareas amss the

region. There is no evidence of rotation d SI with progressive strain and

together with the stylolitic nature of SI, suggests a pure shear origin for SI.

Although some fabrics develop with a shear component as transpressive

stiear, combining pure shear and a shear strain, this does not appear to be

the case hm(se8 Figure 24for definition of pwe shear, transpressive and

Vie hypothetical simple shear).

In kinematics, vergence charecterizes the angular relationship

between a certain fabric and the one that pCBCBded it. The common use of

vergence relates bedding and cleavage in order to define the direction

towards which the fold axes Iean. The gmat variability of the dip direction

of the cleavage produces equally variable vefgenœ directions. Figures 7-5,

76and 7-7 are photographr of thme samples which all exhibit a different

cleavage bedding angle mû cnhq~8ntlydiclmt intenrity or direction of

; vergence. Note in Figure 7.6 the displacement of beâding stylolites at the

base of the oxidked bed, on S1 styîolites. And in Figue 7-7 note th0 relative

intensities of S1 and pressure solution, approximately wual in I noun 71 Phocognph of- FL98031. 8*npk ms Wednd a vsrtical face parallet to 3N0izhiuth wrr cut expsing th. 5, stylolitic deavage. BWing was not prasent at Uib outcrop, how~verthis face cut dearly shows s second consistent stybfikdeMion wNdi Is most Iikdy prmlld to bedding. lt is evident that these are thun the 5, stylolites ôecause they are ait by S,. Outcrop location muy ôe~IaWd on MAP SHEET A at the badt Fiqwr 74 Phamof smpk FtBûll7. Smpk wm cdOcknted snd a vertical face parallel to 03O0azimuth was cut exposi*ng the S, styklitic cfeavage. Vergence is in a soWmsterly diredion. Note the disQlacement of bedding stylolite at the base of o#dMbsd on S, jtyklites. Outocop locatiion is indicated on MAP SHEET A at the back. Figure 7-7 - Photograph of sainplet FL98167. Sample was reOclented and a vertical face parallel to 160°azimuth was eut e~posirigthe S, stylolitic cieavage. Vergence has a northrrîy direction. Note the relative intensities of S, and S, pressure solution, approItimrilely equal in significance. Outmp location may be found on MAP SHEEt A at the ba& . -1 07-

In üm rhrdy mm, folds am vwy gemtle and open,but vergence may still be detemined indicating th diredion of the kinmatic movements. Regionelly, the vqmœdirsaionr, and -y the directions of movment, do not produca a mydePT pattern; tmmver it appean thm is som prefemd orientation to the push diredion8 (Figure 78).

In orâer to i- the deavage vergeme, and in later sections the msults of th AMS anâ AARM studies, m must mi* the tedmic settings which may have ciused in8tability in the mgion. Since the ckpooiüon of the sedimCHlfary covw, thefa have been hno principal sourœ8 d in8t8bility bf Cyprus. FinUy, the

COCdinued uplift d the ophklite cofnplex with periodical incmases in ratas of uplift in localized areas such as the Limamol Fmst Block (Erly Mioume) and Mouit

I ôelieve we can dirmiu ury explneüon dindly mlataâ to suWudion for

ro@rne,I ww# qeda dUydominant single SW vegmœ direction much like in Zone 4. Since thir is not the case haro, I ditgravity sliding, in rsrponro to continued regional uplin, as a antributu to the ôwelopmcnt of the S, styloliüc denvago. Itha Troodor ophidite wu (h. only uplilted or hi- elevatoâ mgion, . vrrgw# drrdionr wwtd k oon&stmUy my from the ophioll complex, in the diredm of gmtity rliding. lhemfwe, (o th.wst, south nd emt of th. Tioodos

Cmvwgenœswouîdh8ve~, raairdwutbastdydirectionr, nrp.divdy. Onœ again, nruk illusîmtmâ in Figun 78nd listaâ in Ti#. 7-1 HGH- FIgun 7-10 Sehematk illwlntionof a brdn uid hlgh lopoOmphy whidi may explain the varlsbk S, vergence dirisdions. 6hdt rmmn repmwnt the possible veqpnce dimdim which couîô rdse fmm wch topography. Such r mode1 wuld producs muîüpîe veipsnw directions, as is îhe case fortha deavogo ve~encediredons of the Myam.

do not entirely agree with mis sœnario.

Sedimentary facies studies have idenüfied numemus basins in the southerly

regions of the island (Onzag-Sprber et a/., 1989; Eaton and Robertson, 1993;

Stow et el., 1995). These basins must have been sumunded by higher elevated

terrain that producd other possible gravity sliding directions, puhdiredion8 anâ

: vergence directions. Further evidenœ of uwvrn topoqephy cornes from dekir

flows and sîump folds shwing dispiaœmmts fmthe north to the south and al80

hmthe south to the north (Eatm adRoktson, 1993).

I believe the best possible int~gonof the multiple phdiredim

observeâ aaou the mgion comes from a basin filled topogrephy, with mvml

higkelevateâ terrains as sources d kcslized gnvity sliding, and continued uplift -111-

as the meChBY)ism initiatino mgional gmwty rliang (Fi7-10). Zona 4, being the

exœpth, ha8 a constant unidirectional SW vergem. In mis case, a subduction

zone migration from the noiai to the wuth initiated a compressional fmnt which

thiusted the uplifting Limpud Fmst Block southward and produced the fou

WNW-NW I ES€-SC compression linesmentS.

7.2 Anirotmpy of Magmtic Surcaptlbility (AMS)

The regional resultr of the AMS magnetic foliation and lineation are

prr#cniteâ in Fi- 7-1 1 md 7-12, m8pctiveIy. Plotteâ are the spatial average8 ~ calculated at stations located at one kilometer intoivals in both the N-S and E-W ~ directions. At each station, the measurements found within a 2.5 km radius am weighted in inverse pioportion to their distants away from the station and then

avmagd. Thrprti*al averaging io prrliWned by Spîwistat, s sahvare program

ôerigned by Dr. Bob Stesky (AwmmBI Figures 0-1 anâ 8-2).

7.21 AMS Fdidon

ïhe MAS Wi1mpmnbâ by th Y, am8 d the magne& susœptibility

ellipsdd8, is in pmt trdonic, but mtaim a strong primuy Wimtsry frbric

eompanwit ~~the~~,&s~pokrtotb~~~foliiplams,rnnearl~

, pwprndiwlar to kdding. ûm $triking ôiibdwem th. AMS foliation anâ bdâhgpiwristhedill~inIh.~dIh.ckr~ofâata.Th.pderto

-1 14- girdle, where 'zone-erismdefines the lindion. Therefore from a horizontal position, the AMS foliation planes Vary by scattered east and west dips.

We can obtain an AMS rnagnetic vergence by examining th relationship between the AMS foliation plane and the bedding plane. Generally, vergence d a certain folding event is detemined by the rdationship of its axial planar deavage with the planar fabric that immediately preceded the folding. In this case, the vergence of AMS foliation plane should k considered vis 8 &the deavage plane.

Hcwever the m0eritationof the cleavage planes is highly variable aoross the study area, partly because of its stylolitic nature. For this reason, the AMS vergence is determined always with respect to Uie bedding plane. The fact that folds of bedding are generally subdued and open validates mis approach. That 0, bedding was essentially planar even Mer F, I S, event occurred.

The AMS vergence directions conristenüy chsracterize a push direded away ftom the ophiolite cornplex (Figure 743). Tectonically, aiis vergence pattern is compatible with ngional gravity sliding causeâ by the uplifting of a single area.

Unlike the highly variable S, vergenœ diredlDonsinfluencd by basin topography, the AMS vergenœ direction dearly point away from the œnter d tedonic upliR, the

Troodor ophiolite cornplex.

In Zone 4, the SW AMS vergence direction favoun a push in the SW direction. This does not cornlate with th mrchsnism dgravity sliding whem the

Traodos ophiolite complax is the tbdonic uplR conter point Hawsvw, gravity sliding may rüll be th8 adive meaianim if the Limassol Forest Blodc is th8 centew Fiaun 7-13 Variation in AMS vergence di~ons,wnn respect to Ming, for e8di zone of the Myam (zone is marlreâ by Itie number rit the and of the ammrs). point of tedonic uplift. Additional evidenw will be given later relating the AMS vergence to the Early to Middle Miocene tedonic uplift of the Limassol Forest Blodc

Therefore, like the other regiom, gravity sliding can explain AMS vergence direction obtained in mis zone but aie source driving the gravity sliding, in zone 4, is different from that of the other regions.

7.2.2 AMS Uneation

The AMS lineation is represented by the Iç, axes of the magnetic wsceptibility ellipsoids. A primary sedimentary fakic with no tectmic overprint and no strong cumnt alignment should have well dusteied minima axes perpendiwlar to the bedding plane and maxiCmaand intsmiediate axes scattered along the beddin~plane. A prhary tedimentary fabric which is pamy overpfhted by a tedonic fakic will also have minima axes dustefeâ mxmel to the bedding and -ma and inteumedipt. am8 akng beddiq pime. Hawbver. the maxima and intemiediate axes wil fonn two distinct dustem along the Minginsteaâ d ôeing scatterad. In the event thet the primary sedimentary faMc is completely ovwprinted by the tedonic fabric, the maxima axes am well durterd in ttw mqmkIIreraon diredm hileth minims and intemiediate axes fmelmgateû dustem defïning a common plam.

~AMSmbfor~~mMmacksrmsgieücli~ionfrm~ digter d axes which lm Hith. ôecjding plane or AMS foliation plane. The

K, axes alm fami a duster within the plane of Mingor foliation. Thetrefwe, fdlowing the statmenb mtioned above, it can be ridthat the AMS fakic is in part t-ic, whero Y, axes represmt the AMS lineatian.

The mean AMS magnetic limation directions con be seen at the bottom of each zone box in Figure 7-12. In each zona, th. lineation is rimilar to the campnding AMS vergence diredion. The lineation dindims are mmor lem

JI dimtd KS with a dight ôeviation lawards ai. AMS vagenœ dimction of that zone. Zme4,~,~ndlblkwthe~~Th.c0m~ressia~lfront1588(~s tobethedominmt~nic~umœinthkron.TtmWbm, itirnotwrpiiringthe -1 17- . Two poS8ible t~ic~cauldhave~the~mignetic lineations. The fint takes into Bccount the similar dentitions betwecwi th AMS vmgma~and th8 AMS lineation. tf gravity rliding away fmm an upliRing Troodos ophiolite ampkproduwd the AMS frkic, then the^ mgnetic lineation represents the gmed di- d gnnty rliding. Thwbtle cham in orientation fim Zona

1 to Zona 6 agrees with this fint possibility.

This second hypotheses considem wpn subduction extension as the tectonic regime responsiblo for the AMS regional magnetic lineation pattern. As mentionai wlier, extension within th^ ovwriding plate occurs in order to compensate for the gap prodwed by the backward migratïng ruWudion zone trench (Figure 7-9). Badnnrerd migration of s &en& ('roll-back') seems to ôe th rwult dasuMucüng ~~blllliccrut WWIis dder, Cd* and consequently ômsw than the mantle it is pemûaüng (Le Pichon and Angelier, 1981). The Hdlenic

Trench, which is westward cmtinurüon of Cypnwi k,ha8 alro barn reporta by LePichon and Angelier (1981) to have umkgme 'ioll-ôack' at a rate

(ôR/ât) d 10.20 anlyr. Thy debmhd the rate by eamining the dative motions d Altica, Europe and Twkey. Roôwbon (lm)states thit du in^ th Miocri#

(-22 to 6 Ma) northwsrd mdwhnting (ruWuction) dong the Cyprsn Arc wu never extensive Md at the most 500 km wm cmsumed. Fmthis infarmrtion I types. These include sœnarios where dSldt = dWdt, dSMt > dRldt, and dSM c

The fint case, where dS/& = dRldt, would produce a tBdonically stagnant situation. That is, neither compression or extension would ooarr. When compressive defornation (folding, mountain building) ocwn at a plate boundary, dSldt > dRIa The third scenario, describes a situation when, dSldt < dWdt and extension deformation (normal faulting, basin formation) is favwred. if w relate the calculatd subduction rate of the Cyprean Arc, fw the Miocene period, of 3 cmEyr to the rate d retreat of 10 - 20 anlyt almg the Hellenic Arc quoteâ by LePichon and Angelier (1mi), with the assumption thrt dR/dt alcmg the Cyprean

Arc would k similar, tedonic extension would be the favend sœnario with dSldt

-dRldt.

Once stafteâ, backward migration of a trench should only cease wtm the denser lithosphere ha8 bemn entirely consurd or when the arc collides with a continental aust (Lonergm and Mite, 1997). In üw case ol the Cyprem arc,

Early Plioœnetemination of the southward migiaüng trench uid rlower subduction -1 1s rates may have bea cmuseâ by the wc cdliding with the Emtoathetm Seumount.

Tho supn ruWudion ar#ion hypoüm808 would produce variable

emdirections in the ovm*dingplate. At difkwnt position along the tnnch,

the extension direction wauld main prpmdiailar to the strike d the tisnch.

Figure 74 1 illustrates lhe relstionrhip bdwwn the mgional magnetic lineation and

th &mpe of the Cyprean Arc. The rympathy between the two (induding Zone 4)

validates this second possible tectmic 8ihration.

7.13 Sunnuy of AMS FJwle

In Chapter 3 the mgnetic mirwwalogy contmlling th AMS fakic was

idmüftd as calcite and quartz wkethe bulk susceptibility is negative, and clays

whm the buk ruccdptibility is posih. WMn the pmsent cheptw, the AMS fakic

hu bem ~~ by its foliation, lineatim, and vwgmœ with mspW to Wing. Two tectonic situations hrw bens~oû fw the formation of the AMS

fmThe fint describes gravity rliding away from the uplifting Troodos ophiolite

cornpiex 00th its vergence pid AMS Iimstiocr direction ws compatibk with tMs

sibritkn. The mmnd deraiôm rupn-uibdudion extension in mpmn to rou(hiniordr miqrlion d the bwich. Onœ -n, line&*m (exaption in zone 4) nd vsrgsrics (exception8 in Zo;# 4 nd 6) dimction8 agm with this mcmd porrible situation.

The apparent Iack of comprtibility of the AMS fdiaüon plam orientaüonr

with eithr rituati0~18,is mort likdy &m b wak rtnin having ' in~~y ovrprinbdîhebeddin~.Thr,amdwakpmbIdig.linvdwdintronsïorrning -120- a completely primary sedirnentary fabric into a completely tedonic fabric in a mdimtary rock sr wu diuxisd ealier in wdim 7.2.2. It appan that the primary faMc compnmt (bedding) ir too drmg far Wain or reuystallization to align #a &,,, axes. Hawmver, I am WKkr the impression that the E-W dimion of the pdes to foliation ir a move toward8 Y, d Mning a common plme normal to th ~~diredion w the zmmis. Even if this b tha case, we are no doser ddhgbe(wrm the Iwo hypdhese8 sincs extension would k in nearty identical directions in both situation.

7.3 Anîsotmpy of Anhystwdt Magindic Ramrn«ic8 (MRM)

The regional nnub d the AARM magnetic foliation and lineation are pmenteâ in Fi7-15 ad 7-16, noprctivdy. Pldhd am the spatial average8 calculated et stations located at one kilometer intemals in boai the N-S and E-W diredions. At .och station, the nmwmmtsfound within a 2.5 km radius am weighted in invmplopoitioon to their distama myfrom the station anâ a#n avwageû. The spatial avmging ir pwf&med by SpîWstat, a sdhmre program designed by Dr. 8oô Stasky (APENDIXC, Figure C-1 Md C-2).

7.3.1 AARM Fdiriflari

The AARM folidion plms, npnr«rtad by the minimum axes of th.

ama. Znrm 4 ddinm a Wiibion direction. Tln pdmto fdioüon dustar in the swthemt quibnt, in Zones 1,2, anâ 3, illustmting a fdidion plana dipping

-123-

-45' to the NW. Zone 4 hm a fdiation plane dipping to the NE by -15'. Zones

5 and 6, to the wst of the rtudy ma, Mmav- foliation planes with much shsllamK dipc than in tfm fimt tfn'w zoms to the wst. uf 25' and 10' respctively. In~mmsmrthat~b~mAMS~~wecendetmim~

AARM mgmœ, mth mpedto Wng. Gmmlly, the AAûM fabric develops et least partly later than the S, deav- and AMS fat. T'harefore, for the same rmdiscussd in section 7.2.1, it ir advisaMe to use the relationship btwwn th AARM folisbion phme and the ôedding plme to detmine the MRM vetgence. lt is most unlikely üuat the AARM fakia developed @or to th AMS fabric, but simAARM vwgenœ is detm*mdwith mpedto Sol mir ir of no conm. AMS foliation planes end am esmnüally not folded, bdh being wb4wizontaI to haizonül. Fufhmom, th AARM foliation is eyvuhmsteeper than both AMS foliation and So maintaining a rimilw ngular mlatioriihip Mai both.

Figure 7-17 shows ais AARM vwgmce dindimr for .rch zone. They range from ES€ to SSE, exce@ in Ton4 wbm the vmgmca is dimded to the 7.3.2 AARM tinoation

The AARM lii,mpsented by th maximum axas of aie anhystemtic remamme ellipsoid, is evwy wtmm dimcted dominantly to the NE. This is a composite fabric betwwn AARM foliation and S, causad by th AARM vergence, wbm AARM, axes fepmms the intersection lineation bahmen S, and AARM l#iraai. Sinœ S,, is mdy horizonfil, the intefsecüon lineation ir shallow dipping and trends purlkl to the striûe d the AARM foliation planes (Figures 7-18).

Consequently, the AARM fat, of mort d the study rnr, is not pudy todonic.

Zoner 4 and S have Iwo' distinct mgnetic limaüon directions. One is orhted NE and SW, coinciding with the oompoiite f.kic ckvelopd evwywbm al. The oth~(gmy nawr in Figus 7-16) hm an ES€ anâ WNW orientation.

Smpkr~~~hdi~ionrwbfouidinmrnityto~YYrnrr and Ayia MMi limament. We have rlmdy interpmted the AARM foliation nd AARM htermedkte uxk

AARM moxirnum axk

TI------1s.

vergence in Zone 4 as a murît d r Imlly diicompres8ion direction. The -1 26- markedly of a non-coaxial shear nature with the crust rotating anticIoclouise (me

Chapter 1 for paleomagnetic euidence).

7.3.3 Summary d AARM Fabric

In Chapter 3, magnetite was identified as the ferramagnetic mineral

controlling the AARM fabric. Above Iruggested that the AARM fabric defines both

a composite and teûonic WC.The composite fabric, producing aie constant NE-

SW lineation, represents the intersection lineation between bedding and foliation

caused by a SE direded AARM vergenœ direction.

Only in the region of the Yeresa and Ayia Mavri lineament h the tectonic

fabric interpreted as the direct result of a tectonic compressive regime with AARM,

axes paraIlel to the X stretching direction of the strain ellipsoid. Compression is

prefened because the lineation direction is parallel to the strike of aie foliation (the

X direction) and parallel to o lineament producd by compression.

7.4 Chiondogy lnterpmtation

In the previous sedion I identifiecl the S, deavae as being tectonic, the

AMS fakic as tedonic in rome areas and diagenetic in othen whereas the AARM

fibric ir (i compotite fabric whem ktrw extension dimtion ir repcesented by the

; AARM, axes exœpt in ari. weII defind region whm the extension direction is

repnsenteâ by the mvmtiona1AARY, axes. In this conduding section, I will

darify the chronology of various tedonie @vents,thst dkted Cypnis rince th.

deposition of the TtOOdOs Sedimcmbry Cover. This in tun,will mveal r mlaüve time frame for the development of the various fabrics.

By the Miocene period, both the Letkara Formation and Pakhna Formation

had bendeposited on top of the Troodos ophiolite, which manemerging from the

ocean in the eady stages of the Miocene (Robertson, 1977). The first signifiant

tedonic event to affect the sedirnentary cover oearrreâ during the Early Miocene

in the vicinity of the Limassol Forest in response to renewed subduction. Payne

and Robertson (1995) suggest that the subduction zone, initially locateâ north of

the Troodos ophiolite cornplex along the present Kyrenia lineament, jumped

southtard to fom the Cyprean Arc south of the island. Under a compressive

regime, the Limassol Forest Wod< was similarîy thnisted southwards producing the

Yeresa fold and thn~stbelt along the rarthwart margin of the blodc Furthemors,

three other lineaments were formed during the compressive regime: the Akrotiri

lineament (south of the Wtiripeninsula), the Ayia MaMi lineament (south=east d

the Limassol Forest block), and the Petounda lineament (ead near Petounda point)

(Eaton and Robertson, 1993) (Figure 7-4).

All four stnidures trend roughly NWSE resulting from a maximum

compmssion directed NE-SW. Of the four structures, th. Yemm fold anâ thrust

kltand tho Ayia Mavri lineament are induded mthin tha present study area. The

Yerem Fold and airwt ben deformation is cnaraderized by rwth veging fol& and

a well developed plane cieavage (Morel, 1960). Cleavage plane #ienWionr

I measusd for the present obidy yi, in agreement (Figum 7-1: the stereographic of the @es to cleava~eplmm for Zone 4). The axial plam chvago 4 28- Mms a sodwdaîy vergema, pualkl to the maximum compmssion direction, ugOorüng a purh fmm lhe nom to the rouai dmto mpid adirolateâ uplin of the

Limassol Forwt blodc duing the Early Miocme.

FU- eviâmœ Of the compressive evmt can be seen in the magmtic fokic, defmed by balh the nkobopy of magnetic susœptibility and the animtropy of anhysteretic magnetizaüon, of wmples in Zones 4 and 5 in the vicinity of the

Ymsa and Ayia Mam* lineamcnit

The vergeme direction of both AMS and AARM, in Zona 4, are to the SW, paraIlel to oie maximwn compression diredim. Furthennore, the AARM mgnetic lineation in these areas cldytnnd NWSE, or pwslkl to the lineaments' tnnd and perpmdiarlsr to the muimum cmpssim dimctim (Figure 7-16).

Comnmdng duing Ihs lahstages dtho Late Mii,follWng th short period dintense localized ampromion, the islanâ of Cyprus war subjW8d to an extembmI mime d tiidaric -. Nunrrwt dudies Obming fault planes, slickmsiâem, anâ extensional joint surkas artüng üwwgh the Troodos sedimentary =ver have defimd two 8)(1on$imdireHom rince îhIate Mi- until the prosent (hpim ef &. , 1Wû, onnd et d.,1 =: ophiolite complex anâ -1 29-

This pdod of extension h.8 been .rraciated with a urpfa-suWudion extension

regiine by Payne nd Rokrbon (1995). An incieased rate of suMMion pehaps

linked to a change in cmv~datation between the Afrim plate and the

Ewasim plate amdthe overriding slab to extend, filling the gap kCt by a ftenctr

migraang rouaiwsrd ('mlling-ôack'). Such a sœnario mwld mate an extensional

frkic in the ovm'ding slab rympathetic to th shpe of the am. Mucimurn

extembn dirsdion w#Jd be per(nindiculu to oie strike d the arc for the adjoining

ana. From th diraission in #dion 7.2.2, the AMS fabric myvwy wII be

By Early Pliocme, SI- subduction rates msmd and tnrnch roll-badc

ceased, ending the ruprs-suWudion nlated extensio(38I regime. Hcwevw

extension during the Pliocme cOnfi*nU8d in a slightly diffemt orientation fming

to ths vmt the Pegia halfqmben (Payne and Robwtron, 1995), the Polerni bmin

(an extension to the Polis graben) nd to the south the Pissouri barin (Omag-

SpoMr ef a/., 1Q89) (Figure 74). Palmgme, Mioam anâ Quatemary

Cypnrr, am cut by ywngerfaub md rrQnrionrljoinh trending 100'-130' /2ûû0-

310" which correlates to a dm8)ctension direcüon of 025' 1205'. l'ha

, ww, ûue abmion ancbjon in AARM composite frkic ir dwlyocientd Soulhwmt, South and Southeast Cyptus

s, axial plensr ckavage -'-w"-4 AMS

NW and ssE îimaüon AMS 4 AARM 7.5 Summary

Table 7-2 rummarizes the relative chrondogical relationship betwwn bedding, stylolitic deavage, AMS lineation and foliation, and AARM lineatim and foliation.

Shortly Mer the deposition and probably during later stages of sedimentation, S, deavage was aquired due to gravity sliding of sdiments in various directions iesulting ftorn basin and iidge topography. Early Miocene compression in the Limassol Forest Blodc region developed an axial planar cleavage verging to the SW, as well as an AMS and AARM vergence direded to the

SW. Finally, Late Miocene supra-subduction extension is expressed by the AMS lineation. However, the AMS fabric could also potentially express Pleistocene age gravity sliding due to localized uplift of Mount Troodos. Chapter 8 - Conclusions

This thesis sought to define the magnetic fabric of the Troodos ophiolite

cirwm sedimentary succession and subsequently interpret the results to shed extra

light on the estaûlished tectonic evolution of Cypms. In the literature, the rnagnetic

fabric of Cypnis rocks ha$ only been previwdy Wedby Tauxe et al. (1998) who

studied the AMS of dikes. Additionally, bedding and stylolitic deavage data, was

colleded in the field and was coupled with the magnetic fabric results.

The study incorporateâ picidominantly ramples from the Lefkara and Pakhna

Fornations (Miocme and older sediments) of the sedimentary succession with

some sedimentary rock samples of Pliocm and younger age. Tectonic adivity

affecting the sedimentary succession indude (Chapter 1):

a aie later stages of a 90 degm wunterclodmise rotation of the TrOOdos

Microplate which terminated in Eariy Eocene tim,

a Eady Miocme age localued uplift and southwestward thniding d the

Limassol Forest Blo& (LFB),

a Mioœne junp of the suWudion zone from a position north of the island to

a position souai of the islak. Continu 'roll-badc' or migration southward

has been postulatd (Chaptw I), wid

PWstoœm cigo localizeâ uplin of the Troodos ophiolite cornplex.

, It is within these tectonic mttings and mechanisms that th obmed pcrofabric

and magneüc fabric of this sampk wite wem interpreted. -1 33-

The goal d thir Qudy, nldkig rock WCto tedonici, could mt k re8chd if petrofabrics al- wwe king intwpmted. On an autcmp scale, portions of th

mineralogy. Within Chepter 4, eviwanâ diraruion of the diamgnatic, para~gneticanâ ferromagnetic contributon wem plesmted. 60th low-field and high-field wsœptibility identifid that dismrgmtic minemls were an important minerdogical liadion of #a mmpkr, wbm AMS masum~syielded negative mean susceptibilities in 37% of the rniples (n-1170) and Micromg results idorMd diamagi#oc mebix in -1 296 d the mpks(n =l7O). The range of man -1 34- ferromagnetic content contributed mon, than 50 % of the surceptibility in 71% of the samples (no1 70), hwever mean low-field susœptibility values would indicate that magnetite makes up less 0.1 % d the cores volume (se9 Table 4-3) in almost the entire sample suite. nierefore, interpmtation of the AMS fabric will refiect the prefwed crystallographic orientation of the dey minerals whereas interpretation of the MMfabric will rd& aie prefemd dimensional orientation of the magnetite grains.

Table 84 summarizes üm petrofabric and magnetic fabric characteristics presented in Chapters 5,6, and 7.

'rbk 8-1 Sumrna AMS AARM NNW, WNW

SW, NNE

NNW to NNE md SSE to SSW

mgnetic foliation -13s- The interpretation and discussion of these retults are found in Chapter 7,

where Table 7-2 summarizes the relative chmnology of the S,, AMS and AARM

fabrics and the mechanisms which possibly generated them. A history is outlined

for ôoth the island as a whole and th8 region of the Yeresa fold and thrust bel.

Proximally to the Limassol Forest Block, the fabricr developed durhg a

single tedonic event (Eaily to Middle Miocene) which uplifted and th~stedthe

Limassol Forest Blodc routhwestward cmating aie Yeresa Fold and thrust belt and

three other compressional linesment S,, AMS and AARM vergencu al1 indicate a

tectonic push directd to aie SW. It is an accapted viw that S, would be the fint

fabric to develop and that AMS and subsequently AARM would follow. Given the

relative time of formation and the apparent antidodom'se rotation of the vergence

direction in this area, Iconduded that the defornation was possibly produoed by

non-coaxial strain.

The fabric developed in other regions of the idand seem dominently

influenced by gravity sliding. A basin topgraphy was suggested to explain th

highly variable S, vergence directions. AMS vergena and magnetic limation

yielded much more consistent orientations, Wich have been interpreted in Mo

weye. The fint associates the AMS ta supra-subduction extension due to a rauthward rnigrating subduction zone during the Miocene (section 7.2.2).

,l Seconâly, the fabric may also bu interpreted as expressing a Pleistoœne age

localiud t8donic upliR of the Troodos ophiolite complex Sima the studies rodc

amples range in aga betwm L.to Cretaceou~and Plioœne, samples ywnger -1 36- than Miocene age could not express a fabric of supra-subduction extension, and thereforo if older samples developed fabric associated with thir event, two AMS fakic should be identifiable. Unfortunately, in mis case, the fakic ptoduwd by supra-subduction extension and that producd by gravity sliding, due to tedonic uplR of the Troodor ophiolite cornplex, would result in rimilsr AMS expressions.

fhe AARM fabric, away fiom the Limassol Fwest Block, is a composite fabric whm the magnetic lineation (MW;Chapter 6) is not expressed by the maximun axes of the AARM ellipooid but instead by the intemiediate axes. The maximum axes npresent the intemedion lineation betwem the MMfoliation plane and Se.

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Ben-Avraham, 2. and Nw, A, 1Qû6, Collisional processes in the Eastern

Barth&, O., Choukroune, P. and Jsgouta;, P., 1979, Orthogneiu, mylonite and noncoaxial defmtion d granites: the example of the South Armoflcen shar zone: JOUmaî ofstnrdud -yI 1: 3142.

Blome, C.D. and Irwin, W.P., 1985, Equivalent radioluian sges fmm ophiolitic tenanes of Cypms and Omn: -yt 13: 401404.

Bmadaik, GeJe, 1991, Comktion ol min with mitotropy uf magnetic wsœpübility (AMS): Purs and AppEsd GdOphysks, 135: 15-29.

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Wood, D. S., Owt81, G., Singh, J. anâ Bc#nat, H. F., 1976, Stnin and aniwtmpy in rocks: ~b8ophWTmnmcüWt ofthe Royd Socrd& &London, MW: 2742. Appendix A x 1 Table A-1 Fidd Data Table A-1 Field Data Table A-1 Field Data Tabîe A-1 Field Data , Table A4 Field Data : Table A-1 Field Data Tabîe A-1 Field Data / Table A-1 Field Data TaMe A4 Field Data -1 54- Table A4 Field Data Tabk A-1 Field Data Table A-1 Field Data 1 I

, Table A-1 Field Data Table A4 Field Data CoonlnCI

-al- Table A-1 Field Data Table A-1 Field Data Table A-1 Field Data Appendix B Table 6-1 AMS Data

SIS 40.4 1S0.8 344.8 178 m.3 SO.4 73.3 118 523 sm.4 214.8 3l *O 344.3 rn.8 39.7 181.2 aos.1 1413 242.8 184.8 Ido.? m.4 a QI 1P 3m *l lm3 271.4 71.1 am.@ sa a.# 2m.8 a72 2l.4 aa3 a2 m.0 2lA m.a lW.2 1- 1- am.4 30.7 =7 Table 011 AMS Data 1.8 ô7.8 11.2 61.3 fa2 a3 90 89 ecns sa.3 m.4 m.3 14.6 a.8 74.3 41.7 m.@ 8.8 2m.a 7m.4 12l.3 W.8 w*1 00.3 ml au i 53.8 P.2 ea8 3n.1 m la63 s.3 134.6 üû.6 41.3 aO.8 124 10 lm w 74.7 34 84.1 106.3 s.0 m4 s.7 ml s7.l a6 73.5 as n m.1 '18 1 ddb ml n.7 a7 a7 lob7 S6.4 117.3 IAO 161.1 m.4 a#4 'CO.? 4 m.# la2 m.6 a13 œ.s m 181.4 '1RO 2aa 747 O PO.1 262 Sn, ma Table B-1 AMS Data 1œ.a 190.1 Sl 3142 213 3m.S m.S 8.7 1m.3 1m.O ss.1 m.s =.a 5P.7 18.4 1552 1x1 1s a2 m.7 1S.7 366.4 la0 le23 155.6 lm7 121.4 ml 30.7 la4 so 1m.2 ins 1QO.8 la4 la7 10.8 3s aB.7 1- 12.8 3.8 72.8 m s6.s

rn m.7 1a.a a@ 0.0 6.0 0.8 99.3 18.4 a2 s7 s 19.4 8.1 13.8 2) 30.4 21 304 ras a4 4.3 1s.s 7.1 12.9 0.1 lm 13 12 12 w.2 6.6 a4 14.0 lad 6.8 18s P 8.9 a.0 B.? 21 11.7 M a3 j TableB-1 AMS Data q

1.s 42 23.4 9.4 S.@ 113 124 16.7 1.9 44.8 13.3 0.7

ses 8.9 23.1 18.4 6.3 13.1 7.4 53.1 29 189 6.4 44.7 s2 103 7 1S.? 18 a8 ab 216 30.4 a4.7 s.3 24.3 91.8 10.8 m 15s 16s 14 15.5 26 m.? la# Sm I i! Table 8-1 AMS Data Table 8-1 AMS Data Table B-1 AMS Data

Table 6-1 AMS Data TaMe 6-1 AMS Data Table B-1 AMS Data

Tabk B-1 AMS Data

T&lû 6-1 AMS Deta

a2 26.3 PO.1 s.8 183.9 16.9 31Q.e le3 1M.a 278.4 40 St.3 18û.6 m4 1m.O UQ.2 1m.5 a6a m.7 m.1 m.1 259.7 36.6 2.2 271 A as 106.3 l2e.2 333.4 308.7 m.? m.7 1893 m.6 1782 al& 1W.7 ma 41 2 m.4 19.ô

331J abd -1 a6

TaMe64 AMS Data Table 6-1 AMS Data Table B-1 AMS Data Distribution of AMS Fc

Flgun 6-1 Spatial dlribution of AMS foliation data. Avemging stations i is indude withh that s1.tmn's average whem the data is wehh

)f AMS Foliation Orientation Spatial Averaging

Awmginq stations am kcrted one kikmtw apad bth in the N-S and EW directions. Data within a 2.5 km radTi ere the data is wsightd Mhrespect to thsir distance hmthe station. n Orientation Spatial Averaging

- - - Dip t- 0-10 110-30 30 - 60 60 - 80 1 80 - 90

ne kibmeter ipwt both in the N-S and E-W directions. Oati within a 2.5 km radius of a station ped to thair dktmnca from the station.

Distribution of AMS Li

Fbun B-2 8-1 distrikition of AMS lineatkn data. Avsnging dations u is kidude within thit station's rwnge where îhe data k wolghll

I of AMS Lineation Orientation Spatial Averaginch

tt'

B. Avemging stitbns rra kcrted one kilomter rpart both in the N-S and EW directions. Data wiaiin r 2.5 km n jhem the dru b wriahted wiîh ns~ctta thdr distance fmm the station.

-1 QO- ln Orientation Spatial Averaging

iilomt@rrpad bath in the N-S riid EW directions. Data within r 2.5 km radius of a station - / to theif distance from the station.

Appendix C Table C-1 AARM Data

Table C-1 AARM Data

FilA Table C-1 AARM Data Distribution of AARM Fa

Fiaun CI1 Spatial distribution of AARM folMn data. Averagiiig stiitkns rm is indude within that station's average whem the data b weighted r ln of MRM Foliation Orientation Spatial Averagii

kn data. Awaging statbns ire kcrted one UbWet8p~t both in the N-S and E-W directions. Data wrtlin a ? rage whem the data is weighted Wh respect to thek distance hom the station. n Orientation Spatial Averaging

b klbfneter aprrl bot h in the N.S and E-W directions. Data within a 2.5 km tadius of a station R to thair distance from the station.

Distribution of AARM I

Figun C-2 Spatial distrikition of MRMline8tion data. Avewhg statbns ami is include withki thit station's avenQuwhere the data is weighted u

1 I

lion Orientation Spatial Averaging

Trend 4 0-10 - 10-30 30 - 60 - 60 - 80 - 80 - 90

p kYomtet apcift both in the N-S and E-W dhdkns. Daîa within a 2.5 km radius of a station t to thek distance mm the station.

Appendix D Table Pl High Field Si~sceptibility Data Table D-1 Higtr Field Susœptibiliîy Data Table D4 High Field Susœptibility Data

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2-a s.4mE40 -40 Table 0-1 High Field Susœptibility Data

Tabk 0-2 Msgnetiz8tion and Cowcivity Paramters Data Tabîe D-2 ~netirationand Cmrcivity Puametc#s Data Table 0-2 Magmtization and Cowcivity Parameters Data wm8 oas O= 0.1 44 O= 038 0.144 0.1 76 Odm 0.18 0.151 0.14 O= 0.t a3 0.181 0.212 0.16 0.1 9 0.1 12 Otl67 0.1 44 Appendix E Ilhm NOTE TO USERS

Oversize maps and charts are microfilmed in sections in the following manner: LEFT TO RIGHT, TOP TO BOTTOM, WlTH SMALL OVERLAPS

This reproduction is the best copy available.

312 ato 30D ,511- g*' bs . P br *=O'wJU

*Mt. Tmodor

Outcrop Locations - MA ations - MAP SHEET A iP SHEET A

Chmuog.k Dun Amr Outcrops

I I , a140 f

1 I

1

1 I 1 l

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i i !

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MAP SHEET B - Solid Geology

MAP SHEET B - Solid Geology of the study Area