Remarkable Variability of Dyke Features at the Vicuña Pampa

Remarkable variability of dyke features at the Vicuña Pampa Volcanic Complex, Southern Central Andes Silvina Guzmán, Marco Neri, Roberto Carniel, Joan Martí, Pablo Grosse, Carolina Montero-López, Adelina Geyer

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Silvina Guzmán, Marco Neri, Roberto Carniel, Joan Martí, Pablo Grosse, et al.. Remarkable variability of dyke features at the Vicuña Pampa Volcanic Complex, Southern Central Andes. Terra Nova, Wiley-Blackwell, 2017, 29 (4), pp.224-232. 10.1111/ter.12268. insu-01522829

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Distributed under a Creative Commons Attribution - NonCommercial - NoDerivatives| 4.0 International License Spain This article isprotected Allrights bycopyright. reserved. 10.1111/ter.12268 version andtheVersi this between differences through the copyediting, typesetting, pagination forpublication accepted This articlehasbeen 4 3 2 1 Montero-López Silvina Guzmán Complex, Southern Central Andes Volcanic Vicuña Pampa atthe dykefeatures of variability Remarkable 06-Apr-2017 date: Accepted 31-Mar-2017 date: received version Revised 17-May-2016 date: Received TER-2016-0055.R2 number: Reference Article type :Paper IDDR. CAROLINA :0000-0002-3943-5648) MONTERO-LÓPEZ (Orcid IDDR. MARCONERI :0000-0002-5890-3398) (Orcid ID :0000-0003-3632-2960) (Orcid DR. SILVINA GUZMAN Lerma, Salta, Argentina – 95123Catania, Italy Instituto de Bioy del 9de Geociencias NOA(IBIGEO), CONICET, UNSa, Julio 14,4405,Rosario de Institute of Earth Sciences Jaume Almera, ICTJA-CSIC, Lluis Sole iSabaris s/n, 08028 Barcelona, Istituto Nazionale diGeofisica e Vulcanologia, Osservatorio Etneo-Sezione diCatania, Piazza Roma, 2 AcceptedLaboratorio di misure e trattamento dei segnali, Dipartimento Politecnico di Ingegneria e Architettura Article

1 1,2 , Adelina Geyer , Adelina , Marco Neri , Marco

3 , Roberto Carniel , Roberto 2

and undergone full peer review buthasnotbeen review undergone fullpeer and on of Record. Please cite of Record. Please on and proofreading process, which may lead to 4 , Joan Martí , Joan 2, a , PabloGrosse this article this as doi: 5 , Carolina This article isprotected Allrights bycopyright. reserved. reinjection ma cooling partialarrest, and new of contacts and enclaves one domain of inside the other are interpreted resulting as fromdyke contact have sharp texturesalways mixed with units.Dykes intrudingfound near-surface areonly textures mixed and with brecciated (coherentandbrecciated textures and conglomerates) tobe tend thicker, have lo textures >60° andhavecoherent intruding layers Dykes stiff intense degradation. al and base the at exposed are (trachy)-andesite, and (trachy)-andesite basaltic aremostly which Complex, Volcanic Pampa Vicuña the at Dykes Abstract Short title: Remarkable variability features ofdyke a 5 (DPIA) Università di Udine, Via delle Scienze, 206- 33100Udine, Friuli, Italy (4405), Rosario deLerma, Salta, Argentina, [email protected]; Tel: +54 387 4931755 Permanent address: Instituto deBioy Geociencias del NOA (IBIGEO), CONICET-UNSa, 9de 14Julio Silvina Guzmán Corresponding Author Géosciences, 1A rue de la Férolerie, F45071, Orleans Cedex 2,France Nowatthe Institut des Sciences de la Terre d’Or Accepted Article andFundación CONICET Miguel Lillo, Miguel Lillo 251,4000 Tucumán, Argentina , whereas dykes intruding, whereasdykes more textural domains inasingletextural orcompounddyke). dykes Single s between domains. Dykes with sinuousdomain Dykes domains. s between leans (ISTO, CNRS),Université d’Orleans, Campus wer dips and have coherent, brecciated or mixed ormixed brecciated coherent, dipsandhave wer ong the walls of a large depression resulting from resultingfrom depression walls ofalarge ong the gma. Dykes with straight domain contacts are are domaincontacts withstraight Dykes gma. (lavas, plugs and necks) are thin, mostly dip thin,mostly dip are necks) and (lavas, plugs

compliant materials (breccias compliant materials(breccias

This article isprotected Allrights bycopyright. reserved. Gudmundsson 2005; Goto al. onth studiesfocusing are several Although there upper layer isstiffer, thedyke tendstobe upper layer ismorecompliant,thedyke changes 2015).Whencrossing and Gudmundsson, Browning at orarrested also foundtobedeflected Gudmundsson rocks (e.g. modulus, “E”)ofthemediumthey wi traverse, Pinel e.g. edifice; the from and distance (loa potential dyke path the along local stresses magm intruding rock and bothhost of parameters physical ofthe emplacement ondyke influence the analyze studies ofthese Many analogue). and/or analytical numerical, (experimental, approach a modelling following or characteristics studi several decades, Inrecent Introduction volcanic textures, Keywords: dyke dykes, solidified one. new dykes, witha compound tobe considered

AcceptedGudmundsson, 1992;Gudm , 1991;Gautneband Article et al., et al et 2008; Kavanagh and Sparks, 2011; Delcamp and Sparks,2011; 2008;Kavanagh ., 2012;Petronis et al. , 2012;Delcamp es haveinvestigated dyke propa et al. , 2013; Geshi andOikawa, massif, Vicuña Pa massif, the contact between layers (Gudmundsson, 2011; (Gudmundsson, betweenlayers thecontact and Jaupart, 2000) and on the stiffness (Young’s (Young’s stiffness onthe 2000)and Jaupart, and deflectedtoformasill (Gudmundsson,2011). d of the volcanic edifice above the dyke, depth dyke, abovethe edifice volcanic d ofthe et al et thickerdykes foundinmorecomplianthost th dyke intruding along the margins of an older, an older, marginsdyke of the intrudingalong from moretolessvertical;however,whenthe e field characteristics of dykes (e.g. Ferrari Ferrari (e.g. dykes of e fieldcharacteristics a. Dyke thickness is highly dependent on the onthe dependent thicknessishighly a. Dyke undsson, 1995; Gudmundsson and Brenner, undsson, 1995;GudmundssonandBrenner, ., 2012;GeshiandNeri,2014).Dyke dipis layers of similar stiffness, or when the stiffness, orwhen ofsimilar layers mpa, Central Andes Andes mpa, Central et al et gation by focusing on their field gationfield focusing by ontheir ., 2012; Daniels ., 2012; 2014; Geshi and Neri, 2014; 2014; GeshiandNeri, et al. , 2012; et et AcceptedThis article isprotected Allrights bycopyright. reserved. massifthat 30 kmwidebroadvolcanic Pe 1980; RosselloandJones, 1999;Viramonteand c and originally (Fig. 1) Altiplano–Puna plateau Complex Volcanic Pampa Vicuña The Miocene Geology theVicuña Pampa of VolcanicComplex andw textures coherent purely textures, brecciated purely with dykes are there complex, volcanic a single in study where, mechanical propertiesthe material of they intr the to berelated to seem dykes ofthese characteristics geometrical The Andes. Central southern outat cropping dykes the describe we Here, of aim tounderstandtheevolution Article that studies in considered be to need of dykes aspects textural the characteristics, geometrical or single dykes were as wellonwhetherthe rock), and host magma between temperature in differences ofemplacement, depth fields, stress segregation, rh viscosity,(magma magma crystal rock host andthe magma intruding the between contrasts thermal and/or mechanical rheological, hist emplacement dyke's information onthe 2014; Vezzoli and Corazza2014; GeshiNeri, and 1992; Goto patternsreceived haveattention less much Ferrari (e.g. on 2016), mostarefocused andCorazzato, Vezzoli et al., 2008;Gudmundsson ith both textural domains. ith bothtextural intrusive episodes in volcanoes. intrusive episodesinvolcanoes. suffered intense degradation (Guzmán (Guzmán intensedegradation suffered et al et ., 2012;Petronis ude, butmost importantly ude, auniquecase theyoffer the Vicuña Pampa Volcanic Complex (VPVC), Complex Volcanic Pampa Vicuña the ory. They can provide information on the information onthe provide can They ory. compound.Thisiswhy, inadditiontotheir eology, host-rock mechan eology, host-rock onsidered to be a colla onsidered tobea trinovic, 1999), was recently interpreted as a asa interpreted trinovic, 1999),wasrecently (VPVC), located at the SE margin of the ofthe margin theSE at located (VPVC), to, 2016). However,can textures provide their geometrical feat their geometrical et al. , 1991; Gautneb and Gudmundsson, and Gautneb , 1991; et al. , 2013;GeshiandOikawa, pse caldera (Rossello, caldera pse ical properties, local ical properties,local ures; their textural ures; theirtextural et al ., 2017). AcceptedThis article isprotected Allrights bycopyright. reserved. dykes, 15ofwhich studied 33 fieldwork we abundantinthewest sheet intrusionsaremost (seeFi composition having adacite composition frombasaltic (trachy)-andesites(trachy)-andesites, to withonly onesampled dyke and undiff Nacimientos Breccia 2,3A),orthemo stiffer RootComplex (seeFig. (Young’s modulus,E,notmeasured,butqualitatively char different have dykes These 2). 2017) (Fig. (Guzmán segments dyke hundreds of by cut The VPVCunitsare VPVC The dykes floorofthedepression (Fig. ontheSW 1;Guzman out cropping Breccia,Bayo complex, possibly during the late Miocene,c and Article depression (Fig. 1).Thesecondvolcaniccycle are cycle volcanic first ofthe units different 13–18 km morphological depression, to during themiddle underwent intensedegradation basaltic andesite (Guzmán toandesite Br(Nacimientos breccias andvolcanic Breccia) MoradoEpiclasticSuccession) succession (Cerro FlowsLava Succession; Upper Succession and Flows Lava (Lower flows lava 12.41Ma), (RootComplex; and necks plugs formed of ont lies VPVC of the cycle volcanic The first g. File 1). 4andSupplementary erentiated epiclastic erentiated wide and 1200 m deep (Guzman mdeep(Guzman wide and1200 et al et ., 2017). After thisfirst After ., 2017). exposed onthefloor and alongexposed thewallsof re compliant Cerro Bayo Breccia (see Fig. 2,3B), 2,3B), Fig. (see Breccia compliantCerroBayo re op of an igneous–metamorphic basement and is basementandis op ofanigneous–metamorphic were sampled, recording their geographic and geographic their recording were sampled, ern portion of the depression (Fig. During portionofthedepression 2). ern eccia) whose composition mainly ranges from from whose compositionmainly ranges eccia) acteristics depending on the relative stiffness therelativestiffness on acteristics depending onsists ofblockandashdepositstheCerro occurred after the main degradation of the themaindegradation ofthe occurred after , block and ash flow deposits(La , blockandashflow Cumbre 12.19 Ma) separated by separated 12.19 Ma) estimated) ofthematerialthey the estimated) intrude: late Miocene that gave rise to a large gaverise toalarge lateMiocenethat /volcanic material. Dykes vary in in Dykes vary /volcanic material.

et al., Dykes andothermagmaticDykes volcanic cycle, the VPVC VPVC the cycle, volcanic et al et 2017;Carniel ., 2017) (Fig. 1). The ., 2017)(Fig. 1).The a thick epiclastic epiclastic a thick et al ., 2017). et al., et

AcceptedThis article isprotected Allrights bycopyright. reserved. withtherocks th show sharpcontacts dy These 3F). (Fig. broken smaller andfrequently a setin hyalocrystalline, seriatetextures (phenocrysts ofplagioclase, clinopyroxene, orthopyroxene ± amphibole) todacitic with intextures a matrix of the same composition (Fig. are The 3E,F). clasts trachyandesitic arecharacterisedDykes withbrecciated textures orthop clinopyroxene, plagioclase, (trachy)-andes They basaltic are (F amicrocrystalline setin textures and seriate 3C). Petrographically, coherent dykes showhyalocrystalline toholocrystalline inequigranular amphibole-phyric with frequently to 6m, andindip between 35°and88°. Porphy Articlerocks, withoutthedevelopmentofglassy orque are mainly porphyritic andless commonly aphanitic. They have sharp contacts withthe intruded ormi textures, orbrecciated havecoherent Dykes dykes VPVC the of characteristics Textural of175m. from 12mto870m,withanaverage vary analysis) image-based 0.4m to6 from measurements) ranges m,with an tolow-an File 1),butmoderate- rangi angles dip have thedykes than 85%of strike,dipandthic stratigraphic position,textures, gle (<60°) inclined sheets are also present. Their thickness (field Theirthickness(field alsopresent. sheetsare gle inclined (<60°) ite (see Supplementary File yroxene ± amphibole and olivine. andolivine. yroxene ± amphibole cm-sized phenocrysts setin cm-sizedphenocrysts ey intrude. They dip between 38° and 79°. and 38° ey intrude. They dipbetween

cryptocrystalline groundmass, where mineralsare where groundmass, cryptocrystalline ng from 60° to 90° (see Table 1 of Supplementary Supplementary 1of Table 60°to90°(see ng from nched margins, andvary nched ig. or 3D), cryptocrystalline vitric groundmass. ig. bywith porphyritic clastsaphyric subangular to average of1m;theirse kes vary in thickness from 1mto3andalsokes vary inthicknessfrom kness (Table 1 of Supplementary File 1). More 1).More File ofSupplementary kness (Table1 xtures of both. Dykes with coherent textures ofboth. Dykes textures coherent xtures with ritic dykes are plagioclase-phyric andless plagioclase-phyric are ritic dykes anaphaniticgroundmass (Fig. 1) and contain phenocrysts of and containphenocrysts of 1) in thicknessfrom0.4 in m gment lengths (satellite AcceptedThis article isprotected Allrights bycopyright. reserved. emplacement. after eroded intensely have been C;see Breccia (group Bayo intruding theCerro Guzmán arid conditions(see surface) topographic closetotheoriginal (fairly this dykesintruding and B(i.e. (Fig dykes feeder and contains central depression Si emplacement. of ages relative we cansuggest combining the stratigraphic relations between and dykes hostrocks with geochemical analysis, We have noclear constraints onthe possible variability emplacement ofdyke depths, butby (Fig. 5D). dip (Fig. 5C)ordyke thickness rock (Fig. dyke 5B), textures dyke geochemical compositionsandthe geochemical datasetlimited between (9analyses), we is a donotsee relationship but the Article by simpleprocesses group beexplained each may SupplementaryFile 1andgroups A,B andCin candistinguishWe threegroupsofdykes acco relationships Dyke–host-rock thickness–texture–composition sharpbutstraight. contacts are enclaves as develops onetexture and 3G,H) (Fig. or cores the coherent and margins brecciated textures withindymixed compound dyke. These textur andcoherent Combinations ofbrecciated et al et and other units) are the youngest, the units)are and other ., 2017). On the other hand, the only group of dykes not ofdykes group theonly the otherhand, ., 2017).On vice versa. Sometimes the contacts are sinuous sinuous are contacts Sometimesthe versa. vice and therefore suffered negligible erosionduring suffered therefore and nce the Cerro Bayo Breccia was formed after the the after wasformed Breccia Bayo Cerro nce the al domains are sometimes found in a single or or sometimesfoundinasingle al domainsare . 3B and 4), we infer that dykes from groups A A groups from dykes that infer 4),we 3B and . Fig. mayFiles) 4andSupplementary possibly Fig. 4).Smallcompositi kes always have sharp contactsbetweenthe havesharp always kes (Fig. 5A), mechanical properties of the host ofthe properties mechanical (Fig. 5A), within the othercases (Fig. inother 3G); the such as different crystallization degrees. The degrees. The crystallization such asdifferent rding to their geocherding totheir were intruded at shallow intruded levels were at mical signatures (see mical signatures (see onal variationswithin This article isprotected Allrights bycopyright. reserved. we foundnodykes 2013, 2015).However, 2008; Geshi matches obtained fully results frommodels the stiffness upto100GPa: Gudmundsson,2006,2011; Gudmundsson al stiffness (typical compliant breccias asthic (Fig. 7), rocks stiffness oftheintruded thicknesses Itseems thatdyke magma composition. indicates thattheirdiff The modest geochemical and mineralogical variability observed among the VPVCdykes Discussion more than 80%are porphyritic. recognised (Fig. 6B).We 64% dipmorethan70° 90°; 60°and between dipvaries Their 6A). m(Fig. 1 80% thinnerthan than withmore and 2m, Root Complex; theirav cut thestiffer 11 dykes 6CandTabl Fig. compound dyke (see asingle or within ones coherent bordersof the and at centre the in both domains brecciated c have dykes These (Fig. 6B). than70° greater Theybeing 35°a thinnerthan3m. dipbetween mandvariesbetween thicknessis1.15 average 22 dykes relatively intrude compliant material, consisting ofbreccias conglomerates.and Their

Accepted., 2012),whilethinner dykes cutbothmorecomplia Article et al et ., 2010, 2012; Gudmundsson ., 2010, erences in geometry and texture cannot texture ingeometry and erences of 1–10 GPa: Gudmundsson, 2006, 2011; Gudmundsson Gudmundsson,2006,2011; 1–10GPa: of e 1 of Supplementary File 1). File 1). e 1ofSupplementary intruding layers with different stiffness.Furthermore, layersintruding withdifferent ker dykes are only found cutting the relatively more relatively the found cutting only are dykes ker et al et erage thickness is 0.6 m and ranges between 0.5 0.5 between ranges erage thicknessis0.6mand and previous field studies (see Keating andpreviousfieldstudies(seeKeating 0.4 and 6 m (Fig. 6A), with 75% of the dykes with 75%ofthedykes 0.4 and6m(Fig. 6A), nd 90°, with 72% of them having dip angles nd 90°,with72%ofthemhaving dipangles oherent, brecciated and mixed textures with textures mixed and oherent, brecciated ., 2012; Geshi and Neri, 2014; Rivalta ., 2012;GeshiandNeri, only coherent textures (Fig. 6C), of which (Fig. 6C),ofwhich textures coherent only are - at least partially - controlled by the the by - controlled partially atleast - are nt and stiffer volcanic sequences (typical nt andstiffervolcanicsequences(typical beattributedtocontrastsin et al et ., 2012).Thisrelation et al et et al et et et ., ., ., AcceptedThis article isprotected Allrights bycopyright. reserved. involving, surface, topographic in is similar tothatproposed by GeshiandOikawa mechanism This 8. figure in presented is stages different the illustrating Asketch emplacement. we invoketh (2003) fortuffisites.Therefore, mechan origin, withafracture non-explosive a indicate to seem all domains brecciated the within shards glass or fragments pumice of absence thehostrock,simila domainsand brecciated VPVC, the At surface. the only near occurrence their basedmainly textures, and mixed brecciated the (Petronis isobserved hostrock crushed fault (e.g. Mathius rocks,resultingintruding fro brecciated host Article andCorazzato, 2016).Otherstudiesshow Vezzoli origin explosively driven an generally, more asprocesses particle- such collision and co wall dykes haspreviously natureof The brecciated Geshi units(e.g. surface >60° material alwayshavedips Dykes cutting materialscompliant more showshallow dips,whereas those intruding stiffer hostrocks. different forthe volcanic edifice onpossibledifferences constraints have we donot et al. et al., , 2008;Petronis 2010,2012). (Fig. and7).Shallowdipsmay 6B indykes occur intruding near- afirststage, materialsfrom et al., et al et (e.g. Geshi and Neri, 2014, and references therein; therein; references 2014,and GeshiandNeri, (e.g. m magma propagation aself-inducedshear m magma along 2013). We discuss here a possible explanation for explanation possible a here discuss We 2013). ., 2013); in these cases a mix of dyke breccia and and ofdyke breccia casesamix ., these 2013); in ism similar to the one proposed by Tuffen ism similartotheoneproposedby Tuffen e possibility duringe apulsating ofbrecciation on the contact relationships of domains and on ofdomainsandon relationships thecontact on (2014) for the propagation of a dyke near the ofadyke the near (2014)forthepropagation been explained as due to mechanical erosion erosion asduetomechanical been explained llapse - or asllapse relatedphreato-magmatic -or to or, r composition of clasts and matrix andther compositionofclastsandmatrix in the local stress and/or field theload a of dykes withbulging margins andlobate

the sharp contacts between dykes with with dykes between sharpcontacts the wall-rock erosion and collapse. erosionandcollapse. wall-rock et al et . AcceptedThis article isprotected Allrights bycopyright. reserved. atthemargin of domainisfound brecciated whenthe or brecciated is dyke whole the (when domains textural brecciated of the formation but with sharp (Fig. one 9A), coherent second showstheorig scenario resulting compound dyke. The intrude, passing the margins between fo ofthe dyke already was totally solidified (Fig. 9).The byexplained theintrusionofaseconddyke in contac of thedyke, andthe the centralportion The deformation. a ductile of evidence other are as thesharpandsinuouscontactspresence Article a1mthick days for (~4.6 very short batch was batc magma first ofthe emplacement the between dyke sectionofthe cross entire the surface, coherent domain(2 (1 portion abrecciated with dyke of the section a cross may see we case, In this strength. failure its exceeding by batch magma first almost-cooled already the pulseof asuccessive of thearrival followed by leadstodr Kerr, 1991), of volatiles(Lister and exsolution by the helped which, temperature, their in a decrease causing surface, the approaching arre totemporary subject may be These dykes nd magma batch; see Fig. 8A). Sometime seeFig. 8A). magma batch; the dyke) indicatesn the dyke) may be brecciated (see Fig. 8B). The time span The timespan 8B). Fig. (see brecciated maybe magma that, in turn, may induce fragmentation of of inducefragmentation magma that,inturn,may dyke; seeestimates dyke; the place where a formerly emplaced pulsating pulsating aformerlyemplaced theplacewhere rmer dyke and the host rock, thus becoming a thusbecoming hostrock, andthe dyke rmer straight contacts. The proposed mechanism of of mechanism proposed The contacts. straight few cases in which the brecciated domain is in domainis thebrecciated inwhich cases few ts between the domains are straight, may be may be arestraight, ts betweenthedomains new dyke uses the previous weakness zone tonew dyke usesthepreviousweaknesszone astic changes in their rheology. This can be can be This intheirrheology. astic changes of enclaves of one textural domainwithinthe ofonetextural of enclaves sts in response to a pressure drop when when drop pressure a to sts inresponse h in the dyke and the arrival of the second thesecond of arrival and the dyke h inthe inal central inal central brecciated s, usually tothetopographic closer st ear-surface conditions. ear-surface magmabatch)remaining a and in the Supplementary File 2), Filein theSupplementary 2), dyke enclosed by a by dyke enclosed AcceptedThis article isprotected Allrights bycopyright. reserved. Gudmundsson. Menand Thierry Browning and the acknowledge We theEnglish. for improving y Cajal her Ramón for grateful grant. AGis CONICET 489,PIP (PIP 286)andCIUNSa JMis grateful 1810. (PRX16/00056) fortheMECD funding for grateful are andPG SG, CML Acknowledgements can be generated when asecond dy within semi-solidifieddyke po shallowlevels;brecci propagation/evolution at Article ofthehostrock, erosion invoke explosivity or andmixed with brecciated ofdykes The presence only (<60°)are stiffness, butinclinedsheets tosub-ve Vertical textures. thethree of have any cutting more compliantmaterials generally are thicker, have highly variablecan dipangles and intruding are stiffer materials always andtend thinner more coherent tobe and vertical; those of units – several intrude andmixed brecciated At the Vicuña Pampa Volcanic dykes Complex, withthree types – oftextures coherent, Conclusions rtions causes their mechanical fragmentation. Compounddykes fragmentation. mechanical rtions causestheir ke intrudes along of the margins ke intrudes and suggestions by the editors, Jean Braun and Agust and Braun editors, Jean by the and suggestions present when intruding compliant materials. materials. whenintruding compliant present by ANPCyT (PICT 2012-0419; PICT 2011-0407), PICT 2011-0407), 2012-0419; ANPCyT (PICT by contract (RYC-2012-11024). S. Conway is thanked S. Conway (RYC-2012-11024). isthanked contract rtical dykes intrude regardless any units oftheir ated result textures whenmagma re-injection the complex with different stiffnesses. Dykes stiffnesses. with different complex the but as a result of arrest events during dyke dyke eventsduring arrest but asaresultof very constructive comments made by John John madeby comments constructive very textures is explained withouttheneedto isexplained textures a previous solidified dyke. solidifieddyke. aprevious AcceptedThis article isprotected Allrights bycopyright. reserved. dikes andfeeder feeders Gudmundsson, A Kusumoto,S.and Geshi, N., Iceland. emplacement inWest Gautneb, H.andGudmundsson,A.,1992 stimare le dilatazioni diun apparato vulcanico Ferrari, L.,and Garduño, V.H. Neri, M., 1991. I di Volcanology andde ofstabilisation Islands:record a F. andDeegan, M.,2012.Dykes stru Torrado, F. J. and R., vanWykDelcamp, A.,Troll,V. deVries, Article1112, doi:10.1130/B30537.1 ofc Evidence fortheinfluence Daniels, 10.1007/s00445-014-0889-4 formation. dike ofring alternative mechanism andGudmundsson,Browning, A.,2015. J. Caldera fau grid-searching algorithm inR. 2017.FI S.andNeri,M., Carniel, R.,Guzmán, References

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, 1-42. 2 , 294-297. AcceptedThis article isprotected Allrights bycopyright. reserved. yellow line). and sinuouscontact(dashed and coherent (Br) brecciated 3G; Fig. in dyke the portions oftheporphyric domainareincludedin withthecoherent(Coh)po contact (blackline) shows abreccia margin SupplementaryFile 1);the some fragments withmixed (dyke withinthe texture breccia. G)Dyke 1in 33inTable dyke ofabrecciated F)Microphotograph breccia. Supplementary dashedblacklinesindica File 1); microcrystalline E)Dyke matrix. withbrecci Table 1inSupplementary Microphoto File 1).D) with cohe Dyke line.C) continuous white – Breccia complia (relatively Bayo Breccia Articlenotescale). personB) (circled) for Dykes –dottedwhite lines along margins –cutting the Cerro Fig. 3:A) describedinthefield). (forthe 33 dykes textures Fig. 2:Dyke distributionwithinthe VPVC, differentiating the unitsthey intrude and their (2017). Vicuñaof theFig. Pampa Volcanic Modified 1:Geological Complex. fromGuzman map captions Figure

Dykes – dotted white lines along margins –intruding (stiff whitelinesalongDykes theRootComplex material; –dotted margins nt material), and asmalllava nt material), the brecciated domain. H) Microphotograph of Microphotographof domain.H) thebrecciated rphyric (circle) inner domain; that note some (Coh) porphyric textures separated by a sharp a sharp by separated textures (Coh)porphyric ated (see texture 8 in Table dyke 1in te the borders of some fragments within the fragments withinthe ofsome te theborders ; dashed yellow; dashed linesindicatethebordersof graph of a dyke with porphyric texture and and texture with porphyric graph adyke of rent plagioclase-phyric texture (see dyke 1 in 1in dyke (see texture rent plagioclase-phyric ted texture (Br) and displays a sharp-ductile a sharp-ductile displays and (Br) ted texture flow above theCerroBayo et al.

AcceptedThis article isprotected Allrights bycopyright. reserved. t batch; of thefirstmagma upw intrudes,producing magma batch In t dyke. pulsating a single formation of Fig. 8:Schematic interpretation ofa pulsating t dyke; dip ofdykes inrela Fig. versus 7:Thickness stiffness. Fig. dyke thickness,(B) 6:Histogramsof(A) Fig. 4. intruded material, thickne C)dyke of Zr diagramsFig. (ppm)vsSr(ppm 5:Harker dykes fromgroup C. Article Sun,1995)ofdiagrams and (McDonough D)dykes fromgroup A,E)dykes fromgroup B andF) Maitre (Le diagram tovariabledegrees elements may berelated ge their tips;B,C) Mainevidencetodiscriminate intrusions and grey post-CerroBayo for Breccia) Vertical prolongation ofdykes is andundiffere older RootComplex post-depression unit) BrecciaCerro Bayo (CBB; ge indicate thedifferent ofthestratigraphi sketch Fig. 4:A)General et al., ochemical groups Notethatdykes ofdykes. fromgroupsAandBochemical cutthe 1989);C)Ba/Th vsEu/Eu*diag 3 showsthefinalresult: acohere represented by dashed lines (black for pre-main-degradation forpre-main-degradation (black dashedlines by represented ss, and D) dyke dip. Coloursindi dyke and D) ss, ntiated volcanic/epiclastic de volcanic/epiclastic ntiated ard pressure (black arrows) and consequent fragmentation fragmentation consequent and arrows) (black pressure ard 1 , the first magma, the first batchemplaced; is int tion tothe they stiffness ofthe units intrude. c relations between dykes and host rocks; colours hostrocks;colours and betweendykes c relations of crystal fractionation. crystal fractionation. of ochemical groups of dykes; differences in major inmajor groups differences ochemical ofdykes; dip and(C)textureas and otherunits,those fromgroup Ccutthe ) asafunctionof:A)textures, B) stiffnessof indicating the possible original locations of of locations possibleoriginal indicatingthe 1 , t 2 andt ram. D–F) Chondrite-normalised ram. D–F) 3 nt core and brecciated margins margins brecciated and nt core indicate three stages during the the during stages three indicate posits (pre-depression units). units). posits (pre-depression cate geochemical groups groups as geochemical in cate B) TotalAlkalisSilica a functionofhost-rock 2 , thesecond AcceptedThis article isprotected Allrights bycopyright. reserved. Article domain. coherent external the by andwrapped contained is domain brecciated schematic Fig. process in Fig. 9:Schematicinte portionofadyke. ingrey. B)Brecciated highlighted are coherent one the inside domain brecciated ofthe enclaves some one; brecciated the inside domain coherent the limitbetween textural domains ismarked bya blackas line, enclaves are small ofthe contacts.A)Port and sinuous sharp by separated rpretation of a compound dyke, formed by an inner pulsating dyke (see aninnerpulsating by ofacompounddyke, (see dyke formed rpretation 8) plus an outer single dyke emplac dyke single 8) plusanouter ion with brecciated margin and coherent core; core; andcoherent margin withbrecciated ion ed along the margins; note the inner margins; theinner note the ed along AcceptedThis article isprotected Allrights bycopyright. reserved. Article

AcceptedThis article isprotected Allrights bycopyright. reserved. Article