NorthCarolinaDepartmentofEnvironmentalQuality NorthCarolinaGeologicalSurveyPolicyandInnovationGroup OpenFileReport2017-14
LS
EXPLANATIONOFMAPSYMBO
CONTACTSANDOTHERFEATURES
infe red
faultinfe red
KennethB.Taylor,StateGeologist
791500 3632'30" 7907'30" 3632'30"
Om 40 40 12 1
Om Occg 24 13
38
24 15 16 10 42 40 20 CGS1.6 Om 13 23 32 OMcc
Om 26 42 45 2 23
45
5 36 75 80 203015 50 139 20 22 80 Occg
5 80
14 24
525 22 70 35 OMcc
Om
70 20 Om Mkg
Occg OMcc
OMcc
3630"00" 3 3630"00"
1 Mkg ZMclm 10 6 MKg
45
Mkg 2 CGS1.5 Mygg
ZMclm
ZMclm Occg
Mygg
Mygg OMcc
2
ZMclm Mygg 8 33
CGS1.4 Mygg Om
42
ZMclm ZMclm
40 36 ZMclm
60
Mygg
52 Zog
Zhrg Zh 42 52
ZMclm
Zog Zog CZqd
Zhrg Zhrg
Zh Zum
Zog
CGSS.2 Zum
Zh
Zum
Zog
CZqd
Zog
3622'30" 3622'30" 7915'00" 7907'30"
approximatelimitofHycoshearzoneconcealed (gradational)
Appropriatestrikeanddipdirection 70 Strikeanddipoflatepegmatitedike
ofmainphasefoliation(Sm), (multipleobservationsatonelocation)
dipnotprovided(dataofKevinWilkins) Strikeoflatepegmatitedike
42 Strikeanddipofinclinedmainphasefoliation(Sm) (multipleobservationsatonelocation)
Strikeanddipofmainphase
Verticalmainphasefoliation 24 foldaxialplane(FM-axialplane)
13
45 Strikeanddipofinclinedmainphasefoliation Bearingandplungeofminerallineation(LM)
andlayering(SM+LYR) Horizontalminerallineation
Verticalmainphasefoliationandlayering 15 Bearingandplungeofminorfoldhinge(FL)
20
Strikeanddipoflatepegmatitedike Horizontallatephasefoldaxis
Observationstationlocation
BlanchPrisonQuary(abandoned)
Prospect U-Pbagedate-327+/-1.5Ma;
11-AngieProspect(mica) Kilgoregranite(Wortmanetal.,1998)
2-J.G.SlaughterProspect(mica)
3-O.W.BarkerProspect(mica) 2017CarolinaGeologicalSocietyfieldtripstoplocation
withnumber(Hibbardetal.,2017)
CGSCGSS.2-HighRockGranitewinginHycoshearzone
Mine 1.4CGS1.4-AleghaniangranitoidinHycoshearzone
11-YarboroNo.1Mine(mica)CGS1.5-KilgoreGranitegneiss
2-YarboroNo.2Mine(feldspar)CGS1.6-ConnelyChurchorthogneiss
IN TRODUCTION
ThisisacompiledgeologicmapofdatafromgeologicinvestigationsalongtheHycoShearZone.Detaileddiscussionsofthe geologicinterpretationsareprovidedinHibbardetal.(1998)andHibbardetal.(2017).G eologicinformationfromWilkins(1994)andunpublishedstationmapswereusedinthiscompilation.ProspectandminelocationsfromUSGSMineralResourcesDataSystem(MRDS).
UN ITDESCRIPTION S
Aleghaniangranitoids(ca.335-319Ma)
Mkg-Kilgoreorthogneiss:Mediumgrey,medium-tocoarse-grained,K-feldspar-plagioclase-quartz-biotiteorthogneiss.Localymegacrysticandheterogeneouslydeformed;feldsparcommonlydisplaysadistinct�clastic�texture.Deformationrangesfroma single,weaktomoderatefoliationtothenorthwesttoanintense,gneissicfoliationinthesoutheast,alongthecontactbetweenthe plutonandadjacentCountryLinecomplex.Inmostplacesalongthecontact,theKilgoregranitegneissisconcordantlyinterlayered withgneissoftheCountryLinecomplex,althoughlocaly,itcrosscutslayeringinthecomplex(She l,1996).TheKilgoregneissalso containsenclavesofamphiboliteanddioritelithicalyidenticaltoimmediatelyadjacentCountryLinecomplexrocksinthehangingwal.Theseenclavesrangefromequidimensionalpodsinthenorthtoelongatenarowlensesandlayersinthesouth.The maficenclavescontainagneissiclayeringandfoliationthatisgeneralyobliquetothefoliationinthesuroundinggranitoid.A327�
1.5MaU-PbzirconagefromtheKilgoregraniteisinterpretedasthecrystalizationageforthepluton(Wortmanetal.,1998).
Mygg-YanceyvilleOrthogneiss(includedintheCountryLinecomplex):Whitishtolightgrey,foliated,medium-tocoarse-grainedbiotitegranitegneiss.OverprintedbythesamesequenceofdeformationasthesuroundingmaficgneissesintheCountryLinecomplex.Containsxenolithsoftheenclosinglayeredmaficgneissesandlocaly,dikesofthegranitegneisscrosscutlayeringinthemaficgneisses(Shel,1996).TheYanceyvilegranitegneisshasaU-Pbzirconageof335.4+/-2.2Ma(Wortmanetal.1998)(ontheYanceyvileQuadrangle).
MiltonTe rane�Milton-ChopawamsicArc(ca.475-450Ma)
Occg�ConnallyChurchorthogneiss:Lightgrey,foliated,fine-tomedium-grained,granticgneiss.Localy,garnetandmagnetitebearing.CorelatedwiththeSheltonIgneoussuiteofHenika(2002),whichincludesgranitegneissdatedatca.450Ma(Coleretal.,2000)nearbyinVirginia.
OMcc-Cunninghamcomplex:Heterogeneousmixtureofmediumtodarkgreybiotitegneissandbiotiteschistrangingfrom massive,equigranulargraniticgneisstolayersandlensesofbiotite�garnet�silimaniteschist.Themostcommonrocktypeisbiotitegneissthatrepresentsahybridbetweenthesetwoend-members,althoughdistinctiregular-shapedareasofeitherend-membercanbefound.ThegraniticgneissislocalyK-feldsparmegacrysticwithcrystalsupto50mmlong.Layering,atcentimetertometerscale,isdefinedbyfeldsparporphyroclastconcentrationaswe lasbiotitecontent;itisgeneralysubtleinmostoftheunit,butitisaccentuatednearthecontactofthegneisseswiththeCountryLinecomplex.Localy,meter-scalepodsofamphibolite,dioriticgneiss,andcalc-slicategneissareenvelopedinamatrixofbiotitegneiss.Thegraniticgneissiscompositionalysimilarto andappearstogradeintotheCarboniferousKilgoreorthogneiss.Thebiotiteschistissimilarto,andappearstogradeintotheOrdovician(?)Miltonschistandparagneiss.ThusthecomplexappearstobeamixtureofOrdovicianandMississippianrocks.
Om�Miltonschistandparagneiss:Unitisdominatedbyadistinctivemedium-grainedgraytogray-brownbiotite�garnet� silimaniteschistandparagneissthatcommonlycontainporphyroclastsoffeldspar�quartz�biotitepegmatitethatrangefrom1mm upto60mmdiameter(She l,1996).Localy,thebiotiteschist-paragneissisinterlayeredwithquartz-muscovite-garnet�silimanite schist,thinlylayeredquartzite,calc-slicategneiss,intermediateamphibolegneiss,amphibolite,andminormarble.N orthwestoftheDanRiver,theareaisdominantlymaficgneissandamphibolite.Primarystructuresinaloftheserockshavebeencompletelyobliteratedbyintensetectonism.TheMiltonschistandparagneissunitiscontinuouswithschistandparagneissinnearbyDanvile,Virginia,thatisinterlayeredwithOrdovicianmetavolcanicrocks(Coleretal.,2000).
CarolinaTe rane
TheCountryLinecomplex(ca.614�323Ma)
ZMclm-NeoproterozoicmaficgneissandamphiboliteinterlayeredwithMississippianpegmatitesandorthogneiss:
Greenschisttoamphibolitefaciesmaficgneisseswithinterlayeredgranitoidsandgraniticpegmatites;subordinatebiotitegneissand minormetapyroxenite,semipeliticschist,andfelsicschist(She l,1996).Themaficgneissesrangefromamphibolitestobiotite�amphibolegneisses.Commonly,theyarelayeredonacentimetertometerscale,althoughinsomeplacestheyaremassive,witha medium-tocoarse-grainedgabbro-liketexture.Themaficgneissesareextensivelyinterlayeredwithgraniticpegmatites,localyenvelopebrownish-grey,fine-grainedgranitoids,andareintrudedbycross-cuttinggraniticpegmatites.
N orthoftheYanceyvilegranitegneiss,thecomplexischaracterizedbyaveryregularlylayered(centimeter-scale),fine-tomedium-grainedgraybiotite+blackishgreenamphibolegneisswithinterlayeredgraniticgneiss(Shel,1996).Localy,overthespanofafew meters,theregularlylayeredgneissgradesintomigmatite(sensulato)withanetworkoffoliatedcoarsegranitoidcontainingmeter scalepodsofamphibolitewithlayeringandfoliationobliquetothatinthegranitoid.
BiotitegneissisaminorcomponentoftheCountryLinecomplex;typicalyitisafine-tomedium-grainedequigranular,grayquartz�feldspar-biotite+garnetgneiss.Generalyitformsmassiveandhomogeneouslens-shapedbodiesthataretoosmaltoberesolved at1:24,000.
Zirconfromalayeredmaficgneisssub-unitintheSouthBoston,VAareahasyieldedadiscordantupperinterceptageof613.9+/�
9.3Mathatisinterpretedtoreflectaprotolithageforthemaficgneisses.Zirconandsphenefromthesamesamplehaveyieldeda concordantageofca.323Ma(Wortmanetal.,1998).ConcordantlyinterlayeredpegmatitesincreaseinvolumetowardstheMississippianYanceyvileorthogneiss,suggestingthattheconcordantpegmatitesarealsoMississippian.Thus,thecomplexisa mixtureofN eoproterozoicandMississippianrocks.
CZqd�Quartzdioriteplutons:Fine-tocoarse-grained,heterogeneouslyfoliated,biotiteand/oramphibolebearing,quartzdiorite.
HycoArc(ca.635-610Ma)
Zhrg-HighRockGranite:Whitish-pink,fine-tocoarse-grained,weaklytostronglyfoliated,localyunfoliated,granite.Major mineralsincludepotassiumfeldspar(orthoclaseandmicrocline),plagioclase,biotiteandquartz.Minormineralsincludemuscovite,garnet,chlorite,sericite,epidote,titaniteandzircon.Muscoviteincreasesinabundanceanddeformationincreasesnortheastwardthroughthestock.(DescriptionfromVinesetal.,1998).TheHighRockgraniteisundated;however,becauseitispetrographicalyidenticaltotheN eoproterozoicOsmondgranite(Vinesetal.,1998)thetwoareconsideredtobemutualycorelative.
Zog-O smondGranite:Lightgrey,fine-tomedium-grained,foliatedbiotitegranite.Wortmanetal.(2000)reportedaU-Pbage upperinterceptdateof612.4+5.2/-1.7Ma.
Zum-CaswellCountyMafic-Ultramaficsuite:Mediumtocoarse-grained,massivetowelfoliated,composedmainlyofhornblende,actinolite,epidote,chloriteandtremolite(Wilson,1975).Enstatite,serpentine,chromite,talc,sphene,pyriteandother opaquemineralsarelocalypresentinvariableamounts.DescriptionfromButler(1989).
Zh-HycoFormation:Dominantlygreenschistfaciesfelsicvolcanicandvolcaniclasticrockswithsubordinateintermediateand maficcomponents.TheformationextendsalongtheeasternmarginoftheHycoshearzone.Primaryfeaturesarewe lpreservedin mostoftheHycoFormation.Themostcommonrocktypeisfelsiccrystaltuffcontainingabundantanhedralcrystalsofeitherquartz orplagioclaseupto3mmindiameter.Thetuffsaretypicalyinterlayeredwithfelsiclapilituffs,quartz-muscovitephylites,pebblyvolcanicconglomerate,andintermediatetomaficcrystaltuffs.TheHycoFormationrecordsfelsictointermediatemagmatismduringaca.20m.y.spanstartingatca.633Ma(Wortmanetal.,2000;BradleyandMiler,201).
REFEREN CES:
Almendinger,R.W .,Cardozo,N.C.,andFisher,D.,2013,StructuralGeologyAlgorithms:VectorsandTensors:Cambridge,England,CambridgeUniversityPress,289pp.Bradley,P.J.andMiler,B.V.,2011,N ewgeologicmappingandageconstraintsintheHycoArcoftheCarolinate raneinOrangeCounty,N orthCarolina:GeologicalSocietyofAmericaAbstractswithPrograms,Vol.43,N o.2.Butler,J.R.,1989,ReviewandclassificationofultramaficbodiesinthePiedmontoftheCarolinas:inMittwede,S.andStoddard,E.,eds.,UltramaficrocksoftheAppalachianPiedmont:G eologicalSocietyofAmericaSpecialPaper231,p.19-31.Cardozo,N.,andAlmendinger,R.W .,2013,SphericalprojectionswithOSXStereonet:ComputersandG eosciences,v.51,no.0,p.193-205,doi:10.1016/j.cageo.2012.07.021Coler,D.G.,W ortman,G.L.,Samson,S.D.,Hibbard,J.P.,andStern,R.,2000,U-Pbgeochronologic,N disotopic,and geochemicalevidenceforthecorelationoftheChopawamsicandMiltonte ranes,PiedmontZone,southernAppalachianorogen.JournalofGeology,v.108,p.363-381.Henika,W .S.,2002,GeologicmapoftheVirginiaportionoftheDanvile30x60minutequadrangle,VirginiaDivisionofMineralResourcesPublication166.Hibbard,J,Bradley,P.andShell,G,2017,RampingthroughthePiedmont�AnoverviewofthegeologyoftheHycoShearZone,north-centralN orthCarolina,inHibbard,J.,Bradley,P.andOwens,B.,RampingthroughthePiedmont�theHycoShearZoneand associatedrocksinN orth-centralN orthCarolina,CarolinaG eologicalSocietyFieldTripGuidebook2017.Hibbard,J.,Shell,G.,Bradley,P.,Samson,S.,andW ortman,G.,1998,TheHycoshearzoneinN orthCarolinaandsouthernVirginia:ImplicationsforthePiedmontZone-CarolinaZoneboundaryinthesouthernAppalachians:AmericanJournalofScience,v.298,p.85-107.Shel,G.S.,1996,N atureoftheCarolinaslatebelt-MiltonbeltboundarynearYanceyvile,N orthCarolina:M.S.thesis,N orthCarolinaStateUniversity,Raleigh,N orthCarolina,96p.Vines,J.,Hibbard,J.,Shell,G.,1998,StructuralgeologyoftheHighRockgranite:ImplicationsfordisplacementalongtheHyco shearzone,N orthCarolina.SoutheasternGeology37,163-176.W ilkins,K.J.,1994,Unpublished,FieldtripguidetotheMiltonbelt�CarolinaslatebeltboundaryregionintheLeasburgandMilton7.5�quadrangles.W ilson,W .F.1975,GeologyoftheWinstead15-minutequadrangle,NorthCarolina.GeologicalMapSeries2,NorthCarolinaGeologicalSurvey.W ortman,G.,Samson,S.,andHibbard,J.,1998,PreciseU-PbtimingconstraintsonthekinematicdevelopmentoftheHycoshear zone,southernAppalachians:AmericanJournalScience,v.298,p.108-130.W ortman,G.,Samson,S.,andHibbard,J.,2000,PreciseU-PbzirconconstraintsontheearliestmagmatichistoryoftheCarolinate rane:JournalofG eology,v.108,p.321-338.
Equal-AreaSchmidtNetProjections andRoseDiagram
PlotsandcalculationscreatedusingStereonetv.8.6.0basedonAlmendingeretal.(2013)andCardozoandAlmendinger(2013).
CompiledGeologicMapoftheHycoShearZonePortionsoftheMiltonandLeasburg7.5-MinuteQuadrangles,OpenFileReport2017-14
EqualAreaSchmidtNetProjectionof EqualAreaSchmidtNetProjectionofContouredPolestoMainPhaseFoliation(SM)[blackcircles]and ContouredPolestoLatePhaseFoliation(SL)BearingandPlungeofMainPhaseLineations(LM)[redtriangles] ContourInterval=2sigma
N=8ContourInterval=2sigmaMainPhaseFoliationN =53LatePhaselineationsN =14
ContoursdisplayedforSMonly
N.C. CompiledGeologicMapoftheHycoShearZonePortionsoftheMiltonandLeasburg7.5-MinuteQuadrangles,CaswellandPersonCounties,NorthCarolina UnidirectionalRoseDiagramofLatePegmatiteDikes N=8OuterCircle=70%
Geologyby:KevinWilkinsandJamesP.Hibbard Meanvector=324degrees
DigitalCartographyby:MichaelA.Medina,PhlipJ.BradleyandBrandonT.Peach ThisisanOpenFileMap.IthasbeenreviewedinternalyforconformitywithNorthCarolinaGeologicalSurveymappingstandardsandwiththeN orthAmericanStratigraphicCode.Furtherrevisionsor corectionstothisOpenFilemapmayoccur.
2017
AcknowledgementsThisresearchwassupportedbytheN ationalScienceFoundation:G rantsEAR-9219979andEAR9506363toJ.HibbardandEAR-9219583toS.Samson.
