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LondonStudentChapter UniversityofWesternOntario SocietyofEconomicGeologists–LondonStudentChapter DetachmentFaultSettingsoftheLowerColorado RiverandDeathValley February11–20,2016 Objective: Theprimaryobjectiveofthistripistoviewpost‐Laramidemid‐Tertiarydetachment faults,thecharacterofsyn‐extensionmagmatism,andthenatureofassociated preciousmetalepithermalandIOCGstylesofmineralization. TripParticipants: Dr.BobLinnen–UWOProfessor&TripLeader(Driver) Dr.NeilBanerjee–UWOProfessor&TripLeader(Driver) JessicaStromberg–GradStudent,TripLeader,SEGStudentChapterVice‐President (Driver) DianaZylik–UndergraduateStudent&SEGLondonStudentChapterSecretary JonO’Callaghan–GraduateStudent ConnorDavis–GraduateStudent DiegoUribe–GraduateStudent SarahCoDyre–GraduateStudent AlexanderMunro–UndergraduateStudent ScottHutchinson–UndergraduateStudent AdamDemedeiros–UndergraduateStudent NeeraSundaralingam–UndergraduateStudent DylanLangille–UndergraduateStudent PovilasGrigutis–UndergraduateStudent MatthewDeGasperis–UndergraduateStudent Thursday,February11th LeftLondonat2AM.DrivetoDetroit,Michigan(DTW).SpiritAirlinesFlight111 departsDTWat6:50AM,arrivesinLasVegas,Nevada(LAS)at8:19AM.Drivesouth toHooverDam,KingmanPeachSpringTuff,andviewNewberryDetachmentbefore overnightinginLaughlin,NVattheAquariusHotel. Figure1.WaterlevelswerelowattheHooverDam. Figure2.TheMioceneagePeachSpringTuff(aweldedashflow)formerly blanketedaminimumareaof2,000squaremileswheniteruptedfromtheSilver CreekCaldera Friday,February12th TouroftheFriscoMine&MossMinenearBullheadCity.Visitthehistorictownof OatmanandtheOatmanEpithermalDistrict.CampneartheMossMineinGrapevine Canyon. Figure3.TheFriscoMineisapastproducingepithermalgoldandsilvermine discoveredin1894andminedintermittentlyuntil1935withbothundergroundand cutandfillworkings.Thegoldandsilveriscontainedinquartz‐calciteveins.The veinsarestrikingroughly055anddipping12,alongthecontactbetweenthe NeoproterozoicKatherineGraniteandthePlioceneGoldenDoorVolcanics.The mineralizationformsinstringerveins,withamaximumwidthof5.5m. Figure4.GoldenVertex’sMossMineisanAu‐Agepithermal,brecciated,low sulphidationquartz‐calciteveinandstockworksystemextendingoverastrike lengthof1.4km.ThegeneralmanageroftheMossProject,JoeBardwichandtwo otheremployeesgaveusatourofthepit,oldmineworkings,aswellastheir cyanideheapleachsystemandassaylab. Saturday,February13th DeparttheBlackMountainsafterlookingattheGoldRoadVeinandSitgreavesPass. HeadfortheghosttownofSwanseaandit’saccompanyingIOCGdeposits.Wehada flattireuponleavingtheblackmountains,sohadtoforegotheGoldRoadVeinand SitgreavespassandinsteaddrivestraighttoSwansea. Figure5.DesertsunsetfromourcampsiteintheSwanseaghosttown.TheSwansea minewasanundergroundCu‐Fe‐Ag‐AuminelocatedinArizona.Themineralization wasofoxidizedcopperores,mixedinwithquartzandchlorite,withtheorebodies locatedonandimmediatelysurroundingadetachmentsurfacerelatedtopost‐ LaramideOligocene‐Mioceneextension.Originallyprospectedinthe1880s,the mineproducedintermittentlyuntil1944. Sunday,February14th ExploreabitaroundSwanseabeforeheadingsouthtoYuma.StopinQuartziteto visittheQuartziteGoldShow.OvernightinYumaattheTravelodge.Inquartzite, studentswerealsointroducedtotheprocessofgemcuttingandsettingwithavisit totheworkshopofalocallapidary. Figure6.ThedetachmentsurfaceatSwanseahasagreaterthan55kmoffset,and theextendedandfractureduppercrusthostsacomplexhydrothermalsystem.The SwanseadistrcitislocatedinadepressedbasinadjacenttotheBucksinmountains, andthepresenceofsiltstone,sandstoneandlimestonesuggestitwasonceflooded. ThissmallhermitdwellingdugintoawashcanyoninMineralWashissituatedinK‐ metasomatizedbasaltvolcanics.ThisK‐metasomatismreducedtheFeOcontent, withconservativeestimatesgivingFeliberationat4x106tofmetallicFe.Similar estimatesforCusuggesttheremovalof14700tofCu. Monday,February15th GeologyoftheCargoMuchachos,withvisitstoLincolnMining’sOroCruzproperty andtheoldAmericanGirlMine.CampintheChocolateMountains. Figure7.TheAmericanGirlopenpit.TheCargoMuchacho‐Tumcodistrictwas discoveredbytheSpaniardsandminedasearlyas1780‐81.Thedistrictisbelieved tohaveproducedthefirstgoldmineinCalifornia.Americansbeganminingthe districtattheendoftheMexican‐AmericanWarin1848.TheCargoMuchacho, Tumco,PasadenaandAmericanGirlMinescomprisethemajorgoldproducersof theCargoMuchachoDistrict.Thisdistrictisbelievedtobethenorthwestern extensionofthefamousgoldbeltoftheAltarDistrictofSonora,Mexico.Although essentiallyagoldminingdistrictsomecopperwasproducedasabyproductofgold mininghere,mainlyattheAmericanGirlMine.Oreinthisdistrictcontainsfree‐ millinggoldorgoldindisseminatedpyrite.Goldaloneandinassociationwithsilver andcopper,andsomesericiteandkyanitearetheonlymineralsextractedfromthe CargoMuchachos,thelattertwomineralshavebeenproducedmainlysince1930. Thequartzveinsareupto8feetthickinthisregionandcontainthehighestgradeof goldorefoundinImperialCounty.” Figure8.TouringtheabandonedTumcominingtown. Tuesday,February16th TourofNewGold’sWesternMesquiteMine.LunchattheAlgodonesDunes.Visitthe rhyolitedomesattheSaltonSeaandpossiblestopatPaintedCanyonbefore overnightinginJoshuaTreeNationalParkwherewehadanotherflattire. Figure9.SunriseoverourcampsiteintheChocolateMountainsneartheMesquite Mine. Figure10.InthepitatNewGoldsMesquiteMinewhereSEGmemberJessica Strombergsetoffadailyproductionblast.Sincethecommencementofcommercial productionin1985,theMesquiteminehasproducedmorethan4millionouncesof gold.TheMesquiteMinecomprisesaseriesofgolddepositslocalizedalongtwosub‐ parallelzonesofnorthwesterlytrendingfaultingthatoverprintsasequenceof gneissichostrocksandlocallyintrudinggranites.MuchoftheMesquitedistrictis coveredbyaveneerofunconsolidatedpost‐mineralsandandgraveldepositsthat varyfromafewtoseveraltensofmetresinthickness.Goldmineralizationat Mesquitewasdepositedinanepithermalsetting,within150to300metresofthe paleo‐surfacesubsequenttoamphibolitegrademetamorphism.Thebulkofthegold mineralizationoccursasdisseminationsandveinsdevelopedalonganorthwesterly trendingsystemofmoderatelytosteeplydippingfaultsandfractures.Gold primarilyoccursasnativegold,ranginginsizefromverycoarsetosubmicron disseminations. Figure11.TheAlgodonesDunesisalargeerg(sanddunefield)locatedinthe southeasternportionoftheU.S.stateofCalifornia,neartheborderwithArizonaand theMexicanstateofBajaCalifornia.Thefieldisapproximately45mileslongby6 mileswideandextendsalonganorthwest‐southeastlinethatcorrelatestothe prevailingnortherlyandwesterlywinddirections. Wednesday,February17th TouraroundtheJoshuaTreearea.OvernightinJoshuaTree. Figure12.BobLinnendiscussinggranitetypeswhilehikingtheCottonwoodtrailto theMastadonMine.MiningisanintegralpartofthehistoryoftheJoshuaTree NationalParkregion.Thereare288abandonedminingsitesinJoshuaTreeNational Parkwith747mineopenings.1Goldwasthecommodityofgreatestinterest. Figure12.TheabandonedMastodonMine. Figure13.TheviewfromthehistoricDesertQueenMine.TheDesertQueenMine isdevelopedintheWhiteTankmonzogranite,southofthecontactwiththe PalmsQuartzMonzonite.Goldisdescribedasbeinginpocketsassociated withdikesofpegmatite,aplite,andesite,andveinsofgoldbearingquartz. Minorveinletsofmalachiteandazurite,pyrolusitedendrites,andprobable turquoiseoccurinfracturesinsomeofthemineralizedpocketsintheaplite andquartzveins.Wasterockpilesarestainedwiththesesecondaryminerals. Thursday,February18th DrivefromJoshuaTreetoDeathValley,stoppingatMojaveGold’sTelegraphMine explorationsite.CampatFurnaceCreekinDeathValleyNationalPark.An impromptustopatAmboycraterwasalsomade. Figure14.SunriseinJoshuaTree. Figure16.ViewfromtherimoftheAmboyCrater,anextinctcinderconetype ofvolcanothatrisesabovea70‐square‐kilometer(27sqmi)lavafield.Thiscinder coneisestimatedtobe79,000yearsold(+/‐5,000years)andwasformedinlayers ofmostlyvesicularpahoehoe–duringthePleistocenegeologicalperiod.The interiorhasalavalake.LavaflowsasoldasAmboyCrateritselfblanketthe surroundingarea.Themostrecenteruptionwasapproximately10,000yearsago. Figure17.MorecarissuesattheTelegraphMineExplorationsite.TheTelegraph Mineisalow‐sulfidation(quartz‐adularia)epithermalgold&silverdeposit.Gold‐ andsilver‐bearingepithermalbreccia‐veins,whichconsistofquartz‐sericite‐ adularia‐pyriteandquartz‐carbonate,cuttheinformallynamedCretaceous Teutoniaadamellite. Friday,February19th GeologytourofDeathValleyNationalPark.DrivetoLasVegas. Figure18.DantesView.Fromthisvantagepointyoucanviewdistant11049ft. TelescopePeaktoBadwater,thelowestpoint(‐282ft.)intheWesternHemisphere. Thisdifferenceinelevationisastaggering11,331feet(3455m)—thegreatest topographicreliefintheconterminousU.S.Thisstrikingtopographyisaproductof DeathValley'sveryactivetectonics. Figure19.SEGmembersJessicaStromberg,DianaZylikandJonO’Callaghanatthe Badwaterbasin,55mbelowsealevel. Figure20.DeathValleywasina“superbloom”duringourvisit. Figure21.Onefinaldesertsunset. Saturday,February20th HiketheGoldstrikeCanyonHotSpringstrail.FlybacktoDetroitfromLasVegas. Figure22.HikingtheGoldstrikeCanyontrail. st Sunday,February21 ArriveinDetroitanddrivebacktoLondon.