Stratigraphy of placer gold deposits; over. urden drilling In Chaudiere Valley, Que ec 1

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1 Stratigraphy f placer gld depsits; ver. urden drilling n Chaudiere Valley Que ec 1 Shilts W.W. and Smith S.L. Stratigraphy f placer gld depsits; verburden drilling in Chaudiere Valley Quebec; in Current Research Part A Gelgical Survey f Canada Paper 8-1A p Abstract Preliminary lgs f recent deep verburden brehles are crrelated with stratigraphic sectins and previus brehle data. The Rtasnic drill system used has prven t be superir t triple-tube methds in its ability t recver intact large diameter cre fr stratigraphic studies. Brehles in the suthern part f the area cnfirm the presence f three tills and assciated thick glacilacustrine sediments representing at least three glacial events. n the nrthern part f the area the verburden is nt s thick and in places appears t be lder than any sediments encuntered in upper Chaudiere Valley. Resume On a cmpare des diagraphies preliminaires de sndages prfnds realises recemment dans des mrts-terrains avec des cupes stratigraphiques et des dnnees de sndages anterieurs. Le systeme de frage Rtasnic s'est revele superieur aux systemes a tris tubes pur recuperer des carttes de grand diametre intactes a des fins d'etudes stratigraphiques. Les sndages dans la partie sud de la regin cnfirment la presence de tris tills et d'epais sediments glcilacustres cnn exes representant au mins tris evenements glaciaires. Dans la partie nrd de la regin les mrts-terrains ne snt pas aussi epais et par endrits ils semblent plus anciens que tus les sediments releves dans la vallee du curs superieur de la riviere Chaudiere. 1 Cntributin t Federal Asbests nitiatives Gescience Research Prgram

2 ntrductin n winter f 1984 and summer f 1985 tw systems fr drilling and cntinuusly sampling deep verburden were tested in upper Chaudiere River valley f the Eastern Twnships Quebec (Fig. 84.1). Selectin f drilling sites ver areas f deepest verburden was made frm the study f hammer and dynamite refractin seismic prfiles carried ut in 198 and The bjectives f this prject funded under the Federal Asbests nitiatives Gescience Research Prgram are 1) t test and cmpare new drilling methds in thick stny verburden typical f the Appalachian regin; 2) t crrelate glacial stratigraphy knwn frm natural and man-made sectins in upper Chaudiere Valley with that in adjacent areas where verburden was mined fr r knwn t have high ptential fr gld and; 3) t drill and sample knwn gldbearing uncnslidated sediments t determine their stratigraphy genesis and the genesis f their gld. t is expected that the results f this prject will cntribute substantially t the ratinalizatin and cst-effectiveness f gld explratin in this regin lng knwn fr its buried and mdern placer depsits. Althugh the Quaternary histry f Chaudiere Valley and adjacent regins has been the subject f a great deal f research ver the past tw decades (Gadd a 1971; McDnald 197; McDnald and Shilts 1971; Gadd et al. 1972; LaSalle et al ; Shilts ; LaSalle 198) and a cnsensus has been reached regarding the majr glacial events t affect the regin (LaSalle 1984) few attempts have been made t drill deep verburden t find lder Quaternary depsits. n additin the stratigraphy f the gld-bearing strata east f Saint-Gerges has never been recnciled with mdern Quaternary stratigraphy the gldbearing "gravels" being assigned a Tertiary age n the basis f their highly xidized appearance (Byle 1979). 4 'N 71 'E 24 Glacial sedimentatin and stratigraphy Briefly the glacial stratigraphy f Chaudiere Valley (Fig. 84.2) cmprises at least three glacial events represented by the Jhnville Chaudiere and Lennxville tills (McDnald and Shilts 1971) respecti vely frm ldest t yungest. At present all f these tills are thught t have been depsited during the Wiscnsinan Stage. Tills and sediments that were depsited in prglacial lakes r glacially fed streams in this part f the Appalachians are grey where fresh and cntain abundant pyrite in the frm f cubes twinned cubes r brken cubes as well as traces f ther sulphides. Lennxville Till which frms the surface unit f mst f the regin is cmmnly weathered t depths f 3-4 m nly the upper metre frming a true slum. Where weathered Lennxville Till and all assciated and lder glacial sediments are stained brwn r tan by irn xides frmed as a result f xidatin f the abundant sulphides in the sand and finer sizes f the matrix (see Shilts 1984 fig. 3). Where this xidatin ccurs sulphides and ther labile minerals such as siderite are destryed making nearsurface gechemical surveys using heavy mineral separates f drift r mdern sediments derived frm drift difficult t interpret. Oxidatin is rarely nted in sectins. Chaudiere Till has never been bserved t be xidized and althugh Jhnville Till is xidized at its surface where bserved it has nly been seen expsed at tw places in the Appalachians. Oxidatin due t grundwater flw thrugh permeable layers has been bserved deep in sme sectins. Quebec 1:' " Maine'"" ) '( ' f f '- -"" r". -. '" r' J '" ''--'-'' - _- L- C Symbls ry Brehles 198 Brehles Sectins ' '"-.;.': 1 N Km Figure Area f study in Eastern Twnships Quebec shwing lcatins f sectins and brehles. 74

3 Sediments separating the till sheets are thick laminated glacilacustrine silty clay and fluvial gravel and silt. Whenever glaciers advanced int Chaudiere Valley r retreated nrthward frm the valley the nrthward draining rivers were blcked frming large lakes int which thick silty clay was depsited. When glaciers std nrth f St. Lawrence River r disappeared altgether allwing free nrthward drainage fluvial gravels sands and fldplain depsits were frmed in the Chaudiere and its tributary valleys. Thus a typical stratigraphic sequence fr ne glacial event might cnsist f fluvial sediments; verlain by thin laminated silty clay which mayr may nt be defrmed by glacial verriding; verlain by till which cmmnly has thin «m) stratified lenses f sand r silty clay in it; verlain by thick laminated silty clay cmmnly with tilllike stny beds thught t be slumped frm the retreating ice frnt in the frm f turbidity current depsits. The cmmn laminated facies f the glacilacustrine depsits may grade int r be replaced by sandy t gravelly deltaic depsits where majr streams entered the lakes r by ice-cntact deltaic depsits where the ice frnt std in ne place in the lake fr a time. t is imprtant t understand these ;::.!!! -:; x c: c: -' '" e '" Cl '" "'. c: :5:E => :;:; E E '" -.. '" l':! ::::J E c: >. c.3 "" : -c = ::::J ;:: c: '" U Massawippi Frmatin lhnville Till.!!! -:; c: c: c: E '" -c a. '" Palezic bedrck l:t.lyl.? (Diagrammatic nt t scale) Figure Cmpsite sectin f quaternary stratigraphy f upper Chaudiere Valley (frm Shil ts 1981). weathering and sedimentatin mdels and the reginal stratigraphy when interpreting the sedimentary facies encuntered in the deep brehles. Preliminary bservatins The stratigraphic drilling carried ut in 1981f-1985 intersected glacial units that generally can be fit int the stratigraphic framewrk prpsed by Shilts (J 981) (Fig. 8lf.3). n places hwever it appears that certain bedrck valleys were filled either with several glacial and nnglacial units early in the Pleistcene (Grande Culee River fr example) r with an abnrmal thickness f a single waterlain prglacial r subglacial unit (>lfo m f ice cntact gravel sand and silty clay in Samsn River) frming a flr between bedrck sides f the valleys ver which several glaciers may have advanced withut having much effect n the valley fill. f this actually happened each glacier may have accmplished little mre in these valleys than t rewrk and redepsit the upper few metres f sediment. Thus there may be a significant uncnfrmity between the surface till and lder tills and assciated sediments particularly in valleys r depressins riented r shaped in such a way that they were prtected frm the glacial ersin that stripped lder uncnslidated sediments frm less ideally lcated valleys. A t present there is n way t judge hw serius an impediment t crrelatin this situatin may be. Althugh Gadd (l95b) suggested that buried valleys may be fund in the Beauceville area by study f aerial phtgraphs bth seismic and drilling results indicate that significant buried valleys f mre than 1 m depth may underlie slpes r mdern alluvial plains with virtually n surface expressin (Fig. 8lf.lf). The nly way that these valleys may be detected reliably is by gephysical r drilling techniques. n many f these buried valleys in upper Chaudiere River valley the sediment fill cmprises substantial thicknesses f silty clay depsited in glacial Lake Gayhurst. The Gayhurst Frmatin is a glacilacustrine unit depsited in a large prglacial lake that filled the Chaudiere and adjacent valleys t elevatins f 39 t lf27 m when the glacier that depsited Chaudiere Till retreated nrthwestward and std against the nrthwest slpe f the Appalachian Highlands. When the glacier readvanced acrss Chaudiere Valley and eventually acrss New England it depsited Lennxville Till ver Gayhurst sediments. Nrth f Saint-Ludger Gayhurst sediments are relatively thin because f glacial ersin r lwer rates f depsitin than suth f Saint-Ludger where mre than 9 m f laminated silt and clay were encuntered in several brehles particularly near Drlet (see Fig. 8lf.l fr lcatins). These thick sediments frm a significant part f the fill in upper Liniere Samsn and Chaudiere valleys and prvide a majr bstacle t mineral explratin and t explitatin f any ld gldbearing beds that might be fund at depth. This prblem shuld be recgnized when planning an explratin prgram in valleys that were inundated by glacial Lake Gayhurst including valleys t the west in the Saint-Franc;is River drainage basin. Gilbert River gld depsits Six hles were drilled t bedrck in the vicinity f the placer gld depsit in the buried valley alng Gilbert River just nrth f Saint-Gerges. The appearance f the glacial units in these hles is generally quite unlike sediment encuntered in any ther f the 25 hles and 2 sectins examined in Chaudiere Valley (Fig. 8lf.5). Sediment at the base f the hles is s thrughly xidized and indurated that it was difficult in preliminary lgging t tell its genesis r 75

4 '- Cf' Metres "'19PG_"'18 "17 e e - :.. PG : A A. A " : ; ii- -:-.c.::. -_- A A r A =c #' fl. All. :== ;' A A -- A A C ' 8 sr A A A ' ms A. C 1 C " ms LEGEND GJ Till Clayey till (Drlet lentil) rn Sandy till Varve. a Sandy varve. Defrmed varve. a Ma lve c y -?- r'_"c: :"'=-J -::::=j D -1- " '" 8 : ' 8 ' -:;; '? J:;--_ ::':. RK 1 ' ' A. "-' Tl Sand Pstglacial PG Cr -bedded.and Gravel Lennxville Till A Alluvium clluvium Gayhurst Frmatin 8 g Turbidite. B Ablatin bulder mantle Chaudlere Till C Shear zne Weatherln g zne Massawlppl B D emlnated rganic Frmatin D fragment. R Mdern.lump Jhnvllle Till E Cntact (defined gradatlnalt Pre-Jhnville sediments F [!J Bedrck 8 --:. h -'--!. RK "18 1 _"'7. B '.4 B 225 RK PG "1 C 8 ' --- 'E ''' F'? cntinuatin f prfile 8 "1A e23 e24 "13 O!Pr.:-- _ c:: :: ::: A ::.:::.:: B '?-- - e? 8g PG 7 "- 8 " 1-_-: -_- e ll -f ;1 D E RK B Feet e4 "12 "14 P '" A " All. ":' A i8 Palezic bedrck RK Hle and were drilled.ub.tantlally belw lcal tpgraphy A B J'? ms Figure (A-C). Diagrams f measured stratigraphic sectins and brehles with assumed crrelatins alng suth t nrth crss-sectin f Chaudiere River valley (see Fig fr lcatins).

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7 4 'N 71 'E Quebec 1> Malne' ') " -" " r" -"' - " ' e' " t ;-::. u. 'Lf J r-''''.'! Burled valley. N 1 ( defined a88umed ) Km Figure Apprximate lcatins f buried valleys as determined by refractin seismic methds. even t differentiate it frm underlying highly weathered bedrck. At present it is believed that till and clluvium verlie the weathered bedrck and are in turn verlain by a fluvial gravel which was the main pay zne sught in the placer peratin. Near the axis f the buried valley up t m f interlaminated grey and red silty clay with interbedded fine- t medium-grained sand verlies the gravel. These beds shw few signs f xidatin and appear t be erded away n the flanks f the buried valley. A till cmplex verlies the varves t the surface. Unlike tills f similar texture elsewhere in the regin these tills are brwn indicating deep xidatin r mre likely that they cntain a large amunt f the highly weathered debris cmmn at the base f the brehles. This debris wuld have been erded frm adjacent areas and transprted acrss the buried valley filling it in. The tills in the brehles and the surface till well expsed alng Gilbert River adjacent t the mine cntain ultramafic clasts transprted frm utcrps nrthwest f the buried channel. Because ultramafic prvenance is detected easily by gechemical and mineralgical means it shuld be easy t differentiate clluvial r preglacial units frm glacial units at this site as well as Chaudiere Till which was depsited by westerly flwing ice that wuld nt have crssed the ultramafic utcrps (Rencz and Shilts 198). The upper till cmplex appears t cmprise mre than ne till sheet and in brehle 13 a highly altered zne within the cmplex has the appearance f a palesl (Fig. 84.5). As many as three till sheets may be represented in brehle 13 suggesting that the varved sequence is much lder than the Gayhurst Frmatin which it superficially resembles and which separates the yungest Lennxville frm lder Chaudiere Till in upper Chaudiere Valley. Because f the imprtance f the Gilbert River site t mdelling the surce f buried and surficial placer gld in the regin a detailed sedimentlgical mineralgical and gechemical study will be made f these beds. DrilJing A Rtasnic drill was used fr the first time in the Eastern Twnships in 1985 and prved t be superir t triple-tube methds tested previusly. The Rtasnic drill utilizes high frequency vibratin t drill recvering an intact cm-diameter cre t bedrck. Brehles were cased t prevent cllapse f material frm the walls and subsequent sample cntaminatin. Access fr drilling was by rad easily travelled by the six-wheel drive vehicle n which the drill head was munted (Fig. 84.). With nly minr breaks fr vehicle repair and maintenance as well as a cuple f days spent at brehle 4 the 24 hles cmprising 191 m f cntinuus cre were drilled in ne mnth. Recvery averaged 9% but varied accrding t sediment chesiveness. Cmpact r chesive till and clay yielded as much a's 1% recvery slightly mre than cmpact sand (85%). Lse sand and gravel cmmnly fell ut f the cre barrel unless blcked by underlying mre chesive sediment. Cnsequently sand and gravel averaged 75% recvery and lse sft clay averaged belw % recvery. n additin sft sediment is squeezed and elngated by the drilling prcess. Bedrck samples als were cllected t depths f at least m int bedrck but sft brittle shales that underlie mst f the regin were cmmnly pwdered by the vibratin. 79

8 '.J METRES a.sj " ( 71 4'E ---" r e12 OC Wde" 2451 pst f mine shaft utcrp buried valley buried valley (assumed). r "' J N 14 t 4 14'N "!==" 1Km " e19 C) it J:J < e2 C)O' '1 ;' < _.C) ' O O 3' '''''<!> 'O -.::: }::" _ 1"' :> e13 '.-r-; e18 D.1 QQ ' :' 1 <:> Q ::':' palesl? f::;!: 1 utcrp FEET a.s e 'b:fj r '-'--' r 8 c 3 :r :s iii Q.:r 845 Q. N _ - C> r Level f xidatin LEGEN 815 Till 8 Varves 785 d. Silt.r!ill] Sand 77O Gravel f-755 Crss sectin f buried valley (cmpressed hrizntal scale) Alluvium clluvium r74 L ' Bedrck Cntact (defined gradatinal) 171 Figure Diagrams f brehles and sectin alng Gilbert River with assumed crrelatins.

9 Preliminary results Frm seismic surveys and frm results f the drilling prgram it is bvius that whatever cntrlled lcal base level in Chaudiere Valley befre glaciatin has been radically mdified by glacial prcesses. Buried valleys have been fund adjacent t mst f the majr rivers whse present channels are suspended in many cases as much as 1 m abve the bedrck flr f the valleys they presently ccupy. Althugh nt much new stratigraphy has been identified in these buried valleys further analysis f the sediment lgs and quantitative data may lead t revisin f the lcal stratigraphy as it has been deduced frm the natural sectins expsed abve river level. Fr example at least 1 m f uncnslidated sediment lies beneath the 4 m-high Samsn River sectin (Shilts 1978) which cntains almst the entire knwn Quaternary sequence f Chaudiere Valley. Acknwledgments The authrs express their thanks t the crew frm Midwest Drilling Yves Harvey Pierre Girux and Jean-Marc Lamthe f Rche Cnsulting Grup fr setting up the lgistics fr the drilling prgram and GPR Gephysics nc. fr the seismic prfiles. Jacques Lcat and Fran<;is Gilbert f Cniagas Ltd. allwed access t the mining prperty arund Saint-Simn-es-Mines and kindly prvided maps and infrmatin that assisted in lcating drill sites. We gratefully acknwledge the effrts f sabelle Prulx and Katharine Rdd in lgging mst f the drill cre. Figure 84 Drilling set-up (A) and clse-up shwing extrusin f cre frm cre barrel (B). Brehles up t 9 m in depth were drilled with little difficulty except fr brehle 4. Vibratin f a thick sequence f clay and fine sand and gravel f the Gayhurst Frmatin(?) led t material settling arund the casing causing it t becme stuck. Water pressure was ineffective t disldge the casing because the water was able t flw freely away in sand and gravel units. Many pieces f metal casing had t be abandned in the hle. A similar situatin als in thick Gayhurst sediments in brehle 23 was nly avided by nt cmpleting the hle. References Byle R.W. 1979: The gechemistry f gld and its depsits; Gelgical Survey f Canada Bulletin p. Gadd N.R. 194: Surficial gelgy Beauceville map-area; Gelgical Survey f Canada Paper a: Surficial gelgy Chaudiere River valley; in Reprt f Activities Gelgical Survey Of Canada Paper 5-1 p b: Buried valleys and gld placers Beauce Cunty; in Reprt f Activities Gelgical Survey Of Canada Paper 5-1 p : Pleistcene gelgy f the central St. Lawrence Lwland (with selected passages frm an unpublished manuscript "The St. Lawrence Lwland" by J.W. Gldthwait); Gelgical Survey f Canada Memir 359. Gadd N.R. McDnald B.C. and Shilts W.W. 1972: Deglaciatin f suthern Quebec; Gelgical Survey f Canada Paper p. LaSalle P. 198: L'r dans les sediments meubles: Frmatin des placers extractin et ccurrences dans e sud-est du Quebec; Ministere de 'energie et des ressurces du Quebec DPV p. 1984: Quaternary stratigraphy f Quebec: A review; in Quaternary Stratigraphy f Canada - A Canadian Cntributin t GCP Prject 24 ed. R.J. Fultn; Gelgical Survey f Canada Paper 84-1 p

10 LaSalle P. Martineau G. and Chauvin L. 197: Gelgie des sediments meubles d'une partie de la Beauce et du Bas Saint-Laurent Quebec; Ministere des richesses naturelles DPV p. 1979: Lits de bryphytes du Wiscnsin Myen Vallee Jnctin Quebec; Jurnal canadien des sciences de la terre v. t" p McDnald B.C. 197: Pleistcene events and chrnlgy in the Appalachian regin f sutheastern Quebec Canada; unpublished Ph.D. dissertatin Department f Gelgy Yale University 11 p. McDnald B.C. and Shilts W.W. 1971: Quaternary stratigraphy and events in sutheastern Quebec; Gelgical Sciety f America Bulletin v. 82 p Rencz A.N. and Shilts W.W. 198: Nickel in sils and terrains; in Nickel ed. J.O. Nriagu; Jhn p vegetatin f glaciated in the Envirnment Wiley and Sns nc. Shilts W.W. 1978: Detailed sedimentlgical study f till sheets in a stratigraphic sectin Samsn River Quebec; Gelgical Survey f Canada Bulletin p. 1981: Surficial gelgy f the Lac Megantic area Quebec; Gelgical Survey f Canada Memir p. 1984: Till gechemistry in Finland and Canada; Jurnal f Gechemical Explratin v. 21 p

11 .! f}tft)t Trc Jl.f1'llt'. QmONS... JAN "" SENT 1 EXPDES GEOLOGCAL SURVEY OF CANADA PAPER 8-1A COMMSSON GEOLOGQUE DU CANADA ETUDE 8-1A CURRENT RESEARCH PART A RECHERCHES EN COURS PARTE A ssued in tw sectinspubliee en deux vlumes: pages andet pages

12 Minister f SLippl y and Services Canada 198 Available in Canada thrugh authrized bkstre agents and ther bkstres r by mail frm Canadian Gvernment Publishing Centre Supply and Services Canada Ottawa Canada KA 59 and frm Gelgical Survey f Canada ffices: Bth Street Ottawa Canada KA OE rd Street N. W. Calgary Alberta T2L 2A7 1 West Pender Street Vancuver British Clumbia VB R8 (mainly B.C. and Yukn) A depsit cpy f this publicatin is als available fr reference in public libraries acrss Canada Cat. N. M44-8AE SBN Canada: $2. Other cuntries: $24. Sld in sets Price subject t change withut ntice Cver Rtated cmpetent amphiblite pd with drag-flded fliatin n its margins Wager Bay area District f Keewatin. This illustratin appears in reprt 27 p. 173 by J.R. Hendersn et al. Page cuverture Masse mineralisee allngee d'amphiblite ayant ete affectee par un muvement de rtatin et dnt la schistsite en brdure se caracterise par des plis d'entra1nementj cette masse se situe dans la regin de la baie Wager district de Keewatin. Cette illustratin paratt a la page 173 du rapprt 27 de J.R. Hendersn et cll.