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OCT-29-96 TUE 12;36 Ptl SHEP ttILLER <br />970 223 7171 <br />• <br />Port .uu seachaminry, mi6de tailings, Wala Amulet. Quebec <br />meat of the ss-deposited nature o! the taiings solids <br />and pore waters. is both the vadofe mne and the <br />wderlying satunud mne. Thu inida! condition, <br />vhieh provitks the basis for all futon gtwJtemiol <br />chaagas is the vadose zone of the tailing. cannot be <br />asaesscd directly hcnux the wtrite Amulet troll <br />tdesed in 1%1. The initial rontlitian o! rata wlin6 nn <br />be inferred, however, from knowledge Of the milling <br />pttxest and from examination of oiling solids and <br />pore warm that pare tto[ been a(ftaed b1 mlfisle <br />oxidation. <br />water samples obtained from pieaomaets ktand <br />deep in the tat7Iags are hlcely w tbntaia mnceo- <br />rratiau of dissolved coactittrem: sinulu to those M <br />the null process-waters discharged with the pilings. <br />Cltemitai anllyses of sstunted-zone pot.-water <br />samples `tom two doep piesoeceten, kxatttd at piez <br />otaeter nest wA22 (Fip 1, 2) ware presented by <br />Dwva a a(. (1986), attd m abuly torn by $]wiK rt <br />d. (1987). These analyses indicted that the water <br />tsex the base of the itapattulmeat is at pH 7-0, and <br />mnnirs high etsrlemttations d Na, Ca. SO,- and <br />Wwu ooncrntntioas o[ dissolved rnetak including <br />Fe, Pb. Zn and Cu. TYiC is similar to the wmptssition <br />atpected for the w7! protzss-waters. <br />Geodxtoial agtalibritua calwlatiom performed <br />using MiIti fEQ. and the dun praeated by DwvE d <br />af, (1986) and S[w¢ a al. (148'J), itsdtote that the <br />water is the lower d m of the tailings (ssauated men) <br />attains or exceeds sattaarion with respect m the <br />sulfate minerals gypwm (GSO. • 2Fi_O) and jaroate <br />(RFe~(SOi}t(Oi~iJ, and wiN repae ro seveta! feme <br />orybydrmtide aueteTab iitcitsdag feniEydrite <br />(Fe(OH1i). gotntiite (aFe00H), sad Icpidotxocite <br />(yFetOOH)-Thin water alvoelosdy approadtes sstu- <br />ration with respect ro aleite (CaCOy) and dabotiu <br />(catfg(cgl ). . <br />ldiaoscvptc cxamivacoo of the pofishcd sections <br />of the Dore ssmplesm0eae,i from below the depth at <br />aecve oxidation ivdotes tlut magnetite and the <br />prl4dpa! wlfides (pyrite and pyrrltocee) t~ancter- <br />iaial(y lack altentitsn. Thc grain edges of pyrrho- <br />are, tlfe sWSde taiaeial most arsapabk to flur- <br />ation, an typicllY sharp and unrtpiaced- In xvcnl <br />samples. however, a lew pyrrhodu grim with <br />altered dots oavr among unaltered graim. 'These <br />altered pyrrhotite grins were likely ottidtzed wiNe <br />hosed oft kietl palegsurfaQS that tayk interrup- <br />dotts mthe acarmdatioa of the pilings. <br />bccryt for the development of thin oxidized layers <br />at paleostafues, the bttQc of the w7ittgs sulfides Hare <br />been unaQected by alteration and Nos are likely w h. <br />Ryrorstau.Y of rue at7ings at the t;ax of depo- <br />Sidon. As indicted by C6, analysis, at feast trace <br />amoartn of urbomte trrinerats. ptiacipa0y altam as <br />confirmed by X-ray methods, zee prtratt thtoughwt <br />the tataltered tailiaxs. The [atliags also contain abw- <br />chat etihednl crystals d gypsmt. rypitapy 0.5 to i.0 <br />arm long, that probably aysullized in sou. The <br />avlliag reagenu possibly txmtnlntud part of the G <br />771 <br />and 50;' .The chaadml mmpoeidogs of the buried <br />railing pore water and th4 Liilmgs sorda are htkrnd <br />m more been simitu ao chose observed momently. Ia <br />the ahseaca of armosplsuic o< dlaaolved O=. sui!!de <br />minerals w.re sabre atd dte pH acrd Mg, Ca. 5o-" <br />and HCOy wncentratiotn were mainnmed at rela- <br />tively ooraam 7eveis M aldtedoksmite and gypwm <br />solub;Gty wmtrbrtrs. <br />Sulfide oaida>torr atd add gntnarian <br />Sulfide-mineral Oxidation is a oomplat process <br />tvhit#l ocars through rex9on steps dot arc In- <br />gtteady catalyzed by sa1B0e-oxidmng bataaria of tlx <br />77+iobadllut soap (t(amstaor, 1983). The pres- <br />sure tN 17rio6adQtis ferreosidmss in the rnlings has <br />been euabfished (DAK a ~.. 1486). Baetettaily- <br />mediated and abiade sW(ide oxidatioe have been <br />eomiited in several detltlad studs because d both <br />the enviroamenal imporntta d these reacaom and <br />the t:mnomic benefict of ttsiig these rtst4ions in orc <br />processing. Ettaaive tcwievs of wlfide-mineral oxi- <br />dation mtxdansms have besa ptesemed by Luxo-~ <br />eaF1r and $¢vaa (1980), ].owtoet (L982) and Noaa- <br />STltdss (1482). <br />fa the waive Amulet tat7ing the artist abemdant <br />sulfide minerals an pyrfae and kyser amound o! <br />pyrrhotiu. The oxidation d pyre. by dissolved <br />mtygea or Ees', is typits0y dtaarlxd ss: <br />FeSr + 720= * H=O ~ <br />Fez'+2So-'+2H' (1) <br />or <br />FeSz + 14F2' + 8H10-. <br />15F: ` +2.40;- + 16H', (2) <br />Reaction 2 k the primary medianis+rt d sulfide <br />otddation at pH wtsdidom of <4 (Noat#no.t, <br />f4~). Ia both tdcrioo (1) and (2) aranopheric <br />oxygen iS the ultimate oadam_ Equation (1) ind- <br />tates roar F2', SO;' and H' an gtzmted u a <br />1:2:2 ratio. The Fe=' grmersted by pyrite ottitladon <br />tray be fucthu oxidized, hydrdyzed and prec~iuted <br />as ferric hydroxide eluasgh the reactiion <br />2Fer' t 1R0: + SliaO ~ 2Fe(OHh + Ui', (7) <br />Raaetioo (7) gentaares m attdtioaal two moles of <br />H' for each mole of pyrite oxidized. Frequeady, in <br />tailings systems. reaction (1) and reaetioa (7) are <br />decottpled. Pyrite oxidation (traction 1) omta near <br />the eailinp surficc. era! rue Fes` released, which is <br />relatively mob7e tinder kxvpH t0 tteuttai•pH moo- <br />dtions, a tnmparted by infiltradng rala sad gtow- <br />melt water along the pilings graundwt[a flow path, <br />nftianteiy ttisc6argiag co a arWa water body. The <br />ratrlr is the nridadoa of Fet' t}aoustt reaction (i) <br />and the generation d H' is streams and lake ad)ac- <br />ent to tailing impowdmcros. <br />Eridenca of sul5deoxidatiun rcactloot in the <br />P. 20 <br />r us.i <br />