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ID~ AUG 24'94 743 No .001 P,07 <br />• <br />Rocks in Category 2 and 3 both consist of altered and tnJnereiize(1 footwall gneiss. 'Pl~e rocks of <br />Category 3 arc ore grade materials which will he processed and thus not used as back +11 material. The <br />routaining Calcgory 2 consists of footwall gneiss which is nun-mineralized or mincraliped w xub• <br />economic grades. 'These rocks represent the only potential source of significant sulfidb wn(:unu•atinns itt <br />the proposed backfill materials. The source of these materials, the "Gneiss Pil Arua"„ was re-evauatcd <br />iu detail ti+r its sultidc and carbonate concentrations by reviewing original rock chip simples an(I the <br />original drill lugs as dist:ussul below. <br />Thu following ntcthodulugy was used to evaluate footwall gneiss backfill materials Crc+Yn the "Gneiss 1'it <br />A+•ca": <br />I) identify all bettcltcs (within final pit wall limits) in cite "Gneiss 1'it At'ea" wl+iclt will <br />serve as a source for hackGll footwall gneiss. <br />2) Identify all exploration drill holes, and corresponding drill hale fuglagcs, <br />wlticlt ittterceptCd lltese waste bcncltes (see I-'igttrc i). <br />3) tielect specific drill holes 1'ur geologic review (l:igtt+•e 3) hase(1 un (pvcrall <br />thickness of fo(twall gneiss waste inlerccp[s (ftigure 2) as well as $ettet'al <br />sptlial distt'ilttttiort covering the source area. <br />4) Re-log the geology, sulfide type and antuunl, and carbonate cone, for alt <br />st:lectecl !toles (33 total) Containing footwall gneiss backfill tnau:rial (see <br />-5) Tabulate/compare new data and data from original geologic logs ('T'able I). <br />G) Select intervals with the highest overall sulfide contents for teslingluf <br />aciditic:uicm/neutralization potentials. SeJeet additional intervals tc~ cover the :+urial <br />extct+t of cite "Gneiss Pit Area" (Table 2). <br />i:xcept where noted, all materials reviewed represent variably altered :utd mineralize tOOIWJII gllelsti <br />waste rock (i.e. hiotite-amphibole quartw-feldspa[hic gneiss as described earlier in II is reprn•t). Spot <br />dtceks were made of "hangingwall" Santa Pc Fm and clay intervals ('l'abia 1) to en u'c th:u <br />assttmptiuus regarding insignificant sulfide enncentratiuns )n these rocks arc correct. <br />Thu duly Iwo sulfides nolcd in these rocks are pyrite (l:cS2) and chalwpyritc (l"Stl(e, 2). Pyrite is by far <br />the dominant sulGdc with total sulfide content generally refleGing pyrite content wit! lilOc cnnu•ibulion <br />frrnn chalcopyrite. In this study, the pyrilc range is estimated at 0-12 vol'7v with lltclhighest average <br />being 5 vol ~~. The overall average pyrite cauent is less titan 2 vol3o. The chalCOp rite range is <br />estimated at t7-1 vol`9 and overall averages only trace amounts. The urigittal dr""ill I g estimations [d' <br />xulfidu crnuents ('l'abia 1) tendcxl to err on the high side where sulfides are in relativ(~ :thun(lance and ou <br />the Inw side wha'e suliidcs arc sparsely dis[rihuted. 'l'hc rc-evaluation conducted fnY this study is <br />considered to be more accm'ala, <br />lslintated carbonate contenlis reported as the degree of effervtaccnee observed withll.hc application of <br />dilute (.1M) hydrochloric acid (HC1,). The observations from this study may be sk(~wul Iu the low si(lu <br />owing to the face that similar tests were conducted for the original geologic lugs aril ~snnte of the <br />original carbonate material may have been wnsumed by this initial application of Herd, (Note: Uuly one <br />ul" pte samples listed in Table 2, "I:R2-23", has nut undergone acid testing for carbu>It:nc, if <br />I). M. Jnttes Page 4 t;tokrgy nJ/7"opoa'cd <br />May 1994 duukjll Wncte Rork <br />