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I~ AUG 24'94 741 No .001 P,04 <br />Introduction <br />13atlle Mountain Resources, Ltc.'s San Luis Mine Project is submitted a permit modifi ation to the <br />Division of Minerals and Geology which proposes to backGll deep portions of the "W~st !'il" with waste <br />rock ntatcrials 1'mm the mining operation. The w•esU; rock materials will cunte from t tc western portion <br />01' the Wcst Pit and ]'ink Gneiss areas (see figures below). This report briefly deecribys Lhe geologic <br />charaucrixtics of the waste rock. <br />Rackgrouud Geology <br />1'ur the purposes of general discussion the geology Of the San Luis Mine Yrojwt. arcs ;may be simplified <br />into five basic lithologic units. 't'hese units maintain a wrtstanf relative supcrpnsitiou iwhich is lists[( <br />below in "top to bou.om" order: <br />1} Quaternary alluviunt/wlluvium (gravels attd san[Js) <br />2) '1'erl.iary Saltla Nc itorntation (interbeddal silts, sands, and gravels) <br />3) Precambrian "pink gneiss" (higlily rectonized, intermixed gneissic pegmatit}s xnd biotite- <br />atnphibu]c glteiss). <br />4) Tcniary fault clay "zone" (fault dislocation surface separating hangingwall (rocks frrnn <br />footwall gneiss). <br />S) Precambrian hiotite~amphihole quat'tzo-tbldapadtic gneiss (footwall to clay yonc and all <br />supetpoxitioncd lilhologies). <br />(Note: lutcrmediatc to fetsic 't'ertiary intrusions are also prescn! within the mine area (hut these aro <br />volwuctrically insignificant and will not he discussed further,) <br />All rn'e-grade materials mined lhom the deposit are hosted within the Precambrian bi tile-amphibole <br />quartet-feldspathic gneisx (NS above). Ilydrothcrmal alteration and mineraliulion sit ur did not <br />signilicaully affect !toils ]-4 (above) and/or mineralized rocks of these lilhologies w C (IGWIIfaUhed to <br />the west in "!'crliary-Quaternary time. Accordingly, Units 1-4 above are wnsiderul Ikt he unmincralizcd <br />and !rave not undergone significant post-depositional alteration. All gold mineralizati~m tut[( associate[( <br />alteration and sulfide depusitirnt ties with Precambrian biotite-amphibole yuarizu-fd(I pathic gneiss. <br />(Nora: 'I'bis background infurtna[ion is based upon extensive surface geologic mapping and geologic logs <br />id drill-hole core and ruck chips.) <br />(ecology of Mined Materials and Proposed Backfill Materials <br />All ore and waste matn•ials wnsist of the litholugics describn(i above, Tor the purp(~scs of evaluating <br />po[ential environmental impact, these lilhologies are best organized into thrw scpara~C categories: <br />(1) Quaternary alluvium/colluvium; Santa Fe Notmatirnr; Precambrian "pink gneiss"; aud, fauh <br />clay zone. <br />(2) Precambrian biolilo-vnphibole yuartZo-feldspathic gneiss mineralized1 to ¢rc gold grades <br />(i.e. >.U18 ounces Au per ton). <br />(3) 1'rccambrian biaifc-amphibole quartzo-feldspathic gneiss (herey/ier rcjrbrred ro as 'footwall <br />gneiss") non-mineralized ur millerali~xd to sub-economic grades (i.cl <.01R ounces Au <br />per ten). <br />U. M../nnra' Yage J G.otogV n/ 1'ropovr[I <br />May /99~i )~uckfrl! Wuare Bock <br />