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<br />0:, - 'J3i <br /> <br />IO <br /> <br />underlain by Precnmbrian met.umorphif'. rocks, which are <br />intnl<led hy granitic rock.._ ~lo5t of till:> reIlhlindef of t.he arca <br />is covcft>d Lv volcAnic rocks of middle Tertiary age. Sedi- <br />mentary rocks of Paleozoic nnd ~Iesozoic ages are e:qlO...;(>d <br />along the south mnr~in of the nrell and extend under the <br />volcanic rocks in the east-ern pliTt of the llfe!1. <br />In llPpruising the minerul-resoUrCtl potentinl of the primi- <br />tive aren, sIwcinl att.ention wns given to ull the mining dis- <br />tricts and to t.he geologic eO\'iroIlJlll'U1S most likely to hu\'e <br />mineral deposits u...;;sncln.ted with them. All nrens of hydro- <br />thermnllv altt'red rocks in the ,"olcllnic field. llnd in Precum- <br />brian roc;ks near volcllnic or intrll:-,ive centers, were exumined <br />and sllmplerl. tiS were possible fo~sil gold plucers1 p,)Titic blu'('k <br />slates. and irou-formution ill Precnmbrillll ro('ks. Sedilllclltury <br />rocks underlying the yol('anic cover in the Clt..;tern ludf of tile <br />areu contain potential oil nud gll.s-hcuring re~('rvoir rot'ks, awl <br />the pos~ibilities of stich occurrences were ilssesseu. F'oot <br />traverses aggregating lIlore thnn 1.000 miles in length wert' <br />lllnde in the urea, and samples were tnken of all rocks that <br />R!>pellred po~ibly mineralized and of st.reurn s(>Jim(>nt~ alo~g <br />a I st.ream;". .I hese ~llmpJes were l~n8lyzed by spect.rograpluc <br />and chemlcnl Inf'thods to df'ternmw met.ul cont('nt1 llnd the <br />llllalyticul datn are pre:-;entcu ill the report. ..Areas found to he <br />tUlOUlu.lously high illlIH'tnJ (;ontent \\'('re further illvesliguted. <br />Within nud Ilt'Rr the primitive urea, evidence of mineral <br />deposits of commercial or Ilcnr-COlllllll'rcinl value wu.:-; found <br />in four nrellS. <br />1. The Needlp :\Iountnins mining dbtrict, in the south- <br />western part of the Pliniltive nrl'n. contllin~ disseminated <br />molybdenite in a hvpnbys~nl illtrll~ivf' pIng, und the 5111'- <br />ronnrling rock is ('.ut hy nl1m('rOll~ metlllliferous veins, some of <br />which hnv(' economic potential. <br />2. \rhiwhend Gulch.. in the northwestern pnrt. of the primi- <br />tive are-n, contuins maIlY small vein5' I1no sporadic deposits, <br />some of which 111'(' of comme1'cinl grntle. <br />3. The Beartnwn mining distIiet, along the north mnrgin <br />of the primitivt' nrt':l, ('outains Il number of golrl-tellurulp <br />veins t.hat );elded high-gmde ore ill the Inte ISOO'!'. Ex- <br />ploration tnrgct.R ~till <,xist, llud, \\;tll impro,"ed accf'~~, the <br />district coul(j ngnin hpcome />rodllctivc.. <br />4. The Trout CrC('k-Alid( Ie Fork Piedra area, ill nnd lld- <br />jacent to the uorthea..:4enl pllrt of the primitive nft'fi, contuill5 <br />deposits of nutivc sulfur in highly :lllt'red voknnic rocks. <br />Of the four :1f('fiS, only the ~l'('dl,-' :\lollHttlins minin~ dis- <br />triet ('ontains appr('('iuhle :lert':I~I' within tIlt' prim.itiv{' urea.. <br />The mirwral pott1nti:l1 of tlH' (our al"l'f1:; ('ould be d(,t{'nnifH.d <br />only "ith extensi\"t_~ pxplomtion. \\-hkh would hp h('}uncl thl' <br />~cope of this inn'stig:ltiono <br />EI~l'wherc in lInd nt'nr tit(' prillliti\"f' al"('n.... --mtill botlip:-:, (If <br />Ie:HI-zin... orf' 0"'<;111' in Ca'op Bl\~in !le:l!" I{unlpu J>urk lllong the <br />south llI11r~n of {he lIrt'a. un.! Il ~1I1:l11 :lIllOlIIH of lImnillnl orf-' <br />htl.:.; bef'1l producl'cI Wl':,t of {II(' Animll~ Hin'r nt':lr till' Wf'~t <br />mllr~in of the primitin. :11'1'11. In the IlIb!.:l few other hWlllitit., <br />};l'hlt'd slO:dl qunntitif':>:' o( hig-h-1!rad<, Ofl', which WtlS packed <br />