Show geology and acdore ore deposits decosi ts of miller hill american ameri can fork mining mini district utah miller hill lying at the head of american fork canyon utah county utah has been the center of mining activity in the american fork district since the discovery and location of the miller mine in 1869 and BY GEO H RYAN brian owing to the faulted condition of the hill it is very difficult to measure the various beds with any degree of accuracy but judging from such evidence as is visible binary reverse faulting than a complete such as is disclosed in the cardiff workings and on mt baldy the entire section of country lying easterly from the west peak of miller hill ulf D C A Z W A 41 46 WA MUM northeast slope of miller hill A A 0 and D faults 1 kalamazoo camp of texan mining co 2 millar peak 3 rock tunnel 4 wyoming tunnel 5 6 lady annie tunnel photo by geo H ryan in view of the present interest being taken in the district a description of the geological features and manner of ore occurrence in this section may be of particular interest miller hill is composed of sedimentary rocks ranging from dark colored pre cambrian quart exposed at the western base in both the main canyon and mary ellen gulch through the lighter colored cambrian quartzite and parting shale to the upper members of the limestone strata which butler 1 classes as middle cam mining alining engineer SQ t newhouse salt lake city in the surface and under ground hantzes Hint zes section 2 measured on the south end of the reed and benson ridge in big cottonwood is typical of the miller hill formations the hill also represents the most southerly overlying block in the great cottonwood fault which may be traced from big cottonwood canyon to the divide at west end of miller hill between the main canyon and mary ellen gulch at this point it has more the appearance of an or 17 1 butler 13 S laughlin G 1 F U 8 G S bull 1 1913 is badly broken by a complicated series of faults one of which in particular seems to be the direct result of the miller hill block overriding the easterly end of red cloud ridge this fault runs in an easterly and westerly direction from a point south of the saddle along the north slope of the hill with a nearly vertical dip and the roll or troughs and ridges resulting from the movement pitch to the west at about 30 degrees which would indicate that eliat the northerly part of the mountain which rests against 2 hintze hintzc F F jr new york aad sel annals 1913 vol 2 23 23 3 ap pp 10 the east end of red cloud had thereby received the greater thrust causing it to move eastward and until the blocky lime on the north side of fault lying next above the shale was brought into con in only a few places the determination of the faults is a rather difficult task veins and ore occurrence the majority of the ore so far produced in the american fork district has come A w div T 4 7 kalamazoo camo of texan mining co in the foreground edge of hole in which ore was found loose in surface debris photo by geo H ryan tact with the thin bedded blue lime on south side of fault lying next below the ore bearing birdseye limestone subsequent erosion has removed the limestone strata on the north side of fault down to the shaley lime overlying overl yint 3 the first blue lime stone which in turn rests on the shale north of this fault there does not appear to be as much faulting as there is to the south of it as will be seen by reference to tile the accompanying map on which this fault is designated AA A A south of this fault the faults BC B C and D occur having a NEN NE N strike and dip to the N W W each of these faults cut the ore body so far developed and are known to limit the ore bodies which were e found to end abruptly against each one of these faults outside the known ore bearing area the faults bif F IF G H and I 1 were observed having displacements ranging from 15 to 90 or feet H fault plane stands about vertical but the movement appears to have between almost horizontal this conclusion was reached however from observation at one point only where a tunnel on west end of the barchfield Sarch field claim lot 51 exposed this fault another fault of considerable extent but not evident on the surface shows in what is known as the upper tree tunnel on the south side of hill this fault has a N W strike and dips at about 30 degrees to the S W several other faults are apparent down the eastern slope of the hill but owing to tile the fact that tile the surface is covered with soil and thick vegetation to such an extent that the edges of the rock strata are visible from the large bedded deposit in the limestone embraced within the claims of the old miller mine on the top of the hill this is a typical replacement deposit occurring along an E W fracture which is W ol 01 wr r C benl r ak ea V ax 1 1 W N 4 rie I 1 P W I 1 A p wl aw N RR i e Y it A southwest slope of miller hill showing tree tunnel in center with dump from old glory hole stop slope to the left photo by geo H ryan crossed by a series of N E S W fissures and tile the greatest replacement appears to have occurred where these fractures intersect the ore body has an E W trend following the main fracture zone except that ore body opened first east cast of fault G irk in this instance the ore occurred along a fissure having a nearly N S strike with avery a very steep dip to the west the southern vart part of this ore body appears to occupy an all enlargement lar gement of the fissure probably due to replacement of the wall rock but not to such an extent that it could be called a bedded deposit the northern end of this body however is distinctly the bedded type currying oc along a fracture zone about parallel to the big ore body to the south the ore was followed south along this fissure to where it intersects the southerly fracture zone where it again bedded out forming the main ore body worked by tyng brothers from 1904 to 1907 these conditions eions s would lead one to the conclusion that wherever reyer the mineralizing mineral izing fissures intersect the E W fracture zones the ore will be found making in the fissure near that point or away from the fissures along the fractures the surface indications of these fissures are a series of parallel seams filled with calcite and sometimes a little galena the faces of the shattered rock are also stained with iron oxide and black manganese some places they show considerable barite and in one place on the sierra claim no 39 the barite is accompanied by and galena this occurrence is noted only where the fissure crops in the upper portion of the ore bearing stratum along the summit of miller and ana r down the eastern slope as far as claim there are six NE SW fissures the outcrops of which can be very easily found and traced where there is not too much brush and soil with two exceptions these outcrops occur in the second or third stratum above the ore bearing lime the most easterly outcrop is in the ore bearing bearin to feet above the ore bearing stratum just why the ore bearing solutions selected this particular stratum is not quite clear but it must be due to two main A 4 j i rock tunnel dump and ore bin miller mine photo by geo H ryan lime on claim as is the outcrop on north end of claim the big replacement deposit which furnished the worth of ore produced from the miller mine to date occurs in a bluish gray limestone through which occur irregular ime gular dark blue areas the texture of the rock throughout is the same at least to the naked eye the main difference being the coloring matter this bed of limestone is about sixty to eighty feet in thickness and its appearance is so distinctive that it is quickly recognized wherever encountered either underground or on the surface it contains numerous small white specks which on close examination are seen to be composed of bunches of small crystals of spar probably dolomite and numerous small holes lined with these same spar crystals this stratum of lime is almost continuous fr from 0 m the old carbonate mine in the south fork of big cottonwood canyon to american fork canyon and has produced large quantities of ore at various P points eints from such mines as the carbonate reed and benson flagstaff and miller in this locality this stratum is within feet above the shale it is by about eighty feet of dark blue thinly bedded fine grained limestone and capped by a stratum of f light gray fine grained limestone which weathers white and is from six to ten feet thick next above this is about sixty feet of lime which very closely resembles the stratum below the ore bearing lime the first bed of lime occurs about causes viz the chemical composition of the limestone and its because in the neighborhood of the fissures A 4 z N A h AMA miller mine on southwest slope 0 of f miller hill showing mormon tunnel camp below glory hole photo by geo H ryan and fracture zones the rock has been ver very y finely crushed for a considerable area thus allowing the solutions easy access to a large amount of surface on which to act ct the stages of replacement can be very clearly seen in this fractured rock near the old the ordinal ore body was first struck on the southwest slope of the hill and followed down to the east until it ended against fault B as shown in the section S small mall irregular bunches of ore were found in the hanging wall side of the fault and followed upward for a short distance but the early operators evidently did not recognize the possibility of getting the continuation above in the foot wall side of the fault for all of the early prospecting was done in the mormon tunnel run from the south side of the hill and the lady annie run from the north side A great deal of work was done on these lower levels but the only ore found was in a seam following a bedding plane in the brown limestone lying about eighty to feet above the shale this flat seam runs up to the fault A which cuts it off considerable gop hering has been done on this vein which has yielded a little high grade lead silver ore carr carrying yint some copper but the thickness does not seem to have exceeded eight inches and the values are quite irregular the early period of production and development lasted from 1872 to 1878 when unable to find a continuation of the bonanza ore body the miller mining smelting smelling Sm elting company abandoned operations and the mine was worked spasmodically modi cally by small leasers leaders until about 1903 when george tyng secured a lease and in a tunnel running southwesterly esterly from the north side of the hill opened the upper end of an ore body about feet east of the 0 Ls S S SA I 1 1 11 SECTION ON OM WK j ORE BODIES ORE point where the original ore was avas cut off by fault B this working of tangs is caved but is stated on good authority that thai the 0 ore was followed upward on its dip a short distance when it ended abruptly against a N W dipping fault about seventy five feet above termination aaion of miller on oil fault B from evidence obtainable in the old workings south of here along the west end of the tyng this is fault C fron from this fault tyng followed the ore north to fault A and east to fault D both of which cut the ore off entirely but small isolated bunches are found in the fault showing conclusively that the faulting is subsequent to ore deposition these conditions leave 9 0 13 J 6 id q 0 V geological MAP OF cf c f MILLER HILL AME VORK FORK RIOT UTAH SOIL QUARTZITE SHALE LIMESTONE al AI qt Ls PORPHYRY FAULTS VEINS ORE lff aie i i f r j T T S sie SCALE i E GE R alj MT M T LAKE link between the the lie connecting original miller and tyng ore bodies still untouched as none one of the previous operators have ever prospected this section of ground the original ore body was about feet wide and six feet to ten feet thick at the point where fault B cut it off and tile the tyng ore body was about thirty feet wide and twelve feet thick where it was cut off by fault C present development in the block between faults B and C lias has just disclosed an EW seam which shows bunches of ga lena and carbonate ore and the surrounding rock is very much shattered and shows a great deal of iron and black manganese stain covered with debris owing to the fact that the edges of the strata on the north side of hill are covered with debris and hidden by the up block on north side of fault A the exact location of the ore bearing stratum between faults B and C could not be ascertained but in drifting northwest from a point fifty feet below the west end of tyng the ore bearing lime was encountered and a 56 foot raise encountered the next overlying stratum so the displacement on fault C must be less than fifty feet on fault D at the eastern end of the tyng ore body the hanging wail majl block has moved down to the southwest and as this point is very close to the surface it is very probable that the stratum containing the eastern extension of this ore body has been broken off by faults A and D and removed by erosion this theory is borne out by the fact that two detached bodies of ore have been found in the loose debris down the north slope of the hill A bedded deposit on the south slope of the hill a bedded deposit of high grade lead carbonate has been opened lying under the old glory hole this ore is froni from eight to twenty four inches thick and has been followed on its dip for about twenty five feet veins in quartzite at the center of claim 54 there is a strong fissure and porphyry dike showing a small bunch of galena on the surface at the collar of a shaft this vein strikes E W and dips vertical running diagonally along claim 99 and across the eastern end of claim 58 is the borussia Bo russia fissure striking about N 50 degrees E dip vertical which has produced some very high grade lead silver and gold ore the former came mostly from the workings on the borussia Bo russia 99 and the latter from a rich pocket on the sunday 58 on the ridge crossing the north end of the bredemeyer claim 49 is a strong quartz vein cropping with a N S strike and dip of 50 degrees to the west at one place on this outcrop scattered bunches of galena can be seen with quartz crystals there is no record of an any production from this vein but the surface indications are very promising this bredemeyer Bre domeyer vein may have been one which was responsible for part of the of the miller hill limestone as a con along its southerly strike would bring it to the miller ore body but on account of fault A the southern ext extension ensio n from the intersection with this fault would likely be found near the center or westerly end of the ore body about feet down the ridge to the east is another vein striking N 20 degrees E and dipping 30 degrees NW which shows considerable fracturing and iron stain but no work has been done on it about feet east of here where the lady annie gulch meets the cliff is another N E S W fissure showing extensive shattering of the quartzite with high grade galena scattered over the faces of the rock this vein may also be one of those through which the mineralizing mineral izing solutions reached the ore bearing lime in the miller hill in view of the recent developments in the pacific mine at the eastern foot of miller hill which has opened a large body of sulphide ore in a N E S W fissure in the quartzite it is reasonable to assume that these other fissures may contain commercial bodies of ore there has not been much prospecting on any of these veins in the quartzite but the surface showing and developments in the pacific are such as to warrant considerable development work especially ally below an ail extensive ore body like the miller igneous intrusions As will be seen by reference to map there are several points where porphyry dikes outcrop in the limestone and quartzite the rys are of two varieties and modes of occurrence that found in the lime is a dark bluish gray rock quite hard on the surface but usually much |