fu\fE-199
UNITED STATES ATOMIC ENERGY COMMISSION GRAND JUNCTION OPERATIONS OFFICE EXPLORATION DIVISION
SUMMARY OF URANIUM EXPLORATION IN THE LUKACHUKAI MOUNTAINS, APACHE COUNTY, ARIZONA 1950-1955
CONTRACT NOS. AT(30-1) 1021, 1139, 1263, 1364; AT(05-l) 234, 257
By
Raymond F. Kosatka
UNEDITED MANUSCRIPT
Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
March 30, 1956
Grand Junction, Colorado Summary of Uranium Exploration In The Lukachukai Mountains, Apache County, Arizona 1950 - 1955
CONTENTS
Abstract ...... iii
Introduction. ••••••••••••• 0 ...... l
Exploration and Mining History...... 1
Genera 1 Geology.. • • • • • • • • • • .. • • • • • • • • • • • • • • • .. • • • • • • • • • • • • • • • • • • • • 2 Sedimentary Rocks. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • .. • • 4 Igneous Rocks. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 4 Tectonic Structures ...... 7 Geologic History. 7
Economic Geology ••••••••••• 7 Mineralogy ••••••••••••• ...... 8 Ore Occurrences •••••••• 8 Types of deposits ••••••••••••••••••••••••••••••••••••••••••• 9 Sandstone lens deposits ••••••••••••••••••••••••••••••••• 9 Mudstone deposits ••••••••••••••••••••••••••••••••••••••• 9 Lithologic Variations in the Ore Unit •••••••••••••••••••••• 9 Size of Ore Deposits ••••••••••••••••••••••••••••••••••••••• 10 Color Alteration •••••••••••••••••••••••••••••••••••••••••••• 10 Ore Guides ...... 10
Exploration Methods ...... ll Reconnaissance •••••••••••••••••••••••••••••••••••••••••••••• ll Mapping of sedimentary trends ••••••••••••••••••••••••••• 12 Mine mapping...... • •••••••••••••••••••••••••• 12 Drilling Program...... ~···········o•o••oo•••••••• l3 Plan of Drilling •••••••••••••••••••••• o ••••••••••••••••• o ••• 14 Subsurface Mapping ••••••••••••••••••••• o •• o ••••••••••••• 15 Comparison of various types of subsurface maps •••••••••• 17
Results Of The Exploration Program •••••••••••••••••••••••••••••• 17 Northeast Rim ••••••••••••••••••••••••••••••••••••••••••••••• 18
Southwest Rim •••••••••• ••••••••••••••• 0 •••• 0 ...... 18 Center Peak area •• 18
Summary and Conclusions...... 0 ...... 0 ••• 19
References ...... 23
i ILLUSTRATIONS
Figure l Index map of the Four Corners region •••••••••••••••••• 3
Figure 2 Geologic map of the Lukachukai Hountains area, Apache County Arizona .•..••••..•.•..••••....•.•• appended
Figure 3 Tectonic map, Four Corners region .•..•..••••••••••••.• 5
Figure 4 Representative section of rocks exposed in the Lukachukai Mountains area ••.••.••.•••..•.••••.• 6
Figure 5 Structure contour, sedimentary trend, joint, and ore deposit map of the Lukachukai Hountains Arizona ...... •.••....•...... •..•.•.• appended
Table 1 Summary of drilling statistics ••.•••••••••••••.•.••••• 20
Table 2 AEC reports. • • • ...... • . • . • • ...... • ...... • . . . . 21
ii ABSTRACT
The U. S. Atomic Energy Commission carried on an exploration program of reconnaissance and drilling in the Lukachukai Hountains, Apache County, Arizona, from September 1950, until August 1955. Objectives of this program were fourfold: (1) to find mineable deposits of uranium ore (2) to develop sufficient reserves to justify construction of a processing mill at Shiprock, New Mexico, (3) to discover and develop ore-finding criteria, ore trends and favorable ground and (4) to evaluate the ore potential of the Lukachukai Mountains.
Uranium ore was found within a 50-foot unit of the Salt Wash member of the Harrison formation, approximately 45 feet above the Salt Wash-Bluff contact. Radioactivity of the ore deposits in the Lukachukai Mountains is in equilibrium and the ore minerals are secondary in origin, principally carnotite and tyuyamunite. Ore bearing sandstones commonly lie between impervious mudstones and have finely disseminated organic matter, calcium carbonate, and iron and manganese oxides associated with the ore. Most ore bodies are in clusters elongated parallel to direction of ancient stream flow, and most uranium is confined to the more permeable portions of sand stone lenses filling scours in Salt Wash stream channels. Tectonic structure has not apparently influenced local deposition of uranium.
A total of 374,198 feet was drilled in 1,837 holes, 242 of which were in ore and 469 mineralized.
iii INTRODUCTION
The Lukachukai Mountains are at 36° 30' north latitude and 1090 15' west longitude near Cove School, Apache County, Arizona, (Fig. l). The Atomic Energy Commission camp at Cove School is reached by 35 miles of graded gravel road which joins U. S. Highway 666 approximately 8 miles south of Shiprock, New Mexico. Any one of three gravel roads from the camp leads to the drilling area where the three connect. An airstrip, for small planes, is located about 3 miles east of Cove School.
All of the Lukachukai Mountains lie within the Navajo Indian Reservation, and the land is administered by the Navajo Tribal Council. Leases and/or mining permits are held by members of the Navajo Tribe and are assigned to private operators. Navajo Uranium Division of Kerr-McGee Oil Industries, Inc., Climax Uranium Company, Walter Duncan Mining Company, Price Exploration Company and Great States Uranium Corporation all have leases and/or mining permits in the drilling area.
The successful completion of the program was made possible by the cooper ation of personnel of the Atomic Energy Commission, Walker-Lybarger Construc tion Company, drilling contractors, and mine operators in the area, and this cooperation is gratefully acknowledged.
EXPLORATION AND MINING HISTORY
In the fall of 1949, F. A. Sitton of Dove Creek, Colorado, became interested in properties claimed by two Navajos, DanK. Phillips and Kaley Black, on which mineralized outcrops occurred. After it became apparent from further prospecting of rims in the area that large tonnages of uranium ore could be postulated for the leases, Mr. Sitton negotiated leases for exploitation of the properties and began construction of access roads to the most favorable outcrop in preparation for mining.
In June 1950, F.A. Sutton, Inc. made the initial ore shipment from Kaley Black's lease on Mesa I. The initial shipment from Dan Phillips lease on Hesa II was made in November 1950.
Late in 1950, Hr. Sutton and Richard 0. Dulaney Jr., also of Dove Greek, Colorado, formed the Navajo Uranium Company and expanded mining operations in the Lukachukais. The Navajo Uranium Company was purchased by Kerr-HcGee Oil Industries, Inc. in Hay 1952.
Frank Nacheenbetah located promising outcrops on Hesa IV l/2 during the summer of 1950, and after assigning his mining permit to Climax Uranium Company, began shipments in April 1951. The early shipments were made to the AEC ore buying station at Honticello, Utah. The AEG opened an ore buying station at Shiprock, New Hexico in January 1952. In July 1952, Walter Duncan Mining Company began ore shipments from Willie Cisco's mining permit on Three Point Hesa.
On August 17, 1953 Kerr-HcGee Oil Industries, Navajo Uranium Division signed a contract with the AEC to produce uranium concentrates from a mill to be built at Shiprock. The mill began operating in October 1954. In 1955 there were ll operating mines in the Lukachukai Mountains.
1 The room and pillar system has been the principal m1n1ng method but rim stripping and open pit mining have also been used to develop surface outcrops on rims. The mine operators in the area have all done core, non core, and underground long hole drilling.
The Lukachukai Mountains area was brought to the attention of the Atomic Energy Commission by Mr. Sitton in 1950, and following preliminary examina tion by geologists of the Grand Junction Exploration Division, an exploration program of reconnaissance and drilling was begun by the Commission. The objectives of this program have been:
(1) To find mineable bodies of uranium ore, (2) to develop sufficient reserves of uranium ore in the areas drilled, by direct delimitation of ore bodies with drill holes, to warrant construction of a 100 ton capacity mill at Shiprock, New Mexico, (3) to discover and develop criteria indicative of ore, ore trends and favorable areas, which would result in geologic informa tion that could be used to evaluate the ore potential of the Lukachukai Mountains and would aid future private exploration and mining in this and adjoining areas.
GENERAL GEOLOGY
The Lukachukai Mountains, covering an area of approximately 72 square miles, are the northernmost extension of the Chuska Mountains and lie along the northeast flank of the Defiance uplift, which forms a structural high between the San Juan Basin to the east and the Black Mesa Basin to the west.
The regional geology of the area has been studied by many writers: Gregory, 1917; Craig et al, 1951; Kelley, 1951; Harshbarger et al, 1951. Much of the literature on the Lukachukai Mountains has been written by Commission geologists working in the region. The author will draw on these reports to a large extent in summarizing the exploraton program conducted by the Atomic Energy Commission in the Lukachukai Mountains.
The Lukachukai Mountains are erosional remnants of Hesozoic and Tertiary sediments which rise nearly 3,000 feet above the Red Rock Valley to an altitude of 9,400 feet. These erosional remnants, referred to as "mesas", are narrow and elongate and are separated by deep precipitous canyons (Fig. 2). The mesas project in northeast and southwest directions from the major northwest trending axis of the mountains and are capped by a Tertiary sandstone that is poorly consolidated in its lower portion but silicified at higher altitudes. The intrusive centers of the Carrizo laccolith lie to the north, the San Juan Basin to the east, and the Black Mesa Basin to the west (Fig. 3).
The rock formations are nearly horizontal producing a gently sloping topography on the mesa tops. The Salt Wash and Recapture members of the Jurassic Morrison formation, in which the major part of the drilling was done, crop out as ledgy shelves somewhat below the mesa tops. Formational boundaries can be distinguished by differences in outcrop characteristics.
Annual rainfall is about 10 inches, but precipitation is much greater at higher altitudes, so that the mountain slopes are well forested with pine, fir, and aspen. The mean annual temperature in the Lukachukai Mountains is approximately 550 F. Temperatures during the summer may reach 105 degrees. During the winter months, temperatures may go down as low as 20 degrees
2 SAN JUAN COUNTY UT )> -o g I rn Newcomb Ill N. .JL ll 0 I 2 4 6 8 10 APPROX. MILES Figure I. Index Map of Four Corners Region 3 below zero, and snow 5 to 7 feet deep in the higher mountains makes much of the area inaccessible. Sedimentary Rocks In the Lukachukai Mountains area, exposed sedimentary rocks range in age from the Upper Triassic Chinle formation to the Tertiary Chuska sandstone (Fig. 4). The upper or Lukachukai member of the Wingate sandstone, which is over lain by Jurassic and Tertiary sediments, forms prominent cliffs at the base of the mesas. The Jurassic Carmel formation is unconformably deposited on the Wingate. The Jurassic Navajo sandstone and the Kayenta formation of questionable Jurassic age, normally present above the Wingate, are missing from the geologic section in the Lukachukai Mountains. The Entrada sand stone, which is immediately above the Carmel, underlies the Summerville formation. The Todilto limestone, which separates these two formations to the northeast, east, and south, is locally absent. Commercial production of uranium and vanadium is limited to the Salt Wash member of the Jurassic Morrison formation. The Salt Wash in the Lukachukai Mountains averages around 120 feet in thickness and consists of very fine to fine grained well sorted quartzitic sandstones interbedded with brown and grey mudstones and siltstones. The contact between the Salt Wash and the subjacent Bluff sandstone is a limey layer of white sandstone com posed of well rounded, etched, and frosted grains. The top of the Salt Wash is a dark grey mudstone which interfingers with the bottom series of inter bedded mudstones and siltstones of the Recapture member of the Morrison formation. It is sometimes difficult to determine the Salt Wash-Recapture contact by distinguishing between mudstones of the two members, but Recapture sandstones are generally coarser-grained than those of the Salt Wash. The Salt Wash ranges in thickness from 115 to 135 feet, where the entire member is present. Masters (1953) reports a measured thickness of 135 feet at Mexican Cry Mesa. At Mesa V, the average thickness is 118 feet, which increases to 133 feet on Mesa I. The Salt Wash has been removed by post Jurassic erosion east of Mesa I and Ttvo Prong Mesa. The Salt Wash in the area has many characteristic sedimentary structures and features. Primary or mechanical features include inclined, concave, and diagonal torrential cross-bedding; stream lineations; scour and fill de posits; ripple marks; mud galls; diagenetic deformation; and, less commonly, graded bedding. Secondary or chemical structures such as concretions, color banding, and calcite veinlets are also found. Igneous Rocks The Tertiary period was a time of regional igneous activity. Although only one igneous occurrence, a small basic dike on Mesa I, is known within the area of exploration under discussion, flows of trachybasalt may be found and small intrusives of minette lava are intruded into Tertiary strata of the Lukachukai and Chuska Mountains. Numerous igneous plugs dot Red Rock Valley. This igneous activity is thought to have taken place in Pliocene time. In the Lukachukai Mountains and elsewhere in the district, alteration at the contacts between igneous and sedimentary rocks is slight or megascop ically invisible. 4 EXPLANATION BLANDING Axis of anticline, showing direction of plunge Axis of anticline, showing direction I of plunge Monotline or steep limb of fold with direction of dip 0 o- Structure contours on top of -2° Chinle, contour interval 2000 feet fault, showing side COLORADO -----+- NEW MEXICO & ~~ SAN JUAN BASIN BLACK MESA BASIN I I I 0 16 Miles S!i modified after Kell Figure 3 Tectonic Mop, Four Corners Region 5 lQi2l Conglomerole r1J Sondstone § Mudstone LITHOLOGY """ [iEJ Sonds!one, conglomerotic ~ Siltstone ~ Limestone Sand:~tone, grayish Mite to I ight brown; fine to medium I rained; :subro11nded, troste::l c,..artz grains .,.; th al:lundllllt bl5ek grains; lower part ver~ frial:lle, 11pper part highly si icifi11d; cross-stratified; locally contains volcanic ash and bentonite; congl Drl'lerat 1c at base, S1111dstone, moderate pink to light brown, medium to coarse grained; -ell-rounded, poorly s:~rted quartz grains with abundl!l'lt quartz overgrowthS; lenticular, cross--:;tratlfied. Interbedded with claystone, greenist>-gray l'ltld pink; silty end sl!lldy. Siltl~~oo~p~~rd~~r~ 01~~~~~~ a~~a~~~s~~~~a:l~fe~~ ~~~Jd!:,n:i'~h q~f~~~;~e~i ~~~~;':~d~~. ~~~ z:i~ t~ 1 ~~ ~~d~. Sandstone, pink to yellowish grey; very fine to fine grained; rubmgulllr q.~artz Cl'meoted by caleite, tnterbeddP.d •ith siltstooe, gr11yiSh green to red, Md c\ "' Sandstone, moder11te reddish orange; very fine grained; cross-strlltified on large scale; a f"" thin b~ds of limestone 11no:l calcareous Sll(ldy mudstone; forms verticil! or undercut cliffs. Siltstone, pale reddiSh brOil'!\; rudely fissile; "'f'((ium scale concave upward cross-stratification; blocky jointing, Claystone, moderate red, ca\carll(l\ls, silty; Interbedded with siltstone, moderate reddish orMtge, .scndy, argilllloC Claystone, dark bluiSh Md purpliSh; snaly, locally sMdy; with thin 5eries of white C11lcareous sandstone, Md 1 in:estone. Claystone, dark gra~iSh red; sMly, ripple-marked; and sandstone, yellowiSh gn~y to conglomeratic, With p~ble.s or Shale, limestone, and petrified oood; c11lcareous, Figure 4. Representative sectian of rocks expased In Lukachukai Mountains area, Apache Co., Arizona Tectonic Structures The most prominent local structure is the Lukachukai "monocline", \vhich is more accurately described as an open asymmetrical, northwesterly plunging syncline the axis of which strikes about N 40° W across the tips of the northeastern mesas, from Mesa I to Mexican Cry Mesa (Fig. 5). The Mesozoic formations dip from l to 2 degrees northeast toward the synclinal axis, where dip sharply reverses to about 25 degrees to the southwest and from there continues northeast dipping gently for several miles. On Mexican Cry Mesa, the synclinal axis swings to strike N 25° E., and minor flexures can be observed. The axial plane of the syncline is inclined to the southwest. Rocks in the Lukachukai Mountains are cut by four sets of steeply dipping or nearly vertical features. Joints plotted from aerial photographs show the most prominent set of fractures striking from N 40° E toN 60° E, and a slightly less prominent set striking N 300 W to N 500 \v. Two less noticeable fracture sets strike N zoo E to N 100 W and N 80° E to due east. Relative age of joint sets has not been determined. Location of ore bodies in unfractured areas, as well as in highly fractured areas of inter secting fracture sets and well up on the sloping limb above the trough of the Lukachukai syncline seems to indicate little local structural control of uranium deposits. Geologic History After final withdrawal of late Permian seas, a period of non-deposition and widespread peneplanation was followed by deposition of the Shinarump conglomerate as a thin discontinuous sheet on an erosion surface of irregular relief. Sedimentation by aggrading streams flowing to the northwest, from a source area to the east, continued through late Triassic time, ending with deposition of the Wingate sandstone, an aqueous-floodplain deposit. Another interval of erosion and non-deposition ensued before sediments of the San Rafael group were laid down under alternating shallow marine and littoral conditions. This epoch was terminated by withdrawal of the seas and deposi tion of the eolian Bluff sandstone. Fluviatile sediments of the Morrison formation were then deposited by streams flowing from the south and west onto the floodplain resulting from this marine regression. The Cretaceous period was a time of continued emergence in general, with repeated advances and subsequent withdrawals of seas lying to the east. Rocks of Cretaceous age, if laid down in the Lukachukai Mountains area, were removed by pre Tertiary erosion. As the Cretaceous period drew to a close, tectonic activity began, resulting in uplift and folding of Mesozoic sediments, and continued into the Tertiary period, culminating in widespread regional igneous activity and renewed sedimentation during Pliocene (?) time. The present landscape, with its rugged rims and deep canyons, resulted from Pliocene to Recent erosion. ECONOMIC GEOLOGY Uranium occurrences extend along the entire Lukachukai Mountains, generally on or near rims and closely following trends of paleostream flow. Stratigraphically uranium ore is confined almost entirely to the Salt Wash member of the Jurassic Morrison formation. Although uranium deposits are found throughout the upper four-fifths of the Salt Wash and in the basal mudstone-siltstone series of the Recapture member, ore is concentrated in 7 the middle third of the Salt Wash, from 45 to 90 feet above the Salt Wash Bluff contact. Ore is usually found in sandstone lenses, interbedded with mudstone beds, between the thick grey mudstone at the top of the Salt Wash and a cyclical series of muds, silts and sands near the bottom of the Salt Wash, 20 feet above the contact of the Bluff and the Salt Wash. No signifi cant mineralization is kno>m lower than twenty feet above the Bluff. Some uranium of ore grade occurs in the uppermost mudstone unit of the Salt Wash, however, and random deposits of sub-ore grade may be found throughout the Salt Wash section. The Salt Wash section increases in sandstone percentage with a decrease in favorability westward toward Mexican Cry Mesa, and a correspondingly de creasing number of mineralized outcrops are found on rims in this direction. Exploration has shmm that mineralization usually occurs in sections where the Salt Wash is composed of equal proportions of interbedded sandstones and mudstones. However, even in areas where the Salt Wash section is largely sandstone, as on Mexican Cry, persistent mudstone beds are found either immediately above or below or both above and below mineralized rock. Mineralogy Ore from the Lukachukai mines is from almost totally oxidized deposits in equilibrium and is seemingly uniform in chemical analyses and physical properties. The principal uranium minerals are yellow carnotite (Kz0.2U03.Vz0s3Hz0) and canary-yellow to green tyuyamu- nite (Ca0.2U03.VzOs.nHzO). These are finely disseminated as flakes, grain coatings, or as crystalline platy aggregates in grey, green, yellow, and white sands, and as coatings on fractures and mudstone surfaces. A few minor occurrences of uraninite as a black sooty mineral or in blebs or irregular corroded grains have been found in the mines. Vanadium is present, partly in association with carnotite, but the major part of it is in the fine hydrous mica clay cement that is present throughout the ore as a matrix material. Minor accessory secondary vana dium minerals, such as hewettite (CaV6016.39Hz0) and rossite (CaVz06.4Hz0) have also been found. The brilliantly colored orange and green vanadates, pascoite (CazV6017•llHzO) and pintadoite (2CaO.Vz0s.9HzO) form efflorescent coatings on some exposed rock surfaces. Melanovanadite (CazV4V60zs) occurs, rarely, as small patches of black needles in vanadium-rich sandstones. A mineral suite commonly associated with uranium is quartz, calcite, montmorillonite (?) clay, hematite, geothite, and manganese oxide. The Salt Wash sandstone in the Lukachukai Mountains is composed mostly of quartz with minor feldspar, some rounded detrital grains of magnetite and scattered flakes of muscovite and biotite. Interstitial clay and calcium carbonate is common, and hematite and limonite are common grain coatings. Carbonaceous matter is not abundant and occurs chiefly as disseminated carbon trash and small leaves or twigs, generally associated with ore. Ore Occurrence Uranium ore deposits in the Lukachukai Mountains are commonly found in bleached tabular channel-fill sandstones which are generally very fine-to fine-grained, friable, thin-bedded with alternating laminae of sandstone and siltstone, and composed predominantly of quartz. Uranium minerals in mudstones below and lateral to the tabular sandstones occur partly along minute cracks and partly on rolls. However, the discordant concretionary 8 "roll11 type of uranium deposit in sandstones, common in other areas, is uncommon in the Lukachukai Mountains. Relationship between ore bodies and lithology and sedimentary structures is marked. All uranium ore occurrences are in favorably colored sand zones which lie parallel to Salt Wash paleo stream courses mapped from sedimentary structures in mines and on rims. Lit tle relationship between mineralization and tectonic structures has been determined. Types of deposits Sandstone lens deposits The greatest production has been from tabular lenses of sandstone which are scour and fill deposits of the festoon and asymmetrical trough types. The width of a festoon or scour may range from 1 to 20 feet, and the thick ness of a lens from 1 inch to 40 feet. Thickness of individual strata range from 0.10 to 0.15 inches. Uranium minerals generally occur in the thicker portion of the lens, parallel to the axis of stream flow. The sandstone is composed of alter nating laminae of very fine to fine, rounded to subangular, well sorted detrital quartz grains and silt. Unfavorable red sandstones and favorable bleached sandstones show no significant differences in permeability, grain size or sorting. Minor accessory minerals, not exceeding 5 per cent of the total rock composition, are magnetite, chert, pyrite, zircon, tourmaline and microcline. Sandstone grains are commonly cemented with calcite, clay, and vanadium bearing micaceous clay minerals. Hematite and goethite commonly coat grains. Calcium carbonate, chiefly calcite, may occur as interstitial cement in and around sand grains, which are commonly corroded, or may occur between fabric grains as groups of crystals from 1 to 10 inches across. Ore bearing sandstones are generally friable and contain less than 6 per cent calcium carbonate, but may be 1vell cemented, however, and contain up to 20 percent calcite. Griffiths and others (1955) found the major difference in mineral composition between ore bearing and barren sandstones to be in the relatively high content of clay pebbles or galls and matrix in the ore sandstone. The more massive sandstones of the flood plain or deltaic type also con tain uranium which is widely disseminated throughout the sandstone and is generally of marginal grade. Mudstone deposits Some uranium is found in disturbed or slumped mudstones largely as coatings on fracture planes. Uranium in mudstones and siltstones is scat tered and discontinuous and is generally of marginal or sub ore grade. The only commercial production of ore from mudstone deposits has been in limited quantity from the mines on Mesa IV. Lithologic Variations in the Ore Unit The ore bearing horizon of the Salt Wash is composed of highly lenticular discontinuous units. Ore deposits are found in the thicker channel sand stones, which parallel the direction of paleostream flow, Ore is appar ently concentrated by the intertonguing of sandstone and mudstone lenses. More interbedded sandstones and mudstones are found toward the edge of the 9 channel, representing flood plain and bar deposits. Favorably colored sand stone lenses will grade into red sandstones at directions perpendicular to paleostream direction, whether or not the sandstone lens interfingers with mudstones or siltstones. Mudstones above and below an ore bearing sandstone may or may not be bleached but are more likely to be altered where an ore bearing sandstone thickens. Size of Ore Deposits The size of ore deposits in the Lukachukai Mountains ranges from pods several feet in diameter to irregular, tabular elliptical bodies 50 feet in width and 75 feet in length. Thickness ranges from a few inches to as much as 18 feet, and the average thickness is about 2.5 feet. Any single ore body is rarely larger than 15,000 tons. Color Alteration Uranium deposits in the Lukachukai Mountains are, in most places, sur rounded by bleached zones in which the normal red color of the Salt \vash is absent, and the sand is grey, tan, green or white. The color change is due to reduction and leaching of ferric iron, possibly caused by the passage of ore bearing solutions. Bleached zones or alteration halos surrounding ore bodies extend lateral ly from a few to several hundred feet. Mineralized zones correlate well with altered or bleached zones within an ore bearing unit, with color alteration of the sand in an ore bearing unit ranging from 50 to 100 percent. Within the favorable zone, sandstones are red if there is enough hematite present, regardless of the other components of the rock. Laverty (1954) states: "Buff sandstones are so colored because of the presence of goethite and the absence of hematite, regardless of other minerals present. In the absence of the iron oxides, chlorite produces a distinct greenish tint in the sandstone, and large percentages of beidellite can produce the same effect in the absence of chlorite. Smaller percentages of beidellite in the absence of both chlorite and the iron oxides results in a grey sandstone - within the favorable zone, sandstones will be colored red if there is enough hematite present, regardless of the other components of the rock. The amount of hematite required to produce a red stain is considerably less than one percent. 11 Color alteration of ore bearing sandstone lenses on the northeast rims differs from the southwest rims in that the entire sand unit is generally altered on the northeast rims, but the bleached zone extends vertically only a short distance above and below mineralization in ore bearing lenses on the southwest mesas. Thin mudstone layers and galls within an ore bearing unit are usually bleached at least on their outer surface, but color alteration of a whole layer or pellet is relatively uncommon. Ore Guides Uranium mineralization in the Lukachukai Mountains was probably accomp lished by circulating aqueous solutions that may have travelled through a complex network of ancient Salt Wash paleostream channels. Precipitation of uranium occurred under certain favorable conditions such as (1) abrupt change in stream direction, (2) presence of carbonaceous material, and (3) 10 interfingering of sandstone and mudstone lenses, with a thickening of sand lenses. Stokes (1953) and Lm During the exploration program, the following criteria proved to be reliable guides to ore: (1) Uranium ore occurs, for the most part, in a 50-foot host unit in the upper 90 feet of Salt Wash. The host unit is located about 45 feet above the base of the Salt Wash. (2) Most ore is found in the thicker parts of tabular lenses of channel fill sandstone 20 to 35 feet thick within the host unit. (3) Ore deposits are generally found in bleached or altered zones in the sandstone lenses. (4) Persistent muds or silts occur above and/or below ore bearing sands. (5) Ore bodies lie within and are aligned parallel to zones of favor ability which closely follow change in paleostream direction. (6) Finely disseminated carbonaceous matter is nearly always associated with ore. Mudstones and siltstones above and belov1 the ore sand are bleached at the contact of their surface with the bleached ore unit. In most places only a thin layer of mud or silt, 0.1 to 1.0 inches thick, is bleached at this contact, but thick beds of altered mudstone are quite common. In general, alteration of muds and silts is less consistent than that of sand. EXPLORATION METHODS Reconnaissance Reconnaissance of the Lukachukai Mountains was correlated almost entirely with the drilling program and was designed to obtain basic geologic information preparatory to recommending areas for drilling. When exploration of the Lukachukai Mountains began, there were no maps of the area, and vertical control was based on an assumed elevation. Topo graphic base maps, prepared by the Topographic Branch of the U. S. Geological Survey from aerial photographs at the request of the Commission, were obtained during fulfillment of the first drilling contract and used for all subsequent mapping. \Vhen topographic maps became available, a primary tri angulation net was established from control stations on aerial photographs from which the base maps were prepared. A secondary system of control was surveyed in by transit and stadia between primary stations. Basic recon naissance consisted of little more than locating the position and shape of mineralized outcrops, measuring on few sections in the Salt Wash, and con structing a structure base map to estimate drilling depths. Altimeter stations along the rim and at outcrops were located by plane table survey, plotted on aerial photographs, and then transferred to topographic base ll maps. Structure contours, drawn on the base of the Salt Wash, ~1ere mapped at 10-foot intervals. Mapping of sedimentary trends The interrelation between directional trends of sedimentation and uranium occurrence is based on the hypothesis that uranium was transported in solu tions which percolated through a complex network of paths of maximum perme ability in sandstone now filling scours in Salt Wash paleostreams. Previous work by C. N. Holmes (1949) emphasized that intersections of ancient stream meanders form favorable environments for uranium deposits, and that mineral ized areas are generally aligned with paleocurrent directions. The Salt Wash in the Lukachukai Mountains has characteristic primary structures such as inclined torrential cross-bedding, stream lineations, scour and fill deposits, and ripple marks which aid in mapping Salt Wash paleostream courses. Early in the exploration program, sedimentary structures at mineral- ized outcrops were plotted to determine channel direction. Since informa tion regarding orientation of the axes of channel fill deposits was then little known, mapping was abandoned when conflicting directions were obtained from different trend indicators. By the conclusion of the second drilling contract, however, J. D. Lowell (1953) had begun accurate mapping of sedi mentary structural trends, using field methods developed in the Carrizo Mountains by W. L. Stokes ( 1953). As more data was accumulated later in the program, geologic reconnais sance became correspondingly more detailed and thorough. In addition to sedimentary trend indicators, fractures, folds, and attitude of bedding, color alteration of ore bearing sandstones, carbon and limonite concentra tion, and selected mines were mapped in detail in the vicinity of recom mended drilling areas. Mine Mapping Prior to the summer of 1954, mapping of mines in the Lukachukai Mountains had been carried out on a limited scale. The pace of drilling had been rapid, and attention concentrated on the search for commercial ore deposits during the early part of the exploration program. Lowell (1953) had mapped the Climax 4-B mine late in 1952 in connection with his study of sedimentary structures and paleostream trends, and nearly all of the mines were mapped for ore reserves during the latter part of 1953 and spring of 1954. No thorough and detailed field study of geologic criteria associated with uran ium had been made, however, before Beam began mapping a group of mines on Mesa 4 1/2 in June 1954. Beam's study (1957) and later mapping brought to light new features associated with uranium in the Lukachukai deposits which could be used as guides to ore and gave evidence to substantiate relationships discovered by earlier drilling. Ore bodies generally lie between thick impervious muds, and ore bearing sandstone lenses grade laterally into silts. From the thicker part of an ore bearing sandstone lens, toward its edges, where sandstone progressively grades into silty sandstone, sandy siltstone, and mudstone, there is a cor responding increase in ratio of vanadium to uranium accompanying the decrease 12 in permeability. Ore sands may be grey, tan, green, or white and are common ly limonitic. Portions of a lens adjacent to or in contact with ore were found to be high in calcium carbonate content and were impregnated with iron oxides and lesser amounts of manganese oxide, Parallel vertical or steeply dipping fractures are more closely spaced in ore zones. Here, from 5 to 10 major fractures or more are found in every 10 feet in contrast to barren zones, where less than 5 fractures are found. Fracture walls are generally tight, but openings between walls may range up to 50 mm in width. Fracture walls are unaltered, and uranium minerals rarely fill fractures except where present day ground water has deposited efflorescent coatings of secondary vanadates. Disseminated carbon flakes and seams of carbonaceous material, which are generally associated with ore and may be found in favorable sand stones are neither found along nor coat walls of fractures. Although uranium minerals are usually found in more intensely fractured zones, an ore body will deviate from a fractured zone to follow an abrupt change in paleostream direction .. Drilling Program Elevations in the drilling area range from 7,500 to 8,500 feet. Most of the area is heavily timbered and covered with soil. In general, the terrain is very rough, relief is high, and slopes are steep. In preparation for drilling, geologic maps of the Salt Wash were con structed and geologic sections were measured. Mineralized outcrops were located and sampled, bleached or favorable colored areas located, and paleo stream directions were obtained by mapping characteristic sedimentary fea tures and structures. A Salt Wash-Bluff structure contour map was construct ed to serve as control in determining drill hole depths. Drilling penetrated all or part of the Bluff, Salt Wash, Recapture, West water Canyon, and Chuska sedimentary units. The drilling target was the upper 90 feet of the Salt Wash in which nearly all of the known uranium de posits are located. Within this upper 90 feet, a zone 45 to 50 feet thick in the middle third of the Salt Wash, located approximately 45 feet above the top of the Bluff formation, contains most of the ore bodies discovered. This zone is known, and shall hereafter be referred to in this report, as the host unit. Core was taken only from the upper 90 feet of the Salt Wash. In offset holes, the cored section was reduced to half that amount or less. On drilling close to rims, where holes were collared in the Salt Wash, above the ore horizon, only 20 to 30 feet of core was taken. Drilling depths ranged from 50 feet on rims to over 950 feet in deeper areas near the center of the mountains. Holes were generally bottomed about 20 feet above the base of the Salt Wash, but an occasional hole was drilled which penetrated the Bluff sandstone to test structural control in new areas where deeper ground was being investigated (Fig. 5). The upper Chuska, which is silicified, was not drilled, and the lower Chuska, a poorly consolidated sand, was encountered in about 10 per cent of the holes. The unconsolidated overburden, consisting mostly of soil, rarely exceeded 25 feet at any one place. In some areas, the surface is strewn with large fragments and boulders of silicified Chuska sandstone, which also occur beneath the soil cover and impede drilling operations, but there is no continuous layer of pediment gravel. The formations dip at an angle of 1 to 2 degrees northeast. 13 When large reserves of mineable uranium ore were found by drilling under the first three of six contracts, construction of a processing mill in Shiprock, New Mexico, was begun. The drilling program was modified to eliminate the offset phase of drilling, and emphasis was shifted to the second major objective of the overall exploration program--discovery and development of ore criteria, ore trends, and favorable ground. Plan of Drilling Diamond drill holes were located by closed traverse and transit and stadia survey. Elevations were determined by running closed differential levels, using a transit as the levelling instrument. Coordinates of drill holes were computed to the nearest foot, and elevations were computed to the nearest tenth of a foot. The drilling program originally consisted of three phases: (l) wide spaced grid pattern, 400- to 800-foot spacing between holes, (2) closed grid pattern, on 100- to 200-foot spacing between holes, and (3) offset drilling 50-foot intervals, including drilling behind outcrops to delimit exposed ore bodies and around ore holes and mineralized ground to develop deposits and reserves. Drilling commenced in selected areas on the rim and was extended, first, to include favorable portions of the rim, and then, to explore deeper ground away from rims. Several deep holes were drilled across the highest part of the mountains to connect and correlate more concentrated drilling areas. As drilling depths became greater, spacing between drill holes increased (Table l). In the original drilling proposal, it was recommended that the major exploratory effort be expended on Mesa I, the discovery area, because of its apparent economic potential and accessibility, although mineralized outcrops were known to exist on other mesas. After drilling started in September 1950, and access roads were completed to Mesas II, III, and IV, the drilling plan was altered to include the exploration of these additional areas. Under the revised program, which provided no increase in total footage, overall hole density was accordingly decreased. Near the end of the first drilling project, shallow wagon drilling was tried on Mesa IV but provided unsatisfactory when cuttings could not be blown up to the surface by compressed air due to excessive wetness of the units. Further portions of the northeast rims were explored by the second drilling contract. Despite negative drilling recommendations resulting from unfavorable reconnaissance reports (King and Ellsworth, 1951, and Ellsworth, 1951), Mesa VII and Mexican Cry were drilled, in addition to Mesas IV l/2 and V. With closely spaced drill holes, large ore deposits were discovered on the latter two mesas. Mesa V, however, has deposits of marginal grade which have little continuity. The southeast rims* were drilled under the third drilling contract. The mesas further to the west, from Flag to Fall Down mesas, were later drilled as part of the final drilling contract. ""From Camp mesa west to Flag mesa. 14 The Cove Mesa if3 contract was amended to allow a portion of the footage under that contract to be transferred to Mesa IV 1/2, where 12,426 feet were drilled under the Lukachukai ift4 contract. As a result of the Lukachukai ift4 drilling and later reconnaissance, N.J. Clinton (1954) discovered a broad zone of bleached grey sandstone forming an arcuate band across the northeast mesas from Mesa IV l/2 to Mesa I. This zone was explored by the fifth dril ling contract. The final drilling contract investigated higher ground adjacent to areas found to be favorable, by following ore favorability trends. It was the only contract, as originally proposed, for which little or no rim information was available, since deeper ground a Sub-surface Mapping Various types of subsurface aids were used during the course of drilling. It was possible to correlate generally the Salt Wash section over much of the drilling area by using a grey lacustrine mudstone at the top of the Salt Wash. This mudstone persists across both the northeast and southwest mesas and has a characteristic bi-lobed gamma log deflection that can be readily identified. Laboratory examination reveals that this anomalous radioactivity is caused by a mixture of very fine, granular secondary hydrated uranium car bonates or oxides (Laverty, 1953). Stafford (1951) reported that considerable difficulty was experienced in coring the friable ore sandstone of Mesa l. This difficulty was overcome, however, by placing a gamma-ray logging unit in operation at the project in October 1950. The presence of ore and a close approximation of its thickness could be noted from the gamma log, and a reasonably exact geologic log could be constructed from it. Lithologic units were correlated with corresponding gamma log deflections, thus adjusting the geologic log for core losses. Use of the gamma log permitted the ore horizon to be located and correlations between drill holes to be made more accurately. On the first two contracts, emphasis was placed on the element of time in the search for uranium, and a hit or miss system of drilling was used to locate ore deposits as rapidly as possible, with a minimum of geologic information collected. A need for more accurate drilling guides, resulted in the start of subsurface studies during the latter part of the second drilling contract (Lowell, 1953). Particular attention was paid during the second contract to such features as color of sandstone or mudstone, thick ness of the unit, presence of cementing material, grain size, bedding, and presence of carbon, all of which may have had some influence on distribu tion of ore. Techniques were discovered and developed more fully during the first part of the succeeding contract (Masters, 1953). During the Lukachukai No. 3 project, subsurface data was used for the first time on a large scale to guide drilling, rather than the systematic geometric grid which had been used to explore unknown areas in earlier projects. The program still consisted of three phases, including offset drilling on 25-and 50-foot centers. Most guides to uranium ore used in the Lukachukai Mountains have been used elsewhere in Salt Hash deposits (Fischer, 1950; Heir, 1951), but most of the mapping techniques were developed by Commission geologists working in 15 the area. These techniques were to prove useful in other areas, and sub surface mapping became accepted procedure for guiding drilling on subsequent contracts. Various types of subsurface maps were constructed to discover which were the most effective guides to ore. Results of experimentation with different map types are more fully discussed in earlier reports by Lowell (1953), Masters (1953), Clinton (1954), but the various types of maps and their use shall be briefly summarized here. Iso Percentage of Bleached Sandstone Map: Ore bodies in the Lukachukai area are, in most places, surrounded by bleached zones in which the sandstone is grey, tan, or white. A color map was drawn on the percentages of bleached sandstone in the ore bearing unit. In the absence of continuous lithologic units in an area of lenticular stratigraphy, the ore bearing host unit 1s best defined by arbitrary planes above and below it, drawn parallel to the base of the Salt Wash and a constant distance above it. These planes determine a zone of constant thickness, which contains the uranium ore deposits and which can be contoured for the sandstone color map. Over most of the drilling area, a constant host unit of 50 feet vertical thickness, ~n which most ore in the Salt Wash occurs, was chosen for mapping. The thickness of bleached sandstone within the host unit is measured in each drill hole and the percentage of total sandstone thickness in the host unit that this represents is calculated. When a sufficient number of holes has been drilled, contour values are obtained from each drill hole, and an iso-percentage favorable color map is plotted from this information. A double line of holes spaced 400 feet apart across trends usually were enough to obtain information to be begin contouring values. Unless care was taken, values could be contoured in several different ways, giving conflicting directional trends of favorability. The areas of the greatest percent of altered sandstone on the map depict a zone in which ore bodies are most likely to be found. Ore deposits are found for the most part in areas in which from 50 to 100 percent of the sandstone in the host unit has been altered or bleached. Favorability zones correspond generally with bleached zones and are elongated along the direction of ancient stream flow. A map showing the percent of favorably colored mudstones, silstones and sandstones in the host unit gave essentially the same information as the percent of favorably colored sandstone map. Through use of these maps, the presence or absence of uranium in a drill hole could be predicted with considerable accuracy. From these first favorability maps, subsequent drilling was planned, following ore favorability trends into deeper unexplored ground. Bleached Sandstone Isopach Map: Isopach maps of favorably colored sandstones were also helpful in planning subsequent phases of drilling. Uranium occurs in the thicker parts of bleached sandstone lenses, but not necessarily in the thickest part. Most of the ore was found in lenses from 20 to 35 feet thick, although mineralization occurs in sandstone lenses as thin as one foot. Mudstone-Sandstone Isofacies Map: During the course of drilling, mudstone sandstone ratio maps showing facies transition from muddy to sandy areas were used in combination with fence diagrams and favorable color sand- stone maps. Ore usually occurs in areas of rapid change from mud to sand where equal quantities of mudstone and sandstone are found and the ratio of mud to sand is not greater than 1:1. Areas of high mud and silt contain dis continuous pods and streaks of ore which do not offer satisfactory drilling targets. 16 Isometric Diagrams: Fence diagrams were constructed from geologic strip logs of drill holes and used to chart changes in lithology across ore favorability trends. These diagrams are most useful in correlating discon tinuous lithologic units in an ore zone of limited extent within a broader host unit, when development of an ore body is planned. Since the position of the host unit in the Salt Wash is well fixed and the unit could be corre lated from area to area quite easily, limited use of these diagrams was made in correlation. It was found that wider changes in favorablity, shown on maps of percent of favorable color sandstone and thickness of favorably colored sandstone, were more effective than limited changes in lithology, shown by fence diagrams, in planning wider spaced drilling. Isoradiation Map: Isoradiation maps, constructed from both measurement of the maximum deflection of the gamma log curve, and measurement by planimeter of the area enclosed under the curve, measure changes in radioactivity and were used to plan closer spaced drilling within an initial grid in areas of favorability. The map derived from planimetric measurement is the more detailed and accurate of the two types, but both maps are similar in general appearance. The developmental phase of drilling was omitted under the last two drilling contracts, and isoradiation maps were not used to a great extent. Carbon and limonite intensity maps: Maps showing intensity of carbon and limonite concentration correlate to some extent with location of ore de posits, but their use alone is limited. Limonite may or may not be associ ated with ore but may occur in favorable or bleached sandstones where uran ium minerals are not present. Miscellaneous maps: Maps showing alteration of mudstone, change in grain size and bedding, and type of cementing material in the host unit and those showing the ratio of U30s to VzOs were also used. The results obtained were either negative or inconclusive. Comparison of various types of subsurface maps The various types of subsurface maps were used in combination with one another to plan drilling and estimate the favorability of an area. The iso-percentage favorable color map was the most effective single guide. A more efficient guide, however, would probably have been a composite favorability map, taking into consideration and weighing such factors as percentage of favorably colored sandstone, thickness of favorable colored sandstone, mudstone-sandstone ratio, amount of radioactivity, and abundance or absence of carbonaceous material. RESULTS OF THE EXPLORATION PROGRAM A detailed reconnaissance of the Lukachukai Mountains was made, with the exception of a sector of the southwest rim between Fall Down and Mexican Cry Mesas, which may be considered inadquately assessed. Approximately three fourths of the Lukachukai Mountains was explored with diamond core drilling. The results of this drilling are summarized in Table 1, which is based on more detailed information such as drill hole data and geologic strip logs, which of necessity cannot be embodied in this report. A total of 374,198 feet was drilled in 1,837 holes, of which 242 are in ore and 469 show anomalous radioactivity or contain uranium of sub-ore grade, for a discovery rate of two mineralized holes for every five holes drilled. 17 Northeast rim Sizeable ore deposits were discovered on Mesas I, II, III, IV, IV l/2 and V, which are no~;v being mined or have been mined, and smaller scattered deposits were discovered on the other mesas between Mesa I and Mesa v. Only one small deposit on Mesa VI was found between Mesa V and Mexican Cry Mesa. Numerous areas of favorability were outlined on the northeast rim. The best and most extensive area extends across Mesa II l/2 to Mesa III and 1s 3,000 feet long and 300 feet wide, paralleling the general southeast trend of paleostream flow. Another extensive favorable area is on Mesa IV l/2, where a north trend of favorability continues from the northern part of the mesa to Mesa V, where it swings to the west. Drilling to extend this trend shows a buildup of favorability to the west. In view of the fact that only one deposit has been found west of Mesa V in general and that drilling depths increase, it would not seem desirable to continue tracing this trend. Small deposits were found on Mesa I 1/2, but the ground is not highly favor able. Small trends of favorability are found on both Mesa I l/4 and Mesa IV l/4. The trend on Mesa I 1/4 is cut off by zones of decreasing favorability and no further exploration is warranted. The zone on Mesa IV l/4 is pro jected into deeper ground, and the objections to tracing the broader trend of favorability on Mesa V, stated above, also apply here. Areas of favor ability discovered by earlier drilling on the noses of the mesas have not been shown since complete information was not available. Southwest rim Mineable ore deposits were found on Camp, Cisco, Three Point, Bare Rock, Flag and Fall Down Mesas. All deposits except those on Bare Rock Mesa are now being mined. Scattered small deposits were found along the southwest rim. To the west of Fall Down Mesa, to Mexican Cry Mesa no mineable deposits are known and only a few scattered outcrops are !mown on Thirsty Mesa. The Texas Mining Company mine on Mexican Cry Mesa is the only producer west of Fall Down Mesa. A broad belt of small parallel zones of favorability, trending east or north of east, extends from Flag to Camp Mesa. Host of these smaller trends project into deeper relatively unexplored ground. On Camp and Cisco Mesas, the extension of areas of high favorability is limited by zones of decreas ing favorability. Undefined zones of favorability on Flag and Little Mesas project into the Center Peak area and should be explored more fully for the extension of known ore bodies. Center Peak area The Center Peak area has several broad zones of favorability but no known ore bodies. Drill holes parallel and in proximity to the major zone of favorability across Mesas II l/2 and III are weakly mineralized. Since the average spacing between drill holes in this area is approximately 550 feet, further exploration of this area should be undertaken. Primary objec tive of this program should be to extend the major zone of favorability on Hesa II 1/2 to the south and to trace and delimit the favorability trends projecting from Flag and Little Mesas on the southwest rim. 18 SUMHARY AND CONCLUSIONS Uranium ore deposits in the Lukachukai Mountains are principally secondary and almost totally oxidized. Ore bodies are confined within a definite horizon in the Salt Wash. Localization of uranium appears to have been controlled by lithologic and permeability changes rather than by structure. Where ore is found in zones of major fracture sets, such as Flag, Three Point, and Cisco Mesas, the fractures parallel subsurface favorability trends and paleostream direction. In mines, ore bodies will deviate from fracture zones to follow abrupt changes in direction of paleostream flow. Many ore deposits are found in areas where fracturing is too slight to be of consequence. As drilling depths and spacing between drill holes increased, the tons of ore discovered per foot drilled decreased. By careful use of subsurface methods, ore trends were projected and favorable ground delimited so that unfavorable ground was eliminated from further investigation. On the later contracts, the guidance of drilling by subsurface mapping was reflected in the increase of tons of ore discovered per hole drilled (Table 1). Favorable areas near and adjacent to known deposits and the relatively unexplored sector on the southwest rim offer targets for further exploration. Even though few deposits or outcrops are knotm in this sector, it may be expected that some deposits of marginal grade will be found. The main deter rent to investigation of favorable deeper ground at the present time appears to be the reluctance of private industry to engage in deeper drilling. The exploration program succeeded in discovering mineable ore deposits and potential reserves to warrant construction of a local mill and discovered and developed ore finding criteria, resulting in information which can be used to aid exploration and mining in the Lukachukai Mountains area, thus ac complishing the objectives of the program. Table 2 lists all of the AEC reports that were written as the result of the exploration in the Lukachukai Mountains. 19 TABLE I Summary of Drilling Statistics Avg. Avg. No. of No. of Percent Total Feet Number Depth, Spacing, Ore Min. Core Project Contractor Duration Drilled of Holes Feet Feet Holes* Holes Recovery Lukachukai #1 Minerals Engi- Sep., 1950- 49,984 322 155.2 213.8 22 88 68.5 AT (30-1)-1021 neering Co. Feb., 1951. Lukachukai #2 Minerals Engi- . 5-11-51 to 89,887 560 160.5 212.0 75 160 88.0 AT(30-l)-1139 neering Co. 11-21-51. Lukachukai #3 Joy Manufac- 6-15-52 to 90,000 544 165.4 262.0 98 155 84.6 AT(30-l)-1263 turing Co. 11-17-53. Lukachukai #4 Minerals Engi- 10-20-52 to 12 ,426 44 282.4 297.0 8 6 85.7 0"' AT (30-1)-1364 neering Co. 4-15-53. Lukachukai #5 Minerals Engi- 7-15-53 to 71,683 241 297.4 389.6 25 33 82.6 AT(05-1)-234 neering Co. 4-30-54. Lukachukai #6 Pennsylvania 7-8-54 to 60,218 124 . 485.6 487.7 14 27 84.7 AT(05-l)-257 Drilling Co. 8-24-55. *An ore hole is defined as containing at least greater than 1 foot of 0.20% u3o8 or equivalent. TABLE 2 AEC Reports Resulting From Exploration in the Lukachukai Mountains* Reports Published By The Technical Information Service, Oak Ridge, Tennessee RME-27 Geology of the Uranium Deposits of the Lukachukai Mountains Area, Northeast Arizona, J.A. Masters, 1953. RME-44 Application of Cross Stratification Studies to Problems of Uranium Exploration, J.D. Lowell, 1953. RM0-754 Geology and Ore Deposits of Mesa V, Lukachukai District, Arizona, J.W. King, 1951. RM0-802 Geology and Ore Deposits of Mesa VI Lukachukai District, Arizona, P.C. Ellsworth, and K.G. Hatfield, 1951. R!10-803 Geology and Ore Deposits of Mesa VII Lukachukai District, Arizona, J.W. King, and P.C. Ellsworth, 1951. RM0-911 Uranium Deposits on Southwest Rim of Lukachukai Mountain, Northeast Arizona, J .A. Masters, 1951. Reports Open-Filed by the Grand Junction Operations Office RME-184 Geology of Lukachukai Mountains Area, Apache County, Arizona, J.A. Masters, with a section on survey control by R.D. Blum, 1952. RM0-629 Geology and Ore Deposits of Mesa V, Lukachukai District, Arizona, with Recommendations for Diamond Drilling, J.W. King, 1951. RM0-688 Geology and Ore Deposits of Mesa VI Lukachukai District, Arizona, 1vith Diamond Drilling Recommendations, P .C. Ellsworth and K .G. Hatfield, 1951. RM0-690 Geology and Ore Deposits of Mesa VII Lukachukai District, Arizona, J.W. King and P.C. Ellsworth, 1951. RM0-696 Results of Diamond Drilling on Mesas I, II, III, and IV, Lukachukai Mountains, Northeastern Arizona, H.S. Stafford, 1951. RM0-699 Geological Investigation of Mexican Cry Mesa, Lukachukai District, Arizona with Diamond Drilling Recommendations, P.C. Ellsworth, 1951. RM0-705 Uranium Deposits on Southwest Rim of Lukachukai Mountains, North-East Arizona, J .A. Masters, 1951. RM0-707 Uranium Deposits on Mesas I-1/2 and II-1/2, Lukachukai Mountains, Northeast Arizona, J.A. Masters and R.D. Blum, 1951. RM0-828 Drilling in the Lukachukai Mountains, Lukachukai No. 2 Project, Apache County, Arizona, M.E. Crew and J.D. Lowell, 1952. RM0-1011 Report on Examination of the Sitton Lease on the Navajo Reserva tion, Apache County, Arizona, S.K. Smyth, 1950. 21 TM-37 Studies of Diamond Drilling at the Lukachukai No. 2 Project, L. Roberts, 1952, (Engineering Report). TM-47 A Preliminary Investigation of Triassic Rocks in the Lukachukai Mountains, Arizona, R.F. Kosatka, 1956. TM-107 Drilling in the Lukachukai Mountains, North Chuska Mountain Area, Apache County, Arizona, Contract No. AT(05-l)-234, J.\-1. Eppich, 1956, (Engineering Report). TM-110 Drilling in the Lukachukai Mountain Area, Apache County, Arizona, Contract No. AT(30-l)-1364, J.F. Brown, 1956, (Engineering Report). TM-115 Ore Occurrence Study, Mesa 4-1/2 Mines, Lukachukai Mountains Apache County, Arizona, T.E. Beam, 1957. TM-143 Drilling in the Lukachukai Mountains, North Chuska Mountain Area, Apache County, Arizona, J.W. Eppich, 1957, (Engineering Report). TM-185 Causes of Color Variations in the Salt Wash & Recapture Members of the Morrison Formation on the Southside Mesas, Lukachukai Mountains, Apache County, Arizona, R.A. Laverty, 1954. TM-245 Drilling in the Lukachukai Mountains, Lukachukai No. 3 Project, Apache County, Arizona, Contract AT(30-l)-1263, R.L. Rock, 1954. *Status as of January 1, 1983 Lithologic logs of AEC drill holes, and drill hole location maps are on open file at the Grand Junction Office. 22 REFERENCES Beam, T. E., 1957, Ore occurrence study, Mesa 4 1/2 mines, Lukachukai Mountains, Apache County, Arizona: U. S. Atomic Energy Comm. TM-115, Open File Report. Clinton, N.J., 1954, Subsurface mapping methods, Mesa 4 1/2, Lukachukai Mountains: U. S. Atomic Energy Comm., Internal Memorandum. Craig, L. c., Holmes, C. N., Cadigan, R. A., Freeman, v. I., Mullens, T. E., and Weir, G. w., 1955, Stratigraphy of the Morrison and related forma tions, Colorado Plateau region, a preliminary report: U. S. Geol. Survey Bull. 1009-E. Ellsworth, P. C., 1951, Geological investigation of Mexican Cry Mesa, Luka chukai district, Arizona, with diamond drilling recommendations: U. S. Atomic Energy Comm. RMD-699, Open File Report. Fischer, R. R., 1950, Uranium-bearing sandstone deposits of the Colorado Plateau: Econ. Geol. Vol., 45, p. 1-11. Gregory, H. E., 1917, Geology of the Navajo country: U. S. Geol. Survey Prof. Paper 93. Griffiths, J. C., Cochran, J. A., Hutta, J. J., and Steinmetz, R., 1955, Petrographical investigations of Salt Wash sediments, Annual Technical Report, April 1954 to April 1955: U. S. Atomic Energy Comm. RME-3122, pt. 1, Tech. Inf. Service, Oak Ridge, Tenn. Harshbarger, J. W., Repenning, C. A, and Jackson, R. L, 1951, Jurassic stratigraphy of the Navajo Country: New Mexico Geol. Soc. Guidebook of the south and west sides of the San Juan Basin, New Mexico and Arizona, 2nd Field Con£., p. 95-99 Holmes, C. N., 1949, Geology of carnotite deposits of the Colorado Plateau: Amer. Assoc. Petroleum Geologists, paper presented at Salt Lake City meeting March, 1949. Kelley, V. C, 1951, Tectonics of the San Juan Basin, in New Mexico Geological Soc.: Guidebook of the south and west sides of theSan Juan Basin, New Mexico and Arizona, 2nd Field Conf., p. 124-131. King, J. W., and Ellsworth, P. C., 1951, Geology and ore deposits of Mesa VII, Lukachukai District, Arizona: U. S. Atomic Energy Comm. RM0-803, Tech. Inf. Service, Oak Ridge, Tenn. Laverty, R. A., 1953, Peak 11 A11 from northside mesas, Lukachukai area, Ari zona: U. S. Atomic Energy Comm. Laboratory Memo 250. Laverty, R. A., 1954, Causes of color variations in the Salt Wash andRe capture member of the Morrison Formation on the southside mesas, Luka chukai Mountains, Apache County, Arizona: U. S. Atomic Energy Comm. TM-185, Open File Report. 23 Lowell, J. D., 1953, Applications of cross-stratification studies to problems of uranium exploration: U. S. Atomic Energy Comm. RME-44, Tech. Inf. Service, Oak Ridge, Tenn. Masters, J. A., 1953, Geology of the uranium deposits of the Lukachukai Mountains area, northeastern Arizona: U. S. Atomic Energy Comm. RME-27, Tech. Inf. Service, Oak Ridge, Tenn. Stafford, H. S., 1951, Results of diamond drilling on Mesas I, II, III, and IV, Lukachukai Mountains, northeastern Arizona: U. S. Atomic Energy Comm. RM0-696, Open File Report. Stokes, W. L., 1953, Primary sedimentary trend indicators as applied to ore finding in the Carrizo Mountains, Arizona and New Mexico: U. S. Atomic Energy Comm. RME-3043 (Pt. l), Tech. Inf. Service, Oak Ridge, Tenn. Stokes, W. L., 1954, Some stratigraphic, sedimentary, and structural rela tions of uranium deposits in the Salt Wash sandstone: U. S. Atomic Energy Comm. RME-3102, Tech. Inf. Service, Oak Ridge, Tenn. Strobell, J.D., Jr., 1956, Geology of the Carrizo Mountains area in north eastern Arizona and northwestern New Mexico: U. S. Geol. Survey, Oil and Gas Inv. Map OM 160. Weir, D. B., 1951, Geologic guides to prospecting for carnotite deposits on the Colorado Plateau: U. S. Geol. Survey TEI Report 119. 24 \ I ' ' \ .. ' ,I ,r1 . ; ' Rw 'l I ... ~ Jkn Rw I I I I I .. .. I r / 140,oooN ( ,I ·~ .J / / Rw \ liw •• \ Rc / f 'I I I I I \ \ I ~-~ ) .._ __ .... \ I ~ \.._,.~ ..... \..,.,! Jsr I I I I l I i' ~_j I Qal l • Rc l r' I ' _; --·-·· /. I / I' I I ..------'(\'\Qi~?I30,oo_o N Jkn (~ Rw Jms c ' /i I r-.., ..,._ ...--- \ I ~ \ I 1 ,./ I . ' {-.1 ' ' ' \ I \\ I ' ' I I I I I I I / Rc 1 · r ' r -~~ r? \ / I I 1 ' .-,, ~- ""-' '- I I '" ' '' I '-" J s r I Jm / ' -, I I J sr I I I I ) I \::._~J_k_n_.. _. Rw Jms- ... - ... ' "' I / I \ ' I / I I I ' I Qal ,,,.~ ...... ' ' Qal ' /-" ,. --- .... ( /' ~--~--. \.I ... --. I I ,I 120,oooN I I ',1 ..I I,' I I ' ' I Rw I' ' " ,l ) ~-.. I I ,~J \ I ~ I ~ I I \' , I' ·, , ~ \,, '"' 7 ( I \: \ \ l ! I \ /1 Rc \ I ~ // •;\.. j __ ,_·.c./ / / \ /\ / -\ / \ !\ ~"' \ t I I / \ ' '··~ ' ,_' ~, 1/. I ,-' ' r '-"' J ' \.. I ...... ---- ~' ', Tc I I ', Rw I 'I ·. ' Rc ' 1- ' I ' / ' r' ( ' Rw \ ' \ I w I I 0 I \ w 0 I 0 0 I \ 0 I ·1 0 0 \ 0 co /, .. ' c. t: Rw I Rc :~'~-"'""~ \ ' Tc ' I Y' ',, I I ' ( '\' 1 - ( MINE LESSEE' I' Mexican Cry Mine Texas Mining 2 Hall·. Mine W.B. Hall 3 Nakci'i Chee Begay W.B. Hall 4 Jimmy King No. 9 E. D. Warren Associates 5 Tommy James Mine Price . Exploration Co. 6 Flog No.I Mine Kerr -Me Gee 7 Flog No.2 Mine " 8 Black No.I Mine " 9 Block No.2 Mine " 10 Joieo Mine Walter Duncan Mining Co. Rc II Cisco Mine H 12 Camp Mine II Tc 13 Colo No.2 Climax Uranium Corp. 14 Meso Y Inc'iine Kerr-McGee Tc :•' 8 ( LUKAA 15 M~so Y Mine " ' ) f2·1. -~ CENTER I I IOO,ooo N 16 Mesa Ill: 1/2 Mine (.12 12) " _.-., I I.,. " \ I ... -~- •' North Portal, Frank No, I .,#_. \ '.. -~~·"'"- ) .. 17 Mine (1207) Climax Uranium Corp...... '\ .... ~_ \ L, li 18 South Porto I, Frank No.I Mine " ... -../ - -'\._\. } . j " \ ' ..---""' rl .._ ___ .,.J· '• 19 Mine No.I Mesa IlL Kerr- McGee ~- ' w ---- 20 Mine No.2 Meso IlL " 0 \ i 0 r-- , 21 Mine No.3 Mesa nz: " 0 22 Meso m Mine " 0 23 Meso III/2 Mine "' " Tc 24 Mine No.I, Pc 150 " 1 I 25 Mine No.I, P-21, Mesa II " ---- i 26 Mine No.2, P-150 " 27 Mine No.I, P-21, Meso I 3/4 (Incline) " i ' lie ' 28 Mine No.l5, Mesa I " 29 Mine No.ll, Mesa I " 'r- ,• .. 30 Mine No. 10, Meso I " " ~- 31 Mine No. 12, Mesa I i 32 Mine No. 13, Meso I " I . ' 33 Mine No. 14, Mesa I ' " 34 Colo No. I Pit, Climax Uranium Corp, '' , I 35 Mesa II Pit (Mine L:- B667) Kerr- McGee / i _.,_I' ' 36 East Meso M.ines Pettigrew and Davis l '1: 37 West Mesa Mine Worley and Pettigrew w E p N 0 X L A A Tl 0 N w 0 90,oooN 0 0 0 0 0 QUATERNARY ci N i \ 0 \ N Alluvium, pediment grovel, and windblown · sand. '.i Geologic contact, dashed where approximately laC:ated; ! ___ .-./ TERTIARY Mine portal .• _.--··· Chuska sandstone. X Open pit ~- JURASSIC Spring Morrison formation, including locally the 1-" Westwater Canyon and Recapture members. 0 Access and haulage rood ·-1 ·.. ·- I 8 Saltwosh member, Morrison formotiort. . i < . San .-Rafael' group, including locally the Carmel, 8 Entrada, Summerville, and Bluff formations. ~···:.~.'· .' J f Kayenta and Navajo formations. ·- I :I EJ . I V' TRIASSIC Geology slightly modified after Strobel!, 1956. j Wingate sandstone, including the upper Lu kochukai 10,000 foot grid based on local_ A.E.C. member, and the lower Rock Point member. coordinate system with point ....ct.'. ~rigin U.S.G,s. 0 2000' 8000 j ',_._., 400;0;...... 6ioi0 00 ' (Harshbarger, et, oL 1957) triangulation station CENTER. '. FEET I' Chinle · formation. I i 1 I . ~. Figure 2. Geologic Map of the Lukachukai Mountains area, ] _l·., ( \ ' A poe he County, Arizona ' I {· ! i ' ·, ' ' i (6} 9500 I 1- 9000 Tc 9500 8000 - MEXICAN CRY MESA MESA 3ZII M E S A 3ZI MESA X MESA ' TIL MESA li MESA I 8000 I Jm 7500 - Jm •/ ____./' ~Jm Jm ®./ Jm Jm © 7500 •J-' J_., 7000 Jsr / .Jsr_ \ ~ __..- Jsr '------/ @ ------" 7000 ' 6500 - Rw Rw -.. - 6500 6000 Rc - 6000 -- -- ... Rc 5500 . Structure cross sect1on through LukacHukai Mountains drawn along axis of Chuska 5500 Syncline. Rc-Chinle fm.; Rw- Wingate ss.; Jsr- Son Rafael Group, includes Carmel fm., Entrada ss.) Summerville fm., and Bluff ss.; Jm-Morrison fm.; Tc- Chusko ss. 130,oooN 130 oooN - _, __ - ----- w 0 0 \ \ ', 862 0 7709 0 0 N ' -" '-" ~"'' 0 0>0 0 0 ,_ i ------, ------MESA 3ZI[ "'-.,~,.,/~,.., n 120 ooo N ---- "\: c- Cove School 120 cooN ~ w 0 0 0 0 ------""' N ------'--- 737 """'\ ·--~. ""' X IIOoooN w 0 0 0 ------>---...----- ::<: 7503 0 ------7515 ro I ',,__ "J6 ~! J','s- \Soltwash removed 7425 - --. \ IOOoaoN EXPLANATION \ Structure contour drawn on base of the Salt Wash member, @ 7500 dashed where inferred, Contour interval 25 feet. St(ike and dip of joints. and location of measurements. Length of line is 'proportional to density. Measurements in Jms unless otherwise noted, Paleostream direcliCn, compiled from past and present work . ....,..,...,... Ore body, size and shape to scale .. - \. ', Salt Wash- Bluff sandstone contact, dashed where inferred. \ X Survey control point, elevation and location by transit ar alidade. ® Survey control poi nl, elevation by two altimeter meth.ad. Control point, elevation from d iomond dri II hole log. (All control 0 point elevations on base of Salt Wash.) w g[ 0 0 0 0 Anticlinal axis, with direction of plunge, dashed where ci 0 x{- 0 0 approximately located N (\j Synclinal axis, with direction of plunge, dashed where A-- approximately located. 0 2000 4000 6000 8000 Geologic base slightly modified after ·Strobel I ( 1956). ® Structure cross. section location. FEET 10,000 foot grid based on A. E.G. co ordinate system, J' with the point of origin U.S.G.S. triangulation station Center. .i , Figure Structure Contou·rs, Sedimentary Trends, Joi~ts, and Ore· Deposits of the Lukachukai Mountains area, A pathe County, Arizona I \ ' r. •