UTAH GEOLOGICAL AND MINERAL SURVEY REPORT OF INVESTIGATION NO. 200 MINERAL OCCURRENCES IN THE EMERGENCY WITHDRAWAL AREA AND ADJACENT LANDS IN THE GREAT SALT LAKE DESERT by J. Wallace Gwynn Keith Clem Mike Shubat Bryce Tripp Paul Sturm September 1985 I. Introduction - This mineral report was prepared to fulfill the requirements of PL 94-579 Sec. 204 (c)(2) for the emergency withdrawal of a portion of the Great Salt Lake Desert. This report covers the actual proposed withdrawal area and the surrounding region (fig. 1 and 2) from township 2S to BN and from range 8W to IBW. A legal description of the actual area subject to inundation is contained in a seperate land report. Geologic data was compiled from published and unpublished Utah Geological and Mineral Survey material and other outside sources. Hellmut H. Doelling's 1980 publication, "Geology and mineral resources of Box Elder County, Utah" and Lehi Hintze's 1973 book "Geologic history of Utah" are probably the best general references for this area. No field work was deemed necessary in light of the availability of adequate geological information. II. General Geology Mountain ranges adjacent to areas affected by the West Desert pumping project are dominantly comprised of Paleozoic to lower Mesozoic carbonate rocks (Fig. 3). Rocks of Cambrian through Devonian age represent shallow marine miogeoclinal deposits and are composed of limestone and dolomite with minor sandstone and shale. The thickness of the miogeoclinal rocks ranges from 15,000 to 16,000 feet (Hintze, 1973). Mississippian to lowermost Mesozoic rocks were largely deposited in the Oquirrh Basin and are comprised of interbedded limestone, sandstone, and shale. Thickness of these rocks ranges from 0 to 26,000 feet due to erosion, nondeposition, and faulting (Hintze, 1973). Establishment of the Oquirrh Study Area Fig. I West Desert Pumping Project Emergency Withdrawal Cub Island Gunnison J Island 1 N, 4 FI.1! z < o 8 ~E3::EH3:::EHa:::JH3::JRe::l0=======31O========210~======~3i: 0=======40:3 Miles IOEHaHDH:DHS::EHti?=====3:lp=====2JPE====~3[p=====4EP~===35.o Kilometers Proposed Dikes Approximate Area Enclosed by 4218' Contour (area inundated) Figure 2- Proposed Dikes and Area of Inundation Great S a I t 7N Lake 6N N ~ 4N N 3N 17W 16W 15W (geol og y mod i fied f rom Hintze 1 L.F., 1980) Quaternary mud and salt flots a 5 IOmi I I I I ..1.-'.. I (scale: I: 500, 000) Quaternary alluvium, colluvium, and marsh sediments Quaternary Lake Bonneville sediments T-ertiary basalt Tertiary Solt Lake Group r-----. ~~J Jurassic intrusive rocks Paleozoic and Mesozoic (sparse) rocks • Fig. 3 - Generalized Geo log'Y Basin and disruption of miogeoclinal conditions is related to the onset of orogenic activity in the Cordillera. From late Triassic to late cretaceous time, the area of concern experienced deformation and uplift of the Sevier orogeny. Folding, uplift, and thrust faulting of Paleozoic rocks during this event resulted in crustal shortening of 40 to 60. miles across the Sevier Belt (Hintze, 1973). Thrust faults·of this episode are such that all pre-Cenozoic'rocks in western Utah are considered to be allochthonous. Several Jurassic-aged quartz monzonite stocks were intruded during the Sevier orogeny. One is located in the northern Newfoundland Mountains and the rest in the Crater Island Mountains (Doel1ing, 1980). From Miocene time to present, during which time the Basin and Range province was established, the area underwent extensional tectonics, broad uplift, and local volcanism. Tertiary ash-flow tuff volcanism was conspicuously absent from the area. Basin and Range block faulting produced the typically north-trending ranges separated by broad alluvium-filled valleys. The extensive mud flats occurring in the West Desert are presumably underlain by up to 15,000 feet of alluvium. Quaternary deposits include the extensive Lake Bonneville Group. Shoreline gravel deposits of Lake Bonneville the mantle mountain ranges in the study area. Lacustrine deposits consist of silt, sand, and clay and comprise the present mud flats. Interstitial brines are present in the subsurface. III. Known Mineral Deposits A. Subsurface Brines - The Great Salt Lake Desert contains vast quantities of subsurface brines within the three principal aquifers These are referred to by Stephens (1974) as the shallow brine aquifer, the alluvial-fan aquifer, and the valley-fill aquifer. Within the northern Great Salt Lake Desert, the shallow brine aquifer covers some 1650 square miles, and occupies the upper 20 to 25 feet of lakebed clays and silts. Brine movement through this upper portion of t~e sediments is believed by Turk (1969) to occur through a network of open jOints. The alluvial-fan aquifer, which contains brackish water, is described by Stephens (1974) as follows: "an 'apron' of unconsolidated alluvium borders much of the floor of the northern Great Salt Lake Desert •••• These surficial alluvial deposits, together with underlying unconsolidated to well-cemented older alluvium ••• that was also deposited as fans or aprons along the mountain flanks, comprise an aquifer referred to herein as the 'alluvial fan' aquifer." Stephens (1974) describes the valley-fill, brine-bearing aquifer as follows: "The largest ground-water reservoir in the northern Great Salt Lake Desert is in unconsolidated to partly consolidated valley-fill •••• The total thickness of valley-fill ranges from zero where older Paleozoic rock crops out .•• to 1,385 feet at Lemay ••• and at least 1,644 feet in the Bonneville Salt Flats area •••• " "Volcanic rocks underlying the unconsolidated sediment (Heylmun, 1965, p.28-29) may also constitute a part of the major ground-water reservoir •••• If those rocks are included, the total thickness of the reservoir rocks may be more than 5000 feet throughout much of the area ... " Near Wendover, 16 to 20 miles west of the West Desert impoundment area (or that area north of the Bonneville Dike)(fig. 4), Kaiser Aluminum and Chemical Corporation produces potash (KCl) from the subsurface brines. The majority of Kaiser's feed brines are collected from the shallow aquifer through a network of open ditches, with a minor amount being pumped from the deep valley-fill aquifer. Through solar evaporation of these low-sulfate desert brines, sylvinite, a mixture of halite and sylvite is produced. Bingham (1980) indicates that the processing of the sylvinite are produces some 85,000 short tons of potash products per year. A magnesium chloride bittern brine is also produced. No commercial use or development of the subsurface brines has ever occurred within the West Desert Impoundment area. B. Metallic Minerals- Nearly all of the impacts on metallic mineral deposits from the West Desert Pumping project have been mitigated by providing for access to the Newfoundland Mountains. No metallic resources are known below the 4218-foot elevation that delineates the area inundated but two areas would have their access affected: the Newfoundland Mountains and a small knoll in T. 6 N., R. 12 W. (Black Magic Claims). Access problems with the Newfoundlands were resolved by providing for a bridge across a canal. No plan is known of for mitigating impact on the Black Magic Claims. The four mining districts occurring in the vicinity of the west Desert Pumping project are the Newfoundland, Crater Island, Silver Island, and Lakeside districts (fig. 5) (Doelling and Tooker, 1983). Commodities present within the four districts include copper, silver, lead, zinc, tungsten, molybdenum, Cub Island Cunnison ~ Island Brine--'.-----, 'N • G J '---.,; ~ ........It· • .::::~ ;:..... It ~t;~ ~~;~f;~t?(: }?t~:~;;:}r!. ~:)Jr{X~~1 ??~~:;:;S~i~· <·i/:t:~j~(J • Lu 40 'E£3::JHS::=t=1E:C:ER:CRR:::J0E======310=======2:E0~=====~3O iO======:::::i Miles IOSH:JH3:JH3:EH3:ES:cEI ====I3:p====2:Ep§::==~33:p=====4EP===3510 Kilometers Proposed Dikes Brine Chemical composition of brines on a dry weight percent basis Area K Na Mg C1 504 . JPS_ Jw_t~/9J)_ A 2.31 35.13 1.30 59.58 1.64 12.89/ 8 1.82 33.68 2.68 57.72 4.06 .17.08/ C 1.19 32.09 4.13 51.41 11.14 4.17/ 0 0.86 34.82 2.28 55.88 6.11 8.66/ E 1.95 33.81 0.76 61.59 1.87 /227.95 F 1.18 35.28 1.17 59.21 2.51 /162.15 G 2.47 31.65 3.30 55.35 7.04 /180-34C Figure 4 - Map of West Desert Containment Area showing shallow aquifer, 4218 foot contour, and sample areas keyed to average brine analyses. gold, barite, clay, and iron. Past production from all districts has been minor. All districts lie well north of the Oquirrh-Uinta mineral belt. Mineral deposits in the Newfoundland Mountains and surrounding areas will be briefly discussed. -1. Newfoundland Mountains- Three subdivisions of the Newfoundland district have been identified (Doelling, 1980) and are shown on figure 5. Additional prospects occur throughout the Newfoundland Mountains but are of small extent. Commodities present in the district include copper, gold, silver, lead, tungsten, and molybdenum. Most deposits are directly or indirectly associated with the Newfoundland stock and occur along the periphery of the intrusion. Mining activity in the district has' be'en intermittent. Mineralization in the Copper Flat area (northernmost end of the range, figure 5) is restricted to a fault zone, from 6 inches to 7 feet wide, striking N 60 Wand dipping 15 to 40 NE. Copper and molybdenum mineralization is reported. Copper minerals include malachite, azurite, chrysocolla, chalcanthite, chalcopyrite, and bornite. Thin, altered, igneous dikes are present and the hosting quartzite is locally silicified. Mineralization in the stone House area (southernmost location in the Newfoundland district shown on figure 5) consists of copper and possible lead and silver.