Floyd Gray

Stratigraphy, geochronology, and geochemistry of the Laramide magmatic arc in north-central Sonora, Mexico

The Laramide magmatic arc in the Arizpe-Mazocahui quadrangle of north-central Sonora, Mexico, is composed of volcanic rocks assigned to the Tarahumara Formation and several granitic plutons that intrude it. The arc was built over juxtaposed crustal basements of the Caborca and Mazatzal provinces. A basal conglomerate of the >4-km-thick Tarahumara Formation overlies deformed Proterozoic igneous rocks and Neoproterozoic to Early Cretaceous strata, thus constraining the age of a contractional tectonic event that occurred between Cenomanian and early Campanian time. The lower part of the Tarahumara Formation is composed of rhyolitic ignimbrite and ash-fall tuffs, andesite flows, and interbedded volcaniclastic strata, and its upper part consists of rhyolitic to dacitic ignimbrites, ash-fall tuffs, and volcaniclastic rocks. The Tarahumara Formation shows marked lateral facies change within the study area, and further to the north it grades into the coeval fluvial and lacustrine Cabullona Group. The age of the Tarahumara Formation is between ca. 79 and 59 Ma; the monzonitic to granitic plutons have ages of ca. 71–50 Ma. The informally named El Babizo and Huepac granites, La Aurora and La Alamedita tonalities, and the Puerta del Sol granodiorite compose the El Jaralito batholith in the southern part of the area. Major and trace element composition of the Laramide igneous rocks shows calc-alkaline differentiation trends typical of continental magmatic arcs, and the isotope geochemistry indicates strong contribution from a mature continental crust. Initial 87Sr/86Sr values range from 0.70589 to 0.71369, and eNd values range from –6.2 to –13.6, except for the El Gueriguito quartz monzonite value, –0.5. The Nd, Sr, and Pb isotopic values of the studied Laramide rocks permit comparison with the previously defined Laramide isotopic provinces of Sonora and Arizona. The El Gueriguito pluton and Bella Esperanza granodiorite in the northeastern part of the study area along with plutons and mineralization of neighboring northern Sonora have isotopic values that correspond with those of the southeastern Arizona province formed over the Mazatzal basement ([Lang and Titley, 1998][1]; [Bouse et al., 1999][2]). Isotopic values of the other Laramide rocks throughout the study area are similar to values of provinces A and B of Sonora ([Housh and McDowell, 2005][3]) and to those of the Laramide Pb boundary zone of western Arizona, while the Rancho Vaqueria and La Cubana plutons in the northernmost part of the area have the isotopic composition of the Proterozoic Mojave province of the southwestern United States. These data permit us to infer that a covered crustal boundary, between the Caborca block with a basement of the Mojave or boundary zone and the Mazatzal province, crosses through the northeastern part of the area. The boundary may be placed between outcrops of the El Gueriguito and Rancho Vaqueria plutons, probably following a reactivated Cretaceous thrust fault located north of the hypothesized Mojave-Sonora megashear, proposed to cross through the central part of the area. [1]: #ref-53 [2]: #ref-13 [3]: #ref-50

Tracing ground water input to base flow using sulfate (S, O) isotopes

Sulfate (S and O) isotopes used in conjunction with sulfate concentration provide a tracer for ground water contributions to base flow. They are particularly useful in areas where rock sources of contrasting S isotope character are juxtaposed, where water chemistry or H and O isotopes fail to distinguish water sources, and in arid areas where rain water contributions to base flow are minimal. Sonoita Creek basin in southern Arizona, where evaporite and igneous sources of sulfur are commonly juxtaposed, serves as an example. Base flow in Sonoita Creek is a mixture of three ground water sources: A, basin ground water with sulfate resembling that from Permian evaporite; B, ground water from the Patagonia Mountains; and C, ground water associated with Temporal Gulch. B and C contain sulfate like that of acid rock drainage in the region but differ in sulfate content. Source A contributes 50% to 70%, with the remainder equally divided between B and C during the base flow seasons. The proportion of B generally increases downstream. The proportion of A is greatest under drought conditions.

Assessment of geochemical and hydrologic conditions near Old Yuma Mine in Saguaro National Park, Arizona, 2014–17

The Old Yuma Mine is an abandoned copper, lead, zinc, silver, and gold mine located within the boundaries of Saguaro National Park, Tucson Mountain District, Arizona. This study analyzed the geochemistry of sediments associated with the Old Yuma mine and assessed hydrologic and geochemical conditions of groundwater to evaluate the area surrounding the Old Yuma Mine. The purpose of the study was to establish the geochemical signature of material associated with the Old Yuma Mine and to compare it with background material and groundwater in the area. Near the mine, groundwater generally flows to the northeast. A locally anomalous steep gradient in groundwater elevation is present beneath alluvial fan deposits in the center of the study area, near the projection of the Old Yuma Fault trend. Few groundwater samples exceeded the EPA drinking water standards. One sample exceeded the EPA primary drinking water standard for arsenic; one sample exceeded the EPA secondary drinking water standard for chloride, iron, and manganese and two other samples exceeded the total dissolved solids secondary drinking water standard. Analysis of groundwater age indicates groundwater with a component of modern water is present on the northwest side of the study area. Groundwater on the southeast side of the study area is primarily older, with a radiocarbon age ranging from approximately 600 to 6,700 years before present. Concentrations of several elements (As, Bi, Cd, Co, Cu, Fe, Hg, In, Li, Mn, Mo, Pb, Sb, U, V, W, and Zn) were elevated in the waste rock and mine tailings compared with concentrations in sediments collected in background areas. Concentrations of four elements (As, Mo, Pb, and V) in some sediment samples were greater than the EPA regional soil screening levels and (or) Arizona Department of Environmental Quality (AZDEQ) soil screening levels. A subset of 15 sediment samples was leached according to the EPA 1312 leachate method to simulate precipitation interacting with the solid material. The pH of the leachate samples increased following the leaching procedure. Several leachate samples had concentrations that exceeded the EPA drinking water standards for As, Mn, and Pb. Analysis of leachate samples compared to groundwater samples suggests that groundwater samples collected in this study are similar to each other and distinct from leachate samples associated with mining related material. Results suggest that at this time groundwater samples collected during this investigation are not influenced by elements leached from Old Yuma Mine materials. Introduction Saguaro National Park consists of two districts, the Rincon Mountain District and Tucson Mountain District on the far eastern and western sides, respectively, of the city of Tucson, Arizona (fig. 1). The Tucson Mountain District historically experienced gold and silver mining activity from 1880 to the 1970s and in 1994 Saguaro National Park acquired one of these mines, the Old Yuma Mine. The Old Yuma Mine was active from the dawn of the twentieth century through World War I, and produced steel-hardening minerals such as wulfenite, molybdenite, and vanadinite, and the base and precious metals lead, copper, zinc, silver, and gold (National Park Service, 2010). Mining History Located on a fault that trends east-northeast and dips steeply to the southeast, the Old Yuma Mine contains a relatively wide lenticular surface expression and a ~300-foot (ft) inclined shaft that dips at an angle of 43° and provides access to its underground workings (Wilson and Schlepp, 2008). Horizontal underground workings occur at the 65-, 100-, 200-, and 300-ft levels off the main incline. Between 1916 and 1947, this underground mine produced 5,700 tons of ore grading 4 percent lead, 1 percent copper, 0.6 percent zinc, 0.3 percent molybdenum, 1 ounce silver per ton, and 0.1 ounce gold per ton. This mine also produced high quality specimens of wulfenite (PbMoO4), a lead-molybdenum oxide, and vanadinite (Pb5(VO4)3Cl), a lead-vanadium mineral. Assessment of Geochemical and Hydrologic Conditions near Old Yuma Mine in Saguaro National Park, Arizona, 2014–17 By Kimberly R. Beisner and Floyd Gray 2 Geochemical and Hydrologic Conditions near Old Yuma Mine in Saguaro National Park The first claim to the Old Yuma Mine was filed in 1885, and a mill capable of handling 100 tons per day was constructed on site in 1916 for concentrating gold, molybdenum, and vanadium (Wilson and Schlepp, 2008). The mine changed ownership in 1930 and occasionally produced dump ore and surface material, but the mine was primarily used for acquiring mineral specimens. Around 1969, the ceiling of the main mine incline shaft caved in and large slabs of rock fell in single pieces. In addition to waste rock located around the property, approximately 7,000 cubic yards of tailings remain stockpiled at the Old Yuma Mine site, though this is only part of the original tailings pile. The remainder of the pile was used for road base in the surrounding area (Michael Baker Jr., Inc., 2005). The current mine site includes a large inclined excavation open to the surface, shafts (inclined and vertical), adits (nearly horizontal passageways into the mine), a headframe that was used to hoist the inclined main access shaft, a concrete mill foundation, a solid waste dumping area, and a small leach pad. The leach pad was constructed in 1984 for the purpose of reducing gold ore from the remnant mine tailings, but it was never operational (Michael Baker Jr., Inc., 2005). A local claimant, Richard A. Bideaux, received a patent on the valid claims from the Bureau of Land Management (BLM) near the time the land transferred from BLM to National Park Service management in 1994 (Comet 1 Lode, Old Yuma #1 Lode, and Old Yuma Placer Mining Claims, which were top-staked on one another and occupied a total of about 22 acres [9 hectares]). Saguaro National Park’s primary concern regarding this mine is potential injury owing to onsite hazards (National Park Service, 2010). Old Yuma Mine is currently under a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, or “Superfund”) investigation (National Park Service, 2010). Geologic Setting The Tucson Mountains, in which the Old Yuma Mine is located, are underlain by Late Cretaceous volcanic rocks interpreted as part of the fill of a large ash-flow caldera (Lipman, 1993). Volcanic rocks of the Old Yuma Mine area consist of compositionally diverse lava flows, intrusive dikes, and interleaved sedimentary rocks. Rock units around the Old Yuma Mine are described as aphanitic andesite [Kya] and aphanitic rhyolite and dacite flows [Kyr] (Lipman, 1993). Aphanitic andesite consists of dark-gray, fine-grained andesitic lava flows containing 20–40 percent small phenocrysts of plagioclase, augite, and serpentine pseudomorphs after olivine or orthopyroxene. Aphanitic rhyolite and dacite flows are described as tan to light-gray lava flows containing minor small phenocrysts of sanidine, plagioclase, and recrystallized biotite (Lipman, 1993). The ore deposit at the Old Yuma Mine consists of a porphyritic andesite or latite dike occupying a dip-slip fault dipping at about 43° through Cretaceous andesite (Wilson and Schlepp, 2008). The average width of the dike is 8–10 ft, but widens to 20 ft on the 65-ft level. The dike contains scattered pods of silver-rich galena altered to anglesite and cerussite, which released lead for the crystallization of vanadinite and wulfenite. Vanadinite and wulfenite occur in distinct zones and were reported to be milled in separate bins; wulfenite is found primarily on the western part of the fissure and vanadinite on the eastern part (Wilson and Schlepp, 2008). Hydrologic Setting No perennial surface water features exist in the study area, but ephemeral washes are present that flow episodically following precipitation events. Groundwater is present in the study area generally as part of fractured bedrock, alluvium, and alluvial fan deposits. Purpose and Scope Updated information on groundwater levels in the Old Yuma Mine area and chemistry of mining-related materials and groundwater are needed by Saguaro National Park for a better understanding of the presence and quality of groundwater near the Old Yuma Mine. This report (1) presents a groundwater surface elevation map to estimate the groundwater elevation below the Old Yuma Mine; (2) characterizes the chemistry of mining-related material, background sediment, and water leached from both of these materials; and (3) compares leachate chemistry to groundwater chemistry from the surrounding area. The study area includes groundwater wells located south of Ina Road, north of Camino del Cerro Road, west of Silverbell Road and east of Golden Gate Road (fig. 1).

Geologic framework and hydrogeology of the Rio Rico and Nogales 7.5’ quadrangles, upper Santa Cruz Basin, Arizona, with three-dimensional hydrogeologic model

..........................................................................................................................................................

Hydrogeologic investigations of the Miocene Nogales Formation in the Nogales Area, Upper Santa Cruz Basin, Arizona

..........................................................................................................................................................

Undiscovered Phanerozoic Porphyry Copper Deposits—A Global Assessment

Porphyry copper deposits represent the principal source of global copper supply. To address the questions of where future copper supplies are likely to come from and how much copper could exist within the upper kilometer of the earth’s crust, the USGS led a cooperative international effort to assess the world’s undiscovered Phanerozoic porphyry copper deposits using a geologybased, probabilistic form of mineral resource assessment (Singer and Menzie, 2010). Globally, 175 tracts permissive for porphyry copper deposits were defined to include volcanic and intrusive rocks of specified ranges of age and composition. The rocks represent: (1) magmatic arcs that developed on continental crust above subducting oceanic plates, (2) island arcs that formed on oceanic crust, and(or) (3) postconvergent magmatic belts within continents. Quantitative assessments of undiscovered resources were done for 155 of those permissive tracts.

Mineral resources of the Eagletail Mountains Wilderness Study Area, La Paz, Maricopa, and Yuma counties, Arizona

The Eagletail Mountains Wilderness Study Area (AZ-020-128) encompasses most of the Eagletail Mountains and parts of adjoining alluvium-filled valleys. At the request of the U.S. Bureau of Land Management, mineral surveys were conducted on 78,020 acres of the wilderness study area. In this report, references to the wilderness study area refer only to that area for which mineral surveys were requested. The U.S. Bureau of Mines and the U.S. Geological Survey carried out fieldwork during 1986 and 1988 to appraise the mineral resources (known) and assess the mineral resource potential (undiscovered) of the study area. No mineral resources were identified within the study area. Several areas have potential for undiscovered resources. One area having moderate potential for silver and lead and low potential for gold, barium, copper, manganese, molybdenum, and zinc resources extends along the length of Cemetery Ridge, which crosses the southwest boundary of the study area. An area northeast of Cemetery Ridge and extending along the south boundary of the study area has low potential for gold, silver, lead, zinc, copper, barium, manganese, and molybdenum resources. One area having moderate and an adjacent area having low potential for gold, silver, lead, zinc, and copper resources lie immediately west of and extend into the northwest corner of the study area. An area including the Double Eagle mine in the southeast corner of the study area has moderate potential for silver and low potential for gold, copper, lead, and zinc. An area along the northeast side of the Eagletail Mountains has moderate potential for gold and silver and low potential for lead, zinc, copper, and molybdenum resources. A minor amount of green tuff has been quarried along the northern boundary of Manuscript approved for publication, March 2, 1989. the study area for use as ornamental stone. Two areas within the study area have low potential for further resources of this tuff. The northernmost of the two areas also has low potential for silver. One area southwest of Courthouse Rock near the center of the study area has low potential for perlite. An area along the southwest margin of the study area and an area along the east boundary of the study area are underlain by a thick accumulation of basin-fill sediments. These two areas have low potential for geothermal resources. The entire study area has low potential for oil and gas resources. Sand and gravel is abundant in the study area, but it has no unique properties and adequate resources are available closer to markets. Character and Setting The Eagletail Mountains Wilderness Study Area comprises 78,020 acres in southwest Arizona, between Phoenix and Quartzite and about 4 mi south of Interstate 10 (fig. 1). The study area includes most of the Eagletail Mountains as well as parts of the surrounding pediments and alluviumfilled valleys. Topography is extremely rugged in the main part of the Eagletail Mountains but subdued to nearly flat in the valleys and on pediments that underlie much of the study area. Elevations range from 3,043 ft on Eagletail Peak to approximately 1,300 ft in the lower parts of adjoining valleys. The pediments are underlain predominantly by crystalline rocks of Proterozoic and (or) Mesozoic age (see appendixes for geologic time chart). Upper OIigocene(?)to Miocene-age basaltic to rhyolitic lava flows and tuffs overlie the crystalline rocks and constitute the topographically high part of the range. Faulting occurred during and following volcanism and is primarily responsible for the northwest trend of the range. Mineral Resources of the Eagletail Mountains Wilderness Study Area, Arizona C1