Twin Buttes Research Articles

Succession of Laramide Magmatic and Magmatic-Hydrothermal Events in the Patagonia Mountains, Santa Cruz County, Arizona

This investigation of the space-time progression of magmatism and hydrothermal activity in the Patagonia Mountains of southern Arizona is based on field and paragenetic relationships, and on U-Pb and 40 Ar/ 39 Ar geochronology of igneous and hydrothermal minerals. The Patagonia Mountains consist of Precambrian, Paleozoic, and Mesozoic sedimentary, granitic, and volcanic rocks, Laramide volcanic rocks, and a core of Laramide intrusions that comprise the Patagonia Mountains batholith. Laramide igneous rocks and adjacent Paleozoic and Mesozoic rocks contain significant porphyry Cu-Mo deposits, Mo-Cu breccia pipes, Ag replacement deposits, and numerous other Cu-Pb-Zn-Ag replacement and vein deposits. Ages of igneous and hydrothermal minerals from 20 U-Pb and 52 40 Ar/ 39 Ar determinations define four magmatic and magmatic-hydrothermal events that formed the batholith and altered parts of it and adjacent rocks; cumulatively the events span at least 16 m.y., from ~74 to 58 Ma. The oldest event of this succession includes the 74 Ma Washington Camp stock and spatially associated Cu-Pb-Zn-Ag replacement deposits in Paleozoic carbonate rocks of the Washington Camp-Duquesne district. Eruption of 73 to 68 Ma volcanic rocks in the northern part of the range was the next youngest event, which coincides temporally with replacement and vein deposits in Paleozoic carbonate rocks at the Flux mine (~71 Ma). An event at 65 to 62 Ma is marked by emplacement of small-volume quartz monzonite, granodiorite, and diorite intrusions, formation of the Ventura breccia deposit in Jurassic granite at 65 to 64 Ma, and formation of other Pb-Zn-Ag-Cu replacement and vein deposits (~62 Ma; Blue Nose and Morning Glory). The Red Mountain porphyry Cu-Mo system is hosted by ~62 Ma granodiorite and Laramide volcanic rocks (73–68 Ma) at the northern end of the batholith. It includes a deep, chalcopyrite-bornite resource (~60 Ma) that is associated with potassic and sericitic alteration and a near-surface chalcocite-enargite resource (60 Ma) that is associated with advanced, supergene-enriched argillic alteration. The youngest event includes the Sunnyside porphyry Cu-Mo system and a Cu-Mo breccia deposit at Red Hill (Four Metals mine), both of which formed in large-volume quartz monzonite, granodiorite, quartz monzonite porphyry, and quartz feldspar porphyry (~61–59 Ma). Similar to the Red Mountain system, the Sunnyside system consists of a deep chalcopyrite resource that occurs in ~60 to 59 Ma quartz feldspar porphyry, and a near-surface, slightly younger (~59–58 Ma) enargite-chalcocite-tennantite resource that occurs in quartz feldspar porphyry, quartz monzonite porphyry, and Mesozoic rocks. The Red Hill Cu-Mo breccia deposit is hosted by large-volume quartz monzonite, granodiorite, and quartz monzonite porphyry (~61–59 Ma). Discrepancies between field and paragenetic relationships and some analytic ages at Sunnyside and Red Hill preclude precise dating of mineralization stages, and may reflect disturbance of isotope systems by multiple, co-spatial to juxtaposed intrusive and hydrothermal events, and/or by unrecognized intrusions. Numerous vein and replacement deposits at the northern end of the batholith, including the Hardshell Ag resource and the Three R supergene chalcocite resource, are distal deposits of the Sunnyside and Red Mountain systems. Small, ~61 to 59 Ma Cu-Mo deposits in large-volume intrusions in the southern part of the batholith consist of hydrothermal quartz, biotite, K-feldspar, muscovite, chalcopyrite, and molybdenite. The age span of magmatic and magmatic-hydrothermal events in the Patagonia Mountains, minimally 16 m.y., is comparable to that of certain other magmatic-hydrothermal successions that contain porphyry Cu-Mo systems. Magmatic-hydrothermal events of the Wasatch-Oquirrh igneous trend, Utah, and the Boulder batholith, Montana, both span ~17 m.y. and include the Bingham and Butte porphyry Cu-Mo, vein and replacement deposits, respectively. Plutons and mineral deposits in the Pima district, Arizona, which includes the porphyry Cu-Mo deposits at Sierrita-Esperanza, Mission-Pima-San Xavier North, and Twin Buttes, formed over an interval of ~14 m.y. The diversity of igneous and hydrothermal products likely reflects evolutionary processes occurring at multiple sites in the lithosphere and at different time scales from >10 m.y. to less than the geochronologic precision currently achievable.

Increasing off-site water yield and grassland bird habitat in Texas through brush treatment practices

Woody shrubs, including honey mesquite ( Prosopis glandulosa Torr. var glandulosa) and juniper ( Juniperus ashei Buckholtz and Juniperus pinchotii Sudh), have invaded the native prairies and savannas of much of central Texas. As a consequence of this “brush” encroachment, many of these grasslands may have lost some ability to provide water yield and habitat for some native wildlife species, particularly grassland birds. In some areas, brush management followed by rangeland manipulation treatments may enhance water yields and improve habitat for some grassland-associated wildlife. The relative effectiveness of brush control treatments varies according to the treatment objective and location within a watershed. There are often multiple objectives when public monies are committed for cost-sharing brush management treatments on private lands. When considering multiple objectives (e.g., water yield and grassland bird habitat), the priority ranking process for determining the most cost-effective treatment locations can be confounded. The goal of this study was to reduce this confounding by creating a methodology for prioritizing areas within two watersheds for brush management cost-share programs. We developed a sub-basin scale prioritization method using total society cost of implementing a brush treatment program, hydrologic impacts and grassland bird responses to brush treatments. Results show which sub-basins within the Edwards Aquifer recharge zone and Twin Buttes reservoir watersheds may be the most attractive candidates for brush treatment cost-share programs with the goal of optimizing water yield and grassland bird habitat. By adjusting weights for water and grassland bird efficiency criteria, this approach can be adapted to prioritize different levels of ecosystem responses to brush treatments.

Economic implications of brush treatments to improve water yield

One possible method of increasing water yield in some water-poor areas is through brush management. Economic modeling of brush control programs designed to improve water yield has been performed for numerous Texas watersheds. These studies assumed a single criteria brush control program. This single criteria program may have negative impacts on certain wildlife habitats, is likely unacceptable to landowners, and does not incorporate additional restoration practices. Our study analyzed the economic consequences of 3 brush management/restoration scenarios for the Edwards Aquifer recharge zone and Twin Buttes watersheds and the drainage basins contained within. Economic measures included total public cost ($) and public cost of producing additional water ($/1000 m3 of added water). Because of its larger size, estimated total public cost was higher for the Twin Buttes watershed than for the Edwards Aquifer recharge zone watershed, despite the fact that the Twin Buttes had lower cost per ha of treated brush. Public cost of additional water is lower for basins within the Edwards Aquifer recharge zone watershed (ranging from $26 to $44 per 1000 m3 of added water) than in the Twin Buttes watershed (ranging from $51 to $129) which suggests that public investment in brush management efforts are likely to be more economically efficient in the Edwards Aquifer area. Within individual basins, public cost of additional water were similar for all 3 brush management/restoration scenarios.

Economic implications of brush treatments to improve water yield

One possible method of increasing water yield in some water-poor areas is through brush management. Economic modeling of brush control programs designed to improve water yield has been performed for numerous Texas watersheds. These studies assumed a single criteria brush control program. This single criteria program may have negative impacts on certain wildlife habitats, is likely unacceptable to landowners, and does not incorporate additional restoration practices. Our study analyzed the economic consequences of 3 brush management/restoration scenarios for the Edwards Aquifer recharge zone and Twin Buttes watersheds and the drainage basins contained within. Economic measures included total public cost () and public cost of producing additional water (/1000 m3 of added water). Because of its larger size, estimated total public cost was higher for the Twin Buttes watershed than for the Edwards Aquifer recharge zone watershed, despite the fact that the Twin Buttes had lower cost per ha of treated brush. Public cost of additional water is lower for basins within the Edwards Aquifer recharge zone watershed (ranging from 26 to 44 per 1000 m3 of added water) than in the Twin Buttes watershed (ranging from 51 to 129) which suggests that public investment in brush management efforts are likely to be more economically efficient in the Edwards Aquifer area. Within individual basins, public cost of additional water were similar for all 3 brush management/restoration scenarios.

Stable isotope (S, O, H and C) studies of the phyllic and potassic–phyllic alteration zones of the porphyry copper deposit at Sungun, East Azarbaidjan, Iran

The porphyry copper deposit (PCD) at Sungun is located in East Azarbaidjan, NW of Iran. The magmatic suites in the Sungun area are a part of the NW–SE trending Cenozoic magmatic belt of Iran. The Sungun porphyries occur as stocks and dikes. The stocks are divided into two groups, I and II. Porphyry Stock II, ranging in composition from quartz monzonite through granodiorite to granite, hosts the Sungun PCD. Four distinct types of hypogene alterations were recognized at Sungun: (1) potassic; (2) potassic–phyllic; (3) phyllic; and (4) propylitic. Stable isotope (S, O, H, and C) studies were restricted to within the phyllic and potassic–phyllic alteration zones, where numerous cross-cutting quartz, sulfides, carbonates, and sulfate veinlets are present. The objective of these studies was to determine the origin of the ore-forming solutions, and their important components (e.g. sulfur and carbon). Twenty sulfide and four sulfate samples were taken from sulfide and gypsum veinlets within Porphyry Stock II and the associated skarn zone for sulfur isotopic analyses. The δ 34S values of sulfides (pyrite, chalcopyrite, molybdenite, galena, sphalerite) and sulfate (gypsum) range from −4.6 to −0.2‰ (mean of −1.5‰) and from 10.9 to 14.4‰ (mean of 12.9‰), respectively. These values are almost analogous to those from El Salvador (Chile) and Ajo (Arizona), and Twin Buttes (Arizona), and strongly suggest a magmatic source for the sulfur at Sungun. Twenty-eight fluid inclusion-rich quartz samples from quartz veinlets beneath the supergene zones of the Porphyry Stock II were chosen for O and H isotopic analyses. The δ 18O (of quartz) and δD (of fluid inclusions in quartz) values range from 8.3 to 10.2‰ (mean of 9.2‰) and −58 to −75‰ (mean of −66‰) relative to Standard Mean Ocean Water (SMOW), respectively. The calculated δ 18O values of the fluids range from 4.4‰ (T=375 ° C) to 7.6‰ (T=570 ° C) with a mean of 6.4‰. The δ 18O and δD values of the fluids lie within the typical range of magmatic waters. Based upon the lowest obtained δD values, the calculated maximum exchangeable meteoric water that might be involved in the phyllic and potassic–phyllic alteration processes was ∼20%. Fourteen calcite samples from carbonate veinlets in the Porphyry Stock II and two samples from associated marble aureole were collected for carbon and oxygen isotopic analyses. The δ 13C (calcite) from Porphyry Stock II and associated marble aureole varies from −0.4 to 2.9‰ and 0.06 to 2‰ relative to the PDB Standard of the University of Chicago, respectively. The corresponding δ 18O (calcite) values range from 6 to 13.2‰ relative to SMOW. The δ 13C values lie within the sedimentary range, suggesting that there was little or almost no magmatic carbon in the hydrothermal system. In contrast, The δ 18O (calcite) values are far lower than that of Cretaceous sedimentary carbonates which suggest that the values were influenced by those of magmatic fluids through isotopic re-equilibration. These isotopic investigations demonstrated that: (1) in contrast to some well-known PCDs, about 80% of the fluids involved in the phyllic and potassic–phyllic alterations at Sungun had a magmatic O and H isotopic signature; (2) the Upper Cretaceous limestone was the potential source of C; and (3) the sulfur had a magmatic origin.

An Archaeological Survey of Twin Buttes Reservoir, Tom Green County, Texas, Volume III

From December of 1998 through November of 1999, the Center for Archaeological Research (CAR), at The University of Texas at San Antonio (UTSA) conducted a Class III archaeology survey of 10,195 acres (4125 ha) within Twin Buttes Reservoir, a flood control and irrigation facility near the city of San Angelo in west-central Tom Green County, Texas. The 100 percent pedestrian survey, conducted for the Department of the Interior, Bureau of Reclamation (BOR), was primarily a section 110, of the National Historic Preservation Act (NHPA), effort. The survey was conducted in conjunction with repair of existing seepage at Twin Buttes Dam. The repair, conducted under the Safety of Dams program, involved the construction of several borrow pits. Since the Safety of Dams repair required BOR to inventory several areas of the reservoir lands under Section 106 of the NHPA, it was decided to expand the section 106 work, and do the entire Section 110 survey of the reservoir. CAR recorded 178 new archaeological sites, and revisited 21 previously recorded sites, within the reservoir. On these 199 sites, 19 historic components were identified, reflecting primarily farming and ranching activities. The prehistoric sites reflect occupation from the early Paleoindian period through the Late Prehistoric period. While recommendations regarding the eligibility of sites to the National Register of Historic Places (NRHP) were not required by the survey, based on the survey results CAR recommends that 13 of the 19 historic components have moderate or high research potential. Within the prehistoric data set, 48 sites have high research potential, 33 have moderate research potential, and 111 sites have limited research value.

An Archaeological Survey of Twin Buttes Reservoir, Tom Green County, Texas

From December of 1998 through November of 1999, the Center for Archaeological Research (CAR), at The University of Texas at San Antonio (UTSA) conducted a Class III archaeology survey of 10,195 acres (4125 ha) within Twin Buttes Reservoir, a flood control and irrigation facility near the city of San Angelo in west-central Tom Green County, Texas. The 100 percent pedestrian survey, conducted for the Department of the Interior, Bureau of Reclamation (BOR), was primarily a section 110, of the National Historic Preservation Act (NHPA), effort. The survey was conducted in conjunction with repair of existing seepage at Twin Buttes Dam. The repair, conducted under the Safety of Dams program, involved the construction of several borrow pits. Since the Safety of Dams repair required BOR to inventory several areas of the reservoir lands under Section 106 of the NHPA, it was decided to expand the section 106 work, and do the entire Section 110 survey of the reservoir.

An Archaeological Survey of Twin Buttes Reservoir, Tom Green County, Texas, Volume II

An Archaeological Survey of Twin Buttes Reservoir, Tom Green County, Texas, Volume II

NEW AND RARE CHRYSOPHYTES FROM WYOMING AND COLORADO LAKES

Colorado and Wyoming lakes with high pH values generally ranging from 8 to 10 are dominated by phytoplankton belonging to the chrysophytes, diatoms and cryptomonads. Our studies on phytoplankton diversity in Dowdy, South Delaney Buttes and Cowdrey Lakes in Colorado and Diamond and Twin Buttes Lakes in Wyoming have yielded several isolates of rare or new chrysophytes. These isolates were examined with light microscopy, SEM, TEM, and novel information regarding their structure is presented. Proposed new species belong to the genera Saccochrysis, Prymnesium and Chrysochromulina. Chrysophytes that were examined for the first time include Monochrysis aphanaster, Uroglenopsis, and a mixotrophic species of Ochromonas, which ingests small diatoms. Probable new species are the following: Saccochrysis sp. nov. differs in chloroplast structure, cell shape and cell number/colony, and absence of a posterior vacuole; Prymnesium sp. nov. is the first freshwater form examined with EM and differs in scale morphology; and Chrysochromulina sp. nov. is similar to Chrysochromulina parva but lacks scales. The ultrastructure of M. aphanaster is unique and appears to be a member of the Chrysophyceae. It has two flagella, one of which is emergent, while the other is hidden within an invagination of the cytoplasm. Diacronema and Sarcinochrysis spp. from these lakes also were isolated and reinvestigated, and some unique cellular features will be discussed.

Mayflies (Ephemeroptera) of the Concho River, Texas

The mayfly fauna of the Concho River, Texas, consisted of 17 species in 7 families as determined from 12 collecting sites sampled at least once monthly for two years for both aquatic nymphs and aerial adults. Nymphs were reared to adults for positive association. Leucrocuta maculipennis (Walsh) is reported from Texas for the first time. Adult descriptions of Leptohyphes packeri Allen and Leptohyphes vescus Allen, previusly known from only the nymphal stage, are presented. Prior to this study only two species of mayflies had been reported from the Concho River, Texas, Callibaetis montanus Eaton and Isonychia sicca Eaton (Traver, 1935). Although a number of species of mayflies are reported from Texas, their distributions in the streams of the state are largely unknown. Only two studies of the mayfly fauna in Texas' rivers have been made. Moore (1950) listed the species collected in Dallas County and in the major rivers between Dallas and San Antonio. Due to the poor taxonomic knowledge of the mayfly nymphs at that time his survey is of limited value. Peters (1977) provided a study of the nymphs of the Guadalupe River in central Texas. STUDY AREA-The Concho River is part of the upper Colorado River drainage basin. Permanent streams are located in Concho, Tom Green, and Irion Counties of Texas. The area is a transition zone containing parts of two biotic provinces, the Balconian and Kansan (Blair, 1950). Elements of the Chihuahuan Province are also present. The river system is divided into three sections. Five streams, the South Concho River, Middle Concho River, Dove Creek, Spring Creek, and Rocky Creek are included in the upstream section to the west and south of San Angelo (Fig. 1). The streams originate as springs and seeps along the eroded northwestern margins of the Edwards Plateau from Cretaceous limestone and resemble other springfed streams of the Edwatds Plateau. Stream flow alternates between shallow pools and riffles with the substrate varying from cobble and gravel to limestone bedrock. Eight sampling sites were located in this section of the system. Water from these streams flows into a manmade impoundment, Twin Buttes Reservoir, located just southwest of San Angelo. The middle section of the system includes Twin Buttes Reservoir, Lake Nasworthy, and the series of impoundments produced by small dams through the city of San Angelo. No regular sampling sites were established in this section because of the paucity of mayflies in this disturbed, urbanized area. In addition, no regular sampling sites were located on the North Concho River. The river flow is intermittent; it is dependent upon rainfall rather than springflow. The Concho River from San Angelo to its junction with the Colorado River flows through an area known as the Lipan Flat. It is largely an alluvial outwash plain of Pleistocene age and is extensively cultivated. The river still alternates between pools and riffles but deposition of sediments in pools and behind numerous small dams is increased. Three sampling sites were located in this section. An additional site was located on the Colorado River downstream from the junction of the Concho River. METHODS AND MATERIALS-Collections were made at least once monthly at all collecting sites (Fig. 1) from May 1979 to March 1981. Nymphs and adults were collected. Nymphs were preserved in 90% ethyl alcohol and adults in 70% ethyl alcohol. Nymphs were obtained by hand picking and by use of an aquatic dip net. Positive association between nymphs and adults was This content downloaded from 157.55.39.170 on Sat, 23 Jul 2016 04:45:24 UTC All use subject to http://about.jstor.org/terms FIG. --Study area and location of primary collection sites. er I D

Hydrogeology of a Possible Geothermal System near Deeth, Nevada: ABSTRACT

Study of a possible geothermal system near Deeth, Elko County, Nevada, included geologic mapping, hydrogeochemical analyses, and geophysical interpretation. Geologic and geophysical methods emphasized structure, particularly Paleozoic thrust faults overprinted by Miocene listric normal faulting. Hydrogeochemical analyses showed geothermal fluids to be sodium-bicarbonate water, probably of meteoric origin. The geothermal model is convection cells caused by deep circulation along the Marys River fault zone. The reservoir is fractured rock along the fault zone. Silica geothermometry predicts a reservoir temperature of 165°C (329°F). A Paleozoic sedimentary range block is separated by the Marys River fault zone from a Tertiary basin-fill sequence to the east. Allochthonous western facies rocks at Twin Buttes were emplaced along the Roberts Mountains thrust. Eastward-thrusted upper Paleozoic units are exposed in the Peko Hills. A thick, bimodal, Oligocene-Pliocene volcanic sequence covers the area's northwest corner. The Miocene Humboldt Formation is a tuffaceous, fluviatile lacustrine basin-fill unit that onlaps the range block and thickens basinward. Quaternary hot-spring deposits are localized along the Marys River fault zone. The Miocene-Pliocene Marys River fault zone is a north-trending, down-to-the-east, normal fault system. A shear zone may be present where the fault zone undergoes right separation. Hydrogeochemical, thermal water, and heat-flow anomalies are localized along the fault zone. The proposed model calls for deep circulation of meteoric water along the Marys River fault zone. Surface water from the Marys River percolates down the fault and is heated to approximately 165°C (329°F). Thermal water migrates laterally, then rises back up the fault. Upwelling thermal water creates the three observed thermal anomalies. Leakage of geothermal fluid into discontinuous sand and gravel channels of the Humboldt Formation gives rise to broad, low-temperature anomalies. The high-temperature reservoir is fractured rock along the Marys River fault zone. End_of_Article - Last_Page 559------------

Pneumatic piezometers: multiple and single installations in vertical and inclined boreholes

A large-scale slope optimization program was undertaken in the Twin Buttes open-pit mine in Arizona, USA. A key element of this program was the depressurization of a fault zone, which intersects the pit wall. In order to monitor the effectiveness of the depressurization program and to establish water pressure gradients within the fault zone affected by surface and underground mining and drilling, multiple installations of up to three sealed pneumatic piezometers in one borehole were installed to depths in excess of 274 m. Special tools were devised to enable installations in angle holes from surface and underground locations. Unstable ground conditions necessitated extensive use of biodegradable drilling muds during the installation of the piezometers. The purpose of the installations and the techniques used to complete them are discussed, and opinions are offered on the effectiveness of the instruments.

Rock stability analysis at Twin Buttes. Symposium. In Stability of rock slopes : Seegmiller, BL Anaconda Co. Salt Lake City, Utah, USA 9F, 6T, 2R. 13th Symposium on Rock Mechanics ASCE, New York, 1972, P511–536

Rock stability analysis at Twin Buttes. Symposium. In Stability of rock slopes : Seegmiller, BL Anaconda Co. Salt Lake City, Utah, USA 9F, 6T, 2R. 13th Symposium on Rock Mechanics ASCE, New York, 1972, P511–536

INFLUENCE OF PLANT EXTRACTS, PROTEINS, AND AMINO ACIDS ON THE ACCUMULATION OF SELENIUM IN PLANTS

INFLUENCE OF PLANT EXTRACTS, PROTEINS, AND AMINO ACIDS ON THE ACCUMULATION OF SELENIUM IN PLANTS

Marcasite in the contact metamorphic ore deposits of the Twin Buttes District, Pima County, Arizona

Marcasite in the contact metamorphic ore deposits of the Twin Buttes District, Pima County, Arizona