Acid-sulfate wall-rock alteration, characterized by the assemblage alunite+kaolinite+ quartz±pyrite, results from base-leaching by fluids concentrated in H2SO4.Requisite amounts of H2SO4 can be generated by different mechanisms in 3 principal geological environments: 1) by atmospheric oxidation of sulfides in the super gene environment, 2) by atmospheric oxidation at the water table in the steam-heated environment, of H2S released by deeper, boiling fluids, and 3) by the disproportionation of magmatic SC>2 to F^S and H2SO4 during condensation of a magmatic vapor plume at intermediate depths in magmatic-hydrothermal environments in silicic and andesitic volcanic terrains.In addition, coarse vein alunite may form in a magmatic-steam environment from rapid release of a SO2-rich magmatic vapor phase at high temperature and low pressure or from the oxidation of a more reduced magmatic vapor by entrained atmospheric oxygen in the carapace of a volcanic edifice.Alunite [KAh(SO4)2(OH)fil contains four stable isotope sites and complete analyses (SD, 818Oso4» 8 °OQH» and 5^4S) are now possible.Except for 818OoH in magmatichydrothermal alunites, primary values are usually retained.In cooperation with many colleagues, over 500 measurements have been made on nearly 200 samples of alunite and associated minerals from 20 localities and 55 additional analyses have been taken from the literature.These complete stable isotope analyses permit recognition of environments of formation and provide information on origins of components, processes (including rates), physical-chemical environments, and temperatures of formation.Supergene acid-sulfate alteration may form over any sulfide zone when it is raised above the water table by tectonics or exposed by erosion.It may overprint earlier acidsulfate assemblages, particularly the magmatic-hydrothermal assemblages which are pyriterich such as at El Salvador, Chile; Rodalquilar, Spain and Goldfield, Nevada.Supergene alunite has S^S virtually identical to precursor sulfides unless bacteriogenic reduction of aqueous sulfate takes place in standing pools of water.SD values will be close to that of local meteoric water unless extensive evaporation occurs, and 8D-818OoH of supergene alunites from a range of latitudes fall in a broad zone parallel to the meteoric water line much the way SD and S18O values of associated halloysite/kaolinite fall near the kaolinite line of Savin and Epstein (1970).S18Oso4 values are kinetically controlled and will reflect the hydrogeochemistry of the environment.A 18OsO4-OH values are grossly out of equilibrium and negative values are usually definitive of a supergene origin.In steam-heated environments, such as those at the Tolfa district, Italy and Marysvale, Utah, and numerous modern geothermal systems, acid-sulfate alteration zones are characterized by pronounced vertical zoning.Such acid-sulfate alteration may occur over adularia-sericite type base-and precious-metal ore deposits such as at Buckskin, Nevada.Initial 8 18OsO4 and 834S values are kinetically controlled, but S18Oso4 values usually reach equilibrium with fluids, and even 834S values may reflect partial exchange with H^S where the residence time of aqueous sulfate are sufficient.Most alunites of steam-heated origin have S^S the same as precursor H2S (and as related sulfides, if present) and SD the same as local meteoric water.In the samples analyzed, 8 18Osot and 818OoH appear to reflect a close approach to equilibrium with the fluid, and A 18Oso4-OH values give depositional temperatures of 90° to 160°C.The 818Oso4 and 818OoH values reflect the degree of exchange of the meteoric fluids with wall rock.Coeval kaolinites typically have 818Oso4 and SD to the left of the kaolinite line.Magmatic-hydrothermal acid-sulfate environments in near-surface epithermal deposits such as Summitville, Colorado; Julcani, Peru and Red Mountain, Lake City, Colorado are characterized by vertical aspect and horizontal zoning, the presence of coeval pyrite and possibly PO4 analogs of alunite, and zunyite, and later gold, pyrite and enargite.Acidsulfate alteration assemblages also occur as late stages in the porphyry-copper deposit at El Salvador.Chile.In the examples studied, magmatic-hydrothermal alunites have SD and initial 518OoH close to values for magmatic water.S34S values are 16 to 28 %c larger than those for associated pyrite, reflecting equilibrium between aqueous H2S and SO4 formed by the disproportionation of magmatically derived SO2.818Oso4 values are 10 to 15 %o and vary systematically with S^S reflecting variations in temperature and/or H2S/SO4 fluid ratios.Further variation of 8 18Oso4 may result if SC>2 condenses in mixed magmaticmeteoric water fluids.A 18Oso4-OH values of magmatic-hydrothermal alunites are generally unsuitable for temperature determinations because of retrograde exchange in the OH site but A^Saiun-py values provide reliable temperature estimates.Magmatic-steam environments appear to occur over a range of depths and are characterized by monomineralic veins of coarse alunite in variably alunitized and kaolinized wall rocks containing minor pyrite.Alunite formed in the magmatic-steam environment can usually be recognized by S^S near 834S£S and 8D and 8 18Oso4 near magmatic values.Magmatic-steam alunite differs from magmatic-hydrothermal alunite by having S^S close to 834Sss of the system.A 18Oso4-OH values of most magmatic-steam alunite give temperatures ranging from 90 to 200°C but, for reasons which are not understood, calculated 518On2O values are often too low for presumed precipitation from a magmatic vapor phase.Magmatic-steam environments may occur over porphyry type mineralization as Red Mountain, CO and Alunite Ridge, UT and over adularia-sericite type deposits as at Cactus, CA.As indicated above, this study has been conducted in cooperation with a number of colleagues engaged in more comprehensive studies of several of the examples chosen for investigation, particularly mineralized areas.Antonio Arribas, Jr., currently studying the Rodalquilar district in Spain as part his Ph.D. program, and Jeff Deen, who recently completed a Ph.D. dissertation on Julcani, Peru each conducted the stable isotope portion of his research in Rye's laboratory, and provided a number of analyses herein reported, in addition to those related to his thesis studies.Each provided geological and mineralogical information and insights that were critical to the interpretation of the stable isotope data.Roger Stoffregen, whose recently published study of the Summitville, Colorado Cu-Au-Ag deposit (Stoffregen, 1987) provided the mineralogical and paragenetic basis for the interpretation of that deposit, supplied samples and cooperated in the interpretation of the stable isotope data for Summitville.Dana Bove worked out the complex paragenesis of acid-sulfate alteration in the Red Mountain district near Lake City, Colorado, and supplied samples based on that paragenesis.In addition, a number of other colleagues supplied samples from various localities.Foremost among these was Cy Field who supplied all the samples from Tolfa, Italy and samples from El Salvador, Chile; Santa Rita, New Mexico; and Mineral Park, Arizona.Rich Fifarek supplied most of the samples on Round Mountain, Nevada.Peter Vikre and Roger Ashley provided samples and shared their knowledge of several districts in Nevada as noted at appropriate places in the text.CoCa Mines permitted access to their Cactus, California gold deposit and Jim Brady shared his knowledge of the district and guided the sampling of the deposit.The stable isotope analysis of all four sites in alunite is a formidable task.Considerable effort was expended in developing mineralogical and chemical separation techniques as well as isotope analytical methods.A summary of the methodology is currently being prepared for publication.The development of these techniques was undertaken by Wasserman with the assistance of Rye on isotope analyses and Arribas and Bethke on mineralogical separation and J. A. Goss and Bethke on the chemical separation of sulfate from alunite.A number of analyses were made by Carol Gent.In addition to those colleagues whose contributions to this study have been cited above, a number of others have contributed suggestions, information and other support.These include
Variation in tropical forest management directly affects biodiversity and provisioning of ecosystem services on a global scale, thus it is necessary to compare forests under different conservation approaches such as protected areas, payments for ecosystem services programs (PES), and ecotourism, as well as forests lacking any formal conservation plan. To examine the effectiveness of specific conservation approaches, we examined differences in forest structure and tree recruitment, including canopy cover; canopy height; seedling, sapling, and adult tree density; and average and total diameter at breast height (DBH) across 78 plots in 18 forests across Costa Rica representing protected areas, private forests utilizing PES and/or ecotourism, and private forests not utilizing these economic incentives. The effectiveness of conservation approaches in providing suitable primate habitat was assessed by conducting broad primate census surveys across a subset of eight forests to determine species richness and group encounter rate of three primate species: mantled howler monkey (Alouatta palliata), Central American spider monkey (Ateles geoffroyi), and the white-faced capuchin monkey (Cebus imitator). Only canopy height was significantly different across the three approaches, with protected areas conserving the tallest and likely oldest forests. Canopy height was also significantly associated with the group encounter rate for both mantled howler and spider monkeys, but not for capuchins. Total group encounter rate for all three monkey species combined was higher in incentivized forests than in protected areas, with capuchin and howler monkey group encounter rates driving the trend. Group encounter rate for spider monkeys was higher in protected areas than in incentivized forests. Incentivized conservation (PES and ecotourism) and protected areas are paragons of land management practices that can lead to variation in forest structure across a landscape, which not only protect primate communities, but support the dietary ecologies of sympatric primate species.
La elevada correlación positiva (r = 0,94) que exhiben los valores Ó0 18 y el contenido de H 2 0 de las rocas calco-alcalinas (CA), calco-alcalinas potásicas (CAK), shoshoníticas (SH) y ultrapotásicas (UP) neógenas del SE de España, indica que las relaciones isotópicas de O obtenidas no son primarias, sino que han sido fuertemente modificadas por procesos secundarios de hidratación/desvitrificación.Los rangos y medias de los valores Ó0 18 corregidos para cada una de las cuatro series de rocas estudiadas son: CA = +8,6 a + 10,2 %o (x = +9,4 %o); CAK = +8,8 a + 11,1 %o (x = +9,9 %o); SH = +8,7 a +11,0 %o (x = +9,6 %o), y UP = +10,2 a +11,8 %o (x = + 10,8 %o).Estos datos confirman la hipótesis de que las lavas del SE de España proceden de un manto peridotítico, altamente contaminado (10-40 %) por fundidos derivados de sedimentos supracorticales subducidos.
The foraging activity of many organisms reveal strategic movement patterns, showing efficient use of spatially distributed resources. The underlying mechanisms behind these movement patterns, such as the use of spatial memory, are topics of considerable debate. To augment existing evidence of spatial memory use in primates, we generated movement patterns from simulated primate agents with simple sensory and behavioral capabilities. We developed agents representing various hypotheses of memory use, and compared the movement patterns of simulated groups to those of an observed group of red colobus monkeys (Procolobus rufomitratus), testing for: the effects of memory type (Euclidian or landmark based), amount of memory retention, and the effects of social rules in making foraging choices at the scale of the group (independent or leader led). Our results indicate that red colobus movement patterns fit best with simulated groups that have landmark based memory and a follow the leader foraging strategy. Comparisons between simulated agents revealed that social rules had the greatest impact on a group’s step length, whereas the type of memory had the highest impact on a group’s path tortuosity and cohesion. Using simulation studies as experimental trials to test theories of spatial memory use allows the development of insight into the behavioral mechanisms behind animal movement, developing case-specific results, as well as general results informing how changes to perception and behavior influence movement patterns.
Tin mineralization in the Black Range is present in a series of Oligocene rhyolite domes that cover an area of approximately 200 km2 in southwestern New Mexico. These rhyolites are typically high silica (76 to 78 percent), peraluminous, and topaz bearing. The δ 18O values (~7.0 ‰) of unaltered rocks are typical of normal I-type granites.
Acid sulfate wall-rock alteration, characterized by the assemblage alunite + kaolinite + quartz + or - pyrite, results from base leaching by fluids concentrated in H 2 SO 4 . Requisite amounts of H 2 SO 4 can be generated by different mechanisms in three principal geologic environments: (1) by atmospheric oxidation of sulfides in the supergene environment, (2) by atmospheric oxidation at the water table in the steam-heated environment of H 2 S released by deeper, boiling fluids, and (3) by the disproportionation of magmatic SO 2 to H 2 S and H 2 SO 4 during condensation of a magmatic vapor plume at intermediate depths in magmatic hydrothermal environments in silicic and andesitic volcanic terranes. In addition, coarse vein alunite may form in a magmatic steam environment from rapid release of an SO 2 -rich magmatic vapor phase at high temperature and low pressure or from the oxidation of a more reduced magmatic vapor by entrained atmospheric oxygen in the carapace of a volcanic edifice.Alunite [KAl 3 (SO 4 ) 2 (OH) 6 ] contains four stable isotope sites and complete analyses (delta D, delta 18 O (sub SO 4 ) , delta 18 O OH , and delta 34 S) are now possible. Except for delta 18 O OH in magmatic hydrothermal alunites, primary values are usually retained. In cooperation with many colleagues, over 500 measurements have been made on nearly 200 samples of alunite and associated minerals from 23 localities, and 55 additional analyses have been taken from the literature. This survey confirms that kinetic factors play an important role in the stable isotope systematics of alunite and acid sulfate alteration. To a very large extent they form the isotopic basis for distinguishing between environments of acid sulfate alteration, and they provide important insights into attendant processes. Stable isotope analyses of alunite, often in combination with those on associated sulfides and kaolinite, permit recognition of environments of formation and provide information on origins of components, processes (including rates), physical-chemical environments, and temperatures of formation.Supergene acid sulfate alteration may form over any sulfide zone when it is raised above the water table by tectonics or exposed by erosion. It may overprint earlier acid sulfate assemblages, particularly the magmatic hydrothermal assemblages which are pyrite rich such as at El Salvador, Chile; Rodalquilar, Spain; and Goldfield, Nevada. Supergene alunite normally has delta 34 S values virtually identical to precursor sulfides unless bacteriogenic reduction of aqueous sulfate takes place in standing pools of water. delta D values are close to that of local meteoric water unless extensive evaporation occurs. delta D and delta 18 O OH values of supergene alunites from a range of latitudes fall in a broad zone parallel to the meteoric water line much the way delta D and delta 18 O values of associated halloysite-kaolinite fall near the kaolinite line of Savin and Epstein (1970). delta 18 O (sub SO 4 ) values are kinetically controlled and will reflect the hydro-geochemistry of the environment. delta 18 O (sub SO 4 -OH) alues are grossly out of equilibrium and large negative values are definitive of a supergene origin.In steam-heated environments, such as those at the Tolfa district, Italy, and Marysvale, Utah, and numerous modern geothermal systems, acid sulfate alteration zones are characterized by pronounced vertical zoning. Such acid sulfate alteration may occur over adularia-sericite-type base and precious metal ore deposits such as the one at Buckskin, Nevada. Initial delta 18 O (sub SO 4 ) and delta 34 S values are kinetically controlled, but delta 18 O (sub SO 4 ) values usually reach equilibrium with fluids, and even delta 34 S values may reflect partial exchange with H 2 S where the residence time of aqueous sulfate is sufficient. Most alunites of steam-heated origin have delta 34 S values the same as those of precursor H 2 S (and as related sulfides, if present) and delta D values similar to that of local meteoric water. In the samples analyzed, most delta 18 O (sub SO 4 -OH) values give reasonable temperatures of 90 degrees to 160 degrees C, indicating that delta 18 O (sub SO 4 ) and delta 18 O OH values reflect a close approach to equilibrium with the fluid. The delta 18 O (sub SO 4 ) and delta 18 O OH values also reflect the degree of exchange of the meteoric fluids with wall rock. Coeval kaolinites typically have delta 18 O and delta D values to the left of the kaolinitc line.Magmatic hydrothermal, acid sulfate alteration zones in near-surface epithermal deposits such as Summitville, Colorado. Julcani, Peru, and Red Mountain and Lake City, Colorado, are characterized by vertical orientation and horizontal zoning, the presence of coeval pyrite, PO 4 analogues of alunite, zunyite, and later gold, pyrite and enargite, and often other Cu-As-Sb-S minerals. Acid sulfate alteration assemblages also occur as late stages in the porphyry-copper deposit at E1 Salvador, Chile. In the examples studied, magmatic hydrothermal alunites have delta D values close to those for magmatic water. delta 34 S values are 16 to 28 per mil larger than those for associated pyrite, reflecting equilibrium between aqueous H 2 S and SO 4 formed by the disproportionation of magmatically derived SO 2 . delta 18 O (sub SO 4 ) values are usually 8 to 18 per mil and vary systematically with delta 34 S values, reflecting variations in temperature and/or H 2 S/SO 4 fluid ratios. Further variation in delta 18 O (sub SO 4 ) values may result if SO 2 condenses in mixed magmatic meteoric water fluids. delta 18 O (sub SO (sub 4-) OH) values of magmatic hydrothermal alunites are generally unsuitable for temperature determinations because of retrograde exchange in the OH site, but delta 34 S (sub alunite-pyrite) values provide reliable temperature estimates.Magmatic steam environments appear to occur over a range of depths and are characterized by monomineralic veins of coarse alunite in variably alunitized and kaolinized wall rocks containing minor pyrite. Alunite formed in the magmatic steam environment can usually be recognized by delta 34 S near delta 34 S (sub Sigma S) values and delta D and delta 18 O (sub SO 4 ) values near magmatic values. Magmatic steam alunite differs from magmatic hydrothermal alunite by having delta 34 S close to delta 34 S (sub Sigma S) values of the system. delta 18 O (sub SO (sub 4-) OH) values of most magmatic steam alunite give temperatures ranging from 90 degrees to 210 degrees C but, for reasons which are not understood, some temperatures as well as calculated delta 18 O (sub H 2 O) values are too low for presumed precipitation from a magmatic vapor phase. Magmatic steam environments may occur over porphyry-type mineralization as at Red Mountain, Colorado, and Alunite Ridge, Utah, and over or adjacent to adularia-sericite-type deposits in volcanic domes as at Cactus, California.
