Depositional Facies and Aqueous-Solid Geochemistry of Travertine-Depositing Hot Springs (Angel Terrace, Mammoth Hot Springs, Yellowstone National Park, U.S.A.)

Abstract

Petrographic and geochemical analyses of travertine-depositing hot springs at Angel Terrace, Mammoth Hot Springs, Yellowstone National Park, have been used to define five depositional facies along the spring drainage system. Spring waters are expelled in the vent facies at 71 to 73؇C and precipitate mounded travertine composed of aragonite needle botryoids. The apron and channel facies (43-72؇C) is floored by hollow tubes composed of aragonite needle botryoids that encrust sulfide-oxidizing Aquificales bacteria. The travertine of the pond facies (30-62؇C) varies in composition from aragonite needle shrubs formed at higher temperatures to ridged networks of calcite and aragonite at lower temperatures. Calcite ''ice sheets'', calcified bubbles, and aggregates of aragonite needles (''fuzzy dumbbells'') precipitate at the air-water interface and settle to pond floors. The proximal-slope facies (28-54؇C), which forms the margins of terracette pools, is composed of arcuate aragonite needle shrubs that create small microterracettes on the steep slope face. Finally, the distal-slope facies (28-30؇C) is composed of calcite spherules and calcite ''feather'' crystals. Despite the presence of abundant microbial mat communities and their observed role in providing substrates for mineralization, the compositions of spring-water and travertine predominantly reflect abiotic physical and chemical processes. Vigorous CO 2 degassing causes a ؉2 unit increase in spring water pH, as well as Rayleigh-type covariations between the concentration of dissolved inorganic carbon and corresponding ␦ 13 C. Travertine ␦ 13 C and ␦ 18 O are nearly equivalent to aragonite and calcite equilibrium values calculated from spring water in the higher-temperature (ϳ50-73؇C) depositional facies. Conversely, travertine precipitating in the lower-temperature (Ͻϳ50؇C) depositional facies exhibits ␦ 13 C and ␦ 18 O values that are as much as 4‰ less than predicted equilibrium values. This isotopic shift may record microbial respiration as well as downstream transport of travertine crystals. Despite the production of H 2 S and the abundance of sulfideoxidizing microbes, preliminary ␦ 34 S data do not uniquely define the microbial metabolic pathways present in the spring system. This suggests that the high extent of CO 2 degassing and large open-system solute reservoir in these thermal systems overwhelm biological controls on travertine crystal chemistry.

Distribution, lithotypes and mineralogical study of newly formed thermogenic travertines in Northern Euboea and Eastern Central Greece

“…The exact conditions that favor aragonite precipitation at one time and calcite at another are unclear. Previous studies [7,14,25] show that the main factors controlling the precipitation of calcite and aragonite can be: temperature [8,14,25,44,49], the Sr content [50,51], (Mg/Ca) ratio [25,52], pCO 2 [38], rate of CO 2 degassing [43] and precipitation rate [53,54]. In our case the temperature in Thermopylae hot springs (predominant phase calcite) ranges from 33 to 40 • C, while the temperature in Euboea hot springs (predominant phase aragonite) ranges from 43 to 82 • C ( The Sr content in Thermopylae hydrothermal fluid reaches 11900 µg/L and in travertines formed in Thermopylae, this reaches 2160 mg/kg [32], with the predominant phase as calcite.…”

“…The most characteristic and studied travertine deposits are in Italy (Bagni San Filippo, Terme San Giovanni, Tivoli, Guidonia Montecelio etc), USA (Yellowstone National Park), Turkey (Pamukkale), etc. [7][8][9][10][11][12][13][14][15][16] In Greece, there are hot springs in many areas. Magmatic and volcanic processes and active fault systems favour the rise of deep waters that are discharged at the surface as hot springs.…”

Comparative study of the Pleistocene Cakmak quarry (Denizli Basin, Turkey) and modern Mammoth Hot Springs deposits (Yellowstone National Park, USA)

“…Maximum temperatures are 73 C and spring waters have a minimum pH of 6 (Sorey and Colvard, 1997;Kharaka et al, 2000). These parameters evolve along the drainage outflow to ambient temperatures and a pH of 8 towards the distal portions of the system (Fouke et al, 2000;Veysey et al, 2008). Spring-water chemistry and travertine d 34 S and 87 Sr/ 86 Sr signatures indicate that waters that emerge at MHS relate to meteoric runoff in the Gallatin Mountain Range that infiltrated and migrated through the subsurface via fracture and fault zones, where it interacted at about 100 C with the Mississippian-age Madison Group limestone and evaporite deposits and potentially mixed with a magmatic-derived water source (Kharaka et al, 2000).…”

“…In the active MHS system, a sequence of five travertine depositional facies have been described along upstream-to-downstream "primary flow path" transects (Fouke et al, 2000;Veysey et al, 2008;Fouke, 2011). As the spring water cools (73 Ce25 C), degasses CO 2 (pH 6e8) and rapidly precipitates travertine (0.1e5 mm/day), a consistent downstream succession of facies forms: i.e.…”

“…Different travertine depositional facies models of modern spring systems have been proposed to describe the complex textural and geometric variations of ancient spring deposits (Guo and Riding, 1998;Fouke et al, 2000;Capezzuoli et al, 2014;Claes et al, 2015;Della Porta, 2015) and to accurately reconstruct the environmental conditions under which ancient deposits originally formed and evolved (Chafetz and Folk, 1984;Veysey et al, 2008;Fouke, 2011;Gandin and Capezzuoli, 2014;Sotohian and Ranjbaran, 2015). A facies, as summarized by James and Dalrymple (2010), is a 'body of (sedimentary) rock characterized by a particular combination of lithology and physical and biological structures that bestow an aspect that is different from the bodies of rock adjacent.…”