Hot Spring Deposits Research Articles

Meridiani Planum hematite deposit and the search for evidence of life on Mars—iron mineralization of microorganisms in rock varnish

The extensive hematite deposit in Meridiani Planum was selected as the landing site for the Mars Exploration Rover Opportunity because the site may have been favorable to the preservation of evidence of possible prebiotic or biotic processes. One of the proposed mechanisms for formation of this deposit involves surface weathering and coatings, exemplified on Earth by rock varnish. Microbial life, including microcolonial fungi and bacteria, is documented in rock varnish matrices from the southwestern United States and Australia. Limited evidence of this life is preserved as cells and cell molds mineralized by iron oxides and hydroxides, as well as by manganese oxides. Such mineralization of microbial cells has previously been demonstrated experimentally and documented in banded iron formations, hot spring deposits, and ferricrete soils. These types of deposits are examples of the four “water–rock interaction” scenarios proposed for formation of the hematite deposit on Mars. The instrument suite on Opportunity has the capability to distinguish among these proposed formation scenarios and, possibly, to detect traces that are suggestive of preserved martian microbiota. However, the confirmation of microfossils or preserved biosignatures will likely require the return of samples to terrestrial laboratories.

Analysis of hot springs and associated deposits in Yellowstone National Park using ASTER and AVIRIS remote sensing

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Airborne Visible/IR Image Spectrometer (AVIRIS) data were used to characterize hot spring deposits in the Lower, Midway, and Upper Geyser Basins of Yellowstone National Park from the visible/near infrared (VNIR) to thermal infrared (TIR) wavelengths. Field observations of these basins provided the critical ground-truth for comparison with the remote sensing results. Fourteen study sites were selected based on diversity in size, deposit type, and thermal activity. Field work included detailed site surveys such as land cover analysis, photography, Global Positioning System (GPS) data collection, radiometric analysis, and VNIR spectroscopy. Samples of hot spring deposits, geyser deposits, and soil were also collected. Analysis of ASTER data provided broad scale characteristics of the hot springs and their deposits, including the identification of thermal anomalies. AVIRIS high spectral resolution short-wave infrared (SWIR) spectroscopy provided the ability to detect hydrothermally altered minerals as well as a calibration for the multispectral SWIR ASTER data. From the image analysis, differences in these basins were identified including the extent of thermal alteration, the location and abundance of alteration minerals, and a comparison of active, near-extinct, and extinct geysers. We determined the activity level of each region using a combination of the VNIR-SWIR-TIR spectral differences as well as the presence of elevated temperatures, detected by the TIR subsystem of ASTER. The results of this study are applicable to the exploration of extinct mineralized hydrothermal deposits on both Earth and Mars.

A new univalve crustacean from the Early Devonian Rhynie chert hot-spring complex

ABSTRACTA new aquatic crustacean is described from the Early Devonian Rhynie chert. The small, broadly oviform carapace consists of a univalve symmetrical about its longitudinal axis, formed by a continuous cuticle with no fold or hinge. In transverse cross-section, the ventral surface exhibits a broadly ‘W’-shaped outline. Areas of fine, setose objects are preserved, positioned antero-ventrally on either side of the mid-line axis. In transverse sections, a ring-shaped internal structure is also visible. In longitudinal cross-section, this structure is resolved into an axially positioned, internally subdivided tube occupying the mid- and posterior part of the carapace. A small, anteriorly positioned rostrum has a deep pit on each side, perhaps indicative of the socket of an antennal appendage. The arthropods are commonly found clustered together around plant axes, comprising groups of up to 25 or more similarly sized individuals. The chert texture enclosing many individual specimens indicates a sub-aqueous preservational environment. The same organism has recently been discovered in preparations from the nearby and equivalently aged Windyfield hot spring deposit. The morphology of this new arthropod suggests affinity with Branchiopoda and it is tentatively placed within the Diplostraca (an order which contains both ‘conchostracans’ and ‘cladocerans’, or water fleas). The presence of a univalve test suggests a cladoceran affinity, but the lack of diagnostic appendages in the present material does not allow us to take the classification any further. This is potentially the earliest known occurrence of the group and would extend their fossil record back from the Early Cretaceous. The remarkable similarity between these arthropods and their present-day representatives strongly indicates morphological stasis within the group from early on in their evolutionary history

Late Pleistocene siliceous sinter associated with fluvial, lacustrine, volcaniclastic and landslide deposits at Tahunaatara, Taupo Volcanic Zone, New Zealand

ABSTRACTThe Tahunaatara sinter, Taupo Volcanic Zone, New Zealand, is a ∼17–20-kyr-old hot-spring deposit of opal-A mineralogy. It is interbedded with fluvial, lacustrine and volcaniclastic sediments, some silicified by infusing thermal waters. The exposed sinter (∼4 m thick, 90 m long) was truncated at its southern margin by a landslide, which deposited a conglomerate (up to 2 m thick, 56 m long) of sinter blocks and associated strata nearby. Kaolinite-rich cobbles at the base of the conglomerate indicate a change in the thermal regime and its probable trigger: acid steamcondensate produced alteration. Clasts in the landslide are oriented SW, the same direction as flattened plant reeds entombed in sinter, and as intercalated fluvial beds. Thus, thermal waters, stream flow and the landslide all likely followed the same palaeo-valley, which is similar in terrain and stratigraphy to the Devonian Rhynie hydrothermal system. The plant-rich, layered, in situ sinter contains fossilised microbes and rare stromatolites, and was deposited on mid- to distal slopes adjacent to marshes. Ash falls, fluvial activity and ponding occurred during and after the thermal activity. Unsilicified tephric Ohakea loess (∼26–17 kyr BP) and Taupo Tephra (1·86 kyr BP) blanket both sinter and landslide. Today, the deposits form resistant remnants in a topographically inverted landscape.

Sedimentology of hot spring systems

Hot springs and geysers hold a special fascination for many people. To the casual visitor and tourist, they provide a powerful visual display of nature at work. If their temperature is tolerable, “taking the waters” can provide relaxation, comfort, and alleged health benefits. To the scientist, however, terrestrial hydrothermal systems are of major importance in many disciplines. They serve as models for understanding the processes in the shallowest part of the geothermal systems that produce epithermal mineral deposits. They are commonly the surface manifestation of large subsurface geothermal systems that may be tapped for geothermal energy. Their fascinating ecosystems are dominated by diverse arrays of microorganisms, many of which thrive in waters of extremely high temperatures and compositions that are toxic to all other organisms. Although the life of a geothermal system may be geologically brief, typically lasting only a few hundred to a few hundred thousand years, many hot springs leave a tangible record of former activity in the deposits that were precipitated in and around their vents. These hot spring deposits, which are composed mainly of calcium carbonate (travertine) and silica (siliceous sinter), are the topic of this Special Issue. Hot spring deposits have been studied seriously for more than a century. The pioneer of their detailed study was Walter Harvey Weed, who in the 1880s was one of the first to examine the deposits of siliceous sinter and travertine at Yellowstone National Park in Wyoming, U.S.A. More than a century ago, Weed (1889 a , 1889 b , 1889 c ) recognized that the abundant microorganisms that inhabit spring environments may play a role in the formation of travertine and sinter. The subsurface geothermal systems that feed hot springs were widely studied with a view to understanding and predicting epithermal mineralization. Interest in surface hot spring deposits, however, …

Diagenetic transformations (opal-A to quartz) of low- and mid-temperature microbial textures in siliceous hot-spring deposits, Taupo Volcanic Zone, New Zealand

Silica sinter is a subaerial hot-spring deposit formed upon cooling (<100 °C) of discharging alkali-chloride waters. Silica deposition traps and fossilizes living microbes in low-temperature (<35 °C) to mid-temperature (~35–59 °C) apron–terrace outflow channels and pools, which record distinctive macrotextures and microtextures along a thermal gradient. Sinters from four geothermal fields, Orakei Korako, northern Waiotapu, Te Kopia, and Umukuri, within the Taupo Volcanic Zone, New Zealand, were sampled from two common microbe-rich microfacies (low-temperature palisade, mid-temperature bubble mat) through a range of ages (modern to ~40 000 years BP). We observed morphologic changes in microbial silicification and stepwise transitions in silica phase mineralogy throughout diagenesis (opal-A to quartz). X-ray powder diffractometry analysis of Taupo Volcanic Zone sinter samples revealed that mode of microbial fossilization is controlled by silica phase mineralogy, which also determines the preservation potential of environmentally significant and measurable filament parameters. Typical low-temperature palisade microfacies display thick sheaths (>3 µm diameter) and coarse tubular filament moulds >5 µm in diameter, whereas mid-temperature bubble mat microfacies characteristically consist of thin sheaths (~1 µm diameter) with fine moulds < 3 µm in diameter. Upon diagenesis and silica phase transformation to opal-CT, the two subenvironments cannot be distinguished based on filament diameter alone. This study of recurring microfacies in sinters of different ages allowed us to systematically track the transformation of mineralogical and morphological changes in biotic–abiotic depositional elements during diagenesis of silica sinter, and therefore enhance the paleoenvironmental, paleobiological, and paleohydrologic utility of hydrothermal deposits in the geologic record.

Depositional Facies and Diagenetic Alteration in a Relict Siliceous Hot-Spring Accumulation: Examples from Yellowstone National Park, U.S.A.

ABSTRACT Siliceous precipitates from portions of an 11-m-long core drilled through a relict Yellowstone hot-spring deposit provide valuable insights into the diagenetic facies in this hydrothermal environment. Most of the core consists of relatively low-temperature siliceous sinter containing abundant plant, diatom, and microbial fossilized remains derived from the distal debris apron and discharge channel/flowpath of the hot spring. A few intervals contain stromatolitic horizons analogous to modern, siliceous pool-margin and discharge channel/flowpath facies. Despite the abundance of silicified microbial remains (e.g., silicified stromatolitic horizons as well as individual filamentous microbes, diatoms), distinctive organic biomarkers are not preserved in the core. The apparent lack of distinctive organic biomarkers is attributable to pervasive diagenetic alteration in the presence of high-temperature, chemically reactive fluids. Numerous diagenetic features have been superimposed on the siliceous sinter, especially considering the relatively shallow depths of burial. The uppermost interval (0 to 1.2 m) consists of highly porous siliceous sinter (opal-A) and interbedded travertine. Amorphous manganese oxides and sparry calcite cements are present and are irregularly distributed throughout this interval. Below is a diagenetic facies (4.8 to 5.3 m) that consists of opal-CT and minor chalcedony. The most pervasive diagenetic alteration in the core is the 6.8 to 11.2 m depth interval, where abundant zeolites (mordenite, heulandite), bladed cristobalite lepispheres, chalcedony cements, and calcite veins are present. Judging by the assemblage of plant and diatom remains, most of this pervasive alteration is superimposed on relatively low-temperature siliceous sinters and is likely the result of migration of hot waters through this interval. The paragenesis of all these intervals is very complex, involving numerous episodes of mineral precipitation and dissolution. This diagenetic alteration is facilitated by the porous nature of the siliceous sinter, thermal convection of superheated fluids or steam, strongly oxidizing spring waters, and fluctuating hydrochemical regimes. Rapid dissolution and/or replacement of organic matter indicates that standard morphological means (e.g., petrographic identification of body fossils) may be the best method by which to identify that organisms were previously present in ancient hot-spring accumulations.

Geology of the Ivanhoe Hg-Au District, Northern Nevada: Influence of Miocene Volcanism, Lakes, and Active Faulting on Epithermal Mineralization

The mercury-gold deposits of the Ivanhoe mining district in northern Nevada formed when middle Miocene rhyolitic volcanism and high-angle faulting disrupted a shallow lacustrine environment. Sinter and replacement mercury deposits formed at and near the paleosurface, and disseminated gold deposits and high-grade gold-silver veins formed beneath the hot spring deposits. The lacustrine environment provided abundant meteoric water; the rhyolites heated the water; and the faults, flow units, and lakebeds provided fluid pathways for the hydrothermal fluids. A shallow lake began to develop in the Ivanhoe area about 16.5 Ma. The lake progressively expanded and covered the entire area with fine-grained lacustrine sediments. Lacustrine sedimentation continued to at least 14.4 Ma, and periodic fluctuations in the size and extent of the lake may have been responses to both climate and nearby volcanism. The eruption of rhyolite and andesite flows and domes periodically disrupted the lacustrine environment and produced interfingered flows and lake sediments. The major pulse of rhyolitic volcanism took place between 15.16 ± 0.05 and 14.92 ± 0.05 Ma. High-angle faulting began in the basement about 15.2 Ma, penetrated to and disrupted the paleosurface after 15.10 ± 0.06 Ma, and largely ceased by 14.92 ± 0.05 Ma. Ground motion related to both faulting and volcanism created debris flows and soft-sediment deformation in the lakebeds. Mercury-gold mineralization was coeval with rhyolite volcanism and high-angle faulting, and it took place about 15.2 to 14.9 Ma. At and near the paleosurface, hydrothermal fluids migrated through tuffaceous sediments above relatively impermeable volcanic and Paleozoic units, creating chalcedonic, cinnabar-bearing replacement bodies and sinters. Disseminated gold was deposited in sedimentary and volcanic rocks beneath the mercury deposits, although the hydrologic path between the two ore types is unclear. Higher-grade gold-silver deposits formed in massive rhyolites and Paleozoic quartzites at deeper levels, and these mineralized zones possibly represent the feeder zones for the higher-level deposits. Fluctuations in the ground-water table locally produced hydrothermal oxidation of the near-surface mercury and disseminated gold deposits. The locus of mineralization shifted with time, moving south and east from its inception point in the west-central part of the district. Thus, although mineralization in the district took place during a span of 300,000 years, the duration of mineralization at any one place probably was much shorter. The low-sulfidation deposits of the Ivanhoe district formed at the same time and under similar conditions as those in the nearby Midas district, 15 km to the northwest, which includes the large, high-grade Ken Snyder gold-silver epithermal vein deposit. The exposures in the Ivanhoe district are interpreted to represent the near-surface example of the paleosurface that originally was present above the Midas mineralizing system. The resulting combined Ivanhoe-Midas model provides an exploration guide for epithermal deposits in similar geologic environments in northern Nevada.

La Marciana Jurassic sinter—implications for exploration for epithermal precious-metal deposits in Deseado Massif, southern Patagonia, Argentina

A well-preserved Jurassic siliceous sinter has been identified at La Marciana farm in southern Patagonia, Argentina. Fossil sinters are a rare occurrence and this example bridges the gap between Devonian/Carboniferous examples and more abundant Tertiary sinters. Its presence is significant in the context of exploration for epithermal precious-metal deposits in the Deseado Massif geological province of southern Patagonia.Field and textural characteristics of the La Marciana siliceous deposit provide unequivocal evidence of its origin. It is located in an appropriate volcanic and epithermal environment and it displays a strongly developed non-planar depositional lamination, elongate cavities parallel to this lamination, small-scale stromatolitic columnar structures, moulds of stems and roots of plants and desiccation cracks.Geochemical and oxygen isotope studies provide additional information compatible with a sinter origin. The content of precious-metal elements—apart from in anomalous hydrothermal breccia—is low, and the average Au, Ag, As and Sb concentrations are similar to those of most known fossil sinters. The 18O SMOW values obtained on La Marciana sinter range from 7.3 to 16‰ and could indicate a lower temperature of formation when compared with quartz-vein isotope data from the Cerro Vanguardia area—the best-known example of an epithermal precious-metal deposit in the Deseado Massif.Hydrothermal alteration of the volcanic rocks and the presence of quartz veinlets and hydrothermal breccias with Au and Ag anomalies in the La Marciana area are indicative of gold- and silver-rich hydrothermal activity. Taken in conjunction with the presence of the La Marciana sinter, which is further evidence of Jurassic hot-spring deposits in the western border of the Deseado Massif, this suggests that exploration in the area should focus on locating epithermal quartz vein systems that may be preserved at depth.

Anatomy of siliceous hot springs: examples from Yellowstone National Park, Wyoming, USA

Numerous siliceous hot spring systems in the Norris and Lower Geyser Basins of Yellowstone National Park, Wyoming, provide insights into spring geometries, depositional facies, and lithofacies associated with modern hot springs. Analyses of active (Cistern Spring, Octopus Spring, Deerbone Spring, and Spindle Geyser) and inactive (Pork Chop Geyser) siliceous hot springs have facilitated the construction of a facies model for siliceous hot spring deposits at Yellowstone. Yellowstone's siliceous springs tend to group into four broad morphological categories: siliceous spires and cones, domal mounds, terraced mounds, and ponds. Siliceous spires/cones are subconical accumulations up to 5–7 m high and about 2 m in diameter, and are common deposits in Yellowstone Lake. Domal mounds are characterized by siliceous precipitates with a broad lens or shield geometry (2–3 m in vertical relief), discharge channels, and an areal accumulation of approximately 150 m 2. In contrast, terraced mounds have a stair-step morphology, a substantial pool (∼8–10 m in diameter), “shrubby” precipitates, and occupy areas of ∼2000 m 2. Siliceous ponds are variable in size, have little outflow, and exhibit low amounts of silica precipitation. Of these morphological varieties, domal mounds and terraced mounds are thought to have the best long-term preservation potential. The four spring morphotypes are composed of up to eight cumulative hot spring depositional facies: (1) vent (>95 °C), (2) proximal vent (<95 °C), (3) pool (∼80–90 °C), (4) pool margin (∼80 °C), (5) pool eddy (<80 °C), (6) discharge channel/flowpath (<80 °C to ambient), (7) debris apron (variable temperatures), and (8) geyser (variable temperatures). This facies model based on numerous springs facilitates our ability to interpret ancient hot spring deposits and to infer depositional conditions. Precipitation of siliceous sinter is the result of abiotic and biotic processes. Abiotic precipitational processes are dominant in the vent area, whereas biotic influences on the precipitate fabric become progressively more important downflow.

Synthesis of zoning-free BaSO4-PbSO4 solid solution and its structural characterizations

Abstract Natural Pb-bearing barite, (Ba,Pb)SO4 “hokutolite”, is a radioactive sulfate mineral occurring in hot-spring deposit. An attempt to synthesize (Ba,Pb)SO4 crystal with a flux-growth process was made in this study. BaSO4 and PbSO4 in various proportions were used as precursor materials with Na2SO4 as a flux agent. The growth was carried out in a platinum crucible at 750-850ºC and ambient pressure conditions. The nucleation and growth were activated by a slow-cooling process at 2ºC/hr cooling rate. The flux-grown (Ba,Pb)SO4 crystals up to 1 mm in dimension were obtained and their chemical compositions were found to cover the entire range between BaSO4 and PbSO4. Thus there does exist a complete solid solution series between the barite (BaSO4) and anglesite (PbSO4) binary system. This result is consistent with that reported for (Ba,Pb)SO4 synthesized with a hydrothermal method. Both natural and hydrothermally synthesized (Ba,Pb)SO4 crystals display a distinct domain structure in which the Ba/Pb ratio varied among different domains. This type of chemical zoning is recognized under an optical microscope to be a banded texture in which dark bands (Ba-rich area) alternate with bright bands (Pb-rich area). In contrast, the (Ba,Pb)SO4 samples synthesized in this work contain no detectable optical bands, and this dramatic difference is believed to be a direct consequence of different growth kinetics. The flux-grown (Ba,Pb)SO4 crystals were determined to be a barite type of structure with the Ba and Pb atoms substituting each other in a fully disordered arrangement. The cell parameters vary continuously and systematically from the Ba-rich end toward the Pb-rich end as dictated by an ideal solid solution series.

The study of Onikobe hot spring deposits through the microbeam X-ray spectroscopy

The study of Onikobe hot spring deposits through the microbeam X-ray spectroscopy

Change in color of the hot spring deposits at the Chinoike-Jigoku hot pool, Beppu geothermal field

The Chinoike-Jigoku hot pool in Beppu geothermal field, Central Kyushu, Japan, displays a blood-red color due to the hematite (Fe 2O 3) deposited at the bottom of the pool. The colors of the deposits collected on 1 October 1990, on 27 March 1995, and on 6 March 1996 were measured with a colorimeter. The results show that the red deposits became yellower in 1995 and 1996 than they were in 1990. X-ray diffraction (XRD) patterns and chemical compositions of the deposits indicate that the discoloration of the Chinoike-Jigoku pool water is caused by an increase in the content of jarosite [KFe 3(SO 4) 2(OH) 6]. The temperature of the subsurface thermal water beneath the Chinoike-Jigoku hot pool, as estimated by the anhydrite chemical geothermometer, has declined from 200 to 150 °C over the past 25 years. The Na and Cl concentrations of the hot spring water discharging from Chinoike-Jigoku have decreased, while the SO 4 concentration has increased. The temporal variations in subsurface temperature and dissolved ion concentrations suggest that the mixing ratio between the high–temperature, neutral Na–Cl type water and the relatively low-temperature, acid H–SO 4 type water that form the thermal water of Chinoike–Jigoku has changed over the last 25 years. Hydrothermal studies of jarosite stability have confirmed that the increase in jarosite content in the deposits was caused by a temperature drop of the mixed thermal water beneath Chinoike-Jigoku pool, due to an increase in the contribution of the cooler H–SO 4 water type to the thermal mixture.

Sublacustrine precipitation of hydrothermal silica in rift lakes: evidence from Lake Baringo, central Kenya Rift Valley

Abstract Many lakes in volcanic regions are fed by hot springs that, in some basins, can contribute a large percentage of the annual recharge, especially during times of aridity. It is important to recognize any contemporary hydrothermal contribution in paleoenvironmental reconstruction of lake basins because recharge from thermal waters can potentially confuse paleoclimatic signals preserved in the lacustrine sedimentary record. Hot spring deposits (travertine, sinter) provide the most tangible evidence for thermal recharge to lakes. Although subaerial spring deposits have been widely studied, lacustrine thermal spring deposits, especially sublacustrine siliceous sinters, remain poorly known. Detailed field, petrographic and scanning electron microscope (SEM) studies have been made of fossil sublacustrine sinter exposed at Soro hot springs along the northeastern shoreline of Ol Kokwe, a volcanic island in Lake Baringo, Kenya. Modern hot springs at Soro, which discharge Na–HCO3–Cl waters from a deep reservoir (∼180 °C ), have thin (1–10 mm), friable microbial silica crusts around their subaerial vents, but thicker (>1 cm) sinter deposits are not forming. The fossil sinter, which is present as intergranular cements and crusts in littoral conglomerates and sandstones, is composed mainly of opaline silica (opal-A). Three types of fossil sinter are recognized: (1) massive structureless silica, which fills intergranular pores and forms crusts up to 5 cm thick; (2) pore-lining silica, some of which is isopachous, and (3) laminated silica crusts, which formed mainly on the upper surfaces of detrital particles. All three types contain well-preserved diatoms including lacustrine planktonic forms. Microbial remains, mainly filamentous and coccoid bacteria (including cyanobacteria) and extracellular polymeric gels, are locally abundant in the opaline silica, together with detrital clays and thin laminae composed of authigenic chlorite (?). Most of the hydrothermal silica precipitated when the thermal springs were submerged by fresh lake water. Silica precipitated upon rapid cooling of thermal (∼90 °C ) waters at and just below their interface with the overlying cooler (∼25 °C ) lake waters. Microbial mats locally acted as a filter that limited mixing and rapid dilution of the thermal fluids. Some of the silica originally may have been soft and partly gelatinous. Planktonic diatoms and detrital clay rained down, then became incorporated in the amorphous silica. Following a fall in lake level, the opal-A lithified and partly altered to cristobalite (opal-C) and chalcedony. The lowest fossil sinters were later encrusted by calcite stromatolites, with calcite and quartz forming late pore-filling cements. The age of the sublacustrine sinters is unknown, but some of the deposits could date back to the late Pleistocene. Similar conglomerates cemented by hydrothermal silica are present along fault lines at neighbouring Lake Bogoria. Such rocks may provide evidence for deep, hot fluid recharge to lakes when encountered in the geological record.

Sedimentary Facies and Mineralogy of the Late Pleistocene Umukuri Silica Sinter, Taupo Volcanic Zone, New Zealand

ABSTRACT The Umukuri silica sinter is a large, late Pleistocene hot-spring deposit exposed along the eastern upthrown block of the Umukuri Fault, one kilometer southwest of the active Orakei Korako geothermal area, Taupo Volcanic Zone, New Zealand. Uplift along the fault has frozen sinter maturation to produce a characteristic silica-phase stratigraphy revealed by X-ray diffraction. Paracrystalline opal-CT dominates upper layers; opal-C occurs throughout middle and lower horizons; and recrystallized fabrics of microcrystalline quartz constitute lowermost exposed layers. Original and secondary matrix fabrics in the sinter include: fine-grained, porous, friable; dense, vitreous; and massive-mottled, diffusely layered. Original fabrics combine with silicified plant matter, peloids, pisoids, sinter fragments, detrital grains, diatoms, ostracodes, and filamentous to tufted microbial remains, to form nine depositional microfacies. Thinly laminated, plant-rich, and palisade types dominate. Sinter breccia and wavy-laminated varieties also are common, whereas curved laminae with lenticular voids ( = bubble mats), clotted, peloidal, and pisolitic microfacies are minor. Umukuri microfacies represent silicification in mid to low temperature waters on sinter apron terrace and slope areas, and in distal, marshy settings. Closely spaced, lateral and vertical intercalation of various microfacies in outcrop implies changing local flow and temperature conditions. No facies typical of high-temperature, proximal vent areas have been identified. Comparison with modern thermal spring analogs suggests that original Umukuri sinter fabrics recorded varying degrees of polymerization vs. monomerization of juvenile opal-A. Mineralogical and textural modification of matrix fabrics reflects a microscale, incremental continuum, following granular or fibrous habits along solution-precipitation pathways. Late-stage quartz rims and infills pores throughout the sinter.

Microbial Construction of Siliceous Stalactites at Geysers and Hot Springs: Examples from the Whakarewarewa Geothermal Area, North Island, New Zealand

Abstract Siliceous stalactites, formed of opal-A laminae that are concentrically arranged around a hollow soda-straw, are common features structures in some of the geyser and hot spring deposits at Whakarewarewa and other geothermal areas of New Zealand. These siliceous stalactites contain diverse biota of bacteria (including cyanobacteria), fungi, and diatoms that lived on the stalactite surfaces, with locally abundant pollen grains, and springtails. The microbes are the templates for much of the opaline silica precipitation and thereby controlled most of the fabrics that form the stalactite laminae. Siliceous stalactites form at sites of dripping water below the overhanging edges of geyserite rims that surround geyser vents, and along the steep margins of sinter terraces on discharge aprons. Stalactites may hang as isolated individuals or may coalesce to form dripstone draperies along terrace or rim margins. Stalactite growth is controlled by the volume, temperature, and the silica concentration of the ...

Microbial Construction of Siliceous Stalactites at Geysers and Hot Springs: Examples from the Whakarewarewa Geothermal Area, North Island, New Zealand

Other| February 01, 2001 Microbial Construction of Siliceous Stalactites at Geysers and Hot Springs: Examples from the Whakarewarewa Geothermal Area, North Island, New Zealand BRIAN JONES; BRIAN JONES 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Search for other works by this author on: GSW Google Scholar ROBIN W. RENAUT; ROBIN W. RENAUT 2Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada Search for other works by this author on: GSW Google Scholar MICHAEL R. ROSEN MICHAEL R. ROSEN 3Wairakei Research Centre, Institute of Geological and Nuclear Sciences, Wairakei Research Centre, Private Bag 2000, Taupo, New Zealand Search for other works by this author on: GSW Google Scholar Author and Article Information BRIAN JONES 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada ROBIN W. RENAUT 2Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada MICHAEL R. ROSEN 3Wairakei Research Centre, Institute of Geological and Nuclear Sciences, Wairakei Research Centre, Private Bag 2000, Taupo, New Zealand Publisher: SEPM Society for Sedimentary Geology Accepted: 07 Oct 2000 First Online: 03 Mar 2017 Online Issn: 1938-5323 Print Issn: 0883-1351 Society for Sedimentary Geology PALAIOS (2001) 16 (1): 73–94. https://doi.org/10.1669/0883-1351(2001)016<0073:MCOSSA>2.0.CO;2 Article history Accepted: 07 Oct 2000 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation BRIAN JONES, ROBIN W. RENAUT, MICHAEL R. ROSEN; Microbial Construction of Siliceous Stalactites at Geysers and Hot Springs: Examples from the Whakarewarewa Geothermal Area, North Island, New Zealand. PALAIOS 2001;; 16 (1): 73–94. doi: https://doi.org/10.1669/0883-1351(2001)016<0073:MCOSSA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract Siliceous stalactites, formed of opal-A laminae that are concentrically arranged around a hollow soda-straw, are common features structures in some of the geyser and hot spring deposits at Whakarewarewa and other geothermal areas of New Zealand. These siliceous stalactites contain diverse biota of bacteria (including cyanobacteria), fungi, and diatoms that lived on the stalactite surfaces, with locally abundant pollen grains, and springtails. The microbes are the templates for much of the opaline silica precipitation and thereby controlled most of the fabrics that form the stalactite laminae.Siliceous stalactites form at sites of dripping water below the overhanging edges of geyserite rims that surround geyser vents, and along the steep margins of sinter terraces on discharge aprons. Stalactites may hang as isolated individuals or may coalesce to form dripstone draperies along terrace or rim margins. Stalactite growth is controlled by the volume, temperature, and the silica concentration of the water supplied to the growth site. These waters mainly originate from geyser or hot spring discharge. The microbes preserved in the stalactites, however, imply that silica precipitation took place after these waters had cooled.The growth and coalescence of geyser stalactites to form complex dripstone draperies plays an important role in the lateral accretion of sinter around the rims of many geysers and in progradation of sinter terraces. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

中国西南部三江造山帯における地熱地帯及び温泉型金鉱床の地質と地化学的特徴

中国西南部三江造山帯における地熱地帯及び温泉型金鉱床の地質と地化学的特徴

Microscopic Physical Biomarkers in Carbonate Hot Springs: Implications in the Search for Life on Mars

Physical evidence of life (physical biomarkers) from the deposits of carbonate hot springs were documented at the scale of microorganisms—submillimeter to submicrometer. The four moderate-temperature (57 to 72°C), neutral pH springs reported on in this study, support diverse communities of bacteria adapted to specific physical and chemical conditions. Some of the microbes coexist with travertine deposits in endolithic communities. In other cases, the microbes are rapidly coated and destroyed by precipitates but leave distinctive mineral fabrics. Some microbes adapted to carbonate hot springs produce an extracellular polymeric substance which forms a three-dimensional matrix with living cells and cell remains, known as a biofilm. Silicon and iron oxides often coat the biofilm, leading to long-term preservation. Submicrometer mineralized spheres composed of calcium fluoride or silica are common in carbonate hot spring deposits. Sphere formation is biologically mediated, but the spheres themselves are apparently not fossils or microbes. Additionally, some microbes selectively weather mineral surfaces in distinctive patterns. Hot spring deposits have been cited as prime locations for exobiological exploration of Mars. The presence of preserved microscopic physical biomarkers at all four sites supports a strategy of searching for evidence of life in hot spring deposits on Mars.

Analysis of simulated advanced spaceborne thermal emission and reflection (ASTER) radiometer data of the Iron Hill, Colorado, study area for mapping lithologies

The advanced spaceborne thermal emission and reflection (ASTER) radiometer was designed to record reflected energy in nine channels with 15 or 30 m resolution, including stereoscopic images, and emitted energy in five channels with 90 m resolution from the NASA Earth Observing System AMI platform. A simulated ASTER data set was produced for the Iron Hill, Colorado, study area by resampling calibrated, registered airborne visible/infrared imaging spectrometer (AVIRIS) data, and thermal infrared multispectral scanner (TIMS) data to the appropriate spatial and spectral parameters. A digital elevation model was obtained to simulate ASTER‐derived topographic data. The main lithologic units in the area are granitic rocks and felsite into which a carbonatite stock and associated alkalic igneous rocks were intruded; these rocks are locally covered by Jurassic sandstone, Tertiary rhyolitic tuff, and colluvial deposits. Several methods were evaluated for mapping the main lithologic units, including the unsupervised classification and spectral curve‐matching techniques. In the five thermalinfrared (TIR) channels, comparison of the results of linear spectral unmixing and unsupervised classification with published geologic maps showed that the main lithologic units were mapped, but large areas with moderate to dense tree cover were not mapped in the TIR data. Compared to TIMS data, simulated ASTER data permitted slightly less discrimination in the mafic alkalic rock series, and carbonatite was not mapped in the TIMS nor in the simulated ASTER TIR data. In the nine visible and near‐infrared channels, unsupervised classification did not yield useful results, but both the spectral linear unmixing and the matched filter techniques produced useful results, including mapping calcitic and dolomitic carbonatite exposures, travertine in hot spring deposits, kaolinite in argillized sandstone and tuff, and muscovite in sericitized granite and felsite, as well as commonly occurring illite/muscovite. However, the distinction made in AVIRIS data between calcite and dolomite was not consistently feasible in the simulated ASTER data. Comparison of the lithologie information produced by spectral analysis of the simulated ASTER data to a photogeologic interpretation of a simulated ASTER color image illustrates the high potential of spectral analysis of ASTER data to geologic interpretation.