Sulfide Chimneys Research Articles

Mineralogy and chemistry of metalliferous muds forming the topstratum of a massive sulfide‐metalliferous sediment sequence from East Pacific rise 18°S: Its origin and implications concerning the formation of ochrous sediments in cyprus‐type deposits

A stratified mound surrounding a massive sulfide chimney was sampled on the East Pacific Rise (EPR) at 18°S and studied with respect to its mineralogical and chemical composition. A tripartite succession was observed, composed—from bottom to top—of massive sulfides, sulfidic debris, and metalliferous mud. These types of sulfide deposits differ from each other significantly by the quantity of ore and gangue minerals, texture, and grain size. Different modifications of Fe disulfides, pyrrhotite, sphalerite, Cu‐Fe‐sulfides, and Zwischenprodukt (intermediate compounds) make up the sulfidic portion of the mineral assemblage. Ferrihydrite was formed during the incipient stages of oxide precipitation and was diagenetically altered to goethite. The reaction of ferrihydrite with silica of hydrothermal and, to a lesser degree, biogenic origin, resulted in the formation of nontronite, which is the only phyllosilicate recognized in this argillaceous rock. In the case of prevailing sulfidic debris, the material may be...

Geology, mineralogy, and chemistry of sediment-hosted clastic massive sulfides in shallow cores, Middle Valley, northern Juan de Fuca Ridge

Middle Valley is a sediment-covered rift near the northern end of Juan de Fuca Ridge. Hydrothermal fluids are presently being discharged at two vent fields about 3 km apart, Bent Hill and the area of active venting. The hydrothermally active chimneys at both Bent Hill and the area of active venting consist of anhydrite and Mg-rich silicates with minor pyrite, Cu-Fe sulfide, sphalerite, and galena. Hydrothermal discharge in these areas appears to be focused along extensional faults. At the Bent Hill massive sulfide deposit, clastic sulfide layers are interbedded with hydrothermally altered and unaltered hemipelagic and turbiditic sediment along the flanks of the sulfide mound. Sulfide textures and mineralogy suggest that the Bent Hill sulfide mound formed by the build-up and collapse of sulfide chimneys, the resedimentation of sulfide debris and the formation of clastic sulfide layers, and the infilling and replacement of clastic sulfides by hydrothermal fluids near vents. Sulfur isotope values that are consistently more positive than basaltic sulfur support the addition of seawater sulfur. Pb isotope values for the Bent Hill deposit that are transitional between midocean ridge basalt (MORB) and Middle Valley sediments indicate that the sulfides probably formed from fluids which originated in the oceanicmore » crust but which have been modified by reaction with lower temperature (<274 C) fluids generated in the sedimentary pile, similar to those now venting in Middle Valley.« less

Drilling successful from ROV Ventana

Cores of granite and deformed sediment from the walls of Monterey Canyon were successfully recovered from December 30 to 31, 1992, by Monterey Bay Aquarium Research Institute's (MBARI) Remotely Operated Vehicle (ROV) Ventana using a small‐diameter, double‐barrel drill with a diamond bit. This HSTR (Holloway‐Stakes‐Tengdin‐Rajcula) drill was developed to drill cores horizontally from sulfide/sulfate walls of active black smokers. The drill was first successfully used by the submersible Alvin in October 1991 to drill into massive sulfide chimneys, on the Juan de Fuca Ridge (Eos, June 30, 1992, p. 273), and it was subsequently used with equal success on the chalcopyrite‐rich chimneys from 21°N and 9°N on the East Pacific Rise. The recent December dives, however, marked the first time that drilling has ever been attempted from the smaller ROV and the first time coring into the harder igneous rock substrate has been attempted.

Volcanism, age, and hydrothermal deposits of the West Valley Segment, Juan de Fuca Ridge

West Valley is a rift valley that forms part of the northernmost segment of Juan de Fuca Ridge. The valley is about 8 km wide, has a relief of 400–800 m along the valley walls, and has been interpreted to have formed recently by tectonic collapse. As part of a comprehensive study of West Valley, photographic images were obtained using a deeply towed camera sled containing a black and white video camera and a colour 35 mm camera. Photos were analyzed for volcanic form and type, tectonic features, and the relative age of the sea floor. Pillow and lobate lavas were the most common flow types observed. Based on sediment cover and an estimate of the hemipelagic sedimentation rate, the flows may be as young as a few hundred to as old as 2000 years. The youngest lavas are associated with small axial volcanoes that form an en echelon pattern within the valley. Newly discovered hydrothermal sulphide mounds and chimneys are spatially associated with moderately young pillow and lobate flows near the base of a small axial volcano. The area is moderately tectonically disrupted, with the most pervasive tectonism localized at the margins of the valley.

Petrology and geochemistry of back-arc basin basalts from Lau Basin spreading ridges at 15�, 18� and 19�S

Fresh back-arc basin lavas were recovered during five dives of the submersible ‘Mir’ during the 1990 cruise of the research vessel ‘Akademik Mstislav Keldysh’ to the Lau Basin. Three dives were conducted on the central spreading center of the ‘King's Triple Junction’ (KTJ) in the northeastern part of the Lau Basin east of Niuafo'ou Island at approximately 15°S. The lavas from the KTJ can be divided into types I and II based on their similarities to N-MORB and the BABB magma type ofSinton andFryer (1987) respectively. One dive each was made on the Central Lau Spreading Center (CLSC) at 18°S and the Eastern Lau Spreading Center (ELSC) at 19°S. Lavas sampled on the CLSC were associated with active hydrothermal sulphide chimneys occurring at the base of a collapsed caldera structure on the central volcanic axial high. Sampled lavas from both the CLSC and ELSC are all of type I geochemistry. The results of the ‘Keldysh’ 90 cruise are integrated with previous work to evaluate the geochemical characteristics of the Lau Basin crust as a whole and geochemical zonation models for back-arc basin development. An important part of this review of Lau Basin basalt geochemistry is the recognition of boninites and rocks of boninitic affinity which occur at off-ridge locations throughout the Lau Basin. These are suggested to erupt during the initial stages of development of new spreading ridges associated with episodes of ridge jump or the propagation of back-arc spreading ridges into arc crust. Hf-Th-Ta systematics of the Lau Basin lavas are used to identify unmodified mantle source compositions and possible subduction-related enriched components. Unmodified mantle source compositions range from D-, N-, and E-MORB to OIB. All Lau Basin lavas show some evidence of enrichment by a H2O ± LILE ± LREE-enriched component, a slab derived hydrous fluid. The slab-derived fluid is not homogeneous in composition perhaps reflecting the presence or absence of a subducted sediment component. The sampled lavas from the KTJ confirm the uniqueness of the BABB magma type ofSinton andFryer (1987).

Radial growth rates and 210Pb ages of hydrothermal massive sulfides from the Juan de Fuca Ridge

Activities of 238U, 228Ra, 226Ra and 210Pb were determined in submarine hydrothermal massive sulfides by nondestructive, gamma-ray spectrometry. The samples were collected by the manned submersible DSRV “Alvin” from active hydrothermal fields on the Endeavour Segment and Axial Seamount of the Juan de Fuca Ridge. 210Pb activities are mostly below the equilibrium level with 226Ra, which is linearly correlated with the concentration of Ba, Sr and Ca in the deposits. The ratios of 226Ra to the alkaline earth elements indicate that hydrothermal alteration of the underlying oceanic crust is the dominant source of Ra in the sulfide deposits. The 210Pb/Pb ratios measured in many of the sulfides are higher than the ratio obtained for a basalt source of 210Pb, probably because of 210Pb ingrowth from 226Ra within the sulfide deposits. An isochron approach employing ratios of 210Pb/Pb and 226Ra/Pb yielded an initial 210Pb/Pb ratio in the range of 0–0.57 dpm/μg Pb, implying that the crustal residence time of the hydrothermal fluid in the Endeavour Segment is very short ( < 10 years) and that basalt alteration is the only source of the 210Pb and Pb. For the hydrothermal fluid in Axial Seamount, a residence time of 10–20 years is estimated on the basis of the initial 210Pb/Pb and 228Ra/ 226Ra ratios of a sulfide chimney. Both residence time estimates are consistent with the results of previous studies. We have estimated the upper limits of sample ages ranging from tens to a hundred years for 12 samples, with the remaining seven samples indicating ages close to or older than 150 years, the practical limit of the 210Pb/Pb dating technique. A concentrically sectioned sulfide chimney from Axial Seamount yielded mean radial growth rates ranging from a few tenths to a few mm/year based on gradients of 210Pb/Pb and 228Ra/ 226Ra activity ratios, whereas a similarly sectioned chimney from the Endeavour Segment, although collected from the top of an active “black smoker” vent, displayed no 210Pb or 228Ra activity. Our results have implications for the duration and periodicity of hydrothermal circulation and associated mineral deposition at mid-ocean ridges.

Consequences of phase separation on the distribution of hydrothermal fluids at ASHES Vent Field, Axial Volcano, Juan de Fuca Ridge

Recent studies of hydrothermal fluid chemistry at the Axial Seamount Hydrothermal Emissions Study (ASHES) vent field of Axial Volcano indicate separation of liquid and vapor phases during the migration of fluids to the seafloor. The brine phase liquid emanates from discrete sulfide chimneys, while fluid which has been through vapor phase separation flows diffusely from fissures in the surrounding basalt. One possible mechanism to explain this spatial segregation of the fluid phases is based on the relative permeability terms in the equations of two‐phase flow. A qualitative model for the distribution of fluids observed at ASHES is postulated in which brine phase fluids are confined within flow conduits by a surrounding relative permeability barrier, while vapor phase fluids flow diffusely into the surrounding host rock.

Southern Juan De Fuca Ridge and Escanaba Trough, Gorda Ridge: Comparison of Hydrothermal Deposits in Sediment-Free and Sediment-Covered Ridge Settings: ABSTRACT

Southern Juan De Fuca Ridge (SJDF) is a low-relief, sediment-starved ridge axis that has a total opening rate of 6 cm/year and is characterized by lobate and brecciated sheet flows and pillows of MORB composition. Sulfide deposits form at {approximately}2,200 m water depth and are concentrated within a narrow graben centered within the ridge axial valley. Solitary and coalesced chimneys (0.25 to 12 m high) rise directly from the basalt basement and are composed predominantly of Zn sulfide accompanied by Fe and Cu-Fe sulfide and traces of Pb sulfide. Anhydrite occurs as a minor phase in some chimneys. Sulfide chimneys were formed by rapid-venting of high temperature ({approximately}285{degree}C) fluids. These acidic fluids (pH {approximately}3.5) are enriched in Cl, Na, and Ca and are depleted in Cu and Zn. In contrast to SJDF, Escanaba Trough (ET) is spreading at {approximately}2.3 cm/year and has the high relief and axial graben morphology typical of the slow-spreading Mid-Atlantic Ridge. The floor of the axial valley is buried by up to 500 m of clay and terrigenous silt. Rare basement exposures reveal unbrecciated sheet flows and pillow basalts of MORB composition. Large chimney-topped sulfide mounds up to 20 m high and hundreds of meters inmore » extent occur at {approximately}3,250 m water depth at the base of sediment hills; sulfide veins, small chimneys, and clastic deposits occur on, and within, the sediment between hills. Two distinct sulfide types occur at ET. Pyrrhotite-rich sulfide is enriched in Fe, Cu, and As and is associated with low-velocity venting of warm (<220{degree} C) alkaline (pH {approximately}5.4) fluids that are currently depositing anhydrite and barite sinter deposits on top of the sulfide mounds.« less

Dynamic character of the hydrothermal vent habitat and the nature of sulphide chimney fauna

A major substratum for vent organisms on Juan de Fuca and Explorer Ridges of the northeast Pacific is the polymetallic sulphide chimney. The deposition processes and subsequent growth of such chimneys provide a dynamic and extreme habitat that changes rapidly. During initial venting stages, colonization must await stabilization of the chimney structure. As the porous anhydrite shell accumulates sulphide minerals, protection from direct hot water contact increases for organisms colonizing the outer walls while sufficient vent water still diffuses for the support of chemosynthesis. Vestimentiferan worms are found on small sulphide mounds but the active growth and collapse of anhydrite spires is a major source of disruption and mortality. High temperature venting and spire growth appear to attract alvinellid polychaetes which may be implicated in the process of strengthening and sealing the anhydrite spires. Fauna on the growing chimney is subject to changes in fluid flow patterns that can make the structure uninhabitable. Large chimneys are inhabited by more species indicating that a diversification of habitat results from variations in mineralization and fluid availability. Chimney fauna has become specialized in exploiting an unpredictable and unstable habitat in an extreme example of the control of biotic development by the physical environment.

An Atlantic hydrothermal plume: Trans‐Atlantic geotraverse (TAG) area, Mid‐Atlantic Ridge crest near 26°N

The physical characteristics of an Atlantic hydrothermal plume and its seafloor sources are described from the first data set of water column properties associated with a high‐temperature source area at a slow‐spreading oceanic ridge. The observations comprise five near‐bottom tows of a camera(color video and still)‐temperature sensor array through the buoyant portion and 23 conductivity‐temperature‐depth (CTD) profiles through the neutrally buoyant portion of the plume made at the Trans‐Atlantic Geotraverse Hydrothermal Field in the rift valley of the Mid‐Atlantic Ridge at 26°08′N, 44°49′W in July 1985. The source area is a mound up to 250 m wide and 50 m high constructed primarily of massive sulfides between depths of 3620 and 3670 m at the base of the east wall. Flow and discharge regimes systematically changed from the center to the edge of the mound. High‐temperature black smokers vented at fast rates (&gt;1 m/s) from discrete sulfide chimneys and at slow rates from fractures, and clear solutions vented at slow rates from diffuse sources in the inner zone of the mound; intermediate‐temperature blue‐white and white smokers vented at slow rates from discrete sulfide/sulfate chimneys, and clear solutions vented from diffuse sources in the middle zone; patchy, diffuse discharge of clear solutions through sulfide talus occurred in the outer zone. The diffuse discharge of clear solutions and the discrete discharge from the white smokers were observed to turbulently rise up to several meters above the seafloor where the discharge was laterally advected in prevailing laminar flow at several centimeters per second. A convective heat flux of 8.8×106 W for only the black smokers that vented from fractures was estimated by applying a buoyant plume model to temperature anomalies measured with the towed array; this value is intermediate between values estimated for entire vent fields at the fast‐spreading East Pacific Rise. Discharge from the black smokers rose to form the neutrally buoyant portion of the plume that was cold and fresh relative to surrounding seawater, where it attained density equilibrium between 190 and 350 m above the mound. In contrast, hydrothermal plumes observed in the Pacific were warm and salty relative to surrounding seawater. The difference is attributed to the effect on plume density of entrainment during rise through opposite salinity profiles that decrease downward in the Atlantic and increase downward in the Pacific, resulting in different temperature‐salinity compensations at neutral buoyancy. The temperature difference between the neutrally buoyant portion of the plume and surrounding seawater (negative for the Atlantic; positive for the Pacific) is not a unique function of convective heat flux from a source area, as a consequence of both the effect of the entrainment of salinity on plume density and the separation of diffuse and discrete components of discharge. The hydrothermal plume and the hydrothermal mound are inferred to have grown in size and complexity in response to the development of hydrothermal flow and discharge regimes for at least the past 104 years.

A novel eye in 'eyeless' shrimp from hydrothermal vents of the Mid-Atlantic Ridge.

Rimicaris exoculata is a shrimp that swarms over high-temperature (350 degrees C) sulphide chimneys at Mid-Atlantic Ridge hydrothermal fields (3,600 m). This shrimp lacks an externally differentiated eye, having instead a pair of large organs within the cephalothorax immediately beneath the dorsal surface of the transparent carapace, connected by large nerve tracts to the supraesophageal ganglion. These organs contain a visual pigment with an absorption spectrum characteristic of rhodopsin. Ultrastructural evidence for degraded rhabdomeral material suggests the presence of photoreceptors. No image-forming optics are associated with the organs. We interpret these organs as being eyes adapted for detection of low-level illumination and suggest that they evolved in response to a source of radiation associated with the environment of hydrothermal vents.

High-temperature, carbonate-hosted Ag-Pb-Zn(Cu) deposits of northern Mexico

The high-temperature, carbonate-hosted Ag-Pb-Zn(Cu) deposits of northern Mexico occur in thick carbonate-dominant Jurassic-Cretaceous basinal sedimentary sequences floored by Paleozoic or older crust. The districts lie within, or on the margins of, a major fold-thrust zone; structures parallel to the trends of this belt control mineralization in many districts. Altered and/or mineralized volcanic and intrusive rocks of Tertiary age are found in all but three of the districts; mineralization apparently occurred during a restricted period 47 to 26 m.y. ago.The deposits are characterized by irregular ore lenses that commonly reveal strong structural controls and are stratigraphically discordant. Orebodies are of three principal morphological types: mantos, chimneys, and pods and are composed of massive sulfides and/or calc-silicate skarn. Sulfide mantos and chimneys are enclosed within carbonate rocks and are generally remote from intrusive bodies. Sulfide mantos commonly grade downward into sulfide chimneys, which may in turn grade downward into skarn chimneys cored by dikes. Podiform skarn and sulfide orebodies principally occur along stock, dike, or sill contacts, but they may also be developed at some distance from an intrusive contact. The associated intrusions are not widely mineralized.Despite the variations between ore types, major similarities are seen in structural controls, host-rock characteristics, and sulfide mineralogy. Structural controls include intrusive contacts, faults, fold axes, fractures, fissures, and cavern zones. Intrusive contacts and intrusion-related faults are most important in the skarns, whereas regional fault, fold, and fracture systems are dominant controls on mantos and chimneys. Mineralization commonly occurs below relatively impermeable shaly units, sills or volcanic rocks, but some extensive orebodies show remarkable restriction to specific horizons within apparently homogeneous carbonate successions. Studies of mineralized and unmineralized strata have found no consistent links between ore deposition and carbonate composition, facies, organic content, or insoluble components. However, zones of secondarily enhanced porosity and permeability induced by recrystallization, heating, deformation, or hydrothermal dolomitization are important mineralization controls.Geochemical data for the deposits are sparse but indicate strongly contrasting conditions among some of the major districts. Fluid inclusion data indicate temperatures in the range 200 degrees to 500 degrees C and salinities ranging from i to 60 equiv wt percent NaCl. The hotter, more saline, solutions are typically from skarn zones. Evidence for boiling has not been reported. The skarn ores of Naica, Concepcion del Oro, and Velardefia show tight clustering of sulfide sulfur isotope values near 0, whereas the skarn and massive sulfide ores of Santa Eulalia show a wide range of values. In most cases there is isotopic disequilibrium between galena and sphalerite, pyrrhotite, or pyrite. Calcite veinlet stockworks above mineralization and limestone wall rocks adjacent to mineralization show shifts of carbon and oxygen isotopes to lighter values. The tightly clustered sulfur isotopes and high-temperature, high-salinity fluid inclusions have been interpreted as indicating a strong magmatic component in the mineralizing fluids at Naica, Concepcion del Oro, and Velardena, but Santa Eulalia and other districts show evidence suggesting extensive mixing between magmatic and meteoric fluids.It appears that the spectrum of mineralization styles shown by these deposits represent differing responses to variations in intrusive associations, depth of emplacement, host-rock characteristics, and geochemical evolution of the individual systems.

Hydrothermal sulfide and oxide deposits on seamounts near 21°N, East Pacific Rise

Hydrothermal deposits were sampled by submersible from the calderas and summit benches of two seamounts 20 and 30 km west of the East Pacific Rise at 21°N. The deposits document a wide variety of off-axis hydrothermal activity, including samples from the interiors of seafloor sulfide deposits. In contrast to most mid-ocean ridge deposits, sulfide deposits on Green Seamount are rich in Si, Fe, and Cu, are poor in Zn, and contain abundant quartz. Sulfide chimneys grew by quenching of hydrothermal fluids and deposition of walls of colloform pyrite, marcasite, Zn sulfide, and minor galena, whereas coarse-grained pyrite and chalcopyrite were deposited at higher temperatures (>250 °C) in chimney interiors. As chimney walls grew outward into sea water, increased temperatures in the inner walls resulted in recrystallization to pyrite and deposition of pyrite and chalcopyrite in pore space. Cooling in the outer portions of chimneys caused deposition of opal at temperatures of about 80–170 °C. As chimneys coalesced and opal-rich material was heated in the interiors of sulfide edifices, opal was recrystallized to chalcedony and quartz. Faulting has exposed the interiors of sulfide deposits, where further recrystallization and deposition of chalcopyrite and quartz occurred at temperatures of 230–320 °C. Clogging of chimneys, changes in flow paths, and cooling of the deposits led to the deposition of late mixed-layer illite-smectite, iron sulfides, Fe-poor sphalerite, opal, and barite. The sulfide deposits formed over a time span of at least 140,000 to 70,000 yr ago, probably coincident with caldera and pit crater formation. The ages of the sulfide deposits provide constraints on the last volcanic and tectonic activity, and they also suggest that it took a maximum of ∼260,000 yr for the seamount to reach its present height. Red Seamount is presently hydrothermally active, and deposits consisting predominantly of amorphous Fe-oxyhydroxide are forming on small pillow cones in the caldera at temperatures of 10–15 °C. Hydrothermal nontronite deposits capped by Mn-oxide crusts cover much of the southern summit bench of Red Seamount and formed at temperatures of around 30 °C. Iron-rich talc and sulfide grains in nontronite provide evidence of former high-temperature activity and suggest that a sulfide deposit is present nearby.

Solid insoluble bitumen in the Magmont West orebody, Southeast Missouri

Solid bitumen (here used to refer to an altered, insoluble crude oil) occurs as black blebs and fracture fillings in the Magmont West orebody of the Viburnum Trend. Today, the bitumen is hard, brittle, and insoluble, but streamers show that in the past it was soft and viscous. In open cavities many of the blebs line up preferentially along organic-rich layers in the dolostone suggesting (though not proving) that the bitumen was sweated out of the organic-rich layers. This preferential alignment, plus the presence of sulfide chimneys, indicates that the bitumen is probably derived from an oil that was immobilized in the act of primary migration from the Cambrian Bonneterre Formation.The bitumen that we observed was most commonly found on the surface of galena and sphalerite crystals. Some bitumen was encased in calcite and dickite which are both generally considered to have formed after lead-zinc mineralization. Thus, paragenetically the bitumen is late and may have even been generated after mineralization.Elemental analyses show the blebs to be predominantly hydrocarbons with an H/C atomic ratio of around 1.4 and an NSO content of 2.6 percent. Pyrolysis gas chromatography of the blebs yields normal alkanes with up to 26 carbon atoms and no odd or even carbon preference. Trace element composition of the bitumen blebs shows enrichment in Zn, Pb, and Cu. The blebs were probably derived from a crude oil that was generated near the end of mineralization and later condensed into an insoluble macromolecular material.

Drilling the Snake Pit hydrothermal sulfide deposit on the Mid-Atlantic Ridge, lat 23°22′N

Research Article| December 01, 1986 Drilling the Snake Pit hydrothermal sulfide deposit on the Mid-Atlantic Ridge, lat 23°22′N: Ocean Drilling Program Leg 106 Scientific Party* Ocean Drilling Program Leg 106 Scientific Party* Ocean Drilling Program Leg 106 Scientific Party* Search for other works by this author on: GSW Google Scholar Geology (1986) 14 (12): 1004–1007. https://doi.org/10.1130/0091-7613(1986)14<1004:DTSPHS>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Ocean Drilling Program Leg 106 Scientific Party*; Drilling the Snake Pit hydrothermal sulfide deposit on the Mid-Atlantic Ridge, lat 23°22′N: Ocean Drilling Program Leg 106 Scientific Party*. Geology 1986;; 14 (12): 1004–1007. doi: https://doi.org/10.1130/0091-7613(1986)14<1004:DTSPHS>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 SocietyGeology Search Advanced Search Abstract A major high-temperature hydrothermal area has been discovered in the Mid-Atlantic Ridge rift valley about 25 km south of the Kane Fracture Zone. The vent field consists of u wide area (>40000 m2) of dark hydrothermal deposits, numerous sulfide chimneys and mounds, some up to 11 m high, and high-temperature “black-smoker” vents. Ten shallow holes, the first ever drilled in an active submarine hydrothermal area, recovered friable, unconsolidated Fe, Cu-Fe, and Zn sulfides and several large fragments of massive sulfide (mainly chalcopyrite) from the locally thick (>13 m) hydrothermal deposits. The vents are also associated with an unusual biological community of smaller, more mobile organisms than reported from the East Pacific Rise. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Growth of ‘black smoker’ bacteria at temperatures of at least 250 °C

Complex communities of thermophilic bacteria have been cultured from the 350 °C waters emanating from sulphide chimneys, or ‘black smokers’, at 21 °N along the East Pacific Rise1. Several of the bacterial communities were shown to grow rapidly at 100 °C and atmospheric pressure, producing methane, hydrogen gas and carbon monoxide. These gases are found in superheated vent water, having previously been attributed to abiogenic reactions. Before concluding that these ‘black smoker’ bacteria actually contribute to the chemistry of the superheated hydrothermal fluids, it was necessary to test their ability to grow and produce gases at in situ vent temperatures and pressures. Here we report that a bacterial community originally cultured from 306 °C water is capable of chemolithotrophic growth in a titanium growth chamber under in situ vent pressure of 265 atm and at temperatures of at least 250 °C. (At 265 atm, seawater remains liquid at temperatures of at least 460 °C2.) Transmission electron microscopy of thin sections of bacteria cultured at 250 °C has revealed the presence of at least two morphologically distinct organisms.

Intense hydrothermal activity at the axis of the east pacific rise near 13�N: Sumbersible witnesses the growth of sulfide chimney

A submersible study of a fast spreading (12 cm yr-1) Mid-Ocean ridge segment (East Pacific Rise near 12°50′ N) led to the discovery of intense hydrothermal activity. Twenty four sites with active vents and sixty inactive hydrothermal deposits were found within a narrow graben averaging about 300 m in width along a 20 km long segment of the ridge crest. The graben is floored with fresh basaltic sheet flows including collapsed pits or lava lake structures. From both deep towed camera stations and manned submersible observations, it is estimated that the average spacing between the ridge axis hydrothermal deposits averaging in size 10–50 m in diameter lies between 100 to 200 m.

Is the CH4, H2 and CO venting from submarine hydrothermal systems produced by thermophilic bacteria?

Submarine hydrothermal vents are a major source of methane to the oceans1,2. The methane, as well as H2 and CO, are generally believed to result from degassing of the mantle or from abiogenic water–rock reactions1, a conclusion supported by direct correlations between 3He and CH4, and generally between CH4, H2 and CO and dissolved silicate in hydrothermal waters2,3. An alternative source for these gases might be microbiological. This would imply that active bacterial communities exist in deep-sea hot water environments, some of which have temperatures exceeding 100 °C; this inference is without precedent. We have now found that the super-heated waters emanating from sulphide chimneys at 21 °N along the East Pacific Rise and samples from the sulphide chimneys themselves harbour complex communities of bacteria capable of growing with generation times of 37–65 min, producing CH4, CO, H2 and traces of N2O in media containing S2O2−3, Mn2+ and Fe2+ as energy sources, and oxidizing CH4, at 100 ± 2 °C at 1 atm. These microbial communities consist of three to five morphologically distinct types and include both oxidative and anaerobic species. These mixed cultures will not grow at temperatures below 70–75 °C. Even though some of the communities originated from water of temperatures >300 °C, it is not known if they can grow and produce CH4, CO and H2 in super-heated waters kept liquid due to hydrostatic pressure. The discovery of these obligately thermophilic, gas-producing and consuming bacterial communities associated with submarine volcanic environments has interesting and important implications for prokaryotic evolution, marine geochemistry, industrial microbiology and exobiology.

Sulfide precipitates at 21°N on the East Pacific Rise: 226Ra, 210Pb and 210Po

Sulfide samples collected by the deep submersible ALVIN from hydrothermal vents at 21°N on the East Pacific Rise have extremely variable contents of uranium series nuclides. In samples we have analyzed, 210Pb and 210Po activities vary by more than an order of magnitude within the same vent. In two out of three samples measured 210Po activities are higher than the parent 210Pb activities. Consideration of 210Pb/Pb in particulate sulfide filtered from hot vent water indicates that the lead in these deposits has a basalt as opposed to a seawater origin. Comparison of 210Po and 210Pb contents of active and inactive vent particulates suggests that the cycle of buildup, cessation and decay by oxidation of these sulfide chimneys is measured in tens to a few hundreds of years.