Encyclopedia of Marine Geosciences

Living Edition
| Editors: Jan Harff, Martin Meschede, Sven Petersen, Jörn Thiede

Black and White Smokers

  • Margaret K. TiveyEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-94-007-6644-0_5-1

Keywords

Hydrothermal Fluid Spreading Center Black Smoker Volcanogenic Massive Sulfide Lost City 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Synonyms

Definition

Black and white smokers. Chimney-like edifices composed of mixtures of copper-, iron-, and zinc-sulfide minerals and calcium- and barium-sulfate minerals. They form as very hot (up to ~400 °C or 750 °F) fluids exit very young seafloor and mix with cold seawater, with the high-temperature fluids passing through channels within the edifices into the deep ocean.

Introduction

Black and white smokers are the portions of seafloor hydrothermal vent deposits through which ~200 °C–400 °C hydrothermal fluids travel and exit into the deep ocean, <1,000–5,000 m below sea level. The hot fluids form as cold seawater percolates down into young, still hot seafloor near the spreading axes of the mid-ocean ridges and spreading centers in back-arc basins; during its transit, the seawater exchanges heat and undergoes chemical reactions with the young oceanic crust. The seawater loses oxygen and sulfate, becomes more acidic (pH decreases), and becomes enriched in metals (e.g., Fe, Mn, Cu, Zn, Pb) and hydrogen sulfide, and its temperature increases from ~2 °C to >400 °C (German and Von Damm, 2006). The hot fluid is very buoyant (because its density decreases to approximately two-thirds of the original density as it is heated to >400 °C) and rises rapidly to the seafloor, exiting at meter-per-second flow rates (Bischoff and Rosenbauer, 1985; Spiess et al., 1980; see “Hydrothermal Vent Fluids”). When the hot, metal- and sulfide-rich, oxygen-poor fluid exits and mixes with cold, sulfate-rich, metal-poor seawater, minerals precipitate rapidly as chimney-like edifices and as particles within plumes (with a smokelike appearance) above the edifice – see Fig. 1.
Fig. 1

Hot (347 °C) vent fluid exits multiple black smokers on the chimney edifice “Homer” near 17.5°S latitude on the southern East Pacific Rise (Courtesy Woods Hole Oceanographic Institution; M. Lilley and K. Von Damm chief scientists)

Discovery

Venting of hydrothermal fluids from the youngest portions of the seafloor along the mid-ocean ridges was first observed in 1977 along the Galapagos Rift where unusual biological communities were found associated with warm vent fluids (17 °C, much warmer than the surrounding 2 °C seawater); the presence of these warm fluids had been predicted based on measurements of heat flow (see “Oceanic Heat Flow: Thermal Models of the Lithosphere”) and bottom seawater thermal anomalies close to the mid-ocean ridge (Corliss et al., 1979). In 1978, massive sulfide deposits that likely formed from much higher temperature fluids were found near 21°N latitude on the East Pacific Rise about 650 m west of the spreading axis (Francheteau et al., 1979). The first actively venting black and white smokers were subsequently discovered in 1979, along the spreading axis of the East Pacific Rise (Spiess et al., 1980) not far from where the deposits were found a year earlier.

The hot fluids were observed exiting “stacks” or “chimneys” that were 1–5 m tall, composed of copper-, iron-, and zinc-sulfide minerals and the mineral anhydrite (calcium sulfate) (Spiess et al., 1980). The observed black chimneys, or black smokers, resembled organ pipes ≤30 cm in diameter and emitted hot (>350 °C) fluid with dark-colored (black) precipitates suspended within the exiting fluid (Spiess et al., 1980). The white chimneys, or white smokers, were covered with worm tubes (making them light-colored) and emitted cooler (<330 °C) fluids at slower flow rates with light-colored precipitates suspended within exiting waters (Spiess et al., 1980; Haymon and Kastner, 1981).

Formation of Black Smoker Chimneys

Black smoker chimneys form in two stages (Haymon, 1983; Goldfarb et al., 1983): (1) deposition of an anhydrite (CaSO4)-dominated wall as hot, calcium-rich vent fluid mixes turbulently with cold, sulfate- and calcium-rich seawater, followed by (2) deposition of a layer of sulfide minerals against the inner side of the anhydrite layer as the Stage 1 anhydrite wall prevents rapid mixing between the hot fluid flowing inside the chimney and the cold seawater present on the outside of the chimney. Chalcopyrite (CuFeS2) is dominant if temperature is >330 °C and pyrite (FeS2) and wurtzite ((Zn, Fe)S) occur at lower temperatures. Infiltration of seawater and hydrothermal fluid components across the porous wall also results in the deposition of sulfide and sulfate minerals and silica in the interstices of the wall, which gradually makes the chimney less porous and more metal-rich – see Fig. 2. Interaction of fluids and biota on chimney exteriors can also result in the formation of an iron-sulfide-rich outermost layer on the chimney (Juniper et al., 1992).
Fig. 2

Schematic drawing showing Stage 1 and Stage 2 growth of black smoker chimneys (After Haymon, 1983 and Goldfarb et al., 1983; figure from Tivey, 1998, courtesy Woods Hole Oceanographic Institution)

Rapid formation of the Stage 1 chimney wall (it can form at rates up to 30 cm per day; Goldfarb et al., 1983) is in part a consequence of anhydrite being an unusual mineral that is more soluble at low temperatures than at high temperatures; if seawater is heated to ~150 °C or greater, anhydrite precipitates (Bischoff and Seyfried, 1978). When the very hot vent fluid exits at meter-per-second velocities into seawater, mixtures above ~150 °C will be saturated in anhydrite, with the sulfate coming from seawater and the calcium from both the vent fluid and seawater (Styrt et al., 1981; Albarède et al., 1981). Metal sulfides and oxides (zinc sulfide, iron sulfide, copper-iron sulfide, manganese oxide, and iron oxide) also precipitate from the vent fluid and vent fluid/seawater mixtures as fine-grained particles. Some of these particles become trapped within and between grains of anhydrite within the Stage 1 chimney walls, giving the anhydrite, which is clear to white in its pure form, a gray to black color (Goldfarb et al., 1983; Haymon, 1983). The remaining particles form a plume of “smoke” above the chimney. Because bottom seawater is denser than the mix of seawater and hydrothermal fluid in the plume, the plume rises a few 100 m above the seafloor to a depth where it is of the same buoyancy as the surrounding ocean water (see “Hydrothermal Plumes”).

Once the initial anhydrite-dominated framework is in place, chalcopyrite (or chalcopyrite and pyrite or chalcopyrite and wurtzite for lower temperature black smokers) precipitates on the inner surface of the chimney. Observed young chimney walls are thin, less than a centimeter to a few centimeters, with one side of the wall very hot and one side much colder. The porous chimney wall is subject to steep gradients of temperature and concentrations of elements. As the chimney evolves, the innermost layer thickens (recovery of a chimney known to be only 1 year old had an innermost chalcopyrite layer that was ~1 cm thick; Koski et al., 1994). At the same time that the innermost layer is thickening, aqueous ions, including copper, iron, hydrogen, oxygen, sulfide, sulfate, zinc, sodium, chloride, and magnesium, are transported from areas of high to low concentrations (by diffusion). These elements also are carried by fluids flowing across the wall from areas of high to low pressure (by advection). As a result of these processes, minerals become saturated and precipitate in the pore spaces within the chimney walls, and favorable conditions for microorganisms are established in the outer parts of the chimney walls. In particular, within the chimney walls at temperatures less than ~120 °C, the steep temperature and concentration gradients provide combinations of reducing chemicals from vent fluids (hydrogen, hydrogen sulfide, ferrous iron) and oxidizing chemicals from seawater (oxygen, sulfate, ferric iron) that can be used by microorganisms (bacteria and archaea) as sources of energy (see “Chemosynthetic Life”; Jannasch, 1995). Larger organisms (e.g., alvinellids and paralvinellids; Haymon and Kastner, 1981; Juniper et al., 1992) also reside on the exteriors of chimneys, and their tubes can become incorporated into chimney walls – see Fig. 3. As the chimney grows, earlier-formed minerals, as they are exposed to hotter fluids, can be replaced by later-formed minerals.
Fig. 3

Photograph of a slab taken perpendicular to the open channel across a black smoker chimney that was venting 336 °C fluid, from the southern East Pacific Rise near 21.5°S. The innermost layer (~1 cm thick) is composed of chalcopyrite (gold in color), and the outer 0.5–3 cm layer is composed of a mixture of anhydrite and sulfide minerals (gray in color). The fossilized tube of an alvinellid is embedded in the chimney wall (right side of image) (Courtesy Woods Hole Oceanographic Institution)

Formation of White Smoker Chimneys

The style of mixing between vent fluid and seawater differs in chimneys that emit lower-temperature, white to clear fluids (~200–330 °C). One major reason for this is that the vent fluid is flowing more slowly. Because the fluid percolates less vigorously through the porous spires, a greater percentage of metal from the fluid precipitates within the deposit instead of being lost to the ocean within particle-laden plumes (e.g., Haymon and Kastner, 1981; Koski et al., 1994). Some of the white smoker chimneys are dominated by zinc- and iron-sulfide minerals, which form both an initial framework and infilling material (Koski et al., 1994 – see Fig. 4). Others contain abundant barite and silica, both as initial framework material and as infilling material, with barite then co-precipitating with silica and sulfide minerals (Hannington and Scott, 1988). Many white smokers lack anhydrite, consistent with a lack of entrained seawater as they form. In contrast to black smokers, where flow is rapid through open conduits of >1 cm diameter, flow in white smokers is through narrow, anastomosing conduits that seal over time, commonly diverting flow horizontally (Fouquet et al., 1993; Koski et al., 1994). Beehive structures or diffusers are another type of smoker found at some vent fields. They have a bulbous morphology, interior temperatures only slightly less than for black smoker chimneys, highly porous interiors, and high-temperature (relative to black and white smoker chimneys) exteriors (up to 70 °C; Fouquet et al., 1993; Koski et al., 1994). They form from less focused high-temperature fluids that exhibit slower flow rates than those from black smokers; as in white smoker chimneys, some flow is diverted and occurs through sides of these smokers (Fouquet et al., 1993; Koski et al., 1994). Within some vent fields, hot fluids are trapped beneath overhanging ledges, termed flanges; fluids percolate up through the porous flange layers or flow horizontally and “waterfall” upwards over the lip of the flange (Delaney et al., 1992).
Fig. 4

Left image is of white smoker chimneys (venting 250–300 °C fluids) from the Kremlin area on the TAG active hydrothermal mound at 26°N on the Mid-Atlantic Ridge (Courtesy of Woods Hole Oceanographic Institution; Peter Rona chief scientist); right image is a photograph of a slab taken perpendicular to the axis of one of the Kremlin chimneys, composed dominantly of zinc-sulfide – note the absence of large conduits and prevalence of very narrow channelways (Courtesy of Woods Hole Oceanographic Institution)

Carbonate-Rich Chimneys

Very different types of chimneys are found at the Lost City vent field, located 15 km from the axis of the Mid-Atlantic Ridge. The Lost City hydrothermal system is hosted in mantle rocks (peridotite and serpentinite – see “Peridotite”), and the venting fluids have a higher pH than seawater, low metal and sulfide concentrations, and low temperature (<100 °C) relative to black smoker and white smoker fluids (Kelley et al., 2005); the very tall spires being deposited from these fluids are composed of calcium carbonate and magnesium hydroxide minerals (calcite and/or aragonite (CaCO3) and brucite (MgOH2)) that are saturated in the high pH, carbonate- and hydroxide-rich fluids.

Summary and Conclusions

The morphologies of actively venting seafloor hydrothermal deposits and the composition and appearance of their hydrothermal plumes reflect the compositions of the fluids (hydrothermal fluid and seawater) from which they form, and the styles of flow and mixing of these fluids. “Black smoker” chimneys with conduit diameters of <2–10 cm form from very high-temperature (>330–400 °C) fluids that flow at rates of meters per second, and the turbulent mixing that results when this fluid exits into seawater results in the formation of particle-laden plumes reminiscent of black smoke. “White smoker” chimneys form from lower-temperature (~200–330 °C) vent fluids that flow less vigorously through anastomosing narrow conduits that can become blocked resulting in diversion of flow; a greater percentage of metals are trapped and deposited within these chimneys than within black smokers, and they tend to be richer in zinc because of the lower temperatures that result in saturation and precipitation of zinc-sulfide minerals.

Over time, collapse and incorporation of these different types of chimneys and flanges onto and into mounds, and subsequent reworking of this material as hot fluids flow through the mounds, forms larger deposits. These larger deposits (see “Volcanogenic Massive Sulfides” and “Marine Mineral Resources”) found along the mid-ocean ridges and along the spreading centers within back-arc basins are analogs for some types of ore deposits found on land (e.g., Cyprus-type massive sulfide ore deposits; Francheteau et al., 1979).

Cross-References

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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  1. 1.Marine Chemistry & Geochemistry, Woods Hole Oceanographic InstitutionWoods HoleUSA