Vent chimneys

Sometimes, the vents have what scientists call chimneys on them. These chimneys are formed when the super hot, chemical-filled water hits the almost freezing seawater and some of the dissolved chemicals precipitate out of solution. Some vent chimneys... 

Deposits which are forming are frequentiy characterized by venting streams of hot (300°C) mineralized fluid known as smokers. These result in the local formation of metalliferous mud, rock chimneys, or mounds rich in sulfides. In the upper fractured zone or deep in the rock mass beneath the vents, vein or massive sulfide deposits may be formed by the ckculating fluids and preserved as the cmstal plates move across the oceans. These off-axis deposits are potentially the most significant resources of hydrothermal deposits, even though none has yet been located. 

Regulatory control is governmental imposition of limits on emission from sources. In addition to quantitative limits on emissions from chimneys, vents, and stacks, regulations may limit the quantity or quality of fuel or raw material permitted to be used the design or size of the equipment or process in which it may be used the height of chimneys, vents, or stacks the location of sites from which emissions are or are not permitted or the times when emissions are or are not permitted. Regulations usually also specify acceptable methods of test or measurement. 

Unvented kerosene and gas space heaters leaking chimneys and furnaces back-drafting from furnaces, gas water heaters, woodstoves, and fireplaces automobile exhaust from attached garages environmental tobacco smoke. Humans are normally the main indoor source of carbon dioxide. Unvented or imperfectly vented combustion appliances can also increase indoor COj concentrations. 

Gas-Fired water heaters are also made more efficient by a variety of designs that increase the recov-ei y efficiency. These can be better flue baffles multiple, smaller-diameter flues submerged combustion chambers and improved combustion chamber geometry. All of these methods increase the heat transfer from the flame and flue gases to the water in the tank. Because natural draft systems rely on the buoyancy of combustion products, there is a limit to the recovery efficiency. If too much heat is removed from the flue gases, the water heater won t vent properly. Another problem, if the flue gases are too cool, is that the water vapor in the combustion products will condense in the venting system. This will lead to corrosion in the chimney and possible safety problems. 

Chimneys, Vents, Fireplaces, and Solid Fuel Burning Appliances 211... 

Central Manus Basin Vienna Woods (3° ID S, 150°17 E) 2500 2-km-wide axial rift graben of the northeast spreading center. Mostly massive pillow lava floor. Sulfide chimneys up to 20 m high are venting clear, milky and black fluids. Sulfate smokers are also present. Sphalerite, wurtzite, pyrite, marcasite, chalcopyrite, galena, amorphous silica, barite. Sulfate chimney anhydrite, silica, barite. 

Eastern Manus Basin Pacmanus field (3°42 S, 151°42.6 E) 1650 Crest of a prominent ridge of dacite flows and domes called Pual Ridge which exists in pull-apart basin. 4-m-high sulfide chimneys venting smoke (no temperature information). Only one ore chip (1 cm) was recovered. Cohesive anhydrite, chalcopyrite, bomite, tennantite and sphalerite. 

Western Woodlaik Basin Franklin Seamount (9°55 S, 151L50 W) 2143-2366 Westernmost propagating tip of spreading center. Basaltic andesite and inferred sodic rhyolite. Spires aud mounds of Fe-Mn-Si oxide up to several meters thick and 200 m in extent. Venting 20-30 C clear solution. Inactive barite silica chimneys contain up to 21 ppm Au. vSi-bearing Fe oxyhydroxide. 

North Gorda Ridge 2700 small vent fields relict chimneys, 247°C sulfide vent ... 

Farrell and Holland (1983) cited ba,sed on Sr isotope study on anhydrite and barite in Kuroko deposits that the most appealing model for the formation of Kuroko strata-bound ores would seem to entail precipitation of the minerals from a hydrothermal solution within the discharge vent or in the interior of a hydrothermal plume formed immediately below above the vent exit in the overlying seawater (Eldridge et al., 1983). The study on the chimney ores from Kuroko deposits support this model which is discussed below. 

Fig. 2.45. Hypothetical mineral paragenesis for a sulfide-sulfate-silica chimney. Approximate temperature ranges for different minerals are based on direct measurements of vent fluid temperatures and analyses of fluid inclusions in real chimneys (Hannington et al., 1995).

Shanks, W.C. Ill and Seyfried, W.E. Jr. (1987) Stable isotope studies of vent fluids and chimney minerals. SJFR. J. Geophys. Res., 92, 11387-11399. 

Routine Vents General ventilation (factory atmosphere) Local extraction (dust, fumes, odour) Flare stacks Normal flaring Chimney... 

NFPA requirements state that if equipment or process vessels, columns of tanks are suitably constructed of substantial steel construction adequately grounded, and do not give off flammable vapors, no other mechanism of lighting protection is required. This is also true of flares, vent stacks and metal chimneys by nature of their construction and grounding facilities. 

The ridge crest is a dynamic setting in which volcanic activity creates new vents while old ones die. On fast-spreading centers, hydrothermal circulation supports focused discharges through chimneys that have an average life span of a few decades. 

---