Deep-sea volcanism

Huber, J. A., D. A. Butterfield and J. A. Baross, 2003, Bacterial diversity in a sub-seafloor habitat following a deep-sea volcanic eruption. FEMS Microbiology Ecology 43, 393 109. 

Deep-sea volcanism including the weathering of deep-sea basalt. 

Holden, J.F., Summit, M. and Baross, J.A. (1998) Thermophilic and hypethermophilic microorganisms in 3-30 degrees C hydrothermal fluids following a deep-sea volcanic eruption. FEMS Microbiology Ecology, 25, 33-41. 

Deep-sea volcanism is also a source of environmental Cd release, but the role of this process in the global Cd cycle remains to be quantified (WHO 1992a). 

Cadmium is widely distributed in the earth s crust at an average concentration of about 0.1-0.2 mg/kg and is commonly found in association with zinc. Volcanic activity is major natural source of cadmium release to the atmosphere. The annual global flux from this source has been estimated to be 820 tons. Deep sea volcanism is also a source of environmental cadmium release, but the role of this process in the global cadmium cycle remains to be quantified (OECD, 1994). About 10-15% of total airborne cadmium emissions arise from natural processes (WHO, 1992a). 

Roberts, D.G., Mortin, A C. and Backmann, J. (1984) Late Paleocene-Eocene volcanic events in the northern North Atlantic ocean. Washington, D.C. U.S. Gov. Printing Office. Initial Report Deep Sea Drilling Project, 81, 913-923. 

Gieskes JM, Lawrence JR (1981) Alteration of volcanic matter in deep sea sediments Evidence from the chemical composition of interstitial waters from deep sea drilling cores. Geochim Cosmochim Acta 45 1687-1703... 

We summarize noble gas amounts in deep-sea and subaerial sediments in Figure 5.1. From the data displayed here, we calculated median values which are shown in Table 5.1. Both Figure 5.1 and Table 5.1 show that even though there is little difference in the lighter noble gas concentration between subaerial and deep-sea sediments (He, Ne, and Ar), heavier noble gases are much more abundant in subaerial sediments than in deep-sea sediments. As in volcanic rocks (cf. Section 6.6), most sediments, either deep-sea or subaerial, show fractionation toward the heavier ones relative to air noble gas, although the mechanism for the fractionation may be different. Figure 5.2 shows noble a gas elemental abundance pattern relative to the air abundance subaerial sediments show much more severe fractionation. 

Marine processes. Sea water reacts with ocean-bed sediments containing volcanic ash, or biogenic silica from Radiolarians, to form zeolites. This process is common in deep-sea sediments and phillipsite makes up 80% of the sediment in the Indian and Pacific Oceans. Clinoptilolite is abundant in Atlantic sediments and both phillipsite and clinoptilolite are found in manganese nodules on the ocean beds. 

Scheidegger, K. F., Volcanic ash layers in deep-sea sediments and their petrological significance, Earth Planet. Sci. Lett., 17, 397-407 (1973). 

The fact that basaltic volcanism is widespread in the deep sea is established and well proved. This volcanism is present in most areas of the deep sea and especially concentrated on spreading ridges. 

Part of the volcanism in the deep sea produces volcanic ash — small glassy splinters of basaltic matter, which widely occur in deep- sediments. This material (called pyroclastica) weathers relatively quickly because of its instable glassy structure and large surface. How far it contributes to the manganese supply of the deep sea, we cannot say yet, but Beiersdorf considers that it plays a dominant role in the creation of manganese nodule fields. 

Manganese nodules result from the precipitation of manganese and iron hydroxides from sea-water or pore-water around an offered nucleus. Nuclei available in the deep sea are pieces of volcanic material (balsalt, pumice) (Fig. 6) or apatitic fossils (shark teeth (Fig. 7), auditory canals of whales). 

The area where the sediments settle down is a deep sea plain, somewhat deeper than 5000 m, interrupted by munerous steep hills of volcanic origin, usually a few hundred of meters high. 

Table 2 Comparison of fission track ages and potassium-argon ages of volcanic material in deep-sea sediments.

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