My work in this area involves study of elemental inputs to the world's oceans during submarine volcanic eruptions. I have focussed specifically on the transfer of elements by a volatile-rich magmatic gas, which I believe can exert a significant control on the composition of sea water near erupting volcanoes. This is a relatively new concept that is not yet widely-accepted by marine scientists. Nevertheless, it is widely acknowledged that similar exchange processes are responsible for much of the geochemistry of aerosol plumes over erupting subaerial volcanoes and so it is merely an inference that the same should be true beneath the sea. It is more difficult to collect and analyze the effluents of submarine eruptions and this is an active research interest of mine. In both marine and subaerial environments, it is useful to first quantify the emission rate of the volatile radionuclide 210Po and then estmate emission rate of other chemical elements by determining their relative proportions in volcanic effluents.
    A second and much better understood mode of chemical transfer involves injection of hydrothermal fluids into the oceans, which takes place both during and between eruption (and for which analogous activity can also be found at subaerial volcanoes). This process involves the transfer of materials dissolved in hot aqueous solutions. The evidence that the two proceses both occur is strong and that they result in distinguishable compositional effects that can be seen in sea water collected near active submarine volcanoes.
    Below is the abstract for a paper I have on this subject in the Sept. 1997 issue (volume 61) of Geochimica et Cosmochimica Acta, a journal dedicated to the study of geochemistry of the earth and other planets.

Abstract- Recently, it has been reported that the element Po degasses from mid-ocean ridge and seamount volcanoes during eruptions. Published and new observations on other volatile metal and metalloid elements can also be interpreted as indicating significant degassing of magmatic vapors during submarine eruptions. This process potentially plays an important role in the net transfer of chemical elements from erupting volcanoes to sea water in addition to that arising from sea floor hydrothermal systems. In this paper, a framework is constructed for predicting and assessing semi-quantitatively the potential magnitude and chemical fingerprints in the water column of metal and metalloid degassing using (1) predictions from a summary of element volatilities during mafic subaerial volcanism world-wide and (2) limited data from submarine volcanic effusives. The latter include analyses of Po and trace metals in near-volcano water masses sampled following a submarine eruption at Loihi seamount, Hawaii (1000 m bsl) in 1996. The element volatility predictions and observations show good agreement, considering the limited data set. Some of the highest volatility main group and transition element enrichments in sea water over Loihi are predicted by the degassing mass transfer model I present. When expanded to cover all submarine volcanic activity, it is predicted that exit fluxes of these elements are up to 10²-10³ greater by degassing than by normal MOR hydrothermalism. In contrast, MOR exit fluxes of low volatility alkali and alkaline earth elements are likely 10²-10⁶ greater from hydrothermal inputs. Degassing inputs to the ocean are probably highly episodic, occurring almost entirely during eruptions; these are times of enhanced and "abnormal" hydrothermalism as well. Although major hydrothermal and degassing events may not be chemically recognizable in real water masses as wholly distinct entities, it is nevertheless possible to predict to what extent each process "flavors" the effluents of the other. Degassing at mid-ocean ridges may explain a variety of observations previously ascribed to "complexities" occurring during hydrothermal venting and/or fluid ascent in the buoyant hydrothermal plumes above ridges.

Related Figures (click on the image to display it full scale)

element volatilities	degassing vs hydrothermal exit fluxes	element behaviors

For more info on this topic, please see:

K.H. Rubin (1997) Degassing of Metals and Metalloids from Erupting Seamount and Mid-Ocean Ridge Volcanoes: Observations and Predictions, Geochim. et Cosmochim. Acta, 61, 3525-3542.

K.H. Rubin, J.D. Macdougall and M.R. Perfit, (1994) ²¹⁰Po-²¹⁰Pb dating of recent volcanic eruptions on the sea floor, Nature, 368, 841-844.

K.H. Rubin (1994) First Estimates of Elemental Fluxes to Sea Water Due to Direct Evaporation from Erupting Magmas using ²¹⁰Po-²¹⁰ Pb Radioactive Disequilibrium in Recently-Erupted 9.5 deg N EPR Lavas, Trans. Amer. Geophys. U, 75, 618.