COASTAL SUBMARINE HYDROTHERMAL ACTIVITY OFF NORTHERN BAJA CALIFORNIA.

Abstract

In situ observations of submarine hydrothermal activity have been conducted in Punta Banda, Baja California, Mexico, approximately 400 m from the coast and at a seawater depth of 30 m. Marked differences exist between the submarine hot springwater, local land hot springwaters, groundwater, and local seawater. SiO//2, HCO//3** minus , Ca, K, Li, B, Ba, Rb, Fe, Mn, As, and Zn are enriched in the submarine hot springwater, while Cl, Na, SO//4**2** minus , Mg, Cu, Ni, Cd, Cr, and perhaps Pb are depleted in relation to average and local seawater values. Very high temperatures, at the hydrothermal vents, have been recorded (102 degree C at 4-atm pressure). Visible gaseous emanations rich in CH//4 and N//2 coexist with the hydrothermal solutions. Metalliferous deposits, pyrite, have been encountered with high concentrations of Fe, S, Si, Al, Mn, Ca, and the volatile elements As, Hg, Sb, and Tl. The data and observations indicate that metal-rich marine sediments and marine ore-forming processes are a concurrent reality and that ores are being formed today in submarine areas of high convective heat flow where hydrothermal activity is the precursor for their occurrence.