GEOCHEMICAL CHARACTERISTICS OF HYDROTHERMAL SULFIDE AT THE PACIFIC RISE

The chemistry of the hydrothermal sulfide taken from the East Pacific Rise at 9°N—10°N (9°50.01'N, 104°17.44'W; at depth of 2200m), demonstrates that it is a kind of hydrothermal sulfide rich in Cu, Co, Se and poor in Pb, Mn, As, Cd, Ba, Au. The content of Cu has obvious positive correlation with Co, Se, Ag, Cd (R²>0.8), but negative correlation with Ca, Ba, Mn, Pb (R²>0.8). Changes in chemical composition is observed in different layers, and the content of rare earth elements gradually becomes higher from the inner to outer part, indicating different minerogenetic conditions in its growth process. On the other hand, the sulfide has a lower content of ∑REE, an obvious negative Ce anomaly and a slight LREE enrichment that is similar to seawater, indicating that the REE of the hydrothermal sulfide is originally from seawater.