Sea water-basalt interaction in the Pacific seamounts: Low-temperature environments

摘要

Volcanic rocks recovered during DSDP/ODP Legs 19 and 55 on the Emperor Seamount chain,ODP Legs 143 and 144 on the West Pacific Guyots, and DSDP Leg 62 on the Hess Rise are hawaiite, alkaline basalt, olivine basalt, tholeiitic picrite, basanite, ankaramite, tholeiiti(n) basalt, and trachyte. All studied rocks have been affected by alteration. The temperature of alteration depends on distance from high-temperature hydrothermal zones. Two types of alteration, oxidative and non-oxidative, were documented. The oxidative alteration of volcanic rocks is characterized by the presence of dioctahedral smectites, Fe-oxides and hydroxides.The non-oxidative alteration of volcanic rocks is characterized by trioctahedral smectite and calcite. Chlorite phases and serpentine are wide spread in basalts with high content of MgO. Illite and K-feldspar are present in alkali rocks. Kaolinite was identified in the laterite-weathered volcanic rocks. Low-temperature alteration of volcanic rocks from the Pacific seamounts due to sea water-rock interaction results in redistribution of Fe, K,Mn, Ca, Si, Mg, Sr, Zn, Na, Rb, and Ba.