Study On Hydrothermal Opal From Southwest Indian Ridge

Submarine hydrothermal activities,hydrothermal sulfide minerals and biological resources constitute a major research area in the current domestic and international marine science,which not only have important scientific significance,but also contain high economic value.Currently,the level of the exploitation and utilization of marine resources is very low;metallic minerals on the seabed have barely been developed.This situation forces people to attach importance to marine resources,and to accelerate the pace of doing research on marine resources.Samples used in this study are from the Fifth Leg,China's Ocean Voyage 20th,in the Southwest Indian Ocean Ridge.We select basalt and opal samples to do petrology mineralogy research,analysis of the geochemical elements(the main elements and trace elements)and electron probe analysis research.Opal samples were consisted of irregular grid hard crust and loose opal.Opals with different colors have different chemical composition.In the process of doing research on samples,we have found filaments structure which probably left by microbial action.The authorinfers that microbeshave playeda certain role in the formation process of opal.According to major elements,basalts are calc-alkaline basalts,belonging to low potassiumtholeiitic series.Magmatic crystallization differentiation degree is low.magma rised fast,arrived at the bottom of the sea,rapidly cooled and diagenesised.According to the Rare Earth Elements(REE),basalt samples have obvious characteristics of oceanic tholeiite,REE curves of opal are the same or similar with basalt samples and seawater,and have the same elementsof loss trends and characteristics.Combining previous study of the fluid inclusions of opal,we infered that magma probaly had gas effect in the process of rising;in the process of through the deep-sea sediment,hydrothermal fluid had probaly overflowed with organic matter in the reaction,and mixed with seawater.The extrusive sea with heat transfer of cooling or heat transfer cooling to 62-192 ?,hydrothermal fluid contains a certain amount of Fe,Mn,forming metal oxide in the process;adjacent or similar regional magmatic activities probaly made the sample contain a certain amount of olivine and mineral crystal.