Mineralogical And Geochemical Characteristics Of Massive Sulfides In The Okinawa Through

Along with the deeper understanding of ocean, hydrothermal fluids activity have drawn more and more attention; the research of the global distribution, scale, chemical components and mechanism on modern hydrothermal fluid massive sulfides, can provide profound ground work to mineralization theory and hydrothermal fluids massive sulfides. Recently, the hydrothermal fluids zone in Okinawa Through has been widely focused, although some conclusions have been drawn according to the mineralogical and geochemical analysis of sediments in Okinawa Through conducted by some scholars, the problems in the mode of occurrence of metal elements, the regularity of minerogenetic enrichment, the division of mineral stages and the origin of mineral materials are still there unsolved. This paper mainly analyzes mineral components and zonal characteristics of massive sulfides in Okinawa Through by means of polished section identification, X-ray diffraction, etc; meanwhile, the testing analysis in macro-elements and trace elements is also conducted to analyze the Black Smoker samples using chemical analysis and inductively coupled plasma mass spectrometry (ICP-MS). Based on the analysis conducted above, this paper also discusses the patterns like transportation, activation and precipitation of various kinds of elements during the revolution of Black Smoker.Based on the analysis from polished section, the dominant mineral materials on the Black Smoker are Sphalerite, Chalcopyrite and pyrrhotite. Sample Sk1031-1 comes from Black Smoker nozzle, which is a classical pathway structural, has the obvious zonal distribution from outer wall to inner wall.; the change from Sphalerite to Chalcopyrite; the ratio Cu/Zn in Black Smoker massive sulfides has been widely known that it's controlled by the thermal history of hydrothermal fluids, rich Zn zone is formed when temperature is below 300 degrees centigrade, whereas rich Cu zone is formed when temperature is above 300 degrees centigrade.According to the chemical testing, analysis to the samples, this massive sulfide is obviously rich in Cu, Fe and Zn, which all have the correlation coefficient larger than 0.8. This means they have obvious concomitance relationship; Au, Ag have lower relativity with dominant mineral material, which means they can exist as independent minerals. The reason why Cu, Fe and Zn in basalt around research zone are lower than the average content in Earth Crust is maybe the extraction resulted from the long-term hydrothermal fluids recycling. The REE content in Black Smoker massive sulfides are relatively low, ranging from 4.45×10-6 to 39.15×10-6, and LREE is richer compared to HREE, where Eu(δEu=5.05-82.01),Ce(δCe=2.89-9.17)has positive anomaly, (Only Sample Sk1030-4a has negative anomaly:δCe=0.76). The conclusion drawn above slightly varies from the former investigators'one which is Element Eu has relative lower negative anomaly. The REE distribution pattern in Black Smoker massive sulfides is very different from the one in sedimentary rock, volcanic rock and ocean water in our research zone, which indicates the multi-origins of massive sulfide materials, and the complexity of fluids system. The REE distribution patterns in massive sulfides can reflect the revolution characteristics of hydrothermal fluids to some extent.