Study On The Suspended Particulate Minerals In The Water Column In The Eastern Equatorial Pacific Ocean And Hydrothermal Active Areas In The Southwest Indian Ocean

54samples of suspended matter at5survey stations in the Eastern Equatorial PacificOcean were collected during Chinese DY105-17Cruise in2005. And86samples ofsuspended mater at7survey stations in the hydrothermal active areas in the Southwest IndianOcean were collected during Chinese DY115-21Cruise in2010. The suspended particulateminerals in the water column in the Eastern Equatorial Pacific Ocean and in the hydrothermalactive areas in the Southwest Indian Ocean were studied systematically based on thesesamples.Concentration of suspended matter, morphology, composition and distribution of thesuspended particulate minerals were studied based on the data of total suspended matter(TSM) about4000SEM images and4000results of EDX analysis of the suspended particlesfrom the Eastern Equatorial Pacific Ocean, their sources and influencial factors werediscussed.The concentration of TSM in the water columns in the Eastern Equatorial Pacific Ocean,ranging from0.01to0.29mg/L, is very low and varies greatly between different stations anddifferent water depths in the same station. The average concentration of the TSM in the WSstation is the highest, being twice of those in the other stations. The vertical profiles of theTSM concentration show the trend of high-low-high from surface to the sea bottom.Based on the on morphological and compositional study on the suspended mineralparticles in the Eastern Equatorial Pacific Ocean,38species of7groups of minerals weredistinguished, among which sulfide particles, Monazite and hydroxide (oxide) of light rareearth elements were found for the first time in the study area. Four possible sources of thesuspended mineral particles were deduced: aerosol origin authigenous origin re-suspensionorigin from the sea floor, and possible origin from sub-marine volcanos.Barite particles were found universal in the water column. Four morphological types of barite crystals were identified:1) ovoid or round crystals;2) rhombic crystals;3) arrow-likecrystals; and4) irregular crystals. Each morphological type was divided into a subtypefeaturing well-formed crystals and subtypes with various dissolution features. The arrow-likemarine barite crystals were found for the first time, and their formation mechanism wasexplained. Various and unique dissolution features with selective dissolution characteristicswere found on the barite crystal surfaces, in the interior of crystals and along their edges.Statistics of the Sr content in barite particles shows that the formation of the various selectivedissolution features and arrow-like crystals are closely linked to the heterogeneousincorporation of Sr into marine barites in biologically maintained solid solutions in themicroenvironments of marine organisms. Based on the study on grain size and numbers ofbarite particles from different water depths, two possible models of the origin of the baritewere proposed: celestite model and organic aggregate model. Aggregated barite particleswere found often enwrapped by organic matter with some siliceous clay or with someCalcium or colloidal hydroxide (oxide) of Titanium. The study on the formation anddissolution of the barite is important and useful to improve our knowledge on thebiogeochemical cycle and to evaluate paleoproductivity in the ocean.Mineral assemblage from3middle stations were mainly terrigenous and authigenousorigins; Minerals from the west station and the east station contain a few metal sulfides andmetal oxide (hydroxide), indicating the possible influence of sub-marine volcanic activities.The difference between the mineral assemblages are related to the regional tectonic activityin the station locations.Concentration of suspended matter, morphology, composition and distribution of thesuspended particle minerals in the waters from the hydrothermal active areas in theSouthwest Indian Ocean were studied based on the data of total suspended matter (TSM)about5000SEM images and5000results of EDX analysis of the suspended particles fromthe hydrothermal active areas. The relationship between suspended minerals andhydrothermal activity in the study area are analyzed and found that anomaly of sulfides couldbe a proxy of the hydrothermal plume.The concentrations of suspended particles in the hydrothermal active areas of SouthwestIndian Ocean ranged from0.17to1.45mg/L, which are about5-10times higher than that in the Eastern Equatorial Pacific Ocean. The average concentration of the total suspendedmatter (TSM) does not vary greatly between stations, while it varies dramatically in thevertical direction. The vertical profiles of the TSM show the trend of high-low-high fromsurface to the bottom water.Total of42species of minerals and3species of structure-unidentified sulfides werefound in the water column in the hydrothermal active areas of Southwest Indian Ocean. The3species and4morphological forms of sulfide minerals were found for the first time, amongwhich ZnS2has not been found in nature and ZnS4has never been reported before.Two sulfides mineral assemblages named “Zinc persulfide-marmatite-pyrite-chalcopyrite” and “chalcopyrite-sphalerite-pyrite-pyrrhotite” were proposed. They mainlyresponsed to hydrothermal plumes erupted in middle-high temperature and high temperature,respectively.The amount, morphology, assemblage and distribution of the suspended sulfideparticles were found to have good accordance with the adjacent hydrothermal active areas inspace and habitude.The species, amounts and distributions of the suspended sulfide particles in thehydrothermal active areas of the Southwest Indian Ocean are much different from that in theEastern Equatorial Pacific Ocean. The abundant species, high amounts and vertical anomalydistribution of the sulfides particles in the water column beyond1500m of depth in thehydrothermal active areas of the Southwest Indian Ocean showed the characteristics of thetrail or scraps of the hydrothermal plume diffusion, which was not found in the EasternEquatorial Pacific Ocean.The study on the suspended particles in the waters from the hydrothermal active areasof Southwest Indian Ocean indicates that the anomaly of suspended sulfides as the proxy ofhydrothermal plume were also exist in the water column. The characteristics such as theassemblage and morphology of the sulfides have good accordance with the adjacenthydrothermal active areas in space and habitude, that would offer a basic judgment of thefeatures of the ocean waters in terms of existence of hydrothermal activities. The research onthe characteristics and distribution of the suspended sulfide particles will be conduce to thehabitude of the hydrothermal vent and the extension of the plume and is more convenient since the distribution of the suspended sulfide particles is more abroad and the samples isrelatively easily to be achieved than the hydrothermal plumes. Therefore, study on theabnormality of the suspended sulfide particles in the hydrothermal active areas could be anew approach to identify and trace hydrothermal plume and the perspective hydrothermalvent areas.