Determination And Application Of Trace-elements And Ultratrace-elements In Polymetallic Sulphides At Seafloor

As the important mineral resources at the sea floor, the polymetallic sulphidesare very difficult to be determined because it contains major sulfur and manycomplicated mineral which leads to the poor accuracy and precision of the data, andmeanwhile, the rare earth elements (lanthanide series) and platine group elements(PGE) are in the ultra-trace level that are far less than the detection limits, In regard tothe above problems and the strategic demand for the ocean minerals, this Paperdesigned the anticorrosive efficient digestion vessel, studies on the determinationmethods of trace elements, rare earth elements (REE) and the PGE as well as thestudies on the correlations between elements in the samples of polymetallic sulphidesand the relationship between REE assemblage and the formation conditions, and thefollowing achievements have been obtained:(1)The design of the anticorrosive efficient digestion vessel. The vessel has thefollowing features: it is made of the anti-corrosion alloy material that is resistant tothe high temperature and high pressure, it is airtight and easy to operate (it can beclosed within1second), it retains no acid on the wall or the top, which improves theeffect of acid dissolving, it is safe and free of tube blasting in the test under thepressure limit, it can be used in any quantity without affecting the results so that thepolymetallic sulphides can be cleared up in batches completely. The bomb is thesymbolic product in the manufacturing of the sample-degesting vessel in China thatenhances the capability to develop the sample-digesting containers independently.(2)The solution to problems on clear-up of sulfide samples. This paper puts forward different methods to clear up the different elements and establishes two methods,one is to detect the Ag and Bi elements with HNO3and the results are proven to beaccurate and reliable, and the other is the method of HCl+HF and HNO3, which canefficiently eliminate the S, completely clear up the sulfide samples and make thesolution clear and transparent, and thus achieving the accurate determination for over30elem-ents including Au, Ba, rare earth elements (REE), etc.(3)The method of determining the REE in the polymetallic sulphides at sea floor.Preference is given to the domestically-made732cationic resin that is eluted with2mol/L of HCl to get rid of the divalent elements like Cu, Fe, Pb and Zn, etc. andeliminate the Ba with2.5mol/L of HNO3, the whole process is in the optimal designand obtains the data of high recovery of REE. The method has been used to determine the REE in pyrites (GBW07267), chalcopyrite (GBW07268), sphalerite (GBW07270)and WMS-1a, the accuracy of the determination is proven with the methods ofverifying the recovery results by adding the standard and of contrasting with thereference values, the method can be used to obtain a high recovery of REE, and thusachieving the accurate determination of REE in the polymetallic sulphides.(4)The method of determining the PGE in the polymetallic sulphides at sea floor.Experiments with the nickel sulphide fire assay method, cation resin exchange andanion resin exchange show that all of those methods have problems, which mainlyincludes the poor experimental effect, great interference, low recovery and instability,etc. which plays a important role in the research of determination of PGE in future.（5）The interactive relation of trace elements in the polymetallic sulphides atsea floor. The test has been conducted to determine13elements including Fe2O3, Cu,Zn, Mn in the sulfide samples at Stations of17A-EPR-TVG1and17A-EPR-TVG2atthe rise of the east pacific ocean, all those samples are Fe-concentrated ones, andanalysis was conducted on the correlation and clustering of those elements, and theresults show that there is a good correlation between Cd and Zn, and between Mo andZn in TVG1, while there is no correlation between Cd and Zn, or between Mo and Znin TVG2, which indicates that the two samples, although collected from the sameposition, have difference in the mechanisms of element concentration and deposition,and further work is required to study the causes and sources of the samples.（6）The tracer role of REE. The study has been conducted on the REE in thepolymetallic sulphides at sea floor of7hydrothermal areas at the rise of the eastpacific ocean, Indian Ridge，Mid-Atlantic Ridge，North Fiji Basin, which showsthat those areas are enriched with LREE while lack of HREE, of which, the elementof Eu features the positive anomalies, negative anomalies and no anomalies; Cefeatures no or slight anomalies, the anomalies of Eu has direct relation with thetemperature at which the polymetallic sulphides take shape, the negative anomalies ofEu is corresponding to the hydrothermal minerals at low temperature and it hasrelations with the low temperature hydrothermal activities, while the positiveanomalies of Eu to the hydrothermal minerals at high temperature, and the hightemperature hydrothermal activities.