| The diagenetic environment of modern sedimentary carbonate rocks is mainly shallow sea environment.Trace elements of authigenic carbonate minerals in sedimentary carbonate rocks have attracted much attention because of their special geochemical properties(marine environmental traceability).For example,in the Tethyan seawater,the distribution model of rare earth elements changed during the Cretaceous period.Through the content and distribution model of trace elements(rare earth elements)in modern marine authigenic carbonate minerals,the redox environment of tethyan seawater during diagenetic period of this authigenic carbonate mineral can be inferred.However,some scholars have proposed that the distribution model of rare earth elements in seawater has hardly changed,and there is no significant difference between the forms of rare earth elements in marine authigenic carbonate minerals and those in seawater.This argument makes us realize that much of the previous marine environment tracer work is likely to be based on the wrong data.In other words,trace elements in authigenic carbonate minerals were probably not accurately determined in previous work.At present,the main methods used for the determination of trace elements in carbonate authigenic carbonate minerals are acid dissolution-ICP-MS method and laser denudation-ICP-MS method,in which acid dissolution-ICP-MS method is more widely used.It is one of the commonly used methods for the determination of trace elements in carbonate minerals.Then,whether this method can really accurately determine the content of trace elements in carbonate minerals and which trace elements can be accurately determined,it needs to be further studied and rejudged.Based on this situation,this paper aims to analyze the feasibility of acid dissolution-ICP-MS method determinating of trace elements in carbonate minerals.The method to judge the feasibility of acid dissolution-ICP-MS method is to analyze the trend of the determination results about elements.If the determination result of trace element showed the same trend as that of calcium,the acid dissolution-ICP-MS method was feasible to determine this element.If the determination result of element showed the same trend as that of aluminum,the acid dissolution-ICP-MS method was not feasible to determine the element.The essence about that acid dissolution-ICP-MS method is feasible is acid dissolution process can effectively eliminate the interference of non-carbonate minerals.Through trend analysis,the feasibility range of acid dissolution-ICP-MS method for determination of trace elements in carbonate minerals can be concluded.In order to carry out trend analysis,sufficient data are needed for theoretical support.Therefore,under the existing experimental conditions,we expand it sufficiently.Finally,14 kinds of different rock samples were selected,and 30 kinds of different acid dissolution test conditions were set for each sample.After each acid dissolution experiment,the filtrate was determined by ICP-MS.Each determination included 41 kinds of trace elements and2 kinds of characteristic elements.In the end,a total of 420 acid dissolution experiments were carried out,and 420 ICP-MS tests were also carried out,and18606 data were finally obtained.After the acid dissolution experiment,the reaction quality of solid samples under different acid dissolution conditions was analyzed to judge the optimum reaction conditions of acid dissolution process.Then,a method for judging the feasibility of acid dissolution-ICP-MS method was established by theoretical derivation.This method can be used to analyze the trend of ICP-MS determination results and to determine the feasible range of acid dissolution-ICP-MS method.The final conclusion is that: Within the range of samples studied in this paper,acid dissolution-ICP-MS method is only applicable to determination of Cr,As,Rb,Nb,Cs,Ba and Ta in general trace elements,but not applicable to determination of 15 rare earth elements(Y,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu).For the other trace elements(Li?Be?V?Mn?Co?Ni?Cu?Zn?Ga?Sr?Zr?Ag?Cd?In?Sn?Tl?Th?U?Sc),the feasibility about acid dissolution-ICP-MS method accurate determinating the content of them is affected by the purity of the sample.The higher the purity of the sample,the greater the feasibility,the lower the purity of the sample,the smaller the feasibility.Finally,in order to improve the feasibility about acid dissolution-ICP-MS method determining trace elements two suggestions are put forward in this paper:First,we shoud seek carbonate rocks with high content of authigenic carbonate minerals to eliminate the interference of impurity components;Second,for samples with low content of authigenic carbonate minerals,the sample should be further treated before determination in order to separate the target components from impurity components.Which will be the next direction we need to work hard. |
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