Geochemical Characteristics And Provenance Of Epidote Grains In Sediments In Estuaries Of The Yellow River And Yangtze River

The material entering the Yellow River and the Yangtze River plays an important role in the land-sea interaction and the exchange of material flux.The huge amount of sediment imported from the Yellow River and the Yangtze River each year is the main source of material in the continental shelf sea area of eastern China,and it has an important impact on the formation of muddy sediments in the continental shelf sea area of eastern China and the marine ecological environment.Epidote is a mineral with a relatively high content of heavy minerals,second only to hornblende in quantity,and is often the second most transparent heavy mineral,and epidote has strong resistance to weathering,which is a relatively stable mineral The study of the chemical composition of family minerals is of great significance to the analysis of rock genesis and provenance.In this paper,in order to study the provenance characteristics of sediments in the Yellow River Estuary,Yangtze River Estuary and South Yellow Sea,the main elements of single minerals in epidote in the three sediments were analyzed with electronic probes,and inductively coupled plasma spectroscopy was used The main minerals and trace elements were analyzed for stone group minerals.Studies have shown that the geochemical characteristics of epidote in the Yellow River Estuary and the Yangtze River Estuary can be used as a source signal to reveal its transport and diffusion patterns,reflect the source information of the source area,and establish a reliable source identification index,which is the eastern sea area of China Provide scientific basis for identification of river source materials.In this paper,the main elements of single minerals in the epidote in the sediments of the Yellow River Estuary?5 cases?,the Yangtze River Estuary?7 cases?and the South Yellow Sea?4 cases?were analyzed with electronic probes,and the Yellow River was analyzed by inductively coupled plasma spectroscopy.The main and trace elements of the epidote group minerals in the mouth?4 cases?,the Yangtze River estuary?5 cases?and the South Yellow Sea?3 cases?were analyzed.The result shows:?1?The sedimentary epidote in the Yellow River Estuary,the Yangtze River Estuary and the South Yellow Sea is mainly granular,and the color is mostly yellow-green,partly light yellow and light gray.The analysis result of single-mineral electron probe of epidote shows that the geochemical values of the major elements of epidote in the Yellow River Estuary,Yangtze River Estuary,and South Yellow Sea are similar,and all have the characteristics of high Fe,Na,low Al,K.The dispersion degree is low,but the samples in the South Yellow Sea are more dispersed than the Yellow River and Yangtze River.?2?The chemical formula of epidote in the Yellow River estuary calculated by the analysis results of epidote single mineral electron probe is Ca_{?2.050-3.426?}Fe³⁺_{?0.106-0.606?}Al_{?0.833-1.716?}[Si_{?3.486-4.300?}O₁₂]OH;The chemical formula of epidote in the Yangtze Estuary is Ca?1.908-3.336?Fe³⁺?0.094-0.607?Al?0.911-1.691?[Si?3.542-4.420?O12]OH;the chemical formula of the epidote in the South Yellow Sea is Ca?2.050-3.419?Fe³⁺?0.096-0.626?Al?0.859-1.720?[Si?3.455-4.079?O12]OH.The epidotes from those three areas have calculated Xps values of mostly0.19?0.30 and TiO2 contents of mostly less than 0.2%.These show that those epidote separates contain major epidote and minor clinozoisite,with their genesis of dominant magmatic,second hydrothermal alteration,and third metamorphic origins.The amounts of different genetic epidote grains are closely related to the geological conditions in the middle and upper streams of those two rivers.Most of the sedimentary epidote in the Yellow River estuary comes from the loess,desert,and Gobi outside the basin,and the parent rock is relatively complex;the sedimentary epidote in the Yangtze River estuary is mostly from the middle and upper reaches of the Yangtze River.Liquid alteration is the main cause of epidote,so it is judged that the source rock type is mainly magmatic rock,followed by metamorphic rock.?3?The results of wet chemical analysis of the minerals of the epidotes group show that the main elements of the three groups are consistent with the characteristics of single minerals.The trace elements in the group are significantly enriched in Sr,V,Cr,Zr,Pb,REE,and REE is significantly enriched.By calculating the difference in the concentration of trace elements,the epidotes in the Yellow River estuary has high Rb,Ba geochemical characteristics,the epidotes in the Yangtze River estuary has high Sr,Pb,Mo geochemical characteristics,and the philophile elements Zr/Hf,Nb/Ta can effectively distinguish the provenance,and the ratios of Sr,Rb,Ba,Pb,Mo element concentration and the philophile elements Zr/Hf,Nb/Ta can be used as indicators to distinguish the provenance of the Yellow River and the Yangtze River.The distribution pattern of rare earth element REE in the three groups is right-inclined,LREE enriched,and HREE flat.Among them,the significant difference between Ce and Eu in the Yellow River Estuary and the Yangtze River Estuary can be used as an effective indicator for provenance identification.?4?The elemental geochemical characteristics of the sedimentary epidote can be used for provenance identification of the sediments of the Yellow River and the Yangtze River.Based on the analysis results of epidote single-mineral electron probes,the chemical formulas and their causes of the three were calculated.The results of the wet chemical analysis of the minerals in the epidotes group showed that the concentrations of Sr,Rb,Ba,Pb,and Mo in the trace elements in the group The ratios of elements Zr/Hf and Nb/Ta and the difference between?Ce and?Eu anomalies can be used as source identification indicators.Studies have shown that the source identification indicators of sedimentary epidote in the South Yellow Sea are closer to the mouth of the Yellow River and the Yangtze River,and most of the material sources of epidote in the South Yellow Sea come from the Yangtze River basin.