Mineralogical Characteristics And Provenance Analysis Of Modern Sediments In The Dongping Lake

Based on XRD diffraction analysis and detrital mineral identification of modern sediments in the Dongping Lake,clay minerals,light minerals,and heavy minerals types as well as their spatial distribution in this lake were studied.Based on the clay minerals,light minerals,and heavy minerals in the sediments of the Yellow River and the Dawen River,the mineralogical characteristics of theses two potential sources were determined.The mineralogical source tracer method was used to explore the relationship of the modern sediments between the Dongping Lake and the Yellow River and the Dawen River.At the same time,the relative contributions of the Yellow River and the Dawen River to the modern sediments of the Dongping Lake were calculated using the Bayesian end-member modeling analysis(BEMMA).The main conclusions of this study are as follows:(1)Illite(56.57%)is the clay mineral with the highest content in the Yellow River sediments,followed by chlorite(21.36%),smectite(12.01%),and kaolinite(10.06%),with an average crystallinity of illite is 0.28.The content of illite in clay minerals in the sediments of the Dawen River was up to 70.66%.Kaolinite(12.24%)and chlorite(11.99%)were next,with only a small amount of monzonite(5.11%).The average crystallinity of illite is 0.46.The average content of illite,smectite,kaolinite,and chlorite is 60.53%,11.37%,12.70%,and 15.40% respectively.The high relative content of illite is distributed in the east of the lake near the entrance of the Dawen River,while the low content appears in the north and southwest of the lake.The areas with the highest kaolinite content occur in the north and south of the lake,while the lowest content is distributed in the northeast of the lake,showing a patchy and uneven distribution in the whole lake.Clay minerals in the study area contains six types of combinations.Type I(illite,chlorite,kaolinite,and smectite)dominates the clay minerals,followed by Type II(illite,chlorite,smectite,and kaolinite).(2)The species and contents of light minerals in the Yellow River and the Dawen River are basically the same.The heavy mineral content in the sediment of the Yellow River is 1.24%,and the heavy mineral assemblage is "common amphibole-epidotelimonite-limonite",and the characteristic mineral is pyroxene.The heavy mineral content in the Dawen River sediments is 3.06%,and the heavy mineral assemblage is "epidotecommon amphibophorite-diophorite",and it is characterized by high epidotes.The average mass fraction of heavy minerals in the Dongping Lake was 0.60%,and9 light minerals and 30 heavy minerals were identified.The light minerals are mainly calcite(38.78%),feldspar(19.69%)and quartz(19.01%).The main heavy minerals were amphiboles(30.19%),epidotes(18.81%),limonite(9.70%)and limonite(9.10%).(3)From the clay mineral content distribution and the clay mineral endmogram,it can be inferred that the clay minerals in the Dongping Lake sediments are mainly influenced by the Yellow River material,and the Dawen River material also has a certain effect on them.According to the cluster analysis,Dongping Lake sediments are divided into three types: the first type is widely distributed in all areas of the lake,except the eastern part of the lake near the Dawen River estuary,where the Yellow River provenance is the main source.The second kind is mostly distributed at the mouth of Dawen River,and the main source is Dawen River.The third kind of sediment has the tendency to spread from the center of the Dawen River estuary to the lake district in all directions,and is the mixture source,that is,the Yellow River-Dawen River mixture is the main one.Dongping Lake sediment clay minerals in the east-west direction show some big % may be the reasons for the spatial variation characteristics of river carries to the material under the action of lake water of the Yellow River flood sediment silting up of Dongping Lake lake basin disturbance effect,under the action of mixing,deposition and resuspension transformed the original sediment in lake basin.According to the distribution of detrital minerals,the material sources in the study area were identified.The Dongping Lake sediments can be divided into three types by cluster analysis.The second type is mainly distributed in the periphery of the first type of sediments,reaching the outlet in the north and the southern end of the lake.The third type of sediments is mainly distributed along the western and northern shores of the lake,which is far away from the estuary of the Dawen River.Besides the influence of the Yellow River and the Dawen River,the sources of heavy minerals in this area may also be influenced by the erosion of mountains around the lake basin and the colluvial process on the lake shore.(4)Based on the BEMMA model,the clay mineral data of modern sediments in the Dongping Lake were analyzed and two end members were obtained,corresponding to the Dawen River and the Yellow River,respectively.Then the source inversion by solving the linear mixing model was carried out to quantify the spatial distribution of the clay minerals in the modern sediments of the Dongping Lake.