Characteristics Of Quartz Inclusions In River Sediment Of The South Yellow Sea During Late Pleistocene And Its Provenance Implications

Several large underwater sedimentary systems have developed on the continental shelf of the South Yellow Sea,including the argillaceous area of the South Yellow Sea,the underwater delta of the Paleo-Yellow River,the radial sand ridges,the Yangtze Shoal and the underwater delta of the Yangtze River.Because of the unique geographical location of the South Yellow Sea,this area has always been a research hotspot in the coastal shelf area,and the sedimentary evolution of the South Yellow Sea and the study of sediment provenance are the current research hotspots in sedimentology.Fluid inclusions retain environmental conditions during mineralization,and different types of fluid inclusions reflect fluid information from different sources.Quartz particles in river sediments are derived from weathering and denudation products of various rocks and ores along the river basin.Fluid inclusions in them record the properties of different source areas.Therefore,the study of fluid inclusions in quartz particles in sediments can become a means to explore the source of sediments.In this study,the characteristics of quartz inclusions in river sediments in the Yangtze River Basin and MSI6 sediments in YZ05 borehole are analyzed.The characteristics of quartz inclusions in the Yangtze River Basin are compared with those in YZ05 borehole sediments in order to provide data support for the study of sediment provenance in the Yellow Sea.Through qualitative and quantitative analysis of the characteristics of quartz inclusions,the following conclusions are obtained.The characteristics of quartz inclusions in YZ05 borehole deposits are as follows:the overall characteristics of quartz inclusions are similar to those in the Yangtze River basin;the size of inclusions is small,ranging from 2 to 14?m,and most of them are 2 to 5 ?m;the proportion of inclusion gas is mostly 10-30%,most of them are liquid-rich,and a small amount of quartz contains gas-rich inclusions;the number of irregularshaped inclusions is small,and most of them are regular-shaped.The inclusions are mainly elliptical or circular,nearly rectangular and shuttle-shaped,while the smaller inclusions are mainly circular or elliptical.From the arrangement of inclusions,there are mainly banded,regional concentrated or isolated distribution,which are ubiquitous in quartz grains.The overall characteristics of quartz inclusions in YZ05 borehole are very close to those of modern estuarine sediments.It can be inferred that the main source of sediments in MSI6 stage is the Paleo-Yangtze River,and the sediments of the Paleo-Yangtze River are similar to those of the modern Yangtze River.The quartz inclusion characteristics(shape,size,quantity per volume and vapor H2O volumetric proportion)of samples were analyzed,to assess the differences for the upper,middle,and lower reaches and to provide the provenance implications.They are as follows:2-15 ?m in size;5-30%of vapor H2O proportion;liquid-rich two-phase inclusions mostly;isolated,regional,and strip distributions;mainly primary inclusions.In the upper,middle,and lower reaches of Changjiang River,the characteristics are different.The size,quantity per volume,and vapor H2O proportion of quartz-inclusion of Shigu sample(upper)are 2-14 ?m,2-166,and 10-90%,respectively;In Yibin(upper),they are 2-12 ?m,1-2 70,and 10-90%respectively;In Yichang(middle),they are 2-10 ?m,2-220,and 10-90%respectively;In Wuhan(middle),they are 2-12 ?m,1-308,and 5-90%respectively;In Chongming(estuary),the results are 2-9 ?m,2-116,and 5-90%respectively.From the upper to the middle reaches,the characteristics show that the fluvial deposit are transferred from tributaries continuously.From Wuhan downward to estuary,they are very similar.Those quartz inclusion characteristics in Changjiang River can make sense to imply sediment provenance in Yellow Sea and East China Sea.The characteristics of the fluid inclusions in the quartz particles retain the original information on the source rock diagenesis and mineralization,and record the nature of the source rocks.The differences in the source rocks are be reflected in the different fluid inclusions.With the influx of tributary sediments,the characteristics of quartz inclusions change,Upon reaching Wuhan,the characteristics of quartz inclusions in sediments are similar to those in estuaries,which shows that the sediments in the Yangtze River Basin continuously mix from upstream to downstream,and the Yangtze River is the main source of sediments in the South Yellow Sea.Analysis of fluid inclusion characteristics could provide database support for the study of new methods of provenance for Yellow Sea and East China Sea.