| The turn of the Permian-Triassic is an important historical period in which the biosphere change.At the end of the Permian period,the third biological extinction event with the greatest impact on geological history occurred,resulting in approximately 97%of marine life and 70%of terrestrial creatures disappear forever.Due to the lack of paleontological fossils in the continental Permian-Triassic,it is difficult to determine the specific horizon of the boundary or the related research of paleoclimate.Due to the extensive distribution of strata and the complete development of sedimentary sequences,the North China region is the key research area of the global continental Permian-Triassic boundary.This paper selects the limestone and mudstone layers at the top of the Shiqianfeng Formation in the Permian-Triassic transitional period of the Qinshui Basin as the research object,using X-ray diffraction?XRD?,inductively coupled plasma mass spectrometry?ICP-MS?,and inductively coupled plasma optical emission spectrometer?ICP-OES?and isotope ratio mass spectrometry?IRMS?were used to characterize the mineralogical,elemental geochemical and isotope geochemical characteristics.The main conclusions were as follows:?1?Through the analysis of the rock flakes and XRD of the sample,the limestone of the Sigou section is mainly composed of calcite and quartz;the main minerals of the Heshun section limestone are mudstone calcite and fine-grain calcite,containing a small amount of siliceous nodules and debris;The main minerals of mudstone are quartz,albite,and illite.?2?The results of the major elements of the sample indicate that the Sigou section limestone samples have high SiO2,CaO and Al2O3,low P2O5,MnO and MgO;and the Heshun limestone samples are dominated by SiO2 and CaO,and the mudstone samples are dominated by SiO2.?3?The trace element results of the sample indicate that the total amount of rare earth elements in the Sigou section limestone sample is relatively high(229ื10-6369ื10-6),and the light rare earth elements are relatively enriched?LREE/HREE is between 2.69 and 5.05?,Ce has a negative anomaly;and?REE of the Heshun section limestone sample is between 141ื10-6and 386ื10-6,and LREE is between 108ื10-6 and 310ื10-6,HREE Between 33.0ื10-676.0ื10-6,the Ce of the limestone sample has negative anomaly,Eu is basically no abnormality,and the?REE of the mudstone sample is between155ื10-6250ื10-6,LREE is Between 122ื10-6 and 213ื10-6,HREE is between 33.0ื10-6 and 37.0ื10-6,and there is basically no abnormality in Ce and Eu.?4?By analyzing the carbon and oxygen isotope test results of the sample,the?13C of the Sigou section limestone sample is between-5.99-4.96,with an average of-5.46;?18OSMOW is between+16.12+20.76.The average is+19.08.The?13C of the Heshun section limestone sample is between-8.99and-5.06,with an average of-6.91and?18OSMOW between+16.11and+18.30,with an average of+17.54.According to the calculation of carbon and oxygen isotope values,the Z value of the Sigou section limestone sample is between 109 and 112,and the Z value of the Heshun section limestone sample isbetween 103 and 110.?5?The ratio of Al2O3/TiO2 in the limestone and mudstone samples of the two sections indicates that the parent rock is mainly derived from felsic rocks,The K2O/Al2O3 ratio indicates that the content of alkaline feldspar inthesourcerocksislow,discriminationdiagramfortheprovenances of mudstone source rocks shows that the source is mainly from feldspathic volcanic rocks;The content of Cd,Mo,V,Cr,U,Th,V/Sc,V/Cr,Ni/Co,U/Th and V/?V+Ni?and their ratios indicate that they are in an oxidizing environment;B,Sr,B/Ga,Sr/Ba,and Z values indicate fresh water deposition and lowsalinity;the paleotemperature value indicates that the temperature of the sedimentary water is higher. |
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