| Carbonate rocks play an important role in paleo-environment inversion(paleoclimate,paleo-salinity,paleo-redox environment,etc.),ore prospecting and the study of climate change.Mashan and Longzhou counties in Guangxi are typical karst landforms with large areas of carbonate rocks outlying.Therefore,the study of major and trace elements in the carbonate rocks in Mashan and Longzhou counties in Guangxi is of great significance for the inversion of paleoclimate,paleenvironment and palegeography in Mashan and Longzhou counties in Guangxi,as well as for the study of current environment and climate change.On the basis of reviewing a large number of relevant literature and the existing research results of our research group,this study took the carbonate rocks in Longzhou and Mashan County of Guangxi as the study area,and studied the sedimentary environment of the carbonate rocks in the study area by analyzing the composition characteristics of Ca,P,Fe,Mn,Mg,Al,V,Ni,Zr and rare earth elements.The main conclusions are as follows:1.The content of Ca elements in the Devonian carbonate rocks in Mashan County ranges from 20.99 % to 40.69 %,with an average of 28.64 %.The content of Ca in Carboniferous is between 0.06 % and 40.74 %,with an average of 31.11 %.The content of Ca in the Permian ranged from 0.05 %to 40.98 %,with an average of 34.08 %.The content of Mg in the Devonian system ranges from 0.14 % to 10.15 %,with an average of 5.77 %.The content of Mg in Carboniferous ranges from 0.04 % to 10.26 %,with an average of1.73 %.The content of Mg in the Permian ranged from 0.03 % to 7.78 %,with an average of 0.93 %.2.The content of Ca elements in the Devonian carbonate rocks in Longzhou County ranges from 19.85 % to 41.67 %,with an average of 24.64 %.The content of Ca in Carboniferous is between 20.90 % and 46.71 %,with an average of 34.46 %.The content of Ca elements in the Permian system ranges from 1.20 % to 51.31 %,with an average of 39.43 %.The content of Mg in the Devonian system ranges from 0.22 % to 9.43 %,with an average of 7.85 %.The content of Mg in Carboniferous ranges from 0.05 % to 9.38 %,with an average of 2.34 %.The content of Mg in the Permian ranged from0.07-7.16 %,with an average of 0.429 %.3.The m value obtained from the major elements Al and Mg indicates that the sedimentary environment of Devonian-Permian carbonate rocks in Mashan County and Longzhou County is Marine environment,with stable and high salinity distribution.4.The total amount of rare earth elements in Longzhou Carboniferous Profile 3 ranges from 4.66-10.702 μg/g,with an average of 8.171 μg/g,and that in Permian profile 6 ranges from 1.742-76.33 μg/g,with an average of 6.702 μg/g.The total amount of rare earth elements in the two profiles is generally low.In the total range of biological limestone rare earth.The LREE/HREE values of Longzhou Carboniferous Profile 3 and Permian profile 6 are 2.677 and 6.801,respectively,indicating that light rare earth is enriched and skewed to the right.The REE elements in the two sections were less affected by terrigenous debris.5.The mean values of Zr/Al ratio,Zr/Y ratio and Yb/La ratio of Longzhou Carboniferous Profile 3 are 0.021,1.0 and 0.158,respectively,indicating that the sedimentary environment of this profile is far away from the terrigenous source area and the sea water is deep.The contents of m and V elements indicate that the sedimentary environment is Marine facies.The ratio of V/(V+Ni)is between 0.073-0.431,and the δCe value is all less than 1,indicates that the oxidation-reduction environment is oxygen-rich.The δCe value of 43.75 % of Longzhou Permian Section 6samples is less than 1,and that of 56.25 % samples is greater than 1,which indicates that the oxidization-reduction environment of carbonate deposits in this section is weak stratified oxygen-rich anoxic environment. |
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