DISCRIMINANT ANALYSIS OF GENETIC TYPE OF CARBONATE ROCK AND DISCUSSION ON GENETIC DOLOMITITE IN BAI YINOBO REGION

Abstract: The writer collected 769 data on bulk analysis of carbonate rock and carbonatite from more than 20 country in the world and 21 provinces of china.Results of statistics and calculation indicated that content ranges of main elements between sedimentary carbonate rock and carbonatite are similar.The carbonatite can be distinguished from sedimentary carbonate rock by discriminant anaalysis.The carbonatite is P₂O₅-rich and usually content of P₂O₅ is more than0.2% .The number of data, P₂O₅ 0.2% , is 86% of all carbonatite data. But sedimentary carbonate rock is P₂O₅-poor.The number of data, P₂O₅0.2% only makes up 12% in all this rock s data.Therefor, content of P₂O₅ is one important standard for discriminanting genetic type of carbonate rock. When eleven variables are adopted in two set discriminant analysis, discriminanting efficiency of various genetic type of calcareous carbonate rocks, dolomitic carbonate rocks and ferruginous carbonate rock is 93.5%, 90.7% and 89.8% separetaly. When P₂O₅, Na₂O, A1₂O₃, MnO, CaO, K₂O and Fe₂O₃ are used as discriminating variables in discriminant analysis of step by step, discriminanting effect of calcareous carbonate rock is the best and discriminanting efficiency is 94. 5%. While FeO, Fe₂O₃, Al₂O₃ and P₂O₅ are adopted in discriminant analysis for dolomitic carbonate fock, process of calculation is more simple and discriminanting efficiency reached 96% . Using CaO. P₂O₅ MgO, SiO₂, Fe₂O₃ and Al₂O₃ for discriminant analysis of ferruginous carbonate rocks, discriminanting efficiency comes up 98. 5% . Generally, discriminanting effect of sedimentary carbonate rocks (near 100%) is better than carbonatite (more than 85% ) , i.e. sedimentary carbonate rock generally isn ' t distinguished.Results of discriminant analysis of limestone and dolomitite from Baiyinobo region indicat that 17 samples of limestone are all distinguished sedimentary carbonate rock, but 3 samples in 57 samples of dolomitite are distinguished sedimentary carbonate rock, making up 5.3% of collecting data, other samples are distinguished carbonatite.The conclusion is in accord with its geological occurrence, geochemical and isotopic composition characteristics