| The high magnetic susceptibility regolith in the eastern Yunnan Plateau has been reported as a special case by the academic circles.However,the cause of the high magnetic susceptibility is not very clear at present.In this paper,the characteristics of magnetic minerals and the degree of chemical weathering of high magnetic susceptibility regolith represented by carbonate and basalt regolith in the eastern Yunnan Plateau are studied,and the following conclusions are drawn roughly:?1?The average mass magnetic susceptibility of carbonate regolith in the eastern Yunnan Plateau is 2578.92×10-8m3/kg,of which the mass magnetic susceptibility of typical carbonate regolith is 5369.92×10-8m3/kg;the average mass magnetic susceptibility of basalt regolith is 1140.44×10-8m3/kg;the mass magnetic susceptibility of typical basalt regolith is 2277.46×10-8m3/kg.The quality magnetic susceptibility of carbonate regolith samples is significantly higher than that of basalt regolith samples.Shell conversion;?2?By means of magnetic parameters,temperature susceptibility,hysteresis loop and X-ray diffraction pattern identification,it is found that siderite is the main magnetic carrier mineral in carbonate regolith parent rock,goethite is the primary weathering mineral,hematite is the main magnetic carrier mineral in regolith,and magnetite is the main magnetic carrier mineral in basalt regolith parent rock.The main magnetic carrying minerals of regolith are magnetite and hematite.?3?By using magnetic parameters and DAY diagram,it is found that the main magnetic-carrying particles in carbonate regolith and basalt regolith are pseudo-single domain particles?PSD?,and the contribution of superparamagnetic particles is not obvious.?4?It is found that the weathering degree of carbonate regolith is higher than that of basalt regolith by calculating chemical weathering indexes such as Rb/Sr,SiO2/Al2O3 and SiO2/Al2O3+Fe2O3.?5?According to the magnetic mineral characteristics of parent rock,primary weathering and final weathering,the magnetic susceptibility enhancement model of carbonate regolith includes two mechanisms:enrichment of magnetic minerals and transformation of low magnetic minerals to strong magnetic minerals during weathering.The transformation of magnetic minerals can be divided into:siderite in bedrock first transforms into goethite and then into maghemite with rock weathering.From the existing clues,the transformation from Goethite to maghemite may be related to regional dry climate.The magnetic susceptibility enhancement model of basalt regolith is also related to weathering,but the overall result is that magnetite with strong magnetism will be transformed into maghemite with relatively weak magnetic susceptibility.Although iron enrichment occurs during this process,the magnetic susceptibility is generally weakened.?6?The results of semi-quantitative and chemical weathering calculation of magnetic-carrying minerals show that the magnetic susceptibility of carbonate regolith is higher than that of basalt weathering crust because carbonate regolith undergoes stronger weathering process than basalt regolith to produce more maghemite,and its magnetic susceptibility enhancement effect exceeds that of basalt regolith. |
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