PROCESS DETERMINING CONTENT OF OXIDES OF MAGNESIUM AND CALCIUM IN MAGNESITE ORE Russian patent published in 2000 - IPC

FIELD: geophysical examination of boreholes, specifically, nuclear physical methods of investigation of mineral resources. SUBSTANCE: process includes sequential irradiation of rocks by fluxes of gamma- quanta and fast neutrons, registration of flux of scattered gamma radiation at fixed distance from gamma source whose intensity is used to evaluate presence of magnesite strata in section of boreholes. Soft N₁ and hard N₂ components of scattered gamma radiation are recorded, flux of thermal neutrons N₃ is measured, effective atomic number Z_eff is calculated and lifetime N₃ of thermal neutrons in strata is computed by intensity of flux τ and known diameter of borehole. Contents of MgO and CaO in strata are found correspondingly by nomograms P(Mg0)=f(Z_eff,τ) and P(CaO)=f(Z_eff,τ). Z_eff=a-b lg N₁/N₂, where a and b are constant coefficients. τ_i in i-th interval of boreholes is found as τ_i, where τ_refN_3i(r,d)/N_3ref(r,d) where τ_ref is lifetime of thermal neutrons in reference interval; N_3i(r,d) and N_3ref(r,d) are counting rate of thermal neutrons in i-th and reference intervals of boreholes with fixed dimension r of sonde and diameter d of borehole. Nomograms (Z_eff,τ) and (Z_eff,τ) are constructed with known computed values Z_eff, τ and with known contents of MgO and CaO in core samples by plotting of isocurves of equal contents of MgO and CaO by interpolation method in coordinates Z_eff, τ. EFFECT: enhanced accuracy of evaluation of quality of magnesite ores. 3 cl, 4 dwg, 1 tbl