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Palaeointensities determined from the middle Cretaceous basalt in Liaoning Province,northeastern China

Ching-Hua Lo

  A palaeomagnetic and geochronologic investigation has been conducted on a basalt lava sequence at Jianguo in Liaoning Province,northeastern China.Radiometric ~(40)Ar/~(39)Ar dating experiments indicate the volcanism occurred in relatively short time intervals between 105.5 and 102.2 Ma.Thermomagnetic experiments and electron microprobe show that main primary carrier of remanence to be titanomagnetite with Curie temperature of~300℃.A modified version of the Thellier-Thellier technique with systematic partial thermoremanent magnetization(pTRM)-checks was used for palaeointensity determinations.Fourteen out of 61 samples from the studied lavas yield reliable palaeointensity estimates with a mean virtual dipole moment(VDM~*) of(4.07±0.2)×10~(22)Am~2,about half the strength of the modern-day field.……