Abstract
We present here an extended investigation of lunar olivine basalt sample 15535,28 which dramatically illustrates unorthodox alternating field (AF) demagnetization behavior as also observed to varying degrees in many lunar rocks. This behavior is characterized by nonreproducible remanent magnetization values upon demagnetization at a given peak AF. In addition, the direction of the remanence in 15535 following AF demagnetization is roughly confined to a particular plane. This behavior is shown to be an intrinsic property of certain magnetic carriers present in the sample. The viscous acquisition and decay coefficients ( S a and S d , respectively) are seen to be related by S a⋍32/S d| , an unexpected result. It is suggested that the above behavior is due to the presence of a few planar, multidomain grains representing a local mineral fabric. These “super-grains” do not demagnetize — neither by AF demagnetization to 1000 Oe nor by heating to moderate temperatures — and hence, if present in a given lunar sample, they could easily render any paleointensity determination of little value.
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