to understand aeromags, page-8

lastly to explain hot and cool red and blue colours in relation to hematite and their correlation......There is none.......external factors play a big part.

ie, cover, faulting, age, erosion, earths polarity at time of formation

Since the emplacement the granite has been exposed to several alteration
processes. The fresh granite shows a ferrimagnetic bulk susceptibility (1 < k <
24 x 10-3 SI-units) and an oblate magnetic ellipsoid with magnetic anisotropy factor
P` ranging between 1.1 and 1.2. This primary magnetic fabric is related to the
magma flow during crystallisation of magnetite. With increasing alteration of magnetite
into hematite (martite) due to an early, pervasive and a later rift-related alteration
the bulk susceptibility (k < 1 x 10-3 SI-units) and the magnetic anisotropy is
reduced (P`< 1.1). Oblate as well as prolate shapes of the ellipsoid occur. Optical microscopy,
scanning electron microscopy, image analyses and temperature-dependent
magnetic susceptibility measurements were used to characterise the decomposition
of magnetite to martite. This transformation is graduallly and starts with the growth
of hematite platelets relative to the {111} planes of magnetite and create an increasingly
disordered arrangement of small hematite grains within the former 400
micrometer-sized magnetite grains. The decomposition is also reflected in measurements
of temperature-dependent magnetic susceptibility (k(T)). While k(T)-curves in
fresh granites indicate a typical reversible multi-domain magnetite course there is an
inreasing irreversibility magnetite course in altered granites with single-domain behaviour.
But no Curie temperature for hematite was observed. Along with this transformation,
the degrees of the alteration index (k(T)cooling- k(T)heating) correlates
with the fabric parameters.