Studies of pyrrhotites from Japan (II) with special reference to their magnetic properties

Abstract

Pyrrhotites of Japan have been studied with special reference to their magnetic properties. The important conclusions are as follows:
(1) The curie point of pyrrhotite is 305°to 320°C.
(2) The magnetic susceptibility of pyrrhotite increases with their atomic ratio of sulphur, and can be divided into the following three growps, 1, 000_??_11, 000×10^-6, 11, 000_??_20, 000×l0^-6 and >20, 000×10^>-6.
(3) From the magnetization-temperature curve, pyrrhotites can be classified into following three groups by their temperature dependency of magnetism: (a) Peak type: α-pyrrhotite with weak magnetism, (b) Weiss type: β-pyrrhotite with strong magnetism which shows no peak on a I-T curve, (c) Peak+Weiss type: mixture of α- and β-pyrrhotites.
(4) Peak type pyrrhotite is converted from weak magnetic to strong magnetic by heating and converted mineral becomes to Weiss type pyrrhotite above the curie point.
(5) Peak type pyrrhotite occurs abundantly in the hydrothermal veins, while weiss type is very frequent in the Kieslager type deposits. This indicates that the peak type pyrrhotites formed primarilly in the hydrothermal veins are transformed secondarily to Weiss type by the later metamorphism.