V. I. Bagin presented the results of his study of the magnetic properties of hematite. According to Bagin's data, this mineral has very high magnetic stability. The thermoremanent magnetizations of hematite and magnetite are commensurable.
During the discussion of these reports it was noted that viscous and temporary magnetization of rocks are both relaxation phenomena, but that the relaxation coefficients of the two are different. It was also noted that the main task at present is to work out improved methods for distinguish ing the primary magnetization or else methods for magnetic cleaning. During the discussion it became evident that the paleomagnetologists present disagreed sharply with respect to the possibility of making use of the Q factor. V. V. Kochegura, A. G. Komarov, and others consider that Q can definitely be used to determine age and, in addition, that it is a very convenient stability criterion. Others (N. M. Efremova, N. P. Mikhai lova, G. N. Petrova, and D. M. Pecherskii) disagreed, and they pointed out that the value of Q depends on the magnitude of the disruptive field, so that only the ages of rocks with specific ferromagnetic components can be determined according to the value of Q. Pecherskii demonstrated in his report that the values of Q for rocks of identical ages and compositions may differ by a factor of ten or more, depending on the conditions under which the rocks were formed.
The fourth group of reports dealt with reverse magnetization in rocks. B. V. Gusev made a study of ultrabasic rocks exhibiting reverse magnetization. When such rocks were heated up to 800°C and then cooled down in a 0.6-oersted field, only a single, normally magnetized component with TK = 300 to 400° appeared. After aging of the samples for times ranging from 10 days to 2 years, self-reversal of the remanent magnetization vector took place; it was established that in this case a new magnetic phase with TK = 600° was initiated.
The report of V. V. Kruglyakov included data on the behavior of hematite and titanomagnetites under supergene conditions. Decomposition of these minerals is observed under such conditions and the magnetite separates out; reverse magnetization may also occur. Consequently,
titanomagnetites cannot always be used for paleomagnetic research.
V. V. Metallova described some studies which were made with samples of reversely magnetized traprocks from the Siberian Platform. She demonstrated that the reverse magnetization in this case was related to the composition of the rocks, rather than to the direction of the geo magnetic field.
A. A. Smelov and L. P. Zhogolev carried out an analysis of the remanent magnetization in rocks from Kazakhstan. Both positively and negatively magnetized rocks were studied. These investigators attribute the reversal of the magnetization to suitable rock composition and to rapid cooling of the rocks. In the discussion of these reports the need for further study of the self-reversal of the magnetization of rocks was stressed; it was also noted that criteria enabling the prediction of self reversal must be worked out. V. V. Kochegura questioned the conclusions of Smelov's study of the rocks from Kazakhstan, and he pointed out that the reverse magnetization of these rocks is related to rotations of the geomagnetic field rather than to self-reversal.
Several reports were read at the meeting on problems of instrumentation, which was organized on the initiative of the participants of the conference. Raising the sensitivity of magnetometers by means of resonance techniques is a basic instrumentation problem.
The Fourth Conference on Paleomagnetism made it clear that Soviet studies of the remanent magnetism of rocks are developing rapidly and leading to significant conclusions. A resolution was adopted, in which the main tasks related to paleomagnetism which still have to be carried out by geophysicists and geologists were cited. Two of the most important of these tasks are: making a detailed study of individual stages in the history of the geomagnetic field; and studying certain stratigraphical sections, with a view toward using paleomagnetic data for geological correlation.