PALEOMAGNETIC STUDY ON PLATE MOTION AND INTRAPLATE MOTIONS OF THE TARIM BASIN, CHINA

摘要

All the samples for paleomagnetic analysis were drilled with a portable gasoline powered drilling apparatus and oriented in situ using an inclinometer and a magnetic compass. Besides, we also recorded the solar azimuth angles for most samples in all possible cases. The oriented cores were further sliced into cylindric specimens 2.5cm long in the laboratory and natural remanent magnetization (NRM) of individual specimens was then measured. Afterwards, the specimens were kept in laboratory of the " zero" field laboratory for a while. Instruments employed for measuring are DSM-1 or DSM-2 Schonstedt spinner magnetometer, 2G-640 or 2G-755-R cryogenic magnetometer and Minispin magnetometer. Systematic demagnetizing proceedings were conducted for all the speciments after viscous magnetization tests. Both alternating field (AF) and thermal demagnetization techniques were used in a stepwise fashion in order to remove secondary components. A Schonstedt TSD-1 furnace and a GSD-5 3-axis self-reversing tumbler were employed in demagnetizing performance. A comparison of the results obtained with these two methods show that thermal treatment works more efficiently than AF does. This led us to give up AF method and applied thermal cleaning to the maffority of the remaining specimens.