Rock Magnetism and Magnetic Anisotropy of Igneous Rocks from Taimyr Peninsula, Arctic Russia

摘要

Studies of rock magnetism and anisotropy of magnetic susceptibility (AMS) on folded igneous rocks from South Taimyr Peninsula, Arctic Russia are presented. The magnetic remanence is principally carried by fine grained, low-temperature oxidized titanomagnetite, and hematite is the secondary carrier in the basalts. The sills display remarkably homogeneous magnetic properties and contain larger grains with ilmenite lamellae, attesting to slow cooling. Basaltic flows possess slightly more variable magnetic properties, and homogeneous skeletal titanomagnetite suggests rapid cooling. Differences in magnetic properties in sills and basalts are caused by titanomagnetite concentration as well as grain size. Stepwise thermal demagnetization shows a stable primary remanence in the sills and basaltic flows; statistic analysis reveals that the characteristic remanence components are isolated with small within-site dispersion of the mean direction. AMS study was performed on untreated samples and samples that had been previously heated to 600°C during a paleomagnetic study to investigate the AMS properties. Laboratory heating did not lead to obviously consistent axis orientations.