12:00 PM - 12:15 PM
[SEM20-12] Strong chemical treatment of sediments for environmental magnetic studies on mineral inclusions
Keywords:environmental magnetism, magnetic mineral inclusion, eolian dust
The intensity of saturation isothermal remanence (SIRM) of quartz and feldspar was on the order of 10-4 Am2/kg. This is about 1-5 % of the SIRM of untreated sample. The signal can be readily measured using cryogenic magnetometers or MPMS. The remanence can also be detected in alternating gradient force magnetometers, but paramagnetic signal from feldspar introduces large background in induced magnetization, making determination of hysteresis difficult. Thermal demagnetization of IRM and low temperature measurements indicate that the magnetic mineral associated with quartz and feldspar is near-stoichiometric magnetite, which is distinct from the more oxidized detrital magnetite. This might reflect magnetite exsolution in feldspar. To check this, a pilot sample was further treated by H2SiO6 to isolate quartz. Low temperature measurements indicate that the quartz also contains near-stoichiometric magnetite, suggesting that the magnetite is primary inclusion and not exsolution. If confirmed, the near-stoichiometric magnetite inclusions may be the characteristics of eolian dust from China, and strong chemical treatment is a promising approach to reveal this hidden property. A comparison with sediment from different region is under way.