Open AccessEfficiency of heavy liquid separation to concentrate magnetic particles
Author(s) -
Franke Christine,
Frederichs Thomas,
Dekkers Mark J.
Publication year - 2007
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2007.03489.x
Subject(s) - magnetite , coercivity , remanence , paramagnetism , magnetization , magnetometer , rock magnetism , ferrimagnetism , saturation (graph theory) , materials science , thermomagnetic convection , environmental magnetism , magnetic field , magnetic separation , mineralogy , geology , condensed matter physics , analytical chemistry (journal) , chemistry , metallurgy , environmental chemistry , physics , mathematics , quantum mechanics , combinatorics
SUMMARY Low‐temperature rock magnetic measurements have distinct diagnostic value. However, in most bulk marine sediments the concentration of ferrimagnetic and antiferromagnetic minerals is extremely low, so even sensitive instrumentation often responds to the paramagnetic contribution of the silicate matrix in the residual field of the magnetometer. Analysis of magnetic extracts is usually performed to solve the problems raised by low magnetic concentrations. Additionally magnetic extracts can be used for several other analyses, for example electron microscopy or X‐ray diffraction. The magnetic extraction technique is generally sufficient for sediments dominated by magnetite. In this study however, we show that high‐coercivity components are rather underrepresented in magnetic extracts of sediments with a more complex magnetic mineralogy. We test heavy liquid separation, using hydrophilic sodium polytungstenate solution Na 6 [H 2 W 12 O 40 ], to demonstrate the efficiencies of both concentration techniques. Low‐temperature cycling of zero‐field‐cooled, field‐cooled and saturation isothermal remanent magnetization acquired at room temperature was performed on dry bulk sediments, magnetic extracts, and heavy liquid separates of clay‐rich pelagic sediments originating from the Equatorial Atlantic. The results of the thermomagnetic measurements clarify that magnetic extraction favours components with high spontaneous magnetization, such as magnetite and titanomagnetite. The heavy liquid separation is unbiased with respect to high‐ and low‐coercive minerals, thus it represents the entire magnetic assemblage.