Abstract
AC susceptibility measurements as a function of field amplitude Hac and of frequency show a strong field dependence for a set of synthetic titanomagnetites (Fe3-xTixO4) and for certain basalts from the SOH-1 Hawaiian drill hole and from Iceland. In-phase susceptibility is constant below fields of about 10-100 A/m, and then increases by as much as a factor of two as Hsc is increased to 2000 A/m. Both the initial field-independent susceptibilities and field-dependence of susceptibility are systematically related to composition: initial susceptibility is 3 SI for a single-crystal sphere of TMO (x = 0) and decreases with increasing titanium content; field-dependence is nearly zero for TM0 and increases systematically to a maximum near TM60 (x = 0.6). This field dependence can in some cases be mistaken for frequency dependence, and leaf to incorrect interpretations of magnetic grain size and composition when titanomagnetite is present.
Original language | English (US) |
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Pages (from-to) | 129-139 |
Number of pages | 11 |
Journal | Earth and Planetary Science Letters |
Volume | 157 |
Issue number | 3-4 |
DOIs | |
State | Published - Apr 30 1998 |
Bibliographical note
Funding Information:This is IRM contribution #9703. The IRM is supported by grants from the National Science Foundation and the W.M. Keck Foundation. We are pleased to acknowledge the indispensable advice and contributions of Jim Marvin and Subir Banerjee, measurement help from Patrick Jackson, and constructive reviews by Horst Worm, Mark Hudson, Steve Harlan, John Dearing, and an anonymous reviewer. [RV]