Anatomy of a pressure-induced, ferromagnetic-to-paramagnetic transition in pyrrhotite: Implications for the formation pressure of diamonds

Simple item page
dc.contributor.authorGilder, Stuart A
dc.contributor.authorEgli, Ramon
dc.contributor.authorHochleitner, Rupert
dc.contributor.authorRoud, Sophie C
dc.contributor.authorVolk, Michael W R
dc.contributor.authorLe Goff, Maxime
dc.contributor.authorde Wit, Maarten
dc.date.accessioned2021-10-08T07:08:09Z
dc.date.available2021-10-08T07:08:09Z
dc.date.issued2011
dc.description.abstractMeteorites and diamonds encounter high pressures during their formation or subsequent evolution. These materials commonly contain magnetic inclusions of pyrrhotite. Because magnetic properties are sensitive to strain, pyrrhotite can potentially record the shock or formation pressures of its host. Moreover, pyrrhotite undergoes a pressure-induced phase transition between 1.6 and 6.2 GPa, but the magnetic signature of this transition is poorly known. Here we report room temperature magnetic measurements on multidomain and single-domain pyrrhotite under nonhydrostatic pressure. Magnetic remanence in single-domain pyrrhotite is largely insensitive to pressure until 2 GPa, whereas the remanence of multidomain pyrrhotite increases 50% over that of initial conditions by 2 GPa, and then decreases until only 33% of the original remanence remains by 4.5 GPa. In contrast, magnetic coercivity increases with increasing pressure to 4.5 GPa. Below ∼1.5 GPa, multidomain pyrrhotite obeys Néel theory with a positive correlation between coercivity and remanence; above ∼1.5 GPa, it behaves single domain-like yet distinctly different from uncompressed single-domain pyrrhotite. The ratio of magnetic coercivity and remanence follows a logarithmic law with respect to pressure, which can potentially be used as a geobarometer. Owing to the greater thermal expansion of pyrrhotite with respect to diamond, pyrrhotite inclusions in diamonds experience a confining pressure at Earth’s surface. Applying our experimentally derived magnetic geobarometer to pyrrhotite-bearing diamonds from Botswana and the Central African Republic suggests the pressures of the pyrrhotite inclusions in the diamonds range from 1.3 to 2.1 GPa. These overpressures constrain the mantle source pressures from 5.4 to 9.5 GPa, depending on which bulk modulus and thermal expansion coefficients of the two phases are used.
dc.identifier.apacitationGilder, S. A., Egli, R., Hochleitner, R., Roud, S. C., Volk, M. W. R., Le Goff, M., & de Wit, M. (2011). Anatomy of a pressure-induced, ferromagnetic-to-paramagnetic transition in pyrrhotite: Implications for the formation pressure of diamonds. <i>Journal of Geophysical Research</i>, 116(B10), 174 - 177. http://hdl.handle.net/11427/34511en_ZA
dc.identifier.chicagocitationGilder, Stuart A, Ramon Egli, Rupert Hochleitner, Sophie C Roud, Michael W R Volk, Maxime Le Goff, and Maarten de Wit "Anatomy of a pressure-induced, ferromagnetic-to-paramagnetic transition in pyrrhotite: Implications for the formation pressure of diamonds." <i>Journal of Geophysical Research</i> 116, B10. (2011): 174 - 177. http://hdl.handle.net/11427/34511en_ZA
dc.identifier.citationGilder, S.A., Egli, R., Hochleitner, R., Roud, S.C., Volk, M.W.R., Le Goff, M. & de Wit, M. 2011. Anatomy of a pressure-induced, ferromagnetic-to-paramagnetic transition in pyrrhotite: Implications for the formation pressure of diamonds. <i>Journal of Geophysical Research.</i> 116(B10):174 - 177. http://hdl.handle.net/11427/34511en_ZA
dc.identifier.issn0022-1406
dc.identifier.issn0148-0227
dc.identifier.issn1934-2098
dc.identifier.issn2156-2202
dc.identifier.ris TY - Journal Article AU - Gilder, Stuart A AU - Egli, Ramon AU - Hochleitner, Rupert AU - Roud, Sophie C AU - Volk, Michael W R AU - Le Goff, Maxime AU - de Wit, Maarten AB - Meteorites and diamonds encounter high pressures during their formation or subsequent evolution. These materials commonly contain magnetic inclusions of pyrrhotite. Because magnetic properties are sensitive to strain, pyrrhotite can potentially record the shock or formation pressures of its host. Moreover, pyrrhotite undergoes a pressure-induced phase transition between 1.6 and 6.2 GPa, but the magnetic signature of this transition is poorly known. Here we report room temperature magnetic measurements on multidomain and single-domain pyrrhotite under nonhydrostatic pressure. Magnetic remanence in single-domain pyrrhotite is largely insensitive to pressure until 2 GPa, whereas the remanence of multidomain pyrrhotite increases 50% over that of initial conditions by 2 GPa, and then decreases until only 33% of the original remanence remains by 4.5 GPa. In contrast, magnetic coercivity increases with increasing pressure to 4.5 GPa. Below ∼1.5 GPa, multidomain pyrrhotite obeys Néel theory with a positive correlation between coercivity and remanence; above ∼1.5 GPa, it behaves single domain-like yet distinctly different from uncompressed single-domain pyrrhotite. The ratio of magnetic coercivity and remanence follows a logarithmic law with respect to pressure, which can potentially be used as a geobarometer. Owing to the greater thermal expansion of pyrrhotite with respect to diamond, pyrrhotite inclusions in diamonds experience a confining pressure at Earth’s surface. Applying our experimentally derived magnetic geobarometer to pyrrhotite-bearing diamonds from Botswana and the Central African Republic suggests the pressures of the pyrrhotite inclusions in the diamonds range from 1.3 to 2.1 GPa. These overpressures constrain the mantle source pressures from 5.4 to 9.5 GPa, depending on which bulk modulus and thermal expansion coefficients of the two phases are used. DA - 2011 DB - OpenUCT DP - University of Cape Town IS - B10 J1 - Journal of Geophysical Research LK - https://open.uct.ac.za PY - 2011 SM - 0022-1406 SM - 0148-0227 SM - 1934-2098 SM - 2156-2202 T1 - Anatomy of a pressure-induced, ferromagnetic-to-paramagnetic transition in pyrrhotite: Implications for the formation pressure of diamonds TI - Anatomy of a pressure-induced, ferromagnetic-to-paramagnetic transition in pyrrhotite: Implications for the formation pressure of diamonds UR - http://hdl.handle.net/11427/34511 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/34511
dc.identifier.vancouvercitationGilder SA, Egli R, Hochleitner R, Roud SC, Volk MWR, Le Goff M, et al. Anatomy of a pressure-induced, ferromagnetic-to-paramagnetic transition in pyrrhotite: Implications for the formation pressure of diamonds. Journal of Geophysical Research. 2011;116(B10):174 - 177. http://hdl.handle.net/11427/34511.en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Geological Sciences
dc.publisher.facultyFaculty of Science
dc.sourceJournal of Geophysical Research
dc.source.journalissueB10
dc.source.journalvolume116
dc.source.pagination174 - 177
dc.source.urihttps://dx.doi.org/10.1029/2011JB008292
dc.subject.otherCrystallography and Materials Science
dc.subject.otherddc:550
dc.titleAnatomy of a pressure-induced, ferromagnetic-to-paramagnetic transition in pyrrhotite: Implications for the formation pressure of diamonds
dc.typeJournal Article
uct.type.publicationResearch
uct.type.resourceJournal Article
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
GilderStuartA_Anatomya_pressu_2011.pdf
Size:
1.66 MB
Format:
Adobe Portable Document Format
Description:
Download
Collections
Journal Articles