Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (7) Citing Articles via Google Scholar Google Scholar Articles by Pósfai, M. Articles by Kontny, A. Search for Related Content GeoRef GeoRef Citation

Pyrrhotite varieties from the 9.1 km deep borehole of the KTB project

¹ Department of Earth and Environmental Sciences, University of Veszprém, Veszprém, POB 158, H-8201, Hungary
² Department of Geology, Arizona State University, Tempe, Arizona 85287-1404, U.S.A.
³ Geologisch-Paläontologisches Institut, Im Neuenheimer Feld 234, D-69117 Heidelberg, Germany

Correspondence: ^* E-mail: posfaim{at}almos.vein.hu

We used transmission electron microscopy (TEM) to study pyrrhotite from the German Continental Deep Drilling ("Kontinentale Tiefbohrung," KTB) project. Our goals were to determine the distribution of structure types with depth and to establish relationships between the bulk thermo-magnetic behavior and the microstructures of pyrrhotite. In samples from the deep section of the borehole (9080 m below surface, which is equivalent to an in-situ temperature of ~260 °C), the dominant variety of pyrrhotite is 1C that has a mostly disordered vacancy distribution. Faint, diffuse superstructure reflections in the selected-area electron diffraction (SAED) patterns indicate some nC-like ordering occurs, probably in small domains. In addition to the disordered pyrrhotite, a 5C type is also present. According to bulk thermomagnetic measurements, pyrrhotite grains from 9080 m are antiferromagnetic at room temperature; we attribute this behavior to the dominance of the disordered 1C type. In the upper section of the hole (at 564 and 2325 m) several pyrrhotite varieties occur, but the 4C type is most common, in agreement with the ferrimagnetic character of most pyrrhotite grains.

Optical microscopy of pyrrhotite grains that are covered with a magnetic colloid reveal intergrown ferrimagnetic and antiferromagnetic lamellae. TEM images show that these grains are intergrowths of 4C, 5C, and nC types. We interpret these microstructural variations to be responsible for the variation in magnetic properties within single pyrrhotite grains.

This article has been cited by other articles:

				E. FERROW, J. ADETUNJI, and J. S. NKOMA Characterization of pyrrhotite in Cu-Ni-ore bodies from mines in Botswana by Mossbauer spectroscopy, X-ray diffraction, and thermomagnetometry European Journal of Mineralogy, October 1, 2006; 18(5): 653 - 664. [Abstract] [Full Text] [PDF]

				S. R. Hem and E. Makovicky THE SYSTEM Fe Co Ni As S. II. PHASE RELATIONS IN THE (Fe,Co,Ni)As1.5S0.5 SECTION AT 650{degrees} AND 500{degrees}C Can Mineral, February 1, 2004; 42(1): 63 - 86. [Abstract] [Full Text] [PDF]

				S. R. Hem, E. Makovicky, and F. Gervilla COMPOSITIONAL TRENDS IN Fe, Co AND Ni SULFARSENIDES AND THEIR CRYSTAL-CHEMICAL IMPLICATIONS: RESULTS FROM THE ARROYO DE LA CUEVA DEPOSITS, RONDA PERIDOTITE, SOUTHERN SPAIN Can Mineral, June 1, 2001; 39(3): 831 - 853. [Abstract] [Full Text] [PDF]

				A. Kontny, H. de Wall, T. G. Sharp, and M. Posfai Mineralogy and magnetic behavior of pyrrhotite from a 260 {degrees}C section at the KTB drilling site, Germany American Mineralogist, October 1, 2000; 85(10): 1416 - 1427. [Abstract] [Full Text] [PDF]