Hydrocarbons and Magnetizations in Magnetite
Published:January 01, 1993
- PDF LinkChapter PDF
R. Douglas Elmore, Scott W. Imbus, Mike H. Engel, David Fruit, 1993. "Hydrocarbons and Magnetizations in Magnetite", Applications of Paleomagnetism to Sedimentary Geology, Djafar M. Aïssaoui, Donald F. McNeill, Neil F. Hurley
Download citation file:
Paleomagnetic, rock magnetic, petrographic, and geochemical studies indicate that hydrocarbons can cause either an increase or decrease in the magnetization in sedimentary rocks. For example, hydrocarbon-impregnated Permian calcite speleothems in southwestern Oklahoma contain a Permian chemical remanent magnetization (CRM) that resides in magnetite. A positive relationship between extractable organic matter and the natural remanent magnetization (NRM) suggests that the chemical conditions created by the hydrocarbons caused precipitation of the magnetite and acquisition of the associated CRM. There is no correlation, however, between percent asphaltenes and NRM in the speleothems. In addition, bitumen speleothems with high NRMs are, in general, less extensively biode-graded. These results suggest that a chemical process, and not biodegradation, is the mechanism for magnetite authigenesis in speleothems. The results from the speleothems suggest that hydrocarbons can cause acquisition of magnetization that can be dated using paleomagnetic analysis. Development of this dating approach, however, requires more work to better understand the mechanism(s) of magnetite precipitation.
Studies of red bed and hydrocarbon-impregnated samples from cores of the Lyons Sandstone in the Denver Basin and from outcrops of the Maroon Formation (Schoolhouse Member) in northwest Colorado indicate that while hydrocarbons can cause precipitation of magnetite, they can also reduce the NRM by dissolution of hematite. This has implications for the various types of magnetic prospecting techniques that have been proposed.
Figures & Tables
Applications of Paleomagnetism to Sedimentary Geology
Applications of Paleomagnetism to Sedimentary Geology - Based on the 1991 SEPM Research Symposium, the results are directed towards bringing the disciplines of Paleomagnetism and sedimentary geology closer together. Advances in the field of sedimentary geology will likely result from continued development of new ideas, questioning of old dogma, and, most importantly, providing means for testing these new hypotheses. It is hoped that the union of these two disciplines will help address many fundamental geological questions, such as the perennial problems of precise age-dating, stratigraphic correlation and geometries, understanding the timing and nature of post-depositional diagenetic fabrics, and the intriguing relationship between hydrocarbons and magnetization. The reader will find an unusual diversity of research topics presented in this volume. This diversity serves as a testimony to the potential applications awaiting the sedimentary geologist willing to explore these new paleomagnetic tools.