Magnetic petrology and magnetic properties of western Pacific guyots; implications for seamount paleopoles

Citation:
Gee, J, Nakanishi M.  1995.  Magnetic petrology and magnetic properties of western Pacific guyots; implications for seamount paleopoles. Proceedings of the Ocean Drilling Program, Scientific Results. 144:615-630.

Keywords:

12, Stratigraphy, alternating field demagnetization, cores, Cretaceous, demagnetization, igneous rocks, induced magnetization, Limalok Seamount, Lo-En, magnetic anomalies, magnetization, Mesozoic, MIT Seamount, north pacific, Northwest Pacific, ocean floors, pacific, Pacific Ocean, paleolatitude, paleomagnetism, pole positions, reversals, seamount, seamounts, thermal demagnetization, Upper Cretaceous, volcanic rocks, West, Wodejebato Seamount

Abstract:

Despite the importance of seamount paleopoles in reconstructing past tectonic motions of the Pacific Plate, few data exist on the magnetic properties and processes of remanence acquisition in seamounts. We present a basic magnetic characterization and a detailed petrographic and microprobe study of the oxide minerals in mildly to strongly alkalic lavas recovered from five western Pacific guyots sampled during Ocean Drilling Program Leg 144. The Ti-rich chrome spinel compositions and Al- and Mg-enrich- ment in titanomagnetites reflect the alkalic nature of the lavas. The alteration history of these samples is diverse, ranging from low-temperature oxidation to highly oxidizing conditions resulting in an assemblage of magnesioferrite + titanohematite. The natural remanent magnetization (NRM) intensities for all five guyots are quite similar, yielding a combined arithmetic mean NRM intensity of 3.53 A/m, similar to previously reported values from dredged and drilled seamount material. The mean KoĢˆnigsberger ratio (9.8) implies an approximate 10% contribution of induced magnetization. Systematic discrepancies between the observed inclinations and inclinations derived from the magnetic anomaly data for Lo-En, MIT, and Takuyo-Daisan guyots are compatible with a significant bias from viscous and induced magnetization in these Cretaceous guyots.

Notes:

n/a

DOI:

10.2973/odp.proc.sr.144.020.1995