Publication Date:
1989-01-01
Description:
Detailed paleomagnetic investigation was carried out on 33 trachyte and trachyandesite rock samples collected at 5 sites from the Aulis volcanics in the Tansen area, the Lesser Himalaya, Nepal. Analysis of magnetic behavior by stepwise alternating field (up to 53 mT) and then thermal demagnetization shows complex multi-component remanence composed of at least four components as follows: 1) Component A(D=001°, I=47°)-of recent field origin, 2) Component B (D=339°, I=32°)-interpreted as acquired during early Miocene, 3) Component C (D=330°, I=-49°)-probably acquired during Late Cretaceous, and 4) Component D, poorly defined, with southerly declination and downward inclination of about 55°-probably acquired prior the acquisition of component C. All these components show in situ grouping suggesting their secondary nature. Thermomagnetic analysis showed double-Curie point curves indicating two major magnetic phases with Curie temperatures around 565°C and 360°C. These phases are interpreted as of Ti-poor magnetite and titanomaghemite, respectively, which were formed due to low-temperature oxidation of original titanomaenetite. Analysis of unblocking temperature spectra suggests that the 360°C phase contributes to the component B magnetization. © 1989, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.
Print ISSN:
0022-1392
Topics:
Geosciences
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