TY - JOUR
T1 - U-Th radioactive disequilibrium and ESR dating of a barite-containing sulfide crust from South Mariana Trough
AU - Takamasa, Asako
AU - Nakai, Shun'ichi
AU - Sato, Fumihiro
AU - Toyoda, Shin
AU - Banerjee, Debabrata
AU - Ishibashi, Junichiro
N1 - Funding Information:
This research was supported by a Grant-in-Aid for Scientific Research on Innovative Areas “TAIGA” of the Ministry of Education, Culture, Sports, Science and Technology (MEXT) , Japan. We thank Kazuhiko Shimada, Department of Earth and Planetary Sciences, Kyushu University, for his assistance with mineral texture observation and EPMA analysis. This manuscript benefited from comments from James Paces, David Richards and an anonymous reviewer.
PY - 2013/2
Y1 - 2013/2
N2 - A block of sulfide crust collected from an active hydrothermal mound in an Archaean site (12°56.4'N, 143°37.9'E; depth ca. 3000 m) of the South Mariana Trough was dated using both 230Th/234U disequilibrium and electron spin resonance (ESR) methods to establish the growth duration. Eight subsamples from the sulfide crust were separated further into magnetic and non-magnetic fractions using a Franz isodynamic separator. Thirteen sulfide samples, soluble in nitric acid, yielded 230Th/234U ages of 0.3-2.2 ka. The magnetic fractions had significantly lower Th/U ratios, which enabled age determinations as precise as ±2% (2σ). The age distribution obtained for the section of sulfide crust analyzed is consistent with deposition of sulfide minerals from the upper surface of the crust to the inner side. The 230Th/234U ages of the sulfide minerals were compared with ESR ages of barites separated from 12 subsamples of the same sulfide crust. ESR ages of 0.27-1.3 ka show a spatial pattern broadly resembling that observed in 230Th/234U dating method. While there are some significant offsets, these results illustrate the potential of the two methods for use in investigation of the evolutional history of a hydrothermal system.
AB - A block of sulfide crust collected from an active hydrothermal mound in an Archaean site (12°56.4'N, 143°37.9'E; depth ca. 3000 m) of the South Mariana Trough was dated using both 230Th/234U disequilibrium and electron spin resonance (ESR) methods to establish the growth duration. Eight subsamples from the sulfide crust were separated further into magnetic and non-magnetic fractions using a Franz isodynamic separator. Thirteen sulfide samples, soluble in nitric acid, yielded 230Th/234U ages of 0.3-2.2 ka. The magnetic fractions had significantly lower Th/U ratios, which enabled age determinations as precise as ±2% (2σ). The age distribution obtained for the section of sulfide crust analyzed is consistent with deposition of sulfide minerals from the upper surface of the crust to the inner side. The 230Th/234U ages of the sulfide minerals were compared with ESR ages of barites separated from 12 subsamples of the same sulfide crust. ESR ages of 0.27-1.3 ka show a spatial pattern broadly resembling that observed in 230Th/234U dating method. While there are some significant offsets, these results illustrate the potential of the two methods for use in investigation of the evolutional history of a hydrothermal system.
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U2 - 10.1016/j.quageo.2012.12.002
DO - 10.1016/j.quageo.2012.12.002
M3 - Article
AN - SCOPUS:84875212644
VL - 15
SP - 38
EP - 46
JO - Quaternary Geochronology
JF - Quaternary Geochronology
SN - 1871-1014
ER -