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Titanium- and water-rich metamorphic olivine in high-pressure serpentinites from the Voltri Massif (Ligurian Alps, Italy): evidence for deep subduction of high-field strength and fluid-mobile elements

Cited 27 time in Web of Science Cited 28 time in Scopus
Authors
De Hoog, Jan C. M.; Hattori, Keiko; Jung, Haemyeong
Issue Date
2014-03
Publisher
Springer
Citation
Contributions to Mineralogy and Petrology, 167:990
Keywords
자연과학Metamorphic olivineClinohumiteSerpentiniteHigh-pressure metamorphismSubduction
recycling of elements
Voltri Massif
Abstract
Titanium- and water-rich metamorphic olivine (Fo 86-88) is reported from partially dehydrated serpentinites from the Voltri complex, Ligurian Alps. The rocks are composed of mostly antigorite and olivine in addition to magnetite, chlorite, clinopyroxene and Ti-clinohumite. In situ secondary ion mass spectrometry (SIMS) data show that metamorphic olivine has very high and strongly correlated H2O (up to 0.7 wt%) and TiO2 contents (up to 0.85 wt%). Ti-rich olivine shows colourless to yellow pleochroism. Olivine associated with Ti-clinohumite contains low Ti, suggesting that Ti-rich olivine is not the breakdown product of Ti-clinohumite. Fourier transform infrared spectroscopy (FTIR) absorption spectra show peaks of serpentine, Ti-clinohumite and OH-related Si vacancies. Combining FTIR and SIMS data, we suggest the presence of clustered planar defects or nanoscale exsolutions of Ti-clinohumite in olivine. These defects or exsolutions contain more H2O (x similar to 0.1 in the formula 4Mg(2)SiO(4)center dot(1-x)Mg(OH, F)(2)center dot xTiO(2)) than Ti-clinohumite in the sample matrix (x = 0.34-0.46). In addition to TiO2 and H2O, secondary olivine contains significant Li (2-60 ppm), B (10-20 ppm), F (10-130 ppm) and Zr (0.9-2.1 ppm). It is enriched in B-11 (delta B-11 = +17 to +23 parts per thousand). Our data indicate that secondary olivine may play a significant role in transporting water, high-field strength and fluid-mobile elements into the deeper mantle as well as introduce significant B isotope anomalies. Release of hydrogen from H2O-rich olivine subducted into the deep mantle may result in strongly reduced mantle domains.
ISSN
0010-7999
Language
English
URI
https://hdl.handle.net/10371/92636
DOI
https://doi.org/10.1007/s00410-014-0990-x
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College of Natural Sciences (자연과학대학)Dept. of Earth and Environmental Sciences (지구환경과학부)Journal Papers (저널논문_지구환경과학부)
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