SIMS lab

To understand what the rock is, firstly we describe distribution and elemental abundances in minerals. Size of a mineral varies from meter- to nano-scale, and our nominal microbeam technique allows description of elemental distribution down to sub-micron scale.

Before and even after analysis, we have to see what is going on there. The optical microscope can see three-dimensional structure when the sample is prepared in thin section.

Following a nominal optical observation, we describe distribution of minerals using electron beam, and quantitatively determine their major element compositions using X-ray spectroscopy, that is, electron probe micro analyzer (EPMA) equipped with five wave-dispersive X-ray spectroscopes (WDS). Our EPMA has the field emission (FE) gun and enables us to easily access highly stable and bright electron beam to achieve high spatial resolution images and elemental maps at submicron scale.

We have interests in distribution of trace elements, too; for this purpose, we apply secondary ion mass spectrometry (SIMS). Ion beam focused to ~10 micron in diameter will sputter area of interest to ionize mineral-consisting elements. The ions of concern are mass filtered and the ion intensities are determined by ion counter. The direct ion detection makes this technique high sensitive and allows determination of trace-element abundances. The nominal sensitivity is 0.1 micro g/g (or ppm).

Since the probe analyses incident charged particles to the surface of the sample, coating to grantee conductivity is necessary. We prefer carbon for electron probe and gold for ion probe.

Methods and techniques:

Trace element analyses
• E. Nakamura and I. Kushiro (1998). Trace element diffusion in jadeite and diopside melts at high pressures and its geochemical implication, Geochimica et Cosmochimica Acta, 62(18), 3151-3160.

Boron isotope geochemistry
• T. Nakano and E. Nakamura (2001). Boron isotope geochemistry of metasedimentary rocks and tourmalines in a subduction zone metamorphic suite, Physics of The Earth and Planetary Interiors, 127(1-4), 233-252.

SIMS Laboratory - Spherical Image - RICOH THETA

Related Work

• Ranaweera et al. (2018). Circa 1 Ga sub-seafloor hydrothermal alteration imprinted on the Horoman peridotite massif, Scientific Reports, 8, 9887.
• Schiavi et al. (2015). Geochemical heterogeneities in magma beneath Mount Etna recorded by 2001-2006 melt inclusions, Geochemistry, Geophysics, Geosystems, 16(7), 2109-2126.
• Malfait et al. (2014). Supervolcano eruptions driven by melt buoyancyin large silicic magma chambers, Nature geoscience, 7, 122-125.
• Bebout et al. (2013). Devolatilization history and trace element mobility in deeply subducted sedimentary rocks: Evidence from Western Alps HP/UHP suites, Chemical Geology, 342, 1-20.
• Nakamura et al. (2012). Space environment of an asteroid preserved on micrograins returned by the Hayabusa spacecraft, Proceedings of the National Academy of Sciences of the United States of America, 109(11), E624-E629.
• Schiavi et al. (2012). Trace element and Pb–B–Li isotope systematics of olivine-hosted melt inclusions: insights into source metasomatism beneath Stromboli (southern Italy), Contributions to Mineralogy and Petrology, 163, 1011-1031.
• Brophy et al. (2011). In situ ion-microprobe determination of trace element partition coefficients for hornblende, plagioclase, orthopyroxene, and apatite in equilibrium with natural rhyolitic glass, Little Glass Mountain Rhyolite, California, American Mineralogist, 96(11-12), 1838-1850.
• Malaviarachchi et al. (2010). Melt-Peridotite Reactions and Fluid Metasomatism in the Upper Mantle, Revealed from the Geochemistry of Peridotite and Gabbro from the Horoman Peridotite Massif, Japan, Journal of Petrology, 51(7), 1417-1445.
• Guo et al. (2009). Mineralogical and geochemical constraints on magmatic evolution of Paleocene adakitic andesites from the Yanji area, NE China, Lithos, 112(3-4), 321–341.
• Ota et al. (2008). Tourmaline breakdown in a pelitic system: implications for boron cycling through subduction zones, Contributions to Mineralogy and Petrology, 155, 19-32.
• Ota et al. (2008). Boron cycling by subducted lithosphere; insights from diamondiferous tourmaline from the Kokchetav ultrahigh-pressure metamorphic belt, Geochimica et Cosmochimica Acta, 72(14), 3531–3541 (2008).
• Guo et al. (2007). Generation of Palaeocene Adakitic Andesites by Magma Mixing, Yanji area, NE China. Journal of Petrology, 48(4), 661-692.
• Ishikawa et al. (2007). Multiple generations of forearc mafic-ultramafic rocks in the Timor-Tanimbar ophiolite, eastern Indonesia. Gondwana Research, 11(1-2), 200-217.
• Usui et al. (2007). Trace element fractionation in deep subduction zones inferred from a lawsonite-eclogite xenolith from the Colorado Plateau, Chemical Geology, 239(3-4), 336-351.
• Usui et al. (2006). Petrology and Geochemistry of Eclogite Xenoliths form the Colorado Plateau: Implications for the Evolution of subducted Oceanic Crust, Journal of Petrology, 47(5), 929-964.
• Ishikawa et al. (2005). Jurassic oceanic lithosphere beneath the southern Ontong Java Plateau: Evidence from xenoliths in alnöite, Malaita, Solomon Islands, Geology, 33(5), 393-396.
• King et al. (2004). Ultrahigh-pressure metabasaltic garnets as probes into deep subduction zone chemical cycling, Geochemistry, Geophysics, Geosystems, 5(12), Q12J14.
• Shimizu et al. (2004). Discovery of Archean continental and mantle fragments inferred from xenocrysts in komatiites, the Belingwe greenstone belt, Zimbabwe, Geology, 32(4), 285–288.
• G. Bebout and E. Nakamura (2003). Record in metamorphic tourmalines of subduction-zone devolatilization and boron cycling, Geology, 31(5), 407–410.
• M. Yoshikawa and E. Nakamura (2000). Geochemical evolution of the Horoman peridotite complex: Implications for melt extraction, metasomatism, andcompositional layering in the mantle, Journal of Geophysical Research, 105(B2), 2879-2901 (2000).