ZrとHfの分別 について 個人的メモのようなもの


個人的なメモ。段々と付け加わっていくかもしれませんし、放置されるかもしれません。


分別は無いし、みんなコンドリティックと言い出した人

  • Jochum, K. P., Seufert, H. M., Spettel, B., & Palme, H. (1986). The solar-system abundances of Nb, Ta, and Y, and the relative abundances of refractory lithophile elements in differentiated planetary bodies. Geochimica et Cosmochimica Acta, 50(6), 1173-1183.https://doi.org/10.1016/0016-7037(86)90400-X

Zr/Hf比のコンドリティック値は30~50くらい。

火成過程での分別

実験岩石学的に決めたモノと天然の試料から考察したものを分けて一覧に。

  • 天然
  • Nash, W. P., & Crecraft, H. R. (1985). Partition coefficients for trace elements in silicic magmas. Geochimica et Cosmochimica Acta, 49(11), 2309-2322. https://doi.org/10.1016/0016-7037(85)90231-5
  • アブストによると"Trace element partition coefficients for 29 elements, including the rare earths, have been calculated for augite, hypersthene, sanidine, plagioclase, quartz, biotite, titanomagnetite and ilmenite from rhyodacite and rhyolite at Twin Peaks, Utah. Partition coefficients are intermediate to those reported from dacite and high silica rhyolite. At Twin Peaks, as in less silicic magmas, partitioning between phenocrysts and melt is governed primarily by crystal structure constraints as opposed to very high silica systems where the structure and volatile content of the melt become the dominant control of trace element partitioning. "
  • Dupuy, C., Liotard, J. M., & Dostal, J. (1992). Zr/Hf fractionation in intraplate basaltic rocks: carbonate metasomatism in the mantle source. Geochimica et Cosmochimica Acta, 56(6), 2417-2423. (マントル内部でのカーボナタイト関連の分別)
  • Cerny, P., Meintzer, R. E., & Anderson, A. J. (1985). Extreme fractionation in rare-element granitic pegmatites; selected examples of data and mechanisms. The Canadian Mineralogist, 23(3), 381-421. (doi見つからず。。。ResearchGateに全文があったのでググってみてください)
  • Wang, X., Griffin, W. L., & Chen, J. (2010). Hf contents and Zr/Hf ratios in granitic zircons. Geochemical Journal, 44(1), 65-72.https://doi.org/10.2343/geochemj.1.0043
  • 実験
  • Forsythe, L. M., Nielsen, R. L., & Fisk, M. R. (1994). High-field-strength element partitioning between pyroxene and basaltic to dacitic magmas. Chemical Geology, 117(1-4), 107-125. https://doi.org/10.1016/0009-2541(94)90124-4
  • "For most ferromagnesian minerals in equilibrium with a depolymerized melt, DHf > DZr. Typical values of DHf/DZr range from 1.5 to 2.5 for clinopyroxene, amphibole, and titanite. Because of the change in the Hf/Zr activity ratio in the melt, the relative fractionation of Zr and Hf by these minerals will disappear or even be reversed when the melt composition approaches that of a metaluminous or peraluminous granite. It is thus not surprising that fractional crystallization of such granitic magmas leads to a decrease in Zr/Hf, whereas fractional crystallization of depolymerized melts tends to increase Zr/Hf. There is no need to invoke fluid metasomatism to explain these effects. Results demonstrate that for ions with identical charge and nearly identical radius, crystal chemistry does not alone determine relative compatibilities. Rather, the effect of changing activity coefficients in the melt may be comparable to or even larger than elastic strain effects in the crystal lattice."
  • Fujinawa, A., & Green, T. H. (1997). Partitioning behaviour of Hf and Zr between amphibole, clinopyroxene, garnet and silicate melts at high pressure. European Journal of Mineralogy, 9(2), 379-391. https://doi.org/10.1127/ejm/9/2/0379
  • David, K., Schiano, P., & Allegre, C. J. (2000). Assessment of the Zr/Hf fractionation in oceanic basalts and continental materials during petrogenetic processes. Earth and Planetary Science Letters, 178(3-4), 285-301. https://doi.org/10.1016/S0012-821X(00)00088-1
  • Linnen, R. L., & Keppler, H. (2002). Melt composition control of Zr/Hf fractionation in magmatic processes. Geochimica et Cosmochimica Acta, 66(18), 3293-3301. https://doi.org/10.1016/S0016-7037(02)00924-9 (花崗岩質メルト中でのZrとHfの溶解度について)
  • ""it has been noted by several authors that Zr/Hf ratios can be variable (e.g., Jochum et al 1986, Dupuy et al 1992. It has been proposed that higher-than-chondritic Zr/Hf ratios in ocean island basalts can largely be explained by clinopyroxene fractionation (David et al., 2000). However, the same authors indicated that lower-than-chondritic Zr/Hf ratios in granitic rocks are still problematic, and they invoked metasomatism by fluorine-rich aqueous fluids as an explanation. Fluid metasomatism has been proposed elsewhere to account for nonchondritic Zr/Hf values in granitic rocks (Bau, 1996), but other authors maintain that this ratio can be explained by crystal fractionation (Pan, 1997). These interpretations were made without the benefit of knowing the relative solubilities of zircon (ZrSiO4) and hafnon (HfSiO4) in different granitic melts, critical experimental data that are lacking."
  • Johnston, A. D., & Schwab, B. E. (2004). Constraints on clinopyroxene/melt partitioning of REE, Rb, Sr, Ti, Cr, Zr, and Nb during mantle melting: First insights from direct peridotite melting experiments at 1.0 GPa. Geochimica et Cosmochimica Acta, 68(23), 4949-4962. https://doi.org/10.1016/j.gca.2004.06.009
  • Pfänder, J. A., Münker, C., Stracke, A., & Mezger, K. (2007). Nb/Ta and Zr/Hf in ocean island basalts—implications for crust–mantle differentiation and the fate of Niobium. Earth and Planetary Science Letters, 254(1-2), 158-172. https://doi.org/10.1016/j.epsl.2006.11.027"

London先生のPegmatite本によると…
" Partitioning studies show that Zr and Hf are highly correlated with one another and with Nb, Ta and Sn. Their compatibility essentially follows that of Tin in mafic silicates and oxide (e.g. Forsythe et al., 1994; Johnson and Schwab, 2004). In pyroxenes and amphiboles, DZr/DHf is >1, whereas the partitioning between garnet and biotite and melt goes in the opposite direction (Nash and Crecraft, 1985; Fujinawa and Green, 1997). The crystalline phases that ultimately control Zr.Hf are those that produce a progressive decrease in CZr/CHf of melt. This is the pattern of these elements in real magmatic suites from granites to evolved pegmatites. " (p. 157より)

※DZr/DHf:
DZr = CZrxl/CZrmelt, DHf = CHfxl/CHfmelt
DZr/DHfが1以上だと、ある鉱物にZrが濃集してメルトにHfが残る。1以下だと逆にHfが鉱物に濃集して、Zrがメルトに残る。上記のLondon先生の説明によると、輝石や角閃石がメルトから落ちるとメルトにHfが残るが、ざくろ石や黒雲母が落ちると逆にHfが吸われてZrがメルトに残る。


海水や化学堆積岩関連

  • Dupuy, C., Liotard, J. M., & Dostal, J. (1992). Zr/Hf fractionation in intraplate basaltic rocks: carbonate metasomatism in the mantle source. Geochimica et Cosmochimica Acta, 56(6), 2417-2423.https://doi.org/10.1016/j.gca.2014.05.036 (マンガン酸化物や水酸化物への吸着度の違いによって分別?)
  • Bau, M. (1996). Controls on the fractionation of isovalent trace elements in magmatic and aqueous systems: evidence from Y/Ho, Zr/Hf, and lanthanide tetrad effect. Contributions to Mineralogy and Petrology, 123(3), 323-333. https://doi.org/10.1007/s004100050159
  • Bolhar, R., Kamber, B. S., Moorbath, S., Fedo, C. M., & Whitehouse, M. J. (2004). Characterisation of early Archaean chemical sediments by trace element signatures. Earth and Planetary Science Letters, 222(1), 43-60. https://doi.org/10.1016/j.epsl.2004.02.016
  • Brengman, L. A., & Fedo, C. M. (2018). Development of a mixed seawater-hydrothermal fluid geochemical signature during alteration of volcanic rocks in the Archean (∼ 2.7 Ga) Abitibi Greenstone Belt, Canada. Geochimica et Cosmochimica Acta, 227, 227-245. https://doi.org/10.1016/j.gca.2018.02.019
  • "Igneous rocks by contrast should possess a flat REE+Y slope, no positive lanthanum anomaly, and should have Y/Ho ratios ranging between 24 and 34, and Zr/Hf ratios between 26 and 46. We used these ratios as a geochemical “fingerprint” to establish fields for chemical precipitates versus igneous rocks and plotted each of the three groups of rocks from the HMG for comparison. "
  • Zr/Hf が 26以下または46以上であるというのは、火成起源ではなく海水からの沈殿であることを判別する基準らしい。


関連する鉱物は以下の通り。


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