Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by Yang, J.-J. Articles by Enami, M. Search for Related Content GeoRef GeoRef Citation

Chromian dissakisite-(Ce) in a garnet lherzolite from the Chinese Su-Lu UHP metamorphic terrane: Implications for Cr incorporation in epidote-group minerals and recycling of REE into the Earth’s mantle

¹ LTE Laboratory, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China
² Department of Earth and Environmental Sciences, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan

Correspondence: ^* E-mail: jjyang{at}mail.igcas.ac.cn

Chromian dissakisite-(Ce), a Cr-enriched Mg analogue of allanite-(Ce), is found in a garnet lherzolite from the Su-Lu ultrahigh-pressure (UHP) metamorphic terrane, eastern China. Major minerals of the lherzolite are olivine [X_Mg = Mg/(Mg + Fe) = 0.92], pyrope-rich garnet (Prp_70.1–73.2Alm_11.3–13.4Grs_6.9–8.3Uvr_3.6–5.1Anr_0–0.4Sps_0.7–1.7), orthopyroxene (X_Mg = 0.92–0.93), and clinopyroxene (X_Mg = 0.92–0.95). The chromian dissakisite-(Ce) occurs as a single-crystal inclusion in a clinopyroxene neoblast that also contains several irregularly shaped olivine grains. It is partly metamict, and there is intensive radial cracking in the surrounding clinopyroxene. Its composition is represented by the averaged formula: (Ca_0.86Na_0.03)_0.89(REE_0.86Th_0.04)_0.90(Mg_0.98Fe²⁺_0.20Fe³⁺_0.21Cr_0.36Al_1.39Ti_0.04)Si_3.03O₁₂(OH), with Ce₂O₃, MgO and Cr₂O₃ contents up to 13.1, 7.3, and 5.4 wt%, respectively. Because the M3 site in the chromian dissakisite-(Ce) is fully occupied by Mg and Fe²⁺, Fe³⁺ and Cr can only occupy the smaller M1 site. Similar site occupancy is noted for a chromian allanite from the Sanbagawa metamorphic belt, Japan, which contains up to 0.547 Cr atoms per formula unit (apfu). Such compositional characteristics of the chromian dissakisite/allanite and existing polarized absorption data on Cr-bearing epidote suggest the existence of possible end-members, "CeCa(Mg,Fe)CrAlSi₃O₁₂(OH)," for the epidote-group minerals, which may form solid solution with Ca₂Al₃Si₃O₁₂(OH) through coupled substitutions of REEMgCa_–1Al_–1, REEFeCa_–1Al_–1, and CrAl_–1. The rare earth elements (REE), Ca, and Na total 1.79 apfu, implying that Mn and Fe²⁺ are also present on the nine-coordinated A1 site. The high REE abundance, the presence of minor Na, and the Mg and Cr-enriched characteristics of the mineral suggest that it was formed as a result of reaction between the host lherzolite and crust-derived melt/fluid at UHP conditions. Textural relations suggest that the chromian dissakisite-(Ce) was unstable in the garnet lherzolite and reacted with olivine to form clinopyroxene. Dissakisite-(REE) in subducted ultramafic rocks can transport rare earth elements into the Earth’s mantle.

This article has been cited by other articles:

				B. Lavina, S. Carbonin, U. Russo, and S. Tumiati The crystal structure of dissakisite-(La) and structural variations after annealing of radiation damage American Mineralogist, January 1, 2006; 91(1): 104 - 110. [Abstract] [Full Text] [PDF]

				M. Hoshino, M. Kimata, N. Nishida, A. Kyono, M. Shimizu, and S. Takizawa The chemistry of allanite from the Daibosatsu Pass, Yamanashi, Japan Mineralogical Magazine, August 1, 2005; 69(4): 403 - 423. [Abstract] [Full Text] [PDF]

				S. Tumiati, G. Godard, S. Martin, P. Nimis, V. Mair, and B. Boyer Dissakisite-(La) from the Ulten zone peridotite (Italian Eastern Alps): A new end-member of the epidote group American Mineralogist, July 1, 2005; 90(7): 1177 - 1185. [Abstract] [Full Text] [PDF]

				Z. M. Zhang, D. Rumble, J.G. Liou, Y. L. Xiao, and Y. J. Gao Oxygen isotope geochemistry of rocks from the Pre-Pilot Hole of the Chinese Continental Scientific Drilling Project (CCSD-PPH1) American Mineralogist, May 1, 2005; 90(5-6): 857 - 863. [Abstract] [Full Text] [PDF]

				M. Enami, J. G. Liou, and C. G. Mattinson Epidote Minerals in High P/T Metamorphic Terranes: Subduction Zone and High- to Ultrahigh-Pressure Metamorphism Reviews in Mineralogy and Geochemistry, January 1, 2004; 56(1): 347 - 398. [Full Text] [PDF]

				R. Giere and S. S. Sorensen Allanite and Other REE-Rich Epidote-Group Minerals Reviews in Mineralogy and Geochemistry, January 1, 2004; 56(1): 431 - 493. [Full Text] [PDF]

				D. Frei, A. Liebscher, G. Franz, and P. Dulski Trace Element Geochemistry of Epidote Minerals Reviews in Mineralogy and Geochemistry, January 1, 2004; 56(1): 553 - 605. [Full Text] [PDF]

				null Zheng Yong-Fei, Y.-F. Zheng, J.-J. Yang, B. Gong, and B.-m. Jahn Partial equilibrium of radiogenic and stable isotope systems in garnet peridotite during ultrahigh-pressure metamorphism American Mineralogist, November 1, 2003; 88(11-12): 1633 - 1643. [Abstract] [Full Text] [PDF]