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 (2) Citing Articles via Google Scholar Google Scholar Articles by Sorensen, S. Articles by Rumble, D. Search for Related Content GeoRef GeoRef Citation

The origin of jadeitite-forming subduction-zone fluids: CL-guided SIMS oxygen-isotope and trace-element evidence

¹ Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560-0119, U.S.A.
² Department of Earth and Planetary Sciences, American Museum of Natural History, Central Park West at 79th St., New York, New York 10024, U.S.A.
³ Geophysical Laboratory, Carnegie Institution of Washington, 5541 Broad Branch Road NW, Washington, D.C. 20015, U.S.A.

Correspondence: ^* E-mail: sorensen{at}si.edu

Jadeitite, a rare high P/T rock, is associated spatially with blueschist and/or eclogite terranes. Scanning electron microscope (SEM) and cathodoluminescence (CL) petrography of jadeitite samples from several major occurrences [in Burma (Myanmar), Guatemala, Japan, Kazakhstan, and the U.S.A.] show that grains were deposited from fluids. Jadeite grain compositions indicate these fluid compositions changed with time.

CL imagery guided the acquisition of oxygen-isotope and trace-element analyses with the ion microprobe. Jadeite grains in each rock grew in cycles that began with red- and/or blue-luminescent and ended with green-luminescent zones. The CL images were used to order the data into crystallization sequences. These data and electron-microprobe, major-element analyses document the association of green CL with increases in Ca, Mg, and Cr: (1) toward grain exteriors; (2) in fine-grained matrix around porphyroblasts; (3) in shear zones that cut grains; (4) in former open spaces now filled with jadeite; or (5) in veins. Abundances of many trace elements are greater in green-CL jadeitite compared with the red- or blue-CL zones. Some of these elements—in particular Li, Rb, Sr, Ti, Hf, Zr, Y, and REE—are unlikely to have been derived from serpentinite. Although crystal-chemical effects may explain some of the trace-element systematics (e.g., preferential incorporation of REE into Ca-richer jadeite), some kinetic control is suggested by sector-zoned, rhythmically zoned grains. The oxygen-isotope data suggest that jadeitite-depositing fluids either had multiple sources or evolved in composition along their flow paths (or both).

Key Words: Gems and gemstones • metamorphic petrology • analysis • chemical • major and minor elements • trace elements and REE • stable isotopes • petrography

This article has been cited by other articles:

				A. M. Hofmeister and M. Pertermann Thermal diffusivity of clinopyroxenes at elevated temperature European Journal of Mineralogy, August 1, 2008; 20(4): 537 - 549. [Abstract] [Full Text] [PDF]

				G. SHI, W. CUI, S. CAO, N. JIANG, P. JIAN, D. LIU, L. MIAO, and B. CHU Ion microprobe zircon U Pb age and geochemistry of the Myanmar jadeitite Journal of the Geological Society, January 1, 2008; 165(1): 221 - 234. [Abstract] [Full Text] [PDF]