Presentation on theme: "CL in Support of Interpreting Gem Deposits G. E. Harlow 1 E. Sahm 1,2 J. Hunt 1,3 1 American Museum of Natural History, New York, NY 2 University of Utah,"— Presentation transcript:
CL in Support of Interpreting Gem Deposits G. E. Harlow 1 E. Sahm 1,2 J. Hunt 1,3 1 American Museum of Natural History, New York, NY 2 University of Utah, Salt Lake City, UT 3 California Institute of Technology, Pasadena, CA MVE (SSS)
Instrumentation Hitachi S-4700 Field-Emission SEM with BSE, EDS and a Gatan MonoCL3 detector & monochromator system (Peltier-cooled high-sensitivity PMT). The grating is a low-dispersion (21.6nm / mm slit width), with peak response (blaze wavelength) at 500nm and useful range of ~ nm.
CL Applications Cathodoluminescence is an extremely powerful technique for examining zoning in minerals and can lead to fundamental interpretations about how they formed. Targets in this presentation: –Jadeitites: jadeite, zircon, grossular? –Corundum deposits: ruby, sapphire, painite
Guatemalan Jadeitites Jadeitites have been interpreted as crystallizations from aqueous fluids derived from subductions channels based, in large part, on CL observations. In Guatemala there are two distinct serpentinite mélanges containing jadeitite, North and South of the Motagua fault. How do the CL signatures of the minerals compare between the two distinct sources.
Jd-1 Jd-2 Zrn Phengite Qtz MVE Phengite Jadeitite, San Jose Ttn Omph SOUTH
Panchromatic 480 nm Blue 270 nm UV Jadeite-phengite rock (MVE – SOUTH) Jadeite SOUTH Jd-1 Jd-2
Jadeite-Phengite rock (MVE SOUTH) Pmp-Grs-Jadeitite (MVE SOUTH) Jadeite ~700 ~560 Altered Jadeite (MVJ84-9B -- NORTH) ~480 Comparison of CL Spectra from Jadeite UV to IR peaks, but too soon to make generalizations other than color zoning observed by Sorensen and co-workers.
Zircon, Meta(?)-Jadeitite (MVJ84-9C -- North) Zircon in lawsonite-eclogite (MVE South) Jadeite-phengite rock (MVE South) Zircon Comparison of CL spectra from zircon Main peak near 500nm and lowest near 250nm, but … All are features show only primary growth.
Ruby (107643), Mogok, Burma in Marble w/ Spinel, Blue Cancrinite, Sodalite, Scapolite, Phlogopite, etc. 694nm - Cr Panchromatic BSE
320 nm UV695 nm Cr-ruby 840 nm IR Artifact of mirror
Painite (CaZrBAl 9 O 18 ) from Namya, Myanmar – rare gem mineral probably grew during skarn formation CL shows fine growth layering, implying growth pulses. Panchromatic Inclusions: Cc, Baddeleyite (ZrO 2 ) & Srilankaite (TiZr 2 O 6 )
Some Conclusions CL in zircon, jadeite and garnet of jadeitites is likely due to REE based on enrichment in these rocks. Zoning structures suggest growth from fluids – for Zircon in jadeitite this implies growth at T = ~ 300°C at P > 1 GPa. Considerable spectral structure from UV to IR is seen via SEM/CL. Lots more to do.
Many Thanks to: Jade & Ruby Helpers Jade & Ruby Helpers: Jinny Sisson, Sorena Sorensen, Carlos Gonzales, Mauricio Chiquin, Will Maze, Bill Larson, George Rossman, Jamie Newman, U Han Htun, Dr. Saw Naung U, Mint Soe The Founders of the Feast The Founders of the Feast: AMNH, NMNH, Frohlich Charitable Trust, Astor Expedition Fund, Sprague Fund, Michael Scott, & the National Science Foundation.