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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,

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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:

1 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)

2 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.

3 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

4 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.

5 Jd-1 Jd-2 Zrn Phengite Qtz MVE Phengite Jadeitite, San Jose Ttn Omph SOUTH

6 Panchromatic 480 nm Blue 270 nm UV Jadeite-phengite rock (MVE – SOUTH) Jadeite SOUTH Jd-1 Jd-2

7 Zircon Panchromatic Jadeite-phengite rock (MVE –SOUTH) Panchromatic Zircon, Secondary Electrons BSE Jd-1 Zrn Jd-2 Zircon

8 505 nm Green685 nm Red 410 nm Blue315 nm UV

9 Zircon in lawsonite-eclogite (MVE – SOUTH) Zircon, Panchromatic 230 nm UV490 nm Blue- green

10 Panchromatic CL BSE Pmp-Grs-Jadeitite (MVE – SOUTH) Grs Jd Pmp Jadeite

11 Panchromatic CL BSE MVE Pmp-Grs-JadeititeJadeite Panchromatic CL SOUTH

12 Panchromatic 300 nm UV 600 nm Green940 nm IR MVE Pmp-Grs-JadeititeJadeite

13 Panchromatic BSE Grs Jd Pmp Grossular ~850 Pmp-Grs-Jadeitite (MVE – SOUTH)

14 Jadeitite, Río La Palmilla, North of MFZ (MVJ84-9D) 2 cm across (courtesy of S. Sorensen) NORTH

15

16 Panchromatic CL image of same area. Note healed fracture in jadeite grain. NORTH

17 Close-up from previous image NORTH

18 Altered Jadeite (MVJ84-9B) at boundary between Jd and Ab+Ne NORTH

19 Scale bar is 1 about micrometer. Room Temperature Spectrum Imaging Spectrum Image (40 X 40 pixels) of adjacent area NORTH

20 Point 0Point 1 Point 2Point 3 Room temperature CCD CL spectra courtesy of Paul Mainwaring Nepheline?Albite? Darker Jadeite Lighter Jadeite ~700 ~560 ~480 ~700~560

21 279 nm UV 350 nm UV547 nm Green Zircon, Meta(?)-Jadeitite (MVJ84-9C – NORTH)

22 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.

23 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.

24 Ruby (107643), Mogok, Burma in Marble w/ Spinel, Blue Cancrinite, Sodalite, Scapolite, Phlogopite, etc. 694nm - Cr Panchromatic BSE

25 320 nm UV695 nm Cr-ruby 840 nm IR Artifact of mirror

26 Ruby-1, Namya, BSE Ruby-1, Namya, CL Ruby-3, Namya, BSERuby-3, Namya, CL

27 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 )

28 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.

29 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.


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