... O 3 -Cr 2 O 3 plot of Giuliani et al. (2015) . Thai/Cambodian rubies and Yogo sapphires generally lie in the “ruby in mafic-ultramafics” field in this plot ( Fig. 4 c). This is generally consistent with our model considering that basic rocks such as anorthosites are commonly genetically similar...

... field. Such a felsic composition is atypical of known primary sapphire deposits and may represent a previously unrecognized deposit type. Mass wasting of this volcanic unit during the Quaternary resulted in the deposition of several debris flow deposits, which constitute the majority of the sapphire...

.... Sapphires, excluding pinks, are classified into six sets of δ 18 O values ( Fig. 1 ): (1) colored and blue sapphires from Montana (Yogo Gulch) hosted in lamprophyres have δ 18 O values between 5.4‰ and 6.8‰ ( n = 16). (2) Sapphires from syenite or anorthoclasite have δ 18 O values between 5.2‰ and 7.8‰ ( n...

... element enrichments found in some sapphires, such as Be, rare-earth elements, and high field strength elements (Zr, Nb, Ta, W). These enrichments are attributed to both ionic radii mismatch and the large difference in ionic charge compared with Al 3+ in corundum, which makes the pentavalent cations more...

... of syenite pegmatites type from Ilmen (blue squares) ( Sorokina et al. 2017 ); (6) sapphires of anatectic type from Montana (purple area) ( Palke et al. 2017 ); (7) sapphires of anatectic type from Yogo Gulch (yellow triangles) ( Palke et al. 2016 ); (8) corundum of syenite type from Yushishan (red circles...

.... , Geisler , T. , and Nagel , T. ( 2017 ) Petrogenesis of alkaline basalt-hosted sapphire megacrysts. Petrological and geochemical investigations of in situ sapphire occurences from Siebengebirge Volcanic Field, Germany . Contributions to Mineralogy and Petrology , 172 , 43 . Cherniak...

.... A GIA matrix-matched corundum standard set was used as external standards ( Stone-Sundberg et al., 2017 ). In the set, one ultra-high-purity undoped Czochralski corundum was used as a blank external standard. Two multi-element doped Czochralski corundums and one homogeneous natural Yogo blue sapphire...

.... and Fielding , P.E. ( 1971 ) The origins of the colours of yellow, green and blue sapphires . Chemical Physics Letters , 10 , 262 – 265 , https://doi.org/10.1016/0009-2614(71)80282-8 . Ferguson , J. and Fielding , P.E. ( 1972 ) The origins of the colours of natural yellow, blue...

..., J., Verdel, C., & Ávila, J.N. (2018) A common origin for Thai/Cambodian rubies and blue and violet sapphires from Yogo Gulch, Montana, USA? American Mineralogist 103 , 469...

...., Ballhaus, C., Gerdes, A., Fonseca, R.O.C., Wirth, R., Geisler, T., & Nagel, T. (2017) Petrogenesis of alkaline basalt-hosted sapphire megacrysts. Petrological and geochemical investigations of in situ sapphire occurrences from the Siebengebirge Volcanic Field...

... crystallization processes, as well as metamorphic and metasomatic processes. Previous δ 18 O data from eastern Australian alluvial sapphire and ruby suggest a mantle source, with minor contributions from crustal material that could have been subducted sediment or crust underlying eastern Australian lava-fields...

... , A.C. , Wong , J. , Verdel , C. , and Ávila , J.N. ( 2018 ) A common origin for Thai/Cambodian rubies and blue and violet sapphires from Yogo Gulch, Montana, U.S.A.? American Mineralogist , 103 , 469 – 479 . Panjasawatwong , Y. , Danyushevsky , L.V. , Crawford , A.J...

... Mountains Basin, Montana [Master's thesis]: Bozeman , Montana State University , 87 p. Harlan , S. S. , 1996 , Timing of emplacement of the sapphire-bearing Yogo dike, Little Belt Mountains, Montana : Economic Geology , v. 91 , p. 1159 – 1162 . Harlan , S. S. , and Lageson , D...

.... ( 1988 ) Geology and origin of the Yogo sapphire deposit, Montana. Economic Geology , 83 , 875 – 880 . Dobrzhinetskaya , L. , Wirth , R. , and Green , H. ( 2014 ) Diamonds in Earth's oldest zircons from Jack Hills conglomerate, Australia, are contamination. Earth and Planetary...

... sequence was being exploited during movement along the Volcano Valley fault zone, consistent with the interpretation shown in Figure 3B . Field relationships within the central Helena salient indicate that the Lombard thrust represents a major out-of-sequence thrust system. The thrust truncates...

...- nificance of breccias in sapphire miner- alization in the Yogo dike, Montana M Stephan Dunn, $3,600, Stellenbosch University, South Africa, M.Sc. 2, Char- acterizing hydrothermal gold miner- alization in the Greater Amani region, southwestern Tanzania M Kyle Eastman, $5,000, University of Tasmania, CODES...