...G. E. Goodspeed Abstract The textural features of magmatic rocks have been described with the emphasis placed upon their relationship to the crystallization sequence of the magma. Examples have been chosen from the basaltic and diabasic dikes in the vicinity of Cornucopia, Oregon, the shonkinite...

... deposit and are embedded in a lamprophyre dike. Similar to Thai/Cambodian rubies, Yogo sapphires were transported to the surface from somewhere deep within the Earth by this lamprophyre, and they are considered to be xenocrysts in the dike. The Yogo lamprophyre is properly classified as a ouachitite...

... and prospectors across Montana, prior to this study, only the Yogo deposit had been traced back to its bedrock source: two ouachitite dikes ( Dahy, 1991 ; Baker, 1994 ). The bedrock source for Montana’s remaining sapphire deposits (Fig. 1 ) has been the topic of several recent papers. Berg (2004) , on the basis...

... was formed by dehydration melting of muscovite through two successive reactions: muscovite → corundum + K-feldspar + liquid, and muscovite + aluminosilicate → corundum + liquid ( Raith et al. 2008 ). Palke et al. (2016) also suggested that corundum (sapphire) from the Yogo lamprophyre dike could have been...

... 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...

.... ( 2016 ) Origin of sapphires from a lamprophyre dike at Yogo Gulch, Montana, USA: Clues from their melt inclusions . Lithos , 260 , 339 – 344 . Palke , A.C. , Renfro , R.D. , and Berg , R.B. ( 2017 ) Melt inclusions in alluvial sapphires from Montana, USA: Formation of sapphires...

... ) Origin of sapphires from a lamprophyre dike at Yogo Gulch, Montana, USA: Clues from their melt inclusions . Lithos , 260 , 339 – 344 . Palke , A.C. , Renfro , N.D. , and Berg , R.B. ( 2017 ) Melt inclusions in alluvial sapphires from, Montana, USA: Formation of sapphires...

... Zealand . J. Metamorph. Geol . 16 , 149 – 167 . Ito , M. , Suzuki , K. & Yogo , S. ( 1997 ): Cambrian granulite to upper amphibolite facies metamorphism of post-797 Ma sediments in Madagascar . J. Earth Planet. Sci., Nagoya Univ . 44 , 89 – 102 . Jarosewich , E...

...Eduardo O. Zappettini; João O.S. Santos Abstract Corundum xenocrysts from ouachititic dikes related to the ultrapotassic Puesto La Peña Complex, Mendoza, Argentina, contain inclusions of oxides, silicides, and silicates. Oxides identified are hibonite, carmeltazite, and as yet unnamed minerals...

... granites outcrop to the southwest of the primary ruby occurrences. Three layers of marbles were found to host rubies. Typically, the mineralized marbles are white to light-grey ( Fig. 5 ); they vary in thickness from <2 m to over 60 m. Pegmatites and felsic dikes are occasionally found along...

... ( Fig. 3 ; Jackson, 1989 ). Paleozoic and Mesozoic strata along the southeastern margin dip ~25°–40° to the south, making the Little Belt Mountains best described as a NW-SE–trending anticline ( Fig. 3 ). Cenozoic (ca. 54–41 Ma) granitoid stocks, sills, and dikes, representing part of the Central...

.... , Renfro , N.D. and Berg , R.B. ( 2016 ) Origin of sapphires from a lamprophyre dike at Yogo Gulch, Montana, USA: Clues from their melt inclusions . Lithos , 260 , 339 – 344 . Paton , C. , Hellstrom , J. , Paul , B. , Woodhead , J. and Hergt , J. ( 2011 ) Iolite...

... Basin and the basement rocks of the Vohibory terrane are crosscut by Cretaceous volcanic dikes. These are related to the Marion hotspot activity (Storey et al. 1995 ) formed during the separation of Madagascar and the India-Seychelles block. The Vohibory Group differs from the more easterly...

...- 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...

... for Montana. His maps cover the Snowy, Iowa. Although he was headquartered in Little Belt, Highwood, Bridger, and Harry Foster Bain, Iowa, he must also have spent time in Castle Mountains, and the ore deposits 1871 1948 Chicago, and as R.A.F. Penrose Jr. was on of Yogo Park, Bearpaw Mountains...