File:Actinolite xenolith in sandorite lamprophyre (Sandor Dike, Neoarchean, 2.703 Ga; Route 17 roadcut northeast of Wasp Lake & north of Wawa, Ontario, Canada) 3 (48342621891).jpg
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Summary[edit]
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| Description |
Actinolite xenolith in sandorite lamprophyre in the Precambrian of Ontario, Canada. This is part of an igneous dike composed of a rare igneous rock called lamprophyre. Such rocks are ultrapotassic, mafic to ultramafic, intrusive igneous rocks. This one is a diamondiferous spessartite lamprophyre called sandorite, with 47% silica and 5% black amphibole macrocrysts, up to 3 millimeters in size. The sandorite here has xenoliths ("xeno" = foreign; "lith" = rock), which are pieces of rock that have fallen from the walls or roof of a cooling magma chamber. At this site, they include mantle and crustal xenoliths. Spessartite lamprophyres are defined in the literature as lamprophyres having phenocrysts of hornblende amphibole or clinopyroxene in a groundmass of sodic plagioclase feldspar, with accessary olivine, biotite mica, apatite, and opaque oxide minerals. Sandorite dikes here represent the hypabyssal facies of a sandorite volcanic complex. The surrounding host rocks are 2.7 billion year old gabbros and volcanic tuffs of the Catfish Assemblage. The greenish object in the picture is a moderately large, coarsely-crystalline xenolith composed of long blades of actinolite amphibole. This is not the primary mineralogy of the xenolith - it has been interpreted as a metapyroxenite mantle xenolith. Upper mantle rocks are dominated by ultramafic igneous rocks such as peridotite (= olivine-bearing) and pyroxenite (= almost exclusively pyroxene). Geologic unit and age: Sandor Dike, Neoarchean, 2.703 Ga (a zircon from a gneissic xenolith has been dated to 2.684 Ga) Locality: roadcut on the eastern side of Route 17, northeast of Wasp Lake & east of McCormick Lake, north of the town of Wawa, Ontario, southeastern Canada (48° 12’ 42.13" North latitude, 84° 50' 52.24" West longitude) See info. at: <a href="https://en.wikipedia.org/wiki/Lamprophyre" rel="noreferrer nofollow">en.wikipedia.org/wiki/Lamprophyre</a> and <a href="https://en.wikipedia.org/wiki/Xenolith" rel="noreferrer nofollow">en.wikipedia.org/wiki/Xenolith</a> |
| Date | |
| Source | Actinolite xenolith in sandorite lamprophyre (Sandor Dike, Neoarchean, 2.703 Ga; Route 17 roadcut northeast of Wasp Lake & north of Wawa, Ontario, Canada) 3 |
| Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/48342621891 (archive). It was reviewed on 9 October 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 06:31, 9 October 2019 | | 4,000 × 3,000 (9.48 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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