Wyomingite (Pleistocene, 950-960 ka; Zirkel Mesa, Leucite Hills, Wyoming, USA) 3 : 無料・フリー素材/写真
Wyomingite (Pleistocene, 950-960 ka; Zirkel Mesa, Leucite Hills, Wyoming, USA) 3 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Wyomingite in the Pleistocene of Wyoming, USA.Southwestern Wyoming's Leucite Hills are a group of Pliocene to Pleistocene volcanic centers that erupted lamproite lavas, a rare extrusive igneous lithology. Based on chemistry and mineral content, the Leucite Hills lamproite lavas have been categorized as wyomingite, orendite, or madupite.Volcanism in this area may possibly be due to Yellowstone Hotspot fringe melting of the mantle. The lamproites appear to be derived from lherzolite-harzburgite mantle rocks that were metasomatically enriched in phlogopitic veins at >1.2 Ga (the latter may be caused by Precambrian subduction along the Wyoming Craton margin).Seen here is a wyomingite exposure at Zirkel Mesa, a volcanic center in the southeastern Leucite Hills. Wyomingite is the most common type of lamproite in the area, and the "state rock" of Wyoming. The lithology is also known as diopside-leucite-phlogopite lamproite. Diopside is a type of pyroxene. Leucite is a feldspathoid mineral. Phlogopite is a golden-brown colored type of mica - this material makes wyomingite rocks sparkle in bright light. Other minerals in wyomingite rocks include richterite amphibole, priderite (= potassium titanium iron oxide), wadeite (= potassium zirconium silicate), and apatite (= calcium phosphate). Zirkel Mesa wyomingite is mafic, with 55% silica.Age: Pleistocene, 950-960 kaLocality: old quarry at the southern edge of western Zirkel Mesa, southeastern Leucite Hills Volcanic Province, Sweetwater County, southwestern Wyoming, USA (vicinity of 41° 47' 19.12" North latitude, 108° 56' 16.02" West longitude)--------------Example Leucite Hills references:Lange, R.A., I.S.E. Carmichael & C.M. Hall. 2000. 40Ar/39Ar chronology of the Leucite Hills, Wyoming: eruption rates, erosion rates, and an evolving temperature structure of the underlying mantle. Earth and Planetary Science Letters 174: 329-340.Mirnejad, H. & K. Bell. 2006. Origin and source evolution of the Leucite Hills lamproites: evidene from Sr-Nd-Pb-O isotopic compositions. Journal of Petrology 47: 2463-2489.Schultz, A.R. & W. Cross. 1912. Potash-bearing rocks of the Leucite Hills, Sweetwater County, Wyoming. United States Geological Survey Bulletin 512. 39 pp. |
| 撮影日 | 2012-07-08 13:14:27 |
| 撮影者 | James St. John |
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