Xenoliths in granodiorite (Giant Forest Granodiorite, mid-Cretaceous, 97-102 Ma; Moro Rock, Sequoia National Park, California, USA) 8 : 無料・フリー素材/写真
Xenoliths in granodiorite (Giant Forest Granodiorite, mid-Cretaceous, 97-102 Ma; Moro Rock, Sequoia National Park, California, USA) 8 / 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 | Xenolith in grandiorite in the Cretaceous of California, USA.Moro Rock is a large exfoliation dome in the Sierra Nevada Mountains of eastern California, USA. It is accessible by road and hiking trail in the western part of Sequoia National Park, a little east of Generals Highway (Rt. 198).Exfoliation domes are common in the Sierra Nevada Mountains. They form by large-scale spheroidal weathering of granites and granitoids of the Sierra Nevada Batholith. The batholith represents a Late Jurassic to Late Cretaceous-aged mass of cooled magma chambers originally beneath a chain of subduction zone stratovolcanoes.Pressure release from erosional unroofing of the batholith resulted in the rocks having curved sheeting joints. Spheroidal weathering followed, akin to peeling the layers from an onion (“exfoliation”). The end result is a rounded mountain top - an exfoliation dome.Moro Rock is the type locality of the Cretaceous-aged Giant Forest Granodiorite, one of numerous specific igneous intrusions in the Sierra Nevada Batholith. Granodiorite is dominated by quartz and sodic plagioclase feldspar and some potassium feldspar. The Giant Forest Pluton is also rich in hornblende amphibole (= black crystals) and relatively rich in small, ~honey-colored crystals of titanite (a.k.a. sphene - CaTiSiO5).The dark-colored masses in the above photo are xenoliths ("xeno" = foreign; "lith" = rock). Xenoliths are pieces of rock that have fallen from the walls or roof of a cooling magma chamber. These xenoliths are rich in mafic minerals, resulting in a dark color. Mafic xenoliths, or "inclusions", are fairly common in the Giant Forest Granodiorite at Moro Rock.Geologic unit & age: Giant Forest Granodiorite, Sequoia Intrusive Suite, late Albian Stage to early Cenomanian Stage, mid-Cretaceous, 97-102 Ma |
| 撮影日 | 2010-07-11 14:35:35 |
| 撮影者 | James St. John |
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