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The Grouse Creek block is a block of 2.5 to 2.6 billion year old orthogneisses (a type of gneiss) and similar metasedimentary rocks. The Grouse Creek block is one of several Proterozoic and Archean accreted terranes that lie to the north and west of the Wyoming craton, including the Farmington Canyon Complex (<2.5 Ga), the Selway terrane (2.4-1.6 Ga), the Medicine Hat block (2.6-3.3 Ga) and the Priest River complex (>2.6-1.5 Ga).〔 Together, these terranes comprise part of the basement rock of the North American continent〔 and have been critical to studies of crustal accretion in the Precambrian. Ongoing study of the Grouse Creek block will contribute to understanding the paleogeography of the Wyoming craton prior to its incorporation into the supercontinent Laurentia approximately 1.86 billion years ago. The name was proposed by David Foster and others.〔 ==Geographic and geologic boundaries== The location of the Grouse Creek block has been determined at some points by determining the age when minerals were metamorphosed through isotopic analysis of uranium, strontium, neodymium and lead. The ages matched characteristic outcropping Archean orthogneisses.〔 Outcrops have been sampled in the Pioneer Mountains,〔〔 the Albion Range,〔Armstrong, R.L.; and Hills, F.A. "Rb–Sr and K–Ar geochrono- logic studies of mantled gneiss domes, Albion Range, southern Idaho, USA." Earth and Planetary Science Letters, 3: 114–124 (1967).〕 the East Humboldt Range,〔〔 and the Grouse Creek Range. Results indicate that while surface exposures of the Grouse Creek block are rare, the extent of the block is large, reaching from southern Idaho to northeastern Nevada and northwestern Utah (Fig. 1).〔Fleck, R.J.; and Wooden, J.L. "Isotopic identification of the Archean/Proterozoic lithosphere." Geological Society of America, Abstracts with Programs, 29:70-71 (1997).〕〔Wolf, D.E.; Leeman, W.P.; and Vervoort, J.D. "U–Pb zircon geochronology of crustal xenoliths confirms presence of Archean basement beneath the central and eastern Snake River Plain." Geological Society of America, Abstracts with Programs, 37: 60 (2005).〕 The boundaries of the block remain a topic of significant study. : North Boundary: Lies within or north of the Snake River Plain of Idaho.〔〔Durk, K.M.; Fanning, C.M.; and Link, P.K. "SHRIMP U-Pb ages for Archean orthogneiss, Mesoproterozoic paragneiss, and Eocene Boulder Creek Pluton, Pioneer Mountains, south-central Idaho, part of the 2600 Ma Grouse Creek Block." Geological Society of America, Abstracts with Programs, 39: 613 (2007).〕〔Fanning, C.M.; and Link, Paul K. "Age and provenance of Precambrian metamorphic rocks in the Pioneer metamorphic core complex, south-central Idaho; the southern edge of the lower Belt Supergroup, the Grouse Creek Block, and hints of a proximal Grenville source in the Northe." Geological Society of America, Abstracts with Programs, 41: 271 (2009).〕 : East Boundary: It is generally accepted that the eastern edge is separated from the Wyoming craton by Paleoproterozoic rocks of the Farmington Canyon Complex〔Foster, D.A.; Mueller, P.A.; Kamenov, G.D.; and Stroud, M. "Isotopic analyses of the Grouse Creek Block; A link to the Wyoming Craton?" Geological Society of America, Abstracts with Programs, 41: 270 (2009).〕 in the Wasatch Range of Utah.〔Nelson, S.; Harris, R.; Dorais, M.; Heizler, M.; Constenius, K.; and Barnett, D. "Basement complexes in the Wasatch fault, Utah, provide new limits on crustal accretion." ''Geology.'' 30:831–834 (2002).〕〔Bryant, B. 1988. "Geology of the Farmington Canyon complex, Wasatch Mountains, Utah." US. Geological Survey Professional Paper 1476.〕 : South Boundary: May occur between the East Humboldt Range and Ruby Mountains in Nevada where U-Pb geochronology and Sr, Nd and Pb isotope analysis of intrusive rocks indicate Archean basement is truncated by Proterozoic basement of the Cheyenne Belt.〔Wright, J.E.; and Snoke, A.W. "Tertiary magmatism and mylonitization in the Ruby – East Humboldt metamorphic core complex, northeastern Nevada; U–Pb geochronology and Sr, Nd, and Pb isotope geochemistry." Geological Society of America Bulletin, 105: 935–952 (1993).〕〔Premo, W.R.; Howard, K.A.; and Castineiras, P. "New SHRIMP U–Pb zircon ages and Nd isotopic signatures for plutonism in the northern Ruby – East Humboldt Ranges of NE Nevada: implications for the timing of Tertiary core complex formation." Geological Society of America, Abstracts with Programs, 37: 359 (2005).〕 : West Boundary: Not well defined largely due to a lack of outcropping rock, though it has been hypothesized that the block could extend to the Neoproterozoic Cordilleran rift margin.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Grouse Creek block」の詳細全文を読む スポンサード リンク
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