Geology of an alpine-type peridotite in the Mount Sorenson area, east-central Alaska

Keith, Terry E.C.; Foster, Helen L.; Foster, Robert L.; Post, Edwin Van Horn; Lehmbeck, William L.

doi:10.3133/pp1170a

Cited by 7 publications

(1 citation statement)

References 10 publications

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“…Prior to the present study, the only petrological evidence for high-P metamorphism in east-central Alaska consisted of the isolated Occurrences of eclogite from two klippen near Fairbanks Brown & Forbes, 1986) and the presence of glaucophane in a single sample of metabasalt within a fault sliver further to the east (Keith et al, 1981). However, % rocks from the Tezlin suture zone and adjacent areas of southern Yukon, thought to be correlative with those in east-central Alaska, record moderate-to high-P (9-17 kbar in upper-plate rocks and 7-13 kbar in lower-plate rocks) under moderate-to high-T conditions (550-750" C) (Hansen, 1992b;Erdmer, 1987).…”

Section: Introductionmentioning

confidence: 98%

High‐pressure amphibolite facies dynamic metamorphism and the Mesozoic tectonic evolution of an ancient continental margin, east‐central Alaska

Dusel-Bacon

Hansen

Scala

1995

Journal Metamorphic Geology

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Ductilely deformed amphibolite facies tectonites comprise two adjacent terranes in east-central Alaska. These terranes differ in protoliths, structural level and cooling ages. A structurally complex zone of gently north-dipping tectonites separates the two terranes. The northern, structurally higher Taylor Mountain terrane includes garnet amphibolite, biotite f hornblende gneiss, marble, quartzite, metachert, pelitic schist and cross-cutting granitoids of intermediate composition (including the Late Triassic to Early Jurassic Taylor Mountain batholith). Lithological associations and isotopic data from the granitoids indicate an oceanic or marginal basin origin for the Taylor Mountain terrane. 40Ar/39Ar metamorphic cooling ages from the Taylor Mountain terrane are latest Triassic to earliest Middle Jurassic. The southern, structurally lower Lake George subterrane of the Yukon-Tanana terrane is made up of quartz-biotite schist and gneiss, augen gneiss, pelitic schist, garnet amphibolite and quartzite; we interpret it to comprise a continental margin and granitoid belt built on North American crust. Metamorphic cooling ages from the Lake George subterrane are almost entirely Early Cretaceous.Geothermobarometric analysis of garnet rims and adjacent phases in garnet amphibolite and pelitic schist from the Taylor Mountain terrane and Lake George subterrane indicate peak metamorphic conditions of 7.5-12kbar at 555-715°C in the northern part of the Taylor Mountain terrane, in which NNE-vergent shear fabrics are preserved; 6.5-10.8 kbar at 520-670" C within the contact zone between the two terranes, in which NW-vergent shear fabrics predominate; and 6.8-11.8 kbar at 570-700" C in the Lake George subterrane of the Yukon-Tanana terrane, in which NW-vergent shear is recorded in the northern part of the study area and SE-vergent shear in the southern part. Where the two shear-sense directions occur together in the northern Lake George subterrane and, locally, in the contact zone, fabrics that record NW-vergent shear are more penetrative and preceded fabrics that record SE-vergent shear.We interpret the pressure, temperature, kinematic and age data to indicate that the metamorphism of the Taylor Mountain terrane and Lake George subterrane took place during different phases of a latest Palaeozoic through early Mesozoic shortening episode resulting from closure of an ocean basin now represented by klippen of the Seventymile-Slide Mountain terrane. High-to intermediate-pressure metamorphism of the Taylor Mountain terrane took place within a SW-dipping (present-day coordinates) subduction system. High-to intermediate-pressure metamorphism of the Lake George subterrane and the structural contact zone occurred during NW-directed overthrusting of the Taylor Mountain, SeventymileSlide Mountain and Nisutlin terranes, and imbrication of the continental margin in Jurassic time. The difference in metamorphic cooling ages between the Taylor Mountain terrane and adjacent parts of the Lake George subterrane is best explained by Early Cretace...

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Section: Introductionmentioning

confidence: 98%

High‐pressure amphibolite facies dynamic metamorphism and the Mesozoic tectonic evolution of an ancient continental margin, east‐central Alaska

Dusel-Bacon

Hansen

Scala

1995

Journal Metamorphic Geology

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Terranes and suture zones in east central Alaska

Churkin¹,

Foster²,

Chapman³

et al. 1982

J. Geophys. Res.

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East central Alaska, with its 17 terranes, forms a part of the mosaic of allochthonous terranes that join the North American and Siberian plates. These terranes range from continental and continental margin, such as the Tatonduk with its thick well‐bedded succession of marine shelf rocks, to seamount, arc, and ocean floor terranes. The Yukon crystalline terrane, the largest described here, is a composite of at least four subterranes juxtaposed across the Tintina fault with the Tatonduk terrane, a northwestern extension of the North American plate in Alaska. Inboard of the Yukon crystalline terrane are packets of closely appressed microterranes separated from the Tatonduk and other terranes belonging to North America by major suture zones. These microterranes lie between North America and the mosaic of accretionary terranes that form the more southerly part of Alaska. The most obviously allochthonous microterranes within the suture zones are the Woodchopper Canyon, an Early Devonian basaltic seamount, and the White Mountains, an Ordovician volcanic arc terrane capped by Silurian and Devonian carbonate bank deposits. The nearest counterpart of these terranes is the Alexander terrane in southeastern Alaska. The Tintina fault of Mesozoic and Cenozoic age, like the Denali fault, primarily follows old suture zones that separate terranes. Strike slip faulting developed after collision in places where further convergence was oblique to the terrane margins. Where terranes met head‐on, their leading edges lie along a multiple set of high‐angle faults that outline microterranes in accretion zones.

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Mantle Exhumation in an Early Paleozoic Passive Margin, Northern Cordillera, Yukon

Canil¹,

Johnston²,

Evers³

et al. 2003

The Journal of Geology

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Geology of an alpine-type peridotite in the Mount Sorenson area, east-central Alaska

Cited by 7 publications

References 10 publications

High‐pressure amphibolite facies dynamic metamorphism and the Mesozoic tectonic evolution of an ancient continental margin, east‐central Alaska

High‐pressure amphibolite facies dynamic metamorphism and the Mesozoic tectonic evolution of an ancient continental margin, east‐central Alaska

Terranes and suture zones in east central Alaska

Mantle Exhumation in an Early Paleozoic Passive Margin, Northern Cordillera, Yukon

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