Granitic Plutonism and Metamorphism, Eastern Alaska Range, Alaska

Richter, Donald H.; Lanphere, Marvin A.; Matson, Neal A.

doi:10.1130/0016-7606(1975)86<819:gpamea>2.0.co;2

Cited by 37 publications

(60 citation statements)

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“…Of particular note are the high Vp/Vs values observed in the southern section (Figures 6a, 6b, 7a, and 7b and Table 1). These values are similar to other measurements of the Wrangellia composite terrane where the crust has generally been found to be of intermediate to mafic composition (including abundant tholeiitic and volcanic basalts and marine sedimentary rocks), and includes some silica-rich plutonic rocks likely related to the long-lived granitoid magmatic arcs that intruded the terrane [Berg et al, 1972;Richter et al, 1975;Plafker et al, 1989;McClelland et al, 1992a;Plafker and Berg, 1994;Nokleberg et al, 1994;Saltus et al, 1999Saltus et al, , 2007Morozov et al, 2003;Hollister and Andronicos, 2006;Glen et al, 2007;Rioux et al, 2007;Snyder and Hart, 2007;Calkins et al, 2010]. Intracrustal discontinuities within the southern section likely result from compositional layering within the overthickened oceanic crust of the Wrangellia composite terrane and are similar to intracrustal features noted along strike of the suture zone near the Coast Range Batholith [Calkins et al, 2010].…”

Section: Southern Sectionsupporting

confidence: 88%

Crustal structure across the central Alaska Range: Anatomy of a Mesozoic collisional zone

Brennan

Gilbert

Ridgway

2011

Geochem Geophys Geosyst

102

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[1] A first-order process in the growth of continents is the collision and accretion of terranes against continental margins. Collision leads to the formation of a suture zone between the accreted terrane and the former continental margin. New insights on the suturing process are observed from two receiver function transects across the Mesozoic Alaska Range suture zone. Three distinct crustal sections are identified from observations of crustal thickness, intracrustal discontinuities, and Vp/Vs: a northern section with ∼27 km thick crust of felsic to intermediate composition, a central section that is ∼37 km thick that exhibits intracrustal discontinuities and has felsic to intermediate composition, and a southern section that is ∼30 km thick and has a more mafic composition. We interpret these sections to correspond with the former continental margin (Yukon composite terrane), the suture zone proper, and the allochthonous oceanic terrane (Wrangellia composite terrane). The boundary between the Yukon composite terrane and the suture zone appears to be a subhorizontal discontinuity that accommodated underthrusting of crust from the suture zone beneath the former continental margin. The boundary between the suture zone and the Wrangellia composite terrane, in contrast, appears to be a relatively discrete, vertical boundary. The observed variability in the crust across the Alaska Range suture zone is likely controlled by the differing compositions of the terranes involved, which influences how each section responds to precollisional, syncollisional, and postcollisional deformation.

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Section: Southern Sectionsupporting

confidence: 88%

Crustal structure across the central Alaska Range: Anatomy of a Mesozoic collisional zone

Brennan

Gilbert

Ridgway

2011

Geochem Geophys Geosyst

102

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“…Bounded to the north by the Denali fault system, the plutons of the Nutzotin-Kluane belt form a narrow, 800km-long belt (Nutzotin-Chichagof belt of Hudson, 1979) that occurs throughout the northern Wrangell Mountains in Alaska (i.e., the Chisana arc of Barker, 1987) and the Kluane Ranges suite in southeastern Yukon (Fig. 2), and into the Alaskan panhandle, where they form the Chichagof belt of Richter et al (1975a). They mainly intrude rocks of the Wrangellia and Alexander terranes, as well as adjacent Jura-Cretaceous flysch.…”

Section: Nutzotin-kluane Belt (118-108 Ma)mentioning

confidence: 99%

“…The plutons are typically large epizonal plutonic complexes and stocks that are elongate and parallel with the regional fabric (Woodworth et al, 1991). They are dominated by hornblende-biotite granodiorite, with lesser quartz diorite and diorite, calc-alkaline, I-type intrusions (Richter et al, 1975a;Campbell and Dodds, 1983;Dodds and Campbell, 1988). Plutons have a wide range of K-Ar dates from 147 to 108 Ma suggesting that some igneous bodies may be part of the older Tosina-St. Elias suite.…”

Section: Nutzotin-kluane Belt (118-108 Ma)mentioning

confidence: 99%

“…All are presently unmined, in large part due to their relatively remote location. Calcic copper, iron, and/or gold skarns occur on both the northern and southern, more accessible flanks of the Wrangell Mountains (Richter et al, 1975a;MacKevett, 1976), with the Nabesna deposit being the economically most significant deposit. Almost 2 t Au have been recovered from pyrite lenses in fractured limestone associated with garnet-pyroxene skarn (Wayland, 1943).…”

Section: Nutzotin-kluane Belt (118-108 Ma)mentioning

confidence: 99%

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The Northern Cordilleran Mid‐Cretaceous Plutonic Province: Ilmenite/Magnetite‐series Granitoids and Intrusion‐related Mineralisation

Hart¹,

Goldfarb

Lewis³

et al. 2004

Resource Geology

104

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Twenty-five Early and mid-Cretaceous (145-90 Ma) plutonic suites and belts are defined across Alaska and Yukon, in the northern North American Cordillera, on the basis of lithological, geochemical, isotopic, and geochronometric similarities. These features are combined with aeromagnetic characteristics, magnetic susceptibility measurements, and whole-rock ferric:ferrous ratios to ascertain the distribution of magnetite-and ilmenite-series plutonic belts. Magnetite-series plutonic belts are dominantly associated with the older parts of the plutonic episode and comprise subduction-generated metaluminous plutons that are distributed preferentially in the more seaward localities dominated by primitive tectonic elements. Ilmenite-series plutonic belts comprise slightly younger, slightly peraluminous plutons in more landward localities in pericratonic to continental margin settings. They were likely initiated in response to crustal thickening following terrane collision. The youngest plutonic belt forms a small, but significant, magnetite-series belts in the farthest inboard position, associated with alkalic plutons that were emplaced during weak extension.Intrusion-related metallogenic provinces with distinctive metal associations are distributed, largely in accord with classical redox-sensitive granite-series. Copper, Au, and Fe mineralisation are associated with magnetite-series plutons and tungsten mineralisation associated with ilmenite-series plutons. However, there are some notable deviations from expected associations, as intrusion-related Ag-Pb-Zn deposits are few, and significant tin mineralisation is rare. Most significantly, many gold deposits and occurrences are associated with ilmenite-series plutons: these form the basis for the newly recognized reduced intrusion-related gold deposit model.

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“…Contemporaneous arc‐related plutons from the Saint Elias plutonic suite to the southeast (present coordinates) contain U‐Pb ages on zircon between 155 and 147 Ma (Beranek et al, ). Chisana arc plutons and volcanic rocks yield circa 126–105 Ma radiometric ages (Graham et al, ; Richter et al, ; Snyder & Hart, ).…”

Section: Provenancementioning

confidence: 99%

Detrital Zircon Record of a Mesozoic Collisional Forearc Basin in South Central Alaska: The Tectonic Transition From an Oceanic to Continental Arc

2018

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The collision of oceanic arcs with continental margins is an important mechanism for the growth of continents. Ancient forearc basin strata in collisional orogens provide a record of the upper crustal response to this tectonic process. In south central Alaska, Mesozoic forearc basin strata are exposed in a complete crustal section. U‐Pb detrital zircon geochronology from the forearc basin strata was analyzed within a ~107 Ma stratigraphic framework. The Jurassic strata contain unimodal detrital zircon populations that become progressively younger upsection and range from 175 to 151 Ma. These strata are derived from the active oceanic Talkeetna arc. The Cretaceous strata were deposited above multiple unconformities that collectively represent as much as ~30 Ma of nondeposition and/or erosion in the forearc basin. Erosion in the forearc basin and a general absence of detrital zircon ages between 140 and 120 Ma are interpreted as a hiatus of magmatism triggered by collision of the oceanic arc with the former continental margin. The Cretaceous strata have two main detrital zircon populations: a Cretaceous population ranging from 90 to 68 Ma that becomes progressively younger upsection and a Jurassic population with a broad range of peak ages from 194 to 144 Ma. The Cretaceous population marks the establishment of an active Cretaceous continental arc following the collisional event, and the older population reflects continued erosion of the remnant Jurassic oceanic arc plutons. Our results show that detrital zircon geochronology provides a powerful approach for delineating stages of forearc basin collision and the erosion of multiple magmatic arcs.

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Granitic Plutonism and Metamorphism, Eastern Alaska Range, Alaska

Cited by 37 publications

References 0 publications

Crustal structure across the central Alaska Range: Anatomy of a Mesozoic collisional zone

Crustal structure across the central Alaska Range: Anatomy of a Mesozoic collisional zone

The Northern Cordilleran Mid‐Cretaceous Plutonic Province: Ilmenite/Magnetite‐series Granitoids and Intrusion‐related Mineralisation

Detrital Zircon Record of a Mesozoic Collisional Forearc Basin in South Central Alaska: The Tectonic Transition From an Oceanic to Continental Arc

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