Bedrock geologic map of the Salcha River-Pogo area, Big Delta Quadrangle, Alaska

Werdon, M. B.; Newberry, R. J.; Athey, J. E.; Szumigala, D. J.

doi:10.14509/3209

Cited by 6 publications

(8 citation statements)

References 4 publications

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“…Biotite dominates over sparse hornblende, and muscovite is rare (e.g., Newberry et al, 1990b). Most reported U-Pb dates for batholiths and plutonic rocks are from 109 to 102 Ma, but many dates from dykes and smaller and more metaluminous/mafic bodies are about 93 Ma, which is similar to a large number of Ar-Ar dates on igneous and hydrothermal micas (Smith et al, 1999;Dilworth et al, 2002;Selby et al, 2002;Day et al, 2003;Werdon et al, 2004). The nature of the plutonic rocks, large batholiths, and high regional metamorphic grade suggest that the intrusions were emplaced at midcrustal levels.…”

Section: Ruby-kaiyuh-nyac Belt (117-108 Ma)mentioning

confidence: 60%

“…3). Limited work on the Goodpaster batholith indicates that ilmenite and titanite are dominant over magnetite, and it has low magnetic susceptibilities (0.1-0.2) and Fe 2 O 3 /FeO ratios (Dilworth, 2003;Werdon et al, 2004).…”

Section: Ruby-kaiyuh-nyac Belt (117-108 Ma)mentioning

confidence: 99%

“…106 and ca. 94 Ma (Werdon et al, 2004). They also have low aeromagnetic signatures, low magnetic susceptibilities, and contain ilmenite (Werdon et al, 2004), although they are slightly more oxidized than the Fairbanks intrusions ( Fig.…”

Section: Fairbanks-salcha Plutonic Suite (94-90 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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Section: Ruby-kaiyuh-nyac Belt (117-108 Ma)mentioning

confidence: 60%

Section: Ruby-kaiyuh-nyac Belt (117-108 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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“…The Salcha River gneiss dome is cored by a 600 km 2 upper amphibolite-facies sillimanite gneiss, with subordinate felsic dikes, quartzite, marble, and amphibolite, and is fl anked by a sequence of middle amphibolite-facies pelitic schist, quartzite, marble, amphibolite, and minor augen gneiss, interpreted to be the lower-grade part of the metamorphic culmination (Dusel- Bacon and Foster, 1983). The nature of the contact between amphibolite-facies tectonites of the Salcha River gneiss dome and the overlying greenschist-facies Butte assemblage and quartzo feldspathic unit (MDmg) is uncertain and has been interpreted as either a thrust fault, with higher-grade rocks forming the footwall (Dusel- or the hanging wall (Foster et al, 1994), a low-angle normal fault (Pavlis et al, 1993;Oliver and Dusel-Bacon, 2003), or a series of steep normal faults (Werdon et al, 2004).…”

Section: Salcha River Area Yukon-tanana Uplandmentioning

confidence: 99%

U-Pb zircon and geochemical evidence for bimodal mid-Paleozoic magmatism and syngenetic base-metal mineralization in the Yukon-Tanana terrane, Alaska

Dusel-Bacon

Wooden

Hopkins

2004

Geol Soc America Bull

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New SHRIMP (sensitive, high-resolution ion microprobe) U-Pb zircon ages and trace element geochemical data for mafi c and felsic metaigneous rocks of the pericratonic Yukon-Tanana terrane in east-central Alaska help defi ne the tectonic setting of mid-Paleozoic magmatism and syngenetic hydrothermal Zn-Pb-Ag mineralization along the ancient Pacifi c margin of North America. We compare data from similar greenschist-facies sequences of bimodal volcanic and subvolcanic rocks associated with carbonaceous and siliciclastic marine sedimentary rocks, in the Wood River area of the Alaska Range and the Salcha River area of the Yukon-Tanana Upland, and from amphibolite-facies augen gneiss and mafi c gneiss (amphibolite) in the Goodpaster River area of the upland. Allowing for analytical uncertainties, igneous crystallization age ranges of 376-353 Ma, 378-346 Ma, and 374-358 Ma are indicated by 13 new SHRIMP U-Pb dates for the Wood River, Salcha River, and Goodpaster River areas, respectively. Bimodal magmatism is indicated by Late Devonian crystallization ages for both augen gneiss (371 ± 3 and 362 ± 4 Ma) and associated orthoamphibolite (369 ± 3 Ma) in the upland and by stratigraphic interleaving of mafi c and felsic rocks in the Alaska Range. Metabasites in all three study areas have elevated HFSE (high fi eld strength element) and REE (rare earth element) contents indicative of generation in a within-plate (extensional) tectonic setting. Within-plate trace element signatures also are indicated for peralkaline metarhyolites that host the largest volcanogenic massive sulfi de deposits of the Bonnifi eld district in the Wood River area and for metarhyolite tuff interlayered with the carbonaceous Nasina assemblage, which hosts sedimentary exhalative sulfi de occurrences in the Salcha River area. Most of the other felsic metaigneous samples from the Alaska Range and the Yukon-Tanana Upland have geochemical signatures that are similar to those of both average upper continental crust and continental-margin arc rocks generated in thick continental crust. Given the absence in our study areas of intermediate-composition magmatic products generally found in most arcs, and the presence of bimodal magmatism, the alkalic within-plate chemistry of the mafi c rocks and some of the felsic rocks, and the widespread occurrence of interlayered carbonaceous sedimentary rocks indicative of deposition within a restricted marine basin or submerged continental margin, we consider it most likely that this prolonged Late Devonian to Early Mississippian magmatic episode resulted from attenuation of the ancient continental margin of western North America, rather than development of an arc, as proposed by many others.

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“…Cretaceous (145–85 Ma) detrital zircon grains, 12% of the total population, may have been derived from Early and mid‐Cretaceous (145–90 Ma) magmatic sources that are widespread throughout eastern Alaska and the Yukon (Figure ). Potential Early and mid‐Cretaceous magmatic sources include plutons of the Yukon composite terrane in east‐central Alaska; reported U‐Pb zircon ages for these plutonic rocks are between 109–102 Ma (Day et al, ; Dilworth et al, ; Smith et al, , ; Werdon et al, ). Mid‐Cretaceous (~105–85 Ma) K‐Ar and Ar‐Ar ages from granitic plutons have been reported to intrude regions north, west, and south of the Taylor Mountain batholith (Dusel‐Bacon et al, ; Wilson et al, ).…”

Section: U‐pb Geochronology and Hf Isotope Interpretations: Ancestralmentioning

confidence: 99%

Geology, U‐Pb Geochronology, and Hf Isotope Geochemistry Across the Mesozoic Alaska Range Suture Zone (South‐Central Alaska): Implications for Cordilleran Collisional Processes and Tectonic Growth of North America

2020

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The Mesozoic Alaska Range suture zone is defined by a transition from oceanic to continental terranes and is part of a 2000-km-long tectonic boundary throughout the northern Cordillera. Surface geologic mapping of the rock types across this suture zone provides critical information about the upper crustal configuration but provides little insight into the sedimentary, igneous, and metamorphic processes that occurred in deeper levels of the collisional zone. To better constrain the timing and mantle-crust sources of collision-related magmatism, we combine U-Pb ages and Hf isotope compositions of detrital zircons from the three main components of the suture zone. U-Pb/Hf data sets from inboard, continental margin samples have Precambrian-Paleozoic ages with epsilon Hf (t) values ranging between +10 and −20. U-Pb/Hf data sets from the outboard, oceanic terrane samples have Pennsylvanian-Permian detrital zircon ages with epsilon Hf (t) values between +16 and +10. The U-Pb/Hf data set of detrital zircons from Mesozoic strata that represent intervening sedimentary basin(s) that formed between the continental margin and oceanic terranes record Precambrian-Mesozoic detrital zircon ages with epsilon Hf (t) values between +14 and −20. Results of the study document four Archean and Proterozoic global crustal magmatic events that are correlated to the tectonic growth of Laurentia. Also, three Phanerozoic magmatic events have been identified that represent more regional tectonic events. This study demonstrates that the combination of U-Pb geochronology and Hf isotope geochemistry applied to detrital zircons is a powerful tool to define sediment provenance in collisional zones and delineate episodes of global and regional magmatism along convergent plate boundaries.

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Bedrock geologic map of the Salcha River-Pogo area, Big Delta Quadrangle, Alaska

Cited by 6 publications

References 4 publications

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

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

U-Pb zircon and geochemical evidence for bimodal mid-Paleozoic magmatism and syngenetic base-metal mineralization in the Yukon-Tanana terrane, Alaska

Geology, U‐Pb Geochronology, and Hf Isotope Geochemistry Across the Mesozoic Alaska Range Suture Zone (South‐Central Alaska): Implications for Cordilleran Collisional Processes and Tectonic Growth of North America

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