Aeromagnetic map and interpretation of magnetic and gravity data, Circle Quadrangle, Alaska

Cady, John W.; Weber, Florence R.

doi:10.3133/ofr83170c

Cited by 8 publications

(21 citation statements)

References 1 publication

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“…For a D of 0.3, the change in Rb from 80 ppm at a DI of 50 to 400 ppm at a DI of 90 requires about 85 percent fractionation (Whalen, 1983), compatible with geophysical data indicating that large granitic bodies underlie known Sn-and W-related plutons (e.g., Cady and Weber, 1983). Similar fractionation (85 to 90 percent) can also account for other metal concentrations seen in granites with DIs of about 90 to 92 ( Newberry and Bums (1987) and this study.…”

Section: Early Differentiation In the Plutonssupporting

confidence: 92%

Comparative petrologic evolution of the Sn and W granites of the Fairbanks-Circle area, interior Alaska

Newberry¹,

Burns²,

Swanson³

et al. 1990

Geological Society of America Special Papers

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Late Cretaceous to Early Tertiary granitic plutons associated with W skarn or Sn greisen-skarn occur interspersed in a belt 70x 200-km-long just northeast of Fairbanks, Alaska. All plutons intrude the late Precambrian-early Paleozoic Yukon-Tanana terrane and are similar in major-element compositions (dominantly granodiorite to monzogranite), initial Sr isotopic ratios (0.710 to 0.719), and Pb isotopic signatures ( 206 Pb/ 204 Pb = 19.17 to 19.37). Biotite compositions and opaque mineral abundances indicate both types of plutons crystallized along a buffered path intermediate between nickel-nickel oxide and quartz-magnetite-fayalite. Both suites contain multiple igneous units, with younger, usually equigranular, units spatially related to mineralized zones. Isotopic, trace-element, and mineralogical data suggest an "I-type," "ilmenite-series" classification for both pluton suites. Because the W and Sn plutons appear to represent magmas with similar origins and source materials, differences in observed metallogeny are thought to be related to differences in environment of crystallization and vapor loss. Such differences include: age (102 to 87 Ma for W plutons, 73 to 50 Ma for Sn plutons), crystallization pressure (1 to 2 kbar for W plutons, <0.5 kbar for Sn plutons), vapor loss history (late for the W plutons and early + late for the Sn plutons), and fluorine trends (decreasing F with increasing differentiation for the W plutons and increasing F for the Sn plutons). Differences in confining pressure (depth) and vapor loss history are associated with differences in age: the younger (Sn) plutons are shallower, and the older (W) plutons are deeper. Trace-element patterns (e.g., Rb, B, Be, W, Sn, Li) are similar for least differentiated units of both pluton types, increasing modestly with increasing differentiation for the W plutons and increasing strongly for the Sn plutons. Data are most compatible with 80 to 95 percent fractionation (crystal-liquid) followed by vapor loss for the W plutons and 80 to 90 percnt fractionation (crystal-liquid) for the Sn plutons, with early vapor loss followed by (liquid-liquid?) "ultrafractionation." Ultrafractionation and subsequent ore element enrichment occurs in the Sn plutons by early vapor loss and subsequent F enrichment in the residual magma. The data suggest that metallogeny differences for W vs. Sn plutons in our study area are not a function of differences in initial metal contents of the magmas but are more likely due to differences in magmatic evolution.

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Section: Early Differentiation In the Plutonssupporting

confidence: 92%

Comparative petrologic evolution of the Sn and W granites of the Fairbanks-Circle area, interior Alaska

Newberry¹,

Burns²,

Swanson³

et al. 1990

Geological Society of America Special Papers

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“…Regional map compilations (1:250,000) by Chapman andothers (1971, 1982) and Foster and others (1983) serve as a basis for current studies in the Livengood area. Reports of particular interest include those by Foster (1968), Brosge and others (1969), Davies (1972), Chapman and others (1979), Foster and others (1982), Weber and Foster (1982), Albanese (1983), Cady and Weber (1983), Robinson (1983), Smith (1983), Gushing and Foster (1984), Weber and others (1985), Blodgett andothers (1987), Wheeler-Crowder andothers (1987), and Weber and others (1988).…”

Section: Livengood Areamentioning

confidence: 99%

Geology of east-central Alaska

Dover¹

1990

Open-File Report

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This report makes available the chapter on the "Geology of east-central Alaska" of the Alaska DNAG volume, which is still in preparation. A few references, given herein as "this volume" citations, refer to other chapters that will appear in the same DNAG volume. These references are necessarily incomplete as to publication date, volume number, and page numbers. Nevertheless, these references are included here to alert the reader to the inclusion and eventual accessibility of the relevant data in the Alaskan DNAG volume.

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“…(Patton and Hoare, 1968) as has been proposed by numerous authors (for example McWhae, 1986). In contrast, the Tintina fault system has a strong gravity and magnetic signature (Cady and Weber, 1983) these, an optimistic evaluation is that gas resources of economic importance for local consumption could be present.…”

Section: Yukon Flats Basin and Tintina Trenchmentioning

confidence: 99%

“…The Tintina trench contains both late Tertiary and early Tertiary to Late Cretaceous (Maastrichtian) nonmarine coal-bearing siliciclastic rocks that are about 1.0 km thick in outcrop (Brabb and Churkin, 1969) and may be as thick as 3.0 km in the Circle Hot Springs gravity low (Cady and Weber, 1983).…”

Section: Yukon Flats Basin and Tintina Trenchmentioning

confidence: 99%

Aeromagnetic map and interpretation of magnetic and gravity data, Circle Quadrangle, Alaska

Cited by 8 publications

References 1 publication

Comparative petrologic evolution of the Sn and W granites of the Fairbanks-Circle area, interior Alaska

Comparative petrologic evolution of the Sn and W granites of the Fairbanks-Circle area, interior Alaska

Geology of east-central Alaska

Alaska onshore national assessment program; geology and petroleum resources potential of six onshore Alaska provinces

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