40Ar/39Ar data from the Talkeetna Mountains C-4 Quadrangle and adjoining areas, central Alaska

Description

This report presents 40Ar/39Ar step-heating geochronology results for igneous and metamorphic rocks from the Alaska Division of Geological & Geophysical Surveys' (DGGS) Talkeetna Mountains C-4 Quadrangle and Adjoining Areas geologic mapping project. Hornblende-bearing gabbro returned a Late Triassic crystallization age consistent with regional results for Nikolai Greenstone-related magmatism. We determined Early Jurassic metamorphic ages for hornblende and sericite from two samples of upper greenschist to amphibolite grade metavolcanic rocks. Our results indicate that a granodiorite pluton intruding Wrangellia in the study area has a Middle Jurassic age consistent with the Talkeetna Arc, indicating that the Wrangellia and Peninsular terranes were joined at that time. Cretaceous plutons and porphyry intrusions in the map area can be divided into two types: reduced granitic to felsic porphyry intrusions with latest Cretaceous ages, and an earlier, oxidized type with early Late Cretaceous ages. This observation corresponds to similar patterns in magmatism in the western Alaska Range, and may indicate geological potential for similar style intrusive-related gold, copper, and molybdenum mineralization in the study area. Finally, we obtained Eocene ages for andesite and rhyolite; these ages constrain the timing of displacement on some of the faults in the map area. Analyses were performed by the University of Alaska Fairbanks (UAF) Geochronology Laboratory, and the results were reported by Jeff Benowitz and Paul Layer. Products included in this data release are a summary of sample collection methods, the laboratory report, analytical data tables and associated metadata, and the plots of the 40Ar/39Ar age spectra, Ca/K, and Cl/K ratios.

Resources

Name Format Description Link
0 CSDGM IMPORT ERROR: No digtinfo/formcont http://dx.doi.org/10.14509/29454
0 http://dx.doi.org/10.14509/29454
0 http://dx.doi.org/10.14509/29119
0 http://dx.doi.org/10.14509/27181
0 http://dx.doi.org/10.14509/27287
0 http://dx.doi.org/10.14509/29140

Tags

  • 40ar/39ar
  • plutons
  • sample location
  • geochronology
  • cretaceous
  • early jurassic
  • analyses
  • middle jurassic
  • eocene
  • volcanic
  • bedrock
  • geology
  • bedrock geology
  • talkeetna mountains quadrangle
  • ar-ar
  • volcanic arc
  • analyses and sampling
  • plutonic rocks
  • wrangellia terrane
  • nikolai greenstone
  • late triassic
  • lab methods
  • strategic and critical minerals assessment project
  • age dates
  • statemap project
  • volcanic rocks
  • analytical results
  • analytical lab results
  • talkeetna arc

Topics

  • Local Government

Categories