This Alaska Division of Geological & Geophysical Surveys (DGGS) Raw Data File presents 40Ar/39Ar age dating results for a volcanic whole-rock sample, selected minerals from various metamorphic rocks and igneous dikes, and white mica from both metamorphic- and hydrothermal-mineralization-related veins encountered on the southern Seward Peninsula, as well as select minerals from one plutonic rock from Cape Denbeigh, eastern Norton Sound, Alaska. Cooling ages on glaucophane, barroisite, amphibole, paragonite, and biotite from metamorphic rocks range from 84 Ma to 209 Ma. The cooling age of white mica in a possible fault zone is 144 Ma. Cooling ages on late-stage metamorphic minerals (winchite and white mica) from veins cutting foliation [...]
Summary
This Alaska Division of Geological & Geophysical Surveys (DGGS) Raw Data File presents 40Ar/39Ar age dating results for a volcanic whole-rock sample, selected minerals from various metamorphic rocks and igneous dikes, and white mica from both metamorphic- and hydrothermal-mineralization-related veins encountered on the southern Seward Peninsula, as well as select minerals from one plutonic rock from Cape Denbeigh, eastern Norton Sound, Alaska. Cooling ages on glaucophane, barroisite, amphibole, paragonite, and biotite from metamorphic rocks range from 84 Ma to 209 Ma. The cooling age of white mica in a possible fault zone is 144 Ma. Cooling ages on late-stage metamorphic minerals (winchite and white mica) from veins cutting foliation in metamorphic rocks range from 117 Ma to 139 Ma. Cooling ages on white mica and adularia from hydrothermal mineralization-related veins range from 105 to 131 Ma. The cooling age for one highly alkalic dike is 107 Ma. Cooling ages for younger mafic dikes range from 80 Ma to 84 Ma. The preferred age on a whole-rock sample of basalt is 0.780 +/- 0.011 Ma. Closure and cooling ages on the Cape Denbeigh granite (hornblende, K-feldspar) are 119 Ma and 113 Ma, respectively.
The Alaska Division of Geological & Geophysical Surveys (DGGS) Mineral Resources Section conducted geologic mapping and a mineral-resource evaluation on the southern Seward Peninsula, Alaska, during the summers of 2003, 2004, and 2006 as part of the state-funded Airborne Geophysical/Geological Mineral Inventory (AGGMI) Program. The DGGS airborne geophysical surveys, 1:50,000-scale surficial and bedrock geologic maps, and supporting geochemical and geochronologic data will foster a better understanding of the geology and mineral potential of the southern Seward Peninsula, Alaska. Additionally, as part of the Coastal Hazards program, the DGGS Engineering Geology Section collected a plutonic sample from Cape Denbeigh in eastern Norton Sound, Alaska.
