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U-Pb Isotopic Data and Ages of Zircon and Titanite from Rocks from the Western Alaska Range, Northern Aleutian Range, Taylor Mountains, and Tikchik Mountains Regions, Alaska

July 23, 2020

This data set contains U-Pb isotopic data and ages of zircon and titanite from igneous and metamorphic rocks collected from the western Alaska and northern Aleutian Range of south-central Alaska. The data sets also contain U-Pb isotopic data and ages of detrital zircon from sedimentary and metasedimentary rocks collected in the same region but also from the Taylor and Wood River Mountains of southwestern Alaska. The entire sample suite was collected as part of geological mapping and supporting geochemical and geochronological analysis conducted from 2004 to 2019 and funded by the Mineral Resources Program of the U.S. Geological Survey (USGS). Zircon and (or) titanite were obtained from igneous and metamorphic rocks to determine the crystallization age and (or) age of metamorphism for the bedrock samples. Bulk rock samples were processed into concentrated mineral separates in USGS laboratories in Denver, Colorado, or by Apatite to Zircon, Inc. (A2Z) and analyzed by USGS research scientists at the Stanford-USGS Sensitive High Resolution Ion Microprobe with Reverse-Geometry (SHRIMP-RG) at Stanford University. Detrital zircon grains were obtained from samples of sedimentary and metasedimentary rocks to determine depositional age and sediment sources. Detrital zircon grains were separated from bulk bedrock samples and analyzed at one of three different laboratories [University of British Columbia (UBC, 2004 to 2006), at A2Z (2006 to 2009), and GeoSep Services (GSS, 2015 to 2019)] using laser-ablation-inductively-coupled-plasma-mass spectrometry (LA-ICP-MS) techniques. The data tables accompanying this data release report the isotopic composition of uranium (U) and thorium (Th) measured in each grain, ratios of two isotopes of lead (207Pb and 206Pb) and two isotopes of uranium (235U and 238U), and the age of each grain. The SHRIMP-RG data table also reports concentrations of selected trace elements measured in each grain.

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