150 Geochronology of Critical Mineral Deposits with Special Reference to U-Th-Pb Dating of Common-Pb-Rich Minerals (Posters)

Radiometric dating of ore deposits containing critical minerals. Studies discussing analytical aspects of methods such as U-Th-Pb, Ar-Ar, Rb-Sr, Sm-Nd, Re-Os and/or using radiometric ages for ore genesis research or critical mineral resource evaluation.

Monday, 20 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

New dating apps: 40Ar/39Ar dating of K-free host minerals

Paper number: 150-6
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

For several decades, geochronologists have raced to harness the newest mass spectrometry and geochemical technologies to achieve ultra-high precision ages for a variety of rock types and geologic processes. However, each radioisotopic geochronometer is limited, in part, by the concentration of parent and daughter in the host mineral. Despite its vast versatility as a geo- and thermochronometer, 40Ar/39Ar dating has been restricted to phases which incorporate structural quantities of Potassium (K). We demonstrate that precise 40Ar/39Ar ages can be produced on K-free accessory minerals such as zircon, apatite, titanite, as well as on quartz and olivine, all of which are the cornerstones of other geo-petro-thermochronological techniques. The structure of these minerals lack K, but they can be 40Ar/39Ar dated due to the presence of tiny (<25 μm) K-bearing, melt or polymineralic melt/microgranite inclusions (“nanogranites”) entrapped at the time of crystal growth. Data will be presented from well-studied igneous localities with independent, existing age constraints. Our results show that it is possible to obtain accurate 40Ar/39Ar plateau ages from K-free minerals that are unrestricted in application by petrogenesis or age. These new mineral chronometers serve as bridges between the higher T chronometers (U-Pb in zircon, Ar/Ar in pyroxene, olivine, and amphibole) and lower T chronometers (U-Th/(He) and fission track), thereby allowing the most complete thermotemporal view of the rock record to date. The exceptionally low K/Ca values (in some cases < 0.001) of the accessory phases + inclusions suggest that lower limit for K content for the Ar chronometer has not yet been realized. Moreover, these findings offer new potential applications to detrital mineral geochronology in a variety of terranes and can provide new types of data pairs for high-precision geochronometer optimization.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413199

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