IN SITU 40Ar/39Ar GEOCHRONOLOGY TO RESOLVE THE AGE OF THE GOW LAKE IMPACT STRUCTURE, CANADA

摘要

Craters produced by meteorite impacts are the dominant surface feature on mostterrestrial planetary bodies, and these events have also been an important determinant ofgeological and biotic evolution on Earth. In order to fully understand the causes and effects ofhypervelocity impacts it is essential to obtain accurate and precise ages for them. ~（40）Ar/~（39）Argeochronology is widely and effectively used to date impact craters as it requires only a smallamount of sample material and all measurements can be carried out with one analysis; theseattributes are especially important given the heterogeneous nature of impact-generated rocks. Insitu laser ablation is particularly useful as it allows for the targeting of specific phases and discreteportions of a sample, and as a result specific microtextures can be correlated with the resultant~（40）Ar/~（39）Ar data. We use impact melt rocks from the Gow Lake impact structure to demonstrate theutility of this technique.