huangyc99 Posted November 8, 2021 Share Posted November 8, 2021 Is this an impact-fused breccia? The brown one is molten glass. But how did that slender crystal vein form? Quote Link to comment Share on other sites More sharing options...
4meter Posted November 8, 2021 Share Posted November 8, 2021 Fist off, you need to describe to us how the two thin sections photos were taken; Did you make the thin sections yourself? What is the thickness of the thin sections? are these plan polar or cross-polar? Looking at the whole rock samples; pic #1, looks like volcanic rocks to me. The pinkish rock on the right looks like a Tuff, the gray rock on the left, looks like an extrusive igneous rock, maybe an Andesite, but hard to say just from just a hand sample without any context. Why do you think these are impact breccias? Quote Link to comment Share on other sites More sharing options...
huangyc99 Posted November 21, 2021 Author Share Posted November 21, 2021 Thank you for your answer. 1: The brown ones are plane-polarized light (2 and 4) and the dark ones are cross-polarized light (3). 2:These samples came from the lip of a circular pit with a diameter of 10km. Suspected meteorite strike crater. 3: There are many Jurassic granite outcrops, but also cretaceous volcanic remains. Quote Link to comment Share on other sites More sharing options...
huangyc99 Posted November 21, 2021 Author Share Posted November 21, 2021 Is this a volcanic breccia or an impact breccia? Quote Link to comment Share on other sites More sharing options...
4meter Posted November 26, 2021 Share Posted November 26, 2021 The pictures of the rock exposure are classic tuff beds. Yes defiantly extrusive volcanic deposits. Think Mt Vesuvius, Pompeii type eruption sequence. The thin sections show a classic Welded Tuff rock type. The "ash" was hot when it came to rest and flowed around some of the rock fragments seen in the picture, before fussing together. The third slide shows a Quart vain cutting across (left to right) the existing rock and may be responsible for the black, square specks, which I am calling Pyrite. The Quartz vain is a later feature, maybe not related to the volcanic sequence. The thin sections, minus the Quartz vain, are further evidence of a volcanic Tuff bed interpretation of the rock exposure, and rock samples. Sorry, no meteorite impact deposits here. 1 Quote Link to comment Share on other sites More sharing options...
BobAK Posted November 26, 2021 Share Posted November 26, 2021 I agree with 4meter, was going to say welded ash Quote Link to comment Share on other sites More sharing options...
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