Help rock slice identifying please

[huangyc99]

Is this an impact-fused breccia? The brown one is molten glass. But how did that slender crystal vein form?

[4meter]

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?

[huangyc99]

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.

[huangyc99]

Is this a volcanic breccia or an impact breccia?

[4meter]

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.

[BobAK]

I agree with 4meter, was going to say welded ash