Thanks very much. There are plenty of useful things to learn from academic study, but I am trying to teach things that geologists learn after they leave university.
Fun to hear a little different pronunciation of basalt and nomenclature than I am used to. i.e Different syllable accented. Always good to be reminded that what I learned might not be correct. Really appreciate your organization, clarity, and concise presentation.
This channel is so amazing, sometimes im still confused on field to differentiate between phreatic magmatic and phreatomagmatic in diatreme, can you explain the fundamental consept differentiate for megascopic condition?? thanks before
As far as I understand, a phreatic breccia is the result of an explosion from overpressured groundwater (probably due to heat from a distant magmatic source). They typically contain a mix of wallrock and vein clasts, but no evidence of igneous magma. A magmatic breccia is one resulting from movement of magma breaking up surrounding rock (not necessarily involving any fluid). They just look like an igneous rock with lots of xenoliths. A phreatomagmatic breccia results from direct contact of magma with groundwater. They look similar to phreatic breccias, but have some clasts of igneous material and sometimes infill of igneous material between clasts.
That's a distinct possibility although I would have expected a few more exotic fragments mixed in from a lake environment and perhaps a little alteration from the interaction with the water.
Glad you finished with the warning about the breccia nomenclature, because it really is a complex rabbit hole and I have never felt comfortable with it. So the fuss about breccias boils down to their high likelyhood as ore deposits due to the way they form and where they form, resulting in them being likely to be mineralised, intruded by ore veins etc?
Thanks Lachlan. Yes, the reason breccias are so nice is that they can create a large volume of open space between the fragments and in almost all hydrothermal ore deposits, the ore minerals precipitate in open space.
