The Boudinage Effect

Boudins (French for saussages) form when rigid bodies are stretched in a plastic host during compressional deformation. The areas between the boudins are domains of dilation that can be a locus for mineralization.
The full Fieldcraft for Geologists series is here: geologyupskill...

[@crazyhans]

I know nothing about geology and work nowhere near the field, but it's nice to watch someone who knows their stuff explain their work. Hope you find lots of nice rocks, geology man ☺

[@GeologyUpSkill]

I'm glad that geologists aren't the only people who enjoy my work.

[@richardhaselwood9478]

Thanks for the structural geology refresher. For some of us, it's been a *very* long time....

[@kirklaird8345]

I enjoy your explanations and descriptions. You are an excellent instructor. Reminds me of a class in undergraduate geology that was taught by a visiting German geology professor in the late 1970s. German standards are a little more relaxed that those in the US. While he was showing a series of photos to demonstrate some examples of structural deformation up popped a photo of very nice outcrop with a buxom topless German lass in the foreground. I was curious as to whether you might consider similar instructional techniques?

[@GeologyUpSkill]

Enthusiasm and humour are great tools for teaching and my passion for geology was certainly shaped by similar teachers at university. Humour is a little tricky on KZbin because it reaches such a wide spectrum of cultures and ages, but I sneak in some easter eggs occasionally ;)

[@getzvalerevich6565]

Like, i am so happy i found this channel. The knowledge is here is on another level

[@GeologyUpSkill]

Great. I'm trying to share information that is genuinely useful!

[@getzvalerevich6565]

@@GeologyUpSkill yeah, amazing stuff. I am use to watching lecturers that sit behind the desk, which is of course very useful too, however you take it to another level and show things physically which REALLY helps.. Thank you so much

[@dlmac]

I am curious at what temperatures the rock had to be at to deform like this? I assume the rock was once at great depth and pressure.

[@GeologyUpSkill]

Yes, you can get some idea of the temperature and pressure by looking at the minerals in the surrounding rock. In this case amphiboles indicate temperature around 500 degrees C and depth of burial some 10s of km. How that rock got down that far and how it got back to the surface so we can see it today is a story that would require a very long video!

[@saskiagilmour5936]

Great video, thank you.

[@GeologyUpSkill]

Thanks Saskia. Glad you found it useful.

[@mrmum8445]

Brilliant 👍

[@manuelrengifo1017]

Excellent, thank you.

[@galatura]

Sausage Roll Gold , Nice :)

[@GeologyUpSkill]

It's a long way to the shop if you want a saussage roll... (ACDC).

[@galatura]

@@GeologyUpSkill LOl, Yes Indeed :)

[@jumigopfamtv8438]

Im here because i have it now i don't know if its gold or not

[@GeologyUpSkill]

Sometimes yes. Most times no, but dilation is always the place to start looking.

[@jdean1851]

WOW" THANKS!

[@GeologyUpSkill]

There are lots of wow rocks around Mt Isa.

[@nicoloussimukoko9784]

👌

[@biglizer]

Damn u good 👍

[@GeologyUpSkill]

Saussages are good!

[@donaldkasper8346]

Marl is slang. Define marl.

[@GeologyUpSkill]

I try not to get hung up on nomenclature definitions... There are so many to choose from!

[@donaldkasper8346]

@@GeologyUpSkill If you look in the literature, the hardest thing to define is marl. So if you use the term, define it. Now for me, when I scan minerals in infrared, I have to deal with slang all the time and try to determine if it means something real, and with many competing ideas, what would I define it as. Otherwise, statistical study of mineral in IR is difficult and gaps open up. In particular, this slang comes from old literature that people just repeat. Marl appears to come from English geology to define muddy limestone. If you disagree, name exactly how you define it. Then, what is sericite, illite, sanidine, vermiculite, celadonite, glauconite, saponite.

[@donaldkasper8346]

@@GeologyUpSkill Using mineral reflectance infrared, I get very hung up on naming. There is no such thing as a slang or cliche name I can use for statistical study of marker bands in infrared, and I want to assign names to what people were calling things for major locales in the past. If someone constantly called an Arkansas novaculite that I would call a chert, a quartz rock with quartzine, okay, what exactly is a quartzine. Is it real? Did the name change later? Is is a moganite? If is is a moganite is there beta-moganite in the field? Well, in terms of infrared from these places, the spectra are different and unique. Okay, so they are not just more quartz and stuff. Slang is just a placeholder for later understanding. For example, opal-A literally means amorphous opal. So what is that supposed to mean? Okay, in X-ray spectroscopy it produces a noisy signal spectrum that cannot be interpreted. Yeah, but in infrared, I get an exact spectrum that is consistent. So do we have to use that name because they used the wrong instrument? For opal-CT, there is no method of spectroscopy that has ever seen cristobalite in this opal, so why is this name used? Because of the plate stacking distance someone seen using electron microscopy, is where it came from. But in XRD and IR there is called zero cristobalite bands identifying cristobalite in opal-CT. So how does using name that does not identify a mineral help us understand what we see in mineralization? A lot of your fluid intrusion vein and dyke system have opal as products of that. This is not to be discussed or you cannot because why?

[@donaldkasper8346]

Why does naming matter? Because it allows proper identification. Why does this matter? Well, for example, when you learn to identify opal-C, you will find it occurs nowhere in the continental geology of the US rocks except in spherulitic geode structures. It has an exact place and marker. When you can see opal-A, you see it in Peru covellite and understand why the refractive index range is so vast. They mix the RI of opal-A and covellite together and get an RI range of a rock by mistake. Then this sits in our literature forever. Opal-A is very low temperature thermal water to surface water formation. If we can see beta-moganite, its transition from alpha has moved up over time in literature now to 354C which is the start of the transition to supercritical. This sits on the hydrothermal metamorphic systems so common to mineralized bodies, so if we find that, we have found the supercritical-subcritical transition where minerals are going to come out of solution and we may get boiling as a byproduct in the process. But to get to that we have to do all the other work such as determine if beta-moganite is just quartzine or something else. These terms have to come out of 1800s science and into the modern science world with spectroscopy instrumentation. XRD, Raman, IR spectroscopy not available in that age.