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GeneralLimestone dark vein in limestone

28th Jan 2021 11:00 UTCRui Nunes 🌟 Expert

What is the geological explanation? How does this happen?

Quarry https://www.mindat.org/loc-308558.html

Thank you

28th Jan 2021 11:58 UTCPeter Nancarrow 🌟 Expert

Can't be certain without seeing the rocks themselves or at least a close-up photo of the contacts, but it looks like s basalt dyke to me.

28th Jan 2021 12:06 UTCKeith Compton 🌟 Manager

I'd have said a dyke .. or dike ((-:) but then I'm not a geologist.

28th Jan 2021 12:29 UTCRui Nunes 🌟 Expert

I observed the geological map and there is volcanic activity in the area. I'm not a geologist either, but when visited this quarry this dark vein don't seem to me to be basalt.

28th Jan 2021 12:30 UTCHarold Moritz 🌟 Expert

Does look like basaltic dike, there is another at upper left and what look like maybe some sills up higher in the photo. I can see a couple of places where a small finger of the basalt protrudes from the main dike, about 1/3 of the way up on the left side for example, and some thin white mineralization, maybe recrystallized calcite, along some of the contacts. Put a little acid on the dark rock.

28th Jan 2021 12:55 UTCRui Nunes 🌟 Expert

Another one

28th Jan 2021 12:56 UTCRui Nunes 🌟 Expert

Spheroidal weathering

28th Jan 2021 12:58 UTCRui Nunes 🌟 Expert

Nothing to collect in this quarry but a nice place

28th Jan 2021 14:01 UTCAmir C. Akhavan Expert

That last photo doesn't look like a "flexural fold", because then you would not see "detached layers" and unfolded gaps in between.
It looks like slumps (not sure about the correct term) in a turbidite, so the soft and wet sediments were deformed while sliding down.

28th Jan 2021 14:07 UTCAmir C. Akhavan Expert

What is the orientation of the bedding of the limestone? The "basalt" does seem to have the same mechanical qualities as the surrounding limestone, even if you take into account that these outcrops are fresh and artificial. Could it be a layer of limestone that is dark (more clay, less oxigen during sedimentation) ?

Edit: o.k., take that back, there seem to be branches in the dike, not a layer.

28th Jan 2021 14:18 UTCRui Nunes 🌟 Expert

Folds - thanks for the correction, Amir.

28th Jan 2021 14:29 UTCRui Nunes 🌟 Expert

A good perspective to observe the dikes in the quarry wall.

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