Obscure topic

[geostudent101]

Hello there, Im a geology student doing some research and have a conundrum...


I have a series of ripples (google URL at bottom of post for diagram) where by on the slip face there is a deposit of Iron oxide coated quartz not seen throughout the rest of the ripple. I figured it was due to a density contrast between the material. Quartz has a density of 2.66g/cm3 whereas Iron oxide 5.24 g/cm³ . Assuming the quartz-oxide is 5% oxide - density = 2.79g/cm3, can I work out the original flow velocity? I came here as a sluice box has the same "physics package" leading to the separation of flow and deposition of the denser material. Obviously here the density contrast is smaller and this represents an inverse problem.
The slope face is not preserved, but I assume an angle of 15 degrees and height (from base to crest-seperation) of 5 cm.

If anybody could give me any help regarding the physics behind this problem I would be most appreciative.
Many thanks and good hunting/panning? to you all!
Alastair

http://people.hofstra.edu/j_b_bennington/135notes/ripple.gif

 

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[Sick4gold]

If you are going to find the answers your looking for I am confident that this is the best forum for it.
It may take some persistence but there are plenty of brilliant people here.
Also if you need the advise of a dumb redneck miner I'm here too!

 

[63bkpkr]

Chris Ralph could be of assistance. chrisralph@icmj.com I saw the title and wondered what you were going to say about me...............63bkpkr

 

[Jason in Enid]

Obscure topic? I can't even understand the question.

 

[DizzyDigger]

I have a series of ripples (google URL at bottom of post for diagram) where by on the slip face there is a deposit of Iron oxide coated quartz not seen throughout the rest of the ripple. I figured it was due to a density contrast between the material. Quartz has a density of 2.66g/cm3 whereas Iron oxide 5.24 g/cm³ . Assuming the quartz-oxide is 5% oxide - density = 2.79g/cm3, can I work out the original flow velocity? I came here as a sluice box has the same "physics package" leading to the separation of flow and deposition of the denser material. Obviously here the density contrast is smaller and this represents an inverse problem.
The slope face is not preserved, but I assume an angle of 15 degrees and height (from base to crest-seperation) of 5 cm.
Alastair

Alastair, I'm no physicist, so take this for what it's worth.

You have calculated the materials density, but there are other factors that I think
would be required to calculate the flow velocity.

Is the bed these ripples are in laying flat, or does it have a downslope angle?

Could the depth of the water flowing over the ripples also have an impact?

 

[Goldwasher]

so your material/spot/ripple is not under water?

 

[pippinwhitepaws]

sorry, I am staying out of this...it appears to be a boobietrap.

 

[Goodyguy]

Try this: Bagnold equation

GG~

 

[Goldwasher]

Flow of wind?...are you just trying to figure out why your seeing a color variation in the Ripples? and believe that as the wind blows the sands of different density they deposit differently, due to mineral make up. And are a making a variegated pattern? That's what it sounds like your describing, do you have a picture of this geological occurrence you are studying?

 

[pippinwhitepaws]

the way I read it....a study of underwater dune formation?
out of my league.

 

[Sick4gold]

Agree out of my league but i also agree that there are many other factors to consider.
A few off the top if my head...
Each grain of material has a different shape, riFFle timing, slope, depth and speed, etc.
Not to mention if you want to get super technical density is a relative measurement as specific gravity changes depending on the temperature of the water it's in. Water is most dense at 39 degrees F.

I'm pretty sure also the physics of a sluice box are not 100% understood. There's plenty of information out there on the subject but I think the only way to get the answers your looking for is a long control test and research.

 

[jcazgoldchaser]

Try over here
Scientific Journal

 

[russau]

HMMMMM?? i cant find my cluckalator and i dont have that many fingers and toes,so i better let someone a LOT smarter than I to do the figerin!

 

[Jason in Enid]

I don't understand why these people come here, register as users, make one ridiculous post and then never come back. The OP hasn't been back since asking his "question". I wouldn't mind seeing a waiting period before people are allowed to post after joining.

 

[geostudent101]

Hi, In reply to Jason in Enid in particular. Im really sorry and feel UNBELIEVABLY guilty!! I thought I set it so that if anybody replied to my post I would get an email. Indeed it is quite shitty for people to reply to your posts then for you to effectively ignore their helpful advice/inquiries. My sincerest and most heartfelt apologies for this! Thanks you all for your replies, even the ones where people dont understand what the hell Im talking about, you took the time of day to read it!!

So....
The bed is underwater but the thickness of the water above is somewhat unknown though interpreted as a near-shore tidal current based on the sediment i.e. say 1m. However I did not think/dont know if this has an impact. I have uploaded a diagram. So my overall question from the diagram is, as there is a density contrast, is it possible to work out the overall flow speed?? Most people to work this out just use the old Hjustrom curve based on the grain size and I can get an answer for this quite easily, but its a really imprecise range based on experimental data of roughly quartz sediment grain sizes. I was just thinking, can I based on these observations get quite a precise answer/range as the density contrast is pretty small. I tried looking at literature but couldnt find anything regarding density contrasts between the slipface and the upslope deposition. Maybe this is a non starter, but if the estimated range fits inside of the hjulstrom curve range it could be quite cool as a practical tool to work out a really precise current from several hundred million years ago.
I WILL CHECK BACK EVERYDAY!!!!!! Sorry for not doing so, thanks again guys(and girl miners)!!!!
Good sluicing to y'all.

 

[geostudent101]

ps grain size is of fine sand ~400 um

 

[geostudent101]

Forgot to mention, given the basin position 500 Ma, 30 degrees on a good day, maybe 22 on a bad. tehehehe But yeh around about 25 degrees I would estimate.

Agree out of my league but i also agree that there are many other factors to consider.
A few off the top if my head...
Each grain of material has a different shape, riFFle timing, slope, depth and speed, etc.
Not to mention if you want to get super technical density is a relative measurement as specific gravity changes depending on the temperature of the water it's in. Water is most dense at 39 degrees F.

I'm pretty sure also the physics of a sluice box are not 100% understood. There's plenty of information out there on the subject but I think the only way to get the answers your looking for is a long control test and research.

 

[Sick4gold]

I didn't really want the water temp, I was simply implying that there are a lot of factors in play here.
Your questions may be better answered on a physics forum. There is a lot of information out there but what I gather from most of it is wind and underwater dune formation is not fully understood.
I'm including a link. Not sure if it will help or not but it's over my head so hopefully you can get something out of it.
http://www-f1.ijs.si/~rudi/sola/Sem4.pdf

 

[Jason in Enid]

Glad to see you back!

I don't know if there are any formulas that would fit what you are asking. Your best method to find an approximate answer would probably be to create a fluid bed and use the same particles you are concerned with. You could adjust the water depth and speed until you get the outcome you are analyzing.

 

[geostudent101]

I didn't really want the water temp, I was simply implying that there are a lot of factors in play here.
Your questions may be better answered on a physics forum. There is a lot of information out there but what I gather from most of it is wind and underwater dune formation is not fully understood.
I'm including a link. Not sure if it will help or not but it's over my head so hopefully you can get something out of it.
http://www-f1.ijs.si/~rudi/sola/Sem4.pdf

I understood your point but I was trying to show how badly I seem to be failing. I think I might try a physics forum though I came here as I a geologist saw many similarities with the sluice box design. Didnt think of trying physics forums; would be a little scared they would tear me to shreds with bosons and all that crap. Personally I feel that this topic does go way above my head. I might just stop as its only a minor, minor part of the project but I must express my thanks for link. Just looking into that now and it seems like it might help somewhat with my problem though. As you said, flow dynamics is poorly understood and largely empirical. Infact I remember reading somewhere that the core stokes laws etc are, though solid and well defined empirically and used for designing aircraft wing tips and a whole host of the stuff, fundamentally quite unknown and compromise one of the the most serious remaining physics phenomena. Millennium problems rings a bell? Figure that, dont even know how aircraft really fly? Cheers though and once again thanks for the link, your time and effort.