QAPF Diagram Tutorial 2 of 2

[@firdushhussain7043]

great tutorial............easy to understand for my B.sc exams..👍👍

[@daneandersen8181]

Firdush Hussain thank you!

[@Rubystarshow]

I am really grateful for explaining this in such an easy and organized manner. Thank you!

[@thandiluciakhoza238]

Geotech Engineer here, thank you so much this helped a lot ❤❤!

[@daneandersen8181]

Happy to help!

[@damongeo840]

Thank you for helping me revise this material; I am doing a master's on natural disasters and I have to write a short report on granite (structure, texture, mineralogical and chemical composition, physical characteristics, etc).

[@Upodia069]

Great Video Dude. I was looking for a way to teach that to my students in my Class and your video just gave me a blueprint how to do it. Thanks man.

[@nobody631136]

Really appreciate your amazing video!

[@jennytically]

Thank you so much bro. I have been trying to understand the QAPF classification of igneous rocks since months. Now after watching your videos (both tutorial 1 & 2) I have well understood. Thanks a lot ❤️

[@AqielJabbarSyadid-bn3kj]

Thank you so much. I have been trying to understand the QAPF classification of igneous rocks . Thank you

[@rimshakhan1282]

great video .......it really helped me for my Bsc exams thank you so much

[@_hiraljain]

This is the best explanation! thanks

[@jasonloxton2785]

Bit confused as to this approach to plotting the diagram, rather than just plotting three lines using each point as 100% (as you do with quartz). That's the standard way of doing it, and it avoids having to normalize a second time (to get relative percentage of feldspars). Is there a reason you do it like this? I've never seen this approach and it's not how I or anyone I know teaches QAPFs. Open to an argument that it's better, but strikes me as more, not less confusing.

[@daneandersen8181]

Can you explain a bit more? This is the way I learned, but not necessarily the best way of course!

[@nanwijanarko1969]

I think it's because the reference line (10, 35, 65, 90) shows the relative abundance of Feldspar and Plagioclase regardless of the amount of Quartz, so the second normalization able you to utilize that line. I'm used to do it the way you describe it though.

[@nanwijanarko1969]

@@daneandersen8181 2 years late, but maybe someone else will find it useful :) the percentage in the ternary diagram is usually represented this way en.wikipedia.org/wiki/File:Blank_ternary_plot.svg, so we can also plot the three lines based on the first normalization result. The difference is the lines will NOT touch the Q point, rather parallel to the line across the intended mineral point.

[@PuddinPie]

There is a 3 axis method and a 2 axis method. 3 axis is plotted from the sides of the triangle, if you don’t have the graph in the comment above then this can be tricky. To utilise the lines that are drawn into a QAPF diagram, the point needs to be plotted as a 2 point axis - vertical and horizontal.

[@SumErgoCogitum]

Please refer to the LeMaitre IUGS "Igneous Rocks - A classification and Glossary of Terms": The vertical lines in the QAPF diagram are of constant plagioclase ratio (page 21 of the above reference). Therefore, you cannot use them as reference lines when you normalize for Q+A+P=100%. The only way to use them as reference lines is to normalize 100%=P+A. This is "Plagioclase ratio"= 100xP/(A+P). With the result of plag. ratio you can use for reference the vertical lines in the QAPF. One way you could check this is to use a classic ternary plot with its subdivisions and some transparency over the QAPF diagram. You are going to realize that the vertical lines in the QAPF differ from the % lines of a ternary plot. Therefore, either you plot using a ternary plot over the QAPF diagram ignoring the vertical lines of the QAPF for A and P values, or you normalize to a second time P+A and obtain the plagioclase ratio, in order to use the vertical lines as a reference. I believe that there is a potential error in the first case, if the user utilize the vertical lines as if they were % divisions in ternary diagrams.

[@syedrizvi1927]

Thanks bro. Yesterday my teacher discussed this topic.U cleared all my doubts.

[@nahzenzak9624]

the best video ever !

[@basshuntet6128]

man...your video really helpful, I like and subscribe.

[@himelhossain9884]

Thanks you sir. It is Helpful for me

[@firdushhussain7043]

what are the drawbacks of the IUGS /QAPF classification

[@daneandersen8181]

Firdush Hussain, I suppose a drawback of this system is that it can't be used to classify all types of igneous rocks.

[@firdushhussain7043]

thanx.......any more

[@daneandersen8181]

Another drawback- if you are classifying rocks in the field using this system, you may not evaluate the percentages of each mineral accurately enough to come up with a definitive rock name. But that's ok- field descriptions are never exact, but usually close enough. Which sums up field geology in a nutshell!

[@magalivallejo6225]

hello,en el caso que no tenga cuarzo ni plagioclasa y solamente tenga feldespato alcalino o solamente tenga plagioclasa y feldespato alcalino,como se hacen los calculos?y como se grafica?...thanks

[@tedtofu5563]

Thanks. You are doing a great job. Grüße aus Deutschland.

[@lujoco7694]

Thank you for helping me out :)))

[@depressing-gamer7127]

THANKS A MILL i needed this so much

[@maciejwoszczyna7658]

Great tutorial dude! Thanks a lot :)

[@myrad9533]

Great refresher! Thanks

[@brendawaters7554]

Thank you! Very helpful.

[@farcebrook]

In my opinion you got the P and A reversed (starting at ~8:28) by plotting 40% P at the 40% A line.... ?

[@shoaibayyaz3820]

can u please explain TAS diagram, if possible ?

[@sujanmarahatta776]

Thank you soo much for this sir.Thanks form nepal..

[@shamithashetty1763]

Thank you sir very helpful 😊

[@jaswantdhayal5482]

Nice👍👍👍👍

[@miisamirotta]

What if the lines cross at the borders so they're between two different types of rock? How do you classify the rock?

[@daneandersen8181]

There’s probably a better explanation, but I would just decide on one or the other and go with that. A lot of geology is open to interpretation

[@trippy8781]

How to tell between gabbro, diorite and athornosite

[@douaaboussboula]

Thant you 🙏🏻very helpful

[@wow12185]

Why are the micas and the amphiboles not included in the diagram?

[@daneandersen8181]

Aishwarya Chandekar- Mica and amphibole are not taken into account when classifying igneous rocks using this system. You can ignore them (and any other mafic minerals), as long as they don't make up over 90% of the minerals in the rock. If there are more than 90% mafics, another diagram is used.

[@wow12185]

+TerraLearn Okay! Thankyou

[@wenniemondejar]

Micas and amphiboles are not rocks. They are minerals.

[@maxwellsiziba139]

great tutorial. thank you so much.

[@sandrafundeiro6186]

Great help! Thanks!!!

[@muhammadadil6455]

great very informative ... thanks

[@skiidzman]

Yeah but how do you plot them with weight percents :(

[@gamearena90]

👌👌👌 thanks

[@ricardogallardo2721]

Thank you!

[@happygwayi7600]

Your too good

[@belfreyajehmesumbe]

❤Geologi

[@herrderinge2759]

Very helpfull!

[@AnamikaPaul-hi1er]

@futurecanoe what are you doing here

[@javisliria9388]

thank-you so much.

[@examspeedo8934]

Very very thank-you

[@y1git]

thanks

[@daneandersen8181]

You're welcome!

[@alexmakoto7969]

Thankyou 👏

[@yuritori2068]

thanks for help

[@3lasamirelmesal752]

thanks for U

[@khalidkarie1278]

Thanky u

[@grego1451]

Why not simplify the analysis? Quartz is 1/3 of the total = 33%. Plagioclase % = 100% x P/(P+A) = 100% x 30/(30+20) = 60%.

[@RockiesCanada]

[@kendir1278]

Thanks