Minetosh online

⬇︎

Minetosh online – Geology
 RockClass Icon
Help and infos

General Information

About the CIPW norm

Norms (from normalize) are simply ways to recalculate chemical analyses of rocks in order to make some comparisons easier than, or at least different from, comparisons of the chemical analyses directly. The norm program here produces a modification of the standard CIPW weight norm that is most commonly used in geology.

This norm has been modified to group all plagioclase components together, and to combine the normative En, Fs, and Wo components into the Diopside and Orthopyroxene components. SO₃ apportionment has been modified to include anhydrite if there is insufficient Na₂O to make Thenardite. Cr₂O₃ apportionment has been modified to include the Magnesiochromite component if there is insufficient FeO to produce Iron-Chromite.

The norms are calculated and listed under the headings "Weight % Norm" and "Volume % Norm", next to the list of "Normative Minerals". Weight norms are the most commonly used. Beneath the norm columns you'll find other calculated values. More infos about these values are provided by clicking the appropriate info-button.

Literature

Data input

Enter the chemical composition of the rock in the appropriate fields under the heading "Rock Analysis". You may use the period (".") or the comma (",") as decimal point. If you wish, select one of the three options under "Options" (normalization, logging, Fe-ratio correction). Different elements should be entered in their oxide weight percents, or in elemental parts per million. These measures correspond to the way these elements are usually given in a common chemical analysis.

After a calculation, you should delete all inputs and results with the button "New calculation". This minimizes the processor load when re-entering! Alternatively, you can reload the page.

Options

Logging

You can activate the output of the intermediate results in the console. This protocol allows a – essentially – direct comparison with the original Excel file. Normally, logging the intermediate results should not be necessary. This is primarily for debugging.

Normalization

The chemical analysis can be recalculated to 100% before calculating the norm.

Fe₂O₃ to FeO ratio (Correction)

You can set the ratio of Fe3⁺/(Fe3⁺+Fe2⁺) to a constant ratio. Type in a zero or a number between 0 and 1. If zero, the Fe₂O₃ and FeO values in the Rock Analysis column are used in the norm calculation. If a value between zero and one is used, this value is used as the ratio of Fe3⁺ to total iron in the norm calculations.

More ...

For more Information about the options please click on the Info-Buttons or the details-elements (▶) on the input page.︎

Normalization / Correction

The corrected analysis

The "Corrected Analysis" column is derived from the "Rock Analysis" column but includes the changes you requested under "Options".

These values have been corrected as follows:

  1. If you selected "Normalization", the values have been recalculated to total 100%. Remember that because of rounding error the total may not be exactly 100%.
  2. If you selected it, the iron oxides have been changed to equal a constant proportion that you chose. In this case the total should be the same as the Rock Analysis total, except for rounding error. Remember that, because of the recalculation, the oxide values will not be exactly the same as in the Rock Analysis.
  3. If your analysis included trace elements, these elements have been recalculated from ppm of the elements to weight % of the oxides (e.g., 500 ppm Zr now equals 0.07 % ZrO₂.

The CIPW-Norm

The CIPW standard minerals

These are the various normative components (minerals) that the norm program calculates. They are picked to be, in a certain sense, similar to the minerals you might find in an igneous rock slowly cooled at low pressure under dry conditions. In a more practical sense, they are standard components which can be used to compare one rock with another in the same way that chemical analyses can be compared. Don't get the idea that you will actually find all these phases in your rocks.

The weight norm

The weight norm is the standard norm that almost everybody uses. The normative components (minerals) are calculated in terms of their weight percent. This type of norm can not be compared with thin section point count modes.

The volume norm

The volume norm is not usually reported in the literature. In a volume norm the normative components (minerals) are calculated in terms of their volume % in the normative rock, rather than weight %. This type of norm can be compared, in some respects, to thin section point count modes. Just remember that the normative components are pure, whereas real minerals are solid solutions. For example, the normative plagioclase and orthoclase could actually be a single mesoperthite or sanidine in a real rock.

The Streckeisen (QAPF) diagram

This function uses the values of the calculated CIPW norm minerals. So first you have to do a calculation of the CIPW standard before a rock can be represented in the diagrams. Choose between "Volcanic rock" and "Plutonic rock" according to your sample so that the correct diagram is displayed. If you do not calculate a CIPW standard, after clicking on the button, only the Streckeisen diagrams without a data point are displayed. Explanations can be found in the drop-down box under the diagram.

The TAS-diagram

For this diagram the data of your chemical analysis are used. A calculation of the CIPW standard is therefore not necessary. An input of SiO₂, Na₂O and K₂O is sufficient for a classification with this diagram. After clicking on the button, the diagram is displayed with the data point. The explanations can be found in the drop-down box under the diagram.

Download results

Download the diagrams

xxx

Save your data

You have the option of downloading the results of the calculations as a csv file. For example, this format can be easily opened in LibreOffice Calc. The csv file contains all calculated values including the comment. However, the Streckeisen- and the TAS diagram must be downloaded separately (using the buttons below the respective diagrams). Before the download you have to enter a name and an identification (these are also included in the csv file). The downloaded file has a name according to the following scheme: CIPW_TheName_Date.csv.

Acknowledgements

This application was originally written as an Excel spreadsheet by Kurt Hollocher (Geology Department, Union College, Schenectady, NY, 12308, United States, e-mail: hollochk at union.edu). For Minetosh online's website, this program was rewritten for JavaScript while preserving the original computational steps and constants. Minetosh online would like to express his thanks for the work of Kurt Hollocher. The original file can be found under the following link:

Original Excel spreadsheet

About this application

Version history

January 2020; RockClass 2020-01-V1: First version

March 2020; RockClass 2020-03-V1.2: Minor fixes; Reset-buttons now work correctly

March 2020; RockClass 2020-03-V1.3: Improved menu: Now works better on mobile devices

Troubleshooting

It is recommended to delete all inputs and results with the button "New calculation" before a new calculation. This minimizes the calculation load when re-entering data and avoids erroneous output!

If the automatic norm-check is showing a red warning message there's is a problem with the norm. This may mean that your rock composition was typed in wrong, that the rock composition lies outside the composition space in which the norm is designed to work, or it may indicate a bug in the calculation program. First, check for data entry errors and control the composition of your rock. If this is not the problem, and should you encounter other strange results, or should the app behave otherwise strangely, the cause may be related to the browser cache. In this case, delete the browser cache or the recent history (often via the "History" menu), taking care not to delete important settings (cookies, etc.) as well. Reload the page. In rare cases it might be necessary to quit the browser and to delete the cache manually in the file system. If all this does not help, please contact Minetosh online.

All functions have been tested with: Firefox, Safari, Google Chrome.

Disclaimer

THERE IS ABSOLUTELY NO GUARANTEE / WARRANTY CONCERNING THE ACCURACY AND PRECISION OF THE RESULTS!

The web-apps on the Minetosh online website are meant for information purposes only. The entire risk as to the quality, accuracy, precision and performance of these programs is with you! ALSO NO RESPONSIBILITY WHATSOEVER WILL BE ACCEPTED FOR ANY OTHER RISCS THAT GO BEYOND THIS. In particular, any damage or any other inconveniences (for example data loss) that may arise from the installation and / or use of these programs and the data produced by them (e.g. should the programs / results prove defective / erroneous)!


Back to data input page

Data input


Back to RockClass Home

Home


Back to Minetosh online

Back to Minetosh online