User`s Manual - Berkeley Geochronology Center
Contents
1. Specify whether you want the reduced Pb U isotopic ratios to be for a 2 dimensional concordia plot that is using radiogenic Pb ratios with the Pb and 9 Pb corrected for common Pb or for a 3 dimensional concordia plot Pb and Pb corrected only for blank Pb You can select how you want your reduced data calculated for both the total Pb isotope ratios and the radiogenic Pb isotope ratios Option 1 for total Pb ratios will yield data for Pp pp Pb Pb isochron plots in which the s ope of the regression line indicates the age of the system Option 2 will give you data for pp 9pp 2 pp Pb isochron plots in which the intercept indicates the age The three concordia plot ratio options yield formats for U Pb isotope concordia plots of respectively conventional style Wetherill 1956 Tera Wasserburg style Tera and Wasserburg 1972 and Tatsumoto style Tatsumoto et al 1972 Note that the raw data input format is always the same though You can specify the default disk path for your LabData files and your raw data files The first time you run PBDAT these will be the same as the PBDAT program You can change the disk path for both of these file types while running PBDAT so don t bother to plan ahead too much at this point Reduced data files can be stored in either a space delimited format column names directly above a row of repeating equals signs each column containing 9 characters or a tab delimite2. Alpha Pb Pb or pp Beta Pb Pb or Pb Pp Gamma Pb Pb or Pb Pb Error correlation for Alpha Beta or 9 Pp 296pp 07pp 296pp Alpha Gamma or Pb SPb 2 Pb SPb uncertainty in radiogenic Pb 3 U or 7 8U Pb or 35 J 207pp 207p p 235L J 2075 p 206D5 or 206Ph 2 Pb Error correlation for 99pp 239LJ 207 pp 235 J or 207pp 206pp 239 J 206pp or 2065 p 207pp 235 J 20 7pp uncertainty in radiogenic 9Pb Th uncertainty in Mu and Nu 89 7 Pb ang U Pb uncertainty in Th Pb Error correlation for Alpha Mu Pb Pb 8U 4Pb Beta Nu 8p p 04pp 235 J 20 ppy j Gamma 232 204 9pp pp Th 2 pp 32 Table 4 Example of LabData File Printout DATA FROM LABDATA FILE ZIRCLAB Pb 208 Spike Pb208 V 208 1 105E 09 1 moles g not a mixed Pb U spike 206 204 17 9 2 0 6 2 0 7 y 4 206 208 0001441 Pb 205 mixed spike Pb205a 205 3 971E 11 1 moles g 235 1 7619E 09 1 moles g 230 1 2909E 09 1 moles g 206 205 001128 238 235 00612 206 204 20 33 232 230 00243 206 207 1 213 206 208 4846 U 235 spike U235 IV 235 2 3695E 08 05 moles g 238 235 007905 Mixed U 233 U 236 Spike U233a 233 4 9584E 09 1 moles g 233 236 1 0172 233 238 2534 Th 230 spike Th230 II 230 7 981E 08 15 moles g 23
3. RAM required by program cece eee eee 2 Raw data files 0 cece eee eee 16 raw data files accessing cece eee eee ee 19 Raw data files reducing data from 20 raw data files specifying default disk path of 4 Raw data files use of embedded specifiers in y Reagent blanks importance of handling evaporation blanks in ccc cece eee eee B RECALL key useofinFORMS eee eee 7 R educed data file formats explanation of 21 reduced data files converting to LO TU S files 21 reduced data files creating cece eee eee 2 reduced data files default format for 5 reduced data files formats for 00 008 21 reduced data files storing on a disk 2 results specifying format of cc ccc eee een 4 SAM SPK ratio cece eee eee eee eens n SAM PLE WEIG H T significanceof 7 Screens specifying typeforPBDAT ssss 4 Source code for PBD AT obtaining 2 space delimited raw datafiles cc cece eee 16 space delimited reduced data files specifying 5 space delimited reduced datafile format specifying RD ou ead avi E a Saree Raa aes 21 Spike concentration uncertainties how to assign 22 24 spikes calibrating concentrations of 005 4 spikes types of that can be used cece ee eee 2 SPLIT program ens sopini ren dened ais eek Goad eee 21 Stacey K ramers g
4. 6444444444444444447 K R Ludwig Lil 5 5 Berkeley Lil rev March 18 1991 5 PBDAT 5 Geochronlogy t ver 1 20 5 5 Center t 9444444444444444448 s i 8 33333332233333233222222323323223222322223233222322121212 d t Spikes Pb 208 U 235 dg d LabData File None gi t Raw Data File None z dg t Output to Screen Only 313223232333313333323222333223322322223232322232212122 LEEEEEEETEEEEETEEEETEEEEETEEEEEEEEEETEEEEEEEEEEEEEEEEEEEEEEEEEEEEE 233333333332322223232222222222222222223222222322222232333232323232222222222222222223 I ll refer to the above display as the Top Level Screen USING PBDAT S PULL DOWN MENUS Each of the categories listed at the top of the display in the Top Level Screen has a pull down menu associated with it There are several ways of interacting with the pull down menus 1 If you have a mouse point to the menu title at the top of the screen with the mouse cursor and click either button Select an item in the pull down menu with the mouse by pointing and clicking again or escape by pointing and clicking outside the menu 2 If you don t have a mouse or don t like to use it press either the ALT key or the slash key followed by either 1 the first letter of the menu of interest or 2 moving the cursor bar with the left right arrow k
5. Suppress Screen is selected only the sample names will be shown on the screen as the data is reduced automatic for printer output also useful for datafile data reduction where the results will be stored in a reduced data file If Printer is selected all of the output will be directed to the printer instead of the screen You can now reduce the data in the raw data file If you want to reduce data for all of the samples in the raw data file just press the ALL key F2 If you want to reduce only part of the data indicate the sample numbers of continuous sequences of data by entering the first and last number of the sequence sep arated by a comma and indicate discrete sample numbers or the start of a different continuous sequence by a semicolon So to specify that sample numbers 1 though 6 then 9 then 12 through 15 be reduced you would enter 1 6 9 12 15 Remember to include rows containing any embedded specifiers if you want those embedded specifiers to take effect Remember also that once an embedded specifier is acted upon it remains in effect until specifically canceled by either another embedded specifier or by softkey commands from the Top Level Screen After you ve specified which samples in the datafile to reduce the program will display the Initial Pb Ratios FORM Enter the initial Pb ratios as discussed earlier or press Esc if you don t want apparent ages to be calculated for any of the samples or if the initial Pb ratios are spec
6. a NM10 206 204 Serr 206 207 Serr 206 208 Serr UNSPKD 7356 6 14 7 10 254 0043 14 325 0054 SPIKED lt 5 in 10 225 012 2 3446 0031 SPIKE 16 2 3128 0000931 BLANK 6 4 18 9 2 7 4 15 55 2 8 4 37 9 1 8 02537 g Pb208 III spiked 9 7922E 09 05 moles 208 g 02774 g U235 III spiked 8 5 9419E 08 05 moles 235 g 02774 g Th230 II spiked 7 981E 08 15 moles 230 g SAMPLE WT TOTAL AL Pb UNSPIKED AL Pb SPIKED AL 01234 14559 53214 21345 grams Pb Unspiked Aliquot Corrected for 065 039 Ng Pb Blank and 11 05 per a m u Mass Discrimination 206 207 206 208 206 204 207 204 208 204 10 246 14 312 7509 732 85 524 67 0545 127 2 07 2 06 2 03 Error Correls 207 204 206 204 9996598 208 204 206 204 9982136 Moles Pb per gram 206 207 208 204 TOTAL 1 969E 07 1 9217E 08 1 3758E 08 2 6222E 11 2 299E 07 t 131 3 3 Ng Common Pb in Unspkd Al 369 PPM PPM Total Pb 47 401 Pb Spiked Aliquot Blank 16 Ng 238 235 5 4376 014 232 2309 7537 032 005 Ng U Blank 008 Ng Th Blank U Th Spiked Al 74559 Grams 238 235 232 Moles per Gram 7 6316E 07 5 535E 09 1 358E 07 182 98 PPM Uranium 453 31 51 PPM Thorium 62 Th U 1722 238 204 29104 235 204 211 08 2 12 232 204 5179 2 16 Rho U 4 6 4 975 Rho U 4 7 4 95742 Rho Th 4 8 4 93779 TOTAL PB 206 238 207 23
7. e e UR Sata I RES 9 Initial PbIsotopeRatio FORM s 9 initial P b isotope ratios significance of errors in 10 initial Pb using embedded specifiers for in a raw data file 18 initial Pb using Stacey K ramers values for in a datafiler zs cou Deeia vete ey pee ERO pnis 18 ISO PLOT program cece eee 2 ISO PLOT automatic access of last reduced data i Mee LE 22 ISO PLOT invoking directly from PBDAT 22 keyboard entering data from ccc cece eee 6 LABDATA file defininganew 005 22 LABDATA file mass discrimination values for 23 LABDATA file printout of values in 23 LabD ata File uncertainties for blanksin 22 LabD ata files uaua 6 LabD ata files creating NeW cece ee eee eee 22 LabD ata files editing values in 005 23 LabD ata files specifying default disk path for 4 LABDATA file changing oicc 23 LABDATA file storing ondisk 0 005 23 LABDATA files description and useof 22 loading LABDATA files cc eee eee eee 23 loading the program ccc cece eee eee eens 3 LO TU S E23 esci eere ders 16 LO TU S 123conversion of reduced data files 21 LOTUS 123raw datafiles 2 16 Macintosh eena veiw en oes ota de 16 mass discrimination values fora LABDATA file reta peers bre Lr DU PEUPLE EE 23 mass fractionation aaa 8 memory RA M required by program 2 men
8. enter SPLIT will add L to the start of the root name for one of the split files and R to the start of the root name for the other split file For example QUEER PRN would become LOUEER PRN and RQUEER PRN Once you ve split the Complete reduced data file you can convert it to a LOTUS file with the macro in the LOTUS CCONVERT file The CCONVERT macro works just like the PCONVERT macro except that you ll need to enter 2 file names to specify the source file Enter the L file first then the R file as created by SPLIT Once you ve created a reduced data file if you invoke SOPLOT directly from PBDAT by pressing ALT I from the top level screen or from the FILES pull down menu SOPLOT versions 2 50 and later will immediately access that reduced data file 22 USING LabData FILES LabData files contain the data for a laboratory s spikes typical blank compositions and typical mass discriminations of isotope ratio measurements Table 4 If necessary you can define several LabData files for the various spikes or other variables that might be used by your lab Defining a New Labdata File To define a new LabData file select the Create New option from the LabData menu PBDAT will ask you which spikes you wish to define and present you with a FORM for each spike The spike FORMS will require the concentrations in moles per gram of the major spike isotope the ratios of the isotopes in the spike these must have already been correct
9. entered a value of zero for the Pb unspiked aliquot weight in the previous FORM the above FORM will ask you for only one ratio the Pb unspiked 206 208 Enter your best estimate for the ratio and 8 the uncertainty in this estimate PBDAT will then carry these absolute values directly through to the reduced data without corrections for blank Pb or fractionation The Pb blank is the blank that corresponds to the unspiked portion of the analysis only So if the dissolution process alone contributed a significant amount to the overall blank you should include only the fraction of the dissolution blank that corresponds to the Pb unspiked aliquot If you didn t measure Pb isotope ratios for the Pb unspiked aliquot just bypass this FORM by pressing Esc The Spiked Aliquot Form Pb Spiked Samples The next FORM requires the isotope ratios for the Pb spiked aliquot as shown below assuming a U 235 uranium spike Spiked Aliquot errors must be 2 sigma in percent 2 0 E24 BALD t2 SECO o 2 2 0167 2 0 8 5 Soe GEGELOL Wn up D3 B23 SN eee GOGO TR vs eco 232 02 304 o meee S Oll se PI lank nanograms lank nanograms The 206 207 ratio for the Pb spiked aliquot is optional if you don t have data for this ratio don t enter any values for it f your sample contains radiogenic Pb though you should always include the 206 207 ratio for the Pb spiked aliquot PBDAT can then calculate the Pb co
10. information on what the significance of that parameter is and what sort of response is required If you ve already entered a set of values to the form for a previous sample for example you can re use the last values entered by pressing F10 or clicking on F10 Recall All with the mouse when the FORM is displayed The last entered values for that FORM will then appear in the current FORM This feature is especially useful if you made an error in entering the data for a sample but didn t notice the error until after you submitted the FORM or if you wish to recycle data with only slight changes The Weights Form for 2 Pb Spiked Samples The above FORM requires values for the various weights involved in a sample analysis Their significance is as follows Sample Weight The weight of the sample that was actually attacked and put into solution in grams Total Aliquot Weight The weight of the total solution of the entire sample in grams Enter a value here if you only put a fraction of the total solution of the sample through chemistry if all of the solution were used so that the Total Aliquot is just the sum of the Unspiked Aliquot and Spiked Aliquot weights you needn t enter any value here PBDAT will then assume the Total Aliquot to be the sum of the spiked and unspiked aliquots Pb Unspiked Aliquot grams The weight of the solution used as the Pb unspiked aliquot Samples spiked with Pb before dissolution will have no Pb
11. initial Pb ratios and uncertainties From columns C to respectively the cells in this row will contain values for the initial Pb 206 204 6 4 error 207 204 7 4 error 208 204 8 4 error and 206 204 207 204 error correlation See below however for obtaining Pb ratios for a Stacey Kramers Pb evolution in a simpler way SK Use the number following this specifier to calculate a Stacey Kramers single stage Pb to use for the initial Pb ratios for example SK 1750 The uncertainty in these ratios will be set to zero Note that if you want to reduce just part of the data in a raw data file you must include the row numbers of the appropriate embedded specifiers in the sample numbers that you request Otherwise PBDAT will never access the embedded specifiers to be able to do what you want So if the embedded specifiers of interest occur in say row 13 of the raw data spreadsheet followed by the actual data in rows 14 through 20 you would have to include the sample number for row 13 for the embedded specifiers to work see example below You ll be able to tell which sample number to use from the printout or display when you access the raw data file from PBDAT Accessing Raw Data Files To load a raw data file into memory select Load Raw Data File from the Files menu The screen will display all files in the current disk and directory the default path for raw data files is shown in PBDATs CONFIGURE screen as well as any other paths
12. is not at all uncommon for Pb blanks to vary by 5096 or more especially if the procedure or reagents vary over time The only time a small value such as 10 is justified is when that value is the 26 variation of many say 5 or more blanks on an unchanging procedure The same com ments hold for the isotope ratios of the blank For blanks which are typically very small and difficult to measure such as for U and Th the uncertainty can be even larger a factor of 2 or more Using fractionation uncertainties derived from replicate runs of standards and applying these uncertainties to samples Fractionation uncertainties derived from pure standards which have not seen any chemistry generally constrain only the minimum fractionation range as such runs are commonly done in a more reproducible manner than actual samples For example the samples have seen a chemical purification which to the extent that it is not perfect can affect the running behavior of the filament load the samples may vary widely in size whereas the standard runs are generally for a relatively constant amount thus the standard runs may have been taken at a much more restricted range of filament temperatures than the samples Assigning a concentration uncertainty to the spikes that reflects the absolute uncertainty in concentration rather than the random sample to sample error To repeat what l ve said earlier in this documentation If most of your data reduction is f
13. ratios must be entered at the 26 level and in absolute values not percent values 10 Note tnterronzero errors for the imitiat P b ratios onty if you have reason to believe that the actual initial Pb isotopic composition was different from sampleto sample or if the sample is not part of a suite If you re reducing data for several cogenetic samples and you intend to pool the data for a concordia diagram treatment enter zero errors even though there is some uncertainty in your estimates of the initial Pb ratios you ll have to estimate the effect of the initial Pb uncertainty by reducing the data set with different initial ratios and performing a Y orkfit and concordia intercept calculation for each set of reduced ratios If you do enter nonzero errors for the initial Pb ratios you ll need to enter an estimate of the correlation between the 206 204 and 207 204 errors This value should always be nonzero typically in the range of 0 8 to 0 95 This error correlation value is the same as the conventional correlation coefficient that you d get if you do a linear regression of the 207 204 versus 206 204 for several samples that represent the true range of initial Pb ratios for the system from which your samples were derived If none of this makes much sense but you still need to enter nonzero errors an error correlation of 0 9 is probably not too far off You can have PBDAT use the Stacey Kramers growth curve values Stacey and Kramers 1975 fo
14. the Utilities menu Enter the 95Pp pp and Pb Pp ratios of interest PBDAT will calculate the model age and y for the specified ratios R atio of U P b normalized for U decay to the present day 25 REFERENCES Ludwig K R 1980 Calculation of uncertainties of U Pb isotope data Earth Planetary Science Letters v 46 p 212 220 ierpeeedeRES 1985a User s guide to ANALYST a computer program for control of an Isomass 54E thermal ionization single collector mass spectrometer U S Geological Survey Open File Report 85 142 72 E 1985b PBDAT200 a computer program for processing raw Pb U Th isotope data U S Geo logical Survey Open File Report 85 547 90 p TM 1991 ISOPLOT for MS DOS A Plotting and Regression Program for Radiogenic Isotope data revision of U S G S Open File Report 88 557 39 p Stacey J S and Kramers J D 1975 Approximation of terrestrial lead isotope evolution by a two stage model Earth Planetary Science Letters v 26 p 207 221 Steiger R H and Jager E 1977 Subcommission on Geochronology Convention on the use of decay constants in geo and cosmo chronology Earth Planet Sci Letters v 36 p 359 362 Tatsumoto M Hedge C E Doe B R and Unruh D M 1972 U Th Pb and Rb Sr measurements on some Apollo 14 lunar samples Proc Third Lunar Science Conf v 2 p 1531 1555 Tera F and Wasserburg G J 1972 U Th Pb systematics in three Apollo 14 basalts and the pr
15. unspiked aliquot nor will blanks In these cases enter Zero Pb Spiked Aliquot grams The weight of the solution spiked with SPb or 99Pp U Th Spiked in Total 1 or Pb spiked 2 Aliquot If the sample were total spiked spiked before attack or before any aliquoting for U Th enter a value of 1 If the U Th spike were added to the same aliquot as the Pb 208 spike though enter a value of 2 Incidentally PBDAT always assumes that if a Th spike were used it was either mixed with the U spike or added to the same aliquot as the U spike Pb Spike U Spike Th Spike Delivered grams The amount of the Pb U or Th spikes delivered in grams If the Th spike is part of a mixed U Th spike then the U and Th spike weights must be the same The Pb Unspiked Ratios Form 7 Pb Spiked Samples After you submit the completed WEIGHTS FORM the next FORM will be Pb Unspiked Aliquot Ratios errors must be 2 sigma in percent 206 204 ei 222 SOGLOL Ae d let ADU S2 TER GET Ol a een ee ZO C2082 e o o SOPLO ki err Pb bilankgenamnogralms se Enter values for the three ratios raw values from the mass spectrometer run NOT corrected for mass fractionation together with their errors The errors should be at the 26 or 95 confidence limit level in percent and should correspond to the statistical errors from the mass spectrometer run without including the uncertainty due to mass fractionation If you
16. 2 230 001292 Average mass discrimination during mass spectrometer runs in amu Po 11 05 Us 25 4 15 Ths 125 93 Average Blanks Uncertainty in assigned amount Pb 60 U 100 Th 100 Pb blank ratios and uncertainties 206 204 18 97 1 207 204 15 73 2 208 204 39 18 1 5 Error Correlations 206 204 207 204 8 206 204 208 204 7 33
17. 5 204 238 Ratios 25801 3 4719 3 436E 05 Errors 472 475 2 12 Rho 68 75 9933962 Rho 68 48 2224 Rho 75 48 2395 Radiogenic Pb 206 207 208 Moles per Gram 1 9648E 07 1 8814E 08 1 2824E 08 Initial Pb 206 2047 15 959 5 207 2045 15 358 05 208 2042 35 596 1 Rho 6 4 7 4 7 206 238 207 235 207 206 208 232 RATIOS 257459 3 39914 0957547 094437 ERRORS 472 476 0614 687 AGES Ma 1476 8 1504 2 1543 1824 Rho 207 235 206 238 9916304 207 206 Age Error 1 2 m y 29 Column c 7 romnmmoo gt HOMODOVOZEACFR gt N lt XS lt C Table 2A Index to LOTUS Column Positions of Raw Data Datafile Parameters For Pb or Pb spiked samples Parameter sample weight in grams actually dissolved weight of solution of dissolved sample before aliquoting weight of Pb unspiked liquid aliquot of dissolved sample weight of Pb spiked liquid aliquot i grams Pb spike delivered to F grams uranium spike delivered either to C D or F thorium NT IR unspiked aliquot 9Pb Pb OR spiked aliquot Pb Pb if the unspiked 99 Pb Pb is unknown and assigned a value of zero uncertainty in J not including mass discrimination error unspiked aliquot 9 9Pb 2 7Pb 96 uncertainty in L not including mass discrimination error unspiked aliquot 9Pb 2 Pp uncertainty in N not including mass discrimination error Pb spiked aliquot 9Pb Pp uncertainty in P n
18. HELP Selecting HELP will give you additional information about the functions in that menu General HELP about the use of the menus and starting PBDAT for the first time is available from the top level menu by pressing either F1 or ALT H The first time that you run PBDAT it s a good idea to browse through the pull down menus and their HELP screens When you first run PBDAT you ll need to specify what kind of screen you re using before anything else Invoke the Output screen with ALT O and select either a Color Monochrome or Compaq screen The Compaq screen option is for monitors that try to emulate a color monitor with different shades of gray or green amber orange Next specify the format for your reduced data output and the default location of LabData and raw data files by selecting the Output Format amp File Location function from the Output menu The screen should look like this CTRL ENTER Finished F9 Recall One Fl Help Reduced Data Format and File Location Concordia Data Radiogenic Pb 2D 1 or Total Pb 3D 2 Reduced data format for total Pb ratios 206 204 207 204 208 204 CEY or 204 206 207 206 208 206 2 Reduced data format for concordia plot ratios 206Pb 238U 207Pb 235U 1 207Pb 206Pb 238U 206Pb 2 or 206Pb 207Pb 235U 207Pb 3 It diskNpath for DLabData files C NPBDAT lt disk path for Raw Data files C LOTUS Reduced data file delimited by Spaces 1 or Tabs 2
19. PBDAT A Computer Program for Processing Pb U Th Isotope Data V ersion 1 24 K R Ludwig UNITED STATES GEOLOGICAL SURVEY OPEN FILE REPORT 88 542 Revision of June 22 1993 This report is preliminary and has not been reviewed for conformity with U S Geological Survey editorial standards and nomen clature Any use of trade names is for descriptive purposes only and does not imply endorsement by the U S Geological Survey Although this program has been extensively tested the U S Geological Survey cannot guarantee that it will give accurate results for all applications nor that it will work on all computer systems Berkeley G eochronology C enter 2455 R idge R oad Berkeley C A 94709 FA X 510 644 9201 E mail kludwig bgc org TABLE OF CONTENTS INTRODUGTION 3 attire de vere Std Ete ae SET QU a etg e ater ei NEA eu ai fte 1 HARDWARE REQUIRED 1512 wp er ee bl ead e EVIL cet gees ele eee aty SEE ans 2 GETTING STARTED zt Rho ethene ere lace reds RU REUS teed Aone Wied dase rea 3 USING PBDAT S PULL DOWN MENUS ssssssss es 3 ENTERING DATA FROM THE KEYBOARD sssssssss e 5 Using PBDAT s FORM Screens 0 00 c cece her 6 The Weights Form for 8Pb Spiked Samples 000 00 cece cece esee 7 Sample Weight rererere tarie til i ealte Bete ei ev ix Ee xn Be WE 7 Total Aliquot Weight eni eresien abe nse again eid Abe eke dena ad ere 7 Pb Unspiked Aliquot grams 0 000 cec
20. Pb Spiked Aliquot Ratios FORM will depend on what type of blank determination you re doing For a total blank enter a blank value of zero you want to know the total contamination For a reagent blank though you should enter the estimated blank for loading plus whatever handling evaporation weighing accompanied the blank procedure It s worth noting that for blanks of very pure reagents for example water the evaporation blank can easily exceed the reagent blank itself Entering Data for Spike Concentration Calibrations Isotope Ratios of Spike Known To calibrate the concentrations of a spike you ll need to have 1 a standard solution or solid with known isotope ratios and concentrations 2 an isotopic analysis of a well mixed mixture of the standard and the spike and 3 an estimate of the true blank corrected ratios of the spike Enter the data into PBDAT in the following way 14 Sample weight Weight of the standard solution or solid Total aliquot weight Zero Pb Unspiked Aliquot weight Zero Pb Spiked Aliquot weight 1 U Th spiked in total 1 or Pb spiked 2 aliquot 1 Pb U or Th Spike grams Weight of the spike delivered delivered to the mixture Blank amounts The nanograms of Pb U or Th contamination that you assign to the mixing loading running and if a solid standard dissolution pro cedure But enter zero for the Pb unspiked aliquot blank Pb isotope ratios For the unspiked aliquot e
21. SAU SA OO a 0 15421 TESI TOLLS 465211 18 943 The top line of the screen shows the title of the raw data file that you put in the top row of the raw data spreadsheet Note the embedded specifiers Reducing Data from a Raw Data File Once a raw data file is in memory PBDAT will display the screen below you can reduce it either by selecting From Datafile from the Input menu or by simply pressing CTRL 4 PBDAT will then ask you to F2 All Sets ER SAMPLE Fl Help 8 3111231 11333 4J KD td 32 2 191 2 8 5 9 ea e Pot ye yes Separate the sample numbers of a continuous sequence with a comma and separate different sequenc S of individual samples with a semicolon example 1 5 12 15 21 Be sure to include rows with embedded specifiers 20 Separate the sample numbers of a continuous sequence with a comma and separate different sequences or individual samples with a semicolon example 1 5 12 15 21 Be sure to include rows with embedded specifiers The output of the reduced data depends on the selections from the Output menu If Pause Screen for Viewing is selected the screen output will pause with each full screen until a key is pressed if Off the screen will scroll continuously as the results are calculated lf 43 line Screen is selected requires an EGA or VGA monitor the screen will contain 43 lines when full instead of 25 lines If
22. accessible from the current path Select a file or a path by moving the file cursor with the cursor control keys or with the key for the first letter of the file or path name for example press H to jump to the first file starting with the letter H press H again to jump to the second file starting with H and so on Path names are indicated with a backslash at the end and the parent directory which is always present is shown by the usual DOS label of Change the disk or path to search with the F2 key if the file or path that you want isn t shown The default file extension for raw data files is RAW RED or TXT for reduced data files Only files with this extension will appear in the directory screen You can change the extension that raw data files Stacey and K ramers 1975 19 must have with the F8 key Change Extension but note that except for a specified extension of all files shown the DOS wildcard characters and will not function Once you ve selected a file the screen will show the file s title and sample names as they are accessed from the disk as well as a few of the isotope ratios for the samples A typical display might look like this East Dakota Zircons 1440 Ma initial NAME Wt g 206 204 206 207 206 208 1 L C PB OLDLAB 2 5 DC DU See Si SENETA 16 162 4 84 TL 1043 200 05432 LOM 2 2 5st BAT O43 rP003 T 50s 2097526 734 24 6 84 TL K feldspar 1043 16129 JA EPIS 8887 ARMS5
23. ar in its place as you type itin Press when you ve finished typing in the sample name and the cursor will move down to the next parameter with the sample name remaining where you typed it To move the response cursor to any par ameter press the up arrow or down arrow keys To enter a value for a parameter move the cursor to the appropriate parameter and type in the value You can edit as you type with the usual cursor control keys When you re satisfied with your response press and the value will be entered for that parameter If you ve made an obvious error PBDAT will display an error message and ask you to re enter the value Note that even if you type something into one of the response areas unless you press it will disappear when you move the cursor to another parameter When you ve entered values for all the required parameters a double question mark in a response area indicates that a response for that parameter is required other parameters may be optional submit the form by pressing CTRL 4 Until you do this none of the values that you entered will be used If you want to escape from the FORM at any time press Esc Pressing Esc causes the program to ignore all of the values in the FORM that you might have just entered If you don t understand the significance of a parameter in the FORM put the cursor on that parameter and either press F1 or click on F1 Help with the mouse A HELP screen will appear to give you more
24. ate these files with LOTUS 1 2 3 EXCEL most other spreadsheet programs or with any word processing program that can create ASCII files PBDAT can read two types of text files space delimited and tab delimited U sethe PF command PRIN T FILE which will create a space delimited PRN file 16 Space Delimited Raw Data Files Space delimited files can be created by LOTUS 1 2 3 and by most word processing programs The numeric data columns must all be 9 characters wide and the sample names must be in the left most column 18 characters wide or 2 columns each 9 characters wide Store the raw data as an ASCII file with a left margin of 0 and a right margin large enough to include all of the relevant columns of columns times 9 You can use the Lotus TEMPLATE file on the PBDAT program disk as a guide This file will give you the correct format and column headings for your raw data files the different rows of the TEMPLATE file are for different ways of spiking excise the appropriate one If you store the raw data file from LOTUS using the PRINT FILE or ASCII FILE option make sure that the range you specify includes all of the required parts of the spreadsheet Include all 9 characters of the right most column The numeric data in the file must be separated from any titles or column headers by a line of repeating equals signs whose length is equal to the number of raw data columns times 9 Tab Delimited Raw Data Files Tab deli
25. d format column names directly above first row of raw data columns separated by tab characters A tab delimited format is probably the most generally useful SOPLOT can read either When you re finished enter the values with CTRL 4 and return to the Top Level screen ENTERING DATA FROM THE KEYBOARD First specify a LabData file for the program to use Load New from the LabData menu The screen will display a list of the LabData files present on the default drive path The first time you run the program just pick any of the example files shown More information on LabData files is given in a later section Using PBDAT s FORM Screens Start raw data entry by selecting From Keyboard from the Input menu or by simply pressing 1 The screen will then show CTRL ENTER Finished F9 Recall One F10 Recall All Fl1 Help E SPIKE amp ALIQUOT WEIGHTS Sample Name Sample Weight gram acces el Total Aliquot Weight gram enter only if appropriat Pb Unspiked Aliquot gram Pb Spiked Aliquot gram U Th Spiked in Total or Pb Spiked Aliquot gram Pb Spike delivered gram U Spike delivered gram Th Spike delivered gram call this a FORM screen When it appears the response to the Sample Name query will be highlighted indicating where the response cursor is Type in a name for the sample whose data you re en tering The double question marks will disappear and your sample name will appe
26. e is for raw UU and 9 U U ratios When you specify a U 233 236 spike PBDAT will ask you which type of input to expect lor Sample 238 S pike 236 if U 236 is the most abundant spike isotope T his applies to all references to Sample 238 S pike 236 in this documentation e For the first type of data input the FORM screen will look like this U Spiked Aliquot errors must be 2 sigma in percent Sample 238 Spike 233 Serror 232 230 Serror lank nanograms lank nanograms Enter the calculated ratio of the moles of U in the U spiked aliquot of the sample to the moles of U that you added from the spike The rest of the FORM is the same as for U spiked samples The second type of 233 236 238 FORM Sample 238 Spike 233 not calculated will look like this U Spiked Aliquot errors must be 2 sigma in percent 233 236 Serror 233 238 Serror 232 230 SEU SUE lank nanograms lank nanograms Just enter the raw uncorrected for fractionation ratios and errors as usual 4f you re using a PU spike without U you can still usethis FO RM by 1 defining the 233236 ratio in your LabD ata file 12 Samples Spiked with a Mixed Pb U Th Spike For samples that were total spiked with a mixed Pb U Th spike the U can be either 235 or 233 236 the first FORM will be Pb 205 Spiked Sample Sample Name Sample Weight grams Pb 205 Spike delivered grams This FORM ass
27. e ett 7 Pb Spiked Aliquot grams liliis III 7 U Th Spiked in Total 1 or Pb spiked 2 Aliquot lille 7 Pb Spike U Spike Th Spike Delivered grams llle 8 The Pb Unspiked Ratios Form Pb Spiked Samples 0 0c eee eens 8 The Spiked Aliquot Form Pb Spiked Samples sisse 8 The Initial Pb Isotope Ratios Form ssslessee n 9 Samples Spiked with a Mixed U 79 U 8 Th Spike 2 0 0 cece cee eee eee 10 Samples Spiked with a Mixed Pb U Th Spike 000s cece cece cece eee eee 12 Entering Data for Blank Determinations 0 0 ccc eect es 13 Entering Data for Spike Concentration Calibrations 20 0 ccc eee 14 Isotope Ratios of Spike Known 0 0 0 cece teens 14 Isotope Ratios of Spike Unknown 0 00 eee eens 15 CREATING AND USING RAW DATA FILES sssssssssls eens 16 Space Delimited Raw Data Files 0 0 ccc teen eees 16 Tab Delimited Raw Data Files 20 0 0 c ccc teens 16 Both Types of Raw Data Files 0 0 00 cece tenes 16 Using Embedded Specifiers within the Raw Data File 2 0 000 a eee eee 17 Accessing Raw Data Files 0 00 c cece tenes 19 Reducing Data from a Raw Data File 6 0 0 eens 19 CREATING AND USING REDUCED DATA FILES 000 000 cece cece teens 20 SING EabData ElbES d tt er Wed RO were TA aed Gan E Rer RR ar eio T AER e
28. ed for mass discrimination bias and the uncertainties of the concentrations If most of your data reduction is for suites of samples where the relative concentration un certainty is of more relevance than the absolute uncertainty you should assign concentration uncertainties of zero unless you have significant random errors such as weighing errors in your spike delivery After you ve defined the spikes for the new LabData file PBDAT will display FORMs for blanks and for mass discrimination The BLANKS FORM will require you to enter typical uncertainties in percent of the amount for any assigned Pb U and Th blanks as well as the Pb isotope ratios of the Pb blank the uncertainty absolute this time not percent in these ratios and the correlations of the ratio uncertainties Realistic uncertainties in the blank amounts are typically very high 30 to 100 for Pb and 100 or more for very low U and Th blanks Also the correlation between the uncertainties of the Pb blank 206 204 and 207 204 ratios is generally rather high 0 7 9 as common leads from random ore deposits whence comes ultimately most of your Pb blank in general will have highly correlated 206 204 and 207 204 ratios This is true also for the 206 204 208 204 uncertainty correlation but to a lesser degree due to the effect of variable Th U ratios for the sources of base metal ore deposits The mass discrimination FORM requires estimates of typical mass discriminat
29. eys to the category of interest and pressing either or the up down arrow keys 3 When you ve invoked a pull down menu you can select an item without using the mouse by either pressing the key corresponding to the emphasized letter in the item name or by moving the cursor bar with the up down arrows and pressing Some of the functions in some of the menus are shown in gray characters These items are inactive and cannot be selected If the reason for the status of such an inactive function changes for example you cannot reduce data from a datafile until that datafile is loaded into memory it will become active Other functions are either On or Off for example whether or not the printer is selected for output or what type of screen is selected An On Off function that is On will be shown with a check mark to the left of the function name Turning an item On will cause any incompatible items to be turned Off auto matically For example if you select a Pb 205 spike from the Spikes menu the Pb 208 spike option will automatically be turned Off Some of the functions in the pull down menus can also be invoked with shortcut keys which will immediately invoke the function without having to invoke a pull down menu If such a shortcut key exists for a function it will be shown to the right of the function name in the menu for example F2 to specify printer output One of the functions in all of the pull down menus is
30. gram will assume one of these depending on 1 whether the sample were spiked with a Pb 205 mixed spike in which case the LabData file will specify a 235 or 233 236 U spike 2 whether you specified a U 235 or U 233 236 spike from the Top Level CRT display 8 which data input format for U 233 U 236 spiked samples you are using and 4 if you have embedded specifiers see below within the sample name columns of the raw data spreadsheet 17 If your data is for U U spiked samples with raw 233 236 and 233 238 ratios the 233 236 ratios and errors must occupy the last two columns of the spreadsheet AB and AC for 208 spiked samples T and U for Pb 205 spiked samples Using Embedded Specifiers within the Raw Data File The raw data spreadsheet can contain all of the necessary information to tell the program how the data is to be reduced including which LabData file to use whether spiked with Pb 208 or Pb 205 U 235 or U 233 236 whether the U Th was spiked in the total aliquot or the Pb spiked aliquot and what initial Pb ratios to use These specifiers can change from sample to sample so that a large raw data spreadsheet can contain data reduced at various times or by various laboratories with different spikes and procedures yet the whole file can be reduced in a single request that creates a single reduced data file Embedded specifiers consist of a few characters enclosed in asterisks and must occur within the sample name column
31. ified in the raw data file itself The data will then be reduced CREATING AND USING REDUCED DATA FILES After all the samples in the raw data file have been reduced unless you ve only reduced data for one or two samples the screen will ask you to specify a name for a reduced data file The screen will show you the default path and extension RED If you want a different disk path or extension enter the desired disk path filename You can specify a tab or space delimited file format with the F2 key PBDAT will now ask you for the format of the reduced data file Zircon Whole Rock or Complete If you store all of the reduced data ratios and errors that PBDAT calculates Complete format see Table 3 you won t be able to access the file from most word processing programs or directly from LOTUS because it will be too wide ISOPLOT won t have any problems with the file though If you want to store just a subset of the calculated data in order to maintain compatibility with another program or just to keep the file compact specify either Zircon or Whole Rock format 21 The Zircon format will contain all of the parameters listed in Table 3 except Pb pp Pb Pb pp 206pp 295pp 2 Pb ratios amp errors the thorium concentration error and the U Pb U Pb Th Pb ratios or errors The Whole Rock format will contain all of the parameters listed in Table 3 except any of the radiogenic isotope ra
32. ination error M observed U U ratio U spike isotope is 235 OR Sample238 Spike233 ratio or Sample238 Spike236 if 236 is the most abundant spike isotope U spike isotopes are 233 236 and SAM SPK is known OR observed 233 238 ratio U spike isotopes are 233 236 but SAM SPK is not known N 96 uncertainty in M O observed Th Th P 96 uncertainty in O not including mass discrimination error Q Pb blank for Pb run in nanograms R U blank for U run in nanograms S Th blank for Th run in nanograms T 283U U of U spiked aliquot only if U spike isotopes are 233 236 and SAM SPK ratio is not known U 96 uncertainty in T if relevant V AB not used for Pb spiked samples 31 Table 3 Column Headings of Reduced Data Files Complete Format Column Heading OONDOAARWDNM Sample weight grams ppm U ppm Th ppm Pb ppm common Pb Nanomoles 7 Pb per gram Raw Pp Pb of either Pb unspiked or Pb spiked aliquot Blank amp mass discr corrected sample Pp Pp or 9 pp ep 207Dp 20 pp or 207pp 206ppy 2085p 20 Dp or 208pp 206pp Radiogenic Pb 8U or 8U Pb or 39LJ pp Radiogenic Pb U Radiogenic Pb Pb or Pb Pb Radiogenic Pb Th 206Pb 8U age Ma or 5U Pb age 207p p 235L J o pp 26pp Qor29pp Pb age 208b p 232TH wow F 738U Pb 6 75UP Pb 232T h 2 4Pb uncertainty in U concentration Th 204DB 206Ph
33. ion arising during measurement in the mass spectrometer for your Pb U and Th runs in percent per mass unit You ll also need to assign uncertainties in your estimates in absolute values So if your typical mass discrimination for Pb runs is 0 11 per mass unit with a possible range 26 of from 0 06 to 0 16 you would enter the uncertainty as 0 05 Other LabData File Operations Positive values indicate enrichment of the lighter isotopes during analysis 23 You can use the Edit option in the LabData menu to edit the values for the spikes mass discriminations or blanks of the LabData file in memory f you want to store your changes on a disk remember to select the Store option from the LabData menu before you exit PBDAT or load another LabData file into memory Use the Re Name option to either rename a LabData file in memory or to store a modified version under a different name Use the Load New option of the LabData menu to switch from one LabData file to another You can inspect or print out the values for the LabData file in memory with the Display and Print options COMMON ERRORS IN USING PBDAT There are several common mistakes that users make in using PBDAT usually because of a misunderstanding about exactly what sort of errors should be entered for the various parameters Some of the more common errors are 1 2 3 Using over optimistic uncertainties for the blank amounts and Blank Pb isotope ratios It
34. laboratories using a variety of spikes including SPb Pb Pb U 2330 380 ang Th These spikes can be delivered either to a liquid aliquot or to the total sample for any combination of Pb and U Th Keyboard data input is managed by a friendly and error resistant screen which makes extensive use of HELP screens and error trapping PBDAT derived from the PBDAT200 program for Hewlett Packard computers Ludwig 1985b is written in QUICK BASIC 4 0 using routines from the PROBAS 3 0 library If you would like a copy of the current version of this program write to me directly and enclose a formatted 312 disk either 720 Kb or 1 44 Mb or a formatted high density 1 2 Mb 514 disk The source code as a text file on another similarly formatted disk is also available on request The decay constants used by PBDAT are those recommended by the I U G S Subcommission on Geochronology Steiger and Jager 1977 155125 x 10 yr for U 98485 x 10 yr for U 049475 x 10 yr for Th and present day UZU 137 88 HARDWARE REQUIRED PBDAT requires an IBM PC compatible computer with at least 384 kbytes of memory running under DOS 2 0 or later A Microsoft compatible mouse is desirable and will be used if installed The program assumes that the printer is connected to the parallel port LPT1 of the computer Use of data files as input instead of typed in values requires a program that can create either space delimited or tab delimited
35. mited files are the text files created by some spreadsheet programs such as EXCEL and by most Macintosh programs Put the sample names in the left most column only the first 18 characters will be used by PBDAT PBDAT will take as the first row of raw data the first row in the file that contains either an asterisk in the sample name column indicating the presence of an embedded specifier or any other characters in the sample name column PLUS a numeric value in the first numeric raw data column the sample weight column Both Types of Raw Data Files The file must be arranged in rows and columns like a spreadsheet with different samples occupying different rows The top row of the raw data spreadsheet can be used for a title of up to 80 characters and will appear on the screen when you access the file from PBDAT You can look at the contents of the currently selected file by pressing the FILE PREVIEW F3 from the Load File screen When the file appears on the screen use the cursor keys to move the screen window to any part of the file If you don t have any data for one of the columns or if that column is irrelevant for example thorium data when you didn t spike the sample for thorium don t enter anything in that column Enter all errors un certainties at the 26 level and in percent Note that the columns for uranium isotope ratios can contain either the 238 235 ratio the Sample 238 Spike 233 ratio or the 233 238 ratio The pro
36. n 22 Defining a New Labdata File 0 cect en 22 Other LabData File Operations 1 0 0 0 0 0 tenet eens 23 COMMON ERRORS IN USING PBDAT sssssssse e 23 UTILITY FUNCTION FOR CALCULATING RADIOGENIC Pp 9Pb AGES LLuuusue 24 UTILITY FUNCTION FOR CALCULATION OF STACEY KRAMERS MODEL AGES 24 REFEBENGES dee armed uel o mart hits Wares oen Ut a e De ath eade a ane ate 25 INTRODUCTION PBDAT takes raw Pb U Th isotope data either typed in from the keyboard or from LOTUS 1 2 3 or other ASCII files including all relevant data from the chemistry laboratory and calculates elemental and isotopic concentrations isotope ratios apparent ages uncertainties and error correlations in these values using the algorithms developed in Ludwig 1980 The resulting data Table 1 is corrected for instrumental mass fractionation laboratory blanks and the initial Pb of radiogenic samples Data defining the particular spikes and blanks of a particular laboratory are entered by each user and stored as user specific data files on the same disk or directory as PBDAT itself Because of this feature several different laboratories can use the same program without program modification Raw data that has been stored as an ASCII file can be converted by the program as a batch either in whole or in part to a reduced data file which is compatible with the ISOPLOT plotting program Ludwig 1991 PBDAT can accept data from
37. ncentration more accurately by mathemat ically compensating for the effect of a varying Pb blank in the spiked aliquot If you didn t enter any Pb unspiked aliquot ratios the FORM will also ask for the estimated Pb blank Enter the Pb blank that corresponds to the Pb spiked aliquot The blank assignments for the U and Th ratios should reflect only the blank for the U Th spiked aliquot You can enter zero if you re sure that the blank is negligible The Initial Pb Isotope Ratios Form If the Pb in the sample is radiogenic and you want to calculate Pb U Th isotope apparent ages you must enter estimated values for the initial Pb isotope ratios in this FORM If the Pb in your sample is nonradiogenic common or if you re not interested in apparent ages just escape from this FORM The initial Pb is defined as the Pb which was present at the time the U Pb system of interest was born Fora mineral or rock this will generally be the Pb present at the time of formation of the mineral or rock The FORM for the Initial Pb ratios is Initial Pb Isotope Ratios errors must be 2 sigma ABSOLUTE 206 206 95 7 4118150 CLEOPR aona 0 20952027 Revie eo ETTOL eon O 2087 204 m 53 8 613 ENCO So 20 206 204 207 204 error correlation 0 9 F2 Use a Stacey Kramers Model Pb for a given age The default values are those for a system with zero age on the Stacey Kramers Pb growth curve Stacey and Kramers 1975 The errors for the
38. ng handling blank the other as a mix with your 15 usual standard Now define a LabData file whose Pb 208 spike is the standard used in the mixed analysis This standard could be a calibrated common Pb solution a pure Pb 206 solution or a solid standard Reduce the data using the LabData file as defined above as follows Sample weight Sum of the weights of a the new spike used for the first pure spike analysis and b for the second mixed analysis Total aliquot weight ignore Pb Unspiked Aliquot weight Weight of the new spike used in the first pure analysis Pb Spiked Aliquot weight Weight of the new spike used in the second mixed analysis U Th spiked in total 1 or Pb spiked 2 aliquot 2 Pb U or Th Spike grams delivered Weight of the standard delivered to the second mixed analysis Blank amounts Nanograms of Pb blank that pertains to the delivery evaporation and loading of the new spike for the first pure spike analysis Pb isotope ratios For the unspiked aliquot enter the ratios from the first pure spike analysis For the spiked aliquot enter the ratios from the second mixed analysis CREATING AND USING RAW DATA FILES The best method for reducing data for more than one or two samples at a time is to put the raw data in a text file so that you can edit the raw data at any time or re reduce some of the data with new LabData file values without having to re enter a lot of data You can cre
39. nter just the accepted or known 206 208 ratio for the standard For the spiked aliquot enter the observed ratios of the mixture Unless you have a combined Pb U Th standard you can only reduce the data for one elemental spike at a time even though all three elements were combined in the mixing stage Examine the indicated concentration of the major spike isotope in the PBDAT printout This is the indicated concentration of that isotope in your standard using the presently defined concentration of your Spike The percent difference in the concentration that you just obtained for the standard is the amount that you need to adjust your spike concentration to make this adjustment change the spike concentration in the LabData file by the percent difference above but in the opposite direction In other words if the spike calibration run indicates that your standard is 196 too high compared to its accepted value then ower the spike concentration in the LabData file by 1 If the indicated standard concentration were 1 too ow then increase the spike concentration in the LabData file Isotope Ratios of Spike Unknown If you don t have any reliable data for the isotope ratios of a new Pb 208 or 206 or 207 or 204 spike though you can do the following procedure to get both the spike s concentration and blank corrected ratios Do 2 isotopic analyses of the new spike one as just the pure spike in a relatively large amount to swamp out any loadi
40. oblem of initial Pb in lunar rocks Earth Planetary Science Letters v 14 p 281 304 Wetherill G W 1956 Discordant uranium lead ages Trans American Geophys Union v 37 p 320 326 26 207 206 ratios radiogenic calculation of ages from x ocv seneLEt E RR RETE RES 24 3 dimensional concordia plots specifying ratios for TM 5 aliquot weights entering ssssss eese 7 ANAY SI ose an heh a e E D ee PL nu ASC II raw datafiles lesse 2 16 BASIC languageversions required s s 2 Blank amounts amp ratios over optimistic errors for oss on a Bagh AAAA Ege 23 blank Pb what it applies to ssssss 8 9 blank samples how to enter raw datafor B blanks Pb unspiked aliquot weight for 7 blanks uncertainties in for LA BD ATA files 22 calibration of spikes 20 kee eee ee 4 C C ON VERT file Lotus format 22 C ode source obtainingforPBDAT 2 C ompaq computers specifying display typefor 4 C omplete format reduced data files 005 21 concordia diagram data entering initial P b errors TOL iot rLUeP DUCI UU MEER Sate 10 C oncordia plot data specifiying concordia plot tyDe oce Li Reo xr FEMA CURE RERO 5 C onfiguration of PBD AT changing 4 C opies of PBD A T obtaining 2 correlation error for initial Pb isotoperatios 10 D ata files for raw data ccc cece eee eee 16 D ata files
41. or suites of samples where the relative concentration uncertainty is of more relevance than the absolute uncertainty you should assign concentration uncertainties of zero except for weighing errors in your spike delivery If you really want to know the effect of the true spike concentration uncertainty for an isochron or concordia intercept age you ll have to vary the spike concentrations 24 by what you think the true error might be re reduce the suite of data and re calculate the regres sion line for the suite 4 Assigning nonzero isotope ratio uncertainties for the initial Pb of a suite of samples that probably shared the same initial Pb This topic is discussed in a note under the discussion of the Initial Pb Isotope Ratios Form UTILITY FUNCTION FOR CALCULATING RADIOGENIC Pb Pb AGES You can use PBDAT as a quick tool for calculating radiogenic Pb 9Pb ages by selecting the Age From Rad 207 206 option from the Utilities menu Enter the radiogenic Pb 9Pb ratio together with the percent error in the ratio optional and the time that radiogenic Pb isotope growth ended also optional If the second optional value is not entered a value of zero is assumed yielding the usual radiogenic 207 206 age UTILITY FUNCTION FOR CALCULATION OF STACEY KRAMERS MODEL AGES To calculate Stacey Kramers Stacey and Kramers 1975 single stage Pb evolution ages and p values select the Stacey Kramers Model Age Mu option from
42. ot including mass discrimination error Pb spiked aliquot 5Pp Pp uncertainty in R not including mass discrimination error 38 J 2 LJ of U spiked aliquot if spiked with U OR Sample U Spike 9 U or 7 U if 236 is the spike s most abundant isotope of U spiked aliquot if spiked with U 233 236 and SAM SPK ratio is used OR 33 J 9 LJ of U spiked aliquot if spiked with U 233 236 and SAM SPK ratio is not used 96 uncertainty in T not including mass discrimination error Th Th of Th spiked aliquot 96 uncertainty in V not including mass discrimination error Pb blank of Pb unspiked aliquot in nanograms U blank of U spiked aliquot in nanograms Th blank of Th spiked aliquot in nanograms 33 J 60J of U spiked aliquot only if SAM SPK ratio not used uncertainty in UAU 30 Table 2B Index to LOTUS Column Positions of Raw Data Datafile Parameters For mixed Pb U Th spiked samples Column Parameter C sample weight in grams D weight g of mixed Pb 7 U Th or 205pp 2330 236 J 29 Th spike delivered E observed Pb Pb not including mass discrimination error F 96 uncertainty in E not including mass discrimination error G observed 9pp pp H 96 uncertainty in G not including mass discrimination error observed 9Pp 2 pp J 96 uncertainty in not including mass discrimination error K observed 9Pp pp L 96 uncertainty in K not including mass discrim
43. r any age by pressing F2 or clicking on F2 Stacey Kramers with the mouse then entering the Stacey Kramers age in Ma The Pb isotope ratios defined by the Stacey Kramers curve for that age will appear in the FORM after which you can either edit the values or accept them as given Note that much of the information that PBDAT can make use of is optional For example if you have only the spiked run data for a 208 spiked Pb aliquot enter zero for the weight of the Pb unspiked aliquot The program will then ask you for only the estimated 206 208 of the unspiked run and the uncertainty o that ratio In such cases though you ll need to know all of the Pb ratios including 206 204 for the spiked aliquot You needn t enter any U or Th data nor an estimate for the initial Pb isotope ratios When none of the parameters in a FORM are known or relevant just press Esc when the FORM appears Samples Spiked with a Mixed U 9U Th Spike For samples spiked with a mixed 9U LJ spike instead of a U spike PBDAT accepts two different types of data input The first type is for data that is already partially reduced so that the Sample 238 Spike 233 SAM SPK ratio has already been calculated This should be the case for data from a mass spectrometer running under ANALYST Ludwig 1985a The Sample 238 Spike 233 ratio is simply the ratio of moles of natural U in the U spiked aliquot to the moles of U delivered as the spike The second typ
44. reducing data from ee eee aee 20 data raw entering from keyboard 6 decay constants used cece cece eee ee eee 2 display type specifying ccc cece eee eee eee 4 DOS version required 0 cc cece eee eee 2 editingLABDATA files 0 cece eee eee 23 Embedded specifiers in Raw D ata files 17 embedded specifiers in raw data files list of y embedded specifiers example of sss 19 embedded specifiers USING 6 cc eee ee eee 20 equipment required ccc cece eee 2 error correlation for initial Pb isotope ratios 10 errors in using PBD AT typical 005 23 errors of input data level Of cc cee eee ee eee 8 errors for initial Pb isotope ratios significanceof 10 errors level of in raw data files 00 y EXGEL ana A ce epe tom Rte gU a age DERE to 16 extension assumed for names of raw data files CHANGING sere ep Nerd 19 extensions required for raw data filenames 19 file preview function naaa 17 FORM screens introduction to o a aa 6 format of reduced data output specifying 4 fractionation errors over optimistic errors for 23 hardware required 6 cece cee eee eee eee eens 2 INDEX 27 H ELP files 2 m uth cok ages Sots Att Aas 3 H ELP softkey for FO RM S ce eee eens 7 history of program asss 2 H P Series 200 300 computers n a sasaaa 2 initial PD Erha
45. rowth curve cece eee eee 10 Stacey K ramers Pb invoking asinitials 18 Stacey K ramers P b evolution model ages obtain Ino eiae cere Prise debates i de Pre rh 24 Steiger and Jager 977 0 cee cece eee ees 2 storing LA BD ATA files on a disk isse 23 storing reduced data files on adisk sius 21 tab delimited raw data files 0000 16 tab delimited reduced data files specifying 5 tab delimited reduced datafile format specifying 21 T atsumoto style concordia plot sssssssse 5 TEMPLATE file x tne erret nep E ERU 16 28 T era W asserburg concordia plot suus 5 T h 230 spiked samples U T h spiked aliquot for 7 Th SPIKE DELIVERED significanceof 8 top level screen 66 eee ees 3 TOTALALIQUOT WEIGHT significance of 7 total spike samples P b unspiked aliquot weight for total spiked samples U T h spiked aliquot for U SPIKE DELIVERED significanceof 8 U Th SPIKED ALIQU OT significance of 7 unspiked aliquot weight entering 0 7 WEIGHTS form for Pb 208 spiked samples 7 Wetherill concordia plot 5 W hole rock format for reduced datafile 21 W hole R ock format reduced data files 21 Z ircon format for reduced data files 21 Z ircon format reduced data files isis 21 Table Example of R educed D ata O utput Sample NZD 45046
46. s The specifiers affect how data for samples below the specifiers are reduced The types of embedded specifiers that you can use are shown below SPECIFIER SIGNIFICANCE L The characters following the specifier indicate the name of the LabData file to be used for example L C PBDAT NEWLAB 205 Samples were spiked with a mixed 205Pb U Th spike the LabData file for the spike determines whether a U or U U spike is assumed 208 Samples were spiked with a 5Pb or SPb spike 235 Samples were spiked with a 7U spike 208 spiked samples only 233 Samples were spiked with a mixed 9U 9U spike 208 spiked samples only TU Samples were total spiked with U Th PU Samples were spiked for U Th in the Pb spiked aliquot if the full path and LabD ata file name are too long to fit in the 18 characters allotted for the sample name you ll have to typein just the name of the LabD ata file and either a enter the disk path for the LabD ata file at the time of data reduction when PBD AT asks you after failing to find the file on the default LabD ata path or b change the default LabD ata path to match the LabD ata file 18 SAMSPK Raw data for any 9U U spiked samples will be in the form of Sample 238 Spike 233 ratios rather than the raw 233 236 and 233 238 ratios 368 Raw data for any 9U 9LJ spiked samples will be in the form of raw 233 236 and 233 238 ratios INIT Use the values in this row as the
47. text files such as LOTUS 1 2 3 EXCEL or even a word processing program But not for uncertainties in the decay constants of U and Th nor the uncertainty in the U U ratio of terrestrial uranium T he decay constants and U isotope ratio used by PBD AT are those recommended in Steiger and J ager 1977 H ammerly C omputer Services Inc 9309 Jasmine C ourt Laurel M D 20707 294 GETTING STARTED First look at the READ ME file that comes with PBDAT for installation instructions and last minute information You can do this by typing in TYPE READ ME MORE and pressing 2 You ll need DOS present either in one of the disk drives if you re using a two floppy system or accessible from the hard disk via the PATH statement in your AUTOEXEC BAT file For a hard disk system copy the PBDAT disk onto a subdirectory for a two floppy system put the PBDAT disk in the other drive Change the default drive and path to be that of PBDAT so that the HELP files will be accessible For example if PBDAT were on the disk in drive A under subdirectory PROGS PB you would type A then CHDIR PROGS PB Type PBDAT to start the program After a few seconds the screen will display 8 3333333222222222222222222222222222222323211133333232222222222222222222222213 2 2 DJ is Files Input Output Spikes Utilities LabData Fl Help T BESSSSESSIASSATESSHSEESHHSHASHSSASASHAHSESAASHHHEHHGHASIAESSASHAHEE HA HE LE z
48. tios or errors and the common Pb concentration amp error When you ve specified the file format PBDAT will ask for a file title This title will occupy the first row of the reduced data file and will appear when you access the file from ISOPLOT PBDATs reduced data files are simple ASCII files which can be accessed with any program that can deal with text files including most word processing programs If you want to convert a Zircon or Whole Rock reduced data file from PBDAT into a LOTUS spreadsheet file though you can use the macro in the LOTUS file named PCONVERT WK1 on the PBDAT disk To use this macro retrieve PCONVERT from LOTUS and set the default directory to the path containing PBDAT s LOTUS files Press ALT G to start the macro Enter the path and name of the reduced data file When the macro pauses and prompts you for another file name enter a name for the LOTUS format file don t include an extension As soon as the macro has stored this LOTUS format file you are ready to press ALT G again to convert another reduced data file Converting a Complete format reduced data file to a LOTUS format file is more complex You ll need to split the source file into two parts with the SPLIT program which accompanies PBDAT SPLIT will ask you for the path that the source file resides on then the name of the source file After some disk accesses the program will then ask you for a root name for the output files Whatever name you
49. umes that the Pb spike was delivered to the total sample represented by the sample weight The next FORM for a Pb spiked sample is Pb Spiked Aliquot errors must be 2 sigma in percent POG YP 0 207 20072 error x 2 2016 52 09 etr IR oro S O15 01 nt P 2 0 67 2210 S Sor ob tu 206 205 Serror Pb Blank nanograms to be 1000 then 2 entering a value of 1 3F 100 for the 233236 ratio in the FO RM where F is the predicted mass fractionation for your uranium runs in percent per mass unit 13 The Pb blank is the blank that corresponds to the complete attack extraction if any and loading procedure The rest of the data input for Pb U Th spiked samples is the same as for PB Spiked samples Entering Data for Blank Determinations For Pb blanks you usually won t have any specific data for the Pb unspiked aliquot ratios and you might not have any data for the Pb spiked 206 204 ratio So for blanks enter the weight of the Pb unspiked aliquot as zero since there wasn t any unspiked aliquot PBDAT will still ask you for an estimated value for the unspiked 206 208 ratio however Enter your best guess for this value unless your blank is very underspiked your guess doesn t have to be too accurate You ll also need to enter an uncertainty in your estimate 5 isn t too large if you know only that the blank Pb is a normal common Pb 206 208 0 46 0 50 The Pb Blank value that you enter into the
50. us pull down how to use cc cece eee eee 3 M istakes in using PBD AT typical 23 mixed P b 205 U T h 230 spiked samples D mixed U 23JU 236 spiked samples sss 1 M odel ages Stacey K ramers calculation of 24 monitor type specifying cece eee eee eee 4 M ouse typerequired 0 0 cece cece eee 2 M ouse using with FORM screens 7 10 M ouse using with pull down menus 3 M u 238 204 calculating for Stacey K ramers curve MID piso de saath neice ete hch E a vente cen cL 24 M u definition Of cece eee eee 24 overview of program function ee cee 2 Pb blank what it applies to eee 8 9 Pb Pb ages calculation Of ccc cee eee eee 24 Pb SPIKE DELIVERED significanceof 8 Pb SPIKED ALIQU OT Significance of 7 Pb Spiked Ratios FORM cc cece eee eee eee 9 Pb UN SPIKED ALIQUOT WEIGHT signifi CANCE re EE 7 Pb U nspiked Ratios FORM for Pb 208 spiked Satnpleo cs noit erem aes gad fig 8 PBD AAL200 rA LER e ree Ret etae 2 PC ON VERT file LOTU S 123 00058 21 PitfallsinusingPBDAT c cece eee ee eee 23 printer port sea ect rere rete qoc doled Geely 2 printing out a LA BD ATA file 0005 23 program list for PBD AT obtaining sess 2 pull down menus how touS cc cece eee eee 3 radiogenic 207 206 ratios calculation of agefrom 24
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