Geological importance of Dykes(CO2)
Contents
1. DIR for display of model Signal field for point colour Depth_Bin_No PNT Signal field for point size Depth_Bin_No PNT Grid for overlay in display of model BH_TMI_ grid GRID Hard Copy Composition Output hard copy specification file for BH_TMI1 map n a presenting the Naudy model Solution hard copy specification file BH_TMI map provided for presenting the Naudy model WORMS 3D Dykes Solution of dykes sorted by 3D bh_dykes csv continuity strike solution quality Linear summary of each dyke Summary_bh_dy csv ke Tip It is optional to also usean Oasis database for the Line dataset 3 From the Project Manager Interpretation menu choose Auto Model This will launch the Naudy Automatic Model tool From the File menu select Load Line dataset Specify the Data type to be TMI Specify BrokenHill DIR as the input dataset BrokenHill1 if you are using UNIX Specify microlevelled as the input signal field 1 This is important INTREPID uses different parameters and filters for TMI and 1VD 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 9 Library Help Top Specify the output dataset Turn on Always Regenerate Model mode Library Help Top lt 4 Back gt INTREPID displays the first line of the survey in the Naudy Automatic Model window The upper panel shows a profile of the line with location along the horizontal2. Non default parameters Use Naudy derived dips ON Line spacing 550 m Calculate Trends from Line Note leave Finishing Depth at the default value of 10000 Visualisation Solution Naudy mode point dataset for display of model naudy_ns DIR Signal field for point colour Depth_Bin_No PNT Signal field for point size Depth_Bin_No PNT Grid for overlay in display of model tmi_ns GRID Hard Copy Composition Output hard copy specification file for presenting the naudy_oill map n a Naudy model Solution hard copy specification file provided for naudy_oil map presenting the Naudy model WORMS 3D Dykes CSV CSV Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 25 Library Help Top lt 4 Back gt When you export the model to a MAPCOMF file use the following parameters and labels Element Value Page size A4 Orientation Portrait Scale 100000 Optional backdrop image tmi_ns use Find Image to locate it Show the bodies as Dip Symbols On Rectangle Off Title North Sea Total Magnetic Intensity Subtitle Naudy Automatic Model General tips for using the Naudy depth estimation method Library Help Top The Naudy Automatic Model tool can produce variable numbers of solutions depending on the solution quality you specify The main parameter th
3. Naudy model point datasets produced using the instructions in this case study The datasets are named BH_TMI_Naudy DIR and BH_lvd_Naudy DIR We have provided these datasets so that you can compare your results after following the case study We recommend that you use the names BH_TMI_Naudy1 and BH_1vd_Naudy1 for the output datasets when you follow the case study Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 6 Library Help Top lt 4 Back gt Steps in the case study Determine the 1 Examine the Clearance field of the dataset to determine the average flying average flying height You can specify this as a parameter in the Naudy Automatic Model tool height Your results will be more reliable and will not contain above ground solutions To examine the field highlight click the BrokenHill DIR dataset in the Filename panel in the INTREPID Project Manager Choose the Statistics tab then highlight the groundClearance field and choose Calculate INTREPID will 2 73 display statistics or a histogram for the field L Library Help Top 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 7 Library Help Top lt 4 Back gt INTREPID displays statistics for the field Project manar io xi File Dataset Editors Level Grid Display Print Filtering Radiometrics Gravity Interpret
4. T Body strike Length of bottom shaft of T Body dip Library Help Top 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual Library Help Top Repeat the steps with TMI data Geological importance of Dykes CO2 21 4 Back gt 7 Print the composition if you wish The composition is A4 size From the File menu choose Print Windows version INTREPID will launch the Print Hard Copy tool and load the composition From the File menu choose Print Preview to preview the plot Then choose Print and respond to the conventional Print dialog box UNIX version INTREPID displays a cascade menu with output format options HP GL PostScript etc Choose the format you require Specify a name for the output file Print the output file in the normal way for your system Tip You can find more detailed instructions for printing and print previewing in Printing your composition in Map composition G17 in the INTREPID Guided Tours Repeat steps 3 24 with the 1VD data producing shallow depth solutions Specify Vertical Derivative of TMI type data in step 3 Use datasets and names as follows Function Dataset or Field Marker file suffix Windows Naudy Automatic Model process Line dataset containing survey BrokenHill DIR Z Field for calculating Naudy model 1lst_V_D LINE Output Naudy model point dataset BH_1lvd_Naudy1 Visualisation Solution Naudy mode point dataset for display of m
5. axis and TMI value along the vertical axis a Intrepid Automatic Modelling Tool 3 2a10 Oo x File Edit View Interpret Help Line 14100 Z Dataset microlevelled Bearing 271 ie Naudy solutions From the File menu choose Save Model As Specify BH_TMI_Naudy1 as the output Naudy model point dataset From the Interpret menu turn on click Always Regenerate Model In this mode each time you view a different line INTREPID will recalculate the model for that line This is analogous to Auto recalculate mode in a spreadsheet such as Excel It involves more processing but avoids confusion for novice users From the Interpret menu choose Earth s Magnetic Field amp Clearance The default is to calculate the Earth s magnetic field using the dataset locations Leave it as it is Check the Remove survey clearance from depth option and enter the average Clearance which you calculated earlier using the Project Manager Choose OK 1 We provide an identical solution dataset called BH_TMI_Naudy 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 10 Library Help Top Set the model parameters Set the advanced options Calculate Naudy solutions for the first line Library Help Top 4 Back gt 7 From the Interpret menu choose Set and Test Parameters Model Parameters and Testing Model Parameters and T esti
6. the solutions If you are processing 1VD data INTREPID will use different filters and parameters Tip If you are already satisfied with the parameters you can skip steps 8 and 9 or even steps 9 14 From the Interpret menu again choose Set and Test Parameters Choose Scan INTREPID will calculate and display the Naudy solutions for the first line in the lower panel of the Naudy Automatic Model window MAX REVERSED MAGNETISATION MAX NORMAL MAGNETISATION 3000 eal REVERSED MAGNETISATION a fi NORMAL MAGNETISATION CLICK TOP OF NAUDY BODY RIGHT MOUSE FOR INFORMATION nb if strike gt 45 or strike lt 135 hotspot Magenta elze grey 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 11 Library Help Top Resample the solutions for the first line Create the model for the first line Library Help Top 4 Back gt 10 Choose Resample INTREPID will refine the set of solutions rejecting those with a high poor similarity coefficient INTREPID displays the refined set of solutions mauuy surauune ete eIn i my o MAX REVERSED MAGNETISATI E REVERSED MAGNETISATION _ 3500 o MAX NORMAL MAGNETISATION i NORMAL MAGNETISATION CLICK TOP OF NAUDY BODY RIGHT MOUSE FOR INFORMATION nb if strike gt 45 or strike lt 135 hotepot Magenta else grey Choose Create the Model and then OK INTREPID ca
7. then examine the Plan view of the model using model plan view Choose Set and Test Parameters from the Interpret menu Change Finishing at Depth to 550 m INTREPID uses this parameter to control the colours in the plan view Choose Plan View from the View menu INTREPID displays a plan view of the model with the inferred structures shown as coloured bars across the lines The direction of each bar indicates the strike of the corresponding inferred structure If the legend is titled Similarity choose Change Mode to switch to Depth mode aft ss GER Stee SS rms me J were p ey SS lt F aun z Fi a LA c TR EE et AE a es PFF e 5 aft FE r EFE a eS z 7 erate i i ee Sextet as i e An Depth ae ey y Be o a eee ee He z fares 7 aS Sa a 4 23 sot st ae Ss z t A A x a gt ae a ae a 7 ite Z SS 550 Change mode Close Tip This display always shows all of the bodies in the model The depth range that you set controls the colours only If you set the finishing depth to a ridiculously low value all of the bodies would appear purple The current version of the tool only allows you to change the finishing depth You can change the maximum depth for display and see the plan view again Simply close the plan view and repeat step 16 using a different finishing depth Library H
8. to this point on a standard desktop computer was around 10 hours In addition this implimentation brings togetehr a few complimentary methods so that the extracted geological information is of practical direct use in building 3D 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 3 Library Help Top 4 Back gt geology models when dyke swarms are an important component Important definitions The Observed Field is the a TMI or b Tensor magnetic gradient data in the input dataset The Naudy Automatic Model tool represents it as a black profile curve in the line profile display area The Calculated Field is the TMI data that would result from the set of inferred geological structures that comprise the current model The Naudy Automatic Model tool represents it as a red profile curve in the line profile display area The Similarity Coefficient is a measure of the similarity between the calculated field and the observed field Its value ranges from 1 to 5 where 0 represents a perfect match and 5 a very low similarity The Scanning Body is a proposed geological structure used to calculate a value for the calculated field INTREPID records the similarity coefficients for the scanning body along the line at each depth It uses this array of similarity coefficients to locate solutions The width of the scanning body increases for greater depths The starting dip of the scannin
9. your dispolsal when it comes to scanning for shallow solutions Just a small variation can sometimes trigger quite a different behaviour on certain lines The starting finishing depth and the Check box Finer sampling for shallow solutions control the total number of scan lines with depth Finer Sampling YES NO The default geometric progression is 1 2 to determine the next for shallow deeper scan line below surface If you check this box the solutions progression factor is reduced to 1 05 resulting in a lot more scan lines near the surface and so many more candidate solution from which to choose or discriminate Width of Naudy 1 5 If this is too wide INTREPID may inadvertently introduce part operator of a neighbouring anomaly into the calculation If it is too narrow INTREPID may only examine the peak of an anomaly and fail to obtain information about its true shape Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Library Help Top Geological importance of Dykes CO2 27 lt 4 Back gt Parameter Default Notes and Variations Use Naudy NO INTREPID calculates a dip for each solution If this option is derived dips on INTREPID will record this dip for the inferred geological structure If it is off INTREPID will use the dip of the scanning body Turn this option off if e You have viewed the Naudy derived dips and they are clearly
10. INTREPID User Manual Geological importance of Dykes CO2 1 Library Help Top 4 Back gt Geological importance of Dykes CQ2 Top It is well known that Earth history is punctuated by events during which large vol umes of mafic magmas were generated and emplaced by processes unrelated to nor mal sea floor spreading and subduction These are recognized as Large Igneous Provinces Systematic Study of dykes helps to understand and solve many geological problems It helps to recognize Large Igneous Provinces LIPs particularly for the Precambrian period Many LIPs can be linked to regional scale uplift continental rifting and breakup and climatic shifts In the Paleozoic and Proterozoic LIPs are typically deeply eroded They are represented by deep level plumbing systems consisting of giant dyke swarms sill provinces and lay ered intrusions In the Archaean the most promising LIP candidates are greenstone belts containing komatiites Detailed study of dykes is therefore considered to be an important tool for Paleo continental reconstructions Paleocontinental reconstructions are critical to provide a tectonic context for major ore deposits the tracing of metallogenic belts between blocks and identifying new prospective regions for mineral deposits of a wide variety of types Dykes are equally important to understand the full context of sedimentary basins their evolution and their hydrocarbon reserves and potential This will h
11. NTREPID User Manual Geological importance of Dykes CO2 20 Library Help Top lt 4 Back gt 6 Use the Hard Copy Composition tool to view the hard copy specification you created in step 19 From the Print menu choose Compose Hardcopy This will launch the Hard Copy Composition tool Make the Hard Copy Composition window as large as possible Open the file BH_TMI map a solution file provided identical to BH_TMI1 map which you created Specify Scale 2 1 using the View menu Intrepid MapComposition Tool V3 2a10 File Edit Geographic Annotation View SAgsddE raidio Jet Broken Hill Total Magnetic Intensity Se ease Noudy Automatic Madel Intrepid M apcomposition T ool ZoomOut 2 Lal 2a ABE Naudy Automatic Model draft Naudy Automatic Model full resolution enlarged Tip The initial view of the composition is at draft resolution showing only a few points from the Naudy Automatic Model When you print the composition you will see all of the points You can increase the resolution as follows Click the data area Choose Edit Detail from the Edit menu Choose PointPlot from the list of objects Select Full from the display resolution options You can also increase the magnification by choosing 1 1 from the Scale cascade in the View menu then increasing the Hard Copy Composition window size The T shaped symbols indicate the following Attribute Meaning Colour Depth Direction of top cross bar of
12. Task Naudy directory Library Help Top 2012 Intrepid Geophysics 4 Back gt
13. _min subdirectory of cookbooks install_path sample_data cookbooks interp_min Original data These datasets are the original data for the Naudy Automatic Model worked examples The grid datasets are for display only and are not involved in the calculation BrokenHill The original line dataset providing the source data microlevelled The magnetic data field 1st_V_D The first vertical derivative of the magnetic data BH_TMI_grid Grid of the microlevelled field of BrokenHill BH_lvd_grid Grid of the 1lst_V_D field of BrokenHill Naudy Automatic Model point datasets These datasets contain Naudy Automatic Model solutions using the source data indicated BH_TMI_Naudy Model calculated from total magnetic intensity with fixed body strike BH_lvd_Naudy Model calculated from first vertical derivative with fixed body strike Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 23 Library Help Top lt 4 Back gt Hard copy composition map and associated legend leg files You can load these files into the Hard Copy Composition tool for viewing and printing the results of the Naudy Automatic Model process Each file has an associated leg file which provides colour assignment information BH_TMI map Composition of the BH_TMI_Naudy Naudy Automatic Model point dataset overlaying the grey scale BH_TMI_grid The legend fil
14. about this tool Location of sample data for Cookbooks Where install_path is the path of your INTREPID installation the project directory for the Cookbooks sample data is install_path sample_data cookbooks For example if INTREPID is installed in C Program Files Intrepid Intrepid4 5 then you can find the sample data at C Program Files Intrepid Intrepid4 5 sample_data cookbooks For information about installing or reinstalling the sample data see Sample data for the INTREPID Cookbooks in Using INTREPID Cookbooks R19 For a description of INTREPID datasets see Introduction to the INTREPID database G20 For more detail see INTREPID database file and data structures R05 Advantages of the Naudy Automatic Model tool Library Help Top Most aeromagnetic datasets will have more dyke like bodies than other shapes This gives the Naudy Automatic Model tool an advantage as a depth estimation option You can use this method for sources at any depth provided the corresponding profile shapes are well defined Where responses are superimposed on each other overlap the Naudy approach still appears to be reliable The method is very fast and can easily work on many very large surveys For instance a recent demonstration was made of using the tool on the complete magnetic line data sets from Botswanna Approximately 4500 dykes could explain the majority of the observed magnetic signal for this dataset The time taken to gwet
15. at controls this is the Threshold for the Similarity Coefficient one of the Resampling criteria Calculate trends information from the dataset where possible It will provide more accurate strike information for the inferred geological structures For shallow sources less than 200 m e Calculate the model using the results of the first vertical derivative 1VD We have found that the Naudy solutions from this data are a good fit for shallow sources Use the Line Filter tool to obtain the 1VD for all lines that you wish to process Save the results as a new field in the line dataset and use the new field for calculating the Naudy model Set the Width of Naudy Operator as a Multiple of Depth to 1 5 We have found that this setting picks most shallow solutions in a complex dataset and gives reasonably accurate depths typically within 10 If the responses are well separated you could increase this to 2 This will give more accurate depths within 5 We recommend a Naudy Threshold for Resampling setting of 2 5 or a value between 2 and 3 for retaining the best solutions For intermediate and deep sources greater than 200 m e Calculate the model using the TMI The first vertical derivative strongly attenuates deeper responses so is not suitable for this depth range Set the Width of the Naudy Operator as a Multiple of Depth to 1 5 for most situations where there is a mixture of overlapping responses If there are w
16. ation Utility Betas Help DA S File name File type Scr Intrepid colour legend E Documents and Settings y i Hy i ERMAPPER Intrepid map file E E Intrepid Intrepid grid file 2a cookbook EP BH_1vo_Naudy DIR Intrepid dataset E gravity fa BH_TMI leg Intrepid colour legend fa interp_min EP BH_TMI map Intrepid map file E interp_oil Z BH_TMI_grid PD ers Intrepid grid file J radiometries EF BH_TMI_Naudy DIR Intrepid dataset E int36e1 35 EF BH_TMI_Naudy2 01R Intrepid dataset C int37 203_cant_dele Ineoii dataset H int37 205_cant_dele SORTS fe int37 223 7 match_filtjob Intrepid job file amp E manuals a match_gria ft File E O tutorials_master E Oasismontaj a ODI File Fields Statistics f m a C Program Files j fidFactor 4 Histogram Statistics 1st Y_D a ma Je nign Statistics Values S E WINNT Je LINETYPE Minimum 60 000000 da e amplit Maximum _ 160 000000 E e microlevelled Mean 60 000000 SFA x Std Dev 0 000000 H E CDimages Samples 95 a Nulis 0 m E DATA I A vince OTOH DFA_administration EA DFA software Calculate pE In our case the Clearance field has been corrected and has a mean value of 60 metres 2 Optional Determining the average line spacing of the dataset If you do not know the average line spacing of the dataset you can measure it with a visualisation KS tool To do this using Windows launch the Visualisation tool Load the line
17. d Geophysics 4 Back gt INTREPID User Manual Library Help Top Library Help Top Geological importance of Dykes CO2 17 lt 4 Back gt t l a 3D BODY CREATION CONTROLS Strike comes from the trends Each profile contributes 2D Hot Spot Bodies Join Hot Spot Bodies using Line Spacing of m MV Calculate 3D Body Linear Approximations Strategies for thinning dyke fault data Always keep start and end points Minimum Original Hot Spot Points 4 l Force Normal polarity M Pick Dykes Faults with best fitting RMS rA Finite Dykes Add zero thickness points at end For magnetic datasets if you allow negative susceptibility dyke solutions or use proximity strike for ring dyke solutions Accept All long thin 3D Bodies Induced long thin 3D Bodies Only C Possibly Remanent Dykes C Find any Ring Dykes M Generate Run Forward model task file Use a facet formulae C Use a infinite thin sheet What response to calculate TMI Magnetic Tensor GridName calculated_dyke ers CellSize 100 00 OK Cancel 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual Library Help Top Create a MAPCOMP hard copy file to show the model Exit from Naudy Automatic Model Library Help Top Geological importance of Dykes CO2 18 lt 4 Back gt 1 Output the model toa MAPCOMP file INTREPID s Hard Copy Composition tool can display and p
18. dataset BrokenHill DIR Select Zoom mouse mode Zoom in on an area that appears to have regular line spacing Select Query mouse mode Left mouse button drag from one line to the next and read the line separation from the Dist m report field Repeat this measurement with one or two other line pairs until you have a reliable estimate for the average line spacing Intrepid Visualisation NT 3 2 _ o x File Line Display Point Display Grid Display Window Help DATASET ype X 533791 8 Y 6493556 9 FIDi 38404 Distance Distfm 98 225589 between lines Value Drag between i km lines to measure distance Zoom In z l Zoom Out Mouse Mode Query C Zoom The average line spacing of the BrokenHill dataset is 100 m Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Library Help Top Launch Naudy Automatic Model Specify the input Library Help Top Tip The following table contains a summary of the input and output data for this section of the exercise Geological importance of Dykes CO2 8 4 Back gt Function Dataset or Field Marker file suffix Windows Naudy Automatic Model process Line dataset containing survey BrokenHill DIR Signal Field for calculating Naudy microlevelled LINE model Output Naudy model point dataset BH_TMI_Naudy1 Visualisation Solution Naudy mode point dataset BH_TMI_Naudy
19. e Naudy solutions When you choose Create the Model INTREPID automatically calculates and resamples the solutions Tip Before viewing the model for other lines you must close the Model Parameters and Testing dialog box Tip Whenever you view a new line INTREPID automatically calculates the model with the current parameters If the line currently has no model OR If the line has a model and the Always Recalculate Model option is on Tip You can automatically create the model with the current settings for some or all lines See the next step for details Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Library Help Top Specify a fresh output dataset and calculate the model for all lines Library Help Top then create a fresh Naudy model for the lines you require Geological importance of Dykes CO2 14 4 Back gt 16 When you are satisfied with your choice of options clear the model for all lines and Tip You may have calculated models for some lines using earlier parameters that you specified during testing To delete these depth solutions and start with a clean model before commencing your final processing choose the Lines option Clear Model for All From the Edit menu choose Clear Model for All Lines Any models generated during the testing phase will now be deleted Create the model for the lines required In this case study we will create the m
20. e for colours associated with depth is BH_TMI leg BH_lvd map Composition of the BH_lvd_Naudy Naudy Automatic Model point dataset overlaying the grey scale BH_lvd_grid The legend file for colours associated with depth is BH_lvd leg Depth estimation example oil exploration This section gives specifications for a Naudy Automatic Model exercise with oil exploration data using the data and parameters in the following table Note that the northsea dataset is located in directory cookbooks interp_oil Library Help Top 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 24 Library Help Top lt 4 Back gt Notes e The Naudy model point dataset creation process in this example is identical to that described in Oil exploration interpretation case study in Presenting regional depth and structure data C06 e This example does not cover the additional steps described in Presenting regional depth and structure data C06 to prepare the dataset for the Magnetic Interpretation Example poster To view the results of this example use the procedure described in the detailed worked example earlier in this chapter Function Dataset or Field Marker file suffix Windows Naudy Automatic Model process Line dataset containing survey northsea DIR Signal Field for calculating Naudy model mag_fin LINE Output Naudy model point dataset naudy_ns1
21. ell isolated broad responses the depth precision will improve with a wider spacing We have found 2 to be the optimal setting in these situations We recommend a Naudy Threshold for Resampling setting of 2 5 or a value between 2 and 3 for retaining the best solutions 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 26 Library Help Top lt 4 Back gt Naudy Automatic Model parameters This section contains a discussion of the parameters that you can specify for this tool their default values and instructions about when to vary them For more information about the parameters see Naudy Automatic Model interpretation T43 Parameter Default Notes and Variations Resampling mode Geolocated Geolocated This resampling mode controls the display of data only The Time based Naudy Automatic Model tool has its own resampling algorithm Fixed for processing the data Data type TMI or 1VD TMI You must specify which of these common types of data you are processing INTREPID uses different parameters and algorithms for each Scanning for Naudy solutions Scan depth range 80 5000 The depth is measured from the observation platform If you are examining shallow sources we recommend that you set the starting scan depth limit to the minimum of the average clearance aircraft height This parameter has been found to be the most sensitive tuning parameter at
22. elp Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 16 Library Help Top lt 4 Back gt 18 Display plan view in Similarity mode If the plan view window is not open choose Plan View from the View menu Ifthe legend is titled Depth choose Change Mode to switch to Similarity mode In this view the inferred structures are colour coded according to their similarity coefficient x 4 ae fray SS F ee F z aS f os it s tof En a al Z ae as re lt EE fie Similarity 0 E f F E pee z 2 ze Z ua 5 Change mode Close Choose Close when you have finished examining the plan view Export the 3D bodies to Geomodeller New to V4 5 is the ability to export the dykes as 3D worms to a CSV file prior to using these observations as structural controls while doing a 3D geology interpretation is say Geomodeller see Tutorial K For mineral exploration cohecrent 3D surfaces as thin bodies or dykes form a very important part of the geology landscape Even if the magnetic response just appears to be dyke like methoids to extract the zone of higher susceptibility in a sheet like body can be significatly helpful A copper CU project that has had a phase change next to a heat anomaly can sometimes have a quite distinctive sheet like response in the magetic record Library Help Top 2012 Intrepi
23. elp to solve puzzle for pre Pangean time back to 2600 Ma and provide constraints on pre Pangean superconti nents Remanence can be implied from TMI data when interpreted 2D dykes are proposed as a negative susceptibility will often emerge as the only way to explain the signal response This is then usually a very good indication that the dyke may be remanent With the advent of Full tensor Magnetic tensor gradient surveys the stroy on this subject changes dramatically More than half the bodies in an average survey can no longer be described as DYKES and then the ability to recover from a model of the DYKE under each survey profile line a magnetic unit vector that best fits the ten sor response to each body gives a direct measure of any divergence from the IGRF vector This is a much finer response than just saying you suspect the dyke to be remanently magnetized In this context it is beholden to develop automatic tools to search the geophysical sur vey records to identify and classify dyke swarms to assist in the large scale regional interpretation of deep crustal process with a view to improving prospecitivty for minearls and oil Depth estimation with Naudy Automatic Model Library Help Top The Naudy Automatic Model tool scans a line dataset for dyke like geological structures The tool examines the measured signal profiles along traverse lines of a dataset It proposes geological structures at a range o
24. equal to the similarity coefficient at that point A graphical representation of this process is given when you use the SCAN button 5 INTREPID then resamples the solutions rejecting those with a similarity coefficient greater than a threshold you specify and selecting the best solution where there is a cluster of them 6 INTREPID creates the model from the set of solutions The characteristics of the scanning body at the location and depth of a solution become the characteristics of 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 4 Library Help Top 4 Back gt an inferred geological structure at that point The position of a solution corresponds to the midpoint of the top of the inferred geological structure 7 The Naudy model data includes location depth width dip susceptibility and similarity coefficient of each inferred geological structure The Naudy Automatic Model tool can optionally refine the model using an inversion process INTREPID varies the properties of each inferred geological structure and calculates the corresponding TMI It selects the set of property values whose TMI profile has the best least squares fit with the observed TMI profile 8 The Naudy Automatic Model tool saves the description of the final set of inferred geological structures as a point dataset 9 After you have calculated the model for the dataset and refined it if required you can
25. examine it in the plan view or include it in a hard copy composition Some of the dyke like structures inferred by the Naudy Automatic Model tool will continue across many lines 10 Inversion is used to check and improve the initial solution This is done in two stages A moving the bodies and checking admissible solutions B Purturbing the dip width to improve the fit 11 The option to join solutions togetehr to produce 3D Dykes is available after the initial profile solutions are calculated and saved to a point dataset This is termed Export worms to Geomodeller A CSV file suitable for examination in EXCEL is produced with an order list of Dykes that are formed according to your preferences If an inferred geological structure continues through adjacent or nearby lines you can have high confidence that it corresponds to a physical structure If there are distortions in the waveform inferred geological structures may be discontinuous on adjacent lines but continued in nearby lines If an inferred geological structure does not appear to continue in nearby lines you should have doubts about its correspondence to a physical structure Suggested ways of examining the solutions graphically so that an integrated geological interpretation can be developed include Use Geomodeller to import the CSV file See Tutorial K for Geomodeller Use MapInfo ArcMap and import the CSV and treaty them as geological structural observation
26. f depths and calculates the body response that would result from them It then selects the set of proposed structures that would 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 2 Library Help Top 4 Back gt produce a calculated signal most closely matching the observed signal profile in the input dataset This selected set of inferred geological structures is the Naudy Automatic Model Naudy Automatic Model calculates the strike of each inferred geological structure using an inbuilt automatic depth dependent trend estimation process The Naudy model point dataset produced by the tool contains location depth width dip strike susceptibility and similarity coefficient closeness of match of the structures The tool has been extended at V4 5 V5 0 during 2011 2012 to support firstly Magnetic tensor gradient signals and to posture the tool s use for gravity gradient signal measurements So the generalization of the meaning of a geophysical signal to include other potential fields is a significant development Generally traditional gravity measurements have not been of sufficient precision and frequency content to be able to be used to good effect in this tool It is the newer development of gravity tensor curvature gradients and the reducing measured wavelengths that the Naudy method can find new application See Naudy Automatic Model interpretation T43 for details
27. ferent depths To obtain data and deep applicable to a depth INTREPID applies an appropriate filter trend filters The filters provided for TMI are provided Shallow residual of 51 point local mean Deep 300 m upward continuation Very deep 5000 m upward continuation Contact our technical support service for further information You can design your own filter as described in Line Filtering T31 Dimensions of 3 5 across measured in line spacings This is the size of the area within search rectangle 3 0 along which INTREPID associates minima and maxima on adjacent lines to detect trends INTREPID automatically estimates line spacing for this process Maximum angle 25 For example lines A and B may have maxima close within the for connecting search rectangle and line C also may have a maximum within trends the rectangle If lines drawn between the A B maxima and the B C maxima are at an angle of less than the size specified here then INTREPID assumes than the three maxima are part of the same anomaly INTREPID will assign a strike matching the angle to inferred geological structures in this area If you decrease the angle INTREPID will be more stringent in detecting trends If you increase it INTREPID will be less stringent Protobuf Data Model At V5 0 Intrepid has published the full datamodel for this tool including examples of how to set values and options The example is to be found under the Examples
28. g body is normally 90 vertical but a range can be used as well The calculated dip is senstive to noise in the observed signal so is adjusted for admissible values How the Naudy Automatic Model tool works Library Help Top The Naudy Automatic Model tool scans a line dataset for dyke like geological structures 1 The tool examines the Total Magnetic Intensity TMI profiles along traverse lines of a dataset It proposes geological structures at a range of depths and calculates the TMI that would result from each proposed structure It compares the calculated TMI of the proposed geological structures with the observed TMI and assigns a similarity coefficient to the proposed structure at that point INTREPID repeats this process along the line at different depths until it has a set of similarity coefficients for each depth along the line 2 INTREPID estimates the trends in the data by comparing positions of maxima and minima in adjacent lines From these estimates it calculates the strike of each inferred geological structure 3 The Naudy Automatic Model tool estimates directional trends in the data by comparing positions of maxima and minima in adjacent lines It estimates the trends at a number of depths From these estimates it calculates the strike of each inferred geological structure 4 INTREPID locates minima in the array of similarity coefficients It records each minimum as a Naudy solution with a similarity coefficient
29. he remanent vector direction Resampling Naudy solutions Threshold for 2 5 1VD 3 INTREPID will reject solutions whose similarity coefficients are similarity TMD greater than this value The range 2 3 is suitable for this coefficient parameter A lower threshold results in rejection of more solutions Minimum 001 nT The default value corresponds to typical noise amplitude in amplitude of 1VD 1 nT magnetic data Anomalies with less than this amplitude are corresponding TMD likely to be noise rather than useful data anomaly in observed field If you know that you have low amplitude anomalies such as in a basin area you can reduce the value of this parameter Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Library Help Top Geological importance of Dykes CO2 28 lt 4 Back gt Parameter Default Notes and Variations Creating the Naudy model Line spacing 200 m You must set this to the acquisition line spacing in the input line dataset It determines the length of the inferred geological structures in the model It does not affect the trend calculation process which has its own line spacing measurement system Refining the Naudy model Number of 20 This parameter determines the number of inversion iterations iterations INTREPID will perform Reduce the value to say 10 To speed up process or Ifyou have found that the inversion result
30. incorrect or e You require a simpler result Reject solutions NO If this option is on INTREPID will reject solutions whose dip with bad Naudy differs by more than 30 from the dip of the scanning body If Derived Dips the Use Naudy Derived Dips option is on INTREPID will turn this option on overriding any setting that you have made If this option is turned on INTREPID will produce higher quality solutions with more accurate depths Turn this option off if INTREPID appears to be eliminating too many solutions for your requirements Calculate model NO Turn this option on if you require solutions corresponding to for steps as well step like structures as dykes Allow negative NO Turn this off if you wish to exclude inferred geological susceptibility structures with negative susceptibility INTREPID weights negative susceptibility lower than positive susceptibility A solution with negative susceptibility therefore acquires a higher similarity coefficient than a positive one with the same magnitude A negative susceptibility can also indicate a strong possibility of remanent magnetization To fit the signal if the remanent magnetization vector was nearly 180 degrees opposite to the current inducing field vector a negative susceptibility would result as the only way to fit TMI data If the signal is a full magnetic tensor gradient this restriction does not apply as the 2D Dyke model can be fully resolved not only for its geometry but also t
31. lculates and displays the Naudy model in the lower panel of the Naudy Automatic Model window Choose Next gt gt and lt lt Previous to view the model for a number of lines Return to the second line 14120 The model for the first and last lines of a dataset will be less reliable than the rest a Intrepid Automatic Modelling v4 1 Release Build 125 0 xi File Edit View Interpret Help Line 14120 Z Dataset microlevelled Bearing 57 T T T 2666 4668 6666 8666 fl 16666 son Ae Bo re oe A Naudy solutions ry oS y 3 1500 2080 Solution quality lt 1 good bird 2500 lt 3 3588 A ml CLICK TOP OF BODY RIGHT FOR INFORMATION LEFT TO EDIT CTRL LEFT TO DELETE gt Poor Done 3 passes of profile for 11 chosen solutions The Naudy model display shows the inferred geological structures colour coded according to similarity coefficient You can Zoom in and out Report information about individual bodies Edit parameters of individual bodies e Delete individual bodies Tip Refining the model The Naudy Automatic Model tool can refine models by varying the position depth size angle and susceptibility of inferred geological structures It chooses the variations that most closely fit the calculated field to the observed field We recommend this process for datasets whose structures are well separated but not where there are overlapping st
32. ng Scan ffor Initial Solutions Starting at Depth 50 00 m and Finishing at D epth 1000 00 m Depth below Magnetometer Resample the Solutions rejecting those with Anomaly Amplitude less than 1 0000 nT OR Similarity Coefficient greater than 3 00 Create the Model assuming a Line Spacing of 199 00 m Refine the Model for upto 5 Inversion Iterations Advanced options OK Cancel For A Scan the default scan Starting at Depth of 50 m approximates the average clearance of 60 m that you checked earlier so no change is required Specify Finishing at Depth of 1000 m For B Resample Leave the defaults as they are For C Create the Model Specify Line Spacing as 100 m Choose OK From the Interpret menu choose Advanced Parameters For Dip Search Strategy select the Use Naudy Derived Dips option For Body Strike Options select the Calculate Trends option Choose OK Tip The Width of the Naudy operator corresponds to the size of the anomalies we are seeking When you calculate the model for 1VD you will specify a much smaller Naudy operator because the 1VD data is sharper The value of this parameter needs to be wide enough to cover an anomaly but narrow enough to avoid overlapping and incorporating adjacent responses Tip Calculating trend information enables INTREPID to assign strike values to the inferred geological structures This improves the quality of
33. ns body at the bottom of the J window Solution quality lt 1 goody aa SE lt 3 lt 1 CLICK TOP OF BODY RIGHT FOR INFORMATION LEFT TO EDIT CTRL LEFT TO DELETE van poor Dyke Width Heiaht x 532707 Done 3 passes of profile for 11 chosen solutions Tip You can also delete an inferred geological structure or edit its specifications To delete a structure from the model hold down CTRL and left button click the top of body To edit a structure left button click the top of it INTREPID displays an edit dialog box You can classify or group the structures according to your own system using the GroupID field INTREPID will record the numbers you enter in the output Naudy model point dataset View other 15 Examine the model for a number of lines i We recommend that you examine the first few lines a couple of lines from the middle and a couple from the end of the dataset Use Next Previous and Goto in the Naudy Automatic Model window When you choose Goto INTREPID displays a dialog box with a list of line numbers for selection Tip If you are adjusting parameters during this examination process ensure that Always Recalculate in the Interpret menu is turned on INTREPID will recalculate the model for each line you subsequently view Tip In the Automatic Modelling Options and Testing dialog box you do not need to choose Scan and Resample before Create the Model unless you wish to examine th
34. odel BH_lvd_Naudy DIR Z field for point colour Depth_Bin_No PNT Z field for point size Depth_Bin_No PNT Grid for overlay in display of model BH_lvd_grid GRID Hard Copy Composition Output hard copy specification file for presenting the BH_1vd1 map n a Naudy model Solution hard copy specification file provided for BH_lvd map n a presenting the Naudy model Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 22 Library Help Top lt sSSsSS Ba When you export the model to a MAPCOMFP file use the following parameters and labels Element Value Page size A4 Orientation Portrait Scale 100000 Optional backdrop image BH_1lvd_grid use Find Image to locate it Show the bodies as Dip Symbols On Rectangle Off Title Broken Hill First Vertical Derivative Subtitle Naudy Automatic Model Summary of minerals exploration worked example files We have provided a complete set of original and solution datasets and auxiliary files with this chapter Installation directory We have configured all task specification job and hard copy specification map files assuming that you have installed the worked example data in the directory cookbooks in the main INTREPID installation directory install_path sample_data cookbooks All datasets and auxiliary files associated with this chapter reside in the interp
35. odel for all lines Choose Process from the Naudy Automatic Model window Ensure that the Select All Lines option is selected and then choose Accept Lines to Process Lines to Process Input Line Dataset D Intrepid tutorials data B rokenHill Output Point Dataset D Intrepid tutorials data BH_1vd_Naudy C Select from List Data Set Line Numbers Selected Line Numbers gt gt Add gt gt lt lt Remove lt lt C Select a Range From Start To End C Select a Line Line Number Start Select All Lines excluding Tie Lines ox Cancel INTREPID will calculate the model for the lines specified minutes Intrepid Automatic Modelling Tool Processing All Flight Lines 50 Completed Abort This will take a few Tip In order to keep the exercise simple we have removed the tie lines from this dataset When you process all or selected lines INTREPID will automatically exclude tie lines if it can identify them For this to occur you must have a line type field where the acquisition lines for process have type 2 The conventional type number for tie lines is 4 You must assign this field to the LineType alias INTREPID will then only process lines whose type is 2 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 15 Library Help Top Back gt Examine the 17 Set the maximum depth for the model to 550 m
36. r Uplifted blocks at the site of a fault such as a Horst Graben Depth estimation worked example mineral exploration This case study shows how a minerals explorer can use the INTREPID Naudy Automatic Model tool to infer a set of dyke like geological structures from a magnetic survey Overview In the case study we will first calculate the Naudy Automatic Model from the total magnetic intensity TMI This will yield the best estimates for bodies at intermediate depth We then demostrate joining the point solutions to form 3D dykes that can extend for several kilometers Summary linear solutions are also available You can go on to calculate the model from the first vertical derivative 1VD data This will yield the best estimates for shallow bodies In each case we will examine the resulting point dataset overlaid on a grid of the source data TMI and 1VD respectively The case study dataset We have provided a sample survey near Broken Hill New South Wales Australia for use in the case study The Cookbook Cookbook sample datasets include this dataset It normally resides in the directory instal1_path sample_data cookbooks interp_min and consists of A line dataset called BrokenHill DIR which is the survey for analysis Grid datasets created from the TMI and 1VD fields in BrokenHill DIR We have performed reduction to the pole on these grids The grids are named BH_TMI_grid and BH_lvd_grid respectively e
37. rint the results From the File menu choose Export Model to MAPCOMP Specify the composition as follows Element Value Mode Map of Naudy bodies Page size A4 Orientation Portrait Scale 100000 Optional backdrop image BH_TMI_grid use Find Image to locate it Show the bodies as Dip Symbols On Rectangle Off Title Broken Hill Total Magnetic Intensity Subtitle Naudy Automatic Model MapPrint information MapPrint information C Landscape Portrait Scale 100000 00 Paper size A4 CA3 CA CAI Name of optional backdrop image Find image C AO Show the bodies as F Rectangles Dip symbols Main title and sub title D Intrepid cookbook interp_min BH_TMI_grid Broken Hill Total Magnetic Intensity Naudy Automatic Model OK Cancel Choose OK Specify BH_TMI1 as the name of the hard copy specification map file We provide the solution file BH_TMI map Later in this example you will print or print preview this hard copy composition 2 Exit from the Naudy Automatic Model tool 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 19 Library Help Top lt 4 Back gt View the model 3 View the Naudy model point dataset overlaid on a sun angle grid of the TMI data laid f ENE Launch the Visualisation tool Load the grid BH_TMI_grid Display it using sun s
38. ructures To test refinement choose Refine the Model in the Model Parameters and Testing dialog box and then examine the results in the window To automatically refine the model when it is calculated turn on Automatically Invert when Calculating Model in the Advanced Model Options dialog box 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 12 Library Help Top lt 4 Back gt Zoom in 12 Zoom in on a section of the line to show more detail Use the left mouse button to define a zoom area rubber band stretch INTREPID will zoom the display to the area you define fodelling v4 1 Release Build 125 Zoom out 13 Zoom out to display the whole line Double click the upper line profile panel Library Help Top 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 13 Library Help Top lt 4 Back gt Query an 14 Display information about one of the inferred geological structures Click the top inferred of the structure using the right mouse button INTREPID displays information ike ical about the body at the bottom of the window structure Intrepid Automatic Modelling v4 1 Release Build 125 x File Edit View Interpret Help Line 14120 Z Dataset microlevelled Bearing 57 Right click the top of this body View data lt lt Previous Goto Next gt gt about the Naudy solutio
39. s e Use EXCEL to examine sort and select any dykes of intrest Structures inferred by the Naudy Automatic Model tool Characteristics of the dyke like structures Dyke like bodies are thin near vertical sheet like geological structures See Shapes of source bodies in Estimating Source Depth Overview C01 for further general discussion about shapes The Naudy Automatic Model tool as currently implemented is designed to detect and determine depth to two dimensional dyke like bodies whose Thickness is less than their depth 2012 Intrepid Geophysics 4 Back gt Library Help Top INTREPID User Manual Geological importance of Dykes CO2 5 Library Help Top lt 4 Back gt Strike extent extent in the direction of their strike is at most 5 times their depth Corresponding TMI profile shapes are well defined Characteristics of the plate like structures whose edges can be found Plate like bodies are thin near horizontal sheet like geological structures Naudy Automatic Model can detect and estimate the depth to the edge of thin plate like structures This method may also be useful for detecting the edge of faulted or sheared blocks where the relative vertical movement is small Characteristics of the step like structures whose edges can be found Step like structures show a sudden change of magnetic response Examples include Contact between large bodies such as between granite and surrounding rocks o
40. s are unstable and you are obtaining clearly incorrect results Invert when NO If you turn this option on INTREPID will automatically include processing lines Body strike calculation the inversion process when it creates the model for the dataset It will vary the properties of each inferred geological structure for a better fit of the calculated field to the observed field Inversion will tend to smooth out small anomalies in the data providing a better overall picture of the dataset Without inversion the Naudy Automatic Model tool will fit small anomalies more closely Turn the option off For faster processing OR Ifa simple set of solutions are adequate OR Ifyou do not wish to smooth out smaller anomalies Body strike options Perpendicul ar to line direction If you do not want to calculate trend information faster process use the default setting If you are aware of a general trend in the dataset specify a fixed body strike 0 North South The Trend Dataset method is now obsolete Contact our technical support service for information if required We recommend that you normally calculate trends from the line data Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Geological importance of Dykes CO2 29 Library Help Top lt 4 Back gt Parameter Default Notes and Variations Filters Use shallow INTREPID calculate trends at dif
41. un angle grid angle Load the point dataset BH_TMI_Naudy Specify the field Depth_Bin_No for both the colour and size of points Examine the display Intrepid isualisation v3 7 release cut 223 File Line Display Point Display Grid Display Polygon Display Window Help Zoom In Zoom Previous A ta De aN Mouse Mode Query C Zoom or Trace Tip The field Depth_Bin_No results from classification of the depth values into groups bins as if you were preparing a histogram For visualisation using bin number instead of depth value helps to achieve a balanced pseudocolour distribution removing the influence of extreme values Zoom in 4 Zoom in on sections of the display for closer examination Select Zoom mouse mode and zoom in on a region suitable for assessing the quality of the model f Intrepid Visualisation NT 3 2a10 Intrepid Visualisation v3 7 release cut 223 2lolx File Line Display Point Display Grid Display Window Help File Line Display Point Display Grid Display Polygon Display Window Help 7 BH_TMI_grid Zoom In Bf Zoom Out oe 4 7e Zoom Previous a a Mouse Mode C Query C Zoom or Trace 5 Exit from the Visualisation tool when you have finished examining the images Now switch to the INTREPID Project Manager 1 When you examine the 1VD data use Declination 315 Inclination 30 and Vertical Exaggeration 1000 Library Help Top 2012 Intrepid Geophysics lt 4 Back gt I
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