Oasis Montaj Complete Workflow Tutorial

CURTIN EXPLORATION EXPLORATION GEOPHYSICS G EOPHYSICS GEOPHYSICS 3000 WORKSHOP 1 – 3 March 2016 OBECTI!E

This workshop is an introduction to the software package Geosoft Oasis Montaj which we will be using extensively in Geophysics Geo physics 3000 and in other units of the Geophysics undergraduate course. n this workshop we will be using aero!agnetic data fro! the "avensthorpe area of #$. This is an interesting and varied dataset fro! an area with known !ineral deposits and potential to find !ore. The dataset is contained within within three files % rav3.xy&' rav(.xy&' rav).xy&. These files are are in the *lackboard folder workshop + , 3 !arch -0+ /ach of these files files contains eastings' northings and aero!agnetic values in that order. eep good detailed notes 1 2O" 4$* *OO – ha"#$r%&&'" a"# '('c&r)"%c *'r+%)"+ 5 on what you do to help you in the learning process and for assess!ent during this course.

STEPS

+. 6opy files files rav3.xy&' rav3.xy&' rav(.xy&' rav(.xy&' rav).xy&' rav).xy&' and !ag!ap.con !ag!ap.con to a working working direct directory ory within your geophysics co!puting account. -. 4og 4og in in to to Oas Oasis is Mont Montaj aj 7tart 8 $ll 9rogra!s 8geosoft 8 oasis !ontaj 8 oasis !ontaj 3. 6reate 6reate new new projec project. t. se se file file 8 project project 8 new new /nter project na!e (. 6reate 6reate new database database , allow allow for for up to to )00 flight flight lines. lines. ey ey in )00 in place place of default value of -00. :atabase 8 1ew :atabase /nter new database na!e ). !port !port rav3.xy& rav3.xy& to the the new database database using :atabas :atabase8 e8 i!port8g i!port8geosoft eosoft xy& This file is in geosoft xy& for!at . !port !port rav(. rav(.xy& xy& into into the the databa database se using using a,,'"# option ;. !port !port rav). rav).xy& xy& into into the the databa database se using using a,,'"# option.

<. 7plit the three lines of data in the database into individual flight lines' using :atabase tools 8line tools 8 split on x'y breaks. 7elect all lines =. 7et coordinate projection para!eters for database. 7teps% Go to >6oordinates?. 7elect current x'y'& coordinates and select x'y and & channel na!es' followed by O  7elect coordinate syste! and go to 6oordinate syste! at botto! of this window 7elect 9rojected @x'yA. 7elect projection !ethod as $ustralian !ap grid &one )+. 7elect datu! $G:<( , this is $ustralian geodetic datu! for +=<( 6heck length units as !etres 6heck table of para!eters and if ok select ok' otherwise !odify. +0. 6reate !ap showing all the flight lines.  Map tools8 new !ap' based on x.y' paper si&e $3 landscape' scale B' line path  This will show dense pattern of lines , can &oo! in and see !ore detail.  #hat is line direction B line spacingCs B @using right !ouse click with cursor on !ap and select ruler function A.  7ave !ap changes. ++. 6reate base !ap with legend' scale bar' north arrow' title block' colour legend  bar.. se !argins around !ap of - c! left' top and botto! and +( c! on right of !ap. se Map tools 8 *ase Map +- Grid the !agnetic data with appropriate grid interval. #hat is your choice and why B se grid and !age 8 gridding 8 !ini!u! curvature etc. +3. :isplay the !agnetic grid using a. single grid option b. 6olour shaded option #hat sun illu!ination options are !ost suitable and why B 7ave !ap changes. To create colour shaded grid !aps' steps are as follows% Grid and !age 8 :isplay 8 Grid /nter grid na!e 8 colour !ethod 8 histogra! eDuali&ation' @for topography use linearA 7elect apply shadow !ore 8shading effect 8 enter inclination' declination and vertical scale factor @typically use )A select new !ap +(. 6reate a new !ap of a +0 x +0 k! subset of the data. se Map Tools 8' new !ap fro! x and y' and key in selected rectangle of coordinates selected using !aps created in steps ++ 5+ -. 6reate a stacked !agnetic profile !ap for this sheet. sing Map Tools 8 9rofile.. 7tart off with coarse vertical scale for profiles and base value of close to average value of &+ eg )<000 1T

To restrict the profiles to just the selected subset area , go to viewCgroup !anager @ left hand icon on third row down of the iconsA' highlight profiles in data area and select >Masked to Eiew region? +). Open database and create profiles of individual lines using split screen , data in top panel' profile in lower panel. +. Grid filtering using M$GM$9 to create derivative in F direction sing input of !agnetic grid created in step ++ of these notes. This derivative is often called the first vertical gradient of the !agnetic field and shows how the !agnetic field varies with height above the ground. t is very useful in interpretation. M$GM$9 is where !ost freDuency do!ain gird filtering is done. 7teps% Gx 8 load !enu8 !ag!ap.o!n This brings up M$GM$9 in top row of options 7elect M$GM$9 +57tep5filtering' n 7et6onile select :erivative in F direction' order +. n 7etTrend select first order and edge points. n 7et/xpand select +0 H expansion and rectangular  n 7etill select !axi!u! entropy option To run select O at botto! left of !ag!ap processing window :isplay this new grid using sun illu!ination. Iow does this grid co!pare with  previous !agnetic grid B #hat is average value of the vertical gradient B +;. 7ave all !ap changes' database changes' save project and exit fro! Oasis Montaj to end session. TO BE CONTINUE- IN WORKSHOP 2

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