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Uranium Metallogenic Studies: New Developments in SRC's Lithogeochemistry Program by Michel Mellinger1

The Saskatchewan Research Council's Lithogeochemistry Program emphasizes the development of expertise in basic methodology and the application of lithogeochemistry to mineral exploration.

Developments in this area were surrrnarized in a two-day seminar in the winter of 1982, which was attended by company and government geologists (Mellil'l]er, 1982a, b). Also, re!X)rts are in preparation that will cover specific applications and new developrnents in the analysis of lithogeochernical data.

'TWO new developnents are briefly presented here. '.!he first is the definition of a data file format for lithogeochemical data, which was carried out with the financial sup!X)rt of Saskatchewan Energy and Mines. The second is the design of a computer system for the interpretation of lithogeochemical data, and is part of SRC's core Lithogeochernistry Program.

The Lithogeochemistry Data File

A re!X)rt describillJ in detail the format and use of the Li thogeochanistry Data File (IDF) is in preparation and will be published shortly. 'Ihe purpose of IDF is to provide a computer-based standard data file structure for the codillJ, storage and retrieval of lithogeochemical data and canplementary information relevant to the interpretation of the data. 'Ille IDF was designed to satisfy two usually contradictory criteria: (1) be exhaustive enough to include all relevant information, and (2) be sufficiently canpact to allow easy manipulation and usage. This was achieved through a dual structure compriSillJ a Header File and a Master File (Fig. la).

This data file is compatible with the Geochemical Data File which is used mainly for surface geochemical data at the Saskatchewan Geological Survey (D..111n, 1978).

'Ille Header File can be used as an index and a catalog, and contains general information about each sample. '!his information is seldom

lsaskatchewan Research Council~ activity reported here received some financial support from the Saskatchewan Geological Survey. Also recorde

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This part of the file is used for data analysis and interpretation work. This file consists of several 80-column records for each sample (Fig. lb), and includes:

'Ihe location and stratigraphic codes are essentially project-dependent. 'Ihe petrographic codes are essentially pre-defined, following nomenclatures from Fblk (1974) for sedimentary rocks, Streckeisen (1976) for igneous rocks, and Williams et al. (1954) and Gilboy and Ray (unpublished) for metamorphic rocks. A hierarchy for the various codes is defined that allows compact coding of the complementary information.

(1) record-type 01: sample nwnber (shortform), location codes (X,Y,Z, flag), stratigraphic codes (unit, sub-unit), petrographic codes (rock type, metamorphic grade, texture, petrographic facies), major element analytical data (12 pre~efined fields), and card-type identifier (= 01). (2) record-type 02 to 04: each record starts

with the sample number (short form) and

Table 1. Cbmparison of characteristics of a mainframe computer and a graphics microcomputer.

Mainframe Cbmputer

(*) large memory space (eventually virtual)

(*) large data storage available

(*) high processing speed

Graphics Microcomputer

Hardware:

limited memory space

large data storage poss ible

low processing speed

System D?sign:

multi-purpose processing and outputs

mostly available on the market

Software:

(*) specialized graphic outputs

mostly developed~ user

Status of user:

customer of the computer center

no direct acquisition cost (hardware)

software cost variable

Cbst to User :

high operating cost, rates based on system usage (CPU, connect, storage , I /0, ••• )

owner/renter

acquisition cost (hardware)

high software cost (mainly in man-yearn)

(*) low operatit"B cost

!'Otes: (*) indicates which characteristics of each computer environment were det erminant in the des ign of the computer system shown in Figure 2.

CPU= central processifB unit (core memory), I/0 operations and devices.

input/out

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ends with the card-type identifier (= 02, 03, 04), and contains trace element data excluding rare earth elements. Seventeen fields are pre-defined for trace elements on each of the 02 and 03 records. '!he 04 record is open for additions as required.

(3) record-type 05 and 06: each record starts with the sample number (short form) and ends with the card-type identifier (= 05, 06), and contains rare earth element (REE) data. Eight fields are pre-defined for those REE data that are easily analyzed by neutron activation; other fields are open for additional REE data. '!he 05 record contains raw REE data, whereas the 06 record contains the chondrite-normalized

REE data (a short FORTRAN program is available for the 05 and 06 conversion) .

(4) other record-types : additional record-types will probably not be required for geochemical data for some time , as t he existing record-types accorrrnodate many combinations of C0111110n analytical data requests. card-type identifiers 91 and 92 are present ly used at SRC for the coding of X-ray dif fraction clay mineral data.

Design of a computer Environment Adapted to Geochemical Investigations

Generally, computer systems must be designed to suit particular applications under given

GEOLOGY, DATA ANALYSIS 6 COMPUTER GRAPHICS

I Host Computer i IBM 4341 I OSI MVS·Jf: S2')

I Stage of the Study ! PROJECT X

FIELDWORK

t

I Graphics System j TEKTRONIX 4051

Checking /Sorting Subfiles selection --- - - - - - --- DATA FILE

i DATA ANALYSIS

I Univariate statistics - - --- --- --Population Analysis - - ---- --- - - - - Hist ograms

I Contingency tables Correlation tables 1----- --- --Correlation Analysis - - - - - - - - - -- Bivariate plots

Description along factors Paflerns in factorial spoce

I E Histograms 1--- ----- Multivariate Analysis Bivariate plots

Description along

l 3-Dim'"'ioool plot, Simulation /Validation j-r---------geographical variables EVALUATION OF RESULTS [

Down-hole prof iles - - - ---1 Cross·section contouring

Decision • oriented characterization l

STOP

STOP

NO

R•fi"' °,:'1 A"olysi, 7 ves

INFORMATION READY FOR DECISION-MAKING_

l Hos the Property

Good Potential ? YESl

------ ~N-'-0--- ------ Pursue Proje ct ? --'Y-"'E"-5 - --- - - --- - - ---- - --~

! ORE BODY

Figure 2- A computer environment adapted to lithogeochemical investigations. applied to mineral exploration

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operational constraints. 'Ihe basic problem here is to establish a computer system that allows: (1) effective data analysis making extensive use of multivariate techniques (such as factor analysis, hierarchical classification), and (2) user-interactive g raphical analysis and visualization of the data and results from data analysis. Many organizations facing the same basic problem have solved it by implementing both of the above fuoctions in the same mainframe computer envirorunent, because of the easy accessibility of such an environment. An alternate approach i nvolves two different computer supports, each of which is specifically adapted to each of the two functions mentioned above : multivariate data analysis and graphical analysis ('!able 1) .

'Ihe general framework adopted in this alternative approach is shown in Fig. 2. The centre column of t he diagram is a flow-chart of a typical lithogeochemical study, starting with f ieldwork and ending with decision-making, and to each side are shown the tasks performed by each comput er system. To t he left i s shown the computer support provided by a mainframe environment (IBM 4341 in our case), which handles large computations and the creati on of outp.it files at the various stages of the study. 'lb the right is shown the computer s ufP()rt provided by a stand-alone local work station specialized in g raphics (TEK'IRJNIX 4050 series in our case) , which allows the user t o examine, interactively and in a flexible way, the data files c reated in the mainframe environment (raw data, factor coordinates, etc.). Electronic corrrnunication channels and procedures are required and ioclude : (1) d irect-l ine access to the mainframe computer to carry out data analysi s ; (2) direct-line link between the mainframe computer and the graphics work station for data fi l e transfer; (3) the use on the mainf rame comp.iter of a standard data file format (the IDF format; see above) and of standard editi l'l3 procedures prior to data file transfer to the graphics work station; and (4) the use of standa rd re -formatting and editirg procedures for data fi l es a t the graphics work s tation, prior t o graphical analysis.

This approach answers operational constraints experieoced by many companies and organizations by taking advantage, at the same time, of the power offered by a mainframe computer, and of the specialized nature and

low operating cost of t he graphics work station ('!able 1). Recent developnents in microcomputer technology and software will make such an approach attractive to more users by offering them more flexibility and easier interaction with their data at an overall lower direct cost.

Pcknowledgements

The Saskatchewan Geological Survey i s gra tefully acknowledged for financial support of the Lithogeochemistry 03.ta Fil e project durirg the year 1980-81; several people f rom the Saskatchewan Geological Survey helped improve an earlier version of the coding scheme, and are acknowledged here collectively for their cooperation.

'Ihe irrplementation of a system for the analysis and visualizat ion of lithogeochemical data would not be possible without the help of J.W.J. (Bill) Smith, whose constant cooperation is greatly appreciated.

Refereoces

D.lnn, C.E. (1978): Geochemical data file of northern Saskatchewan; in Surrmary of Investigations 1978, Sask. Geol. Surv., Misc . Rep. 78-10, p. 141-144.

Folk, R.L. (1974): Petrology of Sedimentary R:>cks; Hemphill Publishing Co., Austin, Texas), 182 p.

Mellirger, M. (1982a): Lithogeochemistry: basic concepts and its application t o expl orat ion - Seminar l'btes; Sask. Res. Counc., Rlbl. It>. G-740-1-D-82, 92 p.

(1982b): Effective 03.ta Analysis of (litho) geochemical data fi l es : an introduction - Seminar l'btes; Sask. REs . Counc . Ribl. It>. G-740-2-D-82, 86 p .

Streckeisen, A. (1976): To each plut onic rock its proper name; Farth Sci . Rev., v. 12, p. 1- 33.

Williams, H., 'I\.Jrner , F.J. and Gil bert, C.M. (1954): Petrography - An Introduction t o the Study of R:>cks in 'Ihin Secti ons ; W.H. Freeman and Co. , 406 p.