exploration method1

8/10/2019 Exploration Method1

1/21

Exploration Methods

ByMark Rebagliati, P.Geo., Consulting Geologist

Rebagliati Geological Consulting Ltd.

Notes byCam Stephen, .C. Stephen !"plorations

What is Mineral Exploration?

#he $ollo%ing is a summary o$ some o$ the reasons $or mineral e"ploration and o$ the e&olution through

%hich e"ploration proceeds.

Berikut ini adalah ringkasan dari beberapa alasan untuk eksplorasi mineral dan

evolusi melalui proses eksplorasi

Mineral Explorationis carried out to $ind ne% ore deposits to'a. replace deposits presently being mined(b. increase a company)s ore reser&es *assets+ in real terms(c. $ind ne% deposits in ans%er to a percei&ed change in commodity markets.

Eksplorasi Mineral dilakukan untuk menemukan cadangan bijih baru untuk:a. mengganti deposit yang sedang ditambang pada saat ini;b. meningkatkan cadangan (aset) bijih perusahaan secara riil;

c. menemukan deposit baru untuk menjawab perubahan yang dirasakan di pasarkomoditas.

Mineral Explorationis conducted %here'a. there are large areas o$ high mineral potential.b. mineral land rights can be obtained under terms %hich are reasonable and %ith long term certainty o$title.c. political and ta" regimes are percei&ed to be relati&ely $a&ourable and stable.

Eksplorasi mineral dilakukan pada:a. daerah yang besar dengan potensi mineral tinggi.

b. mineral hak atas tanah dapat diperoleh dengan persyaratan yang masuk akal dandengan kepastian jangka panjang judul.c. reim politik dan pajak yang dianggap relati! baik dan stabil.


2/21

Mineral Exploratione&ol&es$rom )primiti&e) rock outcrop prospecting in ne%, little kno%n districts, through increasingly sophisticatedand detailed geological, geophysical and geochemical sur&eys, mapping, trenching and drilling, todetailed structural geological studies and deep e"ploration drilling %here masses o$ technical data area&ailable in areas o$ high mineral potential.

Eksplorasi Mineral berevolusidari singkapan "primiti!"roll prospeksi di baru# kabupaten yang kurang dikenal#melalui semakin canggih dan geologi rinci# survei geo!isika dan geokimia#pemetaan penggalian# dan pengeboran# untuk studi rinci struktur geologi danpengeboran eksplorasi secara mendalam di mana massa data teknis yangtersedia di daerah potensi mineral tinggi.Eksplorasi ineral dilakukan dimana:a. ada daerah yang besar potensi mineral tinggi.

b. mineral hak atas tanah dapat diperoleh dengan persyaratan yang masuk akaldan dengan kepastian jangka panjang judul.c. reim politik dan pajak yang dianggap relati! baik dan stabil.

Mineral Explorationentailsa. study o$ historical technical mineral related data(b. systematic regional geological, geochemical and geophysical sur&eys usually carried out by theGeological Sur&ey o$ Canada %ithin Canada or by -nited Nations assisted programs in third %orldcountries(c. regional geological, geophysical and geochemical sur&eys in selected districts by mining companies or

consortiums o$ companies *syndicates+(d. acuisition o$ mineral properties by option $rom /unior companies or indi&idual prospectors, by claimstaking or by application to go&ernments $or e"ploration permits *N0#+ or e"ploration concessions(e. increasingly detailed le&els o$ mapping and sur&eying, o&erburden and rock trenching, sampling o$rock1mineral e"posures, &arious types o$ drilling *percussion, re&erse circulation, diamond drill+,stripping, bulk sampling, underground de&elopment and test milling.

2 Mineral Prospect e&ol&es through success$ul e"ploration $roma. a mineral occurrence *ra% minerali3ed outcrop+ tob. a mineral prospect *indication o$ economic minerals supported by assays, %idths, lengths+ toc. a mineral in&entory *%ith three dimensional e"ploration through drilling to indicate )possible)tonnage1grade+ to

d. a mineral resource *%ith more detailed three dimensional e"ploration to pro&e )probable)tonnage1grade+ toe. a mineable ore reser&e *%ith completion o$ a positi&e $easibility study and mine de&elopment topro&ide a )pro&en) tonnage and grade+.


3/21

What is an Exploration Target?

or

What are You Looking For?

4b&iously the goal o$ e"ploration is to $ind an economic mineral deposit. #he dimensions o$ such adeposit may be &ery small %hen compared %ith the area to be searched, and the probability is that the ore3one %ill be co&ered by ice, lakes, s%amp, soil and possibly by considerable depths o$ barren rock. #hemethods o$ search %ill be discussed in the $ollo%ing pages o$ this paper, but a tongue in cheek typicalscenario %ould be as $ollo%s'

#he traditional pick and hammer prospector is looking $or an outcrop, or a displaced boulder, %hich isminerali3ed and %hich %ill gi&e him a clue to the e"istence o$ a minerali3ed 3one. 2 signi$icant golddisco&ery may be in the $orm o$ a &ein 5 to 6 $eet %ide and 788 $eet long. #he gold %ill not be &isiblee"cept in e"ceptional cases and the &ein %ill be co&ered by si" $eet o$ soil material. 9ence, to besuccess$ul, the prospector must $ind a %eathered out $ragment o$ the uart3 &ein, grind it in a mortar and

pestle, pan out three tiny gold :colours:, stake his claims and ha&e $aith that there is a mine there. 9e mayspend se&eral seasons digging trenches looking $or the source o$ the gold bearing $loat.

Geophysicists %ill choose a $a&ourable geological district and %ill $ly air sur&eys co&ering many suaremiles. #hey %ill be looking $or a particular type o$ magnetic or electromagnetic pattern. 4n completiono$ the sur&ey, the maps %ill sho% do3ens, perhaps hundreds, o$ anomalous patterns. #he ore body, i$ thereis one, could be located beneath one o$ the most inconseuential looking o$ those anomalies. ;t maye&entually be $ound by the 0ith the e"ception o$ the rare bonan3a type o$ mineral disco&ery such as the richsil&er &eins in the Cobalt district o$ 4ntario, %hich produced some ?@8,888,888 ounces sil&er bet%een


4/21

lo%er grades, in the order o$ to


5/21

speci$ic gra&ity o$ ?.8 %ould contain


6/21

Regulations go&erning claim staking in Canada &ary $rom pro&ince to pro&ince and territory to territory.#he method o$ claim staking in the -nited States is generally uni$orm $rom state to state under a ederal2ct. Most commonly, the prospector %ill stake claims by erecting %ooden posts, usually A inches suareby A $eet high, at the corners o$ each claim. Se&eral claims can be staked in a group to co&er the desiredarea. #he indi&idual prospector may not be able to a$$ord the annual assessment %ork costs to maintain alarge claim group and he should there$ore stake his key claims to protect the most important mineralsho%ings at the least cost. ;n de&eloping a mine, mining companies %ill reuire a signi$icant area %ithin%hich to de&elop the mineral deposit, to e"plore $or e"tensions to that deposit, or to $ind related deposits,to erect a mining plant, and to pro&ide space $or %aste dumps and tailings ponds.

#he &ast ma/ority o$ mineral occurrences disco&ered by prospectors do not de&elop into mines. 2s aresult there are many claims or groups o$ claims staked and in good standing at any one time %hich %illbe recei&ing a minimum o$ e"ploration e$$ort. 0ith changes in basic geological or metallurgicalkno%ledge, accessibility, metal prices, or uses and changes in market acti&ity, any one o$ those claimgroups may become desirable and undergo $urther, more ad&anced e"ploration. #he time period bet%eenthe disco&ery o$ a mineral occurrence and de&elopment o$ a mine is usually uite long e"cept in the case

o$ a $e% spectacular disco&eries. #he shortest that ; am a%are o$ %as $or the Cassiar 2sbestos mine,disco&ered in


7/21

pro&ince, %as intimately tied to de&elopment o$ rail%ay transportation. More recently, copper andmolybdenum concentrates $rom the 9ighland Ealley, Gibralter, !ndako and other mines in central B.C.ha&e been shipped by rail. #he large coal de&elopments ha&e depended on rail transportation andde&elopment o$ port $acilities at Roberts Bank and at Prince Rupert. #he 0hite Pass and Hukon rail%ay%as, $or many years, a &ital link $rom the coast in to the Hukon to connect %ith transportation systemsde&eloped out o$ 0hitehorse o&er %hich mineral concentrates $rom 0hitehorse Copper, Deno 9ill, aroand other deposits %ere shipped.

Fe&elopment o$ adeuate road systems, o&er the last thirty years in particular, has replaced most o$ the$ormer %ater%ays transportation and made rail transportation less important e"cept $or certain bulkcommodities such as coal. ;n


8/21

de&elopments in aerial photography, instrumentation $or map making, de&elopment o$ geophysicalinstrumentation and use o$ satellite imagery. Canada has also been $ortunate in maintaining ci&iliancontrol o$ mapping procedures, in contrast to military control, since the latter results in limited access tomaps, as in some countries around the %orld today.

#opographic mapping by :track: sur&eys, and by increasingly sophisticated, but laborious, sur&eymethods, made a giant step $or%ard %ith the de&elopment o$ aerial photography and the instrumentationto produce accurate maps $rom those photographs. #oday, accurate topographic maps are a&ailable onse&eral map scales $or all o$ Canada. #his map base pro&ides $or accurate geological and other mappingas reuired. 0ith the compilation o$ accurate geological in$ormation the e"plorationist has the basicin$ormation to determine areas o$ high mineral potential depending on the commodity being sought.

2erogeophysical sur&eys pro&ed their &alue uickly a$ter their introduction in


9/21

proportion to the total $inancing a&ailable to him. 9o%e&er, e&en the best e"plorationist must ha&e some$inancing you can)t $ind a mine unless you mo&e some dirt.

P#"PE#TY E/PL"#!TI"+

0hether a mineral property is acuired by disco&ery and staking by a prospector, or by staking, option orpurchase by a mining company, a program o$ property e"ploration is necessary to in&estigate its mineralpotential. Generally, the e"ploration program %ill consist o$ se&eral phases, %ith each successi&e phasebeing /usti$ied by positi&e results generated by earlier phases.

I-1. $E"L"$I!L M!PPI+$

4ne o$ the cheapest, most necessary, and too o$ten neglected, phases o$ property e"ploration is

preparation o$ a comprehensi&e, detailed and accurate geological map. #o produce a map, some sort o$ground control is necessary.

;n some cases, geological mapping o$ a preliminary or reconnaissance nature %ill be conducted by paceand compass or tape and compass sur&eys by the geologist. Fepending on the si3e o$ the property and theskill o$ the geologist this type o$ %ork can produce &aluable in$ormation. 9o%e&er, %hen you seere$erence to :tape and compass: sur&eys, you should remember that this is the cheapest, most cursory,type o$ sur&ey.

#he accuracy and detail o$ preliminary mapping can be enhanced by using air photos to help locateoutcrops and to control tra&erses. #his stage can be upgraded cheaply by using enlarged air photos and,again, by using orthophoto maps $or basic topographic control. !ach step adds some additional cost, but italso impro&es the accuracy and detail o$ the resulting map. 4rthophoto maps are produced $rom mosaicso$ air photos corrected $or distortion and ad/usted to %hate&er sur&ey control is a&ailable. #he map isproduced using stereo plotters and sho%s contour lines $or ele&ation as %ell as roads, streams, $orestedareas, etc. 2 good ortho photo map %ill be accurate %ithin a $e% metres. ;ts cost %ill be in the order o$6,888 to


10/21

2s %ork progresses on a property, and as 3ones o$ particular interest are identi$ied, those 3ones %ill bemapped and e"amined in more detail reuiring locali3ed maps at scales ranging $rom


11/21

Belo% the )B) hori3on the soil is generally gray in colour. #his is the )C) hori3on. ;$ the sur$ace isunderlain by glacial till the )C) hori3on %ill simply grade into the ra% glacial till. Glacial till, composed o$unsorted boulders, gra&el and clay, is o$ten imper&ious to ground %ater transport o$ metallic ions $rom theunderlying bedrock and, as a result, soil sample sur&eys are o$ limited use and reliability in such areas.

;$ the )C) hori3on is underlain by bedrock the soil may be directly deri&ed $rom the %eathered rock. 2s the)C) hori3on is penetrated to greater depth, more and more rock $ragments %ill be encountered until thesolid bed rock is reached. ;n such areas soil sampling can be &ery e$$ecti&e since the soils should re$lectany minerali3ation present in the parent rock. Mo&ement o$ ground%ater %ill also ha&e dispersed metallicions up into the )B) hori3on and laterally into streams, producing both silt and soil anomalies $or thegeochemist to $ind.

;n nonglaciated areas and in more tropical climates, in situ %eathering results in saprolitic soils andlateritic soils %hich ha&e di$$erent characteristics than the soils in temperate climates. Geochemicalsur&eys are, ho%e&er, e$$ecti&e %hen these local conditions are recognised. ;n arid regions there may not

be su$$icient ground%ater percolation to bring metallic ions to sur$ace and normal soil sampling may notbe e$$ecti&e.

Geochemical sur&eys may also be conducted using rock chips $rom outcrops, talus or rocky debris.Biogeochemical sur&eys may use lea&es, t%igs or bark in $orested regions or plants such as sage brush inarid regions.

2nalytical procedures ha&e ad&anced by leaps and bounds since the


12/21

Magnetometers are instruments designed to precisely measure the natural magnetic $ield o$ the earth at aparticular point. #he earth)s magnetic $ield, at any such particular point, is in$luenced by the character o$the nearby magnetic, or relati&ely nonmagnetic rocks.

Sur&eys are normally conducted on grid lines, %ith readings being taken at speci$ic inter&als along thoselines. 2s indicated abo&e, grid lines may be spaced at distances &arying $rom 78 to ?88 metres. Magneticreadings along such lines may be taken at inter&als %hich &ary $rom 78 metres to as little as 7 metres.Closer spacing is reuired to detect narro% bodies %ith small magnetic contrast.

Certain minerals, principally magnetite and pyrrhotite, possess natural magnetism, and it is the relati&edistribution o$ these t%o minerals %hich produces the magnetic pattern outlined by a magnetometersur&ey. Both minerals, depending on their $orm and metamorphic history, may be &ariably magnetic,strong to relati&ely %eak, especially in the case o$ pyrrhotite. #he distribution o$ these minerals in therock $ormations may &ary $rom trace disseminations to massi&e minerali3ation and thereby in$luence theearth)s magnetic $ield locally.

;n practice, the instrument operator carries the magnetometer $rom sur&ey station to sur&ey station andrecords the total magnetic $ield, or perhaps only the &ertical component o$ the magnetic $ield, at eachstation. #he readings are corrected $or diurnal changes in the earth)s magnetic $ield and the results areplotted in plan or pro$ile $orm. Modern euipment stores the readings in memory, corrects those readingsto base station records o$ diurnal changes, and can be connected directly to plotters to produce the$inished contour map %ith &ery little manual manipulation.

#he type o$ economic minerali3ation sought may not, itsel$, be magnetic. #he presence o$ thatminerali3ation may be detected so long as there is some relati&ely direct association bet%een that mineraland certain magnetic minerals or to certain rock types %hich can be mapped by magnetic sur&eys. 2nob&ious e"ample %ould be gold minerali3ation associated %ith iron $ormation. Since the iron $ormationcontains magnetite, and in some gold bearing 3ones pyrrhotite as %ell, the magnetometer can be used to

outline the iron $ormation hori3on. 9o% to $ind the gold %ithin the iron $ormation is another story. Goldmay also be hosted by skarn deposits, as at the ortitude mine, Ne&ada, and the skarn host can be outlinedbecause o$ the magnetite and1or pyrrhotite usually associated %ith this rock type.

;n the case o$ some porphyry copper type orebodies the minerali3ing $luids ha&e destroyed the magnetiteassociated %ith the original intrusi&e or &olcanic rocks. Magnetic sur&eys %ould outline positi&emagnetic anomalies o&er the unaltered rock $ormations. #he e"ploration target %ould be the relati&emagnetic lo%s %ithin these $ormations %here magnetite has been altered to a nonmagnetic mineral, suchas pyrite.

Magnetometer sur&eys are e"tremely use$ul in interpretation o$ geological data. Rock outcrop a&ailable tothe geologist $or mapping is limited to those areas o$ &isible rock. Most o$ the sur$ace is co&ered by soil,s%amps, lakes, etc. 2s a result the geologist may ha&e only a $e% percent outcrop to map. 2

magnetometer sur&ey %ill measure the relati&e magnetic patterns o$ the rock $ormations and allo% thegeologist to in$er rock contacts, $aults and other structures to enhance the in$ormation on the geologicalmap.

I-3. )LF-EM 4)E#Y L"W #!%I" F#E5E+Y ELET#"-M!$+ETI6 )EY&

Radio transmitters, used primarily by the military, ha&e been established at se&eral locations around the%orld. #he most important, %ith regards to e"ploration in our portion o$ North 2merica, are the stations


13/21

at 9a%aii, Seattle, Panama and 2nnapolis. #hese stations broadcast at $reuencies bet%een


14/21

$orm a conducti&e body like a sheet o$ metal, in e$$ect. #he abo&e minerals are good conductors and $ormcomponents o$ many economic massi&e sulphide bodies. 9o%e&er these same ore bodies usually containa greater or lesser content o$ 3inc in the $orm o$ the 3inc sulphide, sphalerite, %hich is not a conductor.#he anomaly o&er a massi&e sulphide 3one &ery high in 3inc content may there$ore be %eak and illde$ined. or e"ample, the Chisel Lake, Manitoba, massi&e sulphide deposit %as indicated by a &ery %eakanomaly and it %ould not ha&e been drilled under normal conditions. #he 9udson Bay Mininge"ploration policy %as to drill all !M anomalies and, as a result, this %eak anomaly %as drilled $rom theice o$ Chisel Lake and a &ery rich orebody %as $ound.

!M sur&eys %ill detect conducti&e 3ones caused by minerals or rock $ormations other than the economicminerals mentioned abo&e. Chie$ o$ these :decoy: elements is graphite, %hich is &ery common in certainrock $ormations and in $ault and shear 3ones. Pyrite and pyrrhotite $orm many barren sulphide bodies%hich are good conductors, but are non economic. 0et $ault or shear 3ones may also act as conductorsthough they are generally %eakly conducti&e.

I-8. IP 4I+%E% P"L!#I*!TI"+6 )EY&

;P sur&eys are ground sur&eys conducted along grid lines %ith readings taken at recei&ing electrodesplanted in the earth and mo&ed $rom station to station. #hese electrodes, connected to a recei&er, measurethe )chargeability) and )resisti&ity) e$$ects o$ current $orced into the ground and bedrock by a transmitterthrough transmitter electrodes. #he $reuency o$ the current used %ill be in the range o$ 8.< to


15/21

I-9. :E: &!+ )EY&

2 relati&ely ne% application o$ the ;P sur&ey method is a$$orded by the )!) scan sur&ey. #his method doesa%ay %ith the procedure o$ ha&ing the transmitter and recei&er electrodes $ollo%ing each other do%nsingle sur&ey lines as is done in the ;P sur&ey. ;nstead, the transmitter remains in one location and up to


16/21

F!E &!MPLI+$, T#E+I+$

rom the time a prospector $irst $inds a piece o$ )$loat) minerali3ation until %ell on in the process o$e"ploring a minerali3ed body, sur$ace sampling is important in assessing the probable &alue o$ themineral disco&ery made. Procedures such as pitting and trenching are carried out to assist in the mappingand sampling because, as a rule, the sur$ace o$ the minerali3ation is obscured by &arious types o$o&erburden, or it is %eathered and leached to some depth, thereby obscuring the nature o$ theminerali3ation.

Commonly, one o$ the earliest types o$ samples taken is %hat is called a :grab: sample. 0hen properlyused, the term :grab: sample should mean a composite sample made up o$ random pieces, or hand$uls, o$similarsi3ed pieces taken $rom a rubble area or $rom a dump o$ minerali3ed rock, and roughlyrepresentati&e o$ all the material present. ;n practice, ho%e&er, the term :grab: sample is used to describe%hat is actually a :selected: sample and is, typically, a sample o$ the richest minerali3ation a&ailable.

0hen you see assay results published in a ne%s release, or in a report, and the term :grab: sample isused, you should suspect that the assay represents the highest grade material noted on the prospect.

0hen prospectors $ind a rock outcrop %ith minerali3ation, they %ill usually be looking at something o$&ery limited e"tent and, in their imagination, the possibilities $or e"tension o$ that sho%ing are boundless.;$ they didn)t think that %ay they %ould ha&e to gi&e up prospecting and become accountants.

4$ten the prospector %ill be attracted by a rusty rock sur$ace due to o"idation o$ sulphide minerals. ;$ theo"idation is shallo%, he can generally hammer o$$ a piece and can then see the minerali3ation on a $reshsur$ace using a magni$ying glass to better determine the identity o$ the minerals present. No% theprospector)s thinking has been progressi&ely narro%ed do%n $rom consideration o$ the ?66,577 suaremiles o$ British Columbia to the se&eral tens o$ thousands o$ suare miles o$ the 4mineca district, to the5,6A8 suare miles o$ the McConnell Lake map sheet, to the 7 suare miles o$ the creek drainage he

$ound a piece o$ minerali3ed $loat in and he is no% $ully concentrated on se&eral t%o or three millimetrestreaks and grains o$ chalcopyrite in the rock under his hand lens. 9e has to hope that minerali3ationcontains a $raction o$ a tenth o$ an ounce o$ gold per ton o$ rock in order to make this minerali3ationeconomic.

;n all likelihood the prospector %ill chip o$$ t%o or three pounds o$ the richest material e&ident, put it in abag %ith a numbered sample tag, and e&entually send it o$$ to an assay lab to see ho% much copper and,possibly, gold and sil&er that sample contains.

0hat the prospector should do, ho%e&er, is to clean o$$ the rock sur$ace to e"pose as great a %idth o$minerali3ation as possible *sur$ace stripping+, di&ide up the sur$ace o$ the e"posure by rock type,structure and mineral content, measure the %idth o$ each separate segment and, $rom each segment, chipa representati&e sample o$ the material *measured chip sample+. Properly e"amined, measured, sampled

and described, the data %ill be o$ much greater &alue in the days and %eeks to come %hen an option, anda budget, are being sought to do $urther %ork on the property.

4nce a disco&ery is made, the geological mapping, geochemical and geophysical sur&eys describedabo&e may be undertaken. 4n the minerali3ed sho%ing attempts %ould be made to clean the sur$ace, tocarry out systematic sur$ace sampling, and, as o&erburdened areas are reached, to start test pitting andtrenching.


17/21

;$ a su$$icient area can be cleaned, and the sur$ace is not too %eathered or o"idi3ed, sampling should bedone at right angles to the strike *direction+ o$ the long a"is o$ the mineral sho%ing. #he 3one should bemarked o$$ in segments so that the &arious types or grades o$ minerali3ation are sampled separately.Samples should also be taken beyond the contacts o$ the mineral 3one, into the %all rocks, to check $ormineral &alues in the %alls or %ithin alteration 3ones along the margins o$ the &isible minerali3ation.

Separate lines o$ samples should be taken at inter&als along the strike o$ the minerali3ed 3one. ;n the caseo$ narro%, high grade, or erratically minerali3ed precious metal &eins, these sets o$ samples may be takene&ery one or t%o metres. #he %idth represented by each sample is measured. #hese sample %idths areimportant in recording the total %idth o$ the 3one, but they are indi&idually more important in calculatingthe a&erage assay &alue o$ the 3one. 2s an e"ample, assume a shear 3one is $ound %hich contains se&eralhigh grade silici$ied 3ones and &eins. #he results o$ one line o$ samples across such a 3one may be as$ollo%s'

Sample No. Rock #ype Gold 2ssay

*g1t+ Sample 0idth * metres+ 2ssay" 0idth

8?< 0allrock O8.85


18/21

;$ a company %ere to issue a ne%s release saying :the a&erage o$ the assays obtained across the 3one is


19/21

%hich compressed air *in the case o$ dry ground+, or %ater *in the case o$ %et ground+, is passed. #he air,or %ater, e"its through the center o$ the bit and $orces the drill cuttings up the hole through the spacebet%een the drill rods and the drill hole %all. 2t sur$ace the drill cuttings are passed through a samplesplitter and a sample consisting o$


20/21

around the drill bit $ace and returned up the hole bet%een the drill rods and the drill hole %all carrying thedrill cuttings *sludge+ %hich ha&e been produced by the $ace o$ the drill bit. #he drill core consists o$ thecolumn o$ rock remaining in the center o$ the bit as it cuts a circular hole. #his drill core, as the holeprogresses, stands %ithin the bit and %ithin the $ollo%ing core tube %hich is usually


21/21

o$ sur$ace e"ploration and o$ all the practical sur$ace drilling to outline a mineral deposit, a point isreached %here underground e"ploration becomes necessary in order to in&estigate the deposit in detail.

;n $lat topography, as in most parts o$ the PreCambrian Shield, access to the mineral deposit may reuiredri&ing a )decline) or sinking a )sha$t) to reach the minerali3ed 3one to be e"plored. ;n rugged topographythe 3one may be reached by dri&ing a )decline) or an )adit). 2ppro"imate costs $or such de&elopmentopenings are gi&en in ohn #ully)s paper on mining methods accompanying these lectures. Su$$ice it tosay that the cost o$ these openings is an order o$ magnitude greater than $or any preceding e"plorationphase and that some type o$ pre$easibility report, uite e"pensi&e in itsel$, %ould be reuired be$oreproceeding.

-nderground e"ploration is designed to in&estigate the mineral deposit $or continuity o$ minerali3ation,$or rock stability and detailed structure, $or possible %ater $lo%s, and to pro&ide bulk samples o$signi$icant tonnage $or metallurgical studies and test milling.

Bulk samples range $rom one ton to

exploration method1

Documents