储量定义美国资源局精.docx

储量定义美国资源局精.docx

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储量定义美国资源局精

192

APPENDIXA

AbbreviationsandUnitsofMeasure

1carat（metric（diamond=200milligrams

1flask（fl=76pounds,avoirdupois

1karat（gold=onetwenty-fourthpart

1kilogram（kg=2.2046pounds,avoirdupois

1longton（lt=2,240pounds,avoirdupois

1longtonunit（ltu=1%of1longtonor22.4poundsavoirdupois

longcalcinedton（lct=excludeswaterofhydration

longdryton（ldt=excludesexcessfreemoisture

Mcf=1,000cubicfeet

1metricton（t=2,204.6pounds,avoirdupoisor1,000kilograms

1metricton（t=1.1023shortton

1metrictonunit（mtu=1%of1metrictonor10kilograms

metricdryton（mdt=excludesexcessfreemoisture

1pound（lb=453.6grams

1shortton（st=2,000pounds,avoirdupois

1shorttonunit（stu=1%of1shorttonor20pounds,avoirdupois

shortdryton（sdt=excludesexcessfreemoisture

1troyounce（troz=1.09714avoirdupoisouncesor31.103grams

1troypound=1

2troyounces

APPENDIXB

DefinitionsofSelectedTermsUsedinThisReport

TermsUsedforMaterialsintheNationalDefenseStockpileandHeliumStockpile

UncommittedinventoryreferstothequantityofmineralmaterialsheldintheNationalDefenseStockpile.Nonstockpile-gradematerialsmaybeincludedinthetable;wheresignificant,thequantitiesofthesestockpiledmaterialswillbespecifiedinthetextaccompanyingthetable.

Authorizedfordisposalreferstoquantitiesthatareinexcessofthestockpilegoalforamaterial,andforwhichCongresshasauthorizeddisposaloverthelongtermatratesdesignedtomaximizerevenuebutavoidunduedisruptionoftheusualmarketsandfinanciallosstotheUnitedStates.

DisposalplanFY2011indicatesthetotalamountofamaterialintheNationalDefenseStockpilethattheU.S.DepartmentofDefenseispermittedtosellundertheAnnualMaterialsPlanapprovedbyCongressforthefiscalyear.FY2011（fiscalyear2011istheperiodOctober1,2010,throughSeptember30,2011.Formineralcommoditiesthathaveadisposalplangreaterthantheinventory,actualquantitywillbelimitedtoremainingdisposalauthorityorinventory.Notethat,unliketheNationalDefenseStockpile,heliumstockpilesalesbytheBureauofLandManagementundertheHeliumPrivatizationActof1996arepermittedtoexceeddisposalplans.

DisposalsFY2011referstomaterialsoldortradedfromthestockpileinFY2011.

DepletionAllowance

Thedepletionallowanceisabusinesstaxdeductionanalogoustodepreciation,butwhichappliestoanorereserveratherthanequipmentorproductionfacilities.Federaltaxlawallowsthisdeductionfromtaxablecorporateincome,recognizingthatanoredepositisadepletableassetthatmusteventuallybereplaced.

193APPENDIXC—ReservesandResources

Reservesdataaredynamic.Theymaybereducedasoreisminedand/ortheextractionfeasibilitydiminishes,ormorecommonly,theymaycontinuetoincreaseasadditionaldeposits（knownorrecentlydiscoveredaredeveloped,orcurrentlyexploiteddepositsaremorethoroughlyexploredand/ornewtechnologyoreconomicvariablesimprovetheireconomicfeasibility.Reservesmaybeconsideredaworkinginventoryofminingcompanies’supplyofaneconomicallyextractablemineralcommodity.Assuch,magnitudeofthatinventoryisnecessarilylimitedbymanyconsiderations,includingcostofdrilling,taxes,priceofthemineralcommoditybeingmined,andthedemandforit.Reserveswillbedevelopedtothepointofbusinessneedsandgeologiclimitationsofeconomicoregradeandtonnage.Forexample,in1970,identifiedandundiscoveredworldcopperresourceswereestimatedtocontain1.6billionmetrictonsofcopper,withreservesofabout280millionmetrictonsofcopper.Sincethen,about400millionmetrictonsofcopperhavebeenproducedworldwide,butworldcopperreservesin2011wereestimatedtobe690millionmetrictonsofcopper,morethandoublethosein1970,despitethedepletionbyminingofmorethantheoriginalestimatedreserves.Futuresuppliesofmineralswillcomefromreservesandotheridentifiedresources,currentlyundiscoveredresourcesindepositsthatwillbediscoveredinthefuture,andmaterialthatwillberecycledfromcurrentin-use-stocksofmineralorfrommineralsinwastedisposalsites.Undiscovereddepositsofmineralsconstituteanimportantconsiderationinassessingfuturesupplies.USGSreportsprovideestimatesofundiscoveredmineralresourcesusingathree-partassessmentmethodology（SingerandMenzie,2010.Mineral-resourceassessmentshavebeencarriedoutforsmallparcelsoflandbeingevaluatedforlandreclassification,fortheNation,andfortheworld.

ReferenceCited

Singer,D.A.,andMenzie,W.D.,2010,Quantitativemineralresourceassessments—Anintegratedapproach:

Oxford,UnitedKingdom,OxfordUniversityPress,219p.

PartA—Resource/ReserveClassificationforMinerals