Origins of Chalcocite Defined by Copper Isotope Valuesdownloads.hindawi.com/journals/geofluids/2018/5854829.pdf · 2019-07-30 · copper sulde in supergene enrichment environments

Research ArticleOrigins of Chalcocite Defined by Copper Isotope Values

R Mathur 1 H Falck2 E Belogub3 J Milton2 M Wilson4 A Rose5 and W Powell6

1Department of Geology Juniata College Huntingdon PA USA2Northwest Territories Geological Survey Yellowknife NT Canada3Institute of Mineralogy UB RAS Miass Russia4Carnegie Museum of Natural History Pittsburgh PA USA5Pennsylvania State University State College PA USA6CUNY Brooklyn College New York City NY USA

Correspondence should be addressed to R Mathur mathurjuniataedu

Received 30 August 2017 Accepted 25 December 2017 Published 28 January 2018

Academic Editor Xing Ding

Copyright copy 2018 R Mathur et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The origin of chalcocite is explored through a comparison of the copper isotope values of this mineral from supergene enrichmentsedimentary copperred bed and high-temperature hypogene mineralization around the world Data from the literature and thedata presented here (119899 = 361) reveal that chalcocite from high-temperature mineralization has the tightest cluster of values of12057565Cu = 0 plusmn 06 in comparison to sedimentary copperred bed 12057565Cu = minus09 plusmn 10 and supergene enrichment 12057565Cu = +19 plusmn18 Although the errors of the means overlap large portions of the data lie in different values allowing for distinguishing rangesfor 12057565Cu of ltminus1permil for sedimentary copperred bed between minus1 and +1 for high-temperature hypogene and gt+1 for supergeneenrichment chalcocite The copper isotope values of sedimentary copperred bed and supergene enrichment chalcocite are causedby redox reactions associated with the dissolution and transport of copper whereas the tighter range of copper isotope values forhypogene minerals is associated with processes active with equilibrium conditions

1 The Importance of Chalcocite

Chalcocite is an economically important mineral of copperCrystallographic trace element mineral assemblage andtextural observations and measurements have been used tounderstand the origin of thismineral [1ndash3]Models regardingthe genesis of chalcocite vary substantially with conditionsranging from the highest temperature hydrothermal systemsto ambient temperature weathering solutions and no singlemodel can be used to constrain how all of the occurrences ofthis mineral formed

To contribute to the understanding of how chalcociteforms and what geologic processes lead to its concentrationthis study analyzes copper isotope values from the literatureand from new data presented here The data are used todistinguish different types of mineral deposits ultimatelyrelated to the geological processes that lead to the generationof this essential economically significant mineral

2 Types of Chalcocite Considered andDeposits Analyzed

Thegenesis of chalcocite can be categorized into three generalmodels (1) hypogene hypothermal ores that precipitate fromhydrothermal fluids (gt150∘C) (2) red bed and stratiformldquosedimentaryrdquo ores that precipitate from fluids that circulatethrough sedimentary basins at temperatures lt150∘C and(3) supergene enrichment ores that precipitate from low toambient temperature oxidative fluids in near-surface envi-ronments

The copper isotope composition of chalcocite in thesedeposits varies due to several factors In general the pri-mary source of most copper deposits is a large body ofmagmatic rock with an isotopic composition of approx-imately 12057565Cupermil = 0permil (where 12057565Cupermil = ((65Cu63Cu) sample(65Cu63Cu) Nist 976 minus 1) lowast 1000) [4ndash6]However the relatively minor variations in the isotopic com-position of Cu of the dominantly magmatic source material

HindawiGeofluidsVolume 2018 Article ID 5854829 9 pageshttpsdoiorg10115520185854829

2 Geofluids

Table 1 Summary of deposits analyzed and sources of data considered

Deposit Type of chalcocite Data sourceButte Montana Hypogene Mathur et al 2009 Wall et al 2011Canarico Peru Hypogene Mathur et al 2010Rippoldsau Germany Hypogene Markl et al 2006Coates Lake Canada Sedimentary Cu This documentCoppermine Canada Sedimentary Cu This documentDikulushi DRC Sedimentary Cu Haest et al 2009Kupferschiefer Germany Sedimentary Cu Asael et al 2009Cu Michigan Sedimentary Cu This document Larson et al 2003 Mathur et al 2014Timna Israel Sedimentary Cu Asael et al 2007 Asael et al 2009 Asael et al 2012Udokan Russia Sedimentary Cu This documentBayugo Philippines Supergene Braxton et al 2012Chuquicamata Chile Supergene Mathur et al 2009Collahuasi Chile Supergene Mathur et al 2009El Salvador Chile Supergene Mathur et al 2009Inca de Oro Chile Supergene Mathur et al 2014PCDs Iran Supergene Mirenjad et al 2010 Asadi et al 2012Morenci Arizona Supergene Mathur et al 2010Ray Arizona Supergene Mathur et al 2010 Larson et al 2003Silver Bell Arizona Supergene Mathur et al 2010Spence Chile Supergene Palacios et al 2010

will influence the possible values of Cuwithin the ore solutionand the associated chalcocite More importantly the initialisotopic composition can be affected by fractionation duringleaching of Cu from the source as well as during precipitationof secondary chalcocite The nature of the fractionation isdependent upon the specific dissolution and precipitationprocesses (eg bonding within the solid or in solution)and the physical and chemical conditions (eg temperatureredox) with redox processes leading to stronger bondingenvironments for 65Cu in oxidized products and 63Cu inreduced products In addition the extent of extraction ofcopper from the source and the fraction of copper that isreprecipitated in the ore-forming processes affect fraction-ation If 100 of the Cu is extracted and precipitated thenno evidence of fractionation will be preserved However ifthe chemical transfer is incomplete then the various phases(primary mineral solution and secondary mineral) mayhave differing isotopic compositions based on the degree offractionation

Copper in chalcocite that is associated with hypogenehydrothermal ores is derived from a magmatic hydrothermalfluid or is extracted from country rocks at high temper-atures Moreover extensive studies showed that hypogenehydrothermal copper minerals such as chalcopyrite andbornite do not display appreciable fractionation (gtplusmn1permil) [7ndash11] Similarly chalcocite that precipitated from these high-temperature fluids is not anticipated to contain copper thathas undergone significant copper isotope fractionation Thisstudy includes 18 chalcocite samples from three hypogenedeposits (Table 1) including an archetypal example of hypo-gene chalcocite at Butte Montana [12]

In contrast to hypogene chalcocite the copper associatedwith red bed and stratiform types of chalcocite is derivedfrom leaching of sandstones and shales at low temperaturesby residual brines The source rocks contain Cu2+ that ishosted within detrital mafic minerals or is absorbed ontoFe hydroxides which are formed as products of weatheringand diagenesis A redox shift is thought to occur duringtransport of copper in these formational waters because theinitial state of copper in theweathered sourcematerial is Cu2+but the copper is mobilized in the Cu+ state as CuCl0 orsimilar aqueous species [13 14]Thus the reaction required tomobilize copper for sedimentary deposits involves the reduc-tion of copper which would be expected to induce isotopicfractionation favoring 63Cu assuming that copper extractionfrom the source material was incomplete Dissolved copperremains unchanged until it encounters organic material orother reductants within the sediment where Cu1+ is fixed bysulfide or by reaction with preexisting pyrite [15]

Six locations at which chalcocite occurs within ldquosedimen-taryrdquo copper deposits (a total of 161 samples) are consideredherein (Table 1) Literature sources that reported chalcocite asthe major phase present in the copper isotope analyses wereused [16ndash19] along with new data from Coates Lake CopperMine Michigan and Udokan Data from Kupferschiefer[20] Michigan [21 22] and Coates Lake [23] provide classicexamples of sedimentary copper deposits along with theprospect Coppermine [24] Data from each of these depositsis compiled in Table 2

The copper for supergene-type chalcocite is derived byoxidative weathering of rocks or ores containing Cu sulfide

Geofluids 3

Table 2Copper isotope data from sedimentary copper type depositswhere ccmeans chalcocite and some samples reported trace bn (bornite)

Sample Location Phase 12057565Cu (per mil)1 Udokan Russia cc minus032

2 Udokan Russia cc minus004

3 Udokan Russia cc-bn 04

4 Udokan Russia bn-cc minus034


6 Udokan Russia cc-bn minus061



















9098 Coates Lake Canada cc minus367



NWT 743 B15 Coates Lake Canada cc minus028

JP77 7X1 2122 R2 42 Coates Lake Canada cc 008JP77 36984-4 33815 38 Coates Lake Canada cc minus031

NWT JP77 74121225 45 R8 Coates Lake Canada cc minus027

JP77 COATES 36984-1 1638 36 Coates Lake Canada cc minus072

NWT 7371 Coates Lake Canada cc minus026

NWT 7Y3 B111 Coates Lake Canada cc minus049

NWT JP77 644 3379 39 Coates Lake Canada cc minus020

JP77 781 422 43 R4 Coates Lake Canada cc minus038

9097 cc Coates Lake Canada cc minus201

7371 Coates Lake Canada cc 043


45 r8 Coates Lake Canada cc 062



7358 A Coates Lake Canada cc 014



NWT 7361A Coates Lake Canada cc minus078

JP77 369842 2289 37 Coates Lake Canada cc minus054



NWT KQ 74-11964 Coates Lake Canada cc minus078

CM32619 Baltic Mine Michigan USA cc 047

4 Geofluids

Table 2 Continued

Sample Location Phase 12057565Cu (per mil)CM32620 Baltic Mine Michigan USA cc minus018


CM32622 Baltic Mine Michigan USA cc minus005

jk 10 h12 Coppermine Canada cc minus069

cool rock Coppermine Canada cc minus135

ly 03 h16 Coppermine Canada cc 007

dn 04 Coppermine Canada cc minus111

nr 02 Coppermine Canada cc minus051

h13 Coppermine Canada cc minus055

dt 02 h8 Coppermine Canada cc minus007

rd 04 Coppermine Canada cc minus123

rd 04-2 Coppermine Canada cc minus124


ct 02 h3 Coppermine Canada cc minus149

ly03 Coppermine Canada cc minus010


jk01 Coppermine Canada cc minus002

(eg chalcopyrite CuFeS2) The oxidized copper is trans-

ported downward toward thewater table where it is reprecip-itated [25] Near-surface oxidation zones in porphyry copperdeposits are a classic example of this process Commonlysome Cu remains in the leached capping This incompleteoxidation reaction results in fractionated copper through theweathered profile A reduction reaction of copper at the watertable where freshmetallic surfaces of pyrite and other sulfidesare present results in the precipitation of the reduced copperDue to the increased pH at the water table and effectiveremoval of copper via precipitation onto sulfide minerals amajority of the copper is thought to be recovered from theoxidative solutions [26] Late stage covellite (CuS) normallyaccompanies supergene chalcocite further demonstratingthe reductive nature of the reaction Since reduction at thewater table is essentially complete fractionation preservedin the chalcocite from supergene enrichment will be due tothe oxidation stage weathering and so would be expected tofavor 65Cu Continual reworking of the previous supergeneenrichment layers due to uplift and erosion has beenmodeled[27 28] to illustrate how larger degrees of fractionationwouldevolve

A total of 182 samples from 10 locations are considered(Table 1) Any data from the following sources that had listedchalcocite as an analyzed phase was included [27 29ndash36]Data fromMorenci Ray Chuquicamata and Spence providetype examples of supergene enrichment in classic porphyrycopper deposits

3 The Behavior of Copper Isotopes andPredicted Differences for Redox Reactions

While many reactions can result in a shift in copper isotopevalues redox reactions have been documented to producethe most substantial changes redox reactions that result in

oxidized copper favor the 65Cu isotope whereas reactionsthat result in reduced copper favor the 63Cu isotope due tostronger bonding environments for each isotope [33 37ndash39]Experimental and empirical data support the magnitude anddirection of copper isotope fractionation during the redoxreactions [33 38 39]

In the case of oxidative reactions the weathering ofcopper sulfide in supergene enrichment environments hasbeen studied in the greatest detail Solutions that leachcopper during oxidation from the copper sulfide mineralbecome enriched in the 65Cu isotope due to a strongerbonding environment [33 38 39] Although the degree ofenrichment (fractionation factor) is different for a varietyof copper sulfides (chalcopyrite chalcocite bornite andenargite) in each case the reactions produce cupric copper(Cu+2) in solution which always has greater 12057565Cupermil thanthe starting mineral This phenomenon has been traced innatural aqueous solutions such as rivers lakes groundwaterand seawater [28 40ndash43]

Reduction reactions involving copper have not beenas thoroughly studied Laboratory experiments that reducecopper from oxidized solutions have resulted in precipitatedsolids that have lower 12057565Cupermil values than the startingsolutions [38] Modeling of copper isotopes in sedimentarycopper deposits by Asael et al [16] showed that the reduc-tion of copper during transfer to solution should favor thelighter copper isotope Thus the available data indicate thatreduction reactions favor the lighter copper isotope and thatthe products of the reduction have lower 12057565Cupermil valuesthan the starting materials Furthermore current modelsof copper behavior during redox reactions would predictthat supergene enrichment copper mineralization would beassociated with higher copper isotope values than that ofsedimentary copper deposits

Geofluids 5

Sedimentary CuHypogene oreSupergene enrichment

2

3

1

1

2

3

Evaporites

Bimodal volcanic rocks

3

Cou

nt8070605040302010

06420minus2minus4minus6minus8minus10 108

Hypogene chalcocite2

1

Oxidativetransport of Cu

Reductivetransport of Cu

훿65Cu

Leach cap훿65Cu depleted

nabla

Enrichment훿65Cu enrichedFractures

Basement rock

Red beds

Figure 1 Histogram plot combined with a cartoonmodel of copper isotope values of chalcocite formed in three different environments Datafrom the supergene group show the largest range and overlap the ranges of the other two deposit types

4 Methods for Cu Isotope Data Presented

A total of 68 new Cu isotope measurements from chalcociteare presented The chalcocite samples were handpicked fromveins or disseminations X-ray diffraction techniques wereused to identify mineral species present and those methodsare described by Mathur et al (2005) Approximately 30ndash40milligrams of powdered chalcocite was dissolved in 15mlTeflon jars containing 4ml of heated aqua regia for 12 hoursComplete dissolution was visually confirmed The solutionswere dried and copper was separated using ion exchangechromatography described by Mathur et al (2009)

Isotope measurements were conducted on ICP-MS mul-ticollectors at the University of Arizona and the PennsylvaniaState University Solutions were measured at 100 ppb andmass bias was corrected for by standard-sample-standardbracketing using the NIST 976 standard Instrumentationsetup and run conditions are described in detail by Mathuret al (2005) Errors for the analyses presented are 01permil and2120590 and error calculation is described by Mathur et al (2005)Internal cent standards were measured at both locations

during the analytical sessions and the 1838 cent 12057565Cu =002 plusmn 01 (2120590 119899 = 14)

5 Data and Its Implications

The histogram in Figure 1 compares the distribution ofcopper isotope values of 361 chalcocite samples from threedistinct environments of formation supergene enrichment(182 samples) sedimentary copper deposits (161 samples)and hypogene ores (18 samples) Each datum has an error onthe order of plusmn01permil and data are binned at 05permil incrementsAll data reported here were compared to the NIST 976standard with mass bias controlled by standard bracketing

The mean values and 1-sigma variations for supergeneenrichment chalcocite are 12057565Cu = +19 plusmn 18permil (119899 = 182)for sedimentary copper chalcocite are 12057565Cu = minus09 plusmn 10permil(119899 = 161) and for hypogene chalcocite is 12057565Cu = minus0001 plusmn06permil (119899 = 18) Although the three populations show con-siderable overlap in the weakly fractionated range 64 of thesedimentary copper measurements are less than minus08permil and

6 Geofluids

minus10

Udokan

Michigan

Morenci AZ

PCD Iran

Inca de Oro Chile

Bayugo PhilippinesCoates Lake

Kupferschiefer Silver Bell AZ

Ray AZDikulushi DRC

Timna Israel

minus8 minus6 minus4 minus2 0 2 4 6 8 10훿65Cu (per mil)

Figure 2Mean and 1120590 error plot of specific deposit types comparingthe supergene and sedimentary chalcocite from the presented data

65 of the chalcocite from supergene enrichment has 12057565Cuvalues greater than +1permil The data portrayed in this mannerindicates that the copper isotopic composition of chalcocitecan be related to deposit types with values less than minus1permilmost likely related to sedimentary copper deposits whereasvalues greater than +1permil are most likely formed undersupergene processes To further detail variations in copperisotope compositions between the two genetically distinctlower temperature deposits a deposit specific comparisonis presented in Figure 2 with 1120590 variations calculated bythe standard deviations of all presented data It is significantthat the deposit types have little overlap and lie completelywithin the ranges suggested above Despite the fact thatrange boundaries are approximate and that none of thelimiting values define sharp divide this approach providesa statistically valid means for differentiating chalcocite fromsedimentary and supergene processes based on copper iso-tope composition

Note that the variation associated with the supergeneenrichment deposits is significantly larger than that for theother environments of mineralization and almost twice thatof sedimentary copper deposits This most likely reflects thefact that these supergene systems are still active with con-tinued mobilization and migration of copper with associatedevolution of copper isotopic compositions that is the activesupergene enrichment blanket is continuing to weather andlose 65Cu during oxidation as is evident at Morenci where thetop of the enrichment blanket contains chalcocite with lowercopper isotope values than that found at deeper levels [30]

It is interesting to note that the 12057565Cu range of high-temperature hypogene chalcocite directly overlaps the 0plusmn1permilrange in 12057565Cu that has been documented in other copper-rich sulfide minerals (bornite chalcopyrite) from high-temperature hypogene mineralization as compiled by Wallet al (2011) and Saunders et al (2015)The overlap in isotopiccomposition of high-temperature hypogene chalcocite withthat of high-temperature hypogene chalcopyrite and bornite

suggests that the processes that lead to copper isotope vari-ations at elevated temperature are broadly similar regardlessof the resulting copper mineral assemblage Several studies[44ndash46] suggest that the range of copper isotope values maybe related to changes in pH or Eh or the partitioning ofCu between liquid and vapor phases as the hydrothermalsolution cools Overprinting high-temperature events couldpotentially lead to greater degrees of fractionation howevernone of the samples here have petrographic evidence tosuggest this Additional experimental work is needed toresolve the roles of different mechanisms that lead to thesesmall but measurable copper isotope variations and to decidewhether they vary systematically throughout a deposit assuggested by Mathur et al (2012) and Li et al [10]

6 Transportation of Copper andPrecipitation of Chalcocite in LowerTemperature Solutions

The hydrothermal systems being considered involve metalmigration at lt150∘C in mixtures of brine diagenetic andmeteoric fluids associated with typical sedimentary copperand supergene enrichment processes [15 25] Geochemi-cal modeling of reaction kinetics and equilibrium of theobserved mineral assemblages greatly enhanced our under-standing of how andwhymetalsmove in these environmentsIn general these studies identify the controls of coppertransfer and precipitation in these systems as complicatedand impacted by many interrelated variables such as pH Ehsalinity temperature bulk chemistry of the solution and bulkchemistry of the substrate that initiates precipitation [47ndash50]Coupledwith isotopic studies of these ores and host rocks thereaction sources and pathways can be identified

The copper in chalcocite (Cu2S) from supergene enrich-

ment and sedimentary copper deposits is hypothesized tobe mobilized and transported by two different redox reac-tions For supergene enrichment copper is oxidized frompreexisting copper minerals which are exposed to meteoricfluids during uplift and erosion These fluids are dominantlystrongly acidic due to oxidation of pyrite accompanying theCu sulfidesThe acid allows ready transport of Cu2+ As all ofthe deposits examined are still in the process of developingthe reaction has not been completed and some Cu is leftbehind in the leached zone Thus the source of the copperis well understood

In contrast copper sources in sedimentary copperdeposits are much debated [13 15] However it is agreed thata likely source of the metal is Cu2+ adsorbed onto Fe oxideswithin sandstonesThe following two reactions (Davies 1978)describe how copper adheres to the adsorption of sites of Fe-oxide surfaces (see (1)) and how it is transported (see (2))from adsorption sites

119878OH + Cu+2 (aq) 997888rarr 119878O-Cu+2 +H+ (1)

where 119878 is the surface of the Fe oxide or other minerals

H+ + 119878O-Cu+2 + 2Clminus + eminus 997888rarr CuCl2

minus (aq) + 119878OH (2)

Geofluids 7

With regard to the associated fractionation of copper iso-topes it is important to note that copper is transported in twodifferent redox states In these near-neutral solutions Cu2+ issoluble and transport is asCuCl0 or related complex ions [13]Although many different copper molecules are likely formedin associationwith carbonates sulfates and organic ligands itis the isotopic proportioning potential of the two redox reac-tions and the likelihood of partial extraction that will controlthe measured variations in the copper isotopes As shownin Figures 1 and 2 the supergene enrichment chalcocitepreserves a heavier copper isotope value which most likelyrepresents the transportation and concentration of oxidizedcopper in the supergene In contrast the reduction reactionsthat led to the transport of copper in the sedimentary copperresulted in chalcocite that has significantly lower copperisotope values

The data presented here indicate that redox reactionsassociated with copper transport are the primary means bywhich copper fractionates in low-temperature systems Atthe deposition site precipitation processes appear to have anegligible contribution to the degree of isotopic differentia-tion through fractionation For supergene enrichment copperdeposits the oxidized copper molecule is reduced during theformation of chalcocite when the oxidized waters interactwith the water table and hypogene sulfide minerals Thisreduction process is highly effective in removing copper fromsolution [47] and the essentially complete precipitation ofdissolved copper results erases the record of redox fractiona-tion in this process In sedimentary copper deposits copperthat is transported via CuCl complexes (such as CuCl

2

minus andCuCl3

2minus) does not change redox state upon precipitationThus fractionation due to electron transfer during precip-itation is not thought to occur in the sedimentary copperchalcocite

7 Conclusions

Despite the chemical complexity of the systems from whichchalcocite is produced copper isotope values in chalcociteprovide a means by which the three major sources ofchalcocite may be differentiated (1) 12057565Cu values less thanminus10 are most likely associated with sedimentary copperdeposits (2) 12057565Cu values greater than minus10 are most likelyassociated with supergene enrichment and (3) a tightlyclustered population of 12057565Cu at 00 is most consistent withhypogene ores These distinct variations in 12057565Cu values inchalcocite are controlled predominantly by redox reactionsat low temperature and equilibrium type reactions at hightemperatures Therefore copper isotope values in chalcocitecan provide insights into the genesis of chalcocite and can beused to develop improved mineralization models

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

Theauthors would like to thank J Ruiz andM Baker from theUniversity of Arizona for access and instrumentation setup

on the ISOPROBE andM Gonzalez at the Pennsylvania StateUniversity for the use of Neptune

References

[1] D A Crerar and H L Barnes ldquoOre solution chemistryv solubilities of chalcopyrite and chalcocite assemblages inhydrothermal solution at 200∘C to 350∘Crdquo Economic Geologyvol 71 no 4 pp 772ndash794 1976

[2] H T Evans ldquoCrystal Structure of Low Chalcociterdquo NaturePhysical Science vol 232 no 29 pp 69-70 1971

[3] D J Vaughan ldquoSulfidemineralogy and geochemistry Introduc-tion and overviewrdquo Reviews in Mineralogy and Geochemistryvol 61 pp 1ndash5 2006

[4] W Li S E Jackson N J Pearson O Alard and BW ChappellldquoThe Cu isotopic signature of granites from the Lachlan FoldBelt SE Australiardquo Chemical Geology vol 258 no 1-2 pp 38ndash49 2009

[5] S A Liu J Huang J Liu et al ldquoCopper isotopic composition ofthe silicate Earthrdquo Earth and Planetary Science Letters vol 427pp 95ndash103 2015

[6] E M Ripley S Dong C Li and L E Wasylenki ldquoCuisotope variations between conduit and sheet-style Ni-Cu-PGEsulfide mineralization in the Midcontinent Rift System NorthAmericardquo Chemical Geology vol 414 pp 59ndash68 2015

[7] S Graham N Pearson S Jackson W Griffin and S YOrsquoReilly ldquoTracing Cu and Fe from source to porphyry In situdetermination of Cu and Fe isotope ratios in sulfides from theGrasberg Cu-Au depositrdquo Chemical Geology vol 207 no 3-4pp 147ndash169 2004

[8] K Ikehata and T Hirata ldquoCopper isotope characteristics ofcopper-rich minerals from the horoman peridotite complexHokkaido Northern Japanrdquo Economic Geology vol 107 no 7pp 1489ndash1497 2012

[9] P B Larson K Maher F C Ramos Z Chang M Gasparand L D Meinert ldquoCopper isotope ratios in magmatic andhydrothermal ore-forming environmentsrdquo Chemical Geologyvol 201 no 3-4 pp 337ndash350 2003

[10] W Li S E Jackson N J Pearson and S Graham ldquoCopperisotopic zonation in the Northparkes porphyry Cu-Au depositSE Australiardquo Geochimica et Cosmochimica Acta vol 74 no 14pp 4078ndash4096 2010

[11] G Markl Y Lahaye and G Schwinn ldquoCopper isotopes asmonitors of redox processes in hydrothermal mineralizationrdquoGeochimica et CosmochimicaActa vol 70 no 16 pp 4215ndash42282006

[12] CMeyer et al ldquoOre deposits at ButteMontanardquo inOre depositsof the United States 1967 pp 1373ndash1416 1968

[13] A W Rose ldquoThe effect of cuprous chloride complexes inthe origin of red-bed copper and related depositsrdquo EconomicGeology vol 71 no 6 pp 1036ndash1048 1976

[14] A C Brown ldquoClose linkage of copper (and uranium) transportto diagenetic reddening of ldquoupstreamrdquo basin sediments forsediment-hosted stratiform copper (and roll-type uranium)mineralizationrdquo Journal of Geochemical Exploration vol 89 no1-3 pp 23ndash26 2006a

[15] M W Hitzman D Selley and S Bull ldquoFormation of sedi-mentary rock-hosted stratiform copper deposits through earthhistoryrdquo Economic Geology vol 105 no 3 pp 627ndash639 2010

[16] D Asael A Matthews M Bar-Matthews and L Halicz ldquoCop-per isotope fractionation in sedimentary copper mineralization

8 Geofluids

(Timna Valley Israel)rdquo Chemical Geology vol 243 no 3-4 pp238ndash254 2007

[17] D Asael A Matthews M Bar-Matthews Y Harlavan and ISegal ldquoTracking redox controls and sources of sedimentarymineralization using copper and lead isotopesrdquo Chemical Geol-ogy vol 310-311 pp 23ndash35 2012

[18] D Asael A Matthews S Oszczepalski M Bar-Matthews andL Halicz ldquoFluid speciation controls of low temperature copperisotope fractionation applied to the Kupferschiefer and Timnaore depositsrdquo Chemical Geology vol 262 no 3-4 pp 147ndash1582009

[19] M Haest P Muchez J C J Petit and F Vanhaecke ldquoCuisotope ratio variations in theDikulushi Cu-Ag deposit DRC ofprimary origin or induced by supergene reworkingrdquo EconomicGeology vol 104 no 7 pp 1055ndash1064 2009

[20] E C Jowett ldquoGenesis of kupferschiefer cu-ag deposits byconvective flow of rotliegende brines during triassic riftingrdquoEconomic geology Lancaster Pa vol 81 no 8 pp 1823ndash18371986

[21] A C Brown ldquoGenesis of native copper lodes in the KeweenawDistrict Northern Michigan A hybrid evolved meteoric andmetamophogenic modelrdquo Economic Geology vol 101 no 7 pp1437ndash1444 2006

[22] T J Bornhorst J B Paces N K Grant J D Obradovich andN K Huber ldquoAge of native copper mineralization KeweenawPeninsula Michiganrdquo Economic Geology vol 83 no 3 pp 619ndash625 1988

[23] F M Chartrand and A C Brown ldquoThe diagenetic originof stratiform copper mineralization Coates Lake Redstonecopper belt N W T Canadardquo Economic Geology vol 80 no2 pp 325ndash343 1985

[24] E D Kindle ldquoClassification and description of copperDepositsCoppermine River area District of Mackenzierdquo Tech Rep 2141972

[25] S R Titley and D C Marozas ldquoProcesses and productsof supergene copper enrichmentrdquo Arizona Geological SocietyDigest vol 20 pp 156ndash168 1995

[26] W X Chavez ldquoSupergene oxidation of copper deposits zoningand distribution of copper oxide mineralsrdquo SEG Newsletter vol41 1 pp 10ndash21 2000

[27] D Braxton and R Mathur ldquoExploration applications of copperisotopes in the supergene environment A case study of thebayugo porphyry copper-gold deposit Southern PhilippinesrdquoEconomic Geology vol 106 no 8 pp 1447ndash1463 2011

[28] R Mathur and M S Fantle ldquoCopper isotopic perspectiveson supergene processes Implications for the global Cu cyclerdquoElements vol 11 no 5 pp 323ndash329 2015

[29] S Asadi R Mathur F Moore and A Zarasvandi ldquoCopperisotope fractionation in the Meiduk porphyry copper depositNorthwest of Kerman Cenozoic magmatic arc Iranrdquo TerraNova vol 27 no 1 pp 36ndash41 2015

[30] R Mathur M Dendas S Titley and A Phillips ldquoPatterns inthe copper isotope composition ofminerals in porphyry copperdeposits in Southwestern United Statesrdquo Economic Geology vol105 no 8 pp 1457ndash1467 2010

[31] R Mathur L Munk M Nguyen M Gregory H Annell and JLang ldquoModern and paleofluid pathways revealed by Cu isotopecompositions in surface waters and ores of the Pebble porphyryCu-Au-Mo deposit Alaskardquo Economic Geology vol 108 no 3pp 529ndash541 2013

[32] R Mathur L A Munk B Townley et al ldquoTracing low-temperature aqueous metal migration in mineralized water-sheds with Cu isotope fractionationrdquoApplied Geochemistry vol51 pp 109ndash115 2014

[33] R Mathur J Ruiz S Titley L Liermann H Buss and S Brant-ley ldquoCu isotopic fractionation in the supergene environmentwith and without bacteriardquo Geochimica et Cosmochimica Actavol 69 no 22 pp 5233ndash5246 2005

[34] R Mathur S Titley F Barra et al ldquoExploration potential of Cuisotope fractionation in porphyry copper depositsrdquo Journal ofGeochemical Exploration vol 102 no 1 pp 1ndash6 2009

[35] H Mirnejad R Mathur M Einali M Dendas and S AlirezaeildquoA comparative copper isotope study of porphyry copperdeposits in Iranrdquo Geochemistry Exploration EnvironmentAnalysis vol 10 no 4 pp 413ndash418 2010

[36] C Palacios O Rouxel M Reich E M Cameron and M ILeybourne ldquoPleistocene recycling of copper at a porphyry sys-tem Atacama Desert Chile Cu isotope evidencerdquoMineraliumDeposita vol 46 no 1 pp 1ndash7 2011

[37] D M Borrok D A Nimick R B Wanty andW I Ridley ldquoIso-topic variations of dissolved copper and zinc in stream watersaffected by historical miningrdquo Geochimica et CosmochimicaActa vol 72 no 2 pp 329ndash344 2008

[38] S Ehrlich I Butler L Halicz D Rickard A Oldroyd andA Matthews ldquoExperimental study of the copper isotope frac-tionation between aqueous Cu(II) and covellite CuSrdquo ChemicalGeology vol 209 no 3-4 pp 259ndash269 2004

[39] X K Zhu Y Guo R J P Williams et al ldquoMass fractionationprocesses of transition metal isotopesrdquo Earth and PlanetaryScience Letters vol 200 no 1-2 pp 47ndash62 2002

[40] J Bermin D Vance C Archer and P J Statham ldquoThedetermination of the isotopic composition of Cu and Zn inseawaterrdquo Chemical Geology vol 226 no 3-4 pp 280ndash2972006

[41] S M Ilina J Viers S A Lapitsky et al ldquoStable (Cu Mg) andradiogenic (Sr Nd) isotope fractionation in colloids of borealorganic-rich watersrdquo Chemical Geology vol 342 pp 63ndash752013

[42] S H Little D Vance C Walker-Brown and W M LandingldquoThe oceanic mass balance of copper and zinc isotopes investi-gated by analysis of their inputs and outputs to ferromanganeseoxide sedimentsrdquo Geochimica et Cosmochimica Acta vol 125pp 673ndash693 2014

[43] D Vance C Archer J Bermin et al ldquoThe copper isotopegeochemistry of rivers and the oceansrdquo Earth and PlanetaryScience Letters vol 274 no 1-2 pp 204ndash213 2008

[44] T Fujii F Moynier M Abe K Nemoto and F Albarede ldquoCop-per isotope fractionation between aqueous compounds relevantto low temperature geochemistry and biologyrdquo Geochimica etCosmochimica Acta vol 110 pp 29ndash44 2013

[45] M Pękala D Asael I B Butler A Matthews D Rickard andM Pękala ldquoExperimental study of Cu isotope fractionationduring the reaction of aqueous Cu(II) with Fe(II) sulphides attemperatures between 40 and 200xa0∘Crdquo Chemical Geologyvol 289 no 1-2 pp 31ndash38 2011

[46] J H Seo S K Lee and I Lee ldquoQuantum chemical calculationsof equilibrium copper (I) isotope fractionations in ore-formingfluidsrdquo Chemical Geology vol 243 no 3-4 pp 225ndash237 2007

[47] M S Enders C Knickerbocker S R Titley and G SouthamldquoThe role of bacteria in the supergene environment of theMorenci porphyry copper deposit Greenlee County ArizonardquoEconomic Geology vol 101 no 1 pp 59ndash70 2006

Geofluids 9

[48] A J Hartley and C M Rice ldquoControls on supergene enrich-ment of porphyry copper deposits in the Central Andes Areview and discussionrdquoMineralium Deposita vol 40 no 5 pp515ndash525 2005

[49] R H Sillitoe ldquoSupergene oxidized and enriched porphyry cop-per and related depositsrdquo in Economic Geology 100 AnniversaryVolume pp 723ndash768 2005

[50] E V Belogub K A Novoselov V A Yakovleva and B SpiroldquoSupergene sulphides and related minerals in the supergeneprofiles of VHMS deposits from the South Uralsrdquo Ore GeologyReviews vol 33 no 3-4 pp 239ndash254 2008

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Submit your manuscripts atwwwhindawicom

2 Geofluids

Table 1 Summary of deposits analyzed and sources of data considered

Deposit Type of chalcocite Data sourceButte Montana Hypogene Mathur et al 2009 Wall et al 2011Canarico Peru Hypogene Mathur et al 2010Rippoldsau Germany Hypogene Markl et al 2006Coates Lake Canada Sedimentary Cu This documentCoppermine Canada Sedimentary Cu This documentDikulushi DRC Sedimentary Cu Haest et al 2009Kupferschiefer Germany Sedimentary Cu Asael et al 2009Cu Michigan Sedimentary Cu This document Larson et al 2003 Mathur et al 2014Timna Israel Sedimentary Cu Asael et al 2007 Asael et al 2009 Asael et al 2012Udokan Russia Sedimentary Cu This documentBayugo Philippines Supergene Braxton et al 2012Chuquicamata Chile Supergene Mathur et al 2009Collahuasi Chile Supergene Mathur et al 2009El Salvador Chile Supergene Mathur et al 2009Inca de Oro Chile Supergene Mathur et al 2014PCDs Iran Supergene Mirenjad et al 2010 Asadi et al 2012Morenci Arizona Supergene Mathur et al 2010Ray Arizona Supergene Mathur et al 2010 Larson et al 2003Silver Bell Arizona Supergene Mathur et al 2010Spence Chile Supergene Palacios et al 2010

will influence the possible values of Cuwithin the ore solutionand the associated chalcocite More importantly the initialisotopic composition can be affected by fractionation duringleaching of Cu from the source as well as during precipitationof secondary chalcocite The nature of the fractionation isdependent upon the specific dissolution and precipitationprocesses (eg bonding within the solid or in solution)and the physical and chemical conditions (eg temperatureredox) with redox processes leading to stronger bondingenvironments for 65Cu in oxidized products and 63Cu inreduced products In addition the extent of extraction ofcopper from the source and the fraction of copper that isreprecipitated in the ore-forming processes affect fraction-ation If 100 of the Cu is extracted and precipitated thenno evidence of fractionation will be preserved However ifthe chemical transfer is incomplete then the various phases(primary mineral solution and secondary mineral) mayhave differing isotopic compositions based on the degree offractionation

Copper in chalcocite that is associated with hypogenehydrothermal ores is derived from a magmatic hydrothermalfluid or is extracted from country rocks at high temper-atures Moreover extensive studies showed that hypogenehydrothermal copper minerals such as chalcopyrite andbornite do not display appreciable fractionation (gtplusmn1permil) [7ndash11] Similarly chalcocite that precipitated from these high-temperature fluids is not anticipated to contain copper thathas undergone significant copper isotope fractionation Thisstudy includes 18 chalcocite samples from three hypogenedeposits (Table 1) including an archetypal example of hypo-gene chalcocite at Butte Montana [12]

In contrast to hypogene chalcocite the copper associatedwith red bed and stratiform types of chalcocite is derivedfrom leaching of sandstones and shales at low temperaturesby residual brines The source rocks contain Cu2+ that ishosted within detrital mafic minerals or is absorbed ontoFe hydroxides which are formed as products of weatheringand diagenesis A redox shift is thought to occur duringtransport of copper in these formational waters because theinitial state of copper in theweathered sourcematerial is Cu2+but the copper is mobilized in the Cu+ state as CuCl0 orsimilar aqueous species [13 14]Thus the reaction required tomobilize copper for sedimentary deposits involves the reduc-tion of copper which would be expected to induce isotopicfractionation favoring 63Cu assuming that copper extractionfrom the source material was incomplete Dissolved copperremains unchanged until it encounters organic material orother reductants within the sediment where Cu1+ is fixed bysulfide or by reaction with preexisting pyrite [15]

Six locations at which chalcocite occurs within ldquosedimen-taryrdquo copper deposits (a total of 161 samples) are consideredherein (Table 1) Literature sources that reported chalcocite asthe major phase present in the copper isotope analyses wereused [16ndash19] along with new data from Coates Lake CopperMine Michigan and Udokan Data from Kupferschiefer[20] Michigan [21 22] and Coates Lake [23] provide classicexamples of sedimentary copper deposits along with theprospect Coppermine [24] Data from each of these depositsis compiled in Table 2

The copper for supergene-type chalcocite is derived byoxidative weathering of rocks or ores containing Cu sulfide

Geofluids 3




















































4 Geofluids

Table 2 Continued


























Geofluids 5


2

3

1

1

2

3

Evaporites


3

Cou

nt8070605040302010



1



훿65Cu


nabla


Basement rock

Red beds









6 Geofluids

minus10

Udokan

Michigan

Morenci AZ

PCD Iran

Inca de Oro Chile



Ray AZDikulushi DRC

Timna Israel












119878OH + Cu+2 (aq) 997888rarr 119878O-Cu+2 +H+ (1)



minus (aq) + 119878OH (2)

Geofluids 7



2

minus andCuCl3


7 Conclusions




Acknowledgments



References

















8 Geofluids

































Geofluids 9





Journal of










Volume 2018





Geophysics


Journal of




Microbiology





Agronomy















Geofluids 3




















































4 Geofluids

Table 2 Continued


























Geofluids 5


2

3

1

1

2

3

Evaporites


3

Cou

nt8070605040302010



1



훿65Cu


nabla


Basement rock

Red beds









6 Geofluids

minus10

Udokan

Michigan

Morenci AZ

PCD Iran

Inca de Oro Chile



Ray AZDikulushi DRC

Timna Israel












119878OH + Cu+2 (aq) 997888rarr 119878O-Cu+2 +H+ (1)



minus (aq) + 119878OH (2)

Geofluids 7



2

minus andCuCl3


7 Conclusions




Acknowledgments



References

















8 Geofluids

































Geofluids 9





Journal of










Volume 2018





Geophysics


Journal of




Microbiology





Agronomy















4 Geofluids

Table 2 Continued


























Geofluids 5


2

3

1

1

2

3

Evaporites


3

Cou

nt8070605040302010



1



훿65Cu


nabla


Basement rock

Red beds









6 Geofluids

minus10

Udokan

Michigan

Morenci AZ

PCD Iran

Inca de Oro Chile



Ray AZDikulushi DRC

Timna Israel












119878OH + Cu+2 (aq) 997888rarr 119878O-Cu+2 +H+ (1)



minus (aq) + 119878OH (2)

Geofluids 7



2

minus andCuCl3


7 Conclusions




Acknowledgments



References

















8 Geofluids

































Geofluids 9





Journal of










Volume 2018





Geophysics


Journal of




Microbiology





Agronomy















Geofluids 5


2

3

1

1

2

3

Evaporites


3

Cou

nt8070605040302010



1



훿65Cu


nabla


Basement rock

Red beds









6 Geofluids

minus10

Udokan

Michigan

Morenci AZ

PCD Iran

Inca de Oro Chile



Ray AZDikulushi DRC

Timna Israel












119878OH + Cu+2 (aq) 997888rarr 119878O-Cu+2 +H+ (1)



minus (aq) + 119878OH (2)

Geofluids 7



2

minus andCuCl3


7 Conclusions




Acknowledgments



References

















8 Geofluids

































Geofluids 9





Journal of










Volume 2018





Geophysics


Journal of




Microbiology





Agronomy















6 Geofluids

minus10

Udokan

Michigan

Morenci AZ

PCD Iran

Inca de Oro Chile



Ray AZDikulushi DRC

Timna Israel












119878OH + Cu+2 (aq) 997888rarr 119878O-Cu+2 +H+ (1)



minus (aq) + 119878OH (2)

Geofluids 7



2

minus andCuCl3


7 Conclusions




Acknowledgments



References

















8 Geofluids

































Geofluids 9





Journal of










Volume 2018





Geophysics


Journal of




Microbiology





Agronomy















Geofluids 7



2

minus andCuCl3


7 Conclusions




Acknowledgments



References

















8 Geofluids

































Geofluids 9





Journal of










Volume 2018





Geophysics


Journal of




Microbiology





Agronomy















8 Geofluids

































Geofluids 9





Journal of










Volume 2018





Geophysics


Journal of




Microbiology





Agronomy















Geofluids 9





Journal of










Volume 2018





Geophysics


Journal of




Microbiology





Agronomy
















Journal of










Volume 2018





Geophysics


Journal of




Microbiology





Agronomy















Documents

Origins of Chalcocite Defined by Copper Isotope Valuesdownloads.hindawi.com/journals/geofluids/2018/5854829.pdf · 2019-07-30 · copper sulde in supergene enrichment environments