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Absolute dating of Armenian oreformationsG.P. Bagdasaryan a , R.Kh. Gukasyan a & K.A. Karamyan aa Institute of Geology , Academy of Sciences of theArmenian SSR ,Published online: 04 Sep 2009.

To cite this article: G.P. Bagdasaryan , R.Kh. Gukasyan & K.A. Karamyan (1969) Absolutedating of Armenian ore formations, International Geology Review, 11:10, 1166-1172, DOI:10.1080/00206816909475161

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Absolute dating of Armenian ore formations

G.P. Bagdasaryan, R.Kh. Gukasyan and K.A. Karamyan

GENERAL DATA

The first results of absolute age determina-tions of some Armenian ore deposits were givenby the present authors in 1964 to the 13th Sessionof the Commission for Absolute Age Determina-tions of Geological Formations (Bagdasaryan,Gukasyan, Karamyan, and Sagatelyan, 1966).

By that time we had studied specimens ofhydrothermally altered wall rocks by the K-Armethod (and removed the sericites) from the fol-lowing four Armenian deposits:

A. Alaverdi-Kafan tectonic-metallogeniczone:

1) Shaming copper-pyrite deposit;2) Akhtala polymetallic deposit.

B. Pambak-Zangezur tectonic-metallogeniczone:

3) Kadzharan copper-molybdenumdeposit;

4) Dastakert copper-molybdenumdeposit;

5) Dzhindara copper-molybdenumdeposit.

During the past three years, we have con-tinued our close study (together with other as-pects of the geochronology of Armenian magmaticand metamorphic complexes) of the absoluteages of numerous ores of various compositionsfrom deposits and ore occurrences, spatiallycorrelated with magmatic complexes of differ-ent ages and facies in different structural zones.

Reliable absolute age determination of an.ore formation facilitates study of the links be-tween the mineralization and particular syn-chronous magmatic formations.

During the past three years we have per-formed radiogeochronological investigations onthe following twelve ore deposits and occurrences.

A. Alaverdi-Kafan tectonic-metallogeniczone:

1) Kafan copper-pyrite and polymetal-tic deposit.

Translated from Itogi absolyutnogo datirovaniya ryadarudnykh formatsiy Armyanskoy SSR, Izvestiya AN SSSR,ser. geol., 1968, no. 5, p. 19-28. The authors arewith the Institute of Geology, Academy of Sciences ofthe Armenian SSR.

B. Pambak-Zangezur tectonic-metallogeniczone:

2) Chernorech'ye copper-sulfur-pyritedeposit;

3) Tandzut sulfur-pyrite deposit;4) Ankavan copper-molybdenum deposit;5) Megradzor gold ore deposit;6) Zod gold ore deposit;7) Atkiz polymetallic deposit;8) Katnarat polymetallic ore occurrence;9) Agarak copper-molybdenum deposit;

10) Lichkvaz polymetallic ore occurrence;11) Teisk gold ore occurrence;12) Kaputan apatite-magnetite deposit.

We also studied additional data on the Sham-lug, Akhtal, and Kadzharan deposits.

The specimens of altered wall rocks studiedduring this three-year period were obtained forthe present purpose during field work by inves-tigators of the following ore deposits; Ankavan,Shamlug (G. Bagdasaryan); Aktal (G. Bagdasaryanand S. Zograbyan); Chernorech l ye (G. Bagda-saryan and R. Dzhrbashyan); Tandzut (K. Murad-yan); Megradzor (Sh. Amiryan); Zod (L. Melik-yan); Kadzharan, Aktiz, Agarak, Dastakert,Dzhindara, Lichkvaz, Teisk (K. Karamyan);Kafan (G. Sarkisyan and G. Bagdasaryan); Kapu-tan (I. Sarukhanyan).

We have 216 absolute age determinations of110 characteristic specimens of altered wallrocks and hydrothermally altered rocks fromthese 17 ore occurrences.

INVESTIGATION PROCEDURE

Thin sections of these rocks were subjectedto detailed examination under the microscopeand then crushed, ground and quartered and sentfor chemical and X-ray analyses.

The absolute ages were determined by theK-Ar method, but, beginning in January 1967,we also used isotopic dilution. Furthermore,occasional specimens were determined by theRb-Sr method. In the volumetric method, asample weighing up to 25 g was heated to 150-200°C during evacuation for 1 hr. and thenfused in quartz tubes at 1250°C for 4 hr. Theamount of argon, purified in furnaces with CuOand Ca, was measured with a McLeod gauge.The percent of atmospheric argon in the totalargon content was determined in an MS-2Mmass spectrometer by the twin-beam methodof measuring the Ar36/Ar40 isotopic ratios ofthe specimen and a standard (commercial argon).

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G.P. BAGDASARYAN, R.KH. GUKASYAN AND K.A. KARAMYAN

The isotopic composition of the latter was checkedperiodically against atmospheric argon.

In the case of isotopic dilution, a 10-12 gspecimen was fused in a metal reactor, connectedto an apparatus for volumetric determination ofargon. As the indicator tracer, we used themonoisotope Ar 33 diluted with CO2. The coef-ficient of dilution of the monoisotope (Ar 38 titerin the mixture of Ar38 ± CO2) was determinedin a separate series of experiments by the iso-topic-dilution method. In this case, as thediluent we used atmospheric argon, preparedin the same apparatus from air. To feed mea-sured portions of the Ar38 + CO2 mixture, aspecial dosing device was connected to the ap-paratus. The amount of dosed tracer was mea-sured in an ordinary McLeod gauge; the dosageerror was +O. 5-1 percent. The tracer wasadded after fusion of the specimen and transferof the evolved gases to the measuring part of theapparatus.

We assessed the analytical error of argondetermination as 5-6 percent for both methods.The potassium contents of most specimens weredetermined by the perchlorate method, but aconsiderable number of analyses were also mon-itored or performed by the flame-photometricor dipicrylamine method. The mean discrepancyin potassium determinations by the two methodswas less than 2-3 percent. For the age calcu-lations we used the decay constant recommendedby the Commission for Absolute Geochronologyattached to the ONZ of the Academy of Sciencesof the USSR: Xk = 5.57. 10 -11 years -1 and xp =4. 74- 10 -10 years-1 . The chemical analyseswere performed at various times by M. Gukasyanand S. Shishyan, and the control analyses byV. P. Mikhailova (Sverdlovsk) and A. F. Pogre-binskaya (Institute of Geology of Ore Deposits,Petrography, Mineralogy and Geochemistry ofthe USSR Academy of Sciences).

Argon was separated in two Khlopin-Gerlingdevices by E. A. Sarkisyan and L. M. Khachatryan.The mass-spectrometric isotopic analyses wereperformed by R. Kb. Gukasyan and in some casesby R. S. Mkrtchyan.

GEOLOGICAL CONCEPTS ANDRADIOGEOCHRONOLOGICAL DATA

The geology of the ore deposits and metal-logeny of Armenia has been discussed in numer-ous papers and monographs; we therefore giveonly brief information necessary for character-izing the geological conditions of these deposits.

The Armenian endogenic ore occurrencesare genetically and spatially linked with mag-matic (intrusive and effusive-subvolcanic) com-plexes of different ages, formed in differentstages of the geosynclinal development of theregion. The main role in the spatial distributionof magmatic formations is played by deep faultsand the associated feather-joint zones. Thepyrites and polymetallic formations of the Ala-verdi-Kafan tectonic zone are mainly associatedwith Jurassic-Neocomian magmatism (LowerAlpine tectonic stage), and the copper-molyb-denum, pyrite and iron ore mineralization of thePambak-Zangezur tectonic zone mainly withPaleogene magmatism (Upper Alpine tectonicstage).

A. Alaverdi-Kafan Zone

Opinions differ with regard to the geneticlink between the copper-pyrite and polymetallicmineralization of the Alaverdi-Kafan zone andparticular magmatic complexes. Some inves-tigators relate these ore formations to postin-trusive hydrothermal activity (some considerthat the intrusives are Mesozoic, other Paleo-gene). Other investigators relate the mineral-ization to subvolcanic formations of acid com-position products of Mesozoic magmatism.

The first results of absolute dating of mag-matic formations and modified wall rocks of theAlaverdi ore region, of different ages and facies,obtained by Bagdasaryan et al. in 1964, showedfairly convincingly that the sulfur-pyrite, copper-pyrite and polymetallic mineralization are ofMesozoic origin; however, their links with par-ticular magmatic complexes remained uncertain.

These determinations have now been supple-mented by a wealth of fresh data on the Alaverdiore region, lending support to the first resultsand somewhat improving their accuracy.

The Table gives the results of absolute agedeterminations of the products of alteration inthe vicinity of the ores. The only exceptionsare eight specimens, affected by pre-ore meta-morphism, from the Shamlug deposit.

The deposits are grouped in accordancewith the above listed tectonic-metallogeniczones, within which they are given in order ofnorth-to-south distribution.

The overall error of the absolute age deter-minations was assessed as 7-8 percent. Notethat, to obtain the most reliable and accurateabsolute age values, the whole series of deter-minations on each specimen was generally dup-licated; in some cases, where an appreciablediscrepancy was revealed, a third series ofmeasurements was performed.

Furthermore, as an additional control mea-sure we usually performed periodic controlanalyses of standards of the above-mentionedCommission.

The determinations were performed on therock as a whole and on its sericite.

It will be seen from the Table that the agesof the products of wall rock alteration are as

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t (Mergiret K. basin, E flank, Syunik range)I. Agarak copper pyrites depos

Sericites from hydrothermally modifiedsericite-quartz rocks, ore zone 4 7 37-44

Specimensinvestigated

Deter-minations

Markeddeviat.

age values

min. max

Number of

SEVAN (PAMBAK-ZANGEZURSK) TECTONIC ZONE

I. Deposits of northern and central Armenia

A. Chernorech'ye copper-pyrite deposits (north flank Bazum range; Chernaya)

Zone of ore-bearing hydrothermally al-tered Eocene volcanic rocks (andesite,dacite) 3 5 31-36 32.5 + 1.5

B. Tandzut pyrites deposit (north foot Pambak range)

Zone of ore-bearing hydrothermally al-tered Middle Eocene rocks 2 3 37-38 37 + 1.5

C. Ankavan copper-molybdenum deposit (north foot Pambak range, headwaters of the Marmarik)

Ankavan region. Quartz diorite, Anka-van intrusive, reworked within ore zone 8 12 30-36 33 +. 3 26

Ankavan ore field. Pre-ore dyke se-ries, granite-granodiorite porphyry 9 13 30-34 33 + 2

D. Megradzor gold-bearing deposit (south foot Pambak range

Megradzor region. Quartzified, serici-tized granosyenite with pyrite-polymetal-lic mineralization, sericites from wallrock 2 4 41-43 41.5 + 1

E. Zod gold-bearing deposit (eastern Sevan range)

Central district, Zod deposit. Hydro-thermally altered and wall rock gabbroids 5 10 41-43 43 + 1.5 45

Central district, some parts of adjoin-ing districts. Hydrothermally and wallrock markedly altered dyke bodies 5 11 42-45 43 + 1

II. Deposits of southern Armenia

F. Kadzharan copper-molybdenum deposit (basin of headwaters of the Vokhchi)

Central district of the deposit. Hydro-thermally altered sericite-quartz rocks(monzonites)

G. Atkiz

Sericite from hydrothermally alteredwall rocks

H. Katnarat

Sericites from modification aureole ofpyrite-polymetallic vein

9

polymetallic

1polymetallic

2

19

deposit

2

occurrence

4

20-25

23-25

26-27

22 + 2

24 + 1

27 + 1

18

1

2

3

4

5

6

8

9

10

1142 + 2.5

J. Dzhindara copper pyrites depositSericite from hydrothermally altered

porphyritic granite wall rocks 1 2

K. Lichkvaz gold-polymeta lic ore occurrence

Sericites from hydrothermally modifiedrocks in aureole of pyrite and polymetal-lic vein 2

12

13

3 37-38

21

37.5 + 0.5

Age range(mill. yr. )

Mean value(mill. yr. )

INTERNATIONAL GEOLOGY REVIEW

TABLE I. Principal results of absolute dating of hydrothermal ly altered wall rocks of

ore deposits and occurrences in the Armenian Sit

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8 17 142-155

ore field (South Armenia

2 4

1 2

1 2

4 8

2 4

3 6

142-149

138-144

148-150

148-153

137-142

137-153

G.P. BAGDASARYAN, R.KH. GUKASYAN AND K.A. KARAMYAN

TABLE I. Principal results of absolute dating of hydrothermally altered wall rocks of

ore deposits and occurrences in the Armenian SSR (concluded)

Number of

Specimensinvestigated

Deter-minations

Markeddeviat.

age values

min. max

Age range(mill. yr. )

Mean value(mill. yr. )

Sericites from hydrothermally modified

L. Teisk gold-polymetallic ore occurrence

zone of crush and ore mineralization 4 8 37-39 38 a 2.5

M. Dastaker copper-molybdenum deposit

Sericite from hydrotherinally modifiedwall rocks 3 6 17-22 19 a 2

ALAVERDI-KAFAN TECTONIC ZONE

(Armenian part of Somkhet-Karabakh zone)

I. Deposits, Alaverdi ore region (northern Armenia, Alaverdi anticlinorium)

A. Shamlug copper pyrites deposit

Sericites from sericitized Bajocian pri-mary-volcanic pre-ore (?)metamorphism.Mine no. 1, levels: -140, -185, -90, and-40 m 4 8 154-160 157 a 3

Hydrothermally altered sericitized tuffbreccia of Bajocian andesites and dacitesof pre-ore (?) metamorphism 4 9 155-165 161 ± 4

Quartzified, sericitized tuff breccia ofandesitic porphyrites in contact with cop-per pyrites lens 2 5 154-156 155 a 4

Dykes of quartzified, sericitized, rhyolite-porphyries ("albitophyres") in con-tact with copper pyrites ore 5 12 137-148 142 a 6

14

15

16

17

18

19

151139-148 141 a 5

150 +5.5

144 a 5

141 a 3

149 a 1

148 a 4

140 a 3

145 a 5.5

28

B. Akhtala polymetal ic deposit

Altered wall rocks in contact of poly-metallic ore bodies 12 26

Quartzified, sericitized quartz dacites(quartz-plagioclase-porphyries,from exo-contact and remote from pyrites lens

II. Kafan

Quartz-sericite rocks from selvage ofpolymetallic veins, Khaladzh district,adit 3

Propylitized, pyritized quartz-micro-diorite dyke. Mine 7-10, roadway 3

Sericitized quartzite of Barabatumquartz andesite-dacites ("quartz porphy-rites"), 0.8 km NW of Khlatakh

Sericite-quartzites from secondaryquartzites of Kavartkar from summit andup to 100 m below it

Quartz-sericite rocks from Bajocianlava breccia and tuffites, 150-250 m SWalong highway from "Burtskeh" building

Quartz-sericite rock from Bajocianandesite ore zone

KAPUTAN APATITE-MAGNETITE DEPOSIT (ADIS, CENTRAL ARMENIA)

Western foot, Adis, borehole 92, depth384-420 m; 490-556 m 2 4

20

21

22

23

24

25

26

27

5-6 5.5 a 0.5

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follows: 1) at the contact with the Shamlug cop-per-pyrite ore (17 determinations), 142-155 mil-lion years; 2) at the contact with the polymetal-lic and sulfur-pyrite ores of the Akhtal deposit,141 a 5 million years (from 26 determinations)and 150 ÷ 5 million years (from 17 determina-tions), respectively. Note, however, that theage of the sulfur-pyrite mineralization has notbeen finally determined because the range is rela-tively wide (142-155 million years), correspondingin one case to the polymetallic mineralization, butmuch greater in the other.

Preliminary results of dating of the alteredwall rocks (145 a 5 million years) of the Kafanore field indicate that the mineralization is al-most certainly of Mesozoic origin. Some inves-tigators consider the mineralization as Tertiary,associated with Paleogene intrusions of theneighbouring Pambak-Zangezur zone; however,this argument is not well supported.

A characteristic feature are the fairly nar-row ranges of the absolute ages of the alteredwall rocks in the selvage of the polymetallic orevein (adit no. 3), 114 a 5 million years. Closevalues are also obtained for the sericite-quartzrocks of the ore zone and the secondary quartz-ites. These are apparently products of pre-orehydrothermal alteration and the subsequent min-eralization, synchronous with the mineralization.

Some investigators who consider that theKafan mineralization is Mesozoic assume thatthe ore mineralization is Upper Bajocian to pre-Upper Jurassic, but others link it with post-Jurassic magmatism. Therefore geologicallythe age of the mineralization is still in dispute,but radiological data indicate that it was probablyformed in the Upper Jurassic (145 a 4 millionyears).

Note that comparative study of the datesobtained for the Alaverdi and Kafan ore regionsreveals a fairly similar period of formation,at some time in the Upper Jurassic.

B. The Sevan (Pambak-Zangezur) Zone

It will be seen from the Table that the oredeposits and occurrences of this zone have beenradiogeochronologically characterized from aconsiderable number of examples.

The Chernorech'ye copper-sulfur-pyritemineralization, correlated with Eocene volcanicrocks, is assumed from radiological data to beof radiometric age 32. 5 a 1. 5 million years.The Tandzut sulfur pyrites mineralization is ofabout the same age (37 a 1. 5 million years).These deposits were therefore formed in theLower Oligocene; this agrees with the geologicalpicture.

The Ankavan copper-molybdenum deposit

is spatially correlated with the Artkavan intrusiveof quartz-diorite-granodiorite composition. Theages of these rocks in the hydrothermally altered(with the ore mineralization) zone, assessedfrom 36 determinations, are very close (33 a 3million years). From a wealth of radiologicaldata, the age of the intrusive is clearly Neocomianto pre-Albian (Bagdasaryan, 1966), (i.e. LowerCretaceous) but on the strength of later geologicalconsiderations most investigators assume that itis Upper Cretaceous. Note that the age of theintrusive was formerly considered as Eocene,and that of the copper-molybdenum mineralization,by analogy with the Kadzharan mineralization, asEocene (?) - Miocene (?). Detailed radiologicalinvestigations of all the rock types in the intru-sive revealed, in particular, that it was younger(Lower Oligocene), the age (33 a 2 million years— from 13 determinations ) being unusual for thisintrusive — coarse porphyritic granodiorites andgranites — of a pre-ore dyke series. The fol-lowing conclusions may be drawn from the similarages of the ore mineralization and dyke series,on the one hand, and the detailed absolute datingof the Ankavan complex intrusive as a whole, onthe other:

1. The geological inference that the copper-molybdenum mineralization is linked with theseries of coarsely porphyritic granodioritedykes.

2. These dykes and the mineralization arelinked with the Ankavan intrusive only spatially,the gap between their periods of formation beingabout 80 million years.

According to several investigators, theMegradzor mineralization, consisting of goldore quartz veins and veinlets, is correlatedwith an Upper Eocene granitoid intrusive. Theabsolute age of the mineralization was deter-mined from quartz-sericite wall rocks withpyrite polymetallic "mineralization" from a fewspecimens only; the age (41. 5 a 1 million years)is therefore tentative and the accuracy of thedata must be improved.

According to investigators, the gold oremineralization of the Zod deposit is linked withpre-ore subvolcanic bodies of quartz-plagio-clase porphyries of the gold ore field. Theabsolute age of the mineralization, 41 + 1. 5million years, was determined from hydro-thermally markedly altered quartz -sericiterocks of the true ore stage of mineralization.

Therefore the initial, but by no means final,results of absolute dating of the Megradzor andZod gold ore mineralization, which is clearlyassociated with Eocene rocks, reveal that itwas formed in the Upper Eocene period. How-ever, the data must be supplemented and theiraccuracy improved before the date is consideredfinal.

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G.P. BAGDASARYAN, R.KH. GUKASYAN AND K.A. KARAMYAN

AGE OF DEPOSITS IN THE SOUTHERNSEVAN ZONE

It will be seen from the Table that the abso-lute age values, determined from the hydrotherm-ally altered wall rocks, enable us to divide thedeposits of the copper-molybdenum formations ofsouthern Armenia into two age groups, separatedby about 15-17 million years.

Most of the Lower Miocene deposits belongto the first group. These are the Kadzharan,Dastakert and Dzhindara copper-molybdenumdeposits with absolute ages of 20-24 millionyears — the Aktiz and Katnarat polymetallicdeposits of age 23-27 million years. These de-posits were formed about the same time as theinvasion of the large intrusive of granodioriteporphyry, of which the age (from 100 determina-tions of 50 specimens) is 23 2 million years.

Judging from radiogeochronological inves-tigations, the second group of deposits wasformed in the Upper Eocene-Lower Oligoceneperiod. This group includes the Agarak copper-molybdenum deposit and the Lichkvaz-Teiskgold polymetallic deposit. Their absolute agesare 42 ±. 2.5 million years and 37-39 millionyears, respectively.

The times of formation of these depositscorrespond to the monzonitic and granosyeniticintrusions of the Merga pluton, of which theabsolute age (from analysis of more than 90specimens) is 35-41 million years, for the mostpart 37-38 million years.

As regards the genetic or paragenetic linkbetween the mineralization of these southernArmenian deposits and the synchronous intru-sions, most investigators state unequivocallythat the formation of the first group was due tothe intrusion of porphyritic granites of theMerga pluton. However, opinions differ mark-edly with regard to the age of the second groupof deposits and its relation to the intrusions ofmonzonites and granosyenites.

Thus most investigators (S. S. Mrktchyan,K. A. Karamyan and others) assume that theAgarak copper-molybdenum metallization isalso genetically related to these granodioriteporphyries. One of the present authors, K. A.Karamyan, indicates the close genetic affinity(and therefore synchronicity) of the first andsecond groups. He supports this as follows.

1. Deposits of the first and second groupsare controlled by a single regional zone of crushof the Debakla fault. All the above-mentioneddeposits tend structurally towards the band ofcrush of this fault, and the localizing structuresin these deposits are often the feather joints ofthe Debakla fault.

2. Within these deposits and ore fields we

observe fairly large fields of quartzified andmodified rocks, "secondary quartzites," ofgreater age than the mineralization.

3. In the first and second groups we observea single, distinct sequence of development of theore process, and also uniform and parageneticassociations; this indicates the close geneticaffinity of all the deposits.

According to Bagdasaryan and Gukasyan,there are insufficient grounds for assuming agenetic or paragenetic relationship between thesecond group of deposits (primarily the Agarakcopper-molybdenum mineralization) and theintrusion of granodiorite porphyry of the Mergapluton, for the following reasons.

1. The absolute age of the Agarak copper-molybdenum mineralization corresponds closelyto that of the intrusion of monzonites and grano-syenites; this is confirmed by analysis of muchdata. The ages are spaced fairly uniformly ina narrow range.

We can hardly assume that we are dealingwith artificial raising of the apparent absoluteage by removal of potassium from these sericities,to say nothing of the fact that this "aging" cor-responds closely to the age of the fresh grano-syenites surrounding the ore. Such apparentaging may be due to two reasons.

a) Insufficient metasomatic converti-bility of the wall rock granosyenites, i. e.the presence of relicts of the latter in them.In this case we should expect fluctuationsof the apparent ages of the wall rock meta-somatites of approximately 40 million to20 million years (probably somewhatgreater than 22 million years), but notcorrespondence of these ages to that of thegranosyenite intrusion, which is actuallyobserved.

b) Removal of potassium from thesericites (quartz-sericite metasomatites).From the results of three analyses, themean potassium content of the Agaraksericites is 6.07 percent. For an ageof 22 million years, with the Ar 40 contentobserved we must assume the possibilityof removal of more than half the initialamount of K20 in the sericite.

2. The wealth of data on absolute ages inthe Agarak ore field has not revealed LowerOligocene intrusive formations. The grano-syenites (both fresh and altered) surroundingthe mineralization, the wall rock metasomatites,and the small stocks (clearly separated fromthe intrusion) of granodiorite porphyry and por-phyritic granodiorite of the ore field, relatableto the associated bodies of the porphyritic grano-diorite intrusion, are of Upper Eocene age (37-42 million years).

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3. There are insufficient grounds for assum-ing that the copper-molybdenum mineralizationof the Sevan (Pambak -Zangezur) tectonic metallogenic belt as a whole, particularly the southernArmenian part, is a contemporaneous formation.As already indicated, the Ankavan copper-molyb-denum mineralization in the northern part ofthis belt is of Lower Oligocene age (33 *2 mil-lion years).

Furthermore, we know that in southernArmenia molybdenite has been noted in pegma-tites of the Upper Eocene monzonitic intrusion.

On the strength of these data, Bagdasaryanand Gukasyan make the following assertions.

1. The copper-molybdenum deposits in thecomplex Sevan tectonic-metallogenic zone arefar from being of uniform age. They were prob-ably formed over a relatively lengthy period(the Agarak, Ankavan, and Kadzharan ore fieldsbeing formed in the Upper Eocene, Lower Oligo-cene, and Lower Miocene, respectively).

2. The copper-molybdenum mineralizationis genetically or paragenetically related to theinvasion of intrusions of coarse porphyriticgranodiorites; from radiogeochronological data,the ages of these rocks and the related copper-molybdenum mineralization are Upper Eocene,Lower Oligocene and Lower Miocene.

From an analysis of the data on the al-tered wall rocks of the pyrite, polymetallicand copper-molybdenum deposits in Armenia,we can thus point out the paths which futurework on absolute age determinations of theore deposits should follow. They should haveas their aim improved accuracy of the schemeof historical development of the ore regions,the determination and pin-pointing of the posi-tion of mineralization in the magmatic processby the example of Armenia. This will undoubt-edly involve further study of a considerablenumber of altered wall rocks and postmag-matic metasomatites not only of deposits dis-cussed here, but also of new radiologicallyundated deposits.

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