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Journal of Southeast Asian Earth Sciences, Vol. 8, Nos l-4, pp. 307-31 I. 1993 Printed in Great Britain
0743-9547/93 $6.00 + 0.00 c 1993 Pergamon Press Ltd
Genetic types and metal-formations of molybdenum mineralization in Bulgaria
TODORTODOROV
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Abstract-There are over a hundred deposits and occurrences of molybdenum mineralization in Bulgaria. With respect to genesis they belong to the magmatic (?), pegmatitic, greisen, hydrothermal and iron-sulphide endogenic classes of Smirnov Geology of Ore Deposits Nedra, Moscow, 1982. Using composition, age and morphologic criteria the molybdenum deposits are assigned to two kinds of metal-formations: molybdenite and molybdenum-bearing. To the first type are assigned the molybdenite (f sphalerite) greisens and pseudogreisens (quartz-sericite-fluorite metasomatites), the molybdenum-tungsten-bearing (scheehte, molybdenite, pyrite) quartz-feldspar metasomatites, quartz-molybdenite and molybdenite. The second type comprises the porphyry copper, copper-gold-polymetalhc, polymetallic-silver sulphoarsenidic and fluorite-barite-polymetallic. Only as a mineralogic occurrence, molybdenite has been established in the lead-zinc, fluorite and iron-sulphide deposits and also as an accessory mineral in a number of granitoid massives. Most important for the mining industry are the deposits of porphyry copper.
INTRODUCTION
MORE THAN a hundred occurrences with a proved molyb- denum mineralization are known to exist in Bulgaria. With respect to genesis they are quite varied and can be classified into the magmatic (?), pegmatitic, greisen, hydrothermal and iron-sulphide (pyritic) endogenetic classes of Smirnov (1982). The hydrothermal and greisen occurrences are the most widespread and have quantitat- ive accumulations of molybdenite, while the magmatic (?), pegmatitic and iron-sulphide types of mineralization are rarer and usually are significant only with respect to mineralogy.
The question concerning the classification of the endo- genetic occurrences of the molybdenum mineralization in Bulgaria has been amply discussed (Staikov et al. 1971, Todorov and Staikov 1974, Milev and Bogdanov 1974, Egel 1976, Bogdanov 1976, 1987). Generally the various schemes proposed do not differ substantially and are similar to classifications of the molybdenum deposits of Hrushchov (196 l), Pokalov (1972, 1978) and others.
Recently a new subdivision of metal-formations in Bulgaria was published. It is based on more objective criteria (composition, morphology and age) and ore and ore-bearing formations are defined (Vassilev 1982). This approach eliminates significantly subjective in- terpretation. With a view of not increasing the already numerous names used for the ore formations in Bulgaria, the typification of the molybdenum mineraliz- ation (Table 1) we shall use is a modification of Vassilev (1982). Ore and ore-bearing formations are recognized with molybdenite occurring as a main or one of the main (characterizing) minerals (giving rise to molyb- denum deposits) or as a mineral accompanying the main mineralization (giving rise to molybdenite-bearing deposits).
MOLYBDENUM DEPOSITS
According to Vassilev (1982) molybdenite occur- rences are separated into two ore-bearing formations: molybdenite (+ sphalerite) greisens and pseudogreisens (quartz-sericitefluorite metasomatites) and molyb- denum-tungsten-bearing (scheelite, molybdenite, pyrite) quartz-feldspar metasomatites. However, to this group should also be included numerous minor occurrences belonging to ore molybdenite (disseminations of molyb- denite in pegmatites, aplites, granites and syenites) and to quartz-molybdenite vein formations. The character- istic features of the four ore-bearing and ore formations mentioned here are given below.
The molybdenite ( f sphalerite) greisens and pseudo- greisens (quartz-sericite-fluorite metasomatites)
The occurrences of molybdenite vein mineralization in association with quartz-sericitefluorite metasomatites is concerned here. In the literature, this type of mineral- ization is known as a quartz-molybdenite-sericite ore (Hrushchov 196 1) or as a molybdenitequartz-silicate deposit (Ivanov and Poplavko 1982). To this group are also included several deposits and a whole group of individual molybdenite occurrences, which usually accompany acid granitoids in a number of areas in South Bulgaria (the Rhodopes, Sredna Gora region, the West Balkan, and Kraishtide zone) (Fig. 1). The most substan- tial of them are the mineralizations in West Rhodopes (Babyak deposit) and in the East Sredna Gora (the village of Dolno Panicherevo). The deposits mentioned above are typical representatives of vein (with varied mineral composition, e.g. at the village of Babyak) and stockwork (with poor paragenesis, e.g. at the village of Dolno Panicherevo) structural-morphological types. The ore-formation developed at relatively
307
308 T. TODOROV
high-temperature, multistaged and is accompanied by strong hydrothermal alterations (sericitization and silicification) of the country rocks. Their ores are usually characterized by striped and breccia textures, while the molybdenite is mainly fine-scaled. Also pyrite, scheelite, wolframite, sphalerite, galena, etc. are present.
The molybdenum-tungsten -bearing (scheelite, molybden - ite, pyrite) quartz-feldspar metasomatites
This formation is more weakly developed than the preceding type. It comprises Hercynian mineralizations in the Grancharitza deposit in Central Rhodopes and a great number of ore-formations of Alpine age in the Osogovo Mountain (Kraischtide metallogenic zone). The molybdenite occurrences of this type are developed in aluminosilicate rocks and are accompanied by quartz-feldspar metasomatites. Usually the molybdenite in them quantitatively gives way to tungsten minerals and forms rare disseminations dispersed in the vein quartz. In the literature, this molybdenite mineralization is reported as wolfram (tungsten)-molybdenite deposit (Ivanov and Poplavko 1982).
Quartz-molybdenite ore
This is the molybdenite-quartz of Ivanov and Poplavko (1982). This type is represented by a large number of molybdenite mineralizations of negligible size
in the form of small quartz-molybdenim-chalcopyritic and quartz-molybdenite-pyritic veins in Paleozoic gran- ites and granodiorites and in some metamorphic rocks around the latter. This mineralization is considered to be a result of a one-stage process of mineralization without any particular changes to the country rocks. It is present in the Balkan, Rhodope and partly in the Sredna Gora and Kraishtide zones.
Molybdenite ore
Some minor representatives of this formation are known to exist in some areas of Sredna Gora, Rila and South Pirin Mountains. Here the molybdenite is mainly coarse-scaled with individual injections into the almost unchanged granites and pegmatites of the Vitosha, Plana, Rossen and some other plutons.
MOLYBDENITEBEARING DEPOSITS
The molybdenite-bearing formations are considerably more diverse and varied (deposits and occurrences). On the basis of the abundance and distribution of molybdenites in the ore bodies, two subgroups can be distinguished: a subgroup where the molybdenite is present as an accompanying mineral and a subgroup where the molybdenite is only of mineralogical import- ance (Table 2; Fig. 1).
I. Molybdenite deposits and occurrences in Bulgaria. I-Southern Bulgarian granitoids: granites, granodiorites, etc.; 2-Hercynian granitoids in Stara Planina: quartz-diorites, granodiorites, granites, etc.; 3-Upper Cretaceous granitoids: granites, monzonites, quartz-monzodiorites, syenites, etc.; 4-deposits (in left) and occurences (in right). Structural- metallogenic zones in Bulgaria: MP-Moesian Platform; ZB-Stara Planina zone (ore West Balkan zone); S-Srednogorie zone; RM-Rhodope Massif zone; K-Kraishtide zone. The name of deposits and xcurrences are: I-Granichak; 2-Prekop; 3-Bov; 4-Trudovec; 5-Markova Chukla; 6-Kobilja; 7-Elatsite; 8-Rezidentsijata; 9-Medet; IO--- Christo Danovo; 1 I-Kazanite; 12-Borimechkovo; 13-Sap-dere; I4--Morozovo; IS-Srednareka; IbKazanka; 17-Lozen; 1 I-Dolno Panicherevo; 19-Prochorovo; 20-Rossen; 2 I-Chernomorec; 22-Brodilovo; 23--Bard&; 24-Yugovo; 25-Borovska vodenitsa (Belishka Reka Valley); 2bNarechenski Bani; 27-Grancharitza; 28-Babjak; 29-Sinanitsa; 30-Ljubeshnitsa; 31-Musomishte; 32-Papaz Chair; 33-Kupena; 34-Lehovo; 35-Vladaja; 36
Studenec; 37-Ezdimirtzi (Zlata); 38-Chukarevci; 39-Vlahi.
Gen
etic
cl
ass
acco
rdin
g to
Sm
imov
(19
82)
Pegm
atiti
c
Gre
isen
Hyd
roth
erm
al
Tab
le
1. G
enet
ic
type
s an
d m
etal
-for
mat
ions
of
mol
ybde
num
m
iner
aliz
atio
n in
Bul
gari
a
Met
ailo
geni
c zo
nes
and
mag
mot
ecto
nic
Met
al
form
atio
n cy
cles
O
re d
epos
its
and
occu
rren
ces
Mol
ybde
nite
, or
e fo
rmat
ion
Rho
dope
H
ercy
nian
Pa
az C
hair
, U
rdin
i E
zera
Sr
edno
gori
e H
ercy
nian
L
ozen
(R
uda)
A
lpin
e R
osse
n,
Che
mom
orec
, V
lada
ja,
Kal
kovo
, et
c.
Form
atio
n of
m
olyb
deni
te
grei
sens
an
d ps
eudo
- R
hodo
pe
Her
cyni
an
Bab
yak,
R
usov
o,
Buj
novo
, et
c.
grei
sens
(q
uart
z-se
rici
te-f
luor
ite
met
asom
atite
s),
Alp
ine
Raj
kovo
, L
uki
ore-
bear
ing
form
atio
n St
ara
Plan
ina
Alp
ine
Chr
. D
anov
o,
Kaz
anite
, K
oche
to
chel
o,
etc.
Sr
edno
gori
e H
ercy
nian
D
olno
Pa
nich
erev
o,
Kaz
anka
, L
ozen
, M
aras
hite
, Sa
p-de
re,
Ale
xand
rovo
, B
rodi
lovo
, et
c.
Alp
ine
Kra
isht
ide
Her
cyni
an
Kov
ache
vci,
Popo
vjan
e V
lahi
Fo
rmat
ion
of m
olyb
denu
m-t
ungs
ten-
bear
ing
quar
tz
Rho
dope
H
ercy
nian
G
ranc
hari
tza
feld
spar
m
etas
omat
ites,
or
e-be
arin
g fo
rmat
ion
Kra
isht
ide
Alp
ine
Chu
kare
vci
and
othe
rs
occu
rren
ces
in O
sogo
vo
mou
ntai
n Q
uart
z-m
olyb
deni
te,
ore
form
atio
n R
hodo
pe
Her
cyni
an
Sina
nits
a,
Lub
eshn
itsa,
B
rezn
itsa,
et
c.
Star
a Pl
anin
a H
ercy
nian
B
ov,
Tru
dove
c,
Kob
ilja
Sred
nogo
rie
Her
cyni
an
Rez
iden
cjat
a (P
anag
ujrs
ki
kolo
nii)
K
rash
tide
Her
cyni
an
Ezd
imir
tzi
(Zla
ta),
G
olja
ma
Jase
nica
Gen
etic
cl
ass
acco
rdin
g to
Sm
imov
(1
982)
Hyd
roth
erm
al
Tab
le
2. G
enet
ic
type
s an
d m
etal
-for
mat
ions
of
mol
ybde
num
-bea
ring
m
iner
aliz
atio
n in
Bul
gari
a
Met
allo
geni
c zo
nes
and
mag
mot
ecto
nic
Met
al-f
orm
atio
n cy
cles
O
re d
epos
its
and
occu
rren
ces
Porp
hyry
co
pper
, or
e fo
rmat
ion
Star
a Pl
anin
a H
ercy
nian
G
rani
chak
, B
elog
ragc
hik,
N
emov
ru
t A
lpin
e E
lats
ite,
Mar
kova
ch
ukla
Sr
edno
gori
e A
lpin
e M
edet
, B
ardt
ze,
Proh
orov
o,
Stud
enec
, K
arhe
vo,
Kla
dnits
a,
Plov
div
Cop
per-
gold
-pol
ymet
alhc
, or
e ve
in
and
apos
karn
Sr
edno
gori
e A
lpin
e fo
rmat
ion
Ros
sen,
M
eden
ri
d,
Kor
uche
shm
a,
Sarn
eshk
o kl
aden
che,
Pr
opad
nala
vo
da,
Chi
plak
a,
Bar
dtze
, Pr
opad
a,
Mla
deno
vo
Poly
met
allic
-silv
er,
sulp
hoar
seni
dic,
or
e ap
oska
rn
Star
a Pl
anin
a H
ercy
nian
Pr
ekop
fo
rmat
ion
Rho
dope
H
ercy
nian
M
usom
isht
e,
Kup
ena,
L
ehov
o,
Tes
hovo
, et
c.
Fluo
rite
-bar
ite-p
olym
etal
lic
ore
form
atio
n R
hodo
pe
Alp
ine
Yug
ovo,
N
arec
hens
ki
Ban
i, B
elis
hka
Rek
a V
alle
y,
Hvo
ina
T. TODOROV
The first subgroup includes the deposits and occur- rences of the porphyry copper (pyrite, chalcopyrite L molybdenite), copper-gold-polymetallic (magnetite, hematite, pyrite, chalcopyrite + molybdenite, bornite, sphalerite, galena, gold, bismuthinite), polymetallic- silver sulphoarsenide (galena, sphalerite, pyrite, pyrrhotite, arsenopyrite f cobaltite) and fluoritebarite- polymetallic (quartz, fluorite, barite, galena, sphalerite, chalcopyrite & molybdenite) ore formations. These for- mations were subdivided in Vassilev’s paper (1982).
Porphyry copper (pyrite, chalcopyrite f molybdenite) ore formation
In the literature, this formation is also known as the quartz-molybdenitechalcopyrite-sericite ore forma- tion-porphyry type (Hrushchov 1961) or as copper- molybdenite deposits (Ivanov and Poplavko 1982). Here are included some deposits and occurrences in the Sredna Gora and the Balkan metallogenic zones which are predominantly of Alpine and partly of Hercynian age. The ore bodies are in the form of veinlet- disseminated mineralization and as irregular column-like form of considerably size.
The main component of the ores in this type of deposit is copper (mainly in the form of chalcopyrite and partly in the form of bornite), while molybdenite is only an accompanying mineral (the ratio MO :Cu varies from 1: 30 to 1: 200) (Staikov et al. 1971).
The minerals that are present in this type of deposit are pyrite, chalcopyrite, quartz, carbonates (being the predominant minerals), molybdenite, bornite, magne- tite, hematite, sphalerite, galena, chlorite, zeolites and a number of other subordinate and rare ore and vein minerals. The alteration of the rocks around the ores are expressed in various ways. Along with K-feldspatization, sericitization and silicification also chloritization, bioti- tization and zeolitization are expressed. Ore deposition proceeded in several stages. Molybdenite is deposited as for the quartz-molybdenite formation mentioned above. Molybdenite however is also deposited simultaneously (molybdenite-chalcopyritic paragenesis) with chalco- pyrite. In all the deposits mineralization is post-dyke, which can be established by field relations between the dykes and ore veinlets.
The porphyry copper ore formation is very widespread in Bulgaria. However, not all deposits of the porphyry copper ore formations are distinguished by an enhanced content of molybdenite and respectively of molybdenum. This allows two types of mineralization to be distinguished: molybdenite- copper (Medet, Elatsite, etc.) and copper (Assarel, Tzar Asen, Vlaikov Vrah, etc.) (Staikov et al. 1971, Bogdanov 1987). This subdivision is adapted in the present paper (Table 1, Fig. l), as the two mineralogic types differ from each other not only with respect to the content of copper and molybdenum in the ores (the ratio MO : Cu in the molybdenite-copper mineraliz- ations is 1:30-60, while for the copper mineralizations it is 1: 200), but also with respect to a number of
other characteristics (Staikov et al. 1971, Bogdanov 1987).
Copper-gold-polymetallic (magnetite, hematite, pyrite, chalcopyrite f molybdenite, bornite, sphalerite, galena, gold, bismuthinite) ore formation
Not all deposits of this type contain high amounts of molybdenite. Most characteristic is this mineral in the Rossen vein deposits, which gave grounds to some authors to consider them even to be grouped into the molybdenite (Hrushchov 1961) or quartz-molybde- niteechalcopyritesericite ore formation-vein type (Todorov 1971; Staikov et al. 1971). In the other vein representatives of the ore formation considered (the deposits in the Varlibrezhko and Zidarovo are fields) molybdenite is comparatively rare and in those of the Bakadzhisko ore field it was not found (Todorov 1983).
In structural morphologic respect, the mineralization of the Rossen deposits is present as well expressed veins and vein sheafs which are very long in the direction of the bodies’ dips. Their mineral composition is very rich and includes a greater number of rare minerals than the deposits of the porphyry copper formation. However, the development of the mineralization process in the two formations exhibits certain similarities. Molybdenite is deposited as for the quartz-molybdenite paragenesis, as well as simultaneously (molybdenite-chalcopyrite para- genesis) with the deposition of the main copper mineral in the deposits+halcopyrite. The alterations of country rocks and the interrelations of the vein mineralization with the dykes are identical to those of the porphyry copper deposits (Todorov 1983).
Recently some authors also group the aposkarn copper mineralization in the deposits of the Malko Tarnovo ore field with this formation (Vassilev 1982, Todorov 1983). Out of the deposits mentioned, particu- larly characteristic is the enhanced content of molybden- ite in the Bardtze deposit, which besides the aposkam molybdenite-copper mineralization is also character- ized by a vein and disseminated quartz-molybdenite- chalcopyrite mineralization after the intrusive. The two mineralizations do not differ mineralogically and geo- chemically. The differences in their structure and mor- phology here are related only to the type of the country rock (skarn and intrusive rocks) and not to the origin of the different ore-bearing solutions. The characters stated show that the molybdenite in the deposit is hydrothermal and is not directly related to skarn mineral-formation process. This makes doubtful the separation, made by some authors, of an independent molybdenite-scheelite ore formation (deposits) into skarn (Hrushchov 1961, Pokalov 1972, 1978, Ivanov and Poplavko 1982) regardless of the fact that as a type of deposits the aposkarn mineralization with molybdenite is very characteristic in Bulgaria. However, molybdenite and the sulphide minerals accompanying it are aposkarn and are related to the appearance of a later hydro- thermal process.
Genetic types and metal-formations of molybdenum mineralization in Bulgaria 311
Polymetallic-silver sulphoarsenide (galena, sphalerite, pyrite, pyrrhotite, arsenopyrite f cobaltite) formation
The comments valid for the previous formation are also valid for this formation, because here molybdenite was deposited during the time of a high-temperature hydrothermal process and hence it is aposkarn. The sulphide minerals (arsenopyrite, pyrite, pyrrhotite, mar- casite, molybdenite, galena, sphalerite and chalcopyrite) of this formation are present in garnet-pyroxene skarn, which lie over the contacts of marbles with predomi- nantly intermediate and acid intrusive rocks. Typical representatives are the Prekop deposit in the West Balkan and a number of occurrences in the Rhodope metallogenic zone, most probably all belonging to the Hercynian (Amov et al. 1981).
Fluorite-barite-polymetallic (quartz, fluorite, barite, galena, sphalerite, pyrite, chalcopyrite f molybdenite) ore formation
Here also, not all deposits of the formation contain molybdenite. Its representatives with an enhanced con- tent of molybdenite are the Yugovo deposit and the deposits in the region of Narechenski Bani, Belishka Reka Valley and Hvoina of the Rhodope metallogenic zone. The ore bodies here are predominantly of vein type, metasomatic bodies, bedded in form, forming at some places around the veins, cutting through marble interbeds. The mineral paragenesis of the veins is very typical and specific: fluorite, barite, quartz, pyrite, mol- ybdenite, wolframite, bismuthinite, uraninite, sphalerite, galena, calcite and celestine. The formation is described in literature as a rare metal- fluorite-molybdenite one (Hrushchov 1961).
A second subgroup comprises the greater part of the lead-zinc deposits of the lead-zinc (pyrite, sphalerite, galena) and of the polymetallic-gold (galena, sphalerite, chalcopyrite, gold) ore formations (after Vassilev 1982) and the deposits of fluorite (fluorite formation, after Vassilev 1982), as well as some of the deposits of the copper-polymetallic (chalcopyrite, pyrite, arsenopyrite, galena, sphalerite & gold) and copper-pyritic, gold
(pyrite, chalcopyrite, enargite, bornite, tennantite, chalcocite, gold) ore formations (after Vassilev 1982). These are the main lead-zinc and lead-zinc-copper hydrothermal deposits in the Rhodope (Madan, Laki, Davidkovo, Zvezdel-Galenit and Madzharovo ore fields), the Balkan (Shtastie, Tarapanata) and the
Sredna Gora (Gabrovnica) metallogenic zones, the fluorite deposits of the Rhodope massif (Mihalkovo, Dospat) and the iron-sulphide ore deposit of Krusha in the Sredna Gora metallogenic zone. Here the molybdenite is known only in the form of mineralogic occurrence.
It is worth noting the occurrences of this mineral in the accessory parageneses of the Hercynian and some Alpine granitoids from a number of regions in Bulgaria, as well as its presence in the zone of amphibolization among the ultrabasics near the village of Golyamo Kamenyane- the Rhodope Massif.
REFERENCES
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Bogdanov, B. 1976. Structural-metallogenic zones and genetic features of the ore deposits in Bulgaria. In: Problems of Ore-Deposition, IV Svmnosium of IAGOD. Vol. I, Bulgaria Academv of Science. Sofia. pp. 217-225.
Bogdanov, B. 1987. Copper deposits in Bulgaria. Technika, Sofia, 388 (in Bulgaria).
Egel, L., ed. 1976. Ore formations in Carpato-Balkan region. Nedra, Moscow, 214 (in Russian).
Hrushchov, N. A. 1961. Evaluation ore deposits in time of exploration. Molybdenum. Gosgeohechizdat, Moscow, (in Russian).
Ivanov, V. V. and Poplavko, E. M. 1982. Rhenium in base metal ore deposits and blach shales. In: Complex Ore Deposits of Chalcophile Rare Elemenfs. Nedra, Moscow, 212-242 (in Russian).
Milev, V. and Bogdanov, B. 1974. Structural-metallogenic zone and ore formations in Bulgaria. In: Twelve Ore Deposits of Bulgaria. Bulg. Acad. Sci., Sofia, 29-55.
Pokalov, V. T. 1972. Genetic Types and Exploration Criterias for Endogenetic Deposits of Molybdenum. Nedra, Moscow, 235 (in Russian).
Pokalov, V. T. 1978. Ore deposits of molybdenum. In: Ore Deposits of USSR. (Edited by V. I. Smimov), Nedra, Moscow, 3, 117-175 (in Russian).
Smirnov, V. 1. 1982. Geology of Ore Deposits. Nedra, Moscow, 669 (in Russian).
Staikov, M., Angelkov, K. and Delchev, A. 1971. Structural-genetic types of copper-molybdenum mineralization and regional features of its distribution in Bulgaria. Ann. Comm. Geology 18, 17-27 (in Bulgarian).
Todorov, T. 1971. Hypogenic mineralization in copper-molybdenum deposits of Rossen ore field. Ann. Comm. Geology 20, 527-553 (in Bulgarian).
Todorov, T. 1983. Comparative mineralogical and geochemical analysis of the alpine copper deposits in East Srednogorie. Geol. Bale. 13, 41-58.
Todorov, T. and Staikov, M. 1974. On rhenium content in molyb- denite from some Bulgarian deposits. Bull, Geol. Inst., Ser. Metallic Non-metallic Mineral Deposits 23, 275-287 (in Bulgarian).
Vassilev, L. 1982. Metalloformations in Bulgaria-a classification attempt. Geol. Bale. 12, 3-21 (in Russian).
