The position of the antimony mineralization in the ore-forming process at the Suzdal gold deposit (Eastern Kazakhstan)
Kolesnikova M.K.
V.S. Sobolev Institute of Geology and Mineralogy sb ras, Novosibirsk, Russia
kolesnikova_mk@mail.ru
The problem of the position of antimony mineralization in the ore-forming process is actual for many gold deposits occurring in the black shale sequences of orogenic belts. This mineralization is gold-bearing or superimposed on the gold-bearing ore with redistributing of gold and forming complex mineral assemblages. Antimony mineralization is typical for gold deposits of Yenisei Ridge, Verkhoyansk-Kolyma gold-bearing province [1,2]. It is also occurred on a number of gold deposits of the Western Kalba gold-bearing belt in Eastern Kazakhstan. Antimony mineralization is superimposed on the early productive gold-sulfide ores (Suzdal, Bakyrchik, Bolshevik), gold-bearing granites (Zherek) and metabasalts (Zanan, Alimbet) [3]. The relationship of antimony mineralization with gold sulfide ores is studied on example of Suzdal deposit.
T
he
Suzdal
deposit
is situated
in
Semipalatinsk
region
of Eastern Kazakhstan
in
the northwestern part
of
the Western
Kalba gold belt. It lies in the southern periphery of the Semeitau
volcano–plutonic complex and is located at the juncture of the
NW-trending Char-Gornostai-Zimunai and NE-trending Suzdal fault
zones. The set of basic and acidic dikes, small intrusive stock-like
bodies of monzonite-porphyry and granosyenite-porphyry is widely
occurred in the Suzdal
deposit. The dikes of diabase are most common. Suzdal
deposit
refers to the
type
of
sedement-hosted
gold
deposits
in the
mineralized
zones,
and
hosted
in the
carbonaceous
limestone and terridgenous sequences
of
the
Early
Carboniferous
age.
The
content of sulfides range from 0.5 to 10-15%. The
mineralization is represented by disseminated, nest-veinlet and
stratiform mineralization. The
gold-sulphide mineralization is accompanied by low-temperature
processes of silicification, carbonation, sericitization and
chloritization. The ore bodies are distinguished mostly by the
results of assay. The gold content in ores ranges from 1.5 to 106 ppm
(average 6.4-16.2 ppm). The
process of gold mineralization at the Suzdal deposit had a multistage
and polygenic character. On
the deposit
are
the following
stages
of
ore deposition:
1. Syngenetic
pyrite
mineralization
with
low
gold content
in
the
turbiditic carbonaceous sandstones and siltstones;
2. Early
highly
productive
gold-bearing
pyrite-arsenopyrite
finely
disseminated
mineralization
with
"invisible"
gold
in
sericitized
rocks;
3.
Late
productive
gold-polysulfide
mineralization
with
native
gold
in
zones
of
brecciation
and
silicification
of
rocks;
4. Veins
of
quartz-carbonate-stibnite
composition.
The
main stages 2 and 3 according to 40Ar/39Ar
dating (sericite from the ore association) has age 281.9 ± 3.3 Ma
and 248.3 ± 3.4 Ma. The
main ore minerals of those stages are gold, arsenopyrite, pyrite and
pyrrhotite [4].
Fig. a. Radial stibnite in the nest with the aggregate of quartz. SEM image. b. Association of Ag-containing gold (1), ulmanite (2), arsenopyrite (3), calcite (5) with micaceous aggregate (4). SEM image. c. Replacement of pyrrhotite (1) by stibnite (2). SEM image. d. Berthierite (2) develops along the boundary between the crystals of pyrite (3) and arsenopyrite (1). SEM back-scattered image.
Quartz-carbonate-antimony mineralization is wide spread at the Suzdal deposit, and occurs both in the near-surface and at deeper horizons (500-600m). It is occurred as nests and veinlets with thickness up to several centimeters, and is superimposed on all types of previously mineralized rocks and consists mainly of stibnite, native antimony and rare cinnabar. The gangue minerals are quartz, carbonate and sericite in the selvages of veins. Stibnite is the most abundant mineral. It forms a thin veinlets, spotted or in the form of radiating discharges in quartz-carbonate clods (Fig. a). It occurs in close association with berthierite and native antimony. Berthierite forms tabular crystals (Fig. c). Native antimony is represented by small roundly inclusions in carbonate or stibnite. Stibnite and berthierite often cement and substitute crushed crystals of arsenopyrite and pyrite (Fig. c, d). There are cases of replacement of pyrrhotite by stibnite. As a result superimposed on the antimony mineralization on the gold-sulfide ores formed association of gold with aurostibite, berthierite, villiaumite, ulmanite, breithauptite (Fig. b). A later generation of arsenopyrite is characterized by the presence of antimony from 0.2 to 1.8 wt.%.
According to fluid inclusions study the values of homogenization temperature of the gas-liquid inclusions in quartz and carbonate from this stage are within the range of 230-290º C. Age of antimony mineralization according to the analysis of sericite by 40Ar/39Ar method is 241.9 ± 2.7 Ma. The age gap between antimony mineralization and the late gold-polymetallic association is of about 6 million years.
Quartz-carbonate-stibnite mineralization probably ends the process of mineralization and superimposed on the early gold-bearing ore. Sb mineralization is not a gold-bearing, but it regenerates and redistributes gold of earlier stages.
References:
1. Bortnikov N.S., Gamyanin G.N., Vikenteva O.V., Prokof'ev V.Y., Prokopiev A. V. Sarıl and Sentachan gold-antimony deposits (Sakha-Yakutia): Example of combining mesothermal gold-quartz and epithermal antimonite ore / / Geology of Ore Deposits, 2010, V.52, № 5. P. 381-417. (Published in Russian).
2. Genkin F.D., Lopatin V.A., Savel'ev R.A. and other. Gold ore of the Olympic deposits (Yenisei Ridge, Siberia) // Geology of ore deposits. 1994. V.36. № 2. P. 111-136. (Published in Russian).
3. Metallogeny of Kazakhstan. The ore formation. Deposits of gold / Red. college: Abdulin A.A., Kayupov A.K. etc. - Alma-Ata, "Science" of the Kazakh SSR, 1980. 224 p. (Published in Kazakhstan).
4. Kovalev K.R., Kalinin Y.A., Naumov E.A., Pirajno F., Borisenco A.S. A mineralogical study of the Suzdal sediment-hosted gold deposit, Eastern Kazakhstan: Implication for ore genesis // Ore Geology Reviews. 2009. V. 35. #2 P.185-205.