Download CODES SEG Student Chapter Student-Industry Field Trip South Ural

2013
CODES SEG Student Chapter Student-Industry Field Trip
South Ural Mountains
26th July - 8th August 2013
Group photo of field trip participants back row (l-r): Qiuyue Huang, Ivan (unknown surname),
Sasha (unknown surname), Olga Apukhtina, Daniel Gregory, Don Allen, Igor Zhukov, Douglas
MacQuarrie. Front row (l-r) Francisco Testa, mine geologist (unknown name), mine geologist
(unknown name)
Field Trip Itinerary
Date
Activities
Day 1
26 July
Fri
Travel to Yekaterinburg
Day 2
27 July
Sat
Arrival in Yekaterinburg
Day 3
28 July
Sun
Visit to Saf’yanovka VHMS deposit
Travel to Miass
Visit to Zolotaya Gora gold deposit
Day 4
29 July
Mon
Day 5
30 July
Tues
Visit to Bikkulova Mn deposit
Travel to Baimak
Day 6
31 July
Wed
Visit to Yubileinoe VHMS deposit
Day 7
1 Aug
Day 8
2 Aug
Fri
Day 9
3 Aug
Sat
Travel to Miass
Day 10
4 Aug
Sun
Visit the Bakal iron deposit
Accommodation
Bol’shoi Ural Hotel,
Yekaterinburg
Neptun Hotel, Miass
Visit to Murashkina Gora gold deposit
Visit the Sibai VHMS deposit
Thurs Visit the Kul-Yurt-Tau pyrophyllite deposit
Bashkiriya Hotel,
Baimak
Visit the Yanzigitovo Mn deposit
Visit the Faizullino Mn deposit
Visit the Uchaly VHMS deposit
Day 11
5 Aug
Mon
Day 12
6 Aug
Tues
Miass mineral museum visit
Day 13
7 Aug
Wed
Ore Genesis Conference
Day 14
8 Aug
Thurs
Ore Genesis Conference
Travel to Yekaterinburg
Visit the Zapadno-Ozernoe VHMS deposit
Neptun Hotel, Miass
Map of Southern Ural Mountains
Figure 1. Map of southern Ural Mountains showing approximate mine locations.
Field Trip Participants
Leaders
Prof. Valery V. Maslenikov
Institute of Mineralogy UB RAS, Miass, Russia
Dr. Igor G. Zhukov
Faculty of Geology, Miass Branch, National Research South-Urals
State University Russia.
Student Participants
Francisco Testa
PhD Student, CODES, University of Tasmania
(President of SEG Student Chapter & Trip Coordinator)
Olga Apukhtina
PhD Student, CODES, University of Tasmania
(Vice-President of SEG Student Chapter & Trip Coordinator)
Dan Gregory
PhD Student, CODES, University of Tasmania
Qiuyue Huang
PhD Student, CODES, University of Tasmania
Academic Participants
Dr. Peter McGoldrick
Industry Participants
Don Allen
Douglas MacQuarrie
CODES, University of Tasmania
Introduction
The 6th international student-industry field excursion organised by the CODES SEG Student
Chapter visited a number of significant mineral deposits and geological sites in the southern Ural
Mountains. The sites visited include the extremely well preserved VHMS deposits, several vein
hosted gold deposits, manganese deposits and iron deposits that are historically important in the
area (Fig. 1). The field excursion ended in Miass where a full day seminar at the Ore Genesis
Conference, organised by Institute of Mineralogy, Urals Branch and all of the student participants
presented their current research to the attendees. The trip ended with two full days in Moscow to
give the participants a chance to visit the tourist attractions in the capital city.
We would like to thank our sponsors for their continuing support: Barrick, Anglogold Ashanti,
CODES, Data Metallogenica and the Society of Economic Geologists.
Geological Setting
(summarised from Maslennikov and Yu, 2013 and references there in)
Southern Ural Mountains
The Ural Mountains have been explored and mined for their mineral wealth for millennia and have
produced a large amount of raw minerals and metals. Currently the Urals deposits make up
approximately a quarter of Russia’s mineral resources, despite several of these deposits being
completely mined out. The geology of the Urals can be subdivided into a number of approximately
north-south trending divisions (Figure 2). These subdivisions include: Preuralian Foredeep; West
Uralian Zone; Central Uralian Zone; Tagil-Magnitogorsk Zone; East Uralian Zone and the
Transuralian Zone. The Preuralian Foredeep is composed of a Permian molasse. The West Uralian
Zone that is composed of bathyal Paleozoic sediments that have been intensely folded and thrusted
to the west. Exhumed Precambrian complexes make up the Central Uralian Zone. A combination
of Paleozoic complexes of ocean floor and island arcs concentrically zoned ultramafic massifs
(associated with platinum mineralisation) make up the Tagil-Magnitogorsk Zone. This zone is
offset on the west by the Main Uralian Fault. The East Uralian Zone is made up of a combination
of Precambrian terranes and Paleozoic oceanic and island arc complexes and has been intruded by
the Main Granite Axis (MGA). The westernmost Transuralian Zone is made up of Precambrian
complexes that are considered to be accretionary and unconformably overlying lower
Carboniferous calc-alkaline volcanic rocks.
Several different structural complexes have been developed in the Urals, each with its own zoning
and metallogeny. The oldest is the Pre-Timanides Archean-early Proterozoic complex which
formed during the extension of the crystalline basement of the East-European Platform. The
Timanides formed during a number of rift events in the Meso- and Neoproterozoic followed by
collision and orogeny in the Late Precambrian. The Uralides formed in the Paleouralian Ocean,
which opened as a result of Late Cambrian to Ordovician epicontinental rifting and later oceanic
spreading. Subduction began in the Early Carboniferous and the basin was closed by the collisions
in the Late Paleozoic to Early Jurassic. These collisions formed an orogeny and the subsequent
weathering of the continental material formed the Jurassic-Paleogene platform complex. The Late
Cenozoic neo-orogenic complex formed as new mountains rose along earlier faults to form the
mountains currently observed in the Urals.
Figure 2: Terrane map of the southern Ural region showing VHMS deposits from Hannington et al.
(2005) Ore Geology Reviews.
Summary of South Urals VHMS, manganese and gold deposits
VHMS deposits
There have been four different styles of VHMS deposits identified in the Ural Mountains based on
mineral composition of the ores and geological setting: Ural type, Kuroko (Altai or Baimak) type,
Cyprus (Dombarovka) type and Besshi (Filizchay) type. Ural type is the most economically
important style of VHMS found in the Urals and copper-zinc massive sulfide is the primary ore.
The deposits form within bi-modal rhyolite-basalt complexes of the ensimatic parts of paleo-island
arcs, back-arc and inter-arc basins and marginal seas. These deposits are further subdivided into 3
additional subtypes based on mineralogy: chalcopyrite-sphalerite-pyrite (Cu:Zn ratio<2:1);
sphalerite-chalcopyrite-pyrite (Cu:Zn ratio>2:1) and chalcopyrite-sphalerite-pyrrhotite-pyrite.
The Kuroko type deposits are smaller, more gold rich and polymetallic. They are restricted to
rhyolite-basalt complexes of paleo-island arcs that have blocks of continental crust at the base.
Again three different subtypes can be defined based on mineralogy: chalcopyrite-sphalerite-pyrite
(with gold enrichment), barite-galena-sphalerite-chalcopyrite-pyrite and pyrite. The Cyprus type
deposits are hosted within tholeiitic basalt and ultramafic rocks from inter-arc and back-arc paleobasins and in the melange of the Main Urals Fault. The ore in these deposits is primarily cobaltcopper massive sulphide and they can be subdivided based on mineralogy into chalcopyritesphalerite-pyrite (enriched in Co) and sphalerite-chalcopyrite-pyrite subtypes. The polymetallic
sphalerite-pyrite ores of the Besshi style deposits are predominantly found in the terrigenousvolcanic and terrigenous-carbonate-volcanogenic complexes. A number of different ore styles or
facies have been identified in the VHMS deposits of the southern Ural Mountains. These include:
hydrothermal facies of sulfide mounds with subfacies of sulfide chimneys, ore channels (conduits),
massive diffuse, and hydrothermal veins; hydrothermal-biogenic facies with pelecyodvestimentifera, brachiopod-monoplacophoran, stromatolithic, and polychaeta subfacies; clastic
facies with subfacies of eluvial and colluvial breccias, proximal and distal turbidites; hydrothermalmetasomatic facies and supergene (submarine or continental) facies.
Manganese deposits
The manganese deposits of the southern Ural Mountains were discovered in the late 1800’s in the
Magnitogorsk Paleo-volcanic Belt. These deposits are mostly formed by hydrothermal-sedimentary
processes and have been subsequently modified by metamorphism and supergene refinement. The
deposits are believed to have formed in volcanic complexes that developed in an active continental
margin setting. The mineralisation is predominantly hosted by middle-upper Devonian volcanosedimentary rocks that overly lower-middle Devonian mafic, intermediate and felsic sequences.
The manganese ores occur as layers and lenses up to 2.5 m thick and up to 450 m long. They are
hosted by jasper, jasperites, cherty siltstones, cherty claystone, volcanogenic sandstone and tuffite.
The deposits that are associated with jasperite are considered to be ferroan-siliceous sediments
deposited on the sea floor near low temperature vents. These deposits tend to occur as mound-like
or lenticular bodies that formed proximal to the vent. These vents may be low temperature
analogues of the vents that formed the more economically significant VHMS deposits. Conversely,
the deposits that lack jasperoid bodies were more likely deposited much further from the vent and
occur in monotonous thin banded jaspers. During deformation in the middle Carboniferous to
Permian some of the manganese was remobilised and deposited as veins.
Gold deposits
Several different types of gold deposits have been identified in the Urals and together they make the
Ural Mountains the largest gold-bearing structure in Eurasia. There are several different styles of
gold deposits found in the Ural Mountains. These include gold-quartz deposits, gold-polysulfidequartz deposits, gold-listvenite deposits, gold-sulfide deposits, epithermal deposits and placer gold
deposits (also gold rich VHMS deposits discussed earlier). The gold-quartz deposits are found in or
near fault zones in sedimentary or volcano-sedimentary sequences. They are related to dikes and
small intrusions but are generally some distance from major granitic plutons. The ore is hosted in
veins (concordant and discordant), stringer disseminated zones and mineralized dykes. The
distribution of the gold is highly variable and bonanza grade are encounter, ranging as high as
thousands of grams per tonne, though typical grades of ore range from 10-56 gpt. Gold fineness
ranges from intermediate to high (860-940‰). The gold-polysulfide-quartz deposits are related to
granitic and sub-volcanic complexes. The veins are composed of quartz veins with 3-40% sulfides,
predominantly arsenopyrite, chalcopyrite, sphalerite and galena but also containing sulfosalts,
tellurides and native gold. The gold grains are small (2-3 µm) and are associated with pyrite, galena,
chalcopyrite and fahlores. Fineness is typically high, 800-950 ‰. The gold-listvenite deposits are
hosted in Alpine-type ultramafic rocks and beresite-listvenite altered rocks. Gold mineralisation is
related to quartz veining and predominantly hosted within pyrite-fuchsite-quartz-carbonate
(listvenite) rocks. Free gold hosted in the veins is larger (~1 mm) while gold hosted in listvenites
occurs as small (10-20 µm) inclusions or as tellurides of Au and Ag. Fineness of gold from these
deposits is typically 780-980 ‰. Gold sulfide deposits are found within foliated and sulfidised
volcano-sedimentary sequences that have subsequently been overprinted by Devonian magmatism
and later collision related metamorphism. Gold fineness of these deposits varies widely, ranging
between 516 and 990 ‰. The epithermal deposits found in the Ural Mountains are hosted within
porphyritic quartz diorite and diorite-granodiorite-plagiogranite composition. The deposits are
typically associated with advanced argillic alteration. The ores are typically tellurium-rich and
contain native tellurium and Au, Ag and Pb tellurides. Placer deposits are often found related to
the primary mineralisation. The deposits range from several hundred meters to 1-3 km long and
20-300 m wide. They are typically mined at depths up to 10-20 m.
Geological Sites/ Mines Visited
Saf’yanovka Volcanogenic massive sulfide deposit, Central Urals
The Saf’yanovka VHMS mine is located at 57° 21’ N, 61° 31’ E, approximately 9 km northeast of
the town of Rezh. The ore reserves are approximately 27.5 Mt, grading 2.7% Cu and 1.5% Zn.
The deposit is a Urals-style deposit and is hosted within a rhyolite-dacite island arc complex. The
ore bodies are contained within a thrust plate (related to Early Carboniferous collision of the Urals
paleo-ocean) that is bound by mylonitic zones. Thus, the ore bodies are bound by both structural
and depositional features. There have been several different ore styles identified at the deposit.
These include: massive ores (Cu-Zn, Cu and Fe); banded ores, breccia like ores, stockwork Cu ores
and coarse grained Cu-Zn ore. Deformation has altered the original morphology of the deposit
and it is now represented by two primary sulfide mounds, with the northernmost mound being
particularly well preserved.
The massive ores are composed primarily of pyrite, chalcopyrite and sphalerite with lesser
tennantite and rare marcasite, pyrrhotite, enargite, luzonite and arsenopyrite. Stockwork ores are
predominantly pyrite and chalcopyrite with lesser sphalerite and tennantite and rare tellurides and
sulfo-tellurides. Typical gangue minerals include quartz, sericite, calcite, dolomite, siderite and
barite. Supergene enrichment zones were present at Saf’yanovka and consisted of a 30 cm band
with gold grades up to 100-200 ppm. The textures of the ores at the centre of the mound are
coarse grained with large sulfide clasts and chimney fragments. The mineralised zone grades
outwards into a finer grained sulfide sandstone unit with occasional large chimney clasts and further
transitions into various black shale hosted sulfide turbidite deposits. These textural differences have
been used as evidence to support a traditional collapsed black smoker mound model for the
formation of this deposit.
Figure 3: Banded sulfide ore. In this sample the turbiditic features typical of the ore
distal to the main mound are obvious. Pencil is pointing in the stratigraphically up
direction.
Figure 4: Stockwork chalcopyrite-sphalerite ore with minor covellite.
Figure 5: Large pyrite clast within sulfide breccia, typical of the ore facies between
the main mound and more distal banded ore.
Figure 6: Sof’yanovka VHMS deposit open pit looking north.
Figure 7: Rust coloured oxidation and grey/brown section is the end of the ore in the pit wall.
Zolotaya Gora
The Zolotaya Gora (Gold Mountain) mine is located at 55° 29’ N, 60° 15’ E, adjacent to the town
of Karabash. The Zolotaya gold deposit is hosted within the 12 km by 2.5 km northeast trending
Karabash ultramafic massif. The mineralisation is structurally controlled and related to auxiliary
faults associated with the Main Ural Fault and rodingite dykes. The gold is hosted in quartz veins
associated with small listvenite bodies up to 10 m thick. Six ore zones have been identified. They
dip at 60-75° are 300-700 m long and 2-3 m wide and can be traced to a depth of 200 m. The grade
averages 5-6 g/t but bonanza grades have been identified locally. The gold is associated with
copper and auricupride, tetraauricupride, cuproaurite, mercurian gold, native gold and Au-Ag
amalgams have all been identified on the ores.
There are many different theories for the formation of this deposit. The first suggests that the gold
mineralisation is related to the alteration of the host serpentinites into calc-silicate rodingite rocks.
This theory is supported by the mineralogical zoning of the rodingites. Formation pressures and
temperatures of the cuprous and mercurian gold have been determined to be 390-420°C and 2-4
kbar. A second theory suggests that the gold formed during the listvenitisation of metamafic and
meta-ultramafic rocks. In this model the mineralisation is relatively low temperature (170-200°C)
with moderate salinity fluids.
The town of Karabash has been determined to be one of the most polluted in the world by the
United Nations Environment Programme (UNEP). This is caused by extensive gaseous and
particulate emissions from the nearby smelter, acid drainage from abandoned mines, leachates and
dusts from waste dumps and contaminated stream sediments. However, recent modifications have
made the smelter one of the most environmentally safe copper smelters in the world.
Figure 8: Regional view of the Zolotaya Gora mine showing a number of small deposits along
strike. These are identified by small workings.
Figure 9: Historic adit
Figure 10: The Rodingite dyke is the main controlling structure of the gold
mineralisation.
Figure 11: Small gold workings adjacent to the Rodingite dyke.
Figure 12: Ore sample of vesuvianite, calcite and magnetite with copper and gold.
Murashkina Gora
The Murashkina Gora mine is located at 54° 55’ N, 59° 45’ E, approximately 25 km southeast of
the town of Miass, near the towns of Arkchangelskoe, Verkhnii Iremel and Zelenaya Roshcha. The
ore reserves are approximately 1.35 tonnes of gold with an inferred resource of 3.8 tonnes of gold,
grading 2.7 g/t.
The deposit is one of many small deposits within the Arkchangelskoe gold field. The ore field is
within Main Urals Fault zone and is found within the Talovsk-Kempirsai ultramafic massif. Most
of the deposits were found and mined between the late 19th century and mid-20th century. Gold is
predominantly hosted by aplitic plagiogranite dykes and the accompanying quartz veins that form at
the contact between listvenites and beresites and serpentinites, Devonian volcano-sedimentary
rocks, Carboniferous limestones and Early Paleozoic quartz-sericite schists.
The gold is hosted within three different types of veins. The earliest ones are near-longitudinal
quartz and quartz-carbonate veins up to 5-8 cm thick with pyrite, rare galena and chalcopyrite.
These are crosscut by 20-50° dipping quartz veins. The youngest veins are thick, ocherous, and
near-longitudinal with low gold potential. The orebodies are found within oxidized talcite zones
and quartz and quartz-carbonate veinlets (+/- sulfide minerals) within barren listvenites. Gold
occurs as native gold and is found replacing pyrite, overgrowing pyrite and locally along vein
selvages.
Figure 13: Small WWII era mine shafts.
Figure 14: Mineralised quartz veins in aplitic host rocks.
Figure 15: Quartz vein with small fleck of visible gold (indicated by finger).
Figure 16: Stockwork veins at Murashkina gold deposit.
Bikkulovo Mn deposit
The Bikkulovo deposit is located at 53° 18’ N, 58° 20’ E, approximately 3.5 km northwest of the
town of Magnitogorsk. The ore reserves are not reported but the grade is approximately 36% Mn.
The deposit is small like most Mn deposits in the Ural Mountains and it was mined out during
WWII.
The Mn mineralisation is stratabound and hosted within the Ulutau Formation, near the contact
with the overlying shales of the Mukasova Horizon. The host rocks are believed to be deposited as
siliceous-ferruginous silts near low temperature hydrothermal vents. The ores are associated with
jasperites which support the presence of a hydrothermal source.
The orebody is 1-3 m thick and 340 m long and continues down dip at least 50 m. The ore horizon
is overlain by distinctive, bright red ferrudinous-siliceous tuffites (jasper tuffites) that are a
transitional unit between the jaspers of the Ulutau Formation and the volcanic sandstones of the
overlying units. At Bikkulovo these ferruginous tuffites represent a relatively large volume of rock
compared to the jasperites. This is rare for the Mn deposits of the Urals which usually have much
higher proportions of jasperite than ferruginous tuffite. The dominant mineralogy of the ore is
andradite, rhodonite, caryopilite, parsettensite, hematite, calcite and quartz with piedmontite, Mnepidote and Mn-Pumpellyite in more volcanic-rich areas. Tephroite, ilvaite, johannsenite,
shirozulite, neotocite, rhodochrosite, hausmannite, barite, apatite and native copper are also found
occasionally in the ore.
Figure 17: Example of Mn ore from Bikkulovo.
Figure 18: The uppermost unit is a barren tuffite unit; the middle reddish unit
is the ferruginous tuffite; and the bottom unit is the stratabound Mn ore.
Figure 19: Native copper found as a rare accessory mineral at Bikkulovo.
Figure 20: Clasts of green basaltic tuff and minor jasper in the hanging wall
tuff.
Yubileinoe VHMS Deposit
The Yubileinoe deposit is located at 52° 9’ N, 58° 7’ E. Six different orebodies have been identified
at the deposit. Together they make up a resource of 106 Mt grading 1.5% Cu, 1% Zn and 44% S.
The Yubileinoe VHMS deposit is located within the Buribay VHMS district and is believed to be
formed within the caldera of an axial volcano within an intra-arc rift. The deposit formed within
bonninite-basaltic basement and is classified as a Cyprus-type deposit. The footwall of the deposit
is comprised predominantly of altered pillow basalts and lavas and associated breccias. The hanging
wall is composed of basaltic hyaloclastites, rhyolite, dacite lavas (which also contain several small
polymetallic bodies) and andesitic basalts. The six main orebodies are found between the hanging
wall and footwall sequences and were deposited as sulfide mounds. The main parts of the orebody
are composed of massive sulfide to sulfide breccia. In some areas these contain chimney fragments
and pyritised fossils (corals, tabulate corals and tentaculite) that may represent vent fauna. Away
from the mounds the sulfides transition into bedded and turbiditic sulphide ore, similar to
Saf’yanovka. The mineralogy of the ore is predominantly pyrite, chalcopyrite and sphalerite with
minor marcasite, pyrrhotite, arsenopyrite, galena, fahlores, bornite, magnetite, hematite, barite,
electrum and native gold. Interestingly the chimney fragments contain abundant telluride minerals.
This is typical of Urals deposits found in bimodal mafic sequences of Silurian to Devonian age and
Yubileinoe is the oldest such deposits.
Figure 21: Black smoker fragment (pyrite).
Figure 22: White smoker fragment (sphalerite).
Figure 23: Banded sulfide, pencil points towards stratigraphic up.
Figure 24: Polymetallic sulfide breccia ore.
Novyi Sibai VHMS deposit
The Novyi Sibai deposit is located at 52° 42’ N, 58° 38’ E. The area of the Sibai deposits occurs
within a 300-400 m wide 3-5 km long semi-graben. It classified as Urals style and is made up of
four different deposits: Kamagan, Staryi (old) Sibai, Novyi (new) Sibai and Slepaya (blind). During
this field excursion we visited the Novyi Sibai deposit.
The Novyi Sibai deposit is hosted within the Karmalytah Formation which consists of a series of
four different volcanic units. The basal unit is a 400-800 m thick basaltic/dacitic unit. It is overlain
by a 50-200 m thick basaltic unit. Overlying this basaltic unit is the rhyolitic host sequence that
varies from 100-350 m in thickness. The uppermost unit of the Karmalytah Formation is a 100-500
m thick basalt unit.
The Novyi Sibai deposit consists of 4 ore lenses that dip steeply to the east. The lenses were
formed as sulfide mounds created by the continual growth and collapse of black smoker chimneys,
some of which have been documented as being over a metre in diameter. The stratigraphically
lowest sulfide mound is predominantly chalcopyrite and pyrrhotite in the lower levels and
transitions to magnetite, chalcopyrite, siderite and pyrite in the higher levels of the mound. There is
also a feeder zone underlying the mound that consists of pyrite with chalcopyrite and disseminated
tellurobismuthite and arsenopyrite mineralisation. The other three mounds are dominated by
sphalerite and pyrite. A wide variety of vent fauna, including vestimentifera tubes and bivalves,
have been observed in some of the Novyi Sibai ore lenses. Two previously unidentified species
(Tevidestus seritophormis and Sibaya Ivanovy Little) have also been identified in the ore lenses.
Figure 25: Sibai pit, the largest open pit in Europe.
Figure 26: Ore horizon 3 pinching out inside of the pit. This horizon was originally 2
km long.
Figure 27: Gossanite. Altered glassy hyaloclastite material that reacted with
carbonate and sulfide on the seafloor. It is generally Ag-rich (~150 ppm Ag).
Figure 28: Volcanic debris flow in the host sequence. Grain size fines upwards in the
direction of the hammer’s handle.
Figure 29: Massive sphalerite and chalcopyrite ore.
Figure 30: Pyrrhotite replacing pyrite with minor chalcopyrite.
Kul-Yurt-Tau Pyrophyllite deposit
The Kul-Yurt-Tau deposit is located at 52° 39’ N, 58° 17’ E. The deposit has a resource of 18 Mt.
Pyrophyllite is an economic mineral that is used in the manufacturing of ceramics, fire-resistant
products, insecticides, paper, rubber and plastic. The pyrophyllite orebodies formed as part of the
hydrothermal alteration associated with VHMS deposits and represent the most acidic endmember
of these types of hydrothermal processes. Pyrophyllite was formed by hydrothermal metasomatism
of rhyodacite volcanic edifices at 300-420°C. The type of pyrophyllite orebody and the thickness
are dependent on the pre-existing volcanic flows. Four different types of pyrophyllite orebodies
identified at Kul-Yurt-Tau are:
1 – pyrophyllite-quartz low-alkaline (Na2O + K2O 0.2-0.4%)
2 – sericite-pyrophyllite-quartz alkaline (Na2O + K2O 1.9-2.5%)
3 – diaspore-sericite-pyrophyllite high-alumina (Al2O3 38.0-45.6%)
4 – pyrophyllite alumina (Al2O3 26.7-28.6%)
Molybdenite is also present on the margins of the pyrophyllite mineralisation; however its
concentrations are too irregular to be of economic interest.
Figure 31: Pure pyrophyllite ore.
Figure 32: Kul-Yurt-Tau pit, Pyrophyllite is on the right side of the photograph,
molybdenite is on the associated with white rocks on the left.
Figure 33: Molybdenite found near edge of pyrophyllite mineralisation.
Figure 34: Pyrophyllite in outcrop (white material in centre top of photo).
Figure 35: Molybdenite in outcrop.
Yanzigitovo Manganese Deposit
The Yanzigitovo deposit is located in the south Urals, at the southern end of the Sibai VHMS
district. Though small, the deposit is a classic example of metalliferous oxide-ferrous and
manganese sediments that form at the flanks of massive sulfide bearing regions.
The deposit is hosted at the contact between lower dacite of the volcaniclastic Karamalytash
Formation and the flyshoid volcano-sedimentary rocks of the Ulutau Formation.
The
mineralization occurs within a large lens of hematite-quartz rock within the jaspers of the Bugulygyr
Horizon. The ore is composed of nodules composed of Mn-oxides, clasts of felsic glass and microconcretions of Mn-biotite filaments that occur where the hematite-quartz lens is in contact with the
overlying host jaspers. Several such nodule-rich horizons occur, suggesting a discontinuous and
periodical nodule formation. The primary ore mineral is Ba-psilomelane, though minor supergene
Mn-oxide minerals are present late veins and nests.
Figure 36: Jasperite in vein.
Figure 37: Jasperite with hematite (hematite is the grey spots in the rock).
Figure 38: Jasperoid brecciated by quartz veins. Large clasts are most common at
the base and the clasts fine upwards.
Faizullino Manganese Deposit
The Faizullino manganese deposit is located 20 km southwest of the town of Sibai in eastern
Bashkortostan (52° 26’N 58°12’ E). The mineralization at Faizullino was first discovered in 1890
and was periodically mined until the 1950s, with the majority of exploration taking place during the
1930s and 1940s. Three different deposits have been identified at Faizullino deposit, the North,
Middle and South deposits. All these deposits occur at the contact between the volcano-
sedimentary rocks of the Ulutau Formation and the Rhyolites of the Karamalytash formation. This
contact is a band of silicate rocks called the Bugulygr Horizon.
The Middle and South deposits occur on the western limb of a large syncline while the North
deposit occurs in the folds closure. All three deposits have a similar geology and are vertically
zoned with a basal chain of small 2-4 m thick lens like jasperite bodies. The jasperite is
heterogeneous, the main body is composed of massive and breccia type rocks while Fe-rich globular
rocks occur locally. In some places fossils of macrofauna located near the hydrothermal discharge
areas are present. The jasperite bodies are interpreted to be analogous to ferruginous-siliceous
sediments currently deposited in modern oceans. This transitions into the main part of the cherty
unit which is composed of red-brown banded jasper. Further distil to this jasperites these cherty
layers transition to grey, thinly banded cherty siltstone. The Mn ore occurs in two stratigraphic
positions: at the contact between the jasperoid and the over lying cherty beds and further up in the
sequence in the cherty siltstones. Primary mineralization occurs in two types. The first type is
predominantly quartz, hausmanite, rhodochrosite, tephroite, ribbeite, pyroxmangite and caryopilite;
while type two is composed of hematite, braunite and quartz. However the most thoroughly mined
mineralization is supergene and extends up to 25 m at the different deposits and is composed of
sooty, black manganese oxides and hydroxides.
Figure 39: Open pit of the South Faizullino, volcanoclastic hanging wall rocks
occur on the left, while the ore can be seen as the small island at the far end of the
pit.
Figure 40: Red Jasperoid that forms footwall to the Mn mineralization.
Figure 41: Supergene manganese oxide ore.
Figure 42: Rhodonite from South Faizullino deposit.
Figure 43: Banded chert that hosts some of the Mn ore at South Faizullino deposit.
Figure 44: Manganese nodules within the ore zone at North Faizullino deposit.
Bakal Iron Deposits of the Southern Urals
The group of deposits referred to as the Bakal iron deposits cover an area of approximately 50 km 2
in the vicinity of the Bulandikha, Shuida and Irkuskan mountains. The city of Chelyabinsk is
located in the area and acts the main centre servicing the different mines in the area. The site
visited on the mine tour is typical of the deposits in the region and is located at 54° 56’N 58°51’ E.
The iron deposits are hosted by Precambrian rocks in the western zone of the Bashkirian
meganticlinorium. The Bakal deposits occur within the limestone-dolomite successions (commonly
containing stromatolite beds) of the Bakal Formation in the Burzyan Group and the ZigazaKomarovo Formation of the Yurmata Group. The ore bodies are strata bound and often offset by
a large number of faults (amplitudes 10-100 m) and diabase dykes. The ore beds are intercalated
with dolomites, and to a lesser extent, quartzites and claystones.
Two different types of iron ore have been mined in the Bakal region: siderite ore (predominantly
siderite with lesser amounts of Mg, Ca and Mn) and Fe-oxide ore. The siderite ore generally have
low P (0.012%) and S (0.2%) while the oxide ores have very low amounts of harmful impurities.
There are two theories for the formation of these deposits: 1) they were formed by the
hydrothermal replacement of primary carbonate rocks and 2) they were formed by direct
precipitation in lagoons separated by the main marine basin. Evidence supporting this later theory
includes three main points. First, the primary carbonate ores are confined to horizons within
alternating successions of siderites and dolomites. Second, the presence of siderite pebbles in
sandstones on the lower Zigalga formation indicates that the siderite had formed prior to
emplacement of the sandstone. Third, the frequent alternation of dolomite and siderite layers is
consistent with variations of changes is a paleogeographic regime of a basin.
Figure 45: Open pit of Bakal ore deposit, stratigraphy youngs towards the left.
Figure 46: Course grained siderite ore.
Figure 47: Folded synaresis cracks. Lighter grey, sandy layers infilled drying cracks
then during compactions the cracks folded to form the texture observed in this
figure.
Figure 48: Bladed siderite.
Figure 49: Stromatolite
Figure 50: Stromatolites
Uchaly Volcanogenic Massive Sulphide Deposit, South Urals
The Uchaly deposit is located in the homonymous town in the Bashkortostan Republic (54° 18’N
59°26’ E). Uchaly and Novo-Uchaly are classified as Urals style and are composed of the two large
massive sulfide deposits hosted in the northern flank of the East Magnitogorosk paleo-island arc.
A Middle Devonian basaltic ridge along with a rhyodacite volcanic edifice exhibits the complex
geological setting where the VHMS deposit was emplaced. The N-S trending Uchaly orebody is
located on top of the basaltic basement and is associated with one of the many extrusive-effusive
multiphase domes present in this area. The ore-bearing rhyolite-basalt edifice is overlapped by the
Karalamhytash basaltic slag sequence to the west and by the Ulutau effusive-extrusive andesitic
edifices to the east. The orebody is situated in the inter-dome depressions.
Uchaly orebody is a subvertical lens with a constriction in the centre above the apical part of the
dome and sharply pinches out down the dip with a bed-like morphology along strike. The 2-12 m
thick lens-like disseminated orebodies are hosted in the hanging wall of the Uchaly VHMS. The
funnel shape orebody is interpreted as partially destroyed sulphide mounds.
Mineralisation is massive and disseminated. The massive Cu ores occurs above the footwall of the
orebody as 0.1 to 3 mm anhedral pyrite and interstitial chalcopyrite. The massive Cu-Zn ores
constitute 76% of the total volume and are located in the central and upper section of the deposit.
Less important ore types are: Cu-Fe ore (12%), massive Zn-Fe ore (7%), Fe ore (2%) and
disseminated Cu-Zn, Cu, Zn ore (3%). The massive ores have a Zn:Cu ratio ranging from 3:1 to 6:1
with average grades of 0.97% Cu, 3.8% Zn and 38% S. On the other hand, the layered and
disseminated Cu-Zn ores have a lower average content of 0.6% Cu, 1.6% Zn and 20% S. These
ores occur at the pinches and hanging wall of the mineralised body.
The main sulfides present in the Uchaly VHMS deposit are pyrite (60-90%), sphalerite (up to 25%)
and chalcopyrite (0.1%-10%). Tennantite, galena and magnetite are still abundant but not as major
ore. Marcasite, pyrrhotite, arsenopyrite, altaite, hessite, calaverite, coloradoite. tellurobismutite,
tetradymite and native tellurium associated with pyrite-chalcopyrite veins are some of the rare
minerals found in the deposit.
Three main ore occurrences can be recognised from the bottom to the top of the sequence. The
lowermost disseminated and stockwork stringer ore within the sericite-quartz altered dacitic dome
are overlain by the massive orebody. Relicts of colloform and framboidal pyrite ore are found at the
top sulfide body.
There is a clear zonation of clastic facies from the base towards the top and the flanks of the
deposit. Cu-rich breccias with large ore clast grade into Cu-(Zn) coarse clastic layered facies and
finally Zn-(Cu) fine clastic layered facies.
Figure 51: Uchaly open pit: Left to right, footwall basalt (green rock), ore body and
metasomatic rocks (light brown), felsic rocks (green/red).
Figure 52: Uchaly ore, showing pyrite clasts within a finer grained pyrite/sphalerite
matrix.
Zapadno-Ozernoe Volcanogenic Massive Sulphide Deposit, South Urals
The Zapadno-Ozernoe deposit (54°11' N, 59°17' E) is located to the NW of Uzelga ore field in the
Verhneuralsk mining district. Due to flooding instead of the Zapadno-Ozernoe deposit we visited
the nearby Molodezinge deposit instead. No geological data was available for Molodezinge so
instead the geologic summary for Zapadno-Ozernoe is provided here.
The Middle Devonian Karamalytash Formation is a sequence of basalts overlain by rhyolitesdacites. This unit was covered by an andesitic sequence of the Middle Devonian Ulutau Formation.
The volcanic units are stratified and sub-horizontal. A series of 600 m wide and 3 km long dikes
crosscut the ore zone. They are mainly dacitic andesites and gabbro dolerites.
Fifteen orebodies were identified in two different levels. Some occur in the deeper level occur
along the contact between the Karamalytash and Ulutau formations. The shallow level is associated
with polymictic breccias within Ulutau formation andesites.
About 78% of the reserves are concentrated in the orebody N°1, hosted in the rhyolitic to dacitic
volcaniclastic rocks and lavas intercalated with volcanic sandstones. The 540 m by 600 m irregular
convex ore lens reaches up to 180 m thick. The upper and lower contacts between the orebody and
host rock are sharp except for the central part where the stringer zone occurs. The average content
of Cu, Zn and S for this orebody is 0.91%, 1.09% and 45.21% respectively. A series of thin ore
lenses occur in the overlaying andesitic sequence.
The deposit is classified as Urals style. It is composed of fine grained pyrite with relict colloform
texture as the major ore mineral. Interstitial and vein-like sphalerite and chalcopyrite also represent
important ore minerals although less abundant. Tenanntite, hematite, magnetite, pyrrhotite, galena
and arsenopyrite are some of the rare minerals found in Zapadno-Ozernoe deposit.
The sericite-quartz and sericite-chlorite-quartz altered rocks form a mushroom-like halo around the
orebody N°1. Supergene processes formed a secondary sulphide enriched zone located between the
residual pyritic sands above the massive ore and the overlying quartz-barite leached sands. Galena,
sphalerite, metacinnabar, Se-bearing pyrite, tiemannite, native gold, sulphur and selenium are the
most common minerals of the supergene enrichment zone.
To the northwest of orebody N°1 there is an open pit where the upper part of orebody N°5 is
exposed. This mineralised zone is hosted in a shallow level within dacitic andesites of the Ulutau
Formation. The 120 m strike and 60 m wide elliptical orebody is characterised by grades of 0.6-1.1
wt.% Cu and 1-2 wt.% Zn. It is important to note that the Se and As contents are particularly high
in comparison to most of the VHMS deposits from the Ural Mountains.
Figure 53: Massive sulfide ore lens at Molodezinge deposit.
Figure 54: Massive sulfide ore containing chalcopyrite, pyrite and sphalerite.
Figure 55: Rhyolite with chalcopyrite filling vesicles.
Figure 56: Tiered waste dump in the process of being rehabilitated.