Kan Block Research Articles

Age Benchmark of Granulite Metamorphism in the Angara–Kan Block, South Yenisei Range: Evidence from Zircon Dating of Postcollisional Granite–Aplite Dikes

The paper presents isotope–geochronological data on zircons from a granite–aplite dike that cuts garnet–hypersthene gneisses of the Kuzeyev unit of the Neoarchean–Paleoproterozoic Kan Group in the southern extension of the Ishimba–Tatarka regional shear zone, Kan River. The morphology and internal structure of most of the zircon grains indicate that the zircons are metamorphic and xenogenic and were captured by the acidic magma from the host rocks when the magma intruded the granulites. Based on these data, the obtained Paleoproterozoic U–Pb age of 1784 ± 6 Ma can be interpreted as the age of granulite metamorphism. The interpretation of available geological and isotopic data confirms a postcollisional age of the aplite, which was emplaced nearly synchronously with the formation of anorogenic leucogranites of the late phase of the Tarak complex, during the final stage of the formation of the Nuna supercontinent.

Blastomylonite Complexes of the Western Yenisei Ridge (Eastern Siberia, Russia): Geological Position, Metamorphic Evolution and Geodynamic Models

Metapelites and metabasites within the Yenisei regional shear zone of the Yenisei Ridge underwent strong deformations with substrate recrystallization and blastomylonite formation during the Ediacaran. The geostructural, petrological, and isotopic–geochronological characteristics of development of the Late Neoproterozoic blastomylonite complexes marking the junction zone of the paleocontinental and paleoceanic sectors of the Yenisei Ridge have been analyzed. Two zones of heterogeneous blastomylonite complexes have been recognized from west to east, in order of increasing distance from the paleoceanic structures: (I) high-baric complexes of the suture zone and (II) frontal (above-suture) medium-baric and medium- to low-temperature complexes. The established differences in the Р–Т parameters of metamorphism between strongly and weakly deformed rocks were interpreted using well-known geodynamic models based on different tectonic mechanisms. As a result of the analysis, we found that the polychronous dynamic metamorphism of gneisses of the Angara–Kan block in the south and formation of the bulk of blastomylonites in the northern segment of the shear zone in the Northern Yenisei Ridge occurred with a 1.5–3 kbar increase in pressure along with insignificant increase in temperature and low metamorphic gradient dT/dH < 10°C/km compared to the background values of earlier regional metamorphism. This was probably due to crustal thickening as a result of rapid thrusting/subduction, followed by rapid uplift. The maximum excess values of the thermodynamic parameters of metamorphism were established in apometabasite tectonites of the suture zone with relict glaucophane schist associations that underwent metamorphism with a simultaneous significant increase in pressure by 3–5 kbar and temperature by 180–240°C with a higher dT/dH gradient of 15–20°C/km. Such excess Р–Т values could be due to progressive metamorphism, complicated by local heating of rocks during viscous deformations and excess oriented tectonic pressure over lithostatic in ductile shear zones. The data agree well with the results of numerical experiments, and this confirms the role of tectonic stress as an additional thermodynamic factor of metamorphic alterations in crustal suture zones.

Proterozoic Granitoid Magmatism at the Southwestern Margin of the Siberian Platform in the Tectonic History of the Angara–Kan Block

The large massifs of ancient granitoids of the South Yenisei Ridge are divided into three complexes that differ in the geological, geochemical, and geochronological features. The Tarak massif consists of two complexes of different ages: the S–A-type porphyritic granitoids (collisional) of the Tarak complex (1.84 Ga) and the A-type subalkaline granites (anorogenic) of the Telkun complex (1.76 Ga). The magmatic crystallization of gneiss granites of the Posolnenskii complex is interrelated with the late stage of metamorphism and falls into the age interval between the above two complexes (1789.8 ± 8.9 Ma). Metamorphic transformations of the enclosing formations are recorded by the presence of small bodies of charnockitoids with dates of 1.84 and 1.73 Ga.

Paleoproterozoic Metavolcanosedimentary Sequences of the Yenisei Metamorphic Complex, Southwestern Siberian Craton (Angara–Kan Block): Subdivision, Composition, and U–Pb Zircon Age

Abstract—The results of this study reveal the chemical heterogeneity of the Yenisei metamorphic complex, which is a series of blocks within the Yenisei Fault of the southern Yenisei Ridge (Angara–Kan block). The Yenisei complex is composed of four metamorphic sequences: amphibolite–marble–paragneiss (volcanic–carbonate–terrigenous), amphibolite–orthogneiss (volcanic), marble–paragneiss (carbonate–terrigenous), and paragneiss (terrigenous). Study of the nature of the protoliths of metamorphic rocks shows that gneisses and schists of Sequences I and IV correspond to polymict or arkose sandstones and siltstone–mudstones and can be classified as first-cycle sediments. Garnet–two-mica schists of Sequence III correspond in composition to mudstones and show evidence of recycling. Metavolcanic sequence II is composed of andesite–dacite–trachyrhyodacite, leucobasalt–basalt, and basalt–basaltic-andesite–trachyandesite formations. The metasedimentary rocks are 1.2–1.4 times richer in REE and Th than the average PAAS. The high-alumina varieties have high contents of K, Rb, HFSE, Fe, Cr, Ni, and Co. The total similarity of the average trace-element contents in the rocks of the two complexes suggests that the composition of the Kan granulites was inherited by metasedimentary rocks of the Yenisei complex. The U–Pb zircon dates for granite veins cutting gneisses of amphibolite–marble–paragneiss Sequence I limit the deposition age to 1.84–1.85 Ga and indicate that these rocks were deposited before the emplacement of postcollisional granites of the Taraka massif and thus predate the major orogenic events within the Angara–Kan block. Therefore, these rocks can be correlated with the lower part of the Urik–Iya graben section. The metamorphic rocks from the lower parts of the sections of the Yenisei complex and the Subluk Group formed during the same rifting phase of sedimentation. The amphibolite–orthogneiss (volcanic) sequence formed in the Angara–Kan block of the Yenisei Ridge during the second stage (1.74 Ga). The volcanic rocks formed in an extension setting and thus can be correlated with the emplacement of within-plate granites of the Taraka massif. In the Sayan area, terrigenous sediments and volcanic rocks of various compositions accumulated at the second stage (1.75–1.70 Ga) during the intracontinental extension. Therefore, there is a good correlation between the ages and geodynamic settings of deposition of late Paleoproterozoic volcanic and volcanosedimentary complexes of the Yenisei Ridge and the Sayan region.

Age and Source Areas of Detrital Zircons from the Rocks of the Yenisei Tectonic Zone: to the Problem of Identification of Archean Metamorphic Complexes in the Transangarian Yenisei Ridge

The petrogeochemical and geochronological correlations were carried out between boudined fragments of tonalitic rocks previously dated at Neoarchean, quartzite sandstones, and host amphibolites in the Yenisei Regional Shear Zone of the Yenisei Ridge in order to solve the problem of age of the Transangarian Yenisei Ridge basement. Detrital zircons in metasandstones can be derived from the Neoarchean–Paleoproterozoic crystalline rocks of the Angara–Kan block. Interpretation of available data does not confirm the inferred presence of the Early Precambrian basement of the Siberian Craton beneath the Transangarian Yenisei Ridge.

Nature and Age of Detrital Zircons from Rocks of the Shear Zone: The Problem of Occurrence of the Archean Basement in the Transangarian Yenisei Ridge

Petrogeochemical and geochronological study of boudined quartzite sandstones and tonalites, as well as host amphibolites, in the shear zone showed that potential sources of detrital zircons were Neoarchean–Paleoproterozoic rocks of the Angara–Kan block and products of their metamorphism. Interpretation of the available data does not confirm the inferred presence of the Early Precambrian basement of the Siberian Craton in the Transangara region.

The First Finding of Sapphirine in Granulites of the Angara–Kan Block: Evidence of Ultra-High–Temperature Metamorphism in the SW Siberian Craton

This work reports the first discovery of sapphirine-bearing mineral parageneses in granulites of the Angara–Kan block, information on the mineral assemblage of rocks, and the mineral composition. Based on mineral geothermometers utilizing alumina content in orthopyroxene, reconstruction of the composition of ternary feldspar, and the titanium content in zircon, it was revealed that the peak temperatures of metamorphism reached 1100°C, after which the rocks underwent cooling under sub-isobaric conditions. It is assumed that the pulse of ultra-high-temperature metamorphism correlates with processes of extension and intraplate magmatism during the age interval of 1.78–1.75 Ga.

New Ore Minerals from the Kingash Ultramafic Massif, Northwestern Eastern Sayan

The paper discusses earlier poorly studied mineralized rocks of the Kingash ultramafic complex in the Kan Block of the Eastern Sayan, including the large Cu–Ni–PGE deposit of the same name. Despite many researchers' increased interest in the Kingash massif, a number of questions related to the petrology, formation mechanism, and localization of Cu–Ni–PGE ore remain controversial. Along with already known ore minerals, we have identified and described a number of new mineral species: argentite, Fe-enriched sperrylite, a bismuth variety of merenskyite, gersdorffite, cobaltite, and thorianite. The ore minerals are distinguished by a higher relative amount of Fe, and this makes the Kingash deposits close to other Paleoproterozoic Cu–Ni deposits, e.g., the Jinchuan in China, Pechenga in Russia, Ungava in Canada, Mt. Scholl in Australia, etc.

Особенности химизма мафит-ультрамафитового магматизма Канской глыбы (СЗ Восточного Саяна)

Особенности химизма мафит-ультрамафитового магматизма Канской глыбы (СЗ Восточного Саяна)

Metamorphic evolution of ultrahigh-temperature Fe- and Al-rich granulites in the south Yenisei Ridge and tectonic implications

This study provides the first evidence for the occurrence of ultrahigh-temperature (UHT) granulite-facies metamorphism in the Yenisei Ridge (Angara–Kan block). UHT metamorphism is documented in Fe-Al-rich metapelites on the basis of the garnet–hypersthene–sillimanite–cordierite–plagioclase–biotite–spinel–quartz–K-feldspar assemblage. Microtextural relationships and compositional data for paragneisses of the Kan complex attest to three distinct metamorphic episodes: (M1) pre-peak prograde (820⎯900°C/5.5–7 kbar), (M2) peak UHT (920–1000°C/7–9 kbar), and (M3) post-peak retrograde (770⎯900°C/5.5–7.5 kbar). The observed counterclockwise P–T evolution at a high geothermal gradient (dT/dP = 100–200°C/kbar) suggests that UHT metamorphic assemblages were formed in an overall extensional tectonic setting accompanied by underplating of mantle-derived mafic magmas, which may be sourced from ~1750 Ma giant radiating dike swarms linked to the Vilyuy mantle plume as part of the Trans-Siberian LIP. The broad synchroneity of UHT metamorphism (1744 ± 26 Ma; monazite–zircon isochron age) and rift-related endogenic activity in the region can provide an additional line of evidence for the two-stage evolution of granulite-facies metamorphism in the Angara–Kan block. The Aldan–Stanovoy, Anabar, and Baikal basement inliers of high-grade metamorphic rocks within the Siberian craton record two Paleoproterozoic peaks (1.9 and 1.75 Ga) of granulite-facies metamorphism. The synchronous sequence of tectonothermal events at the periphery of the large Precambrian Laurentian, Baltica, and Siberian cratons provide convincing evidence for their spatial proximity over a wide time interval, which is consistent with the most recent paleomagnetic reconstructions of the Proterozoic supercontinent Nuna.

Convergent boundaries and related igneous and metamorphic complexes in caledonides of Central Asia

Fragments of the crystalline complexes where Vendian metamorphism of moderate and elevated pressure predated Early Paleozoic metamorphism have been established in the accretionary-collisional domain of the eastern segment of the Central Asian Foldbelt (Early Caledonian superterrane of Central Asia). The geodynamic setting of the Vendian (∼560–570 Ma) South Hangay metamorphic belt located in the junction zone of the Baydrag Block and the Late Riphean (∼665 Ma) ophiolite complex of the Bayanhongor Zone is considered. The origination of this belt was related to the formation of the convergent boundary in the framework of the Zabhan microcontinent about 570 Ma ago. At the same time, an island-arc complex was formed in the paleo-oceanic domain. Metamorphism of elevated pressure indicates that Vendian structures with sufficiently thick continental crust were formed in the framework of the continental blocks. Vendian metamorphism is also established in the Tuva-Mongolia Massif and the Kan Block of the Eastern Sayan. These data show that the Late Baikalian stage predated the evolution of the Early Caledonian superterrane of Central Asia. The development of its accretionary-collisional structure was accompanied by Late Cambrian-Early Ordovician low-pressure regional metamorphism. Granulite-facies conditions were reached only at the deep levels of the accretionary-collisional edifice. The outcrops of crystalline complexes in the southern framework of the Caledonian paleocontinent are regarded as fragments of the Early Paleozoic Central Mongolian metamorphic belt.

Lower precambrian metapelites of the Yenisei Range: REE systematics, provenances, paleogeodynamics

The Yenisei Range represents a Precambrianfolded structure in the southwestern margin of theSiberian Craton. The Lower Precambrian rock associations in the southerly located Angara–Kan block arerepresented by the Kan granulite–gneiss and Yeniseischist—gneiss complexes. North of the Angara River,gneisses and crystalline schists outcrop in the Yeniseiand Central horst uplifts (Garevka Group). The easterly Panimba Uplift is characterized by developmentof highaluminous terrigenous and clayey–carbonatesediments of the Teya Group (Karpinskii Khrebet andPenchenga formations, respectively) accumulated atthe Early–Late Precambrian transition. The analysisof the distribution of REEs and some other minor elements in metapelites of these objects revealed thatmost of them are characterized by elevated (relative tothe average postArchean Australian shale or PAAS)REE concentrations and a distinct negative Eu anomaly. Together with specific La, Sc, Th, Co, Hf, Ce, andCr systematics, this indicates the formation ofmetapelites due to erosion of mature sialic crust. Theposition of data points obtained for Lower Precambrian metapelites of the Yenisei Range in some discrimination geodynamic diagrams provides groundsfor the assumption that they were forming in conditions similar to settings of passive and active continental margins.The rocks of the Kan Complex (Atamanovo andKuzeeva sequences) are largely represented by hypersthene and garnet–biotite plagio and twofeldspargneisses with subordinate twopyroxene crystallineschists in the basal part of the section. Aluminousgneisses (metapelites) constitute from 15–20 to 25–30% in the upper part of the section. The U–Pb age ofthe acid orthogneiss protolith is up to 2.6–2.7 Ga andthat of granulite metamorphism is ~1.9 Ma [1]. The

Petrogeochemical typification of the ultramafic rocks from the Idar greenstone belt, Kan block, East Sayan

The ultramafic rocks of the Kan block, East Sayan, are confined mainly to the Idar greenstone belt. In terms of formational affiliation, they are subdivided into two groups: magmatic (Kingash Complex) and residual (Idar Complex) ones. The magmatic ultramafic rocks compose hypabyssal and subvolcanic bodies, which are represented by rocks of dunite-wehrlite-picrite association with cumulate textures. Uninterrupted chemical variations of the magmatic ultramafic rocks indicate subsequent magmatic differentiation of parental picritic melt in the intermediate deep-seated chambers and emplacement of its derivatives in the crystallization site. Differentiation leads to proportional increase of all rare-earth and other incompatible elements. The residual ultramafics occur as boudined dunite-harzburgite bodies showing metamorphic granoblastic textures. They have more homogenous chemical composition close to those of ophiolite complexes, which represent strongly depleted mantle rocks brought to the upper lithospheric levels via deep-seated thrusts. Residual ultramafics differ from magmatic rocks in notably lower contents of some trace and rare earth elements.

Geochemical model of genesis of the Kingash platinoid-copper-nickel deposit

71 Kingash ore field with the deposit of the same name is located within the Archean Kan block of Eastern Sayan and does not go beyond the boundary of the new nickel and platinum bearing province with numerous ore bearing massifs [1]. In plan the Kingash massif forms a lens (Fig. 1) comprising two “megalayers”: lower peridotite–pyroxenite–serpentinite and overly ing gabbroid. In section it presents lopolith with a geo physically reflected gravitational stage approximated with a multichamber incurrent canal [3]. Ultrabasic rocks of the massif contain Pechenga type sulfide ore of chalcopyrite–pentlandite–pyrrhotite composition. Geochemical Model of Genesis of the Kingash Platinoid–Copper–Nickel Deposit O. M. Glazunov and T. A. Radomskaya Presented by Academician A.A. Marakushev April 1, 2009

Vendian stage in formation of the Early Caledonian superterrane in Central Asia

Granitoids and metamorphic rocks of the Baidarik basement block of the Dzabkhan microcontinent are studied in terms of geology, geochronology (U-Pb dating of zircon microfractions and individual grains) and Nd isotopic-geochemical systematics. As is established, the formation history of metamorphic belt (disthene-sillimanite facies) in junction zone of the Baidarik block and Bayankhongor zone of the Late Riphean (∼665 Ma) ophiolite association characterizes development of the Vendian (∼560–570 Ma) active continental margin. The high-P metamorphic rocks of that time span evidence formation of structures with the Earth’s crust of considerable thickness. In Central Asia, events of the Vendian low-gradient metamorphism are established also in the Tuva-Mongolian massif, Kan block of the East Sayan Mountains, and South Chuya inlier of the Caledonides in the Altai Mountains. Based on these data, it is possible to distinguish the Late Baikalian stage in development of the Early Caledonian superterrane of Central Asia, which antedated the subsequent evolution of this structure during the Late Cambrian-Ordovician. The high-gradient metamorphism that affected most intensively the southeastern part of the Baidarik block can be correlated with the Early Paleozoic (525–540 Ma) evolution of active continental margin and associated development of the Vendian oceanic basins and island arcs of the Ozernaya zone.

Petrogeochemical features of metaterrigenous rocks of the Kan Block of the Eastern Sayan: Reconstructions of provenances and sedimentation conditions

Chemical and isotopic compositions of Proterozoic metaterrigenous rocks of the Kan Block (Central and Idar terranes) of the Eastern Sayan are studied. The results of the reconstruction of their provenances and sedimentation conditions are presented. The rocks under investigation correspond by their petrogeochemical composition to graywackes of island arcs. The combination of geochemical and isotope data shows that sediments of the Central terrane had a local provenance represented by Early Proterozoic subduction magmatic complexes, whereas sediments of the Idar terrane formed probably as the result of mixing of terrigenous material related to the destruction of rocks of Meso-Neoproterozoic oceanic and more ancient continental crust.

The Vendian accretionary event in the southwestern margin of the Siberian Craton

The present-day southwestern margin of the Siberian Craton is represented by its Early Precambrian inliers (Angara‐Kan and Sayan) and Mesoproterozoic‐ Neoproterozoic marginal continental region that includes the Yenisei Range and Sayan areas (Fig. 1). The Early Precambrian evolution of structures of the Siberian Craton culminated with formation of the Early Proterozoic Angara continental-margin foldbelt, intense intrusion of granitoids (1.87‐1.84 Ga ago), and its general consolidation [1]. Mesoproterozoic‐Neoproterozoic fold‐thrust complexes in the trans-Angara part of the Yenisei Range and largely riftogenic complexes of the Sayan region demonstrate all features typical of the ensialic marginal continental and intracontinenal structures. Precambrian blocks and terranes in folded structures of the Central Asian foldbelt were united into the Sayan‐Yenisei accretionary belt. The belt includes Early and Late Proterozoic island-arc and oceanic terranes (Central, Idar, and Shumikha‐Kirel terranes in the Kan block; Arzybei, Isakovka, and Predivinsk) or terranes with substantially metasedimentary sections (Derba) and fragments of oceanic and island-arc structures (Kuvai Group) overlain by Vendian‐Cambrian strata in the Man Trough. The age of accretionary‐collision processes, which promoted amalgamation of Precambrian terranes and their amalgamation with the Siberian Craton margin, remains an open problem. Nearly synchronous metamorphism and granite intrusions in two or more terranes, as well as formation of synchronous molasses in foreland basins, serve as indicators of the accretionary‐ collision processes. The purpose of this work is to determine, based on the above-mentioned criteria, the age of the main event that produced the Sayan‐Yenisei accretionary belt and terminated the Neoproterozoic history of the Siberian Craton. We carried out complex Ar‐Ar dating of amphiboles and biotites from metamorphic rocks in Precambrian terranes and from the marginal zone of the Siberian Craton, U‐Pb dating of zircons from collision-related granitoids, and sedimentological studies in Vendian foredeeps. Given below is a brief characteristic of Precambrian terranes, which were the main objects of study. Three terranes (Central, Idar, and Shumikha‐Kirel) are recognized in the structure of the Kan block (Fig. 1). They differ from each other in lithology and age of the constituting rock associations and are characterized by tectonic boundaries [2]. The Central Terrane is represented by the Paleoproterozoic lithotectonic complex and constitutes an old “core” of the block under consideration. The lower part of the section is largely composed of metavolcanics of the tholeiitic‐basaltic and calc-alkaline associations, while metasediments prevail in its upper part. Orthogneisses (metadacites) aged 2.3 Ga are characterized by positive e Nd (from 1.8 to 3.0) and T (DM) = 2.4‐ 2.5 Ga values. Similar values of the model age (2.3‐ 2.6 Ga) are established also for graywackes. Based on characteristic geochemical parameters, the metamorphosed volcanogenic‐terrigenous complex is comparable with igneous associations and graywackes formed in subduction settings. The stratified complex is intruded by Late Vendian (555 ± 5 Ma) trondhjemites of the Verkhnii Kan Massif [2]. The Idar Terrane is separated from the Central Terrane by the thrust zone. The lower part of the stratified complex is composed of metamorphosed rocks of the komatiitic‐tholeiitic series, which are comparable with oceanic volcanics in geochemical properties. They enclose intrusive ultramafic and ultramafic‐mafic massifs crosscut by plagiogranite veins. The section is supplemented in the southeastern direction with a sequence of garnet-bearing biotite and amphibole paragneisses (metagraywackes), which are similar (in the composition of trace elements) to terrigenous sediments of island arcs. Paragneisses are characterized by a wide range of model Nd age varying from 1.3 to 2.5 Ma.

Collisional metamorphism as a result of thrusting in the Transangara region of the Yenisei Ridge

The Yenisei Ridge is one of the most interesting regions in the southwestern folded framework of the Siberian Craton with respect to geodynamics. The regional structure of the Transangara sector of the Yenisei Ridge is traditionally displayed as a NW-trending system of tectonic sheets divided by faults characterized by the collision of blocks and thrusting. Therefore, this region was subject to pressure-variable regional metamorphism expressed in the juxtaposition of lowand moderate-pressure metamorphic facies. Collisionrelated moderate-pressure metamorphism is locally superimposed on the low-pressure (presumably, younger) metamorphic rocks. As a result, andalusite is replaced with kyanite with the formation of new mineral assemblages and deformational structures. The prograde replacement of andalusite with kyanite in the Yenisei Tange is a rare phenomenon, because the stationary continental geotherm commonly does not intersect the andalusite‐kyanite equilibrium line. Such replacements are usually referred to the retrograde stage of metamorphism, but this interpretation comes into conflict with the regional geological situation. Only a few examples are known in the literature (Northwest Cordillera in the United States and Canada, Dalradian in Scotland, central and northwestern Appalachians in the United States, and the Kola Peninsula and Yenisei Ridge in Russia), where prograde transformation of andalusite into kyanite is assigned either to the metastable state of andalusite in the PT stability field of kyanite or to an increase in pressure as a result of thrusting or magmatic loading characterized by different PT trends. While studying collisional metamorphism in the Transangara sector of the Yenisei Ridge, we selected three (Chapa, Mayakon, and Angara) areas composed of Paleoproterozoic, Middle Riphean, and Upper Riphean rocks (Fig. 1). The Chapa and Mayakon areas are located in the Central uplift between the Ishimbino and Tatarka deep faults. The Angara area covers the junction of the Transangara structural units and the Angara‐ Kan block. The Angara area is situated at the interfluve of the Angara, Belokopytovka, and Malaya Sploshnaya rivers. The reference sections are exposed in the Tatarka shear zone along the right bank of the Angara River between the mouths of the Babkin and Polovinkin creeks. The area is composed of the Upper Riphean low-pressure metasedimentary rocks (rhythmic intercalation of quartzites and phyllites of the Sukhoi Ridge Formation). In the study area, this sequence is largely made up of phyllites of the greenschist facies represented by quartz (Qtz), muscovite (Ms), chlorite (Chl), and ilmenite (Ilm). These rocks underwent high-pressure collisional metamorphism with the formation of new (kyanite-bearing) mineral assemblages. Metamorphism occurred simultaneously with the development of steep (80 ° ‐85 ° NW and SE) near-meridional cleavage. The increase in the metamorphic grade in the near-latitudinal direction is marked by the successive formation of chloritoid (apparent thickness 0.5‐0.8 km) and kyanite (~1.5‐1.7 km) zones. These minerals correspond to the conditions of kyanite schist facies. The eastern boundary of these rocks is hidden beneath unmetamorphosed Paleozoic rocks of the Pogromnino basin. In the Kulakovo uplift on the left bank of the Angara River, collisional metamorphism is expressed in the crystallization of kyanite (Ky), chloritoid (Cld), and ilmenite in metapelites consisting of staurolite (St), plagioclase (Pl), Ms, biotite (Bt), Qtz, and garnet (Grt) [2].