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Papers by Dmitry Konopelko

Economic Geology, 2004

The age of mineralization is slightly younger than a U-Pb zircon age of 296.7 ± 4.2 Ma obtained f... more The age of mineralization is slightly younger than a U-Pb zircon age of 296.7 ± 4.2 Ma obtained for the postcollisional Djangart granite, about 80 km southeast of Kumtor, and slightly older than two published U-Pb ages of 268 ± 1 and 280 ± 9 Ma on a postcollisional granite intrusion ...

Mineralium Deposita, 2006

The Altaid orogen was formed by aggregation of Paleozoic subduction–accretion complexes and Preca... more The Altaid orogen was formed by aggregation of Paleozoic subduction–accretion complexes and Precambrian basement blocks between the Late Proterozoic and the Early Mesozoic. Because the Altaids are the site of abundant granitic plutonism and host some of the largest gold deposits in the world, understanding their formation has important implications on the comprehension of Phanerozoic crustal growth and metallogeny. In this study, we present the first extensive lead isotope data on magmatic and metasedimentary rocks as well as ore deposits of the southern part of the Altaids, including the Tien Shan (Tianshan) and southern Altay (Altai) orogenic belts. Our results show that each terrane investigated within the Tien Shan and southern Altay is characterized by a distinct Pb isotope signature and that there is a SW–NE Pb isotope gradient suggesting a progressive transition from a continental crust environment in the West (the Kyzylkum and Kokshaal segments of the Southern Tien Shan) to an almost 100% juvenile (MORB-type mantle-derived) crust environment in the East (Altay). The Pb isotope signatures of the studied ore deposits follow closely those of magmatic and metasedimentary rocks of the host terranes, thus supporting the validity of lead isotopes to discriminate terranes. Whereas this apparently suggests that no unique reservoir has been responsible for the huge gold concentration in this region, masking of a preferential Pb-poor Au-bearing reservoir by mixing with Pb-rich crustal reservoirs during the mineralizing events cannot be excluded.

Mineral Deposit Research: Meeting the Global Challenge, 2005

ABSTRACT The Altaid orogen consists of Paleozoic subduction-accretion complexes and magmatic arcs... more ABSTRACT The Altaid orogen consists of Paleozoic subduction-accretion complexes and magmatic arcs as well as narrow Precambrian basement slivers which were accreted, consolidated and then deformed during Paleozoic collisions and subsequent Alpine-Hima an deformations between the East European craton in the West, the Siberian craton in the East, and the Alai-Tarim and Karakum microcontinents in the South. The Altaids are the site of abundant plutonism and host some of the largest gold deposits in the world, especially of the orogenic gold type.Over 100 new lead isotope data show that each one of the Altaid domains investigated is characterized by distinct lead isotope signatures and that there is an W-E Pb isotope gradient suggesting a progressive transition from a continental crust environment in the west (Western Tien Shan) to an almost 100% juvenile (mantle-derived) crust environment in the east (Chinese Altay).Our data indicate also the locally extensive presence of old continental crust at the base of the Tien Shan east of the Talas-Farghona fault but not west of it.The lead isotope signatures of the ore deposits follow closely those of the magmatic and basement rocks of the host domains suggesting that no unique reservoir has been responsible for the gold concentration in this orogen.

In the Kyrgyz Tien Shan (also known as Tian Shan in literature) the Caledonian (Cambro-Silurian) ... more In the Kyrgyz Tien Shan (also known as Tian Shan in literature) the Caledonian (Cambro-Silurian) intrusions comprise an extensive magmatic arc stretching from east to west for more than 1000 km. The characteristic feature of the arc is its relatively homogeneous composition of rock types over the whole structure. The Kichy-Naryn and Djetim intrusions presented in this study are slightly elongated in an east-west direction and occupy an area of ca. 100 km 2 . The main rock types are diorite, granodiorite and granite. Geological and geochemical features of the Kichy-Naryn and Djetim intrusions demonstrate characteristics of I-type granite series. Rocks of the two intrusions define a continuous high-K calc-alkaline series. Diorite and granite of the Kichy-Naryn intrusion yielded early Silurian crystallisation ages of 436 ± 2 Ma (U-Pb, zircon). Diorite from pebbles in the conglomerate sampled close to the contact of the Kichy-Naryn intrusion yielded a significantly older early Ordovician crystallisation age of 466 ± 10 Ma. The obtained ages of 466 and 436 Ma match ages of two major regional magmatic pulses at ca. 435-440 and 460-470 Ma which took place during continuous subduction from the Cambrian to the Silurian. The amount of granites in the Northern Tien Shan, their prolonged history of formation and pronounced I-type geochemical characteristics suggest their formation in an Andean-type active margin environment.

Ore Geology Reviews, 2009

In the Kyrgyz Tien Shan (also known as Tian Shan in literature) the Caledonian (Cambro-Silurian) ... more In the Kyrgyz Tien Shan (also known as Tian Shan in literature) the Caledonian (Cambro-Silurian) intrusions comprise an extensive magmatic arc stretching from east to west for more than 1000 km. The characteristic feature of the arc is its relatively homogeneous composition of rock types over the whole structure. The Kichy-Naryn and Djetim intrusions presented in this study are slightly elongated in an east-west direction and occupy an area of ca. 100 km 2 . The main rock types are diorite, granodiorite and granite. Geological and geochemical features of the Kichy-Naryn and Djetim intrusions demonstrate characteristics of I-type granite series. Rocks of the two intrusions define a continuous high-K calc-alkaline series. Diorite and granite of the Kichy-Naryn intrusion yielded early Silurian crystallisation ages of 436 ± 2 Ma (U-Pb, zircon). Diorite from pebbles in the conglomerate sampled close to the contact of the Kichy-Naryn intrusion yielded a significantly older early Ordovician crystallisation age of 466 ± 10 Ma. The obtained ages of 466 and 436 Ma match ages of two major regional magmatic pulses at ca. 435-440 and 460-470 Ma which took place during continuous subduction from the Cambrian to the Silurian. The amount of granites in the Northern Tien Shan, their prolonged history of formation and pronounced I-type geochemical characteristics suggest their formation in an Andean-type active margin environment.

Economic Geology, 2004

The age of mineralization is slightly younger than a U-Pb zircon age of 296.7 ± 4.2 Ma obtained f... more The age of mineralization is slightly younger than a U-Pb zircon age of 296.7 ± 4.2 Ma obtained for the postcollisional Djangart granite, about 80 km southeast of Kumtor, and slightly older than two published U-Pb ages of 268 ± 1 and 280 ± 9 Ma on a postcollisional granite intrusion ...

The Devonian-Permian history of magmatic activity in the Tien Shan and its framework has been con... more The Devonian-Permian history of magmatic activity in the Tien Shan and its framework has been considered using new isotopic datings. It has been shown that the intensity of magmatism and composition of igneous rocks are controlled by interaction of the local thermal upper mantle state (plumes) and dynamics of the lithosphere on a broader regional scale (plate motion). The Kazakhstan paleocontinent, which partly included the present-day Tien Shan and Qizilqum, was formed in the Late Ordovician-Early Silurian as a result of amalgamation of ancient continental masses and island arcs. The Devonian began here with heating of the mantle that resulted in the within-plate basaltic volcanism in the southern framework of the Kazakhstan paleocontinent (Turkestan paleoocean) and development of suprasubduction magmatism over an extensive area at its margin. In the Middle-Late Devonian, the margins of the Turkestan paleoocean were passive; the area of within-plate oceanic magmatism shifted eastward, and the active margin was retained at the junction with the Balqash-Junggar paleoocean. A new period of active magmatism was induced by an overall shortening of the region under conditions of plate convergence. The process started in the Early Carboniferous at the Junggar-Balqash margin of the Kazakhstan paleocontinent and the southern (Paleotethian) margin of the Qarakum-Tajik paleocontinent. In the Late Carboniferous, magmatism developed along the northern boundary of the Turkestan paleoocean, which was closing between them. The disappearance of deepwater oceanic basins by the end of the Carboniferous was accompanied by collisional granitic magmatism, which inherited the subduction zones. Postcollision magmatism fell in the Early Permian with a peak at 280 Ma ago. In contrast to Late Carboniferous granitic rocks, the localization of Early Permian granitoids is more independent of collision sutures. The magmatism of this time comprises: (1) continuation of the suprasubduction process (I-granites, etc.) with transition to the bimodal type in the Tien Shan segment of the Kazakhstan paleocontinent that formed;

Journal of Metamorphic Geology

The Makbal Complex in the northern Tianshan of Kazakhstan and Kyrgyzstan consists of metasediment... more The Makbal Complex in the northern Tianshan of Kazakhstan and Kyrgyzstan consists of metasedimentary rocks, which host high-P (HP) mafic blocks and ultra-HP Grt-Cld-Tlc schists (UHP as indicated by coesite relicts in garnet). Whole rock major and trace element signatures of the Grt-Cld-Tlc schist suggest a metasomatized protolith from either hydrothermally altered oceanic crust in a back-arc basin or arc-related volcaniclastics. Peak metamorphic conditions of the Grt-Cld-Tlc schist reached~580°C and 2.85 GPa corresponding to a maximum burial depth of~95 km. A Sm-Nd garnet age of 475 AE 4 Ma is interpreted as an average growth age of garnet during prograde-to-peak metamorphism; the low initial eΝd value of À11 indicates a protolith with an ancient crustal component. The petrological evidence for deep subduction of oceanic crust poses questions with respect to an effective exhumation mechanism. Field relationships and the metamorphic evolution of other HP mafic oceanic rocks embedded in continentally derived metasedimentary rocks at the central Makbal Complex suggest that fragments of oceanic crust and clastic sedimentary rocks were exhumed from different depths in a subduction channel during ongoing subduction and are now exposed as a tectonic m elange. Furthermore, channel flow cannot only explain a tectonic m elange consisting of various rock types with different subduction histories as present at the central Makbal Complex, but also the presence of a structural 'dome' with UHP rocks in the core (central Makbal) surrounded by lower pressure nappes (including mafic dykes in continental crust) and voluminous metasedimentary rocks, mainly derived from the accretionary wedge.

Russian Geology and Geophysics

The Koshrabad massif, referred to as the Hercynian postcollisional intrusions of the Tien Shan, i... more The Koshrabad massif, referred to as the Hercynian postcollisional intrusions of the Tien Shan, is composed of two rock series: (1) mafic and quartz monzonites and (2) granites of the main phase. Porphyritic granitoids of the main phase contain ovoids of alkali feldspar, often rimmed with plagioclase. Mafic rocks developed locally in the massif core resulted from the injections of mafic magma into the still unconsolidated rocks of the main phase, which produced hybrid rocks and various dike series. All rocks of the massif are characterized by high f (Fe/(Fe + Mg)) values and contain fayalite, which points to the reducing conditions of their formation. Mafic rocks are the product of fractional crystallization of alkali-basaltic mantle melt, and granitoids of the main phase show signs of crustal-substance contamination. In high f values and HFSE contents the massif rocks are similar to A-type granites. Data on the geochemical evolution of the massif rocks confirm the genetic relationship of the massif gold deposits with magmatic processes and suggest the accumulation of gold in residual acid melts and the rapid formation of ore quartz veins in the same structures that controlled the intrusion of late dikes. The simultaneous intrusion of compositionally different postcollisional granitoids of the North Nuratau Ridge, including the Koshrabad granitoids, is due to the synchronous melting of different crustal protoliths in the zone of transcrustal shear, which was caused by the ascent of the hot asthenospheric matter in the dilatation setting. The resulting circulation of fluids led to the mobilization of ore elements from the crustal rocks and their accumulation in commercial concentrations.

Ore Geology Reviews

Neoproterozoic volcanics and granitoids formed at Rodinia margins within a time span of 880 Ma-70... more Neoproterozoic volcanics and granitoids formed at Rodinia margins within a time span of 880 Ma-700 Ma, are well-documented in many terranes of the southern Central Asian Orogenic Belt (CAOB). Ages younger than 550 Ma corresponding to the opening of the Terskey Ocean are also common. However, so far, there were very few published ages in the range 700 Ma-550 Ma from the Kyrgyz Tien Shan. In this paper we present new data for the alkaline Chon-Ashu complex emplaced at the end of the Cryogenian Period of the Neoproterozoic (850-635 Ma, Gradstein et al., 2012). The alkaline complex intrudes the Precambrian metamorphic rocks north of the Nikolaev Line which separates the Northern and Middle Tien Shan terranes in the eastern Kyrgyzstan. The undeformed shallow level alkaline rocks range from olivine gabbro to nepheline and cancrinite syenites and leucosyenites. The differentiated rock assemblage can be explained by fractional crystallization of high-silica mineral phases which drives nepheline-normative melts away from the silica saturation boundary. The alkaline rocks of Chon-Ashu are enriched in LILE and HFSE indicative of their origin from lithospheric mantle. An age of 678 ± 9 Ma (U-Pb, SHRIMP) was obtained for a protolith of country gneiss, and an age of 656 ± 4 Ma was obtained for the crosscutting alkaline rocks of the Chon-Ashu complex. Seven zircon grains recovered from gneiss and alkaline rocks had bright overgrown rims which yielded a cumulative age of 400 ± 8 Ma. A metamorphic event, followed by uplift and emplacement of shallow level alkaline complex, constrains the geodynamic setting. Alkaline rocks usually form in an extensional setting and originate from lithospheric mantle. The 690 Ma xenoliths of mafic granulite from the NW Tarim have been interpreted to originate by mafic underplating. This mafic underplating may have been responsible for metamorphism in the middle crust prior to emplacement of the Chon-Ashu complex. The 670 Ma-630 Ma period of extension and emplacement of enriched alkaline rocks can be also traced on a regional scale through southern Kazakhstan and the northern Tarim. We tentatively interpret these events as a result of mafic underplating and subsequent rifting related to the break-up of Rodinia. During field work at Chon-Ashu, rich chalcopyrite mineralization has been discovered in carbonate veinlets in leucosyenite alkaline dikes and has also been found in the adjacent Cambrian gabbro and granites shown on the map as undivided Devonian-Silurian. Stockwork mineralization predominates though disseminated mineralization is also present. The Cu content reaches 16,184 ppm and is associated with elevated concentrations of Pb, Zn and Ag. The polyphase structural evolution of the area suggests that mineralization could have formed in several genetically unrelated stages. Based on structural and mineralogical evidence we tentatively relate the earliest stage of chalcopyrite mineralization to the late magmatic CO 2 -rich fluids emanating from the Cryogenian alkaline complex. The Early Devonian thermal event registered by growth of new zircon at 400 Ma has important metallogenic implications on a regional scale. However the origin of two zones of alteration in the undivided Silurian-Devonian granites is ambiguous because their age was not determined geochronologically. The 522 ± 4 Ma Cambrian gabbro of the Tashtambektor Formation is strongly foliated along the splays of the Nikolaev Line, indicating a Hercynian origin of the fabric. Superimposed mineralized stockwork postdates the foliation and suggests a late-Hercynian age of mineralization in gabbro. The new data enable a reassessment of the metallogenic potential of the Eastern Kyrgyz Tien Shan. Presence of not eroded high-level mineralized Neoproterozoic alkaline intrusions points to a previously underestimated metallogenic potential of pre-Hercynian granitoids which may host preserved porphyry systems, skarns and shear-related mineralization. Finally, the Devonian magmato-metamorphic event which caused formation of a number of ore deposits in central Kyrgyzstan and Kazakhstan could also create potential exploration targets in eastern Kyrgyzstan.

Lithos, 2013

The Makbal Complex in the western Tianshan Mountains of Kazakhstan and Kyrgyzstan consists of HP/... more The Makbal Complex in the western Tianshan Mountains of Kazakhstan and Kyrgyzstan consists of HP/UHP metasedimentary host rocks which enclose various HP mafic blocks or boudins. These mafic rocks comprise rare eclogites (sensu stricto and sensu lato), garnet amphibolites (retrograded eclogites) and a newly discovered glaucophanite (glaucophane-garnet-omphacite bearing rock). So far the Makbal Complex has been interpreted to predominantly consist of continental lithologies and the mafic rocks were considered as dismembered dikes intruding continental metasediments. This interpretation is mainly based on the geological relationship and bulk rock chemistry of the different rock types. It was further suggested that the continental lithologies of the Makbal Complex underwent eclogite-facies metamorphism in a former subduction zone. In the present study we combined conventional geothermometry, P-T pseudosection modeling and major and trace element whole rock geochemistry for different mafic samples (glaucophanite and eclogites (sensu lato)) in order to shed light on both the metamorphic evolution and the protoliths of the mafic HP rocks in the Makbal Complex. Prograde to peak-pressure clockwise P-T paths of glaucophanite and eclogites (sensu lato) were modeled using garnet isopleth thermobarometry. The results show that the glaucophanite and eclogite (sensu lato) samples experienced similar prograde P-T paths and slightly different peak metamorphic conditions at 560°C at 2.4 GPa for the former and between~520°C at 2.2 GPa and~555°C at~2.5 GPa for the latter, corresponding to burial depths between 70 and 85 km. Whole rock major and trace element analyses and petrological evidence imply that the various rock types at the Makbal Complex most likely originated from different precursor rocks. Eclogites (sensu lato) are believed to represent strongly retrogressed former eclogite-facies rocks that had never been eclogites (sensu stricto, i.e. N 70 vol.% garnet and omphacite) due to an unfavorable alkali-poor bulk composition (Na 2 O b 1 wt.%). The four high-pressure mafic samples investigated in this study originated from oceanic crust (Zr/Hf ratio of 33 to 35) which contradicts all previous studies suggesting a continental protolith for all mafic HP/UHP rocks at Makbal. The present study indicates that the mafic high-pressure rocks represent incoherent segments of exhumed oceanic crust. Juxtaposition of different mafic oceanic (this study) and continental rocks is suggested to be due to buoyancy-driven exhumation of the metasedimentary host rock in the subduction channel where dismembered fragments of the subducted oceanic crust were captured in different depths.

Journal of Asian Earth Sciences

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Gondwana Research, 2012

In this paper we present the first results of sensitive high-resolution ion microprobe (SHRIMP) U... more In this paper we present the first results of sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon dating obtained for the ultra-high pressure (UHP) metamorphic rocks of the Makbal metamorphic complex in the Northern Tien Shan, Kyrgyzstan. Zircon grains from two HP eclogite samples and one sample of UHP garnet-talk-chloritoid schist have similar bright rims identified on cathodoluminescence (CL) images. The rims are interpreted as zircon overgrowth during UHP metamorphism. Dating of zircon rims from the three samples yielded similar ages of 509 ± 7 Ma, 502 ± 10 Ma and 498 ± 7 Ma. The time span of 510-500 Ma is considered as the "minimum" age of UHP metamorphism of the Makbal complex. This age is in accordance with Middle Cambrian faunal age of the Kara-Archa ophiolite in the Makbal area. It is suggested that the Makbal rocks were metamorphosed in the Middle Cambrian subduction zone dipping north under the Northern Tien Shan microcontinent. A deformed granodiorite associated with the Makbal metamorphic rocks yielded an age of 514 ± 5 Ma, indicating development of a magmatic arc simultaneously with the UHP metamorphism. Cores of zircon grains from the garnet-talk-chloritoid schist yielded a wide spectrum of ages (1850-800 Ma) characteristic for detrital zircons of continental origin. A depositional age b800 Ma points to a possible derivation from a Riphean passive margin of the Terskey Ocean. Analyses of zircon grains from two eclogite samples fit well-defined discordia lines with upper intercepts at 1446± 25 Ma and 1447± 29 Ma, indicating a homogeneous Mezoproterozoic protolith of these rocks. The possible presence of such protoliths in Makbal is illustrated by a similar age of inherited zircon recovered from the granodiorite (1443 ± 25 Ma) and by Mesoproterozoic detrital zircons from the garnet-talk-chloritoid schist. Ages of Kokchetav, Makbal, Aktyuz and Anrakhai HP-UHP complexes in the Kokchetav-Northern Tien Shan belt vary from 537 to 475 Ma and register subductionaccretion events during the Caledonian orogeny which finally formed the Paleo-Kazakhstan continent prior to Middle Ordovician.

Economic Geology, 2004

The age of mineralization is slightly younger than a U-Pb zircon age of 296.7 ± 4.2 Ma obtained f... more The age of mineralization is slightly younger than a U-Pb zircon age of 296.7 ± 4.2 Ma obtained for the postcollisional Djangart granite, about 80 km southeast of Kumtor, and slightly older than two published U-Pb ages of 268 ± 1 and 280 ± 9 Ma on a postcollisional granite intrusion ...

Mineralium Deposita, 2006

The Altaid orogen was formed by aggregation of Paleozoic subduction–accretion complexes and Preca... more The Altaid orogen was formed by aggregation of Paleozoic subduction–accretion complexes and Precambrian basement blocks between the Late Proterozoic and the Early Mesozoic. Because the Altaids are the site of abundant granitic plutonism and host some of the largest gold deposits in the world, understanding their formation has important implications on the comprehension of Phanerozoic crustal growth and metallogeny. In this study, we present the first extensive lead isotope data on magmatic and metasedimentary rocks as well as ore deposits of the southern part of the Altaids, including the Tien Shan (Tianshan) and southern Altay (Altai) orogenic belts. Our results show that each terrane investigated within the Tien Shan and southern Altay is characterized by a distinct Pb isotope signature and that there is a SW–NE Pb isotope gradient suggesting a progressive transition from a continental crust environment in the West (the Kyzylkum and Kokshaal segments of the Southern Tien Shan) to an almost 100% juvenile (MORB-type mantle-derived) crust environment in the East (Altay). The Pb isotope signatures of the studied ore deposits follow closely those of magmatic and metasedimentary rocks of the host terranes, thus supporting the validity of lead isotopes to discriminate terranes. Whereas this apparently suggests that no unique reservoir has been responsible for the huge gold concentration in this region, masking of a preferential Pb-poor Au-bearing reservoir by mixing with Pb-rich crustal reservoirs during the mineralizing events cannot be excluded.

Mineral Deposit Research: Meeting the Global Challenge, 2005

ABSTRACT The Altaid orogen consists of Paleozoic subduction-accretion complexes and magmatic arcs... more ABSTRACT The Altaid orogen consists of Paleozoic subduction-accretion complexes and magmatic arcs as well as narrow Precambrian basement slivers which were accreted, consolidated and then deformed during Paleozoic collisions and subsequent Alpine-Hima an deformations between the East European craton in the West, the Siberian craton in the East, and the Alai-Tarim and Karakum microcontinents in the South. The Altaids are the site of abundant plutonism and host some of the largest gold deposits in the world, especially of the orogenic gold type.Over 100 new lead isotope data show that each one of the Altaid domains investigated is characterized by distinct lead isotope signatures and that there is an W-E Pb isotope gradient suggesting a progressive transition from a continental crust environment in the west (Western Tien Shan) to an almost 100% juvenile (mantle-derived) crust environment in the east (Chinese Altay).Our data indicate also the locally extensive presence of old continental crust at the base of the Tien Shan east of the Talas-Farghona fault but not west of it.The lead isotope signatures of the ore deposits follow closely those of the magmatic and basement rocks of the host domains suggesting that no unique reservoir has been responsible for the gold concentration in this orogen.

In the Kyrgyz Tien Shan (also known as Tian Shan in literature) the Caledonian (Cambro-Silurian) ... more In the Kyrgyz Tien Shan (also known as Tian Shan in literature) the Caledonian (Cambro-Silurian) intrusions comprise an extensive magmatic arc stretching from east to west for more than 1000 km. The characteristic feature of the arc is its relatively homogeneous composition of rock types over the whole structure. The Kichy-Naryn and Djetim intrusions presented in this study are slightly elongated in an east-west direction and occupy an area of ca. 100 km 2 . The main rock types are diorite, granodiorite and granite. Geological and geochemical features of the Kichy-Naryn and Djetim intrusions demonstrate characteristics of I-type granite series. Rocks of the two intrusions define a continuous high-K calc-alkaline series. Diorite and granite of the Kichy-Naryn intrusion yielded early Silurian crystallisation ages of 436 ± 2 Ma (U-Pb, zircon). Diorite from pebbles in the conglomerate sampled close to the contact of the Kichy-Naryn intrusion yielded a significantly older early Ordovician crystallisation age of 466 ± 10 Ma. The obtained ages of 466 and 436 Ma match ages of two major regional magmatic pulses at ca. 435-440 and 460-470 Ma which took place during continuous subduction from the Cambrian to the Silurian. The amount of granites in the Northern Tien Shan, their prolonged history of formation and pronounced I-type geochemical characteristics suggest their formation in an Andean-type active margin environment.

Ore Geology Reviews, 2009

In the Kyrgyz Tien Shan (also known as Tian Shan in literature) the Caledonian (Cambro-Silurian) ... more In the Kyrgyz Tien Shan (also known as Tian Shan in literature) the Caledonian (Cambro-Silurian) intrusions comprise an extensive magmatic arc stretching from east to west for more than 1000 km. The characteristic feature of the arc is its relatively homogeneous composition of rock types over the whole structure. The Kichy-Naryn and Djetim intrusions presented in this study are slightly elongated in an east-west direction and occupy an area of ca. 100 km 2 . The main rock types are diorite, granodiorite and granite. Geological and geochemical features of the Kichy-Naryn and Djetim intrusions demonstrate characteristics of I-type granite series. Rocks of the two intrusions define a continuous high-K calc-alkaline series. Diorite and granite of the Kichy-Naryn intrusion yielded early Silurian crystallisation ages of 436 ± 2 Ma (U-Pb, zircon). Diorite from pebbles in the conglomerate sampled close to the contact of the Kichy-Naryn intrusion yielded a significantly older early Ordovician crystallisation age of 466 ± 10 Ma. The obtained ages of 466 and 436 Ma match ages of two major regional magmatic pulses at ca. 435-440 and 460-470 Ma which took place during continuous subduction from the Cambrian to the Silurian. The amount of granites in the Northern Tien Shan, their prolonged history of formation and pronounced I-type geochemical characteristics suggest their formation in an Andean-type active margin environment.

Economic Geology, 2004

The age of mineralization is slightly younger than a U-Pb zircon age of 296.7 ± 4.2 Ma obtained f... more The age of mineralization is slightly younger than a U-Pb zircon age of 296.7 ± 4.2 Ma obtained for the postcollisional Djangart granite, about 80 km southeast of Kumtor, and slightly older than two published U-Pb ages of 268 ± 1 and 280 ± 9 Ma on a postcollisional granite intrusion ...

The Devonian-Permian history of magmatic activity in the Tien Shan and its framework has been con... more The Devonian-Permian history of magmatic activity in the Tien Shan and its framework has been considered using new isotopic datings. It has been shown that the intensity of magmatism and composition of igneous rocks are controlled by interaction of the local thermal upper mantle state (plumes) and dynamics of the lithosphere on a broader regional scale (plate motion). The Kazakhstan paleocontinent, which partly included the present-day Tien Shan and Qizilqum, was formed in the Late Ordovician-Early Silurian as a result of amalgamation of ancient continental masses and island arcs. The Devonian began here with heating of the mantle that resulted in the within-plate basaltic volcanism in the southern framework of the Kazakhstan paleocontinent (Turkestan paleoocean) and development of suprasubduction magmatism over an extensive area at its margin. In the Middle-Late Devonian, the margins of the Turkestan paleoocean were passive; the area of within-plate oceanic magmatism shifted eastward, and the active margin was retained at the junction with the Balqash-Junggar paleoocean. A new period of active magmatism was induced by an overall shortening of the region under conditions of plate convergence. The process started in the Early Carboniferous at the Junggar-Balqash margin of the Kazakhstan paleocontinent and the southern (Paleotethian) margin of the Qarakum-Tajik paleocontinent. In the Late Carboniferous, magmatism developed along the northern boundary of the Turkestan paleoocean, which was closing between them. The disappearance of deepwater oceanic basins by the end of the Carboniferous was accompanied by collisional granitic magmatism, which inherited the subduction zones. Postcollision magmatism fell in the Early Permian with a peak at 280 Ma ago. In contrast to Late Carboniferous granitic rocks, the localization of Early Permian granitoids is more independent of collision sutures. The magmatism of this time comprises: (1) continuation of the suprasubduction process (I-granites, etc.) with transition to the bimodal type in the Tien Shan segment of the Kazakhstan paleocontinent that formed;

Journal of Metamorphic Geology

The Makbal Complex in the northern Tianshan of Kazakhstan and Kyrgyzstan consists of metasediment... more The Makbal Complex in the northern Tianshan of Kazakhstan and Kyrgyzstan consists of metasedimentary rocks, which host high-P (HP) mafic blocks and ultra-HP Grt-Cld-Tlc schists (UHP as indicated by coesite relicts in garnet). Whole rock major and trace element signatures of the Grt-Cld-Tlc schist suggest a metasomatized protolith from either hydrothermally altered oceanic crust in a back-arc basin or arc-related volcaniclastics. Peak metamorphic conditions of the Grt-Cld-Tlc schist reached~580°C and 2.85 GPa corresponding to a maximum burial depth of~95 km. A Sm-Nd garnet age of 475 AE 4 Ma is interpreted as an average growth age of garnet during prograde-to-peak metamorphism; the low initial eΝd value of À11 indicates a protolith with an ancient crustal component. The petrological evidence for deep subduction of oceanic crust poses questions with respect to an effective exhumation mechanism. Field relationships and the metamorphic evolution of other HP mafic oceanic rocks embedded in continentally derived metasedimentary rocks at the central Makbal Complex suggest that fragments of oceanic crust and clastic sedimentary rocks were exhumed from different depths in a subduction channel during ongoing subduction and are now exposed as a tectonic m elange. Furthermore, channel flow cannot only explain a tectonic m elange consisting of various rock types with different subduction histories as present at the central Makbal Complex, but also the presence of a structural 'dome' with UHP rocks in the core (central Makbal) surrounded by lower pressure nappes (including mafic dykes in continental crust) and voluminous metasedimentary rocks, mainly derived from the accretionary wedge.

Russian Geology and Geophysics

The Koshrabad massif, referred to as the Hercynian postcollisional intrusions of the Tien Shan, i... more The Koshrabad massif, referred to as the Hercynian postcollisional intrusions of the Tien Shan, is composed of two rock series: (1) mafic and quartz monzonites and (2) granites of the main phase. Porphyritic granitoids of the main phase contain ovoids of alkali feldspar, often rimmed with plagioclase. Mafic rocks developed locally in the massif core resulted from the injections of mafic magma into the still unconsolidated rocks of the main phase, which produced hybrid rocks and various dike series. All rocks of the massif are characterized by high f (Fe/(Fe + Mg)) values and contain fayalite, which points to the reducing conditions of their formation. Mafic rocks are the product of fractional crystallization of alkali-basaltic mantle melt, and granitoids of the main phase show signs of crustal-substance contamination. In high f values and HFSE contents the massif rocks are similar to A-type granites. Data on the geochemical evolution of the massif rocks confirm the genetic relationship of the massif gold deposits with magmatic processes and suggest the accumulation of gold in residual acid melts and the rapid formation of ore quartz veins in the same structures that controlled the intrusion of late dikes. The simultaneous intrusion of compositionally different postcollisional granitoids of the North Nuratau Ridge, including the Koshrabad granitoids, is due to the synchronous melting of different crustal protoliths in the zone of transcrustal shear, which was caused by the ascent of the hot asthenospheric matter in the dilatation setting. The resulting circulation of fluids led to the mobilization of ore elements from the crustal rocks and their accumulation in commercial concentrations.

Ore Geology Reviews

Neoproterozoic volcanics and granitoids formed at Rodinia margins within a time span of 880 Ma-70... more Neoproterozoic volcanics and granitoids formed at Rodinia margins within a time span of 880 Ma-700 Ma, are well-documented in many terranes of the southern Central Asian Orogenic Belt (CAOB). Ages younger than 550 Ma corresponding to the opening of the Terskey Ocean are also common. However, so far, there were very few published ages in the range 700 Ma-550 Ma from the Kyrgyz Tien Shan. In this paper we present new data for the alkaline Chon-Ashu complex emplaced at the end of the Cryogenian Period of the Neoproterozoic (850-635 Ma, Gradstein et al., 2012). The alkaline complex intrudes the Precambrian metamorphic rocks north of the Nikolaev Line which separates the Northern and Middle Tien Shan terranes in the eastern Kyrgyzstan. The undeformed shallow level alkaline rocks range from olivine gabbro to nepheline and cancrinite syenites and leucosyenites. The differentiated rock assemblage can be explained by fractional crystallization of high-silica mineral phases which drives nepheline-normative melts away from the silica saturation boundary. The alkaline rocks of Chon-Ashu are enriched in LILE and HFSE indicative of their origin from lithospheric mantle. An age of 678 ± 9 Ma (U-Pb, SHRIMP) was obtained for a protolith of country gneiss, and an age of 656 ± 4 Ma was obtained for the crosscutting alkaline rocks of the Chon-Ashu complex. Seven zircon grains recovered from gneiss and alkaline rocks had bright overgrown rims which yielded a cumulative age of 400 ± 8 Ma. A metamorphic event, followed by uplift and emplacement of shallow level alkaline complex, constrains the geodynamic setting. Alkaline rocks usually form in an extensional setting and originate from lithospheric mantle. The 690 Ma xenoliths of mafic granulite from the NW Tarim have been interpreted to originate by mafic underplating. This mafic underplating may have been responsible for metamorphism in the middle crust prior to emplacement of the Chon-Ashu complex. The 670 Ma-630 Ma period of extension and emplacement of enriched alkaline rocks can be also traced on a regional scale through southern Kazakhstan and the northern Tarim. We tentatively interpret these events as a result of mafic underplating and subsequent rifting related to the break-up of Rodinia. During field work at Chon-Ashu, rich chalcopyrite mineralization has been discovered in carbonate veinlets in leucosyenite alkaline dikes and has also been found in the adjacent Cambrian gabbro and granites shown on the map as undivided Devonian-Silurian. Stockwork mineralization predominates though disseminated mineralization is also present. The Cu content reaches 16,184 ppm and is associated with elevated concentrations of Pb, Zn and Ag. The polyphase structural evolution of the area suggests that mineralization could have formed in several genetically unrelated stages. Based on structural and mineralogical evidence we tentatively relate the earliest stage of chalcopyrite mineralization to the late magmatic CO 2 -rich fluids emanating from the Cryogenian alkaline complex. The Early Devonian thermal event registered by growth of new zircon at 400 Ma has important metallogenic implications on a regional scale. However the origin of two zones of alteration in the undivided Silurian-Devonian granites is ambiguous because their age was not determined geochronologically. The 522 ± 4 Ma Cambrian gabbro of the Tashtambektor Formation is strongly foliated along the splays of the Nikolaev Line, indicating a Hercynian origin of the fabric. Superimposed mineralized stockwork postdates the foliation and suggests a late-Hercynian age of mineralization in gabbro. The new data enable a reassessment of the metallogenic potential of the Eastern Kyrgyz Tien Shan. Presence of not eroded high-level mineralized Neoproterozoic alkaline intrusions points to a previously underestimated metallogenic potential of pre-Hercynian granitoids which may host preserved porphyry systems, skarns and shear-related mineralization. Finally, the Devonian magmato-metamorphic event which caused formation of a number of ore deposits in central Kyrgyzstan and Kazakhstan could also create potential exploration targets in eastern Kyrgyzstan.

Lithos, 2013

The Makbal Complex in the western Tianshan Mountains of Kazakhstan and Kyrgyzstan consists of HP/... more The Makbal Complex in the western Tianshan Mountains of Kazakhstan and Kyrgyzstan consists of HP/UHP metasedimentary host rocks which enclose various HP mafic blocks or boudins. These mafic rocks comprise rare eclogites (sensu stricto and sensu lato), garnet amphibolites (retrograded eclogites) and a newly discovered glaucophanite (glaucophane-garnet-omphacite bearing rock). So far the Makbal Complex has been interpreted to predominantly consist of continental lithologies and the mafic rocks were considered as dismembered dikes intruding continental metasediments. This interpretation is mainly based on the geological relationship and bulk rock chemistry of the different rock types. It was further suggested that the continental lithologies of the Makbal Complex underwent eclogite-facies metamorphism in a former subduction zone. In the present study we combined conventional geothermometry, P-T pseudosection modeling and major and trace element whole rock geochemistry for different mafic samples (glaucophanite and eclogites (sensu lato)) in order to shed light on both the metamorphic evolution and the protoliths of the mafic HP rocks in the Makbal Complex. Prograde to peak-pressure clockwise P-T paths of glaucophanite and eclogites (sensu lato) were modeled using garnet isopleth thermobarometry. The results show that the glaucophanite and eclogite (sensu lato) samples experienced similar prograde P-T paths and slightly different peak metamorphic conditions at 560°C at 2.4 GPa for the former and between~520°C at 2.2 GPa and~555°C at~2.5 GPa for the latter, corresponding to burial depths between 70 and 85 km. Whole rock major and trace element analyses and petrological evidence imply that the various rock types at the Makbal Complex most likely originated from different precursor rocks. Eclogites (sensu lato) are believed to represent strongly retrogressed former eclogite-facies rocks that had never been eclogites (sensu stricto, i.e. N 70 vol.% garnet and omphacite) due to an unfavorable alkali-poor bulk composition (Na 2 O b 1 wt.%). The four high-pressure mafic samples investigated in this study originated from oceanic crust (Zr/Hf ratio of 33 to 35) which contradicts all previous studies suggesting a continental protolith for all mafic HP/UHP rocks at Makbal. The present study indicates that the mafic high-pressure rocks represent incoherent segments of exhumed oceanic crust. Juxtaposition of different mafic oceanic (this study) and continental rocks is suggested to be due to buoyancy-driven exhumation of the metasedimentary host rock in the subduction channel where dismembered fragments of the subducted oceanic crust were captured in different depths.

Journal of Asian Earth Sciences

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Gondwana Research, 2012

In this paper we present the first results of sensitive high-resolution ion microprobe (SHRIMP) U... more In this paper we present the first results of sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon dating obtained for the ultra-high pressure (UHP) metamorphic rocks of the Makbal metamorphic complex in the Northern Tien Shan, Kyrgyzstan. Zircon grains from two HP eclogite samples and one sample of UHP garnet-talk-chloritoid schist have similar bright rims identified on cathodoluminescence (CL) images. The rims are interpreted as zircon overgrowth during UHP metamorphism. Dating of zircon rims from the three samples yielded similar ages of 509 ± 7 Ma, 502 ± 10 Ma and 498 ± 7 Ma. The time span of 510-500 Ma is considered as the "minimum" age of UHP metamorphism of the Makbal complex. This age is in accordance with Middle Cambrian faunal age of the Kara-Archa ophiolite in the Makbal area. It is suggested that the Makbal rocks were metamorphosed in the Middle Cambrian subduction zone dipping north under the Northern Tien Shan microcontinent. A deformed granodiorite associated with the Makbal metamorphic rocks yielded an age of 514 ± 5 Ma, indicating development of a magmatic arc simultaneously with the UHP metamorphism. Cores of zircon grains from the garnet-talk-chloritoid schist yielded a wide spectrum of ages (1850-800 Ma) characteristic for detrital zircons of continental origin. A depositional age b800 Ma points to a possible derivation from a Riphean passive margin of the Terskey Ocean. Analyses of zircon grains from two eclogite samples fit well-defined discordia lines with upper intercepts at 1446± 25 Ma and 1447± 29 Ma, indicating a homogeneous Mezoproterozoic protolith of these rocks. The possible presence of such protoliths in Makbal is illustrated by a similar age of inherited zircon recovered from the granodiorite (1443 ± 25 Ma) and by Mesoproterozoic detrital zircons from the garnet-talk-chloritoid schist. Ages of Kokchetav, Makbal, Aktyuz and Anrakhai HP-UHP complexes in the Kokchetav-Northern Tien Shan belt vary from 537 to 475 Ma and register subductionaccretion events during the Caledonian orogeny which finally formed the Paleo-Kazakhstan continent prior to Middle Ordovician.