Alexandra Gurova | Novosibirsk State University (original) (raw)
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Papers by Alexandra Gurova
Litosfera, Sep 2, 2022
Аннотация. В статье дан обзор основных этапов магматизма и месторождений и рудопроявлений меди и ... more Аннотация. В статье дан обзор основных этапов магматизма и месторождений и рудопроявлений меди и других металлов Тектурмасского офиолитового пояса (ТОП) и смежных структур Центрального Казахстана. Обсуждают ся возраст, состав и вероятные тектонические обстановки формирования связанного с сульфидной минерализаци ей Cu-Ni оруденения Центрального Казахстана. ТОП состоит из свит трех литологических типов: преимуществен но базальтовых (карамурунская и кузекская), кремнистых (тектурмасская и базарбайская) и обломочных (сарытаусская, аиртаусская и ермекская). Потенциальная рудоносность самого Тектурмасского офиолитового пояса свя зана с плутоническими основными и ультраосновными породами офиолитового разреза в пределах Тектурмасского и Базарбайского сегментов. Смежная с ТОП Успенская рифтовая зона включает в себя три вулканогенно осадочные толщи ранне-среднесилурийского, ранне-среднедевонского и позднедевонско-раннекарбонового воз раста. Успенское месторождение меди приурочено к самой молодой толще. Геологическое строение территории, включающей в себя магматические тела с Cu-Ni оруденением, является основой комплексного подхода к изу чению рудообразующих систем. Наиболее перспективные на медную минерализацию локации в пределах ТОП и Успенской рифтовой зоны-месторождения Камкор и Успенское-Белла, рудопроявления Уртынжал, Ордобасы и Шопа-связаны с основными и ультраосновными интрузивными комплексами. Приведены основные геоло гические характеристики районов этих месторождений и рудопроявлений и типы минерализации. Показано, что Центральный Казахстан имеет мало перспектив для обнаружения крупных медных месторождений, но обнару жение средних и мелких месторождений такого типа вполне возможно. Находка новых значимых объектов Cuпорфирового типа в районе ТОП также маловероятна, но интерес может представлять доизучение и открытие но вых рудных тел в районе уже известных месторождений и рудопроявлений.
Geodynamics & Tectonophysics
The paper presents new petrographic and geochemical data from volcanic and sedimentary rocks and ... more The paper presents new petrographic and geochemical data from volcanic and sedimentary rocks and first U-Pb ages of detrital zircons from sandstones of the Itmurundy zone of central Kazakhstan. The volcanic rocks are aphyric and porphyric basalts, andesibasalt and andesite. The major element composition of tuff and sandstone are close to that of andesite. The poorly sorted greenish grey sandstones carry numerous fragments of volcanic and sedimentary rocks suggesting its greywacke nature which is probably due to. The greywacke probably formed by the destruction of undissected arc. The distribution of U-Pb ages of detrital zircons spanning 505 to 432 Ma has unimodal character peaked at 445 Ma suggesting formation of the sandstones by the destruction and subsequent transportation of clastic material from a late Ordovician intra-oceanic arc. In geochemical diagrams, the tuffs and sandstone plot close to the volcanic rocks. All chondrite-normalized REE spectra show enrichment in LREE (La...
Geotectonics, 2020
Studies of volcanic rocks in orogenic troughs of Eastern Kazakhstan were carried out. The troughs... more Studies of volcanic rocks in orogenic troughs of Eastern Kazakhstan were carried out. The troughs were formed at late-orogenic stages of evolution of Hercynian Altai collision system. Volcanic rocks are represented by basalts, andesites, dacites and rhyolites. Based on geochemical and isotopic data, the basalts and andesites derived from mafic magmas that formed as a result of partial melting of garnet peridotites in the upper mantle under the orogen. U-Pb zircon data prove two volcanic stages: more-scaled Middle Carboniferous (~311 Ma) and less-scaled Early Permian (297-290 Ma). Basalts and andesites in lower parts of the orogenic troughs and independent dacite-rhyolite structures were formed at the Middle Carboniferous stage. Parental mafic magmas were formed as a result of partial melting of mantle substrates in local transtensional zones along large shear faults. The formation of dacites and rhyolites could have been caused by partial melting of crustal substrates under effect of mafic magmas. Transtensional movements in the lithosphere of orogenic belts may indicate the beginning of collapse of orogens. A smaller volume of basalts and andesites formed at the Early Permian stage. Geochemical data prove the independent episode of partial melting in upper mantle. Synchronous basalts and andesites also appeared at wide territory in Tian Shan, Central Kazakhstan, and Central and Southern Mongolia. Early Permian volcanism indicates general extension of the lithosphere at the postorogenic stages. Large-scaled Early Permian mafic and granitoid magmatism in Central Asia has been interpreted in recent years as the Tarim Large Igneous Province caused by Tarim mantle plume activity. Thus, the extension of the lithosphere and associated volcanism in the Early Permian can be an indicator of the onset of the plume-lithosphere interaction process.
Gondwana Research, 2019
Abstract The Itmurundy zone/belt is located in the northern Balkhash area of central Kazakhstan. ... more Abstract The Itmurundy zone/belt is located in the northern Balkhash area of central Kazakhstan. Geologically it belongs to the Kazakh orocline located in the western Central Asian Orogenic Belt (CAOB), north of the Tarim craton and west of the Junggar block. The Itmurundy belt, which surprisingly has remained unstudied in terms of up-to-date geochronological, geochemical and isotope methods compared to other regions of the CAOB, was revisited and reinvestigated. The belt possesses a very complicated geological structure and hosts rocks of mantle, orogenic and post-orogenic associations. This paper focuses on the orogenic association and presents original geological data, first U–Pb age and first up-to-date geochemical and Nd isotope data from igneous rocks. The orogenic association of the Itmurundy belt includes volcanic and sedimentary rocks of three formations, Itmurundy (O1-2), Kazyk (O2-3) and Tyuretai (O3–S1), and represents an accretionary complex. The most lithologically diverse Itmurundy Fm. (O1-2) consists of oceanic basalt, pelagic chert, hemipelagic siliceous mudstone and siltstone, and greywacke sandstones. Both sedimentary and igneous rocks were strongly deformed by syn- and post-accretion processes, which, in places, formed duplex structures. The igneous rocks are basalt/dolerite/gabbro, andesibasalt, trachybasalt and diorite. The diorite yielded a U–Pb age of ca. 500 Ma. The subalkaline volcanic and subvolcanic rocks belong to the tholeiitic series. Based on major oxides three groups of rocks can be distinguished: high-Ti, mid-Ti and low-Ti. The rocks of these three groups are variably enriched in LREE (LaN = 122, 23 and 2 in average, respectively) showing LREE enriched (high-Ti), LREE depleted (mid-Ti) and flat (low-Ti) REE patterns. The high-Ti group shows enrichment in Nb, Th, and Zr compared to the mid-Ti and low-Ti groups. The low-Ti group is special for the Nb troughs in primitive mantle normalized multi-element diagrams, which are typical of supra-subduction settings. The values of eNd are mostly positive for the mid-Ti and low-Ti groups, but negative for the high-Ti group. The geochemical features of the igneous rocks suggest their formation in oceanic (oceanic floor and oceanic island/seamount) and supra-subduction (intra-oceanic arc) settings. In general, the structural position, lithology and deformation styles of Itmurundy sedimentary and igneous rocks and the geochemical features of the igneous rocks all accord well with the models of Ocean Plate Stratigraphy (OPS) and Pacific-type orogeny. Thus, the Itmurundy belt at northern Balkhash represents an Ordovician-Silurian Pacific-type orogenic belt formed at a convergent active margin of the Paleo-Asian Ocean.
Russian Journal of Pacific Geology, 2019
The Itmurundy zone of the northern Balkhash area is a Pacific-type orogenic belt. It possesses a ... more The Itmurundy zone of the northern Balkhash area is a Pacific-type orogenic belt. It possesses a complex geological structure and hosts rocks of mantle, accretionary and post-orogenic associations. The volcanic and sedimentary rocks of the accretionary association belong to three suites: Itmurundy (O 1-2), Kazyk (O 2-3) and Tyuretai (O 3-S 1). The suites are separated by tectonic unconformities or faults of three orders: 1) large regional faults; 2) medium faults separating mantle and oceanic accreted rocks; 3) small faults separating packages consisting of oceanic sediments. The Itmurundy Fm. (O 1-2) is the most lithologically variable consisting of oceanic basalt, pelagic chert, hemipelagic siliceous mudstone and siltstone, and trench greywacke sandstone. The packages, each consisting of chert-siliceous mudstone, are separated from each other by 2 nd and 3 rd order faults of probably thrust nature, i.e. they are parts of duplex structures. The presence of duplex structures and the high degree of deformation of Itmurundy Fm. rocks are typical of accretionary complexes. The associations of volcanic and sedimentary rocks under study represent a full section of oceanic plate stratigraphy (OPS): basalt (MORB, OIB)-chert (pelagic)-siliceous mudstone, siltstone and shale (hemipelagic)-trench sandstones (greywacke). The structural position and the lithology of Itmurundy rocks accord well with the model of formation of accretionary complexes at Pacific-type convergent margins, in particular, those in the western Pacific.
Geological Journal
The Tekturmas ophiolite belt of central Kazakhstan is located in the western Central Asian Orogen... more The Tekturmas ophiolite belt of central Kazakhstan is located in the western Central Asian Orogenic Belt. It consists of three structural‐formational zones: Tekturmas (centre), Bazarbai (north), and Sarysui (south). The Tekturmas zone includes igneous and sedimentary rocks of Karamurun, Tekturmas, and Sarytau formations, which are dominated by volcanogenic, deep sea, and clastic deposits, respectively. The Bazarbai zone consists of Kuzek and Basarbai formations dominated, respectively, by basaltic and sedimentary rocks. The Sarysui zone includes terrigenous Airtau and olistostromic Ermek formations. The age of sedimentary rocks was constrained by microfossils. The igneous rocks of the Karamurun and Bazarbai formations are alkaline and subalkaline basalt/dolerite, andesibasalt, and andesite. There are three main groups of rocks: high‐Ti, mid‐Ti, and low‐Ti. The high‐Ti Karamurun volcanics and low‐Ti Bazarbai are variably enriched in light rare earth element (LREE) showing LREE enriched (high‐Ti) and LREE flat (low‐Ti) REE patterns. The high‐Ti group shows enrichment in Nb, Th, Zr, and Sm compared with the low‐Ti group. The low‐Ti group is special for the Nb troughs in primitive mantle‐normalized multi‐element diagrams, which are typical of supra‐subduction settings. Both groups yielded positive εNd values, although the averages are 4.6 and 7.5 for the high‐ and low‐Ti rocks, respectively. The geochemical features suggest formation of the igneous rocks in oceanic and supra‐subduction (intra‐oceanic arc) settings. The geological and geochemical features of the Tekturmas ophiolite belt accord well with the tectonic emplacement of ophiolites and formation of accretionary complex at a Pacific‐type convergent margin similar to those of the western Pacific.
Litosfera, Sep 2, 2022
Аннотация. В статье дан обзор основных этапов магматизма и месторождений и рудопроявлений меди и ... more Аннотация. В статье дан обзор основных этапов магматизма и месторождений и рудопроявлений меди и других металлов Тектурмасского офиолитового пояса (ТОП) и смежных структур Центрального Казахстана. Обсуждают ся возраст, состав и вероятные тектонические обстановки формирования связанного с сульфидной минерализаци ей Cu-Ni оруденения Центрального Казахстана. ТОП состоит из свит трех литологических типов: преимуществен но базальтовых (карамурунская и кузекская), кремнистых (тектурмасская и базарбайская) и обломочных (сарытаусская, аиртаусская и ермекская). Потенциальная рудоносность самого Тектурмасского офиолитового пояса свя зана с плутоническими основными и ультраосновными породами офиолитового разреза в пределах Тектурмасского и Базарбайского сегментов. Смежная с ТОП Успенская рифтовая зона включает в себя три вулканогенно осадочные толщи ранне-среднесилурийского, ранне-среднедевонского и позднедевонско-раннекарбонового воз раста. Успенское месторождение меди приурочено к самой молодой толще. Геологическое строение территории, включающей в себя магматические тела с Cu-Ni оруденением, является основой комплексного подхода к изу чению рудообразующих систем. Наиболее перспективные на медную минерализацию локации в пределах ТОП и Успенской рифтовой зоны-месторождения Камкор и Успенское-Белла, рудопроявления Уртынжал, Ордобасы и Шопа-связаны с основными и ультраосновными интрузивными комплексами. Приведены основные геоло гические характеристики районов этих месторождений и рудопроявлений и типы минерализации. Показано, что Центральный Казахстан имеет мало перспектив для обнаружения крупных медных месторождений, но обнару жение средних и мелких месторождений такого типа вполне возможно. Находка новых значимых объектов Cuпорфирового типа в районе ТОП также маловероятна, но интерес может представлять доизучение и открытие но вых рудных тел в районе уже известных месторождений и рудопроявлений.
Geodynamics & Tectonophysics
The paper presents new petrographic and geochemical data from volcanic and sedimentary rocks and ... more The paper presents new petrographic and geochemical data from volcanic and sedimentary rocks and first U-Pb ages of detrital zircons from sandstones of the Itmurundy zone of central Kazakhstan. The volcanic rocks are aphyric and porphyric basalts, andesibasalt and andesite. The major element composition of tuff and sandstone are close to that of andesite. The poorly sorted greenish grey sandstones carry numerous fragments of volcanic and sedimentary rocks suggesting its greywacke nature which is probably due to. The greywacke probably formed by the destruction of undissected arc. The distribution of U-Pb ages of detrital zircons spanning 505 to 432 Ma has unimodal character peaked at 445 Ma suggesting formation of the sandstones by the destruction and subsequent transportation of clastic material from a late Ordovician intra-oceanic arc. In geochemical diagrams, the tuffs and sandstone plot close to the volcanic rocks. All chondrite-normalized REE spectra show enrichment in LREE (La...
Geotectonics, 2020
Studies of volcanic rocks in orogenic troughs of Eastern Kazakhstan were carried out. The troughs... more Studies of volcanic rocks in orogenic troughs of Eastern Kazakhstan were carried out. The troughs were formed at late-orogenic stages of evolution of Hercynian Altai collision system. Volcanic rocks are represented by basalts, andesites, dacites and rhyolites. Based on geochemical and isotopic data, the basalts and andesites derived from mafic magmas that formed as a result of partial melting of garnet peridotites in the upper mantle under the orogen. U-Pb zircon data prove two volcanic stages: more-scaled Middle Carboniferous (~311 Ma) and less-scaled Early Permian (297-290 Ma). Basalts and andesites in lower parts of the orogenic troughs and independent dacite-rhyolite structures were formed at the Middle Carboniferous stage. Parental mafic magmas were formed as a result of partial melting of mantle substrates in local transtensional zones along large shear faults. The formation of dacites and rhyolites could have been caused by partial melting of crustal substrates under effect of mafic magmas. Transtensional movements in the lithosphere of orogenic belts may indicate the beginning of collapse of orogens. A smaller volume of basalts and andesites formed at the Early Permian stage. Geochemical data prove the independent episode of partial melting in upper mantle. Synchronous basalts and andesites also appeared at wide territory in Tian Shan, Central Kazakhstan, and Central and Southern Mongolia. Early Permian volcanism indicates general extension of the lithosphere at the postorogenic stages. Large-scaled Early Permian mafic and granitoid magmatism in Central Asia has been interpreted in recent years as the Tarim Large Igneous Province caused by Tarim mantle plume activity. Thus, the extension of the lithosphere and associated volcanism in the Early Permian can be an indicator of the onset of the plume-lithosphere interaction process.
Gondwana Research, 2019
Abstract The Itmurundy zone/belt is located in the northern Balkhash area of central Kazakhstan. ... more Abstract The Itmurundy zone/belt is located in the northern Balkhash area of central Kazakhstan. Geologically it belongs to the Kazakh orocline located in the western Central Asian Orogenic Belt (CAOB), north of the Tarim craton and west of the Junggar block. The Itmurundy belt, which surprisingly has remained unstudied in terms of up-to-date geochronological, geochemical and isotope methods compared to other regions of the CAOB, was revisited and reinvestigated. The belt possesses a very complicated geological structure and hosts rocks of mantle, orogenic and post-orogenic associations. This paper focuses on the orogenic association and presents original geological data, first U–Pb age and first up-to-date geochemical and Nd isotope data from igneous rocks. The orogenic association of the Itmurundy belt includes volcanic and sedimentary rocks of three formations, Itmurundy (O1-2), Kazyk (O2-3) and Tyuretai (O3–S1), and represents an accretionary complex. The most lithologically diverse Itmurundy Fm. (O1-2) consists of oceanic basalt, pelagic chert, hemipelagic siliceous mudstone and siltstone, and greywacke sandstones. Both sedimentary and igneous rocks were strongly deformed by syn- and post-accretion processes, which, in places, formed duplex structures. The igneous rocks are basalt/dolerite/gabbro, andesibasalt, trachybasalt and diorite. The diorite yielded a U–Pb age of ca. 500 Ma. The subalkaline volcanic and subvolcanic rocks belong to the tholeiitic series. Based on major oxides three groups of rocks can be distinguished: high-Ti, mid-Ti and low-Ti. The rocks of these three groups are variably enriched in LREE (LaN = 122, 23 and 2 in average, respectively) showing LREE enriched (high-Ti), LREE depleted (mid-Ti) and flat (low-Ti) REE patterns. The high-Ti group shows enrichment in Nb, Th, and Zr compared to the mid-Ti and low-Ti groups. The low-Ti group is special for the Nb troughs in primitive mantle normalized multi-element diagrams, which are typical of supra-subduction settings. The values of eNd are mostly positive for the mid-Ti and low-Ti groups, but negative for the high-Ti group. The geochemical features of the igneous rocks suggest their formation in oceanic (oceanic floor and oceanic island/seamount) and supra-subduction (intra-oceanic arc) settings. In general, the structural position, lithology and deformation styles of Itmurundy sedimentary and igneous rocks and the geochemical features of the igneous rocks all accord well with the models of Ocean Plate Stratigraphy (OPS) and Pacific-type orogeny. Thus, the Itmurundy belt at northern Balkhash represents an Ordovician-Silurian Pacific-type orogenic belt formed at a convergent active margin of the Paleo-Asian Ocean.
Russian Journal of Pacific Geology, 2019
The Itmurundy zone of the northern Balkhash area is a Pacific-type orogenic belt. It possesses a ... more The Itmurundy zone of the northern Balkhash area is a Pacific-type orogenic belt. It possesses a complex geological structure and hosts rocks of mantle, accretionary and post-orogenic associations. The volcanic and sedimentary rocks of the accretionary association belong to three suites: Itmurundy (O 1-2), Kazyk (O 2-3) and Tyuretai (O 3-S 1). The suites are separated by tectonic unconformities or faults of three orders: 1) large regional faults; 2) medium faults separating mantle and oceanic accreted rocks; 3) small faults separating packages consisting of oceanic sediments. The Itmurundy Fm. (O 1-2) is the most lithologically variable consisting of oceanic basalt, pelagic chert, hemipelagic siliceous mudstone and siltstone, and trench greywacke sandstone. The packages, each consisting of chert-siliceous mudstone, are separated from each other by 2 nd and 3 rd order faults of probably thrust nature, i.e. they are parts of duplex structures. The presence of duplex structures and the high degree of deformation of Itmurundy Fm. rocks are typical of accretionary complexes. The associations of volcanic and sedimentary rocks under study represent a full section of oceanic plate stratigraphy (OPS): basalt (MORB, OIB)-chert (pelagic)-siliceous mudstone, siltstone and shale (hemipelagic)-trench sandstones (greywacke). The structural position and the lithology of Itmurundy rocks accord well with the model of formation of accretionary complexes at Pacific-type convergent margins, in particular, those in the western Pacific.
Geological Journal
The Tekturmas ophiolite belt of central Kazakhstan is located in the western Central Asian Orogen... more The Tekturmas ophiolite belt of central Kazakhstan is located in the western Central Asian Orogenic Belt. It consists of three structural‐formational zones: Tekturmas (centre), Bazarbai (north), and Sarysui (south). The Tekturmas zone includes igneous and sedimentary rocks of Karamurun, Tekturmas, and Sarytau formations, which are dominated by volcanogenic, deep sea, and clastic deposits, respectively. The Bazarbai zone consists of Kuzek and Basarbai formations dominated, respectively, by basaltic and sedimentary rocks. The Sarysui zone includes terrigenous Airtau and olistostromic Ermek formations. The age of sedimentary rocks was constrained by microfossils. The igneous rocks of the Karamurun and Bazarbai formations are alkaline and subalkaline basalt/dolerite, andesibasalt, and andesite. There are three main groups of rocks: high‐Ti, mid‐Ti, and low‐Ti. The high‐Ti Karamurun volcanics and low‐Ti Bazarbai are variably enriched in light rare earth element (LREE) showing LREE enriched (high‐Ti) and LREE flat (low‐Ti) REE patterns. The high‐Ti group shows enrichment in Nb, Th, Zr, and Sm compared with the low‐Ti group. The low‐Ti group is special for the Nb troughs in primitive mantle‐normalized multi‐element diagrams, which are typical of supra‐subduction settings. Both groups yielded positive εNd values, although the averages are 4.6 and 7.5 for the high‐ and low‐Ti rocks, respectively. The geochemical features suggest formation of the igneous rocks in oceanic and supra‐subduction (intra‐oceanic arc) settings. The geological and geochemical features of the Tekturmas ophiolite belt accord well with the tectonic emplacement of ophiolites and formation of accretionary complex at a Pacific‐type convergent margin similar to those of the western Pacific.