TY - JOUR
T1 - The Itmurundy Pacific-type orogenic belt in northern Balkhash, central Kazakhstan
T2 - Revisited plus first U–Pb age, geochemical and Nd isotope data from igneous rocks
AU - Safonova, I.
AU - Savinskiy, I.
AU - Perfilova, A.
AU - Gurova, A.
AU - Maruyama, S.
AU - Tsujimori, T.
N1 - Funding Information:
The study was supported by the Ministry of Education and Science of the Russian Federation (project no. 14.Y26.31.0018 ), Scientific Project of the Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences (state assignments no. 0330-2016-0003 ) and by a professorship program of the Centre for Northeast Asian Studies, the Tohoku University, Sendai, Japan from the Tohoku University (for IS).
Funding Information:
Inna Safonova : Lab Chief at the Geology-Geophysics Department of the Novosibirsk State University; Senior Research Scientist at the Sobolev Institute of Geology and Mineralogy SB RAS, both in Novosibirsk, Russia. M.Sc. (1987) from the Novosibirsk State University (Honors), Ph.D. (2005) from the Institute of Geology SB RAS. Associate Editor of Gondwana Research (2017 Best Editor Award), Geoscience Frontiers (2016 Best Editor Award) and Journal of Asian Earth Sciences. Brain Pool Program Researcher in Korea Institute of Geology and Mineral Resources (2010–2012). Awardee of fellowship programs from JSPS at the Tokyo Institute of Technology (2014–2015) and University of Tokyo (2017), and CNEAS professorship program at Tohoku University (2019), all in Japan. Research fields include Pacific-type orogeny, ocean plate stratigraphy, geochronology, intra-plate and supra-subduction magmatism, mantle plumes. Leader of IGCP#592 Project “Continental construction in the Central Asian Orogenic Belt compared with actualistic examples from the western Pacific” under UNESCO-IUGS (2012–2016), Megagrant Project of the Ministry of Education and Science of Russia “A multidisciplinary study of Pacific-type orogenic belts and development of a holistic model linking evolution of oceans, their active margins and mantle magmatism” (grant no. №14.Y26.31.0018; 2017–2019) and co-leader of IGCP#592 Project “Orogenic architecture and crustal growth from accretion to collision: examples from the Central Asian Orogenic Belt and Tethyan orogen” (2017–2021).
Publisher Copyright:
© 2019 International Association for Gondwana Research
PY - 2020/3
Y1 - 2020/3
N2 - 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 εNd 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.
AB - 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 εNd 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.
KW - Central asian orogenic belt
KW - Intra-oceanic arc
KW - Ocean plate stratigraphy
KW - Ordovician-early silurian
KW - Paleo-asian ocean
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U2 - 10.1016/j.gr.2019.09.004
DO - 10.1016/j.gr.2019.09.004
M3 - Review article
AN - SCOPUS:85074054540
SN - 1342-937X
VL - 79
SP - 49
EP - 69
JO - Gondwana Research
JF - Gondwana Research
ER -