Early Ordovician alkali-ultramafic Zhilandy complex (Central Kazakhstan): structure and age of formation

2019 ◽  
Vol 484 (1) ◽  
pp. 61-65
Author(s):  
R. M. Antonuk ◽  
A. A. Tretyakov ◽  
K. E. Degtyarev ◽  
A. B. Kotov
Keyword(s):  
Complex Formation ◽  
Central Asian Orogenic Belt ◽  
Early Cambrian ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Central Asian ◽  
Geochronological Study ◽  
Three Stages ◽  
Late Neoproterozoic ◽  
Quartz Monzodiorites

U–Pb geochronological study of amphibole-bearing quartz monzodiorites of the alkali-ultramafic Zhilandy complex in Central Kazakhstan, whose formation is deduced at the Early Ordovician era (479 ± 3 Ma). The obtained data indicate three stages of intra-plate magmatism in the western part of the Central Asian Orogenic Belt: Late Neoproterozoic stage of alkali syenites of the Karsakpay complex intrusion, Early Cambrian stage of ultramafic-gabbroid plutons of the Ulutau complex formation, and Late Cambrian–Early Ordovician stage of formation of the Zhilandy complex and Krasnomay complex intrusions.

Cambrian biostratigraphy of the Tal Group, Lesser Himalaya, India, and early Tsanglangpuan (late early Cambrian) trilobites from the Nigali Dhar syncline

2005 ◽  
Vol 142 (1) ◽  
pp. 57-80 ◽  
Author(s):  
NIGEL C. HUGHES ◽  
SHANCHI PENG ◽  
O. N. BHARGAVA ◽  
A. D. AHLUWALIA ◽  
SANDEEP WALIA ◽  
...  
Keyword(s):  
Southwest China ◽  
Early Cambrian ◽  
Lesser Himalaya ◽  
Geographic Proximity ◽  
Late Cambrian ◽  
Assemblage Zone ◽  
Late Neoproterozoic ◽  
Spiti Region ◽  
The Himalaya ◽  
Tethyan Himalaya

Precise biostratigraphic constraints on the age of the Tal Group are restricted to (1) a basal level correlative with the Anabarites trisulcatus–Protohertzina anabarica Assemblage Zone of southwest China, (2) a level near the boundary of the lower and upper parts of the Tal Group correlative with the early Tsanglangpuan Stage (Drepanuroides Zone), and (3) an interval low in the upper part of the Tal Group correlative with later in the Tsanglangpuan Stage (Palaeolenus Zone). These correlations are based on small shelly fossil and trilobite taxa. Other chronostratigraphic constraints include the marked negative δ13C isotopic excursion coincident with the transition from the Krol Group to the Tal Group. This excursion is used as a proxy for the Precambrian–Cambrian boundary in several sections worldwide and, if applied to the Lesser Himalaya, indicates that the boundary is at or just above the base of the Tal Group. The upper parts of the Tal Group may be of middle or late Cambrian age and might form proximal equivalents of sections in the Zanskar–Spiti region of the Tethyan Himalaya. Both faunal content and lithological succession are comparable to southwest China, furthering recent arguments for close geographic proximity between the Himalaya and the Yangtze block during late Neoproterozoic and early Cambrian time. Trilobites from the uppermost parts of the Sankholi Formation from the Nigali Dhar syncline are described and referred to three taxa, one of which, Drepanopyge gopeni, is a new species. They are the oldest trilobites yet described from the Himalaya.

scholarly journals Zircon U–Pb geochronology and geochemistry of granitic rocks in central Mongolia

2020 ◽  
Vol 50 ◽  
pp. 23-44
Author(s):  
Boldbaatar Dolzodmaa ◽  
Yasuhito Osanai ◽  
Nobuhiko Nakano ◽  
Tatsuro Adachi
Keyword(s):  
Tectonic Setting ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
Calc Alkaline ◽  
Volcanic Arc ◽  
Central Mongolia ◽  
Central Asian ◽  
High K ◽  
Three Stages ◽  
Late Neoproterozoic

The Central Asian Orogenic Belt had been formed by amalgamation of voluminous subduction–accretionary complexes during the Late Neoproterozoic to the Mesozoic period. Mongolia is situated in the center of this belt. This study presents new zircon U–Pb geochronological, whole-rock major and trace element data for granitoids within central Mongolia and discusses the tectonic setting and evolution of these granitic magmas during their formation and emplacement. The zircon U–Pb ages indicate that the magmatism can be divided into three stages: the 564–532 Ma Baidrag granitoids, the 269–248 and 238–237 Ma Khangai granitoids. The 564–532 Ma Baidrag granitoids are adakitic, have an I-type affinity, and were emplaced into metamorphic rocks. In comparison, the 269–248 Ma granitoids have high-K, calc-alkaline, granodioritic compositions and are I-type granites, whereas the associated the 238–237 Ma granites have an A-type affinity. The 564–532 Ma Baidrag and 269–248 Ma Khangai granitoids also both have volcanic arc-type affinities, whereas the 238–237 Ma granites formed in a post-collisional tectonic setting. These geochronological and geochemical results suggest that arc magmatism occurred at the 564–532 Ma which might be the oldest magmatic activity in central Mongolia. Between the Baidrag and the Khangai, there might be paleo-ocean and the oceanic plate subducted beneath the Khangai and produced voluminous granite bodies during the 269–248 Ma. After the closure of the paleo-ocean, the post collisional granitoids were formed at the 238–237 Ma based on the result of later granitoids in the Khangai area.

scholarly journals Fluid Evolution, H-O Isotope and Re-Os Age of Molybdenite from the Baiyinhan Tungsten Deposit in the Eastern Central Asian Orogenic Belt, NE China, and Its Geological Significance

Minerals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 664
Author(s):  
Ruiliang Wang ◽  
Qingdong Zeng ◽  
Zhaochong Zhang ◽  
Yunpeng Guo ◽  
Jinhang Lu
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Meteoric Water ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Tungsten Deposit ◽  
Ne China ◽  
Central Asian ◽  
Three Stages ◽  
O Isotope

The quartz-vein-type Baiyinhan tungsten deposit is located at the eastern part of the Central Asian Orogenic Belt, NE China. Analyses of fluid inclusions, H-O isotope of quartz and Re-Os isotope of molybdenite were carried out. Three stages of mineralization were identified: The early quartz + wolframite + bismuth stage, the middle quartz + molybdenite stage and the late calcite + fluorite stage. Quartz veins formed in the three stages were selected for the fluid inclusion analysis. The petrographic observation and fluid inclusion microthermometry results revealed three types of fluid inclusions: CO2-H2O (C-type), liquid-rich (L-type) and vapor-rich (V-type). The homogenization temperatures of C-type, V-type and L-type inclusions were 233–374 °C, 210–312 °C, and 196–311 °C, respectively. The salinity of the three types of inclusions was identical, varying in the range of 5–12 wt%. The H-O isotope analyses results showed that quartz had δ18OH2O and δDSMOW compositions of −2.6‰ to 4.3‰ and −97‰ to −82‰, respectively, indicating that the ore-forming fluids were mainly derived from magmatic water with a minor contribution of meteoric water. The addition of meteoric water reduces the temperature and salinity of the ore-forming fluids, which leads to a decrease of the solubility of tungsten and molybdenum in the fluids and eventually the precipitation of minerals. Re-Os isotopic analysis of five molybdenite samples yielded an isochron age of 139.6 ± 7.6 Ma (2σ) with an initial 187Os of −0.05 ± 0.57 (MSWD = 3.5). Rhenium concentrations of the molybdenite samples were between 3.1 ug/g and 8.5 ug/g. The results suggest that the metals of the Baiyinhan deposit have a crust origin, and the mineralization is one episode of the Early Cretaceous tungsten mineralization epoch which occurred at the eastern part of the Central Asian Orogenic Belt.

Tectonic Position of the Late Neoproterozoic–Early Paleozoic Metamorphic Belts within the Tuva–Mongolian Terrane of the Central Asian Orogenic Belt

Petrology ◽  
2019 ◽  
Vol 27 (1) ◽  
pp. 43-58 ◽  
Author(s):  
I. K. Kozakov ◽  
E. B. Salnikova ◽  
I. V. Anisimova ◽  
P. Ya. Azimov ◽  
V. P. Kovach ◽  
...  
Keyword(s):  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Early Paleozoic ◽  
Central Asian ◽  
Tectonic Position ◽  
Late Neoproterozoic

Middle–Late Cambrian Rankenella–Girvanella reefs of the Mila Formation, northern Iran

2008 ◽  
Vol 45 (6) ◽  
pp. 619-639 ◽  
Author(s):  
Peter D. Kruse ◽  
Andrey Yu Zhuravlev
Keyword(s):  
Low Energy ◽  
Energy Interval ◽  
Early Cambrian ◽  
Northern Iran ◽  
Reef Complex ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Lime Mud ◽  
Shell Beds ◽  
Early Late

Following the collapse of the Early Cambrian archaeocyathan–calcimicrobial reef consortium, the Middle–Late Cambrian – Furongian was an interval dominated by purely microbial dendrolite and stromatolite reefs. However, among these latter, a few exceptional occurrences of metazoan reefs are known. One such reef complex occurs in the late Middle – early Late Cambrian – Furongian portion of the Mila Formation of northern Iran. In the otherwise low-energy interval of this formation, the anthaspidellid demosponge Rankenella hamdii sp. nov. is associated with encrusting Girvanella , eocrinoid plates, rhynchonelliformean brachiopod valves and subordinate hyoliths and trilobites in tempestite shell beds; these beds underwent synsedimentary cementation on the seafloor to form hardgrounds. In the succeeding, higher energy interval, a complex of metre-scale bioherms and (or) taphoherms incorporates toppled or transported Rankenella hamdii in association with brachiopods, echinoderm plates, trilobites and some red argillaceous lime mud. Among these, undoubted reefs were constructed from a framework of digitate Rankenella hamdii with thick Girvanella encrustations. These encrustations locally developed as subvertical columnar ministromatolites, which could also merge laterally to form more extensive masses. Subsequent pervasive cementation generated isopachous rinds that preserved the reef framework intact. Coeval and younger Cambrian anthaspidellid–calcimicrobial reefs are known from California–Nevada and Texas, USA. These were heralds of the Early Ordovician resurgence of metazoan reefs.

scholarly journals Precambrian terrains of Central Asian orogenic belt: comparative characteristics, types and peculiarities of the tectonic evolution

2019 ◽  
pp. 3-43
Author(s):  
V. V. Yarmolyuk ◽  
K. E. Degtyarev
Keyword(s):  
Tectonic Evolution ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
The Earth ◽  
Central Asian ◽  
Intraplate Magmatism ◽  
Formation History ◽  
History Of ◽  
Late Neoproterozoic ◽  
Early Neoproterozoic

The structure and peculiarities of the tectonic evolution of Precambrian terraines included into the structure of Paleozoids in different parts of the Central Asian orogenic belt are reviewed, types and comparative characteristics of Precambrian terraines are provided. We throw light on two types of Precambrian terrains structure: essentially juvenile Neoproterozoic crust (1); Mezo- and Early Neoproterozoic crust formed due to reworking of Early Precambrian formations (2). Terrains with juvenile Neoproterozioc crust, located in the Central and Eastern parts of the Central Asian orogenic belt, were generated in the oceanic sector of the Earth. Their formation was connected to the Early- and Late Neoproterozoic cycles of tectogenesis up to 200 Ma each cycle. Terrains with Mezo- and Early Neoproterozoic crust, found mainly in the West of the Central Asian orogenic belt, generated in the continental sector of the Earth during the Neoproterozoic, their evolution occurred mainly in the intracontinental environments. In the evolution all of considered terrains in the interval 800–700 Ma, an event associated with rift zones formation and intraplate magmatism was revealed, it coincided with the supercontinent Rodinia split. The conducted research allow to connect formation history of the Precambrian terrains of the Central Asian orogenic belt with the processes took place in the edge of the Syberia-Tarim part of the supercontinent Rodinia and the adjacent sector of the paleo-ocean.

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