Early Permian intrusions of the Alai range: Understanding tectonic settings of Hercynian post-collisional magmatism in the South Tien Shan, Kyrgyzstan

Lithos ◽  
2018 ◽  
Vol 302-303 ◽  
pp. 405-420 ◽  
Author(s):  
D. Konopelko ◽  
S.A. Wilde ◽  
R. Seltmann ◽  
R.L. Romer ◽  
Yu.S. Biske
Keyword(s):  
Tien Shan ◽  
Early Permian ◽  
The South ◽  
Tectonic Settings

scholarly journals Chapter 3. Postcollisional intrusions of the Alai Segment of South Tien Shan

2020 ◽  
pp. 70-101
Author(s):  
Dmitry L. Konopelko ◽  
Keyword(s):  
Lithospheric Mantle ◽  
Tien Shan ◽  
Crustal Material ◽  
Residence Times ◽  
Early Permian ◽  
The South ◽  
Geochronological Data ◽  
Alkaline Rocks ◽  
Isotopic Compositions ◽  
Space And Time

The early Permian intrusions of the Alai Segment of the South Tien Shan comprise four geochemically contrasting intrusive series, including (1) I-type and (2) shoshonitic granitoids, (3) peraluminous granitoids including S-type leucogranites and (4) alkaline rocks and carbonatites, closely associated in space and time. New geochronological data indicate that diverse magmatic series of the Alai segment formed virtually coevally in a post-collisional setting. Five U-Pb zircon rock ages in the range 287 – 281 Ma, in combination with published ages, define the main post-collisional magmatic pulse at 290 - 280, which is similar to ages of post-collisional intrusions elsewhere in the South Tien Shan. The Sr-Nd-Pb-Hf isotopic compositions of the studied intrusions are consistent with the reworking of crustal material with 1.6 – 1.1 Ga average crustal residence times indicating the formation of the Alai segment of the South Tien Shan on a continental basement with Mesoproterozoic or older crust. It is suggested that position of the Alai microcontinent between two major sutures enabled delamination of its lithospheric mantle, which triggered the diverse post-collisional magmatism as a result of interaction of ascending asthenospheric material with lithospheric mantle and various crustal protoliths.

Preliminary analysis of the spectral content of P and S waves from local earthquakes in the Garm, Tadjikistan region

1978 ◽  
Vol 68 (4) ◽  
pp. 949-971
Author(s):  
T. G. Rautian ◽  
V. I. Khalturin ◽  
V. G. Martynov ◽  
P. Molnar
Keyword(s):  
Seismic Moment ◽  
Tien Shan ◽  
Wave Spectra ◽  
The South ◽  
Spectral Content ◽  
Preliminary Results ◽  
Local Earthquakes ◽  
Calculated Stress ◽  
Stress Drops ◽  
Lower Frequencies

abstract This paper reports preliminary results of an analysis of the spectral content of seismic waves from over 1,000 local earthquakes in the Garm, Tadjikistan region. Very low values of Q (∼100) were obtained for the Mesozoic and Cenozoic sedimentary rocks of the Peter I Range compared with those in the crystalline rock of the South Tien Shan (Q ≳ 500). For events with the same low frequency spectra, earthquakes in the South Tien Shan are recorded with more energy at higher frequencies than earthquakes in the Peter I Range, at least in part, because of the greater attenuation of the sedimentary rock in the latter region. There is a wide variety of spectra radiated by earthquakes throughout the Garm region, but a marked difference between spectra radiated by earthquakes from these two regions is not apparent. Nevertheless although calculated stress drops of earthquakes appear to vary considerably throughout the region, there appears to be a dependence on the type of rock in which the earthquakes occurred. The variation in calculated stress drops, however, is greater within either region than between the two. For most regions and for most of the range of seismic moments studied the shape of the spectrum is relatively independent of seismic moment. Consequently, calculated stress drops increase with seismic moment, with the functional dependence varying from region to region. For the largest events, the spectrum shifts to lower frequencies with increasing moment and stress drops become essentially independent of moment. Preliminary results suggest that the stress drops are not detectably different for earthquakes with thrust or normal faulting fault-plane solutions. A limited amount of data are consistent with a change in spectral content and stress drop of earthquakes in the vicinity of and before stronger earthquakes but a clear, consistent pattern is not yet evident. Toward high frequencies, S-wave spectra both begin to decrease at lower frequencies and seem to decrease more rapidly than P-wave spectra, in contrast with predictions of published dislocation models of earthquakes.

The petrochemistry of the Lower Proterozoic metamorphic rocks from the Dabieshan-Lianyungang area, the southeastern margin of the North China Platform

1991 ◽  
Vol 55 (379) ◽  
pp. 263-276 ◽  
Author(s):  
Sang Longkang
Keyword(s):  
Continental Margin ◽  
North China ◽  
Active Continental Margin ◽  
The South ◽  
North China Platform ◽  
The North ◽  
Lower Proterozoic ◽  
Southeastern Margin ◽  
Tectonic Settings ◽  
North China Plate

AbstractBased on geological studies, 141 rock analyses and 5 trace element analyses of metabasites, the present paper deals with the rock association, chemical features, protolith formation and the original tectonic settings upwards through the Lower Proterozoic metamorphic strata in the Dabieshan-Lianyungang area, in the south-east of the North China Platform. The results of the study indicate that the lower and middle parts of the metamorphic strata comprise terrigenous clastics, phosphoritic and aluminous sedimentary formations which formed under stable continental margin conditions. In the middle-upper part a calc-alkaline volcano-sedimentary formation under the active continental margin was developed. The Lower Proterozoic meta-strata of sedimentary-volcanosedimentary origin from bottom upwards suggest that the tectonic evolution of the south-eastern margin of the North China Platform is a process from stabilization to mobilization. This process suggests a northward subduction of the Yangtze Plate under the North China Plate during the later part of the early Proterozoic.

Directions of lithosphere interactions in the Pamir – Hindu Kush junction inferred from anisotropic tomography

2020 ◽  
Vol 57 (5) ◽  
pp. 601-616
Author(s):  
Jamshed Aminov ◽  
Ivan Koulakov ◽  
Andrey Jakovlev ◽  
Junmeng Zhao ◽  
Sami El-Khrepy ◽  
...  
Keyword(s):  
Velocity Structure ◽  
Azimuthal Anisotropy ◽  
Tien Shan ◽  
Crustal Material ◽  
Seismic Zone ◽  
The South ◽  
S Wave ◽  
Time Data ◽  
Local Tomography ◽  
Hindu Kush

The Pamir and Hindu Kush are examples of a puzzling collision system where a complex junction of colliding lithospheric plates coexists with intermediate depth seismicity at 300 km. In this study, we constructed a new tomography model using travel time data from local events recorded by the TIPAGE (Tien Shan – Pamir Geodynamic program) network. In addition to the P- and S-wave velocities down to 200 km, we derived the azimuthal anisotropy. The velocity anomalies were consistent with the results of previous studies. In the crust, the velocity structure and anisotropy directions were mainly oriented along major suture zones. At depths of 80–120 km, a narrow low-velocity anomaly coinciding with the distribution of deep seismicity was interpreted as a trace of entrained crustal material by the dipping lithosphere. The anisotropy directions at these depths were mainly oriented northwest–southeast and were interpreted as indicating the direction of the motion of colliding plates. The difference in the magnitude of anisotropy south and north of the Pamir seismic zone suggests that the lithosphere coming from the south possesses less anisotropy than that of the Asian plate. The local tomography model was supplemented by previously computed regional tomography that expanded the area both laterally and axially. Beneath the Pamir, both continental plates coming from the north and south form a drop-shaped anomaly that will possibly delaminate in time. Beneath the Hindu Kush, we could clearly trace a continuous almost vertical subduction of the Katawaz block from the south. Thus, the continental collision beneath the Pamir and subduction beneath the Hindu Kush are separate processes with different rates and directions of plate movement.

scholarly journals Chapter 4. Paleozoic granitoid magmatism of South and Middle Tien Shan in Uzbekistan

2020 ◽  
pp. 102-163
Author(s):  
Dmitry L. Konopelko ◽  
Keyword(s):  
Early Carboniferous ◽  
Tien Shan ◽  
Passive Margin ◽  
Granitoid Magmatism ◽  
Northern Margin ◽  
The North ◽  
History Of ◽  
Different Depths ◽  
Andean Type ◽  
Tectonic Settings

The Paleozoic evolution of the Southern and Middle Tien Shan terranes is generally associated with the history of two ocean basins - the Turkestan and Paleotethys. Ages of ophiolites indicate the opening of the oceans in Cambrian – Ordovician, and partial closure with formation of an island arc in the northern part of the basin in Ordovician - Silurian. At the northern margin of the Turkestan ocean, the northward subduction under the Middle Tien Shan continued until Devonian, which led to formation of an active margin with granitoids emplaced between 429 and 416 Ma. In the late Devonian, subduction-related magmatism terminated and the whole region developed as passive margin. Northward subduction resumed in the early Carboniferous and formed magmatic Andean-type belt exposed in the Chatkal-Kurama terrane. Late Carboniferous collision resulted in crust thickening and emplacement of postcollisional granitoids. Formation of postcollisional intrusions in different terranes took place in various tectonic settings. Shoshonitic granitoids of the Chatkal-Kurama terrane formed as a result of slab break off at postcollisional stage. Voluminous postcollisional magmatism of Kyzylkum can be explained by delamination of lower crust and its replacement by the material of astenospheric mantle. Coeval emplacement of geochemically contrasting granitoids in the North Nuratau fault zone could result from contemporaneous melting of different protoliths at different depths in a translithospheric shear zone.

Proposed chronostratigraphic units for the Carboniferous and Early Permian of the southwestern Gondwana margin

2020 ◽  
pp. SP512-2020-48
Author(s):  
Carlos R. González ◽  
Pamela Díaz Saravia
Keyword(s):  
Ice Age ◽  
South American ◽  
Early Permian ◽  
The South ◽  
Eastern Margin ◽  
South Eastern ◽  
Gondwana Margin ◽  
Central Western Argentina ◽  
Southwestern Margin ◽  
Regional Reference

AbstractThe western Andean belt of Argentina displays a comprehensive record of the Carboniferous and earliest Permian rocks so extensive that it allows an exceptional reconstruction of the Late Palaeozoic Ice Age of the southwestern margin of the South American Gondwana area. Severe endemism of the Gondwana biota during this period makes it difficult to achieve a precise correlation of these glacially influenced deposits with the coeval sequences of the Palaeoequatorial belt, where the subdivisions of the International Chronostratigraphic Chart are currently defined. The abundant paleontological record available from the Upper Palaeozoic deposits of central-western Argentina, central Patagonia, and eastern Argentina, makes it possible to recognize five successive faunal stages that allow a proper ordering of the sequences of this period. The proposed regional stages, and their assumed chronologic position regarding the standards of the current International Chronostratigraphic Chart, are: the Malimanian (late Tournaisian), Barrealian (Mid-Carboniferous or Serpukhovian-Bashkirian), Aguanegrian (Upper Pennsylvanian), Uspallatian (Asselian-Tastubian?) and Bonetian (Sakmarian). This paper aims to reiterate former recommendations about the convenience of having regional reference units and suggests the consideration of the available faunal stages as possible chronostratigraphic subdivisions for the Carboniferous-early Permian of the south-eastern margin of Gondwana.

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