The Post-Oceanic Geodynamics of the South Tien Shan Region

2005 ◽  
Vol 7 (6) ◽  
pp. 1-27
Author(s):  
M. G. Leonov
Keyword(s):  
Tien Shan ◽  
The South

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.

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.

The South Tien Shan Belt of diamondiferous alkaline basic rocks

2007 ◽  
Vol 413 (1) ◽  
pp. 192-194
Author(s):  
V. S. Lutkov ◽  
A. R. Faiziev
Keyword(s):  
Tien Shan ◽  
The South ◽  
Basic Rocks

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

Chapter 24: Muruntau, Uzbekistan: The World’s Largest Epigenetic Gold Deposit

2020 ◽  
pp. 497-521
Author(s):  
Reimar Seltmann ◽  
Richard J. Goldfarb ◽  
Bo Zu ◽  
Robert A. Creaser ◽  
Alla Dolgopolova ◽  
...  
Keyword(s):  
Regional Metamorphism ◽  
Hydrothermal Activity ◽  
Tien Shan ◽  
The South ◽  
Thermal Event ◽  
Tectonic Transition ◽  
Fold And Thrust Belt ◽  
Order Of Magnitude ◽  
Metamorphic Terranes ◽  
East West

Abstract Muruntau in the Central Kyzylkum desert of the South Tien Shan, western Uzbekistan, with past production of ~3,000 metric tons (t) Au since 1967, present annual production of ~60 t Au, and large remaining resources, is the world’s largest epigenetic Au deposit. The host rocks are the mainly Cambrian-Ordovician siliciclastic flysch of the Besapan sequence. The rocks were deformed into a broadly east-west fold-and-thrust belt prior to ca. 300 Ma during ocean closure along the South Tien Shan suture. A subsequent tectonic transition was characterized by left-lateral motion on regional splays from the suture and by a massive thermal event documented by widespread 300 to 275 Ma magmatism. The Besapan rocks were subjected to middle to upper greenschist-facies regional metamorphism, an overprinting more local thermal metamorphism to produce a large hornfels aureole, and then Au-related hydrothermal activity all during early parts of the thermal event. The giant Muruntau Au deposit formed in the low-strain hornfels rocks at ca. 288 Ma at the intersection of one of the east-west splays, the Sangruntau-Tamdytau shear zone, with a NE-trending regional fault zone, the Muruntau-Daugyztau fault, which likely formed as a cross fault during the onset of left-lateral translation on the regional splays. Interaction between the two faults opened a large dilational zone along a plunging anticlinorium fold nose that served as a major site for hydrothermal fluid focusing. The Au ores are dominantly present as a series of moderately to steeply dipping quartz ± K-feldspar stockwork systems surrounding uncommon central veins and with widespread lower Au-grade metasomatites (i.e., disseminated ores). Pervasive alteration is biotite-K-feldspar, although locally albitization is dominant. Sulfides are mainly arsenopyrite, pyrite, and lesser pyrrhotite, and scheelite may be present both in preore ductile veins and in the more brittle auriferous stockwork systems. The low-salinity, aqueous-carbonic ore-forming fluids probably deposited the bulk of the ore at 400° ± 50°C and 6-to 10-km paleodepth. The genesis of the deposit remains controversial with metamorphic, thermal aureole gold (TAG), and models related to mantle upwelling all having been suggested in recent years. More importantly, the question as to why there was such a focusing of so much Au and fluid into this one location, forming an ore system an order of magnitude larger than other giant Au deposits in metamorphic terranes, remains unresolved.

Archaeoseismological studies and structural position of the medieval earthquakes in the South of the Issyk-Kul depression (Tien Shan)

2016 ◽  
Vol 52 (2) ◽  
pp. 218-232 ◽  
Author(s):  
A. M. Korzhenkov ◽  
V. A. Kol’chenko ◽  
D. V. Luzhanskii ◽  
S. V. Abdieva ◽  
E. V. Deev ◽  
...  
Keyword(s):  
Tien Shan ◽  
The South ◽  
Structural Position
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