Buslov, Mikhail

De Grave, Johan

Glorie, Stijn

English

Ghent University Academic Bibliography

Geophysical Research AbstractsVol. 12, EGU2010-1791, 2010EGU General Assembly 2010© Author(s) 2010Thermotectonic evolution of the northern Kyrgyz Tien Shan intrusivesStijn Glorie (1), Johan De Grave (1), and Mikhail Buslov (2)(1) MINPET Geochronology Group, Dept. of Geology and Soil Science, Ghent University, 281/S8 Krijgslaan, B-9000, Ghent,Belgium (Stijn.Glorie@Ugent.be / Tel: +32 9 264 4568 / Fax: +32 9 264 4984), (2) Institute of Geology and Mineralogy,Siberian Branch, Russian Academy of Science, 3 Koptyuga Prospekt, 630090 Novosibirsk, RussiaThe northern Kyrgyz Tien Shan (nKTS) encloses a large number of granitoid intrusions. These plutons intrudedduring the Palaeozoic and are geodynamical related to either Caledonian or Hercynian collisions. The most volu-minous, i.e. the Caledonian intrusion phase is associated with the evolution and closure of the Early PalaeozoicTerskey Ocean (branch of the Turkestan Ocean). Hercynian plutons, smaller in both abundance and dimensions,are thought to have formed during the final closure of the Turkestan Ocean when the Tarim microcontinenteventually collided with the Kazakhstan plate. In the Late Palaeozoic – Early Mesozoic, the nKTS experiencedtectonic quiescence. This geodynamic environment abruptly changed in the Mesozoic, when the Central AsianOrogenic System - including the nKTS - was reactivated as an intracontinental orogen (Cimmerian orogeny).The granitoids embedded in the basement record this phase as a cooling event. This cooling is a consequenceof denudation and exhumation of the nKTS basement associated with this orogeny. The Late Mesozoic – EarlyCenozoic introduced again a period of thermal stability. In the Cenozoic, a new phase of cooling, linked torenewed denudation as a tectonic far-field effect of the India-Eurasia collision, affected the nKTS basement.In this study, we dated each of the aforementioned events and reveal the thermotectonic history of the nKTSgranitoids from emplacement to exhumation. Zircon SHRIMP and LA-ICP-MS U/Pb concordia ages suggesta Middle to Late Ordovician crystallization age (440-470 Ma) for the Caledonian intrusion phase, however thepresence of additional Early Ordovician - Cambrian U/Pb samples, points towards a more prolonged productionof granitoids during the entire Early Palaeozoic. Hercynian samples are constrained to the Late Carboniferous– Permian (260-300 Ma). 40Ar/39Ar stepwise heating plateau-ages (biotite: 400-440 Ma; K-feldspar: 235-375Ma) bear witness to rapid Silurian - Early Devonian post-magmatic cooling of the granitoids, followed by amore modest rate of cooling during the Late Devonian until the Late Triassic. Low-temperature techniquessuch as Apatite Fission Track (AFT) and Apatite (U-Th-Sm)/He (AHe) thermochronology where used to datethe Meso-Cenozoic reactivation (i.e. cooling) phases. Most AFT and AHe ages cluster in the Late Jurassic -Cretaceous (90-160 Ma) while Cenozoic ages (25-60 Ma) pinpoint the most recent exhumation.

Thermotectonic evolution of the northern Kyrgyz Tien Shan intrusives

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Thermotectonic evolution of the northern Kyrgyz Tien Shan intrusives

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