东天山造山带右行剪切变形及构造演化的^(40)Ar-^(39)Ar年代学证据

(40)~Ar-(39)~Ar CHRONOLOGICAL EVIDENCE OF DEXTRAL SHEAR AND TECTONIC EVOLUTION OF THE EASTERN TIANSHAN OROGENIC BELT

对新疆东天山觉罗塔格地区克孜尔塔格岩体(舌状岩体)角闪石、黑云母和钾长石进行了^(40)Ar/^(39)Ar年代学及热年代学研究,为确定该区右行走滑作用及NS向挤压作用结束的时间,提供了科学依据。研究表明,东天山造山带,NS向挤压作用结束于276Ma,右行走滑发生于276Ma至240～239Ma间,主要集中于276～253.9Ma.

To better constrain the timing of the dextral strike-slip movement in the eastern Tianshan orogen, a 40Ar/39Ar thermochronological study has been carried out on a Jiaoluotage granitic batholith. Hornblende, biotite, quartz and k-feldspar selected from quartz-mica diorite, granodiorite and quartz veins have been analyzed. At the same time, their cooling histories have been re-constructed. Ranges of 40Ar/39Ar data indicate that hornblendes of two samples have the same cooling age (276 Ma), but biotite minerals have different ages from 261 Ma to 253.9 Ma. And k-feldspar from the two samples yields the same plateau and isochronal age (240-239 Ma). During 276 Ma to 240-239 Ma, at eastern and western parts of the tongue-shaped granitic batholith, different cooling histories had been recorded, which, perhaps, represent the beginning and ending of dextral strike-slip movement. During the time of 287 Ma (?) to 240-239 Ma, syn-deformation granite was intruded, and at the time of 240-239 Ma, k-feldspar was crystallized and granitic intrusion was completed, during which fast cooling process was developed. 40Ar/39Ar dating and related cooling paths indicate that the N-S compression in the eastern Tianshan orogen was finished before 276 Ma and dextral strike-slip movement occurred during 276 Ma to 240-239 Ma, principally from 276 Ma to 253.9 Ma.