南天山中段桑树园子韧性剪切带的形成时限及其构造意义
Timing of the formation of the Sangshuyuanzi ductile shear zone in the central segment of the South Tianshan and its tectonic significance
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摘要: 提要：南天山中段桑树园子韧性剪切带是一条近东西走向的剪切带，带内面理、线理、不对称构造广泛发育，通过运动学分析判断该剪切带为左旋走滑性质。剪切带内糜棱岩中的白云母40Ar/39Ar测年获得坪年龄（393±6） Ma和等时线年龄（389±3） Ma；带内雁行式裂隙中的黑云母40Ar/39Ar测年获得坪年龄（366.5±2） Ma和等时线年龄（365±3） Ma。结合区域大地构造背景，笔者认为，桑树园子韧性剪切带是由塔里木板块和哈萨克斯坦—伊犁板块斜碰撞产生的同碰撞走滑构造带，在斜碰撞过程中起到平行板块边界方向的应变分解作用。
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关键词:
- 桑树园子韧性剪切带 /
- 40Ar/39Ar定年 /
- 同碰撞 /
- 应变分解
Abstract: Abstract：The Sangshuyuanzi ductile shear zone in the central segment of the South Tianshan is an east-west-trending shear zone, in which foliations, lineations and asymmetric structures are well developed. Based on a kinematic analysis,the authors think that the Sangshuyuanzi ductile shear zone is of sinistral strike-slip nature. 40Ar/39Ar dating of muscovites from mylonite in the shear zone yields a plateau age of 393±6 Ma and an isochron age at 389±3 Ma. 40Ar/39Ar dating of biotites from en-echelon fractures in the zone gives a plateau age of 366.5±2 Ma and an isochron age of 365.0±3 Ma. According to the above-mentioned study, combined with the regional tectonic background, this paper suggests that the Sangshuyuanzi ductile shear zone is a syncollisional strike-slip tectonic zone formed by oblique collision between the Tarim plate and the Kazakhstan-Ili plate, which resulted in strain partitioning parallelly to the boundary of the two plates. -
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