塔里木北缘前寒武基底隆升剥露史:来自磷灰石裂变径迹的证据

Uplift and exhumation history of the Precambrian basement, Northern Tarim : Evidence from apatite fission track data.

库鲁克塔格隆起位于塔里木盆地北缘,广泛出露前寒武基底岩石。辛格尔村附近出露的太古宙杂岩,包括灰色片麻岩、角闪岩、片岩、混合岩和大理岩。新元古代地层出露在库鲁克塔格隆起西部的兴地、西山口、辛格尔和杀马山附近,不整合在古元古代和中元古代的片麻岩、角闪岩和片岩之上,并被早古生代的地层不整合。因此,该地区是了解塔里木盆地前寒武基底热演化史的理想地区。本研究的目的是为了探索:①塔里木基底岩石最初于何时剥露于地表?②塔里木基底剥露以后是否经历过再次埋藏和剥露?③塔里木基底岩石构造热演化过程对大陆边缘不同构造事件的响应。为了获取塔里木北缘剥露史和冷却过程信息,我们开展了裂变经迹的研究。含磷灰石的样品采自库鲁克塔格隆起的兴地断裂两侧。样品池年龄介于146.0±13.4和67.6±6.7Ma 之间,平均经迹长度介于.11.79±0.14和13.89±0.27μm之间。根据样品年龄和样品所处的构造位置,样品可以分为3组。A 组样品包括 F2、F3、F4、F5和 F8,裂变经迹表观年龄约100～110Ma,通常位于未遭断层变形的地区。B 组样品包括 F7、F9和 F10,裂变经迹表观年龄小于80Ma,构造上位于断层上盘并靠近断层。C 组样品 F11具有最大的裂变经迹表观年龄146.0±13.4Ma。热模拟表明,库鲁克塔格地区的隆升剥露作用可以划分为四期,分别是早侏罗世晚期(180Ma)、晚侏罗世—早白垩世(144～118Ma)、晚白垩世早期(94～82Ma)和新生代晚期(约10Ma)。裂变经迹记录的库鲁克塔格多阶段隆升作用,是对亚洲南缘多期地体碰撞增生的响应。

Kuruktag uplift is located to the north of the Tarim basin where the Precambrian crystalline basement rocks are widely crop out. An Archean complex occurs near Qingir village, and is composed of grey gneiss, amphibolite, schist, migmatite and marble. The Neoproterozoic strata occur in Xingdi, Xishankou, Xinger and Saimashan areas in the western Kuruktag. unconformably overlie the Paleoproterozoic to Mesoproterozoic gneisses, amphibolites and schists and are unconformably overlain by the Early Paleozoic rocks. Thus, it is perfect place for understanding the thermal evolution of the Precambrian basement of the Tarim basin. The purpose of this study is to detect that： ① when were the basement rocks exhumed to the surface initially？② did the basement rocks of the Tarim craton experience reburial and re-exhumation？ and ③ the history of thermotectonic evolution of the basement rocks respond to the different tectonic events occurred at Tarim continental margins. In order to obtain information about the exhumation history and processes of cooling in the northern Tarim, fission track methods on apatite were used. Ten apatite-bearlng samples were collected from two sides of the Xingdi fault in the Kuruktag uplift. Pooled ages range from 146.0 ± 13.4 to 67.6±6.7Ma. Mean track lengths range from 11.79 ± 0. 14 to 13.89± 0. 271μm. These samples can be divided into three groups depending on their ages and structural position. Group A will refer to samples F2, F3, F4, F5 and F8 with AFT apparent ages about 100 - 110Ma. , generally associated with areas undeformed by the faults. Group B will refer to samples F7, F9 and F10 with AFT apparent ages lower than 80Ma, mostly structurally associated with hanging wall situations close to the faults. Group C will refer to sample F11 which has the oldest apparent age of 146.0 ± 13.4Ma. The thermal history modeled result shows four periods of exhumation in the Kuruktag uplift occurred in late Early Jurassic （180Ma）, Late Jurassic-Early Cretaceous （144-118Ma）, early Late Cretaceous （94- 82Ma） and Late Cenozoic （about 10Ma）. These uplift events recorded by the apatite fission track data in the Kuruktag are assumed to be in response to be the result of far-field effects from the multi-stage collisions and accretions of terranes in the south Asian continental margin.