南天山库勒湖变质岩系的构造变形特征

STRUCTURAL REFORMATION AND AGE OF METAMORPHIC ROCK SERIES IN LAKE KULE OF SOUTH TIANSHAN

库勒湖变质岩系以断片形式出现于南天山造山带中，出露宽度约３．５ｋｍ。主要由层状大理岩、黑云母石英片岩、糜棱岩化大理岩和碳质灰岩组成。黑云母石英片岩的Ｒｂ－Ｓｒ全岩等时线年龄为６０６．３±４．３９Ｍａ，薄层碳质岩中产晚元古代的疑源类化右和微古植物碎片，如黑色六面膜片Ｂｒｏｃｈｏｌａｍｉｎａｒｉａｎｉｇｒｉｔａ等。该套前寒武系发育有４期变形：第１期变形发生于６０６．３Ｍａ左右，形成矿物的生长线理和片理、大理岩；第２期变形形成于３７０～３３５．５１Ｍａ，为变质岩系的主变形期，表现为拉伸线理、流劈理及韧性剪切带的形成；第３期变形成生于２５９Ｍａ左右。以发育开阔褶皱，平卧、翻卷褶皱及拉伸线理的褶皱为特征；第４期变形主要为脆－塑性变形，可能发生于１４６Ｍａ左右，发育有脆性道冲断层、破劈理和引曳褶皱。这４期变形反映了南天山造山带中的构造演化热事件。

The metamorphic rock series,occured at Lake Kule and outcropped 3. 5 km wide, is a fault sheet in the South Tianshan orogenic belt. It consists of bedded marbles, crystalline schists,mylonited marbles and carbonaceous limestones. The whole-rock Rb-Sr isochron age of micaceous quartzite schists is 606: 3+ 4. 39 Ma. Upper Proterozoic Acritarch and micropalaeobotanic fossils occur in the carbonaceous limestones, like Brocholaminaria nigrita. The first reformation phase occured at about 606. 3 Ma, as a result the mineral growth lineation f schistosity and marbles formed. The second reformation phase as the main structural reformation period, developed at about 370￣335. 51Ma, represented by stretching lineation, flow Cleavage and ductile shear zone.And the third refortnation phase formed at about 259 Ma, during which formed the open fold,recumbent fold,facing down fold and stretching lineation fold, The fourth reformation phase possiblely appeared at about 146 Ma, with the brittle thrust fault,fracture cleavage and drag fold formed, which is the process of brittle-plastic structural re formation. These four re formation phases reflected the thermal events of tectonic evolution in the South Tianshan orogenic belt.