【作者】 时超；

【导师】 李荣社；

【作者基本信息】 中国地质大学（北京） ， 构造地质学， 2011， 硕士

【摘要】 吉塘岩群呈北西-南东向沿他念他翁山分布于西藏东部的巴青、丁青、类乌齐、察雅一带,位于班公湖—怒江缝合带与双湖—澜沧江缝合带之间,隶属“一洋两陆”北部大陆区羌北昌都地块的南部,包含了丰富的变形构造。选择典型地区进行吉塘岩群构造样式和期次研究,探讨吉塘岩群的构造属性、构造作用与矿化的关系等,可为青藏高原腹地羌塘地区的地质构造演化提供新的基础资料。通过宏观和微观相结合,运用构造解析的方法进行研究,得到以下主要结论:1、西藏丁青县吉塘岩群酉西岩组出露的主要岩性为黑云石英片岩、二云石英片岩、绿泥二云石英片岩夹变质砾岩、变基性火山岩,辉绿辉长岩、片麻状黑云二长花岗岩侵入其中,总体呈大有序,小无序成层状分布。经原岩恢复,吉塘岩群酉西岩组主要为一套碎屑岩夹少量基性火山岩组合,形成时代为中新元古代（1048.2±3.3）Ma～（965±55）Ma,与基底变质地层的特点更为接近,不具有增生楔混杂堆积的特点。2、吉塘岩群酉西岩组变形复杂,具有明显的构造置换特点,发育透入性面理和线理,代表了典型的中地壳变形,变质程度最高可达高绿片岩相。根据S-C组构、δ旋转斑系方向的定向测量以及面理产状测量,认为吉塘岩群酉西岩组运动学特点:在水平方向上主要为NW275°～280°向SE95°～100°方向右行剪切运动,在垂向上主要为由北向南的逆冲运动。3、根据西藏丁青县吉塘岩群酉西岩组构造叠加、面理置换、新生变质矿物穿切关系和矿物退变质特征等,可识别出四期变形变质作用:①区域变质作用（发育透入性片理和线理）;②韧性剪切作用（S-C组构、δ旋转斑系）;③高温低压变质作用（红柱石+矽线石+黑云母+电气石）。④退变质作用（黑云母绿泥石化+矽线石绢云母化,出现间隔劈理,晚期逆冲断层）。4、在吉塘岩群韧性剪切带中新发现金矿化线索。简项分析表明,As含量较高(19.7⁵7.6×10^-6),Cu、Au、Ag呈现较高异常,其中Au含量最高达0.15×10^-6。根据矿化产出部位和控矿因素分析,结合矿化蚀变特征,初步认为吉塘岩群中金矿具有一定成矿潜力,矿化与右行韧性剪切作用有着密切的关系,并遭受后期脆性断裂构造改造。5、根据侵入吉塘岩群中的黑云母二长花岗岩年代学测试,得到235.7±0.68Ma和235.1±1.1Ma的年龄数据,结合区域对比,认为吉塘岩群高温变质作用可以与印支期（T₂-T₃）在藏东地区发育大规模构造岩浆侵入事件相对应。更多还原

【Abstract】 Abstract:The Jitang Rock Group, which is extending along the NW-SE portion, outcropping mainly in Baqing, Dingqing, Leiwuqi and chaya counties in eastern Tibet, and locating between Bangonghu-nujiang suture zone and Shuanghu-lancangjiang suture zone, belongs to the north continent of the“one ocean, two continents”system, that is, Northern Qiangtang Block. The deformation is well developed in the Jitang Rock Group. Some typical areas benefit to study the structural features and the deformation stage, on which we discuss the tectonic properties and the relationship between structure and mineralization. This study provides some new geological information on tectonic evolution in Qiangtang area, the northern Qinghai-Tibet Plateau. Combating the field geologic investigation and the microstructure study, we conducted detailed structural analysis on the Jitang Rock Group, and obtained the following conclusions:1. The Youxi Rock Formation of the Jitang Rock Group outcrop in Dingqing County, Tibet Autonomous Region, are mainly consist of biotite-quartz schist, two-mica quartz schist, mica quartz chlorite schist with metamorphic conglomerate, metamorphic baic volcanic rocks, and was latter intruded by diabase gabbro and gneissic biotite monzogranite. The Youxi Rock Formation generally appears layered structure and ordered in wholel, disordered in part. Its protolith association is clastic rock with amount of basic volcanic rocks, which was formed in Meso-Neoproterozoic, about （1048.2±3.3）Ma to （965±55）Ma, are more similar to the metamorphic basement rocks that do not show the properties of melanges in accretionary wedge.2. The Youxi Rock Formation of the Jitang Rock Group showed complex deformation and up-to high-grade greenschist metamorphism, and developed clearly structural replacement, penetrative foliation and lineation, which proves typical deformation in middle crust. According to the analysis on S-C fabric, porphyroclastic system and the foliation, the kinematic characteristics of the rock group has been obtained: dextral shear from NW275°～280°to SE95°～100°in the horizontal direction and thrust from north to south in the vertical direction.3. According to the structural superposition, foliation replacement, the cutting relationship between metamorphic minerals and the retrograde metamorphism, we classified the metamorphic-deformation into four stages: firstly, regionally metamorphism （the development of penetrative foliation and lineation）; secondly, ductile shearing （S-C fabric, porphyroclastic system）; thirdly, high temperature low pressure metamorphism （And. + Sil. + Bt. + Tur.）; fourthly, retrograde metamorphism （chloritization of biotite, sericitization of sillmanite, the formation of spaced cleavage, and thrust fault）.4. The results of simple analysis of the mineralization in Jitang Rock Group demonstrated that it is rich in As (19.7⁵7.6×10^-6), the elements Cu, Au and Ag have share a high anomaly, among which Au anomaly is up to 0.15×10^-6. According the location of mineralization, the ore-controlling factors, and alteration features, we preliminary view that there is a potential Au mineralization in Jitang Rock Group that close relative to ductile shearing.5. Combating the regional geology and the ages of 235.7±0.68Ma and 235.1±1.1Ma of the biotite monzogranite from Jitang Rock Group, we remain that the high-temperature metamorphism may correspond to the large tectonic-magmatic event in Indosinian （T₂-T₃） in eastern Tibet.更多还原