摘要:
青塔山岩体位于东昆仑山西部,岩体的形成时代、环境、岩石类型尚存在争议,对于其成岩的物理化学条件和源区特征的研究程度较低。在系统开展岩石学和岩相学研究的基础上,对黑云母、斜长石和角闪石等主要造岩矿物进行了成分分析,厘定其成岩的物理化学条件,进一步约束岩石成因。研究表明: 青塔山岩体的岩性为英云闪长岩,脉体岩性为石英闪长岩; 岩体中斜长石为中长石和拉长石,黑云母为镁质黑云母,角闪石为镁角闪石,斜长石发育反环带,应为岩浆混合所致; 黑云母的结晶温度为684~693 ℃,结晶压力为(1.86~2.01)×108 Pa,平均值为 1.92×108 Pa,对应结晶深度为6.90~7.46 km,平均7.12 km,属于中深成相。岩体形成时氧逸度较低,为-17.34~-17.04。矿物化学特征显示,青塔山岩体中黑云母的物质来源为钙碱性造山岩套,其形成与壳幔混源岩浆有关。研究成果可为研究青塔山地区晚三叠世—早侏罗世岩浆演化历史提供依据。
Abstract:
Qingtashan rock mass is located in the western section of East Kunlun, and the formation age, environment and rock type of the rock mass are still controversial, with low research degree of the physicochemical conditions during the process of rock formation and its source characteristics. On the basis of systematic lithology and petrographic research, the authors in this paper conducted composition analysis on the main rock-forming minerals such as biotites, plagioclases and hornblendes. The physicochemical conditions during the process of rock formation were identified and petrogenesis of the rock was further constrained. This study shows that the lithology of Qingtashan rock mass is tonalites, and the lithology of the dike is quartz-diorites. The Plagioclase feldspar in the rock mass is andesine and labradorite, the biotite is magnesiobiotite, and the hornblende is magnesiohornblende. An anti-zoning band was developed in the plagioclase, which was caused by magma mixing. The crystallization temperature is 684~693 ℃ and the crystallization pressure is (1.86~2.01)×108 Pa, with average value of 1.92×108 Pa. The corresponding crystallization depth is 6.90~7.46 km, with an average of 7.12 km, belonging to the medium-deep formation phase. The oxygen fugitivity during rock mass formation is low, which is between -17.34 and -17.04. The mineral chemical characteristics show that the material source of the biotite in Qingtashan rock mass is calc-alkaline orogenic suite, and its formation is related to the crust-mantle mixed source magmatic. This study could provide references for the evolution of Late Triassic-Early Jurassic magma in this region.
下载: