CAJ | 학술논문

在羌塘地区开展1∶5万戈木日区域地质调查的过程中，为研究龙木错-双湖板块缝合带的演化历史，探讨青藏高原羌塘中部地区的构造演化，对果干加年山地区的蛇绿岩进行了详细研究。石炭纪蛇绿岩变质堆晶辉长岩是填图过程中的新发现。全岩地球化学研究结果显示，岩石ΣREE较低，LREE弱富集，轻、重稀土元素分异程度不高；富集Rb、Bb等大离子亲石元素，明显亏损Nb、Ta、Ti等元素，具有典型的SSZ型蛇绿岩特征，表明其形成于俯冲带之上。蛇绿岩中变质堆晶辉长岩的LA-ICP-MS锆石U-Pb年龄为354.8Ma±2.4Ma，属于早石炭世。最终研究表明，龙木错-双湖板块缝合带所代表的古大洋至少在早石炭世就已经存在俯冲。石炭纪变质堆晶辉长岩的发现对研究缝合带构造演化历史具有非常重要的意义，也为探讨羌塘地区的大地构造演化提供了基础资料。
재강당지구개전1∶5만과목일구역지질조사적과정중，위연구룡목착-쌍호판괴봉합대적연화역사，탐토청장고원강당중부지구적구조연화，대과간가년산지구적사록암진행료상세연구。석탄기사록암변질퇴정휘장암시전도과정중적신발현。전암지구화학연구결과현시，암석ΣREE교저，LREE약부집，경、중희토원소분이정도불고；부집Rb、Bb등대리자친석원소，명현우손Nb、Ta、Ti등원소，구유전형적SSZ형사록암특정，표명기형성우부충대지상。사록암중변질퇴정휘장암적LA-ICP-MS고석U-Pb년령위354.8Ma±2.4Ma，속우조석탄세。최종연구표명，룡목착-쌍호판괴봉합대소대표적고대양지소재조석탄세취이경존재부충。석탄기변질퇴정휘장암적발현대연구봉합대구조연화역사구유비상중요적의의，야위탐토강당지구적대지구조연화제공료기출자료。
In order to investigate the evolution of the Lungmu Co-Shuanghu plate suture zone and the tectonic history of central Qiangtang, the authors studied Guoganjianian ophiolite in the aspects of petrology, geochemistry and geochronology. The cumulate in Guoganjianian ophiolite was recently discovered during 1∶50000 regional geological survey of the Gemuri area. Geochemical studies show that the cumulate gabbro has low REE content and flatten REE patterns with slight enrichment of LREE, and the degree of differentiation between LREE and HREE is low. These samples are enriched in large ion lithophile elements (LILE) such as Rb and Ba, and depleted in Nb, Ta and Ti, suggesting that they were probably formed in a subduction zone. LA-ICP-MS technique was applied to U-Pb zircon dating of the cumulate gabbro from Guoganjianian ophiolite. The result shows that the ages of cumulate gabbro is 354.8Ma±2.4Ma, suggesting that Lungmu Co-Shuanghu Ocean already began its subduction in Early Carboniferous. The study of Guoganjianian cumulate gabbro provides important basic data for investigating the evolution of Lungmu Co-Shuanghu plate suture zone and the tectonic history of central Qiangtang.