CAJ | 학술논문

针对班公湖-怒江中特提斯洋盆闭合的时间问题，选择西藏日土县班公湖畔蛇绿岩中的小型酸性侵入岩体为研究对象，探讨其岩石成因和构造环境。研究区酸性岩体的岩性为斜长花岗斑岩。地球化学分析显示，岩石SiO2含量介于65.78%~68.76%之间，（K2O+Na2O）含量为6.39%~6.86%；具有轻稀土元素富集、分馏程度高、Eu正异常不明显的特点；富集大离子不相容元素Sr、Ba、Rb，亏损高场强元素Ta、Ti、Nb，并有Ta、Nb元素谷形，显示出典型的岛弧岩浆岩特征。2个斜长花岗斑岩体的LA-ICP-MS锆石206Pb/238U年龄加权平均值分别为96.08Ma±0.22Ma和96.05Ma±0.30Ma，均属于中生代晚白垩世。
침대반공호-노강중특제사양분폐합적시간문제，선택서장일토현반공호반사록암중적소형산성침입암체위연구대상，탐토기암석성인화구조배경。연구구산성암체적암성위사장화강반암。지구화학분석현시，암석SiO2함량개우65.78%~68.76%지간，（K2O+Na2O）함량위6.39%~6.86%；구유경희토원소부집、분류정도고、Eu정이상불명현적특점；부집대리자불상용원소Sr、Ba、Rb，우손고장강원소Ta、Ti、Nb，병유Ta、Nb원소곡형，현시출전형적도호암장암특정。2개사장화강반암체적LA-ICP-MS고석206Pb/238U년령가권평균치분별위96.08Ma±0.22Ma화96.05Ma±0.30Ma，균속우중생대만백성세。
To investigate the closure time of the Bangong-Nujiang Middle Tethys Ocean, the authors chose small acid rock masses in the ophiolitic zone near the Bangong Lake in Rutog County of Tibet as the study object to investigate their petrogenesis and struc-tural environment. The rock type is plagioclase granite-porphyry. Chemically the rocks consist mainly of SiO 2 and (K2O+Na2O), with their content being 65.78%~68.76%and 6.39%~6.86%respectively. In addition, the rocks have high LREE enrichment, high de-gree of fractionation and positive Eu anomalies They are rich in LREE such as Sr, Ba and Rb, but are depleted in high field strength elements (HFSE) like Ta, Ti and Nb, assuming a"valley"form. The depletion of Nb and Ta suggests that they have the typical char-acteristics of arc magmatite. LA-ICP-MS (inductively coupled plasma-mass spectrometer and a laser ablation system) dating shows that the zircon 206Pb/238U weighted mean ages of two plagioclase granite-porphyry samples are 96.08Ma ± 0.22Ma and 96.05Ma ± 0.30Ma respectively, implying that they both belong to the Late Cretaceous period of Mesozoic.