CAJ | 학술논문

西藏北冈底斯早白垩世花岗岩分布广泛；扎独顶岩体作为其中的一个典型代表，其分布广泛，呈岩基型式产出，在岩性上属二长花岗岩。在岩石化学上扎独顶岩体具有富SiO2(70.05%~74.97%)和K2O(4.09%~5.35%)，贫CaO (0.93%~2.19%)、TiO2(0.22%~0.52%)和Al2O3(12.81%~14.24%)的特征；属于准铝质-弱过铝质(A/CNK=0.99~1.0)高钾钙碱性系列。岩体稀土元素总量偏高(∑REE=199.36×10-6~247.91×10-6)，相对富集轻稀土元素(LREE/HREE=5.82~6.88)，Eu负异常明显(δEu=0.30~0.45)，球粒陨石标准化分布模式呈向右缓倾的V型。微量元素显示其富集Rb、Th、K、Zr和Hf，亏损Nb、Ta、Sr、Ba、P和Ti，(Zr+Nb+Ce+Y)平均值为427.63。全岩锆石饱和温度(828~838°C)表明岩浆形成温度高。上述岩石地球化学特征表明扎独顶岩体为A型花岗岩。扎独顶岩体LA-ICP-MS锆石U-Pb年龄为（103.8±1.0）Ma，表明其形成于早白垩世晚期；在构造判别图解上位于碰撞后的A2型花岗岩区，是在碰撞后岩石圈伸展背景下，由于软流圈物质上涌导致岩石圈地幔与壳源熔体部分熔融并经历过一定程度的混合作用而形成的。
서장북강저사조백성세화강암분포엄범；찰독정암체작위기중적일개전형대표，기분포엄범，정암기형식산출，재암성상속이장화강암。재암석화학상찰독정암체구유부SiO2(70.05%~74.97%)화K2O(4.09%~5.35%)，빈CaO (0.93%~2.19%)、TiO2(0.22%~0.52%)화Al2O3(12.81%~14.24%)적특정；속우준려질-약과려질(A/CNK=0.99~1.0)고갑개감성계렬。암체희토원소총량편고(∑REE=199.36×10-6~247.91×10-6)，상대부집경희토원소(LREE/HREE=5.82~6.88)，Eu부이상명현(δEu=0.30~0.45)，구립운석표준화분포모식정향우완경적V형。미량원소현시기부집Rb、Th、K、Zr화Hf，우손Nb、Ta、Sr、Ba、P화Ti，(Zr+Nb+Ce+Y)평균치위427.63。전암고석포화온도(828~838°C)표명암장형성온도고。상술암석지구화학특정표명찰독정암체위A형화강암。찰독정암체LA-ICP-MS고석U-Pb년령위（103.8±1.0）Ma，표명기형성우조백성세만기；재구조판별도해상위우팽당후적A2형화강암구，시재팽당후암석권신전배경하，유우연류권물질상용도치암석권지만여각원용체부분용융병경력과일정정도적혼합작용이형성적。
Early Cretaceous granites are widely distributed in northern Gangdise, Tibet. The Zhaduding intrusive body, which belongs to monzogranite in lithology, is widely distributed and occurs in the form of batholith, being a typical case of the granites. Petrogeochemically it is characterized by high SiO2 (70.05%-74.97%) and K2O (4.09%-5.35%), low CaO (0.93%-2.19%), TiO2 (0.22%-0.52%) and Al2O3 (12.81%-14.24%). Moreover, it belongs to metaluminous or weak peraluminous (A/CNK=0.99-1.06) high-K calc-alkaline series. The rocks are characterized by high REE content (∑REE=199.36 × 10-6-247.91 × 10-6), rich LREE relative to HREE (LREE/HREE=5.82-6.88), and significant negative Eu anomalies (δEu=0.30-0.45). Chondrite-normalized REE patterns exhibit V-type with slight right-oblique feature. Trace elements show that the rocks are enriched in Rb, Th, K, Zr and Hf and depleted in Nb, Ta, Sr, Ba, P and Ti, with average (Zr+Nb+Ce+Y) 427.63. Bulk-rock zircon saturation temperature (828-838°C) shows that the temperature of magma formation was pretty high. The petrogeochemical characteristics show that the Zhaduding rock body is A-type granite. The LA-ICP-MS zircon U-Pb age of 103.8±1.0Ma indicates that Zhaduding rock body was formed in late Early Cretaceous, and is located in the post-collisional A2-type granite area in discrimination diagrams. It was formed by a certain degree of mixing of the lithosphere mantle and the crustal partial melts, resulting from asthenosphere material upwelling in the post-collision extensional setting.