摘要
九曲二云母花岗岩与钨锡成矿关系密切,锆石SHRIMPU-Pb和LA-ICP-MSU-Pb测试结果分别为169±8Ma和169.6±0.8Ma,属于中生代中侏罗世。九曲岩体的钾长石和白云母的Ar-Ar坪年龄分别为100.80±0.76Ma和169.7±1.2Ma,反等时线年龄分别为104.1±3.5Ma和170.4±2.2Ma,分别代表了钾长石和白云母的结晶年龄。九曲岩体具有两阶段的冷却速率,在早阶段其冷却曲线为近垂直于年龄轴的直线,晚阶段的冷却速度为2.90℃/Ma;在地球化学特征上总的特点是富硅、碱,贫钙、镁、钛、磷;DI介于95.04～95.57之间,反映了岩体经历了高程度分异演化作用;属于过铝质的高钾钙碱性系列岩石;稀土配分模式呈稍向左倾的重稀土富集型,Eu强烈负异常,εNd(t)值介于-9.51～-10.12之间,计算的二阶段Nd模式年龄T2DM介于1.83～1.87Ga,推测其可能是由时代相当于元古宙的陆壳富泥质变质沉积岩部分熔融形成的S型花岗岩类,较低的K/Rb值暗示了在演化过程中有挥发分流体参与并经历了较强的分异作用,是岩浆演化到晚期阶段的产物。
The Jiuqu two-mica granite in southern Jiangxi Province, is related to W--Sn mineralizations. The zircon SHRIMP U-Pb and LA-ICP-MS U-Pb dating of the Jiuqu granite gave ages of 169 ± 8Ma and 169.6 ± 0. 8 Ma, which shows that the granite was produced in the Middle Jurassic. The Ar-Ar plateau ages of muscovite and K- feldspar are 100. 80 ±0.76 Ma and 169.7±1.2 Ma, respectively. The Ar-Ar anti-isochron ages of muscovite and K-feldspar are 104. 1 ±3.5 Ma and 170.4 ± 2.2 Ma, respectively. The ages represent the isotopic closure ages of minerals in the rock-forming process. The cooling history of the Jiuqu granitic pluton indicates that the cooling velocity of pluton was faster at the early stage and was slower （ about 2.90℃/Ma） at the late stage. The Jiuqu granites are characterized by being riched in Si, alkaline, and poorer in CaO, MgO, TiO2 and P2 05 ; the DI range from 95.04 - 95. 57 , which reflected the higher evolution of magmatism, and belongs to peraluminous high-K--Ca- Alkaline; the REE pattern is slightly light-inclined REE distribution pattern, and has strongly negative Eu, the εNd （t） values of the Jiuqu granite are -9.51 to -10.12, and T2DM values are 1.83 to 1.87Ga. It is belongs to S- type granite, which derived form the partial melting of continental crust metamorphic sedmentary rocks equal to Proterozoic, and lower K/Rb values indicate abundant fluids and suffered high-degree evolution of magmatism, belong to the record of later stage of magmatism.
出处
《地质论评》
CAS
CSCD
北大核心
2013年第1期83-96,共14页
Geological Review
基金
中国地质调查局基础地质调查项目(编号1212010611805和1212011085446)的成果
关键词
九曲岩体
锆石U—Pb年龄
S型花岗岩
高分异
流体
赣南
Jiuqu granite, Southern Jiangxi Province
zircon U-Ph age
S-type granite
high-degree evolution
abundant fluids
