赣中大王山钨多金属矿床中碱长花岗岩成因：来自LA-ICP-MS锆石U-Pb年代学、岩石地球化学的制约

赣中大王山-南村钨多金属矿集区产出一套与钨、钼多金属矿化有关的中、细粒二云母碱长花岗岩侵入体，本文通 过对大王山矿床赋矿花岗岩进行LA-ICP-MS 锆石U-Pb测年，获得其成岩年龄为147.8±1.9 Ma，属晚侏罗世岩浆活动的产 物，成岩时间与赣中及南岭地区的主要石英脉型钨多金属矿床的成矿时间一致。花岗岩富硅、富碱、强过铝，贫钙、贫 镁、分异指数（DI） 较高，暗色矿物含量极少。REE配分曲线具有“海鸥型”特征，微量元素蛛网图显示亏损Ba，Sr及 Nb，Eu，P，Ti等，富集Rb，Th，U，Pb，K等。在εNd(t)- T图解上，矿集区周边中生代赋矿花岗岩多投点于华南元古代地 壳演化域之上，其T2DM年龄（1.39~1.66 Ga） 亦低于华南地壳的平均年龄（1.7~1.8 Ga），可能与花岗岩形成过程中受到了少 量幔源物质的混染作用有关。结合花岗岩Sr-Yb分类图、Q-Ab-Or三角图以及锆石饱和温度，表明该套花岗岩应该为一套 高分异的过铝质淡色花岗岩。

Genesis of Alkali-Feldspar Granite at Dawangshan Tungsten Polymetallic Ore Concentration Area in Central Jiangxi Province: Constraints from LA-ICP-MS Zircon U-Pb Chronology and Geochemistry

Fine-to medium-grained two-mica alkali-feldspar granites hosting tungsten and molybdenum minerals occur in the Dawangshan tungsten polymetallic ore field in central Jiangxi Province. LA-ICP-MS U-Pb dating of zircon from Dawangshan ore-bearing granites yields an age of 147.8±1.9 Ma, which indicates Late Jurassic time. The intrusion of the granites as evidenced by the U-Pb age, coincided with the ore-forming of the quartz-vein type tungsten polymetallic deposits in central Jiangxi Province and Nanling area. The granites are strongly peraluminous with high differentiation index (DI) and contain minor dark minerals. The granites are enriched in alkali and silicon, and are depleted in calcium and magnesium. The REE partition curve shows a“seagull pattern”. Their primitive-mantle normalized trace element spidergrams indicate depletions in Ba, Sr, Nb, Eu, P and Ti, and enrichment in Rb, Th, U, Pb and K. In the diagram of εNd(t) vs. T, the granite samples are projected in the area between the Proterozoic crustal region of South China and the chondrites mantle, suggesting a source from mantle source material. The results of the T2DM ages of granites (1.39~ 1.66 Ga) are relatively younger than the average age of the crust in South China (1.7~1.8 Ga). These indicate that the formation of granites likely involved a small amount of mantle materials. By combining the Sr-Yb and Q-Ab-Or diagrams as well as the calculated zircon saturation temperatures, we conclude that the granites belong to high-differentiated peraluminous S-type granite and they were formed in a post-orogenic extensional environment with low temperature, low pressure and water-rich conditions.