西藏达布矿区含矿岩体的时代、岩石地球化学特征及岩石成因
Geochronology, Petrogeochemistry and Petrogenesis of Ore-Bearing Rock Massif in Dabu Mining Area, Tibet

达布矿区位于冈底斯成矿带中段南侧，具较大的铜(钼)成矿潜力.通过对达布矿区含矿花岗闪长岩体开展岩石学、LA-ICP-MS锆石U-Pb定年和岩石地球化学等方面的分析研究，结果显示达布矿区花岗闪长岩体是主要的含矿岩体之一，其LA-ICP-MS锆石U-Pb年龄为16.5±0.3 Ma～16.0±0.4 Ma，属中新世(N1).岩体具高Al(Al2O3=15.6%～16.5%)、高Na(Na2O=4.51%～4.82%)、钙碱性系列、弱过铝质；稀土元素具弱正铕异常(Eu/Eu*=1.02～1.27)和正铈异常(Ce/Ce * =0.99～ 1.53)；富集Rb、Ba、Sr和亏损Nb、Ta、Ti、Y.达布矿区花岗闪长岩体属I型花岗岩，类似于典型的C型埃达克岩，明显有别于冈底斯带中新世高K埃达克岩；为印度-亚洲大陆碰撞后局部伸展背景下，由加厚下地壳物质(石榴石角闪岩)较高程度部分熔融的岩浆产物.
Dabu mining area is located in the southern part of the middle Gangdese metallogenic belt, which has great metallogenic potential of Cu (Mo) deposit. In this paper, petrology, LA-ICP-MS zircon U-Pb dating, rock geochemistry of the Dabu orebearing granodiorite body are systematically studied. The results suggest that the Dabu granodiorite pluton is one of the major orebearing rock body, and its LA-ICP-MS zircon U-Pb age is 16.5±0.3Ma-16.0±0.4Ma, with the corresponding age of Miocene (N1). The rock mass has high Al (Al2O3=15.6%-16.5%), high Na (Na2O=4.51%-4.82%), and it is calc alkaline and weakly peraluminous. REE elements have weak positive Eu anomalies (Eu/Eu*=1.02-1.27) and positive Ce-anomalies (Ce/Ce*=0.99-1.53). Trace elements ratio spider diagram displays apparent enrichments of Rb, Ba, Sr and marked depletions of Nb, Ta, Ti, Y. The Dabu granodiorite pluton belongs to I-type granite, which is similar to the typical C-type adakite, but is obviously different from the Miocene highK adakite in the Gangdese belt. It is concluded that Dabu granodiorite pluton is a relatively high degree of partial melting of the thickened lower crust material (garnet amphibolite) formed in the background of partial extension of the India Asian continent postcollision