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

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. 

Geochronology,Petrogeochemistry and Petrogenesis of Ore-Bearing Rock Massif in Dabu Mining Area,Tibet

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.