The Duolong ore concentration area is the most favorable potential prospecting area in the Bangong Co-Nujiang metallogenic belt.Four porphyry Cu-Au deposits have been discovered in the Duolong area,but their metallogenic setting is still in controversy.The Samalong diorite is located in the central part of the Duolong area.Combined with the tectono-magmatic activation,the authors studied geochronology and bulk geochemistry of the Samalong diorite so as to constrain the metallogenic setting of the porphyry deposits.25 zircon samples selected form the Samalong diorite intrusion were analyzed by LA-ICP-MS,which yielded a weighted 206Pb/238U age of 121.6±1.7Ma (MSWD=1.9,n=23),which represents its intrusive age.According to the bulk petrochemical results,the Samalong diorite intrusion belongs to the middle potassium and sodium-rich magmatic series.The Samalong diorite is also enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high field-strength elements,with high Sr and low Y concentrations,suggesting adakite-like affinity.The high initial 87Sr/86Sr values (0.7056～ 0.7073) and low initial 143Nd/144Nd (0.5124～0.5125) and ε Nd(t) (-1.3～0.7) suggest that the Samlong diorite was generated from the lower crust,and its relative high MgO content and incompatible elements (Cr,Ni,etc.) concentrations indicate that there might have been some melt derived from the peridotitic mantle wedge mixed in the source region.The Samalong diorite was cut by the former strike-slip faults,which probably suggests that these later strike-slip faults controlled the formation of the porphyry deposits within 116～121Ma,and the porphyry deposits in the Duolong ore concentration area were formed within the structural transferring period at the last stage of the northward subduction ofBangong Co-Nujiang Neo-Tethys Ocean.%西藏多龙矿集区是目前班公湖-怒江成矿带内最具潜力的找矿远景区,矿集区内已发现4处大型斑岩铜矿,但其成矿背景尚有争议.通过开展成矿前的萨玛隆闪长岩锆石U-Pb测年、岩石化学分析,结合区域内构造发育序次,对系列斑岩铜矿的成矿背景进行探讨.对萨玛隆闪长岩中进行LA-ICP-MS锆石U-Pb测年,获得23颗锆石的206Pb/238U年龄加权平均值为121.6±1.7Ma(MSWD=1.9),代表了闪长岩的成岩年龄.萨玛隆闪长岩的全岩岩石化学分析结果显示,该岩石属于中钾富钠岩石,富集轻稀土元素和大离子亲石元素,亏损重稀土元素和高场强元素,具有高Sr、低Y特征,相对富集Cr、Ni等不相容元素,有埃达克岩的亲和性.闪长岩具相对较高的(87Sr/86Sr)i值和较低的(143Nd/144Nd)i值、εNd(t).全岩岩石化学特征显示,萨玛隆闪长岩起源于下地壳角闪岩相,可能有幔源物质混入.矿区内早期走滑断层切穿萨玛隆闪长岩,指示多龙矿集区内主要控岩-控矿走滑断层可能形成于116～121Ma,多龙矿集区内系列斑岩铜矿形成于班公湖-怒江洋向北俯冲末期的构造转换阶段.
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