藏北多龙矿集区地壳基底性质、演化及其对成矿的制约——来自波龙火山-侵入岩中继承锆石U-Pb年龄的信息

地壳基底性质及其演化对区域金属成矿类型和成矿潜力具有重要影响。藏北多龙矿集区是目前中国规模最大的斑岩-浅成低温热液型铜多金属矿集区之一,其地壳基底性质与演化缺少研究,制约了对区内铜多金属成矿构造背景和成矿物质来源的全面认识。多龙矿集区内波龙火山-侵入岩中继承锆石LA-ICP-MS U-Pb测年结果显示,14颗继承锆石具有新太古代—古元古代年龄(2581~1670Ma),这些锆石多为自形-半自形颗粒,具有原地来源的特征,表明多龙矿集区深部存在新太古代—古元古代结晶基底。该基底应该是南羌塘中心地区古老基底向南延伸的一部分。该基底在中元古代—早古生代遭受多次构造-岩浆热事件改造,尤以泛非期—早古生代最强烈。进入晚中生代后,由于年轻地幔物质的加入,多龙地壳发生明显的垂向生长,形成富含金属和成矿组分的新生下地壳,该新生下地壳在早白垩世发生活化,为多龙成矿体系提供大量的金属及其他幔源有用组分。多龙矿集区是一个"两期岩浆叠加成矿"的典型例子。

Nature and evolution of crustal basement beneath the Duolong ore concentration area, northern Tibet, and their constraints on the metallogenesis: Insights from U-Pb ages of inherited zircons from the Bolong volcanic-intrusive rocks

The nature and evolution of crustal basement controlled the types and potentials of ore deposits. The Duolong ore concentration area, located in northern Tibet, is the largest porphyry-epithermal Cu-Au ore district in China. However, the studies of the nature and evolution of crustal basement beneath the Duolong ore concentration area have been very insufficient. The present study reports LA-ICP-MS U-Pb data of inherited zircons from the Bolong volcanic-intrusive rocks in the Duolong ore concentration area. The authors hold that these data indicate the presence of an Archean-Paleoproterozoic crustal basement beneath the Duolong ore concentration area. This Archean-Paleoproterozoic crustal basement was a part of an extended ancient basement beneath the center of the South Qiangtang terrane, and experienced multiple tectonomagmatic events during the Mesoproterozoic-Early Palaeozoic period. It is also known that the ancient basement beneath the Duolong ore concentration area experienced significant addition of juvenile lower crust (i.e., vertical crustal growth) in the Late Mesozoic, which was induced by the underplating of mantle material. This juvenile lower crust would release substantial metals and other ore-forming components into the magmatic-metallogenic system during subsequent remelting and remobilization.