黑龙江省跃进山铜金矿床花岗斑岩锆石U-Pb定年及地质意义

跃进山铜金矿床是完达山活动带的典型矿床,位于密山—敦化深断裂北侧。本文对含矿花岗斑岩开展了锆石LA-ICP-MS U-Pb测年、主量和微量元素的研究,厘定岩体的形成时代,探讨了成矿构造背景。结果表明与成矿密切相关的花岗斑岩的年龄为(109.17±0.91)Ma。它们为过铝质钙碱性系列岩石,富集Rb、Ba、La、Nd、Hf等元素,亏损Nb、Sr、P、Ti等元素,具俯冲带岩浆岩的基本特征,这些暗示它们形成于岛弧或活动大陆边缘环境。结合岩体的地球化学特征和完达山成矿带的构造岩浆演化,认为该矿床形成于岛弧构造背景,其形成与中生代太平洋的俯冲及早白垩世晚期东亚东部岩浆活动陆缘迁移、构造单元转化有关。

The dating of ore-bearing granite porphyry in the Yuejinshan skarn Cu-Au deposit, Heilongjiang Province, and its tectonic significance

Abstract: The Yuejinshan Cu-Au deposit, located in southeast Heilongjiang Province, is a typical deposit which occurs in the north of Mishan-Dunhua Deep fracture of the Wandashan metallogenic belt. The authors carried out LA-ICP-MS zircon U-Pb dating of main and trace elements in the granite porphyry, and discussed the chronology of the rock mass and the tectonic setting. The results indicate that the ore-related Yuejinshan granite porphyry has a concordia LA-ICP-MS zircon U-Pb age of (109.17±0.91) Ma, which is basically in good consistency with the weighted average age. The Yuejinshan granite porphyry has a geochemical affinity with subduction magmas, characterized by peraluminous nature, enrichment of LILIs (Rb, Ba, La, Nd and Hf), and depletion of HFSE (Nb, Sr, P and Ti). The geochronologic and geochemical characteristics of the Yuejinshan granite porphyry, combined with tectonic evolution of the Wandashan metallogenic belt, suggest that the deposit was formed in a island arc or active continental margin setting and that its formation was probably related to the subduction of the Paleo-Pacific Ocean during the Mesozoic.