巴布亚新几内亚波格拉斑岩型铜—金矿床富Nb碱性火成岩成因新解

New explanation for Nb-enriched alkali igneous rocks in Porgera porphyry copper-gold deposit,Papua New Guinea

巴布亚新几内亚波格拉(Porgera)斑岩铜—金矿床的侵入杂岩岩石类型为碱性玄武岩→夏威夷岩(粗面玄武岩)→橄榄粗安岩套。微量元素总体特征是富集大离子亲石元素(LILE)(Sr、Ba)和高场强元素(HFSE)(Zr、Nb、Th)。在微量元素蛛网图上显示宽的Th、Nb、U峰和Ti、H f、Y的谷。该矿床夏威夷岩和橄榄粗安岩是一套板内富Nb碱性玄武岩系列,属于大陆O IB碱性侵入岩,而不是洋岛OIB系列,与地幔柱活动相关。波格拉侵入杂岩形成于弧—陆碰撞环境,为新生代主动大陆边缘板内碱性玄武岩的典型代表之一。

The intrusive complex in Porgera prophyry copper-gold deposit, Papua New Guinea, is considered as alkali basalts→hawaiites→meteorites rock type. The trace elements in the deposit are characterized by enrichments in large-ion lithophytes element （LILE） （Sr, Ba）and high-field strength elements（HFSE） （Zr,Nb, Th）. It shows positive in Th,Nb,U and Ti ,Hf,and Y on the spider diagrams of trace elements. The hawaiites and meteorites in the deposit are intraplate Nb-enriched alkali basalt series belonging to continental alkali OIB instrument,which are related to mantle plum activity,not belonging to oceanic island （OIB） series. Evidences suggest that the Porgera intrusive complex was formed in arc-continental collision environment. It is one of the representative examples of alkali basalt for Cenozoic active continental margin.