西藏谢通门县雄村斑岩型铜金矿集区I号矿体的岩石地球化学特征：对成矿构造背景的约束

Characteristics of Rock Geochemistry of Orebody No.I in the Xiongcun Porphyry Copper-Gold Metallogenic District,Xietongmen County,Tibet:Constraints on Metallogenic Tectonic Settings

本文以雄村矿集区I号铜金矿体为研究对象,通过对含矿斑岩-含眼球状石英斑晶的角闪石英闪长玢岩、赋矿凝灰岩以及不含矿斑岩-角闪石英闪长玢岩的岩石地球化学研究,认为这三类岩石属钙碱性岩石系列,具有与岛弧火山岩相类似的地球化学特征,表现为Mg#值介于38～78(平均44),高钾、富铝,TiO2含量较低,相对富集LREE、LILE,亏损HREE、HFS,缺少Eu异常。结合雄村矿区I号矿体的成岩成矿时代以及岩石地球化学特征,认为I号矿体的成岩成矿事件应该发生于新特提斯洋壳向北俯冲于拉萨地块之下而形成的岛弧环境,火山/侵入岩可能是俯冲带的新特提斯洋壳释放出的流体交代楔形地幔区的EMI型富集地幔的产物。

In this paper,the Xiongcun orebody I is used as the research object.By the geochemical studies of mineralizing porphyry-hornblende quartz diorite porphyry with big quartz eyes,mineralizing tuff and baring porphyry-hornblende quartz diorite porphyry,we suggest that the three rock type are calc-alkaline rock series,and they have geochemical characteristics similar to the island arc volcanic rock.The geochemical characteristics are as follows：the Mg # values range from 38 to 78 （mean 44）,rich in potassium,with high aluminum,low TiO2 content,relatively enrichment of LREE and LILE,loss ofHFEE and HFS,and lack of Eu anomalies.Combining with rock forming age,mineralizing age and rock geochemical characteristics,the rock forming and mineralization events of the Xiongcun orebody No.I might occur in the island arc environment which was formed by the subduction of the Neo-Tethys oceanic crust under the Lhasa block.The volcano/intrusion of the Xiongcun area is the product of wedge mantle zone’s EMI-type mantle metasomasised by fluid which was released from subducted Tethys oceanic crust.