广东陶锡湖锡多金属矿床花岗斑岩锆石U-Pb年代学、地球化学、Hf同位素组成及其地质意义

陶锡湖锡多金属矿床是粤东锡多金属成矿带内一个与花岗斑岩有关的矿床。本文对与矿化有关的陶锡湖花岗斑岩进行了岩石地球化学、锆石U-Pb年代学和Hf同位素研究。LA-ICP-MS锆石U-Pb定年显示,花岗斑岩侵位年龄为141.8±1.0 Ma,是早白垩世岩浆作用的产物。岩石地球化学特征显示,花岗斑岩属于弱过铝质高钾钙碱性系列,强烈富集Rb、Th、U、K、Pb,亏损Ba、Sr、Ti、P、Nb、Ta,具有明显Eu负异常,属于高分异I型花岗岩。花岗斑岩成矿金属元素丰度值高,属于典型的含锡花岗岩。花岗斑岩锆石εHf(t)从-6.67变化到-2.32,二阶段模式年龄(tDM2)为1343~1615 Ma,表明其成岩物质主要来自古老地壳,可能有少量地幔物质的加入。根据所得地球化学和年代学数据,结合区域构造演化,陶锡湖花岗斑岩及相关的锡多金属矿床形成于古太平洋板块向欧亚大陆俯冲作用有关的区域伸展的动力学背景。

Zircon U-Pb Geochronology,Geochemistry and Lu-Hf Isotopes of Granite Porphyry in Taoxihu Tin Polymetallic Deposit,Guangdong Province,SE China and its Geological Significance

The newly discovered Taoxihu tin polymetallic deposit is associated with granite porphyry,occurring along the Lianhuashan Fault in the eastern Guangdong province.Zircon LA-ICP-MS dating of the granite porphyry yields a concordant age of 141.8±1.0 Ma,which means that the granite porphyry was formed in the Early Cretaceous.The granite porphyry is characterized by weak peraluminous and high-K calc-alkaline,enriched in Rb,Th,U,K and Pb,and depleted in Ba,Sr,Ti,P,Nb and Ta,with strong negative Eu anomalies.Meanwhile,the granite porphyry shows highly fractionated I-type granite affinity.Abundant ore-forming metals and cloze temporal-spatial relationship with the ore bodies exhibit that the granite porphyry is possibly genetically associated with the tin mineralization in this area.εHf(t) values of-6.67 to-2.32 and tDM2 ages of 1343-1615 Ma of the granite porphyry show that the Taoxihu granite porphyry was mainly crustal-derived with mantle input.Combining with the regional tectonic evolution,the granite porphyry and tin polymetallic mineralization of the Taoxihu deposit were likely generated in an extensional tectonic setting,and related to the subduction of the Paleo-Pacific plate beneath the South China Block.