粤东塌山斑岩型锡多金属矿床锆石及锡石U-Pb年代学、Hf同位素组成及其地质意义

Zircon and Cassiterite U-Pb Ages and Lu-Hf Isotopic Compositions of Tashan Tin-bearing Porphyry in Guangdong Province, SE China and its Geological Significance

陆河县塌山斑岩型锡多金属矿床位于粤东地区莲花山断裂带南西段,是粤东锡多金属成矿带内与花岗斑岩和石英斑岩密切相关的锡矿床,同时也是全国三个典型斑岩型锡矿之一。本文对与矿化有关的花岗斑岩进行了锆石U-Pb年代学和Hf同位素综合研究。LA-ICP-MS锆石U-Pb定年显示,花岗斑岩侵位年龄为136.8±1.1 Ma,是早白垩世岩浆作用产物。同时本文对锡石进行了U-Pb定年研究,27个数据在^(206)Pb/^(238)U-^(207)Pb/^(238)U谐和年龄图上获得了133.6±8.6 Ma的下交点年龄,在Tera-Wasserburg年龄图解上获得了136.5±8.1 Ma的下交点年龄,两年龄在误差范围内一致,且与花岗斑岩年龄一致,很好的限定了塌山矿区成矿时代。花岗斑岩锆石εHf(t)从-4.87变化到-2.07,二阶段模式年龄(t_(DM2))为1322～1507 Ma,表明其成岩物质主要来自中元古代地壳岩石,可能有少量地幔物质加入。

The Tashan porphyry tin polymetallic deposit is located at the southwest part of the Lianhuashan Fault in the eastern Guangdong province.It is one of the three typical porphyry tin deposits in China.In this paper,we reported cassiterite and zircon U-Pb ages,geochemistry and Lu-Hf isotopes of the ore-bearing granite porphyry in the orefield.Zircon LA-ICP-MS U-Pb dating yielded a concordant ages of 136.8±1.1 Ma,whereas analyses of cassiterite yielded a 206Pb/238U-207Pb/238U concordia lower intercept age of 133.6±8.6 Ma and a Tera-Wasserburg lower intercept age of 136.5±8.1 Ma,which suggest a genetic link between the granite porphyry and the ore mineralization.TheεHf(t)values of-4.87 to-2.07 and tDM2 ages 1322 Ma to 1507 Ma for zircon from the granite porphyry show that the Tashan granite porphyry was likely derived from partial melting of the Mesoproterozoic crustal rocks with minor input of mantle material.