赣东北茶坑花岗斑岩锆石U-Pb年代学、地球化学特征及地质意义

赣东北茶坑花岗斑岩及围岩中发现了白钨矿化。为了进一步查明钨矿化与花岗斑岩的关系及其成矿潜力,对花岗斑岩开展了锆石U-Pb年代学、岩相学及地球化学研究。结果表明:茶坑花岗斑岩的形成年龄为153~152 Ma;具有高硅(SiO2含量为74.62％~76.09％)、富碱(Na2O+K2O含量为7.14％~8.55％)、富钾(K2O含量为4.95％~5.69％)、强过铝质(A/CNK为1.17~1.39,平均值为1.3)的特征;微量元素相对富集Rb、U、K,亏损Ba、Sr、P、Ti;稀土元素总含量为(62.52~75.13)×10-6, (La/Yb)N=3.73~12.16,平均值为7.81,轻、重稀土元素分馏明显,且相对富集轻稀土,具有中等程度的Eu负异常(δEu为0.55~0.82)。茶坑地区花岗斑岩的W含量为(8.80~160)×10-6,平均值为51.16×10-6,是华南花岗岩W平均含量的15倍,表明该地区花岗斑岩具有形成斑岩型-石英脉型钨矿的潜力。

Zircon U-Pb geochronology,geochemical characteristics and geological significance of the Chakeng granite porphyry,northeast Jiangxi Province

The scheelite mineralization was found in the Chakeng granite porphyry and its surrounding rocks in northeastern Jiangxi Province. In order to ascertain the relationship between the tungsten mineralization and granite porphyry and pursue its metallogenic potential, the zircon U-Pb isotopic dating, geochemical and petrographic studies of granite porphyry were carried out. The results show that the Chakeng granite porphyry is 152~153 Ma in age, characterized with high silicon (content of SiO2 is 74.62％~76.09％), rich alkali (content of Na2O+K2O is 7.14％~8.55％) and kalium (content of K2O is 4.95％~5.69％), as well as strongly peraluminous (A/CNK=1.17~1.39, averagely 1.3); the trace elements are relatively enriched in Rb, U, K, and deficient in Ba, Sr, P, Ti; The total content of rare earths is (62.52~75.13)×10-6, and (La/Yb)N=3.73~12.16, with an average value of 7.81.The fractional distillation of light and heavy rare earth elements is obvious, and the light rare earth elements are relatively enriched, with moderate negative Eu anomaly (δEu is 0.55~ 0.82). The W content in the Chakeng granite porphyries is (8.80~160)×10-6, with an average value of 51.16×10-6, 15 times of the average tungsten content of the granites in South China, indicating that the granite porphyries in the Chakeng area have metallogenic potential of porphyry-quartz vein-type tungsten deposit.