越南东北部静足(T(i)nh Túc)钨锡矿区花岗岩年代学、地球化学与区域构造意义

摘要

The Tuih Trie W-Sn ore deposit in Cao Bang, Northeast Vietnam, is located in the Ngan Soh-TTnh Tuc metallogenic belt, which is a part of the Northeast Vietnam-Southwest China granite-related W-Sn metallognic belt SIMS U-Pb dating results of zircons from the granite samples show that the granite was empaced at 93.9 ± 3. Oma. Geochemical analysis indicates that the granite is S-type granite, charactered by high SiO2(73.5% -74.6%), peraluminous (Al2O3: 14.21% -14.88%), alkali (Na2O + K2O; 6.64% -8.47% ). The rocks are rich in potassium, but poor in sodium (K2O/NajO > 1). They also have relatively high Rb, Th, U, Zr, Hf, and low Ba, Nb, Sr, Ti, Eu. They are rich in LREE, with an obvious negative Eu anomaly. The rocks have initial 87'Sr/86Sr of 0. 749 ±0.027, and their εNd(0 ranges from -10.71 to -10.42. Based on the geochemical results, isotope data and zircon U-Pb results of the Pia Oac granite, it is concluded that the granite was emplaced during a post-orogenic extensional setting and resulted from high differentiation magma. Comparing with the characteristics of the ore-bearing granites in southwestern South China, we suggest that the Pia Oac in TTnh Tuc ore deposit be grouped into the Gejiu-Dachang granite belt After comparison with the granites in the Tengchong-Moulmein granite belt and applying the geochemical discrimination of tectonic settings, we conclude that the Gejiu-Dachang granite belt are related to both Pacific tectonic domain and Tethyan tectonic domain; The latter is predominant relative to the former.%越南东北部高平地区静足(T(i)nh Túc)钨锡矿床分布在银山-静足成矿带上,属于中国西南-越东北花岗岩相关的钨锡成矿带的一部分.花岗岩的锆石SIMS U-Pb测年结果为93.9±3.0Ma,地球化学分析结果显示出过铝质S型花岗岩的特点,高硅(SiO2含量73.5％～74.6％),铝过饱和(A12O3含量14.21％～14.88％),高碱(Na2O+ K2O为6.64％～8.47％)、富钾贫钠(K2O/Na2O＞1),同时富集Rb、Th、U、Zr、Hf,亏损Ba、Nb、Sr、Ti、Eu,轻稀土相对富集,呈现明显的负Eu异常.同位素研究表明,样品的87Sr/86 Sr初始比值为0.749±0.027,εNd(t)为-10.71～-10.42.本文依据派洼花岗岩的地球化学特征,结合花岗岩的锆石U-Pb年代学、同住素分析结果,认为派洼花岗岩为燕山期后造山环境中形成的高度分异岩浆结晶的结果.通过与华南西南部矿床相关岩体比较,将静足派洼岩体归入个旧-大厂花岗岩带.并通过与缅甸境内腾冲-毛淡棉花岗岩带岩体特征对比并结合构造环境判别,提出个旧-大厂花岗岩带的形成可能受到太平洋构造域和特提斯构造域的双重影响,但以后者为主.