浙东南怀溪铜金矿床与曹门碱性花岗岩体成因关系的年代学制约  

Genetic Relationship of the Huaixi Copper-Gold Deposit and the Caomen Alkaline Granite,Southeastern Zhejiang Province,China:Constraint from Geochronologies

作　　者：李艳军[1] 魏俊浩[1] 姚春亮[1] 鄢云飞[2] 谭俊[1] 彭丽娜[1] 肖广玲[1] 叶泽富[3] 

机构地区：[1]中国地质大学资源学院,湖北武汉430074 [2]紫金矿业集团股份有限公司,福建上杭364200 [3]浙江省第十一地质大队,浙江温州325006

出　　处：《地球科学（中国地质大学学报）》2010年第4期585-596,共12页Earth Science-Journal of China University of Geosciences

基　　金：教育部创新团队发展计划(IRT0755);全国危机矿山接替资源找矿项目(No.2006020035);中国地质大学地质过程与矿产资源国家重点实验室基金

摘　　要：怀溪铜金矿床位于浙东南政和-大埔大断裂和长乐-南澳大断裂间坳陷区,为典型的热液脉状充填型Cu-Au多金属矿床.曹门钾长花岗斑岩为矿区内最主要的侵入体,化学成分显示为钾玄质岩系,具高硅、富碱和铁、贫钙和镁的特征,SiO2含量为75.64%～78.00%,K2O为5.38%～5.92%,K2O/Na2O比值为1.94～2.72;富集Ga、Rb、Th、U等元素,亏损Ba、Nb、Sr、P和Ti,REE具明显的负Eu异常,总体呈现右倾"V"型配分模式.矿物组成及地球化学特征与浙闽沿海晚白垩世碱性花岗岩一致.曹门钾长花岗斑岩体锆石LA-ICP-MSU-Pb年代为102±1Ma(MSDW=1.3),而怀溪铜金矿床的石英流体包裹体Rb-Sr等时线年龄为101±2Ma,成岩成矿时代一致.成岩成矿时代的确定为成岩成矿具有密切成因关系提供了重要的年代学制约,表明怀溪铜金矿床是东南沿海晚白垩世后碰撞弧后拉张构造-热事件的产物,为华南中生代第3次大规模成矿的一部分.The Huaixi copper-gold deposit, located in depression area between the Zhenghe-Dapu and Changle-Nan＇ao deep faults in southeastern Zhejiang Province, is a typical hydrothermal vein fillingmetasomatic Cu-Au polymetallic deposit. The Caomen K feldspar granite porphyry pulton is the dominant intrusion in the deposit. Petrography and chemical compositions show that it belongs to shoshonite series characterized by high silicon, and it is enriched in alkali and iron but depleted in phosphorus and titanium. Its SiO2 contents range from 75.64% to 78. 00%, while K2O and K2O/Na2O ratios vary from 5. 38% to 5. 92% and 1.94 to 2.72 respectively. Ga,Rb, Th, U and Pb elements are enriched in the intrusion while Ba, Nb, Sr, P and Ti are depleted. REE is characterized with obvious negative anomalies with Eu/Eu^＊ 0. 06-0. 13 and exhibits right-dipping ＂V＂ patterns with LREE enrichment. Its mineralogy and geochemistry are consistent with those of Late Cretaceous alkaline granites in the coastal areas of Zhejiang Fujian. This study offers the first highly precise dating of the diagenesis and mineralization in the deposit. The dating of zircon from the Caomen alkaline granite puhon determined by LA-ICP-MS yields age of 102±1 Ma （MSDW= 1.3）, while Rb and Sr isotopic dating of fluid inclusions in quartz of the Huaixi copper-gold deposit yields isochron age of 101±2 Ma. The results suggest that Cu-Au mineralization was consistent with granite crystallization. The ages of diagenesis and mineralization provide an important chronological constraint for the close genetic relationship of the deposit and the Caomen intrusion. The Huaixi Cu-Au deposit, originated from back-arc extensional tectonic heat event related to high angle subduction of the ancient Pacific plate, caused by northward movement of the Indian plate, is corresponding to the time of the third large-scale mineralization regionally in the Mesozoic.

关 键 词：锆石LA-ICP-MS U-PB定年 地质年代 碱性花岗岩 怀溪铜金矿床 浙江. 

分 类 号：P597[天文地球—地球化学]