东昆仑造山带东段那更龙洼金矿区富闪镁铁质岩形成时代、地球化学特征及其构造背景与金矿化关系  

Relationship between formation age,geochemical characteristics,tectonic setting and gold mineralization of amphibole-rich mafic rocks of the Nagenglongwa Gold Deposit in the eastern part of the East Kunlun orogenic belt

作　　者：卢寅花 王力[1] 盛建华 李良 Lu Yinhua;Wang Li;Sheng Jianhua;Li Liang(College of Earth Sciences,Jilin University;Yantai Natural Resources and Planning Bureau;College of Resources,Environment and Earth Sciences,Yunnan University)

机构地区：[1]吉林大学地球科学学院,130061 [2]烟台市自然资源和规划局 [3]云南大学资源环境与地球科学学院

出　　处：《黄金》2020年第11期5-15,共11页Gold

基　　金：国家自然科学基金(41402060);自然资源部东北亚矿产资源评价重点实验室自主基金(DBY-ZZ-19-13)。

摘　　要：东昆仑造山带地处青藏高原东北部,是中国青藏高原的主要造山带之一,是研究与原特提斯洋闭合相关的岩浆活动和地球动力学过程的理想地区。那更龙洼金矿床位于东昆仑造山带东南部,为典型的中温热液脉型金矿床。通过对那更龙洼金矿区富闪镁铁质岩进行岩石学、锆石U-Pb年代学、全岩地球化学的研究,探讨其成因类型和源区,并还原其地球动力学背景,在此基础上论述其与金矿化的关系。结果表明:富闪镁铁质岩侵位于424.5 Ma±2.4 Ma,为晚志留世岩浆活动产物;具有低SiO2、高Al2O3、高镁指数等特点,揭示了其幔源属性;具有高K2O的特点,属于高钾钙碱性—钾玄岩系列;强烈富集轻稀土元素,亏损重稀土元素(w(La)N/w(Yb)N值为33.24~52.14);富集大离子亲石元素(Rb、Ba、K、Pb),相对亏损部分高场强元素(Nb、Ta、Ti、Zr、Hf),揭示了其地幔源区已经被流体广泛交代。综上,认为富闪镁铁质岩为俯冲流体交代岩石圈地幔部分熔融的产物。结合区域上其他岩浆和沉积记录等地质证据,认为富闪镁铁质岩是原特提斯洋闭合后俯冲板片断离引发的强烈伸展构造背景下的产物,这一强烈后碰撞伸展背景为含金地幔流体的向上运移提供了必要的热力学和动力学条件。The East Kunlun orogenic belt is located in the northeast of Qinghai-Tibet Plateau,which is one of the main orogenic belts in Qinghai-Tibet Plateau in China.It is an ideal area to study the magmatic activities and geodynamic processes related to the closure of the Proto-Tethys Ocean.The Nagenglongwa Gold Deposit is located in the southeast of the East Kunlun orogenic belt and is a typical mesothermal vein type gold deposit.Based on the study of petrology,zircon U-Pb chronology,and whole-rock geochemistry of the amphibole-rich mafic rocks in the Nageng-longwa Gold District,the genetic types and source region have been discussed,and the geodynamic setting has been restored.On this basis,the relationship with the gold mineralization is discussed.The zircon U-Pb age indicates that the emplacements of the amphibole-rich mafic rocks are located at 424.5 Ma±2.4 Ma,which are the products of magmatic activities in the late Silurian epoch.The petrogeochemistry results indicate that the amphibole-rich mafic rocks have the characteristics of low SiO 2,high Al2O3 and Mg^#,revealing mantle origin attribute.The samples with the high K2O contents belong to the series of high potassium calcium alkaline-potassium basalt.The samples display strong enrichment in light rare earth element and depletion in heavy rare earth element(w(La)N/w(Yb)N value is 33.24-52.14),enrichment of large-ion lithosphile elements(Rb,Ba,K,Pb),and relative depletion of high field-strength elements(Nb,Ta,Ti,Zr,Hf),demonstrating that the mantle source region has been extensively metasomatized by fluid.To sum up,it is considered that the amphibole-rich mafic rocks are the products of partial melting of the lithospheric mantle metasomatized by subduction fluid.Based on the geological evidence of other magmatic and sedimentary records in the region,it is considered that the amphibole-rich mafic rocks are the products of the strong extensional tectonic setting caused by the subduction plate fragments after the closure of the Proto-Tethian Ocean.The strong post-c

关 键 词：东昆仑造山带 那更龙洼金矿区 富闪镁铁质岩 锆石U-PB定年 岩石地球化学 

分 类 号：TD11[矿业工程—矿山地质测量] P618.51[天文地球—矿床学]