湖南锡田含W-Sn A型花岗岩年代学与地球化学特征
Geochronology and Geochemical Characteristics of the Xitian Tungsten-Tin-Bearing A-type Granites, Hunan Province, China
周云 1梁新权 2梁细荣 2伍式崇 3蒋英 1温淑女 1蔡永丰1
作者信息
- 1. 中国科学院广州地球化学研究所,同位素地球化学国家重点实验室,广东广州510640;中国科学院大学,北京100049
- 2. 中国科学院广州地球化学研究所,同位素地球化学国家重点实验室,广东广州510640
- 3. 湖南省地质矿产勘查开发局四一六队,湖南株洲412007
- 折叠
摘要
锡田复式花岗岩体位于湘赣交界处,是南岭地区重要的含W-Sn多金属矿花岗岩体之一.本文对锡田垄上赋矿细粒花岗岩进行了LA-ICP-MS年代学及地球化学研究.锆石U-Pb年代学研究表明,锡田花岗岩结晶年龄为151.7±1.2 Ma,与前人采用SHRIMP锆石U-Pb定年法所获得的年龄一致,表明其形成于燕山早期.锡田垄上细粒花岗岩具有高Si(SiO2=73.44％～78.45％)、高K(K2O/Na2O=1.00～253.77)、低Ca(CaO=0.25％～2.22％)、贫Mg(MgO=0.05％～0.42％)、富AI(AI2O3=11.20％～ 13.90％)的特征,为准铝质至强过铝质(A/CNK=0.90～3.44),同时强烈亏损Sr、Ba、P、Ti、Nb、Eu(δEu=0.004～0.076)等元素,富集高场强元素Th、Ta和nf,以及大离子亲石元素Rb和LREE等.主量元素和微量元素分析表明,锡田垄上细粒花岗岩具有A型花岗岩特征.Sr-Nd同位素研究结果显示,岩石具有相对较高的εNd(t)(-7.30～8.87)值,其两阶段Nd模式年龄集中在1.56～1.69 Ga之间,暗示其可能主要来源于古老地壳物质的部分熔融.综合研究表明,锡田花岗岩的形成可能与古太平洋板块俯冲消减引起的拉张环境有关.同时锡田细粒花岗岩显示出良好的Sn成矿性,是比较典型的含锡花岗岩.
Abstract
The Xitian granites are located in the bordering area of Hunan province and Jiangxi province,which is an important part of the Nanling granite belt closely related to tin-tungsten polymetallic deposits.Zircon LA-ICP-MS U-Pb dating of the Longshang fine-grained granite yields an age of 151.7±1.2 Ma,which is the same as previous reported SHRIMP U-Pb ages,indicating the Xitian granites was emplaced in Yanshanian.The granites are characterized by high contents of silicon (SiO2=73.44％～78.45％),potassium (K2O/Na2O=1.00～253.77),aluminum (A12O3=11.20％～ 13.90％),low in calcium (CaO=0.25％～2.22％) and magnesium (MgO=0.05％～0.42％),metaluminous to strongly peraluminous (A/CNK=0.90～3.44).The granites show strong depletion of Sr,Ba,P,Ti,Nb and Eu (δEu=0.004～0.076),enrichment of Th,Ta,Hf,Rb and LREE.The major and trace element concentrations of the fine-grained granite in Longshang of the Xitian area show that the granite is of A-type.The low εNd(t) (-7.30～-8.87) and two stage Nd modal ages ranging from 1.56 Ga to 1.69 Ga suggest that the magma may have derived mainly from partial melting of the old crustal materials.The formation of the Xitian granites may be related to the extension caused by the subduction of palaeo-Pacific plate.The Xitian granites as typical tin-bearing rocks are promising for Tin exploration.
关键词
锡田/A型花岗岩/地球化学/锆石U-Pb定年Key words
Xitian/A-type granite/geochemistry/zircon U-Pb dating引用本文复制引用
基金项目
国土资源部公益科研专项(201211024-03)
中国科学院重大项目(KZCX1-YW-15-1)
国家自然科学基金(40872080)
国家自然科学基金(41072081)
出版年
2013
NETL
NSTL
万方数据