首页 | 本学科首页   官方微博 | 高级检索  
     检索      

西秦岭天水地区李子园群变质火山岩的地球化学特征及其地质意义
引用本文:裴先治,刘会彬,丁仨平,李佐臣,胡波,孙仁奇,侯育红.西秦岭天水地区李子园群变质火山岩的地球化学特征及其地质意义[J].大地构造与成矿学,2006,30(2):193-205.
作者姓名:裴先治  刘会彬  丁仨平  李佐臣  胡波  孙仁奇  侯育红
作者单位:1. 长安大学地球科学与国土资源学院,陕西,西安,710054
2. 长安大学地球科学与国土资源学院,陕西,西安,710054;甘肃省地质调查院,甘肃,兰州,730000
3. 中国科学院地质与地球物理研究所,北京,100009
基金项目:国家自然科学基金项目(编号:40234041,40572121),教育部科学技术研究重点项目(编号:104175),中国地质调查局地质调查项目(编号:200013000154)联合资助.
摘    要:西秦岭天水地区的早古生代李子园群为一套中浅变质的沉积-火山岩系。沉积岩系主要由变质碎屑岩和碳酸盐岩组成,火山岩系主要由变玄武岩、变玄武安山岩和变安山岩组成,包括岛弧型火山岩和玻安岩。岛弧型火山岩SiO2含量介于48.79%~54.64%之间,TiO2含量较低(0.29%~0.88%);稀土元素分布型式呈LREE略富集型,富集大离子亲石元素(LILE)Cs、Sr、Th、U,相对亏损Rb、K和高场强元素(HFSE)Nb、P、Sm、Ti和Y,具Nb负异常,类似于低钾岛弧拉斑玄武岩和钙碱性玄武岩特征。玻安岩具有中等的SiO2含量(53.59%~59.28%),低的TiO2含量(0.24%~0.48%);相对中等的MgO含量(4.90%~4.96%)、较低的CaO/Al2O3比值(0.39~0.54)和较高的Mg#值(0.54~0.58)、Al2O3/TiO2比值(33.88~64.29);同时具有较低的Ti/Zr比值(15~83)、V/Zr比值(2.18~8.35)和较高的Zr/Y比值(3.82~12.08),相对富集大离子亲石元素(LILE),特别是Rb、Ba、Th,而亏损高场强元素(HFSE),如Nb、Ta、P、Ti、Y、Yb,显示为亏损MREE的U型稀土元素分布型式。岛弧型火山岩和玻安岩的存在表明,李子园群及其中的中基性火山岩系形成于俯冲带之上的岛弧或弧前环境。

关 键 词:李子园群  变质火山岩  玻安岩  岛弧/弧前环境  早古生代  天水地区  西秦岭
文章编号:1001-1552(2006)02-0193-13
收稿时间:2005-06-12
修稿时间:2005-08-15

GEOCHEMICAL CHARACTERISTICS AND TECTONIC SIGNIFICANCE OF THE META-VOLCANIC ROCKS IN THE LIZIYUAN GROUP FROM TIANSHUI AREA, WESTERN QINLING OROGEN
PEI Xianzhi,LIU Huibin,DING Saping,LI Zuochen,HU Bo,SUN Renqi,HOU Yuhong.GEOCHEMICAL CHARACTERISTICS AND TECTONIC SIGNIFICANCE OF THE META-VOLCANIC ROCKS IN THE LIZIYUAN GROUP FROM TIANSHUI AREA, WESTERN QINLING OROGEN[J].Geotectonica et Metallogenia,2006,30(2):193-205.
Authors:PEI Xianzhi  LIU Huibin  DING Saping  LI Zuochen  HU Bo  SUN Renqi  HOU Yuhong
Abstract:The early Paleozoic Liziyuan Group from Tianshui area, Western Qinling consists of a suite of meso-to epi-metamorphic sedimentary-volcanic rock series. The sedimentary rock series are mainly composed of meta-clastic rocks and carbonate rocks; volcanic rock series are mainly composed of meta-basalt, meta-basaltic andesite and meta-andesite, including island arc volcanic rocks and boninite. The SiO_2 of island arc volcanic rocks ranges from between 48.79%~54.64%, while the TiO_2 content is relatively lower (0.29%~0.88%); the chondrite-normalized REE distribution patterns show that the rocks are slightly enriched in LREE, enriched in LILE (Cs, Sr, Th, U), and relatively depleted in Rb, K and HFSE (Nb, P, Sm, Ti, Y), show apparently negative abnormity in Nb; All these demonstrate the low-K island arc tholeiite basalt and calc-alkalic basalt characteristics. Boninites show medium SiO_2 contents (53.59%~59.28%), lower TiO_2 contents (0.24%~0.48%), relatively medium MgO contents (4.90%~4.96%), lower CaO/Al_2O_3 ratios (0.39~0.54), and higher Mg# (0.54~0.58) and Al_2O_3/TiO_2 ratios (33.88~64.29); they also show lower Ti/Zr ratios (15~83) and V/Zr ratios (2.18~8.35), and higher Zr/Y ratios (3.82~12.08), relative enrichment in LILE, especially Rb, Ba, Th, and depletion in HFSE, such as Nb, Ta, P, Ti, Y, Yb. The chondrite-normalized REE distribution patterns show MREE depleted U-type. The existence of island arc volcanic rocks and boninite indicate that Liziyuan Group and the intermediate and basic rocks in this group were formed in island arc or forearc setting in a subduction zone.
Keywords:Liziyuan group  meta-volcanic rocks  boninite  island-arc/forearc setting  early Paleozoic  Tianshui area  Western Qinling
本文献已被 CNKI 维普 万方数据 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号