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| 阿拉善断块富碱侵入岩岩石地球化学和Nd、Sr、Pb同位素特征及其意义 | |
| 引用本文： | 任康绪,阎国翰,牟保磊,蔡剑辉,童英,李凤棠,赵凤三,古丽冰,杨斌,储著银.阿拉善断块富碱侵入岩岩石地球化学和Nd、Sr、Pb同位素特征及其意义[J].地学前缘,2005,12(2):292-302. |
| 作者姓名： | 任康绪 阎国翰 牟保磊 蔡剑辉 童英 李凤棠 赵凤三 古丽冰 杨斌 储著银 |
| 作者单位： | 1. 北京大学,地球与空间科学学院,北京,100871 2. 北京大学,地球与空间科学学院,北京,100871;中国地质科学院,矿产资源研究所,北京,100037 3. 北京大学,地球与空间科学学院,北京,100871;中国地质科学院,地质研究所,北京,100037 4. 中国科学院,地质与地球物理研究所,北京,100029 |
| 基金项目： | 广东省博士启动基金;中国科学院资助项目 |
| 摘 要： | 阿拉善断块富碱侵入岩具有硅过饱和(出现石英,w(SiO2)=62.01%~67.28%)、准铝(w(Al2O3)=12.20%~16.83%)、富碱(w(Na2O) +w(K2O) = 11. 14% ~ 14. 18%,里特曼指数σ= 6. 40 ~ 8. 65)、富钾(w(K2O)/w(Na2O)=1.01~1.79)和低铁、镁的特征。总稀土较高,稀土配分曲线呈陡右倾模式。微量元素强烈富集LILE和LREE,相对亏损Nb、Ta、Ti 和P。上述特征以及低钕(ε(Nd,t) = - 7. 3 ~ - 9. 4)高锶(ε(Sr,t)=+53.9~+99.9)的同位素特征反映物质来源主要与富集型上地幔有关,但受到不同程度壳源物质的混染作用。Nd、Sr、Pb联合示踪表明阿拉善断块富碱侵入岩与华北断块北缘印支期富碱侵入岩带具有相似性,但不同于塔里木北缘富碱侵入岩。结合时空分布、同位素组成以及所处的构造动力学体系等因素将阿拉善断块富碱侵入岩和燕辽—阴山印支期富碱性侵入岩带划归为同一印支期富碱性侵入岩带。指出至少到晚古生代—印支期时阿拉善断块已经与华北断块构成了一个整体。 |
| 关 键 词： | 富碱侵入岩 岩石地球化学特征 Sr Nd和Pb同位素 阿拉善断块 |
| 文章编号： | 1005-2321(2005)02-0292-10 |
| 修稿时间： | 2004年8月24日 |
Geochemistry and Nd, Sr, Pb isotopic characteristics of the alkali-rich intrusive rocks in Alxa Fault Block, Western Inner Mongolia and their implications |
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| REN Kang-xu,YAN Guo-han,MU Bao-lei,CAI Jian-hui,TONG Ying,LI Feng-tang,ZHAO Feng-san,GU Li-bing,YANG Bin,CHU Zhu-yin.Geochemistry and Nd, Sr, Pb isotopic characteristics of the alkali-rich intrusive rocks in Alxa Fault Block, Western Inner Mongolia and their implications[J].Earth Science Frontiers,2005,12(2):292-302. | |
| Authors: | REN Kang-xu YAN Guo-han MU Bao-lei CAI Jian-hui TONG Ying LI Feng-tang ZHAO Feng-san GU Li-bing YANG Bin CHU Zhu-yin |
| Abstract: | The alkali-rich intrusive rocks in Alxa Fault Block are characterized by (1) supersaturation of silica, (with appearance of quartz and concentrations of SiO_2 reaching 62.01%~67.28%), (2) meta-aluminum((wt% Al_2O_3=)12.20%~16.83%), (3) alkali-rich (wt% K_2O+Na_2O=11.14%~14.18% and the Rittmann Index (σ) varing from 6.40 to 8.65), (4) potassium-rich (K_2O/Na_2O=1.01~1.79) and (5) low concentrations of Fe and Mg. The total rare earth element concentrations (∑REE) of the rocks are relatively high, with the REE patterns being sub parallel and with strong LREE enrichment. Multi-element spidergrams exhibit strong LILE and LREE enrichments and Nb, Ta, Ti, P depletion . The (above) together with low Nd (ε(Nd,t)=-7.3~-9.4) and high Sr (ε(Sr,t) =(+53.9~+99.9)) indicate that these rocks originated from an enriched upper mantle but were contaminated by crustally derived materials. Nd, Sr and Pb plots show that the alkali-rich intrusive rocks in Alxa have common features with Indosinian alkali-rich intrusives in Yanliao-Yinshan area. However, they are different from alkali-rich intrusive rocks from the north margin of the Tarim Block.The spatial and temporal distribution data, the isotopic characteristics and the geodynamic settings support the conclusion that the Alxa alkaline-rich intrusive rocks are the westward extension of the Indosinian alkaline-rich intrusion belt of the northern margin in North China Block. The Alxa Fault Block and the North China Block at least since the Late Paleozoic to Indosinian period. |
| Keywords: | alkali-rich intrusive rocks geochemical characteristics Nd Sr and Pb isotopes the Alxa Fault (Block ) |
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