| 内蒙古赤峰市大营子花岗岩体多期次侵入的证据及其地质意义 |
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| 引用本文： | 郗爱华,马艳军,葛玉辉,唐向阳,刘帅,徐博文,刘珏.内蒙古赤峰市大营子花岗岩体多期次侵入的证据及其地质意义[J].吉林大学学报(地球科学版),2015(3):791-803. |
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| 作者姓名： | 郗爱华 马艳军 葛玉辉 唐向阳 刘帅 徐博文 刘珏 |
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| 作者单位： | 1. 吉林大学地球科学学院,长春,130061;2. 西南石油大学资源与环境学院,成都,610500;3. 吉林大学应用技术学院,长春,130012 |
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| 基金项目： | 国家自然科学基金，中国地质调查局计划项目 |
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| 摘 要： | 大营子岩体位于内蒙古赤峰市西北部,多年来因发现碾子沟钼矿床而广受关注。通过研究发现,大营子花岗岩无论是野外空间产状、岩相特点及含矿性,还是岩石地球化学及同位素年代学特征,内部的黑云母二长花岗岩和边缘的正长花岗岩都存在明显的差异,显示了该岩体实际上是一个多期岩浆侵入的复合岩体。整体上大营子岩体岩石地球化学特征表现为高硅、富铝、富碱、低镁、贫钙的特点,富集大离子亲石元素(LILE)Rb、Th,亏损高场强元素(HFSE)Ti,亏损P元素。稀土元素组成总体含量较高,轻、重稀土分馏明显,Eu负异常显著。其中,边缘相正长花岗岩比中心相黑云母二长花岗岩具有更明显的Eu负异常和较低的微量元素U、Ba和Sr。边缘正长花岗岩锆石U-Pb同位素年龄为(267.6±2.8)Ma,属于海西-早印支期华北克拉通北缘岩浆作用的产物,形成于造山晚期或后造山伸展作用诱发的下地壳部分熔融,为季家沟钼矿点(床)的赋矿围岩;中心相黑云母二长花岗岩具有(152.4±1.6)Ma的锆石U-Pb年龄,属于燕山期造山后陆内伸展或岩石圈大规模减薄环境岩浆作用的产物,为碾子沟钼矿床的赋矿围岩。
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| 关 键 词： | 大营子花岗岩 复合侵入体 锆石UPb测年 地球化学 内蒙古赤峰市 |
Multi-Stage Intrusive Evidence and Geological Significance of Dayingzi Granite in Chifeng,Eastern Inner Mongolia |
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| Abstract: | Dayingzi granite,which located in northwest Chifeng,Inner Monggolia,attracts great attention for its relation with Nianzigou molybdenum deposit in recent years.Our study shows that there are significant differences between the interior biotite monzonitic granite and the marginal orthoclase granite on the field occurrence,lithofacies,ore potentiality,petrological geochemistry and isotope chronology.These indicate that the granite is a composite rockmass with multistage intrusion.The overall geochemical features of Dayingzi granite is characterized by its high silicon,aluminumrich ,alkali-rich ,low magnesium ,calcium-poor characteristics,with the enrichment of large ion lithophile elements (LILE)Rb,Th,while depleted of high field strength elements (HFSE)Ti,and P.The content of rare earth elements is high,obvious fractionation of light away from heavy rare earth with remarkable Eu negative anomaly.Even more remarkable Eu negative anomaly and lower trace elements of U,Ba and Sr are detected in marginal orthoclase granite than biotite granite. As ore-hosting rock of Jijiagou molybdenum deposit,the marginal orthoclase granite is a product of magmatism process in north margin of North China craton during Hercynian-Early Indo-Chinese epoch as indicated by its U Pb isotopic age of (267.6± 2.8 );while as ore-hosting rock of Nianzigou molybdenum deposit,the interior biotite adamellite with a U Pb isotopic age of (152.4±1.6)Ma,is a product of the intra-continental extension in a postorogenic or the large scale lithosphere thinning environment during Indo-Chinese Early Yanshanian. |
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| Keywords: | Dayingzi granite composite intrusion Zircon U Pb dating geochemistry Chifeng City in Inner Mongolia |
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