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内蒙古达茂旗北部闪长岩锆石SHRIMP U-Pb、角闪石40Ar/39Ar年代学及其地质意义
Ar-Ar and zircon SHRIMP geochronology of hornblendite and diorite in northern Darhan Muminggan Joint Banner, Inner Mongolia, and its geological significance
  
中文关键词:内蒙古达茂旗  SHRIMP 锆石U-Pb 年代学  40Ar/39Ar年代学  奥陶纪
英文关键词:Darhan Muminggan Joint Banner of Inner Mongolia  SHRIMP zircon U-Pb dating  40Ar/39Ar geochronology  Ordovician
基金项目:国家自然科学基金资助项目(40672146);国家重点基础研究发展计划项目(2007CB411305)
作者单位E-mail
李建锋 北京大学 造山带与地壳演化教育部重点实验室, 北京大学 地球与空间科学学院, 北京100871 zczhang@pku.edu.cn 
张志诚 北京大学 造山带与地壳演化教育部重点实验室, 北京大学 地球与空间科学学院, 北京100871  
韩宝福 北京大学 造山带与地壳演化教育部重点实验室, 北京大学 地球与空间科学学院, 北京100871  
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中文摘要:
      内蒙古达茂旗北部的早古生代闪长岩侵入体产于包尔汉图-白乃庙岛弧带的西部,采用SHRIMP 锆石U-Pb定年及角闪石40Ar/39Ar测年对其进行了精确的年代学研究。两件闪长岩样品分别获得的SHRIMP 锆石U-Pb年龄为453±3 Ma 和446.8±5.3 Ma,角闪石40Ar/39Ar坪年龄为459.2±2.4 Ma和442.9±4.2 Ma。这为研究该时期弧岩浆作用提供了新的年代学证据,并表明该岩浆侵位后,经历了结晶并快速冷却的过程,可能揭示了本区岛弧带和华北板块碰撞的构造意义。
英文摘要:
      The northern Darhan Muminggan Joint Banner of Inner Mongolia, geotectonically crossing two geological-structural units, is divided into two parts by Bayan Obo-Chifeng deep fault (plate boundary fault). To the south of the deep fault is the North China block, and to the north is the accretion zone at the northern edge of North China plate. An important magmatic arc belt mainly composed of diorite, quartz diorite, tonalite and granodiorite is developed near Bart-Obao on the north side of Bayan Obo-Chifeng deep fault. In this paper, precise SHRIMP zircon U-Pb dating and hornblende 40Ar/39Ar dating defining the emplacement age of the intrusion and its thermal evolution history were conducted for inclusions of diorite and hornblendite hosted in granodiorite, and the constraints on Early Paleozoic subduction-collision event of the Paleo-Asian Ocean in central Inner Mongolia were provided from isotope geochronology. SHRIMP U-Pb zircon ages of the two diorite samples are 453±3 Ma and 446.8±5.3 Ma, and hornblende 40Ar/39Ar plateau ages are 459.2±2.4 Ma and 442.9±4.2 Ma. SHRIMP zircon U-Pb dating results indicate that the island arc intrusive rocks were formed around 450 Ma, resulting from the Middle-Late Ordovician (or earlier) oceanic subduction event. The results of SHRIMP zircon U-Pb dating are basically in accordance with those of hornblende conventional 40Ar/39Ar dating method, which suggests the crystallization and rapid cooling after the emplacement of the magma and may reveal collision between the Baoerhantu-Bainaimiao island arc zone and the North China plate. The dating results of the diorite imply that tectonic heat events after the emplacement and the cooling of the intrusive body did not affect the hornblende Ar-Ar closed system, and hence strong tectonic heat events did not occur later.
李建锋,张志诚,韩宝福,2010,内蒙古达茂旗北部闪长岩锆石SHRIMP U-Pb、角闪石40Ar/39Ar年代学及其地质意义[J].岩石矿物学杂志,29(6):732~740.
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