Title

内蒙赤峰楼子店拆离断层带下盘变形花岗质岩石的时代、成因及其地质意义-锆石U-Pb年龄和Hf同位素证据

Translated Titles

Age, Petrogenesis and Geological Significance of the Deformed Granitoids in the Louzidian Metamorphic Core Complex, Southern Chifeng, Inner Mongolia: Evidence from Zircon U-Pb Dates and Hf Isotopes

Authors

王彦斌(Yan-Bin Wang);韩娟(Juan Han);李建波(Jian-Bo Li);欧阳志侠(Zhi-Xia Ouyang);童英(Ying Tong);侯可军(Ke-Jun Hou)

Key Words

锆石年龄 ; Hf同位素 ; 花岗岩 ; 楼子店变质核杂岩 ; 内蒙赤峰 ; zircon ages ; Hf isotope ; granitoid, Louzidian metamorphic core complex ; Chifeng, Inner Mongolia

PublicationName

岩石礦物學雜誌

Volume or Term/Year and Month of Publication

29卷6期(2010 / 11 / 25)

Page #

763 - 778

Content Language

簡體中文

Chinese Abstract

对内蒙赤峰楼子店拆离断层带下盘前人划为前寒武纪岩石的糜棱状花岗质岩石中锆石进行了U-Pb年龄测定和Hf同位素测试,结果显示其时代为晚古生代至中生代。楼子店扎兰营子片麻状花岗岩的锆石206Pb/238U年龄为253.6±1.2 Ma,锆石εHf (t)值为-8.6~-14.6,锆石Hf同位素地壳模式年龄为1.8~2.2 Ga;朝阳沟糜棱岩化片麻状花岗岩的锆石206Pb/238U年龄为150.43±0.79 Ma,锆石εHf (t)值为-5.6~-14.9,锆石Hf同位素地壳模式年龄为1.6~2.1 Ga;莫里海沟片麻状闪长岩的锆石206Pb/238U年龄为127.6±3.1 Ma,锆石εHf (t)值为-5.1~-13.9,锆石Hf同位素地壳模式年龄为1.5~2.1 Ga。不同岩性、不同形成年龄的3个样品的εHf (t)值主要为负值,说明这些岩右主要来自地壳岩石的部分熔融。2.2~1.5 Ga的锆石Hf同位素两阶段模式年龄表明它们可能主要来源于华北克拉通下地壳物质的部分熔融。结合该区已经获得的锆石U-Pb年龄,将该区古生代至中生代花岗质岩浆作用划分为4个时期:早石炭世(327 Ma)、二叠纪(285~252 Ma)、中三叠世-早侏罗世(241~184 Ma)、中侏罗世-早白垩世(163~125 Ma)。早石炭世喇嘛洞混合花岗岩的产出对应于古亚洲洋古生代向南俯冲于华北板块的时期,二叠纪花岗岩是古亚洲洋最后闭合、蒙古弧与华北陆块北缘拼合与伸展有关的岩浆活动的产物,大面积的中三叠世-早侏罗世的花岗岩是西伯利亚与华北陆块碰撞后地壳伸展的记录,中侏罗世-早白垩世(163~125 Ma)岩浆活动则发育在伸展构造背景中,与岩石圈减薄存在密切的成因联系。这些新年龄资料将为华北陆块北缘古生代-中生代的地质构造演化提供重要的年代学制约。

English Abstract

Located in the northern margin of the North China Craton, the Louzidian metamorphic core complex is one of the important areas with widely distributed Palaeozoic-Mesozoic granitoid rocks. The deformed plutonic intrusions in the Louzidian core complex area have not yet been precisely constrained by reliable isotopic ages. The plutons have long been considered to be Precambrian rocks. Recent studies have revealed that the deformed and metamorphosed rocks with protolithes of plutonic intrusions were genetically related to late ductile shear events. This paper presents newly obtained zircon U-Pb ages of the deformed granitoids from Zhalanyingzi (253.6±1.2 Ma), Chaoyanggou (150.42±0.98 Ma), Molihaigou (127.6±3.1 Ma) of the Liuzidian metamorphic core complex area in Chifeng, on the northern margin of the North China Plate. Hafnium analyses show that the three deformed granitoids have negative and variable εHf (t) values (-5.1 to-14.9) and Meso-Palaeoproterozoic (1.5 to 2.2 Ga) depleted-mantle model ages, suggesting the probable derivation from an isotopically heterogeneous old crust source. The source region for these magmas might have been related to Meso-Palaeoproterozoic material of the North China Craton underlying Chifeng. Based on zircon U-Pb data, the authors identified four stages of granitic magmatism, i.e., Late Carboniferous (327 Ma), Permian (285~252 Ma), Early Jurassic-Middle Triassic (241~184 Ma) and Early Cretaceous-Middle Jurassic (163~125 Ma). The new ages indicate that these plutons were emplaced in the late Palaeozoic-Mesozoic period. Early Carboniferous granite implies the existence of an Andean-style continental arc along the northern margin of the North China Block. The Permian granitic magmatism was probably related to the extension due to the final closure of the Paleo-Asian Ocean and the amalgamation of the Mongolian arc terrain with the northern North China Block. These events were followed by post-collisional/post-orogenic extension and large-scale magmatism during Triassic. Early Cretaceous-Middle Jurassic (163~125 Ma) magmatism in the Louzidian core complex area was developed in an extensional setting, possibly induced by lithospheric thinning in the North China Block. The geochronological framework provides important information for the constraint of the Paleozoic-Mesozoic tectonic evolution in the northern margin of the North China Block.

Topic Category 基礎與應用科學 > 地球科學與地質學