内蒙古中部构造混杂带晚古生代-早中生代变质基性岩的地球化学特征及其大地构造意义

CORC > 北京大学 > 地球与空间科学学院

	内蒙古中部构造混杂带晚古生代-早中生代变质基性岩的地球化学特征及其大地构造意义; Geochemical characteristics and tectonic significance of Late Paleozoic-Early Mesozoic meta-basic rocks in the melange zones, Central Inner Mongolia
	张晋瑞 ; 初航 ; 魏春景 ; 王康
刊名	岩石学报
	2014
关键词	变质基性火山岩地球化学构造混杂带内蒙古中部中亚造山带 Meta-basic volcanics Geochemistry Melange zones Central Inner Mongolia Central Asian orogenic belt
英文摘要	内蒙古中部构造混杂带中的变质基性岩可分为南、北两带:南带位于乌兰沟-图林凯地区,被划分至温都尔庙群下部的桑达来因组,主要为一套变质玄武岩和辉长岩、辉绿岩,局部含有超基性岩和碳酸岩透镜体,其中变质基性火山岩以绿片岩相变质为主,局部保留枕状构造或发育蓝片岩,已有的锆石U-Pb年代学数据表明南带变质基性火山岩形成于晚古生代到早中生代;北带位于芒和特-二道井-红格尔一线,主要呈岩块状保存在由绢云绿泥石英片岩、硅质岩、含铁石英岩和少量的大理岩组成的基质中,岩石类型包括蓝片岩、冻蓝闪石片岩、阳起片岩、绿帘角闪片岩等。地球化学研究显示南、北两带的变质基性岩相对低Al(Al2O3=10.66%~14.97%)...; The meta-basic rocks in the melange zones from the Central Inner Mongolia are divided into southern and northern zones. The southern zone meta-basic rocks are distributed in Wulan Valley and Tulinkai areas and have been grouped into the lower part of the Ondor Sum Group, called Sangdalaiyin Formation. The rocks mainly include meta-basalt, meta-gabbro and meta-diabase intercalated with lenses of serpentinite and carbonate. The meta-basic rocks mainly underwent greenschist facies metamorphism, with blueschist developing and pillow structure preserved locally. Available zircon U-Pb age data suggested that the southern zone meta-basic volcanics were formed in the Late Paleozoic to Early Mesozoic. The northern zone meta-basic rocks are distributed from Manghete, eastwards to Erdaojing and Honger and mainly occur as tectonic blocks in a matrix consisting of sericite-chlorite-quartz schist, siliceous rock, ferruginous quartzite and a small amount of marble. The rocks mainly include blueschist, barroisite schist, actinolite schist, epidote amphibole schist. Geochemical study shows that the meta-basic rocks in both the southern and northern zones are characterized by relatively low Al (Al2O3, = 10. 66% similar to 14. 97%), low Ti (TiO2 = 1.27% similar to 1. 96%), high Na (Na2O = 1. 02% similar to 4. 20%) and low K (K2O = 0. 02% similar to 0. 71%), suggesting a transitive feature from tholeiitic series to alkali basalt series. The high ratio of Na2O/K2O (6. 89 similar to 454) indicates that these basic rocks might have experienced spilitization before they underwent the regional metamorphism. As immobile element Zr shows good linear relationships with other high field strength elements (HSFE; Th, Nb, Hf, Ti) and rare earth elements (REE), it is concluded that most HSFE and REE in the meta-basic rocks remain stable during the metamorphic process, and thus can represent the characteristics of their protoliths. According to the distribution patterns of rare earth and trace elements and their ratios, the meta-basic rocks can be subdivided into two groups: Group I has a relatively low REE content (Sigma REE = 46. 00 x 10(-6) similar to 78. 08 x 10(-6)), indistinctive REE fractionation ((La/Yb)(N) = 0. 50 similar to 1. 04), no obvious Eu negative anomaly and a relatively high Hf/Ta ratio (Hf/Ta = 6. 82 similar to 15. 18), resembling normal mid-ocean ridge basalts (N-MORB); Group II is characterized by relatively high REE content (Sigma REE = 58.66 x 10(-6) similar to 151. 3 x 10(-6)), intense fractionation of REE ((La/Yb)(N) = 2. 28 similar to 4. 68), no obvious Eu negative anomaly and a relatively low Hf/Ta ratio (Hf/Ta = 2. 06 similar to 4. 70), showing an affinity to enriched mid-ocean ridge basalts (E-MORB). A few meta-basic rock samples are weakly enriched in large ion lithophile elements (LILE) such as Rb and Ba, probably reflecting a weak crustal contamination during emplacement of the basaltic magma. The above geochemical characteristics suggest that these meta-basic rocks may have formed in limited ocean basins. The previous paleobiogeography research suggested that the study region had been a part of the Jiamusi-Mongolia Paleo-continent in the early Late Paleozoic after closure of the Paleo-Asian Ocean in the Devonian. The Carboniferous sedimentary sequences in the Central Inner Mongolia were dominated by stable neritic facies, while in local areas were developed the Caledonian I type granites and granodiorites which represented a post-orogenic uplift environment. From the Late Carboniferous-Early Permian on, the extensional tectonic environment was prevailed in the Central Inner Mongolia. This extensional setting was supported by the development of a large amount of Early Permian alkaline rocks distributed from Erenhot to East Ujimqin Banner, numerous high potassium calc-alkaline and alkaline granites in the northern margin of North China Craton, and the Early Permian bimodal volcanics grouped into the Dashizhai Formation widely-spreading in the Central Inner Mongolia. The regional extension might have resulted in the formation of sea basins since beginning of the Early Permian, in which developed the neritic sedimentary sequences of the Zhesi and Linxi formations. As a result of the continuous extension, limited ocean basins might have formed, in which developed the ferruginous siliceous rocks and the large amount of Late Paleozoic-Early Mesozoic basic rocks as represented by the Ondor Sum Group. These limited basins might have been passively closed in the Early Mesozoic probably due to the influence of the Early-Middle Triassic collision between the North China Craton and Yangtze plate, which resulted in the extensive greenschist facies metamorphism in the meta-basic rocks and all the Late Paleozoic sedimentary sequences from the Central Inner Mongolia and formation of melange zones and local blueschists as a consequence of subduction of the limited ocean basins.; http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000339456100009&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701 ; SCI(E); 中文核心期刊要目总览(PKU); 中国科技核心期刊(ISTIC); 中国科学引文数据库(CSCD); 10; zhangjinrrui@pku.edu.cn; cjwei@pku.edu.cn; 07; 1935-1947; 30
语种	中文
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/49062]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	张晋瑞,初航,魏春景,等. 内蒙古中部构造混杂带晚古生代-早中生代变质基性岩的地球化学特征及其大地构造意义, Geochemical characteristics and tectonic significance of Late Paleozoic-Early Mesozoic meta-basic rocks in the melange zones, Central Inner Mongolia[J]. 岩石学报,2014.
APA	张晋瑞,初航,魏春景,&王康.(2014).内蒙古中部构造混杂带晚古生代-早中生代变质基性岩的地球化学特征及其大地构造意义.岩石学报.
MLA	张晋瑞,et al."内蒙古中部构造混杂带晚古生代-早中生代变质基性岩的地球化学特征及其大地构造意义".岩石学报 (2014).