Full-Text Search:
Home|About CNKI|User Service|中文
Add to Favorite Get Latest Update

STRATIGRAPHIC SEQUENCES OF THE LANCANG AND CHONGSHAN GROUPS IN WESTERN YUNNAN AND THEIR VOLCANISM AND METAMORPHISM

Wei Guanyi;Feng Guorong;Luo Zaiwen;Wu Shize;Tao Youyi  
Stratigraphic sequences of Chongshan group and Lancang group aredistributed in the western part of Yunnan Province and are extended downsouth into Sanpang of Burma. These rocks form part of the basement ofthe so called Three-River fold system. Lancang group is subdivided into seven formations, which consistmainly of schists, metamorphic sandstones, granulites and green schists.Chongshan group is classified into two members. The upper one comprisesmetamorphic volcanics interbedded with carbonates and the lower oneconsists of granulites, migmatites and schists. They are several thousandmeters in thickness, representing flysch formation intercalated with marinevolcanics of eugeosynclinal environment. The age of sedimentation ofLancang and Chongshan groups should be late Proterozoic and, possibly,part of Cambrian. The stratigraphic level of Chongshan group is slightlyhigher than that of Lancang group, corresponding to the middle to upperparts of the latter. A great abundance of volcanics are developed both in Lancang andChongshan. These are combinations of meta-basalt,meta-andesite, meta-rhyolite and their volcanic clastics, belonging to TH+CA rock system.According to the lithologic characteristics, these rocks are similar to theislaud are volcanic series of the modern continental crust. The formationof the ancient Lancang island are was related to the eastward subductionof the ancient Tibet and Indian plate and the widespreading of the oceanictrench in West Yunnan. The prototype of the ancient Lancang island areshould have been formed at Jinning to early Caledonian period. The rock types of Lancang and Chongshan groups represent products ofmultistaged metamorphism. The regional metamorphic grade of the Lancanggroup belongs to green schist facies,which is characterized by high pressuremetamorphism. The grade of Chongshan group belongs to green schist andamphibolite facies with the characteristics of medium pressure metamorphism
Download(CAJ format) Download(PDF format)
CAJViewer7.0 supports all the CNKI file formats; AdobeReader only supports the PDF format.
©CNKI All Rights Reserved