%0 Journal Article
%T 华夏早古生代俯冲作用( I ):来自糯垌蛇绿岩的新证据<br>EarlyPaleozoicSubductioninCathaysia ( I ): NewEvidencefromNuodongOphiolite
%A 彭松柏
%A 刘松峰
%A 林木森
%A 吴长峰
%A 韩庆森&lt
%A br&gt
%A PengSongbai
%A LiuSongfeng
%A LinMusen
%A WuChangfeng
%A HanQingsen
%J 地球科学(中国地质大学学报)
%D 2016
%R 10. 3799 / dqkx. 2016. 065
%X 早古生代加里东期造山运动(广西运动)的性质是华南大地构造演化长期争议的重大地质问题.桂东南岑溪糯垌一带奥陶纪浅变质地层中出露一套变形变质基性岩系构造岩片，主要由变枕状玄武岩、辉绿岩墙以及少量块状辉长岩和辉石岩组成.变玄武岩、变辉绿岩的SiO2含量为49.20%~52.30%，MgO含量为6.78%~9.11%，Mg#为55~63，TiO2含量为1.02%~1.34%，属低钾拉斑玄武系列基性岩.稀土元素配分平坦，轻稀土亏损，(La/Sm)N为0.72~1.05，(La/Yb)N为0.7~1.0，无明显Eu异常，大离子亲石元素Rb、Ba、Th、U、K、Pb相对富集，高场强元素Nb、Ta、Zr、Hf、Ti平坦-略亏损，Ti/V为21.30~25.12，Nb/Th为2.1~4.2，表现出俯冲带之上(SSZ)蛇绿岩的地球化学特征.变辉绿岩LAICPMS锆石UPb成岩年龄为437±5Ma，表明其形成于早志留世.综合研究表明，糯垌变基性岩系应属早古生代形成于俯冲之上(SSZ)弧前构造环境的肢解蛇绿岩残片，这一发现为华南扬子克拉通与华夏地块之间存在早古生代洋盆和俯冲-增生碰撞造山提供了关键证据.<br>The nature of Early Paleozoic Caledonian orogeny (Guangxi movement), as one of the key geolocial problems of tectonic evolution in South China, has been controversial for a long time. In this study we report a suite of deformed and metamorphosed basic rocks in tectonic slices that are exposed in epimetamorphic Ordovician strata, located at the Nuodong in the Cenxi area of the Southeast Guangxi, South China. This suite of rock is mainly composed of metamorphic basalt, diabase dike and minor pyroxenite. Petrogeochemical data of the metabasalt and metadiabase dike show the content of SiO2=49.20%-52.30%, MgO=6.78%-9.11%, Mg#=55-63, TiO2=1.02%-1.34%, indicating the low potassium tholeiitic series of basic rocks. The chondritenormalized REE distribution patterns are flat type with light rare earths depleted, no obvious Eu anomaly, (La/Sm)N=0.72-1.05, (La/Yb)N=0.7-1.0, while the NMORB normalized spider diagrams show slightly enrichment of LILEs (e.g.Rb, Ba, Th, U, K, Pb) and flatslightly depletion of HFSEs (e.g.Nb, Ta, Zr, Hf, Ti), Ti/V=21.30-25.12, Nb/Th=2.1-4.2. The geological and petrogeochemical features imply that this series of rocks represent a dismembered ophiolites formed in suprasubduction zone (SSZ) tectonic environment.The LAICPMS zircon UPb age of the metadiabase is 437±5Ma, indicating that the ophiolites were formed at the Early Silurian. Based on the above comprehensive study, we propose that the Nuodong metamorphic basic rock series are Early Paleozoic ophiolite fragments formed in a forearc tectonic environment in a suprasubduction zone (SSZ). The document of the Early Paleozoic Nuodong ophiolite provides key evidence for the existence of an Early Paleozoic oceanic basin and subductionaccretionary collisional orogenesis between Yangtze craton and Cathaysia blocks in South Chin
%K 岑溪地区
%K 蛇绿岩
%K 岩石学
%K 地球化学
%K 早古生代洋盆
%K 大地构造意义&lt
%K br&gt
%K SoutheastGuangxi
%K ophiolite
%K petrology
%K geochemistry
%K EarlyPaleozoicoceanicbasin
%K tectonicsignificance
%U http://www.earth-science.net/WebPage/Article.aspx?id=3295