【摘要】：海南島地處印支陸塊和華南陸塊的交界地帶,具有復雜的構(gòu)造演化史,其拼合機制及精細時代一直備受爭議.在海南島昌江-瓊海斷裂以北的晨星地區(qū)識別出一套具高ε_(Nd)(t)值的火山巖,對其進行了全巖40 Ar-39 Ar年代學及主、微量元素和同位素地球化學研究.結(jié)果表明,該火山巖的全巖~(40) Ar~(_39) Ar坪年齡為328.1±2.6Ma,代表了其噴發(fā)年齡;該變基性巖SiO_2含量為46.92%~52.58%,具有低TiO_2、低K_2O、高Al_2O_3的特征;稀土元素豐度為15.1×10~(-6)~28.7×10~(-6),呈現(xiàn)N-MORB型微量元素配分曲線,ε_(Nd)(t)高至9.02~9.85,顯示出高度虧損的地球化學特征;其成因被解釋為源于受流體交代作用改造的MORB型地幔源區(qū).綜合分析表明晨星地區(qū)變基性巖的形成可能與古特提斯洋陸俯沖格局下華南與印支陸塊間的弧后盆地或有限洋演變有關(guān).
[Abstract]:Hainan Island is located at the junction of Indosinian and South China landmasses, and has a complicated history of tectonic evolution. A set of volcanic rocks with high 蔚 _ (Nd) (t) values were identified in the Chenxing area north of the Changjiang-Qionghai fault in Hainan Island. The 40 Ar-39 Ar geochronology of the whole rock and the main, trace elements and isotopic geochemistry of the volcanic rocks were studied. The results show that the whole rock ~ (40) Ar~ (39) Ar plateau age of the volcanic rock is 328.1 鹵2.6 Ma, which represents its eruption age, the SiO_2 content of the altered basic rock is 46.92 and 52.58, and it has the characteristics of low TiO_2, low K _ 2O and high Al_2O_3. The abundance of rare earth elements is 15. 1 脳 10 ~ (-6) ~ (-6) and 28. 7 脳 10 ~ (-6), showing the N-MORB type trace element partition curve, 蔚 _ (Nd) (t) being as high as 9.02 ~ (9.85), showing the geochemical characteristics of high depletion, and its genesis is interpreted as originating from the MORB type mantle source reformed by fluid metasomatism. The comprehensive analysis shows that the formation of basic rocks in Chenxing area may be related to the back-arc basin or finite ocean evolution between South China and Indosinian continental blocks under the PaleoTethys oceanic subduction pattern.
【作者單位】： 中山大學地球科學與地質(zhì)工程學院;廣東省地質(zhì)過程與礦產(chǎn)資源探查重點實驗室;湖南科技大學地質(zhì)系;
【基金】：國家自然科學基金項目(No.41190073) 國家重點基礎研究發(fā)展計劃(973計劃)(No.2014CB440901) 中山大學中央高�；緲I(yè)務費項目
【分類號】：P736.3

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