海南岛晨星早石炭世高度亏损N-MORB型玄武岩及其地质意义
发布时间：2018-09-17 09:59
【摘要】：海南岛地处印支陆块和华南陆块的交界地带,具有复杂的构造演化史,其拼合机制及精细时代一直备受争议.在海南岛昌江-琼海断裂以北的晨星地区识别出一套具高ε_(Nd)(t)值的火山岩,对其进行了全岩40 Ar-39 Ar年代学及主、微量元素和同位素地球化学研究.结果表明,该火山岩的全岩~(40) Ar~(_39) Ar坪年龄为328.1±2.6Ma,代表了其喷发年龄;该变基性岩SiO_2含量为46.92%~52.58%,具有低TiO_2、低K_2O、高Al_2O_3的特征;稀土元素丰度为15.1×10~(-6)~28.7×10~(-6),呈现N-MORB型微量元素配分曲线,ε_(Nd)(t)高至9.02~9.85,显示出高度亏损的地球化学特征;其成因被解释为源于受流体交代作用改造的MORB型地幔源区.综合分析表明晨星地区变基性岩的形成可能与古特提斯洋陆俯冲格局下华南与印支陆块间的弧后盆地或有限洋演变有关.
[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 卤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.
【作者单位】： 中山大学地球科学与地质工程学院;广东省地质过程与矿产资源探查重点实验室;湖南科技大学地质系;
【基金】：国家自然科学基金项目(No.41190073) 国家重点基础研究发展计划(973计划)(No.2014CB440901) 中山大学中央高校基本业务费项目
【分类号】：P736.3
本文编号：2245514
[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 卤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.
【作者单位】： 中山大学地球科学与地质工程学院;广东省地质过程与矿产资源探查重点实验室;湖南科技大学地质系;
【基金】：国家自然科学基金项目(No.41190073) 国家重点基础研究发展计划(973计划)(No.2014CB440901) 中山大学中央高校基本业务费项目
【分类号】：P736.3
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1 许继锋,于学元,李献华,韩吟文,盛吉虎,张本仁;高度亏损的N-MORB型火山岩的发现:勉略古洋盆存在的新证据[J];科学通报;1997年22期
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