海南公爱地区抱板群花岗片麻岩的年代学、地球化学及其构造意义

发布时间：2019-04-02 00:29

【摘要】：海南岛地处华南陆块南缘,紧邻印支陆块,大地构造位置独特,其地质特征一直备受关注。厘定该地区中元古代岩石的成因对恢复华南中元古代构造演化具有重要意义。海南岛西部公爱地区花岗质岩石与围岩抱板群变沉积岩呈侵入接触关系,绝大部分岩石片麻状构造发育、韧性剪切标志明显。这些岩石高SiO_2、K_2O、Al_2O_3、Rb、U,贫CaO、MgO、FeO~T、TiO_2,铝饱和指数A/CNK1.1,具S型花岗岩特点,稀土元素配分模式类似于抱板群变沉积岩,全岩ε_(Nd)(t)=-2.02~-2.38,Nd同位素二阶段亏损模式年龄(t_(DM2)~(Nd))为2.2~2.3 Ga,锆石Hf同位素ε_(Hf)(t)=-5.4~4.0,Hf同位素二阶段亏损模式年龄t_(DM2)~(Hf)=1.71~2.53 Ga。对四个代表性花岗片麻岩样品进行LA-ICP-MS锆石U-Pb定年,其~(207)Pb/~(206)Pb加权平均年龄为1444±15 Ma、1439±19 Ma、1433±31 Ma和1450±23 Ma,属中元古代。综合区域研究资料认为,海南岛西部公爱地区中元古代花岗质岩石的熔融源区为类似抱板群变沉积岩组分,推测其产出于大陆边缘构造背景,是哥伦比亚超大陆边缘的增生产物。
[Abstract]:Hainan Island is located in the southern margin of the South China continental block, adjacent to the Indosinian block, and its geotectonic location is unique, and its geological characteristics have been paid close attention to. It is of great significance to determine the origin of Mesoproterozoic rocks in this area for the restoration of Mesoproterozoic tectonic evolution in South China. There is an intrusive contact relationship between granitic rocks and metamorphic sedimentary rocks in the Gongai area of western Hainan Island. Most of the rocks are gneissic structures with obvious ductile shear markers. These rocks have the characteristics of S-type granite with high SiO_2,K_2O,Al_2O_3,Rb,U,-poor CaO,MgO,FeO~T,TiO_2, aluminum saturation index, and the REE distribution model is similar to that of BaobangGroup metamorphic sedimentary rocks. The whole rock 蔚 _ (Nd) (t) =-2.02 ~ 2.38, ND isotope two-stage depleted model age (t _ (DM2) ~ (Nd) = 2.2? 2.3 Ga,? Hf isotope 蔚 _ (Hf) (t) =-5.4? Hf isotope two-stage depleted model age t _ (DM2) ~ (Hf) = 1.71 ~ 2.53 Ga. The LA-ICP-MS zircon U-Pb dating of four representative granitic gneiss samples shows that the weighted average ages of ~ (207) Pb/~ (206) Pb are 1444 卤15 Ma,1439 卤19 Ma,1433 卤31 Ma and 1450 卤23 Ma, belong to Mesoproterozoic. According to the regional research data, the melting source area of the Mesoproterozoic granitic rocks in the Gongai area of the western Hainan Island is similar to that of the Baoban Group, which is assumed to occur in the tectonic setting of the continental margin. It's a production increase from Colombia's super-continental margin.
【作者单位】：中山大学地球科学与工程学院;广东省地质过程与矿产资源探查重点实验室;
【基金】：国家重点基础研究发展计划(973)项目(2014CB440901) 国家自然科学基金项目(41372198、41402165)联合资助
【分类号】：P595;;P597

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