论文部分内容阅读
我国西南天山地区那拉提北缘断裂北侧出露寒武纪(516.3±7.4Ma)橄榄拉斑玄武岩,其 Al_2O_3(12.71%～14.14%)、P_2O_5(0.09%～0.21%)含量较低,TiO_2(1.39%～2.35%)、MgO(5.35%～8.14%)含量中等,全 Fe_2O_3(11.74%～16.03%)含量较高,球粒陨石标准化稀土分布型式平坦,(La/Sm)_N 和(Y/Nb)_N 比值接近1,为过渡型洋脊玄武岩(T-MORB);并且 Th/Ta 比值(0.8～1.5)低,高场强元素(Nb,Ta,Zr,Hf,P)没有明显亏损,缺乏陆壳混染或俯冲带流体活动的印迹。部分 T-MORB 的 Fe、Ti 含量较高(FeO~T>12%,TiO_2>2%,FeO~T/MgO>1.75),Mg~#值(0.40—0.49)和 Cr(53×10~(-6)～110×10~(-6))含量较低,属于 Fe-Ti 玄武岩(ferrobasalt),应为岩浆依 Fenner 趋势发生较高程度结晶分离演化的产物,很可能形成于洋中脊的扩展型裂谷环境。我们认为,那拉提北缘寒武纪 T-MORB 和 Fe-Ti 玄武岩可能与境外吉尔吉斯斯坦境内北天山南缘的早古生代 Terskey 蛇绿岩带相连,为 Terskey 蛇绿岩的残片;寒武纪我国境内发育 Terskey 洋。那拉提北缘断裂可能与尼古拉耶夫线相连,代表西南天山地区 Terskey 洋闭合形成的一条早古生代缝合带。
In the north of the north margin of Nalati in the southwest Tianshan area, China, the content of Al 2 O 3 (12.71% -14.14%) and P 2 O 5 (0.09% -0.21%) is lower in the Cambrian (516.3 ± 7.4Ma) The contents of TiO_2 (1.39% ~ 2.35%), MgO (5.35% ~ 8.14%) were moderate, and the contents of all Fe_2O_3 (11.74% ~ 16.03%) were higher. The normalized distribution patterns of chondrite melatonites were flat, (La / Sm) Ta / Zr, Hf, P) of transitional oceanic ridge basalt (T-MORB) is close to 1, and the ratio of Th / Ta is low (0.8-1.5) Loss, lack of imprint of contaminating or subducting fluid activities in the continental crust. Some T-MORB had higher content of Fe and Ti (FeO ~ T> 12%, TiO 2> 2%, FeO ~ T / MgO> 1.75), Mg ~ # (0.40-0.49) and Cr -6) ~110 × 10 -6 (-6)) belongs to the Fe-Ti basalt (ferrobasalt), which should be the product of the higher degree of crystallization separation and evolution of the magma by the Fenner trend and is likely to form in the extension of the mid-ocean ridge Rift Environment. In our opinion, the Cambrian T-MORB and Fe-Ti basalts along the northern margin of Nalati may be connected with the Early Paleozoic Terskey ophiolite belt on the southern margin of the northern Tianshan Mountains in Kyrgyzstan and are the fragments of the Terskey ophiolite. The Cambrian Terskey Ocean develops in our country. The northern margin of Nalati may be connected to the Nikolayev line, representing an early Paleozoic suture formed by the closing of the Terskey Ocean in the Tianshan Mountains in the southwest China.