塔里木北缘欧西达坂岩体锆石LA-ICP-MSU-Pb年龄和地球化学特征及构造意义
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摘要
欧西达坂岩体位于塔里木盆地北缘,通过岩石学、地球化学和年代学研究,探讨了该岩体的形成环境及构造意义。LA-ICP-MS锆石U-Pb测量获得该岩体年龄为(408.7±3.1)Ma,形成于早泥盆世。地球化学特征显示:Si O_2含量为60.29%～63.02%,Al_2O_3为14.92%～15.85%,A/NCK值为0.853～0.956,属准铝质岩石;稀土元素球粒陨石标准化曲线显示轻稀土富集,重稀土亏损,轻重稀土分馏明显,La_N/Yb_N值6.80～8.59,δEu值0.71～0.81;原始地幔蛛网图上,Rb、Th、K、Ba等大离子亲石元素和Hf十分富集,而高场强元素Nb、Ta、Ti、P等相对亏损。结合区域地质特征,推断欧西达板岩体形成于板块边缘环境。
Located in the northern margin of Tarim Basin, the Oxidaban pluton has been studied by petrology,geochemistry and chronology. The formation environment and tectonic significance of his pluton are discussed preliminarily. The age value of the pluton obtained by LA-ICP-MS zircon U-Pb measurement is 408.7 ±3.1 Ma,which was formed in the early Devonian. Geochemical Characteristics show that SiO2 content is 60.29% ～63.02%, Al2 O3 is 14.92%～15.85%, A/NCK value is 0.853 ～ 0.956, which is a quasi-aluminous rock. The standardized curve of chondrite of rare earth elements shows that light rare earth elements is rich, heavy rare earth elements is deficient, light and heavy rare earth elements fractionation is obvious, LaN/YbN value is 6.80～ 8.59, δEu value is 0.71～0.81; On the original mantle spider web map, Rb, Th, K, Ba and other big ion lithophile elements and Hf are very rich, while the high field strength element Nb, Ta, Ti, P is relatively deficient. Combined with the regional geological characteristics, it is concluded that the Oxidaban pluton was formed in the plate margin environment.
Located in the northern margin of Tarim Basin, the Oxidaban pluton has been studied by petrology,geochemistry and chronology. The formation environment and tectonic significance of his pluton are discussed preliminarily. The age value of the pluton obtained by LA-ICP-MS zircon U-Pb measurement is 408.7 ±3.1 Ma,which was formed in the early Devonian. Geochemical Characteristics show that SiO2 content is 60.29% ～63.02%, Al2 O3 is 14.92%～15.85%, A/NCK value is 0.853 ～ 0.956, which is a quasi-aluminous rock. The standardized curve of chondrite of rare earth elements shows that light rare earth elements is rich, heavy rare earth elements is deficient, light and heavy rare earth elements fractionation is obvious, LaN/YbN value is 6.80～ 8.59, δEu value is 0.71～0.81; On the original mantle spider web map, Rb, Th, K, Ba and other big ion lithophile elements and Hf are very rich, while the high field strength element Nb, Ta, Ti, P is relatively deficient. Combined with the regional geological characteristics, it is concluded that the Oxidaban pluton was formed in the plate margin environment.
引文
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2 徐学义,马中平,夏祖春,等.天山中西段古生代花岗岩TIMS法锆石U-Pb同位素鼎年及岩石地球化学特征研究[J].西北地质,2006,39(1):50-75
3 杨天南,李锦铁,孙桂华,等.中天山早泥盆纪陆弧:来自花岗质糜棱岩的地球化学及SHRIMP-U/Pb定年的证据[J].岩石学报,2006,22(1):41-48
4 王超,罗金海,车自成,等.新疆欧西达坂花岗质岩体地球化学特征和锆石LA-ICP-MS定年:西南天山古生代洋盆俯冲作用过程的启示[J].地质学报,2009,83(2):273-280
5 李锦铁,王克卓,李亚萍,等.天山山脉地貌特征、地壳组成与地质演化[J].地质通报,2006,25(8):896-906
6 李锦铁,何国琦,徐新,等.新疆北部及邻区地壳构造格架及其形成过程的初步探讨[J].地质学报,2006,80(1):148-168
7 朱志新,王克卓,郑玉洁,等.新疆伊犁地块南缘志留纪和泥盆纪花岗质侵入体锆石SHRIMP定年及其形成时构造背景的初步探讨[J].岩石学报,2006,22(5):1193-1200
8 朱志新,李锦铁,董连慧,等.新疆塔里木北缘色日牙科依拉客一带泥盆纪花岗质侵入体的确定及其地质意义[J].岩石学报,2008,24(05):971-976
9 漆家福,雷刚林,李明刚,等.库车坳陷-南天山过渡带的收缩构造变形模式[J].地学前缘,2009,16(3):121-126
10 毛友亮,樊双虎,陈淑娥,等.南天山高钾钙碱性花岗岩年代学、岩石成因及其地质意义[J].高校地质学报,2014,20(1):58-67
11 李曰俊,宋文杰,买光荣,等.库车和北塔里木前陆盆地与南天山造山带的耦合关系[J].新疆石油地质,2001,22(5):376-381
12 贾晓亮,郭瑞清,柴凤梅,等.新疆库鲁克塔格西段泥盆纪二长花岗岩年龄、地球化学特征及其构造意义[J].地质通报,2013,32(2-3):240-249
13 张斌,陈文,喻顺,尹继元,等.南天山洋古生代期间俯冲作用过程探讨[J].岩石学报,2014,30(8):2351-2359