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| 塔里木盆地西北缘早二叠世后碰撞花岗质岩浆活动及其构造意义 | |
| 引用本文： | 罗金海,张敬艺,王超,车自成,刘良.塔里木盆地西北缘早二叠世后碰撞花岗质岩浆活动及其构造意义[J].地质科学,2010,45(1). |
| 作者姓名： | 罗金海 张敬艺 王超 车自成 刘良 |
| 作者单位： | 1. 西北大学地质学系大陆动力学国家重点实验室,西安,710069 2. 中国石油冀东油田分公司勘探开发 3. 西北大学地质学系大陆动力学国家重点实验室,西安,710069;西安地质矿产研究所中国地质调查局西安地调中心,西安,710054 |
| 基金项目： | 西北大学大陆动力学国家重点实验室科技部专项，科技部科研项目，中国地质调查局青藏高原前寒武纪地质和古生代构造一古地理综合研究项目 |
| 摘 要： | 塔里木地块西北缘的阔什布拉克钾长花岗岩富碱(Na_2O+K_2O平均8.36%8%),富钾(K_2O/Na_2O=1.27～1.47),准铝质(A/CNK=0.82～0.88),属于高钾钙碱性系列岩浆岩。岩石的稀土含量较高(∑REE=263.90×10~(-6)～445.75×10~(-6)),富集Th、U、Ta、Nb、Hf和Y等高场强元素和大离子亲石元素Rb,具有强的负Eu异常(δEu=0.003～0.019),富集高不相容元素(Zr+Nb+Ce+Y=368×10~(-6)～531×10~(-6)350×10~(-6)),高Ga(Ga/Al×10 000=4.17～4.722.6),显示出A型花岗岩的地球化学特征。岩石Th/U比值(平均为3.86)、Nb/Ta比值(平均为12.75)和Rb-Th富集、Ti亏损指示其壳源成因。对花岗岩进行的LA-ICP-MS微区原位锆石U-Pb定年结果表明,花岗岩的结晶侵位年龄为275.4±2.8 Ma。综合西南天山与塔里木盆地早二叠世花岗质岩浆活动的特点,认为早二叠世西南天山的后碰撞岩浆活动不仅在西南天山内部引起了强烈的花岗质岩浆活动,而且对塔里木地块西北边缘的花岗质岩浆活动也有显著的影响。阔什布拉克A型花岗岩也说明西南天山地区的碰撞造山作用在275.4±2.8 Ma之前已经趋于结束,以南天山洋盆为代表的古亚洲洋已基本结束了其演化历史。 |
| 关 键 词： | 塔里木盆地西北缘 西南天山 早二叠世 后碰撞 花岗岩 |
Early Permian post-collisional granitoid magmatism on the northwestern margin of Tarim Basin and its tectonic significance |
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| Luo Jinhai,Zhang Jingyi,Wang Chao,Che Zicheng,Liu Liang.Early Permian post-collisional granitoid magmatism on the northwestern margin of Tarim Basin and its tectonic significance[J].Chinese Journal of Geology,2010,45(1). | |
| Authors: | Luo Jinhai Zhang Jingyi Wang Chao Che Zicheng Liu Liang |
| Abstract: | The Kuoshibulak granites located in the northwestern margin of the Tarim Basin are highK calc-alkaline series,and rich in alkali(Na_2O+K_2O averages 8.36%＞8%)and K(K_2O/Na_2O=1.27～1.47),with the A/CNK values between 0.82 and 0.88,which fall into the range of metaluminous rocks.The rocks with large negative Eu anomaly(δEu=0.003～0.019)are also characterized by enrichment of REE(ΣREE=263.90×10~(-6)～445.75×10~(-6)),HFS elements such as Th,U,Nb,Hf,Y,LILE elements such as Rb,highly incompatible elements(Zr+Nb+Ce+Y=368×10~(-6)～531×10~(-6)＞350×10~(-6))and high-Ga(Ga/Al×10 000=4.17～4.72＞2.6).The geochemical features of the rocks are similar to that of A-type granites.Rb-Th richment,Ti-depletion and the elemental ratios of the Kuoshibulak granites,such as the Th/U(averages 3.86),Nb/Ta(averages 12.75)indicate that it probably derived from crustal source.In situ zircon U-Pb LA-ICP-MS dating on the magmatic zircons yielded an age of 275.4±2.8 Ma,representing the emplacement age of the granites.Combined with Early Permian granitoid magmatism in the southwestern Tianshan orogen and Tarim Basin,it is suggested that the Early Permian post-collisional granitoid magmatism occurs not only in the southwestern Tianshan orogen,but also affects remarkably contemporaneous magmatisms in the northwestern margin of the Tarim block.The Kuoshibulak A-type granites also suggested that the collisional orogeny in the southwestern Tianshan probably finished before 275.4±2.8 Ma,and the paleo-Asia ocean represented by the south Tianshan ocean is closed at that time. |
| Keywords: | Northwestern margin of Tarim Basin Southwestern Tianshan Early Permian Post-collisional orogeny Granite |
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