| 西准噶尔恰达地区哈尔加乌组火山岩锆石U Pb 年代学、地球化学及地质意义 |
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| 引用本文： | 田陟贤,李永军,田猛,杨高学,向坤鹏,佟丽莉.西准噶尔恰达地区哈尔加乌组火山岩锆石U Pb 年代学、地球化学及地质意义[J].吉林大学学报(地球科学版),2016(1):135-145. |
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| 作者姓名： | 田陟贤 李永军 田猛 杨高学 向坤鹏 佟丽莉 |
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| 作者单位： | 长安大学地球科学与资源学院，西安 710054;国土资源部岩浆作用成矿与找矿重点实验室，西安 710054;中国科学院广州地球化学研究所边缘海地质重点实验室，广州 510640;长安大学地球科学与资源学院，西安 710054;国土资源部岩浆作用成矿与找矿重点实验室，西安 710054;新疆维吾尔自治区有色地质矿产勘查院,乌鲁木齐,830000 |
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| 基金项目： | 国家自然科学基金项目(41273033)；新疆维吾尔自治区地质勘查基金项目(XJZBKD200804，XJQDZ200903)Supported by National Natural Science Foundation of China(41273033)，Geological Survey Foundation of Xinjiang Uygur Autonomous Region(XJZBKD200804，XJQDZ200903) |
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| 摘 要： | 恰达地区的二叠系哈尔加乌组火山岩分布于唐巴勒蛇绿岩带东侧、准噶尔盆地西南缘,主要岩性为灰绿色-紫红色(气孔)(杏仁)玄武岩-玄武安山岩-安山岩。LA-ICP-MS锆石U-Pb年龄为(296.6±8.1)Ma,MSWD=7.7(93%置信度),时代属早二叠世。地球化学研究表明:该火山岩属亚碱性系列,全碱含量较高(w(Na2O+K2O)=3.95%~6.39%)且相对富钠。轻稀土(LREE)相对富集((La/Yb)N=3.49~14.66)且分馏较好((La/Sm)N值均大于1.00(1.68~3.51)),重稀土分馏较差((Gd/Yb)N=1.38~2.56)。仅部分样品有微弱的负铕异常(δEu=0.88~1.15)。微量元素具有大离子亲石元素(LILE)相对富集,高场强元素(HFSE)Nb、Ta相对亏损,Zr、Hf轻微富集的特征。综合火山岩的地球化学特征,结合相关构造判别图解及火山岩所处的区域地质背景,认为哈尔加乌组火山岩的形成背景以板内大陆环境为主,兼有部分弧火山岩的特征,形成于俯冲碰撞造山期后的区域伸展背景下,火山岩的岛弧特征是对碰撞前混染弧组分的继承。
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| 关 键 词： | 锆石LA-ICP-MSU-Pb测年 地球化学 构造环境 火山岩 哈尔加乌组 西准噶尔 |
Zircon U Pb Geochronology,Geochemical Characteristics and Geological Significance of Volcanic Rocks of Haerjiawu Formation in Qiada,West Junggar |
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| Tian Zhixian,Li Yongjun,Tian Meng,Yang Gaoxue,Xiang Kunpeng,Tong Lili.Zircon U Pb Geochronology,Geochemical Characteristics and Geological Significance of Volcanic Rocks of Haerjiawu Formation in Qiada,West Junggar[J].Journal of Jilin Unviersity:Earth Science Edition,2016(1):135-145. |
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| Authors: | Tian Zhixian Li Yongjun Tian Meng Yang Gaoxue Xiang Kunpeng Tong Lili |
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| Abstract: | The Early Permian volcanic rocks in Haerjiawu Formation are distributed in eastern Tangbale ophiolite belt on the southwest margin of Junggar basin.The volcanic rocks are mainly composed of greyish-green or purplish-red (vesicular)(amygdaloidal)basalt,basaltic andesite,and andesite.The high-precision LA ICP MS zircon U Pb dating reveals that they were formed in Early Permian at the age of (296.6±8.1)Ma,MSWD=7.7(93% conf.).Geochemically the volcanic rocks belong to sub-alkaline series.They have relatively high content of alkali (w(Na2 O+K2 O)=3.95%6.39%),and enriched in sodium.The LREE are relatively enriched ((La/Yb)N = 3.49 14.66)and well fractionated ((La/Sm)N=1.68 3.51);while the HREE fractionation is weak ((Gd/Yb)N=1.38 2.56).Only some of the samples have weak negative Eu anomalies (δEu=0.88 1.15).All samples are enriched in LILE;while HFSE are relatively depleted in Nb and Ta but slightly enriched in Zr,Hf. These characteristics,along with element correlation diagram,indicate that the volcanic rocks in Qiada area mainly generated in intra-plate continent with partial island arc environments.These volcanic rocks were from extensional setting of post-collisional period.These island-arc characteristics are inherited from pre-collisional arc component. |
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| Keywords: | zircon LA ICP MS U Pb age geochemistry tectonic setting volcanic rocks Haerjiawu Formation west Junggar |
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