| 青藏高原中-南部新生代构造演化的热年代学制约 |
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| 引用本文： | 朱晓青,郭兴伟,张训华,侯方辉,温珍河,耿威,王忠蕾,孙建伟,祁江豪.青藏高原中-南部新生代构造演化的热年代学制约[J].地球科学,2018,43(6):1903-1920. |
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| 作者姓名： | 朱晓青 郭兴伟 张训华 侯方辉 温珍河 耿威 王忠蕾 孙建伟 祁江豪 |
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| 作者单位： | 1.青岛海洋地质研究所, 山东青岛 266071 |
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| 基金项目： | 地质调查专项121201102000150009国家自然科学基金项目41402182地质调查专项Nos.121201004000150013国家自然科学基金项目Nos.41776081国家自然科学基金项目41210005中国博士后科学基金项目No.2017M620290 |
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| 摘 要： | 青藏高原新生代以来的隆升过程及特征长期以来广存争议.岩体中不同单矿物所记录的中低温热年代学信息适用于揭示较新年代地质体的隆升过程，可以为之提供有效制约.在青藏高原部分岩浆岩与变质岩露头区原位采集15块样品，利用锆石与磷灰石裂变径迹等热年代学结果为青藏高原中生代末期以来的隆升过程提供约束.其中，所获10块样品的锆石裂变径迹数据年龄范围为182~33 Ma，分别记录了渐新世之前青藏高原内不同块体间相互碰撞及高原内不同地区的构造热事件.特别是沿雅鲁藏布江缝合带分布的3个样品，锆石裂变径迹年龄结果一致显示始新世末期-渐新世早期该带存在一期显著的构造热事件.该构造热事件暗示在约36~33 Ma沿雅江缝合带发生过强烈的陆-陆硬碰撞.所获14块样品的磷灰石裂变径迹年龄范围为70.4~5.0 Ma，综合热史反演结果显示青藏高原南部中新世中晚期以来存在整体性隆升，特别是从上新世开始隆升速率显著加快.磷灰石裂变径迹年龄在空间分布上具有向高原东南部变年轻的趋势，表明青藏高原东南部在上新世以来的构造隆升较其他地区要强烈，暗示印度-亚洲板块碰撞驱动机制对该时期的高原隆升具有控制作用.此外，青藏高原中部在白垩纪末期-始新世可能即已隆升至相当高度，此后至今保持了相当低的剥蚀速率.
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| 关 键 词： | 青藏高原 热年代学 热史反演 新生代 硬碰撞 构造地质 |
| 收稿时间： | 2017-12-06 |
Thermochronological Constraints on Cenozoic Tectonic Evolution of South-Central Qinghai-Tibet Plateau |
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| Abstract: | The spatial and temporal characteristics of the uplift in the Qinghai-Tibet Plateau since the Cenozoic has long been debated. Medium-and low-temperature thermochronological analysis on the base rocks plays an important role in detecting the uplifting processes of the plateau. Here we collected 15 intermediate-acid and metamorphic rock samples distributed in the Tibetan Plateau. Zircon and apatite fission track (ZFT and AFT) analyses were performed on these samples in order to provide constraints on the uplifting process of the plateau since the Mesozoic. 10 samples' ZFT results show that the ZFT ages range from 182 Ma to 33 Ma, probably recording collisions among different terranes or tectonothermal events in the Tibetan plateau before the Oligocene. Specially, ZFT ages of 3 samples distributed around the Yarlung Zangbo suture zone range from Late Eocene to Early Oligocene, which implies that a hard continent-continent collision occurred during ca. 36 to ca. 33 Ma. The Neocene ages dominate the AFT results, varying from 70.4 Ma to 5.0 Ma. Combined with the AFT reversed modeling results, it is concluded that southern part of Qinghai-Tibet Plateau has apparently experienced uplift since the Middle-Late Miocene. The uplift rates increased rapidly after ca. 5 Ma to ca. 4 Ma. The AFT ages become younger towards southeastern part of the Qinghai-Tibetan Plateau, implying the India and Asia continent collision controls the uplifting process of the Tibetan Plateau. Additionally, the central part of the plateau might have reached high altitude in the Late Cretaceous-Eocene and have kept very low denudation rate up to now. |
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