藏北双湖地区早白垩世晚期赞宗错安山岩:青藏高原早期隆升的时间约束  

Late Early Cretaceous andesites at Zanzong Co area in Shuanghu County,northern Tibet: Chronological constraints for early uplift of Tibetan Plateau

作　　者：胡懿灵 刘治博[2] 王根厚[1] 宋扬[2] 袁国礼[1] 郑明 邵华胜 HU YiLing;LIU ZhiBo;WANG GenHou;SONG Yang;YUAN GuoLi;ZHENG Ming;SHAO HuaSheng(School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质科学院矿产资源研究所,北京100037

出　　处：《岩石学报》2019年第7期2173-2188,共16页Acta Petrologica Sinica

基　　金：公益性基础地质调查项目(DD20160026)资助

摘　　要：班公湖-怒江缝合带中广泛分布早白垩世安山岩,其中碰撞后地壳增生所产生的安山岩对于青藏高原隆升研究具有重要的意义。赞宗错安山岩位于班公湖-怒江缝合带中段下白垩统去申拉组陆相红层中,锆石U-Pb年龄结果表明安山岩形成于113. 44±0. 88Ma^115. 00±0. 51Ma,属早白垩世晚期。岩石地球化学分析结果表明赞宗错安山岩属高钾钙碱性系列,富集大离子亲石元素和轻稀土元素,亏损高场强元素和重稀土元素。同时,安山岩εNd(t)为-3. 56^-1. 40,(87Sr/86Sr)i相对恒定(0. 7069~0. 7079),εHf(t)值为较小的正负值(-3. 66~6. 05)。Sr-Nd-Pb同位素和锆石Hf同位素显示安山岩来自幔源玄武质岩浆上涌造成的镁铁质下地壳部分重熔,为碰撞后地壳增生、下地壳重熔的产物,同时有幔源物质加入,指示了青藏高原中部地壳加厚及隆升。结合拉萨-南羌塘地块碰撞时间,推断赞宗错安山岩发育年代代表了高原中部早期隆升时间。本文为探讨青藏高原早期隆升提供了物质记录和有力证据。The andesites formed by the crustal hyperplasia after the collision of Lhasa terrane and South Qiangtang terrane is of great significance to the uplift of Qinghai-Tibet Plateau. In the middle segment of the Banggong-Nujiang suture zone,Zanzong Co andesites located in the terrestrial red beds of the Lower Cretaceous,provide a record for the early uplift of the Qinghai-Tibet Plateau. Major and trace element,Sr-Nd-Pb and zircon U-Pb and Hf isotope data are presented for the newly discovered Zanzong Co andesites. These results offer new insights into the evolution of the Tibetan Plateau during Cretaceous. Zircon U-Pb dating constrains the timing of emplacement as Early Cretaceous( 113. 44 ± 0. 88 Ma ~ 115. 00 ± 0. 51 Ma) Geochemistry shows that the Zanzong Co andesites belong to high-K calc-alkaline series,and that all the samples are enriched in large ion lithophile elements( LILE) and light rare earth elements( LREE),and depleted in high field strength elements( HFSE) and heavy rare earth elements( HREE). Furthermore,the andesites display negative εNd( t)(-3. 56 ^-1. 40),relatively constant87 Sr/86 Sr ratios( 0. 7069 ~ 0. 7079) and small oscillation with positive or negative εHf( t) values(-3. 66 ~ 6. 05). The Sr-Nd-Pb and Hf isotope signature suggest that the andesites were derived from the anatexis of mafic lower crust by intrusion or underplating of mantle-derived basaltic magma,and were the products of the crust hyperplasia and the remelting of lower crust and mantle material after the collision,indicating the crust thickening and uplift in the central Qinghai-Tibet Plateau. Based on the published collision time between Lhasa terrane and South Qiangtang terrane,it is inferred that the age of andesites represents the early uplift of the central part of Qinghai-Tibet Plateau. The study of Zanzong Co andesites provides robust evidence for the early uplift of the central Qinghai-Tibetan Plateau in the late Early Cretaceous.

关 键 词：青藏高原隆升 班公湖-怒江缝合带 赞宗错安山岩 年代学 地壳增厚 

分 类 号：P588.144[天文地球—岩石学] P597.3[天文地球—地质学]