Constraints on the timing of the India‐Asia collision and unroofing history of the Himalayan orogen using detrital zircon U‐Pb‐Hf and whole‐rock Sr‐Nd isotopes in Cretaceous‐Miocene Lesser Himalayan sedimentary rocks
Constraints on the timing of the India‐Asia collision and unroofing history of the Himalayan orogen using detrital zircon U‐Pb‐Hf and whole‐rock Sr‐Nd isotopes in Cretaceous‐Miocene Lesser Himalayan sedimentary rocks
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DOI：
10.1111/bre.12742
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发表时间：
2022-12
期刊：
影响因子：
3.2
通讯作者：
Wei Feng;Q. Meng;Chunhui Song;X. Fang;G. Zhuang;Pengju He;Shufen Yang;Jing Zhang;Yong-Jun Chen-Yo
中科院分区：
文献类型：
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作者：
Wei Feng;Q. Meng;Chunhui Song;X. Fang;G. Zhuang;Pengju He;Shufen Yang;Jing Zhang;Yong-Jun Chen-Yo
尼泊尔小喜马拉雅地区的白垩纪-中新世沉积岩为解释印度-亚洲碰撞的时间和喜马拉雅造山带的去顶历史提供了一个机会，这对于理解喜马拉雅-西藏造山带的生长过程具有重要意义。我们的新数据表明，白垩纪-中新世小喜马拉雅沉积岩中的碎屑锆石年龄和全岩Sr-Nd同位素经历了两次显著的变化。首先，从上白垩统-古新统Amile组到始新世Bhainskati组，晚元古代-早古生代锆石的比例（以500-1200 Ma/1600-2800 Ma的指数量化）从几乎为0增加到0.7-1.4，中生代锆石的比例从约1.5 - 1.5减少到约1.5。14%至5- 12%。全岩的87 Sr/86 Sr和εNd（t = 0）值从Amile组的0.732139和−17.2显著变化到Bhainskati组的0.718106和−11.4。其次，从Bhainskati组到中新统中下统Dumri组，500-1200 Ma/1600-2800 Ma的指数增加到2.2-3.7，中生代锆石的百分比突然下降到接近0。Dumri组的全岩87 Sr/86 Sr和εNd（t = 0）值显著变化至0.750124和−15.8。Taltung组和Amile组中早白垩世锆石的εHf（t）值在印度起源的U-Pb-εHf（t）场中，而Bhainskati组中三叠纪-古新世锆石的εHf（t）值表明，根据现有数据，始新世亚洲起源的碎屑到达喜马拉雅前陆盆地。我们的数据表明：（1）印度-亚洲碰撞的时间不晚于喜马拉雅中部始新世早中期，（2）大喜马拉雅在中新世早期成为喜马拉雅前陆盆地的源区。当与特提斯喜马拉雅的古新世-早始新世物源记录相结合时，我们的新数据挑战了印度-亚洲两阶段碰撞模型，例如大印度盆地假说及其变体和弧-大陆碰撞模型。
Cretaceous‐Miocene sedimentary rocks in the Nepalese Lesser Himalaya provide an opportunity to decipher the timing of India‐Asia collision and unroofing history of the Himalayan orogen, which are significant for understanding the growth processes of the Himalayan‐Tibetan orogen. Our new data indicate that detrital zircon ages and whole‐rock Sr‐Nd isotopes in Cretaceous‐Miocene Lesser Himalayan sedimentary rocks underwent two significant changes. First, from the Upper Cretaceous‐Palaeocene Amile Formation to the Eocene Bhainskati Formation, the proportion of late Proterozoic‐early Palaeozoic zircons (quantified by an index of 500–1200 Ma/1600–2800 Ma) increased from nearly 0 to 0.7–1.4, and the percentage of Mesozoic zircons decreased from ca. 14% to 5–12%. The whole‐rock 87Sr/86Sr and εNd(t = 0) values changed markedly from 0.732139 and −17.2 for the Amile Formation to 0.718106 and −11.4 for the Bhainskati Formation. Second, from the Bhainskati Formation to the lower‐middle Miocene Dumri Formation, the index of 500–1200 Ma/1600–2800 Ma increased to 2.2–3.7 and the percentage of Mesozoic zircons abruptly decreased to nearly 0. The whole‐rock 87Sr/86Sr and εNd(t = 0) values changed significantly to 0.750124 and −15.8 for the Dumri Formation. The εHf(t) values of Early Cretaceous zircons in the Taltung Formation and Amile Formation plot in the U‐Pb‐εHf(t) field of Indian derivation, whereas εHf(t) values of Triassic‐Palaeocene zircons in the Bhainskati Formation demonstrate the arrival of Asian‐derived detritus in the Himalayan foreland basin in the Eocene based on available datasets. Our data indicate that (1) the timing of terminal India‐Asia collision was no later than the early‐middle Eocene in the central Himalaya, and (2) the Greater Himalaya served as a source for the Himalayan foreland basin by the early Miocene. When coupled with previous Palaeocene‐early Eocene provenance records of the Tethyan Himalaya, our new data challenge dual‐stage India‐Asia collision models, such as the Greater India Basin hypothesis and its variants and the arc–continent collision model.