干旱区生态环境知识资源中心(Arid): 青藏高原东缘中生代若尔盖古高原的发现及其地质意义

Arid

	青藏高原东缘中生代若尔盖古高原的发现及其地质意义
其他题名	Discovery of the Mesozoic Zoige paleo-plateau in eastern Tibetan Plateau and its geological significance
	刘树根 1; 李智武 1; 冉波 1; 李金玺 1; 邓宾 1; 王国芝 1; 杨迪 1; 王自剑 1; 李祥辉 ; 刘顺 1; 李巨初 1
来源期刊	成都理工大学学报. 自然科学版
ISSN	1671-9727
出版年	2019
卷号	46 期号:1 页码:1-28
中文摘要	40 Ma B.P."原青藏高原"的提出使得青藏高原的早期隆升历史受到越来越多的关注,但其向东的延伸情况不明。青藏高原东缘若尔盖高原、龙门山冲断带和四川盆地有机地构建了一个完整的原-山-盆体系,成为揭示青藏高原隆升和生长的理想场所,而位于高原内部若尔盖地块的红参1井更为此提供了宝贵素材。基于红参1井的构造恢复和低温热年代学研究结果,结合区域上已有的低温热年代学和古高程数据,提出青藏高原东缘在早新生代印-亚大陆碰撞之前就已形成了高原,称之为若尔盖古高原,并从基底构造属性、构造变形、地壳缩短与增厚、沉积记录等方面对其进行了论证。红参1井钻井剖面构造恢复结果揭示所钻遇7 000余米的三叠系复理石层系实际上有46%的厚度是由构造重复所致,连同广泛发育的晚三叠世埃达克质花岗岩以及利用中性岩浆岩Sr/Y比值估算的地壳厚度,共同表明青藏高原东部松潘-甘孜地区在晚三叠世就已发生了实质性的地壳加厚。红参1井多重低温热年代学[锆石(U-Th)/He,磷灰石裂变径迹和(U-Th)/He]测试结果揭示若尔盖地块分别在白垩纪中期(约120 Ma B.P.和约80 Ma B.P.)经历了2次快速的冷却事件,累计剥蚀厚度达5 km,之后转入极其缓慢的冷却过程,暗示其已进入高原化阶段;而在整个新生代期间处于近乎"零"剥蚀的状态而被动地抬升到现今高度(不同于常见的山脉隆升,地块隆升代表了一定范围的区域整体抬升)。因此,青藏高原东部若尔盖地块最晚在白垩纪末期就已形成高原,即若尔盖古高原,其范围可能包括三叠系复理石层系覆盖的大部分松潘-甘孜地区,并可能向西与羌塘古高原相连,构成羌塘-若尔盖古高原。若尔盖古高原的形成不仅造成四川盆地西缘在白垩纪中期出现了重要的物源转变,更重要的是加剧了青藏高原东缘白垩纪气候干旱化,出现了大量沙漠沉积和膏盐沉积。若尔盖古高原的发现不仅有助于深化对青藏高原隆升和生长过程的理解,也将引发对青藏高原形成机制的重新思考以及对其气候-环境-资源效应的关注。
英文摘要	The Zoige plateau, Longmenshan thrust belt and Sichuan Basin on the eastern margin of the Tibetan Plateau constitute a united plateau-mountain-basin geodynamic system and the borehole Hongcan 1 (Well HC1) in the Zoige block provides extremely valuable materials for unraveling the uplift, propagation mechanism and eastward extension of the Tibetan Plateau. Based on the structural restoration and low-temperature thermochronology study of the Well HC1, combined with the previous published low-temperature thermochronology and paleo-elevation data, it is proposed that a paleo-plateau, here referred to as the Zoige paleo-plateau, had developed in the eastern Tibetan Plateau prior to the India-Asia collision during the Mesozoic, which is further demonstrated from several aspects such as basement tectonic attribution, deformation, crustal shortening and thickening, and sedimentary records. The structural recovery of the drilling well profile of the Well HC1 reveals that about 46% of the thickness (>7 km of the Triassic flysch strata) was actually caused by structural repetition. The extensive occurrence of the late Triassic adakitic granites and estimated crustal thickness through the Sr/Y ratio of the neutral magmatic rocks imply that substantial crustal thickening occurred in the Songpan-Ganzi area in the eastern Tibetan Plateau during the late Triassic. Multiple low-temperature thermochronology analyses for the Well HC1 [zircon (U-Th)/He, apatite fission track and (U-Th)/He)] reveal that the Zoige block experienced two rapid cooling events at ~120 Ma B.P. and ~80 Ma B.P. (Cretaceous) respectively, with a cumulative exhumation thickness of about 5 km, followed by an extremely slow cooling process thereafter, suggesting that the Zoige block has evolved into a peneplain with significant topography since late Cretaceous, and has been passively uplifted to the present elevation during the entire Cenozoic in a state of near-zero erosion. Therefore, the Zoige block in the eastern Tibetan Plateau has become a plateau no later than the end of the Cretaceous. It is considered that the Zoige paleo-plateau might include most of the Songpan-Ganzi area covered by the Triassic flysch strata, and they connect in the west to the Qiangtang paleo-plateau and form the Qiangtang-Zoige paleo-plateau. The formation of the Zoige paleo-plateau not only caused important provenance change in the west margin of Sichuan Basin during the mid-Cretaceous, but also aggravated the Cretaceous aridification in the eastern Tibetan Plateau and lead to a lot of desert sedimentation and salt deposition. The proposition of the Zoige paleo-plateau may deepen the understanding of the uplift and growth process of the Tibetan Plateau, and promote the formation mechanism research of the Tibetan Plateau and its climate-environment-resource effects.
中文关键词	构造变形 ; 隆升剥蚀 ; 沉积记录 ; 地壳加厚 ; 中生代 ; 古高原 ; 若尔盖地块 ; 青藏高原
英文关键词	tectonic deformation exhumation sedimentary record crustal thickening Mesozoic paleo-plateau Zoige block Tibetan Plateau
语种	中文
国家	中国
收录类别	CSCD
WOS类目	GEOLOGY
WOS研究方向	Geology
CSCD记录号	CSCD:6446480
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/238991
作者单位	1.成都理工大学, 油气藏地质及开发工程国家重点实验室, 成都, 四川 610059, 中国; 2.School of Science, University of Waikato, Hamilton, Lanarkshire 3240, New Zealand
推荐引用方式 GB/T 7714	刘树根,李智武,冉波,等. 青藏高原东缘中生代若尔盖古高原的发现及其地质意义[J],2019,46(1):1-28.
APA	刘树根.,李智武.,冉波.,李金玺.,邓宾.,...&李巨初.(2019).青藏高原东缘中生代若尔盖古高原的发现及其地质意义.成都理工大学学报. 自然科学版,46(1),1-28.
MLA	刘树根,et al."青藏高原东缘中生代若尔盖古高原的发现及其地质意义".成都理工大学学报. 自然科学版 46.1(2019):1-28.