论文摘要
To decipher the geodynamic regime of the Liaodong Peninsula and its vicinity, previous investigators placed great emphasis on the Phanerozoic cover, and not the Precambrian basement. In particular, the Archean basement rocks were often overlooked due to their high-grade metamorphism and multiple deformations. However, there is now emerging a much more comprehensive knowledge of the Archean–Proterozoic history, and these recent studies have deepened our understanding of the Liaodong Peninsula during Precambrian time, as well as the formation and evolution of the North China Craton. To make the Archean–Proterozoic tectonic framework clearer, it is important to examine the major lithotectonic units of the Liaodong Peninsula and to determine their tectonic settings. Here, therefore, we present a comprehensive review of the Neoarchean, Paleoproterozoic and Mesoproterozoic lithotectonic assemblages in the Liaodong Peninsula, and then summarize the Precambrian geodynamic regime. Our data support an Archean proto-mantle plume model based on the following evidence（Li and Wei, 2017）:（1） The large volume of Neoarchean granitoid gneisses with dominantly TTG compositions across the ～800 km wide Eastern Block were emplaced during not a long period, without systematic age or geochemical progression.（2）The late Neoarchean bimodal volcanic assemblages（ultramafic–mafic and dacitic–rhyolitic rocks） over the North China Craton are in contrast with the common unimodal（mainly andesitic） rocks in Phanerozoic magmatic arcs.（3） The depleted basalts in the volcanic assemblages show geochemical characteristics of mixing between oceanic plateau basaltic and arc-related basaltic magmas. That is to say, the rising mantle plume head may govern the genesis of the depleted basalt, suggesting plume–lithosphere interaction.（4） The common occurrences of komatiite and basaltic komatiite within the late Neoarchean greenstone belts in the Eastern Block indicate anomalously hightemperatures, which are too high for subduction zones.（5）The most prominent structural feature is the dome-and-keel structure of the late Neoarchean basement, inconsistent with the linear magmatic arc environment that typifies the Proterozoic and Phanerozoic orogens. What’s more, when applied to the North China Craton, the arc model also conflicts with the rarity of lithologies and associations characteristic of active margins, such as ophiolite, andesite, accretionary mélange, molasse, flysch, high-pressure belt and thrust-and-fold belt. Thus, the evidence listed above can hardly support a magmatic arc setting, whereas they have no controversy with the mantle plume model. Then we synthesize the Paleoproterozoic magmatism, sedimentation, metamorphism and metallogeny against the rift model, and propose a process of arc-continent collision between the northern Longgang and the southern Nangrim Blocks（Li and Chen, 2014）. This conclusion is consistent with the observations, including that（i） the 2.0–2.2 Ga magmatism
论文目录
文章来源
类型: 国际会议
作者: LI Zhuang,WEI Chunjing,CHEN Bin
来源: 第九届世界华人地质科学研讨会 2019-06-01
年度: 2019
分类: 基础科学
专业: 地质学,地质学
单位: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum(Beijing)College of Geosciences, China University of Petroleum(Beijing)The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences,Peking UniversityDepartment of Earth and Space Sciences, Southern University of Science and Technology
分类号: P534.1;P541
DOI: 10.26914/c.cnkihy.2019.028394
页码: 205-206
总页数: 2
文件大小: 79k
下载量: 1