Nature and Evolution of Pre-Neoproterozoic Continental Crust in South China: A Review and Tectonic Implications     

WANG Kai  DONG Shuwen  YAO Weihu  ZHAO Tianyu 《《地质学报》英文版》2020,94(6):1731-1756

South China as an amalgamation of the Yangtze and Cathaysia blocks is composed of Archean to Mesoproterozoic basement overlain by Neoproterozoic and younger cover. Both the constituent Yangtze and Cathaysia blocks contain well-preserved Neoproterozoic rocks that have been extensively studied in terms of the age and tectonic nature, but less is known about their earlier crustal history due to the incomplete rock record. Recent efforts in investigating the yet survived crustal nature based on isotopic and elemental signatures preserved in igneous and sedimentary rocks have steadily improved our knowledge about the pre-Neoproterozoic continental crustal evolution in South China. In this paper, we summarize the up-to-date pre-Neoproterozoic records, including petrological, geochronological, geochemical and geophysical data, across South China, and discuss its spatiotemporal patterns of the pre-Neoproterozoic crust and the relevant tectonic events. While the xenocrystic/inherited and detrital zircon records suggest widespread Archean (mainly ca. 2.5 Ga) crustal components within both the Yangtze and Cathaysia blocks, exposed Archean rocks are only limited to isolated crustal provinces in the Yangtze Block. These Archean rocks are dominated by TTGs (tonalite-trondhjemite-granodiorite) with varied ages (3.3–2.5 Ga) and zircon Hf isotopes, indicating a compositionally heterogeneous nature of the Archean Yangtze Block and, by inference, the development of multiple ancient terranes. The early Paleoproterozoic (2.4–2.2 Ga) tectonomagmatic events characterize the western Yangtze Block and are supportive of an east-west subdivision of the Yangtze basement, whereas the late Paleoproterozoic (2.1–1.7 Ga) orogeneses may have affected a larger area covering both the western and eastern parts of the Yangtze Block, and also the Cathaysia Block. The eastern Yangtze Block with generally northeastward-younging late Paleoproterozoic magmatism and metamorphism likely experienced a prolonged 2.05–1.75 Ga orogenic process welding the various Archean proto-continents, consistent with the documentation of a buried late Paleoproterozoic orogenic belt imaged by deep seismic profiling from its central part and of a slightly older ophiolitic mélange in the northern part. The Cathaysia Block was probably involved in a short-lived 1.9–1.8 Ga orogenic event. The two orogeneses overlapped in time and may have contributed to the cratonization of a possible unified South China, and are referred to be linked with the assembly of the Nuna Supercontinent. The subsequent late Paleoproterozoic to early Mesoproterozoic rift successions and intrusions (1.7–1.5 Ga) in the southwestern Yangtze Block, and the ca. 1.43 Ga rifting in Hainan Island of the Cathaysia Block could be responses to the Nuna break-up. Late Mesoproterozoic (1.2–1.0 Ga) magmatism of varied age and nature in different localities of the Yangtze Block is reflective of a complex tectonic process in the context of the assembly of the Rodinia Supercontinent. Similar-aged metamorphism (1.3–1.0 Ga) is recorded in Hainan Island, reflecting the Grenvillian continental collision during the Rodinia assembly, but further studies are necessary to better constrain the late Mesoproterozoic tectonic framework of South China.  相似文献   

超高压变质带金刚石研究进展     

王晓赛  杜瑾雪  史本巽  王仕林 《岩石矿物学杂志》2020,39(2):183-194

金刚石在自然界中非常稀缺,是极其珍贵的矿产资源。其中,变质成因的金刚石陆续在世界范围内多个超高压变质带被发现,更新了人们对超高压变质作用和板块构造运动的认识,推动了超高压变质带动力学的研究,引起了学术界的广泛关注。然而,对于变质成因金刚石的形成机制,还未形成一致的认识。本文在综述前人研究成果的基础上,介绍了金刚石形成的大地构造背景,研究了其形成所需的地质环境和物理化学条件,并着重对超高压变质带金刚石成因机制进行了探讨,全面分析了温压条件、XCO2、fO2对变质成因金刚石形成的影响。对比发现,当变质作用的峰期压力达到金刚石稳定域且具有较高的温度时(压力>3 GPa,温度为600~1000℃),有利于金刚石的形成,C-O-H流体中的较高CO2含量和较低氧逸度也是超高压变质带金刚石形成的必需因素。另外,金刚石形成后折返早期的降温作用有利于其保存。  相似文献   

三峡库区龙门寨危岩体崩塌产生涌浪研究   总被引：1，自引：1，他引：0  

郑嘉豪  黄波林  张全  赵海林  冯万里  王健  陈小婷 《地质力学学报》2020,26(4):533-543

长江两岸高耸的危岩体对航道、沿岸居民带来巨大安全隐患。大宁河属于长江一级支流，龙门寨危岩体位于大宁河上，距离巫山县城仅1 km。利用FLOW-3D软件，模拟了145 m、175 m两种水位工况下龙门寨危岩体崩塌产生涌浪过程和涌浪传播过程。模拟结果表明，涌浪在145 m水位工况下最大浪高约为17.9 m，175 m水位工况下最大浪高约为11.6 m；在巫山县的五个码头处，两种水位工况最大涌浪爬高分别约为10.9 m、3.8 m；根据涌浪高度，对大宁河进行危险分区，145 m水位工况下极高危险区长度约4.4 km，很高危险区长度约1.9 km；175 m水位工况下极高危险区长度约3.0 km，很高危险区长度约1.0 km。研究结果有助于防控龙门寨危岩体潜在涌浪灾害危害，保障大宁河航道和巫山县码头安全，同时也为三峡库区滑坡涌浪灾害提供了预警依据。   相似文献   

鄂尔多斯地块—扬子地块深部电性结构特征及其动力学意义     

吕宏斌  叶高峰  金胜  魏文博  董浩  张乐天  谢成良  尹曜田 《地质论评》2020,66(4):813-828

位于青藏高原东北缘的秦岭造山带在大地构造上南接扬子地块、北接华北地块,是特提斯构造域和古亚洲洋构造域的转换带。本文基于对一条起始于扬子地块,穿过秦岭造山带和鄂尔多斯地块,到达河套地堑的南北向大地电磁测深剖面的研究,探讨秦岭造山带和其北侧的鄂尔多斯地块、南侧的扬子地块之间的接触关系,以及青藏高原物质东北向逃逸等地学问题。对实测数据进行了张量阻抗分解和维性分析等工作,并对剖面进行了二维反演,获得岩石圈电性结构模型。根据电阻率模型认为:在秦岭造山带北部发现大规模"瓶颈状"分布的低阻异常体(C2),可能为华北、华南地块双向俯冲前缘地幔物质的上涌通道,或者是青藏高原中、下地壳物质沿秦岭造山带中构造薄弱位置向东逃逸的通道;在秦岭造山带和大巴山弧形带边界处发现南倾的低阻异常(C1),解释为大巴山弧形带北缘的逆冲断裂在电性上的反映;电性结构模型中,扬子地块高阻异常体(R2、R3和R4)向北倾斜至秦岭造山带下方,而北部鄂尔多斯地块的高阻异常体(R5和R6)向南倾斜至秦岭造山带下方;高阻异常通常被认为是稳定岩石圈的反映,据此推断这两组相向俯冲至秦岭造山带下方的高阻异常是华北地块和扬子地块向秦岭造山带下方汇聚的电性结构探测依据;鄂尔多斯地块南、北电性差异较大,北部中、下地壳大规模分布电阻率值在3～100Ω·m之间的低阻异常体,可能为地幔上涌导致的局部熔融或含盐流体共同作用的结果。  相似文献   

Asymmetry in oceanic crustal structure of the South China Sea basin and its implications on mantle geodynamics     

Fan Zhang  Xubo Zhang  Weiwei Ding  Tingting Wang  Jian Zhu 《International Geology Review》2020,62(7-8):840-858

ABSTRACT

We investigated the oceanic crustal structure and lithospheric dynamics of the South China Sea (SCS) basin through a comprehensive analysis of residual gravity anomaly and bathymetry combined with seismic constraints and interpretation from geodynamic modelling. We first calculated the residual mantle Bouguer anomaly (RMBA) of the oceanic crustal regions of the SCS by removing from free-air gravity anomaly the predicted gravitational attractions of water-sediment, sediment-crust, and crust-mantle interfaces, as well as the effects of lithospheric plate cooling, using the latest crustal age constraints including IODP Expedition 349 and recent deep-tow magnetic surveys. We then calculated models of the gravity-derived crustal thickness and calibrated them using the available seismic refraction profiles of the SCS. The gravity-derived crustal thickness models correlate positively with seismically determined crustal thickness values. Our analysis revealed that the isochron-averaged RMBA are consistently more negative over the northern flank of the SCS basin than the southern conjugate for magnetic anomaly chrons C8n (~25.18 Ma) to C5Dn (~17.38 Ma), implying warmer mantle and/or thicker crust over much of the northern flank. Computational geodynamic modelling yielded the following interpretations: (1) Models of asymmetric and variable spreading rates based on the relatively high-resolution deep-tow magnetic analysis would predict alternating thicker and thinner crust at the northern flank than the southern conjugate, which is inconsistent with the observed systematically thicker crust on the northern flank. (2) Models of episodic southward ridge jumps could reproduce the observed N-S asymmetry, but only for crustal age of 23.6–20 Ma. (3) Southward migration of the SCS ridge axis would predict slightly thinner crust at the northern flank, which is inconsistent with the observations. (4) Models of higher mantle temperatures of up to 25–50°C or >2% less depleted mantle sources on the northern flank could produce large enough anomalies to explain the observed N-S asymmetries.  相似文献   

The structure,depositional style and accumulation characteristics of continental margin with diachronous breakup in the northern South China Sea     

Yunfan Zhang  Jiangyang Zhang  Lijie Wang 《International Geology Review》2020,62(7-8):1006-1018

ABSTRACT

A typical diachronous breakup developed in the South China Sea (SCS); the breakup has been unequivocally identified, and gradually decreases in age from NE to SW. To illustrate the influence of a diachronous breakup on hydrocarbon accumulation, we used seismic profiles from CNOOC, and analysed crustal extension characteristics, sedimentary style and source rock accumulation. The main conclusions are as follows: (1) Because of the diachronous breakup in the SCS, various tectonic units developed in different positions on the northern continental margin with different degrees of extension. The Pearl River Mouth Basin (PRMB) is closer to the central sea basin of the SCS and has been affected by regional tension stress for a longer time. Tectonic units of proximal domain, necking zone, and distal margin types developed, and the crust structure thinned from the land towards the sea. The Qiongdongnan Basin (QB) is closer to the Southwest Sub-basin. There are symmetrical proximal domains on the southern and northern sides of the QB, with a necking zone in the central part. It presents as an abandoned passive continental margin. (2) The PRMB exhibited rifted cells first, followed by canyon type extensional faulting and horizontal axial transportation, and then by a longitudinal shelf-slope sedimentary style. But the QB has only rifted cells and canyon type faulting stages, no longitudinal shelf-slope sedimentary stage. The major source rocks in the northern SCS become younger from east to west, and the sedimentary facies change from lacustrine facies to marine-continental transitional facies. (3) The diachronous breakup process ultimately affecting oil and gas migration and accumulation process. The PRMB is dominated by deep-water shelf break accumulation with deep-water fan reservoir bodies. The QB is dominated by canyon type accumulation with channels.  相似文献   

南海成因及其演化模式探讨          下载免费PDF全文

李学杰  王哲  姚永坚  高红芳  祝嵩  徐子英 《中国地质》2020,47(5):1310-1322

尽管南海已进行深入的调查与研究，提出多种成因模型，包括挤出模型、弧后扩张模型、古南海俯冲拖曳模型等，但因其所处构造位置特殊，周边构造环境经历了复杂的改造，所有成因模式均未能得到广泛的认可。本文从三大板块相互作用入手，结合南海实测数据，提出南海形成的弧后扩张—左旋剪切模型。认为南海是古南海往北俯冲的弧后盆地，菲律宾海板块往北漂移形成的大规模左旋走滑是南海扩张的触发因素。印度—欧亚碰撞产生中南半岛挤出主要影响西南海盆扩张方向，使得扩张轴从近东西向转为北东向。南海及邻区晚中生代以来的演化可以分为以下阶段：1）早白垩世开始澳大利亚板块往北漂移，新特提斯洋往北俯冲消亡，导致弧后扩张，形成古南海；2）晚白垩世末—始新世，古南海往北俯冲，导致弧后拉张形成陆缘裂谷；3）早渐新世，受菲律宾海板块西缘大型左旋走滑影响，在原有裂谷的基础上从东往西海底扩张，形成南海；4）渐新世末，受俯冲后撤的影响，扩张中心往南跃迁，同时受西缘断裂左旋活动的影响，扩张轴从近东西西逐步转为北东向；5）早中新世晚期，南沙地块—北巴拉望地块与卡加延脊碰撞，南海扩张停止。  相似文献   

辽东岫岩地区下古生界碎屑锆石定年:罗迪尼亚和冈瓦纳超大陆在华北遗留的痕迹？     

董晓杰  陈煜嵩  刘正宏  徐仲元  沙茜 《岩石学报》2020,36(6):1857-1869

超大陆演化是地质研究的重要内容,华北克拉通与不同地质历史时期超大陆汇聚与裂解的联系对反演华北克拉通构造演化历史具有重要意义。本文在辽吉古元古代造山带中段的原划分为辽河群地层中首次识别出一套早古生代沉积建造。这套沉积建造与华北克拉通以浅海相的碳酸盐岩为主的早古生代沉积并不一致,以发育大量的陆源碎屑沉积为特征。我们对2件细砂岩分别进行了锆石LA-ICP-MS和SHRIMP U-Pb定年。定年结果显示,2件样品的最小年龄分别为～482Ma和～498Ma,反映了它们的最大沉积时代。2件样品的碎屑锆石年龄主要介于1600～500Ma,缺乏亲华北的物源信息,表明它们的物源主要来自于华北之外。2件样品年龄谱中最重要的峰值出现在格林威尔期和泛非期,表明华北克拉通曾与罗迪尼亚超大陆和冈瓦纳大陆存在联系。格林威尔期碎屑锆石可能来自于罗迪尼亚超大陆时期波罗地古陆物质在华北克拉通东缘的再循环;泛非期碎屑锆石可能来自于东冈瓦纳大陆的北缘造山带。  相似文献   

新疆伊犁地区季节冻土沿海拔的分布规律及其影响因素     

郝建盛  张飞云  黄法融  李兰海 《冰川冻土》2020,42(4):1179-1185

基于2000 - 2014年新疆伊犁地区不同海拔区域观测的冻融期内的冻土、 积雪和气象数据， 应用相关性分析和回归分析方法， 分析该地区季节冻土沿海拔的分布规律， 以及气温、 积雪对季节冻土特征的影响。结果表明： 伊犁地区表层土壤存在着每年11月份开始结冻， 于次年4月份完全融化的周期性变化。每个周期内土壤冻结时长随海拔以4 d·（100m）^-1的趋势增加， 土壤最大冻结深度随海拔以3.9 cm·（100m）^-1的趋势增加。土壤冻结时长与冻结期的平均气温具有显著负相关关系， 相关系数为-0.98（P<0.05）。土壤冻结日数与积雪覆盖历时呈正相关关系， 土壤的最大冻结深度与最大雪深呈负相关关系。随着海拔升高， 温度递减， 导致伊犁地区土壤最大冻结深度和土壤冻结日数整体呈现增加趋势。但在海拔相对较高的地区， 由于相对较厚积雪的影响， 出现土壤最大冻结深度随海拔升高而减小的反常现象。研究结果可为新疆伊犁地区季节冻土的分布对气候变化的响应研究提供支持， 帮助研究区域生态规划和水资源管理， 为农业发展制定适应气候变化对策。  相似文献   

Radar isochronic layer dating for a deep ice core at Kunlun Station,Antarctica     

Tang  Xueyuan  Sun  Bo  Wang  Tiantian 《中国科学:地球科学(英文版)》2020,63(2):303-308

The ages and accumulation rates of ice are important boundary conditions for paleoclimatic ice models. Radardetected isochronic layers can be used to date the ice column beneath the ice surface and infer past accumulation rates. A Deep Ice-Core Drilling Project has been carried out at Kunlun station in the Dome A region, East Antarctica. Radio echo sounding data are collected during the 2004/2005 Chinese National Research Expedition and the 2007/2008 Dome Connection East Antarctica project of the Alfred Wegener Institute(Germany). Radar isochronic layers from the dataset were linked to compare a new deep ice core site from Kunlun station and the Vostok ice core site. Ten visible layers, accounting for ~50% ice thickness at the Kunlun station ice core site, were dated based on the Vostok ice core chronology. At 1,640 m depth below surface, an age of ~160,400 yr was determined, corresponding to a bright layer at Kunlun station. These layers provided geometric information on the past surface of the ice sheet around the ice core site through the Wisconsin glacial stage, Eemian interglacial and Marine Isotope Stage6. Based on a simple ice flow model and the age-depth relationship, we concluded that the region around the Kunlun ice core site had lower past accumulation rates, consistent with the present pattern. The age-depth relationship would thus be expected to correlate and constrain the chronology of the deep ice core at Kunlun station in the future.  相似文献