Time scale of an early to mid-Paleozoic orogenic cycle of the long-lived Central Asian Orogenic Belt, Inner Mongolia of China: Implications for continental growth

We present a detailed, new time scale for an orogenic cycle (oceanic accretion–subduction–collision) that provides significant insights into Paleozoic continental growth processes in the southeastern segment of the long-lived Central Asian Orogenic Belt (CAOB). The most prominent tectonic feature in Inner Mongolia is the association of paired orogens. A southern orogen forms a typical arc-trench complex, in which a supra-subduction zone ophiolite records successive phases during its life cycle: birth (ca. 497–477 Ma), when the ocean floor of the ophiolite was formed; (2) youth (ca. 473–470 Ma), characterized by mantle wedge magmatism; (3) shortly after maturity (ca. 461–450 Ma), high-Mg adakite and adakite were produced by slab melting and subsequent interaction of the melt with the mantle wedge; (4) death, caused by subduction of a ridge crest (ca. 451–434 Ma) and by ridge collision with the ophiolite (ca. 428–423 Ma). The evolution of the magmatic arc exhibits three major coherent phases: arc volcanism (ca. 488–444 Ma); adakite plutonism (ca. 448–438 Ma) and collision (ca. 419–415 Ma) of the arc with a passive continental margin. The northern orogen, a product of ridge-trench interaction, evolved progressively from coeval generation of near-trench plutons (ca. 498–461 Ma) and juvenile arc crust (ca. 484–469 Ma), to ridge subduction (ca. 440–434 Ma), microcontinent accretion (ca. 430–420 Ma), and finally to forearc formation. The paired orogens followed a consistent progression from ocean floor subduction/arc formation (ca. 500–438 Ma), ridge subduction (ca. 451–434 Ma) to microcontinent accretion/collision (ca. 430–415 Ma); ridge subduction records the turning point that transformed oceanic lithosphere into continental crust. The recognition of this orogenic cycle followed by Permian–early Triassic terminal collision of the CAOB provides compelling evidence for episodic continental growth.     

Heterogenous zircons from Mesozoic igneous rocks in the North China Craton and their tectonic implications

Based on a synthesis of zircon inheritance from Mesozoic igneous rocks in the eastern portion of the North China Craton （NCC） , it is proposed that inherited zircons with Neoproterozoie ages identified from these rocks are of a heterogenous derivation from the Yangtze/South China block, rather than from the NCC itself. The mechanism that introduces these zircons incorporated into the NCC is likely by tectonic underplating during the Triassic continental subduction of the Yangtze block beneath the NCC. Tectonic addition of abundant crustal materials represented by the heterogenous zircons into the NCC, probably along Moho or weak interfaces within the NCC＇s crust, led to the crustal thickening in the NCC. These heterogenous materials, either as （partial） source rocks or as contaminants of the magmas generated during an extension environment following the crustal thickening, were reworked and therefore have significant contribution to petrogenesis of the Mesozoic igneous rocks. The crustal thickening resulted from the tectonic underplating, as indicated by the distribution extent of the heterogenous zircons, is spatially similar to that of the lithospheric thinning, with both mainly occurring in the eastern segment of the NCC. This is probably suggestive of an intrinsic relation between the thickening and thinning events during the Mesozoic evolution of the NCC.     

秦岭中部山地落叶阔叶林超级垂直带的发现与意义

山地垂直带谱是气候和植被水平地带变化和更替的缩影,垂直带的带幅、带间过渡方式、带内结构和垂直带组合方式都表现出高度的异质性和复杂性。本文发现在中国南北过渡带中部太白山发育了世界上最宽的山地垂直带——山地落叶阔叶林垂直带。该垂直带从基带到典型垂直带再到先锋性垂直带皆为山地落叶阔叶林,3种本来可以独立存在的垂直带,连续分布形成了包含3个栎林亚带、2个桦林亚带的“三层五亚带”超级垂直带,远远超过正常情况下山地垂直带1000 m的阈值,且其上限达到了海拔2800 m。它的形成与秦岭所处的过渡性地理位置、秦岭中部垂直带谱的完整性、丰富的落叶木本植物种群及其形成的强大群落竞争优势等因素紧密相关。超级垂直带的发现有多方面的意义：它是中国南北过渡带又一重要的标志性自然地理特征;它表明山地垂直带在特殊的山地环境中可以具有非常复杂的内部结构和宽大带幅,这扩展了我们对山地垂直带谱结构及机理认识的广度,对于创建山地垂直带谱结构理论具有十分重要的意义;超级垂直带的发现,也说明中国南北过渡带还有很多科学内容有待我们去探索和发现,希望本文能起到抛砖引玉的作用,引起学界对超级垂直带形成的气候和生物多样性因素、地理过渡带的结构和生态效应等重大问题进行深入研究。     

几种沙生灌木耐旱生理特性的研究

本文对盐池沙地六种灌木进行了耐旱生理特性的研究。研究内容包括相对含水量, 组织含水量、水势、蒸腾速率和气孔传导速率。结果表明, 毛条和柠条的各项生理指标均表现出较强的耐旱能力; 霸王和白茨以其低水势, 低蒸腾速率和气孔传导速率的方式耐旱; 而花棒和山竹子则以其庞大的根系吸取较多的水分, 维持植株高水势, 以保证其在水分亏缺下体内新陈代谢之需。由此可以认为, 耐旱植物不是循同一途径或方式耐旱的。     

Heterogenous zircons from Mesozoic igneous rocks in the North China Craton and their tectonic implications

Based on a synthesis of zircon inheritance from Mesozoic igneous rocks in the eastern portion of the North China Craton (NCC) , it is proposed that inherited zircons with Neoproterozoic ages identified from these rocks are of a heterogenous derivation from the Yangtze /South China block, rather than from the NCC itself. The mechanism that introduces these zircons incorporated into the NCC is likely by tectonic underplating during the Triassic continental subduction of the Yangtze block beneath the NCC. Tectonic addition of abundant crustal materials represented by the heterogenous zircons into the NCC, probably along Moho or weak interfaces within the NCC's crust, led to the crustal thickening in the NCC. These heterogenous materials, either as ( partial) source rocks or as contaminants of the magmas generated during an extension environment following the crustal thickening, were reworked and therefore have significant contribution to petrogenesis of the Mesozoic igneous rocks. The crustal thickening resulted from the tectonic underplating, as indicated by the distribution extent of the heterogenous zircons, is spatially similar to that of the lithospheric thinning, with both mainly occurring in the eastern segment of the NCC. This is probably suggestive of an intrinsic relation between the thickening and thinning events during the Mesozoic evolution of the NCC.     

早前寒武纪大陆块壳构造理论——华北克拉通早前寒武纪基底构造格架、地壳演化及其与区域地球化学不均一性的关系研究

早前寒武纪大陆块壳构造理论——华北克拉通早前寒武纪基底构造格架、地壳演化及其与区域地球化学不均一性的关系研究张福勤＊＊（中国科学院地球化学研究所，贵阳５５０００２）关键词大陆块壳并合带地壳演化进程地球化学不均一性早前寒武纪地质学研究是地球科学最基础的...     

North-south vegetation transition in the eastern Qinling-Daba Mountains

The Qinling-Daba Mountains are the main body of China's North-South Transitional Zone.Analysis of the north-south gradual variation of vegetation components is significant for understanding the structural diversity and complexity of this transitional zone.In this study,based on survey data of plant communities,the eastern Qinling-Daba Mountains is divided into four geographic units:the north flank of eastern Qinling Mts.,south flank of eastern Qinling Mts.,north flank of eastern Daba Mts.and south flank of eastern Daba Mts.We also explore division of regional climate according to areal differentiation of plant-species,com-munity structure and species-richness,respectively.The results show that,(1)at plant-species level,there are mainly northern plants in north flank of eastern Qinling Mts.with evergreen species and fewer northern plants in south flank of eastern Qinling Mts.;there are mainly southern plants in eastern Daba Mts.(2)At community structure level,there are 4 formations(3 northern formations and 1 widespread formation)in north flank of eastern Qinling,6 formations(3 northern formations,1 southern formation,and 2 widespread forma-tions)in south flank of eastern Qinling,4 formations(2 southern formations and 2 widespread formations)in north flank of eastern Daba Mts.,and 3 formations(3 southern formations)in south flank of eastern Daba Mts.In terms of the numbers and properties of formations,there is a mixture of northern and southern formations only in the south flank of eastern Qinling Mts.(3)At species-richness level,the diversity of families,genera and species decreased with increasing latitude,but the mixing of northern plants and the southern plants began to occur in south flank of eastern Qinling Mts.This means that the south flank of the eastern Qinling Mts.serves more suitably as the dividing line between China's warm temperate and sub-tropical zones.     

中国南北过渡带东段样带植被序列与气候分界问题

国家科技基础资源调查专项“中国南北过渡带综合科学考察”将秦岭—大巴山定义为中国南北过渡带的主体,秦巴山地植被南北变化研究,对于揭示中国南北过渡带地域结构的过渡性、多样性和复杂性具有重要意义。基于植物群落实地调查数据,本文将中国南北过渡带东段分为：东秦岭北麓（EQMN）、东秦岭南麓（EQMS）、东大巴山北麓（EBMN）和东大巴山南麓（EBMS）4个地理单元,从植物物种、群落结构和物种多样性三个层面,对区域气候分界问题进行研究。结果表明：① 植物种类层面,EQMN主要为北方植物,EQMS出现常绿树种且北方植物减少,东大巴山以喜湿喜热的南方植物为主。② 群落结构层面,EQMN群系有4个（北方群系3个,南方群系0个,广布群系1个）、EQMS有6个（北方群系3个,南方群系1个,广布群系2个）、EBMN群系有4个（北方群系0个,南方群系2个,广布群系2个）、EBMS群系3个（北方群系0个,南方群系3个,广布群系0个）,只有EQMS群系出现南北性质混合;③ 丰富度层面,随着纬度增加,科、属、种3个分类群物种多样性均减小,但南北方植物混合现象开始在EQMS出现。本文对植被变化序列的研究增加了对东秦巴山地南北分界线判断的科学性,东秦岭南麓更适合作为暖温带—北亚热带的分界线。     

内蒙古图林凯蛇绿岩中埃达克岩SHRIMP测年：早古生代洋壳消减的证据

内蒙古图林凯蛇绿岩中,新发现了埃达克岩,岩性包括石英闪长岩、奥长花岗岩、斜长岩和英安岩。它们是温都尔庙—图林凯早古生代消减带的一种岩浆岩标志。精确的SHRIMP U-Pb测年表明:①石英闪长岩侵位于约467±13Ma,说明温都尔庙古洋壳的消减可能始于约467±13Ma或更早。随后不久,这一岩石经历了约451±18Ma的高级变质和部分熔融事件。②英安岩喷发于约459±8Ma,奥长花岗岩形成略晚,约451±7Ma,最后形成了斜长岩的岩墙,其时代约为429±7Ma。据此认为,温都尔庙—图林凯古洋壳在早古生代时期,经历了愈38Ma的消减事件。     

农田蒸散双层模型及其在干旱遥感监测中的应用

该文建立了在部分植被条件下估算农田蒸散的双层模型，利用此模型和ＮＯＡＡ－ＡＶＨＲＲ数据对黄淮海平原春季旱情进行了评估，并做出了干旱及蒸散分布图。对双层模型和单层模型的估算结果进行了比较，结果表明在部分植被条件下双层模型估算的精度要高。