探索中国陆块找钾——中国东特提斯域成钾作用及模式

中国陆块海相成钾规律及预测(973)课题五年硏究,完成构建我国海相盆地钾盐成矿理论及"模式"构建。"中国东特提斯域成钾作用及模式"从中国海相蒸发岩盆地成盐聚钾探索中,得出:气侯、物源及构造在时间和空间上"三位一体"耦合作用成钾理论,对东特提斯域成钾提出了"多级盆地"及"深源补给"等成钾模式,为中国陆块找钾提供了理论依据。

古生代与三叠纪中国各陆块在全球古大陆再造中的位置与运动学特征

在尊重比较可靠的、测试精度较高的地块古地磁数据,重视生物古地理与地质构造演化史的相似性和协调性等原则的基础上,笔者编制了中国大陆及邻区各陆块古生代和三叠纪的古地磁数据表,并采用类似的比例尺,将中国各陆块放到相应的全球古大陆复原图上去。由此可以清晰地看出,在古生代早期全球各大陆的主要部分都位于赤道附近及南半球,大致表现为沿纬度、呈东西向排列的特征,中国及邻区的小陆块群在古生代始终都处在劳伦大陆、西伯利亚与冈瓦纳大陆之间;随着西伯利亚大陆的快速北移,在劳伦大陆与冈瓦纳大陆的西部地区发生南北向拼合,亚皮特斯洋和里克洋的消亡,到古生代晚期形成统一的泛大陆;而冈瓦纳大陆的东部(澳大利亚和印度等)则逐渐向南移动、离散,地壳张开,构成古特提斯洋;中国及邻区的小陆块群则一直处在古特提斯洋中,保持离散状态,总体上缓慢地向北运移,并逐渐转为近南北向的排列方式,石炭纪到三叠纪才在天山—兴安岭、昆仑山、秦岭—大别、金沙江和绍兴—十万大山等地段发生一系列局部性的陆陆碰撞,使中国大陆地块的大部分逐渐并入欧亚大陆。

冈瓦纳大陆古生代冰盖分布研究

基于冈瓦纳大陆主要板块冰川沉积地层的对比,并结合古地磁方法对冈瓦纳大陆古生代主要冰期的冰盖分布范围进行再造,认为冈瓦纳大陆在古生代主要经历了3次较大的冰期,分别是:(1)晚奥陶世—早志留世冰期、(2)晚泥盆世—早石炭世冰期、(3)晚石炭世晚期—二叠纪冰期。晚奥陶世—早志留世冰期冰盖主要分布在西冈瓦纳大陆;晚泥盆世—早石炭世冰期冰盖主要分布在南美板块;晚石炭世晚期—二叠纪冰期冰盖在冈瓦纳大陆主要组成板块上均有分布,且冰盖存在时间最长,分布范围最广。3次主要冰期冰盖的中心点位置均靠近南极点,但并不完全重合,可认为气温是影响冈瓦纳大陆上冰盖分布的主要因素,但不是唯一的因素,冰盖的分布范围还受到盆地动力学、地形、冰川属性以及其他具体因素的影响。同时结合在保山地块的野外工作以及前人的研究成果,认为冈瓦纳大陆的3次冰期中,仅晚石炭世晚期—二叠纪冰期对中国的陆块产生了影响,且主要影响了中国的西南陆块群(包括保山地块、腾冲地块、拉萨地块、羌塘地块等)。

中国东北地区泛非造山岩浆活动的记录:来自扎兰屯地区铜山组碎屑锆石年代学和Hf同位素的证据

本文报道了内蒙古扎兰屯地区铜山组的碎屑锆石U-Pb年代学和Hf同位素分析结果,首次发现中国东北地区记录了泛非造山岩浆事件,并探讨了中国东北微陆块的构造归属。年代学研究表明:(1)扎兰屯地区铜山组碎屑岩最年轻锆石年龄峰值为569 Ma,与泛非造山岩浆活动(东、西冈瓦纳大陆碰撞‒拼贴事件)的时代一致;其他3个峰期年龄为873 Ma、1847 Ma和2073 Ma,与兴安‒艾力格庙地块东北部的基底年龄相对应。(2)锆石Hf同位素显示兴安‒艾力格庙地块与松辽‒浑善达克地块新元古代早期年龄峰值(~900 Ma)的εHf(t)值有正有负,二阶段模式年龄反映其是古元古代地壳再造的产物;额尔古纳地块新元古代(~800 Ma)岩浆岩的εHf(t)值为正高值,二阶段模式年龄与形成年龄相近,为中元古代地壳物质再造的产物,与兴安‒艾力格庙和松辽‒浑善达克地块的新元古代早期基底存在明显差异。(3)兴安‒艾力格庙地块和松辽‒浑善达克地块均记录了泛非造山岩浆事件,揭示其与冈瓦纳大陆东北部存在亲缘性。

亚洲地球动力系统的演进与东亚矿产资源效应

本文系统阐述了亚洲中部及邻区地球动力系统的演变进程及其所制约的区域地质和成矿特征,并提出了以下新认识和新观点:①在西伯利亚陆块与中朝—塔里木陆块之间的原"古亚洲洋"区域内是全球地史演化中具有双向侧向陆缘增生与垂向增生同时发展的"双向增生"独特地区。②"古中国陆块群"是位于劳亚古陆和冈瓦纳古陆之间独立存在的古陆。由于它的特殊位置而构成了古亚洲洋与特提斯洋的"分水岭"。③地球动力学的"内动力"归根到底来自地球自身的两个方面:一是地球自转和公转形成的离心力(拉张力)与挤压力,它是地球动力学的基础,二是地球内部永不衰败的"高热能库"。当今地震、火山等等,都是地下过饱和的高热能向地表释放的一瞬间转变为强动能的地质事件。④由地球动力系统演变打造的具有不同特征的断裂系统是控矿储矿的良好空间,因此"断裂系统找矿法"是简便有效的找矿方法之一。据此提出了4个理论指导找矿的试点和验证区。

Research on Strong Earthquake Tendency on Active Tectonic Block Boundaries in the Chinese Mainland

Previous studies have shown that the active tectonic block boundaries in the Chinese mainland are the main belts and concentration areas of strong earthquakes occurring in the Chinese mainland.It is essential to carry out follow-up analysis of strong earthquake risk of active tectonic block boundaries.In this paper,we carry out the analysis on the tendency of strong earthquakes along each active tectonic block boundary from three aspects respectively,including the evolutionary characteristics of the Load/Unload Response Ratio time series,the probability method based on the log-normal distribution function,and variation of b value.The estimation of strong earthquake criticality on each active tectonic block boundary is done based on the evolutionary characteristics of the Load/Unload Response Ratio time series,the cumulative probability and conditional probability,and the decrease of the b value.Finally,according to the results of analyses on the above three aspects,the potential strong earthquake areas in the forthcoming 5 years in the Chinese mainland are discussed.

Tectonics of South China Continent and its implications

This paper aims at exploring the tectonic characteristics of the South China Continent （SCC） and extracting the universal tec- tonic rules from these characteristics,to help enrich the plate tectonic theory and better understand the continental dynamic system. For this purpose, here we conduct a multi-disciplinary investigation and combine it with the previous studies to reas- sess the tectonics and evolution of SCC and propose that the tectonic framework of the continent comprises two blocks, three types of tectonic units, four deformation systems, and four evolutionary stages with distinctive mechanism and tectonic characteris- tics since the Neoproterozoic. The four evolutionary stages are： （1） The amalgamation and break-up of the Neoproterozoic plates, typically the intracontinental rifting. （2） The early Paleozoic and Mesozoic intracontinental orogeny confined by plate tectonics, forming two composite tectonic domains. （3） The parallel operation of the Yangtze cratonization and intracontinental orogeny, and multi-phase reactivation of the Yangtze craton. （4） The association and differentiation evolution of plate tectonics and intraconti- nental tectonics, and the dynamic characteristics under the Meso-Cenozoic modem global plate tectonic regime.

Zircon U/Pb dating and Hf-O isotopes of the Zhouan ultramafic intrusion in the northern margin of the Yangtze Block,SW China:Constraints on the nature of mantle source and timing of the supercontinent Rodinia breakup

The Zhouan ultramafic intrusion in the northern margin of the Yangtze Block is mainly composed of lherzolite. Zircon grains selected from lherzolite are irregular in shape with distinct oscillatory and sector zoning and have Th/U ratios ranging from 0.8 to 10.6, indicating a magmafic origin. The weighted average 206pb/238U age is 637±4 Ma （2σ, n=15）, which can be considered as the crystallization age of the Zhouan intrusion. Zircon grains have δ18O values ranging from 5.2‰to 7.0‰, with an averaged value of 5.8±0.4‰（1 or, n=33）, similar to the mantle δ18O value of zircon. Their 176Hf/177Hf（t） ratios range from 0.282410 to 0.282594 with εHf（t） values ranging from 1.3 to 7.6, lower than the corresponding value of the depleted mantle （~15）, indicating an enriched mantle source. The enriched mantle source may have generated from a metasomatized lithospheric mantle with subducted slab. A number of -635 Ma mafic-ultramafic intrusions in the Suizao basin are associated with coeval bimodal volcanics of the Yaolinghe Formation, indicating a continental rift setting. The ~635 Ma magmafic event in this region may represent the product of the last breakup of the Rodinia supercontinent in the northern margin of the Yangtze Block at Neoproterozoic.

Early Mesozoic structural deformation in the Chuandian N-S Tectonic Belt,China

The Helan-Chuandian N-S Tectonic Belt is a mantle transitional belt in China. The southem part, forming the Chuandian N-S Tectonic Belt, comprises several tectonic systems, each displaying different characteristics. The Chuandian N-S Tectonic Belt along the western margin of yangtze Block is a strike-slip tectonic belt with a series of echelon left-lateral slip faults. The strike-slip fault systems experienced two stages of structural deformation： early NW-SE striking thrust faults formed under a NE-SW compression stress field, and later sinistral strike-slip structures formed along thrust faults under a NW-SE compression stress field. Mesozoic basins developed between the left-lateral slip faults. Sedimentary facies and paleocurrent directions indicate that basin development was controlled by the strike-slip faults. The oldest strata in the Chuandian N-S Tectonic Belt constrain its formation to early Mesozoic. In fact, The slip tectonic belt formed by clockwise rotation and north-directed subduction-collision of the Yangtze Block in Late Triassic-Jurassic. The strike-slip faults that developed within the belt also formed at this time.