The Liaonan metamorphic core complex, Southeastern Liaoning Province, North China: A likely contributor to Cretaceous rotation of Eastern Liaoning, Korea and contiguous areas

The Mesozoic Liaonan metamorphic core complex (mcc) of the southeastern Liaoning province, North China, is an asymmetric Cordilleran-style complex with a west-rooting master detachment fault, the Jinzhou fault. A thick sequence of lower plate, fault-related mylonitic and gneissic rocks derived from Archean and Early Cretaceous crystalline protoliths has been transported ESE-ward from mid-crustal depths. U–Pb ages of lower plate syntectonic plutons (ca. 130–120 Ma), ⁴⁰Ar–³⁹Ar cooling ages in the mylonitic and gneissic sequence (ca. 120–110 Ma), and a Cretaceous supradetachment basin attest to the Early Cretaceous age of this extensional complex. The recent discovery of the coeval and similarly west-rooting Waziyu mcc in western Liaoning [Darby, B.J., Davis, G.A., Zhang, X., Wu, F., Wilde, S., Yang, J., 2004. The newly discovered Waziyu metamorphic core complex, Yiwulushan, western Liaoning Province, North China. Earth Science Frontiers 11, 145–155] indicates that the Gulf of Liaoning, which lies between the two complexes, was the center of a region of major crustal extension.Clockwise crustal rotation of a large region including eastern Liaoning province and the Korean Peninsula with respect to a non-rotated North China block has been conclusively documented by paleomagnetic studies over the past decade. The timing of this rotation and the reasons for it are controversial. Lin et al. [Lin, W., Chen, Y., Faure, M., Wang, Q., 2003. Tectonic implication of new Late Cretaceous paleomagnetic constraints from Eastern Liaoning Peninsula, NE China. Journal of Geophysical Research 108 (B-6) (EPM 5-1 to 5-17)] proposed that a clockwise rotation of 22.5° ± 10.2° was largely post-Early Cretaceous in age, and was the consequence of extension within a crustal domain that tapers southwards towards the Bohai Sea (of which the Gulf of Liaoning is the northernmost part). Paleomagnetic studies of Early Cretaceous strata (ca 134–120 Ma) in the Yixian–Fuxin supradetachment basin of the Waziyu mcc indicate the non-rotation of North China and the basin [Zhu, R.X., Shao, J.A., Pan, Y.X., Shi, R.P., Shi, G.H., Li, D.M., 2002. Paleomagnetic data from Early Cretaceous volcanic rocks of West Liaoning: evidence for intracontinental rotation. Chinese Science Bulletin 47, 1832–1837]. Such upper-plate non-rotation supports our conclusion that the lower plates of the Waziyu and Liaonan metamorphic core complexes were displaced ESE-ward in an absolute sense away from the stable North China block, thus contributing to the rotation of Korea and contiguous areas. Rotation is inferred to have affected only the upper crust above mid-crustal levels into which we believe the Jinzhou and Waziyu detachment fault zones flattened. If this is the case, the regional Tan Lu fault that lies between the two core complexes was truncated at mid-crustal depth, since in areas to the south it forms the boundary between the North and South China lithospheric blocks. It is noteworthy that the two extensional complexes lie not far north of the Bohai Bay, the area proposed by Lin et al. [Lin, W., Chen, Y., Faure, M., Wang, Q., 2003. Tectonic implication of new Late Cretaceous paleomagnetic constraints from Eastern Liaoning Peninsula, NE China. Journal of Geophysical Research 108 (B-6) (EPM 5-1 to 5-17)] as the site of the pole of rotation for Korea's clockwise displacement.Lin et al. [Lin, W., Chen, Y., Faure, M., Wang, Q., 2003. Tectonic implication of new Late Cretaceous paleomagnetic constraints from Eastern Liaoning Peninsula, NE China. Journal of Geophysical Research 108 (B-6) (EPM 5-1 to 5-17)] were unaware of the Liaonan and Waziyu mcc's and argued that most of the regional block rotation was post-Early Cretaceous and, in part, early Cenozoic. However, the ca. 130–120 Ma ages of the two Liaoning mcc's and a Songliao basin mcc (Xujiaweizi), the latter discovered only by recent drilling through its younger stratigraphic cover, support our and some Korean coworkers' conclusions that most of the clockwise rotation was Early Cretaceous.     

辽北太古宙变质岩中的振荡型矿物环带及意义

对辽北太古宙层状变质岩系中石榴石、黑云母的成分分析发现,其中存在明显的振荡型矿物环带。对其形成机理的研究表明,这是矿物在结晶过程中由于偏离理想状态而形成的一种非平衡态自组织现象,即耗散结构。矿物内部成分的振荡性并不是由于外界条件的周期变化所造成的,而是体系内部固有属性的反映。这种认识对研究变质作用的动力学过程具有重要的借鉴意义,文中还就这种振荡性矿物环带在变质作用研究中的意义作了进一步的阐述。     

中国满洲里－绥芬河地学断面域古生代构造单元及其地质演化

额尔古纳－兴安地体（ＥＴ）、松嫩－张广才岭地体（ＳＴ）、佳木斯地体（ＳＴ）是断面域古生代具有独立发展演化历史的地质构造单元，ＥＴ与西伯利亚地台具有亲缘性，ＳＴ－ＪＴ与华北和西伯利亚地台均无亲缘关系；ＳＴ与ＪＴ、ＥＴ与ＳＴ－ＪＴ分别沿牡丹江和嫩江断裂拼贴，最终形成统一亚洲大陆的一部分。     

南水北调漕河渡槽Ⅲ标段桩基13000kN竖向抗压静载试验及分析

漕河渡槽是南水北调中线工程总干渠上的标志性建筑物,其Ⅲ标段渡槽基础采用桩基形式。桩基施工完毕后,为了检测单桩竖向抗压承载力,采用了以堆锚联合反力装置为反力方式的13 000 kN竖向抗压静载试验,实验结果分析表明,本工程单桩的竖向抗压承载力满足设计要求。     

Sunspot groups at high latitude

Data of sunspot groups at high latitude (35°), from the year 1874 to the present (2000 January), are collected to show their evolutional behaviour and to investigate features of the yearly number of sunspot groups at high latitude. Subsequently, an evolutional pattern of sunspot group number at high latitude is given in this paper. Results obtained show that the number of sunspot groups of a solar cycle at high latitude rises to a maximum value about 1 yr earlier than the time of the maximum of sunspot relative numbers of the solar cycle, and then falls to zero more rapidly. The results also show that, at the moment, solar activity described by the sunspot relative numbers has not yet reached its minimum. In general, sunspot groups at high latitude have not appeared on the solar disc during the last 3 yr of a Wolf solar cycle. The asymmetry of the high latitude sunspot group number of a Wolf solar cycle can reflect the asymmetry of solar activity in the Wolf solar cycle, and it is suggested that one could further use the high latitude sunspot group number during the rising time of a Wolf solar cycle, maximum year included, to judge the asymmetry of solar activity over the whole solar cycle.     

基于修正引力模型的中国省际旅游者流空间网络结构特征

高速交通时代旅游者流空间网络结构具有什么特征,是全国旅游流空间组织和管理需要探索的基础问题。贴近客观实际修正引力模型的相关参数,测算中国省际旅游者流,结合复杂网络分析方法,探索空间网络结构的优势、联系和发育水平。分析发现该网络结构稳定,旅游者流大量汇聚于中国的东南半壁、流动不对称、邻近型和跳跃型空间联系结构并存、层级性明显。具体表现为：首先,从优势水平来看,旅游流大量汇聚于上海（东）-广东（南）-四川（西）-河北（北）区域范围内。其次,从联系水平来看,东部三省江苏、浙江、山东是各地优势流量的主要汇聚之所,西藏的排名靠末。最后,从发育水平来看,旅游流动不对称,网络有“紧密团块型”和“飞地跨越型”两种空间联系结构且表现出层级性,不平衡发育状态将在较长时间内保持不变。     

东沙海域复杂海况下单源单缆长排列地震资料处理*

大量研究表明南海北部东沙海域的中生界地层具有很好的油气成藏条件, 是油气勘探的有利区域。但中生界地层构造成像不清晰限制了该区域油气资源的准确评价。本文利用在该海域采用单源单缆长排列采集的三维地震数据, 提出了对该类数据的优化处理技术方案, 以期获得中生界地层的清晰成像。处理过程主要包括各种噪音干扰和不同类型多次波的压制, 尤其是比较严重的海洋湍流干扰压制, 提高中深层反射信号信噪比; 通过压制气泡和压缩子波提高地震反射的分辨率; 同时利用高密度速度分析进行各向异性双谱非双曲线动校正, 提高成像质量, 使波组特征、振幅特征更为明显。针对密集二维采集数据特点, 通过合理的面元规则化处理, 使得覆盖次数均匀和横向分辨率提高, 实现高精度三维成像。本研究针对噪音干扰较严重的单源单缆长排列加密地震资料, 按照三维地震资料进行数据处理, 处理后明显突出了浅、中、深各层的有效信息, 特别是针对中生界的成像质量改善更为明显, 形成了一套行之有效的处理流程, 为今后邻近区块的勘探和资料处理提供了技术基础, 也为东沙海域的油气勘探与评价提供了科学依据。     

大陆岩石圈地幔定年

大陆岩石圈地幔是伴随地壳熔体抽取而形成的低密度地幔残留,是联系软流圈与地壳的重要纽带。虽然大陆岩石圈地幔一直是固体地球科学研究的重要内容,但对其形成时代的准确厘定则是当前研究的难点。传统方法是采用岩石圈地幔中橄榄岩主要元素的贫瘠程度来对岩石圈进行定年,即古老的岩石圈地幔Al2O3和CaO含量低,而MgO含量高(同时导致橄榄石高Fo值),而年轻岩石圈地幔的特征正好相反。显然,这种间接的方法不能给出确切的年龄信息。尽管Sr-Nd和锆石U-Pb等同位素方法也被用来进行地幔橄榄岩定年,但岩石圈地幔通常具有的较高温度使上述同位素体系不能保持封闭,因而给出的年龄大多与岩石圈地幔的形成时代无关。近几年发展起来的Re-Os同位素技术是目前进行岩石圈地幔定年的最理想工具,但也存在一系列需要研究的问题。文中对这一方法的基本原理、发展现状和存在的问题进行了全面的介绍。同时,根据目前获得的Os同位素资料,对中国东部岩石圈地幔的时代进行了讨论,并简要论述所获得的资料对岩石圈减薄研究的启示。     

Re-Os同位素体系理论及其应用

由于Ｒｅ,Ｏｓ独特的地球化学性质,Ｒｅ－Ｏｓ同位素体系可以用来确定特定矿床的形成年龄,特别为金属矿床形成时代的研究开辟了新的途径,同时,由于Ｒｅ,Ｏｓ的元素相容性不同,导致不同地球化学储源库具有不同的Ｏｓ同位素特征,特别是地壳和地幔具有截然不同的Ｏｓ同位素特征,据此可以用来讨论不同类型矿产质和岩浆的来源。     

Important crustal growth in the Phanerozoic: Isotopic evidence of granitoids from east-central Asia

The growth of the continental crust is generally believed to have been essentially completed in the Precambrian, and the amount of juvenile crust produced in the Phanerozoic is considered insignificant. Such idea of negligible growth in the Phanerozoic is now challenged by the revelation of very large volume of juvenile crust produced in the period of 500 to 100 Ma in several orogenic belts. While appreciable volumes of juvenile terranes in North America (Canadian Cordillera, Sierra Nevada and Peninsular Range, Appalachians) have been documented based on Nd isotopic data, the mass of new crust formed in the East-Central Asian Orogenic Belt (ECAOB), eastern part of the Altaid Tectonic Collage, appears to be much greater than the above terranes combined. New and published Nd-Sr isotope data indicate that the Phanerozoic granitoids from the southern belt of the ECAOB (Xinjiang-West Mongolia-Inner Mongolia-NE China) as well as from Mongolia and Transbaikalia were generated from sources dominated by a depleted mantle component. These granitoids represent a significant growth of juvenile crust in the Phanerozoic. Although most plutons in this huge orogenic belt belong to the calc-alkaline series, the ECAOB is also characterized by the emplacement of voluminous A-type granites. The origin of these rocks is probably multiple and is still widely debated. However, the isotopic data (Sr-Nd-O) and trace element abundance patterns of A-type granites from the ECAOB clearly indicate their mantle origin. The evolution of the ECAOB and the entire Altaid Collage is most likely related to successive accretion of arc complexes. However, the emplacement of a large volume of post-tectonic A-type granites requires another mechanism—probably through a series of processes including underplating of massive basaltic magma, partial melting of these basic rocks to produce granitic liquids, followed by extensive fractional crystallization. The proportion of juvenile to recycled, as well as that of arc-related to plume-generated, continental crust remains to be evaluated by more systematic dating and isotope tracer studies.