Jurassic accretion tectonics of Japan

Abstract The Jurassic accretionary complex and coeval granites in Japan represent remnants of the Jurassic arc-trench system developed between the Asian continent and Pacific Ocean. The Jurassic accretionary complex occurs as a large-scale nappe that is tectonically sandwiched between the overlying pre-Jurassic nappes and underlying post-Jurassic nappes. By virtue of new research styles (microfossil mapping and chronometric mapping) the following new views of the Jurassic accretionary complex in Japan, that suggest those for on-land exposed ancient accretionary complexes in general, have been obtained: (i) the accretion age of the Jurassic accretionary complex ranges over ～ 80 million years from the latest Triassic to earliest Cretaceous according to a reconstructed stratigraphy of component rocks (oceanic plate stratigraphy); (ii) the accretionary complex is subdivided into several nappe units, each characterized by unique oceanic plate stratigraphy; (iii) a tectonically downward-younging polarity is observed in the piled nappes; (iv) the Jurassic accretionary complex is composed of coherent-type and chaotic-type units, the former retaining the primary accretionary structures while the latter are characterized by collapsed and secondarily mixed materialslfabrics derived from the former; (v) the chaotic-type units predominate in volume over the coherent-type units; (vi) the accretionary complex suffered from a regional low-grade metamorphism (up to the lower greenschist facies) within ～10–20 million years after the accretion timing; and (vii) the lateral extent of the Jurassic accretionary complex in East Asia is intermittently traced from the Koryak mountains in Russia to North Palawan in the west Philippines for ～6000 km. Discussion focuses on (i) the low preservation ratio of the coherent-type units to the chaotic-type units with respect to frequent subduction erosion by seamount subduction; (ii) absence of the Franciscan-type melange, suggesting sedimentary mixing origin for the chaotic-type unit; (iii) a growth rate of the Jurassic accretionary complex compatible to modern analogues; and (iv) the total volume of the Jurassic accretionary complex in Japan with respect to the most likely terrigeiious elastics source along the 250 Ma continent-continent collision suture in central China (between the Sino-Korean and Yangtze blocks).     

华北太古宙从地幔柱体制向板块构造体制的转化

通过对原岩建造、变南作用、ｐＴｔ轨迹和εＮｄ（ｔ）值等综合研究，提出迁安和怀安为两个 同时代不同性质的陆壳，遵化和崇礼为两个不同性质的深变质绿岩带，遵化为裂谷型绿岩带而崇礼为岛弧型绿岩带，２，７Ｇａ之前受地幔柱活动的影响，导致了上地幔的不均一性和ＴＨ１和ＴＨ２两类拉斑玄武岩的紧密共存，２．７Ｇａ之后从地幔柱体制向板块体制转化，造成了西北岛弧型壳事件和碰撞变质作用。     

全球变化——海洋地学的热点问题

文章对当今海洋地球科学中对全球环境变化有影响的气候变暖、板块构造运动、环境地质和矿产资源开发等热点问题进行了阐述。近百年来，世界气温变化反映全球变暖的趋势。气候变暖引起的海平面上升和厄尔尼诺现象将对沿海国家近岸地区人民的生产和生活带来极大的危害和巨大的经济损失。８０年代以来，全球板块构造运动及其驱动力成为科学家研究的热点；沿岸国家海岸带海陆交互地区的开发活动和日益严重的污染对海洋生态环境造成极大危害。文章亦分析了海洋矿产资源开发的前景和海洋地球科学面临的重要课题，提出２１世纪我国海洋地质调查与研究的主要任务     

郯庐断裂带北段的形成时间及其动力学特征(英文)

郯庐断裂带在中国东北地区延伸，切过辽河盆地东部坳陷后分为依兰－伊通、密山－敦化和四平－长春三条断裂。在依兰－伊通断裂带内利用４０Ａｒ／３９Ａｒ法测得断层岩（云母石英片岩）中黑云母单矿物的年龄为（１００±２．３）Ｍａ。同时测得断裂带内辉绿岩的Ｒｂ－Ｓｒ全岩等时线年龄（１００±５．９）Ｍａ，辉石的４０Ａｒ／３９Ａｒ坪年龄为１０５Ｍａ。从依兰－伊通断裂错开中生代花岗岩体、古生界地层、白垩系泉头组的露头对比，以及断裂带内应变测量等获得区内断层的走滑距离为４ｋｍ左右。断层切过下白垩统泉头组（１２２Ｍａ，Ｋ－Ａｒ法）并被上白垩统嫩江组所覆盖。这段走滑断层的活动对邻近盆地产生了影响，造成盆地中的反转构造。该走滑断层是在中国东部地区逆时针方向的旋转运动基础上形成的，并与俯冲的西太平洋板块及其引起的上地幔物质运动有关     

组合钢板耗能器—一种新型耗能减震装置

本文在吸收普通钢板耗能器和Ｐａｌｌ摩擦耗能器优点的基础上提出了组合钢板耗能器，建立了相应的力学分析和计算模型；通过地震反应分析检验了其减振效果，并与普通钢板耗能器进行了对比。研究结果表明，组合钢板耗能器是一种构造简单，耐久性好，减效果和经济效果俱佳的抗震效果，具有广阔手应用前景。     

Geodynamic implications of chrome-poor enstatitite bodies in the Sukinda-Boula-Nausahi ultramafic suites of Orissa

Within the Brahmani valley granulite terrane (Eastern Ghats) of Dhenkanal district, Orissa the sporadically outcropping pods of chromite-rich serpentinite are devoid of chrome-poor enstatitite which occurs abundantly in the northern Gorumahisani greenstone terrane as well defined units within the chromite-rich suites at Katpal, Sukinda and Boula-Nausahi, Cuttack and Keonjhar districts. Available field evidence is compatible with a model of emplacement of these ultramafic bodies along the contact between the two terranes in a number of stages involving soft and hard collision, subduction of Gorumahisani Group oceanic lithosphere below the Eastern Ghats granulites followed by delamination and asthenospheric upwelling. Falsifiability tests for the model have been indicated.     

米仓山地区岩浆活动与构造演化

扬子板块北缘自晚太古代至早震旦世，先后经历了地壳演化早期、沟－弧－盆和大陆裂谷三个大的发展阶段。与之有关的岩浆活动可划分为前吕梁期、吕梁期、晋宁期及澄江期；地壳演化的不同阶段、不同期次的岩浆岩在岩浆性质、活动方式和规模等方面有较大差别，各具特色。本文论述了各个时期岩浆活动特点、岩石成因及其与区域构造演化之间的密切关系，尤其是充分肯定了澄江期裂谷型岩浆岩在本区岩浆活动历史中的主导地位，这对进一步研究和重新认识扬子板块北缘地质构造演化史具有重要意义。     

海上水下砼灌注施工技术

结合工程实际，介绍海上水下砼灌注中设备的选用与布置、砼灌注等工艺，并分析对比了翻板阀门水下砼灌注的可靠性。     

模喷技术在北京鹰山特大断面隧道中的应用

针对传统的喷射作业，砼的回弹率高，喷射现场粉尘浓度大，介绍了一种“简易模喷”技术，它与“模喷机”相比，具有结构简单，施工方便等特点。