Permian copper–polymetallic mineralization in the southern Great Xing’an Range,Northeast China: the Daolundaba copper–polymetallic deposit example

The Daolundaba Cu–polymetallic deposit is a newly discovered Cu–W–Sn deposit on the western slopes of the southern Great Xing’an Range, and its mineralization was related to an early Permian coarse-grained biotite granite. However, there is little information on the age of formation of the deposit. In this article, we present the results of our investigation into the age of the Daolundaba Cu–polymetallic deposit, which involved the selection of chalcopyrite and pyrrhotite samples for Rb–Sr isochron dating. A Rb–Sr isochron defined by the chalcopyrite samples yielded a Rb–Sr isochron age of 290.0 ± 11 Ma (MSWD = 1.2) with an initial Sr isotopic composition (I_Sr) of 0.71446. The pyrrhotite samples yielded a Rb–Sr isochron age of 283.0 ± 2.6 Ma (MSWD = 1.16) with an initial Sr isotopic composition (I_Sr) of 0.71447. The Rb–Sr isochron age determined from the chalcopyrite and pyrrhotite is 282.7 ± 1.7 Ma (MSWD = 1.13). These results indicate that the Daolundaba Cu–polymetallic deposit formed during the early Permian (282.7–290.0 Ma). The Rb and Sr contents of the chalcopyrite and pyrrhotite range from ~0.1325 to ~3.6810 ppm and from ~0.1219 to ~9.5740 ppm, respectively, and the initial Sr isotope ratios (I_Sr) range from 0.71047 to 0.71869, with an average of 0.714723. These isotopic characteristics indicate the ore-forming minerals of the Daolundaba Cu–polymetallic deposit originated mainly from the crust, but with small amounts of mantle material involved. The copper was derived from the associated magma whereas the W and Sn was derived from the surrounding strata. The Permian mineralization of the Xing’an–Mongolia region occurred in an active continental margin setting during subduction of the Palaeo-Asian oceanic plate beneath the Siberian Plate.     

塔里木盆地西北缘早二叠世后碰撞花岗质岩浆活动及其构造意义

塔里木地块西北缘的阔什布拉克钾长花岗岩富碱(Na_2O+K_2O平均8.36%8%),富钾(K_2O/Na_2O=1.27～1.47),准铝质(A/CNK=0.82～0.88),属于高钾钙碱性系列岩浆岩。岩石的稀土含量较高(∑REE=263.90×10~(-6)～445.75×10~(-6)),富集Th、U、Ta、Nb、Hf和Y等高场强元素和大离子亲石元素Rb,具有强的负Eu异常(δEu=0.003～0.019),富集高不相容元素(Zr+Nb+Ce+Y=368×10~(-6)～531×10~(-6)350×10~(-6)),高Ga(Ga/Al×10 000=4.17～4.722.6),显示出A型花岗岩的地球化学特征。岩石Th/U比值(平均为3.86)、Nb/Ta比值(平均为12.75)和Rb-Th富集、Ti亏损指示其壳源成因。对花岗岩进行的LA-ICP-MS微区原位锆石U-Pb定年结果表明,花岗岩的结晶侵位年龄为275.4±2.8 Ma。综合西南天山与塔里木盆地早二叠世花岗质岩浆活动的特点,认为早二叠世西南天山的后碰撞岩浆活动不仅在西南天山内部引起了强烈的花岗质岩浆活动,而且对塔里木地块西北边缘的花岗质岩浆活动也有显著的影响。阔什布拉克A型花岗岩也说明西南天山地区的碰撞造山作用在275.4±2.8 Ma之前已经趋于结束,以南天山洋盆为代表的古亚洲洋已基本结束了其演化历史。     

Evaluating performance of post‐tensioned steel connections with strands and reduced flange plates

The seismic performance of post‐tensioned steel connections for moment‐resisting frames was examined experimentally and analytically. Cyclic tests were conducted on three full‐scale subassemblies, which had two steel beams post‐tensioned to a concrete‐filled tube (CFT) column with high‐strength strands to provide recentring response. Reduced flange plates (RFPs) welded to the column and bolted to the beam flange were used to increase the dissipation of energy. Test results indicated that (1) the proposed buckling‐restrained RFP could dissipate energy in axial tension and compression, (2) the subassemblies could reach an interstorey drift of 4% without strength degradation, and (3) buckling of the beam occurred towards an interstorey drift of 5%, causing a loss of the strand force, the recentring response, and the moment capacity. A general‐purpose non‐linear finite element analysis program (ABAQUS) was used to perform a correlation study. The behaviour of the steel beam under both post‐tensioning and flexural loadings was compared to the test results and predictions. Copyright © 2006 John Wiley & Sons, Ltd.     

我国地震地下流体观测研究40年发展与展望

本文简要回顾了我国地震地下流体学科40年观测研究发展的历史,分析了目前存在的主要关键科学问题和当前国际地震流体观测研究动态,并对今后的发展趋势提出了一些认识。     

山西朔州井水位的前驱波记录及其讨论

在山西省朔州井水位动态观测的原始记录图中,发现很多远强震前的水位慢波动现象,称其为井水位的前驱波记录．本文介绍了典型的前驱波记录图象,初步分析了该井水位对前驱波的记录特征,发现38％的远大强震前有这种记录,波动周期为数分钟至数十分钟,多在震前两天内出现;讨论了前驱波的成因与传播及其井水位的响应条件,研究了井水位前驱波的科学意义及在地震预测探索中的实用价值．      

Performance evaluation of steel reduced flange plate moment connections

This study details a new moment connection that overcomes difficulties in achieving field‐weld quality and eliminates steel beam buckling encountered in steel moment connections. This study presents cyclic test and finite element analysis results of full‐scale subassemblies using steel reduced flange plates (RFPs) to connect steel beam flanges and the column without any other direct connection. Since the RFP connection is designed as strong column‐strong beam‐weak RFPs, the RFP functions as a structural fuse that eliminates weld fractures and beam buckling. Test and analytical results show that (1) the connections transferred the entire beam flexural strength to the column and reached an interstorey drift of 4% with minor strength degradation, (2) failure of the connections was owing to buckling or fracturing of the RFP and not of the beam, and (3) the RFP connection subassembly, modelled using the nonlinear finite element computer program ABAQUS, exhibited hysteretic behaviour similar to that of the flange plate (FP) moment connection subassembly. The inelastic buckling force of the RFP was also evaluated by nonlinear regression analyses performed on a nonlinear model that relates buckling force to RFP geometries. Copyright © 2007 John Wiley & Sons, Ltd.     

渤海湾西北岸埋藏牡蛎礁体中的 壳体形态与沉积环境*

渤海湾西北岸沿岸平原分布的众多埋藏牡蛎礁体中的壳体形态和泥沙沉积物特征是不尽相同的。不同礁体中的壳体形态有明显的区别,有些礁体中的壳体细窄,有些礁体中的壳体较宽厚; 与此相对应,具有不同壳体形态的礁体中的沉积物颗粒和粘土含量也有明显的差别。文章分别对组成大吴庄和岭头两个礁体剖面的牡蛎壳体和泥质沉积物进行测量和分析,结果表明大吴庄礁体中壳体的重量随高度增长的速率大于岭头礁体中的壳体,而两个礁体中壳体的壳重随体积增长的速率大致相同; 组成礁体的壳体形态与礁体的沉积环境有关,沉积物较细、粘土含量高时发育细窄的壳体,沉积物较粗、粘土含量低时发育宽厚的壳体。渤海湾西北岸地区埋藏牡蛎礁体中的壳体本身记录了其生长时的环境信息,可以通过分析礁体中的壳体形态来恢复礁体建礁过程中的沉积环境。     

我国地震地下流体前兆观测的"九五"进展与台站管理体制的改革意向

主要介绍了我国在“九五”期间实施的前兆台站流体测项的数字化中推广的仪器型号、主要性能指标及改造的规模,观测取得的成果及其有待完善的技术问题;简要介绍了我国长江三峡工程诱发地震监测系统中地下水动态监测井网的布设,观测井下地下水特征,数字化观测技术系统及建设的基本结果;最后介绍了流体学科前兆台站分级分类管理的改革意向。     

我国地震地下流体前兆台站现状的调查与分析

系统介绍了我国地震地下流体前兆台站的产权与管理权关系,观测点的井泉类型、观测井深度,观测层类型与地下水物理化学特征,观测项目及仪器类型与运行现状,井房及其供电与通讯条件,观测人员的学历与专业结构、年龄与工龄结构等,为“十五”台站优化与建设方案的制定提供依据。